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From the start of 2016, the journal uses article numbers instead of page numbers to identify articles. If you are required to add page numbers to a citation, you can do with using a colon in the format [article number]:1–[last page], e.g. 10:1–20.

Materials, Volume 9, Issue 1 (January 2016) – 66 articles

Cover Story (view full-size image): Epitaxial multiferroic composites built from BaTiO3 and BiFeO3 are promising because of their high magnetoelectric voltage coefficient. We found that oxygen-related defects have considerable impact on the functionality of the composite films. The cover figure shows the structure model of oxygen vacancy ordering on the {111} planes of the pseudocubic BaTiO3-type structure. Both modeled (top) and experimental selected area electron diffraction patterns agree well, thus verifying our model. Image is by Gerald Wagner and Oliver Oeckler. View the paper
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266 KiB  
Editorial
Acknowledgement to Reviewers of Materials in 2015
by Materials Editorial Office
Materials 2016, 9(1), 66; https://doi.org/10.3390/ma9010066 - 21 Jan 2016
Viewed by 5666
Abstract
The editors of Materials would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2015. [...] Full article
11409 KiB  
Article
Solid-State Gas Sensors: Sensor System Challenges in the Civil Security Domain
by Gerhard Müller, Angelika Hackner, Sebastian Beer and Johann Göbel
Materials 2016, 9(1), 65; https://doi.org/10.3390/ma9010065 - 20 Jan 2016
Cited by 14 | Viewed by 12258
Abstract
The detection of military high explosives and illicit drugs presents problems of paramount importance in the fields of counter terrorism and criminal investigation. Effectively dealing with such threats requires hand-portable, mobile and affordable instruments. The paper shows that solid-state gas sensors can contribute [...] Read more.
The detection of military high explosives and illicit drugs presents problems of paramount importance in the fields of counter terrorism and criminal investigation. Effectively dealing with such threats requires hand-portable, mobile and affordable instruments. The paper shows that solid-state gas sensors can contribute to the development of such instruments provided the sensors are incorporated into integrated sensor systems, which acquire the target substances in the form of particle residue from suspect objects and which process the collected residue through a sequence of particle sampling, solid-vapor conversion, vapor detection and signal treatment steps. Considering sensor systems with metal oxide gas sensors at the backend, it is demonstrated that significant gains in sensitivity, selectivity and speed of response can be attained when the threat substances are sampled in particle as opposed to vapor form. Full article
(This article belongs to the Special Issue Nanostructured Materials for Chemical Sensing Applications)
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Figure 1

Figure 1
<p>Sensor system for sampling, sorting and converting low vapor pressure target particles into detectable vapors. ESP, electrostatic precipitation.</p> Full article ">Figure 2
<p>Molecular structure of explosives: (<b>a</b>) military high explosives; (<b>b</b>) improvised explosives. All substances contain strongly electron-attracting NO<span class="html-italic"><sub>x</sub></span> side groups (marked by green circles.</p> Full article ">Figure 3
<p>(<b>a</b>) Free-base form of cocaine; (<b>b</b>) salt-like cocaine hydrochloride.</p> Full article ">Figure 4
<p>Molecular structure of illicit drugs. Ephedrine [<a href="#B32-materials-09-00065" class="html-bibr">32</a>] is an easily available substitute for enabling efficient laboratory work. Amine functional groups are highlighted in yellow.</p> Full article ">Figure 5
<p>Proton affinity of selected molecules. The blue line highlights the proton affinity of water, <span class="html-italic">i.e.</span>, the energy released in the gas phase reaction H<sub>2</sub>O + H<sup>+</sup> → H<sub>3</sub>O<sup>+</sup>. Starting from H<sub>3</sub>O<sup>+</sup> ions, protons will be transferred to higher proton-affinity molecules (filled arrow) in the course of gas-kinetic collisions, while a transfer to lower proton-affinity ones is extremely unlikely (empty arrow).</p> Full article ">Figure 6
<p>(<b>a</b>) Collecting trace particle residue from a suspect item using the IonScan 500 sampler “spoon”; (<b>b</b>) IonScan 500 ion mobility spectrometer (IMS) with the insertion port for the sampler spoon (arrow) [<a href="#B34-materials-09-00065" class="html-bibr">34</a>]; (<b>c</b>) example of ion drift spectrum.</p> Full article ">Figure 7
<p>(<b>a</b>) Process of particle sampling and solid-vapor conversion for IMS detection; (<b>b</b>) internal architecture of an IMS, featuring an ionization region (magenta) and two ion drift tubes (blue) with associated detector circuits for positive (Pos.) and negative (Neg.) ions, respectively.</p> Full article ">Figure 8
<p>(Top panel) Radioactive ionization of N<sub>2</sub> molecules by high-energy electrons (β-particles) leading to positive (hydrated protons) and negative (low-energy electrons) ionization products. In the follow-on atmospheric pressure chemical ionization (APCI) processes, the initial ionization products become attached to increasingly higher proton- or electron-affinity molecular species, thus forming positive (left) and negative (right) analyte ions, here represented by NH<sub>3</sub> and NO<sub>2</sub> ones. (CWA: chemical warfare agents; TICs: Toxic industrial compounds). For more details, see [<a href="#B17-materials-09-00065" class="html-bibr">17</a>].</p> Full article ">Figure 9
<p>(<b>a</b>) Evaporation of TNT particles from an electrical heater into a MOX gas sensor array; (<b>b</b>) response of the sensors to the evaporating TNT particles (blue: current input into the heater element; red: resulting temperature ramp; colored curves: relative resistance response of the sensors to the resulting TNT vapor pulses.</p> Full article ">Figure 10
<p>Use of MOX gas sensors for explosives detection: (<b>a</b>) explosives disintegration producing NO<sub>2</sub> vapors; (<b>b</b>) NO<sub>2</sub> sensitivity of a commercial NO<sub>2</sub> sensor featuring a noise-equivalent resistive response of about 10 ppb; (<b>c</b>) an evaporation/disintegration of a 1-µm grain of explosive producing the noise-equivalent NO<sub>2</sub> concentration; (<b>d</b>) thermal conversion of a hand/finger print of explosives producing an easily detectable NO<sub>2</sub> concentration.</p> Full article ">Figure 10 Cont.
<p>Use of MOX gas sensors for explosives detection: (<b>a</b>) explosives disintegration producing NO<sub>2</sub> vapors; (<b>b</b>) NO<sub>2</sub> sensitivity of a commercial NO<sub>2</sub> sensor featuring a noise-equivalent resistive response of about 10 ppb; (<b>c</b>) an evaporation/disintegration of a 1-µm grain of explosive producing the noise-equivalent NO<sub>2</sub> concentration; (<b>d</b>) thermal conversion of a hand/finger print of explosives producing an easily detectable NO<sub>2</sub> concentration.</p> Full article ">Figure 11
<p>(<b>a</b>) Response of a single NO<sub>2</sub> MOX sensor to an empty (black) and a TNT-loaded hotplate (magenta) when the hotplate temperature (red) is ramped up; (<b>b</b>) control experiment in which pure water (blue) and nitrous acid (HNO<sub>3</sub>) are evaporated; (<b>c</b>) control experiment in which many kinds of background particle (liquid) residue were evaporated; (<b>d</b>) same data as in (<b>c</b>), but plotted on a logarithmic scale.</p> Full article ">Figure 12
<p>(<b>a</b>) Relative resistance change of a nano-granular SnO<sub>2</sub> layer in response to oxidizing NO<sub>2</sub> and a range of reducing background gases. A dominating NO<sub>2</sub> response at low sensor operation conditions occurs due to the reactive nature of NO<sub>2</sub> and its thermal instability at higher temperatures (NO<sub>2</sub> → NO + ½ O<sub>2</sub>); (<b>b</b>) nano-morphology of the SnO<sub>2</sub> sensing layer.</p> Full article ">Figure 13
<p>(<b>A</b>) One-step and two-step thermal solid vapor conversion processes; (<b>B</b>) sensor responses to TNT, HNO<sub>3</sub> and water upon first evaporation; (<b>C</b>) sensor responses to TNT, HNO<sub>3</sub> and water upon re-evaporation from the transfer substrate.</p> Full article ">Figure 14
<p>(<b>a</b>) MOX gas sensor operated in the conventional resistive (RES) and (<b>b</b>) in the innovative surface ionization (SI) readout mode. In the RES mode, gas adsorption is monitored via changes in the in-plane resistivity of the MOX sensing layers. The cathode layer is not normally present, but may be used to modify the gas adsorption via the electro-adsorption effect [<a href="#B52-materials-09-00065" class="html-bibr">52</a>]. In the SI readout mode changes in the gas adsorption are monitored by observing flows of positive ions crossing the thin air gap (<span class="html-italic">d</span><sub>air</sub> ~ 0.1–1 mm) in between the heated MOX layer and the negatively-biased counter electrode.</p> Full article ">Figure 15
<p>Free-space ionization energies <math display="inline"> <semantics> <mrow> <msub> <mi>E</mi> <mrow> <mi>I</mi> <mo>_</mo> <mi>v</mi> <mi>a</mi> <mi>c</mi> </mrow> </msub> </mrow> </semantics> </math> of selected molecules [<a href="#B20-materials-09-00065" class="html-bibr">20</a>] in relation to the vacuum energy <math display="inline"> <semantics> <mrow> <msub> <mi>E</mi> <mrow> <mi>v</mi> <mi>a</mi> <mi>c</mi> </mrow> </msub> </mrow> </semantics> </math> and the conduction and valence band edges and the Fermi energy in SnO<sub>2</sub>. Blue and white arrows: free-space and first-order surface ionization energies. Colored rectangles denote different groups of analytes.</p> Full article ">Figure 16
<p>(<b>a</b>,<b>b</b>) Architecture of MOX sensors with SI readout; (<b>c</b>) measurement chamber for SI gas sensing tests. The active sensing area, determined by the size of the adjustable counter electrode, is ~10 mm<sup>2</sup>; (<b>d</b>) Ionization current density as a function of the temperature of a Fe<sub>2</sub>O<sub>3</sub> emitter film. Amine-containing analytes (upper group) and non-amine-containing ones yield vastly different ion current densities.</p> Full article ">Figure 17
<p>(<b>a</b>) Thermal disintegration of illicit drugs yielding hydrocarbon fragments with amine functional groups (circles); (<b>b</b>) process of collection and thermal desorption of analytes into the air gap of an SI detector; (<b>c</b>) SI current response to the evaporation of the drug substitutes ephedrine and ephedrine:HCl. For comparison, the responses to pure solvent water and to an organic decay product (dibutylamine) are shown [<a href="#B49-materials-09-00065" class="html-bibr">49</a>]; (<b>d</b>) response to the evaporation of ephedrine and a range of cutting agents (lactose, caffeine, paracetamol, atropine), which usually contaminate street samples of illicit drugs [<a href="#B50-materials-09-00065" class="html-bibr">50</a>,<a href="#B53-materials-09-00065" class="html-bibr">53</a>,<a href="#B54-materials-09-00065" class="html-bibr">54</a>,<a href="#B55-materials-09-00065" class="html-bibr">55</a>,<a href="#B56-materials-09-00065" class="html-bibr">56</a>]. The red line in (<b>d</b>) mirrors the temperature rise of the SI emitter film when the substance is evaporated into the air gap of the SI detector.</p> Full article ">Figure 18
<p>Molecular structures of the substances used in the evaporation tests reported in <a href="#materials-09-00065-f017" class="html-fig">Figure 17</a>. Color coding of atoms: carbon (black); hydrogen (grey); oxygen (red); nitrogen (blue): (<b>a</b>) substances not detectable by surface ionization, (<b>b</b>) substances well-detectable by surface ionization.</p> Full article ">Figure 19
<p>Injection of ephedrine into the air gap of an SI detector through a chromatographic column. The minimum detectable amount of ephedrine is less than 45 nanograms. Complete evaporation of this amount of ephedrine would yield a concentration of amine-containing molecules in the air gap in the high sub-ppm range.</p> Full article ">Figure 20
<p>(<b>a</b>) Corona discharge arrangement generating a negative corona discharge around the sharply curved wire electrode and a stream of negative ions and a knock-on neutral ion wind moving towards a porous flat-plate collector electrode; (<b>b</b>) corona discharge arrangement with compensated ion wind; (<b>c</b>) corona discharge arrangement with compensated ion wind in the presence of a sampling air stream carrying particles with high electron affinity; (<b>d</b>) same arrangement as in (<b>c</b>), but with a sampling air stream carrying particles with a very low electron affinity.</p> Full article ">Figure 21
<p>Sampling and precipitation of low (<b>a</b>) and high electron-affinity particles (<b>b</b>) using an ESP separator mounted on a hand-portable, battery-operated vacuum cleaner. While low <span class="html-italic">EA</span> particles (blue) follow the aerodynamic flow lines generated by the vacuum cleaner on paths connecting the inlet and outlet and thus become discarded, high <span class="html-italic">EA</span> ones (red) get negatively charged upon passing the corona wire array in the middle and get collected at the positively-charged collector electrode positioned opposite the air flow direction.</p> Full article ">Figure 22
<p>Lugol’s test applied to pure TiO<sub>2</sub> (<b>a</b>) and to pure flour (<b>b</b>) demonstrating the presence of starch in (<b>b</b>); (<b>c</b>) Lugol’s test applied to a mixture of flour and TiO<sub>2</sub>; after passing this mix through the ESP separator, the mix is separated into almost pure fractions of TiO<sub>2</sub> (<b>d</b>) and flour (<b>e</b>).</p> Full article ">Figure 23
<p>(<b>a</b>) ESP sampler system built into a commercial, battery-operated vacuum cleaner. Explosives particles and/or illicit drug residue were extracted from purposely contaminated environments (<b>b</b>,<b>c</b>) and placed onto cotton swabs inserted into the ESP sampler. Solid-vapor conversion and detection still needs to be performed by a separate stationary detector system.</p> Full article ">Figure 24
<p>Detecting explosives and illicit drugs with the help of solid-state gas sensors. In Process Sequence 1, the small amounts of vapors emerging from the particle residue in the lower left corner are directly detected using a solid-state gas sensor. In Process Sequence 2, the solid particle residue is collected, purified, flash-evaporated and vapor-detected.</p> Full article ">Figure 25
<p>Families of chip-sized backend vapor detectors that form viable alternatives to the backend MOX gas sensors used in this work.</p> Full article ">
8616 KiB  
Article
Influence of Radiation Sterilization on Properties of Biodegradable Lactide/Glycolide/Trimethylene Carbonate and Lactide/Glycolide/ε-caprolactone Porous Scaffolds with Shape Memory Behavior
by Piotr Rychter, Natalia Śmigiel-Gac, Elżbieta Pamuła, Anna Smola-Dmochowska, Henryk Janeczek, Wojciech Prochwicz and Piotr Dobrzyński
Materials 2016, 9(1), 64; https://doi.org/10.3390/ma9010064 - 20 Jan 2016
Cited by 15 | Viewed by 7655
Abstract
The aim of the study was the evaluation of gamma irradiation and electron beams for sterilization of porous scaffolds with shape memory behavior obtained from biodegradable terpolymers: poly(l-lactide-co-glycolide-co-trimethylene carbonate) and poly(l-lactide-co-glycolide-co-ɛ-caprolactone). [...] Read more.
The aim of the study was the evaluation of gamma irradiation and electron beams for sterilization of porous scaffolds with shape memory behavior obtained from biodegradable terpolymers: poly(l-lactide-co-glycolide-co-trimethylene carbonate) and poly(l-lactide-co-glycolide-co-ɛ-caprolactone). The impact of mentioned sterilization techniques on the structure of the scaffolds before and after the sterilization process using irradiation doses ranged from 10 to 25 kGy has been investigated. Treatment of the samples with gamma irradiation at 15 kGy dose resulted in considerable drop in glass transition temperature (Tg) and number average molecular weight (Mn). For comparison, after irradiation of the samples using an electron beam with the same dose, no significant changes in structure or properties of examined scaffolds have been noticed. Higher doses of irradiation via electron beam caused essential changes of the scaffolds’ pores resulting in partial melting of their surface. Nevertheless, obtained results have revealed that sterilization with electron beam, when compared to gamma irradiation, is a better method because it does not affect significantly the physicochemical properties of the scaffolds. Both used methods of sterilization did not influence the shape memory behavior of the examined materials. Full article
(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>DSC traces for copolymer (<b>A</b>) LGT21 C; (<b>B</b>) LGT40 C; and (<b>C</b>) LTG C. I-heating run at 20°C/min after γ irradiation with dose: 0 kGy, 10 kGy, 15 kGy, and 25 kGy.</p> Full article ">Figure 1 Cont.
<p>DSC traces for copolymer (<b>A</b>) LGT21 C; (<b>B</b>) LGT40 C; and (<b>C</b>) LTG C. I-heating run at 20°C/min after γ irradiation with dose: 0 kGy, 10 kGy, 15 kGy, and 25 kGy.</p> Full article ">Figure 2
<p>SEM pictures of porous surface of scaffold LGC C: (<b>A</b>,<b>B</b>) before sterilization; (<b>C</b>,<b>D</b>) after γ irradiation with a 25 kGy dose.</p> Full article ">Figure 3
<p>SEM pictures of porous surface of scaffold LGT40 C; (<b>A</b>,<b>B</b>) before sterilization and (<b>C</b>,<b>D</b>) after γ sterilization with irradiation dose of 25 kGy.</p> Full article ">Figure 4
<p>DSC trace for copolymer (<b>A</b>) LGT21 C; (<b>B</b>) LGT40 C; and (<b>C</b>) LGC C. I-heating run at 20 °C/min after electron beam irradiation with dose: 0 kGy, 10 kGy, 15 kGy, and 25 kGy.</p> Full article ">Figure 4 Cont.
<p>DSC trace for copolymer (<b>A</b>) LGT21 C; (<b>B</b>) LGT40 C; and (<b>C</b>) LGC C. I-heating run at 20 °C/min after electron beam irradiation with dose: 0 kGy, 10 kGy, 15 kGy, and 25 kGy.</p> Full article ">Figure 5
<p>SEM pictures of scaffolds pore surface after electron beam sterilization made of terpolymer LGT21 C with dose (<b>A</b>) 10 kGy; (<b>B</b>) 15 kGy; (<b>C</b>) 25 kGy; terpolymer LGT40 C with dose (<b>D</b>) 10 kGy; (<b>E</b>) 15 kGy; (<b>F</b>) 25 kGy and terpolymer LGC C with dose (<b>G</b>) 10 kGy; (<b>H</b>) 15 kGy; and (<b>I</b>) 25 kGy.</p> Full article ">Figure 6
<p>The two-step synthesis procedure of <span class="html-small-caps">l</span>-lactide/glycolide/trimethylene carbonate terpolymers (LGT21 and LGT40).</p> Full article ">Figure 7
<p><span class="html-small-caps">l</span>-lactide/glycolide/caprolactoneterpolymer (LGC) synthesis.</p> Full article ">
2572 KiB  
Article
Influence of Oxygen Concentration on the Performance of Ultra-Thin RF Magnetron Sputter Deposited Indium Tin Oxide Films as a Top Electrode for Photovoltaic Devices
by Jephias Gwamuri, Murugesan Marikkannan, Jeyanthinath Mayandi, Patrick K. Bowen and Joshua M. Pearce
Materials 2016, 9(1), 63; https://doi.org/10.3390/ma9010063 - 20 Jan 2016
Cited by 50 | Viewed by 9938
Abstract
The opportunity for substantial efficiency enhancements of thin film hydrogenated amorphous silicon (a-Si:H) solar photovoltaic (PV) cells using plasmonic absorbers requires ultra-thin transparent conducting oxide top electrodes with low resistivity and high transmittances in the visible range of the electromagnetic spectrum. Fabricating ultra-thin [...] Read more.
The opportunity for substantial efficiency enhancements of thin film hydrogenated amorphous silicon (a-Si:H) solar photovoltaic (PV) cells using plasmonic absorbers requires ultra-thin transparent conducting oxide top electrodes with low resistivity and high transmittances in the visible range of the electromagnetic spectrum. Fabricating ultra-thin indium tin oxide (ITO) films (sub-50 nm) using conventional methods has presented a number of challenges; however, a novel method involving chemical shaving of thicker (greater than 80 nm) RF sputter deposited high-quality ITO films has been demonstrated. This study investigates the effect of oxygen concentration on the etch rates of RF sputter deposited ITO films to provide a detailed understanding of the interaction of all critical experimental parameters to help create even thinner layers to allow for more finely tune plasmonic resonances. ITO films were deposited on silicon substrates with a 98-nm, thermally grown oxide using RF magnetron sputtering with oxygen concentrations of 0, 0.4 and 1.0 sccm and annealed at 300 °C air ambient. Then the films were etched using a combination of water and hydrochloric and nitric acids for 1, 3, 5 and 8 min at room temperature. In-between each etching process cycle, the films were characterized by X-ray diffraction, atomic force microscopy, Raman Spectroscopy, 4-point probe (electrical conductivity), and variable angle spectroscopic ellipsometry. All the films were polycrystalline in nature and highly oriented along the (222) reflection. Ultra-thin ITO films with record low resistivity values (as low as 5.83 × 10−4 Ω·cm) were obtained and high optical transparency is exhibited in the 300–1000 nm wavelength region for all the ITO films. The etch rate, preferred crystal lattice growth plane, d-spacing and lattice distortion were also observed to be highly dependent on the nature of growth environment for RF sputter deposited ITO films. The structural, electrical, and optical properties of the ITO films are discussed with respect to the oxygen ambient nature and etching time in detail to provide guidance for plasmonic enhanced a-Si:H solar PV cell fabrication. Full article
(This article belongs to the Special Issue Photovoltaic Materials and Electronic Devices)
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Figure 1

Figure 1
<p>XRD pattern for ITO films deposited under different oxygen ambient conditions and etched for 1, 3, 5 and 8 min: (<b>A</b>) 0 sccm oxygen; (<b>B</b>) 0.4 sccm oxygen; (<b>C</b>) 1.0 sccm oxygen. Argon flow rate was maintained at 10 sccm for all materials.</p> Full article ">Figure 2
<p>Surface topology image for 2 µm × 2 µm × 0.2 µm of the ITO film deposited under various oxygen environments: (<b>A</b>) 0 sccm oxygen; (<b>B</b>) 0.4 sccm oxygen; (<b>C</b>) 1.0 sccm oxygen, and etched for 8 min; (<b>D</b>) 0 sccm oxygen; (<b>E</b>) 0.4 sccm oxygen and (<b>F</b>) 1 sccm oxygen. (<b>A</b>–<b>C</b>) etched for 1 min and (<b>D</b>–<b>F</b>) films etched for 8 min. The etching was performed at room temperature.</p> Full article ">Figure 3
<p>Raman spectra for the ITO films deposited under various oxygen concentrations and etched for 1, 3, 5 and 8 min., respectively. (<b>A</b>) 0 sccm; (<b>B</b>) 0.4 sccm; (<b>C</b>) 1.0 sccm.</p> Full article ">Figure 4
<p>Optical transmission spectrum for the RF sputter deposited ITO films at different oxygen compositions and etched for min (<b>A</b>) 0 sccm; (<b>B</b>) 0.4 sccm; and (<b>C</b>) 1.0 sccm.</p> Full article ">
2319 KiB  
Article
Comparison of Cyclic Hysteresis Behavior between Cross-Ply C/SiC and SiC/SiC Ceramic-Matrix Composites
by Longbiao Li
Materials 2016, 9(1), 62; https://doi.org/10.3390/ma9010062 - 19 Jan 2016
Cited by 7 | Viewed by 5055
Abstract
In this paper, the comparison of cyclic hysteresis behavior between cross-ply C/SiC and SiC/SiC ceramic-matrix composites (CMCs) has been investigated. The interface slip between fibers and the matrix existed in the matrix cracking mode 3 and mode 5, in which matrix cracking and [...] Read more.
In this paper, the comparison of cyclic hysteresis behavior between cross-ply C/SiC and SiC/SiC ceramic-matrix composites (CMCs) has been investigated. The interface slip between fibers and the matrix existed in the matrix cracking mode 3 and mode 5, in which matrix cracking and interface debonding occurred in the 0° plies are considered as the major reason for hysteresis loops of cross-ply CMCs. The hysteresis loops of cross-ply C/SiC and SiC/SiC composites corresponding to different peak stresses have been predicted using present analysis. The damage parameter, i.e., the proportion of matrix cracking mode 3 in the entire matrix cracking modes of the composite, and the hysteresis dissipated energy increase with increasing peak stress. The damage parameter and hysteresis dissipated energy of C/SiC composite under low peak stress are higher than that of SiC/SiC composite; However, at high peak stress, the damage extent inside of cross-ply SiC/SiC composite is higher than that of C/SiC composite as more transverse cracks and matrix cracks connect together. Full article
(This article belongs to the Section Advanced Composites)
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Figure 1

Figure 1
<p>The undamaged state and five damaged modes of cross-ply ceramic composites: (<b>a</b>) undamaged composite; (<b>b</b>) mode 1: transverse crack; (<b>c</b>) mode 2: transverse crack and matrix crack with perfect fiber/matrix bonding; (<b>d</b>) mode 3: transverse crack and matrix crack with fiber/matrix interface debonding; (<b>e</b>) mode 4: matrix crack with perfect fiber/matrix bonding; and (<b>f</b>) mode 5: matrix cracking with fiber/matrix debonding.</p> Full article ">Figure 2
<p>The matrix cracking mode 3 and mode 5 of cross-ply C/SiC composite under cyclic loading/unloading tensile.</p> Full article ">Figure 3
<p>(<b>a</b>) The theoretical and experimental hysteresis loops; and (<b>b</b>) the interface slip lengths, <span class="html-italic">i.e.</span>, <span class="html-italic">y</span>/<span class="html-italic">l</span><sub>d</sub> and <span class="html-italic">z</span>/<span class="html-italic">l</span><sub>d</sub>, of matrix cracking mode 3 and mode 5 of cross-ply C/SiC composite when <span class="html-italic">σ</span><sub>max</sub> = 60 MPa.</p> Full article ">Figure 4
<p>(<b>a</b>) The theoretical and experimental hysteresis loops; and (<b>b</b>) the interface slip lengths, <span class="html-italic">i.e.</span>, <span class="html-italic">y</span>/<span class="html-italic">l</span><sub>d</sub> and <span class="html-italic">z</span>/<span class="html-italic">l</span><sub>d</sub>, of matrix cracking mode 3 and mode 5 of cross-ply C/SiC composite when <span class="html-italic">σ</span><sub>max</sub> = 80 MPa.</p> Full article ">Figure 5
<p>(<b>a</b>) The theoretical and experimental hysteresis loops; and (<b>b</b>) the interface slip lengths, <span class="html-italic">i.e.</span>, <span class="html-italic">y</span>/<span class="html-italic">l</span><sub>d</sub> and <span class="html-italic">z</span>/<span class="html-italic">l</span><sub>d</sub>, of matrix cracking mode 3 and mode 5 of cross-ply C/SiC composite when <span class="html-italic">σ</span><sub>max</sub> = 100 MPa.</p> Full article ">Figure 6
<p>(<b>a</b>) The theoretical and experimental hysteresis loops; and (<b>b</b>) the interface slip lengths, <span class="html-italic">i.e.</span>, <span class="html-italic">y</span>/<span class="html-italic">l</span><sub>d</sub> and <span class="html-italic">z</span>/<span class="html-italic">l</span><sub>d</sub>, of matrix cracking mode 3 and mode 5 of cross-ply C/SiC composite when <span class="html-italic">σ</span><sub>max</sub> = 120 MPa.</p> Full article ">Figure 7
<p>(<b>a</b>) The theoretical and experimental hysteresis loops; and (<b>b</b>) the interface slip lengths, <span class="html-italic">i.e.</span>, <span class="html-italic">y</span>/<span class="html-italic">l</span><sub>d</sub> and <span class="html-italic">z</span>/<span class="html-italic">l</span><sub>d</sub>, of matrix cracking mode 3 and mode 5 of cross-ply SiC/SiC composite when <span class="html-italic">σ</span><sub>max</sub> = 190 MPa.</p> Full article ">Figure 8
<p>(<b>a</b>) The theoretical and experimental hysteresis loops; and (<b>b</b>) the interface slip lengths, <span class="html-italic">i.e.</span>, <span class="html-italic">y</span>/<span class="html-italic">l</span><sub>d</sub> and <span class="html-italic">z</span>/<span class="html-italic">l</span><sub>d</sub>, of matrix cracking mode 3 and mode 5 of cross-ply C/SiC composite when <span class="html-italic">σ</span><sub>max</sub> = 200 MPa.</p> Full article ">Figure 9
<p>(<b>a</b>) The theoretical and experimental hysteresis loops; and (<b>b</b>) the interface slip lengths, <span class="html-italic">i.e.</span>, <span class="html-italic">y</span>/<span class="html-italic">l</span><sub>d</sub> and <span class="html-italic">z</span>/<span class="html-italic">l</span><sub>d</sub>, of matrix cracking mode 3 and mode 5 of cross-ply SiC/SiC composite when <span class="html-italic">σ</span><sub>max</sub> = 210 MPa.</p> Full article ">Figure 10
<p>The damage parameter <span class="html-italic">η vs.</span> normalized stress <span class="html-italic">σ</span><sub>max</sub>/<span class="html-italic">σ</span><sub>uts</sub> curves of cross-ply C/SiC and SiC/SiC composites.</p> Full article ">Figure 11
<p>The matrix crack density of matrix cracking mode 3 in the 0° plies <span class="html-italic">vs.</span> normalized stress <span class="html-italic">σ</span>/<span class="html-italic">σ</span><sub>max</sub> of cross-ply C/SiC and SiC/SiC composites.</p> Full article ">Figure 12
<p>The hysteresis dissipated energy <span class="html-italic">vs.</span> normalized stress <span class="html-italic">σ</span><sub>max</sub>/<span class="html-italic">σ</span><sub>uts</sub> curves of cross-ply C/SiC and SiC/SiC composites.</p> Full article ">
4154 KiB  
Article
Fabrication of Crack-Free Barium Titanate Thin Film with High Dielectric Constant Using Sub-Micrometric Scale Layer-by-Layer E-Jet Deposition
by Junsheng Liang, Pengfei Li, Dazhi Wang, Xu Fang, Jiahong Ding, Junxiong Wu and Chang Tang
Materials 2016, 9(1), 61; https://doi.org/10.3390/ma9010061 - 19 Jan 2016
Cited by 7 | Viewed by 5916
Abstract
Dense and crack-free barium titanate (BaTiO3, BTO) thin films with a thickness of less than 4 μm were prepared by using sub-micrometric scale, layer-by-layer electrohydrodynamic jet (E-jet) deposition of the suspension ink which is composed of BTO nanopowder and BTO sol. [...] Read more.
Dense and crack-free barium titanate (BaTiO3, BTO) thin films with a thickness of less than 4 μm were prepared by using sub-micrometric scale, layer-by-layer electrohydrodynamic jet (E-jet) deposition of the suspension ink which is composed of BTO nanopowder and BTO sol. Impacts of the jet height and line-to-line pitch of the deposition on the micro-structure of BTO thin films were investigated. Results show that crack-free BTO thin films can be prepared with 4 mm jet height and 300 μm line-to-line pitch in this work. Dielectric constant of the prepared BTO thin film was recorded as high as 2940 at 1 kHz at room temperature. Meanwhile, low dissipation factor of the BTO thin film of about 8.6% at 1 kHz was also obtained. The layer-by-layer E-jet deposition technique developed in this work has been proved to be a cost-effective, flexible and easy to control approach for the preparation of high-quality solid thin film. Full article
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<p>Cone-jet mode of the E-jet deposition.</p> Full article ">Figure 2
<p>Schematic of the E-jet deposition apparatus.</p> Full article ">Figure 3
<p>Relationship between jet height and width of a single deposition line.</p> Full article ">Figure 4
<p>SEM images of the BTO single layer fabricated with different jet heights: (<b>a</b>) 4 mm; (<b>b</b>) 5 mm, (<b>c</b>) 6 mm and (<b>d</b>) 10 mm.</p> Full article ">Figure 5
<p>Relationship between jet height and coverage fraction of the substrate.</p> Full article ">Figure 6
<p>SEM images for four-layer BTO thin film deposited with different jet heights: (<b>a</b>) 4 mm; (<b>b</b>) 5 mm, (<b>c</b>) 6 mm and (<b>d</b>) 10 mm.</p> Full article ">Figure 7
<p>SEM images for two-layer BTO thin film at 4 mm jet height with different line-to-line pitches: (<b>a</b>) 200 μm; (<b>b</b>) 300 μm; (<b>c</b>) 400 μm and (<b>d</b>) 500 μm.</p> Full article ">Figure 8
<p>SEM images for 10-layer BTO thin film prepared with 4 mm jet height and 300 μm line-to-line pitch: (<b>a</b>) top-view; (<b>b</b>) cross-section view.</p> Full article ">Figure 9
<p>The distribution of the particle size on the cross-section.</p> Full article ">Figure 10
<p>XRD pattern of the BTO film sintered at 900 °C for 2 h.</p> Full article ">Figure 11
<p>Temperature dependence of dielectric constant and dissipation factor of the BTO thin film at 1 kHz.</p> Full article ">Figure 12
<p>Frequency dependence of dielectric constant and dissipation factor for the BTO thin film at 25 °C.</p> Full article ">
1800 KiB  
Article
Parameters Influencing the Growth of ZnO Nanowires as Efficient Low Temperature Flexible Perovskite-Based Solar Cells
by Alex Dymshits, Lior Iagher and Lioz Etgar
Materials 2016, 9(1), 60; https://doi.org/10.3390/ma9010060 - 19 Jan 2016
Cited by 37 | Viewed by 7619
Abstract
Hybrid organic-inorganic perovskite has proved to be a superior material for photovoltaic solar cells. In this work we investigate the parameters influencing the growth of ZnO nanowires (NWs) for use as an efficient low temperature photoanode in perovskite-based solar cells. The structure of [...] Read more.
Hybrid organic-inorganic perovskite has proved to be a superior material for photovoltaic solar cells. In this work we investigate the parameters influencing the growth of ZnO nanowires (NWs) for use as an efficient low temperature photoanode in perovskite-based solar cells. The structure of the solar cell is FTO (SnO2:F)-glass (or PET-ITO (In2O3·(SnO2) (ITO)) on, polyethylene terephthalate (PET)/ZnAc seed layer/ZnO NWs/CH3NH3PbI3/Spiro-OMeTAD/Au. The influence of the growth rate and the diameter of the ZnO NWs on the photovoltaic performance were carefully studied. The ZnO NWs perovskite-based solar cell demonstrates impressive power conversion efficiency of 9.06% on a rigid substrate with current density over 21 mA/cm2. In addition, we successfully fabricated flexible perovskite solar cells while maintaining all fabrication processes at low temperature, achieving power conversion efficiency of 6.4% with excellent stability for over 75 bending cycles. Full article
(This article belongs to the Section Energy Materials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Top view SEM images of ZnAc seed layer at (<b>a</b>) 0 min; (<b>b</b>) 5 min; (<b>c</b>) 10 min. Scale bar is 200 nm for images A and C, and 2 μm for image B.</p> Full article ">Figure 2
<p>(<b>a</b>) XRD of the ZnO nanowires (NWs); (<b>b</b>) SEM cross section of the ZnO NWs grown at 90 mM and 75 min; (<b>c</b>) SEM top view of the ZnO NWs grown in the same conditions as in <a href="#materials-09-00060-f002" class="html-fig">Figure 2</a>b; (<b>d</b>) The NWs length as a function of the growth time for the two different concentration regimes.</p> Full article ">Figure 3
<p>(<b>a</b>) The CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite ZnO NWs solar cell structure; (<b>b</b>) The ZnO NWs length and the PV parameters as a function of the growth time at precursor concentration of 90 mM; (<b>c</b>) The change in the ZnO NWs diameter and the open circuit voltage (V<sub>oc</sub>) as a function of the precursor concentration at 75 min growth time; (<b>d</b>) SEM cross section of the CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite ZnO NWs perovskite solar cell.</p> Full article ">Figure 4
<p>(<b>a</b>) IV curves of the ZnO NWs CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite solar cell on rigid substrate; (<b>b</b>) IQE spectra of the corresponding rigid solar cell.</p> Full article ">Figure 5
<p>(<b>a</b>) IV curves of the ZnO NWs CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite solar cell on flexible substrate; (<b>b</b>) IQE spectra of the corresponding flexible solar cell; (<b>c</b>) SEM cross section of the flexible ZnO NWs CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite solar cell; (<b>d</b>) Stability of the flexible solar cell under bending. The bending radius is 1.2 cm. Inset: image showing typical, flexible ZnO NWs CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite solar cell.</p> Full article ">
3827 KiB  
Article
Development of Hollow Steel Ball Macro-Encapsulated PCM for Thermal Energy Storage Concrete
by Zhijun Dong, Hongzhi Cui, Waiching Tang, Dazhu Chen and Haibo Wen
Materials 2016, 9(1), 59; https://doi.org/10.3390/ma9010059 - 19 Jan 2016
Cited by 48 | Viewed by 8994
Abstract
The application of thermal energy storage with phase change materials (PCMs) for energy efficiency of buildings grew rapidly in the last few years. In this research, octadecane paraffin was served as a PCM, and a structural concrete with the function of indoor temperature [...] Read more.
The application of thermal energy storage with phase change materials (PCMs) for energy efficiency of buildings grew rapidly in the last few years. In this research, octadecane paraffin was served as a PCM, and a structural concrete with the function of indoor temperature control was developed by using a macro-encapsulated PCM hollow steel ball (HSB). The macro-encapsulated PCM-HSB was prepared by incorporation of octadecane into HSBs through vacuum impregnation. Test results showed that the maximum percentage of octadecane carried by HSBs was 80.3% by mass. The macro-encapsulated PCM-HSB has a latent heat storage capacity as high as 200.5 J/g. The compressive strength of concrete with macro-encapsulated PCM-HSB at 28 days ranged from 22 to 40 MPa. The indoor thermal performance test revealed that concrete with macro-encapsulated octadecane-HSB was capable of reducing the peak indoor air temperature and the fluctuation of indoor temperature. It can be very effective in transferring the heating and cooling loads away from the peak demand times. Full article
(This article belongs to the Special Issue Development and Characterisation of Encapsulated PCM: Nano-, Micro-, and Macro-Encapsulation)
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Figure 1
<p>DSC curve of octadecane.</p> Full article ">Figure 2
<p>PCM-HSB leakage percentage under different times of thermal cycles.</p> Full article ">Figure 3
<p>Indoor temperature curves of test room models with five different PCM-HSB panels.</p> Full article ">Figure 4
<p>Typical failure patterns of concrete cube (<b>a</b>) PCM-HSB concrete and (<b>b</b>) NWAC concrete.</p> Full article ">Figure 5
<p>Hollow steel ball with hole.</p> Full article ">Figure 6
<p>(<b>a</b>)Washer and (<b>b</b>) rivet.</p> Full article ">Figure 7
<p>Pneumatic rivet gun.</p> Full article ">Figure 8
<p>Glue gun configuration: (<b>a</b>) plastic nozzle; (<b>b</b>) epoxy; (<b>c</b>) glue gun; (<b>d</b>) complete setup.</p> Full article ">Figure 9
<p>Secured paraffin-HSB: (<b>a</b>) secured with rivet and epoxy; (<b>b</b>) section of HSB.</p> Full article ">Figure 10
<p>(<b>a</b>) Concrete panels with different replacement levels of coarse aggregate with PCM-HSB; (<b>b</b>) a test room model installed with a concrete panel made of SC-100%.</p> Full article ">Figure 11
<p>Schematic diagrams of thermal performance experiment setup: (<b>a</b>) component diagram; (<b>b</b>) installation diagram of the specimen; and (<b>c</b>) experiment setup and its top view.</p> Full article ">Figure 12
<p>(<b>a</b>) Multi-channel data log and (<b>b</b>) K type thermal couple.</p> Full article ">
1664 KiB  
Article
The Correlation of Surfactant Concentrations on the Properties of Mesoporous Bioactive Glass
by Shao-Ju Shih, Yu-Chien Lin, Leon Valentino Posma Panjaitan and Dyka Rahayu Meyla Sari
Materials 2016, 9(1), 58; https://doi.org/10.3390/ma9010058 - 19 Jan 2016
Cited by 24 | Viewed by 5544
Abstract
Bioactive glass (BG), a potential biomaterial, has received increasing attention since the discovery of its superior bioactivity. One of the main research objectives is to improve the bioactive property of BGs; therefore, surfactant-derived mesoporous bioactive glasses (MBGs) were developed to provide a high [...] Read more.
Bioactive glass (BG), a potential biomaterial, has received increasing attention since the discovery of its superior bioactivity. One of the main research objectives is to improve the bioactive property of BGs; therefore, surfactant-derived mesoporous bioactive glasses (MBGs) were developed to provide a high specific surface area for achieving higher bioactivity. In this study, various concentrations of typical triblock F127 surfactant were used to manipulate the morphology, specific surface area, and bioactivity of MBG particles. Two typical morphologies of smooth (Type I) and wrinkled (Type II) spheres were observed, and the population of Type II particles increased with an increase in the surfactant concentration. A direct correlation between specific surface area and bioactivity was observed by comparing the data obtained using the nitrogen adsorption-desorption method and in vitro bioactive tests. Furthermore, the optimal surfactant concentration corresponding to the highest bioactivity revealed that the surfactant aggregated to form Type II particles when the surface concentration was higher than the critical micelle concentration, and the high population of Type II particles may reduce the specific surface area because of the loss of bioactivity. Moreover, the formation mechanism of SP-derived MBG particles is discussed. Full article
(This article belongs to the Special Issue Bioactive Glasses)
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<p>XRD patterns of MBG particles prepared using various surfactant concentrations.</p> Full article ">Figure 2
<p>SEM images of MBG particles prepared using various surfactant concentrations of (<b>a</b>) 14 wt %; (<b>b</b>) 31 wt %; (<b>c</b>) 44 wt %; and (<b>d</b>) 53 wt %.</p> Full article ">Figure 3
<p>TEM images of MBG particles prepared using various surfactant concentrations of (<b>a</b>) 14 wt %; (<b>b</b>) 31 wt %; (<b>c</b>) 44 wt %; and (<b>d</b>) 53 wt %.</p> Full article ">Figure 4
<p>Particle size distributions of MBG particles prepared using various surfactant concentrations of (<b>a</b>) 14 wt %; (<b>b</b>) 31 wt %; (<b>c</b>) 44 wt %; and (<b>d</b>) 53 wt %.</p> Full article ">Figure 5
<p>FTIR patterns of various surfactant concentration treated MBG particles immersed in SBF for 1 day.</p> Full article ">Figure 6
<p>Comparison of I<sub>1</sub>/I<sub>2</sub> (bioactivity) and surface area for various surfactant concentrations treated MBG. The values of surfactant concentration are given.</p> Full article ">Figure 7
<p>Relationship between particle shape and surface area for various surfactant concentrations treated MBG powders. The percentage values of Type I and II are given.</p> Full article ">
3587 KiB  
Review
Advanced Engineering Strategies for Periodontal Complex Regeneration
by Chan Ho Park, Kyoung-Hwa Kim, Yong-Moo Lee and Yang-Jo Seol
Materials 2016, 9(1), 57; https://doi.org/10.3390/ma9010057 - 18 Jan 2016
Cited by 40 | Viewed by 8444
Abstract
The regeneration and integration of multiple tissue types is critical for efforts to restore the function of musculoskeletal complex. In particular, the neogenesis of periodontal constructs for systematic tooth-supporting functions is a current challenge due to micron-scaled tissue compartmentalization, oblique/perpendicular orientations of fibrous [...] Read more.
The regeneration and integration of multiple tissue types is critical for efforts to restore the function of musculoskeletal complex. In particular, the neogenesis of periodontal constructs for systematic tooth-supporting functions is a current challenge due to micron-scaled tissue compartmentalization, oblique/perpendicular orientations of fibrous connective tissues to the tooth root surface and the orchestration of multiple regenerated tissues. Although there have been various biological and biochemical achievements, periodontal tissue regeneration remains limited and unpredictable. The purpose of this paper is to discuss current advanced engineering approaches for periodontal complex formations; computer-designed, customized scaffolding architectures; cell sheet technology-based multi-phasic approaches; and patient-specific constructs using bioresorbable polymeric material and 3-D printing technology for clinical application. The review covers various advanced technologies for periodontal complex regeneration and state-of-the-art therapeutic avenues in periodontal tissue engineering. Full article
(This article belongs to the Special Issue Regenerative Materials)
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<p>Anatomical schematic illustration of the periodontal tissue complex and the structure of periodontal tissues (<b>a</b>). (<b>b</b>) Periodontal ligament (PDL), alveolar bone (AB), gingiva (G), inferior alveolar artery (IAA), Volkmann’s canals (VC) [<a href="#B22-materials-09-00057" class="html-bibr">22</a>,<a href="#B23-materials-09-00057" class="html-bibr">23</a>].</p> Full article ">Figure 2
<p>Surgical creation of a three-wall defect in a canine model. After cultivating and harvesting cell sheets, a PGA (poly-glycolic acid) membrane was placed on the tooth-root surface, and β-tricalcium phosphate (β-TCP) was used to fill in the defect (<b>a</b>) [<a href="#B26-materials-09-00057" class="html-bibr">26</a>,<a href="#B27-materials-09-00057" class="html-bibr">27</a>]. (<b>b</b>–<b>d</b>) Micro-computed tomography (Micro-CT) and histology were performed to assess bone regeneration and mineralized tissue formation on the root surface. Moreover, histological and polarized microscopic images demonstrated PDL regeneration with oblique orientations and periodontal attachment. The scale bars: 1 mm for (<b>b</b>) and 500 μm for (<b>c</b>,<b>d</b>) [<a href="#B27-materials-09-00057" class="html-bibr">27</a>].</p> Full article ">Figure 3
<p>Periodontal regeneration construct using a poly-ε-caprolactone (PCL) nanofibrous scaffold with cell sheets. Biphasic scaffolds were fabricated using electrospinning and fused deposition modeling (FDM) (<b>a</b>). The cultured cell sheets were placed on top of the electrospun PCL membrane, and the human dentin blocks were assembled for subcutaneous transplant in athymic rats. Micro-CT demonstrated mineralized tissue formation with the dentin block (<b>b</b>), and hematoxylin and eosin (H&amp;E) staining showed cementum and PDL regeneration on the dentin surface (<b>c</b>). Alkaline phosphatase staining showed bone-like tissue formation (<b>d</b>) [<a href="#B37-materials-09-00057" class="html-bibr">37</a>].</p> Full article ">Figure 4
<p>Cell sheet with CaP-PCL membrane transplantation for periodontal tissue regeneration and attachment. Schematic illustration of cell sheet harvesting and transplanting with a CaP-PCL membranous scaffold (<b>a</b>). 3-D reconstructed micro-CT images demonstrate bone regeneration at 1 and 4 weeks (<b>b</b>), and H&amp;E staining showed periodontal tissue formation around the tooth surface at low and high magnifications (<b>c</b>,<b>d</b>). Cementum formation was analyzed using Azan staining, and PDL fibrous connective tissue attachment was analyzed by H&amp;E staining [<a href="#B39-materials-09-00057" class="html-bibr">39</a>].</p> Full article ">Figure 5
<p>Proof-of-concept using a periodontal-mimic scaffolding system with a human dentin slice. (<b>a</b>) CAD-based 3-D wax molds were manufactured and cast with biodegradable polymeric materials, including poly-glycolic acid (PGA) for the PDL interface in red and poly-ε-caprolactone (PCL) for the bone region in blue. (<b>b</b>) Micro-CT and (<b>c</b>,<b>d</b>) histological image assessments. In the micro-CT image, mineralized tissue (blue) was spatially formed in a bone region of the hybrid scaffold without bone infiltration into the PDL interface (red dashed line). Histologically, dense fibrous connective tissues formed with blood vessels (red triangles) in a perpendicular orientation (black arrows), and cementum-like tissues underwent limited deposition on the dentin surface (yellow triangles). Bone region exhibited mineralized tissue formation. The scale bar: 50 μm [<a href="#B40-materials-09-00057" class="html-bibr">40</a>].</p> Full article ">Figure 6
<p>Preclinical study using image-based 3-D printing technology for periodontal complex regeneration. (<b>a</b>) After surgically creating the periodontal fenestration defect on the buccal side of a mandible, customized fiber-guiding scaffolds were designed and manufactured using 3-D printed wax molds. (<b>b</b>) 3-D reconstructed micro-CT and (<b>c</b>,<b>d</b>) histological image assessments for bone-PDL-cementum. D: dentin; B: bone; yellow triangles: surgically created defect regions on the dentin surface; black dashed arrows: fibrous tissue orientation; white arrows: calcified layer deposition on the dentin surface [<a href="#B6-materials-09-00057" class="html-bibr">6</a>].</p> Full article ">Figure 7
<p>Flow chart for the design of customized, fiber-guiding scaffolds and clinical transplant of the 3-D printed, fiber-guiding scaffold to a labial defect. After the computer design of the customized scaffold, a 3-D printer was used to manufacture the PCL scaffolds. After pre-operative treatments, the PCL scaffold was placed at the defect with poly-D and L-lactic acid pins to secure the scaffold. The implanted site showed no signs of inflammation or infection during the first year after treatment [<a href="#B41-materials-09-00057" class="html-bibr">41</a>,<a href="#B42-materials-09-00057" class="html-bibr">42</a>].</p> Full article ">
16898 KiB  
Article
Thermo-Mechanical Compatibility of Viscoelastic Mortars for Stone Repair
by Thibault Demoulin, George W. Scherer, Fred Girardet and Robert J. Flatt
Materials 2016, 9(1), 56; https://doi.org/10.3390/ma9010056 - 18 Jan 2016
Cited by 2 | Viewed by 5707
Abstract
The magnitude of the thermal stresses that originate in an acrylic-based repair material used for the reprofiling of natural sandstone is analyzed. This kind of artificial stone was developed in the late 1970s for its peculiar property of reversibility in an organic solvent. [...] Read more.
The magnitude of the thermal stresses that originate in an acrylic-based repair material used for the reprofiling of natural sandstone is analyzed. This kind of artificial stone was developed in the late 1970s for its peculiar property of reversibility in an organic solvent. However, it displays a high thermal expansion coefficient, which can be a matter of concern for the durability either of the repair or of the underlying original stone. To evaluate this risk we propose an analytical solution that considers the viscoelasticity of the repair layer. The temperature profile used in the numerical evaluation has been measured in a church where artificial stone has been used in a recent restoration campaign. The viscoelasticity of the artificial stone has been characterized by stress relaxation experiments. The numerical analysis shows that the relaxation time of the repair mortar, originating from a low T g , allows relief of most of the thermal stresses. It explains the good durability of this particular repair material, as observed by the practitioners, and provides a solid scientific basis for considering that the problem of thermal expansion mismatch is not an issue for this type of stone under any possible conditions of natural exposure. Full article
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Graphical abstract
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<p>(<b>a</b>) Common dimension of a flake in a historical building molasse sandstone; (<b>b</b>) Old acrylic-based mortar used in Lausanne, after more than 30 years; (<b>c</b>) Reversibility of the old acrylic-based mortar.</p> Full article ">Figure 2
<p>(<b>a</b>) Schematic of the patch layer on top of the stone substrate; (<b>b</b>) Illustration of the thermal expansion mismatch between the two materials.</p> Full article ">Figure 3
<p>(<b>a</b>) Stress relaxation setup; (<b>b</b>) and its detailed diagram.</p> Full article ">Figure 4
<p>Typical stress-strain curve of the artificial stone. Note the high critical deformation. The red rectangle indicates the area of stress and strain investigated during the relaxation tests.</p> Full article ">Figure 5
<p>The church where the sensors have been applied in Vevey, and a close view of the equipment.</p> Full article ">Figure 6
<p>Thermal expansion of the natural stone (dash line) and the artificial stone (full line) measured by DMA. The coefficient of thermal expansion is reported.</p> Full article ">Figure 7
<p>Evolution of the instantaneous elastic modulus with the temperature, calculated from the measurement of ultrasonic pulse velocity.</p> Full article ">Figure 8
<p>Experimentally-determined stress relaxation curve (made at −5 °C) and its fit with a stretched exponential relaxation function.</p> Full article ">Figure 9
<p>Arrhenius-type dependence of the relaxation time <span class="html-italic">τ</span>.</p> Full article ">Figure 10
<p>Temperature gradient in the depth of the wall. In bold, the temperatures used in the calculation. (<b>a</b>) In summer, a difference of 13.8 °C has been measured between the surface and the first 7 cm of the wall; (<b>b</b>) In winter, the gradient is much smaller, on the order of 1.5 °C in the first 7 cm of the wall.</p> Full article ">Figure 11
<p>Temperature data measured in Notre-Dame de Vevey in the repair layer at a depth of 1 cm. (<b>a</b>) Temperature profile; (<b>b</b>) Temperature amplitude (daily temperature difference); (<b>c</b>) Rate of temperature variation.</p> Full article ">Figure 12
<p>Temperature data measured in Notre-Dame de Vevey in the stone, below the interface with the repair layer, at a depth of 2.5 cm. (<b>a</b>) Temperature profile; (<b>b</b>) Temperature amplitude (daily temperature difference); (<b>c</b>) Rate of temperature variation.</p> Full article ">Figure 13
<p>Stresses calculated from the temperature data measured in Vevey. (<b>a</b>) Stresses, without including the viscoelasticity, in the repair mortar, compared to its tensile strength; (<b>b</b>) Stresses, including the viscoelasticity, in the repair mortar; (<b>c</b>) Induced stresses in the stone.</p> Full article ">Figure 14
<p>(<b>a</b>) Temperature in La Brévine in January 1987; (<b>b</b>) Calculation of the thermal stresses in the repair material, without considering its viscoelasticity; (<b>c</b>) Calculation of the expected viscoelastic stresses in the repair material; (<b>d</b>) Calculation of the thermal stresses in the natural stone.</p> Full article ">Figure 15
<p>(<b>a</b>) The decrease of temperature that could lead to damage in the mortar; (<b>b</b>) The stresses induced in the stone and in the mortar by such a decrease in temperature, compared to the tensile strength of the mortar.</p> Full article ">Figure 16
<p>Strain applied during the stress relaxation experiment.</p> Full article ">
1590 KiB  
Article
Theoretical and Experimental Studies on the Crystal Structure, Electronic Structure and Optical Properties of SmTaO4
by Song Wang, Miao Jiang, Lihong Gao, Zhuang Ma and Fuchi Wang
Materials 2016, 9(1), 55; https://doi.org/10.3390/ma9010055 - 18 Jan 2016
Cited by 22 | Viewed by 6065
Abstract
The crystal structure, electronic structure and optical properties of SmTaO4 were identified through an experimental method and first principles calculation. X-ray powder diffraction (XRD) and a spectrophotometer were used to characterize the crystal structure, reflectivity and band gap of this material; furthermore, [...] Read more.
The crystal structure, electronic structure and optical properties of SmTaO4 were identified through an experimental method and first principles calculation. X-ray powder diffraction (XRD) and a spectrophotometer were used to characterize the crystal structure, reflectivity and band gap of this material; furthermore, the electronic structure and optical properties were investigated according to three exchange-correlation potentials, LDA, GGA and GGA + U. Results show that the SmTaO4 calcined at 1400 °C with the solid-state reaction method is in monoclinic phase in the space group I2/a. In addition, the calculated lattice parameters are consistent with the experimental values. The electron transitions among the O 2p states, Sm 4f states and Ta 5d states play a key role in the dielectric function, refractive index, absorption coefficient and reflectivity of SmTaO4. The calculation of first principles provides considerable insight into the relationship between the electronic structure and optical properties of this material. Full article
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<p>X-ray diffraction patterns of SmTaO<sub>4</sub>: (<b>a</b>) Experimental result; (<b>b</b>) Calculated result.</p> Full article ">Figure 2
<p>Crystal structure of SmTaO<sub>4</sub>.</p> Full article ">Figure 3
<p>Band structure of SmTaO<sub>4</sub> as calculated with (<b>a</b>) local density approximation (LDA); (<b>b</b>) generalized gradient approximation (GGA) and (<b>c</b>) GGA with additional Hubbard correlation terms (GGA + <span class="html-italic">U</span>)<span class="html-italic">.</span></p> Full article ">Figure 4
<p>Total and partial densities of state of SmTaO<sub>4</sub> as calculated with (<b>a</b>) LDA, (<b>b</b>) GGA and (<b>c</b>) GGA+ <span class="html-italic">U.</span></p> Full article ">Figure 5
<p>Optical properties of SmTaO<sub>4</sub> as calculated with GGA + <span class="html-italic">U</span>: (<b>a</b>) dielectric function; (<b>b</b>) refractive index; (<b>c</b>) absorption coefficient and (<b>d</b>) reflectivity.</p> Full article ">
7539 KiB  
Article
Tuning the Performance of Metallic Auxetic Metamaterials by Using Buckling and Plasticity
by Arash Ghaedizadeh, Jianhu Shen, Xin Ren and Yi Min Xie
Materials 2016, 9(1), 54; https://doi.org/10.3390/ma9010054 - 18 Jan 2016
Cited by 72 | Viewed by 13211
Abstract
Metallic auxetic metamaterials are of great potential to be used in many applications because of their superior mechanical performance to elastomer-based auxetic materials. Due to the limited knowledge on this new type of materials under large plastic deformation, the implementation of such materials [...] Read more.
Metallic auxetic metamaterials are of great potential to be used in many applications because of their superior mechanical performance to elastomer-based auxetic materials. Due to the limited knowledge on this new type of materials under large plastic deformation, the implementation of such materials in practical applications remains elusive. In contrast to the elastomer-based metamaterials, metallic ones possess new features as a result of the nonlinear deformation of their metallic microstructures under large deformation. The loss of auxetic behavior in metallic metamaterials led us to carry out a numerical and experimental study to investigate the mechanism of the observed phenomenon. A general approach was proposed to tune the performance of auxetic metallic metamaterials undergoing large plastic deformation using buckling behavior and the plasticity of base material. Both experiments and finite element simulations were used to verify the effectiveness of the developed approach. By employing this approach, a 2D auxetic metamaterial was derived from a regular square lattice. Then, by altering the initial geometry of microstructure with the desired buckling pattern, the metallic metamaterials exhibit auxetic behavior with tuneable mechanical properties. A systematic parametric study using the validated finite element models was conducted to reveal the novel features of metallic auxetic metamaterials undergoing large plastic deformation. The results of this study provide a useful guideline for the design of 2D metallic auxetic metamaterials for various applications. Full article
(This article belongs to the Special Issue Cellular Materials: Design and Optimisation)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) Conventional regular lattice; (<b>b</b>) building unit cell of initial regular lattice; (<b>c</b>) modified unit building cell of microstructure; (<b>d</b>) representative volume element; (<b>e</b>) designed bulk metamaterial with cross-shaped microstructures for experiments.</p> Full article ">Figure 2
<p>Definition of PSF to alter the initial microstructure of a buckling-induced metamaterial. The normalized desired buckling mode shapes scaled by different corresponding DSFs and their most central RVEs. (<b>a</b>) PSF = 0, DSF = 0; (<b>b</b>) PSF = 20%, DSF = 0.00184; (<b>c</b>) PSF = 100%, DSF = 0.0092.</p> Full article ">Figure 3
<p>Tensile test of 3D printed brass dog-bone using MTS machine. (<b>a</b>) Front view of brass dog-bone. (<b>b</b>) Schematic curve of stress-strain for brass.</p> Full article ">Figure 4
<p>The final design of metamaterial employed for FEA and experimental investigation. (<b>a</b>) Front view and perspective view of buckling-induced metamaterial (PSF = 0%; density: 2798.05 kg m<sup>−3</sup>, overall mass: 228.5 g, mass error: 1.08%, height × width × depth: 92.8 mm × 88 mm × 10 mm, Scale bar: 20 mm); (<b>b</b>) front view and perspective view of the metamaterial with altered geometry (PSF = 20%, overall mass: 222.57 g, density: 2725.43 kg m<sup>−3</sup>, mass error: 2.06%, height × width × depth: 92.8 mm × 88 mm × 10 mm, Scale bar: 20 mm); (<b>c</b>) schematic diagram of central region with 16 nodes (PSF = 0%); (<b>d</b>) schematic diagram of central region with 16 nodes (PSF = 20%). The image processing was used to measure the horizontal and vertical center-to-center distances of nodes.</p> Full article ">Figure 4 Cont.
<p>The final design of metamaterial employed for FEA and experimental investigation. (<b>a</b>) Front view and perspective view of buckling-induced metamaterial (PSF = 0%; density: 2798.05 kg m<sup>−3</sup>, overall mass: 228.5 g, mass error: 1.08%, height × width × depth: 92.8 mm × 88 mm × 10 mm, Scale bar: 20 mm); (<b>b</b>) front view and perspective view of the metamaterial with altered geometry (PSF = 20%, overall mass: 222.57 g, density: 2725.43 kg m<sup>−3</sup>, mass error: 2.06%, height × width × depth: 92.8 mm × 88 mm × 10 mm, Scale bar: 20 mm); (<b>c</b>) schematic diagram of central region with 16 nodes (PSF = 0%); (<b>d</b>) schematic diagram of central region with 16 nodes (PSF = 20%). The image processing was used to measure the horizontal and vertical center-to-center distances of nodes.</p> Full article ">Figure 5
<p>Comparison of deformation patterns of three new designed metamaterials between numerical and experimental results. (<b>a</b>) Experimental and numerical results of initial design of auxetic elastic metamaterial (rubber) with PSF = 0%; (<b>b</b>) experimental and numerical results of initial design of metallic metamaterial with PSF = 0%; (<b>c</b>) experimental and numerical results of the new design of auxetic metallic metamaterial with PSF = 20% (Scale bar: 20 mm, load direction Y, strain rate: 5 × 10<span class="html-italic"><sup>−</sup></span><sup>3</sup> S<span class="html-italic"><sup>−</sup></span><sup>1</sup>).</p> Full article ">Figure 6
<p>Comparison of auxetic and non-auxetic behavior of new design of auxetic metallic metamaterial with PSF = 20%, initial design of metallic metamaterial with PSF = 0 and initial design of auxetic elastic metamaterial (rubber) with PSF = 0% (Scale bar: 20 mm, load direction Y, strain rate: 5 × 10<span class="html-italic"><sup>−</sup></span><sup>3</sup> S<span class="html-italic"><sup>−</sup></span><sup>1</sup>).</p> Full article ">Figure 7
<p>(<b>a</b>) Comparison of nominal stress-strain curves of the auxetic metamaterial between experiment and FE results (FE models with 3D shell elements and 3D solid elements) and using energy efficiency method to find densification strain; (<b>b</b>) defining the lower bound and upper bound of effective auxetic strain range.</p> Full article ">Figure 8
<p>Parametric study on influence of PSF on auxetic behavior. (<b>a</b>) Evaluations of Poisson’s ratio as function of applied strain corresponding to different PSF; (<b>b</b>) stress-strain curves corresponding to different PSF; (<b>c</b>) average values of Poisson’s ratio and effective auxetic strain ranges corresponding to different PSF.</p> Full article ">Figure 9
<p>The results of a parametric study on the influence of plastic hardening on the recovery of auxetic behavior. (<b>a</b>) Evaluations of Poisson’s ratio as a function of applied strain corresponding to different hardening ratios for metamaterials with PSF = 0%.; (<b>b</b>) stress-strain curves corresponding to different hardening ratios for metamaterials with PSF = 0%; (<b>c</b>) schematic curve of stress-strain for metallic materials (strain hardening ratio).</p> Full article ">Figure 10
<p>The results of a parametric study on the influence of plastic hardening on the auxetic behavior of a metamaterial with PSF = 20%. (<b>a</b>) Evaluations of Poisson’s ratio as a function of applied strain corresponding to different hardening ratios; (<b>b</b>) stress-strain curves corresponding to different hardening ratios; (<b>c</b>) average values of Poisson‘s ratio and effective auxetic strain ranges corresponding to different strain hardening ratios for metamaterials with PSF = 20%.</p> Full article ">Figure 11
<p>The results of a parametric study on the influence of pattern scale factors on auxetic behavior and effective auxetic strain range. (<b>a</b>) Evaluations of Poisson’s ratio as the function of hardening ratio corresponding to pattern scale factors; (<b>b</b>) evaluations of effective auxetic strain range as the function of hardening ratio corresponding to different pattern scale factors.</p> Full article ">Figure 12
<p>(<b>a</b>) Relation between PSF and corresponding volume fraction; (<b>b</b>) comparison of auxetic behaviors between buckling-induced design with PSF = 0%, buckling pattern-altered design without plates (Scale bar: 20 mm, load direction Y, strain rate: 5 × 10<sup>−3</sup> S<sup>−1</sup>).</p> Full article ">
4078 KiB  
Review
Bottom-Up Synthesis and Sensor Applications of Biomimetic Nanostructures
by Li Wang, Yujing Sun, Zhuang Li, Aiguo Wu and Gang Wei
Materials 2016, 9(1), 53; https://doi.org/10.3390/ma9010053 - 18 Jan 2016
Cited by 58 | Viewed by 10677
Abstract
The combination of nanotechnology, biology, and bioengineering greatly improved the developments of nanomaterials with unique functions and properties. Biomolecules as the nanoscale building blocks play very important roles for the final formation of functional nanostructures. Many kinds of novel nanostructures have been created [...] Read more.
The combination of nanotechnology, biology, and bioengineering greatly improved the developments of nanomaterials with unique functions and properties. Biomolecules as the nanoscale building blocks play very important roles for the final formation of functional nanostructures. Many kinds of novel nanostructures have been created by using the bioinspired self-assembly and subsequent binding with various nanoparticles. In this review, we summarized the studies on the fabrications and sensor applications of biomimetic nanostructures. The strategies for creating different bottom-up nanostructures by using biomolecules like DNA, protein, peptide, and virus, as well as microorganisms like bacteria and plant leaf are introduced. In addition, the potential applications of the synthesized biomimetic nanostructures for colorimetry, fluorescence, surface plasmon resonance, surface-enhanced Raman scattering, electrical resistance, electrochemistry, and quartz crystal microbalance sensors are presented. This review will promote the understanding of relationships between biomolecules/microorganisms and functional nanomaterials in one way, and in another way it will guide the design and synthesis of biomimetic nanomaterials with unique properties in the future. Full article
(This article belongs to the Section Biomaterials)
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<p>Biomimetic nanostructures: (<b>a</b>) DNA 2D structure (Reprinted with permission from [<a href="#B29-materials-09-00053" class="html-bibr">29</a>], published by American Chemical Society, 2005); (<b>b</b>) ferritin-based Pt NPs (Reprinted with permission from [<a href="#B31-materials-09-00053" class="html-bibr">31</a>], published by American Chemical Society, 2013); (<b>c</b>) peptide nanofiber-graphene quantum dot hybrids (Reprinted with permission from [<a href="#B32-materials-09-00053" class="html-bibr">32</a>], published by WILEY-VCH Verlag GmbH &amp; Co., 2015); (<b>d</b>) virus-protein hybrid nanostructures [<a href="#B33-materials-09-00053" class="html-bibr">33</a>]; (<b>e</b>) bacterium-based NPs (Reprinted with permission from [<a href="#B34-materials-09-00053" class="html-bibr">34</a>], published by WILEY-VCH Verlag GmbH &amp; Co., 2005).</p> Full article ">Figure 2
<p>Potential sensor applications of the biomimetic hybrid nanomaterials.</p> Full article ">Figure 3
<p>Biomimetic M13 phage-based colorimetric sensors. (<b>a</b>) Color changes of turkey skin when they get flustered; (<b>b</b>,<b>c</b>) Structural characterizations of turkey skin; (<b>d</b>) Bioinspired M13 phage arrays for colorimetric sensing. (Reprinted with permission from [<a href="#B143-materials-09-00053" class="html-bibr">143</a>], published by Nature Publishing Group, 2014).</p> Full article ">Figure 4
<p>Selective detection of K<sup>+</sup> with telomeric DNA strand and DNA origami.（<b>A</b>） Free telomeric DNA strand; (<b>B</b>) Telomeric DNA strand on DNA origami substrate (Reprinted with permission from [<a href="#B146-materials-09-00053" class="html-bibr">146</a>], published by WILEY-VCH Verlag GmbH &amp; Co., 2014).</p> Full article ">Figure 5
<p>DNA-based protein microarrays for SPR imaging biosensor application (<b>a</b>) Five-component DNA microarray; (<b>b</b>) Spatial diagram of the five components on the DNA microarray; (<b>c</b>) Schematic binding of antibody onto protein microarray; (<b>d,e</b>) SPR imaging taken before and after binding the antibody to (<b>d</b>) D1 and (<b>e</b>) D2; (<b>f</b>) Real-time SPR imaging adsorption kinetics of anti-GFP binding onto D1; (<b>g</b>) The similar adsorption kinetics of anti-luciferase binding onto D2. (Reprinted with permission from [<a href="#B157-materials-09-00053" class="html-bibr">157</a>], published by American Chemical Society, 2012).</p> Full article ">Figure 6
<p>Schematic presentation for the fabrication of core-satellite near-IR SERS sensor (Reprinted with permission from [<a href="#B159-materials-09-00053" class="html-bibr">159</a>], published by WILEY-VCH Verlag GmbH &amp; Co., 2012).</p> Full article ">Figure 7
<p>3D tetrahedral DNA nanostructures for EC biosensing of (<b>a</b>) DNA and (<b>b</b>) thrombin (Reprinted with permission from [<a href="#B165-materials-09-00053" class="html-bibr">165</a>], published by WILEY-VCH Verlag GmbH &amp; Co., 2010).</p> Full article ">Figure 8
<p>Virus-templated nanowires based electrical biosensor: (<b>a</b>) schematic preparation of virus-polymer nanowires; (<b>b</b>) detection mechanism of electrical biosensors; and (<b>c</b>,<b>d</b>) detection of antibodies (Reprinted with permission from [<a href="#B182-materials-09-00053" class="html-bibr">182</a>], published by American Chemical Society, 2010).</p> Full article ">Figure 9
<p>Self-assembled DNA nanostructure-based QCM biosensing of nucleic acids (<b>a</b>) Schematic presentation for the formation of DNA nanostructure for QCM biosensing; (<b>b</b>) Typical AFM image of the self-assembled DNA nanowires; (<b>c</b>) Corresponding QCM response curves related to the steps in (<b>a</b>) (Reprinted with permission from [<a href="#B189-materials-09-00053" class="html-bibr">189</a>], published by Royal Society of Chemistry, 2012).</p> Full article ">
9402 KiB  
Review
Stimuli-Responsive Polymer-Clay Nanocomposites under Electric Fields
by Shang Hao Piao, Seung Hyuk Kwon and Hyoung Jin Choi
Materials 2016, 9(1), 52; https://doi.org/10.3390/ma9010052 - 15 Jan 2016
Cited by 10 | Viewed by 6994
Abstract
This short Feature Article reviews electric stimuli-responsive polymer/clay nanocomposites with respect to their fabrication, physical characteristics and electrorheological (ER) behaviors under applied electric fields when dispersed in oil. Their structural characteristics, morphological features and thermal degradation behavior were examined by X-ray diffraction pattern, [...] Read more.
This short Feature Article reviews electric stimuli-responsive polymer/clay nanocomposites with respect to their fabrication, physical characteristics and electrorheological (ER) behaviors under applied electric fields when dispersed in oil. Their structural characteristics, morphological features and thermal degradation behavior were examined by X-ray diffraction pattern, scanning electron microscopy and transmission electron microscopy, and thermogravimetric analysis, respectively. Particular focus is given to the electro-responsive ER characteristics of the polymer/clay nanocomposites in terms of the yield stress and viscoelastic properties along with their applications. Full article
(This article belongs to the Special Issue Polymer Nanocomposites)
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<p>Scanning electron microscopy (SEM) images of (<b>a</b>) halloysites (HNTs) and (<b>b</b>) PANI/HNT composites (Reprinted from Reference [<a href="#B45-materials-09-00052" class="html-bibr">45</a>] with permission).</p> Full article ">Figure 2
<p>SEM images of pristine clay (<b>a</b>) and fabricated PANI/OMMT nanocomposite particles (<b>b</b>) (Reprinted from Reference [<a href="#B52-materials-09-00052" class="html-bibr">52</a>] with permission).</p> Full article ">Figure 3
<p>Transmission electron microscopy (TEM) images of Pal (<b>a</b>) and Pal/PANI composite particles (<b>b</b>), respectively (Reprinted from Reference [<a href="#B46-materials-09-00052" class="html-bibr">46</a>] with permission).</p> Full article ">Figure 4
<p>TEM image of a poly(methyl methacrylate) (PMMA) nanoparticle stabilized by laponite (Reprinted from Reference [<a href="#B60-materials-09-00052" class="html-bibr">60</a>] with permission).</p> Full article ">Figure 5
<p>X-ray diffraction (XRD) patterns of pure clay (1) and clay sheet-stabilized polyaniline granules (2) (Reprinted from Reference [<a href="#B61-materials-09-00052" class="html-bibr">61</a>] with permission).</p> Full article ">Figure 6
<p>XRD patterns for pristine PANI (<b>a</b>), Pal (<b>b</b>) and Pal/PANI (<b>c</b>) (Reprinted from Reference [<a href="#B46-materials-09-00052" class="html-bibr">46</a>] with permission).</p> Full article ">Figure 7
<p>Thermogravimetric analysis (TGA) curve of HNT and PPy/HNT composite (Reprinted from Reference [<a href="#B68-materials-09-00052" class="html-bibr">68</a>] with permission).</p> Full article ">Figure 8
<p>Optical microscope (OM) images of the electrorheological (ER) fluid based on PS/laponite nanoparticles in the absence of an electric field (<b>a</b>) and in an electric field (<b>b</b>) (Reprinted from Reference [<a href="#B53-materials-09-00052" class="html-bibr">53</a>] with permission).</p> Full article ">Figure 9
<p>Dielectric constants as a function of the applied electrical frequency for bare poly(urethane acrylate) (PUA) and PUA/clay composite particles (Reprinted from Reference [<a href="#B47-materials-09-00052" class="html-bibr">47</a>] with permission).</p> Full article ">Figure 10
<p>Shear stress (<b>a</b>) and shear viscosity (<b>b</b>) curves <span class="html-italic">vs.</span> shear rate for Pal/PANI based on ER fluids (10 vol. %) under a range of electric field strengths, the dashed lines were fitted using a conventional Bingham model, the solid lines were fitted via a suggested CCJ model (Reprinted from Reference [<a href="#B46-materials-09-00052" class="html-bibr">46</a>] with permission).</p> Full article ">Figure 11
<p>Dynamic yield stress as a function of the electric field strength of the Pal/PANI composite particles based ER fluid. The solid line was fitted using the equation, τ<span class="html-italic"><sub>y</sub></span> <math display="inline"> <semantics> <mrow> <mo>∝</mo> </mrow> </semantics> </math> <span class="html-italic">E<sup>2</sup></span> (Reprinted from Reference [<a href="#B46-materials-09-00052" class="html-bibr">46</a>] with permission).</p> Full article ">Figure 12
<p>Effect of volume fraction on electric field viscosity (<span class="html-italic">E</span> = 3 kV/mm, <math display="inline"> <semantics> <mrow> <mover accent="true"> <mi mathvariant="sans-serif">γ</mi> <mo>˙</mo> </mover> </mrow> </semantics> </math> = 1·s<sup>−1</sup>, <span class="html-italic">T</span> = 25 °C). (Reprinted from Reference [<a href="#B81-materials-09-00052" class="html-bibr">81</a>] with permission).</p> Full article ">Figure 13
<p>The change of viscosity with electric field strength, (<span class="html-italic">c</span> = 15 (m/m, %), <math display="inline"> <semantics> <mrow> <mover accent="true"> <mi mathvariant="sans-serif">γ</mi> <mo>˙</mo> </mover> </mrow> </semantics> </math> = 1.0·s<sup>−1</sup>, <span class="html-italic">T</span> = 25 °C). (Reprinted from Reference [<a href="#B80-materials-09-00052" class="html-bibr">80</a>] with permission).</p> Full article ">Figure 14
<p>Storage modulus (<b>a</b>) and loss modulus (<b>b</b>) <span class="html-italic">versus</span> frequency for PPy/HNT composite-based ER fluid (close symbol 10 vol. % and open symbol 15 vol. % particle concentration) under various electric field strengths (Reprinted from Reference [<a href="#B68-materials-09-00052" class="html-bibr">68</a>] with permission).</p> Full article ">Figure 15
<p>(<b>a</b>) Dielectric spectra (ɛ<span class="html-italic">′</span>: closed symbols; ɛ<span class="html-italic">″</span>: open symbols) and (<b>b</b>) Cole–Cole plot of the ER fluids. The fitting lines are generated from Equation (4) (Reprinted from Reference [<a href="#B53-materials-09-00052" class="html-bibr">53</a>] with permission).</p> Full article ">Figure 16
<p>Relaxation modulus <span class="html-italic">G</span>(<span class="html-italic">t</span>) of PANI/HNT composite-based ER fluid as calculated from <span class="html-italic">G</span>′(ω) and <span class="html-italic">G</span>″(ω) (Reprinted from Reference [<a href="#B45-materials-09-00052" class="html-bibr">45</a>] with permission).</p> Full article ">Figure 17
<p>Preparation of the polyaniline (PANI)/clay nanocomposite via an <span class="html-italic">in-situ</span> polymerization (Reprinted from Reference [<a href="#B25-materials-09-00052" class="html-bibr">25</a>] with permission).</p> Full article ">Figure 18
<p>Schematic diagram of the experimental route to synthesize the palygorskite (Pal)/PANI composite particles.</p> Full article ">Figure 19
<p>Mechanism of surfactant-free Pickering emulsion polymerization for polystyrene (PS)/laponite nanoparticles (Reprinted from Reference [<a href="#B53-materials-09-00052" class="html-bibr">53</a>] with permission).</p> Full article ">Figure 20
<p>Schematic diagram of an electric melt pipe equipped with a twin-screw extruder. (Reprinted from Reference [<a href="#B55-materials-09-00052" class="html-bibr">55</a>] with permission).</p> Full article ">
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Article
Acoustic Behavior of Subfloor Lightweight Mortars Containing Micronized Poly (Ethylene Vinyl Acetate) (EVA)
by Luiza R. Brancher, Maria Fernanda de O. Nunes, Ana Maria C. Grisa, Daniel T. Pagnussat and Mára Zeni
Materials 2016, 9(1), 51; https://doi.org/10.3390/ma9010051 - 15 Jan 2016
Cited by 12 | Viewed by 6412
Abstract
This paper aims to contribute to acoustical comfort in buildings by presenting a study about the polymer waste micronized poly (ethylene vinyl acetate) (EVA) to be used in mortars for impact sound insulation in subfloor systems. The evaluation method included physical, mechanical and [...] Read more.
This paper aims to contribute to acoustical comfort in buildings by presenting a study about the polymer waste micronized poly (ethylene vinyl acetate) (EVA) to be used in mortars for impact sound insulation in subfloor systems. The evaluation method included physical, mechanical and morphological properties of the mortar developed with three distinct thicknesses designs (3, 5, and 7 cm) with replacement percentage of the natural aggregate by 10%, 25%, and 50% EVA. Microscopy analysis showed the surface deposition of cement on EVA, with preservation of polymer porosity. The compressive creep test estimated long-term deformation, where the 10% EVA sample with a 7 cm thick mortar showed the lowest percentage deformation of its height. The impact noise test was performed with 50% EVA samples, reaching an impact sound insulation of 23 dB when the uncovered slab was compared with the 7 cm thick subfloor mortar. Polymer waste addition decreased the mortar compressive strength, and EVA displayed characteristics of an influential material to intensify other features of the composite. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
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<p>Rooms of the tests and position of the equipment: (<b>a</b>) concrete slab; (<b>b</b>) subfloor samples; (<b>c</b>) experimental setup without samples; and (<b>d</b>) with samples.</p> Full article ">Figure 2
<p>Samples Morphology: (<b>a</b>) reference mortar; (<b>b</b>) mortar 10%; (<b>c</b>) mortar 25%; and (<b>d</b>) mortar 50% EVA wastes.</p> Full article ">Figure 3
<p>Creep results for subfloor samples.</p> Full article ">Figure 4
<p>Impact noise level one-third octave band frequency for samples of 50% EVA waste.</p> Full article ">
3600 KiB  
Article
Biodegradable Nanocomposite Films Based on Sodium Alginate and Cellulose Nanofibrils
by B. Deepa, Eldho Abraham, Laly A. Pothan, Nereida Cordeiro, Marisa Faria and Sabu Thomas
Materials 2016, 9(1), 50; https://doi.org/10.3390/ma9010050 - 14 Jan 2016
Cited by 160 | Viewed by 12273
Abstract
Biodegradable nanocomposite films were prepared by incorporation of cellulose nanofibrils (CNF) into alginate biopolymer using the solution casting method. The effects of CNF content (2.5, 5, 7.5, 10 and 15 wt %) on mechanical, biodegradability and swelling behavior of the nanocomposite films were [...] Read more.
Biodegradable nanocomposite films were prepared by incorporation of cellulose nanofibrils (CNF) into alginate biopolymer using the solution casting method. The effects of CNF content (2.5, 5, 7.5, 10 and 15 wt %) on mechanical, biodegradability and swelling behavior of the nanocomposite films were determined. The results showed that the tensile modulus value of the nanocomposite films increased from 308 to 1403 MPa with increasing CNF content from 0% to 10%; however, it decreased with further increase of the filler content. Incorporation of CNF also significantly reduced the swelling percentage and water solubility of alginate-based films, with the lower values found for 10 wt % in CNF. Biodegradation studies of the films in soil confirmed that the biodegradation time of alginate/CNF films greatly depends on the CNF content. The results evidence that the stronger intermolecular interaction and molecular compatibility between alginate and CNF components was at 10 wt % in CNF alginate films. Full article
(This article belongs to the Special Issue Green Composites)
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<p>(<b>A</b>) Tensile strength and (<b>B</b>) Tensile modulus of cellulose nanofibril (CNF)-reinforced alginate films as the function of the CNF content (lower case letters (a, b, c) show Duncan grouping; distinct letters represent means significantly different (<span class="html-italic">p</span> &lt; 0.05)).</p> Full article ">Figure 2
<p>Scanning electron microscopy images of cross-section of the (<b>a</b>) alginate; (<b>b</b>) alginate with 5 wt % CNF; (<b>c</b>) alginate with 10 wt % CNF; and (<b>d</b>) alginate with 15 wt % CNF films (arrow indicates the CNF agglomeration in alginate matrix).</p> Full article ">Figure 3
<p>Fourier Transform Infrared (FTIR) spectra of cellulose nanofibrils (CNF), alginate film, alginate with 10 wt % of CNF film.</p> Full article ">Figure 4
<p>Specific surface free energy (<math display="inline"> <semantics> <mrow> <mo>∆</mo> <msubsup> <mi>G</mi> <mi>S</mi> <mrow> <mi>s</mi> <mi>p</mi> </mrow> </msubsup> </mrow> </semantics> </math>) obtained for cellulose nanofibrils (CNF) and alginate films at 25 °C.</p> Full article ">Figure 5
<p>Schematic representation of the interaction between cellulose nanofibrils (CNF) and alginate matrix.</p> Full article ">Figure 6
<p>Effect of CNF content on the moisture absorption and water solubility of alginate/CNF films (lower case letters (a, b, c, d, e) show Duncan grouping; distinct letters represent means significantly different (<span class="html-italic">p</span> &lt; 0.05)).</p> Full article ">Figure 7
<p>Effect of CNF content on the swelling ratio of alginate/CNFfilms (lower case letters (a, b, c, d, e) show Duncan grouping; distinct letters represent means significantly different (<span class="html-italic">p</span> &lt; 0.05)).</p> Full article ">Figure 8
<p>Effect of CNF content on the rate of degradation of alginate/CNF films (lower case letters (a, b, c) show Duncan grouping; distinct letters represent means significantly different (<span class="html-italic">p</span> &lt; 0.05)).</p> Full article ">
4332 KiB  
Article
Preparation of Extracellular Matrix Developed Using Porcine Articular Cartilage and In Vitro Feasibility Study of Porcine Articular Cartilage as an Anti-Adhesive Film
by Ji Hye Baek, Kyungsook Kim, Soon Sim Yang, Seung Hun Park, Bo Ram Song, Hee-Woong Yun, Sung In Jeong, Young Jick Kim, Byoung Hyun Min and Moon Suk Kim
Materials 2016, 9(1), 49; https://doi.org/10.3390/ma9010049 - 14 Jan 2016
Cited by 10 | Viewed by 6157
Abstract
In this study, we examined whether porcine articular cartilage (PAC) is a suitable and effective anti-adhesive material. PAC, which contained no non-collagenous tissue components, was collected by mechanical manipulation and decellularization of porcine knee cartilage. The PAC film for use as an anti-adhesive [...] Read more.
In this study, we examined whether porcine articular cartilage (PAC) is a suitable and effective anti-adhesive material. PAC, which contained no non-collagenous tissue components, was collected by mechanical manipulation and decellularization of porcine knee cartilage. The PAC film for use as an anti-adhesive barrier was easily shaped into various sizes using homemade silicone molds. The PAC film was cross-linked to study the usefulness of the anti-adhesive barrier shape. The cross-linked PAC (Cx-PAC) film showed more stable physical properties over extended periods compared to uncross-linked PAC (UnCx-PAC) film. To control the mechanical properties, Cx-PAC film was thermally treated at 45 °C or 65 °C followed by incubation at room temperature. The Cx-PAC films exhibited varying enthalpies, ultimate tensile strength values, and contact angles before and after thermal treatment and after incubation at room temperature. Next, to examine the anti-adhesive properties, human umbilical vein endothelial cells (HUVECs) were cultured on Cx-PAC and thermal-treated Cx-PAC films. Scanning electron microscopy, fluorescence, and MTT assays showed that HUVECs were well adhered to the surface of the plate and proliferated, indicating no inhibition of the attachment and proliferation of HUVECs. In contrast, Cx-PAC and thermal-treated Cx-PAC exhibited little and/or no cell attachment and proliferation because of the inhibition effect on HUVECs. In conclusion, we successfully developed a Cx-PAC film with controllable mechanical properties that can be used as an anti-adhesive barrier. Full article
(This article belongs to the Special Issue Anti-Infective Materials in Medicine and Technology)
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<p>Schematic diagram for the preparation of UnCx-PAC films and thermal-treated Cx-PAC films.</p> Full article ">Figure 2
<p>Optical images of UnCx-PAC and Cx-PAC film (<b>a</b>) before and (<b>b</b>) after thermal treatment at 45 °C and 65 °C.</p> Full article ">Figure 3
<p>Enthalpy of Cx-PAC film aged zero and two weeks at room temperature for each Cx-PAC film before and after thermal treatment at (<b>a</b>) 45 °C and (<b>b</b>) 65 °C (* <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.001, # <span class="html-italic">p</span> &gt; 0.001).</p> Full article ">Figure 4
<p>(<b>a</b>) Pictures of universal testing machine and film and (<b>b</b>) tensile strength of UnCx-PAC and Cx-PAC films aged for zero and two weeks at room temperature after thermal treatment at 45 °C and 65 °C (* <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.001).</p> Full article ">Figure 5
<p>Contact angles of UnCx-PAC and Cx-PAC films aged for zero and two weeks at room temperature after thermal treatment at 45 °C and 65 °C.</p> Full article ">Figure 6
<p>SEM micrographs showing no cell (control) and HUVECs cultured for one to seven days on plate and Cx-PAC film after thermal treatment at 45 °C and 65 °C. Magnification: 1000× and scale bar represents 10 μm.</p> Full article ">Figure 7
<p>Fluorescent image showing PKH67-labeled HUVECs cultured for one to seven days on well plate and Cx-PAC film after thermal treatment at 45 °C and 65 °C. Magnification: 200× and scale bar represents 100 μm.</p> Full article ">Figure 8
<p>MTT assay of HUVECs cultured for one to seven days on well plates and Cx-PAC films after thermal treatment at 4 °C and 65 °C (* <span class="html-italic">p</span> &lt; 0.001).</p> Full article ">
1424 KiB  
Article
Synthesis, X-ray Structure, Optical, and Electrochemical Properties of a White-Light-Emitting Molecule
by Jiun-Wei Hu, Ying-Hsuan Wu, Hsing-Yang Tsai and Kew-Yu Chen
Materials 2016, 9(1), 48; https://doi.org/10.3390/ma9010048 - 14 Jan 2016
Cited by 6 | Viewed by 6052
Abstract
A new white-light-emitting molecule (1) was synthesized and characterized by NMR spectroscopy, high resolution mass spectrometry, and single-crystal X-ray diffraction. Compound 1 crystallizes in the orthorhombic space group Pnma, with a = 12.6814(6), b = 7.0824(4), c = 17.4628(9) Å, [...] Read more.
A new white-light-emitting molecule (1) was synthesized and characterized by NMR spectroscopy, high resolution mass spectrometry, and single-crystal X-ray diffraction. Compound 1 crystallizes in the orthorhombic space group Pnma, with a = 12.6814(6), b = 7.0824(4), c = 17.4628(9) Å, α = 90°, β = 90°, γ = 90°. In the crystal, molecules are linked by weak intermolecular C-H···O hydrogen bonds, forming an infinite chain along [100], generating a C(10) motif. Compound 1 possesses an intramolecular six-membered-ring hydrogen bond, from which excited-state intramolecular proton transfer (ESIPT) takes place from the phenolic proton to the carbonyl oxygen, resulting in a tautomer that is in equilibrium with the normal species, exhibiting a dual emission that covers almost all of the visible spectrum and consequently generates white light. It exhibits one irreversible one-electron oxidation and two irreversible one-electron reductions in dichloromethane at modest potentials. Furthermore, the geometric structures, frontier molecular orbitals (MOs), and the potential energy curves (PECs) for 1 in the ground and the first singlet excited state were fully rationalized by density functional theory (DFT) and time-dependent DFT calculations. The results demonstrate that the forward and backward ESIPT may happen on a similar timescale, enabling the excited-state equilibrium to be established. Full article
(This article belongs to the Special Issue Materials for Display Applications)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The synthetic route of 4-<span class="html-italic">tert</span>-Butyl-1-hydroxy-11<span class="html-italic">H</span>-benzo[b]fluoren-11-one (<b>1</b>). AIBN: 2,2′-azobisisobutyronitrile; NBS: <span class="html-italic">N</span>-bromosuccinimide.</p> Full article ">Figure 2
<p>Computed energies of different conformers of <b>1</b> (top) and <b>2</b> (bottom) are specified relative to the respective enol-form (DFT/B3LYP/6-31G**).</p> Full article ">Figure 3
<p>Displacement ellipsoid representation of <b>1</b> with the labelling scheme. The ellipsoids are drawn at the 50% probability level and the H atoms are drawn as spheres of arbitrary radii. The black dashed line denotes the intramolecular O-H···O hydrogen bond.</p> Full article ">Figure 4
<p>A packing view of <b>1</b>, viewed along the <span class="html-italic">c</span> axis. Blue dashed lines denote intermolecular C-H···O hydrogen bonds.</p> Full article ">Figure 5
<p>Normalized absorption (dashed line) and emission (solid line) spectra of <b>1</b> in ethyl acetate.</p> Full article ">Figure 6
<p>Schematic representation of the white-light generation process in <b>1</b>. ESIPT: excited-state intramolecular proton transfer.</p> Full article ">Figure 7
<p>The optimized geometric structures of enol (E) and keto (K) form for <b>1</b> in the ground and the first singlet excited state together with the intramolecular hydrogen bond lengths.</p> Full article ">Figure 8
<p>The frontier molecular orbitals of <b>1</b> for E, E*, K, and K*. GSIPT: ground state intramolecular proton transfer.</p> Full article ">Figure 9
<p>Potential energy curves (PECs) from enol form (E) to keto form (K) of <b>1</b> at the ground state and excited state. The calculations are based on the optimized ground state geometry (S<sub>0</sub> state) at the B3LYP/6-31G**/ level using Gaussian 03W.</p> Full article ">Figure 10
<p>The cyclic voltammogram of <b>1</b> measured in dichloromethane solution with ferrocenium/ferrocene, at 200 mV/s.</p> Full article ">
1258 KiB  
Article
Surface Functional Poly(lactic Acid) Electrospun Nanofibers for Biosensor Applications
by Edurne González, Larissa M. Shepherd, Laura Saunders and Margaret W. Frey
Materials 2016, 9(1), 47; https://doi.org/10.3390/ma9010047 - 14 Jan 2016
Cited by 50 | Viewed by 8193
Abstract
In this work, biotin surface functionalized hydrophilic non-water-soluble biocompatible poly(lactic acid) (PLA) nanofibers are created for their potential use as biosensors. Varying concentrations of biotin (up to 18 weight total percent (wt %)) were incorporated into PLA fibers together with poly(lactic acid)-block-poly(ethylene glycol) [...] Read more.
In this work, biotin surface functionalized hydrophilic non-water-soluble biocompatible poly(lactic acid) (PLA) nanofibers are created for their potential use as biosensors. Varying concentrations of biotin (up to 18 weight total percent (wt %)) were incorporated into PLA fibers together with poly(lactic acid)-block-poly(ethylene glycol) (PLA-b-PEG) block polymers. While biotin provided surface functionalization, PLA-b-PEG provided hydrophilicity to the final fibers. Morphology and surface-available biotin of the final fibers were studied by Field Emission Scanning Electron Microscopy (FESEM) and competitive colorimetric assays. The incorporation of PLA-b-PEG block copolymers not only decreased fiber diameters but also dramatically increased the amount of biotin available at the fiber surface able to bind avidin. Finally, fiber water stability tests revealed that both biotin and PLA-b-PEG, migrated to the aqueous phase after relatively extended periods of water exposure. The functional hydrophilic nanofiber created in this work shows a potential application as a biosensor for point-of-care diagnostics. Full article
(This article belongs to the Special Issue Electrospun Materials)
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Graphical abstract
Full article ">Figure 1
<p>SEM images of PLA samples containing different amounts of biotin: (<b>A</b>) 0 wt %; (<b>B</b>) 5 wt %; (<b>C</b>) 10 wt % and (<b>D</b>) 18 wt %.</p> Full article ">Figure 2
<p>Average fiber diameter of PLA and PLA/PLA-<span class="html-italic">b</span>-PEG samples containing different amounts of biotin.</p> Full article ">Figure 3
<p>SEM images of PLA/PLA-<span class="html-italic">b</span>-PEG samples containing different amounts of biotin: (<b>A</b>) 0 wt %; (<b>B</b>) 5 wt %; (<b>C</b>) 10 wt % and (<b>D</b>) 18 wt %.</p> Full article ">Figure 4
<p>Sulfur/carbon (S/C) atom ratio of PLA and PLA/PLA-<span class="html-italic">b</span>-PEG samples with different biotin loading quantify by EDS analysis.</p> Full article ">Figure 5
<p>Illustrations and real pictures of the HABA/avidin solutions. Initially, HABA and avidin form a complex with a strong orange color (absorbs light at 500 nm). When a fiber containing biotin is added to the solution, avidin binds biotin due its higher affinity breaking the HABA/avidin complex and leading to a color change (decrease in the absorbance at 500 nm).</p> Full article ">Figure 6
<p>Surface available biotin of PLA and PLA/PLA-<span class="html-italic">b</span>-PEG samples containing different amounts of overall biotin.</p> Full article ">Figure 7
<p>Surface available biotin of PLA and PLA/PLA-<span class="html-italic">b</span>-PEG fibers containing 18 wt % of biotin after being immersed in water for different periods of time.</p> Full article ">Figure 8
<p>Weight loss of PLA and PLA/PLA-<span class="html-italic">b</span>-PEG fibers containing 0 and 18 wt % of biotin after being immersed in water for different periods of time.</p> Full article ">
2098 KiB  
Letter
Effects of the F4TCNQ-Doped Pentacene Interlayers on Performance Improvement of Top-Contact Pentacene-Based Organic Thin-Film Transistors
by Ching-Lin Fan, Wei-Chun Lin, Hsiang-Sheng Chang, Yu-Zuo Lin and Bohr-Ran Huang
Materials 2016, 9(1), 46; https://doi.org/10.3390/ma9010046 - 13 Jan 2016
Cited by 12 | Viewed by 8032
Abstract
In this paper, the top-contact (TC) pentacene-based organic thin-film transistor (OTFT) with a tetrafluorotetracyanoquinodimethane (F4TCNQ)-doped pentacene interlayer between the source/drain electrodes and the pentacene channel layer were fabricated using the co-evaporation method. Compared with a pentacene-based OTFT without an interlayer, OTFTs [...] Read more.
In this paper, the top-contact (TC) pentacene-based organic thin-film transistor (OTFT) with a tetrafluorotetracyanoquinodimethane (F4TCNQ)-doped pentacene interlayer between the source/drain electrodes and the pentacene channel layer were fabricated using the co-evaporation method. Compared with a pentacene-based OTFT without an interlayer, OTFTs with an F4TCNQ:pentacene ratio of 1:1 showed considerably improved electrical characteristics. In addition, the dependence of the OTFT performance on the thickness of the F4TCNQ-doped pentacene interlayer is weaker than that on a Teflon interlayer. Therefore, a molecular doping-type F4TCNQ-doped pentacene interlayer is a suitable carrier injection layer that can improve the TC-OTFT performance and facilitate obtaining a stable process window. Full article
(This article belongs to the Special Issue Electrode Materials)
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<p>(<b>a</b>) a schematic diagram of the co-evaporation process; (<b>b</b>) a schematic structure of the pentacene-based organic thin-film transistors (OTFTs) with F<sub>4</sub>TCNQ-doped pentacene injection layer, and the molecular structures of (<b>c</b>) F<sub>4</sub>TCNQ and (<b>d</b>) pentacene, respectively.</p> Full article ">Figure 2
<p>Drain current characteristics of top-contact (TC) pentacene-based OTFTs with different F<sub>4</sub>TCNQ:pentacene ratios (Device 1 = 1:1, Device 2 = 1:3, and Device 3 = 1:10) (<b>a</b>) Output curves (<span class="html-italic">I</span><sub>DS</sub>-<span class="html-italic">V</span><sub>DS</sub>). (<b>b</b>) Transfer curves (<span class="html-italic">I</span><sub>DS</sub>-<span class="html-italic">V</span><sub>GS</sub>).</p> Full article ">Figure 3
<p>The <span class="html-italic">R</span><sub>C</sub> value as a function of F<sub>4</sub>TCNQ:pentacene ratio of TC pentacene-based OTFTs for <span class="html-italic">V</span><sub>DS</sub> and <span class="html-italic">V</span><sub>GS</sub> values of −2 and −20 V, respectively.</p> Full article ">Figure 4
<p>Transfer characteristics of pentacene-based OTFTs with (<b>a</b>) F<sub>4</sub>TCNQ-doped pentacene and (<b>b</b>) Teflon interlayers of various thicknesses, and AFM images of pentacene films (<b>c</b>) without and (<b>d</b>) with 5 nm F<sub>4</sub>TCNQ-doped pentacene interlayer.</p> Full article ">Figure 4 Cont.
<p>Transfer characteristics of pentacene-based OTFTs with (<b>a</b>) F<sub>4</sub>TCNQ-doped pentacene and (<b>b</b>) Teflon interlayers of various thicknesses, and AFM images of pentacene films (<b>c</b>) without and (<b>d</b>) with 5 nm F<sub>4</sub>TCNQ-doped pentacene interlayer.</p> Full article ">Figure 5
<p>The <span class="html-italic">R</span><sub>Total</sub> and <span class="html-italic">R</span><sub>C</sub> of pentacene-based OTFTs with the different thickness of the (<b>a</b>) F<sub>4</sub>TCNQ-doped pentacene and (<b>b</b>) Teflon interlayer. (<b>c</b>) The variation of the mobility and <span class="html-italic">R</span>c values with the various carrier-injection interlayer thickness for the devices with F<sub>4</sub>TCNQ-doped pentacene or Teflon interlayers.</p> Full article ">Figure 6
<p>Band diagram of top-contact (TC) pentacene-based OTFTs with various interlayer thicknesses (<b>a</b>) control sample, (<b>b</b>) 5-, and (<b>c</b>) 10-nm-thick Teflon and (<b>d</b>) 5-, and (<b>e</b>) 10-nm-thick F<sub>4</sub>TCNQ-doped pentacene.</p> Full article ">
3281 KiB  
Article
Effect of Rare Earth Metals on the Microstructure of Al-Si Based Alloys
by Saleh A. Alkahtani, Emad M. Elgallad, Mahmoud M. Tash, Agnes M. Samuel and Fawzy H. Samuel
Materials 2016, 9(1), 45; https://doi.org/10.3390/ma9010045 - 13 Jan 2016
Cited by 50 | Viewed by 9663
Abstract
The present study was performed on A356 alloy [Al-7 wt %Si 0.0.35 wt %Mg]. To that La and Ce were added individually or combined up to 1.5 wt % each. The results show that these rare earth elements affect only the alloy melting [...] Read more.
The present study was performed on A356 alloy [Al-7 wt %Si 0.0.35 wt %Mg]. To that La and Ce were added individually or combined up to 1.5 wt % each. The results show that these rare earth elements affect only the alloy melting temperature with no marked change in the temperature of Al-Si eutectic precipitation. Additionally, rare earth metals have no modification effect up to 1.5 wt %. In addition, La and Ce tend to react with Sr leading to modification degradation. In order to achieve noticeable modification of eutectic Si particles, the concentration of rare earth metals should exceed 1.5 wt %, which simultaneously results in the precipitation of a fairly large volume fraction of insoluble intermetallics. The precipitation of these complex intermetallics is expected to have a negative effect on the alloy performance. Full article
(This article belongs to the Special Issue Failure Analysis in Materials)
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<p>Schematic sketch showing the graphite mold used in this study.</p> Full article ">Figure 2
<p>(<b>a</b>) Solidification curve and its first derivative of A356 alloy; (<b>b</b>) Optical microstructure of A356 alloy (coded TB) following solidification at the rate of ~0.8 °C/s: 1—α-Al, 2—eutectic Si, 3—Fe-intermetallic, 4—Mg<sub>2</sub>Si phase; (<b>c</b>) Schematic diagram of a hypothetical cooling curve showing recalescence.</p> Full article ">Figure 3
<p>(<b>a</b>) Solidification curves of La-containing alloys; (<b>b</b>) solidification curves of Ce-containing alloys.</p> Full article ">Figure 4
<p>(<b>a</b>) Solidification curves of La+Sr-containing alloys; (<b>b</b>) solidification curves of Ce+Sr-containing alloys.</p> Full article ">Figure 5
<p>Schematic characterization of the three stages of spheroidization and coarsening of the eutectic silicon phase in the case of (<b>a</b>) unmodified; and (<b>b</b>) modified Al-Si alloy [<a href="#B20-materials-09-00045" class="html-bibr">20</a>].</p> Full article ">Figure 6
<p>Microstructures of different A356-based alloys: (<b>a</b>) base TB alloy (non-modified); (<b>b</b>) TBS alloy (0.01% Sr); (<b>c</b>) T10 alloy (0.2% La); (<b>d</b>) T11 alloy (0.2% Ce); (<b>e</b>) T2 alloy (1% La); and (<b>f</b>) T5 alloy (1% Ce).</p> Full article ">Figure 7
<p>Backscattered electron (BSE) images showing the formation of La- and Ce-rich phases in an A356 alloy sample modified by the combination of 1% La and 1% Ce (T8 alloy) and the corresponding <span class="html-italic">X</span>-ray images of Al, Si, La, Ce and Ti.</p> Full article ">Figure 8
<p>EDS spectrum corresponding to the gray phase observed in the BSE image in <a href="#materials-09-00045-f007" class="html-fig">Figure 7</a> (CP).</p> Full article ">Figure 9
<p>Ce-Sr interactions in A356 alloy modified with 1.0% Ce + 0.01% Sr (T5S alloy).</p> Full article ">Figure 10
<p>La, Si and Sr distribution in A356 alloy modified with 1.0% La + 0.01% Sr (T2S alloy).</p> Full article ">Figure 10 Cont.
<p>La, Si and Sr distribution in A356 alloy modified with 1.0% La + 0.01% Sr (T2S alloy).</p> Full article ">Figure 11
<p>EDS spectrum corresponding to <a href="#materials-09-00045-f010" class="html-fig">Figure 10</a>, revealing a significant peak due to Si.</p> Full article ">Figure 12
<p>(<b>a</b>) The effect of La and Sr on the average of Si particle length; (<b>b</b>) the effect of La and Sr on the average of Si particle area.</p> Full article ">Figure 13
<p>(<b>a</b>) The effect of Ce and Sr on the average of Si particle length; (<b>b</b>) the effect of Ce and Sr on the average of Si particle area.</p> Full article ">Figure 14
<p>Precipitation of La-rich phases in A356 alloy containing 1.5 wt % La (T3 alloy): (1) α-Al; (2) α-Fe and (3) La-rich phase.</p> Full article ">
9750 KiB  
Article
Correlation of High Magnetoelectric Coupling with Oxygen Vacancy Superstructure in Epitaxial Multiferroic BaTiO3-BiFeO3 Composite Thin Films
by Michael Lorenz, Gerald Wagner, Vera Lazenka, Peter Schwinkendorf, Michael Bonholzer, Margriet J. Van Bael, André Vantomme, Kristiaan Temst, Oliver Oeckler and Marius Grundmann
Materials 2016, 9(1), 44; https://doi.org/10.3390/ma9010044 - 13 Jan 2016
Cited by 16 | Viewed by 8762
Abstract
Epitaxial multiferroic BaTiO3-BiFeO3 composite thin films exhibit a correlation between the magnetoelectric (ME) voltage coefficient αME and the oxygen partial pressure during growth. The ME coefficient αME reaches high values up to 43 V/(cm·Oe) at 300 K and [...] Read more.
Epitaxial multiferroic BaTiO3-BiFeO3 composite thin films exhibit a correlation between the magnetoelectric (ME) voltage coefficient αME and the oxygen partial pressure during growth. The ME coefficient αME reaches high values up to 43 V/(cm·Oe) at 300 K and at 0.25 mbar oxygen growth pressure. The temperature dependence of αME of the composite films is opposite that of recently-reported BaTiO3-BiFeO3 superlattices, indicating that strain-mediated ME coupling alone cannot explain its origin. Probably, charge-mediated ME coupling may play a role in the composite films. Furthermore, the chemically-homogeneous composite films show an oxygen vacancy superstructure, which arises from vacancy ordering on the {111} planes of the pseudocubic BaTiO3-type structure. This work contributes to the understanding of magnetoelectric coupling as a complex and sensitive interplay of chemical, structural and geometrical issues of the BaTiO3-BiFeO3 composite system and, thus, paves the way to practical exploitation of magnetoelectric composites. Full article
(This article belongs to the Special Issue Epitaxial Materials 2015)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) X-ray diffraction (XRD) 2θ-ω scans of BaTiO<sub>3</sub>-BiFeO<sub>3</sub> composite thin films grown on SrTiO<sub>3</sub>:Nb(001) at the indicated oxygen partial pressures. The two numbers at the film peaks indicate the total composite film thickness in nm, and the oxygen partial pressure during pulsed laser deposition (PLD) growth, respectively. Note the Kα<sub>1/2</sub> splitting of each peak. W-Lα is a spectral line from the X-ray tube. The single-phase contributions of BaTO<sub>3</sub> and BiFeO<sub>3</sub> cannot be resolved here; see <a href="#materials-09-00044-t001" class="html-table">Table 1</a>. (<b>b</b>) PLD oxygen pressure evolution of the <span class="html-italic">c</span>-axis lattice parameters calculated from 004 peaks of four BaTiO<sub>3</sub>-BiFeO<sub>3</sub> composite thin films grown simultaneously for each growth pressure at the indicated substrates. See <a href="#materials-09-00044-t001" class="html-table">Table 1</a> for the values of the c-lattice parameters and more structural details.</p> Full article ">Figure 2
<p>XRD reciprocal space maps around the symmetric SrTiO<sub>3</sub> 001 peaks of BaTiO<sub>3</sub> (67 wt %)-BiFeO<sub>3</sub> (33 wt %) composite thin films grown at the indicated PLD oxygen partial pressures. The separation of a point-like substrate and a broadened composite film peak decreases with increasing oxygen partial pressure due to decreasing out-of-plane strain; see <a href="#materials-09-00044-t001" class="html-table">Table 1</a>. The horizontal broadening of film peaks is a measure of the tilt mosaicity of the composites. STO stands for SrTiO<sub>3</sub>.</p> Full article ">Figure 3
<p>XRD reciprocal space maps around the asymmetric <math display="inline"> <semantics> <mrow> <mover accent="true"> <mn>1</mn> <mo>¯</mo> </mover> <mn>03</mn> </mrow> </semantics> </math> SrTiO<sub>3</sub> substrate peaks (in the Figures referred to as STO (−103)) of the BaTiO<sub>3</sub>-BiFeO<sub>3</sub> composite films grown at the indicated oxygen partial pressures. The lower intensity film peaks are at the bottom. With increasing oxygen pressure, the film peaks broaden, <span class="html-italic">i.e.</span>, the composite mosaicity increases. However, film-to-substrate peak separation decreases. Note that the vertical q<sub>┴</sub> axis for the two lowest pressures is enlarged. As is visible from the increasing vertical misalignment of film and substrate peaks with increasing growth pressure, the film relaxation increases. The 0.15-mbar sample shows substrate and corresponding crystalline film domains. The peak splitting is due to the Kα<sub>1/2</sub> radiation used.</p> Full article ">Figure 4
<p>Scanning transmission electron microscopy (STEM) bright-field image of the BaTiO<sub>3</sub>-BiFeO<sub>3</sub> composite film grown at 0.01 mbar oxygen pressure shown as the (110) cross-section. Clearly visible is the high density of dislocation lines in this particular composite film. The colored energy dispersive X-ray spectroscopy (EDX) maps demonstrate the homogeneous distribution of elements Ba, Fe, Ti and Bi in the plane of the cross-section. The gold film results from the extraction of the TEM cross-section out of the planar film sample using a focused ion beam. For more EDX maps and elemental analyses, see the <a href="#app1-materials-09-00044" class="html-app">Supplementary Materials, Figures S4, S6, S8 and S9</a>.</p> Full article ">Figure 5
<p>STEM dark-field image of the BaTiO<sub>3</sub>-BiFeO<sub>3</sub> composite film grown at 0.25 mbar on MgO(001) taken from the (110) cross-section. The four selected area electron diffraction (SAED) patterns have been taken from the encircled regions at the interface or the substrate. The main spots from the composite (green circles) confirm the BaTiO<sub>3</sub>-type structure of the composite film. These are forbidden for MgO, as seen bottom right. The additional weak spots in the composite indicate superstructure reflections that are probably due to oxygen vacancy ordering. The red dotted lines show the two possible orientations of oxygen vacancy ordering.</p> Full article ">Figure 6
<p>Structure model of oxygen vacancy ordering in planes parallel (<math display="inline"> <semantics> <mrow> <mover accent="true"> <mn>1</mn> <mo>¯</mo> </mover> <mn>11</mn> </mrow> </semantics> </math>) (<b>left</b>) and (<math display="inline"> <semantics> <mrow> <mn>1</mn> <mover accent="true"> <mn>1</mn> <mo>¯</mo> </mover> <mn>1</mn> </mrow> </semantics> </math>) (<b>right</b>), respectively; projection along [110] (directions according to cubic setting, subscript <span class="html-italic">c</span>; except the additionally indicated [001] direction with respect to the hexagonal setting, subscript <span class="html-italic">h</span>). The indication of atoms is as follows: blue, oxygen; pink, barium; green, titanium.</p> Full article ">Figure 7
<p>Magnetoelectric voltage coefficient α<sub>ME</sub> of BaTiO<sub>3</sub>-BiFeO<sub>3</sub> composite thin films in dependence of (<b>a</b>) temperature and (<b>b</b>) the DC bias magnetic field, for the indicated oxygen partial pressures during the growth of the composites. The legend of (a) is valid for both (a) and (b). The DC bias dependence of α<sub>ME</sub> in (b) is generally weak with a local maximum around 0.5 T. The inset is an expanded view of α<sub>ME</sub>(H<sub>DC</sub>) of the 0.325 mbar sample G5558c, compare <a href="#materials-09-00044-t001" class="html-table">Table 1</a>. For additional field-dependent α<sub>ME</sub> graphs, see the <a href="#app1-materials-09-00044" class="html-app">Supplementary Materials, Figure S12</a>.</p> Full article ">Figure 8
<p>Magnetoelectric voltage coefficients α<sub>ME</sub> of BaTO<sub>3</sub>-BiFeO<sub>3</sub> composite thin films on SrTiO<sub>3</sub>:Nb(001) measured at 300 K and at the DC bias magnetic field with the maximum α<sub>ME</sub>. The number at each data point is the composite film thickness as determined from STEM images of cross-sections prepared by focused ion beam (see the <a href="#app1-materials-09-00044" class="html-app">Supplementary Materials, Figures S14 and S15</a>). The line is drawn to guide the eye only. Using the film thicknesses, structural details of the samples (<a href="#materials-09-00044-t001" class="html-table">Table 1</a>) can be assigned to the α<sub>ME</sub> values.</p> Full article ">
5064 KiB  
Article
Thickness Influence on In Vitro Biocompatibility of Titanium Nitride Thin Films Synthesized by Pulsed Laser Deposition
by Liviu Duta, George E. Stan, Adrian C. Popa, Marius A. Husanu, Sorin Moga, Marcela Socol, Irina Zgura, Florin Miculescu, Iuliana Urzica, Andrei C. Popescu and Ion N. Mihailescu
Materials 2016, 9(1), 38; https://doi.org/10.3390/ma9010038 - 13 Jan 2016
Cited by 28 | Viewed by 8163
Abstract
We report a study on the biocompatibility vs. thickness in the case of titanium nitride (TiN) films synthesized on 410 medical grade stainless steel substrates by pulsed laser deposition. The films were grown in a nitrogen atmosphere, and their in vitro cytotoxicity was [...] Read more.
We report a study on the biocompatibility vs. thickness in the case of titanium nitride (TiN) films synthesized on 410 medical grade stainless steel substrates by pulsed laser deposition. The films were grown in a nitrogen atmosphere, and their in vitro cytotoxicity was assessed according to ISO 10993-5 [1]. Extensive physical-chemical analyses have been carried out on the deposited structures with various thicknesses in order to explain the differences in biological behavior: profilometry, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction and surface energy measurements. XPS revealed the presence of titanium oxynitride beside TiN in amounts that vary with the film thickness. The cytocompatibility of films seems to be influenced by their TiN surface content. The thinner films seem to be more suitable for medical applications, due to the combined high values of bonding strength and superior cytocompatibility. Full article
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<p>Thickness profiles of TiN layers recorded by profilometry.</p> Full article ">Figure 2
<p>Morphology of fibroblasts (Hs27) grown on different substrates (<b>a</b>) bare 410SS; (<b>b</b>) 5A; (<b>c</b>) 10B; and (<b>d</b>) 20C films, respectively. The actin cytoskeleton was stained with phalloidin-AlexaFluor596 (red) and cell nuclei counterstained with DAPI (blue). Objective 10×. Magnification bar = 25 µm.</p> Full article ">Figure 3
<p>Histogram showing the cell proliferation results as obtained by the MTS assay. The values are normalized as the percent to the absorption of the seeding cell number.</p> Full article ">Figure 4
<p>Cytotoxicity of samples: LDH assay. Values are in arbitrary absorption units showing the amount of dead cells in the case of the bare 410SS substrate, 5A, 10B and 20C films, respectively.</p> Full article ">Figure 5
<p>Typical SEM image of the 5A TiN film surface.</p> Full article ">Figure 6
<p>Typical cross-sectional SEM images of the TiN 5A (<b>a</b>), 10B (<b>b</b>) and 20C (<b>c</b>) films deposited onto mirror-polished Si wafers.</p> Full article ">Figure 7
<p>AFM images collected on 2 × 2 µm<sup>2</sup> areas in the case of (<b>a</b>) bare glass substrate, (<b>b</b>) 5A, (<b>c</b>) 10B and (<b>d</b>) 20C TiN films.</p> Full article ">Figure 8
<p>Ti2p XPS spectra recorded at N.E. with respect to the electron analyzer and at a 60° T.O. in order to increase the surface sensitivity, in the case of (<b>a</b>) 5A; (<b>b</b>) 10B and (<b>c</b>) 20C TiN films, respectively.</p> Full article ">Figure 9
<p>N1s XPS spectra of TiN films, recorded at (<b>a</b>) N.E. with respect to the electron analyzer and at (<b>b</b>) a 60° T.O. in order to increase the surface sensitivity; in (<b>c</b>) is depicted the amount of TiN in each sample for both bulk and surface-sensitive measurements.</p> Full article ">Figure 10
<p>XRD patterns of the TiN thin films, recorded in (<b>a</b>) symmetric (θ–θ); and (<b>b</b>) grazing incidence (α = 2°) geometry. Bottom of the figure: ICDD reference file No. 00-038-1420 of cubic TiN.</p> Full article ">Figure 11
<p>Typical contact angle images recoded for bare and TiN-coated substrates. (<b>a</b>) Water; (<b>b</b>) ethylene glycol.</p> Full article ">
1032 KiB  
Article
Influence of Different Post-Plasma Treatment Storage Conditions on the Shear Bond Strength of Veneering Porcelain to Zirconia
by Mun-Hwan Lee, Bong Ki Min, Jun Sik Son and Tae-Yub Kwon
Materials 2016, 9(1), 43; https://doi.org/10.3390/ma9010043 - 12 Jan 2016
Cited by 33 | Viewed by 5984
Abstract
This in vitro study investigated whether different storage conditions of plasma-treated zirconia specimens affect the shear bond strength of veneering porcelain. Zirconia plates were treated with a non-thermal atmospheric argon plasma (200 W, 600 s). Porcelain veneering (2.38 mm in diameter) was performed [...] Read more.
This in vitro study investigated whether different storage conditions of plasma-treated zirconia specimens affect the shear bond strength of veneering porcelain. Zirconia plates were treated with a non-thermal atmospheric argon plasma (200 W, 600 s). Porcelain veneering (2.38 mm in diameter) was performed immediately (P-I) or after 24 h storage in water (P-W) or air (P-A) on the treated surfaces (n = 10). Untreated plates were used as the control. Each group was further divided into two subgroups according to the application of a ceramic liner. All veneered specimens underwent a shear bond strength (SBS) test. In the X-ray photoelectron spectroscopy (XPS) analysis, the oxygen/carbon ratios of the plasma-treated groups increased in comparison with those of the control group. When a liner was not used, the three plasma-treated groups showed significantly higher SBS values than the control group (p < 0.001), although group P-A exhibited a significantly lower value than the other two groups (p < 0.05). The liner application negatively affected bonding in groups P-I and P-W (p < 0.05). When the veneering step was delayed after plasma treatment of zirconia, storage of the specimens in water was effective in maintaining the cleaned surfaces for optimal bonding with the veneering porcelain. Full article
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<p>Study design for one untreated (control) and three plasma-treated groups. In the shear bond strength test, each group was further divided into two subgroups according to the use of a liner prior to veneering.</p> Full article ">Figure 2
<p>Scanning electron microscopy (SEM) (left, magnification: 2000×, bar = 10 μm) and atomic force microscopy (AFM) (right, 5 μm × 5 μm) images of the zirconia surfaces: (<b>a</b>,<b>b</b>) untreated; (<b>c</b>,<b>d</b>) plasma-treated.</p> Full article ">Figure 3
<p>Contact angles of water droplets on the zirconia surfaces (<span class="html-italic">n</span> = 6). Different lowercase letters indicate significant differences (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 4
<p>Survey X-ray photoelectron spectroscopy (XPS) spectra for untreated (<b>a</b>) and plasma-treated (<b>b</b>–<b>d</b>) zirconia surfaces: groups P-I (b); P-W (c); and P-A (d).</p> Full article ">Figure 5
<p>High-resolution X-ray photoelectron spectroscopy (XPS) spectra of O 1s region of untreated (<b>a</b>) and plasma-treated (<b>b</b>–<b>d</b>) zirconia surfaces: groups P-I (b); P-W (c); and P-A (d). Deconvolution of O 1s high resolution spectrum resulted in three components: basic hydroxyl groups at 532.6 eV, acidic hydroxyl groups at 531.8 eV, and ZrO<sub>2</sub> at 530.2 eV.</p> Full article ">Figure 6
<p>Representative SEM images of fractured zirconia sides (magnification: 37×) in the plasma-treated no-liner subgroups (<b>a</b>) and the liner subgroups (<b>b</b>). In <a href="#materials-09-00043-f006" class="html-fig">Figure 6</a>b, the white arrows represent complete delamination of porcelain or liner.</p> Full article ">Figure 7
<p>Schematic illustration of the atmospheric argon plasma system used in this study.</p> Full article ">Figure 8
<p>Porcelain veneering and subsequent shear bond strength testing procedures using Ultradent jig. (<b>a</b>) Zirconia specimen placed into the jig; (<b>b</b>) Liner application; (<b>c</b>) Liner applied to the zirconia surface; (<b>d</b>) Veneering porcelain on the liner; (<b>e</b>) Porcelain veneered on the surface; (<b>f</b>) Shear bond strength testing. In the no-liner subgroups, steps (b,c) were omitted.</p> Full article ">
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Article
Improved Sectional Image Analysis Technique for Evaluating Fiber Orientations in Fiber-Reinforced Cement-Based Materials
by Bang Yeon Lee, Su-Tae Kang, Hae-Bum Yun and Yun Yong Kim
Materials 2016, 9(1), 42; https://doi.org/10.3390/ma9010042 - 12 Jan 2016
Cited by 15 | Viewed by 5770
Abstract
The distribution of fiber orientation is an important factor in determining the mechanical properties of fiber-reinforced concrete. This study proposes a new image analysis technique for improving the evaluation accuracy of fiber orientation distribution in the sectional image of fiber-reinforced concrete. A series [...] Read more.
The distribution of fiber orientation is an important factor in determining the mechanical properties of fiber-reinforced concrete. This study proposes a new image analysis technique for improving the evaluation accuracy of fiber orientation distribution in the sectional image of fiber-reinforced concrete. A series of tests on the accuracy of fiber detection and the estimation performance of fiber orientation was performed on artificial fiber images to assess the validity of the proposed technique. The validation test results showed that the proposed technique estimates the distribution of fiber orientation more accurately than the direct measurement of fiber orientation by image analysis. Full article
(This article belongs to the Special Issue Image Analysis and Processing for Cement-based Materials)
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<p>Dimensions of fibers in the side view and plan view on the cutting plane, which is the horizontal line in side view: (<b>a</b>) 0° orientation and (<b>b</b>) <math display="inline"> <semantics> <mi mathvariant="sans-serif">θ</mi> </semantics> </math> orientation.</p> Full article ">Figure 2
<p><span class="html-italic">l</span>/<span class="html-italic">d</span> ratio of the fiber image plotted as a function of fiber orientation, <math display="inline"> <semantics> <mi mathvariant="sans-serif">θ</mi> </semantics> </math>.</p> Full article ">Figure 3
<p>Error of the measured orientation of an artificial fiber image according to the number of pixels in the diameter.</p> Full article ">Figure 4
<p>Artificial fiber images with a diameter of five pixels in a three-dimensional random distribution in the area of 2000 pixels by 2000 pixels (I05-3): (<b>a</b>) section image and (<b>b</b>) magnified image.</p> Full article ">Figure 5
<p>Artificial fiber images with a diameter of five pixels in a two-dimensional random distribution in the area of 2000 pixels by 2000 pixels (I05-2): (<b>a</b>) section image and (<b>b</b>) magnified image.</p> Full article ">Figure 6
<p>Artificial fiber images with a diameter of 15 pixels in a three-dimensional random distribution in the area of 6000 pixels by 6000 pixels (I15-3): (<b>a</b>) section image and (<b>b</b>) magnified image.</p> Full article ">Figure 7
<p>Artificial fiber images with a diameter of 15 pixels in a two-dimensional random distribution in the area of 6000 pixels by 6000 pixels (I15-2): (<b>a</b>) section image and (<b>b</b>) magnified image.</p> Full article ">Figure 8
<p>Artificial fiber images with a diameter of 25 pixels in a three-dimensional random distribution in the area of 5000 pixels by 5000 pixels (I25-3): (<b>a</b>) section image and (<b>b</b>) magnified image.</p> Full article ">Figure 9
<p>Artificial fiber images with a diameter of 25 pixels in a two-dimensional random distribution in the area of 5000 pixels by 5000 pixels (I25-2): (<b>a</b>) section image and (<b>b</b>) magnified image.</p> Full article ">Figure 10
<p>Probability density functions of the orientation of randomly-generated artificial fibers and the orientation measured by the image analysis technique proposed by Lee <span class="html-italic">et al.</span> (2009): (<b>a</b>) I05-3; (<b>b</b>) I05-2; (<b>c</b>) I15-3; (<b>d</b>) I15-2; (<b>e</b>) I25-3; (<b>f</b>) I25-2.</p> Full article ">Figure 11
<p>Average error per fiber of the measured orientation of the artificial fiber images according to the number of pixels in the diameter.</p> Full article ">Figure 12
<p>Comparison between the measured distribution and the estimated distribution by the technique proposed in this study: (<b>a</b>) I05-3; (<b>b</b>) I05-2; (<b>c</b>) I15-3; (<b>d</b>) I15-2; (<b>e</b>) I25-3; (<b>f</b>) I25-2.</p> Full article ">Figure 13
<p>Comparison between the measured distribution and the estimated distribution by the technique proposed in this study.</p> Full article ">
4276 KiB  
Review
Failure Analysis in Magnetic Tunnel Junction Nanopillar with Interfacial Perpendicular Magnetic Anisotropy
by Weisheng Zhao, Xiaoxuan Zhao, Boyu Zhang, Kaihua Cao, Lezhi Wang, Wang Kang, Qian Shi, Mengxing Wang, Yu Zhang, You Wang, Shouzhong Peng, Jacques-Olivier Klein, Lirida Alves De Barros Naviner and Dafine Ravelosona
Materials 2016, 9(1), 41; https://doi.org/10.3390/ma9010041 - 12 Jan 2016
Cited by 74 | Viewed by 14943
Abstract
Magnetic tunnel junction nanopillar with interfacial perpendicular magnetic anisotropy (PMA-MTJ) becomes a promising candidate to build up spin transfer torque magnetic random access memory (STT-MRAM) for the next generation of non-volatile memory as it features low spin transfer switching current, fast speed, high [...] Read more.
Magnetic tunnel junction nanopillar with interfacial perpendicular magnetic anisotropy (PMA-MTJ) becomes a promising candidate to build up spin transfer torque magnetic random access memory (STT-MRAM) for the next generation of non-volatile memory as it features low spin transfer switching current, fast speed, high scalability, and easy integration into conventional complementary metal oxide semiconductor (CMOS) circuits. However, this device suffers from a number of failure issues, such as large process variation and tunneling barrier breakdown. The large process variation is an intrinsic issue for PMA-MTJ as it is based on the interfacial effects between ultra-thin films with few layers of atoms; the tunneling barrier breakdown is due to the requirement of an ultra-thin tunneling barrier (e.g., <1 nm) to reduce the resistance area for the spin transfer torque switching in the nanopillar. These failure issues limit the research and development of STT-MRAM to widely achieve commercial products. In this paper, we give a full analysis of failure mechanisms for PMA-MTJ and present some eventual solutions from device fabrication to system level integration to optimize the failure issues. Full article
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<p>Magnetic tunnel junction with interfacial perpendicular magnetic anisotropy (PMA-MTJ) consists of several ultra-thin layers: two ferromagnetic layers separated by an oxide barrier. Two heavy metal layers are associated with the two ferromagnetic layers, while the synthetic antiferromagnetic (SAF) layer is inserted adjacent the reference layer and bottom electrode. With the spin transfer torque mechanism, PMA-MTJ changes between two states when a bidirectional current <span class="html-italic">I</span> is higher than the critical current <span class="html-italic">I<sub>c</sub></span><sub>0</sub>.</p> Full article ">Figure 2
<p>Typical flow of magnetic tunnel junction (MTJ) device fabrication, which mainly comprises stack deposition, patterning, etching dielectric encapsulation, and connecting.</p> Full article ">Figure 3
<p>Cross-section image of MTJ stack by transmission electron microscope (TEM), which contains free and synthetic antiferromagnetic (SAF) reference layers separated by ultra-thin 0.88 nm MgO tunnel barrier. This sample was prepared by Anelva HC7100 sputtering equipment. A pinhole exists in the ultra-thinoxide barrier due to rough deposition of MgO, indicated by the red circle.</p> Full article ">Figure 4
<p>Schematic diagram of the generation of a pinhole. It originates from the rough MgO layer, formed by CoFeB deposition upon defective MgO. The existence of pinholes shunts the current, resulting in the degradation of tunnel magneto-resistance ratio (TMR), and may even cause breakdown.</p> Full article ">Figure 5
<p>Magnetic curves (measured by NanoMOKE) of MTJ stacks annealed at different annealing times. The film stack of substrate/Ta(3)/MgO(1)/CoFeB(1.1)/Ta(1.5)/Ru(5)/Ta(5) (units in nm) deposited by magnetic sputtering processing are <span class="html-italic">ex situ</span> annealed at 300 °C for different annealing times (40, 60 and 90 min) with perpendicular <span class="html-italic">H</span> = 0.775 T in a high vacuum chamber.</p> Full article ">Figure 6
<p>Schematic illustration of (<b>a</b>) short-circuit caused by redeposition with no tilt and rotation; (<b>b</b>) cleaned sidewall with beam angle and rotation.</p> Full article ">Figure 7
<p>Etching shadow effect with beam angle θ, which is defined as the angle between incident beam and the normal direction of the wafer. The minimum distance between two nanopillar is determined by the height of the pillar and the beam angle.</p> Full article ">Figure 8
<p>Cross-section image of MTJ stack by scanning electron microscope (SEM), which is etched by inductively-coupled plasma (ICP), shows few redeposition and good device profile.</p> Full article ">Figure 9
<p>Estimated lifetime of dielectric breakdown <span class="html-italic">versus</span> applied bias voltage with different thickness of MgO oxide barrier.</p> Full article ">Figure 10
<p>Cross-section image of MTJ stack by transmission electron microscope (TEM), sputtered by Anelva HC7100 sputtering equipment. Multilayers with different ultra-thin MgO oxide barrier thickness: (<b>a</b>) 0.86 nm and (<b>b</b>) 1.07 nm, respectively, while the nominal thickness is 1 nm.</p> Full article ">Figure 11
<p>Schematic of the hard failure repair technique with redundancy.</p> Full article ">Figure 12
<p>Final failure rate after applying Error correction code (ECC) (with codeword length of 256 bits).</p> Full article ">
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Article
Preliminary Investigation of the Process Capabilities of Hydroforging
by Bandar Alzahrani and Gracious Ngaile
Materials 2016, 9(1), 40; https://doi.org/10.3390/ma9010040 - 12 Jan 2016
Cited by 15 | Viewed by 6380
Abstract
Hydroforging is a hybrid forming operation whereby a thick tube is formed to a desired geometry by combining forging and hydroforming principles. Through this process hollow structures with high strength-to-weight ratio can be produced for applications in power transmission systems and other structural [...] Read more.
Hydroforging is a hybrid forming operation whereby a thick tube is formed to a desired geometry by combining forging and hydroforming principles. Through this process hollow structures with high strength-to-weight ratio can be produced for applications in power transmission systems and other structural components that demands high strength-to-weight ratio. In this process, a thick tube is deformed by pressurized fluid contained within the tube using a multi-purpose punch assembly, which is also used to feed tube material into the die cavity. Fluid pressure inside the thick tube is developed by volume change governed by the movement of the punch assembly. In contrast to the conventional tube hydroforming (THF), the hydroforging process presented in this study does not require external supply of pressurized fluid to the deforming tube. To investigate the capability of hydroforging process, an experimental setup was developed and used to hydroforge various geometries. These geometries included hollow flanged vessels, hexagonal flanged parts, and hollow bevel and spur gears. Full article
(This article belongs to the Special Issue Forming of Light Weight Materials)
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<p>(<b>a</b>) Conventional THF; (<b>b</b>) Tube hydroforging process.</p> Full article ">Figure 2
<p>Families of potential candidate parts for hydroforging.</p> Full article ">Figure 3
<p>Volume calculation scheme.</p> Full article ">Figure 4
<p>Process window for hollow vessel with flange height <span class="html-italic">h<sub>f</sub></span> = 12.7 mm.</p> Full article ">Figure 5
<p>Process window for hollow hexagonal with flange height <span class="html-italic">h<sub>f</sub></span> = 25.4 mm.</p> Full article ">Figure 6
<p>Process window for a ten teeth hollow bevel gear.</p> Full article ">Figure 7
<p>Process window for a ten teeth hollow spur gear.</p> Full article ">Figure 8
<p>Hydroforging (<b>a</b>) and pressure loading schematic (<b>b</b>).</p> Full article ">Figure 9
<p>Schematic of hydroforging experimental setup.</p> Full article ">Figure 10
<p>Exploded model for tube hydroforging tooling.</p> Full article ">Figure 11
<p>Experimental setup parts: (<b>a</b>) Support rings; (<b>b</b>) guiding zone inserts; (<b>c</b>) punch assemblies; (<b>d</b>) die inserts; and (<b>e</b>) bottom sealing inserts.</p> Full article ">Figure 12
<p>Hydroforged parts.</p> Full article ">Figure 13
<p>(<b>a</b>) Hollow vessel, flange = 18 mm and 21 mm; (<b>b</b>) loading for 18 mm flange.</p> Full article ">Figure 14
<p>(<b>a</b>) Hexagonal hollow parts; (<b>b</b>) loading paths.</p> Full article ">Figure 15
<p>(<b>a</b>) Spur gear; (<b>b</b>) loading paths.</p> Full article ">Figure 16
<p>Bevel gear: AL6061(<b>a</b>) and SS304 (<b>b</b>).</p> Full article ">Figure 17
<p>Material failure mode during hydroforging of a bevel gear from AL6061 blank.</p> Full article ">Figure 18
<p>Crack initiation and non-uniform thickness distribution on hexagonal shaped flange.</p> Full article ">
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Article
Synthesis and Characterization of Nanofibrous Polyaniline Thin Film Prepared by Novel Atmospheric Pressure Plasma Polymerization Technique
by Choon-Sang Park, Dong Ha Kim, Bhum Jae Shin and Heung-Sik Tae
Materials 2016, 9(1), 39; https://doi.org/10.3390/ma9010039 - 11 Jan 2016
Cited by 34 | Viewed by 8299
Abstract
This work presents a study on the preparation of plasma-polymerized aniline (pPANI) nanofibers and nanoparticles by an intense plasma cloud type atmospheric pressure plasma jets (iPC-APPJ) device with a single bundle of three glass tubes. The nano size polymer was obtained at a [...] Read more.
This work presents a study on the preparation of plasma-polymerized aniline (pPANI) nanofibers and nanoparticles by an intense plasma cloud type atmospheric pressure plasma jets (iPC-APPJ) device with a single bundle of three glass tubes. The nano size polymer was obtained at a sinusoidal wave with a peak value of 8 kV and a frequency of 26 kHz under ambient air. Discharge currents, photo-sensor amplifier, and optical emission spectrometer (OES) techniques were used to analyze the plasma produced from the iPC-APPJ device. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), gas chromatography-mass spectrometry (GC-MS), and gel permeation chromatography (GPC) techniques were used to analyze the pPANI. FE-SEM and TEM results show that pPANI has nanofibers, nanoparticles morphology, and polycrystalline characteristics. The FT-IR and GC-MS analysis show the characteristic polyaniline peaks with evidence that some quinone and benzene rings are broken by the discharge energy. GPC results show that pPANI has high molecular weight (Mw), about 533 kDa with 1.9 polydispersity index (PDI). This study contributes to a better understanding on the novel growth process and synthesis of uniform polyaniline nanofibers and nanoparticles with high molecular weights using the simple atmospheric pressure plasma polymerization technique. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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<p>Schematic diagram of experimental setup in this study and images of plasmas produced in the recombination region of intense plasma cloud type atmospheric pressure plasma jets (iPC-APPJ), with and without the polytetrafluoroethylene (PTFE) bottom cap.</p> Full article ">Figure 2
<p>Applied voltages, discharge currents, and optical intensities measured in the recombination region of iPC-APPJ, with and without the PTFE bottom cap.</p> Full article ">Figure 3
<p>Optical emission spectra measured in the recombination region of iPC-APPJ, with and without the PTFE bottom cap.</p> Full article ">Figure 4
<p>Scanning electron microscopy (SEM) images of plasma-polymerized aniline (pPANI) nanofibers with nanoparticles (NwN) thin film prepared via iPC-APPJ during various deposition times. (<b>a</b>) Top-view of pPANI after 20 min deposition; (<b>b</b>)–(<b>f</b>) cross-section view of pPANI at various deposition times. Scale bar = 1 µm.</p> Full article ">Figure 5
<p>Transmission electron microscopy (TEM) images of pPANI nanoparticles thin film prepared via iPC-APPJ. (<b>a</b>–<b>d</b>) The different magnifications; the inset in (c) is the selected area electron diffraction (SAED) pattern of pPANI nanoparticles. Scale bar = 2 nm.</p> Full article ">Figure 6
<p>Fourier transform infrared spectroscopy (FTIR) spectrum of pPANI NwN thin film prepared using iPC-APPJ.</p> Full article ">Figure 7
<p>Total ion count chromatogram of pPANI NwN thin film obtained using solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC-MS) prepared using iPC-APPJ.</p> Full article ">
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Article
Antimicrobial Properties and Cytocompatibility of PLGA/Ag Nanocomposites
by Mariangela Scavone, Ilaria Armentano, Elena Fortunati, Francesco Cristofaro, Samantha Mattioli, Luigi Torre, Jose M. Kenny, Marcello Imbriani, Carla Renata Arciola and Livia Visai
Materials 2016, 9(1), 37; https://doi.org/10.3390/ma9010037 - 11 Jan 2016
Cited by 23 | Viewed by 6055
Abstract
The purpose of this study was to investigate the antimicrobial properties of multifunctional nanocomposites based on poly(dl-Lactide-co-Glycolide) (PLGA) and increasing concentration of silver (Ag) nanoparticles and their effects on cell viability for biomedical applications. PLGA nanocomposite films, produced by solvent casting [...] Read more.
The purpose of this study was to investigate the antimicrobial properties of multifunctional nanocomposites based on poly(dl-Lactide-co-Glycolide) (PLGA) and increasing concentration of silver (Ag) nanoparticles and their effects on cell viability for biomedical applications. PLGA nanocomposite films, produced by solvent casting with 1 wt%, 3 wt% and 7 wt% of Ag nanoparticles were investigated and surface properties were characterized by atomic force microscopy and contact angle measurements. Antibacterial tests were performed using an Escherichia coli RB and Staphylococcus aureus 8325-4 strains. The cell viability and morphology were performed with a murine fibroblast cell line (L929) and a human osteosarcoma cell line (SAOS-2) by cell viability assay and electron microscopy observations. Matrix protein secretion and deposition were also quantified by enzyme-linked immunosorbent assay (ELISA). The results suggest that the PLGA film morphology can be modified introducing a small percentage of silver nanoparticles, which induce the onset of porous round-like microstructures and also affect the wettability. The PLGA/Ag films having silver nanoparticles of more than 3 wt% showed antibacterial effects against E. coli and S. aureus. Furthermore, silver-containing PLGA films displayed also a good cytocompatibility when assayed with L929 and SAOS-2 cells; indicating the PLGA/3Ag nanocomposite film as a promising candidate for tissue engineering applications. Full article
(This article belongs to the Special Issue Anti-Infective Materials in Medicine and Technology)
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<p>Atomic force microscopy and water contact angle images of PLGA, PLGA/1Ag, PLGA/3Ag and PLGA/7Ag films.</p> Full article ">Figure 2
<p>Bacterial adhesion to PLGA and PLGA/Ag nanocomposite films. <span class="html-italic">S. aureus</span> and <span class="html-italic">E. coli</span> cell adhesion to PLGA and PLGA/Ag was determined as colony forming units (CFU/mL) after 3 h incubation at 37 °C. Data are expressed as percentage of the ratios between CFU of bacteria adherent to PLGA to CFU of bacteria adherent to 24-well flat-bottom sterile polystyrene microplates. The values represented are the means of the results of each sample performed in duplicate and repeated in three separated experiments. Error bars indicate standard errors of the means. The statistical significance was indicated as follows: * <span class="html-italic">p</span> &lt; 0.05 and ** <span class="html-italic">p</span> &lt; 0.01.</p> Full article ">Figure 3
<p>Antibacterial activity of PLGA and PLGA/Ag nanocomposite films. Surviving fractions of <span class="html-italic">S. aureus</span> (<b>A</b>) and <span class="html-italic">E. coli</span> (<b>B</b>) cells to the indicated PLGA films were determined as CFU/mL after 3 and 24 h incubation times. Data are expressed as percentage of the ratios between CFU of bacteria grown on PLGA films to CFU of bacteria grown in 24-well flat-bottom sterile polystyrene plates. The values represented are the means of the results of each sample performed in duplicate and in three separate experiments. Error bars indicate standard errors of the means. The statistical significance was indicated as follows: ** <span class="html-italic">p</span> &lt; 0.01.</p> Full article ">Figure 4
<p>L929 and SAOS-2 cell viability. At 24 h, 96 h and 240 h of culture, cell viability was determined by the MTT assay performed on PLGA, PLGA/1Ag, PLGA/3Ag and PLGA/7Ag films. Panel (<b>A</b>) shows L929 cells viability whereas panel (<b>B</b>) represents SAOS-2 cells viability cultured in osteogenic medium. The error bars represent the standard deviations.</p> Full article ">Figure 5
<p>Representative SEM images of the cell cultured on PLGA, and PLGA/3Ag films. Both cell types, L929 (<b>A</b>–<b>D</b>) or SAOS-2 (<b>E</b>–<b>H</b>), were seeded and cultivated for 24 h (<b>A</b>,<b>C</b>,<b>E</b>,<b>G</b>) and seven days (<b>B</b>,<b>D</b>,<b>F</b>,<b>H</b>), on PLGA (<b>A</b>,<b>B</b>,<b>E</b>,<b>F</b>) and PLGA/3Ag (<b>C</b>,<b>D</b>,<b>G</b>,<b>H</b>), respectively, and then fixed for SEM observations (×1000 magnification). Both fibroblasts (panels (<b>A</b>,<b>B</b>)) and osteoblasts (panels (<b>E</b>,<b>F</b>)) coated the PLGA surface forming a homogenous layer at 24 h and day 7: individual cells were no longer discernable over the surface and above this layer some cells exhibited a round shape (insert of panels (<b>A</b>,<b>B</b>,<b>E</b>,<b>F</b>) at ×3000 magnification); on the PLGA/3Ag films (<b>C</b>,<b>D</b>,<b>G</b>,<b>H</b>), fibroblasts and osteoblasts did not form a homogenous layer at 24 h or day 7 even if some cells could be observed into the holes of the materials (insert of panels (<b>C</b>,<b>D</b>,<b>G</b>,<b>H</b>) at ×3000 magnification). Scale bars represent 10 μm (<b>A</b>–<b>H</b>) and 2 μm (all the inserts), respectively.</p> Full article ">Figure 6
<p>ALP activity of SAOS-2 cells. Cells were seeded on PLGA, PLGA/1Ag, PLGA/3Ag and PLGA/7Ag films and cultured in osteogenic medium for 10 d. ALP activity was determined colourimetrically, corrected for the protein content measured with the BCA Protein Assay Kit and expressed as millimoles of p-nitrophenol produced per min per mg of protein. Bars express the mean values ± SEM of results from three experiments (* <span class="html-italic">p</span> &lt; 0.05; ** <span class="html-italic">p</span> &lt; 0.01).</p> Full article ">
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