Materials

4553 KiB

Open AccessCommunication

Synthesis of Porous Carbon Monoliths Using Hard Templates

by Olaf Klepel, Nina Danneberg, Matti Dräger, Marcel Erlitz and Michael Taubert

Materials 2016, 9(3), 214; https://doi.org/10.3390/ma9030214 - 21 Mar 2016

Cited by 13 | Viewed by 8497

The preparation of porous carbon monoliths with a defined shape via template-assisted routes is reported. Monoliths made from porous concrete and zeolite were each used as the template. The porous concrete-derived carbon monoliths exhibited high gravimetric specific surface areas up to 2000 m [...] Read more.

The preparation of porous carbon monoliths with a defined shape via template-assisted routes is reported. Monoliths made from porous concrete and zeolite were each used as the template. The porous concrete-derived carbon monoliths exhibited high gravimetric specific surface areas up to 2000 m²·g^?1. The pore system comprised macro-, meso-, and micropores. These pores were hierarchically arranged. The pore system was created by the complex interplay of the actions of both the template and the activating agent as well. On the other hand, zeolite-made template shapes allowed for the preparation of microporous carbon monoliths with a high volumetric specific surface area. This feature could be beneficial if carbon monoliths must be integrated into technical systems under space-limited conditions. Full article

(This article belongs to the Special Issue Porous Monolithic Materials for Applications in Separation Science)

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7631 KiB

Open AccessArticle

On the Behavior of Different PCMs in a Hot Water Storage Tank against Thermal Demands

by Jacobo Porteiro, José Luis Míguez, Bárbara Crespo, José De Lara and José María Pousada

Materials 2016, 9(3), 213; https://doi.org/10.3390/ma9030213 - 21 Mar 2016

Cited by 18 | Viewed by 6293

Abstract

Advantages, such as thermal storage improvement, are found when using PCMs (Phase Change Materials) in storage tanks. The inclusion of three different types of materials in a 60 l test tank is studied. Two test methodologies were developed, and four tests were performed [...] Read more.

Advantages, such as thermal storage improvement, are found when using PCMs (Phase Change Materials) in storage tanks. The inclusion of three different types of materials in a 60 l test tank is studied. Two test methodologies were developed, and four tests were performed following each methodology. A thermal analysis is performed to check the thermal properties of each PCM. The distributions of the water temperatures inside the test tanks are evaluated by installing four Pt-100 sensors at different heights. A temperature recovery is observed after exposing the test tank to an energy demand. An energetic analysis that takes into account the energy due to the water temperature, the energy due to the PCM and the thermal loss to the ambient environment is also presented. The percentage of each PCM that remains in the liquid state after the energy demand is obtained. Full article

(This article belongs to the Special Issue Development and Characterisation of Encapsulated PCM: Nano-, Micro-, and Macro-Encapsulation)

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2064 KiB

Open AccessFeature PaperArticle

Polystyrene-co-Divinylbenzene PolyHIPE Monoliths in 1.0 mm Column Formats for Liquid Chromatography

by Sidratul Choudhury, Laurence Fitzhenry, Blánaid White and Damian Connolly

Materials 2016, 9(3), 212; https://doi.org/10.3390/ma9030212 - 18 Mar 2016

Cited by 14 | Viewed by 6750

Abstract

The reversed phase liquid chromatographic (RP-HPLC) separation of small molecules using a polystyrene-co-divinylbenzene (PS-co-DVB) polyHIPE stationary phases housed within 1.0 mm i.d. silcosteel columns is presented within this study. A 90% PS-co-DVB polyHIPE was covalently attached to [...] Read more.

The reversed phase liquid chromatographic (RP-HPLC) separation of small molecules using a polystyrene-co-divinylbenzene (PS-co-DVB) polyHIPE stationary phases housed within 1.0 mm i.d. silcosteel columns is presented within this study. A 90% PS-co-DVB polyHIPE was covalently attached to the walls of the column housing by prior wall modification with 3-(trimethoxysilyl) propyl methacrylate and could withstand operating backpressures in excess of 200 bar at a flow rate of 1.2 mL/min. Permeability studies revealed that the monolith swelled slightly in 100% acetonitrile relative to 100% water but could nevertheless be used to separate five alkylbenzenes using a flow rate of 40 µL/min (linear velocity: 0.57 mm/s). Remarkable column-to-column reproducibility is shown with retention factor variation between 2.6% and 6.1% for two separately prepared columns. Full article

(This article belongs to the Special Issue Porous Monolithic Materials for Applications in Separation Science)

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GMA-co-EDMA polyHIPE with (a) 4.5% surfactant; and (b) 5.5% surfactant. A GMA-co-EDMA polyHIPE with 4.5% surfactant was formed in (c) unmodified 0.76 mm i.d. PEEK; and (d) GMA-modified 0.76 mm i.d. PEEK. Full article ">Figure 2
PS-co-DVB polyHIPE (90% porosity) formed within 1.0 mm i.d. silcosteel tubing (a); edge magnification of Image (a) showing binding to the column wall (b); typical polyHIPE morphology in the column centre (c); image of the parent, free-standing polyHIPE (d). Full article ">Figure 3
Backpressure profiles of PS-co-DVB polyHIPE monoliths in silcosteel tubing for water (a); methanol (b); and acetonitrile (c). Blue plots represent Column #1 and green plots represent Column #2. Backpressure measurements were made in triplicate at each flow rate. Full article ">Figure 4
Isocratic separation of alkylbenzenes on PS-co-DVB polyHIPEs. (a): Column #1, (b): Column #2. Chromatographic conditions: Column: 1.0 mm × 100 mm 90% porosity PS-co-DVB polyHIPE, Mobile phase: 50% ACN, Flow rate: 40 µL∙min−1, Injection volume: 1 µL, Detection: UV at 214 nm. Peak assignments: (1) toluene, (2) ethylbenzene, (3) propylbenzene, (4) butylbenzene, (5) pentylbenzene. All analytes are 0.1 mg∙L−1. Full article ">

2223 KiB

Open AccessArticle

Photoassisted Electrochemical Treatment of Azo and Phtalocyanine Reactive Dyes in the Presence of Surfactants

by Mireia Sala, Víctor López-Grimau and Carmen Gutiérrez-Bouzán

Materials 2016, 9(3), 211; https://doi.org/10.3390/ma9030211 - 18 Mar 2016

Cited by 13 | Viewed by 5030

Abstract

An electrochemical treatment (EC) was applied at different intensities to degrade the chromophoric groups of dyes C.I. Reactive Black 5 (RB5) and C.I. Reactive Blue 7 (Rb7) until uncolored species were obtained. Decolorization rate constants of the azo dye RB5 were higher than [...] Read more.

An electrochemical treatment (EC) was applied at different intensities to degrade the chromophoric groups of dyes C.I. Reactive Black 5 (RB5) and C.I. Reactive Blue 7 (Rb7) until uncolored species were obtained. Decolorization rate constants of the azo dye RB5 were higher than the phtalocyanine Rb7 ones. In addition, the EC treatment was more efficient at higher intensities, but these conditions significantly increased the generation of undesirable by-products such as chloroform. The combination of EC with UV irradiation (UVEC) drastically minimized the generation of chloroform. The photo-assisted electrochemical treatment was also able to achieve decolorization values of 99%. Finally, mixtures of dyes and surfactants were treated by EC and UVEC. In the presence of surfactants, the decolorization kinetic of dyes was slowed due to the competitive reactions of surfactants degradation. Both methods achieved total decolorization and in both cases, the generation of haloforms was negligible. Full article

(This article belongs to the Special Issue Functional Organic Dyes and Pigments)

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1574 KiB

Open AccessArticle

Effect of Curing Mode on Shear Bond Strength of Self-Adhesive Cement to Composite Blocks

by Jin-Young Kim, Ga-Young Cho, Byoung-Duck Roh and Yooseok Shin

Materials 2016, 9(3), 210; https://doi.org/10.3390/ma9030210 - 18 Mar 2016

Cited by 14 | Viewed by 6662

Abstract

To overcome the disadvantages of computer-aided design/computer-aided manufacturing (CAD/CAM) processed indirect restorations using glass-ceramics and other ceramics, resin nano ceramic, which has high strength and wear resistance with improved polish retention and optical properties, was introduced. The purpose of this study was to [...] Read more.

To overcome the disadvantages of computer-aided design/computer-aided manufacturing (CAD/CAM) processed indirect restorations using glass-ceramics and other ceramics, resin nano ceramic, which has high strength and wear resistance with improved polish retention and optical properties, was introduced. The purpose of this study was to evaluate the shear bond strength and fracture pattern of indirect CAD/CAM composite blocks cemented with two self-etch adhesive cements with different curing modes. Sand-blasted CAD/CAM composite blocks were cemented using conventional resin cement, Rely X Ultimate Clicker (RXC, 3M ESPE, St. Paul, MN, USA) with Single Bond Universal (SB, 3M ESPE, St. Paul, MN, USA) for the control group or two self-adhesive resin cements: Rely X U200 (RXU, 3M ESPE, St. Paul, MN, USA) and G-CEM Cerasmart (GC, GC corporation, Tokyo, Japan). RXU and GC groups included different curing modes (light-curing (L) and auto-curing (A)). Shear bond strength (SBS) analyses were performed on all the specimens. The RXC group revealed the highest SBS and the GC A group revealed the lowest SBS. According to Tukey’s post hoc test, the RXC group showed a significant difference compared to the GC A group (p < 0.05). For the curing mode, RXU A and RXU L did not show any significant difference between groups and GC A and GC L did not show any significant difference either. Most of the groups except RXC and RXU L revealed adhesive failure patterns predominantly. The RXC group showed a predominant cohesive failure pattern in their CAD/CAM composite, Lava^TM Ultimate (LU, 3M ESPE, St. Paul, MN, USA). Within the limitations of this study, no significant difference was found regarding curing modes but more mixed fracture patterns were showed when using the light-curing mode than when using the self-curing mode. Full article

(This article belongs to the Section Advanced Composites)

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3057 KiB

Open AccessArticle

Perpendicular Magnetization Behavior of Low- Temperature Ordered FePt Films with Insertion of Ag Nanolayers

by Da-Hua Wei

Materials 2016, 9(3), 209; https://doi.org/10.3390/ma9030209 - 18 Mar 2016

Cited by 2 | Viewed by 5342

Abstract

FePt-Ag nanocomposite films with large perpendicular magnetic anisotropy have been fabricated by alternate-atomic-layer electron beam evaporation onto MgO(100) substrates at the low temperature of 300 °C. Their magnetization behavior and microstructure have been studied. The surface topography was observed and varied from continuous [...] Read more.

FePt-Ag nanocomposite films with large perpendicular magnetic anisotropy have been fabricated by alternate-atomic-layer electron beam evaporation onto MgO(100) substrates at the low temperature of 300 °C. Their magnetization behavior and microstructure have been studied. The surface topography was observed and varied from continuous to nanogranular microstructures with insertion of Ag nanolayers into Fe/Pt bilayer films. The measurement of angular-dependent coercivity showed a tendency of the domain-wall motion as a typical peak behavior shift toward more like a coherent Stoner-Wohlfarth rotation type with the insertion of Ag nanolayers into the FePt films. On the other hand, the inter-grain interaction was determined from a Kelly-Henkel plot. The FePt film without insertion of Ag nanolayers has a positive ?M, indicating strong exchange coupling between neighboring grains, whereas the FePt film with insertion of Ag nanolayers has a negative ?M, indicating that inter-grain exchange coupling is weaker, thus leading to the presence of dipole interaction in the FePt–Ag nanogranular films. The magnetic characteristic measurements confirmed that the perpendicular magnetization reversal behavior and related surface morphology of low-temperature-ordered FePt(001) nanogranular films can be systematically controlled by the insertion of Ag nanolayers into the FePt system for next generation magnetic storage medium applications. Full article

(This article belongs to the Section Advanced Composites)

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Field emission scanning electron microscope (FE-SEM) surface morphology images for the [Fe/Pt]18 multilayer films (a) without and (b) with two ultrathin Ag (0.5 nm each) nanolayers. The corresponding grain size histograms for evaluating average size and distribution of the FePt films (c) without and (d) with insertion of two Ag nanolayers are related to (a) and (b), respectively. Full article ">Figure 2
Out-of-plane and in-plane magnetization curves for the [Fe/Pt]18 multilayer films (a) without and with insertion of (b) a single and (c) two ultrathin Ag (0.5 nm each) nanolayers denoted as FePt–1Ag and FePt–2Ag, respectively. The magnetic field was applied in the out-of-plane direction (full symbols, ●) and in the in-plane direction (open symbols, o) to the film, respectively. Full article ">Figure 3
(a) Out-of-plane magnetization curves and corresponding (b) normalized initial magnetization curves for the [Fe/Pt]18 multilayer films without and with insertion of two ultrathin Ag (0.5 nm each) nanolayers. Full article ">Figure 4
Angular dependence of coercivity for the [Fe/Pt]18 multilayer films without and with insertion of a single and two ultrathin Ag (0.5 nm each) nanolayers. The angle is referred to that between the easy axis (film normal) and the applied field direction. Full article ">Figure 5
Kelly-Henkel (δM) plot for the [Fe/Pt]18 multilayer films without and with insertion of two ultrathin Ag (0.5 nm each) nanolayers. The magnetic field was applied in the out-of-plane direction to the film. Full article ">Figure 6
X-ray diffraction scan patterns (XRD) for the [Fe/Pt]18 multilayer films (a) without and (b) with two ultrathin Ag (0.5 nm each) nanolayers. The corresponding slow scan curves of the FePt (002) peak in the θ–2θ scan (c) without and (d) with insertion of two Ag nanolayers are related with (a) and (b), respectively. Full article ">

4707 KiB

Open AccessArticle

Site-Control of InAs/GaAs Quantum Dots with Indium-Assisted Deoxidation

by Sajid Hussain, Alessandro Pozzato, Massimo Tormen, Valentina Zannier and Giorgio Biasiol

Materials 2016, 9(3), 208; https://doi.org/10.3390/ma9030208 - 18 Mar 2016

Cited by 4 | Viewed by 5432

Abstract

Site-controlled epitaxial growth of InAs quantum dots on GaAs substrates patterned with periodic nanohole arrays relies on the deterministic nucleation of dots into the holes. In the ideal situation, each hole should be occupied exactly by one single dot, with no nucleation onto [...] Read more.

Site-controlled epitaxial growth of InAs quantum dots on GaAs substrates patterned with periodic nanohole arrays relies on the deterministic nucleation of dots into the holes. In the ideal situation, each hole should be occupied exactly by one single dot, with no nucleation onto planar areas. However, the single-dot occupancy per hole is often made difficult by the fact that lithographically-defined holes are generally much larger than the dots, thus providing several nucleation sites per hole. In addition, deposition of a thin GaAs buffer before the dots tends to further widen the holes in the [110] direction. We have explored a method of native surface oxide removal by using indium beams, which effectively prevents hole elongation along [110] and greatly helps single-dot occupancy per hole. Furthermore, as compared to Ga-assisted deoxidation, In-assisted deoxidation is efficient in completely removing surface contaminants, and any excess In can be easily re-desorbed thermally, thus leaving a clean, smooth GaAs surface. Low temperature photoluminescence showed that inhomogeneous broadening is substantially reduced for QDs grown on In-deoxidized patterns, with respect to planar self-assembled dots. Full article

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SEM images of (a) the silicon mold used for NIL patterning of GaAs; (b) a patterned GaAs (001) surface. Full article ">Figure 2
AFM line scans of hole profiles along (a) [1<math display="inline"> <semantics> <mover accent="true"> <mn>1</mn> <mo>¯</mo> </mover> </semantics> </math>0] and (b) [110] after wet chemical etching, GAD, IAD, GAD followed by 10 nm GaAs, and IAD followed by 10 nm GaAs (each profile represents an average over 15–20 line scans). Inset of panel (b): AFM images of two holes after GAD and IAD, followed by 10 nm GaAs in both cases. Full article ">Figure 3
SEM images of a patterned GaAs surface after in situ oxide removal by (a) Ga-assisted deoxidation; (b) In-assisted deoxidation. Full article ">Figure 4
XPS spectra of (a) Ga 3d; (b) As 3d; (c) O 1s and (d) C 1s core level emissions before oxide removal (red traces) and after In-assisted oxide removal and annealing at 560 °C (black traces) and 540 °C (blue trace, Ga 3d only). Full article ">Figure 5
SEM images of 10nm GaAs deposited on a Ga- (a) and In-deoxidized (b) patterned GaAs surface. Inset in (b) shows two holes of an IAD pattern annealed for longer times (10 min) after In deposition. Full article ">Figure 6
SEM images of (a) a single layer and (b) a tenfold stack of site-controlled InAs/GaAs QDs grown on a nanopatterned GaAs hole array, deoxidized by Ga beams; (c) histogram showing the dot occupancy per hole on GAD patterns for a single layer (red) and a tenfold stack of InAs QDs (blue). Full article ">Figure 6 Cont.
SEM images of (a) a single layer and (b) a tenfold stack of site-controlled InAs/GaAs QDs grown on a nanopatterned GaAs hole array, deoxidized by Ga beams; (c) histogram showing the dot occupancy per hole on GAD patterns for a single layer (red) and a tenfold stack of InAs QDs (blue). Full article ">Figure 7
SEM images of (a) a single layer; and (b) a tenfold stack of site-controlled InAs/GaAs QDs grown on a nanopatterned GaAs hole array, deoxidized by In beams; (c) histogram showing the dot occupancy per hole on IAD patterns for a single layer (red) and a tenfold stack of InAs QDs (blue). Full article ">Figure 8
(a) AFM image of a tenfold stack of site-controlled InAs QDs grown on In-deoxidized hole arrays; (b) histogram of the height distribution relative to single dot-per-hole only. Full article ">Figure 9
Low T PL spectra of single layer of InAs QDs grown on a planar substrate (black line), and of a 10X In0.5Ga0.5As + single InAs QD stack grown on patterned substrate (red line). Inset shows a schematic drawing of the growth sequence for the latter sample. Full article ">

8933 KiB

Open AccessArticle

Fatigue Life Prediction of Fiber-Reinforced Ceramic-Matrix Composites with Different Fiber Preforms at Room and Elevated Temperatures

by Longbiao Li

Materials 2016, 9(3), 207; https://doi.org/10.3390/ma9030207 - 17 Mar 2016

Cited by 17 | Viewed by 6099

Abstract

In this paper, the fatigue life of fiber-reinforced ceramic-matrix composites (CMCs) with different fiber preforms, i.e., unidirectional, cross-ply, 2D (two dimensional), 2.5D and 3D CMCs at room and elevated temperatures in air and oxidative environments, has been predicted using the micromechanics approach. [...] Read more.

In this paper, the fatigue life of fiber-reinforced ceramic-matrix composites (CMCs) with different fiber preforms, i.e., unidirectional, cross-ply, 2D (two dimensional), 2.5D and 3D CMCs at room and elevated temperatures in air and oxidative environments, has been predicted using the micromechanics approach. An effective coefficient of the fiber volume fraction along the loading direction (ECFL) was introduced to describe the fiber architecture of preforms. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. Under cyclic fatigue loading, the fiber broken fraction was determined by combining the interface wear model and fiber statistical failure model at room temperature, and interface/fiber oxidation model, interface wear model and fiber statistical failure model at elevated temperatures, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfies the Global Load Sharing (GLS) criterion. When the broken fiber fraction approaches the critical value, the composites fatigue fracture. Full article

(This article belongs to the Section Advanced Composites)

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2099 KiB

Open AccessArticle

Nitric Acid-Treated Carbon Fibers with Enhanced Hydrophilicity for Candida tropicalis Immobilization in Xylitol Fermentation

by Le Wang, Na Liu, Zheng Guo, Dapeng Wu, Weiwei Chen, Zheng Chang, Qipeng Yuan, Ming Hui and Jinshui Wang

Materials 2016, 9(3), 206; https://doi.org/10.3390/ma9030206 - 17 Mar 2016

Cited by 44 | Viewed by 7802

Abstract

Nitric acid (HNO₃)-treated carbon fiber (CF) rich in hydrophilic groups was applied as a cell-immobilized carrier for xylitol fermentation. Using scanning electron microscopy, we characterized the morphology of the HNO₃-treated CF. Additionally, we evaluated the immobilized efficiency (IE) of [...] Read more.

Nitric acid (HNO₃)-treated carbon fiber (CF) rich in hydrophilic groups was applied as a cell-immobilized carrier for xylitol fermentation. Using scanning electron microscopy, we characterized the morphology of the HNO₃-treated CF. Additionally, we evaluated the immobilized efficiency (IE) of Candida tropicalis and xylitol fermentation yield by investigating the surface properties of nitric acid treated CF, specifically, the acidic group content, zero charge point, degree of moisture and contact angle. We found that adhesion is the major mechanism for cell immobilization and that it is greatly affected by the hydrophilic–hydrophilic surface properties. In our experiments, we found 3 hto be the optimal time for treating CF with nitric acid, resulting in an improved IE of Candida tropicalis of 0.98 g?g^?1 and the highest xylitol yield and volumetric productivity (70.13% and 1.22 g?L^?1?h^?1, respectively). The HNO₃-treated CF represents a promising method for preparing biocompatible biocarriers for multi-batch fermentation. Full article

(This article belongs to the Section Biomaterials)

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Scanning electron microscopy (SEM) images of carbon fibercarrier with raw and treated morphology and immobilized C. tropicalis (a) CF carrier without oxidation by nitric acid; (b) CF carrier after exposure to nitric acid treatment for 3 h; (c) CF carrier after exposure to nitric acid treatment for 6 h; (d) CF carrier without treatment immobilized with C. tropicalis; (e) Immobilized C. tropicalis by CF carrier treated with nitric acid for 3 h; (f) Immobilized C. tropicalis by CF carrier treated with nitric acid for 6 h. Full article ">Figure 2
FTIR spectrum of Raw-CF and CF-Nh3. Full article ">Figure 3
The image of contact angles on Raw-CF and CF-Nh3 (a) Results and image of contact angles on Raw-CF; (b) Results and image of contact angles on Raw-CF. Full article ">Figure 4
Effects of oxidation carriers on immobilized efficiency (IE) and biomass of fermentation (a) Effects of oxidation carriers on the IE; (b) Effects of oxidation carriers on the biomass of fermentation. Biomass was calculated using the amount of free cells and immobilized cells in the third fermentation by immobilized C. tropicalis on CF with and without treatment. Full article ">Figure 5
Effect of oxidation time on the multi-batch xylitol fermentation (a) Effects of oxidation time on the average xylitol yield of fermentation batches; (b) Effect of oxidation time on the average volumetric productivity of the fermentation batches. Full article ">

4835 KiB

Open AccessFeature PaperArticle

Computational Study of the Effect of Cortical Porosity on Ultrasound Wave Propagation in Healthy and Osteoporotic Long Bones

by Vassiliki T. Potsika, Konstantinos N. Grivas, Theodoros Gortsas, Gianluca Iori, Vasilios C. Protopappas, Kay Raum, Demosthenes Polyzos and Dimitrios I. Fotiadis

Materials 2016, 9(3), 205; https://doi.org/10.3390/ma9030205 - 17 Mar 2016

Cited by 6 | Viewed by 5725

Abstract

Computational studies on the evaluation of bone status in cases of pathologies have gained significant interest in recent years. This work presents a parametric and systematic numerical study on ultrasound propagation in cortical bone models to investigate the effect of changes in cortical [...] Read more.

Computational studies on the evaluation of bone status in cases of pathologies have gained significant interest in recent years. This work presents a parametric and systematic numerical study on ultrasound propagation in cortical bone models to investigate the effect of changes in cortical porosity and the occurrence of large basic multicellular units, simply called non-refilled resorption lacunae (RL), on the velocity of the first arriving signal (FAS). Two-dimensional geometries of cortical bone are established for various microstructural models mimicking normal and pathological tissue states. Emphasis is given on the detection of RL formation which may provoke the thinning of the cortical cortex and the increase of porosity at a later stage of the disease. The central excitation frequencies 0.5 and 1 MHz are examined. The proposed configuration consists of one point source and multiple successive receivers in order to calculate the FAS velocity in small propagation paths (local velocity) and derive a variation profile along the cortical surface. It was shown that: (a) the local FAS velocity can capture porosity changes including the occurrence of RL with different number, size and depth of formation; and (b) the excitation frequency 0.5 MHz is more sensitive for the assessment of cortical microstructure. Full article

(This article belongs to the Special Issue Acoustic Waves in Advanced Materials)

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4889 KiB

Open AccessArticle

Cavitation Erosion of Cermet-Coated Aluminium Bronzes

by Ion Mitelea, Octavian Oancă, Ilare Bordeaşu and Corneliu M. Crăciunescu

Materials 2016, 9(3), 204; https://doi.org/10.3390/ma9030204 - 17 Mar 2016

Cited by 7 | Viewed by 5631

Abstract

The cavitation erosion resistance of CuAl10Ni5Fe2.5Mn1 following plasma spraying with Al₂O₃·30(Ni₂₀Al) powder and laser re-melting was analyzed in view of possible improvements of the lifetime of components used in hydraulic environments. The cavitation erosion resistance was substantially [...] Read more.

The cavitation erosion resistance of CuAl10Ni5Fe2.5Mn1 following plasma spraying with Al₂O₃·30(Ni₂₀Al) powder and laser re-melting was analyzed in view of possible improvements of the lifetime of components used in hydraulic environments. The cavitation erosion resistance was substantially improved compared with the one of the base material. The thickness of the re-melted layer was in the range of several hundred micrometers, with a surface microhardness increasing from 250 to 420 HV 0.2. Compositional, structural, and microstructural explorations showed that the microstructure of the re-melted and homogenized layer, consisting of a cubic Al₂O₃ matrix with dispersed Ni-based solid solution is associated with the hardness increase and consequently with the improvement of the cavitation erosion resistance. Full article

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892 KiB

Open AccessArticle

Surface Morphology and Tooth Adhesion of a Novel Nanostructured Dental Restorative Composite

by Marco Salerno, Patrizia Loria, Giunio Matarazzo, Francesco Tomè, Alberto Diaspro and Roberto Eggenhöffner

Materials 2016, 9(3), 203; https://doi.org/10.3390/ma9030203 - 16 Mar 2016

Cited by 20 | Viewed by 4737

Abstract

Recently, a novel dental restorative composite based on nanostructured micro-fillers of anodic porous alumina has been proposed. While its bulk properties are promising thanks to decreased aging and drug delivery capabilities, its surface properties are still unknown. Here we investigated the surface morphology [...] Read more.

Recently, a novel dental restorative composite based on nanostructured micro-fillers of anodic porous alumina has been proposed. While its bulk properties are promising thanks to decreased aging and drug delivery capabilities, its surface properties are still unknown. Here we investigated the surface morphology and the adhesion to tooth dentin of this composite as prepared. For comparison, we used two commercial composites: Tetric EVO Flow (Ivoclar) and Enamel HRi Plus (Micerium). The surface morphology was characterized by atomic force microscopy and the adhesion strength by tensile tests. The experimental composite is rougher than the commercial composites, with root mean square roughness of ~549 nm against 170–511 nm, and presents an adhesion strength of ~15 MPa against 19–21 MPa. These results show at the same time some proximity to the commercial composites, but also the need for optimization of the experimental material formulation. Full article

(This article belongs to the Section Biomaterials)

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3460 KiB

Open AccessFeature PaperArticle

Study of Polydiacetylene-Poly (Ethylene Oxide) Electrospun Fibers Used as Biosensors

by A K M Mashud Alam, Janet P. Yapor, Melissa M. Reynolds and Yan Vivian Li

Materials 2016, 9(3), 202; https://doi.org/10.3390/ma9030202 - 16 Mar 2016

Cited by 26 | Viewed by 8061

Abstract

Polydiacetylene (PDA) is an attractive conjugated material for use in biosensors due to its unique characteristic of undergoing a blue-to-red color change in response to external stimuli. 10,12-Pentacosadiynoic acid (PCDA) and poly (ethylene oxide) (PEO) were used in this study to develop fiber [...] Read more.

Polydiacetylene (PDA) is an attractive conjugated material for use in biosensors due to its unique characteristic of undergoing a blue-to-red color change in response to external stimuli. 10,12-Pentacosadiynoic acid (PCDA) and poly (ethylene oxide) (PEO) were used in this study to develop fiber composites via an electrospinning method at various mass ratios of PEO to PCDA, solution concentrations, and injection speeds. The PEO-PDA fibers in blue phase were obtained via photo-polymerization upon UV-light irritation. High mass ratios of PEO to PCDA, low polymer concentrations of spinning solution, and low injection speeds promoted fine fibers with small diameters and smooth surfaces. The colorimetric transition of the fibers was investigated when the fibers were heated at temperatures ranging from 25 °C to 120 °C. A color switch from blue to red in the fibers was observed when the fibers were heated at temperatures greater than 60 °C. The color transition was more sensitive in the fibers made with a low mass ratio of PEO to PCDA due to high fraction of PDA in the fibers. The large diameter fibers also promoted the color switch due to high reflectance area in the fibers. All of the fibers were analyzed using Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) and compared before and after the color change occurred. The colorimetric transitional mechanism is proposed to occur due to conformational changes in the PDA macromolecules. Full article

(This article belongs to the Section Advanced Composites)

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Schematic representation of the electrospinning of poly (ethylene oxide) (PEO) -Polydiacetylene (PDA) composite fibers. Full article ">Figure 2
Fiber diameters are illustrated as a function of polymer concentration, mass ratios of PEO and PCDA, and injection speed. The injection speed used was 0.1 mL·h−1 (■, ▲ ♦) and 0.2 mL·h−1 (●, ▼, ◄), respectively. Finer fibers were formed at higher mass ratios, lower concentrations, and the lower injection speeds. Full article ">Figure 3
SEM images of PEO-PDA electrospun fibers. Fibers presented in first column (A–F); second column (G–L); and third column (M–R) were prepared at low concentrations, medium concentrations and high concentrations respectively. Respective mass ratio, and injection speed are mentioned respectively at the left and right side of the fiber images. Fibers with beads were prepared at low concentrations (A–F) irrespective of mass ratio of PEO to PCDA. Number of beads were higher at low (0.1 mL·h−1) injection speed (A, C, and E) as compared to the high (0.2 mL·h−1) injection speed (B, D and F). Smooth fibers were developed with an increase in concentration and injection speed. Full article ">Figure 4
(A) Reflectance spectra of the selected PEO-PDA fiber (Fiber #9) treated at selected temperatures (25 °C, 60 °C, 70 °C, 90 °C, 100 °C, and 120 °C). The inserted photographs show the color of the fibers. The fibers treated at 70 °C began to exhibit colorimetric transition on both the reflectance spectra and the photograph. The color switch in the fiber was continuously developed until the temperature was 110 °C. No further change in either reflectance spectra or photograph was observed at 120 °C; (B) Reflectance at 600 nm for the fibers treated at different temperature is plotted as a function of temperature ranging from 25 °C to 120 °C. The same color switch behavior was clearly observed when the temperature was more than 60 °C. Full article ">Figure 5
Normalized reflectance spectra of 18 fibers that were heated at 70 °C for 10 min. (A) Fibers #1–#6 have mass ratio of PEO to PCDA of 2:1; (B): Fibers #7–#12 have mass ratio of PEO to PCDA of 3:1; (C): Fibers #13–#18 have mass ratio of PEO to PCDA of 4:1. The inserted figures show the diameters of the corresponding fibers. Fibers #1–#6 exhibit a more pronounced reflectance switch from blue to red. Full article ">Figure 6
Fourier transform infrared spectroscopy (FT-IR) spectra of PEO-PDA fibers and PDA polymers. The signals correspond to: blue PEO-PDA fibers (A), red PEO-PDA fibers (B), blue PDA (C), and red PDA (D). Full article ">Figure 7
Differential scanning calorimetry (DSC) plot of PEO-PDA fibers: (A) blue fibers; and (B) red fibers. Full article ">Figure 8
An illustration of color transition from blue to red in PEO-PDA fiber mat, which is due to a C-C bond rotation induced by heat treatment. Full article ">

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Open AccessFeature PaperArticle

Controlled Photocatalytic Synthesis of Core–Shell SiC/Polyaniline Hybrid Nanostructures

by Attila Kormányos, Balázs Endrődi, Róbert Ondok, András Sápi and Csaba Janáky

Materials 2016, 9(3), 201; https://doi.org/10.3390/ma9030201 - 16 Mar 2016

Cited by 17 | Viewed by 7190

Abstract

Hybrid materials of electrically conducting polymers and inorganic semiconductors form an exciting class of functional materials. To fully exploit the potential synergies of the hybrid formation, however, sophisticated synthetic methods are required that allow for the fine-tuning of the nanoscale structure of the [...] Read more.

Hybrid materials of electrically conducting polymers and inorganic semiconductors form an exciting class of functional materials. To fully exploit the potential synergies of the hybrid formation, however, sophisticated synthetic methods are required that allow for the fine-tuning of the nanoscale structure of the organic/inorganic interface. Here we present the photocatalytic deposition of a conducting polymer (polyaniline) on the surface of silicon carbide (SiC) nanoparticles. The polymerization is facilitated on the SiC surface, via the oxidation of the monomer molecules by ultraviolet-visible (UV-vis) light irradiation through the photogenerated holes. The synthesized core–shell nanostructures were characterized by UV-vis, Raman, and Fourier Transformed Infrared (FT-IR) Spectroscopy, thermogravimetric analysis, transmission and scanning electron microscopy, and electrochemical methods. It was found that the composition of the hybrids can be varied by simply changing the irradiation time. In addition, we proved the crucial importance of the irradiation wavelength in forming conductive polyaniline, instead of its overoxidized, insulating counterpart. Overall, we conclude that photocatalytic deposition is a promising and versatile approach for the synthesis of conducting polymers with controlled properties on semiconductor surfaces. The presented findings may trigger further studies using photocatalysis as a synthetic strategy to obtain nanoscale hybrid architectures of different semiconductors. Full article

(This article belongs to the Special Issue Advancement of Photocatalytic Materials 2016)

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Open AccessArticle

Effect of Chromium on Corrosion Behavior of P110 Steels in CO₂-H₂S Environment with High Pressure and High Temperature

by Jianbo Sun, Chong Sun, Xueqiang Lin, Xiangkun Cheng and Huifeng Liu

Materials 2016, 9(3), 200; https://doi.org/10.3390/ma9030200 - 16 Mar 2016

Cited by 45 | Viewed by 7088

Abstract

The novel Cr-containing low alloy steels have exhibited good corrosion resistance in CO₂ environment, mainly owing to the formation of Cr-enriched corrosion film. In order to evaluate whether it is applicable to the CO₂ and H₂S coexistence conditions, the [...] Read more.

The novel Cr-containing low alloy steels have exhibited good corrosion resistance in CO₂ environment, mainly owing to the formation of Cr-enriched corrosion film. In order to evaluate whether it is applicable to the CO₂ and H₂S coexistence conditions, the corrosion behavior of low-chromium steels in CO₂-H₂S environment with high pressure and high temperature was investigated using weight loss measurement and surface characterization. The results showed that P110 steel suffered localized corrosion and both 3Cr-P110 and 5Cr-P110 steels exhibited general corrosion. However, the corrosion rate of 5Cr-P110 was the highest among them. The corrosion process of the steels was simultaneously governed by CO₂ and H₂S. The outer scales on the three steels mainly consisted of FeS_1?x crystals, whereas the inner scales on Cr-containing steels comprised of amorphous FeS_1?x, Cr(OH)₃ and FeCO₃, in contrast with the amorphous FeS_1?x and FeCO₃ mixture film of P110 steel. The more chromium the steel contains, the more chromium compounds the corrosion products contain. The addition of chromium in steels increases the uniformity of the Cr-enriched corrosion scales, eliminates the localized corrosion, but cannot decrease the general corrosion rates. The formation of FeS_1?x may interfere with Cr-enriched corrosion scales and lowering the corrosion performance of 3Cr-P110 and 5Cr-P110 steels. Full article

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10376 KiB

Open AccessArticle

Semisolid Microstructural Evolution during Partial Remelting of a Bulk Alloy Prepared by Cold Pressing of the Ti-Al-2024Al Powder Mixture

by Yahong Qin, Tijun Chen, Yingjun Wang, Xuezheng Zhang and Pubo Li

Materials 2016, 9(3), 199; https://doi.org/10.3390/ma9030199 - 16 Mar 2016

Cited by 13 | Viewed by 4715

Abstract

A new method, powder thixoforming, has been proposed to fabricate an in situ Al₃Ti_p/2024Al composite. During partial remelting, the microstructural evolution of the bulk alloy prepared by cold pressing of the Ti, Al, 2024Al powder mixture was investigated, and [...] Read more.

A new method, powder thixoforming, has been proposed to fabricate an in situ Al₃Ti_p/2024Al composite. During partial remelting, the microstructural evolution of the bulk alloy prepared by cold pressing of the Ti, Al, 2024Al powder mixture was investigated, and the formation mechanism of the Al₃Ti particles produced by the reaction between the Ti powder and the Al alloy melt is also discussed in detail. The results indicate that the microstructural evolution of the 2024 alloy matrix can be divided into three stages: a rapid coarsening of the powder grains; a formation of primary ?-Al particles surrounded with a continuous liquid film; and a slight coarsening of the primary ?-Al particles. Simultaneously, a reaction layer of Al₃Ti can be formed on the Ti powder surface when the bulk is heated for 10 min at 640 °C The thickness (X) of the reaction layer increases with the time according to the parabolic law of \(X = -0.43t^{2} + 4.21t + 0.17\). The stress generated in the reaction layer due to the volume dilatation can be calculated by using the equation? \(\sigma_{Al_{3}Ti} = -\frac{ E_{Al_{3}Ti} }{6(1-v{Al_{3}Ti})} \frac{ t^{3}_{Al_{3}Ti} }{t_{Ti}} \left(\frac{1}{R} - \frac{1}{R_{0}} \right) \). Comparing the obtained data with the results of the drip experiment, the reaction rate for the Ti powder and Al powder mixture is greater than that for the Ti plate and Al alloy mixture, respectively. Full article

(This article belongs to the Section Advanced Materials Characterization)

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3078 KiB

Open AccessArticle

Development and Characterization of a Bioinspired Bone Matrix with Aligned Nanocrystalline Hydroxyapatite on Collagen Nanofibers

by Hsi-Chin Wu, Tzu-Wei Wang, Jui-Sheng Sun, Yi-Hsuan Lee, Meng-Han Shen, Zong-Ruei Tsai, Chih-Yu Chen and Horng-Chaung Hsu

Materials 2016, 9(3), 198; https://doi.org/10.3390/ma9030198 - 15 Mar 2016

Cited by 24 | Viewed by 6485

Abstract

Various kinds of three-dimensional (3D) scaffolds have been designed to mimic the biological spontaneous bone formation characteristics by providing a suitable microenvironment for osteogenesis. In view of this, a natural bone-liked composite scaffold, which was combined with inorganic (hydroxyapatite, Hap) and organic (type [...] Read more.

Various kinds of three-dimensional (3D) scaffolds have been designed to mimic the biological spontaneous bone formation characteristics by providing a suitable microenvironment for osteogenesis. In view of this, a natural bone-liked composite scaffold, which was combined with inorganic (hydroxyapatite, Hap) and organic (type I collagen, Col) phases, has been developed through a self-assembly process. This 3D porous scaffold consisting of a c-axis of Hap nanocrystals (nHap) aligning along Col fibrils arrangement is similar to natural bone architecture. A significant increase in mechanical strength and elastic modulus of nHap/Col scaffold is achieved through biomimetic mineralization process when compared with simple mixture of collagen and hydroxyapatite method. It is suggested that the self-organization of Hap and Col produced in vivo could also be achieved in vitro. The oriented nHap/Col composite not only possesses bone-like microstructure and adequate mechanical properties but also enhances the regeneration and reorganization abilities of bone tissue. These results demonstrated that biomimetic nHap/Col can be successfully reconstructed as a bone graft substitute in bone tissue engineering. Full article

(This article belongs to the Section Biomaterials)

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Full article ">Figure 1
XRD patterns of Hap nanocrystals/ type I collagen composite (nHap/Col composite) scaffold after (A) 0.5; (B) 24 h reaction; and (C) standard reference of Hap (JCPDS No. 09-0432). Full article ">Figure 2
Schematic illustration of the biomimetic mineralization process of nHap/Col composite. Full article ">Figure 3
TEM images of mineralized nHap/Col composite material. (A) The c-axis of needle-like shape of Hap nanocrystals was specifically oriented along the longitudinal direction of the collagen fibrils; (B) each bundle consisting of Hap nanocrystals surrounded with Col fibrils; and (C) high-resolution TEM image with interplanar spacing corresponding to the (002) of Hap. Scale bar: (A) 100 nm; (B) 50 nm; and (C) 5 nm. Full article ">Figure 4
FTIR spectra of (a) nHap/Col scaffold after crosslinking; (b) nHap/Col scaffold without crosslinking; (c) pure collagen (Col); and (d) hydroxyapatite (Hap) materials. Full article ">Figure 5
SEM images of nHap/Col composite scaffolds. Scale bar: (A) 100 μm; (B) 5 μm; (C) EDX spectrum of the selected area of nHap/Col nanocomposite scaffold; inset table presents the atomic ratio, percentage of the components in the nHap/Col composite. Full article ">Figure 6
Stress-strain curves of nHap/Col composite scaffolds with different preparation process by compression test: (a) self-assembled mineralization method for 24 h reaction; (b) self-assembled mineralization method for 3 h reaction; (c) hydroxyapatite powder directly added into collagen slurry as simple mixture method. The mechanical properties of nHap/Col composite scaffold were summarized in the table. Full article ">Figure 7
(A,B) H&E; (C,D) ALP; (E,F) Alizarin Red and (G,H) Von Kossa stained histological sections of nHap/Col composite scaffolds in vitro. Full article ">

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Open AccessArticle

Post Processing and Biological Evaluation of the Titanium Scaffolds for Bone Tissue Engineering

by Bartłomiej Wysocki, Joanna Idaszek, Karol Szlązak, Karolina Strzelczyk, Tomasz Brynk, Krzysztof J. Kurzydłowski and Wojciech Święszkowski

Materials 2016, 9(3), 197; https://doi.org/10.3390/ma9030197 - 15 Mar 2016

Cited by 89 | Viewed by 11394

Abstract

Nowadays, post-surgical or post-accidental bone loss can be substituted by custom-made scaffolds fabricated by additive manufacturing (AM) methods from metallic powders. However, the partially melted powder particles must be removed in a post-process chemical treatment. The aim of this study was to investigate [...] Read more.

Nowadays, post-surgical or post-accidental bone loss can be substituted by custom-made scaffolds fabricated by additive manufacturing (AM) methods from metallic powders. However, the partially melted powder particles must be removed in a post-process chemical treatment. The aim of this study was to investigate the effect of the chemical polishing with various acid baths on novel scaffolds’ morphology, porosity and mechanical properties. In the first stage, Magics software (Materialise NV, Leuven, Belgium) was used to design a porous scaffolds with pore size equal to (A) 200 µm, (B) 500 µm and (C) 200 + 500 µm, and diamond cell structure. The scaffolds were fabricated from commercially pure titanium powder (CP Ti) using a SLM50 3D printing machine (Realizer GmbH, Borchen, Germany). The selective laser melting (SLM) process was optimized and the laser beam energy density in range of 91–151 J/mm³ was applied to receive 3D structures with fully dense struts. To remove not fully melted titanium particles the scaffolds were chemically polished using various HF and HF-HNO₃ acid solutions. Based on scaffolds mass loss and scanning electron (SEM) observations, baths which provided most uniform surface cleaning were proposed for each porosity. The pore and strut size after chemical treatments was calculated based on the micro-computed tomography (µ-CT) and SEM images. The mechanical tests showed that the treated scaffolds had Young’s modulus close to that of compact bone. Additionally, the effect of pore size of chemically polished scaffolds on cell retention, proliferation and differentiation was studied using human mesenchymal stem cells. Small pores yielded higher cell retention within the scaffolds, which then affected their growth. This shows that in vitro cell performance can be controlled to certain extent by varying pore sizes. Full article

(This article belongs to the Special Issue Metallic Scaffolds for Bone Regeneration)

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2689 KiB

Open AccessFeature PaperArticle

Blazed Gratings Recorded in Absorbent Photopolymers

by Roberto Fernández, Sergi Gallego, Andrés Márquez, Víctor Navarro-Fuster and Augusto Beléndez

Materials 2016, 9(3), 195; https://doi.org/10.3390/ma9030195 - 15 Mar 2016

Cited by 11 | Viewed by 4895

Abstract

Phase diffractive optical elements, which have many interesting applications, are usually fabricated using a photoresist. In this paper, they were made using a hybrid optic-digital system and a photopolymer as recording medium. We analyzed the characteristics of the input and recording light and [...] Read more.

Phase diffractive optical elements, which have many interesting applications, are usually fabricated using a photoresist. In this paper, they were made using a hybrid optic-digital system and a photopolymer as recording medium. We analyzed the characteristics of the input and recording light and then simulated the generation of blazed gratings with different spatial periods in different types of photopolymers using a diffusion model. Finally, we analyzed the output and diffraction efficiencies of the 0 and 1st order so as to compare the simulated values with those measured experimentally. We evaluated the effects of index matching in a standard PVA/AA photopolymer, and in a variation of Biophotopol, a more biocompatible photopolymer. Diffraction efficiencies near 70%, for a wavelength of 633 nm, were achieved for periods longer than 300 µm in this kind of materials. Full article

(This article belongs to the Special Issue Photopolymers for Holographic Applications)

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Experimental setup used to register and analyze in real-time the DOEs (blazed gratings): D, diaphragm; L, lens; BS, beam splitter; SF, spatial filter; LP, lineal polarizer; RF, red filter; M, mirror. Full article ">Figure 2
(a) The image on the photopolymer provided by the LCoS and captured by the CCD camera; and (b) the intensity profile provided by the LCoS across a vertical line of the image in (a). Full article ">Figure 3
Diagram of the blazed grating recording in the photopolymers with index matching. The “apparent” diffusion is due to the recovering surface changes and the “real” diffusion to the internal monomer motion. Full article ">Figure 4
(a) Comparison of the simulated and experimental DE of a 672 µm blazed grating during an exposure time of 300 s; (b) Comparison of the simulated and experimental DE of a 336 µm blazed grating during an exposure time of 300 s. Full article ">Figure 5
(a) Comparison of the simulated and experimental DE of a 672 um blazed grating recorded in PVA/NaAO material over a period of 300 s; (b) Comparison of the simulated and experimental DE a 336 μm blazed grating recorded in PVA/NaAO material over a period of 300 s. Full article ">Figure 6
Comparison of the simulation results of AA/PVA and PVA/NaAO based materials without the addition of the low pass filtering simulation to simulate the optical system. Full article ">

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Open AccessFeature PaperArticle

Influence of 4,4’-azobis (4-cyanopentanoic acid) in Transmission and Reflection Gratings Stored in a PVA/AA Photopolymer

by Elena Fernandez, Rosa Fuentes, Augusto Belendez and Inmaculada Pascual

Materials 2016, 9(3), 194; https://doi.org/10.3390/ma9030194 - 15 Mar 2016

Cited by 4 | Viewed by 4454

Abstract

Holographic transmission gratings with a spatial frequency of 2658 lines/mm and reflection gratings with a spatial frequency of 4553 lines/mm were stored in a polyvinyl alcohol (PVA)/acrylamide (AA) based photopolymer. This material can reach diffraction efficiencies close to 100% for spatial frequencies about [...] Read more.

Holographic transmission gratings with a spatial frequency of 2658 lines/mm and reflection gratings with a spatial frequency of 4553 lines/mm were stored in a polyvinyl alcohol (PVA)/acrylamide (AA) based photopolymer. This material can reach diffraction efficiencies close to 100% for spatial frequencies about 1000 lines/mm. However, for higher spatial frequencies, the diffraction efficiency decreases considerably as the spatial frequency increases. To enhance the material response at high spatial frequencies, a chain transfer agent, the 4,4’-azobis (4-cyanopentanoic acid), ACPA, is added to the composition of the material. Different concentrations of ACPA are incorporated into the main composition of the photopolymer to find the concentration value that provides the highest diffraction efficiency. Moreover, the refractive index modulation and the optical thickness of the transmission and reflection gratings were obtained, evaluated and compared to procure more information about the influence of the ACPA on them. Full article

(This article belongs to the Special Issue Photopolymers for Holographic Applications)

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Photograph of the photopolymer material after its manufacturing. Full article ">Figure 2
Transmission spectrum of the unexposed photopolymer plate. Full article ">Figure 3
(a) Experimental setup for transmission gratings; (b) experimental setup for reflection gratings. Mi: mirrors, BS: beam splitter, Li: lenses, SFi: microscope objective lens and pinhole, Di: diaphragms, θrecord is the angle with which the recording laser beams impinge in the material, θreconstr is the angle with which the reconstruction laser beam impinges in the material. Full article ">Figure 4
DE as a function of the reconstruction angle for transmission gratings stored with a spatial frequency of 2658 lines/mm for the compositions given in <a href="#materials-09-00194-t001" class="html-table">Table 1</a>, (a) C1 without ACPA; (b) C2 with CACPA = 0.006 M; (c) C3 with CACPA = 0.009 M; (d) C4 with CACP = 0.012 M; and (e) C5 with CACPA = 0.015 M. Full article ">Figure 5
Transmittance as a function of reconstruction wavelength for reflection gratings stored with a spatial frequency of 4558 lines/mm for the compositions of <a href="#materials-09-00194-t001" class="html-table">Table 1</a>, (a) C1 without ACPA; (b) C2 with CACPA = 0.006 M; (c) C3 with CACPA = 0.009 M; (d) C4 with CACPA = 0.012 M; and (e) C5 with CACPA = 0.015 M. Full article ">

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Open AccessArticle

Preparation and Characterization of All-Biomass Soy Protein Isolate-Based Films Enhanced by Epoxy Castor Oil Acid Sodium and Hydroxypropyl Cellulose

by La Wang, Jianzhang Li, Shifeng Zhang and Junyou Shi

Materials 2016, 9(3), 193; https://doi.org/10.3390/ma9030193 - 15 Mar 2016

Cited by 30 | Viewed by 6346

Abstract

All-biomass soy protein-based films were prepared using soy protein isolate (SPI), glycerol, hydroxypropyl cellulose (HPC) and epoxy castor oil acid sodium (ECOS). The effect of the incorporated HPC and ECOS on the properties of the SPI film was investigated. The experimental results showed [...] Read more.

All-biomass soy protein-based films were prepared using soy protein isolate (SPI), glycerol, hydroxypropyl cellulose (HPC) and epoxy castor oil acid sodium (ECOS). The effect of the incorporated HPC and ECOS on the properties of the SPI film was investigated. The experimental results showed that the tensile strength of the resultant films increased from 2.84 MPa (control) to 4.04 MPa and the elongation at break increased by 22.7% when the SPI was modified with 2% HPC and 10% ECOS. The increased tensile strength resulted from the reaction between the ECOS and SPI, which was confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). It was found that ECOS and HPC effectively improved the performance of SPI-based films, which can provide a new method for preparing environmentally-friendly polymer films for a number of commercial applications. Full article

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Graphical abstract
Full article ">Figure 1
Synthesis schematic of ECO. Full article ">Figure 2
1H NMR spectra of (a) castor oil; and (b) ECO. Full article ">Figure 3
ATR-FTIR spectra of SPI-based films: (A) the control, (B) add 1% HPC, (C) add 2% HPC, (D) add 5% HPC, (E) add 2% HPC and 10% ECOS, (F) add 2% HPC, 10% ECOS and alkenyl succinic anhydrides (ASA). Full article ">Figure 4
TG (a); and differential TG (b) patterns of the films: (A) the control, (B) add 1% HPC, (C) add 2% HPC, (D) add 5% HPC, (E) add 2% HPC and 10% ECOS, (F) add 2% HPC, 10% ECOS and alkenyl succinic anhydrides (ASA). Full article ">Figure 5
The XRD patterns (a); and relative crystallinity (b) of the films and HPC: (A) the control, (B) add 1% HPC, (C) add 2% HPC, (D) add 5% HPC, (E) add 2% HPC and 10% ECOS, (F) add 2% HPC, 10% ECOS and alkenyl succinic anhydrides (ASA). Full article ">Figure 6
SEM micrographs showed cross-sections of the six films. Magnification: 1600. (A) the control; (B) add 1% HPC; (C) add 2% HPC; (D) add 5% HPC; (E) add 2% HPC and 10% ECOS; (F) add 2% HPC, 10% ECOS and alkenyl succinic anhydrides (ASA). Full article ">Figure 7
The stress-strain curves of the films. (A) the control, (B) add 1% HPC, (C) add 2% HPC, (D) add 5% HPC, (E) add 2% HPC and 10% ECOS, (F) add 2% HPC, 10% ECOS and alkenyl succinic anhydrides (ASA). Full article ">

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Open AccessArticle

Molecular Mobility in Hyperbranched Polymers and Their Interaction with an Epoxy Matrix

by Frida Román, Pere Colomer, Yolanda Calventus and John M. Hutchinson

Materials 2016, 9(3), 192; https://doi.org/10.3390/ma9030192 - 15 Mar 2016

Cited by 18 | Viewed by 5917

Abstract

The molecular mobility related to the glass transition and secondary relaxations in a hyperbranched polyethyleneimine, HBPEI, and its relaxation behaviour when incorporated into an epoxy resin matrix are investigated by dielectric relaxation spectroscopy (DRS) and dynamic mechanical analysis (DMA). Three systems are analysed: [...] Read more.

The molecular mobility related to the glass transition and secondary relaxations in a hyperbranched polyethyleneimine, HBPEI, and its relaxation behaviour when incorporated into an epoxy resin matrix are investigated by dielectric relaxation spectroscopy (DRS) and dynamic mechanical analysis (DMA). Three systems are analysed: HBPEI, epoxy and an epoxy/HBPEI mixture, denoted ELP. The DRS behaviour is monitored in the ELP system in three stages: prior to curing, during curing, and in the fully cured system. In the stage prior to curing, DRS measurements show three dipolar relaxations: ?, ? and ?, for all systems (HBPEI, epoxy and ELP). The ?-relaxation for the ELP system deviates significantly from that for HBPEI, but superposes on that for the epoxy resin. The fully cured thermoset displays both ?- and ?-relaxations. In DMA measurements, both ?- and ?-relaxations are observed in all systems and in both the uncured and fully cured systems, similar to the behaviour identified by DRS. Full article

(This article belongs to the Section Advanced Materials Characterization)

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Open AccessArticle

Nanotextured Shrink Wrap Superhydrophobic Surfaces by Argon Plasma Etching

by Jolie M. Nokes, Himanshu Sharma, Roger Tu, Monica Y. Kim, Michael Chu, Ali Siddiqui and Michelle Khine

Materials 2016, 9(3), 196; https://doi.org/10.3390/ma9030196 - 14 Mar 2016

Cited by 18 | Viewed by 8301

Abstract

We present a rapid, simple, and scalable approach to achieve superhydrophobic (SH) substrates directly in commodity shrink wrap film utilizing Argon (Ar) plasma. Ar plasma treatment creates a stiff skin layer on the surface of the shrink film. When the film shrinks, the [...] Read more.

We present a rapid, simple, and scalable approach to achieve superhydrophobic (SH) substrates directly in commodity shrink wrap film utilizing Argon (Ar) plasma. Ar plasma treatment creates a stiff skin layer on the surface of the shrink film. When the film shrinks, the mismatch in stiffness between the stiff skin layer and bulk shrink film causes the formation of multiscale hierarchical wrinkles with nano-textured features. Scanning electron microscopy (SEM) images confirm the presence of these biomimetic structures. Contact angle (CA) and contact angle hysteresis (CAH) measurements, respectively, defined as values greater than 150° and less than 10°, verified the SH nature of the substrates. Furthermore, we demonstrate the ability to reliably pattern hydrophilic regions onto the SH substrates, allowing precise capture and detection of proteins in urine. Finally, we achieved self-driven microfluidics via patterning contrasting superhydrophilic microchannels on the SH Ar substrates to induce flow for biosensing. Full article

(This article belongs to the Special Issue Bioinspired and Biomimetic Materials)

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SEM images of shrunk surfaces that were not Ar-treated (A–C); and Ar-treated for (D–F) 1 min; (G–I) 30 min; and (J–L) 60 min. FFT graphs showing spatial frequency of the hierarchical features for shrunk Ar-treated samples at 1, 30, and 60 min (M–O). Full article ">Figure 2
SEM images of flat PO film without Ar treatment (A–C); and with 30 min Ar treatment (D–F). Full article ">Figure 3
Longer Ar plasma treatment times correspond to superhydrophobicity. (A) Water CA; and (B) CAH as a function of Ar plasma treatment time on shrunk PO substrates. Error bars correspond to standard error, and the dashed lines correspond to superhydrophobicity. Full article ">Figure 4
Air plasma was used to chemically pattern an array of hydrophilic anchor points (of sizes 2, 1, and 0.5 mm from top to bottom) from 2, 1, and 0.5 mm) on both non-treated and Ar-treated substrates. On the non-treated surface (left, top, and bottom) fluid (30, 15, and 5 µL) was not confined to the specified footprint. Conversely, on the SH Ar-treated surface (right, top, and bottom), the fluid remained within the patterned anchor point. The top images represent a top-down view of the droplets while the bottom images illustrate the side-view. Full article ">Figure 5
Urine spiked with BSA is detected by patterning the Ar plasma-treated samples for capture. Full article ">Figure 6
Superhydrophilic patterned channels allow fluid to wick along microchannels on the SH Ar-treated (bottom) samples but not along the flat, non-treated samples (top). Full article ">

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Open AccessArticle

A Novel HA/?-TCP-Collagen Composite Enhanced New Bone Formation for Dental Extraction Socket Preservation in Beagle Dogs

by Ko-Ning Ho, Eisner Salamanca, Kuo-Chi Chang, Tsai-Chin Shih, Yu-Chi Chang, Haw-Ming Huang, Nai-Chia Teng, Che-Tong Lin, Sheng-Wei Feng and Wei-Jen Chang

Materials 2016, 9(3), 191; https://doi.org/10.3390/ma9030191 - 11 Mar 2016

Cited by 19 | Viewed by 8169

Abstract

Past studies in humans have demonstrated horizontal and vertical bone loss after six months following tooth extraction. Many biomaterials have been developed to preserve bone volume after tooth extraction. Type I collagen serves as an excellent delivery system for growth factors and promotes [...] Read more.

Past studies in humans have demonstrated horizontal and vertical bone loss after six months following tooth extraction. Many biomaterials have been developed to preserve bone volume after tooth extraction. Type I collagen serves as an excellent delivery system for growth factors and promotes angiogenesis. Calcium phosphate ceramics have also been investigated because their mineral chemistry resembles human bone. The aim of this study was to compare the performance of a novel bioresorbable purified fibrillar collagen and hydroxyapatite/?-tricalcium phosphate (HA/?-TCP) ceramic composite versus collagen alone and a bovine xenograft-collagen composite in beagles. Collagen plugs, bovine graft-collagen composite and HA/?-TCP-collagen composite were implanted into the left and right first, second and third mandibular premolars, and the fourth molar was left empty for natural healing. In total, 20 male beagle dogs were used, and quantitative and histological analyses of the extraction ridge was done. The smallest width reduction was 19.09% ± 8.81% with the HA/?-TCP-collagen composite at Week 8, accompanied by new bone formation at Weeks 4 and 8. The HA/?-TCP-collagen composite performed well, as a new osteoconductive and biomimetic composite biomaterial, for socket bone preservation after tooth extraction. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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580 KiB

Open AccessReview

Repopulating Decellularized Kidney Scaffolds: An Avenue for Ex Vivo Organ Generation

by Robert A. McKee and Rebecca A. Wingert

Materials 2016, 9(3), 190; https://doi.org/10.3390/ma9030190 - 11 Mar 2016

Cited by 19 | Viewed by 7429

Abstract

Recent research has shown that fully developed organs can be decellularized, resulting in a complex scaffold and extracellular matrix (ECM) network capable of being populated with other cells. This work has resulted in a growing field in bioengineering focused on the isolation, characterization, [...] Read more.

Recent research has shown that fully developed organs can be decellularized, resulting in a complex scaffold and extracellular matrix (ECM) network capable of being populated with other cells. This work has resulted in a growing field in bioengineering focused on the isolation, characterization, and modification of organ derived acellular scaffolds and their potential to sustain and interact with new cell populations, a process termed reseeding. In this review, we cover contemporary advancements in the bioengineering of kidney scaffolds including novel work showing that reseeded donor scaffolds can be transplanted and can function in recipients using animal models. Several major areas of the field are taken into consideration, including the decellularization process, characterization of acellular and reseeded scaffolds, culture conditions, and cell sources. Finally, we discuss future avenues based on the advent of 3D bioprinting and recent developments in kidney organoid cultures as well as animal models of renal genesis. The ongoing mergers and collaborations between these fields hold the potential to produce functional kidneys that can be generated ex vivo and utilized for kidney transplantations in patients suffering with renal disease. Full article

(This article belongs to the Special Issue Regenerative Materials)

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2373 KiB

Open AccessArticle

Thermal Mechanical Processing Effects on Microstructure Evolution and Mechanical Properties of the Sintered Ti-22Al-25Nb Alloy

by Yuanxin Wang, Zhen Lu, Kaifeng Zhang and Dalin Zhang

Materials 2016, 9(3), 189; https://doi.org/10.3390/ma9030189 - 11 Mar 2016

Cited by 7 | Viewed by 5171

Abstract

This work illustrates the effect of thermal mechanical processing parameters on the microstructure and mechanical properties of the Ti-22Al-25Nb alloy prepared by reactive sintering with element powders, consisting of O, B2 and Ti₃Al phases. Tensile and plane strain fracture toughness tests [...] Read more.

This work illustrates the effect of thermal mechanical processing parameters on the microstructure and mechanical properties of the Ti-22Al-25Nb alloy prepared by reactive sintering with element powders, consisting of O, B2 and Ti₃Al phases. Tensile and plane strain fracture toughness tests were carried out at room temperature to understand the mechanical behavior of the alloys and its correlation with the microstructural features characterized by scanning and transmission electron microscopy. The results show that the increased tensile strength (from 340 to 500 MPa) and elongation (from 3.6% to 4.2%) is due to the presence of lamellar O/B2 colony and needle-like O phase in B2 matrix in the as-processed Ti-22Al-25Nb alloys, as compared to the coarse lath O adjacent to B2 in the sintered alloys. Changes in morphologies of O phase improve the fracture toughness (K_IC) of the sintered alloys from 7 to 15 MPa·m^?1/2. Additionally, the fracture mechanism shifts from cleavage fracture in the as-sintered alloys to quasi-cleavage fracture in the as-processed alloys. Full article

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1888 KiB

Open AccessFeature PaperArticle

Spatial Frequency Responses of Anisotropic Refractive Index Gratings Formed in Holographic Polymer Dispersed Liquid Crystals

by Yoshiaki Fukuda and Yasuo Tomita

Materials 2016, 9(3), 188; https://doi.org/10.3390/ma9030188 - 10 Mar 2016

Cited by 7 | Viewed by 6618

Abstract

We report on an experimental investigation of spatial frequency responses of anisotropic transmission refractive index gratings formed in holographic polymer dispersed liquid crystals (HPDLCs). We studied two different types of HPDLC materials employing two different monomer systems: one with acrylate monomer capable of [...] Read more.

We report on an experimental investigation of spatial frequency responses of anisotropic transmission refractive index gratings formed in holographic polymer dispersed liquid crystals (HPDLCs). We studied two different types of HPDLC materials employing two different monomer systems: one with acrylate monomer capable of radical mediated chain-growth polymerizations and the other with thiol-ene monomer capable of step-growth polymerizations. It was found that the photopolymerization kinetics of the two HPDLC materials could be well explained by the autocatalytic model. We also measured grating-spacing dependences of anisotropic refractive index gratings at a recording wavelength of 532 nm. It was found that the HPDLC material with the thiol-ene monomer gave higher spatial frequency responses than that with the acrylate monomer. Statistical thermodynamic simulation suggested that such a spatial frequency dependence was attributed primarily to a difference in the size of formed liquid crystal droplets due to different photopolymerization mechanisms. Full article

(This article belongs to the Special Issue Photopolymers for Holographic Applications)

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2027 KiB

Open AccessArticle

PEEK Primary Crowns with Cobalt-Chromium, Zirconia and Galvanic Secondary Crowns with Different Tapers—A Comparison of Retention Forces

by Veronika Stock, Patrick R. Schmidlin, Susanne Merk, Christina Wagner, Malgorzata Roos, Marlis Eichberger and Bogna Stawarczyk

Materials 2016, 9(3), 187; https://doi.org/10.3390/ma9030187 - 10 Mar 2016

Cited by 34 | Viewed by 7833

Abstract

In prosthetic dentistry, double crown systems have proved their suitability as retainers for removable partial dentures. However, investigations in this context, regarding polyetheretherketone, are scarce. Therefore, the aim of this study was to test the retention force (RF) between polyetheretherketone (PEEK) primary and [...] Read more.

In prosthetic dentistry, double crown systems have proved their suitability as retainers for removable partial dentures. However, investigations in this context, regarding polyetheretherketone, are scarce. Therefore, the aim of this study was to test the retention force (RF) between polyetheretherketone (PEEK) primary and cobalt-chromium (CoCr), zirconia (ZrO₂) and galvanic (GAL) secondary crowns with three different tapers. Primary PEEK-crowns were milled with the tapers 0°, 1°, and 2° (n = 10/taper, respectively). Afterwards, 90 secondary crowns were fabricated: (i) 30 CoCr-crowns milled from Ceramill Sintron (AmannGirrbach, Koblach, Austria) (n = 10/taper), (ii) 30 ZrO₂-crowns milled from Ceramill ZI (AmannGirrbach, Koblach, Austria) (n = 10/taper), and (iii) 30 GAL-crowns made using electroforming (n = 10/taper). RF was measured in a pull-off test (20 pull-offs/specimen) and data were analyzed using 2-/1-way Analysis of Variance (ANOVA) followed by the Tukey-Honestly Significant Difference (HSD) post hoc test and linear regression analyses (p < 0.05). The measured mean RF values ranged between 9.6 and 38.2 N. With regard to the 0°, 1°, and 2° tapered crowns, no statistically significant differences between CoCr and ZrO₂ were observed (p > 0.141). At 0° taper, no differences in retention forces between GAL, CrCr, and ZrO₂ crowns were found (p = 0.075). However, at 1° and 2° taper, lower RF for GAL-crowns were observed (p < 0.009, p < 0.001, respectively). According to this laboratory study, PEEK might be a suitable material for primary crowns, regardless of the taper and the material of secondary crown. Long-term results, however, are still necessary. Full article

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4051 KiB

Open AccessArticle

Topological Design of Cellular Phononic Band Gap Crystals

by Yang Fan Li, Xiaodong Huang and Shiwei Zhou

Materials 2016, 9(3), 186; https://doi.org/10.3390/ma9030186 - 10 Mar 2016

Cited by 62 | Viewed by 7868

Abstract

This paper systematically investigated the topological design of cellular phononic crystals with a maximized gap size between two adjacent bands. Considering that the obtained structures may sustain a certain amount of static loadings, it is desirable to ensure the optimized designs to have [...] Read more.

This paper systematically investigated the topological design of cellular phononic crystals with a maximized gap size between two adjacent bands. Considering that the obtained structures may sustain a certain amount of static loadings, it is desirable to ensure the optimized designs to have a relatively high stiffness. To tackle this issue, we conducted a multiple objective optimization to maximize band gap size and bulk or shear modulus simultaneously with a prescribed volume fraction of solid material so that the resulting structures can be lightweight, as well. In particular, we first conducted the finite element analysis of the phononic band gap crystals and then adapted a very efficient optimization procedure to resolve this problem based on bi-directional evolutionary structure optimization (BESO) algorithm in conjunction with the homogenization method. A number of optimization results for maximizing band gaps with bulk and shear modulus constraints are presented for out-of-plane and in-plane modes. Numerical results showed that the optimized structures are similar to those obtained for composite case, except that additional slim connections are added in the cellular case to support the propagation of shear wave modes and meanwhile to satisfy the prescribed bulk or shear modulus constraints. Full article

(This article belongs to the Special Issue Cellular Materials: Design and Optimisation)

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2338 KiB

Open AccessArticle

Strength Development and Hydration Behavior of Self-Activation of Commercial Ground Granulated Blast-Furnace Slag Mixed with Purified Water

by Hyeoneun Park, Yeonung Jeong, Jae-Hong Jeong and Jae Eun Oh

Materials 2016, 9(3), 185; https://doi.org/10.3390/ma9030185 - 10 Mar 2016

Cited by 28 | Viewed by 6518

Abstract

In this study, ground granulated blast-furnace slag (GGBFS) samples from Singapore, Korea, and the United Arab Emirates were hydrated with purified water to estimate the cementing capabilities without activators. Raw GGBFS samples and hardened pastes were characterized to provide rational explanations for the [...] Read more.

In this study, ground granulated blast-furnace slag (GGBFS) samples from Singapore, Korea, and the United Arab Emirates were hydrated with purified water to estimate the cementing capabilities without activators. Raw GGBFS samples and hardened pastes were characterized to provide rational explanations for the strengths and hydration products. The slag characteristics that influenced the best strength of raw GGBFS were identified. Although it is widely recognized that GGBFS alone generally shows little cementing capability when hydrated with water, the GGBFSs examined in this study demonstrated various strength developments and hydration behaviors; one of the GGBFS samples even produced a high strength comparable to that of alkali- or Ca(OH)₂-activated GGBFS. In particular, as the GGBFS exhibited a greater number of favorable slag characteristics for hydraulic reactivity, it produced more C-S-H and ettringite. The results demonstrated a reasonable potential for commercial GGBFS with calcium sulfates to function as an independent cementitious binder without activators. Full article

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Materials, Volume 9, Issue 3 (March 2016) – 95 articles

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