Materials

10 pages, 3626 KiB

Open AccessArticle

Carbon-Bonded Alumina Filters Coated by Graphene Oxide for Water Treatment

by Ondřej Jankovský, Michal Lojka, Adéla Jiříčková, Christos G. Aneziris, Enrico Storti and David Sedmidubský

Materials 2020, 13(8), 2006; https://doi.org/10.3390/ma13082006 - 24 Apr 2020

Cited by 6 | Viewed by 3595

Abstract

The aim of this paper is to prepare nano-functionalized ceramic foam filters from carbon-bonded alumina. The carbon-bonded filters were produced via the Schwartzwalder process using a two-step approach. The prepared ceramic foam filters were further coated using graphene oxide. Graphene oxide was prepared [...] Read more.

The aim of this paper is to prepare nano-functionalized ceramic foam filters from carbon-bonded alumina. The carbon-bonded filters were produced via the Schwartzwalder process using a two-step approach. The prepared ceramic foam filters were further coated using graphene oxide. Graphene oxide was prepared by the modified Tour method. The C/O of the graphene oxide ratio was evaluated by XPS, EDS and elemental analysis (EA). The amount and type of individual oxygen functionalities were characterized by XPS and Raman spectroscopy. The microstructure was studied by TEM, and XRD was used to evaluate the interlayer distance. In the next step, filters were coated by graphene oxide using dip-coating. After drying, the prepared composite filters were used for the purification of the water containing lead, zinc and cadmium ions. The efficiency of the sorption was very high, suggesting the potential use of these materials for the treatment of wastewater from heavy metals. Full article

(This article belongs to the Special Issue Synthesis and Properties of Nano-Based Composites)

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Sorption experiment of the coated ceramic foam filter. Full article ">Figure 2
SEM micrographs (A), EDS maps of elements (B) and TEM images of GO (C). Full article ">Figure 3
Comparison of chemical composition obtained by (a) EDS, (b) EA, (c) XRF and (d) XPS. Full article ">Figure 4
XPS spectra of GO: survey spectra (left) and C1s detail (right). Full article ">Figure 5
XRD diffraction pattern of GO (left) and Raman spectrum of GO (right). Full article ">Figure 6
Photography of ceramic foam filters before the dip-coating (left) and after the dip-coating (right). Full article ">Figure 7
Optical microscopy of ceramic foam filter before the dip-coating: 20x magnification (left) and 50x magnification (right). Full article ">

16 pages, 3068 KiB

Open AccessArticle

Three-Dimensional Printed PLA and PLA/PHA Dumbbell-Shaped Specimens: Material Defects and Their Impact on Degradation Behavior

by Joanna Rydz, Jakub Włodarczyk, Jennifer Gonzalez Ausejo, Marta Musioł, Wanda Sikorska, Michał Sobota, Anna Hercog, Khadar Duale and Henryk Janeczek

Materials 2020, 13(8), 2005; https://doi.org/10.3390/ma13082005 - 24 Apr 2020

Cited by 13 | Viewed by 5084

Abstract

The use of (bio)degradable polymers, especially in medical applications, requires a proper understanding of their properties and behavior in various environments. Structural elements made of such polymers may be exposed to changing environmental conditions, which may cause defects. That is why it is [...] Read more.

The use of (bio)degradable polymers, especially in medical applications, requires a proper understanding of their properties and behavior in various environments. Structural elements made of such polymers may be exposed to changing environmental conditions, which may cause defects. That is why it is so important to determine the effect of processing conditions on polymer properties and also their subsequent behavior during degradation. This paper presents original research on a specimen’s damage during 70 days of hydrolytic degradation. During a standard hydrolytic degradation study of polylactide and polylactide/polyhydroxyalkanoate dumbbell-shaped specimens obtained by 3D printing with two different processing build directions, exhibited unexpected shrinkage phenomena in the last degradation series, representing approximately 50% of the length of the specimens irrespective of the printing direction. Therefore, the continuation of previous ex-ante research of advanced polymer materials is presented to identify any possible defects before they arise and to minimize the potential failures of novel polymer products during their use and also during degradation. Studies on the impact of a specific processing method, i.e., processing parameters and conditions, on the properties expressed in molar mass and thermal properties changes of specimens obtained by three-dimensional printing from polyester-based filaments, and in particular on the occurrence of unexpected shrinkage phenomena after post-processing heat treatment, are presented. Full article

(This article belongs to the Special Issue Applications of Novel Biodegradable Polymeric Materials)

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Macrographic images of the polylactide (PLA) and PLA/polyhydroxyalkanoate (PHA) dumbbell-shaped specimens obtained by 3D printing in horizontal (H) and vertical (V) directions before (A and C) and after 70 days of hydrolytic degradation test at 70 °C (B—the whole specimens after degradation, D—cut in half specimens after degradation). Full article ">Figure 2
Selected SEM micrographs (200×) of the upper (UH) and underside (BH) layers of PLA and PLA/PHA dumbbell-shaped specimens obtained by 3D printing in horizontal (H) and vertical (V) directions before (A) and after 70 days of hydrolytic degradation test at 70 °C (B) the whole specimens after degradation, (C) cut in half specimens after degradation). Full article ">Figure 3
Overlay of selected gel permeation chromatography (GPC) chromatograms of PLA and PLA/PHA dumbbell-shaped specimens obtained by 3D printing in horizontal (H) and vertical (V) directions after 70 days of degradation at 70 °C (column with a linear range up to Mw = 25,000 g/mol). A small picture shows the chromatogram of the material before degradation (two columns with a linear range of Mw = 200–2,000,000 g/mol). Full article ">Figure 4
Selected differential scanning calorimetry (DSC) curves (first heating run) for the PLA dumbbell-shaped specimen obtained by 3D printing in horizontal (H) direction (left) and PLA/PHA dumbbell-shaped specimen obtained by 3D printing in vertical (V) direction (right) before (0) and after 70 days of hydrolytic degradation of whole and cut in half specimens. Full article ">Figure 5
Tg shift of PLA dumbbell-shaped specimens obtained by 3D printing in horizontal (H) and vertical (V) directions in subsequent heating runs. Full article ">Figure 6
Selected DSC curves for the PLA dumbbell-shaped specimen PLA-1/165V-7, obtained by 3D printing at 1 mm/s and 165 min in vertical direction before and after 7 days of hydrolytic degradation. Full article ">Figure 7
Macrographic image of PLA-60/200 specimen conditioned 2 h at 110 °C before (A) and after (B) placing at 110 °C. Full article ">Figure 8
Shrinkage effect considered as thermal retraction; Tdef—deformation temperature, Tr—temperature of retraction process. Full article ">

11 pages, 3543 KiB

Open AccessArticle

Mechanical and Damping Properties of Recycled Aggregate Concrete Modified with Air-Entraining Agent and Polypropylene Fiber

by Chonggang Zhou, Xingwang Pei, Wenlong Li and Yijun Liu

Materials 2020, 13(8), 2004; https://doi.org/10.3390/ma13082004 - 24 Apr 2020

Cited by 11 | Viewed by 3040

Abstract

In this study, recycled aggregate concrete (RAC) modified with polypropylene fiber (PP) and air-entraining agent (AGA) was prepared, and the effects of PP and AGA on the static (compressive strength, Young’s modulus, and splitting tensile strength) and dynamic properties (dynamic modulus of elasticity [...] Read more.

In this study, recycled aggregate concrete (RAC) modified with polypropylene fiber (PP) and air-entraining agent (AGA) was prepared, and the effects of PP and AGA on the static (compressive strength, Young’s modulus, and splitting tensile strength) and dynamic properties (dynamic modulus of elasticity and damping ratio) of RAC were investigated. The experimental results showed that the addition of an AGA and PP had a favorable effect on the damping ratio of the concrete, however, the addition of the AGA had a slightly negative effect on the mechanical performance of the concrete. The AGA and PP contents required to achieve the optimum damping ratio of the concrete with the least reduction in the mechanical performance were 0.02% and 0.10%, respectively. Furthermore, the addition of AGA was more effective than that of PP in improving the damping property of the concrete. Full article

(This article belongs to the Section Construction and Building Materials)

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19 pages, 10289 KiB

Open AccessArticle

Experimental Tests, FEM Constitutive Modeling and Validation of PLGA Bioresorbable Polymer for Stent Applications

by Jakub Bukala, Piotr P. Buszman, Jerzy Małachowski, Lukasz Mazurkiewicz and Kamil Sybilski

Materials 2020, 13(8), 2003; https://doi.org/10.3390/ma13082003 - 24 Apr 2020

Cited by 24 | Viewed by 4628

Abstract

The use of bioresorbable polymers such as poly(lactic-co-glycolic acid) (PLGA) in coronary stents can hypothetically reduce the risk of complications (e.g., restenosis, thrombosis) after percutaneous coronary intervention. However, there is a need for a constitutive modeling strategy that combines the simplicity of implementation [...] Read more.

The use of bioresorbable polymers such as poly(lactic-co-glycolic acid) (PLGA) in coronary stents can hypothetically reduce the risk of complications (e.g., restenosis, thrombosis) after percutaneous coronary intervention. However, there is a need for a constitutive modeling strategy that combines the simplicity of implementation with strain rate dependency. Here, a constitutive modeling methodology for PLGA comprising numerical simulation using a finite element method is presented. First, the methodology and results of PLGA experimental tests are presented, with a focus on tension tests of tubular-type specimens with different strain rates. Subsequently, the constitutive modeling methodology is proposed and described. Material model constants are determined based on the results of the experimental tests. Finally, the developed methodology is validated by experimental and numerical comparisons of stent free compression tests with various compression speeds. The validation results show acceptable correlation in terms of both quality and quantity. The proposed and validated constitutive modeling approach for the bioresorbable polymer provides a useful tool for the design and evaluation of bioresorbable stents. Full article

(This article belongs to the Special Issue Processing, Structure, Dynamics and Mechanical Properties of Polymeric Materials)

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7 pages, 6298 KiB

Open AccessArticle

Vanadium-Oxide-Based Thin Films with Ultra-High Thermo-Optic Coefficients at 1550 nm and 2000 nm Wavelengths

by Mohamed Abdel-Rahman, Esam Bahidra and Ahmed Fauzi Abas

Materials 2020, 13(8), 2002; https://doi.org/10.3390/ma13082002 - 24 Apr 2020

Cited by 2 | Viewed by 2597

Abstract

In this paper, the temperature-dependent dielectric properties of vanadium-sesquioxide-based thin films are studied to assess their suitability for thermally tunable filters at optical communication wavelengths. Spectroscopic ellipsometry is utilized to measure the optical constants of vanadium oxide thin films at temperatures ranging from [...] Read more.

In this paper, the temperature-dependent dielectric properties of vanadium-sesquioxide-based thin films are studied to assess their suitability for thermally tunable filters at optical communication wavelengths. Spectroscopic ellipsometry is utilized to measure the optical constants of vanadium oxide thin films at temperatures ranging from 25 °C to 65 °C. High thermo-optic coefficients (dn/dTs) were observed. The highest dn/dTs, measured at approximately 40 °C, were −8.4 × 10⁻³/°C and −1.05 × 10⁻²/°C at 1550 nm and 2000 nm, respectively. Full article

(This article belongs to the Special Issue Advanced Materials for Photonics and Photovoltaics Applications)

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A schematic diagram of the ellipsometer setup used to measure the psi (Ψ) and delta (Δ) parameters of the vanadium oxide/silicon dioxide/silicon substrate structure. Full article ">Figure 2
Refractive index (n) versus wavelength at temperatures ranging from 25 °C to 65 °C. Full article ">Figure 3
Extinction coefficient (k) versus wavelength at temperatures ranging from 25 °C to 65 °C. Full article ">Figure 4
Real part of the material’s permittivity (ε1) versus wavelength at temperatures ranging from 25 °C to 65 °C. Full article ">Figure 5
Imaginary part of the material’s permittivity (ε2) versus wavelength at temperatures ranging from 25 °C to 65 °C. Full article ">Figure 6
Refractive index (n) versus temperature at 1550 nm and 2000 nm wavelengths. Full article ">Figure 7
Extinction coefficient (k) versus temperature at 1550 nm and 2000 nm wavelengths. Full article ">Figure 8
dn/dT versus temperature at 1550 nm and 2000 nm wavelengths. Full article ">

14 pages, 1664 KiB

Open AccessArticle

Chloride Diffusion in Concrete Protected with a Silane-Based Corrosion Inhibitor

by Luigi Coppola, Denny Coffetti, Elena Crotti, Gabriele Gazzaniga and Tommaso Pastore

Materials 2020, 13(8), 2001; https://doi.org/10.3390/ma13082001 - 24 Apr 2020

Cited by 26 | Viewed by 3531

Abstract

One of the most important parameters concerning durability is undoubtedly represented by cement matrix resistance to chloride diffusion in environments where reinforced concrete structures are exposed to the corrosion risk induced by marine environment or de-icing salts. This paper deals with protection from [...] Read more.

One of the most important parameters concerning durability is undoubtedly represented by cement matrix resistance to chloride diffusion in environments where reinforced concrete structures are exposed to the corrosion risk induced by marine environment or de-icing salts. This paper deals with protection from chloride ingress by a silane-based surface-applied corrosion inhibitor. Results indicated that the corrosion inhibitor (CI) allows to reduce the penetration of chloride significantly compared to untreated specimens, independently of w/c, cement type, and dosage. Reduction of chloride diffusion coefficient (D_nssn) measured by an accelerated test in treated concrete was in the range 30–60%. Natural chloride diffusion test values indicate a sharp decrease in apparent diffusion coefficient (D_app) equal to about 75% when concrete is protected by CI. Mechanism of action of CI in slowing down the chloride penetration inside the cement matrix is basically due to the water repellent effect as confirmed by data of concrete bulk electrical resistivity. Full article

(This article belongs to the Special Issue Corrosion in Concrete: Inhibitors and Coatings)

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12 pages, 3381 KiB

Open AccessArticle

Impact of Laser Structuring on Medical-Grade Titanium: Surface Characterization and In Vitro Evaluation of Osteoblast Attachment

by Kai Borcherding, Dennis Marx, Linda Gätjen, Uwe Specht, Dirk Salz, Karsten Thiel, Britt Wildemann and Ingo Grunwald

Materials 2020, 13(8), 2000; https://doi.org/10.3390/ma13082000 - 24 Apr 2020

Cited by 9 | Viewed by 3192

Abstract

Improved implant osteointegration offers meaningful potential for orthopedic, spinal, and dental implants. In this study, a laser treatment was used for the structuring of a titanium alloy (Ti6Al4V) surface combined with a titanium dioxide coating, whereby a porous surface was created. The objective [...] Read more.

Improved implant osteointegration offers meaningful potential for orthopedic, spinal, and dental implants. In this study, a laser treatment was used for the structuring of a titanium alloy (Ti6Al4V) surface combined with a titanium dioxide coating, whereby a porous surface was created. The objective was to characterize the pore structure shape, treatment-related metallographic changes, cytocompatibility, and attachment of osteoblast-like cells (MG-63). The treatment generated specific bottleneck pore shapes, offering the potential for the interlocking of osteoblasts within undercuts in the implant surface. The pore dimensions were a bottleneck diameter of 27 µm (SD: 4 µm), an inner pore width of 78 µm (SD: 6 µm), and a pore depth of 129 µm (SD: 8 µm). The introduced energy of the laser changed the metallic structure of the alloy within the heat-affected region (approximately 66 µm) without any indication of a micro cracking formation. The phase of the alloy (microcrystalline alpha + beta) was changed to a martensite alpha phase in the surface region and an alpha + beta phase in the transition region between the pores. The MG-63 cells adhered to the structured titanium surface within 30 min and grew with numerous filopodia over and into the pores over the following days. Cell viability was improved on the structured surface compared to pure titanium, indicating good cytocompatibility. In particular, the demonstrated affinity of MG-63 cells to grow into the pores offers the potential to provide significantly improved implant fixation in further in vivo studies. Full article

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Laser process scheme: spot diameter 107 µm (a), line spacing between the spots 107 µm (b), and distance pulses within a line 53.5 µm (c). Full article ">Figure 2
Scanning electron microscopy image of a titanium K-wire surface with (structured surface—right) and without laser treatment (smooth surface—left). Full article ">Figure 3
3D rendered micro-computed tomography (µCT) image of a laser-structured K-wire segment for structural analysis (surface, pores, micro cracking). Full article ">Figure 4
(A) Metallographic (etched) optical and (B) scanning electron microscope images of a titanium plate cross section after laser treatment, showing the structural composition: (1) surface region, (2) transition region, and (3) substrate region. Full article ">Figure 5
Scanning electron microscope image of a titanium plate surface after laser treatment, presented in cross section. Shown are the focused ion beam preparation sites for the (1) surface, (2) transition, and (3) substrate regions, and the corresponding (scanning) transmission electron microscopy images (1T, 2T, 3T) visualizing the crystalline structure. Full article ">Figure 6
Elemental distribution in each crystalline region of the laser-structured titanium plate (surface, transition, and substrate): STEM image of TEM lamella prepared using focused ion beam (FIB); field of analysis for energy-dispersive X-ray spectroscopy (EDX) and corresponding element mapping for titanium (green), aluminum (brown), vanadium (cyan), iron (blue), and oxygen (red) by EDX. Full article ">Figure 7
Scanning electron microscope images (overview, detailed) of human osteoblast-like cells (MG-63), visualizing the adhesion over a period of three days for different surface conditions. Full article ">Figure 8
WST-1 assay of the different surfaces in terms of viability (% of titanium surface). The results are displayed as mean values and standard errors (n = 3). Full article ">

10 pages, 2927 KiB

Open AccessArticle

Novel Graphene/In₂O₃ Nanocubes Preparation and Selective Electrochemical Detection for L-Lysine of Camellia nitidissima Chi

by Jinsheng Cheng, Sheng Zhong, Weihong Wan, Xiaoyuan Chen, Ali Chen and Ying Cheng

Materials 2020, 13(8), 1999; https://doi.org/10.3390/ma13081999 - 24 Apr 2020

Cited by 2 | Viewed by 2566

Abstract

In this work, novel graphene/In₂O₃ (GR/In₂O₃) nanocubes were prepared via one-pot solvothermal treatment, reduction reaction, and successive annealing technology at 600 °C step by step. Interestingly, In₂O₃ with featured cubic morphology was observed [...] Read more.

In this work, novel graphene/In₂O₃ (GR/In₂O₃) nanocubes were prepared via one-pot solvothermal treatment, reduction reaction, and successive annealing technology at 600 °C step by step. Interestingly, In₂O₃ with featured cubic morphology was observed to grow on multi-layered graphene nanosheets, forming novel GR/In₂O₃ nanocubes. The resulting nanocomposites were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), etc. Further investigations demonstrated that a selective electrochemical sensor based on the prepared GR/In₂O₃ nanocubes can be achieved. By using the prepared GR/In₂O₃-based electrochemical sensor, the enantioselective and chem-selective performance, as well as the optimal conditions for L-Lysine detection in Camellia nitidissima Chi, were evaluated. The experimental results revealed that the GR/In₂O₃ nanocube-based electrochemical sensor showed good chiral recognition features for L-lysine in Camellia nitidissima Chi with a linear range of 0.23–30 μmol·L⁻¹, together with selectivity and anti-interference properties for other different amino acids in Camellia nitidissima Chi. Full article

(This article belongs to the Section Carbon Materials)

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(a,b) TEM of GR/In2O3 nanocubes; (c,d) HRTEM of GR/In2O3 nanocubes, inserted image in (c) was electron diffraction of the prepared GR/In2O3 nanocubes. Full article ">Figure 2
(A) XRD spectra of (a) graphene, (b) GR/In(OH)3 intermediate, and (c) GR/In2O3 nanocubes; (B) energy dispersive spectroscopy (EDS) analysis of GR/In2O3 nanocubes. Full article ">Figure 3
Mechanism for the synthesis of the GR/In2O3 nanocubes. Full article ">Figure 4
Current responses obtained by GR/In2O3 nanocube-based electrochemical sensor of amino acids extraction in Camellia nitidissima Chi (extra addition D-Lys with a concentration of 0.45%), applied potential: 0.85 V. Full article ">Figure 5
Differential pulse voltammetry (DPV) responses of L-Lys by (a) electrode without GR/In2O3 nanocubes; (b) GR/In2O3 nanocube-based electrochemical sensor. Full article ">Scheme 1
Synthesis of GR/In2O3 nanocubes. Full article ">Scheme 2
Schematic diagram of GR/In2O3 nanocube-based selective electrochemical sensor for L-Lysine of Camellia nitidissima Chi. Full article ">

9 pages, 1603 KiB

Open AccessFeature PaperArticle

Biphenyl Wrinkled Mesoporous Silica Nanoparticles for pH-Responsive Doxorubicin Drug Delivery

by Jason Lin, Chuanqi Peng, Sanjana Ravi, A. K. M. Nur Alam Siddiki, Jie Zheng and Kenneth J. Balkus, Jr.

Materials 2020, 13(8), 1998; https://doi.org/10.3390/ma13081998 - 24 Apr 2020

Cited by 23 | Viewed by 4655

Abstract

Biphenyl wrinkled mesoporous silica nanoparticles with controlled particle size and high surface area were evaluated for the storage and delivery of doxorubicin. The average particle size and surface area were ~70 nm and ~1100 m²/g. The doxorubicin loading efficiency was 38.2 [...] Read more.

Biphenyl wrinkled mesoporous silica nanoparticles with controlled particle size and high surface area were evaluated for the storage and delivery of doxorubicin. The average particle size and surface area were ~70 nm and ~1100 m²/g. The doxorubicin loading efficiency was 38.2 ± 1.5 (w/w)% and the release was pH dependent. The breast cancer cell line, MCF-7 (Michigan Cancer Foundation-7) was used for the in vitro drug release study. The cytotoxicity of doxorubicin-loaded nanoparticles was significantly higher than free doxorubicin. Fluorescence images showed biphenyl wrinkled mesoporous silica (BPWS) uptake by the MCF-7 cells. The biphenyl bridged wrinkled silica nanoparticles appear promising for hydrophobic drug loading and delivery. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Potential Use in Healthcare )

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Biphenyl bridged wrinkled silica loaded with doxorubicin. Full article ">Figure 2
(a) Transmission electron microscopy (TEM) and (b) scanning electron microscopy (SEM) images of biphenyl wrinkled silica. Full article ">Figure 3
A plot of doxorubicin loading versus time for biphenyl wrinkled mesoporous silica (BPWS) nanoparticles. Full article ">Figure 4
A plot of percentage of doxorubicin (DOX) released versus time at pH 5.5 and pH 7.4. Full article ">Figure 5
A plot of cell viability versus DOX concentration for 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays of MCF-7 Cells with doxorubicin, DOX-loaded BPWS and free BPWS as well as the IC50 after 72 h. Full article ">Figure 6
Fluorescence images of cancer cell permeability and intracellular uptake from the (a) NHS-Fluorescein (FITC) fluorescence signal, (b) 4′,6-diamidino-2-phenylindole (DAPI) fluorescence signal, and (c) bright field merged image from FITC labeled biphenyl wrinkled mesoporous silica (FITC-BPWS) treated cells. Images (d) FITC fluorescence signal, (e) DAPI fluorescence signal, and (f) bright field merged image are from phosphate buffer solution (PBS)-treated cells. Full article ">

9 pages, 799 KiB

Open AccessArticle

3-D Printed Protective Equipment during COVID-19 Pandemic

by Christian Wesemann, Stefano Pieralli, Tobias Fretwurst, Julian Nold, Katja Nelson, Rainer Schmelzeisen, Elmar Hellwig and Benedikt Christopher Spies

Materials 2020, 13(8), 1997; https://doi.org/10.3390/ma13081997 - 24 Apr 2020

Cited by 67 | Viewed by 9465

Abstract

While the number of coronavirus cases from 2019 continues to grow, hospitals are reporting shortages of personal protective equipment (PPE) for frontline healthcare workers. Furthermore, PPE for the eyes and mouth, such as face shields, allow for additional protection when working with aerosols. [...] Read more.

While the number of coronavirus cases from 2019 continues to grow, hospitals are reporting shortages of personal protective equipment (PPE) for frontline healthcare workers. Furthermore, PPE for the eyes and mouth, such as face shields, allow for additional protection when working with aerosols. 3-D printing enables the easy and rapid production of lightweight plastic frameworks based on open-source data. The practicality and clinical suitability of four face shields printed using a fused deposition modeling printer were examined. The weight, printing time, and required tools for assembly were evaluated. To assess the clinical suitability, each face shield was worn for one hour by 10 clinicians and rated using a visual analogue scale. The filament weight (21–42 g) and printing time (1:40–3:17 h) differed significantly between the four frames. Likewise, the fit, wearing comfort, space for additional PPE, and protection varied between the designs. For clinical suitability, a chosen design should allow sufficient space for goggles and N95 respirators as well as maximum coverage of the facial area. Consequently, two datasets are recommended. For the final selection of the ideal dataset to be used for printing, scalability and economic efficiency need to be carefully balanced with an acceptable degree of protection. Full article

(This article belongs to the Special Issue Current and Future Trends in Dental Materials)

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19 pages, 6675 KiB

Open AccessArticle

The Effect of Mixed Doping on the Microstructure and Electrophysical Parameters of the Multicomponent PZT-Type Ceramics

by Dariusz Bochenek, Przemysław Niemiec and Grzegorz Dercz

Materials 2020, 13(8), 1996; https://doi.org/10.3390/ma13081996 - 24 Apr 2020

Cited by 14 | Viewed by 3215

Abstract

This work shows the influence of admixture on the basic properties of the multicomponent PbZr_1−xTi_xO₃ (PZT)-type ceramics. It presents the results of four compositions of PZT-type material with the general chemical formula, Pb_0.99M_0.01((Zr_0.49 [...] Read more.

This work shows the influence of admixture on the basic properties of the multicomponent PbZr_1−xTi_xO₃ (PZT)-type ceramics. It presents the results of four compositions of PZT-type material with the general chemical formula, Pb_0.99M_0.01((Zr_0.49Ti_0.51)_0.95Mn_0.021Sb_0.016W_0.013)_0.9975O₃, where, in the M position, a donor admixture was introduced, i.e., samarium (Sm³⁺), gadolinium (Gd³⁺), dysprosium (Dy³⁺) or lanthanum (La³⁺). The compositions of the PZT-type ceramics were obtained through the classic ceramic method, as a result of the synthesis of simple oxides. The X-ray diffraction (XRD) pattern studies showed that the obtained multicomponent PZT materials have a tetragonal structure with a P4mm point group. The microstructure of the obtained compositions is characterized by a well crystallized grain, with clearly visible grain boundaries. The composition with the admixture of lanthanum has the highest uniformity of fine grain microstructure, which positively affects its final dielectric and piezoelectric properties. In the multicomponent PZT-type ceramic, materials utilize the mixed (acceptor and donor) doping of the main compound. This dopiong method has a positive effect on the set of the electrophysical parameters of ceramic materials. Donor dopants W⁶⁺ (at positions B) and M³⁺ = Sm³⁺, Gd³⁺, Dy³⁺, and La³⁺ (at positions A) increase the dielectric and piezoelectric properties, while the acceptor dopant Sb³⁺ (at positions B) increases the time and temperature stability of the electrophysical parameters. In addition, the suitable selection of the set of admixtures improved the sinterability of the ceramic samples, as well as resulted in obtaining the required material with good piezoelectric parameters for the poling process. This research confirms that all ceramic compositions have a set of parameters suitable for applications in micromechatronics, for example, as actuators, piezoelectric transducers, and precision microswitches. Full article

(This article belongs to the Special Issue The Electrophysical Properties of Ceramic Materials)

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13 pages, 5011 KiB

Open AccessArticle

In Situ Ternary Boride: Effects on Densification Process and Mechanical Properties of WC-Co Composite Coating

by Junfeng Bao, Yueguang Yu, Bowen Liu, Chengchang Jia and Chao Wu

Materials 2020, 13(8), 1995; https://doi.org/10.3390/ma13081995 - 24 Apr 2020

Cited by 2 | Viewed by 2370

Abstract

New coatings resistant to corrosion in high-temperature molten zinc aluminum were prepared by supersonic flame spraying of various composite powders. These composite powders were prepared by mixing, granulation, and heat treatment of various proportions of Mo–B₄C powder and WC and Co [...] Read more.

New coatings resistant to corrosion in high-temperature molten zinc aluminum were prepared by supersonic flame spraying of various composite powders. These composite powders were prepared by mixing, granulation, and heat treatment of various proportions of Mo–B₄C powder and WC and Co powder. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF–STEM), energy dispersive X-ray spectroscopy (EDS), and mechanical analysis were used to study the effects of Mo–B₄C on the microstructure, phase, porosity, bonding strength, and elastic modulus of the composite powder and coating. Results show that the addition of an appropriate quantity of Mo–B₄C reacts with Co to form ternary borides CoMo₂B₂ and CoMoB. Ternary boride forms a perfect continuous interface, improving the mechanical properties and corrosion resistance property of the coating. When the amount of Mo–B₄C added was 35.2%, the mechanical properties of the prepared coating reached optimal values: minimum porosity of 0.31 ± 0.15%, coating bonding strength of 77.81 ± 1.77 MPa, nanoindentation hardness of 20.12 ± 1.85 GPa, Young’s modulus of 281.52 ± 30.22 GPa, and fracture toughness of 6.38 ± 0.45 MPa·m^1/2. Full article

(This article belongs to the Section Advanced Composites)

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18 pages, 5664 KiB

Open AccessArticle

Performance of Ceramic-Metal Composites as Potential Tool Materials for Friction Stir Welding of Aluminium, Copper and Stainless Steel

by Mart Kolnes, Jakob Kübarsepp, Fjodor Sergejev, Märt Kolnes, Marek Tarraste and Mart Viljus

Materials 2020, 13(8), 1994; https://doi.org/10.3390/ma13081994 - 24 Apr 2020

Cited by 15 | Viewed by 3680

Abstract

The aim of the research was to disclose the performance of ceramic-metal composites, in particular TiC-based cermets and WC-Co hardmetals, as tool materials for friction stir welding (FSW) of aluminium alloys, stainless steels and copper. The model tests were used to study the [...] Read more.

The aim of the research was to disclose the performance of ceramic-metal composites, in particular TiC-based cermets and WC-Co hardmetals, as tool materials for friction stir welding (FSW) of aluminium alloys, stainless steels and copper. The model tests were used to study the wear of tools during cutting of metallic workpiece materials. The primary focus was on the performance and degradation mechanism of tool materials during testing under conditions simulating the FSW process, in particular the welding process temperature. Carbide composites were produced using a common press-and-sinter powder metallurgy technique. The model tests were performed on a universal lathe at the cutting speeds enabling cutting temperatures comparable the temperatures of the FSW of aluminium alloys, stainless steels and pure copper. The wear rate of tools was evaluated as the shortening of the length of the cutting tool nose tip and reaction diffusion tests were performed for better understanding of the diffusion-controlled processes during tool degradation (wear). It was concluded that cermets, in particular TiC-NiMo with 75–80 wt.% TiC, show the highest performance in tests with counterparts from aluminium alloy and austenitic stainless steel. On the other hand, in the model tests with copper workpiece, WC-Co hardmetals, in particular composites with 90–94 wt.% WC, outperform most of TiC-based cermet, including TiC-NiMo. Tools from ceramic-metal composites wear most commonly by mechanisms based on adhesion and diffusion. Full article

(This article belongs to the Special Issue New Progresses in the Development, Microstructure and Properties of Ceramic-Metal Composites (Cermets))

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14 pages, 40301 KiB

Open AccessArticle

A Method for Instant Estimation of the Temperature Experienced by Fire-Damaged Reinforced Concrete Structures Using Titanium

by Sang-Rak Sim and Dong-Woo Ryu

Materials 2020, 13(8), 1993; https://doi.org/10.3390/ma13081993 - 24 Apr 2020

Cited by 6 | Viewed by 2459

Abstract

When a concrete structure is exposed to fire, its structural safety is significantly compromised due to the spalling of members and scaling of concrete. In addition, its durability is substantially reduced due to certain chemical changes such as the dehydration of Ca(OH)₂ [...] Read more.

When a concrete structure is exposed to fire, its structural safety is significantly compromised due to the spalling of members and scaling of concrete. In addition, its durability is substantially reduced due to certain chemical changes such as the dehydration of Ca(OH)₂, the main hydration product of concrete, and the rehydration of CaO. Therefore, when fire damage occurs to a reinforced concrete (RC) building, rapid diagnosis and evaluation techniques are required for immediate repair and reinforcement, requiring a crucial step of quantitatively determining the heating temperature. This study aims to demonstrate a method of estimating the heating temperature experienced by fire damaged RC buildings. The experiments utilized two short RC column specimens with embedded titanium strips. The discoloration characteristics of titanium at high temperatures provided a quick, accurate, and simple mechanism for the estimation of the heating temperature by depth. Empirical equations were derived to estimate the heating temperature as a function of the discoloration characteristics of titanium. Thereafter, a comparison of this estimated temperature with the actual heating temperature measured using thermocouples revealed an average error of less than 20 °C, thereby demonstrating a significantly good correlation and an extremely high reliability of the proposed method. Full article

(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)

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11 pages, 5837 KiB

Open AccessArticle

Bone Regeneration in Critical-Sized Bone Defects Treated with Additively Manufactured Porous Metallic Biomaterials: The Effects of Inelastic Mechanical Properties

by Marianne Koolen, Saber Amin Yavari, Karel Lietaert, Ruben Wauthle, Amir A. Zadpoor and Harrie Weinans

Materials 2020, 13(8), 1992; https://doi.org/10.3390/ma13081992 - 24 Apr 2020

Cited by 17 | Viewed by 4111

Abstract

Additively manufactured (AM) porous metallic biomaterials, in general, and AM porous titanium, in particular, have recently emerged as promising candidates for bone substitution. The porous design of such materials allows for mimicking the elastic mechanical properties of native bone tissue and showed to [...] Read more.

Additively manufactured (AM) porous metallic biomaterials, in general, and AM porous titanium, in particular, have recently emerged as promising candidates for bone substitution. The porous design of such materials allows for mimicking the elastic mechanical properties of native bone tissue and showed to be effective in improving bone regeneration. It is, however, not clear what role the other mechanical properties of the bulk material such as ductility play in the performance of such biomaterials. In this study, we compared the bone tissue regeneration performance of AM porous biomaterials made from the commonly used titanium alloy Ti6Al4V-ELI with that of commercially pure titanium (CP-Ti). CP-Ti was selected because of its high ductility as compared to Ti6Al4V-ELI. Critical-sized (6 mm diameter) femoral defects in rats were treated with implants made from both Ti6Al4V-ELI and CP-Ti. Bone regeneration was assessed up to 11 weeks using micro-CT scanning. The regenerated bone volume was assessed ex vivo followed by histology and biomechanical testing to assess osseointegration of the implants. The bony defects treated with AM CP-Ti implants generally showed higher volumes of regenerated bone as compared to those treated with AM Ti6Al4V-ELI. The torsional strength of the two titanium groups were similar however, and both considerably lower than those measured for intact bony tissue. These findings show the importance of material type and ductility of the bulk material in the ability for bone tissue regeneration of AM porous biomaterials. Full article

(This article belongs to the Special Issue Multifunctional Coatings for Bone Regenerative Medicine)

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Region of interest on micro-CT scanning. Bone volume inside (BVi) and bone volume outside (BVo) are defined as bone formed inside and outside the porous space and the medullary canal of the titanium implants. Scale bar indicates 1 µm. Full article ">Figure 2
SEM images of CP-Ti and Ti6Al4V ELI porous implants. Macroscopic overview (A,B), and enlarged details (C–F) of the two different porous titanium implants. Panels (E,F) are zoomed in pictures of panels (C,D). Full article ">Figure 3
Longitudinal quantification of bone regeneration. In vivo µCT scans after zero, four, eight, and eleven weeks; BVi and BVo: defined as bone formed inside and outside the porous space and in the medullary canal of the titanium implants. Values are expressed as mean and SD (n = 8 for CP-Ti and n = 8 for Ti6Al4V-ELI). * Indicates (borderline) significant differences between groups. Full article ">Figure 4
Representative longitudinal micro-CT scans of the femur illustrating the bone regeneration process. In vivo scans of defects grafted with two different titanium implants (CP-Ti or Ti6Al4V-ELI) after four, eight, and eleven weeks. In CP-Ti, there was more bone formation inside the canal of the titanium implants (red arrows), around (solid arrows), and inside (dotted arrows) the titanium implants compared to Ti6Al4V-ELI. Bone formation is mostly growing from the proximal ends. Distally from the Ti6Al4V-ELI implants, bone resorption is visualized (asterisk). Full article ">Figure 5
Histological evaluation of bone bridging. Representative transversal sections of femur defects eleven weeks after implantation of porous titanium implants; CP-Ti (A) and Ti6Al4V-ELI (C), including detailed view for CP-Ti (B) and Ti6Al4V-ELI (D). Sections are stained with basic fuchsine and methylene blue. Basic fuchsine stains bone pink, methylene blue stains fibrous tissue blue. B = bone, BM = bone marrow, F = fibrous tissue, T = titanium. Full article ">Figure 6
Bone bridging and mechanical strength. The remaining gap size after eleven weeks was used to indicate bridging success (A). Mechanical femoral strength (B) and rotation (C) after implantation of different types of porous titanium implants measured by torsion tests. * indicates significant differences between groups. Full article ">Figure 7
Illustration of bone bridging. Representative 3D micro-CT images showing the average extend of bone bridging of the CP-Ti and the Ti6Al4V-ELI titanium implants. Full article ">

12 pages, 1848 KiB

Open AccessArticle

CuSCN as the Back Contact for Efficient ZMO/CdTe Solar Cells

by Deng-Bing Li, Zhaoning Song, Sandip S. Bista, Fadhil K. Alfadhili, Rasha A. Awni, Niraj Shrestha, DeMilt Rhiannon, Adam B. Phillips, Michael J. Heben, Randy J. Ellingson, Feng Yan and Yanfa Yan

Materials 2020, 13(8), 1991; https://doi.org/10.3390/ma13081991 - 24 Apr 2020

Cited by 18 | Viewed by 4646

Abstract

The replacement of traditional CdS with zinc magnesium oxide (ZMO) has been demonstrated as being helpful to boost power conversion efficiency of cadmium telluride (CdTe) solar cells to over 18%, due to the reduced interface recombination and parasitic light absorption by the buffer [...] Read more.

The replacement of traditional CdS with zinc magnesium oxide (ZMO) has been demonstrated as being helpful to boost power conversion efficiency of cadmium telluride (CdTe) solar cells to over 18%, due to the reduced interface recombination and parasitic light absorption by the buffer layer. However, due to the atmosphere sensitivity of ZMO film, the post treatments of ZMO/CdTe stacks, including CdCl₂ treatment, back contact deposition, etc., which are critical for high-performance CdTe solar cells became crucial challenges. To realize the full potential of the ZMO buffer layer, plenty of investigations need to be accomplished. Here, copper thiocyanate (CuSCN) is demonstrated to be a suitable back-contact material with multi-advantages for ZMO/CdTe solar cells. Particularly, ammonium hydroxide as the solvent for CuSCN deposition shows no detrimental impact on the ZMO layer during the post heat treatment. The post annealing temperature as well as the thickness of CuSCN films are investigated. Finally, a champion power conversion efficiency of 16.7% is achieved with an open-circuit voltage of 0.857 V, a short-circuit current density of 26.2 mA/cm², and a fill factor of 74.0%. Full article

(This article belongs to the Special Issue Advances in Cadmium Telluride (CdTe) Thin Film Photovoltaic Solar Cells)

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(a) Solar cell capacitance simulator (SCAPS) modeling determined band diagram for the device with a structure of fluorine doped tin oxide coated glass (FTO)/zinc magnesium oxide (ZMO)/cadmium telluride (CdTe)/copper thiocyanate (CuSCN)/Au. (b) Steady-state PL spectra of CdTe-Cu and CdTe-CuSCN stacks deposited on soda lime glass substrates. Atomic force microscopy images showing the surface morphologies of (c) a bare CdTe film and (d) a CdTe film deposited with CuSCN. Full article ">Figure 2
Statistical results for MZO/CdTe solar cell performances of (a) PCE, (b) VOC, (c) FF, (d) JSC, (e) series resistance (RS), and (f) shunt resistance (RSH) with metallic Cu and spin-coated CuSCN annealed at different temperatures. Full article ">Figure 3
(a) Current density-voltage (J-V) and (b) external quantum efficiency (EQE) curves for the best devices with different back-contact treatment: evaporated Cu metal and spin-coated CuSCN with different annealing temperatures. Full article ">Figure 4
Statistical results for MZO/CdTe solar cell performances of (a) PCE, (b) VOC, (c) FF, (d) JSC, (e) series resistance (RS), and (f) shunt resistance (RSH) with different CuSCN film thicknesses tuned by varying the solution concentration and the spin-coating speed. Full article ">Figure 5
Temperature dependent dark J-V curves for devices with (a) Cu metal and (b) CuSCN as the back contact. (c) Arrhennius plots for the calculation of the back-barrier height for the devices with Cu metal and CuSCN as the back contact. Full article ">

10 pages, 1637 KiB

Open AccessArticle

Digitization of One-Piece Oral Implants: A Feasibility Study

by Stefano Pieralli, Benedikt Christopher Spies, Luisa Valentina Kohnen, Florian Beuer and Christian Wesemann

Materials 2020, 13(8), 1990; https://doi.org/10.3390/ma13081990 - 24 Apr 2020

Cited by 4 | Viewed by 3190

Abstract

For digital impression-making of two-piece oral implants, scan bodies are used to transfer the exact intraoral implant position to the dental laboratory. In this in vitro investigation, the accuracy of digitizing a one-piece ceramic oral implant without a scan body (OC) was compared [...] Read more.

For digital impression-making of two-piece oral implants, scan bodies are used to transfer the exact intraoral implant position to the dental laboratory. In this in vitro investigation, the accuracy of digitizing a one-piece ceramic oral implant without a scan body (OC) was compared to that of a standard two-piece titanium implant with a scan body (TT) and a preparation of a natural single tooth (ST). Furthermore, incomplete scans of OC simulating clinical compromising situations (OC_1–4) were redesigned using a virtual reconstruction tool (RT) and superimposed to OC. OC and TT oral implants and one ST were inserted into a mandible typodont model and digitized (N = 13) using two different intraoral scanners. The resulting virtual datasets were superimposed onto a three-dimensional (3D) laser scanner-based reference. Test and reference groups were aligned using an inspection software according to a best-fit algorithm, and circumferential as well as marginal discrepancies were measured. For the statistical evaluation, multivariate analyses of variance with post-hoc Tukey tests and students t-tests to compare both scanners were performed. A total of 182 datasets were analyzed. For circumferential deviations, no significant differences were found between ST, TT, and OC (p > 0.964), but increased deviations for OC_1–4 (p < 0.001) were observed. The measurements of the marginal deviations revealed that ST had the smallest deviations, and that there were no significant differences between TT, OC, and OC_1–4 (p > 0.979). Except for marginal deviation of OC (p < 0.001), the outcome was not affected by the scanner. Within the limitations of this study, digitization of OC is as accurate as that of TT, but less than that of ST. In the case of known geometries, post-processing of compromised scans with a virtual reconstruction results in accurate data. Full article

(This article belongs to the Special Issue Current and Future Trends in Dental Materials)

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Schematic illustration of the investigation groups. ST, single-tooth preparation; TT, one-piece titanium implant with a scan body; OC, one-piece ZrO2 implant; OC1, OC for matching with reconstruction support; OC2, simulated subgingival insertion of 1.5 mm; OC3, additional occlusal reduction of 1 mm; OC4, additional lateral reduction of 45°. Full article ">Figure 2
(A) Reconstruction tool for unmodified implants (OC1,2); (B) reconstruction tool for intraorally adjusted (OC3,4) implants. Full article ">Figure 3
Reconstruction procedure: (A) OC2 with 1.5 mm missing data marginally; (B) OC2 matched with RT; (C) both datasets combined. Full article ">Figure 4
Box and whisker plots of the minimum, maximum, interquartile range, median, and outliers for the absolute circumferential surface deviations. Full article ">Figure 5
Box and whisker plots of the minimum, maximum, interquartile range, median, and outliers for the absolute marginal surface deviations. Full article ">Figure 6
Representative measurements of OC2 with a tolerance of ±50 µm (green regions) for (A) circumferential deviations and (B) marginal deviations. Full article ">

16 pages, 4418 KiB

Open AccessArticle

Modulation of Entrapment Efficiency and In Vitro Release Properties of BSA-Loaded Chitosan Microparticles Cross-Linked with Citric Acid as a Potential Protein–Drug Delivery System

by Natalia Sedyakina, Andrey Kuskov, Kelly Velonia, Nataliya Feldman, Sergey Lutsenko and Grigory Avramenko

Materials 2020, 13(8), 1989; https://doi.org/10.3390/ma13081989 - 24 Apr 2020

Cited by 32 | Viewed by 4679

Abstract

Microparticles, aimed for oral protein and peptide drug delivery, were prepared via emulsion cross-linking using citric acid as cross-linker and polyglycerol polyricinoleate as surfactant. A comparative study of the interaction between chitosan and citric acid and its effect on the resulting microparticle properties [...] Read more.

Microparticles, aimed for oral protein and peptide drug delivery, were prepared via emulsion cross-linking using citric acid as cross-linker and polyglycerol polyricinoleate as surfactant. A comparative study of the interaction between chitosan and citric acid and its effect on the resulting microparticle properties was performed using different chitosan-to-cross-linker mass ratios and pH-values during fabrication of the microparticles. Non-cross-linked and cross-linked microparticles were studied in terms of size (4–12 μm), zeta potential (−15.7 to 12.8 mV), erosion (39.7–75.6%), a model protein encapsulation efficiency (bovine serum albumin) (6.8–27.6%), and loading capacity (10.4–40%). Fourier transform infrared spectroscopy and X-ray diffraction confirmed the ionic interaction between the protonated amine groups of chitosan and the carboxylate ions of the cross-linking agent. Scanning electron microscopy revealed that the non-cross-linked microparticles had an uneven shape with wrinkled surfaces, while the cross-linked formulations were spherical in shape with smooth surfaces. On the basis of these data, the role of the surfactant and microparticle structure on the release mechanism was proposed. Control of the microparticle shape and release mechanisms is expected to be crucial in developing carriers for the controlled delivery of proteins and peptides. Full article

(This article belongs to the Special Issue Nanomaterials for Drug Delivery Application)

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The effect of the chitosan-to-citric acid mass ratio and of pH of the polymer stock solution on the formation of the chitosan–citric acid complex at 20 °C (a,b) and 60 °C (c,d). Filled symbols (●) denote phase-separated systems, and open symbols (○) denote homogeneous systems. Full article ">Figure 2
Fourier transform infrared spectroscopy (FT-IR) spectra of the non-cross-linked MP5700 (a) and cross-linked MP5708 (b), MP5706 (c), MP5704 (d), MP5008 (e), and MP4008 (f) chitosan microparticles. Full article ">Figure 3
Scanning electron microscopy (SEM) microphotographs of the non-cross-linked MP5700 (a) and cross-linked MP5704 (b), MP5706 (c), MP5708 (d), MP5008 (e), and MP4008 (f) chitosan microparticles. Full article ">Figure 4
Dm (a,b), zeta potential (ZP) (c,d), erosion (e,f), encapsulation efficiency (EE), and loading capacity (LC) (g,h) for the non-cross-linked and cross-linked chitosan microparticles prepared at different polymer-to-crosslinker ratios (a,c,e,g) and pH values (b,d,f,h). The p-values (1—8.48 × 10−4; 2—5.26 × 10−3; 3—1.14 × 10−3; 4—2.1 × 10−7; 5—2.72 × 10−3; 6—2.13 × 10−3; 7—1.59 × 10−7; 8—1.33 × 10−3; 9—4,15 × 10−3; 10—6.92 × 10−6; 11—9.83 × 10−5; 12—4.78 × 10−7) were obtained from the one-way analysis of variance (ANOVA). Full article ">Figure 5
The effect of the chitosan-to-citric acid mass ratio (a) and pH value of the polymer stock solution (b) on the in vitro cumulative release of bovine serum albumin (BSA) from the non-cross-linked and cross-linked chitosan microparticles. Full article ">Figure 6
Schematic representation of proposed microparticle structures and BSA (orange dots) loading patterns: microparticles with core–shell structure (a), microparticles possessing a high degree of cross-linking of the polymer matrix (b), and microparticles possessing a lower degree of cross-linking of the polymer matrix (c). Full article ">

15 pages, 3527 KiB

Open AccessFeature PaperArticle

Analytical Thermal Modeling of Powder Bed Metal Additive Manufacturing Considering Powder Size Variation and Packing

by Jinqiang Ning, Wenjia Wang, Xuan Ning, Daniel E. Sievers, Hamid Garmestani and Steven Y. Liang

Materials 2020, 13(8), 1988; https://doi.org/10.3390/ma13081988 - 24 Apr 2020

Cited by 18 | Viewed by 4841

Abstract

This work presents a computationally efficient predictive model based on solid heat transfer for temperature profiles in powder bed metal additive manufacturing (PBMAM) considering the heat transfer boundary condition and powder material properties. A point moving heat source model is used for the [...] Read more.

This work presents a computationally efficient predictive model based on solid heat transfer for temperature profiles in powder bed metal additive manufacturing (PBMAM) considering the heat transfer boundary condition and powder material properties. A point moving heat source model is used for the three-dimensional temperature prediction in an absolute coordinate. The heat loss from convection and radiation is calculated using a heat sink solution with a mathematically discretized boundary considering non-uniform temperatures and heat loss at the boundary. Powder material properties are calculated considering powder size statistical distribution and powder packing. The spatially uniform and temperature-independent material properties are employed in the temperature prediction. The presented model was tested in PBMAM of AlSi10Mg under different process conditions. The calculations of material properties are needed for AlSi10Mg because of the significant difference in thermal conductivity between powder form and solid bulk form. Close agreement is observed upon experimental validation on the molten pool dimensions. Full article

(This article belongs to the Special Issue Recent Advances in Metal Additive Manufacturing)

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12 pages, 3067 KiB

Open AccessArticle

Porous Silicon-Zinc Oxide Nanocomposites Prepared by Atomic Layer Deposition for Biophotonic Applications

by Mykola Pavlenko, Valerii Myndrul, Gloria Gottardi, Emerson Coy, Mariusz Jancelewicz and Igor Iatsunskyi

Materials 2020, 13(8), 1987; https://doi.org/10.3390/ma13081987 - 24 Apr 2020

Cited by 21 | Viewed by 4175

Abstract

In the current research, a porous silicon/zinc oxide (PSi/ZnO) nanocomposite produced by a combination of metal-assisted chemical etching (MACE) and atomic layer deposition (ALD) methods is presented. The applicability of the composite for biophotonics (optical biosensing) was investigated. To characterize the structural and [...] Read more.

In the current research, a porous silicon/zinc oxide (PSi/ZnO) nanocomposite produced by a combination of metal-assisted chemical etching (MACE) and atomic layer deposition (ALD) methods is presented. The applicability of the composite for biophotonics (optical biosensing) was investigated. To characterize the structural and optical properties of the produced PSi/ZnO nanocomposites, several studies were performed: scanning and transmission electron microscopy (SEM/TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance, and photoluminescence (PL). It was found that the ALD ZnO layer fully covers the PSi, and it possesses a polycrystalline wurtzite structure. The effect of the number of ALD cycles and the type of Si doping on the optical properties of nanocomposites was determined. PL measurements showed a “shoulder-shape” emission in the visible range. The mechanisms of the observed PL were discussed. It was demonstrated that the improved PL performance of the PSi/ZnO nanocomposites could be used for implementation in optical biosensor applications. Furthermore, the produced PSi/ZnO nanocomposite was tested for optical/PL biosensing towards mycotoxins (Aflatoxin B1) detection, confirming the applicability of the nanocomposites. Full article

(This article belongs to the Special Issue Multifunctional Nanostructured Silicon Composites)

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SEM images of porous silicon (PSi) surface before and after 100 cycles of zinc oxide ALD: (a) n-type PSi; (b) p-type PSi; (c,d) n-and p-types PSi after zinc oxide (ZnO) deposition, respectively (insets: an EDX analysis). Full article ">Figure 2
(a) TEM imaging of ZnO nanocrystallites on PSi obtained after 100 ALD cycles; (b) FFT of the PSi/ZnO TEM image; (c) GIXRD spectra of PSi/ZnO nanocomposites with 250, 100, and 50 ALD cycles of ZnO in comparison to GIXRD spectrum of PSi. Standard diffraction peaks of wurtzite (pdf card #36-1451) are presented for reference. Full article ">Figure 3
XPS survey and core-level spectra of PSi/ZnO with 50, 100, and 250 ALD cycles: (a) total survey spectra; (b–d) O 1s, Zn 2p, Si 2p energy regions, respectively. Corresponding binding energy values obtained by the deconvolution of the detected peaks are shown in the insets. Full article ">Figure 4
Optical properties of the fabricated PSi/ZnO nanocomposites: (a) diffuse reflectance spectra of PSi/ZnO nanocomposites; (b) absorption edges and corresponding energy band gap values; photoluminescence spectra for (c) n-PSi/ZnO and (d) p-PSi/ZnO nanocomposites. The energy band diagrams of corresponding excitation mechanisms are depicted in the insets. Full article ">Figure 5
PL response of p-type PSi/ZnO toward different AFB1 concentrations. The inset graph indicates the linearity of PL response to three different concentrations of AFB1 in a half-logarithmic scale with an error bar. Full article ">

20 pages, 3725 KiB

Open AccessArticle

Modern Biodegradable Plastics—Processing and Properties: Part I

by Janusz Sikora, Łukasz Majewski and Andrzej Puszka

Materials 2020, 13(8), 1986; https://doi.org/10.3390/ma13081986 - 24 Apr 2020

Cited by 23 | Viewed by 6556

Abstract

This paper presents a characterization of a plastic extrusion process and the selected properties of three biodegradable plastic types, in comparison with LDPE (low-density polyethylene). The four plastics include: LDPE, commercial name Malen E FABS 23-D022; potato starch based plastic (TPS-P), BIOPLAST GF [...] Read more.

This paper presents a characterization of a plastic extrusion process and the selected properties of three biodegradable plastic types, in comparison with LDPE (low-density polyethylene). The four plastics include: LDPE, commercial name Malen E FABS 23-D022; potato starch based plastic (TPS-P), BIOPLAST GF 106/02; corn starch based plastic (TPS-C), BioComp^®BF 01HP; and a polylactic acid (polylactide) plastic (PLA), BioComp^®BF 7210. Plastic films with determined geometric parameters (thickness of the foil layer and width of the flattened foil sleeve) were produced from these materials (at individually defined processing temperatures), using blown film extrusion, by applying different extrusion screw speeds. The produced plastic films were tested to determine the geometrical features, MFR (melt flow rate), blow-up ratio, draw down ratio, mass flow rate, and exit velocity. The tests were complemented by thermogravimetry, differential scanning calorimetry, and chemical structure analysis. It was found that the biodegradable films were extruded at higher rate and mass flow rate than LDPE; the lowest thermal stability was ascertained for the film samples extruded from TPS-C and TPS-P, and that all tested biodegradable plastics contained polyethylene. Full article

(This article belongs to the Special Issue Processing, Structure, Dynamics and Mechanical Properties of Polymeric Materials)

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21 pages, 3730 KiB

Open AccessArticle

High Functionality Bio-Polyols from Tall Oil and Rigid Polyurethane Foams Formulated Solely Using Bio-Polyols

by Mikelis Kirpluks, Edgars Vanags, Arnis Abolins, Slawomir Michalowski, Anda Fridrihsone and Ugis Cabulis

Materials 2020, 13(8), 1985; https://doi.org/10.3390/ma13081985 - 24 Apr 2020

Cited by 42 | Viewed by 6131

Abstract

High-quality rigid polyurethane (PU) foam thermal insulation material has been developed solely using bio-polyols synthesized from second-generation bio-based feedstock. High functionality bio-polyols were synthesized from cellulose production side stream—tall oil fatty acids by oxirane ring-opening as well as esterification reactions with different polyfunctional [...] Read more.

High-quality rigid polyurethane (PU) foam thermal insulation material has been developed solely using bio-polyols synthesized from second-generation bio-based feedstock. High functionality bio-polyols were synthesized from cellulose production side stream—tall oil fatty acids by oxirane ring-opening as well as esterification reactions with different polyfunctional alcohols, such as diethylene glycol, trimethylolpropane, triethanolamine, and diethanolamine. Four different high functionality bio-polyols were combined with bio-polyol obtained from tall oil esterification with triethanolamine to develop rigid PU foam formulations applicable as thermal insulation material. The developed formulations were optimized using response surface modeling to find optimal bio-polyol and physical blowing agent: c-pentane content. The optimized bio-based rigid PU foam formulations delivered comparable thermal insulation properties to the petro-chemical alternative. Full article

(This article belongs to the Special Issue Performance Research of Polyurethane Foams and Composites)

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16 pages, 2356 KiB

Open AccessArticle

Nonlinear Buckling Behavior of Spiral Corrugated Sandwich FGM Cylindrical Shells Surrounded by an Elastic Medium

by Vu Tho Hung, Dang Thuy Dong, Nguyen Thi Phuong, Le Ngoc Ly, Tran Quang Minh, Nguyen-Thoi Trung and Vu Hoai Nam

Materials 2020, 13(8), 1984; https://doi.org/10.3390/ma13081984 - 24 Apr 2020

Cited by 11 | Viewed by 3100

Abstract

This paper presents a semi-analytical approach for investigating the nonlinear buckling and postbuckling of spiral corrugated sandwich functionally graded (FGM) cylindrical shells under external pressure and surrounded by a two-parameter elastic foundation based on Donnell shell theory. The improved homogenization theory for the [...] Read more.

This paper presents a semi-analytical approach for investigating the nonlinear buckling and postbuckling of spiral corrugated sandwich functionally graded (FGM) cylindrical shells under external pressure and surrounded by a two-parameter elastic foundation based on Donnell shell theory. The improved homogenization theory for the spiral corrugated FGM structure is applied and the geometrical nonlinearity in a von Karman sense is taken into account. The nonlinear equilibrium equation system can be solved by using the Galerkin method with the three-term solution form of deflection. An explicit solution form for the nonlinear buckling behavior of shells is obtained. The critical buckling pressure and the postbuckling strength of shells are numerically investigated. Additionally, the effects of spiral corrugation in enhancing the nonlinear buckling behavior of spiral corrugated sandwich FGM cylindrical shells are validated and discussed. Full article

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13 pages, 10298 KiB

Open AccessFeature PaperArticle

Effects of Mn, Zn Additions and Cooling Rate on Mechanical and Corrosion Properties of Al-4.6Mg Casting Alloys

by Chih-Ting Wu, Sheng-Long Lee, Ye-Feng Chen, Hui-Yun Bor and Kung-Hui Liu

Materials 2020, 13(8), 1983; https://doi.org/10.3390/ma13081983 - 24 Apr 2020

Cited by 7 | Viewed by 2795

Abstract

The mechanical properties of the Al-Mg alloy can be enhanced by adding metallic elements, but a continuous distribution of precipitates at grain boundaries leads to intergranular corrosion during sensitization treatment. In the present work, Mn, Zn additions, water cooling and furnace cooling were [...] Read more.

The mechanical properties of the Al-Mg alloy can be enhanced by adding metallic elements, but a continuous distribution of precipitates at grain boundaries leads to intergranular corrosion during sensitization treatment. In the present work, Mn, Zn additions, water cooling and furnace cooling were executed to investigate their effects on the mechanical and corrosion properties of the Al-4.6Mg alloy. Our results show that adding Mn to Al-4.6Mg alloys may produce grain refinement and dispersion strengthening, increasing tensile strength and hardness. The presence of Mn did not affect the corrosion resistance of Al-Mg alloys. Adding Zn to the Al-4.6Mg alloy increased tensile strength and hardness, but decreased corrosion resistance. Combined, the addition of Mn and Zn to the Al-4.6Mg alloy exhibited the highest tensile strength and hardness, but seriously reduced corrosion resistance. Furnace cooling substituted for water quenching could avoid intergranular corrosion, but slightly decreased the tensile strength and hardness by 7.0% and 6.8%, respectively. Full article

(This article belongs to the Special Issue Advanced Surface Treatment Technologies for Metallic Alloys)

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27 pages, 1356 KiB

Open AccessArticle

Dislocation Density Based Flow Stress Model Applied to the PFEM Simulation of Orthogonal Cutting Processes of Ti-6Al-4V

by Juan Manuel Rodríguez, Simon Larsson, Josep Maria Carbonell and Pär Jonsén

Materials 2020, 13(8), 1979; https://doi.org/10.3390/ma13081979 - 24 Apr 2020

Cited by 12 | Viewed by 4276

Abstract

Machining of metals is an essential operation in the manufacturing industry. Chip formation in metal cutting is associated with large plastic strains, large deformations, high strain rates and high temperatures, mainly located in the primary and in the secondary shear zones. During the [...] Read more.

Machining of metals is an essential operation in the manufacturing industry. Chip formation in metal cutting is associated with large plastic strains, large deformations, high strain rates and high temperatures, mainly located in the primary and in the secondary shear zones. During the last decades, there has been significant progress in numerical methods and constitutive modeling for machining operations. In this work, the Particle Finite Element Method (PFEM) together with a dislocation density (DD) constitutive model are introduced to simulate the machining of Ti-6Al-4V. The work includes a study of two constitutive models for the titanium material, the physically based plasticity DD model and the phenomenology based Johnson–Cook model. Both constitutive models were implemented into an in-house PFEM software and setup to simulate deformation behaviour of titanium Ti6Al4V during an orthogonal cutting process. Validation show that numerical and experimental results are in agreement for different cutting speeds and feeds. The dislocation density model, although it needs more thorough calibration, shows an excellent match with the results. This paper shows that the combination of PFEM together with a dislocation density constitutive model is an excellent candidate for future numerical simulations of mechanical cutting. Full article

(This article belongs to the Section Materials Simulation and Design)

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18 pages, 2598 KiB

Open AccessReview

3D Digital Impression Systems Compared with Traditional Techniques in Dentistry: A Recent Data Systematic Review

by Marco Cicciù, Luca Fiorillo, Cesare D’Amico, Dario Gambino, Emanuele Mario Amantia, Luigi Laino, Salvatore Crimi, Paola Campagna, Alberto Bianchi, Alan Scott Herford and Gabriele Cervino

Materials 2020, 13(8), 1982; https://doi.org/10.3390/ma13081982 - 23 Apr 2020

Cited by 84 | Viewed by 11272

Abstract

The advent of new technologies in the field of medicine and dentistry is giving improvements that lead the clinicians to have materials and procedures able to improve patients’ quality of life. In dentistry, the last digital techniques offer a fully digital computerized workflow [...] Read more.

The advent of new technologies in the field of medicine and dentistry is giving improvements that lead the clinicians to have materials and procedures able to improve patients’ quality of life. In dentistry, the last digital techniques offer a fully digital computerized workflow that does not include the standard multiple traditional phases. The purpose of this study is to evaluate all clinical trials and clinical randomized trials related to the digital or dental impression technique in prosthetic dentistry trying to give the readers global information about advantages and disadvantages of each procedure. Data collection was conducted in the main scientific search engines, including articles from the last 10 years, in order to obtain results that do not concern obsolete impression techniques. Elsevier, Pubmed and Embase have been screened as sources for performing the research. The results data demonstrated how the working time appears to be improved with digital workflow, but without a significant result (P = 0.72596). The papers have been selected following the Population Intervention Comparison Outcome (PICO) question, which is related to the progress on dental impression materials and technique. The comparison between dentists or practitioners with respect to classic impression procedures, and students open to new device and digital techniques seem to be the key factor on the final impression technique choice. Surely, digital techniques will end up supplanting the analogical ones altogether, improving the quality of oral rehabilitations, the economics of dental practice and also the perception by our patients. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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16 pages, 4657 KiB

Open AccessArticle

Residual Compressive Strength of Recycled Aggregate Concretes after High Temperature Exposure

by Francisco B. Varona, Francisco Baeza-Brotons, Antonio J. Tenza-Abril, F. Javier Baeza and Luis Bañón

Materials 2020, 13(8), 1981; https://doi.org/10.3390/ma13081981 - 23 Apr 2020

Cited by 29 | Viewed by 3594

Abstract

Sustainability requirements are gaining importance in the construction industry, which needs to take specific measures in the design and construction of concrete structures. The use of recycled aggregates in concrete may be of special interest. Recycling a construction waste will close the life [...] Read more.

Sustainability requirements are gaining importance in the construction industry, which needs to take specific measures in the design and construction of concrete structures. The use of recycled aggregates in concrete may be of special interest. Recycling a construction waste will close the life cycle of the original materials (e.g., concrete). Thus, environmental benefits would come from the lower waste generation, and from a lower necessity of raw materials for new structures. The current Spanish code for structural concrete considers the use of recycled aggregates in replacement rates up to 20% by aggregate mass, assimilating their properties with those of concretes without aggregate replacement. Higher substitution percentages would require further testing. In this work, substitution of coarse aggregate for recycled aggregates (with replacement percentages of 25%, 50% and 100%) has been studied, and the concrete’s residual properties after exposure to high temperatures (between 350 °C and 850 °C) have been assessed. Compressive strength and capillary water absorption tests were made after heating, and the experiments showed higher residual strength in concretes with the greatest content of recycled aggregates. However, a statistical analysis made with additional data available in the literature seemed to predict otherwise, and the recycled aggregate replacement would have a negative effect on the residual strength. Full article

(This article belongs to the Special Issue The Effects of High Temperature on the Mechanical Properties of Concrete)

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Time evolution of temperature during heating process: (a) thermal saturation during 1 hour; (b) thermal saturation during 2 hours. Full article ">Figure 2
Evolution of density of natural aggregate concrete (NAC) and RAC with temperature. Full article ">Figure 3
External cracking of specimens after high temperature exposure: NAC batches at (a) 550 °C and at (b) 850 °C; RAC batches at (c) 550 °C and at (d) 850 °C. Full article ">Figure 4
Evolution of normalised compressive strength (NRCS) with high temperatures: (a) experimental results for replacements of 0%, 25%, 50% and 100%, compared with NAC curves from Eurocode 2 [<a href="#B21-materials-13-01981" class="html-bibr">21</a>]; (b) experimental results for replacements of 0% and 100%, compared with results from state-of-the-art (SoA). Full article ">Figure 5
Experimental observations of concrete batches A0 (NAC, with R = 0%) and A100 (RAC, with R = 100%) and prediction models for R = 0% and R = 100%, based on a non-linear multiple variable regression analysis sourced from experiments reported here and in the state-of-the-art. Full article ">Figure 6
Evolution of the capillary water absorption with temperature. (a) Coeff. of capillary absorption (b) Normalised capillary absorption. Full article ">Figure 7
Scanning electron microscope photographs: A0 batch at room temperature (a) and at 550 °C (b); A100 batch at room temperature (c) and at 550 °C (d). Full article ">

14 pages, 3443 KiB

Open AccessArticle

Graphene Oxide Carboxymethylcellulose Nanocomposite for Dressing Materials

by Maria Luisa Saladino, Marta Markowska, Clara Carmone, Patrizia Cancemi, Rosa Alduina, Alessandro Presentato, Roberto Scaffaro, Dariusz Biały, Mariusz Hasiak, Dariusz Hreniak and Magdalena Wawrzyńska

Materials 2020, 13(8), 1980; https://doi.org/10.3390/ma13081980 - 23 Apr 2020

Cited by 32 | Viewed by 4624

Abstract

Sore, infected wounds are a major clinical issue, and there is thus an urgent need for novel biomaterials as multifunctional constituents for dressings. A set of biocomposites was prepared by solvent casting using different concentrations of carboxymethylcellulose (CMC) and exfoliated graphene oxide ( [...] Read more.

Sore, infected wounds are a major clinical issue, and there is thus an urgent need for novel biomaterials as multifunctional constituents for dressings. A set of biocomposites was prepared by solvent casting using different concentrations of carboxymethylcellulose (CMC) and exfoliated graphene oxide (Exf-GO) as a filler. Exf-GO was first obtained by the strong oxidation and exfoliation of graphite. The structural, morphological and mechanical properties of the composites (CMCx/Exf-GO) were evaluated, and the obtained composites were homogenous, transparent and brownish in color. The results confirmed that Exf-GO may be homogeneously dispersed in CMC. It was found that the composite has an inhibitory activity against the Gram-positive Staphylococcus aureus, but not against Gram-negative Pseudomonas aeruginosa. At the same time, it does not exhibit any cytotoxic effect on normal fibroblasts. Full article

(This article belongs to the Special Issue Advances in Nanostructured Materials)

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11 pages, 1627 KiB

Open AccessArticle

Electronic and Crystallographic Examinations of the Homoepitaxially Grown Rubrene Single Crystals

by Yasuo Nakayama, Masaki Iwashita, Mitsuru Kikuchi, Ryohei Tsuruta, Koki Yoshida, Yuki Gunjo, Yusuke Yabara, Takuya Hosokai, Tomoyuki Koganezawa, Seiichiro Izawa and Masahiro Hiramoto

Materials 2020, 13(8), 1978; https://doi.org/10.3390/ma13081978 - 23 Apr 2020

Cited by 9 | Viewed by 3671

Abstract

Homoepitaxial growth of organic semiconductor single crystals is a promising methodology toward the establishment of doping technology for organic opto-electronic applications. In this study, both electronic and crystallographic properties of homoepitaxially grown single crystals of rubrene were accurately examined. Undistorted lattice structures of [...] Read more.

Homoepitaxial growth of organic semiconductor single crystals is a promising methodology toward the establishment of doping technology for organic opto-electronic applications. In this study, both electronic and crystallographic properties of homoepitaxially grown single crystals of rubrene were accurately examined. Undistorted lattice structures of homoepitaxial rubrene were confirmed by high-resolution analyses of grazing-incidence X-ray diffraction (GIXD) using synchrotron radiation. Upon bulk doping of acceptor molecules into the homoepitaxial single crystals of rubrene, highly sensitive photoelectron yield spectroscopy (PYS) measurements unveiled a transition of the electronic states, from induction of hole states at the valence band maximum at an adequate doping ratio (10 ppm), to disturbance of the valence band itself for excessive ratios (≥ 1000 ppm), probably due to the lattice distortion. Full article

(This article belongs to the Special Issue Organic Solar Cell and Optoelectronic Functional Materials)

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(a) Molecular structure of rubrene. (b) Photograph of a homoepitaxial rubrene sample for photoelectron yield spectroscopy (PYS) measurements. (c,d) Optical micrographs of the sample shown in (b). (e,f) Crossed-nicols polarized micrographs at the same sample geometries as (c,d), respectively. The scale bars in (c–f) correspond to 0.5 mm. The edge of the rubrene single crystal is highlighted with dashed lines in (c,e). Full article ">Figure 2
(a–d) Two-dimensional grazing incidence X-ray diffraction (2D-GIXD) images of rubrene single crystal samples (a) without and with the homoepitaxially grown rubrene overlayers of (b) 50 nm- and (c) 100 nm-thick. These images are integrated for the sample azimuthal angle over 180° (900 images taken for every 0.2°). Expected positions for the diffraction spots from the (100) surface of rubrene single crystal and Si (powder) are indicated with circle marks and a thick arc, respectively, on (a). (d) Full-width at half-maximum (FWHM) in 2θ direction of the {010} diffraction spots of rubrene [denoted as Rub{010}] collected by high-resolution grazing-incidence X-ray diffraction (HR-GIXD) measurements plotted as a function of the rubrene overlayer thickness. The corresponding crystallographic coherent length (up to 2 μm) estimated from the Scherrer equation is also indicated in the right axis for reference. Full article ">Figure 3
(a) PYS spectra of 20-nm-thick homoepitaxial rubrene overlayers of various doping ratios grown on rubrene single crystal substrates. PYS spectra of a single crystal sample and an amorphous film of rubrene are also displayed as hatched areas. (b) PYS spectra plotted in the cube-root scale of the photoelectron yield. Ionization energy positions derived from least-squares fitting of these spectra are indicated with wedge marks, where thin lines show the fitting results. (Inset) Ionization energy of rubrene overlayers plotted as a function of the doping rate. The ionization energy values for the bare rubrene single crystal (SC) and the amorphous rubrene are also indicated with pink and brown lines, respectively, where light-colored bands indicate error ranges. Full article ">Figure 4
(a–c) Magnified PYS spectra of the (a) bare rubrene single crystal, (b) non-doped homoepitaxial rubrene overlayer, and (c) 10-ppm-doped homoepitaxial rubrene. The vertical scales of each graph are normalized by the intensity factor “A” of the cube-root function. The fitting curves and estimated ionization energy positions for the respective spectra are displayed as thick gray curves and gray wedge marks, respectively. (d,e) Schematic drawings of the expected electronic states of the (d) non-doped and (e) 10-ppm-doped homoepitaxial rubrene samples. Full article ">

17 pages, 3208 KiB

Open AccessArticle

Biocompatible Gels of Chitosan–Buriti Oil for Potential Wound Healing Applications

by Maria Onaira Gonçalves Ferreira, Idglan Sá Lima, Alessandra Braga Ribeiro, Anderson O. Lobo, Marcia S. Rizzo, Josy Anteveli Osajima, Leticia Miranda Estevinho and Edson C. Silva-Filho

Materials 2020, 13(8), 1977; https://doi.org/10.3390/ma13081977 - 23 Apr 2020

Cited by 22 | Viewed by 3752

Abstract

The buriti oil (Mauritia flexuosa L.) can be associated with polymeric matrices for biomedical applications. This study aimed to evaluate the effect of chitosan gel (CG) associated with buriti oil (CGB) as a healing agent. The fatty acids and volatile compounds composition [...] Read more.

The buriti oil (Mauritia flexuosa L.) can be associated with polymeric matrices for biomedical applications. This study aimed to evaluate the effect of chitosan gel (CG) associated with buriti oil (CGB) as a healing agent. The fatty acids and volatile compounds composition of buriti oil were performed and the composite gels were characterized using FTIR and thermal analysis. Biological tests including antimicrobial, antioxidant, anti-inflammatory and healing effects were also investigated. Buriti oil is composed of oleic and palmitic acids, and the main volatile compounds were identified. The buriti oil did not show antimicrobial activity, on the other hand, the composite gel (chitosan and oil) proved to be efficient against Staphylococcus aureus and Klebsiella pneumonia at the 10 mg/mL. Similar behavior was observed for antioxidant activity, determined by the β-carotene bleaching assay, composite gels presenting higher activity and buriti oil showed anti-inflammatory activity, which may be related to the inhibition of the release of free radicals. Regarding wound healing performed using in vivo testing, the composite gel (CGB) was found to promote faster and complete wound retraction. The results indicated that the gel chitosan–buriti oil has a set of properties that improve its antibacterial, antioxidant and healing action, suggesting that this material can be used to treat skin lesions. Full article

(This article belongs to the Special Issue Biopolymers for Technology Applications)

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Thermogravimetric curves (TG) of pure chitosan gel (a), chitosan gel with buriti oil (b), and buriti oil (c), and Derivative Thermogravimetric curves (DTG) of chitosan gel (CG) (d), chitosan gel with buriti oil (e), and buriti oil (f). Full article ">Figure 2
Infrared spectroscopy (FTIR) spectrum of chitosan gel (a), chitosan gel with buriti oil (b), and buriti oil (c). Full article ">Figure 3
Scanning electron microscope (SEM) images of chitosan gel (CG) (a—300 μm, b—100 μm, and c—30 μm) and chitosan gel with buriti oil (CGB) (d—300 μm, e—100 μm, and f—30 μm). Full article ">Figure 4
Evolution of the diameter of the skin lesion in mice on days on 3rd, 7th, 14th, and 21st days of treatment with Physiological Saline (PS), Collagenase Clostridium histolyticum ointment (CC), pure chitosan gel (CG), and chitosan gel with buriti oil (CGB). Full article ">Figure 5
Photomicrographs of skin wounds on 3rd, 7th, 14th, and 21st day of treatment for groups treated with chitosan gel (A–D) and chitosan gel associated with buriti oil (E–H). Hematoxylin-Eosin (H.E.) stain (Scale bar: 2µm, 4 µm, and 10 µm). A and E: Skin ulcer with epidermis showing a large gap between the edges of the lesion (*), fibrin clot (arrows), and inflammatory infiltrate of polymorphonuclear cells in the dermis (detail). B and F: Continuing reepithelialization of the epidermis showing thickening (acanthosis—arrowheads), with keratinocytes meet in the midline beneath the surface scab in F (arrow) and presence of neoformed vessels in granulation tissue in the dermis (circle). C and G: There are epidermal reepithelialization and extensive granulation tissue formation, with neoformed vessels (arrows), and an inflammatory process located in the deepest dermis (circle). D and H: continuing reepithelialization of the epidermis and wound contraction (arrows). Full article ">

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Materials, Volume 13, Issue 8 (April-2 2020) – 210 articles

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