Materials

8454 KiB

Open AccessArticle

Effect of Mg on the Microstructure and Corrosion Resistance of the Continuously Hot-Dip Galvanizing Zn-Mg Coating

by Anping Dong, Baoping Li, Yanling Lu, Guoliang Zhu, Hui Xing, Da Shu, Baode Sun and Jun Wang

Materials 2017, 10(8), 980; https://doi.org/10.3390/ma10080980 - 22 Aug 2017

Cited by 21 | Viewed by 7820

Abstract

The microstructure of continuously hot-dip galvanizing Zn-Mg coating was investigated in order to obtain the mechanism of the effects of Mg on the corrosion resistance. In this paper, the vertical section of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low [...] Read more.

The microstructure of continuously hot-dip galvanizing Zn-Mg coating was investigated in order to obtain the mechanism of the effects of Mg on the corrosion resistance. In this paper, the vertical section of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner was calculated. The results indicates that the phase composition of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner is the same as Zn-Mg binary phase diagram, suggesting Al in the Zn-Mg (ZM) coatings mainly concentrates on the interfacial layer between the coating and steel substrate. The microstructure of continuously hot-dip galvanizing ZM coatings with 0.20 wt % Al containing 1.0–3.0 wt % Mg was investigated using tunneling electron microscopy (TEM). The morphology of Zn in the coating changes from bulk to strip and finally to mesh-like, and the MgZn₂ changes from rod-like to mesh-like with the Mg content increasing. Al in the ZM coatings mainly segregates at the Fe₂Al₅ inhibition layer and the Mg added to the Zn bath makes this inhibition layer thinner and uneven. Compared to GI coating, the time of the first red rust appears increases by more than two-fold and expansion rate of red rust reduces by more than four-fold in terms of salt spray experiment. The ZM coating containing 2.0 wt % Mg has the best corrosion resistance. The enhanced corrosion resistance of ZM coatings mainly depends on different corrosion products. Full article

(This article belongs to the Section Advanced Materials Characterization)

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6544 KiB

Open AccessArticle

Self-Sealing Cementitious Materials by Using Water-Swelling Rubber Particles

by Leyang Lv, Erik Schlangen and Feng Xing

Materials 2017, 10(8), 979; https://doi.org/10.3390/ma10080979 - 22 Aug 2017

Cited by 6 | Viewed by 5228

Abstract

Water ingress into cracked concrete structures is a serious problem, as it can cause leakage and reinforcement corrosion and thus reduce functionality and safety of the structures. In this study, the application of water-swelling rubber particles for providing the cracked concrete a self-sealing [...] Read more.

Water ingress into cracked concrete structures is a serious problem, as it can cause leakage and reinforcement corrosion and thus reduce functionality and safety of the structures. In this study, the application of water-swelling rubber particles for providing the cracked concrete a self-sealing function was developed. The feasibility of applying water-swelling rubber particles and the influence of incorporating water-swelling rubber particles on the mechanical properties of concrete was investigated. The self-sealing efficiency of water-swelling rubber particles with different content and particle size was quantified through a permeability test. The sealing effect of the water swelling rubber particles was monitored by X-ray computed tomography. The experimental results show that, by using 6% of these water swelling rubber particles as a replacement of aggregates in concrete, up to 64% and 61% decrease of water permeability was realized for 0.7 mm and 1.0 mm cracks. Furthermore, when the concrete cracks, the water swelling rubber particles can act as a crack bridging filler, preventing the crack from fully separating the specimens in two pieces. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for the Built Environment)

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4690 KiB

Open AccessArticle

Influence of Binders and Lightweight Aggregates on the Properties of Cementitious Mortars: From Traditional Requirements to Indoor Air Quality Improvement

by Chiara Giosuè, Mattia Pierpaoli, Alessandra Mobili, Maria Letizia Ruello and Francesca Tittarelli

Materials 2017, 10(8), 978; https://doi.org/10.3390/ma10080978 - 22 Aug 2017

Cited by 38 | Viewed by 4881

Abstract

Innovative and multifunctional mortars for renders and panels were manufactured using white photocatalytic and non-photocatalytic cement as binder. Unconventional aggregates, based on lightweight materials with high specific surface and adsorbent properties, were adopted in order to investigate the possible ability to passively improve [...] Read more.

Innovative and multifunctional mortars for renders and panels were manufactured using white photocatalytic and non-photocatalytic cement as binder. Unconventional aggregates, based on lightweight materials with high specific surface and adsorbent properties, were adopted in order to investigate the possible ability to passively improve indoor air quality. The reference mortar was manufactured with traditional calcareous sand. Results show that even if the mechanical properties of mortars with unconventional aggregates generally decrease, they remain acceptable for application as render. The innovative mortars were able to passively improve indoor air quality in terms of transpirability (70% higher), moisture buffering ability (65% higher) and depolluting capacity (up to 75% higher) compared to traditional ones under the current test conditions. Full article

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4043 KiB

Open AccessFeature PaperReview

Potential Applications of Nanocellulose-Containing Materials in the Biomedical Field

by Nadia Halib, Francesca Perrone, Maja Cemazar, Barbara Dapas, Rossella Farra, Michela Abrami, Gianluca Chiarappa, Giancarlo Forte, Fabrizio Zanconati, Gabriele Pozzato, Luigi Murena, Nicola Fiotti, Romano Lapasin, Laura Cansolino, Gabriele Grassi and Mario Grassi

Materials 2017, 10(8), 977; https://doi.org/10.3390/ma10080977 - 21 Aug 2017

Cited by 124 | Viewed by 10980

Abstract

Because of its high biocompatibility, bio-degradability, low-cost and easy availability, cellulose finds application in disparate areas of research. Here we focus our attention on the most recent and attractive potential applications of cellulose in the biomedical field. We first describe the chemical/structural composition [...] Read more.

Because of its high biocompatibility, bio-degradability, low-cost and easy availability, cellulose finds application in disparate areas of research. Here we focus our attention on the most recent and attractive potential applications of cellulose in the biomedical field. We first describe the chemical/structural composition of cellulose fibers, the cellulose sources/features and cellulose chemical modifications employed to improve its properties. We then move to the description of cellulose potential applications in biomedicine. In this field, cellulose is most considered in recent research in the form of nano-sized particle, i.e., nanofiber cellulose (NFC) or cellulose nanocrystal (CNC). NFC is obtained from cellulose via chemical and mechanical methods. CNC can be obtained from macroscopic or microscopic forms of cellulose following strong acid hydrolysis. NFC and CNC are used for several reasons including the mechanical properties, the extended surface area and the low toxicity. Here we present some potential applications of nano-sized cellulose in the fields of wound healing, bone-cartilage regeneration, dental application and different human diseases including cancer. To witness the close proximity of nano-sized cellulose to the practical biomedical use, examples of recent clinical trials are also reported. Altogether, the described examples strongly support the enormous application potential of nano-sized cellulose in the biomedical field. Full article

(This article belongs to the Special Issue Nanocellulose-Based Functional Materials)

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9151 KiB

Open AccessArticle

Preparation and Characterization of Mo Doped in BiVO₄ with Enhanced Photocatalytic Properties

by Bitao Liu, Xuelian Yan, Hengqing Yan, Yucen Yao, Yanhua Cai, Jumeng Wei, Shanyong Chen, Xuhui Xu and Lu Li

Materials 2017, 10(8), 976; https://doi.org/10.3390/ma10080976 - 21 Aug 2017

Cited by 39 | Viewed by 8184

Abstract

Molybdenum (Mo) doped BiVO₄ was fabricated via a simple electrospun method. Morphology, structure, chemical states and optical properties of the obtained catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse [...] Read more.

Molybdenum (Mo) doped BiVO₄ was fabricated via a simple electrospun method. Morphology, structure, chemical states and optical properties of the obtained catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), N₂ adsorption–desorption isotherms (BET) and photoluminescence spectrum (PL), respectively. The photocatalytic properties indicate that doping Mo into BiVO₄ can enhance the photocatalytic activity and dark adsorption ability. The photocatalytic test suggests that the 1% Mo-BiVO₄ shows the best photocatalytic activity, which is about three times higher than pure BiVO₄. Meanwhile, 3% Mo-BiVO₄ shows stronger dark adsorption than pure BiVO₄ and 1% Mo-BiVO₄. The enhancement in photocatalytic property should be ascribed to that BiVO₄ with small amount of Mo doping could efficiently separate the photogenerated carries and improve the electronic conductivity. The high concentration doping would lead the crystal structure transformation from monoclinic to tetragonal phase, as well as the formation of MoO₃ nanoparticles on the BiVO₄ surface, which could also act as recombination centers to decrease the photocatalytic activity. Full article

(This article belongs to the Section Energy Materials)

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3714 KiB

Open AccessArticle

Carbon Nanostructure of Kraft Lignin Thermally Treated at 500 to 1000 °C

by Xuefeng Zhang, Qiangu Yan, Weiqi Leng, Jinghao Li, Jilei Zhang, Zhiyong Cai and El Barbary Hassan

Materials 2017, 10(8), 975; https://doi.org/10.3390/ma10080975 - 21 Aug 2017

Cited by 62 | Viewed by 8315

Abstract

Kraft lignin (KL) was thermally treated at 500 to 1000 °C in an inert atmosphere. Carbon nanostructure parameters of thermally treated KL in terms of amorphous carbon fraction, aromaticity, and carbon nanocrystallites lateral size (L_a), thickness (L_c), [...] Read more.

Kraft lignin (KL) was thermally treated at 500 to 1000 °C in an inert atmosphere. Carbon nanostructure parameters of thermally treated KL in terms of amorphous carbon fraction, aromaticity, and carbon nanocrystallites lateral size (L_a), thickness (L_c), and interlayer space (d₀₀₂) were analyzed quantitatively using X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy. Experimental results indicated that increasing temperature reduced amorphous carbon but increased aromaticity in thermally treated KL materials. The L_c value of thermally treated KL materials averaged 0.85 nm and did not change with temperature. The d₀₀₂ value decreased from 3.56 Å at 500 °C to 3.49 Å at 1000 °C. The L_a value increased from 0.7 to 1.4 nm as temperature increased from 500 to 1000 °C. A nanostructure model was proposed to describe thermally treated KL under 1000 °C. The thermal stability of heat treated KL increased with temperature rising from 500 to 800 °C. Full article

(This article belongs to the Section Advanced Materials Characterization)

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2091 KiB

Open AccessArticle

Preparation and Characterization of Cyclotrimethylenetrinitramine (RDX) with Reduced Sensitivity

by Yuqiao Wang, Xin Li, Shusen Chen, Xiao Ma, Ziyang Yu, Shaohua Jin, Lijie Li and Yu Chen

Materials 2017, 10(8), 974; https://doi.org/10.3390/ma10080974 - 21 Aug 2017

Cited by 26 | Viewed by 6813

Abstract

The internal defects and shape of cyclotrimethylenetrinitramine (RDX) crystal are critical parameters for the preparation of reduced sensitivity RDX (RS-RDX). In the current study, RDX was re-crystallized and spheroidized to form the high-quality RDX that was further characterized by purity, apparent density, size [...] Read more.

The internal defects and shape of cyclotrimethylenetrinitramine (RDX) crystal are critical parameters for the preparation of reduced sensitivity RDX (RS-RDX). In the current study, RDX was re-crystallized and spheroidized to form the high-quality RDX that was further characterized by purity, apparent density, size distribution, specific surface area, impact sensitivity, and shock sensitivity. The effects of re-crystallization solvent on the growth morphology of RDX crystal were investigated by both theoretical simulation and experiment test, and consistent results were obtained. The high-quality RDX exhibited a high purity (≥99.90%), high apparent density (≥1.811 g/cm³), spherical shape, and relatively low impact sensitivity (6%). Its specific surface area was reduced more than 30%. Compared with conventional RDXs, the high-quality RDX reduced the shock sensitivities of PBXN-109 and PBXW-115 by more than 30%, indicating that it was a RS-RDX. The reduced sensitivity and good processability of the high-quality RDX would be significant in improving the performances of RDX-based PBXs. Full article

(This article belongs to the Special Issue Energetic Materials and Processes)

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4593 KiB

Open AccessArticle

Genetically Engineered Phage Induced Selective H9c2 Cardiomyocytes Patterning in PDMS Microgrooves

by Youngjun Kim, Chunga Kwon and Hojeong Jeon

Materials 2017, 10(8), 973; https://doi.org/10.3390/ma10080973 - 21 Aug 2017

Cited by 14 | Viewed by 6876

Abstract

A micro-patterned cell adhesive surface was prepared for future design of medical devices. One-dimensional polydimethylsiloxane (PDMS) micro-patterns were prepared by a photolithography process. Afterwards, recombinant filamentous phages that displayed a short binding motif with a cell adhesive peptide (-RGD-) on p8 proteins were [...] Read more.

A micro-patterned cell adhesive surface was prepared for future design of medical devices. One-dimensional polydimethylsiloxane (PDMS) micro-patterns were prepared by a photolithography process. Afterwards, recombinant filamentous phages that displayed a short binding motif with a cell adhesive peptide (-RGD-) on p8 proteins were immobilized on PDMS microgrooves through simple contact printing to study the cellular response of rat H9c2 cardiomyocyte. While the cell density decreased on PDMS micro-patterns, we observed enhanced cell proliferation and cell to surface interaction on the RGD-phage coated PDMS microgrooves. The RGD-phage coating also supported a better alignment of cell spreading rather than isotropic cell growths as we observed on non-pattered PDMS surface. Full article

(This article belongs to the Special Issue Constitutive Modelling of Biological Tissues and Biomaterials)

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7363 KiB

Open AccessArticle

A Simple Method for High-Performance, Solution-Processed, Amorphous ZrO₂ Gate Insulator TFT with a High Concentration Precursor

by Wei Cai, Zhennan Zhu, Jinglin Wei, Zhiqiang Fang, Honglong Ning, Zeke Zheng, Shangxiong Zhou, Rihui Yao, Junbiao Peng and Xubing Lu

Materials 2017, 10(8), 972; https://doi.org/10.3390/ma10080972 - 21 Aug 2017

Cited by 24 | Viewed by 6003

Abstract

Solution-processed high-k dielectric TFTs attract much attention since they cost relatively little and have a simple fabrication process. However, it is still a challenge to reduce the leakage of the current density of solution-processed dielectric TFTs. Here, a simple solution method is presented [...] Read more.

Solution-processed high-k dielectric TFTs attract much attention since they cost relatively little and have a simple fabrication process. However, it is still a challenge to reduce the leakage of the current density of solution-processed dielectric TFTs. Here, a simple solution method is presented towards enhanced performance of ZrO₂ films by intentionally increasing the concentration of precursor. The ZrO₂ films not only exhibit a low leakage current density of 10⁻⁶ A/cm² at 10 V and a breakdown field of 2.5 MV/cm, but also demonstrate a saturation mobility of 12.6 cm²·V⁻¹·s⁻¹ and a I_on/I_off ratio of 10⁶ in DC pulse sputtering IGZO-TFTs based on these films. Moreover, the underlying mechanism of influence of precursor concentration on film formation is presented. Higher concentration precursor results in a thicker film within same coating times with reduced ZrO₂/IGZO interface defects and roughness. It shows the importance of thickness, roughness, and annealing temperature in solution-processed dielectric oxide TFT and provides an approach to precisely control solution-processed oxide films thickness. Full article

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2934 KiB

Open AccessArticle

Synthesis and Characteristic of Xylan-grafted-polyacrylamide and Application for Improving Pulp Properties

by Gui-Bin Xu, Wei-Qing Kong, Chuan-Fu Liu, Run-Cang Sun and Jun-Li Ren

Materials 2017, 10(8), 971; https://doi.org/10.3390/ma10080971 - 20 Aug 2017

Cited by 10 | Viewed by 4605

Abstract

Recently, more attentions have been focused on the exploration of hemicelluloses in the paper industry. In this work, xylan-grafted-polyacrylamide (xylan-g-PAM) biopolymers were synthesized by the graft copolymerization of xylan with acrylamide, and their interaction with fibers was also investigated to improve waste newspaper [...] Read more.

Recently, more attentions have been focused on the exploration of hemicelluloses in the paper industry. In this work, xylan-grafted-polyacrylamide (xylan-g-PAM) biopolymers were synthesized by the graft copolymerization of xylan with acrylamide, and their interaction with fibers was also investigated to improve waste newspaper pulp properties with or without cationic fiber fines. The influences of synthesis conditions were studied on the grafting ratio and the grafting efficiency of biopolymers. Prepared biopolymers were characterized by FTIR, ¹³C NMR, TGA and rheology. It was found that the grafting of PAM on xylan was conductive to improve xylan properties, such as the solubility in water, rheological features, and thermal stability, and the maximum grafting ratio was achieved to 14.7%. Moreover, xylan-g-PAM could obviously enhance the mechanical properties of waste paper pulps. Xylan-g-PAM also played the dominant role in increasing the strength of paper in the combination with prepared cationic fine fibers. When the amounts of xylan-g-PAM and cationic fiber fines were 1.0 wt % and 0.5 wt %, the mechanical properties such as the tensile index was increased by 49.09%, tear index was increased by 36.54%, and the burst index was increased by 20.67%, when compared with the control handsheets. Therefore, xylan-g-PAM as the new biopolymer could be promising in the application of strength agents for the paper industry as well as cationic fiber fines. Full article

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

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2916 KiB

Open AccessArticle

Influence of Layer Thickness, Raster Angle, Deformation Temperature and Recovery Temperature on the Shape-Memory Effect of 3D-Printed Polylactic Acid Samples

by Wenzheng Wu, Wenli Ye, Zichao Wu, Peng Geng, Yulei Wang and Ji Zhao

Materials 2017, 10(8), 970; https://doi.org/10.3390/ma10080970 - 19 Aug 2017

Cited by 112 | Viewed by 9404

Abstract

The success of the 3D-printing process depends upon the proper selection of process parameters. However, the majority of current related studies focus on the influence of process parameters on the mechanical properties of the parts. The influence of process parameters on the shape-memory [...] Read more.

The success of the 3D-printing process depends upon the proper selection of process parameters. However, the majority of current related studies focus on the influence of process parameters on the mechanical properties of the parts. The influence of process parameters on the shape-memory effect has been little studied. This study used the orthogonal experimental design method to evaluate the influence of the layer thickness H, raster angle θ, deformation temperature Td and recovery temperature Tr on the shape-recovery ratio Rr and maximum shape-recovery rate Vm of 3D-printed polylactic acid (PLA). The order and contribution of every experimental factor on the target index were determined by range analysis and ANOVA, respectively. The experimental results indicated that the recovery temperature exerted the greatest effect with a variance ratio of 416.10, whereas the layer thickness exerted the smallest effect on the shape-recovery ratio with a variance ratio of 4.902. The recovery temperature exerted the most significant effect on the maximum shape-recovery rate with the highest variance ratio of 1049.50, whereas the raster angle exerted the minimum effect with a variance ratio of 27.163. The results showed that the shape-memory effect of 3D-printed PLA parts depended strongly on recovery temperature, and depended more weakly on the deformation temperature and 3D-printing parameters. Full article

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

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12563 KiB

Open AccessArticle

ICP Materials Trends in Corrosion, Soiling and Air Pollution (1987–2014)

by Johan Tidblad, Kateřina Kreislová, Markus Faller, Daniel De la Fuente, Tim Yates, Aurélie Verney-Carron, Terje Grøntoft, Andrew Gordon and Ulrik Hans

Materials 2017, 10(8), 969; https://doi.org/10.3390/ma10080969 - 19 Aug 2017

Cited by 29 | Viewed by 6654

Abstract

Results from the international cooperative programme on effects on materials including historic and cultural monuments are presented from the period 1987–2014 and include pollution data (SO₂, NO₂, O₃, HNO₃ and PM₁₀), corrosion data (carbon [...] Read more.

Results from the international cooperative programme on effects on materials including historic and cultural monuments are presented from the period 1987–2014 and include pollution data (SO₂, NO₂, O₃, HNO₃ and PM₁₀), corrosion data (carbon steel, weathering steel, zinc, copper, aluminium and limestone) and data on the soiling of modern glass for nineteen industrial, urban and rural test sites in Europe. Both one-year and four-year corrosion data are presented. Corrosion and pollution have decreased significantly and a shift in the magnitude is generally observed around 1997: from a sharp decrease to a more modest decrease or to a constant level without any decrease. SO₂ levels, carbon steel and copper corrosion have decreased even after 1997, which is more pronounced in urban areas, while corrosion of the other materials shows no decrease after 1997, when looking at one-year values. When looking at four-year values, however, there is a significant decrease after 1997 for zinc, which is not evident when looking at the one-year values. This paper also presents results on corrosion kinetics by comparison of one- and four-year values. For carbon steel and copper, kinetics is relatively independent of sites while other materials, especially zinc, show substantial variation in kinetics for the first four years, which needs to be considered when producing new and possibly improved models for corrosion. Full article

(This article belongs to the Special Issue Fundamental and Research Frontier of Atmospheric Corrosion)

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2005 KiB

Open AccessFeature PaperArticle

The Effect of Hydrogen Bonding in Enhancing the Ionic Affinities of Immobilized Monoprotic Phosphate Ligands

by Spiro D. Alexandratos and Xiaoping Zhu

Materials 2017, 10(8), 968; https://doi.org/10.3390/ma10080968 - 18 Aug 2017

Cited by 15 | Viewed by 4998

Abstract

Environmental remediation requires ion-selective polymers that operate under a wide range of solution conditions. In one example, removal of trivalent and divalent metal ions from waste streams resulting from mining operations before they enter the environment requires treatment at acidic pH. The monoethyl [...] Read more.

Environmental remediation requires ion-selective polymers that operate under a wide range of solution conditions. In one example, removal of trivalent and divalent metal ions from waste streams resulting from mining operations before they enter the environment requires treatment at acidic pH. The monoethyl ester phosphate ligands developed in this report operate from acidic solutions. They have been prepared on polystyrene-bound ethylene glycol, glycerol, and pentaerythritol, and it is found that intra-ligand hydrogen bonding affects their metal ion affinities. The affinity for a set of trivalent (Fe(III), Al(III), La(III), and Lu(III)) and divalent (Pb(II), Cd(II), Cu(II), and Zn(II)) ions is greater than that of corresponding neutral diethyl esters and phosphonic acid. In an earlier study, hydrogen bonding was found important in determining the metal ion affinities of immobilized phosphorylated polyol diethyl ester coordinating ligands; their Fourier transform infrared (FTIR) band shifts indicated that the basicity of the phosphoryl oxygen increased by hydrogen bonding to auxiliary –OH groups on the neighboring polyol. The same mechanism is operative with the monoprotic resins along with hydrogen bonding to the P–OH acid site. This is reflected in the FTIR spectra: the neutral phosphate diethyl ester resins have the P=O band at 1265 cm⁻¹ while the monoethyl ester resins have the band shifted to 1230 cm⁻¹; hydrogen bonding is further indicated by the broadness of this region down to 900 cm⁻¹. The monoprotic pentaerythritol has the highest metal ion affinities of the polymers studied. Full article

(This article belongs to the Special Issue Sorption Materials for Environment Purification)

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13103 KiB

Open AccessArticle

In Situ Synthesis of Silver Nanoparticles on the Polyelectrolyte-Coated Sericin/PVA Film for Enhanced Antibacterial Application

by Rui Cai, Gang Tao, Huawei He, Pengchao Guo, Meirong Yang, Chaoxiang Ding, Hua Zuo, Lingyan Wang, Ping Zhao and Yejing Wang

Materials 2017, 10(8), 967; https://doi.org/10.3390/ma10080967 - 18 Aug 2017

Cited by 28 | Viewed by 6694

Abstract

To develop silk sericin (SS) as a potential antibacterial biomaterial, a novel composite of polyelectrolyte multilayers (PEMs) coated sericin/poly(vinyl alcohol) (SS/PVA) film modified with silver nanoparticles (AgNPs) has been developed using a layer-by-layer assembly technique and ultraviolet-assisted AgNPs synthesis method. Ag ions were [...] Read more.

To develop silk sericin (SS) as a potential antibacterial biomaterial, a novel composite of polyelectrolyte multilayers (PEMs) coated sericin/poly(vinyl alcohol) (SS/PVA) film modified with silver nanoparticles (AgNPs) has been developed using a layer-by-layer assembly technique and ultraviolet-assisted AgNPs synthesis method. Ag ions were enriched by PEMs via the electrostatic attraction between Ag ions and PEMs, and then reduced to AgNPs in situ with the assistance of ultraviolet irradiation. PEMs facilitated the high-density growth of AgNPs and protected the synthesized AgNPs due to the formation of a 3D matrix, and thus endowed SS/PVA film with highly effective and durable antibacterial activity. Scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, Fourier transfer infrared spectroscopy, water contact angle, mechanical property and thermogravimetric analysis were applied to characterize SS/PVA, PEMs-SS/PVA and AgNPs-PEMs-SS/PVA films, respectively. AgNPs-PEMs-SS/PVA film has exhibited good mechanical performance, hydrophilicity, water absorption capability as well as excellent and durable antibacterial activity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa and good stability and degradability. This study has developed a simple method to design and prepare AgNPs-PEMs-SS/PVA film for potential antibacterial application. Full article

(This article belongs to the Section Biomaterials)

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3294 KiB

Open AccessArticle

Esterification Mechanism of Bagasse Modified with Glutaric Anhydride in 1-Allyl-3-methylimidazolium Chloride

by Huihui Wang, Wei Chen, Xueqin Zhang, Chuanfu Liu and Runcang Sun

Materials 2017, 10(8), 966; https://doi.org/10.3390/ma10080966 - 18 Aug 2017

Cited by 9 | Viewed by 6176

Abstract

The esterification of bagasse with glutaric anhydride could increase surface adhesion compatibility and the surface of derived polymers has the potential of immobilizing peptides or proteins for biomedical application. Due to its complicated components, the esterification mechanism of bagasse esterified with glutaric anhydride [...] Read more.

The esterification of bagasse with glutaric anhydride could increase surface adhesion compatibility and the surface of derived polymers has the potential of immobilizing peptides or proteins for biomedical application. Due to its complicated components, the esterification mechanism of bagasse esterified with glutaric anhydride in ionic liquids has not been studied. In this paper, the homogenous esterification of bagasse with glutaric anhydride was comparatively investigated with the isolated cellulose, hemicelluloses, and lignin in 1-allyl-3-methylimidazolium chloride (AmimCl) to reveal the reaction mechanism. Fourier transform infrared (FT-IR) indicated that the three components (cellulose, hemicelluloses, and lignin) were all involved in the esterification. The percentage of substitution (PS) of bagasse was gradually improved with the increased dosage of glutaric anhydride (10–40 mmol/g), which was primarily attributed to the increased esterification of cellulose and hemicelluloses. However, the PS fluctuation of lignin led to a decrease in the PS of bagasse at high glutaric anhydride dosage (50 mmol/g). The esterification reactivity of bagasse components followed the order of lignin > hemicelluloses > cellulose. The esterification mechanism was proposed as a nucleophilic substitution reaction. Nuclear magnetic resonance (NMR) analysis indicated that lignin aliphatic hydroxyls were prior to be esterified, and primary hydroxyls were more reactive than secondary hydroxyls in cellulose and hemicelluloses. Full article

(This article belongs to the Section Advanced Materials Characterization)

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1941 KiB

Open AccessArticle

Effect of Pullulan Coating on Postharvest Quality and Shelf-Life of Highbush Blueberry (Vaccinium corymbosum L.)

by Karolina Kraśniewska, Iwona Ścibisz, Małgorzata Gniewosz, Marta Mitek, Katarzyna Pobiega and Andrzej Cendrowski

Materials 2017, 10(8), 965; https://doi.org/10.3390/ma10080965 - 18 Aug 2017

Cited by 42 | Viewed by 6836

Abstract

Fruits form an important part of a healthy human diet as they contain many ingredients with proven pro-health effects such as vitamins, phenolic compounds, organic acids, fiber, and minerals. The purpose of this work was to evaluate the effect of pullulan coating on [...] Read more.

Fruits form an important part of a healthy human diet as they contain many ingredients with proven pro-health effects such as vitamins, phenolic compounds, organic acids, fiber, and minerals. The purpose of this work was to evaluate the effect of pullulan coating on the quality and shelf life of highbush blueberry during storage. General appearance, weight loss, dry matter, soluble solid content, reducing sugars, content of L-ascorbic acid, phenolic compounds (total phenolics, phenolics acids and anthocyanins) were determined in uncoated and coated blueberries fruits. The microbiological efficiency of pullulan coating was also evaluated. All parameters were monitored during storage at 4 °C and 16 °C by 28 and 14 days, respectively. The study showed that pullulan coating protects perishable food products especially susceptible to mechanical injury including fruits such as blueberries. Pullulan acts as a barrier that minimizes respiration rate, delaying deterioration and controlling microbial growth. Full article

(This article belongs to the Special Issue Biobased Polymers for Packaging Applications)

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6609 KiB

Open AccessArticle

Mussel-Inspired Dopamine and Carbon Nanotube Leading to a Biocompatible Self-Rolling Conductive Hydrogel Film

by Junzi Jiang, Yong Huang, Yitian Wang, Hui Xu, Malcolm Xing and Wen Zhong

Materials 2017, 10(8), 964; https://doi.org/10.3390/ma10080964 - 18 Aug 2017

Cited by 14 | Viewed by 6434

Abstract

We report a novel self-rolling, conductive, and biocompatible multiwall carbon nanotube (MWCNT)-dopamine-polyethylene glycol (PEG) hydrogel film. The gel can self-fold into a thin tube when it is transferred from a glass slide to an aqueous environment, regardless of the concentrations of the MWCNT. [...] Read more.

We report a novel self-rolling, conductive, and biocompatible multiwall carbon nanotube (MWCNT)-dopamine-polyethylene glycol (PEG) hydrogel film. The gel can self-fold into a thin tube when it is transferred from a glass slide to an aqueous environment, regardless of the concentrations of the MWCNT. The film presents a highly organized pattern, which results from the self-assembly of hydrophilic dopamine and hydrophobic carbon nanotubes. By exploring the biomedical potential, we found that MWCNT-included rolled film is nontoxic and can promote cell growth. For further functional verification by qPCR (quantitative polymerase chain reaction), bone marrow derived mesenchymal cells present higher levels of osteogenic differentiations in response to a higher concentration of CNTs. The results suggest that the self-rolling, conductive CNT-dopamine-PEG hydrogel could have multiple potentials, including biomedical usage and as a conductive biosensor. Full article

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2017 KiB

Open AccessFeature PaperReview

Measurement Techniques of the Magneto-Electric Coupling in Multiferroics

by M. M. Vopson, Y. K. Fetisov, G. Caruntu and G. Srinivasan

Materials 2017, 10(8), 963; https://doi.org/10.3390/ma10080963 - 17 Aug 2017

Cited by 90 | Viewed by 8973

Abstract

The current surge of interest in multiferroic materials demands specialized measurement techniques to support multiferroics research. In this review article we detail well-established measurement techniques of the magneto-electric coupling coefficient in multiferroic materials, together with newly proposed ones. This work is intended to [...] Read more.

The current surge of interest in multiferroic materials demands specialized measurement techniques to support multiferroics research. In this review article we detail well-established measurement techniques of the magneto-electric coupling coefficient in multiferroic materials, together with newly proposed ones. This work is intended to serve as a reference document for anyone willing to develop experimental measurement techniques of multiferroic materials. Full article

(This article belongs to the Special Issue Physics, Measurements and Applications of Multiferroic and Magnetoelectric Materials)

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6114 KiB

Open AccessFeature PaperArticle

Multiphysics Simulation of Low-Amplitude Acoustic Wave Detection by Piezoelectric Wafer Active Sensors Validated by In-Situ AE-Fatigue Experiment

by Md Yeasin Bhuiyan and Victor Giurgiutiu

Materials 2017, 10(8), 962; https://doi.org/10.3390/ma10080962 - 17 Aug 2017

Cited by 15 | Viewed by 6032

Abstract

Piezoelectric wafer active sensors (PWAS) are commonly used for detecting Lamb waves for structural health monitoring application. However, in most applications of active sensing, the signals are of high-amplitude and easy to detect. In this article, we have shown a new avenue of [...] Read more.

Piezoelectric wafer active sensors (PWAS) are commonly used for detecting Lamb waves for structural health monitoring application. However, in most applications of active sensing, the signals are of high-amplitude and easy to detect. In this article, we have shown a new avenue of using the PWAS transducer for detecting the low-amplitude fatigue-crack related acoustic emission (AE) signals. Multiphysics finite element (FE) simulations were performed with two PWAS transducers bonded to the structure. Various configurations of the sensors were studied by using the simulations. One PWAS was placed near to the fatigue-crack and the other one was placed at a certain distance from the crack. The simulated AE event was generated at the crack tip. The simulation results showed that both PWAS transducers were capable of sensing the AE signals. To validate the multiphysics simulation results, an in-situ AE-fatigue experiment was performed. Two PWAS transducers were bonded to the thin aerospace test coupon. The fatigue crack was generated in the test coupon which had produced low-amplitude acoustic waves. The low-amplitude fatigue-crack related AE signals were successfully captured by the PWAS transducers. The distance effect on the captured AE signals was also studied. It has been shown that some high-frequency contents of the AE signal have developed as they travel away from the crack. Full article

(This article belongs to the Special Issue Structural Health Monitoring for Aerospace Applications 2017)

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3283 KiB

Open AccessArticle

A Novel Approach to Eliminate the Effect of External Stress on Interdiffusivity Measurement

by Weimin Chen, Qin Li and Lijun Zhang

Materials 2017, 10(8), 961; https://doi.org/10.3390/ma10080961 - 17 Aug 2017

Cited by 15 | Viewed by 4492

Abstract

In this paper, the interdiffusivities in fcc Co–Ni alloys at 1373 K due to different types of diffusion couple experiments were firstly re-calculated via the unified Wagner method based on the measured composition profiles. Their maximum difference due to different approaches for diffusion [...] Read more.

In this paper, the interdiffusivities in fcc Co–Ni alloys at 1373 K due to different types of diffusion couple experiments were firstly re-calculated via the unified Wagner method based on the measured composition profiles. Their maximum difference due to different approaches for diffusion couple preparation was found to be larger than one order of magnitude. Then, a comprehensive analysis on the effect of different preparation methods was performed. After that, a two-step diffusion couple technique in combination with the pragmatic numerical inverse method was proposed to determine the accurate interdiffusivities by eliminating the effect of external stress. Such a novel approach was successfully applied in the binary fcc Co–Ni alloys for demonstration purposes. Moreover, it is anticipated that such novel approach can be utilized as the standard method for accurate interdiffusivity measurement, and the resultant accurate interdiffusivities in different alloys may serve as a benchmark for the later experimental and theoretical studies. Full article

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7538 KiB

Open AccessFeature PaperArticle

Ag-Coated Heterostructures of ZnO-TiO₂/Delaminated Montmorillonite as Solar Photocatalysts

by Carolina Belver, Mariana Hinojosa, Jorge Bedia, Montserrat Tobajas, Maria Ariadna Alvarez, Vicente Rodríguez-González and Juan Jose Rodriguez

Materials 2017, 10(8), 960; https://doi.org/10.3390/ma10080960 - 17 Aug 2017

Cited by 40 | Viewed by 6119

Abstract

Heterostructures based on ZnO-TiO₂/delaminated montmorillonite coated with Ag have been prepared by sol–gel and photoreduction procedures, varying the Ag and ZnO contents. They have been thoroughly characterized by XRD, WDXRF, UV–Vis, and XPS spectroscopies, and N₂ adsorption, SEM, and TEM. [...] Read more.

Heterostructures based on ZnO-TiO₂/delaminated montmorillonite coated with Ag have been prepared by sol–gel and photoreduction procedures, varying the Ag and ZnO contents. They have been thoroughly characterized by XRD, WDXRF, UV–Vis, and XPS spectroscopies, and N₂ adsorption, SEM, and TEM. In all cases, the montmorillonite was effectively delaminated with the formation of TiO₂ anatase particles anchored on the clay layer’s surface, yielding porous materials with high surface areas. The structural and textural properties of the heterostructures synthesized were unaffected by the ZnO incorporated. The photoreduction led to solids with Ag nanoparticles decorating the surface. These materials were tested as photocatalysts for the degradation of several emerging contaminants with different nitrogen-bearing chemical structures under solar light. The catalysts yielded high rates of disappearance of the starting pollutants and showed quite stable performance upon successive applications. Full article

(This article belongs to the Special Issue Advances in Pillared Clays and Similar Materials: Synthesis, Characterization and Applications)

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2388 KiB

Open AccessArticle

Insights on the Optical Properties of Poly(3,4-Ethylenedioxythiophene):Poly(styrenesulfonate) Formulations by Optical Metrology

by Argiris Laskarakis, Varvara Karagkiozaki, Despoina Georgiou, Christoforos Gravalidis and Stergios Logothetidis

Materials 2017, 10(8), 959; https://doi.org/10.3390/ma10080959 - 17 Aug 2017

Cited by 13 | Viewed by 4628

Abstract

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is among the most widely used polymers that are used as printed transparent electrodes for flexible Organic Electronic (OE) devices, such as Organic Photovoltaics (OPVs). The understanding of their optical properties and the correlation of the optical properties with their electronic [...] Read more.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is among the most widely used polymers that are used as printed transparent electrodes for flexible Organic Electronic (OE) devices, such as Organic Photovoltaics (OPVs). The understanding of their optical properties and the correlation of the optical properties with their electronic properties and metallic-like behavior can lead to the optimization of their functionality as transparent electrodes in multilayer OE device architectures. In this work, we study the optical properties of different PEDOT:PSS formulations by non-destructive Spectroscopic Ellipsometry (SE), from the infrared to the far ultraviolet spectral regions. The optical response of PEDOT:PSS includes an intense optical absorption originated from the conductive part (PEDOT) at lower photon energies, whereas the electronic transition energies of the non-conductive PSS part have been measured at higher photon energies. Based on the different PEDOT:PSS formulations, the optical investigation revealed significant information on the relative contribution of conductive PEDOT and insulating PSS parts of the PEDOT:PSS formulation in the overall optical response, which can strongly impact the final device functionality and its optical transparency. Full article

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10023 KiB

Open AccessArticle

Production of Synthetic Phosphoanhydrite and Its Use as a Binder in Self-Leveling Underlayments (SLU)

by Cecília Ogliari Schaefer, Malik Cheriaf and Janaíde Cavalcante Rocha

Materials 2017, 10(8), 958; https://doi.org/10.3390/ma10080958 - 17 Aug 2017

Cited by 22 | Viewed by 4950

Abstract

An experimental study was conducted to investigate the potential use of phosphogypsum (PG) to produce self-leveling underlayments. The study was designed in two stages. Initially a phosphoanhydrite (PA) was produced by heating phosphogypsum at temperatures of 350 °C, 450 °C, 550 °C, and [...] Read more.

An experimental study was conducted to investigate the potential use of phosphogypsum (PG) to produce self-leveling underlayments. The study was designed in two stages. Initially a phosphoanhydrite (PA) was produced by heating phosphogypsum at temperatures of 350 °C, 450 °C, 550 °C, and 650 °C. Two periods of heating were applied (2 and 4 h). The formation of anhydrite was determined by thermogravimetric analysis (DTA-TG) and confirmed by X-ray diffraction (XRD). The results show that anhydrite II was obtained at temperatures above 450 °C, and at higher calcination temperatures the PA solubility was lower. In the second stage of this research, the PA was used in self-leveling underlayments as the main binder in the ternary system comprised of calcium sulfate, calcium aluminate cement, and Portland cement. Self-leveling mortar screeds produced using PA (550 °C/4 h) and PA (650 °C/4 h) showed the best performance in terms of mechanical strength and no degradation was observed after immersion and immersion-drying tests. The formation of ettringite, identified by scanning electron microscopy (SEM), may have contributed to these results. Morphological changes were studied using the scanning electron microscopy (SEM) technique. Full article

(This article belongs to the Section Advanced Materials Characterization)

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8673 KiB

Open AccessArticle

Grafting Modification of the Reactive Core-Shell Particles to Enhance the Toughening Ability of Polylactide

by Zhaokun Li, Shixin Song, Xuanchen Zhao, Xue Lv and Shulin Sun

Materials 2017, 10(8), 957; https://doi.org/10.3390/ma10080957 - 16 Aug 2017

Cited by 12 | Viewed by 5284

Abstract

In order to overcome the brittleness of polylactide (PLA), reactive core-shell particles (RCS) with polybutadiene as core and methyl methacrylate-co-styrene-co-glycidyl methacrylate as shell were prepared to toughen PLA. Tert-dodecyl mercaptan (TDDM) was used as chain transfer agent to modify the grafting properties (such [...] Read more.

In order to overcome the brittleness of polylactide (PLA), reactive core-shell particles (RCS) with polybutadiene as core and methyl methacrylate-co-styrene-co-glycidyl methacrylate as shell were prepared to toughen PLA. Tert-dodecyl mercaptan (TDDM) was used as chain transfer agent to modify the grafting properties (such as grafting degree, shell thickness, internal and external grafting) of the core-shell particles. The introduction of TDDM decreased the grafting degree, shell thickness and the T_g of the core phase. When the content of TDDM was lower than 1.15%, the RCS particles dispersed in the PLA matrix uniformly—otherwise, agglomeration took place. The addition of RCS particles induced a higher cold crystallization temperature and a lower melting temperature of PLA which indicated the decreased crystallization ability of PLA. Dynamic mechanical analysis (DMA) results proved the good miscibility between PLA and the RCS particles and the increase of TDDM in RCS induced higher storage modulus of PLA/RCS blends. Suitable TDDM addition improved the toughening ability of RCS particles for PLA. In the present research, PLA/RCS-T4 (RCS-T4: the reactive core-shell particles with 0.76 wt % TDDM addition) blends displayed much better impact strength than other blends due to the easier cavitation/debonding ability and good dispersion morphology of the RCS-T4 particles. When the RCS-T4 content was 25 wt %, the impact strength of PLA/RCS-T4 blend reached 768 J/m, which was more than 25 times that of the pure PLA. Full article

(This article belongs to the Special Issue The Brittle Failure of Different Materials)

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13491 KiB

Open AccessArticle

Enhanced Corrosion Resistance of Carbon Steel in Hydrochloric Acid Solution by Eriobotrya Japonica Thunb. Leaf Extract: Electrochemical Study

by Wenjing Yang, Qihui Wang, Ke Xu, Yanjun Yin, Hebin Bao, Xueming Li, Lidan Niu and Shiqi Chen

Materials 2017, 10(8), 956; https://doi.org/10.3390/ma10080956 - 16 Aug 2017

Cited by 26 | Viewed by 6233

Abstract

The biodegradable inhibitors, which could effectively reduce the rate of corrosion of carbon steel, were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The mixed-type inhibitors extracted from Eriobotrya japonica Thunb. leaf exhibited excellent inhibition performance, and the inhibition efficiency for carbon [...] Read more.

The biodegradable inhibitors, which could effectively reduce the rate of corrosion of carbon steel, were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The mixed-type inhibitors extracted from Eriobotrya japonica Thunb. leaf exhibited excellent inhibition performance, and the inhibition efficiency for carbon steel reached 90.0% at 298 K in hydrochloric acid. Moreover, the adsorption mechanism of the inhibitors on a carbon steel surface is described by the Langmuir adsorption isotherm. Simultaneously, the corrosion morphology of the carbon steel and the inhibitor structure were analyzed by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR), respectively. Full article

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3012 KiB

Open AccessArticle

Pt-Co Alloys-Loaded Cubic SiC Electrode with Improved Photoelectrocatalysis Property

by Dan Liu, Tao Yang, Junhong Chen, Kuo-Chih Chou and Xinmei Hou

Materials 2017, 10(8), 955; https://doi.org/10.3390/ma10080955 - 16 Aug 2017

Cited by 10 | Viewed by 5919

Abstract

A novel composite photocatalyst was synthesized by loading 5 wt % of platinum cobalt alloy on 3C-SiC nanowires and powder (Pt-Co-SiC) respectively via a simple polyol reduction method. Pt-Co-SiC were comprehensively characterized by SEM, HRTEM, XRD, PL, and XPS. The results indicated that [...] Read more.

A novel composite photocatalyst was synthesized by loading 5 wt % of platinum cobalt alloy on 3C-SiC nanowires and powder (Pt-Co-SiC) respectively via a simple polyol reduction method. Pt-Co-SiC were comprehensively characterized by SEM, HRTEM, XRD, PL, and XPS. The results indicated that Pt-Co nanoparticles in the size of 2–5 nm were dispersed homogeneously in the SiC nanowires and powders. The photocurrent response of the Pt-Co-SiC increased remarkably with increasing Pt content and the best performance was observed with the sample of Pt₃Co-SiC. Especially, the Pt₃Co-SiC nanowires photoelectrode exhibited improved cathodic current density (0.14 mA·cm⁻²) under the simulated sunlight, which was about 10 times higher than the Pt₃Co-SiC powders. The H₂ production rate for the Pt₃Co-SiC nanowires is 30 times more than that of the pure SiC nanowires. The enhancement of the Pt-Co-SiC properties could be ascribed to the fact that more visible light was harvested and the photogenerated electron and the interfacial electron transfered more easily. Full article

(This article belongs to the Section Energy Materials)

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1269 KiB

Open AccessArticle

Antibacterial Properties of Nonwoven Wound Dressings Coated with Manuka Honey or Methylglyoxal

by Sophie E. L. Bulman, Giuseppe Tronci, Parikshit Goswami, Chris Carr and Stephen J. Russell

Materials 2017, 10(8), 954; https://doi.org/10.3390/ma10080954 - 16 Aug 2017

Cited by 44 | Viewed by 7275

Abstract

Manuka honey (MH) is used as an antibacterial agent in bioactive wound dressings via direct impregnation onto a suitable substrate. MH provides unique antibacterial activity when compared with conventional honeys, owing partly to one of its constituents, methylglyoxal (MGO). Aiming to investigate an [...] Read more.

Manuka honey (MH) is used as an antibacterial agent in bioactive wound dressings via direct impregnation onto a suitable substrate. MH provides unique antibacterial activity when compared with conventional honeys, owing partly to one of its constituents, methylglyoxal (MGO). Aiming to investigate an antibiotic-free antimicrobial strategy, we studied the antibacterial activity of both MH and MGO (at equivalent MGO concentrations) when applied as a physical coating to a nonwoven fabric wound dressing. When physically coated on to a cellulosic hydroentangled nonwoven fabric, it was found that concentrations of 0.0054 mg cm⁻² of MGO in the form of MH and MGO were sufficient to achieve a 100 colony forming unit % bacteria reduction against gram-positive Staphylococcus aureus and gram-negative Klebsiella pneumoniae, based on BS EN ISO 20743:2007. A 3- to 20-fold increase in MGO concentration (0.0170–0.1 mg cm⁻²) was required to facilitate a good antibacterial effect (based on BS EN ISO 20645:2004) in terms of zone of inhibition and lack of growth under the sample. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) was also assessed for MGO in liquid form against three prevalent wound and healthcare-associated pathogens, i.e., Staphylococcus aureus, gram-negative Pseudomonas aeruginosa and gram-positive Enterococcus faecalis. Other than the case of MGO-containing fabrics, solutions with much higher MGO concentrations (128 mg L⁻¹–1024 mg L⁻¹) were required to provide either a bacteriostatic or bactericidal effect. The results presented in this study therefore demonstrate the relevance of an MGO-based coating as an environmentally friendly strategy for the design of functional dressings with antibiotic-free antimicrobial chemistries. Full article

(This article belongs to the Section Biomaterials)

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3917 KiB

Open AccessReview

Samarium Monosulfide (SmS): Reviewing Properties and Applications

by Andreas Sousanis, Philippe F. Smet and Dirk Poelman

Materials 2017, 10(8), 953; https://doi.org/10.3390/ma10080953 - 16 Aug 2017

Cited by 28 | Viewed by 8598

Abstract

In this review, we give an overview of the properties and applications of samarium monosulfide, SmS, which has gained considerable interest as a switchable material. It shows a pressure-induced phase transition from the semiconducting to the metallic state by polishing, and it switches [...] Read more.

In this review, we give an overview of the properties and applications of samarium monosulfide, SmS, which has gained considerable interest as a switchable material. It shows a pressure-induced phase transition from the semiconducting to the metallic state by polishing, and it switches back to the semiconducting state by heating. The material also shows a magnetic transition, from the paramagnetic state to an antiferromagnetically ordered state. The switching behavior between the semiconducting and metallic states could be exploited in several applications, such as high density optical storage and memory materials, thermovoltaic devices, infrared sensors and more. We discuss the electronic, optical and magnetic properties of SmS, its switching behavior, as well as the thin film deposition techniques which have been used, such as e-beam evaporation and sputtering. Moreover, applications and possible ideas for future work on this material are presented. Our scope is to present the properties of SmS, which were mainly measured in bulk crystals, while at the same time we describe the possible deposition methods that will push the study of SmS to nanoscale dimensions, opening an intriguing range of applications for low-dimensional, pressure-induced semiconductor–metal transition compounds. Full article

(This article belongs to the Section Advanced Materials Characterization)

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2084 KiB

Open AccessFeature PaperReview

Combination of Poly(lactic) Acid and Starch for Biodegradable Food Packaging

by Justine Muller, Chelo González-Martínez and Amparo Chiralt

Materials 2017, 10(8), 952; https://doi.org/10.3390/ma10080952 - 15 Aug 2017

Cited by 330 | Viewed by 23410

Abstract

The massive use of synthetic plastics, in particular in the food packaging area, has a great environmental impact, and alternative more ecologic materials are being required. Poly(lactic) acid (PLA) and starch have been extensively studied as potential replacements for non-degradable petrochemical polymers on [...] Read more.

The massive use of synthetic plastics, in particular in the food packaging area, has a great environmental impact, and alternative more ecologic materials are being required. Poly(lactic) acid (PLA) and starch have been extensively studied as potential replacements for non-degradable petrochemical polymers on the basis of their availability, adequate food contact properties and competitive cost. Nevertheless, both polymers exhibit some drawbacks for packaging uses and need to be adapted to the food packaging requirements. Starch, in particular, is very water sensitive and its film properties are heavily dependent on the moisture content, exhibiting relatively low mechanical resistance. PLA films are very brittle and offer low resistance to oxygen permeation. Their combination as blend or multilayer films could provide properties that are more adequate for packaging purposes on the basis of their complementary characteristics. The main characteristics of PLA and starch in terms of not only the barrier and mechanical properties of their films but also of their combinations, by using blending or multilayer strategies, have been analyzed, identifying components or processes that favor the polymer compatibility and the good performance of the combined materials. The properties of some blends/combinations have been discussed in comparison with those of pure polymer films. Full article

(This article belongs to the Special Issue Biobased Polymers for Packaging Applications)

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7055 KiB

Open AccessArticle

A Continuum Damage Mechanics Model for the Static and Cyclic Fatigue of Cellular Composites

by Sergej Diel and Otto Huber

Materials 2017, 10(8), 951; https://doi.org/10.3390/ma10080951 - 15 Aug 2017

Cited by 11 | Viewed by 6593

Abstract

The fatigue behavior of a cellular composite with an epoxy matrix and glass foam granules is analyzed and modeled by means of continuum damage mechanics. The investigated cellular composite is a particular type of composite foam, and is very similar to syntactic foams. [...] Read more.

The fatigue behavior of a cellular composite with an epoxy matrix and glass foam granules is analyzed and modeled by means of continuum damage mechanics. The investigated cellular composite is a particular type of composite foam, and is very similar to syntactic foams. In contrast to conventional syntactic foams constituted by hollow spherical particles (balloons), cellular glass, mineral, or metal place holders are combined with the matrix material (metal or polymer) in the case of cellular composites. A microstructural investigation of the damage behavior is performed using scanning electron microscopy. For the modeling of the fatigue behavior, the damage is separated into pure static and pure cyclic damage and described in terms of the stiffness loss of the material using damage models for cyclic and creep damage. Both models incorporate nonlinear accumulation and interaction of damage. A cycle jumping procedure is developed, which allows for a fast and accurate calculation of the damage evolution for constant load frequencies. The damage model is applied to examine the mean stress effect for cyclic fatigue and to investigate the frequency effect and the influence of the signal form in the case of static and cyclic damage interaction. The calculated lifetimes are in very good agreement with experimental results. Full article

(This article belongs to the Special Issue Syntactic Foams: Microstructural Characterisation and Effective Properties)

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