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Materials, Volume 9, Issue 4 (April 2016) – 91 articles

Cover Story (view full-size image): Photo-electrolysis is a promising strategy to exploit solar energy aimed at producing clean fuels (e.g. H2, CH4, syngas) directly from water and CO2, addressing the current energetic and environmental challenges. In this context, the development of efficient water oxidation catalysts is one of the major barriers to overcome. Mn-oxides, being active, earth-abundant and low-toxicity materials, are currently considered as promising water oxidation catalysts. Hence, the optimization of Mn-oxides electrodes is crucial for future sustainable solar fuels production. View the paper
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4470 KiB  
Article
Mechanics Model for Simulating RC Hinges under Reversed Cyclic Loading
by Ahmad Azim Shukri, Phillip Visintin, Deric J. Oehlers and Mohd Zamin Jumaat
Materials 2016, 9(4), 305; https://doi.org/10.3390/ma9040305 - 22 Apr 2016
Cited by 7 | Viewed by 5514
Abstract
Describing the moment rotation (M/θ) behavior of reinforced concrete (RC) hinges is essential in predicting the behavior of RC structures under severe loadings, such as under cyclic earthquake motions and blast loading. The behavior of RC hinges is defined by localized slip or [...] Read more.
Describing the moment rotation (M/θ) behavior of reinforced concrete (RC) hinges is essential in predicting the behavior of RC structures under severe loadings, such as under cyclic earthquake motions and blast loading. The behavior of RC hinges is defined by localized slip or partial interaction (PI) behaviors in both the tension and compression region. In the tension region, slip between the reinforcement and the concrete defines crack spacing, crack opening and closing, and tension stiffening. While in the compression region, slip along concrete to concrete interfaces defines the formation and failure of concrete softening wedges. Being strain-based, commonly-applied analysis techniques, such as the moment curvature approach, cannot directly simulate these PI behaviors because they are localized and displacement based. Therefore, strain-based approaches must resort to empirical factors to define behaviors, such as tension stiffening and concrete softening hinge lengths. In this paper, a displacement-based segmental moment rotation approach, which directly simulates the partial interaction behaviors in both compression and tension, is developed for predicting the M/θ response of an RC beam hinge under cyclic loading. Significantly, in order to develop the segmental approach, a partial interaction model to predict the tension stiffening load slip relationship between the reinforcement and the concrete is developed. Full article
(This article belongs to the Section Advanced Materials Characterization)
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5045 KiB  
Article
Evaluation of Functionalized Porous Titanium Implants for Enhancing Angiogenesis in Vitro
by Laura Roland, Samantha Backhaus, Michael Grau, Julia Matena, Michael Teske, Martin Beyerbach, Hugo Murua Escobar, Heinz Haferkamp, Nils-Claudius Gellrich and Ingo Nolte
Materials 2016, 9(4), 304; https://doi.org/10.3390/ma9040304 - 22 Apr 2016
Cited by 6 | Viewed by 5867
Abstract
Implant constructs supporting angiogenesis are favorable for treating critically-sized bone defects, as ingrowth of capillaries towards the center of large defects is often insufficient. Consequently, the insufficient nutritional supply of these regions leads to impaired bone healing. Implants with specially designed angiogenic supporting [...] Read more.
Implant constructs supporting angiogenesis are favorable for treating critically-sized bone defects, as ingrowth of capillaries towards the center of large defects is often insufficient. Consequently, the insufficient nutritional supply of these regions leads to impaired bone healing. Implants with specially designed angiogenic supporting geometry and functionalized with proangiogenic cytokines can enhance angiogenesis. In this study, Vascular Endothelial Growth Factor (VEGF) and High Mobility Group Box 1 (HMGB1) were used for incorporation into poly-ε-caprolactone (PCL)-coated porous titanium implants. Bioactivity of released factors and influence on angiogenesis of functionalized implants were evaluated using a migration assay and angiogenesis assays. Both implants released angiogenic factors, inducing migration of endothelial cells. Also, VEGF-functionalized PCL-coated titanium implants enhanced angiogenesis in vitro. Both factors were rapidly released in high doses from the implant coating during the first 72 h. Full article
(This article belongs to the Special Issue Materials for Hard and Soft Tissue Engineering: Novel Approaches)
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2078 KiB  
Review
A Review on Grafting of Biofibers for Biocomposites
by Liqing Wei and Armando G. McDonald
Materials 2016, 9(4), 303; https://doi.org/10.3390/ma9040303 - 22 Apr 2016
Cited by 129 | Viewed by 12495
Abstract
A recent increase in the use of biofibers as low-cost and renewable reinforcement for the polymer biocomposites has been seen globally. Biofibers are classified into: lignocellulosic fibers (i.e., cellulose, wood and natural fibers), nanocellulose (i.e., cellulose nanocrystals and cellulose [...] Read more.
A recent increase in the use of biofibers as low-cost and renewable reinforcement for the polymer biocomposites has been seen globally. Biofibers are classified into: lignocellulosic fibers (i.e., cellulose, wood and natural fibers), nanocellulose (i.e., cellulose nanocrystals and cellulose nanofibrils), and bacterial cellulose, while polymer matrix materials can be petroleum based or bio-based. Green biocomposites can be produced using both biobased fibers and polymers. Incompatibility between the hydrophilic biofibers and hydrophobic polymer matrix can cause performance failure of resulting biocomposites. Diverse efforts have focused on the modification of biofibers in order to improve the performances of biocomposites. “Grafting” copolymerization strategy can render the advantages of biofiber and impart polymer properties onto it and the performance of biocomposites can be tuned through changing grafting parameters. This review presents a short overview of various “grafting” methods which can be directly or potentially employed to enhance the interaction between biofibers and a polymer matrix for biocomposites. Major grafting techniques, including ring opening polymerization, grafting via coupling agent and free radical induced grafting, have been discussed. Improved properties such as mechanical, thermal, and water resistance have provided grafted biocomposites with new opportunities for applications in specific industries. Full article
(This article belongs to the Special Issue Bio- and Natural-Fiber Composites)
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9033 KiB  
Article
In Vitro Evaluation and Mechanism Analysis of the Fiber Shedding Property of Textile Pile Debridement Materials
by Yijun Fu, Qixue Xie, Jihong Lao and Lu Wang
Materials 2016, 9(4), 302; https://doi.org/10.3390/ma9040302 - 22 Apr 2016
Cited by 5 | Viewed by 6299
Abstract
Fiber shedding is a critical problem in biomedical textile debridement materials, which leads to infection and impairs wound healing. In this work, single fiber pull-out test was proposed as an in vitro evaluation for the fiber shedding property of a textile pile debridement [...] Read more.
Fiber shedding is a critical problem in biomedical textile debridement materials, which leads to infection and impairs wound healing. In this work, single fiber pull-out test was proposed as an in vitro evaluation for the fiber shedding property of a textile pile debridement material. Samples with different structural design (pile densities, numbers of ground yarns and coating times) were prepared and estimated under this testing method. Results show that single fiber pull-out test offers an appropriate in vitro evaluation for the fiber shedding property of textile pile debridement materials. Pull-out force for samples without back-coating exhibited a slight escalating trend with the supplement in pile density and number of ground yarn plies, while back-coating process significantly raised the single fiber pull-out force. For fiber shedding mechanism analysis, typical pull-out behavior and failure modes of the single fiber pull-out test were analyzed in detail. Three failure modes were found in this study, i.e., fiber slippage, coating point rupture and fiber breakage. In summary, to obtain samples with desirable fiber shedding property, fabric structural design, preparation process and raw materials selection should be taken into full consideration. Full article
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1743 KiB  
Article
Shape-Dependent Single-Electron Levels for Au Nanoparticles
by Georgios D. Barmparis, Georgios Kopidakis and Ioannis N. Remediakis
Materials 2016, 9(4), 301; https://doi.org/10.3390/ma9040301 - 21 Apr 2016
Cited by 8 | Viewed by 7713
Abstract
The shape of metal nanoparticles has a crucial role in their performance in heterogeneous catalysis as well as photocatalysis. We propose a method of determining the shape of nanoparticles based on measurements of single-electron quantum levels. We first consider nanoparticles in two shapes [...] Read more.
The shape of metal nanoparticles has a crucial role in their performance in heterogeneous catalysis as well as photocatalysis. We propose a method of determining the shape of nanoparticles based on measurements of single-electron quantum levels. We first consider nanoparticles in two shapes of high symmetry: cube and sphere. We then focus on Au nanoparticles in three characteristic shapes that can be found in metal/inorganic or metal/organic compounds routinely used in catalysis and photocatalysis. We describe the methodology we use to solve the Schrödinger equation for arbitrary nanoparticle shape. The method gives results that agree well with analytical solutions for the high-symmetry shapes. When we apply our method in realistic gold nanoparticle models, which are obtained from Wulff construction based on first principles calculations, the single-electron levels and their density of states exhibit distinct shape-dependent features. Results for clean-surface nanoparticles are closer to those for cubic particles, while CO-covered nanoparticles have energy levels close to those of a sphere. Thiolate-covered nanoparticles with multifaceted polyhedral shape have distinct levels that are in between those for sphere and cube. We discuss how shape-dependent electronic structure features could be identified in experiments and thus guide catalyst design. Full article
(This article belongs to the Special Issue Advancement of Photocatalytic Materials 2016)
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4992 KiB  
Article
Temperature-Driven Structural and Morphological Evolution of Zinc Oxide Nano-Coalesced Microstructures and Its Defect-Related Photoluminescence Properties
by Karkeng Lim, Muhammad Azmi Abdul Hamid, Roslinda Shamsudin, N.H. Al-Hardan, Ishak Mansor and Weesiong Chiu
Materials 2016, 9(4), 300; https://doi.org/10.3390/ma9040300 - 20 Apr 2016
Cited by 47 | Viewed by 7103
Abstract
In this paper, we address the synthesis of nano-coalesced microstructured zinc oxide thin films via a simple thermal evaporation process. The role of synthesis temperature on the structural, morphological, and optical properties of the prepared zinc oxide samples was deeply investigated. The obtained [...] Read more.
In this paper, we address the synthesis of nano-coalesced microstructured zinc oxide thin films via a simple thermal evaporation process. The role of synthesis temperature on the structural, morphological, and optical properties of the prepared zinc oxide samples was deeply investigated. The obtained photoluminescence and X-ray photoelectron spectroscopy outcomes will be used to discuss the surface structure defects of the prepared samples. The results indicated that the prepared samples are polycrystalline in nature, and the sample prepared at 700 °C revealed a tremendously c-axis oriented zinc oxide. The temperature-driven morphological evolution of the zinc oxide nano-coalesced microstructures was perceived, resulting in transformation of quasi-mountain chain-like to pyramidal textured zinc oxide with increasing the synthesis temperature. The results also impart that the sample prepared at 500 °C shows a higher percentage of the zinc interstitial and oxygen vacancies. Furthermore, the intensity of the photoluminescence emission in the ultraviolet region was enhanced as the heating temperature increased from 500 °C to 700 °C. Lastly, the growth mechanism of the zinc oxide nano-coalesced microstructures is discussed according to the reaction conditions. Full article
(This article belongs to the Section Advanced Materials Characterization)
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5158 KiB  
Article
Microwave Synthesized ZnO Nanorod Arrays for UV Sensors: A Seed Layer Annealing Temperature Study
by Ana Pimentel, Sofia Henriques Ferreira, Daniela Nunes, Tomas Calmeiro, Rodrigo Martins and Elvira Fortunato
Materials 2016, 9(4), 299; https://doi.org/10.3390/ma9040299 - 20 Apr 2016
Cited by 82 | Viewed by 11170
Abstract
The present work reports the influence of zinc oxide (ZnO) seed layer annealing temperature on structural, optical and electrical properties of ZnO nanorod arrays, synthesized by hydrothermal method assisted by microwave radiation, to be used as UV sensors. The ZnO seed layer was [...] Read more.
The present work reports the influence of zinc oxide (ZnO) seed layer annealing temperature on structural, optical and electrical properties of ZnO nanorod arrays, synthesized by hydrothermal method assisted by microwave radiation, to be used as UV sensors. The ZnO seed layer was produced using the spin-coating method and several annealing temperatures, ranging from 100 to 500 °C, have been tested. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and spectrophotometry measurements have been used to investigate the structure, morphology, and optical properties variations of the produced ZnO nanorod arrays regarding the seed layer annealing temperatures employed. After the growth of ZnO nanorod arrays, the whole structure was tested as UV sensors, showing an increase in the sensitivity with the increase of seed layer annealing temperature. The UV sensor response of ZnO nanorod arrays produced with the seed layer annealed temperature of 500 °C was 50 times superior to the ones produced with a seed layer annealed at 100 °C. Full article
(This article belongs to the Special Issue Microwave Materials Processing)
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4341 KiB  
Article
Mechanical Properties, Short Time Creep, and Fatigue of an Austenitic Steel
by Josip Brnic, Goran Turkalj, Marko Canadija, Domagoj Lanc, Sanjin Krscanski, Marino Brcic, Qiang Li and Jitai Niu
Materials 2016, 9(4), 298; https://doi.org/10.3390/ma9040298 - 20 Apr 2016
Cited by 20 | Viewed by 11146
Abstract
The correct choice of a material in the process of structural design is the most important task. This study deals with determining and analyzing the mechanical properties of the material, and the material resistance to short-time creep and fatigue. The material under consideration [...] Read more.
The correct choice of a material in the process of structural design is the most important task. This study deals with determining and analyzing the mechanical properties of the material, and the material resistance to short-time creep and fatigue. The material under consideration in this investigation is austenitic stainless steel X6CrNiTi18-10. The results presenting ultimate tensile strength and 0.2 offset yield strength at room and elevated temperatures are displayed in the form of engineering stress-strain diagrams. Besides, the creep behavior of the steel is presented in the form of creep curves. The material is consequently considered to be creep resistant at temperatures of 400 °C and 500 °C when subjected to a stress which is less than 0.9 of the yield strength at the mentioned temperatures. Even when the applied stress at a temperature of 600 °C is less than 0.5 of the yield strength, the steel may be considered as resistant to creep. Cyclic tensile fatigue tests were carried out at stress ratio R = 0.25 using a servo-pulser machine and the results were recorded. The analysis shows that the stress level of 434.33 MPa can be adopted as a fatigue limit. The impact energy was also determined and the fracture toughness assessed. Full article
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3217 KiB  
Article
Polyelectrolyte-Functionalized Nanofiber Mats Control the Collection and Inactivation of Escherichia coli
by Katrina A. Rieger, Michael Porter and Jessica D. Schiffman
Materials 2016, 9(4), 297; https://doi.org/10.3390/ma9040297 - 19 Apr 2016
Cited by 19 | Viewed by 6532
Abstract
Quantifying the effect that nanofiber mat chemistry and hydrophilicity have on microorganism collection and inactivation is critical in biomedical applications. In this study, the collection and inactivation of Escherichia coli K12 was examined using cellulose nanofiber mats that were surface-functionalized using three polyelectrolytes: [...] Read more.
Quantifying the effect that nanofiber mat chemistry and hydrophilicity have on microorganism collection and inactivation is critical in biomedical applications. In this study, the collection and inactivation of Escherichia coli K12 was examined using cellulose nanofiber mats that were surface-functionalized using three polyelectrolytes: poly (acrylic acid) (PAA), chitosan (CS), and polydiallyldimethylammonium chloride (pDADMAC). The polyelectrolyte functionalized nanofiber mats retained the cylindrical morphology and average fiber diameter (~0.84 µm) of the underlying cellulose nanofibers. X-ray photoelectron spectroscopy (XPS) and contact angle measurements confirmed the presence of polycations or polyanions on the surface of the nanofiber mats. Both the control cellulose and pDADMAC-functionalized nanofiber mats exhibited a high collection of E. coli K12, which suggests that mat hydrophilicity may play a larger role than surface charge on cell collection. While the minimum concentration of polycations needed to inhibit E. coli K12 was 800 µg/mL for both CS and pDADMAC, once immobilized, pDADMAC-functionalized nanofiber mats exhibited a higher inactivation of E. coli K12, (~97%). Here, we demonstrate that the collection and inactivation of microorganisms by electrospun cellulose nanofiber mats can be tailored through a facile polyelectrolyte functionalization process. Full article
(This article belongs to the Special Issue Electrospun Materials)
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1943 KiB  
Article
Spin-Coated vs. Electrodeposited Mn Oxide Films as Water Oxidation Catalysts
by Simelys Hernández, Carminna Ottone, Sara Varetti, Marco Fontana, Diego Pugliese, Guido Saracco, Barbara Bonelli and Marco Armandi
Materials 2016, 9(4), 296; https://doi.org/10.3390/ma9040296 - 19 Apr 2016
Cited by 33 | Viewed by 6745
Abstract
Manganese oxides (MnOx), being active, inexpensive and low-toxicity materials, are considered promising water oxidation catalysts (WOCs). This work reports the preparation and the physico-chemical and electrochemical characterization of spin-coated (SC) films of commercial Mn2O3, Mn3O [...] Read more.
Manganese oxides (MnOx), being active, inexpensive and low-toxicity materials, are considered promising water oxidation catalysts (WOCs). This work reports the preparation and the physico-chemical and electrochemical characterization of spin-coated (SC) films of commercial Mn2O3, Mn3O4 and MnO2 powders. Spin coating consists of few preparation steps and employs green chemicals (i.e., ethanol, acetic acid, polyethylene oxide and water). To the best of our knowledge, this is the first time SC has been used for the preparation of stable powder-based WOCs electrodes. For comparison, MnOx films were also prepared by means of electrodeposition (ED) and tested under the same conditions, at neutral pH. Particular interest was given to α-Mn2O3-based films, since Mn (III) species play a crucial role in the electrocatalytic oxidation of water. To this end, MnO2-based SC and ED films were calcined at 500 °C, in order to obtain the desired α-Mn2O3 crystalline phase. Electrochemical impedance spectroscopy (EIS) measurements were performed to study both electrode charge transport properties and electrode–electrolyte charge transfer kinetics. Long-term stability tests and oxygen/hydrogen evolution measurements were also made on the highest-performing samples and their faradaic efficiencies were quantified, with results higher than 95% for the Mn2O3 SC film, finally showing that the SC technique proposed here is a simple and reliable method to study the electrocatalytic behavior of pre-synthesized WOCs powders. Full article
(This article belongs to the Special Issue Electrode Materials)
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3914 KiB  
Article
Residual Mechanical Properties of Concrete Made with Crushed Clay Bricks and Roof Tiles Aggregate after Exposure to High Temperatures
by Ivana Miličević, Nina Štirmer and Ivana Banjad Pečur
Materials 2016, 9(4), 295; https://doi.org/10.3390/ma9040295 - 19 Apr 2016
Cited by 13 | Viewed by 6166
Abstract
This paper presents the residual mechanical properties of concrete made with crushed bricks and clay roof tile aggregates after exposure to high temperatures. One referent mixture and eight mixtures with different percentages of replacement of natural aggregate by crushed bricks and roof tiles [...] Read more.
This paper presents the residual mechanical properties of concrete made with crushed bricks and clay roof tile aggregates after exposure to high temperatures. One referent mixture and eight mixtures with different percentages of replacement of natural aggregate by crushed bricks and roof tiles are experimentally tested. The properties of the concrete were measured before and after exposure to 200, 400, 600 and 800 °C. In order to evaluate the basic residual mechanical properties of concrete with crushed bricks and roof tiles after exposure to high temperatures, ultrasonic pulse velocity is used as a non-destructive test method and the results are compared with those of a destructive method for validation. The mixture with the highest percentage of replacement of natural aggregate by crushed brick and roof tile aggregate has the best physical, mechanical, and thermal properties for application of such concrete in precast concrete elements exposed to high temperatures. Full article
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2977 KiB  
Article
Ultrasonic Monitoring of Setting and Strength Development of Ultra-High-Performance Concrete
by Doo-Yeol Yoo, Hyun-Oh Shin and Young-Soo Yoon
Materials 2016, 9(4), 294; https://doi.org/10.3390/ma9040294 - 19 Apr 2016
Cited by 26 | Viewed by 6319
Abstract
In this study, the setting and tensile strength development of ultra-high-performance concrete (UHPC) at a very early age was investigated by performing the penetration resistance test (ASTM C403), as well as the direct tensile test using the newly developed test apparatus, and taking [...] Read more.
In this study, the setting and tensile strength development of ultra-high-performance concrete (UHPC) at a very early age was investigated by performing the penetration resistance test (ASTM C403), as well as the direct tensile test using the newly developed test apparatus, and taking ultrasonic pulse velocity (UPV) measurements. In order to determine the optimum surface treatment method for preventing rapid surface drying of UHPC, four different methods were examined: plastic sheet, curing cover, membrane-forming compound, and paraffin oil. Based on the test results, the use of paraffin oil was found to be the best choice for measuring the penetration resistance and the UPV, and attaching the plastic sheet to the exposed surface was considered to be a simple method for preventing the rapid surface drying of UHPC elements. An S-shaped tensile strength development at a very early age (before 24 h) was experimentally obtained, and it was predicted by a power function of UPV. Lastly, the addition of shrinkage-reducing and expansive admixtures resulted in more rapid development of penetration resistance and UPV of UHPC. Full article
(This article belongs to the Section Advanced Composites)
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1840 KiB  
Article
Study of Charge Carrier Transport in GaN Sensors
by Eugenijus Gaubas, Tomas Ceponis, Edmundas Kuokstis, Dovile Meskauskaite, Jevgenij Pavlov and Ignas Reklaitis
Materials 2016, 9(4), 293; https://doi.org/10.3390/ma9040293 - 18 Apr 2016
Cited by 6 | Viewed by 4521
Abstract
Capacitor and Schottky diode sensors were fabricated on GaN material grown by hydride vapor phase epitaxy and metal-organic chemical vapor deposition techniques using plasma etching and metal deposition. The operational characteristics of these devices have been investigated by profiling current transients and by [...] Read more.
Capacitor and Schottky diode sensors were fabricated on GaN material grown by hydride vapor phase epitaxy and metal-organic chemical vapor deposition techniques using plasma etching and metal deposition. The operational characteristics of these devices have been investigated by profiling current transients and by comparing the experimental regimes of the perpendicular and parallel injection of excess carrier domains. Profiling of the carrier injection location allows for the separation of the bipolar and the monopolar charge drift components. Carrier mobility values attributed to the hydride vapor phase epitaxy (HVPE) GaN material have been estimated as μe = 1000 ± 200 cm2/Vs for electrons, and μh = 400 ± 80 cm2/Vs for holes, respectively. Current transients under injection of the localized and bulk packets of excess carriers have been examined in order to determine the surface charge formation and polarization effects. Full article
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3577 KiB  
Article
Research on Glass Frit Deposition Based on the Electrospray Process
by Yifang Liu, Daner Chen, Zhan Zhan, Chenlei Li, Jianyi Zheng and Daoheng Sun
Materials 2016, 9(4), 292; https://doi.org/10.3390/ma9040292 - 18 Apr 2016
Cited by 4 | Viewed by 5220
Abstract
In this paper, the electrospray technology is used to easily deposit the glass frit into patterns at a micro-scale level. First, far-field electrospray process was carried out with a mixture of glass frit in the presence of ethanol. A uniform, smooth, and dense [...] Read more.
In this paper, the electrospray technology is used to easily deposit the glass frit into patterns at a micro-scale level. First, far-field electrospray process was carried out with a mixture of glass frit in the presence of ethanol. A uniform, smooth, and dense glass frit film was obtained, verifying that the electrospray technology was feasible. Then, the distance between the nozzle and the substrate was reduced to 2 mm to carry out near-field electrospray. The experimental process was improved by setting the range of the feed rate of the substrate to match both the concentration and the flow rate of the solution. Spray diameter could be less at the voltage of 2 kV, in which the glass frit film was expected to reach the minimum line width. A uniform glass frit film with a line width within the range of 400–500 μm was prepared when the speed of the substrate was 25 mm/s. It indicates that electrospray is an efficient technique for the patterned deposition of glass frit in wafer-level hermetic encapsulation. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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33296 KiB  
Article
Development of a Tomography Technique for Assessment of the Material Condition of Concrete Using Optimized Elastic Wave Parameters
by Hwa Kian Chai, Kit Fook Liu, Arash Behnia, Kobayashi Yoshikazu and Tomoki Shiotani
Materials 2016, 9(4), 291; https://doi.org/10.3390/ma9040291 - 16 Apr 2016
Cited by 15 | Viewed by 6318
Abstract
Concrete is the most ubiquitous construction material. Apart from the fresh and early age properties of concrete material, its condition during the structure life span affects the overall structural performance. Therefore, development of techniques such as non-destructive testing which enable the investigation of [...] Read more.
Concrete is the most ubiquitous construction material. Apart from the fresh and early age properties of concrete material, its condition during the structure life span affects the overall structural performance. Therefore, development of techniques such as non-destructive testing which enable the investigation of the material condition, are in great demand. Tomography technique has become an increasingly popular non-destructive evaluation technique for civil engineers to assess the condition of concrete structures. In the present study, this technique is investigated by developing reconstruction procedures utilizing different parameters of elastic waves, namely the travel time, wave amplitude, wave frequency, and Q-value. In the development of algorithms, a ray tracing feature was adopted to take into account the actual non-linear propagation of elastic waves in concrete containing defects. Numerical simulation accompanied by experimental verifications of wave motion were conducted to obtain wave propagation profiles in concrete containing honeycomb as a defect and in assessing the tendon duct filling of pre-stressed concrete (PC) elements. The detection of defects by the developed tomography reconstruction procedures was evaluated and discussed. Full article
(This article belongs to the Special Issue Image Analysis and Processing for Cement-based Materials)
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2855 KiB  
Article
SiO2-CaO-P2O5 Bioactive Glasses: A Promising Curcuminoids Delivery System
by Valentina Nicolini, Monica Caselli, Erika Ferrari, Ledi Menabue, Gigliola Lusvardi, Monica Saladini and Gianluca Malavasi
Materials 2016, 9(4), 290; https://doi.org/10.3390/ma9040290 - 15 Apr 2016
Cited by 12 | Viewed by 5811
Abstract
In this paper, we report the study of the loading and the release of curcuminoids by bioactive glasses (BG) and mesoporous bioactive glasses (MBG). Through a detailed spectroscopic study, it was possible to determine the amount and the type of molecules released in [...] Read more.
In this paper, we report the study of the loading and the release of curcuminoids by bioactive glasses (BG) and mesoporous bioactive glasses (MBG). Through a detailed spectroscopic study, it was possible to determine the amount and the type of molecules released in water and in simulated body fluid (SBF). In particular, curcumin and K2T21 show a good ability to be released in di-keto and keto-enolic form, depending from the pH. However, after 24 h, the amount of pristine curcumin release is very low with a consequent increment of degradation products derived by curcuminoids. The presence of –OH groups on curcuminoids is a fundamental pre-requisite in order to obtain a high loading and release in polar solution such as water and SBF. The substrate on which we loaded the drugs does not seem to affect significantly the loading and the release of the drugs. The environment, instead, affects the release: for all the drugs, the release in SBF, buffered at pH of 7.4, is slightly worse than the release in water (basic pH values). Full article
(This article belongs to the Special Issue Bioactive Glasses)
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2923 KiB  
Article
1-D Compression Behaviour of Acid Sulphate Soils Treated with Alkali-Activated Slag
by Shahidul Islam, Asadul Haque and Ha Hong Bui
Materials 2016, 9(4), 289; https://doi.org/10.3390/ma9040289 - 15 Apr 2016
Cited by 5 | Viewed by 5474
Abstract
Improvements of soft soils by mechanically mixing cementitious additives have been widely practised for construction of infrastructure. Mixing of additives improves strength and compressibility properties of soils through the development of soil structure. This study investigates the 1-D compression behaviour of alkali-activated slag [...] Read more.
Improvements of soft soils by mechanically mixing cementitious additives have been widely practised for construction of infrastructure. Mixing of additives improves strength and compressibility properties of soils through the development of soil structure. This study investigates the 1-D compression behaviour of alkali-activated slag treated acid sulphate soils (ASS) cured up to 365 days. The void ratio-logarithm of pressure (e-logσ′) behaviour of treated ASS, including the destructuration behaviour, with additive contents and curing time have been analysed. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses have been undertaken to explain the observed variations of the 1-D compression behaviour. This paper presents the results of these analyses in view of obtaining an insight into the 1-D compression behaviour of treated ASS with the help of mineralogical analysis. Full article
(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)
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1760 KiB  
Review
Bioactive Glass Nanoparticles: From Synthesis to Materials Design for Biomedical Applications
by Charlotte Vichery and Jean-Marie Nedelec
Materials 2016, 9(4), 288; https://doi.org/10.3390/ma9040288 - 14 Apr 2016
Cited by 231 | Viewed by 16628
Abstract
Thanks to their high biocompatibility and bioactivity, bioactive glasses are very promising materials for soft and hard tissue repair and engineering. Because bioactivity and specific surface area intrinsically linked, the last decade has seen a focus on the development of highly porous and/or [...] Read more.
Thanks to their high biocompatibility and bioactivity, bioactive glasses are very promising materials for soft and hard tissue repair and engineering. Because bioactivity and specific surface area intrinsically linked, the last decade has seen a focus on the development of highly porous and/or nano-sized materials. This review emphasizes the synthesis of bioactive glass nanoparticles and materials design strategies. The first part comprehensively covers mainly soft chemistry processes, which aim to obtain dispersible and monodispersed nanoparticles. The second part discusses the use of bioactive glass nanoparticles for medical applications, highlighting the design of materials. Mesoporous nanoparticles for drug delivery, injectable systems and scaffolds consisting of bioactive glass nanoparticles dispersed in a polymer, implant coatings and particle dispersions will be presented. Full article
(This article belongs to the Special Issue Bioactive Glasses)
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10815 KiB  
Article
A Novel MgO-CaO-SiO2 System for Fabricating Bone Scaffolds with Improved Overall Performance
by Hang Sun, Shiwei He, Ping Wu, Chengde Gao, Pei Feng, Tao Xiao, Youwen Deng and Cijun Shuai
Materials 2016, 9(4), 287; https://doi.org/10.3390/ma9040287 - 14 Apr 2016
Cited by 28 | Viewed by 7200
Abstract
Although forsterite (Mg2SiO4) possesses good biocompatibility and suitable mechanical properties, the insufficient bioactivity and degradability hinders its further application. In this study, a novel MgO-CaO-SiO2 system was developed by adding wollastonite (CaSiO3) into Mg2SiO [...] Read more.
Although forsterite (Mg2SiO4) possesses good biocompatibility and suitable mechanical properties, the insufficient bioactivity and degradability hinders its further application. In this study, a novel MgO-CaO-SiO2 system was developed by adding wollastonite (CaSiO3) into Mg2SiO4 to fabricate bone scaffolds via selective laser sintering (SLS). The apatite-forming ability and degradability of the scaffolds were enhanced because the degradation of CaSiO3 could form silanol groups, which could offer nucleation sites for apatite. Meanwhile, the mechanical properties of the scaffolds grew with increasing CaSiO3 to 20 wt %. It was explained that the liquid phase of CaSiO3 promoted the densification during sintering due to its low melting point. With the further increase in CaSiO3, the mechanical properties decreased due to the formation of the continuous filling phase. Furthermore, the scaffolds possessed a well-interconnected porous structure and exhibited an ability to support cell adhesion and proliferation. Full article
(This article belongs to the Section Biomaterials)
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2133 KiB  
Article
Photocatalytic Properties of g-C3N4–TiO2 Heterojunctions under UV and Visible Light Conditions
by Rachel Fagan, Declan E. McCormack, Steven J. Hinder and Suresh C. Pillai
Materials 2016, 9(4), 286; https://doi.org/10.3390/ma9040286 - 14 Apr 2016
Cited by 84 | Viewed by 11404
Abstract
Graphitic carbon nitride (g-C3N4) and titanium dioxide (TiO2) were chosen as a model system to investigate photocatalytic abilities of heterojunction system under UV and visible light conditions. The use of g-C3N4 [...] Read more.
Graphitic carbon nitride (g-C3N4) and titanium dioxide (TiO2) were chosen as a model system to investigate photocatalytic abilities of heterojunction system under UV and visible light conditions. The use of g-C3N4 has been shown to be effective in the reduction in recombination through the interaction between the two interfaces of TiO2 and g-C3N4. A simple method of preparing g-C3N4 through the pyrolysis of melamine was employed, which was then added to undoped TiO2 material to form the g-C3N4–TiO2 system. These materials were then fully characterized by X-ray diffraction (XRD), Brunauer Emmett Teller (BET), and various spectroscopic techniques including Raman, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), diffuse absorbance, and photoluminescence analysis. Photocatalysis studies were conducted using the model dye, rhodamine 6G utilizing visible and UV light irradiation. Raman spectroscopy confirmed that a composite of the materials was formed as opposed to a mixture of the two. Using XPS analysis, a shift in the nitrogen peak to that indicative of substitutional nitrogen was detected for all doped samples. This is then mirrored in the diffuse absorbance results, which show a clear decrease in band gap values for these samples, showing the effective band gap alteration achieved through this preparation process. When g-C3N4–TiO2 samples were analyzed under visible light irradiation, no significant improvement was observed compared that of pure TiO2. However, under UV light irradiation conditions, the photocatalytic ability of the doped samples exhibited an increased reactivity when compared to the undoped TiO2 (0.130 min−1), with 4% g-C3N4–TiO2 (0.187 min−1), showing a 43.9% increase in reactivity. Further doping to 8% g-C3N4–TiO2 lead to a decrease in reactivity against rhodamine 6G. BET analysis determined that the surface area of the 4% and 8% g-C3N4–TiO2 samples were very similar, with values of 29.4 and 28.5 m2/g, respectively, suggesting that the actual surface area is not a contributing factor. This could be due to an overloading of the system with covering of the active sites resulting in a lower reaction rate. XPS analysis showed that surface hydroxyl radicals and oxygen vacancies are not being formed throughout this preparation. Therefore, it can be suggested that the increased photocatalytic reaction rates are due to successful interfacial interactions with the g-C3N4-doped TiO2 systems. Full article
(This article belongs to the Special Issue Advancement of Photocatalytic Materials 2016)
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4011 KiB  
Article
A Hydrogel Model Incorporating 3D-Plotted Hydroxyapatite for Osteochondral Tissue Engineering
by Michal Bartnikowski, Ashwini Rahul Akkineni, Michael Gelinsky, Maria A. Woodruff and Travis J. Klein
Materials 2016, 9(4), 285; https://doi.org/10.3390/ma9040285 - 14 Apr 2016
Cited by 31 | Viewed by 8350
Abstract
The concept of biphasic or multi-layered compound scaffolds has been explored within numerous studies in the context of cartilage and osteochondral regeneration. To date, no system has been identified that stands out in terms of superior chondrogenesis, osteogenesis or the formation of a [...] Read more.
The concept of biphasic or multi-layered compound scaffolds has been explored within numerous studies in the context of cartilage and osteochondral regeneration. To date, no system has been identified that stands out in terms of superior chondrogenesis, osteogenesis or the formation of a zone of calcified cartilage (ZCC). Herein we present a 3D plotted scaffold, comprising an alginate and hydroxyapatite paste, cast within a photocrosslinkable hydrogel made of gelatin methacrylamide (GelMA), or GelMA with hyaluronic acid methacrylate (HAMA). We hypothesized that this combination of 3D plotting and hydrogel crosslinking would form a high fidelity, cell supporting structure that would allow localization of hydroxyapatite to the deepest regions of the structure whilst taking advantage of hydrogel photocrosslinking. We assessed this preliminary design in terms of chondrogenesis in culture with human articular chondrocytes, and verified whether the inclusion of hydroxyapatite in the form presented had any influence on the formation of the ZCC. Whilst the inclusion of HAMA resulted in a better chondrogenic outcome, the effect of HAP was limited. We overall demonstrated that formation of such compound structures is possible, providing a foundation for future work. The development of cohesive biphasic systems is highly relevant for current and future cartilage tissue engineering. Full article
(This article belongs to the Special Issue Smart Hydrogels for (Bio)printing Applications)
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3101 KiB  
Article
Si96: A New Silicon Allotrope with Interesting Physical Properties
by Qingyang Fan, Changchun Chai, Qun Wei, Peikun Zhou, Junqin Zhang and Yintang Yang
Materials 2016, 9(4), 284; https://doi.org/10.3390/ma9040284 - 13 Apr 2016
Cited by 30 | Viewed by 7145
Abstract
The structural mechanical properties and electronic properties of a new silicon allotrope Si96 are investigated at ambient pressure by using a first-principles calculation method with the ultrasoft pseudopotential scheme in the framework of generalized gradient approximation. The elastic constants and phonon calculations [...] Read more.
The structural mechanical properties and electronic properties of a new silicon allotrope Si96 are investigated at ambient pressure by using a first-principles calculation method with the ultrasoft pseudopotential scheme in the framework of generalized gradient approximation. The elastic constants and phonon calculations reveal that Si96 is mechanically and dynamically stable at ambient pressure. The conduction band minimum and valence band maximum of Si96 are at the R and G point, which indicates that Si96 is an indirect band gap semiconductor. The anisotropic calculations show that Si96 exhibits a smaller anisotropy than diamond Si in terms of Young’s modulus, the percentage of elastic anisotropy for bulk modulus and shear modulus, and the universal anisotropic index AU. Interestingly, most silicon allotropes exhibit brittle behavior, in contrast to the previously proposed ductile behavior. The void framework, low density, and nanotube structure make Si96 quite attractive for applications such as hydrogen storage and electronic devices that work at extreme conditions, and there are potential applications in Li-battery anode materials. Full article
(This article belongs to the Special Issue Computational Multiscale Modeling and Simulation in Materials Science)
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2724 KiB  
Article
Effects of Apatite Cement Containing Atelocollagen on Attachment to and Proliferation and Differentiation of MC3T3-E1 Osteoblastic Cells
by Masaaki Takechi, Yoshiaki Ninomiya, Kouji Ohta, Misato Tada, Kazuki Sasaki, Mohammad Zeshaan Rahman, Akira Ohta, Kanji Tsuru and Kunio Ishikawa
Materials 2016, 9(4), 283; https://doi.org/10.3390/ma9040283 - 13 Apr 2016
Cited by 4 | Viewed by 5139
Abstract
To improve the osteoconductivity of apatite cement (AC) for reconstruction of bone defects after oral maxillofacial surgery, we previously fabricated AC containing atelocollagen (AC(ate)). In the present study, we examined the initial attachment, proliferation and differentiation of mouse osteoblastic cells (MC3T3-E1 cells) on [...] Read more.
To improve the osteoconductivity of apatite cement (AC) for reconstruction of bone defects after oral maxillofacial surgery, we previously fabricated AC containing atelocollagen (AC(ate)). In the present study, we examined the initial attachment, proliferation and differentiation of mouse osteoblastic cells (MC3T3-E1 cells) on the surface of conventional AC (c-AC), AC(ate) and a plastic cell dish. The number of osteoblastic cells showing initial attachment to AC(ate) was greater than those attached to c-AC and similar to the number attached to the plastic cell wells. We also found that osteoblastic cells were well spread and increased their number on AC(ate) in comparison with c-AC and the wells without specimens, while the amount of procollagen type I carboxy-terminal peptide (PIPC) produced in osteoblastic cells after three days on AC(ate) was greater as compared to the others. There was no significant difference in regard to alkaline phosphatase (ALP) activity and osteocalcin production by osteoblastic cells among the three surface types after three and six days. However, after 12 days, ALP activity and the produced osteocalcin were greater with AC(ate). In conclusion, AC(ate) may be a useful material with high osteoconductivity for reconstruction of bone defects after oral maxillofacial surgery. Full article
(This article belongs to the Special Issue Cellular Materials: Design and Optimisation)
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3301 KiB  
Article
Sol-Gel Synthesis of Carbon Xerogel-ZnO Composite for Detection of Catechol
by Dawei Li, Jun Zang, Jin Zhang, Kelong Ao, Qingqing Wang, Quanfeng Dong and Qufu Wei
Materials 2016, 9(4), 282; https://doi.org/10.3390/ma9040282 - 12 Apr 2016
Cited by 12 | Viewed by 6373
Abstract
Carbon xerogel-zinc oxide (CXZnO) composites were synthesized by a simple method of sol-gel condensation polymerization of formaldehyde and resorcinol solution containing zinc salt followed by drying and thermal treatment. ZnO nanoparticles were observed to be evenly dispersed on the surfaces of the carbon [...] Read more.
Carbon xerogel-zinc oxide (CXZnO) composites were synthesized by a simple method of sol-gel condensation polymerization of formaldehyde and resorcinol solution containing zinc salt followed by drying and thermal treatment. ZnO nanoparticles were observed to be evenly dispersed on the surfaces of the carbon xerogel microspheres. The as-prepared CXZnO composites were mixed with laccase (Lac) and Nafion to obtain a mixture solution, which was further modified on an electrode surface to construct a novel biosensing platform. Finally, the prepared electrochemical biosensor was employed to detect the environmental pollutant, catechol. The analysis result was satisfactory, the sensor showed excellent electrocatalysis towards catechol with high sensitivity (31.2 µA·mM−1), a low detection limit (2.17 µM), and a wide linear range (6.91–453 µM). Moreover, the biosensor also displayed favorable repeatability, reproducibility, selectivity, and stability besides being successfully used in the trace detection of catechol existing in lake water environments. Full article
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4701 KiB  
Article
Highly Conductive Carbon Fiber Reinforced Concrete for Icing Prevention and Curing
by Oscar Galao, Luis Bañón, Francisco Javier Baeza, Jesús Carmona and Pedro Garcés
Materials 2016, 9(4), 281; https://doi.org/10.3390/ma9040281 - 12 Apr 2016
Cited by 89 | Viewed by 10221
Abstract
This paper aims to study the feasibility of highly conductive carbon fiber reinforced concrete (CFRC) as a self-heating material for ice formation prevention and curing in pavements. Tests were carried out in lab ambient conditions at different fixed voltages and then introduced in [...] Read more.
This paper aims to study the feasibility of highly conductive carbon fiber reinforced concrete (CFRC) as a self-heating material for ice formation prevention and curing in pavements. Tests were carried out in lab ambient conditions at different fixed voltages and then introduced in a freezer at −15 °C. The specimens inside the freezer were exposed to different fixed voltages when reaching +5 °C for prevention of icing and when reaching the temperature inside the freezer, i.e., −15 °C, for curing of icing. Results show that this concrete could act as a heating element in pavements with risk of ice formation, consuming a reasonable amount of energy for both anti-icing (prevention) and deicing (curing), which could turn into an environmentally friendly and cost-effective deicing method. Full article
(This article belongs to the Section Energy Materials)
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533 KiB  
Article
Liquid Film Capillary Mechanism for Densification of Ceramic Powders during Flash Sintering
by Rachman Chaim
Materials 2016, 9(4), 280; https://doi.org/10.3390/ma9040280 - 11 Apr 2016
Cited by 76 | Viewed by 7106
Abstract
Recently, local melting of the particle surfaces confirmed the formation of spark and plasma during spark plasma sintering, which explains the rapid densification mechanism via liquid. A model for rapid densification of flash sintered ceramics by liquid film capillary was presented, where liquid [...] Read more.
Recently, local melting of the particle surfaces confirmed the formation of spark and plasma during spark plasma sintering, which explains the rapid densification mechanism via liquid. A model for rapid densification of flash sintered ceramics by liquid film capillary was presented, where liquid film forms by local melting at the particle contacts, due to Joule heating followed by thermal runaway. Local densification is by particle rearrangement led by spreading of the liquid, due to local attractive capillary forces. Electrowetting may assist this process. The asymmetric nature of the powder compact represents an invasive percolating system. Full article
(This article belongs to the Collection Spark-Plasma Sintering and Related Field-Assisted Powder Consolidation Technologies)
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2187 KiB  
Article
Fabrication of Pt/Ti/TiO2 Photoelectrodes by RF-Magnetron Sputtering for Separate Hydrogen and Oxygen Production
by Gian Luca Chiarello, Cristina Tealdi, Piercarlo Mustarelli and Elena Selli
Materials 2016, 9(4), 279; https://doi.org/10.3390/ma9040279 - 8 Apr 2016
Cited by 14 | Viewed by 6216
Abstract
Evolution of pure hydrogen and oxygen by photocatalytic water splitting was attained from the opposite sides of a composite Pt/Ti/TiO2 photoelectrode. The TiO2 films were prepared by radio frequency (RF)-Magnetron Sputtering at different deposition time ranging from 1 up to 8 [...] Read more.
Evolution of pure hydrogen and oxygen by photocatalytic water splitting was attained from the opposite sides of a composite Pt/Ti/TiO2 photoelectrode. The TiO2 films were prepared by radio frequency (RF)-Magnetron Sputtering at different deposition time ranging from 1 up to 8 h and then characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet-visible-near infrared (UV-vis-NIR) diffuse reflectance spectroscopy. The photocatalytic activity was evaluated by incident photon to current efficiency (IPCE) measurements and by photocatalytic water splitting measurements in a two-compartment cell. The highest H2 production rate was attained with the photoelectrode prepared by 6 h-long TiO2 deposition thanks to its high content in the rutile polymorph, which is active under visible light. By contrast, the photoactivity dropped for longer deposition time, because of the increased probability of electron-hole recombination due to the longer electron transfer path. Full article
(This article belongs to the Special Issue Advancement of Photocatalytic Materials 2016)
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5289 KiB  
Article
Experimental Study of Damage Evolution in Circular Stirrup-Confined Concrete
by Zuohua Li, Zhihan Peng, Jun Teng and Ying Wang
Materials 2016, 9(4), 278; https://doi.org/10.3390/ma9040278 - 8 Apr 2016
Cited by 12 | Viewed by 7177
Abstract
This paper presents an experimental study on circular stirrup-confined concrete specimens under uniaxial and monotonic load. The effects of stirrup volume ratio, stirrup yield strength and concrete strength on damage evolution of stirrup-confined concrete were investigated. The experimental results showed that the strength [...] Read more.
This paper presents an experimental study on circular stirrup-confined concrete specimens under uniaxial and monotonic load. The effects of stirrup volume ratio, stirrup yield strength and concrete strength on damage evolution of stirrup-confined concrete were investigated. The experimental results showed that the strength and ductility of concrete are improved by appropriate arrangement of the stirrup confinement. Firstly, the concrete damage evolution can be relatively restrained with the increase of the stirrup volume ratio. Secondly, higher stirrup yield strength usually causes larger confining pressures and slower concrete damage evolution. In contrast, higher concrete strength leads to higher brittleness, which accelerates the concrete damage evolution. A plastic strain expression is obtained through curve fitting, and a damage evolution equation for circular stirrup-confined concrete is proposed by introducing a confinement factor (C) based on the experimental data. The comparison results demonstrate that the proposed damage evolution model can accurately describe the experimental results. Full article
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2282 KiB  
Communication
Compact Layers of Hybrid Halide Perovskites Fabricated via the Aerosol Deposition Process—Uncoupling Material Synthesis and Layer Formation
by Fabian Panzer, Dominik Hanft, Tanaji P. Gujar, Frank-Julian Kahle, Mukundan Thelakkat, Anna Köhler and Ralf Moos
Materials 2016, 9(4), 277; https://doi.org/10.3390/ma9040277 - 8 Apr 2016
Cited by 22 | Viewed by 8685
Abstract
We present the successful fabrication of CH3NH3PbI3 perovskite layers by the aerosol deposition method (ADM). The layers show high structural purity and compactness, thus making them suitable for application in perovskite-based optoelectronic devices. By using the aerosol deposition [...] Read more.
We present the successful fabrication of CH3NH3PbI3 perovskite layers by the aerosol deposition method (ADM). The layers show high structural purity and compactness, thus making them suitable for application in perovskite-based optoelectronic devices. By using the aerosol deposition method we are able to decouple material synthesis from layer processing. Our results therefore allow for enhanced and easy control over the fabrication of perovskite-based devices, further paving the way for their commercialization. Full article
(This article belongs to the Section Energy Materials)
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4327 KiB  
Article
In Vitro Testing of Scaffolds for Mesenchymal Stem Cell-Based Meniscus Tissue Engineering—Introducing a New Biocompatibility Scoring System
by Felix P. Achatz, Richard Kujat, Christian G. Pfeifer, Matthias Koch, Michael Nerlich, Peter Angele and Johannes Zellner
Materials 2016, 9(4), 276; https://doi.org/10.3390/ma9040276 - 7 Apr 2016
Cited by 14 | Viewed by 7060
Abstract
A combination of mesenchymal stem cells (MSCs) and scaffolds seems to be a promising approach for meniscus repair. To facilitate the search for an appropriate scaffold material a reliable and objective in vitro testing system is essential. This paper introduces a new scoring [...] Read more.
A combination of mesenchymal stem cells (MSCs) and scaffolds seems to be a promising approach for meniscus repair. To facilitate the search for an appropriate scaffold material a reliable and objective in vitro testing system is essential. This paper introduces a new scoring for this purpose and analyzes a hyaluronic acid (HA) gelatin composite scaffold and a polyurethane scaffold in combination with MSCs for tissue engineering of meniscus. The pore quality and interconnectivity of pores of a HA gelatin composite scaffold and a polyurethane scaffold were analyzed by surface photography and Berliner-Blau-BSA-solution vacuum filling. Further the two scaffold materials were vacuum-filled with human MSCs and analyzed by histology and immunohistochemistry after 21 days in chondrogenic media to determine cell distribution and cell survival as well as proteoglycan production, collagen type I and II content. The polyurethane scaffold showed better results than the hyaluronic acid gelatin composite scaffold, with signs of central necrosis in the HA gelatin composite scaffolds. The polyurethane scaffold showed good porosity, excellent pore interconnectivity, good cell distribution and cell survival, as well as an extensive content of proteoglycans and collagen type II. The polyurethane scaffold seems to be a promising biomaterial for a mesenchymal stem cell-based tissue engineering approach for meniscal repair. The new score could be applied as a new standard for in vitro scaffold testing. Full article
(This article belongs to the Special Issue Regenerative Materials)
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