Next Issue
Volume 8, December
Previous Issue
Volume 8, October
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
5.8
3.1
Journals
Materials
Volume 8
Issue 11
materials-logo

Journal Menu

► Journal Menu

Journal Browser

► Journal Browser
share announcement

Materials, Volume 8, Issue 11 (November 2015) – 61 articles

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
1733 KiB  
Article
TiO2 Nanosols Applied Directly on Textiles Using Different Purification Treatments
by Simona Ortelli, Anna Luisa Costa and Michele Dondi
Materials 2015, 8(11), 7988-7996; https://doi.org/10.3390/ma8115437 - 24 Nov 2015
Cited by 45 | Viewed by 6032
Abstract
Self-cleaning applications using TiO2 coatings on various supporting media have been attracting increasing interest in recent years. This work discusses the issue of self-cleaning textile production on an industrial scale. A method for producing self-cleaning textiles starting from a commercial colloidal nanosuspension [...] Read more.
Self-cleaning applications using TiO2 coatings on various supporting media have been attracting increasing interest in recent years. This work discusses the issue of self-cleaning textile production on an industrial scale. A method for producing self-cleaning textiles starting from a commercial colloidal nanosuspension (nanosol) of TiO2 is described. Three different treatments were developed for purifying and neutralizing the commercial TiO2 nanosol: washing by ultrafiltration; purifying with an anion exchange resin; and neutralizing in an aqueous solution of ammonium bicarbonate. The different purified TiO2 nanosols were characterized in terms of particle size distribution (using dynamic light scattering), electrical conductivity, and ζ potential (using electrophoretic light scattering). The TiO2-coated textiles’ functional properties were judged on their photodegradation of rhodamine B (RhB), used as a stain model. The photocatalytic performance of the differently treated TiO2-coated textiles was compared, revealing the advantages of purification with an anion exchange resin. The study demonstrated the feasibility of applying commercial TiO2 nanosol directly on textile surfaces, overcoming problems of existing methods that limit the industrial scalability of the process. Full article
(This article belongs to the Special Issue Self-Cleaning and Antimicrobial Surfaces)
►▼ Show Figures

Graphical abstract

4952 KiB  
Article
Preparation of Cotton-Wool-Like Poly(lactic acid)-Based Composites Consisting of Core-Shell-Type Fibers
by Jian Wang, Pin Zhou, Akiko Obata, Julian R. Jones and Toshihiro Kasuga
Materials 2015, 8(11), 7979-7987; https://doi.org/10.3390/ma8115434 - 24 Nov 2015
Cited by 5 | Viewed by 8092
Abstract
In previous works, we reported the fabrication of cotton-wool-like composites consisting of siloxane-doped vaterite and poly(l-lactic acid) (SiVPCs). Various irregularly shaped bone voids can be filled with the composite, which effectively supplies calcium and silicate ions, enhancing the bone formation by stimulating the [...] Read more.
In previous works, we reported the fabrication of cotton-wool-like composites consisting of siloxane-doped vaterite and poly(l-lactic acid) (SiVPCs). Various irregularly shaped bone voids can be filled with the composite, which effectively supplies calcium and silicate ions, enhancing the bone formation by stimulating the cells. The composites, however, were brittle and showed an initial burst release of ions. In the present work, to improve the mechanical flexibility and ion release, the composite fiber was coated with a soft, thin layer consisting of poly(d,l-lactic-co-glycolic acid) (PLGA). A coaxial electrospinning technique was used to prepare a cotton-wool-like material comprising “core-shell”-type fibers with a diameter of ~12 µm. The fibers, which consisted of SiVPC coated with a ~2-µm-thick PLGA layer, were mechanically flexible; even under a uniaxial compressive load of 1.5 kPa, the cotton-wool-like material did not exhibit fracture of the fibers and, after removing the load, showed a ~60% recovery. In Tris buffer solution, the initial burst release of calcium and silicate ions from the “core-shell”-type fibers was effectively controlled, and the ions were slowly released after one day. Thus, the mechanical flexibility and ion-release behavior of the composites were drastically improved by the thin PLGA coating. Full article
(This article belongs to the Section Advanced Composites)
►▼ Show Figures

Graphical abstract

4796 KiB  
Article
Growth and Characterization of Lead-free Piezoelectric Single Crystals
by Philippe Veber, Feres Benabdallah, Hairui Liu, Gabriel Buse, Michael Josse and Mario Maglione
Materials 2015, 8(11), 7962-7978; https://doi.org/10.3390/ma8115436 - 24 Nov 2015
Cited by 14 | Viewed by 6444
Abstract
Lead-free piezoelectric materials attract more and more attention owing to the environmental toxicity of lead-containing materials. In this work, we review our first attempts of single crystal grown by the top-seeded solution growth method of BaTiO3 substituted with zirconium and calcium (BCTZ) [...] Read more.
Lead-free piezoelectric materials attract more and more attention owing to the environmental toxicity of lead-containing materials. In this work, we review our first attempts of single crystal grown by the top-seeded solution growth method of BaTiO3 substituted with zirconium and calcium (BCTZ) and (K0.5Na0.5)NbO3 substituted with lithium, tantalum, and antimony (KNLSTN). The growth methodology is optimized in order to reach the best compositions where enhanced properties are expected. Chemical analysis and electrical characterizations are presented for both kinds of crystals. The compositionally-dependent electrical performance is investigated for a better understanding of the relationship between the composition and electrical properties. A cross-over from relaxor to ferroelectric state in BCTZ solid solution is evidenced similar to the one reported in ceramics. In KNLSTN single crystals, we observed a substantial evolution of the orthorhombic-to-tetragonal phase transition under minute composition changes. Full article
(This article belongs to the Special Issue Piezoelectric Materials)
►▼ Show Figures

Figure 1

10491 KiB  
Review
Fiber-Embedded Metallic Materials: From Sensing towards Nervous Behavior
by Nouari Saheb and Samir Mekid
Materials 2015, 8(11), 7938-7961; https://doi.org/10.3390/ma8115435 - 24 Nov 2015
Cited by 36 | Viewed by 8038
Abstract
Embedding of fibers in materials has attracted serious attention from researchers and has become a new research trend. Such material structures are usually termed “smart” or more recently “nervous”. Materials can have the capability of sensing and responding to the surrounding environmental stimulus, [...] Read more.
Embedding of fibers in materials has attracted serious attention from researchers and has become a new research trend. Such material structures are usually termed “smart” or more recently “nervous”. Materials can have the capability of sensing and responding to the surrounding environmental stimulus, in the former, and the capability of feeling multiple structural and external stimuli, while feeding information back to a controller for appropriate real-time action, in the latter. In this paper, embeddable fibers, embedding processes, and behavior of fiber-embedded metallic materials are reviewed. Particular emphasis has been given to embedding fiber Bragg grating (FBG) array sensors and piezo wires, because of their high potential to be used in nervous materials for structural health monitoring. Ultrasonic consolidation and laser-based layered manufacturing processes are discussed in detail because of their high potential to integrate fibers without disruption. In addition, current challenges associated with embedding fibers in metallic materials are highlighted and recommendations for future research work are set. Full article
(This article belongs to the Special Issue Bioinspired and Biomimetic Materials)
►▼ Show Figures

Figure 1

4153 KiB  
Article
Compressive Behavior and Microstructural Characteristics of Iron Hollow Sphere Filled Aluminum Matrix Syntactic Foams
by Attila Szlancsik, Bálint Katona, Kornél Májlinger and Imre Norbert Orbulov
Materials 2015, 8(11), 7926-7937; https://doi.org/10.3390/ma8115432 - 23 Nov 2015
Cited by 44 | Viewed by 7095
Abstract
Iron hollow sphere filled aluminum matrix syntactic foams (AMSFs) were produced by low pressure, inert gas assisted infiltration. The microstructure of the produced AMSFs was investigated by light and electron microscopy, extended by energy dispersive X-ray spectroscopy and electron back-scattered diffraction. The investigations [...] Read more.
Iron hollow sphere filled aluminum matrix syntactic foams (AMSFs) were produced by low pressure, inert gas assisted infiltration. The microstructure of the produced AMSFs was investigated by light and electron microscopy, extended by energy dispersive X-ray spectroscopy and electron back-scattered diffraction. The investigations revealed almost perfect infiltration and a slight gradient in the grain size of the matrix. A very thin interface layer that ensures good bonding between the hollow spheres and the matrix was also observed. Compression tests were performed on cylindrical specimens to explore the characteristic mechanical properties of the AMSFs. Compared to other (conventional) metallic foams, the investigated AMSFs proved to have outstanding mechanical properties (yield strength, plateau strength, etc.) and energy absorbing capability. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
►▼ Show Figures

Figure 1

2154 KiB  
Review
Mechanisms of in Vivo Degradation and Resorption of Calcium Phosphate Based Biomaterials
by Zeeshan Sheikh, Mohamed-Nur Abdallah, Ahmed Abdalla Hanafi, Syed Misbahuddin, Haroon Rashid and Michael Glogauer
Materials 2015, 8(11), 7913-7925; https://doi.org/10.3390/ma8115430 - 23 Nov 2015
Cited by 166 | Viewed by 13498
Abstract
Calcium phosphate ceramic materials are extensively used for bone replacement and regeneration in orthopedic, dental, and maxillofacial surgical applications. In order for these biomaterials to work effectively it is imperative that they undergo the process of degradation and resorption in vivo. This [...] Read more.
Calcium phosphate ceramic materials are extensively used for bone replacement and regeneration in orthopedic, dental, and maxillofacial surgical applications. In order for these biomaterials to work effectively it is imperative that they undergo the process of degradation and resorption in vivo. This allows for the space to be created for the new bone tissue to form and infiltrate within the implanted graft material. Several factors affect the biodegradation and resorption of calcium phosphate materials after implantation. Various cell types are involved in the degradation process by phagocytic mechanisms (monocytes/macrophages, fibroblasts, osteoblasts) or via an acidic mechanism to reduce the micro-environmental pH which results in demineralization of the cement matrix and resorption via osteoclasts. These cells exert their degradation effects directly or indirectly through the cytokine growth factor secretion and their sensitivity and response to these biomolecules. This article discusses the mechanisms of calcium phosphate material degradation in vivo. Full article
(This article belongs to the Special Issue Regenerative Materials)
►▼ Show Figures

Graphical abstract

3615 KiB  
Article
Ultrasound-Assist Extrusion Methods for the Fabrication of Polymer Nanocomposites Based on Polypropylene/Multi-Wall Carbon Nanotubes
by Carlos A. Ávila-Orta, Zoe V. Quiñones-Jurado, Miguel A. Waldo-Mendoza, Erika A. Rivera-Paz, Víctor J. Cruz-Delgado, José M. Mata-Padilla, Pablo González-Morones and Ronald F. Ziolo
Materials 2015, 8(11), 7900-7912; https://doi.org/10.3390/ma8115431 - 23 Nov 2015
Cited by 20 | Viewed by 6306
Abstract
Isotactic polypropylenes (iPP) with different melt flow indexes (MFI) were used to fabricate nanocomposites (NCs) with 10 wt % loadings of multi-wall carbon nanotubes (MWCNTs) using ultrasound-assisted extrusion methods to determine their effect on the morphology, melt flow, and electrical properties of the [...] Read more.
Isotactic polypropylenes (iPP) with different melt flow indexes (MFI) were used to fabricate nanocomposites (NCs) with 10 wt % loadings of multi-wall carbon nanotubes (MWCNTs) using ultrasound-assisted extrusion methods to determine their effect on the morphology, melt flow, and electrical properties of the NCs. Three different types of iPPs were used with MFIs of 2.5, 34 and 1200 g/10 min. Four different NC fabrication methods based on melt extrusion were used. In the first method melt extrusion fabrication without ultrasound assistance was used. In the second and third methods, an ultrasound probe attached to a hot chamber located at the exit of the die was used to subject the sample to fixed frequency and variable frequency, respectively. The fourth method is similar to the first method, with the difference being that the carbon nanotubes were treated in a fluidized air-bed with an ultrasound probe before being used in the fabrication of the NCs with no ultrasound assistance during extrusion. The samples were characterized by MFI, Optical microscopy (OM), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), electrical surface resistivity, and electric charge. MFI decreases in all cases with addition of MWCNTs with the largest decrease observed for samples with the highest MFI. The surface resistivity, which ranged from 1013 to 105 Ω/sq, and electric charge, were observed to depend on the ultrasound-assisted fabrication method as well as on the melt flow index of the iPP. A relationship between agglomerate size and area ratio with electric charge was found. Several trends in the overall data were identified and are discussed in terms of MFI and the different fabrication methods. Full article
(This article belongs to the Special Issue Polymer Nanocomposites)
►▼ Show Figures

Graphical abstract

8946 KiB  
Article
A Direct Electric Field-Aided Biomimetic Mineralization System for Inducing the Remineralization of Dentin Collagen Matrix
by Xiao-Ting Wu, May Lei Mei, Quan-Li Li, Chris Ying Cao, Jia-Long Chen, Rong Xia, Zhi-Hong Zhang and Chun Hung Chu
Materials 2015, 8(11), 7889-7899; https://doi.org/10.3390/ma8115433 - 20 Nov 2015
Cited by 22 | Viewed by 8346
Abstract
This in vitro study aimed to accelerate the remineralization of a completely demineralized dentine collagen block in order to regenerate the dentinal microstructure of calcified collagen fibrils by a novel electric field-aided biomimetic mineralization system in the absence of non-collagenous proteins. Completely demineralized [...] Read more.
This in vitro study aimed to accelerate the remineralization of a completely demineralized dentine collagen block in order to regenerate the dentinal microstructure of calcified collagen fibrils by a novel electric field-aided biomimetic mineralization system in the absence of non-collagenous proteins. Completely demineralized human dentine slices were prepared using ethylene diamine tetraacetic acid (EDTA) and treated with guanidine hydrochloride to extract the bound non-collagenous proteins. The completely demineralized dentine collagen blocks were then remineralized in a calcium chloride agarose hydrogel and a sodium hydrogen phosphate and fluoride agarose hydrogel. This process was accelerated by subjecting the hydrogels to electrophoresis at 20 mA for 4 and 12 h. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) were used to evaluate the resultant calcification of the dentin collagen matrix. SEM indicated that mineral particles were precipitated on the intertubular dentin collagen matrix; these densely packed crystals mimicked the structure of the original mineralized dentin. However, the dentinal tubules were not occluded by the mineral crystals. XRD and EDX both confirmed that the deposited crystals were fluorinated hydroxyapatite. TEM revealed the existence of intrafibrillar and interfibrillar mineralization of the collagen fibrils. A novel electric field-aided biomimetic mineralization system was successfully developed to remineralize a completely demineralized dentine collagen matrix in the absence of non-collagenous proteins. This study developed an accelerated biomimetic mineralization system which can be a potential protocol for the biomineralization of dentinal defects. Full article
►▼ Show Figures

Figure 1

6795 KiB  
Article
Hydrogenation Properties of TiFe Doped with Zirconium
by Catherine Gosselin and Jacques Huot
Materials 2015, 8(11), 7864-7872; https://doi.org/10.3390/ma8115423 - 20 Nov 2015
Cited by 40 | Viewed by 5632
Abstract
The goal of this study was to optimize the activation behaviour of hydrogen storage alloy TiFe. We found that the addition of a small amount of Zr in TiFe alloy greatly reduces the hydrogenation activation time. Two different procedural synthesis methods were applied: [...] Read more.
The goal of this study was to optimize the activation behaviour of hydrogen storage alloy TiFe. We found that the addition of a small amount of Zr in TiFe alloy greatly reduces the hydrogenation activation time. Two different procedural synthesis methods were applied: co-melt, where the TiFe was melted and afterward re-melted with the addition of Zr, and single-melt, where Ti, Fe and Zr were melted together in one single operation. The co-melted sample absorbed hydrogen at its maximum capacity in less than three hours without any pre-treatment. The single-melted alloy absorbed its maximum capacity in less than seven hours, also without pre-treatment. The reason for discrepancies between co-melt and single-melt alloys was found to be the different microstructure. The effect of air exposure was also investigated. We found that the air-exposed samples had the same maximum capacity as the argon protected samples but with a slightly longer incubation time, which is probably due to the presence of a dense surface oxide layer. Scanning electron microscopy revealed the presence of a rich Zr intergranular phase in the TiFe matrix, which is responsible for the enhanced hydrogenation properties of these Zr-doped TiFe alloys. Full article
(This article belongs to the Special Issue Hydrogen Storage Materials)
►▼ Show Figures

Figure 1

5769 KiB  
Article
Characterization of Thermo-Physical Properties of EVA/ATH: Application to Gasification Experiments and Pyrolysis Modeling
by Bertrand Girardin, Gaëlle Fontaine, Sophie Duquesne, Michael Försth and Serge Bourbigot
Materials 2015, 8(11), 7837-7863; https://doi.org/10.3390/ma8115428 - 20 Nov 2015
Cited by 26 | Viewed by 7311
Abstract
The pyrolysis of solid polymeric materials is a complex process that involves both chemical and physical phenomena such as phase transitions, chemical reactions, heat transfer, and mass transport of gaseous components. For modeling purposes, it is important to characterize and to quantify the [...] Read more.
The pyrolysis of solid polymeric materials is a complex process that involves both chemical and physical phenomena such as phase transitions, chemical reactions, heat transfer, and mass transport of gaseous components. For modeling purposes, it is important to characterize and to quantify the properties driving those phenomena, especially in the case of flame-retarded materials. In this study, protocols have been developed to characterize the thermal conductivity and the heat capacity of an ethylene-vinyl acetate copolymer (EVA) flame retarded with aluminum tri-hydroxide (ATH). These properties were measured for the various species identified across the decomposition of the material. Namely, the thermal conductivity was found to decrease as a function of temperature before decomposition whereas the ceramic residue obtained after the decomposition at the steady state exhibits a thermal conductivity as low as 0.2 W/m/K. The heat capacity of the material was also investigated using both isothermal modulated Differential Scanning Calorimetry (DSC) and the standard method (ASTM E1269). It was shown that the final residue exhibits a similar behavior to alumina, which is consistent with the decomposition pathway of EVA/ATH. Besides, the two experimental approaches give similar results over the whole range of temperatures. Moreover, the optical properties before decomposition and the heat capacity of the decomposition gases were also analyzed. Those properties were then used as input data for a pyrolysis model in order to predict gasification experiments. Mass losses of gasification experiments were well predicted, thus validating the characterization of the thermo-physical properties of the material. Full article
(This article belongs to the Special Issue Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers)
►▼ Show Figures

Figure 1

1718 KiB  
Review
Extrinsic Contribution and Instability Properties in Lead-Based and Lead-Free Piezoceramics
by José Eduardo García
Materials 2015, 8(11), 7821-7836; https://doi.org/10.3390/ma8115426 - 19 Nov 2015
Cited by 12 | Viewed by 5723
Abstract
Piezoceramic materials generally exhibit a notable instability of their functional properties when they work under real external conditions. This undesirable effect, known as nonlinear behavior, is mostly associated with the extrinsic contribution to material response. In this article, the role of the ferroelectric [...] Read more.
Piezoceramic materials generally exhibit a notable instability of their functional properties when they work under real external conditions. This undesirable effect, known as nonlinear behavior, is mostly associated with the extrinsic contribution to material response. In this article, the role of the ferroelectric domain walls’ motion in the nonlinear response in the most workable lead-based and lead-free piezoceramics is reviewed. Initially, the extrinsic origin of the nonlinear response is discussed in terms of the temperature dependence of material response. The influence of the crystallographic phase and of the phase boundaries on the material response are then reviewed. Subsequently, the impact of the defects created by doping in order to control the extrinsic contribution is discussed as a way of tuning material properties. Finally, some aspects related to the grain-size effect on the nonlinear response of piezoceramics are surveyed. Full article
(This article belongs to the Special Issue Piezoelectric Materials)
►▼ Show Figures

Figure 1

3836 KiB  
Article
Magnetic Control of Fe3O4 Nanomaterial for Fat Ablation in Microchannel
by Ming Chang, Ming-Yi Chang, Wei-Siou Lin and Jacque Lynn Gabayno
Materials 2015, 8(11), 7813-7820; https://doi.org/10.3390/ma8115429 - 19 Nov 2015
Cited by 7 | Viewed by 5013
Abstract
In this study, surface modification of iron (II, III) oxide Fe3O4 nanoparticles by oleic acid (OA) coating is investigated for the microablation of fat in a microchannel. The nanoparticles are synthesized by the co-precipitation method and then dispersed in organic [...] Read more.
In this study, surface modification of iron (II, III) oxide Fe3O4 nanoparticles by oleic acid (OA) coating is investigated for the microablation of fat in a microchannel. The nanoparticles are synthesized by the co-precipitation method and then dispersed in organic solvent prior to mixing with the OA. The magnetization, agglomeration, and particle size distribution properties of the OA-coated Fe3O4 nanoparticles are characterized. The surface modification of the Fe3O4 nanoparticles reveals that upon injection into a microchannel, the lipophilicity of the OA coating influences the movement of the nanoparticles across an oil-phase barrier. The motion of the nanoparticles is controlled using an AC magnetic field to induce magnetic torque and a static gradient field to control linear translation. The fat microablation process in a microchannel is demonstrated using an oscillating driving field of less than 1200 Am−1. Full article
(This article belongs to the Special Issue Selected Papers from ICETI2014)
►▼ Show Figures

Figure 1

9971 KiB  
Article
Chiral Nematic Structure of Cellulose Nanocrystal Suspensions and Films; Polarized Light and Atomic Force Microscopy
by Derek G. Gray and Xiaoyue Mu
Materials 2015, 8(11), 7873-7888; https://doi.org/10.3390/ma8115427 - 18 Nov 2015
Cited by 95 | Viewed by 12509
Abstract
Cellulosic liquid crystalline solutions and suspensions form chiral nematic phases that show a rich variety of optical textures in the liquid crystalline state. These ordered structures may be preserved in solid films prepared by evaporation of solvent or suspending medium. Film formation from [...] Read more.
Cellulosic liquid crystalline solutions and suspensions form chiral nematic phases that show a rich variety of optical textures in the liquid crystalline state. These ordered structures may be preserved in solid films prepared by evaporation of solvent or suspending medium. Film formation from aqueous suspensions of cellulose nanocrystals (CNC) was investigated by polarized light microscopy, optical profilometry and atomic force microscopy (AFM). An attempt is made to interpret qualitatively the observed textures in terms of the orientation of the cellulose nanocrystals in the suspensions and films, and the changes in orientation caused by the evaporative process. Mass transfer within the evaporating droplet resulted in the formation of raised rings whose magnitude depended on the degree of pinning of the receding contact line. AFM of dry films at short length scales showed a radial orientation of the CNC at the free surface of the film, along with a radial height variation with a period of approximately P/2, ascribed to the anisotropic shrinkage of the chiral nematic structure. Full article
(This article belongs to the Section Biomaterials)
►▼ Show Figures

Figure 1

3967 KiB  
Article
Inhibition of Crystal Growth during Plasma Enhanced Atomic Layer Deposition by Applying BIAS
by Stephan Ratzsch, Ernst-Bernhard Kley, Andreas Tünnermann and Adriana Szeghalmi
Materials 2015, 8(11), 7805-7812; https://doi.org/10.3390/ma8115425 - 18 Nov 2015
Cited by 12 | Viewed by 6172
Abstract
In this study, the influence of direct current (DC) biasing on the growth of titanium dioxide (TiO2) layers and their nucleation behavior has been investigated. Titania films were prepared by plasma enhanced atomic layer deposition (PEALD) using Ti(OiPr)4 as metal [...] Read more.
In this study, the influence of direct current (DC) biasing on the growth of titanium dioxide (TiO2) layers and their nucleation behavior has been investigated. Titania films were prepared by plasma enhanced atomic layer deposition (PEALD) using Ti(OiPr)4 as metal organic precursor. Oxygen plasma, provided by remote inductively coupled plasma, was used as an oxygen source. The TiO2 films were deposited with and without DC biasing. A strong dependence of the applied voltage on the formation of crystallites in the TiO2 layer is shown. These crystallites form spherical hillocks on the surface which causes high surface roughness. By applying a higher voltage than the plasma potential no hillock appears on the surface. Based on these results, it seems likely, that ions are responsible for the nucleation and hillock growth. Hence, the hillock formation can be controlled by controlling the ion energy and ion flux. The growth per cycle remains unchanged, whereas the refractive index slightly decreases in the absence of energetic oxygen ions. Full article
(This article belongs to the Special Issue Atomic Layer Deposition of Functional Materials)
►▼ Show Figures

Figure 1

1775 KiB  
Article
Preparation and Preliminary Dielectric Characterization of Structured C60-Thiol-Ene Polymer Nanocomposites Assembled Using the Thiol-Ene Click Reaction
by Hanaa M. Ahmed, Amber D. Windham, Maryam M. Al-Ejji, Noora H. Al-Qahtani, Mohammad K. Hassan, Kenneth A. Mauritz, Randy K. Buchanan and J. Paige Buchanan
Materials 2015, 8(11), 7795-7804; https://doi.org/10.3390/ma8115424 - 18 Nov 2015
Cited by 16 | Viewed by 6347
Abstract
Fullerene-containing materials have the ability to store and release electrical energy. Therefore, fullerenes may ultimately find use in high-voltage equipment devices or as super capacitors for high electric energy storage due to this ease of manipulating their excellent dielectric properties and their high [...] Read more.
Fullerene-containing materials have the ability to store and release electrical energy. Therefore, fullerenes may ultimately find use in high-voltage equipment devices or as super capacitors for high electric energy storage due to this ease of manipulating their excellent dielectric properties and their high volume resistivity. A series of structured fullerene (C60) polymer nanocomposites were assembled using the thiol-ene click reaction, between alkyl thiols and allyl functionalized C60 derivatives. The resulting high-density C60-urethane-thiol-ene (C60-Thiol-Ene) networks possessed excellent mechanical properties. These novel networks were characterized using standard techniques, including infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermal gravimetric analysis (TGA). The dielectric spectra for the prepared samples were determined over a broad frequency range at room temperature using a broadband dielectric spectrometer and a semiconductor characterization system. The changes in thermo-mechanical and electrical properties of these novel fullerene-thiol-ene composite films were measured as a function of the C60 content, and samples characterized by high dielectric permittivity and low dielectric loss were produced. In this process, variations in chemical composition of the networks were correlated to performance characteristics. Full article
(This article belongs to the Special Issue Polymer Nanocomposites)
►▼ Show Figures

Graphical abstract

4439 KiB  
Article
Variation of Shrinkage Strain within the Depth of Concrete Beams
by Jong-Hyun Jeong, Yeong-Seong Park and Yong-Hak Lee
Materials 2015, 8(11), 7780-7794; https://doi.org/10.3390/ma8115421 - 16 Nov 2015
Cited by 8 | Viewed by 6919
Abstract
The variation of shrinkage strain within beam depth was examined through four series of time-dependent laboratory experiments on unreinforced concrete beam specimens. Two types of beam specimens, horizontally cast and vertically cast, were tested; shrinkage variation was observed in the horizontally cast specimens. [...] Read more.
The variation of shrinkage strain within beam depth was examined through four series of time-dependent laboratory experiments on unreinforced concrete beam specimens. Two types of beam specimens, horizontally cast and vertically cast, were tested; shrinkage variation was observed in the horizontally cast specimens. This indicated that the shrinkage variation within the beam depth was due to water bleeding and tamping during the placement of the fresh concrete. Shrinkage strains were measured within the beam depth by two types of strain gages, surface-attached and embedded. The shrinkage strain distribution within the beam depth showed a consistent tendency for the two types of gages. The test beams were cut into four sections after completion of the test, and the cutting planes were divided into four equal sub-areas to measure the aggregate concentration for each sub-area of the cutting plane. The aggregate concentration increased towards the bottom of the beam. The shrinkage strain distribution was estimated by Hobbs’ equation, which accounts for the change of aggregate volume concentration. Full article
(This article belongs to the Section Advanced Materials Characterization)
►▼ Show Figures

Figure 1

5346 KiB  
Article
New Polylactic Acid Composites Reinforced with Artichoke Fibers
by Luigi Botta, Vincenzo Fiore, Tommaso Scalici, Antonino Valenza and Roberto Scaffaro
Materials 2015, 8(11), 7770-7779; https://doi.org/10.3390/ma8115422 - 16 Nov 2015
Cited by 49 | Viewed by 6748
Abstract
In this work, artichoke fibers were used for the first time to prepare poly(lactic acid) (PLA)-based biocomposites. In particular, two PLA/artichoke composites with the same fiber loading (10% w/w) were prepared by the film-stacking method: the first one (UNID) reinforced [...] Read more.
In this work, artichoke fibers were used for the first time to prepare poly(lactic acid) (PLA)-based biocomposites. In particular, two PLA/artichoke composites with the same fiber loading (10% w/w) were prepared by the film-stacking method: the first one (UNID) reinforced with unidirectional long artichoke fibers, the second one (RANDOM) reinforced by randomly-oriented long artichoke fibers. Both composites were mechanically characterized in tensile mode by quasi-static and dynamic mechanical tests. The morphology of the fracture surfaces was analyzed through scanning electron microscopy (SEM). Moreover, a theoretical model, i.e., Hill’s method, was used to fit the experimental Young’s modulus of the biocomposites. The quasi-static tensile tests revealed that the modulus of UNID composites is significantly higher than that of the neat PLA (i.e., ~40%). Moreover, the tensile strength is slightly higher than that of the neat matrix. The other way around, the stiffness of RANDOM composites is not significantly improved, and the tensile strength decreases in comparison to the neat PLA. Full article
(This article belongs to the Special Issue Green Composites)
►▼ Show Figures

Graphical abstract

9171 KiB  
Review
Creep-Fatigue Failure Diagnosis
by Stuart Holdsworth
Materials 2015, 8(11), 7757-7769; https://doi.org/10.3390/ma8115418 - 16 Nov 2015
Cited by 47 | Viewed by 13315
Abstract
Failure diagnosis invariably involves consideration of both associated material condition and the results of a mechanical analysis of prior operating history. This Review focuses on these aspects with particular reference to creep-fatigue failure diagnosis. Creep-fatigue cracking can be due to a spectrum of [...] Read more.
Failure diagnosis invariably involves consideration of both associated material condition and the results of a mechanical analysis of prior operating history. This Review focuses on these aspects with particular reference to creep-fatigue failure diagnosis. Creep-fatigue cracking can be due to a spectrum of loading conditions ranging from pure cyclic to mainly steady loading with infrequent off-load transients. These require a range of mechanical analysis approaches, a number of which are reviewed. The microstructural information revealing material condition can vary with alloy class. In practice, the detail of the consequent cracking mechanism(s) can be camouflaged by oxidation at high temperatures, although the presence of oxide on fracture surfaces can be used to date events leading to failure. Routine laboratory specimen post-test examination is strongly recommended to characterise the detail of deformation and damage accumulation under known and well-controlled loading conditions to improve the effectiveness and efficiency of failure diagnosis. Full article
(This article belongs to the Special Issue Failure Analysis in Materials)
►▼ Show Figures

Figure 1

1742 KiB  
Article
Origin of the Electroluminescence from Annealed-ZnO/GaN Heterojunction Light-Emitting Diodes
by Kai-Chiang Hsu, Wei-Hua Hsiao, Ching-Ting Lee, Yan-Ting Chen and Day-Shan Liu
Materials 2015, 8(11), 7745-7756; https://doi.org/10.3390/ma8115417 - 16 Nov 2015
Cited by 5 | Viewed by 5592
Abstract
This paper addressed the effect of post-annealed treatment on the electroluminescence (EL) of an n-ZnO/p-GaN heterojunction light-emitting diode (LED). The bluish light emitted from the 450 °C-annealed LED became reddish as the LED annealed at a temperature of 800 °C [...] Read more.
This paper addressed the effect of post-annealed treatment on the electroluminescence (EL) of an n-ZnO/p-GaN heterojunction light-emitting diode (LED). The bluish light emitted from the 450 °C-annealed LED became reddish as the LED annealed at a temperature of 800 °C under vacuum atmosphere. The origins of the light emission for these LEDs annealed at various temperatures were studied using measurements of electrical property, photoluminescence, and Auger electron spectroscopy (AES) depth profiles. A blue-violet emission located at 430 nm was associated with intrinsic transitions between the bandgap of n-ZnO and p-GaN, the green-yellow emission at 550 nm mainly originating from the deep-level transitions of native defects in the n-ZnO and p-GaN surfaces, and the red emission at 610 nm emerging from the Ga-O interlayer due to interdiffusion at the n-ZnO/p-GaN interface. The above-mentioned emissions also supported the EL spectra of LEDs annealed at 700 °C under air, nitrogen, and oxygen atmospheres, respectively. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
►▼ Show Figures

Figure 1

3292 KiB  
Article
Effect of Oxide Coating on Performance of Copper-Zinc Oxide-Based Catalyst for Methanol Synthesis via Hydrogenation of Carbon Dioxide
by Tetsuo Umegaki, Yoshiyuki Kojima and Kohji Omata
Materials 2015, 8(11), 7738-7744; https://doi.org/10.3390/ma8115414 - 16 Nov 2015
Cited by 12 | Viewed by 5455
Abstract
The effect of oxide coating on the activity of a copper-zinc oxide–based catalyst for methanol synthesis via the hydrogenation of carbon dioxide was investigated. A commercial catalyst was coated with various oxides by a sol-gel method. The influence of the types of promoters [...] Read more.
The effect of oxide coating on the activity of a copper-zinc oxide–based catalyst for methanol synthesis via the hydrogenation of carbon dioxide was investigated. A commercial catalyst was coated with various oxides by a sol-gel method. The influence of the types of promoters used in the sol-gel reaction was investigated. Temperature-programmed reduction-thermogravimetric analysis revealed that the reduction peak assigned to the copper species in the oxide-coated catalysts prepared using ammonia shifts to lower temperatures than that of the pristine catalyst; in contrast, the reduction peak shifts to higher temperatures for the catalysts prepared using L(+)-arginine. These observations indicated that the copper species were weakly bonded with the oxide and were easily reduced by using ammonia. The catalysts prepared using ammonia show higher CO2 conversion than the catalysts prepared using L(+)-arginine. Among the catalysts prepared using ammonia, the silica-coated catalyst displayed a high activity at high temperatures, while the zirconia-coated catalyst and titania-coated catalyst had high activity at low temperatures. At high temperature the conversion over the silica-coated catalyst does not significantly change with reaction temperature, while the conversion over the zirconia-coated catalyst and titania-coated catalyst decreases with reaction time. From the results of FTIR, the durability depends on hydrophilicity of the oxides. Full article
►▼ Show Figures

Figure 1

244 KiB  
Article
Ferrocene Orientation Determined Intramolecular Interactions Using Energy Decomposition Analysis
by Feng Wang, Shawkat Islam and Vladislav Vasilyev
Materials 2015, 8(11), 7723-7737; https://doi.org/10.3390/ma8115419 - 16 Nov 2015
Cited by 13 | Viewed by 6428
Abstract
Two very different quantum mechanically based energy decomposition analyses (EDA) schemes are employed to study the dominant energy differences between the eclipsed and staggered ferrocene conformers. One is the extended transition state (ETS) based on the Amsterdam Density Functional (ADF) package and the [...] Read more.
Two very different quantum mechanically based energy decomposition analyses (EDA) schemes are employed to study the dominant energy differences between the eclipsed and staggered ferrocene conformers. One is the extended transition state (ETS) based on the Amsterdam Density Functional (ADF) package and the other is natural EDA (NEDA) based in the General Atomic and Molecular Electronic Structure System (GAMESS) package. It reveals that in addition to the model (theory and basis set), the fragmentation channels more significantly affect the interaction energy terms (ΔE) between the conformers. It is discovered that such an interaction energy can be absorbed into the pre-partitioned fragment channels so that to affect the interaction energies in a particular conformer of Fc. To avoid this, the present study employs a complete fragment channel—the fragments of ferrocene are individual neutral atoms. It therefore discovers that the major difference between the ferrocene conformers is due to the quantum mechanical Pauli repulsive energy and orbital attractive energy, leading to the eclipsed ferrocene the energy preferred structure. The NEDA scheme further indicates that the sum of attractive (negative) polarization (POL) and charge transfer (CL) energies prefers the eclipsed ferrocene. The repulsive (positive) deformation (DEF) energy, which is dominated by the cyclopentadienyle (Cp) rings, prefers the staggered ferrocene. Again, the cancellation results in a small energy residue in favour of the eclipsed ferrocene, in agreement with the ETS scheme. Further Natural Bond Orbital (NBO) analysis indicates that all NBO energies, total Lewis (no Fe) and lone pair (LP) deletion all prefer the eclipsed Fc conformer. The most significant energy preferring the eclipsed ferrocene without cancellation is the interactions between the donor lone pairs (LP) of the Fe atom and the acceptor antibond (BD*) NBOs of all C–C and C–H bonds in the ligand, LP(Fe)-BD*(C–C & C–H), which strongly stabilizes the eclipsed (D5h) conformation by −457.6 kcal·mol−1. Full article
(This article belongs to the Special Issue Organometallic Compounds 2015)
►▼ Show Figures

Graphical abstract

2314 KiB  
Article
A Novel Biodegradable Polycaprolactone Fixator for Osteosynthesis Surgery of Rib Fracture: In Vitro and in Vivo Study
by Yi-Hsun Yu, Chin-Lung Fan, Yung-Heng Hsu, Ying-Chao Chou, Steve W. N. Ueng and Shih-Jung Liu
Materials 2015, 8(11), 7714-7722; https://doi.org/10.3390/ma8115415 - 13 Nov 2015
Cited by 10 | Viewed by 5839
Abstract
Osteosynthesis surgery for rib fractures is controversial and challenging. This study developed a noval poly(ε-caprolactone) (PCL)-based biodegradable “cable-tie” fixator for osteosynthesis surgery for rib fractures. A biodegradable fixator specifically for fractured ribs was designed and fabricated by a micro-injection molding machine in our [...] Read more.
Osteosynthesis surgery for rib fractures is controversial and challenging. This study developed a noval poly(ε-caprolactone) (PCL)-based biodegradable “cable-tie” fixator for osteosynthesis surgery for rib fractures. A biodegradable fixator specifically for fractured ribs was designed and fabricated by a micro-injection molding machine in our laboratory. The fixator has three belts that could be passed through matching holes individually. The locking mechanism allows the belt movement to move in only one direction. To examine the in vitro biomechanical performance, ribs 3–7 from four fresh New Zealand rabbits were employed. The load to failure and stress-strain curve was compared in the three-point bending test among native ribs, titanium plate-fixed ribs, and PCL fixator-fixed ribs. In the in vivo animal study, the sixth ribs of New Zealand rabbits were osteotomized and osteosynthesis surgery was performed using the PCL fixator. Outcomes were assessed by monthly X-ray examinations, a final micro-computed tomography (CT) scan, and histological analysis. The experimental results suggested that the ribs fixed with the PCL fixator were significantly less stiff than those fixed with titanium plates (p < 0.05). All ribs fixed with the PCL fixators exhibited union. The bridging callus was confirmed by gross, radiographic micro-three-dimensional (3D) CT, and histological examinations. In addition, there was no significant inflammatory response of the osteotomized ribs or the PCL-rib interface during application. The novel PCL fixator developed in this work achieves satisfactory results in osteosynthesis surgery for rib fractures, and may provide potential applications in other orthopedic surgeries. Full article
(This article belongs to the Section Biomaterials)
►▼ Show Figures

Figure 1

2644 KiB  
Article
Preparation, Mechanical and Thermal Properties of Cement Board with Expanded Perlite Based Composite Phase Change Material for Improving Buildings Thermal Behavior
by Rongda Ye, Xiaoming Fang, Zhengguo Zhang and Xuenong Gao
Materials 2015, 8(11), 7702-7713; https://doi.org/10.3390/ma8115408 - 13 Nov 2015
Cited by 34 | Viewed by 6698
Abstract
Here we demonstrate the mechanical properties, thermal conductivity, and thermal energy storage performance of construction elements made of cement and form-stable PCM-Rubitherm® RT 28 HC (RT28)/expanded perlite (EP) composite phase change materials (PCMs). The composite PCMs were prepared by adsorbing RT28 into the [...] Read more.
Here we demonstrate the mechanical properties, thermal conductivity, and thermal energy storage performance of construction elements made of cement and form-stable PCM-Rubitherm® RT 28 HC (RT28)/expanded perlite (EP) composite phase change materials (PCMs). The composite PCMs were prepared by adsorbing RT28 into the pores of EP, in which the mass fraction of RT28 should be limited to be no more than 40 wt %. The adsorbed RT28 is observed to be uniformly confined into the pores of EP. The phase change temperatures of the RT28/EP composite PCMs are very close to that of the pure RT28. The apparent density and compression strength of the composite cubes increase linearly with the mass fraction of RT28. Compared with the thermal conductivity of the boards composed of cement and EP, the thermal conductivities of the composite boards containing RT28 increase by 15%–35% with the mass fraction increasing of RT28. The cubic test rooms that consist of six boards were built to evaluate the thermal energy storage performance, it is found that the maximum temperature different between the outside surface of the top board with the indoor temperature using the composite boards is 13.3 °C higher than that of the boards containing no RT28. The thermal mass increase of the built environment due to the application of composite boards can contribute to improving the indoor thermal comfort and reducing the energy consumption in the buildings. Full article
(This article belongs to the Special Issue Development and Characterisation of Encapsulated PCM: Nano-, Micro-, and Macro-Encapsulation)
►▼ Show Figures

Figure 1

4976 KiB  
Article
Preparation of SiO2-Protecting Metallic Fe Nanoparticle/SiO2 Composite Spheres for Biomedical Application
by Pin-Wei Hsieh, Ching-Li Tseng and Dong-Hau Kuo
Materials 2015, 8(11), 7691-7701; https://doi.org/10.3390/ma8115416 - 13 Nov 2015
Cited by 8 | Viewed by 8616
Abstract
Functionalized Fe nanoparticles (NPs) have played an important role in biomedical applications. In this study, metallic Fe NPs were deposited on SiO2 spheres to form a Fe/SiO2 composite. To protect the Fe from oxidation, a thin SiO2 layer was coated [...] Read more.
Functionalized Fe nanoparticles (NPs) have played an important role in biomedical applications. In this study, metallic Fe NPs were deposited on SiO2 spheres to form a Fe/SiO2 composite. To protect the Fe from oxidation, a thin SiO2 layer was coated on the Fe/SiO2 spheres thereafter. The size and morphology of the SiO2@Fe/SiO2 composite spheres were examined by transmission electron microscopy (TEM). The iron form and its content and magnetic properties were examined by X-ray diffraction (XRD), inductively-coupled plasma mass spectrometry (ICP-MS) and a superconducting quantum interference device (SQUID). The biocompatibility of the SiO2@Fe/SiO2 composite spheres was examined by Cell Counting Kit-8 (CCK-8) and lactate dehydrogenase (LDH) tests. The intracellular distribution of the SiO2@Fe/SiO2 composite spheres was observed using TEM. XRD analysis revealed the formation of metallic iron on the surface of the SiO2 spheres. According to the ICP-MS and SQUID results, using 0.375 M FeCl3·6H2O for Fe NPs synthesis resulted in the highest iron content and magnetization of the SiO2@Fe/SiO2 spheres. Using a dye loading experiment, a slow release of a fluorescence dye from SiO2@Fe/SiO2 composite spheres was confirmed. The SiO2@Fe/SiO2 composite spheres co-cultured with L929 cells exhibit biocompatibility at concentrations <16.25 µg/mL. The TEM images show that the SiO2@Fe/SiO2 composite spheres were uptaken into the cytoplasm and retained in the endosome. The above results demonstrate that the SiO2@Fe/SiO2 composite spheres could be used as a multi-functional agent, such as a magnetic resonance imaging (MRI) contrast agent or drug carriers in biomedical applications. Full article
(This article belongs to the Section Biomaterials)
►▼ Show Figures

Figure 1

175 KiB  
Erratum
Erratum: Jarý, V.; et al. Optical, Structural and Paramagnetic Properties of Eu-Doped Ternary Sulfides ALnS2 (A = Na, K, Rb; Ln = La, Gd, Lu, Y). Materials 2015, 8, 6978–6998
by Materials Editorial Office
Materials 2015, 8(11), 7690; https://doi.org/10.3390/ma8115420 - 13 Nov 2015
Viewed by 3140
Abstract
The Materials Editorial Office wishes to make the following erratum to this paper [1]. [...] Full article
5641 KiB  
Article
Chitosan-Coated Collagen Membranes Promote Chondrocyte Adhesion, Growth, and Interleukin-6 Secretion
by Nabila Mighri, Jifu Mao, Frej Mighri, Abdallah Ajji and Mahmoud Rouabhia
Materials 2015, 8(11), 7673-7689; https://doi.org/10.3390/ma8115413 - 13 Nov 2015
Cited by 17 | Viewed by 6840
Abstract
Designing scaffolds made from natural polymers may be highly attractive for tissue engineering strategies. We sought to produce and characterize chitosan-coated collagen membranes and to assess their efficacy in promoting chondrocyte adhesion, growth, and cytokine secretion. Porous collagen membranes were placed in chitosan [...] Read more.
Designing scaffolds made from natural polymers may be highly attractive for tissue engineering strategies. We sought to produce and characterize chitosan-coated collagen membranes and to assess their efficacy in promoting chondrocyte adhesion, growth, and cytokine secretion. Porous collagen membranes were placed in chitosan solutions then crosslinked with glutaraldehyde vapor. Fourier transform infrared (FTIR) analyses showed elevated absorption at 1655 cm-1 of the carbon–nitrogen (N=C) bonds formed by the reaction between the (NH2) of the chitosan and the (C=O) of the glutaraldehyde. A significant peak in the amide II region revealed a significant deacetylation of the chitosan. Scanning electron microscopy (SEM) images of the chitosan-coated membranes exhibited surface variations, with pore size ranging from 20 to 50 µm. X-ray photoelectron spectroscopy (XPS) revealed a decreased C–C groups and an increased C–N/C–O groups due to the reaction between the carbon from the collagen and the NH2 from the chitosan. Increased rigidity of these membranes was also observed when comparing the chitosan-coated and uncoated membranes at dried conditions. However, under wet conditions, the chitosan coated collagen membranes showed lower rigidity as compared to dried conditions. Of great interest, the glutaraldehyde-crosslinked chitosan-coated collagen membranes promoted chondrocyte adhesion, growth, and interleukin (IL)-6 secretion. Overall results confirm the feasibility of using designed chitosan-coated collagen membranes in future applications, such as cartilage repair. Full article
(This article belongs to the Special Issue Cellular Materials: Design and Optimisation)
►▼ Show Figures

Figure 1

2979 KiB  
Article
Enhanced Erbium-Doped Ceria Nanostructure Coating to Improve Solar Cell Performance
by Nader Shehata, Michael Clavel, Kathleen Meehan, Effat Samir, Soha Gaballah and Mohammed Salah
Materials 2015, 8(11), 7663-7672; https://doi.org/10.3390/ma8115399 - 12 Nov 2015
Cited by 25 | Viewed by 6744
Abstract
This paper discusses the effect of adding reduced erbium-doped ceria nanoparticles (REDC NPs) as a coating on silicon solar cells. Reduced ceria nanoparticles doped with erbium have the advantages of both improving conductivity and optical conversion of solar cells. Oxygen vacancies in ceria [...] Read more.
This paper discusses the effect of adding reduced erbium-doped ceria nanoparticles (REDC NPs) as a coating on silicon solar cells. Reduced ceria nanoparticles doped with erbium have the advantages of both improving conductivity and optical conversion of solar cells. Oxygen vacancies in ceria nanoparticles reduce Ce4+ to Ce3+ which follow the rule of improving conductivity of solar cells through the hopping mechanism. The existence of Ce3+ helps in the down-conversion from 430 nm excitation to 530 nm emission. The erbium dopant forms energy levels inside the low-phonon ceria host to up-convert the 780 nm excitations into green and red emissions. When coating reduced erbium-doped ceria nanoparticles on the back side of a solar cell, a promising improvement in the solar cell efficiency has been observed from 15% to 16.5% due to the mutual impact of improved electric conductivity and multi-optical conversions. Finally, the impact of the added coater on the electric field distribution inside the solar cell has been studied. Full article
(This article belongs to the Special Issue Photovoltaic Materials and Electronic Devices)
►▼ Show Figures

Graphical abstract

7196 KiB  
Article
High Temperature Deformation of Twin-Roll Cast Al-Mn-Based Alloys after Equal Channel Angular Pressing
by Přemysl Málek, Michaela Šlapáková Poková and Miroslav Cieslar
Materials 2015, 8(11), 7650-7662; https://doi.org/10.3390/ma8115401 - 12 Nov 2015
Cited by 6 | Viewed by 4996
Abstract
Twin roll cast Al-Mn- and Al-Mn-Zr-based alloys were subjected to four passes of equal channel angular pressing. The resulting grain size of 400 nm contributes to a significant strengthening at room temperature. This microstructure is not fully stable at elevated temperatures and recrystallization [...] Read more.
Twin roll cast Al-Mn- and Al-Mn-Zr-based alloys were subjected to four passes of equal channel angular pressing. The resulting grain size of 400 nm contributes to a significant strengthening at room temperature. This microstructure is not fully stable at elevated temperatures and recrystallization and vast grain growth occur at temperatures between 350 and 450 °C. The onset of these microstructure changes depends on chemical and phase composition. Better stability is observed in the Al-Mn-Zr-based alloy. High temperature tensile tests reveal that equal channel angular pressing results in a softening of all studied materials at high temperatures. This can be explained by an active role of grain boundaries in the deformation process. The maximum values of ductility and strain rate sensitivity parameter m found in the Al-Mn-Zr-based alloy are below the bottom limit of superplasticity (155%, m = 0.25). However, some features typical for superplastic behavior were observed—the strain rate dependence of the parameter m, the strengthening with increasing grain size, and the fracture by diffuse necking. Grain boundary sliding is believed to contribute partially to the overall strain in specimens where the grain size remained in the microcrystalline range. Full article
(This article belongs to the Section Advanced Materials Characterization)
►▼ Show Figures

Graphical abstract

6233 KiB  
Article
Reduction of Adipose Tissue Formation by the Controlled Release of BMP-2 Using a Hydroxyapatite-Coated Collagen Carrier System for Sinus-Augmentation/Extraction-Socket Grafting
by Jung-Seok Lee, Tae-Wan Kim, Soyon Park, Byung-Soo Kim, Gun-Il Im, Kyoo-Sung Cho and Chang-Sung Kim
Materials 2015, 8(11), 7634-7649; https://doi.org/10.3390/ma8115411 - 11 Nov 2015
Cited by 13 | Viewed by 6243
Abstract
The effects of hydroxyapatite (HA)-coating onto collagen carriers for application of recombinant human bone morphogenetic protein 2 (rhBMP-2) on cell differentiation in vitro, and on in vivo healing patterns after sinus-augmentation and alveolar socket-grafting were evaluated. In vitro induction of osteogenic/adipogenic differentiation [...] Read more.
The effects of hydroxyapatite (HA)-coating onto collagen carriers for application of recombinant human bone morphogenetic protein 2 (rhBMP-2) on cell differentiation in vitro, and on in vivo healing patterns after sinus-augmentation and alveolar socket-grafting were evaluated. In vitro induction of osteogenic/adipogenic differentiation was compared between the culture media with rhBMP-2 solution and with the released rhBMP-2 from the control collagen and from the HA-coated collagen. Demineralized bovine bone and collagen/HA-coated collagen were grafted with/without rhBMP-2 in sinus-augmentation and tooth-extraction-socket models. Adipogenic induction by rhBMP-2 released from HA-coated collagen was significantly reduced compared to collagen. In the sinus-augmentation model, sites that received rhBMP-2 exhibited large amounts of vascular tissue formation at two weeks and increased adipose tissue formation at eight weeks; this could be significantly reduced by using HA-coated collagen as a carrier for rhBMP-2. In extraction-socket grafting, dimensional reduction of alveolar ridge was significantly decreased at sites received rhBMP-2 compared to control sites, but adipose tissue was increased within the regenerated socket area. In conclusion, HA-coated collagen carrier for Escherichia coli-derived rhBMP-2 (ErhBMP-2) may reduce in vitro induction of adipogenic differentiation and in vivo adipose bone marrow tissue formation in bone tissue engineering by ErhBMP-2. Full article
(This article belongs to the Special Issue Selected Papers from ICBEI2015)
►▼ Show Figures

Figure 1

2401 KiB  
Article
Modulating the Optoelectronic Properties of Silver Nanowires Films: Effect of Capping Agent and Deposition Technique
by D. Lopez-Diaz, C. Merino and M. M. Velázquez
Materials 2015, 8(11), 7622-7633; https://doi.org/10.3390/ma8115405 - 11 Nov 2015
Cited by 13 | Viewed by 6105
Abstract
Silver nanowires 90 nm in diameter and 9 µm in length have been synthesized using different capping agents: polyvinyl pyrrolidone (PVP) and alkyl thiol of different chain lengths. The nanowire structure is not influenced by the displacement of PVP by alkyl thiols, although [...] Read more.
Silver nanowires 90 nm in diameter and 9 µm in length have been synthesized using different capping agents: polyvinyl pyrrolidone (PVP) and alkyl thiol of different chain lengths. The nanowire structure is not influenced by the displacement of PVP by alkyl thiols, although alkyl thiols modify the lateral aggregation of nanowires. We examined the effect of the capping agent and the deposition method on the optical and electrical properties of films prepared by Spray and the Langmuir-Schaefer methodologies. Our results revealed that nanowires capped with PVP and C8-thiol present the best optoelectronic properties. By using different deposition techniques and by modifying the nanowire surface density, we can modulate the optoelectronic properties of films. This strategy allows obtaining films with the optoelectronic properties required to manufacture touch screens and electromagnetic shielding. Full article
(This article belongs to the Section Advanced Materials Characterization)
►▼ Show Figures

Graphical abstract

Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying articles 1-61
Previous Issue
Next Issue
Back to TopTop