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Materials, Volume 6, Issue 6 (June 2013), Pages 2119-2577

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Open AccessArticle Effect of Core–Shell Ceria/Poly(vinylpyrrolidone) (PVP) Nanoparticles Incorporated in Polymer Films and Their Optical Properties
Materials 2013, 6(6), 2119-2129; doi:10.3390/ma6062119
Received: 8 April 2013 / Revised: 10 May 2013 / Accepted: 13 May 2013 / Published: 24 May 2013
Cited by 3 | PDF Full-text (961 KB) | HTML Full-text | XML Full-text
Abstract
We fabricated hybrid films of pentaerythritol triacrylate (PETA) with core–shell ceria/poly(vinylpyrrolidone) (PVP) nanoparticles, which consist of cerium oxide as the core and PVP as the shell, and investigated the film optical properties. In this study, we used ceria/PVP nanoparticles with average diameters of
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We fabricated hybrid films of pentaerythritol triacrylate (PETA) with core–shell ceria/poly(vinylpyrrolidone) (PVP) nanoparticles, which consist of cerium oxide as the core and PVP as the shell, and investigated the film optical properties. In this study, we used ceria/PVP nanoparticles with average diameters of 37, 49 and 91 nm. We obtained translucent films consisting of PETA with core–shell ceria/PVP nanoparticles. The core–shell ceria/PVP nanoparticles can reduce the transmittance of near-ultraviolet light. The transmittance of visible light and haze values depends not only on the thickness of the films, but also on the average diameter of the nanoparticles. A SEM observation and the optical analyses prove that the core–shell ceria/PVP nanoparticles do not aggregate into the PETA matrix. Full article
Open AccessArticle Full-Field Strain Mapping at a Ge/Si Heterostructure Interface
Materials 2013, 6(6), 2130-2142; doi:10.3390/ma6062130
Received: 8 March 2013 / Revised: 9 May 2013 / Accepted: 13 May 2013 / Published: 24 May 2013
Cited by 6 | PDF Full-text (686 KB) | HTML Full-text | XML Full-text
Abstract
The misfit dislocations and strain fields at a Ge/Si heterostructure interface were investigated experimentally using a combination of high-resolution transmission electron microscopy and quantitative electron micrograph analysis methods. The type of misfit dislocation at the interface was determined to be 60° dislocation and
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The misfit dislocations and strain fields at a Ge/Si heterostructure interface were investigated experimentally using a combination of high-resolution transmission electron microscopy and quantitative electron micrograph analysis methods. The type of misfit dislocation at the interface was determined to be 60° dislocation and 90° full-edge dislocation. The full-field strains at the Ge/Si heterostructure interface were mapped by using the geometric phase analysis (GPA) and peak pairs analysis (PPA), respectively. The effect of the mask size on the GPA and PPA results was analyzed in detail. For comparison, the theoretical strain fields of the misfit dislocations were also calculated by the Peierls-Nabarro and Foreman dislocation models. The results showed that the optimal mask sizes in GPA and PPA were approximately three tenths and one-tenth of the reciprocal lattice vector, respectively. The Foreman dislocation model with an alterable factor a = 4 can best describe the strain field of the misfit dislocation at the Ge/Si heterostructure interface. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Study of PVD AlCrN Coating for Reducing Carbide Cutting Tool Deterioration in the Machining of Titanium Alloys
Materials 2013, 6(6), 2143-2154; doi:10.3390/ma6062143
Received: 5 March 2013 / Revised: 17 April 2013 / Accepted: 3 May 2013 / Published: 24 May 2013
Cited by 4 | PDF Full-text (1433 KB) | HTML Full-text | XML Full-text
Abstract
The manufacture of medical and aerospace components made of titanium alloys and other difficult-to-cut materials requires the parallel development of high performance cutting tools coated with materials capable of enhanced tribological and resistance properties. In this matter, a thin nanocomposite film made out
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The manufacture of medical and aerospace components made of titanium alloys and other difficult-to-cut materials requires the parallel development of high performance cutting tools coated with materials capable of enhanced tribological and resistance properties. In this matter, a thin nanocomposite film made out of AlCrN (aluminum–chromium–nitride) was studied in this research, showing experimental work in the deposition process and its characterization. A heat-treated monolayer coating, competitive with other coatings in the machining of titanium alloys, was analyzed. Different analysis and characterizations were performed on the manufactured coating by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDXS), and X-ray diffraction (XRD). Furthermore, the mechanical behavior of the coating was evaluated through hardness test and tribology with pin-on-disk to quantify friction coefficient and wear rate. Finally, machinability tests using coated tungsten carbide cutting tools were executed in order to determine its performance through wear resistance, which is a key issue of cutting tools in high-end cutting at elevated temperatures. It was demonstrated that the specimen (with lower friction coefficient than previous research) is more efficient in machinability tests in Ti6Al4V alloys. Furthermore, the heat-treated monolayer coating presented better performance in comparison with a conventional monolayer of AlCrN coating. Full article
(This article belongs to the Special Issue Advances in Surface Coatings 2013)
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Open AccessCommunication Synthesis of Isothianaphthene (ITN) and 3,4-Ethylenedioxy-Thiophene (EDOT)-Based Low-Bandgap Liquid Crystalline Conjugated Polymers
Materials 2013, 6(6), 2218-2228; doi:10.3390/ma6062218
Received: 15 April 2013 / Revised: 15 May 2013 / Accepted: 16 May 2013 / Published: 30 May 2013
Cited by 3 | PDF Full-text (1026 KB) | HTML Full-text | XML Full-text
Abstract
Copolymers, consisting of isothianaphthene and phenylene derivatives with liquid crystal groups, were synthesized via Migita-Kosugi-Stille polycondensation reaction. IR absorption, UV-vis optical absorption, and PL spectroscopy measurements were carried out. Thermotropic liquid crystallinity of the polymers with bandgap of ~2.5 eV was confirmed.
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Copolymers, consisting of isothianaphthene and phenylene derivatives with liquid crystal groups, were synthesized via Migita-Kosugi-Stille polycondensation reaction. IR absorption, UV-vis optical absorption, and PL spectroscopy measurements were carried out. Thermotropic liquid crystallinity of the polymers with bandgap of ~2.5 eV was confirmed. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
Open AccessArticle Hydrogen Production by Steam Reforming of Ethanol over Nickel Catalysts Supported on Sol Gel Made Alumina: Influence of Calcination Temperature on Supports
Materials 2013, 6(6), 2229-2239; doi:10.3390/ma6062229
Received: 31 January 2013 / Revised: 7 April 2013 / Accepted: 28 April 2013 / Published: 30 May 2013
Cited by 5 | PDF Full-text (465 KB) | HTML Full-text | XML Full-text
Abstract
Selecting a proper support in the catalyst system plays an important role in hydrogen production via ethanol steam reforming. In this study, sol gel made alumina supports prepared for nickel (Ni) catalysts were calcined at different temperatures. A series of (Ni/AlS.G.)
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Selecting a proper support in the catalyst system plays an important role in hydrogen production via ethanol steam reforming. In this study, sol gel made alumina supports prepared for nickel (Ni) catalysts were calcined at different temperatures. A series of (Ni/AlS.G.) catalysts were synthesized by an impregnation procedure. The influence of varying the calcination temperature of the sol gel made supports on catalyst activity was tested in ethanol reforming reaction. The characteristics of the sol gel alumina supports and Ni catalysts were affected by the calcination temperature of the supports. The structure of the sol gel made alumina supports was transformed in the order of γ → (γ + θ) → θ-alumina as the calcination temperature of the supports increased from 600 °C to 1000 °C. Both hydrogen yield and ethanol conversion presented a volcano-shaped behavior with maximum values of 4.3 mol/mol ethanol fed and 99.5%, respectively. The optimum values were exhibited over Ni/AlS.G800 (Ni catalyst supported on sol gel made alumina calcined at 800 °C). The high performance of the Ni/AlS.G800 catalyst may be attributed to the strong interaction of Ni species and sol gel made alumina which lead to high nickel dispersion and small particle size. Full article
Open AccessArticle High Pressure Compression-Molding of α-Cellulose and Effects of Operating Conditions
Materials 2013, 6(6), 2240-2261; doi:10.3390/ma6062240
Received: 22 January 2013 / Revised: 12 March 2013 / Accepted: 21 May 2013 / Published: 30 May 2013
Cited by 7 | PDF Full-text (1235 KB) | HTML Full-text | XML Full-text
Abstract
Commercial α-cellulose was compression-molded to produce 1A dog-bone specimens under various operating conditions without any additive. The resulting agromaterials exhibited a smooth, plastic-like surface, and constituted a suitable target as replacement for plastic materials. Tensile and three-points bending tests were conducted according to
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Commercial α-cellulose was compression-molded to produce 1A dog-bone specimens under various operating conditions without any additive. The resulting agromaterials exhibited a smooth, plastic-like surface, and constituted a suitable target as replacement for plastic materials. Tensile and three-points bending tests were conducted according to ISO standards related to the evaluation of plastic materials. The specimens had strengths comparable to classical petroleum-based thermoplastics. They also exhibited high moduli, which is characteristic of brittle materials. A higher temperature and higher pressure rate produced specimens with higher mechanical properties while low moisture content produced weaker specimens. Generally, the strong specimen had higher specific gravity and lower moisture content. However, some parameters did not follow the general trend e.g., thinner specimen showed much higher Young’s Modulus, although their specific gravity and moisture content remained similar to control, revealing a marked skin-effect which was confirmed by SEM observations. Full article
(This article belongs to the Special Issue Advances in Cellulosic Materials)
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Open AccessCommunication Plasma Enhanced Chemical Vapour Deposition of Horizontally Aligned Carbon Nanotubes
Materials 2013, 6(6), 2262-2273; doi:10.3390/ma6062262
Received: 10 May 2013 / Revised: 27 May 2013 / Accepted: 28 May 2013 / Published: 31 May 2013
Cited by 2 | PDF Full-text (1277 KB) | HTML Full-text | XML Full-text
Abstract
A plasma-enhanced chemical vapour deposition reactor has been developed to synthesis horizontally aligned carbon nanotubes. The width of the aligning sheath was modelled based on a collisionless, quasi-neutral, Child’s law ion sheath where these estimates were empirically validated by direct Langmuir probe measurements,
[...] Read more.
A plasma-enhanced chemical vapour deposition reactor has been developed to synthesis horizontally aligned carbon nanotubes. The width of the aligning sheath was modelled based on a collisionless, quasi-neutral, Child’s law ion sheath where these estimates were empirically validated by direct Langmuir probe measurements, thereby confirming the proposed reactors ability to extend the existing sheath fields by up to 7 mm. A 7 mbar growth atmosphere combined with a 25 W plasma permitted the concurrent growth and alignment of carbon nanotubes with electric fields of the order of 0.04 V μm−1 with linear packing densities of up to ~5 × 104 cm−1. These results open up the potential for multi-directional in situ alignment of carbon nanotubes providing one viable route to the fabrication of many novel optoelectronic devices. Full article
(This article belongs to the Special Issue Carbon Nanotubes)
Open AccessArticle Dynamic Behavior of Nanocomposites Reinforced with Multi-Walled Carbon Nanotubes (MWCNTs)
Materials 2013, 6(6), 2274-2284; doi:10.3390/ma6062274
Received: 2 May 2013 / Revised: 28 May 2013 / Accepted: 30 May 2013 / Published: 3 June 2013
Cited by 8 | PDF Full-text (448 KB) | HTML Full-text | XML Full-text
Abstract
The influence of multi-walled carbon nanotubes (MWCNT) on the structural dynamic behavior of MWCNT/epoxy nanocomposites was investigated. Two different types of MWCNTs, pristine MWCNT and functionalized MWCNT, were used in this study. Carboxylic acid-functionalized MWCNTs (MWCNT-COOH) were obtained by oxidation pristine MWCNTs via
[...] Read more.
The influence of multi-walled carbon nanotubes (MWCNT) on the structural dynamic behavior of MWCNT/epoxy nanocomposites was investigated. Two different types of MWCNTs, pristine MWCNT and functionalized MWCNT, were used in this study. Carboxylic acid-functionalized MWCNTs (MWCNT-COOH) were obtained by oxidation pristine MWCNTs via sonication in sulfuric-nitric acid and characterized by Fourier transform infrared spectroscopy (FTIR). Dynamic behaviors of the MWCNT reinforced nanocomposite including the natural frequency and damping ratio were determined using free vibration test. Experimental results showed that the damping ratio of the nanocomposite decreases with the increase of the MWCNT addition, while the natural frequency is increasing with the increase of the MWCNT addition. Functionalized MWCNTs improved the interfacial bonding between the nanotubes and epoxy resin resulting in the reduction of the interfacial energy dissipation ability and enhancement of the stiffness. Full article
(This article belongs to the Special Issue Carbon Nanotubes)
Open AccessArticle Synthesis of Li2Ti3O7 Anode Materials by Ultrasonic Spray Pyrolysis and Their Electrochemical Properties
Materials 2013, 6(6), 2285-2294; doi:10.3390/ma6062285
Received: 26 April 2013 / Revised: 24 May 2013 / Accepted: 28 May 2013 / Published: 3 June 2013
Cited by 3 | PDF Full-text (445 KB) | HTML Full-text | XML Full-text
Abstract
Ramsdellite-type lithium titanate (Li2Ti3O7) powders were synthesized by performing ultrasonic spray pyrolysis, and their chemical and physical properties were characterized by performing Scanning Electron Microscope (SEM), powder X-ray Diffraction (XRD), and Inductively Coupled Plasma (ICP) analyses. The
[...] Read more.
Ramsdellite-type lithium titanate (Li2Ti3O7) powders were synthesized by performing ultrasonic spray pyrolysis, and their chemical and physical properties were characterized by performing Scanning Electron Microscope (SEM), powder X-ray Diffraction (XRD), and Inductively Coupled Plasma (ICP) analyses. The as-prepared Li2Ti3O7 precursor powders had spherical morphologies with hollow microstructures, but an irregularly shaped morphology was obtained after calcination above 900 °C. The ramsdellite Li2Ti3O7 crystal phase was obtained after the calcination at 1100 °C under an argon/hydrogen atmosphere. The first rechargeable capacity of the Li2Ti3O7 anode material was 168 mAh/g at 0.1 C and 82 mAh/g at 20 C, and the discharge capacity retention ratio was 99% at 1 C after the 500th cycle. The cycle performance of the Li2Ti3O7 anode was also highly stable at 50 °C, demonstrating the superiority of Li2Ti3O7 anode materials reported previously. Full article
Open AccessCommunication Use of Amphoteric Copolymer Films as Sacrificial Layers for Constructing Free-Standing Layer-by-Layer Films
Materials 2013, 6(6), 2351-2359; doi:10.3390/ma6062351
Received: 21 May 2013 / Revised: 31 May 2013 / Accepted: 3 June 2013 / Published: 6 June 2013
Cited by 3 | PDF Full-text (168 KB) | HTML Full-text | XML Full-text
Abstract
The present paper reports the use of an amphoteric copolymer, poly(diallylamine-co-maleic acid) (PDAMA), as a component of precursor layers (or sacrificial layers) for constructing free-standing layer-by-layer (LbL) films. A PDAMA-poly(styrenesulfonate) (PSS) film or PDAMA-poly(dimethyldiallylammonium chloride) (PDDA) film was coated on the
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The present paper reports the use of an amphoteric copolymer, poly(diallylamine-co-maleic acid) (PDAMA), as a component of precursor layers (or sacrificial layers) for constructing free-standing layer-by-layer (LbL) films. A PDAMA-poly(styrenesulfonate) (PSS) film or PDAMA-poly(dimethyldiallylammonium chloride) (PDDA) film was coated on the surface of a quartz slide at pH 4.0 or 8.0, respectively, as a sacrificial layer that can be removed by changing the pH. The surface of the sacrificial layer was further covered with LbL films composed of poly(allylamine hydrochloride) (PAH) and PSS. The PAH-PSS films were released from the substrate upon immersing the film-coated quartz slide in acidic or neutral/basic solution, respectively, as a result of the pH-induced dissolution of the PDAMA-PDDA or PDAMA-PSS sacrificial layer. Thus, PDAMA-based sacrificial layers have been demonstrated to dissolve in both acidic and neutral solutions, depending on the type of counter polymer. The thicknesses of the sacrificial layers and released LbL films are crucial factors for constructing free-standing LbL films. The releasing kinetics also depended on the thickness of the crucial layers. The free-standing PAH-PSS films obtained were stable in water or in air in the dry state. PDAMA-based sacrificial layers may be useful in constructing free-standing LbL films containing biomolecules with limited pH stability. Full article
Open AccessArticle Structural Properties of Chemically Functionalized Carbon Nanotube Thin Films
Materials 2013, 6(6), 2360-2371; doi:10.3390/ma6062360
Received: 2 May 2013 / Revised: 3 June 2013 / Accepted: 5 June 2013 / Published: 10 June 2013
Cited by 8 | PDF Full-text (496 KB) | XML Full-text
Abstract
Buckypapers are thin sheets of randomly entangled carbon nanotubes, which are highly porous networks. They are strong candidates for a number of applications, such as reinforcing materials for composites. In this work, buckypapers were produced from multiwall carbon nanotubes, pre-treated by two different
[...] Read more.
Buckypapers are thin sheets of randomly entangled carbon nanotubes, which are highly porous networks. They are strong candidates for a number of applications, such as reinforcing materials for composites. In this work, buckypapers were produced from multiwall carbon nanotubes, pre-treated by two different chemical processes, either an oxidation or an epoxidation reaction. Properties, such as porosity, the mechanical and electrical response are investigated. It was found that the chemical pretreatment of carbon nanotubes strongly affects the structural properties of the buckypapers and, consecutively, their mechanical and electrical performance. Full article
(This article belongs to the Special Issue Carbon Nanotubes)
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Open AccessArticle Density Functional Theory (DFT) Study of Coumarin-based Dyes Adsorbed on TiO2 Nanoclusters—Applications to Dye-Sensitized Solar Cells
Materials 2013, 6(6), 2372-2392; doi:10.3390/ma6062372
Received: 1 February 2013 / Revised: 17 April 2013 / Accepted: 18 April 2013 / Published: 10 June 2013
Cited by 22 | PDF Full-text (2041 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Coumarin-based dyes have been successfully used in dye-sensitized solar cells, leading to photovoltaic conversion efficiencies of up to about 8%. Given the need to better understand the behavior of the dye adsorbed on the TiO2 nanoparticle, we report results of density functional
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Coumarin-based dyes have been successfully used in dye-sensitized solar cells, leading to photovoltaic conversion efficiencies of up to about 8%. Given the need to better understand the behavior of the dye adsorbed on the TiO2 nanoparticle, we report results of density functional theory (DFT) and time-dependent DFT (TD-DFT) studies of several coumarin-based dyes, as well as complex systems consisting of the dye bound to a TiO2 cluster. We provide the electronic structure and simulated UV-Vis spectra of the dyes alone and adsorbed to the cluster and discuss the matching with the solar spectrum. We display the energy level diagrams and the electron density of the key molecular orbitals and analyze the electron transfer from the dye to the oxide. Finally, we compare our theoretical results with the experimental data available and discuss the key issues that influence the device performance. Full article
(This article belongs to the Special Issue Advances in Colorants)
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Open AccessArticle Terahertz Wave Propagation in a Nanotube Conveying Fluid Taking into Account Surface Effect
Materials 2013, 6(6), 2393-2399; doi:10.3390/ma6062393
Received: 2 May 2013 / Revised: 3 June 2013 / Accepted: 3 June 2013 / Published: 10 June 2013
Cited by 6 | PDF Full-text (330 KB) | HTML Full-text | XML Full-text
Abstract
In nanoscale structure sizes, the surface-to-bulk energy ratio is high and the surface effects must be taken into account. Surface effect plays a key role in accurately predicting the vibration behavior of nanostructures. In this paper, the wave behaviors of a single-walled carbon
[...] Read more.
In nanoscale structure sizes, the surface-to-bulk energy ratio is high and the surface effects must be taken into account. Surface effect plays a key role in accurately predicting the vibration behavior of nanostructures. In this paper, the wave behaviors of a single-walled carbon nanotube (CNT) conveying fluid are studied. The nonlocal Timoshenko beam theory is used and the surface effect is taken into account. It is found that the fluid can flow at a very high flow velocity and the wave propagates in the terahertz frequency range. The surface effects can significantly enhance the propagating frequency. This finding is different from the classical model where the surface effect is neglected. Full article
Open AccessArticle Cobalt-based Catalysts for Ammonia Decomposition
Materials 2013, 6(6), 2400-2409; doi:10.3390/ma6062400
Received: 11 March 2013 / Revised: 20 May 2013 / Accepted: 5 June 2013 / Published: 10 June 2013
Cited by 5 | PDF Full-text (551 KB) | HTML Full-text | XML Full-text
Abstract
An effect of promoters such as calcium, aluminium, and potassium oxides and also addition of chromium and manganese on the structure of cobalt catalysts was examined. Studies of the catalytic ammonia decomposition over the cobalt catalysts are presented. The studies of the ammonia
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An effect of promoters such as calcium, aluminium, and potassium oxides and also addition of chromium and manganese on the structure of cobalt catalysts was examined. Studies of the catalytic ammonia decomposition over the cobalt catalysts are presented. The studies of the ammonia decomposition were carried out for various ammonia-hydrogen mixtures in which ammonia concentration varied in the range from 10% to 100%. Co(0) catalyst, promoted by oxides of aluminium, calcium, and potassium, showed the highest activity in the ammonia decomposition reaction. Contrary to expectations, it was found that chromium and manganese addition into the catalysts decreased their activity. Full article
(This article belongs to the Special Issue Advances in Catalytic Materials)
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Open AccessArticle Bio-based Films from Linter Cellulose and Its Acetates: Formation and Properties
Materials 2013, 6(6), 2410-2435; doi:10.3390/ma6062410
Received: 23 January 2013 / Revised: 29 May 2013 / Accepted: 3 June 2013 / Published: 14 June 2013
Cited by 6 | PDF Full-text (1050 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes the results obtained on the preparation of films composed of linter cellulose and the corresponding acetates. The acetylation was carried out in the LiCl/DMAc solvent system. Films were prepared from a LiCl/DMAc solution of cellulose acetates (degree of substitution, DS
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This paper describes the results obtained on the preparation of films composed of linter cellulose and the corresponding acetates. The acetylation was carried out in the LiCl/DMAc solvent system. Films were prepared from a LiCl/DMAc solution of cellulose acetates (degree of substitution, DS 0.8–2.9) mixed with linter cellulose (5, 10 and 15 wt %). Detailed characterization of the films revealed the following: (i) they exhibited fibrous structures on their surfaces. The strong tendency of the linter cellulose chains to aggregate in LiCl/DMAc suggests that these fibrous elements consist of cellulose chains, as can be deduced from SEM images of the film of cellulose proper; (ii) the cellulose acetate films obtained from samples with DS 2.1 and 2.9 exhibited microspheres on the surface, whose formation seems to be favored for acetates with higher DS; (iii) AFM analysis showed that, in general, the presence of cellulose increased both the asperity thickness and the surface roughness of the analyzed films, indicating that cellulose chains are at least partially organized in domains and not molecularly dispersed between acetate chains; and (iv) the films prepared from cellulose and acetates exhibited lower hygroscopicity than the acetate films, also suggesting that the cellulose chains are organized into domains, probably due to strong intermolecular interactions. The linter and sisal acetates (the latter from a prior study), and their respective films, were prepared using the same processes; however, the two sets of films presented more differences (as in humidity absorption, optical, and tensile properties) than similarities (as in some morphological aspects), most likely due to the different properties of the starting materials. Potential applications of the films prepared in tissue engineering scaffold coatings and/or drug delivery are mentioned. Full article
(This article belongs to the Special Issue Advances in Cellulosic Materials)
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Open AccessArticle Kinetics of Corrosion Inhibition of Aluminum in Acidic Media by Water-Soluble Natural Polymeric Pectates as Anionic Polyelectrolyte Inhibitors
Materials 2013, 6(6), 2436-2451; doi:10.3390/ma6062436
Received: 2 April 2013 / Revised: 24 May 2013 / Accepted: 29 May 2013 / Published: 17 June 2013
Cited by 9 | PDF Full-text (664 KB) | HTML Full-text | XML Full-text
Abstract
Corrosion inhibition of aluminum (Al) in hydrochloric acid by anionic polyeletrolyte pectates (PEC) as a water-soluble natural polymer polysaccharide has been studied using both gasometric and weight loss techniques. The results drawn from these two techniques are comparable and exhibit negligible differences. The
[...] Read more.
Corrosion inhibition of aluminum (Al) in hydrochloric acid by anionic polyeletrolyte pectates (PEC) as a water-soluble natural polymer polysaccharide has been studied using both gasometric and weight loss techniques. The results drawn from these two techniques are comparable and exhibit negligible differences. The inhibition efficiency was found to increase with increasing inhibitor concentration and decrease with increasing temperature. The inhibition action of PEC on Al metal surface was found to obey the Freundlich isotherm. Factors such as the concentration and geometrical structure of the inhibitor, concentration of the corrosive medium, and temperature affecting the corrosion rates were examined. The kinetic parameters were evaluated and a suitable corrosion mechanism consistent with the kinetic results is discussed in the paper. Full article
(This article belongs to the Special Issue Corrosion Monitoring and Control)
Open AccessArticle Simple Procedure to Compute the Inductance of a Toroidal Ferrite Core from the Linear to the Saturation Regions
Materials 2013, 6(6), 2452-2463; doi:10.3390/ma6062452
Received: 15 April 2013 / Revised: 24 May 2013 / Accepted: 27 May 2013 / Published: 17 June 2013
Cited by 2 | PDF Full-text (743 KB) | HTML Full-text | XML Full-text
Abstract
We propose a specific procedure to compute the inductance of a toroidal ferrite core as a function of the excitation current. The study includes the linear, intermediate and saturation regions. The procedure combines the use of Finite Element Analysis in 2D and experimental
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We propose a specific procedure to compute the inductance of a toroidal ferrite core as a function of the excitation current. The study includes the linear, intermediate and saturation regions. The procedure combines the use of Finite Element Analysis in 2D and experimental measurements. Through the two dimensional (2D) procedure we are able to achieve convergence, a reduction of computational cost and equivalent results to those computed by three dimensional (3D) simulations. The validation is carried out by comparing 2D, 3D and experimental results. Full article
Open AccessArticle Interactions and Diffusion of Methane and Hydrogen in Microporous Structures: Nuclear Magnetic Resonance (NMR) Studies
Materials 2013, 6(6), 2464-2482; doi:10.3390/ma6062464
Received: 9 May 2013 / Revised: 4 June 2013 / Accepted: 5 June 2013 / Published: 17 June 2013
Cited by 2 | PDF Full-text (728 KB) | HTML Full-text | XML Full-text
Abstract
Measurements of nuclear spin relaxation times over a wide temperature range have been used to determine the interaction energies and molecular dynamics of light molecular gases trapped in the cages of microporous structures. The experiments are designed so that, in the cases explored,
[...] Read more.
Measurements of nuclear spin relaxation times over a wide temperature range have been used to determine the interaction energies and molecular dynamics of light molecular gases trapped in the cages of microporous structures. The experiments are designed so that, in the cases explored, the local excitations and the corresponding heat capacities determine the observed nuclear spin-lattice relaxation times. The results indicate well-defined excitation energies for low densities of methane and hydrogen deuteride in zeolite structures. The values obtained for methane are consistent with Monte Carlo calculations of A.V. Kumar et al. The results also confirm the high mobility and diffusivity of hydrogen deuteride in zeolite structures at low temperatures as observed by neutron scattering. Full article
(This article belongs to the Special Issue Diffusion in Micropores and Mesopores 2013)
Open AccessArticle Enhancement of the Mechanical Properties of Basalt Fiber-Wood-Plastic Composites via Maleic Anhydride Grafted High-Density Polyethylene (MAPE) Addition
Materials 2013, 6(6), 2483-2496; doi:10.3390/ma6062483
Received: 17 December 2012 / Revised: 21 May 2013 / Accepted: 31 May 2013 / Published: 18 June 2013
Cited by 7 | PDF Full-text (565 KB) | HTML Full-text | XML Full-text
Abstract
This study investigated the mechanisms, using microscopy and strength testing approaches, by which the addition of maleic anhydride grafted high-density polyethylene (MAPE) enhances the mechanical properties of basalt fiber-wood-plastic composites (BF-WPCs). The maximum values of the specific tensile and flexural strengths are achieved
[...] Read more.
This study investigated the mechanisms, using microscopy and strength testing approaches, by which the addition of maleic anhydride grafted high-density polyethylene (MAPE) enhances the mechanical properties of basalt fiber-wood-plastic composites (BF-WPCs). The maximum values of the specific tensile and flexural strengths are achieved at a MAPE content of 5%–8%. The elongation increases rapidly at first and then continues slowly. The nearly complete integration of the wood fiber with the high-density polyethylene upon MAPE addition to WPC is examined, and two models of interfacial behavior are proposed. We examined the physical significance of both interfacial models and their ability to accurately describe the effects of MAPE addition. The mechanism of formation of the Model I interface and the integrated matrix is outlined based on the chemical reactions that may occur between the various components as a result of hydrogen bond formation or based on the principle of compatibility, resulting from similar polarity. The Model I fracture occurred on the outer surface of the interfacial layer, visually demonstrating the compatibilization effect of MAPE addition. Full article
Open AccessArticle Mechanism of Generation of ZnO Microstructures by Microwave-Assisted Hydrothermal Approach
Materials 2013, 6(6), 2497-2507; doi:10.3390/ma6062497
Received: 15 March 2013 / Revised: 21 May 2013 / Accepted: 13 June 2013 / Published: 18 June 2013
Cited by 6 | PDF Full-text (1036 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this report, a technique for rapid synthesis of ZnO microstructures by microwave-assisted heating of precursors at hydrothermal conditions is demonstrated. Further, the reaction mechanism for the growth of ZnO microstructures is analyzed. An accelerated rate of reaction obtained using microwaves enables a
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In this report, a technique for rapid synthesis of ZnO microstructures by microwave-assisted heating of precursors at hydrothermal conditions is demonstrated. Further, the reaction mechanism for the growth of ZnO microstructures is analyzed. An accelerated rate of reaction obtained using microwaves enables a dissolution-recrystallization mechanism for generation of one dimensional (1D) rod-like structures, thereby showing that time of reaction can be used to dictate ZnO microstructure morphology. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Study of the Microstructure Evolution of Low-pH Cements Based on Ordinary Portland Cement (OPC) by Mid- and Near-Infrared Spectroscopy, and Their Influence on Corrosion of Steel Reinforcement
Materials 2013, 6(6), 2508-2521; doi:10.3390/ma6062508
Received: 9 April 2013 / Revised: 29 May 2013 / Accepted: 29 May 2013 / Published: 18 June 2013
Cited by 3 | PDF Full-text (626 KB) | HTML Full-text | XML Full-text
Abstract
Low-pH cements are designed to be used in underground repositories for high level waste. When they are based on Ordinary Portland Cements (OPC), high mineral admixture contents must be used which significantly modify their microstructure properties and performance. This paper evaluates the microstructure
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Low-pH cements are designed to be used in underground repositories for high level waste. When they are based on Ordinary Portland Cements (OPC), high mineral admixture contents must be used which significantly modify their microstructure properties and performance. This paper evaluates the microstructure evolution of low-pH cement pastes based on OPC plus silica fume and/or fly ashes, using Mid-Infrared and Near-Infrared spectroscopy to detect cement pastes mainly composed of high polymerized C-A-S-H gels with low C/S ratios. In addition, the lower pore solution pH of these special cementitious materials have been monitored with embedded metallic sensors. Besides, as the use of reinforced concrete can be required in underground repositories, the influence of low-pH cementitious materials on steel reinforcement corrosion was analysed. Due to their lower pore solution pH and their different pore solution chemical composition a clear influence on steel reinforcement corrosion was detected. Full article
(This article belongs to the Special Issue Corrosion Monitoring and Control)
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Open AccessArticle Dynamic Morphological Changes Induced By GM1 and Protein Interactions on the Surface of Cell-Sized Liposomes
Materials 2013, 6(6), 2522-2533; doi:10.3390/ma6062522
Received: 25 April 2013 / Revised: 25 May 2013 / Accepted: 29 May 2013 / Published: 19 June 2013
Cited by 3 | PDF Full-text (848 KB) | HTML Full-text | XML Full-text
Abstract
It is important to understand the physicochemical mechanisms that are responsible for the morphological changes in the cell membrane in the presence of various stimuli such as osmotic pressure. Lipid rafts are believed to play a crucial role in various cellular processes. It
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It is important to understand the physicochemical mechanisms that are responsible for the morphological changes in the cell membrane in the presence of various stimuli such as osmotic pressure. Lipid rafts are believed to play a crucial role in various cellular processes. It is well established that Ctb (Cholera toxin B subunit) recognizes and binds to GM1 (monosialotetrahexosylganglioside) on the cell surface with high specificity and affinity. Taking advantage of Ctb-GM1 interaction, we examined how Ctb and GM1 molecules affect the dynamic movement of liposomes. GM1 a natural ligand for cholera toxin, was incorporated into liposome and the interaction between fluorescent Ctb and the liposome was analyzed. The interaction plays an important role in determining the various surface interaction phenomena. Incorporation of GM1 into membrane leads to an increase of the line tension leading to either rupture of liposome membrane or change in the morphology of the membrane. This change in morphology was found to be GM1 concentration specific. The interaction between Ctb-GM1 leads to fast and easy rupture or to morphological changes of the liposome. The interactions of Ctb and the glycosyl chain are believed to affect the surface and the curvature of the membrane. Thus, the results are highly beneficial in the study of signal transduction processes. Full article
(This article belongs to the Special Issue Supported Lipid Membranes)
Open AccessArticle Synthesis of Carbon Nanotubes of Few Walls Using Aliphatic Alcohols as a Carbon Source
Materials 2013, 6(6), 2534-2542; doi:10.3390/ma6062534
Received: 19 April 2013 / Revised: 4 June 2013 / Accepted: 9 June 2013 / Published: 20 June 2013
Cited by 4 | PDF Full-text (2859 KB) | HTML Full-text | XML Full-text
Abstract
Carbon nanotubes with single and few walls are highly appreciated for their technological applications, regardless of the limited availability due to their high production cost. In this paper we present an alternative process that can lead to lowering the manufacturing cost of CNTs
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Carbon nanotubes with single and few walls are highly appreciated for their technological applications, regardless of the limited availability due to their high production cost. In this paper we present an alternative process that can lead to lowering the manufacturing cost of CNTs of only few walls by means of the use of the spray pyrolysis technique. For this purpose, ferrocene is utilized as a catalyst and aliphatic alcohols (methanol, ethanol, propanol or butanol) as the carbon source. The characterization of CNTs was performed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The study of the synthesized carbon nanotubes (CNTs) show important differences in the number of layers that constitute the nanotubes, the diameter length, the quantity and the quality as a function of the number of carbons employed in the alcohol. The main interest of this study is to give the basis of an efficient synthesis process to produce CNTs of few walls for applications where small diameter is required. Full article
(This article belongs to the Special Issue Carbon Nanotubes)
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Review

Jump to: Research

Open AccessReview Films of Carbon Nanomaterials for Transparent Conductors
Materials 2013, 6(6), 2155-2181; doi:10.3390/ma6062155
Received: 10 April 2013 / Revised: 13 May 2013 / Accepted: 14 May 2013 / Published: 27 May 2013
Cited by 10 | PDF Full-text (2074 KB) | HTML Full-text | XML Full-text
Abstract
The demand for transparent conductors is expected to grow rapidly as electronic devices, such as touch screens, displays, solid state lighting and photovoltaics become ubiquitous in our lives. Doped metal oxides, especially indium tin oxide, are the commonly used materials for transparent conductors.
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The demand for transparent conductors is expected to grow rapidly as electronic devices, such as touch screens, displays, solid state lighting and photovoltaics become ubiquitous in our lives. Doped metal oxides, especially indium tin oxide, are the commonly used materials for transparent conductors. As there are some drawbacks to this class of materials, exploration of alternative materials has been conducted. There is an interest in films of carbon nanomaterials such as, carbon nanotubes and graphene as they exhibit outstanding properties. This article reviews the synthesis and assembly of these films and their post-treatment. These processes determine the film performance and understanding of this platform will be useful for future work to improve the film performance. Full article
Open AccessReview Self-Healing in Cementitious Materials—A Review
Materials 2013, 6(6), 2182-2217; doi:10.3390/ma6062182
Received: 18 February 2013 / Revised: 19 April 2013 / Accepted: 25 April 2013 / Published: 27 May 2013
Cited by 75 | PDF Full-text (1275 KB) | HTML Full-text | XML Full-text
Abstract
Concrete is very sensitive to crack formation. As wide cracks endanger the durability, repair may be required. However, these repair works raise the life-cycle cost of concrete as they are labor intensive and because the structure becomes in disuse during repair. In 1994,
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Concrete is very sensitive to crack formation. As wide cracks endanger the durability, repair may be required. However, these repair works raise the life-cycle cost of concrete as they are labor intensive and because the structure becomes in disuse during repair. In 1994, C. Dry was the first who proposed the intentional introduction of self-healing properties in concrete. In the following years, several researchers started to investigate this topic. The goal of this review is to provide an in-depth comparison of the different self-healing approaches which are available today. Among these approaches, some are aimed at improving the natural mechanism of autogenous crack healing, while others are aimed at modifying concrete by embedding capsules with suitable healing agents so that cracks heal in a completely autonomous way after they appear. In this review, special attention is paid to the types of healing agents and capsules used. In addition, the various methodologies have been evaluated based on the trigger mechanism used and attention has been paid to the properties regained due to self-healing. Full article
(This article belongs to the Special Issue Self-healing Concrete)
Open AccessReview Mechanisms of Silver Nanoparticle Release, Transformation and Toxicity: A Critical Review of Current Knowledge and Recommendations for Future Studies and Applications
Materials 2013, 6(6), 2295-2350; doi:10.3390/ma6062295
Received: 29 April 2013 / Accepted: 22 May 2013 / Published: 5 June 2013
Cited by 180 | PDF Full-text (1035 KB) | HTML Full-text | XML Full-text
Abstract
Nanosilver, due to its small particle size and enormous specific surface area, facilitates more rapid dissolution of ions than the equivalent bulk material; potentially leading to increased toxicity of nanosilver. This, coupled with their capacity to adsorb biomolecules and interact with biological receptors
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Nanosilver, due to its small particle size and enormous specific surface area, facilitates more rapid dissolution of ions than the equivalent bulk material; potentially leading to increased toxicity of nanosilver. This, coupled with their capacity to adsorb biomolecules and interact with biological receptors can mean that nanoparticles can reach sub-cellular locations leading to potentially higher localized concentrations of ions once those particles start to dissolve or degrade in situ. Further complicating the story is the capacity for nanoparticles to generate reactive oxygen species, and to interact with, and potentially disturb the functioning of biomolecules such as proteins, enzymes and DNA. The fact that the nanoparticle size, shape, surface coating and a host of other factors contribute to these interactions, and that the particles themselves are evolving or ageing leads to further complications in terms of elucidating mechanisms of interaction and modes of action for silver nanoparticles, in contrast to dissolved silver species. This review aims to provide a critical assessment of the current understanding of silver nanoparticle toxicity, as well as to provide a set of pointers and guidelines for experimental design of future studies to assess the environmental and biological impacts of silver nanoparticles. In particular; in future we require a detailed description of the nanoparticles; their synthesis route and stabilisation mechanisms; their coating; and evolution and ageing under the exposure conditions of the assay. This would allow for comparison of data from different particles; different environmental or biological systems; and structure-activity or structure-property relationships to emerge as the basis for predictive toxicology. On the basis of currently available data; such comparisons or predictions are difficult; as the characterisation and time-resolved data is not available; and a full understanding of silver nanoparticle dissolution and ageing under different conditions is observed. Clear concerns are emerging regarding the overuse of nanosilver and the potential for bacterial resistance to develop. A significant conclusion includes the need for a risk—benefit analysis for all applications and eventually restrictions of the uses where a clear benefit cannot be demonstrated. Full article
(This article belongs to the Special Issue Nanotoxicology)
Open AccessReview Structural Polymer-Based Carbon Nanotube Composite Fibers: Understanding the Processing–Structure–Performance Relationship
Materials 2013, 6(6), 2543-2577; doi:10.3390/ma6062543
Received: 2 May 2013 / Revised: 21 May 2013 / Accepted: 6 June 2013 / Published: 20 June 2013
Cited by 83 | PDF Full-text (2476 KB) | HTML Full-text | XML Full-text
Abstract
Among the many potential applications of carbon nanotubes (CNT), its usage to strengthen polymers has been paid considerable attention due to the exceptional stiffness, excellent strength, and the low density of CNT. This has provided numerous opportunities for the invention of new material
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Among the many potential applications of carbon nanotubes (CNT), its usage to strengthen polymers has been paid considerable attention due to the exceptional stiffness, excellent strength, and the low density of CNT. This has provided numerous opportunities for the invention of new material systems for applications requiring high strength and high modulus. Precise control over processing factors, including preserving intact CNT structure, uniform dispersion of CNT within the polymer matrix, effective filler–matrix interfacial interactions, and alignment/orientation of polymer chains/CNT, contribute to the composite fibers’ superior properties. For this reason, fabrication methods play an important role in determining the composite fibers’ microstructure and ultimate mechanical behavior. The current state-of-the-art polymer/CNT high-performance composite fibers, especially in regards to processing–structure–performance, are reviewed in this contribution. Future needs for material by design approaches for processing these nano-composite systems are also discussed. Full article
(This article belongs to the Special Issue Carbon Nanotubes)

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