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Materials, Volume 7, Issue 5 (May 2014), Pages 3337-4087

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Open AccessArticle Flowable Backfill Materials from Bottom Ash for Underground Pipeline
Materials 2014, 7(5), 3337-3352; doi:10.3390/ma7053337
Received: 14 February 2014 / Revised: 9 April 2014 / Accepted: 23 April 2014 / Published: 25 April 2014
Cited by 1 | PDF Full-text (1184 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this study was to investigate the relationship between strength and strain in manufacturing controlled low strength materials to recycle incineration bottom ash. Laboratory tests for controlled low strength materials with bottom ash and recycled in-situ soil have been carried out.
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The purpose of this study was to investigate the relationship between strength and strain in manufacturing controlled low strength materials to recycle incineration bottom ash. Laboratory tests for controlled low strength materials with bottom ash and recycled in-situ soil have been carried out. The optimum mixing ratios were 25%–45% of in-situ soil, 30% of bottom ash, 10%–20% of fly ash, 0%–3% of crumb rubber, 3% of cement, and 22% of water. Each mixture satisfied the standard specifications: a minimum 20 cm of flowability and 127 kPa of unconfined compressive strength. The average secant modulus (E50) was (0.07–0.08) qu. The ranges of the internal friction angle and cohesion for mixtures were 36.5°–46.6° and 49.1–180 kPa, respectively. The pH of all of the mixtures was over 12, which is strongly alkaline. Small-scale chamber tests for controlled low strength materials with bottom ash and recycled in-situ soil have been carried out. Vertical deflection of 0.88–2.41 mm and horizontal deflection of 0.83–3.72 mm were measured during backfilling. The vertical and horizontal deflections of controlled low strength materials were smaller than that of sand backfill. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle Corrosion of Bronzes by Extended Wetting with Single versus Mixed Acidic Pollutants
Materials 2014, 7(5), 3353-3370; doi:10.3390/ma7053353
Received: 27 January 2014 / Revised: 25 March 2014 / Accepted: 21 April 2014 / Published: 28 April 2014
Cited by 2 | PDF Full-text (1934 KB) | HTML Full-text | XML Full-text
Abstract
The corrosion of bronzes was examined in the context of single-acid versus mixed-acid (as in urban acid rain) solutions. Two bi-component bronzes (copper with either 3% Sn or 7% Sn) that closely represent those of historic artifacts were immersed for five weeks in
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The corrosion of bronzes was examined in the context of single-acid versus mixed-acid (as in urban acid rain) solutions. Two bi-component bronzes (copper with either 3% Sn or 7% Sn) that closely represent those of historic artifacts were immersed for five weeks in conditions designed to replicate those experienced by statues and ornaments in cities where rainfall and humidity constantly produce an electrolyte layer on the surfaces of bronzes. Ions, acids, and particles of pollutants can dissolve in this layer, resulting in a variety of harsh corrosion processes. The kinetics of corrosion and the properties of the resulting patinas were monitored weekly by electrochemical impedance spectroscopy and open-circuit potential measurements. The sizes and appearances of the corrosion products were monitored and used to estimate the progress of the corrosion, whose crystalline structures were visualized using scanning electron microscopy with energy dispersive spectroscopy, identified by X-ray diffraction, and characterized by spectrocolorimetry. The electrochemical measurements demonstrated that greater damage (in terms of color change and corrosion product formation) did not correspond to deficiencies in protection. The mixed-acid solution did not corrode the bronzes, as would be expected from the additive effects of the single acids. The postulated mechanisms of metal dissolution appear to be specific to a particular bronze alloy, with the tin component playing an important role. Full article
(This article belongs to the Special Issue Corrosion of Materials)
Open AccessArticle A Critical Analysis of the Conventionally Employed Creep Lifing Methods
Materials 2014, 7(5), 3371-3398; doi:10.3390/ma7053371
Received: 9 December 2013 / Revised: 10 April 2014 / Accepted: 21 April 2014 / Published: 29 April 2014
Cited by 5 | PDF Full-text (1033 KB) | HTML Full-text | XML Full-text
Abstract
The deformation of structural alloys presents problems for power plants and aerospace applications due to the demand for elevated temperatures for higher efficiencies and reductions in greenhouse gas emissions. The materials used in such applications experience harsh environments which may lead to deformation
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The deformation of structural alloys presents problems for power plants and aerospace applications due to the demand for elevated temperatures for higher efficiencies and reductions in greenhouse gas emissions. The materials used in such applications experience harsh environments which may lead to deformation and failure of critical components. To avoid such catastrophic failures and also increase efficiency, future designs must utilise novel/improved alloy systems with enhanced temperature capability. In recognising this issue, a detailed understanding of creep is essential for the success of these designs by ensuring components do not experience excessive deformation which may ultimately lead to failure. To achieve this, a variety of parametric methods have been developed to quantify creep and creep fracture in high temperature applications. This study reviews a number of well-known traditionally employed creep lifing methods with some more recent approaches also included. The first section of this paper focuses on predicting the long-term creep rupture properties which is an area of interest for the power generation sector. The second section looks at pre-defined strains and the re-production of full creep curves based on available data which is pertinent to the aerospace industry where components are replaced before failure. Full article
(This article belongs to the Section Materials for Energy Applications)
Open AccessArticle Influence of Chloride-Ion Adsorption Agent on Chloride Ions in Concrete and Mortar
Materials 2014, 7(5), 3415-3426; doi:10.3390/ma7053415
Received: 24 February 2014 / Revised: 17 March 2014 / Accepted: 21 April 2014 / Published: 30 April 2014
PDF Full-text (726 KB) | HTML Full-text | XML Full-text
Abstract
The influence of a chloride-ion adsorption agent (Cl agent in short), composed of zeolite, calcium aluminate hydrate and calcium nitrite, on the ingress of chloride ions into concrete and mortar has been experimentally studied. The permeability of concrete was measured, and the chloride
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The influence of a chloride-ion adsorption agent (Cl agent in short), composed of zeolite, calcium aluminate hydrate and calcium nitrite, on the ingress of chloride ions into concrete and mortar has been experimentally studied. The permeability of concrete was measured, and the chloride ion content in mortar was tested. The experimental results reveal that the Cl agent could adsorb chloride ions effectively, which had penetrated into concrete and mortar. When the Cl agent was used at a dosage of 6% by mass of cementitious materials in mortar, the resistance to the penetration of chloride ions could be improved greatly, which was more pronounced when a combination of the Cl agent and fly ash or slag was employed. Such an effect is not the result of the low permeability of the mortar, but might be a result of the interaction between the Cl agent and the chloride ions penetrated into the mortar. There are two possible mechanisms for the interaction between the Cl agent and chloride ion ingress. One is the reaction between calcium aluminate hydrate in the Cl agent and chloride ions to form Friedel’s salt, and the other one is that calcium aluminate hydrate reacts with calcium nitrite to form AFm during the early-age hydration of mortar and later the NO2 in AFm is replaced by chloride ions, which then penetrate into the mortar, also forming Friedel’s salt. More research is needed to confirm the mechanisms. Full article
(This article belongs to the Special Issue Construction Materials)
Open AccessArticle Annealing Effect on the Structural and Optical Properties of Sputter-Grown Bismuth Titanium Oxide Thin Films
Materials 2014, 7(5), 3427-3434; doi:10.3390/ma7053427
Received: 22 January 2014 / Revised: 25 March 2014 / Accepted: 28 March 2014 / Published: 30 April 2014
Cited by 1 | PDF Full-text (578 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this work is to assess the evolution of the structural and optical properties of BixTiyOz films grown by rf magnetron sputtering upon post-deposition annealing treatments in order to obtain good quality films with large grain
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The aim of this work is to assess the evolution of the structural and optical properties of BixTiyOz films grown by rf magnetron sputtering upon post-deposition annealing treatments in order to obtain good quality films with large grain size, low defect density and high refractive index similar to that of single crystals. Films with thickness in the range of 220–250 nm have been successfully grown. After annealing treatment at 600 °C the films show excellent transparency and full crystallization. It is shown that to achieve larger crystallite sizes, up to 17 nm, it is better to carry the annealing under dry air than under oxygen atmosphere, probably because the nucleation rate is reduced. The refractive index of the films is similar under both atmospheres and it is very high (n =2.5 at 589 nm). However it is still slightly lower than that of the single crystal value due to the polycrystalline morphology of the thin films. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle Optimization of Friction Stir Welding Tool Advance Speed via Monte-Carlo Simulation of the Friction Stir Welding Process
Materials 2014, 7(5), 3435-3452; doi:10.3390/ma7053435
Received: 24 February 2014 / Revised: 24 March 2014 / Accepted: 23 April 2014 / Published: 30 April 2014
Cited by 4 | PDF Full-text (930 KB) | HTML Full-text | XML Full-text
Abstract
Recognition of the friction stir welding process is growing in the aeronautical and aero-space industries. To make the process more available to the structural fabrication industry (buildings and bridges), being able to model the process to determine the highest speed of advance possible
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Recognition of the friction stir welding process is growing in the aeronautical and aero-space industries. To make the process more available to the structural fabrication industry (buildings and bridges), being able to model the process to determine the highest speed of advance possible that will not cause unwanted welding defects is desirable. A numerical solution to the transient two-dimensional heat diffusion equation for the friction stir welding process is presented. A non-linear heat generation term based on an arbitrary piecewise linear model of friction as a function of temperature is used. The solution is used to solve for the temperature distribution in the Al 6061-T6 work pieces. The finite difference solution of the non-linear problem is used to perform a Monte-Carlo simulation (MCS). A polynomial response surface (maximum welding temperature as a function of advancing and rotational speed) is constructed from the MCS results. The response surface is used to determine the optimum tool speed of advance and rotational speed. The exterior penalty method is used to find the highest speed of advance and the associated rotational speed of the tool for the FSW process considered. We show that good agreement with experimental optimization work is possible with this simplified model. Using our approach an optimal weld pitch of 0.52 mm/rev is obtained for 3.18 mm thick AA6061-T6 plate. Our method provides an estimate of the optimal welding parameters in less than 30 min of calculation time. Full article
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Open AccessArticle Physics of Free-Standing Lyotropic Films
Materials 2014, 7(5), 3453-3469; doi:10.3390/ma7053453
Received: 17 March 2014 / Revised: 24 April 2014 / Accepted: 28 April 2014 / Published: 30 April 2014
PDF Full-text (53782 KB) | HTML Full-text | XML Full-text
Abstract We explore the structures and properties of stable, free-standing films of lyotropic mesophases drawn on apertures of various shapes in an atmosphere of controlled humidity. New phenomena are uncovered and interpreted. Full article
(This article belongs to the Special Issue Liquid Crystals) Print Edition available
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Open AccessArticle Modeling the Formation of Transverse Weld during Billet-on-Billet Extrusion
Materials 2014, 7(5), 3470-3480; doi:10.3390/ma7053470
Received: 28 February 2014 / Revised: 22 April 2014 / Accepted: 24 April 2014 / Published: 30 April 2014
Cited by 1 | PDF Full-text (1784 KB) | HTML Full-text | XML Full-text
Abstract
A comprehensive mathematical model of the hot extrusion process for aluminum alloys has been developed and validated. The plasticity module was developed using a commercial finite element package, DEFORM-2D, a transient Lagrangian model which couples the thermal and deformation phenomena. Validation of the
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A comprehensive mathematical model of the hot extrusion process for aluminum alloys has been developed and validated. The plasticity module was developed using a commercial finite element package, DEFORM-2D, a transient Lagrangian model which couples the thermal and deformation phenomena. Validation of the model against industrial data indicated that it gave excellent predictions of the pressure during extrusion. The finite element predictions of the velocity fields were post-processed to calculate the thickness of the surface cladding as one billet is fed in after another through the die (i.e., the transverse weld). The mathematical model was then used to assess the effect a change in feeder dimensions would have on the shape, thickness and extent of the transverse weld during extrusion. Experimental measurements for different combinations of billet materials show that the model is able to accurately predict the transverse weld shape as well as the clad surface layer to thicknesses of 50 µm. The transverse weld is significantly affected by the feeder geometry shape, but the effects of ram speed, billet material and temperature on the transverse weld dimensions are negligible. Full article
Open AccessArticle Encapsulation of Hydrophobic Phthalocyanine with Poly(N-isopropylacrylamide)/Lipid Composite Microspheres for Thermo-Responsive Release and Photodynamic Therapy
Materials 2014, 7(5), 3481-3493; doi:10.3390/ma7053481
Received: 6 March 2014 / Revised: 26 March 2014 / Accepted: 21 April 2014 / Published: 30 April 2014
Cited by 3 | PDF Full-text (774 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Phthalocyanine (Pc) is a type of promising sensitizer molecules for photodynamic therapy (PDT), but its hydrophobicity substantially prevents its applications. In this study, we efficiently encapsulate Pc into poly(N-isopropylacrylamide) (pNIPAM) microgel particles, without or with lipid decoration (i.e., Pc@pNIPAM
[...] Read more.
Phthalocyanine (Pc) is a type of promising sensitizer molecules for photodynamic therapy (PDT), but its hydrophobicity substantially prevents its applications. In this study, we efficiently encapsulate Pc into poly(N-isopropylacrylamide) (pNIPAM) microgel particles, without or with lipid decoration (i.e., Pc@pNIPAM or Pc@pNIPAM/lipid), to improve its water solubility and prevent aggregation in aqueous medium. The incorporation of lipid molecules significantly enhances the Pc loading efficiency of pNIPAM. These Pc@pNIPAM and Pc@pNIPAM/lipid composite microspheres show thermo-triggered release of Pc and/or lipid due to the phase transition of pNIPAM. Furthermore, in the in vitro experiments, these composite particles work as drug carriers for the hydrophobic Pc to be internalized into HeLa cells. After internalization, the particles show efficient fluorescent imaging and PDT effect. Our work demonstrates promising candidates in promoting the use of hydrophobic drugs including photosensitizers in tumor therapies. Full article
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Open AccessArticle The Design and Investigation of Nanocomposites Containing Dimeric Nematogens and Liquid Crystal Gold Nanoparticles with Plasmonic Properties Showing a Nematic-Nematic Phase Transition (Nu-Nx/Ntb)
Materials 2014, 7(5), 3494-3511; doi:10.3390/ma7053494
Received: 12 March 2014 / Revised: 11 April 2014 / Accepted: 17 April 2014 / Published: 30 April 2014
Cited by 2 | PDF Full-text (2334 KB) | HTML Full-text | XML Full-text
Abstract
The construction of liquid crystal compositions consisting of the dimeric liquid crystal, CB_C9_CB (cyanobiphenyl dimer = 1'',9''-bis(4-cyanobiphenyl-4'-yl)nonane), and the range of nematic systems is explored. The materials include a laterally functionalized monomer, which was used to construct a phase diagram with CB_C9_CB,
[...] Read more.
The construction of liquid crystal compositions consisting of the dimeric liquid crystal, CB_C9_CB (cyanobiphenyl dimer = 1'',9''-bis(4-cyanobiphenyl-4'-yl)nonane), and the range of nematic systems is explored. The materials include a laterally functionalized monomer, which was used to construct a phase diagram with CB_C9_CB, as well as one laterally linked dimer liquid crystal material and two liquid crystal gold nanoparticle (LC-Au-NPs) systems. For the Au-NP-LCs, the NP diameters were varied between ~3.3 nm and 10 nm. Stable mixtures that exhibit a nematic-nematic phase transition are reported and were investigated by POM (polarizing optical microscopy), DSC (differential scanning calorimetry) and X-ray diffraction studies. Full article
(This article belongs to the Special Issue Liquid Crystals) Print Edition available
Open AccessArticle Frequency and Temperature Dependence of Fabrication Parameters in Polymer Dispersed Liquid Crystal Devices
Materials 2014, 7(5), 3512-3521; doi:10.3390/ma7053512
Received: 15 February 2014 / Revised: 9 April 2014 / Accepted: 28 April 2014 / Published: 2 May 2014
Cited by 2 | PDF Full-text (600 KB) | HTML Full-text | XML Full-text
Abstract
A series of polymer dispersed liquid crystal devices using glass substrates have been fabricated and investigated focusing on their electrical properties. The devices have been studied in terms of impedance as a function of frequency. An electric equivalent circuit has been proposed, including
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A series of polymer dispersed liquid crystal devices using glass substrates have been fabricated and investigated focusing on their electrical properties. The devices have been studied in terms of impedance as a function of frequency. An electric equivalent circuit has been proposed, including the influence of the temperature on the elements into it. In addition, a relevant effect of temperature on electrical measurements has been observed. Full article
(This article belongs to the Special Issue Liquid Crystals) Print Edition available
Open AccessArticle Characteristics of the Dye-Sensitized Solar Cells Using TiO2 Nanotubes Treated with TiCl4
Materials 2014, 7(5), 3522-3532; doi:10.3390/ma7053522
Received: 27 January 2014 / Revised: 24 April 2014 / Accepted: 29 April 2014 / Published: 5 May 2014
Cited by 14 | PDF Full-text (527 KB) | HTML Full-text | XML Full-text
Abstract
The replacement of oxide semiconducting TiO2 nano particles with one dimensional TiO2 nanotubes (TNTs) has been used for improving the electron transport in the dye-sensitized solar cells (DSSCs). Although use of one dimensional structure provides the enhanced photoelectrical performance, it tends
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The replacement of oxide semiconducting TiO2 nano particles with one dimensional TiO2 nanotubes (TNTs) has been used for improving the electron transport in the dye-sensitized solar cells (DSSCs). Although use of one dimensional structure provides the enhanced photoelectrical performance, it tends to reduce the adsorption of dye on the TiO2 surface due to decrease of surface area. To overcome this problem, we investigate the effects of TiCl4 treatment on DSSCs which were constructed with composite films made of TiO2 nanoparticles and TNTs. To find optimum condition of TNTs concentration in TiO2 composites film, series of DSSCs with different TNTs concentration were made. In this optimum condition (DSSCs with 10 wt% of TNT), the effects of post treatment are compared for different TiCl4 concentrations. The results show that the DSSCs using a TiCl4 (90 mM) post treatment shows a maximum conversion efficiency of 7.83% due to effective electron transport and enhanced adsorption of dye on TiO2 surface. Full article
(This article belongs to the Special Issue New Energy Materials)
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Open AccessArticle Improvement on the Fatigue Performance of 2024-T4 Alloy by Synergistic Coating Technology
Materials 2014, 7(5), 3533-3546; doi:10.3390/ma7053533
Received: 16 December 2013 / Revised: 25 April 2014 / Accepted: 25 April 2014 / Published: 6 May 2014
Cited by 4 | PDF Full-text (2180 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, rotating bending fatigue tests of 2024-T4 Al alloy with different oxide coatings were carried out. Compared to the uncoated and previously reported oxide coatings of aluminum alloys, the fatigue strength is able to be enhanced by using a novel oxide
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In this paper, rotating bending fatigue tests of 2024-T4 Al alloy with different oxide coatings were carried out. Compared to the uncoated and previously reported oxide coatings of aluminum alloys, the fatigue strength is able to be enhanced by using a novel oxide coating with sealing pore technology. These results indicate that the better the coating surface quality is, the more excellent the fatigue performance under rotating bending fatigue loading is. The improvement on the fatigue performance is mainly because the fatigue crack initiation and the early stage of fatigue crack growth at the coating layer can be delayed after PEO coating with pore sealing. Therefore, it is a so-called synergistic coating technology for various uses, including welding thermal cracks and filling micro-pores. The effects of different oxide coatings on surface hardness, compressive residual stress, morphology and fatigue fracture morphology are discussed. A critical compressive residual stress of about 95–100 MPa is proposed. Full article
Open AccessArticle Nanosize Control on Porous β-MnO2 and Their Catalytic Activity in CO Oxidation and N2O Decomposition
Materials 2014, 7(5), 3547-3556; doi:10.3390/ma7053547
Received: 1 February 2014 / Revised: 27 March 2014 / Accepted: 29 April 2014 / Published: 6 May 2014
Cited by 4 | PDF Full-text (1101 KB) | HTML Full-text | XML Full-text
Abstract
A major challenge in the synthesis of porous metal oxides is the control of pore size and/or wall thickness that may affect the performance of these materials. Herein, nanoporous β-MnO2 samples were prepared using different hard templates, e.g., ordered mesoporous silica SBA-15
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A major challenge in the synthesis of porous metal oxides is the control of pore size and/or wall thickness that may affect the performance of these materials. Herein, nanoporous β-MnO2 samples were prepared using different hard templates, e.g., ordered mesoporous silica SBA-15 and KIT-6, disordered mesoporous silica, and colloidal silica. These samples were characterized by Powder X-Ray Diffraction (PXRD), Transmission Electron Microscopy (TEM), and N2 adsorption-desorption. The pore size distribution of β-MnO2 was tuned by the different hard templates and their preparation details. Catalytic activities in CO oxidation and N2O decomposition were tested and the mesoporous β-MnO2 samples demonstrated superior catalytic activities compared with their bulk counterpart. Full article
(This article belongs to the Special Issue Advances in Nanoporous Materials)
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Open AccessArticle Influence of Column Axial Load and Heat Affected Zone on the Strength of Aluminium Column Web in Tension
Materials 2014, 7(5), 3557-3567; doi:10.3390/ma7053557
Received: 27 February 2014 / Revised: 12 April 2014 / Accepted: 18 April 2014 / Published: 6 May 2014
PDF Full-text (386 KB) | HTML Full-text | XML Full-text
Abstract
The component method for aluminium joints has been recently introduced in some codes and guidelines. Nevertheless, it is still in need of some development and improvement, as in some cases it was obtained by adapting the existing formulations that are valid for steel.
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The component method for aluminium joints has been recently introduced in some codes and guidelines. Nevertheless, it is still in need of some development and improvement, as in some cases it was obtained by adapting the existing formulations that are valid for steel. The current paper presents the main outcomes of a parametric analysis carried out by means of finite element (FE) numerical models for determining the influence of both column axial load and heat affected zone—in the case of welded details—on the structural response of the column web in a tension component. The proposed study integrates previous research carried out by the authors, where the influence of the assumed alloy was investigated and interpreted by corrective parameters expressed as a function of both the material strain hardening and ductility. Full article
Open AccessArticle Phosphor Deposits of β-Sialon:Eu2+ Mixed with SnO2 Nanoparticles Fabricated by the Electrophoretic Deposition (EPD) Process
Materials 2014, 7(5), 3623-3633; doi:10.3390/ma7053623
Received: 15 January 2014 / Revised: 23 April 2014 / Accepted: 30 April 2014 / Published: 6 May 2014
Cited by 4 | PDF Full-text (2032 KB) | HTML Full-text | XML Full-text
Abstract
The phosphor deposits of the β-sialon:Eu2+ mixed with various amounts (0–1 g) of the SnO2 nanoparticles were fabricated by the electrophoretic deposition (EPD) process. The mixed SnO2 nanoparticles was observed to cover onto the particle surfaces of the β-sialon:Eu2+
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The phosphor deposits of the β-sialon:Eu2+ mixed with various amounts (0–1 g) of the SnO2 nanoparticles were fabricated by the electrophoretic deposition (EPD) process. The mixed SnO2 nanoparticles was observed to cover onto the particle surfaces of the β-sialon:Eu2+ as well as fill in the voids among the phosphor particles. The external and internal quantum efficiencies (QEs) of the prepared deposits were found to be dependent on the mixing amount of the SnO2: by comparing with the deposit without any mixing (48% internal and 38% external QEs), after mixing the SnO2 nanoparticles, the both QEs were improved to 55% internal and 43% external QEs at small mixing amount (0.05 g); whereas, with increasing the mixing amount to 0.1 and 1 g, they were reduced to 36% and 29% for the 0.1 g addition and 15% and 12% l QEs for the 1 g addition. More interestingly, tunable color appearances of the deposits prepared by the EPD process were achieved, from yellow green to blue, by varying the addition amount of the SnO2, enabling it as an alternative technique instead of altering the voltage and depositing time for the color appearance controllability. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Removal of Heavy Metal Ions with Acid Activated Carbons Derived from Oil Palm and Coconut Shells
Materials 2014, 7(5), 3634-3650; doi:10.3390/ma7053634
Received: 30 August 2013 / Revised: 13 March 2014 / Accepted: 14 March 2014 / Published: 7 May 2014
Cited by 10 | PDF Full-text (406 KB) | HTML Full-text | XML Full-text
Abstract
In this work, batch adsorption experiments were carried out to investigate the suitability of prepared acid activated carbons in removing heavy metal ions such as nickel(II), lead(II) and chromium(VI). Acid activated carbons were obtained from oil palm and coconut shells using phosphoric acid
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In this work, batch adsorption experiments were carried out to investigate the suitability of prepared acid activated carbons in removing heavy metal ions such as nickel(II), lead(II) and chromium(VI). Acid activated carbons were obtained from oil palm and coconut shells using phosphoric acid under similar activation process while the differences lie either in impregnation condition or in both pretreatment and impregnation conditions. Prepared activated carbons were modified by dispersing hydrated iron oxide. The adsorption equilibrium data for nickel(II) and lead(II) were obtained from adsorption by the prepared and commercial activated carbons. Langmuir and Freundlich models fit the data well. Prepared activated carbons showed higher adsorption capacity for nickel(II) and lead(II). The removal of chromium(VI) was studied by the prepared acid activated, modified and commercial activated carbons at different pH. The isotherms studies reveal that the prepared activated carbon performs better in low concentration region while the commercial ones in the high concentration region. Thus, a complete adsorption is expected in low concentration by the prepared activated carbon. The kinetics data for Ni(II), Pb(II) and Cr(VI) by the best selected activated carbon fitted very well to the pseudo-second-order kinetic model. Full article
(This article belongs to the Section Porous Materials)
Open AccessArticle Performance Comparison of Al–Ti Master Alloys with Different Microstructures in Grain Refinement of Commercial Purity Aluminum
Materials 2014, 7(5), 3663-3676; doi:10.3390/ma7053663
Received: 21 February 2014 / Revised: 24 April 2014 / Accepted: 28 April 2014 / Published: 7 May 2014
Cited by 3 | PDF Full-text (3006 KB) | HTML Full-text | XML Full-text
Abstract
Three types of Al–5Ti master alloys were synthesized by a method of thermal explosion reaction in pure molten aluminum. Performance comparison of Al–5Ti master alloy in grain refinement of commercial purity Al with different additions (0.6%, 1.0%, 1.6%, 2.0%, and 3.0%) and holding
[...] Read more.
Three types of Al–5Ti master alloys were synthesized by a method of thermal explosion reaction in pure molten aluminum. Performance comparison of Al–5Ti master alloy in grain refinement of commercial purity Al with different additions (0.6%, 1.0%, 1.6%, 2.0%, and 3.0%) and holding time (10, 30, 60 and 120 min) were investigated. The results show that Al–5Ti master alloy with blocky TiAl3 particles clearly has better refining efficiency than the master alloy with mixed TiAl3 particles and the master alloy with needle-like TiAl3 particles. The structures of master alloys, differing by sizes, morphologies and quantities of TiAl3 crystals, were found to affect the pattern of the grain refining properties with the holding time. The grain refinement effect was revealed to reduce markedly for master alloys with needle–like TiAl3 crystals and to show the further significant improvement at a longer holding time for the master alloy containing both larger needle–like and blocky TiAl3 particles. For the master alloy with finer blocky particles, the grain refining effect did not obviously decrease during the whole studied range of the holding time. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle Optical Properties of Electrically Tunable Two-Dimensional Photonic Lattice Structures Formed in a Holographic Polymer-Dispersed Liquid Crystal Film: Analysis and Experiment
Materials 2014, 7(5), 3677-3698; doi:10.3390/ma7053677
Received: 11 March 2014 / Revised: 7 April 2014 / Accepted: 21 April 2014 / Published: 7 May 2014
Cited by 3 | PDF Full-text (16266 KB) | HTML Full-text | XML Full-text
Abstract
We report on theoretical and experimental investigations of optical wave propagations in two-dimensional photonic lattice structures formed in a holographic polymer-dispersed liquid crystal (HPDLC) film. In the theoretical analysis we employed the 2×2 matrix formulation and the statistical thermodynamics model to analyze the
[...] Read more.
We report on theoretical and experimental investigations of optical wave propagations in two-dimensional photonic lattice structures formed in a holographic polymer-dispersed liquid crystal (HPDLC) film. In the theoretical analysis we employed the 2×2 matrix formulation and the statistical thermodynamics model to analyze the formation of anisotropic photonic lattice structures by holographic polymerization. The influence of multiple reflections inside an HPDLC film on the formed refractive index distribution was taken into account in the analysis. In the experiment we fabricated two-dimensional photonic lattice structures in an HPDLC film under three-beam interference holographic polymerization and performed optical measurements of spectral transmittances and wavelength dispersion. We also demonstrated the electrical control capability of the fabricated photonic lattice structure and its dependence on incident wave polarization. These measured results were compared with the calculated ones by means of photonic band and beam propagation calculations. Full article
(This article belongs to the Special Issue Liquid Crystals) Print Edition available
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Open AccessArticle Fabrication of a Low Density Carbon Fiber Foam and Its Characterization as a Strain Gauge
Materials 2014, 7(5), 3699-3714; doi:10.3390/ma7053699
Received: 30 January 2014 / Revised: 28 March 2014 / Accepted: 29 April 2014 / Published: 8 May 2014
Cited by 3 | PDF Full-text (953 KB) | HTML Full-text | XML Full-text
Abstract
Samples of carbon nano-fiber foam (CFF), essentially a 3D solid mat of intertwined nanofibers of pure carbon, were grown using the Constrained Formation of Fibrous Nanostructures (CoFFiN) process in a steel mold at 550 °C from a palladium particle catalysts exposed to fuel
[...] Read more.
Samples of carbon nano-fiber foam (CFF), essentially a 3D solid mat of intertwined nanofibers of pure carbon, were grown using the Constrained Formation of Fibrous Nanostructures (CoFFiN) process in a steel mold at 550 °C from a palladium particle catalysts exposed to fuel rich mixtures of ethylene and oxygen. The resulting material was studied using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX), Surface area analysis (BET), and Thermogravimetric Analysis (TGA). Transient and dynamic mechanical tests clearly demonstrated that the material is viscoelastic. Concomitant mechanical and electrical testing of samples revealed the material to have electrical properties appropriate for application as the sensing element of a strain gauge. The sample resistance versus strain values stabilize after a few compression cycles to show a perfectly linear relationship. Study of microstructure, mechanical and electrical properties of the low density samples confirm the uniqueness of the material: It is formed entirely of independent fibers of diverse diameters that interlock forming a tridimensional body that can be grown into different shapes and sizes at moderate temperatures. It regains its shape after loads are removed, is light weight, presents viscoelastic behavior, thermal stability up to 550 °C, hydrophobicity, and is electrically conductive. Full article
(This article belongs to the Special Issue Carbon Fibers) Print Edition available
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Open AccessArticle Magnetic Properties of the Ferromagnetic Shape Memory Alloys Ni50+xMn27−xGa23 in Magnetic Fields
Materials 2014, 7(5), 3715-3734; doi:10.3390/ma7053715
Received: 23 February 2014 / Revised: 2 April 2014 / Accepted: 4 May 2014 / Published: 8 May 2014
PDF Full-text (743 KB) | HTML Full-text | XML Full-text
Abstract
Thermal strain, permeability, and magnetization measurements of the ferromagnetic shape memory alloys Ni50+xMn27−xGa23 (x = 2.0, 2.5, 2.7) were performed. For x = 2.7, in which the martensite transition and the ferromagnetic transition occur at
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Thermal strain, permeability, and magnetization measurements of the ferromagnetic shape memory alloys Ni50+xMn27−xGa23 (x = 2.0, 2.5, 2.7) were performed. For x = 2.7, in which the martensite transition and the ferromagnetic transition occur at the same temperature, the martensite transition starting temperature TMs shift in magnetic fields around a zero magnetic field was estimated to be dTMs/dB = 1.1 ± 0.2 K/T, thus indicating that magnetic fields influences martensite transition. We discussed the itinerant electron magnetism of x = 2.0 and 2.5. As for x = 2.5, the M4 vs. B/M plot crosses the origin of the coordinate axis at the Curie temperature, and the plot indicates a good linear relation behavior around the Curie temperature. The result is in agreement with the theory by Takahashi, concerning itinerant electron ferromagnets. Full article
(This article belongs to the Special Issue Shape Memory Materials)
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Open AccessArticle Effects of Asymmetric Quantum Wells on the Structural and Optical Properties of InGaN-Based Light-Emitting Diodes
Materials 2014, 7(5), 3758-3771; doi:10.3390/ma7053758
Received: 8 December 2013 / Revised: 17 January 2014 / Accepted: 29 April 2014 / Published: 12 May 2014
Cited by 1 | PDF Full-text (467 KB) | HTML Full-text | XML Full-text
Abstract
A metalorganic vapor phase epitaxy-grown InGaN/GaN multiple-quantum-well (MQW) with three graded-thickness wells (the first-grown well had the greatest width) near the n-GaN was used as the active layer of an LED. For LEDs with an asymmetric quantum well (AQW), high-resolution X-ray diffraction and
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A metalorganic vapor phase epitaxy-grown InGaN/GaN multiple-quantum-well (MQW) with three graded-thickness wells (the first-grown well had the greatest width) near the n-GaN was used as the active layer of an LED. For LEDs with an asymmetric quantum well (AQW), high-resolution X-ray diffraction and transmission electron microscopic reveal that the modified MQWs with a reasonable crystalline quality were coherently strained on the underlying GaN epilayers without any relaxation. In addition, the slight increase of indium segregation in the LED with an AQW may be attributed to variations in indium contents experienced during epitaxial growth of the wide well-containing MQWs. By preventing the energetic electrons from accumulating at the topmost quantum well nearest the p-GaN, the presence of light intensity roll-off in the LED with an AQW is shifted to higher currents and the corresponding maximum light output power is increased with a ratio 7.9% higher than that of normal LEDs. Finally, similar emission wavelengths were observed in the electroluminescence spectra of both LEDs, suggesting that light emitted mostly from the top quantum wells (near the p-GaN) while the emissions from the AQW region were insignificant. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle Chemical, Mechanical, and Durability Properties of Concrete with Local Mineral Admixtures under Sulfate Environment in Northwest China
Materials 2014, 7(5), 3772-3785; doi:10.3390/ma7053772
Received: 1 February 2014 / Revised: 15 April 2014 / Accepted: 4 May 2014 / Published: 13 May 2014
Cited by 7 | PDF Full-text (471 KB) | HTML Full-text | XML Full-text
Abstract
Over the vast Northwest China, arid desert contains high concentrations of sulfate, chloride, and other chemicals in the ground water, which poses serious challenges to infrastructure construction that routinely utilizes portland cement concrete. Rapid industrialization in the region has been generating huge amounts
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Over the vast Northwest China, arid desert contains high concentrations of sulfate, chloride, and other chemicals in the ground water, which poses serious challenges to infrastructure construction that routinely utilizes portland cement concrete. Rapid industrialization in the region has been generating huge amounts of mineral admixtures, such as fly ash and slags from energy and metallurgical industries. These industrial by-products would turn into waste materials if not utilized in time. The present study evaluated the suitability of utilizing local mineral admixtures in significant quantities for producing quality concrete mixtures that can withstand the harsh chemical environment without compromising the essential mechanical properties. Comprehensive chemical, mechanical, and durability tests were conducted in the laboratory to characterize the properties of the local cementitious mineral admixtures, cement mortar and portland cement concrete mixtures containing these admixtures. The results from this study indicated that the sulfate resistance of concrete was effectively improved by adding local class F fly ash and slag, or by applying sulfate resistance cement to the mixtures. It is noteworthy that concrete containing local mineral admixtures exhibited much lower permeability (in terms of chloride ion penetration) than ordinary portland cement concrete while retaining the same mechanical properties; whereas concrete mixtures made with sulfate resistance cement had significantly reduced strength and much increased chloride penetration comparing to the other mixtures. Hence, the use of local mineral admixtures in Northwest China in concrete mixtures would be beneficial to the performance of concrete, as well as to the protection of environment. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Solid-State Synthesis and Photocatalytic Activity of Polyterthiophene Derivatives/TiO2 Nanocomposites
Materials 2014, 7(5), 3786-3801; doi:10.3390/ma7053786
Received: 6 November 2013 / Revised: 14 April 2014 / Accepted: 7 May 2014 / Published: 14 May 2014
Cited by 9 | PDF Full-text (2006 KB) | HTML Full-text | XML Full-text
Abstract
Poly(3,4-propylenedioxy-2,2':5',2"-terthiophene)/TiO2 and poly(3,4-(2,2-dimethylenepropylenedioxy)-2,2':5',2"-terthiophene)/TiO2 nanocomposites were synthesized by a simple solid-state method. Additionally, the poly(3,4-propylenedioxy thiophene)/TiO2 and poly(3,4-2,2-dimethylenepropylenedioxythiophene)/TiO2 nanocomposites were synthesized in a similar manner for comparison. The structure and morphology were characterized by Fourier transform infrared (FTIR), ultraviolet-visible (UV-Vis)
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Poly(3,4-propylenedioxy-2,2':5',2"-terthiophene)/TiO2 and poly(3,4-(2,2-dimethylenepropylenedioxy)-2,2':5',2"-terthiophene)/TiO2 nanocomposites were synthesized by a simple solid-state method. Additionally, the poly(3,4-propylenedioxy thiophene)/TiO2 and poly(3,4-2,2-dimethylenepropylenedioxythiophene)/TiO2 nanocomposites were synthesized in a similar manner for comparison. The structure and morphology were characterized by Fourier transform infrared (FTIR), ultraviolet-visible (UV-Vis) absorption spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The photocatalytic activities of the nanocomposites were examined through the degradation processes of a methylene blue (MB) solution under UV light and sunlight irradiation. The results of FTIR and UV-Vis spectra showed that the composites were successfully synthesized by solid-state method and the poly(3,4-propylenedioxy-2,2':5',2"-terthiophene)/TiO2 and poly(3,4-(2,2-dimethylenepropylenedioxy)-2,2':5',2"-terthiophene)/TiO2 nanocomposite had a higher oxidation degree and conjugation length than others. The results also indicated that the TiO2 had no effect on the crystallinity of composites, but was well embedded in the polymer matrix. Additionally, the highest degradation efficiency of 90.5% occurred in the case of the poly(3,4-propylenedioxy-2,2':5',2"-terthiophene)/TiO2 nanocomposite. Full article
Open AccessArticle Drilling Damage in Composite Material
Materials 2014, 7(5), 3802-3819; doi:10.3390/ma7053802
Received: 27 February 2014 / Revised: 29 April 2014 / Accepted: 8 May 2014 / Published: 14 May 2014
Cited by 8 | PDF Full-text (603 KB) | HTML Full-text | XML Full-text
Abstract
The characteristics of carbon fibre reinforced laminates have widened their use from aerospace to domestic appliances, and new possibilities for their usage emerge almost daily. In many of the possible applications, the laminates need to be drilled for assembly purposes. It is known
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The characteristics of carbon fibre reinforced laminates have widened their use from aerospace to domestic appliances, and new possibilities for their usage emerge almost daily. In many of the possible applications, the laminates need to be drilled for assembly purposes. It is known that a drilling process that reduces the drill thrust force can decrease the risk of delamination. In this work, damage assessment methods based on data extracted from radiographic images are compared and correlated with mechanical test results—bearing test and delamination onset test—and analytical models. The results demonstrate the importance of an adequate selection of drilling tools and machining parameters to extend the life cycle of these laminates as a consequence of enhanced reliability. Full article
(This article belongs to the Special Issue Carbon Fibers) Print Edition available
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Open AccessArticle Carbonized Micro- and Nanostructures: Can Downsizing Really Help?
Materials 2014, 7(5), 3820-3833; doi:10.3390/ma7053820
Received: 6 March 2014 / Revised: 4 April 2014 / Accepted: 25 April 2014 / Published: 14 May 2014
Cited by 6 | PDF Full-text (604 KB) | HTML Full-text | XML Full-text
Abstract
In this manuscript, we discuss relationships between morphology and mechanical strength of carbonized structures, obtained via pyrolysis of polymeric precursors, across multiple length scales, from carbon fibers (CFs) with diameters of 5–10 µm to submicron thick carbon nanofibers (CNFs). Our research points to
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In this manuscript, we discuss relationships between morphology and mechanical strength of carbonized structures, obtained via pyrolysis of polymeric precursors, across multiple length scales, from carbon fibers (CFs) with diameters of 5–10 µm to submicron thick carbon nanofibers (CNFs). Our research points to radial inhomogeneity, skin–core structure, as a size-dependent feature of polyacrylonitrile-based CFs. This inhomogeneity is a surface effect, caused by suppressed diffusion of oxygen and stabilization byproducts during stabilization through skin. Hence, reducing the precursor diameters from tens of microns to submicron appears as an effective strategy to develop homogeneous carbonized structures. Our research establishes the significance of this downsizing in developing lightweight structural materials by comparing intrinsic strength of radially inhomogeneous CFs with that of radially homogeneous CNF. While experimental studies on the strength of CNFs have targeted randomly oriented turbostratic domains, via continuum modeling, we have estimated that strength of CNFs can reach 14 GPa, when the basal planes of graphitic domains are parallel to nanofiber axis. The CNFs in our model are treated as composites of amorphous carbon (matrix), reinforced with turbostratic domains, and their strength is predicted using Tsai–Hill criterion. The model was calibrated with existing experimental data. Full article
(This article belongs to the Section Advanced Composites)
Open AccessArticle Effect of Receptor Structure and Length on the Wrapping of a Nanoparticle by a Lipid Membrane
Materials 2014, 7(5), 3855-3866; doi:10.3390/ma7053855
Received: 4 April 2014 / Revised: 30 April 2014 / Accepted: 4 May 2014 / Published: 14 May 2014
Cited by 1 | PDF Full-text (1360 KB) | HTML Full-text | XML Full-text
Abstract
Nanoparticles have been considered as a type of powerful tool to deliver drugs and genes into cells for disease diagnosis and therapies. It has been generally accepted that the internalization of nanoparticles into cells is mostly realized by receptor-mediated endocytosis. However, for the
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Nanoparticles have been considered as a type of powerful tool to deliver drugs and genes into cells for disease diagnosis and therapies. It has been generally accepted that the internalization of nanoparticles into cells is mostly realized by receptor-mediated endocytosis. However, for the influence of structural factors of receptors on endocytosis, this is still largely unknown. In this paper, computer simulations are applied to investigate the effects of structure (i.e., the number of constituent chains of the receptor) and the length of the receptor on the wrapping behavior of nanoparticles by the lipid membrane, which is a key step of receptor-medicated endocytosis. It is found that these structural factors of receptors have strong effects on the nanoparticle’s final interaction configuration with the membrane in the simulations, such as adhering on the membrane surface or being partly or fully wrapped by the membrane. Furthermore, in some cases, the rupture of the lipid membrane occurs. These results are helpful for the understanding of endocytosis and the preparation of advanced nanoscale drug-delivery vectors. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle CO2 Capture and Separation Properties in the Ionic Liquid 1-n-Butyl-3-Methylimidazolium Nonafluorobutylsulfonate
Materials 2014, 7(5), 3867-3880; doi:10.3390/ma7053867
Received: 4 April 2014 / Revised: 4 May 2014 / Accepted: 5 May 2014 / Published: 14 May 2014
Cited by 2 | PDF Full-text (1370 KB) | HTML Full-text | XML Full-text
Abstract
Recently, the use of ionic liquids (ILs) for carbon capture and separation processes has gained great interest by many researchers due to the high solubility of CO2 in ILs. In the present work, solubility measurements of CO2 in the novel IL
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Recently, the use of ionic liquids (ILs) for carbon capture and separation processes has gained great interest by many researchers due to the high solubility of CO2 in ILs. In the present work, solubility measurements of CO2 in the novel IL 1-n-butyl-3-methylimidazolium nonafluorobutylsulfonate [C4mim][CF3CF2CF2CF2SO3] were performed with a high-pressure view-cell technique in the temperature range from 293.15 to 343.15 K and pressures up to about 4.2 MPa. For comparison, solubilities of H2, N2, and O2 in the IL were also measured at 323.15 K via the same procedure. The Krichevsky-Kasarnovsky equation was employed to correlate the measured solubility data. Henry’s law constants, enthalpies, and entropies of absorption for CO2 in the IL were also determined and presented. The CO2 solubility in this IL was compared with other ILs sharing the same cation. It was shown that the solubility of CO2 in these ILs follows the sequence: [C4mim][CF3CF2CF2CF2SO3] ≈ [C4mim][Tf2N] > [C4mim][CF3CF2CF2COO] > [C4mim][BF4], and the solubility selectivity of CO2 relative to O2, N2, and H2 in [C4mim][CF3CF2CF2CF2SO3] was 8, 16, and 22, respectively. Furthermore, this IL is regenerable and exhibits good stability. Therefore, the IL reported here would be a promising sorbent for CO2. Full article
(This article belongs to the Section Materials for Energy Applications)
Open AccessArticle Synthesis of MgB2 at Low Temperature and Autogenous Pressure
Materials 2014, 7(5), 3901-3918; doi:10.3390/ma7053901
Received: 14 April 2014 / Revised: 4 May 2014 / Accepted: 9 May 2014 / Published: 15 May 2014
Cited by 2 | PDF Full-text (819 KB) | HTML Full-text | XML Full-text
Abstract
High quality, micron-sized interpenetrating grains of MgB2, with high density, are produced at low temperatures (~420 °C < T < ~500 °C) under autogenous pressure by pre-mixing Mg powder and NaBH4 and heating in an Inconel 601 alloy reactor for
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High quality, micron-sized interpenetrating grains of MgB2, with high density, are produced at low temperatures (~420 °C < T < ~500 °C) under autogenous pressure by pre-mixing Mg powder and NaBH4 and heating in an Inconel 601 alloy reactor for 5–15 h. Optimum production of MgB2, with yields greater than 75%, occurs for autogenous pressure in the range 1.0 MPa to 2.0 MPa, with the reactor at ~500 °C. Autogenous pressure is induced by the decomposition of NaBH4 in the presence of Mg and/or other Mg-based compounds. The morphology, transition temperature and magnetic properties of MgB2 are dependent on the heating regime. Significant improvement in physical properties accrues when the reactor temperature is held at 250 °C for >20 min prior to a hold at 500 °C. Full article
(This article belongs to the Section Materials for Energy Applications)
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Open AccessArticle Antimicrobial Activity of Chitosan-Carbon Nanotube Hydrogels
Materials 2014, 7(5), 3946-3955; doi:10.3390/ma7053946
Received: 5 November 2013 / Revised: 2 December 2013 / Accepted: 7 May 2014 / Published: 19 May 2014
Cited by 12 | PDF Full-text (649 KB) | HTML Full-text | XML Full-text
Abstract
In the present study, we have prepared chitosan-carbon nanotube (Chitosan-CNT) hydrogels by the freeze-lyophilization method and examined their antimicrobial activity. Different concentrations of CNT were used in the preparation of Chitosan-CNT hydrogels. These differently concentrated CNT hydrogels were chemically characterized using Fourier Transform-Infrared
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In the present study, we have prepared chitosan-carbon nanotube (Chitosan-CNT) hydrogels by the freeze-lyophilization method and examined their antimicrobial activity. Different concentrations of CNT were used in the preparation of Chitosan-CNT hydrogels. These differently concentrated CNT hydrogels were chemically characterized using Fourier Transform-Infrared Spectroscopy, Scanning Electron Microscopy and Optical microscopy. The porosity of the hydrogels were found to be >94%. Dispersion of chitosan was observed in the CNT matrix by normal photography and optical microscopy. The addition of CNT in the composite scaffold significantly reduced the water uptake ability. In order to evaluate antimicrobial activity, the serial dilution method was used towards Staphylococcus aureus, Escherichia coli and Candida tropicalis. The composite Chitosan-CNT hydrogel showed greater antimicrobial activity with increasing CNT concentration, suggesting that Chitosan-CNT hydrogel scaffold will be a promising biomaterial in biomedical applications. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)
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Open AccessArticle Microstructure Analysis of Ti-xPt Alloys and the Effect of Pt Content on the Mechanical Properties and Corrosion Behavior of Ti Alloys
Materials 2014, 7(5), 3990-4000; doi:10.3390/ma7053990
Received: 20 March 2014 / Revised: 9 May 2014 / Accepted: 12 May 2014 / Published: 21 May 2014
Cited by 1 | PDF Full-text (1945 KB) | HTML Full-text | XML Full-text
Abstract
The microstructure, mechanical properties, and corrosion behavior of binary Ti-xPt alloys containing 5, 10, 15 and 20 wt% Pt were investigated in order to develop new Ti-based dental materials possessing superior properties than those of commercially pure titanium (cp-Ti). All of the Ti-xPt
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The microstructure, mechanical properties, and corrosion behavior of binary Ti-xPt alloys containing 5, 10, 15 and 20 wt% Pt were investigated in order to develop new Ti-based dental materials possessing superior properties than those of commercially pure titanium (cp-Ti). All of the Ti-xPt (x = 5, 10, 15, 20) alloys showed hexagonal α-Ti structure with cubic Ti3Pt intermetallic phase. The mechanical properties and corrosion behavior of Ti-xPt alloys were sensitive to the Pt content. The addition of Pt contributed to hardening of cp-Ti and to improving its oxidation resistance. Electrochemical results showed that the Ti-xPt alloys exhibited superior corrosion resistance than that of cp-Ti. Full article
Open AccessArticle Effect of Polymer Infiltration on the Flexural Behavior of β-Tricalcium Phosphate Robocast Scaffolds
Materials 2014, 7(5), 4001-4018; doi:10.3390/ma7054001
Received: 20 February 2014 / Revised: 22 April 2014 / Accepted: 26 April 2014 / Published: 21 May 2014
Cited by 10 | PDF Full-text (1783 KB) | HTML Full-text | XML Full-text
Abstract
The influence of polymer infiltration on the flexural strength and toughness of β-tricalcium phosphate (β-TCP) scaffolds fabricated by robocasting (direct-write assembly) is analyzed. Porous structures consisting of a tetragonal three-dimensional lattice of interpenetrating rods were impregnated with biodegradable polymers (poly(lactic acid) (PLA) and
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The influence of polymer infiltration on the flexural strength and toughness of β-tricalcium phosphate (β-TCP) scaffolds fabricated by robocasting (direct-write assembly) is analyzed. Porous structures consisting of a tetragonal three-dimensional lattice of interpenetrating rods were impregnated with biodegradable polymers (poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL)) by immersion of the structure in a polymer melt. Infiltration increased the flexural strength of these model scaffolds by a factor of 5 (PCL) or 22 (PLA), an enhancement considerably greater than that reported for compression strength of analogue materials. The greater strength improvement in bending was attributed to a more effective transfer of stress to the polymer under this solicitation since the degree of strengthening associated to the sealing of precursor flaws in the ceramic rod surfaces should remain unaltered. Impregnation with either polymer also improved further than in compression the fracture energy of the scaffolds (by more than two orders of magnitude). This increase is associated to the extraordinary strengthening provided by impregnation and to a crack bridging toughening mechanism produced by polymer fibrils. Full article
(This article belongs to the Special Issue Ceramics for Healthcare 2013)
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Open AccessArticle Comparing Triflate and Hexafluorophosphate Anions of Ionic Liquids in Polymer Electrolytes for Supercapacitor Applications
Materials 2014, 7(5), 4019-4033; doi:10.3390/ma7054019
Received: 28 March 2014 / Revised: 30 April 2014 / Accepted: 30 April 2014 / Published: 21 May 2014
Cited by 11 | PDF Full-text (697 KB) | HTML Full-text | XML Full-text
Abstract
Two different ionic liquid-based biopolymer electrolyte systems were prepared using a solution casting technique. Corn starch and lithium hexafluorophosphate (LiPF6) were employed as polymer and salt, respectively. Additionally, two different counteranions of ionic liquids, viz. 1-butyl-3-methylimidazolium hexafluorophosphate (BmImPF6) and
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Two different ionic liquid-based biopolymer electrolyte systems were prepared using a solution casting technique. Corn starch and lithium hexafluorophosphate (LiPF6) were employed as polymer and salt, respectively. Additionally, two different counteranions of ionic liquids, viz. 1-butyl-3-methylimidazolium hexafluorophosphate (BmImPF6) and 1-butyl-3-methylimidazolium trifluoromethanesulfonate (also known as 1-butyl-3-methylimidazolium triflate) (BmImTf) were used and studied in this present work. The maximum ionic conductivities of (1.47 ± 0.02) × 10−4 and (3.21 ± 0.01) × 10−4 S∙cm−1 were achieved with adulteration of 50 wt% of BmImPF6 and 80 wt% of BmImTf, respectively at ambient temperature. Activated carbon-based electrodes were prepared and used in supercapacitor fabrication. Supercapacitors were then assembled using the most conducting polymer electrolyte from each system. The electrochemical properties of the supercapacitors were then analyzed. The supercapacitor containing the triflate-based biopolymer electrolyte depicted a higher specific capacitance with a wider electrochemical stability window compared to that of the hexafluorophosphate system. Full article
(This article belongs to the Section Materials for Energy Applications)
Open AccessArticle Visible-Light Active and Magnetically Recyclable Nanocomposites for the Degradation of Organic Dye
Materials 2014, 7(5), 4034-4044; doi:10.3390/ma7054034
Received: 2 April 2014 / Revised: 7 May 2014 / Accepted: 13 May 2014 / Published: 21 May 2014
Cited by 8 | PDF Full-text (733 KB) | HTML Full-text | XML Full-text
Abstract
Recyclable visible-light photocatalyst Fe3O4@TiO2 with core-shell structure was prepared by a simple synthetic strategy using solvothermal crystallization of titanium precursor on preformed Fe3O4 nanopartiles. The photo-degradation reaction of neutral red aqueous solution was tested to
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Recyclable visible-light photocatalyst Fe3O4@TiO2 with core-shell structure was prepared by a simple synthetic strategy using solvothermal crystallization of titanium precursor on preformed Fe3O4 nanopartiles. The photo-degradation reaction of neutral red aqueous solution was tested to evaluate the visible-light photocatalytic activity of the as prepared Fe3O4@TiO2 nanoparticles, which show excellent photocatalytic activity compared with commercial P25 catalyst. Moreover, the Fe3O4@TiO2 nanocomposites can be easily separated from the reaction mixture, and maintain favorable photocatalytic activity after five cycles. The high visible light absorption of the Fe3O4@TiO2 nanocomposites may originate from the absence of electronic heterojunction, excellently dispersity and the high specific surface area of the as-synthesized Fe3O4@TiO2 samples. Full article
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Open AccessArticle Novel Discotic Boroxines: Synthesis and Mesomorphic Properties
Materials 2014, 7(5), 4045-4056; doi:10.3390/ma7054045
Received: 8 April 2014 / Revised: 7 May 2014 / Accepted: 8 May 2014 / Published: 22 May 2014
Cited by 4 | PDF Full-text (816 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A new synthetic approach to highly substituted triphenylboroxines 11 is described. Their mesomorphic properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (SAXS, WAXS). The tris(3,4,5-trialkyloxy)phenyl functionalized derivatives 11be showed broad mesophases for a minimum
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A new synthetic approach to highly substituted triphenylboroxines 11 is described. Their mesomorphic properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (SAXS, WAXS). The tris(3,4,5-trialkyloxy)phenyl functionalized derivatives 11be showed broad mesophases for a minimum alkyl chain length of C9. The phase widths ranged from 110 K to 77 K near room temperature, thus decreasing with enhanced alkyl chain lengths. Textures observed under POM indicated a columnar hexagonal (Colh) mesophase symmetry that was confirmed by X-ray diffraction experiments. Full article
(This article belongs to the Special Issue Liquid Crystals) Print Edition available
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Review

Jump to: Research

Open AccessReview Smart Polymer/Carbon Nanotube Nanocomposites and Their Electrorheological Response
Materials 2014, 7(5), 3399-3414; doi:10.3390/ma7053399
Received: 27 December 2013 / Revised: 6 April 2014 / Accepted: 10 April 2014 / Published: 30 April 2014
Cited by 1 | PDF Full-text (749 KB) | HTML Full-text | XML Full-text
Abstract
This review article summarizes the preparation of polymer/carbon nanotube (CNT) nanocomposites and their applications as electrorheological (ER) fluids. These ER fluids exhibited a controllable electro-response under an applied electric field due to the presence of well-dispersed CNTs. The background, morphology, preparations, and characteristics
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This review article summarizes the preparation of polymer/carbon nanotube (CNT) nanocomposites and their applications as electrorheological (ER) fluids. These ER fluids exhibited a controllable electro-response under an applied electric field due to the presence of well-dispersed CNTs. The background, morphology, preparations, and characteristics of these materials are discussed, specifically focusing on the various approaches in the preparation of polymer/CNT nanocomposites, morphology, and their effects on the ER characteristics. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)
Open AccessReview A Review of Polymer-Stabilized Ferroelectric Liquid Crystals
Materials 2014, 7(5), 3568-3587; doi:10.3390/ma7053568
Received: 9 March 2014 / Revised: 13 April 2014 / Accepted: 28 April 2014 / Published: 6 May 2014
Cited by 7 | PDF Full-text (2459 KB) | HTML Full-text | XML Full-text
Abstract
The polymer stabilized state of ferroelectric liquid crystals (FLC) is reviewed; and the effect of a dispersed polymer network in an FLC outlined and discussed. All fundamental material aspects are demonstrated; such as director tilt angle; spontaneous polarization; response time and viscosity; as
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The polymer stabilized state of ferroelectric liquid crystals (FLC) is reviewed; and the effect of a dispersed polymer network in an FLC outlined and discussed. All fundamental material aspects are demonstrated; such as director tilt angle; spontaneous polarization; response time and viscosity; as well as the dielectric modes. It was found that the data can largely be explained by assuming an elastic interaction between the polymer network strands and the liquid crystal molecules. The elastic interaction parameter was determined; and increases linearly with increasing polymer concentration. Full article
(This article belongs to the Special Issue Liquid Crystals) Print Edition available
Open AccessReview Fabrication of Metallic Biomedical Scaffolds with the Space Holder Method: A Review
Materials 2014, 7(5), 3588-3622; doi:10.3390/ma7053588
Received: 14 March 2014 / Revised: 10 April 2014 / Accepted: 18 April 2014 / Published: 6 May 2014
Cited by 17 | PDF Full-text (1230 KB) | HTML Full-text | XML Full-text
Abstract
Bone tissue engineering has been increasingly studied as an alternative approach to bone defect reconstruction. In this approach, new bone cells are stimulated to grow and heal the defect with the aid of a scaffold that serves as a medium for bone cell
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Bone tissue engineering has been increasingly studied as an alternative approach to bone defect reconstruction. In this approach, new bone cells are stimulated to grow and heal the defect with the aid of a scaffold that serves as a medium for bone cell formation and growth. Scaffolds made of metallic materials have preferably been chosen for bone tissue engineering applications where load-bearing capacities are required, considering the superior mechanical properties possessed by this type of materials to those of polymeric and ceramic materials. The space holder method has been recognized as one of the viable methods for the fabrication of metallic biomedical scaffolds. In this method, temporary powder particles, namely space holder, are devised as a pore former for scaffolds. In general, the whole scaffold fabrication process with the space holder method can be divided into four main steps: (i) mixing of metal matrix powder and space-holding particles; (ii) compaction of granular materials; (iii) removal of space-holding particles; (iv) sintering of porous scaffold preform. In this review, detailed procedures in each of these steps are presented. Technical challenges encountered during scaffold fabrication with this specific method are addressed. In conclusion, strategies are yet to be developed to address problematic issues raised, such as powder segregation, pore inhomogeneity, distortion of pore sizes and shape, uncontrolled shrinkage and contamination. Full article
(This article belongs to the Special Issue Light Alloys and Their Applications)
Open AccessReview The Relationship between Biofilm and Physical-Chemical Properties of Implant Abutment Materials for Successful Dental Implants
Materials 2014, 7(5), 3651-3662; doi:10.3390/ma7053651
Received: 8 January 2014 / Revised: 13 March 2014 / Accepted: 16 April 2014 / Published: 7 May 2014
Cited by 4 | PDF Full-text (311 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this review was to investigate the relationship between biofilm and peri-implant disease, with an emphasis on the types of implant abutment surfaces. Individuals with periodontal disease typically have a large amount of pathogenic microorganisms in the periodontal pocket. If the
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The aim of this review was to investigate the relationship between biofilm and peri-implant disease, with an emphasis on the types of implant abutment surfaces. Individuals with periodontal disease typically have a large amount of pathogenic microorganisms in the periodontal pocket. If the individuals lose their teeth, these microorganisms remain viable inside the mouth and can directly influence peri-implant microbiota. Metal implants offer a suitable solution, but similarly, these remaining bacteria can adhere on abutment implant surfaces, induce peri-implantitis causing potential destruction of the alveolar bone near to the implant threads and cause the subsequent loss of the implant. Studies have demonstrated differences in biofilm formation on dental materials and these variations can be associated with both physical and chemical characteristics of the surfaces. In the case of partially edentulous patients affected by periodontal disease, the ideal type of implant abutments utilized should be one that adheres the least or negligible amounts of periodontopathogenic bacteria. Therefore, it is of clinically relevance to know how the bacteria behave on different types of surfaces in order to develop new materials and/or new types of treatment surfaces, which will reduce or inhibit adhesion of pathogenic microorganisms, and, thus, restrict the use of the abutments with indication propensity for bacterial adhesion. Full article
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Open AccessReview A Review of Dissimilar Welding Techniques for Magnesium Alloys to Aluminum Alloys
Materials 2014, 7(5), 3735-3757; doi:10.3390/ma7053735
Received: 24 March 2014 / Revised: 25 April 2014 / Accepted: 25 April 2014 / Published: 8 May 2014
Cited by 20 | PDF Full-text (1981 KB) | HTML Full-text | XML Full-text
Abstract
Welding of dissimilar magnesium alloys and aluminum alloys is an important issue because of their increasing applications in industries. In this document, the research and progress of a variety of welding techniques for joining dissimilar Mg alloys and Al alloys are reviewed from
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Welding of dissimilar magnesium alloys and aluminum alloys is an important issue because of their increasing applications in industries. In this document, the research and progress of a variety of welding techniques for joining dissimilar Mg alloys and Al alloys are reviewed from different perspectives. Welding of dissimilar Mg and Al is challenging due to the formation of brittle intermetallic compound (IMC) such as Mg17Al12 and Mg2Al3. In order to increase the joint strength, three main research approaches were used to eliminate or reduce the Mg-Al intermetallic reaction layer. First, solid state welding techniques which have a low welding temperature were used to reduce the IMCs. Second, IMC variety and distribution were controlled to avoid the degradation of the joining strength in fusion welding. Third, techniques which have relatively controllable reaction time and energy were used to eliminate the IMCs. Some important processing parameters and their effects on weld quality are discussed, and the microstructure and metallurgical reaction are described. Mechanical properties of welds such as hardness, tensile, shear and fatigue strength are discussed. The aim of the report is to review the recent progress in the welding of dissimilar Mg and Al to provide a basis for follow-up research. Full article
(This article belongs to the Special Issue Light Alloys and Their Applications)
Open AccessReview Porous Gold Films—A Short Review on Recent Progress
Materials 2014, 7(5), 3834-3854; doi:10.3390/ma7053834
Received: 25 March 2014 / Revised: 7 May 2014 / Accepted: 8 May 2014 / Published: 14 May 2014
Cited by 13 | PDF Full-text (856 KB) | HTML Full-text | XML Full-text
Abstract
Porous gold films have attracted increasing interest over the last ten years due to the unique properties of high specific surface area and electrical conductivity combined with chemical stability and ability to alter the surface chemistry. Several methods have been developed to synthesize
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Porous gold films have attracted increasing interest over the last ten years due to the unique properties of high specific surface area and electrical conductivity combined with chemical stability and ability to alter the surface chemistry. Several methods have been developed to synthesize porous gold films such as de-alloying, templating, electrochemical, and self-assembling. These porous gold films are used in diverse fields, for example, as electrochemical and Raman sensors or for chemical catalysis. Here, we provide a short review on the progress of porous gold films over the past ten years, including the synthesis and applications of such films. Full article
(This article belongs to the Special Issue Advances in Nanoporous Materials)
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Open AccessReview Functional Films from Silica/Polymer Nanoparticles
Materials 2014, 7(5), 3881-3900; doi:10.3390/ma7053881
Received: 11 April 2014 / Revised: 7 May 2014 / Accepted: 7 May 2014 / Published: 15 May 2014
Cited by 19 | PDF Full-text (1342 KB) | HTML Full-text | XML Full-text
Abstract
High performance functional coatings, based on hybrid organic/inorganic materials, are being developed to combine the polymer flexibility and ease of processing with the mechanical properties and versatility of inorganic materials. By incorporating silica nanoparticles (SiNPs) in the polymeric matrices, it is possible to
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High performance functional coatings, based on hybrid organic/inorganic materials, are being developed to combine the polymer flexibility and ease of processing with the mechanical properties and versatility of inorganic materials. By incorporating silica nanoparticles (SiNPs) in the polymeric matrices, it is possible to obtain hybrid polymer films with increased tensile strength and impact resistance, without decreasing the flexural properties of the polymer matrix. The SiNPs can further be used as carriers to impart other functionalities (optical, etc.) to the hybrid films. By using polymer-coated SiNPs, it is possible to reduce particle aggregation in the films and, thus, achieve more homogeneous distributions of the inorganic components and, therefore, better properties. On the other hand, by coating polymer particles with silica, one can create hierarchically structured materials, for example to obtain superhydrophobic coatings. In this review, we will cover the latest developments in films prepared from hybrid polymer/silica functional systems. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)
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Open AccessReview Carbon Nanofibers and Their Composites: A Review of Synthesizing, Properties and Applications
Materials 2014, 7(5), 3919-3945; doi:10.3390/ma7053919
Received: 28 March 2014 / Revised: 7 May 2014 / Accepted: 7 May 2014 / Published: 15 May 2014
Cited by 29 | PDF Full-text (1247 KB) | HTML Full-text | XML Full-text
Abstract
Carbon nanofiber (CNF), as one of the most important members of carbon fibers, has been investigated in both fundamental scientific research and practical applications. CNF composites are able to be applied as promising materials in many fields, such as electrical devices, electrode materials
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Carbon nanofiber (CNF), as one of the most important members of carbon fibers, has been investigated in both fundamental scientific research and practical applications. CNF composites are able to be applied as promising materials in many fields, such as electrical devices, electrode materials for batteries and supercapacitors and as sensors. In these applications, the electrical conductivity is always the first priority need to be considered. In fact, the electrical property of CNF composites largely counts on the dispersion and percolation status of CNFs in matrix materials. In this review, the electrical transport phenomenon of CNF composites is systematically summarized based on percolation theory. The effects of the aspect ratio, percolation backbone structure and fractal characteristics of CNFs and the non-universality of the percolation critical exponents on the electrical properties are systematically reviewed. Apart from the electrical property, the thermal conductivity and mechanical properties of CNF composites are briefly reviewed, as well. In addition, the preparation methods of CNFs, including catalytic chemical vapor deposition growth and electrospinning, and the preparation methods of CNF composites, including the melt mixing and solution process, are briefly introduced. Finally, their applications as sensors and electrode materials are described in this review article. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessReview Hybrid Materials Based on the Embedding of Organically Modified Transition Metal Oxoclusters or Polyoxometalates into Polymers for Functional Applications: A Review
Materials 2014, 7(5), 3956-3989; doi:10.3390/ma7053956
Received: 12 February 2014 / Revised: 22 April 2014 / Accepted: 25 April 2014 / Published: 20 May 2014
Cited by 27 | PDF Full-text (885 KB) | HTML Full-text | XML Full-text
Abstract
The covalent incorporation of inorganic building blocks into a polymer matrix to obtain stable and robust materials is a widely used concept in the field of organic-inorganic hybrid materials, and encompasses the use of different inorganic systems including (but not limited to) nanoparticles,
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The covalent incorporation of inorganic building blocks into a polymer matrix to obtain stable and robust materials is a widely used concept in the field of organic-inorganic hybrid materials, and encompasses the use of different inorganic systems including (but not limited to) nanoparticles, mono- and polynuclear metal complexes and clusters, polyhedral oligomeric silsesquioxanes (POSS), polyoxometalates (POM), layered inorganic systems, inorganic fibers, and whiskers. In this paper, we will review the use of two particular kinds of structurally well-defined inorganic building blocks, namely transition metals oxoclusters (TMO) and polyoxometalates (POM), to obtain hybrid materials with enhanced functional (e.g., optical, dielectric, magnetic, catalytic) properties. Full article
(This article belongs to the Special Issue Advances in Functional Hybrid Materials)
Open AccessReview Synthetic Strategies in the Preparation of Polymer/Inorganic Hybrid Nanoparticles
Materials 2014, 7(5), 4057-4087; doi:10.3390/ma7054057
Received: 24 February 2014 / Revised: 12 April 2014 / Accepted: 9 May 2014 / Published: 22 May 2014
Cited by 27 | PDF Full-text (1422 KB) | HTML Full-text | XML Full-text | Correction
Abstract
This article reviews the recent advances and challenges in the preparation of polymer/inorganic hybrid nanoparticles. We mainly focus on synthetic strategies, basing our classification on whether the inorganic and the polymer components have been formed in situ or ex situ, of the
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This article reviews the recent advances and challenges in the preparation of polymer/inorganic hybrid nanoparticles. We mainly focus on synthetic strategies, basing our classification on whether the inorganic and the polymer components have been formed in situ or ex situ, of the hybrid material. Accordingly, four types of strategies are identified and described, referring to recent examples: (i) ex situ formation of the components and subsequent attachment or integration, either by covalent or noncovalent bonding; (ii) in situ polymerization in the presence of ex situ formed inorganic nanoparticles; (iii) in situ precipitation of the inorganic components on or in polymer structures; and (iv) strategies in which both polymer and inorganic component are simultaneously formed in situ. Full article
(This article belongs to the Special Issue Advances in Functional Hybrid Materials)

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