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Materials, Volume 6, Issue 9 (September 2013), Pages 3676-4283

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Open AccessArticle Impact of Groundwater Salinity on Bioremediation Enhanced by Micro-Nano Bubbles
Materials 2013, 6(9), 3676-3687; doi:10.3390/ma6093676
Received: 14 June 2013 / Revised: 16 August 2013 / Accepted: 16 August 2013 / Published: 23 August 2013
Cited by 8 | PDF Full-text (420 KB) | HTML Full-text | XML Full-text
Abstract
Micro-nano bubbles (MNBs) technology has shown great potential in groundwater bioremediation because of their large specific surface area, negatively charged surface, long stagnation, high oxygen transfer efficiency, etc. Groundwater salinity, which varies from sites due to different geological and environmental conditions, has
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Micro-nano bubbles (MNBs) technology has shown great potential in groundwater bioremediation because of their large specific surface area, negatively charged surface, long stagnation, high oxygen transfer efficiency, etc. Groundwater salinity, which varies from sites due to different geological and environmental conditions, has a strong impact on the bioremediation effect. However, the groundwater salinity effect on MNBs’ behavior has not been reported. In this study, the size distribution, oxygen transfer efficiency and zeta potential of MNBs was investigated in different salt concentrations. In addition, the permeability of MNBs’ water through sand in different salt concentrations was studied. The results showed that water salinity has no influence on bubble size distribution during MNBs generation. MNBs could greatly enhance the oxygen transfer efficiency from inner bubbles to outer water, which may greatly enhance aerobic bioremediation. However, the enhancement varied depending on salt concentration. 0.7 g/L was found to be the optimal salt concentration to transfer oxygen. Moreover, MNBs in water salinity of 0.7 g/L had the minimum zeta potential. The correlation of zeta potential and mass transfer was discussed. The hydraulic conductivities of sand were similar for MNBs water with different salt concentrations. The results suggested that salinity had a great influence on MNBs performance, and groundwater salinity should be taken into careful consideration in applying MNBs technology to the enhancement of bioremediation. Full article
Open AccessArticle The Mechanism of Pseudomorphic Transformation of Spherical Silica Gel into MCM-41 Studied by PFG NMR Diffusometry
Materials 2013, 6(9), 3688-3709; doi:10.3390/ma6093688
Received: 1 July 2013 / Revised: 16 August 2013 / Accepted: 19 August 2013 / Published: 26 August 2013
Cited by 7 | PDF Full-text (860 KB) | HTML Full-text | XML Full-text
Abstract
The pseudomorphic transformation of spherical silica gel (LiChrospher® Si 60) into MCM-41 was achieved by treatment at 383 K for 24 h with an aqueous solution of cetyltrimethylammonium hydroxide (CTAOH) instead of hexadecyltrimethylammonium bromide (CTABr) and NaOH. The degree of transformation was
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The pseudomorphic transformation of spherical silica gel (LiChrospher® Si 60) into MCM-41 was achieved by treatment at 383 K for 24 h with an aqueous solution of cetyltrimethylammonium hydroxide (CTAOH) instead of hexadecyltrimethylammonium bromide (CTABr) and NaOH. The degree of transformation was varied via the ratio of CTAOH solution to initial silica gel rather than synthesis duration. The transformed samples were characterized by N2 sorption at 77 K, mercury intrusion porosimetry, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Thus, MCM-41 spheres with diameters of ca. 12 μm, surface areas >1000 m2 g−1, pore volumes >1 cm3 g1 and a sharp pore width distribution, adjustable between 3.2 and 4.5 nm, were obtained. A thorough pulsed field gradient nuclear magnetic resonance (PFG NMR) study shows that the diffusivity of n-heptane confined in the pores of the solids passes through a minimum with progressing transformation. The final product of pseudomorphic transformation to MCM-41 does not exhibit improved transport properties compared to the initial silica gel. Moreover, the PFG NMR results support that the transformation occurs via formation and subsequent growth of domains of <1 μm containing MCM-41 homogeneously distributed over the volume of the silica spheres. Full article
(This article belongs to the Special Issue Diffusion in Micropores and Mesopores 2013)
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Open AccessArticle Single Layer Broadband Anti-Reflective Coatings for Plastic Substrates Produced by Full Wafer and Roll-to-Roll Step-and-Flash Nano-Imprint Lithography
Materials 2013, 6(9), 3710-3726; doi:10.3390/ma6093710
Received: 5 July 2013 / Revised: 14 August 2013 / Accepted: 19 August 2013 / Published: 27 August 2013
Cited by 12 | PDF Full-text (804 KB) | HTML Full-text | XML Full-text
Abstract
Anti-reflective coatings (ARCs) are used to lower the reflection of light on the surface of a substrate. Here, we demonstrate that the two main drawbacks of moth eye-structured ARCs—i.e., the lack of suitable coating materials and a process for large area,
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Anti-reflective coatings (ARCs) are used to lower the reflection of light on the surface of a substrate. Here, we demonstrate that the two main drawbacks of moth eye-structured ARCs—i.e., the lack of suitable coating materials and a process for large area, high volume applications—can be largely eliminated, paving the way for cost-efficient and large-scale production of durable moth eye-structured ARCs on polymer substrates. We prepared moth eye coatings on polymethylmethacrylate (PMMA) and polycarbonate using wafer-by-wafer step-and-flash nano-imprint lithography (NIL). The reduction in reflection in the visible field achieved with these coatings was 3.5% and 4.0%, respectively. The adhesion of the coating to both substrates was good. The moth eye coating on PMMA demonstrated good performance in three prototypical accelerated ageing tests. The pencil hardness of the moth eye coatings on both substrates was <4B, which is less than required for most applications and needs further optimization. Additionally, we developed a roll-to-roll UV NIL pilot scale process and produced moth eye coatings on polyethylene terephthalate (PET) at line speeds up to two meters per minute. The resulting coatings showed a good replication of the moth eye structures and, consequently, a lowering in reflection of the coated PET of 3.0%. Full article
Open AccessArticle Synthesis and Characterization of Encapsulated Nanosilica Particles with an Acrylic Copolymer by in Situ Emulsion Polymerization Using Thermoresponsive Nonionic Surfactant
Materials 2013, 6(9), 3727-3741; doi:10.3390/ma6093727
Received: 25 April 2013 / Revised: 27 May 2013 / Accepted: 6 August 2013 / Published: 28 August 2013
Cited by 14 | PDF Full-text (637 KB) | HTML Full-text | XML Full-text
Abstract
Nanocomposites of encapsulated silica nanoparticles were prepared by in situ emulsion polymerization of acrylate monomers. The synthesized material showed good uniformity and dispersion of the inorganic components in the base polymer, which enhances the properties of the nanocomposite material. A nonionic surfactant with
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Nanocomposites of encapsulated silica nanoparticles were prepared by in situ emulsion polymerization of acrylate monomers. The synthesized material showed good uniformity and dispersion of the inorganic components in the base polymer, which enhances the properties of the nanocomposite material. A nonionic surfactant with lower critical solution temperature (LCST) was used to encapsulate the silica nanoparticles in the acrylic copolymer matrix. This in situ method combined the surface modification and the encapsulation in a single pot, which greatly simplified the process compared with other conventional methods requiring separate processing steps. The morphology of the encapsulated nanosilica particles was investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM), which confirmed the uniform distribution of the nanoparticles without any agglomerations. A neat copolymer was also prepared as a control sample. Both the neat copolymer and the prepared nanocomposite were characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analyses (TGA), dynamic mechanical thermal analysis (DMTA) and the flame resistance test. Due to the uniform dispersion of the non-agglomerated nanoparticles in the matrix of the polymer, TGA and flame resistance test results showed remarkably improved thermal stability. Furthermore, DMTA results demonstrated an enhanced storage modulus of the nanocomposite samples compared with that of the neat copolymer, indicating its superior mechanical properties. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Construction of a Novel Magnetic Targeting Anti-Tumor Drug Delivery System: Cytosine Arabinoside-Loaded Bacterial Magnetosome
Materials 2013, 6(9), 3755-3763; doi:10.3390/ma6093755
Received: 7 June 2013 / Revised: 29 July 2013 / Accepted: 30 August 2013 / Published: 3 September 2013
Cited by 6 | PDF Full-text (389 KB) | HTML Full-text | XML Full-text
Abstract
To ease the side effects triggered by cytosine arabinoside (Ara-C) for acute leukemia treatment, a novel magnetic targeting anti-tumor drug delivery system was constructed through bacterial magnetosomes (BMs) from Magnetospirillum magneticum AMB-1 combined with Ara-C by crosslinking of genipin (GP). The results showed
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To ease the side effects triggered by cytosine arabinoside (Ara-C) for acute leukemia treatment, a novel magnetic targeting anti-tumor drug delivery system was constructed through bacterial magnetosomes (BMs) from Magnetospirillum magneticum AMB-1 combined with Ara-C by crosslinking of genipin (GP). The results showed that Ara-C could be bonded onto the membrane surface of BMs effectively through chemical crosslinking induced by dual hand reagents GP. The average diameters of BMs and Ara-C-coupled BMs (ABMs) were 42.0 ± 8.6 and 72.7 ± 6.0 nm respectively, and the zeta potentials (−38.1 ± 9.1) revealed that these systems were stable, confirming the stability of the system. The optimal encapsulation efficiency and drug loading were 89.05% ± 2.33% and 47.05% ± 0.64% respectively when crosslinking reaction lasted for 72 h. The system also presented long-term stability and release behaviors without initial burst release (Ara-C could be released 80% within three months). Our results indicate that BMs have great potential in biomedical and clinical fields as a novel anti-tumor drug carrier. Full article
(This article belongs to the Section Biomaterials)
Open AccessArticle Homogenized Elastic Properties of Graphene for Small Deformations
Materials 2013, 6(9), 3764-3782; doi:10.3390/ma6093764
Received: 8 July 2013 / Revised: 26 August 2013 / Accepted: 27 August 2013 / Published: 3 September 2013
Cited by 4 | PDF Full-text (1704 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we provide the quantification of the linear and non-linear elastic mechanical properties of graphene based upon the judicious combination of molecular mechanics simulation results and homogenization methods. We clarify the influence on computed results by the main model features, such
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In this paper, we provide the quantification of the linear and non-linear elastic mechanical properties of graphene based upon the judicious combination of molecular mechanics simulation results and homogenization methods. We clarify the influence on computed results by the main model features, such as specimen size, chirality of microstructure, the effect of chosen boundary conditions (imposed displacement versus force) and the corresponding plane stress transformation. The proposed approach is capable of explaining the scatter of the results for computed stresses, energy and stiffness and provides the bounds on graphene elastic properties, which are quite important in modeling and simulation of the virtual experiments on graphene-based devices. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Materials Study)
Open AccessArticle Microgel Modified UV-Cured Methacrylic-Silica Hybrid: Synthesis and Characterization
Materials 2013, 6(9), 3805-3825; doi:10.3390/ma6093805
Received: 10 July 2013 / Revised: 1 August 2013 / Accepted: 4 August 2013 / Published: 6 September 2013
Cited by 10 | PDF Full-text (837 KB) | HTML Full-text | XML Full-text
Abstract
An innovative photopolymerizable microgel modified UV-cured acrylic-silica hybrid formulation was developed and characterized for possible use as protective coating for different substrates. A deep investigation, aiming at providing a strong scientific basis for the production of organic-inorganic (O-I) hybrids exhibiting phase co-continuity, was
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An innovative photopolymerizable microgel modified UV-cured acrylic-silica hybrid formulation was developed and characterized for possible use as protective coating for different substrates. A deep investigation, aiming at providing a strong scientific basis for the production of organic-inorganic (O-I) hybrids exhibiting phase co-continuity, was firstly carried out. The O-I hybrid first proposed in this study was obtained from organic precursors with a high siloxane content, which are mixed with tetraethoxysilane (TEOS) in such a way to produce co-continuous silica nanodomains dispersed within the crosslinked organic phase, as a result of the sol-gel process. The first part of the research deals with the selection and optimization of suitable systems through appropriate chemical modifications, in order to ensure that curing reactions can be carried out at room temperature and in the presence of UV radiation. Firstly, the silica domains are formed, followed by crosslinking reactions of the acrylic groups in the oligomer via a free radical polymerization. The crosslinking reaction was controlled with the use of a suitable photoinitiator. Most of the experimental work was devoted to understanding the morphology of the hybrid system, both in uncured and cured states, and to assess its final thermal and optical properties, using different experiential techniques. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)
Open AccessArticle Dopamine-Mediated Sclerotization of Regenerated Chitin in Ionic Liquid
Materials 2013, 6(9), 3826-3839; doi:10.3390/ma6093826
Received: 30 July 2013 / Revised: 30 August 2013 / Accepted: 2 September 2013 / Published: 6 September 2013
Cited by 6 | PDF Full-text (1576 KB) | HTML Full-text | XML Full-text
Abstract
Chitin is a promising structural material for biomedical applications, due to its many advantageous properties and abundance in nature. However, its usage and development in the biomedical field have been stagnant, because of chitin’s poor mechanical properties in wet conditions and the difficulties
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Chitin is a promising structural material for biomedical applications, due to its many advantageous properties and abundance in nature. However, its usage and development in the biomedical field have been stagnant, because of chitin’s poor mechanical properties in wet conditions and the difficulties in transforming it into an applicable form. To overcome these challenges, we created a novel biomimetic chitin composite. This regenerated chitin, prepared with ionic liquid, showed improved mechanical properties in wet conditions by mimicking insect cuticle and squid beak sclerotization, i.e., catechol-meditated cross-linking. By ionic liquid-based heat treatment, dopamine oxidation produced melanin-like compounds and dopamine-meditated cross-links without any solvent evaporation and oxidant utilization. The dopamine-meditated sclerotization increased the ultimate tensile strength (UTS) of the regenerated chitin by 2.52-fold, measured after six weeks of phosphate-buffered saline (PBS) submersion. In addition, the linear swelling ratio (LSR) of the chitin film was reduced by about 22%. This strategy raises a possibility of using regenerated chitin as an artificial hard tissue in wet conditions. Full article
(This article belongs to the Section Biomaterials)
Open AccessArticle Synthesis and Characterization of Novel Epoxy Geopolymer Hybrid Composites
Materials 2013, 6(9), 3943-3962; doi:10.3390/ma6093943
Received: 9 June 2013 / Revised: 1 August 2013 / Accepted: 2 September 2013 / Published: 9 September 2013
Cited by 14 | PDF Full-text (989 KB) | HTML Full-text | XML Full-text
Abstract
The preparation and the characterization of novel geopolymer-based hybrid composites are reported. These materials have been prepared through an innovative synthetic approach, based on a co-reticulation in mild conditions of commercial epoxy based organic resins and a metakaolin-based geopolymer inorganic matrix. This synthetic
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The preparation and the characterization of novel geopolymer-based hybrid composites are reported. These materials have been prepared through an innovative synthetic approach, based on a co-reticulation in mild conditions of commercial epoxy based organic resins and a metakaolin-based geopolymer inorganic matrix. This synthetic strategy allows the obtainment of a homogeneous dispersion of the organic particles in the inorganic matrix, up to 25% in weight of the resin. The materials obtained present significantly enhanced compressive strengths and toughness with respect to the neat geopolymer, suggesting their wide utilization for structural applications. A preliminary characterization of the porous materials obtained by removing the organic phase from the hybrid composites by means of heat treatments is also reported. Possible applications of these materials in the field of water purification, filtration, or as lightweight insulating materials are envisaged. Full article
Open AccessArticle Microstructural and Wear Behavior Characterization of Porous Layers Produced by Pulsed Laser Irradiation in Glass-Ceramics Substrates
Materials 2013, 6(9), 3963-3977; doi:10.3390/ma6093963
Received: 1 July 2013 / Revised: 21 August 2013 / Accepted: 4 September 2013 / Published: 9 September 2013
Cited by 3 | PDF Full-text (683 KB) | HTML Full-text | XML Full-text
Abstract
In this work, wear behavior and microstructural characterization of porous layers produced in glass-ceramic substrates by pulsed laser irradiation in the nanosecond range are studied under unidirectional sliding conditions against AISI316 and corundum counterbodies. Depending on the optical configuration of the laser beam
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In this work, wear behavior and microstructural characterization of porous layers produced in glass-ceramic substrates by pulsed laser irradiation in the nanosecond range are studied under unidirectional sliding conditions against AISI316 and corundum counterbodies. Depending on the optical configuration of the laser beam and on the working parameters, the local temperature and pressure applied over the interaction zone can generate a porous glass-ceramic layer. Material transference from the ball to the porous glass-ceramic layer was observed in the wear tests carried out against the AISI316 ball counterface whereas, in the case of the corundum ball, the wear volume loss was concentrated in the porous layer. Wear rate and friction coefficient presented higher values than expected for dense glass-ceramics. Full article
(This article belongs to the Special Issue Advances in Surface Coatings 2013)
Open AccessArticle Constitutive Behavior and Finite Element Analysis of FRP Composite and Concrete Members
Materials 2013, 6(9), 3978-3988; doi:10.3390/ma6093978
Received: 23 July 2013 / Revised: 19 August 2013 / Accepted: 3 September 2013 / Published: 10 September 2013
Cited by 2 | PDF Full-text (542 KB) | HTML Full-text | XML Full-text
Abstract
The present study concerns compressive and flexural constitutive models incorporated into an isoparametric beam finite element scheme for fiber reinforced polymer (FRP) and concrete composites, using their multi-axial constitutive behavior. The constitutive behavior of concrete was treated in triaxial stress states as an
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The present study concerns compressive and flexural constitutive models incorporated into an isoparametric beam finite element scheme for fiber reinforced polymer (FRP) and concrete composites, using their multi-axial constitutive behavior. The constitutive behavior of concrete was treated in triaxial stress states as an orthotropic hypoelasticity-based formulation to determine the confinement effect of concrete from a three-dimensional failure surface in triaxial stress states. The constitutive behavior of the FRP composite was formulated from the two-dimensional classical lamination theory. To predict the flexural behavior of circular cross-section with FRP sheet and concrete composite, a layered discretization of cross-sections was incorporated into nonlinear isoparametric beam finite elements. The predicted constitutive behavior was validated by a comparison to available experimental results in the compressive and flexural beam loading test. Full article
(This article belongs to the Special Issue Constitutive Behavior of Composite Materials)
Open AccessArticle Effect of Nanopore Length on the Translocation Process of a Biopolymer: Numerical Study
Materials 2013, 6(9), 3989-4000; doi:10.3390/ma6093989
Received: 30 May 2013 / Revised: 25 July 2013 / Accepted: 29 August 2013 / Published: 11 September 2013
Cited by 2 | PDF Full-text (572 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this study, we simulate the electrophoretic motion of a bio-polymer through a synthetic nanopore in the presence of an external bias voltage by considering the hydrodynamic interactions between the polymer and the fluid explicitly. The motion of the polymer is simulated by
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In this study, we simulate the electrophoretic motion of a bio-polymer through a synthetic nanopore in the presence of an external bias voltage by considering the hydrodynamic interactions between the polymer and the fluid explicitly. The motion of the polymer is simulated by 3D Langevin dynamics technique by modeling the polymer as a worm-like-chain, while the hydrodynamic interactions are incorporated by the lattice Boltzmann equation. We report the simulation results for three different lengths of the nanopore. The translocation time increases with the pore length even though the electrophoretic force on the polymer is the same irrespective of the pore length. This is attributed to the fact that the translocation velocity of each bead inside the nanopore decreases with the pore length due to the increased fluid resistance force caused by the increase in the straightened portion of the polymer. We confirmed this using a theoretical formula. Full article
Open AccessArticle New Coating Technique of Ceramic Implants with Different Glass Solder Matrices for Improved Osseointegration-Mechanical Investigations
Materials 2013, 6(9), 4001-4010; doi:10.3390/ma6094001
Received: 9 July 2013 / Revised: 28 August 2013 / Accepted: 4 September 2013 / Published: 11 September 2013
Cited by 3 | PDF Full-text (297 KB) | HTML Full-text | XML Full-text
Abstract
Ceramics are a very popular material in dental implant technology due to their tribological properties, their biocompatibility and their esthetic appearance. However, their natural surface structure lacks the ability of proper osseointegration, which constitutes a crucial process for the stability and, thus, the
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Ceramics are a very popular material in dental implant technology due to their tribological properties, their biocompatibility and their esthetic appearance. However, their natural surface structure lacks the ability of proper osseointegration, which constitutes a crucial process for the stability and, thus, the functionality of a bone implant. We investigated the application of a glass solder matrix in three configurations—consisting mainly of SiO2, Al2O3, K2O and Na2O to TZP-A ceramic specimens. The corresponding adhesive strength and surface roughness of the coatings on ceramic specimens have been analyzed. Thereby, high adhesive strength (70.3 ± 7.9 MPa) was found for the three different coatings. The obtained roughness (Rz) amounted to 18.24 ± 2.48 µm in average, with significant differences between the glass solder configurations. Furthermore, one configuration was also tested after additional etching which did not lead to significant increase of surface roughness (19.37 ± 1.04 µm) or adhesive strength (57.2 ± 5.8 MPa). In conclusion, coating with glass solder matrix seems to be a promising surface modification technique that may enable direct insertion of ceramic implants in dental and orthopaedic surgery. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
Open AccessArticle Observations of Ball-Lightning-Like Plasmoids Ejected from Silicon by Localized Microwaves
Materials 2013, 6(9), 4011-4030; doi:10.3390/ma6094011
Received: 1 August 2013 / Revised: 2 September 2013 / Accepted: 3 September 2013 / Published: 11 September 2013
Cited by 9 | PDF Full-text (3442 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents experimental characterization of plasmoids (fireballs) obtained by directing localized microwave power (<1 kW at 2.45 GHz) onto a silicon-based substrate in a microwave cavity. The plasmoid emerges up from the hotspot created in the solid substrate into the air within
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This paper presents experimental characterization of plasmoids (fireballs) obtained by directing localized microwave power (<1 kW at 2.45 GHz) onto a silicon-based substrate in a microwave cavity. The plasmoid emerges up from the hotspot created in the solid substrate into the air within the microwave cavity. The experimental diagnostics employed for the fireball characterization in this study include measurements of microwave scattering, optical spectroscopy, small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Various characteristics of these plasmoids as dusty plasma are drawn by a theoretical analysis of the experimental observations. Aggregations of dust particles within the plasmoid are detected at nanometer and micrometer scales by both in-situ SAXS and ex-situ SEM measurements. The resemblance of these plasmoids to the natural ball-lightning (BL) phenomenon is discussed with regard to silicon nano-particle clustering and formation of slowly-oxidized silicon micro-spheres within the BL. Potential applications and practical derivatives of this study (e.g., direct conversion of solids to powders, material identification by breakdown spectroscopy (MIBS), thermite ignition, and combustion) are discussed. Full article
(This article belongs to the Special Issue Microwave Processing of Materials)
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Open AccessArticle Thermally Activated Composite with Two-Way and Multi-Shape Memory Effects
Materials 2013, 6(9), 4031-4045; doi:10.3390/ma6094031
Received: 11 July 2013 / Revised: 1 August 2013 / Accepted: 2 September 2013 / Published: 12 September 2013
Cited by 5 | PDF Full-text (755 KB) | HTML Full-text | XML Full-text
Abstract
The use of shape memory polymer composites is growing rapidly in smart structure applications. In this work, an active asymmetric composite called “controlled behavior composite material (CBCM)” is used as shape memory polymer composite. The programming and the corresponding initial fixity of the
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The use of shape memory polymer composites is growing rapidly in smart structure applications. In this work, an active asymmetric composite called “controlled behavior composite material (CBCM)” is used as shape memory polymer composite. The programming and the corresponding initial fixity of the composite structure is obtained during a bending test, by heating CBCM above thermal glass transition temperature of the used Epoxy polymer. The shape memory properties of these composites are investigated by a bending test. Three types of recoveries are conducted, two classical recovery tests: unconstrained recovery and constrained recovery, and a new test of partial recovery under load. During recovery, high recovery displacement and force are produced that enables the composite to perform strong two-way actuations along with multi-shape memory effect. The recovery force confirms full recovery with two-way actuation even under a high load. This unique property of CBCM is characterized by the recovered mechanical work. Full article
(This article belongs to the Special Issue Smart Polymers and Polymeric Structures)
Open AccessArticle Experimental Study on Cementitious Composites Embedded with Organic Microcapsules
Materials 2013, 6(9), 4064-4081; doi:10.3390/ma6094064
Received: 12 July 2013 / Revised: 20 August 2013 / Accepted: 9 September 2013 / Published: 16 September 2013
Cited by 10 | PDF Full-text (971 KB) | HTML Full-text | XML Full-text
Abstract
The recovery behavior for strength and impermeability of cementitious composites embedded with organic microcapsules was investigated in this study. Mortar specimens were formed by mixing the organic microcapsules and a catalyst with cement and sand. The mechanical behaviors of flexural and compression strength
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The recovery behavior for strength and impermeability of cementitious composites embedded with organic microcapsules was investigated in this study. Mortar specimens were formed by mixing the organic microcapsules and a catalyst with cement and sand. The mechanical behaviors of flexural and compression strength were tested. The results showed that strength could increase by up to nine percent with the addition of a small amount of microcapsules and then decrease with an increasing amount of microcapsules. An orthogonal test for investigating the strength recovery rate was designed and implemented for bending and compression using the factors of water/cement ratio, amount of microcapsules, and preloading rate. It is shown that the amount of microcapsules plays a key role in the strength recovery rate. Chloride ion permeability tests were also carried out to investigate the recovery rate and healing effect. The initial damage was obtained by subjecting the specimens to compression. Both the recovery rate and the healing effect were nearly proportional to the amount of microcapsules. The obtained cementitious composites can be seen as self-healing owing to their recovery behavior for both strength and permeability. Full article
(This article belongs to the Special Issue Self-healing Concrete)
Open AccessArticle Aqueous ZrO2 and YSZ Colloidal Systems through Microwave Assisted Hydrothermal Synthesis
Materials 2013, 6(9), 4082-4095; doi:10.3390/ma6094082
Received: 9 July 2013 / Revised: 4 September 2013 / Accepted: 10 September 2013 / Published: 16 September 2013
Cited by 4 | PDF Full-text (697 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the formation of ZrO2 and yttria-stabilised-zirconia (YSZ) aqueous colloidal systems via microwave assisted hydrothermal synthesis is studied. Microwave synthesis allows a fast screening of the influence of different parameters such as time and temperature. The temperature varied from 140
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In this paper, the formation of ZrO2 and yttria-stabilised-zirconia (YSZ) aqueous colloidal systems via microwave assisted hydrothermal synthesis is studied. Microwave synthesis allows a fast screening of the influence of different parameters such as time and temperature. The temperature varied from 140 °C up to 180 °C and the used reaction time varied from 5 min up to 1 h. The synthesised zirconia nanoparticles have a particle size of 50 nm confirmed by TEM. A 1H NMR (nuclear magnetic resonance) study helped to understand the stabilization mechanism of the synthesised particles. By the addition of ytrrium ions into the zirconia colloidal solution, YSZ could be formed via an additional thermal treatment. Hereby, the samples are heated up to 400 °C for 1 h. YSZ colloidal solutions are synthesised by making use of complexing agents such as nitrilotriacetic acid, ethylenediaminetetraacetic acid and citric acid to control the hydrolysis and condensation of both ions to avoid non-stoichiometric phases. The ratio of Zr/Y in the particles is quantified by XRF. The amorphous structure of those particles necessitates an additional thermal treatment up to 600 °C during 1 h in order to obtain crystalline YSZ. Full article
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Open AccessArticle Complete Permittivity Tensor in Sputtered CuFe2O4 Thin Films at Photon Energies between 2 and 5 eV
Materials 2013, 6(9), 4096-4108; doi:10.3390/ma6094096
Received: 26 July 2013 / Revised: 19 August 2013 / Accepted: 26 August 2013 / Published: 16 September 2013
Cited by 4 | PDF Full-text (415 KB) | HTML Full-text | XML Full-text
Abstract
This work is devoted to the systematic study of the optical and magneto-optical properties of sputter deposited CuFe2O4 thin films in the photon energy region between 2 and 5 eV using spectroscopic ellipsometry and magneto-optical Kerr spectroscopy. The spectral dependence
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This work is devoted to the systematic study of the optical and magneto-optical properties of sputter deposited CuFe2O4 thin films in the photon energy region between 2 and 5 eV using spectroscopic ellipsometry and magneto-optical Kerr spectroscopy. The spectral dependence of both the diagonal and off-diagonal elements of the permittivity tensor is determined. A complete picture about the electron transitions in CuFe2O4 is suggested in the frame of intervalence charge transfer and intersublattice charge transfer transitions. The effect of deposition conditions and post-deposition treatment in CuFe2O4 films upon the optical and magneto-optical properties is discussed. Full article
Open AccessArticle The Tension and Puncture Properties of HDPE Geomembrane under the Corrosion of Leachate
Materials 2013, 6(9), 4109-4121; doi:10.3390/ma6094109
Received: 29 July 2013 / Revised: 28 August 2013 / Accepted: 10 September 2013 / Published: 17 September 2013
PDF Full-text (2214 KB) | HTML Full-text | XML Full-text
Abstract
To investigate the gradual failure of high-density polyethylene (HDPE) geomembrane as a result of long-term corrosion, four dynamic corrosion tests were conducted at different temperatures and durations. By combining tension and puncture tests, we systematically studied the variation law of tension and puncture
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To investigate the gradual failure of high-density polyethylene (HDPE) geomembrane as a result of long-term corrosion, four dynamic corrosion tests were conducted at different temperatures and durations. By combining tension and puncture tests, we systematically studied the variation law of tension and puncture properties of the HDPE geomembrane under different corrosion conditions. Results showed that tension and puncture failure of the HDPE geomembrane was progressive, and tensile strength in the longitudinal grain direction was evidently better than that in the transverse direction. Punctures appeared shortly after puncture force reached the puncture strength. The tensile strength of geomembrane was in inversely proportional to the corrosion time, and the impact of corrosion was more obvious in the longitudinal direction than transverse direction. As corrosion time increased, puncture strength decreased and corresponding deformation increased. As with corrosion time, the increase of corrosion temperature induced the decrease of geomembrane tensile strength. Tensile and puncture strength were extremely sensitive to temperature. Overall, residual strength had a negative correlation with corrosion time or temperature. Elongation variation increased initially and then decreased with the increase in temperature. However, it did not show significant law with corrosion time. The reduction in puncture strength and the increase in puncture deformation had positive correlations with corrosion time or temperature. The geomembrane softened under corrosion condition. The conclusion may be applicable to the proper designing of the HDPE geomembrane in landfill barrier system. Full article
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Open AccessArticle High Density Polyethylene Composites Reinforced with Hybrid Inorganic Fillers: Morphology, Mechanical and Thermal Expansion Performance
Materials 2013, 6(9), 4122-4138; doi:10.3390/ma6094122
Received: 26 May 2013 / Revised: 5 September 2013 / Accepted: 9 September 2013 / Published: 17 September 2013
Cited by 14 | PDF Full-text (1069 KB) | HTML Full-text | XML Full-text
Abstract
The effect of individual and combined talc and glass fibers (GFs) on mechanical and thermal expansion performance of the filled high density polyethylene (HDPE) composites was studied. Several published models were adapted to fit the measured tensile modulus and strength of various composite
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The effect of individual and combined talc and glass fibers (GFs) on mechanical and thermal expansion performance of the filled high density polyethylene (HDPE) composites was studied. Several published models were adapted to fit the measured tensile modulus and strength of various composite systems. It was shown that the use of silane-modified GFs had a much larger effect in improving mechanical properties and in reducing linear coefficient of thermal expansion (LCTE) values of filled composites, compared with the use of un-modified talc particles due to enhanced bonding to the matrix, larger aspect ratio, and fiber alignment for GFs. Mechanical properties and LCTE values of composites with combined talc and GF fillers varied with talc and GF ratio at a given total filler loading level. The use of a larger portion of GFs in the mix can lead to better composite performance, while the use of talc can help lower the composite costs and increase its recyclability. The use of 30 wt % combined filler seems necessary to control LCTE values of filled HDPE in the data value range generally reported for commercial wood plastic composites. Tensile modulus for talc-filled composite can be predicted with rule of mixture, while a PPA-based model can be used to predict the modulus and strength of GF-filled composites. Full article
(This article belongs to the Special Issue Constitutive Behavior of Composite Materials)
Open AccessArticle Th(IV) Adsorption onto Oxidized Multi-Walled Carbon Nanotubes in the Presence of Hydroxylated Fullerene and Carboxylated Fullerene
Materials 2013, 6(9), 4168-4185; doi:10.3390/ma6094168
Received: 15 June 2013 / Revised: 18 August 2013 / Accepted: 22 August 2013 / Published: 17 September 2013
Cited by 5 | PDF Full-text (808 KB) | HTML Full-text | XML Full-text
Abstract
The adsorption of Th(IV) onto the surface of oxidized multi-walled carbon nanotubes (oMWCNTs) in the absence and presence of hydroxylated fullerene (C60(OH)n) and carboxylated fullerene (C60(C(COOH)2)n) has been investigated. C60(OH)n
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The adsorption of Th(IV) onto the surface of oxidized multi-walled carbon nanotubes (oMWCNTs) in the absence and presence of hydroxylated fullerene (C60(OH)n) and carboxylated fullerene (C60(C(COOH)2)n) has been investigated. C60(OH)n, C60(C(COOH)2)n and oMWCNTs have been chosen as model phases because of their representative in carbon nano-materials family. Adsorption experiments were performed by batch procedure as a function of contact time, pH, ionic strength, and temperature. The results demonstrated that the adsorption of Th(IV) was rapidly reached equilibrium and the kinetic process could be described by a pseudo-second-order rate model very well. Th(IV) adsorption on oMWCNTs was dependent on pH but independent on ionic strength. Adsorption isotherms were correlated better with the Langmuir model than with the Freundlich model. The thermodynamic parameters calculated from temperature-dependent adsorption isotherms suggested that Th(IV) adsorption on oMWCNTs was spontaneous and endothermic. Compared with the adsorption of Th(IV) on the same oMWCNTs free of C60(OH)n or C60(C(COOH)2)n, the study of a ternary system showed the inhibition effect of C60(OH)n at high concentration on the adsorption of Th(IV) in a pH range from neutral to slightly alkaline; whereas the promotion effect of C60(C(COOH)2)n, even at its low concentration, on Th(IV) adsorption was observed in acid medium. Full article
(This article belongs to the Special Issue Carbon Nanotubes)
Open AccessArticle Effect of Thermal Treatment on Fracture Properties and Adsorption Properties of Spruce Wood
Materials 2013, 6(9), 4186-4197; doi:10.3390/ma6094186
Received: 8 July 2013 / Revised: 2 September 2013 / Accepted: 16 September 2013 / Published: 18 September 2013
Cited by 4 | PDF Full-text (906 KB) | HTML Full-text | XML Full-text
Abstract
The effect of thermal treatment on spruce is examined by analyzing the fracture and hygroscopic properties. Specimens were heated at temperatures within the range 120–200 °C for 1 h. Fracture energy was measured using a single-edge notched bending test and the strain-softening index
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The effect of thermal treatment on spruce is examined by analyzing the fracture and hygroscopic properties. Specimens were heated at temperatures within the range 120–200 °C for 1 h. Fracture energy was measured using a single-edge notched bending test and the strain-softening index was estimated by dividing the fracture energy by the maximum load. Adsorption properties were estimated using adsorption isotherms. Fiber saturation points (FSPs) were estimated by extrapolating the moisture adsorption isotherm curve. Langmuir’s adsorption coefficient and number of adsorption sites were obtained using Langmuir’s theory and the Hailwood-Horrobin theory, respectively. The fracture energy, FSPs, and specimen weights decreased at temperatures higher than 150 °C, but the critical point for the strain-softening index and the number of adsorption sites was shown to be 180 °C. We hypothesize that the fracture energy and FSP depend on the chemical structure of the cell wall, whereas the strain-softening behavior may be influenced by the number of adsorption sites, and in turn the number of hydrogen bonds in hemicellulose. Full article
(This article belongs to the Section Biomaterials)
Open AccessArticle Preparation and Morphology Studies of Nano Zinc Oxide Obtained Using Native and Modified Chitosans
Materials 2013, 6(9), 4198-4212; doi:10.3390/ma6094198
Received: 17 July 2013 / Revised: 26 August 2013 / Accepted: 16 September 2013 / Published: 18 September 2013
Cited by 10 | PDF Full-text (733 KB) | HTML Full-text | XML Full-text
Abstract
Nano zinc oxide (ZnO) with moderate surface area and high pore volume were prepared using a facile preparation method. Chitosan was utilized as both chelating and structure directing agent. The application of chitosans in this study suggested that even biowastes can be served
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Nano zinc oxide (ZnO) with moderate surface area and high pore volume were prepared using a facile preparation method. Chitosan was utilized as both chelating and structure directing agent. The application of chitosans in this study suggested that even biowastes can be served in a productive manner economically. The surface modification of chitosan was carried out in order to increase the interaction between chitosan and zinc ions. The effect of sodium chloroacetate and isopropyl alcohol on the surface modification process was also explored. FT-IR (Fourier transform-infrared spectrometer) and TGA (Thermogravimetric analyses) analyses revealed that modified chitosans are more stable than those of unmodified chitosan. Among surface modified chitosans, CMC1 (1.5 M sodium chloroacetate and 75% isopropyl alcohol) showed enhanced surface properties. Freundlich adsorption isotherms as preliminary studies confirmed that modified chitosan showed enhanced interaction with zinc ions. The interaction of zinc salt with chitosans produced a zinc-chitosan polymer. This finally cleaved upon calcination to produce nano ZnO. The effects of different calcination temperatures indicated that 450 °C is the optimum calcination temperature to produce the nano ZnO with favored surface area (15.45 m2/g) and pore size (221.40 nm). SEM (Scanning electron microscope) and TEM (Transmission electron microscope) of ZnO indicated that uniform particle and shape distributions were obtained at low calcination temperature (450 °C). Full article
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Open AccessArticle Healing of Fatigue Crack by High-Density Electropulsing in Austenitic Stainless Steel Treated with the Surface-Activated Pre-Coating
Materials 2013, 6(9), 4213-4225; doi:10.3390/ma6094213
Received: 22 August 2013 / Revised: 14 September 2013 / Accepted: 16 September 2013 / Published: 23 September 2013
Cited by 5 | PDF Full-text (858 KB) | HTML Full-text | XML Full-text
Abstract
A technique to heal a fatigue crack in austenitic stainless steel SUS316 by applying a controlled, high-density pulsed current was developed. A surface-activated pre-coating (SAPC), which eliminates the oxide layer and coats a Ni film on the crack surface, was used to improve
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A technique to heal a fatigue crack in austenitic stainless steel SUS316 by applying a controlled, high-density pulsed current was developed. A surface-activated pre-coating (SAPC), which eliminates the oxide layer and coats a Ni film on the crack surface, was used to improve the adhesion between crack surfaces. Cracks were observed by scanning electron microscopy before and after the application of high-density electropulsing. To evaluate the healing effect of the SAPC during crack propagation, fatigue tests were conducted under a constant stress intensity factor. The fatigue crack treated with the SAPC was found to be effectively healed as a result of electropulsing, and also showed a slower rate of crack propagation. Full article
Open AccessArticle Unified Formulation for a Triaxial Elastoplastic Constitutive Law for Concrete
Materials 2013, 6(9), 4226-4248; doi:10.3390/ma6094226
Received: 14 June 2013 / Revised: 22 August 2013 / Accepted: 6 September 2013 / Published: 23 September 2013
Cited by 2 | PDF Full-text (1869 KB) | HTML Full-text | XML Full-text
Abstract
A constitutive model to describe the triaxial load-response spectrum of plain concrete in both tension and shear was developed. The inelastic phenomena are described using the plastic flow with direction determined by the gradient of the plastic potential. A new plastic potential is
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A constitutive model to describe the triaxial load-response spectrum of plain concrete in both tension and shear was developed. The inelastic phenomena are described using the plastic flow with direction determined by the gradient of the plastic potential. A new plastic potential is introduced and experimentally fitted to ensure better estimate of the load direction. This approach allows to control the inelastic dilatancy in terms of the inelastic deformation of the material. By overlaying the plastic potential on modified Etse and Willam’s yield surface (both defined on the Haigh–Westergaard coordinates), the results showed that the two curves do not undergo similar stress states for a given strength level. It is, therefore, necessary that each surface goes through the current stress state to ensure adequate evaluation of normal vectors. A closed-form solution to accurately predict the triaxial stress state in concrete has been proposed. The predictive capabilities of the proposed model are evaluated by comparing predicted and measured stresses. The proposed model is shown to be accurate in predicting stress state of concrete. Full article
(This article belongs to the Special Issue Constitutive Behavior of Composite Materials)
Open AccessCommunication Co-Dispersion Behavior of ZrB2–SiC–B4C–C Powders with Polyethyleneimine
Materials 2013, 6(9), 4249-4258; doi:10.3390/ma6094249
Received: 8 July 2013 / Revised: 20 August 2013 / Accepted: 20 August 2013 / Published: 23 September 2013
PDF Full-text (957 KB) | HTML Full-text | XML Full-text
Abstract
The aqueous dispersion behavior of ZrB2, SiC powders with B4C and C as sintering aids was investigated. Well co-dispersed suspension can be obtained in acidic solutions in presence of polyethyleneimine (PEI). The adsorption of PEI on the powder surface
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The aqueous dispersion behavior of ZrB2, SiC powders with B4C and C as sintering aids was investigated. Well co-dispersed suspension can be obtained in acidic solutions in presence of polyethyleneimine (PEI). The adsorption of PEI on the powder surface was measured by thermal gravimetric (TG) analysis. Rheological measurements displayed the effect of dispersant on the flow behavior of as-prepared slurries. An optimum condition was obtained with 1 wt % PEI. The viscosity of 40 vol % ZrB2–SiC–B4C–C (ZSBC) suspension at 100 s−1 was as low as 0.74 Pa·s, which was suitable for aqueous processing. Full article
(This article belongs to the Special Issue Ultra-high Temperature Ceramics)
Open AccessArticle Dislocation Energetics and Pop-Ins in AlN Thin Films by Berkovich Nanoindentation
Materials 2013, 6(9), 4259-4267; doi:10.3390/ma6094259
Received: 31 July 2013 / Revised: 9 September 2013 / Accepted: 17 September 2013 / Published: 23 September 2013
Cited by 9 | PDF Full-text (496 KB) | HTML Full-text | XML Full-text
Abstract
Nanoindentation-induced multiple pop-ins were observed in the load-displacement curves when the mechanical responses of AlN films grown on c-plane sapphire substrates were investigated by using Berkovich indenters. No evidence of phase transformation is revealed by cross-sectional transmission electron microscopy (XTEM) and selected
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Nanoindentation-induced multiple pop-ins were observed in the load-displacement curves when the mechanical responses of AlN films grown on c-plane sapphire substrates were investigated by using Berkovich indenters. No evidence of phase transformation is revealed by cross-sectional transmission electron microscopy (XTEM) and selected area diffraction (SAD) analyses. Instead XTEM observations suggest that these “instabilities” resulted from the sudden nucleation of dislocations propagating along the slip systems lying on the {0001} basal planes and the  pyramidal planes commonly observed in hexagonal compound semiconductors. Based on this scenario, an energetic estimation of dislocation nucleation is made. Full article
Open AccessArticle Influence of Material Microstructures in Micromilling of Ti6Al4V Alloy
Materials 2013, 6(9), 4268-4283; doi:10.3390/ma6094268
Received: 8 June 2013 / Revised: 3 September 2013 / Accepted: 16 September 2013 / Published: 24 September 2013
Cited by 6 | PDF Full-text (1301 KB) | HTML Full-text | XML Full-text
Abstract
In the most recent decades the introduction of unconventional machining processes allowed the development of micromachining techniques. In this work, the influence of material microstructures on the micromilling process was investigated. Ti6Al4V alloy was selected as workpiece material since it is a very
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In the most recent decades the introduction of unconventional machining processes allowed the development of micromachining techniques. In this work, the influence of material microstructures on the micromilling process was investigated. Ti6Al4V alloy was selected as workpiece material since it is a very common material for micro applications and because its duplex microstructure can be easily changed by proper thermal treatments. Four different microstructures (namely bimodal, fully equiaxed, fully lamellar and mill annealed) were obtained through recrystallization annealing treatments carried out at different times and temperatures. The mechanical properties of the samples were assessed by microhardness measurements. Nano-indentations were also performed on single grains to understand how the different hardness of phases and structures present in the Ti6Al4V alloy can affect the micromilling process. Microchannels using two flute flat end mills with a diameter equal to 200 µm were realized on the treated samples. Two different feed-per-tooth values were used during the tests. Cutting force, channel shape and burr dimension were investigated. Morphological and energy dispersive spectroscopy (EDS) analyses were performed on tools by means of a scanning electron microscope (SEM): in this way the phenomena mainly influencing the tool status were also identified. Lower cutting forces and reduced tool wear were observed when working fully lamellar microstructures compared to the other ones. Full article
(This article belongs to the Section Manufacturing Processes and Systems)

Review

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Open AccessReview Nanoscale Design of Nano-Sized Particles in Shape-Memory Polymer Nanocomposites Driven by Electricity
Materials 2013, 6(9), 3742-3754; doi:10.3390/ma6093742
Received: 21 May 2013 / Revised: 6 August 2013 / Accepted: 9 August 2013 / Published: 2 September 2013
Cited by 8 | PDF Full-text (701 KB) | HTML Full-text | XML Full-text
Abstract
In the last few years, we have witnessed significant progress in developing high performance shape memory polymer (SMP) nanocomposites, in particular, for shape recovery activated by indirect heating in the presence of electricity, magnetism, light, radio frequency, microwave and radiation, etc. In this
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In the last few years, we have witnessed significant progress in developing high performance shape memory polymer (SMP) nanocomposites, in particular, for shape recovery activated by indirect heating in the presence of electricity, magnetism, light, radio frequency, microwave and radiation, etc. In this paper, we critically review recent findings in Joule heating of SMP nanocomposites incorporated with nanosized conductive electromagnetic particles by means of nanoscale control via applying an electro- and/or magnetic field. A few different nanoscale design principles to form one-/two-/three- dimensional conductive networks are discussed. Full article
(This article belongs to the Section Advanced Composites)
Open AccessReview Monitoring the Cure State of Thermosetting Resins by Ultrasound
Materials 2013, 6(9), 3783-3804; doi:10.3390/ma6093783
Received: 23 July 2013 / Revised: 20 August 2013 / Accepted: 26 August 2013 / Published: 5 September 2013
Cited by 22 | PDF Full-text (927 KB) | HTML Full-text | XML Full-text
Abstract
The propagation of low intensity ultrasound in a curing resin, acting as a high frequency oscillatory excitation, has been recently proposed as an ultrasonic dynamic mechanical analysis (UDMA) for cure monitoring. The technique measures sound velocity and attenuation, which are very sensitive to
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The propagation of low intensity ultrasound in a curing resin, acting as a high frequency oscillatory excitation, has been recently proposed as an ultrasonic dynamic mechanical analysis (UDMA) for cure monitoring. The technique measures sound velocity and attenuation, which are very sensitive to changes in the viscoelastic characteristics of the curing resin, since the velocity is related to the resin storage modulus and density, while the attenuation is related to the energy dissipation and scattering in the curing resin. The paper reviews the results obtained by the authors’ research group in the last decade by means of in-house made ultrasonic set-ups for both contact and air-coupled ultrasonic experiments. The basics of the ultrasonic wave propagation in polymers and examples of measurements of the time-evolution of ultrasonic longitudinal modulus and chemical conversion of different thermosetting resins are presented. The effect of temperature on the cure kinetics, the comparison with rheological, low frequency dynamic mechanical and calorimetric results, and the correlation between ultrasonic modulus and crosslinking density will be also discussed. The paper highlights the reliability of ultrasonic wave propagation for monitoring the physical changes taking place during curing and the potential for online monitoring during polymer and polymer matrix composite processing. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessReview Calcium Orthophosphate-Based Bioceramics
Materials 2013, 6(9), 3840-3942; doi:10.3390/ma6093840
Received: 20 June 2013 / Revised: 7 August 2013 / Accepted: 19 August 2013 / Published: 6 September 2013
Cited by 37 | PDF Full-text (2259 KB) | HTML Full-text | XML Full-text
Abstract
Various types of grafts have been traditionally used to restore damaged bones. In the late 1960s, a strong interest was raised in studying ceramics as potential bone grafts due to their biomechanical properties. A bit later, such synthetic biomaterials were called bioceramics. In
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Various types of grafts have been traditionally used to restore damaged bones. In the late 1960s, a strong interest was raised in studying ceramics as potential bone grafts due to their biomechanical properties. A bit later, such synthetic biomaterials were called bioceramics. In principle, bioceramics can be prepared from diverse materials but this review is limited to calcium orthophosphate-based formulations only, which possess the specific advantages due to the chemical similarity to mammalian bones and teeth. During the past 40 years, there have been a number of important achievements in this field. Namely, after the initial development of bioceramics that was just tolerated in the physiological environment, an emphasis was shifted towards the formulations able to form direct chemical bonds with the adjacent bones. Afterwards, by the structural and compositional controls, it became possible to choose whether the calcium orthophosphate-based implants remain biologically stable once incorporated into the skeletal structure or whether they were resorbed over time. At the turn of the millennium, a new concept of regenerative bioceramics was developed and such formulations became an integrated part of the tissue engineering approach. Now calcium orthophosphate scaffolds are designed to induce bone formation and vascularization. These scaffolds are often porous and harbor different biomolecules and/or cells. Therefore, current biomedical applications of calcium orthophosphate bioceramics include bone augmentations, artificial bone grafts, maxillofacial reconstruction, spinal fusion, periodontal disease repairs and bone fillers after tumor surgery. Perspective future applications comprise drug delivery and tissue engineering purposes because calcium orthophosphates appear to be promising carriers of growth factors, bioactive peptides and various types of cells. Full article
(This article belongs to the Special Issue Ceramics for Healthcare 2013)
Open AccessReview Consolidation of Hierarchy-Structured Nanopowder Agglomerates and Its Application to Net-Shaping Nanopowder Materials
Materials 2013, 6(9), 4046-4063; doi:10.3390/ma6094046
Received: 5 August 2013 / Revised: 6 September 2013 / Accepted: 9 September 2013 / Published: 16 September 2013
Cited by 7 | PDF Full-text (1719 KB) | HTML Full-text | XML Full-text
Abstract
This paper provides an overview on our recent investigations on the consolidation of hierarchy-structured nanopowder agglomerates and related applications to net-shaping nanopowder materials. Understanding the nanopowder agglomerate sintering (NAS) process is essential to processing of net-shaped nanopowder materials and components with small and
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This paper provides an overview on our recent investigations on the consolidation of hierarchy-structured nanopowder agglomerates and related applications to net-shaping nanopowder materials. Understanding the nanopowder agglomerate sintering (NAS) process is essential to processing of net-shaped nanopowder materials and components with small and complex shape. The key concept of the NAS process is to enhance material transport through controlling the powder interface volume of nanopowder agglomerates. Based upon this concept, we have suggested a new idea of full density processing for fabricating micro-powder injection molded part using metal nanopowder agglomerates produced by hydrogen reduction of metal oxide powders. Studies on the full density sintering of die compacted- and powder injection molded iron base nano-agglomerate powders are introduced and discussed in terms of densification process and microstructure. Full article
(This article belongs to the Special Issue Progress in Net-shaped PM (Powder Metallurgical) Parts)
Open AccessReview SBA-15 Mesoporous Silica as Catalytic Support for Hydrodesulfurization Catalysts—Review
Materials 2013, 6(9), 4139-4167; doi:10.3390/ma6094139
Received: 5 May 2013 / Revised: 27 August 2013 / Accepted: 28 August 2013 / Published: 17 September 2013
Cited by 34 | PDF Full-text (697 KB) | HTML Full-text | XML Full-text
Abstract
SBA-15 is an interesting mesoporous silica material having highly ordered nanopores and a large surface area, which is widely employed as catalyst supports, absorbents, drug delivery materials, etc. Since it has a lack of functionality, heteroatoms and organic functional groups have been incorporated
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SBA-15 is an interesting mesoporous silica material having highly ordered nanopores and a large surface area, which is widely employed as catalyst supports, absorbents, drug delivery materials, etc. Since it has a lack of functionality, heteroatoms and organic functional groups have been incorporated by direct or post-synthesis methods in order to modify their functionality. The aim of this article is to review the state-of-the-art related to the use of SBA-15-based mesoporous systems as supports for hydrodesulfurization (HDS) catalysts. Full article
(This article belongs to the Special Issue Advances in Mesoporous Materials)

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