Showing papers in "Materials in 2011"
TL;DR: This review article is an overview of the current state of research on AAO membranes and the various applications of nanotechnology that use them in the manufacture of nano-materials and devices or incorporate them into specific applications such as biological/chemical sensors, nano-electronic devices, filter membranes and medical scaffolds for tissue engineering.
Abstract: The anodization of aluminum is an electro-chemical process that changes the surface chemistry of the metal, via oxidation, to produce an anodic oxide layer. During this process a self organized, highly ordered array of cylindrical shaped pores can be produced with controllable pore diameters, periodicity and density distribution. This enables anodic aluminum oxide (AAO) membranes to be used as templates in a variety of nanotechnology applications without the need for expensive lithographical techniques. This review article is an overview of the current state of research on AAO membranes and the various applications of nanotechnology that use them in the manufacture of nano-materials and devices or incorporate them into specific applications such as biological/chemical sensors, nano-electronic devices, filter membranes and medical scaffolds for tissue engineering.
336 citations
TL;DR: The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens, in the synthesis and investigation of thermotropic ionic liquid crystals.
Abstract: The last five years' achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.
283 citations
TL;DR: In this article, two chitosans were deacetylated with 45% sodium hydroxide under nitrogen atmosphere at 80 °C or 90 °C for up to 120 min.
Abstract: Degree of deacetylation (DDA) and molecular weight (MW) of chitosans are important to their physical and biological properties. In this study, two chitosans, HS (DDA = 73.3%) and AT (DDA = 76.8%), were deacetylated with 45% sodium hydroxide under nitrogen atmosphere at 80 °C or 90 °C for up to 120 min, to obtain two series of chitosans. The polymers produced were characterized for MW by gel permeation chromatography, DDA by titration and UV-vis methods, and crystallinity, hydrophilicity and thermal stability by X-ray diffraction, water contact angle and differential scanning calorimetry respectively. Films, made by solution casting in dilute acetic acid at ambient conditions, were evaluated for biological activity by albumin adsorption and the attachment and growth of a pre-osteoblast cell line. Chitosans with between 80–93% DDA’s (based on titration) were reproducibly obtained. Even though deacetylation under nitrogen was supposed to limit chain degradation during decetylation, MW decreased (by maximum of 37.4% of HS and 63.0% for AT) with increasing deacetylation reaction time and temperature. Crystallinity and decomposition temperature increased and water contact angles decreased with processing to increase DDA. Significantly less albumin was absorbed on films made with 93% DDA chitosans as compared with the original materials and the AT chitosans absorbed less than the HS chitosans. The cells on higher DDA chitosan films grew faster than those on lower DDA films. In conclusion, processing conditions increased DDA and influenced physicochemical and biological properties. However, additional studies are needed to unambiguously determine the influence of DDA or MW on in vitro and in vivo performance of chitosan materials for bone/implant applications.
255 citations
TL;DR: Mechanical properties, corrosion properties and grindability (wear properties) were evaluated and data was analyzed using ANOVA and a non-parametric method (α = 0.05).
Abstract: This study characterized properties of Ti-6Al-4V ELI (extra low interstitial, ASTM grade 23) specimens fabricated by a laser beam melting (LBM) and an electron beam melting (EBM) system for dental applications. Titanium alloy specimens were made into required size and shape for each standard test using fabrication methods. The LBM specimens were made by an LBM machine utilizing 20 µm of Ti-6Al-4V ELI powder. Ti-6Al-4V ELI specimens were also fabricated by an EBM using 40 µm of Ti-6Al-4V ELI powder (average diameter, 40 µm: Arcam ABO) in a vacuum. As a control, cast Ti-6Al-4V ELI specimens (Cast) were made using a centrifugal casting machine in an MgO-based mold. Also, a wrought form of Ti-6Al-4V ELI (Wrought) was used as a control. The mechanical properties, corrosion properties and grindability (wear properties) were evaluated and data was analyzed using ANOVA and a non-parametric method (α = 0.05). The strength of the LBM and wrought specimens were similar, whereas the EBM specimens were slightly lower than those two specimens. The hardness of both the LBM and EBM specimens was similar and slightly higher than that of the cast and wrought alloys. For the higher grindability speed at 1,250 m/min, the volume loss of Ti64 LBM and EBM showed no significant differences among all the fabrication methods. LBM and EBM exhibited favorable results in fabricating dental appliances with excellent properties as found for specimens made by other fabricating methods.
198 citations
TL;DR: Chitin nanofibers were isolated from the cell walls of five different types of mushrooms by the removal of glucans, minerals, and proteins, followed by a simple grinding treatment under acidic conditions and showed that the α-chitin crystal structure was maintained and glucans remained on the nanofiber surface.
Abstract: Chitin nanofibers were isolated from the cell walls of five different types of mushrooms by the removal of glucans, minerals, and proteins, followed by a simple grinding treatment under acidic conditions. The Chitin nanofibers thus obtained have a uniform structure and a long fiber length. The width of the nanofibers depended on the type of mushrooms and varied in the range 20 to 28 nm. The Chitin nanofibers were characterized by elemental analyses, FT-IR spectra, and X-ray diffraction profiles. The results showed that the α-chitin crystal structure was maintained and glucans remained on the nanofiber surface.
163 citations
TL;DR: Investigations on the effects of salt additives in Hofmeister series on the HPMC gelation with salt ions as well as with the ionic and non-ionic surfactants are presented.
Abstract: Sol-gel transformations in HPMC (hydroxypropyl methylcellulose) are being increasingly studied because of their role in bio-related applications. The thermo-reversible behavior of HPMC is particularly affected by its properties and concentration in solvent media, nature of additives, and the thermal environment it is exposed to. This article contains investigations on the effects of salt additives in Hofmeister series on the HPMC gelation. Various findings regarding gelation with salt ions as well as with the ionic and non-ionic surfactants are presented. The gel formation in physiological salt fluids such as simulated gastric and intestine fluids is also examined with the interest in oral drug delivery systems. The processes of swelling, dissolution and dispersion of HPMC tablets in simulated bio-fluids are explored and the release of a drug from the tablet affected by such processes is studied. Explanations are provided based on the chemical structure and the molecular binding/association of HPMC in a media. The test results at the body or near-body temperature conditions helped in understanding the progress of the gelation process within the human body environment. The detailed interpretation of various molecule level interactions unfolded the sol-gel mechanisms and the influence of a few other factors. The obtained test data and the established mathematical models are expected to serve as a guide in customizing applications of HPMC hydrogels.
158 citations
TL;DR: It is demonstrated that the morphology of the phosphor crystals in the CR imaging plate has a very significant impact on its performance.
Abstract: Computed radiography (CR) uses storage phosphor imaging plates for digital imaging. Absorbed X-ray energy is stored in crystal defects. In read-out the energy is set free as blue photons upon optical stimulation. In the 35 years of CR history, several storage phosphor families were investigated and developed. An explanation is given as to why some materials made it to the commercial stage, while others did not. The photo stimulated luminescence mechanism of the current commercial storage phosphors, BaFBr:Eu2+ and CsBr:Eu2+ is discussed. The relation between storage phosphor plate physical characteristics and image quality is explained. It is demonstrated that the morphology of the phosphor crystals in the CR imaging plate has a very significant impact on its performance.
147 citations
TL;DR: In the present work, the two-photon polymerization technique was applied to develop precisely defined biodegradable 3D tissue engineering scaffolds that support primary adipose-derived stem cell (ASC) adhesion, proliferation and differentiation into the anticipated lineage.
Abstract: In the present work, the two-photon polymerization (2PP) technique was applied to develop precisely defined biodegradable 3D tissue engineering scaffolds. The scaffolds were fabricated via photopolymerization of gelatin modified with methacrylamide moieties. The results indicate that the gelatin derivative (GelMod) preserves its enzymatic degradation capability after photopolymerization. In addition, the developed scaffolds using 2PP support primary adipose-derived stem cell (ASC) adhesion, proliferation and differentiation into the anticipated lineage.
131 citations
TL;DR: A geometrical concept of an ideal amorphous solid is presented as a novel contribution to the understanding of atomic arrangements in amorphously solids.
Abstract: Mechanical, optical, magnetic and electronic properties of amorphous materials hold great promise towards current and emergent technologies. We distinguish at least four categories of amorphous (glassy) materials: (i) metallic; (ii) thin films; (iii) organic and inorganic thermoplastics; and (iv) amorphous permanent networks. Some fundamental questions about the atomic arrangements remain unresolved. This paper focuses on the models of atomic arrangements in amorphous materials. The earliest ideas of Bernal on the structure of liquids were followed by experiments and computer models for the packing of spheres. Modern approach is to carry out computer simulations with prediction that can be tested by experiments. A geometrical concept of an ideal amorphous solid is presented as a novel contribution to the understanding of atomic arrangements in amorphous solids.
121 citations
TL;DR: The dramatic progress in nanotube buckling research during the past few years is reviewed.
Abstract: The nonlinear mechanical response of carbon nanotubes, referred to as their "buckling" behavior, is a major topic in the nanotube research community. Buckling means a deformation process in which a large strain beyond a threshold causes an abrupt change in the strain energy vs. deformation profile. Thus far, much effort has been devoted to analysis of the buckling of nanotubes under various loading conditions: compression, bending, torsion, and their certain combinations. Such extensive studies have been motivated by (i) the structural resilience of nanotubes against buckling, and (ii) the substantial influence of buckling on their physical properties. In this contribution, I review the dramatic progress in nanotube buckling research during the past few years.
117 citations
TL;DR: Improvement of optical properties is advantageous to the practical usage of ZnO nanoparticles, such as bioimaging, because of the varied timing of the addition of the polymer to the ZNO nanoparticle solution.
Abstract: Optical properties of ZnO nanoparticles capped with polymers were investigated. Polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP) were used as capping reagents. ZnO nanoparticles were synthesized by the sol-gel method. Fluorescence and absorption spectra were measured. When we varied the timing of the addition of the polymer to the ZnO nanoparticle solution, the optical properties were drastically changed. When PEG was added to the solution before the synthesis of ZnO nanoparticles, the fluorescence intensity increased. At the same time, the total particle size increased, which indicated that PEG molecules had capped the ZnO nanoparticles. The capping led to surface passivation, which increased fluorescence intensity. However, when PEG was added to the solution after the synthesis of ZnO nanoparticles, the fluorescence and particle size did not change. When PVP was added to the solution before the synthesis of ZnO nanoparticles, aggregation of nanoparticles occurred. When PVP was added to the solution after the synthesis of ZnO nanoparticles, fluorescence and particle size increased. This improvement of optical properties is advantageous to the practical usage of ZnO nanoparticles, such as bioimaging.
TL;DR: In the compounds, Bi3+ ion, located at the A site in the perovskite structure, caused ferroelectric structural distortion, and the B-site ordering of the Ni2 and Mn4+ ions led to ferromagnetism according to the Kanamori-Goodenough rule.
Abstract: New multiferroic compounds with double-perovskite structures were synthesized. Bi 2 NiMnO 6 was synthesized in bulk form by high-pressure synthesis and also in a thin-film form by epitaxial growth. The material showed both ferromagnetic and ferroelectric properties, i.e. , the multiferroic property at low temperature. Bi 2 FeCrO 6 was also fabricated in a (1 1 1) oriented BiFeO 3 /BiCrO 3 artificial superlattice, with a 1/1 stacking period. The superlattice film showed ferromagnetic behavior and polarization switching at room temperature. In the compounds, Bi 3+ ion, located at the A site in the perovskite structure, caused ferroelectric structural distortion, and the B-site ordering of the Ni 2+ and Mn 4+ ions (Fe 3+ and Cr 3+ ions) in a rock-salt configuration led to ferromagnetism according to the Kanamori-Goodenough rule. Keywords: double-perovskite structure; ferromagnetic and ferroelectric properties; high-pressure synthesized bulk; epitaxially grown thin film; artificial superlattice
TL;DR: Models of domain structure in ferroelectric crystals, thin films and bulk materials, including optical, polarized light, scanning electron microscopy, X-ray and neutron diffraction, atomic force microscopy and piezo-force microscopy are reviewed.
Abstract: The present paper reviews models of domain structure in ferroelectric crystals, thin films and bulk materials. Common crystal structures in ferroelectric materials are described and the theory of compatible domain patterns is introduced. Applications to multi-rank laminates are presented. Alternative models employing phase-field and related techniques are reviewed. The paper then presents methods of observing ferroelectric domain structure, including optical, polarized light, scanning electron microscopy, X-ray and neutron diffraction, atomic force microscopy and piezo-force microscopy. Use of more than one technique for unambiguous identification of the domain structure is also described.
TL;DR: Recent advances in the synthesis of binary transition metal nitrides, carbides and borides are summarized focusing on the reaction of the elements at extreme conditions generated within the laser-heated diamond anvil cell.
Abstract: Transition metal nitrides, carbides and borides have a high potential for industrial applications as they not only have a high melting point but are generally harder and less compressible than the pure metals. Here we summarize recent advances in the synthesis of binary transition metal nitrides, carbides and borides focusing on the reaction of the elements at extreme conditions generated within the laser-heated diamond anvil cell. The current knowledge of their structures and high-pressure properties like high-(p; T) stability, compressibility and hardness is described as obtained from experiments.
TL;DR: It is shown that a 100 degree improvement in terms of w-AlN suppression can be achieved, which is of importance when the coating is used as a protective coating on metal cutting inserts.
Abstract: We review results of recent combined theoretical and experimental studies of Ti 1−x Al x N, an archetypical alloy system material for hard-coating applications. Theoretical simulations of lattice parameters, mixing enthalpies, and elastic properties are presented. Calculated phase diagrams at ambient pressure, as well as at pressure of 10 GPa, show a wide miscibility gap and broad region of compositions and temperatures where the spinodal decomposition takes place. The strong dependence of the elastic properties and sound wave anisotropy on the Al-content offers detailed understanding of the spinodal decomposition and age hardening in Ti 1−x Al x N alloy films and multilayers. TiAlN/TiN multilayers can further improve the hardness and thermal stability compared to TiAlN since they offer means to influence the kinetics of the favorable spinodal decomposition and suppress the detrimental transformation to w-AlN. Here, we show that a 100 degree improvement in terms of w-AlN suppression can be achieved, which is of importance when the coating is used as a protective coating on metal cutting inserts.
TL;DR: The interlaminar toughening of a carbon fibre reinforced composite by interleaving a thin layer of poly(hydroxyether of bisphenol A) (phenoxy) nanofibres was explored and results showed that the interleaved did not negatively affect the effective in-plane strength of the composites.
Abstract: The interlaminar toughening of a carbon fibre reinforced composite by interleaving a thin layer (~20 microns) of poly(hydroxyether of bisphenol A) (phenoxy) nanofibres was explored in this work. Nanofibres, free of defect and averaging several hundred nanometres, were produced by electrospinning directly onto a pre-impregnated carbon fibre material (Toray G83C) at various concentrations between 0.5 wt % and 2 wt %. During curing at 150 °C, phenoxy diffuses through the epoxy resin to form a semi interpenetrating network with an inverse phase type of morphology where the epoxy became the co-continuous phase with a nodular morphology. This type of morphology improved the fracture toughness in mode I (opening failure) and mode II (in-plane shear failure) by up to 150% and 30%, respectively. Interlaminar shear stress test results showed that the interleaving did not negatively affect the effective in-plane strength of the composites. Furthermore, there was some evidence from DMTA and FT-IR analysis to suggest that inter-domain etherification between the residual epoxide groups with the pendant hydroxyl groups of the phenoxy occurred, also leading to an increase in glass transition temperature (~7.5 °C).
TL;DR: Porous silicon samples reduced in nanometric particles by a well known industrial mechanical process, the ball grinding in a planetary mill are extended to crystalline silicon for comparison purposes.
Abstract: Porous silicon samples have been reduced in nanometric particles by a well known industrial mechanical process, the ball grinding in a planetary mill; the process has been extended to crystalline silicon for comparison purposes. The silicon nanoparticles have been studied by X-ray diffraction, infrared spectroscopy, gas porosimetry and transmission electron microscopy. We have estimated crystallites size from about 50 nm for silicon to 12 nm for porous silicon. The specific surface area of the powders analyzed ranges between 100 m2/g to 29 m2/g depending on the milling time, ranging from 1 to 20 h. Electron microscopy confirms the nanometric size of the particles and reveals a porous structure in the powders obtained by porous silicon samples which has been preserved by the fabrication conditions. Chemical functionalization during the milling process by a siloxane compound has also been demonstrated.
TL;DR: The use of hydrated vanadium(V)oxide as a replacement of the commonly employed hole transporting material PEDOT:PSS was explored in this work.
Abstract: The use of hydrated vanadium(V)oxide as a replacement of the commonly employed hole transporting material PEDOT:PSS was explored in this work. Polymer solar cells were prepared by spin coating on glass. Polymer solar cells and modules comprising 16 serially connected cells were prepared using full roll-to-roll (R2R) processing of all layers. The devices were prepared on flexible polyethyleneterphthalate (PET) and had the structure PET/ITO/ZnO/P3HT:PCBM/V2O5· (H2O)n/Ag. The ITO and silver electrodes were processed and patterned by use of screen printing. The zinc oxide, P3HT:PCBM and vanadium(V)oxide layers were processed by slot-die coating. The hydrated vanadium(V)oxide layer was slot-die coated using an isopropanol solution of vanadyl-triisopropoxide (VTIP). Coating experiments were carried out to establish the critical thickness of the hydrated vanadium(V)oxide layer by varying the concentration of the VTIP precursor over two orders of magnitude. Hydrated vanadium(V)oxide layers were characterized by profilometry, scanning electron microscopy, energy dispersive X-ray spectroscopy, and grazing incidence wide angle X-ray scattering. The power conversion efficiency (PCE) for completed modules was up to 0.18%, in contrast to single cells where
TL;DR: How the persistent luminescence is affected by the type of codopant and the choice and ratio of the starting products is described, and results show that Ba2Si5N8:Eu(,R) and Ca2Si3N2:EU(, R) are promising persistent phosphors for applications requiring orange or red light.
Abstract: Persistent luminescent materials are able to emit light for hours after being excited. The majority of persistent phosphors emit in the blue or green region of the visible spectrum. Orange- or red-emitting phosphors, strongly desired for emergency signage and medical imaging, are scarce. We prepared the nitrido-silicates Ca2Si5N8:Eu (orange), Sr2Si5N8:Eu (reddish), Ba2Si5N8:Eu (yellowish orange), and their rare-earth codoped variants (R = Nd, Dy, Sm, Tm) through a solid state reaction, and investigated their luminescence and afterglow properties. In this paper, we describe how the persistent luminescence is affected by the type of codopant and the choice and ratio of the starting products. All the materials exhibit some form of persistent luminescence, but for Sr2Si5N8:Eu,R this is very weak. In Ba2Si5N8:Eu the afterglow remains visible for about 400 s, and Ca2Si5N8:Eu,Tm shows the brightest and longest afterglow, lasting about 2,500 s. For optimal persistent luminescence, the dopant and codopant should be added in their fluoride form, in concentrations below 1 mol%. A Ca3N2 deficiency of about 5% triples the afterglow intensity. Our results show that Ba2Si5N8:Eu(,R) and Ca2Si5N8:Eu(,R) are promising persistent phosphors for applications requiring orange or red light.
TL;DR: The industrially-important WC-Co composite materials provide a useful, albeit complicated materials system for understanding the combined influences on hardness and strength properties of the constituent WC particle strengths, the particle sizes, their contiguities, and of Co binder hardness and mean free paths, and in total, the volume fraction of constituents.
Abstract: The industrially-important WC-Co composite materials provide a useful, albeit complicated materials system for understanding the combined influences on hardness and strength properties of the constituent WC particle strengths, the particle sizes, their contiguities, and of Co binder hardness and mean free paths, and in total, the volume fraction of constituents. A connection is made here between the composite material properties, especially including the material fracture toughness, and the several materials-type considerations of: (1) related hardness stress-strain behaviors; (2) dislocation (viscoplastic) thermal activation characterizations; (3) Hall-Petch type reciprocal square root of particle or grain size dependencies; and (4) indentation and conventional fracture mechanics results. Related behaviors of MgO and Al2O3 crystal and polycrystal materials are also described for the purpose of making comparisons.
TL;DR: The microstructures resulting from thermal cure processes were characterized morphologically and also in terms of their effect on the resistivity of printed traces in relation to an Ag nanoparticle ink.
Abstract: Conductive inks are key enablers for the use of printing techniques in the fabrication of electronic systems. Focus on the understanding of aspects controlling the electrical performance of conductive ink is paramount. A comparison was made between microparticle Ag inks and an Ag nanoparticle ink. The microstructures resulting from thermal cure processes were characterized morphologically and also in terms of their effect on the resistivity of printed traces. For microparticle inks, the variability of resistivity measurements between samples as defined by coefficient of variation (CV) was greater than 0.1 when the resistivity was 10 to 50 times that of bulk Ag. When the resistivity was lower (~1.4 times that of bulk Ag) the CV of sample sets was less than 0.1. In the case of the nanoparticle ink, resistivity was found to decrease by a factor ranging from 1.2 to 1.5 after doubling the amount of layers printed prior to curing though it was expected to remain the same. Increasing the amount of layers printed also enhanced the sintering process.
TL;DR: It was concluded that the hot-stretched nanofiber and the PAN/SWNTs nanofibers can be used as a potential precursor to produce high-performance nanocomposites.
Abstract: Partially aligned polyacrylonitrile (PAN)-based nanofibers were electrospun from PAN and PAN/single-walled carbon nanotubes (SWNTs) in a solution of dimethylformamide (DMF) to make the nanofiber composites. The as-spun nanofibers were then hot-stretched in the oven to enhance its orientation and crystallinity. With the introduction of SWNTs and by the hot-stretched process, the mechanical properties will be enhanced correspondingly. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray scattering (XRD), differential scanning calorimetry (DSC), and the tensile test were used to characterize the microstructure and performances of the nanofibers. The orientation and crystallinity of the as-spun and hot-stretched nanofibers confirmed by X-ray have increased. Differential scanning calorimetry showed that the glass transition temperature of PAN increased about 3 °C by an addition of 0.75 wt% SWNTs indicating a strong interfacial interaction between PAN and SWNTs. The tensile strength and the modulus of the nanofibers increased revealing significant load transfer across the nanotube-matrix interface. For PAN nanofibers, the improved fiber alignment, orientation and crystallinity resulted in enhanced mechanical properties, such as the tensile strength and modulus of the nanofibers. It was concluded that the hot-stretched nanofiber and the PAN/SWNTs nanofibers can be used as a potential precursor to produce high-performance nanocomposites.
TL;DR: Inspired by photosynthesis robust photo water-splitting systems using manganese-containing materials including Mn-terpy dimer/titanium oxide, Mn-oxo tetramer/Nafion, and Mn- terpy oligomer/tungsten oxide, in solar fuel production are summarized and evaluated.
Abstract: In nature, the water-splitting reaction via photosynthesis driven by sunlight in plants, algae, and cyanobacteria stores the vast solar energy and provides vital oxygen to life on earth. The recent advances in elucidating the structures and functions of natural photosynthesis has provided firm framework and solid foundation in applying the knowledge to transform the carbon-based energy to renewable solar energy into our energy systems. In this review, inspired by photosynthesis robust photo water-splitting systems using manganese-containing materials including Mn-terpy dimer/titanium oxide, Mn-oxo tetramer/Nafion, and Mn-terpy oligomer/tungsten oxide, in solar fuel production are summarized and evaluated. Potential problems and future endeavors are also discussed.
TL;DR: In this paper, in-vivo µCT scans were used to assess the suitability of rare earths alloys for the examination of their corrosion properties, and the results showed that the location of the implant has a remarkable effect on the corrosion rate.
Abstract: In magnesium alloys, the components used modify the alloy properties. For magnesium implants in contact with bone, rare earths alloys are commonly examined. These were shown to have a higher corrosion resistance than other alloys and a high mechanical strength, but their exact composition is hard to predict. Therefore a reduction of their content could be favorable. The alloys ZEK100 and AX30 have a reduced content or contain no rare earths at all. The aim of the study was to investigate their in vivo degradation and to assess the suitability of the in vivo µCT for the examination of their corrosion. Implants were inserted in rabbit tibiae. Clinical examinations, X-rays and in vivo µCT scans were done regularly. Afterwards implants were analyzed with REM, electron dispersive X-ray (EDX), weighing and mechanical testing. The in vivo µCT is of great advantage, because it allows a quantification of the corrosion rate and qualitative 3D assessment of the corrosion morphology. The location of the implant has a remarkable effect on the corrosion rate. Due to its mechanical characteristics and its corrosion behavior, ZEK100 was judged to be suitable, while AX30, which displays favorable degradation behavior, has too little mechanical strength for applications in weight bearing bones.
TL;DR: The gelatin-g-PMAA hydrogel exhibited a pH-responsiveness character so that a swelling-deswelling pulsatile behavior was recorded at pHs 2 and 8, which makes the hydrogels as a good candidate for controlled delivery of bioactive agents.
Abstract: In this paper, a novel gelatin-based hydrogel was synthesized through crosslinking graft copolymerization of methacrylic acid (MAA) onto gelatin, using ammonium persulfate (APS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. A proposed mechanism for hydrogel formation was suggested and the structure of the product was established using FTIR spectroscopy and gravimetric analysis of the products. Moreover, morphology of the samples was examined by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA/DTG). The effect of reaction variables such as concentration of APS and MBA were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. The gelatin-g-PMAA hydrogel exhibited a pH-responsiveness character so that a swelling-deswelling pulsatile behavior was recorded at pHs 2 and 8. This on-off switching behavior makes the hydrogel as a good candidate for controlled delivery of bioactive agents.
TL;DR: The effect of the cellulose isolation method, particularly the acid treatment time for hemicellulose removal, on cellulose ultrastructural characteristics is examined by studying these effects on cotton, microcrystalline cellulose (MCC) and holocellulose pulped Populus.
Abstract: In order to obtain accurate information about the ultrastructure of cellulose from native biomass by 13C cross polarization magic angle spinning (CP/MAS) NMR spectroscopy the cellulose component must be isolated due to overlapping resonances from both lignin and hemicellulose. Typically, cellulose isolation has been achieved via holocellulose pulping to remove lignin followed by an acid hydrolysis procedure to remove the hemicellulose components. Using 13C CP/MAS NMR and non-linear line-fitting of the cellulose C4 region, it was observed that the standard acid hydrolysis procedure caused an apparent increase in crystallinity of ~10% or less on the cellulose isolated from Populus holocellulose. We have examined the effect of the cellulose isolation method, particularly the acid treatment time for hemicellulose removal, on cellulose ultrastructural characteristics by studying these effects on cotton, microcrystalline cellulose (MCC) and holocellulose pulped Populus. 13C CP/MAS NMR of MCC indicated that holocellulose pulping and acid hydrolysis has little effect on the crystalline ultrastructural components of cellulose. Although any chemical method to isolate cellulose from native biomass will invariably alter substrate characteristics, especially those related to regions accessible to solvents, we found those changes to be minimal and consistent in samples of typical crystallinity and lignin/hemicellulose content. Based on the rate of the hemicellulose removal, as determined by HPLC-carbohydrate analysis and magnitude of cellulose ultrastructural alteration, the most suitable cellulose isolation methodology utilizes a treatment of 2.5 M HCl at 100 °C for a standard residence time between 1.5 and 4 h. However, for the most accurate crystallinity results this residence time should be determined empirically for a particular sample.
TL;DR: The properties of Ni-PZT and NZFO- PZT composites in terms of ME voltage coefficients as a function of frequency and magnetic DC bias are reported.
Abstract: Magnetoelectric (ME) composites that simultaneously exhibit ferroelectricity and ferromagnetism have recently gained significant attention as evident by the increasing number of publications. These research activities are direct results of the fact that multiferroic magnetoelectrics offer significant technological promise for multiple devices. Appropriate choice of phases with co-firing capability, magnetostriction and piezoelectric coefficient, such as Ni-PZT and NZFO-PZT, has resulted in fabrication of prototype components that promise transition. In this manuscript, we report the properties of Ni-PZT and NZFO-PZT composites in terms of ME voltage coefficients as a function of frequency and magnetic DC bias. In order to overcome the problem of toxicity of lead, we have conducted experiments with Pb-free piezoelectric compositions. Results are presented on the magnetoelectric performance of Ni-NKN, Ni-NBTBT and NZFO-NKN, NZFO-NBTBT systems illustrating their importance as an environmentally friendly alternative.
TL;DR: The applied research progress of the metal fiber porous materials in such application areas based on the recent work in the group was reviewed in this paper.
Abstract: Metal fiber porous materials with intrinsic properties of metal and functional properties of porous materials have received a great deal of attention in the fundamental research and industry applications. With developments of the preparation technologies and industrial requirements, porous fiber metals with excellent properties are developed and applied in many industry areas, e.g., sound absorption, heat transfer, energy absorption and lightweight structures. The applied research progress of the metal fiber porous materials in such application areas based on the recent work in our group was reviewed in this paper.
TL;DR: Cell culture experiments employing the MC3T3 murine preosteoblast cell line showed good cell viability and adhesion on the dual-scale scaffolds, and the influence of electrospun fibers on cell morphology and behavior was evident.
Abstract: This research activity was aimed at the development of dual-scale scaffolds consisting of three-dimensional constructs of aligned poly(e-caprolactone) (PCL) microfilaments and electrospun poly(lactic-co-glycolic acid) (PLGA) fibers. PCL constructs composed by layers of parallel microsized filaments (0/90° lay-down pattern), with a diameter of around 365 μm and interfilament distance of around 191 μm, were produced using a melt extrusion-based additive manufacturing technique. PLGA electrospun fibers with a diameter of around 1 μm were collected on top of the PCL constructs with different thicknesses, showing a certain degree of alignment. Cell culture experiments employing the MC3T3 murine preosteoblast cell line showed good cell viability and adhesion on the dual-scale scaffolds. In particular, the influence of electrospun fibers on cell morphology and behavior was evident, as well as in creating a structural bridging for cell colonization in the interfilament gap.