Single phase, a FeVO4 triclinic crystalline structure was successfully synthesized by annealing the mechanochemically milled xV2O5·(1-x)α-Fe2O3 composites (x = 0.5) at 550 °C for 1 h. X-ray powder diffraction (XRD) and Mössbauer spectroscopy were combined for a detailed study of the assisting role of the mechanochemical milling process. Mechanochemical milling homogeneously mixed the starting materials of α-Fe2O3 and V2O5 and substantially decreased their average grain sizes. The partially V5+-substituted α-Fe2O3 phase and Fe3+-substituted V2O5 could be the important intermediate phases in the production of FeVO4 single phase. In addition, xV2O3·(1-x)α-Fe2O3 (x = 0.1, 0.3, 0.5, and 0.7) solid solutions were successfully synthesized by mechanochemical activation of V2O3 and α-Fe2O3 mixtures. Complete solid solutions exist after 12 h ball-milling time for all studied x values. The synthesized xV2O3·(1-x)α-Fe2O3 solid solutions with x = 0.5 and 0.7 were mainly paramagnetic at room temperature. The study demonstrates that the transformation pathway is related to the valence state of the metallic specie of the oxide used in connection with hematite.

The aim of this study was to develop a thermo-responsive and bioactive polymer with suitable mechanical properties for musculoskeletal tissue engineering applications. A copolymer was synthesized that comprised of hydrophilic polyethylene glycol, thermo responsive N-isopropylacrylamide (NIPAAm), 2-hydroxyethyl methacrylate-poly(lactide) (HEMA-PLA) to enhance mechanical strength and an active N-acryloxysuccinimide (NAS) group for conjugation to proteins to enhance biological properties. A model protein such as elastin was used to assess the feasibility of conjugating this polymer to protein. The results of 1HNMR analyses confirmed that random polymerization was viable technique for synthesis of this copolymer. The co-polymers synthesized with PEG content of 3 mol% were water soluble. A hydrogel was created by dissolving the copolymer and elastin below room temperature in aqueous media, followed by rapid gelation at 37°C. The results of Fourier transform infrared analyses confirmed the conjugation of protein to copolymer due to significant reduction of ester group absorption (1735 cm−1). This data confirmed molecular interaction between protein and the temperature responsive co-polymer. Our preliminary results demonstrated that it is viable to tune different properties of this hydrogel by changing the composition of co-polymer.

Heterogeneities at the meso-scale strongly influence the shock compression response of composite materials. Laminated geometries with full density and intimate particle contacts provide a unique system to investigate the influence of microstructure on a propagating shock wave. Computational analysis is used to understand the effects of layer orientation and bilayer spacing on the shock compression response of cold-rolled Ni/ Al multilayers. Real, heterogeneous microstructures, obtained from optical micrographs, are incorporated into the Eulerian, finite volume code CTH. The results show a marked difference in the dissipation and dispersion of the shock wave as the underlying microstructure varies.

The 0.6(Bi0.85La0.15)FeO3-0.4PbTiO3 (BLF-PT) ceramics were prepared by tape casting method. Effects of binder (polyvinylbutyl dibutyl PVB), plasticizer (phthalate-polyethylene glycol DBP-PEG) and dispersant (triethylolamine, TEA) concentration on the rheological properties of BLF-PT slurry were investigated. The optimized component ratio for ceramics powders, binder, plasticizer, dispersant and solvent (ethanol, EtOH) in the slurry was 50 wt.%, 4 wt.%, 6 wt.%, 1 wt.% and 39 wt.%. The dielectric constant ε r , loss tanδ, and remnant polarization P r of BLF-PT ceramics laminated from the tapes were 525 (1 kHz), 1.7% (1 kHz) and 30 μC/cm2 (45 kV/cm), respectively, which were comparable to those of BLF-PT ceramics prepared by traditional solid state reaction method.

We examine the microwave reflection from the high mobility GaAs/AlGaAs two-dimensional electron system (2DES). Strong correlations have been observed between the microwave induced magnetoresistance oscillations and the microwave reflection oscillations in a concurrent measurement of the microwave illuminated magnetoresistance and the microwave reflection from the 2DES. The correlations were followed as a function of the microwave frequency and the microwave power dependent. Different existing theories are considered to explain the results.

Using first-principles calculations, we investigate lithium vacancy and interstitial defects in lithium phosphate (γ-Li3PO4) and in its interface with metallic Li. We find that γ-Li3PO4 is good electronic insulator with a wide band gap of 6 eV. The calculated formation energies of Li vacancies are higher than those of Li interstitials, which indicate that the ionic conductivity is determined by the migration of Li interstitial defects in bulk electrolyte. The Li vacancy-interstitial pair defect formation energy in the Li/γ-Li3PO4 interface is comparable to the sum of Li vacancy defect at the electrode and Li ion interstitial defect in the electrolyte. Our calculation indicates that the low ionic conductivity of Li/electrolyte interface is associated with the high Li ion defect formation energy. Our study provides some useful insights on Li defect formation and migration mechanisms at the electrode-electrolyte interface and, hence, a research direction for designing future Li-ion batteries.

Surface smoothing of a barium borosilicate glass substrate by irradiation of ionic liquid ion beams were investigated. 1-ethyl-3-methylimidaolium tetrafluoroborate (EMIM-BF4) and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) were used for the source liquid. Surface roughness represented as the arithmetic mean value decreased from 0.17 nm to 0.13 nm by the BMIM-PF6 negative ion beam. Secondary electron microscope (SEM) observation for the glass surface irradiated with the BMIM-PF6 negative ion beam showed a clear image without an electrical charge-up, though the EMIM-BF4 negative ion beam irradiated glass yielded a charged up image. X-ray photoelectron spectroscopy (XPS) analysis implied that the surface layer including cation-anion pair of BMIM-PF6 was deposited by the BMIM-PF6 negative ion beam irradiation, while an insulated surface with barium fluoride was formed by the EMIM-BF4 negative ion beam irradiation.

Alloying ZnO with isovalent compounds allows tailoring the material’s optoelectronic properties. In this work, we theoretically analyze the ZnO-based alloys ZnO–X ≡ (ZnO)1−x (X)x where X = GaN and InN, employing a first-principles Green’s function method GW0 based on the density functional approach. Since the alloy compounds are isovalent to ZnO, we find relatively small distortion of the crystalline structure, however, nanocluster structures are expected to be present in the alloy. ZnO–X reveal intriguing optoelectronic properties. Incorporating GaN or InN in ZnO strongly narrows the energy gap. The band gap energy is reduced from E g = 3.34 eV in intrinsic ZnO to ∼2.17 and ∼1.89 eV in ZnO–X by alloying ZnO with 25% GaN and InN, respectively. Moreover, clustering enhances the impact on the electronic structure, and the gap energy in ZnO–InN is further reduced to 0.7–1.5 eV if the 25% compound contains nanoclusters. The dielectric function ε 2(ω) varies weakly in ZnO–GaN with respect to alloy composition, while it varies rather strongly in ZnO–InN. Hence, by properly growing and designing ZnO–X, the alloy can be optimized for a variety of novel integrated optoelectronic nano-systems.

In the present study, we report the enhancement in figure-of-merit (ZT) of nanostructured n-type Silicon-Germanium (Si80Ge20) thermoelectric alloy synthesized using high energy ball milling followed by spark plasma sintering (SPS). After 90 h of ball milling of elemental powders of Si, Ge and P (2 at.%), a complete dissolution of Ge in Si matrix has been observed forming the nanostructured n-type Si80Ge20 alloy powder. X-ray diffraction analysis (XRD) confirmed the crystallite size of the host matrix (Si) to be ∼7 nm and also indicated the formation of an additional phase of SiP nano-precipitates after SPS. HR-TEM analysis revealed that the nano-grained network was retained post-sintering with a crystallite size of size of 9 nm and also confirmed the SiP precipitates formation with a size of 4 to 6 nm. As a result, a very low thermal conductivity of ∼2.3W/mK at 900°C has been observed for Si80Ge20 alloy primarily due to scattering of phonons by nanostructured grains and nano-scaled SiP precipitates which further contribute to this scattering mechanism. Electrical conductivity values of SiGe sintered alloy are slightly lower to that of reported values in literature. This was attributed to the formation of SiP which creates a compositional difference between the grain boundary region and the grain region, leading to a chemical potential difference at interface and the grain region. Figure-of-merit (ZT) of n-type Si80Ge20 nanostructured alloy was found to be ≈1.5 at 900°C, which is the highest reported so far at this temperature.

Biomaterials require thorough in vitro testing before being applied in vivo. Unwanted contaminations of biomaterials but also their intrinsic properties can cause uncontrolled immune response leading to severe consequences for the patient. Therefore, immunological evaluation of materials for biomedical applications is mandatory before entering clinical application. In order to introduce physical netpoints, the aromatic compounds desaminotyrosine (DAT) and desaminotyrosyl-tyrosine (DATT) were successfully used to functionalize linear and star-shaped oligoethylene glycol (lOEG and sOEG) as previously described. The materials showed properties of surfactants and have potential to be used for solubilization of lipophilic drugs in water. Furthermore, the materials are susceptible for H2O2 degradation as determined by MALDI-ToF MS analyses. This is important for potential in vivo applications, as macrophages can release reactive oxygen species (ROS) under inflammatory conditions. As it is known that surfactant solutions of high concentration can lead to cell lysis, the effects of OEG-DAT(T) solutions on murine RAW macrophages were investigated. Even at highest OEG-DAT(T) concentration of 1000 µg·mL-1 the viability of the RAW cells was not significantly impaired. Additionally, the polymers were incubated with whole human blood and the production of inflammatory cytokines such as the tumor necrosis factor (TNF)-α and interleukin (IL)-6 was determined. Only at high concentrations, the OEG-DAT(T) solution induced low levels of TNF-α and IL-6, indicating that a mild inflammatory reaction could be expected when such high OEG-DAT(T) concentrations are applied in vivo. Similarly, the OEG-DAT(T) solution did not induce ROS in monocytes and neutrophils after incubation with whole human blood. Conclusively, the data presented here demonstrate that OEG-DAT(T) do not lead to a substantial activation of the innate immune mechanisms and could therefore be investigated for solubilizing pharmaceutical agents.

Nanoparticles (NPs) with either plasmonic or upconverting properties have been selectively coated onto the surfaces of polystyrene (PS) spheres, imparting their optical properties to the PS colloids. These NP coated PS spheres have many potential applications, such as in medicine as drug-delivery systems or diagnostic tools. To prepare the NP coated PS spheres, gold or core-shell NaYF4Tm0.5Yb30/NaYF4 NPs were synthesized and separately combined with amino-functionalized PS spheres. The mechanism by which the NPs adhered to the PS spheres is attributed to interactions of the NP and a polyvinylpyrrolidone additive with the surfaces of the PS spheres. Two-photon fluorescence microscopy and SERS analysis demonstrate the potential applications of these NP coated PS spheres.

This study described a low-energy atom scattering system combined with a time-of-flight spectrometer and an ultra high vacuum chamber for insulator surface structural analysis. We show one of examples to study of MgO(111) surface analysis. A visual image of Mg atoms due to the projected blocking pattern represents the crystalline structure of the MgO(111) surfaces. This figure shows the trajectory of scattered 4He0 particles due to Mg atoms along low-index lattice planes and crystallographic directions. Insulator surface structural analysis becomes more important in materials sciences.

We demonstrate and analyze a highly efficient on-chip 3D metal-insulator-metal (MIM) nanofocusing structure. Here, we show the in-depth theoretical design, analysis and discussion to provide a detailed picture of the highly efficient, on-chip nanofocusing process which is linearly tapered in 3D.

As incentive programs for solar energy are gradually being phased out around the world, solar must quickly become a viable and competitive option to the mainstream, fossil-based power generation technologies. As such, it must begin to assume more of the characteristics of the traditional technologies in order to be compatible with utility generation business models. With this goal in mind, Solergy has realized a series of innovations that include optics, concentrator module design, and tracking to create a high performing, long-lasting High Concentration Photovoltaic (HCPV) system. Because it is upgradeable, Solergy is the only HCPV system that can actually increase its power output over its lifetime and then subsequently extend its life out to 40 years. This talk will discuss the types of technological advances required to achieve this and share results from the lab and the field. In particular, the talk will cover the world’s only all-glass concentrating lens, high performance tracking, and the unique upgrade mechanism.

Nematic liquid crystals (NLCs) under micron-range confinement exhibit a rich defect phenomenology that can be used to extract elastic (Frank moduli) material parameters of critical importance for next generation electro-optical devices. In this work we develop a model to predict defect-driven textural transformations that arise when a NLC is confined to a circular capillary. In the initial transformation stage an unstable disclination defect of strength +1 nucleates in the axis of the capillary and quickly branches into two stable +1/2 disclination defects. The model includes: (1) the Kirchhoff branch balance equation which predicts the splitting of a +1 into two +1/2 wedge disclinations; (2) the curvature of the +1/2 disclination lines as a function of elastic properties. This model shows that by increasing the ratio of tension strength to bending stiffness, the branch point angle increases, but the final defect distance decreases; and (3) the aperture branching angle of the +1/2 lines as a function of the elastic properties and the magnitude of the curvature at the branch point. These three predictions form the basis for the evaluation of the Frank elastic moduli on NLCs. The key advantage of the implemented methodology is to use time-dependent textural transformations under micron-range capillary confinement to extract elastic parametric data needed to further develop NLCs in functional and structural application.

Al2O3 was deposited on silicon nanowire (SiNW) arrays by atomic layer deposition (ALD) as a passivation layer to reduce surface recombination velocity. As a result, effective minority carrier lifetime was improved from 1.82 to 26.2 μs. From this result, the relative low-surface recombination rate of 2.73 cm/s was obtained from a calculation using one-dimensional device simulation (PC1D). The performance of SiNW solar cells was also simulated by considering the surface recombination velocity on the side of SiNWs using two-dimensional device simulation. It was found that Al2O3 deposited by ALD can improve open-circuit voltage of SiNW solar cells even if the structure has a high-aspect ratio and large surface area. Therefore, improvement in the performance of SiNW solar cells can be expected.

Bone grafts, commonly performed to augment bone regeneration from autologous or alleogeneic sources, carry an enormous cost, estimated at upwards of 21 billion dollars per year. Hydroxyapatite (HAP) bio-ceramic has been widely used in clinic as a bone graft substitute material due to its biocompatibility and the similarity of its structure and composition to bone mineral. However, its applications are limited due to its lack of strength and toughness. Researchers have attempted to overcome these issues by combining HAP bio-ceramics into resorbable polymers to improve their mechanical properties. However, poor bonding between the HAP and the polymer caused separation at the polymer-filler interface. To overcome this, short chains of polymers were grafted directly from the hydroxyl groups on the surface of nanocrystalline HAP. Collagens, being the most abundant proteins in the body, and having suitable properties such as biodegradability, bioabsorbability with low antigenicity, high affinity to water, and the ability to interact with cells through integrin recognition, makes them a very promising candidate for the modification of the polymer surface. In this study, a novel method of synthesizing nano-hydroxyapatite (nHAP)-g-poly(lactide-co-glycolide)-g-collagen polymer was introduced. The synthesis process was carried out in several steps. First, poly (lactide-co-glycolide) (PLGA) polymer was directly grafted onto the hydroxyl group of the surface of n-HAP particles by ring-opening polymerization, and subsequently coupled with succinic anhydride. In order to activate the co-polymer for collagen attachment, the carboxyl end group obtained from succinic anhydride was reacted with N-hydroxysuccinimide (NHS) in the presence of dicyclohexylcarbodiimide (DCC) as the cross-linking agent. Finally, the activated co-polymer was attached to calf skin collagen type I, in hydrochloric acid/phosphate buffer solution and the precipitated co-polymer with attached collagen was isolated. The synthesis was monitored by 1H NMR and FTIR spectroscopies and the products after each step were characterized by thermal analysis (TGA and DSC). These composite materials will be tested as potential scaffolds for tissue engineering applications.

We present neutron diffraction results on superionic materials that are good candidates for use as solid-state electrolytes in next generation Li+ ion batteries. Lithium ion conducting glasses of the compositions xLi2SO4-(1-x) [0.5Li2O-0.5(2NH4H2PO2)] ; x=0 and 0.1 were synthesized by conventional melt-quenching. The transparent homogeneous glassy flakes were thus obtained and used for the characterization. The materials are glassy in nature and composed of a complex network of the following sub-units: Li2O, Li2SO4, and 2NH4H2PO2. This disordered structure is integral to its function in that it promotes Li+ ion conduction while suppressing electronic conduction, the necessary qualities of a good Li+ electrolyte. We used neutron diffraction to study the formation of crystallites upon heating of the material above 400°C. The crystallite formation is understood to be detrimental to the Li+ ion mobility and, hence, is identified with a diminished performance in devices that require heating in their fabrication processs. Here, we report the changes in the material, as observed by neutron diffraction, as a function of annealing temperature and temperature history.

We have measured the attenuation of longitudinal acoustic waves in a series of amorphous and nanocrystalline silicon films using picosecond ultrasonics. We determined the attenuation of amorphous Si to be lower than what is predicted by theories based on anharmonic interactions of the ultrasound wave with localized phonons or extended resonant modes. We determined the attenuation of nanocrystalline Si to be nearly one order of magnitude higher than amorphous Si.