Alloying effects of iridium on the glass formability (GFA) of the Zr–Ir–Cu–Al system have been investigated, and several new bulk metallic glasses (BMGs) with high GFA have been successfully developed. Additions of Ir in the Zr–Cu–Al system can yield a beneficial distribution in atomic sizes, but the strong chemical interaction of the Zr–Ir atomic pair limits the maximum addable Ir contents and the resultant GFA. Our analyses indicate that the optimum composition for alloying elements is determined by not only topological but also chemical factors. Phase competition upon solidification, rather than effects from individual affecting factors, dictates the GFA of BMG systems.

The structural phase stability and electronic properties of the Ti–Al intermetallic compounds were investigated by means of density-functional theory (DFT) calculations in a generalized gradient approximation. Through comparison of the calculated formation energies of the parent and product phases, an in-depth theoretical understanding of the deformation-induced γ ↔ α2 phase transitions observed previously in TiAl alloys was achieved. The formation energy plays an important role in evaluating the feasibility of these phase transformations during plastic deformation of TiAl alloys. In addition, the density of states (DOS) was also calculated and used to analyze the stability of Ti–Al intermetallic compounds. The reasons for the absence of the deformation-induced (DI)-α2 and DI-γ (L12) phases in underformed TiAl alloys were analyzed.

This article reviews the optical polarization properties of unstrained and strained GaN films with a nonpolar orientation. In unstrained a -plane GaN films, the A exciton becomes completely linearly polarized perpendicular to the c-axis, whereas the B and C excitons are only partially polarized. In m -plane or a -plane GaN films under anisotropic in-plane compressive strain, all three interband transitions between the three uppermost valence bands and the conduction band can become linearly polarized for sufficiently large strain values. The complete linear polarization can be directly observed in reflection, transmission, or photoreflectance by a polarization-dependent energy gap. This complete linear polarization can be used to realize polarization-sensitive photodetectors in the ultraviolet spectral range, which do not need a polarization filter in front of the photodetector. By combining a polarization filter and photodetector or two photodetectors from the same material with their c-axes oriented perpendicular to each other, a narrowband photodetection configuration can be achieved in the ultraviolet spectral range with a band width below 8 nm. Since both realizations are also polarization sensitive, a configuration with four photodetectors is necessary to achieve narrow-band sensitivity regardless of the polarization state of the incident light. At the same time, the configuration with four photodetectors allows for the determination of the absolute angle of polarization.

The effect of temperature on grinding-induced texture in tetragonal lead titanate (PT) has been investigated as a function of the magnitude of loading applied to the sample surface during grinding, using in situ x-ray diffraction (XRD) with an area detector. Compared to the ground PT under lower loading conditions (5 N), the ground PT under higher loading conditions (40 N) retains strong ferroelastic texture near the Curie temperature (TC) around 350 °C and undergoes smaller changes in lattice parameter or tetragonality versus temperature during in situ thermal cycling between room temperature and approximately 100 °C above the TC. Inhibited depoling of ground PT materials investigated by in situ texture measurements demonstrates the effects of residual stresses.

Semipolar InGaN/GaN quantum wells (QWs) are quite attractive as visible light emitters. One of the reasons is that a better optical transition probability is expected because of weaker internal electric fields, compared to conventional polar QWs. In addition, in-plane optical polarization anisotropy, which is absent in conventional QWs, is another relevant property because it affects device design and also may provide a means for novel applications. We revealed that the in-plane optical anisotropy in semipolar QWs switched from one direction perpendicular to the [0001] crystal axis to the perpendicular direction as the In composition increases. This is a property unique to semipolar QWs and enables, for example, to make cavity mirrors of laser diodes by cleavage. In this article, we describe the concept of semipolar planes and fabrication of high-quality epitaxial films for semipolar QWs. Furthermore, we discuss device fabrication and optical polarization anisotropy.

A modified method for contact-induced adhesion on the elastic deformation contact between a rigid spherical indenter and a polydimethylsiloxane (PDMS) specimen is proposed in the present study. Adhesion due to van der Waals interactions was found to be minimal during loading processes. During the unloading process, the experimental load-displacement data revealed two-stage phenomena. The successive advancing contacts between the specimen and the indenter were considered to induce interfacial adhesion and resulted in elastic tension outside the Hertzian contact radius. A real-coded genetic algorithm (RGA) was applied to evaluate how adhesion energy varied with penetration depth.

A poly(acrylic acid)/gelatin interpenetrating network hydrogel was synthesized by aqueous solution polymerization. The influences of preparation conditions including cross-linker, initiator, gelatin content, and neutralization degree on the swelling ratios of the hydrogels are investigated. The swelling, mechanical strength, biodegradability, and drug-release properties of poly(acrylic acid)/gelatin hydrogel are evaluated. The hydrogel has excellent mechanical properties; tensile strength is 1500 kPa, and elongation at break is 887%, respectively. The in vitro biodegradation shows that an interpenetrating network structure exists in the poly(acrylic acid)/gelatin hybrid hydrogel. A release study indicates that the theophylline release from the hydrogel depends on the cross-linking density of the hydrogel and pH of the medium, and the drug diffusion obeys an anomalous transport model.

Ferromagnetic Cu-doped GaN film was grown on a GaN-buffered sapphire (0001) substrate by a hybrid physical-chemical-vapor-deposition method (HPCVD). The GaCuN film (Cu: 3.6 at.%) has a highly c-axis-oriented hexagonal wurtzite crystal structure, which is similar to GaN buffer but without any secondary phases such as metallic Cu, CuxNy, and CuxGay compounds. Two weak near-band edge (NBE) emissions at 3.38 eV and donor-acceptor-pair (DAP) transition at 3.2 eV with a typical strong broad yellow emission were observed in photoluminescence spectra for GaN buffer. In contrast, the yellow emission was completely quenched in GaCuN film because Ga vacancies causing the observed yellow emission in undoped GaN were substituted by Cu atoms. In addition, GaCuN film exhibits a blue shift of NBE emission, which could be explained with the +2 oxidation state of Cu ions, replacing +3 Ga ions resulting in band gap increment. The valance sate of Cu in GaCuN film was also confirmed by x-ray photoelectron spectroscopy (XPS) analysis. The GaCuN film shows ferromagnetic ordering and possesses a residual magnetization of 0.12 emu/cm3 and a coercive field of 264 Oe at room temperature. The unpaired spins in Cu2+ ions (d9) are most likely to be responsible for the observed ferromagnetism in GaCuN.

Luminescent silica nanotubes and nanowires were fabricated from cellulose whisker templates by sol-gel processing. The cellulose templates were removed by calcination at 650 °C to generate silica nanotubes with diameters of 15 nm and lengths up to 500 nm. At temperatures of 900 °C the core region previously occupied by the cellulose template was closed yielding silica nanowires. Cathodoluminescence spectra of the silica nanotubes and nanowires were measured in the transmission electron microscope during irradiation with 150 keV electrons. A blue emission at 450 nm was observed for the silica nanowires calcined at 900 °C. This luminescence was found to be related to defects induced by electron irradiation and was investigated in situ as a function of irradiation dose. The as-synthesized and 650 °C calcined nanowires and nanotubes showed a fast decay of the signal. The observed irradiation dose dependent changes in the luminescence spectra will be discussed in terms of defect formation and transformation mechanisms.

The orientation relationships among TiB (B27), B2, and Ti3Al phases have been investigated by transmission electron microscopy. By using the composite selected-area electron diffraction technique, the orientation relationship between TiB (B27) and B2 was determined to be [100]TiB[001]B2, (001)TiB(010)B2; and that between TiB (B27) and Ti3Al was . These orientation relationships have been predicted precisely by the method of coincidence of reciprocal lattice points.

An n-body Ni–Nb–Ta potential is constructed to conduct molecular dynamics simulations using 129 solid solution models with various compositions. Comparing the relative stability of solid solutions versus their disordered counterparts, simulations determine two critical solid-solubility lines, which define a region in the composition triangle. If an alloy is located inside the defined region, a disordered state is energetically favored; if it is located outside, a crystalline solid solution is preserved. The region is therefore named as the metallic glass-forming region.

Nanoindentation creep and uniaxial tension were conducted on pure Mg with a grain size of about 2 μm at room temperature and the data were directly compared. Despite the differences in stress state, the two sets of data were found to match remarkably well with each other. An apparent stress exponent value of 4 was obtained and the deformation mechanism was discussed in light of dislocation slips and twinning in anisotropic Mg.

A comparison between results of a recently published quasi-exact solution of the temperature integral used for the Avrami model of isochronal phase transformations and an analytical phase-transformation model in relation to exact solutions from numerical integration has been performed. The results for the transformed fraction from the quasi-exact solution are more precise than the corresponding results of the analytical model, whereas the results for the transformation rate from both models are sufficiently precise for the nucleation mode of site saturation or continuous nucleation. It has been further shown that an analytical solution of the transformation rate cannot be obtained using a quasi-exact solution of the temperature integral in case of mixed nucleation, and that the results of the corresponding solution with the analytical model substantially alleviate the influence of the approximated temperature integral. By this method, an analytical approach of modeling, which can substantially alleviate the deviation (of model prediction) arising from approximations to the temperature integral, has been developed. The proposed approach has been successfully applied to experimental data of the crystallization of bulk amorphous Pd-Ni-P-Cu alloys.

We report the realization of the p-type conductivity and the enhancement of the photoluminescence (PL) intensity in undoped ZnO films treated with high-energy (1 MeV) electron-beam irradiation (HEEBI), suggesting that the HEEBI process is compatible with a low-temperature requirement for the fabrication of transparent thin film transistors with good efficiency on a plastic substrate. The p-type conductivity of the films was revealed by the Hall, x-ray photoelectron spectroscopy, and PL measurements after being electron-irradiated in air at room temperature. The major acceptor-like defects were determined to be oxygen interstitial and zinc vacancy. A model was proposed in terms of O as well as Zn diffusion to explain the observed results. It was also observed that HEEBI treatment has little influence on the optical transmittance of ZnO films, whereas HEEBI treatment shifts the optical band gap toward the lower energy region from 3.29 to 3.28 eV.

Histidine is an amino acid present in proteins involved in biosilica formation and often found in peptides identified during phage display studies but its role(s) and the extent of its involvement in the silica precipitation process is not fully understood. In this contribution we describe results from an in vitro silicification study conducted using poly-histidine (P-His) and a series of different molecular weight synthetic polymers containing the imidazole functionality (polyvinylimidazole, PVI) for comparison. We show that the presence of imidazole from PVI or P-His is able to catalyze silicic acid condensation; the effect being greater for P-His. The catalytic mechanism is proposed to involve the dual features of the imidazole group—its ability to form hydrogen bonds with silicic acid and electrostatic attraction toward oligomeric silicic acid species.

The clean and ordered surfaces of CdZnTe (111)B grown by the Bridgman method were obtained by Ar ion bombardment and thermal annealing in situ in an ultrahigh vacuum. The surface atomic structures of CdZnTe (111)B after annealing at different temperature were observed by low-energy electron diffraction (LEED). The valence band and work function of CdZnTe (111)B surfaces were determined by synchrotron radiation photoemission spectroscopy. The order of CdZnTe (111)B after annealing at 350 °C will worsen, and the (111)B-(2 × 2) local reconstruction will be formed. The work function of CdZnTe (111)B after annealing at 350 °C is 0.8 eV higher than that of CdZnTe (111)B-(1 × 1), and the local reconstruction may be induced by Te adatoms on top of the ideal truncation.

Porous ZrO2:8 mol% Y2O3 sintered ceramics were prepared by adding graphite powder as pore former before sintering. The thermal elimination of graphite was evaluated by thermogravimetric analysis. Impedance spectroscopy analysis was carried out in the 5 Hz to 13 MHz frequency range in specimens sintered with and without pore former. The deconvolution of the impedance diagrams, [Z″(ω) × Z′(ω)] and [Z″(ω) × log f], and the numerical residuals resulting from the subtraction of normalized impedance spectroscopy diagrams measured in specimens with and without pore formers were evaluated. A comparison of the impedance diagrams of samples sintered with and without pore former shows evidence of a modification of the electrical response caused by pores. The results show the unequivocal ability of the impedance spectroscopy technique to gauge microstructural modification caused by the presence of pores in ionic conducting solids.

The aim of this work is to study the effect of Nb element doping on the microstructure and electrical properties of lead zirconate stannum titanate (PZST) ceramic and to improve phase transition properties of PZST. Nb-doped Pb(Zr,Sn,Ti)O3 ceramic samples were prepared by the conventional mixed oxide method. Phase transitions induced by temperature, pressure, and electric field were measured with electric dielectric permittivity, hydrostatic pressure, and hysteresis. The microstructure of the samples was observed by electron scanning microscope to discuss the effect of Nb doping on PZST ceramics. The experiment results indicated that the remnant polarization (Pr), dielectric constant, phase transition, and microstructure were strongly dependent on Nb doping content.