Sudden jumps in nanoindentation load-displacement curves of bulk metallic glasses (BMGs) signify the onset of plastic deformation. These events are investigated on varying compositions of Zr- and Hf-rich BMGs. Load-versus-displacement graphs for spherical indentations are analyzed to determine displacement, load, intensity of deformation, energy per volume, energy loss, and pressure corresponding to these key locations. Attention is focused on pressure, energy loss, and energy per volume at initial plasticity in response to varying strain rates, indenter tip radii, preload, and material composition. Energy loss was found to correlate with preload. The Zr-rich metallic glass was found to plastically deform in response to smaller loads than Hf-rich specimens.

Exothermic reaction path of the Ni–Ti–B4C system in the differential thermal analysis apparatus proceeded in such a way that Ni initially reacted with B4C and Ti to form Ni–B compounds and Ti2Ni with heat release, respectively; subsequently, the formation of Ni–B eutectic liquid between Ni2B and Ni4B3, and the appearance of Ni–Ti eutectic liquid phase between Ti2Ni and Ti were followed, which enabled the diffusion of Ni, B, C, and Ti in solution to form Ni–Ti–B–C liquid more easily and quickly at a low temperature; finally, TiC and TiB2 were precipitated out of the liquid. The addition of Ni provided an easier route for reactant mass transfer and accelerated the occurrence of complete reaction.

A wurtzite nitrogen-doped MgZnO (MgZnO:N) film was grown by plasma-assisted molecular-beam epitaxy (PAMBE) on c-plane sapphire using radical NO as oxygen source and nitrogen dopant. The as-grown film shows n-type conduction at room temperature, but transforms into p-type conduction after annealed. Photoluminescence (PL) spectrum measured at 80 K is dominated by neutral donor-bound exciton emission (D0X) located at 3.522 eV for the n-type MgZnO:N film, but by neutral acceptor-bound exciton emission (A0X) located at 3.515 eV for the p-type MgZnO:N film. By fitting exciton emission intensity of temperature-dependent PL spectra, the binding energies of the D0X and A0X were estimated to be 32 and 43 meV, respectively. Based on the energy shift of exciton emission, the band gap of the MgZnO:N film is estimated to be 3.613 eV, which is 179 meV larger than that of ZnO. Using the Haynes rule, the acceptor energy level of the MgZnO:N film was evaluated to be about 176 meV above the valence band.

Single-crystalline nanobelts of molybdenum trioxides were grown by direct thermal oxidization evaporation of metal molybdenum foils. Their structures, defects, and optical properties were investigated via x-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), atomic force microscopy, micro-Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible spectroscopy (UV-VIS). Single-crystalline nanobelts were identified as an orthorhombic structure with an average stoichiometry of MoO3.02analyzed by energy dispersive spectroscopy of x-rays. The length, width, and thickness of a nanobelt were determined to be parallel to the b, c, and aaxis of the MoO3unit cell, respectively. The thickness of the nanobelt increased by integer multiples of 0.5ain a layer-by-layer fashion during growth. A density of dislocations as high as about 1.2 × 1013cm−2was formed, which may be attributed to relaxation of large strains during cooling. A special dislocation configuration was observed by HRTEM, which was well reproduced by image simulations based on the proposed model. The resulting morphology of nanobelts was proposed to be governed by growth kinetics. Micro-Raman and FTIR spectra were successfully analyzed on the basis of vibration of MoO6octahedra. It was found that micro-Raman spectra were quite dependent on the size of the nanobelts. A band gap energy of 3.04 eV derived from UV-VIS measurements was observed to be red shifted relative to the previously reported experimental values, which may be due to the presence of a high density of defects.

Biosensors based on lipid membranes promise an inexpensive and versatile platform for application in many fields of molecular sensing. An extensive review of the applications for tethered membranes was reported in the July 2006 MRS Bulletin [A.N. Parikh and J.T. Groves, Materials science of supported lipid membranes. MRS Bull.31(8), 507 (2006)]. The commercial use to which tethered lipid membranes have been applied has been limited by their stability under long-term storage. This report describes a novel membrane construct that is stable at room temperature for months, eliminates the mobile lipid phase present in lipid bilayers, and is robust against detergents under conditions that would destroy a lipid bilayer.

An extended microbridge test (eMBT) was proposed to assess the adhesion of metallic coatings on metallic substrates. Through loading on the backside of narrow striped freestanding coatings, a two-dimensional stable interfacial delamination was introduced. A cross-sectional scanning electron microscope (SEM) was used to examine the interfacial fracture process. A large deflection solution for elastic deformation of the coating was derived, and an approximate model was established for the estimate of interfacial crack extension force G. The eMBT samples of electroplated Ni coatings on C45 carbon steel substrate were tested, and the measured interfacial fracture toughness was about 5.28 J/m2. Cross-sectional SEM examination showed that the interface crack extended along the interface plane, and therefore the interfacial fracture proceeded by the debonding of Ni/steel interface.

A low-temperature plasma-enhanced atomic layer deposition (PEALD) process has been developed for the growth of ultrathin WNxCy films, using a halide-free W precursor. A 32-nm-thick PEALD WNxCy film deposited using this process at 250 °C possesses a composition of W72C20N5, resistivity of ∼250 μΩ·cm, a root-mean-square (rms) surface roughness of 0.23 nm, and a thickness conformality of more than 80% on trench structures with a width of 120 nm and an aspect ratio of 11. The WNxCy films exhibited excellent thermal stability, whereby resistivity, thickness, surface roughness, and crystal structure were stable after 30 min anneals in 700 Torr, forming gas ambient at temperatures up to 700 °C. Copper diffusion barrier performance measurements show that a 9 nm thick WNxCy film could prevent copper diffusion after a 30 min anneal at 700 °C, while a 2-nm-thick film could prevent copper diffusion after a 30 min anneal at 500 °C.

The effect of replacement of Ti with Y or Nb in Ti-rich Ti–Zr–Be–Cu–Ni bulk metallic glasses (BMGs) has been investigated. The minor addition (MA) of Y (Y–Ti: +58 kJ/mol) induced phase separation into Y-rich crystalline particles and Ti-rich amorphous matrix, while the MA of Nb (Nb–Ti: +10 kJ/mol) led to nanocrystallization in Ti-rich BMGs with icosahedral nuclei. This result indicates that MA of elements having positive enthalpy of mixing can induce a different degree of instability in the single amorphous matrix depending on the amount of repulsive interaction energy. In particular, MA of Nb (up to 4 at.%) significantly increased the compressive fracture strain (ϵf) up to ∼9.35 ± 0.2%, which indicates that the plasticity of BMGs can be enhanced by the size-modulated icosahedral phase embedded in the amorphous matrix.

Ce3+-activated lanthanide silicon oxynitride (La5Si3O12N, La4SiO7N2, LaSiO2N, and La3Si8O4N11) phosphors were prepared by firing the mixture of La2O3, Si3N4, SiO2, and CeO2 at 1500–1600 °C under a 0.5 MPa nitrogen atmosphere. Diffuse reflection spectrum, photoluminescence spectra, and temperature-dependent luminescence of these phosphors are presented in this work. A blue emission of Ce3+ in all lanthanide silicon oxynitrides was observed under ultraviolet irradiation, which is strongest in La3Si8O4N11:Ce3+. The concentration quenching and thermal quenching of the samples were discussed.

Lithium ferrite particle/organic hybrid was synthesized in situ from iron–organic and lithium–organic compounds below 100 °C. Spinel ferrite particle/organic hybrid was synthesized by hydrolyzing a mixture of iron (III) 3-allylacetylacetonate (IAA) and lithium acrylate (LA). X-ray diffraction analysis revealed that the crystallinity of spinel particle was dependent on the polymerization treatment and the hydrolysis conditions. The saturation magnetization of hybrid increased with increasing methylhydrazine and water amount of hydrolysis. Nanocrystalline lithium ferrite particle about 5 nm was dispersed in the organic matrix. The hybrid showed neither remanence nor coercive force at room temperature. The magnetization versus field/temperature H/T curves from 100 to 300 K were superimposed on the same curve and satisfied the Langevin equation. The zero-field-cooled (ZFC) and field-cooled (FC) magnetization curve revealed that the blocking temperature was about 75 K. The remanent magnetization and coercive field of the hybrid were 8.9 A·m2/kg and 26.3 kA/m, respectively, at 10 K.

The kinetics of hydride formation and decomposition described by semiempirical models generally do not involve particle and grain-size dependence. However, ball-milled nanocrystalline powders usually exhibit log-normal grain-size and particle-size distribution. Considering size dependence, a total reacted function for a multiparticle system has been developed. We show that the shape of the measured reaction fraction curves do not determine unambiguously the rate-controlling mechanism of hydrogen sorption, since the kinetics are strongly affected by the microstructure. With the application the convolutional multiple whole profile fitting procedure for nanocrystalline MgH2, the parameters, e.g., the median and variance of the log-normal grain-size distribution have been determined. Taking these values into account, the reaction constants corresponding to different sorption states are considerably modified compared with values obtained from classical single-particle models.

Under ambient conditions, plastic flow in metallic glasses is sharply localized into shear bands. The heat content of, and consequent temperature rise at, shear bands in three bulk metallic glasses are compared using a recently reported fusible coating method. The minimum shear offsets necessary to detect local heating are determined. It is shown that the dependence of heat content on offset is consistent with frictional heating in the band. The effective stress on the band undergoing shear is 50–70% of the macroscopic shear stress, a ratio compared with simulations of shear-band initiation and operation. It is also noted that frictional heating can occur not only at shear bands, but also at mixed-mode cracks.

Optimization of the carrier concentration is a key to improve the power factor of thermoelectricity. The carrier concentration of sintered zinc oxides was primarily controlled by impurity doping of aluminum and secondarily adjusted by defect concentration by varying the oxygen partial pressure in the range of 101 to 104 Pa. The resultant carrier concentration measured at room temperature ranged from 1 to 1.8 × 1020 cm−3, which drastically modified the thermoelectricity. The Jonker plot of the measured Seebeck coefficient and conductivity revealed deviation of the slope from k/e (where k is the Boltzmann constant and e is the elemental electric charge), which was attributed to a mobility variation with respect to the carrier concentration. The approach to estimating the optimum conductivity taking into account mobility variation is discussed. Finally, the optimum conductivity is estimated to be 1800 to 2000 S/cm for high-temperature operation (500 to 800 °C).

This work studies the chemical and structural changes that occur in sols upon heating to form ceramics. Ferrimagnetic Y3Fe5O12 (YIG) was chosen because the geometric and structural constraint of ferrimagnetic interactions allow for a direct measurement of the degree of well-defined structure present within the sol at various stages of development. Glycolate sols of 8% mol total metal were prepared using Y(NO3)3 and Fe(NO3)3 hydrates in stoichiometric ratios. Terminal straight-chain diols were used, ranging from 1,2-ethanediol to 1,6-hexanediol. The temperatures at which mass change occurred during heating were determined by thermogravimetric analysis. Samples were heated to these temperatures and examined by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction, and magnetometry to determine chemical, structural, and magnetic changes. Ferrimagnetic ordering was present after the first heating step. Defined structure, determined by x-ray, occurred in the penultimate step. Analysis of FTIR spectra, in conjunction with the results of thermogravimetric analysis, revealed a predictable decomposition pathway.

Si1−xGexOynanowire (SiGeONW) assemblies with cord-, chain-, and tubelike morphologies were grown on a Si substrate via the carbothermal reduction of GeO2/CuO powders at 1100 °C in Ar. The growth of various SiGeONWs assemblies follows the vapor-liquid-solid process. The CuSiGe droplets formed during the growth of SiGeONWs simultaneously play the roles of catalyst and reactant. The morphology of SiGeONWs assemblies is not temperature controlled but dependent on the Cu concentration and the size of CuSiGe catalysts. This phenomenon is unlike the Ge- and Ga-catalyzed growth of SiOxnanowire assemblies. In addition, the processing parameters and the mechanisms for the growth of SiGeONWs assemblies with various morphologies are discussed.

We report the hydrogenation characteristics and mechanical properties of Ti50Zr25Cu25 in situ composite ribbons, composed of β-Ti crystalline phase dispersed in an amorphous matrix. Upon cathodic charging at room temperature, high hydrogen absorption up to ∼60 at.% (H/M = ∼1.2) is obtained. At such a high concentration, hydrogen-induced amorphization occurs. Mechanical tests conducted on the composite with varying hydrogen concentrations indicate that the Ti50Zr25Cu25 alloy is significantly resistant to hydrogen embrittlement when compared to conventional amorphous alloys. A possible mechanism that would contribute toward hydrogen-induced amorphization and hydrogen embrittlement is discussed.

We demonstrate that diffusion of aqueous buffered solutions into strongly hydrophobic nanoporous methyl silsesquioxane glass films can occur without the application of external pressure. The organic component of these glasses in the form of methyl groups imparts the strong hydrophobicity and perception that they are impervious to the ingress of aqueous solutions by capillary action or diffusion. The presence of small concentrations of organic buffering agents in buffered solutions appears to facilitate the diffusion. The diffusion distance followed a square root of time dependence characteristic of Fick’s Law. The diffusion coefficients varied markedly with the concentration of buffering agents, solution pH, and temperature. Similar effects were not observed for nonbuffered solutions that exhibited no detectable diffusion. Likely mechanisms responsible for the observed behavior are proposed.

Hydrogenated amorphous carbon (a-C:H) films were fabricated using mixed acetylene and argon plasma with various flow rate ratios of acetylene to argon. Raman scattering and x-ray photoelectron spectroscopy show that changing the flow rate ratios (FC2H2 to FAr) has a large impact on the structure of the films. Enhanced film hardness and reduced surface roughness were achieved at higher ratios attributable to the high ion flux and efficient etching by hydrogen. However, the film surface exposed to atomic hydrogen at a higher C2H2 flow rate becomes rougher. The sp3 content and film hardness also reach saturation combined with a fissile surface due to the high stress.

The reaction mechanisms and related microstructures in the Cu/Si, Ru/Si, and Cu/Ru/Si metallization system were studied experimentally. With the help of sheet resistance measurements, x-ray diffraction, field-emission scanning electron microscopy, secondary ion mass spectroscopy, and transmission electron microscopy, the metallization structure with Ru barrier layer was observed to fail completely at temperatures around 700 °C, regardless of the Ru thickness because of the formation of polycrystalline Ru2Si3 followed by Cu3Si protrusions.

Poly-vinylpyrrolidones (PVP) with different molecular weights were used to modify the sol-gel solutions for preparing Pb0.91La0.09(Zr0.65,Ti0.35)0.9775O3 (PLZT, 9/65/35) thin films. The crystallization behavior and microstructural development of the PLZT films with and without PVP addition were investigated. It was found that the addition of PVP significantly improved perovskite phase formation of the PLZT films, but the films exhibited rosette-like morphology. Further study on the PLZT films and the gel particles showed that a premature nucleation of PbO grains in the PVP modified sol-gel solution induced the Pb-rich domains in the films, which accelerated the growth of the grains and thus led to the rosette-like structure. In addition, the electrical and optical properties of the PLZT films with rosette-like structure were also studied and discussed.