Si3N4 sintered with Lu2O3 was exposed to 1 atm of oxygen and steam environments at 1200–1400 °C. The effects of additive and impurity species on the morphological development of the oxide layer were examined. Oxide layers grown on as-received samples in oxygen generally contained bubbles and cracks and underwent spallation due to the presence of an initial impurity-laden oxide layer. Oxide layers grown on as-received samples in steam exhibited layered morphology: a glassy outer layer and a cristobalite inner layer with a high population density of Lu2Si2O7 particles between. The Lu2Si2O7 particles accumulated at the interface led to extensive spallation of the upper oxide layer. Removal of the initial oxide by polishing resulted in improved oxidation resistance and oxide morphology in oxygen and in steam.

This paper describes studies on the thermal annealing behavior of Cu films with 2.3 at.% W deposited on Si substrates. The magnetron cosputtered Cu films with insoluble W were vacuum annealed at temperatures ranging from 200 to 800 °C. Twins were observed in focused ion beam and transmission electron microscopy images of as-deposited and 400 °C annealed pure Cu film, and these twins were attributed to the intrinsic low stacking fault energy. Twins in pure Cu film may provide an additional diffusion path during annealing for copper silicide formation. The beneficial effect of W on the thermal stability of Cu film was supported by the following observations: (i) x-ray diffraction studies show that Cu4Si was formed at 530 °C in Cu–W film, whereas pure Cu film exhibited Cu4Si growth at 400 °C; (ii) shallow diffusion profiles for Cu into Si in Cu–W film through secondary ion mass spectroscopy analyses, and the high activation energy needed for the copper silicide formation from the differential scanning calorimetry study; (iii) addition of W in Cu film increases the stacking fault energy and results in a low twin density.

The formation of a composite gel fiber from cellulose acetate and zirconium tetra-n-butoxide was examined. The gel was thought to have formed by the coordination of OH and CO groups of cellulose to zirconium, taking six coordination numbers around the zirconium. The gel fiber had good stability in common solvents, phosphate solution, and electrolyte solution. Then, under mild conditions, a β-galactosidase was entrap-immobilized on it. The apparent Michaelis constant of the Immobilized β-galactosidase was larger than that of native β-galactosidase, whereas the opposite tendency was observed for the maximum reaction velocity. The activity of the immobilized β-galactosidase increased as the fiber diameter decreased. These findings indicated that lactose hydrolysis took place in the vicinity of the fiber surface. The immobilized β-galactosidase had a higher thermal stability than the native type.

Characteristic properties of plastic instabilities were studied using depth-sensing microhardness experiments on an Al–3.3 wt.% Mg alloy and computer simulations based on a macroscopic dynamic model of the experimental setup. A stepwise increase was observed in the indentation depth versus load (d-F) curves measured in constant loading rate mode, indicating hardness oscillations around a nearly constant value of the conventional dynamic microhardness. These oscillations were correlated with plastic instabilities starting from the contact surface between the sample and the indenter head. Taking into account the experimentally determined connection between the hardness oscillations and the indentation velocity, a dynamic model was proposed for the characterization of instability steps.

Rutile nanocrystals were directly prepared under hydrothermal conditions using TiCl4 as the starting material. The formation reactions proceeded by suppressing the crystallization of the other TiO2 polymorphs using a fixed concentration of 0.62 M [Ti4+]. With increasing reaction temperatures from 140 to 220°C, rutile nanocrystals were found to grow from 5.4 to 26.4 nm in size, and by varying the reaction time from 2 to 120 h at 200°C the particle size increased from 17 to 40 nm. The grain-growth kinetics of rutile TiO2 nanocrystals under hydrothermal conditions was found to follow the equation, Dn = k0 × t × e(-Ea/RT) with a grain-growth exponent n = 5 and an activation energy of Ea = 170.8 kJ mol-1. The nanocrystals thus obtained consist of an interior rutile lattice and a surface hydration layer. With decreasing particle size, the hydration effects at the surface increase, while the rutile structure shows a lattice expansion and covalency enhancement in the Ti-O bonding.

The influence of grain size and density of yttria-tetragonal zirconia polycrystals (Y-TZPs) ceramics on mechanical properties and on low-temperature aging degradation (LTD) in air and in hot water was investigated. A TZP powder containing 3 mol% Y2O3 was consolidated by slip casting and densified by the sintering/hot isostatic pressing (HIP) method. Only the presintered samples that contained less than 0.15% open porosity reached near full density after HIP. The best conditions to reach full density were found to be attained by presintering and HIP both at 1400 °C. At these conditions, some of the best mechanical properties such as modulus of rupture and Weibull modulus reached 1397 ± 153 MPa and, 10.6, respectively. These values were clearly higher than those obtained from sintered bodies and samples hot isostatically pressed at 1600 °C. Aging degradation of 3Y-TZP materials can be avoided through microstructural design. Fully dense materials with a critical grain size <0.36 μm did not show any evidence of degradation after extreme aging conditions at pressurized autoclaving in hot water at 100, 200, and 260 °C for 8 h. We propose a criterion to predict degradation in air as well as in hot water for the characterized materials based on the microstructure and density control of the samples.

In this study, the ideal tensile and shear strength of single-crystal β–Si3N4 was calculated using an ab initio density functional technique. The stress-strain curve of the silicon nitride polymorph was calculated from simulations of uniaxial strain deformation. In particular, the ideal strength calculated for an applied ∈11 tensile strain was estimated to be approximately 57 GPa. Recently, a good correlation was reported between the shear modulus of high-strength materials and the experimentally determined Vickers indentation hardness value. Using the reported correlation an estimate was made of the Vickers indentation hardness of single-crystal β–Si3N4: approximately 20.4 GPa.

Having recently succeeded in synthesizing large single crystals of (Ca2CoO3)CoO2 (Co-349) with superior thermoelectric properties using a modified flux method, we have prepared a composite material of Co-349 powder and single crystals and examined its thermoelectric properties. The electrical conductivity σ of this composite, which contained 20 wt.% single crystals, was higher than that of a sample without the single crystals. While the achievable effect has yet to be fully realized, improved grain alignment and the effect of current bypassing grain boundaries through the large single crystals in the composite are thought to cause the increasing σ, which consequently results in an enhanced thermoelectric figure of merit of about 0.56 at 973 K in air.

Structure and ultraviolet emission characteristics of amorphous ZnO films grown on indium tin oxide coated glass substrates by electrophoretic deposition were investigated using Raman spectra and photoluminescence. The Raman spectrum shows a unique resonant multiphonon process within amorphous ZnO films. The photoluminescence spectrum of amorphous ZnO films shows a strong ultraviolet emission while the visible emission is nearly fully quenched. The transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectrum, and infrared spectrum are used to detect the structure of amorphous ZnO powder. The complex water plays an important role in the photoluminescence intensity emission.

Iron oxide (α–Fe2O3) and cobalt oxide (Co3O4) were produced via precipitation reactions carried out in a continuous hydrothermal apparatus. The resulting particles were nanometer-sized because of the high supersaturations generated when metal nitrate solutions are combined with sodium hydroxide or with hot, compressed water. The average particle size increased with the metal nitrate feed concentration and with residence time. A logarithmic relationship was obtained between the particle size and feed concentration and between particle size and residence time in the apparatus. The production of nanoparticles with narrow size distribution was shown to require low metal nitrate feed concentrations and short residence times. In the range of temperatures studied in this work, temperature apparently had no effect on the size except when cobalt nitrate was contacted with supercritical water in the absence of sodium hydroxide. In this case, large cobalt oxide particles were obtained when the temperature was above the critical temperature of water.

In this work, glass formation under high-energy ball milling was investigated for a (Ti0.33Zr0.33Hf0.33)50(Ni0.33Cu0.33Ag0.33)40Al10 high-order alloy system with equiatomic substitution for early and late transition-metal contents. For comparison, an amorphous alloy ribbon with the same composition was prepared using the melt-spinning method as well. Structural features of the samples were characterized using x-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. Mechanical alloying resulted in a glassy alloy similar to that obtained by melt spinning. However, the glass formation was incomplete, and a small amount of unreacted crystallites smaller than 30 nm in size still remained in the final ball-milled product. Like the melt-spun glass, the ball-milled glassy alloy also exhibited a distinct glass transition and a wide supercooled liquid region of about 80 K. Crystallization of this high-order glassy alloy proceeded through two main stages. After the primary nanocrystallization was completed, the remaining amorphous phase also behaved as a glass, showing a detectable glass transition and a large supercooled liquid region of about 100 K.

A semi-empirical interatomic potential of the Ni–W system was developed using a modified embedded-atom method (MEAM) formalism including second-nearest-neighbor interactions. The cross potential was determined by fitting physical properties of tetragonal Ni4W available in the literature. The MEAM potential was used to predict phase stabilities, lattice constants, and bulk moduli of nonequilibrium and equilibrium phases in the Ni–W system. The results were in good agreement with experimental information or first-principles calculation.

The ternary system of lead nickel niobate Pb(Ni1/3Nb2/3)O3 (PNN), lead zinc niobate Pb(Zn1/3Nb2/3)O3 (PZN), and lead zirconate titanate Pb(Zr1/2Ti1/2)O3 (PZT) was investigated to determine the influence of different solid state processing conditions on dielectric and ferroelectric properties. The ceramic materials were characterized using x-ray diffraction, dielectric measurements, and hysteresis measurements. To stabilize the perovskite phase, the columbite route was utilized with a double crucible technique and excess PbO. The phase-pure perovskite phase of PNN–PZN–PZT ceramics was obtained over a wide compositional range. It was observed that for the ternary system 0.5PNN–(0.5 - x)PZN–xPZT, the change in the transition temperature (Tm) is approximately linear with respect to the PZT content in the range x [H11505] 0 to 0.5. With an increase in x, Tm shifts up to high temperatures. Examination of the remanent polarization (Pr) revealed a significant increase with increasing x. In addition, the relative permittivity ([H9280]r) increased as a function of x. The highest permittivities ([H9280]r [H11505] 22,000) and the highest remanent polarization (Pr [H11505] 25 μC/cm2) were recorded for the binary composition 0.5Pb(Ni1/3Nb2/3)O3–0.5Pb(Zr1/2Ti1/2)O3.

Bulk glassy Zr55Al20–xCo25Nbx (x = 0 to 5 at.%) alloys with critical diameters of 2.5–5 mm and supercooled liquid region of 48–75 K were produced by copper-mold casting. These alloys were spontaneously passivated in 3 mass% NaCl and 1 N H2SO4 solutions. The addition of Nb to the alloy enhanced the pitting corrosion resistance in the NaCl solution and enabled the open-circuit potential in the H2SO4 solution. Zr- and Al-enriched passive films formed on the bulk glassy Zr–Al–Co–Nb alloys exposed to air and on those immersed in the solutions. The increase in Nb content of the alloys resulted in an increase in Zr and Nb concentrations and a decrease in Al concentration of the passive film. The Vickers hardness, Young's modulus, compressive fracture strength, fracture strain, and plastic strain of the bulk glassy Zr–Al–Co–Nb alloys were 550, 98 GPa, 2100 MPa, 2.9%, and 0.9%, respectively.

Superconducting Yba2Cu3O7−δ (YBCO) films with critical transition temperature Tc(0) of 90 K were fabricated via a fluorine-free, metal trimethylacetate based sol-gel route. Precursor films were spin-coated onto single-crystal (001) LaAlO3 (LAO) and (001) SrTiO3 (STO) substrates. Optimization of the burnout process resulted in films with excellent out-of-plane and in-plane texture. Transport critical current densities, Jc, of 1.6 and 1.1 MA/cm2 were obtained at 77 K in self-field on films grown on LAO and STO substrates, respectively. This is the first demonstration of high-Jc YBCO film fabrication using a fluorine-free, ex-situ process.

A frequent application of the nanoscratch technique is to estimate hardness of ultrathin films when substrate effects are encountered with the nanoindentation technique. A model based on the work of Goddard and Wilman, which assumes a rigid-plastic behavior of the deformed surfaces, is commonly used for the determination of hardness from scratch tests, yet it overestimates the hardness of materials by as much as a factor of three at very shallow indentation depths on the order of 1–10 nm. The Goddard and Wilman model was extended in this paper to include the effects of the component of the shear stress tangential to the meridianal plane and the elastic recovery of the plastically deformed surfaces assuming elastic-perfectly-plastic material behavior. The proposed model was subsequently verified by performing nanoscratch experiments on fused quartz, which is homogeneous and isotropic with no known surface layers and with known hardness. The hardness was calculated using both the model based on the work of Goddard and Wilman and the extended model. The hardness calculated using the extended model was in very close agreement with the accepted value of bulk hardness of fused quartz over the range of scratch depths tested, showing the importance of the effects of elastic recovery and interfacial shear stress. The model was further verified for the case of a pure aluminum sample and the native thin film coating of alumina that forms on the surface upon air exposure.

In this work, a systematic study of the influence of five deposition parameters, i.e., process pressure, substrate temperature, target power, and substrate bias, as well as gas composition on the residual stress in fully textured polycrystalline aluminum nitride thin films deposited on Si(100) wafers using the reactive sputtering method was performed. Post-growth residual stress measurements were obtained indirectly from radius of curvature measurements of the wafer prior to and after deposition. Two different techniques were used to determine the curvature: an optically levered laser beam and an x-ray diffraction method. Stresses in both cases were then evaluated using the Stoney formulation [G.G. Stoney, Proc. R. Soc. (London) A82, 172 (1909)]. Both methods give similar results, with slight quantitative differences. The existence of a transition region between tensile and compressive stress previously reported in the literature is also confirmed. The transition is shown to be strongly dependent on the process parameters. Optimal films regarding stress were grown at 2 mtorr, 900 W at the target, a 20/45 Ar/N2 gas mixture, and floating potential at the substrate. The substrate temperature did not influence the measured internal stress in the films.

A low-temperature metalorganic chemical vapor deposition process was developed and optimized, using a design of experiments approach, for the growth of ultrathin aluminum oxide (Al2O3) as a potential gate dielectric in emerging semiconductor device applications. The process used the aluminum β-diketonate metalorganic precursor [aluminum(III) 2,4-pentanedionate] and water as, respectively, the metal and oxygen source reactants to grow Al2O3 films over a temperature range from 250 to 450 °C. The resulting films were analyzed by x-ray photoelectron spectroscopy, x-ray diffraction measurements, Rutherford backscattering spectrometry, nuclear-reaction analysis for hydrogen profiling, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The as-deposited Al2O3 phase was amorphous and dense and exhibited carbon and hydrogen incorporation of, respectively, 1 and 10 at.%. Postannealing at 600 °C led to a reduction in hydrogen concentration to 1 at.%, while maintaining an amorphous Al2O3 matrix.

New Cu-based bulk glassy alloys with large supercooled liquid regions and high mechanical strength were formed in Cu–Hf–Al ternary systems. The large supercooled liquid region exceeding 70 K was obtained in the composition range of 40 at.% Hf at 2.5% Al, 37.5–50% Hf at 5% Al, and 45% Hf at 7.5% Al. The largest supercooled liquid region ΔTx(= Tx – Tg) was 91 K for Cu50Hf45Al5 alloy, and the highest reduced glass-transition temperature was 0.63 for Cu50Hf42.5Al7.5 and Cu52.5Hf40Al7.5 alloys. The alloys with large ΔTx values above 50 K were formed into bulk glassy rods with diameters up to 3 mm by copper mold casting, and the glassy alloy rods exhibited high compressive fracture strength of 2260 to 2370 MPa and Young's modulus of 121 to 128 GPa combined with elastic elongation of 1.9% to 2.0% and plastic elongation of 0.2% to 0.6%. No bulk glassy alloys were formed in the Cu–Hf binary system by copper mold casting, and, hence, the addition of 2.5% to 7.5% Al to Cu–Hf alloys was very effective for increasing glass-forming ability as well as the stabilization of supercooled liquid. The effectiveness can be interpreted on the basis of the concept of the formation of a unique glassy structure in special multicomponent alloys with the three component rules.

The valence and coordination structure of implanted Cu and Br ions were investigated by x-ray absorption fine structure spectroscopy in (2.4 MeV 6 × 1016 Br2+ ions cm−2+ 2 MeV 6 × 1016 Cu+ ions cm−2)-implanted silica glass. It was found that the implanted Cu and Br atoms were coordinated by oxygen atoms and silicon atoms, respectively, in as-implanted glass. After heating at 600 °C, at least two-thirds of the Cu atoms were coordinated by Br atoms without the formation of crystals. The γCuBr crystal was formed after heating to 1100 °C. It was deduced that the coordination structure of Cu and Br atoms depends on defects as well as thermochemical stability and mass transport processes.