Multidomained heteroepitaxial WO3 films were grown on Si(100) substrates using a (111)-oriented BaF2 buffer layer at the WO3–Si interface. The 30-nm-thick BaF2 layer, grown by very low rate molecular-beam epitaxy, consisted of four equivalent crystalline domains oriented about the BaF2[111] axis, which provided templates for heteroepitaxial WO3 film growth. The WO3 films were grown by electron cyclotron resonance oxygen plasma-assisted electron beam evaporation of a WO3 source, and the temperature range was varied between 25°C and 600°C. At an optimal deposition temperature of approximately 450°C, monoclinic-phase WO3 films were produced, which consisted of coexisting (002), (020), and (200) in-plane orientations with respect to the BaF2(111)/Si(100) substrate. During growth, an interfacial barium tungstate (BaWO4) reaction product formed at the WO3–BaF2 interface. The {112} planes of this BaWO4 layer also have a multidomained heteroepitaxial orientation with respect to the BaF2(111) buffer layer. Postdeposition annealing experiments in air for 24 h at 400°C indicated that the heteroepitaxial BaWO4 and WO3 layers remain stable. A thermodynamic argument is used to explain the BaWO4 interfacial reaction during initial growth stages, and kinetically limited diffusion processes through the BaWO4layer coupled with lattice matching across the WO3–BaWO4 interface are proposed to be responsible for the formation of stable WO3 films at later growth stages.

The improvement in mechanical properties of blended nanocomposites prepared using a low-viscosity, liquid epoxy resin and purified single-wall carbon nanotubes (SWCNTs) was evaluated. The macroscopic tensile stress–strain behavior for hybrid materials made with varying amounts of SWCNT was determined and showed little improvement in the breaking tensile strength. The corresponding variations in modulus and hardness were obtained using nanoindentation considering time effects and showed quantifiable but modest improvements. The small changes in the observed stiffness and breaking strength of carbon nanotube composites is due to the formation of bundles and their curvy morphology.

The glass transformation (Tg) and onset crystallization temperatures (Tx) of (100 – x) TeO2–(x)V2O5, (x = 10, 35, and 50 mol%) glasses were measured in the temperature range 300–800 K by differential scanning calorimetry at different heating rates. From the variation of the heating rate, the glass transition activation energy was calculated by different methods. The glass stabilization range S = Tx – Tg was calculated for the whole glass series. Quantitative analysis of the glass transformation temperature was carried out using the calculated number of bonds per unit volume and oxygen packing density.

The thermomechanical behavior of Cu thin films, 600–1125 nm thick and encapsulated between SiNx barrier and SiNx or AlNx passivation layers on silicon substrates, was studied during thermal cycling between room temperature and 400 or 500 °C using the substrate curvature method. Films were prepared with varying oxygen contents, and the distribution of oxygen through the thickness of selected films was studied before and after thermal cycling using secondary ion mass spectrometry. Large variations in the thermomechanical behavior with oxygen content were found and correlated with segregation of oxygen to the film/barrier and film/passivation interfaces. These variations are thought to be due to recovery of stored misfit dislocation energy, which is, in turn, controlled by oxygen in the film. Effects of oxygen on film deformation through variations in interfacial adhesion and diffusion-induced dislocation glide are considered.

Surface acoustic wave (SAW) propagation properties of gallium nitride (GaN) epitaxial layers on sapphire were theoretically and experimentally characterized. GaN thin films were grown on a c-plane sapphire substrate using a metalorganic chemical vapor deposition system. The experimental characterization of SAW propagation properties was performed with a linear array of interdigital transducer structures, while SAW velocities were calculated by matrix methods. Experimentally, we found pseudo-SAW and high-velocity pseudo-SAW modes in the GaN/sapphire structure, which had a good agreement with calculated velocities.

Er3+-doped Al2O3 powders were prepared by the sol-gel method, using aluminum isopropoxide [Al(OC3H7)3]-derived Al2O3 sols. The phase content diagram for the Er-doped Al–O system with the doping concentration up to 20 mol% is presented for sintering temperature from 550 to 1250 °C. The different crystalline types of (Al,Er)2O3 phases—γ, θ, α—and two Er-Al-O phases—ErAlO3 and Al10Er6O24—were detected. The Er3+ doping in the Al2O3 phases has a significant effect on phase transformations for γ → θ and θ → α, indicating the enhancement for stability of the γ and θ phases. Compared with the γ–Al2O3 phase, the γ–(Al,Er)2O3 phase can be obtained at high temperatures up to about 1100 °C. The θ–(Al,Er)2O3 phase, together with the α–(Al,Er)2O3 phase, was still observed at 1200 °C under the high Er3+ doping concentration. The Er3+ doping suppressed the crystallization of the γ and θ phases. At a low Er3+ doping concentration from about 2 to 5 mol%, the ErAlO3 phase precipitated out around 1100 °C. The Al10Er6O24 phase was observed at all sintering temperatures; the precipitation was carried out to all Er3+ doping concentrations with increasing sintering temperatures up to about 1200 °C.

Giant magnetoimpedance (GMI) and giant stress-impedence (GSI) effects were realized in multilayered FeSiB/Cu/FeSiB films with a meander structure by magnetron sputtering on thin glass substrates. The GMI and GSI effects were studied in the frequency range of 1–40 MHz for the multilayered FeSiB/Cu/FeSiB films. Experimental results show that a large negative GMI ratio of –23% is obtained at Ha=12 kA/m for a frequency of 20 MHz. The GSI ratio is –20% for a frequency of 1 MHz with the deflection of 150μm of the multilayered FeSiBsCu/FeSiB films. The GSI effect is attractive for stress or pressure sensor applications.

Physical properties of a-Si:C:H films, including composition, optical constants, microhardness, and surface energy, were investigated. A factorial experimental design was employed to establish the effects of plasma-assisted chemical vapor deposition parameters on the physical properties of the films. The dynamics of the plasma deposition process are discussed in relation to the interactions observed among the process variables and the effects of the variables on the physical properties of the films.

A eutectic point in Pr-rich Pr-(Cu,Ni)-Al alloys was experimentally determined by measuring the solidus temperature (Tm) and liquidus temperature (T1). It was found that Pr68(Cu0.5Ni0.5)25Al7 (at.%) is at the eutectic composition in the pseudoternary Pr–(Cu0.5Ni0.5)–Al alloys. The alloy Pr68(Cu0.5Ni0.5)25Al7 exhibits better glass-forming ability (GFA) than the ternary eutectic alloy Pr68Cu25Al7. However, the best GFA was obtained at an off-eutectic composition (Pr54[Cu0.5Ni0.5]30Al16) in the Pr–(Cu0.5Ni0.5)–Al alloys, which can be formed in fully amorphous rods with diameter of 1.5 mm by copper mold casting. Moreover, the glass-transition temperature Tg increases quickly (from 367 to 522 K) with the increasing of the Al content (from 3 to 27 at.%). The deviation of the best GFA composition from the eutectic point [Pr68(Cu0.5Ni0.5)25Al7] was explained in terms of the asymmetric coupled eutectic zone, the competition between growth of crystalline phase and formation of amorphous, and the higher glass-transition temperature Tg on the hypereutectic side.

High critical current density (high-Jc) YBa2Cu3O7–δ (YBCO) films were obtained by pulsed laser ablation on biaxially textured Cu substrates. To achieve epitaxy of LaMnO3 (LMO) on Cu, thin epitaxial Ni overlayers were deposited on Cu tapes. The structure comprises the layer sequence of YBCO/LMO/Ni/Cu. For 200-nm-thick YBCO, self-field Jc values exceeding 1 × 106 A/cm2 at 77 K were achieved. Characterization of these short prototype conductors revealed good structural and morphological properties. Magnetic analysis suggested that hysteretic loss due to the ferromagnetic Ni overlayer is minimal.

The microstructure of the Ni-based superalloy IN100 processed by a powder metallurgy route was evaluated to reveal the structures, volume fractions, distributions, and chemistries of the various phases present. These data were compared with those predicted by computational thermodynamics. It is shown that the microstructural parameters expected on the basis of global equilibrium conditions differ significantly from those measured experimentally. However, modification of these calculations by use of constrained and successive equilibria compensated for kinetic effects and led to accurate (or better) predictions of phase volume fractions and chemistries in this alloy. This demonstrated that such modified phase equilibria calculations could be powerful tools for modeling microstructures, even in complex multicomponent alloys processed under nonequilibrium conditions.

The polarization reversal process in a rhombohedral ferroelectric ceramic material was investigated using field-induced strain measurements and texture development. Special attention was focused on the difference in the field-induced strains between the first quarter cycle and subsequent loading conditions. Results show that the initial field-induced strain is about twelve times greater than the subsequent strain, which immediately suggests that mechanisms involved in these conditions during the polarization reversal process are different. The difference in the magnitude of field-induced strain is discussed in terms of 180° and non-180° domain reorientation processes.

SiC ceramics were prepared from a β–SiC powder doped with two different sintering additives—a mixture of La2O3 and Y2O3 and a mixture of Al2O3 and Y2O3—by hot pressing and annealing. Their microstructures, phase compositions, lattice oxygen contents, and thermal conductivities were evaluated. The SiC doped with rare-earth oxides attained thermal conductivities in excess of 200 W/(m K); however, the SiC doped with additives containing alumina had thermal conductivities lower than 71 W/(m K). The high thermal conductivity of the rare-earth-oxide-doped SiC was attributed to the low oxygen content in SiC lattice, high SiC–SiC contiguity, and lack of β– to α–SiC polytypic transformation. The low thermal conductivity of the alumina-doped SiC was attributed to the point defects resulting from the dissolution of Al2O3 into SiC lattice and the occurrence of polytypic transformation.

The reduction of tungsten carbide (WC) to elemental tungsten by reaction with a Zr–Cu melt was examined. Dense WC disks were immersed in a vertical orientation in molten Zr2Cu at 1150–1400 °C for 1.5–24 h. Continuous, adherent layers of W and ZrC formed at WC/melt interfaces. The rates of thickening of the W and ZrC product layers were examined as a function of reaction time and temperature and position along the vertical WC surface. Such kinetic data, along with microstructural analyses, indicate that the incongruent reduction of tungsten carbide is likely to be controlled by carbon diffusion through one or both of the product layers.

The structural, transport, and magnetic properties of La0.65Ca0.35MnO3 films grown on MgO substrates by pulsed-laser deposition under different substrate arrangements in the laser plume were studied. In addition to the standard substrate arrangement in the main stream of particles, substrate arrangements in the periphery area of the laser plume and in an area shielded from the plume were used. In the latter case, the deposition occurs from the flux that is reflected from a side screen. It was found that the substrate arrangement influences considerably the surface topography, structure, chemical composition, magnetic, transport, and magnetoresistance properties of the films. It was found that the substrate arrangements in the periphery area of the laser plume and in the shielded area of the plume eliminate deposition of large particulates. The latter arrangement is the most effective in elimination of particulate deposition. In this case, the film has the smoothest surface with root mean square roughness of about 2 nm. The data obtained revealed interesting correlations between the structural and transport properties as well. In particular, films deposited in the periphery and shielded areas of the laser plume have increased nonstoichiometry (La deficiency), higher resistivity, and broader magnetic transitions. The polycrystalline nature of the films studied is taken into account in the discussion of their transport properties.

A moderate chemical method [i.e., the reaction of diborane (B2H6) and a mixture gas of ammonia and nitrogen (NH3/N2) over nanoscale iron boride at 1100 °C] was developed to explore the boron nitride (BN) nanostructures. The products were well characterized by high-resolution electron microscopy and energy-dispersive x-ray spectroscopy. Two types of novel core–shell nanocapsules of amorphous boron core encapsulated in crystalline boron nitride shell were obtained. The first one looked like a peanut with an amorphous B core containing a trace of BN crystallites, a transition layer of BN nanofibers and amorphous B, and a thornlike shell of BN nanofibers. The second one looked like a perfect sphere consisting of a pure amorphous B core and a rather smooth crystalline BN shell. These results not only provided us a new chemical method for preparing BN nanostructures but also enriched the important BN nanostructures family. A growth mechanism is also briefly discussed.

This study focused on investigating the role of interfacial microcracking of injection-molded Cr3C2/Al2O3 composite on the erosion mechanism under an impingement erosion test rig. The surface residual strain (stresses) as well as damage were compared in both airborne and wet erosion. The delays in crack propagation at interfacial or triple points and the crack direction changes were frequently observed in the composite. Spontaneous microcracking induced from sintering process, due to thermal expansion mismatch between alumina and chromium carbide, played a key role in erosion mechanism.

A model is developed that describes the sharp indentation behavior of time-dependent materials. The model constitutive equation is constructed from a series of quadratic mechanical elements, with independent viscous (dashpot), elastic (spring), and plastic (slider) responses. Solutions to this equation describe features observed under load-controlled indentation of polymers, including creep, negative unloading tangents, and loading-rate dependence. The model describes a full range of viscous–elastic–plastic responses and includes as bounding behaviors time-independent elastic–plastic indentation (appropriate to metals and ceramics) and time-dependent viscous–elastic indentation (appropriate to elastomers). Experimental indentation traces for a range of olymers with different material properties (elastic modulus, hardness, viscosity) are econvoluted and ranked by calculated time constant. Material properties for these polymers, deconvoluted from single load–unload cycles, are used to predict the indentation load–displacement behavior at loading rates three times slower and faster, as well as the steady-state creep rate under fixed load.

Wetting properties of lead-free solders, Sn–0.7 wt.% Cu and Sn–3.5 wt.% Ag, pure Sn, and conventional Sn–40 w.t% Pb on Ni, Cu, and Ag substrates at 250 and 240 °C were determined by using a wetting balance technique. Wetting times and wetting forces were determined directly from the wetting curves, and surface tensions of molten solders were calculated from the wetting force measurements. A statistic tool, analysis of variance (ANOVA), was used to analyze the experimental results. By using the wetting time as an indication, it was found that Sn–Pb exhibited the best wetting followed by Sn–Ag, Sn–Cu, and Sn, in that order. A very significant but frequently ignored issue is that most solders react with substrates, and the molten solders are not in contact with the original substrates but rather with intermetallic compounds. On the basis of theoretical analysis and experimental observations, it was concluded that the withdrawing forces and the surface tensions of the molten solders determined by the present technique are not significantly affected by the interfacial reactions if the interfacial reactions are not too excessive. However, wetting times are strong functions of both solders and substrates and the interfacial reactions between them.

X-ray powder diffraction studies on (Pb1−xCax)TiO3 ceramic powders revealed the presence of superlattice reflections due to antiphase and inphase tilts of oxygen octahedra for x ≥ 0.421. Rietveld analysis of the powder x-ray diffraction data confirmed that the structure of (Pb1-xCax)TiO3 is orthorhombic with Pbnm space group and a−a−c+ tilt system for x ≥ 0.421. For compositions with 0 < x ≤ 0.416, the structure was tetragonal, and the tetragonality decreased with increasing Ca2+ content.