Thin films of (Y0.92Eu0.08)2O3 were synthesized through chemical vapor deposition of β-diketonate precursors onto glass and sapphire substrates. The films were weakly luminescent in the as-deposited condition and were composed of spherical particles 3 μm in diameter. A KrF laser was pulsed for 25 ns from 1–3 times on the surface of the films. One pulse was sufficient to melt the film and repeated pulses caused ablation of the material. Melting of the film smoothed the surface, increased the density, and increased the photoluminescent emission intensity.

(Ba1−xLax)3Cu3(O, F)y films were prepared using a sol-gel method. Phases, the c lattice parameters of which are about 13.8, 13.1, and 11.6 Å, respectively, were formed in the films. The compound with the c parameter of ˜13.8 Å is considered to be a Ba2−xLaxCuO2F2+δ which has the La2CuO4-type structure inserted with fluorine. The compound with the c parameter of ˜11.6 Å is thought to have a three-layered structure of the perovskite block which is arisen by ordering between La and Ba elements. The films containing these compounds showed some interesting anomalies in SQUID measurements. However, no film showed a drastic decrease of electrical resistance.

Diamond films were deposited on the p-type Si substrate with the hot filament chemical vapor deposition (HFCVD). Residual stresses in the films were measured in air by the laser curvature, the x-ray diffraction (XRD) dϕψ − sin2ψ, and the Raman peak shift methods. All of the measuring methods showed similar behaviors of residual stress that changed from a compressive to a tensile stress with increasing the film thickness. However, values of residual stresses obtained through the Raman and XRD methods were 3–4 times higher than those of the curvature method. These discrepancies involved the setting of materials constants of CVD diamond film, and determination of a peak shifting on the XRD and Raman method. In order to elucidate the disparity, we measured a Young's moduli of diamond films by using the sonic resonance method. In doing so, the Raman and XRD peak shift were calibrated by bending diamond/Si beams with diamond films by a known amount, with stress levels known a priori from the beam theory, and by monitoring the peak shifts simultaneously. Results of each measuring method showed well coincidental behaviors of residual stresses which have the stress range from −0.5 GPa to +0.7 GPa, and an intrinsic stress was caused about +0.7 GPa with tensile stress.

It was demonstrated that liquid phase separation by nucleation and growth (LNG) occurs in undercooled molten Pd40.5Ni40.5P19 for undercoolings ΔT ≤ 60 K (ΔT = Tl − T where Tl is the liquidus and T is the kinetic crystallization temperature), and liquid state spinodal decomposition (LSD) occurs for ΔT ≥ 100. For 60 ≤ ΔT ≤ 100 K, it is the transition regime from LNG to LSD. A ternary phase diagram is introduced to summarize the reactions occurred in undercooled molten Pd40.5Ni40.5P19. Finally, it is suggested that LSD has an important impact on glass-forming ability of metallic alloys.

When molten Pd40.5Ni40.5P19 is undercooled way below its liquidus Tl, liquid state spinodal decomposition is observed. Crystallization of this system is particularly interesting because it has plenty of interfaces. The microstructure of an as-crystallized specimen can be divided into four regions, namely, A: random spinodal; B: aligned and elongated spinodal; C: coarsened spinodal and island structure; and D: rod structure and ternary eutectics. The origin of these different microstructures is discussed.

Environmental and internal-hydrogen embrittlements in stress-relieved and recrystallized Ni−16.5Al−8Cr−0.8Hf−0.1B−0.03Y (at. %) have been studied. The stress-relieved Ni3Al-based alloy showed environmental embrittlement when tested in air or in hydrogen gas. The embrittlement is more severe in hydrogen gas than that in air. The recrystallized Ni3Al-based alloy was not susceptible to air, but it was embrittled severely by hydrogen gas and exhibited not only a grain interior but a severer grain boundary embrittlement. When tested in air, the stress-relieved Ni3Al was insensitive to internal hydrogen; however, the recrystallized Ni3Al showed a certain susceptibility to internal hydrogen. With increasing the internal hydrogen content in the alloy, the ductility of the recrystallized Ni3Al decreased steadily and a certain degree of grain boundary embrittlement was observed.

Fine particles of nickel aluminides were synthesized for the first time by reducing mixtures of AlCl3 + NiCl2 vapors by hydrogen. A thermodynamic equilibrium calculation was carried out in the Ni–Al–H–Cl–Ar system to evaluate the effect of the reactant partial pressures and temperature on the formation of intermetallic phases. A single intermetallic phase was found to be feasible only in a very narrow range of the reactant partial pressures. For all other conditions the predicted solid product was a mixture of two phases. Experimentally, Ni3Al was formed along with metallic Ni. Though the coreduction of NiCl2 and AlCl3 by H2 to form Ni3Al is thermodynamically favorable at 1100 °C, it did not happen experimentally under the conditions of this work. However, with a small addition of aluminum vapor, the coreduction reaction proceeded as expected by thermodynamics. The effects of reactant partial pressures and temperature were studied. The content of Ni3Al was maximized to 52 mol% at 1050 °C under the partial pressures of H2, AlCl3, and NiCl2 at 57, 1.5, and 0.5 kPa, respectively. The product particles, as observed by TEM, were very fine, but usually agglomerated. The electron diffraction analysis identified the particles of NiAl and NiAl3 along with Ni3Al and metallic Ni.

The template-synthetic method is a general approach for preparing tubular micro-and nanostructures. This method has been used to prepare micro- and nanostructures composed of metals, carbons, semiconductors, polymers, and Li+-intercalation materials. This paper describes the use of the template method to prepare composite tubular micro- and nanostructures. These composite structures consist of an outer tubule of one material surrounding inner tubules of different materials. Chemical strategies used to prepare these composite tubular structures include electroless deposition of Au, electropolymerization of conductive and insulating polymers, electrodeposition of metals and semiconductors, carbonization of polymer precursors, chemical vapor deposition synthesis, and sol-gel synthesis.

Electromechanical testing involving simultaneous electrical and mechanical measurements under load was used to study the fiber-matrix interface, the fiber residual compressive stress, and the degree of marcelling (fiber waviness) in carbon fiber composites. The interface study involved single fiber pull-out testing while the fiber-matrix contact electrical resistivity was measured. The residual stress study involved measuring the electrical resistance of a single fiber embedded in the matrix while the fiber was subjected to tension through its exposed ends. The marcelling study involved measuring the electrical resistance of a composite in the through-thickness direction while tension within the elastic regime was applied in the fiber direction.

Zircon-particle-dispersed Al−13.5Si−2.5Mg is a structural composite material being investigated for lightweight, tribological applications. The conventional, powder-processed material, in the temperature range of 22–100 °C, yielded a low coefficient of linear thermal expansion (CTE) of 7.8 × 10−6 °C at 0.15 volume fraction (Vf), a 64% reduction of that of the alloy. The dry sliding wear rate and the coefficient of friction measured by the pin-on-the-plate technique at 4 kg load decreased significantly by 99% and 35.5%, respectively. A significant reduction, by 29%, in wear rate of the alloy was observed to occur only when more than 0.03Vf zircon was dispersed. An x-ray study showed that the interface reaction products consist of compounds of Mg, Ce, Cu, and Nb. Tensile failure of the reaction-sintered parts revealed a ductile mode of fracture, with the path traversing both through voids and the bonded particles while interface failure was observed in parts without Mg. An analysis of both the tribological and tensile properties showed that an optimal performance of this alloy at 0.15Vf zircon is achieved when the Mg content is between 2.5 and 3.5 wt. %.

Several kinds of Cu polycrystals with dispersed SiO2 particles of different volume fractions were tensile tested at high temperatures from 473 K to 1023 K. All of the alloys showed clear intermediate-temperature embrittlement (ITE). Although the temperature of minimum elongation was almost the same in all the alloys, temperature dependence of fracture strain depended strongly on the SiO2 volume fraction: (1) At a fixed temperature, the fracture strain tended to first decrease with increase in SiO2 volume fraction, showed minimum in an alloy with certain volume fraction, and increased again with increase in volume fraction. (2) With increase in SiO2 volume fraction, the temperature range of ITE became narrower and sharper. These results were reasonably understood by considering the occurrence of stress concentration at grain-boundary particles induced by grain-boundary sliding (GBS) and occurrence of dynamic recrystallization and stress relaxation by Cu/SiO2 interfacial diffusion.

Biaxially aligned YSZ thin films with strong [100] fiber texture were formed on a polycrystalline Ni-based alloy by off-normal ion-beam-assisted deposition. Growth structures were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), etc., and the alignment mechanism was discussed using a selective growth model. Peculiar structural evolution of the crystalline orientation was observed and its development was well described by an exponential equation. It was explained as a collaboration of an anisotropic growth condition and epitaxial crystallization. The [100] fiber texture was formed by columnar structures of diameter of 30–100 nm, which were composed of 5–10 nm diameter crystallites. Very smooth surfaces were observed by AFM imaging with a roughness of 2–3 nm and a peculiar ripple structure. The origin of the azimuthal alignment was discussed with emphasis on the surface structure of YSZ films produced using ion-beam-assisted deposition (IBAD) and the etching rate measurements of (100) surfaces of YSZ single crystals.

Hollow cathode arc plasma chemical vapor deposition was employed to grow crystalline diamond films using 1.5% to 7% of methane in hydrogen. The growth rate was as high as 3.2 μ/h when using 5% CH4/H2 at a pressure of 15 Torr and a substrate temperature of 1083 K. However, an intermediate layer of several hundred nanometers was observed at the film-substrate interface by cross-section SEM. Raman and XPS characterizations showed that the interfacial layer consisted of sp2 carbon and TaC with Ta vaporized from the hot cathode tube. XRD and XPS results further showed that the deposited diamond films also contained TaC. Ta composition in the film increased with the increase of growth pressure, the reduction of substrate temperature, and the increase of H2 flow in the Ta tube. The diamond films deposited by using CHCl3 as carbon source had Ta concentrations one order of magnitude higher than those using CH4, as shown by XPS results, but the nucleation densities using CHCl3 were always higher than those using CH4.

Analytical TEM and HREM have been used to examine the structure of BaAl2Si2O8 crystals produced within oxidized Ba–Al–Al2O3–SiO2 precursors upon annealing: (i) at ≤650 °C and (ii) up to 1650 °C. A BaAl2Si2O8 polymorph with a c-axis parameter of 15.6 Å was detected after annealing at ≤650 °C. Stacking faults and antiphase boundaries were detected within this polymorph after the 650 °C treatment. After a 15 h heat treatment at 1650 °C, convergent beam diffraction patterns and HREM confirmed that the predominant phase was β–hexacelsian. Although antiphase boundaries were absent in the β–hexacelsian crystals, dislocations and stacking faults were detected after the 1650 °C anneal. The generation of defects in BaAl2Si2O8 crystals within specimens annealed at ≤650 °C and at 1650 °C is discussed in light of prior structural analyses.

This paper is the first report of the synthesis of a sinteractive single-phase microstructure yttrium disilicate precursor powder using hydrothermal processing. The effect of the pH of the precursor chemicals on the ease of formation of a single-phase material was investigated using x-ray diffraction, TEM, and SEM. Under very acidic conditions (pH 1), the formation of yttrium chloride, in addition to the yttrium disilicate precursors, produced a powder that absorbed moisture, did not sinter well, and produced a two-phase interpenetrating microstructure after sintering. At pH 6, yttrium chloride no longer formed, but the interpenetrating network persisted after sintering. Only under basic conditions (pH 10) did single-phase yttrium disilicate form after sintering. This work is noteworthy because the calcination time of 1 h required for the formation of this ceramic at 1050 °C is over an order of magnitude lower than the calcination times of over 100 h required when calcined in the temperature range 900 °C to 1150 °C, as reported previously by other workers.

Helical etch channels were found to form in α-quartz when treated with anhydrous HF vapor at 400 °C. Both hydrogen and fluorine species were determined to play an important role in helix formation. Crystal orientation, quartz source, etch channel density, and surface pretreatments had no influence. Helix formation was altogether arrested when water was present in the etch vapor. The genesis of the helices remains unknown.

Biaxially textured YSZ films have a large technical relevance for power or electronic applications of HTS films. The YSZ serves as a diffusion barrier and as a template for an epitaxial growth of the HTS. On polycrystalline substrates the biaxial alignment is achieved by using an ion-beam-assisted deposition method. The best obtained textures were characterized by a full width at half maximum of 7° in an 〈111〉 x-ray diffraction Φ scan. The FWHM decreases with increasing film thickness. The growth mechanism is investigated with respect to three important effects: nucleation, growth selection, and homoepitaxial growth. It could be shown that during nucleation at the beginning of deposition the angle between the assisting beam and the substrate normal has to be fixed at 55°, whereas during the growth selection this angle can be varied. Especially the homoepitaxial effects allow changes in the deposition conditions without destroying the already achieved texture quality.

Nineteen disks of IR window grade, hot pressed magnesium fluoride (˜0% porosity, grain size ˜1 μm) previously loaded in ring-on-ring flexure tests were used to analyze the crack branching patterns. Fractal geometry was used to determine the crack branching fractal dimension which was named the crack branching coefficient or CBC. The failure stress was proportional to the CBC and the number of pieces generated during the fracture. Thus, the number of pieces was proportional to the crack branching coefficient. The crack branching coefficient is distinct from the fractal dimension obtained from the onset of mist and hackle on the fracture surface. The fractal dimension of the fracture surface is, in most cases for brittle materials, a constant and related to the crack tip stress field. The crack branching fractal dimension is a function of the stress at fracture and the far-field stress distribution, or in other words, related to both the type and magnitude of loading. The findings in this work have strong implications for many commercial processes such as comminution, attrition, grinding, and basic studies in crack branching.

The effect of shock compression on the solid-state chemical reactivity of titanium and carbon powder mixtures was investigated with the objective of forming net-shaped TiC ceramics with a fine-grain microstructure. The combination of defect states and intimate interparticle contacts introduced during shock compression results in significant enhancement of the otherwise sluggish solid-state diffusion of Ti and C through the TiCx boundary layer. The apparent activation energy for TiCx formation was determined using solid-state reaction kinetics models, and was found to be reduced by four-to-six times that of diffusion of Ti into TiCx and two-to-three times that of diffusion of C in TiCx. As a result, net-shaped sections of shock-densified compacts (˜85% dense) were reaction synthesized via solid-state diffusion, producing microstructures with grain size <6 μm and microhardness of ˜2000 kg/mm2, in contrast to statically pressed powder compacts which reacted by a combustion process resulting in a highly porous product.

Using the hydrolysis of appropriate alkoxide mixtures in water-in-oil microemulsions, nanocrystalline BaTiO3 has been prepared in the form of nonaggregated, cube-shaped crystals at room temperature without any sintering process as is demonstrated by means of x-ray diffractograms and transmission electron micrographs. By variation of the length of the hydrophilic part of the surfactant molecules, the diameter of the water droplets in the microemulsions could be tuned to values between 8 and 55 nm as determined by dynamic light scattering. The size of the resulting nano-BaTiO3 (6 nm ≤ 〈d〉vol ≤ 17 nm) was evaluated from the line broadening of x-ray reflections and correlates to the droplet size. The particle size distribution is very narrow, and in some cases nearly monodisperse.