Scanning electron micrographs of indents in (111) silicon reveal that a thin layer of material immediately adjacent to the indenter is plastically extruded. The fact that the material can be deformed in this way indicates that it has metallic-like mechanical properties. This is presented as new evidence that a pressure-induced phase transformation to the metallic state occurs during the indentation of silicon.

Prolonged exposure of chemical vapor deposited, polycrystalline ZnSe to high ac voltages in the presence of a 1 molal NaCl solution induces severe mechanical damage. The damage takes the form of defects which originate at the surface and grow intergranularly into the bulk with a bush-like morphology. Neither exposure to the salt solution in the absence of the high voltage nor low voltage dc electrolytic exposure produces the defects. The damage may be associated with an intergranular hydride phase or grain boundary impurity segregations present or formed during the environmental exposure.

Films of chemically disordered fcc Ni3Al were synthesized by the vacuum evaporation of Ni3Al onto room temperature and liquid nitrogen temperature substrates. X-ray diffractometry and transmission electron microscopy showed the material to be single phase with an average grain size of about 4 nm. The formation of the equilibrium L12 ordered phase occurred simultaneously with grain growth at temperatures above 350°C. Differential scanning calorimetry provided ordering enthalpies of 7 kJ/mole and 9 kJ/mole for material evaporated onto room temperature and liquid nitrogen temperature substrates, respectively.

A new regime of hillock growth has been observed in patterned Al98.5 W.%Si1.0 Wt.%-Cuo0.5 wt.% films. The “surface” hillock and “side” hillock, which have been seen previously, form on patterned metal lines having linewidths greater than the larger Al alloy grain sizes (∼3 μm). None is seen on the fabricated lines having linewidths between 0.9 and 2 μm where long-range grain boundary diffusion cannot occur because of its bamboo structure. However, a new type of hillock, the “line hillock”, occurs in structures having linewidths of 0.6 μm. The presence of this last type of hillock is inconsistent with the current understanding of hillock formation and may present severe restrictions on the down-sizing of ultra–large–scale integrated devices.

We have measured enthalpies of formation of YBa2Cu3O7−x, Y2BaCuO5, YBa2Cu4O8, and BaCuO2 using high precision isothermal solution calorimetry. Thermodynamic analysis of the calorimetric data indicates that YBa2Cu3O7−x at the pure-phase composition (1:2:3 cation ratio) is metastable at ≍873 K and 1 atm Po2.

Thin-film superconductors of TlBaCaCuO (TBCCO) and YBaCuO (YBCO) were fabricated via an electrodeposition process. The precursors of the superconducting TBCCO films were codeposited at a constant potential of −4 V onto a silver-coated SrTiO3 substrate. The YBCO precursors also were codeposited but under pulsed-potential conditions (in order to improve the film morphology) and onto a silver-coated MgO substrate. The pulsed-potential cycle consisted of 1 s at −4 V followed by 1 s at −1 V. The post-annealed TBCCO film showed zero resistance at about 102 K and critical current density at 76 K of 20 000 A/cm2 in zero magnetic field and 5000 A/cm2 in a 10 kOe field parallel to the film plane. The post-annealed YBCO film showed zero resistance at approximately 80 K and critical current density of 5160 A/cm2 at 4 K in zero magnetic field.

Amorphous powders in the Cs2O–Al2O3−SiO2 system were prepared by sol-gel processing. Gels made from TEOS, Al-chelate, and Cs-acetate were dried and calcined to obtain molecularly mixed powders of analyzed compositions in the range useful for conversion to pollucite (CsAlSi2O6) glass-ceramics. X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetry (TG), and scanning electron microscopy (SEM) were used to characterize the powders. A typical amorphous powder of analyzed chemical composition (in wt.%) = 28.05Cs2O, 37.77SiO2, and 37.96Al2O3 was found to have a glass transition temperature of 945 °C and a glass crystallization temperature of 1026 °C. Preliminary experimental results of densification and crystallization of the amorphous powders show pollucite/mullite phases to be present.

For Y1Ba2Cu3O7, using only reported monocrystal measurements and some analysis–theory, we estimated the complete nine-component orthotropic-symmetry elastic-stiffness matrix, the Voigt Cij matrix. Comparison with very-high-frequency tetragonal-symmetry phonon-dispersion results shows good agreement (9% on average), except for C12.

Experiments were conducted to determine the effect of various implanted species on the hardness of single crystal Ni3Al (Ta, Al, B) and polycrystalline TiAl (Ta, N, B). Implantations were conducted to yield about 7 at. % Ta under the peak and ∼30% Al, N, or B under the peak in the respective targets. Hardness was measured using the Nanoindenter. Results showed that Ta+-implanted Ni3Al softens due to disordering, and subsequent heat treating results in strengthening due to preferential occupation of Al lattice sites. However, B+ and Al+ implantations result in increases in the hardness, while heat treating returns the surface hardness to bulk values. Ta+, N+, and B+ implantations into TiAl all result in hardening with N+ implantation producing the greatest hardening by a factor of ∼1.9. The probable mechanism is solid solution strengthening.

Vacancy diffusion along two different high-angle twist grain boundaries (Σ5 and Σ13) was studied using the Embedded Atom Method (EAM). Vacancy formation energies in all the possible sites were calculated and found to be directly related to the degree of coincidence with the neighboring crystal planes. Optimal migration paths and migration energies were determined and found to be very low. The activation energies for self-diffusion at the boundaries were found to be less than half of the bulk value.

The modulated structure in solid solution Bi2+xSr2−xCu1+yO6+δ (0.1 < x < 0.6, y ∼ x/4) has been investigated by means of powder x-ray diffraction, electron diffraction, and transmission electron microscopy. The [010] component of the modulation vector decreases almost linearly with increasing x, from 5.2b (x = 0.1) to 4.2b (x = 0.5), where b is the unit length of the average structure along the [010] direction, and is little sensitive to excess oxygen content δ. A structure model of the modulation based on a periodic substitution of Sr for Bi and formation of Bi blocks whose size varies with x is proposed. Relations among various modulations appearing in other related phases such as the Pb-substituted 105 K Tc phase are discussed.

Fine powders with high sinterability of KSbOSiO4, an isomorphous derivative of KTiOPO4, have been prepared by a sol-gel route starting from stoichiometric mixtures of KSb(OH)6 and Si(OC2H5)4 with two types of polymerization catalysts: HNO3 and aqueous ammonia. KSbOSiO4 is formed upon calcination of the gels at 1373 K, and the XRPD studies show that HNO3 improves the crystallinity. However, the crystallite size is smaller with aqueous ammonia, which should then improve the sinterability.

Thin films of barium titanate (BaTiO3) have been deposited by pulsed-laser ablation onto (001)-oriented MgO substrates. The films were epitactic with the c-axis perpendicular to the film-substrate interface, as evidenced by both transmission electron microscopy (TEM) and ion-channeling techniques. The elastic resonance of 3.045 MeV α-particles, generating the 16O(α, α)16O reaction was used to determine the oxygen stoichiometry of the film and the minimum yield based on the oxygen peaks, thereby enabling conclusions to be drawn about the crystalline perfection of the oxygen sublattice.

Aluminum carbide was found to form catalytically at aluminum-silicon carbide interfaces upon exposure to water vapor. Samples, composed of approximately 2 nm thick layers of Al on SiC, were fabricated and reacted in vacuo, and analyzed using XPS. Enhanced carbide formation was detected in samples exposed to 500 Langmuirs H2O and subsequently reacted for 600 s at 873 K. The cause of the catalysis phenomenon is hypothesized to be the weakening of silicon-carbon bonds caused by very strong bonding of oxygen atoms to the silicon carbide surface. Aluminum carbide formation is of interest because of its degrading effect on the mechanical properties of aluminum/silicone carbide reinforced metal matrix composites, as well as its effect on the electrical properties of aluminum metallizations on silicon carbide layers in microelectronic components.

Some peculiar positive charge carriers are thermally generated in fused silica above 500 °C. These charge carriers appear to be positive holes, chemically O− states, probably arising from dissociation of peroxy defects. The charge carriers give rise to a pronounced positive surface charge which disappears upon cooling but can be quenched by rapid quenching from ≍800 °C. Reheating to ≍200 °C remobilizes these charge carriers and causes them to anneal below 400 °C. The generation of positive holes charge carriers may be important to understand failure mechanisms of SiO2 insulators.

The atmospheric pressure chemical vapor deposition of aluminum nitride coatings using hexakis(dimethylamido)dialuminum, Al2(NMe2)6, and ammonia precursors is reported. The films were characterized by ellipsometry, transmission electron microscopy, x-ray photoelectron spectroscopy, and Rutherford backscattering spectrometry. The films were deposited at 200–250 °C with growth rates up to 1000 Å/min. They displayed good adhesion to silicon, vitreous carbon, and glass substrates and were chemically inert, except to concentrated hydrofluoric acid. Rutherford backscattering analysis showed that the N/Al ratio ranged from 1.1 to 1.2. Refractive indexes were 1.8–1.9. The films were smooth and amorphous by transmission electron microscopy.

We have studied the electron channeling patterns (ECPs) of both pure a-axis and pure c-axis epitaxial YBa2Cu3O7−δ thin films on various substrates. ECPs from three representative a-axis films [on PrBa2Cu3O7−δ buffered LaAlO3 (001), MgO (001), and SrLaAlO4 (001)] and three c-axis films [on LaAlO3 (001), NdGaO3 (001), and SrTiO3 (001)] are presented. The differences between both sets of ECPs are discussed and recorded as references for future identifications.

The effect of different drying and calcination methods on the ultimate particle size of YBa2Cu3O7 (Y-123) has been investigated. The starting material was a tetramethylammonium (TMA) carbonate-precipitated slurry. Spray-drying the slurry after filtering and reslurrying (to remove residual TMA) was most effective in the ultimate formation of finely divided Y-123. The morphology of the spray-dried powder could be preserved by calcining in very low total pressures of flowing oxygen. When a slurry with 0.16% solids content was spray dried, and this powder calcined at 750 °C in 2 Torr of flowing oxygen, a Y-123 powder of mean particle size 0.74 μm (66% submicron) was obtained.

YBa2Cu3O7−δ superconductor crystals have ferroelastic properties, which makes it possible to interpret their microstructure within the framework of the quasidislocation theory.

Variations in lattice parameters for materials that form very thin lamellae are analyzed using a thermodynamic model that incorporates surface stress effects. It is predicted that lattice spacing variations should be proportional to the reciprocal of the lamella thickness, in agreement with experimental data for polyethylene, n-paraffins, and a copolymer of tetrafluoroethylene and hexafluoropropylene. The model is then used to calculate the surface stress associated with lamella interfaces in these crystalline materials. The calculated surface stress has the same order of magnitude as a surface tension, but is negative. The model is extended so that surface stresses associated with grain boundaries can be measured in very fine-grained metals and ceramics.