Deposited thin films of Cr and Ni on Cu substrates have been melted and intermixed with a frequency-doubled Q-switched Nd:YAG laser. The laser pulses melt the thin films and a shallow portion of the substrate. Resolidification interface volocities are on the order of 1–10 m s−1. Rutherford backscattering, Auger spectroscopy, and energy dispersive x-ray mapping have been used to characterize the elemental distribution. Channeling and transmission electron microscopy were used to investigate the microstructure of the surfaces produced. In contrast to the binary Cr–Cu system, where extended solid solutions are produced, the Cr–Ni–Cu system results in a metallic glass surface. We have found that these metallic glass surfaces, which have been dubbed “stainless coppers,” exhibit excellent hydrogen sulfide corrosion resistance. Their contact resistance is low and stable over long periods of time and through tens of thousands of electronic dial switching cycles.

A detailed characterization study on polycrystalline specimens of YBa2Cu3Oy-x that were prepared by solid-state reaction techniques has been carried out. In the samples studied. magnetization and resistivity measurements indicate superconductivity onset temperatures of up to 89 K. Transmission electron microscopy (TEM) techniques have been used to facilitate direct microstructural characterization. It is shown that the planar defects on (001) planes form during the ion milling of the samples and are not directly connected with superconductivity. Laser Raman spectroscopy has revealed that these materials are sensitive to environmental degradation.

An x-ray diffraction technique has been developed to make in-situ measurements of hydrogen concentration profiles from which diffusivity and solubility values are calculated. Hydrogen is supplied to the metal surface by cathodically polarizing it in a bath of 1N H2SO4 electrolyte. The incident x-ray beam penetrates a thin layer of electrolyte solution at the surface of the sample, thus, x-ray diffraction profile changes can be recorded as a function of charging time and temperature. The applied potential prevents outgassing of the specimen during the measurement. The x-ray diffraction profiles are deconvoluted to remove the α1/α2 doublet and noncompositional broadening effects. Composition-depth profiles are then obtained from an intensity band transformation of the deconvoluted data. A diffusion coefficient is determined by fitting a solution to Fick's second law to the concentration-depth profile. The technique described here was used to measure hydrogen diffusivity in stainless steel in the temperature range 20°–80°C.

Nuclear magnetic resonance (NMR) results are presented for several aluminum alloy samples prepared using the melt-spinning technique including orthorhombic Al6Mn, Al–Mn quasicrystals both with and without doping with Si and Ru, and a T-phase alloy of Al and Pt. With the exception of the orthorhombic material, all of the NMR spectra show a broad distribution of sites. No features unique to the quasicrystal phase are observed. For the orthorhombic material the quadrupole field parameters are found to be ∥VQ∥ − 1.0±0.1 MHz and η = 0.4±0.1.

The effect of boron on the mechanism of strain transfer across grain boundaries in Ni3Al has been investigated by dynamic recording of events occurring during in-situ straining in the transmission electron microscope. Boundaries in both doped and undoped material can act as effective barriers to dislocation motion, large numbers of dislocations being incorporated into the boundary without any plastic strain occurring in the adjacent grain. In the undoped material, the grain-boundary strain is relieved by the sudden failure of the grain boundary. In the doped material the strain is relieved by the sudden generation and emission of large numbers of dislocations from the grain boundary. This effect may be understood by boron either increasing the grain-boundary cohesion or reducing the stress required to operate grain-boundary dislocation sources, rather than easing the passage of slip dislocations through the grain boundary.

Single-phased films of α-Ti1−x Nx, ∊-Ti2Nx, or δ-TiNx with a homogeneous composition on more than 400 nm were produced by ion implantation at several different energies in the TiAl6V4 alloy. Secondary ion mass spectroscopy (SIMS) profiles and ionic images recorded within the tracks after incremented cycles of friction against a 35NCD16 steel ball in air have shown that a Ti–O–C–N film is progressively formed on the surface of α solid solutions, while more concentrated nitride films resist oxidation. The friction and abrasion resistances of ∊ or δ nitride films are initially improved for a time lasting for as long as their N content increases, but they are finally self-destroying. On the contrary, the hardening effect of N in an α-Ti matrix keeps a really severe amount of abrasion from occurring during running in of the implanted surface, without suppressing the building up of a lubricant oxide hardened by N.

The effects of pulsed laser radiation on the corrosion resistance, surface morphology, and composition of liquid-quenched amorphous Fe32Ni36Cr14P12B6 (Allied Corporation Metglas¯ 2826A) are reported. Scanning electron microscopy, Auger depth profiling, and x-ray diffraction were used to characterize the surface, while the corrosion resistance was determined by anodic polarization in H2SO4. The surface of the as-received melt-spun ribbons exhibited many defects, including cracks, compositional irregularities, and microcrystals of Ni5P4. These microcrystals differ from those found upon bulk crystallization. Melting and rapid solidification by radiation with a Q-switched Nd–YAG laser [30 ns full width at half maximum (FWHM)] modified the surface morphology (leaving composition constant), removing the microcrystals and cracks and reducing the carbon and oxygen contamination. The reduction of these surface defects resulted in improved corrosion resistance of the Metglas¯ 2826A ribbon. For example, spontaneous passivation is observed for the laser-treated samples, as opposed to critical current densities of 10μA/cm2 and 1000μA/cm2 for the as-received amorphous and crystallized Metglas¯ alloy, respectively.

A sintered aggregate of hydroxyapatite, Ca10(PO4)(6(OH)2, designed for in vitro simulation of some of the physicochemical processes of dental decay is described and characterized. Diffusivity at 35°C (by tritiated water effusion) was (2.9 + 0.6) ⊠ 10−6 cm2/s. The apparent density (2.50 ± 0.04) g/cm3 gave a porosity of 20.8 ± 1.3 vol % based on the theoretical density of hydroxyapatitc. Estimates of the volume percent porosity from water vapor desorption and tritiated water effusion were 19.2 ± 2.9 and 20.7 ± 1.4, respectively Pore-size distribution measurements using mercury porosimetry showed that most of the porosity (approximately 17% of the sample volume) was concentrated between 30 and 60 nm equivalent pore radius. The material, which has been successfully used to simulate some aspects of the dental decay process, should find further application in this and related fields.

The influence of preparation conditions and microstructure on the superconductive properties of single-phase poly-crystalline YBa2Cu3O7−x was investigated by electron probe microanalysis, transmission electron microscopy (TEM), and x-ray powder diffraction as a function of temperature in various ambients supplemented by resistivity and susceptibility measurements. Leaching of Ba was observed when samples were brought in contact with water. The TEM imaging revealed that individual grains have an extremely defect-rich outer shell and an inner core with a domain structure with a and b axes interchanged. The transition temperature Tc was found to decrease with increasing quench temperature in the range 400–900°C. The Tc was observed to be linearly proportional to the difference in the orthorhombic cell parameters (b-a). Further implications are discussed.

Ion-beam mixing in the Bi/Sb system using Ne+, Ar+, and Kr+ ions in the energy range 40–110 keV has been investigated by Rutherford backscattering analysis. The mixing is shown to be temperature independent in the region of 40–250 K; at higher temperatures the mixing per ion increases rapidly with temperature. Initially, a square-root dependence of the mixing on the ion dose was observed. At higher doses a saturation effect is obtained as the Sb becomes uniformly distributed in depth throughout the film. Also, the mixing was found to increase linearly with the energy deposited into atomic displacement collisions at the Bi/Sb interface. Alloys of Bi1−x Sbx (0<x<0.5) have been produced. The thermoelectric power of the fully mixed alloys reaches a maximum value at an alloy composition of Bi0.87 Sb0.13. The thermoelectric power for partially mixed alloys exhibits almost the same dependence on Ar+ dose as the amount of mixing.

Relaxation effects in Fe–B metallic glasses have been studied through measurements of the Curie temperature (Tc) and changes of enthalpy. A monotonic increase in Tc with annealing temperature is observed for all compositions due to irreversible structural relaxation. This increase continues until the start of surface/bulk crystallization. The observed decrease in Tc, upon further annealing is attributed to the strain introduced in the partially glassy system, which masks any evidence for reversible structural relaxation. Enthalpy measurements do show a small reversible structural relaxation. The magnitude of the effect is about a factor of 6 smaller than in ternary metalloid-containing glasses.

A series of twelve Li1−x Ta1−3x Ti4xO3 solid solution ceramics was sintered following the low-temperature metal alkoxide routes. Measurements of dielectric constants, dielectric losses, and heat capacities as functions of temperature and frequency are presented. The Curie temperature (Tc) in comparison to LiTaO3 was reduced from 620°C to about 358°C in the Li0.91 Ta0.73 Ti0.36O3 ceramics. The heat capacity data showed no dependence on the bulk density or grain size. Also the mechanical properties of the undoped crystals appear to stay undisturbed. On the other hand, an apparently abnormal dependence of the Curie temperature on density was found. Heat capacity and dielectric loss decreased while the dielectric constant increased with the addition of Ti+4 doping in the LiTaO3 structure. Overall, a good detector performance might indeed be obtained from these ceramic materials if they can be poled reproducibly.

Since the discovery of high critical temperature superconducting oxides, an important factor potentially limiting their technological application has been the typically low value of the critical current density that they can carry. Here are presented the results of a transmission electron microscopy study of sintered YBa2Cu3O7−x aimed primarily at the characterization of those elements of the microstructure responsible for the poor current-carrying capacity in the superconducting state. The observations are further discussed in relation both to the flux pinning characteristics required and to the prospect for controlling the microstructure in order to optimize the properties of this material for technological development.

The mercury cation Hg2+ is used to intercalate NbF−6 and TaF−6 anions into pyrolytic graphite (HOPG). The Hg2+ cation in Hg (NbF6)2 and Hg(TaF6)2 oxidizes HOPG to form stage-3 compounds. The Hg2+2 cation is also used as an oxidant to intercalate AsF−6 and SbF−6 ions into graphite. The reduced products of the reactions are identified by Raman spectra. The intercalation compounds are characterized by (00l) x-ray diffraction, and the intercalants are identified with mass spectrometer analysis.

The interactions of the Pt/Ni/Cu and Au/Ni/Cu structures and their ambient dependence are studied. Comparison of the Pt–Cu interdiffusion with that of Au–Cu across the Ni layer shows an interesting relation between the interactions and their ambient dependence. According to the surface potential model, which has been shown to correlate the ambient effects for many systems, diffusion of both Pt and Au into the Cu layer via the Ni layer should be enhanced by oxygen. This is observed for Au but not for Pt. On the other hand, the anticipated oxygen-enhanced diffusion of Cu into Pt and Au layers via the Ni layer is observed in both structures. The difference between the Pt and Au diffusion via Ni is attributed to the presence of competing interdiffusion between Pt and Ni in the Pt/Ni/Cu structure, which is reduced by oxygen, whereas little diffusion of Ni into the Au layer is observed for the Au/Ni/Cu structure. The ambient effects on the trilayer structures are compared with those on the binary Au/Ni, Au/Cu, Ni/Cu, Pt/Ni, and Pt/Cu structures. The diffusion mechanisms are discussed, and relations among various systems are suggested.

During high-temperature storage, glass corrosion in glass-to-metal feedthroughs can limit the lifetimes of lithium batteries designed to operate at ambient temperatures. Ampule tests have been conducted to simulate glass corrosion for Li/So2, Li/SOCl2, and Li/SOCl2 + BrCl batteries. In all lithium battery systems tested, lithium metal has been identified as the source of glass corrosion. On the basis of thermodynamic and kinetic stability, glass compositions have been developed that minimize the corrosion problem in all lithium battery systems tested.

The YBa2Cu3Oz system has been investigated by thermogravimetry in a controlled partial oxygen pressure PO2 ranging from 105-10 Pa. A compound with z = 6.290 was prepared at T = 950°C and PO2 = 105 Pa and identified as a metastable β phase. Subsequent isothermal or isobar phase stability studies were performed. This β phase has a narrow metastability domain 6.25 <z < 6.50 at high temperature. By decreasing the temperature or increasing the PO2, the β phase transforms irreversibly into an α phase characterized by large deviations 7—x from stoichiometry. Near the stoichiometry z = 7, the structure of the a phase is orthorhombic, and fully ionized vacancies are likely to be predominant. By decreasing the PO2, the β phase transforms into a new phase with a lower oxygen content (z < 6.1).

Preliminary procedures have been developed for the ball milling of pristine and brominated P-100 graphite fibers. Because of the lubricative properties of graphite, large ball loads (50% by volume) are required. Use of 2-propanol as a milling medium enhances the efficiency of the process. The fibers, when allowed to settle from the milling medium, tend to be preferentially aligned with rather few fibers standing up. Milled, brominated P-100 fibers have resistivities that are indistinguishable from their pristine counterparts, apparently because of loss of bromine. This suggests that bromine would not be the intercalate of choice in applications where milled fibers of this type are required. It was found that brominated graphite fibers are stable in a wide variety of organic solvents.

Thin LiNbO3 films were prepared from polymerized sol-gel precursor solutions having various concentrations and water:alkoxide ratios in an effort to investigate the effects of these and other processing variables on the resultant film properties and microstructure. Films deposted on silicon substrates were mostly amorphous when pyrolyzed at 435°C for 30 min. Randomly oriented polycrystalline films having distinctive microstnietures were produced using longer heating times or higher temperatures. All of the films exhibited low refractive indices due to porosity, which was attributed to the low level of hydrolysis water required to produce stable polymeric precursor solutions. When single-crystal LiNbO4 was used as the substrate, epitaxial growth of the film resulted. This ideal case establishes the feasibility of producing epitaxial films via sol-gel processing. All films were characterized by transmission electron microscopy (TEM) and thin-film x-ray diffraction patterns.

Inert particles that do not contribute to the densification of a composite powder compact are visualized as located on network sites; the network is defined by the distribution of the particles in the powder matrix. Because the distances between neighboring network sites are not identical, the strain produced by the sintering powder between all inert particle pairs cannot be the same as that for the powder compact without the inert particles. The constrained network model is based on the hypothesis that the densification of the composite will be constrained by the network and will mimic that of the network. The shrinkage of the network, and thus the densification of the composite, is estimated with a periodic network. A distance between the minimum and maximum site pairs within the unit cell defines the distance between site pairs in the random network where the powder between the particles densifies in the same manner as that for the powder without the inert particle. When the particles form a continuous touching network, composite shrinkage and densification is nil. The chosen lattice must also conform to this condition. A simple relation was developed relating the densification behavior of the composite to that of the matrix without the inert particles and the parameter associated with the chosen lattice. By choosing the lattice formed by the tetrakaidecahedron unit cell (volume fraction of particles for a touching network = 0.277), remarkable agreement was achieved for the experimental data concerning the densification behavior of the ZnO/SiC composite system reported by De Jonghe et al. [L. C. De Jonghe, M. N. Rahaman, and C. H. Hsueh, Acta Metall. 34, 1467 (1986)]. The universal nature of this lattice for other composites is discussed with respect to site percolation theory. The application of this concept to powder compacts containing either whiskers or agglomerates is briefly discussed.