The results of a computer simulation study of point defects including vacancy, interstitial, and F+ center in alkaline-earth sulfides are presented. The study is based on ICECAP/HADES simulation procedures and uses empirical interionic potentials obtained from the analysis of macroscopic data for these materials. The results predict the dominance of Schottky disorder and suggest that vacancy migration predominates in alkaline-earth sulfides. Furthermore, the calculated F+ center absorption energy is in good agreement with the experimental data deduced from the optical stimulated studies in these materials.

Ultrafine-grained, nanophase samples of TiO2 (rutile) were synthesized by the gas-condensation method and subsequent in situ compaction. The samples were studied by a number of techniques, including transmission electron microscopy, Vickers microharness measurements, and positron annihilation spectroscopy, as a function of sintering temperature. The nanophase compacts with average initial grain sizes of 12 nm were found to densify rapidly above 500 °C, with only a small increase in grain size. The hardness values obtained by this method are comparable to or greater than those for coarser-grained compacts, but are achieved at temperatures 400 to 600 °C lower than conventional sintering temperatures and without the need for sintering aids.

A new process for making fine (10–1000 nm) oxide powders has been devised. It is based on striking an are between two metallic electrodes submerged in a dielectric liquid, typically water. By controlling the process parameters (voltage, amperage, and composition of liquid), one can obtain fine sols of the anhydrous oxides of Al, Ti, Zr, etc., and exercise some control over the particular phase in variable valence metals such as Cr.

The permeation of oxygen through high-purity, large-grain Ag membranes has been studied over the temperature range of 400–800 °C. The permeability was found to be linear and repeatable, but the magnitude was 3.2 times smaller than that determined by past research. This factor may be due to negligible grain boundary diffusion that exists in this work. Auger electron spectroscopy (AES) does, however, suggest the importance of grain boundaries since intragranular oxygen was virtually undetectable and since AES line scans show substantial oxygen signals around the grain boundaries. The diffusivity measurements were found to exhibit two distinct linear regions, one above and one below a critical temperature of 630 °C. The high-temperature data have an activation energy (11.1 kcal mol−1) similar to that reported by others, but the low-temperature data have a comparatively larger activation energy (15.3 kcal mol−1). Vacuum desorption of the oxygen-saturated Ag was found to occur at the critical temperature of 630 °C, which is consistent with the increased mobility of oxygen atoms in the higher temperature regime. The higher activation energy observed in the lower temperature regime is probably due to the higher efficiency of traps.

A method has been devised for preparing lateral Ni–GaAs diffusion couples for transmission electron microscopy investigations. By annealing diffusion couples in situ in a hot stage, the growth of a ternary phase has been observed in the microscope, and shows parabolic time dependence of the growth. In the temperature range of 200–300 °C, Ni is the predominant diffusing species in the ternary phase while Ga and As are essentially immobile. The experimental results are compared with previous investigations of the reactions of Ni thin films with bulk GaAs.

A system has been designed and constructed to produce diamond particles by inductively coupled radio-frequency, plasma-assisted chemical vapor deposition. This is a low-pressure, low-temperature process used in an attempt to deposit diamond on substrates of glass, quartz, silicon, nickel, and boron nitride. Several deposition parameters have been varied including substrate temperature, gas concentration, gas pressure, total gas flow rate, rf input power, and deposition time. Analytical methods employed to determine composition and structure of the deposits include scanning electron microscopy, absorption spectroscopy, scanning Auger microprobe spectroscopy, and Raman spectroscopy. Analysis indicates that particles having a thin graphite surface, as well as diamond particles with no surface coatings, have been deposited. Deposits on quartz have exhibited optical bandgaps as high as 4 5 eV. Scanning electron microscopy analysis shows that particles are deposited on a pedestal which Auger spectroscopy indicates to be graphite. This is a phenomenon that has not been previously reported in the literature.

The deformation behavior of Tl3AsSe3 (TAS) single crystals has been studied by hardness tests in four different crystal surfaces, the (10$\overline 1$0), (1$\overline 2$10), (0001), and the plane where the normal is tilted 19° off the hexagonal c axis in the b–c plane. The dominant slip planes are of the (10$\overline 1$1) type; the possibility of (10$\overline 1$0) and (0001) slip was also observed. The observed dependence of force on the length of diamond pyramid indentations implies that TAS behaves to some degree like a ductile metal. Measurements of hardness anisotropy are very useful for defining crystal growth and handling conditions that minimize the effect of stresses. X-ray topographs of Knoop hardness indentations indicate that the measured x-ray diffraction contrast is closely related to the rotational component of each individual slip system activated by the hardness indentation.

Molecular behaviors of single isolated chains of various lengths are simulated using four energy potentials: the twisting, bending, stretching, and Van der Waals potentials. The origin and analytical form of these potentials is discussed and easy-to-evaluate quantitative expressions are given. A physically based algorithm for energy minimization is developed and used to determine the static configurations of single chains in their lowest energy states. Not surprisingly, the majority of the energy minima found are local minima implying metastability, which is, of course, a central phenomena in noncrystalline material behavior. A progressive distortion approach is then used to suppress conformational variations that depend on initial conditions from developing, thus making possible study of the force displacement characteristics of single chains of various lengths. The single chain force-displacement curve found in this way has a form comparable with the gentle yield point observed in many bulk polymers but with an initial apparent elastic stiffness higher than that of bulk material. Some aspects of the fracture phenomena of single chains are also discussed.

Depth profiles of 30–150 keV6Li implanted into the photoresist AZ111 have been analyzed through the 6Li(n,a)t nuclear reaction using thermal neutrons. As was found recently for 10B and 19F implanted into the same material, at certain threshold implantation energy the Li ions also split up into a regular and a nonregular distribution. This energy differs from the energies found for 10B and 19F, but at the threshold the electronic stopping power has the same value of about 20 eV/Å in the three cases. The nonregular Li fraction, typically around 10% of the implanted atoms, redistributes according to the TRIM code predicted profile of electronic energy transfer. The regular component exhibits a range profile that is well described by the TRIM code particle distribution predictions. The analysis of the B, F, and Li data shows that there is an approximately linear relation between the nonregular fraction of ions and the density of total deposited energy.