The C-KLL Auger line shapes of the transition metal carbides and some related compounds are examined as a function of the metal and nonmetalloid components (C, N, and O). They are discussed in the context of hole-hole repulsion and screening effects. The effect of π versus σ-bonding and the proportion of ionic versus covalent bonding are correlated with various aspects of the X-CVV Auger line shape, such as relative peak shifts, intensity of a high energy shoulder, and the multiplet splitting of the sp component.

The kinetics of oil absorption into cotton-phenolic ball-bearing retainer material was determined. The results fit a model of two-step absorption in which the first step can be described by capillary rise and the second step by diffusion of oil from the capillaries into the bulk phenolic resin. The capillaries are associated with the cotton threads and are on the order of several micrometers or less in radius. The model successfully describes data for two cotton-phenolics with different cloth weaves, and five nonpolar liquids (four lubricating oils and heptane) with viscosities that vary over 3 orders of magnitude. The total amount of oil absorbed at the completion of the first step (1.5 to 3.4% v/v in this work) is proportional to the volume of the sample, not its surface area, suggesting that the entire volume of the material stores oil and not just the surface region. If the material is not completely dry when submerged in oil, the capillaries are blocked and only surface absorption of oil can take place. The saturation amount of oil in the resin after diffusion is complete at about 2 to 3% v/v (not including the amount of oil stored in the capillaries). The diffusion coefficient calculated using our model is 3 × 10−12 cm2/s, which is reasonable when compared with available literature data on large and small molecules diffusing into polymers.

A review of the structure and properties of fullerenes is presented. Emphasis is given to their behavior as molecular solids. The structure and property modifications produced by alkali-metal doping are summarized, including modification to the electronic structure, lattice modes, transport, and optical properties. Particular emphasis is given to the alkali-metal-doped fullerenes because of their importance as superconductors. A review of the structure and properties of fullerene-based graphene tubules is also given, including a model for their one-dimensional electronic band structure. Potential applications for fullerene-based materials are suggested.

It was found that montmorillonite cation exchanged for 12-aminolauric acid (12-montmorillonite) was swollen by ∊-caprolactam to form a new intercalated compound. Caprolactam was polymerized in the interlayer of montmorillonite, a layer silicate, yielding a nylon 6-clay hybrid (NCH). The silicate layers of montmorillonite were uniformly dispersed in nylon 6. The carboxyl end groups of 12-aminolauric acid in 12-montmorillonite initiated polymerization of ∊-caprolactam, and as 12-montmorillonite content became larger, the molecular weight of nylon was reduced. From the result of end-group analysis, carboxyl end groups were more than amino end groups. The difference between the carboxyl and the amino end groups was attributed to ammonium cations (-NH3+) of nylon molecules, because the difference agreed with the anion site concentration of the montmorillonite in NCH. It is suggested that the ammonium cations in nylon 6 interact with the anions in montmorillonite.

The interaction between SiC and Ti powder at 1073–1523 K was investigated employing a combination of x-ray diffraction, scanning electron microscopy with EDS, Auger spectroscopy, and transmission electron microscopy. As a result of the interaction, a triple-layer reaction zone was formed. The most important part of the reaction zone was a mixed TiC–Ti5Si3(C) layer. Thin TiC sublayers were formed on both the inner and the outer sides of the mixed reaction layer. The reaction zone was found to grow by a parabolic law with the kinetic constant, k = 1.3 × 10−3 exp (-21800/t) cm2/s. The growth process of the SiC/Ti reaction zone was assumed to be controlled by diffusion of all three components of the system: Ti, Si, and C. Thin reaction layers (<5 μm) obtained after short exposures at relatively low temperatures formed coatings on the SiC surface; thicker reaction layers spalled off the ceramic surface. Experiments with the samples partially immersed into the metal powder showed that interaction between SiC and Ti was very sensitive to the environment.

Various nylon 6-clay hybrids, such as molecular composites of nylon 6 and silicate layers of montmorillonite and saponite, NCH's and NCHP's, respectively, have been synthesized. To estimate the mechanical properties of these hybrids, tensile, flexural, impact, and heat distortion tests were carried out. NCH was found superior in strength and modulus and comparable in impact strength to nylon 6. The heat distortion temperature (HDT) of NCH (montmorillonite: 4.7 wt. %) was 152 °C, which was 87 °C higher than that of nylon 6. In NCHP, saponite had a smaller effect on the increase of these mechanical properties. The modulus and HDT of NCH and NCHP increased with an increase in the amount of clay minerals. It was found that these properties were well described by the contribution of the constrained region calculated from the storage and loss modulus at the glass transition temperature. According to the mixing law on elastic modulus, the following expression was obtained between the modulus E at 120 °C and the fraction of the constrained region C, En = Ecn = C, where the values of n and Ec (modulus of the constrained region) were 0.685 and 1.02 GPa, respectively.

When an appropriate mixture of low-softening borosilicate (BSG) and high-softening high silica (HSG) glasses is sintered at temperatures ranging from 800 to 1000 °C, a crystalline phase, identified as cristobalite by XRD, is known to precipitate out of the initial amorphous binary mixture of glasses as the sintering continues. The precipitation of cristobalite is found to originate in HSG and is controlled by the transport of alkali ions (e.g., K, Na, and Li) from BSG to HSG.1 In this paper we report that when a small amount of gallium oxide is present as a dopant in the above binary mixture of BSG and HSG, the cristobalite formation is completely prevented at the sintering temperatures investigated. The above result is attributed to a strong affinity between Ga+3 from gallium oxide particle and alkali ions from BSG, which diverts the diffusion of alkali ions from HSG to gallium oxide, thus forming a K+ and Ga+3-rich reaction layer adjacent to gallium oxide particles far too rapidly compared with that of cristobalite formation.

Ca(1−x)NixO solid-solution films with varying stoichiometry have been prepared by pulsed laser deposition from sintered targets of NiO and CaO. X-ray diffraction data indicate that the films have the structure of sodium chloride. The lattice constants for different stoichiometries vary with film composition. Using the Madelung energy as the binding energy between anions and cations and assuming that nickel and calcium ions are distributed randomly in lattice sites, the lattice constants were calculated and found to compare with experimental results. This study investigated the compositional changes that occur during the target sintering process and the pulsed laser deposition of films. Using these data, a target composition can be prepared to produce Ca(1−x)NixO thin films with any desired lattice constant.

Most of the results of a recent paper by Shi and Seinfeld [J. Mater. Res. 6, 2091 (1991)] are documented in literature in a very similar form. Asymptotic formulas of transient nucleation are briefly reviewed and smooth matching of the nucleation and growth regions is discussed.

The dissipation factor of aluminum nitride ceramics (AlN), doped with various concentrations of oxygen, is probed at 1 kHz before and after exposure to UV radiation. The results of this study show that UV photogenerated carriers, which are trapped at charged oxygen impurity related defect sites, are responsible for the observed dielectric loss. A simple energy level diagram is presented that outlines trapped carrier distributions within the AlN bandgap and is consistent with the experimentally observed changes in dissipation factor as a function of time, UV exposure, and exposure to visible light, which liberates carriers from charged trap sites.

V2O5–TiO2 and V2O5–Al2O3 mixed oxide powders were synthesized in a hydrogen-oxygen flame using VOCl3, TiCl4, and Al(CH3)3 as precursors. The particle formation processes were investigated as a function of VOCl3 concentration by laser light-scattering and by collecting particles directly onto transmission electron microscopy grids. In the V2O5–TiO2 system, the oxides condense as an intimate mixture at all three VOCl3 concentrations. Spherical particles, 40 to 70 nm in diameter, are obtained. In the V2O5–Al2O3 system, chain-like particles composed of an intimate mixture of V2O5 and Al2O3 form at the lowest VOCl3 concentration. At high VOCl3 concentrations, the chain-like particles have a core-mantle structure (a core mainly of Al2O3 and a mantle mainly of V2O5). The crystalline form and the surface area of these mixed oxides were determined by x-ray diffractometry, FT-IR spectroscopy, and BET analysis by nitrogen desorption. These measurements indicate that amorphous vanadium oxide forms at low VOCl3 concentrations, and V2O5 is obtained at the higher VOCl3 concentrations. The structure of the amorphous vanadium oxide matches that published for vanadium oxide “supported” catalysts.

“Hard sphere modeling of the effect of slip on interstitial sites in the B2 structure” [J. Mater. Res. 8, 1203 (1993)]

We show that the assertions of Shneidman made in the previous Comment are incorrect.

“(110)-oriented Bi–Sr–Ca–Cu–O superconducting thin films prepared by metalorganic chemical vapor deposition” [J. Mater. Res. 8, 978 (1993)]

“Epitaxical nucleation of polycrystalline silicon carbide during chemical vapor deposition” [J. Mater. Res. 8, 1086 (1993)]

Polycrystalline silicon carbide was deposited from methyltrichlorosilane in cold-walled and hot-walled reactors, on (100) SiC surface layers that were formed on (100) Si wafers. The initial stages of the process were studied by electron microscopy after relatively short deposition times. Submicron surface features nucleated with a specific crystallographic orientation with respect to the substrate, where {111} planes in the β–SiC substrate coincided with {0001} planes in the α–SiC features. These α–SiC features occurred only at twins on {111} planes of the β–SiC substrate. This demonstrates that nucleation under these conditions is controlled by defects in the substrate. Surface contamination and the reactor configuration also had substantial effects on nucleation.