High-quality single crystals of 6H–SiC have been indented at 1170 °C in vacuum. A TEM study of the indented regions shows that a 6H → 3C polytypic transformation has occurred, further confirming that this phase transformation can be induced by an applied stress.

Amorphous hydrogenated silicon carbide (a–SiC: H) thin films (t < 1 μm) were grown from two different precursor gases, a methane/silane mixture and silacyclobutane (SiC3H8). Plasma enhanced chemical vapor deposition was used to deposit a–SiC: H thin films on silicon substrates at temperatures of 175 °C and 600 °C. These a–SiC: H films were characterized using the mechanical properties microprobe (nanoindenter) and by scratch testing. Data and mechanical properties information collected from these measurements have been correlated with film process conditions and materials characteristics. A simplified approach was used to calculate the average nanoindentation hardness from shallow indentations. Using this technique, results for a silicon wafer are in good agreement with that previously reported. Analysis of the substrate influence on the thin film nanoindentation data implies that the measured hardness is relatively unaffected by the substrate, while the measured elastic properties are somewhat influenced by the substrate. The a–SiC: H film hardness is shown to depend on the precursor gas and molecular bonding, while the elastic properties vary with precursor gas, composition, and density, as influenced by the plasma source deposition power. The MPM data and scratch test data show similar correlations to plasma source power, film structure, and film composition.

Crystalline zinc ferrite particles of the general formulation ZnxFe3−xO4 (O ≤ x ≤ 1) were prepared by aging at elevated temperature solutions containing Zn(NO3)2, Fe(NO3)3, and triethanolamine in the presence and in the absence of hydrazine. The powders were characterized by x-ray diffraction and infrared analyses.

We report measurements and analysis of fracture-induced photon and electron emissions from several polymeric and inorganic systems on time scales of 10−2 to 103 s following fracture. The dominant mechanism for postfracture emission involves the recombination of mobile free carriers (usually electrons) with immobile recombination centers. The emission decays were modeled as (pseudo)unimolecular and bimolecular recombination on fractal lattices as described by Zumofen, Blumen, and Klafter.1 Although the decay kinetics shows a great deal of variability from material to material, this random walk description of the recombination process provides an excellent description of the emissions over long time scales. This analysis shows a strong correlation between the local structure at the fracture surface and the resulting decays.

Molybdenum disulfide is a technologically important solid phase lubricant for vacuum and aerospace applications. Pulsed laser deposition of MoS2 is a novel method for producing fully dense, stoichiometric thin films and is a promising technique for controlling the crystallographic orientation of the films. Transmission electron microscopy (TEM) of self-supporting thin films and cross-sectional TEM samples was used to study the crystallography and microstructure of pulsed laser deposited films of MoS2. Films deposited at room temperature were found to be amorphous. Films deposited at 300 °C were nanocrystalline and had the basal planes oriented predominately parallel to the substrate within the first 12–15 nm of the substrate with an abrupt upturn into a perpendicular (edge) orientation farther from the substrate. Spherically shaped particles incorporated in the films from the PLD process were found to be single crystalline, randomly oriented, and less than about 0.1 μm in diameter. A few of these particles, observed in cross section, had flattened bottoms, indicating that they were molten when they arrived at the surface of the growing film. Analytical electron microscopy (AEM) was used to study the chemistry of the films. The x-ray microanalysis results showed that the films have the stoichiometry of cleaved single crystal MoS2 standards.

Fine granules of poly(tetrafluoroethylene) (PTFE) were heat-treated/annealed on NaCl near its melting temperature (Tm) and/or at a temperature (Tc) between upper and lower feet of the exothermic peak in the DSC cooling process from Tm. Morphological changes of the granules were examined in the bright- and dark-field modes by transmission electron microscopy. When the granules were heat-treated near Tm, microfibrils of 20–30 nm in width and fibrils of 70–120 nm in width came out of the granules. The microfibrils were also observed in the fibrils. The microfibrils formed by heat treatment near Tm seemed to be identified as microfibrils of 20–30 nm in width which were recognized outside the granules annealed at Tc. It is expected that such a microfibril will grow to be a band in the band structure observed on the surface of bulk PTFE. Since the 0015 dark-field images showed that the PTFE chains in such microfibrils and fibrils are set perpendicular to their fibril axis, the chains should fold back and forth repeatedly at both lateral side-surfaces of the microfibrils and fibrils.

Hillebrandite (dicalcium silicate hydrate) was produced by a hydrothermal process. Its crystal structure and microstructures were investigated by conventional TEM and HREM. Most hillebrandite fibers showed their elongation to be parallel to the b axis and tended to lie on the {001} cleavage planes. Selected area diffraction patterns frequently displayed continuous streaking, and corresponding dark-field images revealed stacking disorders perpendicular to the fiber axis. The morphology, stacking disorders, and extinction conditions of {hkO} reflections and hillebrandite resembled those of the minerals wollastonite (CaSiO3) and pectolite (Ca2NaH[SiO3]3). Periodic (100) faulting with a displacement vector 1/2 b is suggested to be the major origin of the streaking and the systematic absences in hillebrandite.

(Ca1−x, Mgx)Zr4(PO4)6 (CMZP) ceramics have been made by sol-gel and solid state reaction methods. Single phase (Ca1−x, Mgx)Zr4(PO4)6 (x = 0.4) has been obtained. The densification of CMZP depends on the powder synthesis method. Near theoretical density can be achieved by cold pressing and sintering with the addition of a sintering aid. Bulk thermal expansion of CMZP is shown to depend on the phase composition, grain size, and presence of microcracks. By choosing different sintering temperatures and times, the thermal expansion of CMZP can be controlled. CMZP (x = 0.4) ceramics exhibit near zero bulk thermal expansion, low thermal expansion anisotropy, low thermal conductivity, and thermal stability up to 1500 °C.

A novel and attractive method for preparing multicomponent electronic ceramics and ceramic-metal composites is the oxidation of solid metallic precursors (SMP). This metallurgical processing route consists of the following steps: (i) preparation of a solid metallic precursor containing the proper ratio of elements for the final ceramic or ceramic-metal composite, (ii) compaction and forming of the metallic precursor into a desired shape, and (iii) oxidation to produce a monolithic ceramic or ceramic-metal composite. While the SMP method has been used to prepare wires and tapes containing a variety of superconducting oxides, this method has not been widely used to synthesize other electronic ceramics. In this paper, the synthesis of dielectric BaTiO3/noble metal laminates from solid metallic precursors is discussed. Ba–Ti precursor powders have been produced by solid-state mechanical alloying. The precursor powder was sealed inside noble metal tubes and rolled to form thin Ba–Ti/noble metal laminates. Exposure of the Ba–Ti core in such tapes to temperatures ≥ 300 °C in pure oxygen resulted in rapid oxidation. Post-oxidation annealing at elevated temperatures (≥900 °C) yielded dielectric BaTiO3/Ag or BaTiO3/Pd laminates.

Synthesizing oxide ceramic powders by application of a microwave plasma is a great advantage. There are two ways the microwave plasma can be used: The first is as a source of heat for the pyrolysis of solutions and the second is to excite gas reactions to obtain nanosized powders. Both applications are superior to standard methods. A microwave cavity well suited for these experiments and its operating characteristics are described. Using a microwave plasma as a source of heat for pyrolytic decomposition of nitrates in aqueous solutions leads to a fine-grained product with particle sizes from 100 to 1000 nm. Crystallite sizes in those particles are in most cases less than 10 nm. This is demonstrated with zirconia-based ceramics, such as ZrO2−3 mol % Y2O3−20 mol % Al2O3. Depending on the conditions during pyrolysis, it is possible to obtain a product in which alumina is either dissolved in zirconia or the onset of the phase separation is observed. The energy efficiency of this process is better than 80%. If the reactants are gaseous, e.g., ZrCl4, it is possible to produce powders with mean particle sizes of about 4 nm. In the case of zirconia, these particles are monocrystalline with a cubic structure. This structure is not in equilibrium under the experimental conditions.

Room temperature, high energy ball milling was applied to various transition aluminas (γ, K, χ), producing thermodynamically stable α-alumina–a phenomenon that could otherwise be achieved only by high temperature (1100–1200 °C) heat treatment. The transformation proceeds in two steps. The first one consists of rapid microstructural rearrangements with continuously increasing α-transformation rate. In the second step (1–2 h from the start), only relatively small changes in morphology are observed with a constant α-transformation rate. The rate is influenced only by the milling intensity. The presence or the absence of oxygen in the milling atmosphere has a large influence on the final surface area of α-alumina.

Alumina aerogels were prepared using supercritical drying methods, and their thermal properties were examined. The effects of several additives to the alumina aerogel and supercritical drying methods were examined in order to improve heat resistance. Silica, phosphoric oxide, barium oxide, lanthanum oxide, and SiC whisker were effective for maintaining a high specific surface area of the alumina aerogel at a temperature over 1200 °C. Silica was found to be the most effective among the additives. The addition of 10 mol % silica resulted in an alumina aerogel with the highest specific surface area, 114.3 m2/g at 1200 °C, and increased the transformation temperature to α alumina. Barium oxide and lanthanum oxide formed smaller crystals within the alumina, compared with those of alumina alone. SiC whisker caused many cracks in the alumina aerogel. When supercritically dried, the alumina aerogel was strengthened by treatment at higher temperature and pressure.