The lanthanum-rich calcium lanthanum sulfide (CLS) was formed by a carbonate coprecipitating method followed by sulfurizing in a CS2 atmosphere at 950 °C for 3 h sulfurization. This powder then was densified by hot-press sintering at the temperature range from 1050 to 1150 °C for 0.5-2 h. The sintered pellets were resulfurized in a CS2 atmosphere at 950 °C for 1 h to restore the sulfur loss. The pellet sintered at 1050 °C for 0.5 h with 1.3 mm thickness had about 46% transmission at 13 μm.

The intermetallic matrix composites reinforced with heat-resistive fibers are expected to improve the ductility and the toughness of intermetallic compounds. Titanium aluminide, TiAl, shows a unique behavior that increases the mechanical strength with increasing temperature up to 1000 K. Vapor phase processings for manufacturing near-net-shaped composites or continuous fiber-reinforced composites will be hopeful methods. The synthesis of TiAl by a magnetron sputtering using a multiple target has been successfully established, and the microcomposites with SiC fibers have been prepared. The TiAl film was evaluated by Auger electron spectroscopy and the x-ray analysis and so on. The tensile strength properties of the SiC/TiAl microcomposites, of which the interface bonding was controlled with the powers of sputtering, were estimated. The results show that the strength properties of SiC/TiAl microcomposites are decreasing with increasing the power of the sputtering, and the irradiation-cured SiC fiber has better compatibility with TiAl than the oxidation-cured SiC fiber.

Titanium carbonitride, TiC0.5N0.5, is synthesized directly by a self-propagating reaction between titanium and carbon in a nitrogen atmosphere. Complete conversion to the carbonitride phase is achieved with the addition of TiN as diluent and with a nitrogen pressure ≥0.6 MPa. Thermodynamic phase-stability calculations and experimental characterizations of quenched samples support a proposed mechanism in which the formation of the carbonitride is a two-step process. The first step involves the formation of the nonstoichiometric carbide, TiC0.5, and is followed by the formation of the product by the incorporation of nitrogen in the defect-structure carbide to form the carbonitride solid solution.

Graphite fiber intercalation compounds were prepared by immersing graphitized thin vapor-grown carbon fibers (VGCF's) with diameters less than 0.5 μm into liquid bromine. The composition of Br2-intercalated VGCF was C70Br-C90Br. The powder resistivity of Br2-intercalated VGCF was estimated as 1/3 of pristine VGCF. An electroconductive plastic composite was prepared by mixing phenol resin with that of bromine intercalated VGCF as a conductive filler, and its electrical properties were investigated. The resistivity of a Br2-intercalated VGCF composite was 1.1 × 10−2 Ω · cm at room temperature, which is about 50% of pristine VGCF composite. Br2-intercalated VGCF-based composite had a high degree of stability against exposure at 150 °C in air and at 85 °C with 90% humidity for 500 h. Br2-intercalated VGCF-based plastic composites could be used as highly electroconductive materials.

A thick as-grown diamond film was examined directly by conventional transmission electron microscopy (TEM) without thinning, and the important microstructures near the growth surface were characterized. Specimen preparation for TEM involved simply fracturing the film; some of the diamond grains located on the specimen edge were thin enough to be directly examined by TEM. The 3-D topography of the diamond grains located at the intersection of the growth and the fracture surfaces was obtained using secondary electron images, so that the 2-D projected grain geometry could be derived easily to help interpret the TEM images. A diamond film grown with a 〈001〉 texture and having grains 2–3 μm diameter with {001} facets parallel to the substrate and four inclined {111} facets was examined. Grains with fracture surfaces that intersected the top (001) facet, grains with fractures that intersected only {111} facets, and unfractured grains were studied. It was found that the core volume bounded by the (001) top facet and its projected column defined by orthogonal internal {110} were free from microtwins, but contained a few dislocations. The remaining volume around this core, bounded by {111} facets (or grain boundaries) and the internal {110}, was filled with microtwins. The microtwins were not merely at the {111} surfaces. Our results reveal a growth mechanism in which microtwins are formed as material is added to {111} but not {001}. The formation of microtwins in CVD diamond is thus clearly associated with growth on {111} surface facets.

Thin films in the system (1 - x) PbTiO3−xLa2/3TiO3 were prepared by the sol-gel and dip-coating methods. Phases deposited in the films and the lattice parameters as a function of the composition were investigated by the x-ray diffraction method. The solid solutions with a perovskite structure were formed as a single phase with x up to 0.9. For the composition of x = 1.0, metastable La-Ti-O perovskite phase with a small amount of the impurity phase, La2Ti2O7, was obtained. Simulation of x-ray diffraction patterns based on the defect structure model shows that the structure of the La-Ti-O perovskite phase includes randomly distributed cation vacancies at the A-site, namely (La2/3□1/3)TiO3.

The differences in interphase development and mechanical properties between Nicalon and Tyranno fiber-reinforced ZrTiO4 matrix composites were assessed. The composites were reinforced with either uncoated or BN-coated fibers. The microstructure and interphase development were analyzed using scanning electron microscopy, transmission electron microscopy, and analytical electron microscopy. Mechanical behavior was characterized by strength and toughness measurements. Tyranno composites developed thinner interphases due to the differences in the structure and chemistry of the starting fiber resulting from the addition of Ti to the starting polymer precursor. BN-coated fiber composites developed a thicker carbon interphase layer due to incorporation of O into the as-received BN coating. Tyranno composites were weakened by fiber clustering and were not as tough as Nicalon composites due to a lack of thermal debonding.

We describe homoepitaxial growth and detailed in situ characterization of MgO(001). We have used, for the first time, high-speed Auger electron spectroscopy as a real-time probe of film composition during growth. Excellent short-range and long-range crystallographic order are achieved in films grown to a thickness of several hundred angstroms in the substrate temperature range of 450 °C to 750 °C. Moreover, the films become more laminar as the growth temperature increases, suggesting that MgO grows homoepitaxially by the step-flow growth mechanism at elevated temperature. The surfaces of films grown at 650°and 750 °C are smoother than those obtained by cleaving MgO(001).

The mixed-oxide compounds of CaO with TiO2 are of interest in the development of container vessels for actinide recycling processes in which Ca (dissolved in molten salt) is used to reduce the actinide oxide to actinide metal. The chemical interactions between the mixed-oxide compounds and molten salt saturated with Ca have been analyzed by applying thermodynamic principles. Although the solubility of CaO in molten salt is suppressed by the formation of mixed oxide with TiO2, thermodynamic calculations show that corrosion of CaO-TiO2 ceramics by molten CaCl2 or CaCl2-20 mole % CaF2 that contains metallic Ca in solution occurs by dissolution of the CaO component of the mixed-oxide compounds in the molten salt and reduction of the TiO2 component by the metallic Ca. The thermodynamic predictions are consistent with the experimental observations. The corrosion products produced and the sequence of the various phases depend upon the activity of the CaO produced in the molten salt by reduction reactions. The results of this study show that ceramic materials in the CaO-TiO2 system are not suitable container materials for actinide recycling.

A newly developed apparatus has been designed for performing fiber push-out testing on continuous fiber-reinforced composites at elevated temperatures. This test measures the force at which a fiber resists being pushed by a flat-bottomed indenter moving at a constant speed. The applied load versus time curve characterizes the fiber debonding and sliding behavior. Extending measurements to elevated temperatures required incorporating sample/indenter heating in a nonoxidizing environment. With this new apparatus, fiber push-out tests have been performed up to 1100 δC in a vacuum of 10-6 Torr. A line-of-sight to the sample is maintained during the test which allows video monitoring of the push-out process. Results are shown for SCS-6 SiC fiber-reinforced Ti-24Al-llNb (at. %) and Ti-15V-3Cr-3Sn-3Al (at. %) matrix composites. The results are discussed in terms of residual stresses, interfacial wear, matrix ductility, and changing modes of interfacial failure. The effect of temperature-dependent interfacial wear on the interfacial roughness contribution to frictional shear stresses during fiber sliding is examined.

Ca0.5Sr0.5Zr4P6O24 (CSZP) powders were prepared by the decomposition/combustion method using Ca(NO3)2 · 4H2O, Sr(NO3)2, ZrO(NO3)2 · xH2O, NH4H2PO4, urea, and NH4NO3 as starting materials. The homogenized slurries of the mixture were heated at 500 °C for 5 min to obtain CSZP powders. The as-synthesized powders were amorphous and crystallized after heating 800 °C for 2 h. The specific surface area of the powder was varied with the batch weight of starting materials or the amount of urea and ammonium nitrate. Powders with high specific surface area (150 m2/g) could be produced by this method. The sinterability of the powders was comparable to that of sol-gel derived powders. The sintered density of the compacts was 99% of theoretical after firing in air at 1350 °C for 6 h.

Ground granulated blast-furnace slag was reacted in 5 M (pH 14.7) and 1.5 M (pH 14.2) NaOH solutions at a water/slag ratio of ∼0.4, and characterized by unconfined compressive strength testing, scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction. The reacted material consisted of a dense layered matrix interspersed with unreacted glass particles and regions of reaction products with higher porosity. CSH(I) and (C, M)4AH13 were identified by x-ray diffraction. The C-S-H (calcium silicate hydrate) phase is proposed to consist mainly of structurally imperfect layers of tobermorite, interleaved with layers of (C, M)4AH13. Other cations, most significantly Na+, are incorporated into the structure. Use of the highly concentrated solution (5 M) produced a higher degree of reaction and, consequently, higher compressive strength (38 MPa after 28 days for 5 M solution vs 21 MPa for 1.5 M).

We have studied the effects of the kinetic energy of mass-separated O+ beams on the growth of CuO thin films deposited on unheated MgO(001) and at 510 °C, in energy ranging from 10 to 200 eV by x-ray photoemission spectroscopy, x-ray diffraction, reflection high-energy electron diffraction, and scanning electron microscopy. The films deposited at 510 °C show a full width at the half maximum (FWHM) of 0.06°for the rocking curve through the (111) peak, regardless of the kinetic energy of oxygen ions. CuO has been epitaxially grown on MgO(001) without heating it in a vacuum of 4 × 10−7 Pa. The x-ray diffraction intensity of the CuO(111) increases with an increase in the kinetic energy of O+, and its FWHM approaches that of the CuO film grown at 510 °C. The surface morphology is improved for the films deposited on unheated substrates.

It has been shown that ion implantation produces remarkable improvements in surface-sensitive mechanical properties, as well as other physical and chemical properties in polymers. To understand mechanisms underlying such property changes, various polymeric materials were subjected to bombardment by energetic ions in the range of 200 keV to 2 MeV. The magnitude of property changes is strongly dependent upon ion species, energy, and dose. Analysis indicated that hardness and electrical conductivity increased by employing ion species with larger electronic cross sections and with increasing ion energy and dose. The results showed that electronic stopping or linear energy transfer (LET, energy deposited per unit track length per ion) for ionization was the most important factor for the enhancement of hardness, while nuclear stopping or linear energy transfer for displacement generally appeared to reduce hardness.

The effect of fiber coating on the creep behavior and damage mechanisms of unnotched SCS-6 fiber-reinforced Ti3Al matrix composites under longitudinal and transverse loading was investigated at 700 °C. Stresses ranging from 700 to 900 MPa and 200 to 400 MPa were used for longitudinal and transverse loading, respectively. An Ag/Ta duplex layer was coated onto the SCS-6 fiber prior to consolidation via physical vapor deposition. The microstructure of the crept composites was examined to determine the creep deformation mechanisms. The creep cracking behavior of the notched composites was also studied at initial stress intensity factors, Ki, ranging from 15 to 20 MPa-m1/2. Microstructural observation revealed that multiple fiber fracture (at low to medium stress levels), microcracking along the reaction zone/matrix interface (at medium stress levels), and matrix cracking extending from the broken fiber ends (at high stress levels) were the major damage mechanisms during quasi-steady state creep under longitudinal loading. The results show that the Ag/Ta duplex coating significantly improved the creep resistance and flexural strength of the composite under transverse loading. The Ag/Ta duplex coating was also shown to significantly prolong the creep rupture life of SiC fiber-reinforced Ti3Al composites.

The interface between diamond and silicon, fabricated by growing diamond films on (001) silicon by microwave plasma assisted chemical vapor deposition (MPACVD), was characterized by high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). Two types of interface morphology were identified. Type A interfaces contain an amorphous transition layer composed of silicon, carbon, and oxygen; the diamond overgrowth on this layer consists of nanocrystalline grains with random orientations. Type B interfaces consist of large diamond grains having special orientations with respect to the silicon substrate, without an obvious presence of a glassy phase and with a much lower oxygen content than type A interfaces.

Dispersions of uniform submicron spherical particles consisting of silica cores and yttria coatings, or vice versa, were prepared by a precipitation technique. The overall size of the particles and the thickness of the shells could be varied over a wide range. Such powders were used to form green bodies by sedimentation, centrifugation, or pressure filtration, and the density and the pore size distribution of the resulting solids were evaluated. The green bodies were sintered and the changes in density, phases, and microstructure were followed with temperature. In general, the coated powders exhibited enhanced densification. On processing composite solids at temperatures <1000 °C, the formation of Y2Si2O7 took place, which caused a pronounced shrinkage of the samples. Powders of coated particles having the same silica/yttria ratios sintered at lower temperatures when the shell was composed of silica rather than of yttria. When either silica or yttria were in molar excess in the coated particles, the sintered products had a mixed composition of Y2Si2O7 and the component in excess. By terminating the sintering process before the grain growth started, the solids displayed a well-defined microstructure with a uniform distribution of areas of one phase in the matrix of the matter in excess. This property was mainly due to the uniformity of initial powders in terms of the particle size and the coating.

A procedure is described that yields uniform spherical colloidal palladium particles of modal diameters ranging between 0.1 and 0.7 μm. The process consists of two stages. First a monodispersed solid composite precursor is precipitated in solutions containing PdCl2, urea, and a nonionic surfactant. The resulting particles are then reduced in aqueous media, either by hydrazine or ascorbic acid in the presence of a protective agent. No change in particle shape occurred during the transformation to pure metals.

A counterflow diffusion flame burner was used to produce nanophase vanadium-phosphorus oxide powders in a hydrogen-oxygen flame. Liquid precursors, i.e., VOCl3 and PCl3, were used as source materials in a 1:1 ratio. In situ formation processes were investigated at two temperatures by laser light scattering, by emission and absorption spectroscopy, and by collecting particles directly onto carbon-coated TEM grids. At the higher temperature, the collected powders are spherical particles about 30 to 50 nm in diameter. At the lower temperature, the powders collected are chain-like structures composed of particles 5 to 10 nm in diameter. Particles formed in the burner were collected also from the burner's flanges and from two auxiliary strips. Their crystalline phases and surface area were determined by x-ray diffractometry, FT-IR spectroscopy, and BET analysis by nitrogen desorption. These results indicate a strong influence of temperature on the crystalline phases of the powders. At the higher temperature, the powder collected is a mixture of VOPO4 · 2H2O and δ-VOPO4. This mixture forms Λ-VOPO4 upon subsequent reheating at 750 °C. At the lower temperature, the powders collected are a VOHxPO4 · yH2O phase and VO(H2PO4)2, and form β-VOPO4 and V(PO3)3, respectively, upon subsequent reheating at 750 °C.

Amorphous calcium phosphate coatings on the order of 1 μm thick were deposited onto titanium and silicon substrates using an ion-beam sputtering technique. The target material utilized for sputter deposition was plasma-sprayed fluorapatite [Ca10(PO4)6F2; FA]. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to analyze the coatings. The amorphous as-deposited coatings were annealed in air (at 500 °C or 600 °C) to a crystalline state consisting of a polycrystalline FA matrix with a small amount of microcrystallites of a different composition. The higher annealing temperature (600 °C) tended to produce coarser FA and microcrystallite grains; however, the coatings buckled on the titanium substrates as a result of the heat treatment. Attempts to form the FA phase by in situ annealing in the vacuum chamber at a substrate temperature of 500 °C were not successful. The average bond strength for the as-deposited and 500 °C post-annealed coatings was comparable, while the lowest bond strength was observed in the 600 °C post-annealed coatings. The results suggest that the 500 °C post-annealed coatings have a suitable structure and possess sufficient adherence to be acceptable for use in certain medical and dental implant applications, and further tests under physiologic conditions will be conducted.