RuO2 single crystals were obtained by evaporation of PbO from Pb2Ru2O6.5 at high temperatures and were verified as good standards for WDS analysis. They were used for the investigation of phase equilibria and the extent of solid solubility in the RuO2–TiO2 system by WDS quantitative microanalysis. The solid solubility at 1350 °C was determined to be 16.5% TiO2 in RuO2 and 13.5% RuO2 in TiO2.

The ac electrical behavior of yttria doped with a zirconia concentration ranging from 0.15 to 20 mole % is investigated in the temperature range of 800 to 1300 °C. The ac electrical data, obtained in the range from 5 Hz to 13 MHz, indicated two distinct relaxations when analyzed in the impedance plane. These relaxations are attributed to lumped grains and trapping within grain boundaries, including possible electrode/sample effects. The admittance plane analysis revealed a semicircular relaxation in the low-frequency region, indicating identical response to that of the low-frequency relaxation of the impedance plane. The incorporation of zirconia into yttria is found to lower the activation energy of conduction in the grains and enhance ionic contribution to the overall electrical conduction. The PO2 studies and transference number measurements near atmospheric region indicate that p-type conduction dominates for the lightly doped yttria. An ionic contribution to the conduction processes becomes significant in heavily doped samples at/near atmospheric PO2.

The in-flight modification of titanium carbide powders was carried out in radio-frequency (rf) inductively coupled plasmas. The powders were partially melted and evaporated, and then subjected to modifications in morphology, size, and chemical composition. Both the Ar–H2 and Ar–N2 plasma treatments induced the formation of carbon-site vacancies in titanium carbide. The mixing of NH3 to Ar–H2 plasma at the plasma tail, and the Ar–N2 plasma treatment resulted in the partial substitution of carbon by nitrogen. The variation in physical and chemical modification was discussed compared with the predictions by the thermochemical analysis, and the numerically obtained heat transfer of our preceding paper.

Metastable δ-Bi12SiO20 may crystallize from the overheated Bi12SiO20 melt and transform into stable γ-Bi12SiO20 at about 569.5 °C during the subsequent slow cooling process. The transition δ-Bi12SiO20 → γ-Bi12SiO20 is irreversible and the γ-Bi12SiO20 is stable up to the melting temperature. By quenching the Bi12SiO20 melt, pure δ-Bi12SiO20 can be obtained at room temperature. The quenched δ-Bi12SiO20 crystal is nontransparent and has a space group of Fm3m (225) and a lattice constant of 55.417 Å at 20 °C. The quenched metastable δ-Bi12SiO20 can transform into pure γ-Bi12SiO20 at 382.5–386.1 °C with an exothermic heat of 31.68–32.38 J/g. The transition-produced δ-Bi12SiO20 crystal is still nontransparent and has a large lattice distortion. The transition δ-Bi12SiO20 → γ-Bi12SiO20 causes about 6% volume contraction, which may result in cracking of the grown crystal. By controlling the growth parameters, this transition can be effectively avoided.

Earlier publications describe the counterflow diffusion flame burner and its unique capability to produce oxide particles having certain structures, such as spheres of one material coated with another, spheres of one composition with attached bulbs of another composition, and uniform multicomponent mixtures. Here we describe the production and properties of bulk quantities of powders produced using this burner. Measurements were made of specific surface area and, for titania, of phase composition. It was found that the controls over powder characteristics used in other forms of flame-synthesis are equally effective in the counterflow diffusion flame burner. We found that the specific surface area of both silica and titania powders decrease with increasing precursor concentrations. Transmission electron microscopy analysis of the titania powders indicates that the mean size of the particles that comprise these powders increases with increasing concentration. These trends are consistent with the collision-coalescence theory of particle growth. In addition, the crystalline phase of titania can be controlled by selecting the appropriate feed stream. For example, over the ranges TiCl4 precursor concentrations tested, feeding it only into the oxidizer stream yields mainly anatase TiO2 powders, while feeding only into the fuel stream yields mainly rutile TiO2 powders. These trends can be explained by the known atmosphere-dependent anatase-rutile transformation. The present data demonstrate that, in addition to its unique capability to produce certain particle shapes and morphologies, the counterflow diffusion flame burner can be manipulated to produce either of the major commercial titania phases, and also silica, with a wide range of specific surface areas.

Thin films in the system BaTiO3–SrTiO3 have been grown on Ti electrodes with control of the Ba/Sr composition in aqueous solutions of (Ba, Sr) (OH)2 by the hydrothermal-electrochemical method. Barium contents of the solid-solution films were always lower than those of the synthesis solutions used. The BaTiO3 and the (Ba, Sr)TiO3 solid-solution films included “crater-shape” defects that resulted from the breakaway of the growing film, whereas no such defects were observed in the SrTiO3 film. This dependence of the defect generation on the film composition was interpreted to be caused by differences of anodically evolved oxygen gas pressure in “short-circuiting paths” that exists characteristically in the films grown by this method.

In this work a hypothesis to explain the alkaline hydrolysis degradation process of calcium aluminate cement concrete (CACC) is presented. The hypothesis is based on x-ray diffraction (XRD) data of some samples taken from real Spanish CACC structures. The identification from XRD data of a hydrated alkaline aluminate could serve as a guide to differentiate both processes of normal carbonation and alkaline hydrolysis.

The surface of Zr41.25Ti13.75Cu12.5Ni10.0Be22.5, a bulk metallic glass prepared by RF induction melting, has been imaged using atomic force microscopy. The untreated surfaces were very smooth; features were no higher than 3 nm over a 10 × 10 μm region, comparable to many polished surfaces. Two types of microstructure were also observed; periodic striations forming either a striped or a checkered structure were present, with wavelengths between 1 and 2 μm, and amplitude of approximately 2 nm; in other cases, “cracked mud”-like patterns were observed. These microstructures could be related to strain-induced surface roughening; preliminary calculations are presented that are consistent with this hypothesis.

A route to prepare nanometer-sized Mo particulates in Al2O3 was attempted by a combination of solution reactions in molecular scale and forcing precipitation by a spray-drying technique. MoO3 was first dissolved in ammonia water and then added in the slurry with high purity, submicrometer Al2O3 powder. Mixed suspension was spray-dried, and then the dried granules were reduced by hydrogen gas and further hot-pressing to a bulky composite at various temperatures. Dissolution of Mo oxide, adsorption reactions on the alumina surface, and surface potential of alumina particles in homogeneous ammonia suspension were studied. Characterization of the granules, including compactability, flowing properties, surface morphology, grain growth of Mo and Al2O3, and mixing homogeneity, were examined. Homogeneity of the spray-dried granules was determined by the calculation of mixing index and the observation of the microstructure of the sintered body. The existence of intergranular, intragranular, and nanosized Mo particulates within Al2O3 grains was observed by transmission electron microscopy (TEM). All the evidence revealed that homogeneous composites with nanometer-sized Mo had been successfully prepared by this attempt with the proposed chemical roue and following the spray-drying process.

Using a prehydrolysis technique, transparent gels with very high aluminum content can be achieved with the use of isopropanol. Here 13C, 27Al, 29Si and 17O NMR at various stages of preparation show that when the aluminum added exceeds the number that silanols can fully protect, the excess aluminum alkoxide groups readily undergo transesterification with isopropanol. The aluminum isopropoxide (Al–OPri) groups thus formed are shown to be sufficiently stable that attack by water is impeded, thus allowing the remaining silicon alkoxide groups to hydrolyze and condense to form a homogeneous gel.

Mesoscopic structures of SiC fibers produced from polycarbosilane by different methods were studied by diffraction and small-angle scattering of neutrons and x-rays. Microvoids of a size of 4–10 Å in diameter have been observed for the first time by neutron scattering in a medium momentum transfer range (Q = 0.1–1.0 Å−1). The size and the volume fraction of β–SiC particles were determined for fibers prepared at different heat-treatment temperatures. The results show that wide-angle neutron scattering measurements are especially useful for the study of the mesoscopic structure of multicomponent materials.

Amorphous hydrogenated silicon carbon alloys were synthesized by C2H2 ions implantation in a silicon substrate at different fluences to obtain samples with different carbon atomic concentrations (10−50 at. %). As-implanted and subsequently annealed samples were investigated by using Rutherford backscattering, infrared, and Raman spectroscopies in order to follow the crystallization process. It was found that crystallization of stoichiometric SiC phase starts at 1000 °C both in low and high containing carbon films, while at the stoichiometric composition silicon (or carbon) was found to clusterize into homonuclear islands even at lower temperatures. The analysis of the fundamental absorption edge reveals the presence of an optical energy gap of about 1.3 eV independently on the film composition in the as-implanted samples, while after the thermal process at 1000 °C it increases to 2 eV for a carbon concentration below 0.5 and up to 1.8 eV for all those samples with a carbon excess.

We have developed a simple and rapid method for the synthesis of a precursor solution used in the production of SBT powders and thin films of the layered-perovskite phase SrBi2Ta2O9 (SBT). Precursor solution preparation takes less than 30 min and involves the generation of two solutions: (a) Bi(O2CMe)3 dissolved in pyridine and (b) Ta(OCH2Me)5 added to Sr(O2CMe)2 and then solubilized by HO2CMe. After stirring separately for 10 min, these solutions are combined, stirred for an additional 10 min, and used without any further modifications. The individual solutions and ternary mixture were studied using a variety of analytical techniques. Films of the layered-perovskite phase were formed at temperatures as low as 700 °C. Ferroelectric testing of SBT films, fired at 750 °C, reveals standard hysteresis loops with no fatigue for up to 4 × 109 cycles.

Small additions of Bi2O3 or bismuth titanate improve the dielectric properties of Ba4.5Nd9Ti18O54 at microwave frequencies. It was found that Bi3+ can replace Nd3+ up to 15 mol%, the limiting composition of solid solution being Ba4.5(Nd0.85Bi0.15)9Ti18O54. At the solid solution limit the temperature coefficient of resonant frequency attains its minimum value. The modified ceramic is distinguished by high permittivity of 99 and a Q-value of 5500. The temperature coefficient of resonant frequency is low, 15 ppm/K. After exceeding the solid solubility limit, additional Bi2O3 concentrates as a Bi-rich phase at the grain boundaries, causing considerable reduction of the Q-value and an increase of τf.

Electrodeposited Cu/Ni multilayers with different modulation lengths Λ = 4–18 nm were examined by means of x-ray diffraction and transmission electron microscopy. Preferred orientations of [111], [110], and [001]-types, as determined from relative x-ray diffraction peak intensities, were seen in the multilayers. By means of computer simulations of the measured x-ray diffraction spectra, several parameters of the multilayers, such as Λ-values and fluctuations ΔΛ, as well as lattice strain, were determined. Multilayers having large Λ were found to be fully relaxed due to interfacial dislocation formation. In short Λ [001]-texture multilayers partial strain relaxation occurs, probably due to the incorporation of Cu into the Ni layers. Both of the processes lead to the diffuse Cu/Ni interfaces. Short wavelength multilayers with a [111]-preferred orientation were almost fully strained. The importance of the [111]-texture in the improvement of mechanical strength of Cu/Ni multilayers resulting from its enhanced ability for stain accommodation is discussed.

Modelling, but more importantly, measurements of residual stresses are needed to guide the design and development of high integrity ceramic/metal joints. This study evaluates the influence of the metal workpiece on the residual stress state present in the ceramic part of the joint. Si3N4 was directly bonded via the active metal brazing route to several metals Cu, Mo, W, Ta, Nb, Zr, Ti, and AISI 316, selected to cover an extended range of thermomechanical properties. The residual strains in the joints were measured using an x-ray diffraction technique. The results indicate that the maximum residual stresses scale with the thermal mismatch for metals with low coefficients of thermal expansion. The experimental results are compared with analytical calculations of the residual stresses.

Specimens of two Al–Cu–Mg (2124) composites, reinforced with 20 vol% of either Si3N4 particulates or Si3N4 whiskers, were tested under experimental conditions close to those for optimum high strain rate superplasticity. Both composites developed extensive internal cavitation during testing, but quantitative measurements show that significant cavity growth occurs throughout the test in the whisker-reinforced composite, but only at strains ≥1.0 in the particulate-reinforced composite. This difference in behavior is attributed to differences in the extent of a discontinuous liquid phase at the grain boundaries and at the matrix/reinforcement interfaces. It is concluded that the presence of an extensive liquid phase in the particulate-reinforced composite is beneficial for attaining high ductility because it relieves the stress concentrations from grain boundary sliding and thereby limits the growth of cavities.

We have used a combination of techniques to examine modifications in the structural characteristics of carbon nanofibers produced from the interaction of cobalt and copper-cobalt powders with ethylene at temperatures over the range 425 to 700 °C. The nanofibers generated from the interaction of cobalt with ethylene at 600 °C were found to be highly crystalline in nature. Incorporation of as little as 2% copper into the cobalt created a major modification in the conformation of the solid carbon deposit, which was composed of multiple nanofiber limbs emanating from a single catalyst particle, and in this state the carbon structures tended to be disordered. As the composition of the bimetallic was progressively changed to the point where copper became the major component, there was a significant increase in the degree of crystalline perfection of the nanofibers even though they maintained their multidirectional form. The transformation in structural characteristics of the carbon nanofibers is rationalized, according to a concept wherein the crystalline order of the deposit is related to the wetting properties of the bimetallic particles with graphite.

Zirconia (ZrO2) thin films were prepared by metalorganic chemical vapor deposition (MOCVD) using ultrasonic nebulization with new source materials, Zr(OBu)4, Zr(OBu)3(acac), Zr(OBu)2(acac)2, and Zr(OBu) (acac)3. This process is a simple and economic method to prepare oxide thin films. Zr(OBu)4 was successfully reacted with acetylacetone at a molar ratio of 1: 3. Polycrystalline thin films were deposited at a substrate temperature range from 300 to 550 °C. The substitution of alkoxy radicals by acetylacetone made the deposition rate higher and insensitive to substrate temperature. The films deposited below 450 °C mostly had a monoclinic structure, and those deposited above 450 °C had a tetragonal structure. The measured optical energy band gap of zirconia film was 5.32 eV.

Competitive gas-solid reactions have been observed during high-energy ball milling of zirconium metal powder under an ammonia atmosphere at room temperature. The milling processes were investigated by monitoring pressure changes and subsequently analyzing milled powders with x-ray diffraction, thermal analysis, and elemental composition analysis. It is shown that during an early stage of milling, while the pressure is decreasing, a hydridation reaction predominates and leads to the formation of ZrH2 phase. During further milling the pressure increases again, and corresponds to a nitridation reaction between ZrH2 and available nitrogen (either excess NH3 or incorporated nitrogen in the powder) to form ZrN. Hydrogen gas is liberated and complete conversion to ZrN occurs after prolonged milling. The above reaction sequence was confirmed by the nitridation reaction of ZrH2 ball milled in NH3 atmosphere.