Superplastic silicon carbide ceramics were fabricated at low temperatures by a liquid phase sintering very fine β–SiC powder. The microstructural features of this material, of both before and after the superplastic deformation, have been investigated by transmission electron microscopy. Evaluated from the point of view of phase transformation, dislocation motion, and dynamic grain growth, the materials show very stable microstructures, indicating that the superplastic deformation process was dominated by the liquid phase assisted grain boundary sliding. In addition, the material is also characterized by the formation of clusters of fine SiC particles (5–20 nm) encapsulated in layered graphitized carbon.

Phase relations in two binary systems MgAl2O4–ZnAl2O4 and MgAl2O4–Mg2TiO4 have been studied and phase diagrams for them have been constructed. Based on the data of x-ray phase and crystal-optical analyses, the formation of a continuous series of solid solutions with spinel structure between the terminal members of the systems studied has been established. In the MgAl2O4–ZnAl2O4 system the solid solution is stable in the range from room temperature to melting temperature. In the MgAl2O4–Mg2TiO4 system the solid solution decomposes below 1380 °C, yielding the formation of limited regions of homogeneity on the basis of MgAlM2O4 and Mg2+2δ Ti1–δO4. Decomposition of the solid solution is accompanied by crystallization of MgTiO3.

A near-surface thin layer is melted when alumina is pulsed-laser-irradiated in an Ar–4% H2 atmosphere or in air. A thin layer of amorphous phase forms when the substrates are irradiated in Ar–4% H2 at 1 to 1.3 J/cm2 with multiple laser pulses. Amorphous phase is also found in samples laser-irradiated in air and oxygen. After a laser pulse at an energy density of 1.6 J/cm2 or higher the melt solidifies epitaxially from the unmelted substrate with a cellular microstructure. There is a decrease in the cooling rate of the melt as the laser energy density is increased because more heat must be dissipated. The amorphous phase forms when the heat input due to the laser pulse produces a superheated melt that cools down sufficiently fast to avoid crystallization. Very small particles of aluminum in the laser-melted and subsequently solidified layer are observed only in samples laser-irradiated in an Ar–4% H2 atmosphere. In this reducing atmosphere, the alumina is possibly reduced to metallic aluminum which is mixed into the melt by the turbulence provoked by the laser pulses. The effects of these metallic particles on copper deposition when the irradiated substrates are immersed in an electroless bath are discussed.

The microstructure of YBa2Cu3O7−δ (YBCO) materials, melt-textured in air and quenched from the temperature range 900–;990 °C, has been characterized using a combination of x-ray diffractometry, optical microscopy, scanning electron microscopy, transmission electron microscopy, and energy dispersive x-ray spectrometry. BaCu2O2 and BaCuO2 were found to coexist in samples quenched from the temperature range 920–960 °C. The formation of BaCu2O2 preceded the formation of YBCO. Once the YBCO had formed, BaCu2O2 was present at the solidification front filling the space between nearly parallel platelets of YBCO. Large Y2BaCuO2 particles at the solidification front appeared divided into smaller ones as a result of their dissolution in the liquid that quenched as BaCu2O2.

A detailed analysis of Pt/Ti, Pt/TiO2, and Pt/ZrO2 electrodes was carried out to develop a bottom electrode stack for sol-gel derived thin film capacitors. For the Pt/Ti stack, the choice of layer thickness and deposition temperature is found to affect adhesion to the SiO2/Si substrate as well as the extent of hillock formation and Pt–Ti interaction. By using elevated temperature deposition, Pt films close to 1 μm in thickness can be produced with relatively good adhesion and morphological stability using Ti adhesion layers. In addition, Pt films grown on ZrO2 and TiO2 adhesion layers exhibit little morphological change and no degradation in sheet resistance after annealing at 650 °C. However, neither ZrO2 nor TiO2 are as effective as Ti metal in promoting Pt adhesion. Experiments aimed at establishing a correlation between hillock formation and capacitor yield revealed two important results. First, the behavior of Pt/Ti stacks during annealing in air is markedly different from their behavior during PZT film crystallization. Second, preannealing of the Pt/Ti in air prior to PZT film growth actually improves capacitor yield, even though hillock formation occurs during the preannealing treatment. Implications of these results regarding the role of hillocks in controlling capacitor yield are discussed.

Potassium acid phthalate (KAP) crystals are promising as substrates for the growth of highly oriented films of conjugated polymers with exceedingly high and fast nonlinear optical response. We report the KAP optical properties (real and imaginary parts of the refractive index ñ = n + ik) in the near infrared and visible range deduced by ellipsometric measurements and direct inversion of transmittance and near-normal incidence absolute reflectance measurements. In the infrared region n was also deduced by the interference fringes.

Careful studies of the corrosion, redox, galvanic, and oxygen evolution/uptake reactions associated with YBa2Cu3O7–δ and related compounds have been completed. These studies have led to an understanding of the many factors that contribute to the poor material characteristics exhibited by these popular high-Tc phases. With knowledge of the structure-reactivity relationships, a powerful crystal engineering approach has been developed that is capable of producing cation substituted versions of YBa2Cu3O7–δ; the resulting compounds therefrom produced exhibit markedly improved processability, oxygen stability, and durability characteristics. These materials have been combined in thin film structures so as to make prototype SNS junctions and SQUID sensors which exhibit promising device performance characteristics.

Small angle neutron scattering investigations performed on Fe1−x–Nix alloys with 0.26 ≤ x ≤ 0.45 revealed a thermodynamically driven decomposition below 800 °C. The miscibility gap extends at least from 30 at.% Ni to 45 at.% Ni. The diffusioncontrolled decomposition produces fractal morphologies during the early stages of the process. During annealing the structure of the precipitated phase densifies continuously from mass fractals with small dimensionality (1 ≤ dm ≤ 3) to surface fractals with 2 ≤ ds ≤ 3. The results are compared with recent simulations of aggregation and growth as well as with a new analysis of spinodal decomposition, both predicting fractal morphologies.

We performed embedded atom method calculations of surface energies and unstable stacking fault energies for a series of intermetallics for which interatomic potentials of the embedded atom type have recently been developed. These results were analyzed and applied to the prediction of relative ductility of these materials using the various current theories. Series of alloys with the B2 ordered structure were studied, and the results were compared to those in pure body-centered cubic (bcc) Fe. Ordered compounds with L12 and L10 structures based on the face-centered cubic (fcc) lattice were also studied. It was found that there is a correlation between the values of the antiphase boundary (APB) energies in B2 alloys and their unstable stacking fault energies. Materials with higher APB energies tend to have higher unstable stacking fault energies, leading to an increased tendency to brittle fracture.

Laminated composites containing alternate layers of Si3N4 and TiN/Si3N4 materials were used as model material for investigating the crack behaviors and mechanical properties. Results indicated that both strength and toughness in laminated composites were higher than that of monolithic silicon nitride. The failure profiles were affected by the stored strain energy prior to failure and the stress gradient in each layer. Cracks deviated successively from one layer to the other due to periodic stress distribution. Samples with better strength and toughness also had a longer crack propagation path and higher amplitude of crack deviation. The periodic stress distribution in laminated composites was confirmed by the measurements of indentation crack length. Results also suggested a tensile stress in the Si3N4 layer and compressive stress in the TiN/Si3N4 layer, in directions normal to the free sample interface.

Thin films of lead titanate were prepared in situ using radio-frequency magnetron sputter deposition. The in situ perovskite phase formation has been studied as a function of the substrate temperature, the sputtered lead flux, and the substrate nature. The incident lead flux is controlled by the lead content in the target. An equilibrium zone, i.e., a saturation effect of the lead incorporation, exists where the films are stoichiometric. The temperature at which this zone appears depends on the sputtered lead flux and the substrate type. The growth mechanism is governed by a competition between the arrival rate of Pb and their re-evaporation from the film during the growth. The in situ formation temperature of the perovskite phase increased when the incident Pb flux increased. As a result, PbTiO3 films have been prepared at low temperature with appropriate combination of the substrate temperature and the lead content in the target, i.e., the sputtered lead flux. Since the lead sticking coefficient is very sensitive to the substrate material, the perovskite phase appears at different temperatures, depending on the substrate nature. PbTiO3 films are obtained at 550 °C on Al2O3 and SrTiO3 substrates; on Si/SiO2/Ti/Pt substrates, stoichiometric films are obtained at 440 °C. The structure and the microstructure of the films were examined at various deposition conditions. The substrate temperature strongly influenced the film orientation, and the crystallinity depended on the incident lead flux. High quality thin films (FWHM = 0.2°) are obtained at 550 °C on SrTiO3 substrates. The films deposited at 440 °C on Si/SiO2Ti/Pt show ferroelectric properties. This self-controlling mechanism of the stoichiometric composition allows the growth of ferroelectric films at low temperature, compatible with semi-conductor technologies for the realization of integrated circuits

Films of Bi–Ca–Sr–Cu–O (BCSCO) superconductor of the Bi2CaSr2Cu2Ox composition have been grown by the liquid phase epitaxy method (LPE) using a partially closed growth chamber. The films were grown on (110) NdGaO3 substrates by slow cooling under optimized conditions below the peritectic melting point (885 °C) of Bi2CaSr2Cu2O8. Optimization of parameters, such as seed rotation, soak of initial growth temperature, and growth period, results in the formation of the 2122 phase of BCSCO. X-ray diffraction (XRD) measurements show that the films grown on (110) NdGaO3 have a preferred (11n) orientation. The best values of zero resistance transition (Tc0) and critical current density (Jc0) obtained for films grown on (110) NdGaO3 substrates are 87 K and 5.7 × 104 A/cm2 (at 20 K), respectively. The films grown at rotation rates of less than 30 and more than 80 rpm are observed to be associated with a subphase in the Bi2CaSr2Cu2O8 system. Electron microprobe analysis indicates the composition of this subphase to be Bi0.07Ca0.93Sr2Cu5O8. Higher growth temperatures (>860 °C) also encourage the formation of this phase.

The evolution of the contact area during an indentation process has been xamined by an ac technique and also by finite element analysis on five mechanically different materials. Constant contact area regimes were observed during the initial unloading stage and the duration of that regime depends strongly on material properties. The consistency of the results obtained by the two approaches not only proves the validity and advantage of the ac indentation technique but also confirms the applicability of contact stiffness equation. The influence of a hardness impression on unloading characteristics has also been clearly demonstrated by numerically simulating a reloading process.

A new class of complex perovskites REBa2ZrO5.5 (where RE = La, Ce, Eu, and Yb) have been synthesized and sintered as single phase materials by the solid state reaction method. The structure of these materials was studied by x-ray diffraction, and all of them were found to be isostructural, having a cubic perovskite structure. X-ray diffraction and resistivity measurements have shown that there is no detectable chemical reaction between YBa2Cu3O7–delta; and REBa2ZrO5.5 even under severe heat treatment at 950 °C, and that the addition of REBa2ZrO5.5 up to 20 vol.% in YBa2Cu3O7–δ shows no detrimental effect on the superconducting properties of YBa2Cu3O7-δ. Dielectric constants and loss factors are in the range suitable for their use as substrates for microwave applications. Thick films of YBa2Cu3O7–δ fabricated on polycrystalline REBa2ZrO5.5 substrates gave a zero resistance transition temperature Tc(0) ∼ 92 K, indicating the suitability of these materials as substrates for YBa2Cu3O7–δ.

Graphite encapsulated nanocrystals produced by a low carbon tungsten arc were analyzed to determine their chemistry, crystallography, and nanostructural morphology. Metallic nanocrystals of Fe, Co, and Ni are in the face-centered cubic (fcc) phase, and no trace of the bulk equilibrium phases of body-centered cubic (Fe) and hexagonal close-packed (Co) were found. Various analytical techniques have revealed that the encased nanocrystals are pure metal (some carbide was found in the case of Fe), ferromagnetic, and generally spherical. The nanocrystals are protected by turbostratic graphite, regardless of the size of the nanocrystals. The turbostratic graphite coating is usually made up of between 2 and 10 layers. No trace of any unwanted elements (e.g., oxygen) was found. The low carbon: metal ratio arc technique is a relatively clean process for the production of graphite encapsulated nanocrystals.

Ultrafine titania particles were synthesized from titanium tetraethoxide (TEOT) dissolved in ethanol. The concentration of water and of the soluble polymer hydroxypropylcellulose (HPC) were varied to control particle size. The HPC adsorbed onto the titania particles during growth, providing a steric barrier to aggregation. Electron microscopy showed that particles smaller than 70 nm were formed at high water concentrations (R > 120 where R is the molar ratio [H2O]/[TEOT]) and in the presence of HPC. The annealing-induced, phase-transformation behavior of these particles (amorphous → anatase → rutile) from 100 to 1000 °C was characterized by x-ray, Raman, and infrared techniques. The conversion of anatase to rutile occurred more readily for particles made at high water concentrations and with HPC. For particles formed by premixing TEOT with HPC prior to hydrolysis at R = 155, an 800 °C anneal yielded a rutile fraction exceeding 95%; particles made at R = 5.5 with no HPC showed negligible conversion at this temperature.

Post formed, silica submicrospheres synthesized by Stober's method have been subjected to a high intensity ultrasound radiation (20 kHz, 100 W/cm2) and their size, morphology, and surface silanol structure modified in situ. The processed silica powders have been characterized by a variety of techniques, such as powder x-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), BET nitrogen adsorption, and FT-IR spectroscopy. The silica microspheres formed through an irreversible sol-gel transition have been shown to aggregate by the condensation of interparticle silanols to larger particles under the influence of the shock waves emanating from an imploding cavity. The particle size as a function of sonication time passes through a maximum, suggesting the disintegration of the aggregates on longer exposure to ultrasound radiation. The sonication of dried silica microspheres in an inert dispersant decalin also led to the aggregation of microspheres to a lesser degree, suggesting the deactivation of surface silanols. Infrared spectroscopic investigations suggest a disruption of the hydrogen bonded network of surface silanols. The observed morphological changes have been discussed in terms of direct effect of cavitation on well-formed spheres rather than changes in growth mechanism and capture of primary particles.

A thermochemical analysis is performed in the quaternary system Cu–In–S–O at 298 K, including the respective four ternaries. The Cu–In phase diagram is updated with respect to the new experimental as well as to the new thermochemical results in the literature. Free energies of In6S7, In2.8S4, CuIn2, and Cu2In2O5 have been estimated. Consistent sets of data are used for the calculations of the ternary systems with the program thermo, and the results are used to calculate the quaternary tetrahedron Cu–In–S–O with the program thermoq; the algorithm is given. Twelve quaternary two-phase equilibria have been found. They are used to calculate predominance area diagrams of the quaternary system with the program stadiaq for different oxygen partial pressures. The algorithm of this program is given. From these diagrams it becomes obvious that CuInS2 is unstable in air and even in UHV systems and should react to form In2(SO4)3 and Cu2S at oxygen pressures larger than log p (pascal) = −51.5. The results are useful for research in fields such as oxidation and crystal growth of CuInS2 and for development of processes for producing this compound.

A new design for solid oxide fuel cells (SOFC's) was developed aiming at the reduction of the total electrical resistance of the cell. The thickness of the electrolyte was decreased, while the anode took on the role of the substrate. The pore structure with respect to gas permeability of this component has to be optimized for the proper operation of this design. Anode substrates, consisting of a cermet (yttrium-stabilized ZrO2 and metallic Ni) and produced by two different processes, coat mix and tape casting, were characterized with respect to pore structure (shape and mean radius), porosity (total, open and permeable), pore size distribution and air permeability. The following methods were used: (i) optical and electron scanning microscopy in combination with image analysis, (ii) mercury porosity, and (iii) air permeability. Correlations between air permeability and porosity and also the percentage of permeable pores in anodes show the superiority of coat mix samples to tape-cast ones. It has been observed that the coat mix process can produce anode substrates with interconnecting porosity, while tape casting, as used in this study, needs some modifications in order to be appropriate for this purpose.

Sedimentation in organic solvents was followed by hot-pressing to produce 2 mole % yttria stabilized zirconia-NiAl functionally graded materials (FGM's). These FGM's were better able to accommodate high levels of residual stress than alumina-NiAl FGM's; this is possibly due to enhanced tetragonal phase retention. However, we found that the zirconia layer in these FGM's subsequently experiences room temperature transformation of t-ZrO2 to m-ZrO2.