The effect of changes in the oxygen partial pressure during the heat treatment of Bi-2223 tapes has been investigated. Distinct differences were observed in the phase assemblages, compositions, and critical current densities. Of particular importance in the correlation of transport properties and microstructure was the redistribution of lead in both the secondary phases and the Bi-2223 matrix. The highest Jc values were associated with tapes that contained Ca2PbO4 as part of the phase assemblage coupled with lower concentrations of lead in the superconducting phase. The high Jc of 30.4 kA/cm2 was obtained in tapes processed at 820 °C where the oxygen partial pressure was increased from 10% O2/Ar to 20% O2/Ar after 25 h of each 50-h sinter cycle. Samples processed only in 10% O2/Ar at 820 °C did not contain Ca2PbO4, had slightly higher concentrations of lead in the superconducting phase, and had significantly lower Jc values.

The alignment and the formation of (Bi, Pb)2Sr2Ca2Cu3O10 inside an Ag sheath were investigated for tapes from four different precursor powders. Microstructural characterization along with in situ transmission x-ray diffraction experiments revealed that the kinetics depended strongly on the processing technique and the phase assemblage of the precursors. The alignment process was governed by the preferential grain growth of the Bi-cuprates along the a-b plane and the constraint applied by the sheath. The formation mechanism of (Bi, Pb)2Sr2Ca2Cu3O10 was either the intercalation or the nucleation and growth, depending on whether excessive liquid is adjacent to the platelets.

Multifilamentary (Bi, Pb)2Sr2Ca2Cu3Ox/Ag composites have been studied by a nondestructive magneto-optical imaging technique in order to determine the effect of filament architecture on the local magnetic flux distribution. The images reveal the homogeneity of the flux distribution in the upper layer filaments under magnetizing and demagnetizing conditions, and the alignment and morphology of these filaments in tapes with nine different composite structures. Certain types of filament arrangements led to homogeneous flux distributions, while other types caused localized inhomogeneities in the flux distribution. Nonuniform filament thickness also resulted in a highly inhomogeneous flux distribution. These results are useful in selecting optimal composite structures for power applications.

The ac magnetic losses at power frequencies (60 Hz) were investigated for mono- and multifilament Ag-sheathed (Bi, Pb)2Sr2Ca2Cu3Oy (BSCCO-2223) tapes with similar Ic values at 77 K. The multifilament sample exhibited higher losses than the monofilament under the same conditions. Loss peaks are discussed in terms of intergranular, intragranular, and eddy current losses. Because of BSCCO's anisotropy, field orientation has a large effect on the magnitude of these peaks, even at relatively small angles. Losses for fields applied parallel to the c-axis of the textured BSCCO grains are larger by over an order of magnitude than those applied perpendicular.

AC susceptibility of ac has been measured simultaneously in three different ranges of Y–Ba–Cu –O ceramic samples in the presence of a large and variable temperature gradient. The results obtained for normal-superconducting or superconducting-normal transitions under the effect of the one-dimensional nonequilibrium temperature distribution reveal the vortex motion to consist of not only conventional flux expulsion (or flux penetration), but flux exchange too, appearing between different ranges of samples and between samples and their close physical environment. The thermal cycles are shown to represent a supplementary heat treatment, increasing the homogeneity of the sample and decreasing the pinning, which accelerate the process of vortex motion.

A polyvinylmethylsilane precursor has been used for the epitaxial growth of SiC thin films on 6H–SiC single crystal substrates. The films were prepared by dipping the single crystal 6H–SiC substrates into the precursor polymer solution with subsequent thermal treatments at different temperatures. Transmission electron microscopy (TEM) was used to characterize the microstructure and chemistry of the different SiC films. At 1100 °C, the film was amorphous and contained substantial oxygen. At 1600 °C, an epitaxial, single crystalline β–SiC film was observed.

Diamond-like carbon (DLC) films have been prepared by electrolysis of methanol solution using a pulse-modulated source. The deposition rate of the films is enhanced significantly compared to that of dc value. That the films do not contain bonded hydrogen is confirmed by infrared spectra. The structures of the films are characterized by Raman spectroscopy. These films show chemical inertness and hardness values in the range 12.5–19 GPa. Current-voltage characteristics of the films are measured, indicating that the resistivity is in the 107 Ω cm range and the breakdown field is larger than 1 MV cm−1.

Polycrystalline Ni50Al50 suitable for high pressure studies was prepared by grinding and subsequent annealing of an inert-gas atomized alloy. The equation of state was determined by energy-dispersive x-ray diffraction in a diamond anvil cell to 25 GPa. The bulk modulus Bo and the pressure derivative of the bulk modulus B′o were found to be Bo = 156 ± 3 GPa and B′o = 4.0 ± 0.5.

The new procedure for the hardness measurements of superhard materials including diamond using the scanning force microscope with the ultrahard fullerite C60 tip was developed. It is shown that diamond is plastically deformed under the indentation by the ultrahard fullerite indenter at room temperature. Now the correct measurements of diamond hardness have become possible. The hardness values measured are 137 ± 6 and 167 ± 5 GPa for the diamond faces (100) and (111), respectively.

Two methods for the preparation of semiconductor doped sol-gel films, for applications in nonlinear optics, have been studied and compared. In the first, porous films are spun from sols containing the cation precursor, and then reacted with H2S gas, and in the second, the cation is adsorbed onto the pore surfaces of passive films from aqueous solution before the gas reaction. Extensive results for CdS doping are given, and preliminary results are reported for other semiconductor species. It is shown that a sputtered silica layer can seal the structure to allow further heat treatment without loss of dopant. The effects of heat treatment of doped films are described, and the limitation of crystallite growth by pore size is shown.

Polyimides can be infused with silver complexes by the use of supercritical fluids. Highly reflective polyimide films were formed by infusing (1,5-cyclooctadiene-1,1,1,5,5,5-hexafluoroacetylacetonato)silver(I) [Ag(COD) (HFA)] into a number of polyimides and then thermally curing those films at 300 °C for time intervals between 30 min and 3 h. Reflectivities of the films exhibited strong dependence on the infusion and cure conditions as well as on the type of polyimide used. The highest reflectivity of 67.1% was achieved with a silvered film prepared from 3,3′,4,4′-benzophenonetetracarboxylic acid dianhydride (BTDA) and oxydianiline (ODA) infused at 5000 psi, 100 °C, for 30 min and cured for 1 h at 300 °C. Reflectivities of silvered surfaces of other polyimides investigated varied from 39% to 61%. A strong correlation between the presence of a ketonic group in the polyimide structure and the formation of mirror surfaces was detected.

The preparation, by direct melt intercalation, and the properties of new hybrid organic-inorganic nanocomposites, consisting of a commercial sample of poly(styrene-b-butadiene) copolymer (SBS) and a commercial organophilic clay containing the dioctadecyl dimethyl ammonium salt are described. In addition, several mixtures between the same copolymer and an unfunctionalized clay were prepared and studied. XRD spectra showed a partial insertion of the SBS block copolymer segments in the interlayers of the organophilic clay, accompanied by a loss of correlation within the layers. The degree of insertion increased by annealing the nanocomposites at 120 °C for increasing time periods. No interaction between the polymer matrix and the unfunctionalized clay was found. The storage modulus value, in the plateau region between the glass transition processes of the polybutadiene and the polystyrene blocks, and the glass transition temperature of the polystyrene block domain increase as both the organophilic clay content and the annealing time increase. The glass transition process of the polybutadiene block domain is practically unaffected by the filler content and the annealing treatments. These data are most promising for upgrading the thermo-mechanical behavior and the application temperature window of the SBS thermoplastic elastomers through the preparation of nanocomposites employing suitably designed organophilic clays.

TiN/Pt multilayers with individual thicknesses between 1 and 8 nm were prepared by ion beam sputtering deposition to simulate the micro-laminated architecture of nacre. Multilayer hardness and the laminated structure were investigated. It was found that sharp but incoherent interfaces were formed between individual layers. The multilayer hardness had strong dependence on layer arrangement. The range of layer thickness appropriate for high hardness was experimentally determined. Hardness enhancement of 30–70% was generally observed. With the layer thickness properly adjusted, the multilayer can even be harder than the hard component (TiN). Annealing experiments indicated that the hardness enhancement was an intrinsic property of the TiN/Pt multilayers.

Submicrometer-sized SiC coated with SiO2 of 0.4–1.8 wt.% and α–Al2O3 powder of median size 0.2 μm were mixed in aqueous solutions in the pH range 3.0–10.0. The SiC/Al2O3 (4.3–6.9 wt. %) powders were consolidated by filtration through gypsum molds and hot-pressed at 1600°–2040 °C under a pressure of 39 MPa. These compacts were densified to near the theoretical density at 1700°–1800 °C. The sintering mechanisms are discussed based on the analysis of shrinkage curves of SiC/Al2O3 compacts during hot-pressing. The equiaxed SiC grains grew with low aspect ratios below 1800 °C and changed to plate-like grains at 1900 °C. The fracture toughness of SiC as a function of average grain size reached a maximum of 5 Mpa · m0.5 at 2.5 μm grains of low aspect ratios of 1–2. The flexural strengths at room temperature were 230–430 MPa in the SiC above 98% of the theoretical density and showed a similar grain size dependence.

The crystallization behavior and microstructure of lithium-calcium aluminogermanate (LCAG) glasses have been studied by using differential thermal analysis (DTA), x-ray diffraction (XRD), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and electron diffraction (ED). Uniform crystallization of the LCAG glass was found to result from two stages of the heating process. The kinetics of crystallization of the LCAG glasses was studied by DTA using the nonisothermal method. The activation energy for 3CaO · Al2O3 · 3GeO2 crystal growth was 693 kJ/mol. The precipitated crystals determined by XRD analysis were mainly 3CaO · Al2O3 · 3GeO2, and minor phases of 2CaO · Al2O3 · GeO2 and Li2O · Al2O3 · 2GeO2. Morphology and microstructure of the glasses after heat treatment determined by SEM and STEM techniques are presented. Crystallization starts at the surface of the glass sample and then proceeds toward the interior of glass matrix. The morphology of 2CaO · Al2O3 · GeO2 is that of a subangular bell-shaped single crystal growing in a preferred orientation through the segregated phase matrix of fine dispersion of 3CaO · Al2O3 · 3GeO2 crystals. The Li2O · Al2O3 · 2GeO2 phase grows anisotropically in the fine fibrillar morphology and parallel to the [331].

X-ray reflectivity and diffraction were applied to characterize the highly (100)-textured thin films of LaNiO3, which were deposited on Si substrate via radio frequency magnetron sputtering at temperatures ranging from 250 to 450 °C. Two interference fringes of different period were observed from the reflectivity curves, and the fitting result indicates that in addition to the normal lanthanum-nickel oxide layer, a transition layer, which has a larger mass density than the previous one, exists in the sputter-deposited films. A comparison of the measured x-ray diffraction intensity with that calculated from layer thickness and mass density obtained from reflectivity data indicates that the transition layer is noncrystalline. The x-ray diffraction result also shows that there is a significant decrease of (100) diffraction intensity relative to that of (200) as increasing the deposition temperature. Using the reflectivity and diffraction data along with results of electron diffraction and film composition analysis from our other studies, such a change of relative intensity between the two diffraction peaks is attributed to the increasing content of two also highly textured La-rich phases, i.e., (110)-textured La4Ni3O10 and (100)-textured La2NiO4, in addition to the LaNiO3.

Strong adhesion between a deposited copper film and an alumina substrate takes place when the substrate is laser-irradiated prior to deposition. A post-deposition annealing is required to achieve the strong bonding. In this work, the interfacial region between the copper film and the alumina substrate was analyzed using Auger Electron Spectroscopy (AES). It was found that a transitional region is always present in couples that have a high adhesion strength, while little or no transitional region was found in weakly bonded couples. The transitional region depends on the laser irradiation atmosphere. In the case of laser irradiation in air, oxygen excess was found on the surface of the alumina substrate, and in the copper/alumina couple the transitional region consists of a copper oxide and a Cu–Al double oxide. When the laser irradiation was performed in a reducing atmosphere (Ar–4% H2), substoichiometric alumina and metallic aluminum were found on the surface of the substrate and also a reaction between copper and the substoichiometric aluminum oxide was detected in the subsurface. Although the substoichiometric alumina is formed on the surface irradiated in Ar–4% H2, a stable Al2O3 thin layer is formed on the outmost surface because the irradiated substrate is exposed to the atmosphere before deposition. This reoxidized layer remains whole at the interface of the couple upon low temperature (at least up to 300 °C) annealing, while it is ruptured upon higher temperature annealing (500 °C in this work). In the latter case, the copper film can contact and react with the substoichiometric alumina formed in the subsurface of the substrate irradiated in the Ar–4% H2 atmosphere. It is concluded that the Cu–Al–O interfacial compound formed in the transitional region causes the strong adhesion between the copper film and the alumina substrate.