Microstructural refinement of the YBa2Cu3O7−x/Ag superconductor composite has resulted in a fracture toughness of 3.6 MPa √ms, as measured by single edge notch beam fracture specimens. This represents the highest bulk fracture toughness value published to date for silver compositions near 20%. A combination of grain size and porosity refinement, in addition to control of silver morphology and distribution, permits the development of fracture toughness levels that compare favorably with many structural ceramics such as SiC and Al2O3.

We investigate the crystal growth of YBa2Cu4O8 and Y2Ba4Cu7C7O15−σ in Al2O3 crucibles at P(O2) = 20 MPa employing commercial O2-HIP equipment. Large crystals of YBa2Cu4O8 up to 1 × 0.5 × 0.05 mm3 are obtained from starting compositions of about 65–67 mol % CuO. When we use a composition of Y: Ba: Cu = 2:6:15, single crystals of YBa2Cu4O8, free from contamination, are obtained at a growth temperature of 1000°C, and those of the Y2Ba4Cu7O15 phase with Al, having the maximum size of 3 × 1.5 × 0.05 mm3, are obtained at a temperature of 1050°C. YBa2Cu4O8 crystals exhibit a superconducting transition temperature Tc of 75 K. Y2Ba4Cu7O15−σ crystals have a Tc of 20 K because of the contamination of aluminum from the crucible.

The filaments have been prepared by dry spinning through a homogeneous aqueous solution containing mixed acetates of Y, Ba, and Cu, polyvinyl alcohol, and organic acids. After spinning, the filament was sintered or partially melted to generate the superconducting phase. Magnetization properties of the filaments are examined. Since solution spinning introduces a fine flux pinning center into the superconducting phase, such as at elemental level, a significantly improved Jc value estimated from the magnetization curves and field dependence of the Jc have been achieved in the solution-spun filament. The phase decomposition from the 124 phase to the 123 phase and partial melting result in an enhancement of flux pinning.

The effect of G/R (temperature gradient, G; growth rate, R) on the crystal alignment and the crystallization mechanism of YBa2Cu3Oy (123) from the partially melting state [in which Y2BaCuO5 (211) and liquid coexist in equilibrium] grown by the horizontal Bridgman method was investigated. Highly aligned 123 crystals containing fine 211 particles were obtained at high G/R ratios. The limit of G/R for continuous growth, necessary for obtaining textured structure, was confirmed to exist between 301 and 482°Ch/cm2. A high critical current density (Jc) of 1.9 × 104 A/cm2 (77 K, 1 T) was measured for a sample grown at the high G/R condition of 482°Ch/cm2, and the 123 grains grown under a condition of G/R lower than the lower limit became coarser with decreasing GR (cooling rate). Entrapment of the 211 particles in the growing 123 crystals occurs after significant coarsening of the particles in the liquid since observed radii of the 211 particles were independent of the distance from the solid/liquid interface in the 123 crystals.

The crystalline structure of the Ba2Y1−xCuxWO6−y system was obtained from x-ray diffraction measurements as a function of copper concentration. Five different x regions are observed, four of which correspond to solid solutions and lie at x ≤ 0.75. The crystalline structure of the phases at these copper concentrations has cubic symmetry with lattice parameters between 0.8382 and 0.8275 nm. At 0.75 < x ≤ 1.0 the samples are a mixture of two phases. In this study we have identified the existence of only two stoichiometric compounds: Ba8Y3CuW4O24 with a cubic crystalline structure with space group Pm3m and lattice parameter of 0.8350(1) nm, and Ba2CuWO6 with a crystalline tetragonal structure and space group I4/mmm and lattice parameters a = 0.5566(1) nm and c = 0.8634(1) nm. The crystalline structure at all copper concentrations is based in the ordered perovskite structure. The samples show electrical insulator behavior.

Layered structures of DyBa2Cu3O7−x and Dy2O3 grown on (100) and (110) oriented SrTiO3 have been examined in cross section by transmission electron microscopy and energy dispersive spectroscopy to determine the feasibility of fabricating tunnel junctions with these materials. DyBa2Cu3O7−x and Dy2O3 exhibit a clear epitaxial relationship, resulting in heteroepitaxial growth of DyBa2Cu3O7−x on Dy2O3. The interfaces between DyBa2Cu3O7−x and Dy2O3 are structurally sharp, but interdiffusion between the chemical constituents occurs. Nevertheless, these results are a strong indication that high quality high-Tc superconductor tunneling junctions can be fabricated in this system.

Bi1.84Pb0.34Sr2.03Ca1.9Cu3.06Oy, bulk superconductors were prepared by hot press sintering at 800°C at a pressure range from 50 kgf/cm2 to 200 kgf/cm2 in air for 2 h. The relative density increased with increasing the hot-pressing pressure, and specimens with various relative densities of 70%–90% were prepared. The flexural strength (σ) at room temperature was related to the porosity (p) as follows: σ = 138 exp(−2.83 p) (MPa). The flexural strengths of the specimen with p = 0.1 were 103 MPa and 113 MPa at room temperature and at 83 K, respectively. The flexural strength tended to increase with decreasing temperature. Anisotropy in flexural strength was observed, which seemed to be due to the grain-oriented microstructure.

The effect of atmosphere on the formation of the 110 K (Bi2Sr2Ca2Cu3O10, 2223) superconductor phase was studied at different oxygen partial pressures and temperatures. Step heating at low oxygen partial pressures with intermediate grinding promoted 110 K phase formation. With this synergy the shortest time for single-phase 110 K superconductor formation was found to be 12 h between 845 and 865°C at Po2 = 0.078 atmosphere. The activation energy of 110 K phase formation is 1513 KJ/mole in air.

A phase diagram study has been made to determine the range of compositions of single phase, Pb-doped R solid solutions in the Bi–Sr–Pb–Cu–O system. These have the formula Bi2+x−zPbzSr2−xCuO6+δ, with 0.15 < x < 0.40 and 0 < z < 0.55 at 750 °C. With increasing z, the unit cell symmetry changes from tetragonal to orthorhombic; cell parameters are given as a function of x and z. From the compositional extent of the solid solutions, in terms of x and z, it is possible to infer that Pb enters predominantly “Bi” sites but also “Sr” sites, in the crystal structure of the R phase, in contrast to Ca which appears to enter exclusively the “Sr” sites. The change from tetragonal to orthorhombic symmetry may be interpreted as indicating the onset of Pb occupation of the “Bi” sites.

The melts of BiSrCaCu2Al0.5Ox were quenched by vacuum casting into fine fused silica tubes (≍ 2 mmÏΦ), resulting in the formation of glass rods. The oxygen absorption during the reheating of the glass specimens was studied by thermogravimetric analysis. It was found that the superconducting properties of glass-ceramics depend on the amount of the oxygen absorption of the specimen during heating and cooling. The increase of Tc with the annealing at lower temperatures was explained in terms of increasing of oxygen in the specimen.

Rapidly solidified Al78Mn20Ge2 alloy exhibits a curious structural feature; this corresponds to the simultaneous occurrence of almost all the quasicrystalline phases, e.g., primitive and face-centered icosahedral phase, rational approximant, and a new metastable cubic phase. The cubic crystalline phase shows yet another type of recently observed twin relation which effectively produces an icosahedral symmetry, a feature that has so far been specific to alloy systems Al–Mn–Si and Al–Mn–Fe–Si only. The diffraction evidences obtained in the present investigation reveal that the orientation of the structural subunit, which is a MacKay icosahedron, remains invariant across the various interphase boundaries. These results elucidate clearly the structural interrelationship among the various phases.

We report on 27Ai, 65Cu, and 51V spin-echo spectra for the amorphous phase and icosahedral quasicrystal of the Al75Cu15V10 alloy, and 27Al, 65Cu, and 55Mn spin-echo spectra for the icosahedral and crystalline phases of the Al67Cu20Mn13 alloy. The line shape and peak shift reveal different local characteristics among those phases. For the Al75Cu15V10 alloy, peak shifts of all constituent nuclei are more positive in the amorphous phase than in the icosahedral phase, indicating a different s-electron density. For the Al67Cu20Mn13 alloy, an as-quenched icosahedral phase transforms to a crystalline phase by heat treatment. Different peak shifts of 27Al and 55Mn except 65Cu between those phases have been found. It is suggested that there are Mn atoms carrying magnetic moment and that there is no difference in the electronic structure of Cu atoms between those phases.

As a possible means of alleviating the severe brittleness in the B2 compounds FeAl and NiAl, the all-electron self-consistent total energy linear muffin-tin orbital (LMTO) method was employed to investigate the possibility of lowering the ⟨111⟩ anti-phase boundary (APB) energies by changing compositions in FeAl and NiAl. For APB's created in the regions with excess Fe (or Ni) atoms, APB energies for the model systems, Fe0.6Al0.4 and Ni0.6Al0.4, were found to be one order of magnitude smaller than those for stoichiometric B2 FeAl and NiAl, respectively. Apparently, the activation of ⟨111⟩ slip became possible in these cases. On the other hand, the APB energies remained at about the same as those in stoichiometric FeAl and NiAl for APB's occurring in regions with equal numbers of Fe (Ni) and Al atoms, implying that the activation of ⟨111⟩ slip in these regions was not eased.

The oxide films formed on SUS430 stainless steel under various conditions have been investigated by using infrared reflection absorption spectroscopy. A comparison of the spectra of the samples oxidized in moist atmosphere with those oxidized in dry atmosphere shows the important role of water vapor at 873 and 973 K. The abnormally rapid oxidation at 873 K in moist atmosphere with low oxygen pressure is characterized by rapid increasing of the intensity of the absorption band at about 550 cm−1. The frequency of this band shifts to a lower wave number as its intensity increases.

Iron-rich Fe–Cu–Si multilayers were made by alternately depositing pure elements in a high vacuum system. The as-deposited films were then subjected to 200 keV xenon ion irradiation to doses ranging from 2 × 1015 to 1.2 × 1016 Xe/cm2 at liquid nitrogen and room temperature. Transmission or scanning electron microscope and in situ energy dispersive spectroscopy were used to characterize the films. It was found that ion irradiation induced the formation of a new metastable phase in many irradiated films. The new phase was identified to be of fee structure with a lattice constant a = 0.423 nm. Strikingly, another phase reflecting sharp diffraction spots with 12-fold symmetry was also observed in a room temperature irradiated sample at a dose of 9 × 1015 Xe/cm2. The distribution of the diffraction spots was shown to be incommensurate and bore a close relationship with the metastable fee phase. Furthermore, scanning electron microscope examination revealed that many clusters with 5-fold symmetry emerged in the corresponding film. The sharp incommensurate diffraction patterns may be ascribed to some incommensurate or quasicrystalline order appearing in the ion-induced structures.

The phase relations and thermal stabilities of phases in sputter deposited Be–Nb alloys (3–14% Nb) have been studied. An amorphous phase forms during deposition at ambient temperatures (30 °C) for compositions >5% Nb. Metastable crystalline phases form during deposition at 350–450 °C as well as during annealing of the amorphous phase. One metastable bcc phase designated as Be12Nb′ can be explained by an extremely high fault density in the Be12Nb structure and is a precursor phase to the formation of both Be12Nb and Be17Nb2. Another metastable bcc phase also forms during high temperature deposition. Transformation to the equilibrium phases occurs at temperatures >800 °C. A stoichiometric range of about 5.5–7.8% is indicated for the Be12Nb phase and is probably due to vacancies on the Nb sublattice. No evidence of a Be5Nb phase was found and the Be17Nb2 phase is stable to room temperature.

Experiments are described that provide evidence for the formation of an excited condensed state of matter in the form of μm to mm size particles. The particles are formed at a high temperature diffusion source, which has been shown to give field ionizable clusters of cesium in previous experiments (Åman et al., 1990). The excited matter formed by cesium, hydrogen, or ethylene in the source is in the present experiments collected on a surface, which is cooled to liquid nitrogen temperature. Subsequently, the excited particles emit their excitation energy in the form of visible “microflashes”, either spontaneously or triggered by impact of low energy ions. An estimate of the visible energy in the microflashes agrees well with the energy contained in an excited state of matter that was predicted by Manykin et al. (1981, 1982). We conclude that our results agree with their predictions.

Diamond thin films have been successfully grown on monocrystalline Si and various polycrystalline substrates, such as Mo, Nb, Zr, Cu, SiC, SiOx2, and WC, by microwave plasma CVD in gas mixtures of methane and hydrogen. For instance, high purity and dense diamond films can be deposited on structurally matched substrates of Si and SiC, in hydrogen containing 0.2% methane. SEM, TEM, XRD, AES, EELS, EDS, and Raman spectroscopy have been utilized to study and characterize the morphology, microstructure, and composition of the deposited films. Results indicate that tetrakaidecahedra are the dominant forms of crystalline diamond. Both {100} and {111} facets were observed on all substrates studied. SiC, SiOx, amorphous carbon, and carbides of refractory metals were the dominant interphases in this study. The composition and microstructure of the interphase appear to have significant effects on the adhesion strength, as shown in the diamond/Mo and diamond/Hf systems. Structural defects such as twins and stacking faults were frequently observed inside the diamond grains, while line defects of dislocations were mainly constrained to the grain boundaries. The diamond nucleation rate could be increased by first modifying the surface of the substrate material using a process that ultrasonically stimulated cavitation-erosion in an aqueous suspension of diamond dust. The diamond crystallites growing on this roughened surface were of a much more uniform size than was achieved after the more conventional lapping process.

An experimental study of the effects of temperature and pressure on the conductivity anisotropy of aligned short carbon fiber filled epoxies is presented. The data give evidence of significant relative changes of the anisotropy whose sign and amplitude depend on the volume concentration near the conductivity threshold. A phenomenological approach involving variations with temperature and pressure of the fiber volume fraction and the fiber aspect ratio is developed. It predicts that the anisotropy change results from two competing contributions in a similar way whether the temperature or the pressure is varied. Although quantitative predictions cannot be made, we show that introducing the available mechanical and thermal materials constants into the theoretical equations accounts, at least qualitatively, for the experimental behaviors.

The effects of scanning speed and constitutional supercooling during zone-melting recrystallization (ZMR) of silicon-on-insulator (SOI) structures were studied numerically. Effects of strip motion and constitutional supercooling on the temperature profiles and the size and structure of the molten region were investigated. The temperature distribution and melt zone width does not alter for processing speeds lower than 400 μm/s. For higher speeds, motion causes the temperature profiles to lag behind the strip. The size of the molten zone decreases for increasing scanning speeds and increases for increasing degrees of supercooling. The combined effects of strip motion and supercooling on the size of the molten zone were determined. Supercooling reduced the size of the solidification region where liquid and solid phase silicon coexist.