Superconducting Bi-Sr-Ca-Cu-O thin films have been prepared for the first time by chemical vapor deposition using triphenyl bismuth and fluorocarbon-based chelates such as bis(hexafluoroacetylacetonate)strontium, bis(hexafluoroacetylacetonate)calcium, and bis(hexafluoroacetylacetonate)copper. After annealing in air, x-ray diffraction data reveal that the films deposited on (001) SrTiO3 substrates have preferential orientation of their crystalline c-axis perpendicular to the substrate surface. Four-probe resistivity measurements reveal the onset of superconductivity at 80 K and zero resistivity at 50 K.

Transmission electron microscopy of two-phase V-Hf-Nb and V-Hf-Nb-Ti alloys plastically deformed at room temperature shows that {111} (112) twinning is a major deformation mode for the HfV2-based Laves phase. Bands of concentrated shear are also observed. Possible approaches to enhance low-temperature deformability in other Laves phases are discussed.

Electron-diffraction techniques have been used to study the ordering of oxygen atoms within the Cu(1)O1-δ plane of YBa2Cu3O7-δ. The results show that ordering along a single axis and ordering along two orthogonal axes both occur and alternate systematically across the composition range 0.06 < δ < 0.75. Where the ordering is restricted to a single axis, it is found to be the crystallographic a axis. Various models of oxygen ordering are proposed to explain the observed diffraction phenomena. In addition to the ordering of oxygen atoms that give the diffuse diffraction spots at (h∗/2,0,0) and (0, k∗/2,0), a second type of ordering reflection that occurs at (h∗/3,0,0) and (0,k∗/3,0) was also observed. These sharper and more strongly streaked diffraction maxima are explained in terms of a defect in the cation sublattice.

The hydration of YBa2Cu3O7-y in water vapor was investigated at various values of y and at two different PH2O by measuring the weight of the specimen. The reaction was relatively insensitive to the values of y and was extensive in the water vapor pressure of 2.7 kPa at room temperature and 140 °C. This was due to the decomposition of YBa2Cu3O7-y by reacting with H2O. The weight gain was also detected in the water vapor pressure of 270 Pa. The weight gain under lower water vapor pressure was supposed to be controlled by diffusion of OH− in YBa2Cu3O7-y. The diffusion coefficient calculated from the measurement was compared favorably with the oxygen diffusion coefficient.

Energy Dispersive X-ray Spectroscopy (EDS) was used to show that the elemental homogeneity of YBa2Cu3O7 powders can be improved substantially by heating the powder in a nitrogen dioxide-containing atmosphere (e.g., 950°C), followed by annealing in oxygen at 950°C, and slow-cooling to room temperature. The improved homogeneity results in a substantially larger flux exclusion signal for the NO2-treated powder, as measured by both ac and dc techniques. The experimental results suggest a mechanism which involves the formation of a small amount of molten Ba(NO3)2, which acts as a flux that dissolves the constituents and reprecipitates them as high purity YBa2Cu3O7.

By monitoring the electrical resistivity of single phase polycrystalline Y1Ba2Cu3O7-δ samples while changing their oxygen content in both ozone and ordinary oxygen environments, we were able to investigate the correlation between their average oxygen content and the diffusion time for oxygen inside the grains. We model the resistivity time dependence as a two-step process and find that this explains our experimental results satisfactorily. From this model we are able to estimate a value of the oxygen diffusion coefficient from our data that agrees well with other measurements. We also conclude that while ozone and ordinary oxygen may have different effects in oxidizing the surface of grains, they show no observable differences in the oxygen diffusion process in the bulk Y1Ba2Cu3O7-δ material.

Experimental results are presented on efforts to maximize the content of the phase responsible for the 110 K superconducting transition, Bi2Ca2Sr2Cu3O2 or (2223), in the system Bi–Ca–Sr–Cu–O. It was found that the content of this phase depends not only on the initial composition of the reacting mixture, but also on the presence of PbO, the temperature of reaction, and the duration of the reaction.

A Bi-Ca-Sr-Cu oxide composition (2:4:2:5) was rapidly solidified from the melt, and the crystallization behavior examined on heat-treatment. Annealing conditions were 865°C for up to 11 days. The high Tc 2223 phase (105 K) evolved from the 2122 phase (80 K), which in turn developed from the 2021 phase (12 K). The high Tc phase developed only in the presence of a liquid phase at 865 °C. Lattice imaging was used to follow the conversion of 2122 phase to 2223. Data are reported for syntactic intergrowths, which became less frequent with time at temperature. EDS results are consistent with the conversion of 2122 to 2223. Crystals of 2223 could not be grown from the melt, nor crystallized from the solid at temperatures below 820 °C. The presence of a Cu- and Ca-rich liquid was essential for the development of 2223 at 865 °C. A tentative model for the formation of 2223 via a liquid mediated reaction is proposed. EDS confirmed the liquid was rich in Ca and Cu near the solid-liquid interface, and precipitates of secondary phases were identified by SEM, TEM, and XRD methods. The presence of CuO and (Ca,Sr)2CuO3 verified the enrichment of Cu and Ca at the solid-liquid interface. The results are consistent with the evolution of structure of a 2223 from a 2425 starting composition.

The compound Sr2Bi2CuO6 should nominally be the phase with n = 1 of the high Tc superconducting series Sr2Bi2CanO4+2n. However, the superconducting phase with n = 1 (with no CaO) occurs only with a gross deficiency in SrO content. Instead, at the composition Sr2Bi2CuO6, a different phase is formed with an x-ray diffraction pattern considerably different from that expected for the n −1 member of the series. This phase has been found, by a combination of electron diffraction and single crystal and powder x-ray diffraction, to have a commensurate lattice with monoclinic symmetry, space group C2/m or Cm, a = 24.473 (2), b = 5.4223 (5), c = 21.959 (2)A, and β = 105.40 (1)°. The actual composition of this phase may be deficient in CuO by as much as 1.0 mole %.

Single crystal growth of CuO, synthetic tenorite, was accomplished in oxygen atmosphere by the chemical vapor transport technique. We present the first systematic study of the growth of CuO in various partial pressures of oxygen. Crystals were grown using trace, 0.1, and 0.5 atm partial pressures of oxygen. The growth temperatures used were 820 and 865 °C. Typical dimensions of the crystals obtained were 1 × 2 × 0.25 mm. We have shown that the stoichiometry of single crystal CuO can be controlled during the growth process. The crystals exhibited cation deficient stoichiometry, Cu1−xO, with x increasing from less than 0.005 with no added oxygen, up to 0.05 with 0.5 atm O2 when grown at 865 °C.

The angles between the zone axes of decagonal quasicrystals in two different Al–Mn alloys have been studied by means of precision tilt experiments in a transmission electron microscope. The results confirm that a tenfold symmetry axis is present in the reciprocal lattice. The angles between the principal axes in the decagonal phase do not coincide with those between the corresponding axes in the icosahedral phase. The presence of this distortion is independent of quenching rate and size of the decagonal quasicrystals.

The dependence of the F-type order and the stability of Al–Cu–Fe quasicrystals on quenching rate and composition are reported. In the Al–Cu–Mn and Al–Cu–Cr systems, where only metastable quasicrystals can be formed, a disordered icosahedral phase is obtained by melt-spinning, and P ⇉ F-type ordering is observed after annealing. Simultaneous evolution of the diffuse scattering and the ordering is observed as well. The quasicrystalline phases, P-type icosahedral as well as decagonal, in the ternary Al–Cu–TM alloys are structurally similar to those in the binary Al–TM alloys. Dislocations in the icosahedral phase have been imaged both by their strain field contrast and in high resolution.

The reaction of SiH4/H2 mixtures with iron and steels was studied at a total pressure of 1 atm and temperatures above 500 °C. When the amount of water vapor in the gas mixture is carefully controlled, a metal silicide diffusion coating forms at low temperatures (below 900°C). Composition and structure of the Si diffusion coatings were determined with Auger depth profiling and x-ray diffraction. Kinetics of the surface reaction between SiH4, and the metal substrate as well as the behavior of these films in severe environments at high temperatures were studied by a microgravimetric technique. Characterization of these Si coatings on iron, low carbon steel (1010), 9% Cr/1% Mo steel (alloy A182F9), and stainless steels (310) and their applications to reduce oxidation, nitriding, or coking at high temperatures or corrosion in mineral acids are described.

Void formation in tensile test under hydrostatic pressure is characterized through quantitative metallography, and the fracture mechanism under pressure is analyzed by fractography. Transition of the fracture surface from the cup-and-cone under atmospheric pressure to a slant structure under high pressure is explained on the basis of the void development leading to fracture and the concomitant change in fracture mechanism. The concept of “shear blocks” is introduced to illustrate the features observed on the fracture surface of specimens tested under high pressure. It is postulated that shear blocks evolve to connect the central crack regions with the shear crack initiated on neck surface due to the severe necking deformation under applied pressure.

The early-stage kinetics of interdiffusion in compositionally modulated films have been studied by Monte-Carlo simulations on an Ising lattice in two and three dimensions, using nearest-neighbor interactions. For a negative heat of mixing and below the order-disorder transition temperature, if a short-wavelength modulation is along a direction that is not consistent with long-range order, then its temporal evolution does not follow the Cahn-Hilliard-Cook theory. The modulation amplitude decreases as a function of time, rather than increases; i.e., no one-dimensional spinodal ordering is observed. This disagreement with the theory implies that ordering in three dimensions cannot be described by a one-dimensional theory.

Ion beam mixing using 120 keV Fe+ ions at doses varying from 3.0 to 20 ⊠ 1015 cm2 was carried out on Pt–Fe bilayer samples over a temperature range from 298 to 523 K to produce alloys of various compositions. The mixing was characterized using Rutherford backscattering with 2 MeV 4He+ ions and transmission electron microscopy. Ion beam mixing and thermal anneals led to grain growth of the polycrystalline films and to formation of Pt3Fe as an alloy phase. At T ≤ 373 K, mixing was athermal and took place by ballistic collisional processes. At T ≥ 473 K, iron migrated rapidly into platinum; the observed activation energy of 0.3 eV suggested that diffusion was of the short-circuit type controlled by lattice vacancy and grain boundary transport. The surface Pt concentration in the mixed films remained high at ∼90 at. %. This resulted in a reduction of ∼25% in the cathodic overpotential compared to pure Fe electrodes for H2 evolution in 30 wt. % KOH solution. An ion beam mixed Pt–Fe surface layer was more stable than Fe coated with evaporated Pt; this is attributed to improved Pt–Fe adhesion as a result of the ion beam mixing process.

Measurements of the emission of charged particles, photons, and radio frequency signals accompanying the deformation and fracture of polycrystalline Ti metal and deuterated Ti are described. Preliminary evidence for charge separation created by crack propagation is presented which supports a proposed fracture mechanism to explain neutron bursts observed during treatment of deuterated metals.

A new parameter, hardness/modulus2 (H/E2), has been derived from the equations used to calculate the hardness and elastic modulus from data taken during continuous depth-sensing microindentation tests. This paper discusses the use of this parameter to treat the data obtained from a sample whose surface roughness was of the same scale as the size of the indents. The resulting data were widely scattered. This scatter was reduced when the data were plotted in terms of H/E2 versus stiffness. The effect of surface roughness on the hardness and elastic modulus results is removed via stiffness measurements, provided single contacts are made between the indenter and the specimen. The function relating the cross-sectional area of the indenter versus the distance from its point is not required for calculation of H/E2, but the hardness and modulus cannot be determined separately. The parameter H/E2 indicates resistance to plastic penetration in this case.

Al2O3 and Si3N4 ceramics were joined to titanium alloy (TA6V) and niobium by active brazing. Chemical reactions between the Cu-40Ag-5Ti braze alloy and these materials were examined, and interfacial reaction products were characterized by scanning electron microscopy and electron probe microanalysis. Results indicate the importance of studying the microstructural features of the joints in order to understand better their effect on the mechanical properties of the interface.

Procedures are described to deposit uniform layers of yttria and yttria-alumina prccursors on fine powders and whiskers of silicon nitride. The coatings were produced by aging at elevated temperatures aqueous systems containing the silicon nitride core particles, yttrium and aluminum nitrates, and urea. Optimum concentrations of the core particles, in relation to the reactants, were established to promote surface deposition of the oxide precursors. Polymeric dispersants were used effectively to prevent agglomeration of the solids during the microencapsulation process. The morphology of the powders was characterized using scanning and transmission electron microscopy. The mechanisms for the formation of the coated layers are discussed. A description is provided that allows qualitative assessment of the experimental factors that determine microencapsulation by a slurry method.