High Tc superconductors need to be fabricated into desirable configurations such as wires for practical applications. Toward this objective, the plastic extrusion process was applied to the fabrication of wires and rods of YBa2Cu3O7−x. The ceramic oxide powder is combined with several organic additives to form a slurry which is extruded by forcing it through a small aperture. This is subjected to a sequence of heat treatments for drying, binder burn-out, and sintering. The critical current density of these wires ranges from 800 A/cm2 to 1500 A/cm2 depending upon the diameter and the current-carrying capacity is uniform over long lengths of up to 140 cm. This process was also applied to fabrication of larger cross-sectional area rods and hollow cylinders, capable of carrying up to 245 A. The mechanical properties of these wires were also investigated.

The feasibility study of electroless plating as carbon fiber modification for aluminum matrix composites was carried out. The comparison of Cu plating and Ni plating of carbon fiber by the electroless method was investigated. The Cu- or Ni-coated carbon fiber reinforced aluminum was fabricated with a centrifugal pressure infiltration method. The mechanical property was metallographically discussed. Electroless plating is able to improve the throwing power of the precipitant into the multifilament and uniformly coat Cu or Ni onto the carbon fiber. The technique using centrifugal casting seems to be an innovative method for fabrication of composite materials. The eutectic reaction between aluminum and Cu or Ni on the fiber appears to improve the affinity of the carbon fiber and aluminum. The Cu-plated carbon fiber reinforced aluminum is two times higher in bending strength than Ni-plated carbon fiber reinforced aluminum.

The thermal diffusivity of several quasicrystalline and related crystalline alloys was measured both at room temperature and as a function of temperature. It is found remarkably small as compared to conventional metallic alloys. It changes slightly when reversible phase transition takes place and is definitely smaller in the quasicrystalline state than in the corresponding “approximant” state.

We have developed a novel approach for quantifying the microstructure of granular thin films using digital image processing and analysis. In the past, conventional scanning electron microscopy of thin films has generated qualitative information on the surface topography and film microstructure. However, when coupled to digital image analysis, the amount or degree of surface contours (i.e., granularity) in SEM micrographs can be quantified in a rapid and reproducible manner. Briefly, SEM micrographs are digitized and the edge boundaries on the film surface are enhanced by a gradient filter; granularity is then quantified by calculating the %AREA covered by the edges with respect to the entire field. Objects of a particular shape, such as phase impurity particles, can be selectively deleted from the image using a specific sequence of shape analysis algorithms and parameter values. In this manner, the contributions of edges from the phase impurity particles is minimized in the final measurement of real surface contours. Statistical analysis of the data yields quantitative information concerning variations in microdomains within single thin films and can detect statistically significant differences among samples. This method is being used in the characterization of the microstructure of superconducting thin films for optimization of their electrical and magnetic properties.

Cobalt (Co)/silicon dioxide (SiO2) reactions during rapid thermal annealing (RTA) in an N2 ambient have been investigated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that islands consisting of Co and the cobalt oxide phase, Co3O4, form during high-temperature anneals (30 s−10 min at 800 °C). After a selective wet etch to remove the islands, groove-like features are produced in the SiO2 layer. The morphologies of the islands and grooves are strikingly similar, which strongly suggest that Co and the underlying SiO2 layer have reacted, most likely to form Co3O4. We propose that small concentrations of O2 are necessary to promote Co/SiO2 interactions.

Simulations of arrays of resistively shunted Josephson junctions containing a crack of uncoupled junctions indicate that the crack can distort the supercurrent flow and provide a nucleation site at the crack tip for the formation of superconducting vortices at applied currents below the critical current of the homogeneous material. An analogy is established between the supercurrent distribution in two dimensions and the stress field distribution around the crack for antiplane mechanical loading. The analogy is used to show that the supercurrent distribution can be described analytically in terms of a Westergaard function used in elasticity theory. In addition, using a correspondence between the forces acting on a vortex and a crystal dislocation, models for screw dislocation emission from a crack tip are transposed to describe vortex emission from a crack tip. These lead to predictions for the pinning force required to prevent dissipation by vortex emission from the crack tip, as well as for the size of a vortex zone ahead of the crack for different values of the ratio of the applied current to the pinning force.

Mechanically alloyed mixtures of elemental Al and Ti powders have been characterized in the as-milled condition, as well as after hot consolidation. Ball-milling in an argon atmosphere first induces alloying of the elements, followed by the formation of a certain amount of an amorphous-like phase. This amount increases as the equiatomic composition is approached. However, milling in nonsealed mills usually leads to the production of some form of titanium nitride, particularly in Ti-rich mixtures. In the consolidated products obtained from long-milled powders, intermetallic compounds were found to be the predominant phases. The existence of an amorphous phase in the as-milled powders considerably facilitates their hot consolidation.

It has been experimentally observed that the application of even a relatively weak magnetic field of 1.6 T during sintering of HoBa2Cu3O7-δ (hereafter HoBCO) results in a significant degree of grain alignment. The orientation of grains is found to be controlled by the direction and magnitude of a magnetic field. The degree of alignment was monitored by x-ray diffraction measurements on the flat surface of the samples and by metallography. It has been observed that the degree of alignment grows as the magnitude of the field increases between 0 and 1.6 T for a fixed temperature and processing time. The degree of alignment also increases when the processing temperature changes from 930 °C to 965 °C for a fixed field and time. It has also been observed that for both a fixed field and processing temperature, the alignment grows when the processing time increases between 16 and 72 h. Metallography measurements on the flat and cross-sectional parts of the samples showed that the texture propagates into the bulk of the samples. In the presence of a sufficient amount of the liquid phase, the enhancement of the grain growth in the direction favorable to the magnetic field produces rather large single crystals (0.3 to 0.5 mm linear size) within the sample.

Silver doping into (Bi, Pb)2Sr2Ca2Cu3O10 superconducting composite tapes was found to accelerate the formation process of high-Tc (2223) phase owing to lowering the partial melting point of the samples. The differential thermal analysis (DTA) results showed that the partial melting temperature of the sample was lowered by about 10 °C from 850 °C to 840 °C by silver doping. However, with sufficient sintering both the silver-doped and undoped samples can reach a very high level of high-Tc phase fraction, suggesting that the silver doping only speeds up the rate of high-Tc phase formation, but does not change the final phase assemblage of the materials. The reaction kinetics was analyzed by using the Avrami equation, and the results indicated that the conversion process of low-Tc (2212) phase to high-Tc (2223) phase was a diffusion-controlled, two-dimensional reaction. The correlation of the phase evolution with electrical property inside the superconducting tape during the process of heat treatment was also discussed.

The formation of TaC and Ta2C by combustion synthesis from their elemental constituents has been studied by time-resolved x-ray diffraction (TRXRD) using synchrotron radiation. The reactions have been followed with a time resolution down to 50 ms. Since the adiabatic temperatures for both reactions are well below any liquidus temperature in the Ta—C phase diagram, no melting occurs and these combustion reactions occur purely in the solid state. The phase transformations associated with these reactions are followed by monitoring the disappearance of reactant and appearance of product powder diffraction peaks in real time as the reaction front propagates through the combusting specimen. In the synthesis of TaC, the results show the formation of the subcarbide (Ta2C phase as an intermediate. In the synthesis of Ta2C, the reaction proceeds directly to the product with no discernible intermediate Ta–C phase within a 50 ms time frame. The chemical dynamics associated with the combustion synthesis of TaC may be described by an initial phase transformation to hexagonal Ta2C arising from carbon diffusion into the Ta metal lattice. As more carbon is available this intermediate subcarbide phase, which has one-half of its octahedral interstices occupied by the carbon, further transforms to the cubic TaC final product, in which all octahedral sites are now occupied. The time-resolved data indicate that the rate of formation of Ta2C is a factor of two faster than that of TaC.

The mechanisms of reaction in sputter-deposited Al–Zr thin film couples have been investigated using extensive transmission electron microscopy (TEM) observations of cross-sectional specimens prepared by the novel use of an ultramicrotome. The TEM observations greatly facilitated understanding of composition-depth profiles obtained by Rutherford backscattering spectroscopy (RBS). The reaction between Al and Zr in thin films, and the influence of Cu on this reaction, was shown by the TEM to be much more complex than previously reported in studies that largely used RBS. Reaction of Al and Zr in sputter-deposited films occurs in two stages. Initially reaction occurs by growth of an amorphous layer at the Zr interface and is promoted by intermixing of Al and Zr during deposition. Growth of an amorphous layer in an Al-transition metal thin film couple has not been reported previously. Subsequently, the amorphous layer is consumed by growth of microcrystalline Al3Zr from the Zr/reaction layer interface. The transition from growth of amorphous to microcrystalline Al3Zr results in thickening of the reaction layer with an overall growth rate exponent of 1/3. The Al3Zr grows with the metastable L12 cubic structure, except in the presence of Cu, when it grows with the tetragonal DO23 structure. The fine initial Al and Zr grain sizes limit the influence of Cu on the morphology of the reaction; in all cases, a continuous and uniform reaction layer thickness is observed by TEM.

A submicrometer-grained (SMG) Al−3% Mg solid solution alloy, with an initial grain size of ∼0.2 μm, was produced by intense plastic straining. Experiments show that tensile specimens of the SMG alloy exhibit high elongations to failure at low testing strain rates at the relatively low temperature of 403 K. The stress exponent is high (∼7–8) and calculations show deformation is within the region of power-law breakdown. The initial microstructure of the alloy consists of diffuse boundaries between highly deformed grains. At strain rates of ∼10−4 s−1 and lower, plastic deformation leads to dynamic recrystallization and the formation of highly nonequilibrium grain boundaries that gradually evolve into a more equilibrated configuration.

Carbon-supported Pt catalysts were prepared from H2PtCl6 or K2PtCl6 aqueous solutions. Particle size and structure after several thermal activation treatments were studied by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Cyclic Voltammetry (CV), and the results of the three techniques were compared. As the catalysts were highly dispersed on an amorphous support, a conventional XRD profile analysis for crystallite size determination could not be performed properly, because of the strong overlapping between the broad Pt peaks superposed to the halos of the amorphous phase. Thus, a new procedure of whole XRD pattern fitting, based on the Rietveld method, was used to have reliable data of Pt particle size (surface area) and lattice parameter. All structural and microstructural parameters were refined within the same procedure, also considering the transparency of the carbon supported catalysts and minimizing the effect of the amorphous background. The method can also take into account the presence of bimodal particle size distributions, which is difficult to study by CV or TEM.

The interaction of molecular oxygen with thin C60 films was investigated using the 3.04 MeV resonance in the 16O(α, α)16O elastic scattering reaction to measure the concentration profile of oxygen in the fullerene films. A thin (d ≍ 20 nm) layer containing oxygen was observed on the surface of C60 films (d ≍ 200 nm) exposed to ∼1 atm of O2 for 1 h in the absence of light. In contrast, oxygen was uniformly distributed throughout the entire film when samples were irradiated for 1 h with either a 488 nm Ar ion laser or Xe lamp in the presence of ∼1 atm of O2. This O2 uptake was found to be both power dependent and reversible.

Growth defects in diamond films grown by plasma-assisted chemical vapor deposition (CVD) were studied by high resolution electron microscopy. Several features of the microstructure were resolved and their importance to the growth of the diamond film was evaluated. The observations included various twin boundaries of the type ∑ = 3, as well as ∑ = 9, ∑ = 27, and ∑ = 81, which form by an interaction of lower order twins. These higher order boundaries are loci of intersection points of growing planes on two adjacent twins and can serve as an indicator for the local crystal growth direction. The central nucleation site for the growing planes in many cases can be traced back to a quintuplet twin point. A twin quintuplet has five re-entrant angles and thus serves as a preferred nucleation site for new planes as the crystal grows.

Rapidly quenched Al86-xNi14Six (x = 0, 2, 6, and 10) alloys have been studied by means of transmission electron microscopy. Two-dimensional (2-D) decagonal quasicrystal with a periodicity of 1.6 nm along its tenfold axis was found in the rapidly quenched Al86Ni14 binary alloy. With the addition of some silicon, such as AlgoNi14Si6, the 2-D decagonal quasicrystal first transforms to a one-dimensional (1-D) quasicrystal that inherits the periodicity along the tenfold axis and has, in addition, translation periodicity in one of the twofold axes of the decagonal phase, and finally transforms to a new orthorhombic crystalline phase (a = 0.78, b = 1.62, and c = 1.48 nm). In the Al76Ni14Si10 ternary alloy, a 2-D decagonal quasicrystal with a periodicity of 0.4 nm and a coexisting crystalline phase with the “Al3Ni2” structure were found, and their orientational relationship has been determined.

The effects of solute-related defects in AICo are measured by changes that they produce in lattice parameter, specific gravity, and elastic moduli. By comparison with the effects of off-stoichiometry on the same parameters in binary Al-Co alloys, the solute-produced defects can be partially characterized. Cell occupancy numbers are calculated and used to infer that vacancies are formed on both sides of stoichiometry and also when solute replaces Al or Co in AICo. These data are also essential to testing the effects of the solutes studied—Mn, Re, and Ti—on mechanical hardening, to be reported separately in Part II.

The coarsening rate of Y2BaCuO5 (211) phase in liquid was investigated by observations of samples which were held at 1070 °C for different holding times. The 211 phase formed rod-like shapes, and the diameters increased with the increase in the holding time. The average diameter increased in proportion to t1/3 (t, holding time). This means that coarsening can be explained by the modified Ostwald ripening theory. Platinum-doping suppressed the coarsening rate and alumina-doping promoted it. However, both coarsening rates were also proportional to t1/3. The changes in the rate can be represented by the changes of the DLΓ value (DL, diffusivity in liquid and Γ, Gibbs—Thomson coefficient) using the Ostwald ripening theory; i.e., the value is made lower by platinum-doping and higher by alumina-doping.

Magnetic and x-ray diffraction measurements on the system (Ti50Al50)100−xMx (M = V, Cr) are used to determine, respectively, the magnetic moment (associated with the dopants M) and changes in the lattice parameters. In addition, site selectivity by the dopants between the Ti and Al sites in the L10 structure is determined by measuring the changes with x (x = 0.12, 0.33, 0.71, and 1.21 at. % for V and x = 0.17, 0.41, 0.88, 1.14, and 1.91 at. % for Cr) the intensities of the (001) and (110) superlattice peaks. These results are compared with our earlier studies of the Mn-doped system that showed that the Mn substitutes for Ti and carries a moment of 2.3 μB/Mn atom. For V and Cr dopings, μ/atom decreases as x increases, the largest values being 1.01 μB/V and 0.55 μB/Cr at the lowest dopings. At the lowest x, V and Cr occupy the Ti sites, but for higher dopings, Ti and Al sites are occupied with about equal probability and μ approaches constant magnitudes of about 0.3 μB. These results suggest that only Ti occupancy results in a localized moment on the dopant. For Mn and V dopings, the magnitudes of the moments are in good agreement with a recent calculation of Khowash et al.

Ni3Al samples were implanted with different doses of 150 keV Cr+ ions to modify the surface region. The high temperature oxidation behavior was tested. The surface layer structure was investigated by AES, TEM, XRD, and optical microscope before and after the test. The experimental results show that chromium ions turn a small amount of ordered superlattice Ni3Al phase into a disordered Ni–Al–Cr phase. Also there is a bcc chromium phase in the implanted sample. Implanted Ni3Al alloy has better oxidation resistance than the unimplanted one at 900 °C. The oxide layer is of a multilayer structure after 50 h oxidation, composed of a NiO inner layer, Cr2O3, spinel NiAl2O4 intermediate layers, and an α–Al2O3 external layer at the oxide/air interface. The α-Al2O3 and Cr2O3 are independent scale-like layers. The two protective layers improve the oxidation resistance significantly. The effects of implanted elements and possible reaction mechanisms are discussed.