Continuous microindentation tests performed on the electropolished surfaces of single crystal Fe (3 wt.% Si), known to have a thin passivation film, show a sharp discontinuity at a load of 1.8 mN. To this point, there was no apparent plastic deformation in the metal in that the loading and unloading curves exactly overlay each other. Stresses at the discontinuity were close to the theoretical strength of the metal. Elastic contact theories of Hertz and Love reproduced the elastic portion of the load-displacement curves. On removing the passivation film with a HCl solution, indentation tests yielded strengths nearly two orders of magnitude smaller. The strength recovered to near its initial value after the liquid evaporated and the passivation film re-formed.

Glass-metal nanocomposites involving copper and nickel, respectively, have been synthesized in bulk form by hot pressing sol-gel derived silica-metal nanoparticle composite powders. The particle diameters range from 9 to 17.5 nm. The specimens exhibit the characteristic behavior of the metallic species in their nanocrystalline forms.

Dependence of the contents and the states of residual carbon in YBa2Cu3O7−x powders synthesized by the sol-gel method on heating conditions, and effects of residual carbon on the superconducting properties were investigated. The carbon content of the powder heated at 950 °C for 20 h was reduced to 0.02%. It has been found that a large number of carbonaceous materials in the starting materials that are used in the sol-gel method does not affect the carbon content of synthesized superconducting powders. The volume of diamagnetism was increased and the Tc,onset was raised as the carbon contents were reduced to 0.04%. These properties were further improved by O2–HIP treatment at 500 °C.

In order to investigate microstructural variation by 2-1-1 addition in partially melted Y–Ba–Cu–O, a specimen resulting from 2-1-1 added to 1-2-3 was heat-treated through the peritectic temperature. Microstructure was observed on the directionally solidified region near the interface of the two samples. The 2-1-1 addition results in a homogeneous microstructure where no remnant liquid phase is present. It reduced the 1-2-3 plate thickness, as well as suppressed the formation of microcracks due to the tetragonal-to-orthorhombic phase transition or the thermal contraction during cooling from the peritectic temperature. The formation of microcracks induced by the phase transition seems to be closely related to the process of oxygen diffusion into a sample. We discuss the formation of microcracks in terms of the oxygen diffusion along the plate boundaries and of the thickness of 1-2-3 plates. The decrease in the plate thickness and the fine dispersion of 2-1-1 particles contribute suppression of the formation of microcracks and their propagation.

Resistivity measurement of an a-axis-oriented YBa2Cu3O7-δ (YBCO) thin film was carried out in a stream of O2/Ar mixtures at 450–650 °C. Rapidly reversible change in the resistivity of the YBCO film was observed as a function of the oxygen partial pressure in the ambient atmosphere due to the oxygen in-/out-diffusion in the YBCO film. Resistivity measurement of YBCO thin films at higher temperatures of 450–650 °C was found to be quite effective to predict the influence of fabricating processes on the superconducting properties of YBCO films.

Optical emission spectroscopy of the rf thermal plasma evaporated YBa2Cu3O7−x has been investigated. The deposited films with the nearly stoichiometric composition could be obtained by using Y-rich powder. From the optical emission spectra, O, Y, Y+, Ba, Ba+, Cu, and YO as the emitting species were observed. The excitation temperature was lower for Y+ than for the other dissociated elements. The relative intensity for YO of a suboxide became larger with a lower plasma torch. It is thought that the deposited film that is poor in Y results from YO sticking to the substrate rather than Y or Y+.

Crystal structure and superconductivity of the Tl–Ba–Ca–Cu–O powder prepared by a solid-state reaction were studied. The results of x-ray diffraction, scanning electron microscopy, and transmission electron microscopy analyses indicate that the powder of a major single 1223 phase was synthesized with a cauliflower-like morphology; by grinding, the powder was partially transformed to an amorphous phase. The measurement of magnetic hysteresis was also performed in the temperature range of 7–75 K up to 5 T from which the weak field-dependent behavior of critical current density was observed. The as-synthesized powder, with Tc = 110 K measured from magnetometer and susceptometer, is considered to consist of weak-linked regions. The results obtained from comparing the as-synthesized and the ground powder imply that in the Tl-1223 system, the Ag-sheathed tapes fabricated by the powder-in-tube process may be benefited by forming other intermediate phases with plate-like morphologies to give better densification or grain alignment.

The microstructure of mixed phase, c-axis oriented Tl–Ca–Ba–Cu–O thin films, exhibiting excellent superconducting properties, has been examined by transmission electron microscopy and x-ray diffraction. Although the stoichiometry of the as-deposited films corresponds to the Tl2Ca2Ba2Cu3O10 phase (Tl-2223, c = 3.6 nm), x-ray diffraction showed these films contain up to 50% of the Tl2CaBa2Cu2O8 phase (Tl-2122, c ≍ 2.9 nm). The x-ray diffraction peaks of the 3.6 nm phase are noticeably broader than those of the 2.9 nm phase, suggesting a smaller coherent size along the c-axis for the 3.6 nm phase Lattice-fringe images of the 2.9 nm phase typically show only an occasional or no defect layer; however, such layer defects are more abundant in the 3.6 nm phase and, though random, occur with sufficiently wide separation and regularity to be consistent with an average coherency of ∼40 nm. The coherent sizes along the c-axis, as determined by x-ray line profile analysis, were 140 nm and 40 nm, respectively, for the 2.9 nm and 3.6 nm phases, in good agreement with those determined by electron microscopy. The estimated width of the layer defects observed in the lattice-fringe images is suggestive, for the most part, of the four Cu-layered phases (Tl-1324 or Tl-2324) and to a lesser degree the two Cu-layered phases (Tl-1122 or Tl-2122).

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.

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.

A small addition of boron is suggested to increase the ductility of the polycrystalline Ni3Al when the Al content is less than 25 at.%. Both metallographic and x-ray investigation have shown the alloys of Ni3Al (24 at.% Al) containing 0.20, 0.42, 0.79, 0.98, and 1.22 at.% B to be of single phase and that of 1.76 at.% B to be of two phase. With the addition of boron, the lattice parameter of the Ni3Al phase is found to increase. Microhardness measurements indicate that initially the hardness decreases for the alloy of 0.20 at.% B, while for the rest of the single phase alloys the hardness is found to increase with further addition of boron. The addition of boron increases the deformation stacking fault probability value except for the alloy with 0.20 at.% B.

A model for the growth of a grain boundary crack in thermomechanical fatigue is derived for a single-phase or low alloy fcc metal at homologous temperatures near 0.5. Crack growth is hypothesized to proceed through vacancies binding in pairs at the crack tip to impurities or an oxide layer. This model is applied to 97Pb−3Sn, and the results compared with experiment. Good agreement is shown between the model and experiment, especially in predicting the effects of frequency and thermal-mechanical phasing. These effects do not appear to have been previously modeled successfully.

A niobium beryllide, Nb2Be17, has been prepared by powder-metallurgy techniques and the mechanical properties characterized both at room and elevated temperatures. Microhardness and fracture toughness were measured at room temperature. Hardness and hot-hardness test results indicated that, although the material was brittle at low temperatures, it became plastic at elevated temperatures (>1000 °C). Creep properties of Nb2Be17 were studied at temperatures from 1250 to 1350 °C and applied stresses from 10 to 90 MPa. The stress exponent, determined from stress-change tests, was about 3, and the activation energy, determined from temperature-change tests, was about 575 kJ/mol. The creep of Nb2Be17 at high temperature is apparently controlled by dislocation glide; this proposal was supported by transient creep experiments. Comparisons have been made between the creep properties of Nb2Be17 and other intermetallics.

The “x-ray tensile test” is the combination of the standard uniaxial tensile test with x-ray diffraction techniques. In this test, in addition to the mechanical stress-strain values usually obtained from a tensile test, one measures the x-ray strain and stress in the diffracting regions of the sample. In multilayer thin films or in multiphase materials, x-ray diffraction enables the determination of strains and stresses in the individual layers or phases. Correlation of the x-ray data with the mechanical stress-strain values may be used to analyze strain and load partitioning within the specimen. In this paper an extended theoretical analysis of this technique and its application to evaporated Cu films on Ni substrates is presented.

Sputter-deposited Co–Gd and Cr–Gd multilayer films were studied by high resolution transmission electron microscopy (HRTEM). These two systems are expected to give rise to quite different structures. In good agreement with predictions, the individual Cr and Gd layers were found to be 100% crystalline with sharp interfaces and no noticeable intermixing. Conversely, the Co–Gd multilayer system underwent a solid state amorphization reaction during the deposition itself. This reaction has been found elsewhere to show an asymmetric character with the order of deposition, strong evidence for which is observed in this work.

A novel spin-polarized scanning electron microscope with capabilities of observing microscopic domain structures and determining in-plane magnetization directions has been used to investigate the stress-induced magnetic domains in the Fe78B13Si9 (Allied 2605-S2) metallic glass. The magnetic structure in the vicinity of shear bands that are produced near a Mode III crack has been examined. On the tensile side of bending, arrays of individual, discontinuous magnetic “islands” of similar shape and size (about 2–10 μm in length, 3 μm in width, and spaced about 2–4 μm apart) are uniformly distributed on one side of the shear bands. Their easy axis is about parallel to the shear bands. On the other hand, well-defined elliptical domains are found between shear bands on the compression side of bending. Their easy axes are approximately perpendicular to the shear bands. These results suggest the existence of isolated defects of similar stress fields located along the shear bands. The possibility that these defects are dislocations will be investigated next.

Particle size distributions derived from SEM micrographs of well-separated diamond particles, deposited on Si(100) substrates by the hot filament CVD method, have been analyzed in connection with previous measurements of particle growth rates. Rates of nucleation have been obtained from this analysis in an extended range of deposition conditions. A previously developed nucleation model has been utilized, and the kinetic parameters provide a framework for modeling the nucleation process from the gas phase.

On the basis of an analysis of experimental data on nucleation rates performed in the preceding paper in this issue, patterns of the process of diamond nucleation from the gas phase on Si(100) substrates have been drawn. A kinetic scheme is proposed which is apparently able to describe the complex behavior of the system in the temperature range 750 K−1225 K, at (CH4/H2) ratios between 0.5 and 2% and at a total pressure of 100 mbar. The model postulates a distribution function of the nucleation centers over the heats of adsorption of active gaseous species and introduces a cut-off criterion based on the necessary condition that adjacent active sites coexist for times longer than the characteristic time of germ growth. Nucleation centers, active sites, germs, and nuclei have been defined by simple molecular models and their rates of transformation discussed, using available literature data.

Photoconductivity was measured on a series of carbon aerogels to investigate their electronic properties. Carbon aerogels are a special class of low-density microcellular foams, consisting of interconnected carbon particles (∼120 Å diameter) and narrow graphitic ribbons (∼25 Å width) intertwined within each particle. Both the dark- and photoconductivities show drastic changes in the temperature range 5–300 K, which are similar to those in a-Si and chalcogenide photoconductors. At high temperatures, the photoconductivity is dominated by the carrier recombination within each particle. The photoconductivity at low temperatures is dominated by the same carrier transport mechanism as that for the dark conductivity, which is based on hopping and tunneling transport. The activation energy values for transport and recombination identify the electronic structure of the particles among samples of different bulk density. The long decay time of the photoconductivity suggests a relaxation mechanism associated with the dangling bonds.

The competition between solid phase epitaxy and random nucleation in amorphous Si implanted with Cu and Ag has been studied. At low metal concentrations, solid phase epitaxy proceeds with slight deviations from the intrinsic rate, with the impurity segregated and evenly distributed in the amorphous layer. At an impurity concentration of 0.12 at.%, rapid nucleation occurs, transforming the remaining layer into polycrystalline Si. The nucleation rate is ≥108 the intrinsic homogeneous rate. The effects of the metals on epitaxy scale with the amount of metal–Si interaction. Nucleation appears to occur when the metal impurities exceed their absolute solubility limit and begin to phase separate.