Whiskers of 2212 phase Bi2Sr2Ca1Cu2Ox were prepared by heating in air the powder-compacted pellets of melt-quenched glassy products in BiSrCaCu2Ox containing a small amount of Al2O3. The dissolved and/or physically mixed Al2O3 in the powder-compacted specimen is found to enhance the whisker formation remarkably.

Compositional dependence of the stress + longitudinal field induced magnetic anisotropy (SLFA) in (Co1−xFex)75Si15B10 (0 ⋚ x ⋚ 1), (Co1−xNix)75Si15B10 (x = 0.22) and [Co1−x(Fe0.5Ni0.5)x]75Si15B10 (x = 0.20, 0.50, and 0.80) amorphous alloy ribbons has been studied. The magnetic field was applied parallel to the ribbon axis. Two mechanisms have been invoked in order to explain the microscopic origin of this anisotropy: the directional ordering of atomic pairs, and the tetrahedral holes like 3Co–1Fe and 1Co–3Fe. The last contribution is found to be similar both in its direction and its value with respect to that obtained for stress + transverse field induced anisotropy (STFA) in the same compositions containing Fe, while in the Co–Ni samples only the first contribution is responsible for the SLFA, depending on its direction for the field annealing.

The morphology of typical CVD diamond thin films has been shown to be controlled by the concentration of methane during deposition. For example, for CH4 concentrations c < 0.4% the (111) faces dominate, while at 0.4% < c < 1.2% (100) faces dominate. Here we showed that the (100) oriented diamond films can be grown on top of the microcrystalline ball-like particles under suitable conditions. These (100) oriented diamond films are grown under the condition of 1.5% methane in hydrogen, substrate temperature of 680 °C–750 °C, and pressure of 30–80 Torr. The bombardment of the diamond thin films by ions in the plasma is believed to be an important factor for the formation of (100) oriented films on top of the ball-like particles. SEM, Raman, and x-ray techniques were used to characterize the deposited (100) oriented diamond thin films.

We prepared MoSi2, two-phase MoSi2/Mo5Si3, and (Mo, W)Si2 solid-solution alloy powders by mechanically alloying mixtures of elemental molybdenum, silicon, and tungsten. These powders were consolidated by hot-pressing them at 1500 °C in graphite dies. We measured the elastic moduli of these alloys by a recently developed technique for non-contact ultrasonic spectroscopy. Second-phase Mo5Si3 additions to MoSi2 result in decreased values for G and E, whereas alloying MoSi2 with WSi2 results in increased values for G and E. An analysis of these Young's moduli and of data from the literature for various intermetallic alloys suggests that for any given alloy system, the Young's moduli for its various intermetallics as a function of density fall on a straight line. Further, the lines for the different alloy systems are approximately parallel.

The extent of phase transformation occurring in silicon during room-temperature indentation experiments has been examined by transmission electron microscopy of low-load microindents. The results show that the entire hardness impression arises from structural transformation and extrusion of a ductile high pressure phase. In particular, there is no dislocation activity or other mechanism of plastic deformation operating outside the clearly demarcated transformation zone. The observable impression consists of an amorphous transformation zone with an adjacent region of plastically extruded material and a layer of polycrystalline silicon at the near-surface transformation interface.

We report on oriented and adherent cubic BN films grown on (001) faces of silicon using the method of ion-assisted pulsed laser deposition. The structure of the films is cubic zinc-blende with a lattice constant of 3.62 Å, as determined by infrared absorption and transmission electron microscopy. The films were found to be polycrystalline, and oriented with the cubic BN [110] axis parallel to the Si [001] direction.

The unidirectional solidification of the zone melt method was performed in order to clarify the growth mechanism on Y-system superconductors. A sharp faceted interface of YBa2Cu3Oy (123) crystals was obtained in the sample grown at the low growth rate of 1 mm/h. The volume of the 211 phase changed drastically from liquid to 123 crystal. These results lead to the idea that the necessary solute for peritectic reaction is provided through a liquid. Based on this idea, we developed a simple solidification model that is in good agreement with the experimental results.

Young's modulus of ceramic YBa2Cu3O7−δ was measured between room temperature and 1000 °C, E(T), by an ultrasonic pulse-echo technique. Experimental results are presented for nonaligned ceramics with average grain sizes from 2 to 10 μm and densities from 80% to 95% of the theoretical value. Young's modulus is shown to be strongly sensitive to oxygen content with the orthorhombic phase being significantly stiffer than the tetragonal phase. In addition, the phase transition is denoted by a pronounced minimum in E(T) relating to softening of certain bonds in the unit cell. At high temperature (>900 °C) melting of the second phase gives a steep drop in E(T) while subsequent densification increases E. Finally, cooling of large-grained ceramic below 450 °C opens microcracks due to anisotropic volume changes. This results in hysteresis between the heating and cooling curves for E(T). Hence the technique is used to show that ceramic, with an average grain size of 2 μm and 85% of theoretical density, is well oxygenated and undamaged by its thermal treatment.

Magnetron sputtering was used to deposit superconducting YBCO thin films on four polycrystalline metal substrates. Yttrium-stabilized zirconia (YSZ) and silver were used as buffer layers. The thermal expansion coefficient of the substrate was apparently correlated to the properties of the superconductor. Auger depth profiles showed that the YSZ buffer blocked diffusion of most metal elements from the substrate. Nevertheless, contamination of the films depressed Tc to 81 K on Hastelloy × from 87 K on single-crystal strontium titanate. The films on metal substrates were c-axis oriented, but with random rotation in the a-b plane and smaller grain size than epitaxial films on single crystals. The weak links from these factors restrict Jc to 104 A/cm2 at 40 K.

Control of the in-plane epitaxial alignment of c-axis YBa2Cu3O7−δ (YBCO) films on yttria-stabilized zirconia (YSZ) substrates is necessary for achieving optimal transport properties. We have used pulsed laser deposition to grow homoepitaxial YSZ and heteroepitaxial CeO2 on YSZ single crystal substrates. This procedure dramatically improves the epitaxy of YBCO and reduces the number of low and high angle grain boundaries. We have also studied the effects of preparing the YSZ growth surface with approximately monolayer amounts of CuO, Y2O3, BaO, and BaZrO3 to determine the effects these compositional variations have on the subsequent YBCO epitaxy. CuO, Y2O3, and BaZrO3 induce an in-plane crystallography of YBCO distinct from that initiated with BaO. Both homoepitaxy and monolayer depositions may be carried out in situ and are simple and effective for controlling the epitaxy and electrical properties of YBCO on YSZ. The effects of substrate temperature, oxygen pressure, and yttria content have also been studied.

Hydrogen implanted into ceramic YBa2Cu3O7−x (YBCO) with a dose of 1 × 1017 H+ cm−2 started to effuse as molecular hydrogen from the YBCO to atmosphere at a temperature of 200 °C, effuse predominantly as water by reacting with oxygen at temperatures of 300–700 °C, and again effuse as molecular hydrogen at temperatures above 800 °C. The improvement of the superconducting properties of the proton implanted YBCO occurred at annealing temperatures for which implanted hydrogen effused predominantly as water by reacting with oxygen.

A detailed study of the crystallization process for compositions near Bi2Sr2Ca1Cu2Oy was undertaken using differential thermal analysis (DTA), transmission and scanning electron microscopy (TEM and SEM), and x-ray diffraction (XRD). Glasses prepared by a splat-quench technique were free of secondary phases in most cases. A two-step crystallization process in oxygen was observed in which partial crystallization of the glass occurs initially with the nucleation of “2201” and Cu2O, and is completed with the formation of SrO, CaO, and Bi2Sr3−xCaxOy. No specific thermal event could be associated with the formation of the “2212” phase. Rather, formation occurs via conversion of 2201 into 2212. This was a kinetically limited process at temperatures below 800 °C as other phases were found to evolve in addition to the 2212 phase during extended anneals. In contrast, a nearly full conversion to the 2212 phase occurred after only 1 min of annealing at 800 °C and above. However, changes in resistivity data, secondary phases, and the measured 2212 composition upon extended anneals at 865 °C showed that considerably longer heat treatments were necessary for the sample to reach its equilibrium state.

Superconducting composite samples were prepared by sintering a mixture of metallic silver and Bi(Pb)–Sr–Ca–Cu–O powder in air. For Ag contents between 0 and ∼15 vol. %, the bulk critical temperature was depressed as much as 40 K, and the relative proportion of the 2223 phase with respect to the 2212 phase was decreased, compared to the pure sample. However, as the Ag content was increased to between 19 and 70 vol. %, critical temperatures above 100 K were measured by transport and ac susceptibility techniques, and the relative proportions of the phases were restored to that of the pure sample. The limit of bulk superconductivity was reached at 73 vol. % Ag where the bulk critical temperature was ∼85 K. For higher Ag contents bulk superconductivity was not observed. Our results also show that sintering in air of silver-clad tapes containing Bi(Pb)–Sr–Ca–Cu–O powder, either by itself or with silver powder, need not be detrimental to the final superconductive properties.

The atmospheric pressure chemical vapor deposition of aluminum nitride coatings from hexakis(dimethylamido)dialuminum, Al2(N(CH3)2)6, and ammonia precursors is reported. The films were characterized by ellipsometry, transmission electron microscopy, x-ray photoelectron spectroscopy, Rutherford backscattering, and forward recoil spectrometry. The films were deposited at 100–500 °C with growth rates up to 1500 Å/min. The films showed good adhesion to silicon, glass, and quartz substrates and were chemically inert. Rutherford backscattering analysis revealed that the N/Al ratio was 1.15 ± 0.05 for films deposited at 100–200 °C and 1.05 ± 0.05 for those deposited at 300–500 °C. Films deposited at 100–200 °C had refractive indexes in the range 1.65–1.80 whereas indexes for films deposited at 300–400 °C were 1.86–2.04. The films were transparent in the visible region. The optical bandgap varied from 5.0 eV for films deposited at 100 °C to 5.77 eV for those deposited at 500 °C. Films deposited at 100–200 °C were amorphous whereas those deposited at 300–500 °C were polycrystalline.

Direct writing of iron lines on glass and Al2O3 has been achieved by CW CO2 laser-driven pyrolytic dissociation of volatile iron pentacarbonyl liquid. Since a very high organometallic molecular density is realized in the solution, use of a liquid precursor has enabled deposition of micron-thick iron films at the writing speeds of 10–400 mm s−1, which are significantly higher as compared to those achievable by the conventional CVD method. The iron stripes deposited on the glass substrate at the laser power density of 5.3 kW cm−2 and the writing speed of 100 mm s−1 are found to have a resistivity of about 580 μohm-cm. These stripes have been found to have an integral bond with the substrate due to the interface reaction.

The phase constitution and the lattice parameter relationships in the rapidly solidified and heat-treated (Mn0.53Al0.47)100−xCx pseudo-binary alloys (x = 0–6) have been investigated by means of x-ray diffraction and transmission electron microscopy. The melt-spun alloys contained a single ∊ phase (cph) with 0.63–4.0 at. % C, and below and beyond this carbon composition range small traces of γ2-MnAl and Al4C3 compounds were formed, respectively. The heat treatment of the melt-spun alloys at 823 K produced a single τ phase (ordered bct, CuAu type I, L10) with 0.63–3.6 at.% C. The c lattice parameter of the ∊ unit cell was observed to increase pronouncedly with the carbon content whereas that of the a-axis revealed no apparent change; the corresponding increase of the unit cell volume was taken to indicate an interstitial dissolution of the carbon atoms in the ∊ lattice. On the other hand, for the τ phase, the c lattice parameter increased markedly with the carbon content while the a parameter decreased slightly, so that a large increase of c/a ratio was produced. The lattice parameter data for the τ phase thus indicated an increase of the unit cell volume with the carbon content, providing new evidence that the carbon atoms dissolve interstitially in the bct lattice. In addition, it was deduced that the higher c/a ratio with increasing carbon content may arise from a preferential site occupation of the carbon atoms at a specific type of octahedral interstitial site lying in the manganese atom layers.

A multiphase oxidation resistant composition (Nb–67Al–7Cr–0.5Y–0.25W) based on NbAl3 was prepared by both induction melting and rapid solidification processing (RSP), followed by grinding to 75 μm powder and consolidating by powder metallurgy techniques (hot pressing, hot isostatic pressing, and Ceracon pressing). Constant strain rate compression tests conducted on consolidated materials in the temperature range 300–1300 K indicated that the RSP material exhibited significantly higher strength and ductility than the induction melted alloy up to 1200 K. Bend strengths measured on induction melted material were significantly lower than the corresponding compressive strengths, suggesting the brittle, flaw-sensitive nature of this alloy. The NbAlCrYW alloy exhibits a brittle-to-ductile transition around 1000 K. The constant load creep tests conducted on the induction melted alloy in the 1200–1300 K temperature range indicated that this alloy shows a power law creep dependency with a stress exponent, n, of 3.2. It was found that the specific strength of this alloy is competitive with other aluminide intermetallics.

An experimental method to obtain the grain boundary geometry using the transmission electron microscope is presented. The method allows Σ determination including grain boundary plane orientation. In order to determine the specialness of the grain boundary, three different criteria for maximum allowable deviations from exact CSL misorientations were examined. We tested these three criteria from a statistical distribution of grain boundary types in terms of Σ. We compared grain boundary distributions from other studies in Ni3Al and found discrepancies among them. It seems that the discrepancy came from the different criteria for special boundaries in Σ determination and different experimental procedures they used. The statistical distribution of grain boundary plane orientations showed that low Σ boundaries (Σ < 11) were oriented to the plane of high density of coincident sites.

The relative stability of standard extended dislocation dipoles and some new stable defects with lozenge-shaped cross sections have been numerically estimated. An earlier study of these defects in an isotropic fee structure has been extended to the anisotropic case to assess the effect of anisotropy on the calculations. The study is further extended to the case of the L12 crystal structure of the ordered alloy Ni3Al, where the Burgers vectors are large. Results indicate that the introduction of anisotropy has a small effect in determining the relative stability of extended dislocation faults. The results also show that the large values of the Burgers vectors stabilize the arrays in Ni3Al and that the most stable defect favored is the screw lozenge array LD.

A new processing route for intermetallics starting from elemental metal powders and using laser beam heating has been investigated, by which three Al3Ti-based ternary intermetallic systems alloyed with Fe, Ni, or Cu, respectively, have been produced. Structures and compositions of five phases found in the three systems have been analyzed using optical metallography, transmission electron diffraction and microscopy, and thin foil energy dispersive x-ray spectrometry. The structure of three matrix phases in the three systems was identified as L12 type, which is consistent with previous work. The space group of the second phases in the two systems alloyed with Fe or Ni was reconfirmed or newly determined as Fm3m, using convergent beam electron diffraction. The lattice parameter measurements of these five found phases indicated atomic size-effect on the formation of intermetallics.