Aluminum ammonium sulfate (AA) solution (0.1 mol/l) and ammonium hydrogen carbonate (AHC) solution (1.2 mol/l) were allowed to react at room temperature. The precipitates formed were kept with the mother liquor in a closed vessel and aged at 100 °C. Acicular-shaped crystalline particles of Al(NH4)CO3(OH)2, (AACH), were obtained after the elongated aging period. Acicular α-alumina particles were obtained through the thermal decomposition at 1300 °C out of the AACH particles which were previously treated with a small amount of tetraethoxysilane (about 1.6 wt. % of SiO2).

The ordering behavior of La-modified lead zirconate titanate relaxor (PLZT 9/65/35) was investigated by use of an x-ray diffractometer (XRD) and high-resolution transmission electron microscopy (HRTEM). It was shown that a {h + 1/2, k + 1/2, 0}-type superlattice exists both in the x-ray diffraction pattern and selected area electron diffraction (SAED) image. High-resolution electron micrographs further demonstrated the existence of the superlattice and exposed the ordered and disordered regions in the lattice level. A model referring to an A-site body-centered pseudo-cubic superstructure was proposed.

Electron emission from chemical vapor deposited (CVD) diamond and amorphous carbon (a-C) films was observed with a simple field emission device (FED). Both diamond and a-C films were prepared with microwave plasma-enhanced CVD techniques. Electron emission in the ficld strength range + 10 to −10 MVm−1 was studied, and the field emission source was confirmed by a diode characteristic of the I-V curve, a straight line in the Fowler-Nordheim (F-N) plot, and direct observation of light emission from a fluorescent screen. The turn-on field strength was ∼5 MVm−1, which was similar for both kinds of carbon films. The highest current density for diamond films, observed at a field strength of 10 MVm−1, was ∼15 μA cm−2. Diamond films yielded a higher emission current than a-C films. The reasons for the observed field emission are discussed.

Molecular dynamics (MD) simulations of diffusion in a Σ5(310) [001] Al tilt grain boundary were performed using for the first time three different potentials based on the embedded atom method (EAM). The EAM potentials that produce more accurate melting temperatures also yield activation energies in better agreement with experimental data. Compared to pair potentials, the EAM potentials also give more accurate results.

YBa2Cu3C7−x (Y123) single crystals have been grown by the modified pulling method (Solute Rich Liquid Crystal Pulling method, SRL-CP). For further superconductor device application, it is important to establish a technique that enables us to produce larger Y123 single crystals consistently. We have investigated the relationship among the crystal size, the crystal rotation rate, the flow pattern in the melt, and the temperature at the crystal growth interface experimentally. Increase of the crystal diameter and/or the crystal rotation rate increased the strength of the forced convection in the melt, and as a result, the temperature at the crystal growth interface increased. This resulted in a reduction of the crystal growth rate. On the other hand, the forced convection should be kept high enough to prevent floating particles attaching to the growing crystal. Therefore, in order to grow a larger single crystal, it was necessary to control the crystal rotation rate according to the change of the crystal diameter with time. We succeeded in crystal pulling along the c-axis of a relatively large Y123 single crystal which was 17 mm × 17 mm and 8 mm in length.

We have estimated the growth rate of the YBa2Cu3Ox crystal grown from the solution by crystal pulling, in terms of solute diffusion in the liquid with convection. The maximum growth rate deduced from the solute diffusion rate is roughly estimated to be about one order larger than the typical measured value. This implies that the driving force for the surface reaction is significantly larger when compared to the total driving force for the growth of YBa2Cu3Ox crystal in our method.

Segregation of second-phase particles within Y1Ba2Cu3O7−y domain was investigated in melt-textured Y-Ba-Cu-O with metal oxide (CeO2, SnO2, and ZrO2) addition. It is found that coarse particles (Y2Ba1Cu1O5) are trapped with a special pattern in the interior of Y1Ba2Cu3O7−y domain, while fine BaCeO3 and BaSnO3 particles are present within the remnant liquid-phase region. During the growth of Y1Ba2Cu3O7−y domain, fine particles appear to be pushed out of the advancing Y1Ba2Cu3O7−y /liquid interface toward the liquid phase. The particle segregation that occurred during peritectic growth of the Y1Ba2Cu3O7−y domain was explained in terms of the Uhlmann-Chalmers-Jackson theory based on the particle interaction at solid/liquid interface.

Important factors governing the size and the morphology of Y2BaCuO5 (Y211) at 1100 °C in air were investigated for three different starting materials having the same nominal composition of Y:Ba:Cu = 1.8:2.4 : 3.4, Y2BaCuO5-BaCuO2-CuO-Pt. Y2O3-BaCuO2-CuO-Pt, and melt-quenched materials from 1400 °C in a Pt crucible. With various amounts of Pt doping, the heating rate and the holding time were employed as the processing parameters. While, with the aid of Pt doping as the effective growth inhibitor, fine round Y211 grains could be obtained by simply employing a refined round Y211 precursor and a rapid healing, there were several important factors for obtaining fine acicular (or needle-like) Y211 grains as follows: (i) The Pt dopants dissolved in the liquid phase should act as the effective heterogeneous nucleation sites. (ii) Y211 grains should grow into the acicular shapes before the system reaches an equilibrium amount of Y211 in the liquid (i.e., reaction-controlled). (iii) A large amount of the liquid phase should be supplied instantly at the partial melt stage with a rapid heating.

We have studied the relative diffusion rates of oxygen through dielectric/buffer layers used in high critical temperature superconducting multilayer structures. Epitaxial bilayer films of dielectric (CeO2, LaGaO3, NdGaO3, LaAlO3, MgO, SrTiO3, LaLiTi2O6, or LaNaTi2O6) on YBa2Cu3O7−δ (YBCO) have been deposited onto (001) oriented single-crystal MgO substrates using pulsed laser deposition. These bilayers have been investigated for oxygen diffusion over the temperature range 350 to 650 °C by postdeposition annealing the films for 20 min in 0.5 atm of 18O enriched molecular oxygen gas. Secondary ion mass spectroscopy was used to depth profile the relative concentration of 18O to 16O in each bilayer. Compared to YBCO, the dielectrics MgO, SrTiO3, LaLiTi2O6, and LaNaTi2O6 are relatively slow diffusers, while CeO2, LaGaO3, NdGaO3, and LaAlO3 are relatively fast diffusers.

The effects of annealing temperature and oxygen partial pressure [p(O2)] were investigated on the crystallization and orientation of YBa2Cu3O7−y (YBCO) films on MgO(001) prepared by the dipping-pyrolysis process. The c-axis oriented films without in-plane alignment were prepared by annealing in the YBCO-unstable region, i.e., at low initial p(O2) of 10−4−10−3 atm and 950 °C followed by O2 treatment, through intermediate Y2BaCuO5 and liquid phase. In-plane aligned c- or c/a-axis films were prepared by similar heat treatment with an initial p(02) of 10−4 atm and 900–925 °C through a mixture of BaCu2O2 and YBa3Cu2O6+x. In contrast, nonoriented YBCO films were obtained by annealing at higher initial p(O2)'s and lower temperatures, i.e., by direct reaction among Y2O3, BaCO3, and CuO.

Gas-phase particle size distributions and lead loss were measured during formation of (Bi,Pb)-Sr-Ca-Cu-O and pure PbO particles by spray pyrolysis at different temperatures. A differential mobility analyzer (DMA) in conjunction with a condensation particle counter (CPC) was used to monitor the gas-phase particle size distributions, and a Berner-type low-pressure impactor was used to obtain mass size distributions and size-classified samples for chemical analysis. For (Bi,Pb)-Sr-Ca-Cu-O, as the processing temperature was raised from 200 to 700 °C, the number average particle size decreased due to metal nitrate decomposition, intraparticle reactions forming mixed-metal oxides and particle densification. The geometric number mean particle diameter was 0.12 μm at 200 °C and reduced to 0.08 and 0.07 μm, respectively, at 700 and 900 °C. When the reactor temperature was raised from 700 and 800 °C to 900 °C, a large number (∼107 no./cm3) of new ultrafine particles were formed from PbO vapor released from the particles and the reactor walls. Particles made at temperatures up to 700 °C maintained their initial stoichiometry over the whole range of particle sizes monitorcd; however, those made at 800 °C and above were heavily depleted in lead in the size range 0.5–5.0 μm. The evaporative losses of lead oxide from (Bi,Pb)-Sr-Ca-Cu-O particles were compared with the losses from PbO particles to gain insight into the pathways involved in lead loss and the role of intraparticle processes in controlling it.

Using an inductive technique, we have measured the in-plane resistivity ρa of stages 2, 4, 5, and 8 SbCl5-GIC's versus temperature T and pressure p in the ranges 130–300 K and 0–0.85 GPa. The room temperature values of ρa range from 4.0 μΩcm for the stages 5 sample to 7.7 μΩcm for the stage 8 sample. At all pressures, ρa shows a metallic temperature dependence ρa ∼ Tα, with 1 ≤ a ≤ 2, but in contrast to the c-axis resistivity ρc, it depends only very weakly on pressure and/or intercalate structural order. We show that the behavior observed is consistent with a band conduction model.

Spray pyrolysis was used to produce submicron Ag-Pd metal alloy particles for applications in electronic component fabrication. The particles were prepared in nitrogen carrier gas from metal nitrate precursor solutions with various compositions. The Ag-Pd alloy was the predominant phase for reactor temperatures of 700 °C and above for all compositions. The 70-30 Ag-Pd partcles were fully dense at 700 °C, but an increased reaction temperature was necessary to produce dense particles at higher Pd to Ag ratios. The extent of palladium oxidation was suppressed with increased amounts of Ag. Single-crystal particles could be produced at sufficiently high temperatures. These results show that particle phase composition, size, oxidation behavior, and morphology can be controlled by the Ag-Pd ratio in the precursor solution and by the reaction temperature.

The analytic solution to the time-dependent nucleation problem by Shi-Seinfeld-Okuyama (SSO) [Phys. Rev. A 41, 2101 (1990)] is reviewed. The singular perturbation solution employed by SSO is extended to examine the effect of initial quench position on the incubation time. Two cases are discussed. The first investigates the role of excess vacancies from the high temperature quench on the transient kinetics. The second case examines the change in the incubation time due to the effects of a preexisting subcritical cluster size distribution which forms during the high temperature anneal.

The measurements of the desorption pressure-composition-temperature (P-C-T) of the TixZr1−xNiyV2−y (0 ≤ x ≤ 1,0 ≤ y ≤ 2) alloy have been investigated by means of a 32 factorial design method. The response surface function of hydrogen desorption between 0.01 and 10 atm was calculated by Yates' algorithm. Alloy with x = 0.35, y = 0.60 (i.e., Ti0.35Zr0.65Ni0.6V1.4) was found to possess maximum hydrogen desorption capacity. When examined by EDAX and SEM, this alloy shows three distinguishable phases and exhibits C14 structure. The effect of substitution of Mn and Ni for V was also studied. Alloy such as Ti0.35Zr0.65Ni1.2V0.4Mn0.4 has nearly a pure C14 structure with 89% hydrogen desorption ability. This alloy has 255 mAh/g, 231 mAh/g, and 210 mAh/g capacities at 25 mA/g, 50 mA/g, and 100 mA/g discharge rates, respectively. This indicates that the substitution of Mn and Ni for V not only can improve its hydrogen desorption ability, but also make the alloy structure more uniform and more suitable to be an electrode material.

Novel microwave-hydrothermal processing has been developed by us recently for the synthesis of a wide variety of ceramic powders. Herein, we report the use of microwave-hydrothermal processing to synthesize several metal powders such as Cu, Ni, Co, and Ag by reducing their corresponding metal salts or hydroxides with ethylene glycol. Metal powders have been produced extremely rapidly a (few minutes) by microwave catalysis. The kinetics of metal powder synthesis have been increased by at least an order of magnitude by microwave-hydrothermal processing compared to the conventional refluxing process in ethylene glycol at about 195 °C.

Thin film cracking has been studied for a nanometer brittle/ductile layered system consisting of Si and Cu. Single Si films and Cu/Si/Cu trilayers were fabricated by physical vapor deposition. The films were deposited onto a ductile substrate consisting of stainless steel with a thin polyimide interlayer. Straining of the substrate induced cracking of the Si. Cracking strains ≥1% were observed, particularly in layers ≤100 nm thick. The critical cracking strain was found to depend upon the Si layer thickness, as well as the thickness and elastic/plastic properties of the adjacent ductile layers. Si cracking was suppressed by the presence of adjacent Cu layers. The measured strains were compared with lower-bound critical strains for tunnel and channel cracking. Comparisons indicated that these mechanisms control the critical strain found in trilayers, because trilayer fabrication introduces edge flaws larger than the Si layer thickness. Conversely, for Si films, the measured critical strains exceed the channel cracking strain, because the flaws in these films are relatively small.

High-pressure, high temperature (HPHT) annealing of synthetic type I diamond crystals at 1200–1700 °C and 50–60 kbar was found to induce aggregate-nitrogen dissociation and metal coalescence as well as heal diamond lattice dislocations. For crystals with low levels of metal inclusions, HPHT annealing was observed to increase the average compressive fracture strength of the crystals by apparently strengthening the strongest crystals of the population. Crystals with high metal-content, or otherwise of low quality, are weakened by anncaling. Strengthening is believed to occur by locally stabilizing the diamond lattice by healing lattice dislocations as well as dispersing nitrogen within the lattice. A general model is presented that ties together these results with those of other researchers.

Tungsten silicide (WSix) thin tilms have been investigated for use as integrated circuit interconnect and self-aligned MESFET (metal-semiconductor field-effect transistor) gates because of their low resistivity and thermal and chemical stability. These same characteristics make them interesting materials for prospective use in micromechanical structures. However, little information on residual stresses, elastic moduli, or other micromechanical properties has been available for refractory metal silicide thin films. This paper presents the morphology and stress characteristics of cosputtered WSix thin films, including crystal structure variations and orientation-dependent stresses, as a function of the deposition pressure. The compositions of WSix thin films were analyzed by Rutherford backscattering spectrometry (RBS). The biaxial elastic modulus and thermal coefficient of expansion were found for the sputtered films. Stress-measurement methods and annealing are discussed. Released diaphragms of different sizes and shapes, having controlled residual stress, have been fabricated.

Crystalline Nb5Si3/Nb microlaminates were fabricated to a thickness of 20 μm by depositing the materials onto elevated temperature (750 °C) substrates. Modulation wavelengths of the microlaminates were varied (λ = 40 and 200 nm) while holding their silicide volume fraction constant to assess the effect of layer thickness on the composite properties. X-ray and selected area diffraction confirmed that both the metal and silicide layers exhibited a polycrystalline structure in the as-deposited microlaminates. Nanoindentation measurements of both microlaminates indicated that calculated elastic modulus values were similar to the values obtained by the rule-of-mixtures (ROM). Nanohardness values of the microlaminates increased with decreasing wavelength in a manner described by the Hall-Petch relationship. Vickers hardness (Hv) measurements were also found to be a function of the modulation wavelength, decreasing from 7.32 GPa at λ = 40 nm to 3.04 GPa at λ = 200 nm. Even with a Nb volume fraction of 50%, the λ = 40 nm microlaminate and the monolithic Nb5Si3 film exhibited similar Vickers hardness values of 7.5 GPa. These results show the significant role of modulation wavelength on the hardness, compressive strength, and toughness characteristics of a microlaminate composite.