Biaxially aligned YSZ thin films with strong [100] fiber texture were formed on a polycrystalline Ni-based alloy by off-normal ion-beam-assisted deposition. Growth structures were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), etc., and the alignment mechanism was discussed using a selective growth model. Peculiar structural evolution of the crystalline orientation was observed and its development was well described by an exponential equation. It was explained as a collaboration of an anisotropic growth condition and epitaxial crystallization. The [100] fiber texture was formed by columnar structures of diameter of 30–100 nm, which were composed of 5–10 nm diameter crystallites. Very smooth surfaces were observed by AFM imaging with a roughness of 2–3 nm and a peculiar ripple structure. The origin of the azimuthal alignment was discussed with emphasis on the surface structure of YSZ films produced using ion-beam-assisted deposition (IBAD) and the etching rate measurements of (100) surfaces of YSZ single crystals.

Recently, a new method, i.e., a plasma jet method, was developed in our lab for the production of ultrafine powders. In the present work, we investigated the formation of binary Al–Fe, Al–Si, Fe–Si, Al–Cu, Al–Ni, Ni–Ti, Fe–Cu, and Fe–Ti ultrafine powders using this method. Premixed pure elemental powders of various compositions of Al–Fe, Al–Si, Fe–Si, Al–Cu, Al–Ni, Ni–Ti, Fe–Cu, and Fe–Ti were used as starting materials. These premixed powders were injected into the plasma jet of Ar–N2 working gas to form ultrafine powders. The obtained ultrafine powders were characterized by x-ray diffraction and transmission electron microscope to check the microstructures of ultrafine particles.

The preparation and structural characterization of carbon nanoclusters of different morphologies produced by three different methods and under a variety of conditions is reported. In a comparative manner, the growth phenomena and structural properties of carbon nanoclusters are investigated as synthesized by (a) the high temperature (˜3000 °C) and high carbon-content process of the conventional arc-discharge, (b) the high temperature but low carbon-content process of the modified arc-discharge, and finally (c) the relatively low temperature (˜500 °C) process of Ni catalytic disproportionation of carbon monoxide.

The nature of dissociated superlattice dislocation cores in Al66Ti25Cr9, deformed at room temperature, has been characterized by weak-beam transmission electron microscopy (TEM) and comparison of experimental images with computer-simulated images. The displacement fields associated with narrowly dissociated APB- and SISF-dissociated ‹110› superdislocations were calculated to account for the asymmetry in dislocation contrast and led to a better understanding of the formation of images. Such calculations are a powerful aid, when coupled with image simulations, in distinguishing the “real” intensity peaks from the supplementary peaks that can be generated under experimental imaging conditions. While both APB- and SISF-dissociated superdislocations were identified, the vast majority of superdislocations were determined to be APB-dissociated. Corrected values of the fault energies (γAPB and γSISF ) have been measured for this alloy. These energies and the observed dissociations are shown to be self-consistent.

A layered perovskite type oxide, K2La2Ti3O10, was prepared by a gel technique using the polymerized complex (PC) method. A single phase K2La2Ti3O10 was obtained by adding twice the potassium required for stoichiometry. The Ni–K2La2Ti3O10 catalyst prepared by the PC method exhibited a higher photocatalytic activity for decomposition of H2O into H2 and O2 than that prepared by a conventional solid state reaction.

A γ-based TiAl alloy with equiaxed microstructure and fine grain size has been studied to analyze the deformation mechanisms responsible for the creep behavior. The microstructures produced by creep and high temperature deformation have been examined by TEM to obtain information about the different aspects characterizing the primary and secondary stages of creep. Mechanical twinning has been confirmed to occur in a fraction of the grains that never exceeds 50% while 1/2 ‹110› dislocations are active within all the γ grains. The twins are only responsible for a small amount of strain, but they lead to a subdivision of the microstructure and determine (directly or indirectly) the hardening process observed during the primary stage of creep. We have proposed that during the secondary stage the creep rate is determined by the unblocking of pinned dislocations by processes such as a pipe diffusion or cross slip that allow thermally activated glide of 1/2‹110› dislocations on (001) planes.

The silicon-rich end of the Si-B phase diagram, defining the silicon boride(s) that coexist in equilibrium with boron-saturated silicon, is poorly known. Understanding this equilibrium has implications for the processing of p+ silicon wafers, whose boron concentrations are near the solubility limit. Additionally, silicon boride precipitates produced by boron-ion-implantation and annealing of crystalline silicon have recently been shown to be efficient internal getters of transition metal ions. The experiments described in this paper probe the stability of these silicon borides. A phase with a boron-carbide-like structure, SiB3, grows from boron-saturated silicon in both the solid and the liquid state. However, SiB3 is not found to be stable in either circumstance. Rather, SiB3 is a metastable phase whose formation is driven by the relative ease of its nucleation and growth. The silicon boride that exists in stable equilibrium with boron-saturated silicon is SiB6. A qualitative understanding of the metastability of SiB3 comes from recognizing the conflict between the bonding requirements of icosahedral borides such as SiB3 and the size mismatch between silicon and boron atoms.

The characteristic platelet-like structure of large grain superconducting Y–Ba–Cu–O fabricated using peritectic solidification techniques has been documented widely as a key microstructural feature of this material. The platelet formation mechanism is investigated via a detailed comparison of the difference in morphology of YBa2Cu3O7–δ (123) growth fronts propagating along different lattice directions. The development of YBa2Cu3O7–δ dendrites between the growth front and local Y2BaCuO5 (211) particles is observed to be a key feature of the growth mechanism along all directions. Dendrites broaden rapidly for growth fronts propagating along the c-axis due to the enhanced growth rate of Y–Ba–Cu–O in the a-b plane to yield a uniform, regular growth morphology. Dendrite broadening is inhibited for grain growth along the a-b directions, however, due to the slower growth rate along the c-axis, which yields an irregular extended growth front. Growth along the a/b direction commonly results in the formation of regions consisting of 123 dendrites which may connect 211 particles. Continued solidification of the 123 phase in such regions results in the development of platelet structures perpendicular to the crystallographic c-axis in the YBa2Cu3O7–δ phase matrix which may impede the flow of current through the grain in the superconducting state.

X-ray powder diffraction was used to characterize a Pt–Si sputtering target and subsequent films. The powder patterns of each sample indicated lines due to diffraction from different phases. We have initiated a preliminary study through which we have analyzed and characterized these films. The results presented for these samples corroborate with results observed for this system in the planar configuration.

Carbon nanotube reinforced aluminum (Al) composites were produced by hot-press and hot-extrusion methods. The interfacial structure between the carbon nanotube and Al was examined using a transmission electron microscope (TEM), and the mechanical properties were measured by a tensile test. TEM observations have shown that the nanotubes in the composites are not damaged during the composite preparation and that no reaction products at the nanotube/Al interface are visible after annealing for 24 h at 983 K. The strength of the composites is only slightly affected by the annealing time at 873 K, while that of the pure Al produced in a similar powder metallurgy process significantly decreases with time. These studies are considered to yield experimental information valuable for producing high performance composites.

Ti and TiNx (x < 1) thin films have been deposited on high speed steel (HSS) substrates by reactive sputtering and then N+ implanted. The increase of the N/Ti ratio of the films during deposition is related to a decrease in their roughness, and N+ implantation produces another additional slight decrease of the roughness. The hardness of samples increases with the nitrogen content in the as-deposited samples; nevertheless, N+-implanted Ti coatings show lower values of hardness than reactive sputtered TiNx films. α–Ti, ε–Ti2N, and δ–TiN phases were identified by grazing x-ray diffraction.

Mixed crystalline titanium (IV) phosphate-phenylphosphonates were synthesized under hydrothermal conditions using tetramethylammonium hydroxide as a templating reagent. It was found that at a relatively low molar ratio H3PO4 : PhPO3H2 in the reaction mixture (<1) only a pure α-titanium phenylphosphonate is formed. At the molar ratio H3PO4 : PhPO3H2 = (3–5): 1 the formation of a novel mixed compound titanium (IV) dihydrogenphosphate-hydrogenphosphate-phenylphosphonate takes place. Further increase of the ratio H3PO4 : PhPO3H2 gives mechanical mixtures of different phases. Preliminary results on the characterization of the novel compound of formula Ti(H2PO4)1.25(HPO4)0.12(C6H5PO3)1.25 · 0.3H2O are presented.

The sintering process and phase transformation of submicrometer powder compacts of TiO2 were investigated using 2.45 GHz microwave radiation. The microwave-sintered samples were densified more rapidly and at much shorter time and lower temperature than that of the conventionally sintered samples. Also, an accelerated phase transformation from anatase to rutile was observed in microwave processing when the dwell time is cut down from 6 h in conventional to 30 min in microwave at 1000 °C. The samples sintered in microwave show a refined microstructure and smaller grain sizes at high density near 98–99% theoretical. In addition, the reasons for rapidly heating behavior and enhanced sintering on TiO2 in microwave are discussed.

Microstructure control of SmBCO superconductor was carried out using the floating zone partial melting and solidification method under 0.01 atm oxygen partial pressure which is a preferable atmosphere to obtain a crystal with stoichiometric SmBCO. The growth rate, initial composition, and addition of small amount of platinum dependences on the microstructure formations of the (Sm211 + L) mixture during melting and the Sm123 or Sm123/211 during solidification were investigated. Furthermore, superconductive properties of the solidified Sm123/211 were measured by SQUID after appropriate oxygen annealing. Estimated critical current density of the single crystalline Sm123/211 was 3.6 × 104 A/cm at 77 K, 1 T.

The effect of the crystal structure of starting alumina powder and electric pulsing on the initial stages of densification has been studied in the temperature range of 1200– 1500 °C. Multiple electric pulsing cycles enhance the densification significantly. The α-alumina powders consolidate more readily in comparison to γ-alumina powders. A high density α-alumina specimen (>98% of theoretical density) was obtained at 1300 °C in less than 10 min.

Hollow cathode arc plasma chemical vapor deposition was employed to grow crystalline diamond films using 1.5% to 7% of methane in hydrogen. The growth rate was as high as 3.2 μ/h when using 5% CH4/H2 at a pressure of 15 Torr and a substrate temperature of 1083 K. However, an intermediate layer of several hundred nanometers was observed at the film-substrate interface by cross-section SEM. Raman and XPS characterizations showed that the interfacial layer consisted of sp2 carbon and TaC with Ta vaporized from the hot cathode tube. XRD and XPS results further showed that the deposited diamond films also contained TaC. Ta composition in the film increased with the increase of growth pressure, the reduction of substrate temperature, and the increase of H2 flow in the Ta tube. The diamond films deposited by using CHCl3 as carbon source had Ta concentrations one order of magnitude higher than those using CH4, as shown by XPS results, but the nucleation densities using CHCl3 were always higher than those using CH4.

The addition of B4C powder retarded the nitridation of the silicon powder green body by the formation of a borosilicate layer in interfaces between Si grains. The viscous layers hindered the SiO formation and the Si and N diffusion. Despite the presence of borosilicate layers, the Fe impurity in the green body still promoted the Si nitridation process by the formation of fluid iron silicide and the promotion of the B4C conversion to BN in gaps or holes in the viscous borosilicate layers. The addition of 5% H2 in the N2 atmosphere accelerated the Si + B4C nitridation, where the hydrogen acted as an oxygen getter, thus reducing the amount of glassy borosilicate in the interface.

Analytical TEM and HREM have been used to examine the structure of BaAl2Si2O8 crystals produced within oxidized Ba–Al–Al2O3–SiO2 precursors upon annealing: (i) at ≤650 °C and (ii) up to 1650 °C. A BaAl2Si2O8 polymorph with a c-axis parameter of 15.6 Å was detected after annealing at ≤650 °C. Stacking faults and antiphase boundaries were detected within this polymorph after the 650 °C treatment. After a 15 h heat treatment at 1650 °C, convergent beam diffraction patterns and HREM confirmed that the predominant phase was β–hexacelsian. Although antiphase boundaries were absent in the β–hexacelsian crystals, dislocations and stacking faults were detected after the 1650 °C anneal. The generation of defects in BaAl2Si2O8 crystals within specimens annealed at ≤650 °C and at 1650 °C is discussed in light of prior structural analyses.

The grain growth of dense, fine-grained Nd1+xBa2−xCu3Oy (x = 0.1−0.4) specimens has been examined in pure O2(g) at 938 °C and 967 °C. No detectable change in average grain size was observed for Nd1.4Ba1.6Cu3Oy within 72 h at 967 °C; however, a significant increase in average grain size developed between 18 and 24 h at 967 °C for Nd1.3Ba1.7Cu3Oy, and within 8−12 h at ≤967 °C for Nd1.2Ba1.8Cu3Oy and Nd1.1Ba1.9Cu3Oy. Microstructural analyses revealed that sudden changes in average grain size coincided with the formation of relatively large (abnormal) grains. A broadening of the grain size distribution was also observed. TEM analyses revealed that grain boundaries were free of second phases. The possible role of anisotropy in grain boundary energy and/or mobility on grain growth is discussed.

The reactions of rare earth (RE) acetates with iron acetylacetonate in 1,4-butanediol at 300 °C (glycothermal reaction) yielded two novel phases depending on the ionic size of the RE element: one was obtained for Er-Lu and the other for Tb and Dy. The former phase was hexagonal REFeO3, while the latter phase has not been identified. The reaction of Y or Ho acetate yielded the mixture of these two phases. When the reactions were carried out in the presence of seed crystals of yttrium aluminum garnet (Y3Al5O12), these phases were not formed but RE iron garnet (RE3Fe5O12) grew on the seed, which suggests that spontaneous nucleation of RE iron garnet does not occur, but crystal growth proceeds easily under the glycothermal conditions. Hydrothermal reaction of the same starting materials yielded a mixture of Fe2O3 and an amorphous RE phase.