The crystallographic structures of some phases present as precipitates in Al–Li–Cu–Mg alloys are not perfectly resolved. In particular, several structural models have been proposed for the S′ phase, and this controversy is not yet resolved. New x-ray powder diffraction measurements have been performed to compare the theoretical powder diffraction patterns associated with each proposed model with the measured spectra obtained from two different kinds of alloys. The structural model of the S′ phase described by Mondolfo [L. F. Mondolfo, Aluminum Alloys Structure and Properties (Butterworths, London, 1976)] agrees with the experimental results and allows us to reject the two other proposed crystallographic models.

The microstructure of the disproportionated NdFeCoZrB alloy during the solid-HDDR (hydrogenation-disproportionation-desorption-recombination) process was investigated by means of scanning electron microscope (SEM) and transmission electron microscope (TEM). Except for a similar colony-type structure to ternary alloy, fine particles including spherical (Fe, Co)2B phase and undecomposed rim-like Nd2(Fe, Co)14B compound were found dispersed within the α–(Fe, Co) matrix of the microstructure of the disproportionated NdFeCoZrB alloy. An unknown Fe-rich phase with a comparable size to that of the matrix grain was also detected by electron diffraction. These results strongly suggest that the undecomposed rim-like Nd2(Fe, Co)14B particles are probably the memory sites for the origin of anisotropy of the received NdFeCoZrB materials.

Sintering of a fine cubic boron nitride (cBN) particle with a grain size of less than 2 μm was successfully carried out under 5.5 GPa pressure at 1720 K for 30 min. TiN–TiB2-coated cBN particles were used as the starting powder without adding any other binding materials. The coating was carried out by dipping the cBN particles in molten salts. The obtained cBN sintered compact shows a smooth microstructure with a well-controlled grain boundary; TiN–TiB2 is distributed over the cBN-grain boundary in the shape of a net mesh similar to tiled floors. The Vickers microhardness of the obtained compact was found to be higher than that of commercially available typical cBN-cutting tools.

The ordering structure of lanthanum-substituted Ba(Mg0.33Ta0.67)O3 was investigated using x-ray diffraction. It was observed that the ordering type of this solid solution transformed from 1: 2 to 1: 1 with 10 mol% substitution of La(Mg0.67Ta0.33)O3. These two types of ordering coexist over a wide range of composition. This coexistence of ordering types was considered as phase coexistence and its physical origin was investigated using microwave measurements. Based on the intensity of superlattice reflections and the discontinuity in dielectric properties, it was suggested that the coexistence of two ordering types originates from the overlap of the two stability regions.

Biaxially textured yttria stabilized zirconia (YSZ) buffer layers are prepared on rotating cylindrical surfaces by an ion-beam-assisted deposition (IBAD) process. A large fraction of the cylinder surface can be coated at the same time, resulting in an effective deposition rate of 40 nm/h for the whole tube circumference (diameter of the tube 12 mm). The in-plane alignment depends on the total film thickness and the rotation velocity. The best in-plane textures achieved so far with a full width half maximum (FWHM) value of 27° are sufficient for the preparation of YbaCuO films with critical current densities above 105 A cm−2 at 77 K and self-fields.

Ba(Mg1/3Ta2/3)O3 thin films were prepared by a sol-gel process involving the reaction of barium isopropoxide, tantalum ethoxide, and magnesium acetate in 2-methoxyethanol and subsequently hydrolysis, spin-coating, and heat treatment. Transmission electron microscopy, x-ray diffraction, and Raman spectroscopy were used for the characterization of the thin films. It was shown that the thin films tend to crystallize with small grains sized below 100 nm. Crystalline phase with cubic (disordered) perovskite structure was formed in the samples annealed at a very low temperature (below 500 °C), and well-crystallized thin films were obtained at 700 °C. Although disordered perovskite is dominant in the thin films annealed below 1000 °C, a low volume fraction of 1 : 2 ordering domains was found in the samples and grows with an increase of annealing temperature.

The phase transformation in Sr1−xBaxNb2O6 (0.25 ≤ x ≤ 0.8) ceramics was investigated. There is an intermediate transitive phase before forming the tungsten bronze phase at higher temperatures. The phase transformation from the intermediate type into tungsten bronze type is sluggish, affected principally by temperature. In the compositions rich in Ba (x > 0.672), Ba ions prefer to occupy the A2 sites rather than the A1 sites of the tungsten bronze structure. The percentages of vacancies in the A1 sites and A2 sites are no longer the same. With the increase of Ba, the vacancies in the A1 sites increase, whereas the vacancies in the A2 sites decrease.

Hollow nanotubes of SiO2, Al2O3, V2O5, and MoO3 have been prepared using carbon nanotubes as templates. The procedure involves coating the carbon nanotubes with tetraethylorthosilicate, aluminum isopropoxide, or vanadium pentoxide gel, followed by calcination and heating at higher temperatures in air to oxidize the carbon. SiO2 nanotubes containing transition metal ions have been prepared by this procedure since such materials may be of use in catalysis.

TiO2-based powders doped with a small amount of SiO2 were prepared by a sol-gel method and subsequently were heated to precipitate fine anatase crystals. Although the obtained powders have large specific surface areas (≈200 m2 · g−1), they showed poorer activity in a photocatalytic property than the undoped TiO2 powders which have the area of 50 m2 · g−1. The SiO2-doped TiO2 powders were treated chemically with aqueous NaOH. Infrared reflection spectra showed that the treatment reduced the amount of SiO2 in the powders. The photocatalytic property of the powders was extremely improved by the treatment, and the powders showed higher activity than the undoped TiO2 powders.

We present experimental measurements of the accessible pore fraction in ceramic matrix composites during consolidation by vapor phase infiltration. For two topologically distinct filament architectures, the accessible pore fraction decreased during consolidation with a power law decay and a critical scaling exponent of 0.41 (R2 = 0.97). A three-dimensional analysis of the percolating pores revealed that the structures became topologically equivalent and simply connected near the critical density.

Carbon nanotubes can be produced by the catalytic decomposition of hydrocarbons on small metal particles. However, nanotubes are generally produced together with non-tubular filaments and tubes coated by pyrolytic carbon. We propose a novel catalyst method for the in situ production, in a composite powder, of a huge amount of single- and multiwalled carbon nanotubes, having a diameter between 1.5 and 15 nm and arranged in bundles up to 100 μm long. We anticipate that dense materials prepared from such composite powders could have interesting mechanical and physical properties.

The combustion reaction while mechanical alloying (MA) the Al–Ti–C system has been detected by in situ thermal analysis and the results of x-ray diffraction (XRD). Based on the information provided by in situ thermal analysis, the reaction temperature is estimated to be 1677 K, which is in good agreement with the value of the adiabatic temperature of 1700 K. It is considered that the formation reaction of Ti–C, which ignited by the heavy collisions of milling balls, induced the following reaction between Ti and Al at high temperature.

We report on the superconducting properties of TlBa2Ca2Cu3O9−y (Tl-1223) thick films grown on smooth and rough Ag substrates. Thallium-free precursor films of the type Ba2Ca2Cu3Ag0.37O7 were deposited on Ag substrates using a spray-pyrolysis technique followed by post-thallination in a two-zone furnace. X-ray diffraction (XRD) results showed the presence of c-axis aligned Tl-1223 films and some degree of local in-plane texture (often referred to as a colony microstructure). The microstructure of the Ag surface dictates the growth behavior of Tl-1223 films. The transport critical-current densities (Jc) for Tl-1223 films grown on smooth and rough Ag substrates were ∼ 65,000 A/cm2 and ˜ 37,000 A/cm2, respectively, at 77 K and zero field. The films grown on smooth Ag substrates were strongly linked and had good in-field properties with a Jc value of ∼104 A/cm2 at 77 K and 0.5 T.

The microstructure of YBa2Cu3O7−δ (YBCO) materials, melt-textured in air and quenched from the temperature range 900–;990 °C, has been characterized using a combination of x-ray diffractometry, optical microscopy, scanning electron microscopy, transmission electron microscopy, and energy dispersive x-ray spectrometry. BaCu2O2 and BaCuO2 were found to coexist in samples quenched from the temperature range 920–960 °C. The formation of BaCu2O2 preceded the formation of YBCO. Once the YBCO had formed, BaCu2O2 was present at the solidification front filling the space between nearly parallel platelets of YBCO. Large Y2BaCuO2 particles at the solidification front appeared divided into smaller ones as a result of their dissolution in the liquid that quenched as BaCu2O2.

Films of Bi–Ca–Sr–Cu–O (BCSCO) superconductor of the Bi2CaSr2Cu2Ox composition have been grown by the liquid phase epitaxy method (LPE) using a partially closed growth chamber. The films were grown on (110) NdGaO3 substrates by slow cooling under optimized conditions below the peritectic melting point (885 °C) of Bi2CaSr2Cu2O8. Optimization of parameters, such as seed rotation, soak of initial growth temperature, and growth period, results in the formation of the 2122 phase of BCSCO. X-ray diffraction (XRD) measurements show that the films grown on (110) NdGaO3 have a preferred (11n) orientation. The best values of zero resistance transition (Tc0) and critical current density (Jc0) obtained for films grown on (110) NdGaO3 substrates are 87 K and 5.7 × 104 A/cm2 (at 20 K), respectively. The films grown at rotation rates of less than 30 and more than 80 rpm are observed to be associated with a subphase in the Bi2CaSr2Cu2O8 system. Electron microprobe analysis indicates the composition of this subphase to be Bi0.07Ca0.93Sr2Cu5O8. Higher growth temperatures (>860 °C) also encourage the formation of this phase.

Bismuth was implanted at room temperature in (100)-Si wafers with controlled energy and doses to result in a plateau-like implantation profile. The van der Pauw Si : Bi samples were characterized by the Hall effect and resistivity measurements from room temperature down to 13 K. The electron concentration of the prepared samples at 290 K varied from 3.0 × 1017 to 1.4 × 1020 cm−3. The resistivity of the Si : Bi samples presents a larger enhancement, compared to other dopants, when decreasing the Bi concentration. The metal-nonmetal transition was determined to be around 2 × 1019 cm−3. The calculated values obtained from the Generalized Drude Approach and an equation derived from Kubo formalism agree very well with the experimental data. The results confirm also the behavior ρc (Bi) < ρc(As) < ρc(P) < ρc(Sb) at 290 K.

Scanning tunneling microscopy images are reported for the wurtzite GaN(0001) surface. Terraces are observed, with three kinds of defect structures that are assigned to ordered N-vacancies: (i) striations perpendicular to the step edges, (ii) row defects spaced about 16 Å that intersect the steps at an angle of 30°, and (iii) “oval” defects that result from intersections of lines of vacancies (oriented at 60° with respect to step edges) with the row defects.

Formation of the ternary compound Cu3BiS3 during annealing of chemically deposited CuS (∼0.3 μm) films on Bi2S3 film (∼0.1 μm on glass substrate) is reported. The interfacial atomic diffusion leading to the formation of the compound during the annealing is indicated in x-ray photoelectron depth profile spectra of the films. The formation of Cu3BiS3 (Wittichenite, JCPDS 9-488) is confirmed by the x-ray diffraction (XRD) patterns. The films are optically absorbing in the entire visible region (absorption coefficient 4 × 104 cm−1 at 2.48 eV or 0.50 μm) and are p-type with electrical conductivity of 102−103 Ω−1 cm−1. Potential applications of these films as optical coatings in the control of solar energy transmittance through glazings and as a p-type absorber film in solar cell structures are indicated.

Effects of interlayers on diamond nucleation were investigated for the Si substrates. Interlayers were deposited on the diamond-abraded Si substrates by rf sputtering prior to diamond growth using microwave plasma chemical vapor deposition (CVD). Compared with 1 × 108/cm2 for the just abraded substrate, the nucleation density was greatly enhanced to 1 ∼ 2 × 109/cm2 by 50 nm thick interlayer, irrespective of the kind of interlayer material used in this study (Si, Mo, Ti, Pt, Ag, TiN, or SiO2). As the thickness of the Si interlayer increased from 20 to 500 nm, the nucleation density reached a maximum value, 3 × 109/cm2 at 100 nm. However, the growth rate was monotonically reduced from ∼300 nm/h to ∼100 nm/h. For the 700 nm thick Si interlayer, no diamond growth was observed. These results indicate that there is an optimum interlayer thickness around 100 nm for the higher nucleation density. The role of the interlayer in enhancing the nucleation density is believed to protect the nucleation sites generated by the diamond abrasion, otherwise they could be considerably etched away by atomic hydrogen during the initial diamond deposition.

The influence of elemental B addition on the heat-treated cast structure of Ti–47Al–2Cr–(2–4)Nb alloys has been investigated using x-ray diffractometry, optical microscopy, scanning and transmission electron microscopy, and tensile testing. The phase sequence is β → β + α → α → α + γ → α + β + γ → β + γ. The addition of (0–2 at. %) B does not change the phase sequence. It, however, tends to stabilize α phase by shifting the (α + β + γ) three-phase region toward a higher (Cr + Nb) content. The B addition does not significantly alter the equilibrium composition within (α + γ) two-phase field. The B addition markedly accelerates the lamellar formation kinetics and enhances the thickening rate of γ plates, despite the fact that it increases both the misfit between α and γ plates and the α/γ interfacial energy. The acceleration of lamellar formation kinetics is thus believed to be primarily due to the enhancement of chemical diffusivity as a result of B addition. The B addition induces a significant refinement of heat-treated cast structure. This is primarily due to the role of boride to disperse the interdendritic γ regions to a fine network and to refine the dendrite cell size. Further refinement arises from the boride's role to act as the nucleation site for γ grains and from the intrinsic B effect to enhance the chemical diffusivity and the γ thickening rate. The addition of a small amount of B enhances both the strength and tensile ductility of near gamma structure. The strengthening arises from grain size refinement and from the boride dispersion. The calculation of fracture strain suggests that an enhancement of ductility for small B addition (up to ∼0.2 at. %) is mostly due to its effect to refine the γ grains.