In order to get detailed information of the core–rim interface of carbides in TiC–20 wt% Mo2C–20 wt% cermet, chemical analysis in the vicinity of the interface was carried out by energy dispersive x-ray spectroscopy equipped with a high-resolution transmission electron microscope (HRTEM) with a field-emission-type gun. It was found that the chemical composition discretely changed across the core–rim interface at a nanoscale level, whereas HRTEM observation revealed that the interface is highly coherent. The discrete change in molybdenum content at the interface may suggest the existence of a miscibility gap between TiC and MoC systems at the sintering temperature.

The effect of carbon black content on the mechanical and electrical properties of carbon-black-filled poly(vinylpyrrolidone) composites was determined. Experimental data show a drop in modulus when the volume of carbon black exceeds 25%, coincident with pore formation documented by scanning electron microscopy. This behavior is consistent with surpassing the critical pigment volume concentration. Electrical conductivity, however, does not show a discontinuous change in behavior at 25 vol% carbon black and continues to increase through a carbon black loading of 35 vol%. A qualitative model of microstructural evolution is presented to explain the observed differences in electrical and mechanical behavior.

Ti–Zr alloy thin films of 20–60 nm in thickness were evaporated on Pt-coated silicon wafers. The films exhibited a layered Ti–Zr depth distribution. The films were then treated hydrothermally in 0.25 M Ba(OH)2 at 150 and 200 °C for 4–8 h. Films treated at 150 °C did not exhibit reflections from the Ba(TixZr1−x)O3 perovskite structure by x-ray diffraction, although a slight barium content was detected by x-ray photoelectron spectrometry. On the other hand, the films treated hydrothermally at 200 °C revealed reflections corresponding to perovskite Ba(TixZr1−x)O3. These films exhibited a homogeneous titanium and zirconium depth distribution, as shown by x-ray photoelectron spectroscopy and Auger depth profiles, proving that either titanium or zirconium ions diffuse during the hydrothemal treatment. The initial Ti–Zr film was completely consumed during the hydrothermal process, leading to a film of homogeneous composition (Ba, Ti, and Zr) up to the interface with the platinum layer.

In this communication a new kind of nanocomposite is reported in which a bridging coordination ligand, 2,2′-bipyrimidine, is used to bind quantum dots of CdS or CdSe (4–6 nm) to larger PbS nanoparticles.

A diffusion model is proposed to fit the measured chemical-transformation rates of the Bi(Pb)CaCuSrO 80-K phase to 110-K phase. Diffusion coefficients and activation energies in PO2 = 0.08 and 0.21 atm are reported. The low diffusion rates and high activation energies suggest cation diffusion controls the transformation.

The sintering characteristics of Y–Ba–Cu–oxide (YBCO)–Agx (x = 0 to 1.2) using thermomechanical analyzer were systematically investigated to understand the sintering mechanism of the metal superconductor composites. The addition of Ag was observed to lower the sintering temperatures, and the apparent densities of the sintered compacts increased with x from 0 to 0.6. A further increase of x above 0.6 decreased the apparent densities of the sintered compacts. The presence of Ag globules in the YBCO–Ag compacts was observed by scanning electron microscopy and energy dispersive x-ray spectroscopy. The apparent activation energies for sintering of the powder compacts were estimated and observed to vary between 900 to 2000 kJ/mol. The formation of AgOx by absorbing oxygen from YBCO and sintering atmosphere possibly controls the sintering and superconducting behavior. Incorporation of Ag into the matrix modifies the weak-link characteristics from superconductor–insulator– normal–superconductor (S–I–N–S) to superconductor–normal–superconductor (S–N–S) type.

A novel one-step solvothermal decomposition process (SDP) was successfully developed for fabrication of Bi2S3 nanowires via a reaction between BiCl3 and thiourea in polar solvents at 140 °C for 6–12 h. The influence of solvents, reaction temperature, and reaction time on the formation of Bi2S3 nanowires was investigated. The yield was as high as 98%. The particle sizes of Bi2S3 nanowires are controlled by the choice of solvents. The possible formation mechanism of Bi2S3 nanowires via the so-called SDP method is proposed. The present technique is expected to synthesize other nanostructural metal chalcogenides under mild conditions.

The photoacoustic (PA) spectra for the porous silicon samples irradiated during or after anodization are reported. The difference between the spectra for the irradiation conditions is discussed. The light irradiation time dependence of the PA spectra is shown. The irradiation after anodization causes the samples to luminesce in the blue region and enhances the photoluminescence signal intensity around 600 nm. It also reduces the PA signal intensity in the shorter wavelength region. The irradiation during the anodization causes enhancement only in the red-region luminescence.

Porosity depth profiles in porous silicon were realized by time modulation of the applied current density during electrochemical etching of crystalline silicon. The samples were investigated by variable angle spectroscopic ellipsometry. Using a basic optical model based on isotropy assumptions and the Bruggeman effective medium approximation, deviations from an ideal profile in terms of an interface roughness between the silicon substrate and the porous silicon layer and a compositional gradient normal to the surface were revealed. Furthermore, optical anisotropy of the sample was investigated by generalized ellipsometry. The anisotropy was found to be uniaxial with the optic axis tilted from surface normal by about 25°. The material was also found to exhibit positive birefringence.

Ceramic compacts of spinel-type ZnIn2S4 and IIIa-ZnIn2S4 polytype with a layer structure were synthesized by the reaction-sintering of mixed powders of ZnS and In2S3 at 723 K and 1073 K in Ar (containing 1° H2) atmosphere, respectively. The thermoelectric properties were investigated in the temperature range from 473 to 873 K. Thermoelectric figure of merit of the IIIa type was much larger than that of the spinel type, and it was slightly higher than the figure of merit of (ZnO)9In2O3, which is known to show the largest value among the oxide homologous compounds. To improve the thermoelectric properties, a c-plane-oriented sintered body of the IIIa polytype was successfully fabricated by a usual ceramic process. The figure of merit in the direction on the c plane was larger than on the ab plane due to higher electrical conductivity on the c plane and increased with increasing temperature showing the largest value of 1.3 × 10−4 K−1 at 873 K.

Important features of the icosahedral reciprocal space have been brought out. All reciprocal vectors up to sixth generation (by addition of icosahedral vectors) have been considered. Some more relationships for indexing the icosahedral phase are derived, and it is shown that the zone law using Cahn indices is also analogous to that valid for crystals. All important vectors, i.e., up to fourth generation and sixth generation, have been identified. Poles of all these vectors have been determined and shown to be one of the zone axes formed by these vectors. The types of indices that the planes and axes will have in three-dimensional and six-dimensional coordinates is discussed.

Microstructure and phase transformation of a furnace-cooled eutectoid Zn–Al-based alloy were studied after laser beam bombardment using low-angle x-ray diffraction (XRD) and backscattered scanning electron microscopy (BSEM). It was found that the microstructure of the laser-beam-treated specimen consisted mainly of the supersaturated Zn-rich β′s phase particulates of about 1−2 μm in diameter. Three structure morphologies were observed. Microcracking occurred in the laserbeam-affected zone during laser processing. Two laser-processing-induced phase transformations, i.e., decomposition of the η′FC phase and a four-phase transformation, were detected using XRD and BSEM techniques, similar to phase transformations that occurred in the same eutectoid Zn–Al-based alloy after various thermal and thermomechanical processing procedures.

A novel Tb3(Fe,Cr)29 single crystal, which has a monoclinic Nd3(Fe,Ti)29-type structure, is obtained using the Czochralski method by performing a proper heat treatment on the Tb2Fe16.46Cr1.23 crystal with a Th2Ni17-type structure. Thermomagnetic curves along the easy axis and magnetization curves along the easy and hard axes are presented for both crystals. The lattice parameters are a = 1.058 nm, b = 0.848 nm, c = 0.968 nm, α = γ = 90°, and β = 96.93° for the Tb3(Fe,Cr)29 single crystal. The Curie temperatures, saturation magnetizations, and magnetocrystalline anisotropy constants are compared between the Tb-2:17 and Tb-3:29 crystals. The magnetization behavior along the hard axis is quite different as a first-order magnetization process (FOMP) of type I for the Tb-2:17, but a FOMP of type II for the Tb-3:29 crystal is observed below room temperature. At low temperatures, magnetohistory effects are detected for both crystals.

A Ni–Al–Cr alloy with an initial grain size of ∼60 μm was subjected to torsion straining to a strain of ∼7 at room temperature, thereby reducing the grain size to ∼34 nm. Similar torsion straining with samples of pure Cu and pure Ni gave grain sizes of ∼170 and ∼130 nm, respectively. Inspection of the Ni–Al–Cr alloy after torsion straining revealed highly strained regions containing dislocations associated with lattice distortions but with an absence of any Ni3Al ordered phase. The ultrafine grains in the Ni–Al–Cr alloy were extremely stable at high temperatures, and it was possible to retain a grain size of less than 100 nm after annealing at temperatures up to ∼900 K. By contrast, there was rapid grain growth in the samples of pure Cu and Ni at annealing temperatures in the vicinity of ∼500 K. The stability of the grains in the Ni–Al–Cr alloy is attributed to the formation of a Ni3Al-based ordered phase after annealing at ∼650–700 K. The presence of this phase also leads to an apparent negative slope in the standard Hall–Petch relationship.

The nucleation behavior of α(TiCrSiO), a 1/1 Fibonacci crystal approximant phase, was investigated in alloys made near the stoichiometric composition. Containerless solidification studies were made with electromagnetic radio-frequency levitation and the 105-m NASA Drop Tube. The solidification microstructures indicate that the α–Ti hexagonal solid solution was the primary crystallizing phase in these alloys, growing dendritically. The α(TiCrSiO) phase nucleated in the remaining liquid. The competition between these two phases resulted from the high oxygen concentration needed to form α(TiCrSiO), which also stabilized the hexagonal-close-packed α–Ti phase.

A series of titanium composites, with varying volume fractions of titanium monoboride (TiB) whiskers, were made by mixing various proportions of titanium (Ti) and titanium diboride (TiB2) powders followed by hot pressing. The phases present were identified by x-ray diffraction. Microstructural examination revealed three different types of TiB whisker morphologies: (i) long and needle-shaped TiB whiskers that are isolated and randomly oriented in the Ti matrix at relatively low volume fractions (0.3), (ii) colonies of refined and densely packed TiB whiskers from intermediatevolume (0.55) to high volume (0.73 and 0.86) fractions, and (iii) coarse and elongated TiB particles with a few needle-shaped whiskers at the highest volume fraction (0.92). In all the composites, TiB was found to be the predominant reinforcement. However, in Ti–TiB composites with 0.86 and 0.92 volume fractions of TiB, a significant amount of TiB2 was also present. The relative volume fractions of Ti, TiB, and TiB2 phases were estimated from the integrated intensities of diffraction peaks by the direct comparison method employing the calculated structure factors and Lorentz polarization factors. The composite microstructure, as well as the evolution of different morphologies, of TiB whiskers is discussed.

By measuring the electrical resistance of a continuous unidirectional carbon fiber epoxy-matrix composite along the fiber direction during loading in this direction, fiber breakage was progressively monitored in real time. Fiber breakage occurred in spurts involving 1000 or more fibers. It started at about half of the failure strain during static tensile loading and at about half of the fatigue life during tension–tension fatigue testing. Immediately before static failure, at least 35% of the fibers were broken. Immediately before fatigue failure, at least 18% of the fibers were broken. The fiber breakage was accompanied by decrease in modulus.

Oxidation resistance of ceramic matrix composites (CMC) of SiC reinforced with C fibers (C/SiC) can be improved by filling the residual porosity. The aim of this work was to design and analyze a dipping infiltration process under ambient conditions (1 atm pressure and room temperature) with silica sol-gel solutions prepared from tetraethyl orthosilicate. Different substrates and solutions have been studied. Thermal treatments, i.e., curing or sintering between infiltrations, increase the efficiency of the process since the densification of infiltrated silica opens up the remaining porosity. Increasing viscosity and/or concentration of the solution lead to greater weight gains. Weight gains are higher in the initial stages of the process because larger diameter porosity remains unfilled. As the process advances, the average pore size decreases, and only the lower viscosity solution can enter the residual porosity.

An infiltration process that uses silica sol-gel solutions was developed to protect C/SiC composites against oxidation. The infiltration is assisted using isostatic pressure. Different process parameters including substrate porosity and solution concentration and viscosity were varied to optimize the infiltration effectiveness. Applied pressure enhances penetration of solutions, reducing the importance of viscosity, an important process variable for dipping infiltration. The effectiveness of the isostatic pressure infiltration method, evaluated through the total weight gains and pore-size distribution of infiltrated samples, is compared with results of dipping infiltration. The oxidation behavior of the infiltrated samples, was evaluated by stepwise oxidation test as well as isothermal tests at 1200 and 1600 °C. The infiltrated SiO2 protects the C/SiC substrate, reducing the burnoff rate of C fibers at low temperature and delaying the oxidation of SiC.

A method is described for the production of dense aluminum matrix composites from elemental powders in one processing step by reactive hot pressing (RHP). It encompasses both the exothermic conversion of reactants to composite product and the following hot compaction of the porous composite product. The RHP method described in this paper takes into account the gas evolution accompanying the exothermic process, ensures complete conversion of reactants, and avoids adverse reactions between aluminum matrix and graphite tooling material. In situ sample temperature measurements enable proper process control, in particular the timing of the full densification step of the hot reaction product.