This communication reports the novel idea of using a magnetic field gradient to hold magnetic nanoparticles at desired densities in a fixed location (e.g., on an electrode surface), while metal atoms are deposited electrochemically in the interstices between them. Using it, nanocomposites consisting of γ–Fe2O3 nanoparticles (with a mean size of about 40 nm) in a copper metal matrix were reproducibly fabricated, with particle volume fractions ranging from 0.2% to 50%. These nanocomposites, ceramic magnetic particles in a conductive metal matrix, are expected to have unusual or enhanced mechanical, electrical, and magnetic properties.

Subsolidus equilibria in air in the La2O3–Ga2O3–CeO2 system were studied with the aim of obtaining information on possible interactions between a LaGaO3-based solid electrolyte and CeO2 during preparation of the anode in solid oxide fuel cells. No ternary compound was found. The tie lines are between La4Ga2O9 and the end of the CeO2 solid solution range with composition La0.5Ce0.5O1.75 and between the LaGaO3 and CeO2 range of solid solutions.

Infrared microscopy was applied to observe the internal structure of alumina powder compact, which was made transparent with an immersion liquid. It provided clear images of nonuniformity in the structure for a specimen as thick as 1 mm. Two types of nonuniformity found in this paper are the large pores made from the pores in powder granules and the low-density region forming network structure, which was formed by the presence of a binder. The minimum size of nonuniformity detected in a structure is under 20 μm.

Physical-vapor-deposited thin metal films often exhibit tensile residual stresses. We studied the stress evolution in thin Cr films and found that increasing bombardment with energetic particles (atoms or ions) at low energies leads to an increase of tensile stress to a maximum followed by a rapid decrease. Microstructural characterization by transmission electron microscopy revealed that two different microstructures are observed for the same level of tensile stress: films processed at low bombardment had columnar porosity while no porosity was observed in films processed at higher bombardment. The observed stress evolution is interpreted by considering how the mean interatomic distance (and hence the force) in the intercolumnar regions is modified by energetic particle bombardment.

Zirconate and titanate pyrochlores were subjected to 1 MeV of Kr+ irradiation. Pyrochlores in the Gd2(ZrxTi1-x)2O7 system (x = 0, 0.25, 0.5, 0.75, 1) showed a systematic change in the susceptibility to radiation-induced amorphization with increasing Zr content. Gd2Ti2O7 amorphized at relatively low dose (0.2 displacement per atom at room temperature), and the critical temperature for amorphization was 1100 K. With increasing zirconium content, the pyrochlores became increasingly radiation resistant, as demonstrated by the increasing dose and decreasing critical temperature for amorphization. Pyrochlores highly-enriched in Zr (Gd2Zr2O7, Gd2Zr1.8Mg0.2O6.8, Gd1.9Sr0.1Zr1.9Mg0.1O6.85, and Gd1.9Sr0.1Zr1.8Mg0.2O6.75) could not be amorphized, even at temperature as low as 25 K.

Variations of the properties of submicron vapor-grown carbon fibers (VGCFs) and nanofibers, with diameters around 0.1–0.2 μm and 80–100 nm, respectively, are observed by Raman spectroscopy as a function of heat-treatment temperature. The microstructural evolution strongly depends on the original properties of the material, such that the main transition temperatures associated with the onset for establishing two-dimensional graphene ordering are defined below 1500 °C for the nanofibers and 2000 °C for the submicron VGCFs, respectively. The relative intensities (ID/IG) of the as-grown phase for submicron VGCFs and nanofibers are 3.44 and 1.35, while those for the corresponding graphitized samples are 0.393 and 0.497, respectively.

In this paper we present a new approach of surface pretreatment for enhancing diamond nucleation. The copper substrates were fixed inside a plastic cylinder container with diamond powder diluted in water. This container was coupled to a vibration unit moving up and down at ˜300 cycles/min with a stroke of 15 mm. Finally, samples pretreated for 30 min were deposited with diamond. A high nucleation density comparable to that on substrate abraded with diamond powder was achieved. This method proved to be more effective than our ultrasonic treatment, keeping the advantages of surface preservation. Being simple and straightforward, this “shaking” pretreatment most fits the cases where a thin interlayer has to be used (like diamond coating on steel) and where the samples have a complex shape.

We report the stability of TlBa2CaCu2O7 and Tl2Ba2CaCu2O8 on LaAlO3(100) epitaxial thin films, under a variety of conditions. All films are stable in acetone and methanol and with repeated thermal cycling to cryogenic temperatures. Moisture, especially vapor, degrades film quality rapidly. These materials are stable to high temperatures in either N2 or O2 ambients. While total degradation, resulting from Tl depletion, occurs at the same temperatures for both phases, 600 °C in N2 and 700 °C in O2, the onset of degradation occurs at somewhat lower temperatures for TlBa2CaCu2O7 than for Tl2Ba2CaCu2O8.

Ion implantation was used to form compound semiconductor nanocrystal precipitates of ZnS, CdS, and PbS in both glass and crystalline matrices. The precipitate microstructures and size distributions were investigated by cross-sectional transmission electron microscopy techniques. Several unusual features were observed, including strongly depth-dependent size variations of the ZnS precipitates and central void features in the CdS nanocrystals. The morphology and crystal structure of the nanocrystal precipitates could be controlled by selection of the host material. The size distribution and microstructural complexity were significantly reduced by implanting a low concentration of ions into a noncrystalline host, and by using multi-energy implants to give a flat concentration profile of the implanted elements.

Highly pure, ultralong, and uniform-sized semiconductor nanowires in bulk quantity were synthesized by thermal evaporation or laser ablation of semiconductor powders mixed with oxides. Transmission electron microscopy study shows that decomposition of semiconductor suboxides and defect structures play important roles in enhancing the formation and growth of high-quality nanowires. A new growth mechanism is proposed on the basis of microstructure and different morphologies of the nanowires observed.

We report here on the results of a numerical study on the effects of intrinsic stress on the growth of SiO2 thin films. In accordance with a widely accepted model of stress effects upon silicon oxidation, we assume that the intrinsic stress affects only the oxidant diffusion rate. We examine several different models of stress-assisted diffusion. In the first of these models, the diffusivity is taken to be an exponential function of the stress, whereas in the second, the stress gradient appears as an additional term in the standard diffusion equation. Intrinsic stress effects result in deviations of up to 18% in expected layer thickness, depending upon the mode of oxidation and the diffusion model adopted. The implications of these results for the measurement of diffusion coefficients in SiO2 films are discussed.

Growth of Cu(In,Ga)Se2 (CIGS) films from In–Ga–Se precursors was characterized by scanning Auger electron spectroscopy (SAES), secondary ion mass spectroscopy (SIMS), x-ray diffraction, scanning electron microscopy, and transmission electron microscopy (TEM). In–Ga–Se precursor layers were deposited on Mo-coated soda-lime glass, and then the layers were exposed to Cu and Se fluxes to form CIGS films. The SIMS and SAES analyses showed a homogeneous distribution of Cu throughout the CIGS films during the deposition of Cu and Se. The phase changes observed in the CIGS films during the deposition of Cu and Se on the In–Ga–Se precursor films were as follows: (In,Ga)2Se3 →[Cu(In,Ga)5Se8] →Cu(In,Ga)3Se5 →Cu(In,Ga)Se2. The grain size increased from the submicron grains of the (In,Ga)2Se3 precursor film to several micrometers in the stoichiometric Cu(In,Ga)Se2 film. A growth model of CIGS crystals is introduced on the basis of the results of TEM observations. CIGS crystals are mainly grown under (In,Ga)-rich conditions in the preparation from In–Ga–Se precursor films.

The objective of this work was to investigate the fundamental factors that govern the formation and magnitude of residual stresses in A2 tool steel fabricated using spray-forming techniques. To that effect, a finite-element method (FEM) was performed by using a commercial code, ABAQUS, to solve for the temperature and displacement fields. Moreover, the residual stresses in the spray-formed materials were measured using x-ray diffraction to compare the FEM results with experimentation. Two types of substrate material, copper and Rescor™ 780 cer-cast ceramic, were used to investigate the influence of heat conduction on residual stress in the preforms. Relatively good agreement was found between experimentation and theory. The results show that the residual stress varies greatly with the position in deposited preform and that heat-transfer coefficient at the interface of spray-formed material/substrate affects the distribution and magnitude of the residual stresses significantly.

The isothermal and cyclic oxidation behavior of PtAl and PtAl + Zr was studied followed by postoxidation microstructural and microchemical analyses. Their isothermal oxidation performance at 1200 °C was similar to that of NiAl and NiAl + Zr. In short (1-h) cycles, the cyclic oxidation resistance of undoped PtAl was found to be substantially better than NiAl. However, with longer (100-h) cycles, little improvement in the metal consumption rate was observed relative to NiAl. The addition of Zr to PtAl significantly improved cyclic oxidation performance in both short- and long-cycle tests. Spatially resolved energy dispersive spectroscopy indicated Zr segregation to both the metal–oxide interface and Al2O3 grain boundaries.

Static and cyclic creep tests of Al–15 vol% TiB2in situ composite were carried out at 573–623 K. The values of apparent stress exponent and activation energy for cyclic creep of the composite were much higher than that for static creep. Furthermore, the cyclic creep rate tended to decrease with increasing percentage of unloading amount but was independent of the loading frequencies under the frequency ranges investigated. Finally, the true stress exponent of the composite was equal to 8, and the true activation energy was close to the value for the lattice self-diffusion of aluminum by incorporating a threshold stress for the analysis.

Binary SiO2/TiO2 and SiO2/Fe2O3 nanoparticle (diameter < 100 nm) aerosols of varying mole ratios of Ti or Fe to Si were generated in a premixed Bunsen-type aerosol flame reactor. The distribution of species within the particles was investigated using transmission electron microscopy, electron energy loss spectrometry, x-ray diffraction, and Fourier transform infrared spectroscopy. Phase segregation was observed to varying degrees in qualitative agreement with segregation expected from binary phase diagrams for the bulk systems. Differences between the SiO2/TiO2 and SiO2/Fe2O3 systems can be explained by considering the variation in the thermodynamically stable liquid-phase solubility and differences in the ability of iron and titanium ions to substitute for silicon ions in the network structure.

The densification of Si3N4 with nano-sized sintering aids that were in situ incorporated by a combustion process was studied in comparison with that of sintering aids mixed by ball milling. The combustion process directly produces amorphous and nano-sized Y–Al oxides within the Si3N4 powder. X-ray diffraction results indicate that amorphous Y–Al oxides begin to crystallize into Y3Al5O12 at about 600 °C. Additionally the nano-sized sintering aids are more homogeneously distributed and thereby promote the formation of eutectic melts at lower temperatures during liquid-phase sintering. Therefore, the densification process of Si3N4 during liquid-phase sintering is strongly accelerated. The microstructure of as-sintered parts from combusted powder seems more dense and homogeneous.

Transmission electron microscopy has shown that the grain size of sol-gel-prepared lanthanum-modified lead titanate films increases from ∼100 to ∼1 μm when the excess of PbO in the precursor solution is reduced from 20 to 10 mol%. Switchable polarization is higher in the films with a smaller grain size. Profilometry and the temperature dependence of the dielectric permittivity indicate that films are tensile stressed by the substrate. The grain-size effect on polarization switching is explainedby taking into account this tensile stress, which is thought to induce some a-domain orientation and 90° domain wall clamping in the grains attached to the substrate.

(1–x)PMN–xPT[PMN, Pb(Mg1/3Nb2/3)O3; PT, PbTiO3] system ferroelectric ceramics with x = 0.30, 0.33, 0.35, and 0.38 were synthesized by the columbite precursor method. Their structure and dielectric behavior were investigated. X-ray diffraction results demonstrate that no two-phase region is presented, but a quasi-cubic to tetragonal phase boundary lies between x = 0.30 and 0.33. Examination of the dielectric behavior reveals that the transformation from relaxor to normal ferroelectric behavior across the morphotropic phase boundary (MPB) is successive and continuous. It is suggested that x 4 0.30 to 0.33 is the composition of MPB for the PMN–PT system. The MPB is also a boundary for the PMN–PT system to transform from relaxor to normal ferroelectrics.

Three kinds of inorganic–organic hybrid gel sheets were prepared from the liquid mixtures of ethyl silicate and water–soluble phenol resin. The prepared transparent gel sheets were fired at various temperatures. The density of the fired sheets jumped up at 773–1023 K with disappearance of organic groups. The sheets kept the prepared shape after the 1273 K firing, and their density increased with the silica content. After the firing at 1873 K, the sheets with high carbon content (C/SiO2: 5.60, 3.52) were converted into the sheets composed of silicon carbide aggregate with excess carbon, while the sheet with low carbon content (C/SiO2: 1.43) was converted into the fragile powders.