This paper discusses the induction of residual stresses during the curing process of thin titania layers, which are derived using a sol-gel process. During this process, stresses may build up in the spinning stage, the drying stage, and the consolidation stage. The magnitude and character of these stresses depend heavily on the morphology of the layers in the various stages and the processing conditions. Dried layers are densified using two different processes, conventional furnace heating and laser heating. X-ray analysis and scanning electron microscopy are used as tools to study crystallization, grain growth, phase transformation, and the evolution of residual stress fields in the thin titania layers. Through an extensive study of the residual stress state in the layers, more insight is gained in the evolution of stresses during the curing process of sol-gel-derived thin titania layers.

This study has shown the possibility of achieving two primary considerations for the advanced fabrication of spodumene with a composition of Li2O · Al2O3 · 4SiO2 · nTiO2 (LAST) glass-ceramics by a sol-gel process, namely, an enormous reduction of sintering temperature from 1600 to 1200 °C together with the appearance of simple phases of β-spodumene/rutile as opposed to products via the conventional melting-crystallization process. Fine glass-ceramic powders with a composition of Li2O · Al2O3 · 4SiO2 (LAS) have been synthesized by the sol-gel process using Si(OC2H5)4, Al(OC2H5)3, LiOCH3, and Ti(OC2H5)4 as the starting materials. The process included well-controlled hydrolysis polycondensation of the raw alkoxides. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron diffraction (ED) analysis were utilized to study the effect of TiO2 addition on the preparation of β-spodumene powders by the sol-gel process. The gelation time of the LAST solution increases as the TiO2 content increases. For the low (<3) or high (>11) pH value, the gelation time was shortened. At pH = 5, regardless of the TiO2 content, the gel has the longest time of gelation. When the dried gels of the LAST system are heated from 800 to 1200 °C, the crystallized samples are composed of the major phase of β-spodumene and a minor phase of rutile (TiO2).

An α–Fe2O3 powder of nanosized particles has been successfully prepared by effectively dispersing the precipitated hydroxide precursor in a sodium chloride matrix. In particular, the hydroxide precursor was converted into crystalline α–Fe2O3 particles approximately 10 nm in size when it was mechanically activated in the sodium chloride matrix for 1 h. The subsequent calcination at 600 °C for 1 h resulted in a limited degree of coarsening in particle size while the crystallinity of α–Fe2O3 was further established. The effectiveness of obtaining ultrafine a–Fe2O3 powders by mechanical activation in the sodium chloride matrix was demonstrated by comparing the powder with those obtained via other routes, such as mechanical activation without sodium chloride as the matrix, calcination at 600 °C, and then mechanical activation in sodium chloride matrix, respectively. None of these processing routes led to a powder comparable in particle characteristics to that derived by the precursor dispersion.

Self-assembling of size, shape, and phase-selected nanocrystals into superlattices in a new approach for synthesizing a new generation of advanced materials with functionality. In this paper, high purity and monodispersive tetrahedral of CoO, with edge lengths of 4.4 ± 0.2 nm, have been synthesized and separated from Co nanocrystals using colloidal chemistry and magnetic separation. The tetrahedral CoO nanocrystals behave like a molecular matter, and their assembling forms superlattices with translational symmetry. The phase transformation of the CoO nanocrystals is examined by ex situ annealing in oxygen, and the results showed the formation of Co3O4 with spinel structure.

A numerical model has been developed to examine the temperature history of a multilayer wafer undergoing rapid thermal processing (RTP) for various doping densities. Partial transparency and thin film interference effects are considered. Doping levels from ∼1015 to ∼1018 cm−3 are examined. Numerical temperature predictions of the lightly doped wafer are compared with experimental measurements. Heating rates for the lightly doped wafer fluctuate due to partial transparency effects and reach a maximum of ∼50 °C/s. The heavily doped wafer sees a maximum heating rate of ∼100 °C/s. Because the wafers are opaque above 700 °C regardless of their level of doping, all wafers reach steady state at ∼845 °C.

We investigated various interactions between alumina and tungsten films that occur during chemical mechanical polishing (CMP). Atomic force microscopy surface topography measurements of post-CMP tungsten indicate that the roughness of the tungsten is independent of polish pressure and rotation rate. Pure mechanical abrasion is therefore an unlikely mechanism of material removal during CMP. Transmission electron microscopy images corroborate these results. The adhesion force between alumina and tungsten was measured in solution. The adhesive force increased with KIO3 concentration. Friction forces were measured in solution using lateral force microscopy. The friction force in buffered solutions was independent of KIO3 concentration. These results indicate that interactions other than purely mechanical interactions exist during CMP.

High dielectric and low loss capacitor thin films of Sr2Nb2O7 (SN), Sr2Ta2O7 (ST), and their solid solution Sr2(Nbx, Ta1−x)2O7 (SNT) were investigated using the sol-gel technique. The SN film grows with the (0n0) orientation in the case of heating at over 700 °C. Heat treatment at a lower temperature results in the polycrystal ST-type structure. The SNT at x < 50% also resulted in the ST type. The dielectric constant for the SN film was 45, within 10% variation at ±0.5 MV/cm. Dielectric loss (tan δ) was 0.3–0.5%. The small variation in dielectric constant and the paraelectricity with low loss are suitable for capacitor applications.

Epitaxial (Ba0.5Sr0.5) TiO3 thin films of two different thickness (∼25 and ∼134 nm) on MgO(001) prepared by a pulsed laser deposition method were studied by synchrotron x-ray scattering measurements. The film grew initially with a cube-on-cube relationship, maintaining it during further growth. As the film grew, the surface of the film became significantly rougher, but the interface between the film and the substrate did not. In the early stage of growth, the film was highly strained in a tetragonal structure (c/a = 1.04) with the longer axis parallel to the surface normal direction. As the growth proceeded further, it relaxed to a cubic structure with the lattice parameter near the bulk value, and the mosaic distribution improved significantly in both in- and out-of-plane directions. The thinner film (∼25 nm) showed only one domain limited mainly by the film thickness, but the thicker film (∼134 nm) exhibited three domains along the surface normal direction.

Platinum and palladium powders with average particle sizes in the submicron range have been synthesized at room temperature by hydrazine reduction of and , respectively, in glycols. Platinum powders contain spherical particles with a bimodal size distribution. Palladium powders also contain spherical particles, but the size distribution is narrow. The effect of both ammonia and hydrazine concentration on the size distribution and average size of palladium particles was investigated.

A contact angle measurement technique has been used to obtain an estimate of the interfacial energy and thermodynamic adhesive strength between copper and polyimide [pyromellitic dyanhydride oxydianalyn (PMDA-ODA) and p-phenylene biphenyltetracarboinide (BPDA-PDA)]. Values of the strength of adhesion from these contact angle measurements are in reasonable agreement with values calculated using the Girifalco–Good–Fowkes nonpolar interfacial adhesion theory. Based on the surface energy it was predicted and experimentally observed that small copper clusters would embed into the polymer matrix if heated under ultrahigh vacuum conditions at temperatures near Tg of the polymer. Controlled embedding of nanometer clusters was utilized to produce a textured interface, where the partially embedded clusters acted as “nanonails” to anchor a metal overlayer to the underlying polyimide substrate. These nanonails greatly increased the bonding between the copper overlayer and the polyimide, as demonstrated by mechanical debonding studies.

Two kinds of high-purity Al2O3 powder were studied with respect to the effects of not only MgO doping but also atmosphere on both densification and grain growth. Controversial results for MgO doping are explained in terms of two roles that MgO can play during these processes: sensitive and insensitive to the experimental procedures. Atmospheres, whether dry or wet, had little influence on densification or grain growth in the early stage. After closed pores appreciably formed, however, both N2 and Ar atmospheres quickly reduced the densification rate.

Microstructural evolution and mechanical properties of gas-pressure-sintered Si3N4 with 4 wt% Yb2O3 as a sintering aid were investigated. The microstructure was not uniform throughout the specimen. Extremely large elongated grains were formed at the outer region near the surface, while relatively small elongated grains were formed at the inner region of the specimen. The outer region expanded inward with the sintering time. Mechanical properties, such as flexural strength, fracture toughness, and R-curve behavior of the specimens were strongly influenced by these variations in microstructure. The fracture toughness and the R-curve behavior of the outer region were higher than those of the inner region of the same specimen. On the other hand, the strength of the inner region was higher than that of the outer region. By controlling the relative thickness of each region, Si3N4 specimens having functionally graded microstructure were obtained. The Si3N4 with such microstructure exhibited high strength, high fracture toughness, and good flaw tolerance at the same time.

The electrical properties of Mn–Zn ferrites undoped and doped with Nb2O5 and V2O5 were investigated by impedance spectroscopy. The observed impedance response corresponded to that of a highly resistive grain boundary component in series with a less resistive bulk component. The presence of Nb5+ and V5+ led to an enhancement in the electrical resistance, especially in grain boundaries, as well as a greater difference in the electrical behavior between bulk and grain boundary components. The different dopant performance of these two components is discussed on the basis of grain boundary structure and chemical data, electrical conductivity, and dielectric dispersion.

Mn–Zn ferrite powders were prepared by hydrothermally aging the coprecipitates of compositional metal ions using ammonium hydroxide as a precipitant. R value (alkalinity) = (moles of added OH−)/[(moles of added Zn2+) × 2 + (moles of added Mn2+) × 2 + (moles of added Fe3+) × 3] was introduced to adjust the amount of added ammonia. The results show that the R value of starting suspension and hydrothermal time have similar and dominant effects on the composition, spinel ratio, and crystallite size of synthesized powders. From the analyses of x-ray diffraction (XRD) and inductively-coupled plasma (ICP), it notes that no α–Fe2O3 peak in the XRD patterns of powders synthesized at R = 2–3, 150 °C × 2 h, may be due to lower degree of crystallinity and less amount of α–Fe2O3 existing in these powders. Both the increase of hydrothermal time and of R value can promote the crystallinity of powders and also cause a significant loss of zinc, hinting that in the hydrothermal process, the loss of zinc may play a crucial role in the crystallinity of hydrothermally synthesized powders.

Polycrystalline, wurtzitic indium nitride was synthesized by saturating indium with nitrogen from microwave plasma sources. The structure was confirmed by x-ray diffraction, electron diffraction, and elemental analysis. Two types of growth were observed: (i) dendritic crystals on the original melt surface, and (ii) hexagonal platelets adjacent to the In metal source on the upper edge of the crucible. The method does not involve a foreign substrate to initiate growth and is a potential alternative to the high-pressure techniques normally associated with bulk growth of indium nitride. The lattice parameters were a = 3.5366 ± 0.0005 Å and c = 5.7009 ± 0.0005 Å, with c/a = 1.612 ± 0.0005.

Using a pulse electric current sintering (PECS) method, β–SiC and α–SiC powders doped with a few weight percent of Al2O3–Y2O3 oxide or Al4C3–B4C–C nonoxide additives were rapidly densified to high densities (95.2–99.7%) within less than 30 min of total processing time. When Al2O3–Y2O3 additive was used, both ceramics resulting from β–SiC and α–SiC had fine, equiaxed microstructures. In contrast, when Al4C3–B4C–C additive was used, the ceramic resulting from α–SiC had a coarse, equiaxed microstructure, whereas the ceramic resulting from β–SiC was composed of large elongated grains whose formation was accompanied by the β →?α phase transformation of SiC. Compared with the Al2O3–Y2O3-doped SiC ceramics, the Al4C3–B4C–C-doped SiC ceramics had higher densities, lower fracture toughness, and higher hardness. The fracture mode of the oxide-doped SiC was mainly intergranular, whereas the nonoxide-doped SiC exhibited almost complete intragranular fracture that was attributed to the higher interfacial bonding strength.

When powder mixtures of {Al2(SO4)3 + Na2SO4}or {γ–Al2O3 [obtained by heating Al2(SO4)3 at 900 °C for 3 h] + Na2SO4} were heated in an alumina crucible at 1100 °C for 1 h, α–Al2O3 platelets were formed. The powder mixture of {Al2(SO4)3 + 2Na2SO4} yielded aggregations of platelets that were less than 5 μm in size. The size of the aggregations increased in proportion to the amount of Na2SO4, and aggregations of 120 μm were obtained using a mixture of {Al2(SO4)3 + 6Na2SO4}. The powder mixture of {γ–Al2O3 + 2Na2SO4 yielded hexagonal platelets having an average diameter of 3.7 μm and an average thickness of 0.3 μm. In addition to aggregation size, the size of the hexagonal platelets also increased in proportion to the amount of Na2SO4, and platelets having an average diameter of 5 μm were obtained using a mixture of {γ–Al2O3 + 6Na2SO4}.

The feasibility of producing (Ba,Pb)TiO3-based thermistor tapes by the oxidation of malleable, metal-bearing precursors has been demonstrated. Intimate Ba–Pb–Ti–TiO2-bearing powder mixtures, produced by high-energy vibratory milling, were packed within a fugitive metal can and then compacted and formed into tapes of uniform thickness by cold drawing and rolling. The tape-shaped precursors were oxidized and converted into (Ba,Pb)TiO3-based tapes with a series of heat treatments at ≤1120 °C. With proper control of thermal treatments and chemical additions (Sb2O3 + MnO2 dopants), positive-temperature-coefficient-of-resistivity thermistors were produced that exhibited significant increases in resistivity commencing at temperatures ≥350 °C.

The chemically modified polycarbosilane (PC) containing organofluoric groups, PCOCF, was synthesized through chemical reaction of PC and fluoric alcohol. Pyrolysis of the polymer precursor occurred in three stages under 1000 °C. Weight loss due to evaporation of low molecular compounds was observed at the first stage below 300 °C, followed by the largest weight loss from 300 to 600 °C at the second stage. At this stage, side chains formed during the chemical reaction were removed. Finally, side chains such as Si–CH3 decomposed at the third stage above 600 °C. At 1000 °C, the chemical modification of PC resulted in high yield of solid product. After coating PCOCF on silicon carbide (SiC) powders, the conversion yield of pyrolyzed PCOCF was further improved due to the interaction between PCOCF and SiC powders. Coating of PCOCF on SiC powders was found to be effective in increasing the green density of uniaxially pressed bodies.

Extremely fine, tubular graphite nanofibers of varying geometries and degrees of crystallinity were produced by the decomposition of CO and hydrogen over various compositions of nickel–iron particles supported on silica. High-resolution transmission electron microscopy coupled with temperature programmed oxidation studies revealed that, as the iron content of the catalyst was increased, the bimetallic particles precipitated a chainlike graphitic fibrous structure in a stepwise mechanism. The high-iron-content system Fe–Ni (8:2) yielded a small amount of these chainlike graphite fibers that were extremely resilient to oxidation, suggesting a highly crystalline structure. When the catalyst particles consisted of a nickel–iron mixture, Fe–Ni (5:5), there was a decrease in the degree of crystallinity of the fibers (78% graphite) and a corresponding increase in the amount of amorphous carbon precipitated (22% amorphous) within the structure. The high-nickel catalyst Fe–Ni (2:8) generated the largest amount of the tubular nanofiber product. It was significant that there was an increase in the amorphous carbon content (58%) precipitated as opposed to graphitic carbon (42%) in the structures. In some cases, amorphous carbon was deposited inside the graphite core of the nanofibers. The influence of the catalyst composition and nature of the metal-support interaction are key factors in the continuing development of graphite nanofibers possessing desired structures for potential uses in a variety of applications.