An “Auto Ignition” technique was utilized in synthesizing Al2O3 –ZrO2 powders with nano/nano microstructure. The process used the corresponding nitrates as oxidizers and urea as the fuel. The as-synthesized powders were characterized by x-ray diffraction and transmission electron microscopy. It was observed that the microstructure consisted of crystallites of Al2O3 and ZrO2, both of which were nanocrystalline. As opposed to the other nanocomposite ceramics, this feature of the microstructure classifies the present powders as nano/nano type. This nanocrystallinity of the microstructure (crystallite size less than 100 nm) was maintained even after a soaking at 1200 °C for 2 h. Since the microstructure is stable at high temperatures, it was possible to densify the powders by hot isostatic pressing at 1200 °C. The product was 99% of the theoretical density and maintained nanocrystalline grain size. The average hardness and toughness values, as determined by an indentation technique, were 4.45 GPa and 8.38 MPa · m1/2, respectively. These values represent evidence of ductility in these composites since transformation toughening was ruled out in this case. The potential application of these results is expected to be in net shape deformation forming of ceramics.

β–Sialon has been prepared by SHS (Self-propagating High-temperature Synthesis) with Si, Al, Al2O3, and β–Si3N4 under high nitrogen pressure. Rod-like crystals of b–Sialon with an aspect ratio of 4–15 and whiskers with various aspect ratios were obtained in the process. Considering the morphologies of the products, it is concluded that VLS (vapor-liquid-solid) is the predominant mechanism of the formation of rod-like crystals and whiskers.

Aerosol-assisted chemical vapor deposition using the β-diketonate precursors Sr(tmhd)2 · 2H2O, Fe(tmhd) 3, and Co(tmhd) 3 was investigated for depositing thin films of the mixed-conducting ceramic SrCoyFe1−yO3−δ onto porous α–Al2O3 substrates. Single-phase SrCoyFe1−yO3−δ perovskite films were obtained at a deposition temperature of 550 °C and pressure of 15 mm Hg, whereas deposition at atmospheric pressure produced mixed-phase films. The Co/Fe elemental ratios in the films reflected those in the precursor solution, but the films were depleted in Sr. Reduced-pressure deposition provided a more uniform film morphology than atmospheric pressure, and led to a supported film which was leak-tight to N2 flow.

RF induction thermal plasma was applied to the chemical vapor deposition of carbon nitride from graphite powders and Ar–N2 gas at about 1 atm. Low-density and fragile amorphous powder-like bulk deposits whose color is light yellow were obtained. Elementary analysis by a combustion method and x-ray photoelectron spectroscopy showed that the N/C ratio is higher than that of stoichiometric C3N4. Also, a large amount of hydrogen and oxygen are included, which seems to be due to the absorption of moisture and oxygen after exposure to air. Infrared absorption spectra suggest the presence of sp CN and sp2 CN bonds, and nitrogen-containing polycondensed ring structures. Thermogravimetric analysis with mass spectroscopy shows that the deposits decompose almost completely at 800 °C, suggesting that the polycondensed rings are not large and not well cross-linked.

Single crystals of barium samarium titanium oxide Ba6−3xSm8+2xTi18O54 (x = 0.27) have been synthesized and studied using x-ray diffraction. Superstructure reflections, which cause a doubling of the cell along the short axis, were taken into account and the refinement was conducted in the orthorhombic space group Pnma. Unit cell parameters from single crystal x-ray diffraction were a = 22.289(1), b = 7.642(1), and c = 12.133(1) Å. Refinement on F resulted in R1 = 5.37% for 1410 Fo > 4σ with the thermal parameters of the Sm and Ba atoms refined anisotropically and the thermal parameters of the Ti and O atoms refined isotropically. The structure is made up of a network of corner sharing TiO6−2 octahedra creating rhombic (perovskite-like) and pentagonal channels. The two pentagonal channels are fully occupied by Ba atoms. The refinement suggests that one rhombic channel is fully occupied by Sm atoms (Sm3/Sm4), one rhombic channel is partially occupied by Sm atoms (100% Sm1/86.25% Sm5), and one rhombic channel is shared by BaySm atoms (59.25% Ba3/40.75% Sm2), resulting in a formula of Ba10.38Sm17.08Ti36O108 with Z = 1. The above site occupancies differ from the site occupancies previously reported in the literature for refinements conducted with the short axis approximately equal to 3.8 Å.

Physical and electrical characterization techniques have been applied to the problem of developing a lower temperature process for spin-on Ba0.7Sr0.3TiO3 thin films and capacitors compatible with on-chip aluminum metallization. The films were prepared by spin-coating from carboxylate precursors and were processed at temperatures between 650 °C and 450 °C. Capacitors annealed at higher temperatures have a dielectric constant (κ) of 382, a C/A of 20 fF/μm2, and a leakage current density of 2 × 10−7 A/cm2 at 3.3 V. Those processed at 450 °C show occasionally promising but inconsistent results, correlated using TEM images with locally variable crystallization into the perovskite phase. The kinetics of the spin-on solution chemical decomposition and crystallization has been investigated through the use of x-ray diffraction (XRD), thermogravimetric analysis (TGA), and Raman spectroscopy.

The dielectrophoretic effect is a phenomenon in which dipole-dipole interactions are induced between particles in a suspension by an electric field.1−5 This dipole interaction leads to the formation of chains or fibrils parallel to the applied electric field. Recently, the dielectrophoretic effect has been shown to be a possible composite assembly technique permitting property changes to be induced with the appropriate electric fields.6,7 The results presented in this paper show that the dielectrophoretic assembly process can be used to engineer anisotropy into composite materials. Various filler materials are aligned in a thermoset polyurethane matrix and the dielectric properties are measured. Comparisons are drawn between the dielectrophoretically assembled composites and those processed conventionally in the absence of an electric field. Dielectric properties are modeled with modified mixing laws and discussed in relation to the composite microstructure and the alpha relaxations of the polymer phase.

Ultrasound radiation is used to prepare a composite material made of polymethylacrylate and amorphous iron nanoparticles. Two preparation methods are described, in which the monomer, methylacrylate, is the starting material. The magnetic properties of the composite material are measured and reveal a superparamagnetic behavior.

The initial stages of silicate growth on graphite are characterized with atomic force microscopy. The morphological development indicates that decomposition of tetra ethyloxysilane at low pressure produces films of 3 nm clusters located at undercoordinated carbon sites. Clusters eventually cover the surface, at which point a second layer grows. In higher pressure deposition multiple layers of clusters grow simultaneously. A comparison of the oxidation behavior of surfaces with defects completely and incompletely terminated with SiOx shows that edge recession is the primary oxidation mechanism and that the site specificity of SiOx is effective in inhibiting oxidation.

Atomic force microscopy, as well as the Brunauer, Emmett, and Teller technique and x-ray diffraction, was used to analyze ultrafine NiZn ferrite powders hydrothermally synthesized at 200 °C, for 5 h. The particle sizes, measured through AFM images acquired from the surface of pressed powders, were 52 ± 6 nm, which were higher than those obtained by the other techniques. The particles were monodispersed in size and approximately spherical, meeting the requirements for the production of high density sintered components. The observations performed on ceramic bodies sintered at different conditions (1100–1400 °C, 5 to 240 min) showed necks characteristic of the early stages of sintering (1100 °C) and the expected pore curvature evolution (1400 °C) with sintering time in the final stage of the sintering process. Using a straightforward sample preparation technique, AFM proved to be a powerful tool for direct analysis of ceramic powder particles on the nanometric scale and sintered ceramics at different sintering stages.

Flexible films of vermiculite have been prepared from aqueous suspensions after swelling by cation exchange and mechanical delamination. Two different swelling cations, lithium and butylammonium, have been investigated. The degree of swelling and delamination during the suspension preparation was characterized by the percentage of water reabsorbed by dried clays and the adsorption of methylene blue. The vermiculite saturated with lithium ions is more easily delaminated but contains more water than those saturated with butylammonium. Good quality coherent flexible films could be prepared from both the lithium and butylammonium exchanged vermiculites but the high percentage of water found in the films has a detrimental effect on their dielectric properties. To reduce the amount of water in the exchanged vermiculites a second ion exchange with potassium, a less hydratable cation, was investigated. Films prepared after exchange with potassium showed significant improvements in their dielectric properties, with a dielectric constant ∈ around 10 and a dissipation factor tan δ around 0.06 at 25 °C and a frequency of 1 kHz.