An advanced wetting method is used to prepare a composite with a high content of ceramic particles in a matrix of photocured polymethylmethacrylate. The method allows for the preparation at minimum stirring of high quality samples with up to 59% solid in volume. The samples present reasonable flow characteristics prior to curing, with high hardness and fracture toughness in the fully cured state. Practical implications of the preparation method for dental restorative applications are studied. The method is also useful in the preparation of similar composites for other practical applications.

Composite preform fiber architectures range from the very simple to the complex, and the extremes are typified by parallel continuous fibers and complicated three-dimensional woven structures. Subsequent processing of these preforms to produce dense composites may depend critically on the geometry of the interfiber porosity. The goal of this study is to fully characterize the structure of a 0°/90° cloth layup preform using x-ray tomographic microscopy (XTM). This characterization includes the measurement of intercloth channel widths and their variability, the transverse distribution of through-cloth holes, and the distribution of preform porosity. The structure of the intercloth porosity depends critically on the magnitude and direction of the offset between adjacent cloth layers. The structures observed include two-dimensional networks of open pipes linking adjacent holes, arrays of parallel one-dimensional pipes linking holes, and relatively closed channels exhibiting little structure, and these different structures would appear to offer very different resistances to gas flow through the preform. These measurements, and future measurements for different fiber architectures, will yield improved understanding of the role of preform structure on processing.

The intercalation in vapor phase of cyclic amines (aniline, benzylamine, cyclohexylamine, piperidine, and pyridine) in α–hafnium bis(hydrogen phosphate) monohydrate (α–HfP) has been investigated. Elemental and thermal analysis lead to the establishment of the intercalate composition. The general formula is x[Hf(HPO4)2 · y amine H2O] (1 - x) α–HfP where y = 2, 1 and x ≤ 1. When y = 1 (piperidine and pyridine) the amines form a monomolecular layer. When y = 2 (aniline, benzylamine, and cyclohexylamine) the arrangement is bimolecular. The results are compared to those described for α–ZrP.

The preferred orientation of the TiN film grown by sputter-deposition was studied by the cross-sectional TEM. The preferred orientation was changed from the (200) through the (110), and then finally to the (111) with the film thickness. The cross-sectional microstructure also shows that the film consists of three layers which are all columnar structure. The (111) preferred orientation was observed in the top layer, and the (110) in the middle layer, and finally the (200) in the bottom layer. It is very surprising that the (110) preferred orientation could be observed in a medium thickness region and there are two kinds of critical thicknesses. These results surely show the strong dependence of the change in the preferred orientation on the strain energy in TiN thin films.

Dibutoxybis (acetylacetonato) zirconium, a difunctional zirconium alkoxide, was polymerized at 130 °C for 5 h in vacuo to produce oligomers that could be pyrolyzed to form a tetragonal zirconia (t-ZrO2), metastable at room temperature. This metastable phase was retained considerably below the equilibrium transformation temperature (∼1200 °C) without the use of dopants. Comparative pyrolysis of the oligomers between 600 and 900 °C in either flowing O2 or N2 for processing times under 12 h indicated t-ZrO2 nucleated first. Pyrolysis in oxygen facilitated transformation to the monoclinic symmetry, whereas pyrolysis in nitrogen demonstrated retention of the tetragonal phase. The formation of oxygen vacancies during pyrolysis, their role in stabilizing the metastable tetragonal phase, and contributions of O2 and crystallite size in the polymorphic transformation are discussed.

“Aging,” defined as the drift of resistance with temperature after 1000 h, was investigated for iron manganite temperature coefficient thermistors. For these devices, aging is relatively large, about 10%. The cationic distributions before and after aging were determined by Mössbauer spectroscopy. These distributions explain all the x-ray diffraction and correlated electrical data. The origin of the aging observed on iron manganites thermistors has been identified. It is due to the migration of Fe3+ ions from tetrahedral to octahedral sites of the spinel structure in order to reach a structural equilibrium.

Ferroelectric Ba0.7Sr0.3TiO3 thin films were successfully deposited on sapphire (r-cut) substrates by the sol-gel process, and the deposited films were annealed at various temperatures and for various soaking times. The compositional and structural characteristics of the films were systematically examined with the aid of x-ray diffraction, scanning electron microscopy, and medium energy ion scattering techniques. Their dependence on thermal processes was investigated. A planar capacitor structure based on the BSTO films was fabricated to evaluate the electrical and dielectric performance. These results, together with the microstructure characteristics, were analyzed and an optimal process was finally established.

We describe the synthesis and characterization of ultrafine TiO2 particles (in both anatase as well as rutile form) produced by a chemical reaction within the aqueous core of a water-in-oil microemulsion. The microemulsion was stabilized and the Ti4+ ions provided by a functionalized surfactant derived from the commercially available Aerosol-OT, i.e., sodium bis (2-ethylhexyl) sulfosuccinate (Na-DEHSS). The Na+ ions in Aerosol-OT were completely replaced by Ti4+ through an ion-exchange reaction in nonaqueous solvents. Ultrafine TiO2 particles were produced by the hydrolysis of the Ti-containing surfactant in the water droplets. The dependence of the size of the precipitated TiO2 · xH2O particles on various structure parameters of the microemulsion was studied in detail.

Functionally gradient materials (FGM) were prepared using layers of ZrO2 –3 mol% Y2O3 ceramic and NiCrAlY powders. A fine-grained zirconia powder was chosen to lower the ceramic sintering temperature and achieve simultaneous metal and ceramic densification. Consolidation of FGM's was achieved by a short time field-assisted sintering technique. Sintering was performed either at a constant temperature or in a temperature gradient by using punches made of different materials (i.e., one graphite and one tungsten). A temperature gradient of at least 100 °C was required with a low value of 1200 °C at the metal end and exceeding 1300 °C at the ceramic end. Increasing the number of intermediate layers alleviates some of the cracks formed during sintering due to different coefficients of thermal expansion.

The microstructural evolution, including preferred orientation and surface morphology, of ZnO films deposited by rf magnetron sputtering was investigated with increasing film thickness. Preferred orientation of the ZnO films changed from (0002) → (1011) → (1120) and fine and dense columnar grains also changed to large elongated grains with increasing thickness. Such selective texture growth was explained with an effect of highly energetic species bombardment on the growing film surface. The relationship between preferred orientation change and microstructural evolution was also discussed.

PLT(28) thin films deposited on glass substrates were studied by two sputtering processes. One is an in situ magnetron sputtering and the other is a low-temperature magnetron sputtering. The sintered PLT ceramic powders are used as a sputtering target for both processes. The influences of sputtering and annealing conditions on structure and crystallinity of the films were investigated. The electro-optic (E-O) properties of PLT(28) thin films prepared by the two processes were determined by a technique according to Faraday effect. The researches showed the E-O properties were strongly affected by the sputtering process. The film with larger grains exhibits stronger E-O effect. The quadratic E-O coefficient of PLT(28) thin film varies in the range of 0.1 × 10−16 to 1.0 × 10−16 (m/v)2.

The conversion of Ba–Al2O3 –Si–SiO2, Ba–Al–Al2O3 –SiO2, and Ba–Sr–Al–Al2O3 –SiO2 precursors into monolithic, monoclinic celsian has been examined. The relative amounts of metal and oxide in each type of precursor were adjusted so that the overall stoichiometry and molar volume were similar to those of the desired product, celsian. Metal + oxide mixtures were mechanically alloyed and then uniaxially pressed to yield 84–92% dense precursor disks. The precursors were converted into celsian by exposure to a series of heat treatments from 300–1500 °C in oxygen-bearing gases. Differences and similarities in the phase evolution of the various precursors are discussed. Celsian disks were produced that retained the precursor shape, dimensions, and relative (% theoretical) density.

Deposition of a (La0.5Sr0.5)CoO3 (LSCO) layer on top of Pt/Ti/Si substrates was observed to substantially improve the stability of the subsequently deposited Pb1−xLaxTi1−x/4O3 (PLT) films. Platinum coating of silicon substrates by itself is known to enhance the formation of PLT phase. In this paper, the elemental depth profile examined by secondary ion mass spectroscopy (SIMS) and the structural profile examined by grazing angle incident x-ray diffractometry (GIXD) reveals that the Ti species precoated underneath the Pt layer diffuses outward through the Pt layer at high temperature, forming a rutile TiO2 layer on top of Pt coating. It is this outermost TiO2 layer which promotes the transformation kinetics of the PLT species adhered onto substrates into the perovskite phase. Thus obtained films (PLT/Pt/Ti/Si) are, however, not stable enough to survive subsequent high-temperature processing. On the other hand, the PLT/LSCO/Pt/Ti/Si films, which incorporate LSCO as buffer layer, can survive 650 °C without significant deterioration.

Due to the convective and radiant heat losses, there exists a maximal converted length of a dense pellet synthesized by the self-propagating high-temperature synthesis (SHS) method. In this paper, we numerically investigate the possibility to increase that maximal converted length by cascading two reactant pellets in series, where an interface is naturally and artificially introduced. First, the impacts of both the bulk and interfacial parameters on the SHS process are estimated. The maximal converted length for a single pellet is computed. Next, by varying the interfacial parameters, it is found that more than 10% of extra converted length is obtained by the proposed cascade arrangement. Effects of the bulk parameters on the same purpose are also addressed.

The phenomena of pile-up and sink-in associated with nanoindentation have been found to have large effects on the measurements of the indentation modulus and hardness of copper. Pile-up (or sink-in) leads to contact areas that are greater than (or less than) the cross-sectional area of the indenter at a given depth. These effects lead to errors in the absolute measurement of mechanical properties by nanoindentation. To account for these effects, a new method of indenter tip shape calibration has been developed; it is based on measurements of contact compliance as well as direct SEM observations and measurements of the areas of large indentations. Application of this calibration technique to strain-hardened (pile-up) and annealed (sink-in) copper leads to a unique tip shape calibration for the diamond indenter itself, as well as to a material parameter, a, which characterizes the extent of pile-up or sink-in. Thus the shape of the indenter tip and nature of the material response are separated in this calibration method. Using this approach, it is possible to make accurate absolute measurements of hardness and indentation modulus by nanoindentation.

Thermal stresses in thin Cu films on silicon substrates were examined as a function of film thickness and presence of a silicon nitride passivation layer. At room temperature, tensile stresses increased with decreasing film thickness in qualitative agreement with a dislocation constraint model. However, in order to predict the stress levels, grain-size strengthening, which is shown to follow a Hall–Petch relation, must be superimposed. An alternative explanation is strain-hardening due to the increase in dislocation density, which was measured by x-ray diffraction. At 600 °C, the passivation increases the stress by an order of magnitude; this leads to a substantially different shape of the stress-temperature curves, which now resemble those of aluminum with only a native oxide layer. The effect of passivation is shown to be very sensitive to the deposition and test conditions.

Iridium dioxide (IrO2) thin films, deposited on Si substrates by reactive rf sputtering method under various conditions, were characterized by atomic force microscopy (AFM), x-ray diffraction (XRD), electrical-conductivity, spectrophotometry, ellipsometry and Raman scattering measurements. The average grain sizes of the films were estimated by AFM. A grain boundary scattering model was used to fit the relation between the average grain size and electrical resistivity. The optical and dielectric constants were determined by the ellipsometry measurements. The results of the electrical and optical studies show a metallic character of the films deposited at higher temperatures. The results of XRD and Raman scattering indicate that the IrO2 films deposited at temperatures higher than 300 °C show the presence of (200) texture.

Subsolidus phase relations in the BaTiO3–La2TiO5–TiO2 part of the ternary BaO–La2O3–TiO2 system at 1300 °C in air were determined. The phases were characterized by x-ray diffraction, scanning electron microscopy, and electron probe wavelength dispersive spectroscopic microanalysis. A combination of techniques was employed because of insensitivity in detecting secondary phases by x-ray diffraction. The location and extent of Ba6−xLa8+2x/3Ti18O54 ternary solid solution 0.2(1) ⩽ x ⩽ 2.3(1) and Ba1−yLayTi1−y/4 (VTi)y/4O3 binary solid solution 0 ⩽ y ⩽ 0.3 at 1300 °C was established. Tie lines between various barium polytitanates with a sequence of Ba6−xLa8+2x/3Ti18O54 solid solution regions were determined.

The thermal decomposition of a heteronuclear complex, La[Fe(CN)6] · 5H2O, leads to the preparation of nanosized single-phase perovskite-type LaFeO3 powders. The microstructural evolution of LaFeO3 with the temperature has been studied by x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The product of the decomposition at 500 °C consists of nanoporous grains which have the morphology of the complex, but diffracting as a monocrystal of LaFeO3. At the higher temperatures, the nanosized particles start to separate from each other, still keeping the shape of the complex grains and forming soft agglomerates. The formation of LaFeO3 from the complex at low temperatures is facilitated by the formation of an orthorhombic transition phase.

Tungsten bronze ferroelectrics with a morphotropic phase boundary (MPB) have become increasingly important for a variety of applications because of their enhanced and unique properties near the MPB. Lead barium niobate (Pb1−xBaxNb2O6) crystals, which have a morphotropic phase boundary between the orthorhombic (1 − x > ∼0.63) and tetragonal (1 − x, <, 0.63) phases, were grown in sealed Pt crucibles by the vertical Bridgman method for tetragonal compositions near the MPB, and their ferroelectric properties were investigated. The ferroelectric domain structures in as-grown crystals were revealed either by etching in hydrofluoric acid or by polishing with colloidal silica, the latter providing clearer features. Domain size on the surface perpendicular to the polar axis was 10–50 μm. Crystals could be poled by slowly cooling from above the Curie temperatures (300–400 °C) under a dc field of 5 V/mm. The spontaneous polarization Ps of tetragonal Pb1−xBaxNb2O6 was found to be in the range of 0.40–0.70 μC/mm2 at room temperature depending on composition and increased as the composition approached morphotropic phase boundary (1 − x = ∼0.63), as expected.