Using titanium nitrate solution stabilized by chelation, amorphous fine particles of the Ba-Ti-O system were prepared by the mist decomposition method in air. After calcination of these particles, barium titanate ceramics were prepared using the hot uniaxial pressing method, and various properties were investigated. As a result, the grain sizes could be controlled over the range from 58 nm to 187 nm by the sintering temperatures and/or the calcination temperatures, keeping the density almost constant. Moreover, the dielectric properties of the samples showed that the relative permittivity decreased with decreasing grain size, and Curie temperature also shifted to lower temperatures in the same way. In this study, we first found that Curie temperature existed in the barium titanate ceramics with grain sizes from 58 to 147 nm.

Novel microwave-hydrothermal processing has been developed by us recently for the synthesis of a wide variety of ceramic powders. Herein, we report the use of microwave-hydrothermal processing to synthesize several metal powders such as Cu, Ni, Co, and Ag by reducing their corresponding metal salts or hydroxides with ethylene glycol. Metal powders have been produced extremely rapidly a (few minutes) by microwave catalysis. The kinetics of metal powder synthesis have been increased by at least an order of magnitude by microwave-hydrothermal processing compared to the conventional refluxing process in ethylene glycol at about 195 °C.

The electromechanical properties of sol-gel-derived ferroelectric Pb(Zr0.53Ti0.47)O3 (PZT 53/47) thin layers deposited on silicon were determined as a function of field strength, measurement frequency, and total thickness. Both electrically induced strains (∊) and piezoelectric properties (d33) were characterized by interferometry. Dielectric spectroscopy and polarization switching (P-E) measurements were determined for comparative purposes. An asymmetry between forward and the reverse bias conditions in the ∊-E displacements was found for both five-layer deposited and nine-layer deposited structures. However, no asymmetry was observed in the P-E hysteresis characteristics. In addition, the electrically induced strains and the piezoelectric response were found to be dependent on measurement frequency. No significant frequency dependence was observed in the polarization or dielectric responses. The results are discussed in terms of a possible clamping effect on polarization switching.

New materials were made by infiltration of sol-gel boehmite thin films with copper acetate. The structure and phase transformation of these materials during heat treatment were studied. It was found that infiltration in the boehmite state did not end up in the same material as direct infiltration in the θ-alumina derived from boehmite, even after both types of materials were heat-treated at 900 °C. Infiltration in boehmite makes it possible to synthesize sandwich structures comprised of alternate layers of CuO and of γ-alumina.

SiC/AlN composites with controlled interfacial solid solution were employed in this present work to investigate the effects of interfacial chemical composition and AlN polytypes on the fatigue properties. The dynamic strength of the SiC/AlN composite was found to decrease initially as the stressing rate decreased. However, the strength increased with a decrease in stress rate at a low stress rate region of below 0.01 MPa/s. Crack arrest could have occurred before exhibiting spontaneous failure at an intermediate stress rate of 0.01 MPa/s. It was found that both the interfacial bonding strength and testing technique had essential effects on the behavior of slow crack growth.

The SiL2.3 emission spectra of amorphous W/Si multilayers were measured. For the as-deposited samples the SiL2,3 emission spectra have been found to be very close to that of amorphous Si. The formation of WSi2 phase during annealing of W/Si multilayers at a temperature ≥50 °C was detected. From the SiL2,3 emission spectra of as-deposited and annealed samples, the amount of W/Si2 phase was estimated. It is shown that this technique can be used for quantitative estimation of the ratio of amorphous Si and WSi2 phases in W/Si multilayers.

The creep properties of lots of NiAl eryomilled with and without Y2O3 have been determined in compression and tension. Although identical cryomilling procedures were used, differences in composition were found between the lot ground with 0.5 vol % yttria and the lot ground without Y2O3. Compression testing between 1000 and 1300 K yielded similar crecp strengths for both materials, while tensile creep rupture testing indicated that the yttria-containing alloy was slightly stronger than the Y2O3-free version. Both compression and tensile testing showed two deformation regimes; whereas the stress state did not affect the high stress exponent (n ≍ 10) mechanism, the low stress exponent regime n was ∼6 in tension and ∼2 in compression. The strengths in tension were somewhat less than those measured in compression, but the estimated activation energies (Q) of ∼600 kJ/mol for tensile testing were closer to the previously measured values (∼700 kJ/mol) for NiAl-AlN and very different from the Q's of 400 and 200 kJ/mol for compression tests in the high and low stress exponent regimes, respectively. A Larson-Miller comparison indicated that cyromilling can produce an alloy with long-term, high-temperature strength at least equal to conventional superalloys.

The high-temperature deformation behavior of a SiC whisker-reinforced, yttria-stabilized, tetragonal zirconia polycrystalline composite containing 20 vol % SiC whiskers (SiC/Y-TZP) has been investigated. Tensile tests were performed in vacuum at temperatures from 1450 °C to 1650 °C and at strain rates from 10−3 to 10−5 s−1. The material exhibits useful high-temperature engineering properties (e.g., ∼100 MPa and 16% elongation at T = 1550 °C and at a strain rate of ∼10−4 s−1). The stress exponent was determined to be n ≍ 2. Scanning electron microscopy was used to characterize the grain size and morphology of the composites, both before and after deformation. The grain size in the composite was initially fine, but coarsened at the test temperatures; both dynamic and static grain growth were observed. The morphology of ceramic reinforcements appears to affect strongly the plastic deformation properties of Y-TZP. A comparison is made between the properties of monolithic Y-TZP, 20 wt. % Al2O3 particulate-reinforced Y-TZP (Al2O3/Y-TZP), and SiC/Y-TZP composites.

Thin films of Lead Lanthanum Titanate (PLT) corresponding to 28 at. % of La were prepared by the metal-organic decomposition (MOD) process. The films were fabricated from two solutions of different composition. The composition of the first solution was determined, assuming that the incorporation of La3+ in the PbTiO3 structure gives rise to A-site or Pb vacancies, whereas for the composition of the other solution the creation of B-site or Ti vacancies was assumed. The effect of excess lead on the microstructure and the optical and electrical properties was studied for 0% to 20% excess PbO. The x-ray diffraction patterns of all films at room temperature indicated a cubic structure with a lattice constant of 3.92 Å. Optical and electrical measurements showed the films made assuming B-site vacancies had better properties. In general, excess PbO was found to improve the optical transmittance as well as the electrical properties of films. However, in films assuming the formation of B-site vacancies, PLT showed improved electrical properties only up to 5–10% excess PbO, while higher PbO additions had a deleterious effect. The films had a high resistivity, good relative permittivity, low loss, very low leakage current density, and high charge storage density. A type-B film with 10% excess Pb had a relative permittivity of 1340 at 100 kHz and a charge storage density of around 16.1 μC/cm2 at a field of 200 kV/cm at room temperature.

The decomposition mechanism of hillebrandite (Ca2SiO4 · H2O) to larnite (β-Ca2SiO4) was studied by conventional and in situ hot-stage TEM methods. The hillebrandite structure is suggested to be a composition of parawollastonite (CaSiO3) and portlandite [Ca(OH)2] adjoining on {001} planes. The larnite fibers showed occasional bending and kinking as well as internal defects such as dislocations and domains. No transformation-related microstructures such as twinning were observed. The preferred orientations in the larnite fibers were not distinct. The decomposition mechanism of hillebrandite in air and in a vacuum may be different. In air, the CaO from the decomposed portlandite layer directly participates in the process of SiO4 chain breaking to form larnite. In the TEM this CaO is removed and apparently reprecipitated, so that hillebrandite converts directly to parawollastonite, A possible lattice correspondence between hillebrandite (C2SH) and larnite (β-C2S), based on crystallographic considerations, is proposed to be bC2SH ¶bβ-c2s, αC2SH ¶ ≍[102]β-C2S, and CC2SH ¶ ≍ [401]β-C2S.

Crack initiation and progression have been studied in nanoscale brittle/ductile multilayers of Cu and Si. Variations in the interface debond energy on the cracking behavior have been examined by using thin interlayers comprising either Cr (strong interface) or Au (weak interface). For strongly bonded Cr interfaces, it has been found that cracks forming in the Si invariably extend through the Cu layers, despite the ductile rupture characteristics of the Cu. This behavior occurs even when the Cu layers comprise more than 70% of the multilayer volume. It also contrasts with the crack arrest capabilities exhibited by relatively thick ductile layers (∼10-100 μm). The disparity in behavior is attributed to the relatively large cracking strain required for the thin brittle layers. Weak Au interfaces result in debonding which, in turn, can suppress the propagation of cracks into adjacent layers. However, when the interface includes strongly bonded sections, the debond arrests, and often kinks into the attached Si. In this case, cracking still progresses sequentially through the Si layers. Careful control of the interface debond energy is needed to fully suppress crack progression in nanoscale multilayers.

By comparing the ultrasonic cavitation in several kinds of transparent liquid mediums, we have investigated the cavitation effect in liquid. It is considered that the shock wave created by the cavitation in aluminum melt induces a high pressure and an elevated temperature field around the fibers, which can promote the wetting between fiber and aluminum and have aluminum melt infiltrate into the fibers. Moreover, the experiment result shows that the fiber resonance matching with the cavitation is also an important factor for SiC/Al composites preparation. There exists a damage of the ultrasonic vibration on SiC fiber, if the fiber is acted long enough.

Cobalt oxide system Co3O4-CoO has been studied on the ZrO2 matrix surfaces with FTIR and XPS. The tetragonal and monoclinic ZrO2 matrix materials have been synthesized from the Zr-n-propoxide-acetylacetone-water-isopropanol system. The study shows that the ZrO2 matrix is able to retain the relative Co3O4:CoO population at elevated temperatures. The thermodynamically stable oxide population (Co3O4:CoO) at room temperature for ZrO2-supported Co3O4-CoO is about 50:50 (Co2+ :Co3+ = 2:1), which is markedly different from the 100:0 case (Co2+ :Co3+ = 1:2) for an unsupported Co3O4-CoO surface oxide system. The relative Co3O4 :CoO ratio in the surface region of the ZrO2 is temperature dependent but matrix-polymorph independent. The composition of an oxide solid solution formed by the Co3O4-CoO and matrices of ZrO2 is determined to have a cobalt molar percentage of 4.5%. Diffusion thermodynamic quantities are investigated, and the measured diffusion activation energy for a cobalt ion in the ZrO2 matrices is 0.21 eV. The mechanism of the ZrO2 memory effect on surface Co3O4-CoO transition will also be addressed.

Physical vapor deposited TiN coatings oxidized by solar beam heat treatment in air were examined by microprobe Raman spectroscopy. The Raman spectra of TiN treated at 400 °C indicated incipient oxidation by the presence of anatase TiO2 and additionally showed a broadband feature around the forbidden TiN vibrational mode. Inhomogeneous mixtures of rutile TiO2 and small amounts of anatase polymorph (< 10%) were detected for the treatments at 600 °C only during the initial stage of oxidation. Prolonged treatment at 600 °C resulted in a complete anatase-to-rutile conversion. Rutile was identified as the single product of oxidation of the TiN samples treated at 800 °C. Peak analysis of the rutile spectra revealed no substantial spectral shifts, demonstrating an oxide growth of nearly stoichiometric rutile with an estimated composition in the range of TiO2±0.02. The Raman scattered light intensity could be correlated with the rutile layer thickness.

The six independent second-order elastic stiffness coefficients of a Ti44Al56 single crystal (L10 structure) have been measured at room temperature for the first time using a resonant ultrasonic spectroscopy (RUS) technique. These data were used to calculate the orientation dependence of Young's modulus and the shear modulus. Young's modulus is found to reach a maximum near a [111] direction, close to the normal to the most densely packed planes. The elastic moduli and Poisson's ratio for polycrystalline materials, calculated by the averaging scheme proposed by Hill, are in good agreement with experimental data and theoretical calculations.

Thin film cracking has been studied for a nanometer brittle/ductile layered system consisting of Si and Cu. Single Si films and Cu/Si/Cu trilayers were fabricated by physical vapor deposition. The films were deposited onto a ductile substrate consisting of stainless steel with a thin polyimide interlayer. Straining of the substrate induced cracking of the Si. Cracking strains ≥1% were observed, particularly in layers ≤100 nm thick. The critical cracking strain was found to depend upon the Si layer thickness, as well as the thickness and elastic/plastic properties of the adjacent ductile layers. Si cracking was suppressed by the presence of adjacent Cu layers. The measured strains were compared with lower-bound critical strains for tunnel and channel cracking. Comparisons indicated that these mechanisms control the critical strain found in trilayers, because trilayer fabrication introduces edge flaws larger than the Si layer thickness. Conversely, for Si films, the measured critical strains exceed the channel cracking strain, because the flaws in these films are relatively small.

High-energy shock plasma deposition techniques are used to produce carbon-nitride films containing both crystalline and amorphous components. The structures are examined by high-resolution transmission electron microscopy, parallel-electron-energy loss spectroscopy, and electron diffraction. The crystalline phase appears to be face-centered cubic with a unit cell parameter approx. a = 0.63 nm, and it may be stabilized by calcium and oxygen at about 1–2 at. % levels. 85 at. % of the carbon atoms appear to have trigonal bonding for the crystalline phase, the remaining 15 at.% having tetrahedral bonding. The amorphous carbon-nitride film component varies from essentially nanocrystalline graphite, containing virtually no nitrogen, to amorphous carbon-nitride containing up to 10 at. % N, where the fraction of sp3 bonds ranges up to approx. 85 at. %. There is PEELS evidence that the nitrogen atoms have sp2 trigonal bonds in both the amorphous and crystalline phases.

Additions of O to 9 mol % Ta2O5 to a lithia-alumina-silica glass-ceramic matrix Nicalon SiC-reinforced composite increased the elastic modulus and ultimate strength of the composite. The additive fostered sphereulitic growth of β-eucriptite solid solution crystals which concentrated Ta2O5 at sphereulite boundaries and adjacent to the fiber-matrix carbon-rich interphases. These regions reacted with the interphases as well as soluble carbon monoxide gas to convert them to TaC. The former reaction was shown to be thermodynamically favorable above 983 °C, while the latter was favorable above 1249 °C. The improvement in mechanical properties was attributed to TaC particulate reinforcement, and suggests a simple glass-ceramic route to the fabrication of particulate-reinforced ceramic matrix composites.

Effects of reduction, reinforcements, and dynamic precipitation on grain refinement by hot extrusion have been investigated in a Si3N4w/Al-Mg-Si (6061) composite by tensile tests and microstructural investigation. The grain refinement was attributed to an interaction of recrystallization and dynamic precipitation, which was enhanced by reinforcements. Not only fine-grained microstructure, but also relaxing stress concentrations which are caused at matrix/reinforcement interfaces during superplastic flow are required to attain large elongations. Partial melting resulting from segregation plays an important role in relaxing the stress concentrations. DSC investigations revealed that the degree of segregation was increased by hot extrusion.

We prepared sol-gel titania by using different hydrolysis catalysts, and characterized it by x-ray powder diffraction. The structure of the crystalline phases—brookite, anatase, and rutile—in the samples annealed between 70 and 900 °C was refined by using the Rietveld technique. From the refinement we obtained the structure parameters, the concentration of each phase, and their average crystallite size. These quantities and their evolution with temperature depended on the hydrolysis catalyst. Anatase and rutile were deficient in Ti, suggesting that their crystalline structure contained hydrogen atoms, forming OH− ions inside. In anatase this deficiency depended on its crystallite size, but it was constant in rutile. When anatase was annealed, it dehydroxylized, producing either crystallitc growing up or its conversion into rutile. From the analysis we also found the conditions for obtaining single-phase samples that could be used as precursors for making up titania single-phase thin films.