This paper focuses on understanding stress development in CuNi42Mn1 thin films during annealing in Ar. In addition to stress-temperature measurements, resistance-temperature investigations and chemical and microstructural characterization by Auger electron spectroscopy, scanning and transmission electron microscopy, x-ray diffraction, and atomic force microscopy were also carried out. The films are polycrystalline with a grain size of 20 nm up to 450 °C. To explain the stress evolution above 120 °C, atomic rearrangement (excess-vacancy annihilation, grain-boundary relaxation, and shrinkage of grain-boundary voids) and oxidation were considered. Grain-boundary relaxation was found to be the dominating process up to 250–300 °C. A sharp transition from compressive to tensile stress between 300 and 380 °C is explained by the formation of a NiO surface layer due to reaction with the remaining oxygen in the Ar atmosphere. This oxidation is masking the inherent structural relaxation above 300 °C.

The change in ultrasonic nonlinear property of a titanium alloy subjected to cyclic loading has been studied, with an objective to develop a new characterization methodology for quantifying the level of damage in the material undergoing fatigue. In order to determine the degree of nonlinearity, the ultrasonic second harmonic generation technique has been used. The second harmonic signal was monitored during the fatigue process, and a substantial increase in the second harmonic amplitude (180% increase in nonlinear factor) was observed. This indicates that the second harmonic signal is very sensitive to the microstructural changes in the material caused by fatigue.

The phase diagram of urea–p-nitrophenol system, in the form of a temperature-composition curve, shows the formation of a 1: 1 molecular complex surrounded by two eutectics containing 0.216 and 0.777 mole fraction of p-nitrophenol. Data on growth velocity (v), obtained by measuring the rate of movement of the interface at different undercoolings (ΔT), suggest that they obey the Hillig–Turnbull equation, i.e., v = u (ΔT)n, where u and n are constants depending on the nature of materials involved. From the heat of fusion values, determined by the differential scanning calorimetry (DSC) method, heat of mixing, entropy of fusion, roughness parameter, interfacial energy, radius of the critical nucleus, and the excess thermodynamic functions were calculated. While the x-ray diffraction data show that the eutectics are not mechanical mixtures of the components under investigation, the microstructural investigations give their characteristic features.

Processes that constrain or promote cavity growth and fast fracture at elevated temperatures are examined. Solutions are given for the stress caused by inhomogeneous deposition of matter in metal-ceramic and alumina grain boundaries and for the tensile stress near the top of a hemispherical pore during pore growth. Velocities of dislocation climb that could promote fast fracture are calculated for elastic stresses acting upon dislocations arising from both a crack tip and interface repulsion. The rates for the atomic diffusive processes and the magnitudes of stresses resulting from them are found to agree well with experimental rate of pore growth, and new data on pore growth and fracture at an aluminum-sapphire interface are presented.

A simple bridging model is proposed for the toughening of a discontinuous fiber-reinforced brittle matrix composite, in which the frictional bridging of fibers during, as well as after, the interfacial debonding is considered. The R-curve behavior and the work-of-fracture of the composite can be theoretically predicted by the computation of the bridging model applying material parameters, such as fiber volume fraction, size and shape of fibers, fiber tensile strength, elastic moduli of fibers and matrix, fracture toughness and work-of-fracture of matrix, and frictional shear stress at interface. The experimental result obtained from a SiC-whisker-reinforced Al2O3 composite confirms the theoretical predictions of the present bridging model. Through the model calculation, the R-curve, crack profile, and bridging stresses of the composite can be estimated correspondingly to the bridging processes.

The chemical and morphological properties of a sol-derived layered perovskite compound, Kca2Nb3O10 (KCN), are presented. Development of this compound is motivated by its use as an interphase fiber-coating material for ceramic matrix composites (CMC's). In such systems, this material is to be placed between the fiber and matrix to control crack propagation in the vicinity of the fiber, thereby enhancing toughness. Comparative analyses are performed between known bulk specimens of KCN and the sol-derived product using transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The suitability of the sol-derived KCN for CMC applications is demonstrated through microstructure and chemical composition similar to that of the known bulk KCN samples.

Yttria-stabilized zirconia (YSZ) thin films grown by the pulsed laser deposition method on (0001) sapphire substrates have been studied by x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM). It was found that the crystal orientation of the YSZ films changes as a function of oxygen pressure during deposition. At low oxygen pressure (50 mTorr), well-defined (111) oriented YSZ films are grown. High oxygen pressure favors the nucleation of (001) oriented YSZ grains. A model to explain the preferred growth direction of (001) YSZ is presented. Utilizing the experimental data, we have developed a two-step process to epitaxially grow high-quality (001) oriented YSZ on (0001) sapphire substrate.

A chemical solution deposition (CSD) procedure was used to prepare epitaxial lanthanum calcium manganese oxide (LCMO) thin films on (100) SrTiO3 single-crystal substrates. The colossal magnetoresistance (CMR) properties of the films were found to be comparable to those processed with vacuum deposition techniques and to bulk samples. The (200) LCMO d-spacing and insulator-metal transition temperature (TIM) were measured for films heat-treated at different temperatures, partial pressures of O2, and different times. The variations observed suggest a direct link between lattice parameter and TIM, as can be understood through their mutual dependence on the Mn4+/Mn3+ ratio. The measurements also suggest that film and powder samples crystallize Mn41-rich with respect to the Ca-substitution level, consistent with the larger lattice parameter and higher TIM observed following short heat treatments at high temperatures or long treatments at lower temperatures. Films refired in reducing conditions had the largest (200) d-spacing and slightly lower TIM, as expected from the 30% Ca-substitution level and consistent with the LCMO electronic/magnetic phase diagram constructed for bulk samples.

Fully stabilized cubic zirconia doped with iron oxide has been synthesized by high-energy ball milling from powder mixtures of monoclinic zirconia and hematite. It is found that the iron ions dissolved in cubic ZrO2 are in substitutional positions with a maximum solubility of approximately 18.5 mol% α–Fe2O3. The unit-cell volume of the cubic ZrO2 phase decreases with increasing iron content. During heating the cubic-to-tetragonal transition occurs at approximately 827 °C and the tetragonal-to-monoclinic transition seems to be absent at temperatures below 950 °C. During cooling the tetragonal-to-monoclinic transition occurs at 900–1100 °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.

Effects of borosilicate glass (BSG) on densification and dielectric and thermal expansion properties of a binary composite of BSG + TiO2 ceramics have been investigated. Two different phases of TiO2 including anatase and rutile are used. A much greater densification is observed with anatase because it has a much better wetting with BSG than rutile. With increasing BSG content, the densification of BSG + TiO2 increased. Activation analysis shows that the densification is controlled by viscous flow of BSG. Both dielectric constant and coefficient of thermal expansion of the binary composite of BSG + TiO2 increase with decreasing BSG content and increasing the degree of anatase-to-rutile transformation, as well.

The perovskite compounds with the composition of (1 – x) Pb(Ni1/3Nb2/3)O3 –xPbZrO3 have been successfully prepared from hydrothermally treated precursors. During calcination, the primary intermediate compound is pyrochlore phase in the Pb(Ni1/3Nb2/3)O3-rich composition, while it is PbZrO3 on the PbZrO3-rich side. On calcination at 800 °C, all precursors convert into perovskite phases. In the formed solid solutions, increasing PbZrO3 content results in a rise in the apparent Curie temperature as well as the maximum dielectric permittivity. The Pb(Ni1/3Nb2/3)O3-rich perovskites (x < 0.8) possess the characteristics of relaxor ferroelectrics. With increasing PbZrO3 content, the dielectric response gradually becomes less diffuse and dispersive, reflecting a reduction in the relaxor characteristics of the formed perovskites.

We have investigated the effect of oxygen vacancies on imprint and fatigue behavior of the PLZT thin films. It is found that the compensation of oxygen vacancies with various dopant concentrations and electrode structures is an important process parameter in determining the tendency to imprint and fatigue. In the case of PLZT thin films, the voltage shifts related to imprint are attributed to the trapping of electrons at ionic defect sites such as oxygen vacancies near the film/electrode interface, the magnitude of polarization, and concentration of defect-dipole complexes involving oxygen vacancies such as V′Pb–V••o. The strong dependence of fatigue rate on electrode material for PLZT thin films is due to the effect of the ferroelectric/electrode interaction on the pinning and/or unpinning rate involving the accumulation of oxygen vacancies near the film/electrode interface during fatigue cycling. By using RuO2 as the top and/or bottom electrode instead of Pt, improved fatigue properties are obtained compared to Pt/PLZT/Pt capacitors. This is because a reduced accumulation of oxygen vacancies near the interface by the oxide electrode such as RuO2 may reduce the electronic charge trapping and, consequently, lead to less domain wall pinning.

The correlations between coarsening (including grain and pore growth) and densification, and the effects of mass transport on particle coarsening and densification were discussed based on the simple particle array models and for the real particle compacts. Grain boundary motion could cause particle coarsening only under a certain particle size distribution but not densification; mass transport is reasoned to contribute to both grain growth (particle coarsening) and shrinkage for one-dimensional particle arrays. Under a certain limitation for the change of the particle size aspect ratio during sintering, very limited effects of grain grown by itself on the shrinkage of particle a rrays throughreinitiating the sintering could be found. For a real powder compact system, mass transport between the particles, which surround a pore, contributes to the particle coarsening and densification when the pore is thermodynamically unstable and only to particle coarsening when the pore is thermodynamically stable. The mass transport mechanism for both particle coarsening and densification would be the same, which cannot exclude, at least on thermodynamics, the contribution from surface diffusion in the intermediate stage of sintering.

Coarsening (including grain growth and pore growth) and densification behavior of superfine Y-TZP and YSZ powder compacts in the intermediate stage were investigated. It has been found that grain growth in the compacts is basically not affected by the compaction properties, and pore growth is driven by both grain growth and densification. Grain growth alone leads to size-proportional pore growth, and densification results in pore shrinkage. The relation between grain size and density is analyzed to be linear when grain growth and densification are believed to be driven by different stresses under an identical diffusion process. Both theoretical and experimental results show that compaction properties and the heating rate do not alter this linear relation between grain size and density but influence the slope of the linear relation. Larger dihedral angle, higher green density, and narrower particle and pore size distributions are found favorable for the achievement of the grain size-density trajectory with promoted densification and minimized grain growth.

Based on the stability analysis of the closed pores in two dimensions which was determined mathematically with their particle coordination number and dihedral angle, the stability of those in three dimensions was determined with a spherical pore model. The model is set up by first excluding the effect of interface tension, so the pore was supposed to be spherical, and then the tensile stress arisen from the interface tension was supposed to act on this hypothesized spherical pore. On the basis of the spherical pore model, microstructure models based on pores, not grains, for the real powder compacts were first established. Densification kinetics were then determined from the models by the densification rate equations, which were derived by relating density to pore size to grain size ratio, for the intermediate and final stages of sintering. The criteria for pore shrinkage were discussed quantitatively. The derived equations can be used to simulate the relation between densification rate and density during heating with a constant rate and for the explanation of the effects of pore size distribution, agglomerates, and green density on sintering.

A disappearing sintering aid was used to promote densification during the initial and middle stages of sintering and to be removed in gaseous form from the specimens during the final stage of sintering. From thermodynamic consideration such as assessment of Gibbs free energy change of formation of Al2O3 compounds including metal-oxide and evaluation of the vapor pressure of metal-oxide, Li2O is expected to become a disappearing sintering aid for AlN sintering. Doping with Li2O resulted in densification of AlN ceramics with Y2O3 and CaO additives by sintering at a firing temperature of 1600 °C. The amount of Li2O in the specimens decreased by volatilization at temperatures higher than 1300 °C, and its amount was at a level of several ppm after firing at 1600 °C for 6 h. Low-temperature densification of AlN specimens by addition of Li2O also caused the improvement of thermal conductivity and mechanical strength of sintered specimens. Present results indicate that a Li2O addition is effective for AlN sintering. Furthermore, LiYO2 was also used as a new sintering aid instead of Li2O and Y2O3, and the results of thermal conductivity and mechanical strength are shown.

Sodium silicate intergranular films (IGF) in contact with the [0001] basal plane of α-alumina were studied using the molecular dynamics computer simulation technique. The results were compared to previous simulations of calcium silicate and sol-gel silica IGF's in contact with alumina. An ordered, cagelike structure was observed at the interface. Sodium ions segregated to the cages at the interfaces. Calcium and hydrogen ions were also observed to segregate to the cages in the previous simulations. The modifier ions were surrounded by more oxygen ions in the cages at the interface than in the bulk of the IGF. This explains the segregation of modifiers at the interface. Interface energy decreased as the sodium content of the IGF increased. Interface energy decreased faster as a function of Na2O content than as a function of CaO content. However, interface energy decreased slower as a function of Na+ content than as a function of Ca2+content.

This paper aims to investigate the initiation and distribution of dislocations and twins in the subsurface of alumina subjected to single-point scratching and to gain a deeper understanding of the mechanisms of ductile-regime grinding of alumina. It found that there generally exist three regions of dislocation and twin systems in the scratched alumina. The first region contains five independent slip systems so that macroscopic plastic flow is possible there. In the second and third regions, not all the systems can be activated, and then microcracking in the subsurface may occur easily. The distribution of these regions varies with the grain size of alumina. In the 25 μm-grained alumina all three regions appear. Thus, in this case, microcracking is difficult to avoid. In the 1 μm-grained alumina, however, only the first region appears, indicating that the material may be scratched under a real ductile mode without microcracking. A comparison shows that theoretical predictions are in good agreement with experimental observations.

Anodic spark deposition (ASD) is an advanced plasma-electrochemical coating process to prepare polycrystalline, ceramic-like conversion coatings on metal surfaces. As an example, polycrystalline barium titanate (BaTiO3) phases have been prepared by the anodic conversion of metal substrate and the metal ions in the electrolyte. By a combination of various characterization techniques, the configuration of the coating was elucidated. On the metal substrate a thin (~50 nm) passivating amorphous film of titania (TiO2) first forms, which subsequently changes to anatase and rutile structures. With increasing anodic potentials, a plasma-chemical conversion reaction starts, leading to the heterogeneous formation of BaTiO3 layers of 2–10 μm thickness. The results of this study lead to the formulation of a model describing a polycrystalline and inhomogeneous layer configuration.