Composites consisting of nanometer-sized nickel–zinc ferrite and α-iron were prepared by subjecting micrometer-sized ferrite particles to a reduction treatment in the presence of α–Fe2O3. The materials were characterized by x-ray diffraction, electron microscopy, Mossbauer spectroscopy, and magnetization measurements. A wide range of saturation magnetization and coercivity can be obtained by changing the reduction schedule. The reduction process appears to break down the particle size of the precursor powder of nickel–zinc ferrite.

A liquid-precursor process was used to produce an epitaxial all-oxide ferroelectric memory device structure. The lanthanum strontium manganate–lead zirconate titanate–lanthanum strontium manganate (LSMO–PZT–LSMO) structure used for this device shows excellent polarization and fatigue behavior with a remnant polarization Pr of 42 µC/cm2 and a coercive field Ec of 68 keV. The polarization was found to only slightly degrade after over 1010 fatigue cycles. This behavior is contrasted with epitaxial PZT using a metal top electrode. In addition, the use of a top LSMO electrode was a sufficient barrier to Pb loss during heating to allow subsequent (or prolonged) heat treatments that would generally lead to Pb loss.

The seeding effects of (001) Nd123/MgO thin films and MgO single crystals were studied in isothermal solidification of YBa2Cu3Oy composite with the additions of 40 mol% Y2BaCuO5, 10 wt% Ag, and 0.5 wt% Pt. Seeding with the Nd123/MgO thin film resulted in single-domain growth of Y123 crystal with a stable growth along the “100”?direction, while seeding with MgO single crystal produced multidomain growth in which the dominant growth facet is rotated 45° about (100) plane of MgO. Multidomain growth in MgO seeded sample was suppressed by decreasing undercooling degree. The effects of undercooling degree and seed size on multidomain growth are discussed in view of classical nucleation and growth theory.

The microstructure and crystallographic orientation relationship of CaF2–MgO eutectics produced for the first time were characterized by electron microscopy. The eutectic contains single-crystal MgO rods (∼0.7 μm in size, spaced ∼8 μm) oriented parallel to the cubic axis of a CaF2 matrix. The rods present low-energy {100}CaF2 //{111}MgO interfaces. Light guiding was experimentally proved and considered for possible optical applications. Crack propagation was also studied to show the potential improvement in fracture toughness through crack deflection at the interfaces.

The structure of γ–α2 interfaces in deformed Ti–48Al–2Cr alloy was analyzed by high-resolution transmission electron microscopy (HREM) and image simulations. Growth of γ–TiAl plate in α2–Ti3Al phase was found to be a result of a ledge mechanism consisting of Shockley partial dislocations on alternate (0001)α2 planes. The height of the ledges was always a multiple of two (0001)α2 planes. The γ → α2 phase transformation was also an interface-related process. Large ledges of six close packed planes (111)γ high were often observed at the γ–α2 interface. Every large ledge consisted of six Shockley partial dislocations that originated from the γ–a2 interfacial lattice misfit. The movement of these partial dislocations accomplished the transformation of γ → α2 phase. Comparing the experimental and simulated HREM image, it was found that atomic reordering appears during the deformation-induced γ↔α2 transformation.

The effects of SiC-nanoparticle and Si3N4-whisker additions on the microstructural evolution and mechanical properties of Si3N4 were investigated. The addition of SiC nanoparticles suppressed Si3N4 grain growth, leading to an improvement in the flexural strength. On the other hand, Si3N4 whiskers in the specimen promoted the formation of large elongated grains, which were found to be beneficial to the fracture toughness of the material. When both SiC nanoparticles and Si3N4 whiskers were added concurrently, large grains were formed in fine matrix grains. The microstructure of Si3N4 was controlled by adjusting the relative concentrations of SiC nanoparticles and the Si3N4 whiskers added. These compositional and microstructural variations of the Si3N4 had significant influence on the mechanical properties, such as strength, fracture toughness, R-curve behavior, and high-temperature strength.

A series of copper phthalocyanine thin films were prepared on amorphous substrates using physical vapor deposition at ambient temperature. Different sample preparation conditions were used: the deposition rate was varied, and the substrates was static or rotating. The preferred orientation in the thin film was studied as a function of the deposition conditions. X-ray diffraction analysis was performed using θ/2θ and pole figure measurements. In the case of layers prepared at low deposition rates and using nonrotating substrates, a very strong fiber texture was detected with (100) crystallographic planes oriented preferably parallel to the substrate surface. At higher deposition rates, an additional second type of preferred orientation was observed with (110) planes oriented preferably parallel to the substrate surface. In the case of layers prepared with rotational substrates, the (110) type of preferred orientation was quantitatively more strongly developed. If we consider electronic band structure calculations, these results imply that the electron/hole transport through the thin films is enhanced for films prepared at high deposition rates and rotating substrates.

The photoacoustic technique and the thermal relaxation method were used to determine the thermal conductivity of some representative samples obtained from an aluminumsilicon casting alloy A319. This material was solidified with an imposed unidirectional thermal gradient to obtain samples with different microstructures characterized by the secondary dendrite arm spacing, which increases as the solidification rate decreases. It was found that the thermal conductivity of the alloy decreases with an increase in the secondary dendrite arm spacing and a decrease in the integral dendrite perimeter.

Polycrystalline Pb(ZrxTi1−x)O3 thin films with x = 0.6 and 1.0 were deposited at low temperatures (450–525 °C) on (111)Pt/Ti/SiO2/Si substrates by metalorganic chemical vapor deposition. The films were characterized by x-ray diffraction, electron microscopy, and electrical measurements. The texture of the films could be improved by using one of two template layers: PbTiO3 or TiO2. Electrical properties, including dielectric constants, loss tangents, polarization, coercive field, and breakdown field, were also examined. PbZrO3 films on Pt/Ti/SiO2/Si with a pseudocubic (110) orientation exhibited an electric-field-induced transformation from the antiferroelectric phase to the ferroelectric phase. The effect of varying processing conditions on the microstructure and electrical properties of the films is discussed.

The role of matrix microstructure on the fracture of Al-alloy composites with 60 vol% alumina particulates was studied. The matrix composition and microstructure were systematically varied by changing the infiltration temperature and heat treatment. Characterization was carried out by a combination of metallography, hardness measurements, and fracture studies conducted on compact tension specimens to study the fracture toughness and crack growth in the composites. The composites showed a rise in crack resistance with crack extension (R curves) due to bridges of intact matrix ligaments formed in the crack wake. The steady-state or plateau toughness reached upon stable crack growth was observed to be more sensitive to the process temperature rather than to the heat treatment. Fracture in the composites was predominantly by particle fracture, extensive deformation, and void nucleation in the matrix. Void nucleation occurred in the matrix in the as-solutionized and peak-aged conditions and preferentially near the interface in the underaged and overaged conditions. Micromechanical models based on crack bridging by intact ductile ligaments were modified by a plastic constraint factor from estimates of the plastic zone formed under indentations, and are shown to be adequate in predicting the steady-state toughness of the composite.

Surface oxidation of an iridium film and the possibility of epitaxial growth of PZT spin-coated film on sputtered iridium were investigated. The free surface on the iridium film oxidized over 400 °C with random orientation. Nevertheless, both the PZT(111)/Ir(111) and PZT(100)/Ir(100) interfaces were realized using the highly oriented iridium layer. These results suggest that PZT nucleation has priority over iridium surface oxidation.

Precursor powders with antimony-to-iron (Sb/Fe) atomic ratios ranging from 0 to 2.0 were prepared by chemical coprecipitation. The origin of enhanced gas-sensing behavior at a higher calcining temperature was investigated, based on phase evolution and microstructure characterized by means of thermal analysis, x-ray diffraction, Brunauer–Emmett–Teller surface area measurement, and electron microscopy. Only one iron–antimony oxide (i.e., FeSbO4) could be obtained under present experimental conditions. Pure FeSbO4 exhibited a high gas sensitivity, only when calcining temperature was below 600 °C. A rapid crystallite growth, as well as hard agglomeration, occurred in pure FeSbO4 powder calcined at 600–1000 °C, and thus led to poor gas-sensing behavior. However, there existed an optimal Sb/Fe ratio range (i.e., 0.25 to 0.65) in which crystallite growth of both α–Fe2O3 and FeSbO4 could be efficiently depressed up to 800 °C. The samples (with Sb/Fe ratio in the range 0.25–0.65) calcined at 600–800 °C displayed a high sensitivity to liquid petroleum gas due to their large specific surface area and poor crystallinity.

This work deals with the measurement of pyrocarbon anisotropy on very thin fiber coatings used to control the interfacial behavior in carbon/carbon composites. Differentiation of the various pyrocarbons was performed through computerized image analysis of the electron diffraction patterns by measuring the azimuth opening of the carbon 002 diffraction arcs. This orientation angle decreases when the texture switches from rough to smooth laminar. The relationship with the polarized light measurement technique at a lower resolution is discussed.

The electrical conductivity of discontinuous filament–reinforced unidirectional composites was investigated. The discontinuous reinforcement used was copper filament, and the matrix materials included solder and epoxy. It was found that the composite conductivity increases with filament length and eventually becomes a constant. Such behavior is described by introducing an interface impedance and the principle of rule of mixture. It was found both experimentally and theoretically that there exists a critical filament length that must be exceeded so the composites will exhibit conductivity as composites having continuous reinforcing filaments.

Chemical coprecipitation was employed to prepare fine particles of barium ferrite with high coercivity (450 kA/m). Magnetic properties of the bonded barium ferrite magnet were measured at different temperatures. The results were found to be fairly close to the theoretical values based on the Stoner–Wohlfarth model. Mechanical milling was utilized to prepare ultrafine dispersed barium ferrite particles. NaF was introduced as a dispersing agent during milling and subsequent heat treatment. The dispersed particles were compacted and then subjected to die upsetting at room temperature. A weak anisotropy in the coercivity and remanence was found in the directions parallel and perpendicular to the compaction direction.

We prepared Ce3+-doped silica by the sol-gel method and studied the effect of annealing on fluorescence of these samples. Different fluorescence was observed for samples annealed at different temperatures, changing gradually from solution like fluorescence to fluorescence similar to that observed in the Ce3+-doped silica prepared by chemical vapor deposition. It was found that the emission intensity first decreased with increasing annealing temperature until 500 °C, and then increased with the temperature ranging from 500 to 950 °C. Meanwhile, the emission peak showed a large red shift and an obvious broadening. These changes were attributed to the annealing-induced structural evolution in silica: Ce3+ ions changed from coordinating with water and terminal OH-groups to embedding in silica network.

Pure stoichiometric ZrO2 films were deposited on amorphous silica substrates by electron beam evaporation of Zr in the presence of an electron cyclotron resonance oxygen plasma. Grain size, strain, and texture were analyzed by x-ray diffraction and reflection high-energy electron diffraction. Films grown at room temperature are polycrystalline and exist in the cubic phase. Growth at elevated temperatures produces coexisting cubic and monoclinic phases and shows a maximum critical grain size of ??~10 nm for stabilization of the cubic phase. Pole figure analysis indicates a preferred cubic [200] fiber axis for room-temperature growth and dual monoclinic {111} and in-plane textures for films grown at 400 °C. Postdeposition annealing experiments confirm the existence of a critical grain size and suggest mechanisms for grain growth.

Recently we showed that, under nonhydrostatic loading, the FR1 →AO polymorphic transformation of unpoled lead zirconate titanate 95/5-2Nb (PNZT) ceramic began when the maximum compressive stress equaled the hydrostatic pressure at which the transformation otherwise occurred. More recently we showed that this criterion seemed not to apply to poled ceramic. However, unpoled ceramic is isotropic whereas poled ceramic is not. If we further assume that the transformation depends on both the stress magnitude and its orientation relative to PNZT's structure, these disparate results can be resolved. This modified hypothesis makes two predictions for transformation of unpoled ceramic under uniaxial compression: (i) it will begin when the compressive stress equals the hydrostatic pressure for transformation, and (ii) steadily increasing stress will be required to drive it to completion. Here we present experimental results that confirm these predictions. We then revisit our earlier results for poled and unpoled PNZT. The new hypothesis quantifies the observed effect of shear stress on the mean stress for onset of the transformation of unpoled ceramic and explains previously reported kinetic effects.

Potassium tantalate thin films (KT) were hydrothermal-electrochemically and electrochemically synthesized on tantalum substrates under galvanostatic conditions in KOH solutions at temperatures from 50 to 150 °C. The pyrochlore structures were characterized by x-ray diffraction and scanning electron microscopy for the films formed under a variety of conditions. It was found that the reaction temperature, potassium hydroxide concentration, and current density significantly affect the formation and the morphology of the KT films. When the reaction temperatures were higher than 80 °C and the KOH concentrations were greater than 2.0 M, very crystalline films with excellent film flatness and good adherence on the substrate were obtained. Based on the experimental results, it was confirmed that the formation and growth of KT films by the hydrothermal-electrochemical and electrochemical method follow a dissolution-crystallization mechanism.

Tantalum zinc oxide (TZO) with the chemical formula Ta2Zn3O8 can be generated from the reaction of 3 mol ZnO and 1 mol Ta2O5 at elevated temperatures. This phase has been shown to exhibit blue cathodoluminescence at low electron beam voltages. It has also been realized in thin film form on silicon substrate, making TZO an important material for monolithic field emission display devices. The structure type of TZO has been investigated using powder x-ray diffraction techniques. The unit cell of this phase has been determined and found to be monoclinic. These results allow for indexing of the powder pattern first reported by Kasper in 1967 and correct for a discrepancy in the single-crystal structure lattice constants reported by Waburg and Muller-Buschbaum in 1984.