Ultrafine BaFe12O19 powder with crystallite sizes less than 200 nm was prepared via a citric acid precursor method. Citric acid was added into an aqueous solution, containing nitrates of Ba2+ and Fe3+ in a stoichiometric ratio to form barium ferrite, to chelate metallic ions in the solution. The pH of aqueous solutions was adjusted with NH4OH. After ethylene glycol was added into the solution and the system temperature was raised, esterification and dehydratation led to the formation of solid ester precursor. The distribution and contents of metallic ions in the ester are affected by the [citric acid]/[metallic ions] molar ratio used and the pH of starting solutions. When the ester-precursor obtained at pH = 9 with [citric acid]/[metallic ions] = 1.5 was used, crystalline BaFe12O19 appeared at temperatures as low as 923 K, and pure barium ferrite was obtained at 1073 K. According to the experimental results obtained, the reaction mechanism involved in the pyrolysis of esters is proposed and discussed.

We investigated the dependence of critical current density (Jc) on thickness of Yba2Cu3O7−δ (YBCO) films grown by pulsed laser deposition on (100) SrTiO3 (STO) and on rolling-assisted biaxially textured substrates (RABiTS). The thickness of YBCO films varied from 0.19 to 3 μm. The highest Jcs of 5.3 and 2.6 MA/cm2 at 77 K, self-field were obtained for 0.19-μm YBCO films on STO and RABiTS, respectively. Jc was found to decrease exponentially with YBCO thickness on both substrates. However, the results suggest different mechanisms are responsible for the Jc reduction in the two cases. On STO, growth of a-axis grains within c-axis films and broadening of the in-plane texture were observed in thick films. On RABiTS, degradation in cube texture as well as development of a porous surface morphology were found to correlate with film thickness.

TiO2 was deposited onto hard alumite (Al/Al2O3/TiO2) by alternating current electrolysis and precipitation in (NH4)2[TiO(C2O4)2] solution at various temperatures, where the hard alumite was prepared by the anodic oxidation of aluminum in sulfuric acid (Al/Al2O3). The TiO2 electrodeposition mainly occurred at temperatures lower than about 50 °C, while the TiO2 deposition due to TiO(C2O4)22− adsorption onto alumina predominantly occurred at temperatures higher than about 50 °C. The amount of deposited TiO2 increased with the increase in the deposition temperature, leading to high photocatalytic activity. The deposited TiO2 at 90 °C followed by heat-treatment at 550 °C had an anatase structure and showed a high photocatalytic activity for the decomposition of acetaldehyde even under fluorescent lamp illumination. The Al/Al2O3/TiO2 prepared at 50 °C was optimal for practical use, because of a relatively high activity and the sufficient adhesion strength between the TiO2 and the Al/Al2O3 substrate due to the presence of the deposited TiO2 in the pores of the alumina film.

Crystalline, pure or Mn-doped ZnGa2O4 powders have been prepared in situ in urea (with or without enzyme urease)-containing Zn and Ga nitrate (and Mn nitrate) solutions by simply holding those for 24–48 h, at 90 °C, in screw-capped glass bottles in a constant-temperature laboratory oven. Single-phase pure or Mn-doped zinc gallate powders synthesized with the spinel crystal structure had an average particle size around 15 to 18 nm. Powders were characterized by x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectroscopy, inductively-coupled plasma atomic emission spectroscopy, simultaneous thermogravimetry and differential thermal analysis, Fourier-transformed infrared spectroscopy, and carbon and nitrogen analyses. Calcination behavior of the as-filtered powders was later studied in an air atmosphere over the temperature range of 90 to 1200 °C.

Phase composition, degree of cation ordering, and dielectric properties of complex perovskites with general formula Ba(B' 1/3B"2/3)O3, where B′ = Mg, Zn, and Ni and B" = Nb and Ta, were analyzed. It was found that all the studied complex perovskites attained high degrees of 1:2 cation ordering at temperatures specific to each composition. A high temperature order–disorder phase transition in Ba(Zn1/3Nb2/3)O3 occurred below 1380 °C. Ba(Ni1/3Nb2/3)O3 (BNN) and Ba(Mg1/3Nb2/3)O3 (BMN) pervoskites remained 100% ordered at temperatures as high as 1500 and 1620 °C, respectively. It was found that in BMN and BNN extrinsic factors, such as the second phase (i.e., Ba3Nb5O15) and point defects, dominated the dielectric loss at microwave frequencies. Ba(Mg1/3Ta2/3)O3 (BMT) remained single phase up to 1630 °C. Above this temperature, the Ba3Ta5O15 second phase was detected. A decrease in the 1:2 cation ordering and increase of dielectric loss in BMT occurred at sintering temperatures above 1590 °C. It was also revealed by electron paramagnetic resonance that all samples studied contained a substantial amount of paramagnetic point defects. These defects contributed to extrinsic dielectric loss at microwave frequencies, thus degrading the Q factor.

Diamondlike carbon (DLC) films were grown on Si and ceramic substrates by very-high-frequency chemical vapor deposition at temperature of approximately 250 °C. Thin metal coatings from Ti, Ni, Pt, and Cu were deposited on the substrates before DLC film deposition. The impact of the pregrowth treatments of the substrates on surface morphology and emission properties of the grown DLC films was studied. The films deposited on ceramic substrates pretreated by Ti, Ni, and Pt coatings, with grainlike structures, demonstrated good emission currents and low threshold voltages among the deposited DLC films.

The formation of superconducting YBa2Cu3O7–x (Y123) by in situ pulsed laser deposition from a stoichiometric Y123 target typically requires an oxygen-ambient environment (P ˜ 100–300-mtorr O2) and appropriate substrate temperature during deposition. We have found that pulsed laser deposition from a Y123 target in vacuo onto a (001) LaAlO3 substrate favors the formation of Y2O3. We observed that the Y2O3 (001) films yield three-dimensional nanoscale morphologies that are markedly different from the planar growth surface of conventional superconducting c-axis Y123 films and Y2O3 films formed from the pulsed laser ablation of a Y2O3 target.

The synthesis and luminescent properties of (Y,Gd)BO3:Eu phosphor were investigated. A coprecipitation method was designed for preparing Eu doped (Y,Gd)BO3. This method features a low-temperature formation of single phase with semi-spherical shape compared with the conventional method. Due to the homogeneous distribution of activator, the emission intensity of the (Y,Gd)BO3:Eu phosphor prepared by the coprecipitation method is higher than the commercially available red phosphor.

We have developed a real-time phase-shifting interferometer capable of imaging interfacial morphology with a depth resolution of approximately 25 Å, with a lateral resolution of approximately 0.5 μm across a field of view of 2 × 2mm2, and with time resolution of 0.1 s. The method is applied in situ to the (101) face of potassium dihydrogen phosphate crystals growing from an aqueous solution. We image the formation and evolution of solution-flow-induced step bunches and determine their characteristic wavelength to be λc = 45 μm. This wavelength is within the range predicted by a stability theory on the basis of the balance between the diffusion interaction between steps and capillarity. The value of λc suggests that step–step interactions are the likely major factor for instability.

The mechanism of reactive wetting of metal/ceramic was investigated on the basis of a detailed description of the thermodynamics of interfacial reactions. The interfacial reaction of the metal/ceramic system has been treated as the reaction between the surface phase of the metal matrix and that of the substrate. It is concluded that reactive wetting is governed not only by the term accounting for the intensity of interfacial chemical reactions but also by the term accounting for the physicochemical properties of the resulting interface. In some cases, only one of them contributes dominantly to wetting. The criteria for the choice of an alloying element to promote wetting should not only include its reactivity with the substrate but also its ability to favorably modify the metal/substrate interface.

An AlN ceramic fired at 2173 K for 100 h under a reduced N2 atmosphere with carbon possessed a room-temperature conductivity of 272 Wm−1K−1, slightly lower than the value for high-purity, single-crystal AlN. However, the thermal conductivity of the ceramic at temperatures below 100 K was much lower than that of single crystal. This is mainly due to phonon scattering by grain junctions that possess an amorphous film with a thickness of under 1 nm. At 500 to 1000 K, no significant difference in the conductivity was observed between the ceramic and the single crystal.

Formation of bulk Fe-based glassy alloys with high corrosion resistance was succeeded in the Fe75–x–yCrxMoyC15B10 alloy system. A large temperature interval of supercooled liquid region (ΔTx) of 40–90 K was obtained over a wide composition range for the Fe75?x–yCrxMoyC15B10 alloys. The Fe75–x–yCrxMoyC15B10 alloys were prepared in a bulk glassy form with diameters of 1.0–2.5 mm by copper mold casting. The bulk glassy Fe75–x–yCrxMoyC15B10 alloys exhibited high corrosion resistance in 1 N HCl solution. The glassy alloys containing Cr were spontaneously passivated with a wide passive region before the transpassive dissolution of Cr. The passive current density decreased significantly with an increase of alloying Cr content, indicating that the addition of Cr was effective on enhancing the corrosion resistance. Excess addition of Mo for replacing Fe in the present alloys was detrimental for the corrosion resistance.

Intercalation of EuCl3 TbCl3, and AlCl3 into graphite was carried out in the presence of chlorine. The observation of products by x-ray diffraction showed that the extent of chloride intercalation could be controlled through adjustment of the pressure of chlorine; increasing pressure tended to increase the extent of intercalation. In the case of EuCl3, the extent of intercalation varied to show a stage transition. In contrast, TbCl3 intercalation gave a mixture of stage 2 or stage 4 graphite intercalation compound (GIC) and remaining graphite, where the extent of intercalation is revealed by the ratio of GIC to graphite. With respect to AlCl3 intercalation, although the preparation of stage 1, 2, and 4 GICs was successful, stage 3 and 5 GICs could not be obtained.

The flow of gas-phase products in three-dimensional porous bodies was modeled for the case when a source term is present. Analytical solutions to the governing partial differential equations were obtained for bodies of parallelepiped and cylindrical geometry. An important feature of the model is that it treats the case where the permeability in the body may be anisotropic. The evolution of pressure within the body depends on a number of parameters, including the rate of production of gas-phase species, and on the dimensions of the body. The model is thus able to describe the pressure within a porous ceramic body arising from flow during a number of elevated-temperature processing operations such as drying, binder burnout, and sintering.

The electrical behavior during compaction of tantalum and aluminum powders was characterized before and after thermal oxidation. The resistivity of unoxidized powders decreased by >106 over a narrow range of stress between 1 and 10 MPa. Thermal oxidation of the powders to produce submicrometer thick oxide layers on the particles increased the precompaction electric breakdown strength from <0.2 to >5 kV/cm but did not have a significant effect on the low field resistivity of the powders during compaction. At higher fields, the decrease in resistivity during compaction occurred at lower stresses and over a much narrower stress range since catastrophic electrical breakdown occurred once a certain level of stress was reached. The breakdown field at constant stress also decreased as the stress was increased for the oxidized powders. These effects are caused by the cracking of the brittle oxide coatings at the contact points between the particles during compaction.

Microstructure in the SrTiO3/Si system has been studied using high-resolution transmission electron microscopy and image simulations. SrTiO3 grows heteroepitaxially on Si with the orientation relationship given by (001)STO//(001)Si and [100]STO//[110]Si. The lattice misfit between the SrTiO3 thin films and the Si substrate is accommodated by the presence of interfacial dislocations at the Si substrate side. The interface most likely consists of Si bonded to O in SrTiO3. The alternative presentation of Sr and Si atoms along the interface leads to the formation of 2× and 3× Sr configurations. Structural defects in the SrTiO3 thin film mainly consist of tilted domains and dislocations.

The effects of thermal treatment on the properties and photoactivities of TiO2 catalysts supported on 316 stainless steel plates were examined. Degussa P-25 was immobilized on 316 stainless steel plates by electrophoretic deposition. These TiO2-coated plates were heated at 473, 673, and 873 K for 1 h. The photoactivities of these TiO2 coatings were determined based on the removal of benzoic acid as the model pollutant. In particular, the photoactivity decreased by 52% in the sample heated at 873 K compared with the unheated sample. The results of x-ray diffraction showed that the crystallinity and the crystallite sizes of the catalysts supported on the plates did not significantly vary with increasing temperature over the range examined. Negligible change in the catalyst phase (the anatase-to-rutile ratio) was indicated from x-ray diffraction and micro-Raman spectroscopy. However, it was found that the Brunauer–Emmett–Teller surface area of the scraped catalysts heated at 873 K decreased by nearly 13% compared with the unheated sample. In addition, scanning electron microscopy/energy dispersive x-ray and x-ray photoelectron spectroscopy analyses also detected the presence of Fe3+ ions at the surface of the supported catalysts heated at 873 K. The drop in surface area and the presence of Fe3+ ions at the catalyst surface, which were considered to function as electron–hole recombination centers, were possible factors leading to the drop in the photoactivity exhibited by the sample. A lower temperature for thermal treatment such as 473 K was proposed to ensure the coating stability and the catalyst photoactivity.

The physical layering of sol-gel-derived lead zirconate titanate (PZT) 52/48 and lanthanum-doped PZT (PLZT) 2/52/48 on platinized silicon substrates was investigated to determine if the ferroelectric properties and fatigue resistance could be influenced by different layering sequences. Monolithic thin films of PZT and PLZT were characterized to determine their ferroelectric properties. Sandwich structures of Pt/PZT/PLZT/PLZT/PZT/Au and Pt/PLZT/PZT/PZT/PLZT/Au and alternating structures of Pt/PZT/PLZT/PZT/PLZT/Au and Pt/PLZT/PZT/PLZT/PZT/Au were then fabricated and characterized. X-ray photoelectron spectroscopy depth profiles revealed that the layering sequence remained intact up to 700 °C for 45 min. It was found that the end layers in the multilayered films had a significant influence on the resulting hysteresis behavior and fatigue resistance. A direct correlation of ferroelectric properties and fatigue resistance can be made between the data obtained from the sandwiched structures and their end-layer monolithic thin film counterparts. Alternating structures also showed an improvement in the fatigue resistance while the polarization values remained between those for PZT and PLZT thin films.

Fracture and deformation in model brittle-outerlayer/metal-core/polymer-substrate trilayer systems in concentrated loading are studied. Model systems for experimental study are fabricated from glass microscope slides glued with epoxy adhesive onto steel and aluminum sheets, and the resulting laminates glued onto polycarbonate substrate bases. Critical loads to initiate two basic fracture modes in the glass layers—cone cracks at the top surfaces and radial cracks at the undersurfaces—are measured as a function of metal thickness by in situ observation through the glass side walls. Finite element modeling (FEM) is used to quantify these competing fracture modes. The more damaging radial fracture mode is attributed to flexure of the glass layers on soft underlayers. Although much of this flexure can be eliminated by removing the soft adhesive interlayer between glass and metal, yield in the metal limits the potential increases in critical load for radial cracking. Trilayer systems consisting of porcelain fused to Co-, Pd- and Au-alloy core support layers relevant to dental crowns are then analyzed by FEM. The hardness (especially) and elastic modulus of the metal are identified as the primary controlling material parameters, with modulus and strength of the brittle layer as supplemental parameters. Guidelines for improving metal-based crownlike layer structures are thereby developed via optimization of metal properties and relative layer thicknesses.

The dielectric properties of the Ba(Ti1–xZrx)O3 (BT1–xZx) ceramics with various compositions were investigated under various DC bias fields. In BT0.94Z0.06 ceramics, the dielectric constants (ε) vs temperature (T) curves without DC bias showed no frequency dependence. Its DC bias dependence exhibited that with increasing DC bias fields, the dielectric constants were suppressed while phase transition peaks slightly shifted to high temperature. In BT0.58Z0.42 ceramics, the ε vs T curves without DC bias showed a broad peak with a clear frequency dependence, which revealed that BT0.58Z0.42 ceramics were the relaxor. Its DC bias dependence exhibited that with increasing DC bias fields, the dielectric constants were suppressed while the phase transition peak largely shifted to low temperatures. In BT0.79Z0.21 ceramics, the ε vs T curves without DC bias showed a broad peak without frequency dependence. Its DC bias dependence revealed that the dielectric peak shifted to high temperature and broadened with increasing DC bias. To explain the above phenomena, it was considered that the role of Zr ions on BT1−xZx ceramics is to make the depth of the potential well shallow successively.