The possibility of an in situ toughening through the β → α phase transition was evaluated on liquid-phase-sintered SiC (with Al2O3 and Y2O3 as additives). Dense hot-pressed materials with an equiaxed morphology were annealed at 1850, 1900 and 1950 °C for 1 to 4 h so the effect of time, temperature, composition, and amount of second phase could be investigated. Microstructure features revealed that 1900 °C was the best temperature in producing a high percentage of elongated grains with limited grain coarsening and reduction of second-phase pockets. Mean grain size and aspect ratios increased from 0.5 to 1.5 μm and to 5, respectively, during the first 2 h of treatment at 1900 °C and then maintained a constant value. The amount and composition of second phase influenced the rate of transformation from equiaxed to elongated grain morphology. Toughness increased from 3.3 to 5.5 Mpa · m1/2 in 1900 °C annealed samples due to a crack-deflection mechanism.

Forced hydrolysis preparation of zirconia sols and powders by microwave heating of zirconium tetrachloride solutions at temperatures equal to 180 °C leads in a few minutes to monodispersed nanoscale zirconia particles. Synthesis was performed in a microwave reactor called the RAMO system. This microwave reactor was designed by the authors. This flash-synthesis process combines the advantages of forced hydrolysis (homogeneous precipitation) and microwave heating (very fast heating rates). The sols and powders were characterized by x-ray diffraction,photon correlation spectroscopy (PCS), small-angle x-ray scattering, and transmission electron microscopy. Sols are colloidally stable, which means that after 6 months no sedimentation is observed and the size distribution given by PCS measurements has not changed. For all synthesis conditions (with or without HCl, zirconium salt concentration, and synthesis time), zirconia polycrystalline particles were produced. According to the different analyses, these zirconia polycrystalline particles were constituted of aggregates of small primary clusters.

The microstructure and shear strength changes of SnAgCu/Cu and SnAgCu/Ni–P/Cu surface mount solder joints during thermal aging at 150 °C and thermal cycling between ?40 and 150 °C were investigated. The reaction rate between SnAgCu and Cu is higher than that between SnAgCu and Ni–P. After long aging time, the SnAgCu/Cu interface becomes the weakest region in the SnAgCu/Cu solder joint, whereas the shear-force-induced cracks in the SnAgCu/Ni–P solder joint appear at the interface of Ni–P/Cu. During thermal cycling, cracks develop in both solder joints and the shear strength decreases. After extensive thermal cycling, the Ni–P layer separates from the Cu substrate and the shear strength of the SnAgCu/Ni–P solder joint decreases drastically.

Highly conductive iridium dioxide (IrO2) thin films have been deposited onto in situ oxidized Si(100) substrates by means of a reactive pulsed laser deposition (PLD) process. The polycrystalline IrO2 films were obtained by ablating a metal iridium target under an optimal oxygen background pressure of 200 mtorr and at different substrate deposition temperatures (Td ) ranging from 350 to 550 °C. Conventional and high-resolution transmission electron microscopy (HRTEM) techniques were used to investigate the micro- and nanostructural changes of the PLD IrO2 films as a function of their deposition temperatures. The microstructure and the morphology of the PLD IrO2 films was found to change drastically from an irregular and loosely packed columnar structure at Td = 300 °C to a uniform and densely packed columnar structure for higher Td (≥350 °C). For IrO2 films deposited in the 350 ≤ Td ≤ 550 °C range, HRTEM have revealed the presence of highly textured arrangements of almost spherical IrO2 nanograins (of 3–5 nm diameter, regardless of Td) in the columns (of which diameter was found to increase from 85 ± 15 to 180 ± 20 nm as Td increases from 350 to 550 °C). Lattice resolution and dark-field imaging have pointed out the presence of large IrO2 crystallites made of many similarly oriented nanograins (i.e., under the same Bragg diffraction conditions). Moreover, a high continuity of the lattice planes across the entire crystallite was clearly observed. This latter aspect together with the highly textured nanostructure of the IrO2 films correlate well with their high conductivity (42 ± 6 μω cm for Td ≥ 400), which was found to be comparable with that of bulk single-crystal IrO2.

This article describes the preparation of gradient porosity thermoset polymers. The technique used is based on polymerizing a solution of cross-linkable dicyclopentadiene and 2-propanol. The forming polymer being insoluble in 2-propanol, phase separation occurs. Subsequent drying of the 2-propanol gives porosities up to 80%. An apparatus was built to produce a gradient in 2-propanol concentration in a flask, resulting in polymerized gradient porosity rods. The resulting materials have been characterized by scanning electron microscopy (SEM) and density measurements. A mathematical model which allows prediction of the gradient produced is also presented.

Gas effusion measurements on zinc phthalocyanine (ZnPc) layers showed the presence of a significant amount of oxygen and water inside the material during exposure to ambient conditions. Of both species the bulk concentration lay in the range of 1020 molecules per cm3. Temperature-dependent analysis indicated that at 296 K all O2 molecules, and roughly one half of the H2O molecules, were mobilized and diffused with diffusion coefficients DO2 of 3 ∗ 10−8 cm2/s and DH2O of 1.3 ∗ 10−10 cm2/s. Electrical analysis of ZnPc layers in controlled atmospheres revealed that the electrical properties of the bulk were determined by O2, whereas H2O influences the surface conductivity. A space-charge density of (1.6 ± 0.2) ∗ 1016 O2− ions per cm3 was measured in atmospheric conditions.

Coordination structures of implanted Fe, Co, and Ni ions were studied in 1.78–2.00-MeV 5 × 1016 ions/cm2-implanted silica glasses by x-ray absorption and optical absorption spectroscopies. It was found from x-ray absorption spectra that the implanted Fe, Co, and Ni ions are coordinated by ca.3 oxygen atoms. The implanted ions dispersed in glass matrix and did not form crystals. The valence of the implanted ions was about 1.5. The Fe–O, Co–O, and Ni–O interatomic distances were 190, 191, and 192 pm, respectively. In addition, it was found from optical absorption spectra that one-fifth of implanted Co ions were present as Co2+ ions in tetrahedral symmetry.

Matrix-assisted pulsed laser evaporation direct-write (MAPLE-DW) is a laser-based method of directly writing mesoscopic patterns of electronic materials. Patterns of composite BaTiO3/SiO2/TiO2 dielectric material were written onto Pt/Au interdigitated-electrode test structures, with precise control over final dielectric properties. Scanning electron microscopy indicates random close-packed structures of BaTiO3 and SiO3 particles, with interstitial spaces partially filled with titania. Depending on the BaTiO3:silica ratio, the dielectric constant ranged from 5 to 55 and followed a 4-component logarithmic rule of mixing. This work demonstrates that the transfer process and the final material properties of MAPLE-DW oxide materials are largely decoupled.

Commercial micrometer Al2O3 powder was sintered at 1550 °C under a mechanical pressure of 30 MPa by pulse electric current sintering (PECS). Microstructure observation was performed on polished, thermal-etched cross sections parallel to the direction of mechanical pressure. Platelike Al2O3 grains formed when the powder was heated at a heating rate of 5 °C/min, while a heating rate of 200 °C/min resulted in equiaxed grains. These results indicated that PECS is an effective approach to hinder grain growth by application of a higher heating rate. However, Al2O3 grains at the upper edge were larger than those at the side edge of the samples in both cases. It implied that there were different temperatures at the upper edge and the side edge of the Al2O3 powder compacts during the PECS process.

The high degree of mixing of W and Cu phases in copper tungstates makes them an attractive source for manufacturing W–Cu composite powders. Hydrogen reduction of copper tungstates provides composite W–Cu powder products with a uniform, homogeneous dispersion of the metal phases. This paper presents test results for a variety of solid-phase reactions to synthesize cupric tungstate (CuWO4). Hydrated, dehydrated, and complex oxides of tungsten and copper have been used as solid reactants. With stoichiometric ratios of reactants, synthesis in air at 800 °C produced 96% to 100% conversion to CuWO4. Heterogeneous synthesis of CuWO4 with the participation of three solid phases (S1 + S2 →S3) required the simplest, most inexpensive equipment. The end product properties of synthesized CuWO4 could be controlled by the proper choice of reactants.

The effect of composition on the thermal properties and the spontaneous emission probabilities of various 0.5 mol% Tm2O3 containing (1 − x)TeO2 + (x)LiCl glasses were investigated using differential thermal analysis (DTA) and ultraviolet–visible– near-infrared (UV/VIS/NIR) absorption measurements. DTA curves of the samples were obtained in the 23–600 °C temperature range with a heating rate of 10 °C/min. The value of the glass transition temperature Tg and the crystallization temperatureTc were found to vary with the glass composition. Melting was not observed for the glasses containing less than 50 mol% LiCl in this temperature range. However, a melting peak was observed at Tm = 401 °C for the glasses having higher than 50 mol% LiCl, which were also found to be moisture-sensitive. Absorption measurements in the UV/VIS/NIR region were used to determine spontaneous emission probabilities for the 4f−4f transitions of Tm3+ ions. Six absorption bands corresponding to the absorption of the 1G4, 3F2, 3F3, 3F4, 3H5, and 3H4 levels from the 3H6 ground level were observed. An integrated absorption cross section of each band, except that of 3H5 level, was found to vary with the glass composition. The role of the Judd–Ofelt parameters and therefore the effect of the glass composition on the radiative transition probabilities for the metastable levels of Tm3+ ions are discussed in detail.

Exposure of benzyldimethylketal (BDK)-doped sol-gel hybrid glass films to ultraviolet light produces a refractive index increase up to 43 × 10−3 and an increase in thickness due to photolocking of the BDK into the sol-gel hybrid glass matrix. Thus, single mode ridge waveguides at λ = 1550 nm can be fabricated by direct laser exposure without using photomask and development processes. The slower laser writing speed gives greater refractive index change producing more circular guided mode profiles.

To develop a highly sensitive gas sensor monitoring NOx, various kinds of n-type semiconductors made of In2O3 were prepared, and the relations between doped elements and gas sensitivities or response times were studied. Consequently, it was found that the samples doped with less than 1 at.% alkali-earth metal components have high sensitivities and responsiveness. The gas-absorbing phenomena were investigated using highly sensitive thermal analysis. From the result, it was indicated that alkali-earth component-doped In2O3 materials have higher adsorption ability of NOx than pure In2O3 has.

Using a new composite flux and an improved growth process, large and high-quality ferroelectric SrBi2Ta2O9 (SBT) single crystals (up to 25 × 20 mm2 area) were successfully grown from high-temperature solutions. The effects of chemical, thermodynamic, and kinetic parameters on the growth results were systematically studied. The optimum system for the growth of SBT crystals has been identified. B2O3 additive was shown to play an important role in improving the effectiveness of the Bi2O3 solvent. The grown SBT single crystals exhibit a dominant (001)-orientation and large single-domain areas. The dielectric and ferroelectric properties measured in relation to crystal orientations have confirmed the absence of any polarization component normal to the (Bi2O2)2+ sheets of the structure, indicating a high anisotropy in the properties.

Experimental evidence of transient self-dewetting of metallic surfaces is presented. Steel surfaces are melted by a pulsed electron gun, and the subsequent fast cooling against its substrate gives rise to the formation of characteristic patterns that we attribute to the dewetting of the liquid film. The patterns formed are similar to those obtained by spinodal dewetting, that is, when the dewetting action develops from a nonlinear instability on the liquid surface, and not from holes nucleation. High-purity iron does not show a similar behavior, indicating that the origin of the instability is due to the influence of the sulfur in the temperature dependence of the surface tension of the melt, which gives rise to a Be’nard-Marangoni instability.

The relationships among structure and properties have been established in copolymers of ethylene and 1-octene, synthesized by a particular metallocene catalyst system. The most important factor affecting the structure and properties of these copolymers is, evidently, the comonomer content. However, the cooling treatment from the melt has been found to be also a very significant factor and, although its influence on the thermal properties is rather small, some structural parameters and the viscoelastic behavior are clearly dependent upon thermal history. These parameters include the degree of crystallinity, lattice constants, relaxation processes, stiffness, and microhardness of the samples. Regarding the viscoelastic behavior, the β relaxation is shifted to lower temperatures and its intensity is increased as 1-octene content raises. On the other hand, the α mechanism, associated with motions within the crystalline regions, is also moved to lower temperatures. Such a relaxation is only observed up to a certain 1-octene content in the copolymer.

The enthalpies of formation for the compounds (RE3+)PO4, (where RE = Sc, Y, La–Nd, Sm–Lu) were determined by oxide-melt solution calorimetry. Calorimetric measurements were performed in a Calvet-type twin microcalorimeter in sodium molybdate (3Na2O · 4MoO3) and lead borate (2PbO · 2B2O3) solvents at 975 K. The experiments were carried out using both powdered single crystals grown by a flux technique and powders synthesized by precipitation. Formation enthalpies were derived from the drop-solution enthalpies for (RE)PO4, RE oxides, and P2O5. Enthalpies of formation for the (RE)PO4 compounds with respect to the oxides at 298 K become more negative with increasing RE3+ ionic radius; i.e., in going from ScPO4 (−209.8 ± 1.0 kJ/mol), to LuPO4 (−263.9 ± 1.9 kJ/mol), to LaPO4 (−321.4 ± 1.6 kJ/mol). From structural considerations, a similar trend is expected for the isostructural RE vanadates and arsenates, as well as for the tetravalent actinide orthosilicates.

The relationship between the dielectric properties of the complex perovskite (Pb1−xCax)(Mg0.33Ta0.67)O3 ceramics, where 0.45 ≤ × ≤ 0.60, and the dielectric polarizability, related to bond valences of A-site ions, was investigated at microwave frequencies. As the Ca content (x) increased, the deviation of the observed dielectric polarizabilities, calculated by the Clausius–Mosotti equation from the theoretical values calculated by the additivity rule of dielectric polarizability, decreased from −3% to −0.69%. It was found that this deviation was related to the bond valence of the A-site. Smaller negative deviation corresponded to the cations with lower bond valence, and larger negative deviation corresponded to the cations with higher bond valence. Also, the temperature coefficient of resonant frequency (TCF) was affected by the bond valence of the A-site, and then TCF decreased with decreasing bond valence of the A-site in ABO3 perovskite compounds.

The in situ reduction method was used to prepare nanocrystalline PbSe in a poly(acrylic acid-co-styrene) matrix. Metal precursor-doped polymer film was treated with selenium and reducing reagent (NaBH4) in ethylenediamine, leading to the formation of assemblies of crystalline semiconductive PbSe in polymer. The preparation was done at room temperature and ambient pressure. X-ray diffraction, x-ray photoelectron spectroscopy, infrared, scanning electron microscopy, transmission electron microscopy, and ultraviolet-visible spectra were used to characterize the as-prepared materials. The key factor for successful preparation of this composite was also discussed.

A combustion synthesis method was developed for synthesis of AlN powder. Al powder and small amounts of NH4Cl were thoroughly mixed and placed in low-melting-point containers made of a thin, perforated aluminum sheet. The combustion reaction was ignited by heating the top surface of the powder stack, and the aluminum container was converted completely to AlN during the combustion reaction. High product yields were obtained under N2 pressures of 0.2–0.5 MPa. The product was composed of a dense outer portion and a loose inner portion. Effects of several process parameters on the product yield were investigated and discussed.