In this communication a new kind of nanocomposite is reported in which a bridging coordination ligand, 2,2′-bipyrimidine, is used to bind quantum dots of CdS or CdSe (4–6 nm) to larger PbS nanoparticles.

The enthalpies of formation of two rare-earth silicates (Y2SiO5 and Yb2SiO5) and a N-containing rare-earth silicate Y10(SiO4)6N2 have been determined using high-temperature drop solution calorimetry. Alkali borate (52 wt% LiBO2·48 wt% NaBO2) solvent was used at 800 °C, and oxygen gas was bubbled through the melt. The nitrogen-containing silicate was oxidized during dissolution. The standard enthalpies of formation are for Y2SiO5, Yb2SiO5, and Y10(SiO4)6N2, respectively, –22868.54 ± 5.34, –22774.75 ± 8.21, and –14145.20 ± 16.48 kJ/mol from elements, and –52.53 ± 4.83, –49.45 6 ± 8.35, and –94.53 ± 11.66 kJ/mol from oxides (Y2O3 or Yb2O3, SiO2) and nitride (Si3N4). The silicates and N-containing silicate are energetically stable with respect to binary oxides and Si3N4, but the N-containing silicate may be metastable with respect to assemblages containing Y2SiO5, Si3N4, and SiO2. A linear relationship was found between the enthalpy of formation of a series of M2SiO5 silicates from binary oxides and the ionic potential (z/r) of the metal cation.

This communication reports rapid, efficient syntheses of the zirconium-organic metal-organic chemical vapor deposition (MOCVD) precursors Zr(acac)4 and Zr(dpm)4 (acac = acetylacetonate; dpm = dipivaloylmethanate) as well as a new, highly volatile, air- and moisture-stable Zr precursor based on a tetradentate Schiff-base ligand, Zr(tfacen)2 (tfacen = bis-trifluoroacetylacetone-ethylenediiminate). The improved one-step synthetic routes employ tetrakis(dimethylamido)zirconium as a common intermediate and represent a major advance over previous methods employing ZrCl4 or diketonate metathesis. Furthermore, Zr(tfacen)2 is shown to be an effective metal-organic precursor for the MOCVD-mediated growth of (100) oriented yttria-stabilized zirconia thin films.

Zirconium aerosol was ignited and burned in atmospheric pressure air in microgravity using a 2.2-s drop tower. Combustion products were collected and analyzed using electron microscopy. The elemental composition analyses indicated that combustion product compositions fell along two linear traces on a ternary Zr–O–N diagram. Currently, the equilibrium Zr–O–N phases are not characterized at temperatures above 2000 °C, typical of zirconium combustion in air, and it is suggested that the phases detected in zirconium combustion products can serve as a guide to further studies of the Zr–O–N system at high temperatures. It is also suggested that experimental metal combustion techniques can be adopted for studying high-temperature metal–gas phase equilibria.

The early stages of oxidation of aluminum nitride have been studied by transmission electron microscopy and electron diffraction. It has been found that the oxide layer grows by the Stranki–Krastonow mechanism, where an initial uniform layer is followed by island formation. The onset of oxidation occurs at 800 °C and the initial oxide phase that forms is γ–Al2O3, one of the transition aluminas. The orientation relationship between the oxide layer and the underlying nitride is (440)γ∥(1120)AIN and [112]γ∥[0110]AIN.

Modern telecommunications require materials with high dielectric constants (κ). The number of suitable elements ultimately limits one approach to the discovery of new materials, targeting compositions with high atomic polarizabilities (α). By decreasing the molar volume of compositions with high α, however, we anticipated dramatic increases in κ and demonstrated that this approach works. The quenched high-pressure perovskite polymorph of Na2MTeO6 (M = Ti, Sn) showed a twofold increase in κ, compared to the ilmenite form. This result suggested the highest values of κ occur for compositions with high α, which form quenchable compounds at high pressures and temperatures.

Physical-vapor-deposited thin metal films often exhibit tensile residual stresses. We studied the stress evolution in thin Cr films and found that increasing bombardment with energetic particles (atoms or ions) at low energies leads to an increase of tensile stress to a maximum followed by a rapid decrease. Microstructural characterization by transmission electron microscopy revealed that two different microstructures are observed for the same level of tensile stress: films processed at low bombardment had columnar porosity while no porosity was observed in films processed at higher bombardment. The observed stress evolution is interpreted by considering how the mean interatomic distance (and hence the force) in the intercolumnar regions is modified by energetic particle bombardment.

Alkyl phosphates can be used as sol-gel precursors for phosphate-based glasses and glass-ceramics. An improvement in the synthesis of alkyl phosphates is presented. Following the procedure here described, it is possible to limit the fraction of condensed phosphates to 1–2%. At the same time, a ratio between mono- and di-substituted phosphates near to that given by the reaction stoichiometry may be attained.

The chemical and microstructural evolution of particulate (Bi,Pb)2223 in contact with pure bulk silver at 830 to 905 °C under flowing air and Ar−5% O2 atmospheres has been studied. Specimens annealed under PO2 and temperature conditions for which the (Bi,Pb)2223 phase itself is stable, based on a critical assessment of the literature, revealed a silver/(Bi,Pb)2223 interface-limited reaction, producing both solid and liquid decomposition phases. The (Bi,Pb)2223 not in direct contact with silver exhibited no reaction under the same conditions. Solid silver dissolves into the (Bi,Pb)2223 incongruent liquid, facilitating the incongruent melting reaction. On cooling, equiaxed metallic silver particles precipitated uniformly throughout bulk specimens partially melted on a silver substrate.

Subsolidus equilibria in air in the La2O3−CeO2−Co2O3 system were studied with the aim to obtain information on possible interactions between LaCoO3-based cathode and CeO2-based solid electrolyte in solid oxide fuel cells (SOFC). No ternary compound was found. The tie line is between LaCoO3 and CeO2.

The influence of composition and high-temperature heat treatment on phase content and superconducting properties of the Yni2B2C phase was investigated. Phase relations in those parts of the Y–Ni–B–C quaternary phase diagram, which are relevant for the YNi2B2C intermetallic phase formation, were revealed by x-ray diffraction, optical and scanning electron microscopy, and high-temperature differential thermoanalysis. A widespread interval of superconducting transition temperatures TC = 10.4–15.2 K and small transition width <0.3 K were determined from samples of different nominal compositions after high-temperature annealing. The different intrinsic properties are ascribed to composition variations of the YNi2B2C phase and related to structure parameters, residual resistance ratios, and element concentrations determined by the electron probe microanalysis.

The third-order optical nonlinearity of glasses of the Na2S–PbS–GeS2 and Na2S–PbO–GeS2 systems was measured by third-harmonic generation method. The third-order nonlinearities of glasses of both systems increase with the increasing lead content. The maximum value of the third-order optical nonlinearity was 3.00 × 10-12 esu. The addition of PbO basically has little influence on third-order optical nonlinearity, and the largest nonlinearity is 1.49 × 10-12 esu. The minimum appearing at 15 mol% PbO can be explained by the decrease of number density of lead and sulfur. Chemical durability of oxysulfide glasses is superior to that of a pure sulfide system; thus the addition of PbO is important in this sense.

In a nanometer order nanoindentation test, roundness or truncation of the indenter tip cannot be avoided. In this paper, we have analyzed the indentation problem of a rounded triangular indentation into a layered elastic half-space by a finite element analysis and then established a method to estimate the intrinsic elastic modulus of the film from the nanoindentation data. The method was applied to analyze the nanoindentation data of a less-than-10 nm penetration depth on a 10 nm thick diamondlike carbon film deposited on a 50 nm thick magnetic layer.

Drop-tube experiments have been performed on YxNd1–xBa2Cu3Oy (0.7 ≤ x ≤ 1.0) to understand the effects of partial substitutions of Nd for Y on the phase relationships in these systems at elevated temperatures. Powders 50–100 μm in diameter were processed in pure O2 at furnace temperatures of 1575–1800 °C, every 25 °C. The resulting samples were examined microstructurally by scanning electron microscopy, energy dispersive spectroscopy, and optical microscopy. Powder x-ray diffraction was performed for phase identification. It was found that Nd substitution alters phase selection by introducing at least one new phase and allowing for solidification of the superconducting composition directly from the melt via undercooling to below the peritectic transformation temperature. A decreasing trend in the overall melting temperature with increasing Nd was also identified.

A novel sol-gel-hydrothermal process for preparation of highly oriented thin films of Pb(Zr0.52Ti0.48)O3 is reported. Pb(Zr0.52Ti0.48)O3 thin films with fully (111) orientation were successfully prepared on platinized silicon substrates at low temperature (100–200 °C) by combining a conventional sol-gel process and hydrothermal method, i.e., sol-gel-hydrothermal technique. The x-ray rocking curve for the (111) reflection as measured by a high-resolution four-crystal diffractrometer showed a narrow full width at half-maximum value of 0.20° for the as-prepared films. A dense, pinhole-free, and uniform surface morphology was observed from atomic force microscopy images of the films. The low leakage current density of the prepared films was also found.

A (110)-oriented diamond film was deposited by hot filament chemical vapor deposition with H2 and CH4 separately introduced into the reactive zone. The film with a degree of orientation I(220)/I(111) of more than 200% and deposition rate of 2–3 μm/h was obtained for a deposition time of 17 h. The long deposition time enlarged the grain size and enhanced the degree of orientation, but too long a deposition time resulted in random growth. The temperature field was measured and also calculated using a simple model. Both results showed that a temperature field existed with varied gradients along the normal of substrate surface. The (110)-oriented diamond film was deposited in the zone with negative temperature gradient. The change in orientation occurring for long deposition times was ascribed to the change of temperature gradient.

The enthalpy of formation of Y2Ba4Cu7O14.864 at room temperature has been determined by using high-temperature reaction calorimetry. The standard enthalpy of formation of the 247 phase is ΔH°f = −5463 ± 18 kJ mol−1. Phase relationships among the superconductors, namely, the 123, 124, and 247, are assessed. It is intrinsic that impurity phases, such as Y2Cu2O5, BaCuO2, CuO, etc., coexist with the superconductors at equilibrium. Equilibria among the superconductor phases in the Y2O3–BaO–Cu–O system have been determined. The results show that, at the 124 bulk composition, the 247 phase coexists with the excess CuO in a narrow area of pO2 ∼ T space confined by the stability fields of the 124 phase and a mixture of the 123 + CuO. The standard free energies of carbonation and hydration of the 247 phase are also determined, which are −629 ± 13 kJ mol−1 and −873 ± 45 kJ mol−1, respectively. Like the 123 and 124 phases, the 247 phase is thermodynamically unstable for corrosion by water vapor and carbon dioxide in ambient atmosphere.

A novel fabrication approach for two- and three-dimensional arrays of magnetic microspheres is presented in this paper. The magnetic microsphere is made from 47 μm size Al2O3 spheres onto which a 2–3 μm thick nickel layer is coated through electroless plating. After proper anneal, the outer nickel layer is converted to exhibit a crystalline structure. As an example for utilizing such magnetic microspheres, a two-dimensional, anisotropically conductive matrix is made by transferring the magnetic microsphere array from a template to a transparent adhesive tape using a magnetic attractive force. In addition, a three-dimensional array has also successfully been constructed on a metal plate. The two-dimensional conductor array may be useful for high-density circuit packaging applications in the semiconductor industry, and the three-dimensional array may open up a possibility for constructing three-dimensional photonic crystals.

Zirconate and titanate pyrochlores were subjected to 1 MeV of Kr+ irradiation. Pyrochlores in the Gd2(ZrxTi1-x)2O7 system (x = 0, 0.25, 0.5, 0.75, 1) showed a systematic change in the susceptibility to radiation-induced amorphization with increasing Zr content. Gd2Ti2O7 amorphized at relatively low dose (0.2 displacement per atom at room temperature), and the critical temperature for amorphization was 1100 K. With increasing zirconium content, the pyrochlores became increasingly radiation resistant, as demonstrated by the increasing dose and decreasing critical temperature for amorphization. Pyrochlores highly-enriched in Zr (Gd2Zr2O7, Gd2Zr1.8Mg0.2O6.8, Gd1.9Sr0.1Zr1.9Mg0.1O6.85, and Gd1.9Sr0.1Zr1.8Mg0.2O6.75) could not be amorphized, even at temperature as low as 25 K.

A diffusion model is proposed to fit the measured chemical-transformation rates of the Bi(Pb)CaCuSrO 80-K phase to 110-K phase. Diffusion coefficients and activation energies in PO2 = 0.08 and 0.21 atm are reported. The low diffusion rates and high activation energies suggest cation diffusion controls the transformation.