Microstructure and texture analysis of YBCO thick film with peritectic growth on unoriented silver substrate

YBCO textured thick film was prepared by direct periteetic growth method. Microstructure of the film was characterized. Electron backscattered diffraction (EBSD) technique was applied to the film for quantitative texture analysis. The main difficulty in resolving the ori-entation of YBCO pseudo-cubic structure was investigated. Automated orientation mapping was performed on YBCO thick film. Local tex-ture was presented in the form of orientation maps. Misorientation distribution and crystal growth characterization in the YBCO thick film were revealed. Large domains with well-aligned YBCO grains were formed. Each domain presented clear in-plane and out-plane textures.     

Densification of nanocrystalline Y2O3 ceramic powder by spark plasma sintering

Nanocrystalline Y₂O₃ powders with 18 nm crystallite size were sintered using spark plasma sintering (SPS) at different conditions between 1100 and 1600 °C. Dense specimens were fabricated at 100 MPa and 1400 °C for 5 min duration. A maximum in density was observed at 1400 °C. The grain size continuously increased with the SPS temperature into the micrometer size range. The maximum in density arises from competition between densification and grain growth. Retarded densification above 1400 °C is associated with enhanced grain growth that resulted in residual pores within the grains. Analysis of the grain growth kinetics resulted in activation energy of 150 kJ mol^?1 and associated diffusion coefficients higher by 10³ than expected for Y³⁺ grain boundary diffusion. The enhanced diffusion may be explained by combined surface diffusion and particle coarsening during the heating up with grain boundary diffusion at the SPS temperature.     

Full process for integrating silicon nanowire arrays into solar cells

A novel process was developed for integrating silicon nanowire arrays into solar cells. n-Type silicon nanowires were grown by chemical-vapour deposition via the gold-catalysed vapour-liquid-solid method, on a p-type silicon substrate. After the growth, the nanowire array was planarized, by embedding the nanowires in a spin-on glass matrix and subsequent chemical-mechanical polishing of the front surface. This planarization step allows to deposit a continuous and uniform conductive film on top of the nanowire array, and thus to form a high-quality front electrical contact. For an illumination intensity of 100 mW/cm², our devices exhibit an energy conversion efficiency of 1.9%. The main performance limiting factor is a high pn junction reverse current, due to contamination by the growth catalyst or to a lack of passivation of surface electronic defects.     

Size Effect on Properties of Varistors Made From Zinc Oxide Nanoparticles Through Low Temperature Spark Plasma Sintering

Conditions for the elaboration of nanostructured varistors by spark plasma sintering (SPS) are investigated, using 8‐nm zinc oxide nanoparticles synthesized following an organometallic approach. A binary system constituted of zinc oxide and bismuth oxide nanoparticles is used for this purpose. It is synthesized at room temperature in an organic solution through the hydrolysis of dicyclohexylzinc and bismuth acetate precursors. Sintering of this material is performed by SPS at various temperatures and dwell times. The determination of the microstructure and the chemical composition of the as‐prepared ceramics are based on scanning electron microscopy and X‐ray diffraction analysis. The nonlinear electrical characteristics are evidenced by current–voltage measurements. The breakdown voltage of these nanostructured varistors strongly depends on grain sizes. The results show that nanostructured varistors are obtained by SPS at sintering temperatures ranging from 550 to 600 °C.     

Influence of Residual Impurities on Phase Partitiioning and Grain Growth Processes of Y-TZP Materials

Microstructural evolution at 1450°C of two 3 mol% Y₂O₃─ZrO₂ tetragonal polycrystals (Y-TZP) containing different residual impurity amounts has been investigated by analytical and scanning electron microscopy in order to clarify the role of the amorphous intergranular phases. Phase partitioning is interpreted as a process based on dissolution/reprecipitation reactions involving mass transport via the liquid impurity phase. Grain growth is inhibited by yttria migration before the phase equilibrium is reached, then increases drastically.     

Multigram synthesis of 1-alkylamido phospholipids

Phospholipids containing a 1-alkylamido linkage have shown promisingin vitro neoplastic cell growth inhibitory properties and anti-human immunodeficiency viral activity. We have synthesized a series of alkylamido ether lipid analogues on a milligram scale for initial evaluation, but for furtherin vivo testing of these bioactive phospholipids, synthesis on a larger scale is required. The multigram synthesis of 1-alkylamido ether phospholipids was accomplished by modifying reaction conditions in the amidation step and changing reagents and solvent systems in both the detritylation and phosphorylation steps. This was most crucial in the phosphorylation step, where in the multigram synthesis 2-bromoethyl dichlorophosphate in diethyl ether/tetrahydrofuran (7∶3, vol/vol) gave much improved yields as compared to the 2-chloro-2-oxo-1,3,2-dioxaphospholane reagent. The modifications also resulted in a product that could be more easily purified in sufficient quantities for use inin vivo inhibition studies.     

Isolation of a lactone,structurally related to the esterifying acids of pyrrolizidine alkaloids,from the costal fringes of male Ithomiinae

Adult male Ithomiinae feed at plants containing pyrrolizidine alkaloids. Certain species secrete on hairs of the costal fringe, a specialized organ on their hindwings, a novel -lactone structurally related to the unusual branched-chain acids that are unique to these alkaloids.