Materials Science Forum Vols. 663-665

Abstract: A new way was developed to grow carbon nanotubes (CNTs) in the downstream zone of high pressure dielectric barrier discharge plasma. Using Ni coated Si as the catalyzed substrate, CH4 as the carbon source, H2, NH3 and water vapor mixtures as the dilution and etching gas, CNTs were grown under temperatures of 630oC and 750 oC. The effects of various etching gas mixtures on the growth of CNTs were investigated respectively. The CNTs were characterized by SEM and high-resolution TEM. The results show that trace addition of Ammonia and water vapor to the plasma atmospheres can influence CNTs growth strongly. In 15% CH4 gas mixtures, CNTs can grown well within an addition of 3% NH3 which showed an improvement of CNTs quality, but no product was founded when adding the NH3 content over 8%. On the contrary, in 15% CH4 and 8% NH3 gas mixtures, CNTs can grow better when adding a small proportion (2‰-6‰) of water vapor to the etching gas and meanwhile optical emission spectrometry (OES) was applied to diagnositic and explain the effects of trace water vapor on the process of CNTs growth.

Abstract: Lithium aluminosilicate (LAS) glass-ceramics with 0 ~ 10 wt% phosphoric anhydride were prepared by sol-gel method and sintering at high temperature. Tetraethyl orthosilicate (TOES), aluminum nitrate, lithium carbonate were used as precursors. Differential thermal analysis (DTA), X-ray powder diffraction (XRD) and thermal expansion coefficient (TEC) were used to characterize the dried LAS gels and glass-ceramic blocks. The results suggest β-spodumene solid-solution is the only crystals phase in the P2O5 doped LAS glass-ceramics when sintering temperature is 950 oC. The thermal expansion coefficient of the P2O5 doped LAS glass-ceramics range from -0.1×10-6 oC-1 to 1.2×10-6 oC-1. Compared with the conventional melt quenching method, this process route provides a low temperature and timesaving method for preparing LAS glass-ceramics.

Abstract: Germanate oxyfluoride glass in CaF2/BaF2-AlF3-SiO2-GeO2 was prepared by melt quenching technique and subsequently converted to glass-ceramics with microstructures comprised nano-crystallites in a residual glass matrix by two-step heat treatments process. DSC, XRD, SEM and IR transmission investigations were used to determine structural characteristics and optical property of the prepared germanate oxyfluoride glass-ceramics. The influences of heat treatment conditions on crystallization behaviors and infrared transmission were discussed. The results show that crystal phase in the glass-ceramics is only Ge2Al6O13 and the crystal size is about 20nm-80nm when treated temperature ranges from 900 oC to 960oC. Good transparency is exhibited in visible light band to midinfrared band (5.0um) when treated temperature is low than 940 oC.

Abstract: The precursor doped with W6+ and Mo6+ ionic was prepared using oxalic acid as reduction acid, V2O5 as vanadium source, (NH4)6W7O24·6H2O and (NH4)6Mo7O24·4H2O as doped sources. The morphology, composition, structure and the thermo-decomposing process of the precursor were characterized by means of SEM, EDS, FTIR and DSC/TG/DTG. The thermal decomposition was confirmed by XRD.

Abstract: The Al-doped ZnO (AZO) films were deposited on the glass substrates by RF magnetron sputtering at different substrate temperatures. The effect of substrate temperature on the structural, optical, and electrical properties of AZO films was investigated. The results indicate each of the films has a preferential c-axis orientation. The grain size increases with substrate temperature increasing. All the films exhibit a high transmittance in visible region and have sharp ultraviolet absorption characteristics. The resistivity decreases with substrate temperature increasing up to 250oC, then increases for higher temperature.

Abstract: In this paper, the effects of different metal contact treatments were systemically investigated. The interfacial properties between Au and CdZnTe (CZT) made by different methods including the electroless deposition, thermal evaporation and sputtering process were investigated by the Auger depth profiles, the adhesion force measurement, and the accelerated aging tests. The current-voltage (I-V) characteristics and the detector response to gamma-rays from 241Am for different Au contact treatments were also identified.

Abstract: Based on a convergent nozzle and a conical nozzle, the simulation of the free jet of assemble nozzles by adopting a three-dimensional axial symmetrical model is presented in the paper. The study reveals the effect of cone angle of conical nozzle and the parabola equation of convergent nozzle on flow field by adjusting nozzles’ interior figure parameters. The distribution of pressure and velocity of gas jet are shown in the investigation. A conical nozzle with cone angle of 30° and a convergent nozzle described by the parabola equation of y=0.207x2 are designed and produced for the laser cutting experiment. Numerical simulation and experimental results are given at the end of the paper.

Abstract: Structural and dynamical properties of the rapid solidification process of liquid Ge have been investigated by molecular-dynamics calculations based on the Stillinger-Weber potential. The variations of microstructures during the solidification process are analyzed by the self-diffusion coefficient D(T), pair correlation function g(r) curves and the HA bond-type index method. The melting point implicated in D(T) is about 2100 K. The pair correlation function g(r) obtained by the simulated in liquid Ge is good agreement with experiment, the fist-peak of g(r) gradually becomes higher and sharper with the temperature decreasing, when temperature drops to 1400 K, the second-peak of g(r) begins to split. The change of HA bond-type indicated that the most important structural change occurs in the temperature range 1400 K-700 K.

Abstract: Lead-free (1-x)K0.49Na0.51NbO3-xLiTaO3 (x=0.00-0.07) piezoceramics were fabricated by the conventional solid-state sintering method, the effects of LiTaO3 content on the phase structure and piezoelectric properties of the ceramics were investigated. All the ceramics show single perovskite structure with a phase transition from an orthorhombic symmetry to a tetragonal one across an orthorhombic-tetragonal coexistence region with 0.04

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