Daiqin Ni

Growth of birefringent Ca3(BO3)2 crystals by the Czochralski method

Copper/silica-based nanostructures with different morphologies and microstructures have been synthesized on Si wafer by thermal evaporation of CuO and SiO powders in an argon-hybridized hydrogen ambient at high temperatures. Systematically studies by scanning electron microscopy with field emission gun and transmission electron microscopy show that the composite nanowires have a core-shell structure with an average diameter of similar to120 nm and lengths of several hundred nanometers to several ten microns. Electron diffraction pattern and electron energy dispersive X-ray spectroscopy analysis reveal that the core coincides with copper and the shell corresponds to amorphous silicon oxide with chemical composition SiO2-x(0 less than or equal to x less than or equal to 0.5). Besides the Cu/SiO2-x nanowires, many other nanostructures such as octpous-, pine-, and chain-like structures have also been found. The growth mechanisms of these products were briefly discussed

Factors affecting the graphitization behavior of the powder source during seeded sublimation growth of SiC bulk crystal

The effects of temperature, temperature gradient and the argon pressure on the graphitization of the powder source during seeded sublimation growth of SiC bulk crystal are investigated. It is found that the graphitization tendency of the powder source becomes obvious with temperature, especially above 2600 K. A higher growth temperature, a larger temperature gradient from the powder source to the growing crystal or a lower argon pressure corresponds to a higher graphitization rate of the powder source. The establishment of a proper temperature gradient in the powder source enabling vapor transporting from the lower part of the powder to the surface is critical to prevent the graphitization of the powder surface. This requires a proper control of the distance between the powder surface and the highest temperature line in the furnace during growth.

Phase relations in the BaO–B2O3–TiO2 system and the crystal structure of BaTi(BO3)2

In this paper, the subsolidus phase relations in the ternary system BaO-B2O3-TiO2 have been investigated. The phase diagram consists of 15 ternary phase regions. There exist I I binary compounds and two ternary compounds. The ternary compound, BaTi(BO3)(2), is isostructural with CaMg(CO3)(2). It crystallizes in a rhombohedral system with the space group R-3. The lattice parameters are a = 5.0205(2) and c = 16.3844(l) Angstrom. Final refinement on the diffraction data converge to R-p = 9.09, R-wp = 12.24, and R-exp = 3.75%

Effects of CaO addition on growth of YVO4 single crystals

YVO4 single crystals doped with CaO are grown by the floating zone method in nitrogen atmosphere. The crystal is colorless and transparent after annealing in oxygen atmosphere. The effects of CaO addition are discussed. The Ca2+ ions can substitute for Y3+ at Y-sites in the YVO4 structure to form oxygen vacancies via which oxide ions can easily diffuse and, consequently, yield transparent crystals

Growth of single crystals of YB2 by a flux method

YB2 crystals with cross-sections of several square millimeters were prepared using Y flux in a pyrolytic BN crucible by a flux method. The as-grown crystals have good structural properties. The electrical resistivity and magnetic susceptibility of YB2 were measured. It is shown that YB2 is a paramagnetic compound and above 20 K the temperature dependence of magnetic susceptibility in YB2 obeys well with the Curie-Weiss law

Computer simulations of fluid flow and heat transfer in metal strip heating zone crystal growth

In conventional floating zone crystal growth, convection, especially Marangoni convection in the melt zone, is very strong. In addition, the quality and shape of the crystal is poor and difficult to control. In view of these problems, a modified floating zone crystal growth has been developed, in which a metal strip is immersed in the melt zone. The purpose of this paper is to simulate the fluid flow and the heat transfer during crystal growth, so that this modified process can be understood better. The flow patterns and temperature fields were calculated for the growth of NaNO3 and Si