Grant-in-Aid for Scientific Research (B)

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Microporous glass-ceramics utilizing spinodal-type phase separation in glass have great advantages over porous ceramics prepared by conventional powder-sintering methods. They have wellcontrolled continuous pores and may be obtained in a desired shape and dimension. This processing is relatively simple and crystalline phases with active function can also be precipitated as the skeleton of the porous materials. Porous glass-ceramics with a skeleton of LiTi_2 (PO_4) _3 show excellent cation exchange properties that Li^+ ions in glass-ceramics are selectively exchanged with Ag^+ ions. In the present work, porous glass-ceramics with the surface phase consisting of predominantly of AgTi_2 (PO_4) _3 crystal and the interior phase of LiTi_2 (PO_4) _3 crystal were prepared by exchange of Ag^+ ions for Li^+ ions. Exchanged Ag^+ ions were chemically stable in water. Silver-containing titanium phosphate crystalline phase in the glass-ceramics did not deteriorated even by heating at 900 ﾟC.The gla … More ss-ceramics showed excellent bacteriostatic properties. Next, novel porous glass-ceramics with a skeleton of CuTi_2 (PO_4) _3 or CuTi_4 (PO_4) _6 were prepared by controlled crystallization of a glass and subsequent chemical leaching of the resulting dense glass-ceramic. A volume-crystallized dense glass-ceramic composed of CuTi_2 (PO_4) _3 and Cu_3 (PO_4) _2 whose surface was covered by a CuO thin layr was prepared by reheating a glass with a nominal composition in the pseudo-binary system CuTi_4 (PO_4) _6 -Cu_3 (PO_4) _2 in air. When the resultant glass-ceramic was leached with dilute H_2SO_4, Cu_3 (PO_4) _2 and CuO phases were dissolved out selectively, leaving a crystalline CuTi_2 (PO_4) _3 skeleton. On the other hand, the HCl-leaching of the same mother glass-ceramic left a crystalline CuTi_4 (PO_4) _6 skeleton. Their specific surface areas of the porous glass-ceramics were 50-70 m^2/g. The porous glass-ceramics showed much higher activity in the conversion reaction of propene into acrolein or 2-propanol into aceton than the catalysts obtained by a conventional sintering of powdery materials. Less