|Budget Amount *help
¥7,600,000 (Direct Cost : ¥7,600,000)
Fiscal Year 1996 : ¥1,600,000 (Direct Cost : ¥1,600,000)
Fiscal Year 1995 : ¥6,000,000 (Direct Cost : ¥6,000,000)
Needlelike HAps were synhthesized by a wet method for the present study. Aqueous solutions of CaCl_2 (A) and K_2HPO_4 (B) with a stoichiometric Ca/P molar ratio (1.67) were slowly and simultaneously dropped, with stirring, into water heated to -100ﾟC.The precipitated products were filtered with suction and dried at -100ﾟC for 24 to -48 h. After drying, the obtained particles were sintered at 1200ﾟC for 1 h.
Longer, needlelike particles of HAp were obtained at a slower dropping rate and in the range of the dilute A and B solutions (<0.3mol/dm^3). The needlelike particles were only nonstoichiometric or Ca-deficient HAps, with a Ca/P ratio of -1.54, as determined by inductively coupled plasma emission spectrometry (ICP). No stoichiometric, needlelike particles of HAp have yet reported.
A preparation of sintered, needle-like HAp filters for an ion-exchange was examined by a doctor blade method in order to facilitate handling in the strongly acidic region, with the following results :
(1) The best aqueous slurry for tape casting was the combination of HAp 20 mass%, binder 15 mass%, plasticizer 15 mass%, dispersant 1 mass% and water including specific amounts of Ca (OH) _2 or Ca (NO_3) _2.
(2) A shear thinning behavior appeared at all aqueous slurries.
(3) The tapes without cracks were obtained by sintering at 1200ﾟC for 1h after freeze-dried.
(4) The removal of Pb^<2+> ions was investigated by passing through the Pb^<2+> solutions into the sintered, needle-like HAp filters at pH2, and was -59% at the first run and reached to -100% after repeated 5 runs with the same procedure as before.