Sinterability of Apatite-Zirconia Comp6site Powder Prepared by Ultrasonic Spray Freeze-Drying Technique

摘要

The hydroxyapatite (Ca_(10) (PO_4)_6 Cl_2; HAp) and chlorapatite (Ca15 (PO_4) eCl2; CAp) powders with addition of tetragonal zirconia (ZrO_2) polycrystals (TZP; 3 mol percent of yttria (Y_2O_3) solid solution) were prepared by two kinds of ultrasonic spray freeze drying (USFD) techniques: single-nozzle (SN) and double-nozzle (DN) USFDs. The SN-USFD was performed (i) using a solution containing 0.50 mol centre dot dm~(-3) Ca (CH_3COO)_2 and 0.30 mol centre dot dm~(-3) PO(OCH_3)_3 with the Ca/P ratio of 1.67 and (ii) using a solution containing 1.00 mol centre dot dm~(-3) ZrOCl_2 and 0.0619 mol centre dot dm~(-3) YC1_3. In this case, each solution was sprayed into a chamber chilled with liquid nitrogen, using an ultrasonic vibrator. The materials were freeze-dried and then calcined to form carbonate-containing HAp and TZP, respectively. The composite powder was prepared by mixing these two kinds of powders mechanically. In the case of DN-USFD, two kinds of solutions described above were simultaneously sprayed into the chamber chilled with liquid nitrogen, using two ultrasonic vibrators. The freeze-dried materials were calcined at 950 deg C for 1 h to form CAp and TZP. When these SN- and DN-USFD-derived composite compacts containing 2 to 80 mol percent of TZP addition were hot pressed at 1100 deg C for 1 h, the relative densities attained approx 95 percent. These hot-pressed composite compacts contained HAp, TZP and their reaction products. Although the grains with sizes of approx 0.5 #mu#m were homogeneously packed in the case of SN- USFD-derived composite compact, the grains with sizes below 0.5 #mu#m were dispersed on boundaries of grains with sizes of 1 to 2 #mu#m in the case of DN-USFD-derived composite compact.