Preparation and sintering of CaSiO 3 from coprecipitated powder using NaOH as precipitant and its apatite formation in s
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Preparation and sintering of CaSiO3 from coprecipitated powder using NaOH as precipitant and its apatite formation in simulated body fluid solution Punnama Siriphannon Department of Inorganic Materials, Tokyo Institute of Technology, O-okayama, Meguro, Tokyo 152-8552, Japan
Shigeo Hayashi Research Institute of Materials and Resources, Mining College, Akita University, Tegatagakuen, Akita 010-8502, Japan
Atsuo Yasumori and Kiyoshi Okadaa) Department of Inorganic Materials, Tokyo Institute of Technology, O-okayama, Meguro, Tokyo 152-8552, Japan (Received 15 April 1998; accepted 8 June 1998)
CaSiO3 powders were prepared from an ethanol solution dissolving Ca(NO3 )2 ? 4H2 O and Si(OC2 H5 )4 by the coprecipitation method using various concentrations of NaOH as precipitants. Some Na component remained in the precipitates without washing and strongly affected the characteristics of the resultant powders, but the Na residue was removed by a washing treatment. The precipitate prepared by using 0.33 molyl of NaOH and twice-washing contained the lowest amount of Na residue. It was calcined at 500 and 900 ±C, respectively, to crystallize CaSiO3 phase and ground by a planetary potmill. The ground CaSiO3 powder was sintered to about 89% theoretical density by firing at 1400 ±C. By soaking the CaSiO3 sintered bodies in simulated body fluid (SBF) solution for various times, an hydroxylapatite (HAp) layer formed as aggregates of ball-like particles on the surface of the CaSiO3 sintered bodies after soaking for a short period; thereby, the CaSiO3 ceramics is suggested to have very good biocompatibility.
I. INTRODUCTION
CaSiO3 (wollastonite) is a ceramic raw material mainly used for tile1 and porcelain.2 In addition to these applications mainly for traditional ceramics, CaSiO3 ceramics is a candidate material for high frequency insulator3 because MSiO3 ceramics (M alkaline earth elements) belonging to this group have very low dielectric loss at high frequency.4–6 Since sinterability of these MSiO3 ceramics is generally low, it is necessary to prepare fine and homogeneous powder as a raw material for sintering. Among various preparation methods, a coprecipitation method using NH4 OH as a precipitant is reported to be the most suitable for preparing sinterable powder.6–8 Hayashi et al.8 prepared CaSiO3 powder by coprecipitation method from an ethanol solution dissolving calcium nitrate and tetraethyl orthosilicate (TEOS) using NH4 OH as a precipitant and succeeded to sinter it by firing at 1400 ±C for 1 h without sintering aid additives. One of the other possible applications for CaSiO3 ceramics is medical use as materials for artificial bone and dental root because some glasses, i.e., bioglass,9 crysa)
Address all correspondence to this author. J. Mater. Res., Vol. 14, No. 2, Feb 1999
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tallized glass,10,11 and ceramics,12 including CaO–SiO2 components, are reported to show good biocompatibility. Kokubo et al.13 first showed rat
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