奈米級氫氧基磷灰石的製程研究

Abstract

本實驗以氫氧化鈣和磷酸為起使原料，利用化學共沉法合成出直徑約10~20 nm，長度約50~100nm的針狀氫氧基磷灰石，藉由一般的無壓燒結方法將所生產的奈米級氫氧基磷灰石燒結成緻密的胚體。本實驗致力於解決奈米粉成團的問題。在氫氧基磷灰石未生成前在漿料內添加分散劑，且利用真空幫浦來抽掉漿料內所溶解的氣體，再利用離心成形的方法得到微結構相當均勻的生胚。假如生胚中仍含有大量或是大尺寸的團塊，此情況將會需要提高燒結溫度來得到緻密胚體，而導致晶粒的大量成長。本實驗改善製程使得相當小尺寸的團塊均勻分佈在生胚中，配合兩段式燒結的方法，在第一階段升溫到1200°C，不持溫，降溫到第二階段1100°C持溫二十個小時，在此燒結條件下，成功的燒結出近乎緻密的胚體，而晶粒大小不到400nm。本實驗利用高解析度的X光繞射儀來做氫氧基磷灰石的相鑑定，在研究溫度範圍內都沒有發現相分解的情形。

Stoichiometric hydroxyapatite precipitates with the size of 10~20 nm in diameter and 50~100nm in length were prepared by using a wet method (chemical co-precipitation) from the precursors of phosphate acid and calcium hydroxide. The nano powder was then used to prepare dense HAp body by using pressureless sintering. The present study strived to solve the problem of agglomeration of the nanocrystalline particles. A dispersant was added into the suspension before precipitates formed. The removal of dissolved gas from the slurry is also critical for the preparation of green compact. The nearly agglomeration-free particles were consolidated by centrifugation. If the agglomerates remain in the powder, higher sintering temperature is needed to eliminate inter-agglomerate pores. For the compact formed by the nearly agglomerate-free powder, nearly fully dense hydroxyapatite body could be produced by 1st step sintering at 1200°C and then 2nd step sintering at 1100°C for 20 hrs. The grain size below 400nm is obtained. High resolution X-ray diffraction analysis demonstrates that no decomposition takes place during the sintering at 1200°C.