水熱法奈米碳酸鈣合成氫氧基磷灰石研究

Abstract

本研究是利用水熱法來製備氫氧基磷灰石(Ca10(PO4)6(OH)2，HAp)，將含有鈣離子(奈米碳酸鈣)及磷離子(磷酸二氫銨)之水溶液，與醋酸或氨水調整pH值後混合於密封壓力釜中，在不同水熱處理下控制長晶條件，形成高結晶性氫氧基磷灰石粉末。實驗結果發現，藉由XRD結果及計算其結晶性質，在pH=6、250℃、96小時之水熱條件下反應後，可達到結晶性最佳的HAp，以及一些殘留的β-磷酸三鈣(β-Ca3(PO4)2，β-TCP)，所以HAp比較容易在水熱法酸性環境中形成。藉由FT-IR可判斷合成HAp的官能基，在pH=6、250℃、96小時所合成的HAp，其OH-和PO43-的吸收峰強度比pH=8和pH=10來的高。由EDX的結果得知於pH=6的條件下最接近HAp之Ca/P化學計量比1.67。由SEM及TEM結果得知HAp為柱狀，長度大約在18μm左右，其結構是屬於六方晶結構。由反應機制推斷，本研究中的HAp是藉由鈣離子溶解到水溶液中成核成長，以及藉由碳酸鈣先形成β-TCP，然後在β-TCP表面反應生成HAp，當pH=6、反應溫度250℃、反應時間為96小時，大部分的β-TCP都會形成HAp，只有少量的β-TCP殘留。

Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) was synthesized by hydrothermal treatment. Nano calcium carbonate (CaCO3) was used as calcium source and diammonium hydrogen phosphate ((NH4)2HPO4) as phosphorous source. The pH value of solution was adjusted by CH3COOH or NH4OH, and then put solution in autoclave under different situation. After hydrothermal reaction finished, the well-crystallized HAp and a small amount of β-TCP were obtained. From FT-IR spectra, we can found that under pH=6, 250℃, 96hr, the functional group of OH- and PO43-, are stronger than pH=8 and pH=10, which suggests that at pH=6, the synthesized powder has more HAp phase than pH=8 and pH=10. From SEM and TEM pictures, HAp shows rod-like shape with length about 18μm and width about 1μm. The structure of HAp is HCP structure. From the reaction growth mechanism, the nucleation and growth of β-tricalcium phosphate (β-TCP) on the surface of calcite particle was observed at the beginning of the reaction of calcite. Some HAp rods were grown by β-TCP convert into HAp. Some HAp rods were grown by heterogeneous nucleation in the solution. After the hydrothermal reaction under pH=6, 250℃ for 96hr, most products are HAp with a small amount of β-TCP synthesized as a byproduct.