Liao C J, Lin F H, Chen K S, Sun J S
Institute of Biomedical Engineering, College of Medicine, National Taiwan University, Taipei, Taiwan.
Biomed Sci Instrum. 1999;35:99-104.
In this paper, the decomposition and reconstruction behavior of hydroxyapatite (HAP) during heating and cooling in air atmosphere were studied. The commercial HAP were chosen and gradually heated to 1500 degrees C and cooled to room temperature by a program controlled SiC heated furnace. X-ray diffractometer (XRD) and Fourier-transformed infrared (FTIR) analysis were used to investigate the change of crystalline phases and functional groups of HAP at different temperatures. Weight change of samples was recorded by thermogravimetric analysis (TGA) during heating and cooling. The results revealed that HAP would gradually release its OH- ions and transform into OHAP in the temperature of 1000-1360 degrees C. Above 1360 degrees C, the OHAP would decompose into TTCP and alpha TCP phase. The OH- stretching bands of HAP could be traced by FTIR even at the temperature of 1350 degrees C which was the eve of HAP decomposition. It reflected that the HAP did not dehydrate completely before decomposed. We speculated that some of OAP might be formed during dehydration and there were a great amount of OHAP still left in the system even up to the temperature of decomposition. In the temperature of 1400-1500 degrees C, there were no significant different in XRD patterns, only TTCP and alpha TCP crystalline phase were observed. When the HAP gradually cooled down from 1500 degrees C, a part of TTCP and alpha TCP would directly reconstruct into oxyapatite (OAP) around 1350 degrees C. OAP existed in the temperature of 1350 to 1300 degrees C during cooling. When the temperature down to 1290 degrees C, a part of TTCP and alpha TCP reconstructed into OHAP by rehydration reaction and OAP were rehydrated into OHAP as well. At 1100 degrees C, the rest of TTCP and alpha TCP would reconstitute into HAP. As the temperature decreased, the OHAP were gradually rehydrated and reconstituted into HAP.
本文研究了羟基磷灰石（HAP）在空气气氛中加热和冷却过程中的分解与重构行为。选用市售HAP，通过程序控制的碳化硅加热炉将其逐步加热至1500℃，然后冷却至室温。采用X射线衍射仪（XRD）和傅里叶变换红外光谱（FTIR）分析来研究不同温度下HAP晶相和官能团的变化。在加热和冷却过程中，通过热重分析（TGA）记录样品的重量变化。结果表明，在1000 - 1360℃温度范围内，HAP会逐渐释放其OH - 离子并转变为OHAP。在1360℃以上，OHAP会分解为TTCP和α - TCP相。即使在1350℃（HAP分解前夕）的温度下，FTIR仍可追踪到HAP的OH - 伸缩带。这表明HAP在分解前并未完全脱水。我们推测在脱水过程中可能形成了一些OAP，并且即使在分解温度下，系统中仍残留大量的OHAP。在1400 - 1500℃温度范围内，XRD图谱无明显差异，仅观察到TTCP和α - TCP晶相。当HAP从1500℃逐渐冷却时，在1350℃左右，一部分TTCP和α - TCP会直接重构为氧磷灰石（OAP）。在冷却过程中，OAP在1350至1300℃的温度范围内存在。当温度降至1290℃时，一部分TTCP和α - TCP通过再水化反应重构为OHAP，OAP也会再水化成为OHAP。在1100℃时，其余的TTCP和α - TCP会重新构成HAP。随着温度降低，OHAP逐渐再水化并重新构成HAP。
