Landi Elena, Tampieri Anna, Celotti Giancarlo, Vichi Lucia, Sandri Monica
Institute of Science and Technology for Ceramics ISTEC-CNR, via Granarolo 64, 48018 (RA), Faenza, Italy.
Biomaterials. 2004 May;25(10):1763-70. doi: 10.1016/j.biomaterials.2003.08.026.
A new method to synthesise carbonate-substituted hydroxyapatite (CHA) powder has been set up introducing a CO(2) flux, as a source of carbonate, in the HA synthesis process based on the neutralisation reaction. The reactants are abundant and inexpensive. The yield is good compared to other CHA powder synthesis. The reaction may be performed at low temperature and without pH control and does not produce any by-products. The influence of the synthesis parameters (temperature, H(3)PO(4) solution dropping rate, i.e. reaction time, CO(2) flux, ageing time) has been tested to optimise the process conditions in order to obtain the highest carbonation degree and favour the B-type CHA precipitation with respect to A-type one. The prepared powder (5.8wt% of total carbonate with an A/B ratio of 0.78) was thermally treated at various temperatures in the range 500-1400 degrees C in different atmospheres (air, wet and dry carbon dioxide). The thermal treatments were performed with a double aim, to eliminate selectively the carbonate groups in A-position maintaining the B-type substitution, and to evaluate the thermal stability of the CHA and the total loss of carbonate as a function of temperature. The thermal treatment at 900 degrees C in wet CO(2) gave the best result in terms of a high carbonate residue and a low A/B ratio. We also investigate the use of different techniques (inductively coupled plasma, TGA, Fourier transformed infrared spectroscopy, X-ray diffraction) for characterising CHA and calculating sensitivity and accuracy in the quantification of carbonate ions for each molecular site.
基于中和反应，已建立一种合成碳酸取代羟基磷灰石（CHA）粉末的新方法，即在HA合成过程中引入CO₂通量作为碳酸盐源。反应物丰富且廉价。与其他CHA粉末合成方法相比，产率良好。该反应可在低温下进行，无需pH控制，且不产生任何副产物。已测试合成参数（温度、H₃PO₄溶液滴加速率，即反应时间、CO₂通量、老化时间）的影响，以优化工艺条件，从而获得最高的碳酸化程度，并有利于相对于A型CHA沉淀出B型CHA。将制备的粉末（总碳酸盐含量为5.8wt%，A/B比为0.78）在500-1400℃的不同温度下于不同气氛（空气、湿二氧化碳和干二氧化碳）中进行热处理。进行热处理有两个目的，一是选择性地消除A位的碳酸根基团，同时保持B型取代，二是评估CHA的热稳定性以及碳酸盐总量随温度的损失情况。在湿CO₂中于900℃进行的热处理在高碳酸盐残留量和低A/B比方面取得了最佳结果。我们还研究了使用不同技术（电感耦合等离子体、热重分析、傅里叶变换红外光谱、X射线衍射）来表征CHA，并计算每个分子位点碳酸盐离子定量的灵敏度和准确性。
