Han Xue, Day Delbert E
Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.
J Mater Sci Mater Med. 2007 Sep;18(9):1837-47. doi: 10.1007/s10856-007-3053-2. Epub 2007 May 8.
This study investigated the transformation of two sodium calcium borate glasses to hydroxyapatite (HA). The chemical reaction was between either 1CaO . 2Na(2)O . 6B(2)O(3) or 2CaO . 2Na(2)O . 6B(2)O(3) glass and a 0.25 M phosphate (K(2)HPO(4)) solution at 37, 75 and 200 degrees C. Glass samples in the form of irregular particles (125-180 microm) and microspheres (45-90 and 125-180 microm) were used in order to understand the reaction mechanism. The effect of glass composition (calcium content) on the weight loss rate and reaction temperature on crystal size, crystallinity and grain shape of the reaction products were studied. Carbonated HA was made by dissolving an appropriate amount of carbonate (K(2)CO(3)) in the 0.25 M phosphate solution. X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy were used to characterize the reaction products. The results show that sodium calcium borate glasses can be transformed to HA by reacting with a phosphate solution. It is essentially a process of dissolution of glass and precipitation of HA. The transformation begins from an amorphous state to calcium-deficient HA without changing the size and shape of the original glass sample. Glass with a lower calcium content (1CaO . 2Na(2)O . 6B(2)O(3)), or reacted at an elevated temperature (75 degrees C), has a higher reaction rate. The HA crystal size increases and grain shape changes from spheroidal to cylindrical as temperature increases from 37 to 200 degrees C. Increase in carbonate concentration can also decrease the crystal size and yield a more needle-like grain shape.
本研究考察了两种硼酸钠钙玻璃向羟基磷灰石（HA）的转变。化学反应发生在1CaO·2Na₂O·6B₂O₃或2CaO·2Na₂O·6B₂O₃玻璃与0.25 M磷酸盐（K₂HPO₄）溶液之间，反应温度为37、75和200℃。为了解反应机理，使用了不规则颗粒（125 - 180微米）以及微球（45 - 90微米和125 - 180微米）形式的玻璃样品。研究了玻璃组成（钙含量）对失重率的影响以及反应温度对反应产物晶体尺寸、结晶度和晶粒形状的影响。通过在0.25 M磷酸盐溶液中溶解适量的碳酸盐（K₂CO₃）制得碳酸化HA。采用X射线衍射、傅里叶变换红外光谱和扫描电子显微镜对反应产物进行表征。结果表明，硼酸钠钙玻璃可通过与磷酸盐溶液反应转变为HA。这本质上是一个玻璃溶解和HA沉淀的过程。转变从非晶态开始，生成缺钙的HA，且不改变原始玻璃样品的尺寸和形状。钙含量较低的玻璃（1CaO·2Na₂O·6B₂O₃）或在较高温度（75℃）下反应，具有较高的反应速率。随着温度从37℃升高到200℃，HA晶体尺寸增大，晶粒形状从球形变为圆柱形。碳酸盐浓度的增加也会减小晶体尺寸，并产生更针状的晶粒形状。
