非理想化学计量配比掺锶磷灰石的高温热稳定性

Thermal Stability of Nonstoichiometric Strontium-Incorporated Hydroxyapatite Synthesized with a Hydration Process

采用水化方法制备出不同掺锶量的非理想化学计量配比掺锶磷灰石,使用XRD、IR与TEM等方法检测其高温热稳定性。结果表明:同一制备条件及相同非理想化学计量配比下,掺锶磷灰石的高温热稳定性不如纯磷灰石,且分解产物磷酸三钙锶(Ca,Sr)3(PO4)2)的相转变(α相→β相)温度低于纯磷酸三钙。掺锶量越多,分解产物磷酸三钙锶中含锶量越多。随加热温度升高,含锶磷灰石与纯磷灰石晶粒均逐渐长大。1200℃以下,掺锶磷灰石晶粒近似等轴状,纯磷灰石形状不规则。1300℃时,两种磷灰石粉末中的晶粒尺寸有大有小,大晶粒为长大的磷灰石,形状不规则;小晶粒为分解生成的磷酸三钙锶(或者磷酸三钙),呈球状。

Several strontium-incorporated nonstoichiometric hydroxyapatites with different contents of strontium were synthesized with a hydration process. Their phase structures, chemical compositions and grain sizes and morphologies were investigated by using XRD, FTIR and TEM to study their thermal ability at various firing temperatures. Results show that the incorporation of strontium into hydroxyapatite crystal by replacing equivalent calcium decreases its thermal stability under a given hydration condition and a same moral ratio of （Ca＋Sr）/P. The decomposed product is the mixed calcium strontium phosphate （（Ca, Sr）3（PO4）2）, whose decomposing temperature is lower than that of pure tricalcium phosphate. The more the content of strontium in place of calcium in hydroxyapatite is, the larger the amount of strontium incorporated into the crystal lattice of tricalcium strontium phosphate is. At elevated firing temperatures, the grains of strontium-incorporated hydroxyapatites and pure hydroxyapatite grow up gradually. However, below 1200℃, the grains of the former hydroxyapatite basically keep an equi-axed SrHA while those of the latter become irregular. At 1300℃, both hydroxyapatites are mainly composed of larger grains and few of small ones. The former is a grown apatite with irregular morphology and the latter is a decomposed mixed calcium phosphate or tricalcium strontium phosphate with spheric morphology.