微反应器结合水热法制备羟基磷灰石纳米粉体

采用Y型微通道反应器与水热法相结合的工艺路线,制备了羟基磷灰石(HAP)纳米粉体,并利用X射线衍射、扫描电镜、透射电镜等分析手段对产物进行了表征。在此基础上,考察了反应物浓度、总流量和流量比等因素对HAP纳米粉体制备的影响以及形成机理。结果表明:HAP纳米粉体的颗粒粒径随着反应物浓度和反应物总流量的增加而先减小后增大,随着反应物流量比的增加而增大;其形成机理是利用微反应器的强制微观混合作用促进过饱和度的均匀分布,使化学沉淀反应的中间产物HAP前驱体以尺寸均一、分散性好的无定形磷酸钙二次颗粒聚集体的形式存在,HAP前驱体在水热处理时,通过ACP二次颗粒聚集体的内部重排及ACP粒子的溶解-重结晶的相转变方式,晶化生长为均匀细小的HAP纳米粉体;当Ca(NO3)2溶液和(NH4)2HPO4溶液的摩尔浓度分别为0.1和0.06mol/L、两溶液的流量比为1∶1、反应物总流量为80mL/min时,可制得平均粒径约为85nm、粒度均匀的短棒状HAP纳米粉体。

Preparation of hydroxyapatite nanoparticles using a microreactor combined with hydrothermal aging

Hydroxyapatite (HAP) nanoparticles have been prepared by the combination of chemical precipitation of Ca(NO₃)₂and (NH₄)₂HPO₄in a Y-type microchannel reactor and hydrothermal aging. The crystal structure, morphology and particle size of the resulting HAP nanoparticles were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The influence of operational parameters such as reactant concentrations, total reactant flow rates and reactant flow rate ratio was investigated. The mechanism of formation of HAP nanoaprticles has also been discussed. The resultsshowed that the mean particle size initially decreased and subsequently increased with increasing reactant concentration and total reactant flow rate, but increased monotonically with increasing Ca(NO₃)₂∶(NH₄)₂HPO₄flow rate ratio. The mechanism of formation of the HAP nanoparticles involved the boosting of the homogeneous micromixing of the reactants by the microreactor and the resulting even distribution of supersaturation, so that the HAP precursor existed in the form of amorphous calcium phosphate (ACP) aggregates with good uniformity and dispersion. After the ACP was treated hydrothermally, uniform and small HAP nanoparticles were formed via two phase transformation modes, namely internal rearrangement of ACP aggregates and dissolution recrystallization of ACP particles. Uniform rod-like HAP nanoparticles with a mean size of about 85 nm were obtained when using a reactant flow rate ratio of 1∶1, a total reactant flow rate of 80mL/min, and concentrations of Ca(NO₃)₂and (NH₄)₂HPO₄solutions of 0.1mol/L and 0.06mol/L, respectively.