Data from: Effect of reaction solvent on hydroxyapatite synthesis in sol-gel process

Synthesis of hydroxyapatite (HA) through sol–gel process in different solvent systems is reported. Calcium nitrate tetrahydrate (CNTH) and diammonium hydrogen phosphate (DAHP) were used as calcium and phosphorus precursors, respectively. Three different synthesis reactions were carried out by changing the solvent media, while keeping all other process parameters constant. A measure of 0.5 M aqueous DAHP solution was used in all reactions while CNTH was dissolved in distilled water, tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) at a concentration of 0.5 M. Ammonia solution (28–30%) was used to maintain the pH of the reaction mixtures in the 10–12 range. All reactions were carried out at 40 ± 2°C for 4 h. Upon completion of the reactions, products were filtered, washed and calcined at 500°C for 2 h. It was clearly demonstrated through various techniques that the dielectric constant and polarity of the solvent mixture strongly influence the chemical structure and morphological properties of calcium phosphate synthesized. Water-based reaction medium, with highest dielectric constant, mainly produced β-calcium pyrophosphate (β-CPF) with a minor amount of HA. DMF/water system yielded HA as the major phase with a very minor amount of β-CPF. THF/water solvent system with the lowest dielectric constant resulted in the formation of pure HA.本研究报道了在不同溶剂体系中通过溶胶-凝胶法合成羟基磷灰石（hydroxyapatite, HA）的实验过程。本实验分别以四水合硝酸钙（calcium nitrate tetrahydrate, CNTH）和磷酸氢二铵（diammonium hydrogen phosphate, DAHP）作为钙源与磷源前驱体。通过调控溶剂介质开展三组不同的合成反应，其余所有工艺参数均保持一致。所有反应均采用0.5 M的DAHP水溶液；而CNTH则分别以0.5 M的浓度溶解于蒸馏水、四氢呋喃（tetrahydrofuran, THF）与N,N-二甲基甲酰胺（N,N-dimethylformamide, DMF）三种溶剂中。使用浓度为28%~30%的氨水溶液，将反应混合体系的pH值维持在10~12区间。所有反应均在40±2℃条件下恒温反应4小时。反应结束后，对产物进行过滤、洗涤，并在500℃下煅烧2小时。通过多种表征手段可明确证实：溶剂体系的介电常数与极性对所合成磷酸钙的化学结构与形貌性能具有显著影响。介电常数最高的水相反应介质主要生成β-焦磷酸钙（β-calcium pyrophosphate, β-CPF），仅伴随少量羟基磷灰石；N,N-二甲基甲酰胺/水（DMF/water）体系则以羟基磷灰石为主要物相，仅含有极少量的β-CPF；介电常数最低的四氢呋喃/水（THF/water）溶剂体系则可生成纯相羟基磷灰石。