固相反应法制备β″-Al2O3粉末的热力学研究

摘要

以Na2CO3和α-Al2O3为原料，Na2CO3与α-Al2O3的物质的量比为1：6，采用固相合成法制备β″/β-Al2O3粉末。通过热力学计算原料粉末在不同温度下可能发生的化学反应的吉布斯自由能，并结合Na2CO3/α-Al2O3混合粉末的 DTA 曲线，研究可能发生的化学反应的温度条件。同时，用 X 射线衍射仪(XRD)对固相合成粉末的物相组成进行分析。结果表明，Na2CO3/α-Al2O3混合粉末在1150℃左右开始发生反应生成β″/β-Al2O3；最适宜的反应温度为1250℃，α-Al2O3全部转化为β/β″-Al2O3，并且β″-Al2O3含量最高；当温度升高到1400℃时，β/β″-Al2O3发生分解，生成α-Al2O3和Na2O，并且随温度升高，更多的β/β″-Al2O3发生分解，而Na2O在高温下挥发会促进β/β″-Al2O3的分解。当煅烧温度超过1500℃时，β″-Al2O3分解还生成微量的NaAlO2。%β″/β-Al2O3 powder was prepared by solid state method using Na2CO3 andα-Al2O3 as raw materials with a molar ratio of 1:6. The reaction temperature of different chemical reactions which might occur during calcination process was investigated by the calculation of Gibbs free energy and differential thermal analysis (DTA) curve of Na2CO3 andα-Al2O3 mixed powder. The phase composition of calcined powder was characterized by X-ray diffraction (XRD). Results show that in the mixed powder, Na2CO3 begins to react withα-Al2O3 to formβ″/β-Al2O3 at the temperature of 1 150℃. The optimum calcination temperature is 1 250℃, at which temperature allα-Al2O3 can transform intoβ″/β-Al2O3 and the content ofβ″- Al2O3 is the most. Theβ″/β-Al2O3 will decompose intoα-Al2O3 and Na2O, when calcining temperature increases to 1 400℃. The decomposition content ofβ″/β-Al2O3 increases with the increasing temperature and the evaporation of Na2O under high temperature accelerates the decomposition ofβ″/β-Al2O3. When the calcining temperature increases to 1 500℃, a small amount of NaAlO2 is produced by the decomposing ofβ″-Al2O3.