纳米锑掺杂氧化锡制备中超临界CO_2干燥的工艺优化及动力学

Process optimization and kinetic study of supercritical CO_2 drying in preparation of nanosized antimony doped tin oxide

纳米锑掺杂氧化锡（ATO）具有优越的光电性能,在制备过程中前驱体干燥处理至关重要。为掌握ATO前驱体的超临界CO2干燥工艺特性,研究了超临界干燥的时间、温度、压力和CO2流量等工艺参数对纳米ATO粒径、比表面积等的影响,进一步探讨了超临界CO2流量对干燥动力学的影响规律,并拟合了干燥曲线方程。结果表明：温度35~40℃、压力10~14 MPa、CO2流量1.2~1.8 L·h-1、干燥5~6 h,最终能够获得平均粒径20~30 nm、高比表面积的纳米ATO材料;流量对干燥速率有明显影响,醇分比0.4为干燥速率由恒速转为降速的临界点,醇凝胶干燥动力学方程能够很好地描述ATO醇凝胶干燥工艺过程。研究结果可为湿法制备纳米材料的湿凝胶干燥工业化生产和控制提供参考。

Antimony doped tin oxide（ATO） has excellent optoelectronic properties. To obtain a small particle size and well-dispersed nano ATO materials in the drying process is a critical step in the preparation. In this paper, the supercritical drying time, temperature, pressure and CO2 flow rate were studied as the main parameters affecting the nano ATO particle＇s size and specific surface area. In addition, the kinetic equations of drying curve were fitted. ATO nano particles with average particle size of 20—30 nm and high specific surface area of 75—80 m2·g-1 were obtained with the supercritical CO2 drying process parameters： temperature（35—40℃）, pressure（10—14 MPa）, CO2 flow rate（1.2—1.8 L·h-1）, drying time（5—6 h）; and alcohol gel drying process could be divided into three stages： rising speed, uniform speed and decreasing speed. There was a critical point in the alcohol ratio（MR） of alcoho gel, and when MR was smaller than 0.4, drying slowed down from uniform speed to decreasing speed. However, large supercritical flow rate could not obviously increase drying rate on the other hand. In addition, the Weibull function was used to describe the kinetics of supercritical CO2 drying process of alcohol gel. As a result, the kinetic model was built and the drying process could accurately be described by the Weibull function. The results could provide helpful reference for industrial production and control of wet gel dried by supercritical CO2 in the preparation of well-dispersed nano particles.