Abstract:

Ceramic membranes are widely used in liquid filtration for their superior chemical resistance, temperature stability and mechanical robustness. Their performance can be further improved by surface modifications, such as liquid phase reactions, which are typically too complicated to control. Atomic layer deposition (ALD), a deposition technique of self-limiting gas/solid phase chemical reactions for growing atomic scale thin films, has been extremely useful for precisely regulating nanoscale pore structures, especially modification and functionalization of porous separation membranes. Most existing ALD equipment are designed for silicon wafer substrate in semiconductor industry, thus design optimization on ALD processes of both precursor flow and surface reactions are needed for application in large-scale ceramic membranes. Computerized fluid dynamics (CFD) modeling was used to investigate ALD process on 1-meter-long single-channeled ceramic membrane by considering both boundary conditions and surface chemical reactions of two precursors pulsed alternatively into the channel. The simulations fitted well with the experimental data at average difference of 1.69% and thus an ALD model for two-way alternatively pulsed rotation was proposed, which would be very helpful in equipment design and process optimization of ALD for large scale ceramic membranes.

Key words: atomic layer deposition, ceramic membranes, computational fluid dynamics, nanoscale structure

摘要：

陶瓷膜具有耐高温、耐酸碱、强度高等优点，在液体分离领域得到了广泛应用。对陶瓷膜进行表面改性，可进一步提升其性能，但基于表面化学反应的改性方法工艺过程复杂，难于控制。原子层沉积（atomic layer deposition，ALD）是基于表面自限制化学反应过程的气固相薄膜沉积技术，可以在纳米尺度精确调控孔道结构，特别适用于多孔分离膜的改性和功能化。目前尚无适用于大尺寸陶瓷膜的ALD设备，需要对ALD过程进行专门的优化设计。通过CFD模型对1 m长的单通道陶瓷膜的ALD过程进行了研究，在数学模型中考虑了两种气体源交替进入腔体中所引发不同的表面反应，并考虑了脉冲边界的影响。模拟计算结果与实验比较平均相对误差为1.69%。在数值模拟的基础上，提出了双向交替旋转脉冲的ALD模式，为陶瓷膜的ALD沉积改性的装备设计和过程优化提供了理论依据。

关键词: 原子层沉积, 陶瓷膜, 计算流体力学, 纳米结构