目前，基于激光粉末床熔融（LPBF）增材制造的成形件会不可避免地存在一定程度的气孔缺陷，为探究该缺陷的形成机理，以AlSi10Mg为研究对象，采用离散元法（DEM）和计算流体力学（CFD）对激光增材制造过程中单层和多层成形的熔池流场进行了数值模拟。通过调节激光功率和扫描间距，分析了加工参数对LPBF单道、多道和多层缺陷的影响机制。结果表明：低功率时，熔道易产生球化、扭曲、气孔等缺陷，而高功率时飞溅现象加剧；对于多道成形，扫描间距过大会使搭接区形成气孔缺陷，扫描间距过小将加剧积热效应。对于层间转角为67°、采用棋盘格扫描策略的多层打印，单棋盘格熔道两端的高度不同和道间沟壑是影响铺粉表面粗糙度的主要因素，凹凸不平的铺粉表面会影响铺粉层的厚度均一性，在激光能量不足时导致层间产生气孔，进而影响层间结合质量；适宜的能量输入有助于形成粗糙度小的铺粉平面和足够的熔深，减少层间气孔缺陷。

建立了原子层沉积 (Atomic Layer Deposition, ALD)反应腔室的三维模型, 利用ANSYS Fluent软件模拟分析了ALD过程中压强、前驱体脉冲时间、温度等工艺参数变化对前驱体分布的影响。模拟结果表明: 反应压强越低, Mg(Cp)2前驱体分子的扩散系数越高, 能更快且更均匀地分布在整个反应腔室之中; 前驱体脉冲时间越长, 在反应腔室内的分布越均匀; 当脉冲时间为250ms时, Mg(Cp)2在反应腔室内分布基本均匀, 反应腔室内各部位的前驱体质量分数基本一致; 当脉冲时间为200ms时, H2O基本均匀分布在反应腔室内。在MgO薄膜的ALD温度窗口内, 反应腔室内温度越高, Mg(Cp)2前驱体分子的扩散效应越强。

Surface modification for micro-nanoparticles at the atomic and close-to-atomic scales is of great importance to enhance their performance in various applications, including high-volume battery, persistent luminescence, etc. Fluidized bed atomic layer deposition (FB-ALD) is a promising atomic-scale manufacturing technology that offers ultrathin films on large amounts of particulate materials. Nevertheless, nanoparticles tend to agglomerate due to the strong cohesive forces, which is much unfavorable to the film conformality and also hinders their real applications. In this paper, the particle fluidization process in an ultrasonic vibration-assisted FB-ALD reactor is numerically investigated from micro-scale to macro-scale through the multiscale computational fluid dynamics and discrete element method (CFD-DEM) modeling with experimental verification. Various vibration amplitudes and frequencies are investigated in terms of their effects on the fluid dynamics, distribution of particle velocity and solid volume fraction, as well as the size of agglomerates. Results show that the fluid turbulent kinetic energy, which is the key power source for the particles to obtain the kinetic energy for overcoming the interparticle agglomeration forces, can be strengthened obviously by the ultrasonic vibration. agglomerate size in the FB. This is bound to facilitate the heat transfer and precursor diffusion in the entire FB-ALD reactor and the agglomerates, which can largely shorten the coating time and improve the film conformality as well as precursor utilization. The simulation results also agree well with our battery experimental results, verifying the validity of the multiscale CFD-DEM model. This work has provided momentous guidance to the mass manufacturing of atomic-scale particle coating from lab-scale to industrial applications.