基于分子动力学的热化学储能过程中CaO/Ca(OH)_(2)分子扩散机制研究  

Study on Diffusion Mechanism of CaO/Ca(OH)_(2) Molecules During Thermochemical Energy Storage Process Based on Molecular Dynamics

作　　者：房意 李英杰[1] 张友浩 任宇 韩奎华[1] 赵建立[1] FANG Yi;LI Yingjie;ZHANG Youhao;REN Yu;HAN Kuihua;ZHAO Jianli(Shandong Engineering Research Center for High-efficiency Energy Storage and Hydrogen Energy Utilization,School of Energy and Power Engineering,Shandong University,Jinan 250061,China)

机构地区：[1]山东大学能源与动力工程学院,高效储能及氢能利用山东省工程研究中心,济南250061

出　　处：《高等学校化学学报》2024年第5期71-80,共10页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金(批准号:52276204)资助.

摘　　要：在CaO/Ca(OH)_(2)热化学储能过程中,CaO晶粒的结构演变会影响材料的储能和机械性能.本文通过分子动力学模拟研究了热化学储能过程中CaO/Ca(OH)_(2)晶粒中分子的扩散强度和晶格结构的变化.结果表明,脱水反应过程中Ca(OH)_(2)分子的运动符合体扩散机制.其中,O/H原子的扩散指前因子为7.9×10^(-8)m^(2)/s,而Ca原子的扩散指前因子仅为4.7×10^(-8) m^(2)/s,O/H的快速扩散破坏了材料原有的晶格结构,使得脱水后CaO的结晶度降低.在水合反应过程中,CaO晶粒外层分子的扩散指前因子为3.2×10^(-8) m^(2)/s,为内层分子的2.5倍,CaO分子扩散符合表面扩散机制.由于水合过程中CaO分子的整体扩散强度较弱,因此对CaO晶格结构影响较小.从分子层面揭示了CaO/Ca(OH)_(2)分子在热化学储能过程中的扩散机制.In CaO/Ca(OH)_(2) energy storage process,the energy storage and mechanical performance are related to the structure of CaO grains.This work investigated the lattice structure and molecular motion of CaO/Ca(OH)_(2) grains during CaO/Ca(OH)_(2) energy storage process using molecular dynamics simulations.The result indicates that during the dehydration stage,the movement of Ca(OH)_(2) molecules is consistent with the bulk diffusion mechanism.The diffusion pre-exponential factor for O/H atoms is 7.9×10^(-8) m^(2)/s,while that for Ca atom is only 4.7×10^(-8) m^(2)/s.The rapid diffusion of O/H destroys the original lattice structure,leading to a reduction in the crystallinity of CaO after dehydration.In the hydration stage,the diffusion pre-factor for outer molecules of CaO grains is 3.2×10^(-8) m^(2)/s,which is 2.5 times higher than that of inner molecules.Consequently,the molecular motion of CaO molecule is consistent with the surface diffusion mechanism.The diffusion strength of CaO molecule is weak during the hydration stage,resulting in minimal impact on the CaO lattice structure.The simulation determines the diffusion mechanisms of CaO/Ca(OH)_(2) molecules in the thermochemical energy storage process.This is crucial to understand the crystal structure evolution of CaO-based materials in CaO/Ca(OH)_(2) energy storage process.

关 键 词：氧化钙/氢氧化钙热化学储能 氧化钙晶粒 机械性能 分子扩散 分子动力学模拟 

分 类 号：O641[理学—物理化学] TK512.4[理学—化学]