异质形核过程中的外延生长

项目名称： 异质形核过程中的外延生长

项目编号： No.51474148

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 矿业工程

项目作者： 夏明许

作者单位： 上海交通大学

项目金额： 83万元

中文摘要： 受制于观察手段，异质形核的研究尚未取得直接证据说明异质形核过程的原子机制。从热力学角度可知，异质形核的形核自由能与固液界面两侧的晶格结构匹配程度、也即晶格错配度密切相关。无论是经验事实或理论计算均证实理想的异质形核核心需满足晶格错配度小于10%~12.5%。申请人在实验中尝试通过选择特定的单晶异质形核基体，将新相/异质相晶格错配度增加到32%，在凝固后的异质相/新相界面观察到外延生长层，证实异质形核在错配度大于12.5%的情况下存在外延生长过程。本研究拟结合TEM、HRTEM等手段，进一步研究异质形核过程中的界面行为、形核自由能及外延生长特性，研究异质形核过程中影响外延生长的可能因素，如异质形核核心的化学成分、晶格常数、熔体中的微量元素、不同形核核心之间的相互作用等。尝试通过对上述因素的研究并结合热力学分析得出影响异质形核外延生长过程的原子机理，并据此探索控制核电用钢的组织控制。

中文关键词： 凝固行为；异质形核；外延生长；组织控制

英文摘要： Heterogeneous nucleation is the major nucleation behavior of liquid metal attracting more and more interesting from all over the research community. But due to the limitation on the spatial and time resolution of the current available facilities, there is no direct evidence at atomic level for heterogeneous nucleation. From thermodynamics point of view, free energy of heterogeneous nucleation is affected by lattice misfit. Both empirical facts or theoretical calculation indicate that the nucleating substrates are potent when the lattice misfit is no larger than 12.5 pct. The applicant has presented the evidence for epitaxial growth in heterogeneous nucleation through the investigation on the nucleation of liquid Al on single crystal substrates with large lattice misfit (32%) . In this research, TEM and HRTEM will be used to further investigate the interface behavior of heterogeneous nucleation and the feature of epitaxial growth during the nucleation. The factors affecting the nucleation behavior of liquid metal like the chemical composition of substrates, the lattice parameters, trace element in liquid metal and the interaction behavior between different substrates will also be investigated combined with thermodynamic analysis in the study to acquire the atomic mechanism of heterogeneous nucleation behavior and to instruct the microstrcutural control in the solidification of the steel for nuclear power station.

英文关键词： solidification behavior;Heterogeneous nucleation;Epitaxial growth;microstructural control