权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Control of the critical undercooling in the heterogeneous nucleation,

控制异质成核中的临界过冷度，

基本信息

批准号：
13650797
负责人：
NAKAJIMA Keiji
金额：
$ 2.18万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13650797/
关键词：
Heterogeneous nucleation catalyst Critical undercooling Selection of primary phase Interfacial free energy Pure Fe Fe-Ni alloy Fe-Cr-Ni alloy

项目摘要

In order to elucidate the nature of the heterogeneous nucleation, a differential sacanning calorimetry (DSC) thermal analysis of pure Fe, Fe-Ni alloys (Ni content : 1 to 30 mass%) and Fe-Cr-Ni alloys (Cr + Ni content : 1 to 30 mass%) containing TiN, Al_2O_3, and Ti_2O_3 was conducted. Then, special attention was paid to the difference in the phase of the primary crystal nucleated by the triggering effect of a catalyst (nucleating agent). Thus some important features on the heterogeneous nucleation were found in a series of DSC thermal analysis.1. The solidification and transformation modes appearing during cooling in these alloys is classified into three cases : F mode, FA mode and A mode. The change of modes and the critical undercooling. ΔT, depend on the kind and the amount of catalyst used as well as the chemical composition. In addition, in spite of the kind of primary crystal the value of ΔT is always small in the order of TiN, Al_2O_3 and Ti_2O_3. That is, the catalytic potency of TiN is greatest.2. The most significant factor for the heterogeneous nucleation is cosθ, that is, the interface free energy ratio, (γ_<CL>-γ_<SC>)/γ_<LS>. The greater catalytic potency indicates a smaller critical undercooling, that is, a cosθ close to unity. The approximately optimum condition is γ_<CL> 【approximately equal】 γ_<LS> and γ_<SC> 【approximately equal】 O. This condition means that there is a close similarity in the crystal structure between the catalyst and the primary crystal. Therefore the lattice disregistry becomes also small. Thus, Bramfit's relation can be qualitatively explained.

为了阐明异质成核的本质，对纯Fe、Fe-Ni合金（Ni含量：1至30质量％）和含有TiN、Al_2O_3和Ti_2O_3的Fe-Cr-Ni合金（Cr+Ni含量：1至30质量％）进行了差示扫描量热法（DSC）热分析。然后，特别关注通过催化剂（成核剂）的触发作用而成核的初晶的相的差异。因此在一系列DSC热分析中发现了异相成核的一些重要特征。 1．这些合金在冷却过程中出现的凝固和转变模式分为三种情况：F模式、FA模式和A模式。模式的变化和临界过冷度。 ΔT，取决于所用催化剂的种类和用量以及化学成分。另外，无论初晶的种类如何，ΔT值总是较小，依次为TiN、Al_2O_3、Ti_2O_3。即TiN的催化效力最大。 2．异相成核最重要的因素是cosθ，即界面自由能比(γ_<CL>-γ_<SC>)/γ_<LS>。催化效力越大，临界过冷度越小，即 cosθ 接近于 1。近似最优条件为γ_<CL>【约等于】γ_<LS>和γ_<SC>【约等于】O。该条件意味着催化剂与初晶的晶体结构非常相似。因此，晶格不重合也变小。因此，Bramfit 关系可以得到定性解释。