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.

为了阐明异质性核化的性质，纯化的sacanning carorimetry（DSC）纯Fe，Fe-Ni合金（NI含量：1至30个质量％）和Fe-Cr-Cr-Ni合金（Cr + Ni含量：1至30 Mass％）的热分析含有TIN，Al_2O_3，Al_2O_3，和TI_2O_________________然后，特别注意通过催化剂的触发作用（成核剂）的核晶体相位的差异。在一系列DSC热分析中发现了异质成核上的一些重要特征1。在这些合金中冷却过程中出现固化和转换模式分为三种情况：F模式，FA模式和A模式。模式的变化和关键的过冷。 ΔT取决于所用的催化剂的种类和量以及化学成分。另外，尽管主要晶体的种类在tin，al_2o_3和ti_2o_3的顺序中始终很小。也就是说，锡的催化效力最大。2。异质核化的最重要因素是cosθ，即界面自由能比，（γ_<cl>-γ_<sc）/γ__<ls>。较大的催化效力表明较小的关键底层过冷，即接近统一的cosθ。大约最佳条件为γ_<cl> [大约相等]γ_<ls>和γ_<sc> [大约等于]O。这种情况意味着催化剂和初级晶体之间的晶体结构有着密切的相似性。因此，晶格的脱离也很小。那就可以定性地解释Bramfit的关系。