Heterogeneous nucleation of metals and colloids on templates - a comparative study

金属和胶体在模板上的异质成核 - 比较研究

• 批准号: 51442215
• 负责人: Professor Dr. Dieter M. Herlach (†)
• 金额: --
• 依托单位: Institut für Experimentalphysik IV: Lehrstuhl für Festkörperphysik
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2010-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/51442215?language=en
• 关键词: Heterogeneous; nucleation; metals; colloids; templates

It is envisaged to investigate heterogeneous nucleation of colloidal systems and metallic alloys on differently structured templates. The structure of the template is changed in crystallography and intermediate distance of lattice sites.The colloidal systems used are consisting of charged particles in a salty solution. By changing the surface charge density and/or the salt concentration the interaction potential between the colloids is tuned. Fused silica templates with simple bcc and fcc structured surfaces will be applied. For this the suspensions will be prepared with a continuous preparation technique which allows for the precise control of interaction parameters. Templates will be fixed in flat flow cells and investigated with microscopy and light scattering. Measurement will be carried out at low to moderate metastability. At higher metastability ultra small angle x-ray scattering is applied. Investigations will focus on the kinetics, the morphological changes and phase behaviour in dependence on structure and orientations of the templates.Also crystallization of metals in contact with templates of different structures is studied. Metallic melts of Fe-Ni are undercooled by containerless electromagnetic levitation and crystallization is externally stimulated by touching the undercooled melt drop at preselected undercooling temperature by different structured nucleation trigger. The effect of these changes on the nucleation barrier of heterogeneous nucleation of phase formation as well as the resulting microstructure formation will be investigated.

设想在不同结构的模板上研究胶体体系和金属合金的异质成核。模板的结构在晶体学和晶格位置的中间距离上发生了变化。所使用的胶体系统由盐溶液中的带电粒子组成。通过改变表面电荷密度和/或盐浓度，调整胶体之间的相互作用电势。将应用具有简单bcc和fcc结构表面的熔融二氧化硅模板。为此，将采用连续制备技术制备混悬液，该技术可精确控制相互作用参数。将模板固定在扁平流动池中，并使用显微镜和光散射进行研究。测量将在低至中等亚稳态下进行。在较高的亚稳性，超小角X射线散射被应用。研究重点是动力学、形态变化和与模板结构和取向相关的相行为。还研究了与不同结构模板接触的金属的结晶。采用无容器电磁悬浮法对Fe-Ni合金熔体进行过冷，并通过不同结构的形核触发器在预定的过冷温度下接触过冷液滴来实现外部激励结晶。这些变化的影响上的异质形核相形成的形核势垒，以及由此产生的微观结构的形成将进行研究。