Flow investigations in liquid metals for crystal growth under the influence of a travelling magnetic field using a dual-plane ultrasound measurement system

使用双平面超声测量系统研究行进磁场影响下晶体生长的液态金属的流动

• 批准号: 269790734
• 负责人: Professor Dr.-Ing. Jürgen W. Czarske
• 金额: --
• 依托单位: Institut für NE-Metallurgie und Reinststoffe
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/269790734?language=en
• 关键词: Flow; investigations; liquid; metals; crystal

The objective of the research project is a detailed investigation of complex flows occurring at the directed solidification of metal melts using the vertical gradient freeze method with a travelling magnetic field. For growing semiconductor crystals from a melt, the crystal quality can be improved by applying spatially and temporally tailored magnetic fields during the growth process. The occurring flow fields are characterized by complex three-dimensional and time-varying structures. The flow measurements have to be performed simultaneously in at least two planes. Up to now, such investigations failed because of the insufficient properties of measurement techniques applicable to liquid metals. To overcome this problem, a novel multi-component dual-plane ultrasound measurement system will be employed which uses ultrasound-arrays driven in a combined time and frequency division multiplexing operation. Due to the progress in available computing power the flow patterns and the temporal evolution from one to another can be recorded and studied in real-time and especially for long measurement time intervals.In this project, imaging investigations of the melt flow in two planes under thermal, geometric and magnetic conditions relevant for crystal growth will be accomplished for the first time. The investigation of transient and fluctuating flow situations in dependence of the melt height takes centre stage. From the fluid mechanical point of view a special interest lies in the point how the transition between two-dimensional and three-dimensional as well as between stationary and time-varying flow patterns takes place. The results gained by experiment will continuously be compared with those of numeric simulation. This benefits not only the development of the model configurations but also the verification of numeric models for flow simulation. The results will be transferred to real crystal growth processes by means of scaling laws which will be developed during the project. They also will be the basis for the development of future strategies for flow control using magnetic fields.

该研究项目的目标是使用行进磁场的垂直梯度冻结方法对金属熔体定向凝固时发生的复杂流动进行详细研究。对于从熔体中生长半导体晶体，可以通过在生长过程中施加空间和时间上定制的磁场来提高晶体质量。发生的流场具有复杂的三维和时变结构的特点。流量测量必须在至少两个平面上同时进行。到目前为止，由于适用于液态金属的测量技术性能不足，此类研究尚未成功。为了克服这个问题，将采用一种新颖的多组件双平面超声测量系统，该系统使用以组合时分和频分复用操作驱动的超声阵列。由于可用计算能力的进步，可以实时记录和研究流动模式和从一个到另一个的时间演变，特别是在长测量时间间隔下。在该项目中，将首次完成与晶体生长相关的热、几何和磁性条件下两个平面中熔体流动的成像研究。对与熔体高度相关的瞬态和脉动流动情况的研究占据了中心位置。从流体力学的角度来看，人们特别感兴趣的是二维和三维之间以及静止和时变流动模式之间的转变是如何发生的。实验获得的结果将不断与数值模拟的结果进行比较。这不仅有利于模型配置的开发，而且有利于流动模拟数值模型的验证。结果将通过项目期间开发的缩放定律转移到真实的晶体生长过程中。它们也将成为未来利用磁场进行流量控制策略开发的基础。