Introduction

Zone refining is a powerful tool for applying coupled melting and freezing operations for manipulating impurities in crystals, as well as for separating liquid or solid mixtures. It was first used to purify germanium in 1952. Zone refining combines the well-known fact that a freezing crystal differs in composition from its corresponding liquid phase, so that passing a short heater along a solid ingot leads to a purification of the ingot. For improving the separation efficiency and reducing time, a series of narrow heaters moving slowly over a solid ingot can be used in multi-pass zone refining.

Several mathematical models have been presented for modelling multi-pass zone refining processes when zone length affects the separation efficiency. Furthermore, variable cross-sectional area ingots with specified volumes have been introduced to improve the separation efficiency. Analogue simulators were used to simulate zone refining by means of a single mathematical equation that expresses solute concentration as a function of distance for any initial distribution of solute and any number of passes through an ingot of a specified length. These simulators include liquid mechanical and electrical analogue simulators. Thousands of significant papers devoted entirely or largely to some aspect of application of zone refining have appeared in the last two decades. For instance, silicon-on-insulator (SOI) films, and semiconducting and superconducting materials were prepared by zone refining operations.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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