Method for preparing ultra-pure cadmium

Abstract

The invention discloses a method for preparing ultrahigh-purity cadmium. The method for preparing the ultrahigh-purity cadmium comprises the following steps of: remelting and shaping: melting a cadmium ingot in a high-purity graphite crucible, pouring the melted cadmium ingot into a graphite boat, and cooling and shaping the melted cadmium ingot again to form the cadmium ingot; acid pickling: after corroding the cadmium ingot obtained in the remelting and shaping step by using a nitric acid aqueous solution for 1.5-2.5 hours, taking out the cadmium ingot, and then cleaning the cadmium ingot byusing a nitric acid ethanol solution until the surface of the cadmium ingot is bright and the cadmium ingot shows the natural color of cadmium metal; and cleaning the surface of the cadmium ingot byusing water until the surface of the cadmium ingot is neutral, and drying the surface moisture in vacuum; and zone melting: carrying out zone melting on the cadmium ingot subjected to the acid pickling step to obtain a finished cadmium product. According to the method for preparing the ultra-pure cadmium, the pre-treatment of the cadmium raw material is added before the zone-melting step, so thatthe purity of a cadmium finished product can be further improved.

Description

technical field [0001] The invention relates to the technical field of cadmium preparation equipment, in particular to a method for preparing ultra-high-purity cadmium. Background technique [0002] Cadmium is a silvery-white shiny metal with high tensile strength. It can be used in electroplating and manufacturing plastic stabilizers and pesticides, etc., and has a wide range of applications. Among them, the cadmium zinc telluride (CZT) nuclear radiation detector and the mercury cadmium telluride (MCT) infrared detector substrate material made of ultra-high-purity cadmium with a purity of 99.99999% (7N) are used in national defense, security, positioning, and guided infrared detection. The field has wide application. Impurities in cadmium directly affect the performance of CZT and MCT crystal materials, and then affect the detection range and detection accuracy of these two detectors. Therefore, it is of great significance to study and prepare an ultra-high-purity cadmium ...

AI Technical Summary

Problems solved by technology

[0004] However, this method has some defects. First, in the process of manufacturing by this method, due to the high content of impurities in the cadmium raw material, and the distribution of impurities is often not very uniform, when it is directly placed on a quartz boat for heating, the distribution is uneven. Uniform impurities are difficult to completely remove, and the impurities contained in them will also cause the carbon film on the quartz boat to fall off, affecting the purification effect of the product

[0005] Secondly, this kind of zone melting heating tube that uses electricity to generate heat basically adopts the structure of resistance wire, but on the one hand, the heat on the external resistance wire will be dissipated during the process of transferring the heat on the external resistance wire to the cadmium raw material in the zone melting tube through heat transfer and heat radiation. A lot of heat is lost, the heat transfer efficiency is low and the ambient temperature is too high; on the other hand, the temperature of the resistance wire is difficult to control accurately, and it is difficult to meet the requirements in the preparation of ultra-high-purity cadmium with very strict precision requirements, and the pass rate is difficult to improve

Furthermore, since the raw materials in the quartz boat need to be heated repeatedly to achieve the target purity, the production cycle of this type of equipment is only a single set of quartz boats and quartz boats, and the efficiency is relatively low.

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