With the development of modern advanced electronic manufacturing technology, it is required to maintain high purity in the processing of electronic products such as monocrystalline silicon wafers, integrated circuit boards, computer hard disk discs, etc., to avoid the introduction of trace impurities that may cause slight changes in the electrical properties of the product, so the grinding and polishing products for the manufacture of high purity products require high purity.DiamondMicro-powderas a raw material.

The other day we introduceddiamond powderof the coarsePurificationProcess, and after sorting, due to the incomplete preliminary coarse purification, the addition of dispersant in the classification process and the existence of pollution in other processes, obviously cannot meet the requirements of high-purity micropowder, so the micropowder products that have completed classification need to be refined again. The specific principle and operation method are the same as those of coarse purification. The determination of purification process mainly depends on the condition of the product itself and the requirements of the market for the product.

Diamond micro-powder products that have completed rough purification and classification will still be present in the product, such as metal elements, silicates andGraphiteA small amount of impurities. According to the different types of impurities, different processes can be selected to remove them respectively. The regular method is the use of perchloric acid to remove metal impurities and residual graphite, the use of hydrofluoric acid to remove silicate, after fine purification of products are generally able to meet the needs of most customers.

Approximate operation steps

Hydrostatic synthesis or detonation synthesis after rough purification of diamond powder raw materials in turn into nitric acid, perchloric acid, hydrofluoric acid and other acid, heated to acid boiling, and kept for several hours, to dissolve the diamond surface of the adsorption of various impurities, and then high purity water rinse to remove the residual acid and various impurities, after drying is high purity diamond powder.

It should be noted that perchloric acid is a strong oxidant, which can slowly oxidize graphite after heating (it should be noted that perchloric acid can only react with graphite at high temperature, and 72% perchloric acid is not enough to oxidize graphite at normal temperature). The materials from which metal catalyst and a large amount of graphite have been removed are placed in a beaker, perchloric acid is poured, sometimes a small amount of catalyst is added, and the reaction starts after heating the solution, the color of the solution is black gray-green-brown-orange red. When the solution is orange red, the graphite has been completely removed. It can be removed from the electric heating plate, cooled to room temperature, poured out the upper liquid, washed with high purity water, and dried until neutral.

Perchloric acid to remove the process of graphite, the reaction is intense, always pay attention to not overflow, sometimes in order to speed up the reaction rate, can be added to the amount of sulfuric acid in perchloric acid.

However, in practice, the use of perchloric acid to remove graphite is costly and pollutes the air. Therefore, the use of perchloric acid to purify diamond graphite process is mostly replaced by shaker, panning tray or mixed acid treatment of sulfuric acid and nitric acid. Perchloric acid treated diamond is used only when it is used for high purity diamond and fine grain size diamond and when treated as a raw material for sintering polycrystalline diamond.

The nitric acid, perchloric acid and hydrofluoric acid used in the acid treatment process are all analytically pure or above-grade reagents, and the reaction vessels used in the treatment process have the characteristics of strong acid corrosion resistance, high temperature resistance, and no dissolution of related metal or non-metal impurities. According to the special requirements of some customers, you can also choose to remove metal elements from the aqua aqua water treatment again, or you can also use high-temperature alkali treatment to treat the silicate in depth.

In order to ensure the purity of the treated product, various fine purification processes should pay attention to the sequence of the process arrangement. Since the metal removal process in the post-treatment generally uses high-temperature resistant glass containers, it is easy to cause silicon to exceed the standard due to continuous stirring and wear, and the chemical reagents used in the silicate removal process will corrode the glass containers, so it is generally arranged to carry out metal removal treatment first and then silicate removal treatment to avoid possible cross-contamination between processes. At the same time, it is required to strictly control the quality of rinsing water at this stage to avoid secondary pollution.

The whole process of purification due to a certain risk, so the operation essentials must be standardized, the need for professional personnel fine operation.