Particle-size composition of electrical periclase

Abstract

One of the indices for evaluating the quality of GOST 13236-73 electrical periclase is the particle-size composition [i]. The standard covers production of two types of periclase, "fine" and "coarse," differing in the ratio of the fractions. The periclase produced by foreign firms differs significantly in particle-size composition from domestic.* A comparative analysis of the periclase produced by firms in Japan, West Germany, and England shows that its particle-size composition is close to the requirements of GOST 13236-73 for the "fine" type (Table i).In investigations conducted earlier the influence of the particle-size composition of periclase on its electrical resistance was studied. However, attempts to find a correlation relationship between particle-size composition, electrical resistance, and dielectric strength did not lead to any conclusion, The statistically treated lots were obtained from different raw materials and differed in chemical composition, To reveal the influence of particle-size composition among a large number of relationships was impossible.In Eastern Refractory Institute an investigation has been made of the influence of particle-size composition on the electrical resistance of periclase with the use of methods of experiment planning. For the investigation periclase of a single lot but differing in fraction in accordance with GOST 13236-73 was taken, The influence of the content of fractions coarser than 0.4, 0,25, 0.16, 0,063, and 0,04 mm and finer than 0.04 mm was studied. Since 6 the weight portions of the fractions are not independent values (~=I), methods for investii=J gating multicomponent mixtures similar to those presented in [2] were used, A simplex-lattice plan of the second order was taken as the experiment plan. In accordance with the matrix of this plan periclase samples of individual fractions and combinations of them were prepared and the electrical resistance at 600, 800, and 1000~ was determined.The highest values of electrical resistance were obtained for compositions containing the fractions from 0.4 to 0.063 mm. Compositions of fractions finer than 0.063 mm are characterized by lower values of electrical resistances. This may be explained by the content in the fine fractions of a large quantity of iron and calcium oxide impurities, which have a negative influence on the electrical resistance of periclase,