Methods for Product Qualification and Quality Assurance

摘要

The improved analytical procedures for stoichiometric determination of boron carbide are described. From a large number of measurements made on boron carbide of various origins, the stoichiometric ratio appears related to the production process. The magnesium reaction process yields a product with stoichiometry Bsub(3.63)C representing the limit of the carbon-rich boron carbide phase. On the other hand, the melting process yields a solid solution Bsub(4.45)C, which shows a congruent melting point at 2450 exp 0 C. Formulation B sub 4 C or B sub 12 C sub 3 is not a limit. Among the quality assurance tests, a non-destructive method based on gamma absorptiometry has been developed in order to check the uniformity of boron carbide pellet density. Accurate pseudo-density curves are obtained owing to the self-calibration method in which the mass absorption coefficient is measured for each individual pellet. Through determination of the non-uniformity index this method permits quantitative assessment of production quality and repeatability. Gamma absorptiometry is also useful to determine the point density of boron carbide pellet prior to irradiation in order to obtain an accurate point swelling measurement. (Atomindex citation 14:788219)