PURPOSE:To obtain a firm molded article of B4C having uniformly dispersed air- permeable pores and improved dimensional accuracy, by blending B4C powder with an organic binder, molding the blend by an extruder, calcining it in a nonoxidizing atmosphere at high temperature. CONSTITUTION:B4C Powder is blended with a binder of an organic compound, and, if necessary, an inorganic binder, a metal, etc. The blend in a plastic state is molded by an extruder into a desired form, dried and calcined at high temperature, so that the binder is carbonated. By tis method, a molded bar article of B4C having about 20-90vol.% B4C content, about 5-40vol.% porosity, uniformly dispersed given amount of air-permeable pores having =4/1 ratio of length/diameter, high strength and improved dimensional accuracy, is obtained. The molded article of B4C is suitable as a control rod for nuclear reactors, etc.
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