Abstract: A siliconized graphite for use in mechanical seals is provided. This material is prepared by reacting graphite at an elevated temperature ranging from 1800.degree. to 2100.degree. C. with silicon monoxide. Silicon monoxide is generated in rate-controlled fashion by reacting either silicon carbide and silica or silicon nitride and silica at an elevated temperature ranging from 1500.degree. to 1800.degree. C.Although the optimum temperature range for the SiO generation and the siliconization of graphite is different by 300.degree. C., size-controlled raw materials (silicon carbide, silicon nitride, and silica) and a unique sample loading method make the whole process occurred in situ and make the production of mechanical seals efficient. Size-controlling of the raw materials is essential for a constant supply of silicon monoxide in controlled fashion, and a unique sample loading method is essential to put the SiO generation and the siliconization of graphite within their optimum temperature ranges.