Relationship between bulk density and fatigue strength of porous carbon materials made from rice hull

New utilization of rice hull, which is one of the agricultural waste in Japan, is required from a viewpoint of the recycling. The authors have developed porous carbon material (Rice Hull Silica Carbon: RHSC) made from rice hull. RHSC is manufactured by mixing and impregnating the rice hull particles with a phenol resin, pressure forming, drying, and then carbonizing it in the nitrogen gas atmosphere at high temperatures. Since the rice hull has a natural porous structure, the RHS carbon is manufactured as a porous carbon material. RHSC has core competencies such as low friction coefficient and water resistance, and it is expected to be applied to linear guide elements and sliding bearing. However, RHSC has pores generated during the manufacturing process, and it is considered that the reliability of strength is lower than commonly used sliding member. In this study, the authors carried out a fatigue test, evaluated of fatigue strength of RHSC and elucidated influence by size effect. The strength of RHSC tended to depend on bulk density. In addition, the authors in order to confirm the characteristics of the test piece broken at a low number of cycles, fracture surface was observed by scanning electron microscope. Moreover, pores were observed on fracture surface of test piece, and RHSC was clarified that pores in structure of RHSC influences the fatigue strength. Therefore, it is suggested that the reliability of RHSC can be obtained by stabilizing the bulk density.