The friction and wear behaviors of rice husk (RH) ceramics, prepared by carbonizing the mixture of rice husk and phenol resin at 900 °C in N 2 gas environment, sliding against high carbon chromium steel (JIS SUJ2), austenitic stainless steel (JIS SUS304), and Al 2 O 3 under dry condition were investigated using a ball-on-disk tribometer. The test results show that the friction coefficient of RH ceramics takes very low values 0.05-0.08 and 0.06-0.11 sliding against SUJ2 and SUS304, respectively, and much higher values around 0.14-0.23 against Al 2 O 3 . It was also shown that SUJ2 provides the lowest specific wear rate values below 10 -9 mm 2 /N, while, those of SUS304 and Al 2 O 3 mostly stayed between 10 -9 to 10 -8 mm 2 /N range. The worn surfaces of counterparts were observed with optical microscopy and analyzed using cross-sectional transmission electron microscopy with energy dispersive X-ray spectroscopy and electron diffraction. It was suggested that the tribological behaviors of RH ceramics are closely related with the formation of a transferred film, consisted of amorphous silica and carbon particles, on a counterpart surface. The transferred film was formed readily on SUJ2 balls, whereas for SUS304 the presence of the film was subject of the sliding conditions. Moreover, formation of the transferred film could not be detected on Al 2 O 3 counterparts.

The authors have developed the new hard porous carbon material "Rice Husk ceramics" (RH ceramics) by carbonizing the mixture of rice husk and phenol resin at 900 °C in inert gas environment. The RH ceramics are composed of amorphous carbon and amorphous silica, about 90 and 10 wt.%, respectively. The friction and wear properties of RH ceramics sliding against austenitic stainless steel (JIS SUS304) were evaluated under dry and water lubricated conditions using a ball-on-disk apparatus. The test results showed that RH ceramics have lower friction coefficients and specific wear rates under dry than under water lubricated condition. The friction coefficient took very low values of 0.06 to 0.11 under dry condition, whereas, it was 0.09 to 0.15 under water lubricated condition. The specific wear rate was less than 10 -8 mm 2 /N under both conditions, though it was much lower under dry than under water lubricated condition. Transmission electron microscopy with energy dispersive X-ray spectroscopy and electron diffraction analyses were employed to characterize the properties of the worn surfaces of SUS304 ball samples. It was found that the tribological behavior of RH ceramics is strongly governed by the characteristics of the transferred film formed on counterpart surfaces.

The new hard porous carbon material called the RH (rice husk) ceramics has been developed by carbonizing rice husk as the main raw material. In order to clarify the friction and wear properties of RH ceramics, a study of the effect of carbonization temperature on the mechanical and tribological properties of RH ceramics was undertaken. RH ceramics samples carbonized at 900, 1400, and 1500 °C were prepared for this study. The RH ceramics samples were inspected using X-ray diffraction, EDX and scanning electron microscopy. Mechanical properties of RH ceramics such as Vickers hardness, compressive strength, and bulk density were also studied. The RH ceramics carbonized at 1500 °C had much higher porosity compared to the ones carbonized at lower temperatures. In addition, the bulk density and compressive strength decreased with increasing carbonization temperature. Whereas, the hardness was higher for the RH ceramics carbonized at higher temperatures. Ball-on-disk sliding tests showed that the RH ceramics carbonized at the conventional 900 °C have better friction and wear properties compared to the ones carbonized at 1400 and 1500 °C under dry condition sliding against austenitic stainless steel (JIS SUS304). The friction coefficient and specific wear rate took very low values of 0.07 and less and 5.0×10 -10 mm 2 /N and less, correspondingly, for the RH ceramics carbonized at 900 °C. Based on the experimental results, friction and wear mechanisms have been summarized for each carbonization temperature.