Microstructural, Mechanical, and Tribological Properties of Rice Husk–Based Carbon: Effect of Carbonizing Temperature

Abstract

In this study, we investigated the microstructural, mechanical, and tribological properties of rice husk (RH)-based carbon carbonized at various carbonizing temperatures under dry conditions. All samples exhibited amorphous carbon structures and the X-ray diffraction spectra of the samples carbonized at 1300 and 1400 °C indicated the presence of a polymorphic crystals of silica. The hardness increased with temperature due to the densification of the structure and the presence of the hard crystalline silica. At low normal loads, the mean friction coefficient of the material decreased as the carbonizing temperature was increased from 600 to 800 °C and slightly decreased as the carbonizing temperature was further increased from 800 to 1400 °C. At the highest load, all samples, except for that carbonized at 600 °C, exhibited extremely low friction coefficients (around 0.05). The wear rates of the all samples were smaller than 10⁻⁵ mm³/N·m, indicating that RH carbon exhibits sufficient wear resistance. A Raman spectroscopic analysis of the worn surface of a steel ball revealed that the transfer layer at 600 °C had a less graphitic structure compared to the other carbonizing temperature. Based on these findings, we recommend an optimal carbonizing temperature for applications of sliding materials exposed to dry sliding contact.

Keywords:

• Carbon
• graphite
• unlubricated friction
• unlubricated wear
• adhesion
• self-lubrication friction
• solid/self-lubrication
• Raman
• XRD
• adhesive wear

Acknowledgement

The authors thank Mr. K. Furukawa for his assistance.