籾殻炭化物からのSi-O-C系繊維の合成 : 生成条件の解明  [in Japanese] Synthesis of Si-O-C Fibers from Rice Husk Carbide : Explanation of Formation Condition  [in Japanese]

In our previous studies, ceramic materials were synthesized by reactions of oxy-silicate minerals such as siliconoxide (SiO_2), talc (3MgO ・ 4SiO_2 ・ H_2O), olivin (2(Mg, Fe)O ・ SiO_2) and chlorite (H_4Mg_2Al_2SiO_9) with carbon, or obtained from carbide of rice husk which is one of natural organic materials. In the previous report, a ceramic fiber with a two or three-layered structure was synthesized; each layer has different concentrations of constituents, Si, O, and C. The aspect ratio of the fiber was large. The yield of the ceramic fiber, however, was small. In this study, an attempt to find suitable experimental conditions for greater yield and homogeneous definite quality of the ceramic fibers was carried out. In addition, the reaction mechanism from rice husk carbide to the fiber was investigated. The obtained optimum conditions were as follows. (1) Reaction temperature was 1480℃; (2) the ratio of mixing N_2 and H_2 was 1 : 2 in volume; (3) the linear velocity of gas flow was about 0.7 cm/s. A gaseous reaction of SiO with CO was clearly shown to be responsible for the production of the ceramic fibers, in comparison with the experiments using standard samples and gases such as Si, SiO and SiO_2, and Ar, N_2, H_2, CO and CO_2.