Formation of SiC whiskers from compacts of raw rice husks

Review on the physicochemical treatments of rice husk for production of advanced materials

“…The rice husks are pyrolyzed in the absence of air at a temperature of 700-900°C and then fired at temperatures of 1500°Cin an inert or reducing atmosphere [195]. Therefore, the carbon/silica ratio of the pyrolyzed rice husks plays a vital role in the formation of silicon carbide.T.Liou showed the carbonzation of raw rice husk under nitrogen atmosphere.…”

Growth of SiC whiskers from hydrogen silicone oil

“…Through the crack deviation, whisker bypass and extraction mechanism, SiC whiskers could improve the quality of ceramic coating [4,5]. Up to now, many preparation methods of SiC whiskers have been reported, such as thermal processing of natural carbon-and silica-containing natural materials [6][7][8][9], electrospinning [10], the chemical vapor deposition (CVD) technique [11], shape memory synthesis over CNTs [12,13] or activated carbon [14] and so on. However, above mentioned methods cannot give consideration to the low cost and free purification.…”

Whiskers

“…Four competitive processes have been identified during direct pyrolysis of rice hulls: (1) formation of SiC whiskers, (2) formation of SiC polycrystals, (3) crystallization of amorphous silica, and (4) formation of graphite from amorphous carbon [44]. More recently, KRISHNARAO et al have reported on the formation of SiC whiskers from compacts of raw rice hulls without coking and catalyst [40]. Using a pyrolysis temperature of 1600 C, they obtained a-and b-SiC whiskers, believed to have been formed by reaction of SiO(g) with CO(g).…”

“…The overall carbothermal reaction is written as [39]: Below 1400 C most of the SiC is produced by reaction (1). At higher temperatures, however, the solid-state reaction is replaced by the gassolid reactions: Other possible reactions for SiC whisker formation are [36], [40]: The most economic and widely used production method based on carbothermal reduction of silica is the pyrolysis of silica and carbon obtained from rice hulls [41][42][43][44][45]. The Silar SC-9 whiskers (Table 1) are manufactured in this way.…”