Lignin–silica hybrids as precursors for silicon carbide
✍ Scribed by Isao Hasegawa; Yoshiaki Fujii; Keiko Yamada; Chieko Kariya; Toshio Takayama
- Book ID
- 101256259
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 176 KB
- Volume
- 73
- Category
- Article
- ISSN
- 0021-8995
No coin nor oath required. For personal study only.
✦ Synopsis
Lignin, prepared by digesting cedar with acetic acid, and tetraethoxysilane have been allowed for a sol-gel reaction in tetrahydrofuran using H 2 SO 4 as catalyst to yield lignin-SiO 2 hybrids in the bulk gel form. The solid-state 13 C nuclear magnetic resonance spectra of the hybrids and products formed solely from the lignin under the acidic conditions revealed that the lignin underwent crosslinking during the sol-gel reaction. The degree of crosslinking increased with an increasing amount of H 2 SO 4 . The powdered hybrids have been heated at 1500°C in Ar for carbothermal reduction, resulting in the formation of SiC powders. The lignin-to-tetraethoxysilane mixing ratio of the starting solutions varied free carbon content in the SiC powders. In addition, the amount of carbonaceous residue formed from the lignin upon heating depended on the degree of crosslinking of the lignin. Thus, to adjust the amounts of both the lignin and H 2 SO 4 was necessary for producing the hybrids suitable for precursors for SiC powders with high purity. Critical adjustment of the amounts led to the formation of SiC powders with a free carbon content of 0.57 wt %, implying that the lignin is a beneficial carbon source for the production of SiC powders by the hybrid route.
📜 SIMILAR VOLUMES
Cross-linking reactions of hydropolysilanes with alkyl halides as cross-linking agents were evaluated in order to obtain high yields of oxygen-free silicon carbide ceramics. On the basis of data from infrared spectroscopy, thermogravimetry, solubility, gel permeation chromatography, and ultraviolet
## Abstract This work presents a study of carbon tetrabromide (CBr~4~) as precursor to deposit 3C‐SiC on (001) and (111) Si by VPE technique at temperatures ranging between 1000 °C and 1250 °C. TEM, AFM and SEM results indicate that the epitaxy proceeds as a 3D growth of uncoalesced islands at low