Synthesis and Properties of Chemically Modified Polycarbosilane Containing Organofluoric Groups
- PDF / 189,713 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 24 Downloads / 206 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Synthesis and properties of chemically modified polycarbosilane containing organofluoric groups Sachiko Okuzakia) and Yuji Iwamoto Fine Ceramics Research Association, Synergy Ceramics Laboratory, 2-4-1 Mutsuno Atsuta-ku, Nagoya 456, Japan
Koichi Kikuta and Shin-ichi Hirano Nagoya University, 1 Furo-cho, Chikusa-ku, Nagoya 464-01, Japan (Received 7 April 1998; accepted 5 October 1998)
The chemically modified polycarbosilane (PC) containing organofluoric groups, PCOCF, was synthesized through chemical reaction of PC and fluoric alcohol. Pyrolysis of the polymer precursor occurred in three stages under 1000 ±C. Weight loss due to evaporation of low molecular compounds was observed at the first stage below 300 ±C, followed by the largest weight loss from 300 to 600 ±C at the second stage. At this stage, side chains formed during the chemical reaction were removed. Finally, side chains such as Si–CH3 decomposed at the third stage above 600 ±C. At 1000 ±C, the chemical modification of PC resulted in high yield of solid product. After coating PCOCF on silicon carbide (SiC) powders, the conversion yield of pyrolyzed PCOCF was further improved due to the interaction between PCOCF and SiC powders. Coating of PCOCF on SiC powders was found to be effective in increasing the green density of uniaxially pressed bodies.
I. INTRODUCTION
Recently, many kinds of carbide and nitride ceramics have been prepared from organometallic polymeric precursors.1,2 Silicon carbide (SiC) or silicon nitride (Si3 N4 ) ceramics using an organometallic polymer as a binder have been reported.3,4 A feature of these systems is to use organometallic compounds as a binder which are then converted into microcrystallite powders by pyrolysis to fill grain boundaries of the matrix ceramic grains. Polycarbosilane (PC) is the most typical polymeric precursor of SiC ceramics. PC can be easily modified by chemical reactions to yield new modified compounds. For example, polytitanocarbosilane has been prepared from PC and titanium alkoxide. This precursor transformed into a SiCytitanium carbide (TiC) composite ceramic during thermal treatment.5 Another example is the synthesis of SiCytantalum carbide (TaC) ceramics from tantalum alkoxide modified polycarbosilane.6 The authors have synthesized polyaluminocarbosilane (PCOAl), with which SiC ceramics consisting of submicron-sized platelet grains were found to be fabricated from combining PCOAl with SiC powder.7 Chemical modification of PC is useful for the control of properties of SiC powders. In this study, chemically modified PC containing organofluoric groups (PCOCF) was synthesized to improve the abilities of handling and a)
Present address: Hitachi Research Laboratory, Hitachi Ltd., 7-1-1 Oomika-cho, Hitchi-shi, Ibaraki 319-12, Japan. J. Mater. Res., Vol. 14, No. 4, Apr 1999
http://journals.cambridge.org
Downloaded: 18 Mar 2015
compaction behavior of SiC powders. This is expected to be essential for increasing the green density of SiC compacts when combined wi
Data Loading...
