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Novel Silicon‐Boron‐Carbon‐Nitrogen Materials Thermally Stable up to 2200°C
Author(s) -
Wang ZhiChang,
Aldinger Fritz,
Riedel Ralf
Publication year - 2001
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2001.tb00984.x
Subject(s) - analytical chemistry (journal) , nitrogen , isothermal process , boron , materials science , annealing (glass) , argon , silicon , atmospheric temperature range , chemistry , nuclear chemistry , metallurgy , physics , chromatography , thermodynamics , meteorology , organic chemistry
Three novel Si‐C‐B‐N ceramic compositions, namely Si 2.9 B 1.0 C 14 N 2.9 , Si 3.9 B 1.0 C 11 N 3.2 and Si 5.3 B 1.0 C 19 N 3.4 , were synthesized using the polymer‐to‐ceramic transformation of the polyorganoborosilazanes [B(C 2 H 4 Si(Ph)NH) 3 ] n , [B(C 2 H 4 Si(CH 3 )NH) 2 –(C 2 H 4 Si(CH 3 )N(SiH 2 Ph))] n , and [B(C 2 H 4 Si(CH 3 )–N(SiH 2 Ph)) 3 ] n , where Ph is phenyl (C 6 H 5 ), at 1050°C in argon. The Si‐B‐C‐N ceramics exhibited significant stability with respect to composition and mass change in the temperature range between 1000° and 2200°C, including isothermal annealing of the samples at the final temperature for 30 min in argon. The mass loss rate at 2200°C was as low as 1.4 wt%·h −1 for Si 5.3 B 1.0 C 19 N 3.4 , 1.7 wt%·h −1 for Si 2.9 B 1.0 C 14 N 2.9 , and 2.4 wt%·h −1 for Si 3.9 B 1.0 C 11 N 3.2 . The measured amount of mass loss rate was comparable to that of pure SiC materials. As crystalline phases, β‐Si 3 N 4 and β‐SiC were found exclusively in the samples annealed at 2200°C at 0.1 MPa in argon. For thermodynamic reasons, β‐Si 3 N 4 should have decomposed into the elements silicon and nitrogen at that particular temperature and gas pressure. However, the presence of β‐Si 3 N 4 in our materials indicated that carbon and boron kinetically stabilized the Si 3 N 4 ‐based composition.