ISSN:
1551-2916
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Maschinenbau
,
Physik
Notizen:
Three novel Si-C-B-N ceramic compositions, namely Si2.9B1.0C14N2.9, Si3.9B1.0C11N3.2 and Si5.3B1.0C19N3.4, were synthesized using the polymer-to-ceramic transformation of the polyorganoborosilazanes [B(C2H4Si(Ph)NH)3]n, [B(C2H4Si(CH3)NH)2–(C2H4Si(CH3)N(SiH2Ph))]n, and [B(C2H4Si(CH3)–N(SiH2Ph))3]n, where Ph is phenyl (C6H5), 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 Si5.3B1.0C19N3.4, 1.7 wt%·h−1 for Si2.9B1.0C14N2.9, and 2.4 wt%·h−1 for Si3.9B1.0C11N3.2. The measured amount of mass loss rate was comparable to that of pure SiC materials. As crystalline phases, β-Si3N4 and β-SiC were found exclusively in the samples annealed at 2200°C at 0.1 MPa in argon. For thermodynamic reasons, β-Si3N4 should have decomposed into the elements silicon and nitrogen at that particular temperature and gas pressure. However, the presence of β-Si3N4 in our materials indicated that carbon and boron kinetically stabilized the Si3N4-based composition.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1151-2916.2001.tb00984.x
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