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Sol‐Gel‐Derived Silicon‐Boron Oxycarbide Glasses Containing Mixed Silicon Oxycarbide (SiC x O 4− x ) and Boron Oxycarbide (BC y O 3− y ) Units
Author(s) -
Gervais Christel,
Babonneau Florence,
Dallabonicola,
Sorarù GianDomenico
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.tb00981.x
Subject(s) - boron , materials science , siloxane , silicon , magic angle spinning , pyrolysis , infrared spectroscopy , amorphous solid , crystallography , nuclear magnetic resonance spectroscopy , analytical chemistry (journal) , chemistry , organic chemistry , composite material , polymer , metallurgy
The introduction of B atoms in SiOC glass networks has been achieved through the pyrolysis of sol‐gel‐derived polyborosiloxanes under an inert atmosphere. The starting gels were obtained from hydrolysis‐condensation reactions of triethylborate (B(OEt) 3 ) and an organically modified trialkoxysilane (EtSi(OEt) 3 ). The resulting hybrid EtSiO 1.5 ‐B 2 O 3 gels showed a homogeneous dispersion of the B atoms in the siloxane network via ≡Si—O—B≦ bonds. The presence of such borosiloxane bridges prevents the formation of cyclic or cage siloxane entities and leads to relatively high ceramic yields (∼80%). The transformation of the polyborosiloxanes into amorphous SiBOC glasses was followed using Fourier transform infrared spectroscopy and multinuclear magic‐angle spinning‐nuclear magnetic resonance (MAS‐NMR) ( 11 B, 13 C, and 29 Si). An important change in the carbon, silicon, and boron environments occurs during pyrolysis. Interestingly, the 11 B MAS‐NMR spectra suggest a progressive replacement of the B—O bonds by B—C bonds, which leads to a distribution of trigonal BC x O 3− x sites in the glass that was pyrolyzed at 1000°C, with a residual amount of B(OSi) 3 sites. The resulting glasses can thus be described as silicon‐boron oxycarbide networks that are based on SiC x O 4− x and BC y O 3− y mixed environments.