ISSN 1070-4272, Russian Journal of Applied Chemistry, 2014, Vol. 87, No. 6, pp. 796−802. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © N.I. Shvets, V.T. Minakov, V.S. Papkov, M.I. Buzin, L.Yu. Bad’ina, A.A. Shimkin, 2014, published in Zhurnal Prikladnoi Khimii, 2014,
Vol. 87, No. 6, pp. 793−799.
AND POLYMERIC MATERIALS
Thermochemical Transformations of Polycarbosilane
Precursors into a Ceramic Matrix
N. I. Shvets
, V. T. Minakov
, V. S. Papkov
, M. I. Buzin
L. Yu. Bad’ina
, and A. A. Shimkin
All-Russian Scientiﬁ c Research Institute of Aviation Materials, ul. Radio 17, Moscow, 105005 Russia
Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
ul. Vavilova 28, Moscow, 117813 Russia
Received April 21, 2014
Abstract—The possibility of preparing polymeric ceramic-forming precursors from polycarbosilane and
oligosilazane was examined. Oligosilazane as a component of polycarbosilane formulations acts as a curing agent,
ensuring curing at 150–300°С in the absence of oxygen and modiﬁ er. Pyrolysis of the cross-linked copolymer in
argon yields an inorganic matrix whose yield is 1.3 times higher than that of pyrolyzates of the starting components.
The major phase of the ceramic products obtained, according to the results of X-ray diffraction and chemical
analyses, is X-ray amorphous silicon carbide. The ceramic obtained is highly resistant to thermal oxidation (up
to 1400°С). The composition of the ceramic and the heat resistance and service characteristics of ceramic-matrix
composite materials prepared on its basis using the “polymer technology” can be controlled by varying the ratio
of the initial oligomers.
Progress of the market of ceramic SiC-matrix com-
posite materials (CCMs) shows that such materials not
only replace traditional monolithic ceramics and metals,
but also, owing to principally new unique properties, ﬁ nd
new application under superextreme conditions involving
the action of such factors as mechanical loads, high tem-
peratures, erosion, radiation, and aggressive media [1–4].
The share of CCMs in the total market of ceramic
items is approximately 4%, and the CCM production
increases by 8–10% annually .
The accumulated experience shows that CCMs of
SiC/C, SiC/SiC, and Si
/С types have real prospects
for application for these purposes. In CCMs fabrication,
the ceramic matrices are produced using gas-phase and
liquid-phase inﬁ ltration methods. Of particular interest
for fabrication of items of complex proﬁ le is the method
of liquid-phase inﬁ ltration based on impregnation of a
reinforcing ﬁ ller with organosilicon polymers, followed
by high-temperature pyrolysis yielding a solid residue
enriched with SiC, Si
, and solid solutions of ternary
or quaternary systems Si–O–C–N, Si–C–N, and Si–B–
C–N [4, 5].
Any organosilicon polymers of branched or cyclolin-
ear structure can be used for preparing ceramic matrices
[5–9]. The yield and composition of the forming inorganic
residues are determined by the nature of the starting
polymer and by the atmosphere in which the pyrolysis
Polycarbosilanes (PCSs), which are organosilicon
oligomers with alternating silicon and carbon atoms in
the molecules and have cyclolinear structure, have the
composition that is the closest in stoichiometry to that
of silicon carbide [7, 8].
The formation of a ceramic from polymeric precursors
involves deep chemical and structural transformations
always accompanied by partial degradation of the starting
polymers and, correspondingly, by the weight loss. One
of key factors determining the suitability of the polymer
for preparing a ceramic and the ﬁ nal properties of the
ceramic is the capability of the polymer to form a large
amount of a ceramic residue.