Pyrolysis of preceramic polymers allows a new type of ceramic materials to be processed at a relatively low temperature. The ceramics via polymer pyrolysis display a number of exceptional mechanical, thermal and chemical properties, including high thermal stability, high oxidation/creep resistance, etc. Moreover, they offer better geometrical accuracy compared to conventional ceramics. In addition, thermal induced pyrolysis of organometallic polymer precursors offers the possibility of net shape manufacturing at a lower temperature compared to traditional powder sintering process. The pyrolysis of polymer precursors involves curing of polymer precursors in which the polymer undergoes cross-linking to form a green body, followed by a pyrolysis stage that involves the formation of amorphous SiC and crystallization of SiC at a higher temperature. The source material changes phase and composition continuously during polymer pyrolysis based ceramic process. Chemical reactions and transport phenomena vary accordingly. To obtain ceramics with high uniformity of microstructure and species without crack, transport phenomena in material processing needs to be better understood and a process model needs to be developed to optimize the fabrication process. In this paper, a numerical model is developed, including heat and mass transfer, polymer pyrolysis, species transport, chemical reactions and crystallization. The model is capable of accurately predicting the polymer pyrolysis and chemical reactions of the source material. Pyrolysis of a sample with certain geometry is simulated. The effects of heating rate, particle size and initial porosity on porosity evolution, mass loss and reaction rate are investigated. Optimal conditions for the manufacturing are also proposed.

1.
Greil
P.
,
Polymer derived engineering ceramics
.
Advanced Engineering Materials
,
2000
.
6
(
2)
: p.
339
348
.
2.
Chan
W. C. R.
,
Kelbon
M.
,
Krieger
B.
,
Modelling and experimental verification of physical and chemical processes during pyrolysis of a large biomass particle
.
Fuel
,
1985
.
64
: p.
1505
1513
.
3.
Riedel
R.
,
Advances ceramics from inorganic polymers. Materials Science and Technology, A Comprehensive Treatment
. In
Processing of Ceramics, part II
,
1996
.
17B
: p.
1
50
.
4.
Kaya
H.
,
The application of ceramic-matrix composites to the automotive ceramic gas turbine
.
Comp. Sci. tech
,
1999
.
59
: p.
861
872
.
5.
Sternitze
M.
,
Review: structural ceramic nanocomposites
.
Journal of the European Ceramic Society
,
1997
.
17
: p.
1061
1082
.
6.
Herrmann
M.
,
Schuber
C.
,
Rendtel
A.
,
Hubner
H.
,
j. Am. Ceram. Soc. Bull
,
1998
.
81
: p.
1095
1108
.
7.
Mauricio
F.
,
Gozzi
E. R.
,
Valeria
I.
,
Yoshida
P.
,
Si3N4/SiC nanocomposite powder from a preceramic polymeric network based on poly(methylsilane) as the SiC precursor
.
Materials Research
,
2001
.
4
(
1)
: p.
13
17
.
8.
Staggs
J. E. J.
,
Modelling thermal degradation of polymers using single-step first-order kinetics
.
Fire Safety Journal
,
1999
.
32
: p.
17
34
.
9.
Interrante, L.V., et al. High yield polycarbosilane precursors to stoichiometric SiC. Synthesis, pyrolysis and application in MRS Symp. Proc. 1994.
10.
Zunjarrao, S., A. Singh, and R.P. Singh, Structure Property Relationships in Polymer Derived Amorphous/Nano-grained Silicon Carbide for Nuclear Applications. Submitted to 14th International Conference on Nuclear Engineering (ICONE), 2006.
11.
Hurwitz
F. I.
,
Kacik
T. A.
,
Bu
X.-Y.
,
Masnovi
J.
,
Heimann
, and
a. B. P. J.
K.
,
Conversion of polymers of methylandvinylsilane to SiC ceramics
.
Journal of Engineering and Applied Science
,
1994
.
346
: p.
623
628
.
12.
Cullity, B.D., Elements of X-ray Diffraction. 1978: Addison-Wesley Publishing Co. Unc., London.
13.
Tinney, E.R., The combustion of wood dowels in heated air. 10th Symposium (International) on combustion, 1965: p. 925–930.
14.
Mota
M.
,
Teixeira
J. A.
,
Bowen
W. R.
,
Yelshin
A.
,
Binary spherical particle mixed beds: porosity and permeability relationship measurement
.
The Filtration Society
,
2001
.
1
(
4)
: p.
101
106
.
15.
Sinha, S., Jhalani, A., Ravi, M. R., Ray, A., Modelling of pyrolysis in wood: a review.
16.
Zhang, H., Moallemi, M.K., Zheng, L.-L., Transient Two-Dimensional Numerical Simulation of Laminar Flame Spread Over a porous Fuel. HTD-Vol. 304, National Heat Transfer Conference-Volume 2, ASME, 1995: p. 53–62.
17.
Gann, R.G., Harris, Jr. R. H., Krasny. J. F., Levine, R. S., Mitler, H. E., Ohlemiller. T. J., The effect of cigarette characteristics on the ignition of soft furnishings. 1988.
18.
Kansa
E. J.
,
Perlee
H. E.
,
Chailen
R. F.
,
Mathematical model of wood pyrolysis including internal forced convection
.
Combustion and Flame
,
1977
.
29
: p.
311
324
.
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