Modeling of Chemical Vapor Infiltration for Pyrocarbon within Capillaries

doi:10.15541/jim20150365

Abstract

Abstract:

Coupling homogeneous gas-phase reaction mechanism with lumped reaction mechanism, the pyrocarbon deposition process of the methane pyrolysis was simulated within the capillaries. The initial concentrations for the involved gas-phase species at the mouth of capillary are obtained firstly by computation of the plug flow using homogeneous gas-phase reaction mechanism during methane pyrolysis. Chemical vapor infiltration of pyrocarbon from methane in the capillary is simulated by deposition model, hydrogen inhibition model and lumped reaction mechanism. Predicted results for the mean deposition rate along the capillary depth are well validated by previously published experimental results, in which, at temperatures of 1373 and 1398 K, methane pressures are ranging from 10 to 20 kPa, and residence times are of 0.08 and 0.2 s. Simulated results show that the gradient of the mean deposition rate profile increases with methane pressure and capillary depth, and the deposition rate for transition capillary is lower than the corresponding closed capillary.

Key words: modeling, pyrocarbon, methane, chemical vapor infiltration, capillary

CLC Number:

TQ174

TANG Zhe-Peng, ZHANG Zhong-Wei, FANG Jin-Ming, PENG Yu-Qing, LI Ai-Jun, ZHANG Dan. Modeling of Chemical Vapor Infiltration for Pyrocarbon within Capillaries[J]. Journal of Inorganic Materials, 2016, 31(3): 298-304.

Figures/Tables 10

Fig. 1 Sketch of the substrates of capillaries with a diameter of 1.0 mm(a) Small reactor; (b) Large reactorNo.4 of small reactor and No.5 of large reactor are transition capillaries

Fig. 2 Computed molar fraction profiles of major gas-phase species during the methane pyrolysis(a,b) 20 kPa, 1398 K and with various residence times in small reactor; (c) 0.08 s, 1398 K and with various pressures in small reactor; (d) 0.08 s, 1373 K and with various pressures in large reactor

Fig. 3 Scheme of interaction between gas phase and surface for pyrocarbon deposition from methane

Table 1 Reaction terms of related species

Species	Index	R_i
CH₄	c₁	c₁(-k₁-Ic₁k₅*S_v)
C₂H₄	c₂	0.5k₁c₁-k₂c₂- Ic₂k₆S_vc₂
C₂H₂	c₃	k₂c₂-k₃c₃- Ic₃k₇S_v*c₃
C₆H₆	c₄	k₃c₃/3- Ic₄k₈S_vc₄
H₂	c₅	k₁c₁+k₂c₂+0.5k₄c₄+2Ic₁k₅S_vc₁+2Ic₂k₆S_vc₂+ Ic₃k₇S_vc₃ +3 Ic₄k₈S_v*c₄

Table 2 Atom/molecular volume increment[12]

Species	C	H	H₂
Diffusion volume /(cm³·mol^-1)	16.50	1.98	7.07

Fig. 4 Comparison of the computational predictions with the experimental data of the mean deposition rates as a function of the capillary depth in small reactor under the reaction conditions of 1398 K, 0.08 s, 10 kPa, and the cloud chart (right) of the related deposition rate for the substrate No.4 is a transition capillary

Fig. 5 Comparison of the computational predictions with the experimental data of the mean deposition rates as a function of the capillary depth in small reactor under the reaction conditions of 1398 K; 0.08 s; 20 kPa, and the cloud chart (right) of the related deposition rate for the substrate No.4 is a transition capillary

Fig. 6 Comparison of the computational predictions with the experimental data of the mean deposition rates as a function of the capillary depth in large reactor under the reaction conditions of 1398 K, 0.08 s and 10 kPa (a), 15 kPa (b) or 20 kPa (c), and the cloud chart (right) of the related deposition rate for the substrateNo.5 is a transition capillary

Fig. 7 Comparison of the computational predictions with the experimental data of the mean deposition rates as a function of the capillary depth in small reactor under the reaction conditions of 1398 K, 0.2 s and 20 kPa, and the cloud chart (right) of the related deposition rate for the substrate No.4 is a transition capillary

Fig. 8 Comparison of the computational predictions with the experimental data of the mean deposition rates as a function of the capillary depth in large reactor under the reaction conditions of 1373 K, 0.2 s and 20 kPa, and the cloud chart (right) of the related deposition rate for the substrate No.5 is a transition capillary

References 23

[1]	FITZER E, MANOCHA L M.Carbon Reinforcements and Carbon/ Carbon Composites. Berlin, Heidelberg: Springer, 1998.
[2]	SUN L, LI H, ZHANG S.Microstructural characteristics of pitch-based carbon-carbon composites. Journal of Inorganic Materials, 2000, 15(6): 1111-1116.
[3]	LUO R, LI H, YANG Z, et al. A study of properties for carbon/carbon composites fabricated by chemical vapour deposition. Journal of Inorganic Materials, 1996, 11(1): 107-112.
[4]	ZHANG W G, HÜETTINGER K J. Simulation studies on chemical vapor infiltration of carbon.Composites Science and Technology, 2002, 62(15): 1947-1955.
[5]	HU Z J, HÜETTINGER K J. Chemical vapor infiltration of carbon- revised, Part II: Experimental results.Carbon, 2001, 39(7): 1023-1032.
[6]	ZHANG W, HUETTINGER K J.Chemical vapor infiltration of carbon-revised, Part I: Model simulations.Carbon, 2001, 39(7): 1013-1022.
[7]	HU Z, SCHOCH G, HUETTINGER K J.Chemistry and kinetics of chemical vapor infiltration of pyrocarbon: VII: infiltration of capillaries of equal size.Carbon, 2000, 38(7): 1059-1065.
[8]	XU W, ZHANG Z, BAI R, et al. Kinetic modeling of gas-phase reactions for CVD from propane. New Carbon Materials, 2014, 29: 67-77.
[9]	LI A J, DEUTSCHMANN O.Transient modeling of chemical vapor infiltration of methane using multi-step reaction and deposition models.Chemistry Engineering Science, 2007, 62(18/19/20): 4976-4982.
[10]	LI A J, NORINAGA K, ZHANG W, et al. Modeling and simulation of materials synthesis: chemical vapor deposition and infiltration of pyrolytic carbon. Composites Science Technology, 2008, 68(5): 1097-1104.
[11]	LI H, LI A J, BAI R, et al. Numerical simulation of chemical vapor infiltration of propylene into C/C composites with reduced multi-step kinetic models. Carbon, 2005, 43(14): 2937-2950.
[12]	IBRAHIM J, PAOLUCCI S.Transient solution of chemical vapor infiltration/deposition in a reactor.Carbon, 2011, 49(3): 915-930.
[13]	BECKER A, HUETTINGER K J.Chemistry and kinetics of chemical vapor deposition of Pyrocarbon: IV. Pyrocarbon deposition from methane in the low temperature regime.Carbon, 1998, 36(3): 213-224.
[14]	BENZINGER W H, HUETTINGER K J.Chemistry and kinetics of chemical vapor infiltration of pyrocarbon: IV. Investigation of methane/hydrogen mixtures.Carbon, 1999, 37(6): 931-940.
[15]	VIGNOLES G L, GOYHENECHE J, SEBASTIAN P, et al. The film-boiling densification process for C/C composites fabrication: from local scale to overall optimization. Chemistry Engineering Science, 2006, 61(17): 5636-5653.
[16]	NORINAGA K, JANARDHANAN V, DEUTSCHMANN O.Detailed chemical kinetic modeling of pyrolysis of ethylene, acetylene, and propylene at 1073 - 1373 K with a plug-flow reactor model.International Journal of Chemical Kinetics, 2008, 40(4): 199-208.
[17]	HUETTINGER K J.CVD in hot wall reactors - the interaction between homogeneous gas-phase and heterogeneous surface reactions.Chemical Vapor Deposition, 1998, 4(4): 151-158.
[18]	DEUTSCHMANN O, TISCHER S, CORREA C, et al. DETCHEM Software Package 2.1 Ed, 2007.
[19]	BENZINGER W H, HUETTINGER K J.Chemistry and kinetics of chemical vapor deposition of Pyrocarbon: II. Pyrocarbon deposition from ethylene, acetylene and 1,3-butadiene in the low temperature regime.Carbon, 1998, 36(3): 23.
[20]	NORINAGA K, DEUTSCHMANN O.Detailed kinetic modeling of gas-phase reactions in the chemical vapor deposition of carbon from light hydrocarbons.Indistrial Engineering Chemistry Research, 2007, 46(11): 3547-3557.
[21]	HU Z, ZHANG W, HUETTINGER K J, et al. Influence of pressure, temperature and surface area/volume ratio on the texture of pyrolytic carbon deposited from methane. Carbon, 2003, 41(4): 749-758.
[22]	LACROIX R, FOURNET R, ZIEGLER D I, et al. Kinetic modeling of surface reactions involved in CVI of pyrocarbon obtained by propane pyrolysis. Carbon, 2010, 48(1): 132-144.
[23]	TANG Z, LI A J, ZHANG Z, et al. Chemistry and kinetics of heterogeneous reaction mechanism for chemical vapor infiltration of pyrolytic carbon from propane. Industrial Engineering Chemistry Research, 2014, 53(45): 17537-17546.