Materials World Network: Multi-Scale Study of Chemical Vapor Infiltrated Carbon/Carbon Composites
Final Report Abstract
Within this project, pyrolytic carbon (PyC) has been investigated aiming at a thermo-mechanical description of its properties under consideration of its structure and decomposition over different length scales. Pyrolytic carbon is a graphite-like material and is used as micro constituent of carbon/carbon or carbon/silicon composites. PyC results from surface deposition of carbon-rich gases at elevated temperatures to form graphite-like structures with varying texture degrees. The microstructure of PyC can be described by an ensemble of graphene planes and manifests itself in terms of projections of the graphene planes in high resolution transmission electron microscope (HRTEM) lattice fringe images. Depending on the width of the orientation distribution of the projected graphene layers three texture degrees have been defined: low textured PyC (LT), medium textured PyC (MT) and high textured PyC (HT). Due to this very complex microstructure on the nano- and on the micro-scale, statistical concepts as well as image processing methods based on available HRTEM images of pyrolytic carbon of different texture degree have been applied. Having applied Fourier-based image processing as well as texture segmentation algorithms based on local binary patterns on the HRTEM images of pyrolytic carbon, an analytic expression as modified Struve function for the orientation distribution function of the graphene planes on nano-scale has been found. Moreover, the assumption of a von Mises-Fisher distribution for the orientation distribution function of the coherent domains (stacks of graphene planes with common normal vector) on micro-scale has been justified. Estimations for the parameters of the different distribution functions for the different texture degrees have been numerically obtained using a Maximum-Likelihood-method. Taking into account not only the volume fractions of the different constituents on the micro-scale but additionally also their distribution functions, quantitative estimations for the thermomechanical material properties both for the domain properties on the micro-scale and for composites on the macro-scale have been achieved for the first time. Based on numerical simulations of the influence of the porosity on the crack propagation on the mesoscale, a methodology for the numerical microstructure optimization for specimen with prescribed boundary conditions has been realized. The manufacturing of pryrolytic carbon by CVI has been simulated with a more detailed reaction mechanism within the framework of two dimensional flow field simulations. It has been found that the reactor is operated far away from thermodynamic equilibrium when ethanol is used as gas precursor. For the first time, a multi-scale microscopical analysis combined with measurement of mechanical behavior of planar PyC deposits has been carried out. CVI conditions responsible for observed textural gradients on PyC deposits have been revealed. In summary, the first steps towards a quantitative understanding between the microstructure and the macro-scale material properties of pyrolytic carbon have been established thereby linking physical properties on different length scales.
Publications
- Chemistry and kinetics of chemical vapor deposition of pyrolytic carbon from ethanol, Proceedings of the Combustion Institute, 33,1843-1850, 2010
A. Li, S. Zhang, B. Reznik, S. Lichtenberg, G. Schoch, O. Deutschmann
- Elastic constants of high-texture pyrolytic carbon measured by ultrasound phase spectroscopy, Carbon; 48(12), 3635-3658, 2010
J.-M. Gebert, B. Reznik, R. Piat, B. Viering, K. Weidenmann, A. Wanner, O. Deutschmann
- Elastic properties of pyrolytic carbon with axisymmetric textures, Technische Mechanik, 30, 4, (2010), 343-353
T. Böhlke, K. Jöchen, R. Piat, T.-A. Langhoff, I. Tsukrov, B. Reznik
- Micromechanical Modeling of CFCs Using Different Pore Approximations. In Ed: Krenkel W., Lamon J.: High Temperature Ceramic Materials and Composites, AVISO Verlagsgesellschaft mbH, Berlin, Germany, 590-597 (2010)
R. Piat, S. Dietrich, J.-M. Gebert, G. Stasiuk, K. Weidenmann, A. Wanner, T. Böhlke, B. Drach, I. Tsukrov, A. Bussiba
- Synthesis of Pyrolytic Carbon Composites Using Ethanol As PrecursorInd. Eng. Chem. Res., 49:10421-10427, 2010
A. Li, S. Zhang, B. Reznik, S. Lichtenberg, O. Deutschmann
- Numerical modeling of carbon/carbon composites with nanotextured matrix and 3D pores of irregular shapes, International Journal of Solids and Structure, 48, (2011), 2447-2457
B. Drach, I. Tsukrov, T. Gross, S. Dietrich, K. Weidenmann, R. Piat, T. Böhlke
- On the ability of nanoindentation to measure anisotropic elastic constants of pyrolytic carbon, ZAMM
T. Gross, N. Timoshchuk, I. Tsukrov, R. Piat
(See online at https://doi.org/10.1002/zamm.201100128) - Homogenization of the Elastic Properties of Pyrolytic Carbon Based on an Image Processing Technique, ZAMM
T. Böhlke, T.-A. Langhoff, S. Lin, T. Gross
(See online at https://doi.org/10.1002/zamm.201100180) - Microstructure characterization of CVI-densified Carbon/Carbon Composites with various fiber distribution, Comp. Sci. and Tech., 72, 15, (2012), 1892-1900
S. Dietrich, J.-M. Gebert, G. Stasiuk, A. Wanner, K. Weidenmann, O. Deutschmann, I. Tsukrov, R. Piat
(See online at https://doi.org/10.1016/j.compscitech.2012.08.009)
