Carbon fibers infiltration

Structures have been produced that utilize all of the above materials and even some other binders. Found in this group of materials are carbon fibers infiltrated and held together with pyrolytic carbon, silicon carbide, glassy carbon, FIFE, methyl methacrylate, epoxies, and petroleum pitches as well as combinations thereof. The structures may contain randomly oriented chopped fibers or long filaments oriented in random, 2, 3 and n dimensions. 

Chemical Vapor Infiltration) [9]. As the carbon fiber itself is the main material, a low cost production process for the composite itself and for coating the composite might be advantageously investigated. 

For applications where only mechanical properties are relevant, it is often sufficient to use resins for the filling and we end up with carbon-reinforced polymer structures. Such materials [23] can be soft, like the family of poly-butadiene materials leading to rubber or tires. The transport properties of the carbon fibers lead to some limited improvement of the transport properties of the polymer. If carbon nanotubes with their extensive propensity of percolation are used [24], then a compromise between mechanical reinforcement and improvement of electrical and thermal stability is possible provided one solves the severe challenge of homogeneous mixing of binder and filler phases. For the macroscopic carbon fibers this is less of a problem, in particular when advanced techniques of vacuum infiltration of the fluid resin precursor and suitable chemical functionalization of the carbon fiber are applied. 

It is also interesting to note that electroless plating of silver on carbon fiber surface improves the wettability between molten aluminum and PAN based carbon fibers using the liquid infiltration technique in vacuum (Warrier et al., 1993). This is attributed to the formation of an eutectic phase between silver and aluminum, and the silver coating of the fibers during processing. 

Carbon/carbon composites fabricated by multiple cycles of liquid impregnation and recarbonization are a typical example of modern petroleum derived carbons. In the 1975 ACS Symposium on Petroleum Derived Carbons (JL), papers were presented on carbon/carbon composite materials formed by pyrolytic infiltration processes (2 ) or by liquid impregnation with petroleum pitch (3,4), on fabrication processes for high-modulus carbon fibers based on polyacrylonitrile (PAN) or pitch precursors ( 5 ), and on the use of carbon materials for thermostructural (6 ) as well as biomedical applications (1 ) ... 

It should be noted that the t-plot analysis shows a very small amount of micropores in the sample studied, which is due to the use of the mesophase pitch as the carbon precursor. It is known that many precursors, e.g., sucrose and polyfurfuryl alcohol, infiltrate well siliceous templates but after carbonization give meso- or macroporous carbons with complementary microporosity. This is not the case for the mesophase pitch, which is used to synthesize carbon fibers that are nonporous materials. 

FIGURE 12.11 Improvements of the mechanical properties of three-dimensional reinforced CMCs by hybrid infiltration routes (a) R.T. flexural stress-strain plots for a three-dimensional carbon fiber reinforced composite before and after cycles of infiltration (comparison between eight cycles with zirconium propoxide and fonr cycles pins a last infiltration with aluminum-silicon ester (b) plot of the mechanical strength as a fnnction of the final open porosity for composites and matrix of equivalent porosity, before and after infiltration (Reprinted from Colomban, R and Wey, M., Sol-gel control of the matrix net-shape sintering in 3D reinforced ceramic matrix composites, J. Eur. Ceram. Soc., 17, 1475, 1997. With permission from Elsevier) (c) R.T. tensile behavior (d) comparison of the R.T. mechanical strength after thermal treatments at various temperatures. (Reprinted from Colomban, R, Tailoring of the nano/microstructure of heterogeneous ceramics by sol-gel routes, Ceram. Trans., 95, 243, 1998. With permission from The American Ceramic Society.)... 

Multidimensional BN fiber infiltrated (matrix) composites are analogous to carbon-carbon composites and overcome the brittleness and low to moderate thermal shock resistance of hot-pressed BN. With the availability of BN fibers (see 17.3.5.4), a weave of three or more dimensions is possible. Chemical vapor deposition may produce a turbostatic BN matrix that is sensitive to H2O, while liquid impregnation requires multiple reimpregnation cycles h One scheme is to impregnate a BN woven fiber preform with H3BO3, dry, sinter in NH3, and hot-press. 

Pemsler et al. earlier introduced the concept of carbon fiber reinforced internal barrier, where diffusion barrier metals are infiltrated electrochemically into matrix-free carbon fibers in a specially oxidized surface ply of C-C. Infiltration was carried out successfully with Re, Rh and Ir. The rhodium coatings were found non-cracked, adherent, and survived thermal cycles to as high as l,600 C. 

Develop a slurry molded carbon fiber material with a carbon chemical vapor infiltrated sealed surface as a bipolar plate. 

The materials used in this investigation are always C/SiC composites, which were processed by the classical chemical vapor infiltration (CVI). CVl processing is used to deposit the PyC interphase on the carbon fibers and infiltrate the SiC matrix into the perform pores. 

In this paper, carbon fiber cloth reinforced SiC-ZrB2 composites (2D C/SiC-ZrBa) were prepared by slutiy infiltration of ZrB2 powders and precursor infiltration and pyrolysis (PIP) process to infiltrate SiC matrix, and accordingly mechanical property, anti-oxidation property, and torch ablation property were investigated. 

The infiltration of carbonaceous structures by liquid silicon or silicon vapor is also an interesting technique to produce SiC components. Especially the Si-inhltration of C-structures coining from natural materials like wood offers the possibility for low cost fabrication of SiC, and has already been described in Sect. 4. Infiltration of polymer-matrix derived carbon fiber reinforced carbon is schematically drawn in Fig. 14 [255, 256]. The production of complex SiC-composite parts and components as well as big parts is possible by this route. 

Fabrication by Liquid Polymer Infiltration (LPI) In the first step of the LPI process, a carbon-fiber preform is infiltrated with resin (e.g. polycarbosilane), to bind the fibers together. Then the polymer is pyrolized to form SiC. These process steps are repeated a number of times until the pores are narrow enough that further... 

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