Rate of Oxidation of Carbon Fiber/Carbon Matrix Composites with Antioxidation Treatment at High Temperature

Abstract

The carbon fiber/carbon matrix composites (C/C composites) are widely used in such systems as rocket nozzles, reentry shields of space vehicles, disk brakes, and heating elements. However, the unprotected C/C composites have very poor oxidation resistance even at temperature as low as 500~ In this work, the oxidation behavior of C/C composites without and with antioxidation treatments was studied in order to improve the oxidation resistance of C/C composites. The specimens were embedded in the mixture of chromium powder, alumina powder, and/or a small quantity of the activator of NH4C1. All the mixture was contained in a graphite crucible of $ 25 • ~b 15 • 35 mm and reacted at 1000~ under argon atmosphere for several hours. The addition of silicon carbide into the matrix of the C/C composites was also tried, It decreased the oxidation rate of the C/C composites under 600~ but had no effect on the oxidation rate over 600~ When the composites were oxidized without any antioxidation treatment, the matrix was easily oxidized compared with the fibers. The chromium coating by pack-cementation with the activator was very useful in preventing the oxidation of the C/C composites. The micromechanism of the coatiflg reactions is discussed on the basis of thermodynamic ~tabilit$ diagram of the Cr-C-C12 system. The chromium powder would produce chromium carbides by the reaction with the C/C composites. The HC1 dissociated from the NH4C1 would react with chromium powder and then produce chromous halide. This liquid chromous halide would react with the C/C composites and yield chromium carbide, Also, this chromous halide would further permeate the openings between the chromium carbide producing chromium carbides in deep sites of the composites. The dense layer of Cr203 would be formed by the oxidation of the chromium coatings, and thus it would prevent the oxidation of the C/C composites.

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“…Coloration of dye-inert fabrics: As a high-performance fibers, carbon fibers play a very important role in a variety of hightech fields, including aerospace, sports, automotive, chemical industry, infrastructure, military, energy, reinforcement in composite materials, textiles, and semiconductors, owing to their remarkable properties, such as high strength, stiffness, heat and chemical resistance, low densities, good thermal and electrical conductivities, excellent creep resistance, biological compatibility, and fatigue resistance [34][35][36][37]. However, coloring of carbon fibers is difficult due to insufficient chemical affinity between carbon fibers and dyes and their high crystallinity.…”

Recent Progress and Future Challenges of Functional Textiles Fabricated by Atomic Layer Deposition

“…Coloration of dye-inert fabrics: As a high-performance fibers, carbon fibers play a very important role in a variety of hightech fields, including aerospace, sports, automotive, chemical industry, infrastructure, military, energy, reinforcement in composite materials, textiles, and semiconductors, owing to their remarkable properties, such as high strength, stiffness, heat and chemical resistance, low densities, good thermal and electrical conductivities, excellent creep resistance, biological compatibility, and fatigue resistance [34][35][36][37]. However, coloring of carbon fibers is difficult due to insufficient chemical affinity between carbon fibers and dyes and their high crystallinity.…”