Characterization of carbon coatings on SiC monofilaments using raman spectroscopy

• Published in: Journal of materials science Vol. 42; no. 13; pp. 5135 - 5141
• Main Authors: WARD, Yanling, YOUNG, Robert J, SHATWELL, Robert A
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01.07.2007; Springer Nature B.V
• Subjects: Accumulation; Applied sciences; Axial stress; Building materials. Ceramics. Glasses; Carbon; Ceramic and carbon fibers; Ceramic industries; Cermets, ceramic and refractory composites; Chemical industry and chemicals; Coatings; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Other materials; Physics; Raman spectroscopy; Residual stress; Shear stress; Silicon carbide; Specific materials; Spectrum analysis; Stresses; Technical ceramics; Thermal expansion; Ceramic matrix composite; Filament; Coating material; Fiber reinforced material; Mechanical properties; Experimental study; Carbon; Modeling; Composite material; Coated material; Characterization; Silicon carbide; Raman spectrum; Residual stress
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-006-1265-3

The axial residual stresses in the carbon coatings deposited onto different silicon carbide monofilaments have been determined experimentally using Raman spectroscopy. The stress-dependent band shift for the carbon G-band at around 1600 cm−1, due to symmetric in-plane stretching mode of graphite, has been found to be −1.6 cm−1/GPa. Using this calibration, the axial residual stresses in carbon coatings can be estimated from measured band shifts between the broken end and middle of the monofilaments. It was found that the stresses in the coatings of all monofilaments were compressive and between −440 and −810 MPa. Modelling indicated that this was consistent with the coating stress arising from the difference in coefficients of thermal expansion of carbon and the underlying silicon carbide. The coating stress was measured as a function of distance from the broken monofilament end. It was found that the distance for the stress to build up varied greatly, from 40 μm in Ultra-SCS to 500 μm in SM1140+. This suggests there are significantly different shear stresses between the coatings and underlying silicon carbide in the different monofilaments.