Characterisation of CVD carbon coatings on Nextel^TM440 fibres

Abstract

Carbon coatings were deposited on Nextel^TM440 fibres using C₃H₆–Ar system by hot wall chemical vapour deposition (CVD) with a total pressure of 1·5 kPa. The morphology and structure of the coatings were characterised by SEM, XRD and Raman spectroscopy. As the deposition temperature increased from 1173 to 1373 K, the growth rate increased complying with the Arrhenius law, and the calculated apparent activation energy was 45·9 kJ mol⁻¹. The coating growth was controlled by surface reaction, and smooth coatings were obtained. Above 1373 K, the free energy barrier for the formation of critical nucleus in gas phase was so low that remarkable nucleation occurred, thereby leading to the growth of rough coatings. The grain size and orientation of the coatings both increased as the deposition temperature increased. Additionally, the strength of the fibres coated at 1173 K was the highest, owing to low fibre degradation and healing effect of the thin coatings.

Keywords:

• Carbon
• Oxide
• Fibre coatings
• Tensile strength
• Chemical vapour deposition

Acknowledgements

This study has been financially supported by the National Natural Science Foundation of China (51202291), Aid Program for Innovative Group of National University of Defense Technology, and Aid program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province.