Improvement of chemical vapor deposition process for production of large diameter carbon base monofilaments

Research was conducted to develop large diameter carbon monofilament, containing 25 to 35 mole % element boron, in the 2.0 to 10.0 mil diameter range using the chemical vapor deposition process. The objective of the program was to gain an understanding of the critical process variables and their effect on fiber properties. Synthesis equipment was modified to allow these variables to be studied. Improved control of synthesis variables permitted reduction in scatter of properties of the monofilaments. Monofilaments have been synthesized in the 3.0 to nearly 6.0 mil diameter range having measured values up to 552,000 psi for ultimate tensile strength and up to 30 million psi for elastic modulus.