The relation between the deposition conditions, structure, and mechanical properties of isotropic pyrolytic carbons deposited at 1220℃ have been investigated. At constant total flow rate of 1.6 ℓ/min and revolution of the reaction tube of 42RPM, carbons were deposited in tumbling bed a number of different fractions of propane and various amount of bed particles.
Structures were characterized by density and crystallite size. The mechanical properties, Young's modulus, fracture strength, and strain energy to fracture, were measured by three point bending of which the knife edge span was 0.35 inch.
The sink-float density and apparent crystallite size were in the range of 1.90 to 1.96 g/㎤ and 25 to 34Å in the pure pyrolytic carbons, respectively, and 1.95 to 2.02 g/㎤ and 29 to 36Å in the SiC alloyed pyrolytic carbons.
The mechanical properties were measured in the range that Young's modulus was 1.8 to 3.6 Mpsi, fracture strength was 15 to 42 ksi, and strain energy to fracture was 53 to 300 psi, respectively. All of these increased with the amount of bed particles and increased with decreasing the propane concentration.
In spite of having similar density and crystallite size, the mechanical properties of pyrolytic carbon deposited in this system were lower than those of carbons deposited in a fluidized bed. These differences could be explained by the soot inclusions, not being present in a fluidized bed, which had non-load-carrying character and behaved as crack.
The Young's modulus and fracture strength of pyrolytic carbon were increased up to 4.5 Mpsi and 50 ksi, respectively, by alloying the SiC up to 9.3 wt.%.
