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Maximum heating rates for producing undistorted glassy carbon ware determined by wedge-shaped samples

Published online by Cambridge University Press:  31 January 2011

Hossein Maleki ,
Lawrence R. Holland ,
Gwyn M. Jenkins ,
R. L. Zimmerman  and
Wally Porter
Hossein Maleki
Affiliation:
Center for Irradiation of Materials, Physics Department, Alabama Agricultural and Mechanical University, Normal, Alabama 35762
Lawrence R. Holland
Affiliation:
Center for Irradiation of Materials, Physics Department, Alabama Agricultural and Mechanical University, Normal, Alabama 35762
Gwyn M. Jenkins
Affiliation:
Center for Irradiation of Materials, Physics Department, Alabama Agricultural and Mechanical University, Normal, Alabama 35762
R. L. Zimmerman
Affiliation:
Center for Irradiation of Materials, Physics Department, Alabama Agricultural and Mechanical University, Normal, Alabama 35762
Wally Porter
Affiliation:
High Temperature Materials Laboratory (HTML), Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831–6062
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Abstract

Polymeric carbon artifacts are particularly difficult to make in thick section. Heating rate, temperature, and sample thickness determine the outcome of carbonization of resin leading to a glassy polymeric carbon ware. Using wedge-shaped samples, we found the maximum thickness for various heating rates during gelling (300 K–360 K), curing (360 K–400 K), postcuring (400 K–500 K), and precarbonization (500 K–875 K). Excessive heating rate causes failure. In postcuring the critical heating rate varies inversely as the fifth power of thickness; in precarbonization this varies inversely as the third power of thickness. From thermogravimetric evidence we attribute such failure to low rates of diffusion of gaseous products of reactions occurring within the solid during pyrolysis. Mass spectrometry shows the main gaseous product is water vapor; some carboniferous gases are also evolved during precarbonization. We discuss a diffusion model applicable to any heat-treatment process in which volatile products are removed from solid bodies.

Type
Articles
Information
Journal of Materials Research , Volume 11 , Issue 9 , September 1996 , pp. 2368 - 2375
Copyright
Copyright © Materials Research Society 1996

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References

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