The influence of crystallite size on the dimensional changes induced in carbonaceous materials by high-temperature irradiation

✍ Scribed by J.C. Bokros; G.L. Guthrie; A.S. Schwartz

• Publisher: Elsevier Science
• Year: 1968
• Tongue: English
• Weight: 737 KB
• Volume: 6
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(68)90050-x

✦ Synopsis

Measurement have been made of the dimensional changes induced by fast neutrons in natural graphite, annealed pyrolytic carbon, catalytically graphitised carbon, and turbostratic carbon, for irradiation temperatures below 1300°C. Plots of the rate of change of the crystallite dimensions vs. temperature show the existence of a minimum rate for all but the natural crystals. This minimum rate occurs at a temperature which increases with increasing crystallite size. For the largest crystallite sizes (natural crystals), the rate decreases monotonically with temperature up to the highest investigated ( 1300°C). For large crystallites (> 200 A) and low irradiation temperatures (-2OO"C), the rate of dimensional change is insensitive to crystallite size. The rate becomes increasingly dependent on crystallite size as the irradiation temperature is increased. At temperatures near 12OO"C, the rate varies by over two orders of magr'ntude for the various crystallite sizes used in the present study. The functional dependencies noted from the data are qualitatively consistent with the ideas of REYNOLDS and THROWER that involve the temperature-dependent heterogeneous nucleation of widely spaced interstitial clusters.