High-temperature neutron irradiation of highly oriented carbons and graphites

✍ Scribed by R.J. Price

• Publisher: Elsevier Science
• Year: 1974
• Tongue: English
• Weight: 918 KB
• Volume: 12
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(74)90022-0

✦ Synopsis

Highly oriented massive pyrolytic carbons were acnealed at, 2900-3300°C to produce apparent crystalline heights (L,) ranging from 220 A to 1660 A. Transmission electron microscopy showed that annealing progressively increased the crystallite width, while the height between twist boundaries was little changed over most of the annealing range. The pyrolytic carbons, together with samples of hot-worked polycrystalline graphite.

were irradiated with fast neutrons at 1300-1500°C to 2x lO"n/cm' (E > 0.18 Mel'). Changes in dimensions, thermal expansivities, apparent crystallite heights (L, ), and unit cell heights (C,,) were measured. At 1300-1500°C the c-axis growth and a-axis contraction of the pyrolytic carbons increased linearly with neutron fluence, while the dimensional change rates of the hot-worked graphite decreased with increasing fluence. The dimensional change rates of the annealed pyrolytic carbons decreased systematically with increasing crystal perfection. During irradiation at 1300-1375°C the thermal expansivity in the principal c-direction of as-deposited massive pyrolytic carbon increased rapidly to nearly the theoretical single-crystal value, while that of the hot-worked graphite initially increased, passed through a maximum. and then declined to less than half its initial value.