The change in the ratio of thermal expansion coefficients of some nuclear graphites at elevated temperatures

Abstract

The coefficients of thermal expansion (CTE) of eleven isotropic and anisotropic nuclear graphites made of either gilsonite coke or needle coke were measured from room temperature to 900°C by using a dilatometer, and they were compared with the BAF (Bacon anisotropy factor) measured at room temperature and the CTE's of crystallites. The CTE for each sample increased and its anisotropic ratio decreased with increasing temperature, and the latter showed the same value of BAF at elevated temperatures. A difference between the CTE of a bulk sample and that of crystallites, and also the change in an accommodation factor, were observed at elevated temperatures.