Properties and high-temperature irradiation behavior of graphites prepared with uncalcined coke

Abstract

Molded graphite compacts, prepared with uncalcined coke or uncalcined coke and pitch binder were studied. Volume shrinkages of 30 per cent were observed during carbonization and graphitization. The volume changes were accompanied by a decrease in electrical resistivity and an increase in the strength of the compacts that contained a pitch binder. The strength of compacts without binder was low. During baking the filler particles developed large basal-plane cracks. Relatively few cracks were formed in the grains of compacts that contained no binder. Increasing the pitch content reduced the total porosity of compacts heat treated to 2600°C but increased the closed porosity, and reduced the anisotropy of the compacts. A decrease in the anisotropy of linear dimensional contractions was observed in the specimens heated to 2600°C and of highest pitch content after irradiation at 1450°C to 3.25 × 10 21n/cm 2 (E > 0.18 MeV). The large basal-plane cracks formed in the filler particles during baking were closed during irradiation. These changes in the microstructure were accompanied by changes in density and porosity. Thermal expansion coefficients increased for samples without pitch binder but no changes were observed in those with pitch binder.