The effect of neutron irradiation on the elastic moduli of graphite single crystals

Abstract

The resonant frequency in transverse vibration of natural single crystals of purified Ticonderoga graphite has been measured as a function of neutron dose. The resonant frequency increases on irradiation by a factor of two and saturates at a dose of ∼4 × 10¹⁷ n.v.t. Annealing reduces the resonant frequency again. The indentation hardness of the crystals has been measured and an electron microscopic investigation of the dislocation distribution in irradiated crystals carried out. The increase in resonant frequency on irradiation is shown to be due to a reduction of the strain produced by dislocation motion. Experimental values for 1/S₄₄ and 1/S₁₁ for graphite are derived.