A study on boron diffusion in high density polyethylene using the (n, α) reaction

Natural boron was diffused in the high-density polyethylene (HDPE) samples through a radiation assisted chemical method. The HDPE samples, each of 25×25×l mm in size, were immersed in a boron–trifluoride–diethyl–ether solution and irradiated with Co-60 gamma-rays at a dose rate of 2.4 KGy h−1. The depth distribution of the diffused boron atoms in the HDPE samples was measured by the nuclear reaction 10B(n, α)7Li, induced by thermal neutrons, with an accuracy of 30 nm. The variation in the depth profile of the diffused boron atoms with radiation dose was studied by changing the irradiation period from 2 to 20 days. A gradual growth in the surface hardness of the HDPE samples with an increase in the boron concentration was observed, however, the latter increased almost linearly with the radiation dose. By exposing HDPE samples to a dose of 1.15 MGy, around 2.7×1016 boron atoms could be diffused over a depth of ≈2 μm. At this boron concentration the surface hardness of the samples enhanced to 8.59 HVN which is 1.7 times that of virgin HDPE.