AbstractMetastable phase formation under highly non-equilibrium thermodynamic conditions within high-energy particle tracks are investigated. In particular, the possible formation of diamond by heavy-ion irradiation of graphite at ambient temperature is examined. This work was motivated, in part, by an earlier study which discovered nanometer-grain polycrystalline diamond aggregates of submicron-size in uranium-rich carbonaceous mineral assemblages of Precambrian age. It was proposed that these diamonds were formed within the particle tracks produced in the carbonaceous minerals by the radioactive decay of uranium. To test the hypothesis that nanodiamonds can form by ion irradiation, fine-grain polycrystalline graphite sheets were irradiated with 400 MeV Kr ions to low fluence (6 × 1012 ions-cm−2). The ion-irradiated (and unirradiated control) graphite were then subjected to acid dissolution treatments to remove the graphite and isolate any diamonds that were produced. These acid residues were characterized by transmission electron microscopy. The acid residue of the ion-irradiated graphite was found to contain nanodiamonds (at several ppm of bulk), demonstrating that ion irradiation of graphite at ambient temperature can produce diamond.
Thermal conductivity measurement of the interaction layer between UMo and Al produced by high-energy heavy ion irradiation
