Formation of TiC coatings by high energy plasma focus carbon ion beams

Abstract

Summary form only given. Among other features, the plasma focus (PF) is a well known source of energetic ion beams, of characteristic energy from hundreds of keV to tens of MeV. We have previously characterized the main features of ion beam emission in a low energy, 1.8 kJ, 160 kA Mather type PF device operating in methane. There we found that for the operational conditions of the PF, the dominant charge states of the carbon ions are C+4 and C+5, with maximum flux on axis of the order of 2ldr1022 ions/m2s, and characteristic energy in the 300 to 1000 keV. We have now investigated the effect of high energy PF carbon ion beams irradiation onto titanium targets. Pure titanium target were located at 0deg, 10deg, 15deg, and 25deg with respect to the PF axis, at 6 cm from the anode edge. The Ti samples were exposed to 50 shots of the PF, operating in methane, at 0.3 torr. The irradiated samples were analyzed with scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis and X-ray diffractometry (XRD). SEM images indicate for samples located at 10deg and 15deg, submicron size, closely packed regular structures form onto the Ti surface. At 0deg, the sample appears as a cracked surface, with some irregular isolated structures, whereas at 25deg, closely packed structures in the submicron size range are also observed, but with an irregular spatial distribution. The EDX analysis indicate the highest atomic carbon content in the irradiated samples corresponds to angular distribution between 10deg and 25deg. The XRD analysis shows that at 0deg the surface has an important content of TiC, which becomes lower at off-axis locations, where different carbon structures, including nanotubes, dominate. The strong angular dependence in surface morphology and composition is related to the axial distribution of carbon ion beams, which has been found to be of maximum energy on axis, but of higher flux in the 10deg to 15deg range. A detailed analysis of the correlations between the irradiated samples properties and the carbon ion beams features will be presented.