Wenjia Han

Surface morphology and crystal orientation of electrodeposited tungsten coatings with different pulse parameters

This study was conducted to investigate the influence of pulse parameters on the surface morphology and crystal orientation of the tungsten coatings electrodeposited on pure copper substrates. The deposited coatings were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS). SEM analysis indicates that pulse parameters have significant influences on the surface morphology of the deposited coatings. Meanwhile, the change in grain size of the tungsten coatings demonstrates that the change in frequency and duty cycle could cause the variation of nucleation rate and grain growth of deposits. Moreover, no obvious diffusion layer at the coating/substrate interface is found by line analysis of EDS. XRD results reveal that tungsten coatings are of bcc structure and the preferred orientation of the deposits varies with duty cycle and period.

Surface Topography and Deuterium Retention of Polycrystalline Tungsten and Nanocrystalline Tungsten Film Exposed to Deuterium Plasma

Abstract In this work, polycrystalline tungsten prepared by powder sintering and naonocrystalline tungsten film deposited by magnetron sputtering were simultaneously exposed to deuterium plasma with energy of 78 eV and fluence of 3.9 × 1024 m−2 at 450 K. The morphologies of both samples before and after deuterium plasma exposure were measured by scanning electron microscopy. Then, the deuterium retention of both samples was determined by thermal desorption spectroscopy. After irradiation, a few blisters were observed on polycrystalline tungsten, but no sign of surface modification was detected on nanocrystalline tungsten film. In addition, the deuterium retention is higher in nanocrystalline tungsten film than in polycrystalline tungsten. The fact that nanocrystalline tungsten film deposited by magnetron sputtering has a larger density of grain boundaries and native defects are responsible for no blistering and high retention in comparison with the polycrystalline tungsten.