Surface Structuring of Zirconium by Thermal Plasma Treatment

The thermal plasma setup was designed, fabricated, and successfully established. The effects of thermal plasma treatment on the surface morphological, compositional, electrical, mechanical, and wettability properties of zirconium (Zr) have been investigated. The Zr targets were treated with atmospheric Ar thermal plasma at different Ar flow rates ranging from 10 to 25 L/min and under different treatment times starting from 10 to 25 min. Scanning electron microscope (SEM) and optical analyses reveal the growth of various kinds of surface structures, such as microrods, flakes, pores, cracks, dendrites, agglomerates, and ridges on treated Zr. This growth is explainable on the basis of ion-induced localized heating, melting, collisional sputtering, Coulomb explosion, and thermal spike model. It was observed that both the size and number density of flakes decrease from 8 to 5 $\mu \text{m}$ and $87\times 10^{6}$ to $37\times 10^{6}$ cm $^{-2}$ with increasing Ar flow rate and treatment time. Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses show that there are no compositional changes in Zr after Ar plasma. However, slight change in crystallite size and dislocation line density is observed. The electrical conductivity has been decreased, while hardness and wettability of Zr are increased after treatment.