Titanium and its alloy components are one of the most important technological materials, which has found extensive application in various industries. However, surface defects play a key role in the mechanical properties of these components. Currently, wet chemical etching is one of the most important procedure for surface processing due to the presence of HF since it can etch metal oxide. Therefore, there still a need to investigate the etching mechanism. In this work, adsorption of HF on TiO2(110) surface has been studied using density functional theory to investigate the fundamental process of etching. HF molecule is adsorbed on the TiO2 surface by dissociation to form Ti-F and O-H species. The interaction between HF and TiO2surface become more favorable at high HF coverage. The pre-adsorbed of water molecule is favorable for HF adsorption process, which is in good agreement with experimental results. Fluorination processes show the formation and desorption of water intermediate at 0.50 ML coverage. We also investigated the relation between the work function and Mulliken charge for HF adsorption. The results indicate that the interaction of F on the surface attracts electrons due to its higher electronegativity than oxygen. Our results suggest that adsorption of HF is considered chemisorption process.
Ti2AlV alloys are commonly employed as structural materials in electronics, metallurgy, and other industries because of their outstanding properties. Knowledge about their surface properties is lacking and limited at the atomic level. In this work, structural, electronic, and stabilities of Ti2AlV surfaces were investigated using the density functional theory approach. This study also looked at the surface energies and work functions of various surfaces. According to our findings, it was found that the (110) surface is thermodynamically stable with lower surface energy than the (100) surface. It was discovered that the surface energy increases with regard to the thickness of the surface slab. Furthermore, the work function of the (110) surface was found to be increasing than that of the (100) surface. Moreover, the work function was found to increase with increasing number of layers in both surfaces. The partial and total density of states of Ti2AlV (100) and (110) were also studied. It was also found that the Fermi level lies at the minimum curve in the TDOS graphs for the Ti2AlV (110) surface while lies at the maximum in (100) surface.
The adsorption and interaction mechanisms of gaseous molecules on ZnO surfaces have received considerable attention because of their technological applications in gas sensing. The adsorption behavior of NH3 and NO2 molecules on undoped and Sn-doped ZnO (101) surfaces was investigated using density functional theory. The current findings revealed that both molecules adsorb via chemisorption rather than physisorption, with all the adsorption energy values found to be negative. The calculated adsorption energy revealed that the adsorption of the NH3 molecule on the bare ZnO surface is more energetically favorable than the adsorption of the NO2 molecule. However, a stable adsorption configuration was discovered for the NO2 molecule on the surface of the Sn-doped ZnO surface. Furthermore, the adsorption on the undoped surface increased the work function, while the adsorption on the doped surface decreased. The charge density redistribution showed charge accumulation and depletion on both adsorbent and adsorbate. In addition, the density of states and band structures were studied to investigate the electronic behavior of NH3 and NO2 molecules adsorbed on undoped and Sn-doped ZnO (101) surfaces.
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