Study on hydrogen adsorption on WO_(3)(001) surface by density functional theory calculation

Hydrogen reduction of tungsten oxide is currently the most widely used technology to produce metal tungsten for its simplicity and pollution-free nature.The computer simulation is a powerful tool for exploring the mechanism of hydrogen reduction of tungsten oxide from a microscopic view.The density functional theory(DFT) is applied to investigate the adsorption characteristic of hydrogen molecule on the surface and inside the lattice of WO_(3).The adsorption energy of hydrogen on the WO_(3)(001) surface is 66.56 kJ.mol^(-1) which is larger than the adsorption energy of hydrogen molecule inside the lattice of WO3 which indicates that once the hydrogen diffuses inside the lattice,it is easier to adsorb on the O atom to break W-O bond.And The diffusion process of a hydrogen molecule from the WO-terminated WO_(3)(001) surface to the inside of the WO_(3) lattice and hydrogen molecule adsorption inside the lattice was investigated.The activation energy of hydrogen molecule diffusion from the surface down to the first interstitial and diffusion from the first interstitial down to the second interstitial is 195.41 and 172.81 kJ·mol^(-1),respectively.The controlling step of hydrogen reduction of tungsten oxide may be the hydrogen molecule diffusion inside the oxides lattice through the interstitial.

Interface reaction of high-strength low-alloy steel with Al-43.4Zn-1.6Si(wt.%)metallic coating

The microstructure,elemental distribution,phase composition,and thickness of intermetallic layers between high-strength low-alloy steel(H420)/mild carbon steel(DC51)and Al–43.4Zn–1.6Si(wt.%)(galvalume,GL)alloy were comparatively investigated.The experimental results reveal that the interfacial reaction layer was composed of Fe2Al5,Fe4Al13,and Al8Fe2Si intermetallic compounds.Moreover,the growth curves of the Fe2Al5 and Fe4Al13 intermetallic layers fit the parabolic law well,and the total thickness of the intermetallic layers of H420+GL was almost the same as that of DC51+GL.However,the thickness of the Fe2Al5 layer in H420+GL was thinner than that in DC51+GL.In addition,first-principle calculations were performed to explore the effect of Mn on the growth of the Fe2Al5 intermetallic phase,and the results indicate that Mn substitution in Fe2Al5 removes electronic charge from the Al atoms,thus decreasing the thickness of the Fe2Al5 interface layer.