Copper and Nitrogen Co-Doping Effect on Visible-Light Responsive Photocatalysis of Plasma-Nitrided Copper-Doped Titanium Oxide Film

In order to clarify the visible-light responsive photocatalysis of TiO2 co-doped with Cu and N atoms, plasma-nitridation was taken place to Cu-doped TiO2 film. Cu-doped TiO2 films were prepared by dip-coating method and they were nitrided by nitrogen plasma in the plasma-enhanced CVD system. Cu-doped TiO2 films before and after plasma-nitridation show similar X-ray diffraction peaks of anatase TiO2. XPS analysis reveals that the ionic states of Ti and Cu in the Cu-doped TiO2 films are Ti4+ and Cu+, respectively. After nitrogen plasma treatment, oxygen atoms are released by substitution of nitrogen atoms in the TiO2 matrix, so that Cu+ is oxidized to generate Cu2+ and at the same time oxygen vacancy is formed. The absorption edge of both Cu-doped and plasma-nitrided Cu-doped TiO2 did red shift. Visible-light responsive photocatalytic activity of the Cu-doped TiO2 film degraded after nitrogen plasma treatment.

CRYSTAL DEFECTS IN PLASMA NITRIDED LAYER CATALYZED BY RARE EARTH

The microstructure of plasma nitrided layer catalyzed by rare-earth elementshas been studied with TEM. The results show that the grains of gamma ft-Fe_4N phase are refined byrare-earth elements and the plane defects in boundary are increased by rare-earth elements. Theaddition of rare-earth element increases the bombardment effect and the number of crystal defectssuch as vacancies, dislocation loops, twins and stacking faults in gamma ft -Fe_4N phase and canproduce the high-density dislocations in the ferrite of diffusion layer at a distance 0.08mm fromthe surface. The production of a number of crystal defects is one of important reasons whyrare-earth element accelerates the diffusion of nitrogen atoms during plasma-nitriding.

Nitrogen-induced optimization of corrosion resistance for nanocrystalline soft magnetic Fe-Zr-B alloys

The poor corrosion resistance restricts the industrial applications of nanocrystalline soft magnetic Fe-Zr-B alloys.We reported a facile plasma-nitriding surface process to enhance the corrosion resistance of a nanocrystalline Fe90 Zr7 B3 alloy without deteriorating its soft magnetic properties.Potentiodynamic po-larization and electrochemical impedance spectroscopy were performed to investigate the corrosion be-havior.The nitrided alloy shows higher corrosion resistance than the untreated alloy,as evidenced by a nobler corrosion potential,lower corrosion current and higher polarization resistance of surface corrosion film,while their magnetic properties are similar.The microstructures of both nanocrystalline alloys were examined by high-resolution transmission electron microscopy(HRTEM)and the compositions of their corrosion films analyzed by X-ray photoelectron spectroscopy(XPS).For the nitrided alloy,a more homo-geneous nanocrystalline structure developed in the surface nitrided layer containing corrosion-resistant nitride phases(Fe3 N and ZrN)provides a higher resistance against chloride corrosion.Moreover,the ni-trided layer facilitates the formation of a more protective corrosion film with the increased ratios of Fe2+/Fe3+and O2−/OH−as well as higher enrichment of Zr-and B-oxides,while the N-species(NH4+and NO3−)formed in the corrosion film behave as good corrosion inhibitors and further enhance the film pro-tection.Our findings provide a simple strategy for the preparation of corrosion-resistant nanocrystalline soft magnetic alloys to satisfy a variety of engineering requirements.