Influence of pH Value on the Performance of Composite Films Prepared from Chromium Residue by Hydrothermal Method

With chromium residue as main raw materials,the composite films were prepared by hydrothermal method.The samples were characterized by SEM,ICP,XRD,FT-IR and film thickness,and the influences of hydrothermal pH value on the performance of composite films were investigated using the films’ refractive index and reflectivity as evaluation indexes.The results show that the perfect three dimension networks are appeared on the film surface when pH value is above 11.At pH value of 9 or 10,Al2O3,Fe2O3,Fe(OH)3,Cr2O3,AlO(OH) and MgO crystals are formed in the sample,and the diffraction peak of them is strong.There are pores and surface absorbed water between internal nanoparticles in the samples.In the process of hydrothermal synthesis,the formation of chemical bonds force between the membrane material and basement are facilitated by the alkaline groups.Meanwhile,the thicker film is the smaller the refractive index of the film will be.At pH value of 11,the film is the thinnest and the refractive index is the biggest.At the initial pH value of 12,the refractive index of the film to ultraviolet light is weaker than glass substrate,and at the initial pH value of 11,the refractive index of the film to visible light is weaker than that of glass substrate.