Transition-Al2O 3 nanopowder was first prepared by the precipitation-coated method combined with the freeze drying technique by using AlCl3·6H2O, ammonia, ammonium chloride （NH4Cl） as raw materials, and then ch...Transition-Al2O 3 nanopowder was first prepared by the precipitation-coated method combined with the freeze drying technique by using AlCl3·6H2O, ammonia, ammonium chloride （NH4Cl） as raw materials, and then characterized with X-ray diffraction （XRD）, thermogravimetric analysis （TGA）, differential scanning calorimetry （DSC）, BET surface area and particle size analyzer.Coating precipitation surface with NH4Cl, adding surface activator, washing with ethanol and freeze drying were used to decrease particle agglomeration.γ-Al2O3 nanopowder with an average diameter of 6.73 nm and γ-δ-Al2O3 nanopowder with an average diameter of 11.92 nm were obtained by calcination of the precursors at 600℃ and 950℃, respectively.Phase transformation of Al2O 3 ,the principle of precipitation surface coated by NH4Cl and the mechanism of anti-agglomeration via surface coating were also investigated.展开更多
Silane coupling agent KH560 was used to modify the surface of nano-α-Al<sub>2</sub>O<sub>3</sub> in ethanol-aqueous solution with different proportions. The particle size of nano-α-Al<sub&...Silane coupling agent KH560 was used to modify the surface of nano-α-Al<sub>2</sub>O<sub>3</sub> in ethanol-aqueous solution with different proportions. The particle size of nano-α-Al<sub>2</sub>O<sub>3</sub> was determined by nano-particle size analyzer, and the effects of nano-α-Al<sub>2</sub>O<sub>3</sub> content, ethanol-aqueous solution ratio and KH560 dosage on the dispersion and particle size of nano-α-Al<sub>2</sub>O<sub>3</sub> were investigated. The material structure before and after modification was determined by Fourier transform infrared spectroscopy (FTIR). Aqueous polyurethane resin and inorganic components are combined with modified nano-α-Al<sub>2</sub>O<sub>3</sub> dispersion to form chromium-free passivation solution. The solution is coated on the galvanized sheet, the adhesion and surface hardness are tested, the bonding strength of the coating and the surface hardness of the substrate are discussed. The corrosion resistance and surface morphology of the matrix were investigated by electrochemical test, neutral salt spray test and scanning electron microscope test. The chromium-free passivation film formed after the modification of nano-α-Al<sub>2</sub>O<sub>3</sub> increases the surface hardness of galvanized sheet by about 85%. The corrosion resistance of the film is better than that of a single polyurethane film. The results show that the surface hardness and corrosion resistance of polyurethane resin composite passivation film are significantly improved by the introduction of nano-α-Al<sub>2</sub>O<sub>3</sub>.展开更多
文摘Transition-Al2O 3 nanopowder was first prepared by the precipitation-coated method combined with the freeze drying technique by using AlCl3·6H2O, ammonia, ammonium chloride （NH4Cl） as raw materials, and then characterized with X-ray diffraction （XRD）, thermogravimetric analysis （TGA）, differential scanning calorimetry （DSC）, BET surface area and particle size analyzer.Coating precipitation surface with NH4Cl, adding surface activator, washing with ethanol and freeze drying were used to decrease particle agglomeration.γ-Al2O3 nanopowder with an average diameter of 6.73 nm and γ-δ-Al2O3 nanopowder with an average diameter of 11.92 nm were obtained by calcination of the precursors at 600℃ and 950℃, respectively.Phase transformation of Al2O 3 ,the principle of precipitation surface coated by NH4Cl and the mechanism of anti-agglomeration via surface coating were also investigated.
文摘Silane coupling agent KH560 was used to modify the surface of nano-α-Al<sub>2</sub>O<sub>3</sub> in ethanol-aqueous solution with different proportions. The particle size of nano-α-Al<sub>2</sub>O<sub>3</sub> was determined by nano-particle size analyzer, and the effects of nano-α-Al<sub>2</sub>O<sub>3</sub> content, ethanol-aqueous solution ratio and KH560 dosage on the dispersion and particle size of nano-α-Al<sub>2</sub>O<sub>3</sub> were investigated. The material structure before and after modification was determined by Fourier transform infrared spectroscopy (FTIR). Aqueous polyurethane resin and inorganic components are combined with modified nano-α-Al<sub>2</sub>O<sub>3</sub> dispersion to form chromium-free passivation solution. The solution is coated on the galvanized sheet, the adhesion and surface hardness are tested, the bonding strength of the coating and the surface hardness of the substrate are discussed. The corrosion resistance and surface morphology of the matrix were investigated by electrochemical test, neutral salt spray test and scanning electron microscope test. The chromium-free passivation film formed after the modification of nano-α-Al<sub>2</sub>O<sub>3</sub> increases the surface hardness of galvanized sheet by about 85%. The corrosion resistance of the film is better than that of a single polyurethane film. The results show that the surface hardness and corrosion resistance of polyurethane resin composite passivation film are significantly improved by the introduction of nano-α-Al<sub>2</sub>O<sub>3</sub>.
