The Preparation, Performance Analysis Of γ-Alumina And Ag₂O/TiO₂ Nanomaterials And The Research Of Their Application

At present the micro/nano science and technology is the core for the development of the industralized country.Great achievements have been made in the study and application of nanomaterials at home and abroad.However,some new,easy operation,economic and green environmental synthetic methods are still nonexistent. In this paper,on the basis of the previous experiments,we also prepare some new nanomaterials by sol-gel and supercritical ethanol drying method,electroless deposition,and ionic liquids graft technology.The catalytic properties of the nanomarials have been investigated.The detailed contents can be summarized as follows:1.Well defined hexagonγ-alumina(γ-Al₂O₃)nanosheets were successfully obtained with a sol-gel process under supercritical ethanol drying condition.The sol-gel of alumina precursors was carried out in refluxing aqueous solutions that contained excess urea and 0.1-0.4 M Al³⁺,always kept the[urea]/[Al³⁺]ratio constant at a value of 3.0.The obtained precursor precipitates were calcined at different temperatures in a muffle furnace in order to compare with supercritical ethanol drying. The resultantγ-alumina nanoparticles were characterized by X-ray diffraction(XRD), field emission scanning electron microscope(FE-SEM),transmission electron microscopy(TEM)and X-ray photoelectron spectroscope(XPS).The effects of reactant original concentrations in the sol-gel solution,sol-gel precursor concentrations in the supercritical ethanol solution and time for removal supercritical ethanol vapor have been studied.Nanoγ-alumina particles obtained by supercritical ethanol drying exhibited hexagon sheet characteristics with the diameter of 5～10 nm and always had theγ-alumina phase.The formation mechanism of nanosheetsγ-alumina was also discussed.The electrocatalytic properties of the nanoγ-alumina/carbon paste electrode for oxidation of alizarin in 1.0M H₂SO₄ solution have been investigated by cyclic voltammetry(CV),and excellent electrocatalytic activity was observed.2.Nano Pt/γ-alumina materials were successfully prepared by room temperature ionic liquids(RTILs)graft technology.The self-made nanoγ-alumina materials were modified by the 1-Ethylcarboxyl-3-methylimidazolium chloride.The supporting of platinum nanoparticles on the modifiedγ-Al₂O₃ nanoparticles was achieved by adsorbing platinum(H₂PtCl₄)on the surface of the modified nanoparticles via ion exchange with the linked ionic liquid groups and then reducing them by hydrazine. The Pt/γ-alumina nanoparticles were characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM)and field Emission scanning electron microscope(FE-SEM),and have fine dispersion and small diameter.The electrocatalytic properties of the nano Pt/γ-alumina for oxidation of methanol in 1.0M H₂SO₄ solution have been investigated by cyclic voltammetry(CV)using the CHI-832 workstation,and excellent electrocatalytic activity was observed.The nano Pt/γ-alumina have potential application in the methanol fuel cell.3.Nanoγ-alumina powders were prepared by the liquid phase method of the homogeneous precipitation using urea and aluminium nitrate as the starting materials in the ultrasound condition.Based on the active marterial of nanoγ-alumina powders, an aluminium ion-selective electrode was fabricated based on acebyl cellulose with a simple method.In the buffer solution of 0.5 mol/L CH₃COOH - CH₃COONa (pH=5.0),the sensor responds to Al³⁺in a linear range from 1.00×10^-5to 1.00×10^-2 mol/L.A near-Nernstian response was obtained and the tested average slope of the calibration curves was 26 mV/decade.The detection limit was 7.90×10^-6mol/L.More than 14 different ions as the considered interferences were tested and the relevant selectivity coefficients were determined using the separate solution method(SSM). The sensor possesses many advantages including short conditioning time,fast response,and,especially,very good selectivity over a wide variety of other co-existing ions and the mechanism of response was discussed.The work was achieved by Chuanli Ma and Lijun He together.4.Titanium trichlorde(TiCl₃)solutions and sliver nitrate(AgNO₃)were directly treated at room temperatures to prepare the Ag₂O/titania nanoparticles.Morphology and size were studied in detail by X-ray diffraction,field emission scanning electron microscope,transmission electron microscopy and fourier transform infrared spectrometer(FTIR).The results show that the titania and Ag₂O/titania nanoparticles have the chestnut ball morphology and the rutile phase titania.The rutile phase nanotitania shows similar photocatalytic activity to commercial nano P25 TiO₂ in the degradation of acid scarlet,but the Ag₂0/titania nanoparticles have the highest photocatalytic activity.