Preparation Of SnO₂Nanocomposites And Their Properties

Nano-materials are structure sensitive materials, small changes of the material structure may leadgreat changes to the properties of the materials.In this condition, designing the the composition andstructure of the material, as well as exploring new preparation process have become theprimary means of synthetic high-performance nano-functional materials.Our research are focused on promoting the performance of tin oxide based on theseideas, including designing composition of the new materials and improving preparationmethods. First, We prepared AgI-SnO2nanocomposites, and analyzed the photocatalyticperformance of AgI-SnO2nanocomposites with defect theory of nano-crystal. then, Wedesign a gas-liquid interface precipitation to deal with the nonhomogeneous precipitationof ATO nanopowders. The prepared ATO exhibited excellent conductive properties, and theinfluencing factors of conductive properties were analyzed.Firstly, the AgI-SnO2nano-composite were prepared by liquid precipitation method,and TG-DTA, XRD, TEM, XPS and ESR and other characterization method were carriedout to study the thermal properties, phase composition, morphology, particle size,elemental composition and defect concentration of the nano-composite powders.photocatalytic properties of AgI-SnO2were estimated by photocatalytic degradation of MB,and the photocatalytic mechanism of AgI-SnO2nano-composit are discussed in this paper.The followings are the main research work and results:(1)The AgI-SnO2nanocomposite powder obtained with500℃calcined for1h,distributed evenly, the size of the crystal is about20nm. XRD analysis showed that thecomposite powders are rutile phase, the characteristic peaks of AgI can be saw. and AgIdoping caused by the growth of the grain size. XPS spectra show that the AgI is the mainform of Ag+and I-in the composite. In addition, a small number of I doped into the latticeof SnO2. Surface analysis showed that the proportion of Sn and O deviate from the2:1,which Indicating that the composite powders contain more oxygen vacancies.The electron spin resonance (ESR) that the2At%doping amount makes the oxygen vacancyconcentration greatly increased32.7times than those undoped.(2) Fourier transform infrared spectroscopy shows that there are still containing asmall amount of-OH in AgI-SnO2nanocomposite even calcined under500℃, Thecharacteristic peaks of AgI appears. UV-VIS diffuse reflectance spectra show that thedoping AgI narrowed the band gap of SnO2, which leading the reducing of opticalabsorption threshold.(3) The degradation of methylene blue demonstrated that the photocatalyticperformance of the nanocomposites has been greatly improved by doping AgI. TheAgI-SnO2composite with2At%AgI doping content display the vintage catalyticdegradation rate. the prepared nanocomposite showed good photocatalytic stability.Secondly, Taking the preparation methods influence to the material properties intoaccount. We design a gas-liquid interface precipitation to process nanometer ATOconductive based on the nonhomogeneous precipitation of preparation of ATO powders.The prepared ATO exhibited excellent conductive properties, and the influencing factors ofconductive properties were analyzed.(1) The ATO nano-powders with different doping content were prepared under the setconditions. XRD analysis showed that the doped composite powders are rutile phasestructure of tin oxide, indicating that Sb replaced Sn4+of tin oxide crystals solid solutioninto the lattice. XRD peak shape indicate that doping with Sb caused peak broadening,TEM showed that the hydrothermal preparation of ATO particle size is smaller, and particlesize are smallest when the doping amount is10At%.(2) EDS and XPS spectras show that the theoretical doping content consistent toexperimental results, indicating that the amount of doping and doping substances indecentralized of the ATO powder can better achieve by gas-liquid interface method. whichalso means the high performance of the ATO powder.(3) The conductive properties of ATO nano-powders that prepared by gas-liquidinterface method were studied.The effects of different doping concentration, reactiontemperature, washing times were take into consider. conductivity reached10-2s.cm-1underhigh frequency condition. Experiments show that the hydrothermal preparation of ATOshowed excellent electrical properties than the high temperature calcination preparation ofATO, and When the Sb doping concentration is10At%, the nanocrystalline ATO exhibit lowest resistivity. Resistance of ATO prepared by high temperature calcination was70.4Ω·cm. Resistance ofATO prepared by hydrothermal method was65.4Ω· cm.