【作者】 文彪；

【导师】 王作山；

【作者基本信息】 苏州大学 ， 材料学， 2012， 硕士

【摘要】 材料具有结构敏感性，纳米材料在尺寸和形貌调控的基础上，其组成和结构上的微小变化有望使材料性能发生明显的改善。因此，借助材料的组成和结构设计，以及探索新型的制备工艺已成为合成高性能纳米功能材料的主要手段。本论文以氧化锡为主体研究对象，从纳米材料的微观组成的设计出发，以复合材料晶体缺陷设计理论为指导，设计制备了新型的AgI-SnO2纳米复合材料，并对其光催化性能进行了系统研究；从探索纳米材料新型制备工艺出发，在综合传统液相沉淀法和气相法的基础上，提出了新型的气--液界面法，并运用该法完成了ATO纳米粉体制备，解决了ATO粉体制备工程中因高水解性掺杂剂存在，而影响沉淀不均匀这一难题。在此基础上，分析了ATO纳米粉体电性能及影响机制。（一）首先从组成上设计、制备AgI-SnO2纳米的复合粉体，实验采用沉淀法制备AgI-SnO2纳米复合粉体。通过TG-DTA、XRD、TEM、XPS和ESR等对纳米复合粉体的热性能、物相组成、微观形貌、粒径大小、晶体表面结构、元素组成及缺陷浓度等进行表征，通过亚甲基蓝降解实验评估了AgI-SnO2复合粉体的光催化性能，并探讨AgI-SnO2复合粉体光催化机理。具体结论如下：（1）前驱体经500℃煅烧1h，所制得的AgI-SnO2纳米复合粉体结晶性好，分散均匀， XRD测试表明复合粉体中的SnO2为四方金红石结构，出现AgI的特征峰，所制备的粉体晶粒尺寸约20nm，AgI的复合引起晶粒尺寸的增长。（2）XPS图谱表明复合粉体中的Ag，I两种元素在复合物中主要以Ag-I键形式存在，仅有少量的I-进入SnO2晶格；AgI-SnO2纳米复合粉体中Sn与O比例偏离2:1，表明复合粉体中含有较多的氧空位(氧缺陷)，电子自旋共振谱（ESR）表明掺杂使得氧空位浓度大大增加，掺杂量为2At%的复合粉体缺陷浓度最高，其缺陷浓度是未掺杂SnO2的32.7倍。（3）傅里叶红外光谱表明经高温转相得到的AgI-SnO2纳米复合粉体中仍含有少量-OH，AgI-SnO2复合粉体的红外光谱出现AgI特征峰；可见-紫外漫反射谱表明掺杂AgI使得SnO2带隙变窄，光吸收阀值降低，对可见亚光的吸收率增加。（4）通过模拟亚甲基蓝降解实验表明：掺杂AgI后复合粉体的光催化性能得到很大的提高，AgI掺杂量为2At%的复合粉体光催化性能最佳，紫外光条件下，20min降解率达96%，所制备的光催化剂重复利用率高，表现出很好的光催化稳定性。（二）从材料制备方法对材料性能的影响出发，设计了气—液界面法制备ATO纳米粉体，解决了传统沉淀法制备ATO粉体存在的掺杂剂分布不均这一难题，并考察了高温煅烧和高温水热两种相转变方式以及掺杂量等因素对ATO粉体电性能的影响。（1）在参考工艺条件下通过气液界面法制备了不同掺杂量ATO纳米粉体，XRD物相分析表明，掺杂后样品仍然保持氧化锡的金红石结构，说明Sb固溶进入氧化锡晶格，通过分析ATO纳米粉体的XRD峰型，掺杂Sb引起XRD峰不同程度的宽化，说明Sb掺杂，引起了样品晶粒尺寸的降低。TEM表明，高温水热制备的ATO纳米粉体粒径更小，掺杂量为10At%时，样品粒径最小，仅6nm。（2）EDS和XPS谱分析表明理论掺杂量跟实验值基本吻合，说明气液界面法制备ATO能更好地实现对掺杂量和掺杂物质分散的控制，从而能制备出高性能的ATO纳米粉体。（3）重点研究了气液界面法的高温煅烧和高温水热两种不同的晶化方式对ATO纳米粉体导电性能的影响，考察了不同掺杂浓度、反应温度、洗涤次数对电性能的影响，同时分析了样品电性能随外加电场频率的变化规律，高频条件下电导率达到10-1s.cm-1，表现出很好的导电性，实验表明高温水热比高温煅烧制备的ATO表现出更加优异的导电性能，当Sb掺杂浓度为10At%时，所制备的纳米ATO电阻率最低，高温煅烧制备的ATO电阻率为70.4cm，高温水热制备的ATO电阻率为65.4cm。更多还原

【Abstract】 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.更多还原