精细结构SnO2纳米球的制备与表征

以SnCl₄·5H₂O为主要原料,用溶剂热技术在油酸体系中成功地合成了具有精细结构的SnO₂纳米球.X射线衍射(XRD)和选区电子衍射(SAED)结果表明,制备出的SnO₂微晶具有良好的结晶性;透射电镜(TEM)结果表明,得到的产物中含有尺寸约为50-80nm的SnO₂纳米球,放大的17EM照片进一步揭示了此纳米球含有粒度为2-6nm超细粒子的精细结构.这种结构趋向于高的比表面积,适合于气敏探测器方面的应用.     

载银SnO2复合微球的制备及表征

以结晶四氯化锡(SnCl4·5H2O)和尿素为原料,采用溶剂热法在180℃下反应12h制备出了单分散性良好的SnO2微球,并通过原位化学还原法在SnO2微球表面沉积银纳米颗粒制备表面载银的SnO2复合微球。考察了表面活性剂的种类及SnCl4·5H2O的浓度对微球形貌的影响,分析了Ag纳米颗粒在微球表面分布的均匀性。通过XRD、SEM、EDS、TEM等分析手段对产物进行了表征。结果表明,以PEG6000为模板导向剂,SnCl4浓度为2mmol时,可以得到分散性良好、直径约为1μm的SnO2微球,微球由平均晶粒尺寸约为5nm的SnO2纳米晶粒组装而成;以Sn2+活化处理SnO2微球,弱还原剂聚乙烯吡咯烷酮(PVP)还原Ag+,可以得到Ag纳米颗粒均匀沉积的载银SnO2复合微球。     

负载型纳米氧化物材料的制备方法设计

依据玻璃分相原理设计了制备负载型纳米氧化物的新方法:熔融-分相法.以Na2O-B2O3-SiO2玻璃系统为基本组成,引入一定量的TiO2(SnO2),在高温下熔融、淬冷,经热处理和化学处理,制备了负载于富硅多孔载体的纳米TiO2(SnO2)材料.结果表明,得到的晶体尺寸和载体的孔径尺度均小于100 nm;负载型纳米TiO2具有良好的光催化性能,负载型纳米SnO2对CO具有催化氧化性能.     

三维多孔C球包覆纳米SnO2复合材料的电化学性能研究

以葡萄糖为碳源,锡酸钠为锡源,通过水热法制备了三维多孔C球包覆纳米SnO2复合材料。结果表明:样品的XRD谱线都出现SnO2的特征峰,多孔SnO2/C球尺寸为100nm左右,10～50nm的SnO2颗粒被均匀地包覆在约30nm的多孔碳层中。考察了水热时间对复合材料电化学性能的影响,在水热时间6h、烧结温度500℃、烧结保温时间2h的条件下,复合电极材料具有较高的可逆容量,首次可逆比容量为581.0mAh/g,首次放充电(嵌脱锂)效率为66.48%,经50次循环后,充电比容量保持在502.9mAh/g,循环效率为99.9%,具有较好的循环性能。     

具有开口结构SnO2空心微球的水热合成及表征

以锡酸钠和尿素为原料,采用水热法制备出具有开口结构的SnO2空心微球。主要考察了尿素浓度和水热时间对空心微球形貌 的影响;利 用XRD、SEM、TEM等分析手段对空心结构进行了表征,并对空心微球的形成机制进行了讨论。结果表明,SnO2空心微球直径约为2μm,球壳由SnO2纳米片或纳米晶粒堆积而成,壁厚约250nm。尿素不仅有助于纳米粒子自组装成微球,其分解产生的气泡还可以作为软模板形成空心结构;同时因气泡逸出形成的特殊开口结构可以为引入功能性粒子提供快速通道,具有很好的应用前景。     

SnO_2纳米颗粒的制备及其发光性能

用大分子网络凝胶法合成了氧化锡(SnO2)纳米颗粒。X射线衍射(XRD)结果表明,合成的SnO2纳米颗粒具有四方金红石结构,不含任何杂质相。扫描电镜(SEM)观察发现,制得的SnO2纳米颗粒形貌规整、呈类菱形。荧光光谱结果表明,在326 nm波长的光激发下,其荧光光谱由四个主发射带组成,其峰值分别位于379,417,450,470 nm。用230 nm波长的光激发,得到一个740 nm的荧光发射峰。基于实验结果,探讨了纳米SnO2的形成机理和发光机制。     

ZnO/Zn2SnO4纳米电缆结构表征与发光特性

ZnO、Zn2SnO4均为直接带隙宽禁带氧化物半导体,是优异的功能材料.以ZnO、SnO2为原料,通过共热蒸发法,合成了ZnO/Zn2SnO4纳米电缆结构.该纳米电缆结构为以ZnO为芯,Zn2SnO4为鞘,直径为50~100nm,长度可达上百微米.通过TEM分析手段,发现该纳米电缆结构中,ZnO的生长方向为<0001>方向,ZnO芯与Zn2SnO4鞘之间形成晶格外延关系.室温下光致发光谱结果显示,该纳米电缆结构在紫外区域(380.58nm附近处)存在很强的带边发光,而在可见光区域没有明显的发光带,这一结果表明:Zn2SnO4鞘层的存在能有效抑制ZnO表面的缺陷发光.ZnO/Zn2SnO4纳米电缆结构可以抑制电子-空穴的复合,在染料敏化太阳能电池等方面有一定的应用潜力.     

SnO2纳米颗粒制备及其对溶胶-凝胶Sb:SnO2薄膜性能的影响

以Sn(OEt)2为起始原料,采用水热晶化法合成了分散性良好的金红石结构的SnO2纳米颗粒.采用X射线衍射对其进行了表征,表明SnO2纳米颗粒的结晶性良好,颗粒尺寸小于10nm.将合成的SnO2纳米颗粒均匀分散到Sb:SnO2镀膜液中,经陈化后制成镀膜溶胶,以溶胶-凝胶浸渍镀膜工艺制备纳米颗粒掺杂Sb:SnO2薄膜.分别采用范德堡(Van Der Pauw)法、UV/VIS分光光度计和FTIR中红外分析仪测量并分析膜层的导电性能、光学性能及结构特征,研究了导电纳米颗粒添加对Sb:SnO2薄膜电性能、光学性能和结构的影响.     

SnO2纳米空心球的合成及在锂离子电池正极方面的应用

采用锡盐溶液浸渍-煅烧锯末法,制备了SnO2纳米空心球.分别用X射线衍射(XRD)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)及恒流充放电技术对产品的结构形态和电化学性质进行了表征.结果表明,SnO2空心球的尺寸在50～120nm之间,壳层厚度约为5nm.在作为锂离子电池正极使用时,初始放电容量为607.7 mAh g-1.     

叠层式TiO2/SnO2复合纳米薄膜制备及其光电性能研究

采用溶胶-凝胶法在不同基体表面制备了叠层式TiO2/SnO2复合纳米薄膜.用扫描电子显微镜(SEM)、X射线衍射(XRD)对复合薄膜表面形貌和晶体结构进行表征.采用紫外-可见吸收光谱法和电化学方法来研究复合薄膜光学与光电化学性能特征.结果表明,所制备的叠层式TiO2/SnO2复合纳米薄膜表面连续、均匀、致密;XRD分析表明纳米TiO2为锐钛矿型结构,SnO2为金红石型结构;紫外-可见吸收光谱测试表明叠层式TiO2/SnO2复合纳米薄膜较纯TiO2薄膜的吸收范围拓宽;稳定电位随时间变化曲线(OCP-t)结果表明,叠层式TiO2/SnO2复合纳米薄膜光照下其光电化学性能高于纯TiO2薄膜;同时,光照后叠层式TiO2/SnO2复合纳米薄膜能有效储存TiO2先生电荷,延续对不锈钢基体的光生阴极保护性能.经比较,叠加3层SnO2的TiO2/3SnO2复合纳米薄膜改善光电性能最佳.     

纳米TiO2微球的制备及光催化性能研究

以钛酸四丁酯为前驱体,在油酸和正己烷的混合溶剂中,采用溶剂热技术成功地合成了纳米TiO2微球.以X射线衍射(XRD)、透射电镜(TEM)等方法对产物进行了表征,并对其光催化降解甲基橙溶液的性能进行了研究.实验结果表明:纳米TiO2微球的平均尺寸约为60nm,其中含有粒径平均约4.5nm的超细粒子.此种结构趋向于高的比表面积,与P-25型光催化剂相比,两者对甲基橙溶液的脱色具有相近的光催化活性.     

乙醇火焰燃烧制备螺旋碳纳米纤维及结构分析

采用乙醇火焰燃烧, 借助于基板材料上涂敷锡盐作为催化剂前驱体, 制备了螺旋结构碳纳米纤维; 借助于扫描电子显微镜、透射电子显微镜、XRD和拉曼光谱等分析了螺旋碳纤维的形貌和结构. 螺旋碳纳米纤维螺旋直径约为100nm, 纤维直径约为50nm, 螺距约80nm. 螺旋碳纤维的石墨层方向基本垂直于轴向, 近似鱼骨型结构, 相邻碳层间距为0.34nm. 借助于高分辨电子显微镜分析了螺旋碳纳米纤维的形成机理, 认为碳原子沿催化剂SnO₂各晶面析出速度不同是形成螺旋碳纳米纤维的主要原因.     

Nanofibers Comprising Yolk–Shell Sn@void@SnO/SnO2 and Hollow SnO/SnO2 and SnO2 Nanospheres via the Kirkendall Diffusion Effect and Their Electrochemical Properties

Nanofibers with a unique structure comprising Sn@void@SnO/SnO₂ yolk–shell nanospheres and hollow SnO/SnO₂ and SnO₂ nanospheres are prepared by applying the nanoscale Kirkendall diffusion process in conventional electrospinning process. Under a reducing atmosphere, post‐treatment of tin 2‐ethylhexanoate‐polyvinylpyrrolidone electrospun nanofibers produce carbon nanofibers with embedded spherical Sn nanopowders. The Sn nanopowders are linearly aligned along the carbon nanofiber axis without aggregation of the nanopowders. Under an air atmosphere, oxidation of the Sn–C composite nanofibers produce nanofibers comprising Sn@void@SnO/SnO₂ yolk–shell nanospheres and hollow SnO/SnO₂ and SnO₂ nanospheres, depending on the post‐treatment temperature. The mean sizes of the hollow nanospheres embedded within tin oxide nanofibers post‐treated at 500 °C and 600 °C are 146 and 117 nm, respectively. For the 250th cycle, the discharge capacities of the nanofibers prepared by the nanoscale Kirkendall diffusion process post‐treated at 400 °C, 500 °C, and 600 °C at a high current density of 2 A g^?1 are 663, 630, and 567 mA h g^?1, respectively. The corresponding capacity retentions are 77%, 84%, and 78%, as calculated from the second cycle. The nanofibers prepared by applying the nanoscale Kirkendall diffusion process exhibit superior electrochemical properties compared with those of the porous‐structured SnO₂ nanofibers prepared by the conventional post‐treatment process.     

Polycrystalline SnO2 nanowires coated with amorphous carbon nanotube as anode material for lithium ion batteries

One-dimensional (1D) SnO₂ nanowires, coated by in situ formed amorphous carbon nanotubes (a-CNTs) with a mean diameter of ca. 60 nm, were synthesized by annealing the anodic alumina oxide (AAO) filled with a sol of SnO₂. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns revealed that the prepared SnO₂ nanowires exist in polycrystalline rutile structure. The coating of carbon nanotubes has some defects on the wall after the internal SnO₂ nanoparticles were removed. The 1D SnO₂ nanowires present a reversible capacity of 441 mAh/g and an excellent cycling performance as an anode material for lithium ion batteries. This suggests that 1D nanostructured materials have great promise for practical application.     

A novel microwave synthesis of nanocrystalline SnO2 and its structural optical and dielectric properties

Nanocrystalline SnO₂ particles with the rutile structure have been successfully synthesized by a novel microwave irradiation method. This process requires less reaction time and low temperature. Transmission electron microscopy studies show that SnO₂ particles are in spherical shape with size about 25–30 nm. Selected area electron diffraction pattern confirms single crystalline nature of the SnO₂. UV–Vis spectrometer was carried out to study the optical properties and estimated band gap energy of SnO₂ particles is 3.55 eV. In Fourier transform infrared study, a defined peak at around 615 cm^?1 is observed due to Sn–O vibration. Frequency dependent dielectric anomaly is observed in SnO₂ nanoparticles at low temperature. It is found that the value of dielectric constant of SnO₂ particles at 10 kHz is found to be 777.5. It systematically decreases with increasing frequency whereas increases with increasing temperature. Further, the prepared samples were characterized by Photoluminescence spectroscopy and energy dispersive spectroscopy.     

由层状钛酸盐纳米管制备SrTiO3纳米粒子及其表征

采用水热法,使用层状钛酸盐纳米管和乙酸锶作为前驱物,在一定反应温度和时间的条件下,制备了SrTiO3纳米粒子.采用X射线粉末衍射(XRD),扫描电镜(SEM),透射电镜(TEM),拉曼光谱(Raman),激发光谱(PL)和比表面积分析等测试技术对SrTiO3纳米粒子进行了表征.测试结果表明,只有在反应条件和反应前驱物配比适当时才能制备得到纯的无序多孔SrTiO3纳米粒子,粒径主要分布在10～30nm之间,无明显团聚现象;随着反应时间的延长或者反应温度的升高,粒径趋于增大,而比表面积趋于减小,对亚甲基蓝在紫外光照下的光降解活性也随之降低.     

Facile synthesis and characterization of ZnFe2O4/α-Fe2O3 composite hollow nanospheres

ZnFe₂O₄/α-Fe₂O₃ composite hollow nanospheres were successfully fabricated via a facile one-pot solvothermal method, utilizing polyethylene glycol as soft template. X-ray diffraction and scanning electron microscopy analysis revealed that the prepared nanospheres with cubic spinel and rhombohedra composite structure had a uniform diameter of about 370 nm, and the hollow structure could be further confirmed by transmission electron microscopy. Energy dispersive X-ray, X-ray photoelectron spectroscopy and Fourier transform infrared techniques were also applied to characterize the elemental composition and chemical bonds in the hollow nanospheres. The ZnFe₂O₄/α-Fe₂O₃ composite hollow nanospheres show attractive light absorption property for potential applications in electronics, optics, and catalysis.     

Structure and field emission properties of SnO2 nanowires

SnO₂ nanowires were fabricated using a simple and economical method of rapid heating SnO₂ and graphite powders at 850 °C in a flow of high-purity N₂ as carrier gas. Research by using X-ray diffraction (XRD) indicates that SnO₂ nanowires are primitive tetragonal in structure with the lattice constant a = b = 0.443 nm and c = 0.372 nm. Observations by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that SnO₂ is of nanowire structure. The selected area electron diffraction (SAED) shows that the nanowires are perfect single crystal structure. The Fourier transform infrared (FT-IR) exhibits the difference of nanostructure materials and general materials. The field emission (FE) properties had also been studied.     

Branched structures of tin oxide one-dimensional nanomaterials

Branched structures of SnO₂ one-dimensional nanomaterials have been successfully fabricated via a novel multi-step process. Scanning electron microscopy indicated that the SnO₂ branches, which sprouted from the SnO₂ stems, had diameters in the range of 30-120 nm. X-ray diffraction, high resolution transmission electron microscopy and selected area diffraction pattern revealed that the branches were single crystalline rutile SnO₂ structures. Room temperature photoluminescence spectrum of the branched product exhibited visible light emission. We suggested that a Au-catalyzed vapor-liquid-solid growth mechanism was responsible for the growth of SnO₂ branches on the SnO₂ stems.