多元醇方法制备SnO2包覆碳纳米管复合材料

本文采用SnC2O4.2H2O为Sn源和乙二醇(ethylene glycol,EG)为反应介质的多元醇法,制备得到SnO2包覆多壁碳纳米管复合材料(SnO2/MWNTs),其中SnO2是通过EG中溶解的O2氧化Sn2+反应生成的.没有加入MWNTs的情况下,SnC2O4.2H2O的水解反应生成Sn6O4(OH)4,SnC2O4.2H2O与EG之间的聚合反应生成聚羟基乙酸锡,由于水解反应降低了EG中Sn2+的浓度,使得聚羟基乙酸锡产量较低.加入MWNTs后,仅有少量聚羟基乙酸锡生成,且没有Sn6O4(OH)4生成,主要产物为包覆在MWNTs表面的SnO2.这是由于SnO2在EG中的溶解度极低,随O2氧化Sn2+反应进行,EG中的Sn2+浓度不断降低,Sn6O4(OH)4的溶解结晶平衡不断向溶解的方向进行,并最终转化为SnO2.以上对多元醇法制备SnO2/MWNTs合成机理的理解,将有助于采用类似的方法设计合理条件制备得到其他种类金属氧化物包覆碳纳米管的复合材料.     

氮掺杂对SnO2薄膜光电性能的影响

SnO2薄膜具有透明导电的特性,因而被制成透明电极而广泛应用于平板显示器和太阳能电池中。研究表明,经掺杂的薄膜具有更优异的光电性能,然而传统的掺杂元素Sb,Te或F较为昂贵且有毒性,因此,掺氮将有望解决上述问题。本文利用反应射频磁控溅射法制备出不同氧含量的SnO2以及氮掺杂SnO2薄膜,并分析了薄膜的形貌结构及光电性能。结果表明:薄膜沉积过程中氧分压和氮掺杂对薄膜性能影响较大。在SnO2薄膜中,晶粒呈包状形态,随着氧分压的增加,晶粒取向从(101)转向(110)方向,晶粒尺寸逐渐变小,可见光透光率提升到80%以上,光学带隙增加到4.05 eV;在氮掺杂SnO2薄膜中,晶粒呈四棱锥形态,晶粒取向为(101)方向,随着氧分压的增加,可见光的透过率同样提升到80%以上,光学带隙增加到3.99 eV。SnO2薄膜和氮掺杂SnO2薄膜的电阻率最低分别达到1.5×10-1和4.8×10-3Ω.cm。     

超声热解法制备SnO2:F薄膜加热管及其性能研究

采用超声喷涂热解淀积方法将SnO2F透明导电薄膜制备于耐高温的硼硅玻璃管内壁.XRD物相分析及SEM、STM形貌分析表明,SnO2F薄膜为多晶结构,平均粒径50nm.分析了薄膜中F取代SnO2中O的形成过程和薄膜电导率增强的机理,解释了不同的工艺条件对薄膜的结构、光电特性的影响,确定了制备SnO2F薄膜加热管的最佳工艺条件.该条件下制备的薄膜的电阻率达4×10-4Ω·cm,可见光透过率高于90%,功率密度平均可达35 W/cm2.     

Cd2SnO4水热制备及其气敏性能研究

以SnCl4.5H2O、CdCl2·1/2H2O和NaOH为原料,采用水热法制备了Cd2SnO4粒子。通过XRD和SEM对其物相和形貌进行了分析,并将其制成气敏元件,进行气敏性能测试。结果表明制得的Cd2SnO4粒子为多面体,对乙醇、丙酮和三乙胺有较高的灵敏度和好的响应-恢复特性。     

复合电沉积制备SnO2/TiO2薄膜及其光电催化性能

为了寻求廉价、高效和稳定的光催化剂,用复合电沉积技术在紫铜片上制备了Sn/TiO2薄膜,经300℃热氧化使之形成SnO2/TiO2复合电极.利用SEM,XRD对薄膜进行了表征,以甲基橙为模型化合物,对复合电极的光催化和光电催化性能进行了测定.研究表明:该薄膜由0.3~1μm的颗粒构成,每个颗粒又由纳米晶粒形成;电极具有多孔结构,膜中的SnO2以两种不同的晶体结构存在;在薄膜质量相等的情况下,SnO2/TiO2薄膜的光催化活性是纯TiO2粒子膜的2.87倍;外加一定偏压下,其催化性能大幅度提高.     

溶胶凝胶法混合掺杂SnO2薄膜的返回特性研究

在常温、加温和光照三种环境下,通过采用溶胶凝胶法在玻璃基片上制备成的混合掺杂Cu_TiO2和Fe_TiO2的SnO2薄膜在乙醇、丙酮两种气氛作用下进行气敏反应前后的光反射谱测试,研究薄膜的返回特性。研究分析表明,掺杂SnO2薄膜在常温返回特性不理想,在100℃加温3分钟和红外线光照10分钟后,掺杂SnO2薄膜测试光反射谱表明返回特性表现良好,能在较短时间和较宽波段内返回。     

TiO2/SnO2纳米晶膜的制备及其电学性能研究

采用丝网印刷的方式制备了TiO2纳米晶薄膜,然后在其上采用浸泡的方式制备了SnO2纳米晶薄膜,形成TiO2/SnO2膜结构的光阳极并应用于染料敏化太阳能电池。用SEM对样品进行了结构形貌分析,用电化学工作站研究表征了SnO2的浸泡溶液浓度和浸泡时间对光阳极的调制改性作用。SEM分析表明在TiO2纳米晶薄膜表面生长的SnO2纳米晶薄膜晶粒比TiO2更加细小,电学性能研究表明TiO2薄膜经过0.4 mol/L SnO2溶液浸泡处理50 min能对TiO2薄膜的结构及性能起到很好的改善作用,电池的光电转化效率提高了约7%。     

ZnO-Nb2O5掺杂SnO2基陶瓷研究

通过常压烧结制备SnO2基陶瓷,研究了ZnO、Nb2O5单掺杂及ZnO-Nb2O5复合掺杂对SnO2基陶瓷的烧结性能及电阻率的影响。采用SEM及XRD对试样分别进行了微观结构观察及物相分析。研究表明,掺杂ZnO能提高陶瓷的体积密度,但对于降低电阻率的影响不明显,当ZnO掺杂量在0.5%～0.75%(质量分数)时,SnO2基体积密度可达到6.67～6.73g/cm3;掺杂Nb2O5不能有效提高烧成陶瓷的体积密度,但能显著降低SnO2基陶瓷的电阻率;0.5%(质量分数)ZnO～1.5%(质量分数)Nb2O5复合掺杂在1450℃下烧成的陶瓷可得到较好的性能,其体积密度可达到6.61g/cm3,常温电阻率为867.84Ω.cm。     

SnO2纳米薄膜的溶胶-凝胶法制备及气敏性能

以SnCl2·2H2O和无水乙醇为原料制备SnO2透明溶胶,通过浸渍法在云母基片上制备了SnO2纳米薄膜.利用XRD和AFM手段研究了薄膜的结构和形貌,结果表明,SnO2纳米薄膜的球形粒径约为15nm;随着薄膜沉积层数的增加或工作温度的升高,薄膜电阻逐渐减小.气敏特性研究表明,薄膜对H2有较好的敏感性.     

SnO2/Fe3O4磁性光催化微纳米材料的制备与性能研究

以磁性纳米颗粒Fe3O4为核,SnCl4.5H2O、氨水、无水乙醇为原料,采用液相共沉淀法在Fe3O4表面包覆一层SnO2光催化剂。采用X射线衍射仪(XRD)及扫描电镜(SEM)分析了其成分和表面形貌。结果显示:Fe3O4纳米颗粒在实验过程中发生了团聚,尺寸增大;当Fe3O4与SnCl4.5H2O物质的量比为(1∶2)～(1∶4)时,SnO2能被较好地包覆在Fe3O4表面,形成核-壳结构的SnO2/Fe3O4复合光催化材料;600℃热处理能够形成结晶性良好的SnO2晶体,但此时Fe3O4转变为Fe2O3,失去了磁性。     

K2(Rb2,Cs2,Tl2)TeBr6(I6) and Rb3(Cs3)Sb2(Bi2)Br9(I9) perovskite compounds

We systematize available experimental data on the crystal structure of the ternary halides K₂(Rb₂,Cs₂,Tl₂)TeBr₆(I₆) and Rb₃(Cs₃)Sb₂(Bi₂)Br₉(I₉), analyze the general trends in the properties of their single crystals, and examine the key features of the physicochemical interaction in related systems.     

Al2O3/SiO2 and HfO2/SiO2 dichroic mirrors for UV solid-state lasers

HfO₂/SiO₂ and Al₂O₃/SiO₂ multilayers to be employed as high reflectance end mirrors in Cerium-doped fluoride solid-state lasers were produced by radio frequency sputtering. The components were designed to have high transmittance at the pumping wavelength and high reflectance in a wavelength band corresponding to the active medium emission. A photoacoustic beam deflection technique and inspection of the irradiated area under a microscope were used to measure the laser induced damage threshold of the mirrors at the pumping wavelength. These coatings were tested in a laser cavity.     

Natural and persistent superhydrophilicity of SiO2/TiO2 and TiO2/SiO2 bi-layer films

Sol-gel SiO₂/TiO₂ and TiO₂/SiO₂ bi-layer films have been deposited from a polymeric SiO₂ solution and either a polymeric TiO₂ mother solution (MS) or a derived TiO₂ crystalline suspension (CS). The chemical and structural properties of MS and CS bi-layer films heat-treated at 500 °C have been investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscospy. Water contact angle measurements show that MS SiO₂/TiO₂ and CS TiO₂/SiO₂ bi-layer films exhibit a natural superhydrophilicity, but cannot maintain a zero contact angle for a long time over film aging. In contrast, CS SiO₂/TiO₂ bi-layer films exhibit a natural, persistent, and regenerable superhydrophilicity without the need of UV light. Superhydrophilic properties of bi-layer films are discussed with respect to the nature of the TiO₂ single-layer component and arrangement of the bi-layer structure, i.e. TiO₂ underlayer or overlayer.     

Crystal Structure of (H3O)2[(UO2)2(SeO4)3(H2O)2](H2O)3.5

Crystals of (H₃O)₂[(UO₂)₂(SeO₄)₃(H₂O)₂](H₂O)_3.5 were prepared from aqueous solutions by evaporation. The crystal structure [monoclinic system, space group P2₁/m, a = 11.9402(11), b = 13.6452(14), c = 13.7271(12) Å, β = 109.436(7)°, V = 2109.1(3) ų] was solved by the direct method and refined to R ₁ = 0. 048 (wR ₂ = 0. 082) for 3677 reflections with |F _hkl |F _hkl |. The structure consists of [(UO₂)₂(SeO₄)₃(H₂O)₂]₂₋ layers arranged parallel to the (010) plane. The layers are formed by uranium and selenium coordination polyhedra sharing common vertices and are linked with each other by hydrogen bonds through the H₂O and H₃O⁺ groups arranged between the layers. __________ Translated from Radiokhimiya, Vol. 47, No. 5, 2005, pp. 412–414. Original Russian Text Copyright ? 2005 by Krivovichev, Kahlenberg.     

The role of TiO2 and ZrO2 in Na2OMO2SiO2 glasses

The glass transition temperatures of $\text{(1?x)}\text{Na}{}_2\text{O}\text{·}\text{1}\text{2}\text{x}\text{MO}{}_2\text{·2}\text{SiO}{}_2$ and Na₂O·xMO₂·(2 ?x)SiO₂ glasses, with M = Ti or Zr, have been related to the structural role and coordination of Ti and Zr. The role of network-former, intermediate or modifier of a cation has been fundamentally linked to ionic field strength; T_g values depend on ionic field strength and coordination. Titanium behaves like an intermediate oxide; its coordination ranges between four and six, depending on $\text{Ti}\text{Si}$ ratio. The role of zirconium changes according to the degree of substitution for Na or Si and progressively approaches that of a modifier ion.     

Syntheses and structures of Ta2(WO2)0.87H0.26(PO4)4 and Ta2(MoO2)(PO4)4

Tantalum hydrogen phosphate, β-TaH(PO₄)₂, has a three-dimensional structure that is stable to remarkably high temperature (∼600 °C) presumably due to the presence of strong hydrogen bonds. Impedance measurements indicate a low conductivity, 2.0 × 10⁻⁶ S/cm at 200 °C in 5% H₂. In further studies aimed at enhancing the conductivity by aliovalent doping, we have investigated systematically the synthesis of compounds in the TaH(PO₄)₂-W₂P₂O₁₁ system at 380 °C. As a result, a new phase, Ta₂(WO₂)_0.87H_0.26(PO₄)₄, was identified and subsequently the molybdenum analog Ta₂(MoO₂)(PO₄)₄ was also prepared. The structures were determined by single crystal X-ray diffraction techniques. The structures of Ta₂(WO₂)_0.87H_0.26(PO₄)₄ and Ta₂(MoO₂)(PO₄)₄ can be formally derived from the structure of β-TaH(PO₄)₂ by the replacement of two P-OH protons with an MO₂²⁺ (M = Mo and W) group together with a change in the orientation of some phosphate tetrahedra.     

超临界流体干燥法制备TiO2/ Fe2O3 和TiO2/ Fe2O3/ SiO2 复合纳米粒子及光催化性能

以TiCl₄ 、Fe (NO₃ )₃·9H₂O 和Na₂SiO₃19H₂O 为原料, 采用溶胶凝胶法结合超临界流体干燥法(SCFD)制备了纳米级TiO₂/ Fe₂O₃ 和TiO₂/ Fe₂O₃/ SiO₂ 复合光催化剂。以光催化降解苯酚对所得催化剂的催化活性进行了评价。结果表明, 纳米TiO₂/ Fe₂O₃ 复合粒子与单组分TiO₂ 比较, 复合粒子光催化活性高于单组分的TiO₂, 6h 苯酚降解率高达95.9 %。SiO₂ 的加入可以抑制纳米粒子粒径的长大和晶相的转变, 增强TiO₂ 纳米粒子的热稳定性。复合光催化剂中Fe₂O₃ 最佳掺入量为0.06 %, SiO₂ 最佳掺入量为10 %(摩尔分数) 。并用XRD、TEM 和FTIR 等手段进行了表征。TiO₂ 以锐钛矿型形式存在, SiO₂ 以无定性形式存在。比较了不同制备方法制得的TiO₂/ Fe₂O₃ 复合光催化剂, 得出超临界干燥法制备的光催化剂具有粒径小、比表面积大、分散性好、光催化活性高等特点。采用超临界流体干燥可直接得锐钛型纳米复合光催化剂。     

Hydrothermal Crystallization in the Systems La2(CO3)3 ? 6H2O-CaCO3(BaCO3)-R-H2O (R = Na2CO3, K2CO3, NaHCO3, KHCO3, NaCl, NH4Cl, CO(NH2)2)

Crystallization in the systems La₂(CO₃)₃ ⋅ 6H₂O-CaCO₃(BaCO₃)-R-H₂O (R = Na₂CO₃, K₂CO₃, NaHCO₃, KHCO₃, NaCl, NH₄Cl, CO(NH₂)₂) was studied under hydrothermal conditions (400–450°C). The solid reaction products were found to contain LaOHCO₃ and NaLa(CO₃)₂. Detailed thermal decomposition schemes were proposed for these phases, and their lattice parameters were refined. __________ Translated from Neorganicheskie Materialy, Vol. 41, No. 11, 2005, pp. 1366–1372. Original Russian Text Copyright ? 2005 by Nikol'skaya, Dem'yanets.     

Microstructure control for sputter-deposited ZrO2, ZrO2·CaO and ZrO2·Y2O3

The microstructure of pure and oxide-stabilized cubic ZrO₂ has been determined as a function of the principal deposition conditions for coatings prepared by r.f. diode reactive sputtering. Broad control of crystal structure, phase composition, grain size and crystallographic orientation is obtained by appropriate selection of the target composition, substrate bias and substrate temperature. The crystal structure and phase composition obtained for coatings are compared with predictions based on the equilibrium phase diagrams. The microstructural control demonstrated in this work should make possible rapid, efficient and systematic optimization of ZrO₂ coatings for future engineering applications.     

Reactivity of the H2O2/TiO2 system

The reactivity of the H₂O₂/TiO₂ system for samples treated at atmospheric pressure is studied by means of Auger Electron Spectroscopy. The most significant changes on the TiO₂ ‘final’ state are: (i) The I(O)/I(Ti) peak-to-peak ratio is diminished by 15%. (ii) The LMV transition suffers an energy shift of +2 eV, whereas the peak-to-peak width diminishes 1.5 eV. (iii) Its structure changes with respect to that of the TiO₂ ‘initial’ state although it is not identified with any one of the known stoichiometric oxides. (iv) When the samples that represent the ‘final’ state are heated up to 650 K, the AES spectrum matches quite well that of the TiO₂ ‘initial’ state.