Thermal transformations in In-MoO3 nanofilms

Transformations in In-MoO₃ nanosystems have been studied by optical spectroscopy, micros-copy, and gravimetry in relation to the thickness of the In and MoO₃ layers and heat-treatment temperature and time. We have measured the contact potential difference across the In and MoO₃ films and the photo-voltage in the In-MoO₃ system and constructed the energy band diagram of the In-MoO₃ system. A model has been proposed for the thermal transformation of the MoO₃ films in In-MoO₃ bilayers, which involves a redistribution of equilibrium charge carriers at the contact, the formation of a [(V _a)⁺⁺e] center during the preparation of the MoO₃ film, transformation of the center into a [e(V _a)⁺⁺e] center during the fabrication of the In-MoO₃ bilayer, and thermal ionization of the [e(V _a)⁺⁺e] center.     

The correlation of various properties of thin films of MoO3 and of the mixed oxide systems MoO3-In2O3 and MoO3-SiO

A discussion of the general properties of three systems of dielectric films i.e. MoO₃ and the mixed oxide systems MoO₃-In₂O₃ and MoO₃-SiO is presented. Composition, film thickness, substrate deposition temperature and annealing all have a substantial effect on the structure and various properties of the films. The general properties of these three systems of dielectric films include analysis by X-ray photoelectron spectroscopy, UV-visible and infrared spectroscopy including the Fourier transform technique, electrical properties both d.c. and a.c. at both low and high fields and electron spin resonance. An attempt is made to show how the variations of properties depend on many disposable parameters. In particular the use of X-ray photoelectron spectroscopy shows how the local atomic and molecular bonding changes as a result of varying preparation parameters and this feature is a recent facility in the field of thin dielectric-semiconducting films. It is expected that the general discussion in this paper may help in the interpretation of results on other thin dielectric and semiconducting films.     

Ambience-sensitive optical refraction in ferroelectric nanofilms of NaNbO3

Optical index of refraction n is studied by spectroscopic ellipsometry in epitaxial nanofilms of NaNbO₃ with thickness ～10 nm grown on different single-crystal substrates. The index n in the transparency spectral range (n ≈ 2.1 – 2.2) exhibits a strong sensitivity to atmospheric-pressure gas ambience. The index n in air exceeds that in an oxygen ambience by δn ≈ 0.05 – 0.2. The thermo-optical behaviour n(T) indicates ferroelectric state in the nanofilms. The ambience-sensitive optical refraction is discussed in terms of fundamental connection between refraction and ferroelectric polarization in perovskites, screening of depolarizing field on surfaces of the nanofilms, and thermodynamically stable surface reconstructions of NaNbO₃.     

Dynamics of liquid nanofilms

The van der Waals forces across a very thin liquid layer (nanofilm) in contact with a plane solid wall make the liquid nonhomogeneous. The dynamics of such flat liquid nanofilms is studied in isothermal case.The Navier–Stokes equations are unable to describe fluid motions in very thin films. The notion of surface free energy of a sharp interface separating gas and liquid layer is disqualified. The concept of disjoining pressure replaces the model of surface energy. In the nanofilm a supplementary free energy must be considered as a functional of the density.The equation of fluid motions along the nanofilm is obtained through the Hamilton variational principle by adding, to the conservative forces, the forces of viscosity in lubrication approximation. The evolution equation of the film thickness is deduced and takes into account the variation of the disjoining pressure along the layer.     

One-step synthesis of MoO3 and MoO3-x nanostructures by condensation in gas: effect of the carrier gas

MoO3 and MoO3-x nanostructures were grown in a simple one-step process by direct evaporation of MoO3 pellets from a tungsten resistive source in presence of helium or hydrogen at pressures from 100 to 1200 Pa. This method uses no templates, catalysts or oxidizing agents. It leads to one dimensional (1-D) crystalline nanostructures mixed with amorphous material in variable ratios. Amorphous structures grew preferentially when hydrogen was used as carrier gas while crystalline material predominated when helium was used. In fact, only crystalline structures were found when the evaporation was carried out under a helium pressure of 600 Pa with source temperatures between 763 and 910 degrees C. Hydrated MoO3 phases with different water concentrations were preferentially formed using hydrogen. X-ray photoelectron spectroscopy detected only molybdenum in its +6 oxidation state in the samples grown under helium, exhibiting the same chemical composition of the source material. Molybdenum in its +6 as well as its +5 oxidation states was detected in the samples obtained under hydrogen at 600 Pa. Hydroxyl groups were identified in samples grown using both gases. The effect of the helium pressure on the growth kinetics and crystallinity of the samples is discussed according to the kinetics conditions (supersaturation, evaporation, cooling and convection rates) driving to the formation of nanostructures in the inert-gas condensation. Finally, the effect of hydrogen on the growth of MoO3 is discussed.     

Photochromic Properties of MoO3-Modified Porous Glasses

MoO₃-modified porous glasses are prepared via impregnation with aqueous ammonium molybdate, followed by thermal decomposition of the salt. With increasing MoO₃ content, the edge of the charge-transfer band shifts to longer wavelengths. The photochromic properties of the modified glass are well defined at an MoO₃ content of about 14 mol/g.     

MoO3纳米纤维TEM图像的多重分形谱

用多重分形方法研究了透射电镜(TEM)观察到的α-MoO3纳米纤维的形貌.TEM观察表明,样品中纳米纤维的分布和均匀程度都随着HNO3浓度的增加而增大,形貌由纤维状向带状过渡.多重分形谱的分析显示,随着HNO3浓度的增加,Δf从0.4345增大到2.4530,样品中纳米纤维的最大概率分布的数目多于最小概率分布的数目,说明纳米纤维数目和宽度均增加;分形谱宽Δα愈来愈小,表明纳米纤维的分布愈来愈均匀.因此,多重分形谱可以很久地表征α-MoO3纳米纤维的分布特性.     

水热法制备薄片状纳米级MoO3微粉

以仲钼酸铵为原料,经过酸化处理后,采用水热法制备薄片状纳米级三氧化钼(MoO3),反应过程主要包括:(1)制备仲钼酸铵饱和溶液;(2)酸化后的仲钼酸铵饱和溶液与模板剂反应生成氧化钼和铵的结合物;(3)处理后制得纯净的薄片状纳米级氧化钼.所得产物经过X射线衍射(XRD)物相鉴定为MoO3晶体结构,用扫描电子显微镜(SEM)表征了产物的形貌和大小.     

A novel method for synthesis of microstructure MoO3

One-dimensional microstructures of orthorhombic molybdenum trioxide (α-MoO₃) have been synthesized via acidification of ammonium heptamolybdate tetrahydrate. A solution of precursor compound, ammonium heptamolybdate tetrahydrate, is acidified to pH 3.5 using diluted glacial acetic acid. Then the intermediate compound is sintered at 300 and 600 °C to give the final α-MoO₃, and the SEM shows that it still keeps its micrometer fibers structure.     

锂掺杂MoO3薄膜的制备及电色性能的研究

采用过氧化氢溶胶－凝胶法成功地在室温下制备了纯的ＭｏＯ_３和锂掺杂的ＭｏＯ_３薄膜．通过ＴＧ－ＤＴＡ热分析、ＦＴＩＲ红外光谱分析、循环伏安和光学特性的测试,研究了薄膜成膜过程中的结构转变过程和薄膜的电化学性能及电变色性能．结果表明通过Ｌｉ^＋掺杂,ＭｏＯ_３溶胶的稳定性和ＭｏＯ_３薄膜的电化学循环稳定性都有了较大的提高．且掺杂锂的ＭｏＯ_３薄膜仍具有良好的电变色性能．     

MoO_3微纳米片的简单制备及其光致发光性能

采用简单热氧化蒸发沉积法在ITO玻璃基片上制备了大面积MoO3微纳米片。制备出的微纳米片具有良好晶体结构,其长度、宽度和片层厚度分别可达100,1~5μm和约100nm;微纳米片沿[001]方向生长,这是因为晶体各方向键合能的不同而具有不同的生长速度,其形成过程遵循气-固生长机制。光致发光谱显示室温下MoO3微纳米片同时具有紫光发射峰、蓝光发射峰和绿光发光带,发射光强度随氧化沉积温度升高而增大,这是由于温度升高,微纳米片缺陷增加导致的。     

Phase equilibria in the Tl2MoO4-Pr2(MoO4)3-Hf(MoO4)2 system and crystal structure of TlPr(MoO4)2

Subsolidus (450–480°C) phase relations in the Tl₂MoO₄-Pr₂(MoO₄)₃-Hf(MoO₄)₂ system have been studied by X-ray diffraction. The system has been shown to contain molybdates with the compositions Tl₅PrHf(MoO₄)₆ (5: 1: 2), TlPrHf_0.5(MoO₄)₃ (1: 1: 1), and Tl₂PrHf₂(MoO₄)_6.5 (2: 1: 4). Single crystals of the double molybdate TlPr(MoO₄)₂ have been grown for the first time from high-temperature solutions through spontaneous nucleation, and their crystal structure has been determined: tetragonal symmetry, sp. gr. P4/nnc, a = 6.3170(1) Å, c = 9.5529(2) Å, V = 381.204(12) ų, Z = 2.     

Phase relations in the MoO3-MgMoO4 system

Journal of Materials Science Letters -     

MoO3在介孔分子筛MCM-41上分散和存在状态的研究

在773K加热MoO₃和MCM-41的机械混合物,可以实现 MoO₃分散在介孔分子筛MCM-41表面,用透射电镜和选区电子衍射,配合XRD和液氮温度下氮吸附-脱附曲线和BJH孔径分布,研究了活性组分MoO₃在有序介孔材料MCM-41上的存在状态,以及MoO₃分散到MCM-41表面后MCM-41的结构变化情况.结果表明:当MoO₃的含量小于单层分散阈值,加热后MoO₃的XRD衍射峰彻底消失;用HRTEM观察不到分散在MCM-41表面或孔道中的MoO₃颗粒,而EDS能谱证明在MCM-41的孔道中有呈分散态的MoO₃存在.MoO₃的含量大于单层分散阈值,通过加热不能使MoO₃完全分散在MCM-41表面,而且XRD、HRTEM、氮吸附-脱附等温线和孔径分布都表明由于MoO₃的分散量较大,载体MCM-41的有序介孔结构遭到破坏.     

塑料基MoO3电致变色薄膜性能

采用溶胶-凝胶工艺,在镀有ITO透明电极的聚对苯二甲酸乙二酯（PET）基体上制备了MoO3电致变色薄膜.用FT-IR和TG-DTA分析了薄膜的成分和热稳定性,用分光光度计、电化学工作站研究了其在1 mol/L的LiClO4碳酸丙烯酯（PC）液体电解质中的电致变色性能.结果表明：薄膜主要成分是含有水合过氧化氢的无定形MoO3;着、退色前后可见光透过率变化△T为40%,在550 nm时的致色效率为44.8 cm^2/C,经1000次循环,电色性能变化很小;着色速度和对比度随着色电压的增加而增加,Li^0的扩散和Li＋的迁移分别控制着着色速度和退色速度.