纳米钛酸钡的水热合成进展

综述了水热合成纳米钛酸钡的影响因素、发展现状及存在的问题，并指出其发展趋势。参考文献57篇。     

纳米晶氧化锡的水热合成与表征

以水热法合成了高比表面积的纳米晶SnO_2粉体，运用FT-IR，XRD，BET，TEM 等手段对粉体的晶化过程进行了分析表征。FT-IR显示120 ℃水热得到的粉体即实 现水合锡化合物的晶化。XRD分析表明所得粉体均匀数纳米，且随水热温度的提高 ，晶粒长大。水热粉体均具有很高的比表面积。TEM显示粉体呈单分散状态。将水 热粉体进行热处理，粉体则长大较快，比表面积降低，分散性能出现反常改善。     

系列纳米结构锰氧化物的水热合成

以KMnO₄为锰源、抗坏血酸(AA)为还原剂,采用水热法制备系列纳米结构锰氧化物。通过调节反应物的物质的量的比、水溶液的pH值、反应温度和反应时间,制备出了不同纳米结构的锰氧化物,包括Mn₃O₄纳米粒子、MnOOH、α-MnO₂和β-MnO₂纳米棒。采用XRD和TEM测试技术对合成产物进行了表征,同时对其反应机理进行了探讨。     

纳米SnO2的水热合成

以ＳｎＣｌ４．５Ｈ２Ｏ为原料，用水热法制备了粒度均匀的纳米ＳｎＯ２微粉，研究了反应温度，介质的酸度和反应物浓度等因素对ＳｎＯ２微晶形成，粒子尺寸及产率的影响。Ｘ射线物相分析表明，在酸性介质中，不同温度（１２０～２２０℃）下所形成的产物都是四方晶系ＳｎＯ２，适当降低反应介质的酸度有得于ＳｎＯ２粒子尺寸的减小和产率的提高，随反应温度升高，ＳｎＯ２粒子逐渐长大，当ｐＨ＝１．４５时，粒子的平均尺寸由大约２     

针状TiO2锐钛矿晶粒溶胶的制备、结构及形成机理研究

The PTA sol was prepared using titanyl sulfate(TiOSO₄), peroxide (H₂O₂) and ammonia (NH₃·H₂O) as raw materials. The semitransparent, light yellow AS(autoclaved sol) with ultra-fine needle-like anatase crystals was synthesized by autoclaving the PTA sol at 80～100 ℃ for different times. The anatase crystals were needle-like and 80 nm in length, 20～30 nm in diameter. The FTIR, XRD, SEM were used to analyse the chemical structure, properties of the AS and influencing factors during the sol preparation. The mechanism model of the AS formation was established based on the inorganic and crystal structural chemistry. The PTA molecules were decomposed to form Ti⁴⁺ under hydrothermal conditions and the Ti⁴⁺ were hydrated with water to get [Ti(OH)₄(OH₂)₂]⁰, a growing units of the anatase crystals. The appearance of the needle-like anatase crystals and the anatase precipitate are also explained in this paper.     

水热合成MoO3纳米带的生长机理研究

以离子交换法制备的氧化钼溶胶为前驱体，在水热条件下制备了单晶MoO₃纳米带，对样品进行了XRD、SEM和TEM分析。通过考察水热反应温度和时间对产物结构和形貌的影响，结合材料热力学和动力学理论，探讨了MoO₃纳米带在水热条件下的生长机理。离子交换法制备的溶胶在水热条件下首先转变为热力学亚稳相h-MoO₃六角柱，随着温度的升高和时间的延长，h-MoO₃按照溶解-重结晶过程转变为稳定相α-MoO₃纳米带。     

基于同步辐射多谱学的电催化材料测量

基于电催化过程的能源转化与存储器件是实现绿色可持续发展的关键,催化剂局域结构与反应过程的精准探测与解析是其中的关键问题,如何准确实现上述结构探测具有一定挑战性.基于同步辐射大科学装置的表征方法为全面解析催化剂结构与反应过程提供了良好的研究平台,促进了研究人员对催化机理的全面理解.本文立足于本团队的研究结果,针对电催化材料研究的共性科学问题,总结并讨论了基于同步辐射表征方法的电催化材料测量的研究进展和科学机遇.重点综述了同步辐射表征方法的基本原理、同步辐射技术在电催化剂结构、反应过程表征中的应用,总结了用于揭示局域结构-中间物种-催化性能的测量方法.最后,对基于同步辐射的电催化材料测量所面临的挑战和科学机遇进行了展望,希望为相关表征方法和材料设计提供思路.     

纳米铁酸锌的水热合成

利用水热合成法制备纳米铁酸锌粉体，使用XRD、TEM研究了铁酸锌晶相组成、粒度大小和形貌，并对影响合成工艺的因素如反应前驱物的pH、反应温度、反应时间与产物的关系进行系统的考察研究。结果表明：前驱物的最佳pH为11－12，反应温度为448K，反应时间为360min，可制得结晶良好、纯度高、分散性好、粒度为纳米级的ZnFe2O4粉体。     

聚丙烯酸辅助水热合成CdS纳米片

利用聚丙烯酸(PAA)和硫代乙酰胺(TAA)合成大分子硫源,采用水热的方法在180℃下制备立方相CdS纳米片,纳米片平均大小在100nm.用X射线衍射仪器(XRD),透射电子显微镜(TEM),红外吸收光谱(FTIR)和紫外吸收光谱(UV-Vis)对CdS纳米片进行了形貌和性能表征,并分析了CdS纳米片形成的可能机理.此外,反应的溶剂对CdS纳米材料的形貌有重要的影响.     

同步辐射及相关核分析技术在纳米材料生物效应研究中的应用

伴随纳米技术的发展,纳米材料的生物效应研究成为热点,然而这一新兴的研究领域对传统的研究方法提出了挑战,其深入研究有赖于方法学的发展。同步辐射是具有高亮度、高准直、宽频谱等优异性质的光源,其在元素分析及物质原子或分子尺度的结构表征方面具有独特的优势。本文介绍了同步辐射及相关核分析技术,主要包括同步辐射X荧光分析、同步辐射X射线吸收光谱(扩展X射线吸收精细结构EXAFS,X射线吸收近边结构XANES)、同步辐射圆二色谱、电感耦合等离子体质谱、中子活化分析、同位素示踪技术等在纳米生物效应研究中的应用,结合本实验室以及国内外的研究工作详细阐述了基于同步辐射以及相关核分析方法应用于纳米材料表征及其在生物体内的定量、分布、结构分析等方面的最新进展。     

Synchrotron Radiation for Structural Chemistry—Endohedral Natures of Metallofullerenes Found by Synchrotron Radiation Powder Method

The recent progress of the structural studies of endohedral metallofullerenes by the synchrotron radiation (SR) powder diffraction utilizing the maximum entropy method (MEM) is reviewed. Results of the endohedral metallofullerenes (Y@C₈₂, La@C₈₂, Sc@C₈₂, Sc₂@C₈₄, Sc₃@C₈₂, Sc₂@C₆₆, La₂@C₈₀ and Sc₂C₂@C₈₄) are given. The precise MEM charge densities of metallofullerenes presents the direct image of endohedral nature of metallofullerenes indicating the charge transfer from metal atoms to carbon cage, which governs the stability of the unique endohedral structures. The MEM/Rietveld method and SR powder method using imaging plate (IP), which are the crucial methods for data analysis and measurement in order to determine structure of fulleride, are also mentioned in some detail.     

同步辐射在分子自组装研究中的应用

同步辐射是一种高亮度、高准直性、宽频谱的优质光源,其在物质原子或分子尺度的结构表征方面具有独特的优势。本文介绍了同步辐射在分子自组装研究中的一些应用,主要包括同步辐射X射线散射、时间分辨的小角X射线散射、时间分辨的X射线衍射、X射线精细结构谱,以及红外光谱,详细阐述了同步辐射X射线散射在层状结构、管状结构以及溶液中的组装体结构表征方面的应用。     

二甲胺同步辐射光电离解离机理的质谱研究

利用同步辐射光源，结合飞行时间质谱，在超声射流冷却条件下研究了(CH_3) _2NH(DMA)的光电离解离机理。实验观察到四种主要离子(CH_3)_2NH·~+， CH_3NH~+CH_2，CH_2NH_2~+和CHNH~+，质荷比分别为m/z = 45，44，30和28。四种 离子的出现势（AE）分别为8.26，9.52，11.93和11.27 eV，其中分子电离热IP = （8.26 ± 0.01） eV，计算得到分子离子的生成热Δ_fH~o = 778.55 kJ/mol。 分析表明离子CH_3NH~+CH_2来自母体离子的α去H过程。其他碎片离子由后续逐级 解离去H反应以及脱CH_3通道生成。     

Electronic and Magnetic Transitions in Europium Compounds Studied by Nuclear Forward Scattering of Synchrotron Radiation

Since its observation in 1985, nuclear resonance scattering of synchrotron radiation has become an excellent tool to study hyperfine interactions as well as dynamical effects in solids. It has proven to be a complementary method to Mössbauer spectroscopy. Nuclear resonance scattering combines the advantages of both local probe experiments and scattering techniques. It gives valuable information as well on electronic and magnetic structures and on dynamics in solids. Experiments benefit from the high beam quality of third-generation synchrotron radiation sources, as the small beam size and divergence. Besides the standard isotope ⁵⁷Fe, other Mössbauer isotopes have become more important in nuclear resonant scattering of synchrotron radiation. This article concentrates on the ¹⁵¹Eu isotope.     

Formation and Fate of Formaldehyde in Methanol‐to‐Hydrocarbon Reaction: In Situ Synchrotron Radiation Photoionization Mass Spectrometry Study

HCHO has been confirmed as an active intermediate in the methanol‐to‐hydrocarbon (MTH) reaction, and is critical for interpreting the mechanisms of coke formation. Here, HCHO was detected and quantified during the MTH process over HSAPO‐34 and HZSM‐5 by in situ synchrotron radiation photoionization mass spectrometry. Compared with conventional methods, excellent time‐resolved profiles were obtained to study the formation and fate of HCHO, and other products during the induction, steady‐state reaction, and deactivation periods. Similar formation trends of HCHO and methane, and their close correlation in yields suggest that they are derived from disproportionation of methanol at acidic sites. In the presence of Y₂O₃, the amount of HCHO changes, affecting the hydrogen‐transfer processes of olefins into aromatics and aromatics into cokes. The yield of HCHO affects the aromatic‐based cycle and the formation of ethylene, indicating that ethylene is mainly formed from the aromatic‐based cycle.     

A Fast,Low-Temperature Synthesis Method for Hexagonal YMnO3: Kinetics,Purity, Size and Shape as Studied by In Situ X-ray Diffraction

The reaction mechanisms, phase development and kinetics of the hydrothermal synthesis of hexagonal-YMnO₃ from Y₂O₃ and Mn₂O₃ using in situ X-ray diffraction are reported under different reaction conditions with temperatures ranging from 300 to 350 °C, and using 1, 5 and 10 m KOH, and 5 m NaOH mineraliser. Reactions initiated with Y₂O₃ hydrating to Y(OH)₃, which then dehydrated to YO(OH). Higher temperatures and KOH concentrations led to faster, more complete dehydrations. However, 1 m KOH led to YO(OH) forming concurrently with Y(OH)₃ before Y(OH)₃ fully dehydrated but yielded a very low phase purity of hexagonal-YMnO₃. Using NaOH mineraliser, no YO(OH) was observed. Dehydration also initiated at a higher temperature in the absence of Mn₂O₃. The evolution of Rietveld refined scale factors was used to determine kinetic information and approximate activation energies for the reaction. The described hydrothermal synthesis offers a fast, low-temperature method for producing anisometric h-YMnO₃ particles.     

Studies on Nuclear Resonant Scattering of Synchrotron Radiation by 40K

The studies on nuclear resonant scattering by ⁴⁰K using synchrotron radiation are reviewed. Brilliant and high pure synchrotron radiation permitted us to observe the nuclear resonant forward scattering by ⁴⁰K in a powdered KCl sample, the excitation of which is impossible with ordinary radioactive sources. Furthermore, nuclear resonant inelastic scattering of synchrotron radiation by ⁴⁰K in the KCl sample at room temperature has been measured using a high-resolution monochromator. Adding to these, from the excitation experiments of ⁴⁰K, the energy and lifetime of the first excited state of ⁴⁰K were confirmed. These measurements clearly show that the studies on the electronic states through hyperfine interactions and the dynamical properties of potassium atoms, which are very important in material science and biology, are possible. It should be noted that ⁴⁰K is the natural isotope of potassium and weakly radioactive. Our observation of forward and inelastic scattering of the radioactive nuclide ⁴⁰K will lead to further studies on other radioactive nuclides the resonant forward and inelastic scattering of which are not observed to date.     

Production of N3 upon Photolysis of Solid Nitrogen at 3 K with Synchrotron Radiation

The photodissociation of gaseous molecular nitrogen has been investigated intensively, but the corresponding knowledge in a solid phase is lacking. Irradiation of pure solid nitrogen at 3 K with vacuum‐ultraviolet light from a synchrotron produced infrared absorption lines of product l‐N₃ at 1657.8 and 1652.6 cm^?1. The threshold wavelength to generate l‐N₃ was determined to be (143.7±1.8) nm, corresponding to an energy of (8.63±0.11) eV. Quantum‐chemical calculations support the formation of l‐N₃ from the reaction N₂+N₂, possibly through an activated complex l‐N₄ upon photoexcitation with energy above 8.63 eV. The results provide a possible application to an understanding of the nitrogen cycle in astronomical environments.     

In Situ Synchrotron X-ray Diffraction Studies of the Mechanochemical Synthesis of ZnS from its Elements

Mechanochemistry, as a synthesis tool for inorganic materials, became an ever-growing field in material chemistry. The direct energy transfer by collision of the educts with the milling media gives the possibility to design environmental-friendly reactions. Nevertheless, the underlying process of energy transfer and hence the kinetics of mechanosynthesis remain unclear. Herein, we present in situ synchrotron X-ray diffraction studies coupled with pressure measurements performed during the formation of ZnS and the subsequent phase transition (PT) from the hexagonal to the cubic modification. Milling Zn and S₈ results in the sublimation of S₈, observed by a sudden pressure increase. Simultaneously, the hexagonal metastable ZnS-modification (wurtzite) forms. Via detection of the pressure maximum, the exact start of the wurtzite formation can be determined. Immediately after the formation of wurtzite, the structural PT to the thermodynamic stable cubic modification sphalerite takes place. This PT can be described by the Prout-Tompkins equation for autocatalytic reactions, similar to thermally induced PT in sulfur vapor at high temperatures (T>1133 K). The increase in the reactivity of the wurtzite formation is explained by the reaction in sulfur vapor and the induction of defect structures by the collisions with the milling media.