时间分辨原位同步X射线衍射技术在分子筛研究中的应用

介绍了时间分辨原位同步X射线衍射技术(in situ TR XRSD)的原理。该技术以其原位测量性和时间分辨性为特征,广泛应用于分子筛研究的各个领域。举例阐述了该技术在水热合成条件的优化、结晶动力学参数测定、成核机理探索、转晶过程和机理、晶体参数变化的监测和骨架外阳离子迁移等过程研究中的应用原理和方法。     

原位变温X射线衍射虚拟仿真实验建设与实践

原位变温X射线衍射实验是物理、化学等相关专业综合和创新性实验项目,基于“以虚代实,虚实结合”的思想开发原位变温X射线衍射虚拟仿真实验系统非常必要。本系统完整地模拟了仪器认知、样品测试、数据计算及应用等实验实景,教学中采用线上线下虚实结合的教学方法,培养学生利用大型仪器解决复杂问题的综合能力和高级思维。     

原位磁场下粉末样品的X射线衍射图谱

To obtain more crystal and magnetic structural information of powder crystals,magnetic field is introduced into X'Pert-MPD XRD apparatus with the strength of 0. 42 T and two different directions:one direction of magnetic field is vertical to the sample holder and another is parallel. XRD patterns in situ magnetic field are obtained for six samples which are representative of paramagnetic,diamagnetic,ferromagnetic,ferrimagnetic,antiferromagnetic substances and reduction product of FeCl2 by NaBH4 respectively. Compared with XRD patterns obtained in the zero magnetic field,there are some diffraction peaks disappear,some occur,or some diffraction angles and counts change. In addition,the patterns are different under the different direction of magnetic field. The cause is that magnetic dipoles in crystals are oriented along with the direction of magnetic field. The oriented magnetic dipoles produce stress in crystals and make crystal lattice changed（such as magnetostriction）or even turn particles aligned along with the direction of magnetic field to form preferred orientation of particles.     

原位变温X射线衍射测试技术及其影响因素

在X射线衍射仪中引入加热台,可以实现原位变温X射线衍射分析.原位试验是研究材料在加热或冷却过程中材料动力学的有效手段.对变温X射线衍射测试样品的要求、测量方法的原理、布鲁克D8 advance衍射仪原位变温的测试步骤以及测试过程中样品的收缩问题、背底衍射峰干扰等常见影响因素进行了详细的说明,为变温X射线衍射测试提供了具体的试验指导.     

微纳米VO2膜层高温相变原位X射线衍射测试方法研究

通过设计、自制加热样品台结合商业X射线衍射仪的小角掠入射衍射模式,开发了微纳米膜层的原位高温相变测试方法,解决了样品表面微纳米膜层材料（厚度 < 10 μm）的高温相变难以原位测量的问题.研究了样品台与膜层表面的温度分布特征,验证了自制加热样品台的控温效果,原位测试了不同温度下二氧化钒（VO₂）膜层的X射线衍射图谱,揭示了VO₂膜层的高温相变行为.     

用于X射线衍射测量的样品加压原位装置

制备了一种用于Ｘ射线衍射测量的样品加压原位图的实验装置。该装置无需对原设备做任何改变，只要旋进螺栓调节到指定压力即可测量，以磁阻材料Ｌａ０．８Ｓｒ０．２ＭｎＯ３为例做了实验，说明了该样品在不同压力下特有的输运性质。     

X射线多重衍射的一些实验研究

使用在试样架上附加有Φ旋转装置的X射线粉末衍射仪,对Si(001)晶片和In1 -xAlxAs/GaAs一维超点阵样品,进行了一些X射线多重衍射实验研究,初步解释了所获得的多重衍射花样 ,得到了一些有关的结构信息。     

粉末X射线衍射结构分析的进展

粉末X射线衍射结构分析自Rietveld 1967. 1969年在中子粉末衍射结构分析中问世后,又经Wiles and Young 1981、1982年介绍到X射线衍射技术中来,近几年来取得了显著的进展。特特是同步辐射光源的建成和应用,取得了和单晶结构分析几乎同样等级的拟合程度和极为相似的结构参数。本文就近几年来粉末X射线衍射对晶体结构分析方面的进展进行综述,着重讨论Bragg衍射的峰形函数,择优取向校正和光学系统改善等方面对结构精化的影响,介绍在某些方面中的应用。     

高温下X射线衍射法对铁氧化过程的研究

在500℃和800℃条件下,采用高温X射线衍射法对铁粉的氧化过程进行研究.结果表明,随着温度升高,铁及其氧化物的晶面间距均有所增加,而温度恒定时晶面间距没有变化,温度是影响晶格变化的主要因素.温度升高,晶面间距加大,为铁离子在氧层中的迁移提供了通道,有利于氧化过程的进行.     

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.     

基于XRD曲线分形维度的丝光沸石晶化动力学行为分析

丝光沸石;水热晶化;分形维度;化学混沌;晶化动力学     

原位反应合成Mo-Si化合物系复合材料

采用反应烧结法原位合成了Mo Si系化合物复合材料，利用X射线衍射仪、扫描电镜和电子探针等考察了材料的显微结构和相组成.结果表明，随原料粉中Mo含量的增加， Mo Si系反应生成物依次向MoSi2→Mo5Si3→Mo3Si变化；各相分布较为均匀，组织致密，晶粒细小.     

Synthesis of Zeolite ZSM-2 Using Zeolite NaX as Seeds

Introduction Oxygen and nitrogen have been produced tradition-ally by cryogenic distillation of air. Methods for the non-cryogenic separation based on selective adsorption have been developed and commercialized since the 1970s and have led to a cost-effective process for this important separation.1 Low-silica zeolites are important materials for producing oxygen by selective adsorption of nitrogen. In 19891990, a new generation of lith-ium-based adsorbents was developed.2,3 Highly lithium exc…     

In Situ Synthesis of NaY Zeolite with Coal—Based Kaolin

NaY zeolites were in-situ synthesized form coal-based kaolin via the hydrothermal method. The effects of various factors on the structure of the samples were extensively investigated.The samples were characterized by N2 adsorption,XRD,IR and DTG-DTA methods,and the results show that the crystallization temperature and amount of added water play an important role in the formation of the zeolite structure.The 4A and P zeolites are the competitive Phaes present in the resulting product.However,NaY zeolites wiht a higher relative crystallinity,excluding impure crystals and the well hydrothermal stapore size distribution,and this means that optimization of this process might result in a commercial route to synthesize NaY zeolites form coal-based kaolin.     

微波辐射法合成NaX分子筛

NaX是低硅铝比的八面沸石,一般在低温水热条件下合成.因反应混合物配比不同,以及采用的反应温度不同,晶化时间为数小时至数十小时不等. 近年来,微波辐射方法被应用于无机及有机化合物的合成中.Chu Pochen等在专利文献中报道了微波辐射法在沸石分子筛合成中的应用,其中提到了NaX分子筛,但对合成     

Desolvation of a Novel Microporous Hydrogen-Bonded Framework: Characterization by In Situ Single-Crystal and Powder X-ray Diffraction

Despite significant structural rearrangement upon desolvation of a three-dimensional molecular framework of hexaaquacobalt cations and redox-active functionalized tetrathiafulvalene anions (see the picture; the area filled with water molecules is shown in gray), monocrystallinity and microporosity are retained. X-ray analyses show that a unique combination of hydrogen bonds and π⋅⋅⋅π interactions within the framework gives this material a structural flexibility not seen in zeolites or their analogues.     

Permeation through a single crystal of Zeolite NaX

Steady state permeation through a 120 μm single crystal of zeolite NaX has for the first time been observed. Each crystal was imbedded in an epoxy film, polished to expose opposite faces to feed and permeate gases, and mounted in an apparatus with pmol/s permeation rate sensitivity. Permeation was constrained to occur by an intracrystalline diffusion mechanism, confirmed by temperature dependence and selectivity measurements. Rates decreased at higher temperatures due to opposing sorption and diffusion effects. Intracrystalline butane diffusivity at 25°C was 3 x 10^?4 cm²/sec, in agreement with other methods. Anomalously long time lags for approach to steady state are explained by a transition between two states of the zeolite, differing in permeability by 10²-10⁴. The state with lower permeability was selectively permeable to isobutane from a methaneísobutane mixture.