Characterization and theory of electrocatalysts based on scanning electrochemical microscopy screening methods

A strategy for finding new electrocatalysts for the oxygen reduction reaction (ORR) in acidic solutions is outlined and illustrated with results for Pd-Co catalysts. This is based on establishing guidelines for selecting test systems, rapid preparation of arrays, and rapid screening by scanning electrochemical microscopy. Promising candidates are further tested as supported electrocatalysts by larger scale electrochemical methods and in fuel cells, with optimization of the composition and structure. Those that emerge are characterized by a variety of methods, including X-ray diffraction, scanning electron microscopy, and X-ray photoemission spectroscopy. Finally, density functional theory is used for detailed calculations of oxygen adsorption and dissociation on the material and provides better guidelines for further testing.     

Novel 1D Ni–Ag composition nanostructure: Synthesis,properties and antioxygenation improvement

Nickel nanochains assembled with submicrometer-sized flowers were synthesized through a mild hydrothermal method without any template and surfactant. Subsequently, nickel–silver metal composition nanostructures were also prepared by taking advantage of reducing property of nickel metal. The resulting chains superstructures were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy and the thermogravimetric analysis (TGA) measurements. This synthesis of such hierarchical structures implies a simple and inexpensive way to prepare bimetallic composite superstructures on a large scale. Furthermore, antioxygenation properties of these bimetallic composites could be improved drastically.     

Synthesis and characterization of boron nitride sponges as a novel support for metal nanoparticles

This paper describes a simple synthetic route for the synthesis of hexagonal boron nitride (h-BN) powders with high specific surface area, in which BBr3, NH4Cl and Al powders are used as starting materials. The structure and composition of the powders were characterized by electron diffraction, Fourier transformation infrared spectroscopy and X-ray photoelectron spectroscopy in the selected area. X-ray diffraction shows wide peaks of crystalline h-BN with the particle size on the nanometer scale, and transmission electron microscopy reveals that the products have a novel spongy morphology. Silver nanoparticles loaded h-BN sponges were prepared via a one-step synthesis method. Different reaction conditions for the formation of h-BN sponges were also investigated.     

On the capabilities of the x-ray diffraction method in determining polytypes in nanostructured layered metal disulfides

By the example of multilayer MoS₂ nanotubes the capabilities of the X-ray diffraction method in determining possible polytypic forms of layered metal dichalcogenides, which may appear due to the nanostructuring of these compounds, are discussed. The conclusion about a low information value of the X-ray diffraction method is drawn, therefore the experimental analysis of the polytypic composition of nanostructures of metal dichalcogenides needs to attract electron microscopy and electronoй tomography methods.     

煤中矿物质及其燃烧后的变化分析

以淮北煤田6煤层煤为样品，采用中子活化法、化学方法、X射线衍射及扫描电镜等方法对煤及其灰样品中的矿物质、微量元素进行了分析，在此基础上，研究了样品中主要矿物的种类及其形成时的影响因素，分析了它们在燃烧前后的主要变化。通过分析可知，样品中主要含有高岭石、石英、方解石和黄铁矿以及多种微量元素；在燃烧过程中，微量元素的含量以及矿物的种类发生了变化，并形成高温稳定的矿物种类。     

Corrosion behavior of 316 stainless steel for advanced high-temperature water-cooled nuclear plant

Corrosion occurs widely in the supercritical water system materials under high temperature and pressure. To select reliable candidate materials, corrosion behavior of many alloys was investigated. This study focused on investigating the corrosion behavior of 316 stainless steel (316 SS) in supercritical water (798 K/24 MPa). After exposed to SCW for 200 h, the oxidation kinetics, surface morphology, and diffusion of elements were investigated by weight measurement, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The surface of 316 SS showed isolated and discontinued oxide scales. The oxide scale was determined to be a monolayer layer, and the main composition was determined to be Fe–Cr-rich spinel with a few amounts of magnetite attached to the surface. A few pores due to pitting corrosion were found on the surface, and the oxidation mechanism was also investigated.     

Microwave synthesis of core-shell gold/palladium bimetallic nanoparticles

The microwave-assisted polyol reduction method was applied to the synthesis of core-shell gold/palladium bimetallic nanoparticles by the simultaneous reduction of the AuIII and PdII ions. The thickness of the palladium shell was calculated to be approximately 3 nm, and the gold core diameter is 9 nm. The structure and composition of the bimetallic particles were characterized by high-resolution transmission electron microscopy equipped with a nanoarea energy-dispersive X-ray spectroscopy attachment, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy.     

AlCo金属间催化剂的合成及炔烃选择加氢性能

以CoCl_2与LiAlH_4为原料,通过化学合成法经过160℃下12 h的化学反应与650℃的退火热解制备了Al-Co金属间化合物纳米粒子.通过改变原料中钴和铝的摩尔比,可调变Al-Co金属间化合物的组成.采用XRD、SEM、EDX、TEM、XPS等技术对催化剂进行系统表征.并以苯乙炔和二苯乙炔的选择加氢为探针反应,结果显示Al-Co金属间化合物对烯烃表现出高选择性,且AlCo的催化活性明显高于其他物相的催化剂.在苯乙炔和二苯乙炔加氢反应中,中间产物苯乙烯和顺-1,2-二苯乙烯的选择性分别高达80%和90%.     

General synthesis of metal sulfides nanocrystallines via a simple polyol route

In this report, a simple and easy polyol route for synthesizing many binary metal sulfides nanocrystallines is demonstrated. Powder X-ray electron diffraction and energy-dispersive X-ray spectrum are applied to investigate the crystallinity and composition of the nanoscale materials. The resulting particle size and morphology are examined by transmission electron microscopy, and the possible mechanism is also briefly discussed.     

Controlled hydrothermal synthesis of bismuth oxyhalide nanobelts and nanotubes

Ternary bismuth oxyhalide crystalline nanobelts (such as Bi24O31Br10, Bi3O4Br, Bi12O17Br2, BiOCl, and Bi24O31Cl10) and nanotubes (such as Bi24O31Br10) have been synthesized by using convenient hydrothermal methods. The composition and morphologies of the bismuth oxyhalides could be controlled by adjusting some growth parameters, including reaction pH, time, and temperature. All the nanostructures were characterized by using various methods including X-ray diffraction, transmission electron microscopy, high-resolution TEM, electron diffraction, and energy-dispersive X-ray analysis. The possible reaction mechanism and growth of the crystals are discussed based on the experimental results.     

Structural characteristics of nanomaterials based on CdS quantum dots

CdS nanoparticles with sizes where a quantum-size effect is observed are structurally characterized in a detailed way. The following complex of structural methods is used to characterize the nanoparticles: electron diffraction; analytical, diffraction, and high-resolution transmission electron microscopy; and small-angle X-ray scattering.     

In vitro corrosion behavior of electrodeposited calcium phosphate coatings on Ti6Al4V substrates

Calcium phosphate coatings on titanium alloy substrates are synthesized by pulsed electrodeposition and characterized by scanning electron microscopy associated to energy dispersive X-ray spectroscopy and by X-ray diffraction. The corrosion behavior of CaP/Ti6Al4V systems and uncoated Ti6Al4V are investigated using electrochemical methods in three physiological solutions and simulated with an equivalent circuit. The results reveal that the calcium phosphate coatings act as a protective layer especially when electrodeposition is carried out in the presence of hydrogen peroxide into the electrolyte which is used to control the chemical composition of the coatings and which implies a control of the corrosion behavior of the prosthetic material.     

Synthesis of single crystal CdMoO4 octahedral microparticles via microemulsion-mediated route

The single crystal octahedra of tetragonal CdMoO4 were synthesized on large scale via a microemulsion-mediated hydrothermal route at 120 degrees C for 10 h. The structures, compositions and morphologies of the as-prepared products were characterized by X-ray power diffraction pattern, field emission scanning electronic microscopy, transmission electron microscopy. Further studies reveal that the octahedral CdMoO4 crystal has eight equivalent exposed crystal faces {101}. The possible growth mechanism of the CdMoO4 octahedral is based on the anisotropic growth habit of CdMoO4 crystals and the selective absorption of surfactant molecules CTAB on the faces of the prime crystals, and the reaction time, composition of the microemulsions and temperature have considerable effects on the final morphology of CdMoO4.     

金属-有机框架作为异相催化剂的表征方法概述

作为一类具有大的比表面积、高孔隙率、合成方便、骨架规模可变、化学可修饰以及结构组成多样等优点的新型多孔材料,金属-有机框架（MOFs）在光电材料、药物传输、气体吸附分离及催化等领域有着广阔的应用前景,成为近年来研究的热点。异相催化是MOFs最具发展潜力的应用领域之一,各种表征方法和研究手段是开展MOFs异相催化研究的工作基础。本文主要围绕表征MOFs作为异相催化剂的常用技术手段进行介绍,包括X-射线单晶衍射、X-射线粉末衍射、热重分析、红外光谱/拉曼光谱分析、透射/扫描电镜等,旨在为开展相关MOFs催化研究提供一定参考。     

壳聚糖修饰的NiB非晶态合金的制备及表征

以壳聚糖(CS)为稳定剂, 采用化学还原法制备了非负载型NiB非晶态合金催化剂(NiB-CS); 并用 X射线衍射(XRD)、电感耦合等离子体发射光谱(ICP)、X射线光电子能谱(XPS)、透射电镜(TEM)、选区电子衍射(SAED)等表征方法研究了催化剂的非晶性质、原子组成及粒径大小等. 考察了催化剂对糠醇加氢制四氢糠醇反应的催化性能, 并与没有壳聚糖保护的NiB催化剂进行了对比. 结果表明, 加入壳聚糖制得的NiB-CS催化剂的活性组分NiB粒径更小, 表面活性组分浓度更高, 催化活性更高.     

Mercury selenide nanorods: Synthesis and characterization via a simple hydrothermal method

HgSe nanorods have been synthesized through a simple hydrothermal reduction approach. The nanorods formed were ≈45 nm average diameter and ≈3 μm nm in length. X-ray diffraction characterization suggested that the product consists of cubic phase pure HgSe. The as-prepared products were also characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). An X-ray energy dispersive spectroscopy (EDX) study further confirmed the composition and purity of the product. The synthesis procedure is simple and uses less toxic reagents than the previously reported methods. The results showed that the capping agent CTAB (cetyltrimethylammoniumbromide) plays a crucial role in the process. Other factors, such as the reaction time, temperature, different capping agent and the reductant type also have an influence on the morphology of the final products to some extent.     

溶剂热法制备银纳米晶

以聚乙烯吡咯烷酮(PVP)作为表面活性剂,利用乙二醇溶剂热法成功制备了银纳米颗粒;利用场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)分析了样品的形貌和晶体结构,并考察了溶剂组成等因素对银纳米颗粒形貌的影响.研究结果表明所得银纳米晶粒径均一,直径约为90nm;增大PVP的加入量会降低产物的粒径,溶剂中水的引入会影响银纳米晶的形貌.     

Analytical electron microscopy of materials

Analytical electron microscopy enables combined crystallographic and chemical information with a high spatial resolution to be gained from microregions of electron-transparent specimens. This is reached by the combined application of imaging, diffraction and spectroscopic methods, using either a dedicated scanning transmission electron microscope or a conventional high-resolution electron microscope (having a strong objective lens) equipped with suitable X-ray or electron spectrometers. Of the diffraction methods especially the technique of convergent beam diffraction is used, yielding valuable information on crystal structures, lattice parameter changes, symmetry variations and crystal perfection, respectively. For chemical analysis, either energy-dispersive X-ray spectroscopy (EDX) is used or electron energy loss spectroscopy (EELS). Finally, high-resolution electron microscopy in the lateral resolution range of some 0.1 nm allows the reliable geometrical inspection of extreme microregions.     

Preparation and characterization of gadolinium hydroxide single-crystalline nanorods by a hydrothermal process

The Gd(OH)3 nanorods with diameters of ca.40-60 nm and lengths of more than 400-550 nm have been prepared by a novelhydrothermal technique.The structural features and chemical composition of the nanorods were investigated by X-ray diffraction(XRD),transmission electron microscopy(TEM),and field emission scanning electron microscope(FESEM),selected areaelectron diffraction(SAED),and high resolution transmission electron microscopy(HRTEM).The possible mechanism for theformation of Gd(OH)3 nanorods was proposed.