Detection of Minor Crystalline Phases in Alumina Ceramics Using Synchrotron Radiation Diffraction

The use of synchrotron radiation diffraction (SRD) in con-junction with conventional laboratory X-ray diffraction (XRD) for analyzing the phase assemblage of selected alu-mina-based ceramics is described. This paper outlines the benefits of synchrotron powder diffraction in resolving mi-norand impurity phases in various alumina ceramics. Laboratory XRD is shown to provide only cursory details of minor crystalline phases which are strikingly evident and clearly defined from application of SRD analysis. The po-tential of SRD techniques to characterize low-level crystal-line phases and as a check for "phase purity" in ceramic systems is considered.     

土壤重金属污染及检测方法的研究进展

文章针对土壤重金属污染问题,重点阐述了重金属离子的检测方法,并且对现有分析手段的优缺点进行比较。展望了其广阔的发展和应用前景,对以后的研究重点和发展方向进行了讨论。     

土壤重金属光谱检测方法的应用研究

针对土壤重金属,在简述其危害的基础上,对其光谱检测方法具体应用进行深入分析,以此为实际的重金属检测工作提供理论参考,保证检测结果准确性与可靠性。     

Airborne Particle Generation Through Acoustic Ejection of Particles-In-Droplets

This article reports a method to produce airborne particles by generating uniformly sized droplets that contain particles, where the droplets are made with an acoustic ejector that does not need any small orifice or nozzle which might become clogged. We demonstrate stable and continuous ejection for more than 10 minutes of 14-μ m droplets containing 1-μ m polystyrene latex (PSL) particles at a concentration of 1% solids. There was no indication of clogging. We have demonstrated ejection of droplets containing PSL at rates up to 3,000 droplets/s (90,000 1-μ m-PSL particles/s). This method should produce, at a known rate, (1) uniform particles of known volume when the particles are soluble in the liquid and/or (2) particles with a statistical distribution (e.g., Poisson distribution) when the particles are aggregates of primary particles. The method should be useful for aerosol generation systems requiring no volatile organic compounds (VOC).     

Observation of Compression and Failure Waves in PMMA by Means of Synchrotron Radiation

The possibility of using synchrotron radiation for density measurements in shockcompressed polymethylmethacrylate destroyed in a failure wave is demonstrated for the first time. Parameters of the compression and failure processes are presented.     

Determination of Phase Transformation Depth Profiles with Synchrotron Radiation

The transformation of tetragonal zirconia to monoclinic in a glass-ceramic as a function of depth from a fracture surface was measured by X-ray diffraction employing synchrotron radiation. The large number of photon energies which can be used in such an experiment permt rigorous testing of models of the transformation zone. A crack plane intersection model has been developed to interpret the observations for two phase-transformation-toughened glass-ceramics of grossly different inicrostructures.     

Chirality Emergence in Thin Solid Films of Amino Acids by Polarized Light from Synchrotron Radiation and Free Electron Laser

One of the most attractive hypothesis for the origin of homochirality in terrestrial bioorganic compounds is that a kind of “chiral impulse” as an asymmetric excitation source induced asymmetric reactions on the surfaces of such materials such as meteorites or interstellar dusts prior to the existence of terrestrial life (Cosmic Scenario). To experimentally introduce chiral structure into racemic films of amino acids (alanine, phenylalanine, isovaline, etc.), we irradiated them with linearly polarized light (LPL) from synchrotron radiation and circularly polarized light (CPL) from a free electron laser. After the irradiation, we evaluated optical anisotropy by measuring the circular dichroism (CD) spectra and verified that new Cotton peaks appeared at almost the same peak position as those of the corresponding non-racemic amino acid films. With LPL irradiation, two-dimensional anisotropic structure expressed as linear dichroism and/or linear birefringence was introduced into the racemic films. With CPL irradiation, the signs of the Cotton peaks exhibit symmetrical structure corresponding to the direction of CPL rotation. This indicates that some kinds of chiral structure were introduced into the racemic film. The CD spectra after CPL irradiation suggest the chiral structure should be derived from not only preferential photolysis but also from photolysis-induced molecular structural change. These results suggest that circularly polarized light sources in space could be associated with the origin of terrestrial homochirality; that is, they would be effective asymmetric exciting sources introducing chiral structures into bio-organic molecules or complex organic compounds.     

Selective Recovery of Platinum Group Metals from Spent Automobile Catalyst by Integrated Ion Exchange Methods

Selective recovery of platinum group metals (PGMs), such as Pd, Pt, and Rh, from spent automobile catalyst has been investigated by integrated ion exchange method using dihexyl sulfide (DHS) impregnated resin and commercial weak anion exchange resin (Diaion WA-21) as adsorbents. Batchwise adsorption revealed that the DHS impregnated resin possesses the selective adsorption ability for Pd and WA-21 possesses selectivity for all PGMs, especially Rh. Chromatographic separation of Pd with column packed with DHS impregnated resin can be selectively achieved. The chromatographic separation of Pd and Pt with a column packed with WA-21 is effectively progressed, while that of Rh is insufficient yield due to a slow adsorption rate. Separation of Rh from other two PGMs can therefore be achieved by switching the eluent. Both adsorbents show almost no adsorption abilities for other heavy metals containing in the spent automobile catalyst. Sequential chromatographic operation of the column packed with DHS impregnated resin followed by the column packed with WA-21 can be finally achieved to recover mutual PGM from leaching solution of spent automobile catalyst.     

应用藻类的荧光响应检测重金属毒性

目前的水质监测生物毒性检测方法,虽然在物质的综合毒性方面比传统的理化方法全面,但其测试程序耗时长,对于测试生物的培养操作也较为复杂。寻求一种快速、准确的方法成为水中毒物生物检测方法的研究热点。以藻类为挈入点,综述了重金属对藻类生长、光合作用、荧光特性等的胁迫表现,介绍了藻类的荧光原理,分析了藻类荧光性在毒性检测方面的前景。     

X射线荧光光谱法检测废旧塑料中的有毒有害重金属

欧盟的RoHS指令对电子电器产品中的有害重金属含量做了严格的限制.X射线荧光光谱法(XRF)能够同时检测Pb、cd、Hg、总Cr与总Br的含量.与传统的重金属检测方法相比,具有检测速度快、分辨率高、稳定性高、可实施无损分析及应用广泛等特点.介绍了废旧塑料中重金属的相关法律法规和检测标准,阐述了X射线荧光法的原理及其应用等.     

Ejection of Clusters from Liquid Beam Surface by IR Laser Irradiation

A continuous liquid flow of an aqueous solution of phenol (Phe) in a vacuum (a liquid beam) was irradiated with an IR laser at 2.85 μm, which is resonant to the vibrational absorption band of the liquid water. The Phe (H₂O)_N, ejected from the liquid beam surface into the gas phase, was ionized by a UV laser at 270 nm into hydrated phenol cluster ions, Phe⁺ (H₂O)_n (n = 0 − 30), and analyzed by a time-of-flight mass spectrometer. The velocity distributions of the product cluster ions were derived from the spatial distributions measured at different elapsed times after the IR laser irradiation. The results and the analysis show that dense neutral clusters are ejected from surface regions locally heated by the intense IR laser.     

Characterization of Ceramic Materials with BIGDIFF: A Synchrotron Radiation Debye-Scherrer Powder Diffractometer

Experiments have been conducted to evaluate the potential of the BIGDIFF Debye–Scherrer diffractometer (radius of 573 mm) for characterizing ceramic materials using synchrotron radiation. The instrument has been tested at a wavelength of 0.1538 nm (1.5378), under in vacuo conditions, with standard reference materials and an alumina-matrix ceramic specimen using capillary-mounted (diameter of 0.5 mm) powdered material. The diffraction patterns that have been recorded with imaging plates over a period of 15 min provide phase detectability that is clearly superior to Bragg-Brentano laboratory X-ray diffractometry data that is collected in 1 h. The superiority of BIGDIFF for the analysis of phase composition becomes very pronounced for trace phases (,1%). The sharper definition of the Bragg peaks with BIGDIFF synchrotron radiation data also leads to improved estimates of nonlinear residual strain and crystallite size data. The superior performance of BIGDIFF is principally due to (i) the intensity of the synchrotron radiation incident beam that is achieved with high collimation and monochromaticity (E/ΔE 10⁴), (ii) the large ratio of the camera radius to the capillary radius, and (iii) the spatial resolution and dynamic range of the imaging plates.     

Spatial distribution of Si in Pinus Insigne (Pinus radiata) Wood using micro XRF by Synchrotron Radiation

Silicon, while not an essential element, is known to have positive roles in certain vegetable species. For instance, it has been recognized to protect them from biotic and abiotic stress. Due to the fact that certain species accumulate the aforementioned element in their tissues, the determination of its concentration is of importance in different disciplines, such as dendrology, plant physiology, forest management, agroecology, and also in the wood industry. Usually, its quantification is preceded by a series of digestion steps that, aside from been time-consuming, and contamination-prone, prevents from conducting a spatial distribution of the element on the sample. In this research, samples of Pinus radiata wood were studied using a synchrotron radiation source that allowed direct scanning of its surface without any treatment, and the determination of silicon as a function of the position and the tree rings, using micro X-ray fluorescence (µXRF). A quantification method based in the fundamental parameters approach was evaluated. It was found that silicon concentration increases near the latewood ring zones, showing a periodical behavior, related to seasonal environmental events.     

消解方式对废电器塑料中重金属测定的影响分析

针对现有消解方法对废电器塑料存在消解不完全的现象,导致无法准确分析出该类型塑料中的重金属成分及含量,从而对后续研究废电器塑料中重金属的迁移转化造成困难。本文对比不同消解方法对废电器塑料中重金属Pb、Cr、Cd、Sb含量测定的影响,通过设置对照实验,以微波消解和电热板消解及不同酸体系为实验条件,比较了四种前处理方法的测试结果、回收率、精密度和检测限。结果表明:微波消解的密闭性、加热效果均好于电热板消解。当采用微波加热、以HNO_3-HBF_4-H_2O_2为消解酸体系时,废电器塑料的消解效果最好,其回收率为85.64%～109.70%,精密度为0.33%～3.86%。该方法检测限低,且操作简单、用时少。     

Ejection of DNA molecules from carbon nanotubes

Ejection of DNA molecule from carbon nanotubes subjected to torsion is investigated with molecular dynamics simulations. The wall of a carbon nanotube undergoes a collapse and a corresponding propagation of the collapse when a torsion loading applied to the tube is beyond a critical value. The van der Waals force between the encapsulated DNA molecule and the collapsed wall of the nanotube on one hand is a driving force to push the molecule out of the tube, while may also prevent the ejection when the onset of the collapsed wall is in front of the molecule. To ensure a complete DNA ejection, a design of a stopper, a small fixed portion on the carbon nanotube to prevent the collapsed wall from propagating in front of the DNA molecule, is developed. The effects of the environmental temperature, the torsion loading, and the size of the nanotube on the delivering process of the DNA molecule are also examined. Simulation results demonstrate the feasibility of ejection of DNA molecules from carbon nanotubes subjected to torsion and provide guidance on designs of the DNA delivery in biology and medical applications.     

Synchrotron Radiation Diffraction Study of the Microstructure Changes in Cement Paste due to Accelerated Leaching by Application of Electrical Fields

An external dc voltage was applied to cured cement pastes to simulate their natural degradation over time; i.e . migration of ions and dissolution of solid phases. The presence of crystalline phases before and after applying a voltage was quantified by powder diffraction using synchrotron X-ray radiation. The results were refined by the Rietveld method. The specimens were also analysed by mercury intrusion porosimetry. Results indicated that a portion of the crystalline phases dissolved and later precipitated as amorphous phases in smaller pores. This accelerated treatment led to the formation of a larger proportion of amorphous phases in the specimens studied.     

地表水中重金属监测预处理方法的探讨

我国的地表水安全形势已经非常严峻,尤其是重金属污染事件的频发。党和政府高度重视饮用水源安全,环保部门加强对饮用水源监测力度。对地表水重金属分析中,地表水标准中对重金属的预处理方法不能满足各种重金属项目监测方法的要求,现对不同的项目进行不同的预处理方法的探讨。     

Elemental Composition of Skeletal Muscle Fibres Studied with Synchrotron Radiation X-ray Fluorescence (SR-XRF)

Diseases of the muscle tissue, particularly those disorders which result from the pathology of individual muscle cells, are often called myopathies. The diversity of the content of individual cells is of interest with regard to their role in both biochemical mechanisms and the structure of muscle tissue itself. These studies focus on the preliminary analysis of the differences that may occur between diseased tissues and tissues that have been recognised as a reference group. To do so, 13 samples of biopsied human muscle tissues were studied: 3 diagnosed as dystrophies, 6 as (non-dystrophic) myopathy and 4 regarded as references. From these sets of muscle biopsies, 135 completely measured muscle fibres were separated altogether, which were subjected to investigations using synchrotron radiation X-ray fluorescence (SR-XRF). Muscle fibres were analysed in terms of the composition of elements such as Br, Ca, Cl, Cr, Cu, Fe, K, Mn, P, S and Zn. The performed statistical tests indicate that all three groups (dystrophies—D; myopathies—M; references—R) show statistically significant differences in their elemental compositions, and the greatest impact, according to the multivariate discriminate analysis (MDA), comes from elements such as Ca, Cu, K, Cl and S.     

土壤重金属分析前处理方法比较

土壤出现重金属的污染会对土壤内的植物和生物等造成很大的危害,甚至对人们的正常生活造成影响,因此,需要做好对土壤内重金属的测定和分析,而样品前处理的方法就是对土壤内重金属的含量进行准确测定的重要途径。就主要针对多种土壤重金属分析前处理方法的回收率以及测定结果的相对误差等进行比较,分析各个方法的优劣性,从而来获取最为科学、准确、便捷的前处理方法。     

由磷石膏微波辐照制备羟基磷酸钙

以工业废弃物磷石膏为原料,结合微波辐照技术制备了具有较高纯度和结晶度的羟基磷酸钙(HAP)。考察了EDTA添加量,微波功率,反应时间及反应温度对产物形貌和形态的影响。其结果显示当Ca2+/EDTA比例为1:1.5时,所制备的HAP具有较高的纯度和发达的孔隙。当微波功率为500W,辐照时间4h,反应温度50℃时,所制备的HAP具有最佳的结晶性。所制备的HAP在治理重金属离子及F-污染水体方面具有广泛的潜在用途。