On the determination of low nitrogen concentration gradients in austenitic CrNi(Mo) steels

For the determination of diffusion coefficients by using the model diffusion into a plate methodical examinations were carried out on samples of austenitic steel that had been nitrided in their marginal zones for 1.5 h at 1523 K.For recording of the concentration of N as a function of the distance from the surface electron-probe microanalysis (EPMA) and the precision determination of the lattice parameters by Kossel technique were applied. Both methods yield comparable results.     

Progress in the field of Kossel and pseudo-Kossel technique

A review of new methods and equipments of Kossel and pseudo-Kossel technique is given. The importance of line profiles for crystal and real structure analysis is stressed. The state of the art for determination of crystallographic parameters is described, and future trends (assessment of dislocation density, investigation of radiation defects) are discussed. A very important application is the optimization of the technology for transformer core sheets.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Precise determination of the lattice constant of LiF by means of X-ray divergent beam (pseudo Kossel-) technique via computer graphics and multiple intersections

The X-ray interference patterns obtained by the divergent beam transmission technique (pseudo Kossel technique in transmission mode) permit an evaluation of high precision. Especially the low resolution triple intersections appearing in the pattern can be utilized for precise determination of lattice constants. For cubic crystals the parameters can be calculated directly using analytical methods. The computer graphics method is also applicable for crystal systems with low symmetry. It is shown on patterns from LiF obtained with Fe-K and Cu-K radiation that the computer graphics method provides a fast way for the precise determination of lattice constants.     

Investigations of precipitates in heat treated AgPd30/CuSn6 layers

The subject of the investigations are precipitation zones, which grew as a result of chemical diffusion in AgPd30/CuSn6 bimetals. These precipitation zones have been characterized by metallography, electron probe microanalysis and x-ray diffraction. The growth of precipitation zones in the plating layer and in the substrate layer in dependence on time have been determined. The use of x-ray diffraction alone for the identification of the precipitates could not supply satisfying results in every case. This problem was solved by the application of electron probe microanalysis using a correction method, which allows the estimation of the chemical composition of small particles.Dedicated to Professor Dr. rer. nat. Dr. h. c. Hubertus Nickel on the occasion of his 65th birthday     

Monte Carlo Simulation of Electron Transport and X-Ray Generation. II. Radiative Processes and Examples in Electron Probe Microanalysis

Theoretical models for Monte Carlo simulation of radiative processes, i.e. bremsstrahlung and characteristic x-ray emission, are presented. Possible strategies for simulating electron transport are briefly described. For mechanisms involving energy loss and angular deflections, difficulties for strict implementation of accurate numerical differential cross sections still remain due to the strong correlations between these variables. Practical solutions for the case of inelastic collisions and bremsstrahlung emission are described. Comparisons of simulation results with experimental data for several problems of interest in electron probe microanalysis are presented.     

Determination of thickness distribution and composition of thin coatings by EPMA: Application in the field of steel sheet production

A new method for the investigation of surface coatings by EPMA is presented. It is based on a physical model which takes into account the X-ray intensity depth distribution, the absorption and the electron backscattering effects at the interface between film and substrate. When combined with the concentration mapping (CM) technique, a two-dimensional film thickness distribution and the film composition can be determined simultaneously. Only bulk standards are required for this method.With some examples in the field of steel sheet production and electrogalvanizing the versatility of the method as well as its high sensitivity are pointed out. Particularly important for practical work is the applicability to almost any combinations of film and substrate materials as well as the wide thickness range from almost the total X-ray emergence depth down to the monolayer range.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Investigation of the three-dimensional microstructure of Cu-Sn(Pb) diffusion zones by means of ion beam sputtering, scanning electron microscopy and lattice source interferences

On model substances of Cu-Sn(Pb) solders it is shown by the combined use of several physical analytical methods that the intermetallic compounds formed during the annealing process have a crystalline structure, which can be observed also three-dimensionally by ion etching. Moreover, grain boundaries as well as phases become visible, and it is possible to determine the crystallographic orientation of the individual crystals in the Cu starting material and in the diffusion zones by means of the Kossel technique. As a result of the investigations, conclusions can be drawn with respect to the diffusion process, especially also to the crystallographic structure of the diffusion zones and the dendritic growth.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Coexistence of Rutile and Trirutile Phases in a Natural Tapiolite Sample

We report X-ray powder diffraction (XRD), electron probe microanalysis (EPMA), and Mössbauer spectroscopy (MS) measurements performed on a natural tapiolite with composition Fe_0.57Mn_0.37Ti_0.10Ta_1.27Nb_0.67O₆. XRD and MS suggest that besides being partially ordered the as-collected sample is a mixture of trirutile (P4₂/mnm, a=4.7532(9) Å, c=9.228(7) Å) and Nb-rich rutile (P4₂/mnm, a=4.856(2) Å, c=3.098(1) Å) structures. The Mössbauer spectra of the rutile (Fe, Mn, Ta, Nb)O₂ were fitted to Δ=1.72±0.05 mm/s and δ=1.10±0.03 mm/s at 300 K and to Δ=2.10±0.06 mm/s and δ=1.18±0.03 mm/s at 80 K. The present results suggest that cation ordering in compounds of the tapiolite series can be easily assessed by Mössbauer spectroscopy in a way similar to that as previously demonstrated for the columbite series.     

Determination of transition and rare earth elements in low-alloy steels as chelates with 4-(2-Thiazolylazo)resorcinol by reversed-phase high performance liquid chromatography

4-(2-Thiazolylazo)resorcinol (TAR) is used as a chelating reagent in the reversed-phase HPLC separation and determination of transition and rare earth elements in low-alloy steels. A precolumn derivatization method is used, followed by separation on an octadecyl-bonded silica stationary phase with a sodium octane-1-sulphonate-tartaric acid mobile phase. The eluted metal chelates are detected by uv-visible spectrophotometry. The requirements for sample preparation, characterization of precolumn derivatization and the optimum conditions for the sensitive detection of metal ions after liquid chromatography (LC) separation are discussed. The influence of the pH of the chelating medium and the eluent, the concentration of TAR and the eluent were investigated. The results are compared with those of other methods such as atomic absorption spectrometry (AAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES).     

Characterization of Ultra‐Thin Temperature‐Responsive Polymer Layer and Its Polymer Thickness Dependency on Cell Attachment/Detachment Properties

Ultra thin poly(N‐isopropylacrylamide) (PIPAAm) modified glass coverslips (PIAPAm‐CS) using electron beam irradiation exhibited a clear relationship between the polymer thickness and thermal cell adhesion/detachment behavior. The polymer thickness dependency and the characteristic of ultra thin PIPAAm layer, has been illustrated in terms of the molecular motion of the modified PIPAAm chains. PIPAAm‐CSs surfaces with various area‐polymer densities and thicknesses were characterized by AFM and protein adsorption assay. The newly obtained results gave a further insight into the illustration. Finally, the future application of intelligent surfaces was discussed for fabricating tissue and organ.

     

Effects of clay nanoparticles and electron irradiation in the crystallization rate of syndiotactic polypropylene

Several composites of a metallocene syndiotactic polypropylene with an organophilic silicate have been prepared and analyzed to investigate the effects of the nanoparticles on the crystallization of syndiotactic polypropylene. Moreover, the influence of an electron‐irradiation dose of 166 kGy on the different materials has been studied. Although the melting temperatures are practically unchanged, irradiation leads to a considerably slower crystallization rate of the syndiotactic polypropylene homopolymer in such a way that an important cold crystallization has been observed in the second melting along with a much higher value of the isothermal crystallization half‐time. On the contrary, the nanocomposites are much less sensitive to irradiation because only a small shift of the crystallization temperature has been observed, and the isothermal crystallization half‐time remains practically unaffected. However, irradiation leads to important changes in the low‐angle region of X‐ray diffractograms. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1068–1076, 2007     

Ultrastructure and microanalysis of silica bodies in Dactylis Glomerata L.

Silica bodies of orchard grass (Dactylis glomerata L.) were analysed by transmission electron microscopy and X-ray microanalysis. Silica bodies are inserted into the epidermis of the leaf and consist of a rather compact amorphous silica and low carbon. In particular regions of the interface between silica body and cell wall, silica is crossed by electron opaque strands, which are similar to filaments of the cell wall and most probably represent cellulose fibrils. The presence of a higher carbon content in this region than in the compact silica supports this notion. Cells with silicified walls or lumen were found apart from typical silica bodies. They most likely represent early or intermediate stages of silica body formation. Some epidermal cells showed silica deposits between protoplast and cell wall with small but regularly detected nitrogen and phosphorus peaks indicating a particular extracellular chemical composition probably involved in silica accumulation.     

NanoSIMS and EPMA analysis of nickel localisation in leaves of the hyperaccumulator plant Alyssum lesbiacum

Certain plants known as ‘metal hyperaccumulators’ can accumulate exceptional concentrations of elements such as zinc, manganese, nickel, cobalt, copper, selenium, cadmium or arsenic in their above ground tissue. In members of the genus Alyssum, nickel concentrations can reach values as high as 3% of leaf dry biomass. These plants must possess very effective mechanisms for the transport, chelation and sequestration of such elements within their tissues to avoid the toxic effects of free metal ions. Evidence from a number of different techniques suggests that nickel is concentrated primarily in the outermost, epidermal tissue of leaves of Alyssum hyperaccumulators, but there is currently no consensus on the principal sites of nickel sequestration. In this study, high resolution secondary ion mass spectrometry (NanoSIMS) analysis has been performed on longitudinal sections of Alyssum lesbiacum leaves. Elemental maps were obtained which revealed the high concentrations of nickel in the peripheral regions of the large unicellular stellate leaf hairs (trichomes) and in the epidermal cell layer. Electron probe microanalysis (EPMA) was used to provide independent confirmation of elemental distribution in the specimens, but the superior spatial resolution and high chemical sensitivity of the NanoSIMS technique provided a more detailed image of elemental distribution in these biological specimens at the cellular level.     

Performance of Pleurotus ostreatus Mushrooms and Spent Substrate for the Biosorption of Cd(II) From Aqueous Solution

The capacities of Pleurotus ostreatus mushroom and spent substrate were evaluated for the biosorption of cadmium (II) from aqueous solution in order to select the most efficient material for bioremediation. The optimum sorption conditions were optimized, including the pH of the aqueous solution, contact time, biomass dosage, initial metal concentration, and temperature. The sorption of cadmium on both biosorbents was also evaluated by several kinetic, equilibrium, and thermodynamic models. The possible heavy metal biosorption mechanisms were evaluated through point of zero charge (pH_pzc), Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDX). Based on the results of column studies, the effectiveness of the P. ostreatus spent substrate was confirmed as a biosorbent for Cd(II) removal from aqueous solutions.     

Kinetic Determination of Nanogram Amounts of Mo(VI) in Solution

A new inhibitory reaction is proposed and a kinteic method developed for the determination of ultra‐micro amounts of Mo(VI) on the basis of its inhibitory activity in oxidation of trimethylenediamine ‐N,N,N′,N′‐tetraacetic acid (TDTA) by KMnO₄ in the presence of hydrochloric acid. Under optimal conditions the sensitivity of the method is 0.5 ng/cm³. The probable relative error is 2.9–3.5% for the concentration range 7.5–2.0 ng/cm³ of Mo(VI). The effect of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method. The selectivity of the method is relatively good. Kinetic equations were proposed for the investigated process. A method has been applied for determination of Mo(VI) in a certain kind of steel.     

Large enhancement of the ionic conductivity in an electron‐beam‐irradiated [poly(ethylene glycol)]xLiClO4 solid polymer electrolyte

The effect of electron‐beam (4–8 MeV) irradiation on the ionic conductivity of a solid polymer electrolyte, poly(ethylene glycol) complexed with LiClO₄, was studied. A large enhancement of the conductivity of nearly two orders of magnitude was observed for the highest dose of irradiation (15 kGy) used. The samples were characterized with differential scanning calorimetry, matrix‐assisted laser desorption/ionization, and electron spin resonance spectroscopy. Although no free radicals were present in the irradiated samples, a decrease in the glass‐transition temperature and an increase in the amorphous fraction were observed. Even though pure poly(ethylene glycol) underwent considerable fragmentation, unexpectedly, no significant fragmentation was observed in the polymer–salt complexes. The enhancement of the conductivity was attributed to an increase in the amorphous fraction of the systems and also to an increase in the flexibility of the polymer chains due to the irradiation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1299–1311, 2004     

High resolution gas chromatography/mass spectrometric characterization of urinary metabolites of N,N-diethyl-m-toluamide (DEET) in man

Studies of the pharmacology and toxicology of the popular insect repellant, N,N-diethyl-m-toluamide (DEET), have largely been done in animal models using radioactive tracing without the structural elucidation of its metabolites. This paper describes a high resolution gas chromatography/mass spectrometry (GC/MS) technique and reports the results of the preliminary characterization of the metabolites of DEET in the urine of a 30-year-old man who had been exposed to DEET contained in a commercial product. The metabolites were extracted and separated with an OV-101 glass capillary column, 30 m × 0.3 mm, and mass spectrometric elucidations were carried out with both Electron Impact (EI) and Chemical Ionization-Methane (MCI) modes. Oxidation of the benzylic moiety and hydroxylation of the sidechain of DEET molecules appeared to be the predominate routes of metabolism in man. The artifacts were also proposed.     

基于扫描电子显微镜-X射线能谱的矿物自动分析系统(BPMA)测定高纯石英砂中杂质矿物

杂质矿物作为高纯石英中杂质元素主要载体之一,是高纯石英砂产品中严格限定的成分,也是影响高纯石英提纯方案的关键因素,对其组成、含量及赋存特征进行准确分析测定对高纯石英砂产品质量评价、原料选择合理性判断及提纯方案制定均有重要意义。采用基于扫描电子显微镜（SEM）和X射线能谱（EDS）的工艺矿物学参数自动分析系统（BPMA）测定了SiO2纯度≥99.998 %（4N8）的高纯石英砂中杂质矿物的组成、含量及嵌布特征,建立了高纯石英砂中杂质矿物的分析测定方法。结果表明：样品中石英的重量百分比为99.9988 %,与高纯石英砂产品质量指标对应的SiO2纯度化学分析结果基本一致;杂质矿物主要为辉石和锆石,偶见极其微量的方解石、磷钇矿、独居石和方铅矿;石英粒度均匀,主要分布在0.020～0.208 mm之间;杂质矿物嵌布粒度较细,绝大多数杂质矿物粒度在43 μm以下,主要以微细粒矿物包裹体的形式嵌布在石英颗粒内。方法简捷高效、测量结果准确可靠,适用于高纯石英砂中杂质矿物组成、含量及赋存特征分析测定,也可以为其它高纯物料中微量杂质矿物检测提供技术借鉴。     

Models for the active site in galactose oxidase: Structure, spectra and redox of copper(II) complexes of certain phenolate ligands

Galactose oxidase (GOase) is a fungal enzyme which is unusual among metalloenzymes in appearing to catalyse the two electron oxidation of primary alcohols to aldehydes and H₂O₂. The crystal structure of the enzyme reveals that the coordination geometry of mononuclear copper(II) ion is square pyramidal, with two histidine imidazoles, a tyrosinate, and either H₂O (pH 7.0) or acetate (from buffer,pH 4-5) in the equatorial sites and a tyrosinate ligand weakly bound in the axial position. This paper summarizes the results of our studies on the structure, spectral and redox properties of certain novel models for the active site of the inactive form of GOase. The monophenolato Cu(II) complexes of the type [Cu(L1)X][H(L1) = 2-(bis(pyrid-2-ylmethyl)aminomethyl)-4-nitrophenol and X⁻ = Cl⁻ 1, NCS⁻ 2, CH₃COO⁻ 3, ClO₄ ⁻ 4] reveal a distorted square pyramidal geometry around Cu(II) with an unusual axial coordination of phenolate moiety. The coordination geometry of 3 is reminiscent of the active site of GOase with an axial phenolate and equatorial CH₃COO⁻ ligands. All the present complexes exhibit several electronic and EPR spectral features which are also similar to the enzyme. Further, to establish the structural and spectroscopic consequences of the coordination of two tyrosinates in GOase enzyme, we studied the monomeric copper(II) complexes containing two phenolates and imidazole/pyridine donors as closer structural models for GOase. N,N-dimethylethylenediamine and N,N’-dimethylethylenediamine have been used as starting materials to obtain a variety of 2,4-disubstituted phenolate ligands. The X-ray crystal structures of the complexes [Cu(L5)(py)], (8) [H₂(L5) = N,N-dimethyl-N’,N’-bis(2-hydroxy-4-nitrobenzyl) ethylenediamine, py = pyridine] and [Cu(L8)(H₂O)] (11), [H₂(L8) = N,N’-dimethyl-N,N’-bis(2-hydroxy-4-nitrobenzyl)ethylenediamine] reveal distorted square pyramidal geometries around Cu(II) with the axial tertiary amine nitrogen and water coordination respectively. Interestingly, for the latter complex there are two different molecules present in the same unit cell containing the methyl groups of the ethylenediamine fragmentcis to each other in one molecule andtrans to each other in the other. The ligand field and EPR spectra of the model complexes reveal square-based geometries even in solution. The electrochemical and chemical means of generating novel radical species of the model complexes, analogous to the active form of the enzyme is presently under investigation.     

Interaction of alkali salt promoters and silicon impurities in Rochow contact masses

Cesium chloride- and rubidium chloride-promoted Rochow contact masses based on both technical-grade and highly pure silicon have been investigated in the Rochow reaction and by REM/EDX surface analysis. The alkali-salt promoters seem to act analogously to the well-known zinc promoter, by localizing the reaction to distinct reactive areas and keeping free the surface area for the reaction, probably for the formation of catalytically active Cu–Si surface species. The alkali salts exhibited their promoting action only in combination with the impurities within the technical-grade silicon. Otherwise, they acted as blocking poisons. The promoter action of alkali chlorides in contact masses based on technical-grade silicon is possibly connected with the formation of salt melts, containing alkali chlorides and impurities. These melts, analogously to zinc chloride, could dissolve oxidic impurities from the silicon surface which otherwise would enhance the blocking of potentially active surface by extensive copper deposition. © 1998 John Wiley & Sons, Ltd.