Energy Dispersive X-ray Detector Research Articles

High capacity co-precipitated manganese oxides sorbents for oxidative mercury capture

Removal of flue gas mercury (Hg) from coal-fired power plants continues to be a challenge and the search for improved sorbents is far from over. Manganese oxides supported on zirconium dioxide (MnOx/ZrO2) prepared by a co-precipitation method, were characterised and evaluated for Hg capture. Relationships between surface area, total pore volume, particle size distribution and mercury capture have been investigated. Material with a particle size range of 75–250μm achieved the greatest Hg breakthrough. Overall, these are greater than those achieved for impregnated activated carbons with higher surface areas (585, 968 and 1014m2/g). Scanning electron microscopy and energy dispersive X-ray detection (SEM/EDAX) indicates that there is uneven dispersion of MnOx and ZrO2 in the sorbent materials, and two distinctive particle types can be identified – the more porous type, which is ‘manganese-rich’ (Mn-rich) and the more smooth with cracks type which is ‘zirconium-rich’ (Zr-rich). Agglomerations of mercury clusters were observed only on the surface of ‘Mn-rich’ particles, so the conclusion can be drawn that the rate of Hg capture on the particle surface area is dependent on manganese content and distribution.

The Effect of Surface Finish on the Scaling Behavior of Stainless Steel in Steam and Supercritical Water

The effect of surface finish on the scaling behavior of Super 304H was investigated in steam and supercritical water (SCW). The oxide scales were analyzed using scanning electron microscope with an energy dispersive X-ray detector, X-ray diffraction, and Raman spectroscopy. The results showed that surface deformation improved the oxidation resistance by promoting the preferable formation of chromia and improving the scale adhesion. In SCW, the absence of hematite may be ascribed to the low oxygen partial pressure; while the whisker growth on the sandblasted sample may have resulted from the low oxygen partial pressure and the increased chromium diffusion flux.

Diffusion of U(VI) in Opalinus Clay: Influence of temperature and humic acid

The diffusion of U(VI) (c0=1×10−6mol/L) in compacted Opalinus Clay from the Mont Terri underground laboratory, Switzerland, was studied in the absence and presence of humic acid (10mg/L) at two different temperatures (25°C, 60°C) under anaerobic conditions. As background electrolyte synthetic Opalinus Clay pore water (pH 7.6, I=0.36mol/L) was used. The diffusion-accessible porosity, ε, was determined for each Opalinus Clay bore core sample by through-diffusion experiments with tritiated water (HTO) before the U(VI) diffusion experiments were carried out. The values for the effective diffusion and distribution coefficients De and Kd obtained for U(VI) and humic acid at 25°C as well as at 60°C showed that humic acid has no significant influence on the U(VI) diffusion. The diffusion profiles of humic acid in Opalinus Clay at 25 and 60°C indicate the contributions of two different humic acid particle size fractions (<1kDa and 10–100kDa). The small-sized humic acid fraction diffused through the whole Opalinus Clay samples at both temperatures within the 3 month duration of the U(VI) diffusion experiments. At 60°C, diffusion profiles of two different U(VI) species were observed. In a separate experiment the U(VI) speciation in the source reservoir solution at 60°C was analyzed by laser-induced fluorescence spectroscopy, photon correlation spectroscopy and scanning electron microscopy with an energy dispersive X-ray detector. The two diffusion profiles could be attributed to an unknown colloidal and a known aquatic U(VI) species (Ca2UO2(CO3)3(aq)). The diffusion results showed that the interaction of U(VI) and of the large-sized humic acid colloid fraction with the clay is stronger at 60°C. An increase of Kd from 0.025±0.003m3/kg at 25°C to 0.25±0.05m3/kg for U(VI)colloidal at 60°C was determined. In addition, the value for De of U(VI) increased with increasing temperature. Using the De values at 25 and 60°C, a preliminary activation energy for the diffusion of U(VI) through Opalinus Clay of 10kJ/mol was calculated. The observed increased Kd and De values for U(VI)aqueous at 60°C compensated each other to almost equal values of the apparent diffusion coefficient Da at 25 and 60°C. Hence, an elevated temperature of 60°C does not impact the migration of U(VI) through OPA significantly.

AgSb(SxSe1−x)2 thin films for solar cell applications

Silver antimony sulfoselenide (AgSb(SxSe1−x)2) thin films were prepared by heating glass/Sb2S3/Ag layers after selenization using sodium selenosulphate solution. First, Sb2S3 thin films were deposited on glass substrates from a chemical bath containing SbCl3 and Na2S2O3. Then Ag thin films were thermally evaporated onto glass/Sb2S3, followed by selenization by dipping in an acidic solution of Na2SeSO3. The duration of selenium dipping was varied as 30min and 2h. The heating condition was at 350°C for 1h in vacuum. Analysis of X-ray diffraction pattern of the thin films formed after heating showed the formation of AgSb(SxSe1−x)2. Morphology and elemental analysis were done by scanning electron microscopy and energy dispersive X-ray detection. Depth profile of composition of the thin films was performed by X-ray Photoelectron Spectroscopy. The spectral study showed the presence of Ag, Sb, S, and Se, and the corresponding binding energy analysis confirmed the formation of AgSb(SxSe1−x)2. Photovoltaic structures (PV) were prepared using AgSb(SxSe1−x)2 thin films as absorber and CdS thin films as window layers on FTO coated glass substrates. The PV structures were heated at 60–80°C in air for 1h to improve ohmic contact. Analysis of J–V characteristics of the PV structures showed Voc from 230 to 490mV and Jsc 0.28 to 5.70mA/cm2, under illumination of AM1.5 radiation using a solar simulator.

Synthesis and Activity of Ag-Doped Bi&lt;sub&gt;2&lt;/sub&gt;WO&lt;sub&gt;6&lt;/sub&gt; Photocatalysts

Ag-doped Bi2WO6 photocatalysts were synthesized by hydrothermal method using from Bi (NO)3·5H2O, NH4VO3, and AgNO3 and further characterized by X-ray diffraction, Scanning electron microscopy, Energy dispersive X-ray detector (EDS) and UV-Vis diffusion reflectance spectra techniques. The photocatalytic activity of Ag-doped Bi2WO6 photocatalysts was evaluated by degrading RhB (10 mg/L) under visible light irradiation (λ &gt; 420 nm). The results showed that in comparison with pure Bi2WO6 the photocatalytic activity of Ag-doped composite photocatalysts was improved significantly, and the degradation rate of RhB was increased about 26% when the Ag+ dopant concentration was 15%.

Performance of μ-XRF with SEM/EDS for trace analysis on the example of RoHS relevant elements – measurement, optimisation and prediction of the detection limits

For ten years μ-XRF (micro-focus X-ray fluorescence) analysis has been performed with SEM/EDS (scanning electron microscope with an energy dispersive X-ray detector) so that non-destructive analysis of elements at trace level concentrations below 100 μg g−1 becomes possible. This can be considered as a valuable completion of the classical electron probe microanalysis by EDS, an analytical method “suffering” from rather poor limits of detection in the range of one to two orders of magnitude higher than those of μ-XRF. Based on a representative actual application, namely analysis of RoHS relevant elements at trace concentration levels, the performance of the rather new analytical method with respect to its limits of detection is systematically evaluated. CRMs (certified reference materials) specially prepared to support the quantitative XRF analysis of RoHS relevant elements were employed. On the other side, based on calculations of μ-XRF spectra according to a recently developed physical model the optimization of the analytical performance is also successfully undertaken.

Mineral behavior of low-temperature lignite ashes under gasification atmosphere

To investigate the mineral behavior of lignite ashes under gasification conditions, 450 °C Xiaolongtan lignite ash samples (XLT-LTA) treated at different temperatures or pressures under reducing atmosphere (H2/CO2=1: 1, volume ratio) have been examined by means of an SC-444 apparatus, a scanning electron microscope with an energy dispersive X-ray detector (SEM-EDX), and by X-ray diffraction (XRD). The results showed the sulfur content in the XLT-LTA to be much higher than that in ashes prepared at 815 °C, as a result of the release of sulfur dioxide during the oxidization of pyrite. With increasing temperature, the XLT-LTA particles gradually agglomerate and form partially molten surface entities with obvious apertures, and the content of iron and calcium in the congeries or molten parts increases due to the fusion of fine ash particles with the enrichment of iron and the formation of low-temperature eutectics of calcium and iron. An increase of pressure restrains the decomposition of calcite and muscovite, and promotes the formation of iron minerals (e.g., hercynite, cordierite, and sekaninaite) and orthoclase. The content of amorphous material also increases with increasing pressure.

INVESTIGATION OF THE INHIBITIVE EFFECT OF OCTANESULFONIC ACID-ZINC ION SYSTEM ON CORROSION OF CARBON STEEL

Inhibition of corrosion of carbon steel in dam water by octanesulfonic acid as its sodium salt (SOS) in the absence and presence of a bivalent cation zinc ion (Zn2+) has been investigated using weight loss, potentiodynamic polarization, AC impedance spectra, Fourier transform-infrared spectroscopy (FT-IR), fluorescence spectra, scanning electron microscopy (SEM), and energy dispersive X-ray detection (EDAX) measurements. The formulation consisting of 250 ppm of SOS and 30 ppm of Zn2+ offers 88% inhibition efficiency (IE) to carbon steel. The influence of sodium potassium tartrate on the IE of the SOS-Zn2+ system has been evaluated. Polarization study reveals that SOS-Zn2+ system controls the anodic reaction predominantly. AC impedance spectra reveal that a protective film is formed on the metal surface. The nature of the protective film formed on the metal surface has been analyzed by FT-IR spectra, SEM, and EDAX analysis.

Lead isotopic analysis within a multiproxy approach to trace pottery sources. The example of White Slip II sherds from Late Bronze Age sites in Cyprus and Syria

Lead isotope analyses were carried out on fragments of White Slip II ware, a Late Bronze Age Cypriote pottery ware, and on raw materials possibly used for their production. Sherds originate from three Late Bronze Age sites (Hala Sultan Tekke and Sanidha in Cyprus and Minet el-Beida in Syria) and clays come from the surroundings of Sanidha, a production site for White Slip ware. X-ray fluorescence (XRF) and a Principal Component Analysis (PCA) are combined with Pb isotope analyses to further investigate the effectiveness of the latter method within a multiproxy approach for pottery provenance study. The pottery sherds from the three sites are compared between themselves and with potential raw material. Additional X-ray diffraction (XRD) and analyses using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray detection (EDX) facility were performed on selected sherds and clays. This work confirms that the clay source used for pottery production in Sanidha derives from local weathered gabbro. It also shows that different origins can be proposed for White Slip II ware sherds from Hala Sultan Tekke and Minet el-Beida and that clays were prepared prior to White Slip II ware production. It finally confirms the effectiveness of Pb isotopes in tracing pottery provenance not only by comparing sherd assemblages but also by comparing sherds to potential raw materials.

Preparation and evaluation of Fe-loaded activated carbon for enrichment of selenium for analytical and environmental purposes

The adsorbent, based on the thermal modification of activated carbon impregnated by iron(III) nitrate(V), has been prepared and applied for selenium enrichment from aqueous solution. Various ratios of the impregnating agent to carbon mass were carefully examined with respect to selenium adsorption capacity and selectivity. The basic Se(VI) ions adsorption parameters affecting the adsorption ability onto the prepared activated carbons were studied. The carbon impregnated by 10% Fe(NO3)2 and thermally treated at 200°C possessed the highest adsorption capacity and selectivity towards selenium ions. The physico-chemical characterization of the prepared adsorbents before and after selenium uptake were carried out using scanning electron microscopy (SEM) equipped with an energy dispersive X-ray detector (EDX) and X-ray photoelectron spectroscopy (XPS). The studies confirmed the surface complexation reactions of iron species and selenium on the Fe-loaded activated carbon. Due to its high adsorption capacity enrichment of selenium on the studied adsorbent has been successfully applied for its determination in the complementary feeds, using the carbon slurry sampling graphite furnace atomic absorption spectrometry technique (GFAAS) and standard calibration method.

Distribution of grafted β-cyclodextrin in porous particles for bone tissue engineering

The spatial distribution of β-cyclodextrin grafted to a range of porous materials was investigated. (3-glycidyloxypropyl)trimethoxysilane was used to facilitate the covalent grafting of β-cyclodextrin. The spatial distribution was analysed by combining results from confocal laser scanning microscopy and electron microscopy fitted with a focused ion beam and an energy-dispersive X-ray detector. Three materials were analysed: Two types of silica gel and one calcium phosphate. The results show that by combining the two methods it is possible to deduce the spatial distribution of the grafted cyclodextrins. Silica gel with small pores could be grafted to a depth of approximately 10μm, whereas calcium phosphate with larger pores indicated a penetration depth larger than 30μm.

Is Scanning Electron Microscopy/Energy Dispersive X‐ray Spectrometry (SEM/EDS) Quantitative?

Scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) is a widely applied elemental microanalysis method capable of identifying and quantifying all elements in the periodic table except H, He, and Li. By following the "k-ratio" (unknown/standard) measurement protocol development for electron-excited wavelength dispersive spectrometry (WDS), SEM/EDS can achieve accuracy and precision equivalent to WDS and at substantially lower electron dose, even when severe X-ray peak overlaps occur, provided sufficient counts are recorded. Achieving this level of performance is now much more practical with the advent of the high-throughput silicon drift detector energy dispersive X-ray spectrometer (SDD-EDS). However, three measurement issues continue to diminish the impact of SEM/EDS: (1) In the qualitative analysis (i.e., element identification) that must precede quantitative analysis, at least some current and many legacy software systems are vulnerable to occasional misidentification of major constituent peaks, with the frequency of misidentifications rising significantly for minor and trace constituents. (2) The use of standardless analysis, which is subject to much broader systematic errors, leads to quantitative results that, while useful, do not have sufficient accuracy to solve critical problems, e.g. determining the formula of a compound. (3) EDS spectrometers have such a large volume of acceptance that apparently credible spectra can be obtained from specimens with complex topography that introduce uncontrolled geometric factors that modify X-ray generation and propagation, resulting in very large systematic errors, often a factor of ten or more.

Confocal micro-x-ray fluorescence spectrometer for light element analysis

An existing micro-x-ray fluorescence (micro-XRF) spectrometer designed for light element analysis (6 ≤ Z ≤ 14) has been extended to confocal geometry: a second polycapillary x-ray optic has been introduced in front of the energy dispersive x-ray detector. New piezo positioners for optimum alignment of both optics have been installed inside the vacuum chamber. The spectrometer offers now the possibility of true 3D elemental analysis in the micrometer regime. Depth resolution varies between 100 μm at 1 keV fluorescence energy (Na-Kα) and 30 μm for 17.5 keV (Mo). To further extend analytical capabilities a second x-ray tube with a Rh anode has been acquired to supplement to existing Mo anode tube. Lower limits of detection have been determined to be in the ppm region for confocal geometry. The spectrometer has been characterized and tested using different samples. Furthermore, results have been compared with SR micro-XRF to show the capabilities and limitations of this spectrometer.

Ag–TiO2 nanocomposites with improved photocatalytic properties prepared by a low temperature process in polyethylene glycol

TiO2 nanotube–nanoparticle mixture was prepared by a rapid anodization process in a perchlorate containing electrolyte followed by an ultrasonic process. Ag–TiO2 nanocomposites were prepared at low temperature in polyethylene glycol (PEG600) solution, in which PEG600 was employed as the stabilizing agent as well as the reducer which can reduce Ag+ on the surface of prepared TiO2 nanocrystals. The synthesized samples were characterized by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray detector, X-ray photoelectron spectroscopy and UV–vis absorption spectroscopy. Results showed that well dispersed Ag nanoparticles with a typical size of 5–10nm can be synthesized on the surface of TiO2 nanocrystals assisted by the PEG600. To investigate the photocatalytic activity of the samples, TiO2 powders with different Ag contents were prepared and employed to decompound methyl orange under UV-light irradiation. Compared with pure TiO2 nanocrystals and commercial P25, a great improvement of photocatalytic performance was found for the Ag–TiO2 nanocomposites. It is believed that the excellent photocatalytic properties of the samples prepared in our experiment mainly result from promoted separation of photogenerated electron-hole pairs and higher reductive power due to the formed heterostructure between TiO2 and Ag as well as the advanced absorption of light due to surface plasmon effect of Ag nanoparticles.

Superhydrophobic Sol-Gel Films Based on Copper Wafer and its Anti-Corrosive Properties

Superhydrophobic copper wafer was prepared using a sol-gel deposition method in the paper. The best superhydrophobic film was prepared with vinyltrimethoxysilane (VTES), ethanol (EtOH), water (H2O) and ammonium hydroxide (NH4OH) at a molar ratio of 1:62.79:8.58:1.49 respectively. The morphologies, chemical compositions and hydrophobicity of the substrates were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray detector (EDX) and water contact angle measurement (CA). The surface morphological study showed that “lotus like structure” silica particles distributed on the copper substrate. The coatings showed the CA as high as 157.8°. The durability properties revealed that the coatings had a good superhydrophobicity deposited in 3.5 wt % sodium chloride solution for up to 14 days.

Effects of pretreatment on MlNi4.00Co0.45Mn0.38Al0.3 hydrogen storage alloy powders and the performance of 6 Ah prismatic traction battery

This paper investigates the effects of pretreatment of the MlNi4.00Co0.45Mn0.38Al0.3 (Ml: Lanthanum rich misch metal) alloy powders in 12 M NaOH solutions with 0.05 M NaBH4 at 110 °C for 3 h and the performance of 6 Ah prismatic traction battery. The alloy powders are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy with energy dispersive X-ray detector, inductively coupled plasma-atomic emission spectroscopy, laser particle size analyzer and BET chemisorptions analyzer. The electrochemical performance of the battery was effectively improved by the pretreatment of alloy powders with a NaOH/NaBH4 solution. It is found that the discharge efficiencies at 30C at room temperature and at 3C at −20 °C are increased from 5.6% to 88.1% and from 3.7% to 83.7%, respectively. The cycle lifetime at 3C of SOC of 80% is increased from 2200 to 4424. The enhanced performance is attributable to the change of the surface structure and properties of alloy powders by pretreatment.

CdS1−yTey thin films: Production and bandgap investigation

In CdS/CdTe solar cells it is necessary to determine the efficiency limitations related with the intermixing at the interface between the CdS window layer and CdTe absorber layer. So understanding the properties of the solid solution (CdSxTe1−x on the CdTe side which is CdTe rich and CdS1−yTey on the CdS side which is CdS rich) that is always formed in this region is essential. We produced thin films of CdS1−yTey solid solution-which is CdS rich – by first producing CdS:In thin films on glass substrates by the spray pyrolysis technique and then annealing the films in nitrogen atmosphere at 400°C in the presence of Te vapor. We are the first who produce this solid solution by this simple and low cost method. The composition and morphology of the films were determined by energy dispersive X-ray detection (EDAX) measurements and scanning electron microscopy (SEM) observations respectively. Eight values of y in the range 0⩽y⩽0.2845 were obtained. The transmittance was measured and used to investigate the optical bandgap energy by using the second derivative of the absorbance. It is found that the films show a single hexagonal phase for y⩽0.0852 and then a mixed (hexagonal and cubic) phase for 0.0997⩽y⩽0.2845. Bandgap energies in the range 2.259⩽Eg⩽2.528eV were obtained. Urbach tailing in the bandgap was also investigated.

Method to improve corrosion resistance of AA 5083 by cerium based conversion coating and anodic polarisation in molybdate solution

The corrosion resistance of aluminium alloys can be improved by the formation of chemical conversion coatings. Usually, chromate pretreatment processes are used. However, because of their high toxicity, alternative methods have been studied in the last years. In the present paper, a process to improve the corrosion resistance of AA 5083 was investigated. The main process consisted of serial immersion in two solutions containing two different cerium salts, followed by a further step involving anodisation in Na2MoO4. The corrosion resistance was investigated by potentiodynamic anodic polarisation tests and electrochemical impedance spectroscopy. The morphology and composition of the oxide layers were characterised by scanning electronic microscopy equipped with an energy dispersive X-ray detector. Serial treatment in the two solutions with different cerium salts and H2O2 produced a more uniform and thicker layer with a larger amount of deposits above the alloy cathodic areas than the single two treatments. In this way, the alloy corrosion resistance in chloride environments was improved and decreased the anodic reaction rate. When anodisation in molybdate salts was added, even better results were found. The corrosion resistance was higher due to a thicker and less conductive passive layer.

LaF3 surface-modified LiCr0.05Mn1.95O4 cathode material with improved high-temperature performances for lithium-ion batteries

The LaF3 surface-modified LiCr0.05Mn1.95O4 samples were synthesized by co-precipitation method and characterized by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray detector (EDX). HAADF-STEM and EDX observations showed that LaF3 deposited on the surface of LiCr0.05Mn1.95O4 particles. When tested as the cathode materials for lithium-ion battery, the LaF3-modified LiCr0.05Mn1.95O4 exhibited significantly improved cyclic and rate performances at high temperature (55 °C). Electrochemical impedance spectrum analyses demonstrated that the surface of LiCr0.05Mn1.95O4 modified by LaF3 was much more stable during the electrochemical process and could greatly facilitate the charge–transfer reaction, which may be attributed to the protection of active material by LaF3 from the HF attack.

Asphaltene Erosion Process in Air Plasma: Emission Spectroscopy and Surface Analysis for Air-Plasma Reactions

Optical emission spectroscopy (OES) was applied for plasma characterization during the erosion of asphaltene substrates. An amount of 100 mg of asphaltene was carefully applied to an electrode and exposed to air-plasma glow discharge at a pressure of 1.0 Torr. The plasma was generated in a stainless steel discharge chamber by an ac generator at a frequency of 60 Hz, output power of 50 W and a gas flow rate of 1.8 L/min. The electron temperature and ion density were estimated to be 2.15±0.11 eV and (1.24±0.05) × 1016 m-3, respectively, using a double Langmuir probe. OES was employed to observe the emission from the asphaltene exposed to air plasma. Both molecular band emission from N2, N+2, OH, CH, NH, O2 as well as CN, and atomic light emission from V and Hγ were observed and used to monitor the evolution of asphaltene erosion. The asphaltene erosion was analyzed with the aid of a scanning electron microscope (SEM) equipped with an energy dispersive X-ray (EDX) detector. The EDX analysis showed that the time evolution of elements C, O, S and V were similar; and the chemical composition of the exposed asphaltenes remained constant. Particle size evolution was measured, showing a maximum size of 2307 μm after 60 min. This behavior is most likely related to particle agglomeration as a function of time.