Microprobe Spectroscopy Research Articles

Comprehensive physical and electrical characterizations of NO nitrided SiO2/4H-SiC(112̄0) interfaces

Nitridation of SiO2/4H-SiC(112̄0) interfaces with post-oxidation annealing in an NO ambient (NO-POA) and its impact on the electrical properties were investigated. Sub-nm-resolution nitrogen depth profiling at the interfaces was conducted by using a scanning X-ray photoelectron spectroscopy microprobe. The results showed that nitrogen atoms were incorporated just at the interface and that interface nitridation proceeded much faster than at SiO2/SiC(0001) interfaces, resulting in a 2.3 times higher nitrogen concentration. Electrical characterizations of metal-oxide-semiconductor capacitors were conducted through capacitance–voltage (C–V) measurements in the dark and under illumination with ultraviolet light to evaluate the interface defects near the conduction and valence band edges and those causing hysteresis and shifting of the C–V curves. While all of these defects were passivated with the progress of the interface nitridation, excessive nitridation resulted in degradation of the MOS capacitors. The optimal conditions for NO-POA are discussed on the basis of these experimental findings.

Uranium retention on iron oxyhydroxides in post-mining environmental conditions

Investigating uranium migration mechanisms related to the weathering of waste rocks is essential for developing strategies that can address the potential environmental issues caused by uranium mining.This work is based on environmental samples containing 2 L ferrihydrite, lepidocrocite and goethite collected in the technosols from granitic waste rock piles, mine drainage conduits and mine waters. The results show the important role of iron oxyhydroxide in U immobilization and re-concentration.EXAFS spectroscopy combined with mineralogical and geochemical studies (Scanning electronic microscopy, Wavelength-dispersive X-ray spectroscopy microprobe, inductively coupled plasma - optical emission spectrometry/mass spectrometry and X-ray diffraction) allowed for the identification of uranyl ternary surface complexes at the ferrihydrite surface that were either composed of phosphate groups or organic matter. Moreover, goethite and lepidocrocite were also identified as a secondary trap for U immobilization. U(VI) is known to be mobile in oxidizing conditions. This study highlights the control of the uranyl mobility by various iron oxyhydroxides in supergene conditions.

Molecular speciation and transformation of soil legacy phosphorus with and without long-term phosphorus fertilization: Insights from bulk and microprobe spectroscopy

Soil legacy phosphorus (P) represents a substantial secondary P resource to postpone the global P crisis. To fully utilize this P reserve, the transformation of legacy P speciation in a black soil with and without P fertilization for 27 years was investigated by chemical fractionation, molecular-level bulk (P K-edge X-ray absorption near-edge, XANES; solution 31P nuclear magnetic resonance) and microprobe (µ-X-ray fluorescence and µ-XANES) spectroscopy. Results from both fractionation and P bulk-XANES concordantly indicated that Ca2-P [Ca(H2PO4)2] acts as a reserve of labile P in response to soils with or without P fertilization. Cropping for 27 years depleted hydroxyapatite while enriched iron-bound P in soils irrespective of P application. Similar accumulation of soil organic P (Po), probably due to root residue inputs, occurred in both soils with and without P fertilization; the accumulated Po was present as orthophosphate diesters in soils with P fertilization more than in soils without P fertilization, suggesting that the release of labile Po was triggered by soil P deficits. These results provide vital information for agronomically and environmentally sustainable P management by demonstrating the potential crop availability of legacy soil P, which could reduce future P fertilization.

“Study of secondary hydriding at high temperature in zirconium based nuclear fuel cladding tubes by coupling information from neutron radiography/tomography, electron probe micro analysis, micro elastic recoil detection analysis and laser induced breakdown spectroscopy microprobe

This paper gives an overview of a multi-scale experimental study of the secondary hydriding phenomena that can occur in nuclear fuel cladding materials exposed to steam at high temperature (HT) after having burst (loss-of-coolant accident conditions). By coupling information from several facilities, including neutron radiography/tomography, electron probe micro analysis, micro elastic recoil detection analysis and micro laser induced breakdown spectroscopy, it was possible to map quantitatively, at different scales, the distribution of oxygen and hydrogen within M5™1 clad segments having experienced ballooning and burst at HT followed by steam oxidation at 1100 and 1200 °C and final direct water quenching down to room temperature. The results were very reproducible and it was confirmed that internal oxidation and secondary hydriding at HT of a cladding after burst can lead to strong axial and azimuthal gradients of hydrogen and oxygen concentrations, reaching 3000–4000 wt ppm and 1.0–1.2 wt% respectively within the β phase layer for the investigated conditions. Consistent with thermodynamic and kinetics considerations, oxygen diffusion into the prior-β layer was enhanced in the regions highly enriched in hydrogen, where the α(O) phase layer is thinner and the prior-β layer thicker. Finally the induced post-quenching hardening of the prior-β layer was mainly related to the local oxygen enrichment. Hardening directly induced by hydrogen was much less significant.

Zinc + Nickel + Microparticles Coatings: Production Process and Structural Characterization

The properties of coatings obtained from Ni-Zn electrodeposition baths containing microparticles is analyzed. The incorporation of alumina or silicon carbide microparticles improves properties of hardness and protection of the coating. The Ni content in the alloy, which normally varies between 10 and 15%, was measured by X-ray fluorescence. ZnNi-particles coatings show a high nickel content and high corrosion resistance. The incorporation of uniformly distributed particles in the coatings is achieved under controlled conditions of current density and mechanical stirring. It was found that in the present case, 8 A/dm2 is theoptimal electrodeposition current density. Frontal coatings samples were studied by scanning electron microscope while cross sectional area by optical microscope. The surface analysis was performed by energy dispersive X-rays spectroscopy microprobe and the structural characterization by X-ray diffraction. The last technique showed that the phase (3,3,0) is reinforced after 10minutes of electrodeposition in the presence of CSi, while there is a change from ZnNi (3,3,0) to ZnNi (1,1,0) in the presence of Al2O3. This led to an increment of the compressive forces in the material. The charge transfer resistance (RTC) of the coating depended on its own thickness. High values of RTC corresponded to lower values of corrosion current J0. Experimental results showed that RTC10 microns> RTC 20 microns > RTC5 microns, indicating that the best properties of the material were obtained at 10 microns. In industrial scale process and in the laboratory, it was found that electrolyzing during 10minutes with different J is: RTC(8 A dm-2) > RTC(10 A dm-2) > RTC(6 A dm-2). Zn-Ni-CSi coatings showed a decrease in the crystal size when saccharin is added to the electrodeposition solution.

FERRO-FERRI-NYBØITE, NaNa2(Fe2+3Fe3+2)(Si7Al)O22(OH)2, A NEW CLINOAMPHIBOLE FROM MONT SAINT-HILAIRE, QUÉBEC, CANADA: DESCRIPTION AND CRYSTAL STRUCTURE

Abstract Ferro-ferri-nyboite, NaNa 2 (Fe 2+ 3 Fe 3+ 2 )(Si 7 Al)O 22 (OH) 2 , is a new mineral of the amphibole group from Poudrette quarry, Mont Saint-Hilaire, La Vallee-du-Richelieu RCM, Monteregie (formerly Rouville County), Quebec, Canada. It occurs in an igneous microbreccia associated with a eudialyte-group mineral, an astrophyllite-group mineral, albite, and nepheline. Crystals are prismatic parallel to [001] with {100} and {110} forms and cleavage surfaces, and the prism direction is terminated by irregular fractures. Grains are up to 3 cm long, and occur as blocky aggregates. Crystals are black with a greyish-green to black streak. Ferro-ferri-nyboite is brittle, has a Mohs hardness of 6 and a splintery fracture; it is non-fluorescent with perfect {110} cleavage, no observable parting, and has a calculated density of 3.424 g/cm 3 . Crystals show extreme optical absorption due to intervalence charge transfer, which inhibited measurement of optical properties. Ferro-ferri-nyboite is monoclinic, space group C 2/ m , a 9.9190(5), b 18.0885(8), c 5.3440(3) A, β 103.813(1)°, V 931.09(13) A 3 , Z = 2. The strongest ten X-ray diffraction lines in the powder pattern are [ d in A( I )( hkl )]: 8.520(100)(110), 3.162(55)(310), 2.834(24)(330), 1.671(19)(461), 2.732(10)(151), 2.552(10)( 2 ¯ 02), 2.344(9)( 3 ¯ 51), 3.298(7)(240), 2.606(6)(061), 1.446(6)( 6 ¯ 61,4.10.0). Analysis by a combination of electron microprobe and Mossbauer spectroscopy gives SiO 2 45.80, Al 2 O 3 3.11, TiO 2 0.50, Fe 2 O 3 11.18, FeO 23.45, MnO 2.28, ZnO 0.12, MgO 0.23, CaO 0.99, Na 2 O 8.01, K 2 O 1.30, F 0.81, H 2 O calc 1.47, O ≡ F−0.34 sum 98.91 wt.%. The formula unit, calculated on the basis of 24 (O + OH + F) with (OH + F) = 2 apfu is (Na 0.66 K 0.27 ) Σ0.93 (Na 1.83 Ca 0.17 ) Σ2.00 (Mg 0.06 Fe 2+ 3.15 Mn 0.31 Zn 0.01 Fe 3+ 1.38 Ti 0.06 Al 0.03 ) Σ5.00 (Si 7.35 Al 0.65 ) Σ8.00 O 22 (OH 1.58 F 0.42 ) Σ2.00 . Ferro-ferri-nyboite, ideally NaNa 2 (Fe 2+ 3 Fe 3+ 2 )(Si 7 Al)O 22 (OH) 2 , is related to endmember nyboite, NaNa 2 (Mg 3 Al 2 )(Si 7 Al)O 22 (OH) 2 by the substitutions Fe 2+ → Mg and Fe 3+ → Al.

Thermodynamics of arsenates, selenites, and sulfates in the oxidation zone of sulfide Ores: Part VII. Solubility of synthetic analogs of erythrite and annabergite at 25°C

Understanding the mechanisms of arsenic’s behavior under near-surface conditions is one of the actual problems of contemporary mineralogy and geochemistry and is important for solving environmental problems. The aim of this study is to synthesize analogs of erythrite and annabergite and to investigate their solubility in water. These phases have been synthesized by the boiling-dry of aqueous solutions of cobalt and nickel nitrates mixed with sodium hydroarsenate alkalized with NaOH. The samples obtained have been identified with electron microprobe, X-ray diffraction, and IR spectroscopy. Solubility has been determined by the isothermal saturation method in ampoules at 25°C. The solubility has been calculated using the Geochemist’s Workbench (GMB 7.0) software package. The measured solubilities of erythrite and annabergite are 10−35.76 and 10−36.43, respectively. Eh-pH diagrams were calculated and plotted using the GMB 7.0 software package. The database comprises the thermodynamic parameters of 46 elements, 47 main particles, 48 redox pairs, 552 particles in solution, 624 solid phases, and 10 gases. The Eh-pH diagrams of the Ni-As-H2O and Co-As-H2O systems were plotted for the average contents of these elements in the acidic waters in the oxidation zones of sulfide deposits. The formation of erythrite and annabergite under near-surface conditions is discussed.

Influence of Process Parameters on the Quality of Bionic Non-Smooth Coatings by Laser Cladding

The non-smooth surfaces on 45 steel were prepared by laser cladding with KF-300A alloy powder on the basis of the bionic non-smooth morphology of shark scales. The rib-type coatings were composed of hot-rolled steel 45 and clad layers containing hard phases such as WC/W2C. In this paper, the influence of laser power and defocusing distance on the quality of cladding layer were investigated. The microstructure of the coatings was analyzed by scanning electron microscopy, with attached energy dispersive spectroscopy microprobe, and by X-ray diffraction. SEM inspection of the samples showed that all coatings exhibited similar phases in their microstructure, but the phases presented differ in morphology, size and distribution. Dilution and interaction zone of the coatings were also discussed in this paper. The results showed that the non-smooth coatings were crack-free and had a good metallurgical bonding with 45 steel trenches with a low dilution under the optimum laser conditions (P=700 W, f =14 mm, V=3 mm/s, continuous powder feeding voltage 2.1 V, nitrogen protection).

Raman microprobe spectrometry of carbon/carbon composites with differently‐textured pyrolytic carbon matrices

AbstractThe microstructure of carbon/carbon composites obtained by chemical vapor infiltration of carbon‐fiber felts was studied comparatively by means of Raman spectroscopy, polarized light microscopy (PLM), scanning electron microscopy (SEM), and X‐ray diffraction. The matrices, which are homogeneously textured according to PLM, exhibit pronounced spatial structural gradients at the sub‐μm scale if investigated by means of Raman microprobe spectrometry. The Raman and SEM observations demonstrate that the high‐temperature treatment correlates with the increasing development of the graphitic ordering in low‐ and high‐textured pyrolytic carbon matrices.

Melt in the impact breccias from the Eyreville drill cores, Chesapeake Bay impact structure, USA

– The center of the 35.3 Ma Chesapeake Bay impact structure (85 km diameter) was drilled during 2005/2006 in an ICDP–USGS drilling project. The Eyreville drill cores include polymict impact breccias and associated rocks (1397–1551 m depth). Tens of melt particles from these impactites were studied by optical and electron microscopy, electron microprobe, and microRaman spectroscopy, and classified into six groups: m1—clear or brownish melt, m2—brownish melt altered to phyllosilicates, m3—colorless silica melt, m4—melt with pyroxene and plagioclase crystallites, m5—dark brown melt, and m6—melt with globular texture. These melt types have partly overlapping major element abundances, and large compositional variations due to the presence of schlieren, poorly mixed melt phases, partly digested clasts, and variable crystallization and alteration. The different melt types also vary in their abundance with depth in the drill core. Based on the chemical data, mixing calculations were performed to determine possible precursors of these melt particles. The calculations suggest that most melt types formed mainly from the thick sedimentary section of the target sequence (mainly the Potomac Formation), but an additional crystalline basement (schist/gneiss) precursor is likely for the most abundant melt types m2 and m5. Sedimentary rocks with compositions similar to those of the melt particles are present among the Eyreville core samples. Therefore, sedimentary target rocks were the main precursor of the Eyreville melt particles. However, the composition of the melt particles is not only the result of the precursor composition but also the result of changes during melting and solidification, as well as postimpact alteration, which must also be considered. The variability of the melt particle compositions reflects the variety of target rocks and indicates that there was no uniform melt source. Original heterogeneities, resulting from melting of different target rocks, may be preserved in impactites of some large impact structures that formed in volatile-rich targets, because no large melt body exists, in which homogenization would have taken place.

Formation of nitrided layers on duplex steel – influence of multiphase substrate

The present paper reports the results of gas nitriding of duplex stainless steel and study of the effect of substrate structure on the nitrided layers. The differences in the growth of the layers on austenitic and ferritic substrate were studied. The microstructure and phase composition of the layers were investigated using light microscopy analysis), X-ray diffraction (XRD and grazing angle XRD – GXRD) and electron microprobe spectrometry. Moreover, the microhardness of the layers was studied. A particular role of steel substrate in layer formation was observed at a low temperature (below 500°C) nitriding. The layers were mostly composed of the S phase and expanded martensite formed on austenite and ferrite grains respectively. The substrate influence was of minor importance at treatment temperature higher than 500°C.

Synchrotron micro-XRF study of metal inclusions distribution and variation in fused silica induced by ultraviolet laser pulses

Metal inclusions play critical roles in laser-induced damage for large fused silica optics. Here, the spatial distribution of sodium, aluminum, iron and copper in as-prepared samples is analyzed by synchrotron based X-ray fluorescence spectrometry microprobe system at the BL15U1 beam line at the Shanghai Synchrotron Radiation Facility. The as-prepared fused silica samples are induced by 355 nm laser pulses with no, or low, or high fluences. The spatial resolution of the obtained elemental maps is up to 50 μm. Analysis of the elemental maps indicates that the distribution of metals has a close association with the laser fluence and pulses. The normalized fluorescence signal attenuation for metal inclusions corresponds to the laser fluence. The decrement of metals depends chiefly upon the fluence other than pulses of the incidence laser, which is most pronounced for iron and least for copper. The decrement is evident for high fluence laser irradiation, while the amount is negligible for low fluence laser irradiation. Among the four metals, iron concentration is suggested as the most destructive factor for optics lifetime, especially under high fluence irradiation. The quasi-periodic feature of elemental distribution is partly ascribed to laser intensity modulation induced by Fresnel diffraction.

Pourous nanoparticles formation using a dendrimer template

We describe the synthesis of porous spherical nanoaggregates derived by the controlled growth of zeolite LTA on a poliamidoamine (Pamam) dendrimer acting as nano-template. The presence of a strong condensed cationic Na + charge all around the dendrimers, which is responsible for the intense electrostatic inter-particle interaction potential, stimulate the condensed growth of the zeolitic phase onto the dendrimer substrate. Moreover, the screening produced by the zeolite grown on the dendrimer surface promote the entanglement process between the primary units with the formation of large porous clusters. The main features of the self-assembly process has been characterised by means of different techniques such as Small Angle X-ray Scattering (SAXS), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Energy Dispersive X-ray (EDX) microprobe spectroscopy. The finding of our results may open new perspectives in the synthesis of organic-inorganic nanostructured materials based on mesoporous frameworks with new characteristics and properties.

Pourous nanoparticles formation using a dendrimer template

We describe the synthesis of porous spherical nanoaggregates derived by the controlled growth of zeolite LTA on a poliamidoamine (Pamam) dendrimer acting as nano-template. The presence of a strong condensed cationic Na+charge all around the dendrimers, which is responsible for the intense electrostatic inter-particle interaction potential, stimulate the condensed growth of the zeolitic phase onto the dendrimer substrate. Moreover, the screening produced by the zeolite grown on the dendrimer surface promote the entanglement process between the primary units with the formation of large porous clusters. The main features of the self-assembly process has been characterised by means of different techniques such as Small Angle X-ray Scattering (SAXS), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Energy Dispersive X-ray (EDX) microprobe spectroscopy. The finding of our results may open new perspectives in the synthesis of organic–inorganic nanostructured materials based on mesoporous frameworks with new characteristics and properties.

An Optimization of Parameters for Application of a Laser-Induced Breakdown Spectroscopy Microprobe for the Analysis of Works of Art

Laser-induced breakdown spectroscopy (LIBS) provides many advantages for analysis of works of art. Both qualitative and semi-quantitative information about the elemental composition of an object can be rapidly obtained using LIBS. The time of response is on the order of a few seconds and no sample preparation is required. The possibility of performing analysis in museums and archeological sites makes LIBS particularly important; the combination of laser ablation and analysis as encountered in LIBS provides means to effectively carry out depth profiling of samples. By combining the use of a microscope, the dimension of the spot of the laser used to carry out analysis can be reduced and the spatial resolution highly improved; in this way, a very small area of the sample (on the order of 10 miccrom) can be analyzed. The aim of this work is to investigate the best working conditions in order to obtain the least amount of material removal during analysis, and, at the same time, the best quality in the spectral response for rapid and reliable identification of the elemental composition of an object. First, investigations were undertaken using metal alloys; second, the optimized LIBS conditions were used for analysis of models of painting layers prepared in the laboratory. Finally, a painting cross-section and a 19th century painted icon were analyzed using the micro-LIBS setup.

Processing of shot-to-shot raw data to improve precision in laser-induced breakdown spectrometry microprobe

In order to set up the precision limit that can be reached with laser-induced breakdown spectrometry microprobe, a steel sample was scanned by using a 6-µm diameter spot. Besides being close to the limit of the technique, such a spot diameter resulted in a small plasma size that minimized self-absorption effects. To minimize shot noise, Cr and Fe were used as test elements because of their high contents. Scan consisted of 25 successive matrices formed by 5 × 6 shots, i.e. a total of 750 shots. Results were studied as a whole, as well as between matrices and within matrices, to search for inhomogeneity, outliers and drift. Except a few outliers, the main contribution in the experimental RSD was the drift either within a matrix or between matrices. Drift attributed to laser warm up could be compensated for either by using a polynomial fitting or by using the other element. %RSD significantly below 2 were then obtained demonstrating that there is no penalty in terms of precision to perform laser microprobe using a series of single shots.

Apatite crystal in hard tissue of conodont fossils

The present study was aimed at examining the nature of apatite crystal in the tooth apparatus of a conodont fossil using transmission electron microscopy (TEM), scanning electron microscopy (SEM), laser Raman microprobe spectrometry and electron-probe microanalysis (EPMA). The hard tissue of the condont consisted of 2 layers and the organization varied with the size of the crystal. Higher magnification showed that the crystals were observed in the lattice of (100) and the central dark lines were not present. Ca, P, and F were detected in the crystal using EPMA. Our results indicate that the apatite crystal in conodont fossils is not hydroxyapatite but fluorapatite.

Implementation of maskless laser lithography using a Raman spectroscopy microprobe

A new use of a Raman spectroscopy microprobe is described. This kind of instrument uses an intense light source, usually a laser, to obtain chemical information from the scattered light sent to the sample through a microscope objective lens. A Raman microprobe is most often equipped with a motorized stage. The coupling of a focused laser light with the possibility of moving the stage under the very same light can be used to perform maskless photolithography as a laser writer. The versatility and resolution of this application are tested and described, producing different arrays of holes on photoresist. Holes as small as 1 mum are produced, thus demonstrating a lateral resolution sufficient for several applications. As an example of application, a pattern of a human protein, fibronectin, has been produced on a gold surface, which can then be used for the study of cell adhesion.

Microchemical imaging of iodine distribution in the brown alga Laminaria digitata suggests a new mechanism for its accumulation.

Brown algal kelp species are the most efficient iodine accumulators among all living systems, with an average content of 1.0% of dry weight in Laminaria digitata. The iodine distributions in stipe and blade sections from L. digitata were investigated at tissue and subcellular levels. The quantitative tissue mapping of iodine and other trace elements (Cl, K, Ca, Fe, Zn, As and Br) was provided by the proton microprobe with spatial resolutions down to 2 mum. Chemical imaging at a subcellular resolution (below 100 nm) was performed using the secondary ion mass spectrometry microprobe. Sets of samples were prepared by both chemical fixation and cryofixation procedures. The latter prevented the diffusion and the leaching of labile inorganic iodine species, which were estimated at around 95% of the total content by neutron activation analysis. The distribution of iodine clearly shows a huge, decreasing gradient from the meristoderm to the medulla. The contents of iodine reach very high levels in the more external cell layers, up to 191 +/- 5 mg g(-1) of dry weight in stipe sections. The peripheral tissue is consequently the main storage compartment of iodine. At the subcellular level, iodine is mainly stored in the apoplasm and not in an intracellular compartment as previously proposed. This unexpected distribution may provide an abundant and accessible source of labile iodine species which can be easily remobilized for potential chemical defense and antioxidative activities. According to these imaging data, we proposed new hypotheses for the mechanism of iodine storage in L. digitata tissues.

Extracellular Proteins Limit the Dispersal of Biogenic Nanoparticles

High-spatial-resolution secondary ion microprobe spectrometry, synchrotron radiation-based Fourier-transform infrared spectroscopy, and polyacrylamide gel analysis demonstrated the intimate association of proteins with spheroidal aggregates of biogenic zinc sulfide nanocrystals, an example of extracellular biomineralization. Experiments involving synthetic zinc sulfide nanoparticles and representative amino acids indicated a driving role for cysteine in rapid nanoparticle aggregation. These findings suggest that microbially derived extracellular proteins can limit the dispersal of nanoparticulate metal-bearing phases, such as the mineral products of bioremediation, that may otherwise be transported away from their source by subsurface fluid flow.