Quantitative Microprobe Analysis Research Articles

Spatial and temporal constraints of leached Cu-Au porphyry shoulder high-sulfidation epithermal deposit: insight from new discovered Kumbokarno Prospect, Trenggalek District, East Java

We conduct microscopic and microprobe quantitative analyses to confine characteristics of the newly found Cu-Au high sulfidation deposit which interestingly seems to highly associate with the presence of iron oxide-hydroxide complex. The resulting paragenesis shows four generation phases, which are magmatic, deep hypogene, shallow hypogene, and supergene. The alteration pattern suggests presence of a concealed intrusion which ascends the hypogene mineralization forming-fluid. Quantitative microprobe analysis shows enrichment of copper and gold in various types of iron oxide-hydroxide texture. A unique repetitive pattern of high and low copper concentration is found overlaps with goethite-hematite band of colloform texture. An interesting pattern between gold and titanium is also found as gold is almost exclusively located inside or near Fe-rich leucoxene. We propose a model of leached Cu-Au porphyry shoulder high-sulfidation epithermal deposit system to explain the prevalent condition of Kumbokarno Prospect where intensive late oxidation acts as the main process of metal concentration.

The Study of Conditions for the Silicon Carbide Crystals Formation in the Complex Composition Metal Melt

The results of thermodynamic modeling and experimental studies are presented in this article. The aim of this work is to determine the conditions of silicon carbide crystals synthesis in the complex composition metal melts. The "FactSage" software was used for thermodynamic modeling. The phase diagrams, in the form of liquidus surfaces, allow determining the metal composition with minimum melting temperature and presenting the ranges of concentrations and temperatures for which the equilibrium product of the interaction between the components of the metal melt is silicon carbide. The results of experimental research confirmed the possibility of growing silicon carbide crystals in the complex metal melts at low temperatures. The results of the obtained sample of complex alloy examination (conducted with the scanning electron microscope JEOL JSM–6460LV with a energy dispersion spectrometer by "Oxford Instruments" used for performing qualitative and quantitative microprobe analysis) helped to reveal the crystals corresponding to SiC composition.

Refinement of the composition and structure of YBaCo4−x Al x O7+δ crystals

YBa(Co4 − x Al x )O7 + δ (114Y) crystals have been grown in the Y-Ba-Co-O system by spontaneous crystallization from a slowly cooled nonstoichiometric melt. To change the oxygen content, the crystals were isothermally annealed in air in the range of 280–490°C. The crystals grown were characterized by scanning electron microscopy and powder X-ray diffraction. According to the data of an X-ray spectroscopic quantitative microprobe analysis, the average compositions of “as-grown” and oxygen-saturated crystals were Y1.04Ba1Co3.54Al0.50O7.8 and Y1.02Ba1Co3.55Al0.51O8.4, respectively. The refinement of the crystal structure after saturation on an automatic Bruker X8APEX diffractometer with a CCD detector (MoKα radiation, graphite monochromator, θmax = 32.54°, sp. gr. P63 mc, a = 6.2746(9), c = 10.257(3) A, V = 349.71(13) A3, Z = 2, d calcd = 5.220 g/cm3) reveals the location of Al in two independent positions of Co atoms and yields the general formula of the compound as YBaCo3.26Al0.74O7. Problems related to the difference in the compositions obtained by different methods are discussed.

Mineral Preservatives in the Wood of Stradivari and Guarneri

Following the futile efforts of generations to reach the high standard of excellence achieved by the luthiers in Cremona, Italy, by variations of design and plate tuning, current interest is being focused on differences in material properties. The long-standing question whether the wood of Stradivari and Guarneri were treated with wood preservative materials could be answered only by the examination of wood specimens from the precious antique instruments. In a recent communication (Nature, 2006), we reported about the degradation of the wood polymers in instruments of Stradivari and Guarneri, which could be explained only by chemical manipulations, possibly by preservatives. The aim of the current work was to identify the minerals from the small samples of the maple wood which were available to us from the antique instruments. The ashes of wood from one violin and one cello by Stradivari, two violins by Guarneri, one viola by H. Jay, one violin by Gand-Bernardel were analyzed and compared with a variety of commercial tone woods. The methods of analysis were the following: back-scattered electron imaging, X-ray fluorescence maps for individual elements, wave-length dispersive spectroscopy, energy dispersive X-ray spectroscopy and quantitative microprobe analysis. All four Cremonese instruments showed the unmistakable signs of chemical treatments in the form of chemicals which are not present in natural woods, such as BaSO4, CaF2, borate, and ZrSiO4. In addition to these, there were also changes in the common wood minerals. Statistical evaluation of 12 minerals by discriminant analysis revealed: a. a difference among all four Cremona instruments, b. the difference of the Cremonese instruments from the French and English antiques, and c. only the Cremonese instruments differed from all commercial woods. These findings may provide the answer why all attempts to recreate the Stradivarius from natural wood have failed. There are many obvious implications with regard to how the green tone wood should be treated, which chould lead to changes in the practice of violin-making. This research should inspire others to analyze more antique violins for their chemical contents.

Thermoelectric and structural properties of a new Chevrel phase: Ti 0.3Mo 5RuSe 8

The new Chevrel phase Ti 0.3Mo 5RuSe 8 has been synthesized and characterized by quantitative microprobe analysis, powder X-ray diffraction, and high-temperature thermoelectric properties measurements. The thermoelectric properties of this compound are compared to the previously reported data for other related Chevrel phases. We report also the results of Rietveld analysis of powder X-ray diffraction data for Ti 0.3Mo 5RuSe 8. This compound adopts the rhombohedral Chevrel phase structure (space group R 3 ¯ , Z=3) with hexagonal lattice constants a=9.75430(25) Å and c=10.79064(40) Å. The low level of incorporation and low scattering power of Ti precluded the identification of the Ti positions, and Rietveld refinement was carried out only for the Mo 5RuSe 8 framework of Ti 0.3Mo 5RuSe 8 ( R p=10.5%, R wp=14.6%). Rietveld analysis was also used to refine the structure of the unfilled phase Mo 5RuSe 8 ( R 3 ¯ , Z=3, a=9.63994(8) Å, c=10.97191(11) Å, R p=8.0%, R wp=10.5%). Comparisons between the two structures are made.

Electron-Probe Microanalysis: Some Revelations in the Investigation of Defects in Steel Products

The unique imaging and microanalytical capability of the electron-probe microanalyser (EPMA) has been exploited in conjunction with light microscopy for exploring the genesis of some defects, which are detrimental to steel product quality. Investigations of surface and internal defects have revealed that defects in the finished steel product are often inherited at upstream stages and accentuated in the later stages of steel processing. While the occurrence of surface defects such as “slivers” in hot-rolled sheets and “linear cracks” in hot-rolled rounds has been largely attributed to subsurface non-metallic inclusions and slag/casting powder entrapment, microprobe analysis of internal defects such as “centre-line cracking” of thick plates have revealed the deleterious role of C and Mn macrosegration inherited during the continuous casting of steel slabs. The paper elucidates some of these findings, as unravelled by both qualitative and quantitative microprobe analysis.

Interaction of Silicate Melts with Hematite

The interaction of sintered hematite Fe2O3 with melts in the PbO–SiO2 system at 900°C and melts in the Na2O–SiO2 system at 1150°C is investigated by the annealing–quenching technique with the use of standard physicochemical methods (X-ray powder diffraction analysis, scanning electron microscopy, quantitative X-ray microprobe analysis). The melting diagrams of the PbO–Fe2O3–SiO2 and Na2O–Fe2O3–SiO2 systems are calculated and constructed on the basis of the model of regular solutions. An analysis of the experimental and calculated data demonstrates that the diffusion dissolution of hematite at the “hematite–melt” heterogeneous interface can be observed only for the PbO melt. For lead and sodium silicate melts, the diffusion process is accompanied by the concurrent redox reaction with the liberation of gaseous oxygen, which appreciably promotes the erosion of solid hematite.

Characterization of amphibole fibres linked to mesothelioma in the area of Biancavilla, Eastern Sicily, Italy

AbstractAn epidemiological and environmental study of the area around Biancavilla (CT, Italy) was prompted by a significant incidence of malignant pleural mesothelioma, which was not related to a specific occupational activity. An environmental dispersion of fibres was found and attributed to local quarry activities, whose extracted volcanic products also contained fibrous amphiboles and had been used extensively in the local building industry, especially in the period 1960–1970.Abundant yellowish and grey-whitish asbestiform amphiboles with strongly asymmetric morphology were identified in this study, intimately associated with albitic feldspar, hematite and very minor orthopyroxene. These minerals fill the pores of the altered volcanic host rock (metasomatized benmoreitic lavas and pyroclastic rocks). The Rietveld method allowed a quantitative mineralogical analysis of the mineral mixture (24% amphiboles-asbestos, 73% feldspar and 3% hematite).The crystal size and morphology of the grey-whitish amphibole fibres do not allow quantitative microprobe analyses; semi-quantitative EDS-SEM analyses of a prismatic mineral known to be fluoroedenite and the unknown fibrous crystals studied here suggest that they are the same mineral, although the fibres are generally depleted in Ca and Mg. The F content is the same in both occurrences. Unitcell parameters of the fibres are: a = 9.815(1), b = 17.992(3), c = 5.2733(6) Å , β = 104.547(9)º, V = 901.4(3)Å3, and the refractive indices are in the range 1.60 –1.63. Optical, chemical and Rietveld analyses of the fibres confirm their similarity with the yellow prismatic fluoro-edenite previously analysed.Biancavilla is the first occurrence of amphibole fibres in a volcanic context (the Etnean volcanic complex). These fibres have a very anomalous composition (high ANa, IVAl and O3F contents) in comparison to other known oncogenic minerals.

Effect of Nb and Ti additions on microstructure, and identification of precipitates in stabilized Ni-Cr cast austenitic steels

Microstructures of three austenitic 30%Ni/18%Cr cast steels with additions of Nb and Ti, in the as-cast and annealed (900 °C for 300 h) state have been studied. The additions of Nb and Ti were as follows (wt.%): 1% Ti (no Nb), 1.71% Nb, (no Ti) and 0.83% Ti and 1.75% Nb, respectively. Microstructural analyses were carried out using scanning microscopy, X-ray diffraction and quantitative microprobe analysis. Depending on chemical composition, the following phases have been identified: NbC, TiC, (Ti,Nb)C, M 23C 6, and Ni- and Si-rich phases (probably G phase). The presence of the Ni–Si-rich phases, found subsequent to the annealing process, appears to be closely associated with the presence of unstable carbide precipitates. Although additions of Ti and/or Nb improved the microstructure, mechanical properties of such modified alloys at temperatures of 20 and 900 °C were markedly lower in comparison to these modified separately by either of these two elements.

Minimizing Errors in Electron Microprobe Analysis

Back in the sixties our ability to do both qualitative and quantitative microprobe analysis was often restricted by many factors we now take for granted. Limitations of power supplies, electron optical systems and the mechanical aspects of specimen stages and crystal spectrometers often led to unacceptable drift in both beam position and x-ray intensity measurements. Detector electronics were relatively primitive and phenomena such as pulse distribution shifts with count rate could cause serious errors when pulse height analysis was incorrectly used for noise reduction. The ZAF method, the principal approach for quantitative analysis, was undergoing frequent modification to make it applicable to a broader range of specimens. There were also continuing disputes about which equations to use for a given situation and what experimentally determined constants worked best in the models. Data logging and specimen stage and spectrometer automation were in their infancy and data processing was done on calculators or in batch mode on central computers. Opportunities for errors in data entry abounded.

PETROMAP: MS-DOS software package for quantitative processing of X-ray maps of zoned minerals

This paper shows an application of energy dispersive spectrometry (EDS) for digital acquisition of multi-element X-ray compositional maps of minerals in polished thin sections. A square matrix of n EDS spectra with known X, Y coordinates is collected, converted and exported to a personal computer. Each spectrum of the matrix is processed and the apparent concentration of each analyzed element is calculated by means of PETROMAP, a program written in Quick-Basic which applies a quantitative ZAF/FLS correction. The results of processing are comparable to the conventional quantitative microprobe analyses, with similar counting statistics. The output is a numerical matrix, compatible with the most popular graphic and spreadsheet programs from which it is possible to produce two-dimensional wt% oxide, mole fractions and mineral end-members pseudocolored or black/white maps. The procedure has been tested using a metamorphic garnet of the medium-grade Stilo unit (Calabrian Arc, Southern Italy).

Beryllium–copper reactivity in an ITER joining environment

Beryllium–copper reactivity was studied using test parameters being considered for use in the ITER reactor. In this application, beryllium–copper tiles are produced using a low-temperature copper–copper diffusion bonding technique. Beryllium is joined to copper by first plating the beryllium with copper followed by diffusion bonding the electrodeposited (ED) copper to a wrought copper alloy (CuNiBe) at 450°C, 1–3 h using a hot isostatic press (HIP). In this bonded assembly, beryllium is the armor material and the CuNiBe alloy is the heat sink material. Interface temperatures in service are not expected to exceed 350°C. For this study, an ED copper–beryllium interface was subjected to diffusion bonding temperatures and times to study the reaction products. Beryllium–copper assemblies were subjected to 350, 450 and 550°C for times up to 200 h. Both BeCu and Be 2Cu intermetallic phases were detected using scanning electron microscopy and quantitative microprobe analysis. Growth rates were determined experimentally for each phase and activation energies for formation were calculated. The activation energies were 66 mol and 62 kJ mol −1 for the BeCu and Be 2Cu, respectively. Tensile bars were produced from assemblies consisting of coated beryllium (both sides) sandwiched between two blocks of Hycon-3. Tensile tests were conducted to evaluate the influence of these intermetallics on the bond strength. Failure occurred at the beryllium–copper interface at fracture strengths greater than 300 MPa for the room-temperature tests. At 300°C, the fracture strength was decreased significantly and, in contrast to the room-temperature tests, the fracture initiated in the copper–copper bond. The change in fracture initiation is attributed to a decrease in the residual stresses at the beryllium–copper interface at the higher temperatures and a decrease in the intrinsic fracture strength of the ED copper.

Grain boundary diffusion in enstatite

We have investigated grain boundary diffusion rates in enstatite by heating single crystals of quartz packed in powdered San Carlos olivine (Mg0.90Fe0.10)2SiO4 at controlled oxygen fugacities in the range 10−5.7 to 10−8.7 atm and temperatures from 1350° to 1450 °C for times from 5 to 100 h at 1 atm total pressure. Following the experiments, the thickness of the coherent polycrystalline reaction rim of pyroxene that had formed between the quartz and olivine was measured using backscatter scanning imaging in the electron microprobe. Quantitative microprobe analysis indicated that the composition of this reaction phase is (Mg0.92Fe0.08)2Si2O6. The rate of growth of the pyroxene increases with increasing temperature, is independent of the oxygen fugacity, and is consistent with a parabolic rate law, indicating that the growth rate is controlled by ionic diffusion through the pyroxene rim. Microstructural observations and platinum marker experiments suggest that the reaction phase is formed at the olivine-pyroxene interface, and is therefore controlled by the diffusion of silicon and oxygen. The parabolic rate constants determined from the experiments were analyzed in terms of the oxide activity gradient across the rim to yield mean effective diffusivities for the rate-limiting ionic species, assuming bulk transport through the pyroxene layer. These effective diffusivities are faster than the lattice diffusivities for the slowest species (silicon) calculated from creep experiments, but slower than measured lattice diffusivities for oxygen in enstatite. Thus, silicon grain boundary diffusion is most likely to be the rate-limiting process in the growth of the pyroxene rims. Also, as oxygen transport through the pyroxene rims must be faster than silicon transport, diffusion of oxygen along the grain boundaries must be faster than through the lattice. The grain boundary diffusivity for silicon in orthopyroxenite is then given by D¯gbSiδ=(3.3±3.0)×10−9f0.0O2e−400±65/RT m3s−1, where the activation energy for diffusion is in kJ/mol, and δ is the grain boundary width in m. Calculated growth rates for enstatite under these conditions are significantly slower than predicted by an extrapolation from similar experiments performed at 1000 °C under high pressure (hydrous) conditions by Yund and Tullis (1992), perhaps due to water-enhancement of diffusion in their experiments.

Correction procedures in electron probe microanalysis of bulk samples

In recent years many of the advances in quantitative microprobe analysis have come from the improved ability to model the complex physics in the computer. This has enabled the accuracy of normal bulk analysis to be improved-right down to the very light elements as far as boron-and has extended the technique to the analysis of multiple thin films and layered samples. It has also allowed the user to shortcut the use of standards, though at the cost of somewhat reduced accuracy. Thus the analyst has come to rely more and more on correction procedures of increasing complexity, yet at the same time must understand their limitations. It is likely that in future the computer itself will be able to accumulate the best practice of expert users, advising the newcomer how these procedures can be best applied and where they are most likely to be in error.

Fluorescence effects in quantitative microprobe analysis

Characteristic fluorescenceThe theory of characteristic fluorescence corrections was first developed by Castaing. The same approach, with an improved expression for the relative primary x-ray intensities of the exciting and excited elements, was used by Reed, who also introduced some simplifications, which may be summarized as follows (with reference to K-K fluorescence, i.e. K radiation of element ‘B’ exciting K radiation of ‘A’):1.The exciting radiation is assumed to be monochromatic, consisting of the Kα line only (neglecting the Kβ line).2.Various parameters are lumped together in a single tabulated function J(A), which is assumed to be independent of B.3.For calculating the absorption of the emerging fluorescent radiation, the depth distribution of the primary radiation B is represented by a simple exponential.These approximations may no longer be justifiable given the much greater computing power now available. For example, the contribution of the Kβ line can easily be calculated separately.

Capabilities and limitations of probe methods for the microanalysis of chemical elements in biology: A brief introduction

This article reviews some of the technical problems involved in achieving high-resolution artefact-free quantitative microprobe analyses of biological specimens, and points to some of the techniques now available to overcome these problems

Practical notes on the production of thin aminoplastic standards for quantitative X-ray microanalysis

Detailed, step-by-step, practical instructions are provided for the production of homogeneous aminoplastic standards containing known concentrations of light and heavy elements. These can be used for the fully quantitative microprobe analyses of both plastic-embedded and cryosectioned biological soft-tissue specimens.

Impregnant composition in dispenser cathodes

The compositions of impregnants inside B-type dispenser cathodes containing barium calcium aluminates were examined by means of quantitative microprobe analysis. The impregnant inside the porous tungsten structure was supported with plastic in order to prevent damage when the cathode was sectioned. The impregnant compositions were found to be consistently deficient in CaO when compared to the nominal composition. Variations and reproducibility in composition are discussed.

Quantitative microprobe analysis of hydrous minerals using OK? line. Estimation of water content in microarea

The electron microprobe analyses of muscovites and zeolites were carried out using OKα line in order to estimate the oxygen content attributed to water in zeolite or hydroxyl group in muscovite under electron bombardment area. Its content was determined by subtracting the oxygen content combined with metals stoichiometrically from the total content of it. The correction method used for the quantitative analyses here consisted of Duncumb-Reed atomic number correction, the new absorption correction proposed by the author and the Casting-Reed fluorescence correction. The number of OH in muscovite in the empirical formula obtained by this method was in good agreement with that of the ideal formula, and also in good agreement with the results given by the ignition loss. In the analyses of zeolites, their empirical formulas calculated from the results obtained by this method were found to be quite reliable, and the obtained water content agreed with the results of thermogravimetric analysis within 10% relative error.

Electron Microscopy and Microanalysis of Uranium Phases in Primary Ores, Eocene and Miocene of South Texas: ABSTRACT

Two contrasting types of roll-front uranium deposits occur in south Texas. In the barrier-bar sands of the Eocene Jackson Group, organic matter was essential to uranium reduction, whereas in the fluvial sands of the Miocene Oakville Formation, epigenetic pyrite was the reductant. In a sample of reduced Oakville ore, a uranium phase with grains ranging in diameter from < 1 to 20µm was recognized by SEM back-scattered-electron imaging and wavelength-dispersive spectrometer (WDS) elemental-dot mapping. Quantitative microprobe analyses indicated that the phase is a uranium-calcium silicate-phosphate with molar Ca/P approximately equal to 1.0, U/P equal to 2.8 ± 0.4 (n = 27), and U/Si approaching 1.0 in samples uncontaminated with quartz, feldspar, or clay minerals. Highest uranium content is 59%. Oakville ore is typically easy to leach by in-situ methods. Jackson ore contains 2 uranium phases. Sulfur-rich organic matter contains 4.1 ± 1.6% uranium (n = 27). Although individual grains of a possible uranium mineral within the organic matter are too small to be resolved by electron imaging, a consistent molar U/Fe (0.5 ± 0.1) suggests a uranium-iron oxide phase. Alternatively, uranium is adsorbed by or otherwise bound to the organic matter. The second phase is a uranium-calcium silicate-phosphate that differs from the Oakville ore. Molar Ca/P equals 0.8 ± 0.2 (n = 13), and U/P equals 4.7 ± 0.4. Small grain size (generally less than 1 µm) prevented analysis of samples uncontaminated with quartz and pyrite. The grain with highest uranium content (43%) has U/Si equal to 0.34. Jackson ore is less favorable for in-situ leaching than Oakville ore in part because the organic-associated uranium is difficult to extract. End_of_Article - Last_Page 500------------