Scanning Electron Microscopy X-ray Microanalysis Research Articles

New computation methods for low-voltage effects in SEM and X-ray microanalysis

Scanning electron microscopy (SEM) equipped with an energy dispersive spectroscopy (EDS) is one of the most popular microanalytical techniques for image characterization and X-ray microanalysis. A low-voltage SEM/EDS analysis offers numerous advantages; however, there are still many challenges in data acquisition and interpretation. New computation methods for low-voltage effects in SEM imaging and X-ray microanalysis are proposed in this study. New expressions for describing the beam energy effects on the probe size, backscattering coefficient, and backscattered electron ranges at low voltages are developed. The analytical sensitivity for X-ray microanalysis with radiations from K, L, and M–shells is thoroughly studied through the experiments and Monte Carlo simulations.

Nano-size effects in graphite/graphene structure exposed to cesium vapor

A thermionic energy converter with a nickel collector and cesium vapor as a working gas was studied, and an abnormally low value of the surface work function of ≈1 eV was obtained if the collector was covered by a thin carbon layer. Scanning electron microscopy x-ray microanalysis data of the elemental composition of the collector's surface after its long exposure to plasma indicate that the carbon structure was intercalated with cesium atoms, and this change to surface structure can be a reason for the anomalously low work function ∼1 eV. The thermionic energy converter with such a collector demonstrated high heat-to-electric power conversion efficiency up to ∼20%.

Electrochemical analysis of gildings in Valencia altarpieces: a cross-age study since fifteenth until twentieth century

The application of the voltammetry of microparticles methodology to the study of gildings in paintings and architectural ornaments is described. Nanosamples from pieces from different churches of the Comunitat Valenciana (Spain) covering since the fifteenth century until nowadays were studied upon attachment to graphite electrodes in contact with aqueous HCl and H2SO4 electrolytes. Electrochemical measurements, combined with field emission scanning electron microscopy X-ray microanalysis (FESEM-EDX) and atomic force microscopy (AFM) data, denoted that a common manufacturing technique was used with minimal variations along time. The relationship between specific voltammetric features associated to bulk gold and active surface sites, however, changed monotonically with time, thus suggesting the possibility of age monitoring.

Analytical study of waterlogged ivory from the Bajo de la campana site (Murcia, Spain)

This work reports an analytical study conducted prior to the conservation intervention of a collection of elephant tusks excavated from a wreck site of a 600–500 BC Phoenician trading vessel in Bajo de la campana (Murcia, Spain). The conservation state of ivory, determined by prolongated immersion in a marine environment, was established by a multi-technique methodology: light microscopy, field emission scanning electron microscopy–X-ray microanalysis (FESEM–EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), spectrophotometry and gas chromatography–mass spectrometry (GC–MS). The analyses demonstrated that the structure and composition of both tusk parts, namely the inner ivory and outer cementum, were altered due to characteristic diagenetic processes of a marine environment. Ca enrichment was observed in both tusk parts, which gave higher Ca/P molar ratio values than for ideal hydroxyapatite. Mg leaching was observed, together with uptake of exogenous elements (F, Cl, Si, Al, S, Na, Fe, Cu, Sr, Pb, Sn, Ag, V, Ni, Cd and Zn), which were prevalently identified in the external tusk part. Uptake of S and Fe was associated with the neoformation of pyrite framboids. The high carbonate content measured by FTIR, which agreed with the higher Ca/P ratios found in the archaeological tusk, was ascribed to the carbonate substitution of phosphate groups (type-B) in the bioapatite accompanied by some authigenic calcium carbonate that infilled ivory. An increased degree of crystallinity was observed when comparing the values of several crystallinity indices found in the archaeological bioapatite with those of a modern tusk, used as the reference material. Increased crystallinity prevalently took place in the cementum. In accordance with increased crystallinity, the HPO42− content index indicated that the hydrated layer of bioapatite nanocrystals diminished in the archaeological tusk, and prevalently in the cementum. All these changes correlated with the significant organic matter loss reported for the archaeological tusk. Interestingly, remaining collagenous matter noticeably altered with enrichment in glycine and depletion in acid amino acids. Changes in the secondary structure of proteins were also recognised and associated with collagen gelatinisation. In addition to proteinaceous materials, small amounts of long-chain fatty acids, monoglycerides and cholesteryl oleate were identified by GC–MS. Cholesteryl oleate was associated with blood, which could have precipitated at the time of specimen death. The identification of large amounts of pyrite framboids and the high oleic acid/palmitic acid ratio in the archaeological tusk suggested minimal oxidative degradation processes, probably due to the slightly anoxic conditions of the underwater Bajo de la campana site environment.

Influence of granulated blast furnace slag on the reaction, structure and properties of fly ash based geopolymer

Ground granulated blast furnace slag (GBFS) has been used to alter the geopolymerisation behaviour of fly ash. The influence of varying amount of GBFS (5–50%) on the reaction kinetics has been studied using isothermal conduction calorimetry. It was observed that the reaction at 27 °C is dominated by the GBFS activation, whereas the reaction at 60 °C is due to combined interaction of fly ash and GBFS. The reaction product of geopolymerisation has been characterised using X-ray diffraction and scanning electron microscopy–X-ray microanalysis. Alumino–silicate–hydrate (A–S–H) and calcium–silicate–hydrate (C–S–H) gels with varying Si/Al and Ca/Si ratio are found to be the main reaction products. Coexistence of A–S–H and C–S–H gel further indicates the interaction of fly ash and GBFS during geopolymerisation. Attempt has been made to relate the microstructure with the properties of the geopolymers.

A combination of a SEM technique and X-ray microanalysis for studying the spore germination process of Clostridium tyrobutyricum

Clostridium tyrobutyricum is an anaerobic bacterium responsible for late blowing defects during cheese ripening and it is of scientific interest for biological hydrogen production. A scanning electron microscopy (SEM) coating technique and X-ray microanalysis were developed to analyze the architecture and chemical composition of spores upon germination in response to environmental changes. In addition, we investigated the effects of different compounds on this process. Agents and environmental conditions inducing germination were characterized monitoring changes in optical density (OD). Among all tested conditions, the greatest drop in OD 625 (57.4%) was obtained when spores were incubated in l-alanine/ l-lactate buffer, pH 4.6. In addition, a carbon-coating SEM technique and X-ray microanalysis were used to observe the architecture of spores and to examine calcium dipicolinate release. Conditions inducing C. tyrobutyricum spore germination were identified and SEM X-ray microanalysis clearly distinguished germinating from dormant spores. We confirmed that calcium dipicolinate release is one of the first events occurring. These microscopy methods could be considered sensitive tools for evaluating morphological and chemical changes in spores of C. tyrobutyricum during the initial phase of germination. Information gathered from this work may provide new data for further research on germination.

Characterization of Iranian Moarraque glazes by light microscopy, SEM-EDX and voltammetry of microparticles

Abstract Glazed ceramics have been traditionally used in Iran for decorating mosques and some civil historical buildings. In particular, Moarraque glazes have been extensively used in the indoor and outdoor decoration of mosques in Iran since the middle 14th century. The pieces have a complex elaboration based on a main glazed piece corresponding to the skeleton structure of the Shah Abbasi flower, which contains a number of holes, where are placed, mosaic-like, smaller glazed pieces forming a compact and single tile. The present work describes the analytical study performed on the glazes of several pieces of Moarraque tiles from the Ali Ebn Abi Taleb Mosque (Esfahan, Iran), which date back from the 1960s. Several advanced instrumental techniques including light microscopy, scanning electron microscopy–X-ray microanalysis and voltammetry of microparticles, have been used to perform the characterization of the glazes. Results obtained suggest that the analysed pieces were made combining the traditional methodologies used by local craftsmen since the 14th century and modern techniques.

Study of ageing of ketone resins used as picture varnishes by FTIR spectroscopy, UV–Vis spectrophotometry, atomic force microscopy and scanning electron microscopy X-ray microanalysis

This paper presents a study of thin films of the commercial ketone resins Laropal K80, Keton N and MS2A, attempting to reproduce the pictorial layers and protective finishes commonly present in contemporary paintings. Chemical and morphological changes due to the degradation effect of environmental agents have been specially considered. For this purpose, three different accelerated ageing processes were applied to a series of specimens prepared from the studied commercial products: thermal, UV light and ageing in an SO(2)-polluted chamber. Spectroscopic techniques such as FTIR spectroscopy and UV-Vis spectrophotometry were applied in combination with microscopic examination techniques, namely, AFM and scanning electron microscopy energy dispersive X-ray microanalysis (SEM-EDX). Chemical changes due to UV light and thermal ageing are in good agreement with those previously reported in the literature. Bleaching exhibited by the three commercial products after exposure to a SO(2)-saturated atmosphere has been related to the diffusion of SO(2)-rich water vapour into the film. This effect was particularly strong in the MS2A resin due to the higher content of hydroxyl groups in this product.

Ecological study of Stephanodiscus rotula during a spring diatom bloom: dynamics of intracellular elemental concentrations and correlations in relation to water chemistry, and implications for overall geochemical cycling in a temperate lake

The population of Stephanodiscus rotula in Rostherne Mere (Cheshire, UK) was studied during the spring of 1996 using light microscopy, hydrochemical analyses and scanning electron microscopy X-ray microanalysis (SEM XRMA). Data obtained were statistically analysed to reveal relationships between the elements within the cells and in the lake water. The results confirmed that algal biomass production was mainly controlled by availability of Si. The depletion of ambient Si coincided with changes in the intracellular elemental composition, particularly a considerable reduction of intracellular Si whose depletion was also reflected in changes of intracellular elemental correlations and ratios. A simple structural model of elemental relationships in S. rotula cells is proposed to explain the pattern of intracellular elemental associations. This model can be used as a reference for species response to changes in environmental parameters. S. rotula provided a significant contribution to overall biogeochemical cycling due to the removal of nutrients from the water column and transporting them to bottom sediments following the culmination of the bloom. The role of S. rotula was particularly prominent in the biogeochemical cycle of silicon, as the diatom’s spring growth may account for more than 20% of its total annual loss to bottom sediments.

Application of SEM XRMA data to lake ecosystem modelling

The model Rostherne represents the first attempt to apply SEM XRMA (scanning electron microscopy X-ray microanalysis) data to lake ecosystem modelling. It considers subsystems proved to be most important for Rostherne mere (Cheshire, UK) with incorporation of uptake dependency of one nutrient upon internal deficiency in another. The model showed a reasonable fit ( R 2=0.87, P<0.001) between measured data and simulation curves for most of the considered variables (i.e. P, Si, chlorophyll- a and algal concentrations in the lake water, nutrient mass fractions of algal cells, etc.) and could, therefore, have been used to estimate some parameters and variables which were not measured otherwise (e.g. sedimentation and growth rates, etc.). The possibility of incorporating alternative expressions for the processes considered is discussed and tasks for future research in relation to coupling of various submodels with the proposed submodel of nutrient uptake are envisaged.

The osmium tetroxide-p-phenylenediamine procedure reveals the chromatid cores and kinetochores of meiotic chromosomes by light and electron microscopy.

We analyzed first-metaphase meiotic chromosomes of the grasshopper Chorthippus jucundus by two different methods, i.e., a silver impregnation technique and the osmium tetroxide-p-phenylenediamine (Os-PPD) procedure. The former was applied on squashed testes previously fixed in ethanol-acetic acid, whereas for Os-PPD the material was not subjected to any previous extraction treatment but was fixed in OsO4, treated with PPD, and embedded in Epon 812. Both techniques revealed chromatid cores and kinetochores regardless of the processing of the material (squashed or sectioned). Unstained Os-PPD sections were analyzed by light microscopy and transmission electron microscopy (TEM). The Os-PPD technique provided a high contrast of chromatid cores and kinetochores in relation to the chromatin, which revealed a low electron density. To determine the Os-PPD reaction mechanism, the PAS procedure, as well as scanning electron microscopy (SEM) backscattering and SEM X-ray microanalysis, was performed on sections. By use of the Os-PPD-PAS procedure, glycol groups formed by oxidation of osmium bound to aromatic substrates were detected in chromatid cores and kinetochores by brightfield and fluorescence microscopy. A high Z contrast was detected in these structures by backscattered electron imaging. SEM X-ray microanalysis showed osmium and phosphorus to be the main elements present on the chromatid cores. Taking into account the known reactivity of OsO4 and the present results, the possible participation of nucleic acids as well as proteins in the Os-PPD reaction mechanism and in the composition of chromatid cores and kinetochores is discussed.

Comprehensive Approach toward Understanding Element Speciation and Leaching Behavior in Municipal Solid Waste Incineration Electrostatic Precipitator Ash

A comprehensive approach was used to characterize speciation and leaching behavior of major, minor, and trace elements in electrostatic precipitator (ESP) ash from a Canadian MSW incinerator. Neutron activation analysis (NAA), X-ray powder diffraction (XRPD), scanning electron microscopy/X-ray microanalysis (SEM/XRM), Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), and X-ray photoelectron spectroscopy (XPS) were used to quantify elements, describe particles and phase associations, identify bulk and surface mineral phases, and identify the speciation of elements. SEM/XRM showed a complex polycrystalline material covering aluminosilicate spheres. XPS, as a surface technique, provided information on speciation at the particle surface where leaching first occurs. SIMS showed molecular fragments indicative of speciation and enrichment of volatile species (K, Zn, Cl, S, Pb) in the fine polycrystalline material. Many of these phases readily dissolve during leaching. Dissolution behavior and pH-dependent leaching could be modeled with the geochemical thermodynamic equilibrium model MINTEQA2. The abilityto model leaching behavior provides an opportunity to examine possible disposal or treatment behavior.

Effects of addition of calcium phosphates on the properties of gypsum : Inomata K. (1990) Jap. J. Dent. Mater.9, 121–132

Calcium hydrogen phosphate (CHP), calcium hydrogen phosphate dihydrate (CHPD) and calcium sulfate dihydrate (gypsum) crystals were added to calcium sulfate hemihydrate as gypsum model materials for improvement of the mechanical properties. The compressive and the bending strength of the hardened mixture were improved by the addition of CHPD, while the addition of CHP and gypsum crystals had no effect. The setting time was markedly reduced by the addition of CHPD, but remarkably increased in the case of CHP crystals. On the other hand, the setting expansion was decreased by the addition of CHP and CHPD crystals. Based on the observation of the surface profile of the calcium sulfate hemihydrate set in contact with glass, and scanning electron microscopy (SEM) of the fractured surface of the hardened mixture, the surface roughness was markedly decreased by the addition of CHPD. When the crystals were added to the metastable solution of calcium sulfate supersaturated with respect to gypsum, the presence of gypsum crystals deposited on the CHPD surface was confirmed by atomic absorption analysis, fourier transform infrared spectroscopy. SEM and electron X-ray microanalysis. Therefore, epitaxial growth of gypsum occurred on the CHPD surface and the addition of CHPD improved the mechanical properties of the gypsum materials.

Effects of addition of calcium phosphates on the properties of gypsum

Calcium hydrogen phosphate (CHP), calcium hydrogen phosphate dihydrate (CHPD) and calcium sulfate dihydrate (gypsum) crystals were added to calcium sulfate hemihydrate as gypsum model materials for improvement of the mechanical properties. The compressive and the bending strength of the hardened mixture were improved by the addition of CHPD, while the addition of CHP and gypsum crystals had no effect. The setting time was markedly reduced by the addition of CHPD, but remarkably increased in the case of CHP crystals. On the other hand, the setting expansion was decreased by the addition of CHP and CHPD crystals. Based on the observation of the surface profile of the calcium sulfate hemihydrate set in contact with glass, and scanning electron microscopy (SEM) of the fractured surface of the hardened mixture, the surface roughness was markedly decreased by the addition of CHPD. When the crystals were added to the metastable solution of calcium sulfate supersaturated with respect to gypsum, the presence of gypsum crystals deposited on the CHPD surface was confirmed by atomic absorption analysis, fourier transform infrared spectroscopy. SEM and electron X-ray microanalysis. Therefore, epitaxial growth of gypsum occurred on the CHPD surface and the addition of CHPD improved the mechanical properties of the gypsum materials.