Energy Dispersive X-Ray Fluorescence Analysis and X-Ray Microanalysis of Medieval Silver Coins

 Austrian medieval silver/copper coins were investigated at their surfaces by energy dispersive X-ray fluorescence analysis (EDXRF) and at the cross-sections by X-ray microanalysis in the scanning electron microscope (SEM/EDX) in order to estimate the error occurring when corroded objects of art and archaeology are analyzed on the surface by non-destructive methods. Additionally, Ag/Cu-standards were treated in diluted sulphuric acid and the depletion of copper on the surface was measured by EDXRF. By calculating the ratio of the Ag-K/Ag-L intensity the process of blanching could be studied.     

Scanning electron microscopy and energy dispersive analysis: applications in the field of cultural heritage

Scanning electron microscopy has been extensively used for the material characterization of objects of artistic and archaeological importance, especially in combination with energy dispersive X-ray microanalysis (SEM/EDX). The advantages and limitations of SEM/EDX are presented in a few case studies: analysis of pigments in cross-sections of paint layers, quantitative analysis of archaeological glass from the Roman period excavated in Ephesos/Turkey, and investigations on glasses with medieval composition concerning their weathering stability and degradation phenomena.     

Electron Probe Microanalysis of Nitrogen in Glasses and Glass Ceramics

 A homogeneous (phosphate glass) and a heterogeneous (glass ceramic) material were chosen to develop a method for electron microprobe analysis of nitrogen in glasses and glass ceramics. The metaphosphate (50 mole-% P₂O₅, 25 mole-% BaO, 25 mole-% Rb₂O) base glass and the silicate glass (composition of the base glass: 6.9 mole-% Al₂O₃, 21.3 mole-% MgO, 47.3 mole-% SiO₂, 5.1 mole-% CaO, 19.4 mole-% AlN) were melted and cooled down to room temperature. In a second step, the two materials were nitrided by applying dry NH₃ in a special tube furnace. Up to 5 wt.-% of nitrogen could be introduced. The ability of energy dispersive (EDX) as well as wavelength dispersive (WDX) electron probe microanalysis to analyze low contents of light elements in combination with highly concentrated heavy elements was tested both for glasses and for glass ceramics. Measuring conditions had to be optimized to get reliable analytical results as well as to avoid radiation damage of the glasses which may occur especially in the case of wavelength dispersive X-ray analysis. The results were compared with two different analytical methods: inductive coupled plasma analysis and a commercial nitrogen-oxygen-analyzer (the specimen is decomposed by heating and the released gases are analyzed spectroscopically (O) and electrically (N)).     

Lead determination in glasses by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been used to determine the lead content of different types of lead silicate glasses commercially designed as sonorous glass (which contain ∼ 10 wt.% PbO); crystal glass (with at least 24 wt.% PbO) and superior crystal glass (with at least 30 wt.% PbO). Seven different types of glass samples were selected, including historic-original, model and commercially available. The selected samples were artificially weathered under neutral, acid and alkaline attack. Analysis by LIBS was carried out in vacuum under excitation at 266 nm and results were compared with those obtained by conventional techniques used for glass characterization. Composition of the bulk glasses was analyzed by XRF (X-ray fluorescence) and the corroded surfaces were characterized by SEM/EDX (scanning electron microscopy/energy dispersive X-ray microanalysis). A linear correlation was obtained between the intensity of selected Pb lines in the LIB spectra and the PbO content. The effect of corrosion could be characterized by comparing successive LIB spectra recorded on the same area; acid attack resulted in a decrease of PbO, CaO and Na₂O content in the surface with respect to the bulk of the sample, while minor changes in the composition were noticed under alkaline attack. These results show LIBS as a useful technique to classify the different types of lead glasses by their lead content and to determine and asses the degree and type of corrosion.     

Oxidation and nitridation of niobium films by rapid thermal processing

The oxidation and nitridation processes of niobium films in a rapid thermal processing (RTP) – system were investigated. 200 and 500 nm niobium films were deposited via sputtering on sapphire-(1-102)-substrate. At first niobium films were oxidized in molecular oxygen at temperatures ranging from 350 to 500 °C and for times of 1, 2 and 5 min and then nitridated in ammonia at 1000 °C for 1 min using an RTP system. For characterisation of the niobium films complementary analytical methods were used: X-ray diffraction (XRD) for phase analysis, secondary ion mass spectrometry (SIMS) for determining the elemental depth profiles of the films, scanning electron microscopy (SEM) and atomic force microscopy (AFM) for characterisation of the surface morphology of the films. The influence of the substrate, single crystalline sapphire, on the reactivity of the niobium films was studied in dependence of temperature, time of reaction and film thickness. The possibility of existence of niobium oxynitride phase was investigated. According to XRD and SIMS data, there is evidence that an oxynitride phase is formed after oxidation and subsequent nitridation in the bulk of some Nb films. In some of the experiments crack formation in the films or even delamination of the Nb films from the substrates was observed.     

Weathering Phenomena on Naturally Weathered Potash-Lime-Silica-Glass with Medieval Composition Studied by Secondary Electron Microscopy and Energy Dispersive Microanalysis

 Samples of two model glasses with chemical compositions similar to medieval stained glass were exposed to the natural environment at 23 test sites for a period of 6 months, 1 and 2 years within an exposure programme of the “Working Group of Effects on Materials, Including Historic and Cultural Monuments” of the Economic Commission for Europe of the United Nations. During the exposure the environmental data were measured and collected at each test site in order to enable a correlation between the pollutant load in the ambient atmosphere and the weathering phenomena of the glass samples. After the exposure, which was performed in a sheltered as well as in an unsheltered mode for gaining information about the influence of dry and wet deposition of air pollutants, the glass samples were analysed in the scanning electron microscope with energy dispersive microanalysis (SEM/EDX). Model glass M1 – a potassium rich glass – was covered to a high amount with crystalline weathering products (above all syngenite), whereas glass M3 – a glass with a higher Ca and Si content – turned out to be more stable against weathering. This glass was covered with gypsum and arcanite crystals but in total to a less extent than glass M1. Received March 30, 1998. Revision February 8, 2000.     

Chemical deposition and characterization of thin polypyrrole films on glass plates: role of organosilane treatment

 Thin chloride-doped polypyrrole films (PPyCl) were deposited chemically onto untreated and silane-treated planar glass plates from aqueous solutions. The organosilanes used to treat the glass substrates were methyltriethoxysilane (Cl), propyltrimethoxysilane (C3), octyltrimethoxysilane (C8) and aminopropyltriethoxysilane (APS). The decreasing order of hydrophobic character of silane-treated glass slides, as measured by water contact angle measurements, was glass–APS ≅ glass–C8 > glass–C3 > glass–C1 > glass. X-ray photoelectron spectroscopy was used to determine the surface chemical composition of the glass plates before and following coating with the silane coupling agents and/or the PPy thin layer, respectively. The attenuation in intensity of the glass Na_{1 s} peak enabled the average thickness of the various organosilane overlayers to be estimated. Atomic force microscopy showed that the morphology of the organosilane overlayers was islandlike. The domains have a structure which depends upon the nature of the organosilane in question. Scanning electron microscope images showed that the morphology of the PPyCl thin films was homogeneous when coated onto glass–APS and glass–C8, but wrinkled at the surface of glass, glass–C1 and glass–C3 plates. Qualitative peel tests using 3M adhesive tape showed very good adhesion of PPyCl to the glass–APS substrate, whereas adhesion was fairly poor in the case of glass–PPy and PPy–alkylsilane–glass interfaces. The results of this multitechnique study suggest that hydrophobic interactions are important to obtain homogeneous and continuous thin PPy films, but Lewis acid–base interactions are the driving forces for strong and durable PPy–glass adhesion. Received: 3 January 2000/Accepted: 19 May 2000     

EPMA and X-Ray Diffraction of the Degraded Fuel Bundle from the Phebus FPT1 Test

 The degraded fuel rod bundle from the second Phebus test (FPT1) was examined at ITU, Karlsruhe. Metallographic and microprobe analysis of the degraded fuel pieces were carried out. The fuel samples from the upper bundle and cavity edge were porous and had remnants of thick oxidised cladding adhering to them. Electron microprobe analysis line scans across the cladding-fuel interface showed interdiffusion of U and Zr, with U diffusing down the grain boundaries of the oxidised cladding, while point analyses revealed noticeable amounts of Zr (1.5–4.2 wt%) in the UO₂ fuel. EPMA oxygen measurements revealed in the upper part of the bundle a superstoichiometry of x = 0.3–0.4 in UO _2 + x , indicating that fuel fragments in this position had undergone considerable oxidation. X-ray diffraction of the corium pool disclosed a deformed cubic fluorite lattice of UO₂. The lattice parameter of a = 5.2984 ? was considerably reduced compared with pure, stoichiometric UO₂ and was consistent with a lattice containing approximately 45 mol% ZrO₂ that had undergone little oxidation. The corium’s nominal composition of (U_0.5Zr_0.5) O₂ also corresponded to its observed single phase microstructure.     

M Spectra of Elements 39 ≤ Z ≤ 56 Measured with an Ultra-Thin Window Si(Li) Detector

 Elements in the range 39 ≤ Z ≤ 56 were excited by electrons of an energy between 3 and 15 keV. The X-rays were detected by means of an energy dispersive Si(Li) spectrometer with an ultra-thin polymer entrance window. In all cases M_ζ = M₅N₃ was found to be the most intense M line. Thus, the relative intensity of this line is by definition 100%. For the heavier of the investigated elements some other M lines were observed: M₅O₃, M_γ and M₂N₄. M_γ was detectable for Z ≥ 47, starting with a relative intensity of about 5%, which increased rapidly with Z to approximately 10%. M₅O₃ was first observed for 49-In, with a relative intensity of less than 10%, which increased up to approximately 50% for 56-Ba. Also, M₂N₄ was observed for Z ≥ 49. The relative intensity of that line is approximately one half of that of M_γ.     

X-Ray Microanalysis in the Environmental SEM: A Challenge or a Contradiction?

 In this paper, the application of X-ray energy dispersive spectroscopy in the environmental scanning electron microscope is reviewed. Various techniques that have been used to remove the effects of the beam spreading in the gaseous environment are discussed, specifically the pressure variation techniques and the beam-stop method. The results of the application of modified versions, developed at the University of Michigan, are also presented. It is shown that quantitative analysis in the environmental SEM, operating at 30 kV, is possible at short working distances (6 mm to 7.2 mm, gas path length 1.2 mm to 2.2 mm) in the 70 to 350 Pa range.     

Laser-ablation ICP-MS analysis of siliceous rock glasses fused on an iridium strip heater using MgO dilution

Trace element determination in rocks by fusion on an iridium strip heater followed by LA-ICP-MS analysis of the glass beads is extended here to SiO₂-rich rocks; rapid fusion of samples with >55 wt% SiO₂ is facilitated by dilution by high purity MgO. The method developed here can rapidly and accurately determine numerous trace elements in a large range of rock compositions in a short time (about 50 samples/day). Systematic evaluation for a large range of rock compositions (natural rocks and reference materials AGV-2, GSP-2, JG-1a) with SiO₂ contents between 45 and 80 wt% shows that reproducibility and accuracy within 10% can be routinely achieved for most of the 28 trace elements investigated (Rb, Sr, Cs, Ba, Ti, Zr, Hf, Nb, Ta, Sc, V, Cr, Ni, Pb, Th, U, REE). The 40 mg sample size is smaller than for XRF, INAA or solution-ICP-MS, detection limits are lower, and trace element palettes more complete than XRF and INAA. This microchemical method is thus attractive for the analysis of all natural geological materials as well as for experimental applications with small samples. Samples with SiO₂-contents >55 wt% require hot and long melting to achieve homogeneous glasses and eliminate all residual minerals, particularly refractory accessory phases. Melting conditions of 1600 °C and 20 s for samples are recommended for SiO₂ contents between 55 and 70 wt%, whereas 1800 °C and 20–30 s are often required for samples with >70 wt% SiO₂. Problems are encountered for Pb and Cs due to volatilization on the Ir strip, for Sc due to interferences, and Zr and Hf due to their sequestration in refractory accessory minerals. Correspondence: Franziska Nehring, Department of Geosciences, University of Mainz, Becherweg 21, 55099 Mainz, Germany     

Different Strategies of Covalent Attachment of Oligonucleotide Probe onto Glass Beads and the Hybridization Properties

The glass bead is a new biochip support material for immobilization biomolecules, due to its independence and convenient rearrangement. In order to optimize the immobilization efficiency of oligonucleotides onto glass beads and obtain the highest hybridization efficiency, three commonly used coupling strategies have been studied for covalently attaching oligonucleotides onto large glass beads. Glass beads with 250 μm diameter were amino-silaned with 2% 3-aminopropyltrimethoxysilane (APTMS) and then reacted separately with glutaraldehyde, succinic anhydride and 1,4-phenylene diisothiocyanate (PDITC) to derive CHO beads, COOH beads and isothiocyanate-modified beads (NCS-Beads) accordingly. Afterwards, amino-terminal oligonucleotides were covalently attached onto the surface of beads achieved by three strategies mentioned above. The immobilization efficiency were studied to compare the three strategies, which turned out 2.55 × 10¹³ probes/cm² for CHO-Beads, 3.21 × 10¹³ probes/cm² for COOH beads and 6.68 × 10¹³ probes/cm² for NCS beads. It meant that the immobilization efficiency based on NCS beads was most acceptable. And the method, developed by attaching amino-terminal oligonucleotides onto these cyanate active beads, could be regarded as an efficient one for immobilizing oligonucleotides onto a solid surface. Moreover, in this paper, the hybridization properties of NCS bead-based oligonucleotides have been studied by employing Cy5-tagged complementary oligonucleotides. It was found that the high probe density NCS beads led to low hybridization efficiency possibly due to the existence of steric crowding. In addition, the equilibrium binding constant K _A was determined by employing Langmuir isotherm model, which was 7.0 × 10⁶ M⁻¹ for NCS beads with the density of 6.7 × 10¹³ probes/cm². Furthermore, it only took 60 min to reach hybridization equilibrium. These large microspheres (>100 μm) can be employed in the mesofluidic systems for automated heterogeneous assays.     

Quantitative Analysis of Thin Aluminium-Oxynitride Films by EPMA

 Thin films of aluminium oxynitride with diverse composition were prepared by dc-magnetron sputtering of aluminium, utilising sputtering power as well as argon, oxygen and nitrogen gas flows to vary the composition. Since film properties depend mainly on the content of incorporated oxygen and nitrogen, a method for quantitative analysis of the main constituents based on electron probe micro analysis with energy dispersive detection was developed. The excellent precision of the quantitative results for aluminium as well as oxygen and nitrogen are shown. Furthermore, a film layer analysis program was applied for the quantification of several films deposited under the same deposition parameters on silicon wafers, from 520 nm down to 40 nm thickness, showing that electron probe micro analysis with energy dispersive detection is a reliable method for quantitative compositional analysis of thin aluminium oxynitride films down to approximately 20 nm thickness. Since this method of analysis provides only bulk information, expected inhomogeneities of the depth distribution of the film components were checked by secondary ion mass spectrometry depth profiles of two thin films and correlated to the EPMA results. The thickness of the films was determined by ellipsometry. Received September 1, 1998     

Investigations of the microscopic structure of poly(vinyl alcohol) hydrogels by confocal laser scanning microscopy

The fluorescence mode confocal laser scanning microscopy (CLSM) is introduced as an alternative method to investigate the bulk structure of poly(vinyl alcohol) (PVA) hydrogel. Investigations of the bulk structure of hydrogel samples, prepared by freezing and controlled thawing of aqueous PVA solutions followed by fluorochrome conjugation, were possible in the native state because with this technique water does not need to be removed prior to examination. This is of advantage to other methods, such as scanning electron microscopy, requiring dehydration by critical-point drying or freeze-etching, because both may result in a significant alteration of the gel structure. CLSM images of the hydrogel bulk structure were taken at several successive intervals from the surface into the hydrogel (up to 60 μm) without freeze-fracturing or cutting the sample. Detailed morphological characterization is achievable by superimposing series of images taken at successive intervals and by magnifying special regions of interest. Images of hydrogel bulk structures revealed a continuous, three-dimensional network that originates from phase-separation (spinodal decomposition) during the freezing period. The pore or mesh size in the cryogel increased, from about 2–7 μm, with decreasing PVA concentration. The surface layer was only a few microns thick, and the bulk structure underneath showed neither porosity gradients nor structural orientations. Received: 29 April 2000/Accepted: 18 August 2000     

Design Features of a High Resolution Microcalorimeter EDX System

 High resolution, superconducting detectors allow energy dispersive X-ray spectrometry (EDX) with energy resolution and energy threshold far beyond the levels obtained with semiconductor detectors. These cryogenic detectors are run at temperatures of less than 100 mK and combine the excellent energy resolution of wavelength dispersive X-ray spectrometry (WDX) with the fast, energy dispersive analysis of EDX. CSP cryogenic spectrometer’s microcalorimeter type EDX cryodetectors are equipped with a mechanical cooling system that runs vibration free and allows completely automated operations on scanning electron microscopes (SEMs), field emission guns (FEGs) and transmission electron microscopes (TEMs). This detector type offers new opportunities in material analysis, especially when low excitation energies are applied or light elements are to be determined.     

Preparation and ionic conductivity of poly(ethylene oxide) oligomers having thiolate groups on the chain ends

Poly(ethylene oxide) (PEO) oligomers having alkali metal thiolate groups on the chain ends (PEO _m -S⁻M⁺) were prepared as an ion conductive matrix. The molecular weight of the PEO part (m) and the content of the thiolate groups in the molecule were changed to analyze the effect of carrier ion concentration in the bulk. In a series of potassium salt derivatives, PEO₃₅₀-SK showed the highest ionic conductivity of 6.42 × 10⁻⁵ S/cm at 50 °C. In spite of a poor degree of dissociation which was derived from the acidity of the thiolate groups, PEO _m -SM showed quite high ionic conductivity among other PEO/salt hybrids. PEO _m -SM had glass transition temperatures (T _g) 20 °C lower than other PEO/salt hybrids. Lowering the T _g was concluded to be effective in providing higher ionic conductivity for PEO-based polymer electrolytes. Received: 30 April 1999 / Accepted: 20 June 1999     

Atomic force microscopy study of salivary pellicles formed on enamel and glass in vivo

This study was performed to evaluate the use of atomic force microscopy (AFM) in examining the surface of the adsorbed layer of salivary proteins (salivary pellicle) formed in vivo on dental enamel and glass surfaces. Enamel and glass test pieces were attached to the buccal surfaces of the upper first molar teeth in two adults using removable intraoral splints. The splints were carried intraorally over periods ranging from 10 min to1 h. Using the contact mode of AFM, pellicle structures could be recognised on intraorally exposed specimens compared to nonexposed enamel and glass surfaces. The surface of the adsorbed salivary pellicle was characterised by a dense globular appearance. The diameter of the globulelike protein aggregates adsorbed onto enamel and glass varied between 80 and 200 nm and 80 and 150 nm, respectively. The structure of the adsorbed protein layer was clearly visible on glass surfaces, even though minor differences in the protein layer between glass and enamel specimens were observed. This study indicates that AFM is a powerful tool for high-resolution examination of the salivary pellicle surface structure in its native (hydrated) state. AFM avoids artefacts due to fixing, dehydration and sputter-coating which occur with scanning electron microscopic analyses. Received: 29 November 2000 Accepted: 14 December 2000     

A MIP-based flow-through fluoroimmunosensor as an alternative to immunosensors for the determination of digoxin in serum samples

This work reports a comparative study of two automated flow-through fluorosensors for the determination of digoxin in serum samples: an immunosensor with an anti-digoxin polyclonal antibody as the reactive phase permanently immobilised on controlled-pore glass and a sensor with a selective reaction system based on a methacrylic molecularly imprinted polymer (MIP) synthesised by bulk polymerisation. The variables affecting the sensitivity and dynamic range of the sensors (e.g. the carrier and elution solutions, flow rates, pH and reagent concentrations) were optimized, and the binding characteristics of their reactive phases were compared in a competitive fluorescent assay. Digoxin was reproducibly determined by both sensors at the milligram per litre level (detection limit = 1.20 × 10⁻³ mg L⁻¹ and RSD = 4–7% for the immunosensor; detection limit = 1.7 × 10⁻⁵ mg L⁻¹ and RSD = 1–2% for the MIP sensor). No cross-reactivity with digoxin-related compounds was seen for either sensor at a digoxin/interferent ratio of 1:100. The lifetime of the immunosensor was about 50 immunoassays; its shelf life, when unused, is about 3 months. The lifetime of the MIP sensor was over 18 months. Both sensors were used to determine the digoxin concentration of human serum samples with satisfactory results.     

In-Depth Analysis of the Early Stage Corrosion of Technical Glass Fibers

 Two commercial glass wool-type fibers, one with standard composition, the other one with a modified composition fulfilling the K_I > ;40 condition (K_I=cancerogeneity index), were subjected to an attack in strongly basic KOH solutions for times up to 240 h and temperatures up to 80 °C. For short times leach analysis displayed a relatively steep increase in the amount of leached Na for the first type of fibers, whereas the modified fiber showed a higher stability. For times > 24 h the leach resistivities of both fibers reversed. In-depth concentration analysis of the fibers in the as-received states revealed a strong pre-experimental attack of the first fiber and a Na₂O enrichment by about a factor of two at the fiber surface. The modified fiber was less attacked and showed a strong Na₂O depletion near the surface. The in-depth concentration profiles of the attacked glass fibers approached similar shapes for both fibers at longer reaction times and showed also that the modified fiber is less stable for the conditions chosen.     

Water-soluble microgels made by radical polymerization in solution

The goal of this study was to prepare and characterize water-soluble, high-molecular-weight microgels. N-Vinylpyrrolidone (NVP) and vinylacetate (VAc) in combination with cross-linkers diethylene glycol dimethacrylate (DEGDMA) or diethylene glycol divinyl ether (DEGDVE) were copolymerized in solution to high conversion. Polymerization was performed in different solvents or solvent mixtures, with solubility parameters ranging from 16.0 to 47.6 J^0.5cm^−1.5, and at different initial monomer concentrations. In solvent mixtures with solubility parameters of 20–40 J^0.5cm^−1.5, macrogelation did not occur below a critical gelation concentration and microgels were formed. For NVP/VAc/DEGDMA (85.0/10.0/5.0 wt%, 84.8/12.9/2.4 mol%) and NVP/VAc/DEGDVE (85.0/10.0/5.0 wt%, 84.8/12.9/3.5 mol%) the critical gelation curves were determined. The molecular weights of the microgels depend on the solvent systems and the initial monomer concentration. Microgels of high molecular weight but low cross-linking density gave aqueous solutions with high viscosities. Increasing the amount of cross-linker to 20 wt% gave high-molecular-weight microgels with lower solution viscosity. Microgels with a monomer composition NVP/VAc/DEGDVE (65.0/15.0/20.0 wt%, 66.2/19.5/14.3 mol%) were prepared in ethanol at different monomer concentrations (3–20 wt%). The molecular weights were determined by a combination of field-flow fractionation and light scattering. By increasing the initial monomer concentration, the molecular weight and the molecular-weight distribution as well as the intrinsic viscosity increased. The exponent of the Mark–Houwink equation was 0.26. Received: 19 March 2001 Accepted: 20 July 2001