Filtern
Dokumenttyp
- Zeitschriftenartikel (34)
- Beitrag zu einem Tagungsband (4)
- Vortrag (4)
- Buchkapitel (1)
Sprache
- Englisch (43) (entfernen)
Schlagworte
- Raman microspectroscopy (12)
- Raman spectroscopy (9)
- Raman microscopy (5)
- Thermal anhydrite (5)
- High-fired gypsum mortar (4)
- Gypsum (3)
- High-fired medieval gypsum mortars (3)
- Nanoparticles (3)
- Analytical methods (2)
- Anhydrite (2)
- Coverslip seal (2)
- Cuprorivaite (2)
- Egyptian blue (2)
- Forsterite (2)
- Gypsum dehydration (2)
- Hot steam (2)
- Laser-induced breakdown spectroscopy (LIBS) (2)
- Luminescence (2)
- Meso Portland cement (2)
- Mounting medium (2)
- Polycrystalline materials (2)
- Soil (2)
- Steel slag (2)
- Temperature (2)
- Tribofilm (2)
- Wear (2)
- X-ray microdiffraction (2)
- (Free) lime (1)
- Absorption spectrometry (1)
- Agricultural (1)
- Alumina (1)
- Aluminium oxide (1)
- Amorphous carbon (1)
- Amperometry (1)
- Atomic force microscopy (1)
- Bassanite (1)
- Bismuth (1)
- Calcite (1)
- Calcium carbonates (1)
- Calcium compounds (1)
- Calcium monofluoride (1)
- Calibration-free analysis (1)
- Calibration-free laser-induced breakdown spectroscopy (1)
- Cement clinker (1)
- Cement clinker remnants (1)
- Ceramic (1)
- Chemical imaging (1)
- Clearing (1)
- Clinker relicts (1)
- Coordination polymer (1)
- Correlative Imaging (1)
- Cyclic voltammetry (1)
- Dedolomite (1)
- Deterioration (1)
- Diaspore (1)
- Dolomite (1)
- EBSD (1)
- Electrochemistry (1)
- Ferrite (1)
- Fixation (1)
- Flexible crystals (1)
- Fourier transform spectroscopy (1)
- Friction (1)
- Graphene (1)
- Graphite furnace (1)
- Gypsum technology (1)
- HR-CS-MAS (1)
- Hemihydrate (1)
- High-fired gypsum (1)
- Hyperspectral imaging (1)
- Immersion oil (1)
- Immunoassay (1)
- In situ EXAFS (1)
- In situ SAXS/WAXS (1)
- Interdisciplinary research (1)
- Interferometric spectroscopy (1)
- Iron oxide (1)
- LIBS (1)
- Lacunary Keggin ion (1)
- Laser induced breakdown spectroscopy (LIBS) (1)
- Laser induced plasma (1)
- Lime cycle (1)
- Lime phases (1)
- Lubricated sliding (1)
- Maceration (1)
- Magnesium carbonates (1)
- Mechanical properties (1)
- Microplastics (1)
- Microscope slides (1)
- Microscopy (1)
- Microspectroscopic imaging (1)
- Microstrain (1)
- Microstrain distribution (1)
- Microstructure (1)
- Mikroplastik (1)
- Mineral identification (1)
- Mineral paragenesis (1)
- Monte Carlo simulation (1)
- Mounting media (1)
- Multivariate classification (1)
- Multivariate data analysis (1)
- Nanosciences (1)
- Ochratoxin A (1)
- Olivine (1)
- Online (1)
- Parallel computing (1)
- Partial least squares regression (PLSR) (1)
- Permeability (1)
- Physico-chemical characterisation of minerals (1)
- Pigments (1)
- Plasma tomography (1)
- Plasmonic heating (1)
- Plastic deformation (1)
- Polarised light microscopy (1)
- Polycrystalline thin films (1)
- Polymers (1)
- Polyoxometalates (1)
- Portland cement (1)
- Post-breakdown laser induced plasma (1)
- Principal component analysis (PCA) (1)
- Process analytical technology (1)
- Prozessanalytik (1)
- Quartz (1)
- Quaternary oxides (1)
- RFA (1)
- Radon transform technique (1)
- Raman (1)
- Raman band width (1)
- Raman band width determination (1)
- Raman-Spektroskopie (1)
- Re-hydration (1)
- Residual cement grains (1)
- Roman cement (1)
- Self-assembly (1)
- Sensor system (1)
- Silicon nitride (1)
- Slag (1)
- Spatial heterodyne spectrometer (1)
- Spectoscopic imaging (1)
- Spectroscopic imaging (1)
- Strontium isotope (1)
- Sulphur isotope (1)
- Surface-enhanced Raman scattering (1)
- Taxonomy (1)
- Teaching (1)
- Thin film (1)
- Thin-film solar cells (1)
- UV–Vis spectroscopy (1)
- Xerogel (1)
- Zirconia (1)
- Zirconium (1)
- a-C:H (1)
Organisationseinheit der BAM
- 1 Analytische Chemie; Referenzmaterialien (25)
- 1.4 Prozessanalytik (18)
- 1.3 Instrumentelle Analytik (8)
- 6 Materialchemie (5)
- 1.0 Abteilungsleitung und andere (3)
- 6.1 Oberflächen- und Dünnschichtanalyse (3)
- 6.3 Strukturanalytik (3)
- 9 Komponentensicherheit (3)
- 9.5 Tribologie und Verschleißschutz (3)
- 1.1 Anorganische Spurenanalytik (2)
Eingeladener Vortrag
- nein (4)
The mechanism of action of zirconium permanent modifiers on graphite surfaces was investigated in order to understand its influence on the analytical signal in atomic and molecular absorption spectrometry (AAS/MAS). For this, the molecule formation of CaF was studied, which is used for the indirect analytical determination of fluorine in high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS). The kinetics of this reaction was established by monitoring its molecular spectrum at different atomisation temperatures. An Arrhenius plot showed a pseudo-first order reaction with respect to fluorine (n = 1). An intermediate state was isolated, and its structure was elucidated by spectroscopic methods: scanning electron microscopy with energy dispersive X-ray spectroscopy (SEMEDX), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XANES and EXAFS), and Raman microspectroscopy. We propose here a mechanism, where ZrO2 acts as a heterogeneous catalyst: after a pyrolytic step, an intermediate state of ZrO(OCaF) is activated, and at higher temperatures, CaF(g) is released from the zirconium-coated graphite surface. No evidence of the formation of zirconium carbide was found. Consequently, as the CaF formation is catalysed by a heterogeneous catalyst, surface modifications with ZrO2 nanoparticles and ZrO xerogels were investigated in order to increase the surface area. Their influence was evaluated in the molecule formation of CaF, CaCl, CaBr, and CaI. Graphite furnace modification with zirconium oxide nanoparticles proves to be the best choice for fluorine analysis with a signal enhancement of more than eleven times with respect a non-coated graphite furnace. However, the influence of zirconium modifications in the analytical signals of Cl, and I is lower than the F signals or even negative in case of the Br. Understanding zirconium modifiers as heterogeneous catalysts offers a new perspective to AAS and MAS, and reveals the potential of surface analytical methods for development of improved permanent modifiers and graphite furnace coatings.
Mechanical flexibility in single crystals of covalently bound materials is a fascinating and poorly understood phenomenon. We present here the first example of a plastically flexible one-dimensional (1D) coordination polymer. The compound [Zn(m-Cl)2(3,5-dichloropyridine)2]n is flexible over two crystallographic faces. Remarkably, the single crystal remains intact when bent to 1808. A combination of microscopy, diffraction, and spectroscopic studies have been used to probe the structural response of the crystal lattice to mechanical bending. Deformation of the covalent polymer chains does not appear to be responsible for the observed macroscopic bending. Instead, our results suggest that mechanical bending occurs by displacement of the coordination polymer chains. Based on experimental and theoretical evidence, we propose a new model for mechanical flexibility in 1D coordination polymers. Moreover, our calculations propose a cause of the different mechanical properties of this compound and a structurally similar elastic material
Measuring the Burning Temperatures of Anhydrite Micrograins in a High-Fired Medieval Gypsum Mortar
(2017)
Typical feature of high-fired medieval gypsum mortars is a compact microstructure of squat gypsum crystals containing firing products as remains of the calcination process. So far, the burning history of the binder is estimated based on morphological characteristics of the latter. A novel Raman microspectroscopy approach provides access to the calcination temperatures of individual anhydrite grains based on quantifiable spectroscopic changes appearing due to gradual variations of crystallinity, as independently confirmed by X-ray diffraction analysis of anhydrites synthesised at temperatures between 500°C and 900°C. The approach was successfully applied to the high-fired gypsum mortar of a South Tyrolean stucco sculpture of a pieta dated around 1420. Microparticles of burned anhydrite II with firing temperatures scattered around 650°C and clusters of thermally damaged natural anhydrite II crystals from the raw material were identified and imaged.
In the second half of the 19th century, Roman and Portland cements played an essential role as active hydraulic binder material in building construction and façade ornamentation. Size and heterogeneous phase assemblage of unhydrated cement clinker remnants in historical cement stone differ significantly from those of remnants occurring in modern Portland cement clinker burnt in rotary kilns due to limitations of the production technology available in the 19th century (e.g., comminution and homogeneity of the feedstock, burning temperature and regime in the intermittently operated shaft kilns, grinding machinery). In the common analytical approach, thin sections and fracture surfaces of historical Roman and Portland cement mortars are characterised regarding their mineralogical composition and microstructure using optical and electron microscopic imaging techniques. Raman microspectroscopy can be additionally employed for petrographic examination, overcoming some limitations of the methods used so far. The determination of the phase content of residual cement clinker grains in the hydrated matrix allows for the differentiation of Roman and Portland cement binders. As marker phases, we propose the calcium aluminates CA, C12A7, C2AS and C3A – besides the commonly used calcium silicates C2S and C3S – because of their different formation temperatures and stability fields. This study focuses on the identification of different calcium aluminate and aluminoferrite phases in clinker remnants in samples of cast ornaments of three buildings in Switzerland raised between 1875 and 1893; the obtained Raman spectra are compared with fingerprint spectra of the corresponding pure, synthesised clinker phases collected with the same instrument for an unambiguous data interpretation. In addition to these phases, mainly minerals showing no hydraulic activity, such as, wollastonite CS, rankinite C3S2, free lime, portlandite, iron oxides, garnets, augite, albite and feldspathoids have been identified in the sampled historical cement stones by Raman microspectroscopy. As there is a strong relationship between coexisting clinker phases and the chemical composition of the raw meal as well as the burning and cooling history during clinkering, the results can help in understanding the physical and mechanical characteristics of historical cement mortars. This knowledge is fundamental for the choice and the formulation of appropriate repair materials with tailored properties employed in the field of restoration and preservation of the architectural heritage of the 19th and early 20th centuries.
Only a few scientific evidences for the use of Egyptian blue in Early Medieval wall paintings in Central and Southern Europe have been reported so far. The monochrome blue fragment discussed here belongs to the second church building of St. Peter above Gratsch (South Tyrol, Northern Italy, fifth/ sixth century A.D.). Beyond cuprorivaite and carbon black (underpainting), 26 accessory minerals down to trace levels were detected by means of Raman microspectroscopy, providing unprecedented insights into the raw materials blend and conversion reactions during preparation, application, and ageing of the pigment. In conjunction with archaeological evidences for the manufacture of Egyptian blue in Cumae and Liternum and the concordant statements of the antique Roman writers Vitruvius and Pliny the Elder, natural impurities of the quartz sand speak for a pigment produced at the northern Phlegrean Fields (Campania, Southern Italy). Chalcocite (and chalcopyrite) suggest the use of a sulphidic copper ore, and water-insoluble salts a mixed-alkaline flux in the form of plant ash. Not fully reacted quartz crystals partly intergrown with cuprorivaite and only minimal traces of silicate glass portend solid-state reactions predominating the chemical reactions during synthesis, while the melting of the raw materials into glass most likely played a negligible role.
The discussed comparative analyses of Roman Imperial pigment balls and fragmentary murals unearthed in the ancient cities of Aventicum and Augusta Raurica (Switzerland) by means of Raman microspectroscopy pertain to a predecessor study on trace compounds in Early Medieval Egyptian blue (St. Peter, Gratsch, South Tyrol, Northern Italy). The plethora of newly detected associated minerals of the raw materials surviving the synthesis procedure validate the use of quartz sand matching the composition of sediments transported by the Volturno river into the Gulf of Gaeta (Campania, Southern Italy) with a roasted sulphidic copper ore and a mixed-alkaline plant ash as fluxing agent. Thus, the results corroborate a monopolised pigment production site located in the northern Phlegrean Fields persisting over the first centuries A.D., this in line with statements of the antique Roman writers Vitruvius and Pliny the Elder and recent archaeological evidences. Beyond that, Raman spectra reveal through gradual peak shifts and changes of band width locally divergent process conditions and compositional inhomogeneities provoking crystal lattice disorder in the chromophoric cuprorivaite as well as the formation of a copper-bearing green glass phase, the latter probably in dependency of the concentration of alkali flux, notwithstanding that otherwise solid-state reactions predominate the synthesis.
The use of high-fired gypsum as binder for masonry and joint mortars or stuccowork in Central Europe in the Early and High Middle Ages was a regional specific as it depended on local gypsum deposits. The calcination technology possible at the time resulted in an assemblage of calcium sulphate phases dehydrated to different degrees and partly thermally damaged accessory minerals of the raw gypsum. Not hydrated clusters of firing products preserved in the binder matrix are a typical feature of such mortars. A novel Raman microspectroscopic approach, providing access to the burning history of individual anhydrite grains, was applied to samples from medieval South Tyrolean stucco decorations and sculptures. Beyond that, Raman microspectroscopy was employed for tracing and visualising pyrometamorphic reactions in natural impurities of the kiln run. In the discussed examples mineral thermometry indicates process temperatures above 800°C: the breakdown of magnesium-rich chlorite led to the formation of forsterite Mg2SiO4, while the thermal decomposition of dolomite CaMg(CO3)2 to periclase MgO and lime CaO yielded – after hydration and carbonation – magnesite MgCO3, CaCO3 polymorphs and magnesian calcite. Hydration of periclase in the mixed gypsum paste containing sulphate ions also resulted in magnesium sulphate hydrates, here identified in the form of hexahydrite MgSO4·6H2O. Lower burning temperatures left the accessory minerals in their pristine form, but can be traced by measuring the spectra of individual anhydrite crystals in grains of firing products and evaluating Raman band widths. Throughout the present study, calcination temperatures ranging from approx. 600°C to 900°C were determined.
Raman microscopic imaging was just recently introduced into the analysis of residual Roman and Portland cement grains in 19th century cement stone, displaying evidence of the experimental adaptation of contemporary technological knowledge and practice to local circumstance. Beyond calcium ferrites, this study deals with ferruginous clinker phases that are atypical compared to present-day commercial conditions of manufacture, such as iron oxides, clinopyroxenes or pyroxenoids. Analog, microtexture, mineralogy and chemical composition of pulverized ferrosilicate slag used in the course of the 19th century as mineral additive in lime mortar reflect local resource utilization, recording the melting history within the furnace and the effectiveness of the reduction process of a single smelting event. In the case of the discussed example, chemical imaging by Raman microscopy allowed deducing a lime-rich, low-silica melt exposed to fairly reducing conditions because of the detection of the pyrometallurgic phases fayalite (Fe2SiO4), kirschsteinite (CaFeSiO4) and calcioolivine (Ca2SiO4) in zoned olivine laths and (with the melilite gehlenite, Ca2Al2SiO7) in the Interstitial matrix, cross-cut by dendritic wuestite (FeO). The presented analytical approach faces the high spatial complexity of such mortar samples by microspectroscopic imaging with micrometer lateral resolution and their chemical complexity by extracting the rich chemical information content from Raman spectra. Intensity maps of marker bands provide spatial phase distributions. Furthermore, maps of peak positions can give access to the dissemination of spectroscopically similar phases of solid solution series (e.g., olivine and calcium Aluminate ferrite) as well as varying amounts of incorporated foreign cations (e.g., in hematite).
The study, dedicated to Beautiful Pietàs conserved in South Tyrol (Northern Italy), aims to establish, for the first time, a connection between Austroalpine raw materials and the high-fired gypsum mortars constituting the Gothic figure groups in question. The origin and chronology of this stylistically and qualitatively differing ensemble have been subject of art historical debate for nearly a century. The discourse is dominated by three main hypotheses: itinerary of an Austrian artist versus itinerary of the work of art created in an artist’s workshop in Austria versus itinerary of the stylistic vocabulary via graphical or three-dimensional models. The comparison of the δ34S values and the 87Sr/86Sr ratios of the gypsum mortars and Austroalpine sulphate deposits (in a compilation of own reference samples and literature data) points to the exploitation of sediments in the Salzkammergut and possibly also in the evaporite district of the Eastern Calcareous Alps, thus evidencing the import of the sculptures and not the activities of local South Tyrolean or itinerant artists. Two geochronological units are distinguishable: The Pietà in the Church St. Martin in Göflan can be assigned to Upper Permian raw material, whereas the metrologically consistent sculptures in the Church of Our Lady of the Benedictine Abbey Marienberg and in the Chapel St. Ann in Mölten correlate with deposits of the Early Triassic (or the Lower-Middle Triassic transition). The medieval gypsum mortars also differ in their mineralogical characteristics, i.e. in their geologically related minor components, as in the first case, characterised by a significant proportion of primary anhydrite, natural carbonate impurities mainly consist of calcite (partly converted to lime-lump-like aggregates), whereas in the second group dolomite (or rather its hydration products after pyrometamorphic decomposition) predominates, accompanied by celestine, quartz and potassium feldspar. The Pietà in the Cathedral Maria Himmelfahrt in Bozen turned out to be made of Breitenbrunn calcareous sandstone (Leitha Mountains, Burgenland, Austria), which is why the sample is not considered in the geochemical analysis.
The improved Monte-Carlo (MC) method for standard-less analysis in laser induced breakdown spectroscopy (LIBS) is presented. Concentrations in MC LIBS are found by fitting model-generated synthetic spectra to experimental spectra. The current version of MC LIBS is based on the graphic processing unit (GPU) computation and reduces the analysis time down to several seconds per spectrum/sample. The previous version of MC LIBS which was based on the central processing unit (CPU) computation requested unacceptably long analysis times of 10's minutes per spectrum/sample. The reduction of the computational time is achieved through the massively parallel computing on the GPU which embeds thousands of co-processors. It is shown that the number of iterations on the GPU exceeds that on the CPU by a factor > 1000 for the 5-dimentional parameter space and yet requires > 10-fold shorter computational time. The improved GPU-MC LIBS outperforms the CPU-MS LIBS in terms of accuracy, precision, and analysis time. The performance is tested on LIBS-spectra obtained from pelletized powders of metal oxides consisting of CaO, Fe2O3, MgO, and TiO2 that simulated by-products of steel industry, steel slags. It is demonstrated that GPU-based MC LIBS is capable of rapid multi-element analysis with relative error between 1 and 10's percent that is sufficient for industrial applications (e.g. steel slag analysis). The results of the improved GPU-based MC LIBS are positively compared to that of the CPU-based MC LIBS as well as to the results of the standard calibration-free (CF) LIBS based on the Boltzmann plot method.