XAFS study of copper and silver nanoparticles in glazes of medieval middle-east lustreware (10th–13th century)

It has recently been shown that lustre decoration of medieval and Renaissance pottery consists of silver and copper nanoparticles dispersed in the glassy matrix of the ceramic glaze. Here the findings of an X-ray absorption fine structure (XAFS) study on lustred glazes of shards belonging to 10th and 13rd century pottery from the National Museum of Iran are reported. Absorption spectra in the visible range have been also measured in order to investigate the relations between colour and glaze composition. Gold colour is mainly due to Ag nanoparticles, though Ag⁺, Cu⁺ and Cu²⁺ ions can be also dispersed within the glassy matrix, with different ratios. Red colour is mainly due to Cu nanoparticles, although some Ag nanoparticles, Ag⁺ and Cu⁺ ions can be present. The achievement of metallic Cu and the absence of Cu²⁺ indicate a higher reduction of copper in red lustre. These findings are in substantial agreement with previous results on Italian Renaissance pottery. In spite of the large heterogeneity of cases, the presence of copper and silver ions in the glaze confirms that lustre formation is mediated by a copper- and silver-alkali ion exchange, followed by nucleation and growth of metal nanoparticles.     

A TEM study of nanoparticles in lustre glazes

Transmission electron microscopy (TEM) has been used to investigate the nanoscale morphology of some contemporary lustre glazes. High-resolution TEM, electron energy-loss spectroscopy and energy-dispersive X-ray analysis data imply that two kinds of nanoparticles are present in the lustre layer, namely metallic Ag and metallic Cu particles. Moreover, these particles appear separated in the material. The dense top layer consists of Ag particles and the particles occurring below this upper layer are metallic Cu. A depth profile of the sizes of the nanoparticles with respect to their penetration depths has been drawn. The particle sizes are mainly situated in the range of 5 nm to 15 nm, though smaller and larger particles occur frequently. PACS 68.37.Lp; 61.46.+w; 81.05.Pj; 79.20.Uv     

Two-dimensional isotropic orientational glasses: a computer-simulation study

The analogue of the Edwards-Anderson model for isotropic vector spin glasses, but taking three-component quadrupoles instead of spins at each lattice site, is studied on the square lattice with extensive Monte Carlo calculations, using a nearest-neighbor symmetric gaussian interaction.It is shown that at low temperaturesT the model develops a short range order both with respect to glass like correlations and with respect to ferromagnetic correlations among the quadrupoles. The associated correlation lengths and susceptibilities diverge asT0, and the critical exponents for this zero-temperature phase transition are estimated.Dynamic correlation functions are analyzed as well and it is shown that the dacay of spatially displaced correlations displays a Kohlrausch-Williams-Watts behavior similar to the self-correlation function of the quadrupole moments.Some quantities are compared to their corresponding counterparts on the threedimensional simple cubic lattice, which also has a zero-temperature transition but at corresponding temperatures has stronger short-range-order.     

Raman spectrometry,a unique tool to analyze and classify ancient ceramics and glasses

Raman micro/macro spectroscopy allows a non-destructive remote analysis: body and glaze, crystalline and amorphous phases can be identified, including the nanosized pigments coloring the glaze. Last-generation instruments are portable, which allows examination in museums, on archaeological sites, etc. This paper gives an overview of the potential of the Raman-spectrometry technique to analyze ancient ceramics and glasses. Selected glasses as well as glazes of various porcelains, celadons, faiences and potteries, representative of the different production technologies used in the Ancient, European, Mediterranean, Islamic and Asian worlds, were studied. Their identification is based on the study of the Raman fingerprint of crystalline and glassy phases. Raman parameters allow for the classification as a function of composition and/or processing temperature. Special attention is given to the spectra of amorphous and coloring phases (pigments). PACS 81.05.Kf; 81.70.Fy; 81.05.Je; 01.65.+g     

Copper blue in an ancient glass bead: a XANES study

The blue colour in ancient soda-lime glasses has been attributed to the presence of copper and/or cobalt but the origin of different shades is not yet fully interpreted. As a contribution to this question, a non-destructive X-ray absorption study at [ _Cu]K-edge was undertaken on the blue (turquoise) layer from a “Nueva Cadiz” type tubular glass bead dated pre-XVII century where copper is the unique colouring agent. Minerals configuring two distinct blue tonalities due to Cu (2+) in similar square coordination were selected as basic model compounds: azurite, which is a classical navy-blue pigment used in ancient wall paintings over plaster, and chalcanthite, displaying exactly the same turquoise-blue tonality of tubular glass beads manufactured since the Egyptian Antiquity. Theoretical modelling of the XAFS spectra was undertaken using the FEFF code. The IFEFFIT software package was used for fitting the calculated spectra to experimental data. EXAFS results are discussed in view of the crystal structures of copper minerals chosen to model the speciation state and structural situation of that element prevailing in the turquoise-blue archaeological glass. Special attention is focused on the difficulties in theoretical modelling [ _Cu]K-XANES spectra of ancient glasses with different colourings. PACS 61.43.Fs; 61.46.+w; 41.60.Ap; 61.10.Ht.     

The cleaning of early glasses: investigation about the reactivity of different chemical treatments on the surface of ancient glasses

X-ray photoelectron spectroscopy (XPS) has been used to evaluate the reactivity of different chemical cleaning procedures on the surface of archaeological glasses. Investigations were performed on a series of Roman glass samples coming from Sicilian excavations. The ancient freshly fractured glass samples were subjected to different cleaning protocols such as piranha solution (solution of sulphuric acid and hydrogen peroxide) and EDTA/ammonia and citric acid/ammonia solutions at different pH values. The atomic concentrations of alkaline and alkaline-earth ions, measured using XPS spectra acquired at the surface of all the samples, revealed that, in acid solution, the reactivities of the EDTA and citric acid solutions were higher than that of the piranha solution. Moreover, in alkaline conditions, the reactivities of the chelating agent/ammonia solutions seem to be very high and effective in taking out alkaline and alkaline-earth ions and in destroying the external glassy structure with the formation of a silica gel thin film. PACS  61.43.Fs; 81.65.Cf; 61.66.Fn; 82.80.Pv     

The native development of ancient Chinese glassmaking: a case study on some early lead–barium–silicate glasses using a portable XRF spectrometer

In this paper, a portable energy‐dispersive X‐ray fluorescence spectrometer was used for the nondestructive analysis of 41 lead–barium–silicate glass artifacts dated from the Warring States Period to the Han Dynasties (475 BC–220 AD). These glasses mainly are ornament, funeral and ritual vessels unearthed from different provinces of China. Based on the chemical compositions obtained, the affects of surface weathering on the quantitative results, the characteristics of chemical compositions and the colorants were discussed. Meanwhile, referred to the research results reported and historical background, the raw materials, the distribution, the cause, the origin and the production center of the lead barium glass were also discussed. The present research provides new valuable information for tracing the origin and transfer of glassmaking techniques of ancient China. Copyright © 2015 John Wiley & Sons, Ltd.     

Copper red glazes: a coating with two families of particles

In order to explain the origin of the deep red color of copper glazes on ceramics, a ceramist has elaborated, by firing under reducing atmosphere, a significant number of tiles. The analysis of the structure and composition of a representative sample by transmission electron microscopy and electron energy loss spectroscopy, followed by an optical characterization and an optical modeling using the radiative transfer approach (four-flux model), have enabled a comprehensive explanation of the origin of the color in these glazes: the presence of two families of copper nanoparticles in the vitreous matrix. The first, purely absorbing, of diameter 10–50 nm, essentially creates color by a subtractive process. The second, due to its larger diameter, 100 nm or more, mainly acts on color by scattering of the visible light. Both act competitively in the layer. A color chart of all the hues which can be reached by this technique has eventually been theoretically calculated.     

Nondestructive identification of ancient Chinese glasses by Raman and proton-induced X-ray emission spectroscopy

Nondestructive Raman spectroscopy and external-beam proton-induced X-ray emission (PIXE) technique to analyze eight ancient glasses unearthed from the provinces of Henan,Hubei,and Jiangsu,which allowes for a good characterization of the glass matrix and chemical compositions,is carried out.The results indicate that all the eight glass samples could be typically divided into three systems: faience (sample No.SZWG-4),PbO-BaO-SiO 2 (sample Nos.NYWKI-5-1,HNWKII-88,and HNWKII-84),and Na 2 OCaO-SiO 2 (sample Nos.HBWKI-16,HBWKI-17,HBWKI-18,and SZWG-1).Additional relationships between the Raman spectra and parameters,such as residues of raw materials and opacifying agent,are also discussed by respectively comparing them with similar glass samples excavated from other historical sites.     

Ag–Ge–Se glasses: a vibrational spectroscopy study

Ag_x(Ge_0.25Se_0.75)_100−x glasses with x varying from 0 to 25 have been shown to exhibit a conductivity threshold around x ~8–10. In this work, the structural changes induced by introduction of Ag in Ge₂₅Se₇₅ glass have been investigated using Raman and infra‐red spectroscopies. In ambient conditions, changes are observed in position, width and intensity for vibrations assigned to Ge–Se bonds, showing that the tetrahedral network is relaxed and gains flexibility as Ag is introduced. High pressure experiments on two glasses containing 5 and 25 at.% Ag confirm that Ag‐rich (25%) glasses clearly exhibit higher compressibility than Ag‐poor (5%) glasses. Copyright © 2013 John Wiley & Sons, Ltd.     

EPR study of impurities in Ge-S glasses

In this paper the results of EPR investigation of Mn, Ag and Cu-doped Ge-S glasses are presented. In Ag and Cu-doped Ge₄₀S₆₀ glasses a new signal was found which is tightly associated with concentration of Ag and Cu. Some valuable information on the structure and the character of bonds in the glass-forming regions of Ge-S system were obtained. We have identified Ge [4 S] and Ge [2 Ge 2 S] tetrahedra as structural units in second glass-forming region of Ge-S system. In the first glass-forming region Ge [4 S] tetrahedra were identified as structural units, however, the nearest neighbours Ge-S distances are shorter and the character of bonds in Ge₂₅S₇₅ glass is much more covalent than in Ge₄₀S₆₀ one.     

ToF-SIMS and XPS study of ancient papers

The surface composition of 18th century papers was investigated by means of ToF-SIMS and XPS. The aim of the present study was to explore the possibility of using these surface sensitive methods to obtain information which can help to determine the manufacturing process, provenance and state of conservation of ancient papers. The ToF-SIMS results indicate that the analyzed papers were sized by gelatin and that alum was added as hardening agent. The paper sheets produced in near geographical areas but in different paper mills exhibit a similar surface composition and morphology of the fibers as shown by the ToF-SIMS measurements. The ToF-SIMS and the XPS results indicate that a significant fraction of the cellulose fibers is not covered by the gelatin layer. This was observed for the ancient papers and for a modern handmade paper manufactured according to the old recipes.     

Tribochemical reduction of Pb in Pb containing glazes: An ESCA investigation

Most white glazes, used in the ceramics industry for the coating of tiles, show deep, black scratches after tribological treatment with other glazes. Contrary to similar scratches produced during scraping with metals, these failures cannot be removed by polishing. ESCA investigations on Pb containing transparent and white glazes have shown unambiguously that during the tribological treatment the Pb in the surface of the glaze is partially reduced to metallic Pb which could at least partially explain the deep, black scratches seen on the tiles after the treatment.     

Molecular dynamics in concentrated sugar solutions and glasses: an NMR field cycling study

The frequency dependence of the proton longitudinal relaxation time in concentrated sugar in water solutions and glasses is compared with various theoretical models and used to derive correlation times characterizing the dynamic state of the water and sugar. It is shown that the water retains a high degree of molecular mobility even in the ‘sugar glass’, while the spectral density of the 3-dimensional glass lattice shows no evidence for a distribution of correlation times.     

XPS study on silica-bismuthate glasses and glass ceramics

X-ray photoelectron spectroscopy (XPS) was used to evidence the effect of the Bi₂O₃ to SiO₂ ratio and of partial crystallisation on the electronic charge density around the atoms entering silica-bismuthate glasses of nominal composition 0.01Fe₂O₃⋅0.99[xSiO₂⋅(100−x)Bi₂O₃] with . The core level spectra show significant composition dependent changes in binding energy, and the full width at half maximum of photoelectron peaks both of cations and of oxygen atoms. The analysis reveals changes in electron density correlated with the ionic and covalent character of the samples. The shift in binding energy suggests charge transfer from silicon and oxygen atoms to bismuth atoms. Contrary to the expected behaviour in conventional silicate oxide systems, the results indicate an increase of ionicity for silicon and of covalency for bismuth atoms. The same evolution of ionicity/covalency is observed after partial crystallisation.     

Comparative simulation study of colloidal gels and glasses

Using computer simulations, we identify the mechanisms causing aggregation and structural arrest of colloidal suspensions interacting with a short-ranged attraction at moderate and high densities. Two different nonergodicity transitions are observed. As the density is increased, a glass transition takes place, driven by excluded volume effects. In contrast, at moderate densities, gelation is approached as the strength of the attraction increases. At high density and interaction strength, both transitions merge, and a logarithmic decay in the correlation function is observed. All of these features are correctly predicted by mode coupling theory.