Opaque Glass Research Articles

The combined use of Raman and micro‐X‐ray diffraction analysis in the study of archaeological glass beads

AbstractThis study proposes a new nondestructive methodology that combines micro‐Raman spectroscopy and micro‐X‐ray diffraction (μ‐XRD), complemented by variable pressure scanning electron microscopy coupled with energy dispersive X‐ray spectrometry, to determine the composition of glass artifacts and the manufacturing techniques employed in their production. The use of micro‐Raman spectroscopy revealed that most samples belong to the alkaline glass family. Chemical analysis also allowed the identification of the main colorants used in the manufacture of the glass beads in this study. Dark blue and turquoise glass were colored using cobalt ions and copper ions, respectively. Amber or light brown hues were produced using the iron–sulfur amber chromophore. Iron ions were also used to produce green, yellow, cream‐colored gray, and black hues. White glass was produced using calcium antimonate phases. These compounds, identified by micro‐Raman spectroscopy and μ‐XRD, were also used as opacifying agents. This study highlights the importance of using micro‐Raman spectroscopy in the study of ancient glass artifacts. In fact, micro‐Raman spectroscopy not only allows the determination of the glass family of heavily degraded samples but was also found to be the only technique capable of identifying evidences of the rearrangement of the silicate network following selective leaching. The combined use of micro‐Raman spectroscopy and μ‐XRD permitted the identification of the opacifying agents and heat treatment used in the manufacture of the opaque glass beads in this study.

Ancient Roman nano-technology: Insight into the manufacture of mosaic tesserae opacified by calcium antimonate

Opaque mosaic glass tesserae containing calcium antimonates from Ancient Messene, Greece (1st–4th century CE) were investigated by scanning electron microscopy, Raman spectroscopy and X-ray diffraction. Both trigonal CaSb2O6 and cubic Ca2Sb2O7, with crystallite diameters below 1 μm, were identified as opacifying agents. To better understand ancient technologies, we prepared model glasses that were opacified by crystallisation via a secondary heat treatment, by direct crystallisation during the melting process, or by the addition of pre-reacted calcium antimonate to a base glass. We found that direct crystallisation replicated the antique glass artefacts most accurately.We demonstrated that 0.2 wt% of nucleating agents like TiO2 and SnO2 already exert significant influence on the crystallisation behaviour of calcium antimonates. Secondary scattering centres such as silica and carbonates contribute to the optical appearance. Concurrently, we reproduced opaque white glass ceramics in a reconstructed, wood-fired, Roman-type glass furnace built by Wiesenberg (2014).

Lines, spots and trails: a microscopic and mineralogical study of antimonate-opacified glass beads from Lofkënd, Albania

This study focuses on a group of decorated glass beads (twelfth–tenth century BC), belonging to a larger assemblage that was excavated from the prehistoric burial tumulus at Lofkend, Albania. The bulk glass, opaque glass decorations, and corroded areas were examined and analyzed using variable pressure-scanning electron microscopy with energy-dispersive spectroscopy (VP-SEM-EDS) and X-ray diffraction (XRD). The four glass beads analyzed were made using a plant ash-based alkali and colored with an iron containing chromophore which gave the glass its dark green color. Calcium antimonate was the predominant white opacifier used. Sodium antimonate was found as the opacifier in one sample. Its occurrence is likely accidental and formed due to a low concentration of calcium in the glass. Lead antimonate was identified in one sample and, along with calcium antimonate which was also present, would have acted as an opacifier for the white glass.

Clarity and brilliance: antimony in colourless natron glass explored using Roman glass found in Britain

This paper discusses the development of Roman antimony decolourised natron glass, its dominance, and subsequent decline, using new trace element data for colourless glass found in Britain. Experimental glasses are used to investigate the influence of different proportions of raw materials (particularly the ratio of natron to calcium carbonate) on the resulting transparency or opacity of glass when antimony is added. Focusing on the 1st to 3rd centuries AD, the study has found that (1) There are chronological differences in antimony colourless glass compositions including (a) some early vessels have abnormally low calcium, aluminium and barium levels; (b) 1st/mid-2nd-century AD vessels in Britain may also contain up to 0.6 wt% lead oxide whereas mid-2nd/3rd-century AD vessels contain less than 300 ppm, and (c) the antimony content tends to decline over time. (2) These developments can be linked to production and recycling practices; but trace elements suggest that all of these antimony colourless glasses share an origin, probably Egypt. (3) Crucially, production of experimental glasses illustrates the inherent suitability of a sodium-rich, calcium-poor base glass composition for making antimony colourless glass, as it readily dissolves added antimony; conversely lower-sodium, higher-calcium glasses start to form opacifying calcium-antimonate crystals with the same quantities of antimony. Thus, the sodium-rich, calcium-poor glass composition from Egypt was ideally suited for decolourising with antimony and formed a water-clear glass. The calcium-rich Syro-Palestine glasses were more easily opacified with antimony to make opaque glass, but were decolourised with manganese, not antimony.

Correlational examples for convolutional neural networks to detect small impurities

Abstract Convolutional neural networks have been significantly improving common object detection performances for a long time. However, targets across frames are independently detected in an image sequence, and object detection methods in multiple frames are generally divided into two main stages: object detection in every single frame and feature map association across frames. In this paper, a multi-frame detection framework is proposed to directly detect small impurities in opaque glass bottles with liquor. Specifically, a convolutional neural network trained with correlational examples simultaneously detects and correlates proposals, and then links them selectively to obtain robust detection results under challenging illuminations. Besides, memory costs of patch pairs become extremely large compared with those of patches, thus a sequential training procedure is introduced to relax hardware requirements. Extensive experiments on impurity datasets demonstrate superior performances of multi-frame detection frameworks with convolutional neural networks than traditional single-frame models.

Caracterización y estudio arqueométrico de un conjunto de vidrios de la edad del hierro de la necrópolis de palomar de pintado (Toledo, España)

Un importante conjunto de vidrios se ha hallado recientemente en la necrópolis de la Edad del Hierro de Palomar de Pintado (Toledo, España). Los vidrios se asocian a tres de las cinco fases cronológicas y se fechan principalmente entre los siglos V y III a.C. Se presentan los resultados de un estudio arqueométrico cuyos objetivos consistieron en determinar su composición química, su tecnología de producción y su posible procedencia geográfica. Se utilizaron técnicas convencionales como microscopía óptica (MO), microscopía electrónica de barrido de emisión de campo (MEBEC) junto con microanálisis de dispersión de energía de rayos X (EDS), difracción de rayos X (DRX) y espectrofotometría UV-visible. Los resultados indicaron que en su mayoría se trataba de vidrios LMG (low magnesium glass) de silicato sódico cálcico de base natrón, procedentes probablemente del Mediterráneo Oriental. Una de las muestras resultó ser un vidrio opaco de color rojo con elevado contenido de PbO y presencia de cristalizaciones de cuprita (vidrio de aventurina de cobre). El hallazgo de un conjunto de vidrios de procedencia foránea en un contexto funerario sugiere que el vidrio era un bien de prestigio para las comunidades de la Edad del Hierro peninsular.

도시형생활주택의 범죄예방환경설계 계획을 위한 국외사례 조사 및 분석 : 북유럽(덴마크, 스웨덴) 주거단지 사례를 중심으로

Purpose: The purpose of this study was to undertake on-site surveys of large scale multi-purpose residential complexes applied with CPTED in Northern Europe (Denmark and Sweden), develop an understanding of the applications of crime prevention through environmental design according to the basic principles of CPTED, and explore planning guidelines that may be applied to urban housing in South Korea. Method: For the purposes of directly surveying CPTED applied residential complexes on-site in Northern European countries and to take photographs of designs applied with CPTED, candidate sites were selected based on the following research method. First, for the purpose of identifying CPTED applied residential complexes among Northern European countries, a keyword search on a search engine was undertaken. Second, for the purpose of extracting specific names and locations of residential complexes of the identified CPTED applied cases found through the initial keyword search, a second keyword search was undertaken. Third, for the purpose of selecting effective case sites among the extracted residential complexes, candidate sites were further examined through Google Street View in Google Maps. Fourth, three residential complexes were selected and further analysis and study regarding the applications of CPTED according to basic CPTED principles in the selected complexes were undertaken. Results: Through case studies of Northern European residential complexes, the following conclusions were reached. First, streetlamp type lights were installed along pedestrian walkways to enable natural surveillance and the lights were installed at consistent intervals to maintain visual continuity. Building arrangements, building entry and exit points, and staircases were planned to face pedestrian walkways to induce the possibility of natural surveillance from pedestrian walkways. In the case of the staircases, the walls enclosing the staircase were finished with a mix of transparent and opaque glass in consideration of privacy issues. In the case of the Hammarby complex, the elevator hall facade was finished with glass to allow natural surveillance of the insides of the moving elevators. Second, for the purpose of strengthening territoriality, all three complexes included an easily accessible and natural surveillance-enabled courtyard or recreational space in the front area of the residential building. In the case of the pedestrian walkway, patterned blocks and various colors were used to strengthen territoriality. Third, regarding access control, entrance and exit doorways of residential buildings were installed with entry and exit control systems, and signs indicating CCTV installations and surveillance in the form of neighbor to neighbor vigilance were installed. Fourth, regarding support for activities and maintenance, the activity levels of a space were enhanced through a space that combines both functions.

Multi-technique characterisation of medieval mastic encrustation sculptures

Mastic incrustation sculptures were used to decorate different types of objects by filling the marble incisions with an impasto containing materials such as crushed pottery, glass or rock fragments, possibly in combination with organic substances, and was employed both in Byzantine and Occidental areas. From the 11th century onwards these sculptures are applied in important churches such as San Marco in Venice (Italy), but, despite their widespread use and conservation problems, the composition of these amalgams has never been thoroughly studied.Here we present the results of the examination of the mastic encrustations present on the medieval marble panels and precious cathedra in the San Nicola church of Bari (Italy). The matrix was analysed with Fourier transform infrared spectroscopy and pyrolysis gas chromatography-mass spectrometry. Organic binders were found and, in particular, the occurrence of heated Pinaceae resin, as well as of beeswax was assessed. The inclusions, including different types of rock, carbon black and opaque glass fragments, were characterised with optical microscopy, scanning electron microscopy, and powder X-ray diffraction. Micro-Raman spectroscopy was carried out on both inclusions and matrix.

Copper-based opaque red glasses – Understanding the colouring mechanism of copper nanoparticles in archaeological glass samples

Red opaque glasses of two different sites in central Germany, a medieval glassworks in Glashütten, Taunus Mountains, and an early modern glassworks in Wieda, Harz Mountains, were analysed with regard to their optical appearance. By scanning electron microscopy and X-ray diffraction, metallic copper nanoparticles were identified as a conspicuous constituent in these glasses. In addition, similar opaque red glasses were reproduced in the laboratory in order to better understand the manufacturing process. Detailed analysis of the optical scattering was conducted in order to evaluate the role of Cu0 nanoparticles in the colouring mechanism relative to other possible reasons of colouration.We find clear differences between the possible contributions of Cu2O (cuprite) particles and metallic copper (Cu0) nanoparticles. Through simulated backscattering spectra we were able to calculate an average copper particle radius in the archaeological glass samples resulting in a value of up to 95 nm, which matches well the results of SEM investigation (minimum 65 nm). Using the methods we applied in this study, it becomes possible to reconstruct various processing conditions as they were applied in medieval manufacture of these particular materials.

Colourants and opacifiers of mosaic glass tesserae from Khirbet al-Mafjar (Jericho, Palestine): addressing technological issues by a multi-analytical approach and evaluating the potentialities of thermoluminescence and optically stimulated luminescence dating

The paper discusses data concerning the secondary manufacture technology of a set of opaque coloured early Islamic mosaic glass tesserae from the qasr of Khirbet al-Mafjar (Jericho, Palestine). Archaeological contextualisation of the site had allowed attributing these finds to the Umayyad occupational phase of the building, and an in-depth study of the composition of the glassy matrix had provided evidence of a double supply of glass from Egypt and the Syro-Palestinian coast occurring in the production of the base glass intended to be used for the manufacture of mosaic tesserae. Here, a multi-methodological approach has been carried out to characterise colourants and opacifiers: visible reflectance spectroscopy (VIS-RS), optical microscopy (OM), scanning electron microscopy coupled with energy dispersion analysis (SEM-EDS), micro-Raman spectroscopy (micro-Raman) and X-ray diffraction (XRD) were performed on the opaque tesserae. Moreover, either optically stimulated luminescence (OSL) or thermoluminescence (TL) protocols for luminescence dating were applied on selected samples, with the aim of relating luminescence properties with the geochemical features of the glass tesserae, in the perspective of deepening the studies towards the absolute dating, an unquestionable help to the stimulating challenge of investigating ancient glass manufacture. Tin-based, phosphorus-based and copper-based opacifiers were identified, and the achieved results suggest the use of the same opacifiers and colouring agents regardless of the different base glass. Furthermore, data obtained by TL and OSL protocols revealed useful and stimulating potentialities these techniques could have in dating opaque glasses.

Compositional study of Byzantine glass bracelets discovered at the Lower Danube

Twenty three glass bracelets fragments of different colors and appearances excavated at Păcuiul lui Soare, Dobrogea, Romania and dated to the 10th–11th century AD were analyzed for their chemical composition using Particle-Induced X-ray Emission (PIXE) and Particle-Induced Gamma-ray Emission (PIGE) techniques at AGLAE accelerator of Centre de Recherche et de Restauration des Musées de France (C2RMF), Paris.Analytical data showed that all bracelets are soda-lime-silica glass of intermediate recipes, with compositional patterns between the natron and plant ash ranges, indicating practices of extensive glass recycling. Păcuiul lui Soare glass bracelets turned out to be similar in composition with the ones found in other nearby coeval sites, but also with bangles discovered in more remote Byzantine sites. The analyses revealed that the same technological choices have been made to produce the bracelets, namely they have been produced in workshops that had access to vitreous artefacts of different compositions, i.e. produced using distinct types of fluxes. Recycling seem to be a characteristics for all glass bangles produced in the Byzantine Empire at the end of the first millennium AD, regardless of their finding place and dating.As concerning the glass color, blue hues in Păcuiul lui Soare were induced by the presence of small amounts of cobalt (hundreds of ppm), while the green and black colors were correlated to high concentrations of iron. Opaque red glass stripes turned out to be rich in copper.The most likely candidate for the pale yellow pigment decorating the outer surfaces of several bracelets was identified as lead tin yellow.Producing these bangles by apparently indiscriminate procedures of glass re-melting involves a certain degree of ease and this might explain the discovery of such an outstanding number of glass bracelets in all the Byzantine sites from the Lower Danube.

Purple haze: Combined geochemical and Pb-Sr isotope constraints on colourants in Celtic glass

The composition of 2977 Late Prehistoric glass objects was investigated to derive information on the nature of the colourants used. 2673 Late Iron Age Celtic (La Tène) bracelet fragments from the Netherlands and Austria and 51 Early Iron Age beads from the Netherlands were analysed. Hand-held XRF analyses demonstrated that all glass objects were of the soda-silica-lime type, which has a presumed origin in the Eastern Mediterranean. Copper was used as colourant, in the form of copper filings, in most of the Early Iron Age glass beads to give recycled glass a blue-green colour.The vast majority (98%) of the translucent Iron Age glass, was coloured using cobalt (blue), manganese (purple; colourless), antimony (colourless) and iron (green). Manganese, however, was added to all glass, contributing additional amounts of elements like copper, cobalt and iron. Opaque decorations were produced using antimony, or a combination of tin and lead.REE analyses on a selection of representative objects indicate that the manganese ores in translucent glass are of hydrogenetic-diagenetic (Early Iron Age) or hydrothermally influenced diagenetic (Late Iron Age) types. Strontium isotope ratios show mixing between a calcite-related seawater source (0.709) and manganese ores with isotope ratios of ∼0.70766. Lead isotope ratios are dominated by colourant-derived Pb. The isotope ratios of the manganese used to produce translucent glass and lead used for opaque glass decorations fall in the same range. The most likely general provenance of both lies on Lavrion or the Western Cycladic Islands, although an origin in the central Taurus or the Sinai mountains cannot be excluded. The conclusion is that manganese ore used for colourants contributes significantly to the REE concentration in the glass, including Nd, as well as to Sr and Pb. This needs to be taken into account when using concentrations or isotope ratios of these elements for provenancing other raw materials like sand and calcium carbonate. This appears to be the case for all antique soda-lime-silica glass.

Synthesis and structure of transparent zinc-niobate-tellurite glasses with low hydroxyl content

Low-hydroxyl (OH)-content, transparent zinc-niobate-tellurite glasses (TeO2-Nb2O5-ZnO and TeO2-Nb2O5-ZnCl2) were synthesized by using dry-air atmospheres, stirring of the melt, and preheat treatment before melt preparation. A low OH level (79.8±6.3ppm) was achieved by performing a preheat treatment of mixed raw chemicals with zinc chloride and then melting in both open- and dry-air atmospheres with several counts of intermittent stirring. However, this sequence of processes resulted mainly in non-crystallized, opaque products. The basis of this opacity was investigated by performing Raman spectroscopy, X-ray diffraction (XRD), and X-ray fluorescence (XRF) measurements on both the opaque and transparent glasses. Raman spectroscopy revealed that the proportion of Te–O–Te bonds, relative to tellurite unit structures (TeO4, TeO3+1, and TeO3), in the opaque glasses decreased with increasing isolated structures of TeO32−. This decrease resulted possibly from atomic-scaled inhomogeneity and immiscible domain formation in the melts and corresponding glasses, which have less amounts of residual OH groups.

Ion beam analysis of glass inlays from the Staffordshire Anglo-Saxon Hoard

The glass inlays in six objects from the Staffordshire Hoard were subjected to compositional analysis by proton induced X-ray and gamma ray emission (PIXE and PIGE) at AGLAE, Paris. The opaque blue and white glasses are of a natron-based composition and are very likely to be reused and reworked Roman glass, possibly mosaic tesserae. The opacifiers used in their production are also those expected for Roman glasses. These glasses share some compositional parallels with the opaque glasses analysed from the Anglo-Saxon Sutton Hoo ship burial. The transparent red glasses in the Staffordshire Hoard have a similar base composition to the opaque blue and white glasses, but with elevated potash and magnesia levels. Glass in this group also appears to have been made of natron glass, but with the addition of what was probably a plant ash. It is possible that this addition was made to extend the amount of glass available to northern European craftsmen. The discovery of transparent red glass in millefiori with a composition related to Anglo-Saxon vessel glass suggests that these millefiori were being produced by contemporary north-western European, and possibly Anglo-Saxon, glass workers.

Vitreous tesserae from the calidarium mosaics of the Villa dei Quintili, Rome. Chemical composition and production technology

The archaeological excavation of the Villa dei Quintili in Rome (2nd century AD) brought to light one of the most impressive residential complexes of the Roman Empire. Among the astonishing number of findings, inside and outside the buildings, a large amount of glass mosaic tesserae were gathered from the thermal bath environments. This work reports the results of a microtextural and microchemical characterization of 29 colored opaque glass tesserae, by using an analytical approach that included the use of scanning electron microscopy with energy-dispersive X-ray spectroscopy, laser ablation-inductively coupled plasma-mass spectrometry. The glass is usually a soda-lime-silicate glass, with the exception of red and orange glass tesserae, which showed the typical composition of lead glasses mixed with plant ashes. Red tesserae were likely produced with a natron-based glass mixed with plant ashes, acting as flux and reducing agent. The opacifiers were all antimony-based with different natures according to the chemical composition: calcium antimonates (white in color) and lead antimonates (yellow in color).In the 29 tesserae studied in this research, the colors of glass were strictly correlated to the concentrations of coloring agents, the two main coloring ions identified were copper, introduced in the majority of samples as bronze scrap, and cobalt. Finally, the levels of trace elements indicate the use of mature sand, rich in quartz and poor in heavy metals and clay minerals, for the production of all samples.

Sub-nanometer glass surface dynamics induced by illumination.

Illumination is known to induce stress and morphology changes in opaque glasses. Amorphous silicon carbide (a-SiC) has a smaller bandgap than the crystal. Thus, we were able to excite with 532 nm light a 1 μm amorphous surface layer on a SiC crystal while recording time-lapse movies of glass surface dynamics by scanning tunneling microscopy (STM). Photoexcitation of the a-SiC surface layer through the transparent crystal avoids heating the STM tip. Up to 6 × 10(4) s, long movies of surface dynamics with 40 s time resolution and sub-nanometer spatial resolution were obtained. Clusters of ca. 3-5 glass forming units diameter are seen to cooperatively hop between two states at the surface. Photoexcitation with green laser light recruits immobile clusters to hop, rather than increasing the rate at which already mobile clusters hop. No significant laser heating was observed. Thus, we favor an athermal mechanism whereby electronic excitation of a-SiC directly controls glassy surface dynamics. This mechanism is supported by an exciton migration-relaxation-thermal diffusion model. Individual clusters take ∼1 h to populate states differently after the light intensity has changed. We believe the surrounding matrix rearranges slowly when it is stressed by a change in laser intensity, and clusters serve as a diagnostic. Such cluster hopping and matrix rearrangement could underlie the microscopic mechanism of photoinduced aging of opaque glasses.

Seeing through the opaque glass, darkly: farmers' perception of climate change

Emergent scientific facts about climate change occurrence, increasing intensity and potential damage to the world have made the issue of policy a necessity objective. In spite of global effort, very little data have been collected and therefore very little is known about support or opposition to mitigation or adaptation policies at any level. Although there are claims that support or opposition to proposed climate policies will be greatly influenced by perceived risks, how this evolves for farmers in a developing country is not understood and may be intricately intertwined with individuals' interpretation of practical experience with climate change impacts. Using a checklist, specific issues relating to climate change are covered through focus group discussions. Results of data analysis show widespread awareness of climate change impacts, reasonable ability to describe its occurrence but lack of fair understanding of the causes of climate change. Impact occurrences from experience and historical accounts are identified determinants in farmers' awareness, concern and risk perception of climate change and thus factor in the identification of relevant policies and decision to support them. The responsibility for ensuring policy effectiveness is said to involve the participatory roles of the farmers themselves, government, non-governmental organizations and international agencies.

Spectroscopic properties of Eu3+/Nd3+ co-doped phosphate glasses and opaque glass–ceramics

This paper reports the fabrication and characterization of Eu3+/Nd3+ co-doped phosphate (PNE) glasses and glass–ceramics as a function of Eu3+ concentration. The precursor glasses were prepared by the conventional melt quenching technique and the opaque glass–ceramics were obtained by heating the precursor glasses at 450°C for 30h. The structural and optical properties of the glass and glass–ceramics were analyzed by means of X-ray diffraction, Raman spectroscopy, UV–VIS–IR absorption spectroscopy, photoluminescence spectra and lifetimes. The amorphous and crystalline structures of the precursor glass and opaque glass–ceramic were confirmed by X-ray diffraction respectively. The Raman spectra showed that the maximum phonon energy decreased from 1317cm−1 to 1277cm−1 with the thermal treatment. The luminescence spectra of the glass and glass–ceramic samples were studied under 396nm and 806nm excitation. The emission intensity of the bands observed in opaque glass–ceramic is stronger than that of the precursor glass. The luminescence spectra show strong dependence on the Eu3+ ion concentration in the Nd3+ ion photoluminescence (PL) intensity, which suggest the presence of energy transfer (ET) and cross-relaxation (CR) processes. The lifetimes of the 4F3/2 state of Nd3+ ion in Eu3+/Nd3+ co-doped phosphate glasses and glass–ceramics under 806nm excitation were measured. It was observed that the lifetimes of the 4F3/2 level of Nd3+ of both glasses and glass–ceramics decrease with the increasing Eu3+ concentration. However in the case of opaque glass–ceramics the lifetimes decrease only 16%.

Revisiting the beginnings of tin-opacified Islamic glazes

The generally accepted theory is that the demand for Islamic glazed pottery started in Abbasid Iraq in the 9th century AD with the production of a range of glazed wares in response to the import of Chinese stonewares and porcelains. However, Oliver Watson has recently proposed that the demand for Islamic glazed pottery first occurred in Egypt and Syria in the 8th century AD resulting in the production of opaque yellow decorated wares. Using a combination of SEM analysis of polished cross-sections, and surface analysis using hand-held XRF or PIXE, Coptic Glazed Ware from Egypt, Yellow Glazed Ware from Syria, and comparable wares from Samarra, Kish and Susa have been analysed. The analyses show that the opaque yellow decoration was the result of lead stannate particles in a high lead glaze, which it is suggested was produced using a lead-silica-tin mixture. The use of lead stannate in the production of yellow opaque glazes is explained in terms of technological transfer from contemporary Islamic glassmakers who continued the Byzantine tradition of glassmaking. It is further argued that the introduction of opaque yellow glazed pottery into Mesopotamia could have provided the social context for the sudden emergence of tin-opacified white glazed pottery in Abbasid Iraq in the 9th century AD. However, in view of the very different glaze compositions employed for the yellow and white opaque glazes, it seems probable that the white tin-opacified glazes used for Abbasid cobalt blue and lustre decorated wares represent a separate but parallel technological tradition with its origins in the production of Islamic opaque white glass.

Effects of In-situ Generated Coinage Nanometals on Crystallization and Microstructure of Fluorophlogopite Mica Containing Glass‒Ceramics

The effects of in-situ generated coinage nanometals (Cu, Ag and Au) on crystallization behavior, microstructure, thermal and mechanical properties of SiO2–MgO–Al2O3–B2O3–K2O–MgF2 (BMAPS) glass‒ceramics were systematically studied. On addition of coinage nanometal, the glass transition temperature (Tg) is increased by 20–30 °C, crystallization temperature (Tc) by 30–50 °C and dilatometric softening temperature (Td) by 10–25 °C. It was found that the density of Cu-containing glass was 2.59 g cm−3 and for other glasses it was in the range of 2.56–2.57 g cm−3. From the non-isothermal differential scanning calorimetry study, the activation energy of crystallization for BMAPS base glass was calculated as 344 kJ/mol, and changed to 406, 334 and 274 kJ/mol on addition of Cu, Ag and Au-nanometals, respectively. Crystals evolved in the opaque BMAPS glass‒ceramics derived by controlled heat treatment, were identified as fluorophlogopite mica (KMg3(AlSi3O10)F2) by X-ray diffraction (XRD) technique and confirmed by Fourier transformed infrared spectroscopy. Presences of copper, silver and gold nanometals were also identified by XRD technique. It is found from field emission scanning electron microscopy that the interlocked grain like microstructure developed in BMAPS glass‒ceramics (being heat-treated at 1050 °C for 4 h) changed to denser house-of-cards like microstructure (containing smaller sized mica crystals) on addition of coinage nanometals. Density of BMAPS base glass‒ceramic was 2.60 g cm−3 and marginally changed to 2.61–2.62 g cm−3 on addition of Cu, Ag and Au-nanometals. The change in microstructure resulted in the decrease of Vickers micro hardness value from 5.37 to 4.12, 4.20 and 4.58 GPa on addition of Cu, Ag and Au, respectively. Coinage nanometal doped mica glass‒ceramics containing interlocked microstructure with higher thermal expansion coefficient, hence, is suitable for high temperature sealing application (like solid oxide fuel cell).