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1
Borges, Roger, Natália Del Rey Menezes et Juliana Marchi. « The influence of gadolinium on the thermal properties of bioactive glasses ». Biomedical Glasses 5, no 1 (1 janvier 2019) : 193–202. http://dx.doi.org/10.1515/bglass-2019-0016.
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Abstract Rare Earth (RE)-containing bioactive glasses has recently gained more relevance in the field of biomaterials due to the unique optical, electronic, and chemical properties of the RE elements. In this work, the influence of gadolinium in the thermal properties of bioactive glasses based on the SiO2-Na2O-CaO-P2O5 containing different Na/Ca ratio was studied. The glasses were obtained by melting-quenching, and their properties were evaluated by differential thermal analysis, X-ray diffraction, and scanning electron microscopy. The results evidenced that Gd tends to increase the working temperature (Tc-Tg) in Ca-rich glasses, which leads to a less tendency to devitrification. On the other hand, in Na-rich glasses, Gd did not play an essential role in crystallization, and the thermal properties of Gd-containing Na-rich glasses were similar to their counterparts. In conclusion, we suggested that it is possible to control the influence of Gd in the glass devitrification by changing the Na/Ca ratio in the glass composition. These results may be interesting for further works to which crystallization may be either a desired or undesired phenomena.
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Gonzalez-Panicello, Laura, Ines Garcia-Lodeiro, Francisca Puertas et Marta Palacios. « Influence of Accelerating Admixtures on the Reactivity of Synthetic Aluminosilicate Glasses ». Materials 15, no 3 (21 janvier 2022) : 818. http://dx.doi.org/10.3390/ma15030818.
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This research aims at gaining a further understanding of the impact of accelerating admixtures on the reactivity of supplementary cementitious materials (SCMs), which are widely used as a clinker replacement in blended cements. This was done on synthetic glasses with controlled composition and structure that mimic two types of real SCMs (slag and calcium-rich fly ash). The effects of DEIPA, TIPA, NaSCN and Na2S2O3 on the glass dissolution, hydration kinetics and reaction products were investigated. The obtained results concluded that the pH of the NaOH solution and the composition of the synthetic glass play a key role on the effect of the admixtures. In 0.1 M NaOH (pH = 13.0), all the studied admixtures inhibited the dissolution of slag-like glasses while they enhanced the dissolution of Ca-rich fly ash-like glasses, being Na2S2O3 the admixture that led to the highest increase of the dissolution rate of the Ca-rich fly ash-type glasses. In 1 M NaOH solutions (pH = 13.8), only the alkali admixtures (NaSCN and Na2S2O3) enhanced the degree of reaction of both glasses. In slag-type glasses pastes mixed with 1 M NaOH, the addition of 2% Na2S2O3 induced the highest increase of their reactivity as inferred by the total heat release and the amount of bound water. This is related to the formation of a high amount of S(II)-AFm, in addition to C-A-S-H, that would increase the aluminium undersaturation of the pore solution and consequently the further dissolution of the glass.
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Mitchell, Roger H. « Coexisting glasses occurring as inclusions in leucite from lamproites : examples of silicate liquid immiscibility in ultrapotassic magmas ». Mineralogical Magazine 55, no 379 (juin 1991) : 197–202. http://dx.doi.org/10.1180/minmag.1991.055.379.07.
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AbstractInclusions occurring in leucites from the Oscar and Zirkel Mesa leucite lamproites consist of high (>10 wt.%) and low (<4 wt.%) K2O discrete glass phases which are interpreted to have resulted from silicate liquid immiscibility. Both glasses are quartz-normative and rich in Ti, Fe, Mg, Ca and Ba and poor in Al. The high-K glass is strongly peralkaline. Neither of the glasses have compositions representative of any known lamproites. These inclusions represent the first described examples of silicate-silicate immiscibility shown by glass in alkaline rocks.
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Fábián, M., Zs Kovács, J. L. Lábár, A. Sulyok, Z. E. Horváth, I. Székács et V. Kovács Kis. « Network structure and thermal properties of bioactive (SiO2–CaO–Na2O–P2O5) glasses ». Journal of Materials Science 55, no 6 (18 novembre 2019) : 2303–20. http://dx.doi.org/10.1007/s10853-019-04206-z.
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AbstractCa- and P-based bioactive glasses are excellent candidates for design and manufacture of biomaterials. Understanding the structure and physico-chemical–thermal behaviour of bioactive glasses is a fundamental step towards the design of a new generation of biocompatible materials. In this study, the structure of SiO2–CaO–Na2O glasses and its derivatives, obtained by substituting Na2O with P2O5 and prepared by melt–quench technique, was studied with neutron and electron diffraction techniques combined with thermal analysis, high-resolution electron microscopy and X-ray photoelectron spectroscopy. Neutron and electron diffraction data were analysed with reverse Monte Carlo simulation and pair distribution function analysis, respectively. Bioactivity of P2O5 substituted glasses was also investigated and proven in vitro using simulated body fluid. Based on the structural analysis, it was found that Si and P atoms are in well-defined tetrahedral units with a bond distance of 1.60 Å for both Si–O and P–O bonds, although P exhibits a higher average coordination number than Si. With increasing phosphate content, tendentious changes in the glass behaviour were observed. Linear increase in Tg, supported by the changes in the average coordination numbers of Si and P, indicates strengthening of network structure with increasing P content and formation of P–O–Ca atomic linkages, which lead to Ca–P-rich atomic environments in the silicate network. These Ca–P-rich environments trap volatile elements and thus decrease the total weight loss during heating at higher P concentrations. In the case of the highest investigated P2O5 content (5 mol%), nanoscale structural inhomogeneity and the formation of Ca–P-rich clusters were also revealed by electron diffraction and atomic resolution imaging. This type of Ca–(Na)–P clustering has a key role in the behaviour of phosphate-substituted silicate glasses under physiological conditions.
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MA, JIE, CHUANZHONG CHEN, DIANGANG WANG, XING DANG, RUILIANG BAO et LIANG YAO. « SURFACE BEHAVIOR OF BIOACTIVE GLASS OF Si–Na–Ca–P SYSTEM IN SIMULATED BODY FLUID ». Surface Review and Letters 14, no 01 (février 2007) : 49–55. http://dx.doi.org/10.1142/s0218625x07009062.
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Glass of the Si – Na – Ca – P system has been synthesized by normal melting and annealing technique. The obtained glass powders and annealed blocks were showed to be amorphous by X-ray diffraction (XRD). The thermal properties of glasses were analyzed by differential scanning calorimetry (DSC), it showed that the glass transformation temperature (Tg) was 556.3°C. The behavior of annealed glass discs in simulated body fluid solution (SBF) was studied in polyethylene containers at a constant temperature of 37°C for different time up to 14 days. The changes in the surface morphology and composition were observed by electronic probe microanalyzer (EPMA) associated with energy dispersive spectroscopy (EDS). Glass surface changed quickly as soon as immersion took place, and after longer soaking time, it showed different superimposed internal and external layers, which were identified as SiO 2-rich and CaO – P 2 O 5-rich layers, and on the external layer, spherical particles were also discovered.
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Silva, A. M. B., Rui N. Correia, J. M. Oliveira et Maria Helena F. V. Fernandes. « Effect of TiO2 and SiO2 on Surface Reactivity of Calcium Phosphate Glasses in Simulated Body Fluid ». Materials Science Forum 587-588 (juin 2008) : 138–42. http://dx.doi.org/10.4028/www.scientific.net/msf.587-588.138.
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This study compares the in vitro behaviour in SBF of glasses from two different systems, TiO2-CaO-P2O5 and SiO2-CaO-P2O5 with the same TiO2 and SiO2 molar content, in order to evaluate the effect of TiO2 and SiO2 on the surface reactivity of those glasses. The glass formation regions in both systems were observed for compositions with less than 40 mol% TiO2 and 40 mol% SiO2, respectively. Four glasses with similar TiO2 and SiO2 molar contents have been selected for comparison. These glasses are equimolar in CaO and P2O5 with TiO2 or SiO2 varying from 4 to 33 mol %. Powder glasses were immersed in Simulated Body Fluid (SBF) and kept at 37°C for different times, up to 14 days. Surfaces were observed by Scanning Electron Microscopy (SEM) and specimen ion leaching to SBF was studied by Inductively Coupled Plasma (ICP) spectroscopy. Preliminary spectroscopic studies by Raman were performed to identify the structure of the glasses. For glasses of the SiO2-CaO-P2O5 system a significant dissolution of all ions was observed together with the formation of phosphoric acid. In opposition, the immersion of TiO2-CaO-P2O5 glasses produced a small Ca consumption and stable Ti and P concentrations, indicating the formation of a Ca-P rich layer on these glasses. The observed differences in the dissolution behaviour are tentatively explained in terms of the glass structures obtained by spectroscopy.
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Laws, Kevin J., Jake D. Cao, Cyndy Reddy, Karl F. Shamlaye, Bulent Gun et Michael Ferry. « Ultra magnesium-rich, low-density Mg–Ni–Ca bulk metallic glasses ». Scripta Materialia 88 (octobre 2014) : 37–40. http://dx.doi.org/10.1016/j.scriptamat.2014.06.002.
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Li, Chao, Heng Hu Sun et Long Tu Li. « Glass Phase Structure of Blast Furnace Slag ». Advanced Materials Research 168-170 (décembre 2010) : 3–7. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.3.
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This paper studies the blast furnace slag glass phase structure by a series of analysis methods. In glass phase, both Si and Al ions are confirmed to occupy only tetrahedral sites, while the [SiO4]4- and [AlO4]5- are separated by Ca and Mg. Furthermore, the glass structure corresponds to micro-crystal model, which means it contains some nano-scaled micro-crystals in the glass phase. In addition, the slag glass may separate into two phases: a calcium rich phase and a silica rich phase. According to devitrification experiment, it has been inferred that the chemical composition and structure of silica rich phase are close to that of akermanite,which means most of Si is distribute around Mg.
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Imbert, T., et A. Desprairies. « Neoformation of halloysite on volcanic glass in a marine environment ». Clay Minerals 22, no 2 (juin 1987) : 179–85. http://dx.doi.org/10.1180/claymin.1987.022.2.06.
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AbstractTransmission electron microscopy of ultramicrotomed thin-sections of Pleistocene and Eocene glass shards revealed the neoformation of (i) illite and (ii) halloysite at the glass periphery. According to previous experimental studies, halloysite neoformation in marine environments can occur on glass shards deposited in Si-rich sediments; an excess of Ca tends to inhibit the reaction.
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Park, Eun Soo, Won Tae Kim et Do Hyang Kim. « Effect of Alloy Composition on the Glass Forming Ability in Ca-Mg-Zn Alloy System ». Materials Science Forum 475-479 (janvier 2005) : 3415–18. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.3415.
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The effect of alloy composition on the glass forming ability (GFA) of the Ca-Zn-Mg alloys has been investigated in the present study. The alloy compositions investigated are near Ca-rich ternary eutectic composition; Ca60Mg15Zn25, Ca65Mg10Zn25, Ca65Mg15Zn20, Ca65Mg20Zn15, and Ca70Mg15Zn15. Bulk metallic glass (BMG) samples with the diameter larger than 5 mm are fabricated by conventional copper mold casting method in air atmosphere. Among the parameters representing the glass forming ability, Trg and γ parameters exhibit good correlation with the maximum diameter of the fully amorphous structure in the alloy compositions investigated in the present study.
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Cheng, Lining, Chao Zhang, Xiaoyan Li, Renat R. Almeev, Xiaosong Yang et Francois Holtz. « Improvement of Electron Probe Microanalysis of Boron Concentration in Silicate Glasses ». Microscopy and Microanalysis 25, no 4 (18 juin 2019) : 874–82. http://dx.doi.org/10.1017/s1431927619014612.
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AbstractThe determination of low boron concentrations in silicate glasses by electron probe microanalysis (EPMA) remains a significant challenge. The internal interferences from the diffraction crystal, i.e. the Mo-B4C large d-spacing layered synthetic microstructure crystal, can be thoroughly diminished by using an optimized differential mode of pulse height analysis (PHA). Although potential high-order spectral interferences from Ca, Fe, and Mn on the BKα peak can be significantly reduced by using an optimized differential mode of PHA, a quantitative calibration of the interferences is required to obtain accurate boron concentrations in silicate glasses that contain these elements. Furthermore, the first-order spectral interference from ClL-lines is so strong that they hinder reliable EPMA of boron concentrations in Cl-bearing silicate glasses. Our tests also indicate that, due to the strongly curved background shape on the high-energy side of BKα, an exponential regression is better than linear regression for estimating the on-peak background intensity based on measured off-peak background intensities. We propose that an optimal analytical setting for low boron concentrations in silicate glasses (≥0.2 wt% B2O3) would best involve a proper boron-rich glass standard, a low accelerating voltage, a high beam current, a large beam size, and a differential mode of PHA.
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Tanaka, Hiromi, Hideki Yoshikawa, Masahiro Kimura, Chusei Tsuruta, Sei Fukushima, Yoshio Matsui, Shingo Nakagawa, Kentaro Kinoshita et Satoru Kishida. « Synthesis and Precise Analysis of Bi2Sr2Can-1CunOy Superconducting Whiskers ». Advances in Science and Technology 75 (octobre 2010) : 192–96. http://dx.doi.org/10.4028/www.scientific.net/ast.75.192.
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We synthesized Ca-rich Bi-based superconducting whiskers by an Al2O3-seeded glassy quenched platelet method. The grown whiskers were precisely characterized by synchrotron radiation X-ray photoemission spectroscopy and high-resolution transmission electron microscopy. The Ca-rich Bi-based superconducting whiskers show a high critical current density of 2×105A/cm2 at 40K in self-field. We found that excess Ca2+ ions substitute for the Sr2+ sites and cause nano crystalline domains with shorter-period modulation embedded in the base crystalline. The embedded nano crystalline domains can result in structural distorted defects which work as strong pinning center.
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Kokubo, T., S. Ito, Z. T. Huang, T. Hayashi, S. Sakka, T. Kitsugi et T. Yamamuro. « Ca, P-rich layer formed on high-strength bioactive glass-ceramic A-W ». Journal of Biomedical Materials Research 24, no 3 (mars 1990) : 331–43. http://dx.doi.org/10.1002/jbm.820240306.
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Duggan, M. B. « Babingtonite and Fe-rich Ca-A1 silicates from western Southland, New Zealand ». Mineralogical Magazine 50, no 358 (décembre 1986) : 657–65. http://dx.doi.org/10.1180/minmag.1986.050.358.11.
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AbstractBabingtonite is a common constituent of calcareous volcanic detritus in the interstices of pillow lavas from an outcrop of the Takitimu Group, western Southland, New Zealand, Associated minerals include Fe-rich prehnite (Fe/(Fe+Al) = 0.12–0.33), Fe-rich epidote (Ps24–53), grandite garnet (av. Andradite70 Grossular30), quartz, calcite, chlorite, and pumpellyite. Babingtonite shows little departure from its ideal composition other than minor Mg, Mn, and Al and a trace of Na.Textural evidence and microprobe data suggest that the babingtonite, Fe-rich epidote, calcite, and quartz formed from hydrothermal solutions by direct precipitation in open cavities and by replacement of higher temperature silicate phases (in particular plagioclase and basaltic glass) in a shallow marine volcanic environment. During subsequent burial and low-grade metamorphism babingtonite was partially replaced by prehnite, less Fe-rich epidote, grandite, and chlorite.
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Zhang, Y. N., G. J. Rocher, B. Briccoli, D. Kevorkov, X. B. Liu, Z. Altounian et M. Medraj. « Crystallization characteristics of the Mg-rich metallic glasses in the Ca–Mg–Zn system ». Journal of Alloys and Compounds 552 (mars 2013) : 88–97. http://dx.doi.org/10.1016/j.jallcom.2012.10.089.
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Ceglia, A., W. Meulebroeck, K. Baert, H. Wouters, K. Nys, H. Thienpont et H. Terryn. « Cobalt absorption bands for the differentiation of historical Na and Ca/K rich glass ». Surface and Interface Analysis 44, no 2 (23 septembre 2011) : 219–26. http://dx.doi.org/10.1002/sia.3810.
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Hu, Jiashan, D. K. Agrawal et R. Roy. « Investigation of hydration phases in the system CaO–SiO2-P2O5-H2O ». Journal of Materials Research 3, no 4 (août 1988) : 772–80. http://dx.doi.org/10.1557/jmr.1988.0772.
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Hydration reactions and their rates have been studied qualitatively in CaO-and P2O5-rich compositional regions of the system CaO–SiO2-P2O5-H2O. Using aqueous solutions of Ca (NO3)2–4H2O, Ludox, and H3PO4 as starting materials, amorphous powders made by the sol-gel process were reacted with water. Some “curing” reactions were carried out at several temperatures: room temperature, 90 °C, and under hydrothermal conditions. Some glasses in the phosphate-rich region of the system were also made and hydrated. The hydration products are OH–Ap [OH–Ap = Ca10(PO4)6-(OH)2], Ca(OH)2 [CH = Ca(OH)2],C–S–H crystalline, C–S–P–H (C = CaO,S = SiO2,P = P2O5,H = H2O) crystalline, C–S–H gel, C–S–P–H gel, Ca(H2PO4)2·H2O, and CaHPO4. All phases have been identified and characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray analysis (EDAX). The reactivities of the precursor materials and the compositional-structural nature of the hydration products formed are discussed. Some new compositions for “cementlike behavior” have been discovered.
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Lottermoser, B. G. « Mobilization of heavy metals from historical smelting slag dumps, north Queensland, Australia ». Mineralogical Magazine 66, no 4 (août 2002) : 475–90. http://dx.doi.org/10.1180/0026461026640043.
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AbstractSlag dumps occur at several historical smelting sites in north Queensland, Australia. The microcrystalline slags contain primary slag phases, relict flux, ore and furnace materials and secondary weathering related minerals. Common primary slag phases are glass, Zn-rich fayalite (± Zn-rich kirschsteinite) and Zn-rich hedenbergite. Other minor minerals include wollastonite, Zn-rich melilite, Zn-rich iscorite (Fe7SiO10), magnetite as well as a number of sulphides (pyrrhotite, galena, bornite, sphalerite, wurtzite), metallic phases (Ag, Cu, Pb, Sb), alloys (Cu3Sn), and unknown metal compounds. The slag materials contain wt.% concentrations of Zn and elevated levels of Ag, As, Cd, Cu, Ni, Pb, Sb and W. Glass, hedenbergite and fayalite/kirschsteinite are the main repositories of Zn, whereas much of the Cu and Pb is hosted by glass, sulphides, Cu3Sn alloys, metallic Cu and Pb, and unknown CuSb, AsSnPb and FeAsCu compounds. The slags are undergoing contemporaneous reaction with air and rainwater. The weathering results in the release of metals and metalloids from primary slag phases, particularly from glass, and the partial immobilization of these metals in secondary soluble and insoluble minerals in the slag heaps. Zinc exhibits pronounced chemical mobility and reports together with elevated Ca and sulphate into surface seepages (up to 10.2 mg l−1 Zn at pH 6.97). The slag dumps represent long-term sources of metal pollutants, particularly of Zn, to local ground and surface waters.
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Silvestri, Alberta, Fabrizio Nestola et Luca Peruzzo. « Manganese-Containing Inclusions in Late-Antique Glass Mosaic Tesserae : A New Technological Marker ? » Minerals 10, no 10 (3 octobre 2020) : 881. http://dx.doi.org/10.3390/min10100881.
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The present study focuses on manganese-containing inclusions identified in late-Antique glass tesserae, light brown/amber and purple in colour, from Padova (Italy), in order to clarify the nature of these inclusions, never identified in glass mosaics until now, and provide new insights on the production technologies of such kinds of tesserae. Multi-methodological investigations on manganese-containing inclusions were carried out in this work by means of optical microscopy (OM), scanning electron microscopy (SEM), micro-X-ray diffraction (micro-XRD), electron backscattered diffraction (EBSD), electron microprobe (EMPA), and micro-Raman spectroscopy. The combination of analytical results shows that inclusions are crystalline, new-formed phases, mainly composed of manganese, silica and calcium, and are mineralogically ascribed as a member of the braunite-neltnerite series, with unit-cell parameters closer to those of neltnerite. However, the low Ca content makes such crystalline compounds more similar to braunite, in more detail, they could be described as Ca-rich braunite. The occurrence of such crystalline phase allows us to constrain melting temperatures between 1000 and 1150 °C, and to hypothesize pyrolusite, MnO2, as the source of manganese. In addition, it is worth underlining that the same phase is identified in tesserae characterised by different colours (light brown/amber vs purple due to different manganese/iron ratios), glassy matrices (soda-lime-lead vs soda-lime) and opacifiers (cassiterite vs no opacifier). This suggests that its occurrence is not influenced by the “chemical environment”, revealing these manganese-containing inclusions as a new potential technological marker.
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Sellappan, Pathikumar, Ali Sharafat, Vincent Keryvin, Patrick Houizot, Tanguy Rouxel, Jekabs Grins et Saeid Esmaeilzadeh. « Elastic properties and surface damage resistance of nitrogen-rich (Ca,Sr)–Si–O–N glasses ». Journal of Non-Crystalline Solids 356, no 41-42 (septembre 2010) : 2120–26. http://dx.doi.org/10.1016/j.jnoncrysol.2010.07.043.
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Bailey, K., S. Kearns, J. Mergoil, J. Mergoil Daniel et B. Paterson. « Extensive dolomitic volcanism through the Limagne Basin, central France : a new form of carbonatite activity ». Mineralogical Magazine 70, no 2 (avril 2006) : 231–36. http://dx.doi.org/10.1180/0026461067020327.
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AbstractRecognition of widespread carbonate volcanism in central Spain has led to another case in France, of similar age (23–0 Ma) but with entirely new features. More than 100 new carbonate volcanoes are indicated already, adding a wholly unexpected dimension to this form of activity. Eruptions form layers, mostly of glassy nephelinite fragments in a dolomitic matrix, but some layers are largely dolomite. Major new findings are phenocrysts of dolomite, magnesite and calcite in silicate glass, and spectacular dolomite-nephelinite melt immiscibility, neither recorded previously. Most volcanic carbonatites are Ca rich, and dolomite is rare. The Limagne dolomites share links with those in Spain and Zambia, with chromite a hallmark in all three. Limagne is exceptional in being the first case where dolomite has erupted with co-genetic silicate melt. Mantle debris and magnesite indicate a source within ∼ 100–150 km. Chromite in the dolomite globules, and in the enclosing silicate glass, is similar to that in high-temperature kimberlites, indicating immiscibility in the deep mantle. Recognition of two large, previously undetected provinces of carbonate volcanism in Europe, where there has been active research for >200 y, must lead to the inference that similar cases may await discovery on other continents.
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Tomioka, Naotaka, et Makoto Kimura. « The breakdown of diopside to Ca-rich majorite and glass in a shocked H chondrite ». Earth and Planetary Science Letters 208, no 3-4 (30 mars 2003) : 271–78. http://dx.doi.org/10.1016/s0012-821x(03)00049-9.
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Gyollai, Ildikó, Ákos Kereszturi et Elias Chatzitheodoridis. « Analysis of shock metamorphic processes in the Zagami meteorite ». Central European Geology 62, no 1 (24 janvier 2019) : 56–82. http://dx.doi.org/10.1556/24.61.2018.12.
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The study of shock-metamorphic features of the Zagami meteorite revealed pseudotachylite-like melt veins with inhomogeneous chemistry and schlieren structure of silica-glass and alkali feldspar melt glass. The feldspar occurs as diaplectic glass in the interstitial area indicating short-time (few seconds) quenching of shock pressure during the impact event, with post-shock annealing. At several locations, apatite needles were identified, which are formed by fluids (cold water with dissolved ions) after the crystallization of cumulate magmatic minerals. Phosphates also could form in impact melts due to circulation of fluids after the impact event. The other signature for the high shock temperature is the presence of Ca–Ti-rich pyroxenes and titanomagnetite, which indicate temperature above 1,200 °C. The formation of silica-rich melt in interstitial area has two scenarios: (a) fractional melting of the Martian crust or (b) formation by pseudotachylite-like impact melting. According to textural observations (schlieren pattern), we propose an impact origin of the large amount of silica-rich melt in this meteorite. Pseudotachylite-like textures were mentioned earlier in terrestrial impact craters; however, we first propose them to form in a Martian meteorite based on their similarity of texture with terrestrial pseudotachylites.
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Mitchell, Roger H., et Anthony N. Mariano. « Primary phases in aluminous slags produced by the aluminothermic reduction of pyrochlore ». Mineralogical Magazine 80, no 2 (avril 2016) : 383–97. http://dx.doi.org/10.1180/minmag.2016.080.009.
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AbstractPhases present in slags from Araxá (Brazil), Oka (Quebec) and Fen (Norway) resulting from the production of ferroniobium by the aluminothermic reduction of pyrochlore-group minerals are a function of composition of the pyrochlore feed and the diverse fluxes (CaO, CaF2) added to the alumina and iron oxide used in the reduction process. Absent from all slags investigated are Fe-bearing compounds. All of the slags are modally-dominated by prismatic crystals of β-alumina or hibonite, with a wide variety of Th-Ba-Ti-Nb-Al-oxide compounds and silico-aluminate glasses occurring in the interstices between these crystals. Slag from Fen consists of a framework of β-alumina (Ba and/or CaTi varieties) with a barian titanian niobate, considered to be an highly reduced Nb3+- and Ti3+-bearing anion deficient perovskite, as the first oxide phase to crystallize. This was followed by a Zr-Ti-Th-niobate (21.7–24.1 wt.% ThO2), a Nb-rich, Thbearing zirconolite-like phase (17.7–21.2 wt.%; Nb2O5; 6.8–9.5 wt.% ThO2) and diverse Th-Nb-rich, Alpoor (< 1 wt.% Al2O3) perovskites (29.4–40.5 wt.% Nb2O5; 3.3–11.4 wt.% ThO2). The latter represents a NaNbO3–CaTiO3–Na2/3Th1/3TiO3–ThTi2O6solid solution. Late Na-rich silicate glass contains celsian. Slag from Araxá also consists of a framework of β-alumina (Ti-poor). Interstitial compounds differ from Fen in being predominantly rare-earth element (REE)-Nb-Al-Th-perovskites belonging to a REEAlO3–Ca2AlNbO6–CaTiO3–ThTi2O6solid solution with minor NaNbO3and CaZrO3, and compositionally diverse barium calcium aluminates [(Ba, Ca)Al2O4] set in a F-bearing (6–7 wt.%) Na-Ba-Si-aluminate glass with minor Ba4Nb2O9, CaF2, BaF2and NaF. Slag from Oka consists of a framework of hibonite [(Ca, REE) (Al, Ti, Mg)12O19] zoned with respect to the REE content. Interstitial compounds are CaZr4O9, Nb-Th-poor perovskites belonging to the REEAlO3–CaTiO3series with minor CaZrO3set in a F-bearing (5–6 wt.%) calcium aluminate glass. These data demonstrate that during ferroniobium production REE, Zr, Th, U and significant amounts of Nb are sequestered in the oxide phases in accord with their lithophile geochemical character. None of these elements are present as compounds in the siderophillic ferroniobium alloys. These data demonstrate that the aluminothermic reduction process results in the loss of significant amounts of Nb to the slag. Perovskite-group compounds are present in all of the slags but differ widely in their composition as a result of compositional differences in the feed pyrochlores and fluxes added to the smelting process. Slags originating from ferroniobium production are enriched in Th and U and could be considered as an environmental hazard if these elements are mobilized during chemical weathering of slag.
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Akizawa, Norikatsu, Tetsu Kogiso, Akira Miyake, Akira Tsuchiyama, Yohei Igami et Masayuki Uesugi. « Formation process of sub-micrometer-sized metasomatic platinum-group element-bearing sulfides in a Tahitian harzburgite xenolith ». Canadian Mineralogist 58, no 1 (16 janvier 2020) : 99–114. http://dx.doi.org/10.3749/canmin.1800082.
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ABSTRACT Base-metal sulfides (BMSs) are minerals that host platinum-group elements (PGE) in mantle peridotites and significantly control the bulk PGE content. They have been investigated in detail down to the sub-micrometer scale to elucidate PGE behavior in the Earth's interior. Base-metal sulfides are supposedly subjected to supergene and seawater weathering, leading to the redistribution of PGEs at low temperatures. Careful and thorough measurements of BMSs are thus required to elucidate PGE behavior in the Earth's interior. In the present study, a sub-micrometer-sized PGE-bearing sulfide inclusion in a clinopyroxene crystal in a harzburgite xenolith from Tahiti (Society Islands, French Polynesia) was investigated in detail (down to the sub-micrometer scale) using transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM-EDS). The sulfide inclusion is of carbonatitic metasomatic origin, as it is enveloped by carbonaceous glass, and forms a planar inclusion array with other PGE-bearing sulfide inclusions. The following sulfide phases were identified using TEM-EDS: Fe- and Ni-rich monosulfide solid solutions (MSSs), Fe- and Ni-rich pentlandite, sugakiite, heazlewoodite, chalcopyrite, and Cu-Ir-Pt-Rh-thiospinel (cuproiridsite–malanite–cuprorhodsite). We established the formation process of the metasomatic PGE-bearing sulfide inclusion by considering morphological and mineral characteristics in addition to the chemical composition. A primary MSS first crystallized from metasomatic sulfide melt at ca. 1000 °C, followed by the crystallization of an intermediate solid solution (ISS) below 900 °C. A high-form (high-temperature origin) Fe-rich pentlandite simultaneously crystallized with the primary MSS below ca. 850 °C and recrystallized into a low-form (low-temperature origin) Fe-rich pentlandite below ca. 600 °C. The primary MSS decomposed to Fe- and Ni-rich MSSs, low-form Ni-rich pentlandite, sugakiite, and heazlewoodite. The ISS decomposed to chalcopyrite below ca. 600 °C. Meanwhile, a Cu-Ir-Pt-Rh-thiospinel crystallized directly from the evolved Cu-rich sulfide melt below ca. 760 °C. Thus, Ir, Pt, and Rh preferentially partitioned into the melt phase during the crystallization process of the metasomatic sulfide melt. Metasomatic sulfide melts could be a significant medium for the transport and condensation of Pt together with Ir and Rh during the fractionation process in the Earth's interior. We hypothesize that the compositional variability of PGEs in carbonatites is due to the separation of sulfide melt leading to the loss of PGEs in the carbonatitic melts.
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Lloyd, F. E., A. D. Edgar, D. M. Forsyth et R. L. Barnett. « The paragenesis of upper-mantle xenoliths from the Quaternary volcanics south-east of Gees, West Eifel, Germany ». Mineralogical Magazine 55, no 378 (mars 1991) : 95–112. http://dx.doi.org/10.1180/minmag.1991.055.378.08.
Texte intégralRésumé :
AbstractGroup I xenoliths, orthopyroxene-rich and orthopyroxene-free, contain Cr-spinel and clinopyroxene ± phlogopite, and occur together with Group II clinopyroxenites ± Ti-spinel ± phlogopite in K-mafic pyroclastics southeast of Gees. The petrography and clinopyroxene chemistry of orthopyroxene-rich (opx-rich sub-group) Group I xenoliths is consistent with an ‘original’ harzburgitic mantle that has been transformed to lherzolite by the addition of endiopside. In harzburgites, orthopyroxenes are reacting to diopside + olivine + alkali-silicate melt, and, by inference, the orthopyroxene-free (opx-free subgroup) Group I, dunite-wehrlite series can be linked to the opx-rich sub-group via this reaction. Progressive enrichment of dunitic material in endiopside-diopside has resulted in the formation of wehrlite. Phlogopite is titaniferous and occurs as a trace mineral in opx-rich, Group I xenoliths, whereas substantial phlogopite vein-networks are confined to the opx-free sub-group (dunite-wehrlite series). Interstitial, alkali-felsic glass occurs are veins within, and as extensions of, the phlogopite networks. Clinopyroxenes in phlogopite-veined xenoliths are decreased in Mg/(Mg + FeTotal) (mg) and Cr and increased in Ti, Al and Ca, compared with clinopyroxenes in xenoliths which have trace phlogopite. It is proposed that harzburgitic and dunitic mantle has been infiltrated by a Ca- and alkalirich, hydrous silicate melt rather than an ephemeral carbonatite melt. Dunite has been transformed to phlogopite wehrlite by the invasion of a Ca-, Al-, Ti- and K-rich, hydrous silicate melt. Ca-activity was high initially in the melt and was reduced by clinopyroxene precipitation. This resulted in enhanced K-activity which led to phlogopite veining of clinopyroxene-rich mantle. Group II phlogopite clinopyroxenites contain Ti-spinel and salites that are distinct in their Ti, Al and Cr contents from endiopsides and diopsides in Group I xenoliths. It is unlikely that these Group II xenoliths represent the culmination of the infiltration processes that have transformed dunite to wehrlite, nor can they be related to the host melt. These xenoliths may have crystallised from Ca- and K-bearing, hydrous silicate melts in mantle channelways buffered by previously precipitated clinopyroxene and phlogopite. Gees lherzolites contain pyroxenes and spinel with distinctly lower Al contents than these same minerals in lherzolites described previously from other West Eifel localities, which may reflect a distinctive lithology and/or processes of modification for the Gees mantle.
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Bretado-Aragón, Luis A., Dora A. Cortés-Hernández, José C. Escobedo-Bocardo, J. M. Almanza-Robles et J. Ivan Escalante G. « In Vitro Bioactivity Assessment of Ceramics in the SiO2–CaO–MgO System ». Materials Science Forum 560 (novembre 2007) : 35–40. http://dx.doi.org/10.4028/www.scientific.net/msf.560.35.
Texte intégralRésumé :
Both solid-state reaction and glass-ceramic methods are used to obtain bioactive materials (CaSiO3) with different concentrations of MgO (6, 8, and 10 wt %) on the basis of the stoichiometric composition of CaO·SiO2. The in vitro bioactivity assessment is performed by immersing samples in SBF (simulated body fluids) for different periods of time. The analysis of the materials before immersion indicates the presence of different phases (akermanite, wollastonite and diopside) in the materials obtained by the solid state reaction method. It is possible to obtain wollastonite with incorporation of magnesium in its structure ((Ca, Mg)·SiO6) by the glass-ceramic method. The results obtained after immersing the samples in SBF indicate that a Ca, P-rich layer is formed on all the materials tested, even in those containing a high quantity of MgO. However, the layer formed in the MgO-free CaSiO3 ceramic is thicker than that formed in the MgO-containing materials.
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Martínez Cortizas, A., I. Rozas Muñiz, T. Taboada, M. Toro, I. Granados, S. Giralt et S. Pla-Rabés. « Factors controlling the geochemical composition of Limnopolar Lake sediments (Byers Peninsula, Livingston Island, South Shetland Island, Antarctica) during the last ca. 1600 years ». Solid Earth 5, no 2 (10 juillet 2014) : 651–63. http://dx.doi.org/10.5194/se-5-651-2014.
Texte intégralRésumé :
Abstract. We sampled a short (57 cm) sediment core in Limnopolar Lake (Byers Peninsula, Livingston Island, South Shetland Islands), which spans the last ca. 1600 years. The core was sectioned at high resolution and analyzed for elemental and mineralogical composition, and scanning electron microscope and energy dispersive X-ray spectrometer (SEM-EDS) analysis of glass mineral particles in selected samples. The chemical record was characterized by a contrasted pattern of layers with high Ca, Ti, Zr, and Sr concentrations and layers with higher concentrations of K and Rb. The former were also enriched in plagioclase and, occasionally, in zeolites, while the latter were relatively enriched in 2 : 1 phyllosilicates and quartz. This was interpreted as reflecting the abundance of volcaniclastic material (Ca rich) versus Jurassic–Lower Cretaceous marine sediments (K rich) – the dominant geological material in the lake catchment. SEM-EDS analysis revealed the presence of abundant volcanic shards in the Ca-rich layers, pointing to tephras most probably related to the activity of Deception Island volcano (located 30 km to the SE). The ages of four main peaks of volcanic-rich material (AD ca. 1840–1860 for L1, AD ca. 1570–1650 for L2, AD ca. 1450–1470 for L3, and AD ca. 1300 for L4) matched reasonably well the age of tephra layers (AP1 to AP3) previously identified in lakes of Byers Peninsula. Some of the analyzed metals (Fe, Mn, Cu, and Cr) showed enrichments in the most recent tephra layer (L1), suggesting relative changes in the composition of the tephras as found in previous investigations. No evidence of significant human impact on the cycles of most trace metals (Cu, Zn, Pb) was found, probably due to the remote location of Livingston Island and the modest research infrastructures; local contamination was found by other researchers in soils, waters and marine sediments on areas with large, permanent research stations. Chromium is the only metal showing a steady enrichment in the last 200 years, but this cannot be directly attributed to anthropogenic pollution since recent research supports the interpretation that climatic variability (reduced moisture content and increased wind intensity) may have resulted in enhanced fluxes of mineral dust and trace elements (Cr among them) to Antarctica. At the same time, some features of the chemical record suggest that climate may have also played a role in the cycling of the elements, but further research is needed to identify the underlying mechanisms.
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Kapur, S., N. Sakarya, E. A. Fitzpatrick, M. Pagliai, G. Kelling, E. Akça, C. Karaman et B. Sakarya. « Mineralogy and micromorphology of İznik ceramics ». Anatolian Studies 48 (décembre 1998) : 181–89. http://dx.doi.org/10.2307/3643055.
Texte intégralRésumé :
AbstractThe study of İznik ceramics of different periods revealed that temperatures of about 800–900°C were produced during firing. Glass fragments added to the body for strengthening resulted in the formation of fibrous minerals as clusters in the pores and protruding in the glaze together with Ca and P rich minerals in the raw materials used. The pore size distribution of the pores indicates a uniform temperature rise and fall during the production of the microstructure.
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Wan, Wei, Yongchang Zhu, Xingquan Zhang, Debo Yang, Yonglin Huo, Chong Xu, Hongfu Yu, Jian Zhao, Jichuan Huo et Baojian Meng. « Borosilicate Glass-Ceramics Containing Zirconolite and Powellite for RE- and Mo-Rich Nuclear Waste Immobilization ». Materials 14, no 19 (1 octobre 2021) : 5747. http://dx.doi.org/10.3390/ma14195747.
Texte intégralRésumé :
In order to increase the loading of rare earth- and molybdenum-rich high-level waste in the waste forms, zirconolite- and powellite-based multi-phase borosilicate glass-ceramics were synthesized via an in-situ heat treatment method. The effects of the CTZ (CaO, TiO2 and ZrO2) content on the crystallization, microstructure and aqueous durability of the multi-phase borosilicate glass-ceramics were studied. The results indicate that the increase of CTZ content can promote crystallization. The glass-ceramics presented even structures when the CTZ content was ≥ 40 wt%. For the glass-ceramic with 40 wt% CTZ, only zirconolite and powellite crystals were detected and powellite crystals were mainly distributed around zirconolite, whereas for the glass-ceramics with 50 wt% CTZ, perovskite was detected. Furthermore, the leaching rates of Na, Ca, Mo and Nd were in the ×10−3, ×10−4, ×10−3 and ×10−5 g·m−2·d·−1 orders of magnitude on the 28th leaching day, respectively.
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Li, Yu, Yan Bing Zong et Da Qiang Cang. « Effect of Phase Separation Structure on the Crystallization Property of Blast Furnace Slag ». Advanced Materials Research 105-106 (avril 2010) : 787–90. http://dx.doi.org/10.4028/www.scientific.net/amr.105-106.787.
Texte intégralRésumé :
Performance of slag glass ceramic largely depends on the phase separation structure formed in heat treatment. In the paper, the crystallization properties and its relation with phase separation structure of blast furnace slag (BFS) are researched. Three water-quenched samples and an air-quenched sample were respectively prepared. After conducting temper experiments and analyzing XRD and DTA results, the following conclusions have been acquired. Two crystallization regions exist in BFS system. In parent glass with phase separation structure, Ca3Mg(SiO4)2 and Ca2MgSi2O7 would form at lower temperature but Ca2Al2Si2O7 would appear at higher temperature than that in parent glass with homogenous structure. The former contributes to the existence of lower polymerized [SiO4] units and more Ca2+ or Mg2+ in Ca-rich phase of phase separation glass, while the later is due to the diffusing hindrance of [AlO4] in diffusing path and interface resistance in phase separation structure.
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Hurt, Andrew P., Aimee A. Coleman, Haosen Ma, Qiu Li et Nichola J. Coleman. « Calcium Silicate Hydrate Cation-Exchanger from Paper Recycling Ash and Waste Container Glass ». Ceramics 5, no 3 (22 juillet 2022) : 301–17. http://dx.doi.org/10.3390/ceramics5030024.
Texte intégralRésumé :
Synthetic 11 Å tobermorite (Ca5Si6O16(OH)2.4H2O) and its Al-substituted analogue are layer-lattice ion-exchangers with potential applications in nuclear and hazardous wastewater treatment. The present study reports the facile one-pot hydrothermal synthesis of an Al-tobermorite-rich cation-exchanger from a combination of paper recycling ash, post-consumer container glass, and lime, with compositional ratios of [Ca]/[Si + Al] = 0.81 and [Al]/[Si + Al] = 0.18. The reaction products were characterized by powder X-ray diffraction analysis, 29Si magic angle spinning nuclear magnetic resonance spectroscopy, and scanning electron microscopy. Hydrothermal processing in 4 M NaOH(aq) at 100 °C for 7 days yielded an Al-tobermorite-rich product that also contained katoite (Ca3Al2SiO12H8), portlandite (Ca(OH)2), calcite (CaCO3), and amorphous silicate gel. The hydrothermal product was found to have a Cs+ cation exchange capacity of 59 ± 4 meq 100 g−1 and selective Cs+ distribution coefficients (Kd) of 574 ± 13 and 658 ± 34 cm3 g−1 from solutions with molar ratios [Cs+]:[Na+] and [Cs+]:[Ca2+] of 1:100. In a batch sorption study at 20 °C, the uptakes of Pb2+, Cd2+, and Cs+ were determined to be 1.78 ± 0.04, 0.65 ± 0.06, and 0.36 ± 0.03 mmol g−1, respectively. The kinetics of Pb2+, Cd2+, and Cs+ removal were described by the pseudo-second-order rate model, which gave respective rate constants (k2) of 0.010, 0.027, and 1.635 g mmol−1 min−1, and corresponding correlation coefficients (R2) of 0.997, 0.996, and 0.999. The metal ion sorption properties of the tobermorite-rich product compared favorably with those of other waste-derived tobermorites reported in the literature. Potential strategies to improve the yield, crystallinity, and sorption characteristics of the product are discussed.
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Jilani, Sidra, Leah S. Koloadin, David M. Miskovic et Kevin J. Laws. « Solvent-rich magnesium-based bulk metallic glasses in the Mg–Pd–Ca and Mg–Pd–Yb alloy systems ». Scripta Materialia 204 (novembre 2021) : 114120. http://dx.doi.org/10.1016/j.scriptamat.2021.114120.
Texte intégral
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Dostiev, Tarikh M. « Glassware of Medieval Shamkir Town of Early Islamic Period ». Povolzhskaya Arkheologiya (The Volga River Region Archaeology) 2, no 36 (25 juin 2021) : 18–31. http://dx.doi.org/10.24852/pa2021.2.36.18.31.
Texte intégralRésumé :
The author studies the collection of glassware of the 8th–10thcenturies, found in the medieval town of Shamkir, which is located in the western region of the Republic of Azerbaijan. On a functional basis, this collection is represented by tableware, perfumery and drugstore dishes. Drinking vessels prevail among tableware. Perfumery and pharmaceutical utensils are represented mainly by samples of bottles. In the manufacture of glassware, various manufacturing techniques were used, in particular, blowing into a mold and free blasting. The techniques of stretching, welding, polishing, grinding were also used. Glassware of Shamkir belongs to the chemical class Na–Ca–Si with a predominance of the type Na (K)–Ca(Mg)–Al–Si. Most of the glass vessels were decorated with relief geometric ornaments in the form of ovals, circles, and radiating figures, "vortical rosette", "honeycomb" ornaments. The rich raw material resources, professional traditions and innovations which existed here created favorable conditions for the development of glassware production. In the everyday life glassware for various purposes was widely used. Material evidences testify to a great shift in the glass production of Shamkir in the 8th–10th centuries and the production of glassware had a prominent role in the city's economy.
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Ettler, Vojtěch, Martin Mihaljevič, Jean-Claude Touray et Patrice Piantone. « Leaching of polished sections : an integrated approach for studying the liberation of heavy metals from lead-zinc metallurgical slags ». Bulletin de la Société Géologique de France 173, no 2 (1 mars 2002) : 161–69. http://dx.doi.org/10.2113/173.2.161.
Texte intégralRésumé :
Abstract Pb-Zn metallurgical slags are defined by European Community regulations either as waste (hazardous materials) or as secondary commercial substances. The knowledge of their stability is essential in order to assess strategies for their management. A scientific understanding of metal release requires (i) knowledge of the phases hosting the different hazardous metals (e.g., Pb) and (ii) knowledge of the relative solubility of these phases. This paper is devoted to a mineralogical characterisation of slags resulting from different processing technologies and to long-term static leaching experiments run under different pH-conditions. The main mineral phases of slags are spinel-family oxides, Ca-Fe aluminosilicates (clinopyroxene, olivine-type phases, melilite, garnet), silicate glass, sulphide (galena, wurtzite) and intermetallic droplets. Leaching experiments were conducted on polished sections, which were introduced into batch reactors and leached by the following solutions: (i) citric acid-sodium citrate buffer at pH ~ 3 (organic soil-simulating solution), (ii) deionised water without any pH control and (iii) calcium hydroxide saturated solution buffered at pH ~ 12.5 (concrete-simulating solution). Sulphide/metallic phases display an extremely low stability whatever the solution. Under organic-acid conditions, Ca-rich (melilite) and Fe-rich (fayalite) phases are preferentially dissolved. Spinel-family oxides are always extremely stable. SEM observations evidence the important role of citrate, which favours the extraction through chelation of metallic elements on the slag surface. The silicate glass and sulphide/metallic droplets are the most unstable phases under intermediate conditions (deionised water). However, under such conditions, the mobility of Pb, Zn and As is drastically limited by precipitation/adsorption processes, as shown by geochemical modelling (PHREEQC, EQ3NR). A preferential dissolution of glass, clinopyroxene and garnet occurs in alkaline environments. Additionally, lead is significantly released by the dissolution of galena and remains dissolved. On the contrary, zinc content is likely controlled by precipitation of secondary zincite (ZnO) or zinc hydroxide, as predicted by the EQ3NR calculations. The results of static leaching experiments under various conditions confirm that the disposal of slag in organic-rich environments (e.g., peat soil) or the use of slag in concrete technology should be avoided due to the high mobilisation of Pb and other toxic elements.
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Çiflikli, M., E. Çiftçi et H. Bayhan. « Alteration of glassy volcanic rocks to Naand Ca-smectites in the Neogene basin of Manisa, western Anatolia, Turkey ». Clay Minerals 48, no 3 (juin 2013) : 513–27. http://dx.doi.org/10.1180/claymin.2013.048.3.08.
Texte intégralRésumé :
AbstractAlkali- and Ca-rich smectites occur in association with Neogene lacustrine sedimentary rocks and high-K calc-alkaline volcanic rocks with compositions ranging from andesite to rhyolite in western Anatolia (Turkey). Major clay occurrences are associated predominantly with the Foça and Akçaköy ignimbrites and with the ignimbrites within the Rahmanlar pyroclastics. Experimental studies indicate that the main clay minerals present are Na- and Ca-smectite and subordinate illite, associated with silica polymorphs, trace clinoptilolite and chlorite. The authigenic minerals formed by weathering and metasomatic reactions between hot volcanic material and lake water. Smectite was produced as a result of argillic alteration of the volcanic glass and feldspars of the ignimbrites, Rahmanlar pyroclastics and reworked volcaniclastic sediments through chemical weathering and dissolution-precipitation processes and formed as authigenic phases both in terrestrial and nearby shallow lacustrine environments under prevalent humid or semi-humid climate during the Neogene.
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Mulvaney, R. « Iron ore sinter in the analytical transmission electron microscope ». Mineralogical Magazine 51, no 359 (mars 1987) : 61–69. http://dx.doi.org/10.1180/minmag.1987.051.359.06.
Texte intégralRésumé :
AbstractIron ore sinters prepared for the blast furnaces at Scunthorpe, Humberside, comprise iron oxides bound in a matrix of aluminium- and silicon-rich calcium ferrites with some calcium orthosilicate and a residual silicate glass. A super-silicon-deficient clinopyroxene with up to half of the Si in the chain replaced by Fe3+ and Al3+ precipitates from the glass in some areas. The iron oxides are principally magnetite and hematite with some wüstite in highly reduced areas. The calcium orthosilicate has been previously reported as the mineral larnite, β-Ca2SiO4. This study found a range of Fe for Ca substitution and three polymorphs were recognised: the range Ca2SiO4 to Ca1.85Fe0.15SiO4 has the structure of larnite; the range Ca1.85Fe0.15SiO4 to Ca1.6Fe0.4SiO4 has the structure of bredigite, α′-Ca2SiO4. Iron substitution beyond this, and up to a maximum of about Ca1.5Fe0.5SiO4, was not recognisable as a polymorph of Ca2SiO4, but an orthorhombic cell is tentatively proposed. The complex ferrite SFCA (silico-ferrite of Ca and Al) is variable in composition, but has a minimum of about 3 wt. % Al2O3 and contains 20 wt. % CaO and SiO2 with a Ca: Si ion ratio of about 2 : 1. A C-face centred monoclinic cell has been deduced: a 15.70, b 9.70, c 8.48 Å; β 105°30′. The Al appears critical for the formation of SFCA in sinter; without it, a eutectic of magnetite and bredigite precipitates in preference.
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Hurai, V., M. Huraiová, P. Konečný et R. Thomas. « Mineral-melt-fluid composition of carbonate-bearing cumulate xenoliths in Tertiary alkali basalts of southern Slovakia ». Mineralogical Magazine 71, no 1 (février 2007) : 63–79. http://dx.doi.org/10.1180/minmag.2007.071.1.63.
Texte intégralRésumé :
AbstractTwo types of carbonatic cumulate xenoliths occur in alkali basalts of the northern part of the Carpatho-Pannonian region, Central Europe. One is dominated by Ca-Fe-Mg carbonates with randomly distributed bisulphide globules (Fe1+xS2, x = 0–0.1), Mg-Al spinel, augite, rhönite, Ni-Co-rich chalcopyrite, and a Fe(Ni,Fe)2S4 phase. The second, carbonatic pyroxenite xenolith type, is composed of diopside, subordinate fluorapatite, interstitial Fe-Mg carbonates, and accessory K-pargasite, F-Al-rich ferroan phlogopite, Mg-Al spinel, albite and K-feldspar. All accessory minerals occur in ultrapotassic dacite-trachydacite glass in primary silicate melt inclusions in diopside, together with calcio-carbonatite and CO2-N2-CO inclusions. Textural evidence is provided for multiphase fluid-melt immiscibility in both xenolith types. The carbonatic pyroxenite type is inferred to have accumulated from differentiated, volatile-rich, ultrapotassic magma derived by a very low-degree partial melting of strongly metasomatized mantle. Mineral indicators point to a genetic link between the carbonatite xenolith with olivine-fractionated, silica-undersaturated alkalic basalt ponded at the mantle-crust boundary.
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Limtrakun, P., Khin Zaw, C. G. Ryan et T. P. Mernagh. « Formation of the Denchai gem sapphires, northern Thailand : evidence from mineral chemistry and fluid/melt inclusion characteristics ». Mineralogical Magazine 65, no 6 (décembre 2001) : 725–35. http://dx.doi.org/10.1180/0026461016560004.
Texte intégralRésumé :
AbstractThe Denchai gem sapphire deposits in Phrae Province, northern Thailand are closely associated with late Cenozoic alkaline basaltic rocks. The sapphires occur in alluvial placer deposits in palaeo-channels at shallow depths. Electron microprobe analysis of minor and trace element contents (Fe, Ti, Cr, Ga and V) of the sapphires indicate the following oxide abundances: Fe2O3 (0.32–1.98 wt.%), TiO2 (0.01–0.23 wt.%), Cr2O3 (<0.01 wt.%), Ga2O3 (0.01–0.03 wt.%) and V2O5 (<0.03 wt.%). Optical studies of sapphires revealed three types of primary fluid/melt inclusions. CO2-rich inclusions (Type I) contain three phases (LH2O + LCO2 + V) with the vapour phase comprising <10–15 vol.%. The presence of CO2 was confirmed by microthermometry and laser Raman analysis. Polyphase inclusions (Type II) (vapour + liquid + solid) contain a fluid bubble (20–30 vol.%), an aqueous phase (10–15 vol.%) and several solid phases. Silicate-melt inclusions (Type III) comprise vapour bubbles, silicate glass and solid phases. Proton-induced X-ray emission (PIXE) analysis revealed high concentrations of K (~;4 wt.%) as well as Ca (~;0.5 wt.%), Ti (~;1 wt.%), Fe (~;2 wt.%), Mn (~;0.1 wt.%), V (<0.03 wt.%), Rb (~;70 ppm) and Zr (~;200 ppm) in the silicate glass. The Ga2O3 abundances and Cr2O3/Ga2O3 values (<1) of the sapphires favour their formation by magmatic processes. The presence of CO2-rich fluids and high K concentrations in the silicate melt inclusions link the origin of the Denchai gem sapphires to CO2-rich alkaline magmatism.
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Donaldson, C. H. « Convective fractionation during magnetite and hematite dissolution in silicate melts ». Mineralogical Magazine 57, no 388 (septembre 1993) : 469–88. http://dx.doi.org/10.1180/minmag.1993.057.388.09.
Texte intégralRésumé :
AbstractSingle crystals of magnetite and of hematite have been dissolved at atmospheric pressure in superheated melts in the systems CaO-MgO-Al2O3-SiO2 and CaO-Al2O3-SiO2, and in a basalt. The crystals were suspended in alumina crucibles containing ca 3.5 cm 3 of melt. Quenched run products were examined optically and by electron probe analysis to establish the distribution of Fe in the glassy charges. There is usually a concentration of Fe at the base of a run product, consistent with flow of dissolved matter from the crystal to the floor. One or more columns of brown, Fe-rich glass may extend from the underside of a relic crystal towards the floor. In CMAS run products, such columns typically extend this entire distance, whereas in the CAS and basalt run products, the columns are either detached from the crystal or do not reach the floor. In the CMAS melt (viscosity ~1 poise) there is apparently continuous release of Fe-bearing melt from around a dissolving crystal, whereas in the CAS and basalt melts (viscosities 7000 and 300 poise, respectively) release is intermittent. In CMAS run products the Fe content is usually greatest, in glass, at the base, and declines gradually upwards; in CAS and basalt runs the bottom of a crucible is occupied by discrete, sharply bounded pillows of Fetich glass, with only slight, or no, gradation in composition. Rising gas bubbles can elevate small blobs of the denser, Fe-bearing melt from around a dissolving crystal, and trains of bubbles in the CAS melt may guide this Fe-bearing melt, against gravity, to the surface of the charge. When the bubbles burst at the surface, this dense melt is left in an unstable location and releases diapirs which descend to the bottom of the crucible. In spite of the evidence that convective fractionation occurs in these haplomagmas and in the basalt, it remains to be demonstrated that it will occur during sidewall crystallization or during the growth of minerals in a cumulus mush to cause magmatic differentiation.
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LISTER, JOHN R., ALICE B. THOMPSON, ANTOINE PERRIOT et LAURENT DUCHEMIN. « Shape and stability of axisymmetric levitated viscous drops ». Journal of Fluid Mechanics 617 (25 décembre 2008) : 167–85. http://dx.doi.org/10.1017/s0022112008003868.
Texte intégralRésumé :
We consider levitation of an axisymmetric drop of molten glass above a spherical porous mould through which air is injected at a constant velocity. Owing to the viscosity contrast, the float height for a given shape is established on a much shorter time scale than the subsequent deformation of the drop under gravity, surface tension and the underlying lubrication pressure. Equilibrium shapes, in which an internal hydrostatic pressure is coupled to the external lubrication pressure through the total curvature and the Young–Laplace equation, are determined using a numerical continuation scheme. The set of solution branches is surprisingly complicated and shows a rich bifurcation structure in the parameter space (Bo=ρgV2/3/γ, Ca=μav/γ), where Bo is bond number and Ca is capillary number, ρ and V are the drop density and volume, γ the surface tension, μa the air viscosity and v the injection velocity. The linear stability of equilibria is determined using a boundary-integral representation for drop deformation that factors out the rapid vertical adjustment of the float height. The results give good agreement with time-dependent simulations. For sufficiently large Ca there are intervals of Bo for which there are no stable solutions and, as Ca increases, these intervals grow and merge. The region of stability decreases as the mould radius aM increases with an approximate scaling Ca~aM−5, which imposes practical limitations on the use of this geometry for the manufacture of lenses.
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Martínez Cortizas, A., I. Rozas Muñiz, T. Taboada, M. Toro, I. Granados, S. Giralt et S. Pla-Rabés. « Factors controlling the geochemical composition of Limnopolar lake sediments (Byers Peninsula, South Shetland Island, Livingston Island, Antarctica) during the last ∼ 1600 years ». Solid Earth Discussions 6, no 1 (11 mars 2014) : 761–92. http://dx.doi.org/10.5194/sed-6-761-2014.
Texte intégralRésumé :
Abstract. We sampled a short (57 cm) sediment core in Limnopolar Lake (Byers Peninsula, Livingston Island, South Shetlands Islands), which spans the last ~ 1600 years. The core was sectioned at high resolution and analyzed for elemental and mineralogical composition, and SEM-EDS analysis of glass mineral particles in selected samples. The chemical record was characterized by a contrasted pattern of layers with high Ca, Ti, Zr, and Sr concentrations and layers with higher concentrations of K and Rb. The first also enriched in plagioclase and, occasionally, in zeolites, while the later were relatively enriched in 2:1 phyllosilicates and quartz. This was interpreted as reflecting the abundance of volcaniclastic material (Ca-rich) vs. Jurassic-Lower Cretaceous marine sediments (K-rich) – the dominant geological material in the lake catchment. SEM-EDS analysis revealed the presence of abundant volcanic shards in the Ca-rich layers, pointing to tephras most probably related to the activity of Deception Island volcano (located 30 km to the SE). The ages of the four main peaks of volcanic-rich material (AD ~ 1840–1860 for L1, AD ~ 1570–1650 for L2, AD ~ 1450–1470 for L3, and AD ~ 1300 for L4) matched reasonably well the age of tephra layers (AP1 to AP3) previously identified in lakes of Byers Peninsula. Some of the analyzed metals (Fe, Mn, Cu and Cr) showed enrichments in the most recent tephra layer (L1), suggesting relative changes in the composition of the tephras as found in previous investigations. No evidence of significant human impact on the cycles of most trace metals (Cu, Zn, Pb) was found, probably due to the remote location of Livingston Island and the modest research infrastructures – local contamination was found by other researchers in soils, waters and marine sediments on areas with large, permanent, research stations. Chromium is the only metal showing a steady enrichment in the last 200 years that could be interpreted as recent anthropogenic contamination. At the same time, some features of the chemical record suggest that climate may have also played a role in the cycling of the elements, but further research is needed to identify the underlying mechanisms.
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Haubner, Roland, et Susanne Strobl. « Slag Investigation from Iron Smelting and Iron Processing Sites in Austria – From Hallstatt and Medieval Period and the 19th Century ». Materials Science Forum 782 (avril 2014) : 635–40. http://dx.doi.org/10.4028/www.scientific.net/msf.782.635.
Texte intégralRésumé :
Slags from three iron smelting and processing sites were investigated. The composition of the slags is connected to the metallurgical processes and the investigation should provide an indication of the process conditions.A slag from a small bloomery furnace at the archaeological site Waschenberg (Hallstatt period) was investigated. Slags from the medieval period were found near Eisenerz and at this time iron was produced in developed bloomery furnaces (Stuckofen). These slags are termed fayalitic slags and they consist of wustite (FeO), fayalite (Fe2SiO4) and glass-phase (amorphous silicates) in various concentrations. Three solidification-types were described and correlated with the microstructures and the FeO-SiO2-CaO2 phase diagram.During the 19th century steel was produced in puddling furnaces by remelting iron products from Eisenerz. Such slags, from this process, found in the surroundings of Palfau, were investigated and contain FeO and Ca rich glass-phase, but no fayalite.Due to the different compositions of the slags the solidification and the microstructures are different.
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Liang, Hong Yu, Qing Nan Zhao, Feng Gao, Wen Hui Yuan et Yu Hong Dong. « Effect of RF Sputtering Power on the Structural, Optical and Hydrophobic Properties of SiNx Thin Film ». Advanced Materials Research 194-196 (février 2011) : 2340–46. http://dx.doi.org/10.4028/www.scientific.net/amr.194-196.2340.
Texte intégralRésumé :
With a mixture gas of N2 and Ar, silicon nitride thin films were deposited on glass substrates by different radio frequency (RF) magnetron sputtering power without intentional substrate heating. The chemical composition, phase structure, surface morphology, optical properties, refractive index, hydrophobic properties of the films were characterized by X-ray energy dispersive spectroscopy(EDS), X-ray diffraction(XRD), field emission scanning electron microscopy(FESEM), ultraviolet-visible spectroscopy(UV-Vis), nkd-system spectrophotometer and CA-XP150 contact angle analyzer, respectively. The results showed that silicon nitride thin films were amorphous and rich in Si; the transmittance reduced but refractive index and surface roughness increased; and the hydrophobic properties of SiNx became better with the increase of RF power.
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Owocki, Krzysztof, et Andrzej Muszyński. « Shock veins in the Sahara 02500 ordinary chondrite ». Geologos 18, no 2 (1 août 2012) : 111–18. http://dx.doi.org/10.2478/v10118-012-0006-0.
Texte intégralRésumé :
Shock veins in the Sahara 02500 ordinary chondriteA specimen of the Sahara 02500 ordinary chondrite contains shock-produced veins consisting of recrystallised fine-grained pyroxenes that include small droplets of Ni-rich metal. Non-melted olivines and pyroxenes show planar deformations filled by shock-melted and -polluted metal and troilite. Shock-melted feldspathic glass is present close to the shock veins. Geothermometric estimations indicate that the meteorite locally experienced moderate shock metamorphism with a minimum local peak temperature above 1400°C, resulting in partial melting of Ca-poor pyroxene and full melting of feldspars, metal and sulphides. The mineral assemblage in the shock veins suggests a pressure during melt recrystallisation below 10 GPa.
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Caurant, Daniel, Pascal Loiseau, Isabelle Bardez et Christel Gervais. « Effect of Al2O3 concentration on zirconolite (Ca(Zr,Hf)Ti2O7) crystallization in (TiO2,ZrO2,HfO2)-rich SiO2–Al2O3–CaO–Na2O glasses ». Journal of Materials Science 42, no 20 (9 juillet 2007) : 8558–70. http://dx.doi.org/10.1007/s10853-007-1810-8.
Texte intégral
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Meneghini, C., S. Mobilio, L. Lusvarghi, F. Bondioli, A. M. Ferrari, T. Manfredini et C. Siligardi. « The structure of ZrO2phases and devitrification processes in a Ca–Zr–Si–O-based glass ceramic : a combined a-XRD and XAS study ». Journal of Applied Crystallography 37, no 6 (11 novembre 2004) : 890–900. http://dx.doi.org/10.1107/s0021889804022307.
Texte intégralRésumé :
The structure of the Zr atomic environment in a CaO–ZrO2–SiO2glass ceramic as a function of thermal treatments has been studied, combining X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) and anomalous XRD (a-XRD) techniques. The analysis of XRD patterns demonstrates that the devitrification process proceeds through the partial segregation of Zr-depleted phases (wollastonite-like) and Zr-rich phases (Zr oxides). The XAS and a-XRD measurements at the ZrK-edge have been exploited in order to obtain a closer insight into the atomic structure around the Zr atoms. In the as-quenched glass the Zr atom is sixfold coordinated to O atoms in an amorphous environment rich in Ca and Si. Thermal treatment firstly (T= 1273–1323 K) causes partial segregation of Zr in the form of an oxide with a tetragonal zirconia (t-ZrO2) crystalline structure. Raising the temperature (T= 1373 K) causes the formation of ZrO2crystallites in the monoclinic crystallographic phase (baddeleyite, m-ZrO2). Analysis of the XAS data shows that a considerable amount of Zr remains in an amorphous calcium silicate phase.
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Ekіncі Şans, B., F. Esenlі, S. Kadir et W. C. Elliott. « Genesis of smectite in siliciclastics and pyroclastics of the Eocene İslambeyli Formation in the Lalapaşa region, NW Thrace, Turkey ». Clay Minerals 50, no 4 (septembre 2015) : 459–83. http://dx.doi.org/10.1180/claymin.2015.050.4.04.
Texte intégralRésumé :
AbstractThe Eocene İslambeyli Formation in the Lalapaşa region (NW Thrace, Turkey) consists predominantly of siliciclastic clayey clastics at the bottom and of claystone, tuff and tuffaceous claystone/ sandstone/limestone in the middle and uppermost parts of this formation. Some tuff-tuffaceous beds of the middle–upper parts of the formation are economically viable bentonite depoits. The İslambeyli Formation exhibits vertical variations in the mineralogy, elemental compositions, and smectite-forming processes. Smectite was formed by weathering and diagenetic processes in the fluvial-shore environments in the lower part and by diagenetic alteration in a shallow-marine environment in the middle–upper parts of the formation. Ca-smectite flakes were formed by two processes: direct precipitation; and by means of a dissolution-precipitation mechanism from feldspar and mica. Dissolution-precipitation was most prevalent in the siliciclastic lower part of the formation. The amounts of Al, Fe, Mg and Ca required to form smectite and accessory illite were supplied mainly from the alteration of feldspars, mica and glass shards. The origin of smectite can also be explained by the inferred solution compositions given the parent phases in this formation, and the devitrification of glass shards in pyroclastic-rich middle–upper parts of the formation. In the upper beds, the observed decrease of K and Fe in the smectite structure coincided with both the increase in the amount of smectite and the increase in solution pH suggesting that precipitation of smectite developed over a prolonged period and under arid conditions.
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Dolníček, Zdeněk, Ladislav Kandrnál, Jana Ulmanová, Ester Vratislavská et Pavel Hojač. « Strusky a železo z experimentální tavby železa realizované na hradě Buchlově (jv. Chřiby) v roce 2018 ». Bulletin Mineralogie Petrologie 28, no 1 (2020) : 58–68. http://dx.doi.org/10.46861/bmp.28.058.
Texte intégralRésumé :
During experimental smelting of iron in a replica of historical shaft furnace, which was held at the Buchlov Castle in 2018, charcoal and Mn-enriched pelosiderite-limonite iron ore from the locality Strážovice near Kyjov were used. The obtained furnace slag is practically completely formed by glass phase; only rare small domains also contain olivine. The glass phase is compositionally heterogeneous and contains 0.7 - 10.7 wt. % MnO, whereas olivine corresponds to fayalite with elevated contents of tephroite (ca. 12 mol. %), forsterite (ca. 4 mol. %) and dicalciumsilicate (1 mol. %) components. The produced metallic iron is also compositionally heterogeneous, rich in phosphorus and in places it contains small spherical inclusions of pyrrhotite. The phase composition of slag differs significantly from those of typical iron slags. The reason can be seen either in anomalous chemical composition of used ore (the elevated contents of Mn could potentially act as an inhibitor of crystallization), or in too high temperatures during smelting (the phase relations in metallic iron suggest temperatures exceeding 1500 °C) in combination with rapid cooling of the furnace content after finishing of smelting. Both phase composition of slag as well as chemical composition of individual slag phases and metallic iron are significantly different from those of local historical artefacts from the period of usage of technology of direct production of iron. These findings do not support the idea that local pelosiderite iron ores were used for production of iron already during this early period.
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Wagner, Christiane, Abdelkader Mokhtari et Danielle Velde. « Xenocrystic richterite in an olivine-nephelinite : destabilisation and diffusion phenomena ». Mineralogical Magazine 57, no 388 (septembre 1993) : 515–25. http://dx.doi.org/10.1180/minmag.1993.057.388.12.
Texte intégralRésumé :
AbstractA partly destabilised Na-richterite has been found in an olivine-nephelinite from Morocco. The riehterite crystal (600 × 420 μm) is surrounded by a reaction zone (400-700 μm) of K- and Si-rich glass containing small (<50 μm) olivine (Fo80-83%) and endiopside crystals. Outwards, another zone is formed of normal magmatic minerals and circumscribes the original crystal, indicating that the destabilisation event took place at the end of the crystallisation sequence. Estimated ascent time of about 100 hours would have completely decomposed an isolated richterite crystal, which suggests that the amphibole was originally included in a xenolith. A mass-balance calculation shows that the fichterite isovolumic decomposition was accompanied by exchanges with the magma. The loss of Na from the reaction zone and the gain of AI from the magma allowed the precipitation of an analcime-rich zone observed around the destabilised amphibole and the concentration of K in the reaction zone glass. Compositional variations, Fe and Ti increase and Mg, Ca and F decrease at the richterite edge are interpreted as the result of a diffusion process. No alkali gradients are observed. The diffusion phenomenon lasted less than 100 hours and ceased to be operative at a temperature of 900-950°C i.e. just below the solidus temperature. Diffusion coefficients for the amphibole are proposed: e.g 10−9 cm2 s−1 for K2O and 10−10 for FeO at 900°C