Artigos de revistas: "Copper silicates"

1

Titley, Spencer R. "Silicates flushed with copper". Nature 334, n.º 6182 (agosto de 1988): 472–73. http://dx.doi.org/10.1038/334472a0.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

2

Pan, Yuanming, e Michael E. Fleet. "Mineralogy and genesis of calc-silicates associated with Archean volcanogenic massive sulphide deposits at the Manitouwadge mining camp, Ontario". Canadian Journal of Earth Sciences 29, n.º 7 (1 de julho de 1992): 1375–88. http://dx.doi.org/10.1139/e92-111.

Texto completo da fonte

Resumo:

Skarn-like calc-silicate rocks are reported in spatial association with the Archean Cu–Zn–Ag massive sulphide deposits at the Manitouwadge mining camp, Ontario. Calc-silicates in the footwall of the Willroy mine occur as matrix to breccia fragments of garnetiferous quartzo-feldspathic gneiss and as lenses within garnetiferous quartzo-feldspathic gneiss and are composed of clinopyroxene, garnet, calcic amphiboles, wollastonite, plagioclase, K-feldspar, epidote, quartz, calcite, magnetite, and minor sulphides. Calc-silicates within the main orebody of the Geco mine are characterized by clinopyroxene, calcic amphiboles (Cl–K-rich hastingsitic and ferro-edenitic hornblende, ferro-edenite (up to 4.7 wt.% Cl); and ferroactinolite (6.7 wt.% MnO)), garnet, epidote (including an epidote rich in rare-earth elements and Cl), calcite, quartz, and abundant sulphides. Calc-silicates within the basal 4/2 Copper Zone of the Geco mine contain garnet, gahnite, sphalerite, ferroactinolite (8.5 wt.% MnO), epidote, quartz, biotite, plagioclase, chlorite, muscovite, K-feldspar, and pyrosmalite (with Mn/(Mn + Fe) ratio ranging from 0.21 to 0.61, and up to 3.9 wt.% Cl). The calc-silicates probably represent metasomatic remobilization of dispersed Ca (and Cl) from sea-floor hydrothermal alteration of mafic to intermediate volcanic rocks and are only indirectly related to the hypothesized syngenetic ore-forming processes for the associated base metal sulphide deposits. The calc-silicates formed initially at about 600 °C and 3–5 kbar (1 kbar = 100 MPa) in a mildly reducing environment (from 1 log unit above to 1 log unit below the fayalite–magnetite–quartz buffer) during the upper-amphibolite- to granulite-facies regional metamorphism and were altered subsequently at lower temperatures (<500 °C).

Estilos ABNT, Harvard, Vancouver, APA, etc.

3

Vítková, M., V. Ettler, Z. Johan, B. Kříbek, O. Šebek e M. Mihaljevič. "Primary and secondary phases in copper-cobalt smelting slags from the Copperbelt Province, Zambia". Mineralogical Magazine 74, n.º 4 (agosto de 2010): 581–600. http://dx.doi.org/10.1180/minmag.2010.074.4.581.

Texto completo da fonte

Resumo:

AbstractPyrometallurgical slags from three Cu-Co smelters (Nkana, Mufulira, Chambishi) in the Copperbelt Province, Zambia, were studied from mineralogical and chemical points of view. The slags were enriched in metals and metalloids, mainly Cu (up to 35 wt.%), Co (up to 2.4 wt.%) and As (up to 3650 ppm). The following primary phases were observed in slags: Ca-Fe silicates (clinopyroxene, olivine) and leucite, oxides (spinel-series phases), ubiquitous silicate glass and sulphide/metallic droplets of various sizes. The presence of glass and skeletal/dendritic crystal shapes indicated rapid cooling of the slag melt. Copper and cobalt were found in low concentrations in the majority of silicates (olivine, clinopyroxene) and oxides, substituting for Fe in their structures (up to 7.15 wt.% CoO in olivine, 4.11 wt.% CuO in spinel). Similarly, up to 0.91 wt.% CoO and 6.90 wt.% CuO were observed in the interstitial glass. Nevertheless, the main carriers of these metals in the slags studied were Cu sulphides (digenite, chalcocite, bornite, chalcopyrite), Co-Fe sulphides (cobaltpentlandite), Co-bearing intermetallic phases ((Fe,Co)2As) and alloys. Weathering features corresponding to the presence of secondary metal-bearing phases, such as malachite (Cu2(CO3)(OH)2), brochantite (Cu4SO4(OH)6) and sphaerocobaltite (CoCO3), were observed on the slag surfaces. They indicate that the slags studied are reactive on contact with water/atmosphere and that their environmental stability and release of potentially harmful metals and metalloids must be evaluated further.

Estilos ABNT, Harvard, Vancouver, APA, etc.

4

Ilton, Eugene S., e David R. Veblen. "Copper inclusions in sheet silicates from porphyry Cu deposits". Nature 334, n.º 6182 (agosto de 1988): 516–18. http://dx.doi.org/10.1038/334516a0.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

5

Tshilombo, Odilon M., e Tunde V. Ojumu. "Investigation of the Effect of pH Operating Conditions on Bioleaching of Low-Grade Chalcopyrite in Column Reactors". Advanced Materials Research 825 (outubro de 2013): 401–5. http://dx.doi.org/10.4028/www.scientific.net/amr.825.401.

Texto completo da fonte

Resumo:

Bioleaching of low-grade sulphide minerals is now an established process, with much interest in chalcopyrite. However few studies have been carried out on ores containing silicates gangue materials. Chalcopyrite has been reported to be refractory at ambient temperature. Several factors that influence bioleaching kinetics are well documented such as particle size, pH, temperature, galvanic interaction and microbial activity. The purpose of this research was to investigated the effect of pH as well as pre-leaching on bioleaching of silicate rich and low-grade chalcopyrite using mixed thermophilic cultures, with a view to maximize copper solubilization rate in a column reactor operated at 70°C. The column was packed with low-grade chalcopyrite of the size range -20+15 mm. Leaching was monitored at specific time intervals (3 days) by measuring the pH, the redox potential, the copper and iron concentration in the solution. The results of the investigation have shown that copper extracted was highest at pH 1.3 and at moderately low redox potential (410 – 430 mV) using Ag/AgCl electrode, and that pre-leaching contributed insignificantly to the leaching rate. At pH 2.5, the copper extraction was low due to the jarosite. Furthermore, the analysis XRD of leached residues has indicated that the main passivating products were gypsum, jarosite, hexahydrite, and silica. However, although low pH resulted to high copper recovery, the results also showed that the pregnant leach solution (PLS) contained high concentrations of dissolved ions which might have inhibited the microbial activities.

Estilos ABNT, Harvard, Vancouver, APA, etc.

6

Cruz, Rosenira S. da, Juliana M. de S. e. Silva, Ulrich Arnold, Maurício S. Sercheli e Ulf Schuchardt. "Copper Containing Silicates as Catalysts for Liquid Phase Cyclohexane Oxidation". Journal of the Brazilian Chemical Society 13, n.º 2 (2002): 170–76. http://dx.doi.org/10.1590/s0103-50532002000200007.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

7

Karakassides, Michael A., Kostas G. Fournaris, Anastasios Travlos e Dimitris Petridis. "The Synthesis of Mesoporous Copper Silicates Using Organofunctional Silicon Alkoxides". Advanced Materials 10, n.º 6 (abril de 1998): 483–86. http://dx.doi.org/10.1002/(sici)1521-4095(199804)10:6<483::aid-adma483>3.0.co;2-m.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

8

Wang, Xiqu, Lumei Liu e Allan J. Jacobson. "Nanoporous Copper Silicates with One-Dimensional 12-Ring Channel Systems". Angewandte Chemie International Edition 42, n.º 18 (9 de maio de 2003): 2044–47. http://dx.doi.org/10.1002/anie.200351121.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

9

Stebbins, Jonathan F. "Toward the wider application of 29Si NMR spectroscopy to paramagnetic transition metal silicate minerals: Copper(II) silicates". American Mineralogist 102, n.º 12 (1 de dezembro de 2017): 2406–14. http://dx.doi.org/10.2138/am-2017-6176.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

10

Henne, Anicia, Dave Craw, David Paterson e Gordon Southam. "Textures and mineralogy of residual supergene copper silicates in oxidised overburden". Minerals Engineering 163 (março de 2021): 106775. http://dx.doi.org/10.1016/j.mineng.2021.106775.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

11

Ganebnykh, E. V., A. V. Sviridov, V. V. Sviridov, S. S. Naboichenko e G. I. Mal’tsev. "Recovery of copper from solutions by highly dispersed modified aluminum silicates". Russian Journal of Non-Ferrous Metals 57, n.º 2 (março de 2016): 81–84. http://dx.doi.org/10.3103/s106782121602005x.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

12

Lambert, U., e W. Eysel. "New Copper (II) — Rare Earth (III) Compounds II. Crystal Chemistry of CuLn2Ge2O8, CuLn2Si4O12 and CuLn2Ge4O12". Powder Diffraction 1, n.º 3 (setembro de 1986): 256–60. http://dx.doi.org/10.1017/s0885715600011799.

Texto completo da fonte

Resumo:

AbstractTwenty seven new rare earth (Ln) compounds CuLn2 Ge2O8, CuLn2Ge4O12 and CuLn2Si4O12 have been synthesized. The powder diagrams were indexed and solid solutions of silicates and germanates were investigated. Structural variations with temperature, lanthanide contraction and Ge/Si substitution are described. Indications for second order phase transitions were found.

Estilos ABNT, Harvard, Vancouver, APA, etc.

13

Panova, Olena, Grigory Krasnyansky e Irina Aznauryan. "EVALUATION OF ELECTROMAGNETIC RADIATION SHIELDING CHARACTERISTICS OF FACING BUILDING VATERIALS". Management of Development of Complex Systems, n.º 48 (20 de dezembro de 2021): 152–59. http://dx.doi.org/10.32347/2412-9933.2021.48.152-159.

Texto completo da fonte

Resumo:

The article presents the results of theoretical studies of the protective properties of composite facing materials based on a dielectric matrix with an electrically conductive non-magnetic filler in a wide frequency range of incident electromagnetic radiation. Expressions are got for the values of the transmission, reflection and absorption, and the electromagnetic radiation shielding efficiency calculated on their basis. The dependences of the permittivity and electrical conductivity of the composite on the volume fraction of the electrically conductive additive required for calculations were got based on the hypothesis of similarity, considering the nonzero conductivity of the dielectric matrix. Satisfactory agreement between the calculation results and the measured shielding characteristics of specimens of metal silicate materials based on calcium hydro silicates and copper powder was established. The results presented show the adequacy of the proposed calculation method and indicate that it can be used for preliminary estimates of the shielding characteristics when designing electromagnetic radiation shields based on composite facing materials.

Estilos ABNT, Harvard, Vancouver, APA, etc.

14

Stoulil, J., P. Šedá, M. Anisová, Z. Fencl, P. Novák e J. Děd. "Defects of copper patina / Vady mìdìných patin". Koroze a ochrana materialu 59, n.º 3 (1 de novembro de 2015): 87–90. http://dx.doi.org/10.1515/kom-2015-0015.

Texto completo da fonte

Resumo:

Abstract The paper is focused on analyses of dark copper patina defects that were formed on one sheet under the same conditions. Roofs of ten historical buildings were studied by image analysis and samples of two roofs were subjected to more detailed destructive analysis. These samples were studied by means of scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction and infrared spectroscopy. Both types of patina are composed of brochantite. Green patinas consisted of a pure brochantite and they had a fl at and compact surface. Conversely, black patina contained a high degree of impurities (ammonia cations, nitrates, silicates) and the surface was rough. The proportion of dark patina was higher in south and east facing surfaces, where washing by rainfall is more difficult.

Estilos ABNT, Harvard, Vancouver, APA, etc.

15

Kou, M. R. Sun. "Naturally-Occurring Silicates as Carriers for Copper Catalysts Used in Methanol Conversion". Clays and Clay Minerals 40, n.º 2 (1992): 167–74. http://dx.doi.org/10.1346/ccmn.1992.0400205.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

16

Chen, Weibo, Yeqi Shi, Zhi Chen, Xiangwen Sang, Shuhong Zheng, Xiaofeng Liu e Jianrong Qiu. "Near-Infrared Emission and Photon Energy Upconversion of Two-Dimensional Copper Silicates". Journal of Physical Chemistry C 119, n.º 35 (20 de agosto de 2015): 20571–77. http://dx.doi.org/10.1021/acs.jpcc.5b04819.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

17

Chanquía, Corina M., Leandro Andrini, Julio D. Fernández, Mónica E. Crivello, Félix G. Requejo, Eduardo R. Herrero e Griselda A. Eimer. "Speciation of Copper in Spherical Mesoporous Silicates: From the Microscale to Angstrom". Journal of Physical Chemistry C 114, n.º 28 (24 de junho de 2010): 12221–29. http://dx.doi.org/10.1021/jp102622v.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

18

Araujo, A. C. P. C. de, e M. G. Cavalcante. "Effect of divalent chloride salts on lamellar silica conductivity". Cerâmica 59, n.º 352 (dezembro de 2013): 588–91. http://dx.doi.org/10.1590/s0366-69132013000400015.

Texto completo da fonte

Resumo:

Silica is an important raw material in the production of soluble silicates, silicon and its derivatives: silicon carbide and silicone, which are converted into the lamellar form using the sol-gel process. This compound, which has been extensively studied because it is structurally organized, can be used for selective adsorption of toxic substances or immobilization of photo-active species. Impedance spectroscopy was used in a study of the electrical properties of lamellar silica doped with the following metal salts: nickel chloride, manganese chloride, and copper chloride, in order to observe the cation effect in their structure. In this study, the following order of conductivity was obtained: manganese chloride nickel chloride copper chloride. This effect was also observed using X-ray diffraction analysis.

Estilos ABNT, Harvard, Vancouver, APA, etc.

19

Lonzinger, Tatiana M., Vadim A. Skotnikov e Alexey M. Sukharev. "Study of the Process of Heavy Metals Cations Mineralization by Poly-Component Structures Based on Calcium and Magnesium Silicates". Materials Science Forum 989 (maio de 2020): 103–9. http://dx.doi.org/10.4028/www.scientific.net/msf.989.103.

Texto completo da fonte

Resumo:

In order to achieve the goal of absorption of environmental pollutants, poly-component materials based on magnesium and calcium silicates - metal cations mineralizers – have been synthesized. The study of the processes of mineralization was carried out using model solutions containing soluble sulphates of copper, zinc, manganese and iron. The studies carried out have shown that the synthesized mineralizer based on calcium and magnesium silicates has a multicomponent structure with active electrochemically inhomogeneous centres on its surface as a result of breaking the Ca-O-Si, Mg-O-Si bonds, hydration and leaching of the Ca2+ and Mg2+ ions. In an acidic environment, the leaching reaction is activated due to H+ adsorption and the weakening of the bond between Ca2+ and O2-, thus making the transition of Ca2+ into the liquid phase more advantageous. As a result, a negatively charged ≡Si-O-layer enriched with silicon is formed, which is able to interact chemically with heavy metal ions present in the electrolyte solution.

Estilos ABNT, Harvard, Vancouver, APA, etc.

20

McKenzie, William F., e Harold C. Helgeson. "Phase relations among silicates, copper iron sulfides, and aqueous solutions at magmatic temperatures". Economic Geology 80, n.º 7 (1 de novembro de 1985): 1965–73. http://dx.doi.org/10.2113/gsecongeo.80.7.1965.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

21

Stuckey, Jason W., Jovan Livada e Carmen Enid Martínez. "Structural charge location dictates speciation and lability of copper in swelling layer silicates". Applied Clay Science 216 (janeiro de 2022): 106332. http://dx.doi.org/10.1016/j.clay.2021.106332.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

22

Rumsey, M. S., M. D. Welch, A. R. Kampf e J. Spratt. "Diegogattaite, Na2CaCu2Si8O20·H2O: a new nanoporous copper sheet silicate from Wessels Mine, Kalahari Manganese Fields, Republic of South Africa". Mineralogical Magazine 77, n.º 8 (dezembro de 2013): 3155–62. http://dx.doi.org/10.1180/minmag.2013.077.8.09.

Texto completo da fonte

Resumo:

AbstractDiegogattaite (IMA2012-096), Na2CaCu2Si8O20·H2O, is a new mineral from the Wessels mine in the Kalahari manganese fields of South Africa. It occurs as a minor phase with other copper-bearing silicates, Cu-rich pectolite, sugilite, quartz, aegirine and undifferentiated Fe-Mn oxides. Diegogattaite is pale turquoise through teal blue. It is found as sub-mm sized grains in a main crystalline patch 3–4 mm in size, and is currently known from only one sample. The mineral is transparent with a vitreous lustre and may have a good cleavage on {001}. It is brittle, with an uneven fracture and a very pale-blue streak. It is non-fluorescent in short- and long-wave UV light and has an estimated Mohs hardness of ∼5–6. Diegogattaite is biaxial (–), α = 1.598(2), β = 1.627(2), γ = 1.632(2); 2Vmeas = 44.0(6)°, 2Vcalc = 44.5°; dispersion: strong r < v, orientation: X = b, Y ≈ ⊥(001), Z ≈ a; pleochroism X colourless << Y ≈ Z blue green. The calculated density is 3.10 g/cm3. Electron-microprobe analysis gave: Na2O 8.07, CaO 7.3, CuO 20.5, FeO 0.36, SiO262.4, H2O(calc) 2.34, total 100.97 wt.%. A charge-balanced formula on the basis of 21 oxygen a.p.f.u. is: Na2.00Ca1.00Cu1.98Fe0.04Si7.99H2O21. Diegogattaite is monoclinic, space group C2/m, a = 12.2439(6) Å, b = 15.7514(4) Å, c = 10.6008(3) Å, β = 125.623(2)°, V = 1661.87(10) Å3 and Z = 4. The five strongest lines in the X-ray powder pattern are [dobs in Å (Iobs)(hkl)]: 4.25(75)(002,22,220), 3.951(77)(040), 3.261(100)(31,13), 2.898(89)(042,03,003), 2.332(66)(331,43,62,260,043). The crystal structure of diegogattaite was determined by single-crystal X-ray diffraction to final agreement indices of R1 = 0.027, wR2 = 0.071 and GoF = 1.090. It represents a completely new silicate topology based upon a double-sheet of SiO4 tetrahedra composed of connected 6482 cages. The structure of diegogattaite is related to those of synthetic nanoporous Na-Cu-Si-O-(OH)-H2O (CuSH) compounds, which are of interest to the solid-state chemistry community as potential ion-exchangers, catalysts and molecular sieves. The structure of diegogattaite forms a bridge between these structures and those of the gillespite-group minerals, including wesselsite. The close spatial association of wesselsite and diegogattaite suggests a possible reaction between them that may point to a synthetic route for the production of novel alkaline-earth-based nanoporous copper silicates.

Estilos ABNT, Harvard, Vancouver, APA, etc.

23

Balassone, Giuseppina, Carmela Petti, Nicola Mondillo, Taras L. Panikorovskii, Roberto de Gennaro, Piergiulio Cappelletti, Angela Altomare, Nicola Corriero, Maria Cangiano e Loredana D’Orazio. "Copper Minerals at Vesuvius Volcano (Southern Italy): A Mineralogical Review". Minerals 9, n.º 12 (26 de novembro de 2019): 730. http://dx.doi.org/10.3390/min9120730.

Texto completo da fonte

Resumo:

This work is part of a project focused on the Somma–Vesuvius volcano and aimed at identifying Cu minerals related to mineralizing processes associated with magmatic activity in an active magmatic-hydrothermal system. A mineralogical survey was carried out on a set of samples represented by sublimates and fumarolic products from the collection of the Mineralogical Museum of the University of Naples Federico II (Italy). These samples are mainly related to most recent eruptive episodes of Vesuvius activity, from 1631 onward. Copper-bearing minerals were characterized, as well as associated minerals, by X-ray diffraction (XRD) scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). An investigation on the structural complexity of Cu-mineral assemblages with different temperature formations was also carried out using the TOPOS software package. The main copper phases are sulfates, followed by vanadates, hydroxyhalides, oxides, carbonates, silicates and finally, phosphates. New mineral occurrences for Vesuvius, both Cu-bearing and Cu-free, are described. Nevertheless, the fumarolic/alteration minerals at Vesuvius cannot be considered of economic relevance as a copper reservoir, this type of mineralizations are significant for copper crystal chemistry and for the knowledge of the mineralogical variants. The obtained datasets can be of interest for the knowledge of volcanic byproducts of copper ore deposits (i.e., porphyry copper systems) and of (base) metal segregation processes.

Estilos ABNT, Harvard, Vancouver, APA, etc.

24

Einaudi, Marco T. "Phase relations among silicates, copper iron sulfides, and aqueous solutions at magmatic temperatures; discussion". Economic Geology 82, n.º 2 (1 de abril de 1987): 497–501. http://dx.doi.org/10.2113/gsecongeo.82.2.497.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

25

McKenzie, William F., e Harold C. Helgeson. "Phase relations among silicates, copper iron sulfides, and aqueous solutions at magmatic temperatures; reply". Economic Geology 82, n.º 2 (1 de abril de 1987): 501–2. http://dx.doi.org/10.2113/gsecongeo.82.2.501.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

26

Fang, Weijun, Chaofa Xu Chaofa Xu, Jun Zheng, Guangjun Chen e Kong Jiang. "Fabrication of Cu–Ag bimetal nanotube-based copper silicates for enhancement of antibacterial activities". RSC Advances 5, n.º 49 (2015): 39612–19. http://dx.doi.org/10.1039/c5ra06065f.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

27

Jose, Sheethu, e Mundlapudi Lakshmipathi Reddy. "Lanthanum–strontium copper silicates as intense blue inorganic pigments with high near-infrared reflectance". Dyes and Pigments 98, n.º 3 (setembro de 2013): 540–46. http://dx.doi.org/10.1016/j.dyepig.2013.04.013.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

28

Sharygin, Victor, Vadim Kamenetsky, Liudmila Zhitova, Alexander Belousov e Adam Abersteiner. "Copper-Containing Magnesioferrite in Vesicular Trachyandesite in a Lava Tube from the 2012–2013 Eruption of the Tolbachik Volcano, Kamchatka, Russia". Minerals 8, n.º 11 (8 de novembro de 2018): 514. http://dx.doi.org/10.3390/min8110514.

Texto completo da fonte

Resumo:

Cu-rich magnesioferrite was found in vesicular basaltic trachyandesite in one of lava tubes (Duplex) that formed during the 2012–2013 eruption of the Tolbachik volcano, Kamchatka. This mineral is commonly associated with hematite, tenorite, halite, sylvite, and Ca-rich silicates (mainly, esseneite and Na-rich melilite) in high-temperature (800–1000 °C) reactionary zones (up to 100 µm) covering vesicular rocks and lava stalactites in the Duplex tube. The mineral relationships of this assemblage indicate the following crystallization sequence: Ca-rich silicates + hematite → Cu-rich magnesioferrite → tenorite → chlorides. This formed due to the reaction of hot gases containing Cu, alkalis, and Cl with solidified lava rock. The composition of magnesioferrite varies strongly in CuO (5.8–17.3 wt %; cuprospinel end-member—15–47 mol %), whereas the contents of other oxides are minor, indicating the main isomorphic substitution is Mg2+ ↔ Cu2+. Compositions with maximal CuO content nominally belong to Mg-rich cuprospinel: (Cu0.48Mg0.41Mn0.09Zn0.02Ca0.02) (Fe3+1.94Al0.03Ti0.02)O4. Increasing CuO content of the Duplex Cu-rich magnesioferrite is reflected in Raman spectra by moderate right shifting bands at ≈700–710 and 200–210 cm−1 and the appearance of an additional band at 596 cm−1. This supports the main isomorphic scheme and may indicate a degree of inversion in the spinel structure.

Estilos ABNT, Harvard, Vancouver, APA, etc.

29

Castillo, Hengels, Thomas Droguett, Mario Vesely, Pamela Garrido e Sergio Palma. "Simple Compressive Strength Results of Sodium-Hydroxide- and Sodium-Silicate-Activated Copper Flotation Tailing Geopolymers". Applied Sciences 12, n.º 12 (9 de junho de 2022): 5876. http://dx.doi.org/10.3390/app12125876.

Texto completo da fonte

Resumo:

Geopolymers are created by mixing a source of aluminosilicates, which can be natural or by-products of other industries, with an alkaline solution, which dissolves the aluminates and silicates present in this source, where after a polymerization process, an N-A-S-H gel is formed, which is responsible for providing the properties that characterize geopolymers. Among the variety of existing geopolymers, those based on by-products from other industries stand out since they were demonstrated to be a less-polluting alternative for concrete production than ordinary Portland cement (OPC). Due to the above, it is essential to study copper flotation tailings as raw material to generate geopolymers. The excessive amounts of existing tailing deposits also produce different risks for the nearby communities. Therefore, using this industrial waste as a construction material would provide several environmental and economic benefits. This article reports on the experimental work carried out in the laboratory of the Sustainable Mining Research Center CIMS of the Engineering Consulting Company JRI, where the effect of the alkaline activator type on the compressive strength of geopolymers based on copper flotation tailings was analyzed. For this purpose, two geopolymeric mixtures were made with different kinds of alkaline activators; one activated using 100% NaOH and the other activated with 100% sodium silicate (SS). From the results, it was found that the geopolymers activated with 100% SS obtained the highest compressive strength, reaching 36.46 MPa with 7 days of curing at 90 °C, followed by the geopolymers activated with 100% NaOH, where a compressive strength of 22.98 MPa was obtained under the same curing conditions. On the other hand, it was found that both geopolymers created were not leachable according to the TCLP test performed, and thus, these geopolymers were classified as non-toxic materials. In addition, it was found that both geopolymers presented a high infiltration value, making them practically impermeable.

Estilos ABNT, Harvard, Vancouver, APA, etc.

30

Neves, Patrícia, Anabela A. Valente e Zhi Lin. "Mild Liquid Phase Oxidation of Benzyl Alcohol in the Presence of Microporous Framework Copper Silicates". European Journal of Inorganic Chemistry 2020, n.º 13 (28 de fevereiro de 2020): 1172–76. http://dx.doi.org/10.1002/ejic.201901349.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

31

Wu, Shang-Feng, Yun-Jie Lai, Zeng-Yei Hseu e Yaw-Terng Chern. "Evaluation of Land Use Adaptation by Sequential Extraction of Soil Trace Elements at an Abandoned Gold and Copper Refinery Site in Northern Taiwan". Sustainability 14, n.º 11 (24 de maio de 2022): 6423. http://dx.doi.org/10.3390/su14116423.

Texto completo da fonte

Resumo:

This study site is located at an abandoned factory of mining, smelting, and refining of gold and copper in north Taiwan for more than one hundred years. The present study used soil background investigation out of the site and the sequential extraction procedures for arsenic and copper to assess the reutilization potential of brownfields at the site. The upper limit of background concentration out of the site was 300 mg/kg for arsenic and 700 mg/kg for copper. The soil arsenic within the site was mainly in the immobile fraction, such as forms fixed by layer silicates, that were very low risk for environmental releases. The soil copper in the abandoned sedimentation basin, gold refinery, and copper refinery was in the mobile fractions such as acid extractable, reducible, and oxidizable forms with higher release risk; therefore, except merely those three zones in the entire site with higher risk for environmental releases of copper, the release risks of trace elements are quite low in the rest of the areas, and land reuse without contact with soil or plant non-edible plants is possible. Therefore, in response to public demand for opening part of the site to promote local tourism development, appropriate control and isolation measures can be implemented to prevent the toxic elements from affecting human health through soil ingestion, skin contact, and other exposure pathways. In terms of pollution control, reducing dust inhalation is also an option to efficiently reduce health risks to an acceptable level and achieve the goal of sustainable land use at the contaminated site.

Estilos ABNT, Harvard, Vancouver, APA, etc.

32

Kostin, Aleksey. "Mineralization in the andesitic lava from Kildyam volcanic complex, central Yakutia, Russia". IOP Conference Series: Earth and Environmental Science 906, n.º 1 (1 de novembro de 2021): 012006. http://dx.doi.org/10.1088/1755-1315/906/1/012006.

Texto completo da fonte

Resumo:

Abstract This contribution presents the first detailed analysis of a new volcanic succession of olivine-pyroxenites, andesite, and dacite discovered in the Kildyam Late Jurassic complex in Central Yakutia. Petrographic and microprobe studies confirmed the liquid immiscibility in silicate melts during crystallization. Immiscible liquids are preserved as globules of one glass in another in andesites and as melted inclusions of native iron in matrix, clinopyroxene and plagioclase phenocrysts. Our analyses reveal the complex textural relationships between silicates and Fe-oxides, native iron and (Cu, Pb, Ag and Au)-rich phases, and provide unequivocal textural evidences, not observed previously. Purpose of this research is to preserve a very important data on IO (Iron Oxide) or IOCG (Iron Oxide Copper Gold) mineralization. Obtained results support occurrence and diverse of gold, silver, copper and lead minerals in magnetite lavas. During the early stage of fine-grained subvolcanic olivine-clinopyroxenite end pyrrhotite, globular igneous sulfides is a first proposed style of economic deposit formation. The second proposed style of economic mineralization in Kildyam is to be a magnetite-bearing lava; iron enrichment of the melilitic melt phase, followed by iron depletion and silica enrichment. The vesicle-hosted alloys and sulfides provide significant new data on metal transport and precipitation from high-temperature magmatic vapors. During syneruptive vapor phase exsolution, volatile metals (Cu-Zn, Fe-Al-Cu, Ni-Fe-Cu-Sn) and Ag-Cu-sulfides contribute to the formation of economic concentrations. Major conclusions contribute to 3-step genetic model. (1) Early-formed magmatic minerals led to partial dissolution of olivine-clinopyroxenite and their enrichment in Cu, Co and Ni relative to other metals, while troilite globules droplets grew.(2) First stage of division into two immiscible silicate and sulfide melt liquids (a) K-rich dacitic and rhyolithic glass, and (b) vesicles of heavy sulfide minerals with a large segregations and drops of native iron. (3) Lava of fused magnetite crystals and voids enriched in silver and gold, and (b) globular disseminated chalcopyrite in mineralized melilitic rocks.

Estilos ABNT, Harvard, Vancouver, APA, etc.

33

Dubovina, Milos, Nenad Grba, Dejan Krcmar, Jasmina Agbaba, Srdjan Roncevic, Djurdja Kerkez e Bozo Dalmacija. "Characterization of landfill deposited sediment from dredging process during different maturation stages". Journal of the Serbian Chemical Society 87, n.º 1 (2022): 133–44. http://dx.doi.org/10.2298/jsc210830102d.

Texto completo da fonte

Resumo:

A long-term monitoring of deposited sediment in the environment is considered in order to examine the mechanism of incorporation of Cu and Cd into mineral fractions and to investigate their bioavailability during landfill maturation. Using the sequential extraction technique (Community Bureau of Reference, BCR), the dominant presence of Cu and Cd in the oxidation and residual fraction was determined, which suggests a low risk of bioavailability of these metals in the environment. The maturation of the deposited sediment indicates that the Cu and Cd content decreases over time in the exchangeable fraction and increases in the oxidation fraction. X-ray techniques XRF and EDS indicated a prevalence of silicates in the tested samples, which suggests the possibility of presence of silicate compounds that can bind metals and thus convert them into less mobile forms in the sediment. By imaging the samples with a scanning electron microscope SEM, the formation of heterogeneous structures over time was determined, which confirms the formation of new minerals and the potential possibility of incorporating copper and cadmium in them. In order to determine the mineral forms and dominant compounds in the examined sediment samples, X-ray diffraction analysis was applied, and the transformation pathways were explained.

Estilos ABNT, Harvard, Vancouver, APA, etc.

34

Kontonikas-Charos, Alkis, Cristiana L. Ciobanu, Nigel J. Cook, Kathy Ehrig, Roniza Ismail, Sasha Krneta e Animesh Basak. "Feldspar mineralogy and rare-earth element (re)mobilization in iron-oxide copper gold systems from South Australia: a nanoscale study". Mineralogical Magazine 82, S1 (28 de fevereiro de 2018): S173—S197. http://dx.doi.org/10.1180/minmag.2017.081.040.

Texto completo da fonte

Resumo:

ABSTRACTNanoscale characterization (TEM on FIB-SEM-prepared foils) was undertaken on feldspars undergoing transformation from early post-magmatic (deuteric) to hydrothermal stages in granites hosting the Olympic Dam Cu-U-Au-Ag deposit, and from the Cu-Au skarn at Hillside within the same iron-oxide copper-gold (IOCG) province, South Australia. These include complex perthitic textures, anomalously Ba-, Fe-, or REE-rich compositions, and REE-flourocarbonate + molybdenite assemblages which pseudomorph pre-existing feldspars. Epitaxial orientations between cryptoperthite (magmatic), patch perthite (dueteric) and replacive albite (hydrothermal) within vein perthite support interface-mediated reactions between pre-existing alkali-feldspars and pervading fluid, irrespective of micro-scale crystal morphology. Such observations are consistent with a coupled dissolution-reprecipitation reaction mechanism, which assists in grain-scale element remobilization via the generation of transient interconnected microporosity. Micro-scale aggregates of hydrothermal hyalophane (Ba-rich K-feldspar), crystallizing within previously albitized areas of andesine, reveal a complex assemblage of calc-silicate, As-bearing fluorapatite and Fe oxides along reaction boundaries in the enclosing albite-sericite assemblage typical of deuteric alteration. Such inclusions are good REE repositories and their presence supports REE remobilization at the grain-scale during early hydrothermal alteration. Iron-metasomatism is recognized by nanoscale maghemite inclusions within ‘red-stained’ orthoclase, as well as by hematite in REE-fluorocarbonates, which reflect broader-scale zonation patterns typical for IOCG systems. Potassium-feldspar from the contact between alkali-granite and skarn at Hillside is characterized by 100–1000 ppm REE, attributable to pervasive nanoscale inclusions of calc-silicates, concentrated along microfractures, or pore-attached. Feldspar replacement by REE-fluorcarbonates at Olympic Dam and nanoscale calc-silicate inclusions in feldspar at Hillside are both strong evidence for the role of feldspars in concentrating REE during intense metasomatism. Differences in mineralogical expression are due to the availability of associated elements. Lattice-scale intergrowths of assemblages indicative of Fe-metasomatism, REE-enrichment and sulfide deposition at Olympic Dam are evidence for a spatial and temporal relationship between these processes.

Estilos ABNT, Harvard, Vancouver, APA, etc.

35

Ren, Yanping, Ruiyu Ding, Hairong Yue, Siyang Tang, Changjun Liu, Jinbo Zhao, Wen Lin e Bin Liang. "Amine-grafted mesoporous copper silicates as recyclable solid amine sorbents for post-combustion CO 2 capture". Applied Energy 198 (julho de 2017): 250–60. http://dx.doi.org/10.1016/j.apenergy.2017.04.044.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

36

Chanquía, Corina M., Analía L. Cánepa, Julián Bazán-Aguirre, Karim Sapag, Enrique Rodríguez-Castellón, Patricio Reyes, Eduardo R. Herrero, Sandra G. Casuscelli e Griselda A. Eimer. "Copper-containing spherical mesoporous silicates prepared by template-ion exchange: A multitechnique characterization and oxidation properties". Microporous and Mesoporous Materials 151 (março de 2012): 2–12. http://dx.doi.org/10.1016/j.micromeso.2011.07.001.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

37

Koud, Jean-Mathias. "Genèse et évolution des silicates de cuivre dans le gisement de Mindouli au Congo. / Genesis and evolution of copper silicates in the ore deposit of Mindouli, Congo". Sciences Géologiques. Bulletin 41, n.º 3 (1988): 279–88. http://dx.doi.org/10.3406/sgeol.1988.1799.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

38

SHESTAKOV, N. I., A. V. KORSHUNOV e S. V. PUTILIN. "PROSPECTS FOR THE APPLICATION OF COPPER MELTING SLAG IN ROAD CONSTRUCTION". Building and reconstruction 98, n.º 6 (2021): 90–97. http://dx.doi.org/10.33979/2073-7416-2021-98-6-90-97.

Texto completo da fonte

Resumo:

The article discusses the option of strengthening the soils of the roadbed of highways with complex binders based on granular slag of copper smelting production and air lime. The characteristics of the investigated slag, photomicrographs of its surface, as well as the chemical and phase compositions are presented. A detailed description of the X-ray diffractogram of the studied slag with the processing of the obtained reflections using the ICDD PDF-2 database is presented. Calculations of hydrolytic equilibria were carried out using the main phases found from the data of X-ray phase analysis. It was found by the calculation method that at pH = 11-12 in the lime-slag mixture decomposition of iron silicates and aluminosilicates occurs with the formation of gels of iron and aluminum hydroxides, as well as amorphous silica. On the basis of the obtained complex binder, standard samples of strengthened soil based on loam were made and tested to determine the physical and mechanical properties. The results of the experiments carried out create an opportunity for obtaining hardened soils based on a complex mineral binder with a compressive strength of up to 2.2 MPa.

Estilos ABNT, Harvard, Vancouver, APA, etc.

39

Marinho-Reis, Amélia P., Cristiana Costa, Fernando Rocha, Mark Cave, Joanna Wragg, Teresa Valente, Amália Sequeira-Braga e Yves Noack. "Biogeochemistry of Household Dust Samples Collected from Private Homes of a Portuguese Industrial City". Geosciences 10, n.º 10 (1 de outubro de 2020): 392. http://dx.doi.org/10.3390/geosciences10100392.

Texto completo da fonte

Resumo:

The main objectives of the present study were to (i) investigate the effects of mineralogy and solid-phase distribution on element bioaccessibility and (ii) perform a risk assessment to calculate the risks to human health via the ingestion pathway. Multiple discriminant analysis showed that the dust chemistry discriminates between indoor and outdoor samples. The solid-phase distribution of the elements in indoor dust indicated that a large proportion of zinc, nickel, lead, copper, and cobalt is associated with an aluminum oxy-hydroxides component, formed by the weathering of aluminum silicates. This component, which seems to influence the mobility of many trace elements, was identified for a group of indoor dust samples that probably had a considerable contribution from outdoor dust. An iron oxide component consisted of the highest percentage of chromium, arsenic, antimony, and tin, indicating low mobility for these elements. The bioaccessible fraction in the stomach phase from the unified BARGE method was generally high in zinc, cadmium, and lead and low in nickel, cobalt, copper, chromium, and antimony. Unlike other potentially toxic elements, copper and nickel associated with aluminum oxy-hydroxides and calcium carbonates were not extracted by the stomach solutions. These trace elements possibly form stable complexes with gastric fluid constituents such as pepsin and amino acid. Lead had a hazard quotient >1, which indicates the risk of non-carcinogenic health effects, especially for children.

Estilos ABNT, Harvard, Vancouver, APA, etc.

40

Popovic, Aleksandar, e Dragana Djordjevic. "Speciation of selected trace and major elements in lignite used in "Nikola Tesla A" power plant (Obrenovac, Serbia)". Journal of the Serbian Chemical Society 70, n.º 12 (2005): 1497–513. http://dx.doi.org/10.2298/jsc0512497p.

Texto completo da fonte

Resumo:

Four samples of milled lignite used in the "Nikola Tesla A" power plant located in Obrenovac near Belgrade, were subjected to a five-step sequential extraction, comprising of the following phases: distilled water, 1M ammonium acetate, 0.2M ammonium oxalate/0.2M oxalic acid, acidic solution of H2O2and a 6M solution of HCl. The concentrations of the different elements obtained in the extractions were statistically analyzed. The majority of the examined elements were found to be most probably associated with inorganic fractions of lignite, only aluminum, silicon, chromium and arsenic have a larger extractable organic/sulfide fraction than an extractable inorganic fraction. Alumosilicates of magnesium (carriers of arsenic, zinc, lead, copper and chromium), silicates of potassium (scavengers of lead and nickel), mixed aluminates of iron and magnesium (carriers of arsenic, zinc, copper and chromium) and compounds of iron that do not contain aluminum and magnesium (scavengers of manganese) were dissolved in the fifth phase of the sequential extraction. Copper is a substrate of alumosilicates of potassium and magnesium, while zinc and chromium are substrates of compounds of iron leached in the third phase of the sequential extraction. Interphase correlation revealed that the adsorbed and ion-exchangeable fractions of most of the examined elements do not exhibit preferential binding to the components of the inorganic matrix of lignite ash.

Estilos ABNT, Harvard, Vancouver, APA, etc.

41

Karimova, L. M., e Y. T. Kairalapov. "Percolation leaching of clay mixed copper ores". iPolytech Journal 26, n.º 1 (5 de abril de 2022): 142–53. http://dx.doi.org/10.21285/1814-3520-2022-1-142-153.

Texto completo da fonte

Resumo:

The present work addresses the problem of improving the percolation properties of heap leaching piles of clay, slime-oxidised and mixed ores. These ores are prone to colmatation, which hinders percolation of the solution through the ore layer. Laboratory tests on percolation leaching were carried out using a 2 m column having an internal diameter of 190 mm, loaded with 89.42 kg of ore material having a grain size of -55+0 mm. In order to eliminate colmatation, the ore layer was divided into two equal parts by a drainage layer of polystyrene foam. The research object was ore material extracted from the northern Nurkazgan deposit (Karaganda region, Republic of Kazakhstan), in which copper is present in the form of sulphide (53.48%) and oxidised minerals (46.52%), including 23.5% of chrysocolla. The mineral composition of a test sample determined by optical and electron microscopy, X-ray diffraction, local X-ray spectral, X-ray fluorescence and inductively coupled plasma mass spectrometry was characterised by 93.78% of rock-forming minerals, 53.23% of which comprised layered silicates, namely, mica, chlorite and kaolinite. Ore mineralisation was characterised by both sulphide (copper sulphides, pyrite) and oxide (malachite, iron hydroxides and manganese oxides) phases. The content of easy-sliming minerals equalled 56.30%. Prior to leaching, moisture saturation during the period of one day was carried out. The ore was top irrigated with a solution of sulphuric acid having a concentration of 60 g/dm3. Pregnant solutions were processed following a sorption method (sorption/desorption–electrolysis). The copper extraction into the solution yielded 60.04% with a sulphuric acid consumption of 50.0 kg/t ore at an average irrigation rate of 10.58 dm3/(m2h) or 0.1058 dm/h per clear opening. Therefore, heap leaching of ores at a layer height of lower than 1 m can be performed following the "leaching–extraction/re-extraction or sorption/desorption–electrolysis" scheme.

Estilos ABNT, Harvard, Vancouver, APA, etc.

42

Kłonkowski, Andrzej M., Beata Grobelna, Teresa Widernik, Anna Jankowska-Frydel e Włodzimierz Mozgawa. "The Coordination State of Copper(II) Complexes Anchored and Grafted onto the Surface of Organically Modified Silicates†". Langmuir 15, n.º 18 (agosto de 1999): 5814–19. http://dx.doi.org/10.1021/la981256+.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

43

Hinokuma, Satoshi, Saaya Kiritoshi, Yusuke Kawabata, Kento Araki, Shun Matsuki, Tetsuya Sato e Masato Machida. "Catalytic ammonia combustion properties and operando characterization of copper oxides supported on aluminum silicates and silicon oxides". Journal of Catalysis 361 (maio de 2018): 267–77. http://dx.doi.org/10.1016/j.jcat.2018.03.008.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

44

Zhang, Yanshuang, Yubai Zhang, Xinqiao Zhao e Yujun Zhang. "Sol–gel synthesis and properties of europium–strontium copper silicates blue pigments with high near-infrared reflectance". Dyes and Pigments 131 (agosto de 2016): 154–59. http://dx.doi.org/10.1016/j.dyepig.2016.04.011.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

45

Thomas, Mark. "Understanding gangue acid consumption in copper sulfide heap leaching: Predicting the impact of carbonates, silicates and secondary precipitates". Minerals Engineering 171 (setembro de 2021): 107090. http://dx.doi.org/10.1016/j.mineng.2021.107090.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

46

Kazin, Pavel E., Mikhail A. Zykin, Olga R. Gazizova e Yury D. Tretyakov. "Introduction of Copper Ions in the Hexagonal Channels of the Apatite Type La-Sr and La-Ca Silicates". Zeitschrift für anorganische und allgemeine Chemie 635, n.º 12 (outubro de 2009): 2072–76. http://dx.doi.org/10.1002/zaac.200900209.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

47

Lam, Elizabeth J., Vicente Zetola, Yendery Ramírez, Ítalo L. Montofré e Franco Pereira. "Making Paving Stones from Copper Mine Tailings as Aggregates". International Journal of Environmental Research and Public Health 17, n.º 7 (3 de abril de 2020): 2448. http://dx.doi.org/10.3390/ijerph17072448.

Texto completo da fonte

Resumo:

Copper mining, the central axis of Chile’s economic development, produces a large number of tailings, which become a potential environmental risk. This study aims to evaluate the mechanical properties resulting from the making of Portland cement mixtures with tailings as aggregates so that they can be eventually used in paving stones for building inactive tailings dams. Tailings coming from two dams at a concentration plant located in Taltal (Chile) were used. Currently, Dam 1 is inactive, while Dam 2 is active. The tailings samples obtained from both dams were granulometrically characterized by sieving. In addition, pH, humidity, Eh, and mineralogical assays (sulfides, oxides, sulfates, carbonates, phosphates, and silicates) were measured. The fines content of the tailings from Dams 1 and 2 with a sieve size of N°200 ASTM were 76.2% and 29.6%, respectively. Therefore, owing to their high percentage of fines, they cannot be as used as concrete aggregates. Aggregates must contain a maximum percentage of fines so that mortars and concrete can meet Chilean standards. In this paper, to comply with a 7% and 15% fines content lower than 0.075 mm, tailings materials were mixed with conventional aggregates containing very little fines. In addition, a reference mixture was made with only tailings aggregates with and without a superplasticizer additive. To measure the mixtures of cement, aggregates, and tailings, bending and compression strength assays were made of the specimens after a 28-day curing, according to the Chilean standard. The results of the study show that the addition of only part of the tailings to the mixture increases bending strength by 26% and compression strength by 180% compared with the reference mortar, with a fines content lower than 0.075 mm in the 7% mixture, thus allowing paving stone manufacture with tailings materials. In addition, it was possible to increase the workability of the reference mixture by using superplasticizers as additives.

Estilos ABNT, Harvard, Vancouver, APA, etc.

48

Pekov, Igor V., Natalia V. Zubkova e Dmitry Yu Pushcharovsky. "Copper minerals from volcanic exhalations – a unique family of natural compounds: crystal-chemical review". Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 74, n.º 6 (1 de dezembro de 2018): 502–18. http://dx.doi.org/10.1107/s2052520618014403.

Texto completo da fonte

Resumo:

The crystal-chemical characterization of oxysalts (sulfates, arsenates, vanadates, selenites, silicates, molybdates and borates), chlorides and oxides with species-defining Cu2+ formed in volcanic fumaroles (96 minerals representing 80 structure types; 81 species are endemic to fumarolic formation) is given. Copper minerals are known only from oxidizing-type fumaroles. The most diverse copper mineralization occurs at the Tolbachik volcano (Kamchatka, Russia). Copper minerals from fumarolic systems are subdivided into two genetic groups: Group I are minerals formed in the hot zones of fumaroles (>473 K, mainly 673–973 K) and Group II are minerals formed in the moderately hot zones of fumaroles (<473 K, mainly at 343–423 K). Group I includes 81 mineral species. Their most defining chemical feature is that all of them are hydrogen-free, and many of them contain the additional anion O2−. In comparison with minerals from other geological environments, in minerals of Group I the Cu2+ cation exhibits the strongest affinity for four- and fivefold coordinations and the strongest distortion of Cu2+-centred octahedra. Group II consists of 15 chlorides and sulfates including 13 H-bearing species. In these minerals the Cu2+ cation shows affinity for octahedral coordination, with OH− and/or H2O0 as ligands. In terms of crystal chemistry these minerals are closer to supergene minerals rather than to high-temperature fumarolic species. Temperature is the major factor governing the crystal chemistry of Cu2+ oxysalts and chlorides in low-pressure systems. The defining feature of fumarolic copper mineralization over this whole temperature range is the important role of alkali cations. The available data on complexes of Cu2+-centred polyhedra in the structures of natural oxysalts and halides are summarized and reviewed. Isomorphism in copper minerals from volcanic exhalations is discussed. The structures of high-temperature Cu oxysalts with additional O2− anions (i.e. O atoms non-bonded to S6+, Mo6+, As5+, V5+, Se4+ or B3+) are also interpreted using an approach based on oxocentred tetrahedra.

Estilos ABNT, Harvard, Vancouver, APA, etc.

49

Costa, Leonor, Margarida Nunes, Sónia Costa, Milene Trindade, Catarina Miguel e Teresa Ferreira. "Unveiling the Ambrotype: Characterization of Two 19th Century Photographs". Microscopy and Microanalysis 25, n.º 1 (2 de agosto de 2018): 203–13. http://dx.doi.org/10.1017/s1431927618000429.

Texto completo da fonte

Resumo:

AbstractThis work used a multi-analytical approach to characterize two 19th century ambrotypes and was motivated by the lack of insight on these historical objects. Photographic imaging and optical microscopy (OM) were used to identify abrasions, cracks related to reticulation, tarnishing, and other aspects associated to production and degradation processes. With variable pressure scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (EDS) these processes were seen with great detail and further characterized. Elemental point analysis and elemental mapping showed that the photosensitive material used was silver iodide. Degradation compounds were found as silver and chlorine-containing compounds. In one of the items, the tarnishing area also contained redeposited silver in a ring-shape surrounding a nucleus rich in silver, copper, and sulfur, in addition to copper-based salts. EDS analyses also identified that the supports were common soda–lime–silica glasses, refined with arsenic; and showed that a pigment rich in iron was used in both items to hand color the cheeks, extended with aluminum silicates alone or mixed with barium sulfate. Theμ-Raman study pointed out that a synthetic Mars pigment was employed.μ-Fourier-transform infrared spectroscopy analyses identified collodion as the binder. Shellac was used as a protective varnish in one of the items and a gum was possibly employed on the other. Bitumen was used for the background in one ambrotype.

Estilos ABNT, Harvard, Vancouver, APA, etc.

50

Song, In Gu, Christopher Timmons, Galit Levitin e Dennis W. Hess. "Photoresist Removal Using Alternative Chemistries and Pressures". Solid State Phenomena 145-146 (janeiro de 2009): 303–10. http://dx.doi.org/10.4028/www.scientific.net/ssp.145-146.303.

Texto completo da fonte

Resumo:

Approximately 20% of the processing steps in integrated circuit (IC) fabrication involve surface cleaning and removal of photoresist and plasma etch residues. Continuous device minimization requires the use of thin films (<20 nm), closely spaced features, and ultra shallow junctions (<50nm); as a result, the challenges associated with effective surface cleaning are intensified. In addition, to insure high device performance, incorporation of alternate materials such as copper, ruthenium, and molybdenum, porous low dielectric constant SiO2-based insulators, and hafnium or zirconium oxides or silicates into device structures is taking place. Integration of these materials into working devices requires precise control of surface properties. In order to eliminate damage to films or substrates, avoid modification of surfaces, promote contaminant removal rates and enhance process control, approaches such as use of downstream plasmas, liquid cleaning with low concentrations of reactive chemicals, mechanical agitation, and liquid or particle jets have been implemented [1].

Estilos ABNT, Harvard, Vancouver, APA, etc.

Artigos de revistas sobre o tema "Copper silicates"

Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos