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Articoli di riviste sul tema "Copper Spinel"

Autore: Grafiati

Pubblicato: 12 ottobre 2024

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1

Białas, Anna, Kamil Rugała, Cezary Czosnek, Grzegorz Mordarski e Jacek Gurgul. "Copper Aluminum Spinels Doped with Cerium as Catalysts for NO Removal". Catalysts 10, n. 12 (28 novembre 2020): 1388. http://dx.doi.org/10.3390/catal10121388.

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Cu-Ce(Mn)-Al oxide catalysts to NO removal in the broad temperature range were synthesized and tested. The precursor of copper aluminium spinel was obtained with the coprecipitation method. By this method, Cu–Al spinels with various amounts of manganese and cerium were synthesized as well. These oxides crystallized in the structure of inverse spinel; however, Ce doping caused the appearance of additional CeO2 phase as determined by XRD. The samples were mesoporous solids with moderate surface area and porosity measured by low temperature sorption of nitrogen. The addition of another metal to Cu–Al spinel caused an increase of activity in selective catalytic reduction of nitrogen oxide with ammonia. The presence of manganese caused the formation of a higher amount of N2O by-product. The catalytic activity increased with the cerium concentration. For the sample with the atomic ratio Ce0.15Cu0.18, ca. 90% of NO conversion was registered between 200 and 350 °C. As examined with XPS spectroscopy, such conversion was attained due to the good dispersion of copper on the catalyst surface. This copper was placed mainly in spinel octahedral positions which enable its easier reduction. The spinel structure causes the presence of cerium as the trivalent cation important in redox cycles with the participation of copper.

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2

Fan, Fenglan, Lingjuan Wang, Lei Wang, Jinyu Liu e Minghui Wang. "Low-Temperature Selective NO Reduction by CO over Copper-Manganese Oxide Spinels". Catalysts 12, n. 6 (29 maggio 2022): 591. http://dx.doi.org/10.3390/catal12060591.

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Selective catalytic reduction of NO with CO (CO-SCR) has been suggested as an attractive and promising technology for removing NO and CO simultaneously from flue gas. Manganese-copper spinels are a promising CO−SCR material because of the high stability and redox properties of the spinel structure. Here, we synthesized CuxMn3−xO4 spinel by a citrate-based modified pechini method combining CuO and MnOx, controlling the molar Cu/Mn concentrations. All the samples were characterized by SEM, EDX, XRD, TEM, H2−TPR, XPS and nitrogen adsorption measurements. The Cu1.5Mn1.5O4 catalyst exhibits 100% NO conversion and 53.3% CO conversion at 200 °C. The CuxMn3−xO4 catalyst with Cu-O-Mn structure has a high content of high valence Mn, and the high mass transfer characteristics of the foam-like structure together promoted the reaction performance. The CO-SCR catalytic performance of Cu was related to the spinel structure with the high ratio of Mn4+/Mn, the synergistic effect between the two kinds of metal oxides and the multistage porous structure.

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3

Mandal, Siba Prasad. "Analysis of DC Conductivity and I-V Characterization of Nanocrystalline Copper Ferrite Sample at and above Room Temperature". Materials Science Forum 1103 (25 ottobre 2023): 121–28. http://dx.doi.org/10.4028/p-s3luqw.

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Spinel copper ferrite nanoparticles have wide spread technological applications. Polycrystalline copper ferrite nanoparticles is prepared by sonochemical method. The structural property is investigated by X-ray diffraction study, which reveals cubic spinel structure of copper ferrite NPs with average crystalline size of 20 nm. The temperature variation of DC conductivity of copper ferrite nanoparticles is studied. The conductivity is observed to increase with temperature which implies semiconducting nature of copper ferrite. The Mott study reveals that conduction process is three dimensional in present case. Again, p-n junction formation in the ferrite system is observed from the current voltage (I-V) study. This study further shows that the trap height increases with temperature. Ideality factor with values greater than 1 has been observed in present case.

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4

Sahu, Sulata K., e Alexandra Navrotsky. "Thermodynamics of copper‐manganese and copper‐iron spinel solid solutions". Journal of the American Ceramic Society 100, n. 8 (22 aprile 2017): 3684–92. http://dx.doi.org/10.1111/jace.14813.

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5

Ahmed, Awad I., S. E. Samra e S. A. El-Hakam. "Structural and surface aspects of thermally treated copper aluminium mixed hydroxides". Canadian Journal of Chemistry 69, n. 10 (1 ottobre 1991): 1511–15. http://dx.doi.org/10.1139/v91-223.

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CuO–Al2O3 catalysts containing various amounts of copper oxide have been prepared by precipitation. The phase changes were studied by X-ray diffraction. The results obtained revealed that the thermal treatment of solid CuO–Al2O3 at 700 °C produced only crystalline CuO. Heating to 900 °C led to the formation of copper alumina spinel together with unreacted CuO and γ-Al2O3. The spinel content was found to increase with increasing copper content. Nitrogen adsorption–desorption isotherms on the calcined samples have been measured. Surface areas have been calculated and the pore structure analysed. The textural properties of the system were found to depend on both the copper content and the calcination temperature. Key words: CuO, Al2O3 catalysts, structure, surface area, pore structure.

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6

Othéro de Brito, Vera Lúcia, Stéphanie Alá Cunha, Ana Paula Ribeiro Uchoas, Fabiana Faria de Araújo, Cristina Bormio Nunes e Luis Antonio Genova. "Evaluation of the Sinterability of Copper-Substituted Ferrites by Means of Dilatometric Thermal Analysis". Materials Science Forum 805 (settembre 2014): 254–59. http://dx.doi.org/10.4028/www.scientific.net/msf.805.254.

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Cobalt and cobalt-manganese spinel ferrites have magnetostrictive properties suitable for application in magneto-electric and magneto-mechanical transducers. In this work, copper-substituted ferrites of these compositions were processed by means of the ceramic method and their sinterabilities were evaluated by dilatometric thermal analyses. The results obtained suggest that copper affects the solid-state reactions for the spinel formation and lowers the required sintering temperature for the ferrites. However, the densification obtained with sintering of the copper-substituted ferrites at 950oC for 6h was only 64%, which indicates that further adjustments on the processing route must be made in order to obtain higher densities.

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7

Flores-Lasluisa, Jhony Xavier, Javier Quílez-Bermejo, Ana Cristina Ramírez-Pérez, Francisco Huerta, Diego Cazorla-Amorós e Emilia Morallón. "Copper-Doped Cobalt Spinel Electrocatalysts Supported on Activated Carbon for Hydrogen Evolution Reaction". Materials 12, n. 8 (20 aprile 2019): 1302. http://dx.doi.org/10.3390/ma12081302.

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The development of electrocatalysts based on the doping of copper over cobalt spinel supported on a microporous activated carbon has been studied. Both copper–cobalt and cobalt spinel nanoparticles were synthesized using a silica-template method. Hybrid materials consisting of an activated carbon (AC), cobalt oxide (Co3O4), and copper-doped cobalt oxide (CuCo2O4) nanoparticles, were obtained by dry mixing technique and evaluated as electrocatalysts in alkaline media for hydrogen evolution reaction. Physical mixtures containing 5, 10, and 20 wt.% of Co3O4 or CuCo2O4 with a highly microporous activated carbon were prepared and characterized by XRD, TEM, XPS, physical adsorption of gases, and electrochemical techniques. The electrochemical tests revealed that the electrodes containing copper as the dopant cation result in a lower overpotential and higher current density for the hydrogen evolution reaction.

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8

Komova, Oksana V., Valentina I. Simagina, Alena A. Pochtar, Olga A. Bulavchenko, Arcady V. Ishchenko, Galina V. Odegova, Anna M. Gorlova et al. "Catalytic Behavior of Iron-Containing Cubic Spinel in the Hydrolysis and Hydrothermolysis of Ammonia Borane". Materials 14, n. 18 (19 settembre 2021): 5422. http://dx.doi.org/10.3390/ma14185422.

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The paper presents a comparative study of the activity of magnetite (Fe3O4) and copper and cobalt ferrites with the structure of a cubic spinel synthesized by combustion of glycine-nitrate precursors in the reactions of ammonia borane (NH3BH3) hydrolysis and hydrothermolysis. It was shown that the use of copper ferrite in the studied reactions of NH3BH3 dehydrogenation has the advantages of a high catalytic activity and the absence of an induction period in the H2 generation curve due to the activating action of copper on the reduction of iron. Two methods have been proposed to improve catalytic activity of Fe3O4-based systems: (1) replacement of a portion of Fe2+ cations in the spinel by active cations including Cu2+ and (2) preparation of highly dispersed multiphase oxide systems, involving oxide of copper.

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9

Zhao, B., P. Hayes e E. Jak. "Effects of CaO, Al2O3 and MgO on liquidus temperatures of copper smelting and converting slags under controlled oxygen partial pressures". Journal of Mining and Metallurgy, Section B: Metallurgy 49, n. 2 (2013): 153–59. http://dx.doi.org/10.2298/jmmb120812009z.

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Phase equilibria of silicate slags relevant to the copper smelting/converting operations have been experimentally studied over a wide range of slag compositions, temperatures and atmospheric conditions. Selected systems are of industrial interest and fill the gaps in fundamental information required to systematically characterise and describe copper slag chemistry. The experimental procedures include equilibration of synthetic slag at high temperatures, rapid quenching of resulting phases, and accurate measurement of phase compositions using electron probe X-ray microanalysis (EPMA). The effects of CaO, Al2O3 and MgO on the phase equilibria of this slag system have been experimentally investigated in the temperature range 1200 to 1300 oC and oxygen partial pressures between 10-5 and 10-9 atm. It was found that spinel and silica are major primary phases in the composition range related to copper smelting/converting slags. In addition, olivine, diopside and pyroxene also appear at certain conditions. The presence of CaO, MgO and Al2O3 in the slag increases the spinel liquidus and decreases the silica liquidus. Liquidus temperatures in silica primary phase field are not sensitive to Po2; Liquidus temperatures in spinel primary phase field increase with increasing Po2. At 1300 oC and low Po2, the spinel (Fe2+,Mg2+)O.(Al3+,Fe3+) primary phase field can be replaced by wustite (Fe2+,Mg2+)O.

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10

Wang, N., M. Chen, Z. Zou, Z. Zhang, Y. Xiao e Y. Yang. "Liquidus and phase equilibria in CaO-Al2O3-FeOx-SiO2 system under intermediate oxygen partial pressure". Journal of Mining and Metallurgy, Section B: Metallurgy 49, n. 2 (2013): 139–44. http://dx.doi.org/10.2298/jmmb120826014w.

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Abstract (sommario):

Phase equilibria of silicate slags relevant to the copper smelting/converting operations have been experimentally studied over a wide range of slag compositions, temperatures and atmospheric conditions. Selected systems are of industrial interest and fill the gaps in fundamental information required to systematically characterise and describe copper slag chemistry. The experimental procedures include equilibration of synthetic slag at high temperatures, rapid quenching of resulting phases, and accurate measurement of phase compositions using electron probe X-ray microanalysis (EPMA). The effects of CaO, Al2O3 and MgO on the phase equilibria of this slag system have been experimentally investigated in the temperature range 1200 to 1300 oC and oxygen partial pressures between 10-5 and 10-9 atm. It was found that spinel and silica are major primary phases in the composition range related to copper smelting/converting slags. In addition, olivine, diopside and pyroxene also appear at certain conditions. The presence of CaO, MgO and Al2O3 in the slag increases the spinel liquidus and decreases the silica liquidus. Liquidus temperatures in silica primary phase field are not sensitive to Po2; Liquidus temperatures in spinel primary phase field increase with increasing Po2. At 1300?C and low Po2, the spinel (Fe2+,Mg2+)O.(Al3+,Fe3+) primary phase field can be replaced by wustite (Fe2+,Mg2+)O.

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11

de WILDE, E., I. BELLEMANS, M. CAMPFORTS, M. GUO, B. BLANPAIN, N. MOELANS e K. VERBEKEN. "Sessile drop evaluation of high temperature copper/spinel and slag/spinel interactions". Transactions of Nonferrous Metals Society of China 26, n. 10 (ottobre 2016): 2770–83. http://dx.doi.org/10.1016/s1003-6326(16)64344-3.

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12

Mindru, Ioana, Dana Gingasu, Luminita Patron, Gabriela Marinescu, Jose Maria Calderon-Moreno, Silviu Preda, Ovidiu Oprea e Sultana Nita. "Copper aluminate spinel by soft chemical routes". Ceramics International 42, n. 1 (gennaio 2016): 154–64. http://dx.doi.org/10.1016/j.ceramint.2015.08.058.

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13

Ye, Ming Quan, Ai Jun Han, Zhou Shuo Chu, Jian Fei Che e Chen Wang. "Synthesis and Characterization of Mn-Doped Copper Chromite Black Pigments". Advanced Materials Research 602-604 (dicembre 2012): 71–75. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.71.

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Mn-doped black pigments CuMnxCr2-xO4(x=0, 0.05, 0.10, 0.15, 0.20 and 0.25) were synthesized by precursor coprecipitation method, and characterized by TG-DTA, XRD, FTIR and colorimetric analysis. The TG-DTA curves showed the crystal transition temperature was at about 800°C and mass loss ended at about 450°C. The infrared spectra displayed vibrations of spinel phase. XRD patterns displayed the characteristic peaks of the tetragonal phase spinel structure and proved that Mn substituted Cr in the spinel crystal lattice. L*a*b* analysis showed that all samples are black pigments with blue intensity, and Mn-doping could strengthen the black intensity and weaken the blue intensity of such black pigments.

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14

Adarakatti, Shashidhar N., Veeresh S. Pattar, Prashant K. Korishettar, Bhagyashri V. Grampurohit, Ravindra G. Kharabe, Akshay B. Kulkarni, Shridhar N. Mathad, Chidanandayya S. Hiremath e Rangappa B. Pujar. "Synthesis, Structural and Electrical Studies of Li-Ni-Cu Nano Ferrites". Acta Chemica Iasi 26, n. 1 (1 luglio 2018): 1–12. http://dx.doi.org/10.2478/achi-2018-0001.

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Abstract Li-Ni ferrite has gained great scientific elicit owing to of its unparalleled properties and applications. The copper doped Li-Ni ferrite has been synthesized by sucrose method. The structure was characterized by X-ray diffraction, which has confirmed the formation of single-phase spinel structure. X-ray diffraction and FTIR data reveals the formation of cubic structure phase. Unit cell parameters vary with copper content; overall variation of the unit cell parameters obeys Vegard’s law. The main absorption bands of spinel ferrite have appeared through IR absorption spectra recorded in the range of 300–700 cm−1. The copper concentration dependence of lattice parameters obeys Vegard’s law. DC electrical resistivity of the prepared samples decreases with increasing in the temperature which shows the semiconducting behaviour of all nano ferrites. The most prominent influence copper doping on the electrical properties of Li-Ni ferrites has been reported.

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15

M., Ankushev, Zaykov V., Molchanov I., Koryakova L., Panteleyeva S. e Yuminov A. "Metallurgical Slags and Ore Fragments from the Kamenny Ambar Bronze Age Settlement (Southern Urals): a Key to Knowledge of Copper Sources". Teoriya i praktika arkheologicheskikh issledovaniy 33, n. 1 (2021): 34–57. http://dx.doi.org/10.14258/tpai(2021)33(1).-03.

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Abstract: The paper presents the characteristics of metallurgical slags and copper ore fragments from the Kamenny Ambar settlement of the Bronze Age. According to the mineral and chemical compositions we have distinguished two types of the slags: Cr-rich spinel containing olivine slags and sulfide-containing olivine slags. The Cr-rich spinel containing olivine slags are the product of oxidized ore from the copper deposits in ultramafic rocks exploited in the early Sintashta-Petrovka period the settlement functioning. The sulfide-containing olivine slags are the result of the secondary sulfide ores from the massive-sulfide, and less likely copper porphyry deposits during the latter Srubnaya-Alakul period. A similar change in the copper ore raw material type was also recorded in other Bronze Age settlements in the Southern Urals. In the Kamenny Ambar settlement and analogs, we have defined the main indicating minerals which allow us to determine the source for the Cu raw metal in historical time: Cr-rich spinels, sulfides, and tourmalines. Keywords: metallurgical slags, Bronze Age, Kamenny Ambar, South Ural, copper ores, mineral inclusions Acknowledgements: This work was supported by the Russian Science Foundation project No. 16–18– 10332‑P: analysis of slags and ores was carried out by M. N. Ankushev, V. V. Zaykov, A. M. Yuminov; the archaeological aspect of the work was analyzed by L. N. Koryakova, I. V. Molchanov (chronostratigraphic distribution of slags), S. E. Panteleeva (chronostratigraphic distribution of ceramics and ores). The authors are grateful to I. P. Alaeva, D. A. Artemyev, E. V. Belogub, A. V. Epimakhov, V. A. Kotlyarov, G. F. Lonschakova, M. S. Svirenko, L. G. Udachina. Filippova K. A., Khvorov P. V., Churin E. I., Sharapova S. V.

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16

Heni, Souhir, Sobhi Hcini, Mohamed Lamjed Bouazizi, Lamjed HajTaieb, Abdessalem Dhahri e Habib ben Bacha. "Improving the optical properties of magnesium spinel chromites through Ni and Cu substitutions for optoelectronic applications". RSC Advances 14, n. 36 (2024): 26340–53. http://dx.doi.org/10.1039/d4ra03342f.

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17

Ajeesha, T. L., Ashwini Anantharaman, Jeena N. Baby e Mary George. "Structural, Magnetic, Electrical and Photo-Fenton Properties of Copper Substituted Strontium M-Hexagonal Ferrite Nanomaterials via Chemical Coprecipitation Approach". Journal of Nanoscience and Nanotechnology 20, n. 3 (1 marzo 2020): 1589–604. http://dx.doi.org/10.1166/jnn.2020.17132.

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Copper substituted strontium ferrite nano spinels were synthesized by facile chemical coprecipitation method. Structural properties of all the nano materials were examined using Powder X-ray Diffraction of size ranging 22–50 nm and High Resolution Transmission Electron Microscopy which further revealed the formation of hexagonal spinel structure. The analysis of FT-IR spectra of all the samples confirmed the formation of M–O bond with spinel structure having characteristic peaks at 422 cm-1 and 586 cm-1. All the samples were subjected to dielectric studies at room temperature. A quite narrow band gap around 1.5–1.6 eV for all the samples indicates that these ferrites can behave as visible light photocatalysts. The as synthesized nano spinels were proposed to be promising heterogeneous Photo-Fenton catalysts under visible light for the degradation of organic pollutants. The photo catalytic degradation results revealed 94% degradation for all the prepared nano catalysts. The materials displayed remarkable photo-stability with recyclability up to five consecutive cycles. VSM studies of the materials exhibited weak ferromagnetic property with high surface area. Therefore, these magnetic materials presented no significant loss in activity specifying an exceptional capacity of ferrites to remove organic pollutants from wastewater.

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18

Flores, Ariadna, Karina Nesprias, Paula Vitale, Julia Tasca, Araceli Lavat, Nora Eyler e Adriana Cañizo. "Heterogeneous Photocatalytic Discoloration/Degradation of Rhodamine B with H2O2 and Spinel Copper Ferrite Magnetic Nanoparticles". Australian Journal of Chemistry 67, n. 4 (2014): 609. http://dx.doi.org/10.1071/ch13435.

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The discoloration/degradation of the artificial dye Rhodamine B (RhB) was investigated using advanced oxidation technologies. Aqueous solutions of RhB containing spinel copper ferrites (CuFe2O4) as a heterogeneous catalyst were exposed to UV irradiation/hydrogen peroxide. Under these experimental conditions the discoloration/degradation of RhB is strongly promoted by copper ferrites, reaching 95 % discoloration of the dye in 10 min and 97 % degradation in 200 min. The influence of the catalyst amount, H2O2 concentration, light source, and UV light intensity were studied. Optimum concentrations of H2O2 and catalyst dosage were found for the RhB degradation reaction. The catalyst had high magnetic sensitivity under an external magnetic field, which allowed its magnetic separation from water avoiding secondary pollution processes, and its recycling. A markedly synergetic effect of spinel copper ferrite and UV light irradiation was observed for the RhB discoloration/degradation with H2O2 as a green oxidant.

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19

Shapovalov, V. A., H. Szymczak, S. Piechota e V. V. Shapovalov. "Jahn-Teller Effect in Copper-Doped Spinel Group". Le Journal de Physique IV 07, n. C1 (marzo 1997): C1–243—C1–244. http://dx.doi.org/10.1051/jp4:1997193.

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Kishimoto, Y., T. Ohno, T. Kanashiro, K. Miyatani e M. Ishikawa. "NMR study of spinel type copper sulfide Cu1.5Rh1.5S4". Physica C: Superconductivity 235-240 (dicembre 1994): 1635–38. http://dx.doi.org/10.1016/0921-4534(94)92042-7.

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Aminov, T. G., E. V. Busheva e G. G. Shabunina. "Magnetic Properties of Copper–Indium Doped Spinel FeCr2S4". Russian Journal of Inorganic Chemistry 64, n. 12 (dicembre 2019): 1592–99. http://dx.doi.org/10.1134/s0036023619120039.

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22

De Wilde, Evelien, Inge Bellemans, Mieke Campforts, Muxing Guo, Bart Blanpain, Nele Moelans e Kim Verbeken. "Investigation of High-Temperature Slag/Copper/Spinel Interactions". Metallurgical and Materials Transactions B 47, n. 6 (7 settembre 2016): 3421–34. http://dx.doi.org/10.1007/s11663-016-0805-8.

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Tang, Yuanyuan, Kaimin Shih e King Chan. "Copper aluminate spinel in the stabilization and detoxification of simulated copper-laden sludge". Chemosphere 80, n. 4 (giugno 2010): 375–80. http://dx.doi.org/10.1016/j.chemosphere.2010.04.048.

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Shabelskaya, Nina, Asatullo Radzhabov, Vitalii Taranushich, Victor Chernyshev, Vasilii Demyan e Vera Ulyanova. "Synthesis and catalytic properties of nickel (II) - copper (II) ferrite". E3S Web of Conferences 247 (2021): 01020. http://dx.doi.org/10.1051/e3sconf/202124701020.

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This work studies the process of formation of the spinel structure of nickel (II) -copper (II) ferrite. A possible mechanism for the formation of single-phase spinel samples is considered. It consists of the stage of formation of chelate complexes of nickel (II), copper (II), iron (III) cations with citric acid and their subsequent thermal decomposition. The materials obtained are studied by X-ray phase analysis and the BET technique. The catalytic activity of the synthesized ferrite Cu0.5Ni0.5Fe2O4 in the process of oxidative destruction of methyl orange in the presence of hydrogen peroxide is established. It is shown that the process is significantly accelerated with increasing temperature. The activation energy of the reaction was computed. It was found that the activation energy decreases in the presence of a catalyst. The results can be used to obtain materials suitable for industrial wastewater treatment using organic dyes in production cycles.

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Smyrnioti, Maria, e Theophilos Ioannides. "Dimethyl Ether Oxidation over Copper Ferrite Catalysts". Catalysts 12, n. 6 (2 giugno 2022): 604. http://dx.doi.org/10.3390/catal12060604.

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The depletion of fossil energy sources and the legislation regarding emission control demand the use of alternative fuels and rapid progression of aftertreatment technologies. The study of dimethyl ether (DME) catalytic oxidation is important in this respect, as DME is a promising clean fuel and at the same time a VOC pollutant present in the tail gases of industrial processes. In the present work, copper ferrite catalysts synthesized via the citrate complexation method have been evaluated in DME oxidation. N2-physisorption, XRD, H2-TPR, and XPS were employed for the characterization of the mixed oxide catalysts. The copper ferrite spinel phase was detected in all samples accompanied by a gradual decrease in the bulk CuO phase upon increase in iron content, with the latter never vanishing completely. The Fe0.67Cu0.33 catalyst exhibited the highest catalytic activity in DME oxidation, attaining approximately a 4-fold higher oxidation rate compared to the respective pure copper and iron oxides. The enhanced catalytic performance was attributed to the higher specific surface area of the catalyst and its enhanced redox properties. Highly dispersed copper species were developed owing to the formation of the spinel phase. DME-TPD/TPSR experiments showed that the surface lattice oxygen of the Fe0.67Cu0.33 catalyst can oxidize preadsorbed DME at a lower temperature than all other catalysts which is in agreement with the H2-TPR findings.

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Pekov, Igor, Fedor Sandalov, Natalia Koshlyakova, Marina Vigasina, Yury Polekhovsky, Sergey Britvin, Evgeny Sidorov e Anna Turchkova. "Copper in Natural Oxide Spinels: The New Mineral Thermaerogenite CuAl2O4, Cuprospinel and Cu-Enriched Varieties of Other Spinel-Group Members from Fumaroles of the Tolbachik Volcano, Kamchatka, Russia". Minerals 8, n. 11 (1 novembre 2018): 498. http://dx.doi.org/10.3390/min8110498.

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This paper is the first description of natural copper-rich oxide spinels. They were found in deposits of oxidizing-type fumaroles related to the Tolbachik volcano, Kamchatka, Russia. This mineralization is represented by nine species with the following maximum contents of CuO (wt.%, given in parentheses): a new mineral thermaerogenite, ideally CuAl2O4 (26.9), cuprospinel, ideally CuFe3+2O4 (28.6), gahnite (21.4), magnesioferrite (14.7), spinel (10.9), magnesiochromite (9.0), franklinite (7.9), chromite (5.9), and zincochromite (4.8). Cuprospinel, formerly known only as a phase of anthropogenic origin, turned out to be the Cu-richest natural spinel-type oxide [sample with the composition (Cu0.831Zn0.100Mg0.043Ni0.022)Σ0.996(Fe3+1.725Al0.219Mn3+0.048Ti0.008)Σ2.000O4 from Tolbachik]. Aluminum and Fe3+-dominant spinels (thermaerogenite, gahnite, spinel, cuprospinel, franklinite, and magnesioferrite) were deposited directly from hot gas as volcanic sublimates. The most probable temperature interval of their crystallization is 600–800 °C. They are associated with each other and with tenorite, hematite, orthoclase, fluorophlogopite, langbeinite, calciolangbeinite, aphthitalite, anhydrite, fluoborite, sylvite, halite, pseudobrookite, urusovite, johillerite, ericlaxmanite, tilasite, etc. Cu-bearing spinels are among the latest minerals of this assemblage: they occur in cavities and overgrow even alkaline sulfates. Cu-enriched varieties of chrome-spinels (magnesiochromite, chromite, and zincochromite) were likely formed in the course of the metasomatic replacement of a magmatic chrome-spinel in micro-xenoliths of ultrabasic rock under the influence of volcanic gases. The new mineral thermaerogenite, ideally CuAl2O4, was found in the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption. It forms octahedral crystals up to 0.02 mm typically combined in open-work clusters up to 1 mm across. Thermaerogenite is semitransparent to transparent, with a strong vitreous lustre. Its colour is brown, yellow-brown, red-brown, brown-yellow or brown-red. The mineral is brittle, with the conchoidal fracture, cleavage is none observed. D(calc.) is 4.87 g/cm3. The chemical composition of the holotype (wt.%, electron microprobe) is: CuO 25.01, ZnO 17.45, Al2O3 39.43, Cr2O3 0.27, Fe2O3 17.96, total 100.12 wt.%. The empirical formula calculated on the basis of 4 O apfu is: (Cu0.619Zn0.422)Σ1.041(Al1.523Fe3+0.443Cr0.007)Σ1.973O4. The mineral is cubic, Fd-3m, a = 8.093(9) Å, V = 530.1(10) Å3. Thermaerogenite forms a continuous isomorphous series with gahnite. The strongest lines of the powder X-ray diffraction pattern of thermaerogenite [d, Å (I, %) (hkl)] are: 2.873 (65) (220), 2.451 (100) (311), 2.033 (10) (400), 1.660 (16) (422), 1.565 (28) (511) and 1.438 (30) (440).

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27

Usoltseva, Natalya, Valery Korobochkin, Alesya S. Dolinina e Alexander M. Ustyugov. "Infrared Spectra Investigation of CuO-Al₂O₃ Precursors Produced by Electrochemical Oxidation of Copper and Aluminum Using Alternating Current". Key Engineering Materials 712 (settembre 2016): 65–70. http://dx.doi.org/10.4028/www.scientific.net/kem.712.65.

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Joint electrochemical oxidation of copper and aluminum using alternating current (AC) was performed. The electrolysis products were dried on air (method carbonate) and at the residual pressure of 3-5 kPa (oxide method). Cu-Al layered double hydroxide (Cu-Al/LDH) are formed at air carbonization. Oxide method saves copper (I) oxide. Heat treatment causes the decomposition of LDH to CuO and Al2O3 as well as Cu2O oxidation to CuO. Copper-aluminum spinel (CuAl2O4) is the product of solid-phase interaction of copper and aluminum oxides. Infrared spectra revealed that oxide method provides the boehmite dehydration and metal oxides interaction at lower temperature despite the fact that the poorly crystallized copper (II) oxide is formed at LDH decomposition.

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28

Stewart, S. J., R. C. Mercader, G. Punte, J. Desimoni, G. Cernicchiaro e R. B. Scorzelli. "Shifting the Superparamagnetic Limit of Nanosized Copper Iron Spinel". Hyperfine Interactions 156/157, n. 1-4 (2004): 89–95. http://dx.doi.org/10.1023/b:hype.0000043206.60778.18.

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29

Luadthong, Chuleeporn, Pongtanawat Khemthong, Waraporn Nualpaeng e Kajornsak Faungnawakij. "Copper ferrite spinel oxide catalysts for palm oil methanolysis". Applied Catalysis A: General 525 (settembre 2016): 68–75. http://dx.doi.org/10.1016/j.apcata.2016.07.002.

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30

Matsukata, Masahiko, Shigeyuki Uemiya e Eiichi Kikuchi. "Copper–Alumina Spinel Catalysts for Steam Reforming of Methanol". Chemistry Letters 17, n. 5 (5 maggio 1988): 761–64. http://dx.doi.org/10.1246/cl.1988.761.

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31

Murthy, K. S. R. C., e J. Ghose. "CO Oxidation on Substituted Copper Chromite Spinel Oxide Catalysts". Journal of Catalysis 147, n. 1 (maggio 1994): 171–76. http://dx.doi.org/10.1006/jcat.1994.1127.

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32

Amini, Mojtaba, Maryam Hosseinpour Kafshdouzsani, Ali Akbari, Sanjeev Gautam, Cheol-Hwee Shim e Keun Hwa Chae. "Spinel copper ferrite nanoparticles: Preparation, characterization and catalytic activity". Applied Organometallic Chemistry 32, n. 9 (29 giugno 2018): e4470. http://dx.doi.org/10.1002/aoc.4470.

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33

Zhao, Hongyuan, Fang Li, Xiuzhi Bai, Tingting Wu, Zhankui Wang, Yongfeng Li e Jianxiu Su. "Enhanced Cycling Stability of LiCuxMn1.95−xSi0.05O4 Cathode Material Obtained by Solid-State Method". Materials 11, n. 8 (27 luglio 2018): 1302. http://dx.doi.org/10.3390/ma11081302.

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Abstract (sommario):

The LiCuxMn1.95−xSi0.05O4 (x = 0, 0.02, 0.05, 0.08) samples have been obtained by a simple solid-state method. XRD and SEM characterization results indicate that the Cu-Si co-doped spinels retain the inherent structure of LiMn2O4 and possess uniform particle size distribution. Electrochemical tests show that the optimal Cu-doping amount produces an obvious improvement effect on the cycling stability of LiMn1.95Si0.05O4. When cycled at 0.5 C, the optimal LiCu0.05Mn1.90Si0.05O4 sample exhibits an initial capacity of 127.3 mAh g−1 with excellent retention of 95.7% after 200 cycles. Moreover, when the cycling rate climbs to 10 C, the LiCu0.05Mn1.90Si0.05O4 sample exhibits 82.3 mAh g−1 with satisfactory cycling performance. In particular, when cycled at 55 °C, this co-doped sample can show an outstanding retention of 94.0% after 100 cycles, whiles the LiMn1.95Si0.05O4 only exhibits low retention of 79.1%. Such impressive performance shows that the addition of copper ions in the Si-doped spinel effectively remedy the shortcomings of the single Si-doping strategy and the Cu-Si co-doped spinel can show excellent cycling stability.

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34

Zeeshan, Talat, Safia Anjum, Hina Iqbal e Rehana Zia. "Substitutional effect of copper on the cation distribution in cobalt chromium ferrites and their structural and magnetic properties". Materials Science-Poland 36, n. 2 (25 giugno 2018): 255–63. http://dx.doi.org/10.1515/msp-2018-0011.

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AbstractA series of copper substituted cobalt chromium ferrites, CuxCo1 - xCr0.5Fe1.5O4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) has been synthesized, by employing powder metallurgy method. Calcination of the samples has been carried out for 24 hours at 1100 °C. The resultant materials have been investigated by using a variety of techniques, including X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM)), scanning electron microscopy (SEM), and ultraviolet visible spectroscopy (UV-Vis). The XRD patterns confirmed that all compositions had a cubic spinel structure with a single phase and the lattice parameter was found to increase with increasing copper concentration. FT-IR spectroscopy has been used for studying the chemical bonds in the spinel ferrite. Shifting of the bands ν1 and ν2 has been observed. It has been revealed from VSM analysis that saturation magnetization and coercivity decrease with rising the Cu+2 doping. Magnetic properties have been explained on the basis of cation distribution. Scanning electron microscopy (SEM) has been used to study the surface morphology of prepared samples. UV-Vis analysis revealed the optical absorption of the samples. An increase in band gaps has been observed with increasing copper concentration in the sample.

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35

Nguyen, Martin, e Radomír Sokolář. "Corrosion Resistance of Novel Fly Ash-Based Forsterite-Spinel Refractory Ceramics". Materials 15, n. 4 (12 febbraio 2022): 1363. http://dx.doi.org/10.3390/ma15041363.

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This article aims to investigate the corrosion resistance of novel fly ash–based forsterite–spinel (Mg2SiO4-MgAl2O4) refractory ceramics to various corrosive media in comparison with reactive alumina–based ceramics. Because fly ash is produced in enormous quantities as a byproduct of coal-burning power stations, it could be utilized as an affordable source of aluminum oxide and silicon oxide. Corrosion resistance to iron, clinker, alumina, and copper was observed by scanning electron microscope with an elemental probe. The influence on the properties after firing was also investigated. Fly ash–based and reactive alumina–based mixtures were designed to contain 10%, 15% and 20% of spinel after firing. Raw material mixtures were sintered at 1550 °C for two hours. X-ray diffraction analysis and scanning electron microscopy were used to analyze sintered samples. The apparent porosity, bulk density, modulus of rupture, and refractory and thermo–mechanical properties were also investigated. The experimental results disclosed that the modulus of rupture, thermal shock resistance and microstructure were improved with increasing amounts of spinel in the fired samples. An analysis of the transition zones between corrosive media and ceramics revealed that all mixtures have good resistance against corrosion to iron, clinker, aluminum and copper.

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36

Adaika, K., M. Diaifi e C. Liaidi. "Structural, elastic and optical properties of nickel aluminate spinel nano crystalline". Digest Journal of Nanomaterials and Biostructures 16, n. 2 (2021): 669–76. http://dx.doi.org/10.15251/djnb.2021.162.669.

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Ni1-xCuxAl2O4nano-crystalline, was made to synthesize by sol–gel method and study their micro-structural, optical and electrochemical properties. All investigated samples were characterized using different techniques such as X-ray diffraction (XRD), Fouriertransform infrared (FTIR) analysis, thermal gravimetric analysis (TG), and transmission electron microscope (TEM), optical absorption and electrochemical measurements. Powder X-ray diffraction (XRD) analysis was confirmed the formation of single phase, cubic spinel structure without other impurities. Average crystallite sizes of the samples were found to be in the range of 44 nm to 57 nm by Scherrer’s method. FT-IR spectra showed the stretching frequencies corresponding to the M–Al–O bond of spinel structure. The SEM micrographs suggest homogeneous distribution of the nanocrystallites in the samples. The optical band decreases with increasing copper substitution from 2.41 to 1.98 eV. The study of electrochemical behavior shows that the electrode with large copper content has a better electrocatalytical activity.

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37

Parajuli, D., e K. Samatha. "Structural and cation distribution analysis of Nickel-Copper/Nickel-Magnesium Substituted Lithium Ferrites". BIBECHANA 21, n. 1 (8 marzo 2024): 74–82. http://dx.doi.org/10.3126/bibechana.v21i1.61270.

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Abstract (sommario):

Lithium ferrite (Li0.5Fe2.5O4) shows significant promise in electrical and electronic engineering. It possesses a crystal spinel crystal structure denoted as AB2O4, with "A" and "B" representing specific tetrahedral and octahedral lattice sites respectively. Analysis of X-ray diffraction (XRD) patterns aligns well with the JCPDS card (no. 38-0259), confirming the spinel structure with the Fd3m space group. However, an additional peak at 211 in the basic lithium ferrite suggests a subtle Fd3m to the P4132 phase change with a minor secondary hematite phase. Investigating the cation distribution in these ferrites is crucial for further exploration of their magnetic and dielectric properties. These ferrites find widespread applications in microwave technology and magnetic and electric energy storage devices.

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38

Górecka, Sylwia, Kateřina Pacultová, Kamil Górecki, Aneta Smýkalová, Katarzyna Pamin e Lucie Obalová. "Cu-Mg-Fe-O-(Ce) Complex Oxides as Catalysts of Selective Catalytic Oxidation of Ammonia to Dinitrogen (NH3-SCO)". Catalysts 10, n. 2 (28 gennaio 2020): 153. http://dx.doi.org/10.3390/catal10020153.

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Multicomponent oxide systems 800-Cu-Mg-Fe-O and 800-Cu-Mg-Fe-O-Ce were tested as catalysts of selective catalytic oxidation of ammonia to dinitrogen (NH3-SCO) process. Materials were obtained by calcination of hydrotalcite-like compounds at temperature 800 °C. Some catalysts were doped with cerium by the wet impregnation method. Not only simple oxides, but also complex spinel-like phases were formed during calcination. The influence of chemical composition, especially the occurrence of spinel phases, copper loading and impregnation by cerium, were investigated. Materials were characterized by several techniques: X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), low-temperature nitrogen adsorption (BET), cyclic voltammetry (CV), temperature programmed reduction (H2-TPR), UV-vis diffuse reflectance spectroscopy and scanning electron microscopy (SEM). Examined oxides were found to be active as catalysts of selective catalytic oxidation of ammonia with high selectivity to N2 at temperatures above 300 °C. Catalysts with low copper amounts (up to 12 wt %) impregnated by Ce were slightly more active at lower temperatures (up to 350 °C) than non-impregnated samples. However, when an optimal amount of copper (12 wt %) was used, the presence of cerium did not affect catalytic properties. Copper overloading caused a rearrangement of present phases accompanied by the steep changes in reducibility, specific surface area, direct band gap, crystallinity, dispersion of CuO active phase and Cu2+ accessibility leading to the decrease in catalytic activity.

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39

Klenushkin, Anatoly, Boris Medvedev, Yuri Kabirov e Mikhail Evdokimov. "Iron Oxide Materials for Positive Electrodes of Lithium and Lithium-Ion Batteries". Advanced Materials Research 705 (giugno 2013): 46–51. http://dx.doi.org/10.4028/www.scientific.net/amr.705.46.

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New iron cathode materials: strontium hexaferrite, spinel-like ferrites of copper, lithium, and zinc, as well as α-and γ-phases of iron (3+) oxide are proposed. Chronopotentiometry method allowed demonstrating the possibility to use ferrites and iron (3+) oxides as the positive electrode materials for lithium batteries.

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40

Mugnier, Emmanuelle, Isabelle Pasquet, Antoine Barnabé, Lionel Presmanes, Corine Bonningue e Philippe Tailhades. "Nanocomposites of metallic copper and spinel ferrite films: Growth and self-assembly of copper particles". Thin Solid Films 493, n. 1-2 (dicembre 2005): 49–53. http://dx.doi.org/10.1016/j.tsf.2005.06.092.

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41

Liu, Tangkang, Di Xu, Dengdeng Wu, Guoliang Liu e Xinlin Hong. "Spinel ZnFe2O4 Regulates Copper Sites for CO2 Hydrogenation to Methanol". ACS Sustainable Chemistry & Engineering 9, n. 11 (12 marzo 2021): 4033–41. http://dx.doi.org/10.1021/acssuschemeng.0c07682.

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42

Kim, Kwang Joo, Jongho Park e Jae Yun Park. "Magnetic and Electrical Properties of Spinel Copper Ferrite Thin Films". Journal of Magnetics 23, n. 1 (31 marzo 2018): 1–4. http://dx.doi.org/10.4283/jmag.2018.23.1.001.

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43

Roy, S., e J. Ghose. "Syntheses and studies on some copper chromite spinel oxide composites". Materials Research Bulletin 34, n. 7 (maggio 1999): 1179–86. http://dx.doi.org/10.1016/s0025-5408(99)00109-9.

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44

Durr, J., M. Lenglet e M. H. Thuilier. "The Jahn Teller distortion of copper environment in spinel oxide". Journal de Chimie Physique 86 (1989): 1547–54. http://dx.doi.org/10.1051/jcp/1989861547.

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45

Batool, Kiran, Malika Rani, Ayesha Younus, Arshad Mehmood, Sikander Azam, Bakhtiar Ul Haq, Rubia Shafique, Naseem Akhtar, Wilayat Khan e Thamraa Alshahrani. "Nanosized Magnesium doped Copper Chromites Spinel Particles Synthesis and Characterization". ECS Journal of Solid State Science and Technology 9, n. 12 (8 dicembre 2020): 126005. http://dx.doi.org/10.1149/2162-8777/abce00.

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46

Wei, Ping, M. Reza Bateni e Anthony Petric. "Conversion of copper and manganese metallic films to spinel coating". Journal of Materials Science 47, n. 13 (30 marzo 2012): 5205–15. http://dx.doi.org/10.1007/s10853-012-6404-4.

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47

Papavasiliou, Joan, George Avgouropoulos e Theophilos Ioannides. "Steam reforming of methanol over copper–manganese spinel oxide catalysts". Catalysis Communications 6, n. 7 (luglio 2005): 497–501. http://dx.doi.org/10.1016/j.catcom.2005.04.015.

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48

Bueno, J. M. Correa, M. Gazzano, M. Goncalves Coelho e A. Vaccari. "Synthesis and reactivity of copper-containing nonstoichiometric spinel-type catalysts". Applied Catalysis A: General 103, n. 1 (settembre 1993): 69–78. http://dx.doi.org/10.1016/0926-860x(93)85174-n.

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49

Everbroeck, Tim Van, Radu-George Ciocarlan, Wouter Van Hoey, Myrjam Mertens e Pegie Cool. "Copper-Containing Mixed Metal Oxides (Al, Fe, Mn) for Application in Three-Way Catalysis". Catalysts 10, n. 11 (19 novembre 2020): 1344. http://dx.doi.org/10.3390/catal10111344.

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Abstract (sommario):

Mixed oxides were synthesized by co-precipitation of a Cu source in combination with Al, Fe or Mn corresponding salts as precursors. The materials were calcined at 600 and 1000 °C in order to crystallize the phases and to mimic the reaction conditions of the catalytic application. At 600 °C a mixed spinel structure was only formed for the combination of Cu and Mn, while at 1000 °C all the materials showed mixed spinel formation. The catalysts were applied in three-way catalysis using a reactor with a gas mixture containing CO, NO and O2. All the materials calcined at 600 °C displayed the remarkable ability to oxidize CO with O2 but also to reduce NO with CO, while the pure oxides such as CuO and MnO2 were not able to. The high catalytic activity at 600 °C was attributed to small supported CuO particles present and imperfections in the spinel structure. Calcination at 1000 °C crystallized the structure further which led to a dramatic loss in catalytic activity, although CuAl2O4 and CuFe2O4 still converted some NO. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, H2-Temperatrue Programmed Reduction (H2-TPR), N2-sorption and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX).

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50

Evans, David M. "Significance of compositional zoning in cumulate chromites of the Kabanga chonoliths, Tanzania". Mineralogical Magazine 82, n. 3 (7 maggio 2018): 675–96. http://dx.doi.org/10.1180/mgm.2018.87.

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ABSTRACTCompositional zoning is observed rarely in chrome-spinel grains from slowly-cooled layered intrusions because diffusion of cations continues within the spinel to low temperatures. However, in certain circumstances, such gradational zoning of both divalent and trivalent cations is observed and may be useful in deciphering the thermal history of the host intrusions. The accessory chrome-spinels of the Kabanga mafic-ultramafic chonolith intrusions of the Kibaran igneous event in north western Tanzania are notable because they have preserved gradational compositional zoning. This zoning is demonstrated to predate and be independent of later hydrous alteration of the silicate assemblage. At Kabanga, most chrome-spinel grains within olivine-rich cumulate rocks are gradationally and cryptically zoned from Fe2+-Cr3+ rich cores to more Mg2+-Al3+ rich rims (normal zoning). A few grains are zoned from Mg2+-Al3+ rich cores to more Fe2+-Cr3+ rich rims (reverse zoned). The zoning of divalent cations is proportional to that of trivalent cations with Mg2+ following Al3+ and Fe2+ following Cr3+ from core to rim. The zoning of trivalent and tetravalent cations is interpreted to be caused by either new growth from an evolving melt or peritectic reactions between evolved or contaminated melt and adjacent Al-Cr-bearing ferromagnesian minerals, which is preserved by relatively rapid initial cooling in the small chonolith intrusions. Divalent cation zoning is controlled by sub-solidus exchange of Fe2+ and Mg with adjacent ferromagnesian minerals and continues to lower temperatures, indicated to be 580 to 630°C by the spinel-olivine geothermometer. Preservation of such zoning is more likely in the smaller chonolith intrusions that typically host magmatic nickel-copper sulfide deposits and can be used as an exploration indicator when interpreting chromite compositions in regional heavy indicator mineral surveys.

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