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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mikhlin Y., Vorobyev S., Romanchenko A., Karasev S., Karacharov A., Zharkov S. M.
Заглавие : Ultrafine particles derived from mineral processing: A case study of the Pb-Zn sulfide ore with emphasis on lead-bearing colloids
Место публикации : Chemosphere: Elsevier, 2016. - Vol. 147. - P.60-66. - ISSN 00456535 (ISSN), DOI 10.1016/j.chemosphere.2015.12.096
Примечания : Cited References: 47. - This research was supported by the Russian Science Foundation, Grant No. 14-17-00280.
Предметные рубрики: GALENA DISSOLUTION
METALLIC COPPER
NANOPARTICLES
SOIL
ENVIRONMENT
SEPARATION
TRANSPORT
FLOTATION
WATER
SIZE
Ключевые слова (''Своб.индексиров.''): lead sulfide--lead-zinc ore--lead sulfide--ultrafine particles--aquatic nanoparticles
Аннотация: Although mining and mineral processing industry is a vast source of heavy metal pollutants, the formation and behavior of micrometer- and nanometer-sized particles and their aqueous colloids entered the environment from the technological media has received insufficient attention to date. Here, the yield and characteristics of ultrafine mineral entities produced by routine grinding of the Pb-Zn sulfide ore (Gorevskoe ore deposit, Russia) were studied using laser diffraction analysis (LDA), dynamic light scattering (DLS) and zeta potential measurement, microscopy, X-ray photoelectron spectroscopy, with most attention given to toxic lead species. It was revealed, in particular, that the fraction of particles less that 1 ?m in the ground ore typical reaches 0.4 vol. %. The aquatic particles in supernatants were micrometer size aggregates with increased content of zinc, sulfur, calcium as compared with the bulk ore concentrations. The hydrodynamic diameter of the colloidal species decreased with time, with their zeta potentials remaining about -12 mV. The colloids produced from galena were composed of 20-50 nm PbS nanoparticles associated with lead sulfate and thiosulfate, while the surface oxidation products at precipitated galena were largely lead oxyhydroxides. The size and zeta potential of the lead-bearing colloids decreased with time down to about 100 nm and from -15 mV to -30 mV, respectively. And, conversely, lead sulfide nanoparticles were mobilized before the aggregates during redispersion of the precipitates in fresh portions of water. The potential environmental impact of the metal-bearing colloids, which is due to the large-scale production and relative stability, is discussed. © 2015 Elsevier Ltd.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ovchinnikov S. G., Nekrasov I. A., Pchelkina Z. V.
Заглавие : Electronic Structure of p-Type La1-xMx2+MnO3 Manganites in the Ferromagnetic and Paramagnetic Phases in the LDA plus GTB Approach
Разночтения заглавия :авие SCOPUS: Electronic structure of p-Type La 1-x M x 2+ MnO 3 manganites in the ferromagnetic and paramagnetic phases in the LDA + GTB approach
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 112, Is. 5. - P860-876. - ISSN 1063-7761, DOI 10.1134/S1063776111030101
Примечания : Cited References: 47. - This study was supported financially by integration project no. 40 of the Ural and Siberian Branches of the Russian Academy of Sciences, the program "Strong Electron Correlations" of the Russian Academy of Sciences, and the Russian Foundation for Basic Research (project no. 10-02-00251-a).
Предметные рубрики: DOUBLE-EXCHANGE
COLOSSAL MAGNETORESISTANCE
THIN-FILMS
PHYSICS
LA1-XSRXMNO3
RESISTIVITY
SEPARATION
TRANSPORT
MODEL
Ключевые слова (''Своб.индексиров.''): complex structure--cubic materials--ferromagnetic phase--half metals--jahn teller effect--metal properties--metal types--orbitals--p-type--paramagnetic phase--paramagnetic phasis--quasi particles--spectral intensity--spin projections--strong electron correlations--barium--density functional theory--electron correlations--electron density measurement--electronic properties--electronic structure--fermi level--ferromagnetic materials--ferromagnetism--manganese oxide--manganites--paramagnetic materials--paramagnetism--valence bands--lanthanum
Аннотация: The band structure, spectral intensity, and position of the Fermi level in doped p-type La1-xMx2+ MnO3 manganites (M = Sr, Ca, Ba) is analyzed using the LDA + GBT method for calculating the electronic structure of systems with strong electron correlations, taking into account antiferro-orbital ordering and using the Kugel-Khomskii ideas and real spin S = 2. The results of the ferromagnetic phase reproduce the state of a spin half-metal with 100% spin polarization at T = 0, when the spectrum is of the metal type for a quasiparticle with one spin projection and of the dielectric type for the other. It is found that the valence band becomes approximately three times narrower upon a transition to the paramagnetic phase. For the paramagnetic phase, metal properties are observed because the Fermi level is located in the valence band for any nonzero x. The dielectrization effect at the Curie temperature is possible and must be accompanied by filling of d(x) orbitals upon doping. The effect itself is associated with strong electron correlations, and a complex structure of the top of the valence band is due to the Jahn-Teller effect in cubic materials. DOI: 10.1134/S1063776111030101
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Petrakovskii G. A., Vasiliev V. N., Velikanov D. A., Sablina K. A., Patrin K. G.
Заглавие : Observation of mixed two-phase state in Eu0.7Pb0.3MnO3 single crystal by magnetic resonance method
Место публикации : Physica B. - 2002. - Vol. 324, Is. 1-4. - P.254-260. - ISSN 0921-4526, DOI 10.1016/S0921-4526(02)01397-2
Примечания : Cited References: 19
Предметные рубрики: OPTIMALLY DOPED MANGANITES
COLOSSAL MAGNETORESISTANCE
PARAMAGNETIC ANOMALIES
CURIE-TEMPERATURE
LA1-XCAXMNO3
RELAXATION
SEPARATION
Ключевые слова (''Своб.индексиров.''): manganites--cmr--magnetic resonance--phase separation--cmr--magnetic resonance--manganites--phase separation--europium compounds--ferromagnetic materials--paramagnetic resonance--phase separation--phase transitions--manganites--single crystals
Аннотация: The magnetic resonance measurements show that the mixed two-phase state takes place in the Eu0.7Pb0.3MnO3 single crystal. The coexistence of the magnetic phases is observed in vicinity of the magnetic phase transition, where the sample exhibits the effect of the CMR. The frequency-field dependencies of the spectra allow to conclude that these phases are paramagnetic and ferromagnetic ones. Moreover, the study of the frequency dependencies shows the sensitivity of the mixed-phase state to the external magnetic field. This suggests that the scenario of the phase separation is realized in this case and the mixed two-phase state is not related to simple chemical inhomogeneity. (C) 2002 Elsevier Science B.V. All rights reserved.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Petrakovskii G. A., Vasil'ev V. N., Sablina K. A.
Заглавие : Two-phase paramagnetic-ferromagnetic state of La0.7Pb0.3MnO3 single-crystal lanthanum manganite
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2002. - Vol. 44, Is. 7. - P1350-1354. - ISSN 1063-7834, DOI 10.1134/1.1494635
Примечания : Cited References: 17
Предметные рубрики: COLOSSAL MAGNETORESISTANCE
MAGNETIC-RESONANCE
DOPED MANGANITES
LA1-XCAXMNO3
SEPARATION
TRANSITION
RELAXATION
EPR
Аннотация: Two phases, paramagnetic and ferromagnetic, were shown by the magnetic resonance method to coexist below the temperature T-C in La0.7Pb0.3MnO3 single crystals exhibiting colossal magnetoresistance. The magnetic resonance spectra were studied in the frequency range 10-78 GHz. The specific features in the behavior of the spectral parameters were observed to be the strongest at the temperatures corresponding to the maximum magnetoresistance in the crystals. The concentration ratios of the paramagnetic and ferromagnetic phases in the samples were found to be sensitive to variations in temperature and external magnetic field. This behavior suggests realization of the electronic phase separation mechanism in the system under study. (C) 2002 MAIK "Nauka/Interperiodica".
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrakovskii G. A., Volkov N. V., Vasil'ev V. N., Sablina K. A.
Заглавие : Magnetic resonance spectrum of a two-phase state in single crystals of La0.7Pb0.3MnO3 lanthanum manganite
Место публикации : JETP Letters. - 2000. - Vol. 71, Is. 4. - P.144-147. - ISSN 0021-3640, DOI 10.1134/1.568300
Примечания : Cited References: 10
Предметные рубрики: FERROMAGNETIC-RESONANCE
LA1-XCAXMNO3
SEPARATION
Аннотация: Two absorption lines are observed over a wide temperature range below T-c in the magnetic resonance spectrum of an La0.7Pb0.3MnO3 single crystal. These lines correspond to two magnetic phases in the sample. The frequency-field dependence of spectra obtained in the range of microwave radiation frequencies 10-77 GHz allows these phases to be interpreted as ferromagnetic and paramagnetic phases. The phase volume ratio depends on the temperature and the magnitude of the external magnetic field. Features in the temperature behavior of parameters of the magnetic absorption line are observed in the region of the highest magnetic resistance of the sample. The results are interpreted within the mechanism of electronic phase separation. (C) 2000 MAIK "Nauka/Interperiodica".
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Myagkov V. G., Bykova L. E., Bondarenko G. N.
Заглавие : Multiple self-propagating high-temperature synthesis and solid-phase reactions in thin films
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 1999. - Vol. 88, Is. 5. - P963-967. - ISSN 1063-7761, DOI 10.1134/1.558878
Примечания : Cited References: 28
Предметные рубрики: DENSE BRANCHING MORPHOLOGY
SINGLE-CRYSTAL GROWTH
PATTERN-FORMATION
AL-GE
CHEMICAL-REACTIONS
CRYSTALLIZATION
SEPARATION
HEAT
Аннотация: A variety of self-propagating high-temperature synthesis in thin films has been found and investigated. This modification, called multiple self-propagating high-temperature synthesis, occurs in the solid phase and is a reversible phase transition. Multiple self-propagating high-temperature synthesis is similar in many respects to a metal-insulator phase transition. It is shown that for eutectic systems it is equivalent to a repeated transition through the eutectic temperature of bulk samples. It is inferred that multiple self-propagating high-temperature synthesis in bilayer films is governed by phase separation mechanisms that take place during eutectic solidification and eutectoid decomposition. (C) 1999 American Institute of Physics. [S1063-7761(99)01705-9].
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ryzhkov I. I., Shevtsova V. M.
Заглавие : Convective stability of multicomponent fluids in the thermogravitational column
Место публикации : Phys. Rev. E: AMER PHYSICAL SOC, 2009. - Vol. 79, Is. 2. - Ст.26308. - ISSN 1539-3755, DOI 10.1103/PhysRevE.79.026308
Примечания : Cited References: 26
Предметные рубрики: THERMAL-DIFFUSION
SORET COEFFICIENT
MIXTURES
SEPARATION
LIQUID
Ключевые слова (''Своб.индексиров.''): convection--density--flow instability--galerkin method--heat transfer--mass transfer--thermal diffusion--binary mixtures--fluids--galerkin methods--linear stability analysis--ternary systems--thermal diffusion--planes--binary fluids--convective stabilities--cross-diffusion effects--density stratifications--individual components--linear stabilities--longitudinal instabilities--longitudinal waves--multi-component fluids--separation ratios--soret effects--stability problems--temperature gradients--ternary fluids--ternary mixtures--thermal diffusion coefficients--transversal waves--vertical axis--vertical directions--system stability
Аннотация: A comprehensive linear stability analysis of convection in the thermogravitational column is first performed for multicomponent fluids. Two types of perturbations are investigated: Longitudinal waves propagating in vertical direction of the column and transversal waves propagating perpendicular to the vertical axis and temperature gradient. The stability problems are reduced to those without cross-diffusion effect by a special transformation. The calculations are performed for binary and ternary mixtures by the Galerkin method. It is found that in binary fluids, the onset of longitudinal instability can be monotonic or oscillatory depending on the separation ratio, which characterizes the Soret effect. The difference between stability characteristics of binary and ternary fluids is associated with different diffusion times of components in a ternary system. It is shown that the mechanism of transversal instability is related to the unstable density stratification in the column (in total or due to individual components). The unstable stratification can only be realized in fluids with negative Soret effect. The analogue of exchange of stabilities principle for a plane column with a multicomponent fluid is proved. The obtained results indicate that the thermogravitational column can be used for measuring diffusion and thermal diffusion coefficients in ternary and higher mixtures with one or several components having negative Soret effect.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kononova O.N., Melnikov A.M., Borisova T.V., Krylov A. S.
Заглавие : Simultaneous ion exchange recovery of platinum and rhodium from chloride solutions
Место публикации : Hydrometallurgy. - 2011. - Vol. 105, Is. 3-4. - P.341-349. - JAN. - ISSN 0304-386X, DOI 10.1016/j.hydromet.2010.11.009
Примечания : Cited Reference Count: 46
Предметные рубрики: GROUP-METALS PGM
SEPARATION
CATALYST
ANION
ADSORPTION
EXTRACTION
CHEMISTRY
RESIN
Ключевые слова (''Своб.индексиров.''): platinum--rhodium--sorption--anion exchangers--chloride solutions--anion exchangers--chloride solutions--platinum--rhodium--sorption--ammonium thiocyanate--anion exchangers--basic parameters--chemical structure--chloride solutions--diffusion coefficients--distribution coefficient--exchange capacities--kinetic properties--noble metals--purolite--rhodium chloride--separation factors--sorption ability--work focus--ammonium compounds--chlorine compounds--desorption--hydrochloric acid--ion exchange--ion exchange resins--ions--platinum--platinum compounds--potassium hydroxide--precious metals--recovery--rhodium--sulfuric acid--thioureas--urea--rhodium compounds
Аннотация: This work focuses on the sorption recovery of platinum (II, IV) and rhodium (III) simultaneously present in chloride solutions, freshly prepared and stored over 3 months, on commercial anion exchangers with different physical and chemical structure. The sorption was carried out from solutions with 0.001-4.0 mol/L HCl. The initial platinum and rhodium concentrations in contacting solutions were 0.25-2.5 mmol/L Sorption and kinetic properties of the chosen anion exchangers were investigated and the basic parameters of exchange capacity, recovery, distribution coefficients, separation factors, process rate, diffusion coefficients and half-exchange times were calculated. It is shown that anion exchangers investigated possess high sorption ability to platinum and rhodium chloride complexes, which does not deteriorate in case of stored solutions. Desorption of platinum and rhodium from the resins investigated was carried out with hydrochloric acid (2 mol/L), thiourea (1 mol/L) in sulfuric acid (2 mol/L) or in potassium hydroxide (2 mol/L) as well as by ammonium thiocyanate (2 mol/L). It was shown that complete separation of platinum and rhodium can be carried out with 2 mol/L HCl on anion exchanger Purolite S 985, whereas 2 mol/L NH(4)SCN as an elution agent leads to complete separation of noble metals on anion exchangers Purolite S 985, Purolite A 500 and AM-2B. (C) 2010 Elsevier B.V. All rights reserved.
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