We present new mineralogical data of cronstedtite from the Southern-2 orebody, located in the South-Western branch of the Talnakh intrusion (Noril'sk area) composed of massive sulfides in which the ...total amount of oxides and silicates does not exceed 1-3 vol%. The petrographic and mineralogical features of these ores indicated occurrence of fine-grained, fibrous needle like clusters < 50-µm-sized grains of cronstedtite (7.09 Å along its c-axis). This mineral confirmed by a number of analytical techniques (powder X-ray diffraction of balk samples, transmission electron microscopy, scanning electron microscopy, Raman and Infrared spectroscopy). Cronstedtite sporadically contains signals of Al, Ni, Ca and filling the cracks and cavities between sulfides of copper (chalcopyrite) and iron (pyrrhotite, pentlandite). In some cases, cronstedtite contains micron-sized PGM, and associates with magnetite. According the X-ray diffraction analysis of the bulk massive ores besides cronstendtite are established kaolinite, gypsum, calcite, quartz, and cristobalite. The findings of cronstedtite in Noril'sk area have never been mentioned publicly before. Its occurrence is the northernmost known locality in the world. Our results imply that the formation of cronstedtite in the Talnakh intrusion could be possible by the active participation low-temperatures fluids within the relatively near-surface (< 2 km of paleosurface) conditions of intrusion emplacement, in contrast to other deep-seated supergiant Cu-Ni-PGE deposits in the world. The conditions of formation in isolated cavities in fresh pyrrhotite-pentlandite-chalcopyrite massive ores of deep level of the Talnakh intrusion could be favorable for the formation of cronstendtite.
Hydroformylation is an important industrial process applied for the production of many highly-demanded chemicals. For now, only the Co/phosphine, Rh/phosphine, or ligand-free systems are used in ...industry. Although most of the research dealing with hydroformylation also considers systems with phosphorus-containing ligands or heterogeneous materials, the interest in developing phosphorus-free nitrogen-containing systems tends to grow during the last decade. N-ligands can be easier to synthesize, more stable towards oxidation, and at the same time add some useful features, such as the higher activity in the tandem hydroformylation-based reactions. The review is focused on the progress made in the design of N-ligands for homogeneous and biphasic hydroformylation of unsaturated compounds, as well as N-containing heterogeneous catalysts for the process. In addition, the data on tandem reactions, such as reductive hydroformylation and hydroaminomethylation, are systematized and discussed.
Display omitted
•Publications on N-containing phosphorus-free systems in hydroformylation are reviewed.•Rh/N systems are useful for applied hydroformylation-based reactions.•Rh/NR3 systems are effective for reductive hydroformylation.•Prospects of biphasic and heterogeneous Rh/N systems are discussed.
Display omitted
•Solketal methyl ether (SME) has been prepared from glycerol via two-step procedure.•Ketalization of glycerol and its monomethyl ether ran analogously.•Measured bRON values for SME ...(52–62) were twice lower than for solketal (100–110).•Free –OH group of solketal is proposed to be the “bearer” of anti-knock properties.•Antiknock properties for solketal – MTBE (MTAE, ethanol) mixtures were estimated.
Solketal methyl ether (SME) was synthesized from glycerol by conversion with methanol followed by ketalization with acetone. The values for the equilibrium constant of the ketalization of glycerol and glycerol 1-monomethyl ether in the temperature range of 298–323 K were determined experimentally, and its thermodynamic parameters (ΔH0, ΔS0, ΔG0) have been calculated, which appear to be very close for these two reactions. The gasoline blending properties of SME have been studied in comparison with solketal by examining the effects of solketal and SME additives on the fractional composition, saturated vapor pressure, oxidation induction period, existent gum content, density, and antiknock value of gasoline components and a model fuel blend. It has been shown that SME has better volatility, but a much lower antiknock value than solketal. The influence of the solketal additive on the antiknock value of components of compounded gasoline (alkylate, reformate, FCC gasoline) and the performance of composite additives based on solketal with ethanol, MTBE, and TAME are described.
The subject of this paper is microlasers with the emission spectra determined by the whispering gallery modes. Owing to the total internal reflection of light on the sidewalls, a high Q-factor is ...achieved until the diameter is comparable to the wavelength. The light emission predominantly occurs in the plane of the structure, which facilitates the microlaser integration with other elements. We focus on microdisk lasers with various types of the In(Ga)As quantum dots (QDs). Deep localization of charge carriers in spatially separated regions suppresses the lateral diffusion and makes it possible to overcome the undesirable effect of non-radiative recombination in deep mesas. Thus, using conventional epitaxial structures and relatively simple post-growth processing methods, it is possible to realize small microlasers capable of operating without temperature stabilization at elevated temperatures. The low sensitivity of QDs to epitaxial and manufacturing defects allows fabricating microlasers using III-V heterostructures grown on silicon.
Gain saturation in a semiconductor optical amplifier with an array of quantum dots is studied analytically and by numerical simulation on the basis of an analysis of rate equations. It is shown that, ...at a moderate injection level, the saturation power increases in proportion to the current density, and then reaches its maximum value, limited by the rate of carrier delivery to the ground state and by the number of quantum dots interacting with photons. Expressions are proposed that allow explicit description of the dependence of the saturation power on current and its relationship with the internal parameters of the active region.
Using numerical simulation, the search for designs of asymmetric barrier layers (ABLs) in a laser diode with a GaAs waveguide emitting at a wavelength of λ = 980 nm is carried out. A pair of ABLs ...adjoining the active region on both sides blocks undesired charge-carrier flows and suppresses parasitic spontaneous recombination in the waveguide layers. Optimal designs of ABLs based on AlGaAsSb and GaInP for blocking electrons and holes, respectively, are proposed, which make it possible to reduce the parasitic recombination current down to less than 1% of the initial value. To suppress electron transport, an alternative structure based on three identical AlInAs barriers is also proposed. The GaAsP spacer layers separating these barriers from each other have different thicknesses. Due to this, the set of quasibound (resonant) states is formed in each spacer layer that is different from the set of states of the neighboring spacer layer. As a result, the resonant tunneling channels are blocked, and the parasitic electron flow is reduced by several tens of times in comparison with the case of spacers of identical thickness.
Display omitted
•Eight derivatives of glycerol, ethylene and 1,2-propylene glycol were synthesized.•The compounds were characterized by the main physical properties.•The gasoline-blending properties ...of the compounds have been estimated.•Blending antiknock indices for the compounds were between 67 and 126.•Glycerol 1,3-di-tert-butyl ether was the most efficient octane booster.
The main physico-chemical features, as well as gasoline blending features of eight diol derivatives (1,3-diisopropyl and 1,3-di-tert-butyl glycerol ethers – di-GIPE and di-GTBE; O-isopropyl and O-tert-butyl solketal ethers – SIPE and STBE; isopropylidene ketals of ethylene and propylene glycol – DMD and TMD; cyclic ketals of glycerol with the methyl ethyl ketone and the methyl isobutyl ketone – GBK and GHK) have been estimated in order to reveal the relations between the molecular structures of the compounds and their efficiency as the gasoline oxygenated additives. For the oxygenates, the experimental values of the density, the boiling/melting point, the viscosity and the net heat of the combustion have been obtained. The characteristics of the estimated oxygenate-gasoline blends have involved their density, the calorific value, the fractional composition, the saturated vapor pressure, the research octane number and the motor octane numbers (ON), the oxidation stability, the gum content and the pour point. For di-GTBEs, as the most effective octane booster (among the compounds tested), the effect on the gasoline calorific value has been researched in the combination with the antiknock features improvement, which shows the evident advantages over ethanol and MTBE relatively to ΔAKI/ΔNHOC ratio.
We report room temperature injection lasing in the yellow-orange spectral range (599-605 nm) in (Al
Ga
)
In
P-GaAs diodes with 4 layers of tensile-strained In
Ga
P quantum dot-like insertions. The ...wafers were grown by metal-organic vapor phase epitaxy side-by-side on (811), (211) and (322) GaAs substrates tilted towards the direction with respect to the (100) surface. Four sheets of GaP-rich quantum barrier insertions were applied to suppress leakage of non-equilibrium electrons from the gain medium. Laser diodes having a threshold current densities of ~7-10 kA/cm
at room temperature were realized for both (211) and (322) surface orientations at cavity lengths of ~1mm. Emission wavelength at room temperature ~600 nm is shorter by ~8 nm than previously reported. As an opposite example, the devices grown on (811) GaAs substrates did not show lasing at room temperature.
This review provides an analysis of recent scientific and engineering literature on chemical methods for CO
2
processing using heterogeneous catalysts. The following major uses of carbon dioxide are ...discussed: exhaustive hydrogenation; synthesis of hydrocarbons including light olefins; synthesis of oxygenates; and production of cyclic carbonates. Furthermore, the paper highlights the main design approaches for CO
2
conversion catalysts and formulates priorities for decarbonization using heterogeneous catalytic reactions.
PDF
