Chemical and phase transitions in oxidized manganese ore in the presence of carbon

In the present work, thermodynamic modeling of the chemical and phase transitions in a system consisting of oxidized manganese ore and reducing agent (carbon) is based on Astra 4 software developed at Bauman Moscow State Technical University. The phase composition and equilibrium characteristics are calculated by means of a database regarding the properties of individual materials. The database in Astra 4 software consists of thermodynamic, thermophysical, and thermochemical properties of materials. It includes data systematized at the Institute of High Temperatures, Academy of Sciences of the USSR and at the United States National Standards Bureau; data published in journals, monographs, and handbooks; and also data analyzed and calculated at Bauman Moscow State Technical University. The chemical and phase transformations in the system are simulated in the range 1573–2573 K, with 5, 10, and 15% C in the system, at a pressure of 0.1 MPa. Modeling shows that the maximum conversion of manganese to Mn3Si3 (in the condensed state) is 95.3 at T = 1873 K, with 30% carbon in the system. With further increase in temperature, the manganese begins to enter the gas phase. In comparison with manganese, silicon is less easily reduced and, with increase in the temperature, it begins to enter the gas phase. The best temperature range for the reduction of silicon is 1773–1873 K, with 15–30% C in the system. Calculation of the iron transfer αFe (%) as a function of the temperature and the carbon content indicates that the temperature range 1773–1873 K is optimal, with 15% C. On the basis of thermodynamic modeling of the phase transitions in a system consisting of oxidized manganese ore and reducing agent, it is possible to assess the possibility of producing ferrosilicomanganese by the electrosmelting of Western Kamys ore, which is hard to enrich.     

Structure and properties of low-alloy Cr-Mo-V steel after austenitization in the intercritical temperature range

The structure formation in 26X1MΦA steel as a result of double quenching (the second time from the intercritical temperature range A _c1-A _c2) and high tempering is established. By EBSD, the crystallographic features of the ferritic-martensitic structure formed in single and double quenching and stabilized on tempering are studied. The prospects for improving the mechanical properties of low-alloy, low-carbon Cr-Mo-V steel by quenching from the intercritical temperature range are considered     

Composition,structure, and photocatalytic properties of Fe-containing oxide layers on titanium

The composition, optoelectronic properties, and surface and cross-section morphology of coatings formed by the method of plasma electrolytic oxidation in electrolytes containing sodium phosphate or silicate with or without addition of K₃[Fe(CN)₆] have been investigated. The coatings were studied by the methods of spectrophotometry, X-ray diffraction analysis, electron microscopy, and X-ray photoelectron spectroscopy. The photocatalytic activity of oxide coatings was studied in the reaction of phenol degradation under ultraviolet irradiation in the presence of hydrogen peroxide. The highest photocatalytic activity in the reaction of phenol degradation in the presence of hydrogen peroxide was manifested by Fe-containing coatings formed in the silicate electrolyte with addition of 8.0 g/L of K₃[Fe(CN)₆].     

Control of the axial coordination of a surface-confined manganese (III) porphyrin complex

The organization and thermal lability of chloro(5,10,15,20-tetraphenyl porphyrinato)manganese(III) (Cl-MnTPP) molecules on the Ag(111) surface have been investigated under ultra-high vacuum conditions, using scanning tunnelling microscopy, low energy electron diffraction and x-ray photoelectron spectroscopy. The findings reveal the epitaxial nature of the molecule-substrate interface, and moreover, offer a valuable insight into the latent coordination properties of surface-confined metalloporphyrins. The Cl-MnTPP molecules are found to self-assemble on the Ag(111) surface at room temperature, forming an ordered molecular overlayer described by a square unit cell. In accordance with the threefold symmetry of the Ag(111) surface, three rotationally equivalent domains of the molecular overlayer are observed. The primitive lattice vectors of the Cl-MnTPP overlayer show an azimuthal rotation of ±15° relative to those of the Ag(111) surface, while the principal molecular axes of the individual molecules are found to be aligned with the substrate (0(-)11) and ((-)211) crystallographic directions. The axial chloride (Cl) ligand is found to be orientated away from the Ag(111) surface, whereby the average plane of the porphyrin macrocycle lies parallel to that of the substrate. When adsorbed on the Ag(111) surface, the Cl-MnTPP molecules display a latent thermal lability resulting in the dissociation of the axial Cl ligand at ~423 K. The thermally induced dissociation of the Cl ligand leaves the porphyrin complex otherwise intact, giving rise to the coordinatively unsaturated Mn(III) derivative. Consistent with the surface conformation of the Cl-MnTPP precursor, the resulting (5,10,15,20-tetraphenyl porphyrinato)manganese(III) (MnTPP) molecules display the same lattice structure and registry with the Ag(111) surface.     

Electroextraction of lead from a lead trilonate solution

Laboratory studies of the cathode process of the electroextraction of zinc from the trilonate electrolyte obtained after the purification of solutions after leaching lead cakes of zinc production are performed. The potential scan rate is determined by recording potentiodynamic curves; the optimal electrolyte acidity, the composition, and the temperature are established. Values of activation energy confirming the concentration nature of process polarization are found.     

Preparation and structure of multiwalled carbon nanotubes

The structure of oxidized multiwalled carbon nanotubes has been studied by transmission electron microscopy and X-ray diffraction. The results demonstrate that oxidation disrupts nanotubes. Subsequent heat treatment at 300°C also changes the structure of the nanotubes, increasing their inner diameter and reducing their outer diameter.