CATALYTIC PROPERTIES IN THE HETEROGENEOUS FENTON REACTION OF THE SURFACE OF NANOPOROUS IRON OBTAINED BY ELECTROCHEMICAL DEALOIYNG IN MELTED CHLORIDE MIXTURES

Исследованы образцы частично окисленного микро- и нанопористого железа, полученного методом высокотемпературного деаллоинга железо-марганцевого сплава в солевом расплаве. При помощи электронной микроскопии получены данные о морфологии образцов и составе их поверхности, установлено, что уже после отмывки при комнатной температуре на воздухе образовались оксидные фазы железа в виде вискеров толщиной порядка 10 нм. В ходе получения образцов достигалось количественное удаление марганца из исходного сплава. Оценена каталитическая активность полученных образцов в гетерогенной реакции Фентона по окислению красителя метилового оранжевого пероксидом водорода. На первом этапе протекания реакции, описываемой уравнением реакции первого порядка, ее скорость определялась наиболее активной расходуемой частью образцов, далее реакция переходила в стационарный режим. Более высокой каталитической активностью обладали нанопористые образцы. The samples of partially oxidized micro- and nanoporous iron obtained by high-temperature dealloing of an iron-manganese alloy in a molten salt were investigated. The data concerning the structure of the samples and the composition of their surface were obtained by electron microscopy; it was found that after washing at room temperature in air the oxide phases of iron were formed as whiskers with a thickness of about 10 nm. During the preparation of the samples a quantitative removal of manganese from the initial alloy was achieved. The catalytic activity of the obtained samples in the heterogeneous Fenton reaction was estimated by oxidation of methyl orange by hydrogen peroxide. The rate of the first stage of the reaction, which was described by the first-order equation, was determined by the most active spent part of the samples, and then the reaction passed into the stationary mode. The nanoporous samples possessed a higher catalytic activity.

IINVESTigation of the catalytic and isomerization activity of multi-component skeletal nickel catalysts in the hydrogenation of hexene-1

In this work, the effect of the amount of catalyst, modifying additives, and the phase composition of the alloys on the catalytic and isomerizing activity of skeletal in the hydrogenation reaction of hexane-1 is investigated. It has been shown that for all studied catalysts, the yield of products in the processes of migration and isomerization depends very strongly on the weighed portion of the catalyst introduced into the reaction medium. So, for example, the yield of hexane-2 with an increase in the catalyst weight increases linearly to 0.5g of nickel, while at the initial stage of the reaction the yield of hexane-2 reaches 62%. With a further increase in the catalyst weight (up to 1 g of Ni), the yield of hexane-2 decreases. The results of chromatographic analysis indicate a high activity of modified skeletal nickel catalysts in the reaction of migration of -C = C- bonds during hydrogenation of hexene-1. Modification of Fe, Pd, Sn and Ag increases the migration coefficient (Kmigr) from 0.66 to 0.70-0.77, while additions of Ti, Mo, Ti-Mo and Zr practically do not change it. The activity of the catalyst increases with the introduction of the metals Cu, Zn, Pb, Ti-Mo, Mo, Bi, Ag, and Mo-Cu (W=120-290 cm3/min·g Ni) into the initial alloy, while the addition of Fe, Pd and Mn (W=56-80 cm3/min·g Ni), while the influence of the components Ti, Zr and Sn is insignificant (W=115-117 cm3/min·g Ni).

LIQUID-PHASE HYDROGENATION OF CYCLOPENTADIENE ON MODIFIED SKELETAL NICKEL CATALYSTS

This paper presents the results of a study on the hydrogenation of cyclopentadiene on modified skeletal nickel catalysts. It is shown that the activity of multicomponent skeletal nickel catalysts in the hydrogenation of cyclopentadiene is largely due to the nature of the additives introduced into the initial alloy. The introduction of Cu, Pb, Ta, Zn, Mo-Cu, Bi and Mo into the alloy leads to an increase in the activity (W = 14-280 cm3/min g Ni) and selectivity (Ks = 0.93-0.99) of cyclopentadiene hydrogenation, additions of Cr, Ti, Sn and Cr-Cu have no significant effect. As a result, when cyclopentadiene is hydrogenated, an intermediate alkene, cyclopentene, is formed. This is due to the cyclic structure of cyclopentadiene, which causes the formation of identical cycloalkene molecules when hydrogen is added to any position. The saturation of cyclopentadiene is completely completed upon absorption of 1 mole of hydrogen, and cyclopentene can be obtained in high yield.

OXIDATION KINETICS OF ALUMINUM ALLOY АЖ2.4М5.3МГ1.1Ц4КР3, ALLOYED WITH TIN, IN SOLID STATE

The purpose of this work was to find out the features of oxidation of the aluminum alloy АЖ2.4М5.3Мг1.1Ц4Кр3 doped with tin and to develop new alloy compositions with improved characteristics. The thermogravimetric method was used to determine the oxidation kinetics of the aluminum alloy АЖ2.4М5.3Мг1.1Ц4Кр3, containing up to 0.5 wt% tin. The results showed that the process of weight gain of alloys during first 15-20 minutes of oxidation grows intensively, and then acquires an almost constant value. Oxide films formed at the beginning of the oxidation process did not possess protective properties, that fact explains an increase in the rate of oxidation of alloys with temperature in the first period. An increase in the rate of oxidation of alloy samples with temperature is noted. As well, the results revealed that tin at concentrations of 0.01 - 0.5 wt.% reduces the oxidability of the initial alloy, which is accompanied by an increase in the apparent activation energy from 82.1 to 104.3 kJ/mol.

Production of WC-15Co ultrafine-grained hard alloy from powder obtained by VK15 alloy waste spark erosion in water

The study covers the possibility of WC-15Co ultrafine cemented carbide production from powder obtained by spark erosion (SE) of VK15 cemented carbide waste in water. As a result of SE in an oxygen-containing liquid (H2O), the carbon content in the resulting powder decreases from 5.3 to 2.3 %. When the powder is heated to 900 °C in vacuum, the carbon content decreases to 0.2 % due to the presence of oxygen. The powder obtained consists of WC, W2C and Co phases. Particles have a dendritic structure consisting of newly formed tungsten-containing grains and cobalt interlayers. The controlled removal of oxygen and carbon replenishment in the resulting powder were carried out by heating in the CO atmosphere to t = = 900 °C. The processed powder has a required phase composition (WC + Co) and carbon content (5.3 %). Particles retain their spherical shape after carbon replenishment. WC grains in particles become plate-shaped with the space between them filled with cobalt. The average grain diameter is smaller than in the initial alloy. The vacuum sintering of the resulting powder at 1390 °C made it possible to obtain WC–15Co ultrafine-grained cemented carbide with an average WC grain diameter of 0.44 μm. It is several times smaller than the average grain diameter in the initial alloy (1.8 μm). Most grains retain their plate shape. The resulting alloy combines high hardness (1620 HV), increased fracture toughness (13.2 MPa·m1/2) and strength (1920 MPa) due to its fine-grain structure and 15 % cobalt content. In terms of the set of its properties, this alloy is not inferior to analogues obtained by other methods.

Impact of Pretreatment of Metal Glass Fe70Cr15B15 on Anodization in 1-butyl-3-methylimidazolium Tetrafluoroborate Ionic Liquid

The impact of preliminary treatment (mechanical abrasion; chemical etching and anodization in ionic liquid) on the surface structure and corrosion behavior of Fe70Cr15B15 metal glass was studied. The detachment of the anodic oxide film from untreated Fe-amorphous alloy under anodization in ionic liquid was observed for the first time. The formation of hexagonal nanostructures (cells) on the surface of the Fe70Cr15B15 alloy after mechanical abrasion and following anodization in 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) ionic liquid was also detected for the first time. Electrochemical corrosion of the initial and pretreated amorphous alloy was tested in a Na2SO4 aqueous solution. The resistance to corrosion was found to be enhanced slightly after mechanical abrasion. The sample with hexagonal nanostructures obtained after anodization of the mechanically abraded sample demonstrated a more significant anodic shift in the corrosion potential (Ecorr = + 379 mV) compared with that for the initial alloy (Ecorr = −125 mV).

Heat capacity and thermodynamic functions of aluminum conductive alloy E-AlMgSi (Aldrey) doped with gallium

Aluminum — a metal whose scope of application is constantly expanding. At present, aluminum and its alloys in a number of areas successfully displace traditionally used metals and alloys. The widespread use of aluminum and its alloys is due to its properties, among which, first of all, low density, satisfactory corrosion resistance and electrical conductivity, ability to apply protective and decorative coatings should be mentioned. All this, combined with the large reserves of aluminum in the earth’s crust, makes the production and consumption of aluminum very promising. One of the promising areas for the use of aluminum is the electrical industry. Conductive aluminum alloys type E-AlMgSi (Aldrey) are representatives of this group of alloys.One of the promising areas for the use of aluminum is the electrical industry. Conducting aluminum alloys of the E-AlMgSi type (Aldrey) are representatives of this group of alloys. The paper presents the results of a study of the temperature dependence of heat capacity, heat transfer coefficient, and thermodynamic functions of an aluminum alloy E-AlMgSi (Aldrey) with gallium. Research conducted in the “cooling” mode. It is shown that the temperature capacity and thermodynamic functions of the E-AlMgSi alloy (Aldrey) with gallium increase, while the Gibbs energy decreases. Gallium additives up to 1 wt.% Reduce the heat capacity, enthalpy, and entropy of the initial alloy and increase the Gibbs energy.

OXIDATION KINETICS OF ALUMINUM ALLOY AK12M2, MODIFIED BY BARIUM, IN SOLID STATE

The oxidation kinetics of the AK12M2 aluminum alloy modified to 1.0% by barium was studied using thermogravimetry method. It was shown that the addition of barium to the alloy and the increase in temperature increase the oxidation rate of the initial alloy in the solid state. The apparent activation energy of the oxidation process of the AK12M2 aluminum alloy is 127.73 kJ/mol and decreases to 71.85 kJ∕mol for the alloy with 1.0% barium. The oxidation curves of the AK12M2 aluminum alloy with barium in the solid state are described by polynomials indicating the hyperbolic mechanism of that process. The mechanism of influence of barium on the oxidability of the AK12M2 aluminum alloy was established. It lies in the fact that barium in the range of 0.3-1.0% plays a dominant role in the formation of an oxide film, which is characterized by low protective properties. Barium influence is explained by its physicochemical properties as one of the alkaline earth metals.

Shape regulation of high-index facet nanoparticles by dealloying

Tetrahexahedral particles (~10 to ~500 nanometers) composed of platinum (Pt), palladium, rhodium, nickel, and cobalt, as well as a library of bimetallic compositions, were synthesized on silicon wafers and on catalytic supports by a ligand-free, solid-state reaction that used trace elements [antimony (Sb), bismuth (Bi), lead, or tellurium] to stabilize high-index facets. Both simulation and experiment confirmed that this method stabilized the {210} planes. A study of the PtSb system showed that the tetrahexahedron shape resulted from the evaporative removal of Sb from the initial alloy—a shape-regulating process fundamentally different from solution-phase, ligand-dependent processes. The current density at a fixed potential for the electro-oxidation of formic acid with a commercial Pt/carbon catalyst increased by a factor of 20 after transformation with Bi into tetrahexahedral particles.

Effect of warm equal channel angular pressing on the structure and mechanical properties of Ti0.16Pd0.14Fe (wt%) alloy

Here we analyze the microstructure and phase composition of a Ti alloy with 0.16Pd and 0.14Fe (wt%) alloy exposed to warm equal channel angular pressing (ECAP) at 648 K. The analysis shows that after four ECAP passes, the material assumes a submicrocrystalline structure with an average grain size of 0.28 μm, as against its initial value 10 μm, and that the α phase dominates in the alloy both before and after ECAP. The initial alloy reveals a high content of Fe and Pd atoms near grain boundaries compared to central grain regions. Such near-boundary zones contain orthorhombic α′′ martensite in addition to the α phase, and β or α + β particles are found directly at the grain boundaries. These features of the phase composition are inherited after ECAP. The yield strength of the ECAP treated alloy is 500 MPa, being greater than the initial strength 350 MPa, and its margin of plasticity is rather high. The torsional strain up to fracture in the initial and in the ECAP treated alloy is 70% and 50%, respectively.