Composites based on Nb3(Fe, Al)3 C η-carbide obtained by mechanical alloying are studied. Microstructural and quantitative phase analyses are performed. The phase composition, the density and the hardness are determined. It is shown that mechanical fusion of the elemental components in liquid hydrocarbon followed by annealing can be used to synthesize an Nb3(Fe, Al)3 C η-carbide phase. Spark plasma sintering is used to obtain a composite based on η-carbide (60 wt.

Изучена электрокаталитическая активность в реакции выделения водорода ряда механоактивированных/механосплавленных карбидных фаз железа и вольфрама, а также биметаллических карбидов Fe 3 W 3 C и Fe 6 W 6 C. Электрокатализаторы готовили прессованием карбидных частиц с проводящим полимером (полианилин). Наибольшей активностью характеризовались нанокристаллические частицы Fe 3 C и WC. Наличие металлических фаз в составе частиц значительно снижало скорость реакции выделения водорода. Дополнительный отжиг таких частиц приводил к превращению металлических фаз в биметаллические карбиды, что повышало скорость водородной реакции. Активность фаз биметаллических карбидов Fe 3 W 3 C и Fe 6 W 6 C в реакции выделения водорода достаточно высока, хотя они уступают нанокристаллическим частицам Fe 3 C и WC.

Исследованы композиты на основе h-карбида Nb3(Fe, Al)3C, полученные с использованием метода механического сплавления. Определен фазовый состав композитов. Проведены микроструктурный и количественный фазовый анализы. Определены плотность и твердость композитов. Проведены испытания на изнашивание. Показано, что механическим сплавлением элементарных компонентов в жидком углеводороде с последующим отжигом возможен синтез фазы h-карбида Nb3(Fe, Al)3C. Методом электроимпульсного плазменного спекания получен композит на основе h-карбида (60 масс. %), остальное — фазы Nb5Al3Cx, Nb3Al, Nb, Nb2C и ~ 5 % (масс.) нанопластинок графита. Композит имеет плотность 5,11 ± 0,05 г/см3 при пористости ~ 20 %, твердость 1,4 ± 0,6 ГПа и практически не изнашивается при испытаниях в условиях сухого трения с шариками из закаленной стали и сплава ВК6.

The Ti5Si3Сх-based composites containing 10 vol % Ti2AlC, which are prepared by mechanical alloying of Ti, Si, and Al powders in a liquid hydrocarbon and subsequent heat treatment, are studied. The carbosilicide phase is found to form based on a silicide already at the mechanical alloying stage, whereas Ti2AlC forms during subsequent heat treatment. It is shown that, at 1300°С, the sintering of a sample takes place, which results in the formation of a porous (~13%) composite with a density of 3.75 ± 0.01 g/cm3 and a hardness of 10 ± 1 GPa. The dry friction coefficient of the composite, which is determined upon frictional tests with the WC/6Co alloy counterbody, is ~0.55.

The possible synthesis of hexagonal titanium carbohydride-copper composites by two- and three-stage mechanical activation of titanium and copper powders in liquid hydrocarbon followed by magnetic-pulse pressing has been studied in this work. Surfactant used for the three-stage synthesis enable one to restrain the formation of intermetallic phases in the process of mechanical activation and reduce the fraction of intermetallic phases in consolidated samples. The density, microhardness, abrasion resistance, and wear parameters under conditions of dry friction with a steel ball have been estimated. Two- and three-stage methods of producing powders have been shown to be preferable, since friction coefficients and wear in friction pairs are much lower than that of composites produced by the one-stage method.

Abstract The X-ray photoelectron spectroscopy method has been used to study the alpha case formed on the surface of a titanium alloy during its casting into ceramic molds, based on a mixture of oxides of magnesium, silicon, calcium, and water glass, as a binder. It is established that the alpha case consists of mold metal oxides, titanium oxides and complex intermetallic compounds based on titanium and mold elements.

The XPS method has been used to study the chemical composition of the surface of sand forms based on magnesium oxide. The original and modified forms were investigated. Modification of the form was carried out by plasma deposition of a titanium coating on the inner surface. The surface of the initial form consists of the initial oxides and intermetallic compounds based on the elements of the form. In the surface layers of the modified form, TiO2 is the main titanium-containing compound, silicon titanates and intermetallic compounds based on the elements of the form and titanium are present.

The structural and phase state of the samples obtained by co-grinding of Ti and Cu powders under different conditions (with graphite, in petroleum ether, and in xylene) is investigated. It is demonstrated that after thermal treatment of powders obtained by milling of titanium, copper, and graphite in petroleum ether, both cubic titanium carbide and hexagonal titanium carbohydride are formed, whereas by milling without graphite, only hexagonal carbohydride possessing high thermal stability is formed. CuTi and CuTi2 intermetallic phases are formed under all examined conditions of mechanosynthesis.

Mechanical activation of titanium in petroleum ether with subsequent heat treatment produced titanium carbohydrides with hexagonal close-packed and face-centered cubic lattices. The effect of iron and copper additions on the structural and phase composition of the titanium-based powders after the mechanical activation and heat treatment was studied. In these systems, both titanium carbohydrides, and the intermetallics Ti–Cu, Ti–Fe, and Ti–Fe–Cu formed. All the obtained powders contained ~1 wt % hydrogen. The release of hydrogen by heating the powders was investigated, and the lowest release temperatures (220–500°C) were detected for the phase Ti–Fe–Cu.

Structural and phase composition and magnetostatic and microwave properties of Fe 70 Co 30 –SiO 2 systems obtained by high-energy milling in acetone for different times (from 6 to 48 h) are studied. It is found that, after the longest milling time, the obtained particles have sizes from 0.5 to 5 μm, are covered with a thin layer of SiO 2 , and contain 10 wt % iron carbides. Milling-induced change in the phase composition of the particles influences their specific magnetization of saturation and coercive force, but has a small effect on the microwave permittivity of composite materials containing these particles in the frequency range of 0.1–6 GHz. As the milling time grows, the imaginary part of the microwave permeability decreases at frequencies below 1 GHz.

The results of investigation of the morphology, structure–phase composition, surface structure, and properties of iron particles, which were prepared by mechanoactivation in planetary ball mill in cis - and trans -polyisoprenes and cis -polybutadiene in the presence of perfluorononanoic acid acting as a surfactant, are given. It is determined that there are high-disperse carbides in bulk particles, whose major part is formed during the grinding with polybutadiene. The difference in phase composition of particles does not affect the UHF characteristics of composites. The organic layer is formed on a surface of particles that contains modified molecules of polymers and perfluorononanoic acid and is thinnest after grinding with cis -polyisoprene. The thickness of the organic layer does not influence either the UHF values of the dielectric and magnetic permittivities of composites or the corrosion properties of particles in acidic media. Material parameters of UHF composite materials filled by the powders under study are mainly determined by the shape of powder particles.

Ultrafine iron particles prepared via mechanical activation in a planetary ball mill in polydiene solutions with surface-active substances (SASs) are studied in this work. It is shown that carbides are disposed in the particle bulk, whereas an organic layer with modified (oxidized) polymer molecules and SASs is formed at the surface of particles. Adsorption of polydienes on the particle surface is due to alcohol and carboxyl groups. It is established that modification of iron particles with polybutadiene leads to the formation of a polymeric film with a maximum protective effect.