ВведениеРедкоземельные металлы (РЗМ) широко ис-пользуются в интенсивно развивающихся отрас-лях промышленности. Особого внимания заслу-УДК 541. 48 -14: 541.1 : 546.65 DOI dx.doi.org/10.17073/199748 -14: 541.1 : 546.65 DOI dx.doi.org/10.17073/ -308X-2016 Получение сплавов-покрытий на никеле и кобальте методом диффузионного насыщения диспрозием в расплаве LiCl-KCl-DyCl 3 С использованием гравиметрического метода изучено влияние температуры (Т) и продолжительности процесса (τ) на удельное изменение массы (Р) никелевых и кобальтовых образцов при бестоковом диффузионном насыщении их диспро-зием в расплавленной эвтектической смеси хлоридов лития и калия с добавлением 5 мас.% хлорида диспрозия. По резуль-татам опытов были рассчитаны математические зависимости Р(τ) для никелевых образцов в интервале Т = 773÷973 К при τ = 1÷8 ч, для кобальтовых -при Т = 873÷973 К и τ = 1÷7 ч. Их анализ показал, что лимитирующей стадией процесса бесто-кового переноса диспрозия на Ni-и Co-образцы является диффузия в твердой фазе. Состав сплавов-покрытий изучен с использованием рентгенофлуоресцентного спектрометра, рентгеноспектрального микроанализатора и сканирующего микроскопа. Установлено, что в условиях эксперимента формирующееся на поверхности никелевой подложки покрытие состоит из одной структурной зоны, а когда подложкой является кобальт, покрытие имеет две структурные зоны, что согла-суется с имеющимися в литературе сведениями о сплавообразовании аналогичных биметаллических систем.Ключевые слова: диспрозий, никель, кобальт, диффузионное насыщение, бестоковый перенос, сплав-покрытие. Obtaining of nickel and cobalt coating alloys by diffusion saturation with dysprosium in LiCl-KCl-DyCl 3 meltA gravimetric method was used to study the influence of process temperature (Т) and duration (τ) on the specific mass variation of nickel and cobalt specimens during their currentless diffusion saturation with dysprosium in a liquated eutectic mixture of lithium and potassium chlorides with dysprosium chloride added (5 wt.%). The experimental results allowed to calculate the mathematical dependences Р(τ) for nickel specimens in the temperature range of Т = 773÷973 К at τ = 1÷8 h, and for cobalt specimens in the temperature range of Т = 873÷973 К at τ = 1÷7 h. Their analysis showed that the solid-state diffusion is the rate-controlling step of currentless dysprosium transfer to Ni and Co specimens. The composition of coating alloys was studied using the X-ray fluorescence spectrometer, X-ray microanalyzer, and scanning microscope. It was found that under experimental conditions, the coating forming on the nickel substrate surface consists of one structural zone, but when substrate material is cobalt, the coating consists of two structural zones. This is consistent with available literature data on the alloying of similar bimetallic systems. Keywords
High tech industrial fields on modern development stage are in need of construction materials with an optimal ratio of volume and surface properties, along with low cost of material itself. As evidenced by studies, in order to give a set complex of properties to a workpiece that operates under specific conditions, it is often sufficient to only modify its surface area. Over the course of studies, by means of gravimetric, influence of technological parameters (temperature and time samples are kept in the melt) on specific mass change of cobalt samples, that act as substrate, during electroless diffusive saturation with dysprosium in eutectic melt of lithium and Original Research Article: full paper (2019), «EUREKA: Physics and Engineering» Number 6 4 Chemical Engineering potassium chlorides have been studied. A mathematical dependency was established for specific mass change of cobalt samples on time spent in melt for temperature range of 873-973 K. Composition of intermetallic coats obtained on surface of cobalt samples was studied means of EDX and SEM analyses. It was discovered, that for chosen temperature range, diffusion layers formed on surface of cobalt samples consists of two structural zones that correspond to Co-Dy and Cp 2 Dy phases.
Interest to rare-earth metals (REM) and their alloys is due to the possibility of using them for the creation of new materials need for modern technology. For instance, REM as alloying components allows for preparation of material with special magnetic properties. A promising method for forming such coating is the surface treatment of metals. This process has an electrochemical character as such for the organization of technology the knowledge of kinetics and mechanism of these processes is important. Despite significant interest in rare-earth metals, these issues are not well described in the literature. In order to choose an adequate mathematical model for calculation of kinetic primers, preliminary experiments that allow evaluating the reversibility of the electrode process have been conducted. Based on that, it was concluded that cathodic reduction of terbium and holmium ions in equimolar NaCl-KCl melt is irreversible. By means of voltammetric analysis, kinetic parameters (transfer coefficients, heterogeneous constants of charge transfer rate) of terbium and holmium electroreduction in equimolar NaCl-KCl melt were determined. The experiment was conducted in a three-electrode cell under a purified argon atmosphere. A dependency of kinetic parameters on the concentration of terbium and holmium chlorides wt (%): 1, 3, 5, 7, 10, was determined. The experiment was conducted in 1073–1173K temperature range. Values of kinetic parameters increase with temperature but decrease with the increase of REM chloride. Based on obtained data, it was found that electroreduction of chloride complexes LnCl63– (Ln–Tb, Ho) in equimolar NaCl-KCl melt is irreversible in the studied range of temperatures and REM concentrations. In summary of experimental data, in range of temperature and rare-earth chloride concentration, and assumption was made that reduction of terbium and holmium ions occurs in two stages. The process includes the preceding stage of complex dissociation. A mechanism of LnCl63– complex reduction in the mentioned melt is proposed. The obtained results are in agreement with literate data for analogues systems.
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