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Titanium alloys are indispensable in the aerospace, nuclear and automotive industries due to their high specific strength, excellent creep resistance and corrosion resistance, but their use is seriously limited due to poor wear resistance. The method of еlectrospark deposition using a non-localized electrode consisting of a mixture of titanium granules with the addition of 6 –12 vol.% boron carbide powder was used to obtain metalloceramic coatings Ti-TiB2 / TiC onto Ti-6Al-4V titanium alloy. The results of the study show that the coatings contain αTi, TiB, TiB2 and TiC phases. It was found that with an increase in the content of boron carbide powder in the electrode to 12 vol.%, the total ceramics concentration increases to 93 vol.%. According to the metallographic analysis data, the coating thickness varied from 43.6 to 57.6 μm. The Vickers microhardness of the coatings increased monotonically from 8.13 to 12.02 GPa with increasing ceramic concentration. The use of the developed coatings allows increasing the wear resistance of the surface of the Ti-6Al-4V titanium alloy by 48 and 71 times at loads of 25 and 50 N, respectively. The technology is proposed for applying metal-ceramic coatings to the Ti-6Al-4V alloy using B4C powder, which surpasses the corresponding laser coatings in hardness and wear resistance due to a many times higher concentration of reinforcing phases: TiB2 and TiC.
Enhancing the strength, hardness, and wear resistance of aluminum alloys can be done through composite forming. According to the methods of production, composites can be classified into two types: ex situ and in situ composites. In ex situ composites, the reinforcing particles do not interact with the matrix, whereas in in situ composites, a chemical reaction occurs between the reinforcing particles and the matrix. Friction stir processing (FSP) is a promising approach to forming in situ composites, as it involves the frictional mixing of solid-state metal through the combined rotational and linear movement of the tool. The aim of this work was to study the impact of multi-pass FSP on the microstructure and microhardness of the in situ composite formed on the surface of an AA6063 alloy with pre-incorporated NiO particles. For this purpose, 4-, 10-, and 20‑pass FSP of AA6063 alloy sheets with grooves filled with fine NiO powder were performed. The chemical reaction between NiO and the aluminum matrix leading to the formation of Al3Ni and Al2O3 was studied using EDS, EBSD and X-ray diffraction techniques. It was found that the quantity of Al3Ni and Al2O3 particles increased with the number of FSP passes. The maximum surface microhardness of 253 HV is reached after 10 passes. As the number of FSP passes increases, the grain / subgrain sizes of the aluminum matrix decrease. After 10 passes, the grain / subgrain sizes stabilize at a level of 0.8 – 0.9 μm.
In this work, an ab initio study of a triangulated boron nanotube as an anode material for lithium-ion and sodium-ion batteries was performed for the first time. In the work, two boron nanotubes of “armchair” type (21, 0) and “zigzag” type (14, 0) were considered. The parameters such as Li / Na adsorption energy, electrical conductivity, specific capacitance, diffusion barriers and open-circuit voltage in a boron nanotube were calculated for varying Li / Na concentration upon three charge / discharge cycles. The study revealed that: a) Li / Na atoms are strongly bonded to the atomic structure of boron nanotube and their adsorption energy does not exceed the cohesive energy for bulk Li / Na; b) the energy barrier for Li / Na diffusion in the boron nanotube is 26.2 meV for Li and 17.0 meV for Na; c) the specific capacitance of a boron nanotube is 619.8 mAhg−1 at an average open circuit voltage of 0.70 V (relative to Li / Li+) and 0.66 V (relative to Na / Na+); d) calculation of electrical conductivity showed an increase in the resistance of the boron nanotube after three charge / discharge cycles up to 931 Ohm for Li and 632 Ohm for Na; e) after three charge / discharge cycles, the total energy of the boron nanotube reduced by 273 meV (Li) and 364 meV (Na) indicating an improvement in the equilibrium state after cycling. Analysis of the results confirms that triangulated boron nanotube is a very promising anode material for lithium-ion and sodium-ion batteries.