Vol 53, No 4 (2017)

Comprehensive pilot studies of the influence of one- and two-component nanodimensional powder additives on the operational properties of transmission TM-3-18 oil (GOST (State Standard) 23652-79 TAP-15V) are implemented. Introduction of nanopowder tin bronze and aluminum oxide additives into the base oil is found to increase the antifriction, antiwear, and antiwelding properties of the latter, as well as the cogwheel durability of units, which limits the service life of tractor transmission equipment.

The relaxation time of a near-electrode space charge in magnetic colloids based on dielectric liquids is experimentally established via electrooptical methods as being in the range of 0.05–0.3 s depending on the conductivity of the sample. The results agree with the data of the electrosurface effect in magnetic colloids.

Results of structural studies of metals electrodeposited exposed to an external force directed perpendicular or at an angle to the crystallization front have been described. It has been found that there is an increase in the dislocation density in metals electrodeposited exposed to a minor external force directed perpendicular to the crystallization front. It has been revealed that the surface layers of electrodeposited metals undergo plastic deformation caused by solid particles that move under the action of a minor external force directed at an angle to the crystallization front. It has been found that the solid particles leave imprints representing the particle shape and morphology at sites of separation from the surface of the metal electrodeposits formed exposed to a minor external force directed at an angle to the crystallization front. The existence of phase formation through a liquid state stage in electrodeposited metals has been proven.

Electrocatalytically active Cu-Ni alloy coatings have been developed from a simple electrolyte having only Cu⁺² and Ni⁺² ions, without the use of any additive. Electrocatalytic character of the coatings was tested for their hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH medium, alongside with their corrosion behaviours. Cyclic voltammetry and chronopotentio-metry study revealed that the deposition current density has a prominent role on the alkaline water splitting behaviour of the coatings, depending on their phase structure, composition and surface morphology. It was found that the c.d. has an inverse dependence on HER and OER. The Cu-Ni alloy coatings developed, respectively at 3.0 and 4.0 A dm^–2, were found to be the best coatings for HER and OER, depending on the surface morphology. The electrocatalytic activity of Cu-Ni alloy coating for HER, deposited at 3.0 A dm^–2 (optimal), was further improved through electrochemical dissolution of the as-deposited coating. The increase in the electrocatalytic activity for HER has been attributed to the enhancement in the exposed surface area of Ni active sites due to the leaching of Cu from the alloy matrices, evidenced by the energy-dispersive X-ray spectroscopy and scanning electron microscopy. The dependencies of HER and OER on to the surface of Cu-Ni alloy coatings were analysed in terms of deposition c.d. of the coatings, and the results are discussed.

This paper deals with the optimization of the micro-hardness and the tribological properties of the anodized Al 5754 aluminium alloy. A sulphuric anodizing process was considered. Three anodizing bath parameters, namely: the bath temperature, the current density, and the sulphuric acid concentration, were varied using Doehlert experimental design. The selected responses were: the micro-hardness, the wear rate and the growth rate of the anodic oxide layer. The variance analysis was used to check the adequacy of response models. Additional tests were performed to validate the obtained model. In order to maximize the growth rate and the micro-hardness of the anodic oxide layer and to minimize the wear rate at the same time, a multi-criteria optimization using the desirability function was performed. The main finding of this study indicated that under optimal anodizing conditions (T = 11.1°C, J = 2.1 A/dm², C_sul = 198 g/L), the estimated values responses were 0.64 μm/min, 442 HV, and 4.8% for the growth rate, micro-hardness and wear rate, respectively. The best friction behavior and the lowest wear rate of the optimum anodic layer could be correlated with the surface morphology of the anodic oxide layer revealed by the scanning electron microscopy and optical observations during friction and scratch tests.

efficiency of short- and medium-wave infrared (IR) heat sources used to mount and dismount electronic modules is assessed. The analysis of the models of thermal fields shows that for KGM 30/300 halogen IR lamps, the heating nonuniformity for a printed circuit board is 45–55°С, and for the casings of electronic components, the temperature varies from 90 to 100°С. For an Elstein SHTS/4 ceramic IR heater, the heating nonuniformity for a printed circuit board is 8–13°С, the temperature of SMD component casings differs from temperature of the the printed circuit board: in BGA by 28–32°С, in QFP by 24–26°С, and in SMD by 5–20°С. The application of medium-wave ceramic infrared sources makes it possible to attain a higher heating uniformity in the working area and ensure an optimal temperature profile when mounting and dismounting surface-mounted electronic components.