The good wear-resistance of state-of-the-art liquid lubricants is due to the formation of complex metal and organometallic films onto the friction surface, reducing the friction and wear. For this ...purpose, various additives of metal nanopowders are used, especially ones based on copper. The formation and growth of Cu nanoparticles, as well as the tribotechnical characteristics of lubricants, are mainly affected by the choice of stabilizer, because nanoparticles cannot resist the external conditions without protecting their surface. According to quantum chemical studies, the best stabilizer in the series of gelatin, ammonia, sodium borohydride, and sodium citrate is gelatin due to the very large amount of functional groups in its structure. The characterization of physicochemical properties via dynamic light scattering, atomic force microscopy, and electron microscopy, as well as the tribotechnical characteristics of liquid lubricants with stabilized Cu nanoparticles, are consistent with quantum chemical calculations, confirming that Cu nanoparticles stabilized in gelatin possess the better tribotechnical properties than other stabilizers.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The formation of complexes of nitrogenated molecules with a small copper cluster Cun (n=1-7, 13) is systematically studied through the calculations by the density functional theory method. It is ...shown that the molecules of R1N=Y (Y=CR2R3, NR2, O) are promising for searching agents for copper clusters, as they are synthetically-available, can exert reducing properties, are firmly bound to the copper atoms, and do not distort the original cluster structure. Using any bulky substituent R, it is possible to block access to a large surface area of the cluster for aggressive compounds. Oxygen complexes on the surface of the copper cluster drastically fall short of the strength of the structures formed by molecules R1N=Y (Y=CR2R3, NR2, O). Depending on the cluster size, the interaction force varies in a sinusoidal manner from minimum to maximum.
Purpose. Reducing the downtime of transport equipment due to technical malfunction of the chain transmission by disclosing the uncertainty in the friction change of the plate roller open-chain ...through the estimation of the chain friction coefficient at idle speed. Methodology. To achieve the goal, the following tasks were set: to carry out a research on the change in the plate roller chain friction at idle speed; to develop a method for evaluating friction in the roller plate chain at idle speed. Research on the state of the roller plate chain in laboratory conditions is carried out on the bench by measuring the motor torque during the rotation of the chain. Data processing of the random process of changing the state of the plate roller open-chain predetermines the use of methods of mathematical statistics and correlation analysis. Findings. The research carried out to control the state of the plate roller chain made it possible to disclose the static dependence of the change in friction per day and the correlation dependence of the change in friction in the chain for all days of the experiment. To estimate the change in the state of the conveyor chains, a method was developed for determining the friction coefficient of the plate roller chain through the torque of the motor rotating the open-chain. During the experiment, the increase in the coefficient of friction was more than 20 percent. Originality. The relation of the change in the parameter of the torque of the motor rotating the chain at idle speed during the experiment due to the change in the friction of the chain or the sliding speed in the joints of the chain was disclosed. Practical value. It consists in using the developed method for estimation of the friction in the open-chain at idle speed for planning the timing of scheduled maintenance of transport equipment. An increase in the magnitude of the motor torque that rotates the open-chain at idle speed is associated with a decrease in the sliding speed of the chain joints, an increase in the friction coefficient, which is a criterion for estimation the state of the drive chain. The results of changing the friction coefficient of the developed method showed similarity with the results of the correlation method for estimation of the state of the roller plate chain.
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