Milica Vlahović

Modelling, simulation and optimisation of pulse-reverse regime of copper, silver and gold electrodeposition

Abstract Pulse-reverse power modes are used in galvanotechniques in order to obtain coatings with better characteristics in terms of gloss, adhesion, tracking sharp edges and uniform distribution of deposits on complex shape objects, compared with the coatings produced by constant current modes. Pulse-reverse modes also allow the use of a higher current density, and thus the production speed of electroplating cells increases. Systems for standard electroplating of copper, silver and gold are optimised by the suitable choice of duration and intensity of the pulses. It is shown that coatings with satisfactory quality can be deposited using higher current density, different modes of pulsed current in a very short period of time, without expensive and often dangerous additives in the electrolyte. Parameters of the model for certain electrochemical systems were determined by modelling and computer simulation, so the system behaviour under different circumstances becomes predictive.

Investigation of the possibility of binding fly ash particles by elemental sulphur

Thermal power plants in Serbia use lignite for electrical power production The secondary product of coal combustion is fly ash in the amount of 17%. Fly ash causes the pollution of air, water and soil, and also cause many human, especially lung diseases. Secondary sulphur is a product of crude oil refining. The aim of this study was to investigate the use of sulphur as a bonding material in ultra fine particle agglomeration (smaller than 63 μm) in fly ash. The agglomeration should make the ash particles larger and heavy enough to fall without flying fractions. The experiments showed that during the homogenization of the ashes and sulphur from 150 to 170 °C in a reactor with intensive mixing, an amount of 15% sulphur was sufficient to bond particles and cause agglomeration without visible flying fractions.