Showing papers by "Peter Baláž published in 2006"

Ball milling-induced reduction of MoS2 with Al

Abstract: The ball milling-induced reduction of MoS2 by Al has been investigated. Although this is a highly exothermic reaction that, based on its thermodynamic properties, should progress as a self-sustaining process, ignition could not be achieved by ball milling. In order to identify the reason, XRD, particle size distribution, SEM, and DTA measurements were carried out on a series of samples milled for different durations. It was found that the largest composite agglomerates broke up due to the presence of a fine dispersion of MoS2 particles. SEM also revealed that the grains are packed rather loosely within the agglomerates. These results indicate that a self-sustaining process can take place only if large and well-compacted composite particles are present.

The influence of mechanical activation of chalcopyrite on the selective leaching of copper by sulphuric acid

Abstract: In this paper chalcopyrite, CuFeS 2 , has been selective leached by H 2 SO 4 as leaching agent (170 g/dm 3 ) in procedure of hydrometallurgical production of copper. Mechanical activation of the chalcopyrite resulted in mechanochemical surface oxidation as well as in the mineral surface and bulk disordering. Furthermore, the formation of agglomerates during grinding was also occured. Surface changes of the samples using infrared spectroscopy and scanning electron microscopy methods were investigated before and after leaching. The leaching rate, specifi c surface area, structural disorder as well as copper extraction increased with the mechanical activation of mineral. Utjecaj mehanicke aktivacije halkopirita na selektivno izluživanje bakra sumpornom kiselinom. U ovom je radu halkopirit, CuFeS 2 , selektivno izluživan sumpornom kiselinom (170 g/dm 3 ) u postupku hidrometalurske proizvodnje bakra. Mehanicka aktivacija halkopirita rezultirala je mehanokemijskom oksidacijom povrsine te nepravilnoscu povrsine i unutrasnjosti minerala. Nadalje, također se događalo stvaranje nakupina tijekom mljevenja. Povrsinske promjene uzorka istraživane su prije i poslije izluživanja uporabom infracrvene spektroskopije i metodom pretražne elektronske mikroskopije. Za karakterizaciju cvrstog ostatka poslije izluživanja koristena je rentgenska difrakcijska analiza. Brzina izluživanja, specifi cna povrsina, strukturna nepravilnost i izdvajanje bakra povecavaju se s mehanickom aktivacijom minerala. Kljucne rijeci: halkopirit, mehanicka aktivacija, izluživanje sumpornom kiselinom, selektivnost

Mechanochemistry in the preparation of advanced materials

Abstract: Mechanochemistry is a branch of solid state chemistry which inquires into processes which proceed in solids due to the application of mechanical energy. At present, mechanochemistry appears to be a science with a sound theoretical foundation which exhibits a wide range of potential application. Amongst the potential viable processes we can mention the modification of properties of building materials, the new method of fertilizer production, the activity enhancement and regeneration of catalysts, the new method of modification of solubility and bioavailability of drugs in pharmacy, the control of reaction kinetics in the chemical technology and last but not least the recent achievements in the synthesis of advanced materials. In this review paper, the definition of mechanochemistry and its history is given with the types of mills applied. Theoretical background for enhanced reactivity is given, several characterization methods and two examples of application in materials science and pharmacy are described.