In this study, the influence of pH, electrolyte concentration and type of ionic species (such as LiCl, NaCl, KCl, RbCl, CsCl, CaCl2, AlCl3) on the electrokinetic properties (zeta potential and electrokinetic charge density) of montmorillonite has been quantified. The zeta potential of montmorillonite particles did not change significantly with change in pH. The valencies of the ions have proven to have a great influence on the electrokinetic behaviour of the suspension. There is a gradual decrease in the zeta potential (from —24 mV to —12 mV) with increase in monovalent electrolyte concentration (from 10-4 M to 10-1 M). At any monovalent electrolyte concentration, the magnitude of the zeta potential increased with the electrolytes in the order Li+ > Na+ > K+ > Rb+ > Cs+. The zeta potential of the montmorillonite minerals in CaCl2 solutions illustrated the same behaviour as the monovalent cations. Less negative values were obtained for the CaCl2 electrolyte (∼–10 mV) due to the greater valence of the ions. A sign reversal was observed at an AlCl3 concentration of 5 x 10-4 M, and, at greater concentrations, zeta potential values had a positive sign (∼20 mV).The electrokinetic charge density of montmorillonite showed similar trends of variation in mono and divalent electrolyte solutions. Up to concentrations of ∼10-3 M, it remained practically constant at ∼0.5 x 10-3Cm-2, while for greater electrolyte concentrations the negative charge produced more negative values (–16 x 10-3Cm-2). The electrokinetic charge density of montmorillonite particles was constant at low AlCl3 concentrations, but at certain concentrations it increased rapidly and changed sign to positive.

SYNTHESIS OF Ti 3 SiC 2 MAX PHASE FROM ELEMENTAL POWDERS ABSTRACTIn MAX phase material family, Ti-Si-C system and especially 312 Ti 3 SiC 2 phase is the most attracted and investigated structure. It can be produced from different methods. As expected, each method differs processing methods, experimental conditions and parameters depending on the starting composition. In this article, the processing of high purity Ti 3 SiC 2 phase was studied using Ti, Si and C powders. The powders were mixed in stoichiometric ratio to obtain pure Ti 3 SiC 2 phase. Both of the initial and the obtained product samples were characterised using SEM, XRD, XRF, TG/DTA methods. The results showed that, the silicon content was important and carbon plays critical role. X-ray diffraction analysis showed that the 312 TiSiC phases was formed after the sintering at temperature of 1350 ˚C for 2 h. If excess carbon is present in the system, the formed MAX phase was converted into binary carbide phases.