Papers by Author: N. Ivanović

Abstract: Effects induced by uniaxial compression and external electric field in P2P to P6P oligophenylene molecules are investigated by versatile calculations. In this way some useful relations between particular values of compression or field directions and intensities to specific changes in molecular structure and properties have been established, enabling estimation of possibilities for tuning the materials characteristics and their spectroscopic analyses. The results are compared to the existing experimental data and similar calculations, and some consequences for applications of oligophenylenes-based materials are discussed.

Abstract: The investigated nanometric magnetite powders were synthesized electrochemically, and examined by XRD and SEM techniques. Their reduction was conducted through the isothermal heating in hydrogen in the temperature range from 600 to 860 K. Kinetics of the hydrogen recovery process during oxidation of freshly formed Fe powders in a water vapor stream was also studied. It was assumed that the solid-gas reaction is diffusion controlled, and Jander’s model was applied to describe it. The experimental data suggest that the reoxidation process proceeds in two stages, at various activation energies. By changing the conditions of the electrochemical (EC) process we were able to produce the iron oxide powders with optimal particle size and activity, for pure hydrogen production through appropriate reduction/oxidation processes.

Abstract: Using semi-empirical quantum mechanic (AM1, ZINDO/S) and ab-initio Hartree-Fock (HF) calculations we investigated selected structural, electronic and vibrational properties of phenylene-based oligomers from biphenyl P2P to para-sexiphenil P6P. Special attention is paid to the interplay of electrostatic and conjugation effects on torsion barrier, energy gap, charge distribution and selected vibrational modes, and their dependence on torsion angle and oligomer size.

Abstract: Structural, magnetic and electrical properties of iron oxide nano-sized powders synthesised electrochemically under various conditions are presented. The influence of the temperature and current density of synthesis on particular powder characteristics is established. Possibilities for co-existence of various phases and their impact on powder properties, as well as feasible paths of phase relaxation and transition during non-isothermal heating are investigated, too. In this way, optimal procedures for the preparation and stabilisation of iron oxides nano-sized powders of different characteristics are evaluated.