Search

The bentonite was treated in different ways and the changes in structure were monitored. Acid activation with sulphuric acid of investigated bentonite caused the increase in specific volume of micropore-mesopore. It was shown that activation by acid obtained at a constant temperature and constant period of time provides the possibility to obtain samples of bentonite of searched porosity only by changing the concentration of sulphuric and hydrochloric acid. By thermal activation of bentonite clay in the temperature range 100-1100 0C, samples of desired porosity were acquired. [Projekat Ministarstva nauke Republike Srbije, br. 174007i br. TR 34020]

The materials based on BaTiO3 can be controlled using different technological parameters and different additives. The influence of different temperature levels of sintering (1320°C, 1350°C and 1380°C) on the size of contact area for 0.1% Ho2O3 doped BaTiO3-ceramics has been investigated. Microstructural investigations were carried out using scanning electron microscopy (JEOL-JSM 5300) equipped with EDS (QX 2000S) system. Grain size distribution was determined by quantitative metallography method. The new correlation between microstructure and dielectric properties of doped BaTiO3-ceramics based on fractal geometry and contact surface probability is recently developed. The presented results indicate that statistical model of contact surfaces is important for the prognosis of BaTiO3-ceramics microstructure and dielectric properties. [Projekat Ministarstva nauke Republike Srbije, br. 172057: Directed synthesis, structure and properties of multifunctional materials i br. III44006]

Organic modification of mineral clay using the monomer ethenyl acetate was performed. The exchange of inorganic interlayer clay cations was achieved using the cationic surfactant Genamine CTAC and Asepsol. Aiming to investigate the influence of organic modifications on adsorptive clay properties, dried composites of clay/ethenyl acetate, with different percentages of clay were soaked in distilled water. The influence of the temperature on the adsorptive properties of organoclays was also followed. The adsorptive properties of the obtained composites of organoclays with Luviskol, Carbopole and purine were investigated along with their capability for removing Pb2+ from water in charged systems. [Projekat Ministarstva nauke Republike Srbije, br. TR 34020, br. 172047 i br. 174007]

La/Mn-codoped BaTiO3 systems, obtained by solid state reactions, were investigated regarding their microstructure characteristics and ferroelectric properties. Different concentrations of La2O3 were used for doping, ranging from 0.1 to 5.0 at% La, while a content of Mn was constant at 0.05 at%. For all samples sintered below the eutectic temperature (1332°C), a uniform microstructure was formed with average grain size from 1-3 μm. The appearance of secondary abnormal grains with (111) double twins grains with curved or faceted grain boundaries were observed in La/Mn BaTiO3 ceramics after sintering at temperatures above the eutectic temperature. All sintered samples exhibited a high electrical resistivity. Better dielectric performances were obtained for low doped samples (0.1 at% La) sintered at 1350°C. For samples with La content above 1.0 at% a lower value in dielectric permittivity at higher sintering temperature is due to secondary abnormal grain growth, and to the presence of a non-ferroelectric phase rich in La. The Curie constant together with other dielectric parameters were also calculated.