Papers by Author: Witold Łojkowski

Abstract: The luminescence of nanocrystalline tetragonal and cubic ZrO2 has been investigated. The tetragonal undoped ZrO2 revealed two luminescence bands, at ~2.0 eV and 2.7 eV , but only one band at ~2.7 eV was observed from cubic ZrO2. This luminescence was shown to be intrinsic. The regular zirconium-oxygen complex excited state is suggested as being responsible for intrinsic luminescence.

Abstract: The aim of the work is to establish if maleic anhydride copolymer acts as a grain growth modulator and/or as a biocompatible functionalisation agent for hydroxyapatite. Experimental work was developed in three directions: nanocomposites synthesis, nanocomposites characterization and citotoxicity tests on nanocomposites. Maleic anhydride copolymer – HAp nanocomposites were prepared by in situ functionalisation in hydrothermal conditions and were characterized by chemical quantitative analysis, XRD, FT-IR, SEM, specific surface area and picnometric densities. Chemical bonding between the copolymer carboxyl groups and calcium ions of HAp induced a peak of 1577 cm-1 on the FT-IR analysis. Following the evolution of this characteristic peak with the hydrothermal synthesis conditions (different temperatures and pressures) and corroborates the results with XRD and SEM analysis it was pointed out the copolymer grain growth modulator behaviour. Citotoxicity studies in vitro on mice fibroblast cultures were performed. The results proved the biocompatibility of new hybrid –polymer nanocomposites.

Abstract: The preparation of transparent nanoceramics from nanocrystalline Y3Al5O12 (YAG) powders doped with rare-earth ions has been described and the results of investigation of the structure and morphology have been presented. Decomposition of YAG nanocrystals into YAlO3 (YAP) was observed. The temperature and pressure for the decomposition was much lower than that reported for larger crystals. The transformation was connected with grain coarsening. The influence of the method of preparation of the YAG nanopowders on the final transparency of the nanoceramic produced was determined. Preliminary results of the dependence of luminescence properties on the structural transformation of the nanograins are presented.