Nadir toprak element (Nt) oksitlerinin nano boyutlu parçaciklarinin ve meso-gözenekli zirkonyum oksitlerin sentezlenmesi ve karakterizasyonu

The thesis work consists of two main parts. The first one is focused on the synthesis of rare earth oxides having nanometer particle size via two methods: liquid crystal templating and sol-gel method. The samples were characterized by DTA/TG measurements combined with Mass spectroscopy, XRPD, DLS, FTIR and HR-TEM investigations. The average crystalline grain size was calculated from the XRPD data based on the Debye-Scherrer?s equation.The precursors in liquid crystal templating method were rare earth nitrates, RE(NO3)3.nH2O (n = 4-6; RE = Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu) and non-ionic surfactant C12H25(CH2CH2O)10OH (Brij 56®) was used as surface-active agent. The XRPD results reveal that all as-prepared samples consist of oxides - hydroxides. The crystalline oxide formation of these rare earths was determined and for most of the investigated elements it took place at ~773 K under constant air flow. Unlike the other investigated elements, neodymium as-prepared sample shows different thermal behavior and forms oxide carbonate, Nd2O2CO3, when annealed in the presence of CO2. The liquid crystal templating resulted oxide nanoparticles with the mean particle size less than 15 nm except Sm2O3 where the mean particle size was 23 nm. According to HR-TEM investigations, the oxide nanoparticles possess disordered nanoporous structures.The second method is based on a modified sol-gel route to prepare nanoparticles of Eu2O3, Gd2O3 and Er2O3. Precipitations of the rare earth hydroxides was achieved for the first time by passing gaseous ammonia trough the suspension of RE(NO3)3.nH2O (n = 4-6; RE = Eu, Gd Er) dispersed in the mixture of diethylene glycol (DEG) and tetraethylene glycol (TEG). The XRPD results showed that, precipitates after gaseous ammonia purge have amorphous structure. The DTA/TG experiments confirmed the oxides formation takes place at ~573 K in one exothermic step in line with the XRPD results. The average particle sizes of the oxides were 10-35 nm. The Eu2O3 powders were successfully infiltrated into Al2O3 inverse opals as well. These samples were illuminated by 355 nm laser light and they exhibited red luminescence of Eu2O3.In the second part of the study, nanoporous zirconium oxides were synthesized based on surfactant templating. Two different surface directing agents, cationic hexadecyl-trimethyl-ammonium bromide CH3(CH2)15N(CH3)3Br (CTAB) and nonionic C12H25(CH2CH2O)10OH (Brij56®), were studied. The synthesis was carried out in the presence of two series of precursors, zirconium oxychloride, ZrOCl2.8H2O and zirconium (IV) ethoxide, Zr(OC2H5)4. The thermal behavior was investigated by DTA/TG and mass spectroscopy measurements. The analysis of the different phases and their chemical composition were studied by XRPD, FTIR and HR-TEM experiments.In the presence of CTAB, the XRPD and DTA/TG results showed that in both precursor cases the as-prepared amorphous hybrid oxide-hydroxide (containing both inorganic and organic compounds) transforms to crystalline tetragonal zirconium oxide when annealing at 923 K. The FTIR investigations confirmed that organic surfactant decomposes at ~650 K and leaves high purity stable tetragonal phase behind. The HR-TEM results taken from the samples synthesized from Zr(OC2H5)4 precursor indicated partial hexagonal pore arrangements after annealed at 723 K. At this temperature, the sample synthesized from ZrOCl2.8H2O precursor possessed ordered pore structure and uniform pore size of 2.8 nm with amorphous walls.In the presence of Brij56 similar to the CTAB system both precursor resulted amorphous hybrid oxide-hydroxide. Based on the DTA/TG investigations the organic surfactant decomposed at ~650 K while increasing the temperature to 723 K mainly monoclinic zirconium oxide with some tetragonal phase formed. Further heat treatment at 923 K caused phase transformation to tetragonal modification when ZrOCl2?8H2O was applied as starting material. For the Zr(OC2H5)4 precursor some monoclinic phase was also identified in the main tetragonal phase. Similar heat treatment at 723 K results in both cases in formation of porous with a high pore size distribution.