Vera Serga

Cathodoluminescence characterization of polystyrene-BaZrO3 hybrid composites

The radiation properties and the electronic structure of hybrid composites based on suspension polystyrene (PS) and nanocrystals of BaZrO3 (BZO) (d < 50 nm) have been studied using luminescent spectroscopy and x-ray analysis. A strong cathodoluminescence (CL) in BZO-nanocrystals is observed in temperature range 80–293 K. It is modified in BZO-PS composites: both the low- and a high-energy bands (near 4 eV) appear, together with a significant reduction in the CL intensity. A decrease of the lattice parameter a for BZO phase in the composite and the modification of CL spectra indicate for changes in the nanocrystalline structure induced by the polymer.

Selective Oxidation of Glycerol to Glyceraldehyde over Novel Monometallic Platinum Catalysts

Several novel monometallic platinum catalysts supported on metal oxides (Al2O3, Y2O3, γ-Al2O3, Lu2O3, ZrO2-Y2O3 TiO2, SiO2, γ-AlO(OH)) and activated carbon (C) were synthesized by extractive-pyrolytic method and tested in glycerol oxidation processes without base addition to obtain glyceraldehyde. It was found that Pt catalyst activity is strongly influenced by support nature, oxygen partial pressure and Pt loading. Pt/Al2O3 and Pt/SiO2 catalysts exhibited the highest activity but selectivity to glyceraldehyde significantly decreased when glycerol conversion increased.

Catalyst activation of silica nano-based pore structure material for hydrogen storage

Silica based composite material with palladium synthesized by extractive-pyrolytic method is used for hydrogen absorption-desorption experiments. The results obtained of the study on dynamic sorption experiments showed that Pyrex glass based composite sample reaches high hydrogen concentration in the material quite fast. Thought silica gel based composite material rapidly reaches 1/2 of hydrogen load but afterwards the amount of hydrogenation increases slowly. The overall amount of absorbed hydrogen for Pyrex glass based material exceeds the amount of absorbed hydrogen by silica gel based material approximately 5.6 times.

Production of glycolic acid from glycerol using novel fine-disperse platinum catalysts

Using extractive-pyrolytic method fine-disperse Pt containing composites were synthesized and tested in catalytic glycerol oxidation. Catalyst activity and selectivity to glycolic acid was determined oxidizing glycerol in mild conditions. It was concluded that only iron containing platinum catalysts were selective to glycolic acid. Selectivity to glycolic acid reached 53-60% with glycerol conversion 12-56%.

Extractive-Pyrolytic Method for Au/MeOx Nanocomposites Production

Au/MeOx (MeOx - SiO2, Al2O3 and TiO2) nanocomposites have been produced by the extractive-pyrolytic method. An organic extract – a solution of n-trioctylammonium tetrachlorolaurate ([Oct3NH]AuCl4) in toluene – was used as a gold-containing precursor. The produced samples were analyzed by IR spectroscopy, X-ray diffraction and scanning electron microscopy. The performed studies have shown that the mean size of the metal crystallites vary within wide limits: on Al2O3 from 60 nm to 35 nm; on SiO2 from 33 nm to 23 nm; on TiO2 from 50 nm to 13 nm.

Novel fine-disperse bimetallic Pt-Pd/Al2O3 catalysts for glycerol oxidation with molecular oxygen

Using extractive-pyrolytic method several Pt-Pd bimetallic catalysts supported on plasma-processed alumina nanopowder were synthesized. Pt-Pd loading and glycerol oxidation process parameter influence on catalyst activity and selectivity was determined oxidizing glycerol in mild conditions. Novel bimetallic catalysts in neutral water solutions were practically inactive (glycerol conversion was only 3%) whereas in alkaline solutions they were active and selective to glyceric acid. Using 1.2%Pt-1.2%Pd/Al2O3 catalyst glyceric acid was obtained with 65% selectivity (glycerol conversion was 96%). It was shown that novel fine-disperse bimetallic Pt-Pd/Al2O3 catalysts were more active compared to analogous monometallic Pt/Al2O3 and Pd/Al2O3 catalysts.

STRUCTURE AND MAGNETIC PROPERTIES OF COBALT FERRITE PARTICLES PRODUCED BY METHOD OF PYROLYTIC SYNTHESIS

ABSTRACT Magnetic fine particles of cobalt ferrite have been prepared by method of pyrolytic synthesis. X-ray diffraction confirmed the formation of single-phase cobalt ferrite nanoparticles in the range 6–50 nm. The size of the particles varies depending on matrix dispersity and mass content in the organic precursors. A large coercivity observed to be small for smaller single-domain particles due to superparamagnetic behavior.

Phase Composition and Morphology of Tungsten Oxide Nanoparticles Produced via a Pyrolytic Process

The chemical synthesis is a leading route for the purposeful design of nanomaterials, whereas the tungsten oxides are employed in a variety of special applications. The production of nanomaterials by traditional synthetic methods is still a cumbersome multistep procedure. Here we propose an improved method to produce tungsten oxide nanoparticles via a pyrolytic process. A tungsten-containing precursor was prepared by liquid extraction using n-trioctylamine (C8H17)3N solution in toluene. We have shown that the conditions of thermal treatment of the W-based precursor determine the crystalline structure and nanomorphology of the final product. Monoclinic WO3 nanocrystallites are produced conducting the pyrolysis above 450 °C. The proposed method is a facile and versatile route to produce and control the phase composition and morphology of tungsten oxide-based nanomaterials.

NiO and CoOx Promoted Pt Catalysts for Glycerol Oxidation

Two kinds of Pt/CeO2 catalysts supplemented with NiO or CoOx additives were synthesized by extractive-pyrolytic method and tested in glycerol oxidation processes. It was found that only NiO additive promotes Pt/CeO2 catalysts activity and selectivity to glyceric acid. NiO promoted Pt catalysts activity depends on NiO composites’ calcination temperature, oxygen partial pressure, initial NaOH concentration, as well as temperature. Glycerol conversion increases along with increased oxygen partial pressure from1 to 6 atm and along with decreased glycerol/Pt molar ratio from 5000 to 300. It was found that presence of base is significant in the glycerol oxidation processes over NiO promoted Pt/CeO2 catalysts, and optional NaOH initial concentration is 0.6 mol/L. The best yield of glyceric acid (68%) was reached in the presence of 4.8wt%Pt/5wt%NiO/CeO2 (300 °C) catalyst, when temperature was elevated up to 70 °C.

Production of Nano-Sized Co3O4 by Pyrolysis of Organic Extracts

The most promising application field of materials based on nano-sized Co3O4 is catalysis. The method of production is one of the factors, which greatly affects the catalytic activity of Co3O4 catalysts. The aim of this research is to study possibilities of a new promising extractive-pyrolytic method (EPM) for the production of Co3O4 nanopowders and silica- and ceria-supported Co3O4 nanocomposites. Solutions of cobalt hexanoate in hexanoic acid and trioctylammonium tetrachlorocobaltate in toluene preliminary produced by solvent extraction were used as precursors. The precursors’ thermal stability, phase composition, morphology and the magnetic properties of the final products of pyrolysis were studied. The performed investigations have shown that the mean size of the Co3O4 crystallites in the materials produced by the EPM varies from amorphous to 55 nm due to the production conditions.