Browsing by Author "Dimitrov T."

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    Alternative technological approach for synthesis of ceramic pigments by waste materials recycling
    (2016-01-01) Doynov M.; Dimitrov T.; Kozhukharov S.
    Alternative technological approach is proposed enabling utilization of raw materials from an oil refinery, such as waste guard layers from reactors. Reagent grade and purified MgO, Cr2O3, Fe2O3, and nitric acid (HNO3), were used as additional precursors. The homogeneous mixtures obtained were formed into pellets and sintered at different temperatures. The main phase was proved by X-ray phase analysis (XRD) and compared to ICPDS database. The main phase in the ceramics synthesized was solid solution of spinel MgAl2O4 and magnesiochromite. These minerals are classified as chromspinelide MgCr1.2Al0.4Fe0.4O4 and alumochromite MgCr1.6Al0.4O4. Additional SEM observations, combined with EDX analysis were performed, evincing agglomeration at lower temperatures, followed by agglomerate crumbling, at elevated calcination temperature. The complete transformation of initial precursors into the final ceramic compounds was found to occur at 800°C - 1 h. The ceramic samples synthesized had high density of 1.72-1.93 g/cm3 and large absorption area - 32.93% which is probably due to the high porosity of the sample.
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    Synthesis of pigments of Fe2O3·SiO2 system, with Ca, Mg, or Co oxide additions
    (2017-03-01) Dimitrov T.; Kozhukharov S.; Velinov N.
    The present research work is based on the comparative evaluation of the Ca, Mg, and Co dopant impact on the properties of new ceramic pigments from the system Fe2O3·SiO2 obtained via classical ceramic technology. This approach enabled determination of the optimal temperature for the synthesis and the most appropriate mineralizer. The obtained specimens were submitted to systematical analysis, including X-ray Diffraction (XRD) spectroscopy, Electron Paramagnetic Resonance (EPR) analysis and Mössbauer spectroscopy for crystalline phase determination. The color characteristics are quantified by spectrophotometric measurements. The pigments particle size has been determined by Scanning Electron Microscopy (SEM), combined by Energy Dispersion X-ray spectroscopy (EDX). The obtained results enabled to determine the correlation between the calcination temperature and the phase compositions of the obtained pigments. In addition, some interesting magnetic properties were detected for the Co-doped composition.