LOW-TEMPERATURE SYNTHESIS OF FINE-POROUS CORUNDUM BASED ON INCORPORATED GRAPHENE NANOSTRUCTURES Adriana Asenova Georgieva, Fila Slavova Yovkova, Margarita Anatolievna Georgieva, Irena Georgieva Markovska Journal of Chemical Technology and Metallurgy, 2024 In the present paper, the effect of the addition of graphene nanostructures and 3 mass % TiO2 on the microstructure and properties of sintered corundum ceramics were studied. Fine-porous corundum ceramics were obtained by the method of solid-phase sintering at relatively low temperatures of 1450oC, by adding graphene nanostructures in an amount of 2 % or 20 %. To lower the synthesis temperature, 3 mass % TiO2 was added to the initial ceramic blends. As a result of the solid solution formed between Al2O3 and TiO2, a well-sintered corundum ceramic is obtained at synthesis temperature lower than that of pure corundum - 1450oС. For the characterization of the initial blends and the ceramic samples, the methods of X-ray phase analysis, infrared spectroscopy, SEM, TEM EDS and visual microscopy were used. Besides, the basic physicochemical properties of the samples synthesized based on corundum were determined, e.g. water absorption (WA, %), apparent density (AD, %) and apparent (open) porosity (Pa, %).
OBTAINING OF GARNET CERAMIC MATERIALS BY UTILIZATION OF RICE HUSK ASH AS SILICA SOURCE Mariela Ganeva Minova, Adriana Asenova Georgieva, Tsvetan Ivanov Dimitrov, Fila Slavova Yovkova, Irena Georgieva Markovska Journal of Chemical Technology and Metallurgy, 2024 The current research aims at the obtaining of new type pigments from the garnet mineral group by utilizationof rice husk ash as silica source (RHA). At the beginning, the mixtures prepared from the starting raw materials areground in a ball mill and then subjected to high temperature treatment. Green pigments were synthesized at twotemperatures: 1000°C and 1100°C. Using the tintometer RT 100 Lovibond the colour characteristics were measuredspectrophotometrically. The rice husk ash was investigated using scanning electron microscopy. The conducted hot-stage microscopic studies show that the pigments remain thermally stable when heated. The highest fire resistance - upto temperatures of 1380°C - 1400°C show the uvarovite pigments with main phase 3CaO.Cr2O3.3SiO2 or by a generalformula Ca3Cr2[SiO4 ]3. They are suitable for inserting into ceramic glazes without danger of decomposition or reaction.Keywords: ceramic pigments, SEM, colour determination, Hot-stage microscopy.
USING THE ADVANTAGES OF NANOTECHNOLOGY FOR THE PRODUCTION OF COMPOSITE MATERIALS OF THE TYPE NGO/CERAMIC MATRIX Adriana Asenova Georgieva, Margarita Anatolievna Georgieva, Fila Slavova Yovkova, Krasi Zlatinova Panayotova, Irena Georgieva Markovska Journal of Chemical Technology and Metallurgy, 2024 Using the advantages of nanotechnology, composite ceramic materials of the type of graphene oxide nanocolloid/ceramic matrix were obtained in two stages. First, finely porous corundum (1500ºC) and barium titanate (1300ºC)ceramic samples containing 2 mass % graphene structures nanoplatelets were synthesized. The next stage of the study involved the preparation of graphene oxide in nanocolloid form (2 mg/ml, dispersion in H2O) which was impregnated in the solid porous ceramic samples to obtain composite materials. For the characterization of the ceramic samples, mainly infrared spectroscopy, X-ray phase analysis, scanning electron microscopy and light microscopy were used. The results obtained from the studies carried out showed that with the introduction of small amount of graphene nanoplatelets in the initial blends followed by solid state sintering, part of the added graphene is burned out which imparts significant porosity to the ceramics obtained. On the other hand, the addition of graphene initiates the formation of well-shaped fine-grain structure of the ceramic samples, and they had sufficient porosity.
OBTAINMENT OF BARIUM TITANATE CERAMIC SAMPLES AND DETERMINATION OF THEIR BASIC PHYSICOCHEMICAL PROPERTIES Oxidation Communications, 2023
SYNTHESIS AND PROPERTIES OF CHROMIUM-BASED GARNET PIGMENTS Journal of Chemical Technology and Metallurgy, 2023
Experimental determination of mass transfer coefficient by rectification in a laboratory column equipped with three sieve trays Oxidation Communications, 2019
Obtaining nanostructured catalyst systems and study of catalytic efficiency Oxidation Communications, 2019
Determination of Interphase surface by rectification process in a laboratory column Oxidation Communications, 2018
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