Adriana Asenova Georgieva
@btu.bg
Department of Chemical technology, Faculty of Technical science
Bourgas Prof. Assen Zlatarov University
RESEARCH INTERESTS
Chemical engineering, Mechanic of fluids, Heat and Mass transfer, Nanotechnology, Nanoparticles
Scopus Publications
Scholar Citations
Scholar h-index
Scopus Publications
Adriana Asenova Georgieva, Fila Slavova Yovkova, Margarita Anatolievna Georgieva, and Irena Georgieva Markovska
University of Chemical Technology and Metallurgy
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, %).
Mariela Ganeva Minova, Adriana Asenova Georgieva, Tsvetan Ivanov Dimitrov, Fila Slavova Yovkova, and Irena Georgieva Markovska
University of Chemical Technology and Metallurgy
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.
Adriana Asenova Georgieva, Margarita Anatolievna Georgieva, Fila Slavova Yovkova, Krasi Zlatinova Panayotova, and Irena Georgieva Markovska
University of Chemical Technology and Metallurgy
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.