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Tibor Kovacs - One of the best experts on this subject based on the ideXlab platform.
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dependence of radon emanation of red mud bauxite processing wastes on heat treatment
Journal of Hazardous Materials, 2009Co-Authors: Viktor Jobbagy, Janos Somlai, Jozsef Kovacs, G Szeiler, Tibor KovacsAbstract:Abstract Natural radioactivity content, radon emanation and some other physical characteristics of red mud were investigated, so that to identify the possibilities of the safe utilization of such material as a building material additive. Based on the radionuclide concentration, red mud is not permitted to be used directly as a building material, however, mixing of a maximum 20% red mud and 80% clay meets the requirements. The main aim of this work was to determine the dependence of the emanation factor of red mud Firing Temperature and some other parameters. The relevant experimental procedure was carried out in two different ways: without any additional material, and by adding a known amount of sawdust (5–35 wt%) then Firing the sample at a given Temperature (100–1000 °C). The average emanation factor of the untreated dry red mud was estimated to 20%, which decreased to about 5% at a certain heat treatment. Even lower values were found using semi-reductive atmosphere. It has been concluded that all emanation measurements results correlate well to the Firing Temperature, the specific surface and the pore volume.
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dependence of radon emanation of red mud bauxite processing wastes on heat treatment
Journal of Hazardous Materials, 2009Co-Authors: Viktor Jobbagy, Janos Somlai, Jozsef Kovacs, G Szeiler, Tibor KovacsAbstract:Natural radioactivity content, radon emanation and some other physical characteristics of red mud were investigated, so that to identify the possibilities of the safe utilization of such material as a building material additive. Based on the radionuclide concentration, red mud is not permitted to be used directly as a building material, however, mixing of a maximum 20% red mud and 80% clay meets the requirements. The main aim of this work was to determine the dependence of the emanation factor of red mud Firing Temperature and some other parameters. The relevant experimental procedure was carried out in two different ways: without any additional material, and by adding a known amount of sawdust (5-35 wt%) then Firing the sample at a given Temperature (100-1000 degrees C). The average emanation factor of the untreated dry red mud was estimated to 20%, which decreased to about 5% at a certain heat treatment. Even lower values were found using semi-reductive atmosphere. It has been concluded that all emanation measurements results correlate well to the Firing Temperature, the specific surface and the pore volume.
Viktor Jobbagy - One of the best experts on this subject based on the ideXlab platform.
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dependence of radon emanation of red mud bauxite processing wastes on heat treatment
Journal of Hazardous Materials, 2009Co-Authors: Viktor Jobbagy, Janos Somlai, Jozsef Kovacs, G Szeiler, Tibor KovacsAbstract:Abstract Natural radioactivity content, radon emanation and some other physical characteristics of red mud were investigated, so that to identify the possibilities of the safe utilization of such material as a building material additive. Based on the radionuclide concentration, red mud is not permitted to be used directly as a building material, however, mixing of a maximum 20% red mud and 80% clay meets the requirements. The main aim of this work was to determine the dependence of the emanation factor of red mud Firing Temperature and some other parameters. The relevant experimental procedure was carried out in two different ways: without any additional material, and by adding a known amount of sawdust (5–35 wt%) then Firing the sample at a given Temperature (100–1000 °C). The average emanation factor of the untreated dry red mud was estimated to 20%, which decreased to about 5% at a certain heat treatment. Even lower values were found using semi-reductive atmosphere. It has been concluded that all emanation measurements results correlate well to the Firing Temperature, the specific surface and the pore volume.
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dependence of radon emanation of red mud bauxite processing wastes on heat treatment
Journal of Hazardous Materials, 2009Co-Authors: Viktor Jobbagy, Janos Somlai, Jozsef Kovacs, G Szeiler, Tibor KovacsAbstract:Natural radioactivity content, radon emanation and some other physical characteristics of red mud were investigated, so that to identify the possibilities of the safe utilization of such material as a building material additive. Based on the radionuclide concentration, red mud is not permitted to be used directly as a building material, however, mixing of a maximum 20% red mud and 80% clay meets the requirements. The main aim of this work was to determine the dependence of the emanation factor of red mud Firing Temperature and some other parameters. The relevant experimental procedure was carried out in two different ways: without any additional material, and by adding a known amount of sawdust (5-35 wt%) then Firing the sample at a given Temperature (100-1000 degrees C). The average emanation factor of the untreated dry red mud was estimated to 20%, which decreased to about 5% at a certain heat treatment. Even lower values were found using semi-reductive atmosphere. It has been concluded that all emanation measurements results correlate well to the Firing Temperature, the specific surface and the pore volume.
Enrico Bernardo - One of the best experts on this subject based on the ideXlab platform.
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Glass powders and reactive silicone binder: Application to digital light processing of bioactive glass-ceramic scaffolds
Ceramics International, 2020Co-Authors: Hamada Elsayed, Martiniano Picicco, Arish Dasan, Jozef Kraxner, Dušan Galusek, Enrico BernardoAbstract:Abstract Powdered ‘silica-defective glasses’, mixed with silicones, have been already shown as a promising solution for the sintering, in air, of glass-ceramics with complex geometries. A fundamental advantage of the approach is the fact silicones act as binders up to the Firing Temperature, at which they transform into silica. A specified ‘target’ glass-ceramic formulation is achieved through the interaction between glass powders and the binder-derived silica. The present paper is dedicated to the extension of the approach to the digital light processing of reticulated glass-ceramic scaffolds, for tissue engineering applications, starting from glass powders suspended in an engineered photocurable silicone-based binder. The silicone component, besides providing an extended binding action up to the maximum Firing Temperature, stabilizes the 3D-printed shapes during sintering. The formation of a rigid silica skeleton, from the transformation of the silicone binder, prevents from excessive viscous flow of softened glass. The final phase assemblage does not depend simply on glass devitrification but also on the glass/silica skeleton interaction.
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porous glass ceramics from alkali activation and sinter crystallization of mixtures of waste glass and residues from plasma processing of municipal solid waste
Journal of Cleaner Production, 2018Co-Authors: Patricia Rabelo Monich, Daniel Höllen, Acacio Rincon Romero, Enrico BernardoAbstract:Abstract Alkali-activated aqueous slurries of fine glass powders, mostly deriving from the plasma processing of municipal solid waste (‘Plasmastone’), were found to undergo progressive hardening at low Temperature (75 °C) owing to the formation of C S H (calcium silicate hydrate) gels. Before complete setting, slurries could be easily foamed by vigorous mechanical stirring, with the help of a surfactant; finally, the resulting open-celled structure could be ‘frozen’ by a subsequent sintering treatment, with crystallization of Ca Fe silicates. The densification of the struts upon Firing was enhanced by mixing Plasmastone with up to 30 wt% recycled glasses and increasing the Firing Temperature from 800 to 1000 °C. A total porosity exceeding 75 vol%, comprising both well-interconnected macro- and micro-sized pores on cell walls, was accompanied by good compressive strength, well above 1 MPa. The stabilization of pollutants generally increased with increasing Firing Temperature and glass content, with some exceptions; no practical leaching was observed from samples deriving from Plasmastone combined with 30 wt% boro-alumino-silicate glass from the recycling of pharmaceutical vials.
Yiannis Pontikes - One of the best experts on this subject based on the ideXlab platform.
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effect of Firing Temperature and atmosphere on sintering of ceramics made from bayer process bauxite residue
Ceramics International, 2009Co-Authors: Yiannis Pontikes, P Nikolopoulos, Christina Rathossi, George N. Angelopoulos, D. Doni Jayaseelan, William E. LeeAbstract:Bauxite residue, the principal waste from the Bayer process, was dried, pressed and studied for its thermal and sintering behaviour under different atmospheres, up to 1100 °C. For sintering in air and N 2 , shrinkage begins at 800 °C and ranges from 2.6% to 13.9%, after Firing at 1000-1100 °C. Bulk density varies from 1.7 to 2.3 g/cm 3 whereas water absorption from 31.5% to 17.7%. The main crystalline phases identified on Firing in air were hematite (Fe 2 O 3 ), gehlenite (Ca 2 Al 2 SiO 7 ) and perovskite (CaTiO 3 ) whereas magnetite (Fe 3 O 4 ) was also found on Firing in N 2 . Microstructures are characterised by irregularly shaped, <20 μm Feret diameter, pores in a ceramic matrix with interconnected porosity. The average pore size is greater in samples fired in N 2 . On sintering in 4%H 2 /Ar, shrinkage begins at 710 °C. After Firing at 1100 °C, shrinkage is 20.1% and water absorption 1 %. The main crystalline phases are magnetite, wustite (FeO), gehlenite and perovskite. Microstructures are characterised by a compact heterogeneous matrix, with isolated <15 μm Feret diameter, closed pores. The grains have reacted with the adjacent phase and their shape is rounded with no sharp facets. Increased sintering Temperature results in improved physical properties for all atmospheres tested and in higher average pore size when sintering takes place in air and N 2 . The use of magnetite-reducing sintering conditions can potentially assist in the production of a variety of ceramic compositions containing bauxite residue.
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thermal behaviour of clays for traditional ceramics with soda lime silica waste glass admixture
Journal of The European Ceramic Society, 2007Co-Authors: Yiannis Pontikes, Arianna Tucci, L Esposito, G N AngelopoulosAbstract:Abstract The thermal behaviour of clay body mixtures with soda–lime–silica waste glass for the production of traditional ceramics was assessed. The effect of calcite content in the body mixture, of the particle size distribution of glass and of the Firing Temperature was investigated. In the case of calcite-rich mixtures with glass, increased expansion may take place during Firing, at Temperatures slightly higher than 700 °C. This effect is attributed to the entrapment of released gases, mainly CO 2 . Sintering starts at lower Temperatures for the samples with glass, whereas, a second shrinkage zone was observed for Temperatures approaching 1000 °C. The content of calcite is one of the main factors determining the mineralogy of the sintered body and the extent of glass devitrification. Devitrite, cristobalite and wollastonite are the products of devitrification within the glass grains, whereas, sodium aluminum silicate, most probably nepheline, has been formed at the inter-granular rim, between glass and ceramic matrix. Increase in the Firing Temperature and/or decrease in the particle size distribution of glass promotes the densification of the body.
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thermal behaviour of clay mixtures with bauxite residue for the production of heavy clay ceramics
Journal of The European Ceramic Society, 2007Co-Authors: Yiannis Pontikes, P Nikolopoulos, G N AngelopoulosAbstract:Abstract “Bauxite Residue”, BR, is the main by-product of the alumina-producing Bayer cycle. Aiming at its utilisation in the production of heavy-clay ceramics, the thermal behaviour of clay body mixtures with BR was investigated. The process parameters examined were the calcite content in the clay body mixture and the Firing Temperature, in relation to different BR additions in the clay body mixture. The Firing process was studied by means of DTA–TG and dilatometry whereas the mineralogy was determined by XRD. The DTA–TG curves did not reveal cross-reactions between body mixture and BR. However, in the mixtures with BR, sintering initiated at a lower Temperature and the Firing shrinkage was increased. Moreover, a second shrinkage zone was observed for high BR content and Firing Temperature above 950 °C, suggesting the development of a low viscosity liquid phase. The main mineralogical phases present in the BR modified mixtures after Firing were quartz, hematite, clinopyroxenes, gehlenite and plagioclase. The formation of clinopyroxenes and gehlenite seems to be dependant on all process parameters examined, i.e. calcite content in the clay body mixture, BR addition and Firing Temperature.
S W Glunz - One of the best experts on this subject based on the ideXlab platform.
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impact of the Firing Temperature profile on light induced degradation of multicrystalline silicon
Physica Status Solidi-rapid Research Letters, 2016Co-Authors: Rebekka Eberle, Wolfram Kwapil, Florian Schindler, Martin C Schubert, S W GlunzAbstract:Light- and elevated Temperature-induced degradation in multicrystalline silicon can reduce the efficiency of solar cells significantly. In this work, the influence of the Firing process and its Temperature profile on the degradation behaviour of neighbouring mc-Si wafers is analysed. Five profiles with measured high peak Temperatures ≥800 °C and varying heating and cooling ramps are examined. With spatially resolved and lifetime calibrated photoluminescence images, normalized defect concentrations N*t are calculated to determine the degradation intensity. Wafers that underwent a fast Firing process typical for industrial solar cell production show a significantly stronger degradation than samples that were subjected to the same peak Temperature but with slower heating and cooling rates. A spatially resolved analysis of the carrier lifetime in the whole wafer shows that the degradation begins in low lifetime areas around dislocation clusters, spreading into good grains after several hours. By the use of optimized ramp-up and/or ramp-down rates during the Firing even at very high peak Temperatures, light and elevated Temperature induced degradation can be suppressed. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)
