Browsing by Author "Aras, Aydin"

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The Differences Between Alkaline- and Alkaline-Earth Effects on High-Temperature Phase Change of Clay Based Ceramic
(Elsevier, 2018) Aras, Aydin
The differences of the effects of alkaline (illitic clay, K and Ca-Na feldspar) and alkaline-earth flux additions (sepiolitic-dolomite, talc, huntite, hydromagnesite, magnesitic clay and Calcite) on the high-temperature-phases (HTP) of ceramic bodies derived from ball clay of Westerwald-(Germany) or Sile (Turkey) area were investigated. This investigation was carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM) attached with energy dispersive spectrometry (EDS). The type and amount of HTP do not only depend on the type and amount of flux additions alone but also depend on the optimal distribution of these flux cations which are largely determined by the extent of the mixing. No Cristobalite was present and secondary mullite and quartz were the only crystalline phases present in these bodies composed of 50 wt% illite KW and Westerwald ball clay HB or this mixture mixed with 20% K or Ca-Na feldspar. These additions render >= 2 wt% K2O in bulk chemical composition of these alkaline bodies and are enough to inhibit cristobalite formation. The identified major HTP in ceramic bodies derived from 15 wt% Ca carbonate and 5 wt% sepiolitic dolomite, or magnesitic clay or talc and Sile ball clay were identified only as melilite (gehlenite) and plagioclase (anorthite) group minerals. The pyroxene group minerals (protoenstatite, clinoenstatite, and diopside) occurred only in the body derived from Sile ball clay mixture mixed with > 5 wt% Mg-Ca flux at over 1000 degrees C.
Effect of Addition of Molybdenum on Photon and Fast Neutron Radiation Shielding Properties in Ceramics
(Elsevier Sci Ltd, 2019) Oto, Berna; Kavaz, Esra; Durak, Halil; Aras, Aydin; Madak, Zekiye
In the present research, standard ceramic and Molybdenum (Mo) doped ceramics were fabricated to determine the shielding properties against gamma and fast neutron radiation. The ceramics were exposed to photons with 81, 276, 302, 356, 383 keV energies emitted from 3 Ci Ba-133 radioactive source and the photon intensities were detected by utilizing Ultra Ge detector. With the obtained results, the gamma shielding parameters; mass attenuation coefficients (mu(rho)), the mean free paths (mfp), half value layers (HVL), tenth value layers (TVL), effective atomic numbers (Z(eff))and effective electron densities (N-el) were obtained experimentally and compared to the theoretical outcomes computed by utilizing WinXCOM program. It was found that, S4 ceramic containing 30% Mo element has higher mu(rho) and Z(eff ) value and lower MFP, TVL and HVL values than the other ceramics. The EBF and EABF values of S4 ceramic were lower than the values of other investigated ceramics. Thus, it has been concluded that the use of Mo element in ceramic increases the gamma shielding property of the ceramics. When the ceramics were examined in terms of fast neutron shielding, no important difference was found between the ceramics.
The Impact of Co Addition on Neutron-Photon Protection Characteristics of Red and Yellow Clays-Based Bricks: an Experimental Study
(Pergamon-elsevier Science Ltd, 2022) Durak, Halil; Kavaz, Esra; Oto, Berna; Aras, Aydin
High strength and heat resistance properties of radiation shielding materials are among the most sought properties. Due to their mechanical and thermal properties, bricks can be a good alternative for radiation protection applications. In this respect, nuclear radiation attenuation parameters of seven brick samples containing different amounts of Cobalt metal (0, 5, 10, 20, 30, 40, 50 %wt) were examined in this study. Initially, SEM-EDX analysis of bricks were carried out to determine the elemental composition and structure of the bricks. Next, the bricks were exposed to gamma rays with 53.16, 79.61, 80.99, 276.39, 302.85, 356.01, 383.84 keV photon energies emitted from Barium-133 radioactive source and the transmitted photon intensities were detected by utilizing Ultra-Ge detector. Mass attenuation coefficient (MAC), effective atomic number (Z(eff)), Half Value Layer (HVL), Mean Free Path (MFP) and exposure buildup factors (EBF) values of bricks were determined by experimentally and EpiXS program. At 53.-383 MeV photon energy interval, it is found that the MAC values for S0-S6 brick samples range between 0.427 and 0.097 cm(2)/g and 1.130-0.0961 cm(2)/g. In addition, the neutron shielding features of the bricks under study were assessed by calculating effective removal cross section (Sigma(R) ). It is noticed that the Sigma(R) values of the samples gradually grow from 0.057 cm(-1) to 0.1392 cm(-1) with increasing Co addition. It has been concluded that rising the Co addition improves the gamma and neutron shielding capacity of the brick samples.
Α-Cristobalite Formation in Ceramic Tile and Sewage Pipe Bodies Derived From Westerwald Ball Clay and Its Effect on Elastic-Properties
(Elsevier, 2019) Aras, Aydin; Kristaly, Ferenc
The formation of alpha-cristobalite and its effect on the elastic modulus (E modulus) was investigated in sewage pipe (SP) and tile bodies derived from Westerwald ball day (WBC), employing the results of previous research on WBC as a baseline. In this study, the SP and tile bodies derived from WBC are compared with the bodies derived from two residual Turkish kaolin and one Turkish ball clay, resulting in four sources of alpha-cristobalite formation: tile, SP, residual kaolin and ball clay. The crystallization of alpha-cristobalite in the fired WBC results from two primary pathways. The first pathway occurs as a devitrification product from the glass phase saturated with excess silica, which is typically present in ball clay after a >= 1100 degrees C; the second pathway results from a minor amount of transformation of peripheries of quartz crystals, firing at over a >= 1200 degrees. In addition to these two sources, other a-cristobalite sources for sewage-pipe bodies include smectitic clay and chamotte (prefired clay) addition. Conversely, no alpha-cristobalite occurred in tile mixture bodies containing approximate to 2 wt% potassium oxide (K2O). The alpha-cristobalite phase only forms in kaolinite-rich ball clay when K2O content is less than approximate to 2 wt% because devitrification of excess silica phase of tile bodies is primarily governed by K2O content. The 2 wt% K2O ratio inhibited a-cristobalite formation in tile bodies, while the same percentage or greater of K2O content in SP bodies did not inhibit the alpha-cristobalite formation due to the presence of chamotte and smectitic clay in the SP mixture. The measured minimum E moduli were attributed to cristobalite formations because of chamotte and smectitic clay additions to SP bodies. In the bodies derived from Turkish residual kaolin at over 1000 degrees C, the opaline and chalcedonic silica phase are transformed to a-cristobalite at a lower temperature than those observed for rock crystal quartz and Si-rich glassy phase in WBC bodies. Thus, determining the different alpha-cristobalite sources in clay-based ceramic bodies derived from either the ball clay, the residual kaolin or the bodies containing smectitic clay together with chamotte provides the essential pre-condition for the optimum admixing ratio in industrial SP and tile bodies.