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    Corrosion behaviours of MgO-C refractories: Incorporation of graphite or pyrolytic carbon black as a carbon source
    (Elsevier Sci Ltd, 2018) Bahtli, Tuba; Hopa, Derya Yesim; Bostanci, Veysel Murat; Ulvan, Nesibe Sevde; Yasti, Serife Yalcin
    In this study, corrosion behaviours of MgO-C refractories produced by the incorporation of carbon and pyrolytic carbon black obtained from waste tire pyrolysis under either argon or oxygen atmospheres were investigated. Moreover, the effect of porosity on the corrosion resistance of those refractories was studied. The microstructures of corroded refractories were characterized by Scanning Electron Microscopy (SEM)/EDX. Experimental studies indicated that refractories produced by the use of pyrolytic carbon black as a carbon source had higher amount of porosity due to their lower packing density and lower corrosion resistance than those of ones produced by the incorporation of graphite.
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    Corrosion resistances of C30 concrete: Effect of finely ground bronze sawdust waste
    (Elsevier Science Sa, 2020) Bahtli, Tuba; Ozbay, Nesibe Sevde
    Corrosion resistances and service life for concrete structures as well as the recycling of wastes are quite important for either economical gain or the reduction of environmental problems. In this study, finely ground CuAl10Ni bronze sawdust waste (1, 3 and 5% by weight) was incorporated into C30 concrete in order to improve the corrosion resistance, and density, open porosity (%) and corrosion resistances were determined. Additionally, SEM/EDX analyses were performed in order to analyze the microstructures of concretes before and after corrosion test. It was observed that concretes including bronze sawdust generally showed higher corrosion resistances than that of pure concrete due to high corrosion-acid-seawater resistances of bronze addition.
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    Effect of precision casting sand waste of 4140 steel on the sintering and densification behaviour of chamotte refractories
    (Springer, 2020) Bahtli, Tuba; Bostanci, Veysel Murat
    In this study, the sintering behaviour and densifications of chamotte refractories that were produced by incorporation of 4140 precision casting sand waste at different ratios are investigated. Thermal properties are examined using thermogravimetry and differential scanning calorimetry thermal analysis methods. Open porosities and densities of refractories have been determined using Archimedes principles according to ASTM C20. The chemical analysis of raw material and phase analysis of refractories, and also chamotte raw material and sintered chamotte material at 1723 K, are obtained by X-ray fluorescence and X-ray diffraction, respectively. In addition, the changes in microstructure are characterized using a scanning electron microscope. According to the results, chamotte refractory that was produced by 10% 4140 precision casting sand waste has the highest density and lowest open porosity due to the smallest grain size after sintering compared with those of pure (C0) refractory and chamotte refractory with the addition of 20% 4140 precision casting sand waste.
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    Effect of ZrSiO4 on the corrosion behavior of MgO-FeAl2O4 composite refractory materials
    (Carl Hanser Verlag, 2016) Bahtli, Tuba; Aksel, Cemail; Kavas, Taner
    In this study, the corrosion behavior of refractory materials that were produced by incorporating ZrSiO4 (zircon) at different ratios into MgO-FeAl2O4 (hercynite) were investigated. The values of density and open porosity of those samples were also measured, and the corrosion behaviors of those materials produced were examined. After performing corrosion tests, the corrosion resistance of composite refractory materials were determined by measuring the penetration distances and spreading areas. The incorporation of ZrSiO4 into MgO-FeAl2O4 generally decreased the porosity of composite refractory materials, and consequently reduced the penetration distances and spreading area values of the corroded regions of refractories as well. In addition, the formation of new phases and the microstructural changes which occurred were determined by XRD measurements and SEM analyses. On the basis of microstructural characterization carried out in the interface of clinkerrefractory, the following observations had been determined: i) Ca2+ and Y3+ elements forming CaZrO3 were located together in the same regions, ii) forsterite phase was formed due to the reaction between SiO2, which is released after dissociation of zircon as ZrO2 and SiO2 during sintering, and MgO, iii) the formation of new CaZrO3 and forsterite (Mg2SiO4) phases made a barrier effect against clinker, and iv) the amount of CaO decreased based on the EDX analysis made from clinker to refractory in a corroded region. The penetration of clinker to refractory showed a minimum level for the composition of MgO-5 wt.-% FeAl2O4-5 wt.-% ZrSiO4 and an improvement by about 38 % as compared to MgO-5 wt.-% FeAl2O4. This improvement is associated with a long service life of MgO-FeAl2O4-ZrSiO4 refractories for industrial applications.
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    Investigation of thermal shock behaviour of MgO-C refractories by incorporation of pyrolytic liquid as a binder
    (Elsevier Science Sa, 2018) Bahtli, Tuba; Hopa, Derya Yesim; Bostanci, Veysel Murat; Yasti, Serife Yalcin
    Tire waste is a serious problem for environment, health, and safety due to growing in volumes of its production. Recycling and recovery of waste tire as a useful product has a real importance. In this study, pyrolytic liquid obtained by waste tire pyrolysis was incorporated into MgO-C refractory as a binder to investigate the effects of its utilization on the thermal shock resistance of MgO-C refractories. The physical properties such as open porosities, densities, and mechanical properties such as Cold Crushing Strength (CCS) and 3-Bending Strength were investigated before and after thermal shock test at 1000 degrees C. The microstructure and fracture surfaces were characterized by using the Scanning Electron Microscopy (SEM). Elemental analysis of those refractories were examined by the Energy Dispersive X-Ray (EDX) analysis. Experimental studies showed that refractories produced by the use of pyrolytic liquid as a binder could have less reduction in their strength values after the thermal shock test. (C) 2018 Elsevier B.V. All rights reserved.
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    Thermal conductivity of MgO-C refractory ceramics: Effects of pyrolytic liquid and pyrolytic carbon black obtained from waste tire
    (Elsevier Sci Ltd, 2018) Bahtli, Tuba; Hopa, Derya Yesim; Bostanci, Veysel Murat; Yasti, Serife Yalcin
    In the present study, thermal conductivity and mechanical properties of MgO-C refractory ceramic bricks were investigated. Pyrolytic liquid and pyrolytic carbon black obtained from pyrolysis of waste tires were used as a resin and carbon source, respectively. The pyrolysis of the tires was conducted in a fixed bed reactor at the temperature of 500 degrees C with a 15 degrees C/min heating rate under nitrogen flow (0.5 It/min). Before using in MgO-C refractory ceramic blends, pyrolytic products were purified with the acidic extraction methods which resulted in 61 and 66 wt%. decreases in sulfur and ash contents in pyrolytic carbon, respectively. After this treatment of pyrolytic liquid, the sulfur content was reduced by 24 wt%. Eight different blends of MgO-C refractory ceramics consisting of different pyrolytic product contents were prepared, pressed, and tempered at 250 degrees C, and then characterized in terms of porosity, thermal conductivity, and density. The mechanical behavior of the samples was tested using a three-point bending test. Archimedes test was employed to determine the porosity and density. Surface properties of the bricks were analyzed by scanning electron microscopy (SEM). The obtained results were compared with a reference consisting of graphite and resin. The results revealed that mechanical and thermal properties of the developed bricks were highly sensitive to the porosity and the carbon source as well as the type of binder.
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    The use of foundry waste sand from investment casting in the production of porcelain tiles
    (Elsevier Sci Ltd, 2022) Bahtli, Tuba; Erdem, Yusuf
    In this study, the effects of different types of investment casting waste sand were investigated in porcelain tile production in place of clay and kaolin. Dry and firing shrinkages, water absorption, dry and firing strengths and densities of porcelain tile bodies were determined. In addition, color measurements, XRD analysis and SEM analyses of the relevant samples were also investigated. A1, A2, A3, B and C porcelain tiles had higher density, firing shrinkage and firing strength values. However, they had lower water absorption, dry shrinkage and dry strength values than those of the reference porcelain tile. Quartz, mullite and albite were found in all the bodies as main phases and, in addition, zircon phase was determined in bodies in which waste sand was incorporated.