Browsing by Subject "Manganese compounds"
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Item Activity of MnO in MnO-CaO-MgO-SiO2-Al2O3 slags at 1500°C(Verlag Stahleisen GmbH, 2006) Cengizler H.; Eric R.H.A thermodynamic study was made on the MnO-CaO-MgO-SiO2-Al 2O3 slags that are typical of the production of ferromanganese in submerged arc furnaces. The Al2O3 content of the slags was kept constant at 5 per cent by mass. The activity-composition relationship in Pt-Mn binary alloys were re-determined for calibration purposes at 1300, 1400 and 1500°C and pO2 values between 5.40×10-6 and 4.54×10-13 atm. A linear regression equation was derived to predict the activity coefficients of manganese, in Pt-Mn alloys at 1500°C. The effect of concentration, basicity ratio and CaO-to-MgO ratio on MnO activities in above mentioned complex slags was investigated at 1500°C and at two different pO2 values of 4.76×10-7 and 5.80×10-8 atm. It was found that aMnO values increase with increasing MnO, and tend to increase with an increasing CaO-to-MgO ratio. The aMnO values also increase with increasing basicity ratio. The activity coefficient of MnO increases with an increase in its mole fraction in the slag. Quadratic multivariable regression model equations which represent the activity data successfully and which can be used to predict the MnO activities in the compositional range of this study were developed. The MnO activity data was interpreted in terms of a slag model which describes the thermodynamic properties of the slag successfully.Item Amethyst and morion quartz gemstone raw materials from Turkey: Color saturation and enhancement by gamma, neutron and beta irradiation(2010) Hatipoǧlu M.; Helvac C.; Kibar R.; Çetin A.; Tuncer Y.; Can N.Color-enhancement investigations without using heating treatment from dull or pale to ideal saturation and/or changes to the formation of the rarer attractive colors are widely conducted to revalue abandoned gem material sources in the world. Such an investigation is carried out on pale or dull purple-colored amethyst and smoky-colored morion samples, which are two important gem species of the crystalline quartz (SiO2) mineral that are currently abandoned in natural deposits in Turkey because of their unattractive coloration. The results of color enhancements observed on these samples, after irradiation with artificial gamma, neutron and beta beams, were examined by comparing with samples with the ideal color saturation and also with colorless samples, using optical absorption (OA) and radioluminescence (RL) spectroscopy. The ICP-AES analyses reveal that the main impurity elements of over 100ppm in abundance in these quartz species are aluminum, iron and titanium for amethyst, and aluminum, iron, titanium and manganese for morion. The OA spectra indicate that vivid purple coloration of amethyst is due to the transmittance at about 395-420nm band gap as a result of absorbance peaks at 375, 480 and 530nm. These absorbances may be related to the unusual oxidized small proportions of certain impurity ions, after being exposed mainly to gamma irradiation, such as Al(IV) from the total aluminum, Ti(V) from the total titanium and Fe(IV) from the total iron, respectively. However, the RL spectroscopy of amethyst samples before and after they were exposed to artificial gamma, neutron and beta radiation beams demonstrates that the ions most affected by irradiation are Fe(IV) first and Al(IV) and Ti(V) second, and these ions represent the RL peaks at 600, 720 and 495nm, respectively. The OA spectra indicate that dark smoky coloration in morion is due to a lack of transmittance at the visible region as a result of the absorbance peaks at 375, 450-490, 620 and 730nm. These absorbances also may be related to the unusual oxidized small proportions of certain impurity ions by irradiation, such as Al(IV) from the total aluminum, Ti(V) from the total titanium and Mn(III) from the total manganese, respectively. In addition, the buoyancies of these absorbance peaks in the visible region produce the color hues between light smoky and dark smoky colorations in morion samples. These oxidized ion states are more resistant and stable against environmental destructive conditions in comparison with amethyst. Thus, the dark smoky coloration of morion becomes dull or pale after relatively longer periods. But, the RL spectroscopy of morion before and after being exposed to gamma, neutron and beta irradiation beams demonstrates that the most induced ions from the irradiation are Mn(III) and Al(IV) first and Ti(V) second. These ions represent the RL peaks at about 400, 720 and about 500nm, respectively. © 2010 Taylor & Francis.Item Selected kinetic properties of polyphenol oxidase extracted from rosmarinus officinalis l(2010) Aydemir T.Polyphenol oxidase from Rosmarinus officinalis L. (PPO, EC 1:14:18.1) was extracted and partially purified by using (NH4)2SO 4 precipitation and dialysis. Stable and highly active PPO extracts were obtained using 0.5% (w/v) PEG and 0.5% (w/v) Triton X-100 in 0.1 M phosphate buffer 7.0. KM values were found to be as 14.3 mM for catechol. Four isoenzymes of Rosemary PPO were detected by PAGE with DL-dopa substrate. The enzyme was strongly inhibited by dithiotreitol, sodium metasulfite, sodium thiosulfate, ascorbic acid, and L-cysteine. Metal ions Ca++, Mg++, and Mn++ were poor inhibitors of rosemary PPO at 10 Mm. Copyright © Taylor & Francis Group, LLC.Item Luminescence behavior and Raman characterization of jade from Turkey(2011) Tuncer Arslanlar Y.; Garcia-Guinea J.; Kibar R.; Çetin A.; Ayvacikli M.; Can N.Results are presented for the cathodoluminescence (CL), radioluminescence (RL) and thermoluminescence (TL) of jade from Turkey. Jade samples show broad band luminescence from green to red, which, using lifetime-resolved CL, reveals seven overlapping emissions, of which two are dominant. Green emission obtained using spatially resolved CL was associated with Mn2+ and emission bands centered near at 480 and 530nm were attributed to 3P0-3H4 and 1D2-3H4 transitions of Pr3+, respectively. Different shifts of the peak-wavelengths for 326 and 565nm were observed with varying jade compositions. The incorporation of the larger K ion causes non-linear variations of the cell dimensions and therefore changes in the Fe-O band distance. We suggest that stress of the jade structure can be linked to the luminescence emission at 326nm. Raman spectra have also been recorded in order to provide an unequivocal identification of the type of jade. The mechanism for the luminescence of the jade is considered. © 2011 Elsevier Ltd.Item Radioluminescence and thermoluminescence of albite at low temperature(2011) Can N.; Garcia-Guinea J.; Kibar R.; Etin A.; Ayvackl M.; Townsend P.D.Feldspar as an archaeological and geological natural material for dating and retrospective dosimetry is receiving more and more attention because of its useful luminescence properties. In this study, the 25-280 K thermoluminescence (TL) and radioluminescence (RL) spectra in albite, which is a component of the two main feldspar series, the alkali feldspar (Na, K)AlSi3O 8 and the plagioclases (NaAlSi3O8-CaAl 2Si2O8) have been presented for aliquots along (001) and (010) crystallographic orientations. There are four main emission bands that are considered to arise from complexes of intrinsic defects linked in larger complexes with impurities such as Na+, Mn2+ or Fe3+ ions. The consequence of their association is to produce different luminescence efficiencies that produce wavelength sensitive TL curves. Radioluminescence data at low temperature for albites is distorted by contributions from the TL sites, even when the RL is run in a cooling cycle. This indicates the potential for a far more general problem for analysis of low temperature RL in insulating materials. © 2011 Elsevier Ltd. All rights reserved.Item Structural and luminescence characterization of Ce3+ and Mn2+ co-activated zinc silicate nanocrystal obtained by gel combustion synthesis(Elsevier Ltd, 2021) Portakal-Uçar Z.G.; Oglakci M.; Yüksel M.; Ayvacıklı M.; Can N.The structural, morphological, and luminescence properties, including photoluminescence (PL) and thermoluminescence (TL), of newly produced Zn2SiO4 co-activated by Ce3+ and Mn2+ ions using the gel-combustion synthesis, are investigated in deep. To determine the co-dopant effect precisely, non-doped, Ce3+ doped, and Ce3+ and Mn2+ double doped Zn2SiO4 phosphors are evaluated. The fluorescence decay curves indicate that a shorter decay time at relatively high Mn concentrations takes place. The TL glow curve readouts observed by applying the dose range between 0.1 and 2000 Gy after 150 °C preheat are performed at a linear heating rate of 2 °C/s from room temperature (RT) to 500 °C. An anomalous heating rate behavior is observed when the influence of different heating rates on TL characteristics is reported. An excellent agreement is found between the TL kinetic parameters analyzed by the initial rise (IR) with TM–Tstop analysis and computerized glow curve deconvolution (CGCD) methods. © 2020 Elsevier LtdItem Synthesis and characterizations of LaMnO3 perovskite powders using sol–gel method(Springer, 2021) Çoban Özkan D.; Türk A.; Celik E.The present research demonstrates the synthesis and characterization of LaMnO3 perovskite powders using the sol–gel technique for solar cell applications. With this respect, LaMnO3 powders were synthesized at two different annealing temperatures by the sol–gel method using La- and Mn-based precursors. Thermal, structural, microstructural, optical and magnetic properties of the powders were characterized through differential thermal analysis-thermogravimetry (DTA-TG), Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Malvern zeta sizer (PSD), UV–Vis spectrometer and vibrating sample magnetometer (VSM). LaMnO3 was synthesized successfully at 500 °C and 850 °C synthesis temperatures, and the bandgap was determined as 1.27 eV for both. The analysis revealed that magnetic properties, crystalline and particle sizes change according to the heat of synthesis. The obtained results indicate promise, especially the low bandgap, that LaMnO3 powders can be used in solar cell applications and can positively affect performance and efficiency. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Item Synthesis and characterization of sol–gel derived LaFe0.5Mn0.5O3 perovskite powders for dye-sensitized solar cell applications(Springer, 2022) Çoban Özkan D.; Türk A.; Çelik E.In the present work, structural, microstructural, thermal, magnetic and optical properties of LaFe0.5Mn0.5O3 prepared perovskite powders were exclusively compared for processing temperatures for applications of dye-sensitized solar cells. In this framework, LaFe0.5Mn0.5O3 perovskite powders were synthesized with the sol–gel method at 500 °C and 850 °C (according to DTA/TG results). They were characterized through DTA/TGA (Thermogravimetric and Differential Thermal Analysis), FTIR (Fourier Transformed Infrared Spectroscopy), XRD (X-Ray Diffractometer), XPS (X-Ray Photoelectron Spectroscopy), PSA (Particle Size Analysis), SEM (Scanning Electron Microscopy), VSM (Vibrating Sample Magnetometer) and UV–Vis Spectrometer. In line with the obtained results, ferroelectric perovskite powders were successfully produced. These powders have crystallite sizes of 27.38–35.74 nm, bandgap values of 1.19–0.93 eV, particle sizes of 28–358 nm and ferromagnetic properties. In addition to the effect of synthesis temperature on LaFe0.5Mn0.5O3 synthesis with these characterization processes, it was found that the production of sustainable and applicable dye-sensitized solar cells using LaFe0.5Mn0.5O3 powders can be useful as innovative and futuristic approaches. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Item Kinetic parameters and luminescence properties of rare earth (Tb, Nd) doped and transition metal (Mn) doped/co-doped YAlO3 prepared via sol-gel method(Elsevier B.V., 2023) Gökçe S.; Keskin İ.Ç.; Katı M.İ.; Kibar R.; Çetin A.; Tuncer Arslanlar Y.In this work, phosphor materials with the formula YAlO3 were synthesized via sol-gel method by using the stoichiometric amounts of yttrium nitrate and aluminum nitrate as base materials. The obtained phosphors were doped/co-doped with Tb3+, Nd3+ rare earth ions and Mn2+ transition metal ion. For evaluating the influence of the dopants, the grain size and morphology of the samples by scanning electron microscopy (SEM) and the phase and crystallinity of the synthesized materials by X-ray diffraction (XRD) were investigated. Optical absorption spectra, photoluminescence (PL) and thermoluminescence (TL) were performed to determine a relationship the changing dopant on luminescence properties of YAlO3. Moreover, the kinetic parameters namely activation energy (E), order of kinetics (b) and frequency factor (s) of the synthesized pure and doped materials were calculated using Computerized Glow Curve Deconvolution (CGCD) and Peak Shape Method for a better understanding of the optical properties that change with the doping process. Strong green emission was detected in the sample doped with Mn2+ correspond to 4T1(G)→6A1(S) transition. As for YAlO3: Nd3+, characteristic emissions originated from 4G11/2 → 4I9/2 (∼423 nm), 4G9/2 → 4I9/2 (∼460 nm) and 4G7/2 → 4I9/2 (∼540 nm) transitions were seen. The optical band gap of undoped sample was calculated as 2.79 eV and depending on the presence of Nd3+ and Tb3+ dopant ions this value was decreased to the range 2.46–2.56 eV. © 2023 Elsevier B.V.Item Failure analysis of cardan shaft’s flange yoke fracture occurred during torsional fatigue test; [Torsiyonel yorulma testi sırasında kırılan kardan miline ait çatallı flanş parçasının hasar analizi](Gazi Universitesi, 2023) Akkaş O.; Işık E.; Çulha O.In this study, the analysis and characterization of the failure that occurred during the torsional fatigue test of the flange yoke unit part of the cardan shaft used in heavy commercial vehicles were carried out. In order to determine the root cause of the failure according to the production, structure, property and performance relationship in materials science, chemical analysis of the steel raw material used in the production of flange yoke, hardness measurement, grain size analysis, decarburization measurement, inclusion analysis and raw material characterization by scanning electron microscopy (SEM) were carried out. As a result of the studies, it was determined that the values obtained for 41Cr4 steel raw material were conformant according to the TS EN ISO 683-2 standard, but in the SEM examination and EDS analysis, elongated MnS inclusions in the microstructure and cracks were detected at the interface of the metal matrix and MnS inclusions. In this context, as a result of the characterization of the flange yoke unit part, it was determined that the MnS ratio was 2-4 μm x 898-1.181 μm according to the ASTM E45 standard, at the same level as the raw material and equivalent to the A-type value of 3.0-3.5. It was determined that MnS inclusion formations in the subsurface region formed crack propagation zones. © 2023 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.