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- MakaleYalnız künye2026Scopus SJRQ1Influence on the thermoelectric characteristics of the growth parameters of BiSeTe thin films
Yüzüak, G. Durak; Yüzüak, E.
This study systematically investigates the influence of magnetron sputtering parameters on the structural, electronic, and thermoelectric properties of 100 nm thick Bi2SexTe3-x thin films deposited on Si(100). The initial parameters for applied film deposition are used to set the x value. The films are fabricated with sputtering powers ranging from 30 to 100 W and pressures from 3 to 15 mTorr, with films grown under optimal conditions selected for post-deposition annealing at 523 K. A comprehensive characterization suite, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and Kelvin probe force microscopy (KPFM), is used to establish direct correlations between processing, structure, and performance. XRD analysis reveals that increasing the sputtering pressure from 3 to 15 mTorr was critical for enhancing film crystallinity and promoting a strong (015) preferred orientation, while AFM showed a corresponding increase in average grain size from similar to 46 to similar to 60 nm via heat treatment (HT). EDS shows that films grown at 10 mTorr were almost certainly stoichiometric, but increasing the power to 15 mTorr caused tellurium deficiency. The films exhibited a power factor ranging from 2.5 to 2.8 mW m(- 1) K- 2 at 40 degrees C. HT improved the Seebeck coefficient from -115 mu V K- 1 to -140 mu V K- 1 and decreased the electrical resistivity by over 25 % through defect reduction and enhanced crystalline order. KPFM supported these findings, directly linking the crystallographic texture to the surface electronic structure and enhanced Seebeck effect.
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İncele - MakaleYalnız künye2026Scopus SJRQ2Practical one-step solvothermal synthesis of photoactive lanthanum(III)hydroxide-metaborate composite nanosheets with suitable band gap for optoelectronics
Karaduman, Oktay
Rare earth compounds, including lanthanide hydroxides, have been greatly interested for their promising uses, such as in optoelectronics or photonics, due to their unique electronic and optical transitions properties based on their 4f electron shells. In this work, for the first time new transparent flower-like lanthanum(III)hydroxide (La(OH)3) with borate (LaB3O6) composite nanosheets having a semiconducting band gap suitable for optoelectronics were synthesized by a very simple one-step solvothermal method from a mixture of pure lanthanum oxide and boron without using water or any acidic solvent or surfactant. The practical synthesis was made for two different solvothermal time durations. The synthesized nanocomposites were investigated by XRD, FIB-SEM imaging, EDS, FTIR, UV-vis absorbance, Raman, Ellipsometry, and TG-DTA analyses. The pure precursors lanthanum oxide (La2O3) and boron converted to La(OH)3 and LaB3O6. EDS elemental mapping showed the homogeneous distribution of elements in the nanocomposites. A strong deep-UV absorbance band was detected. The very low reflectance and excellent visible transmittance (exceeding 86% for the sample with a longer solvothermal process time) reaching infrared region were achieved. The direct and indirect band gap energies were estimated by the Tauc plot method for both of the composite samples. Adding boron reduced the literature given direct band gap value (around 4.5-5.5 eV) of pure La(OH)3. DTA and TGA results revealed the steps of mass losses, including decomposition of La(OH)3. FTIR analyses confirmed the presence of the formed compounds. All results showed that the La(OH)3+LaB3O6 nanocomposites can be suitably used in related applications, including electro-optic, photonic, solar cell, catalysts etc.
- MakaleYalnız künye2020Scopus SJRQ4Electrochemical behaviour of cross-linker glutaraldehyde as a receptor for carbaryl biosensor
Ipek, Yeliz
Glutaraldehyde (GA) is a famous cross-linker that is used for immobilization of enzyme or biologic material on electrochemical biosensor electrodes. It has an important role in pesticide biosensor studies. Because of the inhibitor effect of pesticides on acetylcholine esterase enzyme (AChE), it is generally immobilized on the electrode by cross-linking method. Glutaraldehyde is used as cross-linker agent to immobilize the enzyme on the electrode surface. Acetylcholine esterase activity is inhibited by pesticides or other neurotoxic compounds. This inhibition helps us to detect the pesticide residual. Although numerous electrochemical pesticide biosensors are based on generally the immobilization of the enzyme in the literature, an enzymeless biosensor based on GA has been developed in this study for the first time. Enzyme biosensors have high cost and needs special storage conditions. In this study, glutaraldehyde detected the carbaryl pesticide as sensitive as an acetylcholine esterase enzyme biosensor. The biosensor electrode was constructed with coating GA on glassy carbon electrode (GCE). Thus, it is a simple, low cost and practical method for pesticide detection in the water samples with low detection limit of 5x10(-9) mol L--(1).
AtıfWoS3İncele - MakaleYalnız künye2026Scopus SJRQ2An integrated process for rare earth elements recovery and silica production from Turkish bauxite-related ores
Uysal, Turan; Erüst, Ceren; Erdemoglu, Murat; Sis, Hikmet
The evaluation of bauxite-associated shales as a secondary source of rare earth elements (REEs) is strategically important for securing a sustainable supply of critical raw materials used in advanced technologies. In this study, shale ore associated with bauxite, unsuitable for aluminium production due to its high silica content, was investigated as a potential resource for valuable REEs. The effect of thermal activation on REE recovery was examined, and the potential use of the leach residue as a silica source was assessed. Based on acid leaching results, the optimum calcination temperature was identified as 700 degrees C. Under these conditions, high REE recoveries were achieved: 92.9% La, 89.9% Ce, 89.0% Pr, 88.7% Nd, and 73.0% Sm. After leaching, the residue was enriched in alumina and silica. To improve silica purity and recover remaining REEs and Al, a second-stage leaching process was applied. This resulted in a byproduct containing 55% SiO2 with a specific surface area of 48 m2 g-1, indicating its potential as a silica source. The results demonstrate that bauxite-associated shale can be sustainably valorised through intensive milling, calcination, and acid leaching, enabling efficient REE recovery and the production of a silica-rich byproduct. L'& eacute;valuation de schistes associ & eacute;s & agrave; la bauxite comme source secondaire d'& eacute;l & eacute;ments de terres rares (ETR) est strat & eacute;giquement importante pour garantir un approvisionnement durable en mati & egrave;res premi & egrave;res critiques utilis & eacute;es dans les technologies avanc & eacute;es. Dans cette & eacute;tude, on a examin & eacute; le minerai de schiste associ & eacute; & agrave; la bauxite, inappropri & eacute; & agrave; la production d'aluminium en raison de sa teneur & eacute;lev & eacute;e en silice, comme ressource potentielle d'ETR pr & eacute;cieux. On a examin & eacute; l'influence de l'activation thermique sur la r & eacute;cup & eacute;ration des ETR et l'on a & eacute;valu & eacute; l'utilisation potentielle du r & eacute;sidu de lixiviation comme source de silice. D'apr & egrave;s les r & eacute;sultats de la lixiviation acide, on a identifi & eacute; la temp & eacute;rature optimale de calcination & agrave; 700 degrees C. Dans ces conditions, on a obtenu des r & eacute;cup & eacute;rations d'ETR & eacute;lev & eacute;es: 92.9% de La, 89.9% de Ce, 89.0% de Pr, 88.7% de Nd et 73.0% de Sm. Apr & egrave;s la lixiviation, le r & eacute;sidu & eacute;tait enrichi en alumine et en silice. Afin d'am & eacute;liorer la puret & eacute; de la silice et de r & eacute;cup & eacute;rer les ETR et l'Al restants, on a appliqu & eacute; une deuxi & egrave;me & eacute;tape de lixiviation. Cela a engendr & eacute; un sous-produit contenant 55% de SiO2 et pr & eacute;sentant une surface sp & eacute;cifique de 48 m2/g, indiquant son potentiel en tant que source de silice. Les r & eacute;sultats d & eacute;montrent que le schiste associ & eacute; & agrave; la bauxite peut & ecirc;tre valoris & eacute; de mani & egrave;re durable par broyage intensif, calcination et lixiviation acide, permettant une r & eacute;cup & eacute;ration efficace des ETR et la production d'un sous-produit riche en silice.
- MakaleAçık Erişim2020Scopus SJRQ3Modeling of Drying Processes of Dates (Phoenix, Arecaceae) with Oven or TGA and Microbiological Properties of Fresh and Dried Dates
Ertekin, Özlem; İpek, Yeliz
Drying method, which is one of the oldest preservation methods, is important for preserving fruits. Date palm fruit is an important food in human nutrition due to some vitamins, minerals, sugar, phenolic components, and high fiber content. In the literature, date palm drying was not studied sufficiently in the aspect of mathematical modeling and the effect of drying process on the microbiological properties. In this novel study, date palm drying process was applied with four different temperatures of 50°C, 70°C, 90°C, and 110°C with two different drying techniques; drying with oven and drying with thermogravimetric analysis (TGA). Chemical changes in the date palm structure after drying at different temperatures were investigated with FTIR analysis. Fibrous structure of palm fruit is also exhibited with SEM analysis. On the other hand, microbiological studies were applied both for fresh and dried date palm to observe the drying process effect on the growth of different types of microorganisms. Consequently, drying time decreased with increasing drying temperature while the color of the dried date palm fruit became darker with increasing temperature. However, the chemical structure was not affected. Drying time of oven drying technique was longer than drying with TGA technique. The mathematical model of the drying temperature depending on drying time is calculated as (Formula presented.) for TG-DTA drying experiments and (Formula presented.) for drying process with oven. In addition, the microbiological load has significantly decreased or disappeared with the drying process.
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