Browsing by Author "Acar S."

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Effect of Ni and Al doping on structural, optical, and CO2 gas sensing properties of 1D ZnO nanorods produced by hydrothermal method
(2022-04-01) Bulut F.; Ozturk Ö.; Acar S.; Yildirim G.
In the present study, the one-dimensional ZnO nanorod structures are produced within the different nickel and aluminum molecular weight ratios of 0–7% using the hydrothermal method. It is found that the aluminum (Al) and nickel (Ni) impurities with different ionic radius, chemical valence, and electron configurations of outer shell cause to vary the fundamental characteristic features including the crystallinity quality, crystallite size, surface morphology, nanorod diameter, optical absorbance, energy band gap, resistance, gas response, and gas sensing properties. The structural analyses performed by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that the samples are found to crystallize in the hexagonal wurtzite structure. The presence of optimum nickel and aluminum in the crystal system improves considerably the crystallinity quality and surface morphology. Additionally, the combination of electron dispersive X-ray (EDX) and XRD results declare that the Ni and Al impurities incorporate successfully into the ZnO crystal structure. Moreover, the diameters of nanorod structures in 1D orientation are determined to be 80 nm or below. The hexagonal wurtzite-type ZnO nanorod structure prepared by 5% Ni has more space between the nanorods and thus presents higher response to the CO2 detection. Further, the optical absorbance spectra display that the band gap value is observed to decrease regularly with the increment in the doping level as a result of band shrinkage effect depending on the enhancement of mobile hole carrier concentrations in the crystal structure. In other words, the doping mechanism leads to vary the homogeneities in the interfacial charges, nanorod diameters, ZnO oxide layer composition and thickness. The last test conducted in this study is responsible for the determination of CO2 gas sensing levels. The obtained gas sensing results are further compared with each other and literature findings. It is observed that 5% Ni-doped sample provides more successful results than other samples in the sensing CO2 gas at the different concentrations. All in all, the paper establishing a strong methodology between doping mechanism and change in the fundamental characteristic features of hexagonal wurtzite-type ZnO with the aid of advanced microscopy techniques will become pioneering research to answer key questions in materials sciences and electronic research.
Influence of Temperature on the Peculiarities of Electret State in Microporous Zeolite
(2019-11-01) Soltabayev B.; Hilal Kurt H.; Acar S.; Salamov B.
In this work, the temperature dependent electret state (ES) effect on the resistivity of microporous clinoptilolite was studied. The current–voltage characteristics with an unusual hysteresis in the clinoptilolite wafers were measured for different temperatures in the range of 30–260°C. After the application of a constant electric field of 2 kV cm−1 in air medium for 24 h, the effect of the electric field on the electrical properties of clinoptilolite wafers was investigated. A significant change in the stability of the ES was observed for clinoptilolite plates. The transport properties were restored, which confirmed the presence of the initial electret state in clinoptilolite plates at atmospheric pressure. Differences in transport properties remain for several days. It is considered that the electric field E produces a polarization inside the sample, where the carriers move through the dielectric and they are captured at the traps by resulting in a certain distribution of space charge in atmospheric pressure.
Morphological and taxonomic investigations on a local endemic species: Allium ilgazense N. Özhatay
(2015-01-01) Acar S.; Ayan S.; Bani B.
The genus Allium is represented by a high number of taxa and a high endemism ratio in Turkey. Moreover, the genus has medicinal and economic importance because some of its species can be regarded as among mankind's the most important and the most ancient cultivated crops (onion, garlic, and leek). In this study, the morphological features and taxonomic status of a local endemic species (Allium ilgazense) were determined and the recommendations dealing with its conservation status were presented. For this purpose, a total of 30 individuals collected from 3 different populations (10 individuals per population) of the species that grow in different locations and ecologies were investigated. The morphological results clearly indicated that A. ilgazense is a polymorphic species and shows distinct variation in almost all of the quantitative characters (21 out of 36), although the qualitative characters (15 out of 36) are more stable. The diagnostic characteristics of A. ilgazense were specified as 'colour of flowers', 'indumentum and shape of inner and outer perianth segments', 'shape of spathe valves', 'colour of anthers' and 'slightly exserted stamens'. The UPGMA analysis, based on morphological similarities and dissimilarities (21 selected morphological characters) among 30 individuals from 3 populations of A. ilgazense and 10 individuals of A. jubatum, presented that A. ilgazense is a clearly distinct species and there is no significant specialization among its populations distributed in different ecologies. Moreover, in order to protect the natural populations of A. ilgazense, the threat factors were determined. According to the IUCN criteria, a new threat category (EN, Endangered) was recommended for the species.