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Öğe Coercivity and exchange bias in ti-doped maghemite nanoparticles(MDPI, 2022) Narayanaswamy, Venkatesha; Al-Omari, Imaddin A.; Kamzin, Aleksandr S.; Khurshid, Hafsa; Khaleel, Abbas; Issa, Bashar; Obaidat, Ihab M.Ti-doped maghemite nanoparticles of average crystallite size 12.9 nm were synthesized using the sol-gel method. The XRD profile mainly showed the presence of maghemite phase with very small phases of TiO2 (rutile and anatase). Magnetization hysteresis loops of the nanoparticles were obtained between -4 T to +4 T at temperatures of 2, 10, 30, 50, 70, 100, 150, 200, and 300 K under field cooling (FC) of 1, 2, 3, and 4 T and zero-field cooling conditions (ZFC). The coercivity displayed nonmonotonic field dependence while it decreased sharply with temperature and vanished at 150 K at all fields. Horizontal hysteresis loop shifts were observed in the 2-150 K temperature range in both the ZFC and FC conditions. The exchange bias effect became negligible in both ZFC and FC states above 50 K. Magnetization vs. applied field measurements were conducted in both ZFC and FC cooled conditions at several temperatures in the range of 2-400 K, with spin freezing being observed below 50 K. The exchange bias effect obtained below 50 K is suggested to be attributed to the competing roles of the long-range dipolar and short-range exchange coupled interactions.Öğe Exploring critical behavioral differences in physical, structural, and nuclear radiation attenuation properties of produced High Entropy Alloy (HEA) and Refractory-High Entropy Alloy (RHEA) samples(Elsevier, 2024) Guler, Seval Hale; Guler, Omer; Kavaz, E.; Almisned, Ghada; Issa, Bashar; Tekin, H. O.Refractory-High entropy alloys (RHEAs) are known for their exceptional mechanical and radiation-resistant properties, making them promising materials for use in nuclear reactors. Their high entropy composition, which consists of multiple elements in roughly equal proportions, can create a stable microstructure that withstands high levels of radiation damage. The objective of this work is to further our comprehension of the unique behavioral, physical, structural, and nuclear radiation attenuation characteristics shown by High-Entropy Alloys (HEA) and Refractory-High entropy alloy (RHEA) materials. Accordingly, two high entropy alloy (HEA) samples through two different compositions were produced. The first composition under consideration is the typical high-entropy alloy (HEA) defined as MnCrFeNiCoMo0.5. The second composition under consideration is a refractory high entropy alloy (RHEA) characterized by the following elemental composition: TiZrNbHfVTa0.1. SEM and EDX analyses were conducted in terms of determining their physical and structural attributes. Next, a133Ba radioisotope together with a HPGe detector were utilized for gamma-ray transmission experiments. Finally, a241Am/Be source and a gas proportional detector were used for neutron absorption experiments for HEA and RHEA samples. The alloy structures displayed a unique degree of uniformity. Throughout the RHEA phase, the incorporation of refractory elements did not provide any discernible adverse impacts on the physical stability. The counting spectrum provided a clear explanation of the gamma ray absorption features shown by the RHEA (R) sample, highlighting its exceptional absorption properties. Regarding the absorption properties of neutrons, it was observed that RHEA had a comparatively reduced amount of absorption. Therefore, it can be concluded that the basic structure of RHEA grants it superior gamma-ray attenuation qualities compared to HEA. It can be concluded that RHEA demonstrates superior applicability as a material in comparison to HEA, especially in situations involving the use of fuel rods, where maintaining of neutron quantity has paramount importance for achieving optimum neutron activation.Öğe Fabrication and structural, physical, and nuclear radiation shielding properties for Oxide Dispersion-Strengthened (ODS) alloys through Erbium (III) oxide, Samarium (III) oxide, and Praseodymium (III) oxide into 316L matrix(Elsevier Sci Ltd, 2024) Guler, Seval Hale; Guler, Omer; Kavaz, E.; Almisned, Ghada; Albayrak, M. Gokhan; Issa, Bashar; Tekin, H. O.We report a comprehensive investigation on customization process of Oxide Dispersion-Strengthened alloys through Sm2O3, Pr2O3, and Er2O3 incorporation into 316L stainless steel matrix in terms of a desired enhancement in structural, physical, and nuclear radiation shielding properties. Oxide powders are incorporated into 316L stainless steel powder all with the same purity of 99.5%. These were Erbium oxide (Er2O3), Praseodymium oxide (Pr2O3), and Samarium oxide (Sm2O3). First, X-Ray diffraction and Scanning Electron Microscope/Energy-dispersive X-ray spectroscopy analyses are conducted in order to investigate their physical and structural properties. Next, two different experimental setups are employed using a133Ba and 241Am/Be sources for the measurements of gamma-ray and neutron transmission properties of Oxide Dispersion -Strengthened alloys. The maximum density increment is achieved through Er2O3 compared to other rein-forced oxides. The detector counting value reached its minimum level when a 5% Er2O3 oxide dispersion was introduced into the 316L SS matrix. Similarly, the most significant degree of photon absorption, the highest values of mass attenuation coefficient, lowest half value layer, and most effective atomic number, were all attained by the same sample. Based on the findings derived from the investigation, it can be concluded that incorporating Er2O3 oxide into 316L steel can be considered as a viable option in terms of enhancing the critical properties of Oxide Dispersion-Strengthened alloys for extreme conditions such as nuclear reactors and other similar fields, where the behavioral attributes of the utilized materials are at utmost importance.Öğe Hyperthermia of magnetically soft-soft core-shell ferrite nanoparticles(MDPI, 2022) Narayanaswamy, Venkatesha; Jagal, Jayalakshmi; Khurshid, Hafsa; Al-Omari, Imaddin A. A.; Haider, Mohamed; Kamzin, Alexander S. S.; Obaidat, Ihab M. M.; Issa, BasharMagnetically soft-soft MnFe2O4-Fe3O4 core-shell nanoparticles were synthesized through a seed-mediated method using the organometallic decomposition of metal acetyl acetonates. Two sets of core-shell nanoparticles (S1 and S2) of similar core sizes of 5.0 nm and different shell thicknesses (4.1 nm for S1 and 5.7 nm for S2) were obtained by changing the number of nucleating sites. Magnetic measurements were conducted on the nanoparticles at low and room temperatures to study the shell thickness and temperature dependence of the magnetic properties. Interestingly, both core-shell nanoparticles showed similar saturation magnetization, revealing the ineffective role of the shell thickness. In addition, the coercivity in both samples displayed similar temperature dependencies and magnitudes. Signatures of spin glass (SG) like behavior were observed from the field-cooled temperature-dependent magnetization measurements. It was suggested to be due to interface spin freezing. We observed a slight and non-monotonic temperature-dependent exchange bias in both samples with slightly higher values for S2. The effective magnetic anisotropy constant was calculated to be slightly larger in S2 than that in S1. The magnetothermal efficiency of the chitosan-coated nanoparticles was determined by measuring the specific absorption rate (SAR) under an alternating magnetic field (AMF) at 200-350 G field strengths and frequencies (495.25-167.30 kHz). The S2 nanoparticles displayed larger SAR values than the S1 nanoparticles at all field parameters. A maximum SAR value of 356.5 W/g was obtained for S2 at 495.25 kHz and 350 G for the 1 mg/mL nanoparticle concentration of ferrogel. We attributed this behavior to the larger interface SG regions in S2, which mediated the interaction between the core and shell and thus provided indirect exchange coupling between the core and shell phases. The SAR values of the core-shell nanoparticles roughly agreed with the predictions of the linear response theory. The concentration of the nanoparticles was found to affect heat conversion to a great extent. The in vitro treatment of the MDA-MB-231 human breast cancer cell line and HT-29 human colorectal cancer cell was conducted at selected frequencies and field strengths to evaluate the efficiency of the nanoparticles in killing cancer cells. The cellular cytotoxicity was estimated using flow cytometry and an MTT assay at 0 and 24 h after treatment with the AMF. The cells subjected to a 45 min treatment of the AMF (384.50 kHz and 350 G) showed a remarkable decrease in cell viability. The enhanced SAR values of the core-shell nanoparticles compared to the seeds with the most enhancement in S2 is an indication of the potential for tailoring nanoparticle structures and hence their magnetic properties for effective heat generation.Öğe Occupational radiation dose assessment for nuclear medicine workers in Turkey: A comprehensive investigation(Elsevier B.V., 2022) Elshami, Wiam; Erdemir, R. Uslu; Abuzaid, M.M.; Cavlı, Barış; Issa, Bashar; Tekin, Hüseyin OzanObjective: Radioisotopes are used extensively in nuclear medicine. Analysis of occupational doses received by medical radiation workers, especially nuclear medicine staff dealing with radioisotopes, contributes significantly to enhancing safe practice and promoting radiation protection measures in the radiology department. The current study aimed to determine the time trend and the differences in occupational radiation dose among nuclear medicine workers. Methods: Readings of 394 OSL dosimeters were obtained from 31 medical workers and grouped into five worker groups (technologist, physician, nurse, radio-pharmacist, and radio-physicist). Results: The average number of workers dropped to 4.5 in 2020 and 2021 compared to 14.4 in 2014 to 2019. The average annual effective dose and skin dose for all workers based on measurements for a typical yearly workload of 5000 patients were 1.21 (±1.15) mSv and 2.86 (±1.32) mSv, respectively. The highest average annual effective and skin dose was 5.41 and 5.82 mSv, respectively. The NM technologist working in PET/CT received higher mean and maximum effective and skin doses than the other worker groups. Conclusion: The annual effective and skin doses were below the national legislation and international standards. However, improvements in radiation protection practices could be implemented to reduce occupational radiation dose to NM technologists, the most exposed worker group in this study. © 2022 The Author(s)
