Makale 2020-2029 yılları

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Browsing Makale 2020-2029 yılları by Publisher "ELSEVIER"

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    Achieving superior strength and ductility in oxide dispersion strengthened IN625 alloy produced by laser powder bed fusion
    (ELSEVIER, 2024-12-19) Demirci, Kadir Tuğrul; Özalp, Ali; Güner Gürbüz, Selen Nimet; Bükülmez, İlhan; Aksu, Erhan; Aydoğan, Eda
    In this study, a new grade of oxide dispersion strengthened (ODS) Inconel 625 (IN625) alloy having the composition of 0.3 wt% Y2O3 – 0.4 wt% Hf – IN625 has been developed and produced by laser powder bed fusion (L-PBF). Production parameters have been determined for standard and ODS IN625 alloys to yield >99.9% densification. Microstructural analyses reveal similar texture along <001> while a larger but homogenous strain distribution exist in ODS IN625. Nano-particles are determined to be mostly Y-Hf-O and Y2O3 with an average size of ~30 ± 18 nm and 2.2 ± 1.1x1013 m-2 areal fraction. Tensile tests at room temperature (RT) and 700 °C demonstrate superior mechanical properties of ODS-IN625, particularly at elevated temperatures. While the yield strengths of standard and ODS IN625 alloys are similar (~680 MPa), ductility of ODS IN625 is slightly larger at RT. However, the yield strength of ODS-IN625 increased by 7.4%, reaching ~580 MPa, compared to the standard IN625, which has a yield strength of ~540 MPa at 700 °C. More notably, the ductility of ODS IN625 shows a remarkable improvement, increasing from ~12% in the standard IN625 to ~22%, representing an increase of more than 80%. Detailed microstructural analyses on the fracture surfaces of the ODS IN625 alloys exhibit submicron dimples, as well as an extensive amount of dislocation loops, Lomer-Cortrel (L-C) locks, and stacking fault tetrahedra. Nano-oxides were determined to be responsible for the dislocation wall structure and dislocation distribution which in turn improves the mechanical properties. This study sheds light on tailoring the strength-ductility balance in IN625 alloys by introducing the nano-oxide particles and perceiving the mechanism of this improvement.
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    Assessment of low-energy electron beam irradiation for effective surface microbial decontamination of fresh lettuce (Lactuca sativa L.) leaves
    (ELSEVIER, 2025-05-12) Turan, Ozlem; Cetintas, Aydin Ozan; Gokalp, Metin; Halkman, Hilal Beyhan; Ic, Erhan; Kantoglu, Omer; Kantoglu, Kadriye Yaprak
    Microbial contamination in fresh produce, particularly leafy greens such as lettuce and spinach, constitutes a significant public health concern due to infections caused by enteropathogens. Therefore, low-energy electron beam (LEEB) irradiation has been introduced to ensure microbial decontamination, analogous to conventional irradiation applications. This study examines the efficacy of LEEB irradiation in reducing bacterial contamination in lettuce (Lactuca sativa L.) and determines the radiation sensitivity of target microorganisms through D10 values compares it with the gamma-ray treatment. Hydroponically cultivated lettuce samples were inoculated with Escherichia coli, Salmonella Enteritidis, Listeria monocytogenes, and E. coli O157:H7. Following LEEB treatment, the D10 values of four pathogens were calculated between 0.371, and 0.737 kGy, whereas gamma irradiation resulted in lower values of 0.262-0.327 kGy. These results suggest that LEEB doses in the range of approximately 1.7 to 3 kGy may be sufficient to achieve an average 4-log reduction in pathogens. Additionally, the effects of LEEB irradiation on the physicochemical properties of lettuce were evaluated immediately after irradiation at doses of 1, 3, and 5 kGy. While no statistically significant differences were observed in color and total vitamin C (p>0.05), bioactive compound levels increased at higher doses (p<0.05). Fourier Transform Infrared (FT-IR) spectroscopy confirmed minimal structural alterations. These findings suggest that LEEB irradiation effectively decontaminates lettuce while maintaining its physicochemical integrity and enhancing its bioactive properties, presenting a promising and very important approach for improving fresh produce safety.
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    Impact of low energy proton radiation on lentil seeds (Lens culinaris) for sustainable space breeding
    (ELSEVIER, 2025-10-26) Fırat, Suna; Opçin, Büşra; Yıldırım. Aydın
    The effects of low energy proton irradiation on lentil (Lens culinaris) seeds were investigated to evaluate their potential for space-based breeding. Seeds of a local cultivar were exposed to 2.28 MeV protons for 5 min at beam currents ranging from 50 to 225 nA, corresponding to absorbed doses of 8.45–38.02 kGy, alongside a nonirradiated control group. Germination was assessed on day 5, and survival rate, seedling height, first true leaf length, and biomass were measured after 27 days of greenhouse growth. Linear energy transfer (LET) analysis using SRIM indicated that maximum energy deposition occurred within the outer cotyledon layers. Beam currents up to 75 nA showed no significant differences from the control in germination or survival, whereas currents above 150 nA markedly suppressed growth parameters, with survival reduced by up to 92.5% at 225 nA. As observed in studies with other ionizing radiation types, low current, low energy exposures produced no adverse effects, suggesting that lentil seeds may tolerate low-dose proton irradiation. These results highlight the importance of radiation shielding in deep-space missions and support the use of lentils as a candidate crop for controlled breeding systems in extraterrestrial environments.
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    Influence of calcination conditions on deep eutectic solvents (DES) leaching efficiency of light rare earth elements in bastnasite ore
    (ELSEVIER, 2024-11-02) Kaplan, S. Samet; Kurtulan, Cisem Celik; Gurmen, Sebahattin; Orhan, Gokhan; Sonmez, Mehmet Seref
    In this century, our daily life is surrounded by technological devices, and Rare Earth Elements (REE) are at the heart of this technological revolution. They are always listed having the highest supply risk in critical minerals published by different countries. From that point of view, their extraction, and creating a secured supply chain is always crucial. In this research, the influence of calcination conditions on REE extraction from bastnasite ore was studied. Identical leaching in Ethylene Glycol (EG)-FeCl3 media which is one of the Deep Eutectic Solvents (DES) was applied to different calcines to understand calcination parameters on leaching efficiency. After conducting experiments created by Box-Behnken approach with different parameters of temperature, duration, and particles size, the highest Light Rare Earth Elements (LREE) extraction efficiency of 67.22 wt% was achieved at 900◦ C. However, while conducting control experiments, the highest extraction efficiency was found to be 75.986 wt% as a median of the experiments conducted at 500 ◦C during 180 min, and with particles finer than 25 µm. This efficiency increase with decreasing temperature is explained by Ce phase transformation from Ce2O3 to CeO2 as proved by XRD analysis. In addition to temperature, particle size was also found highly effective in extraction efficiency especially in Ce extraction. At the experiments conducted at 900 ◦C, and 270 min but with particles at different size ranges, Ce extraction dramatically dropped from 71.061 wt% to 9.587 wt% at the experiment conducted with finer particles. This lose in efficiency is directly correlated to increasing Ce phase transformation rate due to increasing surface area of fine particles. Non-calcined ore was also leached with DES, and only 10.977 wt% LREE could be extracted. Furthermore, it is concluded that calcination is of vital importance to transform the ore into a soluble form, and temperature, and particle size ranges are found to be two fundamental parameters for tuning the extraction efficiency.
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    Natural radioactivity and radiological hazards in ultrapotassic rocks from the Central Pontides, Türkiye
    (ELSEVIER, 2025-05-27) Yıldırım; Aydın; Gülmez; Fatma
    Primordial radionuclides (226Ra, 232Th, 40K) are key contributors to natural radiation and tend to concentrate in specific lithologies in the Earth’s crust. This study investigates Upper Cretaceous ultrapotassic rocks from the Central Pontides in Türkiye, where increasing constructional and industrial activities raise concerns about radiological exposure and environmental health risks. Gamma spectrometry analysis of powdered rock samples reveals that 226Ra (10.0–53.6 Bq/kg) and 232Th (9.3–65 Bq/kg) generally fall below global averages, whereas 40K reaches notably high levels (97–1940 Bq/kg). Elevated 40K levels in trachytic, leucitebearing, and lamprophyric rocks from Amasya, Tosya, and Kalecik, result in radiological hazard parameters exceeding recommended limits, despite relatively modest 226Ra and 232Th activities. Correlation analyses indicate moderate relationships between 226Ra and 232Th, but weak correlations with 40K, suggesting postmagmatic processes possibly influenced these rocks. These findings underscore the importance of ultra- and high-potassic rocks as potential gamma radiation sources in areas where land use, construction, and dust or soil mobilization increase interactions with biological organisms. Continuous monitoring of potassium-40 pathways and the proper management strategies are critical to mitigate possible health risks associated with elevated radionuclide concentrations.