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Öğe A comparison of magnetic, structural and thermal properties of NiFeCoMo high entropy alloy produced by sequential mechanical alloying versus the alloy produced by conventional mechanical alloying(Elsevier, 2021) Şimşek, Tuncay; Akgül, Şaban; Güler, Ömer; Özkul, İskender; Avar, Barış; Chattopadhyay, Arun K.; Canbay, Canan A.The soft ferromagnetic materials are of great industrial importance for their applications in magnetic cores for transformers, electric motors, inductors, and generators. In recent years, the trend has been to use magnetic high entropy alloys (HEAs) owing to their superior magnetic properties compared to the conventional magnetic materials. In this study, the traditional magnetic materials, (NiFeCo)(95)Mo-5 and (NiFeCo)(90)Mo-10 produced by conventional mechanical alloying method, were compared with the NiFeCoMo high entropy alloy produced by the sequential mechanical alloying method. Unlike conventional mechanical alloying, NiFeCoMo HEA was produced by mechanical alloying using sequential additions of Co and Mo to the preformed Fe-Ni alloy. Besides its magnetic properties, the effect of Co and Mo on the overall characteristics of the alloy was also investigated. In 60 h milled samples of the (NiFeCo)(95)Mo-5 and (NiFeCo)(90)Mo-10 alloys, the crystallite sizes were estimated as 10.5 and 10.8 nm respectively, whereas the crystallite size for the NiFeCoMo HEA was 15 nm. The presence of Mo in the alloy induced the formation of lamellar or layered structures of the particles. During the sequential milling to form NiFeCoMo HEA, it was noticed that the addition of Co into the preformed Fe-Ni alloy increased the magnetic saturation value due to the formation of FeCoNi alloy phase. However, further addition of Mo into the FeCoNi alloy phase reduced the magnetic saturation value of NiFeCoMo alloy significantly. After 60 h of milling the magnetic saturation value was dropped from 102.48 emu/g for the NiFeCo alloy to 60.52 emu/g for the NiFeCoMo alloy.Öğe A critical review of the refractory high-entropy materials: RHEA alloys, composites, ceramics, additively manufactured RHEA alloys(Elsevier, 2025) Güler, Seval Hale; Yakın, Alican; Güler, Ömer; Chattopadhyay, Arun K.; Şimşek, TuncayIn this study, the traits, production methods, and applications of refractory high-entropy materials-including refractory high-entropy alloys (RHEAs), refractory high-entropy composites (RHE-Cs), and refractory high- entropy ceramics (RHE-Ce)-which are part of the broader category of refractory high-entropy materials with a wide range of applications, have been thoroughly examined and discussed. RHEAs have emerged as materials that exhibit superior properties, such as high melting temperatures, excellent temperature resistance, and high wear and corrosion resilience, in addition to high mechanical and fatigue strength. These attributes have made them extensively studied materials in recent times. The properties of RHEAs suggest their safe operation in challenging environments such as nuclear reactors, gas turbines, aerospace, and energy production. Among refractory materials, RHE-Cs stand out for their high strength and low density, showing significant potential for use in the automotive, aerospace, and space industries. Another group with a wide range of applications, RHE-Ce materials, is distinguished by their high-temperature resilience, high hardness, and low thermal conductivity, making them suitable for high-temperature environments. Refractory materials are generally fabricated using traditional techniques such as arc melting, powder metallurgy, and magnetron sputtering. In this study, along with traditional production methods, additive manufacturing techniques which have revolutionized the manufacturing field are discussed concerning their applications in refractory material production. Additive manufacturing methods enable the achievement of high temperatures and the production of homogeneous, single-phase solid solutions, making them suitable for fabricating refractory materials with high melting points.Öğe A review of soft magnetic properties of mechanically alloyed amorphous and nanocrystalline powders(Springernature, 2023) Yakın, Alican; Şimşek, Tuncay; Avar, Barış; Şimşek, Telem; Chattopadhyay, Arun K.The development of soft magnetic materials is fundamentally important for improving operational efficiencies of the ever-growing field of power electronics, electrical motors, and generators. It requires to meet the challenges of constantly changing fields of modern areas of applications starting from spaceships to day-to-day electronics. Many new materials with soft magnetic properties, viz. ferrous alloys, soft ferrites, amorphous and nanocrystalline magnetic alloys, have been continuously evolving since the inception of electromagnetic induction. The main drive for the continuous improvements of soft magnetic materials is primarily to enhance energy efficiency, to reduce size and weight, and to boost the power of high-frequency power electronics and electrical machines of high rotational speed. Despite some predicaments, the amorphous and nanocrystalline soft magnetic materials have become a field of major research interest since their invention four decades ago. It has been observed that the amorphous and nanocrystalline alloys exhibit better magnetic properties than the conventional soft magnetic alloys. This group of materials is produced adapting various production techniques. In this review, amorphous, nanocrystalline, and high entropy alloys (HEA) are discussed as soft magnetic materials and their electromagnetic properties are assessed. However, this review will particularly focus on the mechanically alloyed amorphous, nanocrystalline, and HEA soft magnetic materials. The soft magnetic alloys of interest for this review are grouped on the basis of Fe, Co, Ni, and FeCoNi. Furthermore, the effect of MA parameters and subsequent annealing processes on the magnetic properties is also assessed. This review brings forth a great promise in the field of soft-core magnets for high-end applications.Öğe A single step synthesis by mechanical alloying and characterization of nanostructured Fe2B of high magnetic moment(Elsevier Sci Ltd, 2021) Şimşek, Telem; Avar, Barış; Şimşek, Tuncay; Yıldız, Büşra; Chattopadhyay, Arun K.; Özcan, ŞadanThis paper delineates a single-step production method of nanostructured diiron boride (Fe2B) and its structural, magnetic and magnetothermal properties. Structurally Fe2B resembles the tetragonal copper aluminide, CuAl2. The samples of nanostructured Fe2B were synthesized by milling Fe and B powders without any pre-treatment. Single phase Fe2B nanoparticles were successfully produced with the crystallite sizes of 68 and 46 nm after milling the powders for 10 h and 20 h, respectively. The saturation magnetization of the samples was found to decrease with increased milling time indicating that the surface spin disorder plays a crucial role in the magnetic properties. The highest saturation magnetization (Ms) of 141 emu/g with low coercivity (Hc) of 48 Oe was obtained for the 10 h milled sample of Fe2B, whereas the 20 h milled sample exhibited Ms and Hc as 129 emu/g and 149 Oe. This paper also presents a detailed information on the total and atom projected densities of state functions as well as the magnetic moment contribution of the individual atoms of Fe and B in Fe2B explaining the strong room temperature ferromagnetic properties contributed by the large number of unpaired 3 d electrons in Fe. The magnetothermal properties of the as-made Fe2B nanocrystals of high magnetic moment were investigated by measuring the rise in temperature as a function of time in the presence of AC magnetic fields. The magnetic Fe2B nanocrystals show significant thermal response with the high specific absorption rate of 172 W/g, demonstrating the advantages of using Fe2B nanocrystals for the application in magnetic fluid therapy for hyperthermia.Öğe Activity of nanosized copper-boron alloys against Phytophthora species(Springer, 2024) Yiğit, Uğur; Türkkan, Muharrem; Ilhan, Hasan; Şimşek, Tuncay; Güler, Ömer; Derviş, SibelThis study aimed to evaluate the antifungal activity of copper-boron (Cu-B) nanoalloys against a range of Phytophthora species, including P. capsici, P. citrophthora, P. palmivora, P. cinnamomi, P. nicotianae, P. cactorum, P. plurivora, P. inundata, and P. megasperma. The nanoalloys were synthesized via mechanical alloying under an argon atmosphere, resulting in the formation of nanocrystalline Cu-B nanoalloys with irregular morphology and particle sizes ranging from 50 to 240 nm. At a concentration of 250 mu g mL(-1), the Cu-B nanoalloys demonstrated complete inhibition of mycelial growth, sporangium production, and zoospore germination in all tested Phytophthora species. The EC50 values for mycelial growth ranged from 28.02 to 120.17 mu g mL(-1), while for sporangium production and zoospore germination, they were below 10 mu g mL(-1). Furthermore, the nanoalloys exhibited fungicidal activity against specific Phytophthora species, such as P. capsici, P. citrophthora, P. inundata, and P. megasperma, at concentrations of 100, 250, 250, and 250 mu g mL(-1), respectively. Notably, the Cu-B nanoalloys displayed significant protective and curative effects on tuber rot severity in P. nicotianae-inoculated potatoes, resulting in reductions of 94.13% and 92.61% compared to the control, respectively, at a concentration of 10 mu g mL(-1) (P < 0.05). These findings highlight the potential of Cu-B nanoalloys as a promising fungicide for the management of plant diseases caused by Phytophthora spp.Öğe Correction: Experimental investigation of the effects of different quaternary elements (Ti, V, Nb, Ga, and Hf) on the thermal and magnetic properties of CuAlNi shape memory alloy (Journal of Materials Research, (2022), 37, 14, (2271-2281), 10.1557/s43578-022-00625-y)(Springer Nature, 2022) Özkul, İskender; Karaduman, Oktay; Şimşek, Telem; Şimşek, Tuncay; Canbay, Canan Aksu; Ibrahim, Pshdar Ahmed; Arpa, İpek AkThis article was updated to correct İpek A. K. Arpa’s name. © The Author(s), under exclusive licence to The MaterialsResearch Society 2022.Öğe Emerging of high entropy alloy reinforced composites radiation shielding materials: Configurational structure and radiation shielding properties(Elsevier Ltd, 2025) Uyar, Esra; Pul, Muharrem; Akay, Defne; Şimşek, TuncayIn this study, equimolar high entropy FeCoNiCrNb nanocrystal material was added to 2024 quality aluminum alloy with powder metallurgy technique at 2 %, 4 %, 8 %, 16 %, 32 % and 64 % weight ratios to obtain nanocomposite structures. The microstructures of the obtained composite samples were examined by SEM imaging, elemental distributions by EDS analysis and phase structures by XRD analysis techniques. Then, in order to examine the radiation shielding feature, measurements were carried out with HPGe detector using 241Am, 133Ba, 57Co, 137Cs, 54Mn, and 60Co point sources with gamma energy in the energy range of 59.5 keV-1332.5 keV. In the final stage of the study, a series of mechanical property assessments were conducted on the nanocomposite structures, including hardness measurements, compressive strength tests and abrasive wear tests. In SEM examinations, it was observed that there was homogeneity in the surface grain distribution and the homogeneity gradually improved with the increase in the FeCoNiCrNb reinforcement ratio. However, it was determined that the increasing reinforcement amount caused agglomeration in places. The chemical presence of main matrix aluminum and high entropy reinforcement elements was determined by EDAX analysis. From the XRD analyses of composite structures, it has been determined that the Al phase is the dominant phase within the structure, the HEA alloy maintains its stability, and no interphase has formed between the HEA alloy and the main matrix. According to the linear attenuation coefficient, radiation protection efficiency, mean free path, and half value layer data obtained from this experimental study, it was concluded that the high entropy FeCoNiCrNb material provides a large amount of gamma-ray radiation shielding property, especially in the low energy region (92 % shielding efficiency at 59.5 keV, 76 % at 81 keV). Additionally, it has been determined that the hardness, compressive strength and abrasive wear resistance of composite structures are increased with the addition of high entropy FeCoNiCrNb. © 2024 Elsevier B.V.Öğe Mekanik Alaşımlama ile Sentezlenen Eş-molar Fe-Si-Cu/Nb (at.%) Nanokristallerinin Yapısal, Morfolojik ve Manyetik Özelliklerinin Araştırılması(2023) Güler, Seval Hale; Şimşek, TuncayBu çalışmada mekanik alaşımlama yöntemi ile Argon atmosferi altında eş molar nanokristal Fe-Si-Cu (at.%) ve Fe-Si-Nb (at.%) alaşımları sentezlenmiştir. Deney parametreleri 350 rpm, 10:1 BPR, 120 saat olarak belirlenmiştir. Sentezlenen alaşımların faz yapıları X-Işınları difraktometresi ile, morfoloji ve elementel analizleri SEM-EDS ile, manyetik özellikleri ise oda sıcaklığında titreşimli örnek manyetometresi (VSM) tekniği ile araştırılmıştır. Fe-Si-Cu alaşımının kristalit boyutu öğütme başlangıcı, 30, 60 ve 120 saat öğütme sonrası sırasıyla 102.3, 22.5, 15.9 ve 8.6 nm, örgü gerinimleri ise % 0.164, % 0.510, %0.672 ve %1.165 olarak bulunurken, Fe-Si-Nb alaşımı için ise kristalit boyutlar 140.8, 42.9, 16.8 ve 7.8 nm, örgü gerinimleri ise % 0.134, % 0.301, % 0.639 ve % 1.271 olarak hesaplanmıştır. Manyetizma sonuçlarına göre, Fe-Si-Cu (at.%) alaşımının doyum manyetizasyonu (Ms) 3146 emu/g olarak bulunurken, Fe-Si-Nb (at.%) alaşımının doyum manyetizasyonu 8.91 emu/g olarak bulunmuştur. Fe-Si alaşım sistemine Nb katkısının kuarzivite değerlerinde artışa sebep olduğu belirlenmiştir.
