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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.Öğe Solid-State Synthesis and Characterization of the Stable Nanostructured Ni21Ti2B6 Phase(Wiley-V C H Verlag Gmbh, 2021) Şimşek, Tuncay; Avar, Barış; Özcan, Şadan; Chattopadhyay, Arun K.; Kalkan, BoraHerein, nanostructured ternary Ni-Ti-B alloy synthesized by mechanical alloying from the elemental Ni, Ti, and B powders by high energy ball milling is described. The synthesized alloy of nominal composition of Ni70Ti10B20 results in the formation of a unique stable phase of Ni21Ti2B6, which happens to be stoichiometrically very close to Ni70Ti10B20 in the cubic symmetry. The synthesized alloy samples also show amorphization together with the formation of nanocrystalline phases of Ni21Ti2B6 at both early and later stages of the alloying process. Thermal analysis carried out on Ni70Ti10B20 induces crystallinity and reveals the formation of crystalline Ni-Ti-B ternary alloy, Ni21Ti2B6, above 523 K, confirming the stability of the ternary crystalline phase of the alloy. The magnetic saturation of the alloy is measured as 0.95 emu g(-1) for the starting amorphous phase that increases to 9.05 emu g(-1) for the crystalline phase upon annealing. Correspondingly, the coercivity value for the annealed sample is reduced to 70 Oe from 194 Oe for the amorphous phase. This is the first time that an evidence of the stable crystalline Ni-Ti-B ternary alloy is reported.Öğe Structural stability of mechanically alloyed amorphous (FeCoNi)70Ti10B20 under high-temperature and high-pressure(Elsevier Science Sa, 2021) Avar, Barış; Şimşek, Tuncay; Özcan, Şadan; Chattopadhyay, Arun K.; Kalkan, BoraNanostructured (FeCoNi)(70)Ti10B20 (at%) alloy was synthesized by mechanical alloying from elemental powder mixture of Fe, Co, Ni, Ti and B using ball milling. The effect of ball milling time on the evolution of structure and morphology was investigated by X-ray diffraction, scanning and transmission electron microscopy and differential thermal analysis. It was observed that the formation of solid solution of (FeCoNi)(70)Ti10B20 started from the very onset of the milling process. Crystallite size and lattice strains seemed to be leveled off after 20 h of milling with no further major changes. The milling process for longer periods introduced severe plastic deformations causing formation of amorphous phase of (FeCoNi)(70)Ti10B20. The amorphous alloy composition was confirmed by energy dispersive X-ray spectroscopy analysis that showed an excellent homogeneity of the alloying elements. The phase stability of the mechanically alloyed amorphous sample was further verified by employing high-temperature and high-pressure studies. The alloy samples heat-treated at 700 degrees C revealed crystallization of the amorphous phase. However, synchrotron-based high-pressure ambient temperature X-ray diffraction studies confirmed that the amorphous phase of the alloy remained stable up to the pressure of 30 GPa. The 50 h milled sample after being annealed at 350 degrees C showed improvement in the soft magnetic properties of the alloy, which was due to the probable elimination of the residual stress in the amorphous phase of the alloy powders. (C) 2020 Elsevier B.V. All rights reserved.Öğe Synthesis and characterization of amorphous-nanocrystalline Fe70Cr10Nb10B10 powders by mechanical alloying(Springer Heidelberg, 2022) Avar, Barış; Chattopadhyay, Arun K.; Şimşek, Tuncay; Şimşek, Telem; Özcan, Şadan; Kalkan, BoraIn this study, structural, morphological, thermal and magnetic properties of amorphous-nanocrystalline Fe70Cr10Nb10B10 (at.%) alloy are discussed. The formation and evaluation of amorphous-nanocrystalline structures of the alloy were followed by XRD, SEM-EDX, TEM, DTA, and VSM techniques. After 50 h of milling Cr, Nb, and B were completely dissolved into the Fe lattice forming 82% of the amorphous phase of the alloy. A gradual dissolution of the alloying elements also increased the lattice parameters concurrently. The lattice parameters reached a maximum value of 2.908 angstrom after 20 h of milling and then leveled off to a value of 2.891 angstrom at the end of 50 h of milling. Based on the XRD data, crystallite size and lattice strain of the alloy were calculated as 3.2 nm and 3.34% respectively. TEM analyses revealed that the alloy particulates comprised needle-shaped nanoparticles of an average size of 21 nm. The room temperature magnetic hysteresis loops showed that the increased duration of milling decreased the saturation magnetization from 91 to 24 emu/g. This was mainly due to the upsurge on the amorphous phase content in the alloy as the milling progressed. The increase in amorphous phase content and the subsequent reduction of the saturation magnetization were due to the inter-diffusion of the non-ferromagnetic Cr and B atoms into the Fe lattice. Thermal studies revealed that around 350 degrees C the amorphous phase of the alloy began crystallizing. The magnetic saturation of the heat-treated alloy also increased with the growth in the crystalline phases. The 50 h milled sample annealed at 700 degrees C was found to have the highest magnetic anisotropy as observed from the temperature-dependent zero-field cooled and field cooled magnetization measurements. The high-pressure X-ray diffraction measurements revealed that the amorphous state of the alloy remained stable up to 11.3 MPa. It also revealed the structural similarities of the Fe70Cr10Nb10B10 alloy with those of the Fe70M10B20 (M = Nb and Cr) types. For all practical purposes, the microstructural stability under high compressive pressure represents the consolidation properties of the nanostructured magnetic materials since both pressure and temperature-induced phase transformations are the primary controlling factors for the specific magnetization properties of the alloy.Öğe Synthesis of biocompatible Ti-6Al-4V composite reinforced with ZrO2 and bioceramic produced by powder metallurgy: Morphological, structural, and biocompatibility analysis(Wiley, 2024) Pul, Muharrem; Erdem, Ümit; Bozer, Büşra Moran; Şimşek, Tuncay; Yılmazel, Rüstem; Erten, Mustafa YasinIn this experimental study, the initial phase involved preparing composite structures with various mix ratios using the Ti-6Al-4V alloy, widely used in clinical applications, in conjunction with ZrO2 and hydroxyapatite (HA) synthesized via the precipitation method, employing powder metallurgy techniques. Subsequently, the microstructures of the resultant hybrid composite materials were imaged, and x-ray diffraction (XRD) phase analyses were conducted. In the final phase of the experimental work, tests were performed to determine the biocompatibility properties of the hybrid composites. For this purpose, cytotoxicity and genotoxicity assays were carried out. The tests and examinations revealed that structures compatible both morphologically and elementally were obtained with no phase transformations that could disrupt the structure. The incorporation of ZrO2 into the Ti-6Al-4V alloy was observed to enhance cell viability values. The value of 98.25 +/- 0.42 obtained by adding 20% ZrO2 gave the highest cell viability result. The addition of HA into the hybrid structures further increased the cell viability values by approximately 10%. All viability values for both HA-added and HA-free groups were obtained above the 70% viability level defined in the standard. According to the genotoxicity test results, the highest cytokinesis-block proliferation index values were obtained as 1.666 and 0.620 in structures containing 20% ZrO2 and 10% ZrO2 + 10% HA, respectively. Remarkably, all fabricated composite and hybrid composite materials surpassed established biocompatibility standards and exhibited nontoxic and nongenotoxic properties. This comprehensive study contributes vital insights for future biomechanical and other in vitro and in vivo experiments, as it meticulously addresses fundamental characterization parameters crucial for medical device development.Öğe Synthesis of boron-based alloys and compounds by mechanical alloying: A review(Elsevier, 2023) Yakın, Alican; Avar, Barış; Şimşek, Tuncay; Chattopadhyay, Arun K.Boron and its derivatives are highly valued in many alloy systems for their ability to enhance material strength, hardness, thermoelectric properties, wear and corrosion resistance, and electromagnetic properties. Incorporating boron-based derivatives like boron nitride (BN), boron carbide (B4C), hexaborides, and metal borides into composites, amorphous alloys, high entropy alloys (HEAs), and magnetic alloys results in materials with superior properties compared to those without boron. As a result, there is growing market interest in advanced material applications of these boron-based alloys, which are utilized in diverse fields from health and automotive to space exploration, smart engineering materials, manufacturing industry, glass and ceramics, cleaning materials, hightech electronics, and modern household appliances. The use of boron and its derivatives has spurred innovation in the production of new materials, with the mechanical alloying (MA) method being a desirable option for synthesizing boron-based alloys with desired properties by adjusting alloying parameters. This review examines the properties of boron-based alloys synthesized by MA methods, providing valuable insights into the potential applications of these materials. Overall, this review provides a comprehensive survey of boron-based alloys and their potential for advanced material applications.Öğe The effect of Cr and Nb addition on the structural, morphological, and magnetic properties of the mechanically alloyed high entropy FeCoNi alloys(Springer Heidelberg, 2022) Yakın, Alican; Şimşek, Telem; Avar, Barış; Chattopadhyay, Arun K.; Özcan, Şadan; Şimşek, TuncayIn this study, four different equimolar compositions of FeCoNi, FeCoNiNb, FeCoNiCr, and FeCoNiNbCr were synthesized by the mechanical alloying method. The effects of Cr and Nb addition on the structural, morphological, and magnetic properties of FeCoNi alloy were investigated in detail. The structural aspects of the samples were analyzed by X-ray diffractometer and scanning electron microscope equipped with an energy dispersive X-ray spectrometer. High and low-temperature magnetic properties were evaluated by a vibrating sample magnetometer. It was noticed that the addition of Nb caused amorphization, while Cr promoted crystallization in the alloys. The crystallite sizes were calculated as 9.7, 3.1, 8.3, and 4.4 nm for the FeCoNi, FeCoNiNb, FeCoNiCr, and FeCoNiCrNb alloys, respectively, after 20 h of milling. The SEM images of the as-milled alloys revealed irregular and layered structures for FeCoNi and FeCoNiCr alloys of mean particle sizes around 140 and 120 mu m. In contrast, the addition of Nb in these alloys, viz. FeCoNiNb and FeCoNiNbCr alloys, formed mostly spherical with irregular morphologies of particle sizes ranging between 55 and 80 mu m. It was noticed that the low solubility of Cr caused precipitation at the grain boundaries of the alloy particles, and it contributed to the formation of hard structures of irregular and layered morphologies. The observed increase in the lattice parameters and lattice strain in the solid solution phases of all-alloy systems studied was mainly due to the lattice distortion and intense plastic deformations. The maximum saturation magnetization obtained from the room temperature hysteresis loops was 150.4 emu/g for the FeCoNi alloy after 10 h of milling. The additions of non-magnetic Cr, Nb, and both into FeCoNi, caused a significant decrease in the saturation magnetization. The coercivity of the as-milled alloys was also found to decrease with the reduction in the nano-crystallite sizes, which elucidated that the crystallite sizes of the alloys were smaller than the magnetic exchange length. The high-temperature magnetization curves revealed that all alloys studied had Curie temperature higher than 700 K.
