Sürdürülebilir Kalkınma Amaçları

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Araştırmacılar(7)

• Angur, G. Ersever
• Aydın, Ekrem
• Doğan, Fatih
• Erust, Ceren
• Kanca, M. Sait
• Tam, Gürkan
• Uysal, Turan

• MakaleYalnız künye2027Scopus SJRQ2/r/munzur/1135
  Design, structural characterization, and simulated radiation-transport assessment of high-entropy (GdErSmEuYb)2X2O7 (X = Hf, Zr, Ce, Si) rare-earth oxides

  Güler, Ömer; Güler, Seval Hale; Yayla, Nihal; Baykal, Duygu Sen; Durmus, Hasan; Tekin, Huseyin Ozan; ALMisned, Ghada

  This study investigates the structural, microstructural, surface-chemical, and radiation attenuation behaviour of high-entropy rare-earth oxide (HEO) powder compositions synthesized as TBC-related candidate coating materials, whose radiation attenuation potential was assessed within a computational Inconel-718-based sandwich model. Four compositions, namely (GdErSmEuYb)2Hf2O7, (GdErSmEuYb)2Ce2O7, (GdErSmEuYb)2Zr2O7, and (GdErSmEuYb)2Si2O7, were synthesized via high-energy ball milling followed by calcination at 1200 °C. X-ray diffraction results revealed the formation of distinct crystal structures depending on B-site chemistry, including defective fluorite and silicate-type phases. SEM-EDS mapping confirmed homogeneous elemental distribution, while XPS analysis demonstrated mixed valence states and different oxygen vacancy concentrations across the compositions. To evaluate radiation attenuation performance, a sandwich-type geometry consisting of a 10 mm Inconel-718 core with symmetrically defined simulated HEO layers was modelled using Monte Carlo simulations. Gamma-ray transmission was analyzed over an energy range of 0.276-1.332 MeV, and fast neutron attenuation was assessed at 4.5 MeV. The results showed that transmission factors decreased with increasing coating thickness, with the effect being more pronounced at lower photon energies. Among the investigated compositions, the Hf-based system exhibited the most favorable predicted attenuation response for both gamma rays and fast neutrons under the defined simulation conditions. Theoretical half-value layer calculations also showed good agreement with the simulation results. Overall, the findings indicate that high-entropy rare-earth oxide coatings may provide an additional radiation attenuation contribution when incorporated as layers in Inconel-718-based systems. However, since direct thermal-barrier properties such as thermal conductivity, thermal diffusivity, thermal cycling resistance, and thermal-stress behavior were not evaluated in the present work, the present study should be interpreted as a structural and radiation-transport assessment of TBC-related coating candidates rather than a direct demonstration of thermal-barrier performance.

  İncele
• MakaleYalnız künye2026Scopus SJRQ1/r/munzur/4915
  Influence on the thermoelectric characteristics of the growth parameters of BiSeTe thin films

  Yüzüak, G. Durak; Yüzüak, E.

  This study systematically investigates the influence of magnetron sputtering parameters on the structural, electronic, and thermoelectric properties of 100 nm thick Bi2SexTe3-x thin films deposited on Si(100). The initial parameters for applied film deposition are used to set the x value. The films are fabricated with sputtering powers ranging from 30 to 100 W and pressures from 3 to 15 mTorr, with films grown under optimal conditions selected for post-deposition annealing at 523 K. A comprehensive characterization suite, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and Kelvin probe force microscopy (KPFM), is used to establish direct correlations between processing, structure, and performance. XRD analysis reveals that increasing the sputtering pressure from 3 to 15 mTorr was critical for enhancing film crystallinity and promoting a strong (015) preferred orientation, while AFM showed a corresponding increase in average grain size from similar to 46 to similar to 60 nm via heat treatment (HT). EDS shows that films grown at 10 mTorr were almost certainly stoichiometric, but increasing the power to 15 mTorr caused tellurium deficiency. The films exhibited a power factor ranging from 2.5 to 2.8 mW m(- 1) K- 2 at 40 degrees C. HT improved the Seebeck coefficient from -115 mu V K- 1 to -140 mu V K- 1 and decreased the electrical resistivity by over 25 % through defect reduction and enhanced crystalline order. KPFM supported these findings, directly linking the crystallographic texture to the surface electronic structure and enhanced Seebeck effect.

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  AtıfWoS2·OpenAlex2

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• MakaleYalnız künye2026Scopus SJRQ2/r/munzur/4866
  Practical one-step solvothermal synthesis of photoactive lanthanum(III)hydroxide-metaborate composite nanosheets with suitable band gap for optoelectronics

  Karaduman, Oktay

  Rare earth compounds, including lanthanide hydroxides, have been greatly interested for their promising uses, such as in optoelectronics or photonics, due to their unique electronic and optical transitions properties based on their 4f electron shells. In this work, for the first time new transparent flower-like lanthanum(III)hydroxide (La(OH)3) with borate (LaB3O6) composite nanosheets having a semiconducting band gap suitable for optoelectronics were synthesized by a very simple one-step solvothermal method from a mixture of pure lanthanum oxide and boron without using water or any acidic solvent or surfactant. The practical synthesis was made for two different solvothermal time durations. The synthesized nanocomposites were investigated by XRD, FIB-SEM imaging, EDS, FTIR, UV-vis absorbance, Raman, Ellipsometry, and TG-DTA analyses. The pure precursors lanthanum oxide (La2O3) and boron converted to La(OH)3 and LaB3O6. EDS elemental mapping showed the homogeneous distribution of elements in the nanocomposites. A strong deep-UV absorbance band was detected. The very low reflectance and excellent visible transmittance (exceeding 86% for the sample with a longer solvothermal process time) reaching infrared region were achieved. The direct and indirect band gap energies were estimated by the Tauc plot method for both of the composite samples. Adding boron reduced the literature given direct band gap value (around 4.5-5.5 eV) of pure La(OH)3. DTA and TGA results revealed the steps of mass losses, including decomposition of La(OH)3. FTIR analyses confirmed the presence of the formed compounds. All results showed that the La(OH)3+LaB3O6 nanocomposites can be suitably used in related applications, including electro-optic, photonic, solar cell, catalysts etc.

  İncele
• MakaleAçık Erişim2026/r/munzur/6103
  The New Dynamic of Global Competition: The Technological Utilization of Rare Earth Elements and Their Impact on International Relations

  Durmuş, İrfan; Tam, Gürkan

  Aim: This study aims to analyze the technological utilization, global reserve distribution, and production structures of rare earth elements (REEs), as well as the structural concentration and vulnerability of their supply chains, and to evaluate their implications for international relations, geopolitical power dynamics, and economic dependency. The study examines the strategic consequences of China’s dominance in global REE production and processing and develops policy recommendations regarding Türkiye’s potential integration into global value chains. Method: The research is designed as a secondary-data-based study employing a structured descriptive and comparative content analysis. Quantitative and qualitative datasets obtained from internationally recognized institutions, including the International Energy Agency (IEA), the U.S. Geological Survey (USGS), European Commission reports, and relevant national authorities, were systematically analyzed to assess reserve distribution, production concentration, and sectoral utilization patterns. Results: The findings demonstrate that REEs have evolved beyond their role as industrial raw materials and have become strategic instruments of global power projection. The high concentration of global production and processing capacity in China generates significant supply security risks and structural economic dependencies for advanced economies. While Türkiye’s declared reserve potential in Beylikova represents a substantial strategic opportunity, limitations in domestic processing capacity and high value-added manufacturing constitute major structural challenges. Conclusion: REEs have emerged as strategic commodities at the center of twenty-first-century geoeconomic competition, particularly in the contexts of energy transition, defense industries, and digital technologies. Ensuring sustainable supply security requires not only reserve diversification but also the development of refining capabilities, recycling technologies, and multilateral cooperation mechanisms. Türkiye’s ability to position itself as a reliable actor in global REE markets depends on the formulation of an integrated national strategy. Originality: This study contributes to the literature by approaching REEs through an interdisciplinary framework that integrates technological, geoeconomic, and international relations perspectives, thereby moving beyond purely geological or technical analyses.

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• MakaleYalnız künye2026Scopus SJRQ2/r/munzur/4383
  An integrated process for rare earth elements recovery and silica production from Turkish bauxite-related ores

  Uysal, Turan; Erüst, Ceren; Erdemoglu, Murat; Sis, Hikmet

  The evaluation of bauxite-associated shales as a secondary source of rare earth elements (REEs) is strategically important for securing a sustainable supply of critical raw materials used in advanced technologies. In this study, shale ore associated with bauxite, unsuitable for aluminium production due to its high silica content, was investigated as a potential resource for valuable REEs. The effect of thermal activation on REE recovery was examined, and the potential use of the leach residue as a silica source was assessed. Based on acid leaching results, the optimum calcination temperature was identified as 700 degrees C. Under these conditions, high REE recoveries were achieved: 92.9% La, 89.9% Ce, 89.0% Pr, 88.7% Nd, and 73.0% Sm. After leaching, the residue was enriched in alumina and silica. To improve silica purity and recover remaining REEs and Al, a second-stage leaching process was applied. This resulted in a byproduct containing 55% SiO2 with a specific surface area of 48 m2 g-1, indicating its potential as a silica source. The results demonstrate that bauxite-associated shale can be sustainably valorised through intensive milling, calcination, and acid leaching, enabling efficient REE recovery and the production of a silica-rich byproduct. L'& eacute;valuation de schistes associ & eacute;s & agrave; la bauxite comme source secondaire d'& eacute;l & eacute;ments de terres rares (ETR) est strat & eacute;giquement importante pour garantir un approvisionnement durable en mati & egrave;res premi & egrave;res critiques utilis & eacute;es dans les technologies avanc & eacute;es. Dans cette & eacute;tude, on a examin & eacute; le minerai de schiste associ & eacute; & agrave; la bauxite, inappropri & eacute; & agrave; la production d'aluminium en raison de sa teneur & eacute;lev & eacute;e en silice, comme ressource potentielle d'ETR pr & eacute;cieux. On a examin & eacute; l'influence de l'activation thermique sur la r & eacute;cup & eacute;ration des ETR et l'on a & eacute;valu & eacute; l'utilisation potentielle du r & eacute;sidu de lixiviation comme source de silice. D'apr & egrave;s les r & eacute;sultats de la lixiviation acide, on a identifi & eacute; la temp & eacute;rature optimale de calcination & agrave; 700 degrees C. Dans ces conditions, on a obtenu des r & eacute;cup & eacute;rations d'ETR & eacute;lev & eacute;es: 92.9% de La, 89.9% de Ce, 89.0% de Pr, 88.7% de Nd et 73.0% de Sm. Apr & egrave;s la lixiviation, le r & eacute;sidu & eacute;tait enrichi en alumine et en silice. Afin d'am & eacute;liorer la puret & eacute; de la silice et de r & eacute;cup & eacute;rer les ETR et l'Al restants, on a appliqu & eacute; une deuxi & egrave;me & eacute;tape de lixiviation. Cela a engendr & eacute; un sous-produit contenant 55% de SiO2 et pr & eacute;sentant une surface sp & eacute;cifique de 48 m2/g, indiquant son potentiel en tant que source de silice. Les r & eacute;sultats d & eacute;montrent que le schiste associ & eacute; & agrave; la bauxite peut & ecirc;tre valoris & eacute; de mani & egrave;re durable par broyage intensif, calcination et lixiviation acide, permettant une r & eacute;cup & eacute;ration efficace des ETR et la production d'un sous-produit riche en silice.

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  İncele
• MakaleYalnız künye2026Scopus SJRQ1/r/munzur/1523
  Compositionally segmented thermoelectric BiSbTe thin films on Cr/Si(100)

  Yüzüak, G. Durak; Yüzüak, E.

  Compositionally segmented thermoelectric (CS-TE) structures improve thermal energy conversion efficiency across large thermal gradients. However, their increased design complexity complicates performance modeling and optimization. In this study, we fabricate CS-TE BiSbTe thin films on Cr-buffered Si(100) substrates. By adopting a multidisciplinary approach, we aim to broaden the technological applicability and strategic relevance of advanced TE systems. We systematically analyze the influence of deposition pressures (5, 7, and 10 mTorr) on TE performance. Variations in working pressure alter the Bi/Sb atomic ratio in the films, while the Te content remains stable. This enables the controlled formation of CS structures. At 323 K, the power factor (PF) of TE thin films reaches 0.7, 2.4, and 7.3 mW/mK2 under 5, 7, and 10 mTorr deposition conditions, respectively. The Cr-buffered layer significantly improves the electrical conductivity of CS-TE BiSbTe films. We further engineer a p-type single-leg device integrating nanostructured Bi0.35Sb1.65Te3, Bi0.37Sb1.63Te3, and Bi0.4Sb1.60Te3 layers. These materials are optimized to achieve peak TE PF values across a wide temperature range (320 to 500 K) while ensuring robust interfacial adhesion. The CS-TE device generates 3 mW/cm2, showing a 15% improvement over single-composition samples at a 100 K temperature difference.

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  AtıfScopus3·WoS3·OpenAlex2

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• MakaleAçık Erişim2026Scopus SJRQ2/r/munzur/1513
  Microstructure and Dry-Sliding Tribology of HVOF-Sprayed NiCrBSi/WC-Co Coatings on AZ91D

  Gürgenç, Turan; Macit, Cevher Kürşat; Sömer, Medeni; Aksakal, Bünyamin; Ayık, Merve; Say, Yakup

  High-velocity oxy-fuel (HVOF)-sprayed NiCrBSi coatings containing 0, 10, 30, and 50 wt.% WC-Co were evaluated on AZ91D magnesium alloy to determine how the discrete reinforcement level affects surface topography, phase constitution, Vickers microhardness, dry-sliding friction, mass loss, and wear-track microchemistry. As-sprayed surfaces were characterized by three-dimensional profilometry; coating cross-sections and worn surfaces by optical microscopy and SEM/EDS; phase constitution by XRD; and mechanical response by HV0.1 indentation. Dry-sliding tests were performed at 10, 30, and 50 N over 100–1000 m. Increasing WC-Co content raised Sa from 8.8 ± 0.3 to 13.0 ± 0.5 µm and Vickers microhardness from 776 ± 4 to 959 ± 5 HV0.1. XRD indicated a γ-Ni-based matrix containing boride/carbide constituents, while WC, W2C, and Co became increasingly prominent in the reinforced coatings. Boride assignments are based on diffraction evidence, whereas B and C EDS signals were treated semi-quantitatively. The 50 wt.% WC-Co coating exhibited the lowest mass loss and mean coefficient of friction at every load. Its mean friction coefficients were 0.31, 0.35, and 0.41 at 10, 30, and 50 N, corresponding to reductions of 40.1%, 38.9%, and 36.2% relative to AZ91D. At 1000 m, its mass-normalized wear rate indices were 9.0 × 10−4, 4.0 × 10−4, and 5.3 × 10−4 mg N−1 m−1, respectively. Post-wear mapping showed the largest field-scale W-Co-rich fraction in the 50 wt.% coating; however, isolated spectra containing more than 94 wt.% Mg are compatible with local coating penetration/substrate exposure and/or Mg-rich debris. The 50 wt.% composition therefore provided the best combined response among the four tested levels, while intermediate compositions are required to identify a continuous-composition optimum.

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• MakaleYalnız künye2026Scopus SJRQ1/r/munzur/1499
  Impact of hybrid Er2O3 and B4C additions on structural characteristics and experimental gamma-ray transmission behavior of Ni–Co–Fe–Cr–Mo high-entropy alloys

  Özkul, İskender; Güler, Ömer; Durmus, Hasan; Camgoz, Berkay; ALMisned, G.; Yaprak, Gunseli; Tekin, H.O.

  This study examines how Er2O3 and B4C additions affect the structural, microstructural, mechanical, and gamma-ray attenuation behaviour of Ni–Co–Fe–Cr–Mo high-entropy alloy composites. Five samples, labelled S0–S4, were produced by vacuum arc melting with different single and combined reinforcement contents. Thermodynamic calculations showed that the metallic matrix meets the general conditions expected for solid-solution HEA formation. XRD results indicated that an FCC-based matrix remained dominant in all samples. Reflections related to Er2O3 were identified in the Er2O3-containing compositions, while several weak secondary reflections could not be assigned with certainty because of their low intensity and peak overlap. SEM-EDS analysis confirmed the presence of Er-, O-, B-, and C-containing regions and also revealed local compositional variations within the microstructure. The reinforcement additions produced a clear increase in microhardness, with the highest value of 693 ± 51 HV0.5 obtained for the hybrid-reinforced S3 sample. Gamma-ray attenuation was measured at 276, 302, 356, and 383 keV using a high-purity germanium (HPGe) detector under narrow-beam condition. S4 showed the lowest nominal transmission factor at most energies at its actual sample thickness. However, after correcting for thickness using the Beer-Lambert relationship, S2 generally showed the highest nominal linear attenuation coefficient, while S4 gave closely comparable values at several energies. Some of the differences between samples were within the propagated counting uncertainties and were therefore interpreted with caution. Overall, the results show that the composition giving the highest hardness does not necessarily provide the strongest thickness-normalized gamma-ray attenuation. The attenuation behaviour is influenced by several factors, including reinforcement composition, sample thickness, density, phase distribution, microstructural heterogeneity, and measurement uncertainty. These findings highlight the need to optimize reinforced HEA composites according to the specific mechanical and radiation-related property being targeted.

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• MakaleYalnız künye2026Scopus SJRQ1/r/munzur/1486
  Exploring the photocatalytic potential of NbTiZrW-based high-entropy alloys with Hf/Mo/Ta additions: Influence of alloying elements on their structural and photocatalytic performance

  Zakir, O.; Guler, O.; Idouhli, R.; Aklalouch, M.; Dikici, B.; Khadiri, M.E.; Abouelfida, A.; Selen, V.; Şimşek, T.

  In this study, the photocatalytic performance of NbTiZrW-based high-entropy alloys (HEAs) with Hf, Mo, and Ta additions was investigated. The alloys were synthesized by mechanical alloying for 120 h under a high-purity Ar atmosphere to prevent oxidation. The photocatalytic activity of the samples was evaluated based on the degradation of methylene blue (MB) under UV irradiation. Structural and chemical characterizations were performed using energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The results showed that MB removal by adsorption reached 22.96 % for NbTiZrWHf, 21.90 % for NbTiZrWTa, and 47.01 % for NbTiZrWMo. The incorporation of Mo into the NbTiZrW alloy was found to enhance electrostatic interactions between MB molecules and the alloy surface. Upon UV irradiation, the degradation efficiency increased significantly, reaching 32.84 % for NbTiZrWHf, 82.02 % for NbTiZrWTa, and 46.13 % for NbTiZrWMo within 3 h. The improved performance of the NbTiZrWHf alloy was attributed to its low particle size, which provided a larger number of active sites for photocatalytic activity, as confirmed by SEM analysis.

  AtıfScopus1·OpenAlex1

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• MakaleAçık Erişim2026Scopus SJRQ2/r/munzur/1455
  Comparative Microstructural, Mechanical, and Tribological Evaluation of Cu Matrix Composites Reinforced with B4C, B, Cr, Co, Al2O3, and Graphite via Powder Metallurgy

  Macit, Cevher Kursat; Gürgenç, Turan; Aksakal, Bunyamin; Aslan, Naim

  Copper and its alloys are widely used in electrical, automotive, aerospace, and energy applications because of their excellent thermal and electrical conductivity. However, the low hardness and poor wear resistance of pure Cu limit its use under tribologically demanding sliding conditions. In this study, Cu matrix composites reinforced with 1 wt.% boron carbide (B4C), boron (B), chromium (Cr), cobalt (Co), alumina (Al2O3), and graphite (Gr) were fabricated by powder metallurgy and comparatively evaluated under identical processing and testing conditions. Phase constitution and microstructural characteristics were analyzed by XRD, SEM, and EDS, while mechanical and tribological behavior was assessed by Vickers hardness and dry sliding wear tests. All reinforcements improved the hardness of the Cu matrix compared with unreinforced Cu. The hardness increase followed the order Cu–B4C (68.91%) > Cu–B (66.43%) > Cu–Gr (63.97%) > Cu–Al2O3 (61.79%) > Cu–Cr (42.69%) > Cu–Co (36.04%). Dry sliding wear tests, performed under a 10 N normal load, 0.05 m s−1 sliding speed, and 1000 m sliding distance against a 316L stainless-steel ball, showed that all reinforced composites exhibited lower mass loss and more stable sliding behavior than pure Cu. Among all samples, Cu–B4C displayed the best wear performance, with a 154.8% improvement in wear resistance relative to pure Cu. SEM analysis of the worn surfaces revealed that reinforcement addition reduced severe plastic deformation, groove formation, and delamination, leading to a more stable wear regime. Graphite- and boron-containing composites benefited from interfacial lubrication and contact stabilization, whereas B4C and Al2O3 improved wear resistance through rigid-particle strengthening and enhanced load-bearing capacity. By comparing ceramic, metalloid, metallic, oxide, and solid-lubricating reinforcements at the same low addition level and under identical processing and testing conditions, this study provides a reinforcement-selection framework for Cu-based composites requiring improved hardness and dry-sliding durability.

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