Research Project: Kobalt-Metal-Bor (Metal=Ni,Fe,Ti) Esaslı Üçlü Metal Borürlerin Klorür Hammaddelerden Alternatif Düşük Sıcaklık Yöntemleri İle Sentezi, Karakterizasyonu Ve Katalizör/Magnet/Hibrit Kompozit Üretimi Alanlarına Yönelik Uyguylama Çalışmaları
Loading...
Contributors
Funders
ID
TB.00331
Authors
Balcı, Özge
Researcher
Publications
Cob-tib2 crystalline powders: synthesis, microstructural analysis and their utilization as reinforcement agent
(Elsevier, 2020) Altıntaş, Zerrin; Balcı, Özge; Khoshsima, Sina; Somer, Mehmet Suat; Burkhardt, Ulrich; Schmidt, Marcus; Prashanth, K. G.; Department of Chemistry; KUBAM (Koç University Boron and Advanced Materials Application and Research Center); Yes; College of Sciences; Research Center
Due to promising mechanical and chemical properties, transition metal borides have attracted attention, and numerous studies have investigated various combinations of transition elements in hopes of acquiring a final product with desired properties combined. In this study, novel low-temperature approach was adopted for the synthesis of cobalt-titanium-boron based crystalline powders. The method was based on the single-step direct reaction of CoCl2(s), TiCl4(l) and NaBH4(s) in a sealed reactor under autogenic pressure. After the reaction of the precursors at 850 degrees C by using the molar ratios of metal chlorides to NaBH4 as 1:3, CoB and TiB2 phases were formed in-situ. The subsequent annealing process at 1100 degrees C achieved a full conversion of metal chlorides to CoB-TiB2 composite nanostructures. It was concluded that the binary forms of the borides tend to form as separate phases, which is illustrated in the SEM/EDS analyses with different morphologies. Amorphous boron layer surrounded TiB2 particles with an average particle size of 60 nm, whereas the CoB particles formed agglomerates with an average size of 450 nm. The use of synthesized composite powders as reinforcement in metal matrices resulted in enhanced hardness (506 HV) and compressive strength (1682 MPa) of the Ti6Al4V bulk samples.
Crystalline Co–Fe–B nanoparticles: synthesis, microstructure and magnetic properties
(Elsevier, 2019) Khoshsima, Sina; Altıntaş, Zerrin; Somer, Mehmet Suat; Balcı, Özge; Schmidt, Marcus; Bobnar, Matej; Department of Chemistry; KUBAM (Koç University Boron and Advanced Materials Application and Research Center); Yes; College of Sciences; Research Center
A new approach for in-situ synthesis of crystalline Co–Fe–B nanoparticles was presented in which low temperature methods were developed by using metal chlorides and NaBH4 in an inorganic molten salt environment. Effects of different reaction systems/conditions on the phase formation, thermal behavior and microstructure were investigated. The melting point of reactants and impurities in final powders were reduced by the use of molten salt technique. After a reaction of CoCl2, FeCl3 and NaBH4 at 850 °C in sealed tubes, CoB and Fe3B phases formed separately. After a reaction under Ar flow; however, CoFeB2 solid solution nano powders were obtained in one step at 850 °C with an average size of 60 nm. After annealing at 1100 °C, stable and highly crystalline (CoFe)B2 solid solution phase with a Co:Fe molar ratio of 1:1 was achieved. As-synthesized particles exhibited ferromagnetic property, and possessed a narrow hysteresis curve characteristic of soft magnetic materials. Extended reaction temperature from 650 to 850 °C is seen to produce coercivity enhancement up to 500 Oe without significant reduction in saturation magnetization. On the other hand, after an annealing process and subsequent phase and chemical change, crystalline (CoFe)B2 particles exhibited superparamagnetic property.
Low-cost and reusable iron- and nickel-based metal boride nanoparticles for efficient catalytic hydrolysis of sodium borohydride
(Elsevier, 2022) Balcı, Özge; Öztulum, Samira Fatma Kurtoğlu; Paksoy, Aybike; Yağcı, Mustafa Barış; Department of Chemistry; Graduate School of Sciences and Engineering; KUBAM (Koç University Boron and Advanced Materials Application and Research Center); KUYTAM (Koç University Surface Science and Technology Center); Department of Chemical and Biological Engineering; KUTEM (Koç University Tüpraş Energy Center); No; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center; College of Engineering
Development of efficient catalysts for hydrogen evolution reaction is of key importance for the safe storage and utilization of hydrogen from the hydrolysis of NaBH4. In this study, a series of nanocatalysts containing iron-and nickel-based metal borides were developed through a mechanochemical route followed by a wet milling step. The use of the mole ratio of metal chlorides to NaBH4 as 1:2 enabled the simultaneous formation of Ni3B and FeB phases, while the room-temperature synthesis method caused a uniform morphology with an average particle size and surface are of 70 nm and 41.8 m2/g, respectively. This powder showed the best catalytic performance compared to other samples with a hydrogen gen-eration rate value of 758 ml H2 min-1 gcat-1 at room temperature and an activation energy of 40.8 kJ/mol. The catalyst performed good durability for each cycle and retained about 70% of its initial catalytic activity after 5 cycles. The availability of active iron, nickel, and boron species on the surface contributed to the enhancement of catalytic activity. As -prepared catalysts can be considered as low-cost and reusable materials for the efficient hydrolysis of sodium borohydride.
