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Öğe Boron-Functionalized Graphene Oxide-Organic Frameworks for Highly Efficient CO2 Capture(Wiley-V C H Verlag Gmbh, 2017) Haque, Enamul; Islam, Md. Monirul; Pourazadi, Ehsan; Sarkar, Shuranjan; Harris, Andrew T.; Minett, Andrew I.; Yanmaz, EkremThe capture and storage of CO2 have been suggested as an effective strategy to reduce the global emissions of greenhouse gases. Hence, in recent years, many studies have been carried out to develop highly efficient materials for capturing CO2. Until today, different types of porous materials, such as zeolites, porous carbons, N/ Bdoped porous carbons or metal-organic frameworks (MOFs), have been studied for CO2 capture. Herein, the CO2 capture performance of new hybrid materials, graphene-organic frameworks (GOFs) is described. The GOFs were synthesized under mild conditions through a solvothermal process using graphene oxide (GO) as a starting material and benzene 1,4-diboronic acid as an organic linker. Interestingly, the obtained GOF shows a high surface area (506 m(2)g(-1)) which is around 11 times higher than that of GO (46 m(2)g(-1)), indicating that the organic modification on the GO surface is an effective way of preparing a porous structure using GO. Our synthetic approach is quite simple, facile, and fast, compared with many other approaches reported previously. The synthesized GOF exhibits a very large CO2 capacity of 4.95 mmol g(-1) at 298K (1 bar), which is higher those of other porous materials or carbon-based materials, along with an excellent CO2/N-2 selectivity of 48.8.Öğe Bulk Mgx B2 superconductor production by excess Mg and hot press methods and their properties(TENMAK Bor Araştırma Enstitüsü, 2017) Yanmaz, Ekrem; Castillo-Berrio, Claudia; Alkan, Ümit; Ülgen, Asaf Tolga; Karaboğa, Fırat; Enis, Osman; Cingi, Didem Odabaşı; Alcan, Pelin; Saraçoğlu, İlkayFour different nominal compositions MgB2 , Mg1.5B2 , Mg2 B2 and Mg2.5B2 were produced by excess Mg method and hot press. These superconducting samples were compared in terms of structural, electric and magnetic properties. The superconducting phase was determined by XRD analysis, which indicated the formation of MgB2 structure as a main matrix with some amount of nonsuperconducting phases, such as metallic Mg and minor amount of MgO. The electric properties of the samples were characterized by low temperature resistivity measurements under different magnetic fields 0.5, 1.0, 3.0 T. The results showed that the superconducting Tc,onset and Tc,offset transition temperatures moved to lower values. These results indicate that excess Mg method improves the superconducting and magnetic properties of MgB2 , as well as enhanced the rigidity and ductility of the samples. Experimental results showed the advantages of the proposed methods, established the most suitable transition temperature of the samples, as well as the decline from the superconducting to normal state.Öğe Bulk ngB2 superconductor production by excess Mg and hot press methods and their properties(2017) Yanmaz, Ekrem; Cingi, Didem Odabaşı; Alcan, Pelin; Saraçoğlu, İlkay; Berrio, Claudia Castillo; Alkan, Ümit; Ülgen, A. TolgaFour different nominal compositions MgB, MgB, MgB and MgB were produced by excess Mg method and hot press. These superconducting samples were compared in terms of structural, electric and magnetic properties. The superconducting phase was determined by XRD analysis, which indicated the formation of MgB structure as a main matrix with some amount of nonsuperconducting phases, such as metallic Mg and minor amount of MgO. The electric properties of the samples were characterized by low temperature resistivity measurements under different magnetic fields 0.5, 1.0, 3.0 T. The results showed that the superconducting Tc,onset and Tc,offset transition temperatures moved to lower values. These results indicate that excess Mg method improves the superconducting and magnetic properties of MgB, as well as enhanced the rigidity and ductility of the samples. Experimental results showed the advantages of the proposed methods, established the most suitable transition temperature of the samples, as well as the decline from the superconducting to normal stateÖğe Cyano-Bridged Trimetallic Coordination Polymer Nanoparticles and Their Thermal Decomposition into Nanoporous Spinel Ferromagnetic Oxides(Wiley-V C H Verlag Gmbh, 2016) Zakaria, Mohamed B.; Hossain, Md. Shahriar A.; Shiddiky, Muhammad J. A.; Shahabuddin, Mohammed; Yanmaz, Ekrem; Kim, Jung Ho; Belik, Alexei A.The synthesis of a novel family of cyano-bridged trimetallic coordination polymers (CPs) with various compositions and shapes has been reported by changing the compositional ratios of Fe, Co, and Ni species in the reaction system. In order to efficiently control the nucleation rate and the crystal growth, trisodium citrate dihydrate plays an important role as a chelating agent. After the obtained cyanobridged trimetallic CPs undergo thermal treatment in air at three different temperatures (250, 350, and 450 degrees C), nanoporous spinel metal oxides are successfully obtained. Interestingly, the obtained nanoporous metal oxides are composed of small crstalline grains, and the grains are oriented in the same direction, realizing pseudo-single crystals with nanopores. The resultant nanoporous spinel oxides feature interesting magnetic properties. Cyano-bridged multimetallic CPs with various sizes and shapes can provide a pathway toward functional nanoporous metal oxides that are not attainable from simple cyano-bridged CPs containing single metal ions.Öğe Mesoporous TiO2 Thin Film Formed From a Bioinspired Supramolecular Assembly(Wiley-V C H Verlag Gmbh, 2016) Wu, Yi-Chen; Lu, Y. S.; Bastakoti, Bishnu Prasad; Li, Yunqi; Pramanik, Malay; Hossain, M. Shahriar; Yanmaz, EkremIn this study we synthesize a novel mesoporous titanium oxide (TiO2) through calcination of a bioinspired supramolecular assembly of polymeric micelles, based on the thymine-functionalized homopolymer, poly(4-vinylbenzyl triazolylmethyl-methylthymine), complexed with Ti(OH)(2)(2+) ions. We characterize thin films of these structures using wide-angle X-ray diffraction, small-angle X-ray scattering, nitrogen adsorption/desorption isotherms, transmission electron microscope, and scanning electron microscope. This approach is simple, effective, and inexpensive when compared with the synthesis of diblock or triblock copolymers typically required to prepare soft templates. This new mesoporous material exhibits superior photocatalytic activity for the degradation of the organic dye methylene blue almost three times higher than that of bulk TiO2.Öğe A new approach to a superconducting joining process for carbon-doped MgB2 conductor(Iop Publishing Ltd, 2016) Patel, Dipak; Al Hossain, Md Shahriar; Maeda, Minoru; Shahabuddin, Mohammed; Yanmaz, Ekrem; Pradhan, Subrata; Tomsic, MikeWe report a new approach to a superconducting joining process for unreacted in situ carbon (C)-doped magnesium diboride (MgB2) wires. To operate a magnetic resonance imaging (MRI) magnet in the persistent mode, the superconducting joints between two conductors are as critical as the other key components. In addition, a stable and reliable joining process enables the superconducting magnet to operate without an external power supply. However, joint results using unreacted in situ C-doped MgB2 wires, which are used for high-field operation, have been limited, and only very poor performance has been obtained. By controlling the pressure inside a joint part, in this study, we successfully obtained current carrying retention in the joint of up to 72% compared to wire without a joint. The closedcircuit resistance of our closed-loop coil was less than 1.8 x 10(-13) Omega at 16.7 +/- 4.7 K, as measured by the field-decay measurement method. These results indicate that MgB2 has a promising future in MRI application.Öğe Synthesis of Cobalt Sulfide/Sulfur Doped Carbon Nanocomposites with Efficient Catalytic Activity in the Oxygen Evolution Reaction(Wiley-V C H Verlag Gmbh, 2016) Qian, Huayu; Tang, Jing; Wang, Zhongli; Kim, Jeonghun; Kim, Jung Ho; Alshehri, Saad M.; Yanmaz, EkremCobalt sulfide/sulfur doped carbon composites (Co9S8/S-C) were synthesized by calcining a rationally designed sulfur-containing cobalt coordination complex in an inert atmosphere. From the detailed transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses, the electrocatalytically active Co9S8 nanoparticles were clearly obtained and combined with the thin sulfur doped carbon layers. Electrochemical data showed that Co9S8/S-C had a good activity and long-term stability in catalyzing oxygen evolution reaction in alkaline electrolyte, even better than the traditional RuO2 electrocatalyst. The excellent electrocatalytic activity of Co9S8/S-C was mainly attributed to the synergistic effect between the Co9S8 catalyst which contributed to the oxygen evolution reaction and the sulfur doped carbon layer which facilitated the adsorption of reactants, prevented the Co9S8 particles from aggregating and served as the electrically conductive binder between each component.Öğe Zeolitic imidazolate framework (ZIF-8) derived nanoporous carbon: the effect of carbonization temperature on the supercapacitor performance in an aqueous electrolyte(Royal Soc Chemistry, 2016) Young, Christine; Salunkhe, Rahul R.; Tang, Jing; Hu, Chi-Chang; Shahabuddin, Mohammed; Yanmaz, Ekrem; Hossain, Md. Shahriar A.Nanoporous carbon materials are a versatile source of carbons that would be useful in applications ranging from electronics to electrochemical energy storage. Here, we focus on nanoporous carbon materials prepared by direct carbonization of zeolitic imidazolate frameworks (ZIF-8) towards supercapacitor applications. Several types of nanoporous carbons have been prepared by varying the applied carbonization temperature. The symmetric devices assembled using nanoporous carbon electrodes were tested for their optimal performance in the electrolyte of sulfuric acid solution. We demonstrate the effects of various factors (e.g., surface area, nitrogen content, degree of graphitization, and relative percentage of micropores) on the performance.Öğe Zeolitic imidazolate framework (ZIF-8) derived nanoporous carbon: the effect of carbonization temperature on the supercapacitor performance in an aqueous electrolyte (vol 18, pg 29308, 2016)(Royal Soc Chemistry, 2017) Young, Christine; Salunkhe, Rahul R.; Tang, Jing; Hu, Chi-Chang; Shahabuddin, Mohammed; Yanmaz, Ekrem; Hossain, Md. Shahriar A.[Abstract Not Available]Öğe ZnO-loaded mesoporous silica (KIT-6) as an efficient solid catalyst for production of various substituted quinoxalines(Elsevier, 2017) Hamid, Oveisi; Chari, M. Adharvana; Chi Van Nguyen; Chen, Jeffrey E.; Alshehri, Saad M.; Yanmaz, Ekrem; Hossain, Shahriar A.Conventional homogeneous and microporous heterogeneous catalysts for quinoxalines production from diamines and diketones usually suffer from difficult separation or harsh reaction conditions. Here, we demonstrate the production of various substituted quinoxalines using ZnO nanoparticle-loaded, highly ordered, mesoporous silica KIT-6 materials as solid catalysts in room temperature. The results show that the KIT-6-130-10Zn sample (aged at 130 degrees C and containing 10 wt% ZnO) effectively produces quinoxalines up to the maximum of 99%. We propose that the enhanced performance of the ZnO-loaded KIT-6 materials resulted from the homogeneous distribution of ZnO nanoparticles, along with the KIT-6's high specific surface area and large pore sizes. (C) 2016 Elsevier B.V. All rights reserved.
