Search for: cobalt-compounds
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    Self-encapsulation of single-texture CoSi2 nanolayer by TaSi2

    , Article Thin Solid Films ; Volume 516, Issue 18 , 31 July , 2008 , Pages 6008-6012 ; 00406090 (ISSN) Akhavan, O ; Azimirad, R ; Moshfegh, A. Z ; Sharif University of Technology
    In this work, we have studied single-texture formation of CoSi2 layer in heat-treated Co/Ta0.7W0.3/Si(100) structure. Moreover, self-encapsulation process of the CoSi2 layer and surface roughness of the encapsulated layer, as a contact layer, has been examined. A direct current magnetron co-sputtering technique was employed to deposit a 10 nm Ta0.7W0.3 alloy intermediate layer. After growth of the layer on the Si substrate, a 25 nm Co layer was deposited using thermal evaporation method. Post-annealing process of the films was treated in an N2(80%) + H2(20%) ambient in a temperature range from 400 to 1000 °C for 60 min. X-ray diffraction analysis showed that a single-texture CoSi2 layer with... 

    Arithmetic circuits verification without looking for internal equivalences

    , Article 2008 6th ACM and IEEE International Conference on Formal Methods and Models for Co-Design, MEMOCODE'08, Anaheim, CA, 5 June 2008 through 7 June 2008 ; 2008 , Pages 7-16 ; 9781424424177 (ISBN) Sarbishei, O ; Alizadeh, B ; Fujita, M ; Sharif University of Technology
    In this paper, we propose a novel approach to extract a network of half adders from the gate-level net-list of an addition circuit while no internal equivalences exist. The technique begins with a gatelevel net-list and tries to map it into word-level adders based on an efficient bit-level adder representation. It will be shown that the proposed technique is suitable for several gate-level architectures of multipliers, as it extracts adder components in a step-wise method. This approach can also be generalized to other arithmetic circuits. In order to evaluate the effectiveness of our approach, we run it on several arithmetic circuits and compare experimental results with those of... 

    On graphs whose star sets are (co-)cliques

    , Article Linear Algebra and Its Applications ; Volume 430, Issue 1 , 2009 , Pages 504-510 ; 00243795 (ISSN) Akbari, S ; Ghorbani, E ; Mahmoodi, A ; Sharif University of Technology
    In this paper we study graphs all of whose star sets induce cliques or co-cliques. We show that the star sets of every tree for each eigenvalue are independent sets. Among other results it is shown that each star set of a connected graph G with three distinct eigenvalues induces a clique if and only if G = K1, 2 or K2, ..., 2. It is also proved that stars are the only graphs with three distinct eigenvalues having a star partition with independent star sets. © 2008 Elsevier Inc. All rights reserved  

    Promising new catalytic properties of a Co (II)-carboxamide complex and its derived Co3O4 nanoparticles for the Mizoroki-Heck and the Epoxidation reactions

    , Article Applied Organometallic Chemistry ; Volume 34, Issue 11 , November , 2020 Kiani, M ; Bagherzadeh, M ; Meghdadi, S ; Fadaei Tirani, F ; Babaie, M ; Schenk Joß, K ; Sharif University of Technology
    John Wiley and Sons Ltd  2020
    The new Co(II) - carboxamide complex (1) and Co3O4 nanoparticles (2), by way of thermal decomposition of (1) have been efficiently synthesised in the environment-friendly. X-ray diffraction reveals a slightly distorted octahedral coordination of cobalt (four nitrogens and two oxygens) in (1) and regular octahedral or tetrahedral ones (oxygens only) in (2). The investigation of (1) and (2) in the Mizoroki-Heck and epoxidation of alkens reactions showed them both to be powerful, green and inexpensive catalysts. © 2020 John Wiley & Sons, Ltd  

    Structure transition of single-texture CoSi 2 nanolayer grown by refractory-interlayer-mediated epitaxy method

    , Article Applied Surface Science ; Volume 253, Issue 5 , 2006 , Pages 2953-2957 ; 01694332 (ISSN) Akhavan, O ; Moshfegh, A. Z ; Sharif University of Technology
    Elsevier  2006
    In this investigation, the crystalline structure of a nanometric CoSi 2 layer, formed in heat treated Co/W x Ta (1-x) /Si(1 0 0) systems, has been studied by XRD analysis. Careful measurements of the diffraction intensities revealed that temporary formation of a metastable diamond cubic structure of CoSi 2 phase, rather than its usual CaF 2 structure, was occurred. It has been shown that formation of this metastable structure depends on the kind of the applied interlayer in addition to the annealing temperature. Among the studied systems with x = 0, 0.25, 0.5, 0.75 and 1, the second and the last systems resulted in growing a (1 0 0) single-texture CoSi 2 layer with the preferred usual CaF 2... 

    Surface modification of exchange-coupled Co/NiO x magnetic bilayer by bias sputtering

    , Article Applied Surface Science ; Volume 252, Issue 2 , 2005 , Pages 466-473 ; 01694332 (ISSN) Sangpour, P ; Akhavan, O ; Moshfegh, A. Z ; Jafari, G. R ; Kavei, G ; Sharif University of Technology
    Elsevier  2005
    We have investigated the effect of bias voltage on sheet resistance, surface roughness and surface coverage of Co/NiO x magnetic bilayer. In addition, interface topography and corrosion resistance of the Ta/Co/Cu/Co/NiO x /Si(1 0 0) system have been studied for Co layers deposited at an optimum bias voltage. Atomic force microscopy (AFM) and four point probe sheet resistance (Rs) measurement have been used to determine surface and electrical properties of the sputtered Co layer at different bias voltages ranging from 0 to -80 V. The Co/NiO x bilayer exhibits a minimum surface roughness and low sheet resistance value with a maximum surface coverage at Vb=-60 V resulted in a slight increase of... 

    Synthesis, characterizations and catalytic studies of a new two-dimensional metal-organic framework based on Co-carboxylate secondary building units

    , Article Journal of Solid State Chemistry ; Volume 223 , March , 2015 , Pages 32-37 ; 00224596 (ISSN) Bagherzadeh, M ; Ashouri, F ; Daković, M ; Sharif University of Technology
    Academic Press Inc  2015
    A metal-organic framework [Co3(BDC)3(DMF)2(H2O)2] was synthesized and structurally characterized. X-ray single crystal analysis revealed that the framework contains a 2D polymeric chain through coordination of 1,4-benzenedicarboxylic acid linker ligand to cobalt centers. The polymer crystallize in monoclinic P21/n space group with a=13.989(3) Å, b=9.6728(17) Å, c=16.707(3) Å, and Z=2. The polymer features a framework based on the perfect octahedral Co-O6 secondary building units. The catalytic activities of [Co3(BDC)3(DMF)2(H2O)2]n for olefins oxidation was conducted. The heterogeneous catalyst could be facilely separated from the reaction mixture, and reused three times without significant... 

    Novel multifunctional capacitor-varistor ceramics based on SnO2

    , Article Ceramics International ; Volume 44, Issue 16 , 2018 , Pages 20386-20390 ; 02728842 (ISSN) Maleki Shahraki, M ; Alipour, S ; Mahmoudi, P ; Karimi, A ; Sharif University of Technology
    Elsevier Ltd  2018
    Up to now, multifunctional varistor-capacitor materials were based on TiO2, even though these materials failed to have practical applications. For the first time, in this research, multifunctional varistor-capacitor properties are observed in the CuO-doped SnO2-CoO-Sb2O3 system. The XRD analysis showed that this system has a single phase microstructure. SEM images indicated that the CuO addition resulted in a better densification and larger grain size. The very low electric breakdown field of the CuO-doped SnO2-CoO-Sb2O3 system (12 V/mm, similar to TiO2), is a consequence of coarse-grained microstructure. This varistor had a suitable surge withstand capability as well. The colossal... 

    Construction of a ternary nanocomposite, polypyrrole/fe-co sulfide-reduced graphene oxide/nickel foam, as a novel binder-free electrode for high-performance asymmetric supercapacitors

    , Article Journal of Physical Chemistry C ; Volume 124, Issue 8 , 2020 , Pages 4393-4407 Karimi, A ; Kazeminezhad, I ; Naderi, L ; Shahrokhian, S ; Sharif University of Technology
    American Chemical Society  2020
    The development of asymmetric supercapacitors requires the design of electrode construction and the utilization of new electroactive materials. In this regard, an effective strategy is the loading of active materials on an integrated 3D porous graphene-based substrate such as graphene foam (GF). Herein, we successfully designed and fabricated a novel ternary binder-free nanocomposite consisting of polypyrrole, Fe-Co sulfide, and reduced graphene oxide on a nickel foam electrode (PPy/FeCoS-rGO/NF) via a facile, cost-effective, and powerful electrodeposition method for application in high-performance asymmetric supercapacitors. The monolithic 3D porous graphene foam (GF) obtained by the facile... 

    Crystallinity of CoSi2 nanolayer grown by refractory metal interlayer and cap layer methods

    , Article Journal of Physics: Conference Series ; Volume 100, Issue PART 4 , 2008 ; 17426588 (ISSN) Akhavan, O ; Moshfegh, A. Z ; Sharif University of Technology
    Institute of Physics Publishing  2008
    Epitaxial formation of CoSi2 nanolayer by solid state reaction of Co-Si in refractory metal intermediate-layer and cap-layer systems was investigated. Thin films of Ta and W, as the refractory metal intermediate or cap layers of the Co film, were deposited on Si(100) substrate and then heat-treated. The both interlayers resulted in formation of epitaxial CoSi 2 with (100) crystallographic orientation at 900°C. However, in the Ta intermediated system, the grown CoSi2 layer was thermally unstable at 1000°C, unlike the W system with a stable silicide layer. We found that use of W cap-layer cannot yield an epitaxial CoSi2 phase. But, a Ta cap-layer resulted in formation of epitaxial CoSi2(100)... 

    Co-evolutionary reliability-oriented high-level synthesis

    , Article 2008 IEEE International Symposium on Circuits and Systems, ISCAS 2008, Seattle, WA, 18 May 2008 through 21 May 2008 ; 2008 , Pages 2026-2029 ; 02714310 (ISSN) ; 9781424416844 (ISBN) Safari, S ; Aminzadeh, S ; Sharif University of Technology
    The main contribution of this paper is utilizing bio-inspired evolutionary algorithm for reliability oriented high level synthesis. In this paper genetic algorithm is used to schedule a data-flow graph considering latency and resource allocation considering resource constraints and area overhead. Then a co-evolutionary strategy merges the results of these solutions to find the RT level design of the circuit which satisfies both performance and area constraints. To satisfy the user-defined reliability, another genetic algorithm is developed to insert some hardware redundancies to the resulted data-path. Experimental results show using the proposed approach results in an acceptable reliability... 

    Nano cobalt-copper ferrite catalyzed regioselective α-C(sp3)–H cyanation of amines: Secondary, tertiary, and drug molecules

    , Article Catalysis Communications ; Volume 149 , 2021 ; 15667367 (ISSN) Matloubi Moghaddam, F ; Pourkaveh, R ; Heidarian, M ; Sharif University of Technology
    Elsevier B.V  2021
    Oxidative cyanation of sp3C–H bonds at the α position of amines was achieved using CoCuFe2O4 as a catalyst and NaCN as an inexpensive cyanide source at room temperature. CoCuFe2O4 was found to be an active catalyst for Csp [3]-Csp coupling, efficiently delivering valuable α-aminonitriles from tertiary/secondary amines in good yields. The corresponding products were obtained with high selectivity toward α position. In addition, functional group tolerance offered the opportunity for application in late-stage functionalization of biologically active molecules. This transformation proceeds convenient on a gram-scale, and the catalyst can be reused for several runs with consistent catalytic... 

    3D flower-like nickel cobalt sulfide directly decorated grassy nickel sulfide and encapsulated iron in carbon sphere hosts as hybrid energy storage device

    , Article Applied Surface Science ; Volume 558 , 2021 ; 01694332 (ISSN) Shahi, M ; Hekmat, F ; Shahrokhian, S ; Sharif University of Technology
    Elsevier B.V  2021
    Developing high-performance supercapacitors is of great significance in the area of renewable energies by virtue of having both high energy and power densities. In this work, an innovative strategy is employed for the fabrication of binder-free binary nickel–cobalt-sulfide (NCS) nanosheets (NSs) directly decorated onto the hydrothermal nickel-sulfide (Ni3S2) nanowires (NWs) as the positive electrodes. The NCS/Ni3S2-nickel foam (NF) positive electrodes rendered superior specific capacity of 499.1 mAh.g−1 at 6 A.g−1. Encapsulated iron into the carbon sphere hosts (Fe-HTCSs) are used as the negative counterparts, exhibiting remarkable specific capacitance of 336.6 F.g−1 (at 0.1 A.g−1). The... 

    Facile synthesis of highly efficient bifunctional electrocatalyst by vanadium oxysulfide spheres on cobalt-cobalt sulfonitride nanosheets for oxygen and hydrogen evolution reaction

    , Article Electrochimica Acta ; Volume 391 , 2021 ; 00134686 (ISSN) Asen, P ; Esfandiar, A ; Sharif University of Technology
    Elsevier Ltd  2021
    Synthesis of efficient, low-cost, and stable bifunctional electrocatalysts with earth-abundant resources for electrochemical water electrolysis is a challenging subject for large-scale energy conversion processes. Herein, we report a high-performance electrocatalyst based on vanadium oxysulfide/cobalt-cobalt sulfonitride (VOS/Co-CoSN) for oxygen and hydrogen evolution reaction (OER and HER). The Co-CoSN film was synthesized on a copper sheet (CS) by a facile electrodeposition method. Then, VOS was electrochemically grown onto the Co-CoSN@CS electrode at various deposition times. At the optimal deposition time (300 s), the obtained VOS-300/Co-CoSN catalyst was studied for OER and HER in... 

    Carbon-paste electrode modified with cobalt-5-nitrolsalophen as a sensitive voltammetric sensor for detection of captopril

    , Article Sensors and Actuators, B: Chemical ; Volume 109, Issue 2 , 2005 , Pages 278-284 ; 09254005 (ISSN) Shahrokhian, S ; Karimi, M ; Khajehsharifi, H ; Sharif University of Technology
    The electrochemical behavior of captopril at the surface of a carbon-paste electrode (CPE) modified with cobalt-5-nitrolsalophen (CoNSal) is described. The prepared electrode shows an excellent electrocatalytic activity toward the oxidation of captopril, which is leading to marked lowering in the anodic overpotential and considerable improvement of sensitivity (anodic current). Whereas at the surface of unmodified electrode an electrochemical activity for captopril cannot be observed, a very sharp anodic wave with an anodic peak potential about 650 mV (versus Ag/AgCl) is obtained using the prepared modified electrode. This catalytic wave is assigned to mediating of Co(III)/Co(II) redox... 

    CVD-grown TiO2 particles as light scattering structures in dye-sensitized solar cells

    , Article RSC Advances ; Volume 2, Issue 32 , 2012 , Pages 12278-12285 ; 20462069 (ISSN) Pazoki, M ; Taghavinia, N ; Abdi, Y ; Tajabadi, F ; Boschloo, G ; Hagfeldt, A ; Sharif University of Technology
    Chemical vapour deposition (CVD) at atmospheric pressure, using TiCl 4 as a precursor, was used to grow nanostructured TiO2 films on glass substrates. At relatively low temperatures (∼245 °C) and using relatively high reactant concentrations, different nano-morphologies of TiO2 were formed simultaneously, such as spheres, nanowires and mesoporous structures. The TiO2 spheres were successfully applied as light-scattering particles in dye-sensitized solar cells, either by direct deposition onto electrodes in the reactor, or by preparation of a printing paste from the deposited particles. For dye-sensitized solar cells using the organic dye D35 as sensitizer and a cobalt-complex based redox... 

    ICoSim-FMS: An intelligent co-simulator for the adaptive control of complex flexible manufacturing systems

    , Article Simulation Modelling Practice and Theory ; Volume 19, Issue 7 , August , 2011 , Pages 1668-1688 ; 1569190X (ISSN) Shirazi, B ; Mahdavi, I ; Mahdavi Amiri, N ; Sharif University of Technology
    We describe an intelligent co-simulator for real time production control of a complex flexible manufacturing system (CFMS) having machine and tool flexibility. The manufacturing processes associated with the CFMS are complicated with each operation being possibly done by several machining centers. The co-simulator design approach is built upon the theory of dynamic meta-model based supervisory control with the cooperation of its own embedded intelligent blocks. The system is implemented by coupling of the centralized simulation controller (CSC) and real-time simulator for enforcing dynamic strategies of shop floor control. The posteriori adaptive co-simulator is equipped with a concurrent... 

    RETRACTED ARTICLE: Study of stabilities of L-cysteine and L-methionine with divalent metal ions: A comparison of thermodynamic data

    , Article 5th International Conference on Bioinformatics and Biomedical Engineering, iCBBE 2011 ; 2011 ; 9781424450893 (ISBN) Sajadi, S. A. A ; Sharif University of Technology
    The acidity and stability constants of M-Met (M: M2+; Met 1: L-methionine) complexes, determined by potentiometric pH titrations, were used to make a comparative investigation with L-cysteine (Cys). It is shown that regarding to M ion - binding properties vital differences on complex bilding were considered. It is demonstrated, that in M-Met complexes, M ion is coordinated to the carboxyl group, M ion is also able to build macrochelate over amine group. The upmentioned results demonstrate that for M-Met complex the stability constants is also largly determined by the affinity of Cu2+ for amino group but in opposite to Met, some metal ions such as Co2+, Cu2+, and Zn2+ build with Cys 2... 

    Extraction of ZN, MN and CO from ZN-MN-CO-CD-NI containing solution using D2EHPA, Cyanex® 272 and Cyanex® 302

    , Article International Journal of Engineering, Transactions B: Applications ; Volume 24, Issue 2 , 2011 , Pages 183-192 ; 1728-144X (ISSN) Darvishi, D ; Haghshenas, D. F ; Alamdari, E. K ; Sadrnezhaad, S. K ; Sharif University of Technology
    Effects of pH, D2EHPA, Cyanex® 272 and Cyanex® 302 on extraction of zinc, manganese and cobalt from a Zn-Mn-Co-Cd-Ni containing solution at the room temperature was comprehensively investigated. Addition of Cyanex® 302 indicated a left-shifting-effect on the extraction curve of zinc, a right-shifting-effect on the extraction curve of manganese and no effect on the extraction of cobalt. Addition of Cyanex® 272 shifted all three curves to the right. Therefore, the most suitable extractant for separation of zinc from manganese was therefore 0.3-0.3 mixture of D2EHPA and Cyanex® 302, and that for separation of manganese from cobalt was pure D2EHPA. The stoichiometric coefficient for the... 

    Synthesis and characterization of ultrasound assisted "graphene oxide-magnetite" hybrid, and investigation of its adsorption properties for Sr(II) and Co(II) ions

    , Article Applied Surface Science ; Volume 353 , 2015 , Pages 350-362 ; 01694332 (ISSN) Tayyebi, A ; Outokesh, M ; Moradi, S ; Doram, A ; Sharif University of Technology
    Elsevier  2015
    Magnetite nanoparticles with a size distribution of 15-21 nm were synthesized and decorated onto surface of graphene oxide by ultrasound assisted precipitation. Size and size distribution of the obtained M-GO hybrid were appreciably finer than the hybrids prepared by stirring method. M-GO is a superparamagnetic material with saturation magnetization of 31 emu g-1. The Langevin equation was successfully applied for estimation of size of Fe3O4 nanoparticles in M-GO hybrid, with maximum error of 17.5%. The study put forward a formation mechanism for M-GO, based on instrumental analyses. Adsorption isotherms of Sr2+ and Co2+ ions, which were fitted by Langmuir monolayer...