Sharif Digital Repository

Research and development efforts continue to improve oxidation resistance and electrical conductivity of solid oxide fuel cell (SOFC) interconnects. This research evaluates the performance of a ferritic stainless steel (AISI 430 - a candidate SOFC interconnect material) with and without a Co coating (via sol-gel dip coating technique) with various pre-treatments, during cyclic oxidation exposures up to 750°C in laboratory air. A pre-treatment exposure of Co coated samples to a 750°C reducing atmosphere (prior to oxidation exposures) led to the formation of an effective Co-based spinel oxide coating that lowers oxidation rates by more than 40 times, and substantially lowers area specific... 

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... 

Water adsorption by bis-2-ethylhexyl phosphoric acid (D2EHPA) during the extraction of zinc, cobalt and nickel using a D2EHPA-kerosene/H2O mixture is investigated. Based on the experimental results, about 1 mol of water is adsorbed by 2 mol of D2EHPA (which exists in the form of a dimer), irrespective of the pH. Water adsorption decreases with presence of zinc, cobalt and nickel. The stoichiometric coefficients of D2EHPA in water adsorption reactions are determined with and without zinc, cobalt and nickel by applying the slope-analysis method. It is experimentally confirmed that 1.0, 1.8 and 1.2 mol of adsorbed water will be rejected from the organic phase when zinc, cobalt and nickel are... 

Synergistic effects of Cyanex 272 mixed with D2EHPA and Cyanex 302 mixed with D2EHPA were investigated for the separation of cobalt and nickel from a dilute sulfate media with the aim of reducing the reagent cost. Selective extraction of cobalt over nickel improved with respect to D2EHPA, but worsened with respect to Cyanex 272. By the application of the slope analysis method, the stoichiometric coefficient of the extractant was found to be four for cobalt and five for nickel, in a mixture of D2EHPA with Cyanex 302. However, it was four for both cobalt and nickel in a mixture of D2EHPA with Cyanex 272. Fourier Transform Infrared Spectroscopy (FT-IR) was utilized to examine the... 

The treatment facility of Albourz Industrial City was established in 1999 at the southeast of Albourz Mountain with an area of 200,000 square meters. Currently, 40,000 cubic meters of industrial wastes are treated daily utilizing biological method of activated sludge up to the second phase without chlorination in this treatment facility. Then, the discharged wastes are directed toward the lower agricultural lands. The environmental status of the region was investigated by testing the impact of wastewater and agricultural products in four tries. In two tries, the levels of COD and BOD were higher than the environmental standards, but there was no trace of heavy metal contamination in any of... 

The water-soluble cobalt(II) tetradentate Schiff base complex [Co(II)L](ClO4)2, L: (N,N′-bis{5-[(triphenylphosphonium)-methyl]salicylidine}-o-phenylenediamineperchlorate has been synthesized and characterized. This complex forms charge transfer (CT) complexes with imidazole and 1-methylimidazole. The formation constant, molar absorptivity (ε′), and thermodynamic parameters for charge transfer complexes formation of cobalt(II) Schiff base complexes with imidazole derivatives were determined by using UV-vis spectrophotometric method in aqueous solutions at constant ionic strength (I = 0.2 mol dm-3 KNO3) at pH 6.0 and various temperatures between 292 and 315 K. © 2007 Elsevier B.V. All rights... 

Water-soluble cobalt(II) tetradentate Schiff base complexes have been shown to form charge transfer (CT) complexes with a series of nucleoside monophosphates including adenosine-5′-monophosphate (AMP) and cytidine-5′-monophosphate (CMP). The investigated water-soluble cobalt(II) Schiff base complexes are (i) disodium[{bis(5-sulfo-salicylaldehyde)-o-phenylenediiminato}cobalt(II)], Na 2[Co(SO3-salophen)] (1); (ii) disodium[{bis(5-sulfo-salicylaldehyde)-4,5-dimethyl-o-phenylenediiminato} cobalt(II)], Na2[Co(SO3-sal-4,5-dmophen)] (2) and (iii) disodium[{bis(4-methoxy-5-sulfo-salicylaldehyde)-4, 5-dimethyl-o-phenylenediiminato}cobalt(II)], Na2[Co(SO 3-4-meosal-4,5-dmophen)] (3). The formation... 

The formation constants for 1:1 molecular complex formation between water-soluble cobalt(II) tetradentate Schiff base complex, disodium[{bis(4- methoxy-5-sulfo-salicylaldehyde)-4,5-dimethyl-o-phenylenediiminato}cobalt(II)], Na2[Co(SO3-4-meosal-4,5-dmophen)], and nucleotides, adenosine-5′-triphosphate (ATP) and cytidine-5′-triphosphate (CTP), in mixed solvent systems of ethanol and water with different volume fractions of ethanol and water have been determined spectrophotometrically at constant ionic strength (I = 0.2 mol dm-3 NaClO4) and temperature 278 K. Trends in the values of formation constants according to the volume fractions of ethanol and water in ethanol and water mixed solvent... 

The novel unsymmetrical tetradentate Schiff base complexes of Co(II) and Pd(II) with the general formula M(SaI.Phen.Acac.) and M(Sal.Phen. Naph.), have been synthesised by template and non-template method  

An efficient electrocatalyst for Pt-free I−/I3 − reduction has been synthesized by high temperature treatment of graphene oxide-cobalt phthalocyanine mixtures. The graphitic material was characterized by various techniques and was found to consist of reduced graphene oxide carrying CoN3 entities, obtained by thermal decomposition of cobalt phthalocyanine. This material had an ionization potential equal to 4.9±0.1 eV and thus it was judged appropriate to act as reduction electrocatalyst for the I−/I3 − redox electrolyte. It was subsequently deposited as thin film on FTO electrodes, which were employed as counter electrodes for dye-sensitized solar cells. Its capacity to reduce I−/I3 − redox... 

In this paper, the interactions of cobalt(III) tetradentate Schiff-base complexes, [Co(S-MeO-salophen)]ClO4, (1), [Co(5-NO 2-salophen)]ClO4, (2), and [Co(5-Br-salophen)]ClO 4, (3), with dopamine, an important neurotransmitter, have been investigated. The formation and kinetic constants for complex formation of [Co(3-MeO-salophen)]ClO4, (1), with dopamine were determined spectrophotometrically in H2O/EtOH solution (4:1) at 30°C by using the Benesi-Hildbrand and Guggenheim equations, respectively. The stoichiometry has been found to be 1:1. The rate and equilibrium constants for the coordination of dopamine to (Co(3-MeO-salophen)]ClO4 were found to be 0.0053 min-1 and 1600 dm3 mol-1,... 

Optimization of transient liquid phase (TLP) bonding variables is essential to achieve a joint free from deleterious intermetallic constituents as well as with appropriate mechanical properties. In this research, TLP bonding of FSX-414 superalloy was performed using the MBF-80 interlayer. The effects of bonding time (1-30. min) and gap size (25-100 μm) were studied on the joint microstructure and its mechanical properties. Continuous centerline eutectic phases, characterized as nickel-rich and chromium-rich borides, were observed at the joints with incomplete isothermal solidification. The globular and acicular phases were seen at diffusion affected zone (DAZ). These phases could be... 

Abstract: The effect of de-siliconization on the oxidation behavior of AISI 430 stainless steel used for solid oxide fuel cell interconnect application was investigated. De-siliconization treatment was conducted via heating steel parts in an H2 environment. The de-siliconized substrates were then coated with a Mn1.5Co1.5O4 spinel coating, using wet spray method. For comparison, a similar coating process was applied on the as-received AISI 430 stainless steel specimens. Oxidation kinetics of coated interconnects were evaluated at 700, 800 and 900 °C in air. Results showed that the de-siliconization surface treatment decreased oxidation rates, with kinetic rates (g2 cm−4 s−1) of 4.39 × 10−14... 

H2S and CO2 are the main impurities in raw natural gas, which needs to be purified before use. However, the comprehensive utilization of H2S and CO2 has been ignored. Herein, we proposed a fully resource-based method to convert toxic gas H2S and greenhouse gas CO2 synchronously into CO and elemental S by using a novel electrochemical reactor. The special designs include that, in the anodic chamber, H2S was oxidized rapidly to S based on the I−/I3− cyclic redox system to avoid anode passivation. On the other hand, in the cathodic chamber, CO2 was rapidly and selectively reduced to CO based on a porous carbon gas diffusion electrode (GDE) modified with polytetrafluoroethylene and cobalt... 

Ni-Co/SiC nanocomposite coatings were electrodeposited in a modified watt type of Ni-Co bath containing 20 nm SiC particles to be codeposited. Potentiodynamic polarization tests were conducted to study the effect of the SiC particulates on the electrodeposition of Ni and Co. Scanning electron microscopy was used to assess the morphology of the Ni-Co alloy and Ni-Co/SiC nanocomposite coatings. The distribution of the particulates in the matrix was considered by means of transmission electron microscopy. Applying nanomechanical testing instruments coupled to atomic force microscopy, mechanical properties of the alloy and composite coatings were studied and compared. The presence of 11 vol.%... 

In this research, cobalt ferrite (CoFe2O4) magnetic nanoparticles as well as MIL-53(Fe) structure were synthesized by the hydrothermal and solvothermal methods, respectively. Moreover, magnetic composites of MIL-53(Fe)/CoFe2O4 nanoparticles with different cobalt ferrite loadings (i.e.; 0.05, 0.1 and 0.2 g) were prepared via the solvothermal method. The main novelty of the present research was to synthesize a magnetic composite of MIL-53(Fe)/CoFe2O4 nanoparticles in order to perform rapid photodegradation of Direct Red 23 (DR23) dye under the LED visible light irradiation. Good magnetic properties of the fabricated composite led to easy separation and rapid retrieval of the catalyst from the... 

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... 

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... 

In this work, for the first time, different forms of nanocomposites based on rGO and MWCNT were prepared in conjoining with the bioactive glass (BioGlass). In the carbonic layers, a highly toxic nanoparticle, CoNi2S4, was intercalated, and the role of this nanoparticle in the alkaline phosphatase activity, relative cell viability on different cell lines, and also the effect on the cell walls and cell morphologies were investigated. From another perspective, the ability of the chemotherapy drug loading to the prepared nanocomposites was investigated, and the use of leaf extracts was thought of as a green method to lower the cytotoxicity and regulate the genotoxicity of the generated... 

Herein, MIL-101(Fe), CoFe2O4, novel binary (MIL-101(Fe)/CoFe2O4, MIL-101(Fe)/GO and CoFe2O4/GO), and ternary (MIL-101(Fe)/CoFe2O4/(3%)GO and MIL-101(Fe)/CoFe2O4/(7%)GO) magnetic composites based upon the MIL-101(Fe) were synthesized. The XRD, FESEM, TEM, EDX, BET-BJH, FTIR, VSM, DRS, PL, EIS and other electrochemical analyses were applied to characterize samples. The MIL/CoFe2O4/(3%)GO demonstrated the best performance compared to other samples for visible light photocatalytic and photo-Fenton-like degradation of Direct Red 23 (DtR-23), Reactive Red 198 (ReR-198) dyes as well as Tetracycline Hydrochloride (TC-H) antibiotic. Degradation of dyes using the ternary composite after 70 min of...