CoSO4 Research Articles

Producing cobalt–graphene composite coating by pulse electrodeposition with excellent wear and corrosion resistance

Cobalt (Co) and graphene oxide/cobalt (GO/Co) composite coatings were fabricated by pulse electrodeposition technique from an aqueous bath containing cobalt sulfate and GO, etc. Effect of the incorporations of GO on morphology, phase structure, average grain size and corrosion and wear resistance of the resulting composite coatings were evaluated in detail. Scanning electron microscope (SEM) and energy dispersed X-ray (EDX) show that the GO nanosheets disperse homogeneously in the composite coating and the incorporations of GO change the morphologies of the deposit from conical shaped structure to protruding structure. In addition, the co-deposition GO with Co ions favor the formation of hcp (100), (002) and (101) textures in the composite coating and have functions of grain refining and hardness enhancement. The wear tests show that the incorporations of GO in the coating improve the wear resistance and friction reduction of the deposit. The electrochemical corrosion tests using potentiodynamic polarization and electrochemical impedance spectroscopy show that the GO/Co composite coating possesses better corrosion resistance than the pure Co coating.

Room-temperature synthesis of air stable cobalt nanoparticles and their use as catalyst for methyl orange dye degradation

An easy, green and economically viable approach has been made to synthesize highly active and ordered structures of cobalt nanoparticles. The air stable nanoparticles were prepared from cobalt sulphate using tetra butyl ammonium bromide as surfactant and sodium borohydride as reductant. The cobalt nanocolloids in aqueous medium were found to be efficient as catalysts for the degradation of toxic organic dyes. Our present study involves degradation of methyl orange using cobalt nanoparticles and easy recovery of the catalyst from the system. The recovered nanoparticles could be recycled several times without loss of catalytic activity. Palladium nanoparticles prepared from palladium chloride and the same surfactant was found to degrade the organic dye effectively but lose their catalytic activity after recovery. Based on chemical and kinetic studies an attempt has been made to elucidate the mechanism of dye degradation using the nanoparticles.

Facile microwave-assisted synthesis of sheet-like cobalt hydroxide for energy-storage application: Effect of the cobalt precursors

This work reported the synthesis of cobalt hydroxide using different cobalt precursors via a simple, operable and rapid microwave-assisted method and their electrochemical capacitors application. The experimental results demonstrated that cobalt precursors remarkably impacted on not only microscopic dimensions and morphologies but also crystalline phase. Especially, the loose-packed lamellar α-cobalt hydroxide was synthesized using cobalt sulfate as the precursor. The electrochemical properties of the as-obtained samples were investigated in detail by cyclic voltammetry and galvanostatic charge/discharge tests. The results of electrochemical tests demonstrated that the loose-packed lamellar structure endowed the cobalt hydroxide with a superior specific capacitance of 711.3F/g in a potential window of 0–0.55V. In addition, the asymmetric supercapacitor, fabricated by using the obtained cobalt hydroxide as positive electrode material and oxygen-rich porous carbon as negative electrode material, exhibited excellent rate performance. This work held an important guideline value for the development of cobalt-based electrochemical capacitors.

Template synthesis of 1D hierarchical hollow Co3O4 nanotubes as high performance supercapacitor materials

One-dimensional (1D) hierarchical hollow Co3O4 nanotubes have been controllably fabricated via a facile two-step strategy including template-hydrothermal reaction and calcination, in which cobalt sulfate heptahydrate, guanidine hydrochloride and activated carbon are used as cobalt precursors, precipitant and hard template, respectively. The resultants of Co3O4 are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) patterns and N2 adsorption and desorption. The novel precipitant guanidine hydrochloride and hard template activated carbon contributed to the interesting morphology, and plus Kirkendall effect leading to producing hollow structure with hierarchical porous. The electrochemical properties of prepared different Co3O4 samples are evaluated and compared through cyclic voltammetry (CV), charge–discharge and electrochemical impedance spectroscopy (EIS) in 2.0M KOH electrolytic solution. The results show that the 1D hierarchical hollow Co3O4 nanotubes exhibit a large specific capacitance of 1006Fg−1 at 1Ag−1, an outstanding cyclic stability with a capacitance retention of 91% after 1000cycles of charge–discharge and a low resistance.

Simultaneous Densitometric Determination of First Line Anti-TB Drugs in Binary, Ternary, and Quaternary Mixtures

This article presents the development of a new densitometric method for the simultaneous separation and determination of isoniazid (INH), ethambutol (EMB), rifampicin (RIF), and pyrazinamide (PZA). INH, RIF, and PZA were determined by UV detection at 270 nm, and then EMB was derivatized and detected at 250 nm. The studied drugs were determined in their pure forms, available pharmaceutical preparations, binary, ternary, and quaternary synthetic mixtures. The study was performed on precoated silica gel TLC plates using acetonitrile:chloroform:2-propanol:4 N ammonia as a mobile phase (34:31:34:1 v/v/v/v). The studied drugs have been satisfactorily resolved with Rf values 0.31 ± 0.01, 0.48 ± 0.03, 0.73 ± 0.02, and 0.09 ± 0.01 for INH, RIF, PZA, and EMB, respectively. The developed method has been validated according to ICH guidelines providing good correlation coefficients (0.9991–0.9998) with a detection limit of 18.14 to 94.34 ng/band for all studied drugs. The proposed method has the potential to determine INH, RIF, and PZA simultaneously (before spraying) and EMB after spraying of the plate with cobalt sulfate without any interference. The method is new, rapid, and inexpensive compared to the official and reported methods for the assay of the quaternary mixture of the studied drugs.

Investigation of nanocrystalline cobalt films electrodeposited at different current densities

In this paper, a study has been performed of nanocrystalline cobalt films electrodeposited at different current densities in the range from 40 to 50 mA/cm2. The films were thick (about 40 µm) and were prepared from a cobalt sulfate solution with pH value of 4.5 at room temperature. Suitable values for cobalt film deposition potential were chosen on the basis of the recorded cyclic voltammograms. The chemical composition on the surface of the films was investigated by X-ray photoelectron spectroscopy. The morphological structure of the films was made visible with scanning electron microscopy. As the current density was increased, the amount of cracks, nodules and cavities on the surface of the films were observed to be larger, due to increased tensile stress in the films. The morphological structure was composed of irregular, densely packed grains with sizes mainly in the range of 50–100 nm. The average grain size decreased with increasing current density.

Corrosion behaviour of electrodeposited nanocrystalline Co and Co/ZrO2 nanocomposite coatings

Nanocrystalline Co and Co/nano-ZrO2 composite coatings were electrodeposited from cobalt sulphate based solutions. Deposition rate, morphology, microstructure, microhardness and corrosion behaviour of the produced coatings were investigated. The results indicated that optimum electrolyte temperature for the best combination of deposition rate and microhardness was 45°C. Incorporation of nanoparticles was increased from 0 to 4·9 vol.-% by increasing of bath ZrO2 concentration. Co/4·4 vol.-%ZrO2 nanocomposite coating had the highest hardness value as compared to the composites containing higher or lower volume fractions of incorporated ZrO2 particles. The polarisation tests in Hanks’ solution revealed that the corrosion potential shifted to more positive values, corrosion current density decreased and polarisation resistance increased by the incorporation of ceramic particles. Impedance tests also confirmed the polarisation results and improvement of pure cobalt corrosion resistance by codeposition of ZrO2 nanoparticles.

Corrosion Behavior of a Novel Hybrid Co/UHMWPE Composite Biocoating with Potential Application as a Biomaterial

In the present paper we report the acquisition of a composite coating based on cobalt and ultra high molecular weight polyethylene (Co/UHMWPE) as a novel hybrid biocoating with potential application as a biomaterial, using the electrochemical deposition technique at room temperature. Three different concentrations of UHMWPE, namely 20 gL-1, 30 gL-1 and 50 gL-1, were used in a cobalt sulphate bath. The corrosion behaviour of the Co/UHMWPE hybrid biocoating was studied in comparison with pure cobalt coating at different exposure times in Hanks’ solution as simulated body fluid (SBF), using the electrochemical impedance spectroscopy method. The polarisation resistance of the Co/UHMWPE hybrid biocoating increased during immersion time in the SBF medium in comparison to the pure cobalt coating. An easy way to prepare Co/UHMWPE hybrid biocoatings was identified: namely, by properly incorporating UHMWPE microparticles into a Co matrix using electrocodeposition from a cobalt electrolyte plating bath with increasing corrosion resistance in a solution simulating body fluid.

Recovery of Co metal and Electrolytic Manganese Dioxide (EMD) from Co–Mn sludge

A process flow sheet has been developed to produce cobalt metal and Electrolytic Manganese Dioxide (EMD) from Cobalt–Manganese Bromide (CMB) spent catalyst sludge. The Co–Mn sludge was leached in sulphuric acid media followed by the removal of organic matter from the leach liquor through adsorption by activated charcoal. Co–Mn separation was carried out by precipitating cobalt as mixed cobalt sulphide. The cobalt mixed sulphide was roasted and then leached in sulphuric acid to produce cobalt sulphate solution. Co metal and EMD were electrodeposited from their respective sulphate solutions. The optimal conditions during sludge leaching, Co–Mn separation, roasting of Co mixed sulphide, dissolution of the roasted material, electrodeposition of Co metal and EMD have been studied. The EMD was characterized for its suitability for the use in batteries and a tentative flow sheet for processing Co–Mn sludge is presented.

Effect of saccharin and thiourea on electrodeposition of cobalt and characteristics of deposits

Cobalt electrodeposits have been produced from two types of baths. In the bath containing cobalt sulphate, cobalt chloride and boric acid, saccharin is found effective as a brightener additive. In the bath containing cobalt sulphate, potassium chloride and potassium citrate, thiourea is found to be effective as a brightener additive. Results of solution characteristics such as conductivity of the electrolytes, cathode current efficiency and rate of deposition are compared. The effect of additives on brightness, roughness, orientation of the crystal, grain size and surface morphology of the cobalt deposits are reported. The X-ray diffraction pattern obtained for electrodeposited cobalt showed a polycrystalline nature with hexagonal close packed structure. A smooth uniform and pore free surface was observed under scanning electron microscopy and atomic force microscopy analysis. Potentiodynamic polarisation and electrochemical impedance measurements in sodium chloride solution showed that a higher corrosion resistance was observed for the deposit from the second type of bath containing an additive.

Optimization in Mediated Electrochemical Oxidation Using Cobalt Sulfate as a Mediator

Optimization of the Mediated Electrochemical Oxidation (MEO) for destructing a dissolved organic compound has been studied. The experiment was carried out in a 100mL electrolytic cell equipped with a rotameter, an outlet tube of “tetradent” designs, a collecting tube, a stabilized DC power supply, and electrodes which were fabricated from platinum foil. It has been found that optimum efficiency of destruction of glucose as a model of compound could be achieved by using cobalt sulfate as a mediator, at its optimum concentration of 0.43M, in a 2M sulfuric acid solution, for a glucose concentration of 0.2M. The time required for optimum destruction efficiency was 2hours.

Anisotropic SmCo<sub>5</sub>/FeCo core/shell nanocomposite chips prepared via electroless coating

We report the preparation of anisotropic SmCo₅/FeCo<b> </b>core/shell<b> </b>nanocomposite chip-like particles via an electroless coating process. The anisotropic SmCo₅ nanoscale chips were first prepared by surfactant-assisted ball milling then coated with soft magnetic FeCo using cobalt sulfate (CoSO₄.7H₂O) and iron sulfate (FeSO₄.7H₂O) as metal precursors in presence of complexing agents. The influence of the soft-phase coating on the magnetic properties of the nanocomposite particles has been studied. The saturation magnetization of the composite particles increases with increasing coating while the coercivity decreases. The FeCo coated chips have an enhanced remanence (<i>M_r</i> = 44.5 emu/g with 16 wt % of FeCo) compared to the uncoated chips (<i>M_r</i> = 36.7 emu/g), indicating exchange coupling between the hard and soft phases for the optimal soft-phase coating. Results of magnetic field alignment show the strong anisotropy of SmCo₅/FeCo<b> </b>core/shell<b> </b>nanocomposite particles which can be used as building blocks of high-strength anisotropic magnets.

Recovery of Cobalt Ion into Polyethyleneglycol (PEG) Gel Phase as Thiocyanato Complex

This study outlines the recovery of cobalt (Co) ion as a gel phase consists of PEG and Co-thiocyanato complex (Co(NCS)4) from aqueous solution. Taking advantage of gel precipitation with composition written as (PEG)nCo(NCS)4K2, a novel process for the efficient recovery of Co was proposed. Composition of gel phase and load capacity of Co ion in it was investigated by fundamental experiment. Gel precipitation from aqueous solution of nickel sulfate (NiSO4), cobalt sulfate (CoSO4) and potassium thiocyanate (KSCN) was observed by mixing it with polyethyleneglycol (PEG#4000, molar weight; 2,70033,500) aqueous solution. The results confirmed the large load capacity of Co (6.8 © 1014mol/1 g of gel phase) compared to the sorption to polyurethane foam reported in the past. Percentage of Co ion to the total amount of Ni and Co ions in gel phase were more than 99.6 at%, revealing excellent condensation efficiency for Co. Furthermore, Co ion was extracted and separated from SCN and PEG in gel phase, by utilizing solvent extraction. From the set of experimental results, feasibility of the proposed process was discussed. [doi:10.2320/matertrans.M2014428]

Separation of Nickel and Cobalt Utilizing Selective Reduction of Nickel in Acidic Aqueous Solution

With the aim of separating nickel (Ni) from cobalt (Co) in acidic aqueous solution, selective reduction of Ni was examined. Sodium hypophosphite (NaH2PO2) was selected as a reductant, and reacted with aqueous solution containing 0.1mol L11 nickel sulfate (NiSO4·6H2O) and 030.05mol L11 cobalt sulfate (CoSO4·7H2O) for 3 hours at 90°C. As a result, Ni was selectively reduced and separated from Co in the acidic region (pH = 4.8). Differences in reduction rate between Ni and Co were discussed, and the influence of impurities on the reduction of Ni was also examined by adding copper (Cu), iron (Fe), and zinc (Zn) ions to the feed solution. [doi:10.2320/matertrans.M-M2014846]

Synthesis of electrocrystallized cobalt ferrite nanopowders by tuning the cobalt salt concentration

Cobalt ferrite nanopowders were electrocrystallized in an electrochemical cell containing two iron electrodes, and an electrolyte solution of cobalt sulphate.

OS1407-230 電気めっきを用いた高傾斜組成を有するCo-Cu合金薄膜の作製

A Co-Cu alloy film having high composition gradient was fabricated by electrodeposition method. The electrodeposition was conducted in the single electrolyte consisting of cobalt sulfate and copper sulfate, in which composition of electrodeposited alloy depends on applied electrochemical potential. The potential was controlled such that the electrodeposited film has a constant composition gradient of 8.0×10^<-4>nm^<-1>. By stacking the films having positive and negative gradients alternately, we could fabricate the high composition-gradient film of pm total thickness. This gradient structure was consistent with the x-ray diffraction analysis that a single broad (111) peak appeared in between the diffraction angles of fcc-Co and Cu crystals. Vickers hardness of the composition gradient film was Hv298, which was certainly higher than that of the Co/Cu multilayered film having 500nm layer thickness. The high strength of the gradient film can be contribute to the misfit dislocations distributing over the film and/or the internal stress arising from lattice constant mismatch.

스프레이 기술을 이용한 세라믹 표면 코팅에 대한 황화코발트 첨가량의 영향

본 연구는 코발트 코팅 두께에 따른 점토 표면과의 반응성을 연구하였다. 시편에서 표면으로 부터 일정한 두께로 코발트가 확산된 것을 볼 수가 있으며, 황화코발트의 도포양과 함께 청자토보다 백자토에서 확산층의 두께가 증가하였다. 백자토에 코팅된 시편은 grayish blue가 blue 색으로 변화되는 것을 알 수 있으며 <TEX>$L^*$</TEX>값이 51.78에서 37.61로 감소하고, 청자토에 코팅된 시편인 경우 dark olive gray에서 dark gray색으로 <TEX>$L^*$</TEX>값이 53.91에서 38.93로 적어지는 것을 알 수가 있다. 시편의 물성 평가는 XRD, SEM, 열팽창기, TG-DTA, UV-vis spectrophotometer와 HRDPM을 이용하였다. This study was carried on the phenomena in reactivity with the clay surface according to the thickness of the cobalt component coating. In the coated specimen, it was observed that the cobalt component was spreaded to diffuse with a constant thickness from the surface of it and the diffusion layer at the white porcelain soil was more increased with the increase of the amount of cobalt sulfate than at the celadon porcelain one. It was evaluated that the color of the surface on the coated specimen at the white porcelain soil was changed from grayish blue to blue and the <TEX>$L^*$</TEX> value was decreased from 51.78 to 37.61 and also in the case of the coated specimen in celadon porcelain soil, <TEX>$L^*$</TEX> value was from 53.91 to 38.93 and the color was from dark olive gray to dark gray. The physical properties of the specimen were characterized by X-ray diffraction, Scanning electron microscope, Dilatometer, TG-DTA, UV-vis spectrophotometer and HRDPM.

Commercial process development for synthesis of spherical cobalt nanopowder by wet chemical reduction reaction

A commercial process for synthesis of spherical cobalt nanopowder has been developed. Based on laboratory scale experimental data, pilot plant production and reproducibility of the developed process has been investigated and optimized. Cobalt nanopowder were synthesized from reduction of cobalt sulfate salt, using hypo-phosphorous acid as a reductant in solution of sodium hydroxide. The effect of various process parameters on morphology and structure of the cobalt nanopowder synthesis, both at laboratory scale and pilot scale processes were optimized and compared. The developed proposed flow sheet is a techno economical feasible process for commercial production of spherical cobalt nanopowder in the range of 100–300nm size. An indigenous designed pilot plant, capable of handling 30L solution per batch has been developed.

Effect of Carbon Nanotubes on Corrosion and Tribological Properties of Pulse-Electrodeposited Co-W Composite Coatings

Cobalt-Tungsten (Co-W) alloy coatings possessing high hardness and wear/corrosion resistance, due to their ecofriendly processing, have been of interest to the researchers owing to its various industrial applications in automobile, aerospace, and machine parts. This technical paper reports Co-W alloy coatings dispersed with multiwalled carbon nanotubes (MWCNTs) produced by pulse electrodeposition from aqueous bath involving cobalt sulfate, sodium tungstate, and citric acid on stainless steel substrate (SS316). Studies on surface morphology through SEM, microhardness by Vickers method, microwear by pin-on-disk method, and corrosion behavior through potentiodynamic polarization method for the Co-W-CNT coatings were reported. Characterization studies were done by SEM and EDX analysis. The results showed that the corrosion and tribological properties of the pulse-electrodeposited Co-W-CNT alloy coatings were greatly influenced by its morphology, microhardness, %W, and MWCNT content in the coatings.

The use of boric acid (H3BO3) and boron oxide (B2O3) for co-precipitation synthesis of cobalt-boron catalysts: Catalytic activity in hydrogen generation

The use of boric acid (H3BO3) and boron oxide (B2O3) for the synthesis of cobalt-based catalysts by the co-precipitation technique was investigated and catalytic activities in hydrogen generation were evaluated. Different cobalt salts [cobalt (II) chloride (CoCl2 · 6H2O), cobalt sulfate (CoSO4 · 5H2O) and cobalt(II) nitrate (Co(NO3)2 · 7H2O)] were used with H3BO3 and B2O3 to prepare Co based catalysts. Crystalline, surface and chemical characteristics were clarified using X-ray diffraction (XRD); low temperature adsorption of nitrogen (BET), scanning electron microscopy (SEM), and inductively coupled plasma optical emission spectroscopy (ICP-OES). Three types of powder samples were obtained according to the different boron sources and cobalt salts, and it was found that an efficient Co based catalyst was obtained by co-precipitation of B2O3 and CoCl2 · 6H2O salt. Additionally, the effect of temperature, stabilizer ratio and NaBH4/catalyst ratio on parameters, characterizing the reaction of hydrogen generation was investigated. The zero order, first order and Langmuir-Hinshelwood kinetic models were used to identify the effect of Co based catalysts on the behavior of the catalytic system in hydrogen generation. Kinetic parameters of hydrogen generation for zero-order kinetic model were calculated for the following conditions: the rate of hydrogen generation is 0.93 L H2 g−1 catalyst min−1, the activation energy is 43.55 kJ mol−1 and the constant of Arrhenius equation is 11 min−1.