Synthesis of Commercial-Scale Tungsten Carbide-Cobalt (WC/Co) Nanocomposite Using Aqueous Solutions of Tungsten (W), Cobalt (Co), and Carbon (C) Precursors

This paper reports the chemical synthesis of tungsten carbide/cobalt (WC/Co) nanocomposite powders via a unique chemical processing technique, involving the using of all water soluble solution of W-, Co- and C-precursors. In the actual synthesis, large quantities of commercial-scale WC-Co nanocomposite powders are made by an unique combination of converting a molecularly mixed W-, Co-, and C-containing solutions into a complex inorganic polymeric powder precursor, conversion of the inorganic polymeric precursor powder into a W-Co-C-O containing powder intermediates using a belt furnace with temperature at about 500°C - 600°C in an inert atmosphere, followed by carburization in a rotary furnace at temperature less than 1000°C in nitrogen. Liquid phase sintering technique is used to consolidate the WC/Co nanocomposite powder into sintered bulk parts. The sintered parts have excellent hardness in excess of 93 HRA, with WC grains in the order of 200 - 300 nm, while Co phase is uniformly distributed on the grain boundaries of the WC nanoparticles. We also report the presence of cobalt Co precipitates inside tungsten carbide WC nanograins in the composites of the consolidated bulk parts. EDS is used to identify the presence of these precipitates and micro-micro-diffraction technique is employed to determine the nature of these precipitates.

In-situ growth of vertically aligned nickel cobalt sulfide nanowires on carbon nanotube fibers for high capacitance all-solid-state asymmetric fiber-supercapacitors

Fiber-supercapacitors(FSCs)are promising power sources for miniature portable and wearable electronic devices.However,the development and practical application of these FSCs have been severely hindered by their low volumetric capacitance and narrow operating voltage.In this work,vertically aligned nickel cobalt sulfide(Ni Co2S4)nanowires grown on carbon nanotube(CNT)fibers were achieved through an in-situ two-step hydrothermal reaction method.The as-prepared Ni Co2S4@CNT fiber electrode exhibits a high volumetric capacitance of 2332 F cm-3,benefiting from its superior electric conductivity,large surface area,and rich Faradic redox reaction sites.Furthermore,a Ni Co2S4@CNT//VN@CNT(vanadium nitride nanosheets grown on CNT fibers)asymmetric fiber-supercapacitor(AFSC)was successfully fabricated.The device exhibits an operating voltage up to 1.6 V and a high volumetric energy density of 30.64m Wh cm-3.The device also possesses outstanding flexibility as evidenced by no obvious performance degradation under various bending angles and maintaining high capacitance after 5000 bending cycles.This work promotes the practical application of flexible wearable energy-storage devices.

Determination of Cobalt in Food, Environmental and Water Samples with Preconcentration by Dispersive Liquid-Liquid Microextraction

A new method for the determination of cobalt was developed by dispersive liquid-liquid microextraction preconcentra-tion and flame atomic absorption spectrometry. In the proposed approach, 1,5-bis(di-2-pyridyl) methylene thiocarbohydrazide (DPTH) was used as a chelating agent, and chloroform and ethanol were selected as extraction and dispersive solvents. Some factors influencing the extraction efficiency of cobalt and its subsequent determination, including extraction and dispersive solvent type and volume, pH of sample solution, concentration of the chelating agent, and extraction time, were studied and optimized. Under the optimum conditions, a preconcentration factor of 8 was reached. The detection limit for cobalt was 12.4 ng?mL–1, and the relative standard deviation (RSD) was 3.42% (n = 7, c = 100 ng?mL–1). The method was successfully applied to the determination of cobalt in food, environmental and water samples.

Effects of cobalt carbide on Fischer–Tropsch synthesis with MnO supported Co-based catalysts

Cobalt carbide(Co2C)was considered as potential catalysts available for large-scale industrialization of transforming syngas(H2 and CO)to clean fuels.Herein,we successfully synthesized Co-based catalysts with MnO supported,to comprehend the effects of Co2C for Fischer–Tropsch synthesis(FTS)under ambient conditions.The huge variety of product selectivity which was contained by different active sites(Co and Co2C)has been found.Furthermore,density functional theory(DFT)shows that Co2C is efficacious of CO adsorption,whereas is weaker for H adsorption than Co.Combining the advantages of Co and Co2C,the catalyst herein can not only obtain more C5+products but also suppress methane selectivity.It can be a commendable guide for the design of industrial application products in FTS.

In-Situ Microscopic FTIR Spectroelectrochemistry of Ascorbic Acid in Poly(ethylene glycol)/LiClO_4 Electrolyte Paste and in the Presence of Dispersed Cobalt Hexacyanoferrate Microcrystalline Powder

In-situ microscopic FTIR spectroelectrochemical technique(MFTIRs) was applied to studying the electrochemical oxidation of ascorbic acid(AA) in poly(ethylene glycol)(PEG) paste at a 100 μm diameter Pt disk electrode. Using this technique, the catalytic ability of cobalt hexacyanoferrate(CoHCF) microcrystalline toward AA oxidation was also studied. It was found that the dispersed CoHCF powder in the PEG paste can generate well shaped thin layer cyclic voltammetric waves with the peak height proportional to the scan rate, corresponding to the Fe centered redox reactions. This oxidation step catalyzed the AA oxidation. Also, this pasted CoHCF powder generated well resolved in situ MFTIRs spectra, by which a chemical interaction between CC bond of AA ring and CoHCF lattice was revealed. A corresponding surface docking mechanism for the catalytic reaction has been proposed.

A Study of Neutron and Gamma-Ray Interaction Properties with Cobalt-Free Highly Chromium Maraging Steel

Cobalt-free maraging steels of different compositions have been prepared by electro-slag remelting technique using titanium and chromium instead of cobalt. Neutron removal cross-sections have been calculated, also mass attenuation coefficients and effective electron densities have been determined for the prepared samples in the photon energy range up to 2.8 MeV. Other steel alloys and lead samples have also been investigated for the sake of comparison. The results prove the superiority of cobalt-free maraging steels compared with the other steel types to be used as a proper shielding material in the nuclear field. Among the investigated steels, the steel “0.045%C- 13.35%Ni-2.05%Cr-4.5%Mo-0.06%Ti” has the best attenuation properties.

Electrocatalytic water splitting at nitrogen-doped carbon layers-encapsulated nickel cobalt selenide

Generally,the catalytic overpotentials of hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)are unavoidable because of the low charge transfer.In this work,two strategies of alloying of Co with Ni and enclosing of electrocatalysts with carbonaceous materials were both used to accelerate the catalytic efficiency of cobalt selenide for water splitting.The nitrogen-doped carbon(NC)layer improves the reaction kinetics by efficient charge transfer.The alloying of metal into composited electrocatalysts can modify the electronic properties of host materials,thereby tuning the adsorption behavior of intermediate and improving the electrocatalytic activity.As expected,Nyquist plots reveal that the charge-transfer resistance(Rct)of nickel cobalt selenide encapsulated into nitrogen-doped carbon layer(CoNiSe/NC-3,Co:Ni=1:1)are just 5 and 9 for HER and OER,respectively,which are much lower than those of CoSe/NC-1(Co:Ni=1:0)(81 and 138)and CoNiSe/NC-3 without NC(CoNiSe-3)(54 and 25).With the high charge transfer and porous structure,CoNiSe/NC-3 shows good performance for both HER and OER.When current density reaches 10 m A cm-2,only 100 and 270 mV overpotentials are required for HER and OER,respectively.With the potential of 1.65 V,full water splitting also can be catalyzed by Co Ni Se/NC-3 with current density of 20 m A cm-2,suggesting that CoNiSe/NC-3 could be used as replacement for noble metal electrocatalysts.

Hollow cobalt oxide nanoparticles embedded in nitrogen-doped carbon nanosheets as an efficient bifunctional catalyst for Zn–air battery

Rational design of low-cost, highly electrocatalytic activity, and stable bifunctional electrocatalysts for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) has been a great significant for metal–air batteries. Herein, an efficient bifunctional electrocatalyst based on hollow cobalt oxide nanoparticles embedded in nitrogen-doped carbon nanosheets(Co/N-Pg) is fabricated for Zn–air batteries. A lowcost biomass peach gum, consisting of carbon, oxygen, and hydrogen without other heteroatoms, was used as carbon source to form carbon matrix hosting hollow cobalt oxide nanoparticles. Meanwhile, the melamine was applied as nitrogen source and template precursor, which can convert to carbon-based template graphitic carbon nitride by polycondensation process. Owing to the unique structure and synergistic effect between hollow cobalt oxide nanoparticles and Co-N-C species, the proposal Co/N-Pg catalyst displays not only prominent bifunctional electrocatalytic activities for ORR and OER, but also excellent durability. Remarkably, the assembled Zn–air battery with Co/N-Pg air electrode exhibited a low discharge-charge voltage gap(0.81 V at 50 mA cm^-2) and high peak power density(119 mW cm^-2) with long-term cycling stability. This work presents an effective approach for engineering transition metal oxides and nitrogen modified carbon nanosheets to boost the performance of bifunctional electrocatalysts for Zn–air battery.

Psychotropic effects of aspirin, acetylsalicylate cobalt and acetylsalicylate zinc at various doses

For the first time it is shown that psychotropic action of acetylsalicylates at various doses is manifested as a nonmonotonic dependence having its peaks at therapeutic and ultra-low dose zones. It is discovered that development of effects of aspirin resembles that of acetylsalicylate zinc. Acetylsalicylate cobalt at extremely low doses zone showed the highest antidepressant activity, demonstrating toxicity at high doses. Generally, it is revealed that the use of aspirin and its salts at high doses range causes maximum psychotropic effects development, usually accompanied by side-effects. Therefore, aspirin, acetylsalicylate cobalt and zinc at extremely low doses are recommended for further study as psychotropic medications.

Decorating cobalt phosphide and rhodium on reduced graphene oxide for high-efficiency hydrogen evolution reaction

Electrochemical reduction of water to hydrogen holds great promise for clean energy,while its widespread application relies on the development of efficient catalysts with large surface area,abundant exposed active sites and superior electron conductivity.Herein,we report a facile strategy to configure an electrocatalyst composed of cobalt phosphide and rhodium uniformly anchored on reduced graphene oxide for hydrogen generation.The hybrids effectively integrate the exposed active sites,electron conductivity and synergistic effect of the catalyst.Electrochemical tests exhibit that the catalyst shows superior hydrogen evolution reaction catalytic activity and stability,with a small Tafel slope of 43 m V dec-1.Overpotentials as low as 29 and 72 mV are required to achieve current densities of 2 and 10 mA cm-2in 0.5M H2SO4,respectively.The hybrid constitution with highly active sites on conductive substrate is a new strategy to synthesize extremely efficient electrocatalysts.Especially,the efficient synergistic effect among cobalt phosphide,rhodium and reduced graphene oxide provides a novel approach for configuring electrocatalysts with high electron efficiency.

Synthesis, Characterization and Crystal Structure of Cobalt(II) Complex of a Schiff Base Derived from Isoniazid and Pyridine-4-Carboxaldehyde

A new hydrogen bonded Cobalt(II) Schiff base complex,?N’-(pyridine-4-carboxaldehyde) isonicotinoylhydrazone Cobalt(II), has been synthesized from isoniazid and pyridine-4-carboxaldehyde and characterized by IR spectroscopy, 1H-NMR, elemental analysis, TGA and single crystal X-ray structure determination. X-ray crystal structure analysis shows an octahedral complex with a metal centre coordinated to two ligand molecules through the pyridine nitrogen atoms and four water molecules and containing two nitrate groups as counter ions. The complex crystallizes in the monoclinic crystal system and P2(1)/n space group. The unit cell dimensions are: a = 7.2108(4) Å, b = 16.6020(9) Å, c = 13.0389(6) Å,α = 90°, β = 103.972(4)°, γ = 90°. The molecule is symmetrical about the cobalt centre as observed from the 1H-NMR and 13C-NMR and confirmed by the single crystal X-ray structure of the complex. Thermogravimetric analysis shows two steps decomposition of the complex to leave a metal oxide residue. The title compound is expected to be biologically active as one of the precursors (isoniazid) is a therapeutic agent with well-established clinical applications.

Toward Flexible and Wearable Embroidered Supercapacitors from Cobalt Phosphides-Decorated Conductive Fibers

Wearable supercapacitors(SCs)are gaining prominence as portable energy storage devices.To develop high-performance wearable SCs,the significant relationship among material,structure,and performance inspired us with a delicate design of the highly wearable embroidered supercapacitors made from the conductive fibers composited.By rendering the conductive interdigitally patterned embroidery as both the current collector and skeleton for the SCs,the novel pseudocapacitive material cobalt phosphides were then successfully electrodeposited,forming the first flexible and wearable in-plane embroidery SCs.The electrochemical measurements manifested that the highest specific capacitance was nearly 156.6 mF cm?2(65.72 F g?1)at the current density of 0.6 mA cm?2(0.25 A g?1),with a high energy density of 0.013 mWh cm?2(5.55 Wh kg?1)at a power density of 0.24 mW cm?2(100 W kg?1).As a demonstration,a monogrammed pattern was ingeniously designed and embroidered on the laboratory gown as the wearable in-plane SCs,which showed both decent electrochemical performance and excellent flexibility.

Size-dependent catalytic activity of cobalt phosphides for hydrogen evolution reaction

Transition metal phosphides are a class of promising electrocatalysts for hydrogen evolution reaction(HER) to replace noble metals.In this work,we for the first time synthesize carbon supported CoP nanoparticles with the average particle sizes from 3.3 to 9.2 nm,via a solvothermal process followed by low-temperature topological phosphorization,and the size-dependent HER activity of the CoP is investigated by virtue of TEM,XRD,XPS and the electrochemical techniques.It is discovered that the 9.2nm-CoP particles possess high intrinsic HER catalytic activity as compared to the 3.3nm-CoP,although the smaller one displays a high mass activity due to the large surface area.Detailed studies manifest that the small CoP particles suffer from serious oxidation once exposing to air.In contrast,most cobalt remains in the quasi-metallic state in the relatively large CoP particles,which is beneficial for the desorption of Hads,the rate determining step of the HER process over CoP surface.In addition,the low charge transfer resistance across the liquid/solid interfaces also contributes to the excellent HER activity of the relatively large CoP particles.

Voltammetric sensor based on cobalt-poly(methionine)-modified glassy carbon electrode for determination of estriol hormone in pharmaceuticals and urine

A voltammetric sensor based on the electropolymerization of cobalt-poly(methionine)(Co-poly(Met)) on a glassy carbon electrode (GCE) was developed and applied for the determination of estriol by differential pulse voltammetry (DPV) for the first time. The electrochemical properties of the Co-poly(Met)/GCE were analysed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the polymers on the GCE surface. The deposition of the Co-poly(Met) film on the GCE surface enhanced the sensor electronic transfer. CV studies revealed that estriol exhibits an irreversible oxidation peak at t0.58 V for the Co-poly(Met)/GCE (vs. Ag/AgCl reference electrode) in 0.10 mol/L Britton-Robinson buffer solution (pH=7.0). Different voltammetric scan rates (10-200 mV/s) suggested that the estriol oxidation on the Co-poly(Met)/GCE surface is controlled by adsorption and diffusion processes. Based on the optimized DPV conditions, the linear responses for estriol quantification were from 0.596 μmol/L to 4.76 μmol/L (R2 =0.996) and from 5.66 μmol/L to 9.90 μmol/L (R2 =0.994) with a limit of detection (LOD) of 0.0340 μmol/L and a limit of quantification (LOQ) of 0.113 μmol/L. The DPV-Co-poly(Met)/GCE method provided good intra-day and inter-day repeatability with RSD values lower than 5%. Also, no interference of real sample matrices was observed on the estriol voltammetric response, making the DPV-Copoly( Met)/GCE highly selective for estriol. The accuracy test showed that the estriol recovery was in the ranges 96.7%-103% and 98.7%-102% for pharmaceutical tablets and human urine, respectively. The estriol quantification in pharmaceutical tablets performed by the Co-poly(Met)/GCE-assisted DPV method was comparable to the official analytical protocols.

Further study of sources of the imported cobalt-blue pigment used on Jingdezhen porcelain from late 13 to early 15 centuries

Based on the conclusion of modern scientific analysis: the cobalt-blue pigment applied on Jingdezhen official porcelain during Yuan Dynasty and prior to Xuande reign of Ming Dynasty (1271―1425) contains high iron and low manganese con- tents, and the cobalt during Xuande and after Xuande periods (after 1426) of Ming Dynasty contains high manganese and low iron contents, in combination with the traditional archaeological method, the related historical textual records were in- vestigated and analyzed, the imported cobalt employed on Jingdezhen official porcelain was studied comprehensively, systematically and logically. In fact, 'Su Ma Li Qing' (Samarra-blue) and 'Su Bo Ni Qing' (Sumatra-blue) are definitely different cobalt ores originated in different places, because of their very similar translitera- tions in Chinese, the confusion has appeared in ancient books for more than 400 years, which considered 'Su Ma Li Qing' and 'Su Bo Ni Qing' as the same co- balt-blue pigment. In this article the mistake was corrected, the possible producing places and the approximate eras of the two pigments imported to China and used at Jingdezhen were also suggested.

EFFECT OF ELECTROLESS PLATING COBALT UPON CHARACTERISTICS OF NICKEL HYDROXIDE ELECTRODEFORRECHARGEABLEALKALINEBATTERIES

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Investigation of a Modified Cobalt-Free Alloy for Nuclear Application

Cobalt-free alloy of constituent’s “0.045%C-12.73%Ni-6.53%Cr-3.2%Mo-0.02%Ti-0.01%V” has been prepared by electro slag remelting technique. Mass attenuation coefficient, half value layer and effective atomic number have been determined for the prepared sample at photon energies 235 - 2700 keV. The results are compared with the corresponding theoretical calculations based on XCOM program and a fair agreement is obtained.

Morphology and Crystallinity-controlled Synthesis of Manganese Cobalt Oxide/Manganese Dioxides Hierarchical Nanostructures for High-Performance Supercapacitors

We demonstrate a novel preparative strategy for the well-controlled MnCo_2O_(4.5)@MnO_2 hierarchical nanostructures.Bothδ-MnO_2 nanosheets andα-MnO_2 nanorods can uniformly decorate the surface of MnCo_2O_(4.5)nanowires to form core-shell heterostructures.Detailed electrochemical characterization reveals that MnCo_2O_(4.5)@δ-MnO_2 pattern exhibits not only high specific capacitance of 357.5 F g^(-1)at a scan rate of 0.5 A g^(-1),but also good cycle stability(97%capacitance retention after 1000 cycles at a scan rate of 5 A g^(-1)),which make it have a promising application as a supercapacitor electrode material.

Fischer–Tropsch synthesis on impregnated cobalt-based catalysts:New insights into the effect of impregnation solutions and pH value

The Co-based catalysts were prepared with different cobalt acetate solutions. Effects of pH value were studied deeply on Fischer–Tropsch synthesis (FTS) through a semi-batch reactor. Among all impregnation solutions (water, butanol, amyl alcohol, acetic acid, nitric acid and ammonium nitrate), the catalyst prepared by NH4NO3solution showed the highest catalytic activity due to its small particle size and high reduction degree. However, the catalyst with the smallest particle size derived from water as impregnation solution exhibited low activity as well as high methane selectivity since it was difficult to be reduced and inactive in FTS. According to FT-IR spectra results, the low intensity of absorbed CO on the catalyst prepared from water solution resulted in low FTS activity. Whereas, the high activity of catalysts prepared from NH4NO3solution could be explained by the high intensity of absorbed CO on the catalysts. The cobalt species on the catalysts prepared under lower pH conditions exhibited smaller particle size distribution as well as lower CO conversion than those prepared at higher pH value. © 2016 Science Press

Solvent-free synthesis of alumina supported cobalt catalysts for Fischer–Tropsch synthesis

A novel mechano-synthesis method has been elaborated in this work for the design of efficient cobalt-based Fischer–Tropsch catalysts. The process aims to reduce the total number of steps involved in the synthesis of solid catalysts and thus to avoid relevant toxic solutions generated during the catalyst preparation. The mechano-synthesis of the Co/Al2O3catalyst was processed in a low-energy vibratory micro mill and high energy planetary ball mill. Porous spherical γ-aluminas (1860 µm and 71 µm mean particle diameter) were used in this work as host compounds. Co3O4(3 µm mean particle diameter) has provided guest particles for mechano-synthesis. The catalysts were characterized by textural (surface area, porosity and particle size) and structural analyses (X-ray diffraction, TPR, SEM-EDX and microprobe). The microprobe images show deposition of Co3O4on the surface of the alumina and indicated no Co3O4diffusion inside the alumina pores. SEM-EDX mapping illustrated that cobalt coating tended to occur on surface of rounded shape of cracked alumina fragments. After milling, the crystallite size of Co3O4decreased to 15 nm from 30 to 50 nm. The TPR profiles indicated very low concentrations of inactive cobalt aluminate mixed compounds which are usually produced during the catalyst preparation by impregnation. In Fischer–Tropsch synthesis, the catalysts prepared using mechano-synthesis methods showed catalytic performance comparable to the catalysts prepared by impregnation. © 2016 Science Press