Papers by Keyword: Cobalt

Abstract: A ferruginous nickel laterite was leached by sulfuric acid at atmospheric pressure. Nickel extraction was largely dependent on sulfuric acid concentration and leaching temperature. Besides these two factors, leaching time and liquid/solid ratio also influenced cobalt extraction significantly. Nickel was easier to be extracted than cobalt. About 95% nickel and cobalt could be extracted when leaching with 5mol/L sulfuric acid for 2h at 100°C, and the acid consumption was 1.417kg H2SO4/kg dry ore.

Abstract: Dimethyldithiocarbamate precipitation is a secondary resource containing nickel and cobalt, which are formed by adding sodium dimethyldithiocarbamate to purify the neutralized filtrate of pyrolusite reductive leaching process. The extraction of nickel and cobalt from dimethyldithiocarbamate precipitation was investigated using nitric acid as oxidant in dilute sulfuric acid medium in this paper. The effects of concentrations of nitric acid and sulfuric acid, leaching temperature as well as reaction time were discussed. The results showed that high nickel and cobalt recovery could be obtained by analyzing the leaching efficiencies of nickel and cobalt during the leaching process. The optimal leaching condition was 1.47 mol/L H2SO4 and 1.16 mol/L HNO3 for 30 min at 45 °C while using particles smaller than 0.420 mm. And the leaching efficiencies were 98% for Co and 95% for Ni, respectively.

Abstract: Effect of metal modification to carbon paper as the anode of mediator-aided yeast-based microbial fuel cell on the cell performance was investigated using methylene blue as an exogenous mediator. The modification was conducted using a sputtering technique by depositing Co or Au thin layer, 30 nm. The electrode performance was evaluated by measuring the electrode potentials and the fuel cell power output. The metal modification significantly increased the mediator-aided MFC performance.

Abstract: Effect of modification of carbon paper with a thin layer of cobalt or gold on the performance of yeast-based microbial fuel cells was investigated. The modification was conducted by depositing Co or Au thin layer with different thickness, 5 nm and 30 nm, using a sputtering technique. The electrode performance was evaluated by measuring the electrode potentials and the fuel cell power output. The Co modification significantly increased the performance of the fuel cell, while the Au modification inhibited the performance. SEM observation indicated that the adhesion density of the yeast cells on the electrode surface was affected by the metals. It was confirmed that the electron transfer took place through the surface confined species at the mediatorless anode.

Abstract: The allotropic phase transformation of cobalt powder prepared by high-energy ball milling was investigated as a function of milling time. Measurement of crystallite size and micro-strain in the powder systems milled for different times were conducted by X-ray diffractometry. The X-ray diffraction (XRD) peaks were analyzed using the Pearson VII profile function in conjunction with Rietveld method. X-ray diffraction line broadening revealed that allotropic transformation between face-centred-cubic phase (fcc) and hexagonal close-packed phase (hcp) in cobalt is grain size dependent and also on the accumulation of structure defects. The results showed that the phase formation of cobalt depends on the mill intensity that influences of both the grain size and the accumulation of structure defects. However, this theory alone is not adequate to explain the effects in this work. It was found that the total surface energy (Ω) theory satisfactorily explains the phase transformation behavior of cobalt. The smaller value of surface energy (Ω) of the fcc crystal than the hcp phase when size decreases may alter the qualitative aspects of the phase formation.

Abstract: In this paper, a batch of M- type strontium hexaferrite samples with nominal composition of SrFe_12-xCo_xO₁₉(where x= 0- 2), have been synthesized via sol- gel method. In the synthesis of samples, first a precursor gel was prepared, and then dry- gel was calcined at 1000°C for 2 hours to obtain the nano- SrFe_12-xCo_xO₁₉. The XRD results revealed that for SrFe12-xCoxO19 samples with x≤0.5, all of them have single- phase hexaferrite structure and also this data suggests that the F ³⁺ ions are substituted by Co²⁺ ions in the crystallography sites of the SrFe_12-xCo_xO₁₉, but for the samples with x>0.5, the second phase of CoFe2O4 is appeared and suggests that the Co²⁺ ions also make a distinct phase in the samples. The magnetic properties, such as saturation magnetization (Ms), magnetic remanence (Mr), magnetic coercivity (Hc), squareness ratio (Mr/Ms), crystalline anisotropy field (Ha), energy product [(BH)max] and the susceptibility χ as the derivative of M with respect to H of the upper branch of the hysteresis loop were discussed by measurements of M-H curves with vibrating sample magnetometer (VSM). The magnetic measurements revealed that the coercively (Hc) values of all the samples decrease with increasing dopant contents.

Abstract: The effects of aqueous delithiation of lithium cobalt oxide crystals on the crystal texture and etching patterns has been studied by electron microscopy, x-ray and neutron diffraction at high resolution. The delithiation proceeds to exfoliation and in the process textural patterns that appear have been associated with periodic strains in the crystals developed by the delithiation.

Abstract: A New Complex Crystal [Co(Hdmg)₂(Him)₂]·(ClO4) (H2dmg = Dimethylglyoxime,Him = Imidazole) Had Been Synthesised in Aqueous Solution and Was Characterized by X-ray Diffraction and IR Spectrum. the Complex Crystallizes in Triclinic Space Group with Cell Constants a= 20.868(7)Å, B=11.408(4)Å, C=15.816(4)Å, α=90.00°, β=116.97(2)°, γ= 90.00°, V= 3355.8(17) Å3, Z=4, F(000)=1732. the Coordination Environment of Cobalt Atom Is a Slightly Distorted Octahedron. the Four Equatorial Donors Are Four Nitrogen Atoms from Two Bidentate Chelate Hdmg Anion Ligands. the Apex Points Are Occupied by Two Nitrogen Atoms from him Ligands. the Co-N(Him) Distance Is 1.930Å, and the Co-N(dmg) Distances Are Varying in the Range from 1.886Å to 1.993Å which Are in Agreement with Corresponding Reported in a Number of other Structurally Related Copper(II) Complexes.

Abstract: In the dual-phase model of interacting nanoparticles stretching leads to a decrease in both coercive force H_c and saturation remanence I_rs , and compression — to their growth. Magnetostatic interaction between particles also decreases both H_c and I_rs . Theoretical analysis was carried out in the framework of the dual-phase system of interacting particles on the example of nanoparticles γ-Fe₂ O₃, epitaxially coated with cobalt.

Abstract: Abstract. The novel tetraphenylethylene (TPE) based sensor 1 bearing bis(2-pyridin-2-ylmethyl) amine (BPA) unit and BODIPY unit linked with triazole moieties could be obtained by click reaction efficiently. It was employed as a fluorescence probe for the selective recognition of Cu²⁺ and Co²⁺. They form stable 1:1 stoichiometric complexes and the lowest limit of detection was 1×10-7 M.