Papers by Keyword: Cobalt

Abstract: The reduction behaviour of cobalt doped with nickel oxide and undoped nickel oxide (NiO) by hydrogen (H₂) in nitrogen (20%, v/v) and carbon monoxide (CO) in nitrogen (40%, v/v) atmospheres have been investigated by temperature programmed reduction (TPR). The phases formed of partially and completely reduced samples were characterized by X-ray diffraction spectroscopy (XRD). TPR results indicate that the reduction of Co doped and undoped nickel oxide in both reductants proceed in one step reduction (NiO → Ni) without intermediate. TPR results also suggested that by adding Co metal into NiO, the reduction to metallic Ni by both reductant gaseous give different intensity of the peak. The reduction process of Co and undoped NiO become faster when H₂ was used as a reductant. Furthermore, in H₂ atmosphere, Co-NiO give complete reduction to metallic Ni at 700 °C. Meanwhile, XRD analysis indicated that NiO without Co composed better crystallite phases of NiO with higher intensity.

Abstract: The modification and tailoring characteristic of nanostructured materials are of great interest due to controllable and unusual inherent properties in such materials. Cobalt-doped zinc oxide (Co:ZnO) thin films were prepared using the sol-gel technique with the spin coating method. The optical and physical properties of Co:ZnO films were tailored by the adjustment of Co concentration, which was realised by varying the ratio. The morphology and structure properties were characterised, and the effects of Co doping and post-annealing were investigated. Similar with undoped ZnO, the synthesised Co:ZnO films have a hexagonal wurtzite structure with the crystallinity deteriorated, and present high visible transparency with the absorption edge redshifted. Debye–Scherrer analysis of XRD pattern reveals an increase of the crystallite size with doping concentration. The bandgap, calculated using a Tauc Plot method, reveals a decrease in the absorption onset with an increase in the doping level.

Abstract: Zirconia (ZrO₂) powders doped with cobalt were prepared by sol-gel method using inorganic salt of zirconium (IV) chloride (ZrCl₄) as precursor. The amount of cobalt was varied in the range of 4–16% weight percent to study the effect to structural properties. X-ray diffraction (XRD) analysis suggested the resulting phases were zirconium oxide (Baddeleyite) with monoclinic crystal system along with cobalt oxide as secondary phase. The increasing cobalt content caused the XRD peaks to shift into lower angle due to substitution of Zr atom to smaller Co atom in crystal lattice. Scanning electron microscope (SEM) images showed the samples with higher Co content had smoother surface. Generally, the microstructures of Co doped zirconia powders consisted of large agglomerates with small particles on the surface.

Abstract: The current state of the issue of the slag waste processing was considered, using the example of the Southern Urals Nickel Plant. The average analysis of the chemical composition of the slag was performed; the determined phases contained iron, cobalt, nickel and chromium. The maps of the distribution of these elements in the slag were obtained.

Abstract: Higher efficiency in raw material recycling is discussed as a key strategy to decrease the environmental impact of resource consumption and to improve materials’ availability in order to mitigate supply risks. However, particularly in the case of technology metals, demand is driven by specific emerging technologies from which recycling will not be possible before the end of their useful lifetimes. Hence, the availability of secondary materials is limited by the amount of obsolete products as well as their collection, separation and treatment during waste management and recycling. In this paper, we present the results of a dynamic material flow model for cobalt as a key raw material for lithium-ion batteries at an European level (EU28). This model aims at quantifying the current state of recycling and future recycling potentials from end-of-life (EoL) product flows. While it is expectable that obsolete large battery packs from (hybrid) electric vehicles will be efficiently collected in future, EoL Li-ion battery flows will remain dominated by smaller electronic equipment (smartphones, laptops etc.) in the coming years and the model results show a significant potential for improvements in collection and material recovery from EoL batteries in Europe. A major challenge will be the collection of smaller batteries and Waste Electrical and Electronic Equipment (WEEE) in general from which a significant share of total European cobalt demand could be recovered in the coming years.

Abstract: The crystal structure of the (Cr,Ni)₄Si phase with and without Co was refined from X-ray powder diffraction data. The compound crystallises with an Au₄Al-type structure (Pearson symbol cP20, space group P2₁3): unit-cell parameter a = 0.611959(6) nm for the composition (Cr_0.312Ni_0.688)₄Si, a = 0.612094(6) nm for (Cr_0.375Ni_0.625)₄Si, and a = 0.612316(6) nm for (Cr_0.337Co_0.063Ni_0.600)₄Si. The magnetic susceptibility was measured in external fields up to 7 T at temperatures between 1.8 and 400 K. The three investigated samples exhibited paramagnetic behaviour described by the modified Curie-Weiss law: χ₀ = 146∙10^-6 emu g-at.^-1, μ_eff = 0.21 μ_B/atom, θ_P = -13 K for (Cr_0.312Ni_0.688)₄Si; χ₀ = 158∙10^-6 emu g-at.^-1, μ_eff = 0.20 μ_B/atom, θ_P = -15 K for (Cr_0.375Ni_0.625)₄Si; χ₀ = 169∙10^-6 emu g-at.^-1, μ_eff = 0.18 μ_B/atom, θ_P = -52 K for (Cr_0.337Co_0.063Ni_0.600)₄Si.

Abstract: The interaction of components and structure formation were studied in liquid phase sintering of Co-Sn and Co-Sn-Cu powder materials. The powders of commercially pure metals were mixed with an organic binder and applied on the steel substrate. Sintering was performed under vacuum at temperatures of 820 and 1100 °C. The structure of sintered alloys was investigated by X-ray diffractometry and electron probe microanalysis, and microhardness (HV_0.01) of the structural components was measured. It has been found that the nature of interaction of the liquid tin with the solid phase at the initial stage of sintering affects the formation of structure and porosity of Co-Sn and Co-Sn-Cu alloys considerably. In Co-Sn alloys, diffusion of tin into cobalt particles leads to the formation of intermetallic compounds, which hinders spreading of the liquid phase. This results in a porous defect structure formed in Co-Sn alloys. In Co-Sn-Cu alloys, at the initial stage of sintering the liquid phase enriched with copper is formed that wets the cobalt particles and contributes to their regrouping. As a result of this, materials with minor porosity are formed.

Abstract: Structure formation of diamond-containing composites with Sn-Cu-Co-W binders has been studied within the range of sintering temperatures of 780–820°C. The specimens were obtained by rolling the paste-like mixtures of metallic powders and diamonds on steel substrates, with sintering performed in vacuum. The structure of the sintered specimens was studied by optical metallography, X-ray diffractometry and electron probe microanalysis. Hardness of the materials was identified by Rockwell method (scale B). It has been found that the process of composites sintering is largely affected by oxide films available on the surface of the powders. In order to obtain composites having less than 10% porosity and up to 96–98 HRB hardness, they have to be sintered at the temperature of 820°C which eliminates the oxide films.

Abstract: The paper dwells upon the specifics of worn spots being formed on a silicon-carbide crystal in microscratching of iron, cobalt, and nickel. Analysis was done using a Versa 3D dual-beam electron microscope. The chemical composition of worn spots was studied by local X-ray microanalysis. It was found out that the amount of metal transferred to the silicon-carbide worn spot was associated with the electron structure of metal atoms.

Abstract: Silicon-cobalt nanocomposites on NrGO, Si-Co/NrGO, were synthesized by the modified polyol method. Rice husk was used as the silicon source. The composites were primarily characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy equipped with energy dispersive spectroscopy. The small-sized particles of the silicon-cobalt product were effectively distributed on the NrGO. Finally, these anode materials were tested in lithium-ion batteries by haft-coin cell assembly. Electrochemical properties were measured and the result showed an initial capacity of 975 mAh g^-1. This material is expected to be used as a high-performance anode, suitable for the next generation of anode materials in lithium-ion batteries.