Pure Cobalt Research Articles

Co2.8Mg0.2O4 as a promising thermochemical energy storage material with lower reduction onset temperature and higher energy density

Co-based oxides have been considered as one of the most promising materials for thermochemical energy storage (TCES) systems, however, the high operation temperature limits their applications. Specially, when Co3O4-based materials are used in concentrated solar power (CSP) system, a large mirror field area is required to meet the high endothermic temperature, which significantly increases the cost of a CSP system. In addition, the high cost of Co-based materials also limits its application. Improving the energy density can effectively reduce the use of the materials. Thus, in this work, to reduce the reduction onset temperature and increase the energy density of Co-based oxides, the TCES performance of Co3-xMgxO4 oxides is investigated. Co2.8Mg0.2O4 shows the best TCES performance. The reduction onset temperature of Co2.8Mg0.2O4 is ∼775.6 °C, which is 133.7 °C lower than that of the pure Co3O4 (∼909.3 °C). Mg-decoration can also improve the energy density of Co3O4 by 8.02 %. Furthermore, the in situ XRD spectra of the oxides indicate that precipitation of MgO from the Co3O4 lattice during the reduction reaction result in a metastable structure of the oxide, which is conducive to its reduction reaction. Density functional theory calculations indicate that Co2.8Mg0.2O4 possessed a higher defect formation energy and shorter chemical bonds than the pure cobalt oxide, which result in its lower reduction onset temperature and higher energy density. The cost-benefit analysis results showed that Mg-decoration could significantly reduce the area of mirror field and the use of energy storage material for a CSP system.

Transition of deformation mechanisms from twinning to dislocation slip in nanograined pure cobalt

• Gradient nanograined structures were prepared by plastic deformation in a pure cobalt sample. • Atomic-scale observation for microstructure characteristics was conducted in nanograined cobalt. • Comparing deformation mechanisms between nanograins and submicron-grains indicates a transition of governing deformation mechanism as reducing the gain size to nanoscale. Deformation mechanisms of nanograined and submicron-grained pure cobalt processed by means of high strain rate shear deformation at cryogenic temperatures were studied. Microstructural analysis revealed a transition of governing deformation mechanism from deformation twinning and < a > dislocation slip in submicron-grains to < c + a > and < a > dislocations slip in nanograins. Microhardness tests illustrated that the Hall-Petch relation slope changes consequently with the transition of deformation mechanism.

A persulfate oxidation system for removing acid orange from aqueous solution: Evaluation and degradation mechanism

Peroxymonosulfate-based advanced oxidation (PMS-AOP) is a promising technology for the degradation of environmental pollutants. PMS can be activated by various transition metals, especially cobalt-based catalysts, but pure cobalt catalyst suffers from severe metal leakage and poor cyclicality. This study synthesized NiCo2O4 using a co-precipitation hydrothermal method. The structures, morphologies, and chemical states of the prepared catalysts were hexagonal sheet structures. The activation of PMS by catalyst (NiCo2O4) is investigated in a PMS/carbonate (PC) system for Orange II degradation. The observed pseudo-first-order rate constants (k1) were assessed by the effects of different water matrices and operation conditions. The results show that kobs with NiCo2O4 were increased by 13 times than that of treatment without NiCo2O4. This was mainly due to Co3+ and Ni3+ act as electron acceptors to capture electrons from the PMS/PC system, forming a good redox cycle with HSO5−/SO5− and oxidizing Co2+/Ni2+ to produce a large amount of more active components (e.g., 1O2 and SO4⋅-). The good reusability and high stability of NiCo2O4 were demonstrated by five recycle tests. These results suggest that the NiCo2O4/PC system is an efficient and stable method of pollution remediation.

Nanostructuring Effect of Nano-CeO2 Particles Reinforcing Cobalt Matrix during Electrocodeposition Process.

The electrodeposition method was used to obtain nanostructured layers of Co/nano-CeO2 on 304L stainless steel, from a cobalt electrolyte in which different concentrations of CeO2 nanoparticles (0, 10, 20, and 30 g/L) were dispersed. The electrodeposition was performed at room temperature using three current densities (23, 48, and 72 mA cm−2), and the time was kept constant at 90 min. The influence of current densities and nanoparticle concentrations on the characteristics of the obtained nanostructured layers is also discussed. An X-ray diffractometer (XRD) was used to investigate the phase structure and cobalt crystallite size of the nanostructured layers, and a contact angle (sessile drop method) was used to assess the wettability of the electrodeposited layers. The roughness of the surfaces was also studied. The results show that the nanostructured layers became more hydrophilic with increasing nanoparticle concentration and increasing current density. In the case of pure cobalt deposits, an increase in the current density led to an increase in the size of the cobalt crystallites in the electrodeposited layer, while for the Co/nano-CeO2 nanostructured layers, the size of the crystallites decreased with increasing current density. This confirms the nanostructuring effect of nano-CeO2 electrocodeposited with cobalt.

High-performance different shape carbon decorated asteroidea-like cobalt diselenide electrode for energy storage device

Presently, the selenides-based transition metal appears to be one of the encouraging materials utilized in energy conservation, and storage applications. In this report, we presented the pure cobalt diselenide (CoSe2) and its composite with different shaped carbon using the one-step hydrothermal method. The CoSe2 with activated carbon composite exhibited the highest electrochemical performance among all prepared samples. It depicts retention of capacitance at around 80 % for 5000 cycles. A symmetric device prototype cell has been designed using a CoSe2/activated carbon composite electrode which displays the highest specific energy and power density as 83 Wh kg−1 at 1622 W kg−1. The maximum specific capacitance displayed by it is 886 F g−1 for a constant 10 mV s−1 Further, a possible charge storage mechanism related to the fabricated cell is proposed. The fabricated device application in practical life has been tested via a glowing panel containing 17 light-emitting diodes (LEDs) and its performance remains the same after six months too. The noteworthy improved capacity, good cycling stability, and high specific energy for the CoSe2 with activated carbon composite material is possibly considered a potential candidate for energy storage devices, and portable electronics.

The Effect of Nano-ZrO2 Dispersed Phase into Cobalt Plating Electrolyte on Layer Thickness and Current Efficiency

The aim of this work is to obtain nanocomposite layers having a cobalt matrix with zirconium oxide nanoparticles (mean diameter 30 nm) through the electrodeposition process. The plating electrolyte suspension is prepared by adding ZrO2 nanoparticles in a sulfate-chloride cobalt electrolyte at a concentration of 0 and 10 g·L−1. The electrodeposition is performed at room temperature, using three current densities of 23, 48 and 72 mA·cm−2 and three deposition times of 30, 60 and 90 min. The influence of current density, time and nanoparticles concentrations on the characteristics of the obtained nanostructured layers are also discussed. ZrO2 ceramic nanoparticles as a dispersed phase in the cobalt deposition electrolyte modify the mechanism of its electro-crystallization, so they participate in this process by increasing the rate of cobalt deposition, confirmed by the thickness of the nanocomposite layers obtained. The paper presents some of the comparative results obtained regarding the thickness of the layers, the current efficiency and the inclusion of the nanoparticles into nanocomposite layers depending on the current density and time of the electrodeposition process. The analysis of Co/nano-ZrO2 nanocomposite layers with the help of optical light microscopy and electronic microscopy in cross-section highlights the good degree of adhesion of the layers to the metallic substrate made of 304L stainless steel. The results of the study show that as the current density and time increase, the thickness of the composite layers increases. The efficiency of the process is improved compared to the electrodeposition of pure cobalt layers. The degree of inclusion of ZrO2 nanoparticles increases with time and decreases with increasing of imposed current density on the electrodeposition process. The distribution of the dispersed phase in the cobalt metallic matrix is uniform. The layers obtained in this study can be applied in aircraft technology, in the automotive industry, as well as in biomedical applications in order to improve the properties and to increase the corrosion or tribocorrosion resistance in a specific environment.

Operando identification of active sites in Co-Cr oxyhydroxide oxygen evolution electrocatalysts

Identifying the active sites and their dynamic changes is of critical significance for designing efficient oxygen evolution reaction (OER) catalysts, but remains challenging owing to the complexity in structure and reaction process. Herein, using various operando characterizations, we identify the origin of a 12-time enhancement of OER activity over pure cobalt oxyhydroxide achieved by confining high-valance chromium into its lattice. Operando X-ray absorption spectroscopy reveals in-situ generation of high-valence Cr state with shortened CrO bond relative to original state, indicating potential-dependent formation of OER intermediates on Cr sites. Operando electrochemical impedance and infrared spectroscopy provide direct spectroscopic evidence of OOH* on Cr site. Combined with theoretical calculations, the confined Cr is identified as the active site with improved bonding strength with O*, exhibiting a lower overpotential than that on Co site. This study elucidates the dynamic behaviour of active sites and provides guiding for improving OER catalysts via introducing high-valance metals.

Electronic structure and reactivity indexes of cobalt clusters, both pure and mixed with NO and [Formula: see text] ([Formula: see text], [Formula: see text] and [Formula: see text]).

Among the most popular motivations for environmental scientists is improving materials that could be useful to fight or avoid pollution. This work shows a study of neutral and cationic cobalt clusters from 4 to 9 atoms ([Formula: see text], q = 0,1 and n = 4-9) to model their separate interaction with contaminant nitric and nitrous oxides. This study is within the framework of the density functional theory in the Kohn-Sham scheme by using BPW91 functional and 6-311G and 6-31G* basis sets to calculate global and local reactivity indexes. The effect of spin multiplicity is also determined. Results on the geometries of pure cobalt clusters agree with previously reported structures. Global minimum energy structures showed a marked preference towards the interaction of nitric and nitrous oxide molecules with cobalt clusters through chemisorptive dissociation, with the dissociation of the corresponding nitrogen oxide. Reactivity indexes reveal an even-odd alternate, which is related to electron counts. Moreover, the chemical potential is lowering after interaction with nitrogen oxides. The Fukui function illustrates the reactive zones with a high probability of chemisorption of more nitrogen oxide molecules.

Solvent Extraction for Separation of 99.9% Pure Cobalt and Recovery of Li, Ni, Fe, Cu, Al from Spent LIBs

In this work, hydrometallurgical recycling of metals from high-cobalt-content spent lithium-ion batteries (LIBs) from laptops was studied using precipitation and solvent extraction as alternative purification processes. Large amounts of cobalt (58% by weight), along with nickel (6.2%), manganese (3.06%) and lithium (6.09%) are present in LiCoO2 and Li2CoMn3O8 as prominent Co-rich phases of the electrode material. The pregnant leach solution (PLS) that was generated by leaching in the presence of 10% H2O2 using 50 g/L pulp density at 80 °C for 4 h contained 27.4 g/L Co, 3.21 g/L Ni, 1.59 g/L Mn and 3.60 g/L Li. The PLS was subjected to precipitation at various pH using 2 M NaOH but the purification performance was poor. To improve the separation of Mn and other impurities and in order to avoid the loss of cobalt and nickel, separation studies were carried out using a solvent extraction technique using di-(2-ethylhexyl) phosphoric acid (D2EHPA) and bis-(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272). Overall, this study examines the fundamentals of separating and synthesizing 99.9% pure Co sulfate from leach liquor of spent laptop LIBs with remarkably high cobalt content.

The influence of crystal growth mechanism based on various sulfur sources on the morphology, component and electrochemical performance of cobalt sulfide as anode material for sodium-ion batteries

Cobalt sulfides (CoS x ) have been paid lots of attention as promising anode candidates for sodium-ion batteries owing to their merits of high theoretical capacity, good electrochemical reversibility and superior thermal stability. However, the preparation of cobalt sulfide with the excellent rate capability and long-term cyclic stability is still a great challenge. Herein, we have prepared cobalt sulfides by one-step solvothermal method using four sulfur sources including sodium thiosulfate, thioacetamide, thiourea and L -Cysteine, respectively. And the mechanism of the bond energies and groups of sulfur source molecules influence the crystal growth process are studied. Moreover, the four cobalt sulfides with different components, morphologies and structures are tested and analyzed as the anode materials for sodium-ion batteries (SIBs). The CoS x using sodium thiosulfate as the sulfur source achieves an excellent cycling performance, which still has a capacity of 690.0 mAh g −1 after 1000 cycles at 2 A g −1 with the retention of 98.1% and an outstanding rate capability of 626.6 mAh g −1 at 5 A g −1 . This superiority may be attributed to its pure component cobalt disulfide (CoS 2 ) with abundant active sites and the unique morphology leading to the high material utilization. Our studies give a clear evidence that sulfur sources play an important role in the crystal growth and constructing high-performance sulfide-based anode materials. • Cobalt sulfides were prepared by solvothermal method with different sulfur sources. • The bond energies and amino group of sulfur sources play an important role in the cobalt sulfide crystal growth mechanism. • The phase components and micromorphologies of cobalt sulfides are influenced by the species of sulfur source. • A high-performance cobalt sulfide is obtained with 626.6 mAh g −1 at 5 A g −1 and 690.0 mAh g −1 after 1000 cycles at 2 A g −1 .

Finite element analysis of class II mandibular unilateral distal extension partial dentures

The current paper aims to investigate the stress distribution developed in Kennedy Class II mandibular distal extension removable partial dentures due to applying a unilateral load condition in both vertical and lateral oblique directions. 3D models of mandible bone and RPD framework were first built based on actual patient data and later exported to ANSYS software to implement the numerical analysis. For realistic analysis, the model considered the frictional contact between the RPD retainers with the teeth and mucosa with the resin denture base by applying the feature of small sliding. To ensure maximum longevity and suitability of restoration, two different metallic RPDs constructed from commercially pure titanium (CP Ti) and cobalt–chromium (Co-Cr) base materials were investigated within the proposed model. It was found that the highest stress value was seen within the Co-Cr framework followed by the titanium framework, particularly within the bar clasp under both loading directions. The principle abutment of the distal extension side carried the highest stress value under both RPD models in both loading cases. Also, it was found that the captured von Mises stress levels within the titanium bar clasps were lower than that in Co-Cr demonstrating both long durability and high flexibility of Ti clasps.

Sonochemical Combined Synthesis of Nickel Ferrite and Cobalt Ferrite Magnetic Nanoparticles and Their Application in Glycan Analysis.

The combination of the sonochemical activation of Ni(NO3)2 and Co(NO3)2 in the presence of Fe(NO3)3 and polyethylene glycol and consecutive heat treatment of the formed metal hydroxides offers a cheap and efficient method for the preparation of nickel ferrite and cobalt ferrite magnetic nanoparticles, which can be successfully applied in the selective capture of fluorescently derivatized N-glycans from human serum. XRD measurement revealed that, besides the ferrite phase, nickel and cobalt oxides also form during heat treatment. The amount of simple metal oxides can be well controlled by the temperature of the heat treatment, since increasing temperature yielded higher spinel content. For both nickel and cobalt, the best heat treatment temperature was found to be 673 K, where the samples contained 84.1% nickel ferrite, and in the case of cobalt, almost pure (99.6%) cobalt ferrite could be prepared. FT-IR and zeta potential measurements indicated the presence of surface OH groups, which aided in the dispersion of the particles in water and, in addition, can promote the adsorption of polar compounds. The practical applicability of the magnetic nanopowders was demonstrated in the purification of fluorescently derivatized N-glycans (from human serum). Cobalt ferrite was found to be the most effective. Owing to the easy preparation and the simplicity of the magnetic separation the pure cobalt ferrite, magnetic nanoparticles could be efficient tools for the selective enrichment of serum N-glycans in HPLC measurements.

Synthesis, Characterization of CoFe2O4 and CoAl0.8Fe2O4: A Novel Catalyst for the Synthesis of 12-Aryl/Hetroaryl-8,9,10,12-Tetrahydrobenzo[a]Xanthen-11-Ones Derivatives in Semi-Aqueous Condition

The current research focuses on the utilization of cobalt ferrite and Al-doped cobalt ferrite as catalysts for the synthesis of 12-aryl/heteroaryl-8,9,10,12-tetrahydrobenzo[a]xanthene-11-ones derivatives in semi-aqueous conditions. Doping some aluminum metal into CoFe2O4 improved its catalytic potential, which was then utilized in chemical synthesis. The produced catalyst was recycled in numerous reactions to test its stability. Characterization of the catalysts was done using FT-IR, XRD, BET, and SEM techniques. The grade of the catalysts was also determined by the yield of xanthene derivatives. The effect of pure cobalt ferrite and varied molar ratios of aluminum cobalt ferrite on the yield and reaction time of xanthene derivatives has been thoroughly explored. Xanthene derivatives having aryl moiety showed better results in terms of reaction times and yield as compared to heteroaryl. Cost-effective, recyclable catalysts producing excellent yield in short reaction time, with easy work method are some salient features of current research.

Recrystallization behavior and phase transformation in a hot-rolled pure cobalt during annealing at the elevated temperature

The evolution of microstructures and properties of the hot rolled cobalt (Co) during the isothermal annealing at different temperature was investigated. Recrystallization only occurred in hexagonal closed-packed (HCP) Co below martensitic transformation temperature (400 °C), the proportion of face-centered cubic (FCC) Co decreased dramatically and the Co sample became an HCP-Co single-phase with increasing annealing time due to the diffusive phase transformation promoted by high angle boundaries (HABs). For samples annealed at 400 °C, recrystallization occurred in both of HCP-Co and FCC-Co. The proportion of FCC-Co reached the highest value of 50% in sample annealed at 400 °C for 4 h, and the average grain size was less than 2.5 μm even after 12 h annealing due to the formation of special boundaries, annealing twins and the alternate permutation of nano FCC-Co lamellae and HCP-Co lamellae. The recrystallization mechanism was analyzed by the Johnson-Mehl-Avrami-Kolmogorov model and modified Arrhenius relationship. The nucleation and grain growth through the migration of HABs promoted the FCC→HCP diffusive phase transformation below martensitic transformation temperature. At temperature above martensitic transformation temperature, recrystallization kinetics of HCP-Co and migration of HABs was hindered by reverse martensitic transformation.

Microhardness and heat-resistance performance of ferromagnetic cobalt-molybdenum nanocrystals electrodeposited from an aqueous solution containing citric acid

Using a potentiostatic electrodeposition technique, nanocrystalline cobalt-molybdenum (Co-Mo) superalloys containing molybdenum oxide (MoOX) were synthesized from an aqueous solution containing citric acid. Molybdenum content in the alloys was controlled up to approximately 53% by adjusting the cathode potential during the alloy electrodeposition. Based on the XRD profiles and electron diffraction patterns, an amorphous-like nanocrystalline structure was observed in the alloys with high molybdenum content. XPS analysis revealed that the chemical state of electrodeposited molybdenum was almost metallic and the oxide state was also detected partially. According to the magnetization curves, the coercivity of electrodeposited Co-Mo alloys decreased down to approximately 72 Oe with increasing the molybdenum content up to around 53%. The microhardness reached 845 kgf mm−2 in the electrodeposited Co-53%Mo alloy and greatly exceeded that of pure cobalt (ca. 250–300 kgf mm−2). Heat resistance performance of the electrodeposited nanocrystalline Co-53%Mo alloy was improved by the Mo alloying effect because the recrystallization and oxidation behavior were not observed even if the annealing temperature was increased up to 700 °C.

Real-Time Monitoring the Growth of Epitaxial CoxFe3-xO4 Ultrathin Films on Nb-Doped SrTiO3(001) via Reactive Molecular Beam Epitaxy by Means of Operando HAXPES.

In this work, we present a comprehensive study on real-time monitoring the growth of epitaxial CoxFe3−xO4 thin films grown on SrTiO3(001) substrates via reactive molecular beam epitaxy. The growth process was monitored during evaporation by means of time resolved operando hard X-ray photoelectron spectroscopy (HAXPES). We prepared ultrathin ferrite films using different oxygen partial pressures, showing pure metallic, light oxidic, and cobalt ferrite-like growth. Additional X-ray diffraction measurements confirm HAXPES results.

Water dissociation on mixed Co–Fe oxide bilayer nanoislands on Au(111)

We investigate the hydroxylation behaviour of mixed Co–Fe oxide nanoislands synthesized on a Au(111) surface under exposure to water vapour at vacuum conditions. The pure Co and Fe bilayer oxides both become hydroxylated by water exposure in vacuum conditions, albeit to a very different extent. It is however an open question how mixed oxides, exposing sites with a mixed coordination to Fe and Co, behave. By forming surface O species with a mixed Fe/Co coordination, we can investigate the nature of such sites. By means of scanning tunnelling microscopy and x-ray photoelectron spectroscopy, we characterize a series of Co–Fe oxides samples with different Fe contents at the atomic scale and observe a scaling of the hydroxylation degree with the amount of Fe inside the Co–Fe oxides. Our results indicate that the Fe dopants within the Co–Fe oxides have opposing effects on edge and basal plane sites modifying the maximum hydroxylation degree of pure cobalt oxide, perturbing the original binding sites of H, releasing the absorbed H or blocking the diffusion pathway of H.

Nanocrystalline structure and microhardness of cobalt-chromium alloys electrochemically synthesized using a metal hydroxide coprecipitation technique

The effect of glycine as a complexing agent on metal hydroxide formation, such as Co(OH)2 and Cr(OH)3, was investigated based on potential-pH diagrams and titration curves for Co2+-H2O and Cr3+−H2O systems. Using a potentiostatic electrodeposition technique, Co–Cr alloy-based composite films containing Cr2O3 were synthesized from a non-suspended aqueous solution within an optimized pH range. Chromium content in the composite films was controlled up to 38.9% by adjusting the cathode potential during the alloy electrodeposition. Based on the XRD profiles and electron diffraction patterns, an amorphous-like nanocrystalline structure was observed in the composite films with high chromium content. The average crystal grain size declined due to Cr2O3 particles and hydrogen evolution during the electrodeposition process. Saturation magnetization of the composite films decreased with an increase in the chromium content. Synergistic contribution of increasing dislocation density and refining crystal grain size improved the microhardness of the composite films. The microhardness reached 624.2 kgf mm−2 and greatly exceeded that of pure cobalt (ca. 250–300 kgf mm−2).

Bimetallic Oxide Catalyst for the Dehydrogenative Oxidation Reaction of Alcohols: Practical Application in the Synthesis of Value-Added Chemicals

This work demonstrates the preparation of zinc cobalt oxide materials (ZCO-1, ZCO-2, and ZCO-3) via thermal annealing of novel zinc cobalt acetate hydroxide precursors prepared in three different Co/Zn molar ratios (2:1, 1:1, and 1:2). Among these, the ZCO-1 sample displayed superior catalytic activity for the dehydrogenative oxidation of alcohols to carboxylic acids, exhibiting wide substrate applicability and high yield output with concomitant evolution of hydrogen gas (latent fuel) under oxidant-free conditions. The high catalytic activity of ZCO-1 can be accredited to synergistic effects arising from a balanced molar ratio of Co/Zn (2:1), which led to the formation of pure spinel-structured zinc cobalt oxide and a sufficiently high surface area capable of furnishing copious active sites, resulting in faster reaction kinetics and higher productivity. Moreover, the practical utility of the current protocol was displayed via ZCO-1-catalyzed gram-scale synthesis of value-added chemicals like nicotinic acid, terephthalic acid, and succinic acid.

Eco-friendly synthesis of cobalt-zinc ferrites using quince extract for adsorption and catalytic applications: An approach towards environmental remediation

Cobalt-zinc ferrite nanoparticles were synthesized using environmentally friendly approach with quince extract as a reducing agent. Crystal structure and morphology of the obtained materials were studied by XRD, SEM-EDS, Mössbauer and IR spectroscopy. The synthesized nanoparticles have a cubic spinel structure and crystallite size ranging from 5 to 9 nm. The infrared spectra contain characteristic absorption bands for the MA-O (∼560 cm−1) and MB-O bonds (∼420 cm−1). Force constants were calculated for both tetrahedral and octahedral bonds. As the Co content increases, the force constant for the tetrahedral bond increases and the force constant for the octahedral bond decreases. The obtained ferrite nanoparticles have good magnetization as shown by VSM (in the range from 36 to 67 emu/g). Magnetic nanoparticles CoxZn1-xFe2O4 were also tested for induction heating with electromagnetic field. The sample with x (Co) = 0.4 has the highest specific absorption rate. The synthesized samples were tested as adsorbents using the Congo Red dye as model pollutant. The best adsorbent was pure zinc ferrite with the adsorption capacity of 24.7 mg/g. The catalytic activity of the obtained ferrites for the decomposition of H2O2 was studied as well. The most active catalyst was pure cobalt ferrite. Probably, the active centers are octahedral cobalt ions. Thus, the obtained magnetic nanoparticles can be used for the adsorptive removal of pollutants, catalytic decomposition of the H2O2 and low-frequency hyperthermia.