High Cobalt Content Research Articles

Californian red worm biomass increase and its cobalt accumulation under different concentrations of the metal in nutrient medium

<p>Californian red worms hybrid biomass is a biologically valuable feed supplement for livestock, poultry and fish. The worm body contains a significant amount of protein, lipids, vitamins and minerals. The chemical composition of worms depends on the nutrient medium in which they were grown. Worms can accumulate minerals from the nutrient medium in the body which called forth conducting research on obtaining worms biomass enriched with Cobalt with the prospect of its further use in fish feeding.<br />It has been found out that the worms quantity and the mass increase depends on the content of Cobalt in the nutrient medium. Adding 20 mg / kg of Cobalt to the nutrient medium contributed to 38.0% and 40.4% increased amount of worms weighing 0.4-0.8 g respectively. The study reveals that the number of immature worms increased by 32.2%. Adding 40 mg / kg of Cobalt to the nutrient medium resulted in worms number and mass increased by 45.9 and 51.1% respectively. Adding 160 mg / kg of Cobalt resulted in 6.5-27.7% smaller amount of worms weighing 0.4-0.8 g as compared with the experimental groups. It has been found out that the number of small worms reduced by 24.0-50.7% compared with the experimental groups under adding 160 mg / kg of Cobalt. The weight reduced by 22.4% and amount of young worms compared with the control has been revealed.<br />We have established the pattern that as Cobalt amount in the nutrient medium increases, its concentration in the worms biomass increases as well. The highest content of Cobalt was found in the biomass dry matter of worms grown in the nutrient medium enriched with the studied metal in the amount of 160 mg / kg.<br />Biomass of worms grown in the nutrient medium with 40 mg / kg of the studied metal added can be used in fish feeding as a protein supplement with a high content of Cobalt.</p>

Study into formation of cobalt-containing peo-coatings on АК12М2МgN from a pyrophosphate electrolyte

We studied the process of formation of cobalt-containing oxide coatings using plasma-electrolytic oxidizing of the aluminum alloy AK12M2MgN in pyrophosphate electrolytes. It was established that the use of given type solutions contributes the homogenization of silumin surface and creates preconditions for the dopants incorporation to the growing oxide coating. It is shown that PEO parameters depend on the concentration ratio of cobalt sulfate and potassium pyrophosphate in a working solution. Based on the results of experimental study, we demonstrated the ways to control the structure and surface morphology of cobalt-containing PEO-coatings through the variation in the concentrations of electrolyte components. The composition of a pyrophosphate electrolyte for the formation of oxide PEO-coatings with a high cobalt content and developed surface morphology is substantiated. It is noted that the obtained oxide coatings could be used in catalytic reactions in order to decompose natural and technogenic toxicants.

Formation of a hexagonal closed-packed phase in Al0.5CoCrFeNi high entropy alloy

Abstract

Synthesis and properties of Co-carbon nanocomposites using synthetic fulvic acids

New simple, rapid, cheap and effective method for preparation of magnetic carbon encapsulated Co nanoparticles by catalytic carbonization of cobalt(II) fulvate is presented. The ≿obalt(II) fulvate being obtained by precipitation of synthetic fulvic acid by Co(NO3)2 was used both as the metal containing precursor and as a source of carbon. The structure and composition of the products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), voltamperometry, and elemental analysis. The nanocomposites have high content of cobalt (44%) and possess very high saturation magnetization (Ms = 162.5 emu/g) and low coercivity (Hc = 0.018 KOe). The treatment of the obtained nanocomposite by the hot concentrated nitric acid results in a complete dissolution of the metal. The TEM study of the received graphite like phase has shown the presence in the composition of the elongated structures that can be carbon nanotubes with lots of layers or carbon nanofibers. The porous structure of nanocomposite and the graphite like phase were investigated using the nitrogen volumetric adsorption.

Mesoporous manganese Cobaltite nanocages as effective and reusable heterogeneous peroxymonosulfate activators for Carbamazepine degradation

Mesoporous MnxCo3−xO4 nanocages with high cobalt content, large surface area and high pore volume were synthesized through a self-assembly method. The as-prepared MnxCo3−xO4 nanocages displayed satisfactory catalytic activity toward peroxymonosulfate (PMS) and the metal ions leaching concentration could be negligible. Sulfate radical was identified as the predominant active species through radical quenching experiments and electron spin resonance spin-trapping technique. The kinetics of the oxidation process was of pseudo-first order. The increasing cobalt content in MnxCo3−xO4 NCs was in favor of enhancing the decomposition of PMS. MnxCo3−xO4 nanocages dosage, PMS concentration and reaction temperature put the promoting effect on the degradation, while initial CBZ concentration had the retarding impact. MnxCo3−xO4 nanocages could efficiently operate over a wide pH range of 5.0–8.0. Coexisting chloride ions exerted a dual role in the decomposition of PMS and this role was concentration-dependent. XPS analysis confirmed the reversible valence equilibrium between metal ions and the recovery of surface adsorbed oxygen, which ensured their sustainable catalytic activity even after five consecutive runs. Based on the main intermediates identified by liquid chromatography-tandem mass spectrometry, a possible pathway of CBZ oxidation was proposed. The potential risk resulting from the highly toxic intermediates can also be effectively controlled by MnxCo3−xO4 NCs activated PMS system.

Design of friction and wear resistant titanium- and cobalt-modified nickel-base repair alloys by spray forming

Powder injection molding (PIM) is a newly developed method for repairing gas turbine components in recent years. However, the PIM method needs a sacrificial binder, which increases working procedure and cost. To overcome this disadvantage, a new method of maintenance, i.e. spray forming (SF) technique, is put forward in this study. Three kinds of Ni-base repair alloys have been designed and prepared by the SF process. And these alloys were subjected to friction, wear and material analysis tests. Results reveal that the alloy with high titanium and cobalt content has the best friction and wear resistance. The increase in titanium and cobalt content will result in the increase of γ/γ′ misfit, grain size, and coherent γ′ size, and enhance the formation of good oxides lubricants, which leads to a decrease of the coefficient of friction. Moreover, with increasing titanium and cobalt content, the predominant wear mechanism changes from delamination wear to abrasive wear and adhesive wear. The high titanium and cobalt content give a large improvement in wear resistance by strongly hindering dislocations motion and reducing crack growth rate, which resists delamination wear.

Thermodynamics of oxygen solutions in titanium-containing Fe–Co melts

Performed for the first time, the thermodynamic analysis of oxygen solutions in titanium-containing Fe–Co melts showed that the deoxidizing power of titanium with increasing cobalt content of the melt first decreases, reaches a minimum at a cobalt content of 20%, and then increases. The titanium contents [%Ti]* at equilibrium points between the oxide phases TiO2, Ti3O5, and Ti2O3 were determined. The curves of the oxygen solubility in titanium-containing iron–cobalt melts pass through a minimum, which shifts toward lower titanium contents with increasing cobalt content of the melt. Further alloying with titanium leads to an increase in the oxygen concentration of the melt so that the higher cobalt content of the melt, the steeper the increase in the oxygen content after the minimum as titanium is added to the melt.

Small Energy Multi-Impact and Static Fatigue Properties of Cemented Carbides

The small energy multi-impact (SEMI) and static fatigue properties of cemented carbides with different Co content (11, 15, and 18%) are studied. It is established that the cemented carbide with higher cobalt content ensures longer SEMI and static fatigue life, when the impact energy is lower than the impact fracture energy at one time and the static stress is lower than the bending strength (σbb). However, with the same value of λ (the ratio of the impact energy to the impact fracture energy at one time) and θ (the ratio of the static stress to the bending strength), the SEMI and static fatigue life of three alloys decrease with increasing the Co content. It is determined that the cemented carbide with a Co content of 18% has a higher dynamic fatigue and static fatigue sensitivity and corresponding weak fatigue crack propagation resistance, which means that high cobalt alloys need a higher safety factor under operating conditions. The static fatigue life of notched samples is lower than that of smooth samples. When θ equals to 0.8, the fatigue life ratio of three smooth samples and three notched samples (with Co content of 18, 15, and 11%) is approximately 1 : 2 : 7 and 1 : 1 : 2, respectively, indicating that pre-notched samples cover the defects of cemented carbides. The fracture of the hardmetals bearing low energy (SEMI and static fatigue) results from the growth and connection of holes (or coarse WC) and micro-cracks.

Observation of resistivity minimum at low temperature inCoxCu1−x(x∼0.17–0.76) nanostructured granular alloys

Electrical resistivity of nanostructured granular alloys ${\mathrm{Co}}_{x}{\mathrm{Cu}}_{1\ensuremath{-}x}$ ($x\ensuremath{\sim}0.01$--$0.76$) prepared by the chemical reduction method is investigated in the temperature range 2--300 K. The samples with a low cobalt content of $x\ensuremath{\le}0.1$ show a metallic resistivity behavior. For samples with a higher cobalt content, $x\ensuremath{\ge}0.17$, the resistivity shows a minimum. The minimum becomes more pronounced as Co content ($x$) increases and also as the temperature of minimum resistivity, ${T}_{\text{min}}$, increases with $x$. The resistivity minimum is obtained in this magnetic alloy system even for a cobalt concentration as high as $\ensuremath{\sim}76%$. Application of an external magnetic field has a negligible effect on the resistivity behavior. Detailed analysis suggests that the low-temperature upturn in resistivity most probably arises due to elastic electron-electron interaction (the quantum-interference effect). Magnetic measurements at 4 K on the same samples show the absence of long-range magnetic interaction and evidence of increasing magnetic disorder as $x$ increases beyond $\ensuremath{\sim}10%$. Combining the results of the two types of measurements, a model of formation of these alloy particles involving random clusters of Co atoms within the Cu matrix has been proposed.

Corrosion and Redox Potential Control of High Temperature Materials in Fluoride and Chloride Molten Salts

Concentrating solar power (CSP) systems that can operate at higher temperatures can achieve higher efficiencies and power production using high temperature power cycles. Operating at these higher temperatures requires identifying heat transfer fluids and materials of construction for heat transfer systems that will provide good operating characteristics and long system lifetimes under these conditions. Advanced power cycles such as the supercritical CO2 Brayton cycle can operate above 800°C and molten salts are one of the best options to transfer heat at these conditions due to their very high boiling points and good heat transfer properties. However, a potential drawback with using high temperature molten halide salts is materials corrosion. Therefore, it is important to identify pairs of heat transfer materials and molten salts that will have the mechanical properties and chemical stability that will provide long system lifetimes. Several alloys that can be used for high temperature operation includes alloys with high nickel and chromium content, such as Haynes 230, and high cobalt and chromium content, such as Haynes NS-163. However, weight loss by dealloying of Cr from high temperature alloys containing Cr was observed. In this work, several high temperature alloys were exposed to molten KCl-MgCl2 and FLiNaK (LiF-NaF-KF) at several temperatures ranging from 750 to 950 °C for 100 hours. For redox potential control, Mg and Zr were added into the test. The alloys were examined via SEM/EDS post corrosion at the surface and cross-section to account for the corrosion attack and element depletion from bulk. The salts were analyzed via ICP-OES to quantify the elements that were depleted and diffused into the salt.

Reprint of “A study of CVD diamond deposition on cemented carbide ball-end milling tools with high cobalt content using amorphous ceramic interlayers”

In this paper, CVD diamond coatings are deposited on cemented carbides with 10wt.% Co using amorphous SiO2 and amorphous SiC interlayers. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Raman spectrum and X-ray diffraction (XRD) are carried out to characterize the microstructure and composition of as-deposited films. Moreover, the adhesion and cutting performance of as-fabricated diamond coatings are studied. Indentation tests show that the amorphous ceramic interlayers can enhance the adhesion between diamond films and WC–Co substrates. The cutting tests against zirconia indicate that the tools with amorphous ceramic interlayered diamond coatings exhibit improved cutting performance. The amorphous ceramic interlayers can improve the adhesive strength and wear endurance of diamond coatings on WC–10wt.% Co substrates, which provide a viable way for adherent diamond coatings on cemented carbide tools with high cobalt content.

Assessment of Heavy Metal Levels in the Soils of Ohyia Kaolin Mining Site and Screening of Three Local Herbaceous Species for Use in Phytoremediation

The study assessed three local plant species Chromolaena odorata, Ipomoea involucrata and Mariscus alternifolius commonly found at abandoned kaolin mining site at Ohiya, Umuahia Abia state for their efficacy in phyto-remediation of heavy metals contaminated soil using a pot experiment. Soils from Ohiya kaolin mining site were used as medium for growing the species. Pre-experiment assessments of the concentrations of six heavy metals (Cr, Pb, Ni, Cd, Co and Se) were carried out in the soil and plant tissues to be used for the experiment. The experiment was laid out in a Randomized Complete Block Design (RCBD) with 6 replicate pots each. The physico-chemical properties of the experimental soil showed high content of lead (Pb) and cobalt (Co) contamination which were (2.40mg/kg) and (9.84mg/kg) respectively. Post-trial plant analysis revealed that the three plant species used for the study accumulated appreciable quantities of the heavy metals. The ranges of Pb in the species were as follows C. odorata (0.80-1.00mg/kg), I. involucrata (1.00-2.00mg/kg), M. alternifolius (0.40-0.70mg/kg). The ranges of Cr were: C. odorata from (0.00-0.07mg/kg), I. involucrata (0.30-0.42mg/kg), M. alternifolius (0.01-0.10mg/kg). The ranges of Cd in the species were: C. odorata (0.02-0.30mg/kg), I. involucrata (0.10-0.70mg/kg), M. alternifolius (0.10-0.60mg/kg) and Co concentrations were: C. odorata (2.00-3.07mg/kg), I. involucrata (2.01-4.01mg/kg), M. alternifolius (2.01-2.10mg/k). Ipomoea involucrata had significantly higher accumulation of Pb and Co than the two other plant species used and should be preferred in phytoremediation activities in the kaolin mine site at Ohiya or soils with high concentrations of heavy metals.

Electrical Properties of Cobalt Oxide/Silica Nanocomposites Obtained by Sol-Gel Technique

This work is an extension of our previous studies on cobalt oxide nanoparticles impeded in a silica matrix. Here we study the preparation and characterization of high cobalt content materials (60-90 wt%). In addition, the DC electrical conductivity of the prepared materials in a wide temperature range (350-673 K) was measured and discussed. The activation energy has been obtained according to Mott’s Small-Polaron Hopping (SPH) and Mott’s and Greaves Variable Range Hopping (VRH) models.

A study of CVD diamond deposition on cemented carbide ball-end milling tools with high cobalt content using amorphous ceramic interlayers

In this paper, CVD diamond coatings are deposited on cemented carbides with 10wt.% Co using amorphous SiO2 and amorphous SiC interlayers. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Raman spectrum and X-ray diffraction (XRD) are carried out to characterize the microstructure and composition of as-deposited films. Moreover, the adhesion and cutting performance of as-fabricated diamond coatings are studied. Indentation tests show that the amorphous ceramic interlayers can enhance the adhesion between diamond films and WC–Co substrates. The cutting tests against zirconia indicate that the tools with amorphous ceramic interlayered diamond coatings exhibit improved cutting performance. The amorphous ceramic interlayers can improve the adhesive strength and wear endurance of diamond coatings on WC–10wt.% Co substrates, which provide a viable way for adherent diamond coatings on cemented carbide tools with high cobalt content.

Electrodeposition of black chromium–cobalt alloy based on trivalent sulfate electrolyte

This study is aimed to improve the corrosion resistance, adhesion strength, and color of trivalent black chromium coatings on steel substrates by using chromium sulfate bath and chromium chloride bath. The effects of the electrodeposition current density on the trivalent black chromium coatings were studied. Surface morphology and chemical composition of coatings have been investigated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques. The protective behavior from substrates of trivalent black chromium coatings was studied in (3.5 wt. % NaCl) solution by potentiodynamic polarization technique. The better protective behavior from substrates was shown by coatings that formed in chromium sulfate bath. The coatings deposited at low current densities (10 A/dm2) showed high cobalt content because cobalt is more easily reduced than chromium on a cathode. The enhancement of the driving force caused chromium and cobalt to change into oxides and hydroxides when current density increased to more than 30 A/dm2. The best homogeneity of the black color, the degree of blackening and the protective behavior from substrates of coatings occurred at current density 50 A/dm2. The results of XPS indicated that the coatings contained not only chromium oxides and hydroxides but also cobalt oxides and hydroxides. Of all the constituent compounds, Co3O4 was the most dominant in influencing the degree of blackness.

Effect of Binder Composition on WC Grain Growth in Cemented Carbides

In this work, the effects of cobalt content and C/W ratio on grain growth are studied, in order to better understand the mechanisms. Powder compacts were sintered at 1410°C for 1 and 5 h. The relative contribution of carbide dissolution in the binder and grain growth for the evolution of the size distribution is discussed. Grain size measurements were made with the Electron BackScattered Diffraction technique. The distribution of 2D equivalent disk diameters was converted in a distribution of 3D equivalent sphere diameters, with the Saltykov method. High cobalt content favors grain growth in W‐rich samples whereas it has a slight influence on C‐rich samples. But still grain growth is significantly faster in C‐rich samples. Variation in the D90/D10 ratio indicates a tendency to abnormal growth, with a broadening of the size distribution between 1 and 5 h, favored by high binder content.

Low-Temperature Prepared Lithium-Cobalt-Nickel-Oxide Spinels

LiMn2O4-based spinel materials have been one of the most important types of cathode materials in current lithium-ion batteries since layered LiCoO2 was used in the first commercial products by Sony Corporation in 1991. While LiCoO2 is still the preferred cathode of choice for portable electronic devices such as mobile phones, cameras, and laptop computers, the LiMn2O4-based spinels, which have low price and high power performance, are finding application in batteries for electric vehicles.1 Compared to the extensive understanding of manganese-based spinel materials, relatively little is known about the structural and electrochemical properties of cobalt-nickel-based spinel electrodes, since lithium-cobalt-nickel-oxides stabilize as a layered structure during high-temperature synthesis. However, low-temperature firing of precursor materials during the solid state synthesis of layered oxide compositions, particularly those with high cobalt content, can result in intermediate structures with quasi-spinel character.2,3 A significant advantage of these Li-Co-Ni-O (LCNO-S) spinel structures is that they offer an attractive ~3.6 V vs. lithium, i.e., approximately 600 mV higher than their manganese analogues. Moreover, unlike manganese, cobalt has a lower propensity to migrate during the electrochemical reactions. In this presentation, the low-temperature prepared LCNO-S materials will be revisited to delve into their structural and electrochemical properties.

CO2 reforming of methane over Ni–Co/ZSM5 catalysts. Aging and carbon deposition study

The wet impregnation method was used to prepare ZSM5 supported nickel and/or cobalt monometallic and bimetallic catalysts with a 7 wt.% total metal loading. The CO2 reforming of methane reaction was carried out in the 600 °C–800 °C temperature range over the different catalysts (GHSV 60000 mL g−1 hr−1). The cobalt containing catalysts favored the reverse water gas shift reaction at high temperature and cobalt acted as a synergist to nickel, as overall, bimetallic catalysts showed better catalytic performance. Carbon deposition was less expressed over catalysts with high cobalt content. Following 12 h on stream at 700 °C, the bimetallic catalyst with cobalt to nickel ratio of 2, showed high CO2 and CH4 conversions (∼60%) accompanied with the lowest carbon deposition (5%). The thermal analysis of aged catalysts showed that among the deposited carbon species, it is the carbon present in the proximity of nickel and/or cobalt catalytic sites that is responsible of deactivation.

Synthesis and catalytic application of SAPO-5 by dry-gel conversion for the epoxidation of styrene with air

High silica content SAPO-5(d) with an AFI topology has been synthesized by dry-gel conversion (DGC) method. Various techniques have been used to characterize the structures of molecular sieves. XRD patterns show high crystallinity and purity of the DGC samples. XRF analyses prove high silica content of SAPO-5(d). The SAPO-5(d) has small particle size of 0.5–1 μm with large BET surface area. Co-SAPO-5-0.6(d) exhibits a high activity for the epoxidation of alkenes with air to achieve 94.5 mol% conversion of styrene and 87.2% selectivity of epoxide. Recycling studies and control experiments show the recyclable stability of Co-SAPO-5-0.6(d) as a heterogeneous catalyst. As a comparison, SAPO-5(h) samples by hydrothermal synthesis (HTS) method have also been prepared and applied in the epoxidation reaction. However, the catalytic activity of Co-SAPO-5-x(d) (82.2–94.5 mol%) is higher than that of Co-SAPO-5-x(h) (72.9–85.5 mol%), which can be correlated with high silica content, high cobalt content, small particle size and large surface area.

Double Negative Property in Co/YIG Prepared by Low Temperature Impregnation Process

Impregnation method was used for fabricating Co/YIG (Y3Fe5O12) composites under low temperature, and the electromagnetic properties were tuned by adjusting the content (0 wt% - 35 wt%) and microstructure of the metal in composites. The XRD and SEM were used to analyze the phase and microstructure. Electromagnetism properties including reactance, permittivity and permeability of the composites were tested using impedance analyzer (10 MHz~1 GHz). The results indicated that, the high cobalt content leads to the formation of three-dimensional cobalt networks on the pore walls of porous YIG gradually, and their electromagnetic properties have also been changed significantly with the Co content increasing. Especially, double negative properties were achieved in Co/YIG composites when the content of Co reached 35 wt% at the frequency band of 575 MHz-1 GHz. The appearance of double negative properties in cermets provides promising applications in electromagnetic stealth materials, microwave antenna, and traveling wave tubes.