Cobalt Powder Research Articles

Eco-friendly combustion-based synthesis of metal aluminates MAl2O4 (M = Ni, Co)

Nanosized metal aluminates, MAl2O4 (M = Ni, Co), have been prepared following a nonpolluting, low temperature, and self-sustaining starch single-fuel combustion synthesis. The mixed fuel-coordinating actions of starch have given rise to an intermediary precursor which afforded monodisperse metal aluminate nanoparticles. The thermal analysis of the [M(II), Al(III)]-starch precursors indicates a similar thermochemical reactivity for the two compounds, displaying a sequence of well-defined decomposition stages associated with three endothermic effects and three/four (nickel/cobalt) exothermic ones. The XRD data confirm the formation of spinelic phase and a continuous growth of particle sizes with the increase of calcination temperatures. The mechanisms proposed for the formation of metal aluminates essentially consist in a combination of solid-state reactions of amorphous NiO/Co3O4 and Al2O3 simple oxides. The evaluation criterion of Ni(II) cations into the spinelic lattice is original and is based on the distinct occupancy degree of tetrahedral and octahedral sites in NiAl2O4 and γ-Al2O3. TEM/HRTEM investigations performed on the cobalt(II) and nickel(II) aluminate oxide powders resulted after calcination at 800 and 900 °C, respectively, for 1 h show the formation of irregular and isolated plate-like particles for Co(II)-based spinelic oxides (the average particle size is 16.6 nm) and submicron aggregates of small, bimodal, and almost uniform (as shape and size) of NiAl2O4 mixed oxide (the mean particle size is 33.6 nm). The NIR–UV–Vis spectra for the resulted MAl2O4 (M = Co, Ni) mixed oxides reveal a massive presence of tetrahedral divalent cations both for short- and long-time calcined samples. NiO impurities are detected using FTIR and electronic spectra for all NiAl2O4 samples.

Solid-Liquid Reaction for Synthesis of Rodlike Submicron Oxalate and the Thermolysis to Nanostrings of Co<sub>3</sub>O<sub>4</sub> Nanobeads

A novel solid-liquid reaction route has been developed to synthesize rodlike submicron cobalt oxalate via dissolution of cobalt powders by oxalic acid. The rod diameter and length of the oxalate particles were found to be remarkably altered by using HCl or HNO3as additive. With HCl as additive rice-shaped particles were generated while with HNO3slender needlelike particles were created with an average aspect ratio up to 42. Furthermore, strings of Co3O4nanobeads were obtained by calcination of the slender precursor particles in air. The CoC2O4·2H2O submicron rods and Co3O4nanobeads were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TG), and X-ray diffraction (XRD).

Preparation of Metal Cobalt Powder by Co-Precipitation and Heat Decomposition Method

A novel chemical precipitation method was studied to prepare the metal cobalt powder from the precursor Co(OH)x(CO3)y powder. From XRD and IR analysis, it was proved that there were interactions between the NH4+, Cl- and the precursor powder of Co(OH)x(CO3)y. Based on DSC-TGA analysis, the influence of additive and temperature on the cobalt powder preparation process was observed during heat decomposition. The results showed that pure metal cobalt was obtained when the amount of the additive tartaric acid was about 60% and calcination temperature was 500°C.

Sol-Gel Derived Ferrites: Synthesis and Characterization

In the present work, the sinterability and formation of nanosized yttrium iron garnet (Y3Fe5O12), yttrium perovskite ferrite (YFeO3), cobalt, nickel and zinc iron spinel (CoFe2O4, NiFe2O4 and ZnFe2O4, respectively) powders by an aqueous sol-gel processes are investigated. The phase purity of synthesized nano-compounds was characterized by powder X-ray diffraction analysis (XRD). The microstructural evolution and morphological features of obtained transition metal ferrites were studied by scanning electron microscopy (SEM). The possible application of these nanosized transition metal ferrites as ceramic pigments was demonstrated.

Influence that cobalt hydroxide reduction regimes have on dispersion and reduction degree of cobalt nanopowders

The influence that regimes of the hydrogen reduction of cobalt hydroxide have on the reduction degree, dispersion, and structural composition of cobalt powders is studied. It is established that, with an increase in the reduction temperature from 320 to 420°C, the specific surface of cobalt nanopowder decreases from 4.96 to 3.39 m2/g. If the reduction temperature changes from 150 to 320°C, the reduction degree increases from 5 to 100 vol %.

New Tungsten Chloride Cluster Compounds Containing Iron or Cobalt: MW2Cl10 and MW6Cl14 (M = Fe, Co)

AbstractThe reduction of tungsten hexachloride with iron powder or cobalt powder resulted in the formation of MW2Cl10 (M = Fe and Co) in fused silica tubes at 250 °C and 225 °C, respectively. Crystal structures of the new compounds were refined isotypically from X‐ray powder diffraction patterns [C2/c, Z = 4, a = 6.1226(1) Å, b = 16.7943(1) Å, c = 12.3737(1) Å, and β = 108.99(1)° for FeW2Cl10, and a = 6.111(1) Å, b = 16.696(1) Å, c = 12.384(1) Å, and β = 108.97(1)° for CoW2Cl10]. The structures of Fe1/5W2/5Cl2 and Co1/5W2/5Cl2 can be considered as a cation‐deficient CdI2‐type structure, in which bioctahedral [W2Cl10]n– anions with n ≈︁ 2 introduce significant distortions. The compounds MW6Cl14 (M = Fe and Co) were prepared following the same procedure at 475 °C. Their crystal structures were refined isotypically [Pn3, Z = 4, a = 12.567(1) Å for FeW6Cl14, and 12.525(1) Å for CoW6Cl14] to the structure of PbMo6Cl14 from X‐ray powder diffraction patterns.

Hydrothermal synthesis of ultra fine β-Co(OH)2 nanowires with novel morphologies using supercritical water

Different morphologies of single-crystalline β-cobalt hydroxide (β-Co(OH)2) nanostructures are successfully synthesized in large quantities by a facile hydrothermal synthetic method with cobalt powder as the cobalt source, supercritical water and triethylamine as both an alkaline and a complexing reagent. This synthetic method has good prospects for the future large-scale production of single-crystalline β-Co(OH)2 nanostructures owing to its high yield, low cost, and simple reaction apparatus. Ultra fine nanowires, nanowires with branched ultra fine nanoneedle (forest) and nanobelt with branched nanoneedles (pan trees) like structures of cobalt hydroxide are obtained with varying the ratio between supercritical water and triethylamine by 1:0, 2:1 and 1:2, respectively. The obtained morphologies are hexagonal phase of β-cobalt hydroxide with high crystallinity.

Mechanism of Chromium Oxide Formation in Cobalt–Chromium–Molybdenum (F75) Alloys Prepared Using Spark Plasma Sintering

AbstractMetallic implants are known to have higher wear rates compared to ceramic. This causes more wear debris to be produced and results in the release of toxic metal ions to the surrounding areas. The strengthening mechanism in cobalt based cast orthopedic alloys depends upon carbides present in the microstructure, but these cause problems when dislodged between articulating surfaces, accelerating wear by abrasion and fretting. Thus, in order to improve the performance of these implants a novel method of processing the alloys, namely by spark plasma sintering (SPS) of fine powders, has been used as it generates hard oxides and not carbides in the microstructure. The oxide in the SPS processed alloy is identified as chromium oxide formed by a redox reaction between cobalt oxide found on the surface of cobalt particles and chromium. The oxygen associated with the cobalt powder is displaced and combines with the chromium during SPS. This oxide in the microstructure of the alloy can be more beneficial than carbides due to its higher hardness, resulting in lower wear rates and less wear particles. With the oxide in the microstructure, the hardness of the alloy becomes closer to that of ceramics. Also its lower density enables the alloy to be lighter. The chemical stability of the oxide ensures that it remains intact and due its insolubility in water, no carcinogenic or toxic reactions will occur.

Effect of pressure on the formation of superelastic hard particles in a metal-fullerene system and the tribological properties of composite materials reinforced with such particles

Raman spectroscopy, X-ray diffraction, and microhardness and modulus of elasticity measurements are used to study the influence of compacting pressure (5, 8 GPa) on the structure and properties of the phases prepared from fullerene soot extract (mixture of C60 and C70 crystallites) in a mixture with a cobalt powder. Carbon particles synthesized during high-temperature treatment at a pressure of 5 or 8 GPa and reinforcing composite samples have a universal hardness H u (hardness measured from the total (elastic and plastic) strain under loading) of 12 or 25 GPa, respectively. After heating of samples to 900°C, the values of H u of the particles decrease to 9–11 GPa at elastic recovery of the phase more than 85%. The dry friction coefficients of iron- and cobalt-based composite materials in contact with tool steel are 0.08 and 0.04, respectively.

Effects of cobalt on structure and properties of TiC0.3N0.7-TiB2 matrix composite ceramics prepared by self-reactive spray forming method

In order to improve the structure and properties of TiC0.3N0.7-TiB2 composite ceramics produced by self-reactive spray forming, TiC0.3N0.7-TiB2 composite ceramics were produced based on the main system of Ti-B4C-C (sucrose as the precuror of carbon)-5 wt.%Al, and the cobalt powders with different mass ratios were added. The effects of cobalt on the structure and properties of the ceramic perform samples were studied. The results show that after the addition of cobalt, the main phases of the sample are still consisted of TiC0.3N0.7 and TiB2, and there are a few TiCo white new phase, meanwhile TiC0.3N0.7 grains are refined, and its relative density, hardness and fracture toughness are improved obviously. With increasing of the content of cobalt, TiC0.3N0.7 grains are refined while TiB2 grain sizes increase, and the relative density and fracture toughness of performs increases while its hardness first decrease and then increase. So the properties of the preforms could be improved by adding cobalt to Ti-B4C-C-5 wt.%Al spray forming system.

Development of new material for the environmental-friendly energy generation processes

The aim of this study was to develop a new material which has high hydrogen storage capacity and hydrogen absorption/desorption rate. This material, which is based on cobalt powder onto which palladium was chemically deposited can be used in environmentally friendly energy generation processes, thus ensuring preventive protection of human health. Hydrogen absorption was investigated using differential scanning calorimetry (DSC) and by measuring hydrogen pressure under isothermal and non-isothermal conditions in a chamber containing either pure cobalt powder either cobalt powder onto which palladium was chemically deposited (Co-0.003 Pd). The mechanism of hydrogen absorption has been described. It was noticed that palladium catalyses hydrogen absorption by dissociating the adsorbed H2 molecules into H atoms more rapidly on its own atoms than on cobalt ones. The catalysis of dissociation of H2 molecules enabled hydrogen absorption into Co-0.003 Pd powder to occur at lower temperatures. The results of this study enable integration of technological and public health investigation in order to ensure preventive protection of human health through enviromental protection.

Increasing the dimensional stability of diamond wheels for machine grinding of high-quality and art glass

Higher productivity and lower costs of grinding articles made of high-quality and art glass are achieved by using special multispindle profiling machines or CNC machines. The dimension stability of diamond wheels for machine processing was increased by increasing the durability of the binder. It was established that adding 10% cobalt powder to the binder is optimal and results in 45 – 50% lower relative consumption of diamonds and 40 – 45% higher dimensional stability of wheels. New wheels for machine grinding of high-quality and art glass with 10% cobalt powder added to the binder are recommended for commercial use.

The phase structure and morphology of electrodeposited nickel-cobalt alloy powders

Cobalt and nickel powders of three different compositions: Ni0.8Co0.2, Ni0.55Co0.45 and Ni0.2Co0.8 were obtained by electrodeposition from an ammonium chloride-sulphate solution. It was shown that the microstructure and morphology of the powders depended on the deposition current density as well as on the bath composition. Amorphous powder of Ni0.8Co0.2 was obtained at the current density higher than 200 mA cm-2, but nanocrystalline powders having the same composition were obtained at current densities lower than 200 mAcm-2. The nanocrystalline powders with lower Ni contents (0.55 and 0.2) obtained at a current density ranging from 40 mA cm-2 to 450 mA cm-2 were solid solutions of two phases, FCC (?-Ni) and HCP (?-Co) ones. The increase of the HCP phase in the powder was a result of both the Co content increase in the powder and decrease of the deposition current density.

A Novel Flow Sheet for Processing of Used Lithium-ion Batteries for Recycling

In recent years, the demand for the lithium-ion battery is increasing due to the increasing demand for laptop computer, cellular phone and automobiles. The positive electrode of the lithium-ion secondary battery is made of lithium oxide with mainly cobalt, nickel and manganese etc.. An effective recycling method not only would collect cobalt and lithium, but also separate other materials from the used batteries. In this research, the optimum processing flow sheet is investigated and their efficiency is evaluated. The battery is safely decomposed by underwater explosion and then cutter mill. After the over 1mm in size particles are separated by the magnetic separation, eddy current separation and gravity separation by air table, the plastic, Al, Fe, and Cu products are obtained. On the other hand, the particles less than 1mm in size are effectively separated by flotation and carbon and positive electrode powders are recovered. The lithium cobalt powders are leached, neutralized and heated as Co3O4 and lithium is recovered by the adsorption method.

Characterization of NiAl with cobalt produced by combustion synthesis

In this study, as an alloying element the effect of cobalt addition by 2.5 wt.% and 5 wt.% on the NiAl intermetallic compound produced by pressure-assisted combustion synthesis method was investigated. As starting materials aluminum powder with 15 μm size, carbonyl-nickel 4–7 μm size and cobalt powders 10–44 μm size having 99%, 99.8% and 99.9% purity, respectively were used. The formation temperature of intermetallic compound for three different powders mixture determined by DSC analysis was approximately 654 °C. The production of NiAl was carried out in electrical resistance furnace in open air with a uniaxial pressure of 150 MPa at 1050 °C for 60 min. Optical and SEM studies showed that intermetallic compounds have low porosity and phase transformation has been completed. The distribution of alloying elements was confirmed by EDS analysis. The presence of NiAl and CoAl phases was determined by XRD analysis. The relative density of pure NiAl, NiAl + 2.5 wt.% Co and NiAl + 5 wt.% Co materials was 99.65%, 99.48% and 99.30% and the microhardness of materials was about 368 HV 1.0, 398 HV 1.0 and 425 HV 1.0, respectively.

Synthesis and processing of nanocrystalline tungsten carbide: Towards cemented carbides with optimal mechanical properties

Nanocrystalline tungsten carbide has been obtained by reduction/carburization at low temperature from precursors obtained by freeze-drying of aqueous solutions. Nanocrystalline WC powders with a adequate content of carbon were mixed with submicrometric Cobalt powder (12 wt.%), obtained by same synthesis method, and sintered in vacuum furnace. The cemented carbides fabricated from experimental powders were compared with both commercial ultrafine and nanocrystalline WC-12Co mixtures consolidated by the same route. The synthesised powders were characterized by X-ray powder diffraction, elemental analysis and scanning and high resolution transmission electron microscopy. On the other hand, density, microstructure, hardness and fracture toughness together with X-ray diffraction analysis of the sintered materials were evaluated. The cemented carbides obtained from synthesised powders exhibited a WC platelet-based homogeneous microstructure. This anisotropic growth might be due to the presence of stacking faults parallel to the basal plane in the starting WC powder, which would promote the defect-assisted preferential growth. These materials showed excellent mechanical properties, with a superior hardness/fracture toughness combination compared to materials prepared from commercial mixtures.

Improvement of press dies used for the production of diamond composites by means of DUPLEX-PVD-coatings

In the machining of hard materials such as glass or stone, cemented carbides have been recently replaced by diamond tools, consisting of a metallic carrier, on to which diamond segments are brazed. One of the most economic ways for the production of diamond segments is the cold compaction of the mixture of a metallic powder and diamond particles. Due to a highly abrasive sliding contact between diamond particles and the die walls, the wear rate of the press dies is very high. As a result of a low lifetime of the press dies, they must be replaced in short time periods. To avoid the costly and time-consuming substitution of the press dies, in this work PVD-coatings were deposited on the inner surface of the pre-plasma nitrided press dies (DUPLEX treatment). Thereby, various high and low alloy tool steels were treated by means of plasma nitriding process. Subsequently, a nanocomposite TiAlN coating (nc-TiAlN) was deposited by means of a high ionization magnetron sputtering device on nitrided and non-nitrided steel substrates. The mechanical and tribological properties of these coating systems were studied by means of several standard tests such as nanoindentation, ball-on-disc and scratch test. The most wear resistant coating system was chosen to employ on the inner surface of the press dies. The wear resistance of the press dies developed in this study was tested under real loading condition during compaction of the mixture of diamond particles and cobalt powder. It was revealed that employing plasma nitrided tool, steels coated with nanocomposite TiAlN decreases the wear rate of the press dies up to 76%.

Improvement of mechanical performance of epoxy resins filled with cobalt and chromium powders

AbstractEpoxy/ powder metal composites have interesting electrical properties, becoming conductors above the percolation threshold. To complete this study, mechanical investigations have been carried out to show the influence of the fillers on the mechanical performance of these composites. In this framework, different epoxy/metallic powders (Cobalt, Chromium) composites were prepared. Scanning Electron Microscopy showed that the dispersion of the metallic fillers in the matrix is almost homogeneous. The dynamic mechanical thermal analysis (DMTA) measurements showed the dependence of the viscoelastic parameters with the frequency, temperature, nature, and content of fillers. The main relaxations observed are the primary α relaxation (associated to the glass transition, Tg) and a secondary β relaxation. A second DMTA run on the same samples showed a slight increase of the Tg. It clearly showed that the used metallic fillers improve the mechanical properties of the obtained composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synthesis and magnetorheology of suspensions of submicron-sized cobalt particles withtunable particle size

Different samples of cobalt powder were synthesized. Particle size and shape werecharacterized using electron microscopy and light scattering. These measurements showedthat the synthesized powders consisted of monodisperse spheres with average diametersranging between 63 and 760 nm. These powders were used for the preparation ofmagnetorheological (MR) fluids by dispersing them in silicone oil. The MR properties ofthese MR fluids were investigated. It was found that particle size did not have muchinfluence on the MR response of MR fluids, for average particle diameters larger than100 nm. On the other hand, the MR response decreased appreciably when the averageparticle diameter was diminished below 100 nm; a theory based on the change ofthe shape of the aggregates with the size of the particles could explain theseobservations.

Liquid-Phase Sintering of Tungsten Heavy Alloys

Elemental powders of tungsten, nickel, iron and cobalt of compositions corresponding to (W-3.2Ni-0.8%Fe), (W-3.5Ni-1.5%Fe), and (W-4.5Ni-1.0Fe-1.5%Co) were mechanically alloyed in a tumbler rod mill for 2 hrs. Mechanically alloyed powders were liquid phase sintered at 1500oC for 90 min in vacuum. The sintered materials were heated up to 1150-1200oC in vacuum atmosphere, followed by quenching in water to suppress the impurity segregated at grain boundary. The sintered materials were subjected to cold-working by swaging from 8-30% reduction in area. The swaged specimens were age-hardened at 700oC. Full characterization for both the elemental powders and the sintered tungsten alloys were performed using optical microscopy, SEM analysis, EDS quantitative analysis, X-ray diffraction, hardness and compression testing. This paper will discuss the effects of the elemental powders characterization and the liquid phase sintering parameters on the microstructure and strength of these three tungsten heavy alloys.