Cobalt Powder Research Articles

Effect of process parameters on the microstructure and mechanical properties of vacuum hot-press sintered Co-50 mass% Cr alloys

ABSTRACTIn the present research, two different compositions of submicron-structured cobalt (800 ± 45 nm) and chromium (700 ± 50 nm) powders are mixed to fabricate Co-50 mass% Cr alloys by the vacuum hot-press sintering technique. This study imposes various hot-press sintering temperatures (1150, 1200, 1250 and 1300°C) and pressures (20, 30, 40 and 50 MPa) while maintaining the sintering time at 1 h, respectively. The experimental results show that the optimum parameters of hot-press sintered Co-50 mass% Cr alloys are 1200°C at 50 MPa for 1 h. Meanwhile, the sintered density reaches 7.73 g cm−3, the closed porosity decreases to 0.31%, and the hardness and transverse rupture strength values increase to 80.6 ± 0.3 HRA and 1052.9 ± 17.5 MPa, respectively. Grain growth is not obviously generated after 1200°C hot-press sintering at 50 MPa for 1 h. Consequently, the optimal solid-phase sintering process effectively improved hot-press sintered Co-50 mass% Cr alloys, which resulted in the good properties.

OBTAINING DIAMOND-METAL COMPOSITES BY MEANS OF BRAZES CONTAINING REFRACTORY FILLERS

The interaction of Sn-Cu-Co-W brazes containing cobalt and tungsten powder as refractory fillers with the synthetic diamonds AS150 is studied. It was found, that addition into braze the cobalt powder provides the wetting of diamonds at brazing and their strong fixation in metal matrix of composite.

Development of a new nanocrystalline alloy for X-ray shielding

ABSTRACTThe purpose of this study was to develop a new nanocrystalline alloy material, which can replace lead for the purposes of radiation shielding as it is not hazardous to the human body and it is light in weight, to use the developed alloy in a fiber, and to evaluate its performance. This study used tungsten carbide and cobalt as the base metals and developed a new nanocrystalline alloy material. Then, radiation-shielding fibers 0.2 and 0.4 mm thick were created from the prepared tungsten carbide and cobalt powder. Equivalent dose was measured and shielding rate was obtained by the lead-equivalent test method for X-ray protection of goods suggested in the Korean Standard. According to our results, the shielding rate of the 0.2-mm-thick WC–Co alloy was 96.52% at a tube voltage of 50 kVp, 94.86% at a tube voltage of 80 kVp, and 94.10% at a tube voltage of 100 kVp. The shielding rate of the 0.4-mm-thick WC–Co alloy was 97.47% at a tube voltage of 50 kVp, 96.57% at a tube voltage of 80 kVp, and 95.63% at a tube voltage of 100 kVp. It is believed that the nanocrystalline WC–Co alloy developed for radiation shielding in this study will contribute to a decrease in primary X-ray exposure as well as exposure to low-dose secondary X-rays, such as scattered rays. Furthermore, the use of a nanocrystalline WC–Co alloy oxide rather than lead will allow for the development of shielding wear that is lighter and contribute to the development of various radiation-shielding products made of environmentally friendly materials.

Cracking of Heavy Hydrocarbon Feedstocks in the Presence of Cobalt

More than 70% of the world’s reserves of hydrocarbons is in the form of heavy petroleum feedstocks. Increasing the efficiency and depth of processing of such feedstocks is an important problem of petroleum refining. Cobalt powders and their catalysts prepared in a single stage are tested for the first time in the cracking process at the Novokuibyshevsk petroleum refinery. The composition and properties of the samples are studied via X-ray phase analysis, scanning electron microscopy, and temperature-programmed reduction. Surfaces of cobalt contains oxygen in Co3O4 and CoO inside layers, while mechanoactivation redistributes some of these oxides and alters the composition of products of tar cracking. Cobalt has more catalytic activity in the cracking of tar after mechanoactivation than the original powder. The yield of light fractions is 70% with mechanically activated cobalt, 10 wt % higher than without mechanoactivation, and 25% higher than with no cobalt powders.

MECHANICAL ALLOYING WITH PARTIAL AMORPHIZATION OF FE–CR–CO–NI–MN MULTICOMPONENT POWDER MIXTURE AND ITS SPARK PLASMA SINTERING FOR COMPACT HIGH-ENTROPY MATERIAL PRODUCTION

This paper presents the results of studying the mechanical alloying (MA) effect on the surface morphology, microstructure and atomic-crystal structure of multicomponent Fe–Cr–Co–Ni–Mn powder mixture particles. The following materials were used as initial components: radio-engineering carbonyl iron powder (R-10 with an average particle size d = 3,5 μm), nickel powder (NPE-1, d = 150 μm), cobalt powder (PK-1u, d <71 μm), chromium powder (PH-1М, d <125 μm) and manganese powder (MR0, d <400 μm) were used. MA of the prepared mixture was carried out in the AGO-2 water-cooled mechanical activator using 9 mm steel balls with an acceleration of 90 g in air. Alloying time varied between 5 and 90 minutes. The ratio of ball mass to the mass of the mixture was 20 : 1. X-ray patterns of the initial and alloyed mixtures and the sample obtained by sintering were made on the DRON 3M diffractometer on FeKα radiation in the range of angles 2θ = 30°÷100°. The particle microstructure of the mixtures and compact sample section after sintering was studied by scanning electron microscopy. It is found that no peaks of the initial components are present on the X-ray pattern of the mixture after 90 minutes of mechanical activation, but there are peaks corresponding to the γ-Fe-based solid solution phase having a face-centered crystal lattice with an amorphous phase content increased by 20 %. A compact single-phase material was obtained by spark plasma sintering at 800 °С for 10 minutes from the mixture after 90-minute alloying. Material density was 7,49 kg/cm3, specific electrical resistivity was 0,94÷0,96·10–6 ·m, microhardness was 306÷328 kg/mm2, and the phase was distributed uniformly throughout the volume.

EFFECTS OF LEVETINOL ON EPILEPTIFORM ACTIVITY OF THE BRAIN IN RATS WITH COBALT-INDUCED EPILEPSY

The aim of this study was to evaluate the anti-seizure effect of Levetinol tablet (Geropharm) on the cobalt-induced chronic epilepsy. Materials and methods . A model of cobalt-induced epilepsy was created by applying cobalt powder to the sensorimotor zone of the rat cortex. The effects of Levetinol were studied at the early stage of the epileptic system (ES) formation (on day 2 after the cobalt application), and then at the stage of fully developed ES (on day 6 after the cobalt application). Results . The present study showed that at the early stage of ES development, Levetinol at doses of 50 and 200 mg/kg had no statistically significant effect on the development of paroxysmal activity in both primary and secondary epileptic foci: in the ipsi- and contralateral cortex, hypothalamus and hippocampus. On day 6 of the cobalt-induced epilepsy, a significant suppression of paroxysmal activity in the above structures of the brain was observed with the administration of Levetinol at a dose of 200 mg/kg. The most pronounced anti-seizure effect was found in the hippocampus; that was expressed in normalization of the bioelectrical activity and appearance of the regular theta rhythm. Conclusion . The effects of Levetinol are largely manifested in the hippocampal foci of epileptiform activity and, to a lesser extent, in the cortical foci.

The role of cobalt addition in magnetic and mechanical properties of high intrinsic coercivity Nd-Fe-B magnets

The role of cobalt addition in magnetic and mechanical properties of high intrinsic coercivity Nd-Fe-B magnets by adding cobalt element and blending micron cobalt powder was investigated. The results showed that the excellent magnetic properties of high intrinsic coercivity Nd-Fe-B magnets were obtained at the Co content of 1.5 wt%, and then the intrinsic coercivity and fracture toughness decline after blending 3 wt% micron Co powder. Blending Co powder increased the Co content of main phase grain and Nd-rich phase, and the phenomenon that the Co powder additive is in the presence of pure Co particles was not been found in the sample. Simultaneously, blending Co powder reduced the heavy rare earth content of main phase grain, and new phases containing heavy rare earth and Co were formed, such as soft ferromagnetic phase R(FeCo)3, the low-anisotropy phase R(FeCo)5 and rich-B phase R1.1(FeCo)4B4. These phenomena lead to a decrease in the intrinsic coercivity of high intrinsic coercivity Nd-Fe-B magnets. Further investigation on the grain and grain boundary indicated that the effect mechanism of blending Co powder on magnetic properties is not the same as that of the traditional alloying route.

Development of the electrochemical synthesis method of ultrafine cobalt powder for a superalloy production

The electrochemical synthesis method for the preparation of ultrafine cobalt powder from the sulfate-ammonium electrolyte for the preparation of superalloys , has been developed. It was proposed to introduce ammonia to the electrolyte until рН=11. The electrolyte composition and the mechanism behind electrochemical processes during cobalt powder synthesis have been studied. The formation of the Co 2+ ammine complex has been observed. The precipitate dissolved in the mother liquor during a week, with the formation of a purple-red solution. By recording cathodic and cyclic cathodic-anodic curves, it was discovered that the solution with dissolved precipitate contained Со 3+ . It was revealed that the synthesis process occurs in two stages «Со 3+ –Со 2+ –Со 0 », which results in the increased polarization and formation of ultrafine cobalt powder. The influence of electrolyte temperature on electrolysis and powder characteristics has been studied. It was revealed that higher temperatures lead to larger particle size and formation of compact metal particles. It has been determined that the maximum electrolyte temperature should not exceed 30 °С. It is shown that under these conditions, the Co powder is composed of spherical particles that form coral-like aggregates with the size of 35–150 µm, which can be easily ground. The cobalt powder forms with the cathodic current yield of 39 % and specific power consumption of 48 kW·h/kg, which indicates a high effectiveness of the developed method.

Cracking of Heavy Hydrocarbon Feedstock in the Presence of Cobalt

Heavy oils are more than 70 % of the world proven oil reserves that makes it an urgent problem of modern refinery to improve the efficiency and oil conversion ratio. Cobalt powders and one-stage prepared cobalt-based catalysts were first tested for tar cracking at the Novokuibyshevsk Refinery Plant. XRD, SEM and TPR techniques were used for studying the compositions and properties of the prepared samples. It was shown that the cobalt surface contained oxygen in the form of layer-by-layer stacked Co 3 O 4 and CoO; the mechanical activation of the catalysts resulted in redistribution of the oxide quantities and in changes in the composition of tar cracking products. The mechanoactivated cobalt was more active to tar cracking than the initial powder. The yield of light fractions was 70 % in the presence of the mechanoactivated cobalt that was 10 wt % higher than with non-activated cobalt and 25 % higher than in the absence of cobalt.

Synthesis of Cobalt Powder by Reduction of Cobalt Oxide with Ethanol

In this study, ethanol (C2H5OH) was used as a reducing agent for Co powder synthesis from Co3O4. It aimed to investigate the effects of temperature (700–900 K), reaction time (0–60 min), and gas flow rate on the reaction behavior of Co3O4 in ethanol flow. Mass measurement, x-ray diffraction, and scanning electron microscopy techniques were used to characterize the products. Single-phase Co powders with mean particle sizes of 0.51 μm and 0.70 μm were obtained within ~ 10 min at 800 K and 900 K, respectively. Above 800 K, external mass transfer controlled the reduction process (Qa = 0.52 kJ/mole). Below 800 K, the process (Qa = 20.17 kJ/mole) was partly controlled by external mass transfer and partly by intrinsic chemical reaction kinetics. Significant C uptake was observed at 700 K and 750 K within 60 min. The reactions were discussed in the light of thermodynamic results, which predicted Co formation from Co3O4 and C2H5OH.

Analysis of impurity elements in high purity cobalt powder by inductively coupled plasma tandem mass spectrometry

An analytical method for the determination of 26 impurity elements in high purity cobalt powder was established by inductively coupled plasma tandem mass spectrometry (ICP-MS/MS). The high purity cobalt powder was disposed by microwave digestion using a mixture of nitric acid and hydrochloric acid as the digestion reagent and then determined directly by ICP-MS/MS. In the MS/MS mode, the mass spectral interferences on the analytes by polyatomic ions could be eliminated by adding different reaction gases into the collision/reaction cell (CRC). Using O2 as the reaction gas, the mass-shift reaction of P+, S+, V+, As+, Se+ with O2 occurred, and the corresponding oxide ions generated were used for the measurement. When H2 was added to the CRC as the reaction gas, the mass-shift reaction between the interfering ions and H2 occurred. Si+ and Ca+ were determined by on-mass method. When NH3/He was added as the reaction gas, cluster ions generated by the mass-shift reaction of Ti+, Cr+, Mn+, Fe+, Ni+, Cu+, and Zn+ with NH3/He. The mass-shift method was used for determination by employing the mass-shift reaction between interfering ions and NH3/He, and Na+, Mg+, A1+, and K+ were determined by the on-mass method. The matrix effect was corrected via on-line addition of the internal standard elements. The results showed that the detection limit of analyte was in the range 0.02–97.5ng/L, and the linear correlation coefficients were ≥0.9996, showing a good linear relationship. Moreover, the spike recoveries were in the range 91.6%–109.2%. Therefore, this method is well suited for the determination of 26 impurity elements in high purity cobalt powder above 5N (≥99.999%).

Effect of Pressing Parameters on the Structure of Porous Materials Based on Cobalt and Nickel Powders

Porous materials with a bulk porosity of more than 68% were synthesized by powder metallurgy methods from a cobalt–nickel mixture. The effect of the ratio of nickel and cobalt powders used in the synthesis of this porous material (including cases when either nickel or cobalt alone was applied) and the conditions of their compaction on structural parameters, such as open and closed porosities and pose size, was established.

Influence of Co and W powders on viscosity of composite solders during soldering of specially shaped diamond-abrasive tools

The influence of Co and W powders on the structure and the viscosity of composite solders Sn-Cu-Co-W used for the manufacture of the specially shaped diamond tools has been studied. The solders were obtained by mixing the metallic powders with an organic binder. The mixtures with and without diamonds were applied to steel rollers and shaped substrates. The sintering was carried out in a vacuum at 820 ° C with time-exposure of 40 minutes. The influence of Co and W powders on the viscosity solders was evaluated on the basis of the study of structures and according to the results of sintering specially shaped diamond tools. It was found that to provide the necessary viscosity and to obtain the uniform diamond-containing layers on the complex shaped surfaces, Sn-Cu-Co-W solder should contain 27–35 vol % of solid phase. This is achieved with a total solder content of 24–32 wt % of cobalt powder and 7 wt % of tungsten powder.

Structural, optical and electrical properties of Ni-doped Co3O4 prepared via Sol-Gel technique

In this article, Nickel doped Cobalt oxide thin films and powders have been prepared on glass substrates using sol gel based dip coating process in order to investigate their optical, structural and electrical properties. The Ni concentration was changed from 0 to 9 wt(%).The synthesized samples were characterised by Ultraviolete visible analysis, X-ray diffraction, Fourier transform infrared spectroscopy and Complex impedance spectroscopy to depict the optical, structural, vibrational and electrical properties. Our structural results show that the obtained samples were composed of (Co3O4) polycrystalline with spinel-type preferentially oriented in the (311) plane. Our optical results show that the films have high transparency over the visible region (85% for Co3O4 and ∼ 60-75% for all doped samples). The optical band gaps were found to be (Eg1 = 1.50 eV, Eg2 = 2.20 eV) and (Eg1 = 1.42 eV, Eg2 = 2.07 eV) for the case of (pure Co3O4 and 9% Ni-doped Co3O4) respectively. The complementary phase information is provided by FT-IR spectroscopy. FT-IR spectra confirms the presence of Co2+-O and Co3+-O vibrations in the spinel lattice. The Nyquist plots suggests that the equivalent circuit of our films is an parallel circuit RpCp. It was found that the resistance Rp decreases whereas the capacity Cp increases with increasing doping levels.

Powder Co2Er Intermetallic Compound Synthesis Conditions in a Halide Melt

The no-current diffusion saturation method is used to study the possibility to synthesize a powder Co2Er intermetallic compound in the molten eutectic mixture of lithium and potassium chlorides at a fixed temperature of 850 K. Based on the results obtained, the conditions of synthesizing the powder Co2Er intermetallic compound of a given composition are determined. The range of metallic-phase component blending ratios for a reaction mixture is determined; within this range, the powder compound free from impurity intermetallic compounds and unreacted base metal (powder cobalt) can be synthesized. The reliability of the results obtained is confirmed by X-ray fluorescent and X-ray diffraction analyses using an EDX-720 energy dispersive X-ray fluorescent spectrometer and an XRD-700S diffractometer, respectively.

Nickel-Iron-Copper Alloy as Inert Anode for Ternary Molten Carbonate Electrolysis at 650°C

The anodic behavior of Ni11Fe10Cu alloy was investigated in molten Li2CO3-Na2CO3-K2CO3 at 650°C. A conductive oxide scale consisting of NiO-rich inner layer and LiFeO2-rich outer layer is formed on the alloy surface after anodic polarization at 0.25V (vs. Ag2SO4/Ag reference electrode) for 40 h. Further prolonging the polarization time leads to a three layered film with layered LiFeO2, NiO and Cu, respectively. The octahedral LiFeO2 and NiO in a size of several microns build a dense outermost layer, providing high stability and excellent catalytic activity for oxygen evolution. Behind the layer, NiO and Cu-rich layers contribute enough high electronic conductivity and good adhesion of the scale. The electrode shows a lower onset potential for O2 evolution than Pt and much better catalytic activity for O2 evolution reaction (OER) than SnO2 anode in the melt. To prove the effectiveness of the anode, cobalt powder with high purity was produced using the electrochemically pre-oxidized Ni11Fe10Cu anode in the ternary carbonate eutectic at 650°C.

Nonequilibrium Diamond Growth during the High-Temperature High-Pressure Synthesis of a Composite Material Made of a Mixture of Cobalt and Fullerene Powders

A composite material (CM) reinforced by diamond particles is fabricated from a mixture of cobalt and 10 wt % C60 powders at a pressure of 8 GPa and a temperature of 1200–1300°C, which is close to the melting temperature of the metastable Co–C eutectic. The results of X-ray diffraction, Raman spectroscopy, and electron-probe microanalysis demonstrate that the CM consists of diamond and the Co3C carbide. Diamond crystals are shown to grow as plates parallel to a {100} plane according to the mechanism of nonequilibrium normal growth during liquid-phase CM synthesis. The diamond particles have a hardness of 82 GPa at an elastic recovery of 95%. The structure of the synthesized cobalt-based CM with diamond inclusions ensures its ultrahigh wear resistance and antifriction properties.

Electrochemical separation and extraction of cobalt and tungsten from cemented scrap

Abstract Molten salt electrolysis was utilized for the separation of cobalt and tungsten from cemented carbide scrap in the NaCl–KCl melt at 1023 K (750 °C). The WC-15 Co sacrificial anode was dissolved to cobalt and tungsten ions and consequently discharged on the cathode to deposit cobalt and tungsten during electrolysis. The carbon remained at the anode with a porous structure. The oxidation potential of the cobalt and the tungsten carbide in the cemented carbide were analyzed through the electrochemical method. The effects of anode potential, current and duration on the dissolution were investigated. The anodic dissolution processes under different conditions were characterized through SEM and EDX. Subsequently to the two-step electrolysis, the cobalt powders of 100 nm in diameter, the tungsten powders of below 200 nm in diameter and a porous structure of carbon were obtained.

RESEARCH OF INFLUENCE OF PARAMETERS OF DISPERSION IN THE PARTICLE SIZE COBALT POWDERS ARE OBTAINED FOR ADDITIVE TECHNOLOGIES EDM DISPERSION IN ALCOHOL

Currently, there is a need of adaptation of the Russian production of powders and market metal-powder compositions under the conditions and requirements of modern installations additive 3D technologies. Based on the characteristics of the methods of obtaining spherical powders with the aim of obtaining spherical granules of the regulated grain technology offers electroerosion dispersion characterized by relatively low energy costs and environmental cleanliness of the process. The main advantage of the proposed technology is the use as raw materials waste, which is much cheaper than the pure components used in traditional technology. In addition, this technology allows to vary the granulometric composition of the obtained powder by changing electrical parameters. The aim of this work was to study the impact of dispersion on the particle size cobalt powders are obtained for additive technologies electroerosion dispersing in alcohol. For the proposed studies selected waste cobalt alloy brand CHMS "CELLET". As working fluid - a isobutyl alcohol. To obtain cobalt powders by the method of electroerosion dispersion used for the installation of AED dielectric materials. Waste was loaded into the reactor filled with the working liquid isobutyl alcohol, the process is carried out at the following electrical parameters: capacitance of the discharge capacitor 48 microfarads; pulse frequency 80 Hz; voltage: 100 (sample 1); 120 (sample 2); 140 (sample 3). The result of the local effects of intermittent electrical discharges between the electrodes was the destruction of the waste material with the formation of dispersed particles of powder. Granulometric composition of the obtained powders were investigated using the device Analysette 22 NanoTec . The results of the research aimed to study the impact of dispersion on the particle size cobalt powders are obtained for additive technologies EDM by dispersion in alcohol, it was found that when the voltage on the electrodes of 100 V, 120 V, 140 V, the average particle size is microns of 27.09, 31,59 33,61 µm and µm, respectively.

Effect of Y2O3 doping on FCC to HCP phase transformation in cobalt produced by ball milling and spark plasma sintering

In this paper, high purity cobalt (Co) powder and fine Y2O3 powder were used to fabricate Y2O3 doped Co bulks through ball milling and spark plasma sintering (SPS). The transformation from face-centered cubic (FCC) structure to hexagonal close-packed (HCP) structure during the cooling process after SPS was investigated. It has been shown that the addition of Y2O3 decreases significantly the grain size from 682nm to 374nm, since Y2O3 particles can effectively inhibit the grain growth by pinning the boundary migration. After doping the Y2O3, the FCC structured Co with a large volume fraction of over 70% can stably coexist with the HCP structured Co at room temperature, resulted from two possible reasons. First, Y2O3 particles hinder the dislocation movements. Second, Y2O3 particles occupy the deformation center of some defects in the FCC structure to reduce the number of potential nucleus of the HCP structure. In addition, due to the lower stacking fault energy of the FCC structured Co than that of the HCP structured Co, a lot of twins can be observed in the FCC grains in Y2O3 doped Co bulks after SPS.