Effect Of Cobalt Addition Research Articles

Effects of cobalt metal addition on sintering and ionic conductivity of Sm(Y)-doped ceria solid electrolyte for SOFC

The effects of cobalt addition (0.5 and 1 wt.%) on densification and ionic conductivity of Ce 0.9Sm 0.1O 1.95 (10SDC) and Ce 0.9Sm 0.075Y 0.025O 1.95 (2.5Y-SDC) have been studied. X-ray diffraction (XRD) showed that Co had changed to Co 3O 4 and Co 3O 4 + CoO after firing at 900 °C and 1300 °C respectively. The addition of Co promoted densification to occur at lower temperatures with a more uniform grain growth and greatly improved both grain boundary and bulk conductivity for 10SDC. Significant improvement of grain boundary for the 2.5Y-SDC samples was obtained, even at 1300 °C sintering, while bulk conductivity was slightly improved. Rapid grain growth along with improvement of ionic conductivity was observed when the samples were sintered further at higher temperature. Superior ionic conductivity of the 2.5Y-SDC samples with Co addition to that of the bare 10SDC suggested the potential use of Co as the co-dopant in this system to reduce the content of costly rare earth usage.

The effect of cobalt addition on sintering and microstructural behaviour of silver–tungsten (Ag–W) composite

The present investigation has been revealed that homogeneous silver-tungsten (Ag–W) composite powders doped with cobalt as sinter aid can be produced by the two-stage reduction of co-precipitated tungstate. The sintering of the powders has been studied using dilatometry and the results showed that the critical level for activated sintering is of the order of 0.3 mass percent cobalt with respect to the tungsten content of the compact powder. This critical level is equivalent to approximately six to seven atomic layer coverage of the tungsten particles by cobalt. The levels of cobalt addition above the critical amount leads to the formation of cobalt tungsten (CoW3) intermetallic compound precipitates, which become trapped within the silver phase in the sintered composite material. Microstructural evaluation of sintered specimens has been carried out using optical and electron microscopy. Transmission electron microscopy results revealed the neck formation between adjacent tungsten particles along with the presence of silver around the tungsten particles. Energy dispersive X-ray (EDX) analysis also confirmed that amounts of cobalt was 0.3 mass percent, in the region containing the silver at the tungsten particle interface which agreed with the level of activated sintering.

Investigation and optimization of interface reactivity between Ce0.9Gd0.1O1.95 and Zr0.89Sc0.1Ce0.01O2−δ for high performance intermediate temperature-solid oxide fuel cells

The effects of cobalt addition on the sintering, thermal, and electrical properties of Ce 0.9 Gd 0.1 O 1.95 (GDC) and Zr 0.89 Sc 0.1 Ce 0.01 O 2− δ (ScSZ) were investigated. A small addition of cobalt oxide remarkably enhanced the sinterability of GDC, especially for GDC powder with a specific surface area of 40 m 2 g −1 , which was synthesized via a citrate method. Relative densities of approximately 95% can be achieved for GDC pellet samples using 2 mol% Co dopant and sintering at 1100 °C for 10 h. The thermal expansion and electrical conductivity of 2 mol% Co-doped GDC were comparable to those of the non-doped sample. The thermal expansion of ScSZ with various amounts of Co addition was linear in both oxidizing and reducing atmospheres. The electrical conductivity of Co-doped ScSZ decreased with increasing Co content; however, this decrease was not dramatic. These results suggest that the addition of cobalt oxide is a promising method for obtaining GDC buffer layers that are sinterable at low temperatures for use in intermediate temperature-solid oxide fuel cells.

The effect of cobalt additions on the mechanical and electrical properties of Cu–Cr–Zr melt-spun ribbons

A Cu–2.92 at.% Cr–1.87 at.% Zr alloy was processed by chill block melt spinning (CBMS) and the influence of cobalt additions on its microstructure and on its mechanical and electrical properties was evaluated in the as-spun condition and after ageing at 400 and 450 °C. When added to the Cu–Cr–Zr alloy, cobalt formed an intermetallic phase with Cr and Zr during melt spinning, thus limiting the amount of both solutes incorporated in solid solution, and consequently, reducing the mechanical properties obtained on ageing.

Effect of cobalt addition on BaCe0˙8Gd0˙2O2˙9 as electrolyte of solid oxide fuel cell

The effect of cobalt oxide addition on the sintering process and electrical performance of BaCe0˙8Gd0˙2O2˙9 (BCGO) ceramics has been evaluated. By adding 1 mol.-% (1CoBCGO) and 2 mol.-% (2CoBCGO) of cobalt, the density of 1CoBCGO and 2CoBCGO samples can reach 91 and 94% respectively, after sintering at 1300°C for 10 h, and the open current voltages (OCV) of H2/air fuel cell with the electrolytes of which were over 0˙95 V at different temperatures. Moreover, there were abnormal OCV decreases for the two samples under 700°C. AC impedance and fuel cell testing showed 1CoBCGO sintered at 1300°C had a higher electrical performance than that of 2CoBCGO, and was very similar to that of BCGO sintered at 1500°C.

Effect of cobalt additives on the structure and properties of powders of the Fe-O system after mechanochemical treatment and annealing

The structure of alloys obtained as a result of crushing of mixtures of Fe2O3+ Fe + Co powders in a high-power mill and subsequent annealing is studied by methods of x-ray diffraction analysis, transmission and scanning electron microscopy, and Mossbauer spectroscopy. The magnetic properties of the powders are measured using a vibromagnetometer at room temperature. The distribution of Co in the segregated phases is determined.

The effect of cobalt additions on the shock response of nickel

The effect of the addition of an alloy element to a pure metal upon its behaviour under shock loading had been investigated. Two materials had been chosen: nickel, a face centred cubic material, and nickel–60 wt% cobalt, also a face centred cubic material but with a much reduced stacking fault energy (SFE). The influence on the shock response of cobalt additions had been studied by the plate impact technique (uniaxial strain). The experimental results allowed the determination of characteristic properties of both materials. The Hugoniots of pure nickel and its alloy were established and compared, for the range of stress 0–20 GPa. The dynamic tensile stress (pull-back stress) was then investigated at low-stress amplitudes as a function of specimen thickness to investigate the nucleation of damage. The Hugoniot elastic limit (HEL) was investigated and the dynamic tensile stress under different incident conditions was presented and discussed. The cobalt additions did not modify the shock properties in compression. The sensitivity to the pulse length duration was observed for the alloy in tension.

A microscopic and impedance spectroscopy study of Finemet–Co amorphous alloys

Structural characterization of some Finemet–Co alloys is performed by scanning and transmission electron microscopies. The results show a response independent of the composition and state. In addition to this, electrode impedances were measured in 0.5 N KOH water solution. Three time constants were found for the electrode reaction at open circuit potential. The effect of cobalt addition was analyzed as well as the influence of the thermal treatment (TT). The values of the different parameters indicates that both, the substitution of iron by cobalt and the TT result in the increase of the stability of the oxide layers.

Effect of cobalt additions on the age hardening of Cu-4.5Ti alloy

The effects of 0.9 and 1.8 wt% cobalt additions on the age hardening behaviour of Cu-4.5Ti alloy have been investigated. It has been observed that though Co addition results in the refinement of grain size and the Cu-Ti-Co alloys exhibit age hardening (giving rise to peak hardness on aging at 400°C for 16 hours), the peak hardness as well as the corresponding yield and tensile strengths were found to decrease with increasing cobalt content. The electrical conductivities of 0.9 and 1.8 wt% Co alloys were found to be 6% and 10% International Annealed Copper Standard (IACS) and 7% and 14% IACS in solution treated and peak aged conditions, respectively. Like in the binary Cu-Ti alloys, precipitation of ordered, metastable and coherent Cu4Ti(β1) precipitate was found to be responsible for maximum strengthening in these alloys. In addition, coarse intermetallic phases of Ti and Co, viz. Ti2Co and TiCo particles have been observed in all the conditions studied. The inferior mechanical properties of Cu-Ti-Co alloys compared with those of the binary Cu-Ti alloys are attributed to the depletion of Ti from matrix, which is consumed to form Ti2Co and TiCo phases.

Effect of Cobalt Additives on Charge/Discharge Properties of Nickel Hydroxide Electrode

Effect of Cobalt Additives on Charge/Discharge Properties of Nickel Hydroxide Electrode

Effect of cobalt addition on grain growth kinetics in CuZnAl shape memory alloys

Abstract β-phase in copper alloys present a rapid growth. Coarse grain size materials should be avoided since they decrease the uniformity and reproducibility of properties, they can cause pseudoelastic brittleness and they decrease the stresscorrosion resistance. The grain size produces changes in the transformation temperatures and in the stress required to induce the martensitic phase. The purpose of this work is to show the effect of cobalt addition on grain growth kinetic in Cu-ZnAl shape memory alloys. The cobalt was added with the purpose of refining the grains. Grain growth kinetics have been evaluated in Cu-Zn-Al shape memory alloys with different cobalt contents by the calculation of several grainsize parameters (perimeter, area and diameter) at different temperatures and heat treatment times. The growth exponent values have been determined and the activation energies estimated.

CoMo bimetallic nitride catalysts for thiophene HDS

CoMo bimetallic nitride catalysts were prepared by temperature-programmed reduction of CoMo oxides with flowing ammonia, and the effects of cobalt addition on the thiophene hydrodesulfurization (HDS) reaction were investigated. MoO3 transformed into Mo2N, while cobalt oxide was just reduced to Co metal rather than Co nitride. When Co was added to Mo, the surface area decreased significantly but the new bimetallic nitride phase of Co3Mo3N was produced. The addition of Co could improve the HDS conversion, and the high specific activity of the bimetallic nitride catalyst was believed to be related with the new Co3Mo3N phase.

Effects of cobalt in lead/acid batteries

The effects of cobalt additions (0.1–1 g/1) to the electrolyte have been studied by anodic corrosion tests on sheets of various alloys, and by continuous charge, cycling and charge retention tests on thick plate automotive-type of batteries. Positive grid corrosion decreases with increase in cobalt concentration but the effect is less marked for alloys with high intrinsic corrosion resistance. Cobalt oxidizes some types of separator even at a relatively low concentration. The top-of-charge voltage is reduced by the presence of cobalt, the effect occurring mainly at the positive plate. Cobalt causes increased open-circuit losses but the effect is fairly small at low concentrations (0.1–0.15 g/1).

96/06088 Effect of cobalt addition to nickel hydroxide as a positive material for rechargeable alkaline batteries

96/06088 Effect of cobalt addition to nickel hydroxide as a positive material for rechargeable alkaline batteries

Effect of cobalt addition on the performance of titanium-based hydrogen-storage electrodes

The influence of cobalt addition on the performance of a Ti 2Ni hydrogen-storage alloy is examined. The cobalt addition is confirmed by energy dispersive spectroscopy compositional analysis. X-ray diffraction (XRD) results reveal that cobalt partially substitutes the nickel in the Ti 2Ni alloy. Charge/discharge cycle measurements show that the specific capacity of Ti 2Ni electrodes increases with cobalt addition, reaches a maximum at a cobalt content of 0.67 at.% (Ti 2Ni 0.98Co 0.02), and then falls with further addition. The cycle life of Ti 2Ni electrodes increases significantly with cobalt addition. Scanning electron microscopy analysis reveals that cobalt is effective in reducing the disintegration of the Ti 2Ni hydrogen-storage alloy powder, while XRD analysis shows that cobalt restricts the oxidation of the Ti 2Ni hydrogen-storage alloy. By contrast, the addition of cobalt does not inhibit the formation of the irreversible Ti 2NiH 0.5 hydride phase.

Effect of cobalt addition on the liquid-phase sintering of W-Cu prepared by the fluidized bed reduction method

A new process, fluidized bed reduction (FBR) method, was applied for fabrication of uniform W-Cu sintered material. Liquid-phase sintering was carried out to obtain fully densified W-Cu composite, and the effect of cobalt addition on the sintering behavior was investigated. It was found that fully densified material could not be obtained even after sintering at 1200 °C for 4 hours in the case of 75W-25Cu, while more than 96 pct density could be obtained as soon as the sintering temperature reached 1200 °C when 0.5 wt pct cobalt was added prior to the sintering. It has been found that the wetting angle of the liquid copper is reduced significantly by the addition of cobalt, and the formation reaction of Co7W6 intermetallic compound at the surface of the tungsten powder is mainly responsible for the enhancement of the densification process.

Growth, magnetic properties and the effect of cobalt addition in metal-organic chemical vapour deposited (MOCVD) gamma iron oxide thin films for magnetic recording applications

The present study aims at investigating MOCVD technique for the deposition of magnetic oxide thin films using volatile metal-organic compounds as source material. A three-step scheme has been described to form γ-Fe2O3 phase starting from α-Fe2O3 films as-deposited in optically heated atmospheric cold wall CVD reactor. Growth of γ-Fe2O3 in a two-step process has been performed by depositing Fe3O4 phase directly by resistively heated low-pressure CVD (LPCVD) technique. Role of substrate temperature in controlling the oxidation leading to direct formation of metastable γ-Fe2O3 phase (single-step scheme) by atmospheric CVD technique has been described. A new mode of introduction of cobalt in the film, namely heterogeneous dispersion of cobalt in the γ-Fe2O3 matrix, has also been described. Crystallographic structure, microstructure and magnetic properties of the films have been studied in detail. Biaxial vector coil and high-temperature magnetic studies were carried out for determining the nature of anisotropy in the γ-Fe2O3 film. Growth of γ-Fe2O3 films in different schemes have been discussed from the studies of growth kinetics in a cold-and hot-wall-type reactor chambers.

Effect of Co content on magnetic properties of hot-worked Nd-Dy-Ce-Fe-Co-B magnets

The effect of cobalt addition on magnetic properties of hot-worked Nd-Dy-Ce-Fe-Co-B magnets was studied. Ribbons with composition (Nd/sub 11.6/Dy/sub 1/Ce/sub 1/) (Fe/sub 80.4-x/Co/sub x/)B/sub 6/, where x=0, 2.8, 5.5, 8.4, and 11.2, were prepared by melt spinning. Anisotropic magnets were made by die upsetting at 1073 K with 55.6% reduction in height. The temperature coefficient of Br, alpha , was improved with increase in cobalt content. Addition of 2.8 at.% cobalt considerably improved the temperature coefficient of Hci, beta , compared to the base alloy; however, further additions of cobalt did not improve beta . Also, irreversible flux losses showed similar behavior as beta . Microstructural investigations showed the existence of a cobalt-rich phase in the 11.2 at.% cobalt specimen. Lower values of beta with cobalt-containing specimens may be ascribed to a combination of the changes in the anisotropy field of 2-14-1 phase and their microstructure. >

Effect of cobalt addition on transformation behavior and drawability of hypereutectoid steel wire.

The grain boundary cementite and Widmanstatten cementite consisted in a hypereutectoid steel have been considered to cause the brittle fracture. In this study, the effect of cobalt addition on the transformation behavior of the hypereutectoid steel has been examined in order to control the grain boundary cementite precipitation. It was found that in the case of hypereutectoid steels containing carbon content less than 1.3 wt%, the grain boundary cementite precipitation could be suppressed with the cobalt addition and patenting treatment.By suppression of grain boundary cementite, the hypereutectoid steel showed good drawability comparable with that of eutectoid steel and the increase of tensile strength comparing with eutectoid steel. The analysis using Embury-Fisher relation showed that the increase of workhardening rate was due to the refinement of lamellar spacing, which was confirmed by microstructural observation. Furthermore, it was found that refinement of lamellar spacing was attributed to increased carbon content in the case of fully pearlitic microstructure. The effect of cobalt addition on the transformation behavior was also discussed from CCT curves.

Some effects of cobalt hydroxide upon the electrochemical behaviour of nickel hydroxide electrodes

The effects of cobalt addition upon the behaviour of the nickel hydroxide electrode have been studied using linear potential sweep, EDAX, scanning electron microscopy, and X-ray analysis. Thin film, homogeneous electrodes prepared by cathodic deposition from nitrate solutions containing 0 – 100% cobalt were examined and were found to exhibit a change in oxidation level achieved by the nickel along with a change in film structure. The nickel component reached a maximum oxidation level of (IV) when around 50% cobalt was present and the electrode capacity was also maximised at this level of additive. Evidence of a two-step oxidation process was observed over a 25% – 75% cobalt range, and the changes in electrode behaviour have been shown to be related to the film morphology. X-ray analysis showed that the addition of cobalt stabilised the alpha-and gamma-phases of the active material.