Influence Of Co Content Research Articles

Effect of Co content on precipitation behavior of γ′ phase strengthened CoNi-based alloys

The CoNi-based alloys with nano-precipitates exhibit significant advantages in high-temperature applications due to their excellent thermal stability. This study investigates the influence of Co content (0 at%, 22.5 at%, 45.0 at%) on the morphological evolution, coarsening kinetics of γ' phases, and γ/γ' lattice misfit. The results reveal that the γ/γ' lattice misfit increases with increasing Co content. The addition of Co not only increases the number density of γ' phases but also effectively suppresses the coarsening of precipitates. Moreover, the coarsening rate constant of the γ' phase decreases with increasing Co content, with the alloy containing 45.0 at% Co exhibiting the lowest coarsening rate at 1.04 × 10−28 m3/s. Additionally, the increase in Co content enhances the hardness of the alloy, primarily due to the increased volume fraction of the γ' phase. This study contributes to understanding the mechanism of Co content variation on the characteristics and thermal stability of precipitates, providing support for the design of CoNi-based alloys.

In-situ crystallization of CoCr2O4 in tellurite glass with enhanced optical nonlinear limiting, photoluminescence, and magnetic properties: Influence of Co content

This article reports the in-situ growth of spinel CoCr2O4 nanocrystals (NC) in tellurite glass through tailoring the Co content by melt-quenching method. The microstructure, optical, and magnetic properties of NC/ glass systems were systematically studied using various techniques. Well-defined 30 nm crystallization of CoCr2O4 (space group of Fd3m) homogeneously distributed in the glassy matrix and the concurrent formation of cubic BiCoO3 (space group of P4mm) when the Co content exceeds 3%. The coexistence of multivalence and coordination states of Co and Cr significantly modified the glass structure with conversion of TeO4→TeO3, BO4→BO3, and CoO4→CoO6 units. Exceptional performance of the glass containing 5% Co-tuned CoCr2O4 was obtained, showcasing the decrease of Eg (2.09 eV), strong ferro-magnetization of 7.04 emu/g, large α3 (4.88×10−10 m/W) and good optical limiting property (threshhold of 1.31×1012 W/m2). Furthermore, the same glass showed excellent red emission between 650 and 800 nm under the excitation of 460 nm, with an increased lifetime (2.648 ms) and good stability of 90.7% within 25–300 °C. The emission mechanism was discussed. EPR analysis confirmed the active role and spin-states of magnetic Cr and Co ions, contributing synergistically to the improved optical and magnetic properties of the glasses.

Influence of Co-Content on the Optical and Structural Properties of TiOx Thin Films Prepared by Gas Impulse Magnetron Sputtering

Nonstoichiometric (Ti,Co)Ox coatings were prepared using gas-impulse magnetron sputtering (GIMS). The properties of coatings with 3 at.%, 19 at.%, 44 at.%, and 60 at.% Co content were compared to those of TiOx and CoOx films. Structural studies with the aid of GIXRD indicated the amorphous nature of (Ti,Co)Ox. The fine-columnar, homogeneous microstructure was observed on SEM images, where cracks were identified only for films with a high Co content. On the basis of XPS measurements, TiO2, CoO, and Co3O4 forms were found on their surface. Optical studies showed that these films were semi-transparent (T > 46%), and that the amount of cobalt in the film had a significant impact on the decrease in the transparency level. A shift in the absorption edge position (from 337 to 387 nm) and a decrease in their optical bandgap energy (from 3.02 eV to more than 2.60 eV) were observed. The hardness of the prepared films changed slightly (ca. 6.5 GPa), but only the CoOx film showed a slightly lower hardness value than the rest of the coatings (4.8 GPa). The described studies allowed partial classification of non-stoichiometric (Ti,Co)Ox thin-film materials according to their functionality.

A Study on the Co-Content Optimization of the DD15 Single-Crystal Superalloy

The fourth-generation single-crystal superalloy DD15 with 6% Co, 9% Co and 12% Co was cast using the vacuum directionally solidified furnace, while other alloying element’s content remained unchanged. The long-term aging experiment was conducted at 1100 °C for 1000 h after standard heat treatment. The stress rupture tests of the alloy were conducted at 1100 °C/137 MPa and 1140 °C/137 Mpa. The influence of Co content on the microstructure and stress rupture properties of DD15 alloy had been investigated to optimize the Co content to obtain excellent comprehensive performance. The results showed that the primary dendrite arm spacing of the alloy decreases at first and increases afterwards, and the volume fraction of γ-γ′ eutectic decreases with the growth of Co content in the as-cast microstructures. The size, cubic degree and volume fraction of the γ′ phase of the alloy after standard heat treatment all decrease with the increase in Co content. The microstructure stability of the alloy is enhanced with the increase in Co content. No TCP phase was present in the alloy with 12% Co precipitate even after aging 1000 h. The stress rupture lives at two conditions, both reduced in different degrees with the increase in Co content. The effect of Co on the stress rupture life of the alloy improves with the increase in Co content or test temperature. The acicular TCP phase appeared in the 6% Co alloy and 9% Co alloy in the microstructure of the ruptured specimens with different Co contents. Moreover, the TCP phase content in the 6% Co alloy is much more than that in the 9% Co alloy. There is no TCP phase precipitation in the 12% Co alloy. At last, the relationship between microstructure stability, stress rupture properties and Co content of the alloy is discussed. The alloy containing 9% Co is the best choice considering the microstructure stability and stress rupture properties.

Influences of Co-Content on the Physico-Chemical and Catalytic Properties of Perovskite GdCoxFe1−xO3 in CO Hydrogenation

The effect of the substitution of cobalt into the GdFeO3 perovskite structure on the selective hydrogenation of CO was investigated. A series of GdCoxFe1−xO3 (x = 0; 0.2; 0.5; 0.8; 1) samples were synthesized by sol-gel technology and characterized by XRD, BET specific area, DSC, TG, EDX and XPS. The experimental data made it possible to reveal a correlation between the state of iron and cobalt atoms, the fractions of surface and lattice oxygen, and catalytic characteristics. It has been found that varying the composition of GdCoxFe1−xO3 complex oxides leads to a change in the oxygen-metal binding energy in Gd-O-Me, the ratio of metals in various oxidation states, and the amount of surface and lattice oxygen, which affects the adsorption and catalytic characteristics of complex oxides.

The Influence of Co Content and Sintering Time in Al–Al9Co2–Al13Co4 Composites on Microstructure and Corrosion Performance in NaOH Environment

The Influence of Co Content and Sintering Time in Al–Al9Co2–Al13Co4 Composites on Microstructure and Corrosion Performance in NaOH Environment

Influence of Co content on the simultaneous enhancement of strength and ductility in severely drawn textured Ni-Co microwires

ABSTRACT This study examines the deformation behaviour of Ni-Co microwires exhibiting high strengths and ductility, where the addition of Co is intended to decrease the stacking fault energy. A reduction in stacking fault energy is likely to retard the recovery processes, refine grain size and enhance strain hardening by dislocation interactions at twin boundaries. Microwires were drawn to a strain of 5.88, from annealed Ni-Co alloys with Co content varying from 30 to 60 wt%. Subsequent tensile testing revealed a simultaneous increase in strength and ductility with an increase in Co content. The enhanced strength is a consequence of the finer grain size with an increase in Co, and the larger ductility is related to a combination of greater strain hardening and a higher strain rate sensitivity with an increase in Co. The textured drawn Ni-Co wires exhibited higher strengths than those obtained by severe plastic deformation with comparable grain sizes.

Rational construction of Co-promoted 1T-MoS2 nanoflowers towards high-efficiency 4-nitrophenol reduction.

Developing efficient and cost-effective non-noble metal catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) is of great importance. Herein, Co-promoted 1T-MoS2 nanoflowers were synthesized via a one-step hydrothermal method. The influence of Co content on the structure and catalytic performance of 1T-MoS2 was studied in detail. It was found that Co doping not only enhanced the electronic conductivity but also increased the hydrogen adsorption ability of 1T-MoS2. Meanwhile, the highest activity was achieved due to the synergy effect of Co-Mo-S and CoS2 active phase. In the catalytic reduction of 4-NP, the reaction rate constant of Co/1T-MoS2-0.3 was as high as 0.908min-1 and the catalyst exhibited excellent stability after recycling five times. The present work provides new insights for the rational design of highly efficient metal-doped MoS2 catalysts towards 4-NP reduction in wastewater.

Influence of Co Content on Cracking Behavior and Wear Resistance of WCp-Reinforced FeCrMnCox HEAs Fabricated by the Laser Cladding Method

High-entropy alloys (HEAs) have excellent properties of high strength–ductility, thermal stability, corrosion resistance, etc. HEAs can be considered as one of the most interesting structural or functional candidate materials and have been extensively studied based on different multiple elements in the past decades. However, the previous works focus mainly on overcoming strength–ductility trade-off. In this study, a series of WCp-reinforced FeCrMnCox (x values in atomic ratio, x = 0, 2, 4, 6, 8, and 10 at.%) HEAs are fabricated to investigate the influence of Co on the microstructures, microhardness, cracking behavior, and wear resistance. The results indicate that γ phase (fcc structure) can be formed in the designed HEA with a small amount of α phase (bcc structure). Stress can result in cracking initiation owing to the formation of lattice distortion caused by the decomposition and diffusion of WC into the matrix, and the cracking phenomenon is more serious when Co content is decreased gradually. In addition, microhardness is also increased gradually with the decrease in Co content, and the maximum microhardness reaches 680 HV for the 0–2 sample without Co. Furthermore, excellent wear resistance of the designed materials can be attributed mainly to hardness rather than friction coefficient. A conspicuous monotonic decrease in the wear rate is discovered with a monotonic increase in microhardness, adhesive wear mechanism appears mainly in the samples with higher Co content, and the wear mechanism is transformed gradually from a typical adhesive wear mechanism to an abrasive wear mechanism with the reduction in Co content.

Transition metal catalysis in lithium-ion batteries studied by operando magnetometry

Owing to the potential ability of metal nanoparticles to enhance the performance of energy storage devices, their catalytic performance has been studied by many researchers. However, a limited number of suitable characterization techniques does not allow fully elucidating their catalytic mechanism. Herein, high-accuracy operando magnetometry is employed to investigate the catalytic properties of a cobalt oxide electrode for lithium-ion batteries fabricated by magnetron sputtering. Using this technique, the magnetic responses generated by the Co-catalyzed reversible formation and decomposition of a polymer/gel-like film are successfully detected. A series of CoO/Co films are prepared by magnetron sputtering in different environments at various sputtering times to study the influence of Co content and film thickness on their catalytic properties. It is clearly demonstrated that increasing the Co content enhances the magnetic signal associated with the catalysis process. Furthermore, decreasing the electrode thickness increases the area affected by the catalytic reactions, which in turn enhances the corresponding magnetic responses. The obtained results experimentally confirm the catalytic activity of Co metal nanoparticles and provide a scientific guidance for designing advanced energy storage devices. This work also shows that operando magnetometry is a versatile technique for studying the catalytic effects of transition metals.

High-Temperature Oxidation Behavior of AlTiNiCuCox High-Entropy Alloys.

In this study, the high-temperature oxidation behavior of a series of AlTiNiCuCox high-entropy alloys (HEAs) was explored. The AlTiNiCuCox (x = 0.5, 0.75, 1.0, 1.25, 1.5) series HEAs were prepared using a vacuum induction melting furnace, in which three kinds of AlTiNiCuCox (x = 0.5, 1.0, 1.5) alloys with different Co contents were oxidized at 800 °C for 100 h, and their oxidation kinetic curves were determined. The microstructure, morphology, structure, and phase composition of the oxide film surface and cross-sectional layers of AlTiNiCuCox series HEAs were analyzed using scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and X-ray diffraction (XRD). The influence of Co content on the high-temperature oxidation resistance of the HEAs was discussed, and the oxidation mechanism was summarized. The results indicate that, at 800 °C, the AlTiNiCuCox (x = 0.5, 1.0, 1.5) series HEAs had dense oxide films and certain high-temperature oxidation resistance. With increasing Co content, the high-temperature oxidation resistance of the alloys also increased. With increasing time at high temperature, there was a significant increase in the contents of oxide species and Ti on the oxide film surface. In the process of high-temperature oxidation of AlTiNiCuCox series HEAs, the interfacial reaction, in which metal elements and oxygen in the alloy form ions through direct contact reaction, initially dominated, then the diffusion process gradually became the dominant oxidation factor as ions diffused and were transported in the oxide film.

Influence of Co Content and Chemical Nature of the Co Binder on the Corrosion Resistance of Nanostructured WC-Co Hardmetals in Acidic Solution.

The electrochemical corrosion resistance of nanostructured hardmetals with grain sizes dWC < 200 nm was researched concerning Co content and the chemical nature of the Co binder. Fully dense nanostructured hardmetals with the addition of grain growth inhibitors GGIs, VC and Cr3C2, and 5 wt.%Co, 10 wt.%Co, and 15 wt.%Co were developed by a one cycle sinter-HIP process. The samples were detailly characterized in terms of microstructural characteristics and researched in the solution of H2SO4 + CO2 by direct and alternative current techniques, including electrochemical impedance spectroscopy. Performed analysis revealed a homogeneous microstructure of equal and uniform grain size for different Co contents. The importance of GGIs content adjustment was established as a key factor of obtaining a homogeneous microstructure with WC grain size retained at the same values as in starting mixtures of different Co binder content. From the conducted research, Co content has shown to be the dominant influential factor governing electrochemical corrosion resistance of nanostructured hardmetals compared to the chemical composition of the Co binder and WC grain size. Negative values of Ecorr measured for 30 min in 96% H2SO4 + CO2 were obtained for all samples indicating material dissolution and instability in acidic solution. Higher values of Rp and lower values of icorr and vcorr were obtained for samples with lower Co content. In contrast, the anodic Tafel slope increases with increasing Co content which could be attributed to more pronounced oxidation of the higher Co content samples. Previously researched samples with the same composition but different chemical composition of the binder were introduced in the analysis. The chemical composition of the Co binder showed an influence; samples with lower relative magnetic saturation related to lower C content added to the starting mixtures and more W dissolved in the Co binder during the sintering process showed better corrosion resistance. WC-5Co sample with significantly lower magnetic saturation value showed approximately 30% lower corrosion rate. WC-10Co sample with slightly lower relative magnetic saturation value and showed approximately 10% lower corrosion rate. Higher content of Cr3C2 dissolved in the binder contributed to a lower corrosion rate. Slight VC increase did not contribute to corrosion resistance. Superior corrosion resistance is attributed to W and C dissolved in the Co binder, lower magnetic saturation, or WC grain size of the sintered sample.

Influence of Co contents on the microstructure and SERS performance of self-formed Ag nanoparticles/Ag-Co alloy films on flexible substrates

Self-formed Ag nanoparticles/Ag-Co alloy films with various Co contents were fabricated by sputtering Ag-Co composite target. Effects of Co contents in Ag-Co films on the microstructure and SERS performance of nanoparticles/alloy films were thoroughly investigated through SEM, TEM and Raman spectrometer. Amorphous Co in Ag-Co films restricted the growth of Ag grains in the films and promoted the formation and growth of Ag nanoparticles on the film’s surface. The size and number of Ag nanoparticles grown on the surface were closely related to Co contents in Ag-Co films, Ag-Co film thicknesses and annealing temperatures. Ag nanoparticles/Ag-Co films covered with Ag layers performed ultra-sensitive Raman signals due to forming abundant active hot spots. This flexible SERS substrate could detect 10−12 mol/L Rhodamine 6G (R6G), which indicated that this novel type of Ag nanoparticles/Ag-Co alloy films could be used and applied as high-efficient SERS substrates.

Influence of Co content on microstructure and hardness of AlCoxCrFeNi (0 ≤ x ≤ 1) high-entropy alloys produced by self-propagating high-temperature synthesis

In an effort to reduce energy consumption and expensive Co content, herein we report the effects of Co content on microstructure and microhardness of widely studied AlCoxCrFeNi high-entropy alloys produced by cost-efficient aluminothermic self-propagating high-temperature synthesis (SHS) method. Accordingly, the feasibility of SHS technique in the production of AlCoxCrFeNi master high-entropy alloys was discussed. In order to investigate the effect of further casting, the SHS alloys were also subjected to vacuum arc melting/suction casting process. Prior to SHS; phase diagram, raw material amounts and adiabatic temperatures were calculated via thermochemical modelling. The calculated equilibrium phase diagram suggested a full BCC structure over the whole Co range. However, according to XRD results, as-cast alloys consisted of BCC and FCC phases, having microhardness values ranging in between 385 HV and 504 HV, depending on Co content. The increase in Co content, enlarged the grains, altered the spinodal decomposition morphology and led to the formation of dual-phase (FCC + BCC) alloys, which in return had a significant effect on the microhardness values. Overall hardness values were increased due to finer microstructure obtained by suction casting. Also, Widmanstätten plate-like growth of the FCC phase inside the BCC cores was kinetically suppressed due to higher cooling rate. It was concluded that AlCoxCrFeNi master high-entropy alloys can be successfully produced by SHS method and the attained dual-phase microstructures could be beneficial in tailoring mechanical properties as well as reducing the total cost of the AlCoxCrFeNi HEAs system in addition to the significant energy reduction obtained via SHS route.

An investigation on the relationship between physicochemical characteristics of alumina-supported cobalt catalyst and its performance in dry reforming of methane.

This study deals with the development of alumina-supported cobalt (Co/Al2O3) catalysts with remarkable performance in dry reforming of methane (DRM) and least carbon deposition. The influence of Co content, calcination, and reduction temperatures on the physicochemical attributes and catalyst activity of the developed catalysts was extensively studied. For this purpose, several characterization techniques including ICP-MS, H2 pulse chemisorption, HRTEM, H2-TPR, N2 adsorption desorption, and TGA were implemented, and the properties of the developed catalysts were carefully analyzed. The impact of reaction temperature, feed gas ratio, and gas hourly space velocity (GHSV) on the reactants conversion and products yield was investigated. Use of 10%Co/Al2O3 catalyst, calcined at 500°C and reduced under H2 at 900°C in DRM reaction at 850°C, CH4/CO2 ratio of 1:1, and GHSV of 6 L.g-1.h-1 resulted in a remarkable catalytic activity and sustainable performance in long-term operation where great CO2 (96%) and CH4 (98%) conversions and high H2 (83%) and CO (91%) yields with a negligible carbon deposition (3 wt%) were attained in 100-h on-stream reaction. The good performance of the developed catalyst in DRM reaction was attributed to the small Co particle size with well-dispersion on the alumina support which increased the catalytic activity and also the strong metal-support interaction which inhibited any serious metal sintering and enhanced the catalyst stability.

Influence of Co content on the microstructures and mechanical properties of a Ni–Co base superalloy made by specific additive manufacturing process

Microstructures and tensile properties of a Ni–Co base superalloy containing different Co contents made by additive manufacturing (AM) after standard heat treatment have been investigated. Microstructure observation by scanning electron microscopy (SEM) reveals that a great deal of η precipitates form in the interdendritic region and distribute linearly along the columnar microstructure in 5Co alloy. In addition, transmission electron microscopy (TEM) results reveal that spherical γ′ phase can be found in 5Co alloy and nearly cuboidal γ′ phase can been observed in 23Co alloy. The different morphologies of the γ′ precipitate can be attributed to the different γ′ compositions and the differences in γ/γ′ lattice misfit in the two alloys. The results of tensile tests reveal that, when tested below 500 °C, the ultimate strength and the elongation of the alloys made by AM are lower than that of the cast & wrought (C&W) alloys. When tested at 750 °C and 800 °C, alloys made by AM exhibit higher yield strength and superior plasticity. With the increment of the testing temperature, deformation mechanism of the alloys transforms from dislocation glide to stacking fault shearing and deformation twinning. Increasing of Co content can decrease the stacking fault energy (SFE) and facilitate the initiation of twinning, therefore, deformation mechanisms between the 5Co alloy and 23Co alloy made by AM are of notable difference.

Influence of Co contents and super-gravity field on refinement of in-situ ultra-fined fibers in Al-2.5Ni eutectic alloys

We reported the influence of Co contents (0%, 0.1 at.%, 0.15 at.% and 0.2 at.%) and super-gravity field on the refinement of the in-situ eutectic structure in Al–Ni alloys. Our results indicate that trace amounts of Co addition (0.1 at.%) could lead to the refinement of ultra-fined Al3Ni fibers under both normal gravity and super-gravity field. The refining efficiency of the Co addition is significantly enhanced under super-gravity filed. In addition to the refinement of Al3Ni fibers, the coarse Al9Co2 phase (plate-like) can be observed under normal gravity field with Co content up to 0.2 at.%. Noted that the orientation relationship of the Al3Ni fiber with respect to Al matrix is adopted Al3Ni[010]//Al[1−12] based on the SAED pattern. The refinement mechanism of Al3Ni under normal gravity and super-gravity field was discussed in details.

Effect of Co Content on Microstructures and Magnetic Properties of Anisotropic Bulk TbCu7-type Sm-Co Nanocrystalline Magnets

The influences of Co content on the microstructures and magnetic properties of the anisotropic bulk TbCu7-type Sm-Co nanocrystalline magnets prepared by high-pressure thermal compression (HPTC) from amorphous SmCox precursors with 6.37 ≤ × ≤ 8.5 had been investigated. We found that with Co content x = 6.37, the TbCu7-type Sm-Co phase and a small amount of CaCu 5 -type Sm-Co crystallized from the precursors; from x = 6.7 to x = 8.5, only single TbCu 7 -type Sm-Co phase generated during the HPTC process. When x = 6.37, an obvious (00l) texture was formed, and with increasing Co content, the (00l) texture of the synthesized magnets showed a decreasing trend. With increasing Co content, the remanence B r and saturation magnetization M s of the nanostructure significantly increased while the coercivity H ci gradually decreased, and at x = 7.25, a peak value of the maximum energy product (BH) max = 19.7 MGOe was obtained. The detailed mechanism was also discussed.

Effects of Cobalt Content on the Microstructure, Mechanical Properties and Cavitation Erosion Resistance of HVOF Sprayed Coatings

Cobalt-based alloy coatings and WC-Co-based ceramic–metal (cermet) coatings have been widely used because of their desirable mechanical properties and corrosion resistance. In this work, the influence of Co content on the microstructure, mechanical properties and cavitation erosion (CE) resistance were investigated. A cobalt-based alloy coating, a WC-12Co coating, and a WC-17Co cermet coating were deposited by high-velocity oxygen fuel (HVOF) spraying on 1Cr18Ni9Ti substrates. Results indicate that the cobalt-based alloy coating had the largest surface roughness because surface-bonded particles of lower plastic deformation were flattened. The existence of WC particles had led to an increase in hardness and improved the fracture toughness due to inhibit crack propagation. The pore appeared at the interface between WC particles, and the matrix phase had introduced an increase in porosity. With the increase in Co content, the cohesion between matrix friction and WC particles increased and then decreased the porosity (from 0.99% to 0.84%) and surface roughness (Ra from 4.49 to 2.47 μm). It can be concluded that the hardness had decreased (from 1181 to 1120 HV0.3) with a decrease in WC hard phase content. On the contrary, the fracture toughness increased (from 4.57 to 4.64 MPa∙m1/2) due to higher energy absorption in the matrix phase. The WC-12Co and WC-17Co coatings with higher hardness and fracture toughness exhibited better CE resistance than the cobalt-based alloy coating, increasing more than 20% and 16%, respectively. Especially, the WC-12Co coating possessed the best CE resistance and is expected to be applicable in the hydraulic machineries.

The influence of Co content on the luminescence properties of Co-doped ZnO nanoparticles

Co-doped ZnO nanoparticles have been synthesized by co-precipitation technique. Photoluminescence spectra change in the range from 350 nm to 600 nm and remain unchanged at about 690 nm with the Co content increase. The UV emission is assigned to exciton emission. The density of band-edge states increases with Co content. The blue emission could be ascribed to the recombination of electrons in Co[Formula: see text] ions and holes in the valence band, whose relative intensity and full-width at half-maximum (FWHM) increase with the increase of cobalt concentration. The red emission results from the intra-d-shell emission at Co, which is independent of Co content. The relative density and energy-level position of green emission centers are also influenced by Co content.