Influence Of Co Addition Research Articles

Ni50Mn37.5Sn12.5 Heusler Alloy: Influence of Co Addition on the Structure, Martensitic Transition, and Magnetic Properties

The impact of Co-addition (x = 0, 2, 4, and 6 at. %) in the as-cast and annealed Ni50Mn37.5Sn12.5 Heusler alloy at 900 °C for 24 h on the microstructure, magnetic properties, and the martensitic transition was studied using X-ray diffraction (XRD), scanning electron microscopy, vibrating sample magnetometry, and differential scanning calorimetry. The crystal structure of as-cast samples consists of a 14M modulated martensite structure, a face-centered (FCC) γ phase, and a face-centered tetragonal (FCT) MnNi-type phase L10. The as-cast samples show a dendritic microstructure with different contrasts and non-uniform distribution. The annealed samples exhibit dual 14M and γ phases for the Co0 and Co2, but 14M + γ + MnNi for the Co4 and Co6. The appearance of the martensitic transformation in the annealed Co0 and Co2 samples can be due to the disappearance of the dendritic microstructure. The characteristic temperatures (martensite start, Ms; martensite finish, Mf; austenite start, As; and austenite finish, Af) decrease with Co addition. A ferromagnetic-like order exists at a lower temperature of 1.8 K for the as-cast and annealed samples and decreases at 300 K. The annealing increases the fraction of the AFM contributions at 300 K. The exchange bias values of the Co0, An-Co2, and An-Co6 are 146.7 Oe, 24 O2, and 32.6 Oe, respectively, at 300 K.

Effect of ingredients proportions on mechanical properties in laser-coated WC-blend welds

Abstract In this study, we investigated ceramic-matrix composite coatings created by laser cladding on 45 steel using tungsten carbide (WC) powder with varying weight percentages of Co or Ni additives. Our analysis focused on the influence of Co additives in WC powders on the key properties of the coatings, including the microstructural evolution, hardness, wear, and residual stress behaviors. High residual stresses led to significant cracking in coatings comprising 100% WC. The addition of Co at a concentration of 20% to WC reduces the cracking activity. The microhardness of the coating exceeded that of the substrate by a factor of more than five. The microstructural evolution revealed a typical intergranular fracture in the molten zone, with cracks propagating through the interior of the unmelted WC at 100% WC. In addition, by adding Ni alloys, the composite coatings were extended to three mixtures: WC-Co, WC-Ni, and WC-Co-Ni. The relationship between the three-component mixtures and wear volume of the laser cladding was established, and the ratios of the three-component mixtures were optimized. A reduced quadratic model for three-component mixtures, which provided a better mixture ratio pattern, showed an excellent fit. Based on the experimental results, the developed three-component mixture with better mixture ratios can enhance anti-wear behavior. A satisfactory agreement was obtained between the predicted and experimental values of the wear volume of the laser-coated welds. Overall, our study accomplishes the optimization of the mixture ratio of the three components, which ensured a reduction in the wear of the welds, thereby improving the performance of laser-coated welds.

Influence of CO addition on the flame structure and temperature of a micro-jet methane diffusion flame

ABSTRACT Although the micro-jet flame has received a lot of attention, there is a lack of studies on the influence of the composition variation of the CO/methane blended fuels. The present work reveals the impact of CO addition on the combustion characteristics of the micro-jet methane flame so as to improve the combustion stability for the practical utilization of the MEMS (Micro Electro Mechanical System). It is found that the flame height decreases with the increase of CO, which means that the increase of flame height with the increased inlet velocity can be inhibited by the addition of CO. The flame structures are similar for different CO addition fraction. Interestingly, the flame temperature increases first and then decreases with the increased CO because the present flame temperature is mainly determined by the physical effect of CO addition on the chemical reaction. The addition of CO also affects the flame-wall thermal interaction. Due to the competitive relationship between the flame position and temperature, the heat loss of the flame through the wall will increase first and then decrease with the increase of CO. Similarly, the preheating heat of fresh fuel also shows the similar trend with the heat loss and the preheating temperature of the new fuel reaches the highest in the case of 10%CO-90%CH4. All in all, the addition of CO can significantly affect the position, temperature, and behavior of the micro-jet flame.

The Influence of Co Addition on the Structure and Mechanical Properties of Tungsten Heavy Alloys.

This study shows the results of Ni replacement with Co in a W-Ni-Co-type tungsten heavy alloy (WHA) in terms of the structure and mechanical properties. Five alloys containing 92 wt. % of tungsten plus Ni and Co changing in the proportions (Co:Ni) of 1:9, 2:8, 3:7, 4:6, and 5:5 were prepared using liquid phase sintering (LPS). The specimens were studied directly after sintering and after solution heat treatment. The tensile strength, yield strength, and elongation were evaluated. The results of tensile tests were supplemented with microhardness measurements of tungsten grains and matrix. Light microscopy was used for the microstructure, and a scanning electron microscope (SEM) equipped with an EDS attachment was applied for the assessment of the fracture mode and chemical microanalysis. It was concluded that the replacement of Ni with Co led to a tensile property increase that was accompanied by a gradual decrease in elongation that started to be critical for a Co:Ni ratio higher than 4:6.

Effect of Minor Co Substitution for Fe on the Formability and Magnetic and Magnetocaloric Properties of the Amorphous Fe88Ce7B5 Alloy

A small amount of Co was added to the Fe88Ce7B5 glass forming alloy for the possibility of improving its glass formability and magnetocaloric effect. The Curie temperature of the amorphous Fe88-xCe7B5Cox (x = 0, 1, 2, 3) ribbons increases linearly with the Co content, while the maximum magnetic entropy change (−ΔSmpeak) increases to 3.89 J/(kg × K) under 5 T at x = 1 and subsequently decreases with further Co addition. The mechanism for the influence of Co addition on magnetic properties and the magnetocaloric effect of the amorphous alloys was investigated. Furthermore, a flattened −ΔSm profile was designed in the amorphous laminate composed of the amorphous Fe88-xCe7B5Cox (x = 0, 1, 2) ribbons. The high average −ΔSm from ~287 K to ~320 K indicates the potential application perspective of the amorphous hybrid as a magnetic refrigerant of a domestic refrigerator.

Influence of Co addition on microstructure evolution and mechanical strength of solder joints bonded with solid–liquid electromigration

Influence of Co addition on microstructure evolution and mechanical strength of solder joints bonded with solid–liquid electromigration

Influence of Co addition on Ni-Co mixed oxide catalysts toward the deep oxidation of low-rank unsaturated hydrocarbons

A series of single (NiO, Co3O4) and mixed (NiCoO2, NiCo2O4) oxides were prepared using chemical vapor deposition procedure. All samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) to understand their physico-chemical properties. The as-prepared catalysts were successfully tested towards the total oxidation of C2H2/C3H6. However, NiCo2O4 exhibits the best catalytic performance and stability. SEM revealed thin films displaying sphere-like nanocrystals with variable particle sizes. Meanwhile, XPS results confirmed the presence of Co, Ni and O species with respective ratios of their oxidation states [Co2+/(Co2++Co3+) and Ni3+/(Ni2++Ni3+)], and surface-adsorbed oxygen (OAds.) to lattice oxygen (OLat.) species increasing with Co content in the Ni-Co-O matrix. Therefore, NiCo2O4 remarkable catalytic performance is suggested to be related to the synergistic effects between the higher population of Co2+/Co3+ and Ni2+/Ni3+ redox couples, co-existing with surface-active OAds. and OLat. as well as the nanosphere-like morphology with open porosity.

ZrN/ZrSi2/Co Cermet by Combustion Synthesis under Pressure: Influence of Co Addition

High-density ZrN/ZrSi2composites for use in decoration and as abrasives were synthesized by dynamic-compaction combustion synthesis from Zr–Si3N4–Co powder blends. The effect of Zr mean particle size $$\bar {d}$$ , compression load P, and Co addition on composite properties was investigated. In the absence of Co, the ZrN/ZrSi2 composite prepared from Zr with $$\bar {d}$$ = 14.23 µm at P = 234 MPa showed a porosity of 2.3 vol % and a Vickers hardness of 1115 HV. In addition to enhanced composite hardness, 10% Co additive was also found to result in formation (at P = 327 MPa) of shiny luster particles with a maximum hardness of 1244 HV and a porosity of below 1.0 vol %.

The Influence of Co Additive on the Sintering, Mechanical Properties, Cytocompatibility, and Digital Light Processing Based Stereolithography of 3Y-TZP-5Al2O3 Ceramics.

Nanocrystalline 3 mol% yttria-tetragonal zirconia polycrystal (3Y-TZP) ceramic powder containing 5 wt.% Al2O3 with 64 m2/g specific area was synthesized through precipitation method. Different amounts of Co (0–3 mol%) were introduced into synthesized powders, and ceramic materials were obtained by heat treatment in the air for 2 h at 1350–1550 °C. The influence of Co addition on the sintering temperature, phase composition, microstructure, mechanical and biomedical properties of the obtained composite materials, and on the resolution of the digital light processing (DLP) printed and sintered ceramic samples was investigated. The addition of a low amount of Co (0.33 mol%) allows us to decrease the sintering temperature, to improve the mechanical properties of ceramics, to preserve the nanoscale size of grains at 1350–1400 °C. The further increase of Co concentration resulted in the formation of both substitutional and interstitial sites in solid solution and appearance of CoAl2O4 confirmed by UV-visible spectroscopy, which stimulates grain growth. Due to the prevention of enlarging grains and to the formation of the dense microstructure in ceramic based on the tetragonal ZrO2 and Al2O3 with 0.33 mol% Co the bending strength of 720 ± 33 MPa was obtained after sintering at 1400 °C. The obtained materials demonstrated the absence of cytotoxicity and good cytocompatibility. The formation of blue CoAl2O4 allows us to improve the resolution of DLP based stereolithographic printed green bodies and sintered samples of the ceramics based on ZrO2-Al2O3. The developed materials and technology could be the basis for 3D manufacturing of bioceramic implants for medicine.

Influence of Co addition on the deformation behavior and mechanical properties of Ni–16Cr–11Mo–2Cu alloy

The roles of Co on the strain-hardening behavior, deformation mechanism, mechanical properties and facture mode of Ni–16Cr–11Mo–2Cu alloy were thoroughly investigated using tensile tests, SEM, EBSD, TEM and HRTEM. Two alloys with a similar sole FCC-γ phase constitution, near grain size only except the composition difference of 30 wt% Co were fabricated in purpose. Co addition can overcome the strength-ductility trade-off by enhancing the strain-hardening rate and capacity. The deformation behavior evolves from slip-dominated to SFs-dominated after Co addition, due to significant decrease of stacking fault energy, the critical stresses for both SFs and twinning by Co addition. In terms of facture mode, dimples-dominated ductile fracture is transformed to quasi-cleavage fracture composed of cleavage planes and dimples after Co addition. This is probably owing to the special role of SFs on intensifying stress/strain incompatibility phenomenon in polycrystalline alloys.

Influence of CO addition on the toluene total oxidation over Co based mixed oxide catalysts

Hydrotalcite like compounds containing Co, Al and Ce were synthesized by co-precipitation. The mixed oxides obtained after calcination were characterized by several techniques: XRD, BET, H2-TPR and XPS. Activities of mixed oxides were evaluated in toluene total oxidation in presence or in absence of carbon monoxide. The benzene, benzyl alcohol and benzaldehyde are principal by-products observed during toluene oxidation in presence of CoAl(Ce) mixed oxides. Moreover, presence of carbon monoxide improves toluene total oxidation over CoAlCe mixed oxides. Stability of the two best catalytic materials has been tested in the two conditions and show no deactivation.

Effect of disorder on magnetic properties and martensitic transformation of Co-doped Ni-Mn-Al Heusler alloy

Influence of Co addition on magnetic, transport properties and electron structure of Ni50−xCoxMn31+yAl19−y (x = 0-10, y = 0-3) Heusler alloys were investigated experimentally and theoretically by first-principles calculations in the framework of density functional theory with an account of supercell approach. Cobalt doping from 0 to 10 at. % was found to increase the martensitic transition temperature T0 = (Ms + Af)/2 from 280 to 365.5 K. Magnetization of austenite phase sharply increases and magnetic order changes from antiferromagnetic to ferromagnetic state, while in martensite phase magnetization slightly growing with cobalt content. From theoretical point of view, Co-doping leads to formation of additional exchange interactions between magnetic moments of Co-Mn and Ni-Co atoms, which leads to ferromagnetism in austenite. Theoretical calculations show that from 4.68 at. % of Co content ferromagnetic order is preferred. Martensitic transformation is suppressed in alloys with more than 9.5 at. % of cobalt. It was supported by theoretical calculations of the energy difference between austenite and martensite states as a function of cobalt content. We show that the energy difference between austenite and martensite phases in L21 structure from x ≥ 6.25 at. % of Co became negative, what points on the absence of martensitic transformation. For B2 structure, the energy difference is positive for all concentrations of cobalt, that proves that phase transition is likely to occur.

Secondary hardening behavior in ausformed martensitic alloys with different Co content

The influence of Co addition on the secondary hardening behavior in ausformed high Co-Ni secondary hardening alloy steels was analyzed using small-angle neutron scattering and differential scanning calorimetry coupled with a modified Johnson-Mehl-Avrami kinetic model. In severely ausformed alloy steels, an increase in Co content increased the degree of secondary hardening but did not accelerate their aging kinetics. This was determined by Co-independent cementite precipitation, thus leading to the precipitation of M2C carbide nucleated around and/or on cementite during the same aging time of 5 h.

Influence of cobalt addition on microstructure and hot workability of IN713C superalloy

In the present research, the influence of Co addition on the microstructure and hot workability of IN713C alloy was investigated in detail by scanning electron microscope (SEM), transition electron microscope (TEM) and electron backscattering diffraction (EBSD) etc. Substitution of Ni by Co leads to lower driving force for formation of γ′ phase. In addition, with the increase of Co fraction, the γ′ phase precipitates turned finer and more cuboidal shape. As a result, the hot workability of IN713C alloy was improved significantly by Co addition. This can be ascribed to the decrease in activation energy, misfit between γ/γ′ phase lattice, the stacking fault energy as well as the fraction of γ′ phase at elevated temperature after adding Co.

Stable magnetocaloric effect and refrigeration capacity in Co-doped FeCoMnZrNbB amorphous ribbons near room temperature

The Fe-based amorphous alloys are promising candidates for magnetic refrigeration due to their large magnetocaloric effect, outstanding mechanical property and high electrical resistivity. In this paper, the influence of Co addition on the magnetocaloric effect and refrigeration capacity has been studied for Fe82−xCoxMn4Zr8Nb2B4 ribbons. X-ray diffraction patterns indicate that the Co-doped ribbons are amorphous. The Curie temperature can be adjusted from 271 to 363 K with the Co atomic concentration changing from 2 to 8. Favorably, both isothermal entropy change (ΔST) and refrigeration capacity (RC) remain nearly the same magnitude for the Co-doped ribbons. For a field change of 3 T, the maximum −ΔST is about 1.7 J/kgK and the RC is about 115 J/kg for a temperature span of 80 K. The stable magnetocaloric effect and refrigeration capacity near room temperature reveals that the Co-doped amorphous ribbons may be considered as refrigerants for magnetic refrigeration.

Microstructure and martensitic transformation and mechanical properties of cast Ni rich NiTiCo shape memory alloys

The influence of Co additions on the microstructure, second phase precipitates, phase transformation and mechanical properties of cast Ni51−xTi49Cox (x = 0, 0·5, 1·5 and 4 at-%) shape memory alloys was investigated. At the expense of Ni, Co added to NiTi alloy significantly increases the martensitic transformation temperature. The matrix phase in the microstructure of Ni51Ti49Co0 alloy is the austenite phase (B2) in addition to martensite phase (B19′) and precipitates of NiTi intermetallic compounds. However, the parent phase in the other three alloys, Ni50·5Ti49Co0·5, Ni49·5Ti49Co1·5 and Ni47Ti49Co4, is martensite. Ti2Ni phase was found in the microstructures of the all investigated alloys; however, Ni3Ti2 phase precipitated only in the NiTi alloy with 0 at-%Co. The volume fraction of Ti2Ni phase decreased by the additions of 0·5 and 1·5 at-%Co, while it is slightly increased with 4 at-%Co. The hardness value of NiTi alloy is affected by Co additions.

Effect of Co addition on the atomic ordering of FeCo-phase in nanocrystalline Fe81-xCoxNb7B12alloys (x = 20.25, 27, 40.5, 54, 60.75): An anomalous diffraction and Mössbauer study

The influence of Co addition on the atomic ordering of bcc FeCo-phase in partially nanocrystalline Fe81-xCoxNb7B12 alloys (x = 20.25, 27, 40.5, 54, 60.75) was investigated using synchrotron radiation based x-ray diffraction (SR-XRD) and 57Fe Mossbauer spectroscopy (MS). The results indicate that as the Co content in the alloy increases, there is a decrease in the thermal stability against crystallization of the amorphous phase. In the pure amorphous state, topological ordering as well as compositional homogeneity of the amorphous phase increases with Co addition (x ≥ 40.5). In the partially nanocrystalline state (isothermally annealed at 823 K for 1 h), the anomalous diffraction measurements close to Fe K-edge provide unambiguous evidence of atomically ordered α′-FeCo phase (CsCl type) as the nanocrystalline ferromagnetic phase by the presence of (100) super-lattice reflection for the alloys with x ≥ 40.5. However, alloys with x ≤ 27 present a disordered structure as confirmed by the absence of superlatti...

Influence of Cobalt on Rubidium-Promoted Alumina-Supported Molybdenum Carbide Catalysts for Higher Alcohol Synthesis from Syngas

The influence of Co addition on the activity and selectivity of Rb-promoted Mo2C/α-Al2O3 catalysts in CO hydrogenation was explored. The reaction was performed in a fixed-bed reactor system operating at 573 K, 30 bar, and CO/H2 ratio of 1. Addition of Co enhanced the production rates of hydrocarbons and higher alcohols over Rb-promoted Mo2C/α-Al2O3 by about 60 % without significantly increasing the production rate of methanol, thus shifting the alcohol selectivity toward larger molecules. The addition of Co also lessened the negative impact of CO conversion on oxygenate selectivity over Rb-promoted Mo2C/α-Al2O3. Results from X-ray absorption spectroscopy revealed that highly dispersed Co and Mo domains remained more reduced in the bimetallic carbide samples than the corresponding monometallic samples.

Phase transformation behavior and mechanical properties of Ti50Ni49−x Fe1Co x shape memory alloys

In this article, the influence of Co addition on phase transformation behavior and mechanical properties of TiNiFe shape memory alloy was investigated extensively. Differential scanning calorimetry (DSC) measurements shows that martensitic start transformation temperatures (M s) decrease drastically with increasing Co content, while the R phase transformation start temperatures (R s) vary slightly. Nevertheless, the substitution of Ni with Co does not exert substantial influence on the two-stage transformation behavior of the TiNiFe alloy. The results from stress–strain curves indicate that higher critical stress for stress-induced martensitic transformation (σ SIM) has been obtained because of Co addition. In such cases, the Ti50Ni48Fe1Co1.0 alloy maintains a good shape memory effect, and a maximum recoverable strain of 7.5 % can be obtained.

Microstructural and electrical characterizations of chemically prepared Ce0.8Gd0.2− x(Ag, Sr)xO1.9 (0 ≤ x ≤ 0.02)

Gadolinia-doped ceria with co-additions of Sr and Ag were prepared by the cation complexation technique. The influence of co-additives on the densification, microstructure and electrical conductivity of the matrix were investigated by dilatometry, scanning electron microscopy and impedance spectroscopy, respectively. Both co-additives promoted changes on the densification behavior of the matrix. Strontium promoted densification and grain growth, whereas silver did not change the mean grain size but slowed down the densification of gadolinia-doped ceria. The grain conductivity of samples containing silver is considerably higher than that of pure gadolinia-doped ceria. The effect of strontium addition is predominant on the grain boundary by reducing the blocking effect. The apparent activation energy for grain conduction is lower for samples containing co-additives.