Effect Of Co Addition Research Articles

Ni-Alloy Fuel Electrodes for Reversible Solid Oxide Cells

Introduction Reversible solid oxide cells (r-SOCs, or solid oxide reversible cells) are devices that can efficiently operate in both fuel cell and electrolysis operating modes. It is expected that they can serve as a technology for green, flexible, and efficient energy systems coupled with renewable energy (1). However, a fuel electrode of r-SOCs might be degraded due to redox cycles in switching operation modes. In our research group, we have fabricated redox-resistant anodes with Ni-Co alloy cermet (2). Here in this study, we apply such alloy-based cermet to the fuel electrode, and evaluate electrochemical performance, reverse cycling durability, and the effect of Co addition. Moreover, we compare the cell performance of Ni-Co alloy cermet with conventional Ni-ScSZ fuel electrode. Experimental In this study, scandia-stabilized zirconia (ScSZ, 10mol% Sc2O3-1mol% CeO2-89mol% ZrO2) was used as the solid electrolyte. The powder prepared by mixing Ni-Co-based oxide powder prepared by ammonia co-precipitation with Ce0.9Gd0.1O2 (GDC) in a weight ratio of 48.1:51.9, was used as the fuel electrode material. Ni-Co-GDC fuel electrode with x mol% of Co added to Ni, is denoted as Ni(100 – x)Cox -GDC fuel electrode. The fuel electrodes of x = 0, 5, 10, and 20 were fabricated. Two types of Ni-GDC cermet were prepared. One was fabricated by using NiO powder by ammonia co-precipitation, and the other was by using commercial NiO powder (Kanto Chemical, Japan). We prepared the Ni-Co alloy cermet by mixing powder and binder, preparing and printing electrode paste on the electrolyte plate, followed by heat treatment. (La0.6Sr0.4)(Co0.2Fe0.8)O3 (LSCF) was used as the air electrode material. The electrochemical characteristics and r-SOC reversible cycle durability of the fuel electrodes were evaluated under the condition at an operating temperature of 800℃, while 100 ml/min of 50%-humidified hydrogen fuel was supplied to the fuel electrode, and 150 ml/min of air was supplied to the air electrode. Electrochemical characteristics were evaluated by electrochemical impedance measurements (1255WB, Solartron, UK), which separate ohmic and non-ohmic resistances. The durability in reverse r-SOC operation was evaluated by repeatedly varying current density within ± 0.2 A cm-2 at a current sweep rate of 1.56 mA cm-2 s-1 up to 1,000 cycles. The degradation was evaluated by averaging the percentage change in fuel electrode potential at ± 0.2 A cm-2. Results and discussion Figure 1 shows the initial performance of the cells with each fuel electrode. Figure 2 shows the degradation of each fuel electrode within 1,000 cycles after the r-SOC reverse durability test. The initial performance of Ni-Co-GDC was superior to Ni-ScSZ, and it increased with decreasing Co content. Two types of Ni-GDC exhibited identical performance. Similarly, the r-SOC reverse durability of Ni-Co-GDC was superior to Ni-ScSZ, and it increased with decreasing Co content. Furthermore, two types of Ni-GDC exhibited almost the same durability. These results indicate that GDC contributes to the increased cell performance and durability rather than alloying or the feature of original NiO powder. It appears that Co is not essential for r-SOC fuel electrodes in terms of r-SOC durability. However, fuel electrode materials should be selected by comprehensively considering the performance and the durability at both SOFC and SOEC modes. As Ni-Co alloy shows higher redox cycle durability compared with Ni-GDC (3), Ni-Co alloy is still one of the promising materials for r-SOC fuel electrodes. Acknowledgements A part of this study was supported by “Research and Development Program for Promoting Innovative Clean Energy Technologies Through International Collaboration” of the New Energy and Industrial Technology Development Organization (NEDO). References N. Q. Minh and M. B. Mogensen, Electrochem. Soc. Interface, 22, 55 (2013).Y. Ishibashi, S. Futamura, Y. Tachikawa, J. Matsuda, Y. Shiratori, S. Taniguchi, and K. Sasaki, J. Electrochem. Soc., 167, 124517 (2020).K. Matsumoto, Y. Tachikawa, J. Matsuda, S. Taniguchi, and K. Sasaki, ECS Trans., 103, 1549 (2021). Figure 1

Effects of Co-Addition of Au and CuO to Macroporous SnO2 Microspheres on Their Acetone and Toluene Sensing Properties As Thick Film Sensors

Controlling of meso- and macro-porous structure of semiconductor metal oxide particles used as sensor materials is of primary importance in improving their gas response properties. To date, we could improve H2 and NO2 response properties of SnO2 [1] and In2O3 [2] thick film sensors by the introduction of macropores into these oxide particles, by employing ultrasonic spray pyrolysis (USP) of the oxide precursor solution containing polymethylmethacrylate (PMMA) microspheres as a template. We also demonstrated the usefulness of the Au loading on macroporous In2O3 (pr-In2O3) and the PdOx-CuOx loading on pr-WO3 in improving NO2 [3] and methylmercaptan [4] response properties, respectively.By the way, toluene and acetone are typical organic solvents used widely in many fields, but are very toxic and hazardous gases to be detected and then eliminated by suitable methods form the viewpoint of our safe and reliable life. In addition, the patients suffering from lung cancer and diabetes are known to release high concentrations of toluene and acetone, respectively. Therefore, the development of gas sensors capable of detecting these gases sensitively and selectively may offer a new and non-invasive diagnostic method of these diseases.In the present study, attempts were made to improve acetone and toluene response properties of thick film sensors fabricated by pr-SnO2 microspheres prepared by the USP method. Effects of the CuO addition to pr-SnO2 microspheres (pr-(CuO-SnO2)) and the additive methods of different amounts of Au to pr-(CuO-SnO2) microspheres on their response properties to both two gases have been examined.The aqueous solution containing 5.0×10-3 mol of SnCl4･5H2O and 3.2 g of PMMA microspheres (ca. 70 nm in size) per 100 mL of deionized water was used as the base precursor solution. The precursor mists were carried into the electronic furnace heated at 1,100°C to prepare pr-SnO2 microspheres. In preparing pr-(xCuO-SnO2) and pr-(yAu-xCuO-SnO2) (x and y: the additive amounts in wt% per the SnO2 weight), appropriate amounts of CuCl2･2H2O and HAuCl4･4H2O were added to the base precursor solution. Besides, an appropriate amount of Au was loaded on pr-(xCuO-SnO2) by a conventional impregnation method. Thick film sensors (10 - 15 mm in thick) were fabricated by screen printing of the slurry of thus-prepared pr-SnO2-based microspheres on an alumina substrate equipped with a pair of Pt electrodes, and their sensing properties to 20–100 ppm acetone, toluene and ethanol were measured in the temperature range of 300–500°C in air. The gas response is defined as the ratio of the sensor resistance value in air (Ra) to that in a sample gas (Rg). The sensors thus fabricated are referred to as the abbreviations of sensor materials.Figure 1 shows FE-SEM photographs of pr-SnO2-based microspheres prepared. All kinds of microspheres are confirmed to show similar porous structure formed by the thermal decomposition and evaporation of PMMA microspheres contained in the mists of the precursor solutions, except for 3.0Au/pr-(2.0CuO-SnO2). The appearance of 3.0Au/pr-(2.0CuO-SnO2) microspheres indicates partial filling of the loaded Au inside of the pores especially for the outermost surface of macroporous microspheres. Figure 2 shows variations in response to 100 ppm acetone of pr-SnO2-based sensors with operating temperature. The order of sensor resistance value in air was pr-(3.0Au-2.0CuO-SnO2) ³ pr-(2.0CuO-SnO2) > pr-(5.0Au-2.0CuO-SnO2) > 5.0Au/pr-(2.0CuO-SnO2) > 3.0Au/pr-(2.0CuO-SnO2) > pr-SnO2 at 350°C. Although the physicochemical states of Au and CuO in pr-(5.0Au-2.0CuO-SnO2) are not clarified yet, the addition of CuO to pr-SnO2 resulted in an increase in sensor resistance in air, due to the formation of p-n heterojunction in the macroporous microspheres. In contrast, the Au addition to or the Au loading on pr-(2.0CuO-SnO2) led to a decrease in sensor resistance. Among the sensors tested, pr-(3.0Au-2.0CuO-SnO2) showed the largest response to 100 ppm acetone at 350°C. Therefore, high sensor resistance in air is one important factor for the largest acetone response, but the added Au in pr-(3.0Au-2.0CuO-SnO2) is considered to accelerate the reaction of acetone with chemisorbed oxygen effectively. The smaller acetone response observed with 3.0Au/pr-(2.0CuO-SnO2) is considered to arise from the decrease in reaction site, as is confirmed by Fig. 1 d). The detailed gas response properties of these sensors, including those to toluene and ethanol, the latter is a possible interference gas in detecting acetone and toluene, will be reported in the presentation.[1] K. Hieda, et al., Sens. Actuators B, 133(1), 144-150 (2008).[2] T. Hyodo, et al., Sens. Actuators B, 187, 495-502 (2013).[3] T. Ueda, et al., Front. Mater., 6, 1-10 (2019).[4] N. Tammanoon, et al., ACS Appl. Mater. Interfaces, 2020, 12, 41728-41739 (2020). Figure 1

Effect of Co addition on solidification velocity, hardness and refined structure transformation mechanisms of undercooled Ni-Cu-Co alloys

In this work, the effect of Co addition on the solidification velocity, hardness and refined structure transformation of the undercooled Ni-Cu-Co alloys have been systematically investigated. The results show that the grain refinement of Ni-Cu-Co ternary alloys at low undercooling is caused by the intense dendrite remelting. However, the grain refinement at high undercooling is attributed to recrystallization, and the driving force of recrystallization comes from the stresses and plastic strains accumulated by the interaction between liquid flow induced by rapid solidification and primary dendrites. The Co addition can significantly increase the solidification velocity and recalescence effect of Ni-Cu-Co alloys by increasing the number of solidified crystal nucleus and solute diffusion velocity. Under the same undercooling level, the increase of solidification velocity and recalescence effect have strengthened the remelting effect and stress accumulation, which can enlarge the critical range for grain refinement gradually. Meanwhile, due to the significant improvement of solidification velocity and stress-induced deformation effect by Co addition, the low angle GBs in the refined structure of Ni-Cu-Co alloys increase and the grain size decreases significantly, which have significantly improved the average hardness of the refined structure. When Co addition reaches 6 %, the refined structures can appear in almost the whole undercooling range and the hardness are improved by more than 100 % compared with the as-cast structure.

Effects of CO addition and multi-factors optimization on hydrogen/air combustion characteristics and thermal performance based on grey relational analysis

Power output and efficiency of the micro-thermophotovoltaic generator are limited by flame instability, tremendous heat loss ratio and short residence time. H2/air premixed combustion with varied CO blending ratios is conducted in a combustor with exit-step, and multi-factors of burner design and operation are discussed for improving the generator thermal performance and broadening its application. Results indicate that CO addition in H2/air premixed combustion contributes to the relocation and stretch of flame, and the comprehensive thermal performance of the burner is significantly augmented. Moreover, combustor structures also effectively alter flame anchoring and heat transmission, and a higher radiation power can be achieved with appropriate exit-step length and height. Particularly, stagger step can further boost radiation power and efficiency of the system. The CO proportion and step height play an important role in radiation power and efficiency based on grey relational analysis. Furthermore, the optimal comprehensive working performance is achieved by combustor St-12-0.4 and the radiation efficiency is 24.8% higher than that of the straight-channel combustor, which provides the highest system efficiency 2.62% and electrical power 2.33 W for the micro-thermophotovoltaic generator under the conditions of CO blended proportion 15% and equivalence ratio 1.0.

Effect of Co addition on magneto structural characteristics of Ni50−xCoxMn30Al20 Heusler alloys obtained by mechanical alloying process

Off-stoichiometric Ni50−xCoxMn30Al20 Heusler alloys were prepared by mechanical synthesis to study their structure, microstructure, morphology, chemical composition, and magnetic properties as a function of Co addition and at high temperature, using X-ray diffraction, SEM-EDS analysis, and VSM technique. At the end of the milling process, homogeneous mixtures consisting mainly of agglomerated grains of rounded shape with some debris of MICA-shaped particles were formed. All alloys have a nanocrystalline structure with an ordered Heusler B2 phase at 800 K. With increasing magnetization temperature, the crystallite size increases significantly by >100%, however, the rate of microstrain decreases drastically due to the relaxation of residual stresses. High-temperature magnetic characterizations have shown that the addition of cobalt has a direct effect on the curie temperature of the alloys as well as on their magnetic parameters Hc, Mr, and Ms. As the percentage of Co decreases, the curie temperature drops until it reaches 300 K by replacing 5% of Ni with Co. Ni45Co5Mn30Al20 has the lowest curie temperature close to 300 K and exhibits a soft magnetic behavior characterized by high saturation magnetization (Ms), and low coercivity (Hc) with an interesting coupling-magnetic exchange, which makes it a suitable candidate for soft magnetic applications.

Effects of CO addition on shock wave propagation, self-ignition, and flame development of high-pressure hydrogen release into air

In this study, an experimental investigation is conducted to study the effects of CO addition (0%–7.5% vol.) on the self-ignition of pressurized hydrogen leakage. The result shows that more CO addition significantly decreases the likelihood of self-ignition inside the tube and the formation of self-sustained jet flame outside the tube. This can be mostly explained by the reduction of leading shock intensity inside the tube. Furthermore, CO addition effectively inhibits the flame propagation and development inside the tube. For pure hydrogen, the ignited flame quickly develops an intense flame spanning the tube width and eventually form a jet flame in ambient air. However, the H 2 –CO diffusion flame initiated approaching tube sidewall tends to propagate adjacent to the wall or be soon quenched with more CO addition. If the CO-weakened flame spouts to the tube exit, it may not survive the expansion at the tube exit and thus it is quenched. • The shock intensity is reduced in the presence of CO. • The critical pressure for self-ignition increases with CO addition concentration. • Shock intensity variation by CO addition is the main factor affecting self-ignition onset. • Small CO addition can effectively inhibit flame development inside the tube. • H 2 –CO flame spouting from the tube exit tends to be blown out.

Effect of Co addition on the microstructure, thermal stability and anti-corrosion properties of AlNiZrYCox high-entropy metallic glass ribbons

In this current research, the effect of Co addition on the microstructure and anti-corrosion properties of equiatomic AlNiZrY high-entropy metallic glass (abbreviated to HE-MG) ribbons were investigated. Also, the thermal stability and crystallization activation energy of these HE-MG ribbons have been studied. Ribbons of composition (Al1/4Ni1/4Zr1/4Y1/4)100-xCox (x= 0, 5, 8, 12) were synthesized via arc-melting method and melt-spinning technique. By increasing the content of Co, we found that the melt-spun equiatomic AlNiZrY and Co-containing AlNiZrY HE-MG ribbons could still remain amorphous state. The thermal stability of ribbons were conducted by means of a differential scanning calorimeter (DSC), which suggested that the thermal stability of four kinds of HE-MG ribbons is higher than common Al-Ni-based amorphous alloys. The maximum apparent activation energy of crystallization through thermodynamic analysis at different heating rates can reach ∼630 kJ/mol for (Al1/4Ni1/4Zr1/4Y1/4)92Co8 HE-MG ribbons. The microstructure characterization of each HE-MG ribbon before and after one-day corrosion immersion was done by scanning electron microscopy (SEM). In order to evaluate the microhardness and corrosion resistance of the as-received HE-MG ribbons with and without the addition of Co, the microhardness measurements and the electrochemical corrosion tests in 3.5 wt.% NaCl solution were carried out. The results revealed that the average microhardness value of HE-MG ribbons are all above 470 HV0.1, regardless of whether the ribbons immersed in corrosive media for one-day immersion or not. The corrosion current density of (Al1/4Ni1/4Zr1/4Y1/4)88Co12 HE-MG ribbons is around 0.46 μA/cm2, which possesses the sterling anti-corrosion property and opens vital possibilities for the development of high-performance metal coatings under the condition of harsh marine environment.

Effect of co-addition of SiC and WC on the densification behaviour and microstructural evolution of TiC-based composites

In the present study, the effect of simultaneous incorporation of SiC and WC additives on the densification behaviour and microstructural development of TiC-based composites is studied. Four different TiC-SiC-WC (TSW) composites with varying SiC and WC content were synthesized by ultrasonic wet milling followed by spark plasma sintering (SPS) at 1750 °C for 5 min under 40 MPa external pressure. The average particle size of the ultrasonic wet-milled mixture underwent an appreciable refinement from 2.48 μm (un-milled powder) to between 0.9 and 1.25 μm. The sintered compacts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and thermodynamic assessment. All TSW sintered specimens exhibited a relative density of greater than 98% with TiC +10 wt% SiC +15 wt% WC reaching the highest value of 99.2%. The XRD analysis and microstructural evaluation confirmed the in-situ formation of Ti3SiC2 compound for specimens TiC +15 wt% SiC +10 wt% WC and TiC +20 wt% SiC +5 wt% WC as suggested by the thermodynamic evaluation. Besides, except for specimen TiC +20 wt% SiC +5 wt% WC, some of the SiC grains with unclean grain boundaries were found to be dissolved partially within the (Ti, W) C solid solution, thereby indicating the formation of (Ti, W, Si) C solid solutions as confirmed by the SEM/EDS analysis. The optimum hardness and indentation fracture toughness of 22.43 GPa and 6.54 MPa m½ were obtained for the samples TS10W15 and TS15W10, respectively. Crack deflection, branching, and bridging induced by the untwine SiC grains, partly un-dissolved WC particles, and (Ti, W) C solid solution phase are among the main toughening mechanisms responsible for improving the fracture toughness of the co-reinforced specimens besides the break of intertwining SiC grains.

Effect of Co Addition on the Structural Evolution and Magnetic Properties of Nanocrystalline Fe50ni50-Xcox Alloys Prepared by Mechanical Alloying

Effect of Co Addition on the Structural Evolution and Magnetic Properties of Nanocrystalline Fe50ni50-Xcox Alloys Prepared by Mechanical Alloying

Effect of co-addition of WC and MoSi2 on the microstructure of ZrB2–SiC–Si composites

In this paper, ZrB2–SiC–Si-based ceramic composites with WC and MoSi2 additives were fabricated using SPS method and their densification behavior was investigated by phase and microstructural studies. During the SPS process and according to the prevailing conditions, WC and MoSi2 additives reacted with the surface oxide impurities of the main raw materials. As a result of these reactions and the decomposition of some raw materials, a series of oxide liquid phases formed, which were often Si-based, and due to their good fluidity, undissolved and free elements such as Zr, Mo and W moved to open porosities and grain boundaries. According to the established thermodynamic conditions, binary solid solutions and new phases such as MoB, ZrC and WB formed. The synthesis of such phases boosted the densification of the composites due to the fact that they formed in porosities or voids between the main grains. The results showed that the sample doped with 2.5 vol% WC and 2.5 vol% MoSi2 had the highest relative density (about 99%). Meanwhile, microstructural studies showed that homogeneous and dense parts can be achieved by SPS technology.

The characterization and sodium borohydride electrooxidation of novel carbon nanotube supported copromoted Pd as anode catalyst for fuel cell

AbstractIn the present study, the effect of Co addition on Pd is investigated. Pd/CNT and PdCo/CNT catalysts are prepared via the sodium borohydride (SBH, NaBH4) reduction method. The X‐ray diffraction, transmission electron microscope, and inductively coupled plasma‐mass spectrometry analyses are performed to characterize the PdCo(70‐30)/CNT catalyst. These characterization results reveal that Pd/CNT and PdCo/CNT catalysts are prepared successfully. NaBH4 electrooxidation activities of PdCo/CNT catalysts are examined with electrochemical methods such as cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. PdCo(70‐30)/CNT catalyst has 11.52 mA/cm2 specific activity, 477.18 m2/g electrochemical active surface area, and the best electrochemical stability. Pd is a promising catalyst for NaBH4 electrooxidation reaction.

A Synergy Effect of Coadditives for Vertical Orientation of Two-Dimensional Perovskite Solar Cells Based on Butylammonium Iodide with Improved Efficiency

Two-dimensional (2D) perovskites show better resistance and optoelectronic characteristics than three-dimensional compounds. However, the high exciton energy and insufficient interfacial charge flo...

Effect of Co-Addition of Ag and Cu on Mechanical Properties of Sn\u20135Sb Lead-Free Solder

Sn–Sb lead-free solders are considered to substitute the tin–lead solders due to their great mechanical properties. At room temperature, the mechanical properties of Ni/Au/Sn–5Sb/Au/Ni and Ni/Au/Sn–5Sb–0.3Ag–0.05Cu/Au/Ni linear solder joints were investigated by nanoindentation experiments at different loads. The results showed that the Sn–Sb intermetallic compound (IMC) was distributed in the β-Sn matrix in Ni/Au/Sn–5Sb/Au/Ni solder joints. Co-addition of Cu and Ag resulted in the formation of the rod-shaped Cu6Sn5 and the fine granular Ag3Sn IMCs. At the same load and loading/unloading rate, the indentation depth and residual indentation morphologies of Ni/Au/Sn–5Sb–0.3Ag–0.05Cu/Au/Ni solder joints were smaller than those of Ni/Au/Sn–5Sb/Au/Ni solder joints. The hardness of the two kinds of solder joints decreased with the increase in load, while the Young’s modulus was independent of load. In addition, compared to the Ni/Au/Sn–5Sb/Au/Ni solder joints, the hardness, Young’s modulus and stress exponents of Ni/Au/Sn–5Sb–0.3Ag–0.05Cu/Au/Ni solder joints achieved an improvement due to the co-addition of Ag and Cu.

Effect of Co addition on hardness and electrical conductivity of Cu–Si alloys

Effect of Co addition on hardness and electrical conductivity of Cu–Si alloys

Effects of co-addition of ammonium, nitrite, and glucose with methionine on soil nitrogen.

Methionine is one of the many amino acids in the soil. In order to study the role of methionine in acidic forest soil, the effect of methionine (Met) was compared with control together with addition of ammonium (Met + A), nitrite (Met + N), and glucose (Met + C) under 60% or 90% water holding capacity (WHC), because ammonium and nitrite are important factors in nitrification, and glucose affect the heterotrophic nitrification and nitrogen immobilization. We found that methionine addition significantly reduced NO3- concentration in acidic forest soil. Compared to Met, Met + A and Met + N treatments non-significantly enhanced nitrification; however, Met + C treatment decreased NH4+ concentration which suggested that soil autotrophic and heterotrophic nitrification were limited in the presence of methionine at 60% WHC. Further, our findings of 15N-labeled treatment showed the impact and priming effect of methionine was negative for NO3- concentration and positive for N2O emission, which were observed mainly from the soil N source rather than methionine. At 90% WHC, Met + C treatment significantly lessened concentrations of NH4+ and NO3-, nonetheless improved N2O compared to Met treatment. Therefore, besides the denitrification and dissimilatory NO3- reduction to ammonia, the immobilization might be the key factor to explain this decrease in NO3- concentration at 90% WHC, while these processes were induced with the C addition. This study indicated that the positive role of amino acids in soil N cycling might be overrated.

Effects of Co Addition on the Microstructure and Properties of Elastic Cu-Ni-Si-Based Alloys for Electrical Connectors.

The properties and microstructure evolution of quaternary Cu-Ni-Co-Si alloys with different Ni/Co mass ratios were investigated. The microstructure and morphological characteristics of the precipitates were analyzed by using electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The mechanical properties and conductivity of the alloys were significantly improved after the addition of Co. The grains presented an obvious growth trend with an increase in Ni/Co mass ratios, and the appropriate Co accelerated the recrystallization process. The δ-(Ni, Co)2Si phases of the Cu-Ni-Co-Si alloys and δ-Ni2Si phases of the Cu-Ni-Si alloys shared the same crystal structure and orientation relationships with the matrix, which had two variant forms: δ1 and δ2 phases. The precipitates preferential grew along with the direction of the lowest energy and eventually exhibited two different morphologies. Compared with that of the Cu-Ni-Si alloy, the volume fraction of precipitates in the alloys with Co was significantly improved, accompanied by an increase in the precipitated phase size. The addition of Co promoted the precipitation of the precipitated phase and further purified the matrix. A theoretical calculation was conducted for different strengthening mechanisms, and precipitation strengthening was the key reinforcement mechanism. Moreover, the kinetic equations of both alloys were obtained and coincided well with the experimental results.

Direct production of hydrogen peroxide over bimetallic CoPd catalysts: Investigation of the effect of Co addition and calcination temperature

A series of CoPd/KIT-6 bimetallic catalysts with various Co:Pd molar ratios at different calcination temperatures were prepared and used for the direct synthesis of H2O2 from H2 and O2. These catalysts were characterized by nitrogen adsorption–desorption, low and wide-angle X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), elemental mapping and energy-dispersive X-ray (EDX) methods. It was found that the particle size, electronic interactions, morphology, and textural properties of these catalysts as well as their catalytic activity in the reaction of H2 with O2 were affected by Co addition and different calcination temperatures. Also, the results showed that while the H2O2 selectivity depends on Pd2+ species, the H2 conversion is related to Pd0 active sites. Among these catalysts, CoPd/KIT-6 calcined at 350 °C (CoPd/KIT-350 catalyst) showed the best catalytic activity with 50% of H2O2 selectivity and 51% conversion of H2.

Effect of Co addition on the high-temperature oxidation behavior of oxide-dispersion-strengthened FeCrAl alloys

The effect of Co addition on the high-temperature oxidation behavior of oxide dispersion-strengthened (ODS) FeCrAl alloys was investigated at 1000 °C in air. Exclusively α-Al2O3 scale formed on the surfaces of alloys containing 5 wt.% Al, and Y segregation was observed at the grain boundaries of Al2O3 scale. The solute Y in the Fe12Cr5Al-ODS (wt.%) alloy substrate was decreased by Co addition, thus limiting Y segregation at grain boundaries of the Al2O3 scale. The diminished Y segregation was inferred to cause grain size coarsening, which accounted for the slower oxidation kinetics of 5Al alloys with Co addition.

Effect of Co addition on microstructural and mechanical properties of WC–B4C–SiC composites

In this study, the effect of Co addition on microstructural and mechanical properties of WC-B4C–SiC composites sintered by spark plasma sintering (SPS) method was investigated. For this purpose, three batches of WC-B4C–SiC with different contents of Co (10 vol%, 15 vol%, and 20 Vol %) were sintered at 1400 °C. The results of X-ray diffraction (XRD) analysis of the samples indicated the formation of W2B5, W3CoB3 as well as the remained C phases and unreacted SiC phase. It was observed that by increasing the Co content, the amount of W2B5 phase reduces and W3CoB3 and C contents increase. Therefore, W2B5 peaks were not detected in the sample containing 20vol% Co. Relative density values above 97% were obtained for all the composites. However, a decrease was observed in relative density by increasing the Co content in the composites. The highest flexural strength (510 ± 42 MPa), fracture toughness (10.34 ± 0.82 MPa m1/2), and hardness (20.63 ± 0.75 GPa) were also obtained for the sample containing 10vol% Co compared to the other samples. In addition, Transgranular fracture of SiC as well as pulling out of W3CoB3 and W2B5 particles were observed in the fracture surface micrographs of the samples. The presence of micro-cracks in the SiC grains, fracture of W3CoB3 grains, and crack deflection was reported as dominant toughening mechanisms.

Large magnetocaloric effect in rapidly quenched Mn50− x Co x Ni40In10 nanomaterials

The effect of Co addition on magnetic hysteresis, martensitic transformation temperature, and magnetic entropy change of rapidly-quenched Mn50−x Co x Ni40In10 alloy nanomaterials has been investigated. The melt-spun Mn50Ni40In10 sample exhibits a small magnetic hysteresis which is further reduced by Co doping as measured between 0 and 2 T. The martensitic transformation temperature increases linearly with the electron concentration in the alloy from 195 K for Mn50Ni40In10 to 378 K for Mn45Co5Ni40In10. The Mn47Co3Ni40In10 alloy, which has phase-transition temperature close to room temperature, exhibits a substantial peak entropy change of 29.7 J kg−1 K−1 at magnetic field change of 2 T. Our results demonstrate that Mn47Co3Ni40In10 nanomaterial exhibits promising magnetocaloric properties for near-room-temperature magnetic refrigeration.