We report infrared spectroscopic observations of the incorporation of CO2 into pyrophyllite that has been heated between 200°C and 1250°C for periods of 15 min, 1 h and 5 days. The presence of CO2 is characterized by the ν3 band of CO2 near 2347 cm−1, detectable in samples in which dehydroxylation has commenced after heating above 450°C. With increasing temperature, the CO2 signal becomes more intense. The signal reaches its maximum intensity near 800°C with an annealing time of 15 min. Further heating leads to a decrease in the CO2 signal and the occurrence of an extra signal near 2156 cm−1 that implies the presence of CO. The process is characterized by significant time-dependence, indicating its kinetic nature. The peak positions of CO2 signals show systematic variations with temperature. Our results suggest that the CO2 molecule is associated with the local structure rather than being present as free gaseous CO2, and that the local structure of pyrophyllite is gradually modified during high-temperature treatments. However, no signals related to carbonate molecules ($({\text{CO}}_3^{2-})$) were detected. The results suggest that CO2 or other carbon-based molecules may diffuse into some clay minerals during dehydroxylation and may become altered due to structural modifications at high temperatures. This may have significance for possible CO2 sequestration in shales and clay formations.

In the present paper, the authors investigated the microstructures and mechanical properties of dual-phase Co–Ti–V-based superalloys with different additions of Ru. The results showed that with the increase of Ru contents, the size of γ′ precipitates of the alloy gradually raised, the volume fraction of γ′ phase slightly, and the lattice misfit between γ/γ′ phases increased. Ru was enriched in the γ′ phase, and the elemental partition coefficients (KX = Cγ′/Cγ) of Ti and V increased with the increment of Ru. The Ru contents have no remarkable influence on the solvus temperatures of γ′ in the Co–Ti–V alloys. The yield strength at 1000 °C of the Co–10Ti–11V–0.5Ru alloy was the highest, while the yield strength of the 1Ru alloy was the smallest. Transmission electron microscopy and scanning electron microscopy observations showed that the γ′ shape in the compressed specimen containing 0.5Ru remain integrated, while the γ′ in other alloys were cut into several parts.

The present work aims to explore the tribological behavior of the laser texturing process with different patterns on a Co based alloy using a pulsed Nd: YAG laser. Different parameters such as peak power, speed and spot diameter of the laser were explored for the experimental setting. The microstructural analysis was performed using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and nanoindentation tests. The influence of the different textured patterns of the tribological performance tested with a pin-on-disc tribometer under lubricated sliding condition was evaluated. The results showed that typical interdendritic structures in the as-cast CoCr alloy condition were refined due to the heat input and fast cooling rate during the laser treatment. The refined microstructure showed less volumetric loss resulting in a increment of wear resistance and a better tribological performance than as-cast alloy. The correlation among laser parameters, microstructural effect and their influence in wear resistance is discussed.

A new generation of cementitious materials is being engineered to selectively inhibit the growth of Acidithiobacillus, which are a key genera of acid-generating bacteria responsible for microbially induced concrete corrosion (MICC). In this context, the substitution of metal-laden granular activated carbon (GAC) particles and/or steel slag for a fraction of the fine aggregates traditionally used in concrete mixture has proven useful. While the antimicrobial properties of specific heavy metals (i.e. copper and cobalt) have been leveraged to inhibit acid-generating bacteria growth on sewer pipes, few studies have researched how biocidal aggregates may affect the microstructural and mechanical properties of cementitious materials. We report here on the effects that these biocidal aggregates substitutions can have on compressive strength, flowability, and setting times of cement-based formulations. Results showed that increases in compressive strength, regardless of the presence or absence of biocidal metals, resulted from the GAC incorporation where sand replacement was 3% by mass or lower, while flowability decreased when percentages higher than 3% of GAC was incorporated in a cement mix. When substituting fine aggregate with steel slag particles in mass ratios between 5% and 40%, compressive strength was not affected, regardless of the presence or absence of copper. Setting times were not affected by the inclusion of GAC or steel slag particles except when substituting GAC particles at 10% of the fine aggregate mass; under this condition both initial and final setting times were decreased. Results suggest that in order to have enhanced inhibition potential against acidophilic microorganisms and equal or improved mechanical properties, a combination of 1% metal-laden GAC and 40% copper-laden steel slag is an optimum fine aggregate substitution scenario.

Concerted efforts by stakeholders could overcome the hurdles and enable a viable recycling system for automotive LIBs by the time many of them go out of service.

Lithium-ion batteries (LIBs) were commercialized in the early 1990s and gained popularity first in consumer electronics, then more recently for electric vehicle (EV) propulsion, because of their high energy and power density and long cycle life. Their rapid adoption brings with it the challenge of end-of-life waste management. There are strong arguments for LIB recycling from environmental sustainability, economic, and political perspectives. Recycling reduces material going into landfills and avoids the impacts of virgin material production. LIBs contain high-value materials like cobalt and nickel, so recycling can reduce material and disposal costs, leading to reduced EV costs. Battery recycling can also reduce material demand and dependence on foreign resources, such as cobalt from Democratic Republic of the Congo, where much production relies on armed aggression and child labor.

Several companies are finding ways to commercialize recycling of the increasingly diverse LIB waste stream. Although Pb-acid battery recycling has been successfully implemented, there are many reasons why recycling of LIBs is not yet a universally well-established practice. Some of these are technical constraints, and others involve economic barriers, logistic issues, and regulatory gaps. This paper first builds a case as to why LIBs should be recycled, next compares recycling processes, and then addresses the different factors affecting LIB recycling to direct future work towards overcoming the barriers so that recycling can become standard practice.

Zirconium has attracted a lot of attention recently due to its distinctive properties that make it suitable for extensive applications in the nuclear power and chemical industry. Zirconium and its alloys are undergoing long-term development as promising materials for the nuclear industry and power engineering. Recently, advanced Zr-based alloys are aimed for service in more severe operating conditions such as higher burn-up, increased operation temperature, and high-PH operation. In this work we observe the temperature dependence of Zr50Nb50, Zr78Nb22, Zr78Nb19Co3 and Zr50Nb49Sn1. It was observed that ternary additions with small atomic percentages of Co and Sn have significant impact on Zr-Nb alloy; and their elastic properties showed a possible enhancement on high temperature applications and physical strength.

Nanosized CeO2-CuO (CeCu, 2:1) and CeO2-CoO (CeCo, 2:1) were synthesized by co-precipitation from nitrate precursors using 25% ammonia solution (NH4OH) as the precipitating agent. The catalysts were calcined in air at 800°C for 4h to evaluate the thermal stability. Powder x-ray diffraction (XRD) and Dynamic Light Scattering (DLS) techniques were used for catalyst characterization. A Thermo Gravimetric/Differential Thermal Analyzer (TG/DTA) was used to determine the catalytic efficiency and soot oxidation activity. Ce-composite nanoparticles heightens the redox properties of the catalyst relative to undoped ceria. The Ce-composite samples exhibited excellent soot catalytic combustion performance by decreasing activation energy of soot oxidation.

Binary transition metal oxides, such as NiCo2O4 (NCO) electrode have been demonstrated to be promising candidates for high-performance supercapacitors. However, their low electrical conductivity and poor stability made the electrochemical performance of most current NCO electrodes yet below the expectation. Herein, a novel electrode (NCC) consisting of binary transition metal (Ni–Co) nanoparticles embedded N-doped porous carbon matrix on graphite papers (GPs) has been developed with a high specific capacitance of 933.5 F/g at 1 mA/cm2 which is substantially 10 times than that of the NCO electrode (99.3 F/g) and much higher than those of most reported NCO based electrode. Moreover, this NCC electrode has an ultrahigh rate capability of 725.5 F/g at 10 mA/cm2 with excellent electrochemical durability (no capacitance decreases after 10,000 cycles). These results indicate a promising potential application of Ni–Co metal composite embedded carbon matrix for using as an effective electrode material in supercapacitors.

The plastic deformation mechanisms and the microstructure development during creep deformation of L12-hardened Co-base superalloys show a number of unique features. The preferred orientation of rafting is determined by their positive lattice mismatch. In addition, the regular interfacial dislocation networks often found in rafted specimens of other types of superalloys do not form. While the ordered γ′-L12 precipitates are supposed to harden the material, they are actually found to be frequently cut by partial dislocations generating stacking faults. In this work, specimens from creep tests interrupted at different strains were investigated using transmission and scanning electron microscopy. By this, it is possible to find out which of these processes take place in which stage of creep deformation. For a better understanding of creep deformation, the balance between γ′ cutting and dislocation activity within the matrix channels is of special interest.

This paper presents the high temperature yield and fatigue strength as well as thermophysical properties of two polycrystalline wrought γ/γ′ Co-base superalloys developed for application in a temperature regime above 700 °C. The alloys CoWAlloy1 (Co42Ni32Cr12Al6W3Ti2.5Ta1.5 + Si,C,B,Zr,Hf) and CoWAlloy2 (Co41Ni32Cr12Al9W5 + Ti,Ta,Si,C,B,Zr,Hf) exhibited solidus temperatures of 1070 °C and 1030 °C, respectively, and a γ′ fraction of about 50%. CoWAlloy2 displayed a rather high Young’s modulus of 250 GPa. The two Co-base superalloys showed a good high temperature strength exceeding Ni-base disc alloys U720Li and Waspaloy at temperatures above 800 °C. When comparing the yield strength from tensile and compression tests, no asymmetry could be found. The low-cycle fatigue life of CoWAlloy2 at a total strain amplitude of 0.5% is similar to that of U720Li and Waspaloy (about 370 cycles, R = −1). During long-term aging for 1024 h at 750 °C, no additional phases were formed and the room temperature hardness barely changed.

The element Re is known to be a very potent strengthener concerning the creep properties of Ni-base superalloys. In this paper the influence of Re on the properties of new γ′-strengthened Co-base superalloys is addressed. Atom probe tomography reveals that Re partitions preferentially to the γ phase, but not as pronounced as in ni-base superalloys. Nanoindentation and micro-pillar compression tests of the γ′ phase indicate an increase of the hardness and the critical resolved shear stress caused by a considerable concentration of Re in the γ′ phase. Creep investigations show that the positive effect of Re is by far not as pronounced as in Ni-base superalloys. Several effects, which can contribute to this behavior, such as the lower Re concentration in γ and hence a slightly reduced effective diffusion coefficient, a smaller diffusion barrier of Re in Co compared to Ni, a slightly lower lattice misfit and γ′ volume fraction of the Re-containing alloy, are discussed.

The development of highly efficient and stable inexpensive catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 in an aqueous solution by utilizing metal-organic frameworks (MOFs) as precursor and template remains a hot topic. Herein, a simple self-template strategy was developed to synthesize a porous nitrogen-doped carbon frameworks embedded with zinc and cobalt nanoparticles (Zn0.3Co2.7@NC) catalyst by thermal annealing of the bimetallic zinc-cobalt zeolitic imidazolate framework (Zn0.3Co2.7-ZIF) as an effective precursor and template. The resulting Zn0.3Co2.7@NC catalysts show an excellent catalytic activity for the reduction of 4-NP and the reduction reaction was completed only in 5 min with nearly 100% conversion. The apparent rate constant for the reaction of 4-NP reduction was estimated to be 0.683 min−1. Moreover, the catalyst was extended to reduce other nitro compounds and exhibited excellent catalytic activity. When compared to other related catalysts in the literature, the catalytic activity of catalyst is superior. Therefore, the resulting Zn0.3Co2.7@NC is expected to get more extensive application in the field of catalysis.

There has been a continuous call for active, durable, and low-cost catalysts for a range of catalysis reactions. In this paper, porous Co@C composed of uniformly dispersed Co metal nanoparticles in hexagonal-shaped prisms carbon matrix were fabricated by in situ pyrolysis of hexagonal-shaped prismatic Co-MOF-74 crystals. The obtained nanoporous carbons have a high surface area of 195.2 m2/g and a strong magnetic response, thereby realizing fast molecular diffusion of reactant and easy magnetic separation. The resulting Co@C catalyst show a superior and durable catalytic activity for reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Moreover, Co@C can be recycled and still retains more than 75% of its original catalytic activity after 6 cycles. Therefore, it is reasonable to believe that such Co@C nanocomposites have great potential as a highly efficient and low-cost heterogeneous catalyst. It is believed that MOFs can be used to produce other catalysts with high porosity and uniformly dispersed active sites.

Monte Carlo (MC) simulations of the magnetization states of disordered self-assembled arrays of particles consisting of Co87Cu13 alloy are investigated. The assemblies of magnetic particles with ellipsoidal shapes and volumes ranging from 5 to 50 µm3 exhibit densities of about 3 × 106 particles per mm2. Magnetization was obtained in the framework of Stoner–Wohlfarth model extended to include phenomenological contributions of second-order magnetic anisotropy and coercivity mechanism with distinct configuration of easy axes of magnetization. MC simulations for assemblies containing no more than 100 particles with negligible magnetic interaction between each other and exhibiting saturation magnetization and magnetic anisotropy constant values close to those found for cobalt in bulk are in good agreement with experimental results. We evaluate and validate our computational modeling using samples having particles with different sizes and different angular distributions of the easy axis of magnetization. A simple numerical approach with minimum of parameters was used to take into account the coercive fields of the samples. Reasonable simulation results are generated based on realistic size distributions and angular distributions of easy axis of magnetization.

PACS numbers: 75.30.Gw,75.60-d,75.70-i

The effect of Co on element segregation and microstructure is investigated in the third generation Ni-based single crystal superalloys with 4, 8.5, and 11.5 wt% Co addition. The results show that the increase of Co content leads to a severe element segregation in as-cast microstructure. After heat treatment, the size of γ′ phase is slightly reduced with Co content increase. During the thermal exposure, the γ′ phase coarsens gradually but its coarsening rate decreases with increasing Co content. In addition, some acicular and blocky topologically close-packed (TCP) phases are precipitated in 4% Co and 8.5% Co alloys. However, no TCP phase can be found in 11.5% Co alloy. Finally, it may be concluded that although a higher Co content is harmful for the element segregation, it is beneficial to maintain the cuboidal morphology of γ′ phase, decrease its coarsening rate, and impede the precipitation of TCP phase.

The laser cladding Co–Cr–W coating has coarse dendritic and network carbides, which can lead to crack and exfoliation easily, limiting the application of Co–Cr–W coating. In this work, friction stir processing (FSP) was carried out on a laser cladding Co–Cr–W alloy coating to modify its microstructure. FSP transforms the laser clad coarse dendritic grains (grain size: 2–4 μm) into nanograins (grain size: 50–200 nm) and crushes the network carbides into nanoparticles dispersed in Co-base solution. The microstructure and thickness of plastic surface layer are controllable by the condition of FSP. Moreover, a WCx reinforced Co–Cr–W thin layer was formed because the WC particles of stir tool were squeezed into the Co–Cr–W coating surface layer. More interestingly, when the FSP rotary speed was 1500 rpm, an interlocking bonding between Co–Cr–W coating and steel substrate was formed, which was favorable for the connection with substrate. The surface nanocrystallization significantly strengthened the laser clad Co–Cr–W alloy after FSP.

Oxidation tests of Cr containing Co-based superalloys with compositions of Co-20at.%Ni-9at.%Al-9at.%W-x at.%Cr (x = 2, 4, 6, 8 and 10) have been carried out at 1173 and 1273 K in air. Oxidation resistance is improved upon alloying with Cr not only at 1173 K but also at 1273 K. The weight gain of the 10at.%Cr alloy oxidized at 1173 K is similar to that of the 5th generation Ni-based superalloy of TMS-173. Alloying with Cr is efficient to improve oxidation resistance, however, the shape of γ’ precipitates is rounded and the alignment of the precipitates along the <100> direction becomes less pronounced upon alloying with Cr.

The effects of alloying elements (Ni/Ta) on the temperature dependence of yield stress in Co3(Al,W) with the L12 structure have been investigated through compression tests of nearly single-phase polycrystalline alloys in the temperature range between room temperature to 1,473K. Compared with a ternary Co3(Al,W), a Ni/Ta-added Co3(Al,W) alloy exhibits a higher γ΄ solvus temperature and lower onset temperature of the yield stress anomaly (positive temperature dependence of yield stress), suggesting that the CSF energy is increased by Ni/Ta addition. As a consequence, the high-temperature strength in Co3(Al,W) is considerably enhanced.

Electrochemical Double Layer Capacitors, EDLC, using Cobalt sulfide- Graphene (CoSG) composite electrodes, were fabricated and the storage process was studied. CoSG composite was prepared by a simple chemical route. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and Field Emission Scanning Electron microscopy (FESEM) were used to characterized the as prepared composites which indicated formation of Co S phase. Solutions of perfluorosulfonic acid and Polyvinylidene Fluoride (PVDF) were used as electrode binding material. The storage capacitance of the composites were studied in 1M KCl and 6M KOH electrolytes using standard electrochemical techniques like cyclic voltammetry, CV, electrochemical impedance spectroscopy, EIS, and discharge profiles. The capacitance was estimated for various binder concentrations for both the electrolytes. The concentration of perflurosulfonic acid binder of 0.8 wt% and PVDF of 0.04 wt% showed optimized specific capacitances of 657.8 F/gm and 1418.8 F/g, respectively. Some of the problems in storage density in activated carbon, like varying micro or meso pores, poor ion mobility due to varying pore distribution, low electrical conductivity, can be overcome by using Graphene and composites of Graphene. Graphene in various structural nomenclatures have been used by different groups for charge storage. Optimization of the electrode structure in terms of blend percentage, binder content and interface character in the frequency and time domain provides insights to the double layer interface structure.

To enhance the reliability of Pb-free solders in high temperature and high humidity conditions, the minor alloying elements of Be and Co are investigated in terms of the growth of Sn whiskers and various properties of Sn-based Pb-free solders. Sn whisker growth is suppressed by adding up to 0.02 wt% Be to Sn-based solders. Adding Be and Co can effectively reduce the undercooling of Sn–1.0Ag–0.5Cu (wt%) solders. And the microstructures of Sn–1.0Ag–0.5Cu–0.02Be solders are similar to those of Sn–1.0Ag–0.5Cu. Furthermore, adding Co to solders increases the microhardness number as a result of the solid solution hardening. Adding Be causes no changes in the morphology or thickness of Cu6Sn5 at the Cu/OSP (organic solderability preservative) under bump metallurgy interface. However, the scallop-like Cu6Sn5 microstructure changes to a flat (Cu,Co)6Sn5 microstructure when 0.05 wt% of Co is added to Sn–1.0Ag–0.5Cu–0.02Be solders.