Does high entropy alloy has higher microstructural stability than nickel-based superalloy?5 answersHigh entropy alloys (HEAs) exhibit varying degrees of microstructural stability compared to nickel-based superalloys. While some HEAs like Ni-Co-based HEA display a hierarchical microstructure with good yield strength and strain rate insensitivity, others may undergo phase decomposition during creep, leading to instability. The thermal stability of HEAs can be influenced by factors like cooling rate, thermal exposure, and eutectic morphology, affecting the precipitation behavior and mechanical properties. Additionally, the microstructure of refractory HEAs can undergo phase separation at lower temperatures, but both single-phase metastable and as-cast states show comparable mechanical properties, suggesting practical applicability. Therefore, the microstructural stability of HEAs compared to nickel-based superalloys varies depending on the specific alloy composition and processing conditions.
Does high entropy alloy has higher solvus temperature than nickel-based superalloy?5 answersHigh entropy alloys (HEAs) exhibit promising high-temperature properties, potentially surpassing nickel-based superalloys. HEAs are designed with a near-equal atomic ratio of multiple principal elements, leading to enhanced strength and sluggish diffusion at elevated temperatures. In contrast, nickel superalloys are traditionally composed of mainly one or two principal elements. Research on a specific Ni-Co-Cr-Al-Ti-Mo-W-Nb-Ta HEA demonstrated that at 1150 °C, it achieved a density of 7.92 g cm−3 and a hardness of 1050 HV, showcasing improved mechanical properties with increasing temperature. Furthermore, the study on CoCrCoFeNiGa filler alloy for vacuum brazing aimed to lower the liquidus temperature below 1270 °C, indicating the potential for high entropy alloys to have comparable or higher solvus temperatures than nickel-based superalloys.
What is the recent development beyond nickel based superalloys?5 answersRecent developments beyond nickel-based superalloys include the exploration of High Entropy Superalloys (HEAs) as potential alternatives for gas turbine applications. HEAs are considered the most promising materials for gas turbine engine applications due to their advanced manufacturing technique of laser surface modification and their superior properties. Another development is the design and manufacture of new wrought polycrystalline Ni-base superalloys for critical engineering applications, with a focus on improving thermal efficiency and reducing emissions. Additionally, a new γ′-strengthened Co-Ni-base superalloy has been developed, exhibiting high strength, creep resistance, and resistance to environmental damage. These superalloys can be processed via powder metallurgy and have potential applications in turbines, automotive exhaust systems, and internal combustion engines. The development of nickel-based superalloys is ongoing, with research focusing on composition, microstructures, strengthening mechanisms, processing methods, and component production.
How do alloying elements affect the microstructure of nickel-based superalloys and their high-temperature strength?5 answersAlloying elements such as chromium, molybdenum (+tungsten), and copper can be added to nickel-based alloys to improve their corrosion resistance and promote oxide passivity. In nickel-based superalloys, plastic strain evolution affects rafting, which reduces the service life of these materials at high temperatures. The microstructure of nickel-based superalloys can be influenced by the addition of alloying elements such as silicon, iron, and copper, which affect the precipitation strengthening phase sequence, type, and phase transformation. The addition of elements like aluminum, tungsten, and nickel improves the cyclic oxidation resistance of Co-Al-W alloys, reducing oxide scale spallation. Zirconium addition to IN100 superalloys affects the solidification zone, promotes the formation of γ-γ' eutectics, and influences the morphology of carbides.
Why Nickel-Based Catalyst Methane?5 answersNickel-based catalysts are commonly used for methane conversion due to their low cost and high efficiency. These catalysts can promote the directional regulation of reaction products, leading to faster reactions, energy savings, and reduced consumption. However, challenges such as Ni agglomeration and carbon deposition during high-temperature reactions need to be addressed. Extensive research has been conducted to design and synthesize more active nickel-based catalysts for high CO2 conversion and CH4 selectivity. The introduction of a catalyst in the CO2-CH4 reforming reaction can overcome issues such as low conversion rates, long reaction times, and high energy consumption. Nickel-based catalysts have been shown to exhibit high catalytic performance in methane combustion. Additionally, the use of nickel clusters supported by titanium carbide has been found to be effective in the nonoxidative conversion of methane to C2 products. Overall, nickel-based catalysts offer a promising solution for methane conversion, with ongoing research focused on improving their performance and stability.
Which type of nickel is used in batteries ?3 answersNickel is used in various types of batteries. Nickel-cadmium (NiCd) batteries, invented in the 19th century, utilize nickel and cadmium as their active materials. Nickel-metal hydride (NiMH) batteries also use nickel, but with a different negative electrode material. In the case of alkaline zinc-nickel flow batteries, a modified nickel cathode with nickel phosphide alloy is used to address volume expansion and oxygen evolution side reactions. Additionally, tube type nickel electrodes for alkaline batteries consist of a conductive base core, collector electrode, and rack tubes filled with active substances. Lastly, nickel-based cathodes have become popular in lithium-ion batteries, with Nickel-Manganese-Cobalt (NMC) and Nickel-Cobalt-Aluminum (NCA) being commonly used materials.