scholarly journals Self-regeneration of supported transition metals by a high entropy-driven principle

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shengtai Hou ◽  
Xuefeng Ma ◽  
Yuan Shu ◽  
Jiafeng Bao ◽  
Qiuyue Zhang ◽  
...  
Keyword(s):  
Transition Metals ◽  
Current Theory ◽  
Transition Metal Catalysts ◽  
Host Matrix ◽  
High Entropy ◽  
Redox Cycles ◽  
Core Issue ◽  
Sintering Resistance ◽  
Resistance Performance

AbstractThe sintering of Supported Transition Metal Catalysts (STMCs) is a core issue during high temperature catalysis. Perovskite oxides as host matrix for STMCs are proven to be sintering-resistance, leading to a family of self-regenerative materials. However, none other design principles for self-regenerative catalysts were put forward since 2002, which cannot satisfy diverse catalytic processes. Herein, inspired by the principle of high entropy-stabilized structure, a concept whether entropy driving force could promote the self-regeneration process is proposed. To verify it, a high entropy cubic Zr0.5(NiFeCuMnCo)0.5Ox is constructed as a host model, and interestingly in situ reversible exsolution-dissolution of supported metallic species are observed in multi redox cycles. Notably, in situ exsolved transition metals from high entropy Zr0.5(NiFeCuMnCo)0.5Ox support, whose entropic contribution (TΔSconfig = T⋆12.7 J mol−1 K−1) is predominant in ∆G, affording ultrahigh thermal stability in long-term CO2 hydrogenation (400 °C, >500 h). Current theory may inspire more STWCs with excellent sintering-resistance performance.

In Situ Study on the Compression Deformation Behavior of MoNbTaVW High-Entropy Alloy

2020 ◽  
Author(s):  
Congyan Zhang ◽  
Binbin Yue ◽  
Uttam Bhandari ◽  
Oleg Starovoytov ◽  
Yan Yang ◽  
...  
Keyword(s):  
Deformation Behavior ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Compression Deformation

A novel in-situ exothermic assisted sintering high entropy Al2O3/(NbTaMoW)C composites: Microstructure and mechanical properties

2021 ◽  
Vol 212 ◽  
pp. 108681
Author(s):  
Diqiang Liu ◽  
Aijun Zhang ◽  
Jiangang Jia ◽  
Jiesheng Han ◽  
Junyan Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Entropy ◽  
Microstructure And Mechanical Properties

scholarly journals Understanding Selectivity in CO2 Hydrogenation to Methanol for MoP Nanoparticle Catalysts Using In Situ Techniques

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 143
Author(s):  
Melis S. Duyar ◽  
Alessandro Gallo ◽  
Samuel K. Regli ◽  
Jonathan L. Snider ◽  
Joseph A. Singh ◽  
...  
Keyword(s):  
Formation Rate ◽  
Methanol Conversion ◽  
Transition Metal Catalysts ◽  
Colloidal Synthesis ◽  
X Ray ◽  
In Situ Techniques ◽  
Methanol Formation ◽  
Diffuse Reflectance Infrared ◽  
Formate Intermediate

Molybdenum phosphide (MoP) catalyzes the hydrogenation of CO, CO2, and their mixtures to methanol, and it is investigated as a high-activity catalyst that overcomes deactivation issues (e.g., formate poisoning) faced by conventional transition metal catalysts. MoP as a new catalyst for hydrogenating CO2 to methanol is particularly appealing for the use of CO2 as chemical feedstock. Herein, we use a colloidal synthesis technique that connects the presence of MoP to the formation of methanol from CO2, regardless of the support being used. By conducting a systematic support study, we see that zirconia (ZrO2) has the striking ability to shift the selectivity towards methanol by increasing the rate of methanol conversion by two orders of magnitude compared to other supports, at a CO2 conversion of 1.4% and methanol selectivity of 55.4%. In situ X-ray Absorption Spectroscopy (XAS) and in situ X-ray Diffraction (XRD) indicate that under reaction conditions the catalyst is pure MoP in a partially crystalline phase. Results from Diffuse Reflectance Infrared Fourier Transform Spectroscopy coupled with Temperature Programmed Surface Reaction (DRIFTS-TPSR) point towards a highly reactive monodentate formate intermediate stabilized by the strong interaction of MoP and ZrO2. This study definitively shows that the presence of a MoP phase leads to methanol formation from CO2, regardless of support and that the formate intermediate on MoP governs methanol formation rate.

scholarly journals Erosion and Corrosion Resistance Performance of Laser Metal Deposited High-Entropy Alloy Coatings at Hellisheidi Geothermal Site

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3071
Author(s):  
Andri Isak Thorhallsson ◽  
Francesco Fanicchia ◽  
Emily Davison ◽  
Shiladitya Paul ◽  
Svava Davidsdottir ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Microstructural Characterization ◽  
Corrosion Damage ◽  
Process Equipment ◽  
High Entropy Alloy ◽  
Low Alloy Steels ◽  
Manufacturing Defects ◽  
High Entropy ◽  
Alloy Steels ◽  
Resistance Performance

Geothermal process equipment and accessories are usually manufactured from low-alloy steels which offer affordability but increase the susceptibility of the materials to corrosion. Applying erosion-corrosion-resistant coatings to these components could represent an economical solution to the problem. In this work, testing of two newly developed laser metal deposited high-entropy alloy (LMD-HEA) coatings—CoCrFeNiMo0.85 and Al0.5CoCrFeNi, applied to carbon and stainless steels—was carried out at the Hellisheidi geothermal power plant. Tests in three different geothermal environments were performed at the Hellisheidi site: wellhead test at 194 °C and 14 bar, erosion test at 198 °C and 15 bar, and aerated test at 90 °C and 1 bar. Post-test microstructural characterization was performed via Scanning Eletron Microscope (SEM), Back-Scattered Electrons analysis (BSE), Energy Dispersive X-ray Spectroscopy (EDS), optical microscopy, and optical profilometry while erosion assessment was carried out using an image and chemical analysis. Both the CoCrFeNiMo0.85 and Al0.5CoCrFeNi coatings showed manufacturing defects (cracks) and were prone to corrosion damage. Results show that damage in the CoCrFeNiMo0.85-coated carbon steel can be induced by manufacturing defects in the coating. This was further confirmed by the excellent corrosion resistance performance of the CoCrFeNiMo0.85 coating deposited onto stainless steel, where no manufacturing cracks were observed.

scholarly journals In-Situ TEM Annealing Observation of Helium Bubble Evolution in Pre-Irradiated FeCoNiCrTi0.2 Alloys

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3727
Author(s):  
Huanhuan He ◽  
Zhiwei Lin ◽  
Shengming Jiang ◽  
Xiaotian Hu ◽  
Jian Zhang ◽  
...  
Keyword(s):  
Vacuum Arc ◽  
In Situ Tem ◽  
Face Centered Cubic ◽  
Helium Bubble ◽  
High Entropy ◽  
Helium Bubbles ◽  
Transmission Electron ◽  
Bubble Evolution ◽  
Face Centered

The FeCoNiCrTi0.2 high-entropy alloys fabricated by vacuum arc melting method, and the annealed pristine material, are face centered cubic structures with coherent γ’ precipitation. Samples were irradiated with 50 keV He+ ions to a fluence of 2 × 1016 ions/cm2 at 723 K, and an in situ annealing experiment was carried out to monitor the evolution of helium bubbles during heating to 823 and 923 K. The pristine structure of FeCoNiCrTi0.2 samples and the evolution of helium bubbles during in situ annealing were both characterized by transmission electron microscopy. The annealing temperature and annealing time affect the process of helium bubbles evolution and formation. Meanwhile, the grain boundaries act as sinks to accumulate helium bubbles. However, the precipitation phase seems have few effects on the helium bubble evolution, which may be due to the coherent interface and same structure of γ’ precipitation and matrix.

Tungsten particles reinforced high-entropy alloy matrix composite prepared by in-situ reaction

2020 ◽  
pp. 158037
Author(s):  
Gang Chen ◽  
Tao Luo ◽  
Shucheng Shen ◽  
Jixiang Zheng ◽  
Xiaotian Tang ◽  
...  
Keyword(s):  
Matrix Composite ◽  
High Entropy Alloy ◽  
Alloy Matrix ◽  
High Entropy ◽  
In Situ Reaction
Sign in / Sign up

Export Citation Format

Share Document