Natural biomass-derived carbon material is one promising alternative to traditional graphene-based catalyst for oxygen electrocatalysis.However,their electrocatalytic performance were constrained by the limited modula...Natural biomass-derived carbon material is one promising alternative to traditional graphene-based catalyst for oxygen electrocatalysis.However,their electrocatalytic performance were constrained by the limited modulating strategy.Herein,using N-doped commercial coconut shell-derived activated carbon(AC)as catalyst model,the controllably enhanced sp^(2)-C domains,through an flash Joule heating process,effectively improve the edge defect density and overall graphitization degree of AC catalyst,which tunes the electronic structure of N configurations and accelerates electron transfer,leading to excellent oxygen reduction reaction performance(half-wave potential of 0.884 VRHE,equivalent to commercial 20%Pt/C,with a higher kinetic current density of 5.88 mA cm^(−2))and oxygen evolution reaction activity(overpotential of 295 mV at 10 mA cm^(2)).In a Zn-air battery,the catalyst shows outstanding cycle stability(over 1200 h)and a peak power density of 121 mW cm^(−2),surpassing commercial Pt/C and RuO_(2)catalysts.Density functional theory simulation reveals that the enhanced catalytic activity arises from the axial regulation of local sp^(2)-C domains.This work establishes a robust strategy for sp^(2)-C domain modulation,offering broad applicability in natural biomass-based carbon catalysts for electrocatalysis.展开更多
β-Sialon has emerged as a promising material for enhancing the service life of Al_(2)O_(3)-C refractories due to its excellent physicochemical properties.The impact of varying concentrations of nanometer Al/Si alloy ...β-Sialon has emerged as a promising material for enhancing the service life of Al_(2)O_(3)-C refractories due to its excellent physicochemical properties.The impact of varying concentrations of nanometer Al/Si alloy on the in-situ synthesis of β-Sialon within Al_(2)O_(3)-C refractory materials,as well as its oxidation behavior,was investigated.The findings indicate that the presence of Al/Si alloy promotes the formation of AlN and SiC whiskers at 1300℃,which subsequently facilitate the production of plate-like β-Sialon at 1500℃.Density functional theory analysis reveals that the(020)crystal plane of β-Sialon exhibits the lowest adsorption energy for Al2O and AlO molecules under the influence of iron atoms,suggesting a solid-liquid-vapor growth mechanism for β-Sialon formation.The introduction of these ceramic phases significantly enhances the mechanical properties of Al_(2)O_(3)-C refractories.Specifically,the addition of 6 wt.%Al/Si alloy yielded specimens with the highest cold modulus of rupture and cold crushing strength at 1500℃,achieving values of 35.2 and 127.5 MPa,respectively--representing increases of 40.1%and 37.4%.Furthermore,during high-temperature oxidation,the formation of plate-like β-Sialon leads to the development of a dense protective layer on the surface.This impedes the diffusion pathways of oxygen and consequently enhances the oxidation resistance of the refractory.展开更多
In order to explore the corrosion mechanism of Al_(2)O_(3)-C refractories in the mold flux bearing MnO,the immersion test of Al_(2)O_(3)-C refractories in CaO-SiO2-CaF2-MnO slag with different MnO contents was carried...In order to explore the corrosion mechanism of Al_(2)O_(3)-C refractories in the mold flux bearing MnO,the immersion test of Al_(2)O_(3)-C refractories in CaO-SiO2-CaF2-MnO slag with different MnO contents was carried out at 1550℃.The results show that Mn particles were observed in the slag after experiment,due to the reduction of MnO by graphite in refractories.Large amounts of graphite were observed at the interface between refractories and slag,indicating that the oxidation of graphite is limited by the poor contact between graphite and molten slag.Therefore,the oxidation of graphite is not the main cause of damage to refractories.A small quantity of CaO·2Al_(2)O_(3)(CA_(2))and CaO·6Al_(2)O_(3)(CA_(6))adjacent to Al_(2)O_(3) grain was detected at the slag/reaction layer interface.CA_(2) and CA_(6) possess relatively high melting points,which is beneficial to hindering the further penetration of slag.However,the dissolution of Al_(2)O_(3) into slag is still the main cause for refractories damage.The increase in the MnO content of mold slag decreases the viscosity and then results in the severe corrosion of Al_(2)O_(3)-C bricks.展开更多
To address the issues of reduced performance and shortened lifespan during the low-carbonizating process of Al_(2)O_(3)-C refractories,nano-crystalline ZrC modified graphite was prepared using Zr powder and flake grap...To address the issues of reduced performance and shortened lifespan during the low-carbonizating process of Al_(2)O_(3)-C refractories,nano-crystalline ZrC modified graphite was prepared using Zr powder and flake graphite as raw materials,with NaCl and NaF mixed salt serving as the medium.The flake graphite was gradually replaced by ZrC modified graphite in the preparation of Al_(2)O_(3)-C refractories,and its impact on the material’s structure and properties was investigated.The results indicate that,compared to samples with only flake graphite,the introduction of 1 mass%to 5 mass%nano-crystalline ZrC modified graphite can significantly enhance the mechanical performance of low-carbon Al_(2)O_(3)-C refractories.When 5 mass%ZrC modified graphite is added,the mechanical properties of the samples are optimal,with the cold modulus of rupture and elastic modulus reaching 22.5 MPa and 65.0 GPa,respectively.展开更多
基金supported by National Natural Science Foundation of China (No. 32371810)China Postdoctoral Science Foundation (2023M731702)+5 种基金National Key Research and Development Program of China (2023YFB4203702)the Foundation Research Project of Jiangsu Province (BK20221338)Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest ResourcesInternational Innovation Center for Forest Chemicals and Materials,Nanjing Forestry Universitymerit-based funding for Nanjing innovation and technology projectsthe Foundation of Jiangsu Key Lab of Biomass Energy and Material (JSBEM-S-202101)
文摘Natural biomass-derived carbon material is one promising alternative to traditional graphene-based catalyst for oxygen electrocatalysis.However,their electrocatalytic performance were constrained by the limited modulating strategy.Herein,using N-doped commercial coconut shell-derived activated carbon(AC)as catalyst model,the controllably enhanced sp^(2)-C domains,through an flash Joule heating process,effectively improve the edge defect density and overall graphitization degree of AC catalyst,which tunes the electronic structure of N configurations and accelerates electron transfer,leading to excellent oxygen reduction reaction performance(half-wave potential of 0.884 VRHE,equivalent to commercial 20%Pt/C,with a higher kinetic current density of 5.88 mA cm^(−2))and oxygen evolution reaction activity(overpotential of 295 mV at 10 mA cm^(2)).In a Zn-air battery,the catalyst shows outstanding cycle stability(over 1200 h)and a peak power density of 121 mW cm^(−2),surpassing commercial Pt/C and RuO_(2)catalysts.Density functional theory simulation reveals that the enhanced catalytic activity arises from the axial regulation of local sp^(2)-C domains.This work establishes a robust strategy for sp^(2)-C domain modulation,offering broad applicability in natural biomass-based carbon catalysts for electrocatalysis.
基金supported by the Natural Science Foundation of Henan Province(No.232300420329)Key Scientific Research Project of Colleges and Universities in Henan Province(Nos.23B430012,22A430028,and 25B430022)+2 种基金Henan Provincial Science and Technology Research Project(No.242102231064)National Natural Science Foundation of China(No.52202064)Luoyang Major Science and Technology Innovation Project(No.2301009A).
文摘β-Sialon has emerged as a promising material for enhancing the service life of Al_(2)O_(3)-C refractories due to its excellent physicochemical properties.The impact of varying concentrations of nanometer Al/Si alloy on the in-situ synthesis of β-Sialon within Al_(2)O_(3)-C refractory materials,as well as its oxidation behavior,was investigated.The findings indicate that the presence of Al/Si alloy promotes the formation of AlN and SiC whiskers at 1300℃,which subsequently facilitate the production of plate-like β-Sialon at 1500℃.Density functional theory analysis reveals that the(020)crystal plane of β-Sialon exhibits the lowest adsorption energy for Al2O and AlO molecules under the influence of iron atoms,suggesting a solid-liquid-vapor growth mechanism for β-Sialon formation.The introduction of these ceramic phases significantly enhances the mechanical properties of Al_(2)O_(3)-C refractories.Specifically,the addition of 6 wt.%Al/Si alloy yielded specimens with the highest cold modulus of rupture and cold crushing strength at 1500℃,achieving values of 35.2 and 127.5 MPa,respectively--representing increases of 40.1%and 37.4%.Furthermore,during high-temperature oxidation,the formation of plate-like β-Sialon leads to the development of a dense protective layer on the surface.This impedes the diffusion pathways of oxygen and consequently enhances the oxidation resistance of the refractory.
基金the National Natural Science Foundation of China(52274305 and U1860205)Young Elite Scientists Sponsorship Program by CAST(2022QNRC001).
文摘In order to explore the corrosion mechanism of Al_(2)O_(3)-C refractories in the mold flux bearing MnO,the immersion test of Al_(2)O_(3)-C refractories in CaO-SiO2-CaF2-MnO slag with different MnO contents was carried out at 1550℃.The results show that Mn particles were observed in the slag after experiment,due to the reduction of MnO by graphite in refractories.Large amounts of graphite were observed at the interface between refractories and slag,indicating that the oxidation of graphite is limited by the poor contact between graphite and molten slag.Therefore,the oxidation of graphite is not the main cause of damage to refractories.A small quantity of CaO·2Al_(2)O_(3)(CA_(2))and CaO·6Al_(2)O_(3)(CA_(6))adjacent to Al_(2)O_(3) grain was detected at the slag/reaction layer interface.CA_(2) and CA_(6) possess relatively high melting points,which is beneficial to hindering the further penetration of slag.However,the dissolution of Al_(2)O_(3) into slag is still the main cause for refractories damage.The increase in the MnO content of mold slag decreases the viscosity and then results in the severe corrosion of Al_(2)O_(3)-C bricks.
文摘To address the issues of reduced performance and shortened lifespan during the low-carbonizating process of Al_(2)O_(3)-C refractories,nano-crystalline ZrC modified graphite was prepared using Zr powder and flake graphite as raw materials,with NaCl and NaF mixed salt serving as the medium.The flake graphite was gradually replaced by ZrC modified graphite in the preparation of Al_(2)O_(3)-C refractories,and its impact on the material’s structure and properties was investigated.The results indicate that,compared to samples with only flake graphite,the introduction of 1 mass%to 5 mass%nano-crystalline ZrC modified graphite can significantly enhance the mechanical performance of low-carbon Al_(2)O_(3)-C refractories.When 5 mass%ZrC modified graphite is added,the mechanical properties of the samples are optimal,with the cold modulus of rupture and elastic modulus reaching 22.5 MPa and 65.0 GPa,respectively.
