Bio-carbonation of reactive MgO has been regarded as a promising and eco-friendly method for construction and demolition waste(CDW)cementation in various geotechnical engineering applications.However,the beneficial ef...Bio-carbonation of reactive MgO has been regarded as a promising and eco-friendly method for construction and demolition waste(CDW)cementation in various geotechnical engineering applications.However,the beneficial effect of bio-carbonation of reactive MgO cemented CDW(BCM-samples)can be altered when exposed to wetting-drying cycles induced by extreme climate changes or groundwater fluctuations.To better understand the durability of BCM-samples and their underlying deterioration mechanisms,a series of BCM-samples was prepared to investigate their physical-mechanical performance and microstructure evolution subjected to the wetting-drying cycles.The results indicated that the wetting-drying cycles can deteriorate the BCM-samples,and their physical-mechanical behaviors change quickly at the cycle beginning and then smoothly after 2 cycles.With the increase in cycling,the apparent deterioration with efflorescence and microcrack development can be observed.The mass loss and water absorption rates increased while the dry density,compressional wave velocity,and unconfined compression strength decreased.Urea pre-hydrolysis treatment can significantly improve the durability of BCM-samples,as the more hydrated magnesia carbonates(HMCs)enhance the cementing effects.After 10 cycles,the UCS of pre-hydrolyzed samples decreased 25.4%to 4.45 MPa,while that of ordinary samples decreased 50.7%to 1.20 MPa.The deterioration of BCM-samples caused by wetting-drying cycles can be attributed to two factors.One of the main factors is the structural integrity changes caused by the rapid loss of soluble material at the initial cycling stages.Another factor is the decrease in cementation induced by the loss of brucite and HMCs at the following cycle stages.展开更多
The performance of iron ore pellets was influenced by gangue mineral interactions and alkali metal migration during the oxidation and reduction processes.A novel synergistic strategy was proposed to optimize pellet pr...The performance of iron ore pellets was influenced by gangue mineral interactions and alkali metal migration during the oxidation and reduction processes.A novel synergistic strategy was proposed to optimize pellet properties by regulating the liquid phase content coupled with MgO addition.The effects of SiO2and MgO contents on liquid phase generation,pellet microstructure,compressive strength,reduction swelling index(RSI),and reduction index(RI)were systematically investigated.The results showed that the increasing SiO2content significantly enhanced liquid phase formation,thereby improving compressive strength and reducing RSI,but lowering RI.MgO promoted the formation of MgxFe3-xO4during oxidation,increasing porosity and enhancing RI while slightly compromising mechanical strength.In addition,MgxFe3-xO4reduced the expansion during the initial reduction stage(Fe2O3→Fe3O4).Optimal performance was achieved when the liquid phase content in the roasted pellet was maintained at 11%-13%and MgO at 2.0%-2.6%,with compressive strength exceeding 2500 N,RSI below 20%,and RI above 64%.In addition,doubling the liquid phase content reduced the concentration of alkali metals diffused into the iron oxide lattice by approximately 50%,mitigating the localized precipitation of metallic iron whiskers during the final reduction stage(FexO→Fe).Alkali metal doped into iron oxides during oxidation had a more pronounced effect on swelling behavior than the reduction process.These findings offered practical insights into high-performance pellet production under industrial conditions.展开更多
The erosion patterns of MgO·Al2O3 spinel as a crucible material in special steel smelting and its impact on molten steel cleanliness are investigated.MgO·Al2O3 spinel refractories used in industr...The erosion patterns of MgO·Al2O3 spinel as a crucible material in special steel smelting and its impact on molten steel cleanliness are investigated.MgO·Al2O3 spinel refractories used in industrial high-nitrogen stainless steel bearing steel smelting are analyzed and tested.Results indicate that during vacuum carbon deoxidation,MgO·Al2O3 spinel partially decomposes,and the released[Mg]reacts with Al2O3 inclusions in the steel to form MgO·Al2O3 inclusions,promoting inclusion flotation and improving molten steel cleanliness.Due to the unique structure of MgO·Al2O3 spinel,iron diffuses into the spinel form MgAl1.9Fe0.1O4,which prevents further erosion.The high-pressure nitrogen smelting process also causes a small amount of AlN on the surface of the MgO·Al2O3 spinel crucible,further enhancing its high-temperature performance.After smelting,a deposit layer primarily composed of MgO,Al2O3,and MgO·Al2O3 spinel forms on the inner wall of the crucible,indicating that floating inclusions adhere to the spinel surface,thereby reducing the incorporation into the steel and improving molten steel cleanliness.These findings provide a theoretical foundation for broader application of MgO·Al2O3 spinel as a crucible material in the field of high-quality steel.展开更多
Y2O3-enhanced MgO refractory crucibles were fabricated based on a novel design of Y2O3crystal boundary-enhanced magnesia raw materials,and the interface reactions between the Y2O3-enhanced MgO refrac...Y2O3-enhanced MgO refractory crucibles were fabricated based on a novel design of Y2O3crystal boundary-enhanced magnesia raw materials,and the interface reactions between the Y2O3-enhanced MgO refractory crucibles and Ni-TiAl superalloy were explored.Micro-CT analysis revealed no substantial infiltration or structural damage to the crucible after two cycles of melting.Y2O3was found to uniformly distribute along MgO grain boundaries,forming a protective core-shell structure that effectively isolates MgO grains from direct contact with the alloy melt.This unique core-shell structure significantly enhanced the crucible’s corrosion resistance.Furthermore,a dense MgCr2O4spinel layer formed at the alloy-crucible interface,serving as a robust barrier against further refractory corrosion.The utilization of high-purity magnesia from Salt Lake resources not only minimized impurity-driven interfacial reactions but also endowed the crucible with superior performance.展开更多
Multicomponent synergistic catalysis offers a promising strategy to address the severe coking in dry reforming of methane(DRM).In this study,a multicomponent Ni0.05Mn0.05Co0.05Zn0.05Mg0.8O catalyst was ...Multicomponent synergistic catalysis offers a promising strategy to address the severe coking in dry reforming of methane(DRM).In this study,a multicomponent Ni0.05Mn0.05Co0.05Zn0.05Mg0.8O catalyst was developed,with Zn stabilized MnO(Mn-Zn-O active phase)promotes the DRM performance of exsolved NiCo nanometals from MgO-based oxide.Zn doping improves MnO dispersion and enrichment on MgO support during reduction by forming Mn-Zn-O active phase,in which Mn serves as a redox-active promoter to enhance activation and dissociation of CH4and CO2.The reduction of Mn to a lower valence state can facilitate CO2adsorption and dissociation on the surface of catalysts,which also enhanced oxygen mobility to promote CH4activation and coke removal.The optimized Ni0.05Mn0.05Co0.05Zn0.05Mg0.8O catalyst demonstrates exceptional stability in thermal DRM at 800℃for 100 h.And in photothermal DRM,the catalyst also achieves outstanding activity under high gas flow rates with well-designed three-dimensional porosity catalytic reactor.展开更多
A MgO/biochar composite(MBC)with a wide range of pore sizes was prepared by a MgCl2-NaOH co-impregnation method using lavender stalks as the biochar source,which can effectively remove Pb(Ⅱ)and Cd(Ⅱ)from wastewat...A MgO/biochar composite(MBC)with a wide range of pore sizes was prepared by a MgCl2-NaOH co-impregnation method using lavender stalks as the biochar source,which can effectively remove Pb(Ⅱ)and Cd(Ⅱ)from wastewater.The co-impregnation treatment resulted in a specific surface area of the MBC that was approximately 54 times greater than that of the biochar derived from untreated stalks.The ion-exchange capacity of MBC was increased by the incorporation of MgO nanoparticles,which increased the alkali metal ion(Mg2+)content.These specific structures and compositions gave the MBC a high adsorption capacity for Pb(Ⅱ)and Cd(Ⅱ).The adsorption data followed a quasi second-order kinetic model.For Cd(Ⅱ)and Pb(Ⅱ),the maximum adsorption capacities of MBC-700(treated at 700℃for 2 h)reached 520 mg/g and 808 mg/g,respectively.The primary adsorption mechanisms were ion exchange,precipitation,electrostatic attraction and surface complexation.Furthermore,metallic lead was recovered by using the reducing properties of the biochar at high temperatures.This study provides a reference for developing inexpensive and efficient heavy metal adsorbents and the low-carbonization utilization of biomass waste.展开更多
Ethylene(C2H4)in vehicle exhaust is a highly reactive volatile organic compound(VOC).Its photooxidative reaction with NOx contributes to the formation of O3 and secondary organic aerosols(SOA),the latter being a...Ethylene(C2H4)in vehicle exhaust is a highly reactive volatile organic compound(VOC).Its photooxidative reaction with NOx contributes to the formation of O3 and secondary organic aerosols(SOA),the latter being a key precursor of PM2.5.In this study,a novel MgO-supported Ag-Cu bimetallic catalyst was designed and investigated using density functional theory(DFT).The effects of Ag and Cu loading on the geometric structure,stability,and reactant adsorption characteristics of the catalyst were analyzed,and the catalytic oxidation pathways of C2H4over AgCu-MgO was elucidated.The results indicate that loading Ag significantly enhances the adsorption of C2H4.The incorporation of Cu into Ag-MgO to form a AgCu-MgO bimetallic catalyst(dual atom catalyst,DACS)further improves the oxidative activity toward C2H4.Based on the binding energies of the Ag and Cu bimetallic sites and the adsorption energies of C2H4and O2,three representative configurations were selected for detailed reaction pathway analysis.Among them,Configuration 6 of AgCu-MgO exhibited the highest catalytic oxidation performance.This study provides new atomic-scale insights for the rational design of efficient catalysts targeting olefinic pollutants in automotive emissions and offers valuable guidance for advancing exhaust after-treatment technologies.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42525201 and 42230710).
摘要Bio-carbonation of reactive MgO has been regarded as a promising and eco-friendly method for construction and demolition waste(CDW)cementation in various geotechnical engineering applications.However,the beneficial effect of bio-carbonation of reactive MgO cemented CDW(BCM-samples)can be altered when exposed to wetting-drying cycles induced by extreme climate changes or groundwater fluctuations.To better understand the durability of BCM-samples and their underlying deterioration mechanisms,a series of BCM-samples was prepared to investigate their physical-mechanical performance and microstructure evolution subjected to the wetting-drying cycles.The results indicated that the wetting-drying cycles can deteriorate the BCM-samples,and their physical-mechanical behaviors change quickly at the cycle beginning and then smoothly after 2 cycles.With the increase in cycling,the apparent deterioration with efflorescence and microcrack development can be observed.The mass loss and water absorption rates increased while the dry density,compressional wave velocity,and unconfined compression strength decreased.Urea pre-hydrolysis treatment can significantly improve the durability of BCM-samples,as the more hydrated magnesia carbonates(HMCs)enhance the cementing effects.After 10 cycles,the UCS of pre-hydrolyzed samples decreased 25.4%to 4.45 MPa,while that of ordinary samples decreased 50.7%to 1.20 MPa.The deterioration of BCM-samples caused by wetting-drying cycles can be attributed to two factors.One of the main factors is the structural integrity changes caused by the rapid loss of soluble material at the initial cycling stages.Another factor is the decrease in cementation induced by the loss of brucite and HMCs at the following cycle stages.
基金the Science and Technology Innovation Program of Hunan Province(Nos.2023RC1025 and 2024RC3022)the Basic Science Center Project(No.72088101).
摘要The performance of iron ore pellets was influenced by gangue mineral interactions and alkali metal migration during the oxidation and reduction processes.A novel synergistic strategy was proposed to optimize pellet properties by regulating the liquid phase content coupled with MgO addition.The effects of SiO2and MgO contents on liquid phase generation,pellet microstructure,compressive strength,reduction swelling index(RSI),and reduction index(RI)were systematically investigated.The results showed that the increasing SiO2content significantly enhanced liquid phase formation,thereby improving compressive strength and reducing RSI,but lowering RI.MgO promoted the formation of MgxFe3-xO4during oxidation,increasing porosity and enhancing RI while slightly compromising mechanical strength.In addition,MgxFe3-xO4reduced the expansion during the initial reduction stage(Fe2O3→Fe3O4).Optimal performance was achieved when the liquid phase content in the roasted pellet was maintained at 11%-13%and MgO at 2.0%-2.6%,with compressive strength exceeding 2500 N,RSI below 20%,and RI above 64%.In addition,doubling the liquid phase content reduced the concentration of alkali metals diffused into the iron oxide lattice by approximately 50%,mitigating the localized precipitation of metallic iron whiskers during the final reduction stage(FexO→Fe).Alkali metal doped into iron oxides during oxidation had a more pronounced effect on swelling behavior than the reduction process.These findings offered practical insights into high-performance pellet production under industrial conditions.
基金supported by National Key Research and Development Program of China(2021YFB3701404)the National Natural Science Foundation of China(Grant Nos.52174302 and 52304347)+4 种基金the Fundamental Research Funds for the Central Universities(N2409008)Postdoctoral Fellowship Program of CPSF(GZB20230122)Doctoral Start-up Foundation of Liaoning Province(2023-BSBA-107)China Baowu Low Carbon Metallurgy Innovation Foundation(BWLCF202320)Young Elite Scientist Sponsorship Program by Cast(Grant No.YESS20240132).
摘要The erosion patterns of MgO·Al2O3 spinel as a crucible material in special steel smelting and its impact on molten steel cleanliness are investigated.MgO·Al2O3 spinel refractories used in industrial high-nitrogen stainless steel bearing steel smelting are analyzed and tested.Results indicate that during vacuum carbon deoxidation,MgO·Al2O3 spinel partially decomposes,and the released[Mg]reacts with Al2O3 inclusions in the steel to form MgO·Al2O3 inclusions,promoting inclusion flotation and improving molten steel cleanliness.Due to the unique structure of MgO·Al2O3 spinel,iron diffuses into the spinel form MgAl1.9Fe0.1O4,which prevents further erosion.The high-pressure nitrogen smelting process also causes a small amount of AlN on the surface of the MgO·Al2O3 spinel crucible,further enhancing its high-temperature performance.After smelting,a deposit layer primarily composed of MgO,Al2O3,and MgO·Al2O3 spinel forms on the inner wall of the crucible,indicating that floating inclusions adhere to the spinel surface,thereby reducing the incorporation into the steel and improving molten steel cleanliness.These findings provide a theoretical foundation for broader application of MgO·Al2O3 spinel as a crucible material in the field of high-quality steel.
基金funded by the Key Project of the National Natural Science Foundation of China(Grant No.U21A2058)Research Project of Hubei Provincial Department of Science and Technology(2024CSA075)National Natural Science Foundation of Henan(252300420486).
摘要Y2O3-enhanced MgO refractory crucibles were fabricated based on a novel design of Y2O3crystal boundary-enhanced magnesia raw materials,and the interface reactions between the Y2O3-enhanced MgO refractory crucibles and Ni-TiAl superalloy were explored.Micro-CT analysis revealed no substantial infiltration or structural damage to the crucible after two cycles of melting.Y2O3was found to uniformly distribute along MgO grain boundaries,forming a protective core-shell structure that effectively isolates MgO grains from direct contact with the alloy melt.This unique core-shell structure significantly enhanced the crucible’s corrosion resistance.Furthermore,a dense MgCr2O4spinel layer formed at the alloy-crucible interface,serving as a robust barrier against further refractory corrosion.The utilization of high-purity magnesia from Salt Lake resources not only minimized impurity-driven interfacial reactions but also endowed the crucible with superior performance.
基金supported by the National Key R&D Program of China(2023YFB4104600)the National Natural Science Foundation of China(52572313)+1 种基金the Tangshan Talent Funding Project(A202202007)the Shenzhen Science and Technology Innovation Commission(20231120185819001).
摘要Multicomponent synergistic catalysis offers a promising strategy to address the severe coking in dry reforming of methane(DRM).In this study,a multicomponent Ni0.05Mn0.05Co0.05Zn0.05Mg0.8O catalyst was developed,with Zn stabilized MnO(Mn-Zn-O active phase)promotes the DRM performance of exsolved NiCo nanometals from MgO-based oxide.Zn doping improves MnO dispersion and enrichment on MgO support during reduction by forming Mn-Zn-O active phase,in which Mn serves as a redox-active promoter to enhance activation and dissociation of CH4and CO2.The reduction of Mn to a lower valence state can facilitate CO2adsorption and dissociation on the surface of catalysts,which also enhanced oxygen mobility to promote CH4activation and coke removal.The optimized Ni0.05Mn0.05Co0.05Zn0.05Mg0.8O catalyst demonstrates exceptional stability in thermal DRM at 800℃for 100 h.And in photothermal DRM,the catalyst also achieves outstanding activity under high gas flow rates with well-designed three-dimensional porosity catalytic reactor.
基金funded by the National Natural Science Foundation of China(52563033)Xinjiang Natural Science Fund for Distinguished Young Scholars(2022D01E37)+1 种基金Xinjiang Tianshan Talent Project(2024TSYCCX0007)Key programs of Xinjiang Natural Science Foundation(2022B02051,2023B2045 and 2024LQ01001-3).
摘要A MgO/biochar composite(MBC)with a wide range of pore sizes was prepared by a MgCl2-NaOH co-impregnation method using lavender stalks as the biochar source,which can effectively remove Pb(Ⅱ)and Cd(Ⅱ)from wastewater.The co-impregnation treatment resulted in a specific surface area of the MBC that was approximately 54 times greater than that of the biochar derived from untreated stalks.The ion-exchange capacity of MBC was increased by the incorporation of MgO nanoparticles,which increased the alkali metal ion(Mg2+)content.These specific structures and compositions gave the MBC a high adsorption capacity for Pb(Ⅱ)and Cd(Ⅱ).The adsorption data followed a quasi second-order kinetic model.For Cd(Ⅱ)and Pb(Ⅱ),the maximum adsorption capacities of MBC-700(treated at 700℃for 2 h)reached 520 mg/g and 808 mg/g,respectively.The primary adsorption mechanisms were ion exchange,precipitation,electrostatic attraction and surface complexation.Furthermore,metallic lead was recovered by using the reducing properties of the biochar at high temperatures.This study provides a reference for developing inexpensive and efficient heavy metal adsorbents and the low-carbonization utilization of biomass waste.
基金Supported by the National Natural Science Foundation of China Project(22362018)the Yunnan Fundamental Research Projects(202401AS070102)。
摘要Ethylene(C2H4)in vehicle exhaust is a highly reactive volatile organic compound(VOC).Its photooxidative reaction with NOx contributes to the formation of O3 and secondary organic aerosols(SOA),the latter being a key precursor of PM2.5.In this study,a novel MgO-supported Ag-Cu bimetallic catalyst was designed and investigated using density functional theory(DFT).The effects of Ag and Cu loading on the geometric structure,stability,and reactant adsorption characteristics of the catalyst were analyzed,and the catalytic oxidation pathways of C2H4over AgCu-MgO was elucidated.The results indicate that loading Ag significantly enhances the adsorption of C2H4.The incorporation of Cu into Ag-MgO to form a AgCu-MgO bimetallic catalyst(dual atom catalyst,DACS)further improves the oxidative activity toward C2H4.Based on the binding energies of the Ag and Cu bimetallic sites and the adsorption energies of C2H4and O2,three representative configurations were selected for detailed reaction pathway analysis.Among them,Configuration 6 of AgCu-MgO exhibited the highest catalytic oxidation performance.This study provides new atomic-scale insights for the rational design of efficient catalysts targeting olefinic pollutants in automotive emissions and offers valuable guidance for advancing exhaust after-treatment technologies.