Ethylene(C_(2)H_(4))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(C_(2)H_(4))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 PM_(2.5).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 C_(2)H_(4)over AgCu-MgO was elucidated.The results indicate that loading Ag significantly enhances the adsorption of C_(2)H_(4).The incorporation of Cu into Ag-MgO to form a AgCu-MgO bimetallic catalyst(dual atom catalyst,DACS)further improves the oxidative activity toward C_(2)H_(4).Based on the binding energies of the Ag and Cu bimetallic sites and the adsorption energies of C_(2)H_(4)and O_(2),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
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 erosion patterns of MgO·Al_(2)O_(3) spinel as a crucible material in special steel smelting and its impact on molten steel cleanliness are investigated.MgO·Al_(2)O_(3) spinel refractories used in industr...The erosion patterns of MgO·Al_(2)O_(3) spinel as a crucible material in special steel smelting and its impact on molten steel cleanliness are investigated.MgO·Al_(2)O_(3) spinel refractories used in industrial high-nitrogen stainless steel bearing steel smelting are analyzed and tested.Results indicate that during vacuum carbon deoxidation,MgO·Al_(2)O_(3) spinel partially decomposes,and the released[Mg]reacts with Al_(2)O_(3) inclusions in the steel to form MgO·Al_(2)O_(3) inclusions,promoting inclusion flotation and improving molten steel cleanliness.Due to the unique structure of MgO·Al_(2)O_(3) spinel,iron diffuses into the spinel form MgAl_(1.9)Fe_(0.1)O_(4),which prevents further erosion.The high-pressure nitrogen smelting process also causes a small amount of AlN on the surface of the MgO·Al_(2)O_(3) spinel crucible,further enhancing its high-temperature performance.After smelting,a deposit layer primarily composed of MgO,Al_(2)O_(3),and MgO·Al_(2)O_(3) 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·Al_(2)O_(3) spinel as a crucible material in the field of high-quality steel.展开更多
文摘为抑制碱激发胶凝材料(AASM)因水化反应集中、孔隙失水引起的显著自收缩,本文提出采用MgO与Na_(2)SiO_(3)复配为复合激发剂,系统研究其对AASM凝结行为、水化产物组成、孔结构特征、强度发展与自收缩性能的影响规律。通过XRD(X-ray diffraction)与NMR(nuclear magnetic resonance)等手段表征发现:随着复合激发剂中MgO比例的增加,体系内类水滑石相生成显著增多,同时最可几孔径向10~20 nm区间集中,孔隙率有所上升。上述微观结构演变导致以下宏观性能变化:一方面,MgO的弱碱性质延缓了矿渣的水化进程,凝结时间延长,抗压强度随其掺量增加而降低;另一方面,类水滑石相的体积膨胀效应与孔隙率的提高共同缓解了毛细孔应力,使AASM的自收缩显著减小。研究表明,MgO与Na_(2)SiO_(3)在调控反应进程与水化产物组成方面具有协同作用。Na_(2)SiO_(3)提供强碱性环境以保障早期强度发展,而MgO则通过促进膨胀性产物生成,优化孔隙结构,有效抑制收缩开裂。该复合激发策略为兼顾AASM力学性能与体积稳定性提供了可行途径。
基金Supported by the National Natural Science Foundation of China Project(22362018)the Yunnan Fundamental Research Projects(202401AS070102)。
文摘Ethylene(C_(2)H_(4))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 PM_(2.5).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 C_(2)H_(4)over AgCu-MgO was elucidated.The results indicate that loading Ag significantly enhances the adsorption of C_(2)H_(4).The incorporation of Cu into Ag-MgO to form a AgCu-MgO bimetallic catalyst(dual atom catalyst,DACS)further improves the oxidative activity toward C_(2)H_(4).Based on the binding energies of the Ag and Cu bimetallic sites and the adsorption energies of C_(2)H_(4)and O_(2),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.
基金supported by the National Natural Science Foundation of China(Grant Nos.42525201 and 42230710).
文摘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).
文摘The erosion patterns of MgO·Al_(2)O_(3) spinel as a crucible material in special steel smelting and its impact on molten steel cleanliness are investigated.MgO·Al_(2)O_(3) spinel refractories used in industrial high-nitrogen stainless steel bearing steel smelting are analyzed and tested.Results indicate that during vacuum carbon deoxidation,MgO·Al_(2)O_(3) spinel partially decomposes,and the released[Mg]reacts with Al_(2)O_(3) inclusions in the steel to form MgO·Al_(2)O_(3) inclusions,promoting inclusion flotation and improving molten steel cleanliness.Due to the unique structure of MgO·Al_(2)O_(3) spinel,iron diffuses into the spinel form MgAl_(1.9)Fe_(0.1)O_(4),which prevents further erosion.The high-pressure nitrogen smelting process also causes a small amount of AlN on the surface of the MgO·Al_(2)O_(3) spinel crucible,further enhancing its high-temperature performance.After smelting,a deposit layer primarily composed of MgO,Al_(2)O_(3),and MgO·Al_(2)O_(3) 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·Al_(2)O_(3) spinel as a crucible material in the field of high-quality steel.
