Silicon anodes are promising for use in lithium-ion batteries.However,their practical application is severely limited by their large volume expansion leading to irreversible material fracture and electrical disconnect...Silicon anodes are promising for use in lithium-ion batteries.However,their practical application is severely limited by their large volume expansion leading to irreversible material fracture and electrical disconnects.This study proposes a new top-down strategy for preparing microsize porous silicon and introduces polyacrylonitrile(PAN)for a nitrogen-doped carbon coating,which is designed to maintain the internal pore volume and lower the expansion of the anode during lithiation and delithiation.We then explore the effect of temperature on the evolution of the structure of PAN and the electrochemical behavior of the composite electrode.After treatment at 400℃,the PAN coating retains a high nitrogen content of 11.35 at%,confirming the presence of C—N and C—O bonds that improve the ionic-electronic transport properties.This treatment not only results in a more intact carbon layer structure,but also introduces carbon defects,and produces a material that has remarkable stable cycling even at high rates.When cycled at 4 A g^(-1),the anode had a specific capacity of 857.6 mAh g^(-1) even after 200 cycles,demonstrating great potential for high-capacity energy storage applications.展开更多
ZrB_(2)-based ceramics typically necessitate high temperature and pressure for sintering,whereas ZrB_(2)-SiC ceramics can be fabricated at 1500℃using the process of reactive melt infiltration with Si.In comparison to...ZrB_(2)-based ceramics typically necessitate high temperature and pressure for sintering,whereas ZrB_(2)-SiC ceramics can be fabricated at 1500℃using the process of reactive melt infiltration with Si.In comparison to the conventional preparation method,reactive synthesis allows for the more facile production of ultra-high temperature ceramics with fine particle size and homogeneous composition.In this work,ZrSi_(2),B4C,and C were used as raw materials to prepare ZrB_(2)-SiC via combination of tape casting and reactive melt infiltration herein referred to as ZBC ceramics.Control sample of ZrB_(2)-SiC was also prepared using ZrB_(2) and SiC as raw materials through an identical process designated as ZS ceramics.Microscopic analysis of both ceramic groups revealed smaller and more uniformly distributed particles of the ZrB_(2) phase in ZBC ceramics compared to the larger particles in ZS ceramics.Both sets of ceramics underwent cyclic oxidation testing in the air at 1600℃for a cumulative duration of 5 cycles,each cycle lasting 2 h.Analysis of the oxidation behavior showed that both ZBC ceramics and ZS ceramics developed a glassy SiO_(2)-ZrO_(2) oxide layer on their surfaces during the oxidation.This layer severed as a barrier against oxygen.In ZBC ceramics,ZrO_(2) is finely distributed in SiO_(2),whereas in ZS ceramics,larger ZrO_(2) particles coexist with glassy SiO_(2).The surface oxide layer of ZBC ceramics maintains a dense structure because the well-dispersed ZrO_(2) increases the viscosity of glassy SiO_(2),preventing its crystallization during the cooling.Conversely,some SiO_(2) in the oxide layer of ZS ceramics may crystallize and form a eutectic with ZrO_(2),leading to the formation of ZrSiO_(4).This leads to cracking of the oxide layer due to differences in thermal expansion coefficients,weakening its barrier effect.An analysis of the oxidation resistance shows that ZBC ceramics exhibit less increase in oxide layer thickness and mass compared to ZS ceramics,suggesting superior oxidation resistance of ZBC ceramics.展开更多
The Mg-Sn alloys,with basal or prismatic Mg2Sn laths,were employed to reveal the effect of precipitate orientation on twinning behavior quantitatively.The Mg-5wt.%Sn alloys with basal or prismatic Mg2Sn were compresse...The Mg-Sn alloys,with basal or prismatic Mg2Sn laths,were employed to reveal the effect of precipitate orientation on twinning behavior quantitatively.The Mg-5wt.%Sn alloys with basal or prismatic Mg2Sn were compressed to study the twinning behaviors.Subsequently,an Orowan strengthening model was developed to quantitatively investigate the critical resolved shear stress(CRSS)increment of precipitates on twinning.The results revealed that the prismatic precipitates hindered the transfer and growth of tensile twins more effectively compared with the basal precipitates.The decreased proportion of tensile twins containing prismatic Mg2Sn might be attributed to a larger CRSS increment for tensile twins compared with that for basal precipitates.The obvious decreased twinning transfer in the alloy with prismatic Mg2Sn could be due to its higher geometrically necessary dislocation and enhanced CRSS of tensile twins.Notably,the prismatic precipitates have a better hindering effect on tensile twins during compression.展开更多
The magnetization reduction of hematite using biomass waste can effectively utilize waste and reduce CO_(2) emission to achieve the goals of carbon peaking and carbon neutrality.The effects of temperatures on suspensi...The magnetization reduction of hematite using biomass waste can effectively utilize waste and reduce CO_(2) emission to achieve the goals of carbon peaking and carbon neutrality.The effects of temperatures on suspension magnetization roasting of hematite using biomass waste for evolved gases have been investigated using TG-FTIR,Py-GC/MS and gas composition analyzer.The mixture reduction process is divided into four stages.In the temperature range of 200-450℃ for mixture,the release of CO_(2),acids,and ketones is dominated in gases products.The yield and concentration of small molecules reducing gases increase when the temperature increases from 450 to 900℃.At 700℃,the volume concentrations of CO,H_(2) and CH_(4) peak at 8.91%,8.90% and 4.91%,respectively.During the suspension magnetization roasting process,an optimal iron concentrate with an iron grade of 70.86%,a recovery of 98.66% and a magnetic conversion of 45.70% is obtained at 700℃.Therefore,the magnetization reduction could react greatly in the temperature range of 600 to 700℃ owing to the suitable reducing gases.This study shows a detail gaseous evolution of roasting temperature and provides a new insight for studying the reduction process of hematite using biomass waste.展开更多
文摘Silicon anodes are promising for use in lithium-ion batteries.However,their practical application is severely limited by their large volume expansion leading to irreversible material fracture and electrical disconnects.This study proposes a new top-down strategy for preparing microsize porous silicon and introduces polyacrylonitrile(PAN)for a nitrogen-doped carbon coating,which is designed to maintain the internal pore volume and lower the expansion of the anode during lithiation and delithiation.We then explore the effect of temperature on the evolution of the structure of PAN and the electrochemical behavior of the composite electrode.After treatment at 400℃,the PAN coating retains a high nitrogen content of 11.35 at%,confirming the presence of C—N and C—O bonds that improve the ionic-electronic transport properties.This treatment not only results in a more intact carbon layer structure,but also introduces carbon defects,and produces a material that has remarkable stable cycling even at high rates.When cycled at 4 A g^(-1),the anode had a specific capacity of 857.6 mAh g^(-1) even after 200 cycles,demonstrating great potential for high-capacity energy storage applications.
基金National Key R&D Program of China(2022YFB3707700)Shanghai Science and Technology Innovation Action Plan(21511104800)+3 种基金National Natural Science Foundation of China(52172111)National Science and Technology Major Project(2017-IV-0005-0042)Key Research Program of the Chinese Academy of Sciences(ZDRW-CN-2021-2-2)Science Center for Gas Turbine Project(P2022-B-IV-001-001)。
文摘ZrB_(2)-based ceramics typically necessitate high temperature and pressure for sintering,whereas ZrB_(2)-SiC ceramics can be fabricated at 1500℃using the process of reactive melt infiltration with Si.In comparison to the conventional preparation method,reactive synthesis allows for the more facile production of ultra-high temperature ceramics with fine particle size and homogeneous composition.In this work,ZrSi_(2),B4C,and C were used as raw materials to prepare ZrB_(2)-SiC via combination of tape casting and reactive melt infiltration herein referred to as ZBC ceramics.Control sample of ZrB_(2)-SiC was also prepared using ZrB_(2) and SiC as raw materials through an identical process designated as ZS ceramics.Microscopic analysis of both ceramic groups revealed smaller and more uniformly distributed particles of the ZrB_(2) phase in ZBC ceramics compared to the larger particles in ZS ceramics.Both sets of ceramics underwent cyclic oxidation testing in the air at 1600℃for a cumulative duration of 5 cycles,each cycle lasting 2 h.Analysis of the oxidation behavior showed that both ZBC ceramics and ZS ceramics developed a glassy SiO_(2)-ZrO_(2) oxide layer on their surfaces during the oxidation.This layer severed as a barrier against oxygen.In ZBC ceramics,ZrO_(2) is finely distributed in SiO_(2),whereas in ZS ceramics,larger ZrO_(2) particles coexist with glassy SiO_(2).The surface oxide layer of ZBC ceramics maintains a dense structure because the well-dispersed ZrO_(2) increases the viscosity of glassy SiO_(2),preventing its crystallization during the cooling.Conversely,some SiO_(2) in the oxide layer of ZS ceramics may crystallize and form a eutectic with ZrO_(2),leading to the formation of ZrSiO_(4).This leads to cracking of the oxide layer due to differences in thermal expansion coefficients,weakening its barrier effect.An analysis of the oxidation resistance shows that ZBC ceramics exhibit less increase in oxide layer thickness and mass compared to ZS ceramics,suggesting superior oxidation resistance of ZBC ceramics.
基金National Natural Science Foundation of China(Nos.52004227,U22A20187,52201106)the China Postdoctoral Science Foundation(No.2020M683240)+1 种基金the Key Area Research and Development Program of Guangdong ProvinceChina(No.2020B090924002)。
文摘The Mg-Sn alloys,with basal or prismatic Mg2Sn laths,were employed to reveal the effect of precipitate orientation on twinning behavior quantitatively.The Mg-5wt.%Sn alloys with basal or prismatic Mg2Sn were compressed to study the twinning behaviors.Subsequently,an Orowan strengthening model was developed to quantitatively investigate the critical resolved shear stress(CRSS)increment of precipitates on twinning.The results revealed that the prismatic precipitates hindered the transfer and growth of tensile twins more effectively compared with the basal precipitates.The decreased proportion of tensile twins containing prismatic Mg2Sn might be attributed to a larger CRSS increment for tensile twins compared with that for basal precipitates.The obvious decreased twinning transfer in the alloy with prismatic Mg2Sn could be due to its higher geometrically necessary dislocation and enhanced CRSS of tensile twins.Notably,the prismatic precipitates have a better hindering effect on tensile twins during compression.
基金Project(52022019)supported by the National Natural Science Foundation of China。
文摘The magnetization reduction of hematite using biomass waste can effectively utilize waste and reduce CO_(2) emission to achieve the goals of carbon peaking and carbon neutrality.The effects of temperatures on suspension magnetization roasting of hematite using biomass waste for evolved gases have been investigated using TG-FTIR,Py-GC/MS and gas composition analyzer.The mixture reduction process is divided into four stages.In the temperature range of 200-450℃ for mixture,the release of CO_(2),acids,and ketones is dominated in gases products.The yield and concentration of small molecules reducing gases increase when the temperature increases from 450 to 900℃.At 700℃,the volume concentrations of CO,H_(2) and CH_(4) peak at 8.91%,8.90% and 4.91%,respectively.During the suspension magnetization roasting process,an optimal iron concentrate with an iron grade of 70.86%,a recovery of 98.66% and a magnetic conversion of 45.70% is obtained at 700℃.Therefore,the magnetization reduction could react greatly in the temperature range of 600 to 700℃ owing to the suitable reducing gases.This study shows a detail gaseous evolution of roasting temperature and provides a new insight for studying the reduction process of hematite using biomass waste.
