The rapid development of communication technology and high-frequency electronic devices has created a need for more advanced electromagnetic interference(EMI)shielding materials.In response to this demand,a study has ...The rapid development of communication technology and high-frequency electronic devices has created a need for more advanced electromagnetic interference(EMI)shielding materials.In response to this demand,a study has been conducted to develop multifunctional carbon nanofibers(CNFs)/polyaniline(PANI)aerogels with excellent electromagnetic interference shielding,flame retardancy,and thermal insulation performance.The process involved freeze-drying of electrospun CNFs and PANI nanoparticles followed by in situ growth PANI to coat the CNFs,creating the core-shell structured CNFs/PANI composite fiber and its hybrid aerogels(CP-3@PANI).The interaction between PANI and aniline(ANI)provides attachment sites,allowing additional ANI adsorption into the aerogel for in situ polymerization.This results in PANI uniformly covering the surface of the CNFs,creating a core-shell composite fiber with a flexible CNF core and PANI shell.This process enhances the utilization rate of the ANI monomer and increases the PANI content loaded onto the aerogel.Additionally,effective connections are established between the CNFs,forming a stable,conductive three-dimensional network structure.The prepared CP-3@PANI aerogels exhibit excellent EMI shielding efficiency(SE)of 85.4 dB and specific EMI SE(SE d^(-1))of 791.2 dB cm^(3)g^(-1)in the X-band.Due to the synergistic flame-retardant effect of CNFs,PANI,and the dopant(phytic acid),the CP-3@PANI aerogels demonstrate outstanding flame-retardant and thermal insulation properties,with a peak heat release rate(PHRR)as low as 7.8 W g^(-1)and a total heat release of only 0.58 kJ g^(-1).This study provides an effective strategy for preparing multifunctional integrated EMI shielding materials.展开更多
Given the importance of lithium-ion cell safety,a comprehensive review on the thermal stability of lithium-ion cells investigated by accelerating rate calorimetry(ARC),is provided in the present work.The operating mec...Given the importance of lithium-ion cell safety,a comprehensive review on the thermal stability of lithium-ion cells investigated by accelerating rate calorimetry(ARC),is provided in the present work.The operating mechanism of ARC is discussed first,including the usage and the reaction kinetics.Besides that,the thermal stability of the cathode/anode materials at elevated temperatures is revealed by examining the impacts of some significant factors,i.e.,the lithium content,particle size,material density,lithium salt,solvent,additive,binder and initial heating temperature.A comparison of the common cathode materials indicates that the presence of Mn and polyanion could significantly enhance the thermal stability of cathode materials,while the doping of Al also helps to restrain the reactivity.Except for their high capacity,some alloy materials demonstrate more competitive safety than traditional carbon anode materials.Furthermore,the thermal behaviors of full cells under abusive conditions are reviewed here.Due to the sensitivity of ARC to the kinetic parameters,a reaction kinetic modeling can be built on the basis of ARC profiles,to predict the thermal behaviors of cell components and cells.Herein,a shortcircuit modeling is exampled.展开更多
Perovskite oxides has been attracted much attention as high-performance oxygen carriers for chemical looping reforming of methane,but they are easily inactivated by the presence of trace H_(2)S.Here,we propose to modu...Perovskite oxides has been attracted much attention as high-performance oxygen carriers for chemical looping reforming of methane,but they are easily inactivated by the presence of trace H_(2)S.Here,we propose to modulate both the activity and resistance to sulfur poisoning by dual substitution of Mo and Ni ions with the Fe-sites of LaFeO_(3)perovskite.It is found that partial substitution of Ni for Fe substantially improves the activity of LaFeO_(3)perovskite,while Ni particles prefer to grow and react with H_(2)S during the long-term successive redox process,resulting in the deactivation of oxygen carriers.With the presence of Mo in LaNi_(0.05)Fe_(0.95)O_(3−σ)perovskite,H_(2)S preferentially reacts with Mo to generate MoS_(2),and then the CO_(2)oxidation can regenerate Mo via removing sulfur.In addition,Mo can inhibit the accumulation and growth of Ni,which helps to improve the redox stability of oxygen carriers.The LaNi_(0.05)Mo_(0.07)Fe_(0.88)O_(3−σ)oxygen carrier exhibits stable and excellent performance,with the CH_(4)conversion higher than 90%during the 50 redox cycles in the presence of 50 ppm H_(2)S at 800℃.This work highlights a synergistic effect in the perovskite oxides induced by dual substitution of different cations for the development of high-performance oxygen carriers with excellent sulfur tolerance.展开更多
As crucial nodes in railway transportation networks,railway passenger stations can suffer significant casualties and adverse societal impacts during fire accidents.A numerical simulation test was conducted on fire smo...As crucial nodes in railway transportation networks,railway passenger stations can suffer significant casualties and adverse societal impacts during fire accidents.A numerical simulation test was conducted on fire smoke spread and personnel evacuation in a rail-way passenger station.The results indicate that the structural span and floor height of the passenger terminal influence the smoke conditions at a height of 1.8 m such that the critical thresholds for smoke visibility,smoke temperature and carbon monoxide(CO)concentration are not surpassed.However,the smoke in the vicinity of a fire source can affect the surrounding environment.Notably,within each waiting hall,the spatial extent of the influence of smoke temperature is broader than that of smoke visibility and CO concentration.Moreover,the orthogonal test analysis reveals that the factors influencing personnel evacuation time,in descending order of impact,are the number of gates opened,personnel density,baggage weight and personnel ratio.The number of gates opened is the key factor affecting safe personnel evacuation,with at least three gates needing to be opened to meet safety requirements for evacuation.In addition,a nonlinear prediction equation is established to relate the personnel evacuation time to various influenc-ing factors,and its prediction accuracy is found to be more pronounced when the evacuation duration exceeds 100 s.Furthermore,regardless of the specific waiting hall where the fire originated or the effectiveness of the automatic sprinkler system,the smoke temperature has the most prominent influence on the time required for safe evacuation.展开更多
Various N-doped hierarchical porous carbons were prepared by using a new mixed-ligand ZIF(zeolitic imidazolate framework)(JUC-160)as the precursor in a one-step synthetic route without any additional carbon sources or...Various N-doped hierarchical porous carbons were prepared by using a new mixed-ligand ZIF(zeolitic imidazolate framework)(JUC-160)as the precursor in a one-step synthetic route without any additional carbon sources or purification steps.The effect of the ZIF precursor crystal size on the textural properties of the derived porous carbons was systematically studied.Microporosity was dominant in micron-sized JUC-160 crystal derived porous carbons,while more mesopore volume was present in porous carbons obtained from nanometre-sized JUC-160 crystals.The mJUC160-900 sample,which had a high nitrogen content and micropore volume,exhibited the highest CO_(2) uptake,which is 5.50 and 3.50 mmol g^(-1) at 273 and 298 K,respectively.Moreover,the analysis based on the ideal adsorbed solution theory(IAST)exhibited a high adsorption selectivity for CO_(2)/N_(2) at 298 K and 1 bar(Sads=29).展开更多
Radioactive iodine element mainly in CH3I is a key fission product of concern in the nuclear fuel cycle,which directly threat-ens human health if released into the environment.Effective capture of the I element is ess...Radioactive iodine element mainly in CH3I is a key fission product of concern in the nuclear fuel cycle,which directly threat-ens human health if released into the environment.Effective capture of the I element is essential for human health protection.The iodine filter,consisting of an activated carbon inner core and cotton filter,is the most common radioactive iodine pro-tection product.Currently,the activated carbon inside the iodine filter suffers from the weak adsorption efficiency and high cost.Herein,a process based on a strong alkali activation method was developed to significantly improve iodine absorption and reduce the cost.A series of flexible porous carbon fibers with a high specific surface area(up to about 1,500~2,200 m^(2)/g)were prepared by carbonation of the phenolic resin fibers(PF,prepared through melt spinning and crosslink)followed by activation via KOH treatment.Meanwhile,the nitrogen-doped sp^(2)-heterogeneous carbon atoms were prepared by add-ing nitrogen sources such as urea which led to a high surface area nano-porous fibers with an average pore size of~2.4 nm.The nitrogen-doped porous carbon fibers exhibit very high adsorption for liquid iodine and iodine vapor.The liquid iodine adsorption capacity of nitrogen-doped porous carbon NDAC-4 prepared under 800°C reaches 2,120 mg/g,which is 2.1 times higher than that of the commercial iodine filter,and for iodine vapor the capacity can reach 5,330 mg/g.Meanwhile,the CH_(3)I adsorption capacity is 510 mg/g,which is 3.4 times higher than that of commercial unmodified viscose fibers and has greater stability and circularity.Importantly,the research has met the requirements of industrial production,and the fabrication of phenolic-fibers-based protection equipment can be widely used in the nuclear radiation industry.展开更多
The oxygen vacancy formation energy and chemical looping dry reforming of methane over metal-substituted CeO_(2)(111)are investigated based on density functional theory calculations.The calculated results indicate tha...The oxygen vacancy formation energy and chemical looping dry reforming of methane over metal-substituted CeO_(2)(111)are investigated based on density functional theory calculations.The calculated results indicate that among the various metals that can substitute for the Ce atom in the CeO_(2)(111)surface,Zn substitution results in the lowest oxygen vacancy formation energy.For the activation of CH4 on CeO_(2)(111)and Zn-substituted CeO_(2)(111)surfaces,the calculated results illustrate that the dissociation process of CH_(3)(ads)is very difficult on pristine surfaces and unfavorable for CHO(ads)on substituted surfaces.Furthermore,the dissociative adsorption of CO and H_(2)on the Zn-substituted CeO_(2)(111)surface requires high energy,which is unfavorable for syngas production.This work demonstrates that excessive formation of oxygen vacancy can lead to excessively high adsorption energies,thus limiting the conversion efficiency of the reaction intermediates.This finding provides important guidance and application prospects for the design and optimization of oxygen carrier materials,especially in the field of chemical looping dry methane reforming to syngas.展开更多
基金the financial support from the Shenzhen Biodegradable Polymer Materials and Materials Genetic Evaluation Research Project Team (JCYJ20220818100217037)Science and Technology Program of Shenzhen (JSGG20200924171000001)+4 种基金the Key-Area Research and Development Program of Guangdong Province (2019B010941001)the Guangdong Provincial Key Laboratory of Energy Materials for Electric Power(2018B030322001)the National Key Research and Development Program of China (2018YFB0704100)Joint Laboratory of Radiation Protection and Material Genetic Engineering Applications in Nuclear Facilitiessupported by the Pico Center at SUSTech CRF which receives support from the Presidential Fund and Development and Reform Commission of Shenzhen Municipality。
文摘The rapid development of communication technology and high-frequency electronic devices has created a need for more advanced electromagnetic interference(EMI)shielding materials.In response to this demand,a study has been conducted to develop multifunctional carbon nanofibers(CNFs)/polyaniline(PANI)aerogels with excellent electromagnetic interference shielding,flame retardancy,and thermal insulation performance.The process involved freeze-drying of electrospun CNFs and PANI nanoparticles followed by in situ growth PANI to coat the CNFs,creating the core-shell structured CNFs/PANI composite fiber and its hybrid aerogels(CP-3@PANI).The interaction between PANI and aniline(ANI)provides attachment sites,allowing additional ANI adsorption into the aerogel for in situ polymerization.This results in PANI uniformly covering the surface of the CNFs,creating a core-shell composite fiber with a flexible CNF core and PANI shell.This process enhances the utilization rate of the ANI monomer and increases the PANI content loaded onto the aerogel.Additionally,effective connections are established between the CNFs,forming a stable,conductive three-dimensional network structure.The prepared CP-3@PANI aerogels exhibit excellent EMI shielding efficiency(SE)of 85.4 dB and specific EMI SE(SE d^(-1))of 791.2 dB cm^(3)g^(-1)in the X-band.Due to the synergistic flame-retardant effect of CNFs,PANI,and the dopant(phytic acid),the CP-3@PANI aerogels demonstrate outstanding flame-retardant and thermal insulation properties,with a peak heat release rate(PHRR)as low as 7.8 W g^(-1)and a total heat release of only 0.58 kJ g^(-1).This study provides an effective strategy for preparing multifunctional integrated EMI shielding materials.
基金supported by NSERC,Tesla Motors,the National Natural Science Foundation of China (No.52204213,52272396)the China Postdoctoral Science Foundation (No.2022M711602)+2 种基金the Opening Fund of State Key Laboratory of Fire Science (SKLFS) (No.HZ2022-KF07)the Jiangsu Project Plan for Outstanding Talents Team in Six Research Fields (No.TD-XNYQC-002)the support of the China Scholarship Council。
文摘Given the importance of lithium-ion cell safety,a comprehensive review on the thermal stability of lithium-ion cells investigated by accelerating rate calorimetry(ARC),is provided in the present work.The operating mechanism of ARC is discussed first,including the usage and the reaction kinetics.Besides that,the thermal stability of the cathode/anode materials at elevated temperatures is revealed by examining the impacts of some significant factors,i.e.,the lithium content,particle size,material density,lithium salt,solvent,additive,binder and initial heating temperature.A comparison of the common cathode materials indicates that the presence of Mn and polyanion could significantly enhance the thermal stability of cathode materials,while the doping of Al also helps to restrain the reactivity.Except for their high capacity,some alloy materials demonstrate more competitive safety than traditional carbon anode materials.Furthermore,the thermal behaviors of full cells under abusive conditions are reviewed here.Due to the sensitivity of ARC to the kinetic parameters,a reaction kinetic modeling can be built on the basis of ARC profiles,to predict the thermal behaviors of cell components and cells.Herein,a shortcircuit modeling is exampled.
基金financially supported by the National Natural Science Foundation of China (Nos. 52174279, U2202251, and 52266008)Applied Basic Research Program of Yunnan Province for Distinguished Young Scholars (No. 202201AV070004)+1 种基金Central Guiding Local Science and Technology Development Fund (No. 202207AA110001)the Yunnan Fundamental Research Projects (No. 202301AU070027, 202401AT070388)
文摘Perovskite oxides has been attracted much attention as high-performance oxygen carriers for chemical looping reforming of methane,but they are easily inactivated by the presence of trace H_(2)S.Here,we propose to modulate both the activity and resistance to sulfur poisoning by dual substitution of Mo and Ni ions with the Fe-sites of LaFeO_(3)perovskite.It is found that partial substitution of Ni for Fe substantially improves the activity of LaFeO_(3)perovskite,while Ni particles prefer to grow and react with H_(2)S during the long-term successive redox process,resulting in the deactivation of oxygen carriers.With the presence of Mo in LaNi_(0.05)Fe_(0.95)O_(3−σ)perovskite,H_(2)S preferentially reacts with Mo to generate MoS_(2),and then the CO_(2)oxidation can regenerate Mo via removing sulfur.In addition,Mo can inhibit the accumulation and growth of Ni,which helps to improve the redox stability of oxygen carriers.The LaNi_(0.05)Mo_(0.07)Fe_(0.88)O_(3−σ)oxygen carrier exhibits stable and excellent performance,with the CH_(4)conversion higher than 90%during the 50 redox cycles in the presence of 50 ppm H_(2)S at 800℃.This work highlights a synergistic effect in the perovskite oxides induced by dual substitution of different cations for the development of high-performance oxygen carriers with excellent sulfur tolerance.
基金funded by the Project of Science and Technology Research of Colleges and Universities in Hebei Province(Grant No.BJK2023109)the Natural Science Foundation of Shanghai(Grant No.24ZR1473000)+1 种基金the National Key R&D Program of China(Grant No.2023YFC3009904 and 2024YFC3016500)the Development Program of SINOPEC(Grant No.323139).
文摘As crucial nodes in railway transportation networks,railway passenger stations can suffer significant casualties and adverse societal impacts during fire accidents.A numerical simulation test was conducted on fire smoke spread and personnel evacuation in a rail-way passenger station.The results indicate that the structural span and floor height of the passenger terminal influence the smoke conditions at a height of 1.8 m such that the critical thresholds for smoke visibility,smoke temperature and carbon monoxide(CO)concentration are not surpassed.However,the smoke in the vicinity of a fire source can affect the surrounding environment.Notably,within each waiting hall,the spatial extent of the influence of smoke temperature is broader than that of smoke visibility and CO concentration.Moreover,the orthogonal test analysis reveals that the factors influencing personnel evacuation time,in descending order of impact,are the number of gates opened,personnel density,baggage weight and personnel ratio.The number of gates opened is the key factor affecting safe personnel evacuation,with at least three gates needing to be opened to meet safety requirements for evacuation.In addition,a nonlinear prediction equation is established to relate the personnel evacuation time to various influenc-ing factors,and its prediction accuracy is found to be more pronounced when the evacuation duration exceeds 100 s.Furthermore,regardless of the specific waiting hall where the fire originated or the effectiveness of the automatic sprinkler system,the smoke temperature has the most prominent influence on the time required for safe evacuation.
基金supported by the National Natural Science Foundation of China(21390394,21571076,21571079,and 21261130584)the“111”project(B07016)the Guangdong Science and Technology Department Project(2009B090300432).
文摘Various N-doped hierarchical porous carbons were prepared by using a new mixed-ligand ZIF(zeolitic imidazolate framework)(JUC-160)as the precursor in a one-step synthetic route without any additional carbon sources or purification steps.The effect of the ZIF precursor crystal size on the textural properties of the derived porous carbons was systematically studied.Microporosity was dominant in micron-sized JUC-160 crystal derived porous carbons,while more mesopore volume was present in porous carbons obtained from nanometre-sized JUC-160 crystals.The mJUC160-900 sample,which had a high nitrogen content and micropore volume,exhibited the highest CO_(2) uptake,which is 5.50 and 3.50 mmol g^(-1) at 273 and 298 K,respectively.Moreover,the analysis based on the ideal adsorbed solution theory(IAST)exhibited a high adsorption selectivity for CO_(2)/N_(2) at 298 K and 1 bar(Sads=29).
基金The authors acknowledge the financial support from Key-Area Research and Development Program of Guangdong Province(2019B010941001)Science and Technology Program of Shenzhen(JSGG20200924171000001)+3 种基金Shenzhen Science and Technology Innovation Committee(no.JCYJ20200109140812302)2019 Dong guan Postgraduate Joint Training(Practice)Workstation Project(Grant No.2019707126017)Department of Science and Technology of Guangdong Province(2017ZT07Z479)Atomic-resolution high-angle annular darkfield(HAADF)-scanning TEM(STEM)was carried out on microscope Titan Themis G260-300 maintained by Southern University of Science and Technology Core Research facilities.
文摘Radioactive iodine element mainly in CH3I is a key fission product of concern in the nuclear fuel cycle,which directly threat-ens human health if released into the environment.Effective capture of the I element is essential for human health protection.The iodine filter,consisting of an activated carbon inner core and cotton filter,is the most common radioactive iodine pro-tection product.Currently,the activated carbon inside the iodine filter suffers from the weak adsorption efficiency and high cost.Herein,a process based on a strong alkali activation method was developed to significantly improve iodine absorption and reduce the cost.A series of flexible porous carbon fibers with a high specific surface area(up to about 1,500~2,200 m^(2)/g)were prepared by carbonation of the phenolic resin fibers(PF,prepared through melt spinning and crosslink)followed by activation via KOH treatment.Meanwhile,the nitrogen-doped sp^(2)-heterogeneous carbon atoms were prepared by add-ing nitrogen sources such as urea which led to a high surface area nano-porous fibers with an average pore size of~2.4 nm.The nitrogen-doped porous carbon fibers exhibit very high adsorption for liquid iodine and iodine vapor.The liquid iodine adsorption capacity of nitrogen-doped porous carbon NDAC-4 prepared under 800°C reaches 2,120 mg/g,which is 2.1 times higher than that of the commercial iodine filter,and for iodine vapor the capacity can reach 5,330 mg/g.Meanwhile,the CH_(3)I adsorption capacity is 510 mg/g,which is 3.4 times higher than that of commercial unmodified viscose fibers and has greater stability and circularity.Importantly,the research has met the requirements of industrial production,and the fabrication of phenolic-fibers-based protection equipment can be widely used in the nuclear radiation industry.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.52466006,U2202251 and 52174279)Yunnan Fundamental Research Projects(Grant Nos.202301AU070027 and 202401AT070388)+3 种基金Major R&D Special Project of Yunnan Province“Research and Application of Catalytic Conversion of CO_(2)to High Value Chemicals”(Grant No.202302AG050005)Applied Basic Research Program of Yunnan Province for Distinguished Young Scholars(Grant No.202201AV070004)Central Guiding Local Science and Technology Development Fund(Grant No.202207AA110001)the Analysis Test Fund of Kunming University of Science and Technology(Grant No.2023T20210207).
文摘The oxygen vacancy formation energy and chemical looping dry reforming of methane over metal-substituted CeO_(2)(111)are investigated based on density functional theory calculations.The calculated results indicate that among the various metals that can substitute for the Ce atom in the CeO_(2)(111)surface,Zn substitution results in the lowest oxygen vacancy formation energy.For the activation of CH4 on CeO_(2)(111)and Zn-substituted CeO_(2)(111)surfaces,the calculated results illustrate that the dissociation process of CH_(3)(ads)is very difficult on pristine surfaces and unfavorable for CHO(ads)on substituted surfaces.Furthermore,the dissociative adsorption of CO and H_(2)on the Zn-substituted CeO_(2)(111)surface requires high energy,which is unfavorable for syngas production.This work demonstrates that excessive formation of oxygen vacancy can lead to excessively high adsorption energies,thus limiting the conversion efficiency of the reaction intermediates.This finding provides important guidance and application prospects for the design and optimization of oxygen carrier materials,especially in the field of chemical looping dry methane reforming to syngas.
