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
目前国内大多数放射治疗剂量只能溯源到^(60)Co γ射线空气比释动能,与溯源至空气比释动能相比,将放射治疗剂量直接溯源至水吸收剂量的不确定度要小很多。为了解决^(60)Co γ射线水吸收剂量量值溯源与传递问题,进一步提升^(60)Co γ射...目前国内大多数放射治疗剂量只能溯源到^(60)Co γ射线空气比释动能,与溯源至空气比释动能相比,将放射治疗剂量直接溯源至水吸收剂量的不确定度要小很多。为了解决^(60)Co γ射线水吸收剂量量值溯源与传递问题,进一步提升^(60)Co γ射线水吸收剂量的量值溯源与传递能力,中国测试技术研究院(National Institute of Measurement and Testing Technology,NIMTT)采用水量热法建立了^(60)Co γ射线水吸收剂量绝对测量装置,实现了水吸收剂量的绝对测量,复现了^(60)Co γ射线水吸收剂量,其量值复现的相对标准不确定度为0.45%。为了进一步验证^(60)Co γ射线水吸收剂量复现结果的准确性与一致性,将NIMTT实验室与加拿大国家研究委员会(National Research Council,NRC)实验室的复现结果进行了实验室之间的比对,结果在相对标准不确定度0.71%以内呈现一致性,归一化误差En值为-0.45。表明NIMTT具有^(60)Co γ射线水吸收剂量量值溯源与传递的能力,本研究结果也为^(60)Co γ射线吸收剂量的绝对测量提供了参考。展开更多
The effects of the water-cement ratio and the molding temperature on the hydration heat of cement were investigated with semi-adiabatic calorimetry.The specimens were prepared with water-cement ratios of 0.31,0.38,and...The effects of the water-cement ratio and the molding temperature on the hydration heat of cement were investigated with semi-adiabatic calorimetry.The specimens were prepared with water-cement ratios of 0.31,0.38,and 0.45,and the molding temperature was specified at 10 and 20℃.The experimental results show that,as the water-binder ratio increases,the value of the second temperature peak on the temperature curve of the cement paste decreases,and the age at which the peak appears is delayed.The higher the water-cement ratio,the higher the hydration heat release in the early period of cement hydration,but this trend reverses in the late period.There are intersection points of the total hydration heat curve of the cement pastes under the influence of the water-cement ratio,and this law can be observed at both molding temperatures.With the increase in the molding temperature,the age of the second temperature peak on the temperature curve of the cement paste will advance,but the temperature peak will decrease.The higher the molding temperature,the earlier the acceleration period of the cement hydration began,and the larger the hydration heat of the cement in the early stage,but the smaller the total heat in the late period.A subsection function calculation model of the hydration heat,which was based on the existing models,was proposed in order to predict the heat of the hydration of the concrete.展开更多
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.
文摘目前国内大多数放射治疗剂量只能溯源到^(60)Co γ射线空气比释动能,与溯源至空气比释动能相比,将放射治疗剂量直接溯源至水吸收剂量的不确定度要小很多。为了解决^(60)Co γ射线水吸收剂量量值溯源与传递问题,进一步提升^(60)Co γ射线水吸收剂量的量值溯源与传递能力,中国测试技术研究院(National Institute of Measurement and Testing Technology,NIMTT)采用水量热法建立了^(60)Co γ射线水吸收剂量绝对测量装置,实现了水吸收剂量的绝对测量,复现了^(60)Co γ射线水吸收剂量,其量值复现的相对标准不确定度为0.45%。为了进一步验证^(60)Co γ射线水吸收剂量复现结果的准确性与一致性,将NIMTT实验室与加拿大国家研究委员会(National Research Council,NRC)实验室的复现结果进行了实验室之间的比对,结果在相对标准不确定度0.71%以内呈现一致性,归一化误差En值为-0.45。表明NIMTT具有^(60)Co γ射线水吸收剂量量值溯源与传递的能力,本研究结果也为^(60)Co γ射线吸收剂量的绝对测量提供了参考。
基金the National Natural Science Foundation of China(Nos.52368032 and 51808272)the China Postdoctoral Science Foundation(No.2023M741455)+1 种基金the Tianyou Youth Talent Lift Program of Lanzhou Jiaotong UniversityGansu Province Youth Talent Support Project(No.GXH20210611-10)。
文摘The effects of the water-cement ratio and the molding temperature on the hydration heat of cement were investigated with semi-adiabatic calorimetry.The specimens were prepared with water-cement ratios of 0.31,0.38,and 0.45,and the molding temperature was specified at 10 and 20℃.The experimental results show that,as the water-binder ratio increases,the value of the second temperature peak on the temperature curve of the cement paste decreases,and the age at which the peak appears is delayed.The higher the water-cement ratio,the higher the hydration heat release in the early period of cement hydration,but this trend reverses in the late period.There are intersection points of the total hydration heat curve of the cement pastes under the influence of the water-cement ratio,and this law can be observed at both molding temperatures.With the increase in the molding temperature,the age of the second temperature peak on the temperature curve of the cement paste will advance,but the temperature peak will decrease.The higher the molding temperature,the earlier the acceleration period of the cement hydration began,and the larger the hydration heat of the cement in the early stage,but the smaller the total heat in the late period.A subsection function calculation model of the hydration heat,which was based on the existing models,was proposed in order to predict the heat of the hydration of the concrete.
