建立了用液相色谱-三重四极杆串联质谱(liquid chromatography-triple quadrupole tandem mass spectrometry,LC-MS/MS)检测聚对苯二甲酸乙二醇酯/低密度聚乙烯(polyethylene terephthalate/low-density polyethylene,PET/LDPE)复合膜中...建立了用液相色谱-三重四极杆串联质谱(liquid chromatography-triple quadrupole tandem mass spectrometry,LC-MS/MS)检测聚对苯二甲酸乙二醇酯/低密度聚乙烯(polyethylene terephthalate/low-density polyethylene,PET/LDPE)复合膜中3种抗氧剂(抗氧剂1076、抗氧剂168、2,4-二叔丁基苯酚)的方法,研究3种抗氧化剂向异辛烷和95%(体积分数)乙醇2种食品模拟物的迁移,利用Crank模型计算迁移扩散系数。结果表明,用LC-MS/MS检测3种抗氧剂的检出限均为0.2μg/L,定量限均≤0.8μg/L,在5~240μg/L线性良好,相关系数均>0.998;在20、40、60、70℃条件下,3种抗氧剂从PET/LDPE复合膜向2种食品模拟物迁移的迁移量均会随迁移温度的升高和迁移时间的延长而增加直至达到迁移平衡,且温度越高,越快达到迁移平衡状态,用Crank模型能较好拟合迁移实验数据,3种抗氧剂的迁移扩散系数与温度的关系符合Arrhenius公式;在70℃、2 h,40℃、72 h迁移条件下,3种抗氧剂分别从LDPE膜和PET/LDPE复合膜向食品模拟物迁移的迁移率差异性不显著(P>0.05),表明LDPE膜与PET膜复合后,在特定迁移条件下,PET膜不会对LDPE膜中3种抗氧剂的迁移产生显著影响。展开更多
The particle migration and coalescence(PMC) kinetics of a supported metal are the main deactivation mechanisms restricting the successful industrialization of nanoparticles, but the theoretical insights regarding thes...The particle migration and coalescence(PMC) kinetics of a supported metal are the main deactivation mechanisms restricting the successful industrialization of nanoparticles, but the theoretical insights regarding these kinetics are lacking. One key issue is the lack of a physical model to predict the effects of metal-support interaction(MSI) on PMC kinetics. In this paper, we report a theoretical study of PMC kinetics and their dependence on MSI. A new particle diffusion model is proposed based on the surface premelting hypothesis that considers the contact angle of a hemispherical particle on the support. Enhanced MSI suppresses PMC by increasing the radius of curvature and the interfacial adhesion energy, even though the accompanying reduction in the geometry factor partially promotes PMC kinetics. The increased surface energy increases the chemical potential of the atoms in the particle, which is conducive to PMC; an increased surface energy also results in enhanced MSI, which suppresses PMC. The competition between these two contradictory effects leads to a critical contact angle where the surface energy has no influence on the diffusion and resulting PMC kinetics. The proposed diffusion theory mode lincluding the effects of the support and the corresponding kinetic simulations, shed light onto the support-dependence of PMC kinetics and provide a foundation for further optimization and design of supported particles with better stability.展开更多
Under laboratory conditions (i.e. a sealed system in which the temperature may vary according to air tem- perature), the migration of radon in upward, downward and horizontal directions has been investigated. After a ...Under laboratory conditions (i.e. a sealed system in which the temperature may vary according to air tem- perature), the migration of radon in upward, downward and horizontal directions has been investigated. After a period of accumulation, the spatial distribution profile of radon was drawn on the basis of the experimental data. The profile showed whorl-shape with bigger ends. The longer the accumulation time, the bigger the whorl end, and the higher the radon concentration is. By fitting the experimental data by least-square statistical method, we find that the distribu- tions of radon follow negative exponential functions in the upward, downward and horizontal directions. However, exponents for the three directions are not exactly identical. The upward migration is more effective than the down- ward one and both upward and downward migrations are more effective than the horizontal one.展开更多
The effect of curing age on chloride diffusion coefficient of recycled aggregate concrete subjected to different compressive stresses was investigated.A compression loading setup was both designed and fabricated.The c...The effect of curing age on chloride diffusion coefficient of recycled aggregate concrete subjected to different compressive stresses was investigated.A compression loading setup was both designed and fabricated.The chloride diffusion coefficients of recycled aggregate concrete under compressive stresses were measured by the rapid chloride ion migration(RCM)method.The experimental results show that the chloride diffusion coefficients of recycled aggregate concrete(RAC)under different compressive stress ratios generally decrease with the increase of curing age.For RAC subjected to the same compressive stress ratios,the chloride diffusion coefficients approximately have power functions with curing ages and the relationship models are proposed.Moreover,the influence of curing age on chloride diffusion coefficient firstly decreases and then increases as the compressive stress ratio increases.展开更多
文摘建立了用液相色谱-三重四极杆串联质谱(liquid chromatography-triple quadrupole tandem mass spectrometry,LC-MS/MS)检测聚对苯二甲酸乙二醇酯/低密度聚乙烯(polyethylene terephthalate/low-density polyethylene,PET/LDPE)复合膜中3种抗氧剂(抗氧剂1076、抗氧剂168、2,4-二叔丁基苯酚)的方法,研究3种抗氧化剂向异辛烷和95%(体积分数)乙醇2种食品模拟物的迁移,利用Crank模型计算迁移扩散系数。结果表明,用LC-MS/MS检测3种抗氧剂的检出限均为0.2μg/L,定量限均≤0.8μg/L,在5~240μg/L线性良好,相关系数均>0.998;在20、40、60、70℃条件下,3种抗氧剂从PET/LDPE复合膜向2种食品模拟物迁移的迁移量均会随迁移温度的升高和迁移时间的延长而增加直至达到迁移平衡,且温度越高,越快达到迁移平衡状态,用Crank模型能较好拟合迁移实验数据,3种抗氧剂的迁移扩散系数与温度的关系符合Arrhenius公式;在70℃、2 h,40℃、72 h迁移条件下,3种抗氧剂分别从LDPE膜和PET/LDPE复合膜向食品模拟物迁移的迁移率差异性不显著(P>0.05),表明LDPE膜与PET膜复合后,在特定迁移条件下,PET膜不会对LDPE膜中3种抗氧剂的迁移产生显著影响。
基金supported by the National Key R&D Program of China(Grant Nos.2018YFA0208603,2017YFB0602205)the Chinese Academy of Sciences(Grant No.QYZDJ-SSW-SLH054)the National Natural Science Foundation of China(Grant No.91645202)
文摘The particle migration and coalescence(PMC) kinetics of a supported metal are the main deactivation mechanisms restricting the successful industrialization of nanoparticles, but the theoretical insights regarding these kinetics are lacking. One key issue is the lack of a physical model to predict the effects of metal-support interaction(MSI) on PMC kinetics. In this paper, we report a theoretical study of PMC kinetics and their dependence on MSI. A new particle diffusion model is proposed based on the surface premelting hypothesis that considers the contact angle of a hemispherical particle on the support. Enhanced MSI suppresses PMC by increasing the radius of curvature and the interfacial adhesion energy, even though the accompanying reduction in the geometry factor partially promotes PMC kinetics. The increased surface energy increases the chemical potential of the atoms in the particle, which is conducive to PMC; an increased surface energy also results in enhanced MSI, which suppresses PMC. The competition between these two contradictory effects leads to a critical contact angle where the surface energy has no influence on the diffusion and resulting PMC kinetics. The proposed diffusion theory mode lincluding the effects of the support and the corresponding kinetic simulations, shed light onto the support-dependence of PMC kinetics and provide a foundation for further optimization and design of supported particles with better stability.
基金Supported by the Bureau of Science and Technology of Fujian Province, China (No. 2003J010) and National Natural Science Foundation of China (No.10575022)
文摘Under laboratory conditions (i.e. a sealed system in which the temperature may vary according to air tem- perature), the migration of radon in upward, downward and horizontal directions has been investigated. After a period of accumulation, the spatial distribution profile of radon was drawn on the basis of the experimental data. The profile showed whorl-shape with bigger ends. The longer the accumulation time, the bigger the whorl end, and the higher the radon concentration is. By fitting the experimental data by least-square statistical method, we find that the distribu- tions of radon follow negative exponential functions in the upward, downward and horizontal directions. However, exponents for the three directions are not exactly identical. The upward migration is more effective than the down- ward one and both upward and downward migrations are more effective than the horizontal one.
基金supported by the Fundamental Research Funds for the Central UniversitiesFoundation of Graduate Innovation Center in Nanjing University of Aeronautics and Astronautics (No.kfjj20150105)the National Natural Science Foundation of China (No. 51279074)
文摘The effect of curing age on chloride diffusion coefficient of recycled aggregate concrete subjected to different compressive stresses was investigated.A compression loading setup was both designed and fabricated.The chloride diffusion coefficients of recycled aggregate concrete under compressive stresses were measured by the rapid chloride ion migration(RCM)method.The experimental results show that the chloride diffusion coefficients of recycled aggregate concrete(RAC)under different compressive stress ratios generally decrease with the increase of curing age.For RAC subjected to the same compressive stress ratios,the chloride diffusion coefficients approximately have power functions with curing ages and the relationship models are proposed.Moreover,the influence of curing age on chloride diffusion coefficient firstly decreases and then increases as the compressive stress ratio increases.
