This paper focuses on the space charge and breakdown characteristics of polypropylene(PP)-based insulation interface in extrusion moulded joint(EMJ)for high-voltage direct current(HVDC)submarine cables.The double-laye...This paper focuses on the space charge and breakdown characteristics of polypropylene(PP)-based insulation interface in extrusion moulded joint(EMJ)for high-voltage direct current(HVDC)submarine cables.The double-layered flat samples and cylindrical samples are prepared to imitate the interface in the PP-insulated EMJ.The DC conductivity,space charge,and breakdown strength are tested.The results demonstrate that in the EMJ manufacturing process,the lower wielding temperature leads to microdefects at the insulation interface.As shallow traps,the microdefects exacerbate hetero charge accumulation,thereby intensifying the electric field distortion and increasing the conductivity.Meanwhile,the interfacial microdefects lead to a reduction in the insulation breakdown strength.At 90°C,the normal and tangential breakdown strengths decrease by a maximum of 20.6%and 54.5%,respectively.Notably,the space charges and microdefects lead to a rapid decline in the breakdown strength after hetero polarity pre-stressing.Especially for the tangential breakdown strength,the maximum decrease rate reaches 22.9%.Therefore,the interfacial microdefects caused by the drop in the welding temperature are the primary factors leading to a serious decrease in the electrical properties of EMJ insulation,making the EMJ insulation weaker than PP cable insulation.展开更多
We report an experimental study of electron transport properties of MnSe/(Bi,Sb)_(2)Te_(3) heterostructures,in which MnSe is an antiferromagnetic insulator,and(Bi,Sb)_(2)Te_(3) is a three-dimensional topological insul...We report an experimental study of electron transport properties of MnSe/(Bi,Sb)_(2)Te_(3) heterostructures,in which MnSe is an antiferromagnetic insulator,and(Bi,Sb)_(2)Te_(3) is a three-dimensional topological insulator(TI).Strong magnetic proximity effect is manifested in the measurements of the Hall effect and longitudinal resistances.Our analysis shows that the gate voltage can substantially modify the anomalous Hall conductance,which exceeds 0.1 e^(2)/h at temperature T=1.6 K and magnetic field _(μ0)H=5 T,even though only the top TI surface is in proximity to MnSe.This work suggests that heterostructures based on antiferromagnetic insulators provide a promising platform for investigating a wide range of topological spintronic phenomena.展开更多
The thermodynamic adhesion between a metal and a ceramic crystal was believed to be the result of theelectron transfer from the metal into the cerainic crystal. From an electronic point of view, such an electrontransf...The thermodynamic adhesion between a metal and a ceramic crystal was believed to be the result of theelectron transfer from the metal into the cerainic crystal. From an electronic point of view, such an electrontransfer at the metal/ceramic interface may be represented by the tunnelling of the metal conduction electron into the ceramic bandgap. Theoretical analysis of the quantum tunnelling process at an intimate rnetal-semicon-ductor contact were performed . and the relationship between adhesion energies and Schottky barrier heights ofvarious metal/semiconductor or insulator interfaces was dcduced .展开更多
Direct growth of graphene on insulators is expected to yield significant improvements in performance of graphene-based electronic and spintronic devices. In this study, we successfully reveal the atomic arrangement an...Direct growth of graphene on insulators is expected to yield significant improvements in performance of graphene-based electronic and spintronic devices. In this study, we successfully reveal the atomic arrangement and electronic properties of a coherent heterostructure of single-layer graphene and α-Al2O3（0001）. The analysis of the atomic arrangement of single-layer graphene on α-Al2O3（0001） revealed an apparentcontradiction. The in-plane analysis shows that single-layer graphene grows not in a single-crystalline epitaxial manner, but rather in polycrystalline form, with two strongly pronounced preferred orientations. This suggests relatively weak interfacial interactions are operative. However, we demonstrate that unusually strong physical interactions between graphene and α-Al2O3（0001） exist, as evidenced by the small separation between the graphene and the α-Al2O3（0001） surface. The interfacial interaction is shown to be dominated by the electrostatic forces involved in the graphene n-system and the unsaturated electrons of the topmost O layer of α-Al2O3（0001）, rather than the van der Waals interactions. Such features causes graphene hole doping and enable the graphene to slide on the α-Al2O3（0001） surface with only a small energy barrier despite the strong interfacial interactions.展开更多
基金National Natural Science Foundation of China under the Grant 52477151 and 52077148Key Science and Technology Programme of Yunnan Province,China under Grant 202202AC080002.
文摘This paper focuses on the space charge and breakdown characteristics of polypropylene(PP)-based insulation interface in extrusion moulded joint(EMJ)for high-voltage direct current(HVDC)submarine cables.The double-layered flat samples and cylindrical samples are prepared to imitate the interface in the PP-insulated EMJ.The DC conductivity,space charge,and breakdown strength are tested.The results demonstrate that in the EMJ manufacturing process,the lower wielding temperature leads to microdefects at the insulation interface.As shallow traps,the microdefects exacerbate hetero charge accumulation,thereby intensifying the electric field distortion and increasing the conductivity.Meanwhile,the interfacial microdefects lead to a reduction in the insulation breakdown strength.At 90°C,the normal and tangential breakdown strengths decrease by a maximum of 20.6%and 54.5%,respectively.Notably,the space charges and microdefects lead to a rapid decline in the breakdown strength after hetero polarity pre-stressing.Especially for the tangential breakdown strength,the maximum decrease rate reaches 22.9%.Therefore,the interfacial microdefects caused by the drop in the welding temperature are the primary factors leading to a serious decrease in the electrical properties of EMJ insulation,making the EMJ insulation weaker than PP cable insulation.
基金Supported by the National Key Research and Development Program of China (Grant No.2016YFA0300600)the National Natural Science Foundation of China (Grant No.11961141011)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)。
文摘We report an experimental study of electron transport properties of MnSe/(Bi,Sb)_(2)Te_(3) heterostructures,in which MnSe is an antiferromagnetic insulator,and(Bi,Sb)_(2)Te_(3) is a three-dimensional topological insulator(TI).Strong magnetic proximity effect is manifested in the measurements of the Hall effect and longitudinal resistances.Our analysis shows that the gate voltage can substantially modify the anomalous Hall conductance,which exceeds 0.1 e^(2)/h at temperature T=1.6 K and magnetic field _(μ0)H=5 T,even though only the top TI surface is in proximity to MnSe.This work suggests that heterostructures based on antiferromagnetic insulators provide a promising platform for investigating a wide range of topological spintronic phenomena.
文摘The thermodynamic adhesion between a metal and a ceramic crystal was believed to be the result of theelectron transfer from the metal into the cerainic crystal. From an electronic point of view, such an electrontransfer at the metal/ceramic interface may be represented by the tunnelling of the metal conduction electron into the ceramic bandgap. Theoretical analysis of the quantum tunnelling process at an intimate rnetal-semicon-ductor contact were performed . and the relationship between adhesion energies and Schottky barrier heights ofvarious metal/semiconductor or insulator interfaces was dcduced .
基金We are grateful to the ＇Chebishev＇ and ＇Lomonosov＇ supercomputers of Moscow State University for providing the chance of using a cluster computer for quantum-chemical calculations. S.E. thanks Prof. H. Kondo （Keio University） and Prof. T. Shimada （Hirosaki University） for NIXSW measurements. This work was partly supported by Grants-in-Aid for Young Scientists B （Grant No. 22760033） from the Japan Society for the Promotion of Science. The present work has been performed under the approval of the Photon Factory Program Advisory Committee （PF PAC Nos. 2010G660 and 2012G741）. P.V.A., P.B.S. and L.Y.A. acknowledge the support from the Russian Science Foundation （project No. 14-13-00139）.
文摘Direct growth of graphene on insulators is expected to yield significant improvements in performance of graphene-based electronic and spintronic devices. In this study, we successfully reveal the atomic arrangement and electronic properties of a coherent heterostructure of single-layer graphene and α-Al2O3（0001）. The analysis of the atomic arrangement of single-layer graphene on α-Al2O3（0001） revealed an apparentcontradiction. The in-plane analysis shows that single-layer graphene grows not in a single-crystalline epitaxial manner, but rather in polycrystalline form, with two strongly pronounced preferred orientations. This suggests relatively weak interfacial interactions are operative. However, we demonstrate that unusually strong physical interactions between graphene and α-Al2O3（0001） exist, as evidenced by the small separation between the graphene and the α-Al2O3（0001） surface. The interfacial interaction is shown to be dominated by the electrostatic forces involved in the graphene n-system and the unsaturated electrons of the topmost O layer of α-Al2O3（0001）, rather than the van der Waals interactions. Such features causes graphene hole doping and enable the graphene to slide on the α-Al2O3（0001） surface with only a small energy barrier despite the strong interfacial interactions.
