In this paper a fully parametrized finite element simulation model of the stator bar end is created using the COMSOL Multiphysics.The model allows conducting the comparison of different corona protection structures’d...In this paper a fully parametrized finite element simulation model of the stator bar end is created using the COMSOL Multiphysics.The model allows conducting the comparison of different corona protection structures’design,various materials properties,and finally optimizing the corona protection system.Several samples of SiC based nonlinear conductivity materials for corona protection were fabricated in laboratory and then investigated.The conductivity dependencies on electric field(0.05 to 1 kV/mm)and temperature(20 to 155℃)were measured.By comparing the heat-resistant grades of the corona protection material and the insulating material,the maximum working temperature of the corona protection material corresponds to the heat-resistant grade F of the insulating material.As the temperature increases,the nonlinear characteristics of the corona protection material in the experiment decrease dramatically,reducing the heat-resistant grade of the corona protection material.The decrease in the nonlinear characteristics of the corona protection material at the maximum operating temperature causes the maximum electric field strength at the end of the HV rotating machines end corona protection(ECP)exceeding the corona discharge electric field strength,resulting in corona phenomenon.展开更多
In recent years,the development and research of electrochemical energy storage systems that can efficiently transform chemical energy into electrical energy with a long service life have become a key area of study.Sod...In recent years,the development and research of electrochemical energy storage systems that can efficiently transform chemical energy into electrical energy with a long service life have become a key area of study.Sodium-ion batteries,leveraging their chemical similarity to lithium-ion batteries,along with their abundant resources and low cost,are seen as a viable alternative to lithium-ion batteries.Additionally,all-solid-state sodium-ion batteries have drawn significant attention due to safety considerations.Among the solid electrolytes for all-solid-state sodium-ion batteries,the NASICON solid-state electrolyte emerges as one of the most promising choices for sodium battery solid electrolytes.However,to date,there has not been a comprehensive review summarizing the existing problems of NASICON electrolyte materials and the corresponding specific modification methods.This review simply summarizes the present issues of NASICON for all-solid-state sodium-ion batteries,such as,the low ionic conductivity,the poor interface stability and compatibility,and the dendrite formation.Then,the corresponding solutions to address these issues are discussed,including the ion doping,the interface modification,the sintering parameters optimization,and the composite electrolytes regulation.Finally,the perspectives of NASICON solid-state electrolyte are discussed.展开更多
The crystalline structure and surface morphology of TiO2 semiconductor coating play an important role in the conversion efficiency of dye-sensitized solar cells. In order to obtain TiO2 coating with controllable morph...The crystalline structure and surface morphology of TiO2 semiconductor coating play an important role in the conversion efficiency of dye-sensitized solar cells. In order to obtain TiO2 coating with controllable morphology and high porosity, nanoporous TiO2 films were fabricated on conducting glass （FTO） substrates, Ti thin films （1.5-2 gin） were deposited on conducting glass （FTO） substrates via the DC sputtering method, and then electrochemically anodized in NH4F/ethylene glycol solution. The crystalline structure and surface morphology of the samples were characterized by X-ray diffraction （XRD） and field emission scanning electron microscopy （FESEM）, respectively. The influences of anodizing potential, electrolyte composition, and pH value on the surface morphology of nanoporous TiO2 films were extensively studied. The growth mechanism of nanoporous TiO2 films was discussed by current density variations with anodizing time. The results demonstrate that nanoporous TiO2 films with high porosity and three-dimensional （3D） networks are observed at 30 V, when the NH4F concentration in ethylene glycol solution is 0.3% （mass fraction） and the electrolyte pH value is 5.0.展开更多
文摘In this paper a fully parametrized finite element simulation model of the stator bar end is created using the COMSOL Multiphysics.The model allows conducting the comparison of different corona protection structures’design,various materials properties,and finally optimizing the corona protection system.Several samples of SiC based nonlinear conductivity materials for corona protection were fabricated in laboratory and then investigated.The conductivity dependencies on electric field(0.05 to 1 kV/mm)and temperature(20 to 155℃)were measured.By comparing the heat-resistant grades of the corona protection material and the insulating material,the maximum working temperature of the corona protection material corresponds to the heat-resistant grade F of the insulating material.As the temperature increases,the nonlinear characteristics of the corona protection material in the experiment decrease dramatically,reducing the heat-resistant grade of the corona protection material.The decrease in the nonlinear characteristics of the corona protection material at the maximum operating temperature causes the maximum electric field strength at the end of the HV rotating machines end corona protection(ECP)exceeding the corona discharge electric field strength,resulting in corona phenomenon.
基金Projects(52204378,22309209)supported by the National Natural Science Foundation of ChinaProject(2023JJ40709)supported by the Natural Science Foundation of Hunan Province,China。
文摘In recent years,the development and research of electrochemical energy storage systems that can efficiently transform chemical energy into electrical energy with a long service life have become a key area of study.Sodium-ion batteries,leveraging their chemical similarity to lithium-ion batteries,along with their abundant resources and low cost,are seen as a viable alternative to lithium-ion batteries.Additionally,all-solid-state sodium-ion batteries have drawn significant attention due to safety considerations.Among the solid electrolytes for all-solid-state sodium-ion batteries,the NASICON solid-state electrolyte emerges as one of the most promising choices for sodium battery solid electrolytes.However,to date,there has not been a comprehensive review summarizing the existing problems of NASICON electrolyte materials and the corresponding specific modification methods.This review simply summarizes the present issues of NASICON for all-solid-state sodium-ion batteries,such as,the low ionic conductivity,the poor interface stability and compatibility,and the dendrite formation.Then,the corresponding solutions to address these issues are discussed,including the ion doping,the interface modification,the sintering parameters optimization,and the composite electrolytes regulation.Finally,the perspectives of NASICON solid-state electrolyte are discussed.
基金Projects(21171027,50872014) supported by the National Natural Science Foundation of ChinaProject(K1001020-11)supported by the Science and Technology Key Project of Changsha City,China
文摘The crystalline structure and surface morphology of TiO2 semiconductor coating play an important role in the conversion efficiency of dye-sensitized solar cells. In order to obtain TiO2 coating with controllable morphology and high porosity, nanoporous TiO2 films were fabricated on conducting glass （FTO） substrates, Ti thin films （1.5-2 gin） were deposited on conducting glass （FTO） substrates via the DC sputtering method, and then electrochemically anodized in NH4F/ethylene glycol solution. The crystalline structure and surface morphology of the samples were characterized by X-ray diffraction （XRD） and field emission scanning electron microscopy （FESEM）, respectively. The influences of anodizing potential, electrolyte composition, and pH value on the surface morphology of nanoporous TiO2 films were extensively studied. The growth mechanism of nanoporous TiO2 films was discussed by current density variations with anodizing time. The results demonstrate that nanoporous TiO2 films with high porosity and three-dimensional （3D） networks are observed at 30 V, when the NH4F concentration in ethylene glycol solution is 0.3% （mass fraction） and the electrolyte pH value is 5.0.
