In this paper, the effects of annealing time on the dielectric properties of the Spark Plasma Sintered (SPS) BaMn3Ti4O14.25 pellets were detail studied by the crystal structure analysis, micro structural observation a...In this paper, the effects of annealing time on the dielectric properties of the Spark Plasma Sintered (SPS) BaMn3Ti4O14.25 pellets were detail studied by the crystal structure analysis, micro structural observation and electrical properties research. The results showed that long annealing time was beneficial to the recovery of crystal structure damage caused by SPS, the formation of a reoxidation layer at the surface of grains and decreasing of the electrically insulating phase. All of these resulted in an increase in dielectric constant and loss, and a reduction in breakdown voltage.展开更多
A novel partial silicon-on-insulator （PSOI） high voltage device with a low-k （relative permittivity） dielectric buried layer （LK PSOI） and its breakdown mechanism are presented and investigated by MEDICI. At a l...A novel partial silicon-on-insulator （PSOI） high voltage device with a low-k （relative permittivity） dielectric buried layer （LK PSOI） and its breakdown mechanism are presented and investigated by MEDICI. At a low k value the electric field strength in the dielectric buried layer （EI） is enhanced and a Si window makes the substrate share the vertical drop, resulting in a high vertical breakdown voltage; in the lateral direction, a high electric field peak is introduced at the Si window, which modulates the electric field distribution in the SOI layer; consequently, a high breakdown voltage （BV） is obtained. The values of EI and BV of LK PSOI with ki = 2 on a 2μm thick SOI layer over 1μm thick buried layer are enhanced by 74% and 19%, respectively, compared with those of the conventional PSOI. Furthermore, the Si window also alleviates the self-heating effect.展开更多
It is well known that work done on a material by conservative forces (electrical, mechanical, chemical) will increase the Gibbs Potential of the material. The increase in Gibbs Potential can be stored in the material ...It is well known that work done on a material by conservative forces (electrical, mechanical, chemical) will increase the Gibbs Potential of the material. The increase in Gibbs Potential can be stored in the material and is free/available to do work at some later time. However, it will be shown in this paper that while in this state of higher Gibbs potential, the material is metastable and the material will degrade spontaneously/naturally with time in an effort to reach a lower Gibbs Potential. A generalized Gibbs Potential Model is developed herein to better understand its impact on a materials degradation rate. Special attention will be given to dielectrics degradation.展开更多
The present work aims to develop a new vegetable insulating fluid for power transformers based on Jatropha curcas oil. Besides its technical benefits, Jatropha curcas oil has a socio-economic role by promoting income ...The present work aims to develop a new vegetable insulating fluid for power transformers based on Jatropha curcas oil. Besides its technical benefits, Jatropha curcas oil has a socio-economic role by promoting income to rural families, contributing to the countryside development and avoiding rural exodus. Thus, the entire transformer oil production (extraction, processing, characterization and accelerated aging) was covered and a new process was developed. For oil extraction, the most suitable process was the solvent extraction (5 mL of hexane per gram of crushed non-peeled seeds during 30 minutes) with an oil yield of 32%. In raw oil processing stage, the degumming, with 0.4 g of phosphoric acid per 100 g of oil, at 70°C, was used to remove phosphatides. Then, free fatty acids were 96% neutralized with a sodium hydroxide solution (0.5% w/w) at room temperature. For the oil clarification, the combination of 5% w/woil of activated carbon and 1% w/woil of MgO resulted in a bright, odorless and clear oil with an acid number of 0.04 mgKOH·g﹣1. The oil drying in a vacuum rotary evaporator, at 70°C, for 2 hours reduced the water content to 177 ppm. The processed oil was characterized following ASTM D6871 methods. This oil presented higher dielectric breakdown voltage (55 kV) than commercial transformer fluids (BIOTEMP?, EnvirotempFR3?, and Bivolt?), which increases transformer safety, capacity and lifetime. In addition, the processed oil has a lower viscosity than BIOTEMP? fluid, which can enhance the heat dissipation efficiency in the transformer. Moreover, the processed oil flash and fire points of 310°C and >340°C, respectively, confirm the great security of vegetable insulating fluids. The analyzed properties of the processed oil fulfill all the ASTM D6871, ABNT NBR 15422 and IEC 62770 specifications. Therefore, Jatropha curcas oil is a potential substitute formineral insulating fluids.展开更多
The shortcomings of oil-immersed transformer solid insulation like low high-temperature resistance of the insulation paper and the uneven distribution of electric field caused by the large difference of dielectric con...The shortcomings of oil-immersed transformer solid insulation like low high-temperature resistance of the insulation paper and the uneven distribution of electric field caused by the large difference of dielectric constants between insulation paper and transformer oil,restricted the development of transformer with smaller size and larger capacity.In view of this situation and the transformer’s demand for the dielectric physicochemical and mechanical property of insulation material,polycarbonate,polyester film and polyphenylene sulfide with high high-temperature resistance were chosen for the comparison analysis in this paper We did the 300-day thermal aging experiment on four samples in transformer oil under different aging temperatures of90°C,110°C and 130°C,then analyzed the changes of their dielectric properties.The experiment results are as follows;the permittivity and dielectric dissipation factor of the three polymer materials are apparently smaller than those of the paper both before and after 300-day aging;the volume resistivity and partial discharge inception voltage of the three materials are higher than those of the paper both before and after aging;and the breakdown field strength of polycarbonate is higher than that of the paper both before and after aging,while that of polyester film and polyphenylene sulfide are slightly lower than that of the paper.展开更多
The applications of two-dimensional semiconductors strictly require the reliable integration of ultrathin high-κdielectric materials on the semiconductor surface to enable fine gate control and low power consumption....The applications of two-dimensional semiconductors strictly require the reliable integration of ultrathin high-κdielectric materials on the semiconductor surface to enable fine gate control and low power consumption.As layered oxide materials,MoO_(3) can be potentially used as a high-κtwo-dimensional material with a larger bandgap and high electron affinity.In this work,relying on the oxidization of molybdenum chlorides,we have synthesizedα-MoO_(3) single crystals,which can be easily exfoliated into flakes with thicknesses of a few nanometers and sizes of hundreds of micrometers and fine thermal stability.Based on measurement results of conventional metal/insulator/metal devices and graphene based dual-gate devices,the as-received MoO_(3) nanosheets exhibit improved dielectric performance,including high dielectric constants and competitive breakdown field strength.Our work demonstrates that MoO_(3) with improved crystalline quality is a promising candidate for dielectric materials with a large gate capacitance in future electronics based on two-dimensional materials.展开更多
This study presents a numerical method based on parallel RC equivalent circuit model fitting methodology for analysis and modeling of dielectric materials.The proposed method employs gradient-descent optimization meth...This study presents a numerical method based on parallel RC equivalent circuit model fitting methodology for analysis and modeling of dielectric materials.The proposed method employs gradient-descent optimization method(GDOM)to estimate parallel RC equivalent circuit model from current waveforms by minimizing sum of squared difference(SSD)error.Estimation of parallel RC equivalent circuit parameters from measured current waveforms provides a useful tool for identification,simulation and analysis of dielectric materials.Moreover,applications of the proposed method for time and frequency analyses of dielectric materials are demonstrated numerically.Numerical simulations were presented to discuss efficiency of the proposed method for modeling,analysis and monitoring of insulator materials.展开更多
文摘In this paper, the effects of annealing time on the dielectric properties of the Spark Plasma Sintered (SPS) BaMn3Ti4O14.25 pellets were detail studied by the crystal structure analysis, micro structural observation and electrical properties research. The results showed that long annealing time was beneficial to the recovery of crystal structure damage caused by SPS, the formation of a reoxidation layer at the surface of grains and decreasing of the electrically insulating phase. All of these resulted in an increase in dielectric constant and loss, and a reduction in breakdown voltage.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60806025 and 60976060)the National Laboratory of Analog Integrated Circuit (Grant No. 9140C0903070904)the Youth Teacher Foundation of the University of Electronic Science and Technology of China (Grant No. jx0721)
文摘A novel partial silicon-on-insulator （PSOI） high voltage device with a low-k （relative permittivity） dielectric buried layer （LK PSOI） and its breakdown mechanism are presented and investigated by MEDICI. At a low k value the electric field strength in the dielectric buried layer （EI） is enhanced and a Si window makes the substrate share the vertical drop, resulting in a high vertical breakdown voltage; in the lateral direction, a high electric field peak is introduced at the Si window, which modulates the electric field distribution in the SOI layer; consequently, a high breakdown voltage （BV） is obtained. The values of EI and BV of LK PSOI with ki = 2 on a 2μm thick SOI layer over 1μm thick buried layer are enhanced by 74% and 19%, respectively, compared with those of the conventional PSOI. Furthermore, the Si window also alleviates the self-heating effect.
文摘It is well known that work done on a material by conservative forces (electrical, mechanical, chemical) will increase the Gibbs Potential of the material. The increase in Gibbs Potential can be stored in the material and is free/available to do work at some later time. However, it will be shown in this paper that while in this state of higher Gibbs potential, the material is metastable and the material will degrade spontaneously/naturally with time in an effort to reach a lower Gibbs Potential. A generalized Gibbs Potential Model is developed herein to better understand its impact on a materials degradation rate. Special attention will be given to dielectrics degradation.
文摘The present work aims to develop a new vegetable insulating fluid for power transformers based on Jatropha curcas oil. Besides its technical benefits, Jatropha curcas oil has a socio-economic role by promoting income to rural families, contributing to the countryside development and avoiding rural exodus. Thus, the entire transformer oil production (extraction, processing, characterization and accelerated aging) was covered and a new process was developed. For oil extraction, the most suitable process was the solvent extraction (5 mL of hexane per gram of crushed non-peeled seeds during 30 minutes) with an oil yield of 32%. In raw oil processing stage, the degumming, with 0.4 g of phosphoric acid per 100 g of oil, at 70°C, was used to remove phosphatides. Then, free fatty acids were 96% neutralized with a sodium hydroxide solution (0.5% w/w) at room temperature. For the oil clarification, the combination of 5% w/woil of activated carbon and 1% w/woil of MgO resulted in a bright, odorless and clear oil with an acid number of 0.04 mgKOH·g﹣1. The oil drying in a vacuum rotary evaporator, at 70°C, for 2 hours reduced the water content to 177 ppm. The processed oil was characterized following ASTM D6871 methods. This oil presented higher dielectric breakdown voltage (55 kV) than commercial transformer fluids (BIOTEMP?, EnvirotempFR3?, and Bivolt?), which increases transformer safety, capacity and lifetime. In addition, the processed oil has a lower viscosity than BIOTEMP? fluid, which can enhance the heat dissipation efficiency in the transformer. Moreover, the processed oil flash and fire points of 310°C and >340°C, respectively, confirm the great security of vegetable insulating fluids. The analyzed properties of the processed oil fulfill all the ASTM D6871, ABNT NBR 15422 and IEC 62770 specifications. Therefore, Jatropha curcas oil is a potential substitute formineral insulating fluids.
基金supported by the National Natural Science Foundation of China(Grant No.50977025)
文摘The shortcomings of oil-immersed transformer solid insulation like low high-temperature resistance of the insulation paper and the uneven distribution of electric field caused by the large difference of dielectric constants between insulation paper and transformer oil,restricted the development of transformer with smaller size and larger capacity.In view of this situation and the transformer’s demand for the dielectric physicochemical and mechanical property of insulation material,polycarbonate,polyester film and polyphenylene sulfide with high high-temperature resistance were chosen for the comparison analysis in this paper We did the 300-day thermal aging experiment on four samples in transformer oil under different aging temperatures of90°C,110°C and 130°C,then analyzed the changes of their dielectric properties.The experiment results are as follows;the permittivity and dielectric dissipation factor of the three polymer materials are apparently smaller than those of the paper both before and after 300-day aging;the volume resistivity and partial discharge inception voltage of the three materials are higher than those of the paper both before and after aging;and the breakdown field strength of polycarbonate is higher than that of the paper both before and after aging,while that of polyester film and polyphenylene sulfide are slightly lower than that of the paper.
基金financially supported by the National Key Research and Development Program of China(2022YFA1204900)the National Natural Science Foundation of China(No.52372038 and T2188101).
文摘The applications of two-dimensional semiconductors strictly require the reliable integration of ultrathin high-κdielectric materials on the semiconductor surface to enable fine gate control and low power consumption.As layered oxide materials,MoO_(3) can be potentially used as a high-κtwo-dimensional material with a larger bandgap and high electron affinity.In this work,relying on the oxidization of molybdenum chlorides,we have synthesizedα-MoO_(3) single crystals,which can be easily exfoliated into flakes with thicknesses of a few nanometers and sizes of hundreds of micrometers and fine thermal stability.Based on measurement results of conventional metal/insulator/metal devices and graphene based dual-gate devices,the as-received MoO_(3) nanosheets exhibit improved dielectric performance,including high dielectric constants and competitive breakdown field strength.Our work demonstrates that MoO_(3) with improved crystalline quality is a promising candidate for dielectric materials with a large gate capacitance in future electronics based on two-dimensional materials.
文摘This study presents a numerical method based on parallel RC equivalent circuit model fitting methodology for analysis and modeling of dielectric materials.The proposed method employs gradient-descent optimization method(GDOM)to estimate parallel RC equivalent circuit model from current waveforms by minimizing sum of squared difference(SSD)error.Estimation of parallel RC equivalent circuit parameters from measured current waveforms provides a useful tool for identification,simulation and analysis of dielectric materials.Moreover,applications of the proposed method for time and frequency analyses of dielectric materials are demonstrated numerically.Numerical simulations were presented to discuss efficiency of the proposed method for modeling,analysis and monitoring of insulator materials.
