微秒脉冲下碳酸丙烯酯的击穿特性

采用紧凑Tesla变压器型脉冲功率驱动源及球电极击穿试件,通过改变初级充电电压,开展了微秒级充电条件下碳酸丙烯酯及其与碳酸乙烯酯的混合液的击穿实验研究。由结果和分析可知：碳酸丙烯酯理论工作温度可低至-55 ℃,这意味着它可以成为一种低温下的良好液体电介质;碳酸丙烯酯耐压性能与去离子水相当,且实测电阻率达到了10 Mcm以上;向碳酸丙烯酯中添加碳酸乙烯酯后,介电常数可提高至80以上,耐压强度也有所提升;将碳酸丙烯酯、碳酸乙烯酯/碳酸丙烯酯混合液用于脉冲形成线作为储能介质无需附加去离子处理系统,有利于装置的紧凑化和小型化。     

微秒脉冲下碳酸丙烯酯的击穿特性

采用紧凑Tesla变压器型脉冲功率驱动源及球电极击穿试件,通过改变初级充电电压,开展了微秒级充电条件下碳酸丙烯酯及其与碳酸乙烯酯的混合液的击穿实验研究。由结果和分析可知:碳酸丙烯酯理论工作温度可低至-55℃,这意味着它可以成为一种低温下的良好液体电介质;碳酸丙烯酯耐压性能与去离子水相当,且实测电阻率达到了10 MΩ·cm以上;向碳酸丙烯酯中添加碳酸乙烯酯后,介电常数可提高至80以上,耐压强度也有所提升;将碳酸丙烯酯、碳酸乙烯酯/碳酸丙烯酯混合液用于脉冲形成线作为储能介质无需附加去离子处理系统,有利于装置的紧凑化和小型化。     

加压乙二醇/水混合液耐μs级高电压击穿实验研究

采用同轴电极实验装置,在μs级充电时进行了加压乙二醇/水混合液正电极击穿实验,并对实验结果进行了分析和解释,得出结论如下：击穿场强随静压以1/8次幂的关系而增加;击穿场强系数随乙二醇浓度的增加而增加;加压和添加乙二醇对于提高水介质耐高电压击穿的能力具有可叠加性,加压比添加乙二醇更有效;在静压12×105 Pa下乙二醇浓度80%的混合液击穿场强比常压下纯水击穿场强高112.2%。加压提高乙二醇/水混合液击穿场强的主要机制是加压增加了击穿延迟时间。     

加压乙二醇/水混合液耐μs级高电压击穿实验研究

 采用同轴电极实验装置,在μs级充电时进行了加压乙二醇/水混合液正电极击穿实验,并对实验结果进行了分析和解释,得出结论如下：击穿场强随静压以1/8次幂的关系而增加;击穿场强系数随乙二醇浓度的增加而增加;加压和添加乙二醇对于提高水介质耐高电压击穿的能力具有可叠加性,加压比添加乙二醇更有效;在静压12×10⁵ Pa下乙二醇浓度80%的混合液击穿场强比常压下纯水击穿场强高112.2%。加压提高乙二醇/水混合液击穿场强的主要机制是加压增加了击穿延迟时间。     

μs级充电时水介质同轴电容击穿实验研究

 研制了水介质同轴电容的实验装置，在此装置上进行了大量的实验。测得μs级充电时，水介质同轴电容分别在正脉冲和负脉冲充电时的击穿电压，负击穿电压的理论值与测量值相差较大，正击穿电压的理论值大于测量值的18%左右，对此实验结果进行了分析。此外，当去离子水的电阻率从13MΩ·cm降到5 MΩ·cm时，水介质同轴电容器的击穿电压基本不变。     

脉冲变压器充电过程中次级线圈匝间电压的分布

实验发现线绕的螺旋形脉冲变压器在充电期间存在击穿的现象,有时甚至在原边刚导通的时刻就发生击穿,而此时副边并无电压输出。为解释这种实验结果和避免击穿,提高耐压水平,利用简化的多导体传输线方法,在忽略了充电过程中的位移电流情况下,给出了变压器在不同时刻次级绕组层间电压分布。结果表明:变压器层间电压分布随时间变化,且与电路外部参数如失谐、原边电容电压等存在关系。失谐系数较小时,可能在充电的初始时刻就发生变压器击穿。可以利用这些特性来改进螺旋形线绕变压器的设计,使电压分布尽可能均匀,提高耐压强度。     

脉冲变压器充电过程中次级线圈匝间电压的分布

实验发现线绕的螺旋形脉冲变压器在充电期间存在击穿的现象,有时甚至在原边刚导通的时刻就发生击穿,而此时副边并无电压输出。为解释这种实验结果和避免击穿,提高耐压水平,利用简化的多导体传输线方法,在忽略了充电过程中的位移电流情况下,给出了变压器在不同时刻次级绕组层间电压分布。结果表明:变压器层间电压分布随时间变化,且与电路外部参数如失谐、原边电容电压等存在关系。失谐系数较小时,可能在充电的初始时刻就发生变压器击穿。可以利用这些特性来改进螺旋形线绕变压器的设计,使电压分布尽可能均匀,提高耐压强度。     

基于磁场闪络抑制技术的真空沿面闪络实验研究

为解决脉冲功率系统中击穿电压最低的部分,即真空固体绝缘界面,采用磁场闪络抑制技术提高闪络电压,为研究磁场和沿面闪络电压的关系,针对不同介电常数的样品开展了一系列相关实验。实验结果表明:采用电容器对通电螺线管充电产生的脉冲强磁场稳定可靠,并且当施加在绝缘子表面磁场强度为1.1 T时,PMMA材料的闪络电压可以提高至1.8倍。     

基于磁场闪络抑制技术的真空沿面闪络实验研究

为解决脉冲功率系统中击穿电压最低的部分,即真空固体绝缘界面,采用磁场闪络抑制技术提高闪络电压,为研究磁场和沿面闪络电压的关系,针对不同介电常数的样品开展了一系列相关实验。实验结果表明：采用电容器对通电螺线管充电产生的脉冲强磁场稳定可靠,并且当施加在绝缘子表面磁场强度为1.1 T时,PMMA材料的闪络电压可以提高至1.8倍。     

μs级充电时水介质同轴电容击穿实验研究

研制了水介质同轴电容的实验装置,在此装置上进行了大量的实验。测得μs级充电时,水介质同轴电容分别在正脉冲和负脉冲充电时的击穿电压,负击穿电压的理论值与测量值相差较大,正击穿电压的理论值大于测量值的18%左右,对此实验结果进行了分析。此外,当去离子水的电阻率从13MΩ·cm降到5 MΩ·cm时,水介质同轴电容器的击穿电压基本不变。     

Structural study of aqueous solutions of tetrahydrofuran and acetone mixtures using dielectric relaxation technique

The complex permittivity, static dielectric constant and relaxation time for tetrahydrofuran-water and acetone-water mixtures have been determined at 0°, 10°, 25° and 35°C using time domain reflectometry technique (TDR). The behaviour of relaxation time of the mixture shows a maxima for the mixture with 30% of water by volume. This suggests that the tendency to form cluster between water and solute molecule is maximum for this mixture. The excess permittivity for both tetrahydrofuran-water mixture and acetone-water mixtures, are found to be negative. The Kirkwood correlation factor has been determined at various concentrations of water. Static dielectric constant for the mixtures have been fitted well with the modified Bruggeman model. The values of the Bruggeman parametera for tetrahydrofuran is found to be more than the corresponding value for acetone.     

Dielectric properties of moist disperse materials in the microwave range

The behavior of the dielectric permittivity of a mixture of disperse materials is investigated for a change in the volume content of the component with a high value of the dielectric permittivity. An analysis is performed from the viewpoint of computing the dielectric permittivity of such mixtures. A formula is proposed for computation of the dielectric permittivity of mixtures of disperse materials with water.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 74–78, July, 1981.     

1,2,5-三苯基吡咯的合成及其聚集程度对发光强度的影响

采用Schulte-Reisch方法,在氯化亚铜催化下,由1,4-二苯基丁二炔与苯胺反应成功制备了1,2,5-三苯基吡咯(TPP)。通过将溶液反应改进为本体反应,不仅提高了收率,而且降低了反应温度,缩短了反应时间。当水的含量在THF-水混合溶剂中低于60％时,因TPP没有产生聚集,其荧光强度基本没有发生变化;但水含量增加到70％时,因聚集紧密程度较低,π—π堆积作用诱发非辐射能量转移,使荧光强度被猝灭;而当水的含量超过80％以上时,TPP呈现高紧密聚集,使分子内旋转受到限制,降低了非辐射能量转移,使发光得到增强。由于乙腈与TPP之间所形成的较强电荷转移相互作用影响了聚集紧密程度,没有呈现高聚集诱导发光增强性质。     

Influence of the geometric factor on the volume properties of triple mixtures

For model mixtures it is established that the concentration behavior of the molar volume that obeys the additive rule with respect to mole fraction is explained by the difference in geometric structures of pure liquids constituting mixture. It is revealed that the geometric factor (the difference in volumes of molecules and packing densities of the initial liquids constituting mixture) brings significant contribution to the excess molar volume of water mixtures of nonelectrolytes. Within the framework of the suggested approach, a maximum contribution of this factor to the relative excess volume of triple mixtures is estimated.     

Dielectric permittivity, density, viscosity and refractive index of binary mixtures of anisole with methanol and 1-propanol at different temperatures

Static dielectric permittivity, density, viscosity, and refractive index of anisole (AN), methanol (MeOH), 1-propanol (1-PrOH) and binary mixtures of AN with MeOH and 1-PrOH at nine different concentrations, were measured at 303, 313 and 323 K temperatures. Measured properties of pure AN, MeOH and 1-PrOH were compared with literature values and they were found in good agreement. The investigation of binary mixtures showed a systematic change in static dielectric permittivity, density and viscosity with change in concentration of anisole in the mixture. Measured properties of liquid samples were used to calculate Kirkwood correlation factor and excess parameters such as excess dielectric permittivity, excess molar volume and excess viscosity. Determined parameters have been interpreted in terms of molecular interaction among the molecular species of the binary mixtures.     

Concentration and temperature dependent interaction studies using dielectric and thermodynamic methods on mixtures of anisole with o-toluidine and m-toluidine

Molecular interactions in mixtures of anisole with o-toluidine and anisole and m-toluidine have been studied at three different temperatures using the dielectric method with measurements of the static permittivity and permittivity at optical frequency. From the measured values, the Kirkwood correlation parameter, Bruggeman parameter, excess permittivity and thermodynamic excess free energy were computed for the mixtures. Positive and negative values of excess permittivity were obtained for both mixtures. The excess free energy for the anisole+o-toluidine mixture is positive at all three temperatures, whereas mixed values (positive and negative) are obtained for the anisole+m-toluidine mixture. Alignment of the dipoles in both mixtures was identified by Kirkwood factors. The investigation shows that the interaction between the components changes systematically with concentration and temperature and the change is minimum.     

GROMOS polarisable model for acetone

A polarisable model for acetone, COS/A, is proposed that is based on the charge-on-spring (COS) polarisation model and is compatible with the polarisable COS/D2 and COS/G2 models for liquid water. A series of acetone-water mixtures at different acetone mole fractions was simulated using the new model in conjunction with the mentioned polarisable and the non-polarisable SPC and SPC/E water models. The model was parameterised to reproduce the following liquid acetone properties: density, heat of vaporisation, surface tension, dielectric permittivity, self diffusion and heat capacity and subsequently tested in mixtures with water using different water models. For pure liquid acetone the polarisable COS/A model agrees better with experimental data than the non-polarisable Kirkwood-Buff derived force field (KBFF) model, which was parameterised using experimental data for a 0.5 mole fraction acetone-water mixture. For such mixtures the polarisable models yield better agreement with experiment than the non-polarisable models for the heat of vaporisation and dielectric permittivity, while worse agreement for diffusion. The computational cost of simulating the polarisable acetone-water mixtures is a factor of 3 to 4 higher compared with the non-polarisable models due to the increased number of interaction sites and the multiple iterations required to evaluate self-consistently the positions of the COS sites at every simulation step. The COS/A acetone model can be used in biomolecular simulations in conjunction with the mentioned polarisable water models to solvate biomolecules.     

Effect of surface modification on dielectric and magnetic properties of metal powder/polymer nanocomposites

Metal nanopowder (Co and Fe)/polymer composites, both with and without surface modification by behenic acid, were fabricated and their dielectric and magnetic properties were measured at 1 GHz to study the effect of surface modification on the electromagnetic properties. The relative permittivity and the real part of the permeability of the composites with surface modified powders were higher than those with unmodified powders. Related dielectric losses remained at almost the same level, but magnetic losses were somewhat increased. The increase of relative permittivity could result from the increased volume fraction of interphase with a slightly higher relative permittivity at the particle/polymer interface than that of the bulk polymer. The increase in the real part of the permeability may be caused by suppression of the induced demagnetizing field due to suppression of eddy currents by a better particle distribution and a decrease in effective agglomerate size because of the surface modification.     

紫外辐照对聚醚酰亚胺薄膜介电性能的影响

研究了不同紫外辐照时间对聚醚酰亚胺(PEI)薄膜介电性能的影响。采用FT-IR和SEM表征了PEI薄膜的分子结构和微观形貌。结果表明,紫外辐照后PEI薄膜在1742 cm-1处的吸收峰比原薄膜增大,说明PEI分子链中的C=O基团随辐照时间的增加而增加,并在薄膜表面产生了微裂纹。对PEI薄膜的介电性能进行的研究结果表明,随着紫外辐照时间的增加,PEI薄膜的介电常数和介电损耗增大,而表面电阻率下降,体积电阻率基本不变。并随紫外辐照时间的增加,直流击穿强度呈先增加后降低的趋势,一定辐照剂量可使薄膜发生交联反应,使击穿场强较原薄膜提高20%以上。