SF_6/N_2混合气体绝缘特性的试验研究及理论分析

应用自制的试验模型对SF6/N2混合气体的绝缘能力进行了试验研究,并和纯净的SF6、N2的绝缘能力进行了比较,获得了SF6/N2混合气体在不同比例下的击穿电压与气体间隙距离之间的曲线.经综合比较、分析确定50%SF6 50%N2的混合气体的经济技术指标比较高,可以在电气设备中作为绝缘介质广泛应用.     

Rh掺杂质单壁碳纳米管表面NO吸附反应的第一性原理研究

由于局部放电,SF6∕N2混合气体会发生分解.基于密度泛函理论研究SF6∕N2混合气体的一种分解产物NO对铑掺杂单壁碳纳米管表面的气敏特性.模拟和分析了NO气体靠近铑掺杂SWCNT(8,0)表面的吸附结构、吸附能量、电荷转移量、态密度等.结果表明,NO在Rh-SWCNT上的吸附过程是放热的.根据DOS分析,NO气体吸附在Rh-SWCNT表面后,NO与Rh-SWCNT的相互作用力变强,共价性增加.分析得出Rh-SWCNT材料可能适合作为检测SF6∕N2气体绝缘设备中NO的气体传感器.     

浅析气体分解产物检测应用技术

气体绝缘设备中SF6气体分解产物检测为设备故障诊断提供了有效依据,本文对SF6气体分解产物的检测技术、试验研究及其在设备故障诊断应用等方面的国内外研究现状进行了综述,结合设备状态评价的需求,以期得到设备故障诊断的SF6气体分解产物判据,及气体绝缘设备的运行管理.     

大型地下变电站GIS现场绝缘试验方法

针对大型地下变电站空间相对狭窄的特点,提出交流耐压试验配合灵敏局放测量的地下变电站GIS现场绝缘试验方案,其中GIS耐压试验采用SF6气体绝缘的试验电抗器实现.试验表明,该方案可行性强、有效性高,适合在大型地下变电站中现场推广应用.     

混合气体绝缘设备充、补气技术研究

混合绝缘气体充气、补气是混合气体绝缘设备运维的重要环节。现有的分压充、补气方法,难以精确控制气体混合比例,不能满足混合气体绝缘设备大规模推广的技术要求。为此结合SF_6气体现场充、补气技术经验,提出以动态配气原理为基础的SF_6、N_2等组分精确加压配气技术方案,研制新型混合气体加压配气补气装置,装置能够实现SF_6气体与N_2等两组分混合绝缘气体的现场连续精确配制,气体混合比例范围0%～100%可调,配气误差小于1%,满足不同设备精确配比加压充补气要求。同时提出混合绝缘气体现场补气比例的计算公式,可根据混合气体绝缘设备实际比例,获得合适的补气浓度。     

SF_6-N_2中粒子动力学特性的蒙特卡罗仿真

为了模拟SF6-N2混合气体的汤逊脉冲实验过程,求出不同状态下混合气体的电子能量分布特性,在电场强度与气体分子密度之比为(250～450)Td范围内,采用蒙特卡罗法仿真了SF6-N2混合气体的电子雪崩发展过程.求出了电子能量分布随电场强度与气体分子密度之比的变化规律、有效电离系数及临界耐电强度随SF6分压比变化的规律,且与实验结果作了比较和分析.结果表明,混合气体临界击穿场强Eb随着SF6分压比的增加而提高,与实验结果比较,有很好的一致性.     

六氟化硫气体分解产物分析对气体绝缘开关设备（GIS）潜伏性故障判断的应用

六氟化硫（SF6）气体在电弧、电火花和电晕放电的作用下会发生分解,产生二氧化碳（CO2）、四氟化碳（CF4）等分解产物。SF6气体组分分析（可在设备带电状态下进行）是诊断SF6气体绝缘设备内部运行情况的一个强有力的手段,据此可判断设备是否故障,并确定故障的具体部位,近年来已有不少成功案例,但判断电气设备潜伏性故障的经验不多。本文总结了广东省部分变电站组合电器（GIS）气室中SF6分解产物的含量,并进行SF6组分分析,为SF6GIS潜伏性故障及其故障类型判断累积经验。     

利用SF_6气体分解产物检测和诊断GIS绝缘故障

论述了SF6气体分解产物检测技术的发展历史、局部放电下SF6气体的分解机理、SF6气体分解产物的常见检测方法,以及SF6分解产物与绝缘类型之间的关系等,结合最新研究进展,提出利用SF6气体分解组分的含量比值来识别缺陷类型,进而对设备内部绝缘进行故障诊断和状态评估,并指出了下一步需要研究解决的关键问题.     

c-C4F8及其混合气体的灭弧性能

六氟化硫（SF6）气体以其优良的绝缘和灭弧性能广泛应用于各种高压电力设备中,但它也是一种对环境有很大危害的高温室效应气体,因此迫切需要寻找新的低温室效应的、环境友好的气体替代SF6．研制了灭弧试验装置,对温室效应值较低的c-C4F8气体及其混合气体进行了灭弧试验,利用麦也尔电弧模型得到了电弧时间常数和散出能量常数,并分析了其灭弧性能．结果表明,c-C4F8气体在电力设备中具有一定的应用研究价值．     

火花放电下SF6分解组分的红外光谱特性

在SF6放电分解试验平台上,探究针-板绝缘缺陷下产生火花放电引起SF6分解产生的特征组分.在40 kV下进行96 h放电试验,采用傅里叶变换红外光谱法进行检测,分析SF6分解组分吸光度随时间变化的规律.试验结果显示:间隙火花放电下,SF6分解特征有SO2,SO2F2,SOF2;放电24 h后,能明显检测到SO2,SO2F2,SOF2的吸收峰.     

SnO2及SnO2／Fe2O3复合微米材料的合成及表征

本文首先以SnCl2·2H2O为主要原料,无水乙醇为溶剂,利用溶剂热法于180℃反应24h得到了SnO2微球;再以所制备的SnO2微球为前驱体,FeCl3·6H2O为主要原料,通过水热法得到SnO2／Fe2O3复合材料．利用X射线粉末衍射仪（XRD）和扫描电子显微镜（SEM）对所得产物进行了表征．结果表明：所得的SnO2为四方锡石型,形貌为微球,平均直径约为2．0μm;复合后得到的SnO2／Fe2O3微球平均直径约为2．5μm．其中,Fe2O3为六方赤铁矿型,在复合物的表面以小颗粒的形式存在,尺寸约为200nm．另外,也对SnO3与SnO2／Fe2O3微球的形成过程进行了讨论．     

Temperature dependence on reaction of CaCO3 and SO2 in O2/CO2 coal combustion

The temperature dependence on the reaction of desulfurization reagent CaCO₃ and SO₂ in O₂/CO₂ coal combustion was investigated by thermogravimetric analysis, X-ray diffraction measurement and pore structure analysis. The results show that the conversion of the reaction of CaCO₃ and SO₂ in air is higher at 500–1 100 °C and lower at 1 200 °C compared with that in O₂/CO₂ atmosphere. The conversion can be increased by increasing the concentration of SO₂, which causes the inhibition of CaSO₄ decomposition and shifting of the reaction equilibrium toward the products. XRD analysis of the product shows that the reaction mechanism of CaCO₃ and SO₂ differs with temperature in O₂/CO₂ atmosphere, i.e. CaCO₃ directly reacts with SO₂ at 500 °C and CaO from CaCO₃ decomposition reacts with SO₂ at 1 000 °C. The pore analysis of the products indicates that the maximum specific surface area of the products accounts for the highest conversion at 1 100 °C in O₂/CO₂ atmosphere. The results reveal that the effect of the atmosphere on the conversion is temperature dependence.     

Preparation of TiO2 photocatalyst loaded with V2O5 for O2 evolution

TiO₂ photocatalysts loaded with V₂O₅ were prepared via a modified hydrolysis process, and characterized by X-ray diffraction, transmission electron microscopy, Raman spectra and diffuse reflectance UV-Vis spectra measurements. The photocatalytic activity of V₂O₅/TiO₂ was investigated by employing splitting of water for O₂ evolution. The results indicate that V₂O₅ loading can pronouncedly improve the photocatalytic activity of TiO₂ with Fe³⁺ as an electron acceptor under UV or visible light irradiation. The optimum mass fraction of the loaded V₂O₅ is 8%, and the largest speed of O₂ evolution for 8%V₂O₅ (mass fraction) loaded TiO₂ catalyst is 118.2 μmol/(L·h) under UV irradiation, and 83.7 μmol/(L·h) under visible light irradiation.     

Bi2O3和Fe2O3掺杂对BaTiO3陶瓷显微结构的影响

利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线能量色散谱(EDAX)等结构分析技术,研究了施主(Bi     

Dielectric properties of Pb (Zn1/3 Nb2/3) O3?PbZrO3?PbTiO3 solid solution near morphotropic phase boundary

The dielectric properties of Pb(Zn_1/3Nb_2/3) O₃-PbZrO₃−PbTiO₃ (PZN-PZ-PT) system near the rhombohedral/tetragonal morphotropic phase boundary (MPB) are carefully studied in this paper. It is found that, for all samples, the curves around the temperatures of dielectric permittivity peak show the characteristics of diffuse phase transition. The change in PbZrO₃/PbTiO₃ ratio has much influence on the dielectric properties of the samples. The extent of diffuse phase transition increases with the increasing Zr/Ti ratio. The samples in rhombohedral region have typical diffuse phase transition in the temperature range measured. However, for the samples with tetragonal symmetry, a spontaneous normal ferroelectric-relaxor phase transition exists at temperature lower than that of permittivity peak. This normal ferroelectric-relaxor phase transition is confirmed by the experiment of thermally driven current. The analysis of TEM reveals that the samples in tetragonal region show a 90% macrodomain structure, while the samples in rhombohedral region have the configuration of microdomain structure.     

Characteristics of LiCoO2, LiMn2O4 and LiNi0.45Co0.1Mn0.45O2 as cathodes of lithium ion batteries

LiNi_0.45Co_0.10Mn_0.45O₂ was synthesized from Li₂CO₃ and a triple oxide of nickel, cobalt and manganese at 950 °C in air. The structures and characteristics of LiNi_0.45Co_0.10Mn_0.45O₂, LiCoO₂ and LiMn₂O₄ were investigated by XRD, SEM and electrochemical measurements. The results show that LiNi_0.45Co_0.10Mn_0.45O₂ has a layered structure with hexagonal lattice. The commercial LiCoO₂ has sphere-like appearance and smooth surfaces, while the LiMn₂O₄ and LiNi_0.45Co_0.10Mn_0.45O₂ consist of cornered and uneven particles. LiNi_0.45Co_0.10Mn_0.45O₂ has a large discharge capacity of 140.9 mA · h/g in practical lithium ion battery, which is 33.4% and 2.8% above that of LiMn₂O₄ and LiCoO₂, respectively. LiCoO₂ and LiMn₂O₄ have higher discharge voltage and better rate-capability than LiNi_0.45Co_0.10Mn_0.45O₂. All the three cathodes have excellent cycling performance with capacity retention of above 89.3% at the 250th cycle. Batteries with LiMn₂O₄ or LiNi_0.45Co_0.10Mn_0.45O₂ cathodes show better safety performance under abusive conditions than those with LiCoO₂ cathodes. Foundation item: Project(50302016) supported by the National Natural Science Foundation of China; Project(2005037698) supported by the Postdoctoral Science Foundation of China     

Modification of nano-TiO2 by Al2O3 in-situ coating

A novel technology of in-situ coating Al₂O₃ on the surface of H₄TiO₄ was developed to prevent the aggregation of nano-TiO₂ powders and improve the dispersibility and thermal stability in the way of forming a uniform coating layer. The heterogeneous nucleation was conducted to prepare the precursor of nano-TiO₂ and then Al₂O₃ was coated on the surface of precursor. The effects of Al₂O₃ in-situ coating on the properties of nano-TiO₂ were investigated. The results show that H₄TiO₄ can be dispersed well under alkaline condition (pH 8.5) and the heterogeneous nucleation can be controlled easily. The optimized uniform coating layer is obtained by adding 5% (mass fraction) and 10% of Al₂O₃ and the aggregation of nano-TiO₂ powders is effectively inhibited and the dispersibility is obviously improved. The crystal sizes of TiO₂ powders are 12.3, 11.4 and 8.7 nm after coating 0,5% and 10% of Al₂O₃ respectively. Al₂O₃ on the surface of particulates in amorphous phase could increase the thermal stability of nano-particles after calcined at 550 °C. Foundation item: Project(04GK2007) supported by Hunan Industrial Key Project of Science and Technology     

三氧化二铝是导致建筑物火灾的严重隐患

建筑物供电线路中的铜线与铝线连接处常常生成一种灰白物质－－三氧化二铝,极易引发建筑物火灾。着重介绍和分析这种灰白物质的成分、生成原因、危害以及防止其生成的主要措施。     

一种基于 MXene 的Fe2O3/Nb2O5/Nb4C3Tx 高灵敏丙酮传感器

MXene 具有较大比表面积和优异的导电性, 当与金属氧化物半导体结合时可以抑制片层团聚, 还可以大大提高载流子转移速率, 提高气敏性能。通过简单的水热和煅烧两步法成功合成了Fe₂O₃/Nb₂O₅/Nb₄C₃T_x 三元复合材料。通过表征, Fe₂O₃ 微米球分布在 MXene 纳米片层之间。气敏测试结果表明, 与原始Fe₂O₃相 比, Fe₂O₃/Nb₂O₅/Nb₄C₃T_x 传感器对丙酮的响应能力有明显的提高。传感器灵敏度高, 选择性较好, 对环境中 浓度为 5 ×10^?6 的丙酮响应高 (R_a /R_g = 7.81, 30% RH), 响应和恢复速度快, 具有出色的重复性和长期稳定性。Fe₂O₃/Nb₂O₅/Nb₄C₃T_x 传感器具有良好的气敏性能, 主要因为三元复合材料提供了较大比表面积和丰富的氧空位, 增强了活性位点, 使得气体易于在传感器表面扩散, 为开发丙酮敏感复合材料提供了参考。     

Electrolysis expansion performance of semigraphitic cathode in [K3AlF6/Na3AlF6]-AlF3-Al2O3 bath system

The electrolysis expansion of semigraphitic cathode in [K₃AlF₆/Na₃AlF₆]-AlF₃-Al₂O₃ bath system was tested by self-made modified Rapoport apparatus. A mathematical model was introduced to discuss the effects of α _CR (cryolite ratio) and β _KR (elpasolite content divided by the total amount of elpasolite and sodium cryolite) on performance of cathode electrolysis expansion. The results show that K and Na (potassium and sodium) penetrate into the cathode together and have an obvious influence on the performance of cathode electrolysis expansion. The electrolysis expansion and K/Na penetration rate increase with the increase of α _CR. When α _CR=1.9 and β _KR=0.5, the electrolysis expansion is the highest, which is 3.95%; and when α _CR=1.4 and β _KR=0.1, the electrolysis expansion is the lowest, which is 1.28%. But the effect of β _KR is correlative with α _CR. When α _CR=1.6 and 1.9, with the increase of β _KR, the electrolysis expansion and K/Na penetration rate increase. However, when α _CR=1.4, the electrolysis expansion and K/Na penetration rate firstly increase and then decrease with the increase of β _KR. Foundation item: Project (2005CB623703) supported by the Major State Basic Research and Development Program of China; Project (2008AA030502) supported by the National High-Tech Research and Development Program of China