Surface charge properties of titanium dioxide in water and propylene g lycol have been discussed by proton-transfer phenomena.Electrophoresis shows s ignificant differences between each type of titanium dioxide partic...Surface charge properties of titanium dioxide in water and propylene g lycol have been discussed by proton-transfer phenomena.Electrophoresis shows s ignificant differences between each type of titanium dioxide particles and betwe en the two dispersion media.In aqueous solvent,the sign of the charge for tita nium dioxide would change due to pH and surface chemical composition.However,i n propylene glycol pH value could not result in the sign of the charge for uncoa ted titanium dioxide.Furthermore,the effects of both alumina and silica coatin gs and media on the surface charge properties of titanium dioxide are due to pro ton-transfers.The acidity of hydroxyl groups on oxides surface is believed to be the direct reason that make them have different charge properties in solvents .It is favorable for the hydroxyl groups on the surface of particles to donate protons,as was observed by negative charge pertaining for dispersion in water a t most values of pH.While in propylene glycol titanium dioxide particles are fo rced to accept protons,resulting in positively charged particles.Small amounts of water have a significant effect on the sign of the charge for uncoated titan ium dioxide.展开更多
文摘Surface charge properties of titanium dioxide in water and propylene g lycol have been discussed by proton-transfer phenomena.Electrophoresis shows s ignificant differences between each type of titanium dioxide particles and betwe en the two dispersion media.In aqueous solvent,the sign of the charge for tita nium dioxide would change due to pH and surface chemical composition.However,i n propylene glycol pH value could not result in the sign of the charge for uncoa ted titanium dioxide.Furthermore,the effects of both alumina and silica coatin gs and media on the surface charge properties of titanium dioxide are due to pro ton-transfers.The acidity of hydroxyl groups on oxides surface is believed to be the direct reason that make them have different charge properties in solvents .It is favorable for the hydroxyl groups on the surface of particles to donate protons,as was observed by negative charge pertaining for dispersion in water a t most values of pH.While in propylene glycol titanium dioxide particles are fo rced to accept protons,resulting in positively charged particles.Small amounts of water have a significant effect on the sign of the charge for uncoated titan ium dioxide.
文摘在气体绝缘变电站(gas insulated substation,GIS)的实际运行工况中,开关操作会使GIS设备承受操作冲击过电压,导致盆式绝缘子表面积聚表面电荷,表面电荷的存在不仅会使得局部电场发生畸变,更为沿面放电的发展提供了电荷,是造成绝缘子沿面闪络的重要因素。该文以实际的252k V GIS盆式绝缘子为试验模型,建立了表面电荷测量试验平台,采用静电探头法测量了SF6气体密闭环境下盆式绝缘子的表面电荷,获得了操作冲击电压作用下盆式绝缘子表面电荷积聚特性及其外施电压作用次数和电压幅值对其的影响。研究结果表明:无论在正极性或负极性操作冲击电压下,绝缘子表面均同时积聚正负极性电荷,但是负极性电荷相比于正电荷积聚量更大,且正极性电压下此现象更为明显;正极性操作冲击电压下,随着电压幅值的增加,绝缘子表面电荷平均积聚量明显增加,最高电荷幅值为-0.52μC/m^2,而负极性电压下,电荷平均积聚量表现出先增大后减小的趋势,其电荷平均密度最大为-0.16μC/m^2;表面电荷积聚量随着外施电压次数的增加逐渐增大,正极电压下表面电荷积聚量的增幅明显,而负极性电压下表面电荷增幅较小,但分布较均匀。该文研究所得到的操作冲击电压下GIS表明电荷积聚特性,进一步强调了由表面电荷引起的实际工况下设备绝缘问题的重要性,可为GIS设备绝缘子的优化设计提供参考。
