特殊纳米SiO₂溶胶的制备及其在铝电解电容器中的应用

【作者】 范中晓；

【导师】 何为；

【作者基本信息】 电子科技大学 ， 应用化学， 2005， 硕士

【摘要】 铝电解电容器的关键技术是铝箔化成技术和工作电解液技术,本文将制备的纳米SiO₂ 乙二醇溶胶加入工作电解液,然后制成高压铝电解电容器。通过测试发现,使用纳米SiO₂ 溶胶电解液的铝电解电容器的电性能优于使用普通电解液的电容器。由于纳米SiO₂粒子的高活性,解决制备和使用过程中SiO₂溶胶容易凝胶化的问题显得非常重要。本文采用正交实验设计法,通过摸底实验和正交实验,初步找到了先用离子交换法制备SiO₂ 水溶胶,再用溶剂置换的方法制备稳定纳米SiO₂ 乙二醇溶胶的实验条件。找到的优化实验条件为:离子交换时Na₂SiO₃ 溶液的浓度为35%,有机硅偶联剂CH₃Si（OC₂H₅）₃的加入量为2.5%,陈化温度为60℃,陈化时间为1 小时,溶剂置换温度为90℃减压蒸馏,pH 控制在弱酸性,制得的SiO₂ 乙二醇溶胶浓度为5%。在此条件下制得的SiO₂ 乙二醇溶胶性能稳定,不易凝胶化,Cl-、SO₄^2-等有害杂质离子含量低,可以用于配制铝电解电容器工作电解液。用纳米SiO₂溶胶配制成SiO₂浓度为2%的溶胶电解液,以不含纳米SiO₂粒子的电解液做对照电解液。测得纳米SiO₂ 溶胶电解液30℃下的电导率为1830μS/cm;对照电解液的电导率为1800μS/cm,前者比后者有小幅提高;纳米SiO₂ 溶胶电解液的闪火电压达520V,比对照电解液的闪火电压460V 高出13%。纳米SiO₂溶胶电解液的升压速度为4.24V/s,对照电解液的升压速度为1.83 V/s。电导率提高的原因是:纳米SiO₂ 胶粒表面羟基的电离,使电解液中参与导电的电荷数增多。闪火电压和升压速度提高的原因是:带负电的纳米SiO₂ 胶粒在阳极氧化膜薄弱点发生电吸附,并且成为新生成氧化膜的一部分,从而加快了铝箔表面氧化膜瑕疵的修复速度。分别用SiO₂ 浓度为2%的溶胶电解液和未加SiO₂ 溶胶的对照电解液制成电容器。在425V 电压下老练后,使用纳米SiO₂ 溶胶电解液的电容器tgδ平均为更多还原

【Abstract】 Aluminum foil electrochemical forming and preparation of working electrolyte are the key techniques in Aluminum electrolytic capacitor R&D. In this paper, a kind of working electrolyte containing nano size silica glycol sols was prepared. We found that the Aluminum electrolytic capacitors using this kind of working electrolyte achieved the excellent electrical behaviors, such as low tgδ, low Il （leakage current） and high working voltage. The gelating of nano size silica glycol sols is a serious problem to be solved. In this paper orthogonal experimental design was used to seek the optimized conditions to prepare steady nano size silica glycol sols. Firstly, the silica water sols was prepared use the Na2SiO3 reaction with cation exchange resin, Secondly the H2O in the sols was replaced by HOCH2CH2OH , then the silica glycol sols was yield. After experiment in orthogonal method, we found that under this given conditions a clear and steady nano size silica glycol sols was prepared. The condition is: concentration of Na₂SiO₃ is 35%; CH₃Si（OC₂H₅）₃ is 2.5%; aging temperature is 60℃; aging time is 1 hour; under 90℃H2O is replaced by glycol by vacuum evaporation; pH between 5 7; SiO₂ concentration in glycol sols is 5%. The deleterious ions such as Cl-, SO42-have not been detected in the yield sols. We got the working electrolyte （I） by mix the silica glycol sols and other ingredients together, and another working electrolyte （II） containing no silica particles as contrast sample. Under 30℃, the conductivity of electrolyte （I） is 1830μS/cm is higher than that of electrolyte （II） is 1800μS/cm. The reason is, considered in this paper, the ionization of hydroxide in the surface of SiO₂ particles made the free charge in the electrolyte increased. So, the conductivity of electrolyte （I） is higher than that of contrast sample. The Us （spark voltage） of electrolyte （I） is 520V , voltage increase rate during aging process is 4.24V/s; these factors of electrolyte （II） are 460V and 1.83V/s. The reason is: the negative charged SiO₂ particles is adsorbed by anode at the weak point of the Oxide layer. The SiO₂ particles become a part of the Oxide layer, so it accelerates heal up speed of the Al2O3 film on the anode. Capacitors using electrolyte （I） and （II） were assembled. After 425V aging, tgδand Il of capacitors using electrolyte （I） were 4.86% and 4.0μA , these factors of更多还原