Fly ash floating bead（FAFB） was modified by the nonionic surfactant polyethylene glycol（PEG） under various concentrations to improve its hydrophobility,and then PEG modified FAFB composited with polyaniline（FAFB-PEG/PAn） by emulsion polymerization method using different feed ratios of FAFBPEG.The chemical structure,phase structure,microstructure,conductivity,and dielectric properties were studied by FT-IR,XRD,SEM,four-probe technique,and LCR digital bridge,respectively.It was demonstrated that the optimal concentration of PEG was 1 mol/L and the corresponding grafting ratio was 1.42%.The phase structure of FAFB was not destroyed after modification by PEG,while the surface became smoother and could be coated by PAn successfully according to SEM technique.Compared to that of dodecylbenzenesulfonic acid doped PAn（PAn-DBSA）,the conductivity of FAFB-PEG/PAn was decreased by 10-100 times after introduction of various amounts of FAFB-PEG,especially the value could be decreased to 0.01 S cm^-1 if 50 wt%of FAFBPEG was provided.Additionally,the dielectric constant and loss factor of FAFB-PEG/PAn composites gradually decreased with increasing amount of FAFB-PEG in the frequency range of 100 KHz-2 MHz,namely,the dielectric constant could be still kept at 500 and correspondingly the loss factor decreased to 4.7 at 100 KHz if50 wt%of FAFB-PEG was provided.The leaking current phenomenon derived from PAn-DBSA could also be weakened by FAFB-PEG.
首先利用原位化学氧化聚合法将聚苯胺包覆在粉煤灰漂珠表面(FAFB/PAn),再利用低温溶胶凝胶-水热法制备BaTiO_3包覆FAFB/PAn的复合材料(FAFB/PAn/BaTiO_3),形成内核为空心漂珠、外壳依次为导电层、绝缘层的核/壳结构.采用FTIR、XRD、SEM、数字式四探针以及LCR介电谱仪对FAFB/PAn/BaTiO_3复合材料的结构与性能进行分析;以FAFB/PAn/BaTiO_3为分散相制备的电流变液,对其悬浮性及外加电场下的剪切应力进行测试.FTIR和XRD结果证明了利用本文的实验方法可成功将PAn和BaTiO_3引入到FAFB表面.电导率测试结果表明,复合材料电导率为7.8×10^(-4)S·cm^(-1),相对BaTiO_3提高了近2个数量级.在1~2000 k Hz交变电场频率测试范围内,FAFB/PAn/BaTiO_3具有相对较好的介电性能:当f=1 k Hz时εr最大为598,随电场频率的增加介电常数逐渐减小,对应的介电损耗tanδ最大为1.14,且随电场频率的增加介电损耗逐渐减小,当f=200 k Hz时tanδ=0.75,后趋于平稳.比较了7天的悬浮稳定性发现,FAFB/PAn稳定性最好,悬浮率可达88%,而包覆BaTiO_3后与纯BaTiO_3相当,仅为60%.在电场作用下FAFB/PAn/BaTiO_3表现出较明显的电流变性能,即当E=4.0 k V/mm时,剪切应力达631 Pa,且具有较好的抗击穿能力.
本文采用乳液聚合法制备了十六烷基三甲基溴化铵改性漂珠/聚苯胺复合材料(FAFB-HDTMA/PAn),利用FTIR、SEM对产物的结构与形貌进行分析,并讨论了不同氧化剂过硫酸铵(APS)浓度对FAFB-HDTMA/PAn复合材料的产物颜色及其电学性能的影响。实验结果表明:利用FTIR和SEM分析证明HDTMA对FAFB修饰改性成功,FAFB-HDTMA被PAn包覆;通过观察复合产物颜色可知,随着APS∶An浓度比的增加,产物颜色更趋近于掺杂态PAn的颜色;利用四探针技术测试发现,聚苯胺的电导率随着改性粉煤灰漂珠(FAFB-HDTMA)的加入而降低了近100倍;利用LCR数字电桥测试发现,在100 k Hz^2 MHz的频率范围内,FAFB-HDTMA/PAn复合材料的相对介电常数和介电损耗随外加频率的增大而减小,进而可知当APS:∶An浓度比为0.8时,FAFB-HDTMA/PAn复合材料的电导率和相对介电性能均为最优效果。
