BaTiO_3包覆粉煤灰漂珠/聚苯胺复合材料的制备及电流变性能

Synthesis and Electrorheological Property of BaTiO_3 Coated Fly Ash Floating Bead/PAn Composites

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.

The fly ash floating beads were covered by polyaniline（ FAFB/PAn） by using in situ polymerization method. Sol gel-hydrothermal method was introduced to prepare FAFB/PAn/BaTiO_3 composites. FAFB/PAn/BaTiO_3 composites had core/shell structure with multilayer,which was composed of the core as hollow FAFB and the first shell as conductive layer PAn and the second one as insulating layer BaTiO_3. The structure and performance of the composites were analyzed by FTIR,XRD,SEM,four point probe technique and LCR. The suspension and shear stress of electrorheological fluid were tested. The results of FTIR and XRD showed that PAn and BaTiO_3 could successfully be coated on the surface of FAFB by this method.The results of conductivity showed that the value of FAFB/PAn/BaTiO_3 was 7. 8 × 10^（-4）S·cm^（-1）,and rose almost by two orders of magnitude in comparison with BaTiO_3. It had better dielectric properties in the 1- 2000 k Hz frequency range. The max value of εrreached 598 if f = 1 k Hz was provided and with the increase of frequency,the dielectric constant decreased correspondingly. The maximum of tanδ was 1. 14 at f = 1 k Hz and its value decreased to 0. 75 until 200 k Hz. Comparison with the suspension stability of them,FAFB/PAn showed better suspension ratio as 88% than BaTiO_3 and FAFB/PAn/BaTiO_3 after 7 days,while the values of the latter two was similar as only 60%. FAFB/PAn/BaTiO_3 based electrorheological fluid showed a significant ER effect and obvious higher capability of breakdown resistance under electric field. When the applied electric field was 4. 0 k V/mm,the shear stress arrived at 631 Pa.