新型纳米ZrO2/聚酰亚胺复合超薄膜的制备表征及其介电性能

以油酸为有机配体，采用两相方法合成了油溶性的超小尺寸纳米晶体纳米ZrO₂（nano ZrO₂），并对nano ZrO₂表面包覆的油酸改性使纳米晶体与聚酰胺酸（PAA）接枝，通过旋膜法热亚胺化后形成nano ZrO₂/聚酰亚胺（PI）复合超薄膜。利用TEM、XRD、FTIR和SEM等对nano ZrO₂及nano ZrO₂/PI复合超薄膜进行表征，并对nano ZrO₂/PI复合超薄膜的介电性能进行了探究。结果显示，nano ZrO₂尺寸均一（5.0 nm左右），为锐钛矿晶型，其晶体结构和尺寸不受改性接枝影响。nano ZrO₂在复合超薄膜中分散良好。电学研究表明，复合超薄膜的介电性能受nano ZrO₂与PAA质量比及制膜热亚胺化温度的影响。当PAA∶ZrO₂质量比为2∶3、热亚胺化温度为320℃时，介电常数达到最大，几乎是纯PI薄膜的2倍。两相法-改性接枝-热亚胺化制备PI复合超薄膜的方法简单高效，能够避免无机粒子在PI基体内的团聚并提高介电性能，对于PI基复合薄膜的制备、应用及推广具有重要意义。

Fabrication and characterization and dielectric property of nano ZrO2/polyamide ultra-thin composite films

Oleic acid-capped nanocrystals (nano ZrO₂) were fabricated via two-phase approach, modified and grafted onto polyamic acid (PAA). After the imidization of nano ZrO₂/PAA, nano ZrO₂/polyamide (PI) ultra-thin composite films were finally obtained. The nanocrystals and nano ZrO₂/PI ultra-thin composite films were characterized by TEM, XRD, FTIR and SEM, and the dielectric properties of the nano ZrO₂/PI ultra-thin composite films were also exploited. The results demonstrate the nano-size (about 5.0 nm) and mono-dispersity of ZrO₂, the morphology and crystallinity of the nanocrystals are not negatively influenced by modification or grafting. The nanocrystals are homogenously dispersed in the bulk of PI. The dielectric properties of nano ZrO₂/PI ultra-thin composite films are influenced by the mass fraction of nanocrystals and the filming condition (i.e., imidization temperature). With a PAA:ZrO₂ mass ratio of 2:3 and aimidization temperature of 320℃, the dielectric constant exhibites the maximum, around twice that of pure PI thin films. Overall, nano ZrO₂/PI ultra-thin composite film fabrication method (general nanocrystal preparation-modification-grafting-imidization) exhibites its efficiency, feasibility, flexibility and versatility. This method can be extended by evolving other nanoparticles with high dielectric constant, tailor the properties by tuning the content of nanoparticles and filming condition, and obtain high dielectric constant composite films with low cost and pollution.