Effects of Material Preparation in Polyimide/SiO2 Nanocomposites for Low-Temperature Dielectric Applications

Introducing nanomaterial fillers into a host polymer can significantly change its properties and affect its behaviors. The resulting nanocomposites have the potential to possess new, often enhanced characteristics, making them uniquely qualified for a broader spectrum of new applications. This research investigates the effects of material preparation on nanocomposites using polyimide (PI) as the host polymer and silicon dioxide (SiO
₂
) nanoparticles as the filler. The fabrication and characterization of the PI/SiO
₂
nanocomposites were explored based on samples produced from two different approaches—a direct mixing process using as-purchased SiO
₂
nanoparticles and a sol-gel process that relied on chemical reactions to produce SiO
₂
inside a solvent. The prepared samples and the distribution of the SiO
₂
nanoparticles in the nanocomposites were characterized with profilometry and scanning electron microscopy (SEM). The characterization showed that the directly mixed samples contained visible nanoparticle agglomerates while the sol-gel films had the nanoparticles uniformly distributed inside the host polymer. The DC dielectric breakdown testing revealed that the sol-gel films outperformed the directly mixed samples at both room (300 K) and cryogenic (164 K) temperatures. When the temperature is cooled down to 92 K, the sol-gel samples demonstrated higher dielectric strengths than pure PI films. Our investigation shows that high-quality PI/SiO
₂
nanocomposites, especially when prepared through the sol-gel process, are promising candidates as dielectrics that can be used in a variety of cryogenic applications.