▎ 摘　　要

NOVELTY - Preparing polyimide-based graphene complex foam material with multilevel structure comprises (i) preparing of polyimide foam including uniformly mixing water-soluble polyamic acid prepolymer, water and triethylamine and carrying out sol-gel reaction to obtain polyamic acid hydrogel obtained, freezing and drying polyamic acid hydrogel, and performing heat treatment, (ii) preparing of two-stage polyimide-graphene/polyimide complex foam including dispersing graphene oxide in water to obtain graphene oxide dispersion liquid, dissolving water-soluble polyamic acid prepolymer in water to obtain polyamic acid solution, stirring and mixing graphene oxide dispersion liquid and polyamic acid solution, immersing polyimide foam in mixed solution by vacuum immersing method, saturating adsorption, freezing and drying and performing heat treatment, and (iii) preparing of three-stage polyimide-graphene/polyimide-graphene complex foam including dispersing graphene oxide in water. USE - The method is useful in the field of building, automobile, aerospace, household appliances, electromagnetic shielding and electromagnetic absorption (claimed). ADVANTAGE - The method: is simple, easy and environmental friendly; and broadens the application range of polyimide foam. The polyimide-based graphene complex foam has a stable structure, low shrinkage rate, high thermal stability, wider bandwidth and excellent comprehensive performance; and achieves absorption of incident electromagnetic waves while maintains excellent heat insulation and thermal stability. DETAILED DESCRIPTION - Preparing a polyimide-based graphene complex foam material with a multilevel structure comprises (i) preparing of polyimide foam including uniformly mixing the water-soluble polyamic acid prepolymer, water and triethylamine, and carrying out sol-gel reaction to obtain polyamic acid hydrogel, freezing and drying the polyamic acid hydrogel, and performing heat treatment, (ii) preparing of two-stage polyimide-graphene/polyimide complex foam including dispersing graphene oxide in water to obtain a graphene oxide dispersion liquid, dissolving the water-soluble polyamic acid prepolymer in water to obtain a polyamic acid solution, stirring and mixing the graphene oxide dispersion liquid and the polyamic acid solution, immersing the polyimide foam obtain in the step (i) in the mixed solution by vacuum immersing method, saturating the adsorption, freezing and drying and performing heat treatment, and (iii) preparing of three-stage polyimide-graphene/polyimide-graphene complex foam including dispersing graphene oxide in water to obtain a graphene oxide dispersion liquid, immersing the two-stage polyimide-graphene/polyimide complex foam obtained in the step (ii) by a vacuum immersing method, saturating the adsorption, freezing and drying and performing heat treatment. An INDEPENDENT CLAIM is also included for a polyimide-based graphene complex foam material with a multilevel structure prepared by above mentioned method.