Modification of surface structure and mechanical properties in polyimide aerogel by low-energy proton implantation

In this work, the structure and mechanical properties of polyimide aerogel under low energy proton implantation were investigated. The results indicated that the three-dimensional network of aerogel would become densification and even transform into the layer-by-layer structure with increasing the proton fluence. Furthermore, the layer-by-layer structure was observed firstly near the end of the proton range and then expanded gradually out to the sample surface, moreover the layered region tends to be thicker with the proton fluence. The results of fluorescence spectroscopy and Raman spectra indicated that the molecular chains of polyimide would be degraded firstly and then rearrange to form amorphous carbonized structure. The nano-indentation results shown that the average contact pressure and elastic modulus of the implanted surface were detected about twice that of the as-received aerogel. This work paths a new way of proton implantation to control the surface structure and mechanical properties of organic aerogel.