Donghua University, China
Title: The control of pore sizes in porous carbon fiber and its enhanced microwave absorption
Dr. Guang Li received her M.Sc in Chemistry from China Textile University in 1985, and her Ph.D in material science and engineering from Donghua University in 2006. She was a Senior Visiting Scholar in the University of Twente (Netherlands). She has been a full Professor at Donghua University sine 1999, and continuously working on high performance polymer , porous carbon fibers and their associated processing and applications. She has published more than 100 scientific papers in high-impacting peer-reviewed journals and has given more than 24 keynote/invited/oral presentations, co-authored 4 books, and owns 26 patents. Dr. Li has been awarded several prizes for recognizing her contributions to science and technology.
As one of carbon materials, the porous carbon fiber has played a great role as catalyst support, separation by absorption, gas storage etc. based its high aspect ratio. Among related publications, few studies focused on the microwave absorption characteristics of porous carbon fibers, although a great number of papers concerned carbon materials such as carbon black, fiber, tube as microwave absorbents[1-3]. In this study, Porous carbon fibers were prepared through carbonization of the blend fibers composed of poly(acrylonitrile) (PAN) and poly(methyl methacrylate) (PMMA）with 70 wt % of PAN. The pore size in porous carbon fibers could be controlled by changing the average molecular weight of PAN, The pores of 1-10μm and 0.1-1μm in diameter were obtained from the blend fibers where the average molecular weight of PAN is 51000 and 83000 g/mol, respectively(Figure 1). The obtained porous carbon fibers were used as absorbents to make epoxy composites with addition of 2-6 wt %. The microwave absorption properties were stimulated based on a model for a single-layer plane wave absorber. The results explained the porous carbon fiber showed much better microwave absorption than carbon nanofiber, and the porous carbon fiber with small size of pores showed much better microwave absorption than that with large size of pores, as shown in figure 2. It is believed that the enhanced microwave absorption from the porous carbon fibers is due to a combination of the dielectric-type absorption and the interference of multi-reflected microwaves[3-6]. When the pore size in porous carbon fibers is large, the air-absorber interfaces could be reduced at the same pore volume. Therefore, the superior microwave absorption of composites filled by porous carbon fiber with smaller pore size may be ascribed to the combination of absorption and interference of microwaves