Biporous nanocarbon foams and the effect of the structure on the capillary performance

Biporous nanocarbon foams (NC foams) which have both nano-pores and micro-pores, were fabricated and used to explore the liquid transportation in the porous structures formed by nanomaterials. Scanning electron microscopy was utilized to observe the structure of the NC foams. Capillary rise tests using acetone as the working fluid were conducted by the IR thermal imaging method. The results show that the capillary rise height of the NC foam with 65 mu m micro-pore size was 47% higher than that with 9 mu m micro-pore size in 50 s. The capillary performance of the NC foams was reduced when its density was higher than 60 mg/cm(3). A model is built to illustrate the effect of both nano-structure and micro-structure on the transportation of working fluid in the biporous foam. The data indicates that the nano-structure generated high capillary pressure while the microstructure provided low resistant pathways for fast liquid transportation. The size of micro-pores and the ratio of micro-pores to nano-pores were two important factors. It is demonstrated that the NC foams had large sorption capacity up to 878 mg/cm(3) and their capillary performance was further enhanced when using a substrate.