Microstructure of low temperature processed CNFs/glass nanocomposites

Carbon nanofibers/glass (CNF/G) nanocomposites were obtained from a glass powder of low melting point and pristine CNFs. Green bodies containing from 0 to 22 % (v/v) of CNFs were sintered under nitrogen atmosphere in the 550–700 °C temperature range with different holding times. A fully microstructure characterization, by means of Hg porosimetry and N2 adsorption, was carried out for understanding the CNFs/G composites behavior during the sintering process. This understanding is required to optimize the microstructural design of CNFs/glass nanocomposite materials. During sintering two different and simultaneous phenomena occur the matrix crystallization and the pore formation. The glass matrix crystallization temperature decreases from 650 to 550 °C, when CNFs concentration increases to 22 % (v/v). The glass matrix produces the CNFs degradation and generates gaseous species which lead to homogeneous or foamy materials. This depends on the CNFs concentration and thermal treatment conditions. Foamy nanocomposites present pore size distributions with pores <0.1 and close to 20 μm. The glass matrix wets the CNFs and produce their degradation been of 1 % of carbon loss in all nanocomposites.