Synthesis and characterization of carbon nanofiber/alumina composite by extrusion casting

A macroscopic carbon nanofiber (CNF)/alumina composite was synthesized by extrusion casting. Its textural and mechanical properties, crystallinity, surface acidity and thermal stability were investigated using N2 physisorption, scanning electron microscopy, temperature programmed desorption of NH3 (NH3-TPD), X-ray diffraction and thermal gravimetric (TG) analysis. It was shown that the CNFs and alumina were evenly and intimately blended in the composite which displayed a lateral crushing strength greater than 100 N/cm. The composite had a mesoporous structure, possessing a surface area greater than 320 m2/g and a narrow pore size distribution. NH3-TPD results demonstrated that, compared to those on commercial alumina, the total number of acid sites on the composite (related to the total amount of desorbed NH3) was significantly increased while the number of strong acid sites (related to the amount of desorbed NH3 between 400 and 500 °C) was distinctly decreased. TG analysis revealed that the composite was stable up to 600 °C in air or 900 °C in an inert atmosphere.