Study On Synthesis, Character And Properties Of Carbon Nanomaterials

In recent years, carbon nanomaterials have been paid tremendous attention due to their excellent properties and potential applications in many fields.In this paper, carbon nanotubes were prepared via the decomposition reaction of (C5H5)2 Fe at low temperatures. After (C5H5)2 Fe was kept at 550℃for 30 h, large numbers of carbon nanotubes with good uniformity were prepared, which could be observed by TEM and FESEM. XRD patterns and TEM pictures indicate that there were a small quantity ofα-Fe nanoparticles at the top of carbon nanotubes. Raman analysis results indicate the relative disorder and low graphitic crystallinity of the product. The sizes of carbon nanotubes can be controlled by the reaction temperatures and holding times.Pure carbon nanomaterials with high surface area were prepared via the reaction between hollow carbon spheres and KOH. XRD and Raman analysis results indicate the relative disorder and low graphitic crystallinity of the products. The products have many holes, rough surface and thin carbon walls, which can be observed by HRTEM and FESEM. In a general way, the surface area and pore volume increase with the rising content of KOH. But if KOH is excessive, or the activation time is too long, the surface area and pore volume will decrease. When the value of KOH:C is 6, the maximum of surface area reaches 950 m2/g; when the value of KOH:C is 8, the maximum of pore volume reaches 0.636 cm3/g.The activation of hollow carbon spheres by KOH can be promoted by KBr. The content of KBr is higher, the promotion effect is more obvious. K+ can make the number of microporous increase greatly at the beginning. Br-can promote the transmission of electron, and improve the activation ability of activation centers. If KBr is excessive, the surface area and pore volume will decrease.The microwave absorption properties of products are controlled by the activation degree, instead of surface area and pore volume. The rising contents of KOH and KBr can both promote the activation of hollow carbon spheres, increase the permittivity and reflection loss, and improve the microwave absorption properties. The hollow carbon spheres which were activated by KOH and KBr have lower surface area and pore volume, but more excellent microwave absorption properties due to the further activation.