Effect of purification methods on the cross-sectional field emission properties of carbon nanotube and graphene composite films

Carbon nanotubes (CNTs) are excellent materials for field emission because of their large aspect ratio, low-threshold field and stable chemical structure. However, the low adhesive bonding strength between CNTs and the supports presents a practical challenge in environments with a high field emission current density. We used a vacuum filtration method to prepare multiwalled CNT (MWCNT)/reduced grapheme oxide (r-GO) composite films in which CNTs were uniformly dispersed in the r-GO layers. Compared with unmodified films, films in which CNTs are dispersed show better field emission performance, and the adhesive bonding strength between the CNTs and the supports is enhanced. At the same time, because MWCNTs grown by chemical vapor deposition (CVD) contain impurities such as carbonaceous materials and catalyst particles, we use different purification methods to treat the MWCNTS, and the effects of these purification methods on the field emission properties of the composite films are analyzed. A comparison of the field emission properties of the unpurified, calcined, calcined/centrifuged and acid-purified composite films shows that the calcined/centrifuged composite films have the best field emission performance.