Formation of three-dimensional carbon nanotube structures by controllable vapor densification

A new and versatile vapor densification method is developed to fabricate various three-dimensional and dual-porosity carbon nanotube (CNT) structures. By introducing the exposure time of CNTs to the solvent vapor as a control parameter to vary the amount of collected solvent, this method is capable of producing different degrees of densification with high controllability and uniformity. It is also found that the densification effect is highly dependent on the original CNT volume fractions in their forest form, low volume fraction causing shape distortion in densification. An O-2 plasma etching of the entangled nanotubes can help maintain the shapes of CNT forests, but only for those in a limited range of CNT volume fraction.