Synthesis of Silane-Modified Carbon Nanotubes via a Sol–Gel Process and Their Characteristics for Field Emission Applications

Abstract

The silane-modified, acid-treated carbon nanotubes (silane-modified HCNTs) were prepared using acid-treated carbon nanotubes (HCNTs) and octyltriethoxysilane (OTES) via the sol–gel process. The silane-modified HCNTs and the HCNTs were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and transmission electron microscopy (TEM). The Raman spectra showed that there were larger reactive sites on nanotubes treated in the H2SO4/HNO3 mixture acid for 2 h. The chemical structural effects on the morphology, dispersion, and thermal and emission properties of the carbon nanotube emitter paste were investigated by scanning electron microscopy (SEM), SEM mapping, ultraviolet–visible (UV–vis) spectrophotometry, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), emission pattern, and current–voltage curve measurements. The UV–vis spectrophotometry indicated that the silane-modified HCNTs could be stably dispersed in toluene over 96 h. It was found that the compatibility between silane-modified HCNTs and the matrix material was mainly due to the interpenetrating polymer network structure between them. The thermal stability of the silane-modified HCNT emitter paste was improved by increasing the content of silane-modified HCNTs. A homogeneous emission was observed when using the silane-modified HCNT emitter paste. The current density extracted from the sample with the silane-modified HCNT emitter paste was higher than that with the HCNT emitter paste at a constant voltage. The turn-on fields of 3 wt % silane-modified HCNT emitter paste and HCNT emitter paste were 1.9 and 5.6 V/µm, respectively.