Multiwalled carbon nanotubes and their composites as alcohol sensors and field electron emission cathodes / Faridah Abdul Razak

• Main Author: Faridah, Abdul Razak
• Format: Thesis
• Published: 2016
• Subjects: Q Science (General); T Technology (General)
• Online Access: http://studentsrepo.um.edu.my/6613/4/faridah.pdf; http://studentsrepo.um.edu.my/6613/

Composites of multiwalled carbon nanotubes (MWCNTs) with polyethylene oxide and hybrid films of MWCNT with oxide materials (TiO2 and ZnO) were prepared for alcohol vapor sensing and field electron emission studies. The justification for fabricating such materials was to overcome the problem associated with using pure MWCNTs where adhesions to substrates surfaces were generally poor. Poly(ethylene oxide)/multiwalled carbon nanotube (PEO/MWCNT) composites were fabricated using the solution cast technique and characterized using field emission scanning electron microscopy (FESEM), fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and conductivity analyses. Results of the analysis showed good distribution of MWCNT in the composite which were used as alcohol vapor sensors. It was discovered that a poly(ethylene oxide)/multiwalled carbon nanotube (PEO/MWCNT) composite provided the best sensitivity for both ethanol and methanol vapor with detection limits down to 10 ppm. The effect of MWCNT loading the composites on the sensitivity to ethanol and acetone sensing showed an increase in the sensitivity with decreasing loading and increasing in dynamic range with increase loading. This shows that the amount of MWCNT loading will determine the application trade off, either for high sensitivity or high dynamic range. Hybrid material films of TiO2 and ZnO with MWCNT were fabricated using the electrophoresis process on silver substrates. FESEM and Raman spectroscopy were used to analyze the deposited composite materials. Field electron emission properties were studied as a function film thickness and compared with pure MWCNT results. For all films, the maximum current densities were observed with the thinnest films deposited for 1 minute. This was due to the shielding effect in the thicker films. Also, the inclusion of the oxide materials into the films resulted in significant increase in the maximum current densities compare to iv the corresponding pure MWCNT films. This is evident that the oxide particles acted as spacers which spread the MWCNT and reduced the shield effect.