Papers by Author: Shafreeza Sobri

Abstract: Multi walled carbon nanotubes (MWCNTs) were synthesized using floating catalyst-chemical vapor deposition (FC-CVD) with ferrocene and benzene as catalyst and carbon source, respectively. Argon was used as a purging gas while hydrogen was used as a carrier gas. Hydrogen flow rate, reaction time and reactor temperature were varied to obtain high yield and purity of MWCNTs. The morphology and microstructures of MWCNTs produced were studied using Scanning Electron Microscopy (SEM). It was found that the maximum yield and purity of MWCNTs were produced at hydrogen flow rate of 300 ml/min with reactor temperature of 900°C and reaction time 45 minutes. It was observed that the MWCNTs are film-like, randomly oriented and in some cases entangled with uniform diameter.

Abstract: This research was carried out to monitor and investigate the gas sensing effects on carbon nanotubes (CNTs) by a systematic study of the variations in the electrical resistance as sensor signal induced by adsorption of CO2 and CH4 gaseous molecules. The CNTs were synthesized by Floating Catalyst Chemical Vapor Deposition (FC-CVD) method on quartz substrate under benzene bubble at temperature of 700°C. Then, they were tested for gas sensing applications operating at room temperature. Upon exposure to gaseous molecules, the electrical resistance of CNTs dramatically increased for both CO2 and CH4 gases with short response time and high sensitivity. It was also observed that the CNTs device behaves as a p-type semiconductor when exposed to gaseous molecules. In addition, the recovery of the sensors and mechanism of gas sensing procedure are discussed.

Abstract: This research was carried out to investigate the effect of gas adsorption towards the electrical resistance of carbon nanotubes (CNTs) thin film. CNTs were synthesized by Floating Catalyst Chemical Vapor Deposition (FC-CVD) method on quartz substrate at 950°C under methane gas flow rate of 150 Standard Cubic Centimeters per Minute (SCCM). Then, the electrical resistance of CNTs was measured by exposing the sensors to CO2 and CH4 gases operating at room temperature. The sensors showed high responses to the gaseous molecules. In the same experimental conditions, the recovery of the sensors was different for CO2 and CH4. It was also observed that the CNTs device behaves as a p-type semiconductor when exposed to gaseous molecules. The fabrication process was relatively simple and did not require special techniques.