Product Code: ICAL06_M1107

Light Emission Characterization from Multiwalled Carbon Nanotubes under CO2 Laser Irradiation
Yong Zhang, Tsinghua University; Beijing Peoples Republic of China
Dehai Wu, Tsinghua University; Beijing Peoples Republic of China
Minlin Zhong, Tsinghua University; Beijing Peoples Republic of China
Tao Gong, Tsinghua University; Beijing Peoples Republic of China
Wenjin Liu, Tsinghua University; Beijing Peoples Republic of China
Presented at ICALEO 2006

Since their discovery in 1991, carbon nanotubes (CNTs) have demonstrated many remarkable mechanical, electrical and thermal properties, showing very attractive potentials in many fields. This paper investigates the interaction between infrared laser and carbon nanotubes. A visible light emission was observed from well oriented multiwalled carbon nanotubes (MWNTs) when irradiated by a 25W and 1mm diameter focused CW CO2 laser (λ=10.6µm) in a 1.010-3Pa vacuum chamber. The uniform and well oriented MWNT films with thickness of 3mm-thick used in the experiments were synthesized by chemical vapor deposition. In our experiments, MWNTs act like an incandescent lamp. The influence of incident angle of laser beam (defined by angle between laser beam and grown-orientation of MWNTs) on this light emission was studied. Irradiance and spectrum of such light emission and temperature of MWNTs during the irradiation, were measured. The results showed that the irradiance of the light emission is closely related to the incident angle. When incident angle varied from 0° to 90°, i.e. laser beam varied from parallel to vertical to the axis of MWNTs, irradiance decreased. The minimum irradiance was approximately 180Lux by a distance of 14cm. Similarly, temperature of MWNTs also revealed to be dependent to incident angle. However the light emission spectra were found to have similar line shapes versus different incident angles and be much different from blackbody body curve at the same temperature. It indicated that light emission spectrum was independent of incident angle and was not simply caused by Joule-heating, which originated from the thermal effect of CO2 laser. Since invisible IR laser was converted to visible light, this kind of light emission showed a feature of blueshift. This light emission from oriented MWNTs under CO2 laser was considered to be the combination of laser-induced photoluminescence and Joule-heating.

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