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Measurement of Thermal Diffusivity and the Optical Properties of a Carbon Nanotube Dispersion by Using the Thermal Lens Effect
New Phys.: Sae Mulli 2018; 68: 1167~1172
Published online November 30, 2018;
© 2018 New Physics: Sae Mulli.

Hyunwoo PARK1, Hyunki KIM1, Sok Won KIM*1, Joohyun LEE2

1 Department of Physics, University of Ulsan, Ulsan 44610, Korea
2 Korea Research Institute of Standards and Science, Daejeon 34113, Korea
Correspondence to:
Received September 16, 2018; Revised October 12, 2018; Accepted October 17, 2018.
cc This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Carbon nanotubes (CNTs) are structures of carbon atoms bonded together in hexagonal honeycomb shapes, with multi-walled CNTs having a very high thermal conductivity of 3000 W/m$\cdot$K and single-walled CNTs having a conductivity of 6000 W/m$\cdot$K. In this work, the transmittance and the thermal diffusivity of a multi-walled carbon nanotube dispersion with a concentration of 1.5 M were measured using a single beam method, a dual beam method, and the thermal lens effect. The nonlinear optical coefficients were obtained by using the z-scan method, which moved the sample in the direction of propagation of the single laser beam, propagation and the thermal diffusivity was measured using a double laser beam. As a pump beam, a diode-pumped solid state (DPSS) laser with a wavelength of 532 nm and an intensity of 100 mW was used. As the probe beam, a He-Ne laser having a wavelength of 633 nm and an intensity of 5 mW was used. The experimental result shows that when the concentrations of the sample were 9.99, 11.10, 16.65, and 19.98 mM, the nonlinear absorption coefficients were 0.046, 0.051, 0.136 and 0.169 m/W, respectively. Also, the nonlinear refractive indices were 0.20, 0.51, 1.25 and 1.32 $\times$ 10$^{-11}$ m$^2$/W, respectively, and the average thermal diffusivity was 1.33 $\times$ 10$^{-6}$ m$^2$/s.
PACS numbers: 66.30.Xj, 42.65.-k, 61.48.De
Keywords: Thermal lens effect, Multi-walled carbon nanotube, Z-scan, Nonlinear optical coefficient, Thermal diffusivity

February 2019, 69 (2)
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