npsm 새물리 New Physics : Sae Mulli

pISSN 0374-4914 eISSN 2289-0041


Research Paper

New Phys.: Sae Mulli 2018; 68: 1167-1172

Published online November 30, 2018

Copyright © New Physics: Sae Mulli.

Measurement of Thermal Diffusivity and the Optical Properties of a Carbon Nanotube Dispersion by Using the Thermal Lens Effect

열렌즈 효과를 이용한 탄소 나노 튜브 분산액의 열확산도와 광학적 특성 측정

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


Received: September 16, 2018; Revised: October 12, 2018; Accepted: October 17, 2018

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.

Keywords: Thermal lens effect, Multi-walled carbon nanotube, Z-scan, Nonlinear optical coefficient, Thermal diffusivity

탄소 나노 튜브는 탄소 원자들이 육각형의 벌집모양으로 서로 연결된 고분자 탄소동소체로 다중벽일 경우 3000 W$\cdot$m$^{-1}\cdot$K$^{-1}$, 단일벽일 경우 6000 W$\cdot$m$^{-1}\cdot$K$^{-1}$ 정도로 매우 높은 열전도도를 보인다. 본 연구에서는 단일 빔과 이중 빔 방법으로 열렌즈 효과를 이용하여, 1.5 M 다중벽 탄소 나노튜브 분산액의 투과율과 열확산도를 측정하였다. 단일 레이저 빔의 진행방향으로 시료를 움직이는 z-scan 방법을 통해 비선형 광학계수들을 구하고, 이중 레이저 빔을 이용하여 열확산도를 측정하였다. 펌프 빔으로는 파장 532 nm이고 세기가 100 mW인 DPSS (Diode-pumped solid state, DPSS) 레이저를 사용하였고, 프로브 빔으로는 파장이 633 nm이며 세기가 5 mW인 He-Ne 레이저를 사용하였다. 실험 결과 농도가 9.99, 11.10, 16.65, 19.98 mM일 때 비선형 흡수계수는 각각 0.046, 0.051, 0.136, 0.169 m/W였다. 또한 비선형 굴절률은 0.20, 0.51, 1.25, 1.32 $\times$ 10$^{-11}$ m$^2$/W였고, 열확산도 평균치는 1.33 $\times$ 10$^{-6}$ m$^2$/s이었다.

Keywords: 열렌즈 효과, 다중벽 탄소 나노 튜브, Z-스캔, 비선형광학계수, 열확산도

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