Stabilization and thermal conductivity measurement of MWCNT nanofluids by using the $3-{\omega}$ method

3-${\omega}$ 방법을 이용한 다중벽 탄소나노튜브 나노유체의 침전 안정성 및 열전도계수 측정에 관한 실험적 연구

The 3-omega (3-${\omega}$) method is utilized to measure the thermal conductivity of nanofluids. A metal line heater on a silicon nitride membrane bridge structure is microfabricated by a bulk silicon etching method. Localized measurement of the thermal conductivity within the nanofluids droplet is possible by the fabricated 3-${\omega}$ sensor. Time varying AC temperature amplitudes and thermal conductivities are measured to check the stability of the nanofluids containing multi-wall carbon nanotubes (MWCNTs). Stabilities of MWCNT nanofluids prepared with different chemical treatments are compared. Acid treated MWCNT showed best dispersion stability in water while MWCNTs dispersed in water with surfactants such as Gum Arabic and Sodium dodecyl benzene sulfate showed clear sign of gravity dependence.