정전기 방전에 의해 제조된 흑연박리 그래핀 첨가 폴리이미드 막의 열전도 향상 = Thermal Conductivity Enhancement of Polyimide Film Induced from Exfoliated Graphene Prepared by Electrostatic Discharge Method

국문 초록 (Abstract)

본 연구에서는 폴리이미드(polyimide; PI) 막(film)의 열전도도를 향상시켜 그 응용성을 확대하고자, 정전기 방전법을 이용하여 흑연봉으로부터 그래핀을 제조하고 제조된 그래핀을 첨가하여 폴리아믹산(polyamic acid; PAA) 전구체로부터 200 μm두께의 폴리이미드 기반 열전도 막을 제조하였다. 정전기 방전 기법으로 생산된 그래핀은 라만, XPS, TEM등을 이용하여 물성을 평가하였다. 제조된 그래핀은 라만 스펙트럼 분석 결과 I_D/I_G 값이 0.138이며, XPS 분석 결과 C/O 비율이 24.91로 구조적, 표면화학적으로 우수한 물성을 나타내었다. 또한, 흑연 박리 그래핀의 첨가량에 따라 폴리이미드 막의 열전도도는 지수함수적으로 증가하였으며, 그래핀 함량을 40% 초과 시에는 폴리이미드 막을 제조할 수 없었다. 그래핀을 폴리아믹산 중량 대비40 wt% 첨가하여 제조된 폴리이미드 막의 열원반(hot disk) 열전도도는 51 W/mK를 나타내었으며, 순수한 폴리이미드 막의 열전도도(1.9 W/mK)보다 크게 향상되었다. 이 결과는 정전기 방전기법으로 제조된 박리 그래핀의 우수한 물성에 기인한 것으로 판단된다.

다국어 초록 (Multilingual Abstract)

A thermally conductive 200 μm thick polyimide-based film was made from a polyamic acid (PAA) precursor containing graphene prepared from graphite rod using an electrostatic discharge method in order to improve the thermal conductivity and expand the applicability of polyimide (PI) film. Properties of graphene produced by electrostatic discharge were measured by Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy (XPS). As a result of Raman spectrum and XPS analyses of as-prepared graphene, the I_D/I_G ratio was 0.138 and C/O value was 24.91 which are excellent structural and surface chemical properties. Moreover, thermal conductivities of polyimide films increased exponentially according to graphene contents but when the graphene content exceeded 40%, the polyimide film could not maintain its shape. The thermal conductivity of carbonized PI film made from PAA containing 40 wt% of graphene was 51 W/mK which is greatly enhanced from the pristine carbonized PI film (1.9 W/mK). This result could be originated from superior properties of graphene prepared from the electrostatic discharge method.

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