Although graphite has excellent thermal conductivity of 200-800 W/mK, there are definite limits when applying graphite to thermally conductive materials, such as a coating material for printed circuit boards (PCB), an additive to the adhesive for the assembly of electronic chips, and a filler for thermal spreader pads. The problems are largely attributed to the electrically conductive property. To endow graphite with an electrically insulating property, graphite was coated with a well-grown alumina layer using polyvinylpyrrolidone (PVP) as a cohesive promotor. Aluminum isopropoxide (AIP) was used as the alumina precursor and PVP was used to improve the cohesion between graphite and alumina. An alumina-coating on graphite was conducted by a base-catalyzed sol-gel reaction. The changes in the morphology and the amounts of coated alumina, as well as the electrically insulating properties were investigated. An optimized condition to make alumina@PVP@graphite was determined by changing the amounts of AIP and PVP. The synthesized alumina@PVP@graphite was categorized as an electrical insulator with a high surface resistivity of about 1012 ohm/sq.

흑연은 200~800 W/mK의 우수한 열전도성을 지니고 있으나, 인쇄회로기판의 코팅 재료, 반도체 실장용 접착제의 충전제, 열확산 쉬트와 같은 열전도성 복합재료로 사용하기에 한계가 있다. 이는 전기 전도성에 기인한 것으로, 흑연에 전기 절연성을 부여하기 위하여 폴리비닐피롤리돈(PVP)을 접착력 향상제로 사용하여 알루미나 층을 코팅하였다. 알루미늄 이소프로폭사이드(AIP)를 알루미나의 전구체로 사용하였다. 알루미나 코팅은 염기성 촉매하에서 졸-젤 반응을 통하여 이루어졌다. 제조된 결과물의 모폴로지 변화, 코팅된 알루미나의 양 및 전기 절연성이 조사되었으며, 최적의 알루미나@PVP@흑연의 합성 조건을 찾기 위하여 AIP와 PVP의 양을 변화시켰다. 합성된 알루미나가 코팅된 흑연은 면저항이 1012 ohm/sq으로 전기 절연성을 보유하였다.

Keywords: alumina coating; graphite; sol-gel reaction