투명 알파 알루미나 코팅층의 미세구조와 투광성에 미치는 원료분말의 영향

Abstract

Raw powders(AP450, AL-160SG3, KLS-51, KAM)of alpha alumina which have different mean particle sizes were selected for investigating relationship between the mean particle size and transmittance of alpha alumina films. A mean particle size was measured by a particle size analyzer. Mean particle size of AP450, AL-160SG3, KLS-51 and KAM were 0.8㎛, 0.84㎛, 1.77㎛ and 4.44㎛, respectively. It was confirmed through XRD(X-ray diffraction) that raw powders were in alpha phase. For fabrication of alpha alumina films by GSV(granule spray in vacuum), raw powders were granulated by spray drying. Granules were heated to remove binders at 650℃ for 2hours in an electric furnace and then sieved for filtering large agglomerates. After heating and sieving, transparent and dense alumina films were successfully deposited on slide glass and quartz by GSV. Phases of alumina films were determined alpha by SAD(selective area diffraction). Three alumina films were fabricated by AL-160SG3 granules on quartz and their thicknesses were approximately 0.1㎛, 0.5㎛, 1.0㎛. Transmittances of alumina films were measured through UV visible spectrometer. It was confirmed that the transmittance of alumina films decreased as thickness of alumina films increased. Thicknesses of alumina films made by GSV using four kinds of granules which have different mean particle sizes were controlled to be approximately 1㎛. As particle size of alumina raw power increased, the transmittance of the alumina film decreased. Surface roughness values (Ra, Rq) of alumina films made from AP450 and AL-160SG3 were smaller than those of alumina films made from KLS-51 and KAM. The microstructures and cross-sections of alumina films were observed by TEM. Alumina films have nanoscale microstructure and their grain size were mostly 5-10nm. Above results revealed that the particle size of raw powder was closely related to the surface roughness of the alumina film. But any consistent relationship between the grain size in alumina films and particle size of raw powder/transmittance was not found.