Gas desorption and adsorption properties of inner coating materials used for cathode ray tube - graphite, titanium oxide and water glass mixed material

Abstract

The gas desorption properties of carbon based materials coated on inner wall of a cathode ray tube were examined by using a technique of thermal desorption spectroscopy (TDS). This material consists of graphite powder, titanium oxide (TiO2) powder and water glass. The major outgassing species observed in the temperature range from RT to 500 °C were CO2 and H2O. The major outgassing source was graphite. In order to reduce the gas desorption in the cathode ray tube, the heat treatment with temperature higher than 400-500 °C is necessary. Since the surface morphology of graphite-water glass material was dense, the degassing was insufficient by baking treatment in the atmosphere. On the other hand, the degassing was very easy for graphite-TiO2-water glass material, because of the porous structure. The gas adsorption experiments were also conducted. The adsorption amount of H2O or CO2 increased as the composition ratio of graphite powder. The gas adsorption capacity largely increased by the addition of TiO2 powder into the graphite-water glass material. The enhancement of adsorption capacity is due to that the surface structure became porous and also the effective surface area large by the addition of TiO2 powder.