The properties of excited xenon atoms in the discharge cells of a plasma display panel are investigated by measuring the excited atom density via laser absorption spectroscopy. The density of the excited xenon atoms in the metastable state increases from zero, reaches its peak, and decreases with time in the discharge cells, as expected from a theoretical model. The profile of an excited xenon atom is also studied in terms of the xenon mole fraction. The typical density of excited xenon atoms in a metastable state is on the order of 1013 atoms/cm3.

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A thick ZrC layer was successfully coated on top of a SiC buffer layer on carbon/carbon (C/C) composites by vacuum plasma spray (VPS) technology to improve the ablation resistance of the C/C composites. An optimal ZrC coating condition was determined by controlling the discharge current. The ZrC layers were more than 70 µm thick and were rapidly coated under all spraying conditions. The ablation resistance and the oxidation resistance of the coated layer were evaluated in supersonic flames at a temperature exceeding 2000 °C. The mass and linear ablation rate of the ZrC-coated C/C composites increased by 2.7% and 0.4%, respectively. During flame exposure, no recession was observed in the C/C composite. It was demonstrated that the ZrC coating layer can fully protect the C/C composites from oxidation and ablation.

The exited Xe atoms in the 1s 5 metastable state and the 1s 4 resonance state across the two sustaining electrode have been monitored in a micro-discharge cell of alternating current plasma display panels (PDPs) by laser absorption spectroscopy. In this study, it is found that the maximum excited xenon density is 5 4 10 12 cm 3 in the 1s 5 metastable state and 1 2 10 12 cm 3 in the 1s 4 resonance state for the PDP cell with gap distance of 150 m and width of 350 m under the fixed gas pressure of 350 torr and a mixture of Xe content ratio of 10% with Ne under driving frequency of 35 kHz. It is also observed that the exited Xe atom density and the plasma ion density are strongly correlated with one another in this experiment. It is noted that the plasma ion density reaches a minimum at the center of electrode gap and a maximum of 9 0 10 11 cm 3 in a region located 200 m away from this center under the filling pressure of 350 torr, which corresponds to the strongest discharge in alternating current plasma display panel (ac-PDP). When increasing PDP driving frequency from 35 kHz, 50 kHz up to 100 kHz, it is found that density of excited Xe atom in the 1s 5 metastable state increase from 6 5 10 12 cm 3 up to 1 39 10 13 cm 3Index Terms-Alternating current plasma display panel, excited Xe atom, laser absorption spectroscopy, metastable state, plasma ion density, resonance state.

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In this paper, spatiotemporal behavior of the excited Xe-atom density of 1s 5 metastable state was investigated by laser-absorption spectroscopy in alternating-current plasma display panel in accordance with the Xe mole fraction to Ne, which can be connected to the relative luminous efficiency over all spaces in a discharge cell. The various test panels with Xe mole fractions of 4%, 7%, 10%, and 15% to Ne have been used in this paper, in which discharge cell with T-typed indium-tin-oxide electrode and closed-barrier rib has been adopted. In this paper, the density of metastable state for the excited Xe atom is found to increase slowly beyond the Xe mole fraction of 10%. It is also accordingly noted that the luminous efficiency increases slowly beyond the Xe mole fraction of 10%, which is similar to that of the density of the excited Xe atoms in the metastable state in this paper.Index Terms-Excited Xe-atom density, laser-absorption spectroscopy, metastable state, plasma display panels (PDPs), Xe mole fraction.

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Thermal plasma wind tunnels with power of 0.4 MW and 2.4 MW have been constructed at Chonbuk National University (CBNU) in Korea. This facility is capable of producing a heat flux greater than 10 MW/m2, a level that is relevant for testing thermal protection materials that are used for re-entry vehicles in space transportation. A segmented arc plasma torch was adopted as a plasma source; this was designed to have high thermal efficiency and long life, and to produce a supersonic plasma flow with enthalpy greater than 10 MJ/kg. We investigated the characteristics of the supersonic plasma flow using intrusive and non-intrusive diagnostic systems. Ablation characteristics of potential thermal protection materials such as carbon/carbon composites and graphite were investigated with the plasma wind tunnel. Cracks and pores in the materials accelerated the erosion. For carbon/carbon composites, the pores grew and the cracks which occurred at the interfaces between the carbon fibres and the matrix propagated, while for the graphite, the erosion started at the pores and peeled off the surface.