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The four kinds of Al₂O₃ composite ceramics were prepared using a mixture of 85 wt.% Al₂O₃ (mean size 0.5 μm), 15 wt.% SiC powder with Y₂O₃ as an additive powder (0, 1, 3 and 5 wt.%). The crack-healing strengths were studied as functions of crack-healing temperature and amount of Y₂O₃. The in-situ crack-healing behavior was observed at 1,573 K for 1 h in the air. The heat treated specimen with 3 wt.% of Y₂O₃ showed better crack-healing ability than specimen with 1 or 5 wt.% of Y₂O₃. In case of specimen with 3 wt.% of Y₂O₃, the bending strength of the crack-healed specimen at 1,473 K was recovered to the bending strength of smooth specimen treated at 1573 K. The heat-resistance limit temperature of Al₂O₃ composite ceramics was 1,073 K, 1,373 K, 873 K for the specimen with 1, 3, 5 wt.% of Y₂O₃.
In this paper, we firstly proposed to the boost type PFC circuit for a power factor improving and a harmonic decreasing. The predict current control method is used to control these PFC circuit This current control method has a merit that is possible to improve power factor and harmonics. In addition, we suggested to the active DC filter, which is connected with the DC output terminal, in order to compensate the DC ripple components. Consequently, these results are proved by the simulation tool, PSIM, which is an exclusive simulator of power electronics.
Al₂O₃/SiC composite ceramics were sintered to evaluate the bending strength and elastic wave characteristics. The three-point bending test was carried out under room temperature. The elastic wave was detected by fracture wave detector. The crack healing behavior was investigated from 1373 K to 1723 K. The bending strength of Al₂O₃/SiC composite by nanocomposite is higher than that of Al₂O₃ monolithic. Crack-healing behavior depended on an amount of additive powder Y₂O₃. In Al₂O₃/SiC composite ceramics with 3 wt. % Y₂O₃ for additive powder, the bending strength at 1573 K is about 100% increase than that of the smooth specimens. The strength of Al₂O₃/SiC composite ceramics was a little higher than those of Al₂O₃ monolithic. In proposition to an amount of additive, a large amount of Si and O, and little C were detected.