In-Situ Processing of Laminated Ceramic Composite for Electrochemical NOx Reduction System

摘要

Electrochemical NOx reduction system composed of three-layered laminate, 8 mol percent Y_2O_3-ZrO_2 (YSZ)//70 vol percent YSZ/BaMnAl_(11)O_(19) (BMA)//30 vol percent YSZ/BMA, could be successfully synthesized at 1550 deg C by taking into account the shrinkage mismatch between YSZ and YSZ/BMA layers. Two types of alumina, alpha- and gamma-phase, were used as an alumina source for the in-situ processing of the laminate. The total shrinkage of the precursor powder for the composite using gamma-alumina was closer to that of YSZ than that using alpha-alumina. The shrinkage rate of the precursor powder was adjusted to that of YSZ at the heating rate of 2 deg C/min. The shrinkage curve of YSZ/BMA composite consisted of the first shrinkage region, a plateau region and the second shrinkage region. The plateau region, in which the formation of BMA crystallites inhibited the growth and sintering of YSZ, decreased with increasing YSZ/BMA ratio. The control of heating rate and the use of the intermediate layer with compositional gradient lead to the development of the three-layered laminate tightly bonded with each other without any separation, which can be applied for the electrochemical NOx reduction system.