蜂窝堇青石陶瓷负载的CaZr_4P_6O_(24)涂层的制备及表征

采用溶胶-凝胶法制备了化学组成为CaZr4P6O24(CZP)的溶胶态前驱物,用其涂覆薄壁蜂窝堇青石陶瓷,经过700℃焙烧2h转化为具有低热膨胀特性的结晶态CZP涂层。用X射线衍射和BET(Brunauer-Emmett-Teller)氮吸附法表征了涂层的物相和孔结构,用扫描电镜观察了涂层表面及涂层与基体的界面结合处的形貌,用能量色散光谱仪分析了涂层中的元素分布及含量。结果表明:在蜂窝堇青石陶瓷基体上形成的涂层组成为CZP;表面沉积了19.5%(质量分数)CZP的蜂窝堇青石陶瓷的BET比表面积、孔体积和平均孔径分别为16.4m2/g,0.0225mL/g和2.74nm。CZP涂层与蜂窝堇青石基体的界面结合良好。发动机台架性能试验结果表明:"CZP-蜂窝堇青石"复合载体负载的单钯催化剂表现出与"γ-Al2O3-蜂窝堇青石"负载的单钯催化剂相近的三效转化活性。

PREPARATION AND CHARACTERIZATION OF CaZr_4P_6O_(24) COATING SUPPORTED ON CORDIERITE HONEYCOMBED CERAMIC

Cordierite honeycombed ceramic substrate was coated by the precursor sol of CaZr_4P_6O_(24) (CZP) prepared by sol-gel route. The CZP coating calcined at 700 ℃ for 2 h has low thermal expansion performance. The phase structure and pore structure of the CZP coating were characterized by X-ray diffraction and Brunauer-Emmett-Teller (BET) nitrogen adsorption method, respectively. The morphology of the interfacial joint between the CZP coating and the substrate was observed by scanning electron microscopy. In addition, the elements distribution in CZP coating was analyzed by energy dispersive spectrometer. The results show that the chemical composition of coating formed on the cordierite honeycombed ceramic substrate is CZP. The specific surface area, pore volume and average pore diameter of the cordierite honeycombed ceramic coated by 19.5% in mass CZP are 16.4 m~2/g, 0.022 5 mL/g and 2.74 nm, respectively. The bonding between the CZP coating and cordierite honeycombed ceramic substrate is very good. The results of bench test indicate that the palladium-only catalyst supported by CZP coating has very close three-way catalytic activities to the palladium-only catalyst supported by γ-Al_2O_3 coating.