摘要: 采用连续浸渍法制备了一系列非贵金属稀燃NO x 阱(LNT)催化剂CuO-K 2 CO 3 /TiO 2 , 考察了Cu负载量对EXAFS), 氢气程序升温还原(H 2 -TPR)和原位漫反射红外光谱(in-situ DRIFTS)等技术详细表征了催化剂的结 构. 结果表明, 不同Cu负载量的催化剂中, 铜物种均主要以CuO相存在. 铜的负载量直接影响铜物种、钾物种 的存在状态, 高分散的CuO相与表面K 2 CO 3 之间存在较强相互作用, 这种相互作用不仅有利于NO x 的储存, 而 且有利于增强催化剂的稳定性. in-situ DRIFTS结果表明, NO x 储存过程中产生的两个负峰(1436和1563 cm -1 )缘于碳酸盐的分解, 这间接证明了碳酸盐作为储存介质参与到NO x 储存反应中. EXAFS结果表明, 经过 15个稀燃/富燃循环测试, 催化剂中的CuO相仍保持稳定. 基于以上表征结果, 提出了CuO和K 2 CO 3 在催化剂表 面的分布模型, 并探讨了NO x 储存还原的可能机理.

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La 0.8 Sr 0.2 Mn 1-x Co x O 3 (x = 0, 0.1, 0.3) samples were prepared via the conventional high-temperature solid-state reaction method. The effects of Co doping on Griffiths phase, magnetic entropy change, critical behavior, and electrical transport properties of La 0.8 Sr 0.2 MnO 3 (LSMO) polycrystalline samples were systematically investigated. Results show that the prepared polycrystalline samples all have rhombohedral symmetry structures with Griffiths phase above the low temperature magnetic transition temperature (T C2). When magnetic field is applied to the La 0.8 Sr 0.2 Mn 1-x Co x O 3 (x = 0, 0.1, 0.3) samples, the maximum magnetic entropy change ΔS max for 7 T is −2.88, −2.05, and −2.75 J/(kg•K), respectively. Doping of Co element makes ΔS max decrease first and then increase. The critical behavior of the parent phase fits best with the mean field model, and that of the sample after doping fits best with the 3D Heisenberg model. The mother phase is a semiconductor material, and the metal insulator transition appears near the low temperature magnetic transition temperature (T C2) when the Co element doping amount reaches 0.1. The conductivity of the three samples in high temperature region satisfies the small polaron model.

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