In-situ Methods to Determine High Oxygen Deficits in Ceria-Zirconia Mixed Oxides for Exhaust Gas Aftertreatment

CeO2除了具有良好的催化性能外，还具有很高的储氧容量，非常适合用于储存催化剂和水蒸气重整装置。为提高稳定性，使用了CeO_2-ZO_2复合氧化物。可以建立一个相对较高的缺氧率，这只能用间接的或详细的实验室方法来研究。为了使上述系统更加有效，必须对CeO2-ZrO2混合氧化物的缺氧量进行现场监测。在这一点上，共振纳米天平和基于微波的方法代表着有希望的机会。然而，后者已经在汽车尾气中进行了研究，而不是对基本材料特性的详细了解。因此，本课题的目的是从材料科学的角度为所选成分的CeO_2O_3复合氧化物中氧缺陷的原位分析提供必要的材料科学依据。为此目的，利用共振高温纳米尺度(TU Clausthal)和间接微波方法(Univ.拜罗伊特)。研究了混合氧化物的电学和力学性质对频率和阻尼的影响。测量是在允许快速调整缺陷平衡的高温下进行的。初步工作原则上证实了所提出的方法在研究氧缺乏方面的适用性。除了开发新的原位方法外，还应同时应用常规方法确定高氧缺氧混合氧化物的稳定极限。感兴趣的性质包括缺陷和输运机制以及样品形貌的影响。此外，预计将测量混合氧化物的其他热物理性质，如化学膨胀，以评估机械稳定性。最后，应测定氧化铈-氧化锆混合氧化物的微波介电性能，并将其纳入描述运行中的三效催化剂的微波介电性能的模型中。科学方法包括共同样品的制备和两个实验室的研究。此外，数据应该相互关联，并包括在一个共同的模型中。因此，该项目利用了两个合作伙伴的互补能力。数据的部分冗余提高了它们的可靠性。预期的结果扩大了对高度缺氧的CeO2-ZrO2混合氧化物缺陷化学的理解，并使相关高温系统的现场监测成为可能。

Besides its good catalytic properties, ceria provides a high oxygen storage capacity and is, therefore, highly suited for the application in storage catalysts and steam reformers. To in-crease the stability, ceria-zirconia mixed oxides are used. A comparatively high oxygen defi-ciency can be established, which has only been studied with indirect or elaborated laboratory methods. To make the above-mentioned systems more effective, the oxygen deficiency of ceria-zirconia mixed oxides must be monitored in situ. At this point, resonant nano balances and microwave-based approaches represent promising opportunities. The latter are already studied in automotive exhausts without, however, detailed knowledge of the fundamental materials properties. Further, the defect chemical mechanisms of the ceria-zirconia mixed oxides must be better understood, especially for high oxygen deficiencies.Therefore, the aim of this project is to provide from a materials science point of view the re-quirements for in situ analysis of the oxygen deficiency in ceria-zirconia mixed oxides of se-lected compositions. For this purpose, a direct measurement of the oxygen deficiency by means of a resonant high-temperature nano scale (TU Clausthal) and an indirect microwave-based method (Univ. Bayreuth) are envisaged. The influence of the electrical and mechani-cal properties of mixed oxides on frequencies and damping is used. The measurements are performed at high temperatures that allow a fast adjustment of the defect equilibrium.The preliminary work confirms, in principle, the suitability of the proposed methods to investi-gate the oxygen deficiency. Besides the development of the new in situ methods, the stability limits of the highly oxygen deficient mixed oxides should be determined by simultaneous ap-plication of conventional methods. The properties of interest include the defect and transport mechanisms as well as the effect of sample morphology. Further, the measurement of other thermo physical properties of the mixed oxides such as chemical expansion is anticipated in order to evaluate the mechanical stability. Finally, the microwave dielectric properties of the ceria-zirconia mixed oxides should be determined and included in a model that describes the microwave properties of three-way-catalysts under operation.The scientific approach includes the preparation of common samples and their investigation in both laboratories. Furthermore, the data should be correlated and included in a common model. Thereby, the project takes advantage of the complementary competencies of both partners. Partial redundancy of the data improves their reliability. The expected results broaden the understanding of the defect chemistry of highly oxygen deficient ceria-zirconia mixed oxides and enable the in situ monitoring of related high-temperature systems.