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

除了其良好的催化性能外，二氧化铈还提供了高储氧能力，因此非常适合用于储存催化剂和蒸汽重整器。为了提高稳定性，使用了铈锆混合氧化物。可以建立一个相对较高的氧缺乏，这只是用间接或详细的实验室方法进行了研究。为了使上述系统更有效，氧化铈-氧化锆混合氧化物的缺氧必须进行现场监测。在这一点上，谐振纳米天平和基于微波的方法代表了有前途的机会。后者已经在汽车尾气中进行了研究，但没有详细了解基本材料特性。此外，还必须更好地理解铈锆复合氧化物的缺陷化学机制，特别是对于高氧缺陷，因此，本项目的目的是从材料科学的角度为特定组成的铈锆复合氧化物的氧缺陷的原位分析提供要求。为此，设想了通过共振高温纳米尺度（TU Clausthal）和间接基于微波的方法（拜罗伊特大学）来直接测量氧缺乏。利用混合氧化物的电性能和机械性能对频率和阻尼的影响。测量是在高温下进行的，允许快速调整的缺陷平衡。初步工作证实，在原则上，所提出的方法来调查，门的氧缺乏的适用性。除开发新的原位测定方法外，还应同时应用常规方法测定高氧贫复合氧化物的稳定极限。感兴趣的性质包括缺陷和传输机制以及样品形态的影响。此外，为了评价机械稳定性，预期测量混合氧化物的其他热物理性质，例如化学膨胀。最后，应确定氧化铈-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性能的模型中。科学方法包括制备共同样品并在两个实验室进行研究。此外，数据应相互关联，并纳入一个共同的模型。因此，该项目利用了双方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。预期的结果拓宽了理解的缺陷化学的高度缺氧的氧化铈-氧化锆混合氧化物，并使相关的高温系统的原位监测。

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.