Klebeverbindung von Katalysatoren

Translated title of the contribution: Adhesive bonding of catalysts

Stefan Wegscheider

Research output: ThesisMaster's Thesis

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Abstract

Exhaust gas treatment for combustion processes requires the use of catalysts to reduce nitrogen oxides. Components for this purpose are build up as stacks of individual catalyst bodies, so called modules. The aim of the present work is to find an adhesive that can withstand the application-relevant load and environmental (thermal or chemical) attack cases in an exhaust system fired with undefined fuels. This is intended to replace an essential component of the modules, the fiber mat, which acts as a buffer between the ceramic bodies. A further goal was to develop a test method with which the adhesive bond can be characterized. The method shall be applied to investigate the effect of various critical environmental attack types on the bond strength of selected adhesives. Test material was available as extruded rods from the catalyst material. The suitability of the developed test procedure shall be demonstrated and additional insight into the behavior of adhesives shall be gained through thermal analyses of catalyst material and adhesives as well as through light and electron optical microscopy. The analysis of possible mechanical load cases that act on the bond in modules showed, that flexure tests as commonly used for ceramics and shear tests in compression are suitable to model in service load cases. Other critical conditions are exposure to temperatures below the dew point, thermal shock and thermal fatigue as well as chemical attack. Such conditioning can be performed on the test bodies prior to strength testing. Flexure tests could only be performed on rods from base material. Bonded rods had no sufficient tensile strength to survive set-up of the tests. Based on the available rod material, test bodies for shear tests under compression were developed and optimized. Special emphasis was put on reproducible specimen preparation. Setting jigs were constructed and additively manufactured from polymers. With the shear test in compression specimens which were pre-conditioned by artificial weathering and thermal shock were tested. It was shown that the strength of the substrate material does not degrade by thermal shock. Only with the multi-component adhesive on the basis of colloidal silica a sufficient bonding could be achieved. This bond loses part of its strength upon exposure to dew conditions and after air quenching from 200°C to room temperature. Apart from the adhesion on the substrate an important factor for strength of the bond was the homogeneity of the components of the adhesive.
Translated title of the contributionAdhesive bonding of catalysts
Original languageGerman
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Lube, Tanja, Supervisor (internal)
Award date30 Jun 2023
DOIs
Publication statusPublished - 2023

Bibliographical note

no embargo

Keywords

  • joining technology
  • adhesive bonding
  • 3-point-bending
  • 4-point-bending
  • shear test
  • oxidic ceramic
  • catalysts
  • weathering
  • thermal shock

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