Projects on Experimental Shaping and Characterizations

Experimental Tape Casting of Adjacently Graded Materials for Magnteic Refrigaration:

Magnetic Refrigeration is an emerging technology becoming a potential alternative to the conventional refrigeration sources because of the number advantages such as environmentally neutrality, high cycle efficiency and silence. Operating principle of these systems is based on magnetocaloric effect which can be described as a reversible change of magnetocaloric materials’ temperature under the exerted magnetic field. Running temperature interval is required to be as large as possible and be close to room temperature. For higher efficiency materials with a graded Curie temperature (T_C) that could be achieved by using functional ceramics with continuously variable composition and transition temperature may be used.
The main goal of this project is a deep research of side by side tape casting (SBSTC) with the focus on exploration of interfaces between stripes. To achieve desired magnetic properties, the border in transition region is required to be well defined and steep. For practical application graded materials with La_0.85Sr_0.15MnO₃ and La_0.85Sr_0.25MnO₃ (LSM15-LSM25), La_0.85Sr_0.15MnO₃- and La_0.85Sr_0.15MnO₃/Ce_0.9Gd_0.1O₂ (LSM15-LSM15/CGO10) and La_0.67Ca_0.33-xSr_xMn_1.05O₃ (x = 0.03–0.09) (LCSM) compositions are interesting.. The powders are relatively cheap. Fundamental knowledge, control of experiment SBSTC technique and analytical tools will be used for in-depth material research.
With the overall aim of improving both the SBSTC processing and investigating magnetic properties of the targeted materials, a number of experiments will be carried out. The object of this work is to be able to predict morphological, mechanical and magnetic properties of post-sintering tapes given the initial production conditions, i.e. slurries composition and rheological characteristics as well as tape casting and sintering parameters. Results of experiments will be compared with the modeling implemented in another PhD project, which like the present project is a sub-project of the large OPTIMAC project.

Experimental Extrusion of Tubular Multilayer Materials for Oxygen Membrane:

The findings of modeling projects described above together with the exsting activities at Risø DTU as well as EMPA a tubular multilayer structure will be fabricated using extrusion. during the co-extrusion process, many of the process parametrs will be meausred in-situ: velocity, pressure and temprature at the die. These meausred values will be used for verification of the simulations and for the optimization of the process parameters. The optimal design parameters for the fabrication of extruded tubular multilayer materials for oxygen membrane will then be used to develop, charactrize and test these parts.

Sintering Behaviour of Complex Structures:

The findings of modeling projects described above together with the exsting activities at Risø DTU as well as Sandia Nat. Lab and Fraunhofer-Inistitute the effect of each layer on teh overall graded and multilayer microstructures and properties, such as shrinakge, creep and porosity will be studied under different conditions, such as temprature, dwell time and atmosphere. Deeper understanding on the parameters influencing the shrinkage and deformation during de-binding and sintering will be gained by correlating and supplementing thermal analysis with advanced microstructural invetsigations of actual sintering processes using microtomography and optical dilatometer in different conditions.

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