![]() ![]() Sublimation occurs when a solid material transforms into a gas, skipping the liquid phase. After the freezing stage is complete, the mold is transferred to a freeze drying apparatus to remove the frozen solvent. The freezing step is very important in developing the microstructure as the material is not able to revert form once frozen and the manner in which the solvent solidifies will dictate the formation of pores within the structure. Many process parameters affect the resultant microstructure including freezing temperature, casting time, freezing rate, solids loading and others. During this step the solvent is solidified in order to template the ceramic material. In the freezing step, the water or solvent is frozen into the slurry. Once the mold is filled, freezing can begin. Many different techniques are being studied for this procedure to best optimize the results of experimentation. The green body will act as the anode support layer, mechanically supporting the cell and providing gas delivery pathways, which will be further processed with electrolyte and cathode layers to complete the fuel cell.įilling the Mold is an important step during freeze casting as the material must be processed by a freezing medium in order to solidify. The green body is sintered to burnout unneeded additives and to agglomerate the ceramic powders. After the slurry has been mixed, it is injected into the mold, frozen, and then sublimated to create a green body. This mixture is called slurry, slip, or ink and are considered complex multiphase systems. Preparation of the suspension includes mixing the ceramic materials, solvent and any other additives, adjusting pH levels and fine tuning slurry rheology. The four basic steps in the Freeze Casting include: Material Preparation, Filling the Mold, Freezing, and Freeze Drying. Figure 1 shows the mold setup during freeze casting and freeze drying stages. ![]() The goal of freeze casting, with regards to solid oxide fuel cell research, is to develop a porous layer that will allow gas to easily diffuse into the cell, increasing its efficiency and power output. When the solvent is fully removed, a porous structure remains where the ice was formed. ![]() Sublimation is the direct transformation of a material from the solid phase to the vapor phase, without passing through the liquid phase. After the suspension is fully solidified, the frozen solvent is removed via sublimation. As the solvent, or liquid phase, in the material is frozen, the solidifying growth front separates the solid phase particles, segregating and templating the particles into a distinctive pattern.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |