Freeze foaming: a novel process for the synthesis of foam ceramics
Johnson, Nathaniel Peyton
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Foam is a class of materials that was developed only after World War II and ceramic foams are still in development. Many of the processes for synthesizing ceramic foam require the burning out of a polymer scaffold or the use of chemical reactions to generate pores. This thesis investigates the development of a novel synthesis approach called freeze foaming. In the freeze foaming process, pores are made by putting an aqueous solution under vacuum. The reduced pressure causes the air within the slurry to expand and form bubbles. Then once the foam is formed, it is frozen into place. Then the water is removed from the system through sublimation. Finally, the foam is densified by traditional sintering. After successfully creating ceramic foam samples, the parameters in the freeze foaming process were identified and investigated. Foam samples were characterized by taking density measurements, examining the macrostructure and microstructure with light microscopy, and determining mechanical properties through compression testing. In the end, highly porous foam samples with adjustable properties were synthesized using a novel manufacturing process.