Oligocrystalline Shape Memory and Pseudoelastic Ceramics
Shape memory and pseudoelastic ceramics have applications in mechanical actuators, mechanical couplings, armor materials, biomedical devices, and electrically controlled actuators.
Researchers
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oligocrystalline ceramic structures for enhanced shape memory and pseudoelastic effects
United States of America | Granted | 9,512,039
Technology
Ceramic powders were made using co-precipitation methods followed by compaction and sintering to make a bulk polycrystalline specimen. Single crystal ceramic pillars were then fabricated using focused ion beam milling. Mechanical compression tests were carried out using nanoindentation techniques, showing pseudoelastic behavior with strains up to ~10%, stresses up to 1200MPa, and a damping figure of merit of 1.4.
Problem Addressed
Shape memory ceramics rely on martensitic transformations which are similar to those found in more common metallic shape memory materials. Ceramics offer advantages such as higher operating temperatures and larger transformation stresses which exceed those found in metals. Previous polycrystalline shape memory ceramics have only shown recoverable strains up to ~1%. However, this technology uses an oligocrystalline regime, where the total surface area is greater than the total grain boundary area, meaning that grains are coordinated mostly by unconfined free surfaces rather than rigid boundaries with other grains, to achieve total transformation strain up to ~10%.
Advantages
- Increased transformation strains
- Increased operating temperatures
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