Shape Memory and Pseudoelastic Ceramics

Technology #15550

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 FIGS. 1A-1D are schematic views of a cylindrical ceramic structure undergoing a martensitic transformation cycle exhibiting a shape memory effectFIG. 3 is a general plot of ceramic material stress as a function of applied temperature, indicating various temperature regimes for the martensitic and austenitic phases of material;
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Inventors
Professor Christopher Schuh
Department of Materials Science and Engineering, MIT
External Link (schuh.mit.edu)
Alan Lai
Department of Materials Science and Engineering, MIT
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Ceramic Structures for Enhanced Shape Memory and Pseudoelastic Effects

US Patent 9,018,117
Publications
Shape Memory and Superelastic Ceramics at Small Scales
Science, 27 Sep 2013: Vol. 341, Issue 6153, pp. 1505-1508

Applications

Shape memory and pseudoelastic ceramics have applications in actuators, couplings, armor materials, and biomedical devices.

Problem Addressed

Previous ceramic shape memory materials are polycrystalline, and during the shape memory effect, or pseudoelastic loading, the grains may change shape in opposing directions causing internal stress concentrations. This invention utilizes single crystal ceramic materials to overcome the stress concentrations found in polycrystalline materials.

Technology

Ceria-doped zirconia is one ceramic material investigated. The material is made into a powder through a co-precipitation technique. The powder is uniaxially pressed into disks and then sintered at 1500oC. The grain size is proportional to the sintering time (i.e. longer sintering time leads to larger grains). After sintering, single crystal pillars are made using focused ion beam (FIB) milling on individual grains. The resulting single crystal materials are able to undergo the phase transformations without cracking.

Advantages

  • Ability to induce phase transformations with an electric or magnetic field
  • Ceramic shape memory and pseudoelastic materials

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