Superelastic Shape Memory Ceramic Particles

Technology #16922

Questions about this technology? Ask a Technology Manager

Download Printable PDF

Image Gallery
Figure 1 working mechanism of the SMC particles(A) Pillar milled from austenite before deformation [deff = 1.02 μm, pillar J in (24)] (B) Pillar after bending at room temperature in the martensite phase. (C) Heating induces the phase transformation to austenite and leads to recovery of the original shape, which is retained upon cooling to a state comparable to that in (A).(A) Microcompression stress-strain curve for superelastic zirconia pillar [effective diameter deff = 1.82 μm, pillar B in (24)], in which the initial elastic loading of austenite is followed by forward transformation plateaus during the formation of martensite. This is followed by elastic unloading and reverse transformation plateaus with a reversion to austenite. (B) Stress-strain curves for a pillar with deff = 1.19 μm [pillar G in (24)]. The superelastic response stabilizes after ~10 cycles.
Categories
Inventors
Professor Christopher Schuh
Department of Materials Science and Engineering, MIT
External Link (schuh.mit.edu)
Zehui Du
Nanyang Technological University
Chee Lip Gan
Nanyang Technological University
Hang Yu
Department of Materials Science and Engineering, MIT
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Superelastic Shape Memory Ceramic Particles and the Preparation Therefore

PCT Patent Application Filed
Publications
Shape Memory and Superelastic Ceramics at Small Scales
Science, 27 Sep 2013: Vol. 341, Issue 6153, pp. 1505-1508

Applications

Superelastic shape memory ceramics (SMCs) exhibit a combination of high strength, large recoverable strain, large energy damping, and are light weight. These features are useful as an energy-damping layer for armor systems or as an energy absorber for automobiles, sports equipment, and aerospace applications.

Problem Addressed

Zirconia has a well-studied martensitic transformation between tetragonal (austenite) and monoclinic (martensite) phases with associated shear strains of up to 15%. However, the mismatch stresses in the polycrystalline zirconia prevents the shape memory and superelastic behavior and induces brittle fracture failure in the material. This technology solves the cracking problem by creating small-volume ceramics with few crystals in particle form, such that they have a large free surface area and few grain boundaries to enable robust superelasticity properties.

Technology

SMC particles can be prepared in large scale by a solid-state sintering method modified with polymers containing rich aromatic rings, or a spray drying method. The crystal structure of the particles are controlled by using a fast sintering scheme and the particle size distribution are controlled by tuning the precursor viscosity, inlet temperature and gas pressure. The resulting samples exhibit highly repeatable superelasticity with cycling over one hundred times at strains up to 7% compared to regular polycrystalline zirconia that cracks at strains of 1-2% and after only a few cycles.  Additionally, these ceramics can withstand very large stresses (~0.5-3GPa) and reversibly damp mechanical energy up to ~40MJ/m3, which is much higher than that of shape memory alloys, fiber-reinforced composites, or rubbers.  The SMC particles can be used as a filler in composites with polymer, metal or ceramics as matrix to enhance their energy absorbance or used alone as a powder compact for impact energy damping. Figure 1 shows the working mechanism of the SMC particles.

Advantages

  • Highly reliable and repeatable
  • Up-scalable, time-saving, and cost-effective
  • Enhances energy damping/absorbance efficiency