HOLLOW SUPERELASTIC SHAPE MEMORY ALLOY PARTICLES
Hollow superelastic shape memory alloy particles are disclosed herein. An example of the hollow superelastic shape memory particle includes an outer shell of a shape memory alloy having an Austenite finish temperature (Af) that is lower than a temperature encountered in an application in which the particle is used so that the shape memory alloy exhibits stress-induced superelasticity. The hollow superelastic shape memory particle also includes an interior hollow portion at least partially surrounded by the outer shell.
1 . A hollow superelastic shape memory particle, comprising:
an outer shell of a shape memory alloy having an Austenite finish temperature (A f ) that is lower than a temperature encountered in an application in which the particle is used so that the shape memory alloy exhibits stress-induced superelasticity; and
an interior hollow portion at least partially surrounded by the outer shell.
2 . The hollow superelastic shape memory particle as defined in claim 1 wherein the outer shell has a wall thickness ranging from about 1 μm to about 500 μm.
3 . The hollow superelastic shape memory particle as defined in claim 2 wherein the wall thickness varies.
4 . The hollow superelastic shape memory particle as defined in claim 1 wherein the outer shell has a wall thickness that is less than 5% of a radius of the particle.
5 . The hollow superelastic shape memory particle as defined in claim 1 wherein the shape memory alloy is chosen from a copper-zinc-aluminum-nickel alloy, a copper-aluminum-nickel alloy, a nickel-titanium alloy, a zinc-copper-gold-iron alloy, a gold-cadmium alloy, an iron-platinum alloy, a titanium-niobium alloy, a gold-copper-zinc alloy, an iron-manganese alloy, a zirconium-cobalt alloy, a zinc-copper alloy, and a titanium-vanadium-palladium alloy.
6 . The hollow superelastic shape memory particle as defined in claim 1 wherein the outer shell is non-porous.
7 . The hollow superelastic shape memory particle as defined in claim 6 wherein the non-porous outer shell includes surface irregularities.
8 . The hollow superelastic shape memory particle as defined in claim 1 wherein the outer shell is porous.
9 . The hollow superelastic shape memory particle as defined in claim 8 wherein the porous outer shell includes a single gap.
10 . The hollow superelastic shape memory particle as defined in claim 8 wherein the porous outer shell includes a plurality of pores.
11 . The hollow superelastic shape memory particle as defined in claim 1 wherein a diameter of the particle ranges from about 20 μm to about 20 mm.
12 . The hollow superelastic shape memory particle as defined in claim 1 having a shape selected from regular three-dimensional geometric shapes and irregular three-dimensional geometric shapes.
13 . The hollow superelastic shape memory particle as defined in claim 12 wherein the regular three-dimensional geometric shape is selected from a sphere, a prism, a pyramid, or a cylinder.
14 . The hollow superelastic shape memory particle as defined in claim 1 wherein the Af ranges from about −150° C. to about 150° C.
15 . The hollow superelastic shape memory particle as defined in claim 1 wherein the Af is within 5° C. below the temperature encountered in the application in which the particle is used.