Foams made of amorphous hollow spheres and methods of manufacture thereof

Patent metadata

Field	Value
Publication number	US-10005690-B2
Application number	US-201514790348-A
Country	US
Kind code	B2
Filing date	Jul 2, 2015
Priority date	Mar 23, 2011
Publication date	Jun 26, 2018
Grant date	Jun 26, 2018

Abstract

Novel cellular solids and foams from amorphous materials with a glass transition temperature (T g ) and methods of forming such materials are provided. In particular, foams are formed by expanding or compressing hollow spheres made of a high strength amorphous material, which is defined as a material having high strength characteristics, but also possessing a glass transition within a confined space. Using such a method, it has been unexpectedly found that it is possible to make cellular structures, including both open and closed cell foams, with customizable properties from materials that have been inaccessible with conventional methods. Moreover, based on calculations high specific strengths and stiffnesses are expected.

First claim

What is claimed is:

1. A method of forming a cellular solid from an amorphous material comprising,
obtaining an amorphous material exhibiting a glass transition at a glass transition temperature, and having a material yield strength greater than 500 MPa;
forming a plurality of hollow spheres wherein at least the outer surface of the sphere is formed from the amorphous material, the hollow spheres each having an internal pressure;
confining the hollow spheres within a confining body having a fixed volume and having an atmosphere;
heating the plurality of hollow spheres to a temperature above the glass transition temperature of the amorphous material; and
applying a pressure differential between the internal pressures of the plurality of hollow spheres and the pressure of the atmosphere within the confining body, wherein the internal pressures of the plurality of hollow spheres is higher than the pressure of the atmosphere within the confining body such that the plurality of hollow spheres undergo an expansion within the boundary defined by the confining body such that adjacent hollow spheres make contact to form a cellular solid.

2. The method of claim 1 , wherein the plurality of hollow spheres expand until the spaces between the adjacent hollow spheres are entirely closed.

3. The method of claim 1 , wherein the plurality of hollow spheres bond together upon making contact.

4. The method of claim 3 , wherein the outer surfaces of the plurality of hollow spheres undergo a surface treatment that enhances the bonding of spheres at contact points.

5. The method of claim 4 , wherein the surface treatment is selected from the group consisting of cleaning, etching, exposure to a plasma and processing in inert atmosphere.

6. The method of claim 1 , wherein the internal pressures within the plurality of hollow spheres and the pressure of the atmosphere within the confining body are equal to each other and greater than atmospheric pressure, and the pressure differential is generated by depressurizing the atmosphere within the confining body thereby causing the plurality of hollow spheres to expand.

7. The method of claim 1 , wherein the pressure of the atmosphere within the confining body is greater than the internal pressures within the plurality of hollow spheres, and wherein the pressure of both are greater than atmospheric pressure, and the pressure differential is generated by depressurizing the atmosphere within the confining body thereby causing the plurality of hollow spheres to expand.

8. The method of claim 1 , wherein the internal pressures within the plurality of hollow spheres and the pressure of the atmosphere within the confining body are both equal to or less than atmospheric pressure, and the pressure differential is generated by exposing the atmosphere within the confining body to a lower pressure thereby causing the plurality of hollow spheres to expand.

9. The method of claim 1 , wherein the internal pressures within the plurality of hollow spheres is greater than the pressure of the atmosphere within the confining body such that when the plurality of hollow spheres are heated above the glass transition temperature the plurality of hollow spheres expand as the internal pressure within the plurality of hollow spheres and the atmosphere within the confining body move toward equilibrium.

10. The method of claim 1 , wherein at least two of the plurality of hollow spheres have different internal pressures.

11. The method of claim 1 , wherein at least two of the plurality of hollow spheres are formed in at least two sizes.

12. The method of claim 1 , wherein at least two of the plurality of hollow spheres have at least two wall thicknesses.

13. The method of claim 1 , wherein a non-amorphous material is included in one of either the inside volume of the plurality of hollow spheres or within the confining body.

14. The method of claim 1 , wherein the internal volume of the plurality of hollow spheres are filled with a material reactive to the amorphous material.

15. The method of claim 1 , wherein the plurality of hollow spheres are formed in an inert atmosphere.

16. The method of claim 1 , wherein at least one of the plurality of hollow spheres has one of either a positive or negative charge thereon.

17. The method of claim 1 , wherein the plurality of hollow spheres are sorted and arranged within the confining body prior to expansion.

18. The method of claim 1 , further comprising inserting a ductile inclusion within the internal volumes of the plurality of hollow spheres.

19. The method of claim 1 , wherein the plurality of hollow spheres are submerged in a pressurized fluid and the plurality of hollow spheres compressed until the internal pressures of the plurality of hollow spheres equals the pressure of the fluid such that the plurality of hollow spheres have internal pressures greater than the initial pressure.

20. The method of claim 1 , wherein at least two of the plurality of hollow spheres are filled with different gasses.

21. The method of claim 1 , wherein at least two of the plurality of hollow spheres are formed of different amorphous materials.

22. The method of claim 1 , wherein the plurality of hollow spheres include one of either a liquid or solid blowing agent.

Assignees

• Us Navy

Inventors

• Wiest Aaron
• Macdougall Craig Andrew
• Conner Robert Dale

Classifications

• B32B2266/06

  Open cell foam · CPC title

• C03B19/107

  Forming hollow beads (chemical aspects C03C11/002) · CPC title

• C03C11/002

  Hollow glass particles · CPC title

• B29C70/66 Primary

  the filler comprising hollow constituents, e.g. syntactic foam · CPC title

• B29C44/445

  in the form of expandable granules, particles or beads · CPC title