Support for Nano-Thickness Membranes

Abstract

A porous support for nano-thickness membranes of less than 100 nanometers local surface roughness, suitable for the support of single-layer membranes of from about 1 to 500 nanometers in thickness, and for multiple layer membranes of up to about 2000 nanometers in aggregate thickness. The support also has a surface pore size of less than 100 nanometers and a surface porosity of less than 50 percent.

Claims

1. A membrane support having a local surface roughness of less than 100 nanometers.

2. The support of claim 1, wherein the support comprises a ceramic.

3. The support of claim 1, wherein the support has a porosity of less than 50%.

4. The support of claim 1, wherein the support has a mechanical strength sufficient to support single or multiple layers of nano coating, to a total coating thickness of less than 2000 nm.

5. The support of claim 1, wherein the support further comprises a metal.

6. The support of claim 1, wherein the support further comprises a metal oxide.

7. The support of claim 1, wherein the support further comprises an inorganic-material selected from the inorganic materials including: Al, Al.sub.2O.sub.3, TiO.sub.2, ZrO.sub.2, BN, YSZ, Ni, NiO, SiO.sub.2, PZT, PE, PP, PEI.

8. The support of claim 1, wherein the support has a local surface roughness of less than 100 nm on at least one side of a planar configuration.

9. The support of claim 1, wherein the support has a local surface roughness of less than 100 nm on at least two sides of a planar configuration.

10. The support of claim 1, wherein the support has a local surface roughness of less than 100 nm on at least one surface selected from the group of surfaces consisting of an inside surface and an outside surface of a tubular configuration.

11. The support of claim 1, wherein the support has a local surface roughness of less than 100 nm on both an inside surface and an outside surface of a tubular configuration.

12. The support of claim 1, wherein the support has a microstructure having a mechanical permeability of greater than 10.sup.−10 mol/(Pa.Math.s.Math.m.sup.2).

13. The support of claim 1, wherein the support has a surface deposition of at least one nano-thickness material having a thickness of between 25-500 nm.

14. The support of claim 1, wherein the support has a surface deposition of a plurality of layers having an aggregate thickness less than or equal to 2000 nm.

15. The support of claim 19, wherein the surface deposition comprises a polymer.

16. The support of claim 19 wherein the surface deposition comprises an inorganic material.

17. The support of claim 20, wherein the surface deposition comprises a polymer.

18. The support of claim 20, wherein the surface deposition comprises an inorganic material.

19. The support of claim 19, wherein the surface deposition is applied by a method selected from at least one of the group of methods consisting of dip coating, flow coating, spraying, and vapor deposition.

20. The support of claim 20, wherein the surface deposition is applied by a method selected from at least one of the group of methods consisting of dip coating, flow coating, spraying, and vapor deposition.

Description

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0009] To produce a defect-free supported nano-thickness membrane structure (with single layers in the 1-500 nm thickness range and multi-layers up to 2000 nm total thickness), the membranes must be deposited on a porous support with sufficient mechanical strength to support the membrane, without surface defects and a local surface roughness of less than 100 nm on any location of the membrane deposition area of the support. This can be achieved, for instance, by making the support through assembly of particles followed by thermochemical processing such as drying, oxidation and conversion of added components, and sintering. In this process the particle size, shape, and extent of agglomeration must be controlled. Sintering is a surface-energy-driven process in which touching particles from strong necks so that the overall structure obtains sufficient strength. Surface defects are deviations from the quasi-homogeneous microstructure that adversely affects membrane quality. Examples of surface defects are support surface pores with a diameter that are much larger than the average pore diameter and particles in or on the surface that are much larger than the average grain size. Particles at the surface with a shape that deviates substantially from spherical are also considered defects. Large support surface pores are often caused by bubbles and low-density agglomerates that collect at the support surface during processing. Large particles are often caused by airborne contamination or abrasion from processing equipment. For extruded and/or polished support surfaces, the surface roughness is limited and/or defined by abrasion from the processing equipment, for example the extrusion spider dye, or the grit of the media being used in polishing. Polishing of the support surface also results in a lowering of open, or useable, porosity and unwanted introduction of debris into the membrane pores.

[0010] Applications for membranes include high-selectivity gas separation and liquid purification, sensing and electrochemical conversion devices. The full range of applications may include, but is not limited to, production of fuel cells, electrochemical pumps, chemicals, polymers, steel, petro-chemicals, semiconductor devices, gas separation, energy-conversion, environmental applications, agriculture, and the food and drink industries. The separation of oxygen and hydrogen are two examples where nano-thickness membranes on porous inorganic ceramic supports can have a major impact.

[0011] Other examples of use, as would be known by one skilled in the art, are for the sequestration of carbon dioxide gas and wastewater treatment. The support may be used to carry membranes for the separation of gases such as O.sub.2, N.sub.2, H.sub.2, CO.sub.2, and He, as well as the purification of liquids such as water.

[0012] The porous supports as described in this disclosure have a local surface roughness of <100 nm, a porosity of 5-45%,with a microstructure, thermal and structural properties that enable the deposition of nano-thickness membrane layer or layers for a range of applications described in this disclosure.

[0013] A method for making the support may begin with the provision of a powder that is processed into mostly individually mobile particles with a size of 50 nm to 20 μm. The powder may then be mixed with a binder and liquid medium to form a dispersion. The dispersion may then be formed into a flat plate or tube or any usable geometry using a colloidal casting process. This process results in a particle packing with a porosity of 30-40% and a support surface roughness of <25 nm, with a surface pore size of ˜40 nm. After casting, the “green” tube is dried in a controlled environment. After drying the tube is heated in a controlled environment from 100 to 1000° C. The tube is then inspected for any defects and possibly used for the deposition of one or more nano-membrane layers.

[0014] Numerous alterations, modifications, and variations of the preferred embodiments disclosed herein will be apparent to those skilled in the art and they are all anticipated and contemplated to be within the spirit and scope of the disclosed specification. For example, although specific embodiments have been described in detail, those with skill in the art will understand that the preceding embodiments and variations can be modified to incorporate various types of substitute and or additional or alternative materials, relative arrangement of elements, order of steps and additional steps, and dimensional configurations. Accordingly, even though only few variations of the products and methods are described herein, it is to be understood that the practice of such additional modifications and variations and the equivalents thereof, are within the spirit and scope of the method and products as defined in the following claims. The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or acts for performing the functions in combination with other claimed elements as specifically claimed.