US-12616944-B2 - Tunable graphene-based membranes and method of making the same

Abstract

There is provided a graphene-based membrane where the mechanical properties, thermal conductivity, electrical conductivity, and/or three-dimensional curvature of the membrane have been tuned according to the desired application of the membrane. Methods of accelerating the vacuum-assisted self-assembly (VASA) process for graphene-based membranes and methods for accelerating the process of removing liquid from a graphene-based dispersion are also provided. The method can include two steps of reduction to both minimize the filtration time and to substantially restore the electrical and thermal properties of a graphene-based membrane at low temperature.

Inventors

• Kaiwen HU
• Xavier Cauchy
• Robert-Eric GASKELL

Assignees

• ORA GRAPHENE AUDIO INC.

Dates

Publication Date

20260505

Application Date

20180424

Claims (9)

1. 1 . A method of forming a graphene-based membrane, the method comprising: a) obtaining a dispersion comprising graphene material dispersed within a solvent, the graphene material having at least one of graphene oxide and reduced graphene oxide; and b) filtering the dispersion through a filter membrane supported by a porous funnel having a tridimensional curved shape and giving the filter membrane a tridimensional curved geometry corresponding to the porous funnel's geometry, said filtering including the solvent flowing through the filter membrane, thereby forming the graphene-based membrane, the graphene-based membrane having a tridimensional curved shape mimicking the tridimensional curved geometry of the filter membrane, wherein the filtering of the dispersion is performed by a pressure assisted vacuum filtration including pumping compressed air to apply a positive pressure on the feed side of the filter membrane, the positive pressure being above atmospheric pressure, and applying a vacuum on the filtrate side of the filter membrane, the vacuum being below atmospheric pressure, and wherein the graphene-based membrane has a thickness greater than 5 μm.
2. 2 . The method of claim 1 wherein the tridimensional curved geometry of the filter membrane has a conical geometry, the tridimensional curved shape of the graphene-based membrane having a corresponding conical geometry.
3. 3 . The method of claim 2 wherein the tridimensional curved geometry of the filter membrane has a truncated conical geometry, the tridimensional curved shape of the graphene-based membrane having a corresponding truncated conical geometry.
4. 4 . The method of claim 1 , wherein the graphene-based membrane comprises at least one of the graphene oxide and the reduced graphene oxide.
5. 5 . The method of claim 4 , wherein the filter membrane is selected from natural polymers, synthetic polymers, inorganic fibers, carbon nanotubes, and any combination thereof.
6. 6 . The method of claim 1 , further comprising exfoliating the dispersion to obtain a uniform dispersion.
7. 7 . The method of claim 4 , wherein the graphene-based membrane further comprises up to 60 wt. % of a filler material.
8. 8 . The method of claim 7 , further comprising before filtering the dispersion, forming a precoat layer of filler material by filtering a dispersion of the filler material through the filter membrane.
9. 9 . The method of claim 8 , wherein the filler material is selected from cellulose fibers, polyester fibers, glass fibers, carbon nanofibers and combinations thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S) This application claims the benefit of priority from U.S. Provisional Patent Application No. 62/489,335 filed on Apr. 24, 2017, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The following relates generally to graphene-based membranes with physical properties that may be tuned during the manufacture thereof. BACKGROUND Graphene, in its pristine state, is a hydrophobic material. As such, modification is required to obtain stable, uniform dispersions of single graphene sheets. Such dispersions are desirable for the controlled handling of graphene-based materials. For example, the coating of a substrate with graphene material or the incorporation of graphene sheets in a polymer matrix. Among these modification methods, the oxidation of graphene sheets is a common technique known in the art. This oxidation process occurs naturally during the exfoliation of graphene sheets through widely adopted methods such as those described by Hummers et al. in J. Am. Chem. Soc. 1958, 80, 1339, and modifications thereof. Graphene oxide, the result of such a modification process, includes individual graphene sheets grafted to oxygen-containing groups such as hydroxyls, carboxylic acids and epoxides. With the incorporation of the hydrophilic groups, the sheets may be readily dispersed in water upon the application of mild sonication. Vacuum filtration of such dispersions through a filter media can produce graphene oxide membranes with a highly aligned laminar structure, as described by Dikin et al. in Nature 2007, 448, 7152. However, the accumulation of graphene sheets during the filtration process has been found to hinder the flow of water through the filter media. This has led to dewatering times that can reach many days for 50 μm thick membranes. An example of such undesirable dewatering time can be found in U.S. Pat. No. 8,709,213 to Compton et al. The above method has also been found to produce membranes with inconsistent mechanical properties as a result of several manufacturing factors. Furthermore, the membranes produced through this method do not share the desirable electrical or thermal properties of pristine graphene. To recover these properties, the graphene oxide materials may undergo chemical reduction by electromagnetic or thermal reduction processes. The thermal and electromagnetic methods typically induce rapid outgassing of the oxygen species grafted to the graphene sheets. The outgassing leads to the delamination of the graphene-based membrane and ultimately results in a dramatic decrease in mechanical properties thereof. Moreover, very high temperatures are needed in order to impart the membrane with desirable electrical conductivity. Therefore, it is an object of the following to address at least one of the above disadvantages or drawbacks. SUMMARY OF THE INVENTION It is recognized that there is a desire for graphene-based membranes with tunable physical properties and a method for making the same. In an example aspect, a graphene-based membrane is provided, where the mechanical properties, thermal conductivity, electrical conductivity, and/or three-dimensional curvature of the membrane have been tuned according to the desired application of the membrane. In another aspect, methods of accelerating the vacuum-assisted self-assembly (VASA) process for graphene-based membranes and methods for accelerating the process of removing liquid from a graphene-based dispersion. In another aspect, the method involves two steps of reduction to both minimize the filtration time and to substantially restore the electrical and thermal properties of a graphene-based membrane at low temperature. It will be appreciated that the aspects and features described in this summary section are non-limiting and that additional features and embodiments are provided in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments will now be described by way of example only with reference to the appended drawings wherein: FIGS. 1A-D are a series of cross-sectional side views of the vacuum filtration process for the manufacture of a cellulose/graphene oxide (GO) composite membrane; FIG. 2 is a cross-sectional side view of the pressure assisted vacuum filtration process for the manufacture of a cellulose/GO composite membrane; FIGS. 3A-C are a series of cross-sectional side views of the vacuum filtration process for the manufacture of a GO membrane; FIGS. 4A-C are a series of cross-sectional side views of the vacuum filtration process for the manufacture of a gelated GO membrane; FIG. 5A is an electron micrograph of a partially-reduced GO membrane; FIG. 5B is an electron micrograph of a partially-reduced gelated GO membrane; FIG. 5C is an electron micrograph of a partially-reduced cellulose/GO composite membrane; and FIG. 6 represents an analysis showing the density and Young's modulus of graphene-based membranes of various compositions. DETAILE