Graphene Membrane Assembly With Faster Dewatering and Tuned Conductivity
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Solution Overview
Problem
Existing methods for producing graphene-based membranes result in inconsistent mechanical properties, extended dewatering times, and a loss of desirable electrical and thermal properties due to oxidation and reduction processes.
Innovation Solution
A method involving vacuum-assisted self-assembly (VASA) with controlled pH adjustment, partial reduction, and the use of filler materials to form graphene-based membranes, allowing for tunable mechanical, thermal, and electrical conductivity properties, and reduced dewatering times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If vacuum filtration is used to produce graphene oxide membranes, then the membranes can be formed with aligned laminar structure, but the dewatering time becomes excessively long (reaching many days for 50 μm thick membranes)
Solution Approach 1:
The patent applies preliminary action by pre-treating the graphene oxide dispersion with crosslinking agents before filtration. This pre-crosslinking creates a more structured dispersion that filters more efficiently, reducing dewatering time while maintaining the aligned laminar structure of the membrane.
Solution Approach 2:
The patent changes parameters of the dispersion by adjusting pH, ionic strength, and adding crosslinking agents. These parameter modifications alter the dispersion's rheological properties and filtration characteristics, enabling faster dewatering while preserving membrane structure.
2Reliability
If thermal or electromagnetic reduction is applied to restore electrical conductivity, then the electrical properties are improved, but rapid outgassing occurs causing delamination and dramatic decrease in mechanical properties
Solution Approach 1:
The patent replaces thermal reduction methods with chemical reduction using crosslinking agents. This substitution eliminates the need for high-temperature heating, preventing outgassing and delamination while restoring electrical conductivity through chemical means rather than thermal means.
Solution Approach 2:
The patent introduces crosslinking agents as intermediary substances that facilitate reduction without causing harmful outgassing. These agents mediate the reduction process, enabling conductivity restoration while maintaining mechanical integrity by preventing direct thermal interaction with the graphene structure.
3Reliability
If high temperatures are used during reduction to impart desirable electrical conductivity, then electrical conductivity is improved, but the membrane undergoes delamination and loss of mechanical properties
Solution Approach 1:
The patent changes the reduction method from thermal to chemical, operating at ambient or mild temperatures instead of high temperatures. This parameter change enables electrical conductivity restoration without compromising membrane structural stability, as the chemical reduction pathway does not require the extreme temperatures that cause delamination.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enables the production of graphene-based membranes with tailored properties, including electrical conductivity up to 4000 S/m and thermal conductivity greater than 10 W/mK, while significantly reducing dewatering times and maintaining mechanical integrity.
Implementation Method 1
the oxidation of graphene sheets is a common technique known in the art. This oxidation process occurs naturally during the exfoliation of graphene sheets
Implementation Method 2
Vacuum filtration of such dispersions through a filter media can produce graphene oxide membranes with a highly aligned laminar structure
Implementation Method 3
the graphene oxide materials may undergo chemical reduction by electromagnetic or thermal reduction processes
Implementation Method 4
the sheets may be readily dispersed in water upon the application of mild sonication
Data Source
AI summary
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.