Graphene Paper Production via Segmented Substrate Assembly
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Solution Overview
Problem
Existing methods for producing graphene paper face limitations such as restricted size, wrinkle formation, delamination, and the need for plasticizers, which affect its conductivity and shielding effectiveness, especially in the frequency range of 50 to 300 GHz.
Innovation Solution
A method involving the distribution of a graphene paste on substrates, followed by drying and thermal treatment, including annealing at specific temperatures, to produce graphene paper with controlled thickness and composition, free from additives like plasticizers, ensuring high conductivity and shielding effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If vacuum filtration or mould casting methods are used to produce graphene paper, then the production process is simple and easy to manufacture, but the size of the produced graphene paper is limited to the size of the membranes or moulds used
Solution Approach 1:
The invention divides the large-area substrate into multiple smaller substrates that can be individually processed through vacuum filtration. These smaller substrates are then assembled together to form a large-area graphene paper product, effectively overcoming the size limitation of the filtration membrane while maintaining the simplicity of the vacuum filtration process.
Solution Approach 2:
Multiple smaller graphene paper sheets produced by vacuum filtration are nested or assembled together to form a larger composite structure. This allows the final product to exceed the dimensions of individual filtration membranes used in the manufacturing process.
2Ease of manufacture
If graphene paper is freely dried without support, then the drying process is simple, but the paper tends to wrinkle, delaminate and crush
Solution Approach 1:
A flexible porous support film is introduced during the drying process to provide mechanical strength and structural stability to the graphene paper. This support film prevents wrinkling, delamination, and crushing while allowing the graphene paper to be freely dried without complex fixtures. The support film can be removed after drying completes.
Solution Approach 2:
The porous support film acts as an intermediary between the graphene paper and the drying environment. It provides the necessary mechanical support during the critical drying phase, preventing structural defects, and can be subsequently removed or retained depending on the application requirements.
3Strength
If plasticisers are added to minimise wrinkle and delamination, then the mechanical properties improve, but the conductivity and shielding effectiveness are reduced
Solution Approach 1:
Instead of adding plasticisers that compromise electrical properties, a porous support film is used during drying to provide mechanical strength. This film does not interfere with the electrical conductivity or shielding effectiveness of the graphene paper, as it can be removed after drying or is inherently electrically transparent.
Solution Approach 2:
The harmful plasticisers are completely eliminated from the process. The mechanical support function previously fulfilled by plasticisers is instead achieved through a removable porous support film, extracting the harmful chemical additive while retaining the beneficial mechanical support function.
4Reliability
If thermal treatment at high temperatures is applied to improve conductivity, then the electrical properties improve, but the production time and energy consumption increase
Solution Approach 1:
The thermal treatment process is divided into multiple sequential heating stages with intermediate cooling periods. This periodic heating allows for progressive reduction of graphene oxide without requiring excessively high temperatures or prolonged single-stage heating, thereby reducing overall energy consumption and production time while maintaining improved conductivity.
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 results in graphene paper with improved conductivity and shielding effectiveness, allowing for large-scale production of ultra-thin, flexible sheets that effectively absorb microwaves across a wide frequency range without the use of plasticizers, enhancing mechanical and chemical properties.
Implementation Method 1
drying the graphene paste formed on at least one substrate
Implementation Method 2
thermal treatment of the graphene paper: at 80-120°C for 24 hours and then at 180-220°C for 24 hours
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
The invention concerns graphene paper whose conductivity ranges from 0.00001 to 100 S/cm, wherein the graphene paper consists in 17-55% of oxygen and up to 2% of marginal substances, while the rest is composed by carbon. The invention further concerns the method of producing said graphene paper that comprises the following steps: spreading a graphene paste between substrates, forming the graphene paste spread between two substrates, drying the graphene paste shaped between two substrates, and reduction during which the graphene paper is gradually annealed: at 80-120°C for 24 hours and then at 180-220°C for 24 hours, as well as the use of the produced graphene paper for microwave adsorption.