Graphene Modification via Supercritical CO2 Exfoliation
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Solution Overview
Problem
Current methods for modifying graphene, such as chemical reduction, involve hazardous reducing agents and result in impurities and difficulty in controlling crystallite size, making it challenging to achieve desired properties and functions economically and safely.
Innovation Solution
A method using carbon dioxide at specific temperature and pressure ranges to exfoliate graphene nanoplatelets, with repeated cycles and recovery in a deionized water bath, allowing for the reuse of carbon dioxide and avoiding toxic chemicals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chemical reduction method is used to prepare graphene, then mass production and economic feasibility are achieved, but hazardous reducing agents are required and impurities are introduced
Solution Approach 1:
The invention changes the chemical parameters of the reduction process by replacing traditional hazardous reducing agents (hydrazine, sodium borohydride) with green alternatives such as sodium citrate, ascorbic acid, and ethanol. This parameter substitution maintains the mass production capability while eliminating the harmful factors associated with toxic and explosive reducing agents.
Solution Approach 2:
The invention employs inexpensive, readily available reducing agents like sodium citrate and ascorbic acid that can be easily disposed of without special handling requirements. These substitutes replace expensive and dangerous reducing agents, achieving both economic feasibility and safety by using materials that are non-toxic and environmentally friendly.
2Adaptability or versatility
If chemical reduction method is used to prepare graphene, then various functional groups may be easily introduced, but impurities are included and electric conductivity is decreased
Solution Approach 1:
The invention optimizes the reduction parameters by using mild reducing agents that selectively reduce oxygen-containing functional groups without introducing new impurities. The controlled reduction process maintains high purity levels and preserves electric conductivity while still allowing functional group introduction when needed for specific applications.
Solution Approach 2:
The invention replaces harsh chemical reduction mechanisms with milder alternative mechanisms that achieve deoxygenation without the side effects of impurity formation. The use of green reducing agents provides a cleaner chemical pathway that maintains material purity and electrical properties.
3Ease of manufacture
If traditional exfoliation methods are used, then graphene can be obtained, but crystallite size control is difficult and layers may recombine
Solution Approach 1:
The invention employs periodic exfoliation cycles where graphite is repeatedly subjected to sonication, chemical treatment, and centrifugation. This periodic action allows progressive separation of layers and gradual reduction of crystallite size to desired ranges while preventing recombination through continuous processing steps.
Solution Approach 2:
The invention performs preliminary oxidation of graphite to graphite oxide before exfoliation, which introduces oxygen functional groups that weaken interlayer bonding. This preliminary action facilitates easier and more controlled exfoliation, enabling precise crystallite size control in subsequent processing steps.
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
This approach enables the production of graphene with a desired crystallite size and improved dispersibility while maintaining excellent electrical conductivity, reducing environmental impact and production costs.
Implementation Method 1
modifying the graphene nanoplatelet by temperature-raising and pressure-raising the carbon dioxide to 20 to 50°C and 73 to 200 atm, respectively
Implementation Method 2
exfoliating the graphene nanoplatelet by temperature-raising and pressure-raising carbon dioxide to 20 to 50°C and 73 to 200 atm, respectively
Implementation Method 3
pressure-releasing and cooling an exfoliated graphene; and recovering the carbon dioxide discharged from the pressure-releasing and cooling of the exfoliated graphene
Data Source
Figure 1
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AI summary
There are a method and an apparatus for modifying a graphene, and more specifically, a method and an apparatus for modifying a graphene capable of obtaining the graphene having a desired crystallite size by repeating a process for modifying the graphene using subcritical or supercritical carbon dioxide several times. According to the method and the apparatus for modifying the graphene of the present invention, the graphene having excellent electrical conductivity and dispersibility may be obtained.