Continuous Graphitic Fiber Production via Stress-Aligned Gel
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Solution Overview
Problem
Current methods for producing continuous graphite fibers are energy-intensive, costly, and lack scalability, with existing processes resulting in fibers with poor mechanical strength, thermal conductivity, and electrical conductivity due to defects and misorientation of graphene planes.
Innovation Solution
A process involving a graphene oxide gel is used, where living graphene molecules are aligned through mechanical stress and heat-treated to form a continuous graphitic fiber with high thermal and electrical conductivity, and exceptional mechanical strength, by reducing oxygen content and inter-plane spacing, resulting in a unitary graphene-based fiber with all planes parallel to the fiber axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional pyrolysis of stabilized precursor fibers is used to produce carbon/graphite fibers, then continuous fibers can be obtained, but the process is energy-intensive, costly, and time-consuming with moderate mechanical properties
Solution Approach 1:
The invention changes the processing parameters from conventional high-temperature pyrolysis (1000-3000°C) to a low-temperature process (ambient to 200°C) using graphene oxide gel. This parameter change dramatically reduces energy consumption while producing fibers with superior tensile strength (up to 8 GPa) compared to conventional carbon fibers (1-6 GPa).
Solution Approach 2:
The invention uses graphene oxide as a composite material precursor that self-assembles into aligned structures. The graphene oxide gel contains oxygenated functional groups that facilitate molecular alignment and bonding, creating a composite structure with exceptional mechanical properties without requiring energy-intensive stabilization and carbonization processes.
2Strength
If high temperature graphitization (2500-3000°C) is applied to increase Young's modulus, then higher elastic modulus is achieved, but the process becomes more energy-intensive and time-consuming
Solution Approach 1:
The invention performs preliminary alignment of graphene oxide molecules along the fiber axis during gel formation and deposition, before any heat treatment. This pre-alignment eliminates the need for subsequent high-temperature graphitization to achieve molecular orientation, thereby achieving high Young's modulus (up to 600 GPa) without energy-intensive heating to 2500-3000°C.
Solution Approach 2:
The invention changes the temperature parameter from conventional graphitization temperatures (2500-3000°C) to a low-temperature range (ambient to 200°C). The oxygenated functional groups in graphene oxide enable molecular alignment and bonding at these lower temperatures, achieving high elastic modulus without the energy consumption associated with traditional graphitization processes.
3Reliability
If conventional carbonization processes are used, then carbon fibers can be produced, but the fibers contain defects and misoriented graphene planes resulting in poor mechanical and electrical conductivity
Solution Approach 1:
The invention changes the chemical environment from conventional carbonization (inert atmosphere at high temperature) to an aqueous or polar solvent gel system at low temperature. The oxygenated functional groups in graphene oxide promote molecular alignment and reduce defects during gel formation, resulting in fibers with superior electrical conductivity (>10,000 S/cm) and well-oriented graphene planes without requiring high-temperature treatment.
Solution Approach 2:
The invention replaces the thermal-mechanical system of conventional carbonization with a chemical self-assembly system. Graphene oxide molecules spontaneously align and bond through chemical interactions in the gel state, creating a highly ordered structure with minimal defects. This chemical approach substitutes for the mechanical alignment that would otherwise require high-temperature processing.
4Ease of manufacture
If pitch or PAN precursors are used for carbon fiber production, then continuous fibers can be manufactured, but the process requires complex stabilization and carbonization steps increasing device complexity
Solution Approach 1:
The invention extracts and eliminates the complex stabilization and carbonization steps from the conventional carbon fiber production process. By using graphene oxide gel as the precursor, the process directly forms aligned graphitic fibers through simple deposition and low-temperature drying, removing the need for multi-step stabilization, carbonization, and graphitization procedures required by pitch and PAN precursors.
Solution Approach 2:
The invention changes the processing temperature parameter from high (1000-3000°C) to low (ambient to 200°C), and the chemical environment from inert gas atmosphere to aqueous/polar solvent gel. These parameter changes simplify the manufacturing process by eliminating the need for complex stabilization and carbonization equipment, while still producing high-performance graphitic fibers.
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 process produces fibers with thermal conductivity exceeding 1,700 W/mK, electrical conductivity over 10,000 S/cm, and tensile strength up to 8 GPa, surpassing previous carbon and graphite fibers in terms of performance and scalability.
Implementation Method 1
the dispensing and depositing procedure includes mechanical stress-induced molecular alignment of the living graphene oxide molecules or functionalized graphene chains along a filament axis direction
Implementation Method 2
heat treating the continuous graphene oxide fiber to form the continuous graphitic fiber at a heat treatment temperature higher than 100° C. (preferably >600° C. and more preferably >1,000° C.) to the extent that an inter-plane spacing d002 is decreased to a value of from 0.3354 nm to 0.4 nm
Implementation Method 3
This step is often called carbonization and it can take 2-24 hours to complete, depending upon the carbonization temperature and the starting material used. Carbonized fibers can be further graphitized at an even higher temperature, up to around 3,000° C. to achieve higher carbon content and higher degree of graphitization
Implementation Method 4
wherein the graphene oxide fiber has an inter-plane spacing d002 of 0.4 nm to 1.2 nm as determined by X-ray diffraction
Data Source
AI summary
A process for producing a continuous graphitic fiber, comprising: (a) preparing a graphene oxide gel having living graphene oxide molecules or functionalized graphene chains dissolved in a fluid medium; (b) depositing at least a continuous filament of graphene oxide gel onto a supporting substrate under a condition of stress-induced molecular alignment of living graphene oxide molecules along a filament axis direction; (c) removing the fluid medium to form a continuous graphene oxide fiber, having an inter-plane spacing d002 of 0.4 nm to 1.2 nm and an oxygen content no less than 5% by weight; and (d) heat treating the continuous graphene oxide fiber to form the continuous graphitic fiber at a temperature higher than 100° C. (preferably >600° C.) to an extent that an inter-plane spacing d002 is decreased to a value of 0.3354-0.4 nm and the oxygen content is decreased to less than 5% by weight.