Method for preparing medium- and high-modulus large tow carbon fibers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current graphitization technologies for large tow carbon fibers face challenges in achieving uniform high-modulus properties due to uneven heating and high energy consumption, limiting their application fields and increasing production costs.
Innovation Solution
A method involving microwave graphitization of low-modulus large tow carbon fibers using in-phase microwave heating and controlled current density (60-330 A/m) to rapidly and uniformly increase the surface temperature to 2000-3000° C, achieving a tensile modulus of 300-600 GPa and maintaining tensile strength at 3.5-5.0 GPa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional graphitization technology is used on large tow carbon fibers, then production cost is reduced and production capacity is increased, but tensile modulus remains low (230-280 GPa) and application fields are limited
Solution Approach 1:
The patent applies parameter changes by controlling current density (60-330 A/m) and temperature (2000-3000°C) during microwave graphitization to transform low-modulus large tow carbon fibers into medium- and high-modulus fibers, achieving tensile modulus of 300-600 GPa while maintaining large tow specifications
Solution Approach 2:
The patent replaces conventional thermal field graphitization with microwave field graphitization, using electromagnetic energy to directly heat carbon fibers through dielectric loss and ohmic loss, achieving more efficient and controllable graphitization with higher modulus improvement
2Use of energy by moving object
If conventional heating methods are used for graphitization, then energy consumption is high and heating is uneven, but the process is simpler to implement
Solution Approach 1:
The patent applies self-service by utilizing the inherent dielectric loss and ohmic loss of carbon fibers to generate heat directly within the material during microwave irradiation, eliminating the need for external heating sources and achieving uniform heating throughout the fiber bundle
Solution Approach 2:
The patent uses periodic microwave irradiation with controlled current density cycles to achieve uniform graphitization, where the alternating electromagnetic field continuously reheats and evenly distributes thermal energy throughout the carbon fiber tow
3Speed
If current density is increased to improve graphitization efficiency, then heating speed increases, but fiber strength may be compromised due to excessive temperature
Solution Approach 1:
The patent applies dynamics by dynamically adjusting current density within the range of 60-330 A/m during microwave graphitization, allowing real-time optimization of heating rate while preventing excessive temperature that would compromise fiber strength, achieving both high heating speed and strength retention
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 method enables the production of medium- and high-modulus large tow carbon fibers with uniform properties, reducing production costs and improving the performance-cost ratio, while maintaining fiber strength and achieving continuous production.
Implementation Method 1
The surface temperature of each large tow carbon fiber is rapidly and uniformly increased by microwave graphitization to 2000-3000° C.
Implementation Method 2
regulating and controlling a current density on surfaces of the low-modulus large tow carbon fibers... so that a current density on the surface of each carbon fiber... is the same or nearly the same
Data Source
AI summary
A method for preparing medium- and high-modulus large tow carbon fibers includes performing in-phase microwave heating on low-modulus large tow carbon fibers, and regulating and controlling a surface current density of the carbon fibers in the range of 60-330 A/m to rapidly reach graphitization temperature of the carbon fibers, thereby completing a uniform and rapid graphitization process. The medium- and high-modulus large tow carbon fibers obtained by the preparation method of the present application can have a tensile modulus reaching 300-600 GPa, and a tensile strength maintained to be 3.5-5.0 GPa, and a dispersion of the tensile modulus of the carbon fibers is less than 1.5%.