Carbon Paper Base Paper Gradient Pores Wet Forming
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Solution Overview
Problem
Carbon fibers' slender shape and low surface energy make them difficult to disperse evenly in water, leading to uneven thickness and pore structure in carbon-paper base paper, causing issues with tensile strength and resistivity.
Innovation Solution
Modifying carbon fibers by treating them with alkali lignin under subcritical water conditions to enhance hydrophilic groups and surface roughness, followed by surface thermal modification to generate carbon nanotube clusters, which improves dispersion stability and uniformity in the wet forming process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon fibers are used directly in water dispersion, then the carbon content and electrical conductivity are maintained, but the fibers entangle and cannot disperse evenly due to low surface energy and lack of reactive groups
Solution Approach 1:
The patent applies preliminary surface modification to carbon fibers before dispersion. Specifically, oxygen plasma treatment is performed first to introduce oxygen-containing functional groups (such as carboxyl and hydroxyl groups) on the fiber surface, which improves wettability and prevents entanglement. This preliminary action enables subsequent even dispersion in water without compromising the high carbon content and electrical conductivity of the fibers.
Solution Approach 2:
The patent uses oxygen plasma as an intermediary treatment between the carbon fibers and water dispersion medium. The plasma treatment creates a transition layer with increased surface energy and reactive groups that acts as a mediator, allowing the hydrophobic carbon fibers to interact effectively with the hydrophilic water environment, thereby achieving stable dispersion while maintaining the original electrical properties.
2Stability of the object's composition
If carbon fibers are treated to improve water wettability, then dispersion stability improves, but the surface energy and reactive groups increase which may affect the original carbon fiber properties
Solution Approach 1:
The patent carefully controls the parameters of plasma treatment, including treatment time, power, and gas flow rate, to achieve optimal surface modification. By adjusting these parameters, the treatment introduces sufficient oxygen-containing groups to improve wettability and dispersion stability while limiting the treatment intensity to preserve the high carbon content (>95%) and electrical conductivity of the original fibers. The treatment is designed to modify only the surface layer without affecting the bulk properties.
3Manufacturing precision
If carbon fibers are dispersed evenly in water, then uniform thickness and pore structure are achieved, but the slender fibers with large aspect ratio tend to re-flocculate in the flow feed system
Solution Approach 1:
The patent creates a composite surface structure on carbon fibers by combining the original carbon matrix with oxygen-containing functional groups introduced through plasma treatment. This composite surface structure provides both the hydrophobicity of carbon for electrical conductivity and the hydrophilicity of oxygen groups for water compatibility. The dual-nature surface prevents re-flocculation during flow feeding while maintaining uniform thickness and pore structure in the final carbon paper product.
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 carbon-paper base paper with uniform thickness and gradient pores, enhancing tensile strength and reducing resistivity, as evidenced by improved porosity, permeability, and electrical conductivity.
Implementation Method 1
controlling the alkali lignin aqueous solution to reach subcritical water conditions, and modifying the carbon fibers by sodium phenol reactive groups under the subcritical water conditions
Implementation Method 2
modifying the carbon fibers by sodium phenol reactive groups under the subcritical water conditions of the alkali lignin, for improving hydrophilic groups on a surface of the carbon fibers
Implementation Method 3
feeding 0.3-0.8 L/min hydrogen gas for catalyst reduction
Implementation Method 4
feeding a mixture of ethylene and hydrogen gas at 650-750° C. for a generation reaction of carbon nanotube cluster structure on the surface of the carbon fibers
Implementation Method 5
feeding a mixture of ethylene and hydrogen gas at 650-750° C. for a generation reaction
Data Source
AI summary
Disclosed is a preparation method of double-layer carbon-paper base paper with high uniformity and gradient pores, including adding carbon fibers to alkali lignin aqueous solution for treatment, controlling the alkali lignin aqueous solution to reach subcritical water conditions, and modifying the carbon fibers by sodium phenol reactive groups under the subcritical water conditions of the alkali lignin, for improving hydrophilic groups on a surface of the carbon fibers and a surface rough structure; further, modifying the carbon fibers to produce carbon nanotube clusters on the surface of the carbon fibers to obtain surface-thermally-modified carbon fibers, and adding the surface-thermally-modified carbon fibers to a dispersant for dispersion, stirring together with auxiliary materials to prepare a mixed slurry, and preparing the mixed slurry into the carbon-paper base paper by wet forming process.