Carbon Nanotube Composite Grain Boundary Conductivity
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Solution Overview
Problem
Existing carbon nanotube composite materials face issues with low conductivity due to oxide film formation, air gaps, elastomer residue, high production costs, and lengthy processing times, particularly when using a cellulation structure with a high compounding ratio of carbon nanotubes.
Innovation Solution
A carbon nanotube composite material is developed with a polycrystalline metallic base and carbon nanotube conductive paths that form conductive paths along grain boundaries, produced through a process involving a green compact forming step under pressure and extrusion processing at elevated temperatures, reducing the carbon nanotube content to 0.1-1 mass% and eliminating the need for elastomers, thereby enhancing conductivity and reducing production time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a cellulation structure with high carbon nanotube compounding ratio (0.2-5 mass%) is used, then strength is enhanced, but conductivity decreases and production cost increases
Solution Approach 1:
The patent applies local quality by positioning carbon nanotubes specifically at grain boundaries rather than uniformly distributing them throughout the metal matrix. This localized placement at critical interfaces provides both strengthening (by blocking dislocation motion at grain boundaries) and conductive pathways (by forming continuous networks along grain boundaries), thereby resolving the contradiction between strength enhancement and conductivity maintenance with reduced overall CNT content
Solution Approach 2:
The patent creates a composite material structure where carbon nanotubes are integrated with metal grains at their boundaries, forming a hybrid system that combines the metallic matrix with CNT reinforcement at strategic locations. This composite approach allows the CNTs to serve dual functions of strengthening and conducting electricity while minimizing the total amount needed
2Strength
If a cellulation structure with high carbon nanotube compounding ratio (0.2-5 mass%) is used, then strength is enhanced, but production cost increases
Solution Approach 1:
By concentrating carbon nanotubes at grain boundaries rather than uniform distribution, the patent achieves effective reinforcement with significantly reduced overall CNT content (0.01-0.1 mass%), thereby maintaining strength while reducing material cost
Solution Approach 2:
The patent applies partial action by placing carbon nanotubes only where most needed (at grain boundaries) rather than throughout the entire matrix, achieving sufficient strengthening effect with minimal material quantity
3Ease of manufacture
If elastomer is used in the mixture, then processing is enabled, but residue remains on the surface decreasing conductivity
Solution Approach 1:
The patent extracts and removes the harmful elastomer component from the mixture, replacing it with metal powder that serves the binding function without leaving conductive-degrading residues on the surface, thereby eliminating the trade-off between processing capability and conductivity
Solution Approach 2:
The patent replaces the elastomer binder with metal powder that can be sintered and removed or integrated into the final structure, eliminating the problematic organic residue issue while maintaining processing feasibility
4Ease of manufacture
If vaporization of elastomer and plasma sintering are performed, then composite material wire is obtained, but production time is long (3 hours vaporization + 20 minutes sintering)
Solution Approach 1:
The patent removes the time-consuming elastomer vaporization step by replacing elastomer with metal powder binder that can be directly sintered, significantly reducing the overall production cycle time while maintaining manufacturing feasibility
Solution Approach 2:
The patent enables continuous sintering processing without the need for separate vaporization and sintering stages, allowing the binding and consolidation processes to occur in a more integrated and time-efficient manner
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 solution results in a carbon nanotube composite material with improved conductivity and a reduced carbon nanotube content, produced in a shorter time, without the need for elastomers, addressing the limitations of previous materials by optimizing the carbon nanotube distribution and processing methods.
Implementation Method 1
a green compact forming step of forming a powder green compact by applying a pressure to mixed powder containing metal powder and a carbon nanotube
Implementation Method 2
an extrusion processing step of implementing extrusion processing for the powder green compact under vacuum atmosphere, at 400° C. or more
Implementation Method 3
a carbon nanotube conductive path, which is composed of a carbon nanotube, and forms a conductive path allowing electricity to conduct therethrough
Implementation Method 4
an extrusion processing step of implementing extrusion processing for the powder green compact
Data Source
AI summary
A carbon nanotube composite material includes a metallic base composed of a polycrystalline substance in which a plurality of rod-shaped metallic crystal grains are oriented in a same direction and a carbon nanotube conductive path, which is composed of a carbon nanotube, and forms a conductive path allowing electricity to conduct therethrough in a longitudinal direction of the metallic base by being present in a part of grain boundaries between the rod-shaped metallic crystal grains on a transverse plane of the metallic base, and being present along the longitudinal direction of the metallic base.