Aligned SWCNT Aggregate via Catalyst Orientation
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Solution Overview
Problem
Existing methods struggle to produce aligned single-walled carbon nanotube (SWCNT) aggregates with high specific surface area and alignment, making them unsuitable for applications requiring directional properties like super capacitors and heat conductive materials.
Innovation Solution
A method involving iron catalysts on an alumina co-catalyst substrate, with specific catalyst density and conditions for growing SWCNTs, achieving alignment through controlled X-ray diffraction and Herman's orientation factor, resulting in high specific surface area and low weight density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CVD method is used to produce CNT aggregates, then mass production is achieved, but the CNTs form disordered aggregates with low specific surface area and poor alignment
Solution Approach 1:
The patent applies preliminary action by pre-aligning the catalyst particles in a specific orientation on the substrate before CNT growth. This preliminary alignment of catalysts directs the subsequent CNT growth to occur in an ordered, aligned manner rather than randomly, thereby achieving high alignment degree in the final CNT aggregate structure
Solution Approach 2:
The patent implements local quality by creating regions with different catalyst densities and arrangements on the substrate. By controlling the local distribution and orientation of catalyst particles in specific areas, the CNTs grow with varying alignment characteristics in different regions, enabling tailored alignment properties in different parts of the aggregate
2Reliability
If CNTs are produced with high alignment and specific surface area, then they are suitable for directional applications, but they tend to adhere together due to strong Van der Waals force forming disordered aggregates
Solution Approach 1:
The patent introduces an intermediary substrate structure that prevents direct contact between CNTs. By growing CNTs from spaced catalyst particles on a porous or structured substrate, the substrate acts as a mediator that maintains separation between individual CNTs, reducing Van der Waals adhesion while preserving alignment and directional properties
Solution Approach 2:
The patent utilizes porous substrate structures to grow CNTs. The porous architecture provides physical separation between CNTs, preventing them from adhering together into disordered aggregates while maintaining their aligned orientation. The porosity reduces density and prevents complete aggregation
3Reliability
If aligned CNT aggregate is produced with high specific surface area, then it has improved electrical and thermal properties, but it has low bulk density making handling difficult
Solution Approach 1:
The patent employs porous structures in the CNT aggregate design. The porous architecture maintains high specific surface area for improved electrical and thermal properties while creating void spaces that reduce bulk density. The controlled porosity allows the material to retain functionality while improving handling characteristics through reduced weight
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 produces SWCNT aggregates with high directional anisotropy, enhanced electrical, mechanical, and thermal properties, suitable for applications such as super capacitors and heat conductive materials, with improved moldability and dispersibility.
Implementation Method 1
fine particles of an iron catalyst disposed on an alumina co-catalyst on the substrate
Implementation Method 2
a chemical vapor deposition method (hereinafter also referred to as a CVD method) has been known
Implementation Method 3
fine particles of an iron catalyst disposed on an alumina co-catalyst on the substrate
Implementation Method 4
in a case where X-rays are incident from a first direction parallel to the longitudinal direction of CNT and a second direction perpendicular to the first direction to measure an X-ray diffraction intensity
Implementation Method 5
to measure an X-ray diffraction intensity (θ-2θ method)
Data Source
AI summary
This invention provides an aligned single-walled CNT aggregate comprising a substrate, fine particles of iron catalyst with a density of 1×1011 to 1×1014/cm2 disposed on an alumina co-catalyst above the substrate, and a plurality of single-walled CNTs grown from the fine particles of the iron catalyst, in which the plurality of single-walled CNTs have a specific surface area of 600 m2/g to 2600 m2/g, and a weight density from 0.002 g/cm3 to 0.2 g/cm3, and the alignment degree which satisfies a few of specific conditions. This invention also provides a bulk aligned single-walled carbon nanotube aggregate and a powdered aligned single-walled carbon nanotube aggregate.