Highly Oriented Graphene Structure via Low-Temperature Heat Treatment
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Solution Overview
Problem
Current methods for producing bulk graphitic materials, such as highly oriented pyrolytic graphite, face challenges in achieving high thermal and electrical conductivity, mechanical strength, and elastic modulus due to inadequate alignment of graphene planes, which results in lower-than-predicted properties and high production costs.
Innovation Solution
A process for producing a bulk highly oriented graphene structure (HOGS) with all graphene planes parallel to each other, involving the preparation of a graphene oxide dispersion, orientation-induced stress, and heat treatment to achieve exceptional thermal and electrical conductivity, mechanical strength, and elastic modulus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional chemical vapor deposition (CVD) followed by ultra-high temperature graphitization is used to produce highly oriented pyrolytic graphite (HOPG), then the graphene planes can be aligned to some extent, but the alignment remains inadequate and the production process is energy intensive, costly, and time-consuming
Solution Approach 1:
The invention changes the temperature parameter from ultra-high temperature (3000-3500°C) to low temperature (700-1500°C) during heat treatment, achieving superior graphene plane alignment without the energy-intensive conventional graphitization process. This parameter change enables the formation of highly oriented graphene structures at commercially viable temperatures.
Solution Approach 2:
The invention replaces the thermal-mechanical system (ultra-high temperature and pressure) with a chemical-based system using graphene oxide dispersion and controlled heat treatment. This substitution eliminates the need for energy-intensive equipment while achieving better alignment through chemical bonding mechanisms during low-temperature heat treatment.
2Reliability
If conventional CVD and ultra-high temperature graphitization are used to produce HOPG, then some orientation is achieved, but the thermal conductivity, electrical conductivity, and mechanical properties remain significantly lower than theoretically predicted
Solution Approach 1:
The invention performs preliminary orientation of graphene planes during the dispersion and deposition stages before heat treatment. The graphene oxide sheets are pre-aligned on the substrate through controlled deposition, and this preliminary orientation is then locked in during low-temperature heat treatment, resulting in superior final alignment and properties compared to post-forming alignment methods.
Solution Approach 2:
The invention uses graphene oxide as an intermediate composite material that combines the advantages of graphite (layered structure) with enhanced processability. The graphene oxide dispersion allows for controlled deposition and alignment, and subsequent heat treatment converts it to highly oriented graphene with superior properties that exceed theoretical predictions for conventional HOPG.
3Ease of manufacture
If conventional methods are used to produce bulk graphitic materials, then the materials can be manufactured, but the production cost is high and the process is not scalable
Solution Approach 1:
The invention uses liquid-based graphene oxide dispersion and hydraulic deposition methods to achieve large-area coverage and uniform thickness control. This liquid-phase processing approach is inherently more scalable and cost-effective than vacuum-based CVD methods, enabling commercial production while maintaining high material quality and consistency.
4Manufacturing precision
If ultra-high temperature graphitization is applied to achieve high orientation, then the process time and energy consumption increase significantly
Solution Approach 1:
The invention fundamentally changes the temperature parameter from ultra-high (3000-3500°C) to low (700-1500°C), which dramatically reduces process time while achieving superior orientation. The low-temperature heat treatment process completes in hours rather than days, eliminating the time penalty associated with conventional high-temperature graphitization.
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 results in a HOGS with thermal conductivity exceeding 1,500 W/mK, electrical conductivity over 10,000 S/cm, and elastic modulus greater than 120 GPa, surpassing the properties of conventional graphitic materials of similar thickness, while being more cost-effective and scalable.
Implementation Method 1
the dispensing and depositing procedure includes subjecting the graphene oxide dispersion to an orientation-inducing stress
Implementation Method 2
heat treating the mass of multiple layers or pieces of dried graphene oxide to produce the highly oriented graphene structure
Implementation Method 3
heat treating the mass of multiple layers or pieces of dried graphene oxide to produce the highly oriented graphene structure at a first heat treatment temperature higher than 100° C. to an extent that an inter-plane spacing d002 is decreased to a value less than 0.4 nm and the oxygen content is decreased to less than 5% by weight
Implementation Method 4
stacking the first layer of dried graphene oxide with the at least second layer of dried graphene oxide under an optional first compressive stress
Implementation Method 5
the graphene planes are stacked and bonded via van der Waal forces in the crystallographic c-direction (perpendicular to the graphene plane or basal plane)
Data Source
AI summary
A process for producing a bulk highly oriented graphene structure, comprising: (a) preparing a graphene oxide dispersion having graphene oxide (GO) sheets dispersed in a fluid medium; (b) dispensing and depositing the dispersion onto a surface of a supporting substrate to form a layer of GO, wherein the dispensing and depositing procedure includes subjecting the dispersion to an orientation-inducing stress; (c) removing the fluid medium to form a dried layer of GO having an inter-plane spacing d002 of 0.4 nm to 1.2 nm; (d) slicing the dried layer of GO into multiple pieces of dried GO and stacking at least two pieces of dried GO to form a mass of multiple pieces of GO; and (f) heat treating the mass under an optional first compressive stress to produce the highly oriented graphene structure at a first heat treatment temperature higher than 100° C. to an extent that an inter-plane spacing d002 is decreased to a value less than 0.4 nm.