Liquid Metal Synthesis of Large Wrinkle-Free 2D Material Sheets
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Solution Overview
Problem
Current methods for manufacturing large, high-quality two-dimensional materials like graphene are limited by the difficulty in producing specimens larger than 1-3 cm^2 due to issues such as wrinkling, folding, and impurities, and the challenge of achieving economies of scale.
Innovation Solution
A method involving a liquid precursor composition on a flat surface of a liquid metal with a melting point of less than or equal to 250°C, allowing for the formation of large sheets of two-dimensional material without the binding issues associated with solid substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Chemical Vapour Deposition (CVD) is used to manufacture graphene, then graphene specimens can be produced, but the specimens are limited to a maximum size of around 1-3 cm^2 and exhibit wrinkles, folds, and cracks
Solution Approach 1:
The invention changes the substrate state from solid to liquid, and reduces the operating temperature from 1200°C to room temperature or slightly elevated temperatures. This parameter change allows for larger substrate areas and eliminates the thermal contraction issues that cause wrinkles and cracks in CVD-produced graphene.
Solution Approach 2:
The invention utilizes the liquid phase of metal substrates (such as gallium, indium, or their alloys) instead of the solid phase used in CVD. The liquid substrate maintains a flat surface during deposition and does not undergo thermal contraction, thereby producing large-area, high-quality graphene without defects. After deposition, the liquid substrate can be solidified or the product removed.
2Area of stationary object
If large substrates with suitable crystal faces are provided for CVD, then larger graphene specimens may be produced, but the manufacturing complexity and cost increase significantly
Solution Approach 1:
The invention changes the substrate from solid to liquid state, eliminating the need for complex crystalline face preparation. Liquid metals naturally provide flat, defect-free surfaces without requiring specialized crystallographic orientations, thereby simplifying the manufacturing process while enabling large-area production.
Solution Approach 2:
The liquid metal substrate can be easily replaced or regenerated. Unlike expensive, specially-prepared solid substrates that require complex preparation and cleaning, the liquid substrate system allows for simple disposal or renewal, reducing manufacturing complexity and cost for large-area production.
3Manufacturing precision
If copper or nickel substrates are used in CVD, then graphene can be formed, but the different contraction rates between substrate and product cause wrinkles, folds, and cracks
Solution Approach 1:
The invention uses liquid metal substrates that remain in the liquid phase during the deposition and cooling process. Since the substrate does not undergo phase transition to solid, there is no thermal contraction, and thus no mismatch in contraction rates between substrate and graphene product. This eliminates wrinkles, folds, and cracks that plague CVD processes.
Solution Approach 2:
The invention dramatically reduces the operating temperature from 1200°C to room temperature or slightly elevated temperatures. This temperature reduction, combined with using liquid substrates, eliminates the thermal stress and contraction issues that occur when hot-deposited graphene cools on solid substrates with different thermal expansion coefficients.
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
Enables the synthesis of arbitrarily large, high-quality two-dimensional material sheets with reduced defects, facilitating easier separation from the substrate and potentially lowering production costs through economies of scale.
Implementation Method 1
The graphene precursor atoms must then cool down to ambient temperatures in vacuo on a solid substrate to form graphene
Implementation Method 2
the methane feedstock is heated to a molecular decomposition temperature of some 1200° C
Data Source
AI summary
A method of synthesizing a layer of two-dimensional material or a stack of layers of two-dimensional material comprises: providing (101) a liquid precursor composition on a flat surface of a liquid metal, the liquid metal being a metal or metal alloy having a melting point of less than or equal to 250° C. at a pressure of 1 atm; and forming (102) at least one layer of material on the surface of the liquid metal from the liquid precursor composition. By forming the layer or stack on the surface of the liquid metal, large layers and stacks which are free of wrinkles and creases may be obtained. Also provided are an apparatus useful for performing the method, and products such as energy storage devices obtainable by the method.