Silicone Oxidation Coating for Carbon-Carbon Crack Sealing
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Solution Overview
Problem
Carbon-carbon composite structures are prone to oxidation at high temperatures, leading to material loss and strength degradation due to oxygen infiltration, which existing oxidation protection systems inadequately address.
Innovation Solution
A silicone-based oxidation protection system is applied to carbon-carbon composite structures, comprising a primary layer with metal pigments and a sealing layer formed from a glass mixture, which creates a microporous framework to block oxygen diffusion and penetrate any defects, using a combination of leafing and non-leafing pigments to enhance barrier effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional oxidation protection coating is applied to carbon-carbon composite, then oxidation resistance is improved, but the coating contains microcracks and defects that allow oxygen diffusion
Solution Approach 1:
The patent applies a composite coating system consisting of multiple layers with different functions: a bottom coat containing reactive metal particles (aluminum, silicon, magnesium) that react with oxygen to form protective oxide scales, and a top seal coat containing glass particles that fill microcracks and pores. This multi-layer composite structure combines the benefits of active oxidation protection with physical barrier sealing, effectively addressing both oxidation resistance and crack prevention
Solution Approach 2:
The patent utilizes phase transitions and chemical reactions triggered by temperature changes. Upon heating, the reactive metal particles undergo oxidation reactions to form protective oxide scales, while the glass particles in the seal coat soften and flow to fill microcracks. This parameter-based activation (temperature-induced phase change and chemical reaction) enables the coating to dynamically adapt and seal defects under service conditions
2Reliability
If metal pigments are added to silicone-based coating, then barrier effectiveness is improved, but coating complexity increases
Solution Approach 1:
The reactive metal particles serve multiple functions simultaneously: they act as pigments for coloration, create a reactive barrier to oxygen diffusion through oxide scale formation, and provide thermal stability. The glass particles in the seal coat also perform multiple roles: filling microcracks, providing a physical barrier to oxygen, and enhancing coating adhesion. This multi-functionality reduces the need for separate specialized components
Solution Approach 2:
The patent combines the protective functions of multiple materials into a single integrated coating system. The bottom coat and top seal coat are applied as a unified system where the metal-rich bottom layer provides chemical protection through oxidation reactions, while the glass-containing top layer provides physical barrier protection. This merging of functions into a coordinated multi-layer system achieves superior protection without requiring separate complex subsystems
3Object-affected harmful factors
If glass mixture with different viscosity-temperature profiles is used in sealing layer, then crack sealing capability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs glass particles with specifically selected viscosity-temperature characteristics that undergo softening and flow at elevated temperatures. When the coating is heated during curing or service, the glass particles soften and flow into microcracks and pores, effectively sealing them. This temperature-dependent parameter change enables automatic defect sealing without requiring precise viscosity control during application
Solution Approach 2:
The glass particles are pre-positioned in the seal coat formulation before application. During the heating cycle that follows coating application, these pre-positioned glass particles soften and flow to seal defects. This preliminary placement combined with subsequent thermal activation simplifies the manufacturing process compared to requiring real-time viscosity adjustment during application
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 system significantly extends the lifespan of carbon-carbon composite components by forming a robust barrier against oxidation, reducing material loss and maintaining structural integrity under high-temperature conditions.
Implementation Method 1
forming a barrier to block oxygen diffusion into the C/C substrate
Implementation Method 2
oxygen gettering phase is also incorporated in the coating structure to remove O2 molecules that diffused into the coating through fine cracks and defects
Implementation Method 3
a sealing layer coupled to the primary layer, the sealing layer configured to penetrate a microporous framework of the primary layer
Implementation Method 4
the first glass compound having a first viscosity-temperature profile that is at least two orders of magnitude below a second viscosity-temperature profile of the second glass compound
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A method for forming an oxidation protection system on a carbon-carbon composite structure (102) comprises applying a silicone-based slurry to the carbon-carbon composite structure, the silicone-based slurry including metal pigments disposed therein; applying a sealing slurry to the silicone-based slurry; and heating the carbon-carbon composite structure.