Composite Oxidation Coating with Self-Healing Boron-Silicon Layers
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Solution Overview
Problem
Existing oxidation protection systems for carbon-carbon composites fail to prevent oxidation at high temperatures, particularly in aircraft braking systems, due to migration and cracking, exposing the composite to oxygen and causing material loss.
Innovation Solution
A multi-layer oxidation protection system comprising a boron layer, a silicon layer, and sealing layers of monoaluminum phosphate and phosphoric acid, applied using a boron slurry and silicon slurry, which forms a boron and silicon coating on the composite structure, providing self-healing properties to mitigate oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphate glass-based oxidation protection systems are applied to non-wear surfaces of brake disks, then oxidation protection is provided, but the OPS migrates away from non-wear surface edges proximate to wear surfaces at high operating temperatures, leaving the composite material vulnerable to oxidation
Solution Approach 1:
The patent applies different materials to different regions of the brake disk. A phosphate-based oxidation protection system is applied to the non-wear surface, while a migration-resistant material (such as borosilicate glass, alumina, or zirconia) is applied specifically to the edges proximate to wear surfaces. This local differentiation ensures that the edge regions, which are prone to OPS migration, are protected by materials that maintain their structural integrity and resist migration at high temperatures.
Solution Approach 2:
The patent uses composite material structures combining phosphate-based oxidation protection systems with migration-resistant materials. The composite structure leverages the oxidation barrier properties of phosphate glass while incorporating materials with high thermal stability and low migration tendency. This composite approach allows the system to simultaneously achieve effective oxidation protection and resistance to thermal migration at the edges of brake disks.
2Object-affected harmful factors
If phosphate-based oxidation protection systems are used, then infiltration of oxygen and oxidation catalysts is reduced, but significant oxidation of carbon-carbon composites still occurs during operation due to cracks in the protection system
Solution Approach 1:
The patent incorporates inert or oxidation-resistant materials such as borosilicate glass, alumina, and zirconia into the oxidation protection system. These materials create a more inert environment at the edges of the brake disk, preventing oxygen and oxidation catalysts from reaching the carbon-carbon composite substrate even when cracks are present in the phosphate-based protection system. The inert materials act as a secondary barrier that maintains protection effectiveness despite system degradation.
3Reliability
If a multi-layer system with boron and silicon compounds is applied, then self-healing properties are achieved to mitigate oxidation, but the system complexity increases
Solution Approach 1:
The patent incorporates boron and silicon compounds into the oxidation protection system that can react with oxygen and metal oxides at high temperatures to form protective glassy phases in situ. This self-service mechanism allows the coating to automatically repair itself by forming healing products that seal cracks and prevent further oxidation, without requiring external intervention or complex active control systems.
Solution Approach 2:
The patent utilizes temperature-dependent parameter changes to activate the self-healing mechanism. At elevated operating temperatures, the boron and silicon compounds undergo chemical transformations, reacting with oxygen and metal oxides to form protective glassy phases. This parameter-based activation (temperature-triggered chemical reaction) provides a simple yet effective self-healing mechanism that does not require complex system architecture.
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 effectively prevents oxidation by maintaining the integrity of the protection layers at high temperatures, reducing material loss and oxidation through self-healing mechanisms, even in the presence of cracks and extreme conditions.
Implementation Method 1
A method for forming an oxidation protection system on a composite structure includes heating the composite structure to form a boron layer from the boron slurry and heating the composite structure to form a silicon layer from the silicon slurry
Implementation Method 2
Phosphate-based oxidation protection systems may reduce infiltration of oxygen and oxidation catalysts into the composite structure
Implementation Method 3
at such high operating temperatures, phosphate glass-based oxidation protection systems (OPS) applied to non-wear surfaces of brake disks may experience decreasing viscosity, which may cause the OPS to migrate away from non-wear surface edges
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
An oxidation protection system disposed on a substrate is provided, which may comprise a boron layer comprising a boron compound disposed on the substrate; a silicon layer comprising a silicon compound disposed on the boron layer; and at least one sealing layer comprising monoaluminum phosphate and phosphoric acid disposed on the silicon layer.