Composite Oxidation Coating With Hydrolysis-Resistant Glass Layers
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Solution Overview
Problem
Existing oxidation protection systems for carbon-carbon composite structures, such as those used in aircraft wheel brake assemblies, face challenges due to hydrolytic instability caused by the water solubility of boron oxide (B2O3) formed at high temperatures.
Innovation Solution
A method is disclosed for forming an oxidation protection system on carbon-carbon composite structures, involving the application of pretreating compositions, followed by the application of boron and silicon slurries comprising specific glass compounds and modifiers. The boron slurry includes a mixture of boron carbide and boron nitride powders, while the silicon slurry includes silicon carbide and borosilicate glass, all combined with glass formers and modifiers to enhance stability and oxidation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If layers of boron carbide and silicon carbide are used for oxidation protection, then oxidation resistance is improved, but hydrolytic stability deteriorates due to water solubility of boron oxide
Solution Approach 1:
The patent applies composite materials by combining boron carbide, silicon carbide, and glass compounds (such as borosilicate glass) into a multi-component oxidation protection system. This composite approach allows the system to maintain oxidation resistance from the carbide layers while the glass compound forms a hydrophobic network that reduces water solubility of boron oxide, thereby improving hydrolytic stability without sacrificing oxidation protection.
Solution Approach 2:
The patent changes the chemical and physical parameters of the protection system by incorporating glass compounds that modify the properties of boron oxide. The glass former (such as SiO2) and glass modifiers alter the molecular structure and solubility characteristics of boron oxide, transforming it from a water-soluble substance into a stable, integrated part of the glass matrix that resists hydrolysis.
2Reliability
If boron oxide is formed during high-temperature operation, then oxidation protection is achieved, but water solubility increases causing hydrolytic instability
Solution Approach 1:
The glass compound acts as an intermediary between boron oxide and water. The glass former and modifiers create a matrix that intermediates the interaction between boron oxide and moisture, preventing direct contact and dissolution. This intermediary structure allows boron oxide to remain in a stable, non-soluble form while maintaining the oxidation protection function.
Solution Approach 2:
The patent converts the harmful water solubility of boron oxide into a benefit by incorporating it into a glass matrix. The boron oxide, which would normally be harmful due to its solubility, becomes a beneficial component of the glass compound that enhances the protection system's overall performance while eliminating the hydrolytic instability issue.
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 proposed method effectively forms a stable boron-glass and silicon-glass layer on the composite structure, significantly reducing oxidation and enhancing the water stability of the oxidation protection system, thereby protecting the carbon-carbon composite structures from high-temperature oxidation.
Implementation Method 1
applying a boron slurry to the carbon-carbon composite structure, applying a silicon slurry to the carbon-carbon composite structure, and heating the carbon-carbon composite structure
Implementation Method 2
The carbon-carbon composite structure is porous and the second pretreating composition penetrates a pore of the composite structure
Implementation Method 3
Oxidation protection systems including layers of boron carbide and silicon carbide may reduce infiltration of oxygen and oxidation catalysts into the composite structure
Data Source
AI summary
Systems and methods for forming an oxidation protection system on a composite structure are provided. In various embodiments, the oxidation protection system comprises a boron-glass layer formed on the composite substrate and a silicon-glass layer formed over the boron-glass layer. Each of the boron-glass layer and the silicon-glass layer include a glass former and a glass modifier. The boron-glass layer includes a boron compound comprising a mixture of boron carbide (B4C) powder and cubic boron nitride (BN) powder.