Composite Oxidation Coating for Hydrolytic Stability
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Solution Overview
Problem
Oxidation protection systems for carbon-carbon composite structures face hydrolytic instability due to the water solubility of boron oxide formed at high temperatures, leading to increased oxidation and material loss.
Innovation Solution
A method involving the application of a boron slurry and a silicon slurry, each comprising specific glass compounds and modifiers, is used to form a boron-glass and silicon-glass layer on the composite structure, with cubic boron nitride and colloidal silica enhancing oxidation resistance and water stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If boron carbide and silicon carbide layers 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 introduces glass compounds (such as borosilicate glass, aluminosilicate glass) as intermediary substances between the boron carbide/silicon carbide layers and the external environment. These glass compounds form a protective glassy matrix that encapsulates the boron oxide, preventing its direct contact with water and eliminating hydrolytic instability while maintaining oxidation protection capabilities.
Solution Approach 2:
The patent creates a composite oxidation protection system combining boron carbide, silicon carbide, and glass compounds in a multi-phase structure. This composite material integrates the high-temperature oxidation resistance of boron carbide/silicon carbide with the hydrolytic stability and protective properties of glass compounds, achieving both required performance characteristics simultaneously.
2Reliability
If boron oxide is formed during high-temperature operation, then oxidation protection function is achieved, but water solubility increases leading to material loss
Solution Approach 1:
The glass compounds act as intermediary substances that trap and stabilize boron oxide within a glassy matrix, preventing its dissolution in water. This intermediary layer maintains the oxidation protection function while eliminating the harmful water solubility of boron oxide, thereby preventing carbon material loss.
Solution Approach 2:
The patent converts the harmful water-soluble boron oxide into a beneficial component by incorporating it within the glass matrix. The boron oxide that would normally cause material loss is transformed into a stable part of the glassy protective layer, turning a detrimental substance into a functional component of the protection system.
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 solution effectively reduces oxidation and improves water stability of the oxidation protection system, maintaining material integrity under high-temperature conditions.
Implementation Method 1
applying a boron slurry and a silicon slurry, each comprising specific glass compounds and modifiers, is used to form a boron-glass and silicon-glass layer on the 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
heating the carbon-carbon composite structure
Data Source
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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.