Borosilicate Oxidation Coating for Hydrolysis-Resistant Composites
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Solution Overview
Problem
Existing oxidation protection systems for carbon-carbon composite structures, such as those used in aircraft braking systems, face hydrolytic instability due to the formation of water-soluble diboron trioxide (B2O3) at high temperatures, leading to potential material loss and degradation.
Innovation Solution
A method involving the application of a boron slurry and a silicon slurry to a carbon-carbon composite structure, followed by heating, to form a boron-glass and silicon-glass layer. The slurries include boron compounds, glass compounds, glass formers, and carrier fluids, with specific compositions that enhance stability and self-healing properties.
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-soluble diboron trioxide formation
Solution Approach 1:
A glass layer acts as an intermediary barrier between the boron carbide/silicon carbide oxidation protection layer and the water-containing environment. This glass intermediary prevents direct contact between water and the hydrolytically unstable B2O3, thereby maintaining both oxidation resistance and hydrolytic stability simultaneously.
Solution Approach 2:
The protection system uses a composite structure combining multiple materials: boron carbide, silicon carbide, and glass layers. This composite approach allows each material to perform its specialized function - boron carbide and silicon carbide provide oxidation resistance while the glass layer provides hydrolytic stability, resolving the contradiction between these two requirements.
2Loss of substance
If boron carbide and silicon carbide layers are applied for high-temperature protection, then material loss from oxidation is reduced, but water solubility of formed compounds increases leading to degradation
Solution Approach 1:
The glass layer serves as a protective intermediary that prevents water from reaching the boron-containing compounds formed during high-temperature operation. This intermediary barrier maintains the benefits of oxidation protection while eliminating the water solubility problem.
Solution Approach 2:
The harmful water-soluble diboron trioxide is effectively 'taken out' of the system by blocking its exposure to water through the glass layer. This extraction approach removes the source of degradation while preserving the oxidation protection function.
3Temperature
If traditional oxidation protection systems are used, then high-temperature oxidation resistance is achieved, but long-term stability in humid environments deteriorates
Solution Approach 1:
The multi-layer composite structure combines materials with complementary properties: boron carbide and silicon carbide for high-temperature oxidation resistance, and glass layers for long-term hydrolytic stability. This composite design allows the system to maintain both high-temperature performance and long-term stability in humid environments.
Solution Approach 2:
The glass layer acts as a stable intermediary that protects the underlying oxidation-resistant layers from water attack over long periods, enabling the system to maintain both high-temperature capability and long-term environmental stability.
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 significantly improves the water stability and high-temperature performance of the oxidation protection system, reducing material loss and degradation by forming a stable borosilicate layer that self-heals and resists hydrolysis.
Implementation Method 1
each of the first glass former and the second glass former may comprise colloidal silica
Implementation Method 2
forming a stable borosilicate layer that self-heals and resists hydrolysis
Implementation Method 3
heating the carbon-carbon composite structure
Implementation Method 4
heating the brake disk at a first temperature
Implementation Method 5
oxidation protection system on a carbon-carbon composite structure
Implementation Method 6
resists hydrolysis
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 includes a glass former.