Boron-Silicon-Glass Coating to Prevent Composite Edge Oxidation
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Solution Overview
Problem
Carbon-carbon composite structures in high-temperature applications, such as aircraft braking systems, face significant oxidation issues despite existing oxidation protection systems, with phosphate-based systems experiencing viscosity decrease and migration at non-wear surface edges, and CVD-based systems being costly.
Innovation Solution
A boron-silicon-glass composite slurry is applied to the composite structure, comprising boron carbide, silicon carbide, and borosilicate glass, which forms a boron-silicon-glass layer upon heating, providing effective oxidation protection and self-healing properties without the need for chemical vapor deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphate-based oxidation protection systems are applied to carbon-carbon composites, then oxidation resistance is improved, but the system experiences viscosity decrease and migration at high temperatures, causing protection failure at non-wear surface edges
Solution Approach 1:
The patent modifies the chemical composition parameters of the oxidation protection system by incorporating boron carbide particles (5-20 micrometers) and boron nitride particles (5-20 micrometers) into the phosphate glass matrix. This compositional adjustment maintains high-temperature viscosity stability while preserving oxidation resistance, preventing the migration issue that plagues conventional phosphate-based systems.
2Reliability
If CVD process is used to apply boron carbide and silicon carbide coatings, then oxidation protection effectiveness is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent replaces the expensive CVD process with a cost-effective slurry application method. The oxidation protection layer is applied as a slurry containing phosphate glass powder, boron carbide particles, and boron nitride particles, then cured at relatively low temperatures (200-400°C). This approach achieves comparable oxidation protection to CVD while dramatically reducing manufacturing costs and equipment requirements.
3Object-affected harmful factors
If phosphate-based oxidation protection systems are used, then initial oxidation protection is provided, but significant oxidation of carbon-carbon composites still occurs during operation at high temperatures
Solution Approach 1:
The patent creates a composite oxidation protection layer by combining phosphate glass matrix with boron carbide and boron nitride particles. This composite structure provides superior oxidation resistance compared to conventional phosphate-based systems, significantly reducing carbon material loss during high-temperature operation. The boron-containing particles form protective borosilicate glass phases that effectively barrier oxygen diffusion.
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 boron-silicon-glass layer significantly reduces material loss due to oxidation, offering superior protection compared to phosphate-based systems and comparable effectiveness to CVD-based systems while minimizing costs and migration issues.
Implementation Method 1
Oxidation protection system having coatings of boron carbide and silicon carbide applied via chemical vapor deposition (CVD) have demonstrated effective oxidation protection at high operating temperature.
Implementation Method 2
heating the composite structure to a temperature sufficient to form a boron-silicon-glass layer on the composite structure
Implementation Method 3
Phosphate-based oxidation protection systems may reduce infiltration of oxygen and oxidation catalysts into the 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, an oxidation protection system disposed on a substrate may comprise a boron-silicon-glass layer formed directly on the composite structure. The boron-silicon-glass layer may comprise a boron compound, a silicon compound, and a glass compound.