Borosilicate Overcoat for High-Temperature Composite Oxidation Protection
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Solution Overview
Problem
Phosphate-based oxidation protection systems for carbon-carbon composite structures face challenges at high temperatures, including viscosity decrease and migration away from non-wear surface edges, leaving these areas vulnerable to oxidation, especially in aircraft braking systems.
Innovation Solution
A method involving the formation of a borosilicate glass layer and a phosphate glass base layer, optionally with a sealing layer, applied to carbon-carbon composite structures using slurry compositions and carrier fluids, where the borosilicate glass layer helps prevent migration and enhance oxidation protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphate-based oxidation protection systems are applied to carbon-carbon composites, then oxidation protection is provided, but the system migrates away from non-wear surface edges at high temperatures, leaving these areas vulnerable
Solution Approach 1:
The oxidation protection system is divided into multiple functional layers: a phosphate-based base layer providing oxidation protection, and a borosilicate glass overcoat layer preventing migration. This segmentation allows each layer to perform its specific function - the base layer provides chemical protection while the overcoat layer provides physical stability and prevents flow.
Solution Approach 2:
The invention uses a composite structure combining phosphate glass and borosilicate glass layers. The phosphate glass provides oxidation resistance while the borosilicate glass adds high-temperature stability and migration prevention. This composite material approach allows the system to simultaneously achieve both oxidation protection and positional stability at elevated temperatures.
2Loss of substance
If phosphate-based oxidation protection systems are used, then carbon material loss is reduced, but viscosity decreases at high temperatures causing migration from non-wear surface edges
Solution Approach 1:
The borosilicate glass overcoat acts as an intermediary layer between the phosphate-based oxidation protection system and the external environment. This overcoat layer has higher viscosity at operating temperatures and serves as a barrier that prevents the phosphate glass from migrating, while still allowing the underlying system to provide oxidation protection.
Solution Approach 2:
The invention changes the physical and chemical parameters of the protection system by introducing borosilicate glass with different thermal properties. The borosilicate glass maintains higher viscosity at elevated temperatures compared to phosphate glass alone, thereby preventing migration while the composite system continues to reduce carbon material loss through oxidation protection.
3Stability of the object's composition
If multiple layers are applied to prevent migration, then protection stability is improved, but manufacturing complexity increases
Solution Approach 1:
The borosilicate glass overcoat is applied in advance as a thin layer before or with the phosphate-based oxidation protection system. This preliminary action ensures that the migration-prevention barrier is already in place before the phosphate glass is applied, preventing migration during subsequent heating cycles without requiring complex post-processing steps.
Solution Approach 2:
The invention merges the application processes by allowing the borosilicate glass overcoat and phosphate-based oxidation protection system to be applied in sequence or simultaneously in a single manufacturing cycle. The layers are combined through co-firing or sequential firing, integrating multiple functions into a unified manufacturing process that reduces overall complexity.
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 borosilicate glass layer effectively prevents migration of the oxidation protection system, maintaining better protection for carbon-carbon composite materials at high temperatures, reducing weight loss and oxidation risks, as demonstrated by comparative testing.
Implementation Method 1
The borosilicate glass layer effectively prevents migration of the oxidation protection system, maintaining better protection for carbon-carbon composite materials at high temperatures
Implementation Method 2
Phosphate-based oxidation protection systems may reduce infiltration of oxygen and oxidation catalysts into the composite structure
Implementation Method 3
heating the composite structure to a temperature sufficient to form a borosilicate glass layer on the composite structure
Implementation Method 4
heating the composite structure to a temperature sufficient to form a borosilicate glass layer on the composite structure
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
Systems and methods for forming an oxidation protection system, on a composite structure is provided. In various embodiments, an oxidation protection system disposed on a substrate may comprise a borosilicate glass layer comprising a borosilicate glass, a base layer comprising a first pre-slurry composition comprising a first phosphate glass composition, and/or a sealing layer comprising a second pre-slurry composition comprising a second phosphate glass composition. The borosilicate glass layer, base layer, and/or sealing layer may be disposed in any suitable order relative to the composite structure.