Phosphate Glass Coating for Carbon-Carbon Composite 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, leading to material loss and structural weakening due to infiltration of oxygen and catalytic contaminants.
Innovation Solution
A method involving the application of a phosphate glass-based coating system, comprising a base layer formed from a first slurry with a primary flow modifier like cellulose and a secondary flow modifier like poly(vinyl alcohol), and a sealing layer, which are applied and heated to adhere to the composite structure, providing enhanced oxidation protection by reducing hydrolytic instability and mass loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If phosphate-based oxidation protection systems are used, then infiltration of oxygen and oxidation catalysts is reduced, but significant oxidation of carbon-carbon composites still occurs during operation
Solution Approach 1:
The oxidation protection system is divided into multiple functional layers: a base layer containing phosphate glass and refractory materials for foundational protection, and an outer sealing layer with different composition for enhanced oxidation resistance. This layered segmentation allows each layer to perform its specific function optimally, with the base layer providing structural support and the sealing layer providing superior oxidation barrier properties.
Solution Approach 2:
The patent employs composite coating materials combining phosphate glass with refractory materials such as aluminum oxide, silicon oxide, and various metal oxides. This composite approach creates a coating system that leverages the low melting point and glass-forming capabilities of phosphate glass while incorporating the high-temperature stability and oxidation resistance of refractory materials, achieving superior overall protection effectiveness.
2Stability of the object's composition
If phosphate glass composition is used in coating, then hydrolytic stability is improved, but mass loss still occurs at high temperatures
Solution Approach 1:
The patent systematically varies the chemical composition parameters of the phosphate glass, including ratios of P2O5 to metal oxides, incorporation of specific refractory materials, and adjustment of glass former content. These parameter changes optimize the balance between hydrolytic stability (maintained through phosphate glass network integrity) and mass loss resistance (improved through refractory material incorporation and controlled glass composition).
Solution Approach 2:
By creating composite phosphate glass systems incorporating refractory materials like aluminum oxide, silicon oxide, and metal oxides, the patent achieves a material that maintains the hydrolytic stability of phosphate glass while gaining high-temperature stability and reduced mass loss characteristics from the refractory components.
3Object-affected harmful factors
If base layer and sealing layer are applied, then oxidation protection is enhanced, but coating process complexity increases
Solution Approach 1:
The protection system is segmented into two layers with distinct functions: the base layer provides foundational protection and adhesion to the substrate, while the sealing layer provides enhanced oxidation barrier properties. This segmentation allows for optimized composition in each layer and simplifies the manufacturing process by enabling separate application and curing of each layer, making the overall complex protection goal achievable through manageable steps.
Solution Approach 2:
The base layer is applied and cured first to establish a stable foundation with good adhesion to the substrate. This preliminary action creates a prepared surface that enhances the performance and adhesion of the subsequent sealing layer, allowing the final oxidation protection system to achieve superior performance through this sequential, preparatory approach.
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 phosphate glass coating system significantly reduces oxidation and mass loss of carbon-carbon composite structures at high temperatures, offering improved hydrolytic stability and durability, thereby enhancing the structural integrity of components like aircraft brake components.
Implementation Method 1
heating the composite structure to a temperature sufficient to adhere the base layer to the composite structure
Implementation Method 2
Phosphate-based oxidation protection systems may reduce infiltration of oxygen and oxidation catalysts into the composite structure
Data Source
AI summary
The present disclosure provides a method for coating a composite structure, comprising forming a first slurry by combining a first pre-slurry composition comprising a first phosphate glass composition, with a primary flow modifier and a first carrier fluid, wherein the primary flow modifier comprises at least one of cellulose or calcium silicate; applying the first slurry on a surface of the composite structure to form a base layer; and heating the composite structure to a temperature sufficient to adhere the base layer to the composite structure.