Multilayer Ceramic Coatings for Oxidation-Resistant C-C Composites
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Solution Overview
Problem
Carbon-carbon composite materials used in high-temperature applications are susceptible to oxidation, leading to deterioration of their physio-mechanical properties, which existing coatings fail to adequately address.
Innovation Solution
A high-temperature coating system comprising a crystallized metal carbide undercoat and multiple layers of ultra-high melting point refractory ceramic particles in a polymer-derived ceramic matrix, applied through a process that allows customization of properties such as thermal expansion, conductivity, and porosity to protect against oxidation and thermal degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carbon-carbon composite materials are used in high temperature applications, then they provide good mechanical properties and low mass density, but they become susceptible to oxidation leading to deterioration of physio-mechanical properties
Solution Approach 1:
The patent applies composite materials by creating a multi-layer coating system consisting of an undercoat layer and multiple overcoat layers. The undercoat layer comprises a polymer-derived ceramic matrix with refractory ceramic particles, while overcoat layers include additional protective components. This composite structure provides both mechanical strength and oxidation resistance, resolving the contradiction between maintaining mechanical properties and protecting against oxidation at high temperatures.
Solution Approach 2:
The patent creates an inert protective environment by forming a dense, crystallized ceramic matrix coating that acts as a barrier between the carbon-carbon substrate and the oxidizing atmosphere. The polymer-derived ceramic matrix and refractory ceramic particles form an inert layer that prevents oxygen access to the substrate, thereby protecting against oxidation while maintaining the substrate's mechanical properties.
2Reliability
If existing coatings are applied to carbon-carbon composites, then they provide some protection, but they fail to adequately address oxidation and thermal degradation at extreme temperatures
Solution Approach 1:
The patent applies parameter changes by utilizing the polymer-derived ceramic matrix transformation process. The organic polymer coating is converted through pyrolysis and crystallization into an inorganic ceramic matrix with fundamentally different and superior high-temperature properties. This parameter change from organic to inorganic state enables the coating to withstand extreme temperatures and provide reliable protection against thermal degradation and oxidation.
Solution Approach 2:
The patent uses an intermediary approach by introducing a polymer-derived ceramic matrix as an intermediate layer between the carbon-carbon substrate and the harsh high-temperature oxidizing environment. This intermediary layer undergoes transformation to become a stable ceramic barrier that effectively mediates the interaction between the substrate and extreme thermal conditions, providing adequate protection where existing coatings failed.
3Object-affected harmful factors
If a dense crystallized ceramic matrix coating is formed, then oxidation protection is improved, but the coating complexity and manufacturing process increase
Solution Approach 1:
The patent applies segmentation by dividing the protective coating into distinct functional layers: an undercoat layer providing base protection and adhesion, and multiple overcoat layers providing enhanced oxidation and thermal resistance. Each layer can be independently optimized and applied, which manages complexity by breaking down the overall protective function into manageable segments rather than requiring a single complex coating system.
Solution Approach 2:
The patent applies preliminary action by first applying an organic polymer coating that serves as a precursor material. This preliminary coating is then transformed in situ through controlled pyrolysis and crystallization processes to form the dense crystallized ceramic matrix. This preliminary action simplifies the manufacturing process compared to directly applying complex ceramic coatings, as the ceramic structure is generated from a simpler organic precursor that is already in place on the substrate.
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 coating system effectively protects carbon-carbon composite substrates from oxidation and thermal degradation, providing enhanced durability and stability at extreme temperatures, suitable for aerospace and other high-temperature applications.
Implementation Method 1
The mixture is heated to a heat treatment temperature to pyrolyze the pre-ceramic polymer and form the overcoat layer
Implementation Method 2
the overcoat layer includes a crystallized ultra-high melting point polymer-derived ceramic matrix
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
A method includes forming a crystallized metal carbide undercoat on a surface of a carbon-carbon composite substrate. The method further includes forming an overcoat on a surface of the undercoat. The overcoat includes a plurality of crystallized ultra-high melting point overcoat layers. Each overcoat layer is sequentially formed by applying a mixture to a surface of an underlying layer and heating the mixture. The mixture includes a plurality of ultra-high melting point refractory ceramic particles and a pre-ceramic polymer. The mixture is heated to a heat treatment temperature to pyrolyze the pre-ceramic polymer and form the overcoat layer in an inert atmosphere or under vacuum. As a result, the overcoat layer includes a crystallized ultra-high melting point polymer-derived ceramic matrix that includes the plurality of ultra-high melting point refractory ceramic particles.