Carbon-Carbon Composite Coating for High-Temperature Oxidation Protection
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Solution Overview
Problem
Oxidation protection systems for carbon-carbon composite structures, such as those in aircraft brake disks, face challenges in maintaining material integrity at high temperatures due to oxidation, which is exacerbated by catalytic and thermal effects, leading to material loss and structural weakening.
Innovation Solution
A method involving the application of a ceramic layer slurry comprising aluminum and silicon powders, followed by heating in a nitrogen and oxygen environment to form a continuous alumina layer, and a sealant layer comprising a phosphate glass composition, applied to non-friction surfaces of carbon-carbon composite structures to create an effective oxidation protection system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CVD processes are used to deposit ceramic layers for oxidation protection, then oxidation protection performance is improved, but manufacturing cost increases significantly
Solution Approach 1:
The invention changes the deposition method from CVD (chemical vapor deposition) to a slurry-based dip-coating or spray-coating process followed by thermal treatment. This parameter change in the manufacturing process significantly reduces equipment requirements and operational costs while achieving comparable oxidation protection performance through the formation of a dense ceramic layer containing alumina, silica, and mullite phases.
Solution Approach 2:
The invention uses a disposable slurry composition that can be applied directly to the carbon-carbon composite substrate. The slurry contains inexpensive ceramic precursors (alumina, silica, mullite) in a liquid carrier that can be applied via simple coating methods and then thermally processed to form the protective layer, eliminating the need for expensive CVD equipment and complex process control.
2Loss of substance
If ceramic layers are formed to protect against oxidation at high temperatures, then material loss from oxidation is reduced, but the complexity of the manufacturing process increases
Solution Approach 1:
The invention combines multiple protective functions into a single ceramic layer formulation. The slurry contains alumina, silica, and mullite precursors that collectively provide oxidation resistance, thermal stability, and mechanical protection. This merged approach eliminates the need for multiple separate coating steps or complex multi-layer structures, simplifying the manufacturing process while maintaining comprehensive protection against carbon material loss.
Solution Approach 2:
The invention applies the ceramic precursor slurry to the carbon-carbon composite substrate before the substrate undergoes its service environment exposure. The slurry is applied as a liquid coating that can penetrate surface pores and defects, then undergoes thermal treatment to form a dense, adherent ceramic layer that pre-establishes protection against oxidation and material loss before the component is put into service.
3Object-affected harmful factors
If a dense ceramic layer is formed to inhibit oxidation, then oxidation resistance is improved, but porosity control becomes more difficult
Solution Approach 1:
The invention controls porosity by adjusting parameters in the slurry formulation and processing conditions, including ceramic precursor particle size distribution, slurry viscosity, drying rate, and thermal treatment temperature and atmosphere. These parameter changes enable the formation of a dense ceramic layer with minimized porosity that effectively blocks oxygen diffusion pathways, achieving excellent oxidation resistance without requiring extremely tight manufacturing tolerances.
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 described method significantly reduces material loss by forming a robust ceramic layer with alumina and aluminum nitride, combined with a sealant layer, which effectively inhibits oxidation, thereby enhancing the structural integrity and longevity of carbon-carbon composite components at elevated temperatures.
Implementation Method 1
heating the composite structure in an environment comprising nitrogen gas and oxygen gas to form a ceramic layer on the composite structure, wherein the ceramic layer comprises between 50% and 94% alumina by weight
Implementation Method 2
heating the composite structure in an environment comprising nitrogen gas and oxygen gas to form a ceramic layer on the composite structure, wherein the ceramic layer comprises between 50% and 94% alumina by weight
Implementation Method 3
applying a sealant slurry to the composite structure, wherein the sealant slurry comprises a sealant pre-slurry composition and a sealant carrier fluid, wherein the sealant pre-slurry composition comprises a sealant phosphate glass composition; and heating the composite structure to form a sealant layer on the composite structure
Data Source
AI summary
A method for forming an oxidation protection system on a composite structure may comprise: applying a ceramic layer slurry to the composite structure, wherein the ceramic layer slurry comprises aluminum and silicon in a solvent or carrier fluid; and heating the composite structure in an environment comprising nitrogen gas and oxygen gas to form a ceramic layer on the composite structure, wherein the ceramic layer comprises aluminum nitride and alumina.