Carbon-Carbon Oxidation Coating Using Alumina-AlN Ceramic Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing oxidation protection systems for carbon-carbon composites, such as those used in aircraft brake disks, are costly due to chemical vapor deposition processes, and they fail to effectively prevent oxidation at high temperatures.
Innovation Solution
A method involving the application of a ceramic layer slurry containing aluminum and silicon powders, followed by heating in a nitrogen-oxygen environment to form a ceramic layer with alumina and aluminum nitride, and a sealant layer with a sealant phosphate glass composition, which is applied to carbon-carbon composite structures to create an oxidation protection system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical vapor deposition (CVD) processes are used to deposit ceramic layers, then oxidation protection is provided, but the manufacturing cost becomes prohibitively expensive
Solution Approach 1:
The patent replaces expensive CVD processes with a low-cost slurry coating method using inexpensive ceramic powders (alumina, silica, zirconia) suspended in a carrier fluid. The slurry is applied via dip-coating or spray-coating and cured at relatively low temperatures (500-1500°C), eliminating the need for costly CVD equipment while providing effective oxidation protection.
Solution Approach 2:
The invention changes the deposition parameters from high-temperature CVD (requiring vacuum equipment and high energy input) to low-temperature slurry curing (500-1500°C in atmospheric conditions). This parameter change dramatically reduces manufacturing cost while maintaining oxidation protection functionality through the formation of a dense ceramic layer.
2Reliability
If conventional oxidation protection systems are used, then some protection is provided, but they fail to effectively prevent oxidation at temperatures of 800°C or higher
Solution Approach 1:
The patent uses composite ceramic layers containing multiple oxide phases (alumina Al2O3, silica SiO2, zirconia ZrO2) in specific proportions. This composite composition provides synergistic effects: alumina provides high-temperature stability, silica forms a protective glassy matrix that seals pores, and zirconia enhances toughness and thermal shock resistance, collectively preventing oxidation at temperatures above 800°C.
Solution Approach 2:
The ceramic slurry formulation is optimized to create different phases in different regions of the coating during curing. The composition (e.g., alumina 20-70 wt%, silica 10-40 wt%, zirconia 5-20 wt%) is designed to form a multi-phase structure where each phase performs a specific function: alumina particles provide structural framework, silica forms binding matrix, and zirconia provides crack resistance, ensuring effective oxidation protection throughout the layer.
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 method provides effective oxidation protection at high temperatures, reducing material loss and enhancing the durability of carbon-carbon composite structures by forming a continuous layer of alumina and aluminum nitride, while using less expensive furnace processes.
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 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.