Carbon Composite Oxidation Protection via Dual-Phase Phosphate Coating
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Solution Overview
Problem
Current methods for protecting carbon-containing composite materials, such as carbon/carbon composite brake disks, from oxidation are inadequate in wet environments and in the presence of catalysts, with boron-based solutions being toxic and unstable, and boron oxide being sensitive to moisture, leading to limited protection lifespan.
Innovation Solution
A method involving a coating composition of metallic phosphate, titanium powder, and boron carbide (B4C) powder applied in an aqueous suspension, followed by heat treatment between 330° C to 730° C to create a crystalline and amorphous metallic phosphate phase, providing both catalytic oxidation protection and self-healing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If boron oxide B2O3 is used for protection against oxidation, then protection against catalytic oxidation is provided, but B2O3 presents high sensitivity to moisture and vaporizes at temperatures below 900° C., leading to limited protection lifespan
Solution Approach 1:
The patent changes the chemical form of boron from oxide (B2O3) to carbide (B4C). This parameter change transforms the material properties: B4C is stable in moisture and does not vaporize at service temperatures, thereby resolving the contradiction between providing effective oxidation protection and maintaining long-term durability in wet environments.
Solution Approach 2:
The patent introduces B4C as an intermediary substance that releases B2O3 in a controlled manner during oxidation. The B4C acts as a stable reservoir that gradually provides the necessary B2O3 for protection without being directly exposed to moisture, thus extending the protection lifespan while maintaining effectiveness.
2Reliability
If boron powder and B2O3 are used in the composition, then protection against oxidation is achieved, but the composition may be unstable and difficult to use, since boron and B2O2 react with monoaluminum phosphate
Solution Approach 1:
The patent changes the chemical form of boron from powder/oxide to carbide (B4C). This parameter change eliminates the instability issue because B4C is chemically stable and does not react with monoaluminum phosphate under normal storage and application conditions, while still providing the necessary oxidation protection when oxidized.
3Reliability
If internal protection is provided by impregnating with metallic phosphate solution and heat treatment, then some oxidation protection is achieved, but protection against catalytic oxidation in wet environments remains insufficient
Solution Approach 1:
The patent creates a composite protective coating combining metallic phosphate (for internal protection and adhesion) with B4C and titanium compounds (for catalytic oxidation resistance). This composite structure provides synergistic protection: the metallic phosphate fills pores and adheres to the substrate, while B4C and titanium compounds resist catalytic oxidation even in the presence of moisture and catalysts.
Solution Approach 2:
The patent introduces B4C as an intermediary substance that provides stable boron source for catalytic oxidation protection. B4C gradually oxidizes to form B2O3 on the surface, providing continuous protection against catalytic oxidation without being directly exposed to moisture, thus enhancing protection in wet environments.
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 solution offers enhanced protection against oxidation in wet environments and high temperatures, with boron carbide providing a stable and durable source of boron, and the amorphous phase ensuring cohesion and filling of surface pores, while the crystalline phase traps oxidation catalysts, resulting in improved durability and resistance to thermal and catalytic oxidation.
Implementation Method 1
applying heat treatment to the coating composition applied during step a) with a treatment temperature lying in the range 330° C. to 730° C. being imposed during the heat treatment in order to obtain a coating on the outside surface of the part, the coating comprising a first phase in which the metallic phosphate is in crystalline form and a second phase in which the metallic phosphate is in amorphous form
Implementation Method 2
In service and in an oxidizing medium, TiB2 oxidizes so as to form B2O3, thereby regenerating the B2O3 and conserving a borosilicate glass phase
Implementation Method 3
the amorphous phase ensuring cohesion and filling of surface pores
Implementation Method 4
the crystalline phase traps oxidation catalysts
Data Source
AI summary
A method of protecting a part made of carbon-including composite material against oxidation, the method including a) applying a coating composition on at least a portion of the outside surface of the part, the coating composition being in the form of an aqueous suspension including: a metallic phosphate; a powder of a compound comprising titanium; and a B4C powder; and b) applying heat treatment to the coating composition applied during step a) with a treatment temperature lying in the range 330° C. to 730° C. being imposed during the heat treatment in order to obtain a coating on the outside surface of the part, the coating including a first phase in which the metallic phosphate is in crystalline form and a second phase in which the metallic phosphate is in amorphous form.