Multilayer Composite Coating to Prevent Delamination
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Solution Overview
Problem
Existing composite materials with single-layer or boron nitride/silicon nitride coatings face issues with delamination and degradation due to reactions with preceramic polymers, leading to compromised interfacial bonding and mechanical properties, especially in aerospace and structural components.
Innovation Solution
A multilayer coating system comprising an inner boron-containing layer, an outer boron-containing layer that acts as a sacrificial layer converting to borosilicate glass, and an intermediate silicon-containing ceramic layer, which protects the inner layer and maintains mechanical integrity by limiting reactions with preceramic polymers during infiltration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer boron nitride coating is used, then interfacial bonding is achieved, but delamination and degradation occur due to reactions with preceramic polymers
Solution Approach 1:
The single-layer coating is segmented into a multilayer system consisting of an inner boron-containing layer, an intermediate silicon-containing layer, and an outer boron-containing layer. This segmentation allows each layer to perform specific functions: the inner layer provides interfacial bonding, the intermediate layer prevents unwanted reactions, and the outer layer protects during infiltration, thereby eliminating delamination and degradation issues.
Solution Approach 2:
The intermediate silicon-containing layer acts as a mediator between the inner boron-containing layer and the outer boron-containing layer. It prevents direct contact and unwanted reactions between the preceramic polymer and the inner boron-containing layer during infiltration, while still allowing the inner layer to maintain interfacial bonding with the reinforcement fibers.
2Ease of manufacture
If boron nitride/silicon nitride coatings are used, then coating formation is simplified, but reactions with preceramic polymers compromise mechanical properties
Solution Approach 1:
Different regions of the coating system are assigned different compositions and properties tailored to local requirements. The inner layer uses boron-containing material for interfacial bonding, the intermediate layer uses silicon-containing material for reaction protection, and the outer layer uses boron-containing material for infiltration protection. This local differentiation maintains mechanical properties while enabling controlled manufacturing.
3Object-affected harmful factors
If the outer layer is consumed in reaction with preceramic polymer, then unwanted reactions with reinforcement fibers are limited, but the outer layer material is depleted
Solution Approach 1:
The outer boron-containing layer is designed as a sacrificial, consumable protective layer that reacts with the preceramic polymer during infiltration. This disposable outer layer protects the more critical inner boron-containing layer and reinforcement fibers from unwanted reactions, accepting its own consumption as a necessary trade-off to preserve the integrity of the underlying structures.
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 multilayer coating system prevents delamination and enhances interfacial bonding, providing improved resistance to environmental degradation and maintaining mechanical properties in composite articles, unlike single-layer or boron nitride/silicon nitride coatings that suffer from 'eyebrowing' and delamination.
Implementation Method 1
consuming the outermost layer of boron-containing material in a reaction with the preceramic polymer material
Implementation Method 2
converting the preceramic polymer material to a ceramic matrix material
Data Source
Figure 1~2
AI summary
A composite article includes a substrate (22) and a multilayer coating (24) on the substrate (22). The multilayer coating (24) includes an inner layer (26) near the substrate (22), and outermost layer (28) on the inner layer (26), and an intermediate layer (30) between the inner layer (26) and the outermost layer (28). The inner layer (26) and outermost layer (28) are boron-containing materials, and the intermediate layer (30) is a silicon-containing ceramic material.