In-Situ Hexagonal Boron Nitride Coating for Ceramic Matrix Composites
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Solution Overview
Problem
Ceramic matrix composites require a protective boron nitride layer to prevent molten silicon attack and high-temperature oxidation, but existing amorphous or turbostratic boron nitride coatings are not sufficiently resistant and reactive.
Innovation Solution
A method for forming a highly crystalline, hexagonal boron nitride layer in situ by reacting boron carbide (B4C) and silicon nitride (Si3N4) at temperatures above 1200 degrees Centigrade, either on the surface or surrounding the fiber reinforcement material within a ceramic matrix composite.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amorphous or turbostratic boron nitride coatings are used, then the fiber interface coating can be formed, but the resistance against molten silicon attack and high-temperature oxidation is insufficient
Solution Approach 1:
The patent applies parameter changes by heating the B4C and Si3N4 materials to temperatures above 1200 degrees Centigrade (specifically 1400-1500 degrees Centigrade) to transform the boron nitride from amorphous or turbostratic structure to highly crystalline hexagonal structure, thereby improving resistance against molten silicon attack and oxidation
Solution Approach 2:
The patent uses a composite approach by combining boron carbide (B4C) and silicon nitride (Si3N4) materials that react in-situ to form hexagonal boron nitride, leveraging the properties of both parent materials to create a more stable and protective coating structure
2Stability of the object's composition
If chemical vapor deposition is used to deposit boron nitride layers, then the coating can be formed on fiber reinforcement material, but the crystallinity and protective stability are insufficient
Solution Approach 1:
The patent applies preliminary action by first depositing layers of B4C and Si3N4 materials on the fiber reinforcement material, then heating them to high temperatures to induce in-situ reaction and form the highly crystalline hexagonal boron nitride structure, simplifying the overall manufacturing process
Solution Approach 2:
The patent uses self-service by allowing the B4C and Si3N4 materials to react in-situ on the fiber surface when heated, automatically forming the protective hexagonal boron nitride coating without requiring separate deposition or treatment steps
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 resulting highly crystalline boron nitride layer provides enhanced resistance to molten silicon and oxidative attacks, improving the mechanical properties and durability of ceramic matrix composites, particularly in high-temperature applications like gas turbine engine components.
Implementation Method 1
forming in situ a layer of boron nitride on the fiber reinforcement material... heating the B4C material and the Si3N4 material to a temperature above 1200 degrees Centigrade... forming a hexagonal boron nitride reaction product
Implementation Method 2
a more highly crystalline boron nitride phase is desirable... forming highly crystalline, hexagonal boron nitride... heating to a temperature in the range of from 1400 degrees Centigrade to 1500 degrees Centigrade to form the boron nitride reaction product
Data Source
AI summary
A method for forming in situ a boron nitride reaction product locally on a reinforcement phase of a ceramic matrix composite material includes the steps of providing a ceramic matrix composite material having a fiber reinforcement material; and forming in situ a layer of boron nitride on the fiber reinforcement material.