Self-Healing Ytterbium Silicate-Alumina Barrier for Silicon-Containing CMCs
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Solution Overview
Problem
Existing environmental barriers for ceramic matrix composites (CMCs) face challenges in achieving high density and self-healing capabilities while being compatible with substrates containing free silicon, particularly when exposed to high temperatures and corrosive environments, as traditional sintering agents like MgO and Fe2O3 compromise these properties.
Innovation Solution
A ceramic matrix composite part with an environmental barrier comprising Yb2-2γGd2γSiO5, Yb2-2γGd2γSi2O7, and alumina (Al2O3) is developed, allowing for a liquid phase formation above 1300°C, promoting densification and self-healing properties, even with substrates containing free silicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sintering temperature is increased to achieve high barrier seal, then sealing quality is improved, but substrate containing free silicon thermally decomposes above 1400°C
Solution Approach 1:
The patent changes the chemical composition parameters of the environmental barrier coating by incorporating ytterbium silicate and controlling alumina content between 5-15%, which modifies the liquid phase formation temperature to occur below 1400°C. This parameter adjustment allows achieving high density and sealing quality at temperatures compatible with silicon-containing substrates, resolving the contradiction between seal quality and substrate integrity.
2Temperature
If traditional sintering agents like MgO or Fe2O3 are added to reduce sintering temperature, then sintering temperature is reduced, but self-healing capacity and barrier stability are compromised
Solution Approach 1:
The patent extracts and eliminates traditional sintering agents (MgO, Fe2O3) from the environmental barrier coating composition. Instead, it relies on the inherent liquid phase formation of ytterbium silicate-alumina system at controlled temperatures to achieve both low-temperature sintering and self-healing capabilities, thus resolving the contradiction between temperature reduction and property preservation.
Solution Approach 2:
The patent creates a composite material system combining ytterbium silicate with controlled alumina content (5-15%), which synergistically provides liquid phase formation at appropriate temperatures. This composite approach enables simultaneous achievement of low sintering temperature, high density, and self-healing capacity without compromising barrier stability.
3Reliability
If alumina is used as sintering agent for self-healing barriers, then self-healing capability is achieved, but liquid phase formation temperature exceeds substrate compatibility limit
Solution Approach 1:
The patent precisely controls the alumina content parameter within 5-15% range in the ytterbium silicate-based environmental barrier coating. This parameter optimization adjusts the liquid phase formation temperature to occur below 1400°C, simultaneously achieving self-healing capability and substrate compatibility, thus resolving the contradiction between self-healing and temperature control.
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 provides excellent resistance to oxidation and corrosion, with a densified barrier that can repair cracks and relax thermomechanical stresses, ensuring prolonged part life and protection against oxidizing and corrosive species.
Implementation Method 1
allowing for a liquid phase formation above 1300°C, promoting densification and self-healing properties
Implementation Method 2
provides excellent resistance to oxidation and corrosion, with a densified barrier that can repair cracks
Data Source
Figure 1~2
AI summary
The invention relates to a part comprising a substrate (11) made of ceramic matrix composite material, the substrate comprising silicon, the part further comprising an environmental barrier (12) formed on at least one surface (S) of the substrate, the part being characterised in that the environmental barrier comprises at least one compound selected from Yb2-2γGd2γSiO5 and Yb2-2γGd2γSi2O7, where γ is between 0.05 and 0.15, and also characterised in that the environmental barrier further comprises alumina Al2O3, the molar content of alumina being between 5 and 15% of the total composition of the environmental barrier.