CMC Fiber Preform Coating via Solvent Vapor Pressure
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Solution Overview
Problem
Ceramic matrix composites (CMCs) face challenges in achieving a smooth surface due to the wicking effect of solvents during slurry infiltration, which retains the woven texture of the fiber preform, affecting aerodynamic performance.
Innovation Solution
Infiltrating a fiber preform with a solvent of lower vapor pressure, followed by applying a slurry coating with a solvent of higher vapor pressure, preventing capillary wicking and allowing for a uniform, porous surface coating to be formed, which is then dried to create a smooth surface layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a slurry-based surface coating is applied to improve surface uniformity, then surface smoothness is improved, but capillary wicking causes localized consolidation and persistent woven texture
Solution Approach 1:
The fiber preform is pre-infiltrated with a first solvent that fills the interstices between fibers before slurry application. This preliminary action creates a barrier that prevents capillary wicking of the slurry coating, allowing smooth surface formation without localized consolidation or persistent woven texture.
Solution Approach 2:
A first solvent acts as an intermediary substance between the fiber preform and the slurry coating. This solvent fills the interstices of the fiber preform and prevents the second solvent in the slurry from being wicked away, enabling uniform surface coating while maintaining the integrity of the slurry composition.
2Manufacturing precision
If the slurry coating is dried to remove solvent, then surface coating forms, but the first solvent continues to evaporate slowly from the preform
Solution Approach 1:
The invention utilizes differences in vapor pressure parameters between two solvents to control evaporation rates. The second solvent in the slurry coating has higher vapor pressure and evaporates quickly to form the surface coating, while the first solvent with lower vapor pressure remains in the preform interstices and evaporates slowly afterward, enabling staged drying without compromising surface quality.
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 results in a smooth, uniform surface layer on CMC components, eliminating the woven texture and enabling improved aerodynamic performance by preventing capillary wicking and allowing for tailored slurry viscosity adjustments.
Implementation Method 1
infiltrating a fiber preform with a first solvent, which fills interstices between fibers
Implementation Method 2
During drying, the second solvent evaporates from the slurry coating before the first solvent evaporates from the solvent-filled preform
Implementation Method 3
the first solvent prevents or inhibits capillary wicking of the second solvent
Data Source
AI summary
A method of controllably coating a fiber preform has been developed. The method includes infiltrating a fiber preform with a first solvent to form a solvent-filled preform. After the infiltration, a slurry is applied to one or more outer surfaces of the solvent-filled preform to form a slurry coating thereon. The slurry coating comprises particulate solids dispersed in a second solvent having a vapor pressure higher than that of the first solvent. The slurry coating and the solvent-filled preform are dried. During drying, the second solvent evaporates from the slurry coating before the first solvent evaporates from the solvent-filled preform. The slurry coating dries to form a porous surface coating comprising the particulate solids on the one or more outer surfaces of the solvent-filled preform. The drying of the solvent-filled preform continues after formation of the porous surface coating to remove the first solvent.