Melt-Infiltrated CMC Slurry Design for Rapid Infiltration
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Solution Overview
Problem
Conventional methods for producing silicon-containing ceramic matrix composite (CMC) articles through melt infiltration face challenges such as 'choking' due to excessive SiC formation from carbon black, requiring controlled atmospheres and pressures, which slows infiltration and affects mechanical properties.
Innovation Solution
A matrix slurry composition with high SiC powder content and no carbon particulate, using primary resin binders that yield carbon char upon firing, allowing for rapid and complete infiltration without controlled atmospheres or pressures, promoting open porosity and controlled SiC formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional matrix slurry containing carbon black is used for preform fabrication, then SiC formation occurs during melt infiltration, but excessive SiC formation blocks pores and chokes infiltration
Solution Approach 1:
The invention removes carbon black from the matrix slurry composition, extracting the harmful element that causes excessive SiC formation. By eliminating carbon black, the preform contains only controlled carbon char from resin binders, preventing pore blockage and choking during melt infiltration while still allowing necessary SiC formation at fiber-matrix interfaces.
Solution Approach 2:
The invention changes the carbon content parameter in the slurry from high (carbon black + resin) to controlled (resin only). This parameter change transforms the carbon availability during infiltration, enabling SiC formation without excessive precipitation that would block pores and choke infiltration.
2Productivity
If controlled atmosphere and pressure are applied during melt infiltration, then infiltration can proceed, but process complexity and cost increase
Solution Approach 1:
The invention makes the preform self-sufficient by incorporating controlled carbon char within the matrix structure that naturally regulates SiC formation during infiltration. This self-service mechanism eliminates the need for external controlled atmosphere and pressure systems, as the preform itself prevents choking and enables complete infiltration under simple atmospheric conditions.
Solution Approach 2:
The invention removes the requirement for complex atmosphere and pressure control systems by extracting the root cause of infiltration problems (excessive carbon black). Without carbon black, the infiltration process no longer requires sophisticated control mechanisms, simplifying the overall process equipment and operation.
3Quantity of substance
If carbon black is present in the slurry, then SiC precursor is available, but pore blockage occurs during infiltration
Solution Approach 1:
The invention extracts carbon black from the slurry composition, removing the source of uncontrolled carbon that leads to pore blockage. Only resin binder carbon remains, which forms controlled char that does not precipitate excessively and block pores during the infiltration process.
Solution Approach 2:
The invention creates local quality differences in carbon distribution by using resin-derived carbon char that forms uniformly within the matrix structure rather than having concentrated carbon black particles. This local quality ensures carbon is available where needed (at fiber-matrix interfaces) without creating localized blockages in the pore network.
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
Enables faster and more complete infiltration, reduces the need for controlled environments, and enhances the mechanical robustness of CMC articles by preventing choking and maintaining porosity, allowing for infiltration in as little as two to ten minutes.
Implementation Method 1
A portion of the molten silicon is reacted with elemental carbon present in the porous preform, such as the aforementioned carbon black originally present in the slurry as a precursor, and/or any carbon char formed by pyrolysis of organic binders. The molten silicon and carbon black react to form additional silicon carbide that fills the porosity to yield the final CMC component.
Implementation Method 2
any carbon char formed by pyrolysis of organic binders
Implementation Method 3
the molten silicon and/or silicon alloy infiltrates into the porosity of the preform
Data Source
Figure 1
Figure 2
AI summary
A process for producing silicon-containing CMC articles. The process entails producing a matrix slurry composition that contains at least one resin binder and a SiC powder (24). The SiC powder is a precursor for a SiC matrix (22) of the CMC article and the resin binder is a precursor for a carbon char (30) of the matrix (22). A fiber reinforcement material is impregnated with the slurry composition to yield a preform (20), which is then heated to form a porous preform (20) that contains the SiC matrix (22) and porosity (26) and to convert the resin binder to the carbon char (30) that is present within the porosity. Melt infiltration of the porosity (26) is then performed with molten silicon or a molten silicon-containing alloy to react the carbon char (30) and form silicon carbide that at least partially fills the porosity (26) within the porous preform (20). The carbon char (30) constitutes essentially all of the elemental carbon in the porous preform (20).