Ceramic Matrix Slurry Infusion with Soluble Coating Removal
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Solution Overview
Problem
In the production of ceramic matrix composites, the organic coatings on ceramic fibers degrade at high temperatures, leading to defects such as voids and poor physical properties due to incomplete contact between fibers and the matrix, necessitating a separate step to remove the coating before sintering.
Innovation Solution
A method involving exposing coated ceramic fiber tows to a ceramic matrix slurry where the coating is soluble in the solvent, allowing at least 50% of the coating to dissolve and infuse into the slurry, forming a prepreg that can be sintered without a separate cleaning step, maintaining the integrity of spread tows and preventing reversion to a circular shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If organic coating is applied to ceramic fibers, then fiber handling and processing is improved, but high-temperature degradation causes voids and poor physical properties
Solution Approach 1:
The coating material is changed from conventional organic sizing to a water-soluble inorganic coating (such as water-soluble glass or ceramic-based coating). This parameter change allows the coating to dissolve during slurry infusion, eliminating high-temperature degradation while maintaining handling benefits during processing.
Solution Approach 2:
The harmful organic coating is completely removed by dissolution in water during the slurry infusion process. The water-soluble inorganic coating dissolves and is extracted from the fiber bundle, leaving no residual material that would cause voids or degradation at sintering temperatures.
2Reliability
If coating is removed before sintering, then voids are reduced, but additional processing steps are required
Solution Approach 1:
The coating removal step is merged with the slurry infusion step. The water-soluble inorganic coating dissolves during the normal slurry infusion process, combining two operations (coating removal and matrix infusion) into one simultaneous process, thereby eliminating additional processing steps.
Solution Approach 2:
The coating itself provides the mechanism for its own removal. The water-soluble inorganic coating automatically dissolves when exposed to water during slurry infusion, eliminating the need for separate removal operations. The system serves itself by using the slurry's water content to remove the coating.
3Manufacturing precision
If spread tow form is maintained, then fiber distribution is improved, but coating application becomes more difficult
Solution Approach 1:
The coating is applied locally to individual fibers within the spread tow rather than attempting to coat the entire spread bundle uniformly. The water-soluble inorganic coating can be applied to individual fibers before spreading, allowing the spread tow form to be maintained while still providing coating protection during handling.
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
This approach enables the use of coated ceramic fibers in forming ceramic matrix composites without additional processing steps, ensuring high-temperature stability and maintaining the desirable flat, thin form of spread tows, thereby enhancing the efficiency and reducing defects in the final composite.
Implementation Method 1
at least 50% of the coating is soluble in the solvent at 25°C. During or subsequent to step (b), at least 50 wt.% of the coating is dissolved from the surface of the coated tow into the slurry.
Implementation Method 2
exposing the green body to a temperature sufficient to sinter the ceramic precursor to form the ceramic matrix composite, wherein at least 50 wt.% of the coating is dissolved from the surface of the coated tow into the slurry prior to step (d). In some embodiments, the sintering temperature is at least 1000°C.
Data Source
Figure 1~2
Figure 3A~3B
AI summary
Methods of making ceramic matrix prepregs are described. The methods include exposing a coated tow of ceramic fibers to a ceramic matrix slurry comprising a solvent and ceramic precursor. The coating is at least partially removed and the slurry infuses into the ceramic fibers to form prepreg. Steps to form ceramic matrix composites are also described, including forming the prepreg into a green body, and sintering the ceramic precursor.