Ceramic Matrix Prepreg with Solvent-Dissolved 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 coatings before sintering.
Innovation Solution
A method involving exposing coated ceramic fiber tows to a ceramic matrix slurry with a solvent, where at least 80% of the coating is soluble, allowing the coating to dissolve and infuse into the slurry, thereby removing it before sintering, eliminating the need for a separate cleaning step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If organic coatings are applied to ceramic fibers to maintain tow form and prevent fiber flyaway, then handling and processing ease is improved, but high-temperature degradation causes voids and poor physical properties
Solution Approach 1:
The patent converts the harmful effect of organic coatings (which degrade at high temperatures causing voids) into a beneficial process by using the coating's solubility in the ceramic matrix slurry. The coating dissolves during slurry infusion, and the coating solvent acts as a co-solvent to enhance slurry penetration and fiber wetting, transforming the previously harmful organic material into a useful component that improves both handling and final composite quality.
2Reliability
If organic coatings are removed before sintering to prevent defects, then composite integrity is improved, but an additional process step is required
Solution Approach 1:
The patent merges the coating removal function with the slurry infusion process. By formulating the ceramic matrix slurry with coating solvent as a co-solvent, the coating dissolves automatically during the normal slurry infusion step, eliminating the need for separate coating removal steps. This combines multiple functions (coating removal and matrix infusion) into a single integrated process step.
Solution Approach 2:
The ceramic matrix slurry performs the dual function of both infusing the matrix material and removing the organic coating through its co-solvent system. The slurry autonomously dissolves the coating during the infusion process without requiring external intervention or separate processing steps, allowing the system to self-clean while building the composite structure.
3Productivity
If coated ceramic fiber tows are used without coating removal, then process steps are reduced, but voids and poor fiber-matrix contact occur
Solution Approach 1:
The patent changes the chemical parameters of the slurry system by incorporating coating solvent as a co-solvent. This parameter change enables the slurry to chemically interact with and dissolve the organic coating, transforming the interface between fiber and matrix from poor contact with voids to complete wetting and intimate contact, thereby maintaining high manufacturing precision while preserving production efficiency.
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 defects, maintaining the desirable form of spread tows and improving the integrity of the composite by ensuring complete matrix-fiber contact during high-temperature processing.
Implementation Method 1
at least 80 percent by weight of the coating is soluble in the solvent at 25° C.
Implementation Method 2
exposing the green body to a temperature sufficient to sinter the ceramic precursor to form the ceramic matrix composite
Data Source
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.