Hollow Ceramic Matrix Composite Preform Core Oxidation
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Solution Overview
Problem
Existing methods for producing hollow ceramic matrix composite (CMC) parts, such as turbine nozzles, face challenges due to material thermal expansion differences between the silicon core and carbon or metal molds, leading to dimensional variability and complex infiltration processes.
Innovation Solution
A method involving shaping a hollow fibrous preform with an oxidizable core, consolidating the preform, and removing the core through oxidation, allowing for precise control of dimensions and simplifying the infiltration process by using a catalyst like potassium acetate and mechanical scraping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a silicon core is used in the hollow area of a porous preform, then the preform can be consolidated by infiltration, but thermal expansion differences between the core and mould cause dimensional variability
Solution Approach 1:
The invention extracts the core from the system after consolidation. The core is removed by oxidation in a controlled atmosphere furnace, eliminating the source of thermal expansion problems while preserving the consolidated preform structure.
Solution Approach 2:
The preform is consolidated before core removal. This preliminary consolidation action ensures the preform has sufficient structural integrity to maintain its shape and dimensions after the core is extracted, avoiding the need for complex compensation mechanisms.
2Manufacturing precision
If the volume of the silicon core is not correctly dimensioned, then infiltration completeness is compromised, but correcting this requires additional complex equipment
Solution Approach 1:
Instead of trying to manage excess silicon through drainage means or supplementing with crucibles, the invention extracts the entire core after consolidation. This eliminates the need for complex volume control mechanisms during infiltration.
Solution Approach 2:
The core serves as a temporary placeholder that is later replaced. Its exact volume during infiltration is less critical because it will be completely removed and replaced with the desired hollow cavity, simplifying volume control requirements.
3Ease of operation
If the core is removed before consolidation, then extraction is easier, but the preform loses its shape and dimensions
Solution Approach 1:
The preform is consolidated before core removal. This preliminary consolidation provides the structural strength needed to maintain shape and dimensions during and after core extraction, while still allowing relatively easy removal through oxidation.
Solution Approach 2:
Mechanical core removal is replaced with chemical oxidation. The core is removed by heating in an oxidizing atmosphere, which converts the core material to removable oxides without requiring mechanical forces that could damage the consolidated preform structure.
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 ensures accurate core removal without damaging the preform, maintaining its shape and dimensions, and simplifies the manufacturing process by eliminating the need for complex drainage systems and additional silicon supply.
Implementation Method 1
extracting the core by oxidising said core
Implementation Method 2
This heating can be carried out in the presence of a catalyst, such as potassium acetate
Implementation Method 3
heating the preform, in which the core is inserted, in a furnace under an oxidising atmosphere
Data Source
AI summary
A method for producing a hollow part made of a ceramic matrix composite material. The method includes shaping a hollow fibrous preform. A core of oxidizable material is housed or inserted into the preform. The method also includes consolidating the preform and extracting the core by oxidising the core.