Carbonized Preform Separator for CVI/CVD Non-Stick
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Solution Overview
Problem
Existing separators used in chemical vapor infiltration and deposition (CVI/CVD) processes for carbon-carbon composite production often adhere to the densified material, leading to increased costs and reduced production cycles due to the need for frequent reworking or replacement, especially when made from expensive materials like inconel metal.
Innovation Solution
The development of CVI/CVD preform separators composed of thin sheet organic fiber layers with intermediate adhesive layers, which are carbonized under controlled conditions to form non-stick surfaces, allowing for multiple use cycles without adhering to densified preforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If separators are made from inconel metal, then they provide structural strength and durability, but they become expensive and adhere to densified material requiring frequent reworking
Solution Approach 1:
The separator material undergoes parameter change through carbonization treatment, transforming from organic fiber layers to a carbonized state that provides both strength and non-stick properties. The carbonization process changes the material's surface characteristics to prevent adhesion while maintaining structural integrity.
Solution Approach 2:
The separator uses a composite structure combining organic fiber layers (cellulose, glass, or graphite) with adhesive layers. This composite approach allows the separator to achieve both mechanical strength from the fiber layers and controlled surface properties from the adhesive, resulting in a material that is both strong and resistant to adhesion.
2Ease of manufacture
If separators are made from inexpensive organic materials, then they reduce cost, but they may lack the structural strength needed for high-temperature CVI/CVD processes
Solution Approach 1:
The organic fiber materials undergo carbonization, a parameter change that transforms them into a stronger, heat-resistant carbonized state. This process converts inexpensive organic materials into a form that can withstand high-temperature CVI/CVD processes while maintaining cost-effectiveness.
Solution Approach 2:
The separators are pre-carbonized before use in the CVI/CVD process. This preliminary action of carbonization strengthens the organic materials in advance, ensuring they have the required structural strength for the high-temperature application without needing to use expensive materials from the outset.
3Strength
If carbonization temperature is increased to improve separator performance, then separator strength increases, but material shrinkage and distortion increase
Solution Approach 1:
The separators are pre-carbonized under controlled conditions before final use. This preliminary carbonization allows the material to achieve necessary strength while maintaining dimensional stability, as the pre-carbonization process can be optimized to minimize shrinkage and distortion before the separator is put into service.
Solution Approach 2:
The carbonization process parameters (temperature, heating rate, atmosphere) are carefully controlled and adjusted to achieve the optimal balance between strength development and dimensional stability. By managing these parameters, the separator gains sufficient strength while minimizing unwanted shrinkage and distortion.
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 non-stick separators reduce material buildup, enabling easy separation from densified parts and extending their usable life, thereby reducing production costs and increasing efficiency in CVI/CVD processes.
Implementation Method 1
the separators are produced by carbonization of the body including the plurality of the thin sheets and adhesive layers. In exemplary arrangements the carbonization is carried out under pressure that is applied transversely to flat planar opposed side surfaces of the separator body. Carbonization in exemplary arrangements is carried out in a non-oxidizing atmosphere and at maximum temperatures from about 700-1100° C.
Data Source
AI summary
Preform separators are operative to separate porous preforms that undergo chemical vapor integration and deposition (CVI/CVD) to form components such as carbon-carbon composite disc brake rotors. The exemplary preform separators are comprised of thin sheets of organic fibers separated by layers containing adhesives and other materials. Bodies comprised of the plurality of thin sheets and layers undergo carbonization at a controlled rate in a non-oxidizing atmosphere. The preform separators have flat planar opposed side faces which abut porous preforms during the CVI/CVD process. Exemplary separators include channels that facilitate the infiltration of carbon carrying gas into the preforms to aid in densification. The preform separators are reusable in a plurality of densification cycles and have non-stick properties.