Ceramic Preform Joining Method for SiSiC Shrinkage Control
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Solution Overview
Problem
Existing methods for producing ceramic components, such as silicon-infiltrated silicon carbide (SiSiC), face challenges in achieving precision and uniformity, particularly for larger components with complex shapes, due to significant shrinkage and inhomogeneities caused by chemical reactions during the siliconizing process.
Innovation Solution
A method involving the assembly of preforms from carbon composite materials, using a joining compound containing silicon carbide and a polymer adhesive, which is cured to form a stable bond, allowing for silicon infiltration without reacting with the silicon carbide, thereby reducing shrinkage and enhancing homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a molded element undergoes siliconizing process to produce SiSiC, then residual porosity is reduced, but significant shrinkage occurs and material homogeneity deteriorates
Solution Approach 1:
The component is divided into multiple smaller preforms that are assembled and joined together. Each preform can be siliconized separately to control shrinkage, and the joining layer accommodates dimensional changes while maintaining overall component integrity and material homogeneity.
Solution Approach 2:
A joining layer composed of carbon powder and organic binder is introduced between preforms. This intermediary layer absorbs shrinkage stresses during siliconizing and prevents direct contact between siliconized surfaces, thereby maintaining material homogeneity while allowing dimensional precision.
2Length of stationary object
If carbon powder and organic binder are used for joining preforms, then preforms can be assembled into larger components, but microcracks form during pyrolysis and subsequent siliconizing causes inhomogeneities
Solution Approach 1:
The organic binder is specifically selected to have controlled decomposition characteristics during pyrolysis. By adjusting binder composition and pyrolysis parameters, the decomposition occurs gradually without forming microcracks, and the resulting carbon structure remains homogeneous after siliconizing.
Solution Approach 2:
The joining layer is designed to maintain a controlled porous structure after pyrolysis. These pores allow uniform silicon infiltration during siliconizing process, preventing inhomogeneities while enabling the joining layer to accommodate shrinkage and maintain material uniformity throughout the component.
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 method enables the production of large, complex ceramic components with reduced density variations and consistent material properties, such as thermal conductivity and flexural strength, by avoiding undesirable reactions and maintaining porosity within the joining layer.
Implementation Method 1
the paste is pyrolyzed at a temperature of from 800° C. to 1200° C.
Implementation Method 2
silicon infiltrates both the microcracks in the paste and microcracks in the carbon fiber reinforced plastic
Implementation Method 3
silicon infiltrates both the microcracks in the paste and microcracks in the carbon fiber reinforced plastic, and may thus react with the carbon fibers of the components and with the carbon powder of the paste to form silicon carbide
Data Source
AI summary
A method for producing a component includes a) providing at least two preforms each made of a carbon composite material, b) joining the at least two preforms at least at one respective connecting surface to form a composite, in which a joining compound is introduced between the joining surfaces of the preforms and then cured and the joining compound contains silicon carbide and at least one polymer adhesive, and c) siliconizing the composite to form the component. A component, such as an optical component produced thereby, is also provided.