Ceramic Composite Materials for High-Temperature EM Shielding
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Solution Overview
Problem
Existing electromagnetic (EM) shielding materials are inadequate for high-temperature applications exceeding 700°C due to limitations in electrical conductivity, oxidation resistance, and sinterability, and current methods do not provide suitable materials for harsh environments.
Innovation Solution
Composite materials comprising ultra-high temperature ceramic particles and polymer-derived ceramic (PDC) are formed by mixing UHTC particles with a liquid preceramic precursor, curing, and sintering to create a core-shell structure, which enhances electrical conductivity and EM shielding effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional metal or polymer-based EM shielding materials are used, then EM shielding effectiveness is achieved, but the materials cannot withstand temperatures greater than 700°C due to melting and decomposition
Solution Approach 1:
The patent uses ultra-high temperature ceramic particles (such as HfB2, ZrB2, TaC, or TiC) dispersed in a polymer-derived ceramic matrix to create a composite material that combines the high-temperature stability of ceramics with the processability of polymers. This composite structure enables the material to maintain EM shielding effectiveness at temperatures up to 1500°C while avoiding the melting and decomposition issues of traditional metals and polymers
Solution Approach 2:
The patent changes the fundamental material parameters by transitioning from metallic or polymeric shielding materials to ceramic-based composites with ultra-high temperature stability. The use of PDC precursors that convert to ceramic matrices during processing allows achieving temperatures exceeding 700°C without material degradation, fundamentally altering the thermal parameter range where EM shielding can be effectively implemented
2Reliability
If high concentrations of iron powders are used for EM shielding, then shielding effectiveness is improved, but the materials become heavy and costly
Solution Approach 1:
The patent changes the material composition parameters by replacing traditional iron powder fillers with ultra-high temperature ceramic particles. This substitution maintains the electromagnetic shielding effectiveness through the ceramic particles' inherent properties while significantly reducing the density and weight of the shielding material, making it suitable for weight-sensitive applications
Solution Approach 2:
The patent creates a composite material system using ceramic particles in a PDC matrix that achieves EM shielding through mechanisms other than high concentrations of dense metal powders. The composite structure provides adequate shielding performance with lower density materials, resolving the contradiction between shielding effectiveness and weight
3Reliability
If carbon materials like CNTs and graphite flakes are used for low temperature applications, then EM shielding is achieved, but the materials are not suitable for high temperature oxidizing environments
Solution Approach 1:
The patent creates a composite material where ultra-high temperature ceramic particles (which possess excellent oxidation resistance) are dispersed in a polymer-derived ceramic matrix. This composite structure provides both EM shielding effectiveness and protection against oxidation at high temperatures, overcoming the limitation of carbon-based materials that degrade in oxidizing environments above 700°C
Solution Approach 2:
The patent changes the chemical composition parameters by replacing carbon-based materials with ceramic-based composites that have superior oxidation resistance. The ceramic particles and PDC matrix are specifically selected to maintain stability and resist oxidation at temperatures up to 1500°C, fundamentally changing the material's chemical resistance parameters
4Temperature
If conventional ceramic processing is used, then high-temperature stability is achieved, but the ability to produce complex shapes is limited
Solution Approach 1:
The patent applies preliminary action by using polymer-derived ceramic precursors that can be molded into complex shapes before the final ceramic conversion. The PDC precursors are processed at lower temperatures to form the desired complex geometry, and then converted to the final ceramic structure at higher temperatures, enabling complex shape fabrication that would be difficult with conventional direct ceramic processing
Solution Approach 2:
The patent changes the processing temperature parameters by using a two-stage approach: first processing the PDC precursor at lower temperatures to form complex shapes, then converting to the final ceramic at higher temperatures. This parameter change enables complex geometry fabrication while maintaining the high-temperature stability of the final ceramic product
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 composite materials maintain EM shielding effectiveness at temperatures up to 1500°C and in oxidizing environments, offering improved conductivity and durability for applications like aircraft nosecones.
Implementation Method 1
Three different mechanisms, including reflection (R), absorption (A), and multiple internal reflections (M) may contribute to the overall attenuation
Implementation Method 2
The primary mechanism of EM shielding is typically the reflection from the shield surface
Implementation Method 3
heating the mixture at a temperature for a time effective to cure the liquid preceramic precursor to form a solid mixture
Implementation Method 4
pressing the particles of the solid mixture into a mold having a pre-selected shape to form the composite material. In some embodiments, the methods also include sintering the composite material
Implementation Method 5
This mechanism may occur when a shield material is electrically conducting. The second mechanism of EM shielding is absorption, which usually requires the shield material to include enough electric and/or magnetic dipoles to interact with the EM wave in the radiation
Data Source
AI summary
Methods of forming composite materials, composite materials, and articles. The composite materials may include electromagnetic shielding materials. The methods may include providing a mixture of ultra-high temperature ceramic particles and a liquid preceramic precursor, curing the mixture to form a solid mixture, forming particles of the solid mixture, and pressing the particles into a mold.