Graphite-Polyimide X-Ray Window for Low Outgassing Reliability
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Solution Overview
Problem
Existing x-ray windows face challenges in achieving a balance of low gas permeability, low outgassing, high strength, low visible and infrared light transmission, high x-ray flux, low atomic number materials, corrosion resistance, high reliability, and low-cost, particularly in environments with differential pressures and corrosive conditions, which are critical for reliable and efficient x-ray detection systems.
Innovation Solution
The development of x-ray windows comprising a thin graphite layer combined with a thin polyimide polymer layer, where the graphite layer faces ambient pressure and the polymer layer faces the vacuum, ensuring low gas permeability and outgassing, while the graphite layer provides strength and high x-ray transmission, and the polyimide layer enhances corrosion resistance and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a thin graphite layer is used for high x-ray transmission, then x-ray flux is improved, but gas permeability and outgassing increase
Solution Approach 1:
The patent combines graphite and polyimide into a composite film structure where graphite provides high x-ray transmission due to its low atomic number and crystalline structure, while polyimide provides low gas permeability and low outgassing properties. The composite leverages the complementary strengths of both materials to resolve the contradiction between x-ray flux and reliability.
Solution Approach 2:
The patent applies different materials to different functional requirements within the same film: graphite layers are positioned to optimize x-ray transmission pathways, while polyimide layers are positioned to provide barrier properties against gas permeation and outgassing. This local differentiation of material properties resolves the contradiction by assigning specific functions to specific material regions.
2Strength
If graphite layer faces ambient pressure to provide strength, then structural integrity is improved, but corrosion resistance may worsen
Solution Approach 1:
The composite structure pairs graphite's mechanical strength properties with polyimide's chemical inertness and corrosion resistance. The polyimide layer acts as a protective barrier that prevents corrosive substances from degrading the graphite, while the graphite provides the necessary structural integrity to withstand differential pressures.
Solution Approach 2:
The polyimide layer serves as an intermediary protective barrier between the graphite and the external environment. It mediates the interaction by providing corrosion resistance while allowing the graphite to maintain its structural function, thus resolving the contradiction between strength and corrosion resistance.
3Reliability
If polyimide layer faces vacuum to reduce outgassing, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The correct orientation of the polyimide layer toward the vacuum side is predetermined in the film manufacturing process itself. This preliminary action ensures that when the film is installed, the proper side is already facing the vacuum, eliminating the need for complex post-manufacturing orientation procedures and reducing manufacturing complexity while maintaining reliability.
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 configuration results in x-ray windows with improved reliability, high x-ray flux transmission, and reduced noise interference, suitable for demanding applications such as x-ray detectors in harsh environments, while maintaining a low-cost and durable design.
Implementation Method 1
the graphite layer provides strength and high x-ray transmission
Implementation Method 2
ensuring low gas permeability and outgassing
Data Source
AI summary
The x-ray windows herein can have low gas permeability, low outgassing, high strength, low visible and infrared light transmission, high x-ray flux, low atomic number materials, corrosion resistance, high reliability, and low-cost. The x-ray window can include a film 11 with a polymer layer 22 and a graphite layer 21. The film 11 can consist essentially of graphite and polymer. Most of the film 11 can be the graphite layer 21. The polymer layer 22 can be a small portion of the film 11.