Brazed Carbon Fiber Cathode Structure for High-Vacuum Emission
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Solution Overview
Problem
Field emission cathodes using carbon-to-carbon or carbon-to-epoxy bonding face challenges such as high resistivity, limited temperature operability, and vacuum quality issues due to the epoxy layer, which reduces the efficiency of electron transfer and increases the complexity of fabrication.
Innovation Solution
A field emission cathode with a carbon-to-metal bond layer between carbon fibers and a metal substrate, utilizing a carbon fiber fabric bonded to a metal substrate through a brazing process, eliminating the need for epoxy and allowing for better vacuum properties and higher temperature operability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If carbon-to-epoxy bonding is used in field emission cathodes, then the fabrication process is simplified, but the vacuum quality deteriorates and temperature operability is limited
Solution Approach 1:
The patent removes the epoxy layer from the cathode structure, extracting the harmful component that outgases in vacuum. The carbon fiber fabric is bonded directly to the metal substrate without epoxy, eliminating the vacuum quality problem while maintaining structural integrity through direct carbon-to-metal bonding.
Solution Approach 2:
The patent employs a composite structure consisting of carbon fiber fabric directly bonded to metal substrate. This composite material approach eliminates the need for epoxy bonding while maintaining the structural and functional requirements of the cathode, achieving both ease of manufacture and vacuum quality.
2Ease of manufacture
If carbon-to-epoxy bonding is used in field emission cathodes, then the fabrication process is simplified, but the temperature operability deteriorates
Solution Approach 1:
The epoxy layer is completely removed from the cathode structure. Without epoxy, the cathode can operate at higher temperatures since epoxy has limited thermal stability and would degrade at elevated temperatures. The direct carbon-to-metal bonding withstands high temperature operation.
Solution Approach 2:
The carbon fiber-metal substrate composite structure provides high temperature operability. Both carbon and metal materials maintain their structural integrity at elevated temperatures, unlike epoxy which degrades thermally, enabling the cathode to function in high temperature environments.
3Ease of manufacture
If bulk carbon or graphite is used as cathode substrate, then the material is easier to work with, but the electron transfer efficiency deteriorates due to higher resistivity
Solution Approach 1:
The patent creates a composite structure where carbon fiber fabric (maintaining ease of manufacture) is directly bonded to metal substrate (providing low electrical resistivity). This composite approach combines the manufacturing advantages of carbon with the electrical conductivity advantages of metal, eliminating the energy loss problem while retaining workability.
Solution Approach 2:
Different regions of the cathode structure have different material properties optimized for their specific functions. The carbon fiber fabric provides ease of manufacture and field emission properties, while the metal substrate provides low electrical resistivity for efficient electron transfer. Each material is placed where it performs best.
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 solution enhances the efficiency of electron transfer, improves vacuum quality, simplifies fabrication, and allows for higher temperature operation, resulting in a more effective and reliable field emission cathode.
Implementation Method 1
At least a portion of the patterned carbon fiber fabric is brazed to the metal cathode substrate
Data Source
AI summary
Systems, methods and apparatus related to a method for constructing a field emission device. The method includes providing a metal cathode substrate; shaping a carbon fiber fabric into a pattern, creating a patterned carbon fiber fabric; and brazing at least a portion of the patterned carbon fiber fabric to the metal cathode substrate.