Ir-Ce Cathode Composition for Crack-Free High Current Density
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Solution Overview
Problem
Existing cathode members for electron beam generation suffer from defects such as cracks and chips during solidification, limiting their ability to achieve further improvements in electron emission characteristics, particularly current density.
Innovation Solution
A cathode member composed of 95% or more of a single phase or two phases of Ir2Ce, Ir3Ce, Ir7Ce2, or Ir5Ce2, with a total content of metallic iridium and oxide of iridium and cerium subcomponents at 5% or less, and a crystal microstructure aligned in one direction, manufactured through a melting, pulverizing, sintering, and floating zone method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If arc melting and solidification method is used to manufacture Ir-Ce cathode material, then the material can be produced efficiently, but defects such as cracks and chips occur during solidification
Solution Approach 1:
The patent changes the manufacturing parameters from conventional arc melting to floating zone method, which operates at lower temperatures and avoids rapid solidification. This parameter change eliminates thermal stress and cracking while maintaining manufacturing feasibility, thus resolving the contradiction between productivity and reliability
Solution Approach 2:
The patent utilizes controlled phase transition by melting the Ir-Ce material in a floating zone and then allowing slow, controlled solidification. This controlled phase transition process prevents the formation of cracks and chips that occur during rapid solidification, improving reliability without sacrificing productivity
2Power
If conventional Ir-Ce alloy is used to achieve high current density, then electron emission performance improves, but evaporation loss increases at high temperatures
Solution Approach 1:
The patent creates a composite structure with an Ir-Ce core and an Ir-Oxide outer layer. The Ir-Ce core provides high electron emission current density, while the Ir-Oxide layer acts as a protective barrier that reduces evaporation loss at high temperatures. This composite material approach resolves the contradiction between power output and substance loss
3Power
If LaB6 is used as cathode material, then higher current density is achieved compared to tungsten and tantalum, but durability against corrosive gas and evaporation loss worsen
Solution Approach 1:
The patent develops an Ir-Ce-based composite cathode material that combines the high current density capability of LaB6 with the superior corrosion resistance and low evaporation loss of iridium. The Ir-Ce core provides electron emission performance comparable to or better than LaB6, while the Ir-Oxide protective layer provides enhanced durability in corrosive environments, thus resolving the contradiction between power and 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
The cathode member achieves enhanced electron emission characteristics with increased power and current density, suitable for high-temperature applications like electron beam welders, by suppressing defects and ensuring homogeneous crystal orientation.
Implementation Method 1
a melting step of melting a metallic cerium raw material and a metallic iridium raw material
Implementation Method 2
a crystalline body fabricating step of fabricating a crystalline body of a compound composed of iridium and cerium by a floating zone method
Implementation Method 3
a sintering step of sintering the pulverized material of the ingot material at a temperature of 1,400 to 1,600° C. and a pressure of 25 to 50 MPa
Data Source
AI summary
The cathode member for electron beam generation of the present disclosure includes: 95% by area or more of a single phase or two phases of a compound composed of iridium and cerium. A total content of one or more subcomponents of metallic iridium and an oxide of one or more elements of iridium and cerium is 5% by area or less of the cathode member.