Low-Oxygen Metal Powder via Plasma Reduction
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Solution Overview
Problem
Existing methods for producing metal powders, such as heat treatment in a reducing gas atmosphere or thermal plasma flame, are ineffective in significantly reducing oxygen content within the powder particles, especially for metal powders with high melting points or porous structures.
Innovation Solution
Coating raw metal powder particles with a hydrocarbon organic compound and passing them through a thermal plasma flame, primarily composed of an inert gas, to enhance the reduction of oxygen content, followed by optional heat treatment under vacuum or in a hydrogen atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If powder particles with large specific surface area (porous, sponge-like, or dendritic structures) are used in the powder sintering method, then the powder can be effectively sintered to form target material, but the oxidized layers on the powder particle surfaces increase significantly, leading to higher oxygen content in the produced target material
Solution Approach 1:
The patent applies inert atmosphere by conducting the sintering process in a vacuum environment (10^-3 to 10^-6 Pa) or under protective gas atmosphere (argon or nitrogen). This prevents oxidation of the powder particles during sintering, allowing the use of high-surface-area powders without incorporating excessive oxygen into the final target material. The inert environment maintains low oxygen content while enabling effective sintering of the powder particles.
2Quantity of substance
If conventional heat treatment in reducing gas atmosphere is applied to decrease oxygen content, then surface oxide layers are reduced, but oxygen existing inside the powder particles cannot be effectively reduced
Solution Approach 1:
The patent employs extreme parameter changes by utilizing vacuum conditions (10^-3 to 10^-6 Pa) combined with elevated temperatures (room temperature to melting point of the metal). This creates a highly effective oxygen removal environment where oxygen diffusion is enhanced by the temperature gradient while the vacuum pressure prevents re-oxidation and facilitates oxygen escape from particle interiors. This parameter combination achieves comprehensive oxygen reduction both on surfaces and within particles, overcoming the limitations of conventional reducing gas atmospheres.
3Stability of the object's composition
If melting method is used to produce target material, then the material structure can be homogenized effectively, but it is difficult to melt metals with high melting points
Solution Approach 1:
The patent replaces the thermal melting process with a powder sintering process conducted under vacuum or protective atmosphere. Instead of melting the metal (which requires temperatures above the melting point), the powder particles are sintered at lower temperatures through diffusion bonding in a controlled atmosphere. This substitution achieves homogeneous material structure through particle bonding without requiring the extreme temperatures needed for melting, making it feasible for high-melting-point metals.
4Stability of the object's composition
If plastic working is applied to homogenize material structure, then the structure can be uniformized, but it is difficult to perform plastic working on metals with high melting points
Solution Approach 1:
The patent replaces mechanical plastic working with a thermal-diffusion sintering process. Instead of applying mechanical deformation to homogenize the structure (which requires the metal to be in a ductile state), the powder particles are heated in a controlled atmosphere to enable diffusion bonding and structural homogenization. This substitution achieves uniform material structure through thermal activation of atomic diffusion rather than mechanical deformation, bypassing the need for high ductility that limits plastic working of high-melting-point metals.
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 process efficiently decreases the oxygen content in metal powders, improving their quality and making them suitable for use in sputtering target materials by reducing oxides effectively and preventing sintering.
Implementation Method 1
passing them through a thermal plasma flame, primarily composed of an inert gas
Implementation Method 2
reducing the content of oxygen in the raw metal powder
Implementation Method 3
particles of the raw metal powder have been previously coated with a hydrocarbon organic compound which has been provided on the particles in a thermally melted state
Implementation Method 4
the metal powder having passed through the thermal plasma flame is subject to heat treatment under vacuum
Implementation Method 5
the metal powder having passed through the thermal plasma flame is subject to heat treatment in a hydrogen atmosphere
Data Source
AI summary
A process for producing a low-oxygen metal powder, comprising passing a raw metal powder coated by hot melting of a hydrocarbon organic compound through thermal plasma flame composed mainly of an inert gas so as to reduce the content of oxygen in the raw metal powder. Preferably, the obtained metal powder is subjected to heat treatment in vacuum or hydrogen atmosphere. Preferred example of the hydrocarbon organic compound is stearic acid.