Metal Powder Salt Coating Oxidation Prevention
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Solution Overview
Problem
The utility of metal powders is limited by surface oxide films and oxygen content, which affects sintering and other characteristics, restricting their applications.
Innovation Solution
A method involving liquid phase reduction of metal halides to produce metal particles coated in salts, preventing oxidation and allowing for a range of applications by controlling particle sizes and processing conditions, including the use of molten sodium as a reductant to form metal powders with selected properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal powders are produced by conventional methods, then metal powder can be obtained, but the surface is coated in oxide films and contains oxygen that limits applications
Solution Approach 1:
The patent employs an inert atmosphere environment during metal powder production to prevent oxidation of metal surfaces. By conducting the reduction process in an atmosphere free of oxygen and other reactive gases, the method eliminates the formation of surface oxide films that would otherwise limit the powder's applicability in sensitive processes such as sintering and electronic component manufacturing.
Solution Approach 2:
The patent uses a liquid halide solvent as an intermediary medium to facilitate the reduction of metal halides to metal powders. This liquid phase medium allows for controlled reduction reactions while preventing direct contact between the metal powder and atmospheric oxygen, thereby producing powder with minimal surface oxidation.
2Reliability
If liquid phase reduction of metal halides is used, then metal particles coated in salts are produced preventing oxidation, but additional processing steps are required
Solution Approach 1:
The patent extracts the metal powder from the liquid halide solvent through filtration or decantation, separating the desired metal product from the reaction medium. This extraction step removes the protective salt coating that formed during reduction, yielding clean metal powder while the solvent can be regenerated and reused, thereby simplifying the overall process.
Solution Approach 2:
The patent recovers and regenerates the liquid halide solvent after the reduction reaction. By recovering the solvent through distillation or other separation techniques and reusing it in subsequent batches, the method eliminates the need for continuous solvent disposal and replacement, reducing processing complexity and improving economic viability.
3Reliability
If salt coating is removed to avoid solvent contamination, then clean metal powder is obtained, but exposure to solvent brings surface contamination
Solution Approach 1:
The patent performs preliminary passivation of the metal powder surface by controlling the reduction conditions in the liquid halide solvent. The metal surface is pre-treated during the reduction process itself, forming a controlled surface layer that prevents subsequent contamination when the powder is exposed to air or solvents during handling and processing.
Solution Approach 2:
The patent produces metal powder with a composite surface structure consisting of the base metal and a controlled surface layer formed during reduction. This composite surface provides both the desired metal properties and protection against contamination, eliminating the need for complete salt removal and subsequent re-contamination risks.
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
Enables the production of metal powders with controlled properties, preventing oxidation and allowing for various applications such as porous structures, coatings, and sintering without deleterious gas inclusion, enhancing the range of possible uses and economic viability.
Implementation Method 1
liquid phase reduction of a metal halide, or a mixture of metal halides, to produce a metal particle, coated in salts produced as a reaction byproduct
Implementation Method 2
reducing a mixture of at least one metal halide by molten metal reduction of the liquid phase of the metal halide in a reductant selected from an alkali or alkaline earth metal
Implementation Method 3
the salt coating prevents oxidation (or reaction with other atmospheric gases)
Data Source
AI summary
The present invention is directed to a method of manufacture of metal or alloy powders that uses liquid phase reduction of a metal halide, or a mixture of metal halides, to produce a metal particle coated in salts produced as a reaction byproduct. The reaction conditions can be chosen to select a range of metal particle sizes, and the salt coating prevents oxidation (or reaction with other atmospheric gases) and permits a range of applications hitherto difficult to achieve using metal powders.