Phosphate-Coated SmFeN Magnetic Powder for Coercivity and Oxidation Resistance
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Solution Overview
Problem
Existing methods for producing phosphate-coated SmFeN-based anisotropic magnetic powders do not achieve sufficient intrinsic coercive force and oxidation resistance.
Innovation Solution
A method involving a phosphate treatment of a slurry containing SmFeN-based anisotropic magnetic powder, water, a phosphate source, and an aluminum source, followed by optional calcium addition, to form a dense phosphate coating, which is then oxidized to enhance coercive force and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phosphate coating is formed on SmFeN-based anisotropic magnetic powder using conventional methods, then the intrinsic coercive force is enhanced, but the oxidation resistance remains insufficient
Solution Approach 1:
The patent applies composite materials by forming a dual-layer coating structure: an inner phosphate layer (from phosphate source) and an outer oxide layer (from controlled oxidation). This composite structure combines the benefits of phosphate coating (coercive force enhancement) with oxide protection (oxidation resistance), resolving the contradiction between improving coercive force and maintaining oxidation resistance.
Solution Approach 2:
The patent applies preliminary action by first forming the phosphate coating layer before performing controlled oxidation. This sequence ensures that the phosphate layer is established as a base structure, and subsequent oxidation occurs on this protected surface, preventing direct oxidation of the magnetic powder core while still providing oxidation resistance.
2Reliability
If the phosphate coating density is increased to improve coercive force, then the intrinsic coercive force increases, but the oxidation resistance may be compromised
Solution Approach 1:
The patent resolves this contradiction by creating a composite coating system where the phosphate layer provides density for coercive force enhancement, while the outer oxide layer provides protection against oxidation. The two layers work synergistically, with each performing its specialized function.
Solution Approach 2:
The patent applies local quality by giving different regions of the coating different properties: the inner phosphate layer has high density for magnetic property enhancement, while the outer oxide layer has protective characteristics for oxidation resistance. Each layer is optimized for its specific local function.
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 method results in a phosphate-coated SmFeN-based anisotropic magnetic powder with significantly higher intrinsic coercive force and improved oxidation resistance, suitable for use in bonded magnets with enhanced hot water resistance.
Implementation Method 1
stirring a slurry containing a raw material SmFeN-based anisotropic magnetic powder, water, a phosphate source, and an aluminum source to obtain a SmFeN-based anisotropic magnetic powder having a surface coated with a phosphate
Implementation Method 2
stirring a slurry containing a raw material SmFeN-based anisotropic magnetic powder, water, a phosphate source, and an aluminum source
Data Source
AI summary
A method of producing a phosphate-coated SmFeN-based anisotropic magnetic powder, the method including stirring a slurry containing a raw material SmFeN-based anisotropic magnetic powder, water, a phosphate source, and an aluminum source to obtain a SmFeN-based anisotropic magnetic powder having a surface coated with a phosphate.