Nd2Fe14B Grain Recovery via Electrochemical Etching
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Solution Overview
Problem
Current recycling methods for neodymium iron boron (Nd-Fe-B) magnets are energy intensive, chemically demanding, and environmentally harmful, with limited efficiency in recovering the critical Nd2Fe14B phase, leading to degraded magnetic properties and increased costs due to residual oxide phases and the need for additional rare earth elements.
Innovation Solution
An electrochemical etching process using a non-aqueous solvent and anodic oxidation to selectively recover Nd2Fe14B grains from bulk sintered Nd-Fe-B magnets or scraps, allowing for direct reuse in new magnet production without the need for high-temperature processing or excessive chemical usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pyrometallurgical routes are used to remelt and extract REEs from Nd-Fe-B magnets, then REE separation and recovery is achieved, but energy consumption increases significantly due to high operating temperatures (750-950°C)
Solution Approach 1:
The patent changes the temperature parameter from high (750-950°C in pyrometallurgy) to low (room temperature or mild heating in electrochemical etching), and changes the chemical environment from molten salt to aqueous electrolyte, thereby achieving REE recovery with dramatically reduced energy consumption
Solution Approach 2:
The patent replaces the thermal-mechanical pyrometallurgical system with an electrochemical system that uses electrical energy to drive selective dissolution of the Nd-rich grain boundary phase, achieving separation without high-temperature melting and extraction processes
2Quantity of substance
If hydrometallurgical processes are used to completely dissolve Nd-Fe-B magnets with acid, then REEs can be concentrated and precipitated, but large amounts of acid and precipitation agents are consumed and cannot be recycled
Solution Approach 1:
The patent extracts only the Nd-rich grain boundary phase selectively through electrochemical etching, leaving the bulk Nd2Fe14B phase intact. This selective extraction avoids the need for complete dissolution and subsequent precipitation steps, dramatically reducing chemical consumption and waste generation
Solution Approach 2:
The electrochemical etching process uses electricity as the driving force, and the dissolved Nd ions can be directly recovered through electroplating or other electrochemical methods, creating a self-contained process that minimizes external chemical inputs and outputs
3Object-affected harmful factors
If physical/mechanical processing is used to recycle magnet scraps, then environmental footprint is reduced, but oxygen content in the REE-rich grain boundary phase increases (2000-5000 ppm)
Solution Approach 1:
The patent replaces mechanical processing with an electrochemical process that selectively dissolves the oxidized Nd-rich grain boundary phase without requiring high-energy milling or re-sintering, thereby recovering magnetic material with low oxygen content while maintaining a low environmental footprint
Solution Approach 2:
The patent changes the processing mechanism from mechanical force to electrochemical dissolution, enabling selective removal of oxidized phases without introducing additional oxygen or requiring high-energy operations that would increase the environmental footprint
4Ease of manufacture
If roasting pretreatment at 900°C is applied before hydrometallurgical processing, then REEs become more accessible for dissolution, but energy consumption and equipment complexity increase
Solution Approach 1:
The patent applies preliminary electrochemical activation or mild surface treatment to make the Nd-rich grain boundary phase more accessible to the electrolyte, eliminating the need for high-temperature roasting while still achieving effective dissolution and REE recovery
Solution Approach 2:
The patent changes the pretreatment temperature parameter from 900°C to room temperature or mild heating, and changes the chemical environment from oxidative roasting atmosphere to controlled electrolyte solution, thereby improving REE accessibility without the energy cost of high-temperature roasting
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 method enables a cost-effective, environmentally friendly, and energy-efficient recovery of Nd2Fe14B grains, reducing chemical consumption and environmental impact while maintaining magnetic properties, with potential for high recovery rates and reduced waste generation.
Implementation Method 1
The Nd-Fe-B magnets are etched in an electrochemical cell having an anode, a cathode and a reference electrode where the Nd-Fe-B magnets serve as the anode. The Nd-rich grain boundary phase is selectively dissolved by applying a current density in the range of 2-48 mA·cm-2
Implementation Method 2
A method for recovery of Nd2Fe14B grains from bulk sintered Nd-Fe-B magnets and/or magnet scraps by electrochemical etching
Implementation Method 3
Metallic Fe is simultaneously deposited on the cathode
Implementation Method 4
The collected Nd2Fe14B grains are not oxidized and are ready for a direct new magnet production
Data Source
Figure 1
Figure 2a~2d
Figure 3
AI summary
The invention relates to a method for recovery of Nd2Fe14B grains from bulk sintered Nd-Fe-B magnets and/or magnet scraps. In this method the Nd-Fe-B magnets (1) and/or magnet scraps are anodically oxidized using a non-aqueous liquid electrolyte (5), said anodic oxidation releasing the Nd2Fe14B grains (6) in said Nd-Fe-B magnets (1) and/or magnet scraps. The released Nd2Fe14B grains (6) are collected during and/or after said anodic oxidation. The proposed method allows a more environmental friendly and cost-effective way for recycling EOL Nd-Fe-B magnets / Nd-Fe-B magnet scraps.