NdFeB Magnet Nitride Phase Coercive Force
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Solution Overview
Problem
The existing production methods for NdFeB rare earth permanent magnets consume high amounts of scarce heavy rare earth elements like Dy, leading to increased costs and material inefficiencies, and the magnetic performance is affected by nitrogen content during the sintering process.
Innovation Solution
A high-performance NdFeB permanent magnet is produced using a nitride phase with controlled nitrogen content, where nitrogen is incorporated into the main phase instead of the grain boundary phase through fluctuation sintering, and ultrafine powders are processed to absorb nitrogen, reducing the formation of nitrogen compounds and enhancing magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy rare earth elements like Dy are used to increase coercive force and service temperature, then magnetic performance is improved, but resource scarcity and cost increase
Solution Approach 1:
The patent changes the chemical composition parameters by introducing nitrogen into the NdFeB magnet system. Specifically, nitrogen is added to form nitride phases that replace traditional heavy rare earth element grain boundary phases, achieving coercive force enhancement without increasing Dy consumption. The nitrogen content is controlled at 0.01-0.05 wt% to optimize performance while reducing rare earth usage.
Solution Approach 2:
The patent creates a composite microstructure consisting of Nd2Fe14B main phase and rare earth nitride grain boundary phase. This composite structure combines the high coercivity benefits of nitride phases with the magnetic properties of the NdFeB matrix, eliminating the need for heavy rare earth elements like Dy while maintaining or improving magnetic performance.
2Reliability
If nitrogen is added during sintering to form nitride phase, then coercive force and service temperature increase, but nitrogen may form harmful compounds and affect magnetic performance
Solution Approach 1:
The patent applies local quality by concentrating nitrogen specifically in the grain boundary regions where rare earth nitride phases form, rather than uniform distribution throughout the magnet. This localized nitrogen placement ensures nitride phase formation at grain boundaries for coercivity enhancement while preventing excessive nitrogen in the main phase that would harm magnetic performance.
Solution Approach 2:
The patent employs an inert atmosphere during the sintering process to control nitrogen incorporation. By maintaining controlled atmospheric conditions, nitrogen is selectively introduced to form beneficial nitride phases at grain boundaries while preventing uncontrolled oxidation and formation of harmful nitrogen compounds that would degrade magnetic properties.
3Object-affected harmful factors
If ultrafine powders are discharged with airflow during jet mill processing, then oxygen contamination is reduced, but ultrafine powders are wasted as they are inflammable
Solution Approach 1:
The patent converts the previously harmful effect of ultrafine powder discharge into a beneficial process feature. By intentionally directing airflow through the powder bed during jet mill operation, the process promotes nitrogen incorporation into the ultrafine powders, forming nitride phases that enhance coercivity. The discharged powders are no longer waste but carry beneficial nitride characteristics.
Solution Approach 2:
The patent changes the operational parameters of the jet mill process by controlling airflow rate, powder bed density, and nitrogen atmosphere conditions. These parameter adjustments ensure that ultrafine powders discharged with the airflow have incorporated sufficient nitrogen to form beneficial nitride phases, transforming what was previously a loss mechanism into a nitrogen incorporation pathway.
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 approach increases the coercive force and service temperature of the NdFeB magnets, reduces the consumption of heavy rare earth elements, and improves the machining efficiency and cost-effectiveness by minimizing the rejection rate of products.
Implementation Method 1
nitrogen is incorporated into the main phase instead of the grain boundary phase through fluctuation sintering, and ultrafine powders are processed to absorb nitrogen
Implementation Method 2
nitrogen is incorporated into the main phase instead of the grain boundary phase through fluctuation sintering
Data Source
AI summary
A high-performance NdFeB permanent magnet including a nitride phase and a production method thereof are provided. A main phase of the NdFeB permanent magnet has a structure of R2T14B; a grain boundary phase is distributed around the main phase and contains N, F, Zr, Ga and Cu; a composite phase containing R1, Tb and N exists between the main phase and the grain boundary phase and includes a phase having a structure of (R1, Tb)2T14(B, N). R represents at least two rare earth elements, and includes Pr and Nd; T represents Fe, Mn, Al and Co; R1 represents at least one rare earth element, and includes at least one of Dy and Tb; the main phase contains Pr, Nd, Fe, Mn, Al, Co and B; and the grain boundary phase further contains at least one of Nb and Ti. Through placing partially B by N, a magnetic performance is increased.