Bonded NdFeB Magnets Research Articles

Research on Compound Powder of Bonded NdFeB Magnets from Injection Molding

The injection molding of magnetic powder could cost-effectively mass-produce net shape magnets. In order to prepare the injection molding bonded NdFeB permanent magnet material with better combined properties, the effect of binder on the magnetic property, mechanical property and fluidity of injection molding magnets and its mechanism microcosmically were investigated. The effect of additives such as silicone coupling agent, compound lubricants and antioxidant on the properties of injection molding magnets are discussed. The injection molding bonded magnets were prepared by using the MQP-B rapidly quenching NdFeB magnetic powder and polyamide 12. The magnetic properties are :Br=0.539T, Hcb=345.37kA/m, Hci=681.02kA/m, and (BH)max=47.37kJ/m3.

High performance bonded neo magnets using high density compaction

This paper presents a manufacturing method called Combustion Driven Compaction (CDC) for the manufacture of isotropic bonded NdFeB magnets (bonded Neo). Magnets produced by the CDC method have density up to 6.5 g/cm3 which is 7–10% higher compared to commercially available bonded Neo magnets of the same shape. The performance of an actual seat motor with a representative CDC ring magnet is presented and compared with the seat motor performance with both commercial isotropic bonded Neo and anisotropic NdFeB rings of the same geometry. The comparisons are made at both room and elevated temperatures. The airgap flux for the magnet produced by the proposed method is 6% more compared to the commercial isotropic bonded Neo magnet. After exposure to high temperature due to the superior thermal aging stability of isotropic NdFeB powders the motor performance with this material is comparable to the motor performance with an anisotropic NdFeB magnet.

A New Anisotropic Bonded NdFeB Permanent Magnet and Its Application to a Small DC Motor

This paper reports the method of preparing 4-pole-oriented anisotropic bonded NdFeB magnet and presents an application to a small size dc motor. The influence on the magnet performance in terms of alignment magnetic field intensity, powder filling density, and the temperature of compression mold tools are investigated. The design and optimization of the magnet and motor were done with the aid of electromagnetic field analysis based on the finite element method. Experimental results with a designed dc motor adopting the developed anisotropic bonded NdFeB magnet show 50% reduction of weight and volume.

Effect of bonding process on the properties of isotropic epoxy resin-bonded Nd-Fe-B magnets

Bonded NdFeB magnets were prepared by compression molding. The effect of preparation technology on their magnetic and mechanical properties was studied through the analysis of density, Br, Hcj, (BH)max, bending strength, and compressive strength of the bonded magnets. The results showed that the magnetic properties decreased with increasing binder content, whereas the mechanical properties increased. Br and (BH)max increased with rising pressure, whereas Hcj decreased. For a fixed mass fraction of the binder, the optimal pressure was 620 MPa and the best thermosetting temperature was 160°C. These conditions made the bonded magnets have the optimal mechanical properties. Scanning electron microscopy (SEM) analyses of the fracture surfaces indicated that the epoxy resin bonded magnets exhibited brittle behavior.

Anisotropic bonded NdFeB magnets with radial oriented magnetization by 2-step warm compaction process

Anisotropic bonded NdFeB magnets obviously have better magnetic properties than those of conventional isotropic bonded NdFeB magnets. The anisotropic bonded magnets can be used to make some magnetic devices with special oriented magnetization, such as radial oriented rings. In order to increase the magnetic properties and prolong the life of the molding die, the anisotropic bonded NdFeB magnets with radial oriented magnetization were prepared by 2-step warm compaction molding, which were called the aligning step and densifying step, respectively. In the aligning step, the magnetic powder particles aligned along the radial direction of the magnetic field (1.0 T) and are compressed under 143 MPa at 393 K. (BH) max and density of the magnets were 146 kJ/m 3 and 5.7 g/cm 3, respectively. Then the ring compacts were re-compressed under 800 MPa at 420 K in the densifying step. The density increased to 6.2 g/cm 3 and magnetic properties were: Br = 0.92 T, Hcj = 1020 kA/m, (BH) max = 168 kJ/m 3. SEM micrograph showed that the magnets had excellent microstructure and the magnetic particles were evenly coated by binder.

Effect of process on the magnetic properties of bonded NdFeB magnet

The effects of magnetic separation, coupling treatment, lubricating treatment, preform and biaxial molding on the density and magnetic properties of bonded NdFeB magnet were investigated. The results demonstrate that magnetic separation separates the powders with low coercive force; coupling treatment improves the interfaces between the powders and the binders; decrease in volume fraction of the binder increases magnetic properties of the magnet; granular arrangement improves both the magnetic and mechanical properties when powders are arranged in certain size; lubricating treatment improves the formability of the magnet and preform and biaxial molding improves both density and magnetic properties greatly. Combining these methods, the density of the bonded NdFeB magnet can reach 6.52 g/cm 3 and the maximum energy product can reach 114 kJ/m 3.

Use of Paired, Bonded NdFeB Magnets in Redox Magnetohydrodynamics

Bonded neodymium-iron-boron (NdFeB) permanent magnets in a paired configuration were successfully used to control mass transport in redox-based, magnetohydrodynamics (MHD). Control of fluid flow based on magnetic fields has potential for use in portable lab-on-a-chip (LOAC) and analytical devices. Bonded magnets, composed of magnetic powder and organic binder materials, are less expensive and easier to fabricate and pattern than electromagnets and sintered permanent magnets, which have been previously used in MHD studies on electrochemical systems. The ability to pattern bonded magnets near and around the electrodes is expected to allow for better control over the magnetic field distribution and solution flow. Current was generated at an 800-microm-radius platinum disk electrode in a solution of 0.06 M nitrobenzene and 0.5 M tetra-n-butylammonium hexafluorophosphate in acetonitrile. Increases in limiting current in the presence of the magnetic field, which indicate enhancement in mass transport, for sintered (210+/-14%, N = 4, where B(r) = 1.23 T and magnetic field strength is 0.55 T) and bonded (94+/-8%, N = 4, where B(r) = 0.41 T and magnetic field strength is 0.20 T) magnets, were similar to those obtained using an electromagnet with the same magnetic flux densities. The magnetic field strength and not the magnet type is important in controlling fluid flow, which is encouraging for integration of bonded permanent magnets into LOAC devices.

The Effects of Surface Modification on the Properties of Bonded NdFeB Magnets

Two cladding methods for NdFeB powders, i.e., the modified organic silicon (MOS) cladding and the dichromate passivation reducing (DPR) cladding are exploited respectively for the preparation of polymer-bonded magnet and metal-bonded magnet. The effects of their cladding conditions and coating compositions, together with the effects of modifying additives are discussed. Compared with the conventional polymer-bonded magnet, MOS polymer-bonded sample shows better comprehensive properties including magnetic properties, compression strength and corrosion resistance. Providing a feasible method for Nd–Fe–B type metal-bonded magnet, DPR Sn-bonded NdFeB magnet presents superior compression strength despite a little inferior magnetic property.

ChemInform Abstract: Recent Development in Bonded NdFeB Magnets.

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Recent development in bonded NdFeB magnets

The magnetic properties of isotropic NdFeB powders used for bonded magnets are compared. The characteristics of two newly developed powders, namely MQP-13-9 and MQP-S-9-8 were compared with respect to existing powders. The advantages of spherical powders for injection molding were highlighted. Development targets for the 180°C application and NdFeB nanocomposites were also discussed.

Bonded hybrid magnets

The magnetic properties of bonded magnets on the basis of NdFeB-alloy powders blended with ferrite or carbonyl-Fe (hybrid magnets) were investigated. They exhibit better properties than bonded ferrites and show smaller values of TK(HcJ) compared to isotropic bonded NdFeB magnets. In addition an enhancement of Br is observed upon blending with carbonyl-Fe.

Fabrication and measurements on polymer bonded NdFeB magnets

This paper presents measurements on polymer bonded NdFeB permanent magnets. These permanent magnets are fabricated by mixing NdFeB ribbons and binder epoxy resin under 5 ton/cm 2 pressure. The ribbons of NdFeB alloy are prepared by melt-spinning process. The performances of ribbon quenched at different rates and polymer bonded magnet are investigated by x-ray diffraction, DTA, SEM and VSM. The crystal lattice constants of the main phase Nd 2Fe 14B are found to be a = 8.73 Å, c = 12.48 Å. Effect of annealing at different temperature and time are also investigated.