Magnetic Particle: Familiar or Strange?

When it comes to magnets, we are no strangers to everyone. In everyone’s mind, magnetic particle is the magnetic particle that falls off the magnet, but this is only part of the real face of the magnetic particle. The world of magnetic particle can be much more than just as simple as you think. Let me reveal the magical side of themagnetic particle you are familiar with!

What is the standard definition of magnetic particle?

Magnetic particle is a hard magnetic single domain particle. It is made into a magnetic paste with a binder, a solvent, etc., and coated on the surface of a plastic or metal substrate to form a magnetic recording material such as a magnetic tape, a magnetic disk, or a magnetic card. Commonly used magnetic particles are two major types of metal magnetic particles: oxide magnetic particle and metal magnetic particle.

Various uses of magnetic particle

Excellent performance in inspection work

Magnetic particle testing is a magnetic flaw detection method based on the principle of magnetic flux leakage. After the ferromagnetic material and the workpiece are magnetized, due to the discontinuity, the magnetic field lines on the surface of the workpiece and the near surface are locally distorted to generate a leakage magnetic field, the magnetic particle applied on the surface of the workpiece is adsorbed to form a magnetic field visible under suitable illumination, and traces, showing the location, shape and size of the discontinuities.

Nano Fe3O4 is a common material for magnetic flaw detection and belongs to nanoparticles. There are eight main advantages:

v Characteristics of high magnetic permeability, low coercivity, and low remanence;

v Good dispersibility, not easy to agglomerate, strong magnetic;

v Good magnetic permeability and good mobility;

v Mixing of nanomaterials with different dimensions can improve the performance of magnetic particle testing process;

v It can be combined with organic materials to modify nano magnetic materials;

v It can achieve consistent particle size and meet the needs of special testing;

v The detection rate of particle crack is high, and it has good performance for small crack detection;

v Low manufacturing costs.

n Advantages and limitations of magnetic particle testing

Advantages of magnetic particle detection method:

Ø The shape, position and size of the defect can be visually displayed, and the properties can be roughly determined;

Ø This method can detect cracks with a minimum length of 0.1 mm width and micron order, which is very High sensitivity;

Ø It is not restricted by the size and shape of the test piece;

Ø The method is simple to use, less polluted, and low in cost, and the detection speed is fast; 5 can be repeatedly tested.

Limitations of the magnetic particle detection method:

Ø It can only be used for ferromagnetic materials;

Ø it is only for the surface and near surface defects of the material;

Ø it is subject to the magnetization direction, and the defect direction is approximately parallel to the magnetization direction or the defect and the surface of the workpiece When the angle is less than 200, it is difficult to find defects.

Ø It will be restricted by the geometry, and it is easy to produce non-correlated display; 5 If the surface of the workpiece has a cover layer, it may affect the detection result of the magnetic particle.

Electric vehicle magnetic particle brake control technology

The magnetic particle brake is a kind of magnetic particle filled in the working gap between the stator and the rotor, the magnetic particle is combined by the electromagnetic attraction force and the friction between the magnetic particle and the working surface transmits power and movement, and can control the torque adjustment system. The physical object of the magnetic particle brake is shown on the right.

Magnetic particle brake has the advantages of fast reaction speed, no pollution, no noise, energy saving, etc. It is a multi-purpose, superior performance automatic control component. Under the premise of ensuring safety, the advantage of electric vehicle magnetic particle brake is to improve energy utilization, as well as reduce mechanical wear of mechanical and hydraulic braking modes, achieve more precise braking control, and reduce traditional vehicles. Braking thermal decay caused by temperature rise during braking.

A good helper to optimize water quality

With the acceleration of industrialization and urbanization in China, a large amount of untreated industrial sewage and domestic sewage are directly discharged into the river, the eutrophication of water bodies is becoming more and more serious, anaerobic bacteria are multiplied, organic matter is spoiled, decomposed, fermented, and finally black.

The test shows that it is feasible to purify the black odor river water by adding magnetic particle. Compared with other flocculants, it has the characteristics of short sedimentation time, stable treatment effect, green environmental protection, no secondary pollution, etc. Controlling eutrophication of water bodies is a simple and efficient technique for polluting river water.

Ø The combination method of laying the magnet at the bottom further shortens the processing time, improves the processing efficiency, increases the treatment effect, can effectively reduce the volume of the treatment structure, and greatly reduces the investment cost.

Ø The magnetic particle can be mostly recovered, and the magnetic particle is reused, the dosage of the medicine is reduced, and the running cost is reduced.

Ø The technology can be applied to the treatment of high suspended solids production wastewater such as paper making, fiberboard processing, coal washing, desulfurization wastewater, graphite, marble processing.

Ø The disadvantage of this method is that it has a removal effect on dissolved pollutants, and can be combined with bio-ecological technology to further improve the treatment efficiency of black odorous water.

The future of magnetic particles

Now, do you have a new understanding of magnetic particle? It must be said that in addition to magnetic particle, magnetic beads and magnetic microspheres are also part of this family; they are showing their unique charm for human biology and medicine. At this stage, the basic theoretical research of magnetic particle testing has been relatively mature, and we believe that the future magnetic particle will have a broader application prospect!


[1] Experimental Study on Removal of Pollutants with Magnetic Powder from Black – and – Malod orous Water Body. Jouranal of Taishan University. Vol.39 NO.6 Nov. 2017.

[2] On Application of Magnetic Powder Detection in the Pressure Vessel Inspection. 1006-4311(2014)09-0019-02.