Magnetic powder, and manufacturing method thereof
A magnetic powder contains magnetic particles, a first coating layer disposed on surfaces of the magnetic particles and containing a first glass, and a second coating layer disposed on the first coating layer and containing a second glass different from the first glass. A method of manufacturing magnetic powder includes preparing magnetic particles, forming a first coating layer containing a first glass on surfaces of the magnetic particles, and forming a second coating layer containing a second glass different from the first glass on the first coating layer.
1. A method of manufacturing magnetic powder, the manufacturing method comprising:
preparing magnetic particles;
softening first glass powder in a first dry state by heat, so as to form first coating layers, containing a first glass made of the first glass power, respectively on surfaces of the magnetic particles, so as to form interim particles including the magnetic particles respectively coated with the first coating layers; and
softening second glass powder different from the first glass powder in a second dry state by heat, so as to form second coating layers, containing a second glass made of the second glass power, respectively on surfaces of the first coating layers of the interim particles, so as to form the magnetic powder including the magnetic particles coated with the first coating layers and the second coating layers.
2. The method of claim 1 , wherein the heat is generated by mechanical friction induced by high-speed rotation of a friction part inside a chamber in which the first coating layers and the second coating layers are sequentially formed on the magnetic particles.
3. The method of claim 1 , wherein the second glass has a softening point lower than that of the first glass.
4. The method of claim 1 , wherein a difference in the softening point between the first and second glasses is 20° C. or more.
5. The method of claim 1 , wherein the magnetic particles are formed of an iron (Fe) based alloy.
6. The method of claim 1 , wherein the magnetic particles have a particle size of 5 μm to 100 μm.
7. The method of claim 1 , wherein the first and second coating layers have different specific resistance values from each other.