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Carbonyl iron powder
- Characteristics
- Carbonyl iron powder is a very commonly used magnetic particle in magnetorheological fluids. It has characteristics such as high purity, fine and uniform particle size. Its particle size is generally in the micron level, for example, commonly 3 – 5 microns.
- Carbonyl iron powder has a relatively high saturation magnetization intensity, which enables it to quickly form a chain – like structure under the action of a magnetic field, thereby effectively changing the rheological properties of the magnetorheological fluid.
- Preparation method
- It is usually prepared by the carbonyl method. Under high – temperature and high – pressure conditions, iron reacts with carbon monoxide to produce iron pentacarbonyl, and then carbonyl iron powder is obtained through thermal decomposition. The iron powder obtained by this method has high purity and is approximately spherical in shape, suitable as a magnetic particle in magnetorheological fluids.
- Characteristics
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Iron – cobalt alloy powder
- Characteristics
- Compared with pure iron powder, iron – cobalt alloy powder has a higher saturation magnetization intensity. For example, the saturation magnetization intensity of some iron – cobalt alloys can reach above 2.4T, while the saturation magnetization intensity of carbonyl iron powder is generally about 2.1T.
- This high saturation magnetization intensity enables the iron – cobalt alloy powder to produce a stronger magnetorheological effect under the action of a magnetic field, and thus can achieve a larger yield stress under a lower magnetic field intensity.
- Application considerations
- However, the cost of iron – cobalt alloy powder is relatively high, and its chemical stability may not be as good as that of carbonyl iron powder. It is prone to chemical reactions such as oxidation in certain environments, which limits its wide application to a certain extent.
- Characteristics
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Ferrite powder
- Characteristics
- Ferrite powder is a material with ferrimagnetism, and common ones include manganese – zinc ferrite and nickel – zinc ferrite, etc. It has good chemical stability and corrosion resistance.
- Although its saturation magnetization intensity is lower than that of carbonyl iron powder and iron – cobalt alloy powder, ferrite powder is a suitable choice for some application scenarios with low requirements for magnetic field intensity but high requirements for stability.
- Application scenarios
- For example, in the application of magnetorheological dampers that are in a humid or corrosive environment for a long time, ferrite powder can better maintain the stable performance of the magnetorheological fluid and extend the service life of the dampers.
- Characteristics
