Significantly improve the mechanical properties of nano-soft crystalline materials

Everyone knows that the iron-based ultrafine nanocrystalline materials have the most wonderful soft magnetic properties today. However, it is obvious that after heat treatment to reach the nanocrystalline state, the alloy crystals are often brittle.

Applications of super soft nanocomposite magnetic materials

Researchers at the US Naval Laboratory and Clark Atlanta University have improved the technique of using cobalt (Co) bands to significantly improve the toughness of old commercial materials that still retain Good soft adjectives. These materials can also be used in high temperature applications (such as inductors, power transformers, rotor motors .).

Crystalline nanoparticles (eg Finemet FeSiBNbCu, Nanoperm FeCoZrB .) are the best soft magnetic materials currently made by rapid cooling techniques to create structured alloy tapes. amorphous, then annealing at crystalline temperature to form crystalline particles in nanometer size. As a result, we obtained a nanostructure consisting of crystalline particles (iron-rich magnetic phase) embedded in the amorphous amorphous matrix.

The soft magnetic properties are achieved by two factors : superfine crystal nanoparticle structure (only 10 nm in size) and the combination of properties of two phases: nanocrystals and amorphous matrices residual. Nanocrystalline soft magnetic materials (also known as nanocomposite magnetic materials) have excellent soft magnetic properties: have extremely small magnetic resistance, high permeability, large magnetic induction, capable used at high frequencies . Some commercial form materials have names like Finemet (FeSiBNbCu), Nanoperm (FeZrBCu), Hitperm (FeCoZrBCu) . are all alloys on iron (Fe). When in the form of amorphous magnetic tapes, they have very good toughness properties, but most of them become hard and brittle after heat treatment, which is a poor point of this material.

Figure 1. Surface faults in different samples observed by scanning electron microscopy
(Applause. Phys. Lett. 90 (2007) 212508).

Matthew Wilard and colleagues have shown that using these alloys with cobalt (Co) substrate will give the material 2 times more flexibility than iron-based alloys such as Finemet, Nanoperm . but still retains excellent soft magnetic properties. For example, the material after incubation at 550 ^° C will be from 131 Am2 saturation / kg, with extremely small magnetic resistance up to 8 A / m. The Naval Research Laboratory team has discovered that these alloys have very high thermal stability, have low latency at temperatures up to 300 ^° C, meaning they are suitable for applications. Use high temperature.

Figure 2. The stress at the surface depends on the cobalt content
(Applause. Phys. Lett. 90 (2007) 212508).

The research team obtained the results of the study by performing fracture and deformation tests on the samples to determine the fracture stress and the durable limits in the 6-component cobalt (Co) rich components. has three times tougher properties than commercial ingredients and increases according to Co content.

Wilard said that rich Co alloys are suitable for use as magnetic conductors, chokes, for high-power and high-frequency electronic systems, such as transformer cores, dynamic coils, dynamic rotors. Mechanical, even used in high temperature environments. The team is also conducting trials with different components to understand the mechanistic improvement mechanism to achieve more complete results in the future. (See more details on these results on Appl. Phys. Lett. 90 (2007) 212508).

Figure 3. Magnetic attenuation based on temperature and curve from late
(Applause. Phys. Lett. 90 (2007) 212508).

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According to NanotechWeb.org & Applied Physics Letters, Vietnamese Physics