CN106086776B - A kind of low-temperature plasma nitridation preparation method of fe nitride magnetic powder - Google Patents

Abstract

A kind of low-temperature plasma the present invention relates to fe nitride magnetic powder nitrogenizes preparation method.The invention is 2 ~ 80 μm of atomized iron powder, hydroxy iron powder or reduced iron powder for raw material using average grain diameter；It is passed through O₂, 1 10h is aoxidized at 300 ~ 400 DEG C, to obtain brown iron oxide；Hydrogen is passed through, 4 20h are reduced at 300 ~ 400 DEG C, to regain iron powder；Low-temperature plasma nitrogenizes, and control temperature nitrogenizes 1 ~ 30h at 120 ~ 200 DEG C；Cooling cools to room temperature with the furnace, takes out sample.This method carries out nitriding using cryogenic nitrogen plasma, solves the bottleneck problem that ammonia decomposition efficiency is low in ammonia nitriding process, is effectively improved nitriding efficiency.

Description

A kind of low-temperature plasma nitriding preparation method of iron nitride magnetic powder

technical field

The invention relates to a low-temperature plasma nitriding preparation method of iron nitride magnetic powder, which belongs to the field of material preparation.

Background technique

The excellent soft magnetic properties, oxidation resistance and wear resistance of Fe-N compounds make them ideal materials for magnetic recording media and magnetic sensing elements, and have attracted people's attention. Fe-N compounds mainly include Fe ₃ N, Fe ₄ N and α"-Fe ₁₆ N _2. According to domestic and foreign literature reports, the magnetic properties of α"-Fe ₁₆ N ₂ are the best among iron nitrogen compounds , its saturation magnetization reaches 280emu/g, which is higher than that of pure iron, and it is the material with the highest saturation magnetization found so far.

Since the α"-Fe ₁₆ N ₂ phase is a metastable phase at room temperature, its formation region is very narrow, so it is very difficult to prepare α"-Fe ₁₆ N ₂ , and the preparation of α"-Fe 16 N 2 ₁₆ N ₂ experiments are basically not repeatable, and the results of each experiment cannot be exactly the same. Over the years, many scientists have tried to reproduce α"-Fe ₁₆ N ₂ with high saturation magnetization from the perspective of physical mechanism and application , Also used a lot of methods, such as nitriding annealing method, eutectoid method, ion implantation method, chemical vapor deposition method, physical vapor deposition method and so on.

At present, the most successful team to prepare α"-Fe ₁₆ N ₂ is the research group composed of Professor Takahashi Ken of the Graduate School of Tohoku University, Tomoyuki Ogawa and Assistant Professor Toda Kogyo. They successfully produced α"-Fe 16 N 2 in units of grams α"-Fe ₁₆ N ₂ powder. This is the world's _first reproducible generation of α"-Fe ₁₆ N ₂ with a purity of up to 91% _. The saturation magnetization is 230emu/g at 50K and 221emu/g at room temperature, which is higher than that of pure iron.

In view of the above, the present invention adopts oxidation, reduction, and low-temperature plasma nitriding methods to prepare ferromagnetic materials containing α"-Fe ₁₆ N ₂ phase.

Contents of the invention

The object of the present invention is to provide a low-temperature plasma nitriding preparation method of iron nitride magnetic powder.

When gas-phase nitriding is used to prepare α"-Fe ₁₆ N ₂ , an ammonia atmosphere is usually used, which is carried out through the adsorption, decomposition and diffusion of ammonia on the surface of α-Fe. The most critical step is the ammonia gas in the α-Fe The decomposition of the Fe surface is also the key to determine the nitriding efficiency. The present invention adopts low-temperature plasma technology to directly use high-energy ionized nitrogen to nitride α-Fe, effectively increasing the nitriding efficiency.

Concrete steps of the present invention are:

1) Material preparation

Choose iron powder with an average particle size of 2~80μm as the raw material, and the iron powder can be atomized iron powder, hydroxyl iron powder or reduced iron powder;

2) oxidation

Put the iron powder in a heat treatment furnace, feed O ₂ at a constant rate, and oxidize it at 300-400°C for 1-10 hours to obtain iron oxide powder;

3) restore

Introduce hydrogen and reduce at 300~400℃ for 4-20h to regain iron powder;

4) Low temperature plasma nitriding

Low-temperature plasma nitriding, control the temperature at 120-200°C, nitriding for 1-30h; lower the temperature, cool to room temperature with the furnace, and take out the sample.

The invention has the advantages that: the low-temperature nitrogen plasma is used for nitriding, which solves the bottleneck problem of low ammonia gas decomposition efficiency in the ammonia gas nitriding method, and effectively improves the nitriding efficiency.

Detailed ways

The present invention will be described in detail below in conjunction with the embodiments, so as to better understand the purpose, characteristics and advantages of the present invention. While the invention is described in conjunction with this specific embodiment, it is not intended to limit the invention to the specific embodiment described. On the contrary, alternatives, improvements and equivalent implementations to the implementations that may be included in the protection scope defined in the claims of the present invention all belong to the protection scope of the present invention. For the process parameters that are not specially marked, it can be carried out according to conventional techniques.

Concrete steps of the present invention are:

1) Material preparation

Choose iron powder with an average particle size of 2~80μm as the raw material, and the iron powder can be atomized iron powder, hydroxyl iron powder or reduced iron powder;

2) oxidation

Put the iron powder in a heat treatment furnace, feed O ₂ at a constant rate, and oxidize it at 300-400°C for 1-10 hours to obtain iron oxide powder;

3) restore

Introduce hydrogen and reduce at 300~400℃ for 4-20h to regain iron powder;

4) Low temperature plasma nitriding

Low-temperature plasma nitriding, control the temperature at 120-200°C, nitriding for 1-30h; lower the temperature, cool to room temperature with the furnace, and take out the sample.

The invention can more effectively prepare the iron nitride magnetic powder containing α"-Fe ₁₆ N ₂ phase.

Example 1:

The steps are:

1) Material preparation

Choose atomized iron powder with an average particle size of 2 μm as the raw material;

2) oxidation

Put the iron powder in a heat treatment furnace, pass O ₂ at a constant rate, and oxidize at 300°C for 10 hours to obtain iron oxide powder;

3) restore

Introduce hydrogen and reduce at 300°C for 20 hours to regain iron powder;

4) Low temperature plasma nitriding

Low-temperature plasma nitriding, control the temperature at 120°C, nitriding for 30h; lower the temperature, cool to room temperature with the furnace, and take out the sample.

The sample prepared in Example 1 was characterized by XRD, and the α"-Fe ₁₆ N ₂ phase was detected.

Example 2:

The steps are:

1) Material preparation

Select hydroxyl iron powder with an average particle size of 4 μm as the raw material;

2) oxidation

Put iron powder in a heat treatment furnace, pass O ₂ at a constant rate, and oxidize at 320°C for 8 hours to obtain iron oxide powder;

3) restore

Introduce hydrogen and reduce at 320°C for 15 hours to regain iron powder;

4) Low temperature plasma nitriding

Low-temperature plasma nitriding, control the temperature at 140°C, nitriding for 20h; lower the temperature, cool to room temperature with the furnace, and take out the sample.

The sample prepared in Example 2 was characterized by XRD, and the α"-Fe ₁₆ N ₂ phase was detected.

Example 3:

The steps are:

1) Material preparation

Select hydroxyl iron powder with an average particle size of 10 μm as the raw material;

2) oxidation

Put the iron powder in a heat treatment furnace, pass O ₂ at a constant rate, and oxidize at 340°C for 6 hours to obtain iron oxide powder;

3) restore

Introduce hydrogen and reduce at 340°C for 10 hours to regain iron powder;

4) Low temperature plasma nitriding

Low-temperature plasma nitriding, control the temperature at 160°C, nitriding for 15 hours; lower the temperature, cool to room temperature with the furnace, and take out the sample.

The sample prepared in Example 3 was characterized by XRD, and the α"-Fe ₁₆ N ₂ phase was detected.

Example 4:

The steps are:

1) Material preparation

Choose atomized iron powder with an average particle size of 20 μm as the raw material;

2) oxidation

Put the iron powder in a heat treatment furnace, pass O ₂ at a constant rate, and oxidize at 360°C for 4 hours to obtain iron oxide powder;

3) restore

Introduce hydrogen and reduce at 360°C for 8 hours to regain iron powder;

4) Low temperature plasma nitriding

Low-temperature plasma nitriding, control the temperature at 170°C, nitriding for 10h; lower the temperature, cool to room temperature with the furnace, and take out the sample.

The sample prepared in Example 4 was characterized by XRD, and the α"-Fe ₁₆ N ₂ phase was detected.

Example 5:

The steps are:

1) Material preparation

Choose reduced iron powder with an average particle size of 40 μm as the raw material;

2) oxidation

Put the iron powder in a heat treatment furnace, pass O ₂ at a constant rate, and oxidize at 380°C for 2 hours to obtain iron oxide powder;

3) restore

Introduce hydrogen and reduce at 380°C for 6 hours to regain iron powder;

4) Low temperature plasma nitriding

Low-temperature plasma nitriding, control the temperature at 180°C, nitriding for 4 hours; lower the temperature, cool to room temperature with the furnace, and take out the sample.

The sample prepared in Example 5 was characterized by XRD, and the α"-Fe ₁₆ N ₂ phase was detected.

Embodiment 6:

The steps are:

1) Material preparation

Choose hydroxy iron powder with an average particle size of 80 μm as the raw material;

2) oxidation

Put the iron powder in a heat treatment furnace, pass O ₂ at a constant rate, and oxidize at 400°C for 1 hour to obtain iron oxide powder;

3) restore

Introduce hydrogen and reduce at 400°C for 4 hours to regain iron powder;

4) Low temperature plasma nitriding

Low-temperature plasma nitriding, control the temperature at 200°C, nitriding for 1h; lower the temperature, cool to room temperature with the furnace, and take out the sample.

The sample prepared in Example 6 was characterized by XRD, and the α"-Fe ₁₆ N ₂ phase was detected.

Claims (1)

1. a low-temperature plasma nitriding preparation method of iron nitride magnetic powder, characterized in that the specific steps are: 1) Material preparation Choose iron powder with an average particle size of 2~80μm as the raw material, and the iron powder is atomized iron powder, hydroxyl iron powder or reduced iron powder; 2) oxidation Put the iron powder in a heat treatment furnace, feed O ₂ at a constant rate, and oxidize it at 300-400°C for 1-10 hours to obtain iron oxide powder; 3) restore Introduce hydrogen and reduce at 300~400℃ for 4-20h to regain iron powder; 4) Low temperature plasma nitriding Low-temperature plasma nitriding, control the temperature at 120-200°C, nitriding for 1-30h; lower the temperature, cool to room temperature with the furnace, and take out the sample.