CN103121666B - Method for preparing Fe4-xMxN (M=Ni,Co) soft-magnetism powder with favorable electromagnetic properties - Google Patents

Abstract

The invention discloses a method for preparing Fe _4-x M _x N (M=Ni, Co) soft magnetic powder with excellent electromagnetic properties, belonging to the field of new materials. The inventive method uses FeNi and FeCo alloy powders as raw materials, adopts solid-gas reaction method to nitride in the atmosphere of _NH3 and _H2 , the heating process adopts two-step method, and first eliminates the residual stress generated in the process of raw material powder preparation at high temperature , and make the multiphase existing in the raw material powder form a single γ phase at high temperature; then nitriding at low temperature. Nitriding to obtain Fe _4-x M _x N (M=Ni, Co) ternary iron nitrogen compound, wherein the range of x in Fe _4-x Ni _x N is 0.01≤x≤3, and in Fe _4-y Co _y N The range of y is 0.01≤y≤0.4. The dispersibility of the product powder particles is good, the average particle size is 5 μm, and it has high saturation magnetization and low coercive force.

Description

A method for preparing Fe4-xMxN (M=Ni, Co) soft magnetic powder with excellent electromagnetic properties

technical field

The invention relates to a method for preparing a third element Ni and Co doped _Fe4N material to obtain Fe4 _{-xMxN (} M=Ni, Co) soft magnetic powder, which belongs to the field of new materials.

Background technique

In recent years, with the continuous development of the electronic industry and wireless communication, various digital and high-frequency electronic and electrical equipment such as computers and mobile phones have rapidly become popular in people's daily life. They radiate to space while bringing convenience to people's life. A large number of electromagnetic waves of different frequencies. Electromagnetic waves will not only cause harm to human health, but also cause interference between electromagnetic waves of different frequencies, which will affect the normal use of electronic and electrical equipment. Electromagnetic pollution produced by electromagnetic waves has gradually attracted people's attention and concern. Fe ₄ N material is expected to be an excellent artificial electromagnetic medium due to its excellent magnetic properties (saturation magnetization is 190Am ² /kg), good chemical stability and high mechanical strength. However, the low resistivity, small skin depth and poor processability of Fe ₄ N material limit its practical application.

Doping the third element into Fe ₄ N material is an effective way to improve its soft magnetic properties and processing performance. Substitution of the Fe atom at the vertex position in the Fe ₄ N antiperovskite structure by a third element atom will inevitably lead to a decrease in the saturation magnetization M _s , and the initial permeability of the material is proportional to the square of the saturation magnetization M _s of the material . In order to ensure that the doped material has a higher magnetic permeability, the doping elements are selected from ferromagnetic transition group metal elements Ni and Co. At present, there are three main methods for preparing Fe _4-x M _x N (M=Ni, Co) ternary iron-nitrogen compounds:

1. Oxalate nitriding method. First, the chemical co-precipitation process is used to obtain oxalate powder containing Fe ions, Ni ions or Co ions. Then this oxalate precursor was nitrided in a mixed atmosphere of _NH3 and _H2 at a certain volume ratio, and the nitriding temperature was determined according to the ratio of Ni ions and Co ions to metal ions.

2. Mechanical alloying method. Firstly, Nitriding Fe powder in NH ₃ atmosphere to obtain Fe ₂ N powder, and then put Fe ₂ N powder, high-purity Fe powder and metal powder of elements to be doped in a high-energy ball mill tank according to a certain stoichiometric ratio Fe _4-x M _x N powder is obtained by high-speed ball milling with inert gas.

3. Magnetron sputtering coating method. The composite target of Fe target and Ni target (or Co target) is used as the target material, and the content of Ni in the film is changed by controlling the amount of Ni (or Co) on the Fe target. The atmosphere used for sputtering is a mixed gas of argon and nitrogen, and the content of N in the film is changed by controlling the partial pressure of nitrogen. the

The above method is mainly used in the laboratory to study the crystal structure, atomic occupancy, ultrafine magnetic field, isobaric energy transfer, etc. of Fe _4-x M _x N (M=Ni, Co) ternary nitrides. The problem is that the preparation process is complicated and it is not convenient for mass production. At the same time, there are not many studies on Fe _4-x M _x N (M=Ni, Co) materials used in artificial electromagnetic media.

Contents of the invention

The invention provides a method for preparing ternary iron-nitrogen compound Fe _4-x M _x N (M=Ni, Co) soft magnetic powder, which has the characteristics of simple and easy preparation process and strong product controllability. Soft magnetic powder has excellent electromagnetic properties and can be an excellent artificial electromagnetic medium, which has practical application significance.

The preparation method of Fe _4-x M _x N (M=Ni, Co) soft magnetic powder is characterized in that it comprises the following steps:

① The raw material used to prepare Fe _4-x M _x N (M=Ni, Co) soft magnetic powder is FeNi, FeCo alloy powder, which can be deposited by carbonyl method, atomization method, mechanical alloying method or physical vapor phase deposition method to get;

② Evenly spread the raw material powder in the alumina crucible, place the crucible in a vacuum tube furnace and then vacuumize it, then feed the mixed gas of _NH3 and _H2 , and then raise the temperature of the vacuum tube furnace to a certain temperature and keep it for a period of time;

③ control the temperature to drop from the temperature in step ② to the nitriding temperature within 1-2h, keep it warm for a period of time, and simultaneously adjust the volume ratio of _NH3 and _H2 to control the concentration of nitrogen atoms in the furnace tube;

④ After nitriding, cool with the furnace, and take out the powder sample after the furnace has dropped to a certain temperature. the

The scope of the atomic percentage w of Ni in the raw material FeNi alloy powder in the preferred step 1. is 0.25%≤w≤75%, and the scope of the atomic percentage w of Co in the FeCo alloy powder is 0.25%≤w≤10%;

In the preferred step 2., the temperature selection is to make the adopted alloy be a single γ phase under this temperature condition, and when the raw material is FeNi alloy powder, the temperature range is the phase transition line ABC in the Fe-Ni binary phase diagram (shown in Figure 1 ) above 10°C-100°C, when the raw material is FeCo alloy powder, the temperature range is 10°C-100°C above the phase transition line DE in the Fe-Co binary phase diagram (shown in Figure 2), and the holding time is 0.5h-2h . The volume fraction of _NH3 in the mixed gas is in the range of 0-50%.

Preferred step 3. nitriding temperature is in a temperature interval below the phase transition line of the selected alloy, and when the raw material is FeNi alloy powder, the nitriding temperature range is the phase transition line ABC in the Fe-Ni binary phase diagram (accompanying drawing 1 Shown) below 10°C-300°C, when the raw material is FeCo alloy powder, the nitriding temperature range is 300°C-500°C below the phase transition line DE in the Fe-Co binary phase diagram (shown in Figure 2), and the holding time is 3h -8h. The volume fraction of NH ₃ in the mixed gas is in the range of 50%-100%.

Preferably, the temperature at which the sample is released from the furnace in step ④ is below 300°C. the

The technical scheme of the present invention is: use FeNi, FeCo alloy powder as raw material, use solid-gas reaction method to nitride in the mixed atmosphere of _NH3 and _H2 , and control the concentration of nitrogen atoms in the furnace tube by adjusting the flow rate of the two gases . The heating process adopts a two-step method, first in the Fe-Ni, Fe-Co binary phase diagram of the phase transition line from single phase to two phase transition (ABC line in Figure 1, DE line in Figure 2) above 10 ℃-100℃ for a period of time, one is to eliminate the residual stress generated during the preparation of the raw material powder, and the other is to make the multi-phase in the raw material powder form a single γ phase at high temperature, so that the phase is homogeneous. The volume fraction of NH ₃ in the medium is in the range of 0-50%. Then nitriding at a suitable nitriding reaction temperature, the specific temperature range is 10°C-300°C below the phase transition line ABC in the Fe-Ni binary phase diagram, and 300°C below the phase transition line DE in the Fe-Co binary phase diagram. ℃-500℃, this stage is the nitriding reaction stage, and the volume fraction of NH ₃ in the atmosphere in this process is in the range of 50%-100%.

The advantages of the present invention are: the process of preparing Fe _4-x M _x N (M=Ni, Co) soft magnetic powder by using alloy powder as raw material by two-step heating has the advantage that the content of doping elements is controllable, and can be prepared according to the requirements of use. The ratio of each constituent element in the iron-nitrogen compound can be adjusted more conveniently, and the purity of the ternary nitride in the product can be improved.

Effect of the present invention is:

The invention provides a method for preparing ternary iron nitrogen compound Fe _4-x M _x N (M=Ni, Co) soft magnetic powder, the main effects of which are:

1. Synthesize Fe _4-x M _x N (M=Ni, Co) ternary iron nitrogen compound, wherein the range of x in Fe _4-x Ni _x N is 0.01≤x≤3, Fe _4-y Co _y N The range of y in is 0.01≤y≤0.4.

2. The product powder particles have good dispersion and uniform size, with an average particle size of 5 μm. the

3. The prepared Fe _4-x M _x N (M=Ni, Co) ternary iron nitrogen compound has excellent magnetic properties, high saturation magnetization and low coercive force.

Description of drawings

Figure 1: Phase diagram of Fe-Ni binary alloy;

Figure 2: Phase diagram of Fe-Co binary alloy;

Fig. 3: the X-ray diffraction spectrum of nitriding product in embodiment 1;

Fig. 4: the hysteresis loop diagram of nitriding product in embodiment 1;

Fig. 5: the X-ray diffraction spectrum of nitriding product in embodiment 2;

Fig. 6: the X-ray diffraction pattern of nitriding product in embodiment 5;

Fig. 7: the scanning electron microscope picture of nitriding product in embodiment 5;

Fig. 8: Hysteresis loop diagram of the nitrided product in Example 5. the

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments. the

Embodiment 1: The raw material is FeNi alloy powder prepared by the carbonyl method, and the atomic percentage of Ni element is 0.25%. The powder sample of 3g is weighed and placed in an alumina crucible, and two-step heating is adopted in a vacuum tube furnace. Raise the temperature to 860°C at a rate of 10°C/min, and keep at 860°C for 30 minutes. During this process, only H ₂ was introduced, and the gas flow rate of H ₂ was 200ml/min. Afterwards, the temperature was lowered from 860°C to 550°C within 2 hours, and kept at 550°C for 3 hours. During this process, only NH ₃ was fed, and the gas flow of NH ₃ was 200ml/min. After cooling with the furnace, take out the sample from the furnace tube when the temperature drops below 300°C.

According to XRD measurement, Fe _3.99 Ni _0.01 N phase was formed by nitriding, and the XRD pattern is shown in Figure 3. The particle size of powder particles after nitriding is 5 μm. The hysteresis loop measured by the vibrating sample magnetometer is shown in Figure 4, the saturation magnetization is 182emu/g, and the coercive force is 17Oe.

Embodiment 2: The raw material is FeNi alloy powder prepared by the carbonyl method, and the atomic percentage of Ni element is 5%. The powder sample of 4g is weighed and placed in an alumina crucible, and two-step heating is adopted in a vacuum tube furnace. Raise the temperature to 900°C at a rate of 10°C/min, and keep at 900°C for 1 hour. In this process, a mixed gas of H ₂ and NH ₃ is introduced, and the volume ratio of H ₂ and NH ₃ is 1:1. Afterwards, the temperature dropped from 800°C to 500°C within 1.5 hours, and kept at 500°C for 5 hours. During this process, a mixed gas of H ₂ and NH ₃ was introduced, and the gas flow rate was 200ml/min. After cooling with the furnace, take out the sample from the furnace tube when the temperature drops below 300°C.

According to XRD measurement, Fe _3.8 Ni _0.2 N phase was formed by nitriding, and the XRD pattern is shown in Fig. 5 . The particle size of the powder particles after nitriding was 5 μm. The saturation magnetization of the product measured by a vibrating sample magnetometer is 177emu/g, and the coercive force is 38Oe.

Embodiment 3: The raw material is FeNi alloy powder prepared by the carbonyl method, and the atomic percentage of Ni element is 30%. The powder sample of 4g is weighed and placed in an alumina crucible, and two-step heating is adopted in a vacuum tube furnace. Raise the temperature to 600°C at a rate of 10°C/min, and keep at 600°C for 1 hour. In this process, a mixed gas of H ₂ and NH ₃ is introduced, and the volume ratio of H ₂ and NH ₃ is 2:1. Afterwards, the temperature was lowered from 600°C to 400°C within 1 hour, and kept at 400°C for 5 hours. During this process, the mixed gas of H ₂ and NH ₃ , the volume ratio of H ₂ and NH ₃ was 1:2. After cooling with the furnace, take out the sample from the furnace tube when the temperature drops below 300°C.

According to XRD measurement, Fe _2.8 Ni _1.2 N phase was formed by nitriding, and the particle size of powder particles after nitriding was 5 μm.

Embodiment 4: The raw material is FeNi alloy powder prepared by the carbonyl method, and the atomic percentage of Ni element is 40%. The powder sample of 4g is weighed and placed in an alumina crucible, and two-step heating is adopted in a vacuum tube furnace. Raise the temperature to 500°C at a rate of 10°C/min, and keep at 500°C for 2 hours. In this process, a mixed gas of H ₂ and NH ₃ is introduced, and the volume ratio of H ₂ and NH ₃ is 4:3. Afterwards, the temperature was lowered from 500°C to 350°C within 1.5 hours, and kept at 350°C for 6 hours. During this process, a mixed gas of H ₂ and NH ₃ was introduced at a flow rate of 200ml/min. After cooling with the furnace, take out the sample from the furnace tube when the temperature drops below 300°C.

According to XRD measurement, Fe _2.4 Ni _1.6 N phase was formed by nitriding, and the particle size of powder particles after nitriding was 5 μm. The saturation magnetization of the product measured by a vibrating sample magnetometer is 100emu/g, and the coercive force is 10Oe.

Embodiment 5: The raw material is FeNi alloy powder prepared by the carbonyl method, and the atomic percentage of Ni element is 75%. The powder sample of 3g is weighed and placed in an alumina crucible, and two-step heating is adopted in a vacuum tube furnace. Raise the temperature to 600°C at a rate of 10°C/min, and keep at 600°C for 1 hour. During this process, only H ₂ was introduced, and the gas flow rate of H ₂ was 200ml/min. Afterwards, the temperature was lowered from 600°C to 450°C within 1 hour, and kept at 450°C for 8 hours. During this process, only NH ₃ was fed, and the gas flow of NH ₃ was 200ml/min. After cooling with the furnace, take out the sample from the furnace tube when the temperature drops below 300°C.

As determined by XRD, FeNi ₃ N phase was formed by nitriding, and the XRD pattern is shown in FIG. 6 . The microscopic morphology of powder particles after nitriding is shown in Figure 7, with an average particle size of 5 μm. The saturation magnetization of the magnetic powder is 72.7emu/g, the coercive force is 29.5Oe, and the hysteresis loop is shown in FIG. 8 .

Example 6: The raw material is FeCo alloy powder, and the atomic percentage of Co element is 10%. Weigh 3g of the powder sample and put it in an alumina crucible, and heat it in a vacuum tube furnace in two steps, first at 10°C/ The heating rate of min was raised to 930°C, and the temperature was kept at 930°C for 0.5h. During this process, H ₂ and NH ₃ are fed, and the volume ratio of H ₂ and NH ₃ is 5:3. After that, the temperature dropped from 930°C to 620°C within 1 hour, and kept at 620°C for 5 hours. During this process, a mixed gas of NH ₃ and H ₂ was introduced, and the volume ratio of H ₂ and NH ₃ was 3:5. After cooling with the furnace, take out the sample from the furnace tube when the temperature drops below 300°C.

According to XRD measurement, Fe _3.6 Co _0.4 N phase was formed by nitriding, the particle size of the powder particles after nitriding was 5 μm, and the saturation magnetization of the magnetic powder was 159 emu/g.

Example 7: The raw material is FeCo alloy powder, and the atomic percentage of Co element is 5%, and a 3g powder sample is weighed and placed in an alumina crucible, and heated in a vacuum tube furnace in two steps, first at 10°C/ The heating rate of min was increased to 950°C, and the temperature was kept at 950°C for 2 hours. During this process, only H ₂ was introduced, and the gas flow rate of H ₂ was 200ml/min. Afterwards, the temperature dropped from 950°C to 500°C within 1.5 hours, and kept at 500°C for 3 hours. During this process, a mixed gas of NH ₃ and H ₂ was introduced, and the volume ratio of H ₂ and NH ₃ was 1:1. After cooling with the furnace, take out the sample from the furnace tube when the temperature drops below 300°C.

According to XRD measurement, Fe _3.8 Co _0.2 N phase was formed by nitriding, the particle size of the powder particles after nitriding was 5 μm, and the saturation magnetization of the magnetic powder was 172 emu/g.

Example 8: The raw material is FeCo alloy powder, and the percentage of Co element is 0.25%. Weigh 4g of the powder sample and put it in an alumina crucible, and heat it in a vacuum tube furnace in two steps, first at 10°C/min The heating rate was raised to 1020°C, and the temperature was kept at 1020°C for 1 hour. During this process, a mixed gas of H ₂ and NH ₃ was introduced, and the volume ratio of H ₂ and NH ₃ was 1:1. Afterwards, the temperature was lowered from 1020°C to 420°C within 2 hours, and kept at 420°C for 8 hours. During this process, only NH ₃ was fed, and the gas flow of NH ₃ was 200ml/min. After cooling with the furnace, take out the sample from the furnace tube when the temperature drops below 300°C.

According to XRD measurement, Fe _3.99 Co _0.01 N phase was formed by nitriding, and the particle size of powder particles after nitriding was 5 μm. The saturation magnetization of this magnetic powder was 181 emu/g.

Claims (1)

1. a preparation method for ternary iron nitride, this ternary iron nitride chemical formula is Fe _4-xm _xn, M are Ni or Co element, this ternary iron nitride by FeNi or FeCo alloy powder at NH ₃and H ₂atmosphere in adopt two-step method to add tropical resources to obtain, wherein Fe _4-xni _xin N, the scope of x is 0.01≤x≤3, Fe _4-yco _yin N, the scope of y is 0.01≤y≤0.4;

It is characterized in that concrete steps are:

1. in raw material FeNi alloy powder, the scope of the atomic percent w of Ni is 0.25%≤w≤75%, in FeCo alloy powder, the scope of the atomic percent w of Co is 0.25%≤w≤10%, this alloy powder by carbonyl process, atomization, mechanical alloying method or physical gas-phase deposite method obtain;

2. material powder is evenly laid in alumina crucible, crucible is put in after in vacuum tube furnace and vacuumizes process, pass into NH afterwards ₃and H ₂mist, wherein NH ₃volume fraction within the scope of 0-50%, then vacuum tube furnace is made to be heated to a temperature 0.5h-2h, when raw material is FeNi alloyed powder, this temperature range is in Fe-Ni binary phase diagraml more than phase change line 10 DEG C-100 DEG C, and when raw material is FeCo alloyed powder, this temperature range is in Fe-Co binary phase diagraml more than phase change line 10 DEG C-100 DEG C;

3. control temperature in 1-2h from step 2. temperature drop to nitriding temperature, when raw material is FeNi alloyed powder, nitriding temperature scope is in Fe-Ni binary phase diagraml below phase change line 10 DEG C-300 DEG C, when raw material is FeCo alloyed powder, nitriding temperature scope is in Fe-Co binary phase diagraml below phase change line 300 DEG C-500 DEG C, under nitriding temperature, be incubated 3h-8h, the atmosphere in this process is NH ₃and H ₂mist, wherein NH ₃volume fraction within the scope of 50%-100%;

4. nitrogenize cools with stove after terminating, and drops to after below 300 DEG C take out powder sample until stove.