Multicomponent magnetic alloy for long-term use at high temperatures, its production and use

Abstract

The application relates to a multi-element magnetic alloy applied for a long time at high temperature and preparation and application thereof, which is prepared from raw materials with the following mass fractions: iron nitrate 40-60 wt%; cobalt nitrate 30-40 wt%; nickel nitrate 2-10 wt%; and aluminum nitrate 0-10 wt%. The multi-element magnetic alloy applied for a long time at high temperature is prepared through doping of Al atoms and a simple process, has the characteristics of hollow structure, strong oxidation resistance, stable magnetic performance at high temperature, excellent microwave absorption performance, and solves the problems of poor oxidation resistance of the magnetic alloy in the prior art and unstable magnetism at high temperature.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials technology, and relates to a multi-element magnetic alloy that can be used for a long time at high temperatures, as well as its preparation and application. Background Technology

[0002] Microwave absorbing materials are crucial for applications in electronic security, wireless charging, and military stealth. Common microwave absorbing materials, such as magnetic alloys, function effectively at room temperature. However, due to the complex environments in which military weapons operate, the working environments of microwave absorbing materials are becoming increasingly demanding. Solving the application of microwave absorbing materials in these complex environments has become a priority, especially in high-temperature environments. High temperatures easily cause oxidation of magnetic alloys, weakening their magnetism and leading to a decline in microwave absorption performance, potentially resulting in the detection and destruction of military weapons. Therefore, developing magnetic alloys that are magnetically stable at high temperatures, have strong oxidation resistance, and possess excellent microwave absorption performance is urgently needed.

[0003] Medium- and high-entropy magnetic alloys, due to the "cocktail effect," possess excellent magnetic properties, as well as corrosion resistance, high hardness, high temperature resistance, and oxidation resistance, earning them the title of "king of future materials" and making them a promising material for solving current challenges. However, as research into medium- and high-entropy magnetic alloys deepens, studies have shown that excessively pursuing high entropy values ​​can lead to lower electromagnetic properties and impedance mismatch, hindering their practical application in high-temperature microwave absorption.

[0004] Chinese patent CN202210373663.2 discloses a FeCoNi-based porous high-entropy alloy material for electromagnetic wave absorption and its preparation method. The method involves solid-solution of aluminum powder, iron powder, cobalt powder, and nickel powder into a high-entropy alloy powder, followed by a porosification treatment to obtain the target high-entropy alloy material. The preparation of this alloy material is relatively complex, and its fluidity, compositional uniformity, and / or wave absorption performance still need improvement. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-element magnetic alloy that can be used at high temperatures for extended periods, as well as its preparation and application. This alloy features a hollow structure, strong oxidation resistance, stable magnetic properties at high temperatures, and excellent electromagnetic properties.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] One of the technical solutions of the present invention provides a method for preparing a multi-element magnetic alloy for long-term use at high temperatures, comprising the following steps:

[0008] (1) Weigh the metal salt particles and disperse them in deionized water, add a binder, stir magnetically until the solution is uniform, and then spray dry to obtain powder A. The metal salt particles include iron nitrate, cobalt nitrate, nickel nitrate and aluminum nitrate added in a mass ratio of 40-60 wt%: 30-40 wt%: 2-10 wt%: 0-10 wt%.

[0009] (2) Heat-treat powder A in air atmosphere to obtain powder B;

[0010] (3) Heat-treat powder B under a reducing atmosphere to obtain powder C, which is the target product, multi-element magnetic alloy.

[0011] In this invention, when the amount of aluminum nitrate added is 0 wt%, it means that no aluminum nitrate is added; preferably, the amount of aluminum nitrate added is not 0. Furthermore, the mass ratio of ferric nitrate, cobalt nitrate, nickel nitrate, and aluminum nitrate can be 40–50 wt%: 30–35 wt%: 2–8 wt%: 2–10 wt%, or any other value not exceeding the corresponding range of "40–60 wt%: 30–40 wt%: 2–10 wt%: 0–10 wt%".

[0012] The reason why the metal salt particles of the present invention use nitrates is that nitrates are easily decomposed by heat, and nitrogen can be more easily removed to obtain a pure alloy.

[0013] Furthermore, the binder is sucrose. Sucrose is a polyhydroxy organic compound that can combine with various metal cations. Simultaneously, sucrose acts as a matrix, mitigating the hygroscopic effect of nitrates.

[0014] Furthermore, the binder accounts for 30-50 wt% of the total mass of the metal salt particles. Preferably, the proportion is 45 wt%.

[0015] Furthermore, the spray drying process conditions are as follows: feed rate of 2.5 ml / min, inlet temperature of 160℃, and outlet temperature of 80℃.

[0016] Furthermore, in step (2), the heat treatment temperature is 400-600℃, preferably 600℃, and the time is 2-4 hours. Excessive carbon elements will be reduced to amorphous carbon or graphitized carbon under a protective atmosphere, weakening the impedance matching of the magnetic multi-element alloy. Therefore, a low-temperature, long-term heat treatment is used to convert carbon elements into carbon dioxide for removal.

[0017] Furthermore, in step (3), the heat treatment temperature is 700-900℃, and the time is 1-2 hours. Medium-entropy oxides have weak electrical conductivity and magnetism, resulting in poor microwave absorption performance. Therefore, reducing the oxide to an alloy is necessary to obtain better electromagnetic parameters and microwave absorption performance.

[0018] Furthermore, in step (3), the reducing atmosphere is a mixture of hydrogen and argon. Even further, the reducing atmosphere is a mixture of 5% hydrogen by volume and 95% argon by volume.

[0019] The second technical solution of the present invention provides a multi-element magnetic alloy that can be used for a long time at high temperature, which is prepared by any of the preparation methods described above.

[0020] The third technical solution of the present invention provides the application of a multi-element magnetic alloy that can be used for a long time at high temperatures. This multi-element magnetic alloy is used as a microwave absorbing material in the field of microwave absorption.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) This invention improves the magnetic stability of FeCoNi alloy at high temperatures by doping with Al atoms. Compared with FeCoNi alloy, FeCoNiAl alloy exhibits stronger oxidation resistance, better high-temperature magnetic stability, superior high-frequency magnetic stability, stronger reflection loss, and a wider effective microwave absorption bandwidth.

[0023] (2) This invention optimizes the oxidation resistance of multi-component magnetic alloys by doping with Al atoms, stabilizes the magnetic stability of multi-component magnetic alloys at high temperatures, and optimizes the electromagnetic parameters of multi-component magnetic alloys.

[0024] (3) The morphology of the present invention is a hollow structure with microspheres having a particle size of 1-4 μm. The hollow structure is beneficial to reducing the density of the material and also to the entry of incident waves, which is beneficial to optimizing impedance matching.

[0025] (4) The method of this invention synthesizes multi-component magnetic alloys through a simple spray drying and heat treatment. Compared with existing technologies, this product has low equipment cost, low raw material cost, short synthesis time, and easy operation and control of the preparation process. Using the process of this invention has significant economic benefits and is environmentally friendly. Attached Figure Description

[0026] Figure 1 SEM image of the multi-element magnetic alloy prepared in Example 1 that can be used at high temperatures for a long time;

[0027] Figure 2 SEM image of the multi-element magnetic alloy prepared in Example 2 that can be used for a long time at high temperature;

[0028] Figure 3 TEM image of the multi-element magnetic alloy prepared in Example 1 that can be used at high temperatures for a long time;

[0029] Figure 4The XRD diffraction patterns of the multi-element magnetic alloys prepared in Examples 1 and 2 that can be used at high temperatures for a long time are shown.

[0030] Figure 5 Thermogravimetric curves of oxidation of the multi-element magnetic alloys prepared in Examples 1 and 2 that can be used at high temperatures for a long time;

[0031] Figure 6 The diagram shows the remanence of the multi-element magnetic alloys prepared in Examples 1 and 2 that can be used at high temperatures for a long time at high temperatures.

[0032] Figure 7 This is a comparison of the microwave absorption performance in the 2-18 GHz band of the multi-element magnetic alloys prepared in Examples 1, 2, 1, and 2 that can be used for a long time at high temperatures. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0034] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0035] Example 1

[0036] Step 1: Precursor preparation;

[0037] Add 40.3g of ferric nitrate, 23.2g of cobalt nitrate, and 5g of nickel nitrate to 1L of deionized water and stir for 2 hours to mix thoroughly. Then add 30.8g of sucrose to the well-mixed solution and stir again for 1 hour.

[0038] The parameters for the spray dryer are set as follows: feed rate of 2.5 ml / min, inlet temperature of 160℃, and outlet temperature of 80℃.

[0039] Add the prepared solution to the set spray dryer, wait 400 minutes, and collect yellow powder A.

[0040] Step 2: Remove carbon from powder A;

[0041] The collected powder A is placed in a crucible and heat-treated in a muffle furnace.

[0042] The muffle furnace parameters are set as follows: holding temperature is 600℃, heating rate is 5℃ / min, holding time is 2h, and natural cooling is allowed after the holding period.

[0043] Collect black powder B.

[0044] Step 3: Reduce powder B to an alloy;

[0045] The black powder B was placed in a tube furnace for heat treatment, and the atmosphere used was a mixture of 5% hydrogen and 95% argon.

[0046] The parameters for the tubular furnace were set as follows: holding temperature 800℃, heating rate 5℃ / min, holding time 2h, and natural cooling after holding.

[0047] Collect the final sample C.

[0048] Example 2

[0049] Step 1: Precursor preparation;

[0050] 40.3g of ferric nitrate, 23.2g of cobalt nitrate, 2.5g of nickel nitrate, and 3.7g of aluminum nitrate were added to 1L of deionized water and stirred for 2 hours to ensure uniform mixing. Then, 31.4g of sucrose was added to the well-mixed solution, and the mixture was stirred again for 1 hour.

[0051] The parameters for the spray dryer are set as follows: feed rate of 2.5 ml / min, inlet temperature of 160℃, and outlet temperature of 80℃.

[0052] Add the prepared solution to the set spray dryer, wait 400 minutes, and collect yellow powder A.

[0053] Step 2: Remove carbon from powder A;

[0054] The collected powder is placed in a crucible and then heat-treated in a muffle furnace.

[0055] The muffle furnace parameters are set as follows: holding temperature is 600℃, heating rate is 5℃ / min, holding time is 2h, and natural cooling is allowed after the holding period.

[0056] Collect black powder B.

[0057] Step 3: Reduce powder B to an alloy;

[0058] The black powder B was placed in a tube furnace for heat treatment, and the atmosphere used was a mixture of 5% hydrogen and 95% argon.

[0059] The parameters for the tubular furnace were set as follows: holding temperature 800℃, heating rate 5℃ / min, holding time 2h, and natural cooling after holding.

[0060] Collect the final sample C.

[0061] Example 3

[0062] Step 1: Precursor preparation;

[0063] 40.3g of ferric nitrate, 23.2g of cobalt nitrate, 3.7g of nickel nitrate, and 1.9g of aluminum nitrate were added to 1L of deionized water and stirred for 2 hours to ensure uniform mixing. Then, 31.1g of sucrose was added to the well-mixed solution, and the mixture was stirred again for 1 hour.

[0064] The spray dryer parameters are set as follows: feed rate 2.5 ml / min, inlet temperature 160℃, and outlet temperature 80℃.

[0065] Add the prepared solution to the set spray dryer, wait 400 minutes, and collect yellow powder A.

[0066] Step 2: Remove carbon from powder A;

[0067] The collected powder is placed in a crucible and then heat-treated in a muffle furnace.

[0068] The muffle furnace parameters are set as follows: holding temperature is 600℃, heating rate is 5℃ / min, holding time is 2h, and natural cooling is allowed after the holding period.

[0069] Collect black powder B.

[0070] Step 3: Reduce powder B to an alloy;

[0071] The black powder B was placed in a tube furnace for heat treatment, and the atmosphere used was a mixture of 5% hydrogen and 95% argon.

[0072] The parameters for the tubular furnace were set as follows: holding temperature 800℃, heating rate 5℃ / min, holding time 2h, and natural cooling after holding.

[0073] Collect the final sample C.

[0074] Example 4

[0075] Step 1: Precursor preparation;

[0076] Add 40.3g of ferric nitrate, 23.2g of cobalt nitrate, 1.2g of nickel nitrate, and 5.6g of aluminum nitrate to 1L of deionized water and stir for 2 hours to ensure homogeneity. Then add 31.6g of sucrose to the homogeneous solution and stir again for 1 hour.

[0077] The spray dryer parameters are set as follows: feed rate 2.5 ml / min, inlet temperature 160℃, and outlet temperature 80℃.

[0078] Add the prepared solution to the set spray dryer, wait 400 minutes, and collect yellow powder A.

[0079] Step 2: Remove carbon from powder A;

[0080] The collected powder is placed in a crucible and then heat-treated in a muffle furnace.

[0081] The muffle furnace parameters are set as follows: holding temperature is 600℃, heating rate is 5℃ / min, holding time is 2h, and natural cooling is allowed after the holding period.

[0082] Collect black powder B.

[0083] Step 3: Reduce powder B to an alloy;

[0084] The black powder B was placed in a tube furnace for heat treatment, and the atmosphere used was a mixture of 5% hydrogen and 95% argon.

[0085] The parameters for the tubular furnace were set as follows: holding temperature 800℃, heating rate 5℃ / min, holding time 2h, and natural cooling after holding.

[0086] Collect the final sample C.

[0087] Comparative Example 1

[0088] Step 1: Precursor preparation;

[0089] 40.3g of ferric nitrate, 23.2g of cobalt nitrate, 2.5g of nickel nitrate, and 3.7g of aluminum nitrate were added to 1L of deionized water and stirred for 2 hours to ensure uniform mixing. Then, 31.4g of sucrose was added to the well-mixed solution, and the mixture was stirred again for 1 hour.

[0090] The parameters for the spray dryer are set as follows: feed rate of 2.5 ml / min, inlet temperature of 160℃, and outlet temperature of 80℃.

[0091] Add the prepared solution to the set spray dryer, wait 400 minutes, and collect yellow powder A.

[0092] Step 2: Reduce powder A to an alloy;

[0093] Black powder A was placed in a tube furnace for heat treatment, and the atmosphere used was a mixture of 5% hydrogen and 95% argon.

[0094] The parameters for the tubular furnace were set as follows: holding temperature 800℃, heating rate 5℃ / min, holding time 4h, and natural cooling after holding.

[0095] Collect final sample B.

[0096] Comparative Example 2

[0097] Step 1: Precursor preparation;

[0098] 40.3g of ferric nitrate, 23.2g of cobalt nitrate, 2.5g of nickel nitrate, and 3.7g of aluminum nitrate were added to 1L of deionized water and stirred for 2 hours to ensure uniform mixing. Then, 31.4g of sucrose was added to the well-mixed solution, and the mixture was stirred again for 1 hour.

[0099] The parameters for the spray dryer are set as follows: feed rate of 2.5 ml / min, inlet temperature of 160℃, and outlet temperature of 80℃.

[0100] Add the prepared solution to the set spray dryer, wait 400 minutes, and collect yellow powder A.

[0101] Step 2: Remove carbon from powder A;

[0102] The collected powder is placed in a crucible and then heat-treated in a muffle furnace.

[0103] The muffle furnace parameters are set as follows: holding temperature is 600℃, heating rate is 5℃ / min, holding time is 2h, and natural cooling is allowed after the holding period.

[0104] Collect final sample B.

[0105] Sample Analysis

[0106] Morphological observations were performed on Examples 1 and 2: Figure 1 This is a SEM image of the multi-element magnetic alloy prepared in Example 1. From... Figure 1 We can clearly observe that the multi-element magnetic alloy is composed of many small particles assembled into spheres with a particle size of 2.4 μm. These small particles are FeCoNi alloy. Figure 2 This is a SEM image of the multi-element magnetic alloy prepared in Example 2. From... Figure 2 We can see that the prepared multi-element magnetic alloy FeCoNiAl is also composed of many small particles assembled into spheres, with a particle size of 3.5 μm. Figure 2 See, the multi-element magnetic alloy FeCoNiAl has a hollow structure. Figure 3 This is a TEM image of Example 2. From Figure 3 The hollow structure of Example 2 can be seen.

[0107] Figure 4 The XRD diffraction patterns are those of the multi-element magnetic alloys prepared in Examples 1 and 2. Figure 4The lower line represents the XRD pattern of Example 1, where three distinct diffraction peaks are observed at 2θ = 44.9°, 65.4°, and 82.9°. These correspond to the (110), (200), and (211) planes (represented by black peach blossom symbols) of the body-centered cubic FeCo alloy (PDF#65-4131). Therefore, nickel atoms are considered to be inserted into the iron-cobalt alloy as interstitial particles, rather than splitting into iron-nickel or cobalt-nickel phases. Figure 4 The upper line represents the XRD pattern of Example 2, where the main phase corresponds to the body-centered cubic FeCo phase, and there is no elemental Al phase, indicating that Al atoms were successfully doped into the FeCoNi alloy. The three distinct diffraction peaks at 2θ = 43.6°, 50.8°, and 74.6° correspond to Fe... 0.64 Ni 0.36 The (110), (200) and (211) planes of the alloy (PDF#47-1405) (represented by black clover symbols) Therefore, in the FeCoNiAl alloy, nickel atoms are considered to be partly inserted into the iron-cobalt alloy as interstitials, and partly split into the iron-nickel phase.

[0108] The oxidation resistance of the multi-element magnetic alloys prepared in Examples 1 and 2 under long-term use at high temperatures was tested: Figure 5 The thermogravimetric curves (TGA) of the multi-element magnetic alloys used for long-term high-temperature applications in Examples 1 and 2 are shown at 0-1000℃. The circular dotted line represents the TGA of the FeCoNiAl alloy, and the square dotted line represents the TGA of the FeCoNi alloy. Figure 5 It can be clearly observed that the significant oxidation of the FeCoNi alloy occurs at 375.7℃ and ends at 764.4℃, while the significant oxidation of the FeCoNiAl alloy occurs at 322.2℃ and ends at 901.7℃. This means that Al atom doping reduces the oxidation rate of FeCoNi in air, because Al atoms are oxidized at low temperatures instead of magnetic materials, and the Al2O3 generated from the oxidation of Al atoms protects the magnetic components at high temperatures. This demonstrates that the FeCoNiAl alloy possesses excellent oxidation resistance.

[0109] Figure 6 The diagram shows the remanence of the multi-element magnetic alloys prepared in Examples 1 and 2 under long-term high-temperature application. It illustrates the rate of magnetism decrease in the prepared multi-element magnetic alloys at high temperatures. Figure 6It can be observed that the rate of decrease in saturation magnetization of FeCoNi is significantly faster than that of FeCoNiAl alloy. At 500.6℃, FeCoNi alloy loses 30% of its saturation magnetization, while FeCoNiAl alloy requires 612.7℃ to lose the same proportion. This demonstrates that Al atom doping slows down the decrease in magnetism of FeCoNi alloy at high temperatures. This indicates that FeCoNiAl alloy possesses excellent magnetic stability at high temperatures.

[0110] FeCoNi alloy and FeCoNiAl alloy were mixed with paraffin wax and pressed into coaxial ring samples in a mold. The electromagnetic parameters and wave absorption properties of the materials were tested. The mixing ratio was 70 wt% alloy sample and 30 wt% paraffin wax. Figure 7 a and 7b are microwave absorption performance graphs in the 2-18 GHz frequency band of the multi-element magnetic alloys prepared in Examples 1 and 2, respectively, after long-term use at high temperatures. Figure 7 The results show that the FeCoNi alloy has the lowest reflection loss of -30.3dB at 1.6mm and the highest absorption bandwidth of 5.28GHz (8.88GHz-14.16GHz) at 2mm. From... Figure 7 b. The FeCoNiAl alloy exhibits a minimum reflection loss of -48.9 dB at 1.7 mm and a maximum absorption bandwidth of 5.84 GHz (12.16 GHz - 18 GHz) at 1.6 mm. This indicates that Al atom doping enhances the FeCoNi alloy's strongest reflection loss and broadens its effective absorption bandwidth, which is beneficial for microwave absorption. Compared to powder sample C from Example 2, powder sample B obtained in Comparative Example 1 does not contain carbon elements from the binder remaining during spray granulation that can be volatilized as CO2. Therefore, a large amount of amorphous carbon remains in the alloy, resulting in impurity. Similarly, compared to powder sample C from Example 2, powder sample B obtained in Comparative Example 2, after heat treatment in air without H2 / Ar mixed gas heat treatment to remove excess oxygen, will have a large oxide layer, leading to impurity. Figure 7 c and 7d are the microwave absorption performance diagrams of the alloys prepared in Comparative Example 1 and Comparative Example 2 in the 2-18 GHz frequency band, respectively. Neither of them has effective absorption in the entire band (RL<-10dB), which proves the necessity of low-temperature heat treatment in air atmosphere before reduction treatment and heat treatment reduction.

[0111] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a multi-element magnetic alloy for long-term use at high temperatures, characterized in that, Includes the following steps: (1) Weigh the metal salt particles and disperse them in deionized water, add a binder, stir magnetically until the solution is uniform, and then spray dry to obtain powder A. The metal salt particles include iron nitrate, cobalt nitrate, nickel nitrate and aluminum nitrate added in a mass ratio of 40~60wt%:30~40wt%:2~10wt%:0~10wt%. (2) Heat-treat powder A in air atmosphere to obtain powder B; (3) Heat-treat powder B in a reducing atmosphere to obtain powder C, which is the target product, multi-element magnetic alloy; The binder is sucrose; The spray drying process conditions are: feed rate of 2.5 ml / min, inlet air temperature of 160℃, and outlet air temperature of 80℃. In step (2), the heat treatment temperature is 400-600℃ and the time is 2-4h; In step (3), the heat treatment temperature is 700-900℃ and the time is 1-2h.

2. The method for preparing a multi-element magnetic alloy for long-term use at high temperatures according to claim 1, characterized in that, The binder accounts for 30-50 wt% of the total mass of the metal salt particles.

3. The method for preparing a multi-element magnetic alloy for long-term application at high temperatures according to claim 1, characterized in that, In step (3), the reducing atmosphere is a mixture of hydrogen and argon.

4. The method for preparing a multi-element magnetic alloy for long-term application at high temperatures according to claim 3, characterized in that, The reducing atmosphere is a mixture of 5% hydrogen and 95% argon by volume.

5. A multi-element magnetic alloy for long-term use at high temperatures, which is prepared by the preparation method described in any one of claims 1-4.

6. The application of the multi-element magnetic alloy as described in claim 5 for long-term use at high temperatures, characterized in that... This multi-element magnetic alloy is used as a microwave absorbing material in the field of microwave absorption.

Images