Preparation method of surface-coated modified carbonyl iron powder composite absorbent

Abstract

The invention relates to the technical field of metal powder surface protection and modification, and in particular to a method for preparing a surface-coated modified carbonyl iron powder composite absorbent; the method comprises the following steps: 1) mixing carbonyl iron powder with a certain amount of surfactant aqueous solution, and mechanically stirring to obtain a carbonyl iron powder mixed solution; 2) taking a certain amount of room-temperature blackening agent and mixing the mixture evenly with water in a specific proportion, and setting the mixture aside; 3) weighing a certain amount of the carbonyl iron powder mixed solution from step 1) and the room-temperature blackening agent aqueous solution from step 2), and mechanically stirring the mixture until the reaction is complete; 4) filtering and washing the product to neutrality; and 5) vacuum drying the product at a specific temperature to obtain the carbonyl iron powder composite absorbent. The method controls the temperature resistance and wave absorbing performance of the carbonyl iron powder by adjusting the concentration of the blackening solution, the oxidation time, the type of surfactant, and the like. The process flow is simple, can be used for mass production of the composite absorbent, and is easy for industrial production and application.

Description

Technical Field

[0001] The invention relates to the technical field of metal powder surface protection and modification, and in particular to a method for preparing a surface-coated modified carbonyl iron powder composite absorbent. Background Art

[0002] Nowadays, aircraft, missiles, and other weapons and equipment are flying at ever-increasing speeds. Friction between the skin and the air generates significant heat. To achieve stealth, absorbing materials must be both heat-resistant and oxidation-resistant. However, most absorbing materials currently being researched in China are room-temperature absorbing materials, and most lack both high-temperature absorbing and oxidation-resistant properties. Absorbing materials generally consist of an absorbent and a matrix. For high-temperature, oxidation-resistant absorbents, the matrix must possess these characteristics, including high-temperature resistance, oxidation resistance, high strength, and lightweight. Furthermore, an absorbent with antioxidant properties is added to achieve the goal of integrating the absorbent matrix. Therefore, the antioxidant properties of the absorbent are crucial.

[0003] Currently, carbonyl iron powder is the most important electromagnetic wave absorber material, offering numerous advantages. Industrially produced carbonyl iron powder boasts high production volume and stable quality. It also boasts high magnetic saturation strength, high magnetic loss, and a wider absorption bandwidth at the same thickness. More importantly, its high Curie temperature (770°C) suggests potential high-temperature applications. However, its poor oxidation resistance prevents prolonged use at high temperatures. Therefore, surface modification is necessary to improve its oxidation resistance.

[0004] Generally speaking, applying an organic or inorganic modified layer to the surface of carbonyl iron powder particles improves its protective properties while reducing the electrical polarization of the material system. This reduces the dielectric constant while barely affecting the magnetic permeability of the carbonyl iron powder, thereby improving impedance matching, enhancing microwave absorption, and broadening the absorption bandwidth. The main methods for organic coating of carbonyl iron powder particles include: ① surface modification with organic resins; ② coating with silane coupling agents. The main inorganic coating methods include: ① SiO2 coating; ② acidification to deposit a dense oxide layer; ③ deposition of a high-temperature and corrosion-resistant metal and its oxide, such as Co, ZnO, or MgO. Post-treatment processes such as annealing, high temperature, and applied magnetic fields can also be used to further enhance the material's corrosion and high-temperature resistance. However, these methods still present a number of challenges, including complex preparation processes and high raw material costs. Limited research has been reported in existing patents on surface coating modification of carbonyl iron powder using room-temperature blackening oxidation. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a surface-coated modified carbonyl iron powder composite absorbent. The carbonyl iron powder absorbent prepared by the method of the present invention has excellent performance.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions: 1. A method for preparing a surface-coated modified carbonyl iron powder composite absorbent, characterized by comprising the following steps:

[0007] 1) Blackening oxidation pretreatment: Mix carbonyl iron powder with a certain amount of surfactant aqueous solution and mechanically stir to obtain a carbonyl iron powder mixed solution;

[0008] 2) Take a certain amount of room temperature blackening agent and mix it evenly with water in a specific proportion and set aside;

[0009] 3) taking a certain amount of the carbonyl iron powder mixed solution from step 1) and the room temperature blackening agent aqueous solution from step 2), and mixing them mechanically until the reaction is complete;

[0010] 4) Filter and wash the product after the reaction in step 3) until the pH reaches 7;

[0011] 5) The product obtained in 4) is vacuum dried at a specific temperature to obtain carbonyl iron powder / Fe +2 Fe2 +3 O4 composite absorbent.

[0012] Furthermore, in step 1), the volume ratio of the surfactant to deionized water is 1:1-3, and the mass ratio of the carbonyl iron powder to the surfactant is 5:1.

[0013] Furthermore, the surfactant in step 1) is one of the cationic surfactant cetyltrimethylammonium bromide, the anionic surfactant sodium dodecylbenzenesulfonate, and the zwitterionic surfactant glycine polydimethylsiloxane.

[0014] Furthermore, in step 2), the volume ratio of the room temperature blackening agent to water is 1:1.

[0015] Furthermore, in step 3), the volume ratio of the carbonyl iron powder mixed solution to the room temperature blackening agent aqueous solution is 1:1, the mechanical stirring rate in step 3) is 300-1000 r / min, and the stirring time is 1-10 h.

[0016] Furthermore, in step 4), deionized water is used for washing, or deionized water is used for washing first and then anhydrous ethanol is used for washing.

[0017] Furthermore, in step 5), the vacuum drying temperature is 50-150° C., and the holding time is 6-48 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The room-temperature blackening agent of this invention has the advantages of low raw material cost and wide availability. By adjusting the blackening solution concentration, oxidation time, and surfactant type, the heat resistance and microwave absorption properties of the carbonyl iron powder can be controlled.

[0020] 2. The surface-coated modified carbonyl iron powder composite absorbent of the present invention is prepared by a chemical reaction method. The process is simple and can be used for mass production of composite absorbents, making it easy to industrialize and apply.

[0021] 3. The present invention adopts a room temperature stirring and mixing reaction, which is easy to operate and can ensure that the carbonyl iron powder in the solution and the blackening solution react fully. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a surface morphology of the carbonyl iron powder in Example 1 of the present invention.

[0023] Figure 2 The carbonyl iron powder / Fe in Example 1 of the present invention +2 Fe2 +3 Surface morphology of O4 composite absorbent. Implementation Method

[0024] The present invention will be further described below with reference to specific embodiments. Example

[0025] A surface-coated modified carbonyl iron powder composite absorbent. The carbonyl iron powder in the invention is flaky carbonyl iron powder with a diameter in the range of 1-10 μm and a thickness of less than 1 μm.

[0026] This embodiment also provides a method for preparing a surface-coated modified carbonyl iron powder composite absorbent, comprising the following steps:

[0027] (1) The zwitterionic surfactant glycine was mixed with deionized water in a volume ratio of 1:1 to obtain a zwitterionic surfactant glycine aqueous solution.

[0028] (2) The carbonyl iron powder was mixed with an aqueous solution of a zwitterionic surfactant glycine and mechanically stirred for 30 minutes to obtain a carbonyl iron powder mixture, wherein the mass ratio of carbonyl iron powder to glycine was 5:1.

[0029] (3) Take a certain amount of room temperature blackening agent and mix it evenly with deionized water in a volume ratio of 1:1 and set aside.

[0030] (4) Weigh a certain amount of carbonyl iron powder mixed solution and mix it with the room temperature blackening agent aqueous solution in (3) (the volume ratio of the two is 1:1), and mechanically stir for 6 hours at a stirring rate of 500 r / min until the reaction is completed.

[0031] (5) After the reaction is completed, filter and clean, wash with deionized water 3 times, and wash with anhydrous ethanol 3 times.

[0032] (6) The product of (5) was heated to 80 o C for 6 h to obtain carbonyl iron powder / Fe +2 Fe2 +3 O4 composite absorbent.

[0033] The carbonyl iron powder / Fe prepared in this example +2 Fe2 +3 The wave absorbing performance of the O4 composite absorber was tested, and the minimum reflectivity value was -21dB, and the effective bandwidth in the entire X-band was less than -5dB. Example

[0034] A surface-coated modified carbonyl iron powder composite absorbent. The carbonyl iron powder in the invention is flaky carbonyl iron powder with a diameter in the range of 1-10 μm and a thickness of less than 1 μm.

[0035] This embodiment also provides a method for preparing a surface-coated modified carbonyl iron powder composite absorbent, comprising the following steps:

[0036] (1) Polydimethylsiloxane and deionized water are mixed at a ratio of 1:3 to obtain a polydimethylsiloxane aqueous solution.

[0037] (2) The carbonyl iron powder was mixed with the polydimethylsiloxane aqueous solution and mechanically stirred for 30 minutes to obtain a carbonyl iron powder mixed solution, wherein the mass ratio of the carbonyl iron powder to the polydimethylsiloxane was 5:1.

[0038] (3) Take a certain amount of room temperature blackening agent and mix it evenly with deionized water in a ratio of 1:1 and set aside.

[0039] (4) Weigh a certain amount of carbonyl iron powder mixed solution and mix it with the room temperature blackening agent aqueous solution in (3) (the volume ratio of the two is 1:1), and mechanically stir for 1 hour at a stirring rate of 300 r / min until the reaction is completed.

[0040] (5) After the reaction is completed, filter and clean, and rinse with deionized water until Ph = 7.

[0041] (6) The product of (5) was added at 100 o C for 6 h to obtain carbonyl iron powder / Fe +2 Fe2 +3 O4 composite absorbent.

[0042] The carbonyl iron powder / Fe prepared in this example +2 Fe2 +3The wave absorbing performance of the O4 composite absorber was tested, and the minimum reflectivity value was -13dB. The effective bandwidth of the X-band was less than -5dB and was 2.2GHz.

Claims

1. A method for preparing a surface-coated modified carbonyl iron powder composite absorbent, characterized in that: The following steps are involved: 1) Blackening oxidation pretreatment: carbonyl iron powder is mixed with a certain amount of surfactant aqueous solution and mechanically stirred to obtain a carbonyl iron powder mixed solution; the volume ratio of the surfactant to deionized water is 1:1-3, and the mass ratio of the carbonyl iron powder to the surfactant is 5:1; the surfactant is one of the cationic surfactant hexadecyltrimethylammonium bromide, the anionic surfactant sodium dodecylbenzenesulfonate, and the zwitterionic surfactant glycine polydimethylsiloxane; 2) Take a certain amount of room temperature blackening agent and water in a volume ratio of 1:1 and mix them evenly, then set aside; 3) Weighing a certain amount of the carbonyl iron powder mixed solution from step 1) and the room temperature blackening agent aqueous solution from step 2) in a volume ratio of 1:1, and mechanically stirring until the reaction is complete; the mechanical stirring rate is 300-1000 r / min, and the stirring time is 1-10 hours; 4) Filter and wash the product after the reaction in step 3) until the pH reaches 7; 5) The product obtained in 4) was vacuum dried at 50-150°C for 6-48h to obtain carbonyl iron powder / Fe +2 Fe2 +3 O4 composite absorbent.

2. The method for preparing a surface-coated modified carbonyl iron powder composite absorbent according to claim 1, characterized in that: In step 4), deionized water is used for cleaning, or deionized water is used for cleaning first and then anhydrous ethanol is used for cleaning.

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