Preparation method and application of thermal decomposition MAX or MAB phase wave-absorbing powder

Abstract

The invention discloses a preparation method and application of thermal decomposition MAX or MAB phase wave-absorbing powder, and belongs to the technical field of wave-absorbing material development. The invention develops a plasma spray gun capable of instantly performing nanocrystallization thermal decomposition on sheet-shaped MAX or MAB phase powder, a plasma arc generated by the plasma spray gun is short and wide and is positioned in front of an anode nozzle, and after the sheet-shaped MAX or MAB phase powder is fed into the plasma arc, instant high-temperature nanocrystallization in-situ thermal decomposition of the powder can be realized without blocking the nozzle. According to the plasma spray gun, an inert gas protection area can be formed at the front end of the anode nozzle, and sheet-shaped MAX or MAB phase powder is effectively prevented from being oxidized. The composite wave-absorbing powder is convenient to prepare, low in cost and excellent in performance, has a wide application prospect, can be mixed with matrixes such as resin to prepare a wave-absorbing coating, and is used for efficiently absorbing waves for a long time in a high-temperature environment.

Description

Technical Field

[0001] The invention relates to the field of wave-absorbing materials, and in particular to a method for preparing thermally decomposed MAX or MAB phase wave-absorbing powder and applications thereof. Background Art

[0002] The layered ternary compounds MAX and MAB phases have excellent metal-like and ceramic-like comprehensive properties, including good electrical and thermal conductivity, machinability, low hardness, thermal shock resistance, high damage tolerance, high elastic modulus, excellent high temperature strength, and oxidation and corrosion resistance. They can be used as functional materials in various fields, including automotive engine parts, heating elements, rocket engine nozzles, aircraft brakes, racing brake pads, and low-density armor. (Reference: MW Barsoum et al., Nature Materials, 2003, 2 (2), 107–111) In the field of electromagnetics, MAX and MAB phase materials have certain electromagnetic loss capabilities due to their special layered structure and the interaction of internal elements. They can interact with electromagnetic waves and absorb and attenuate them. It is an innovative research idea to use MAX or MAB phase materials in the preparation of absorbing coatings after thermal decomposition. The nano-thermal decomposition process can form dispersed nano-scale decomposition phase particles inside the MAX or MAB phase material, including one of metal carbides (TiC, etc.), metal nitrides (TiN, etc.), metal borides (TiB, etc.) and intermetallic compounds (Ti x A y These decomposed phases can not only further optimize the electromagnetic properties of the material, introduce multiple loss mechanisms such as interface polarization relaxation loss and defect-induced polarization loss, and enhance its absorption and loss capacity of electromagnetic waves, but also improve the compatibility and interfacial bonding between the material and other components (such as binders, additives, etc.), thereby improving the comprehensive performance of the absorbing coating. The absorbing powder prepared in this way is expected to overcome the many shortcomings of traditional absorbing materials, while ensuring good absorbing performance, achieving goals such as lightweight, broadband and strong environmental adaptability, providing strong support for electromagnetic protection and stealth technology in the fields of military defense, aerospace, electronic communications, etc., and has extremely important research significance and broad application prospects. (Reference: CSMa et al., CRIT REVSOLID STATE, 2023, 48 (6), 726-753) Based on this, new requirements are put forward for the nano-thermal decomposition treatment of flake-shaped MAX or MAB phase powders.

[0003] The traditional thermal decomposition treatment method of the flake-shaped MAX or MAB phase cannot obtain intermetallic compound MA and nano-phase MX or MB particles. Because the time window of the heat treatment method of heating equipment such as the muffle furnace is too long, the weak MA bond in the flake-shaped MAX or MAB phase makes it easy for the A-position atoms to diffuse outward under high temperature conditions, generating micron-sized rather than nano-sized MX or MB, especially the flake-shaped MAX or MAB phase containing Al (Ti2AlC, Ti3AlC2, Cr2AlC, Mo2AlB) and Si (Ti3SiC2). (Reference: XHZha et al., Inorg.Chem, 2022, 61(4), 2129–2140.) Furthermore, the flake-shaped MAX or MAB phase will generate micron-sized M and A oxides after long-term high-temperature oxidation. For example, under vacuum, Ti3SiC2 will decompose into Si, TiC x and / or Ti5Si3C x , thus becoming unstable. (Reference: Low, IM et al., MATERIALS, 2019, 12(3)) Similar phenomena are also observed in Ti3AlC2 and Ti2AlN, that is, they decompose under vacuum to form TiC x and TiN x This process is mainly through the sublimation of A-site elements such as Al or Si to form porous MX on the surface. x . In the atmosphere, Ti2AlC can be simultaneously converted into Ti3AlC2, TiC and Al2O3 at temperatures above 800°C, with the Al2O3 formed on the surface and TiC inside. Subsequently, the Al atoms in Ti3AlC2 diffuse outward to form α-Al2O3 and fill the pores, while TiC is formed in situ, and TiO2 is formed after long-term high-temperature oxidation. (Reference: WBYu et al., J.Eur.Ceram.Soc, 2020, 40(5), 1820–1828) Therefore, the traditional heat treatment decomposition method cannot achieve the nanoscale decomposition of the flake-shaped MAX or MAB phase.

[0004] At present, there are also studies on the use of laser cladding technology to process sheet-shaped MAX or MAB phase materials. For example, Zhou et al. used a focused high-energy pulsed laser to process Ti3AlC2 ceramics in air. Due to the high concentration of laser beam energy, Ti3AlC2 decomposed into TiC and Al at high temperature, and the Al in Ti3AlC2 evaporated directly and quickly outward. In this process, oxygen diffused inward to form powdered TiC x O ySolid solution, after rapid cooling, the solid solution re-solidifies to form a coating. (Reference: Q.Zhou et al., CERAMICS INTERNATIONAL, 2024, 50 (12), 21945-21950) This shows that the required nano-scale TiC distributed in TiAl cannot be obtained by laser cladding. In addition, the spot of laser cladding is too small and difficult to control, the molding quality is too poor and the preparation efficiency is low. Therefore, laser cladding technology is not suitable for directly processing flake MAX or MAB phase powders. In recent years, the plasma thermal spraying technology with DC arc plasma as the heat source has gradually developed and is expected to become a new preparation process for achieving nano-scale thermal decomposition of flake MAX or MAB phases. Through investigation, it was found that researchers have carried out research on the preparation of flake MAX or MAB phase composite coatings using plasma spraying technology. For example, Xu et al. used Ti3SiC2 and Cu powder as raw materials and prepared composite coatings using atmospheric plasma spraying technology. Ti3SiC2 is partially decomposed into nano to submicron TiC x Particles, however, the droplets are oxidized in the plasma jet to generate oxides such as TiO2 and SiO2. This shows that the atmospheric plasma sprayed MAX phase cannot achieve complete nano-decomposition and is very easy to produce oxide impurities. (Reference: HBXu et al., SURFACE&COATINGS TECHNOLOGY, 2023, 460) Similarly, Zhang et al. found that a large amount of TiC (37.0wt%) was introduced into the coating during the spraying process of the plasma sprayed Ti2AlC coating due to the thermal decomposition of Ti2AlC. (Reference: Z. Zhang et al., J. Alloy. Compd, 2019, 790, 536–546) Analysis of the current research status shows that there is currently no research on the use of plasma thermal spraying technology to nano-thermally decompose the sheet-shaped MAX or MAB phase. The reason is that the existing plasma spraying equipment mainly uses Laval nozzles. The plasma arc generated by the Laval nozzle is too long, and the sheet-shaped MAX or MAB phase powder stays in the plasma arc for too long, which is very easy to oxidize and produce oxide impurities. In addition, its unique structural design causes the melting and decomposition to start from inside the nozzle when spraying flake MAX or MAB phase, which can easily cause nozzle blockage and seriously restrict the spraying efficiency. Therefore, the existing Laval nozzle and the matching plasma spray gun equipment cannot achieve nano-decomposition of flake MAX or MAB phase powder.

[0005] In summary, the main limiting factor for achieving efficient nano-thermal decomposition of flake-shaped MAX or MAB phase powders is the length of the plasma arc generated at the nozzle and the design and research of its nozzle structure. In order to achieve instantaneous high-temperature nano-decomposition of flake-shaped MAX or MAB phase powders, we have developed a plasma spray gun and a corresponding MAX or MAB phase absorbing powder preparation method described in this patent. The plasma flame temperature generated by the spray gun can reach above 6000°C, and the flame range is large, which can achieve efficient and large-scale processing of flake-shaped MAX or MAB phase powders. In addition, in view of the characteristics of rapid escape of A-layer atoms in the high-temperature environment of flake-shaped MAX or MAB phase powders and the actual needs of efficient nano-thermal decomposition preparation, this patent shortens the powder transportation path in the plasma compared to the traditional Laval nozzle, realizes rapid nano-thermal decomposition inside the powder, and avoids the problem of excessive melting of the powder and then blocking the nozzle due to the accumulation of a large amount of heat. At the same time, considering the limitation of the oxidation of the powder, the flake-shaped MAX or MAB phase raw material powder described in this patent will quickly cool down and solidify after high-speed collision with the substrate, and the time window of thermal decomposition is very small, which can avoid oxidation at high temperature to generate oxide impurities. The plasma spray gun described in this patent can also achieve efficient dual water cooling, synchronous efficient powder feeding and good insulation performance. The MAX or MAB phase raw material powder treated by nano-thermal decomposition by the plasma spray gun described in this patent is applied to the preparation of absorbing coatings, which is expected to overcome some defects of traditional absorbing materials and has important research significance and application value. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing a thermally decomposed MAX or MAB phase absorbing powder and its application, so as to solve the shortcomings of existing absorbing materials.

[0007] The method for preparing the thermally decomposed MAX or MAB phase absorbing powder of the present invention comprises the following steps:

[0008] Select a high-purity flake-shaped MAX or MAB phase raw material powder, place it in a powder feeder, and adjust the powder feeding amount (2-10g / min) to obtain the most uniform feeding effect. Adjust the parameters of the plasma spraying equipment, including current (300-500A), voltage (60-100V), gas flow (argon 90-110L / min, hydrogen 18-25L / min), spraying distance (90-150mm), etc., to obtain the best nano-thermal decomposition effect. Use the plasma spray gun described in the present invention to instantaneously nano-thermally decompose the raw material powder, feed the raw material powder into the plasma spray gun, and under the high temperature of the plasma arc, the powder is heated to a molten or semi-molten state, and is sprayed into an alumina crucible at high speed for collection.

[0009] The beneficial effects of the present invention are as follows:

[0010] 1. The plasma spray gun provided by the present invention can realize instantaneous high-temperature nano-decomposition of flake-shaped MAX or MAB phase powders, thereby avoiding the phenomenon of nozzle clogging caused by excessive heating time and excessive melting of the powders.

[0011] 2. The present invention uses MAX or MAB phase materials as a basis, and forms a nanoscale decomposed phase inside the materials through nano-thermal decomposition treatment, which effectively improves the electromagnetic loss performance of the materials and broadens the wave absorption band.

[0012] 3. Compared with traditional absorbing materials, the absorbing powder of the present invention has a relatively low density while ensuring good absorbing performance, which is beneficial to reducing the weight of equipment and improving the maneuverability and fuel efficiency of equipment.

[0013] 4. The preparation process is relatively simple, easy to operate and control, can be realized in large-scale industrial production, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0015] Figure 1 Schematic diagram of the overall structure of the plasma spray gun in an embodiment of the present invention.

[0016] Figure 2 It is a side view of the overall structure of the plasma spray gun in an embodiment of the present invention.

[0017] Figure 3 The following are the overall physical pictures of the plasma spray gun in the embodiment of the present invention. Among them, (a) is the overall front view of the spray gun, and (b) is the overall physical picture of the spray gun taken from the nozzle direction.

[0018] Figure 4 The XRD pattern evolution of the MAX or MAB phase powder in the embodiment of the present invention.

[0019] Figure 5 The SEM images of the microscopic morphology of the MAX or MAB phase powder before and after the plasma treatment and nano-decomposition in the embodiment of the present invention. Among them, (a) is the morphology of the Ti2AlC powder after plasma treatment, and (b) is the SEM image of the microscopic morphology of the nano-decomposition inside the Ti2AlC powder.

[0020] Figure 6 This is a comparison chart of the microwave absorption performance of MAX or MAB phase powder before and after nano-decomposition by plasma treatment in the embodiments of the invention. DETAILED DESCRIPTION

[0021] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0022] Embodiment 1:

[0023] Select Ti2AlC raw material powder with high purity, place it in the powder feeder, adjust the powder feeding amount to 6g / min, current to 450A, voltage to 80V, argon flow rate to 110L / min, hydrogen flow rate to 24L / min, spraying distance to 110mm, use the plasma spray gun of the present invention to instantaneously nano-thermally decompose the raw material powder, and collect it with an alumina crucible. The powder has broad application prospects and can be mixed with a matrix such as resin to prepare an absorbing coating for efficient and long-term absorbing in a high temperature environment.

[0024] Embodiment 2:

[0025] According to the steps similar to those in Example 1, some parameters were changed, such as selecting Cr2AlC powder as the raw material, adjusting the powder feeding amount to 5 g / min, the current to 400 A, the voltage to 750 V, the argon flow rate to 100 L / min, the hydrogen flow rate to 22 L / min, and the spraying distance to 150 mm.

[0026] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing thermally decomposed MAX or MAB phase absorbing powder and its application, characterized in that: The preparation method comprises: using a self-developed novel plasma spray gun to instantaneously thermally decompose flake-shaped MAX or MAB phase powder to obtain MAX or MAB phase wave-absorbing powder.

2. The self-developed new plasma spray gun according to claim 1 is characterized in that: The plasma spray gun comprises a connecting plate, a cathode assembly, a gun body and an anode nozzle which are sequentially connected from top to bottom.

3. The plasma spray gun according to claim 2, characterized in that: The cathode assembly comprises a cathode pressure cap, a tungsten electrode located inside the cathode pressure cap, and an elastic cathode clamp for fixing the tungsten electrode.

4. The plasma spray gun according to claim 2, characterized in that: The gun body comprises a cathode seat, an insulating seat, an anode seat, a cathode water inlet and outlet nozzles installed on the cathode seat, and an anode water inlet and outlet nozzles installed on the anode seat.

5. The plasma spray gun according to claim 2, characterized in that: The gun body is connected with a working gas input pipe, a protective gas input pipe, a water inlet pipe, a water return pipe and a powder delivery pipe.

6. The plasma spray gun according to claim 2, characterized in that: A symmetrical powder delivery channel is arranged inside the anode seat.

7. The MAX or MAB phase absorbing powder according to claim 1, characterized in that: The powder is partially decomposed into one of metal carbides (TiC, etc.), metal nitrides (TiN, etc.), metal borides (TiB, etc.) and intermetallic compounds (Ti x A y wait).

8. The MAX or MAB phase absorbing powder according to claim 1, characterized in that: The powder dielectric constant ranges from 5<ε'<20 and 1<ε"<10.

9. The MAX or MAB phase absorbing powder according to claim 1, characterized in that: The effective absorption bandwidth EAB of the powder is ≥3.0 GHz.

10. Use of the absorbing powder according to any one of claims 1 to 9 in the preparation of anti-electromagnetic wave pollution materials or radar stealth absorbing materials.

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