MgH2 / Mg-Al high-activity composite metal combustion agent of a grid structure and a preparation method thereof

Abstract

The application belongs to the field of energetic materials, and particularly relates to a MgH2 / Mg-Al high-activity composite metal combustion agent with a grid structure and a preparation method thereof. Mg-Al alloy particles are taken as a basic powder, and hydrogenation is carried out in a hydrogen reaction kettle. Since Mg atoms in the Mg-Al alloy particles are segregated and enriched in the form of Mg2Al3 phase near the grain boundaries, hydrogen atoms rapidly penetrate into the particle interior along the Mg-Al alloy grain boundaries during the hydrogenation process, and combine with the Mg atoms enriched near the grain boundaries to form MgH2, thereby preparing the MgH2 / Mg-Al high-activity composite combustion agent in which MgH2 is distributed in a grid in the particle. In the oxidation combustion process, the high-activity MgH2 enriched at the grain boundaries is ignited preferentially, and the released hydrogen gas will deflagrate along the alloy grain boundaries, and the alloy particles are blasted into many small particles, thereby greatly improving the oxidation combustion completion rate of the metal combustion agent and the energy performance of the explosive and propellant.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of energetic materials, and particularly relates to a MgH2 / Mg-Al high-activity composite metal combustion agent with a grid structure and a preparation method thereof. BACKGROUND

[0002] Metal combustion agents are added to explosives and solid propellants, and can release a large amount of heat after combustion, thereby greatly improving the energy performance of the explosives and propellants. Aluminum powder has a relatively high theoretical heat value (mass heat value 31 MJ / kg, volume heat value 83.7 MJ / L), and is easy to obtain and cheap. In addition, it has good comprehensive performance in safety, stability, processability and long-term storage, and is still widely used in various explosive and propellant formulations. However, during the combustion and oxidation process of aluminum particles, a very dense Al2O3 layer is formed on the surface of the aluminum particles, and the melting point and boiling point of Al2O3 are relatively high (melting point 2054℃, boiling point 2980℃). These result in problems such as long ignition delay time, low combustion rate, incomplete combustion, and a large increase in two-phase flow loss (alumina particle size increase and formation of a solid phase) of the aluminum powder during the combustion process.

[0003] Metal and metal alloy hydrides have large hydrogen storage energy density, which can be comparable to liquid and solid hydrogen. Hydrogen exists in metals at very high concentrations, and is stored by forming metal hydrides. The reversibility of metal hydride phase change can release the stored hydrogen when necessary for utilization.

[0004] As a single light metal hydride, the density of magnesium hydride (MgH2) is relatively high, 1.45 g / cm 3 , and the hydrogen storage capacity reaches 7.6%, which is much higher than that of magnesium-based hydrogen storage alloy hydrides and other metal hydrides. At the same time, the hydrogen release temperature of MgH2 is as high as about 300℃, and it has high thermal stability. In addition, the active metal Mg released by the decomposition of MgH2 has a low boiling point, and the primary combustion product mainly exists in the gas phase, which is generally used as an auxiliary additive to improve the afterburning efficiency when mixed with other fuels. Therefore, MgH2 is very suitable as a component of explosives and solid propellants.

[0005] At present, the application research of MgH2 in explosives and solid propellants mostly adopts the method of ball milling mechanical alloying to embed MgH2 into metal particles with Al as matrix to prepare high-performance energetic composite metal combustion agent applied in explosives and propellants to obtain better energy performance. The high-energy metal combustion agent with MgH2 prepared by mechanical alloying has MgH2 particles dispersed in Al matrix particles, which releases hydrogen in the process of oxidation combustion to play a certain effect of promoting combustion and afterburning. However, since MgH2 particles are dispersed in Al matrix, which is equivalent to being wrapped by Al, and Al itself has a dense and refractory alumina film on the surface, the oxidation combustion performance of MgH2 cannot be fully utilized. SUMMARY

[0006] In order to solve the above problems, the purpose of the present application is to provide a grid structure MgH2 / Mg-Al high-activity composite metal combustion agent and a preparation method thereof. The composite metal combustion agent prepared by the method has excellent low-temperature ignition performance, high oxidation combustion completion rate and can greatly improve its energy release efficiency.

[0007] In order to achieve the above purpose, the technical scheme of the present application is as follows:

[0008] A grid structure MgH2 / Mg-Al high-activity composite metal combustion agent, which is prepared by putting Mg-Al alloy powder as base powder into a high-temperature and high-pressure hydrogen atmosphere reaction kettle to carry out hydrogen charging reaction to obtain the grid structure MgH2 / Mg-Al high-activity composite metal combustion agent.

[0009] The grid structure MgH2 / Mg-Al high-activity composite metal combustion agent has MgH2 in a grid distribution in the Mg-Al alloy.

[0010] The grid structure MgH2 / Mg-Al high-activity composite metal combustion agent has Mg content of 5% to 30% in the Mg-Al alloy, and the rest is Al.

[0011] The grid structure MgH2 / Mg-Al high-activity composite metal combustion agent has spherical Mg-Al alloy particles with particle size of 200 to 1250 mesh.

[0012] The preparation method of the grid structure MgH2 / Mg-Al high-activity composite metal combustion agent includes but is not limited to atomization method, and the structure of the Mg-Al alloy powder is as-cast metal organization structure with Mg segregation.

[0013] The grid structure MgH2 / Mg-Al high-activity composite metal combustion agent uses high-purity hydrogen with purity ≥ 99.9999% for hydrogen charging.

[0014] The grid structure MgH2 / Mg-Al high-activity composite metal combustion agent contains a MgH2 phase, and the mass content of MgH2 is 1.7% to 27.5%.

[0015] The grid structure MgH2 / Mg-Al high-activity composite metal combustion agent contains a MgH2 phase, and the mass content of MgH2 is 1.7% to 27.5%.

[0016] The grid structure MgH2 / Mg-Al high-activity composite metal combustion agent contains a MgH2 phase, and the mass content of MgH2 is 1.7% to 27.5%.

[0017] (1) Mg-Al alloy powder pretreatment: the Mg-Al alloy powder is pretreated in a dilute hydrochloric acid aqueous solution to remove surface oil stains and impurities; the dilute hydrochloric acid aqueous solution is composed of 2 to 5 drops of hydrochloric acid added to 500 mL of distilled water, so that the concentration of the dilute hydrochloric acid is 3 to 7 mol / L, 5 to 30 g of Mg-Al alloy powder is added to 500 mL of the dilute hydrochloric acid aqueous solution, and stirring treatment is performed for 8 to 15 hours, followed by repeated washing and drying in a vacuum drying box to obtain the alloy powder;

[0018] (2) vacuum extraction and powder preheating: the Mg-Al alloy powder treated in step (1) is placed into a hydrogen charging reaction kettle, and the reaction kettle is loaded into a high-temperature and high-pressure hydrogen charging system; the vacuum pump of the hydrogen charging system is started, and when the vacuum degree of the hydrogen charging system reaches 1×10 1 Pa to 5×10 -1 Pa, the reaction kettle is heated to 80 to 150℃ at a heating rate of 2 to 10℃ / min;

[0019] (3) hydrogen gas replacement of the reaction kettle: the vacuum pump of the hydrogen charging system is closed, high-purity hydrogen gas is introduced into the reaction kettle of the hydrogen charging system, the gas pressure is controlled between 0.1 to 0.5 MPa, and maintained for 2 to 5 minutes; then the hydrogen charging valve is closed, the vacuum pump is started, and the vacuum degree of the reaction kettle is extracted to 1×10 1 Pa to 5×10 -1 Pa, and maintained for 2 to 5 minutes, and this replacement is repeated for 3 to 5 times;

[0020] (4) high pressure hydrogenation: high purity hydrogen is introduced into the reactor, the gas pressure is controlled between 2-5 MPa, and heating is started, the temperature of the reactor is heated to 350-450℃, the heating rate is 2-10℃ / min, at this time, hydrogen will quickly penetrate into the particle interior along the grain boundary of Mg-Al alloy, and MgH2 is generated by reaction, the treatment time is 5-16 hours; after hydrogenation, the heating is turned off, the hydrogen atmosphere is maintained, the gas pressure is maintained between 1-5 MPa, and the furnace is cooled to below 50℃, then the hydrogenation valve is closed, and the sample is taken out, to obtain the grid structure MgH2 / Mg-Al high activity composite metal combustion agent.

[0021] The design idea of the present application is:

[0022] In the process of preparing Mg-Al alloy powder by atomization method, Mg atoms cannot completely exist in the form of substitutional solid solution in the grain interior. In the process of solidification of Al melt, supersaturated Mg is precipitated in the form of coarse β phase (Al3Mg2) on the grain boundary, thereby forming a magnesium-rich grid segregation area. The atomized Mg-Al alloy powder is placed in a reactor with a certain temperature and pressure hydrogen atmosphere, hydrogen atoms will quickly penetrate through the grain boundary of the Mg-Al alloy particles, and combine with the Mg atoms enriched near the grain boundary to form MgH2, thereby realizing the grid distribution of MgH2 in the alloy, and preparing the grid structure MgH2 / Mg-Al high activity composite metal combustion agent. This is conducive to continuous combustion of MgH2, thereby more fully exerting the characteristics of low temperature easy ignition and complete combustion. On the other hand, a large amount of hydrogen gas is released during the combustion of MgH2 distributed at the grain boundary, and the deflagration of hydrogen gas will break the Al matrix into countless tiny Al particles. Unlike nano Al metal combustion agent which needs surface passivation, the content of active Al in these Al particles is very high, so the energy release efficiency of the Al matrix is greatly improved.

[0023] The present application utilizes the grain boundary segregation of Mg atoms in the Mg-Al alloy particles to in-situ hydrogenate Mg, and prepare grid-distributed energy-containing composite particles with MgH2 in the alloy particles, and the main advantages and technical effects are as follows:

[0024] 1. The composite metal combustion agent prepared by the present application has a hydrogen release temperature of 350-380℃ under normal pressure, and has very high thermal stability and safety, which is conducive to improving the safety and stability of the prepared pharmaceutical, and the transportation and storage safety of propellants.

[0025] 2. In the combustion and explosion process of the grid structure MgH2 / Mg-Al high activity composite metal combustion agent prepared by the present application, the released hydrogen gas can play a blasting role, breaking the larger metal composite particles into very small high activity particles, thereby improving the oxidation combustion completion rate of the metal combustion agent, and greatly improving the energy performance of explosives and propellants.

[0026] 3. The composite metal fuel prepared by the present application has a nearly spherical particle shape, good flowability and is easy to be formed into a propellant.

[0027] 4. The MgH2 / Mg-Al high-activity composite metal fuel with a grid structure prepared by the present application has dense internal powder particles and high bulk density, which is beneficial to improve the volumetric heat value of the propellant. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 X-ray powder diffraction (XRD) structure diagram of the grid structure MgH2 / Mg-Al high-activity composite metal fuel prepared for Example 1 of the present application. In the diagram, the horizontal coordinate 2θ is the diffraction angle (°), and the vertical coordinate Intensity is the relative intensity (a.u.).

[0029] Figure 2 Scanning electron microscope (SEM) photo of the grid structure MgH2 / Mg-Al high-activity composite metal fuel prepared for Example 1 of the present application.

[0030] Figure 3 Element distribution photo of the grid structure MgH2 / Mg-Al high-activity composite metal fuel prepared for Example 1 of the present application.

[0031] Figure 4 X-ray powder diffraction (XRD) structure diagram of the grid structure MgH2 / Mg-Al high-activity composite metal fuel prepared for Example 2 of the present application. In the diagram, the horizontal coordinate 2θ is the diffraction angle (°), and the vertical coordinate Intensity is the relative intensity (a.u.).

[0032] Figure 5 Mg element distribution diagram of the grid structure MgH2 / Mg-Al high-activity composite metal fuel prepared for Example 2 of the present application. DETAILED DESCRIPTION

[0033] In the specific implementation process, the application provides a preparation method of a grid structure MgH2 / Mg-Al high-activity composite metal combustion agent. The Mg-Al alloy particles prepared by the atomization method are used as the base powder, and the base powder is placed in a high-temperature and high-pressure hydrogen atmosphere reaction kettle for hydrogen charging. In the atomization-prepared Mg-Al alloy particles, most of the Mg atoms are segregated and enriched in the form of Mg2Al3 phase near the alloy grain boundaries. Therefore, during the hydrogen charging process, hydrogen atoms will rapidly penetrate into the particle interior along the Mg-Al alloy grain boundaries and combine with the Mg atoms enriched near the grain boundaries to form MgH2, so that the MgH2 / Mg-Al high-activity composite metal combustion agent with grid-distributed MgH2 in the Mg-Al alloy particles is prepared. In the oxidation combustion process of the grid structure MgH2 / Mg-Al composite metal combustion agent prepared by the method, the high-activity MgH2 enriched at the grain boundaries is preferentially ignited and combusted, the released hydrogen gas will deflagrate along the alloy grain boundaries, and the alloy particles are blasted into many fine particles, thereby greatly improving the oxidation combustion completion rate of the metal combustion agent and the energy performance of the explosive and propellant.

[0034] The technical solutions of the application will be described clearly and completely in combination with the drawings and examples. Obviously, the described examples are part of the examples of the application, rather than all the examples. Based on the examples in the application, all other examples obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0035] Example 1

[0036] In this example, the Mg-Al alloy with a 20wt% Mg content prepared by the atomization method is selected as the base powder, which is placed in a high-temperature and high-pressure hydrogen atmosphere reaction kettle for hydrogen charging to prepare the grid structure MgH2 / Mg-Al high-activity composite metal combustion agent. In the Mg-Al alloy, the Mg content accounts for 20% by mass percentage, and the rest is Al. The Mg-Al alloy is a spherical particle with a particle size of-325 mesh. The preparation method of the Mg-Al alloy particle is the atomization method, and the structure is as-cast structure with Mg segregation. The hydrogen used for hydrogen charging is high-purity hydrogen with a hydrogen volume purity of ≥99.9999%.

[0037] The preparation method of the grid structure MgH2 / Mg-Al high-activity composite metal combustion agent includes the following steps:

[0038] (1) Mg-Al alloy powder pretreatment: Mg-Al alloy powder is pretreated in dilute hydrochloric acid aqueous solution to remove surface oil stains and impurities. The solution composition is: 500 mL of distilled water, 3 drops of hydrochloric acid, the concentration of dilute hydrochloric acid is 5 mol / L, 6 grams of Mg-Al alloy powder is added to the dilute hydrochloric acid aqueous solution, stirring treatment for 10 hours, and after repeated washing, the treated alloy powder is dried in a vacuum drying oven;

[0039] (2) Vacuum and powder preheating: the Mg-Al alloy powder treated in step (1) is put into a hydrogen charging reaction kettle, and the reaction kettle is loaded into a high-temperature and high-pressure hydrogen charging system. Start the vacuum pump of the hydrogen charging system, when the vacuum degree of the hydrogen charging system reaches 0.3 Pa, open the heater to heat the reaction kettle to 120℃, the heating rate is 6℃ / min;

[0040] (3) Reaction kettle hydrogen replacement: close the vacuum pump of the hydrogen charging system, introduce high-purity hydrogen into the reaction kettle of the hydrogen charging system, control the gas pressure at 0.2 MPa, and maintain for 4 minutes; then close the hydrogen charging valve, start the vacuum pump, and the vacuum degree of the reaction kettle is extracted to 0.3 Pa, and maintained for 4 minutes, which is repeated for 5 times;

[0041] (4) High-pressure hydrogen charging: introduce high-purity hydrogen into the reaction kettle, control the gas pressure at 3.5 MPa, and at the same time, open the heater to heat the reaction kettle to 420℃, the heating rate is 7℃ / min, the treatment time is 10 hours; after the hydrogen charging is completed, the heater is turned off, the hydrogen atmosphere is maintained, the gas pressure is maintained at 2 MPa, and the furnace is cooled to below 50℃, then the hydrogen charging valve is closed, and the sample is taken out, then the grid structure MgH2 / Mg-Al high-activity composite metal combustion agent is obtained.

[0042] The MgH2 / Mg-Al composite metal combustion agent prepared by the above method is detected by XRD method. As shown in Figure 1 the XRD pattern analysis of the MgH2 / Mg-Al composite metal combustion agent can determine that the composite particles contain MgH2 phase, MgH2 is obtained by the reaction of hydrogen and magnesium element in the alloy matrix during the hydrogen charging reaction process, and the mass content of MgH2 is 7.44%.

[0043] The MgH2 / Mg-Al composite metal combustion agent prepared by the above method is detected by scanning electron microscopy method. As shown in Figure 2As shown in the scanning electron microscope photos of the MgH2 / Mg-Al composite metal propellant, the MgH2 / Mg-Al composite metal particles prepared under the conditions of the present embodiment basically retain the shape of the base powder Mg-Al alloy particles, which are also spherical. However, the surface morphology of the MgH2 / Mg-Al composite metal particles prepared under the conditions of the present embodiment is different from that of the base powder particles before hydrogenation, and many crack-like or gully-like morphologies appear, because hydrogen gas rapidly penetrates through the grain boundaries of the Mg-Al alloy particles during hydrogenation to react to form magnesium hydride, thus forming the crack-like or gully-like morphologies.

[0044] The MgH2 / Mg-Al composite metal propellant prepared by the above method was detected for the distribution of Mg elements in the particles by electron probe microanalysis (EPMA). As shown in Figure 3 As shown in the Mg element distribution diagram of the MgH2 / Mg-Al composite metal propellant, Mg is distributed in a grid-like manner in the particles.

[0045] The hydrogen storage capacity of the MgH2 / Mg-Al composite metal propellant prepared by the above method was actually measured by the drainage gas collection method, and the hydrogen content (mass content) was 0.57%. The theoretical hydrogenation content of the base powder Mg20Al80 was 1.63%, and by calculation, the hydrogenation rate of Mg in the base powder was 35.0%.

[0046] The combustion heat value of the MgH2 / Mg-Al composite metal propellant prepared by the above method was measured by an oxygen bomb calorimeter, and the combustion heat value was 29.18 MJ / kg, which was 1.21% higher than that of the base powder Mg20Al80 (the actually measured combustion heat value was 28.83 MJ / kg).

[0047] Example 2

[0048] In the present embodiment, an atomized 30wt% Mg content Mg-Al alloy was selected as the base powder, which was placed in a high-temperature and high-pressure hydrogen atmosphere reaction kettle to react and hydrogenate to prepare a grid-structured MgH2 / Mg-Al high-activity composite metal propellant. In terms of mass percentage, the Mg content in the Mg-Al alloy was 30%, and the rest was Al. The Mg-Al alloy was a spherical particle with a particle size of minus 325 mesh. The Mg-Al alloy particles were prepared by an atomization method, and the structure was as-cast structure with Mg segregation. The hydrogen used for hydrogenation was high-purity hydrogen with a purity of ≥99.9999%.

[0049] The preparation method of the grid-structured MgH2 / Mg-Al high-activity composite metal propellant comprises the following steps:

[0050] (1) Mg-Al alloy powder pretreatment: Mg-Al alloy powder is pretreated in dilute hydrochloric acid aqueous solution to remove surface oil stains and impurities. The solution composition is: 500 mL of distilled water, 3 drops of hydrochloric acid, the concentration of dilute hydrochloric acid is 4 mol / L, 6 g of Mg-Al alloy powder is added to the dilute hydrochloric acid aqueous solution, stirring treatment for 10 hours, repeated washing and drying in a vacuum drying oven to obtain treated alloy powder;

[0051] (2) Vacuum and powder preheating: the Mg-Al alloy powder treated in step (1) is put into a hydrogen charging reaction kettle, and the reaction kettle is loaded into a high-temperature and high-pressure hydrogen charging system. Start the vacuum pump of the hydrogen charging system, and when the vacuum degree of the hydrogen charging system reaches 0.1 Pa, start the heater to heat the reaction kettle to 120℃, and the heating rate is 6℃ / min;

[0052] (3) Reaction kettle hydrogen replacement: close the vacuum pump of the hydrogen charging system, and introduce high-purity hydrogen into the reaction kettle of the hydrogen charging system, and control the gas pressure at 0.3 MPa for 2 minutes; then close the hydrogen charging valve, start the vacuum pump, and the vacuum degree of the reaction kettle is extracted to 0.1 Pa and maintained for 2 minutes, and the replacement is repeated for 5 times;

[0053] (4) High-pressure hydrogen charging: high-purity hydrogen is introduced into the reaction kettle, and the gas pressure is controlled at 3.5 MPa, and the heater is started at the same time, and the temperature of the reaction kettle is heated to 430℃, and the heating rate is 8℃ / min. At this time, hydrogen will quickly penetrate into the interior of the particles along the grain boundary of the Mg-Al alloy and react to form MgH2, and the treatment time is 12 hours; after the hydrogen charging is completed, the heating is turned off, the hydrogen atmosphere is maintained, the gas pressure is maintained at 2.5 MPa, and the furnace is cooled to below 50℃, then the hydrogen charging valve is closed, and the sample is taken out, and the grid structure MgH2 / Mg-Al high-activity composite metal combustion agent is obtained.

[0054] The MgH2 / Mg-Al composite metal combustion agent prepared by the above method is detected by XRD method. As shown in Figure 4 , it can be determined from the XRD pattern analysis of the MgH2 / Mg-Al composite metal combustion agent that the composite particles contain MgH2 phase, MgH2 is obtained by the reaction of hydrogen and magnesium element in the alloy matrix during the hydrogen charging reaction, and the mass content of MgH2 is 11.36%.

[0055] The MgH2 / Mg-Al composite metal combustion agent prepared by the above method is detected by electron probe (EPMA) method to detect the distribution of Mg element in the particle interior. As shown in Figure 5 , it can be seen from the Mg element distribution map of the MgH2 / Mg-Al composite metal combustion agent that Mg is richly distributed in the grid shape in the particle interior.

[0056] The hydrogen storage capacity of the MgH2 / Mg-Al composite metal fuel prepared by the method is measured by drainage gas collection, and the hydrogen content (mass content) is 0.87%. The theoretical hydrogen storage capacity of the base powder Mg30Al70 is 2.43%, and the hydrogenation rate of Mg in the base powder is 35.8% by calculation.

[0057] The combustion heat value of the MgH2 / Mg-Al composite metal fuel prepared by the method is measured by an oxygen bomb calorimeter, and the combustion heat value is 28.69 MJ / kg, which is 1.24% higher than that of the base powder Mg30Al70 (the measured combustion heat value is 28.34 MJ / kg).

[0058] The results of the examples show that the MgH2 / Mg-Al composite metal particles prepared by the method have a spherical shape, good flowability, and are beneficial to the preparation of explosives, and the preparation method has a simple process flow. The MgH2 is distributed in a grid shape in the particles, the hydrogenation rate of Mg in the powder is about 35%, and the heat value of the powder is slightly higher than that of the base powder. It can be seen that the grid structure MgH2 / Mg-Al composite metal particle powder prepared by the method has the advantages of improving the energy of the powder, significantly reducing the ignition temperature of the fuel, improving the burning rate of the powder, and greatly improving the combustion efficiency of the powder, and is expected to be applied in practical engineering.

[0059] The above only describes the optimal embodiments of the present application. It should be pointed out that all those skilled in the art can make changes and / or modifications to the examples without departing from the spirit and principles of the appended claims and the present application, and these changes should also be considered as the protection scope of the present application.

Claims

1. A grid-structured MgH2 / Mg-Al highly active composite metal combustion agent, characterized in that, Using Mg-Al alloy powder as the base powder, it is placed in a high-temperature and high-pressure hydrogen atmosphere reactor to carry out a hydrogen-filled reaction to obtain a MgH2 / Mg-Al highly active composite metal combustion agent with a grid structure.

2. The MgH2 / Mg-Al highly active composite metal combustion agent with a mesh structure according to claim 1, characterized in that, MgH2 is distributed in a grid pattern inside the Mg-Al alloy.

3. The MgH2 / Mg-Al highly active composite metal combustion agent with a mesh structure according to claim 1, characterized in that, By mass percentage, Mg-Al alloys contain 5% to 30% Mg, with the remainder being Al.

4. The MgH2 / Mg-Al highly active composite metal combustion agent with a mesh structure according to claim 1, characterized in that, Mg-Al alloys are spherical particles with a particle size between 200 and 1250 mesh.

5. The MgH2 / Mg-Al highly active composite metal combustion agent with a mesh structure according to claim 1, characterized in that, The preparation methods of Mg-Al alloy powder include, but are not limited to, atomization, and its structure is a cast metal microstructure with Mg segregation.

6. The MgH2 / Mg-Al highly active composite metal combustion agent with a mesh structure according to claim 1, characterized in that, The hydrogen used for charging is high-purity hydrogen with a purity of ≥99.9999%.

7. The MgH2 / Mg-Al highly active composite metal combustion agent with a mesh structure according to claim 1, characterized in that, The MgH2 / Mg-Al highly active composite metal fuel contains a MgH2 phase, with a MgH2 mass content of 1.7% to 27.5%.

8. The MgH2 / Mg-Al highly active composite metal combustion agent with a mesh structure according to claim 1, characterized in that, In the MgH2 / Mg-Al highly active composite metal fuel, the mass content of hydrogen is 0.13% to 2.4%.

9. A method for preparing a MgH2 / Mg-Al highly active composite metal combustion agent with a mesh structure as described in any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Pretreatment of Mg-Al alloy powder: The Mg-Al alloy powder is pretreated in a dilute hydrochloric acid aqueous solution to remove surface oil stains and impurities; the dilute hydrochloric acid aqueous solution is composed of 2-5 drops of hydrochloric acid added to every 500 mL of distilled water to make the concentration of dilute hydrochloric acid 3-7 mol / L, and 5-30 g of Mg-Al alloy powder added to every 500 mL of dilute hydrochloric acid aqueous solution. The mixture is stirred for 8-15 hours, washed repeatedly, and then dried in a vacuum drying oven to obtain the alloy powder. (2) Vacuuming and powder preheating: Place the Mg-Al alloy powder treated in step (1) into a hydrogen-filled reactor, and then load the reactor into a high-temperature and high-pressure hydrogen-filling system; start the vacuum pump of the hydrogen-filling system, and wait for the vacuum degree of the hydrogen-filling system to reach 1×10 1 Pa ~ 5 × 10 -1 When Pa, turn on the heating to heat the reactor to 80-150°C at a heating rate of 2-10°C / min. (3) Hydrogen purging of the reactor: Turn off the vacuum pump of the hydrogen charging system, introduce high-purity hydrogen into the reactor of the hydrogen charging system, control the gas pressure between 0.1 and 0.5 MPa, and maintain it for 2 to 5 minutes; then close the hydrogen charging valve, start the vacuum pump, and evacuate the reactor to a vacuum degree of 1×10⁻⁶. 1 Pa ~ 5 × 10 -1 Maintain the pressure between Pa for 2-5 minutes, and repeat this replacement 3-5 times. (4) High-pressure hydrogen charging: High-purity hydrogen gas is introduced into the reactor, and the gas pressure is controlled between 2 and 5 MPa. At the same time, the heating is turned on to heat the reactor temperature to 350 to 450°C at a heating rate of 2 to 10°C / min. At this time, the hydrogen gas will quickly penetrate into the particles along the grain boundaries of the Mg-Al alloy and react to generate MgH2. The treatment time is 5 to 16 hours. After the hydrogen charging is completed, the heating is turned off, the hydrogen atmosphere is maintained, and the gas pressure is maintained between 1 and 5 MPa. The furnace is cooled to below 50°C, and then the hydrogen charging valve is closed. The sample is taken out to obtain a MgH2 / Mg-Al high-activity composite metal combustion agent with a grid structure.

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