Al-RE rare earth alloy powder fuel capable of forming oxygen diffusion channel at grain boundary and application of Al-RE rare earth alloy powder fuel

Abstract

The invention provides an Al-RE rare earth alloy powder fuel forming an oxygen diffusion channel at a grain boundary, which is characterized in that a rare earth intermediate alloy Al-RE is added into a pure Al melt, alloying is carried out, and a solidification structure capable of diffusing oxygen atoms is formed after supersonic atomization of an inert gas atomization system, non-equilibrium cooling and staged treatment. In the high-temperature oxidation environment, the rare earth alloy powder fuel is oxidized, meanwhile, the grain boundary also starts to be oxidized, oxygen is diffused from the surface of the powder to the interior, an oxygen diffusion channel and a microstructure are formed through grain boundary oxidation, and complete oxidation combustion is achieved. The micron-sized powder fuel with the oxygen diffusion channel formed at the crystal boundary in the alloy powder fuel is low in production cost and easy to store, and has the advantages of reaction characteristics of nano-particle powder and high combustion efficiency. And due to the existence of an oxygen diffusion channel in the powder, internal crystal grains can be oxidized to a great extent, and almost no unburned residue exists, so that the combustion efficiency and the economic benefit of the fuel are improved, and the propelling capacity of the fuel is also greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth alloy powder fuel, and in particular relates to an Al-RE rare earth alloy powder fuel with an oxygen diffusion channel formed at a grain boundary and application thereof. Background Art

[0002] Rocket propellant is a key factor in long-distance aviation and aerospace technology, directly affecting the thrust, speed and overall performance of the rocket. With the advancement of science and technology and the continuous deepening of space exploration, people's requirements for the performance of rocket engines are constantly increasing. Traditional chemical energy rocket propellants cannot meet the needs, and metal-based propellants have become a new fuel option. Aluminum, as a high-energy and low-pollution metal fuel, has quickly been widely used in rocket propellants due to its unique physical and chemical properties. The combustion product of aluminum is aluminum oxide, which has a high heat of formation. Adding aluminum to solid propellants can significantly increase the specific impulse and explosion heat, and improve the combustion efficiency to a certain extent. The combustion products basically do not produce harmful substances, which can meet environmental protection requirements.

[0003] However, pure aluminum powder particles in fuel have major defects. The dense outer oxide shell will hinder the contact between the internal aluminum core and oxygen, which makes the aluminum particles unable to undergo deep oxidation, thus wasting most of the fuel and reducing the propulsion capability. Reducing the powder particle size can increase the reactivity of aluminum powder, so people try to reduce the powder to micrometer and nanometer scales for research. Nano aluminum powder is rarely used in practical applications because it contains significantly less active ingredients than micron powder and is very easy to deactivate during the mixing process of energetic systems. The reduction in particle size will increase the specific surface area, while the thickness of the aluminum oxide film on the surface of the aluminum particles will not change, which means that the content of aluminum oxide in small particles will be higher. There are also many problems in the preparation of propellants containing nano powders, including high powder viscosity, electrostatic discharge, impact risk, difficult manufacturing process, and high cost. Although micron-level aluminum powder is relatively simple to prepare, its reaction sensitivity and combustion performance are low, and it needs to be oxidized at a higher temperature than nano powder. Due to the relatively large particles, insufficient oxygen supply and powder activity, micron aluminum powder is difficult to completely oxidize in an oxidizing environment, which will lead to incomplete combustion and low combustion efficiency. A single type of aluminum powder may not meet the requirements of combustion performance, so different types of active metals need to be used in combination to make up for the shortcomings of a single aluminum powder. Subsequently, alloy aluminum powder became a new research direction, and some active metals were added (such as magnesium, boron, lithium, etc.) to form binary or multi-element alloys to prepare powdered fuel as propellant, but there is still a lack of combustion efficiency. The main reason is that the degree of oxidation is not thorough enough, or the reaction sensitivity with oxygen is low, and the oxidation temperature required by the alloy is very high.

[0004] Therefore, we propose to explore a powder fuel that can react quickly and efficiently, and can also allow oxygen to diffuse deeply and thus be fully oxidized. By adding rare earth elements to the aluminum matrix to make alloy powder, a channel structure that can diffuse oxygen is formed at the grain boundary to improve the oxidation mechanism inside the powder particles, and an alloy aluminum powder that can become an oxygen diffusion channel at the grain boundary is designed to meet the high requirements in the field of new rocket propellants. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries and its application in view of the deficiencies of the above-mentioned prior art. The Al-RE rare earth alloy powder fuel completely improves the microstructure of oxidation combustion inside the powder to overcome the deficiencies of the existing alloy powder fuel.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: an Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries, and the preparation method of the Al-RE rare earth alloy powder fuel is:

[0007] Rare earth master alloy Al-RE is added to pure Al melt to form Al-RE rare earth alloy melt, which is electromagnetically stirred and supersonic atomized by an inert gas atomization system, then subjected to non-equilibrium cooling and graded treatment to form a solidified organizational structure capable of oxygen atom diffusion, i.e., Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at grain boundaries; RE, Rare Earths, may be one of the rare earth elements.

[0008] Preferably, the mass fraction of the rare earth element in the Al-RE rare earth alloy melt is 1% to 3%.

[0009] Preferably, the Al-RE rare earth alloy powder fuel forming the oxygen diffusion channel at the grain boundary has a spherical structure with a particle size of ≤100 μm.

[0010] Preferably, the Al-RE rare earth alloy powder fuel has micron-sized powder separated into a plurality of nano-sized particles by grain boundaries.

[0011] Preferably, after the non-equilibrium cooling of the Al-RE rare earth alloy powder fuel, free RE exists in the internal structure, and rare earth metal intermetallic compound Al is precipitated. x RE y At the same time, grain boundaries are formed; the x is the number of Al atoms, and the y is the number of RE atoms.

[0012] Preferably, the rare earth master alloy Al-RE is Al-50Ce.

[0013] Preferably, the Al-Ce rare earth alloy powder fuel has free Ce, and the rare earth metal compound Al precipitated at the grain boundary 11 Ce3.

[0014] The present invention also provides an application of the Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries, wherein the Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries is used as a propellant for a solid rocket engine;

[0015] The Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries burns in an oxidizing medium. The Al-RE rare earth alloy powder fuel surface catalytically burns while the grain boundaries also start catalytically burning, and the catalytic combustion is continuously diffused from the surface to the inside. The post-combustion products include metal oxide Al x RE y O z ; x is the atomic number of Al, y is the atomic number of RE; z is the atomic number of O.

[0016] Preferably, the metal oxide Al x RE y O z The oxidizing medium is a loose structure. After continuously diffusing in the loose structure, the oxidizing medium continues to oxidize the unreacted cores and internal nano-scale particles inside the Al-RE rare earth alloy powder fuel to achieve complete combustion.

[0017] Preferably, when the Al-RE rare earth alloy powder fuel is an Al-Ce rare earth alloy powder fuel, the grain boundaries of the Al-Ce rare earth alloy powder fuel begin to oxidize while the Al-Ce rare earth alloy powder fuel is oxidized, so that oxygen diffuses from the powder surface to the inside and oxidizes, and the oxidation products are Al2O3, CeAl 11 O 18 and CeO2.

[0018] The alloy powder prepared by the present invention thoroughly improves the microstructure of internal oxidation of the powder to overcome the shortcomings of existing alloy powder fuels.

[0019] The Al-Ce rare earth alloy powder fuel of the present invention forms a network of grain boundaries, on which rare earth metal intermetallic compound Al 11 Ce3, due to non-equilibrium supersonic atomization cooling, also forms free Ce, which becomes an active point for oxidation and combustion of tiny grains.

[0020] The particle size of Al-Ce rare earth alloy powder fuel is micron-sized, which can be regarded as a micron-sized large-particle powder containing a lot of nano-powders. Because each micron-sized particle has such a grain boundary inside, it forms a lot of grains, which can also be regarded as a nano-sized particle surrounded by a grain boundary, thus storing a lot of nano-sized particles in a powder. The micron-sized powder is divided into a lot of nano-sized particles by the grain boundary.

[0021] The rare earth master alloy in the present invention can also be any one of Al-Ce, Al-La, Al-Pr, Al-Nd, Al-Pm, Al-Sm, Al-Eu, Al-Gd, Al-Tb, Al-Dy, Al-Ho, Al-Er, Al-Tm, Al-Yb, Al-Lu, Al-Sc, and Al-Y.

[0022] A master alloy is added to pure aluminum melt to form a rare earth alloy powder fuel material.

[0023] The particle size of the rare earth alloy Al-RE powder material of the present invention is micron-level, and the grain boundaries formed by the rare earth metal intermetallic compounds divide the micron-level particles into a large number of nano-level grains, and the nano-level grains are regarded as an ultra-clean and unoxidized nano-level particle; this structure allows each micron-level powder to store multiple nano-level particles; therefore, it has the advantages of micron-level and ultra-clean nano-level metal fuels.

[0024] In the present invention, the free Ce in the active point of the Al-Ce rare earth alloy powder in an oxidizing environment is rapidly oxidized from the surface of the powder to the inside, and at the same time, the grain boundaries also begin to oxidize and burn, so that oxygen diffuses from the surface of the powder to the inside and rapidly oxidizes and burns. The products formed by oxidation and combustion are Al2O3, CeAl 11 O 18 and CeO2.

[0025] Al-Ce rare earth alloy powder is oxidized and burned in an oxidizing environment. The ability of oxides to diffuse oxygen is ranked from strong to weak as CeO2>CeAl 11 O 18 ; In CeO2 crystal, each Ce 4+ The ions are located in the 8 O 2- ions are the center of the cube, so each Ce 4+ With eight O 2- coordination; at the same time, each O 2- With four Ce 4+ Coordination. CeO2 with this face-centered cubic crystal structure can smoothly transfer and diffuse oxygen atoms. Al2O3 is dense and hardly diffuses oxygen.

[0026] The Al-Ce rare earth alloy powder is spherical, and the particle size of the Al-Ce rare earth alloy powder is D. Powders with D≤100 μm can be used with high catalytic activity.

[0027] The present invention can prepare Al-Ce rare earth alloy powder containing active point-free Ce and grain boundary through supersonic atomization and non-equilibrium cooling, and the rare earth metal intermetallic compound precipitated on the grain boundary is oxidized and burned to form a loose product. The crystal structure of the product CeO2 is face-centered cubic, which can quickly transport oxygen and form a channel for diffusing oxygen.

[0028] The microstructure of the grain boundary catalytic combustion and oxygen diffusion mechanism and the metal fuel of the present invention are widely applicable and can be used for rare earth aluminum binary alloy powder (Al-RE), rare earth ternary alloy powder and other metal fuels. The rare earth master alloys include: Al-Ce, Al-La, Al-Pr, Al-Nd, Al-Pm, Al-Sm, Al-Eu, Al-Gd, Al-Tb, Al-Dy, Al-Ho, Al-Er, Al-Tm, Al-Yb, Al-Lu, Al-Sc, Al-Y; the elements with high enthalpy that can be considered to be added include B, Be, Mg, Ca, Li, Ti, Zr, Si, etc.

[0029] The preparation method of the present invention can also prepare powdered metal fuels such as Mg-RE, Al-B-RE, Al-Si-RE, etc., which are used as propellants for solid rocket engines.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] The chemical activity of the alloy powders forming oxygen diffusion channels at the grain boundaries of the present invention is very high, and it is very easy to generate compounds with oxygen. For example, cerium can form loose and cracked oxides at a relatively low temperature. By utilizing the crystal structure characteristics of rare earth aggregation and precipitation at the grain boundaries, the powder begins to oxidize and burn while the grain boundaries within the powder also begin to oxidize and burn. The oxidized products are CeO2, CeAl 11 O 18It can make oxygen transfer from the surface to the deep inside and form a channel for oxygen diffusion, so as to achieve the purpose of complete oxidation of aluminum powder. The powder particle size is micron-level, so each micron-level particle has such a grain boundary inside to form a number of grains, which can also be regarded as a nano-level particle wrapped by a grain boundary, so that a powder storing a number of nano-level particles is divided into a number of nano-level particles by the grain boundary. Compared with traditional pure aluminum powder, Al-Ce alloy powder has the characteristics of low production cost and easy storage of micron-level particles, and also has the advantages of reaction characteristics and high efficiency of nano-level particles. Due to the existence of oxygen diffusion channels, there are loose oxides with sufficient oxygen supply, and the internal grains can be oxidized and burned to a great extent, with almost no pure aluminum residue, which improves the combustion efficiency and economic benefits of the fuel, and its propulsion capacity will also be greatly improved.

[0032] The present invention is further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a SEM image of the solidified cross-sectional structure of the Al-3Ce alloy powder fuel of Example 3 of the present invention.

[0034] Figure 2 This is the SEM of the solidified cross-section structure of pure Al powder.

[0035] Figure 3 It is the XRD diagram of Al-1Ce, Al-2Ce and Al-3Ce alloy powder fuels of Examples 1-3 of the present invention.

[0036] Figure 4 It is the XRD diagram of Al-1Ce, Al-2Ce, Al-3Ce alloy powder fuel and pure aluminum powder after combustion in air in Examples 1-3 of the present invention.

[0037] Figure 5 This is the SEM morphology of the loose oxides after the Al-1Ce alloy powder fuel of Example 1 is burned.

[0038] Figure 6 It is the first principle calculation result of the diffusion degree of oxygen atoms in the oxides Al2O3, Ce2O3 and CeO2 in the present invention. DETAILED DESCRIPTION

[0039] Example 1

[0040] The preparation method of the Al-Ce rare earth alloy powder (Al-1Ce) with oxygen diffusion channels formed at the grain boundaries of this embodiment is as follows:

[0041] S1. In a smelting furnace, a pure Al ingot is melted into a pure Al melt, and then a rare earth master alloy Al-50Ce is added to the pure Al melt to form a rare earth Al-Ce alloy melt; the mass fraction of the rare earth element Ce in the rare earth Al-RE alloy melt is 1%;

[0042] Rare earth master alloy Al-50Ce, wherein the mass fraction of Ce is 50%, the rare earth master alloy Al-50Ce is purchased from Kairui New Materials (Beijing) Technology Co., Ltd.;

[0043] S2, after electromagnetic stirring, the rare earth Al-Ce alloy melt obtained in S1 is poured into a tundish, and then the rare earth Al-Ce alloy melt is introduced into an inert gas atomization system from the bottom of the tundish, wherein the inert gas is nitrogen, and supersonic atomization is performed, and the rare earth alloy powder obtained after the inert gas atomization is collected and gathered in a powder collecting tube;

[0044] S3, the rare earth alloy powder obtained in S2 after inert gas atomization is subjected to non-equilibrium cooling, and the air flow velocity of the supersonic atomizing nozzle is 600m / s, then the corresponding cooling temperature is 1.062e 2 k, and then pneumatically transported to a powder classifier by inert gas nitrogen, and subjected to classification treatment in a nitrogen atmosphere, to obtain an Al-Ce rare earth alloy powder with a particle size of ≤100 μm and oxygen diffusion channels formed at the grain boundaries, which is named Al-1Ce alloy powder fuel, abbreviated as Al-1Ce, that is, a solidified organizational structure capable of oxygen atom diffusion is formed, and rare earth metal intermetallic compounds are formed at the grain boundaries.

[0045] In this embodiment, non-equilibrium rapid cooling forms a network of grain boundaries, on which rare earth metal intermetallic compound Al 11 Ce3 also forms an active point - free Ce.

[0046] Example 2

[0047] The preparation method of the Al-Ce rare earth alloy powder (Al-2Ce) with oxygen diffusion channels formed at the grain boundaries in this embodiment is the same as that in Example 1, except that the mass fraction of the rare earth element Ce in the rare earth Al-Ce alloy melt in step S1 is 2%, and the prepared Al-Ce rare earth alloy powder with a particle size of ≤100μm with oxygen diffusion channels formed at the grain boundaries is named Al-2Ce alloy powder fuel, abbreviated as Al-2Ce.

[0048] Example 3

[0049] The preparation method of the Al-Ce rare earth alloy powder (Al-3Ce) with oxygen diffusion channels formed at the grain boundaries in this embodiment is the same as that in Example 1, except that the mass fraction of the rare earth element Ce in the rare earth Al-Ce alloy melt in step S1 is 3%, and the prepared Al-Ce rare earth alloy powder with a particle size of ≤100μm with oxygen diffusion channels formed at the grain boundaries is named Al-3Ce alloy powder fuel, abbreviated as Al-3Ce.

[0050] In the present invention, both the atomizing gas and the inert gas for powder classification are inert gases that do not react with aluminum and rare earth, and nitrogen is also used from the perspective of reducing production costs. Nitrogen and Al can form AlN compounds on the powder surface, thereby having the effect of passivating Al-Ce powder. Nitrogen is provided to the preparation system through a liquid nitrogen system for supersonic atomization to obtain alloy powder.

[0051] The preparation method of the present invention can also be used to prepare rare earth alloy powders with other chemical compositions of grain boundary catalytic combustion and oxygen diffusion mechanisms, such as Al-B-Ce alloy powders.

[0052] Figure 1 is a SEM image of the solidified cross-sectional structure of the Al-3Ce alloy powder fuel prepared in Example 3. Figure 2 This is the SEM image of the solidified cross-section structure of pure Al powder. No grain boundaries can be seen in the solidified structure.

[0053] contrast Figure 1 and Figure 2 It can be clearly seen that a large number of grain boundaries and nano-grains are formed in the internal microstructure of the aluminum alloy powder with rare earth Ce element added, and there are obvious grain boundaries to divide the grains. The internal grains can be regarded as small particles of nano-scale aluminum powder. The entire micron aluminum powder is a collection of nano aluminum powder. It has the advantages of high reactivity of nano aluminum powder and easy preparation of micron aluminum powder. Figure 2 There is no obvious distinction between grains and grain boundaries in the cross-sectional structure of medium-purity aluminum powder.

[0054] Figure 3 The X-ray diffraction (XRD) curves of the Al-Ce rare earth alloy powders (Al-1Ce, Al-2Ce, Al-3Ce) prepared in Examples 1-3 with oxygen diffusion channels formed at the grain boundaries are shown in Table 1. The XRD results show that the aluminum diffraction peaks in each sample are high and sharp, proving that aluminum is the main substance, followed by the rare earth metal intermetallic compound Al. 11 Ce3 and free rare earth Ce, due to the extremely low solubility of Ce in Al (0.05.%, 637℃), most of the rare earth Ce is concentrated at the grain boundary, and the intermetallic compound Al 11 Ce3 mainly precipitates on the grain boundaries to form channels that are easy to catalyze combustion and oxidative diffusion.11 The decomposition of Ce3 will form initial oxidation products such as Al oxide (Al2O3) and rare earth Ce oxide (Ce2O3), which provides reaction engineering conditions for the subsequent formation of oxygen diffusion channels.

[0055] In Example 1-3, a network of grain boundaries is formed in the Al-Ce rare earth alloy powder fuel, and rare earth metal intermetallic compound Al is precipitated on the grain boundaries. 11 Ce3, due to non-equilibrium supersonic atomization cooling, also forms free Ce, and the free Ce becomes an active point for oxidation combustion.

[0056] The particle size of Al-Ce rare earth alloy powder fuel is micron-sized, which can be regarded as a micron-sized large-particle powder containing a lot of nano-powders. Because each micron-sized particle has such a grain boundary inside, it forms a lot of grains, which can also be regarded as a nano-sized particle surrounded by a grain boundary, thus storing a lot of nano-sized particles in a powder. The micron-sized powder is divided into a lot of nano-sized particles by the grain boundary.

[0057] Figure 4 X-ray diffraction (XRD) results of Al-Ce rare earth alloy powders (Al-1Ce, Al-2Ce, Al-3Ce) with oxygen diffusion channels formed at the grain boundaries of Examples 1-3 and pure Al powder after combustion in air. Figure 4 The diffraction peaks of medium-pure Al powder indicate that there is still a large amount of unoxidized Al in pure aluminum powder. Al-Ce alloy powder (Al-1Ce, Al-2Ce, Al-3Ce) does not have unoxidized Al, and the main products are Al2O3, CeAl 11 O 18 and CeO2.

[0058] 2CeAl 11 O 18 =11Al2O3+Ce2O3

[0059] 2Ce2O3+O2=4CeO2

[0060] CeAl 11 O 18 The magnetoplumbite structure with hexagonal space group P63 / mmc is composed of mirror images of spinel blocks. The spinel blocks are composed of [AlO4] tetrahedrons, [AlO5] hexahedrons and [AlO6] octahedrons, which are connected by shared corners or shared edges and appear as long columns in the alloy particles. Large columnar CeAl 11 O 18 The presence of CeAl can limit the growth of dense Al2O3 grains. 11 O 18It is a complex of Al2O3 and Ce2O3. During the high-temperature oxidation process, as the temperature rises, the unstable Ce2O3 3+ It will be further oxidized to form Ce under the action of oxygen atmosphere. 4+ , thus forming a more stable CeO2. The smaller subcrystal size and larger specific surface area of ​​CeO2 make CeO2 crystals looser, and this loose structure forms a favorable channel for oxygen diffusion. Oxygen atoms can form diffusion grain boundaries with the help of CeO2, diffuse from the outside air to the core of the powder particles, so that the deep Al oxidation combustion releases heat, the powder fuel is fully burned, and the fuel utilization rate and combustion efficiency are improved.

[0061] Figure 5 This is the SEM morphology of the oxide after the combustion of the Al-1Ce alloy powder fuel of Example 1. There are a large number of holes in the oxide leading to the deep layer of the fuel, and the structure is extremely loose, indicating that during the combustion process, the outer layer of powder fuel will produce a pore structure for oxygen diffusion after combustion, so that the deeper fuel can also have sufficient oxygen supply, so as to deeply oxidize and fully complete the combustion. It shows the oxygen diffusion characteristics of the Al-Ce material described in the present invention.

[0062] Figure 6 It is the first principle calculation result of the diffusion degree of oxygen atoms in oxides Al2O3, Ce2O3, and CeO2. MSD stands for the mean square displacement of O atoms and characterizes its diffusion degree.

[0063] It can be seen from the figure that the ability of Al2O3 to pass oxygen atoms is very weak, the diffusion coefficient is a horizontal line, and the diffusion capacity is almost 0, indicating that the diffusion of oxygen atoms or molecules in Al2O3 is very limited. The oxygen diffusion coefficient in Ce2O3 is relatively weak, but slightly higher than that in Al2O3, indicating that the diffusion of atoms or molecules in Ce2O3 is also relatively limited, but stronger than that in Al2O3. The diffusion coefficient of oxygen atoms in CeO2 shows a clear upward trend and increases linearly with time, which indicates that its atoms or molecules follow normal diffusion behavior, that is, the intensity of oxygen atom diffusion is almost proportional to time. Moreover, CeO2 has a fluorite structure, in which there are many octahedral vacancies, allowing oxygen atoms to diffuse rapidly, thus forming a physical channel for rapid oxidation, with mobile oxygen vacancies. The atoms or molecules in CeO2 have a strong diffusion ability, which is closely related to the grain boundary catalytic combustion and oxygen diffusion mechanism.

[0064] The invention also provides application of Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at grain boundaries, which is used for solid rocket engine propellant.

[0065] In the present invention, under high-temperature oxidation environment, the Al-RE rare earth alloy powder fuel sphere is very easy to oxidize to form oxides. The characteristics of rare earths gathering at the grain boundaries to form rare earth metal compounds are utilized, especially cerium can form loose and cracked oxides at lower temperatures. When the aluminum alloy powder particles are oxidized, the grain boundaries also begin to oxidize. In this process, oxygen will diffuse from the surface of the powder to the inside, so the grain boundary oxidation forms an oxygen diffusion channel and microstructure, thereby achieving the purpose of complete oxidation and combustion of the rare earth aluminum alloy powder. In the present invention, multiple grains are formed inside each micron-sized powder particle, and the grain boundaries separate these grains, so that each particle is actually composed of multiple nano-sized grains wrapped by the grain boundaries. This structure allows each micron-sized powder to store multiple nano-sized particles. The micron-sized powder with oxygen diffusion channels formed at the grain boundaries in the alloy powder prepared by the present invention has the economic advantages of low production cost and easy storage, and also has the reaction characteristics of nano-particle powder and high combustion efficiency. Due to the existence of oxygen diffusion channels inside the powder, there is a sufficient oxygen supply environment, so that the internal grains can be oxidized to a great extent, and there is almost no unburned residue, which improves the combustion efficiency and economic benefits of the fuel, and its propulsion capability will also be greatly improved.

[0066] In the present invention, rare earth metal compounds are formed at the grain boundaries of the Al-Ce rare earth alloy powder, forming free Ce and rare earth metal compounds Al precipitated at the grain boundaries. 11 Ce3.

[0067] In the present invention, the free Ce in the active point of the Al-Ce rare earth alloy powder in an oxidizing environment is rapidly oxidized from the surface of the powder to the inside, and at the same time, the grain boundaries also begin to oxidize and burn, so that oxygen diffuses from the surface of the powder to the inside and rapidly oxidizes and burns. The products formed by oxidation and combustion are Al2O3, CeAl 11 O 18 and CeO2.

[0068] Al-Ce rare earth alloy powder is oxidized and burned in an oxidizing environment. The ability of oxides to diffuse oxygen is ranked from strong to weak as CeO2>CeAl 11 O 18 ; In CeO2 crystal, each Ce 4+ The ions are located in the 8 O 2- ions are the center of the cube, so each Ce 4+ With eight O 2- coordination; at the same time, each O 2- With four Ce 4+ Coordination. CeO2 with this face-centered cubic crystal structure can smoothly transfer and diffuse oxygen atoms. Al2O3 is dense and hardly diffuses oxygen.

[0069] The Al-Ce rare earth alloy powder is spherical, and the particle size of the Al-Ce rare earth alloy powder is D. Powders with D≤100 μm can be used with high catalytic activity.

[0070] The present invention can prepare Al-Ce rare earth alloy powder containing active point-free Ce and grain boundary by supersonic atomization and non-equilibrium cooling method, and the rare earth metal intermetallic compound precipitated on the grain boundary is oxidized and burned to form loose products. The crystal structure of the product CeO2 is face-centered cubic, which can quickly transport oxygen and form a channel for diffusing oxygen.

[0071] The particle size of the rare earth alloy Al-RE powder material of the present invention is micron-level, and the grain boundaries formed by the rare earth metal intermetallic compounds divide the micron-level particles into a large number of nano-level grains, and the nano-level grains are regarded as an ultra-clean and unoxidized nano-level particle; this structure allows each micron-level powder to store multiple nano-level particles; therefore, it has the advantages of micron-level and ultra-clean nano-level metal fuels.

[0072] The rare earth alloy Al-RE powder material of the present invention burns in an oxidizing medium. The powder surface catalytically burns while the grain boundaries also begin to catalytically burn, and the catalytic combustion continues to diffuse from the surface to the inside. The product after combustion is the metal oxide Al x RE y O z .

[0073] The product after combustion is a loose structure of Al x RE y O z The oxide and oxidizing medium diffuse continuously in this loose structure and continue to oxidize the unreacted core inside the powder while also oxidizing the internal nano-particles; thus, continuous grain boundary catalytic combustion and oxygen diffusion ensure the complete combustion of the metal fuel.

[0074] The microstructure of the grain boundary catalytic combustion and oxygen diffusion mechanism and the metal fuel of the present invention are widely applicable and can be used for rare earth aluminum binary alloy powder (Al-RE), rare earth ternary alloy powder and other metal fuels. The rare earth master alloys include: Al-Ce, Al-La, Al-Pr, Al-Nd, Al-Pm, Al-Sm, Al-Eu, Al-Gd, Al-Tb, Al-Dy, Al-Ho, Al-Er, Al-Tm, Al-Yb, Al-Lu, Al-Sc, Al-Y; the elements with high enthalpy that can be considered to be added include B, Be, Mg, Ca, Li, Ti, Zr, Si, etc.

[0075] The present invention can also prepare powdered metal fuels such as Mg-RE, Al-B-RE, Al-Si-RE, etc., which are used as propellants for solid rocket engines.

[0076] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. An Al-RE rare earth alloy powder fuel having oxygen diffusion channels formed at grain boundaries, characterized in that: The preparation method of the Al-RE rare earth alloy powder fuel is as follows: Rare earth master alloy Al-RE is added to pure Al melt to form Al-RE rare earth alloy melt, which is electromagnetically stirred and supersonic atomized by an inert gas atomization system, then subjected to non-equilibrium cooling and graded treatment to form a solidified organizational structure capable of oxygen atom diffusion, i.e., Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at grain boundaries.

2. The Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries according to claim 1, characterized in that: The mass fraction of the rare earth element in the Al-RE rare earth alloy melt is 1% to 3%.

3. The Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries according to claim 1, characterized in that: The Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries is a spherical structure with a particle size of ≤100 μm.

4. The Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries according to claim 3, characterized in that: The Al-RE rare earth alloy powder fuel has micron-sized powder separated into a plurality of nano-sized particles by grain boundaries, that is, the Al-RE rare earth alloy powder fuel is a large-particle powder storing nano-particles.

5. The Al-RE rare earth alloy powder fuel having oxygen diffusion channels formed at the grain boundaries according to claim 1, characterized in that: The Al-RE rare earth alloy powder rare earth alloy powder fuel forms free RE after non-equilibrium cooling, and the rare earth metal intermetallic compound Al x RE y Precipitation forms grain boundaries; the x is the number of Al atoms, and the y is the number of RE atoms.

6. The Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries according to claim 2, characterized in that: The rare earth master alloy Al-RE in the embodiment is specifically Al-50Ce.

7. The Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries according to claim 5, characterized in that: The Al-Ce rare earth alloy powder fuel has free Ce, and the rare earth metal compound Al precipitated at the grain boundary 11 Ce3.

8. The use of the Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries according to any one of claims 1 to 7, characterized in that: The Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries is used as a propellant for a solid rocket engine; The Al-RE rare earth alloy powder fuel with oxygen diffusion channels formed at the grain boundaries burns in an oxidizing medium. The Al-RE rare earth alloy powder fuel surface catalytically burns while the grain boundaries also start catalytically burning, and the catalytic combustion is continuously diffused from the surface to the inside. The post-combustion products include metal oxide Al x RE y O z ; x is the atomic number of Al, y is the atomic number of RE; z is the atomic number of O.

9. The use according to claim 8, characterized in that: The metal oxide Al x RE y O z The oxidizing medium is a loose structure. After continuously diffusing in the loose structure, the oxidizing medium continues to oxidize the unreacted cores and internal nano-scale particles inside the Al-RE rare earth alloy powder fuel to achieve complete combustion.

10. The use according to claim 9, characterized in that: When the Al-RE rare earth alloy powder fuel is an Al-Ce rare earth alloy powder fuel, the grain boundaries of the Al-Ce rare earth alloy powder fuel begin to oxidize while the Al-Ce rare earth alloy powder fuel is oxidized, so that oxygen atoms continuously diffuse from the powder surface to the inside and oxidize, and the oxidation products are Al2O3, CeAl 11 O 18 and CeO2.

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