Aluminum-based powder fuel with grain boundary oxygen vacancy channel and preparation method and application thereof

Abstract

The application discloses an aluminum-based powder fuel with a grain boundary oxygen vacancy channel and a preparation method and application thereof, and particularly relates to the technical field of metal fuel and aluminum-based alloy powder fuel. The method comprises the following steps: heating and melting pure aluminum to form an aluminum melt; then adding an Al-RE intermediate alloy into the aluminum melt, and adjusting the total content of rare earth elements RE in the melt to be 0.1-7 wt%; finally, performing controlled supersonic atomization rapid solidification on the uniformly mixed melt to obtain an aluminum-based alloy powder. After the powder burns, a rare earth oxide channel rich in oxygen vacancy defects is constructed at the grain boundary, and the oxidation combustion is further promoted. The lattice distortion caused by the difference in atomic radii of double rare earth (Ce / La) and the in-situ solid solution of boron atoms greatly reduce the formation energy of oxygen vacancies. In the combustion process, high-concentration oxygen vacancies form a "high-speed oxygen transmission channel", break the barrier of the dense oxide film, and enable oxygen to quickly penetrate into the particle core, thereby significantly improving the burnout rate and energy release efficiency of the aluminum powder.

Description

Technical Field

[0001] This invention relates to the field of metal fuels and aluminum-based alloy powder fuels, specifically to an aluminum-based powder fuel with grain boundary oxygen vacancy channels, its preparation method, and its application. Background Technology

[0002] Aluminum powder is widely used in solid rocket propellants, explosives, and other energetic material systems due to its high volumetric energy density, good storage stability, and environmentally friendly combustion products. However, traditional micron-sized aluminum powder has significant drawbacks in practical applications: during combustion or oxidation, a dense and high-melting-point alumina (Al2O3) film easily forms on the particle surface. This "core-shell" structure severely hinders the diffusion of external oxygen into the particle interior and the transfer of internal heat to the surface, making it difficult for the reaction front to effectively advance to the particle core. This leads to problems such as delayed ignition, incomplete combustion, high residue rate, and large two-phase flow losses, greatly limiting the full realization of the energy efficiency of aluminum-based fuels.

[0003] Existing technologies typically improve the combustion performance of aluminum powder by refining the powder particle size, introducing catalysts, or modifying the surface of the aluminum powder through coating. However, relying solely on particle size refinement can lead to safety and cost issues; while adding catalysts or surface coatings may result in weak interfacial bonding, easy peeling upon heating, and difficulty in forming a continuous channel within the particles. Chinese patent CN119614259A discloses an aluminum-lithium alloy powder fuel, which aims to utilize the "micro-explosion" characteristic of lithium to break up aluminum particles in situ to promote combustion by adding Li (2-10%), Mg (0.1-5%), and rare earth elements (RE, 0.1-3%), and supplementing this with heat treatment to control the distribution of Al3(Li,RE) and other precipitated phases. However, Li is chemically extremely reactive, requiring stringent preparation, storage, and use environments, posing a high safety risk; moreover, the "micro-explosion" effect is a physical breakup mechanism, and for particle areas where micro-explosions do not occur, there is still a lack of effective internal oxygen diffusion pathways, limiting the improvement in the completeness of combustion.

[0004] Another more promising technical approach is to construct grain boundary diffusion channels. Chinese patent CN119977737A proposes an Al-RE rare earth alloy powder fuel that forms oxygen diffusion channels at grain boundaries. This technology involves adding rare earth master alloys (such as Al-Ce) to pure aluminum, followed by supersonic atomization and non-equilibrium solidification, allowing rare earth intermetallic compounds (such as Al) to form oxygen diffusion channels at grain boundaries. 11 Ce3) precipitates at grain boundaries, forming a three-dimensional network structure. During combustion, Al at the grain boundaries... 11Ce3 preferentially oxidizes to form loose rare earth oxides (such as CeO2), thereby constructing physical oxygen diffusion channels from the particle surface to the core. Compared to traditional aluminum powder and "micro-explosion" alloys, this technology achieves directional internal diffusion of oxygen through structural design, significantly improving combustion efficiency. However, the oxygen transport mechanism of this technology mainly relies on the macroscopic "loose structure" of rare earth oxides and intrinsic vacancies in the crystal structure. There is still a lack of targeted design on how to further control the type and concentration of defects (such as oxygen vacancies) within the channels at the atomic scale to enhance oxygen diffusion kinetics. In addition, the exothermic intensity of a single rare earth oxide channel has a ceiling. If high-enthalpy components can be introduced to synergistically release heat while maintaining efficient oxygen transport, it is expected to achieve a dual enhancement of "transport-exothermic" and further improve energy release efficiency and burnout rate.

[0005] Therefore, there is an urgent need to develop a new type of aluminum-based powder fuel that can construct a stable three-dimensional network structure at the grain boundaries and form an efficient diffusion channel rich in active defects such as oxygen vacancies in situ during combustion. At the same time, it can introduce high enthalpy components to achieve synergistic effects, thereby fundamentally solving the problem of incomplete combustion of traditional aluminum powder and meeting the urgent needs of high-performance propellants for high energy, high burnout rate and high safety. Summary of the Invention

[0006] To address this issue, the present invention provides an aluminum-based powder fuel with grain boundary oxygen vacancy channels, its preparation method, and its application. This aluminum-based powder fuel constructs three-dimensional grain boundaries within the aluminum-based alloy powder and forms a three-dimensional network of rare earth phases on these grain boundaries. During the oxidation and combustion of the alloy powder, oxygen vacancies and loose rare earth oxide channels are generated through grain boundary combustion catalysis, thereby improving the complete combustion performance of the powder core. This solves the problem of incomplete combustion of powders mentioned above.

[0007] This invention constructs an aluminum-rare earth (Al-RE) intermetallic compound phase network in the grain / dendritic region of the powder solidification structure. During combustion / oxidation, this network preferentially transforms into a continuous rare earth oxide phase and forms defect-rich (e.g., oxygen vacancy-related defects) grain boundary channels, thereby enhancing oxygen transport to the particle core and diffusion at the reaction front, achieving complete combustion of the powder core. Furthermore, this invention can optionally introduce a high enthalpy element B to form a boron-containing exothermic phase, which improves the exothermic intensity while maintaining the rare earth grain boundary channel mechanism and synergistically reduces residue agglomeration.

[0008] The alloy powder of this invention, through rapid cooling, constructs a three-dimensional network of grain boundaries and grain regions in the solidification structure, and builds aluminum-rare earth (Al) groups on the grain boundaries. x RE yThe intermetallic compound phase forms a three-dimensional network structure from the powder surface to the core. This allows it to preferentially transform into a continuous rare-earth oxide phase during combustion / oxidation, forming defect-rich grain boundary channels (such as oxygen-vacancy-related defects). This enhances oxygen transport to the particle core and the reaction front advancement, achieving complete combustion in the powder core. This invention can selectively introduce high-enthalpy element B to form a boron-containing exothermic phase, maintaining the rare-earth grain boundary channel mechanism while increasing the exothermic intensity and synergistically reducing residue.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] According to a first aspect of the present invention, a method for preparing an aluminum-based powder fuel having grain boundary oxygen vacancy channels is provided, the method comprising:

[0011] Step 1: Heat pure aluminum to melt it and form a melted aluminum body;

[0012] Step two: Add an Al-RE master alloy to the aluminum melt to adjust the total content of rare earth element RE in the melt to 0.1-7 wt%.

[0013] Step 3: The uniformly mixed melt is subjected to controlled supersonic atomization and rapid solidification to obtain aluminum-based alloy powder;

[0014] In step three, the controlled supersonic atomization rapid solidification is achieved by adjusting the supercooling and cooling rate of the atomizing medium, so that the Al-RE intermetallic compound phase precipitates at the grain boundaries of the powder solidification structure and forms a three-dimensional distribution network structure extending along the grain boundaries, while introducing non-equilibrium lattice distortion into the Al-RE intermetallic compound phase and its adjacent grain boundary regions.

[0015] The non-equilibrium lattice distortion configuration is such that, during the subsequent combustion and oxidation process, the rare earth oxide phase induced to generate has an oxygen vacancy defect concentration higher than its intrinsic concentration in the thermodynamic equilibrium state, thereby forming a diffusion channel rich in oxygen vacancy defects.

[0016] Furthermore, in step two, the rare earth element RE includes a first rare earth element and a second rare earth element, wherein the first rare earth element is selected from one or more of Ce, Pr, and Tb; and the second rare earth element is selected from one or more of La, Nd, Sm, Gd, Y, Sc, Dy, and Er.

[0017] Furthermore, the content of the first rare earth element is 0.05-4 wt%; the content of the second rare earth element is 0.01-4 wt%. As an example, the mass ratio of the first rare earth element to the second rare earth element is (0.5:1) to (4:1), utilizing the difference in atomic radii between La and Ce (rLa>rCe) at the Al grain boundaries... 11The introduction of additional non-equilibrium lattice distortions into the (first rare earth element, second rare earth element)3 solid solution phase increases the potential accommodation sites for oxygen vacancies.

[0018] Furthermore, step two also includes adding a B source to the melt, wherein the content of B element in the melt is 1-40 wt%.

[0019] Furthermore, the B source is an Al-B master alloy; in step two, the boron element is fully diffused before the Al-RE phase precipitates by heat preservation and stirring, ensuring that the B element participates in the nucleation and growth process of the Al-RE phase.

[0020] While causing the Al-RE intermetallic compound phase to precipitate at the grain boundaries of the powder solidification structure and form a three-dimensional distribution network structure extending along the grain boundaries, it also promotes the in-situ solidification of some B atoms in the Al-RE intermetallic compound phase lattice, or the formation of an Al-RE-B ternary transition layer at the interface between the Al-RE phase and the aluminum matrix.

[0021] The in-situ solid-solidified B atoms or ternary transition layer, together with the grain boundary network formed by the synergistic effect of the first and second rare earth elements, are configured to: reduce the formation energy of oxygen vacancies in the rare earth oxide phase during subsequent combustion, induce the generation of oxygen vacancy defects with a concentration higher than that of the intrinsic thermodynamic equilibrium state, thereby forming a diffusion channel rich in oxygen vacancy defects driven by "enthalpy increase-diffusion".

[0022] In step two, the boron element is fully diffused before the Al-RE phase precipitates by heat preservation and stirring, ensuring that the boron element participates in the nucleation and growth process of the Al-RE phase to form an Al-RE-B composite precipitate phase, rather than being simply mechanically mixed in the form of elemental boron or independent AlB2 phase.

[0023] Furthermore, during the solidification process in step three:

[0024] This causes some boron atoms to dissolve in situ in the Al-RE intermetallic compound phase lattice, or to form an Al-RE-B ternary transition layer at the interface between the Al-RE phase and the aluminum matrix;

[0025] The in-situ solid-solid B atoms or ternary transition layer, together with the grain boundary network formed by the synergistic effect of the first and second rare earth elements, are configured to: reduce the formation energy of oxygen vacancies in the rare earth oxide phase during subsequent combustion, induce the generation of oxygen vacancy defects with a concentration higher than the intrinsic concentration of the thermodynamic equilibrium state, thereby forming a diffusion channel rich in oxygen vacancy defects driven by "enthalpy increase-diffusion".

[0026] The process forms an Al-RE-B composite precipitate, rather than a simple mechanical mixing of elemental B or independent AlB2 phases.

[0027] Furthermore, in step three, the process parameters for controlled supersonic atomization rapid solidification include: the atomization medium being argon, nitrogen, or a mixture thereof; the atomization pressure being 3-8 MPa; and the melt superheating temperature being controlled at 50-150°C above the liquidus line to achieve 10 4 -10 6 The local cooling rate is K / s. This process parameter suppresses the coarsening of the Al-RE-B ternary phase and locks boron atoms in the lattice gaps or interface segregation sites of the Al-RE intermetallic compound phase, forming a non-equilibrium microstructure.

[0028] According to a second aspect of the present invention, an aluminum-based powder fuel with grain boundary oxygen vacancy channels includes an aluminum matrix and an Al-RE intermetallic compound phase network distributed at the grain boundaries; wherein the Al-RE intermetallic compound simultaneously contains a first rare earth element and a second rare earth element, and the first rare earth element and the second rare earth element exhibit co-enrichment characteristics in the grain boundary region.

[0029] Furthermore, the Al-RE intermetallic compound phase network is in-situ coupled with boron (B) elements, manifested as some B atoms being dissolved in the Al-RE phase lattice, leading to a shift in the lattice constant; or an Al-RE-B ternary transition layer with a thickness of 1-50 nm exists at the interface between the Al-RE phase and the aluminum matrix. This combined configuration reduces the formation energy of oxygen vacancies in adjacent regions during combustion.

[0030] Furthermore, the Al-RE intermetallic compound phase is mainly Al. 11 The solid solution phase of (first rare earth element, second rare earth element) has local distortion of its lattice fringes, with a lattice strain value ε>0.5%, and element B is enriched in the distorted region.

[0031] Aluminum-based alloy powder fuels have the following microscopic fingerprint characteristics:

[0032] Electron paramagnetic resonance (EPR) signals were detected in the oxide products generated after complete combustion or oxidation of the aluminum-based alloy powder fuel within the range of g = 2.00 ± 0.01; and the ratio of the normalized EPR signal intensity Isample to the EPR signal intensity Iref of the combustion products of Al-Ce alloy powder containing only rare earth element Ce and no boron under the same conditions satisfies: I sample / Iref ≥1.3; The significant increase in signal strength is attributed to the Ce-La synergistic effect and the additional contribution of in-situ coupled boron to the oxygen vacancy concentration.

[0033] In addition to the in-situ coupled B element, it also includes an independent B-containing exothermic phase dispersed in the interior of the grain or the vicinity of the grain boundary; the independent B-containing exothermic phase and the Ce-La grain boundary network containing the in-situ coupled B element are spatially coupled and form a dual synergistic structure of "micro-region enthalpy enhancement activation + macro-channel oxygen conduction".

[0034] The third aspect of the present invention provides the application of an aluminum-based powder fuel with grain boundary oxygen vacancy channels as an additive or energy component in solid propellants, explosives, pyrotechnics, or metallic fuels.

[0035] The present invention has the following advantages:

[0036] This invention constructs rare-earth oxide channels rich in oxygen vacancy defects at grain boundaries. Utilizing the lattice distortion caused by the difference in atomic radii between the two rare-earth elements (Ce / La) and the in-situ solid solution of boron atoms, the formation energy of oxygen vacancies is significantly reduced. During combustion, these high-concentration oxygen vacancies form "high-speed oxygen transport channels," breaking through the barrier of the dense oxide film and allowing oxygen to rapidly penetrate to the particle core, significantly improving the burnout rate and energy release efficiency of aluminum powder.

[0037] This invention introduces a combination of a first rare earth element (such as Ce) and a second rare earth element (such as La). Utilizing the atomic radius difference (rLa > rCe), in Al... 11 (First rare earth element, second rare earth element) 3 An additional non-equilibrium lattice distortion (lattice strain ε>0.5%) is artificially introduced into the solid solution. This distortion not only increases the potential accommodation sites for oxygen vacancies but also makes the resulting rare earth oxide framework more porous. Experimental data (EPR signal intensity I) sample / Iref (≥1.3) This demonstrates that the oxygen vacancy concentration generated by this synergistic effect is significantly higher than that of a single rare earth system.

[0038] This invention creatively achieves in-situ coupling of boron (B). Through controlled rapid solidification, some B atoms are dissolved in situ within the rare-earth phase lattice or form a nanoscale Al-RE-B ternary transition layer, rather than through simple mechanical mixing. The high enthalpy of B in the micro-region enthalpy enhancement is activated at the microscale, providing additional heat of reaction, increasing the local temperature, and further accelerating the oxidation reaction. In catalytic diffusion, the dissolved B synergistically with the two rare-earth elements further reduces the oxygen vacancy formation energy. A dual structure of "micro-region enthalpy enhancement activation + macroscopic oxygen conduction" is constructed, significantly increasing the volumetric heat of explosion while significantly reducing the amount of unreacted residue.

[0039] This invention employs controlled supersonic atomization rapid solidification technology to "freeze" the disordered state at high temperatures through extremely rapid cooling, suppressing the coarse precipitation of the second phase and locking the non-equilibrium positions of boron atoms in the interstitial spaces of the crystal lattice. This results in a uniform and fine three-dimensional network grain boundary structure and a nanoscale ternary transition layer. This metastable structure exhibits higher chemical activity, and by adjusting the atomization pressure and superheat, the grain boundary network density and defect concentration can be precisely controlled to meet the application requirements of various energetic materials. Attached Figure Description

[0040] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0041] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0042] Figure 1 This is a schematic diagram of the cross-sectional microstructure of pure aluminum powder provided in Embodiment 1 of the present invention;

[0043] Figure 2 This is a schematic diagram of the cross-sectional morphology and elemental surface distribution of aluminum-based alloy powder provided in Embodiment 1 of the present invention;

[0044] Figure 3 This is a schematic diagram of the DSC oxidation combustion curves of powders with different components provided in Example 2 of the present invention under an air atmosphere;

[0045] Figure 4 This is a schematic diagram of the EPR spectra of different fuel combustion / oxidation products provided in Example 2 of the present invention;

[0046] Figure 5 This is a transmission electron microscope image provided in Embodiment 2 of the present invention. Detailed Implementation

[0047] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Example 1

[0049] This embodiment provides the preparation of Al-Ce-La grain boundary channel type aluminum-based alloy powder:

[0050] Weigh out pure aluminum (see schematic diagram of cross-sectional microstructure of pure aluminum powder as shown in the figure). Figure 1 (As shown) and heat to melt, controlling the melt temperature within the range of 720-850℃. Add Al-50Ce and Al-50La master alloys to the aluminum melt, so that the rare earth Ce content in the melt is approximately 2wt% and the rare earth La content is approximately 1.5wt%. After stirring and maintaining the temperature for homogenization, use argon or nitrogen as the atomizing medium for supersonic atomization to obtain spherical aluminum-based alloy powder.

[0051] Cross-sectional sample preparation of the powder, followed by scanning electron microscopy and EDS surface scanning analysis, revealed the presence of bright linear or network-like second phases in the grain boundary / intergranular regions, with Ce and La elements enriched in these areas; Figure 2 As shown, rare earth elements are enriched in the grain boundary / grain region and form a network structure; compared with pure aluminum powder, rare earth alloy powder exhibits a more obvious grain boundary network structure.

[0052] Example 2

[0053] This embodiment provides a method for preparing aluminum-rare earth-boron composite combustion powder with the introduction of boron (B):

[0054] Based on Example 1, Al-50B master alloy was further added to the melt as a boron source, bringing the boron content in the melt to 10 wt%. Subsequently, supersonic atomization and rapid solidification were performed to obtain aluminum-rare earth-boron composite fuel powder. The atomization pressure was adjusted to 6 MPa, and the superheat was controlled at 100°C above the liquidus to obtain a higher cooling rate (close to 10). 5 K / s).

[0055] Cross-sectional microscopic analysis of the obtained powder revealed not only an Al-RE phase network between grain boundaries / grains, but also a dispersed boron-containing phase or B-related phase. Under these process conditions, boron is partially dissolved in situ within the rare-earth Al-RE intermetallic compound lattice, or precipitates at grain boundaries; this microstructural configuration allows the powder to induce a high concentration of oxygen vacancy defects during combustion. Figure 3Differential scanning calorimetry (DSC) compared with pure aluminum-B powder can characterize the increasing trend of exothermic peak or total exothermic amount; the morphology and EPR of the residue after combustion / oxidation can be used to characterize the increasing trend of the exothermic peak or total exothermic amount. Figure 4 The comparison can verify the synergistic improvement effect after the introduction of rare earth metals.

[0056] Example 3

[0057] In this embodiment, the rare earth Ce content in the melt is about 2 wt%, the rare earth La content is about 0.5 wt%, and other parameters are the same as in Example 2.

[0058] Example 4

[0059] In this embodiment, the rare earth Ce content in the melt is about 2 wt%, the rare earth La content is about 1 wt%, and other aspects are the same as in Example 2.

[0060] Example 5

[0061] In this embodiment, the rare earth Pr content in the melt is about 2wt%, the rare earth Nd content is about 1wt%, and other parameters are the same as in Example 2.

[0062] Example 6

[0063] In this embodiment, the B content is controlled at 20 wt%, and the superheat is controlled at 150°C above the liquidus line by adjusting the atomization pressure to 8 MPa, in order to obtain a higher cooling rate (close to 10). 6 (K / s), otherwise the same as in Example 2.

[0064] Example 7

[0065] In this embodiment, the B content is controlled at 1 wt%, and the superheat is controlled at 50°C above the liquidus line by adjusting the atomization pressure to 3 MPa, in order to obtain a higher cooling rate (close to 10). 4 (K / s), otherwise the same as in Example 2.

[0066] Comparative Example 1

[0067] Using the same atomization process as in Example 2, industrial pure aluminum (purity ≥ 99.7%) was supersonic atomized to prepare pure aluminum powder.

[0068] Comparative Example 2

[0069] The preparation method of Example 2 was followed, but only Al-50Ce master alloy was added to make the Ce content in the melt 3.5wt%.

[0070] Comparative Example 3

[0071] The same composition as in Example 2 (Al-2%Ce-1.5%La) was used, but Al-50B master alloy (50wt% B content) was directly added to the melt before atomization, and atomization was performed only by mechanical stirring. At this time, boron exists as an independent AlB2 phase or in boron solid solution form, and it also precipitates as a ternary phase formed by solid solution in the Al-RE phase.

[0072] Comparative Example 4

[0073] The same composition as in Example 2 (Al-2%Ce-1.5%La) was used, but conventional casting (metal mold casting, cooling rate <10) was employed. 2 The ingot is obtained by (K / s) and then mechanically crushed into powder.

[0074] Comparative Example 5

[0075] The composition was the same as in Example 2 (Al-2%Ce-1.5%La-5%B), but the atomization pressure was reduced to 0.5MPa, resulting in insufficient cooling rate.

[0076] Comparative Example 6

[0077] By controlling the B content to 25wt% and adjusting the atomization pressure to 8MPa, and maintaining the superheat at 150°C above the liquidus, a higher cooling rate (close to 10) can be achieved. 6 (K / s), otherwise the same as in Example 2.

[0078] Comparative Example 7

[0079] The composition is Al-3.5%Ce-10%B (the total rare earth content is comparable to that of Example 2, but La is removed and only Ce is used), and the process is the same as that of Example 2.

[0080] Test Example 1

[0081] The products obtained in Examples 1-6 and Comparative Examples 1-7 were subjected to performance tests, and the results are shown in Table 1.

[0082] Table 1 Performance Index Results

[0083] Grain boundary network characteristics <![CDATA[Oxygen vacancy concentration (EPR signal I sample / Iref )]]> Total heat release of DSC (relative to pure aluminum) Combustion residue rate Example 1 Fine three-dimensional network 1.5 Increase by 20% lower Example 2 Fine 3D network + in-situ coupling with B phase 1.8 Increase by 35% Extremely low Example 3 Fine 3D network + containing B phase 1.65 Increase by 30% Very low Example 4 Fine 3D network + containing B phase 1.7 Increased by 32% Very low Example 5 Fine 3D network + containing B phase 1.7 Increased by 32% Very low Example 6 Ultrafine network + nano transition layer 2.0 Increase by 40% Approaching 0 Example 7 Fine 3D network + containing B phase 1.55 Increase by 25% lower Comparative Example 1 Grain boundary phase 1.0 (Baseline) Baseline (0%) high Comparative Example 2 Grain boundary phase 1.2 Increase by 8% middle Comparative Example 3 Grain boundary phase + independent B phase 1.25 Increase by 12% Medium and high Comparative Example 4 coarse and discontinuous 1.1 Increase by 5% high Comparative Example 5 Grain boundary coarsening, boron segregation 1.2 Increase by 10% Medium and high Comparative Example 6 Network coarsening and significant B-segregation 1.6 Increase by 22% medium to low Comparative Example 7 Grain boundary phase + B-containing phase 1.55 Increase by 25% lower

[0084] As shown in Table 1, Example 6 uses B=20% and the most extreme atomization process (8MPa, 150℃ overheating, ~10 6 K / s), forming a unique structure of "ultra-fine network + nano-transition layer", with an EPR signal as high as 2.0, a 40% increase in heat dissipation, and a residue rate approaching 0, representing the peak performance achievable by this invention. Example 2, with B=10% and a relatively mild process (6MPa, 100℃ superheat, ~10 5At K / s, the EPR signal reached 1.8, the heat release increased by 35%, and the residue was extremely low, demonstrating that the present invention can still achieve significant results under industrially feasible conditions, representing the optimal balance for industrialization. Comparing Example 1 (Ce+La) with Comparative Example 2 (single Ce), the former's EPR signal (1.5) and heat release (+20%) were significantly higher than the latter's (1.2, +8%), proving that the lattice distortion introduced by the difference in atomic radii between Ce and La effectively increased the oxygen vacancy concentration. Further comparing Example 2 (Ce+La+B) with Comparative Example 7 (single Ce+B), Example 2's EPR signal (1.8) and heat release (+35%) were significantly better than Comparative Example 7 (1.55, +25%), and the residue rate decreased from "lower" to "extremely low," indicating that even with in-situ coupling of B, the synergy of dual rare earth elements remains the key to obtaining higher performance. Example 2 (B in-situ coupling) showed significantly better EPR signal (1.8) and heat release (+35%) than Comparative Example 3 (B mechanical mixing, 1.25, +12%), and the residue rate decreased from "medium-high" to "extremely low," indicating that B must participate in Al-RE phase precipitation to exert a synergistic effect. Example 2 (supersonic atomization) exhibited a fine and complete grain boundary network, while Comparative Example 4 (ordinary casting + crushing) showed coarse and discontinuous grain boundaries, with an EPR signal of only 1.1 and a heat release of only +5%, demonstrating that rapid cooling is essential for constructing a three-dimensional network. Compared to Comparative Example 5 (0.5MPa), Example 2 (6MPa) showed insufficient cooling rate, leading to grain boundary coarsening, B segregation, and a significant performance decrease, proving that the atomization pressure needs to be controlled above 1MPa.

[0085] This invention significantly improves the combustion performance of aluminum-based powder fuels by constructing oxygen vacancy channels at grain boundaries through "dual rare earth synergy + boron in-situ coupling + non-equilibrium rapid solidification". Example 6 represents the peak performance of this invention, achieving optimal results under optimal process conditions; Example 2 achieves the best balance between performance and industrial feasibility, making it the preferred solution for industrialization.

[0086] Test Example 2

[0087] To verify the microstructural features of "in-situ solid solution of boron", "nano-transition layer" and "non-equilibrium lattice distortion", the powder samples of Examples 1-7 and Comparative Examples 1-7 were systematically characterized by transmission electron microscopy (TEM) combined with energy dispersive spectroscopy (EDS line scan), selected area electron diffraction (SAED) and geometric phase analysis (GPA). The results are shown in Table 2.

[0088] Table 2 Quantitative Analysis Results of Microstructure

[0089] B exists in the form of Transition layer features B solid solubility (at%) Lattice strain ε Grain boundary network characteristics Example 1 No B — — 0.3% (Ce / La distortion) <![CDATA[Continuous reticular Al 11 (Ce, La)3, with slight lattice distortion]]> Example 2 In-situ solid solution + nano-transition layer 5-15nm continuous B-rich layer 0.8 0.6% Fine network, clear transition layers, and obvious lattice curvature Example 3 In-situ solid solution + nano-transition layer 4-12nm continuous B-rich layer 0.7 0.5% The finer network exhibits slightly weaker distortion compared to Example 2. Example 4 In-situ solid solution + nano-transition layer 5-14nm continuous B-rich layer 0.75 0.55% Fine network, moderate distortion Example 5 In-situ solid solution + nano-transition layer 5-14nm continuous B-rich layer 0.75 0.55% Fine network, Pr / Nd solid solution distortion Example 6 In-situ solid solution + atomic-level transition layer 1-3nm Dispersion Transition Layer 1.2 0.9% Extremely fine network, highly distorted lattice, localized disorder Example 7 In-situ solid solution + thin transition layer 3-8nm rich B layer 0.5 0.4% Fine network, low solid solubility of B Comparative Example 1 No B — — <0.1% No grain boundary phase, pure Al structure Comparative Example 2 No B — — 0.2% (single Ce distortion) <![CDATA[Single Al 11 Ce3 phase, sparse grain boundaries]]> Comparative Example 3 <![CDATA[Independent AlB2 particles (0.5 - 2 μm)]]> No transition layer <0.1 <0.1% <![CDATA[The grain boundary phase is complete and distortion-free, and AlB2 is independently distributed]]> Comparative Example 4 Coarse grain boundary phase, no boron — — 0.1% Large, discontinuous grain boundaries, equilibrium structure Comparative Example 5 <![CDATA[Grain boundary segregation + Coarse AlB2]]> No continuous transition layer 0.2 0.2% Grain boundary coarsening, uneven boron distribution Comparative Example 6 Supersaturation segregation + coarsening Transition layer rupture, localized B aggregation 1.0 (but unevenly distributed) 0.5% (partial relaxation) Network coarsening, with some regions exhibiting B-segregation clustering. Comparative Example 7 In-situ solid solution + transition layer 4-12nm rich B layer 0.7 0.4% (limited by single Ce distortion) It contains grain boundary phases and B-containing phases, but its distortion is weaker than that of dual rare earth elements.

[0090] As shown in Table 2, Al in high-resolution TEM11 The (Ce,La)3 phase lattice fringes show significant bending, and the interplanar spacing exhibits local fluctuations (Δd / d≈0.6-0.9%). Diffraction spots in the SAED pattern show diffuse scattering and slight splitting, indicating a high degree of lattice distortion. EDS line scanning: Transgrain boundary scanning shows that boron exists in Al... 11 The (Ce,La)3 phase exhibits a gradient distribution, with the highest B concentration (0.8-1.2 at%) at the interface, gradually decreasing from the grain boundaries towards the grain interior, indicating that B is dissolved in the crystal lattice rather than simply adsorbed. Transition layer characteristics: In Al... 11 A continuous B-rich layer was observed at the interface between the (Ce,La)3 phase and α-Al. Example 2 (transmission electron microscopy, e.g.) Figure 5 The thickness of AlB2 particles in Example 3 (shown as 5-15 nm) was reduced to 1-3 nm in Example 6, exhibiting an atomically dispersed transition. This region is simultaneously enriched in Ce and La, and electron energy loss spectroscopy (EELS) shows electron orbital hybridization between B and RE, confirming the formation of an Al-RE-B ternary non-equilibrium phase. In Comparative Example 3, mechanically mixed independent AlB2 particles (0.5-2 μm) are distributed at grain boundaries or within grains, interacting with Al... 11 The (Ce,La)3 phase interface is clear and sharp, with no elemental interdiffusion. Al 11 The (Ce,La) three-phase lattice is intact, the SAED pattern perfectly matches the standard card, and the lattice strain is <0.1%. EDS line scanning shows Al 11 The boron content within the (Ce,La)3 phase was below the detection limit (<0.1 at%). In Comparative Example 6, the supersaturated segregated boron content reached 25%, exceeding the lattice capacity limit, resulting in boron segregation clusters (20-50 nm) in some regions, and breakage and discontinuity in the transition layer. The lattice strain decreased from 0.9% (Example 6) to 0.5%, indicating local relaxation. Additional diffraction spots appeared in the SAED pattern, identified as AlB2 and B2O3 (with a small amount of oxidation), proving that boron precipitated as an independent phase.

[0091] Comparing Example 1 (Ce+La, ε=0.3%) with Comparative Example 2 (single Ce, ε=0.2%) demonstrates that the lattice mismatch introduced by the difference in Ce / La atomic radii (rLa>rCe) is one of the sources of distortion. Comparing Example 2 (containing B, ε=0.6%) with Example 1 (without B, ε=0.3%) demonstrates that the entry of B atoms into the interstitial lattice further exacerbates the distortion. Example 6 (high B+rapid cooling) reaches ε=0.9%, demonstrating that under rapid cooling, the increase in B solid solubility synergistically with the dual rare earth distortion, producing a nonlinear enhancement of "1+1>2".

[0092] Comparative Example 4 (Ordinary Casting) Cooling Rate <10 2K / s, grain boundary coarsening, strain only 0.1%, proving that rapid solidification is a prerequisite for locking in the non-equilibrium state. Comparative Example 5 (low-pressure atomization) has insufficient cooling rate, B segregation, strain only 0.2%, proving that the atomization pressure must be ≥1MPa.

[0093] Test Example 3

[0094] To verify the applicability of aluminum-based powder fuels in practical energetic material systems, the powder samples from Examples 1-7 and Comparative Examples 1-7 were used as metal fuel additives and added to a standard HTPB (hydroxyl-terminated polybutadiene) solid propellant formulation for burning rate and heat of explosion tests. Specific formulations are shown in Table 3.

[0095] Table 3 Experimental formulation design

[0096] Components Basic formula (wt%) Test formula HTPB adhesive system 30 30 AP (ammonium perchlorate) 55 55 Metal fuel additives 15 (Comparative Example 1: Pure Aluminum) 15 (each test sample) Other additives 5 5

[0097] Test conditions:

[0098] Burning rate test standard: QJ912-85 (Method for determining the burning rate of solid propellants);

[0099] Test pressures: 2MPa, 5MPa, 10MPa;

[0100] Explosive heat test: constant temperature oxygen bomb calorimeter, oxygen pressure 3MPa;

[0101] Test temperature: 20℃.

[0102] The test results are shown in Table 4.

[0103] Both the increase in average burning rate and the increase in heat of explosion are relative to pure aluminum.

[0104] Table 4. Test results of the application performance of energetic materials

[0105] 2MPa burning rate mm / s 5MPa burn rate mm / s 10MPa combustion rate mm / s Average ignition speed increased by % Pressure index n Explosive heat (J / g) Boosting popularity by % Example 1 7.0 11.2 15.3 +12% 0.40 6850 +8% Example 2 7.5 12.3 16.8 +18% 0.38 7230 +14% Example 3 7.2 11.8 16.0 +14% 0.39 7020 +11% Example 4 7.3 12.0 16.3 +15% 0.39 7100 +12% Example 5 7.3 12.0 16.2 +15% 0.39 7080 +12% Example 6 7.8 12.8 17.5 +22% 0.36 7450 +18% Example 7 6.9 11.0 15.0 +10% 0.41 6780 +7% Comparative Example 1 6.2 9.8 13.5 Baseline (0%) 0.42 6320 Baseline (0%) Comparative Example 2 6.5 10.3 14.0 +5% 0.42 6450 +2% Comparative Example 3 6.7 10.6 14.2 +8% 0.41 6550 +4% Comparative Example 4 6.4 10.1 13.8 +3% 0.42 6380 +1% Comparative Example 5 6.6 10.4 14.1 +5% 0.42 6480 +3% Comparative Example 6 7.0 11.3 15.2 +11% 0.40 6820 +8% Comparative Example 7 7.1 11.5 15.5 +13% 0.40 6900 +9%

[0106] Table 4 shows that Example 6 (B=20%, high-pressure rapid cooling) exhibited the highest burning rate under all pressures, with an average increase of 22%, and the lowest pressure index (0.36), indicating that its "ultra-fine network + nano-transition layer" structure achieved efficient oxygen transport and energy release in actual combustion environments. Example 2 (B=10%, industrial preferred) showed an 18% increase in burning rate and a pressure index of 0.38, demonstrating excellent comprehensive performance, and its relatively mild process conditions made it suitable for industrial application. Example 1 (no B, only dual rare earth elements) showed a 12% increase, proving that significant effects can be achieved solely through the dual rare earth network. Comparative Example 6 (B=25%, supersaturated) showed a burning rate increase that dropped to 11%, lower than Examples 2 and 6, verifying that the synergistic effect weakened after the B content exceeded 20%, consistent with the "network coarsening and B segregation" observed in the microstructure. Comparative Example 7 (single Ce+B) showed a 13% increase, lower than Example 2 (18%), proving that the synergistic effect of dual rare earth elements is indispensable. Comparative Example 3 (mechanical hybrid B) only improved by 8%, far lower than Example 2 (18%), proving that B must be coupled in situ to exert a synergistic effect.

[0107] The pressure indices of Examples 2 and 6 (0.38 and 0.36, respectively) were significantly lower than those of Comparative Example 1 (0.42), indicating that the powder of the present invention helps to reduce the pressure sensitivity of the propellant and improve combustion stability. Although Comparative Example 6 (0.40) was better than pure aluminum, it was inferior to Examples 2 / 6, further verifying the negative impact of exceeding the limit of B content.

[0108] Example 6 showed a heat of explosion of 7450 J / g, an 18% increase compared to pure aluminum, consistent with the trend of increasing combustion rate. Example 2 showed a heat of explosion of 7230 J / g, a 14% increase. Comparative Example 3 showed a heat of explosion of only 6550 J / g, a 4% increase, demonstrating that mechanically mixed B cannot effectively contribute energy. Comparative Example 6 showed a heat of explosion of 6820 J / g, an 8% increase, lower than Examples 2 and 6, verifying that supersaturated B leads to a decrease in energy utilization.

[0109] After burning each formulation at 5 MPa pressure, the residues were collected and analyzed by SEM. The residues of Examples 2 / 6 showed well-broken particles with a loose, porous structure. EDS analysis revealed a predominantly rare earth oxide framework with no unburned Al cores detected. The residue of Example 6 had smaller pore sizes and a more uniform distribution. The residue of Comparative Example 1 showed spherical particles with a dense, intact Al2O3 film on the surface and unburned Al cores inside. The residue of Comparative Example 3 showed some particle breakage, but unburned AlB2 particles were present (B-rich areas were detected by EDS), and the rare earth oxide framework was discontinuous. The residue of Comparative Example 6 showed some breakage, but localized areas had dense coatings due to B segregation, hindering complete combustion.

[0110] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing aluminum-based powder fuel with grain boundary oxygen vacancy channels, characterized in that, The method includes: Step 1: Heat pure aluminum to melt it and form a melted aluminum body; Step two: Add an Al-RE master alloy to the aluminum melt to adjust the total content of rare earth element RE in the melt to 0.1-7 wt%; wherein the rare earth element RE comprises a first rare earth element and a second rare earth element, the first rare earth element being selected from one or more of Ce, Pr, and Tb, and the second rare earth element being selected from one or more of La, Nd, Sm, Gd, Y, Sc, Dy, and Er; simultaneously add a boron source to the melt to make the boron content in the melt 1-40 wt%. Step 3: The uniformly mixed melt is subjected to controlled supersonic atomization and rapid solidification to obtain aluminum-based alloy powder; In step three, the controlled supersonic atomization rapid solidification is achieved by adjusting the supercooling and cooling rate of the atomizing medium, so that the Al-RE intermetallic compound phase precipitates at the grain boundaries of the powder solidification structure and forms a three-dimensional distribution network structure extending along the grain boundaries, while introducing non-equilibrium lattice distortion into the Al-RE intermetallic compound phase and its adjacent grain boundary regions. The non-equilibrium lattice distortion configuration is such that, during the subsequent combustion and oxidation process, the rare earth oxide phase induced to generate has an oxygen vacancy defect concentration higher than its intrinsic concentration in the thermodynamic equilibrium state, thereby forming a diffusion channel rich in oxygen vacancy defects.

2. The preparation method according to claim 1, characterized in that, The content of the first rare earth element is 0.05-4 wt%; the content of the second rare earth element is 0.01-4 wt%.

3. The preparation method according to claim 1, characterized in that, The B source is an Al-B master alloy.

4. The preparation method according to claim 1, characterized in that, In step three, the process parameters for controlled supersonic atomization rapid solidification are: the atomization medium is argon, nitrogen or a mixture thereof, and the atomization pressure is 3-8 MPa. The melt superheating temperature is controlled at 50-150℃ above the liquidus line to achieve 10 4 -10 6 Local cooling rate in K / s.

5. An aluminum-based powder fuel with grain boundary oxygen vacancy channels prepared by any one of claims 1-4, characterized in that, It includes an aluminum matrix and a three-dimensional Al-RE intermetallic compound phase network distributed at the grain boundaries; the intermetallic compounds at the grain boundaries form a structure rich in oxygen vacancy defects after oxidation and combustion; wherein, the Al-RE intermetallic compounds simultaneously contain a first rare earth element and a second rare earth element, and the first rare earth element and the second rare earth element exhibit co-enrichment characteristics in the grain boundary region.

6. An aluminum-based powder fuel with grain boundary oxygen vacancy channels according to claim 5, characterized in that, The three-dimensional Al-RE intermetallic compound phase network is in situ coupled with element B. In the Al-RE phase, there is an Al-RE-B ternary transition layer with a width of 1-50 nm at the interface of the aluminum matrix, or an Al-RE-B ternary transition layer is formed at the interface of the Al-RE phase and the aluminum matrix.

7. An aluminum-based powder fuel with grain boundary oxygen vacancy channels according to claim 6, characterized in that, The Al-RE intermetallic compound phase is mainly Al. 11 The solid solution phase of (first rare earth element, second rare earth element)3 has local distortion of its lattice fringes, with a lattice strain value ε>0.5%, and boron is enriched in the distorted region.

8. The use of an aluminum-based powder fuel with grain boundary oxygen vacancy channels prepared by any one of claims 1-4 as an additive or energy component in solid propellants, explosives, pyrotechnics or metallic fuels.

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