Composite metal fuel powder and preparation method thereof

Abstract

The invention relates to composite metal fuel powder which comprises metal fuel particles, a metal oxide layer and an organosilane layer, the metal oxide layer is located on the surfaces of the metal fuel particles, and the organosilane layer is located on the surface of the metal oxide layer; the organosilane layer includes an organosilane, and the organosilane includes a hydrophobic hydrocarbyl chain. According to the composite metal fuel powder, the metal oxide layer can cut off a channel for water and oxygen to diffuse and permeate into the metal fuel particles, the organosilane layer with the hydrophobic alkyl chain enables water molecules to be difficult to wet and adsorb on the surfaces of the metal fuel particles, and the hydrophobic capacity of the metal fuel powder is improved; the metal oxide layer and the organosilane layer work synergistically, so that the metal fuel powder has certain environmental inertia, the storage safety is improved, and the safety risks of nature, gas production or heating and the like are reduced.

Description

Composite metal fuel powder and its preparation method Technical Field

[0001] This invention relates to the field of surface treatment technology, and in particular to composite metal fuel powders and their preparation methods. Background Technology

[0002] Metal fuels, as high-energy-density energy materials, are attracting increasing attention due to their growing application demands in aerospace, military, and other fields. In particular, aluminum, magnesium, boron, and lithium possess high energy density and excellent combustion characteristics, offering even higher energy density. Despite their enormous potential, metal fuels still face a series of challenges in practical applications. For example, because metal fuels consist of relatively reactive elements, they are highly susceptible to spontaneous oxidation, hygroscopic reactions, and even surface pulverization during storage, transportation, and use. This affects the stability and safety of the metal fuels, limiting their application as high-energy solid propellants. Therefore, higher requirements are placed on the chemical stability and storage safety of metal fuel powders. Summary of the Invention

[0003] Therefore, it is necessary to provide a composite metal fuel powder and its preparation method, aiming to improve the chemical stability and storage safety of the metal fuel powder.

[0004] In one aspect, the present invention provides a composite metal fuel powder comprising metal fuel particles, a metal oxide layer and an organosilane layer, wherein the metal oxide layer is located on the surface of the metal fuel particles and the organosilane layer is located on the surface of the metal oxide layer; the organosilane layer comprises an organosilane, wherein the organosilane comprises a hydrophobic hydrocarbon chain.

[0005] The aforementioned composite metal fuel powder has a metal oxide layer that physically blocks the channels for water and oxygen to diffuse and penetrate into the metal fuel particles. The organosilane layer formed by the organosilane with hydrophobic hydrocarbon chains makes it difficult for water molecules to wet and adsorb onto the surface of the metal fuel particles, further improving the hydrophobicity of the metal fuel powder. The synergistic effect of the metal oxide layer and the organosilane layer gives the metal fuel powder a certain degree of environmental inertness. The aforementioned composite metal fuel particles can be exposed to air or humid environments for a long time with less performance degradation, thereby improving storage safety to a certain extent and reducing safety risks such as natural disasters, gas generation, or heat generation.

[0006] In one embodiment, the hydrocarbon chain includes one or more of hydrocarbon groups with ≥8 carbon atoms and halohydrocarbon groups with ≥8 carbon atoms.

[0007] In one embodiment, the organosilane includes an alkoxy group bonded to a silicon atom, the alkoxy group including one or more of ethoxy and methoxy groups, and the number of the alkoxy groups is 1 to 3.

[0008] In one embodiment, the organosilane includes one or more of tridecafluorooctyltriethoxysilane, heptadecafluorooctyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, n-octyltri(trimethylsiloxy)silane, octadecyltrimethoxysilane, and n-dodecyltrimethoxysilane.

[0009] In one embodiment, one or more of the following conditions are met:

[0010] (1) The organosilane layer has a mass content of 0.05wt% to 3wt% relative to the metal fuel particles;

[0011] (2) The metal oxide layer has a mass content of 0.1wt% to 5wt% of the metal fuel particles.

[0012] In one embodiment, one or more of the following conditions are met:

[0013] (1) The thickness of the metal oxide layer is 1 nm to 20 nm;

[0014] (2) The thickness of the organosilane layer is 0.5 nm to 10 nm.

[0015] In one embodiment, the metal oxide layer and the organosilane layer are connected by chemical bonds, including Si-O bonds.

[0016] In one embodiment, the metal oxide layer includes one or more of aluminum oxide, titanium oxide, zirconium oxide, yttrium oxide, and zinc oxide.

[0017] In one embodiment, the metal fuel particles include one or more of the following: aluminum hydride particles, aluminum particles, aluminum-lithium alloy particles, aluminum-magnesium alloy particles, aluminum-boron alloy particles, aluminum-zinc alloy particles, aluminum-zirconium alloy particles, aluminum-titanium alloy particles, aluminum-cerium alloy particles, aluminum-tungsten alloy particles, aluminum-nickel alloy particles, and aluminum-molybdenum alloy particles.

[0018] Another aspect of the present invention provides a method for preparing composite metal fuel powder, comprising the following steps:

[0019] A metal oxide layer is deposited on the surface of the metal fuel particles to obtain the metal fuel particles coated with the metal oxide layer.

[0020] The organosilane is dissolved in an organic solvent to form an organosilane solution;

[0021] The metal fuel particles coated with the metal oxide layer are mixed and reacted with the organosilane in a solvent to obtain an organosilane layer on the surface of the metal oxide layer.

[0022] The above-mentioned method for preparing composite metal fuel powder uses atomic layer deposition technology to prepare a metal oxide layer on the surface of metal fuel particles, which can precisely control the thickness of the metal oxide layer. At the same time, organosilane is used as a coupling agent to hydrolyze in the liquid phase and react with the hydroxyl groups on the surface of the metal oxide to form an organosilane layer on the surface of the metal oxide layer. This method is suitable for batch processing, has relatively simple equipment requirements, and is easy to scale up from laboratory production to process-level production. Attached Figure Description

[0023] Figure 1 shows a transmission electron microscope image and an energy scattering spectrum of the composite metal fuel powder of Example 1;

[0024] Figure 2 shows the hygroscopic oxidation performance test results of the composite metal fuel powders of Example 1, Comparative Example 1, and Comparative Example 2.

[0025] Figure 3 shows scanning electron microscope images of the composite metal fuel powders of Comparative Example 1 and Comparative Example 2.

[0026] Figure 4 shows the scanning electron microscope image and energy scattering spectrum of the composite metal fuel powder of Comparative Example 2. Detailed Implementation

[0027] To facilitate understanding of the present invention, a more complete description will be given below with reference to relevant embodiments. Preferred embodiments of the invention are shown below. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough and complete understanding of the disclosure of the invention will be achieved.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] Metallic fuels, as high-energy fuels, are mainly composed of light elements such as aluminum, magnesium, iron, boron, beryllium, and lithium. Their core value lies in their extremely high energy density and reactivity, making them widely used in demanding applications such as solid propellants, high-energy explosive systems, and aerospace propulsion systems. However, due to their extremely high chemical reactivity, metallic fuel powders are prone to spontaneous oxidation and hygroscopic reactions during storage, transportation, and use, thereby reducing their energy density and safety. Therefore, a passivation coating layer is usually constructed around the metallic fuel powder to ensure its transportation safety and energy density.

[0030] Traditional coating materials mainly include paraffin wax, polytetrafluoroethylene, polyvinyl alcohol, stearic acid, oleic acid, and metal salts. These materials have poor compatibility with metallic fuel powders, resulting in a loose and porous passivation layer that cannot effectively prevent the intrusion of water and oxygen from the air in the long term. While coating metallic fuel powders with single-component inorganic metal oxides can prevent the intrusion of water and oxygen from the air, these metal oxides are rich in hydroxyl groups on their surface, exhibiting hydrophilic properties. Even if water and oxygen can be blocked from penetrating the metallic fuel powder, the hydroxyl groups on the surface will still adsorb water from the air over a long period, posing a certain risk.

[0031] To address the aforementioned issues, this invention proposes a composite coating strategy: First, atomic layer deposition (ALD) is used to grow a dense, continuous inorganic metal oxide film on the surface of metallic fuel powder under fluidized conditions, constructing a highly efficient oxygen barrier layer. Then, an organosilane is introduced onto the surface of this inorganic metal oxide film using a liquid-phase method, forming an organosilane layer, ultimately constructing an "inorganic-organic" bilayer composite coating structure. This composite coating system combines the dense isolation of the inorganic layer with the hydrophobic and interface-modifying functions of the organic layer, effectively blocking the penetration of water vapor and oxygen, significantly improving the dispersibility and surface compatibility of the powder, and thus enhancing the chemical stability and storage and transportation safety of the metallic fuel powder.

[0032] A method for preparing composite metal fuel powder includes metal fuel particles, a metal oxide layer, and an organosilane layer, wherein the metal oxide layer is located on the surface of the metal fuel particles, and the organosilane layer is located on the surface of the metal oxide layer; the organosilane layer includes organosilanes, and the organosilanes include hydrophobic hydrocarbon chains.

[0033] The aforementioned composite metal fuel powder has a metal oxide layer that physically blocks the channels for water and oxygen to diffuse and penetrate into the metal fuel particles. The organosilane layer formed by the organosilane with hydrophobic hydrocarbon chains makes it difficult for water molecules to wet and adsorb onto the surface of the metal fuel particles, further improving the hydrophobicity of the metal fuel powder. The synergistic effect of the metal oxide layer and the organosilane layer gives the metal fuel powder a certain degree of environmental inertness. The aforementioned composite metal fuel particles can be exposed to air or humid environments for a long time with less performance degradation, thereby improving storage safety to a certain extent and reducing safety risks such as natural disasters, gas generation, or heat generation.

[0034] In one embodiment, the hydrocarbon chain includes one or more of hydrocarbon groups with ≥8 carbon atoms and halohydrocarbon groups with ≥8 carbon atoms.

[0035] The aforementioned composite metal fuel powder has a hydrocarbon chain with ≥8 carbon atoms and a relatively long hydrocarbon chain. The long hydrophobic hydrocarbon groups and hydrophobic halogenated hydrocarbon groups give the organosilane layer a certain degree of flexibility and deformability, which can absorb and disperse the external force and thermal stress on the metal fuel particles, thereby buffering the impact on the brittle metal oxide layer and reducing the possibility of cracks in the metal oxide layer.

[0036] In one embodiment, the number of carbon atoms in the hydrocarbon group and / or the halogenated hydrocarbon group is 8 to 20. As an example, the number of carbon atoms in the hydrocarbon group and / or the halogenated hydrocarbon group may be 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or within the range of any two of the above values, such as 8 to 18.

[0037] Furthermore, the halogen element in the haloalkyl group includes one or more of fluorine, chlorine, and bromine, with fluorine being the preferred choice, exhibiting excellent hydrophobicity. Furthermore, the total number of halogen elements in the haloalkyl group is 1 to 20.

[0038] In one embodiment, the metal oxide layer and the organosilane layer are connected by chemical bonds, including Si-O bonds.

[0039] In the aforementioned composite metal fuel powder, the metal oxide layer and the organosilane layer are connected by strong Si-O chemical bonds, which forms a relatively stable interface between the organosilane layer and the metal oxide layer. This prevents the organosilane layer from peeling off or shifting under mechanical external forces such as mixing, pressing, and transportation, and improves the stability of the moisture absorption and antioxidant properties of the metal oxide layer and the organosilane layer.

[0040] In one embodiment, the organosilane includes alkoxy groups bonded to silicon atoms. These alkoxy groups include one or more of ethoxy and methoxy groups, and the number of alkoxy groups is 1 to 3. Understandably, the hydroxyl groups on the surface of the metal oxide layer and the alkoxy groups in the organosilane layer are chemically bonded to form Si-O bonds. The number of alkoxy groups in the organosilane in the reacting organosilane layer is 0 to 2.

[0041] In one embodiment, the organosilane includes one or more of tridecafluorooctyltriethoxysilane, heptadecafluorooctyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, n-octyltri(trimethylsiloxy)silane, octadecyltrimethoxysilane, and n-dodecyltrimethoxysilane.

[0042] In one embodiment, the organosilane layer has a mass content of 0.05wt% to 3wt% relative to the metal fuel particles.

[0043] In one embodiment, the metal oxide layer has a mass content of 0.1 wt% to 5 wt% for the metal fuel particles.

[0044] In one embodiment, the thickness of the metal oxide layer is 1 nm to 20 nm.

[0045] In one embodiment, the thickness of the organosilane layer is 0.5 nm to 10 nm.

[0046] In one embodiment, the metal oxide layer includes one or more of aluminum oxide, titanium oxide, zirconium oxide, yttrium oxide, and zinc oxide.

[0047] Optionally, the metal oxide layer includes titanium oxide.

[0048] In one embodiment, the metal fuel powder comprises at least one substance such as aluminum, magnesium, iron, boron, beryllium, and lithium.

[0049] In one embodiment, the metal fuel particles include one or more of the following: aluminum hydride particles, aluminum particles, aluminum-lithium alloy particles, aluminum-magnesium alloy particles, aluminum-boron alloy particles, aluminum-zinc alloy particles, aluminum-zirconium alloy particles, aluminum-titanium alloy particles, aluminum-cerium alloy particles, aluminum-tungsten alloy particles, aluminum-nickel alloy particles, and aluminum-molybdenum alloy particles.

[0050] Optionally, the metal fuel pellets include one or more of aluminum hydride pellets and lithium aluminum alloy pellets.

[0051] Furthermore, the lithium mass fraction in the aluminum-lithium alloy powder is 1wt% to 15wt%. As an example, the lithium mass fraction in the aluminum-lithium alloy powder can be 1wt%, 5wt%, 10wt%, 15wt%, or within the range of any two of the above values, such as 5wt% to 10wt%.

[0052] In one embodiment, the average particle size of the metal fuel powder before coating modification is 1 μm to 100 μm. As an example, the average particle size of the metal fuel powder can be 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or within the range of any two of the above values, for example, 5 μm to 50 μm.

[0053] In another aspect of the present invention, a method for preparing composite metal fuel powder includes the following steps:

[0054] Metal oxides are deposited on the surface of metal fuel particles in an atomic layer to obtain metal fuel particles coated with a metal oxide layer.

[0055] Organosilanes are dissolved in organic solvents to form organosilane solutions;

[0056] Metal fuel particles coated with a metal oxide layer are mixed and reacted with organosilane in a solvent to obtain an organosilane layer on the surface of the metal oxide layer.

[0057] The above-mentioned method for preparing composite metal fuel powder uses atomic layer deposition technology to prepare a metal oxide layer on the surface of metal fuel particles, which can precisely control the thickness of the metal oxide layer. At the same time, organosilane is used as a coupling agent to hydrolyze in the liquid phase and react with the hydroxyl groups on the surface of the metal oxide to form an organosilane layer on the surface of the metal oxide layer. This method is suitable for batch processing, has relatively simple equipment requirements, and is easy to scale up from laboratory production to process-level production.

[0058] In one embodiment, the metal fuel particles coated with a metal oxide layer are mixed and reacted with an organosilane in a solvent, including the following steps:

[0059] Metal fuel particles coated with a metal oxide layer are added to an organosilane solution and stirred for 0.4 h to 26 h. As an example, the stirring time can be 0.4 h, 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, 26 h, or any two of the above values, for example, 0.5 h to 24 h.

[0060] In one embodiment, the temperature of the organosilane solution is 20°C to 80°C. As an example, the temperature of the organosilane solution may be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or any two of the above values, for example, 25°C to 40°C.

[0061] In one embodiment, the stirring speed is 50 rpm to 500 rpm. As an example, the stirring speed can be 50 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, or any two of the above values, such as 200 rpm to 400 rpm.

[0062] In one embodiment, the organosilane content relative to the metal fuel particles is 15wt% to 35wt%. As an example, the organosilane content relative to the metal fuel particles may be 15wt%, 17wt%, 20wt%, 22wt%, 25wt%, 27wt%, 30wt%, 32wt%, 35wt%, or any two of the above values, for example, 15wt% to 27wt%.

[0063] In one embodiment, the solvent includes at least one of alcoholic organic solvents, alkane organic solvents, and ketone organic solvents.

[0064] In one embodiment, the alcoholic organic solvent includes at least one of ethanol, isopropanol, and ethylene glycol.

[0065] In one embodiment, the alkane organic solvent includes at least one of n-hexane, cyclohexane, and isopentane.

[0066] In one embodiment, the ketone organic solvent includes at least one of acetone, butanone, cyclohexanone, and methyl isobutyl ketone.

[0067] In one embodiment, metal fuel particles coated with a metal oxide layer are mixed and reacted with an organosilane in a solvent, followed by the following steps:

[0068] Solid-liquid separation is performed, and the separated solid is washed and dried to obtain composite metal fuel powder.

[0069] In one embodiment, solid-liquid separation includes at least one of filtration and centrifugation.

[0070] In one embodiment, the washing process includes washing the separated solids with a solvent 1 to 4 times. As an example, the number of washes may be 1, 2, 3, 4, or any two of the above values, such as 2 to 3 times.

[0071] In one embodiment, the drying process involves drying the washed solids at an environment of 50°C to 120°C and 0.01 MPa to 0.04 MPa for 2 hours to 6 hours. As an example, the drying temperature can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, or any two of the above values, for example, 60°C to 95°C. As an example, the drying pressure can be 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.04 MPa, or any two of the above values, for example, 0.01 MPa to 0.02 MPa. As an example, the drying time is 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or any two of the above values, for example, 3 hours to 5 hours.

[0072] In one embodiment, depositing a metal oxide layer on the surface of metal fuel particles includes the following steps:

[0073] Metal fuel particles are placed in a fluidized bed holder within the atomic layer deposition reaction chamber. The fluidized bed holder is rotated, and an inert fluidizing medium is introduced into the atomic layer deposition reaction chamber, so that the metal fuel particles are in a fluidized state.

[0074] In one embodiment, the fluidized bed holder rotates at a speed of 20 rpm to 130 rpm, and the volumetric flow rate of the inert fluidizing medium is 400 sccm to 1100 sccm. As an example, the rotational speed of the fluidized bed holder can be 20 rpm, 30 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, 100 rpm, 110 rpm, 120 rpm, or 130 rpm, or any two of the above values, for example, 30 rpm to 120 rpm. As an example, the volumetric flow rate of the inert fluidizing medium can be 400 sccm, 500 sccm, 600 sccm, 700 sccm, 800 sccm, 900 sccm, 1000 sccm, or 1100 sccm, or any two of the above values, for example, 500 sccm to 1000 sccm.

[0075] The above-mentioned method for preparing composite metal fuel powder uses specific fluidized bed rotation speed and gas fluidization parameters to make the metal fuel particles tumble continuously, avoiding the agglomeration of metal fuel particles. This results in a more uniform coating of metal oxide layer, and a relatively dense and continuous metal oxide layer is obtained by atomic layer deposition on the surface of metal fuel particles. The metal oxide layer can isolate moisture and oxygen in the air to a certain extent, slowing down the oxidation and deactivation process of metal fuel particles, thereby significantly improving its chemical stability and storage safety.

[0076] In one embodiment, the transport pipeline corresponding to the inert fluidizing medium and the metal oxide layer is subjected to a heat treatment of 90°C to 170°C. As an example, the temperature at which the transport pipeline is subjected to the heat treatment can be 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or any two of the above values, for example, 100°C to 160°C.

[0077] In one embodiment, heating the delivery pipeline can be achieved by means of a heat exchanger or the like.

[0078] The above-mentioned method for preparing composite metal fuel powder prevents the inert fluidizing medium and the reactants corresponding to the metal oxide layer from condensing during the transportation process by applying a heating treatment to the conveying pipeline, thereby affecting the precision control of the deposited metal oxide layer.

[0079] In one embodiment, depositing a metal oxide on the surface of a fluidized metal fuel powder includes the following steps:

[0080] A metal oxide layer is deposited on the surface of a metal fuel powder by alternating and sequentially using a first reactant and a second reactant. The first reactant is a gaseous metal-based precursor, and the second reactant is a gaseous reactant that can oxidize the first reactant to obtain the metal oxide.

[0081] In one embodiment, the first reactant includes at least one of trimethylaluminum, dimethylaluminum isopropylidene oxide, tetraisopropyl titanate, tetra(dimethylamino)titanium, tetra(dimethylamino)zirconium, tetra(ethylmethylamino)zirconium, diethylzinc, tris(sec-butylcyclopentadienyl)yttrium, and N,N-diisopropylacetamidineyttrium, and the second reactant includes at least one of H2O, O2, H2O2, and O3.

[0082] Optionally, the first reactant includes tetrakis(dimethylamino)zirconium, and the second reactant includes H2O.

[0083] Optionally, the first reactant includes trimethylaluminum, and the second reactant includes H2O.

[0084] Optionally, the first reactant includes tetraisopropyl titanate, and the second reactant includes H2O.

[0085] Optionally, the first reactant includes diethylzinc, and the second reactant includes H2O.

[0086] The above-mentioned method for preparing composite metal fuel powder can coat different types of metal oxide layers on the outside of metal fuel particles by selecting different types of metal precursors as the first reactants, demonstrating that the coating modification method of fluidized bed treatment combined with atomic layer deposition has a wide range of applicability.

[0087] In one embodiment, a metal oxide layer is deposited on the surface of metal fuel particles using alternating and sequential first and second reactants, comprising the following steps:

[0088] The first and second reactants are alternately and sequentially introduced into the cavity of the atomic layer deposition reaction chamber, so that the first and second reactants react on the surface of the metal fuel particles to obtain a metal oxide layer; the above operation is repeated until the thickness of the metal oxide layer reaches the target value.

[0089] In one embodiment, after a single introduction of the first reactant and / or the second reactant into the cavity of the atomic layer deposition reaction chamber, the gas flow is stopped and the vacuum pump is turned off, followed by a pressure holding operation for 20 to 200 seconds. As an example, the pressure holding time can be 20 seconds, 30 seconds, 60 seconds, 90 seconds, 120 seconds, 150 seconds, 180 seconds, 200 seconds, or any two of the above values ​​within a range, such as 30 seconds to 120 seconds.

[0090] In one embodiment, the single-pass introduction time of the first and second reactants is 1s to 20s, and the internal temperature of the atomic layer deposition reaction chamber is 100°C to 200°C. As an example, the single-pass introduction time of the first and second reactants can be 1s, 2s, 4s, 10s, 15s, 20s, or any two of the above values, for example, 2s to 15s. As an example, the internal temperature of the atomic layer deposition reaction chamber can be 100°C, 125°C, 150°C, 175°C, 200°C, or any two of the above values, for example, 125°C to 175°C.

[0091] In one embodiment, after a single introduction of the first reactant into the cavity of the atomic layer deposition reaction chamber, the gas supply is stopped and the vacuum pump is turned off. A pressure holding operation is performed for 20s to 200s to allow the surface of the metal fuel particles to fully adsorb the first reactant. Then, an inert gas is introduced into the cavity of the atomic layer deposition reaction chamber for 20s to 100s to purge any unadsorbed first reactant.

[0092] In one embodiment, after a single introduction of the second reactant into the cavity of the atomic layer deposition reaction chamber, the gas flow is stopped and the vacuum pump is turned off. A pressure holding operation is performed for 20 to 200 seconds to allow the first reactant adsorbed on the surface of the metal fuel particles to fully react with the second reactant to form a metal oxide layer. Subsequently, an inert gas is introduced into the cavity of the atomic layer deposition reaction chamber for 20 to 100 seconds to purge unreacted second reactant and byproducts. As an example, the inert gas introduction time can be 20 seconds, 30 seconds, 60 seconds, 90 seconds, 100 seconds, or any two of the above values, for example, 30 to 90 seconds.

[0093] In one embodiment, the inert gas includes at least one of nitrogen and argon. Optionally, the purity of the inert gas is ≥99.999%.

[0094] In the above-mentioned method for preparing composite metal fuel powder, the metal fuel particles in a fluidized state are subjected to a pressure-holding operation to ensure that the first reactant and the second reactant can be fully adsorbed and reacted in the metal fuel particles, thereby obtaining a dense and uniform metal oxide layer to protect the metal fuel particles from being effectively encapsulated.

[0095] The following are specific examples.

[0096] Example 1

[0097] S1. Place 1g of aluminum-lithium alloy particles with a lithium mass fraction of 5wt% into a fluidized bed holder, and place the fluidized bed holder inside the cavity of the atomic layer deposition reaction chamber.

[0098] S2. The interior of the atomic layer deposition reaction chamber is evacuated and heated, and the fluidized bed holder is rotated. At the same time, an inert fluidizing medium is introduced into the chamber to fluidize the aluminum-lithium alloy particles. The interior temperature of the atomic layer deposition reaction chamber is 150℃, the vacuum degree of the atomic layer deposition reaction chamber is 1Pa, the rotation speed of the fluidized bed holder is 120rpm, the volumetric flow rate of the inert fluidizing medium is 1000sccm, and the delivery pipeline is heated to 100℃.

[0099] S3. Deposit a titanium oxide layer on the surface of the aluminum-lithium alloy particles. Specific steps include: introducing tetraisopropyl titanate into the reaction chamber for 15 seconds, stopping the gas flow and turning off the vacuum pump, maintaining pressure for 180 seconds to allow the aluminum-lithium alloy particles to fully adsorb the tetraisopropyl titanate; then introducing nitrogen gas into the atomic layer deposition (ALD) reaction chamber for 90 seconds to purge any unadsorbed tetraisopropyl titanate; introducing H₂O into the reaction chamber for 15 seconds, stopping the gas flow and turning off the vacuum pump, maintaining pressure for 180 seconds to allow the adsorbed tetraisopropyl titanate on the aluminum-lithium alloy particles to fully react with the H₂O to form a titanium oxide layer; then introducing nitrogen gas into the ALD reaction chamber for 90 seconds to purge any unadsorbed H₂O and byproducts. The above method of alternating and sequentially depositing tetraisopropyl titanate and H₂O on the surface of the aluminum-lithium alloy particles constitutes one cycle, and is repeated 30 times to generate a titanium oxide layer of approximately 2.4 nm on the surface of the aluminum-lithium alloy particles.

[0100] S4. Organosilane coating. 0.5 g of aluminum-lithium alloy particles with a titanium oxide layer deposited on their surface, obtained in step S3, were dispersed in 50 mL of cyclohexane. 100 μL of heptadecafluorooctyltriethoxysilane (approximately 21.9 wt% relative to the mass of the aluminum-lithium alloy particles) was added to the cyclohexane. The coating was applied at a temperature of 25℃±5℃ and a pressure of (1.01±0.01)×10⁻⁶. 5 Under a controlled environment of Pa, the magnetic stirrer was used for 24 hours at a speed of 300 rpm.

[0101] S5. Solid-liquid separation, washing, and drying. The liquid after stirring in step S4 is centrifuged at 5000 rpm for 10 min to obtain a solid. The solid is washed three times with cyclohexane. The washed solid is then dried in a vacuum drying oven at 95℃ for 4 h to obtain composite-coated modified aluminum-lithium alloy powder.

[0102] Example 2

[0103] The preparation method of Example 2 is basically the same as that of Example 1, except that octadecyltrimethoxysilane is used instead of heptadecafluorooctyltriethoxysilane in Example 1.

[0104] Right now:

[0105] Steps S1 to S3 are the same as in Example 1.

[0106] S4. Organosilane coating. 0.6 g of aluminum-lithium alloy particles with a titanium oxide layer deposited on their surface, obtained in step S3, were dispersed in 60 mL of n-hexane. 150 μL of octadecyltrimethoxysilane (approximately 17.6 wt% relative to the mass of the aluminum-lithium alloy particles) was added to the n-hexane. The coating was applied at a temperature of 25℃±5℃ and a pressure of (1.01±0.01)×10⁻⁶. 5Under a controlled environment of Pa, the magnetic stirrer was used for 12 hours at a speed of 200 rpm.

[0107] S5. Solid-liquid separation, washing, and drying. The liquid after stirring in step S4 is centrifuged at 6000 rpm for 8 min to obtain a solid. The solid is washed three times with n-hexane. The washed solid is then dried in a vacuum drying oven at 75℃ for 5 h to obtain composite-coated modified aluminum-lithium alloy powder.

[0108] Example 3

[0109] The preparation method of Example 3 is basically the same as that of Example 1, except that aluminum hydride particles are used instead of aluminum-lithium alloy particles in Example 1.

[0110] Right now:

[0111] S1. Place aluminum hydride particles in a fluidized bed holder and place the fluidized bed holder inside the cavity of the atomic layer deposition reaction chamber.

[0112] S2. The interior of the atomic layer deposition reaction chamber is evacuated and heated, and the fluidized bed holder is rotated. At the same time, an inert fluidizing medium is introduced into the chamber to fluidize the aluminum hydride particles. The interior temperature of the atomic layer deposition reaction chamber is 75℃, the vacuum degree of the chamber is 1Pa, the rotation speed of the fluidized bed holder is 30rpm, the volumetric flow rate of the inert fluidizing medium is 500sccm, and the delivery pipeline is heated to 100℃.

[0113] S3. Deposit a titanium oxide layer on the surface of aluminum hydride particles. Specific steps include: introducing tetraisopropyl titanate into the reaction chamber for 15 seconds, stopping the gas flow and turning off the vacuum pump, maintaining pressure for 180 seconds to allow sufficient adsorption of tetraisopropyl titanate on the surface of the aluminum hydride particles; then introducing nitrogen gas into the atomic layer deposition (ALD) reaction chamber for 90 seconds to purge unadsorbed tetraisopropyl titanate; introducing H₂O into the reaction chamber for 15 seconds, stopping the gas flow and turning off the vacuum pump, maintaining pressure for 180 seconds to allow sufficient reaction between the adsorbed tetraisopropyl titanate and H₂O to form a titanium oxide layer; then introducing nitrogen gas into the ALD reaction chamber for 90 seconds to purge unadsorbed H₂O and byproducts. The above method of alternating and sequentially depositing a titanium oxide layer on the surface of aluminum hydride particles using tetraisopropyl titanate and H₂O constitutes one cycle, and is repeated 30 times to generate a titanium oxide layer of approximately 2.4 nm on the surface of the aluminum hydride particles.

[0114] S4. Organosilane coating. 0.4 g of aluminum hydride particles with a titanium oxide layer deposited on their surface, obtained in step S3, were dispersed in 20 mL of ethanol. 100 μL of heptadecafluorooctyltriethoxysilane (approximately 25.9 wt% relative to the mass of the aluminum hydride particles) was added to the ethanol. The mixture was then coated at a temperature of 40℃±5℃ and a pressure of (1.01±0.01)×10⁻⁶. 5 Under a sealed environment of Pa, the magnetic stirrer was used for 0.5 hours at a speed of 400 rpm.

[0115] S5. Solid-liquid separation, washing, and drying. The liquid after stirring in step S4 is centrifuged at 8000 rpm for 5 min to obtain a solid. The solid is washed twice with ethanol, and then dried in a vacuum drying oven at 60℃ for 3 h to obtain composite-coated modified aluminum hydride powder.

[0116] Comparative Example 1

[0117] Uncoated and unmodified aluminum-lithium alloy particles.

[0118] Comparative Example 2

[0119] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that the step of coating with an organosilane layer is omitted; that is, the aluminum-lithium alloy particles are only coated with a titanium oxide layer with a thickness of about 2.4 nm.

[0120] Comparative Example 3

[0121] The preparation method of Comparative Example 3 is basically the same as that of Example 1, except that the metal oxide modification coating is omitted; that is, the aluminum-lithium alloy particles are directly coated with an organosilane layer with a thickness of about 6 nm without being coated with a titanium oxide layer.

[0122] Performance testing

[0123] The performance of the metal fuel powders prepared in each embodiment and comparative example was tested, including...

[0124] (1) Scanning electron microscope (SEM) was used to observe the morphology of the metal fuel powder and the coating layer on the surface of the metal fuel powder;

[0125] (2) Energy scattering spectroscopy (EDS) was used to perform qualitative and quantitative analysis of the elemental composition of the metal oxide layer and organosilanes on the surface of the metal fuel powder;

[0126] (3) Transmission electron microscopy (TEM) was used to observe the morphology and thickness of the metal oxide layer and organosilane layer on the surface of the metal fuel powder. At the same time, the interface structure of the metal oxide layer and organosilane layer was analyzed in combination with the EDS surface scan results.

[0127] (4) Hygroscopic oxidation performance test: The hygroscopic oxidation test was carried out under constant temperature and humidity conditions of 25℃ and 75% relative humidity. The weight change of the metal fuel powder over time was recorded and the weight gain rate was calculated.

[0128] The transmission electron microscopy (TEM) and energy scattering spectroscopy (ESS) results of the composite-coated modified aluminum-lithium alloy powder prepared in Example 1 of this application are shown in Figure 1, where (a) is the TEM image and (b) is the EDS elemental distribution map.

[0129] The hygroscopic oxidation performance test results of Example 1, Comparative Example 1 and Comparative Example 2 of this application are shown in Figure 2.

[0130] The scanning electron microscope results of Comparative Examples 1 and 2 of this application are shown in Figure 3, where (a) is Comparative Example 1 and (b) is Comparative Example 2.

[0131] The scanning electron microscope (SEM) results and energy scattering spectroscopy (ESS) surface scan results of Comparative Example 2 of this application are shown in Figure 4, where (a) is the SEM image and EDS elemental distribution map, and (b) is the EDS elemental mass content map.

[0132] As shown in Example 1, Comparative Example 2, and Figure 1, a bilayer modified structure consisting of a titanium oxide layer and an organosilane layer was formed on the surface of the aluminum-lithium alloy powder. The organosilane layer was approximately 6 nm thick, and the titanium oxide layer was approximately 2.4 nm thick. The interfaces between the titanium oxide layer, the organosilane layer, and the aluminum-lithium powder were clear. The titanium oxide layer was continuous and dense, and the organosilane layer had a stable structure. Furthermore, the Ti, Al, and Si elements were uniformly distributed, demonstrating the uniformity of the titanium oxide layer and the organosilane layer.

[0133] As shown in Example 1, Comparative Examples 1-2, and Figure 2, the weight gain rate of Example 1 was 1.1% in the 32-hour hygroscopic oxidation performance test, the weight gain rate of Comparative Example 1 was 7%, and the weight gain rate of Comparative Example 2 was 6%. This demonstrates that the titanium oxide layer and the organosilane layer have a synergistic effect in reducing the hygroscopic oxidation rate of metal fuel powder, and neither can be omitted.

[0134] As can be seen from Comparative Example 2 and Figures 3-4, the morphology of the lithium aluminum oxide powder changed significantly before and after coating with titanium oxide. Before coating, the lithium aluminum oxide powder had a relatively rough morphology with obvious irregular protrusions, which were presumably natural oxidation products of the lithium aluminum oxide powder. After coating with titanium oxide, the surface of the lithium aluminum oxide powder became uniform and smooth, and the outline of the powder particles was clearer, proving that the atomic layer was deposited on the surface of the lithium aluminum oxide powder to form a continuous titanium oxide layer.

[0135] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0136] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A composite metal fuel powder, characterized in that, It includes metal fuel particles, a metal oxide layer, and an organosilane layer, wherein the metal oxide layer is located on the surface of the metal fuel particles, and the organosilane layer is located on the surface of the metal oxide layer; the organosilane layer includes organosilanes, and the organosilanes include hydrophobic hydrocarbon chains.

2. The composite metal fuel powder as described in claim 1, characterized in that, The hydrocarbon chain includes one or more of hydrocarbon groups with ≥8 carbon atoms and halohydrocarbon groups with ≥8 carbon atoms.

3. The composite metal fuel powder as described in claim 1, characterized in that, The organosilane includes an alkoxy group bonded to a silicon atom, and the alkoxy group includes one or more of ethoxy and methoxy groups, and the number of the alkoxy groups is 1 to 3.

4. The composite metal fuel powder as described in claim 1, characterized in that, The organosilanes include one or more of tridecafluorooctyltriethoxysilane, heptadecafluorooctyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, n-octyltri(trimethylsiloxy)silane, octadecyltrimethoxysilane, and n-dodecyltrimethoxysilane.

5. The composite metal fuel powder as described in claim 1, characterized in that, The following conditions must be met: (1) the mass content of the organosilane layer relative to the metal fuel particles is 0.05wt% to 3wt%; (2) the mass content of the metal oxide layer relative to the metal fuel particles is 0.1wt% to 5wt%.

6. The composite metal fuel powder as described in claim 1, characterized in that, The following conditions must be met: (1) the thickness of the metal oxide layer is 1 nm to 20 nm; (2) the thickness of the organosilane layer is 0.5 nm to 10 nm.

7. The composite metal fuel powder according to any one of claims 1 to 6, characterized in that, The metal oxide layer and the organosilane layer are connected by chemical bonds, including Si-O bonds.

8. The composite metal fuel powder according to any one of claims 1 to 6, characterized in that, The metal oxide layer includes one or more of aluminum oxide, titanium oxide, zirconium oxide, yttrium oxide, and zinc oxide.

9. The composite metal fuel powder according to any one of claims 1 to 6, characterized in that, The metal fuel particles include one or more of the following: aluminum hydride particles, aluminum particles, aluminum-lithium alloy particles, aluminum-magnesium alloy particles, aluminum-boron alloy particles, aluminum-zinc alloy particles, aluminum-zirconium alloy particles, aluminum-titanium alloy particles, aluminum-cerium alloy particles, aluminum-tungsten alloy particles, aluminum-nickel alloy particles, and aluminum-molybdenum alloy particles.

10. A method for preparing the composite metal fuel powder according to any one of claims 1 to 9, characterized in that, The process includes the following steps: depositing a metal oxide layer on the surface of the metal fuel particles to obtain metal fuel particles coated with the metal oxide layer; dissolving the organosilane in an organic solvent to form an organosilane solution; and mixing and reacting the metal fuel particles coated with the metal oxide layer and the organosilane in a solvent to obtain an organosilane layer on the surface of the metal oxide layer.

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