Boron-supported three-layer composite fuels of elemental metals and metal oxides and their preparation methods

Abstract

This invention provides a three-layer composite fuel consisting of boron-supported elemental metal and metal oxide, and its preparation method. The middle layer is an elemental Mo layer, and the surface layer is a dense NbOx or TiO2 thin film oxide layer. The NbOx or TiO2 thin film oxide layer can completely cover the elemental Mo layer. This invention uses atomic layer deposition (ALD) to deposit elemental Mo on the surface of boron particles to prepare a B@Mo composite material. To prevent oxidation of the surface Mo, an in-situ preparation method is used to deposit a dense NbOx or TiO2 thin film of a certain thickness on the Mo film surface via ALD. This NbOx and TiO2 film effectively isolates oxygen from the air, effectively preventing the oxidation of the Mo film. In the composite fuel, elemental Mo not only improves the combustion efficiency of boron particles but also effectively increases the heat release of the composite fuel. The NbOx and TiO2 films not only isolate oxygen but also have a catalytic effect, significantly improving the combustion performance of the composite fuel.

Description

Technical Field

[0001] This invention belongs to the field of high-energy fuel technology, and relates to boron fuel, specifically to a three-layer composite fuel consisting of boron-supported elemental metal and metal oxide, and its preparation method. Background Technology

[0002] Metallic fuels have long been a hot research topic in the field of propellants and explosives due to their high energy density and high heat release during combustion. For propulsion systems with limited volume, fuels with high energy density and high heat release during combustion are crucial. Metals also offer other advantages as fuels and fuel additives, such as reducing combustion instability, increasing combustion speed, reducing detonation sensitivity, and facilitating supply.

[0003] Boron (B) is an important metalloid in conventional solid propellants and blended fuels for space exploration due to its high calorific value (58.30 MJ / kg) and high volumetric calorific value (136.44 KJ / cm³). 3 Therefore, boron is considered a promising fuel. In terms of combustion, the melting and boiling points of Mg, Al, and B increase sequentially, and the difficulty of combustion also increases accordingly. Theoretically, B has always been considered the most attractive fuel. Despite its high energy content, B rarely realizes its potential in propulsion systems due to several factors that hinder its implementation. The high melting point of the boron oxide layer on the boron surface impedes its combustion. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a three-layer composite fuel consisting of boron-loaded elemental metal and metal oxide and a preparation method thereof, thereby solving the technical problem that the combustion performance of composite fuels in the prior art needs to be further improved.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A three-layer composite fuel consisting of boron-supported elemental metal and metal oxide, wherein the middle layer of the composite fuel is an elemental Mo layer.

[0007] The surface layer of the composite fuel is an NbOx thin film oxide layer, and the three-layer composite fuel of boron-supported elemental metal and metal oxide is a B@Mo@NbOx three-layer composite fuel.

[0008] Alternatively, if the surface layer of the composite fuel is a TiO2 thin film oxide layer, then the boron-supported metal element and metal oxide three-layer composite fuel is a B@Mo@TiO2 three-layer composite fuel.

[0009] The present invention also has the following technical features:

[0010] Preferably, the NbOx thin film oxide layer and the TiO2 thin film oxide layer can completely cover the elemental Mo layer.

[0011] Preferably, the thickness of the elemental Mo layer is 0.1–10 nm, and the thickness of the NbOx thin film or TiO2 thin film oxide layer is 2–5 nm.

[0012] Preferably, the oxidation exothermic peak temperature of the B@Mo@NbOx three-layer composite fuel and the B@Mo@TiO2 three-layer composite fuel is more than 110°C earlier than that of boron particles; the heat release of the B@Mo@NbOx three-layer composite fuel and the B@Mo@TiO2 three-layer composite fuel is increased by 4.3% to 9.7% compared with boron particles.

[0013] This invention also protects a method for preparing a boron-loaded three-layer composite fuel of elemental metal and metal oxide. The method first uses atomic layer deposition to load elemental Mo onto the surface of boron particles to form a Mo film, obtaining B@Mo fuel. Then, an in-situ preparation method is used to deposit a NbOx film or a TiO2 film on the Mo film surface of the B@Mo fuel using atomic layer deposition, to obtain the boron-loaded three-layer composite fuel B@Mo@NbOx or B@Mo@TiO2.

[0014] Preferably, in the B@Mo fuel preparation process, the pressure in the reaction chamber of the atomic layer deposition method is below 150 Pa; the temperature in the reaction chamber of the atomic layer deposition method is 200°C; in the NbOx thin film deposition process on the Mo film surface, the pressure in the reaction chamber of the atomic layer deposition method is below 150 Pa; the temperature in the reaction chamber of the atomic layer deposition method is 220°C; in the TiO2 thin film deposition process on the Mo film surface, the pressure in the reaction chamber of the atomic layer deposition method is below 150 Pa; the temperature in the reaction chamber of the atomic layer deposition method is 150°C.

[0015] Preferably, in the B@Mo fuel preparation process, the number of deposition cycles of atomic layer deposition is 1 to 20; in the process of depositing NbOx thin film on the Mo film surface, the number of deposition cycles of atomic layer deposition is 20 to 50; and in the process of depositing TiO2 thin film on the Mo film surface, the number of deposition cycles of atomic layer deposition is 20 to 50.

[0016] Specifically, the preparation method of the B@Mo fuel includes the following steps:

[0017] Step 101: Spread boron particles evenly on the sample stage, then place the sample stage in the reaction chamber of the atomic layer deposition equipment, use a mechanical pump to evacuate the reaction chamber to below 150 Pa, and set the temperature of the reaction chamber to 200 °C.

[0018] Step 102: Si2H6 is injected into the precursor storage. The carrier gas and the pneumatic valve of the mechanical pump are closed to bring the atomic layer deposition equipment to a quasi-static state. Then, the precursor in the precursor storage is injected into the reaction chamber for 30 seconds to allow the precursor to be saturated and adsorbed on the boron particles. After sufficient adsorption, the pneumatic valve of the mechanical pump is opened to remove excess precursor or physically adsorbed precursor from the reaction chamber for 25 seconds. Then, the carrier gas is started for purging for 25 seconds.

[0019] Step 103: MoF6 is injected into the precursor storage chamber. The pneumatic valves of the carrier gas and mechanical pump are closed, bringing the atomic layer deposition equipment to a near-static state. Then, the precursor from the precursor storage chamber is injected into the reaction chamber over 30 seconds, allowing MoF6 to fully react with Si2H6 adsorbed on the boron particles. After the reaction is complete, the pneumatic valve of the mechanical pump is opened to remove excess precursor or byproducts from the reaction chamber over 25 seconds. Then, the carrier gas is used for purging over 25 seconds. The carrier gas is high-purity argon or high-purity nitrogen.

[0020] Steps 104, 102, and 103 constitute one cycle of elemental Mo deposition. Repeating this process for multiple deposition cycles yields B@Mo fuel.

[0021] Specifically, the preparation method of the B@Mo@NbOx three-layer composite fuel includes the following steps:

[0022] Step 201: After the B@Mo fuel preparation is completed, keep the sample in situ, set the reaction chamber temperature of the atomic layer deposition equipment to 230°C, set the temperature of the niobium ethanol storage tank to 120°C, and set the carrier gas flow rate to 105 ml / min.

[0023] Step 202: Niobium ethanol vapor is introduced into the reaction chamber by carrier gas through bubbling, so that the niobium ethanol vapor molecules are adsorbed on the surface of B@Mo fuel. The introduction time is 60s. Then, the niobium ethanol physically adsorbed on the sample surface is blown off the sample surface for 60s.

[0024] Step 203: Inject water vapor into the reaction chamber to allow water molecules to fully react with niobium ethanol molecules chemically adsorbed on the surface of B@Mo fuel. The injection time is 60s. Then, excess water molecules and byproducts are blown away from the sample surface for 60s.

[0025] Steps 204, 202, and 203 are for NbO x One deposition cycle is repeated for multiple deposition cycles to obtain a B@Mo@NbOx three-layer composite fuel.

[0026] Specifically, the preparation method of the B@Mo@TiO2 three-layer composite fuel includes the following steps:

[0027] Step 301: After the B@Mo fuel preparation is completed, keep the sample in situ, set the reaction chamber temperature of the atomic layer deposition equipment to 150°C, set the temperature of the tetraisopropoxide titanium storage tank to 50°C, and set the carrier gas flow rate to 110 ml / min.

[0028] Step 302: Tetraisopropoxide vapor is introduced into the reaction chamber by bubbling with carrier gas, so that the tetraisopropoxide vapor molecules are adsorbed on the surface of B@Mo fuel. The introduction time is 60s. Then, the tetraisopropoxide vapor physically adsorbed on the sample surface is blown off the sample surface for 60s.

[0029] Step 303: Inject hydrogen peroxide vapor into the reaction chamber to allow H2O2 molecules to fully react with the tetraisopropoxide titanium molecules chemically adsorbed on the B@Mo surface. The injection time is 60s. Then, excess H2O2 molecules and byproducts are blown away from the sample surface for 60s.

[0030] Steps 304, 302, and 303 are for NbO x One deposition cycle is repeated for multiple deposition cycles to obtain a B@Mo@TiO2 three-layer composite fuel.

[0031] Compared with the prior art, the present invention has the following technical effects:

[0032] (I) This invention employs atomic layer deposition (ALD) to deposit elemental Mo on the surface of boron particles, preparing a B@Mo composite material. To prevent surface Mo oxidation, an in-situ preparation method is used to deposit a dense NbOx or TiO2 film with a certain thickness on the Mo film surface via ALD. This NbOx or TiO2 film effectively isolates oxygen from the air, effectively preventing the oxidation of the Mo film. In the composite fuel, elemental Mo not only improves the combustion efficiency of boron particles but also effectively increases the heat release of the composite fuel. Furthermore, the NbOx or TiO2 film not only isolates oxygen but also has a catalytic effect, significantly improving the combustion performance of the composite fuel.

[0033] (II) The sandwich-structured B@Mo@NbOx and B@Mo@TiO2 composite fuels prepared by this invention not only have excellent ignition and combustion performance, but also have improved heat release compared with boron raw materials.

[0034] The heat of combustion of B@Mo-5cy@TiO2-20cy and B@Mo-5cy@TiO2-20cy is increased by 4.3%-9.7% compared to boron feedstock.

[0035] (III) The thickness of the outer NbOx or TiO2 isolation layer prepared by the present invention is precisely controllable, and the film precision of the inner elemental Mo is also highly adjustable.

[0036] (IV) The preparation method adopted in this invention has high control precision and is easy to industrialize, showing good application prospects in the field of high-energy solid fuel modification.

[0037] (V) The preparation method of the present invention is simple, efficient, reproducible and low in cost; it has good application prospects. Attached Figure Description

[0038] Figure 1 This is a TEM image of boron particles.

[0039] Figure 2 This is a TEM image of B@Mo-5cy.

[0040] Figure 3 TEM image of B@Mo-5cy@TiO2-20cy.

[0041] Figure 4 XPS spectra of raw material B, B@Mo-5cy, and B@Mo-5cy@NbOx-25cy for B 1s, Mo 3d, O 1s, and Nb 3d: where a0 is raw material B, a1 is B@Mo-5cy, and a2 is B@Mo-5cy@NbOx-25cy.

[0042] Figure 5 XPS spectra of raw material B, B@Mo-5cy, and B@Mo-5cy@TiO2-20cy for B 1s, Mo 3d, O 1s, and Ti 2p: where a0 is raw material B, a1 is B@Mo-5cy, and a2 is B@Mo-5cy@TiO2-20cy.

[0043] Figure 6 DSC data for raw material B, B@NbOx-25cy, B@Mo-5cy, and B@Mo-5cy@NbOx-25cy.

[0044] Figure 7 DSC data for raw material B, B@TiO2-20cy, B@Mo-5cy, and B@Mo-5cy@TiO2-20cy.

[0045] Figure 8 The calorific value data for raw material B, B@Mo-5cy, B@NbOx-25cy, B@TiO2-20cy, B@Mo-5cy@TiO2-20cy and B@Mo-5cy@TiO2-20cy.

[0046] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0047] It should be noted that, unless otherwise specified, all materials and equipment used in this invention are those known in the art. For example, the atomic layer deposition equipment used is an atomic layer deposition equipment known in the prior art.

[0048] In this invention, boron particles refer to boron powder; the two are the same concept. The boron particles are amorphous boron particles and / or crystalline boron particles, with a particle size distribution ranging from micrometers to nanometers.

[0049] In this invention, B@Mo refers to the deposition of elemental Mo on boron particles using atomic layer deposition (ALD). B@Mo@NbOx refers to the deposition of a dense NbOx or TiO2 insulating layer with a certain thickness on the Mo film surface of the prepared B@Mo fuel using ALD in an in-situ preparation method.

[0050] In this invention, x = 2 in NbOx is preferred.

[0051] To improve the combustion performance of boron, B-Mg, B-Al, and B-Ni composites have shown good results. Therefore, it is speculated that B-Mo composites should also be effective, as elemental Mo possesses good electrical conductivity, easy ignition, and good thermal conductivity, and its combustion releases a significant amount of heat. However, elemental Mo is easily oxidized in air. Therefore, to isolate elemental Mo from oxygen in the air, a dense insulating layer on its surface is ideal. Niobium oxide and titanium oxide are good choices for dense insulating layers because, in addition to their dense structure, their oxides themselves have catalytic effects. In our previous studies, titanium oxide demonstrated excellent catalytic effects on the exothermic combustion of boron, significantly reducing the peak temperature of boron particle oxidation and significantly shortening its ignition delay time.

[0052] This invention employs atomic layer deposition (ALD) to deposit elemental Mo onto boron particles by injecting precursors in a quasi-static state, forming a B@Mo fuel coated with a Mo film. However, since the Mo film is easily oxidized, an in-situ preparation method is used to deposit a NbOx or TiO2 thin film with a certain thickness and a dense structure on the surface of the Mo film via ALD.

[0053] The NbOx and TiO2 films effectively isolate oxygen from the air, preventing the oxidation of the Mo film. In the composite fuel, elemental Mo not only improves the combustion efficiency of boron particles but also effectively increases the heat release of the composite fuel. The NbOx and TiO2 films not only isolate oxygen but also have a catalytic effect, significantly improving the combustion performance of the composite fuel. The sandwich-structured B@Mo@NbOx and B@Mo@TiO2 composite fuel prepared by this invention has a lower initial oxidation reaction temperature and a significantly improved heat of combustion, showing excellent application prospects.

[0054] In this invention, the intermediate elemental Mo serves to make the composite fuel easier to ignite and increase the heat release of the composite fuel. The surface NbOx or TiO2 layer isolates oxygen in the air, preventing the intermediate elemental Mo from being oxidized, and also has a catalytic effect during the combustion of the composite fuel.

[0055] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0056] Example 1:

[0057] This embodiment provides a method for preparing B@Mo fuel, wherein the B@Mo fuel is B@Mo-ncy, and the method is carried out according to the following steps:

[0058] Step 101: Spread boron powder evenly on the sample stage, then place the sample stage in the reaction chamber of the atomic layer deposition equipment. Use a mechanical pump to create a negative pressure in the reaction chamber at 100 Pa, and set the temperature of the reaction chamber to 200 °C. Pour Si₂H₆ into an adjustable precursor memory at a time of 2 seconds. This memory allows for precise control of the amount of precursor entering the chamber.

[0059] Step 102: Close the pneumatic valves of the carrier gas and mechanical pump to bring the atomic layer deposition equipment to a quasi-static state. Then, inject Si2H6 from the memory into the reaction chamber for 35 seconds to allow the precursor to be saturated and adsorbed on the boron particles. After sufficient adsorption, open the pneumatic valve of the main mechanical pump to remove excess precursor or physically adsorbed precursor from the reaction chamber for 25 seconds. Then, open the pneumatic valve of the auxiliary pump for another 25 seconds. Finally, start the carrier gas purging for 25 seconds.

[0060] Step 103: MoF6 is injected into an adjustable precursor storage device for 2 seconds. This device allows for precise control of the amount of precursor entering the device. The pneumatic valves of the carrier gas and mechanical pump are closed, bringing the atomic layer deposition equipment to a near-static state. The precursor from the storage device is then injected into the reaction chamber for 35 seconds, allowing the elemental metal precursor to fully react with the reducing agent adsorbed on the boron particles. After the reaction is complete, the pneumatic valve of the main mechanical pump is opened to remove excess precursor or byproducts from the reaction chamber for 25 seconds. Then, the pneumatic valve of the auxiliary pump is opened for another 25 seconds. Finally, the carrier gas is used for purging for 25 seconds.

[0061] Steps 104, 102, and 103 constitute one cycle of elemental Mo deposition. This cycle is repeated for five cycles to obtain the B@Mo-5cy sample.

[0062] Figure 1 The images show TEM images of boron particles. Under low magnification, the surface of the boron particles is clean, and under high magnification, the edges of the boron particles are intact and clean.

[0063] Figure 2 TEM image of B@Mo-5cy: Under low magnification electron microscope, there is a faintly dark film at the edge of the B@Mo-5cy sample. Under high magnification electron microscope, the film at the edge of the B@Mo-5cy sample is very clear, and the film thickness is less than 1 nm.

[0064] Example 2:

[0065] This embodiment provides a method for preparing a three-layer composite fuel consisting of boron-supported elemental metal and metal oxide. The three-layer composite fuel is B@Mo-5cy@NbOx-25cy. The method is carried out according to the following steps:

[0066] Step 201: After the B@Mo fuel preparation is completed, keep the sample in situ, set the reaction chamber temperature of the atomic layer deposition equipment to 230°C, set the niobium ethanol storage tank temperature to 120°C, and set the carrier gas flow rate to 105 ml / min.

[0067] Step 202: Niobium ethanol vapor is introduced into the reaction chamber by bubbling with carrier gas, so that the niobium ethanol vapor molecules are adsorbed on the B@Mo surface. The introduction time is 60s. Then, the niobium ethanol physically adsorbed on the sample surface is blown off the sample surface for 60s.

[0068] Step 203: Inject water vapor into the reaction chamber to allow water molecules to fully react with niobium ethanol molecules chemically adsorbed on the B@Mo surface. The injection time is 60s. Then, excess water molecules and byproducts are blown away from the sample surface for 60s.

[0069] Steps 204, 202, and 203 constitute one cycle of NbOx deposition. The number of repeated deposition cycles is 25, resulting in a B@Mo-5cy@NbOx-25cy three-layer composite fuel.

[0070] Example 3:

[0071] This embodiment provides a method for preparing a boron-supported three-layer composite fuel of elemental metal and metal oxide. The three-layer composite fuel is B@Mo-5cy@TiO2-20cy. The method is carried out according to the following steps:

[0072] Step 301: After the B@Mo fuel preparation is completed, keep the sample in situ, set the reaction chamber temperature of the atomic layer deposition equipment to 150°C, set the temperature of the tetraisopropoxide titanium storage tank to 50°C, and set the carrier gas flow rate to 110 ml / min.

[0073] Step 302: Tetraisopropoxide vapor is introduced into the reaction chamber by bubbling with carrier gas, so that the tetraisopropoxide vapor molecules are adsorbed on the B@Mo surface. The introduction time is 60s. Then, the tetraisopropoxide vapor physically adsorbed on the sample surface is blown off the sample surface for 60s.

[0074] Step 303: Inject hydrogen peroxide vapor into the reaction chamber to allow H2O2 molecules to fully react with the tetraisopropoxide titanium molecules chemically adsorbed on the B@Mo surface. The injection time is 60s. Then, excess H2O2 molecules and byproducts are blown away from the sample surface for 60s.

[0075] Steps 304, 302, and 303 constitute one cycle of TiO2 deposition. The number of repeated deposition cycles is 20 to obtain the B@Mo-5cy@TiO2-20cy three-layer composite fuel.

[0076] Figure 3 This is a TEM image of the B@Mo-5cy@TiO2-20cy composite fuel. Under low magnification, a thin film is clearly visible on the sample surface. Under high magnification, the film thickness is approximately 3 nm. Figure 2 Since the Mo film thickness is less than 1 nm, the TiO2 film thickness is slightly higher than 2 nm.

[0077] Figure 4XPS spectra of raw material B, B@Mo-5cy, and B@Mo-5cy@NbOx-25cy for B, Mo 3d, O 1s, and Nb 3d are shown below: a0 represents raw material B, a1 represents B@Mo-5cy, and a2 represents B@Mo-5cy@NbOx-25cy. The B 1s spectrum shows a decrease in peak intensity with the deposition of Mo and NbOx species. The Mo 3d peak indicates that almost no Mo signal is visible on B@Mo-5cy@NbOx-25cy, suggesting that the NbOx insulating layer completely covers the Mo, effectively isolating it from the air. The binding energy of raw material B and B@Mo-5cy in O 1s is 532.4 eV, attributed to oxygen adsorbed from the air in the sample. The binding energy of B@Mo-5cy@NbOx-25cy is 530.8 eV, attributed to lattice oxygen in NbOx. The Nb3d spectrum at 206.6 eV is assigned to Nb x+ .

[0078] Figure 5 XPS spectra of raw material B, B@Mo-5cy, and B@Mo-5cy@TiO2-20cy for B, Mo 3d, O 1s, and Ti 2p are shown below: a0 represents raw material B, a1 represents B@Mo-5cy, and a2 represents B@Mo-5cy@TiO2-20cy. The B 1s spectrum shows a decrease in peak intensity with the deposition of Mo and TiO2 species. The Mo 3d peak indicates that almost no Mo signal is visible on B@Mo-5cy@TiO2-20cy, suggesting that the TiO2 insulating layer completely covers the Mo, effectively isolating it from air. The binding energy of raw material B and B@Mo-5cy in O 1s is 532.4 eV, attributed to oxygen adsorbed from the air in the sample. The binding energy of B@Mo-5cy@TiO2-20cy is 530.8 eV, attributed to lattice oxygen in TiO2. The Ti 2p spectrum at 459.0 eV is attributed to Ti... 4+ .

[0079] Example 4:

[0080] This embodiment provides the TG-DSC test of B@Mo@NbOx and B@Mo@TiO2 composite fuels. Specifically, B@Mo@NbOx and B@Mo@TiO2 composite fuels are weighed into an alumina crucible, and the crucible is placed on the sample stage of the TG-DSC testing equipment. The instrument's heating rate is set to 10K / min, the test temperature range is room temperature to 900℃, and the test atmosphere is air. In this way, the TG and DSC curves of the composite boron fuels can be obtained.

[0081] Figure 6The images show the DSC data for raw material B, B@NbOx-25cy, B@Mo-5cy, and B@Mo-5cy@NbOx-25cy. The combustion exothermic peak temperature of the raw material is 660℃, B@NbOx-25cy is 575℃, B@Mo-5cy is 593℃, and B@Mo-5cy@NbOx-25cy is 550℃. The effect of B@Mo-5cy is relatively low because the Mo film on the surface is easily oxidized in air, resulting in a lower performance for this sample. However, B@Mo-5cy@NbOx-25cy shows better performance. This indicates that the NbOx isolation layer not only isolates oxygen from the air and prevents the oxidation of the intermediate Mo layer, but also has a catalytic effect, significantly reducing the combustion exothermic peak temperature of the boron powder.

[0082] Figure 7 The images show DSC data for raw material B, B@TiO2-20cy, B@Mo-5cy, and B@Mo-5cy@TiO2-20cy. The combustion exothermic peak temperature of the raw material is 660℃, B@TiO2-20cy is 563℃, B@Mo-5cy is 593℃, and B@Mo-5cy@TiO2-25cy is 547℃. The effect of B@Mo-5cy is relatively low because the Mo film on the surface is easily oxidized in air, resulting in a lower effect for this sample. However, B@Mo-5cy@TiO2-20cy shows better performance. This indicates that the TiO2 isolation layer not only isolates oxygen in the air and prevents the oxidation of the intermediate Mo layer, but also has a catalytic effect, significantly reducing the combustion exothermic peak temperature of boron powder.

[0083] Example 5:

[0084] This embodiment provides a test for the heat of combustion of B@Mo@NbOx and B@Mo@TiO2 composite fuel. Specifically, 100mg-200mg of B@Mo@NbOx and B@Mo@TiO2 composite fuel is weighed into a certain mass of lens paper, and the sample is completely wrapped with the lens paper and placed in the oxygen bomb crucible of the oxygen bomb calorimeter. The sample mass and the lens paper mass are entered, and the test begins.

[0085] Figure 8The calorific values ​​of raw material B, B@Mo-5cy, B@NbOx-25cy, B@TiO2-20cy, B@Mo-5cy@TiO2-20cy, and B@Mo-5cy@TiO2-20cy are as follows: B@Mo-5cy has a calorific value of 27.9 kJ / g, B@NbOx-25cy has a calorific value of 26.6 kJ / g, B@TiO2-20cy has a calorific value of 27.1 kJ / g, B@Mo-5cy@TiO2-20cy has a calorific value of 30.6 kJ / g, and B@Mo-5cy@TiO2-20cy has a calorific value of 29.1 kJ / g. It is noteworthy that the heat of combustion decreased after oxide deposition on B. This is because although oxides catalyze the combustion of boron particles and significantly reduce the peak temperature of combustion exotherm in the DSC curve, the oxides themselves are not combustible and do not release heat, thus reducing the effective energy-releasing component in the composite fuel, resulting in a decrease in the heat of combustion. The reason why the heat of combustion of B@Mo-5cy is the same as that of the feedstock is that Mo underwent partial oxidation, resulting in the formation of oxides on the Mo surface, and therefore the heat of combustion of B@Mo-5cy did not increase. By depositing isolation layers of NbOx and TiO2 on the surface of B@Mo-5cy in situ, the oxidation of Mo can be prevented. Therefore, the heat of combustion of B@Mo-5cy@TiO2-20cy and B@Mo-5cy@TiO2-20cy is improved compared to the B feedstock, by 4.3%-9.7%, respectively.

[0086] Compared with existing technologies, the B@Mo@NbOx and B@Mo@TiO2 composite fuels prepared by this invention have advantages such as good repeatability, environmental friendliness, and high combustion performance. The preparation process of this type of composite fuel, which involves depositing elemental metals on the surface of boron powder, is simple and convenient. The atomic layer deposition technique used in this experiment employs mild conditions, and the reagents used are all commonly available in laboratories. The sample preparation cost is low. The B@Mo@NbOx and B@Mo@TiO2 composite fuels of this invention are easy to prepare, have good repeatability, and are inexpensive, significantly reducing the preparation cost of boron powder-based fuels and showing great application potential.

Claims

1. A three-layer composite fuel consisting of boron-supported elemental metal and metal oxide, characterized in that, The intermediate layer of the composite fuel is a single-element Mo layer; The surface layer of the composite fuel is an NbOx thin film oxide layer, and the three-layer composite fuel of boron-supported metal element and metal oxide is a B@Mo@NbOx three-layer composite fuel. If the surface layer of the composite fuel is a TiO2 thin film oxide layer, then the boron-supported metal element and metal oxide three-layer composite fuel is a B@Mo@TiO2 three-layer composite fuel. The NbOx thin film oxide layer and TiO2 thin film oxide layer can completely cover the elemental Mo layer; In the NbOx mentioned above, x=2.

2. The boron-supported three-layer composite fuel of elemental metal and metal oxide as described in claim 1, characterized in that, The thickness of the elemental Mo layer is 0.1–10 nm, and the thickness of the NbOx thin film or TiO2 thin film oxide layer is 2–5 nm.

3. The boron-supported three-layer composite fuel of elemental metal and metal oxide as described in claim 1, characterized in that, The oxidation exothermic peak temperature of the B@Mo@NbOx three-layer composite fuel and the B@Mo@TiO2 three-layer composite fuel is more than 110°C earlier than that of boron particles; the heat release of the B@Mo@NbOx three-layer composite fuel and the B@Mo@TiO2 three-layer composite fuel is increased by 4.3% to 9.7% compared with boron particles.

4. A method for preparing a three-layer composite fuel of boron-supported elemental metal and metal oxide as described in any one of claims 1 to 3, characterized in that, This method first uses atomic layer deposition to load elemental Mo onto the surface of boron particles to form a Mo film, thus obtaining B@Mo fuel. Then, an in-situ preparation method is used to deposit a NbOx film or a TiO2 film on the Mo film surface of the B@Mo fuel using atomic layer deposition, thus obtaining a three-layer composite fuel of boron-loaded elemental metal and metal oxide, namely B@Mo@NbOx three-layer composite fuel or B@Mo@TiO2 three-layer composite fuel.

5. The method for preparing the boron-supported three-layer composite fuel of elemental metal and metal oxide as described in claim 4, characterized in that, In the B@Mo fuel preparation process, the pressure in the reaction chamber of the atomic layer deposition method is below 150 Pa; the temperature in the reaction chamber of the atomic layer deposition method is 200℃. In the NbOx thin film deposition process on the Mo film surface, the pressure in the reaction chamber of the atomic layer deposition method is below 150 Pa; the temperature in the reaction chamber of the atomic layer deposition method is 220℃. In the TiO2 thin film deposition process on the Mo film surface, the pressure in the reaction chamber of the atomic layer deposition method is below 150 Pa; the temperature in the reaction chamber of the atomic layer deposition method is 150℃.

6. The method for preparing the boron-supported three-layer composite fuel of elemental metal and metal oxide as described in claim 4, characterized in that, In the B@Mo fuel preparation process, the atomic layer deposition method has 1 to 20 deposition cycles; in the NbOx film deposition process on the Mo film surface, the atomic layer deposition method has 20 to 50 deposition cycles; in the TiO2 film deposition process on the Mo film surface, the atomic layer deposition method has 20 to 50 deposition cycles.

7. The method for preparing the boron-supported three-layer composite fuel of elemental metal and metal oxide as described in claim 4, characterized in that, The method for preparing the B@Mo fuel includes the following steps: Step 101: Spread boron particles evenly on the sample stage, then place the sample stage in the reaction chamber of the atomic layer deposition equipment, use a mechanical pump to evacuate the reaction chamber to below 150 Pa, and set the temperature of the reaction chamber to 200 °C. Step 102: Si2H6 is injected into the precursor memory, and the pneumatic valves of the carrier gas and mechanical pump are closed to bring the atomic layer deposition equipment to a quasi-static state. Then, the precursor in the precursor memory is injected into the reaction chamber for 30 seconds to allow the precursor to be saturated and adsorbed on the boron particles. After sufficient adsorption, the pneumatic valve of the mechanical pump is turned on to remove the excess precursor or physically adsorbed precursor from the reaction chamber for 25 seconds. Then, the carrier gas is turned on for 25 seconds to purge. Step 103: MoF6 is injected into the precursor storage, and the pneumatic valves of the carrier gas and mechanical pump are closed to bring the atomic layer deposition equipment to a quasi-static state. Then, the precursor in the precursor storage is injected into the reaction chamber for 30 seconds to allow MoF6 to fully react with Si2H6 adsorbed on the boron particles. After the reaction is complete, the pneumatic valve of the mechanical pump is turned on to remove excess precursor or byproducts from the reaction chamber for 25 seconds. Then, the carrier gas is turned on for 25 seconds. The carrier gas is high-purity argon or high-purity nitrogen. Steps 104, 102, and 103 constitute one cycle of elemental Mo deposition. Repeating this process for multiple deposition cycles yields B@Mo fuel.

8. The method for preparing the boron-supported three-layer composite fuel of elemental metal and metal oxide as described in claim 4, characterized in that, The preparation method of the B@Mo@NbOx three-layer composite fuel includes the following steps: Step 201: After the B@Mo fuel preparation is completed, keep the sample in situ and directly set the temperature of the reaction chamber of the atomic layer deposition equipment to 230°C, the temperature of the niobium ethanol storage tank to 120°C, and the carrier gas flow rate to 105 ml / min. Step 202: Niobium ethanol vapor is introduced into the reaction chamber by bubbling with carrier gas, so that the niobium ethanol vapor molecules are adsorbed on the surface of B@Mo fuel. The introduction time is 60s. Then, the niobium ethanol physically adsorbed on the sample surface is blown off the sample surface for 60s. Step 203: Inject water vapor into the reaction chamber to allow water molecules to fully react with niobium ethanol molecules chemically adsorbed on the surface of B@Mo fuel. The injection time is 60s. Then, blow away excess water molecules and byproducts from the sample surface for 60s. Steps 204, 202, and 203 are for NbO x One deposition cycle is repeated for multiple deposition cycles to obtain a B@Mo@NbOx three-layer composite fuel.

9. The method for preparing the boron-supported three-layer composite fuel of elemental metal and metal oxide as described in claim 4, characterized in that, The preparation method of the B@Mo@TiO2 three-layer composite fuel includes the following steps: Step 301: After the B@Mo fuel preparation is completed, keep the sample in situ and directly set the temperature of the reaction chamber of the atomic layer deposition equipment to 150°C, the temperature of the tetraisopropoxide titanium storage tank to 50°C, and the carrier gas flow rate to 110 ml / min. Step 302: Tetraisopropoxide vapor is introduced into the reaction chamber by bubbling with carrier gas, so that the tetraisopropoxide vapor molecules are adsorbed on the surface of B@Mo fuel. The introduction time is 60s. Then, the tetraisopropoxide vapor physically adsorbed on the sample surface is blown off the sample surface for 60s. Step 303: Inject hydrogen peroxide vapor into the reaction chamber to allow H2O2 molecules to fully react with the tetraisopropoxide titanium molecules chemically adsorbed on the B@Mo surface. The injection time is 60s. Then, the excess H2O2 molecules and byproducts are blown away from the sample surface for 60s. Steps 304, 302, and 303 constitute one cycle of TiO2 deposition. Repeating this process for multiple deposition cycles yields the B@Mo@TiO2 three-layer composite fuel.

Images