A method for increasing the combustion pressure of Al / MoO 3 nanothermite

Abstract

The invention discloses a method for improving the combustion pressure of Al / MoO3 nano-thermite. The method obtains two-dimensional flaky MoO3 metal oxide by a hydrothermal method. Then, the flaky MoO3 metal oxide is dispersed in a solution containing lanthanide metal elements by ultrasonic dispersion, heated to 70°C in a water bath, and a hydrogen peroxide (H2O2) aqueous solution is added dropwise. After sufficient stirring, the flaky MoO3 doped with lanthanide metal elements is obtained by suction filtration and drying. The Al / MoO3 aluminothermic system doped with lanthanide metal elements is prepared by ultrasonic dispersion. The preparation conditions of the invention are mild, the reaction process is simple, the preparation cost is low, and the invention is suitable for industrial production and batch preparation. Since the doping of lanthanide metal elements significantly changes the interface properties of MoO3, the solid-solid reaction temperature of the Al / MoO3 aluminothermic system is reduced, the energy release rate of the aluminothermic system is accelerated, and the combustion pressure and the pressure increase rate thereof are significantly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of energetic materials, and relates to the regulation of the energy release rate of Al / MoO 3 nanothermite. Background Art

[0002] Energetic materials (EMs) are substances that store a large amount of chemical energy by themselves and can independently carry out chemical reactions under the excitation of external energy and output energy to do work externally in the form of combustion or explosion. The main body of the thermite composite is a mixture composed of metallic aluminum (Al) and metal or non-metal oxides (such as MoO 3 , CuO, Fe 2 O 3 , Co 3 O 4 , SiO 2 , etc.). When the components are stimulated by external energy (such as heat, mechanical action, etc.), they can undergo a violent redox reaction and release a large amount of heat, and the adiabatic reaction temperature can reach up to about 2800K at most. (S.H. Fischer, M.C. Grubelich. A survey of combustible metals, thermites, and intermetallics for pyrotechnic applications[C]. 32th AIAA / ASME / SAE / ASEE joint propulsion conference. 1996, 1-13.).

[0003] The combustion of thermite is ultimately a redox reaction between fuel and oxidant. Whether the mass transfer ability of the oxidant at the reaction interface can promote the efficient energy release of thermite has also received extensive attention from researchers at home and abroad. Defect construction, as a regulation strategy for the crystal form and electronic structure of the surface and interface of oxidants in recent years, has been applied to fields such as new energy and electrocatalysis. By realizing the construction of oxygen vacancies and doping with heterogeneous metal elements on the surface or boundary of metal oxides, the binding energy between metal and oxygen can be effectively reduced, thereby reducing the reaction temperature of the thermite system and increasing its energy release rate.

[0004] Lanthanide metal elements have significant advantages such as large atomic radius and many outer empty orbitals, and can be used as doping elements to improve the interface electronic structure of transition metal oxides. Taking Ce as an example, its outer electron structure is 4f15d16s2, which can easily achieve charge transfer. In addition, the advantage of a large atomic radius can make there be a large number of dislocations and lattice distortions on the surface of transition metal oxides, thereby enhancing the oxygen ion conductivity of transition metal oxides. Summary of the Invention

[0005] The object of the present invention is to provide a method for increasing the combustion pressure of an Al / MoO 3 nanothermite. This method uses lanthanide metal elements to dope molybdenum oxide, and applies the doped MoO 3 to the thermite system, thereby greatly increasing the combustion pressure of the Al / MoO 3 thermite system.

[0006] The technical solution for achieving the object of the present invention is as follows:

[0007] A method for increasing the combustion pressure of an Al / MoO 3 nanothermite, which is a preparation method for obtaining an Al / MoO3 nanothermite doped with lanthanide metal elements, and includes the following steps:

[0008] Step 1: Dissolve molybdenum powder in an aqueous solution of H 2 O 2 with a mass fraction of 30 wt%. After it is fully dissolved, stir it vigorously for 30 min. Transfer the above-mentioned clear solution to a polytetrafluoroethylene inner liner, and generate a molybdenum oxide suspension through a hydrothermal reaction. Finally, collect the product by high-speed centrifugation and dry it completely.

[0009] Preferably, the size of the molybdenum powder is 3 - 10 μm.

[0010] Preferably, the molar ratio of H 2 O 2 to molybdenum powder is not less than 1.

[0011] Preferably, the hydrothermal reaction time is 24 - 48 h.

[0012] Step 2: The MoO 3 containing lanthanide metal elements is obtained by wet doping. First, ultrasonically disperse the molybdenum oxide obtained in Step 1 and lanthanide metal nitrate in deionized water, then heat it in a water bath to 70 °C, and dropwise add the H 2 O 2 solution. After fully stirring the above mixture for 4 - 8 h, the MoO 3 doped with lanthanide metal elements can be obtained. (Such as MoO 3 @Ce, MoO 3 @La, MoO 3 @Sm, etc.).

[0013] Preferably, the lanthanide metal source is one of lanthanum nitrate, cerium nitrate, samarium nitrate, and ammonium cerium nitrate.

[0014] Preferably, the volume ratio of the H 2 O 2 solution to deionized water is 1:40.

[0015] Preferably, the water bath stirring time is 4 - 8h.

[0016] Step 3: The thermite doped with lanthanide metal elements is obtained by mechanical mixing. The thermite doped with lanthanide metal elements is obtained by mechanical mixing; Weigh the MoO doped with lanthanide metal elements obtained in Step 2 in proportion 3 and nano - aluminum powder according to the mass ratio of 1:2.5, ultrasonically disperse them in isopropanol, and finally stir, filter by suction, and dry to obtain the nano - thermite.

[0017] Preferably, the stirring time is 12 - 24h.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) In the prior art, in order to increase the combustion reaction pressure of the thermite system, most use additives with large gas production such as fluorine - containing compounds and carbon materials for simple physical mixing, which will reduce the energy density and component consistency of the thermite system to a certain extent. However, in this method, lanthanide metal elements are introduced into transition metal oxides (MoO 3 ) through wet doping. The product has high consistency and the doping amount is controllable. By improving lattice distortion and oxygen ion conductivity, the combustion reaction pressure of the thermite system can be simply and effectively increased; (2) This method proposes interface defects to increase the combustion reaction pressure of the thermite system, and the doping method is simple and efficient. In addition, this method also greatly reduces the thermal decomposition reaction temperature of the thermite system, making the energy release of the thermite faster. (3) This method can also achieve different crystal form transformations by controlling the doping amount, and further achieve the purpose of adjusting the burning rate of the thermite. Description of the Drawings

[0020] Figure 1 For the X - ray photoelectron spectroscopy diagrams of MoO 3 , MoO 3 @Sm, MoO 3 @La, MoO 3 @Ce.

[0021] Figure 2 For the scanning electron microscope diagram of nAl / MoO 3 @Ce in Example 1.

[0022] Figure 3 For the transmission electron microscope diagrams of MoO 3 and MoO 3 @Ce prepared in Example 1. Among them Figure 3 (a) is the transmission electron microscope diagram of MoO 3 , Figure 3 (b) is the transmission electron microscope diagram of MoO 3 @Ce.

[0023] Figure 4 To prepare nAl / MoO 3 and nAl / MoO 3 @Ce nanothermites for comparison of combustion pressure and pressure rise rate. Among them, Figure 4 (a) is the curve of the combustion pressure of nAl / MoO 3 changing with time, Figure 4 (b) is the curve of the combustion pressure of nAl / MoO 3 @Ce changing with time. Specific implementation mode

[0024] The present invention will be further described below through examples and drawings.

[0025] Example 1

[0026] 1.92 g of molybdenum powder is dissolved in 20 mL of an aqueous solution with a mass fraction of 30 wt% H 2 O 2 and stirred for 0.5 h. Then, a hydrothermal reaction is carried out at 160 °C for 48 h to obtain flaky MoO 3 ; 0.01 mol of flaky MoO 3 powder and 0.002 mol of cerium nitrate are dispersed in 40 ml of deionized water and ultrasonicated for 0.5 h. Then, the mixture is heated to 70 °C in a water bath, 1 mL of H 2 O 2 solution is added dropwise, and the mixture is stirred for 4 h, filtered, washed, and dried to obtain MoO 3 @Ce powder; finally, MoO 3 @Ce powder and nano-Al powder are ultrasonically treated for 30 min, stirred for 12 h, filtered, washed, and dried to obtain the Al / MoO 3 @Ce composite material.

[0027] Example 2

[0028] 1.92 g of molybdenum powder is dissolved in 20 mL of an aqueous solution with a mass fraction of 30 wt% H 2 O 2 and stirred for 0.5 h. Then, a hydrothermal reaction is carried out at 160 °C for 48 h to obtain flaky MoO 3 ; 0.01 mol of flaky MoO 3 powder and 0.002 mol of lanthanum nitrate are dispersed in 40 ml of deionized water and ultrasonicated for 0.5 h. Then, the mixture is heated to 70 °C in a water bath, 1 mL of H 2 O 2 solution is added dropwise, and the mixture is stirred for 4 h, filtered, washed, and dried to obtain MoO 3 @La powder; finally, MoO 3In @La powder and nano-Al powder, ultrasonic treatment for 30 min and stirring for 12 h were carried out. After filtration, washing, and drying, the Al / MoO 3 @La composite material was obtained.

[0029] Example 3

[0030] 1.92 g of molybdenum powder was dissolved in 20 mL of an aqueous solution with a mass fraction of 30 wt% H 2 O 2 and stirred for 0.5 h. Hydrothermal reaction was carried out at 160 °C for 48 h to obtain flaky MoO 3 ; 0.01 mol of flaky MoO 3 powder and 0.002 mol of samarium nitrate were dispersed in 40 ml of deionized water and ultrasonicated for 0.5 h. Then, the mixture was heated in a water bath to 70 °C, and 1 mL of H 2 O 2 solution was added dropwise, and the mixture was stirred for 4 h, filtered, washed, and dried to obtain MoO 3 @Sm powder; finally, in MoO 3 @Sm powder and nano-Al powder, ultrasonic treatment for 30 min and stirring for 12 h were carried out. After filtration, washing, and drying, the Al / MoO 3 @Sm composite material was obtained.

[0031] It can be seen from Figure 4 that after introducing lanthanide metal atoms into MoO 3 the pressure rise time and pressure rise rate of the nanothermite have been significantly improved.

Claims

1. A method for increasing the combustion pressure of Al / MoO 3 nanothermite It is characterized in that The method for obtaining Al / MoO 3 nanothermite includes the following specific steps: Step 1: Dissolve molybdenum powder in H 2 O 2 aqueous solution, stir vigorously after it is fully dissolved; transfer the above-mentioned clear solution to a container, generate a molybdenum oxide suspension through hydrothermal reaction; finally, collect the precipitate by high-speed centrifugation and dry it completely to obtain two-dimensional flaky MoO 3 ; Step 2: Obtain La-series metal element-containing MoO through wet doping 3 ; First, ultrasonically disperse the molybdenum oxide obtained in Step 1 and lanthanide metal nitrate in deionized water, then heat it to 70 °C in a water bath and add H 2 O 2 solution; After fully stirring the above mixture for 4 - 8 h, La-series metal element-doped MoO 3 can be obtained; The volume ratio of the H 2 O 2 solution to deionized water is 1:40; The lanthanide metal nitrate is lanthanum nitrate, cerium nitrate or samarium nitrate; Step 3: Obtain the thermite doped with lanthanide metal elements by mechanical mixing; Weigh the MoO doped with lanthanide metal elements obtained in Step 2 in proportion 3 and nano-aluminum powder are ultrasonically dispersed in isopropanol according to a mass ratio of 1:2.5, and finally, the nano-thermite can be obtained by stirring, suction filtration, and drying.

2. The method according to claim 1, It is characterized in that In step one, the particle size of the molybdenum powder is selected to be 1-10 μm, and the mass fraction of hydrogen peroxide is selected to be 30 wt%.

3. The method according to claim 1, It is characterized in that The time of vigorous stirring is 30 min and the speed is 500 revolutions per minute.

4. The method according to claim 1, It is characterized in that In step one, the container is a polytetrafluoroethylene inner liner.

5. The method according to claim 1, It is characterized in that The speed of high-speed centrifugation is 10,000 revolutions per minute.

6. The method according to claim 1, It is characterized in that In step one, the hydrothermal reaction temperature is 160-200 °C and the reaction time is more than 24 h.

7. The method according to claim 1, It is characterized in that In step three, during the preparation of the thermite, the ultrasonic dispersion time is not less than 30 min.

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