Al / (NH4) xFeFy metastable intermolecular compound and preparation method thereof

Abstract

The invention discloses an Al / (NH4) xFeFy metastable intermolecular compound and a preparation method of the Al / (NH4) xFeFy metastable intermolecular compound. The method comprises the following steps: firstly, preparing needle-shaped stacked microsphere (NH4) xFeFy by a solvothermal method, and then compounding nano aluminum powder (n-Al) with (NH4) xFeFy in an ultrasonic-assisted dispersion manner to form an Al / (NH4) xFeFy metastable intermolecular compound with good dispersity. (NH4) xFeFy is stimulated to release HF and NH3 gaseous products, the HF gaseous products etch a passivation layer, the NH3 gaseous products provide kinetic energy for fuel, a large number of hot spots are formed, and secondary combustion is triggered. And the combustion performance is explored through combustion experiments in an open environment and a closed environment. Compared with a typical Al / FeF3 metastable state intermolecular compound, Al / (NH4) xFeFy has the remarkable advantages of being low in reaction starting temperature, high in heat release enthalpy, large in flame area, high in F release capacity and the like, and the combustion efficiency of the aluminum powder is greatly improved. The Al / (NH4) xFeFy metastable intermolecular compound has great application value in the fields of gas generators, propellants and combustion bombs.

Description

Technical Field

[0001] The present invention relates to the field of micro-nano composite energetic materials, in particular to an Al / (NH4) x FeF y Metastable intermolecular complexes and methods for preparing the same. Background Art

[0002] Aluminum powder is the most common solid fuel. Due to its advantages such as high energy density, self-heating characteristics and high combustion enthalpy, it is used as an energetic additive in the fields of propellants, explosives and liquid fuels. With the nano-sizing of metal aluminum powder, its surface atomic exposure ratio increases, and highly reactive and highly active nanoparticles often obtain excellent ignition and combustion performance, and the combustion efficiency will be greatly improved. The reduction in size often causes the inactivation of a large number of active components. In addition, the sintering and agglomeration of nano-aluminum powder during the reaction process will lead to incomplete combustion of solid fuels and reduction of energy release performance. The presence of the passivation layer has a huge impact on the process that depends on diffusion reactions. Metastable intermolecular complexes are formed by adding solid oxidant components to aluminum powder. The preparation methods of various composite materials make the micro-nanoscale fuel and oxidant have good dispersion at the microscopic level, which makes the oxidation process of aluminum powder easier to achieve and makes the energy release of aluminum powder faster and more efficient.

[0003] The use of some new additives or oxidants will also greatly improve or regulate the combustion and energy release performance of aluminum powder. By introducing energetic metal organic frameworks into Al-based metastable molecular complexes, the metal oxides produced by the decomposition of EMOF react with the fuel, and the decomposition and etching reaction of EMOF produces a large amount of gas in the interface layer, avoiding sintering, and improving the heat release and combustion efficiency of the metastable molecular complex. The introduction of Si powder into Al / FeO can effectively regulate the energy release process. Al-Si alloys affect the transfer and diffusion of oxygen during the reaction process. Compared with pure aluminum powder, the ignition temperature of the energetic polymer GAP as a coating layer is also greatly reduced, and the ignition efficiency and combustion heat are greatly improved. Compared with the traditional Al / FeO oxidant, Al / FeNCN prepared with FeNCN as an oxidant shows a stronger combustion phenomenon and produces a large amount of gas.

[0004] Currently, in order to solve the problem that the passivation layer of nano-aluminum powder hinders mass transfer during the reaction, a more effective way is to use fluorinating agents, such as fluorinated polymers or metal fluorides, to pre-react with Al2O3 to cause the destruction of the passivation layer. The density and thermal conductivity of organic fluorides are often lower than those of metal oxides or metal fluorides. Metallic fluorides tend to have strong hygroscopicity and weak ability to release F. Therefore, it is an extremely effective method to improve the ignition and combustion performance and combustion efficiency of fuel aluminum powder by developing new fluorinating agents and additives. Summary of the invention

[0005] The object of the present invention is to provide an Al / (NH4) x FeF y Preparation method of metastable intermolecular complex. First, needle-stacked microspheres (NH4) were prepared by solvothermal method. x FeF y Fluorine-containing oxidant. Then, it is compounded with n-Al by ultrasound-assisted dispersion to form Al / (NH4) with good dispersion. x FeF y Metastable intermolecular complex. The use of the fluorine-containing oxidant significantly improves the combustion efficiency of n-Al.

[0006] The present invention synthesizes high entropy needle-shaped stacked microspheres (NH4) by a simple solvent thermal method x FeF y and combined with aluminum to form an Al / (NH4) x FeF y Metastable intermolecular complex. (NH4) x FeF y The gaseous products HCl and NH3 produced by thermal decomposition will destroy the passivation layer of aluminum powder, making the aluminum core more susceptible to contact with the oxidant. In addition, the high-temperature thermal expansion of the gas provides some kinetic energy for the combustibles, which helps the secondary combustion of the fuel. The research results also show that (NH4) x FeF y Compared with FeF3, it has a better F release ability. In general, (NH4) x FeF y It is an excellent fluorinating agent, which greatly improves the combustion performance of aluminum powder. Al / (NH4) x FeF y Metastable intermolecular complexes have great application value in the field of solid fuels.

[0007] The technical solution for achieving the purpose of the present invention is as follows:

[0008] A kind of Al / (NH4) x FeF yThe method for preparing a metastable intermolecular complex comprises the following steps:

[0009] Step 1, anhydrous FeCl3 is added to a mixed solution of glycerol and ethanol, and dissolved by heating in a water bath. Then, NH4F solid particles are added to the solution, and the solution is heated and stirred for a certain period of time, and then transferred to a high-temperature and high-pressure reactor to continue the reaction for a period of time.

[0010] Step 2: Separate the solid phase product after high temperature and high pressure reaction by high speed centrifuge, wash it with dispersant several times, and dry it to obtain product (NH4) x FeF y .

[0011] Step 3: Accurately weigh a certain mass of n-Al and (NH4) x FeF y In a container filled with 20 mL of anhydrous ethanol, ultrasonic dispersion was performed at a frequency of 40 kHz for 40 min and then dried to obtain Al / (NH4) x FeF y Metastable intermolecular complexes.

[0012] Furthermore, in step 1, anhydrous FeCl3 can be replaced by other metal chlorides, such as FeCl2 and CoCl2.

[0013] Furthermore, in step 1, the temperature of the water bath heating process is selected to be 40-60° C., and the time is 1-2 hours. After complete dissolution, the solution is transparent and blood red.

[0014] Furthermore, in step 1, the NH4F solid particles are continuously stirred for 1 to 2 hours, and after the color of the solution gradually changes from blood red to light yellow, the solution can be transferred to a high temperature and high pressure reactor.

[0015] Furthermore, in step 1, the liquid phase reaction (including water bath stirring and high temperature and high pressure reaction stage) needs to be magnetically stirred, and the stirring rate is 300 rpm.

[0016] Furthermore, in step 2, the centrifuge speed is 6000-10000 rpm, and the centrifugation time is 3-5 min.

[0017] Furthermore, in step 2, the washing solvents are ethanol and deionized water, and the washing is performed alternately.

[0018] Further, in step 2, the product obtained is a mixture of NH4FeF4 and (NH4)3FeF6, and (NH4) x FeF y Instead, where x takes the values ​​1 and 3, the corresponding y takes the values ​​3 and 6 respectively.

[0019] Furthermore, in step 3, during the ultrasonic dispersion process, pay attention to the water temperature in the ultrasonic equipment to prevent oxidation of n-Al at a higher temperature.

[0020] Furthermore, in step 3, the drying process is carried out in a vacuum oven at a drying temperature of 50 to 70°C.

[0021] The above preparation method can obtain Al / (NH4) x FeF y Metastable intermolecular complexes.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) Needle-stacked microspheres (NH4) prepared by solvothermal method x FeF y It has a unique micro-nanostructure and is easily decomposed into functional gaseous products such as HF and NH3 after heating. The former will etch the passivation layer, and the latter will provide kinetic energy for the fuel, forming a large number of hot spots and triggering secondary combustion. (2) Compared with the typical Al / FeF3 metastable intermolecular complex, Al / (NH4) x FeF y It has significant advantages such as lower reaction starting temperature, higher exothermic enthalpy, larger flame area and stronger F release ability, which greatly improves the combustion efficiency of aluminum powder.

[0024] The present invention will be further described below by way of examples and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 (NH4) x FeF y Preparation flow chart of .

[0026] Figure 2 (NH4) x FeF y Microscopic morphology of .

[0027] Figure 3 (NH4) x FeF y Comparison of XRD patterns with those of standard cards.

[0028] Figure 4 (NH4) x FeF y FTIR data curve collected at 27.3min during the programmed temperature rise process.

[0029] Figure 5 (NH4) x FeF ySchematic diagram of the combustion mechanism.

[0030] Figure 6 Al / FeF2 and Al / (NH4) x FeF y TG-DSC curve of . DETAILED DESCRIPTION

[0031] The present application is further described below in conjunction with the accompanying drawings.

[0032] Al / (NH4) x FeF y The preparation process of the metastable intermolecular complex includes the following steps:

[0033] Step 1, add 0.84g of anhydrous FeCl3 to the solution, heat in a water bath at 50°C and perform magnetic stirring to dissolve; then add 0.57g of NH4F solid particles to the container, continue heating and stirring; after complete dissolution, transfer the solution to a high-temperature and high-pressure reactor and react at 150°C; finally, centrifuge, wash and dry the obtained solid phase product to obtain (NH4) x FeF y .

[0034] Step 2: The obtained (NH4) x FeF y and n-Al were accurately weighed in a certain mass ratio and placed in a dispersant, a suspension was prepared by ultrasound-assisted dispersion, and the solvent was evaporated in an oven to finally obtain Al / (NH4) x FeF y Metastable intermolecular complexes.

[0035] Specifically, both the water bath heating and the high temperature and high pressure reactor reaction processes require magnetic stirring, and the stirring rate is 300 rpm.

[0036] Specifically, the solution components include ethanol and glycerol in a volume ratio of 1:1.

[0037] Specifically, the water bath time before adding NH4F solid is 1 to 2 hours. The specific time can be determined by observing the changes in the solution. For example, the solution after complete dissolution is clear and transparent blood red. At this time, NH4F solid can be added. Similarly, when the solution becomes clear and transparent light yellow, it can be transferred to the reactor for reaction.

[0038] Specifically, the solid phase product after the high temperature and high pressure reaction is centrifuged by a centrifuge at a rotation speed of 8000 rpm.

[0039] Specifically, the washing process requires alternating washing with anhydrous ethanol and deionized water for multiple times, followed by drying in a vacuum oven at 70°C.

[0040] Specifically, the ultrasonic-assisted dispersion time is 40 minutes. The liquid phase temperature needs to be controlled and ice cubes are used for cooling to prevent the n-Al from being oxidized prematurely due to excessive temperature.

[0041] Example 1

[0042] Step 1, add 0.84g of anhydrous FeCl3 to a mixed solution of 30mL of glycerol and ethanol, heat in a water bath at 50°C and stir magnetically for 2h to completely dissolve; then add 0.57g of NH4F solid particles to the container, continue heating and stirring for 1.5h; after complete dissolution, transfer the solution to a high-temperature and high-pressure reactor and react at 150°C for 12h; finally, centrifuge the obtained solid phase product at 8000rpm, wash it four times with anhydrous ethanol and deionized water alternately, and then dry it in a vacuum oven at 70°C for 12h to obtain (NH4) x FeF y .

[0043] Example 2

[0044] 50mg n-Al and 100mg (NH4) x FeF y Place in 20 mL of anhydrous ethanol, ultrasonically disperse for 40 min, and then place in a vacuum oven at 70 °C to evaporate the ethanol to prepare Al / (NH4) x FeF y Metastable intermolecular complexes.

[0045] Example 3

[0046] 100mg n-Al and 100mg (NH4) x FeF y Place in 20 mL of anhydrous ethanol, ultrasonically disperse for 40 min, and then place in a vacuum oven at 70 °C to evaporate the ethanol to prepare Al / (NH4) x FeF y -1.

[0047] Example 4

[0048] 200mg n-Al and 100mg (NH4) x FeF y Place in 20 mL of anhydrous ethanol, ultrasonically disperse for 40 min, and then place in a vacuum oven at 70 °C to evaporate the ethanol to prepare Al / (NH4) x FeF-2.

[0049] Figure 1 (NH4) x FeF y Preparation flow chart of Figure 2 As shown, the (NH4) having a needle-like stacked microsphere structure can be obtained by the steps described. x FeF y . Figure 3 (NH4) x FeF y The XRD test results show that the diffraction peaks correspond exactly to the standard card, and no other impurity peaks appear. Figure 4 (NH4) x FeF y The FTIR data curve during the programmed heating process shows that (NH4) x FeF y It has a strong F release ability. When stimulated by heat, it will release HF and NH3 gaseous products at a lower temperature. The former will etch the passivation layer, and the latter will provide kinetic energy for the fuel, forming a large number of hot spots and triggering secondary combustion (such as Figure 5 ), which improves the combustion efficiency of aluminum powder. Figure 6 Comparison of Al / FeF2 and Al / (NH4) x FeF y The reaction characteristics of Al / (NH4) x FeF y It has lower reaction starting temperature and pre-ignition temperature, and higher exothermic enthalpy.

[0050] The anhydrous FeCl3 in the present invention can be replaced by FeCl2 or CoCl2.

[0051] The above embodiments are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. Al / (NH4) x FeF y A method for preparing a metastable intermolecular complex, characterized in that: The following steps are involved: Step 1, adding anhydrous FeCl3 to a mixed solution of glycerol and ethanol, and dissolving it by heating in a water bath; then, adding NH4F solid particles to the solution, continuing to heat and stir for a certain period of time, and then transferring it to a high-temperature and high-pressure reactor to continue reacting for a period of time; Step 2: Separate the solid phase product after high temperature and high pressure reaction by high speed centrifuge, wash it with dispersant several times, and dry it to obtain product (NH4) x FeF y ; Step 3: Mix n-Al and (NH4) in a mass ratio of 1:

2. x FeF y Place it in a container filled with anhydrous ethanol, disperse it ultrasonically at a frequency of 40kHz for 40 minutes, and then dry it to obtain Al / (NH4) x FeF y Metastable intermolecular complexes.

2. The preparation method according to claim 1, characterized in that: In step 1, anhydrous FeCl3 can be replaced by other metal chlorides, FeCl2 or CoCl2.

3. The preparation method according to claim 1, characterized in that: In step 1, the volume ratio of glycerol to ethanol is 1:

1.

4. The preparation method according to claim 1, characterized in that: In step 1, the temperature of the water bath heating process is selected to be 40-60° C., and the time is 1-2 hours. After complete dissolution, the solution is transparent and blood red.

5. The preparation method according to claim 1, characterized in that: In step 1, the NH4F solid particles continue to be stirred for 1 to 2 hours. After the color of the solution gradually changes from blood red to light yellow, the solution is transferred to a high temperature and high pressure reaction. In step 1, the liquid phase reaction includes water bath stirring and high temperature and high pressure reaction stages, both of which require magnetic stirring at a stirring rate of 300 rpm.

6. The preparation method according to claim 1, characterized in that: In step 2, the centrifuge speed is 6000-10000 rpm, and the centrifugation time is 3-5 min; the washing solvent is ethanol and deionized water, and the washing is performed alternately.

7. The preparation method according to claim 1, characterized in that: In step 2, the product obtained is a mixture of NH4FeF4 and (NH4)3FeF6. x FeF y Instead, where x takes the values ​​1 and 3, the corresponding y takes the values ​​3 and 6 respectively.

8. The preparation method according to claim 1, characterized in that: In step 3, during the ultrasonic dispersion process, note that the temperature in the ultrasonic equipment is between 20 and 40°C.

9. The preparation method according to claim 1, characterized in that: In step 3, drying is carried out in a vacuum oven at a drying temperature of 50 to 70°C.

10. Al / (NH4) prepared according to the preparation method of claims 1-9 x FeF y Metastable intermolecular complexes.

Images