阅读说明：本技术 利用氟代烷基化合物改性铝粉以提高稳定性和燃烧性能的方法 (Method for improving stability and combustion performance by modifying aluminum powder with fluoroalkyl compound ) 是由 张俊平 李凌霄 杨燕飞 李步成 于 2020-05-21 设计创作，主要内容包括：本发明提供了一种利用氟代烷基化合物改性铝粉以提高稳定性和燃烧性能的方法,是将铝粉超声分散于有机溶剂中,得到铝粉分散液；再向铝粉分散液中加入氟代烷基化合物,搅拌使氟代烷基化合物与铝粉表面的氧化铝发生化学反应,在铝粉表面形成致密的氟代烷基化合物包覆层；然后经抽滤、洗涤、真空干燥,即得氟代烷基化合物改性铝粉。本发明通过氟代烷基化合物与铝粉表面氧化铝的化学反应牢固键合于铝粉表面,形成致密的氟代烷基化合物包覆层,一方面通过氟代烷基链的疏水、疏油作用提高了铝粉在热水、热溶剂中的稳定性,一方面通过燃烧时氟代烷基链与氧化铝、铝粉的反应,提高了铝粉的燃烧性能。(The invention provides a method for improving stability and combustion performance by modifying aluminum powder with fluoroalkyl compounds, which is characterized in that aluminum powder is ultrasonically dispersed in an organic solvent to obtain an aluminum powder dispersion liquid; then adding a fluoroalkyl compound into the aluminum powder dispersion liquid, stirring to enable the fluoroalkyl compound to have a chemical reaction with aluminum oxide on the surface of the aluminum powder, and forming a compact fluoroalkyl compound coating layer on the surface of the aluminum powder; and then carrying out suction filtration, washing and vacuum drying to obtain the fluoroalkyl compound modified aluminum powder. According to the invention, the fluoroalkyl compound is firmly bonded on the surface of the aluminum powder through the chemical reaction of the aluminum oxide on the surface of the aluminum powder to form a compact fluoroalkyl compound coating layer, so that on one hand, the stability of the aluminum powder in hot water and a hot solvent is improved through the hydrophobic and oleophobic effects of the fluoroalkyl chain, and on the other hand, the combustion performance of the aluminum powder is improved through the reaction of the fluoroalkyl chain with the aluminum oxide and the aluminum powder during combustion.)

1. A method for modifying aluminum powder by utilizing fluoroalkyl compounds to improve stability and combustion performance comprises the steps of ultrasonically dispersing the aluminum powder in an organic solvent to obtain an aluminum powder dispersion liquid; then adding a fluoroalkyl compound into the aluminum powder dispersion liquid, stirring to enable the fluoroalkyl compound to have a chemical reaction with aluminum oxide on the surface of the aluminum powder, and forming a compact fluoroalkyl compound coating layer on the surface of the aluminum powder; and then carrying out suction filtration, washing and vacuum drying to obtain the fluoroalkyl compound modified aluminum powder.

2. The method of claim 1 for modifying aluminum powder with fluoroalkyl compounds to improve stability and flammability performance, wherein: the aluminum powder is micron aluminum powder and nano aluminum powder.

3. The method of claim 1 for modifying aluminum powder with fluoroalkyl compounds to improve stability and flammability performance, wherein: the solvent is one of n-hexane, n-octane, petroleum ether, toluene, ethanol and methanol.

4. The method of claim 1 for modifying aluminum powder with fluoroalkyl compounds to improve stability and flammability performance, wherein: the concentration of the aluminum powder dispersion is 1-15 wt.%.

5. The method of claim 1 for modifying aluminum powder with fluoroalkyl compounds to improve stability and flammability performance, wherein: the fluoroalkyl compound is at least one of perfluorooctanoic acid, perfluorodecanoic acid, perfluoropolyether carboxylic acid, perfluorododecanethiol, perfluorodecanethiol, perfluorodecyltrimethoxysilane, perfluorodecyltriethoxysilane, perfluorodecyltrichlorosilane, perfluorooctyltrimethoxysilane, perfluorooctyltriethoxysilane, perfluorooctyltrichlorosilane, perfluorooctylamine, and perfluorodecylamine.

6. The method of claim 1 for modifying aluminum powder with fluoroalkyl compounds to improve stability and flammability performance, wherein: the mass ratio of the aluminum powder to the fluoroalkyl compound is 1: 0.01-1: 0.1.

7. The method of claim 1 for modifying aluminum powder with fluoroalkyl compounds to improve stability and flammability performance, wherein: the stirring is carried out at normal temperature for 5-120 min.

8. The method of claim 1 for modifying aluminum powder with fluoroalkyl compounds to improve stability and flammability performance, wherein: the content of the fluoroalkyl compound in the obtained modified aluminum powder is 1-10 wt.%.

Technical Field

The invention relates to an aluminum powder modification method, in particular to a method for improving the stability and the combustion performance of aluminum powder by modifying the aluminum powder with fluoroalkyl compounds, belonging to the technical field of energetic materials.

Background

The aluminum powder is used as a common energetic material component, and has high energy density, high combustion heat and high activity, so that the aluminum powder is widely applied to the fields of solid propellants, explosives, thermites and the like to improve the density specific impulse and combustion temperature of the propellants, the detonation heat, the detonation temperature, the work doing capability and the like of the explosives. Because the micro/nano aluminum powder has higher surface energy, the micro/nano aluminum powder can easily react with oxygen in the air at normal temperature and normal pressure to form a compact and corrosion-resistant inert oxidation film. Although the inert oxide film prevents the aluminum powder from being further oxidized and plays a certain role in protecting the internal aluminum powder, the activity of the aluminum powder is reduced, the energy release rate is slowed down, and the use of the aluminum powder in a propellant or an explosive is seriously influenced.

Researches show that the core-shell structure is constructed by coating the surface of the micro/nano aluminum powder, so that the core-shell structure can not only block air and keep the activity of the aluminum powder, but also modify the surface of the aluminum powder. CN103772078A discloses a preparation method of energetic polymer surface modified aluminum powder, and the modified aluminum powder improves the surface hydrophobicity, mechanical property and high-temperature reactivity. CN108687340B discloses a method for improving the high-temperature thermal reaction performance of aluminum powder by surface modification, which improves the high-temperature oxidation rate, heat release rate and high-temperature oxidation combustion performance of the aluminum powder. CN110550990A discloses a preparation method of high-activity aluminum powder/silicon powder coated with polymeric tannic acid, which can effectively protect the activity of the aluminum powder or the silicon powder, can provide additional combustion heat, and promotes the rapid combustion reaction of the aluminum powder or the silicon powder, thereby improving the combustion performance of a solid propellant. CN109704896A provides a modified aluminum powder based on a polydopamine interface regulated nitramine explosive and a preparation method thereof, so as to improve the energy and density of aluminum-containing explosives. However, the assembly and the forming of the aluminum-containing explosive are usually completed under the conditions of hot water and hot solvent. Although the invention improves the reactivity of the aluminum powder in the propellant and the explosive, the invention can not resist the oxidative corrosion of hot water and hot solvent to the modified aluminum powder in the assembling and forming processes of the aluminum-containing explosive, and obviously can not meet the requirements of the actual assembling and forming processes of the aluminum-containing explosive.

Disclosure of Invention

The invention aims to provide a method for improving the stability and the combustion performance of aluminum powder by utilizing surface modification of a fluoroalkyl compound aiming at the defect that modified aluminum powder in the prior art cannot resist hot water and hot solvents, so that the stability of the aluminum powder in hot liquid can be improved, the combustion performance of the aluminum powder can be improved, and the method plays a vital role in assembly molding and practical application of aluminum-containing explosives, propellants and the like.

Preparation of modified aluminum powder

The invention relates to a method for modifying aluminum powder by utilizing a fluoroalkyl compound, in particular to a method for improving the stability and the combustion performance of the aluminum powder by utilizing the fluoroalkyl compound, which is to ultrasonically disperse the aluminum powder in an organic solvent to obtain an aluminum powder dispersion liquid; adding a fluoroalkyl compound into the aluminum powder dispersion liquid, stirring at normal temperature for 5-120 min, and enabling the fluoroalkyl compound to react with aluminum oxide on the surface of the aluminum powder to form a compact fluoroalkyl compound coating layer on the surface of the aluminum powder; and then carrying out suction filtration, washing and vacuum drying to obtain the fluoroalkyl compound modified aluminum powder.

Wherein the aluminum powder is micron aluminum powder and nano aluminum powder, and the organic solvent is one of n-hexane, n-octane, petroleum ether, toluene, ethanol and methanol; the concentration of the aluminum powder dispersion is 1-15 wt.%.

The fluoroalkyl compound is at least one of perfluorooctanoic acid, perfluorodecanoic acid, perfluoropolyether carboxylic acid, perfluorododecyl mercaptan, perfluorodecyl trimethoxy silane, perfluorodecyl triethoxy silane, perfluorodecyl trichlorosilane, perfluorooctyl trimethoxy silane, perfluorooctyl triethoxy silane, perfluorooctyl trichlorosilane, perfluorooctylamine and perfluorodecyl amine, and the mass ratio of the aluminum powder to the fluoroalkyl compound is 1: 0.01-1: 0.1.

The content of the fluoroalkyl compound in the obtained modified aluminum powder is 1-10 wt.%.

Secondly, testing the stability of the modified aluminum powder in hot liquid

In order to confirm that the modified aluminum powder prepared by the invention has excellent stability in hot water and hot organic solvents, the modified aluminum powder prepared by the invention is compared with unmodified aluminum powder.

FIG. 1 is a transmission electron microscope image of the perfluorooctyl trichlorosilane modified nano aluminum powder (upper) and unmodified aluminum powder (lower) of the invention. The transmission electron microscope photo shows that a compact coating layer is formed on the surface of the modified nano aluminum powder, which is beneficial to improving the stability of the aluminum powder in hot liquid.

FIG. 2 is a transmission electron microscope image of the perfluoropolyether carboxylic acid modified micron aluminum powder of the present invention. Transmission electron microscope photos show that a compact coating layer is formed on the surface of the modified micron aluminum powder, and the stability of the aluminum powder in hot liquid is favorably improved.

FIG. 3 is a comparison of the stability of perfluorodecyltrimethoxysilane modified nano aluminum powder of the present invention (left) and unmodified nano aluminum powder (right) in hot liquid. The result shows that no air bubble is generated in the process of heating the modified aluminum powder in the mixed solution of ethyl acetate and water at 70 ℃ for 1h, and then the modified aluminum powder is still placed in the solution for 10 days without obvious change. And the unmodified aluminum powder is heated in a mixed solution of ethyl acetate and water at 70 ℃ for 10 min, hydrogen is obviously generated, and after 1h, the aluminum powder reacts with the solvent to turn white, so that the aluminum hydroxide is generated. Therefore, the modified aluminum powder can effectively improve the stability of the aluminum powder in the hot ethyl acetate/water mixed solution.

The experiments show that the modified aluminum powder prepared by the invention has excellent oxidation resistance. Can be stably stored in the air for more than 5 years; can stably exist in hot water at 70 ℃ and a hot organic solvent for more than 4 hours, has no hydrogen release, and can meet the assembly and forming process conditions of most aluminum powder.

Thirdly, the combustion performance of the modified aluminum powder

In order to confirm that the modified aluminum powder prepared by the invention has excellent combustion performance, the ignition speed and ignition time delay test is carried out on the modified aluminum powder. Through comparison, the initial micron aluminum powder is not ignited, and the burning rate of the modified micron aluminum powder is increased to 100-120 cm ms^-1Ignition delay is 50 ms; the burning rates before and after the modification of the nano aluminum powder are respectively 150 and 700-740 cm ms^-1The ignition delay is 150 ms and 25 ms respectively. Therefore, the modified aluminum powder prepared by the method obviously improves the combustion performance of micro-nano aluminum powder.

In summary, compared with the prior art, the invention has the following beneficial effects:

1. according to the invention, the fluoroalkyl compound is added into the aluminum powder dispersion liquid, then the mixture is stirred and reacts at normal temperature, and is firmly bonded to the surface of the aluminum powder through the chemical reaction of the fluoroalkyl compound and aluminum oxide on the surface of the aluminum powder to form a compact fluoroalkyl compound coating layer, so that on one hand, the stability of the aluminum powder in hot liquid is improved through the hydrophobic and oleophobic effects of the fluoroalkyl chain, on the other hand, the combustion performance of the aluminum powder is improved through the reaction of the fluoroalkyl chain with the aluminum oxide and the aluminum powder during combustion, the detonation performance of an explosive can be improved, and a technical support is provided for the practical application of the aluminum powder in an energetic material;

2. the compact coating layer formed by adopting the fluoroalkyl compound has higher long-term stability, can improve the surface electrical property of aluminum powder particles, is favorable for preventing agglomeration among the particles and improves the dispersion suspension property;

3. compared with preparation methods such as laser, electric arc, vapor deposition and the like, the method has the advantages of low equipment requirement, simplicity, easiness in operation, low cost, easiness in large-scale production and the like, and provides an aluminum powder modification technical approach which is easy to industrialize for assembly forming and practical application of aluminum-containing explosives, propellants and the like.

Drawings

FIG. 1 is a transmission electron microscope image of the perfluorooctyl trichlorosilane modified nano aluminum powder (upper) and unmodified aluminum powder (lower) of the invention.

FIG. 2 is a transmission electron microscope image of the perfluoropolyether carboxylic acid modified micron aluminum powder of the present invention.

FIG. 3 is a comparison of the stability of perfluorodecyltrimethoxysilane modified nano aluminum powder and unmodified nano aluminum powder in hot liquid.

Detailed Description

The preparation method and properties of the modified aluminum powder of the present invention are further illustrated by the following specific examples.