Boron-containing composite particle and preparation method thereof

Abstract

The invention relates to a boron-containing composite particle and a preparation method thereof. The boron-containing composite particle comprises hydrofluorinated amorphous boron, fluororubber and an oxidizing agent, according to the hydrofluorinated amorphous boron, amorphous boron is activated by adopting a hydrofluorination process; the boron-containing composite particles are prepared from the following raw materials in parts by weight: 100 parts of hydrofluorinated amorphous boron, 10-55 parts of an oxidizing agent and 3-8 parts of fluororubber, and fluorine and hydrogen are adsorbed on the surface of the hydrofluorinated amorphous boron by amorphous boron through a hydrofluorination process. It is determined through experiments that the explosion reaction complete rate of boron in the boron-containing composite particles reaches 80% or above, the combustion heat of the boron-containing composite particles is remarkably improved, and the combustion heat is not lower than 30 MJ / kg; and the boron-containing composite particles have the advantage of low sensitivity, and the mechanical sensitivity of the boron-containing composite particles is lower than 40%.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of explosive materials, and relates to a boron-containing composite particle and a preparation method thereof, which can be used as a high-energy combustible agent in composite explosives and composite propellants. BACKGROUND

[0002] Metal fuel is the main component and energy source of explosive, and its performance determines the damage ability of ammunition. The most commonly used fuel in explosive is aluminum (Al) and boron (B). Compared with Al, the heat value of complete combustion of B is higher, but B powder is difficult to burn completely. B has a very high melting and boiling point, and there is an initial oxidation layer of boron oxide (B2O3) on the surface. The melting point of B2O3 is low and the boiling point is high, which is difficult to evaporate. During combustion, it will melt into a liquid film on the surface of B particles, preventing B from contacting with external oxygen, making it difficult to ignite. Improving the complete combustion of B has been the persistent pursuit of explosive researchers. Making B burn completely through combustion-supporting technology is an important research direction.

[0003] According to literature analysis, domestic and foreign scholars have adopted various ways to improve the reaction completeness of boron. Among them, “Influence of Fluorine-containing Binder on Reaction Completeness of Boron Powder in Explosion Process” (Fireworks, Issue 5, 2022) uses a fluorine-containing binder to coat, and the oxidation rate of boron is increased to more than 43%. There is no standard method for testing the reaction rate of boron, and the test results between different methods differ greatly, but improving the reaction completeness of boron has always been a difficult problem in the industry.

[0004] The general theory in the industry believes that the reason for the low reaction completeness of boron is that it will melt into a liquid film on the surface of B particles during combustion, preventing B from contacting with external oxygen, making it difficult to ignite. From theoretical derivation, the amount-of-substance ratio of boron and aluminum reacting with oxygen is the same, both consuming 1.5 moles of oxygen per mole of boron or aluminum. However, due to the lower molecular weight of boron than aluminum, the oxygen consumption of unit mass of boron is much higher than that of aluminum. From the perspective of reaction kinetics, increasing the concentration of reaction oxygen can increase the reaction rate of boron. A large number of literature and patents report the use of oxidizing agents combined with boron to improve the reaction activity of boron, but the effect is very small. SUMMARY

[0005] In order to solve the above problems, the present application provides a boron-containing composite particle and a preparation method thereof. Amorphous boron is first activated, and then fluorine rubber is coated to form an energetic metal particle with an oxidizing agent, thereby improving the reaction completeness of boron.

[0006] The present application is based on a large amount of basic research, and it is believed that direct contact between boron and oxidizing agent will lead to secondary oxidation of boron, and the activation of boron will fail. If boron can be activated, maintained active, and maintained high concentration of boron reaction, it is inevitable to improve the reaction activity of boron, and the process also maintains the stability and safety of the material, preventing the oxidation and decomposition of the oxidizing agent to produce gas.

[0007] The method of the present application mainly includes the following four steps: The first step is to mechanically activate amorphous boron to remove the surface oxide layer, which is a very mature technology.

[0008] The second step is to coat fluorine. Due to the uncertainty of the form of amorphous boron, there are a large number of microcavities and microresistance after mechanical activation. After the activation of amorphous boron, the amorphous boron is placed in the fluorination solution for fluorination coating. The fluorination solution is composed of perfluoropolyether, pentafluoropropionic acid and sodium petroleum sulfonate. The molecular chain of perfluoropolyether is composed of carbon, fluorine and oxygen. Perfluoropolyether can provide fluorine atoms for the oxidation reaction of boron, and the oxidation product of fluorine and boron will not be coated on the surface of boron like oxidized boron. Perfluoropolyether has excellent chemical inertness and shows strong chemical inertness to most acids, bases and oxidizing agents. Even at high temperature, it can remain stable and not react with these corrosive chemicals. However, the bond energy of C-F bond in perfluoropolyether is about 485 kJ / mol, which is much larger than the bond energy of C-H bond (about 413 kJ / mol) and C-C bond (about 347.7 kJ / mol); the electronegativity difference of C-F bond is about 1.5, and the bond length is 1.35 Å, while the electronegativity difference of C-H bond is about 0.3, and the bond length is about 1.09 Å. The strong electron-withdrawing effect of fluorine atoms on the electron cloud of carbon atoms leads to the chemical bond polarity of C-F bond much larger than that of C-H bond. The volume of fluorine atom is also larger, which can tightly arrange around the carbon chain and form strong shielding effect on the main carbon chain. The physical and chemical properties of perfluoropolyether make it difficult to fully contact with boron and fluorination effect. In order to improve the effect of perfluoropolyether, the present application uses pentafluoropropionic acid and sodium petroleum sulfonate to modify perfluoropolyether. Pentafluoropropionic acid has a small molecular weight, which promotes the fluorination of boron. The disadvantage is that pentafluoropropionic acid is acidic and will react with boron to form boric acid, resulting in boron deactivation. After mixing perfluoropolyether and pentafluoropropionic acid, the concentration of pentafluoropropionic acid is reduced. The present application strictly controls the acidity of the fluorination solution to below the acidity threshold of amorphous boron reaction to form boric acid. The present application uses sodium petroleum sulfonate to open a reaction channel for boron and perfluoropolyether. On the one hand, the surfactant connects boron and pentafluoropropionic acid / perfluoropolyether mixed solution to form a reaction channel, and on the other hand, a large amount of perfluoropolyether reduces the concentration of pentafluoropropionic acid, reduces the acidity effect, and ensures the basic activity of boron.

[0009] The third step is hydrogen fluoride catalysis, filtering to remove fluorination liquid, and transferring into a high-pressure bottle. Through the physical action of high-pressure hydrogen, active hydrogen and fluorination liquid are adsorbed to the surface of boron. Hydrogenation treatment is adopted. Through the combustion of hydrogen, a higher temperature is provided for the reaction of boron, and a basic energy and temperature environment are provided for the boron-oxygen reaction. On the other hand, the process of hydrogenation does not increase the volume of the particles, but improves the energy density of the composite particles.

[0010] Finally, the hydrogen fluoride amorphous boron is prepared into composite particles with an oxidizing agent. A direct granulation process is adopted to dissolve fluororubber into ethyl acetate, add an oxidizing agent, mix, and then add hydrogen fluoride amorphous boron to prepare composite particles. It needs to be clear that the process cannot use high-temperature volatile solvents, and the system temperature cannot exceed 60℃, otherwise it will cause the dehydrogenation of activated amorphous boron.

[0011] Based on the above principles and design ideas, the present application is a kind of boron-containing composite particles and a preparation method thereof. The boron-containing composite particles include hydrogen fluoride amorphous boron, fluororubber and an oxidizing agent. The hydrogen fluoride amorphous boron is activated by hydrogen fluoride process. The boron-containing composite particles, by weight, are composed of 100 parts of hydrogen fluoride amorphous boron, 10-55 parts of an oxidizing agent and 3-8 parts of fluororubber. The hydrogen fluoride amorphous boron is obtained by adsorbing fluorine and hydrogen on the surface of amorphous boron through hydrogen fluoride process.

[0012] Further, the hydrogen fluoride process includes mechanical activation, fluorine infiltration coating and hydrogen fluoride catalysis, and the specific steps are as follows: (1) Mechanical activation: amorphous boron is activated by grinding under the immersion of anhydrous ethanol in a nitrogen atmosphere. After activation, it is washed with anhydrous ethanol. After washing, the excess anhydrous ethanol is removed by filtration and other means to obtain a mixture of amorphous boron and anhydrous ethanol particles. Drying is prohibited. (2) Fluorine infiltration coating: pour the mixture of mechanically activated amorphous boron and anhydrous ethanol into the fluorination liquid to ensure that the mixture particles are completely immersed in the fluorination liquid. The immersion time is not less than 24h. The fluorination liquid is composed of perfluoropolyether, pentafluoropropionic acid and sodium petroleum sulfonate, wherein perfluoropolyether is 100 parts, pentafluoropropionic acid is 4.8-6.6 parts and sodium petroleum sulfonate is 1 part.

[0013] (3) Hydrogen fluoride catalysis: filter to remove fluorination liquid, transfer into a high-pressure bottle, vacuum, then introduce hydrogen to normal pressure, vacuum again, then introduce hydrogen. The hydrogen pressure is not less than 1.0MPa, and the pressure holding time is not less than 72h. After releasing hydrogen, dry to obtain hydrogen fluoride amorphous boron.

[0014] Further, the preparation process of the boron-containing composite particles is as follows: (1) Dissolve fluororubber into ethyl acetate, add an oxidizing agent, mix, and then add hydrogen fluoride amorphous boron. (2) continue mixing under open condition, volatilize solvent, temperature 45-60 DEG C, until the drug slurry is thick slurry; (3) adopt sieving granulation or granulator granulation to prepare boron-containing composite particles.

[0015] Further, the fluorine rubber is a vinylidene fluoride-chlorotrifluoroethylene copolymer or a vinylidene fluoride-hexafluoropropylene copolymer, and the oxidant includes ammonium perchlorate, or other nitro compound oxidants, or a mixture of multiple oxidants.

[0016] The present application is only applicable to amorphous boron, and is not applicable to crystal boron.

[0017] The present application has the following advantages: The present application modifies the perfluoropolyether by using pentafluoropropionic acid and petroleum sulfonic acid sodium, the molecular weight of the pentafluoropropionic acid is small, which promotes the fluorination of boron, and the ratio of the perfluoropolyether, the pentafluoropropionic acid and the petroleum sulfonic acid sodium is determined by strict proportion control, the acidity of the fluorination liquid is controlled to be below the acidity threshold of the reaction of the amorphous boron and the boric acid, the petroleum sulfonic acid sodium opens a reaction channel for the boron and the perfluoropolyether, on one hand, the surfactant connects the boron and the pentafluoropropionic acid / perfluoropolyether mixed liquid to form a reaction channel, on the other hand, a large amount of the perfluoropolyether reduces the concentration of the pentafluoropropionic acid, reduces the acidic effect, and ensures the basic activity of the boron. The physical effect of the high-pressure hydrogen gas adsorbs the active hydrogen and the fluorination liquid to the surface of the boron. The hydrogenation treatment provides a high temperature for the reaction of the boron by the combustion of the hydrogen gas, provides a basic energy and temperature environment for the boron-oxygen reaction, and the process of the hydrogenation does not increase the volume of the particles, but improves the energy density of the composite particles.

[0018] Finally, through experiments, the complete rate of the explosion reaction of the boron in the boron-containing composite particles of the present application reaches more than 80%, the combustion heat of the boron-containing composite particles is significantly improved, and the combustion heat is not less than 30 MJ / kg; and the boron-containing composite particles have the advantage of low sensitivity, and the mechanical sensitivity of the boron-containing composite particles is less than 40%.

[0019] The present application will be described in detail below in combination with examples. DETAILED DESCRIPTION

[0020] The following examples facilitate better understanding of the present application, but do not limit the present application.

[0021] Examples

[0022] The present embodiment consists of the following raw materials by weight: 100 g of hydrogen-fluorinated amorphous boron, 25 g of oxidizing agent, and 8 g of fluorine rubber. The fluorination liquid consists of perfluoropolyether, pentafluoropropionic acid, and petroleum sulfonate sodium, wherein the perfluoropolyether is 100 g, the pentafluoropropionic acid is 6.6 g, and the petroleum sulfonate sodium is 1 g; the fluorine rubber is a vinylidene fluoride-chlorotrifluoroethylene copolymer, and the oxidizing agent is ammonium perchlorate.

[0023] Preparation process of hydrogen-fluorinated amorphous boron: (1) Mechanical activation: the amorphous boron is activated by grinding under the condition of nitrogen atmosphere and ethanol immersion, and then washed with anhydrous ethanol. After washing, the excess anhydrous ethanol is removed by filtration, and a mixture of amorphous boron and anhydrous ethanol is obtained. Drying is prohibited. (2) Fluorine infiltration coating: the mixture of amorphous boron and anhydrous ethanol after mechanical activation is poured into the fluorination liquid, and the mixture is ensured to be completely immersed in the fluorination liquid for not less than 24 hours. (3) Hydrogen-fluorine catalysis: the fluorination liquid is filtered and removed, and then transferred into a high-pressure bottle. After vacuumizing, hydrogen is introduced to normal pressure, and then vacuumized again. Hydrogen is introduced again, and the hydrogen pressure is not less than 1.0 MPa. The pressure maintaining time is not less than 72 hours. After releasing the hydrogen, the hydrogen-fluorinated amorphous boron is obtained by drying.

[0024] Preparation process of composite particles: (1) The fluorine rubber is dissolved in ethyl acetate, and the oxidizing agent is added. After mixing, the hydrogen-fluorinated amorphous boron is added. (2) The mixing is continued under the condition of opening, and the solvent is volatilized. The temperature is 45-60°C, and the slurry is thickened until the slurry is formed. (3) The boron-containing composite particles are prepared by sieving or using a granulator.

[0025] Embodiment

[0026] The present embodiment consists of the following raw materials by weight: 100 g of hydrogen-fluorinated amorphous boron, 25 g of oxidizing agent, and 8 g of fluorine rubber. The fluorination liquid consists of perfluoropolyether, pentafluoropropionic acid, and petroleum sulfonate sodium, wherein the perfluoropolyether is 100 g, the pentafluoropropionic acid is 6.6 g, and the petroleum sulfonate sodium is 1 g; the fluorine rubber is a vinylidene fluoride-chlorotrifluoroethylene copolymer, and the oxidizing agent is ammonium perchlorate.

[0027] The preparation process of hydrogen-fluorinated amorphous boron and the preparation process of composite particles in the present embodiment refer to those in Embodiment 1.

[0028] Embodiment

[0029] This example consists of 100 g of hydrogen-fluorinated amorphous boron, 55 g of oxidizer, and 8 g of fluorine rubber, by weight. The fluorination liquid consists of perfluoropolyether, pentafluoropropionic acid, and sodium petroleum sulfonate, wherein the perfluoropolyether is 100 g, the pentafluoropropionic acid is 6.6 g, and the sodium petroleum sulfonate is 1 g; the fluorine rubber is a vinylidene fluoride-hexafluoropropylene copolymer; and the oxidizer is RDX.

[0030] This example hydrogen-fluorinated amorphous boron preparation process and composite particle preparation process refer to Example 1.

[0031] Comparative Example 1 The ratio, hydrogen-fluorinated amorphous boron preparation process, and composite particle preparation process are the same as in Example 1, except that the fluorination liquid consists entirely of perfluoropolyether and does not include pentafluoropropionic acid or sodium petroleum sulfonate.

[0032] Comparative Example 2 The ratio, hydrogen-fluorinated amorphous boron preparation process, and composite particle preparation process are the same as in Example 1, except that the hydrogen-fluorinated amorphous boron preparation process only includes the first two steps and does not include the hydrogen-fluorine catalysis process.

[0033] Comparative Example 3 The ratio, hydrogen-fluorinated amorphous boron preparation process, and composite particle preparation process are the same as in Example 1, except that the hydrogen-fluorinated amorphous boron preparation process only includes mechanical activation and hydrogen-fluorine catalysis and does not include fluorine infiltration coating.

[0034] Performance Evaluation (1) Mechanical sensitivity: The friction sensitivity test was performed using the GJB772A-97 method 602.1 explosion probability method.

[0035] (2) Combustion heat test: The GJB5891.29-2006 method was used, with a quartz crucible as the container, an oxygen pressure of 2.8 MPa, and 2 L of distilled water.

[0036] (3) Explosion reaction completeness: The heat values of the boron-containing composite particles and the base material without boron when exploded in an oxygen environment were tested. During the heat value test of the boron-containing composite particles, 50 g of the sample was weighed, 30 g of TNT was added, the sample was pressed into a 30 mm diameter, 95% theoretical density pellet; the heat value test of the base material without boron was performed according to the ratio of Example 1, using alumina instead of amorphous boron to prepare the base material without boron, 50 g of the base material without boron was weighed, 30 g of TNT was added, and the sample was pressed into a 30 mm diameter, 95% theoretical density pellet. The explosion heat tester was used to test the explosion heat values of the two materials, with reference to the explosion heat test method in the "Measurement Method of Explosion Energy of Thermal-Pressure Explosives" (Chinese Journal of Explosives and Propellants, 2013, No. 2), in an oxygen environment at a pressure of 0.1 MPa.

[0037] The reaction complete rate (gamma) of boron in the boron-based composite material is: gamma = (Q1-Q0) / (QB*alpha) Wherein, Q1 is the calorific value of the boron-containing material Q0 is the calorific value of the material without boron QB is the theoretical calorific value of boron Alpha is the mass content of B Implementation effect

[0038] The performance test results of the inventive examples and the comparative examples are shown in Table 1 as follows: Table 1

[0039] Effect analysis of implementation: (1) From Example 1, the present application realizes that the explosion reaction complete rate of boron reaches more than 80%, significantly improves the combustion heat of the boron-based composite material, and reduces the sensitivity of the material, wherein the alpha value is 0.463.

[0040] (2) As can be seen from Comparative Example 1 and Comparative Example 1, the fluorination liquid composed of pentafluoropropionic acid and sodium petroleum sulfonate can significantly reduce the mechanical sensitivity of the material, improve the combustion heat value of boron, and at the same time improve the reaction complete rate of boron.

[0041] (3) As can be seen from Comparative Example 1 and Comparative Example 2, the hydrogen fluoride catalytic process can significantly reduce the mechanical sensitivity of the material, and improve the combustion heat value of boron.

[0042] (4) As can be seen from Comparative Example 1 and Comparative Example 3, the fluorine infiltration coating process can significantly reduce the mechanical sensitivity of the material, improve the combustion heat value of boron, and at the same time improve the reaction complete rate of boron.

[0043] The above is an example of the best embodiment of the present application, wherein the parts not described in detail are the common knowledge of ordinary skilled in the art. The protection scope of the present application is subject to the content of the claims, and any equivalent transformation based on the technical inspiration of the present application is also within the protection scope of the present application.

Claims

1. A method for producing a boron-containing composite particle, characterized by comprising: The method comprises the following steps: ​ Step 1, mechanically activating amorphous boron to remove the surface oxide layer; Step 2, infiltrating the mechanically activated amorphous boron into a fluorination liquid to perform fluorine coating, Step 3, after removing the fluorination liquid by filtration, performing high-pressure hydrogen catalytic treatment, through the physical action of high-pressure hydrogen, active hydrogen and the fluorination liquid are adsorbed to the surface of the boron, obtaining hydrogen-fluorinated amorphous boron; Step 4, using a granulation process to make the hydrogen-fluorinated amorphous boron into boron-containing composite particles.

2. The method for producing a boron-containing composite particle according to claim 1, characterized by, In the step 2, the fluorination liquid is obtained by modifying the perfluoropolyether with five-fluoropropionic acid and sodium petroleum sulfonate.

3. The method for producing a boron-containing composite particle according to claim 2, characterized by, In terms of weight, the perfluoropolyether is 100 parts, the five-fluoropropionic acid is 4.8-6.6 parts, and the sodium petroleum sulfonate is 1 part.

4. The method for producing a boron-containing composite particle according to claim 1, characterized by, The specific steps of the step 3 are as follows: After removing the fluorination liquid by filtration, the high-pressure bottle is transferred, vacuum is drawn, hydrogen is introduced to normal pressure, vacuum is drawn again, hydrogen is introduced, the hydrogen pressure is not less than 1.0 MPa, the pressure maintaining time is not less than 72 hours; after releasing the hydrogen, the hydrogen-fluorinated amorphous boron is obtained by drying.

5. The method for producing a boron-containing composite particle according to claim 1, characterized by, The specific steps of the step 4 are as follows: Step 4.1, dissolving the fluororubber into ethyl acetate, adding an oxidizing agent, mixing, and then adding the hydrogen-fluorinated amorphous boron; Step 4.2, continuing to mix under open conditions, volatilizing the solvent, the temperature is 45-60℃, until the slurry becomes thick slurry; Step 4.3, using sieving granulation or granulator granulation to prepare the boron-containing composite particles.

6. The method for producing a boron-containing composite particle according to claim 4, characterized by, In the step 4.1, the oxidizing agent includes any one or more of ammonium perchlorate and nitro compound oxidizing agents.

7. The method of producing a boron-containing composite particle according to claim 1, characterized by, In the step 4.1, in terms of weight, the hydrogen-fluorinated amorphous boron is 100 parts, the oxidizing agent is 10-55 parts by weight, and the fluororubber is 3-8 parts.

8. A boron-containing composite particle, characterized by comprising: Prepared by the method of any one of claims 1-7.

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