Composite thermite for forcible entry and preparation method thereof

Abstract

The invention relates to a composite thermite for forcible entry and a preparation method thereof. The composite thermite comprises an aluminothermic reaction agent; a fluxing agent; a binder; and a strong oxidant. Wherein the thermit reaction agent is mixed powder composed of fuel metal particles and metal oxide particles, and the surfaces of the fuel metal particles are subjected to coating modification treatment through a fluorine-containing polymer; in the composite thermite, the mass ratio of the thermite reaction agent is 40%-75%, the mass ratio of the fluxing agent is 2%-10%, the mass ratio of the binder is 5%-20%, and the mass ratio of the strong oxidant is 5%-30%. The composite thermite disclosed by the invention is prepared into a blocky or columnar structure through a compression molding process or a curing molding process, is used for forcible entry of metal or non-metal obstacles, improves the forcible entry performance, is high in medicament environment adaptability and good in use effect, and can be produced on a large scale.

Description

Technical Field

[0001] The present invention relates to a composite thermite, specifically a composite thermite for demolition, and belongs to the technical field of thermite demolition. The present invention also relates to a preparation method of the composite thermite. Background Art

[0002] The thermite reaction can release a large amount of heat and a certain amount of high-temperature molten slag, which can quickly melt metals or burn non-metallic organic materials, thereby achieving demolition. In the existing thermite demolition technology, the particle size of the commonly used thermite components is large. For example, aluminum powder mostly uses particles of dozens of micrometers in size. The reason is that after reducing the particle size of aluminum particles, the thermite reaction will become violent, making the reaction process uncontrollable. The problem with such a particle size design is that the effective contact area between the thermite reactants is very small, thereby affecting its energy output efficiency. Therefore, a large amount of thermite needs to be used during the demolition process to make up for the lack of heat.

[0003] Large aluminum or magnesium particles are prone to sintering and forming aggregates during the combustion process, resulting in incomplete combustion, thereby affecting the combustion performance. Therefore, the particle size can be reduced to promote complete reaction, or it can be modified so that sintering does not occur during the combustion process. Currently, there are many studies on the reaction characteristics of micro / nano thermites. The research results show that reducing the particle size of the reactants can significantly increase the reaction rate, the heat release of the reaction, and lower the ignition temperature. Therefore, reducing the particle size of the thermite components to improve the reaction characteristics is an effective method. Coating and modifying the surface of aluminum particles with fluorides to reduce the sintering and aggregation of aluminum particles has been widely studied. However, the application lags behind the research, especially for the application of large-dose composite thermites.

[0004] Fluorine-containing polymers can be used as binders in thermites and can also undergo redox reactions with active metals such as aluminum, releasing much more heat than traditional thermites. Recent research shows that the molten slag particles produced by thermites added with fluorine-containing polymers are smaller and the reaction is more complete. Compared with binders that do not participate in the reaction, the energy density of the reaction system of thermites added with fluorine-containing polymers is higher.

[0005] Common strong oxidants are generally nitrate substances, which contain a relatively high content of oxygen atoms and can undergo redox reactions with reducing substances under certain conditions, such as heating, friction, or impact. The oxidizing property of sulfate substances is slightly weaker than that of nitrate substances, but they also exhibit strong oxidizing properties at high temperatures. To a certain extent, thermite containing sulfates is more insensitive. Adding a strong oxidant to the composite thermite can effectively reduce the content of residual carbon substances, thereby increasing the fluidity of the slag. Moreover, the large amount of gas released by the thermal decomposition of the strong oxidant can also increase the gas production of the composite thermite, further promoting the flow of the slag. The good fluidity of the slag and strong gas production capacity are conducive to heat transfer, enabling the melting of metal obstacles or the burning of non-metal obstacles in a shorter time. Sulfate as an oxidant is insensitive to humid environments, so the composite thermite is not prone to spontaneous combustion during storage in the daily environment.

[0006] Related patent literature: CN108794283A discloses a composite thermite for destroying unexploded ordnance and its preparation method. The composite thermite for destroying unexploded ordnance includes the following components in parts by mass: 18.0 - 19.4 parts of aluminum powder, 17.7 - 19.1 parts of Fe3O4 powder, 8.2 - 8.9 parts of KNO3 powder, 22.5 - 24.2 parts of CuO powder, 17.7 - 19.2 parts of Cr2O3 powder, 7.5 - 14 parts of CaO powder, and 1.7 - 1.9 parts of magnesium powder. It is prepared by mixing aluminum powder, Fe2O3, KNO3, CuO, and Cr2O3, drying, then mixing with CaO powder, drying, cooling, and then mixing with magnesium powder.

[0007] The deficiencies of the above patent literature technology are as follows: (1) It does not have bonding properties and cannot be formed. A large amount of medicine is required during use, and the energy utilization rate is low; (2) The number of components is large, and it contains environmentally sensitive components KNO3 and CaO. In a humid environment, CaO will react with H2O to generate a large amount of heat, activating the thermite reaction, and there is a probability of spontaneous combustion.

[0008] The above technology does not give a specific guidance plan on how the present invention can improve the demolition performance and have good use effects. Summary of the Invention

[0009] The purpose of the present invention is to provide a composite thermite for demolition, which can improve the demolition performance, has good use effects, and can be mass-produced.

[0010] Therefore, the present invention also provides a preparation method for the composite thermite for demolition, which can mass-produce the composite thermite.

[0011] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0012] A composite thermite for demolition, in terms of its technical solution, the composite thermite has the following:

[0013] Thermite reaction agent;

[0014] Flux;

[0015] Binder;

[0016] Strong oxidizer;

[0017] Among them, the thermite reaction agent is a mixed powder composed of fuel metal particles and metal oxide particles. The surface of the fuel metal particles is coated and modified with a fluoropolymer (the fuel metal particles mentioned later are all particles coated and modified with a fluoropolymer on the surface); in the composite thermite, the mass ratio of the thermite reaction agent is 40% - 75%, the mass ratio of the flux is 2% - 10%, the mass ratio of the binder is 5% - 20%, and the mass ratio of the strong oxidizer is 5% - 30%.

[0018] In the above technical solution, a preferred technical solution may be that the equivalent ratio of the fuel metal particles to the metal oxide particles is (1 - 2):1,

[0019] The definition of this equivalent ratio is where m fuel and m oxide are the masses of the fuel metal particles and the metal oxide particles respectively, and act and st represent the actual mixing ratio conditions and the standard stoichiometric mixing ratio conditions respectively; theoretically, under the standard stoichiometric mixing ratio conditions, the fuel metal particles and the metal oxide particles just completely react.

[0020] The fuel metal particles are composed of one or two kinds of particles of aluminum and magnesium, and the mass ratio is arbitrary when the two kinds of particles are combined; the metal oxide particles are composed of one kind of particle or several kinds of particles of magnetite, iron oxide (ferric oxide), copper oxide, molybdenum trioxide, and manganese dioxide, and the mass ratio is arbitrary when several kinds of particles are combined.

[0021] The above fuel metal particles are spherical micron-sized powder coated and modified with fluoropolymer (fluorinated polymer) in the particle size range of 0.5 - 5 μm (the particle size is preferably 1 μm), the active content of the fuel metal before coating and modification is ≥ 95 wt%, and the active metal content after coating and modification is ≥ 75 wt%; the metal oxide particles are micro / nano-sized powder in the particle size range of 0.1 - 80 μm (the particle size is preferably 5 μm), and the purity of the metal oxide is ≥ 98%.

[0022] In the above technical solution, a preferred technical solution may further be that the method for coating and modifying the surface of the fuel metal particles with a fluorine-containing polymer is as follows: Pour 10 g of aluminum or magnesium micro-powder (the particle size can be 1 μm) into 30 - 33 mL of absolute ethanol. After ultrasonic dispersion to form a uniform suspension, while stirring, drop industrial polytetrafluoroethylene emulsion into the suspension at a rate of 2 - 3 mL / min. The mass percentage of polytetrafluoroethylene in the polytetrafluoroethylene emulsion is 57 - 63 wt%. After dropping 3 - 4 mL of the emulsion, filter the liquid from the metal particle suspension and dry it to remove ethanol, obtaining the fuel metal particles with a surface-coated modification. The flux is industrial fluorite powder, mainly composed of calcium fluoride powder with a mass percentage of 85% - 98% and silicon dioxide powder with a mass percentage of 2% - 15%. The above strong oxidant is composed of one or several powders of potassium sulfate, sodium sulfate, and calcium sulfate. When several powders are combined, their mass ratio is arbitrary. Among them, the water content of the strong oxidant should be ≤1%. The oxidizing property of the above strong oxidant is only for the high-temperature environment of the thermite reaction because sulfates only show strong oxidizing properties to combustible metal powders in high-temperature environments and do not show oxidizing properties at normal temperature.

[0023] In the above technical solution, a preferred technical solution may further be that the binder is a combination of a liquid adhesive and a curing agent. The liquid adhesive is composed of one or two of epoxy resin glue and phenolic resin glue. The liquid adhesive is preferably epoxy resin glue, and the binder preferably has a mass percentage of 20%. The mass ratio of the liquid adhesive to the curing agent is 1:1. The preparation method of the composite thermite for demolition includes the following steps:

[0024] S1. Coating and modifying the surface of the fuel metal particles;

[0025] S2. Obtaining the composite thermite powder:

[0026] Adopt a die pressing process. Mix the fuel metal (powder) particles, metal oxide (powder) particles, flux, and strong oxidant in the above proportions to obtain a mixed powder. Take 45 - 50 g of the mixed powder and add it to a (250 mL) ball mill tank for ball milling and mixing. Note that the ball mill tank needs to be symmetrically placed on the ball mill. Add 30 - 35 mL of ethanol dispersion liquid to the ball mill tank so that the dispersion liquid can completely wet the powder. Start the ball mill (add an appropriate amount of steel balls), and perform ball milling at a low speed of 100 - 200 revolutions per minute to fully mix the powder. The low-speed ball milling condition means giving low-energy impact to the mixed powder, not changing the microscopic morphology of the particles and achieving uniform mixing. The low-speed ball milling time is 3 - 5 minutes. Then collect the well-mixed powder and dry it in an oxygen-free environment at 50 - 70 °C for 12 - 36 hours to remove the ethanol dispersion liquid, obtaining the mixture, which is the composite thermite powder;

[0027] S3. Curing and forming the composite thermite

[0028] Pour liquid adhesive and curing agent into a container in sequence. After fully stirring for 1 - 2 minutes, pour in the composite thermite powder and continuously stir for 10 - 15 minutes until all the powder is evenly mixed with the liquid adhesive to obtain a mixed jelly-like substance. The mass ratio of the liquid adhesive, the curing agent, and the composite thermite is 1:(1 - 1.5):(18 - 20). Fill the mixed jelly-like substance into the device. If the viscosity of the jelly-like substance is too high, pressure needs to be applied for molding, and then it is left to cure statically. The curing time is 15 - 36 hours, and the specific time depends on the ambient temperature and the quality of the mixed jelly-like substance.

[0029] In the above technical solution, a preferred technical solution may also be that the binder is a solid binder, and the binder is a powder of a fluorine-containing polymer, which is composed of one or several powders of polytetrafluoroethylene, tetrafluoroethylene - hexafluoropropylene copolymer, polyvinylidene fluoride, and fluororubber; wherein, the particle size of the solid binder, i.e., the fluorine-containing polymer powder, is 4 - 25 μm, preferably 15 μm, and the solid binder is preferably polytetrafluoroethylene powder, and the mass ratio of the solid binder is preferably 5%. The preparation method of the composite thermite for demolition includes the following steps:

[0030] S1. Surface coating modification of fuel metal particles;

[0031] S2. Prepare the composite thermite powder:

[0032] Adopt a die pressing molding process. Add 45 - 50 g of each raw material, namely fuel metal (powder) particles, metal oxide (powder) particles, flux, solid binder, and strong oxidant, into a (250 mL) ball mill tank according to the above ratio for ball milling and mixing. Note that the ball mill tank needs to be symmetrically placed on the ball mill. Add 30 - 35 mL of ethanol dispersion liquid into the ball mill tank to ensure that the dispersion liquid can completely wet the powder. Start the ball mill (add an appropriate amount of steel balls), and carry out ball milling at a low speed of 100 - 200 revolutions per minute to fully mix the powder. The low-speed ball milling condition means applying low-energy impact to the mixed powder, without changing the microscopic morphology of the particles and achieving uniform mixing. The low-speed ball milling time is 3 - 5 minutes; then collect the mixed powder and dry it in an oxygen-free environment at 50 - 70 °C for 12 - 36 hours to remove the ethanol dispersion liquid and obtain the mixture, i.e., the composite thermite powder;

[0033] S3. Die pressing molding of the composite thermite powder:

[0034] Weigh a certain mass of the composite thermite powder and fill it into a mold (a container made of high-strength material) for powder die pressing molding; wherein, the shape of the formed composite thermite is related to the internal structure of the container, and the pressure required for the powder die pressing molding is 100 - 200 MPa, and the pressure is maintained for ≥1 minute during the pressing process.

[0035] During use, the composite thermite formed by the present invention and the mold are integrated and act together. The composite thermite is ignited and burned in the mold to achieve the demolition function.

[0036] It should be noted that all powders should be dried before weighing to ensure the effective mass of the powders. Specifically, the raw material powders can be dried at 65 - 75°C (using 70°C) for a time ≥ 6 hours, and then the raw material powders are weighed according to the ratio.

[0037] The present invention provides a composite thermite for demolition and its preparation method, belonging to the technical field of micro / nano energetic materials, and is used for demolishing metal or non-metal obstacles. The composite thermite is formed by mixing thermite reaction agents, fluxes, binders, and strong oxidants to form a composite powder, and then is prepared into a block or columnar structure through a die pressing forming process or a curing forming process. The present invention can be used for demolishing metal obstacles with a diameter not exceeding Φ8mm or a thickness not exceeding 6mm; it can be used for demolishing metal or non-metal obstacles with a diameter not exceeding Φ10mm or a thickness not exceeding 6mm; it can be used for demolishing metal or non-metal obstacles with a diameter not exceeding Φ16mm or a thickness not exceeding 10mm; it can be used for demolishing metal or non-metal obstacles with a diameter not exceeding Φ16mm or a thickness not exceeding 10mm; and so on. The preparation method has a simple process, is green and environmentally friendly, and the raw materials are all industrial products, which can be produced on a large scale.

[0038] In summary, the present invention provides a composite thermite for demolition and its preparation method. The composite thermite for demolition improves the demolition performance, the performance of the agent is stable in the daily storage environment, the use effect is good, and it can be produced on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is the SEM image of the micron aluminum powder particles coated with polytetrafluoroethylene in the present invention.

[0040] Figure 2 It is the SEM image of the unformed composite thermite powder after being uniformly mixed in the present invention.

[0041] Figure 3 It is the layout diagram before the composite thermite of the present invention perforates the 10mm thick Q235 steel plate.

[0042] Figure 4 It is the perforation process diagram of the composite thermite of the present invention for the 10mm thick Q235 steel plate.

[0043] Figure 5 It is the perforation diagram of the composite thermite of the present invention for the 10mm thick Q235 steel plate. DETAILED DESCRIPTION OF THE INVENTION

[0044] To make the object, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. Based on these embodiments, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present invention.

[0045] Example 1: As Figure 1 , Figure 2 , Figure 3 shown, Figure 1 is the SEM image of the micron aluminum powder particles coated with polytetrafluoroethylene in the present invention. Figure 2 is the SEM image of the unformed composite thermite powder after being mixed evenly in the present invention. Figure 3 is the perforation effect diagram of the composite thermite of the present invention on a 10 mm thick Q235 steel plate.

[0046] In the present invention, all powders should be dried before weighing to ensure the effective mass of the powders. Specifically, the raw material powders can be dried at 70 °C for a time ≥ 6 hours (8 hours are adopted), and then each raw material powder is weighed according to the ratio.

[0047] The composite thermite for demolition comprises: thermite reaction agent, flux, binder, and strong oxidant. Among them, the thermite reaction agent is a mixed powder composed of fuel metal particles and metal oxide particles. The surface of the fuel metal particles is coated and modified with a fluoropolymer (the fuel metal particles mentioned later are all particles coated and modified with a fluoropolymer on the surface); in the composite thermite, the mass ratio of the thermite reaction agent is 75%, the mass ratio of the flux is 5%, the mass ratio of the binder is 5%, and the mass ratio of the strong oxidant is 15%. The equivalent ratio of the above-mentioned fuel metal particles to metal oxide particles is 1.66:1. The fuel metal particles are aluminum powder, which is a spherical micron powder with a particle size of 1 μm. After coating and modification, the active content of the fuel metal is ≥ 75 wt%; the metal oxide particles are iron oxide powder, which is a micron powder with a particle size of 5 μm, and the purity of the metal oxide is ≥ 98%. The above-mentioned flux is industrial fluorite powder, which is composed of calcium fluoride powder with a mass ratio of 85% and silicon dioxide powder with a mass ratio of 15%. The above-mentioned strong oxidant is potassium sulfate powder. Among them, the water content of the strong oxidant should be ≤ 1%. The above-mentioned binder is a solid binder, and polytetrafluoroethylene powder is used; among them, the particle size of the solid binder, that is, the fluoropolymer powder, is 15 μm, and polytetrafluoroethylene powder is selected as the solid binder.

[0048] The preparation method of the composite thermite for demolition includes the following steps:

[0049] S1. Coating and modification of the surface of fuel metal particles:

[0050] The method for coating and modifying the surface of fuel metal particles with a fluorine-containing polymer is as follows: Pour 10 g of aluminum powder (micron powder particles with a particle size of 1 μm) into 30 mL of anhydrous ethanol. After ultrasonic dispersion for 30 min to form a suspension, then drop industrial polytetrafluoroethylene emulsion into the suspension at a rate of 2 mL / min while stirring. The mass fraction of polytetrafluoroethylene in the polytetrafluoroethylene emulsion is 60 wt%. After dropping 3 mL of the emulsion, filter the liquid from the metal particle suspension and dry it to remove ethanol (dispersion liquid), obtaining fuel metal particles with a surface-coated modification.

[0051] S2. Prepare the composite thermite powder:

[0052] Adopt a molding process. Weigh 16 g of spherical coated and modified micron aluminum powder with a particle size of 1 μm, 21.5 g of iron oxide powder with a particle size of 0.5 μm, 2.5 g of industrial fluorite powder, 2.5 g of polytetrafluoroethylene powder with a particle size of 15 μm, and 7.5 g of potassium sulfate powder. At this time, the equivalent ratio of fuel metal to metal oxide is approximately 1.66:1. After simple physical mixing of the powder (obtaining a mixed powder), take 50 g of the mixed powder and add it to a 250 mL ball milling tank of a planetary ball mill for ball milling and mixing. Two ball milling tanks are symmetrically placed on the planetary disk of the ball mill. Another 250 mL ball milling tank also needs to add 50 g of the mixed powder (with the same ratio). In each ball milling tank, add (pour) 30 mL of ethanol dispersion liquid and 400 g of stainless steel grinding balls to ensure that the dispersion liquid can fully wet the powder, and the volume of the powder does not exceed 1 / 2 of the volume of the ball milling tank. Finally, ensure that the total mass of each ball milling tank differs by no more than 50 g. Start the ball mill and perform ball milling at a low speed of 100 revolutions / min to fully mix the powder. The low-speed ball milling time is 3 min. Then collect the mixed powder, collect the mixture (mixed powder) into a beaker, and dry it in an oxygen-free environment at 60 °C (fill nitrogen in the drying oven). The drying time is 24 h to obtain a mixture, that is, the composite thermite powder.

[0053] S3. Molding of the composite thermite powder:

[0054] Pour the composite thermite powder obtained in step S2 into a cylindrical mold with a diameter of Φ20 mm for powder molding. The pressure required for the powder molding is 150 MPa, and the pressure holding time during the pressing process is 5 min. In this way, the powder is compacted into a dense block under a pressure of 150 MPa to obtain a molded composite thermite block. The block can be directly burned in the mold (device) and can be used for the demolition of metal obstacles with a diameter not exceeding Φ8 mm or a thickness not exceeding 10 mm.

[0055] Example 2: The composite thermite for demolition comprises: thermite reaction agent, flux, binder, and strong oxidizer. Among them, the thermite reaction agent is a mixed powder composed of fuel metal particles and metal oxide particles. The surface of the fuel metal particles is coated and modified with a fluoropolymer (hereinafter referred to as fuel metal particles, all of which are particles coated and modified with a fluoropolymer on the surface); in the said composite thermite, the mass ratio of the thermite reaction agent is 70%, the mass ratio of the flux is 5%, the mass ratio of the binder is 15%, and the balance is the strong oxidizer. The sum of the mass ratios of the thermite reaction agent, the flux, the binder, and the strong oxidizer is 100%. The equivalent ratio of the above-mentioned fuel metal particles to the metal oxide particles is about 1.81:1. The fuel metal particles are 13.5 g of aluminum powder, which is a coated and modified spherical micro-powder with a particle size of 1 μm. After coating, the active content of the fuel metal is ≥ 75 wt%. The metal oxide particles are composed of two (powder) particles, 6.5 g of iron oxide with a particle size of 0.5 μm and 15 g of copper oxide with a particle size of 5 μm. The purity of the metal oxide is ≥ 98%. The above-mentioned flux is 2.5 g of industrial fluorite powder, which is composed of calcium fluoride powder with a mass ratio of 85% and silicon dioxide powder with a mass ratio of 15%. The above-mentioned strong oxidizer is 5 g of calcium sulfate powder, among which the water content of the strong oxidizer is ≤ 1%. The above-mentioned binder is a solid binder, which is 7.5 g of tetrafluoroethylene-hexafluoropropylene copolymer powder with a particle size of 15 μm.

[0056] The preparation method of the said composite thermite for demolition comprises the following steps:

[0057] S1. Coating and modification of the surface of fuel metal particles: Refer to Example 1.

[0058] S2. Obtaining the composite thermite powder:

[0059] Using the compression molding process, weigh 13.5 g of spherical coated and modified micron aluminum powder with a particle size of 1 μm, 6.5 g of iron oxide powder with a particle size of 0.5 μm, 15 g of copper oxide powder with a particle size of 5 μm, 2.5 g of industrial fluorite powder, 7.5 g of tetrafluoroethylene-hexafluoropropylene copolymer powder with a particle size of 15 μm, and 5 g of calcium sulfate powder. After simple physical mixing, take 50 g of the mixed powder and add it to a 250 mL ball milling jar of a planetary ball mill for ball milling and mixing. Two ball milling jars are symmetrically placed on the planetary disk of the ball mill. Another 250 mL ball milling jar also needs to be added with 50 g of the mixed powder (with the same ratio). Pour 30 mL of ethanol dispersion and 400 g of stainless steel grinding balls into each ball milling jar to ensure that the dispersion can fully wet the powder, and the volume of the powder does not exceed 1 / 2 of the volume of the ball milling jar. Finally, ensure that the total mass of each ball milling jar differs by no more than 50 g. Turn on the ball mill and perform ball milling at a low speed of 100 revolutions per minute to fully mix the powder. The low-speed ball milling time is 3 minutes. Then collect the mixed powder, collect the mixture (mixed powder) into a beaker, and dry it in an oxygen-free environment at 60 °C (fill nitrogen in the drying oven). The drying time is 24 hours to obtain a mixture, that is, the composite thermite powder.

[0060] S3. Compression molding of the composite thermite powder:

[0061] Pour the composite thermite powder obtained in step S2 into a cylindrical mold with a diameter of Φ20 mm for powder compression molding. The pressure required for the powder compression molding is 150 MPa, and the pressure holding time during the pressing process is 5 minutes. In this way, the powder is compacted into a dense block under a pressure of 150 MPa to obtain a compression-molded composite thermite block. The block can be directly burned in the mold (device) and can be used for the demolition of metal or non-metal obstacles with a diameter not exceeding Φ10 mm or a thickness not exceeding 6 mm.

[0062] Example 3: The composite thermite for demolition comprises: thermite reaction agent, flux, binder, and strong oxidizer. Among them, the thermite reaction agent is a mixed powder composed of fuel metal particles and metal oxide particles, and the surface of the fuel metal particles is coated and modified with a fluoropolymer (hereinafter referred to as fuel metal particles, all of which are particles coated and modified with a fluoropolymer on the surface); in the said composite thermite, the mass ratio of the thermite reaction agent is 74%, the mass ratio of the flux is 5%, the mass ratio of the binder is 16%, and the balance is the strong oxidizer, and the sum of the mass ratios of the thermite reaction agent, the flux, the binder, and the strong oxidizer is 100%. The equivalent ratio of the above-mentioned fuel metal particles to the metal oxide particles is 1.56:1. The fuel metal particles are 15 g of aluminum powder, which is a spherical micron powder with a particle size of 1 μm, and the active content of the fuel metal is ≥90 wt%. The metal oxide particles are composed of two (powder) particles, 15 g of molybdenum trioxide with a particle size of 5 μm and 7 g of copper oxide with a particle size of 5 μm, and the purity of the metal oxide is ≥98%. The above-mentioned flux is 2.5 g of industrial fluorite powder, which is composed of 85% calcium fluoride powder and 15% silicon dioxide powder by mass. The above-mentioned strong oxidizer is 2.5 g of sodium sulfate powder, among which the water content of the strong oxidizer is ≤1%. The above-mentioned binder is a solid binder, which is 8 g of polytetrafluoroethylene powder with a particle size of 15 μm.

[0063] The preparation method of the said composite thermite for demolition comprises the following steps:

[0064] S1. Coating and modification of the surface of the fuel metal particles: Refer to Example 1.

[0065] S2. Obtaining the composite thermite powder:

[0066] Adopt the molding process. Weigh 15 g of spherical coated modified micron aluminum powder with a particle size of 1 μm, 15 g of molybdenum trioxide powder with a particle size of 5 μm, 7 g of copper oxide powder with a particle size of 5 μm, 2.5 g of industrial fluorite powder, 8 g of polytetrafluoroethylene powder with a particle size of 15 μm, and 2.5 g of sodium sulfate powder. After simple physical mixing, take 50 g of the mixed powder and add it to a 250 mL ball milling tank of a planetary ball mill for ball milling and mixing. Two ball milling tanks are symmetrically placed on the planetary disk of the ball mill. Another 250 mL ball milling tank also needs to be added with 50 g of the mixed powder (with the same ratio). Pour 30 mL of ethanol dispersion liquid and 400 g of stainless steel grinding balls into each ball milling tank to ensure that the dispersion liquid can completely wet the powder, and the volume of the powder does not exceed 1 / 2 of the volume of the ball milling tank. Finally, ensure that the total mass of each ball milling tank differs by no more than 50 g. Start the ball mill and perform ball milling at a low speed of 100 revolutions / min to fully mix the powder. The low-speed ball milling time is 3 min. Then collect the mixed powder, collect the mixture (mixed powder) into a beaker, and dry it in an oxygen-free environment at 60 °C (fill nitrogen in the drying oven). The drying time is 24 h to obtain a mixture, that is, the composite thermite powder body.

[0067] S3. Molding of the composite thermite powder body:

[0068] Pour the composite thermite powder body obtained in step S2 into a cylindrical mold with a diameter of Φ20 mm for powder molding. The pressure required for the powder molding is 150 MPa, and the pressure holding time during the pressing process is 5 min. In this way, the powder is compacted into a dense block under a pressure of 150 MPa to obtain a molded composite thermite block. The block can directly burn in the mold (device) and can be used for the demolition of metal or non-metal obstacles with a diameter not exceeding Φ16 mm or a thickness not exceeding 10 mm.

[0069] Example 4: The composite thermite for demolition comprises a thermite reaction agent, a flux, a binder, and a strong oxidizer. Among them, the thermite reaction agent is a mixed powder composed of fuel metal particles and metal oxide particles, and the surface of the fuel metal particles is coated and modified with a fluoropolymer (hereinafter referred to as fuel metal particles, all of which are particles coated and modified with a fluoropolymer on the surface); in the composite thermite, the mass ratio of the thermite reaction agent is 65%, the mass ratio of the flux is 5%, the mass ratio of the binder is 10%, and the balance is a strong oxidizer. The sum of the mass ratios of the thermite reaction agent, the flux, the binder, and the strong oxidizer is 100%. The above-mentioned binder is a combination of a liquid adhesive and a curing agent. The liquid adhesive is 2.5 g of epoxy resin glue (mucus), and the mass ratio of the liquid adhesive to the curing agent can be 1:1. The equivalent ratio of the above-mentioned fuel metal particles to the metal oxide particles is 1.90:1. The fuel metal particles are 16.5 g of magnesium powder, which is a coated and modified spherical micron powder with a particle size of 1 μm. After coating and modification, the active content of the fuel metal is ≥ 75 wt%. The metal oxide particles are composed of two (powder) particles of 8 g of molybdenum trioxide with a particle size of 5 μm and 8 g of copper oxide with a particle size of 5 μm. The purity of the metal oxide is ≥ 98%. The above-mentioned flux is 2.5 g of industrial fluorite powder, which is composed of 85% calcium fluoride powder and 15% silicon dioxide powder by mass. The above-mentioned strong oxidizer is 10 g of calcium sulfate powder, and the water content of the strong oxidizer is ≤ 1%.

[0070] The preparation method of the composite thermite for demolition described above comprises the following steps:

[0071] S1. Coating and modification of the surface of fuel metal particles: Refer to Example 1.

[0072] S2. Obtaining the composite thermite powder:

[0073] Adopt the molding process. Weigh 16.5 g of spherical coated modified micron magnesium powder with a particle size of 1 μm, 8 g of molybdenum trioxide powder with a particle size of 5 μm, 8 g of copper oxide powder with a particle size of 5 μm, 2.5 g of industrial fluorite powder, and 10 g of calcium sulfate powder with a particle size of 15 μm. After simple physical mixing, take 45 g of the mixed powder and add it to a 250 mL ball milling tank of a planetary ball mill for ball milling and mixing. Two ball milling tanks are symmetrically placed on the planetary disk of the ball mill. Another 250 mL ball milling tank also needs to be added with 45 g of the mixed powder (with the same ratio). Pour 30 mL of ethanol dispersion liquid and 400 g of stainless steel grinding balls into each ball milling tank to ensure that the dispersion liquid can fully wet the powder, and the volume of the powder does not exceed 1 / 2 of the volume of the ball milling tank. Finally, ensure that the total mass of each ball milling tank differs by no more than 50 g. Turn on the ball mill and perform ball milling at a low speed of 100 revolutions per minute to fully mix the powder. The low-speed ball milling time is 3 minutes. Then collect the mixed powder, collect the mixture (mixed powder) into a beaker, and dry it in an oxygen-free environment at 60 °C (fill nitrogen in the drying oven). The drying time is 24 hours to obtain a mixture, that is, the composite thermite powder.

[0074] S3. Curing and forming of the composite thermite:

[0075] Pour 2.5 g of epoxy resin glue (mucus) and 2.5 g of curing agent into a container (beaker) in sequence. After fully stirring for 1 minute without wire drawing phenomenon, pour in the composite thermite powder and continuously stir for 10 minutes (gradually pour the composite thermite powder into the glue mucus while stirring) until all the powder is evenly mixed with the liquid adhesive to obtain a mixed jelly-like substance. The mass ratio of the liquid adhesive, curing agent, and composite thermite is 1:1:18. The curing agent can use the original biuret curing agent 24A-100 sold on the market. Pour the obtained mixed jelly-like substance into a cylindrical mold with an inner diameter of Φ20 mm, apply a pressure of 20 MPa to eliminate voids through plastic deformation, and then let it stand for 18 hours for curing and forming to obtain a cured and formed composite thermite block. The combustion of this block in the device (mold) can be used for the demolition of metal or non-metal obstacles with a diameter not greater than Φ16 mm or a thickness not exceeding 10 mm.

[0076] From Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5As can be seen from Examples 1 to 4, the present invention can be used for the demolition of metal obstacles with a diameter not exceeding Φ8 mm or a thickness not exceeding 6 mm; it can be used for the demolition of metal or non-metal obstacles with a diameter not exceeding Φ10 mm or a thickness not exceeding 6 mm; it can be used for the demolition of metal or non-metal obstacles with a diameter not exceeding Φ16 mm or a thickness not exceeding 10 mm; it can be used for the demolition of metal or non-metal obstacles with a diameter not exceeding Φ16 mm or a thickness not exceeding 10 mm; and so on. From Figure 4 It can be seen that the volume ratio of the solid-phase product in the combustion process of the composite thermite is low, and the fluidity of the jet is good; from Figure 5 It can be seen that after the demolition of metal obstacles by the present invention, the remaining metal slag is easy to remove and will not form welding at the demolition site, which is conducive to smooth demolition.

[0077] In summary, the above embodiments of the present invention provide a composite thermite for demolition and its preparation method. The composite thermite for demolition improves the demolition performance, the performance of the agent is stable in the daily storage environment, the use effect is good, and it can be mass-produced.

Claims

1. A composite thermite for demolition, characterized in that, The composite thermite comprises: Thermite reaction agent; Flux; Binder; Strong oxidizer; Among them, the thermite reaction agent is a mixed powder composed of fuel metal particles and metal oxide particles, and the surface of the fuel metal particles is coated and modified by a fluoropolymer; in the composite thermite, the mass ratio of the thermite reaction agent is 40% - 75%, the mass ratio of the flux is 2% - 10%, the mass ratio of the binder is 5% - 20%, and the mass ratio of the strong oxidizer is 5% - 30%.

2. The composite thermite for demolition according to claim 1, characterized in that, In the above aluminothermic reaction agent, the equivalent ratio of the fuel metal particles to the metal oxide particles is (1-2):1, and the definition of this equivalent ratio is where m fuel and m oxide are the masses of the fuel metal particles and the metal oxide particles respectively, and act and st represent the actual mixing conditions and the standard stoichiometric mixing conditions; theoretically, under the standard stoichiometric mixing conditions, the fuel metal particles and the metal oxide particles just completely react; The fuel metal particles are composed of one or two kinds of particles of aluminum and magnesium, and the mass ratio is arbitrary when the two kinds of particles are combined; The metal oxide particles are composed of one or several kinds of particles of iron tetroxide, iron oxide, copper oxide, molybdenum trioxide, and manganese dioxide, and the mass ratio is arbitrary when several kinds of particles are combined.

3. The composite thermite for demolition according to claim 1, characterized in that, The above fuel metal particles are spherical micro-powder with a particle size range of 0.5 - 5μm and coated and modified by fluoropolymer. The active content of the fuel metal before coating is ≥95wt%, and the active metal content after coating and modification is ≥75wt%; the metal oxide particles are micro / nano powder with a particle size range of 0.1 - 80μm, and the purity of the metal oxide is ≥98%.

4. The composite thermite for demolition according to claim 1, characterized in that, The method for coating and modifying the surface of the fuel metal particles with a fluoropolymer is to pour 10g of aluminum or magnesium micro-powder into 30 - 33mL of absolute ethanol, form a suspension after ultrasonic dispersion, and then drop industrial polytetrafluoroethylene emulsion into the suspension at a rate of 2 - 3mL / min while stirring. The mass ratio of polytetrafluoroethylene in the polytetrafluoroethylene emulsion is 57 - 63wt%; after dropping 3 - 4mL of the emulsion, filter the liquid from the metal particle suspension and dry it to remove ethanol to obtain the fuel metal particles with a coated and modified surface.

5. The composite thermite for demolition according to claim 1, characterized in that, The above flux is industrial fluorite powder, which is composed of calcium fluoride powder with a mass ratio of 85% - 98% and silicon dioxide powder with a mass ratio of 2% - 15%.

6. The composite thermite for demolition according to claim 1, characterized in that, The above strong oxidizer is composed of one or several kinds of powders of potassium sulfate, sodium sulfate, and calcium sulfate, and the mass ratio is arbitrary when several kinds of powders are combined. Among them, the water content of the strong oxidizer should be ≤1%, and the oxidizing property of the above strong oxidizer is only for the high-temperature environment of the thermite reaction.

7. The composite thermite for demolition according to claim 1, characterized in that, The above binder is a combination of a liquid adhesive and a curing agent. The liquid adhesive is composed of one or two of epoxy resin glue and phenolic resin glue, and the mass ratio of the liquid adhesive to the curing agent is 1:

1.

8. The composite thermite for demolition according to claim 1, characterized in that, The above binder is a solid binder, and the binder is a powder of fluoropolymer, which is composed of one or several kinds of powders of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, and fluororubber; among them, the particle size of the solid binder, that is, the fluoropolymer powder, is 4 - 25μm.

9. A preparation method of the composite thermite for demolition according to claim 7, characterized in that, It includes the following steps: S1. Coating and modification of the surface of the fuel metal particles; S2. Preparation of the composite thermite powder: Using a molding process, fuel metal particles, metal oxide particles, a flux, and a strong oxidizer are mixed in the above proportions to obtain a mixed powder. Take 45 - 50 g of the mixed powder and add it to a ball mill jar for ball milling and mixing. Add 30 - 35 mL of an ethanol dispersion liquid to the ball mill jar so that the dispersion liquid can completely wet the powder. Start the ball mill and perform ball milling under low-speed conditions of 100 - 200 revolutions per minute to fully mix the powder. The low-speed ball milling conditions refer to applying low-energy impact to the mixed powder, without changing the microscopic morphology of the particles and achieving uniform mixing. The low-speed ball milling time is 3 - 5 minutes. Then collect the well-mixed powder and dry it in an oxygen-free environment at 50 - 70 °C for 12 - 36 hours to obtain a mixture, namely the composite thermite powder. S3. Molding and curing of the composite thermite: Pour the liquid adhesive and the curing agent into a container in sequence. After fully stirring for 1 - 2 minutes, then pour in the composite thermite powder and continuously stir for 10 - 15 minutes until all the powder is evenly mixed with the liquid adhesive to obtain a mixed jelly-like substance. The mass ratio of the liquid adhesive, the curing agent, and the composite thermite is 1:1 - 1.5:18 - 20. Put the mixed jelly-like substance into a device. If the viscosity of the jelly-like substance is too high, pressure needs to be applied for molding, and then let it stand for curing. The curing time is 15 - 36 hours.

10. A preparation method of the composite thermite for demolition according to claim 8, characterized in that, It includes the following steps: S1. Surface coating and modification of fuel metal particles; S2. Preparation of the composite thermite powder: Using a molding process, fuel metal particles, metal oxide particles, a flux, a solid binder, and a strong oxidizer are ball milled and mixed in the above proportions. A total of 45 - 50 g of each raw material is added to a ball mill jar for ball milling and mixing. Add 30 - 35 mL of an ethanol dispersion liquid to the ball mill jar so that the dispersion liquid can completely wet the powder. Start the ball mill and perform ball milling under low-speed conditions of 100 - 200 revolutions per minute to fully mix the powder. The low-speed ball milling conditions refer to applying low-energy impact to the mixed powder, without changing the microscopic morphology of the particles and achieving uniform mixing. The low-speed ball milling time is 3 - 5 minutes. Then collect the well-mixed powder and dry it in an oxygen-free environment at 50 - 70 °C for 12 - 36 hours to obtain a mixture, namely the composite thermite powder. S3. Molding of the composite thermite powder by pressing: Weigh a certain mass of the composite thermite powder, put it into a mold, and perform powder molding by pressing. Among them, the pressure required for the powder molding by pressing is 100 - 200 MPa, and the pressure is maintained for ≥1 minute during the pressing process.

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