Combustible foil for area-type infrared decoy flare and preparation method therefor

Abstract

The present invention relates to an infrared interference technology, in particular to a flammable foil for a surface-type infrared decoy, and a method for preparing the flammable foil. In order to solve the problems in the prior art that production raw materials and a production process are extremely hazardous in the process of producing equipment decoys, and are not conducive to environmental protection, and at the same time, the obtained decoy has short combustion time and low combustion temperature, the flammable foil of the present invention can quickly spontaneously ignite in air, and the heat radiation temperature can reach 1300K or more. During manufacturing, a metal foil is coated with an ignition agent and a combustive agent by an adhesive, and then the ignition agent is activated to obtain a flammable foil which is stored in an inert atmosphere glove box for subsequent use.

Description

TECHNICAL FIELD

[0001] The present invention relates to an infrared interference technology, in particular to a flammable foil for a surface-type infrared decoy, and a method for preparing the flammable foil.BACKGROUND

[0002] With the continuous development of modern optoelectronic technologies such as infrared imaging and spectral recognition, new infrared detection and infrared guidance technologies have been rapidly developed and improved, and infrared guided missiles have gradually shown their unique advantages and enormous combat power. The hit rate and strike strength of these guided weapons against intended targets have been greatly improved. In modern warfare, combat aircraft, ships, armored vehicles and other ground fortifications may be severely threatened by precision guided weapons. Infrared guided missiles have become the most threatening "enemy" of combat facilities and equipment such as combat aircraft and ships. In the face of the severe situation faced by the survival of military targets in modern battlefields, passive interference techniques using imitation decoys as decoys to interfere with enemy detection and guidance has been paid more and more attention, and it can be expected that in the future, infrared decoys will inevitably adopt advanced countermeasure techniques in a targeted manner and undergo continuous upgrades and iterations.

[0003] Infrared decoy materials play a very important role as equipment decoys. This material can be used to cover a path of aircraft and other combat weapons passing through a specific area to dissipate anti-aircraft firepower and prevent anti-aircraft artillery attacks. Conventional point source infrared decoy materials are infrared pyrotechnic agents consisting of magnesium (Mg), polytetrafluoroethylene (PTFE), and Viton, and currently, methods of producing magnesium-polytetrafluoroethylene mixtures require the use of solvents that are highly polluting to the environment and flammable. As in the known methods, an adhesive is deposited onto the mixture by solvent evaporation using acetone or methyl ethyl ketone, and the mixture is dried and cured by pressing or extrusion to form an agent, and acetone and methyl ethyl ketone are flammable, and thus, the materials used and the production process are extremely hazardous and not conducive to environmental protection. In addition, in practical applications, infrared decoy materials need to have the characteristics of fast combustion response time, combustion temperature and time that meet the requirements, and the like, and most point source infrared decoy materials have short combustion time and low combustion temperature, which cannot meet practical needs.

[0004] Whereas a flammable chaff bomb capable of producing high-intensity infrared radiation was invented early in Germany to interfere with incoming infrared guided missiles and make them deviate from a target. The decoy is made by coating thin paper or a metal foil with a polyvinyl chloride adhesive, a dioctyl phthalate softener, a combustible agent and a dispersing agent. The combustible agent is commonly magnesium powder, aluminum powder or red phosphorus powder. U.S. Patent No. 4624186A introduces a composite interference material, which uses a metal foil as a substrate, a layer of burning ointment is pressed on the surface of the substrate, and a burning rate is controlled by adjusting the amount of a combustible material in the ointment, and the composite interference material can simultaneously interfere with infrared and millimeter waves; and U.S. Patent No. 6013144A describes another composite material, which uses carbon fibers as a substrate, and the surface of the substrate is fully coated with a spontaneously combustible coating by vapor deposition. This spontaneously combustible coating can provide infrared radiation during the continuous combustion process, and the intensity and wavelength of infrared radiation are changed by adjusting the formula composition, and it is a highly controllable decoy material; and U.S. Patent No. 6193814B1 introduces a composite material with a novel process, which uses a tin-plated tinplate as a substrate, the surface of the substrate is coated with an active metal coating, and heating is performed to 700-900°C under oxygen barrier conditions to form a spontaneously combustible composite material.

[0005] Thus, it can be seen that in the prior art, raw materials that can spontaneously ignite in the air are directly used for production and processing, resulting in a complex production process and a hazardous processing process. Therefore, decoy materials that are less hazardous and environmentally, friendly, and can have both long combustion time and high combustion temperature need to be developed urgently.SUMMARY

[0006] An object of the present invention is to solve the problems in the prior art that production raw materials and a production process are extremely hazardous in the process of producing equipment decoys, and are not conducive to environmental protection, and at the same time, the obtained decoy has short combustion time and low combustion temperature. The present invention provides a flammable foil for a surface-type infrared decoy, and a method for preparing the flammable foil.Inventive concept

[0007] Studies have shown that flammable foils are a new generation of interference materials for realizing infrared source countermeasures at present, and can rapidly ignite spontaneously in air, and the present invention develops flammable foils having a heat radiation temperature up to 1300K or more, and an ignition time of 1.0s or less, and adapting to the assembly requirements of infrared decoys based on the actual needs of surface-type infrared decoys.

[0008] To achieve the above object, the technical solutions provided by the present invention are as follows.

[0009] Provided is a flammable foil for a surface-type infrared decoy, wherein the flammable foil includes a metal foil and a mixture coating a surface of the metal foil, the mixture including an adhesive, an ignition agent and a combustive agent; the adhesive includes a silicate; and the ignition agent is a material that can spontaneously ignite in air.

[0010] Further, the ignition agent is formed by activating a nickel-aluminum alloy or an iron-aluminum alloy with a strong alkali solution, and a proportion of aluminum in the nickel-aluminum alloy or the iron-aluminum alloy is 30wt.%-60wt.%; and a mass ratio of the nickel-aluminum alloy or the iron-aluminum alloy to the combustive agent is 1:(0.1-0.5). If the aluminum content in the nickel-aluminum alloy or the iron-aluminum alloy is too small, the ignition agent formed will release too little heat and cannot be ignited; and when the aluminum content is too high, the adhesive sodium silicate or potassium silicate is a salt of a strong alkali and a weak acid, and the two will react to produce gas, causing the adhesive to be jelly-like and cannot be coated.

[0011] Further, the adhesive further includes a viscosity enhancer, and the viscosity enhancer is one or more of sodium tripolyphosphate, polyvinyl alcohol, hydroxyethyl cellulose, and methyl cellulose; the silicate is one or both of sodium silicate and / or potassium silicate having a modulus of 2.0-3.4; the combustive agent includes an alloy powder composed of one or more of magnesium, zinc, titanium, and boron, with an impurity content of less than 20% of a total mass. The modulus of the silicate is preferably 2.0-3.4. If the modulus is too high, the viscosity of the adhesive will be too high, and it is difficult for the adhesive to coat the metal foil. If the modulus is too low, the alkalinity of sodium silicate or potassium silicate is too high, sodium silicate or potassium silicate will easily react with the iron-aluminum alloy, and the viscosity of the adhesive will be reduced. The viscosity enhancer is used to increase the viscosity of the adhesive, increasing the stability of the flammable foil.

[0012] Further, the ignition agent is formed by activating the iron-aluminum alloy with a NaOH solution, and the combustive agent is magnesium; and the adhesive is sodium silicate, and the viscosity enhancer is sodium tripolyphosphate.

[0013] Meanwhile, the present invention also provides a method for preparing a flammable foil for a surface-type infrared decoy, including the steps of: Step 1) preparation of an alloy slurry uniformly mixing an adhesive with an energetic alloy powder to obtain the alloy slurry, wherein the adhesive is an aqueous silicate solution, and the energetic alloy powder includes a raw material of an ignition agent and a combustive agent; Step 2) coating and roasting Step 2.1) uniformly coating a surface of a metal foil with an energetic slurry obtained in the step 1), and performing drying to remove moisture from the energetic slurry; and Step 2.2) roasting the metal foil under inert atmosphere conditions, and performing cooling to room temperature for standby application; and Step 3) immersing the metal foil obtained in the step 2) in a strong alkali solution to activate the raw material of the ignition agent to form an ignition agent, taking out the foil after completion of activation, performing washing with water, performing vacuum drying to obtain a flammable foil, and storing the flammable foil in an inert atmosphere glove box.

[0014] Further, in the step 2.1), a temperature of the drying is 60°C or less, and a time of the drying is 1h or less; and the method further includes cutting the metal foil according to different needs after drying; and in the step 2.2), a temperature of the roasting is 400°C-700°C, a time of the roasting is 10min-60min, and a roasting atmosphere is nitrogen. If the temperature of the roasting is too low, the silicate foaming is insufficient, and the adhesion of the energetic alloy powder cannot meet the requirements; and if the temperature of the roasting is too high, a surface layer of the energetic alloy powder on the metal foil will be peeled off due to high-temperature sintering, so preferably, a better effect is achieved at 400°C-700°C.

[0015] Further, the step 1) specifically includes: Step 1.1) dissolving a silicate, or a silicate and a viscosity enhancer in water to prepare an aqueous silicate solution having a mass concentration of 20wt.%-30wt.% as an adhesive, wherein the silicate is one or both of sodium silicate or potassium silicate, sodium silicate or potassium silicate having a modulus of 2.0-3.4; and the viscosity enhancer is one or more of sodium tripolyphosphate, polyvinyl alcohol, hydroxyethyl cellulose, and methyl cellulose, and a proportion of the viscosity enhancer in the adhesive is 0.5wt.%-1.0wt.%; Step 1.2) weighing and mixing the raw material of the ignition agent and the combustive agent to prepare an energetic alloy powder having a mass ratio of the raw material of the ignition agent to the combustive agent being 1:(0.1-0.5); and Step 1.3) uniformly mixing the adhesive with the energetic alloy powder to obtain an alloy slurry having a solid content of 50wt.%-80wt.%, the solid content referring to a mass proportion of the energetic alloy powder in the alloy slurry.

[0016] Further, in the step 1.2), the raw material of the ignition agent is nickel-aluminum alloy or iron-aluminum alloy powder with a particle size of 90µm or less, wherein a proportion of aluminum is 30wt.%-60wt.%; and the combustive agent includes an alloy powder composed of one or more of magnesium, zinc, titanium, and boron with a particle size of 90µm or less, with an impurity content of less than 20% of a total mass.

[0017] Further, in the step 3), the strong alkali solution is a 20wt.%-40wt.% NaOH solution, a time of the activation is 10min-30min, and a temperature of the activation is 50°C-100°C; and a temperature of the vacuum drying is 150°C-300°C, and a time of the vacuum drying is 0.5h-3.0h. The strong alkali solution may also be a potassium hydroxide solution or other strong alkali solutions.

[0018] Further, in the step 1.1), the silicate is sodium silicate, the viscosity enhancer is sodium tripolyphosphate, a proportion of sodium tripolyphosphate in the adhesive is 1.0wt.%, and a sodium silicate aqueous solution of 25wt.% is prepared; in the step 1.2), the raw material of the ignition agent is an iron-aluminum alloy, wherein a mass proportion of aluminum is 50wt.%, the combustive agent is magnesium, and the mass ratio of the raw material of the ignition agent to the combustive agent is 1:0.25; in the step 1.3), the solid content is 60wt.%; in the step 2.2), the inert atmosphere is a nitrogen atmosphere, the roasting temperature is 600°C, and the roasting time is 30min; and in the step 3), a mass concentration of the NaOH solution is 30%, the activation time is 20min, the inert atmosphere is nitrogen or helium, and both the oxygen content and the water content in the inert atmosphere glove box are not greater than 100ppm. The concentration of the NaOH solution, the activation time, and the activation temperature cooperate with each other to perform an activation reaction, and a better activation effect can be achieved, and if the concentration of the NaOH solution is too high, the activation temperature is too high, and the activation time is too long, the activation reaction will be excessive, so that the ignition agent and the combustive agent fall off; and if the concentration of the NaOH solution is small, the time is short and / or the temperature is low, the activation reaction is insufficient, the ignition agent generated by the activation may be insufficient, and the ignition effect cannot meet the requirements.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. The flammable foil prepared in the present invention innovatively proposes an inventive concept of a two-component system of the "ignition agent" and the "combustive agent", enabling the flammable foil to be quickly oxidized and release heat to generate spontaneous combustion when encountering air, meeting the requirements of rapid ignition of infrared decoy materials. 2. The energetic metal powder is introduced into the combustive agent in the present invention, so that the prepared flammable foil has good combustion and ignition characteristics, and can provide relatively ideal infrared radiation energy, and there is only slight spark or no spark burst in the combustion process, meeting the requirements of cold flame combustion. 3. The present invention makes full use of the ability of rapid reaction of porous nickel or porous iron formed after activation of the alloy component of the raw material of the ignition agent with the strong alkali solution, and by combining the ignition agent with the combustive agent in a specific ratio, quick ignition can be performed while ensuring the duration and temperature of combustion. 4. The present invention makes full use of the promoting effect of the viscosity enhancer in the adhesive, so that the adhesion between the energetic metal powder and the foil in the prepared flammable foil is high, and thus, the prepared flammable foil is excellent in service durability. 5. The preparation method of the present invention adopts a simple coating activation method, is a preparation process which is high in operability, high in practicability and ideal in effect, and has a very broad promotion and application prospect. After the adhesive and the energetic alloy powder are mixed, the metal foil is coated with the mixture, and the ignition agent is then obtained by activation. Therefore, no flammable material is contained in the processing steps before the activation, and the processing process is safe and environmentally friendly. 6. In the present invention, the particle sizes of the raw material of the ignition agent and the combustive agent are further limited, preferably in the range of 90 µm or less, to further increase the rate of combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a process flow diagram of the present invention; FIG. 2 is a particle size distribution curve of a raw material of an ignition agent, i.e., an iron-aluminum alloy in Examples 1-4 of the present invention; FIG. 3 is an ignition-combustion performance curve of flammable foils in Examples 1-4 of the present invention; FIG. 4 is an ignition-combustion performance curve of flammable foils in Example 1 and Comparative examples 1-2 of the present invention; FIG. 5 is an SEM image of a flammable foil in Example 1 of the present invention; and FIG. 6 is an XRD pattern of a raw material of an ignition agent, i.e., an iron-aluminum alloy for the flammable foil in Example 1 of the present invention. DETAILED DESCRIPTIONExample 1

[0021] The present invention provides a method for preparing a flammable foil for a surface-type infrared decoy, a process flow is shown in FIG. 1, and the method includes the following steps: Step 1) a key material, i.e., an alloy slurry for the flammable foil was prepared.

[0022] Step 1.1) an adhesive was prepared, namely sodium silicate, sodium tripolyphosphate and water were mixed in a mass ratio of 25:1:74, and heating and stirring were performed to dissolve sodium silicate and sodium tripolyphosphate to prepare an adhesive having a sodium silicate concentration of 25wt.%, wherein sodium silicate has a modulus of 2.5;

[0023] Step 1.2) an energetic alloy powder was prepared, namely, an iron-aluminum alloy powder and a magnesium powder were weighed, and physical mixing was performed in a mass ratio of 1:0.25 to obtain the energetic alloy powder, wherein a mass proportion of aluminum in the iron-aluminum alloy was 50wt.%, an impurity content of the magnesium powder was less than 20%, and both the iron-aluminum alloy powder and the magnesium powder have a particle size in the range of 0-30µm; and Step 1.3) the adhesive obtained in the step 1.1) and the energetic alloy powder obtained in the step 1.2) were mixed according to a solid content of 60wt.% by a simple solid-liquid mixing method, and mixed uniformly by mechanical stirring to obtain the alloy slurry. The solid content refers to a mass proportion of the energetic alloy powder in the alloy slurry.

[0024] Step 2) The surface of a metal foil was uniformly coated with the alloy slurry obtained in the step 1), and the metal foil was blown dry in hot air and cut, and then roasted at 600°C for 30min under a nitrogen atmosphere, and then naturally cooled to room temperature for standby application.

[0025] The metal foil needed to be pre-treated before use, the pre-treatment including washing, degreasing, and drying.

[0026] The drying temperature of blowing drying in the hot air was not more than 60°C, the drying time was not more than 1 h, the higher the temperature, the shorter the drying time, and the alloy slurry was prevented from being excessively dry and difficult to cut.

[0027] In other examples of the present invention, normal temperature drying may be used to remove moisture from the alloy slurry, and the time of the normal temperature drying is not limited.

[0028] Step 3) The roasted foil obtained in the step 2) was immersed in a 30% NaOH solution to be activated at 80°C for 20min, and the foil was taken out after completion, washed with water, and placed in a vacuum oven to be dried at 200°C for 2.0h to obtain a flammable foil for an infrared decoy, designated as A1. The flammable foil was stored in an inert atmosphere glove box to avoid spontaneous combustion while facilitating assembly in subsequent use. As shown in FIG. 5, it is an SEM image of A1.

[0029] The inert atmosphere was nitrogen or helium, and both the oxygen content and the water content in the glove box were not greater than 100ppm.Example 2

[0030] Step 1) an alloy slurry for a flammable foil was prepared.

[0031] Step 1.1) an adhesive was prepared, namely sodium silicate, sodium tripolyphosphate and water were mixed in a mass ratio of 25:1:74, and heating and stirring were performed to dissolve sodium silicate and sodium tripolyphosphate to prepare an adhesive having a sodium silicate concentration of 25wt.%, wherein sodium silicate has a modulus of 2.5;

[0032] Step 1.2) an energetic alloy powder was prepared, namely an iron-aluminum alloy powder and a magnesium powder were weighed, and physical mixing was performed in a mass ratio of 1:0.25 to obtain the energetic alloy powder, wherein a mass proportion of aluminum in the iron-aluminum alloy was 50wt.%, and both the iron-aluminum alloy powder and the magnesium powder have a particle size in the range of 0-60 µm; and

[0033] Step 1.3) the adhesive obtained in the step 1.1) and the energetic alloy powder obtained in the step 1.2) were mixed according to a solid content of 60wt.% by a simple solid-liquid mixing method, and mixed uniformly by mechanical stirring to obtain the alloy slurry.

[0034] Step 2) The surface of a metal foil was uniformly coated with the alloy slurry obtained in the step 1), and the metal foil was blown dry in hot air and cut, and then roasted at 600°C for 30min under a nitrogen atmosphere, and then naturally cooled to room temperature for standby application.

[0035] Step 3) The roasted foil obtained in the step 2) was immersed in a 30% NaOH solution to be activated at 80°C for 20min, and the foil was taken out after completion, washed with water, and placed in a vacuum oven to be dried at 200°C for 2.0h to obtain a flammable foil A2 for an infrared decoy. The flammable foil was stored in an inert atmosphere glove box.Example 3

[0036] Step 1) an alloy slurry for a flammable foil was prepared.

[0037] Step 1.1) an adhesive was prepared, namely sodium silicate, sodium tripolyphosphate and water were mixed in a mass ratio of 25:1:74, and heating and stirring were performed to dissolve sodium silicate and sodium tripolyphosphate to prepare an adhesive having a sodium silicate concentration of 25wt.%, wherein sodium silicate has a modulus of 2.5;

[0038] Step 1.2) an energetic alloy powder was prepared, namely an iron-aluminum alloy powder and a magnesium powder were weighed, and physical mixing was performed in a mass ratio of 1:0.25 to obtain the energetic alloy powder, wherein a mass proportion of aluminum in the iron-aluminum alloy was 50wt.%, and both the iron-aluminum alloy powder and the magnesium powder have a particle size in the range of 0-90 µm; and

[0039] Step 1.3) the adhesive obtained in the step 1.1) and the energetic alloy powder obtained in the step 1.2) were mixed according to a solid content of 60wt.% by a simple solid-liquid mixing method, and mixed uniformly by mechanical stirring to obtain the alloy slurry.

[0040] Step 2) The surface of a metal foil was uniformly coated with the alloy slurry obtained in the step 1), and the metal foil was blown dry in hot air and cut, and then roasted at 600°C for 30min under a nitrogen atmosphere, and then naturally cooled to room temperature for standby application.

[0041] Step 3) The roasted foil obtained in the step 2) was immersed in a 30% NaOH solution to be activated at 80°C for 20min, and the foil was taken out after completion, washed with water, and placed in a vacuum oven to be dried at 200°C for 2.0h to obtain a flammable foil A3 for an infrared decoy. The flammable foil was stored in an inert atmosphere glove box.Example 4

[0042] Step 1) an alloy slurry for a flammable foil was prepared.

[0043] Step 1.1) an adhesive was prepared, namely sodium silicate, sodium tripolyphosphate and water were mixed in a mass ratio of 25:1:74, and heating and stirring were performed to dissolve sodium silicate and sodium tripolyphosphate to prepare an adhesive having a sodium silicate concentration of 25 wt.%, wherein sodium silicate has a modulus of 2.5;

[0044] Step 1.2) an energetic alloy powder was prepared, namely an iron-aluminum alloy powder and a magnesium powder were weighed, and physical mixing was performed in a mass ratio of 1:0.25 to obtain the energetic alloy powder, wherein a mass proportion of aluminum in the iron-aluminum alloy was 50wt.%, and both the iron-aluminum alloy powder and the magnesium powder have a particle size in the range of 0-120µm; and

[0045] Step 1.3) the adhesive obtained in the step 1.1) and the energetic alloy powder obtained in the step 1.2) were mixed according to a solid content of 60wt.% by a simple solid-liquid mixing method, and mixed uniformly by mechanical stirring to obtain the alloy slurry.

[0046] Step 2) The surface of a metal foil was uniformly coated with the alloy slurry obtained in the step 1), and the metal foil was blown dry in hot air and cut, and then roasted at 600°C for 30min under a nitrogen atmosphere, and then naturally cooled to room temperature for standby application.

[0047] Step 3) The roasted foil obtained in the step 2) was immersed in a 30% NaOH solution to be activated at 80°C for 20 min, and the foil was taken out after completion, washed with water, and placed in a vacuum oven to be dried at 200°C for 2.0h to obtain a flammable foil A4 for an infrared decoy. The flammable foil was stored in an inert atmosphere glove box.Example 5

[0048] Step 1) an alloy slurry for a flammable foil was prepared.

[0049] Step 1.1) an adhesive was prepared, namely sodium silicate, polyvinyl alcohol and water were mixed in a mass ratio of 20:0.75:79.25, and heating and stirring were performed to dissolve sodium silicate and polyvinyl alcohol to prepare an adhesive having a sodium silicate concentration of 20wt.%, wherein sodium silicate has a modulus of 2.0;

[0050] Step 1.2) an energetic alloy powder was prepared, namely an nickel-aluminum alloy powder and a zinc powder were weighed, and physical mixing was performed in a mass ratio of 1:0.1 to obtain the energetic alloy powder, wherein a mass proportion of aluminum in the nickel-aluminum alloy is 30wt.%, and both the nickel-aluminum alloy powder and the zinc powder have a particle size in the range of 0-60µm; and Step 1.3) the adhesive obtained in the step 1.1) and the energetic alloy powder obtained in the step 1.2) were mixed according to a solid content of 50wt.% by a simple solid-liquid mixing method, and mixed uniformly by mechanical stirring to obtain the alloy slurry.

[0051] Step 2) The surface of a metal foil was uniformly coated with the alloy slurry obtained in the step 1), and the metal foil was blown dry in hot air and cut, and then roasted at 400°C for 60 min under a nitrogen atmosphere, and then naturally cooled to room temperature for standby application.

[0052] Step 3) The roasted foil obtained in the step 2) was immersed in a 20% NaOH solution to be activated at 50°C for 30min, and the foil was taken out after completion, washed with water, and placed in a vacuum oven to be dried at 150°C for 3.0 h to obtain a flammable foil A5 for an infrared decoy. The flammable foil was stored in an inert atmosphere glove box.Example 6

[0053] Step 1) an alloy slurry for a flammable foil was prepared.

[0054] Step 1.1) an adhesive was prepared, namely potassium silicate, hydroxyethyl cellulose, methyl cellulose and water were mixed in a mass ratio of 30:0.5:0.5:69, and heating and stirring were performed to dissolve potassium silicate, hydroxyethyl cellulose and methyl cellulose to prepare an adhesive having a potassium silicate concentration of 30 wt.%, wherein potassium silicate has a modulus of 3.4;

[0055] Step 1.2) an energetic alloy powder was prepared, namely an iron-aluminum alloy powder and a titanium powder were weighed, and physical mixing was performed in a mass ratio of 1:0.5 to obtain the energetic alloy powder, wherein a mass proportion of aluminum in the iron-aluminum alloy was 60wt.%, and both the iron-aluminum alloy powder and the titanium powder have a particle size in the range of 0-60µm; and

[0056] Step 1.3) the adhesive obtained in the step 1.1) and the energetic alloy powder obtained in the step 1.2) were mixed according to a solid content of 80 wt.% by a simple solid-liquid mixing method, and mixed uniformly by mechanical stirring to obtain the alloy slurry.

[0057] Step 2) The surface of a metal foil was uniformly coated with the alloy slurry obtained in the step 1), and the metal foil was blown dry in hot air and cut, and then roasted at 700°C for 10 min under a nitrogen atmosphere, and then naturally cooled to room temperature for standby application.

[0058] Step 3) The roasted foil obtained in the step 2) was immersed in a 40% NaOH solution to be activated at 100°C for 10min, and the foil was taken out after completion, washed with water, and placed in a vacuum oven to be dried at 300°C for 0.5h to obtain a flammable foil A6 for an infrared decoy. The flammable foil was stored in an inert atmosphere glove box.Comparative Example 1

[0059] The steps in Comparative Example 1 were essentially the same as those in Example 1, except that only a raw material of an ignition agent, i.e., a Fe-Al alloy was present in an energetic alloy slurry in Comparative Example 1 without a component of a combustive agent to obtain a flammable foil B1.Comparative Example 2

[0060] The steps in Comparative Example 2 were essentially the same as those in Example 1, except that the adhesive used in an energetic alloy slurry in Comparative Example 2 was a pure sodium silicate solution without a viscosity enhancer to obtain a flammable foil B2.

[0061] Combustion performance testing: the ignition-combustion characteristics of the flammable foil were tested by a PS400 AutoNavi infrared thermal imager. Specifically: the flammable foil was taken out from a glove box, after the foil was in contact with air, it will quickly ignite and burn, emitting strong light and heat, and a camera was aimed at the foil to measure a temperature field to verify the combustion performance of the flammable foil. The present invention uses technical specifications that require the flammable foil to have: the ignition time of 1.5s or less (increasing from room temperature to 900 K); and a combustion duration of 3.0s or more (900K or above).

[0062] Adhesion performance testing: a test method for a powder shedding situation of the flammable foil during use is a visual observation and acceptance judgment method. A sample was bent in a glove box by using a bending tool, and a powder shedding situation at gaps of bent parts on both sides of the foil was visually observed. If a substrate of the foil was not leaked, it was judged as qualified. Table 1 Comparison of ignition-combustion performance data for flammable foils of the present inventionSerial numberIgnition time / sDuration / sMaximum temperature / KPowder shedding situationExample 1 (A1)0.565.101584.1QualifiedExample 2 (A2)0.824.951584.8QualifiedExample 3 (A3)1.055.431579.0QualifiedExample 4 (A4)1.255.781578.6QualifiedExample 5 (A5)0.514.541577.3QualifiedExample 6 (A6)1.185.831586.5QualifiedComparative Example 1 (B1)0.980.00895.7QualifiedComparative Example 2 (B2)0.726.151616.1Unqualified

[0063] As can be seen from the comparison of performance test data for the flammable foils, the overall performance of the flammable foils in the two Comparative Examples is poor. An ignition-combustion performance curve is shown in FIG. 4. The combustion temperature and duration of the flammable foil in Comparative Example 1 do not meet the requirements of usage indexes. Although the flammable foil in Comparative Example 2 has better ignition-combustion characteristics, its adhesion performance cannot meet the use requirements of the foil. The flammable foil obtained in the invention, through a composite two-component system of the ignition agent and the combustive agent, wherein the ignition agent and the combustive agent have a specific ratio and cooperate with each other, not only solves the problem that the foil quickly ignites when exposed to air, but also realizes the purpose that the foil can be continuously burned at high temperature and release heat. The particle size distribution of the flammable foils in Examples 1-4 is shown in FIG. 2, and the ignition-combustion performance curve is shown in FIG. 3. The porous iron ignition agent after NaOH activation ignites magnesium powder, and combustion is performed to emit strong infrared radiation light, and the smaller the particle size of the raw material of the ignition agent, the faster an ignition speed. When the particle size of the raw material of the ignition agent is large, due to the intense combustion of crystal nuclei, strong sparks will be emitted during the combustion process, which affects the use performance of the flammable foil. For example, in Example 6, the raw material of the ignition agent has a particle size in the range of 0-120µm, and a small amount of spark burst occurs during combustion. Therefore, the raw material of the ignition agent and the combustive agent preferably has a particle size of 90µm or less. Taking the above performance data together, it can be seen that the flammable foils in the examples have the best performance, having a longer duration and a maximum temperature after combustion, while having a shorter ignition time.

[0064] At the same time, in the examples of the present invention, the adhesion performance of the flammable foils obtained in Examples 1-6 and Comparative Example 1 all meets the use requirements, while the flammable foil in Comparative Example 2 has a powder shedding situation, which is mainly due to the introduction of the viscosity enhancer into the adhesive used in the present invention, and the introduction of the viscosity enhancer can effectively improve the bonding ability of the adhesive, so that the powder shedding situation after the flammable foil is loaded into a decoy can meet the use requirements of environmental adaptability such as vibration.

Claims

1. A flammable foil for a surface-type infrared decoy, characterized by comprising: a metal foil and a mixture coating a surface of the metal foil, wherein the mixture comprising an adhesive, an ignition agent and a combustive agent; the adhesive comprising a silicate; and the ignition agent is a material that can spontaneously ignite in air.

2. The flammable foil for a surface-type infrared decoy according to claim 1, characterized in that: the ignition agent is formed by activating a nickel-aluminum alloy or an iron-aluminum alloy with a strong alkali solution, and a proportion of aluminum in the nickel-aluminum alloy or the iron-aluminum alloy is 30wt.%-60wt.%; and a mass ratio of the nickel-aluminum alloy or the iron-aluminum alloy to the combustive agent is 1:(0.1-0.5).

3. The flammable foil for a surface-type infrared decoy according to claim 1 or 2, characterized in that: the adhesive further comprising a viscosity enhancer, and the viscosity enhancer is one or more of sodium tripolyphosphate, polyvinyl alcohol, hydroxyethyl cellulose, and methyl cellulose; and the silicate is sodium silicate and / or potassium silicate having a modulus of 2.0-3.4; and the combustive agent comprising an alloy powder composed of one or more of magnesium, zinc, titanium, and boron, with an impurity content of less than 20% of a total mass.

4. The flammable foil for a surface-type infrared decoy according to claim 3, characterized in that: the ignition agent is formed by activating the iron-aluminum alloy with a NaOH solution, and the combustive agent is magnesium; and the adhesive is sodium silicate, and the viscosity enhancer is sodium tripolyphosphate.

5. A method for preparing a flammable foil for a surface-type infrared decoy, characterized by comprising the steps of: Step 1) preparation of an alloy slurry uniformly mixing an adhesive with an energetic alloy powder to obtain the alloy slurry, wherein the adhesive is an aqueous silicate solution, and the energetic alloy powder comprises a raw material of an ignition agent and a combustive agent; Step 2) coating and roasting Step 2.1) uniformly coating a surface of a metal foil with an energetic slurry obtained in the step 1), and performing drying to remove moisture from the energetic slurry; and Step 2.2) roasting the metal foil under inert atmosphere conditions, and performing cooling to room temperature for standby application; and Step 3) immersing the metal foil obtained in the step 2) in a strong alkali solution to activate the raw material of the ignition agent to form an ignition agent, taking out the foil after completion of activation, performing washing with water, performing vacuum drying to obtain a flammable foil, and storing the flammable foil in an inert atmosphere glove box.

6. The method for preparing the flammable foil for a surface-type infrared decoy according to claim 5, characterized in that: in the step 2.1), a temperature of the drying is 60°C or less, and a time of the drying is 1h or less; and the method further comprising cutting the metal foil according to different needs after drying; and in the step 2.2), a temperature of the roasting is 400°C-700°C, a time of the roasting is 10min-60min, and a roasting atmosphere is nitrogen.

7. The method for preparing the flammable foil for a surface-type infrared decoy according to claim 5 or 6, characterized in that: the step 1) specifically comprising: Step 1.1) dissolving a silicate, or a silicate and a viscosity enhancer in water to prepare an aqueous silicate solution having a mass concentration of 20wt.%-30wt.% as an adhesive, wherein the silicate is one or both of sodium silicate or potassium silicate, sodium silicate or potassium silicate having a modulus of 2.0-3.4; and the viscosity enhancer is one or more of sodium tripolyphosphate, polyvinyl alcohol, hydroxyethyl cellulose, and methyl cellulose, and a proportion of the viscosity enhancer in the adhesive is 0.5wt.%-1.0wt.%; Step 1.2) weighing and mixing the raw material of the ignition agent and the combustive agent to prepare an energetic alloy powder having a mass ratio of the raw material of the ignition agent to the combustive agent being 1:(0.1-0.5); and Step 1.3) uniformly mixing the adhesive with the energetic alloy powder to obtain an alloy slurry having a solid content of 50wt.%-80wt.%, the solid content referring to a mass proportion of the energetic alloy powder in the alloy slurry.

8. The method for preparing the flammable foil for a surface-type infrared decoy according to claim 7, characterized in that: in the step 1.2), the raw material of the ignition agent is nickel-aluminum alloy or iron-aluminum alloy powder with a particle size of 90µm or less, wherein a proportion of aluminum is 30wt.%-60wt.%; and the combustive agent comprises an alloy powder composed of one or more of magnesium, zinc, titanium, and boron with a particle size of 90µm, with an impurity content of less than 20% of a total mass.

9. The method for preparing the flammable foil for a surface-type infrared decoy according to claim 8, characterized in that: in the step 3), the strong alkali solution is a 20wt.%-40wt.% NaOH solution, a time of the activation is 10min-30min, and a temperature of the activation is 50°C-100°C; and a temperature of the vacuum drying is 150°C-300°C, and a time of the vacuum drying is 0.5h-3.0h.

10. The method for preparing the flammable foil for a surface-type infrared decoy according to claim 9, characterized in that: in the step 1.1), the silicate is sodium silicate, the viscosity enhancer is sodium tripolyphosphate, a proportion of sodium tripolyphosphate in the adhesive is 1.0wt.%, and a sodium silicate aqueous solution of 25wt.% is prepared; in the step 1.2), the raw material of the ignition agent is an iron-aluminum alloy, wherein a mass proportion of aluminum is 50wt.%, the combustive agent is magnesium, and the mass ratio of the raw material of the ignition agent to the combustive agent is 1:0.25; in the step 1.3), the solid content is 60wt.%; in the step 2.2), the inert atmosphere is a nitrogen atmosphere, the temperature of the roasting is 600°C, and the time of the roasting is 30min; and in the step 3), a mass concentration of the NaOH solution is 30%, the activation time is 20min, the inert atmosphere is nitrogen or helium, and both the oxygen content and the water content in the inert atmosphere glove box are not greater than 100ppm.

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