Core-shell type azide thin film and method for preparing the same

Abstract

The application discloses a kind of core-shell azide film and preparation method thereof, belong to energetic material technical field.The core-shell azide film is with azide as core, with carbon film as shell, and the core-shell azide film is obtained by coaxial electrospinning technology.The core-shell azide film obtained by the application is compared with traditional azide, and the electrostatic safety is greatly improved.The carbon material wrapped outside azide provides good thermal conductivity and electrical conductivity for the system, effectively alleviating the effect of external stimulus.The film material is easy to be processed, and can be compatible with MEMS process, effectively reducing the instability of powder charge.

Description

[0001] Technical Field: This invention belongs to the field of energetic materials technology, and relates to a core-shell type azide thin film and its preparation method. Background Technology

[0002] To meet the needs of the development of informationized and miniaturized weapons, the advantages of using MEMS technology to design and manufacture pyrotechnics have become increasingly apparent. The micro-energetic chip portion primarily employs loading processes and micro / nano-structured pyrotechnic agents compatible with MEMS technology. Currently, commonly used pyrotechnic agents mainly include lead azide, lead stearate, and copper azide and silver azide, which offer higher initiation performance and are more environmentally friendly. However, their high sensitivity and poor ignition capability limit their practical application, and powdered charges are not easily compatible with MEMS technology, leading to instability. To address this, many researchers have used carbon nanomaterials with excellent thermal and electrical conductivity (such as graphene, graphene oxide, and carbon nanotubes) to encapsulate highly sensitive azides, forming a core-shell structure to mitigate external electrostatic and mechanical stimuli, thereby improving the sensitivity performance of azide initiating explosives. Other researchers have constructed carbon frameworks and porous copper structures to reduce particle aggregation and static charge accumulation, achieving a certain degree of desensitization. However, the above methods are relatively complex to prepare, with high material and synthesis costs, and the prepared azides are mostly in powder form with low safety factors. Therefore, it is of great significance to design an azide initiator that is easy to prepare, has low manufacturing cost, moderate sensitivity, and is suitable for micro-charges in MEMS pyrotechnics.

[0003] Electrospinning technology offers advantages such as simple fabrication processes, low production costs, and the ability to achieve mass production. The resulting thin film materials are easily processed and molded, and readily compatible with MEMS processes. The emerging coaxial electrospinning technology can spin non-spinnable materials and fabricate fiber films with special structures such as core-shell and hollow structures. Therefore, it can be applied to the preparation of MEMS pyrotechnic agents, producing core-shell azide films. By encapsulating the azide core material with a carbon shell, sensitivity performance can be controlled. Furthermore, the films can be processed into shapes compatible with MEMS, ultimately yielding core-shell azide films with moderate sensitivity suitable for MEMS micro-packing processes. Summary of the Invention

[0004] The purpose of this invention is to provide a core-shell azide thin film with moderate sensitivity suitable for MEMS micro-packing and its preparation method. This core-shell structure uses an azide core and a carbon film as the shell, utilizing carbon materials with good electrical and thermal conductivity to encapsulate the azide, thereby achieving control over the sensitivity of the azide.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A core-shell type azide energetic thin film is designed and prepared. This thin film material is easier to process and can be compatible with MEMS processes. The core-shell type azide thin film is prepared using coaxial electrospinning technology, and a core-shell structure is obtained with an azide core and a carbon film as the shell.

[0006] The specific steps of the method for preparing the core-shell type azide thin film involved in this invention are as follows:

[0007] Step 1: Place the soluble metal salt in a solvent at a certain ratio and stir at a certain temperature for a certain time until it is completely dissolved. Then, place a certain proportion of the easily spinnable polymer in a solvent of the same content and stir until it is completely dissolved, obtaining a core solution and a shell solution respectively. Inject the two solutions into two syringes for later use.

[0008] Step 2: Assemble the syringes containing the core solution and shell solution from Step 1 in parallel onto an electrospinning apparatus, connect them to a coaxial nozzle, and perform coaxial spinning under a certain voltage and injection rate. After spinning is complete, peel off the prepared film and place it in an oven to dry for a period of time.

[0009] Step 3: The thin film prepared in Step 2 is calcined at high temperature in a nitrogen atmosphere to obtain a core-shell carbon-based thin film with metal particles as the core and carbon film as the shell.

[0010] Step 4: Sodium azide and stearic acid are mixed evenly in a gas generator. The core-shell carbon-based thin film obtained in Step 3 is placed in a one-way gas tube. At 120°C, the azido acid gas generated by the azide reaction is introduced into the metal-based thin film through the one-way gas tube. After reacting with the metal-based thin film for 24 hours, a core-shell azide thin film is obtained.

[0011] In a preferred embodiment, the soluble metal salts in step one include copper nitrate, copper acetate, lead nitrate, lead acetate, silver nitrate, silver acetate, cadmium nitrate, and cadmium acetate; the polymers include polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyvinyl butyral (PVB), polyethylene oxide (PEO), and polystyrene (PS).

[0012] In a preferred embodiment, the concentration of the metal salt and the polymer in step one is 3-15%.

[0013] In a preferred embodiment, the reaction temperature in step one is 30–90°C, and the stirring time is 2–8 hours.

[0014] In a preferred embodiment, the spinning negative voltage in step two is -2kV, the positive voltage is 8-20kV, the push column speed is 0.05-0.2mm / min, and the core-shell solution injection speeds are 1:1, 1:2, 2:1, 1:3, 3:1, 1:4, 4:1, 1:5, 5:1, 1:10, and 10:1, respectively.

[0015] In a preferred embodiment, the high-temperature calcination temperature in step three is 400–800°C, and the calcination time is 10–120 min.

[0016] The principle of this invention is as follows: Core-shell carbon-based thin films containing copper, lead, silver, and cadmium metals can be easily prepared through coaxial electrospinning and high-temperature calcination. During coaxial electrospinning, as the voltage increases, when the charge on the surface of the outer solution increases and accumulates to a certain level, the outer solution is stretched and dragged, forming a composite Taylor cone at the nozzle, and creating a core-shell coaxial composite structure encapsulated by a shell layer. This ultimately forms a core-shell fiber membrane on the receiving device. After a subsequent carbonization process, the core-shell thin film not only uniformly loads metal particles but also coats the surface of the metal particles with a carbon film, effectively improving its electrostatic safety. More importantly, the thin film obtained by electrospinning is easy to process and shape; after a subsequent azidation process, a core-shell azidized thin film compatible with MEMS processes can be directly obtained.

[0017] The beneficial effects of this invention are as follows:

[0018] (1) The core-shell azide film of the present invention uses azide as the core and calcined carbon film as the shell to form a core-shell structure wrapped by carbon material, which is beneficial to enhancing its thermal and electrical conductivity. The film has moderate sensitivity, good safety performance, and can successfully detonate high-energy explosives such as CL-20. Moreover, the process is simple and the manufacturing cost is low.

[0019] (2) The core-shell type azide film of the present invention is in the form of a film, which has the characteristics of being cut and easy to process and form. Its safety performance is far higher than that of powdered pyrotechnic agents, and it is compatible with MEMS process and is suitable for MEMS micro-packing. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a core-shell type carbon-based fiber.

[0021] Figure 2 It is a thin film material that is easy to process and shape.

[0022] Figure 3 This is a TEM image of a core-shell coaxial electrospun sample. Detailed Implementation

[0023] The present invention is implemented through the following embodiments, but the conditions and results described in the implementation do not constitute a limitation on the content and rights of the invention.

[0024] Example 1

[0025] Preparation of core-shell copper azide thin films:

[0026] Raw materials: Polyacrylonitrile (PAN), copper nitrate (Cu·(NO3)2), N,N-dimethylformamide (DMF), sodium azide (NaN3), ethanol, stearic acid (CH3(CH2)). 16 COOH).

[0027] Main instruments and equipment: electrospinning machine, magnetic stirrer, drying oven, tube furnace.

[0028] 1 g of polyacrylonitrile was placed in 10 mL of DMF solution and heated to 80 °C with magnetic stirring for 6 h. The homogenized solution was then injected into a 5 mL syringe as the shell solution. 1 g of copper nitrate was also placed in 10 mL of DMF solution and heated to 80 °C with magnetic stirring for 6 h. The homogenized solution was then injected into a 5 mL syringe as the core solution. Two syringes containing the core and shell solutions were connected in parallel using coaxial nozzles of size 15 / 20G (15G nozzle inner diameter 1.45 mm, nozzle outer diameter 1.81 mm; 20G nozzle inner diameter 0.62 mm, nozzle outer diameter 0.90 mm). The negative voltage was adjusted to -2 kV and the positive voltage to 20 kV, and electrospinning was performed side-by-side at a push rate of 0.1 mm / min. Under electrostatic stretching, the outer shell solution and the core solution formed a composite Taylor cone at the nozzle, creating a core-shell coaxial composite structure. The spun film was dried in a 50 °C oven for 12 h. The obtained film was placed in a tube furnace and carbonized at 600°C for 30 min in a nitrogen atmosphere to obtain the carbonized film. Finally, the carbonized product was placed in a container through which azidoic acid gas generated by the reaction of sodium azide and stearic acid passed, and the azidation reaction was carried out at 120°C for 24 h to obtain a core-shell copper azide thin film material.

[0029] Example 2

[0030] Preparation of core-shell silver azide films:

[0031] Raw materials: Polyvinyl alcohol (PVA), silver nitrate (AgNO3), sodium hydroxide (NaOH), sodium azide (NaN3), ethanol, stearic acid (CH3(CH2)). 16 COOH).

[0032] Main instruments and equipment: electrospinning machine, magnetic stirrer, drying oven, tube furnace.

[0033] 1 g of polyvinyl alcohol was placed in 10 mL of deionized water and heated to 90 °C with magnetic stirring for 6 h. The homogenized solution was then injected into a 5 mL syringe as the shell solution. 1 g of silver nitrate was placed in 10 mL of deionized water and magnetically stirred at room temperature for 6 h. The homogenized solution was then injected into a 5 mL syringe as the core solution. Two syringes containing the core and shell solutions were connected in parallel using a 15 / 20G coaxial nozzle. The negative voltage was adjusted to -2 kV and the positive voltage to 20 kV, and electrospinning was performed side-by-side at a push rate of 0.1 mm / min. Under electrostatic stretching, the outer shell solution and the core solution formed a composite Taylor cone at the nozzle, creating a core-shell coaxial composite structure. The spun film was dried in a 50 °C oven for 12 h. The resulting film was then placed in a tube furnace and carbonized at 600 °C for 30 min in a nitrogen atmosphere to obtain the carbonized film. The carbonized film was then immersed in NaOH solution for 30 min and dried in an oven. Finally, the carbonization product was placed in a container through which azido acid gas generated by the reaction of sodium azide and stearic acid passed, and the azidation reaction was carried out at 120°C for 24 hours to obtain a core-shell silver azide thin film material.

[0034] Example 3

[0035] Preparation of core-shell lead azide thin films:

[0036] Raw materials: Polyvinyl alcohol (PVA), lead acetate ((CH3COO)2Pb), sodium azide (NaN3), ethanol, stearic acid (CH3(CH2) 16 COOH).

[0037] Main instruments and equipment: electrospinning machine, magnetic stirrer, drying oven, tube furnace.

[0038] 1 g of polyvinyl alcohol was placed in 10 mL of deionized water and heated to 90 °C with magnetic stirring for 6 h. The homogenized solution was then injected into a 5 mL syringe as the shell solution. 1 g of lead acetate was placed in 10 mL of deionized water and magnetically stirred at room temperature for 6 h. The homogenized solution was then injected into a 5 mL syringe as the core solution. Two syringes containing the core and shell solutions were connected in parallel using a 15 / 20G coaxial nozzle. The negative voltage was adjusted to -2 kV and the positive voltage to 20 kV, and electrospinning was performed side-by-side at a push rate of 0.1 mm / min. Under electrostatic stretching, the outer shell solution and the core solution formed a composite Taylor cone at the nozzle, creating a core-shell coaxial composite structure. The spun film was dried in a 50 °C oven for 12 h. The resulting film was then placed in a tube furnace and carbonized at 600 °C for 30 min in a nitrogen atmosphere to obtain the carbonized film. Finally, the carbonization product was placed in a container through which azido acid gas generated by the reaction of sodium azide and stearic acid passed, and the azidation reaction was carried out at 120°C for 24 hours to obtain a core-shell type lead azide thin film material.

[0039] Example 4

[0040] Preparation of core-shell copper azide thin films:

[0041] Raw materials: Polyvinylidene fluoride (PVDF), copper acetate (Cu(CH3COO)2·H2O), sodium azide (NaN3), DMF, stearic acid (CH3(CH2) 16 COOH).

[0042] Main instruments and equipment: electrospinning machine, magnetic stirrer, drying oven, tube furnace.

[0043] 1 g of polyvinyl alcohol was placed in 10 mL of DMF solvent and heated to 80 °C with magnetic stirring for 6 h. The homogenized solution was then injected into a 5 mL syringe as the shell solution. 1 g of copper acetate was placed in 10 mL of DMF and magnetically stirred at room temperature for 6 h. The homogenized solution was then injected into a 5 mL syringe as the core solution. Two syringes containing the core and shell solutions were connected in parallel using a 15 / 20G coaxial nozzle. The negative voltage was adjusted to -2 kV and the positive voltage to 20 kV, and electrospinning was performed side-by-side at a push rate of 0.1 mm / min. Under electrostatic stretching, the outer shell solution and the core solution formed a composite Taylor cone at the nozzle, creating a core-shell coaxial composite structure. The spun film was dried in a 50 °C oven for 12 h. The resulting film was then placed in a tube furnace and carbonized at 600 °C for 30 min in a nitrogen atmosphere to obtain the carbonized film. Finally, the carbonization product was placed in a container through which azido acid gas generated by the reaction of sodium azide and stearic acid passed, and the azidation reaction was carried out at 120°C for 24 hours to obtain a core-shell copper azide thin film material.

[0044] Example 5

[0045] Preparation of core-shell cadmium azide thin films:

[0046] Raw materials: Polyvinyl alcohol (PVA), cadmium acetate ((CH3COO)2Cd), sodium azide (NaN3), ethanol, stearic acid (CH3(CH2) 16 COOH).

[0047] Main instruments and equipment: electrospinning machine, magnetic stirrer, drying oven, tube furnace.

[0048] 1 g of polyvinyl alcohol was placed in 10 mL of deionized water and heated to 80 °C with magnetic stirring for 6 h. The homogenized solution was then injected into a 5 mL syringe as the shell solution. 1 g of cadmium acetate was placed in 10 mL of deionized water and magnetically stirred for 6 h. The homogenized solution was then injected into a 5 mL syringe as the core solution. Two syringes containing the core and shell solutions were connected in parallel using a 15 / 20G coaxial nozzle. The negative voltage was adjusted to -2 kV and the positive voltage to 20 kV, and electrospinning was performed side-by-side at a push rate of 0.1 mm / min. Under electrostatic stretching, the outer shell solution and the core solution formed a composite Taylor cone at the nozzle, creating a core-shell coaxial composite structure. The spun film was dried in a 50 °C oven for 12 h. The resulting film was then placed in a tube furnace and carbonized at 600 °C for 30 min in a nitrogen atmosphere to obtain the carbonized film. Finally, the carbonization product was placed in a container through which azidoic acid gas generated by the reaction of sodium azide and stearic acid passed, and the azidation reaction was carried out at 120°C for 24 hours to obtain a core-shell cadmium azide thin film material.

[0049] Example 6

[0050] Preparation of core-shell silver azide films:

[0051] Raw materials: Polyvinylpyrrolidone (PVP), silver nitrate (AgNO3), sodium azide (NaN3), sodium hydroxide (NaOH). Deionized water, stearic acid (CH3(CH2)). 16 COOH).

[0052] Main instruments and equipment: electrospinning machine, magnetic stirrer, drying oven, tube furnace.

[0053] 1 g of polyvinylpyrrolidone was placed in 10 mL of deionized water and heated to 80 °C with magnetic stirring for 6 h. The homogenized solution was then injected into a 5 mL syringe as the shell solution. 1 g of silver nitrate was placed in 10 mL of deionized water and magnetically stirred for 6 h. The homogenized solution was then injected into a 5 mL syringe as the core solution. Two syringes containing the core and shell solutions were connected in parallel using a 15 / 20G coaxial nozzle. The negative voltage was adjusted to -2 kV and the positive voltage to 20 kV, and electrospinning was performed side-by-side at a push rate of 0.1 mm / min. Under electrostatic stretching, the outer shell solution and the core solution formed a composite Taylor cone at the nozzle, creating a core-shell coaxial composite structure. The spun film was dried in a 50 °C oven for 12 h. The resulting film was then placed in a tube furnace and carbonized at 600 °C for 30 min in a nitrogen atmosphere to obtain a carbonized film. This carbonized film was then immersed in NaOH solution for 30 min and dried in an oven. Finally, the carbonization product was placed in a container through which azido acid gas generated by the reaction of sodium azide and stearic acid passed, and the azidation reaction was carried out at 120°C for 24 hours to obtain a core-shell silver azide thin film material.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A core-shell azide thin film, characterized in that, This core-shell azide film is prepared by using azide as the core and carbon film as the shell, through coaxial electrospinning technology and high-temperature carbonization and azideization processes. The steps include the following: Step 1: Soluble metal salt and easily spinnable polymer are used as the core solution and shell solution, respectively, and injected into two syringes for later use; Step 2: Assemble two syringes containing the core solution and the shell solution in parallel on an electrospinning machine, connect them to a coaxial nozzle for spinning, and place them in an oven to dry. Step 3: The thin film product obtained in Step 2 is calcined at high temperature under a nitrogen atmosphere to obtain a core-shell carbon-based thin film with metal particles as the core and carbon film as the shell. Step four: Azide gas is introduced into the thin film product obtained in step three to carry out an azidization reaction, and finally a core-shell azide thin film is obtained. In step three, the high-temperature calcination temperature is 400–800℃, and the calcination time is 10–120 min. As the voltage increases, when the charge on the surface of the outer solution increases and accumulates to a certain extent, the outer solution is dragged and stretched, forming a composite Taylor cone at the nozzle, and forming a core-shell coaxial composite structure wrapped by the shell layer. Finally, a core-shell fiber membrane is formed on the receiving device. After the subsequent carbonization process, the core-shell film can uniformly load metal particles while also coating a carbon film on the surface of the metal particles, effectively improving its electrostatic safety. More importantly, the film obtained by electrospinning technology is easy to process and shape. After the subsequent azidation process, a core-shell azid film compatible with MEMS technology can be directly obtained.

2. The core-shell azide film according to claim 1, characterized in that: The metal salts in step one include copper nitrate, copper acetate, lead nitrate, lead acetate, silver nitrate, silver acetate, cadmium nitrate, and cadmium acetate; the polymers include polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyvinyl butyral (PVB), polyethylene oxide (PEO), and polystyrene (PS).

3. The core-shell azide thin film according to claim 1, characterized in that: In step two, the spinning negative voltage is -2kV, the positive voltage is 8-20kV, the pusher speed is 0.05-0.2mm / min, and the core-shell injection speeds are 1:1, 1:2, 2:1, 1:3, 3:1, 1:4, 4:1, 1:5, 5:1, 1:10, and 10:1, respectively.

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