Film medium suitable for rapid laser ignition of pyrotechnic composition

Abstract

The invention belongs to the field of laser ignition, and discloses a film medium suitable for rapid laser ignition of pyrotechnic composition, the film medium is composed of a transparent substrate, a metal film deposited on the surface of the transparent substrate and an isolation chamber connected with the metal film, the metal film is a Ti-Al double-layer film, and the isolation chamber is a rigid sheet with a round hole in the center. The film medium can obviously shorten the laser ignition delay time on the premise of not changing the physicochemical properties of the pyrotechnic composition and not influencing the laser sensitivity of the pyrotechnic composition under the combined action of jet impact heat transfer and film fragment impact of film ablation products such as plasma and metal vapor converted from pulse laser energy.

Description

Technical Field

[0001] The invention belongs to the field of laser ignition, and in particular relates to a thin film medium suitable for rapid laser ignition of pyrotechnic powder. Background Art

[0002] Laser ignition technology is an important development direction of new ignition technology because of its strong anti-electromagnetic interference ability, reliable action, multi-point synchronous ignition, and non-destructive self-test. At present, laser ignition technology has been successfully applied to many military and civilian fields such as rocket / missile engine ignition, aircraft escape and life-saving devices, artillery ignition, and ground bomb disposal systems. Ignition delay time is an important performance parameter of laser ignition technology. A shorter laser ignition delay time improves the action time accuracy of the ignition system, which is of great significance in application scenarios that require instantaneous and synchronous ignition. At present, the mainstream method of laser ignition is laser direct ignition, that is, the laser directly acts on the energetic material, and the agent continuously accumulates heat under the action of the photothermal effect, and then completes the ignition. One of the effective ways to shorten the ignition delay time is to modify the energetic material to make it more sensitive to the laser, such as doping the energetic material with highly light-absorbing materials such as graphite and carbon black, and refining the agent particles. However, the modification process may have a negative impact on the stability, safety, and work output performance of the energetic material, which is not conducive to the practical application of laser ignition.

[0003] A layer of metal film medium is placed close to the surface of the agent, and the high-temperature and high-pressure plasma, metal vapor and other ablation products generated by laser irradiation of the film are used to work on the agent. The laser ignition delay time can be shortened without changing the properties of the energetic material itself. The metal film medium currently used by researchers is usually a single-layer Al film or Cu film. These two metal materials have a high reflectivity (>90%) to near-infrared lasers, which leads to a decrease in the laser ignition sensitivity of energetic materials. Higher laser energy is required to obtain a shorter laser ignition delay time. Reference 1 (Wang Zigeng. Study on medium effect during laser ignition [D]. Nanjing University of Science and Technology, 2007.) Al film and Cu film with thicknesses of 400nm and 830nm respectively are used as thin film media for laser ignition of B / KNO3 ignition powder. The corresponding laser ignition energy thresholds are 100.9mJ and 45.7mJ respectively. When the laser energy density is 7.2J / cm 2 The ignition delay times are 1.5ms and 3.0ms respectively, which is not significantly improved compared to laser direct ignition. Summary of the invention

[0004] The object of the present invention is to provide a thin film medium suitable for rapid laser ignition of pyrotechnic powder, which can significantly shorten the laser ignition delay time without changing the physical and chemical properties of the energetic material itself and without affecting the laser ignition sensitivity.

[0005] In order to achieve the above technical effects, the present invention provides the following technical solutions:

[0006] A thin film medium suitable for rapid laser ignition of pyrotechnic powder, the thin film medium comprising a transparent substrate, a metal film deposited on the surface of the transparent substrate and an isolation chamber connected to the metal film.

[0007] Furthermore, the transparent substrate adopts K9 glass.

[0008] Furthermore, the metal film is a Ti-Al double-layer film composed of a Ti layer and an Al layer, and its total thickness is 200nm to 900nm, wherein the thickness of the Ti layer is 90nm to 150nm, and the thickness of the Al layer is 50nm to 810nm.

[0009] Furthermore, the total thickness of the Ti-Al double-layer film is 500 nm, wherein the thickness of the Ti layer is 130 nm, and the thickness of the Al layer is 370 nm.

[0010] Furthermore, the Ti layer of the Ti-Al double-layer film is connected to the transparent substrate, and the Al layer is connected to the isolation chamber.

[0011] Furthermore, the Ti-Al double-layer film is prepared by radio frequency magnetron sputtering technology.

[0012] Furthermore, the isolation chamber is a rigid thin sheet with a circular hole in the center. The material of the isolation chamber is T10 steel, the thickness is 0.1 mm to 0.3 mm, and the diameter of the central circular hole is 0.4 mm to 0.6 mm.

[0013] Furthermore, the thickness of the isolation chamber is 0.1 mm, and the diameter of the central circular hole is 0.6 mm.

[0014] Compared with the prior art, the advantages of the present invention are as follows:

[0015] (1) The present invention adds a layer of Ti film on the basis of the traditional single-layer Al film, and utilizes the high absorption of Ti to near-infrared laser to improve the utilization rate of the film to laser energy and reduce the laser ignition energy threshold.

[0016] (2) The present invention adheres an isolation chamber to the surface of the metal film. The isolation chamber separates the metal film and the reagent by a certain gap. On the one hand, the plasma, metal vapor and other ablation products generated by the pulsed laser irradiating the metal film form a high-temperature jet under the joint constraints of the isolation chamber and the substrate, so that the heated area of ​​the reagent is more concentrated. On the other hand, the isolation chamber provides an acceleration distance for the unablated part of the film, so that it forms high-speed flying fragments driven by the rapidly expanding plasma, which collide with the surface of the reagent to form pits, thereby expanding the heat transfer area. Therefore, under the combined effect of the high-temperature jet impact heat transfer and the impact of the film fragments, the laser ignition delay time of the pyrotechnic powder can be significantly shortened. According to experimental tests, when the B / KNO3 ignition powder is laser ignited using the present invention as a medium, the 50% ignition energy is ≯12.2mJ, and the laser energy density is >7.5J / cm 2 The ignition delay time is stable at around 1.0ms. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure is a schematic diagram of the laser ignition action principle of the thin film medium suitable for rapid laser ignition of pyrotechnic powder according to the present invention.

[0018] Figure 2 This is the actual picture of the prepared Ti-Al double-layer film.

[0019] Figure 3 This is the SEM image of the cross section of the Ti-Al double-layer film.

[0020] Figure 4 This is the step gauge characterization result of Ti-Al double-layer film.

[0021] Figure 5 This is a real picture of the isolation chamber.

[0022] Figure 6 This is the reflectivity test result of Ti-Al double-layer film and single-layer Al film.

[0023] Figure 7 is the laser ignition energy threshold of B / KNO3 under different medium conditions.

[0024] Figure 8 This is the relationship between the laser ignition delay time and laser energy density of B / KNO3 under different medium conditions. DETAILED DESCRIPTION

[0025] The implementation effects of the present invention are further illustrated below in conjunction with the accompanying drawings, specific embodiments and comparative examples.

[0026] Combination Figure 1The laser ignition principle of the thin film medium suitable for laser rapid ignition of pyrotechnics described in the present invention is that a 1064nm pulse laser penetrates a glass substrate to ablate a Ti-Al double-layer film to cause it to undergo processes such as melting, vaporization, and ionization. Under the constraint of an isolation chamber, plasma and metal vapor generated by the ablation of the thin film form a high-temperature jet, and the unablated portion forms high-speed flying fragments driven by the rapidly expanding plasma. The pyrotechnics can ignite rapidly under the combined effects of the high-temperature jet impact heat transfer and the impact of the fragments.

[0027] Example 1

[0028] S1. After ultrasonic cleaning of the K9 glass substrate with acetone, anhydrous ethanol and deionized water for 30 minutes, fix it on the top of the vacuum chamber of the magnetron sputtering system. After polishing the pure Ti and pure Al targets to remove the surface oxide layer, install them on the target head in the vacuum chamber.

[0029] S2. Turn on the vacuum pump and heating power supply and wait until the pressure in the vacuum chamber drops to 5×10 -3 When the temperature reaches 200°C, introduce argon gas at a flow rate of 8 SCCM, turn on the ion beam pre-sputtering power supply, adjust the beam current to about 60 mA, adjust the bias current to 90 mA, and pre-sputter for 5 minutes to further clean and activate the K9 glass substrate to form dangling bonds on its surface.

[0030] S3. Turn on the RF power supply for thin film deposition, adjust the argon flow rate to 30 SCCM, adjust the vacuum chamber pressure to 0.4 Pa after ignition, adjust the sputtering power to 150 W, and sputter the Ti layer for 1 min and the Al layer for 20 min. The front and back sides of the prepared Ti-Al double-layer thin film sample are as follows Figure 2 shown.

[0031] S4. Perform SEM and step gauge characterization on the prepared film. The results are as follows: Figure 3 As shown, the total thickness of the Ti-Al double-layer film prepared in this embodiment is 487nm, of which the thickness of the Ti layer is 129nm and the thickness of the Al layer is 358nm. The film was tested for near-infrared reflectivity, and the results showed that the reflectivity of the film in the wavelength range of 900nm to 1700nm is about 35%.

[0032] S5. The film prepared in this embodiment is closely attached to an isolating chamber having a thickness of 0.1 mm and a central aperture of 0.6 mm. The isolating chamber is shown in the actual diagram. Figure 5 As shown, the density of the other side of the isolation chamber and the pressed medicine is 1.5g / cm 3 The end face of the B / KNO3 column (existing pyrotechnic powder) was closely attached to the laser ignition performance test. The laser ignition light source was a pulsed laser with a wavelength of 1064nm. The test results were: 50% ignition laser energy was 12.2mJ, and the laser energy density was >7.5J / cm2 The ignition delay time is stable at around 1.0ms.

[0033] Comparative Example 1

[0034] The difference from Example 1 is that in S3, no Ti layer is sputtered, only Al layer is sputtered for 25min, and a single-layer Al film is prepared. The other steps are the same. Characterization shows that the thickness of the single-layer Al film is 490nm, and the near-infrared reflectivity is about 78%. The near-infrared reflectivity of the Ti-Al double-layer film (Example 1) and the single-layer Al film (Comparative Example 1) is compared. Figure 6 The laser ignition performance test results are as follows: 50% ignition laser energy is 18.4mJ, laser energy density>10.0J / cm 2 The ignition delay time is stable at around 1.7ms.

[0035] Comparative Example 2

[0036] The difference from Example 1 is that there is no isolation chamber in S5, and the Ti-Al double-layer film is directly attached to the end face of the charge column. The other steps are the same. The laser ignition performance test results are: 50% ignition laser energy is 12.0mJ, laser energy density>10.5J / cm 2 The ignition delay time is stable at around 3.5ms.

[0037] Comparative Example 3

[0038] This comparative example is used as a blank control. The uncoated K9 glass substrate is placed close to the end face of the drug column and ignited directly by laser. The test results of laser ignition performance are: 50% ignition laser energy is 18.4mJ, laser energy density>10.0J / cm 2 The ignition delay time is stable at about 1.5ms. The laser ignition performance test results are: 50% ignition laser energy is 11.2mJ, laser energy density>10.5J / cm 2 The ignition delay time is stable at around 3.0ms.

[0039] Comparison of laser ignition energy thresholds of B / KNO3 under four different medium conditions in Example 1 and Comparative Examples 1 to 3 Figure 7 As shown, from Figure 7 It can be seen that the laser ignition energy threshold corresponding to the Ti-Al double-layer film in Example 1 is significantly lower than that of the single-layer Al film in Comparative Example 1, and is close to the energy threshold of direct laser ignition. This is because the low reflectivity of the Ti layer to near-infrared laser improves the utilization rate of the film to laser energy.

[0040] The relationship between laser ignition delay time and laser energy density of B / KNO3 under four different medium conditions is shown in the figure. Figure 8 As shown. Figure 8It can be seen that the shortest ignition delay time can be obtained under the conditions of the Ti-Al double-layer film / isolation chamber of Example 1. This is because the isolation chamber introduces the impact heat transfer of the ablation product jet and the impact of the film fragments into the laser ignition process. Compared with the case where the film medium and the charge are directly in close contact in Comparative Example 2, the heated area of ​​the agent is more concentrated and the heat transfer area is larger, so it can ignite more quickly.

Claims

1. A thin film medium suitable for rapid laser ignition of pyrotechnic powder, characterized in that: The thin film medium consists of a transparent substrate, a metal film deposited on the surface of the transparent substrate, and an isolation chamber connected to the metal film.

2. The thin film medium according to claim 1, characterized in that: The transparent substrate is made of K9 glass.

3. The thin film medium according to claim 1, characterized in that: The metal film is a Ti-Al double-layer film composed of a Ti layer and an Al layer, and its total thickness is 200 nm to 900 nm, wherein the thickness of the Ti layer is 90 nm to 150 nm, and the thickness of the Al layer is 50 nm to 810 nm.

4. The thin film medium according to claim 1, characterized in that: The metal film is a Ti-Al double-layer film composed of a Ti layer and an Al layer, and has a total thickness of 500 nm, wherein the thickness of the Ti layer is 130 nm, and the thickness of the Al layer is 370 nm.

5. The thin film medium according to claim 1, characterized in that: The metal film is a Ti-Al double-layer film composed of a Ti layer and an Al layer. The Ti layer of the Ti-Al double-layer film is connected to the transparent substrate, and the Al layer is connected to the isolation chamber.

6. The thin film medium according to claim 1, characterized in that: The metal film is prepared by adopting radio frequency magnetron sputtering technology.

7. The thin film medium according to claim 1, characterized in that: The isolation chamber is a rigid thin sheet with a circular hole in the center. The material is T10 steel, the thickness is 0.1 mm to 0.3 mm, and the diameter of the central circular hole is 0.4 mm to 0.6 mm.

8. The thin film medium according to claim 1, characterized in that: The thickness of the isolation chamber is 0.1 mm, and the diameter of the central circular hole is 0.6 mm.

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