Carbon dot-based photosensitive composite energetic micro-unit and preparation method thereof

Abstract

The invention relates to the field of preparation of composite energetic materials, and particularly discloses a carbon dot-based photosensitive composite energetic micro-unit and a preparation method thereof. The composite energetic micro-unit takes carbon dots (CD) as a photosensitive material, a nano high explosive as an energetic component and a water-soluble polymer material / sodium alginate aqueous solution as a liquid-phase carrier, and the photosensitive material and the energetic component are dispersed into the liquid-phase carrier to prepare a precursor with flowability. And then, dropwise adding the precursor into an aqueous solution with an ion replacement material through a needle head in a manner of combining a sol-gel method and a ball dropping process, and carrying out ion replacement, pre-freezing and freeze-drying to obtain the photosensitive composite energetic micro-unit. The photosensitive composite energetic micro-unit prepared by the invention is uniform in component distribution, can be reliably ignited under multi-angle incident laser irradiation, is beneficial to improving the reliability of laser ignition high explosives, and has important practical application value in micro ignition and micro detonation.

Description

Technical Field

[0001] This invention relates to the field of composite energetic materials preparation, specifically to a carbon dot-based photosensitive composite energetic microunit and its preparation method. Background Technology

[0002] Laser-ignited high explosives utilize laser energy to trigger a chemical reaction in the explosive. This method boasts excellent resistance to electromagnetic interference and is a crucial means of controlled energy release in weapon systems and aerospace applications. However, it's important to note that despite these advantages, the inherently poor light absorption characteristics of high explosives often necessitate the use of specific wavelengths of laser light and high energy during ignition, which is detrimental to successful laser ignition. To address this, photosensitive materials are often introduced into the high explosive to form a composite energetic system, reducing laser ignition energy and improving ignition reliability. However, since high explosives are organic materials while photosensitive materials are often inorganic or metallic, their differing properties during mixing / composite processes often prevent the formation of strong interactions. This can lead to uneven distribution of the photosensitive material within the composite energetic system, hindering the formation of a uniform light absorption and photothermal conversion interface.

[0003] To address these issues, researchers have introduced low-dimensional materials rich in active groups into composite energetic systems, such as hydroxyl-rich graphene oxide. Small, 2019, 1900338 Modified carbon nanotubes and other materials can be introduced into composite energetic systems, or photothermal conversion materials can be fabricated into photothermal conversion films to achieve laser ignition (CN113353924B). However, it is important to note that graphene oxide (GO) and carbon nanotubes (CNTs) are two-dimensional and one-dimensional materials, respectively. These materials inevitably face the orientation problem of laser irradiation during light absorption. For example, graphene oxide only achieves its maximum effect when the laser irradiates its surface perpendicularly, which is disadvantageous for laser ignition, a highly directional ignition method. On the other hand, although the orientation problem of laser irradiation can be solved by prefabricating structures for photothermal conversion films, the potential interfacial combination problem between the photothermal conversion film and the high explosive material must be considered. Furthermore, based on currently available information, there are no reports on the use of carbon dots as photosensitive materials for laser ignition of energetic materials. Summary of the Invention

[0004] This invention addresses the challenge of forming a uniform light absorption and photothermal conversion interface in composite energetic systems due to the uneven distribution of photosensitive materials, as well as the orientation problem of laser absorption in energetic composite systems. It provides a method for preparing carbon dot-based photosensitive composite energetic microunits. This invention selects carbon dots (CDs), which possess "zero-dimensional" characteristics, contain active groups on their surface and interface, exhibit stable properties, and have photothermal conversion capabilities, as the photosensitive material. Using the sol-gel method, a carbon dot-based photosensitive composite energetic microunit is constructed. Through hydrogen bonding between the abundant -OH and -COOH functional groups on the carbon dot surface and the polymer material, the problem of uneven distribution of the photosensitive material in the composite energetic microunit and the heat transfer problem at the photothermal heterogeneous interface is solved. Simultaneously, the zero-dimensional nature of CDs can avoid the orientation problem of laser absorption in one-dimensional or two-dimensional photosensitive materials, which is beneficial for achieving a homogeneous response under multi-angle laser irradiation.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for preparing carbon dot-based photosensitive composite energetic microunits, comprising the following steps: Step 1: Using a water-soluble polymer and sodium alginate aqueous solution as a liquid phase carrier, nano-explosive as a solid phase component, and water-soluble carbon dots as a photosensitive material, the solid phase component and photosensitive material are mixed into the liquid phase carrier by ultrasonic dispersion and physical stirring to form a precursor. Step 2: The precursor is added dropwise to an aqueous solution containing dissolved transition metal ion salts using a syringe. A gel is formed through the ionic cross-linking reaction between the transition metal ions and sodium alginate in the precursor, thus initially shaping the photosensitive composite energetic microunit. Step 3: After pre-freezing and freeze-drying the initially formed photosensitive composite energetic microunits, the final photosensitive composite energetic microunits are obtained.

[0006] As a further limitation of the technical solution of the present invention, the water-soluble polymer mentioned in step one is at least one of polyvinyl alcohol (PVA), hydroxypropyl methylcellulose (HPMC), carboxymethyl chitosan and hydroxyethyl cellulose.

[0007] As a further limitation of the technical solution of the present invention, the water-soluble carbon dots mentioned in step one are at least one of coal tar pitch carbon dots, graphene carbon dots and carbonized polymer carbon dots; the particle size is 4-20nm and the mass percentage range is 0.5%-10%.

[0008] As a further limitation of the technical solution of the present invention, the nano-explosive in step one is CL-20, HMX or RDX.

[0009] As a further limitation of the technical solution of the present invention, in step one, the liquid carrier is a mixture of a 0.5%-1.5% mass concentration high molecular weight polymer aqueous solution and a 1% mass concentration sodium alginate aqueous solution in a mass ratio of 1-2:1-4; the mass ratio of the liquid carrier, water-soluble carbon dots and nano-explosive is 63-71:1-2.6:27.5-34.4.

[0010] As a further limitation of the technical solution of the present invention, the diameter of the syringe needle in step two is 0.1mm-1.6mm.

[0011] As a further limitation of the technical solution of the present invention, the transition metal ion salt mentioned in step two is at least one of copper chloride, copper sulfate, ferrous chloride, ferric chloride, cobalt chloride, nickel chloride and aluminum chloride; the mass concentration of the aqueous solution of the transition metal ion salt is 1%-5%.

[0012] As a further limitation of the technical solution of the present invention, the mass ratio of the precursor to the aqueous solution of the transition metal ion salt in step two is 1:10-30.

[0013] As a further limitation of the technical solution of the present invention, the pre-freezing in step three uses refrigeration equipment, the temperature is maintained at -10℃ to -30℃, the freezing time is 6h-24h, and the freeze-drying time is 9-12h.

[0014] The present invention also provides carbon dot-based photosensitive composite energetic microunits prepared by the above method.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention employs a combination of the sol-gel method and the drop ball process. Carbon dots and nano-explosives are suspended in a liquid carrier containing a water-soluble polymer and sodium alginate. The drop ball process then adds these materials dropwise into an aqueous solution containing transition metal ions, allowing the Na+ in the sodium alginate to dissolve. + The cross-linking and substitution reaction with transition metal ions forms a gel, which shapes the carbon dot-based photosensitive composite energetic microunits. This preparation method has advantages such as high sphericity, controllable particle size, simple process, and repeatability, which is conducive to realizing batch preparation.

[0016] This invention selects carbon dots, which are water-soluble and rich in active groups on their surface, as photosensitive materials. Their interfaces contain abundant -OH and -COOH functional groups, which facilitates the formation of tight interfacial coupling with other components through non-covalent interactions such as hydrogen bonding. This promotes the effective transfer of photo-thermal energy between heterogeneous interfaces in the composite energetic system, and can solve the problems of uneven dispersion and orientation of light absorption in the composite energetic system. It is beneficial to achieve homogeneous response under multi-angle laser irradiation and plays an important role in the quality control of composite energetic micro-units. Attached Figure Description

[0017] Figure 1 This is a SEM image of the CD / CL-20-based composite energetic microunit from Embodiment 1 of the present invention.

[0018] Figure 2 This is an ignition and combustion diagram of the CD / CL-20-based composite energetic microunit in Embodiment 1 of the present invention.

[0019] Figure 3 This is a SEM image of the CD / HMX-based composite energetic microunit from Embodiment 2 of the present invention.

[0020] Figure 4 This is an ignition and combustion diagram of the CD / HMX-based composite energetic microunit in Embodiment 2 of the present invention.

[0021] Figure 5 This is a SEM image of a CD / RDX-based composite energetic microunit from Embodiment 3 of the present invention.

[0022] Figure 6 This is an ignition and combustion diagram of the CD / RDX-based composite energetic microunit in Embodiment 3 of the present invention.

[0023] Figure 7 This is a SEM image of the GO / CL-20-based composite energetic microunit, which is a comparative example of the present invention.

[0024] Figure 8 This is an ignition and combustion diagram of the GO / CL-20-based composite energetic microunit, which is a comparative example of the present invention.

[0025] Figure 9 This is a schematic diagram illustrating the fabrication of the carbon dot-based photosensitive composite energetic microunit of the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments. Example 1

[0027] The preparation process of CD / CL-20 based composite energetic microunits includes the following steps: First, PVA was dissolved by stirring at 95℃ for 5 hours to prepare a 1% PVA aqueous solution as solution A. A 1% SA (sodium alginate) aqueous solution was prepared at room temperature as solution B. Then, solutions A and B were weighed into beakers at a mass ratio of 2:3 and stirred for 1 hour to mix them evenly to prepare the liquid carrier. CD and nano CL-20 were added to the liquid carrier (the mass ratio of CD, nano CL-20 and liquid carrier was 1:32:67) to form a precursor dispersion. After ultrasonic dispersion until there were no obvious particle agglomerates, the uniformly mixed suspension (precursor dispersion) was transferred to a syringe and rotated at 1200 r / min for 2 min to remove air bubbles from the suspension. Finally, the precursor dispersion was squeezed out and dropped into a 2% CuCl2·2H2O aqueous solution using a syringe pump for crosslinking for 24 hours (the mass ratio of the precursor dispersion to the CuCl2·2H2O aqueous solution was 1:10). The needle diameter was 0.37 mm. The solution was washed three times with deionized water to remove excess CuCl2. After cleaning the pellets, they were frozen at -24℃ for 24 hours and then freeze-dried for 10 hours to obtain CD / CL-20-based composite energetic microunits. Their SEM images are shown below. Figure 1 As shown.

[0028] CD / CL-20 based composite energetic microunits were placed in a sample cell and ignition tests were performed using a 1064nm wavelength laser. The angles between the laser incident angle and the sample cell plane were 30°, 60°, and 90°, respectively. High-speed photography was used to capture their combustion characteristics. Ignition and combustion diagrams are shown below. Figure 2 As shown in the figure, the experimental results show that CD / CL-20-based composite energetic micro-units can be successfully ignited under laser energies of 1J, 1.2J and 1J, respectively, demonstrating good ignition stability. Example 2

[0029] The fabrication process of CD / HMX-based composite energetic microunits includes the following steps: First, at room temperature, HPMC was dissolved in an aqueous solution by stirring for 5 hours to prepare a 0.5% HPMC aqueous solution as solution A. SA was dissolved in an aqueous solution by stirring for 2 hours to prepare a 1% SA aqueous solution as solution B. Then, solutions A and B were weighed into beakers at a mass ratio of 1:4 and stirred for 2 hours to mix them evenly, thus preparing the liquid phase carrier. CD and nano HMX were added to the liquid carrier (the mass ratio of CD, nano HMX and the carrier was 1.5:27.5:71) to form a precursor dispersion, which was then ultrasonically dispersed until there were no obvious particle agglomerates. The well-mixed suspension, i.e. the precursor dispersion, is transferred into a syringe and rotated at 1200 r / min for 2 min to remove air bubbles from the suspension. Finally, the precursor dispersion was squeezed out and dropped into a 2% FeCl3 aqueous solution using a syringe pump for crosslinking for 24 hours (the mass ratio of the precursor dispersion to the FeCl3 aqueous solution was 1:20, the needle diameter was 0.5 mm, and it was washed 3 times with deionized water to remove excess FeCl3). After cleaning the pellets, they were frozen at -24°C for 24 hours and then freeze-dried for 12 hours to obtain HMX-based composite energetic microunits. Their SEM images are shown below. Figure 3 As shown.

[0030] CD / HMX-based composite energetic microunits were placed in a sample cell and ignition tests were performed using a 1064nm wavelength laser. The angles between the laser incident angle and the sample cell plane were 30°, 60°, and 90°, respectively. High-speed photography was used to capture their combustion characteristics. Ignition and combustion images are shown below. Figure 2 As shown, the experimental results indicate that CD / HMX-based composite energetic microunits can be successfully ignited under laser energies of 16.2 J, 16.5 J, and 16 J, respectively, demonstrating good ignition stability. Example 3

[0031] The fabrication process of CD / RDX-based composite energetic microunits includes the following steps: First, at room temperature, CMC is dissolved in an aqueous solution by stirring for 2 hours to prepare a 1.5% CMC aqueous solution as solution A. SA is dissolved in an aqueous solution by stirring for 2 hours to prepare a 1% SA aqueous solution as solution B. Then, solutions A and B are weighed into beakers at a mass ratio of 1:1 and stirred for 1 hour to mix them evenly, thus preparing the liquid phase carrier.

[0032] CD and nano-RDX were added to the liquid carrier (the mass ratio of CD, nano-RDX and the carrier was 2.6:34.4:63) to form a precursor dispersion. After ultrasonic dispersion until there were no obvious particle agglomerates, the uniformly mixed suspension, i.e. the precursor dispersion, was transferred to a syringe and rotated at 1200 r / min for 2 min to remove air bubbles from the suspension. Finally, the precursor dispersion was squeezed out and dropped into a 2% CuSO4·5H2O aqueous solution using a syringe pump for crosslinking for 24 hours (the mass ratio of the precursor dispersion to the CuSO4·5H2O aqueous solution was 1:15). The needle diameter was 0.7 mm. The solution was washed three times with deionized water to remove excess CuSO4. After cleaning the pellets, they were frozen at -24°C for 24 hours and then freeze-dried for 9 hours to obtain RDX-based composite energetic microunits. Their SEM images are shown below. Figure 5 As shown.

[0033] CD / RDX-based composite energetic microunits were placed in a sample cell and ignition tests were performed using a 1064nm wavelength laser. The angles between the laser incident angle and the sample cell plane were 30°, 60°, and 90°, respectively. High-speed photography was used to capture their combustion characteristics. Ignition and combustion diagrams are shown below. Figure 6 As shown in the figure, the experimental results show that CD / HMX-based composite energetic micro-units can be successfully ignited under laser irradiation with energies of 20.8 J, 20.5 J and 20.5 J, respectively, demonstrating good ignition stability.

[0034] Comparative Example The preparation process of GO / CL-20 based composite energetic microunits includes the following steps: First, PVA was dissolved by stirring at 95℃ for 5 hours to prepare a 1% PVA aqueous solution as solution A. A 1% SA aqueous solution was prepared at room temperature as solution B. Then, solutions A and B were weighed into beakers at a mass ratio of 2:3 and stirred for 1 hour to mix them evenly to prepare a liquid carrier. GO and nano CL-20 were added to the liquid carrier (the mass ratio of GO, nano CL-20 and liquid carrier was 1:32:67) to form a precursor dispersion. After ultrasonic dispersion until there were no obvious particle agglomerates, the uniformly mixed suspension, i.e. the precursor dispersion, was transferred to a syringe and rotated at 1200 r / min for 2 min to remove air bubbles from the suspension. Finally, the precursor dispersion was extruded and dripped into a 2% CuCl2·2H2O aqueous solution using a syringe pump for crosslinking for 24 hours (the mass ratio of the precursor dispersion to the CuCl2·2H2O aqueous solution was 1:10). The syringe diameter was 0.37 mm. The solution was washed three times with deionized water to remove excess CuCl2. After cleaning the pellets, they were frozen at -24°C for 24 hours and then freeze-dried for 10 hours to obtain CL-20-based composite energetic microunits. Their SEM images are shown below. Figure 7 As shown.

[0035] GO / CL-20 based composite energetic microunits were placed in a sample cell and ignition tests were performed using a 1064nm wavelength laser. The angles between the laser incident angle and the sample cell plane were 30°, 60°, and 90°, respectively. High-speed photography was used to capture their combustion characteristics. Ignition and combustion diagrams are shown below. Figure 8 As shown, the experimental results indicate that GO / CL-20-based composite energetic micro-units can be successfully ignited under laser energies of 6J, 5J, and 4.5J, respectively. However, the energy required for ignition varies significantly at each angle, demonstrating the selectivity of GO to the laser direction.

Claims

1. A method for preparing a carbon dot-based photosensitive composite energetic microunit, characterized in that, Includes the following steps: Step 1: Using a water-soluble polymer and sodium alginate aqueous solution as a liquid phase carrier, nano-explosive as a solid phase component, and water-soluble carbon dots as a photosensitive material, the solid phase component and photosensitive material are mixed into the liquid phase carrier by ultrasonic dispersion and physical stirring to form a precursor. Step 2: The precursor is added dropwise to an aqueous solution containing dissolved transition metal ion salts using a syringe. A gel is formed through the ionic cross-linking reaction between the transition metal ions and sodium alginate in the precursor, thus initially shaping the photosensitive composite energetic microunit. Step 3: After pre-freezing and freeze-drying the initially formed photosensitive composite energetic microunits, the final photosensitive composite energetic microunits are obtained.

2. The method for preparing a carbon dot-based photosensitive composite energetic microunit according to claim 1, characterized in that, The water-soluble polymer mentioned in step one is at least one of polyvinyl alcohol, hydroxypropyl methylcellulose, carboxymethyl chitosan, and hydroxyethyl cellulose.

3. The method for preparing a carbon dot-based photosensitive composite energetic microunit according to claim 1, characterized in that, The water-soluble carbon dots mentioned in step one are at least one of coal tar pitch carbon dots, graphene carbon dots, and carbonized polymer carbon dots; the particle size is 4-20 nm, and the mass percentage range is 0.5%-10%.

4. The method for preparing a carbon dot-based photosensitive composite energetic microunit according to claim 1, characterized in that, The nano-explosive in step one is CL-20, HMX, or RDX.

5. The method for preparing a carbon dot-based photosensitive composite energetic microunit according to claim 1, characterized in that, In step one, the liquid carrier is a mixture of a 0.5%-1.5% (w / w) high molecular weight polymer aqueous solution and a 1% (w / w) sodium alginate aqueous solution in a mass ratio of 1-2:1-4; the mass ratio of the liquid carrier, water-soluble carbon dots and nano-explosive is 63-71:1-2.6:27.5-34.

4.

6. The method for preparing a carbon dot-based photosensitive composite energetic microunit according to claim 1, characterized in that, The diameter of the syringe needle mentioned in step two is 0.1mm-1.6mm.

7. The method for preparing a carbon dot-based photosensitive composite energetic microunit according to claim 1, characterized in that, The transition metal ion salt mentioned in step two is at least one of copper chloride, copper sulfate, ferrous chloride, ferric chloride, cobalt chloride, nickel chloride, and aluminum chloride; the mass concentration of the aqueous solution of the transition metal ion salt is 1%-5%.

8. The method for preparing a carbon dot-based photosensitive composite energetic microunit according to claim 1, characterized in that, The mass ratio of the precursor to the aqueous solution of the transition metal ion salt in step two is 1:10-30.

9. The method for preparing a carbon dot-based photosensitive composite energetic microunit according to claim 1, characterized in that, The pre-freezing described in step three uses refrigeration equipment, with the temperature maintained between -10°C and -30°C, and the freezing time is 6-24 hours; the freeze-drying time is 9-12 hours.

10. The carbon dot-based photosensitive composite energetic microunit obtained by the preparation method according to any one of claims 1-9.

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