Photothermal conversion material and application thereof

Abstract

The invention relates to a photothermal conversion material and application thereof, and belongs to the technical field of laser ignition. The photothermal conversion material comprises a composite material formed by loading gold particles on titanium carbide nanosheets and fluorinated alkyl bonded on the surface of the composite material. Gold particles are loaded on the titanium carbide nanosheets, the photothermal conversion performance of the titanium carbide nanosheets can be enhanced on the physical level, meanwhile, fluorinated alkyl silane is adopted for modifying the composite material, the photothermal conversion material can generate CFx free radicals under laser irradiation, oxygenolysis of the titanium carbide nanosheets is accelerated through a chemical reaction, and the photothermal conversion performance of the titanium carbide nanosheets is improved. A TiO2 hardened layer generated by the titanium carbide nanosheet under laser irradiation is broken through, the titanium carbide nanosheet is completely oxidized, energy release of the titanium carbide nanosheet is improved to the maximum extent, high-temperature pulses are instantly generated, and when the titanium carbide nanosheet is used for laser ignition, combustion of energetic materials can be rapidly triggered under low laser energy irradiation.

Description

Technical Field

[0001] The present invention relates to a photothermal conversion material and its application, belonging to the technical field of laser ignition. Background Art

[0002] Lasers play an important role in the fields of aerospace. Among them, laser ignition, as a new type of ignition technology that combines safety, reliability, and portability, has been widely used in the fields of aviation, aerospace, and military. Laser ignition technology refers to the technology of detonating or igniting energetic materials with high-energy lasers. Laser ignition technology can transmit energy to the ignition position through optical fibers. Therefore, compared with traditional electric initiation methods, laser ignition technology is less affected by external electromagnetic signals. In addition, lasers can output high energy instantaneously, thereby realizing the ignition of insensitive explosives. And laser ignition technology can achieve multi-point synchronous ignition, can be reused, and also has the advantages of small size, light weight, and strong environmental adaptability. Therefore, lasers are one of the most advanced and promising ignition energy sources at present.

[0003] Currently, the common laser ignition method is to physically mix energetic materials with photothermal materials. However, the physical mixing process has potential hazards, and the composite materials obtained by physical mixing have the drawback of uneven distribution of photothermal materials. Moreover, this ignition method will cause the heat formed by the photothermal effect to be more dispersed. Since the laser ignition process is affected by the laser transmission depth, during the laser ignition process, only the photothermal materials on the surface layer of the composite material are heated, while the photothermal materials in the deep layer cannot play the role of photothermal conversion. To overcome the above disadvantages, an interface heating type laser ignition technology has been developed. The interface heating type laser ignition technology is to centrally place the photothermal material in the form of a thin film on the surface of the energetic material. During the laser ignition process, the incident laser energy is converted into heat energy by the photothermal conversion material thin film and ignites the energetic material in the form of interface heating. Since the photothermal effect is concentrated in a limited thin film space and a limited time irradiated by the laser pulse during the ignition process, the interface heating type laser ignition technology can achieve the concentrated utilization of laser energy in time and space. However, with the development of laser ignition technology, more stringent requirements are put forward for the photothermal efficiency of photothermal conversion materials. To meet the high-performance laser ignition use requirements under low starting energy, the photothermal conversion material needs to rapidly increase its temperature under the irradiation of millisecond pulsed light.

[0004] Mxene is a series of novel two-dimensional materials composed of transition metal carbides and / or carbonitrides. Mxene is a two-dimensional material with functional groups on the surface obtained by chemically or electrochemically etching the intermediate A layer of MAX (M is a transition metal element, A is Al or Si, and X is C or N). The chemical formula of MXene can be expressed as M n+1 X nTx, where M is a transition metal element, X is an element of C or N, n represents the quantity, and T is a functional group. MXene can be divided into multi-layer and single-layer types. Single-layer MXene can be prepared by ultrasonic dispersion of multi-layer MXene. MXene has electrical and thermal conductivity comparable to that of graphene, and also has excellent catalytic properties, mechanical properties, thermal stability, flame retardancy, electromagnetic shielding properties, as well as electrical conductivity, thermal conductivity, and energy storage properties, etc., and is widely used in the preparation of electrode materials, energy storage, chemical catalysis and other fields. In recent years, MXene has attracted extensive attention from researchers in many fields due to its rich raw material sources, low price, and properties of both electrical conductivity, hydrophilicity, and adjustable surface (functional group) structure. It is reported that the internal photothermal conversion efficiency of titanium carbide nanosheets (Ti3C2Tx MXene) is 100%, and its metastable structure can induce an exothermic oxidation reaction during the photothermal process, and further convert the absorbed light into more heat through a physical / chemical coupling mechanism. However, for some special application fields, such as the laser ignition of high-energy materials, under pulsed laser irradiation, the heat generated by pure Ti3C2Tx MXene materials is still not high enough. This is because after its surface layer is oxidized, a plate-like TiO2 will be formed, preventing oxygen from entering its interior, resulting in incomplete oxidation of the material and a reduction in heat release.

[0005] To improve the photothermal conversion performance of Mxene, Chinese patent document CN114672233A discloses a preparation method of a photothermal superhydrophobic coating based on MXene@Au hybrids. This patent document uses MXene@Au hybrids as photothermal fillers. The surface plasmon effect and synergistic photothermal effect possessed by MXene@Au hybrids can effectively improve the photothermal conversion efficiency of the coating. Chinese patent document CN116689772A discloses a high-efficiency photothermal conversion material. The photothermal conversion material disclosed in this patent document is MXene / Au@Cu 2-x S, 0 < x < 2, and the said MXene / Au@Cu 2-x S is composed of MXene nanosheets and Au@Cu 2-x S core-shell heterostructure materials are obtained by chemical reaction compounding. The molar ratio of the said MXene nanosheets to the Au@Cu 2-x S core-shell heterostructure materials is 1:(0.1 - 1). This patent document strongly couples nano-metals with plasmon resonance effects and semiconductors to improve the photothermal conversion efficiency. At the same time, the Au@Cu 2-x S core-shell heterostructure materials are combined with ultrathin MXene nanosheets through chemical bonds, so that the obtained photothermal conversion material MXene / Au@Cu 2-x S has good light absorption from visible light to near-infrared light and has an excellent synergistic photothermal conversion effect. The photothermal conversion material MXene / Au@Cu 2-xS is used in the desalination of seawater or the purification of sewage, with a high water evaporation rate, stability, and excellent seawater desalination and sewage treatment effects. However, the photothermal conversion efficiency of the photothermal conversion materials disclosed in the above patent documents is still relatively low and cannot meet the usage requirements of laser ignition under low starting energy. Summary of the Invention

[0006] The object of the present invention is to provide a photothermal conversion material, which can solve the problem of relatively low photothermal conversion efficiency existing in current Mxene-based materials.

[0007] Another object of the present invention is to provide an application of a photothermal conversion material in laser ignition, which can solve the problem that current Mxene-based materials cannot meet the usage requirements of laser ignition under low starting energy.

[0008] In order to achieve the above objects, the technical solution adopted by the photothermal conversion material of the present invention is as follows:

[0009] A photothermal conversion material is prepared by a method including the following steps:

[0010] S1, mixing and reacting a first soluble gold source, an alkaline compound, a first reducing agent, titanium carbide nanosheets, and gold seeds in water, standing to obtain a composite material; the gold seeds are prepared by a reduction reaction of a second soluble gold source and a second reducing agent in water; the first soluble gold source and the second soluble gold source are independently chloroauric acid and / or a hydrate of chloroauric acid;

[0011] S2, mixing and reacting the composite material and a fluorinated alkylsilane in a solvent, performing solid-liquid separation, and then drying the solid obtained by solid-liquid separation to obtain a photothermal conversion material.

[0012] The photothermal conversion material of the present invention includes a composite material formed by gold particles loaded on titanium carbide nanosheets and fluorinated alkyls bonded to the surface of the composite material. By loading gold particles on titanium carbide nanosheets, the present invention can physically enhance the photothermal conversion performance of titanium carbide nanosheets. At the same time, by modifying the composite material with fluorinated alkylsilane, the photothermal conversion material can generate CFx free radicals under laser irradiation. Through a chemical reaction, the oxidation decomposition of titanium carbide nanosheets is accelerated, the TiO2 caking layer formed by titanium carbide nanosheets under laser irradiation is broken, and the titanium carbide nanosheets are completely oxidized, maximizing the energy release of titanium carbide nanosheets and instantaneously generating a high-temperature pulse, which can be used to quickly trigger the combustion of energetic materials under low laser energy irradiation during laser ignition.

[0013] Preferably, the first reducing agent is hydroxylamine hydrochloride. Preferably, the second reducing agent is citrate. For example, the second reducing agent is an alkali metal citrate. The reasons for using hydroxylamine hydrochloride as the first reducing agent and citrate as the second reducing agent are as follows: The reducibility of hydroxylamine hydrochloride is relatively low, and it will not cause secondary nucleation of gold particles during the reduction process. The prepared gold nanoparticles have better dispersibility and better operation repeatability; using citrate as the second reducing agent to prepare gold nanoseeds can make the particle sizes of the prepared gold nanoseeds consistent, and the size of the gold nanoparticles can be adjusted by controlling the amount of the alkali metal citrate.

[0014] Preferably, the mass ratio of the gold element in the second soluble gold source to the second reducing agent is (2 - 4):(8 - 12). For example, the mass ratio of the gold element in the second soluble gold source to the second reducing agent is 4:12. Preferably, the temperature of the reduction reaction for preparing the gold seeds is 95 - 100 °C, and the time is 18 - 20 min. Preferably, the reduction reaction for preparing the gold seeds is to mix the aqueous solution of the second soluble gold source and the aqueous solution of the second reducing agent; the mass fraction of the aqueous solution of the second soluble gold source is 0.01 - 0.02%, and the mass fraction of the aqueous solution of the second reducing agent is 1 - 1.5%.

[0015] Preferably, the mass ratio of the gold element in the first soluble gold source, the basic compound, the first reducing agent, the titanium carbide nanosheet, and the gold element in the gold seeds is (9 - 12):(4 - 6):(1.5 - 2):(25 - 30):(2 - 3). For example, the first soluble gold source is chloroauric acid tetrahydrate, and the mass ratio of the gold element in the first soluble gold source, the basic compound, the first reducing agent, the titanium carbide nanosheet, and the gold element in the gold seeds is 9:4:1.5:25:2.

[0016] In order to further improve the photothermal conversion efficiency of the photothermal conversion material, preferably, the thickness of the titanium carbide nanosheet is 1.5 - 1.7 nm, the sheet diameter is 0.5 - 1 μm, and the number of layers is 2 - 3 layers.

[0017] Preferably, the time of the mixing reaction for preparing the composite material in step S1 is 8 - 10 min, and the standing time is not less than 24 h. For example, the time of the mixing reaction for preparing the composite material in step S1 is 10 min, and the standing time is 24 h.

[0018] Preferably, the mixing reaction carried out when preparing the composite material in step S1 includes the following steps: mixing an aqueous solution of a first soluble gold source and an aqueous solution of an alkaline compound to obtain a mixed solution, and then mixing the mixed solution, an aqueous dispersion of titanium carbide nanosheets, an aqueous solution of hydroxylamine hydrochloride, and an aqueous dispersion of gold seeds; the mass fraction of the aqueous solution of the first soluble gold source is 0.01-0.02%, the concentration of the aqueous solution of the alkaline compound is 1-1.5 mol / L, the mass fraction of the aqueous dispersion of titanium carbide nanosheets is 5-6%, the mass fraction of the aqueous solution of hydroxylamine hydrochloride is 0.14-0.2%, and the aqueous dispersion of gold seeds is a system after mixing and reacting an aqueous solution of a second soluble gold source and an aqueous solution of a second reducing agent.

[0019] Preferably, the mass ratio of titanium carbide nanosheets to fluorinated alkylsilane in the composite material is (1-2):(10-16). For example, the mass ratio of titanium carbide nanosheets to fluorinated alkylsilane in the composite material is 1:10.

[0020] Preferably, the fluorinated alkylsilane is a perfluoroalkyltrialkoxysilane; the perfluoroalkyl is a C8-C10 perfluoroalkyl, and the alkoxy group is a C1-C3 alkoxy group. For example, the fluorinated alkylsilane is perfluorodecyltriethoxysilane, perfluorodecyltrimethoxysilane. Compared with other fluorosilane coupling agents, the selection of perfluorodecyltriethoxysilane and perfluorodecyltrimethoxysilane has a high fluorine content, can generate more CFx free radicals under laser irradiation, and has strong hydrophobicity to maintain the stability of MXene / AuNFs.

[0021] Preferably, the solvent includes a water-soluble organic solvent and water; the water-soluble organic solvent is an alcohol solvent. For example, the water-soluble organic solvent is methanol, ethanol.

[0022] Preferably, the method for mixing and reacting the composite material and the fluorinated alkylsilane in the solvent includes the following steps: under stirring, adding an alcohol solution of the fluorinated alkylsilane to the aqueous dispersion of the composite material, and then continuing to stir; the mass fraction of the alcohol solution of the fluorinated alkylsilane is 0.5-0.8%, and the aqueous dispersion of the composite material is the system after the mixing reaction carried out when preparing the composite material.

[0023] In order to reduce costs and at the same time obtain a photothermal conversion material with a certain appearance shape (for example, film-like), preferably, the solid-liquid separation is filtration. Preferably, the filtration is carried out under negative pressure. Preferably, the drying is vacuum freeze-drying of the filter cake on the filtered membrane. Preferably, the vacuum freeze-drying includes freezing and vacuum drying carried out in sequence.

[0024] Preferably, the photothermal conversion material is a film-like material. Making the photothermal conversion material into a film-like material can be directly applied to the field of laser ignition, and at the same time has high photothermal conversion efficiency and hydrophobic performance, and can be used as a solar photothermal water evaporator for seawater desalination.

[0025] The technical solution adopted for the application of the photothermal conversion material of the present invention in laser ignition is as follows:

[0026] An application of the photothermal conversion material as described above in laser ignition.

[0027] When the photothermal conversion material of the present invention is used in laser ignition, the photothermal conversion material can instantaneously generate high-temperature pulses and can quickly trigger the combustion of energetic materials under low laser energy irradiation.

[0028] It can be understood that the application of the photothermal conversion material in laser ignition refers to using the photothermal conversion material as a light-controlled detonator in laser ignition. Description of the Drawings

[0029] Figure 1 It is a schematic diagram of the temperature-time curve during the thermal decomposition of MXene / AuNFs / PFTE and MXene thin film materials in Experimental Example 1 of the present invention;

[0030] Figure 2 It is a schematic diagram of the heat release during the thermal decomposition of MXene / AuNFs / PFTE and MXene thin film materials in Experimental Example 1 of the present invention;

[0031] Figure 3 It is a schematic diagram of the transient temperature curve of different photothermal conversion thin film materials under different intensity laser inductions in Experimental Example 2 of the present invention;

[0032] Figure 4 It is a schematic diagram of the peak temperature curve of different photothermal conversion thin film materials under different intensity laser inductions in Experimental Example 2 of the present invention;

[0033] Figure 5 It is a schematic diagram of the results of characterizing the surface and cross-section of MXene / AuNFs / PFTE and MXene thin film materials after being irradiated by a laser with an intensity of 79.6 W·cm -2 in Experimental Example 3 of the present invention; wherein, Figure 5 a is the appearance diagram of the surface of the MXene thin film material after laser irradiation at a high magnification, Figure 5 b is the appearance diagram of the surface of the MXene thin film material after laser irradiation at a low magnification, Figure 5 c is the appearance diagram of the cross-section of the MXene thin film material after laser irradiation; Figure 5Figure d shows the appearance of the surface of the MXene / AuNFs / PFTE thin film material after laser irradiation at a high magnification. Figure 5 Figure e shows the appearance of the surface of the MXene / AuNFs / PFTE thin film material after laser irradiation at a low magnification. Figure 5 Figure f shows the appearance of the cross-section of the MXene / AuNFs / PFTE thin film material after laser irradiation.

[0034] Figure 6 These are the conventional images of the ignition process of CL-20 initiated by using MXene / AuNFs / PFTE and MXene thin film materials as high-temperature pulse generators in Experimental Example 4 of the present invention.

[0035] Figure 7 These are the schlieren imaging pictures of the ignition process of CL-20 initiated by using MXene / AuNFs / PFTE and MXene thin film materials as high-temperature pulse generators in Experimental Example 4 of the present invention.

[0036] Figure 8 This is a schematic diagram of the curve of the ignition delay time versus the laser intensity measured during the laser ignition experiment using MXene / AuNFs / PFTE and MXene thin film materials in Experimental Example 4 of the present invention. Detailed Implementation Modes

[0037] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0038] I. Specific embodiments of the photothermal conversion material of the present invention are as follows:

[0039] Embodiment

[0040] The photothermal conversion material of this embodiment is prepared by a method including the following steps:

[0041] (1) Add a certain amount of HAuCl4·4H2O solution with a mass fraction of 0.01% into a flask. Then, under vigorous stirring, heat the HAuCl4·4H2O solution in the flask to 100°C. Then add a certain amount of sodium citrate solution with a mass fraction of 1% into the flask. Then control the materials in the flask at 100°C to keep them in a boiling state, and stir and react for 20 min to obtain a gold seed dispersion. In this step, the mass ratio of the gold element in the HAuCl4·4H2O solution to the sodium citrate in the sodium citrate solution is 4:12.

[0042] (2) Add a certain amount of HAuCl4·4H2O solution with a mass fraction of 0.01% to the flask, then add an appropriate amount of 1 mol / L sodium hydroxide solution to the flask until the pH of the materials in the flask is 11.5. Then, sequentially add a certain amount of titanium carbide nanosheet dispersion with a mass fraction of 5%, a certain amount of hydroxylamine hydrochloride solution with a mass fraction of 0.14%, and a certain amount of the gold seed dispersion prepared in step (1) to the flask under vigorous stirring. Stir and react for 10 min, stop stirring, and then let the materials in the flask stand at room temperature for 24 h to obtain a composite material dispersion. In this step, the mass ratio of gold element in the HAuCl4·4H2O solution, sodium hydroxide in the sodium hydroxide solution, hydroxylamine hydrochloride in the hydroxylamine hydrochloride solution, titanium carbide nanosheets in the titanium carbide nanosheet dispersion, and gold element in the gold seed dispersion is 9:4:1.5:25:2. The titanium carbide nanosheet dispersion is prepared from titanium carbide nanosheets and water. The thickness of the titanium carbide nanosheets is 1.5 - 1.7 nm, the sheet diameter is 0.5 - 1 μm, and the number of layers is 2 - 3 layers;

[0043] (3) Add 1H,1H,2H,2H - perfluorodecyltriethoxysilane to absolute ethanol and stir at room temperature for 10 min to obtain a 1H,1H,2H,2H - perfluorodecyltriethoxysilane ethanol solution with a mass fraction of 0.5%. Then, slowly add a certain amount of the 1H,1H,2H,2H - perfluorodecyltriethoxysilane ethanol solution to a certain amount of the composite material dispersion prepared in step (2) (the mass ratio of titanium carbide nanosheets in the composite material in the composite material dispersion to 1H,1H,2H,2H - perfluorodecyltriethoxysilane in the 1H,1H,2H,2H - perfluorodecyltriethoxysilane ethanol solution is 1:10) under stirring. Stir at room temperature for 2 h to obtain a photothermal conversion material dispersion. Then, perform vacuum filtration on the photothermal conversion material dispersion, and then freeze the photothermal conversion material on the filter membrane after vacuum filtration at -20 °C for 2 h. Then, freeze - dry at a vacuum of 1 Pa and room temperature for 2 h to obtain a photothermal conversion thin - film material. Name the photothermal conversion thin - film material prepared in this example as MXene / AuNFs / PFTE;

[0044] Comparative Example 1

[0045] The photothermal conversion material of this comparative example is prepared by a method including the following steps:

[0046] The titanium carbide nanosheet dispersion with a mass fraction of 5% was subjected to vacuum filtration. Then, the photothermal conversion material on the filter membrane after vacuum filtration was frozen at -20°C for 2 h, and then freeze-dried at a vacuum of 1 Pa and room temperature for 2 h to obtain the photothermal conversion thin film material. The photothermal conversion thin film material prepared in this comparative example was named Mxene; the titanium carbide nanosheet dispersion used in this comparative example was the same as the titanium carbide nanosheet dispersion in the example.

[0047] Comparative Example 2

[0048] The photothermal conversion material of this comparative example was prepared by a method comprising the following steps:

[0049] (1) This step was the same as step (1) of the example;

[0050] (2) This step was the same as step (2) of the example;

[0051] (3) The composite material dispersion obtained in step (2) was subjected to vacuum filtration. Then, the photothermal conversion material on the filter membrane after vacuum filtration was frozen at -20°C for 2 h, and then freeze-dried at a vacuum of 1 Pa and room temperature for 2 h to obtain the photothermal conversion thin film material. The photothermal conversion thin film material prepared in this comparative example was named MXene / AuNFs.

[0052] Comparative Example 3

[0053] The photothermal conversion material of this comparative example was prepared by a method comprising the following steps:

[0054] 1H,1H,2H,2H-perfluorodecyltriethoxysilane was added to absolute ethanol and stirred at room temperature for 10 min to obtain a 1H,1H,2H,2H-perfluorodecyltriethoxysilane ethanol solution with a mass fraction of 0.5%. Then, a certain amount of the 1H,1H,2H,2H-perfluorodecyltriethoxysilane ethanol solution was slowly added to a certain amount of the titanium carbide nanosheet dispersion with a mass fraction of 5% (the mass ratio of titanium carbide nanosheets in the titanium carbide nanosheet dispersion to 1H,1H,2H,2H-perfluorodecyltriethoxysilane in the 1H,1H,2H,2H-perfluorodecyltriethoxysilane ethanol solution was 1:10) under stirring at room temperature, and stirred for 2 h to obtain the photothermal conversion material dispersion. Then, the photothermal conversion material dispersion was subjected to vacuum filtration. Then, the photothermal conversion material on the filter membrane after vacuum filtration was frozen at -20°C for 2 h, and then freeze-dried at a vacuum of 1 Pa and room temperature for 2 h to obtain the photothermal conversion thin film material. The photothermal conversion thin film material prepared in this comparative example was named MXene / PFTE.

[0055] Comparative Example 4

[0056] The difference between the photothermal conversion material of this comparative example and that of the example lies only in that in step (3) of preparing the photothermal conversion material of this comparative example, 1H,1H,2H,2H-perfluorodecyltriethoxysilane is replaced by perfluorobutyltriethoxysilane, and the mass of perfluorobutyltriethoxysilane in this comparative example is twice the mass of 1H,1H,2H,2H-perfluorodecyltriethoxysilane in the example. The photothermal conversion thin film material prepared in this comparative example is named MXene / HFBE.

[0057] II. The following are specific examples of the application of the photothermal conversion material of the present invention in laser ignition:

[0058] Just use the photothermal conversion material of the example in laser ignition.

[0059] Experimental Example 1

[0060] In order to evaluate the thermal decomposition properties of the photothermal conversion thin film materials prepared in the example and Comparative Example 1, the temperature-time curves and heat release amounts during the thermal decomposition of MXene / AuNFs / PFTE and MXene thin film materials were respectively tested. The test method is as follows: Take 2.5 mg of the sample, and heat the sample from room temperature to 1000 °C at a heating rate of 10.0 °C / min under an air flow rate of 60 mL / min (the instrument used during the test is TGA / DSC 1LF, Mettler-Toledo, Germany). When calculating the heat release amount of each sample, each sample was repeated three times. The test results are as Figure 1 and Figure 2 shown. From Figure 1It can be seen that the DSC curve of the MXene film material has a small exothermic peak at 270°C. It should be that part of the Ti atoms on the surface of the MXene are oxidized to form TiO2, which in turn hinders the penetration of oxygen. The internal Ti atoms do not react, so the heat release is small. As the temperature rises, oxygen penetrates into the interior of the MXene, and most of the Ti and C atoms are oxidized, releasing a large amount of heat, corresponding to a sharp peak in the DSC curve. After treating MXene / AuNFs with fluorinated silane PFTE, it can be seen that the small peak at 270°C in the DSC curve disappears. In the DSC curves of MXene / AuNFs / PFTE and MXene film materials, there is a sharp peak at 339°C and a relatively gentle peak at around 385°C. Compared with MXene film materials, the exothermic peak of MXene / AuNFs / PFTE film materials moves forward from 396°C to 339°C. The above results show that 1H,1H,2H,2H-perfluorodecyltriethoxysilane does accelerate the oxidation reaction of MXene. The exothermic peak at 339°C should be the CFx produced by the thermal decomposition of 1H,1H,2H,2H-perfluorodecyltriethoxysilane, which reacts with MXene, causing part of the Ti atoms on the surface of MXene to generate volatile gas TiF4, and part of the Ti atoms react with oxygen to become TiO2. Because there are defects on the surface, it is easier for oxygen molecules to enter the interior, causing the internal Ti and C to continue to oxidize, which should be the gentle exothermic peak at the back; Figure 2 It can be seen that the heat release of MXene / AuNFs / PFTE film material increased significantly, reaching 7292 J / g, which is 1600 J / g higher than that of MXene film material. The above results confirm that 1H,1H,2H,2H-perfluorodecyltriethoxysilane can indeed accelerate the oxidation of MXene and increase the heat release of its oxidation reaction, and the content of F element has a greater influence on the oxidation reaction of MXene.

[0061] Experimental Example 2

[0062] In order to evaluate the laser-to-high-temperature pulse conversion performance of the photothermal conversion film materials prepared in the embodiments and comparative examples 1-4, the photothermal conversion film materials prepared in the embodiments and comparative examples 1-4 were cut into disc-shaped test samples with a thickness of 10 μm and a diameter of 4 mm, and then the laser-to-high-temperature pulse conversion performance was tested using a diode-pumped solid-state laser (MFSC-10, Maxphotonics Co., Ltd., China). The laser wavelength used in the test was 1064 nm, the laser beam spot size was 4 mm, the laser pulse time was set to 100 ms, and the laser intensity was set to 7.9, 15.9, 23.9, 31.8, 47.8, 63.7 and 79.6 W / cm, respectively. -2, in the experiment, the laser was vertically irradiated on the surface of the test sample by adjusting the optical path system. The infrared thermometer was installed above the test sample and its angle was adjusted to coincide with the laser spot to capture the temperature change of the test sample. The transient temperature curves of different photothermal conversion thin film materials under different intensities of laser induction are as Figure 3 shown, and the peak temperature curves of different photothermal conversion thin film materials under different intensities of laser induction are as Figure 4 shown.

[0063] It can be seen from Figure 3 that different photothermal conversion thin film materials all show a rapid temperature rise and decay trend at each laser intensity, proving that the MXene-based materials have strong laser-high temperature pulse conversion performance. It can be seen from Figure 4 that the peak temperatures of the photothermal conversion thin film materials prepared in the examples at each laser intensity are higher than those of the photothermal conversion thin film materials prepared in Comparative Examples 1-3 at the corresponding laser intensities. When the laser intensity reaches 79.6 W·cm -2 , the peak temperature of the photothermal conversion thin film materials prepared in the examples reaches 810 °C. Under the irradiation of the same intensity of laser, the peak temperatures of MXene / AuNFs / PFTE, MXene / AuNFs and MXene thin film materials gradually increase, indicating that introducing gold nanoflower particles and fluorosilane molecules between MXene sheets can improve their photothermal performance.

[0064] The peak temperatures of MXene / AuNFs / PFTE, Mxene, MXene / AuNFs, MXene / PFTE and MXene / HFBE thin film materials at each laser intensity are summarized in Table 1.

[0065] Table 1 Peak temperatures of different photothermal conversion thin film materials at each laser intensity

[0066]

[0067] Experimental Example 3

[0068] In order to investigate the changes in the surface morphology and composition of the photothermal conversion thin film materials prepared in the examples after laser irradiation, the surfaces and cross-sections of MXene / AuNFs / PFTE and MXene thin film materials after laser irradiation with an intensity of 79.6 W·cm -2 were characterized by electron microscopy, and the results are as Figure 5 shown. Among them, Figure 5 a and Figure 5 b are the appearance diagrams of the surface of the MXene thin film material after laser irradiation at different magnifications, Figure 5 c is the appearance diagram of the cross-section of the MXene thin film material after laser irradiation; Figure 5 d andFigure 5 Figure e shows the appearance of the surface of the MXene / AuNFs / PFTE thin film material after laser irradiation at different magnifications. Figure 5 Figure f shows the appearance of the cross-section of the MXene / AuNFs / PFTE thin film material after laser irradiation.

[0069] As Figure 5 can be seen, after laser irradiation, small cubic particles are distributed on the surfaces of both the MXeneAuNFs / PFTE thin film and the Mxene thin film. It is speculated that they should be TiO2 crystals, and the underlying support layer should be amorphous carbon. The TiO2 formed on the surface of the Mxene thin film is a compact layered structure. The TiO2 on the surface of the MXeneAuNFs / PFTE thin film is a non-compact structure, which is beneficial for oxygen molecules to enter the interior of the MXeneAuNFs / PFTE thin film to make it more fully oxidized. Moreover, the TiO2 particles on the surface of the MXeneAuNFs / PFTE thin film are significantly fewer, indicating that a part of Ti reacts with fluorine atoms to form volatile TiF4. From the SEM images of the cross-sections of the MXeneAuNFs / PFTE thin film and the Mxene thin film after laser irradiation, it can be seen that there is an obvious compact layer of TiO2 about 300 nm thick on the upper surface of the Mxene thin film, and the structure of the lower layer has no obvious change and no small particles are formed. It can be speculated that the oxidation inside the MXene is incomplete. After the MXeneAuNFs / PFTE thin film is irradiated by laser, there is no thick compact TiO2 on the surface of the thin film. The whole thin film becomes a granular structure from top to bottom and still remains a layered structure without aggregating together. The microscopic changes of each layer are consistent, indicating that after introducing fluorosilane, the whole MXene film is fully oxidized, forming TiO2 particles and an amorphous carbon template support.

[0070] Experimental Example 4

[0071] To evaluate the actual application effect of the photothermal conversion thin film materials prepared in the examples and Comparative Examples 1-4 in laser ignition, hexanitrohexaazaisowurtzitane (CL-20) was selected as the ignition object for laser ignition experiments. During the experiment, the granular hexanitrohexaazaisowurtzitane was pressed into a pellet with a diameter of 7 mm and a height of 1 mm. The spot size of the laser beam used in the experiment was 4 mm, and the pulse time of the laser in the laser ignition experiment was set to 50 ms. The conventional images and schlieren imaging of the ignition process of CL-20 induced by using the MXene / AuNFs / PFTE and Mxene thin film materials as high-temperature pulse generators under a laser with an intensity of 79.6 W·cm -2 are shown as Figures 6 - 7 shown, and the curves of the ignition delay time versus the laser intensity measured during the laser ignition experiment using the MXene / AuNFs / PFTE and Mxene thin film materials are as Figure 8as shown

[0072] It can be seen from Figures 6 - 7 that pure CL-20 was still not successfully ignited under the irradiation of a strong pulsed laser (wavelength of 1064 nm, pulse time of 50 ms, intensity of 318.5 W·cm -2 ), only a large amount of gas was generated, and this gas should be produced during the pyrolysis process of CL-20. After attaching the photothermal conversion thin film material to the surface of the CL-20 column, CL-20 can be successfully ignited at a lower laser intensity (wavelength of 1064 nm, pulse time of 50 ms, intensity of 79.6 W·cm -2 ) and in a shorter time. It can be seen from Figure 8 that the delay time of the MXene / AuNFs / PFTE thin film material at each laser intensity is shorter than that of the MXene thin film material. Especially when the laser intensity is 23.9 W·cm -2 , the delay time of the MXene / AuNFs / PFTE thin film material is only 66 ms, which is two orders of magnitude smaller than the delay time of the MXene thin film material.

[0073] The ignition delay times of the MXene / AuNFs / PFTE, Mxene, MXene / AuNFs, MXene / PFTE, and MXene / HFBE thin film materials at each laser intensity are summarized in Table 2.

[0074] Table 2 Ignition delay times of different photothermal conversion thin film materials at each laser intensity

[0075]

Claims

1. A photothermal conversion material, characterized in that, Prepared by a method comprising the following steps: S1. Mix and react a first soluble gold source, an alkaline compound, a first reducing agent, titanium carbide nanosheets, and gold seeds in water, and let stand to obtain a composite material; the gold seeds are prepared by a reduction reaction of a second soluble gold source and a second reducing agent in water; the first soluble gold source and the second soluble gold source are independently chloroauric acid and / or a hydrate of chloroauric acid; S2. Mix and react the composite material and a fluorinated alkylsilane in a solvent, perform solid-liquid separation, and then dry the solid obtained by the solid-liquid separation to obtain a photothermal conversion material.

2. The photothermal conversion material according to claim 1, wherein, The first reducing agent is hydroxylamine hydrochloride; the second reducing agent is citrate.

3. The photothermal conversion material according to claim 1, wherein The mass ratio of the gold element in the second soluble gold source to the second reducing agent is (2-4):(8-12).

4. The photothermal conversion material according to claim 1, wherein The temperature of the reduction reaction carried out when preparing the gold seeds is 95-100 °C, and the time is 18-20 min.

5. The photothermal conversion material according to any one of claims 1-4, characterized in that, The mass ratio of the gold element in the first soluble gold source, the alkaline compound, the first reducing agent, the titanium carbide nanosheets, and the gold element in the gold seeds is (9-12):(4-6):(1.5-2):(25-30):(2-3).

6. The photothermal conversion material according to any one of claims 1-4, characterized in that, The thickness of the titanium carbide nanosheets is 1.5-1.7 nm, the sheet diameter is 0.5-1 μm, and the number of layers is 2-3 layers.

7. The photothermal conversion material according to any one of claims 1-4, characterized in that When preparing the composite material in step S1, the time of the mixing reaction is 8-10 min, and the standing time is not less than 24 h.

8. The photothermal conversion material according to any one of claims 1-4, characterized in that The mass ratio of the titanium carbide nanosheets in the composite material to the mass of the fluorinated alkylsilane is (1-2):(10-16).

9. The photothermal conversion material according to any one of claims 1-4, characterized in that, The fluorinated alkylsilane is a perfluoroalkyltrialkoxysilane; the perfluoroalkyl is a C8-C10 perfluoroalkyl, and the alkoxy group is a C1-C3 alkoxy group.

10. Application of a photothermal conversion material according to any one of claims 1-9 in laser ignition.

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