阅读说明：本技术 一种核壳结构硼颗粒-金属氧化物及其制备方法 (Core-shell structure boron particle-metal oxide and preparation method thereof ) 是由 杜淼 李帅 邓学元 杨素媛 郝雷 米菁 付正盛 许科 于 2021-09-06 设计创作，主要内容包括：本发明公开了属于推进剂用高能添加剂材料技术领域的一种核壳结构硼颗粒-金属氧化物及其制备方法。所述核壳结构硼颗粒-金属氧化物,以硼颗粒作为核心,通过水热反应在其表面成核并长大,生成包覆在硼颗粒表面的金属氧化物纳米颗粒。所述壳核结构能够有效降低硼颗粒的点火温度,改善复合粉体的点火延迟时间、燃烧效率以及放热量。所述方法制备的复合材料包覆更均匀,包覆颗粒小,催化活性更高,性能更为优良,且水热法简单易行、成本低廉,采用水热的方法包覆金属氧化物较为经济且易于实现批量生产和工业化。(The invention discloses a core-shell structure boron particle-metal oxide and a preparation method thereof, belonging to the technical field of high-energy additive materials for propellants. The boron particle-metal oxide with the core-shell structure takes boron particles as cores, and the boron particles nucleate and grow on the surfaces of the boron particles through hydrothermal reaction to generate metal oxide nano particles coated on the surfaces of the boron particles. The shell-core structure can effectively reduce the ignition temperature of boron particles and improve the ignition delay time, the combustion efficiency and the heat release of the composite powder. The composite material prepared by the method has the advantages of more uniform coating, small coated particles, higher catalytic activity, more excellent performance, simple and feasible hydrothermal method and low cost, and the hydrothermal method for coating the metal oxide is more economical and is easy to realize batch production and industrialization.)

1. The core-shell structure boron particle-metal oxide is characterized in that boron particles are used as cores, and the metal oxide is nucleated on the surfaces of the boron particles through a hydrothermal reaction and grows in situ to form metal oxide nanoparticles.

2. The core-shell boron particle-metal oxide according to claim 1, wherein the core-shell boron particle-metal oxide comprises 1-30% by mass of metal oxide and 70-99% by mass of boron powder.

3. The core-shell boron particle-metal oxide according to claim 2, wherein in the core-shell boron particle-metal oxide,

when the content of the metal oxide is 1-5 wt.%, metal oxide nanoparticles are uniformly attached to partial surface regions of the boron particles, and the metal oxide nanoparticles form incomplete coating on the surfaces of the boron particles;

when the content of the metal oxide is 5-30 wt.%, the nano metal oxide particles form complete coating on the surface of the boron particles.

4. The boron particle-metal oxide with core-shell structure of claim 1, wherein the boron particle is micron-sized or nano-sized boron powder with a particle size of 50nm to 100 μm; the particle size of the metal oxide nanoparticles is 4-20 nm.

5. The core-shell boron particle-metal oxide of claim 1, wherein the metal oxide comprises CuO, Fe₂O₃、ZnO、SnO₂、TiO₂、ZrO₂And NiO.

6. The preparation method of the boron particle-metal oxide with the core-shell structure, which is disclosed by claim 1, is characterized by comprising the following steps of:

1) adding metal salt, a precipitator, an additive and boron powder into a beaker according to a ratio, and adding a solvent to obtain a suspension containing metal ions;

2) ultrasonically dispersing the suspension obtained in the step 1) for 10-120 min to obtain a uniform dispersion liquid of boron powder and metal salt;

3) pouring the dispersion liquid obtained in the step 2) into a reaction kettle with a stirring function, wherein the volume filling degree is 50% -90%, heating to 80-260 ℃ at the speed of 3-6 ℃/min, keeping the temperature for 1-72 hours, and naturally cooling to room temperature to obtain a hydrothermal product;

4) and (3) performing centrifugal separation on the hydrothermal product obtained in the step 3), washing with deionized water and absolute ethyl alcohol for 2-3 times respectively, performing centrifugal separation, and drying at 70-120 ℃ for 30-300 min to obtain the core-shell structure boron particle-metal oxide.

7. The preparation method according to claim 6, wherein the metal salt in step 1) comprises one of copper salt, iron salt, zinc salt, tin salt, titanium salt, zirconium salt and nickel salt, and the concentration of the metal salt is 0.001-1 mol/L.

8. The preparation method of claim 6, wherein the precipitant in step 1) comprises one of ammonium bicarbonate, urea, ammonia water, sodium hydroxide and sodium oleate, and the concentration of the precipitant is 0.001-2 mol/L.

9. The method according to claim 6, wherein the solvent in step 1) comprises one or both of deionized water and absolute ethanol.

10. The method of claim 6, wherein the additive in step 1) comprises one or two of oleic acid, cetyltrimethylammonium bromide, hexamethylenetetramine, sodium citrate and polyvinylpyrrolidone.

Technical Field

The invention belongs to the technical field of high-energy additive materials for propellants, and particularly relates to a boron particle-metal oxide with a core-shell structure and a preparation method thereof.

Background

In order to increase the energy level of the propellant, substances which release a large amount of heat upon combustion are added to the propellant formulation in order to increase the combustion temperature and to obtain a high specific impulse and characteristic speed. The mass heat value of boron is 58.28kJ/g, which is 2.3 times and 1.9 times of magnesium and aluminum, and the combustion product of boron is clean and has no pollution to environment. Although boron has many excellent performance characteristics, its potential as a high energy fuel or fuel additive has not been realized, mainly because of the presence of an oxide film on the surface of the boron powder that prevents it from burning sufficiently. Typically, the boron particles each include an oxide layer, predominantly B, on the outer surface thereof₂O₃The oxide layer has a low melting point of about 723K and a high boiling point of about 2320K, and is easy to form a compact molten layer at a low temperature to coat the surface of boron powder, so that the ignition and combustion processes of boron are hindered, the ignition performance of boron is poor, the boron is difficult to burn out, the combustion efficiency is low, and the heat value of the boron cannot be fully utilized.

The ignition performance and the combustion efficiency of the boron powder can be obviously improved by coating a layer of transition metal or transition metal oxide on the surface of the boron powder. For example, patent CN103396280A discloses a modified boron powder coated with nano lead oxide, which has low ignition temperature and high combustion efficiency, but its metal oxide with too high content can significantly reduce the overall energy level of the composite powder, and its coating lead oxide can cause harm to the environment, and these disadvantages severely limit its application in the field of high-energy additive materials for propellant.

CN111689821 discloses an active boron powder and a preparation method thereof, the invention utilizes a mechanical ball milling method to coat nano metal oxide and active metal on the surface of the boron powder to form composite powder similar to thermite, which can reduce the ignition temperature of the boron powder and improve the combustion efficiency of the boron powder. However, the preparation method of the ball milling easily causes the agglomeration of metal or metal oxide powder, and the contact area of boron powder and metal oxide particles is small, thereby affecting the reactivity of the boron powder.

During combustion of boron powder, nano-metal oxide particles generally have better catalytic activity than ordinary metal oxide particles. This is mainly due to the higher specific surface area of the nanoparticles, which results in a larger contact area between the nano-metal oxide particles and the boron particles and higher reactivity. However, since the nanoparticles are prone to agglomeration, it is usually necessary to support the nanoparticles on boron particles to ensure the dispersibility of the metal oxide particles.

In contrast, the method for chemically plating the cladding metal adopted in patent CN103086816 can better ensure the amount and morphology of the metal particles and ensure the catalytic performance thereof, but the process is relatively complex and has a high requirement for the morphology of the boron powder.

Disclosure of Invention

In order to solve the problems, the invention provides a boron particle-metal oxide with a core-shell structure, wherein the boron particle-metal oxide with the core-shell structure takes a boron particle as a core, and the metal oxide is nucleated on the surface of the boron particle through a hydrothermal reaction and grows in situ to form a metal oxide nanoparticle.

The metal oxide is prepared by generating metal oxide nano particles on the surface of boron particles in situ through a hydrothermal reaction, and coating the metal oxide nano particles on the surface of the boron particles to form a shell-core structure. In the core-shell structure, the nano metal oxide particles are in close contact with the boron particles, the metal oxide particles are not easy to agglomerate, and the size is kept in a nano scale, so that the structure has high reaction activity.

In the boron particle-metal oxide with the core-shell structure, the mass percent of the metal oxide is 1-30%, and the mass percent of the boron powder is 70-99%.

In the core-shell structure boron particle-metal oxide,

when the content of the metal oxide is 1-5 wt.%, metal oxide nanoparticles are uniformly attached to partial surface regions of the boron particles, and the metal oxide nanoparticles form incomplete coating on the surfaces of the boron particles;

when the content of the metal oxide is 5-30 wt.%, the nano metal oxide particles form complete coating on the surface of the boron particles.

The boron particles are micron-sized or nano-sized boron powder, and the particle size is 50 nm-100 mu m; the particle size of the metal oxide nanoparticles is 4-20 nm.

The metal oxide comprises CuO and Fe₂O₃、ZnO、SnO₂、TiO₂、ZrO₂And NiO.

A hydrothermal reaction preparation method of core-shell structure boron particles-metal oxide comprises the following steps:

1) adding metal salt, a precipitator, an additive and boron powder into a beaker according to a ratio, and adding a solvent to obtain a suspension containing metal ions;

2) ultrasonically dispersing the suspension obtained in the step 1) for 10-120 min to obtain a uniform dispersion liquid of boron powder and metal salt;

3) pouring the dispersion liquid obtained in the step 2) into a reaction kettle with a stirring function, wherein the volume filling degree is 50% -90%, heating to 80-260 ℃ at the speed of 3-6 ℃/min, keeping the temperature for 1-72 hours, and naturally cooling to room temperature to obtain a hydrothermal product;

4) and (3) performing centrifugal separation on the hydrothermal product obtained in the step 3), washing with deionized water and absolute ethyl alcohol for 2-3 times respectively, performing centrifugal separation, and drying at 70-120 ℃ for 30-300 min to obtain the boron particle-metal oxide core-shell structure material.

Wherein, the metal oxide (M)_xO) combustion of a boron particle-metal oxide core-shell structure prepared by coating boron particle surfaces involves the following three reactions:

2B+3M_xO→B₂O₃+3x M (formula 1)

2x M+O₂→2M_xO (formula 2)

4B+3O₂→2B₂O₃(formula 3)

Wherein, the metal oxides CuO and Fe₂O₃、ZnO、SnO₂、TiO₂、ZrO₂And the NiO is used as an oxidizing agent to perform oxidation-reduction reaction with the boron particles, and the reaction formula is shown as a formula 1. This will reduce the oxidation temperature of the boron particles by 40-300 deg.C and the ignition temperature of the boron particles. The higher the content of metal oxide, the more pronounced the reduction. After the metal oxide is consumed in the reaction of the formula 1, oxygen cannot be rapidly diffused to the surface of the boron particle due to the existence of liquid boron oxide on the surface of the metal oxide, the subsequent oxidation of the boron particle is slow, and the combustion cannot be maintained. At this time, the simple metal substance generated by the reaction of formula 1 can be oxidized again by air by formula 2 to generate a metal oxide. And the metal oxide can be dissolved in the liquid boron oxide, quickly diffused to the surface of the boron particles, and contacted with the boron particles again to generate the reaction shown in the formula 1. The reactions of formula 1 and formula 2 are cycled back and forth to transfer oxygen from the ambient environment to B-B₂O₃At the interface, oxidation of the boron particles proceeds, thereby promoting ignition and combustion of boron. In addition dissolved in liquid B₂O₃The metal oxide in the layer generates mechanical stress on the interface when the temperature is increased, so that the oxide layer on the surface of the boron particles is cracked, and the reaction of the formula 3 is continued, and the ignition and combustion of boron are further promoted.

The metal salt in the step 1) comprises one of copper salt, iron salt, zinc salt, tin salt, titanium salt, zirconium salt and nickel salt, and the concentration of the metal salt is 0.001-1 mol/L.

The precipitator in the step 1) comprises one of ammonium bicarbonate, urea, ammonia water, sodium hydroxide and sodium oleate, and the concentration of the precipitator is 0.001-2 mol/L.

The solvent in the step 1) comprises one or two of deionized water and absolute ethyl alcohol.

The additive in the step 1) comprises one or two of oleic acid, Cetyl Trimethyl Ammonium Bromide (CTAB), hexamethylene tetramine (HMTA), sodium citrate and polyvinylpyrrolidone (PVP), and mainly has the main functions of improving the morphology of metal oxide nanoparticles and improving the dispersibility of boron powder.

The ultrasonic dispersion is used for dispersing agglomerated boron powder, and high-energy ultrasonic dispersion is used for 1-10 min or wet ball milling is carried out on powder which is difficult to disperse.

The invention has the beneficial effects that:

1. according to the invention, a hydrothermal method is adopted to generate nanoscale metal oxide particles on the surface of micron or nanometer boron powder in situ at a reaction temperature of 80-260 ℃, and an oxide shell layer grows on the surface of the boron particles. Under the same condition, compared with the original boron powder, the ignition delay time can be reduced by 3-10 s, the combustion heat value is improved by 100-200%, and the initial oxidation temperature is reduced by 40-300 ℃.

2. Compared with the original coating method, the composite powder obtained by the hydrothermal method has good dispersibility, the nano metal oxide particles obtained by the hydrothermal reaction are not easy to agglomerate, the size is kept in a nano scale, the dispersibility of the nano metal oxide particles can be improved, high reaction activity and catalytic activity can be obtained, the ignition combustion process of boron particles can be catalyzed, the function of a propellant can be exerted, and the thermal decomposition of other components can be promoted.

3. The preparation method is simple and easy to implement, has low cost, can adjust the adding proportion of the boron powder and the metal salt according to actual requirements, has economic and efficient preparation process, and is easy to realize batch production and industrialization, and the reaction conditions of the hydrothermal method are easy to control.

Drawings

FIGS. 1a and 1b are schematic structural diagrams of a boron particle-metal oxide core-shell structure in which the metal oxide is completely coated and incompletely coated; wherein, the shape of the boron particles is not limited, and the growth space of the metal oxide can be ensured;

FIGS. 2a and 2b are views of the present invention2% and 10% SnO in example 1₂Content of B-SnO₂A transmission electron microscope photo of the core-shell structure composite powder;

FIG. 3 shows B-SnO in examples of the present invention₂XRD pattern of the core-shell structure composite powder;

FIG. 4 shows B-SnO in examples of the present invention₂Thermogravimetric analysis TG curve of the core-shell structure composite powder;

FIG. 5 shows B-SnO in an example of the present invention₂Differential Scanning Calorimetry (DSC) curve of the core-shell structure composite powder.

FIG. 6 is a 5 wt.% B-SnO prepared using a ball milling process₂TG-DSC curve of the composite powder.

Detailed Description

The invention is described in further detail below with reference to the following figures and specific examples:

example 1

Preparation of B-SnO by hydrothermal method₂Core-shell structure composite powder

1) Weigh 0.2g NaSnO₃Putting (sodium stannate), 1.8g of urea and boron powder into a beaker, wherein the average particle size of the boron powder is 4 mu m, and the adding amounts are 1.3g, 0.65g, 0.325g and 0.13g respectively, firstly adding 18mL of absolute ethyl alcohol, then adding 34mL of deionized water, and stirring the suspension until no obvious precipitate exists;

2) carrying out high-energy ultrasonic treatment on the suspension obtained in the step 1) for 2min, and then carrying out common ultrasonic treatment for 20min to completely disperse the powder and the solution to obtain a uniform dispersion liquid of sodium stannate, urea and boron powder;

3) pouring the dispersion liquid obtained in the step 2) into a high-temperature reaction kettle of 80mL, putting the reaction kettle into a high-temperature furnace, and rotationally stirring the reaction kettle by using a motor to prevent precipitation. The temperature program was set to: heating from 20 deg.C to 170 deg.C for 40 min; keeping the temperature at 170 ℃ for 12 h; cooling the furnace to room temperature;

4) taking out the reaction kettle, pouring out the hydrothermal product, centrifuging at 10000r/min for 10min, pouring out the supernatant, washing with deionized water twice, washing with anhydrous ethanol twice, centrifuging at 10000r/min for 10min after each washing, pouring out the supernatant, and finally drying at 80 ℃ for 2h to obtain B-SnO₂A core-shell structure composite powder. Wherein the prepared sample SnO₂The weight percentages are respectively 2%, 5%, 10% and 20% (respectively corresponding to the steps)1, the adding amount of boron powder is respectively 1.3g, 0.65g, 0.325g and 0.13g) of B-SnO₂A core-shell structure composite powder. As can be seen from TEM and XRD results in FIG. 3, B-SnO was obtained₂The core-shell structure composite powder has good coating effect. In FIGS. 1b and 2a, SnO₂At a content of 2 wt.% the boron particles are not completely coated; FIGS. 1a and 2b show SnO₂At a content of 10 wt.%, the boron particles are completely coated, and the coating layer is SnO₂Nanoparticles of (A)<20nm)。

Example 2

Hydrothermal method for preparing B-Fe₂O₃Core-shell structure composite powder

1) 2.16g FeCl was weighed₃·6H₂O, 0.96g of urea and 1.5g of boron powder with the average particle size of 4 mu m are put into a beaker, 64mL of absolute ethyl alcohol is added, and the suspension is stirred until no obvious precipitate is generated;

2) performing high-energy ultrasonic treatment on the suspension obtained in the step 1) for 2min, and performing common ultrasonic treatment for 20min to completely disperse the powder and the solution to obtain FeCl₃A homogeneous dispersion of urea and boron powder;

3) pouring the dispersion liquid obtained in the step 2) into a high-temperature reaction kettle of 80mL, putting the reaction kettle into a high-temperature furnace, and rotationally stirring the reaction kettle by using a motor to prevent precipitation. The temperature program was set to: heating from 20 deg.C to 160 deg.C for 40 min; keeping the temperature at 160 ℃ for 16 h; cooling the furnace to room temperature;

4) taking out the reaction kettle, pouring out the hydrothermal product, centrifuging at 10000r/min for 10min, pouring out the supernatant, washing with deionized water for three times, washing with anhydrous ethanol for two times, centrifuging at 10000r/min for 10min after each washing, pouring out the supernatant, and finally drying at 80 ℃ for 2h to obtain B-Fe₂O₃A core-shell structure composite powder.

Example 3

Hydrothermal method for preparing B-CuO core-shell structure composite powder

1) Weigh 0.33gCu (CH)₃COO)₂·H₂O (copper acetate), 1.026g CTAB (hexadecyl trimethyl ammonium bromide) and 0.5g boron powder with the average particle size of 800nm are put into a beaker, 54mL deionized water is added, the suspension is stirred until no obvious precipitation exists, and 5mL0.5mol/L of NaOH dilute solution is slowly added;

2) carrying out high-energy ultrasonic treatment on the suspension obtained in the step 1) for 5min, and then carrying out common ultrasonic treatment for 30min to completely disperse the powder and the solution to obtain a uniform dispersion liquid;

3) pouring the dispersion liquid obtained in the step 2) into a high-temperature reaction kettle of 80mL, putting the reaction kettle into a high-temperature furnace, and rotationally stirring the reaction kettle by using a motor to prevent precipitation. The temperature program was set to: heating from 20 deg.C to 120 deg.C for 30 min; keeping the temperature at 120 ℃ for 12 h; cooling the furnace to room temperature;

4) taking out the reaction kettle, pouring out the hydrothermal product, centrifuging for 10min at 10000r/min, pouring out supernatant, washing for three times with deionized water, washing for two times with absolute ethyl alcohol, centrifuging for 10min at 10000r/min after washing each time, pouring out supernatant, and finally drying for 2h at 80 ℃ to obtain the B-CuO core-shell structure composite powder.

Example 4

Hydrothermal method for preparing B-ZnO core-shell structure composite powder

1) Weigh 0.22g Zn (CH)₃COO)₂·2H₂Placing O (zinc acetate), 0.12g of urea, 0.5g of PVP (polyvinylpyrrolidone) and 0.12g of boron powder with the average particle size of 4 mu m in a beaker, adding 60mL of deionized water, and stirring the suspension until no obvious precipitate exists;

2) carrying out high-energy ultrasonic treatment on the suspension obtained in the step 1) for 2min, and then carrying out common ultrasonic treatment for 20min to completely disperse the powder and the solution to obtain a uniform dispersion liquid of zinc acetate, urea, PVP and boron powder;

3) pouring the dispersion liquid obtained in the step 2) into a high-temperature reaction kettle of 80mL, putting the reaction kettle into a high-temperature furnace, and rotationally stirring the reaction kettle by using a motor to prevent precipitation. The temperature program was set to: heating from 20 deg.C to 120 deg.C for 30 min; preserving heat for 8 hours at 120 ℃; cooling the furnace to room temperature;

4) taking out the reaction kettle, pouring out the hydrothermal product, centrifuging for 10min at 10000r/min, pouring out supernatant, washing with deionized water for three times, washing with absolute ethyl alcohol for two times, centrifuging for 10min at 10000r/min after each washing, pouring out supernatant, and finally drying for 2h at 80 ℃ to obtain the B-ZnO core-shell structure composite powder.

Example 5

Hydrothermal preparation of B-TiO₂Core-shell structure composite powder

1) 4.8g of titanium sulfate (TiSO) was weighed₄) 4.8g of urea, 0.14g of Hexamethylenetetramine (HM)TA) and 0.8g of boron powder with the average particle size of 4 mu m are put into a beaker, 60mL of deionized water is added, and the suspension is stirred until no obvious precipitate is generated;

2) performing high-energy ultrasonic treatment on the suspension obtained in the step 1) for 2min, and performing common ultrasonic treatment for 20min to completely disperse the powder and the solution to obtain uniform dispersion liquid of titanium sulfate, urea, HMTA and boron powder;

3) pouring the dispersion liquid obtained in the step 2) into a high-temperature reaction kettle of 80mL, putting the reaction kettle into a high-temperature furnace, and rotationally stirring the reaction kettle by using a motor to prevent precipitation. The temperature program was set to: heating from 20 deg.C to 240 deg.C for 60 min; keeping the temperature at 240 ℃ for 12 h; cooling the furnace to room temperature;

4) taking out the reaction kettle, pouring out the hydrothermal product, centrifuging at 10000r/min for 10min, pouring out the supernatant, washing with deionized water for three times, washing with anhydrous ethanol for two times, centrifuging at 10000r/min for 10min after each washing, pouring out the supernatant, and finally drying at 80 ℃ for 2h to obtain the B-TiO₂A core-shell structure composite powder.

Example 6

Hydrothermal method for preparing B-ZrO₂Core-shell structure composite powder

1) Weighing 0.534g of zirconium oxychloride, 0.72g of urea, 0.2g of sodium citrate and 0.6g of boron powder with the average particle size of 4 mu m in a beaker, adding 54mL of deionized water, and stirring the suspension until no obvious precipitate exists;

2) carrying out high-energy ultrasonic treatment on the suspension obtained in the step 1) for 2min, and then carrying out common ultrasonic treatment for 20min to completely disperse the powder and the solution to obtain a uniform dispersion liquid of zirconium oxychloride, urea, sodium citrate and boron powder;

3) pouring the dispersion liquid obtained in the step 2) into a high-temperature reaction kettle of 80mL, putting the reaction kettle into a high-temperature furnace, and rotationally stirring the reaction kettle by using a motor to prevent precipitation. The temperature program was set to: heating from 20 deg.C to 130 deg.C for 30 min; preserving heat for 48h at 130 ℃; cooling the furnace to room temperature;

4) taking out the reaction kettle, pouring out the hydrothermal product, centrifuging at 10000r/min for 10min, pouring out the supernatant, washing with deionized water for three times, washing with anhydrous ethanol for two times, centrifuging at 10000r/min for 10min after each washing, pouring out the supernatant, and finally drying at 80 ℃ for 2h to obtain the B-ZrO₂A core-shell structure composite powder.

Example 7

Preparation of B-NiO core-shell structure composite powder by hydrothermal method

1) 1.308g of Ni (NO) were weighed₃)₂·6H₂O (nickel nitrate), 0.81g of urea and 0.6g of boron powder with the average particle size of 4 mu m are put into a beaker, 60mL of deionized water is added, and the suspension is stirred until no obvious precipitate is generated;

2) carrying out high-energy ultrasonic treatment on the suspension obtained in the step 1) for 2min, and then carrying out common ultrasonic treatment for 20min to completely disperse the powder and the solution to obtain a uniform dispersion liquid of nickel nitrate, urea, sodium citrate and boron powder;

3) pouring the dispersion liquid obtained in the step 2) into a high-temperature reaction kettle of 80mL, putting the reaction kettle into a high-temperature furnace, and rotationally stirring the reaction kettle by using a motor to prevent precipitation. The temperature program was set to: heating from 20 deg.C to 80 deg.C for 20 min; keeping the temperature at 80 ℃ for 6 h; cooling the furnace to room temperature;

4) taking out the reaction kettle, pouring out the hydrothermal product, centrifuging for 10min at 10000r/min, pouring out the supernatant, washing for three times with deionized water, washing for two times with absolute ethyl alcohol, centrifuging for 10min at 10000r/min after washing each time, pouring out the supernatant, and finally drying for 2h at 80 ℃ to obtain the B-NiO core-shell structure composite powder.

Performance testing

1. Under the condition of not adding a combustion improver, original boron powder and B-SnO are respectively tested by adopting a combined thermal analyzer (TG-DSC) and an oxygen bomb calorimeter (Parr 6200)₂Oxidation performance and combustion heat value of the core-shell structure composite powder. The TG-DSC test is carried out in an air atmosphere, the temperature range is 25-1100 ℃, and the heating rate is 10 ℃/min. The powder mass is 0.2g in single test of combustion heat value test, the atmosphere is oxygen, and the water equivalent is 1.0088 multiplied by 10^-2MJ/K and gas pressure 3 MPa. As shown in FIG. 4, FIG. 5 and Table 1, B-SnO was compared to the original pure boron powder₂The low-temperature thermal oxidation performance of the core-shell structure composite powder is obviously improved, and the core-shell structure composite powder is specifically represented by lower initial oxidation temperature and small increase of oxidation weight gain.

As shown in fig. 6, the ball milling method is used to replace the hydrothermal method of the present invention for in-situ growth of the metal oxide shell layer, but most of the powder in the composite powder prepared by the ball milling method is in a mechanically mixed state, and no interaction occurs. Therefore, the reaction activity is low and the oxidation temperature is loweredIs not obvious. At 5 wt.% SnO₂The oxidation temperature of the solution decreased by about 37 ℃. Under the same conditions, the B-SnO of the invention₂The reaction activity of the composite powder is obviously higher when the temperature of the sample is reduced by 52 ℃ by-5%.

Also according to Table 1, B-SnO₂The combustion heat value of the core-shell structure composite powder is also obviously improved.

TABLE 1 original boron powder and EXAMPLE 1 different B-SnO contents₂Performance parameters of core-shell structure composite powder

Name of powder	Virgin boron powder	B-SnO2-2％	B-SnO2-5％	B-SnO2-10％	B-SnO2-20％
						Initial Oxidation temperature (. degree.C.)	738	696	686	672	603
Oxidative weight gain (%)	94.95	99.91	100.14	89.82	72.19
						Calorific value of combustion (kJ/g)	14.65	39.47	37.81	32.66	23.62

2. CO is used without adding combustion improver₂The laser ignition device tested the original boron powder and the boron particle-metal oxide powder with core-shell structure (i.e., the boron particle-metal oxide powder with core-shell structure obtained by coating the boron powder with different metal oxides in examples 1-7, wherein B-SnO was selected in example 1₂SnO of core-shell structure composite powder₂5 percent by mass, namely B-SnO₂-5%) ignition delay time. The powder mass for single test is 50mg, the laser power is 135W, the atmosphere is air, three groups of parallel experiments are carried out on each powder, and the test results are shown in the following table 2.

TABLE 2 ignition delay time of original boron powder and boron particle-metal oxide powder of core-shell structure prepared in different examples

3. Under the condition of not adding a combustion improver, original boron powder and boron particle-metal oxide powder with a core-shell structure (namely, boron particle-metal oxide powder with a core-shell structure obtained by coating boron powder with different metal oxides in examples 1-7, wherein B-SnO selected in example 1 is tested by adopting an oxygen elasticity calorimeter (Parr 6200)₂SnO of core-shell structure composite powder₂5% by mass) of the fuel. The powder mass is 0.2g in single test, the atmosphere is oxygen, and the water equivalent is 1.0088 multiplied by 10^-2MJ/K, gasThree parallel runs were performed for each powder at a pressure of 3MPa, and the test results are shown in Table 3 below.

TABLE 3 Heat value of Combustion of original boron powder and boron particle-Metal oxide powder of core-Shell Structure prepared in different examples