阅读说明：本技术 一种制备包覆型硼粉的方法及包覆型硼粉 (Method for preparing coated boron powder and coated boron powder ) 是由 朴俊宇 张龙 邓利 于 2021-02-03 设计创作，主要内容包括：本发明公开了一种制备包覆型硼粉的方法,涉及金属燃料技术领域。包括以下步骤：(1)将原材料硼粉浸没并分散在溶剂中,搅拌或超声适当时间；(2)在搅拌中加入适量的水与包覆剂；(3)调节pH；(4)加入适量甲醛溶液；(5)在合适温度下搅拌适当时间；(6)通过过滤或离心等方式分离出溶液中的粉末,即得到包覆型硼粉。本发明可以在去除硼粉的表面氧化层的同时抑制硼粉的表面氧化,从而有效提升硼粉以及含硼火炸药的点火特性与贮存特性。本发明可以在很大程度上解决影响硼粉燃烧特性的表面氧化问题,具有较高的实用化前景。(The invention discloses a method for preparing coated boron powder, and relates to the technical field of metal fuels. The method comprises the following steps: (1) immersing and dispersing raw material boron powder in a solvent, and stirring or ultrasonically treating for a proper time; (2) adding a proper amount of water and a coating agent while stirring; (3) adjusting the pH value; (4) adding a proper amount of formaldehyde solution; (5) stirring for a proper time at a proper temperature; (6) and separating powder in the solution by filtration or centrifugation and the like to obtain the coated boron powder. The invention can remove the surface oxide layer of the boron powder and inhibit the surface oxidation of the boron powder, thereby effectively improving the ignition characteristic and the storage characteristic of the boron powder and the boron-containing explosive. The invention can solve the problem of surface oxidation which influences the combustion characteristic of boron powder to a great extent, and has higher practical prospect.)

1. A method of making a coated boron powder, comprising the steps of:

(1) immersing and dispersing raw material boron powder in a solvent, and stirring or ultrasonically treating for a proper time;

(2) adding a proper amount of water and a coating agent while stirring;

(3) adjusting the pH value;

(4) adding a proper amount of formaldehyde solution;

(5) stirring for a proper time at a proper temperature;

(6) and separating powder in the solution by filtration or centrifugation and the like to obtain the coated boron powder.

2. The method of claim 1, wherein the solvent in step (1) is one or more of methanol, ethanol, propanol, butanol, ethylene glycol, and glycerol.

3. The method of claim 1, wherein the boron powder concentration is from 1mg/ml to 50mg/ml and the stirring or sonication time is from 5min to 120 min.

4. The method of claim 1, wherein the boron powder concentration is from 5mg/ml to 20 mg/ml; stirring or ultrasonic treating for 20-0 min.

5. The method of claim 1, wherein the volume of water in step (2) is 1 to 5 times the volume of the solvent in step (1), and the concentration of the capping agent in step (2) is 0.5 to 10 mg/ml.

6. A method of producing a coated boron powder according to claim 1, characterized in that the volume of water in step (2) is 1.5 to 3 times the volume of the solvent in step (1); the concentration of the coating agent in the step (2) is 1mg/ml-5 mg/ml; in the step (2), the coating agent is one or more of urea, melamine, phenol, benzenediol, aminophenol and nitrophenol.

7. A method of producing an encapsulated boron powder as claimed in claim 1, characterized in that in step (3) the pH is adjusted to 1-12.

8. A method of producing a coated boron powder according to claim 1, characterized in that the amount of formaldehyde added in step (4) is between 0.2mg/ml and 3 mg/ml.

9. A method of producing a coated boron powder according to claim 1, characterized in that the stirring temperature in step (5) is 10-35 ℃; the stirring time is 2-48 hours.

10. A coated boron powder, characterized in that it is produced by the method according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of metal fuels, in particular to a method for preparing coated boron powder and the coated boron powder.

Background

Among common metal fuels, boron powder has the highest combustion heat; wherein the mass combustion heat is 58.81MJ/kg, which is 1.9 times of aluminum powder and 2.3 times of magnesium powder; the volume combustion heat is 137.94kJ/cm3, which is 1.66 times of that of the aluminum powder and 3.09 times of that of the magnesium powder. Therefore, the boron powder is considered as the metal fuel with the best energy characteristics and has important application value in the field of explosives and powders. For example, the boron-containing propellant is the only propulsion energy source which can enable the specific impulse of the solid ramjet to reach more than 10 kN.s < -1 >. kg < -1 >; and the B/KNO3 ignition charge is the only allowable ignition charge in an in-line ignition system.

However, an oxide layer having a main component of B2O3 or B (oh)3 tends to exist on the surface of boron powder. This surface oxide layer prevents the boron powder from contacting the oxidizing agent and, due to its high boiling point, requires a large amount of energy to remove during the ignition process. Therefore, the existence of the surface oxidation layer leads to higher ignition temperature of the boron powder, and the heat release capacity can not reach the theoretical level. Moreover, in the process of use and storage, under the combined action of temperature and humidity, the surface oxidation degree of boron powder is gradually deepened, so that the performance of the boron-containing explosive is irreversibly reduced, and the performance cannot be completely recovered even if the boron-containing explosive is dried again. B2O3 has a band gap of 4.55eV, which is smaller than the band gap of boron (5.64eV), and introduces an energy level within the band gap of boron; therefore, surface oxidation of boron powder leads to an increase in boron powder conductivity, resulting in a decrease in B/KNO3 ignition charge insulation resistance. Therefore, removing the surface oxidation layer of the boron powder and inhibiting the surface oxidation of the boron powder are the key points for improving the ignition characteristics and the storage characteristics of the boron powder and the boron-containing explosive.

The existing common solutions mainly fall into two categories aiming at the problem of surface oxidation of boron powder.

The first method is solvent purification of boron powder. The solvent capable of dissolving B2O3 and B (OH)3 can be selected, and the oxide layer on the surface of the boron powder is removed by spraying or dipping. However, studies have shown that once the boron powder from which the surface oxide layer has been removed is re-exposed to air, the surface thereof is rapidly re-oxidized, and agglomeration are accelerated. Therefore, the solvent purification method is not suitable for use alone as a method for activating boron powder.

The second method is surface coating of boron powder. At present, the commonly used coating agents are also classified into two types. The first is that LiF, Viton A and the like can react with an oxide layer on the surface of boron powder in the ignition process to generate substances of volatile compounds; and the other is a substance such as ammonium perchlorate which can decompose and release oxygen in the ignition process so as to promote the combustion of boron powder. However, both of these coating agents cannot reduce the degree of surface oxidation of the boron powder itself, so that the ineffective weight of the explosive is higher; and because extra energy is required to be consumed to remove the oxide layer on the surface of the boron powder in the ignition process, the energy output capacity of the explosive is often lower than that predicted by theory. In addition, the existing coating method essentially belongs to the adsorption of the substrate material to small particles of the coating; the uniformity and integrity of the small particle adsorption are difficult to ensure, so that uniform and complete coating is difficult to realize, and the continuous oxidation of the surface of the boron powder in the using and storing processes cannot be prevented.

In view of the above, there is still a need to develop a surface coating method more suitable for boron powder, which can reduce the degree of surface oxidation of boron powder and inhibit the surface oxidation of boron powder.

Disclosure of Invention

Firstly, the oxide layer on the surface of the boron powder is dissolved by using a solvent, and then the boron powder is coated in situ in the solution, so that the reoxidation of the surface of the boron powder is avoided. By the method, on one hand, the surface oxide layer of the boron powder can be removed to a great extent, and the surface oxidation degree of the boron powder is reduced; on the other hand, a combustible coating layer can be formed on the surface of the boron powder, so that the surface oxidation of the boron powder can be suppressed without inhibiting the combustion of the boron powder.

In order to achieve the above object, the present invention proposes a method for preparing a coated boron powder by coating a boron powder in a solvent. This method comprises the steps of:

(1) immersing and dispersing raw material boron powder in a solvent, and stirring or ultrasonically treating for a proper time;

(2) adding a proper amount of water and a coating agent while stirring;

(3) adjusting the pH value;

(4) adding a proper amount of formaldehyde solution;

(5) stirring for a proper time at a proper temperature;

(6) and separating powder in the solution by filtration or centrifugation and the like to obtain the coated boron powder.

Further, the solvent in the step (1) is one or more of methanol, ethanol, propanol, butanol, glycol and glycerol; the concentration of the boron powder is 1mg/ml-50mg/ml, preferably 5mg/ml-20 mg/ml; the stirring or ultrasonic treatment time is 5min-120min, preferably 20min-40 min.

Further, the volume of water in the step (2) is 1 to 5 times, preferably 1.5 to 3 times of the volume of the solvent in the step (1); in the step (2), the coating agent is one or more of urea, melamine, phenol, benzenediol, aminophenol and nitrophenol, and the concentration of the coating agent is 0.5mg/ml-10mg/ml, preferably 1mg/ml-5 mg/ml.

Further, in step (3), the pH should be adjusted to 1 to 12, preferably 2 to 10.

Further, the amount of formaldehyde added in step (4) is 0.2mg/ml to 3mg/ml, preferably 0.5mg/ml to 2 mg/ml.

Further, the stirring temperature in the step (5) is 10-35 ℃, preferably 15-25 ℃; the stirring time is 2 to 48 hours, preferably 4 to 24 hours.

The invention further provides coated boron powder prepared by the method.

Compared with the prior art, the invention has the beneficial effects that:

the invention can remove the surface oxide layer of the boron powder and inhibit the surface oxidation of the boron powder, thereby effectively improving the ignition characteristic and the storage characteristic of the boron powder and the boron-containing explosive. The invention can solve the problem of surface oxidation which influences the combustion characteristic of boron powder to a great extent, and has higher practical prospect.

Drawings

Fig. 1 is a scanning electron micrograph of the urea resin coated boron powder obtained in example 1 and EDS elemental analysis results thereof.

Fig. 2 is a DSC test result of the urea resin surface-coated boron powder obtained in example 1 mixed with three times the mass of potassium nitrate.

Fig. 3 is a scanning electron micrograph of the boron powder coated with the phenolic resin obtained in example 2 and an EDS elemental analysis result thereof.

Fig. 4 is a DSC test result of the boron powder coated with a phenol resin on the surface obtained in example 2 mixed with three times the mass of potassium nitrate.

Detailed Description

The present invention will be further described with reference to the following examples, which are intended to illustrate only some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, other embodiments used by those skilled in the art without any creative effort belong to the protection scope of the present invention.

Example 1

Preparation of boron powder coated with urea-formaldehyde resin on surface

In a flask, 5g of boron powder was dispersed in 250ml of ethanol and stirred for 30 min. 750ml of water and 10g of urea are added, the pH value is adjusted to 2 by hydrochloric acid, 2ml of formaldehyde solution is added, and the mixture is stirred for 24 hours. Filtering, washing and drying to obtain the boron powder coated with the urea-formaldehyde resin.

Fig. 1 is a scanning electron micrograph of the urea resin coated boron powder obtained in example 1 and EDS elemental analysis results thereof. It can be seen that a nitrogen-containing coating layer is present on the surface of the boron powder.

Fig. 2 is a DSC test result of the urea resin surface-coated boron powder obtained in example 1 mixed with three times the mass of potassium nitrate. It can be seen that the boron powder coated can be ignited at a lower temperature and with a higher exotherm.

Example 2

Preparation of boron powder with surface coated with phenolic resin

In a flask, 5g of boron powder was dispersed in 250ml of ethanol and stirred for 30 min. Then, 500ml of water and 2g of aminophenol were added, the pH was adjusted to 10 with ammonia water, and 2ml of formaldehyde solution was added and stirred for 8 hours. Filtering, washing and drying to obtain the boron powder coated with the phenolic resin.

Fig. 3 is a scanning electron micrograph of the boron powder coated with the phenolic resin obtained in example 2 and an EDS elemental analysis result thereof. It can be seen that a nitrogen-containing coating layer is present on the surface of the boron powder.

Fig. 4 is a DSC test result of the boron powder coated with a phenol resin on the surface obtained in example 2 mixed with three times the mass of potassium nitrate. It can be seen that the boron powder coated can be ignited at a lower temperature and with a higher exotherm.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.