CN115626859B - Metal composite boron powder and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of composite boron powder, and particularly relates to metal composite boron powder and a preparation method thereof, wherein the preparation method comprises the following steps: (1) Carrying out ball milling and mixing on boron powder and metal oxide powder to obtain mixed powder; (2) And carrying the mixed powder by carrier gas after optional vacuum drying, and conveying the mixed powder to a position 10-30cm below the bottommost part of the plasma flame, and controlling the plasma power to be 20-30kw so that the metal oxide is gasified and reacts with hydrogen to generate metal particles, and the metal particles are distributed on the surface of the boron particles to obtain the metal composite boron powder. The method can enable the metal oxide and the hydrogen to generate gas phase reaction to generate extremely fine nano-scale metal particles which are dispersed and distributed in a simple substance form and adsorbed on the surfaces of the boron powder particles, and the prepared metal composite boron powder has good dispersibility, uniform compounding and good combustion performance, and the compounding process can be continuously carried out, thereby being suitable for industrial production.

Description

A kind of metal composite boron powder and preparation method thereof

technical field

The invention belongs to the technical field of composite boron powder, and in particular relates to a metal composite boron powder and a preparation method thereof.

Background technique

Amorphous boron powder has high energy characteristics, but its surface has a dense low-melting point oxide layer. During the combustion process, the oxide layer forms a liquid state, which will hinder the further diffusion of oxygen. When it is used in high-energy solid fuels, explosives and other fields , has problems such as difficulty in continuous combustion after ignition, poor combustion performance, and its high-energy characteristics cannot be fully exerted. Many scholars have proposed many possible solutions for how to eliminate or suppress the oxide layer. Various scholars have proved through experiments that the combustion performance of boron composite powder treated with metal surface coating is significantly improved compared with the original sample, including but not limited to shortened ignition time, increased burning speed, increased burning time and reduced total boron remaining in residues, etc., and The compatibility of the treated metal composite boron powder with the propellant system has been improved to a certain extent.

In the prior art, some work has been carried out in the preparation of metal composite boron powder, and the preparation of metal composite boron powder can be realized by multi-arc ion coating (PVD) method, ball milling method, etc. When preparing metal-coated boron powder by PVD method, there will be a problem that the metal is difficult to uniformly cover the surface of boron powder, and this method is limited by the target material, the preparation cost is high, the efficiency is low, and it is difficult to achieve mass production. The ball milling method realizes the combination of boron powder and metal micrometallurgy by grinding boron powder and metal powder for a long time. The uniformity and microscopic dispersion of the compound are not ideal, and for the compounding of refractory metals such as tungsten and molybdenum, a large amount of material will appear during the ball milling process. Deposition leads to failure of homogeneous recombination.

Contents of the invention

The purpose of the present invention is to provide a kind of metal composite boron powder and its preparation method in order to overcome defects such as poor combustion performance of metal composite boron powder caused by the poor uniformity of boron powder and metal composite existing in the prior art, and the metal composite boron powder prepared by the method The powder has good dispersibility, uniform compounding, and good combustion performance. The compounding process can be carried out continuously, which is suitable for industrial production.

In order to achieve the above object, in a first aspect, the present invention provides a method for preparing metal composite boron powder, comprising the following steps:

(1) Ball milling and mixing boron powder and metal oxide powder to obtain mixed powder;

(2) After the mixed powder is optionally vacuum dried, it is carried by the carrier gas and sent to the bottom 10-30cm of the plasma flame, and the plasma power is controlled at 20-30kw, so that the metal oxide Gasify and react with hydrogen to form metal particles, which are distributed on the surface of boron particles to obtain metal composite boron powder.

Preferably, in step (1), the mixed powder is carried by the carrier gas and sent to a place 10-25 cm below the bottom of the plasma flame.

In some preferred embodiments, in step (2), the feeding rate of the mixed powder is 10-30 g/min.

More preferably, the feeding rate of the mixed powder is 10-20 g/min.

In some preferred embodiments, in step (2), the gas source of the plasma includes argon and hydrogen, the flow rate of the hydrogen is not more than 100 L/min, and the flow ratio of the argon to the hydrogen is 1 -3:1.

In some preferred embodiments, the particle size of the boron powder in the mixed powder is 0.3-6 μm, and the particle size of the metal oxide powder is 5-45 μm.

In some preferred embodiments, in step (1), the metal oxide includes molybdenum oxide and/or tungsten oxide.

In some preferred embodiments, in step (1), the mass ratio of the metal oxide to boron powder is 1:4-45.

In some preferred embodiments, in step (1), the conditions of the ball mill mixing include: a ball-to-material ratio of 5-8:1, a frequency of 15-25 Hz, and a time of 30-240 min.

In some preferred embodiments, step (1) further includes: pre-dispersing the boron powder by ball milling before ball milling.

More preferably, the conditions of the ball milling pre-dispersion treatment include: a ball-to-material ratio of 10-15:1, a frequency of 10-30 Hz, and a time of 60-300 min.

In a second aspect, the present invention provides a metal composite boron powder prepared by the method described in the first aspect, the metal composite boron powder includes micron-sized boron particles and nano-sized metal particles dispersed on the surface of the boron particles, the The mass content of metal in the metal composite boron powder is 2-15%, and the laser particle size of the metal composite boron powder satisfies: D ₅₀ <1 μm, D[4,3] <1 μm.

Preferably, the particle size of the boron particles in the metal composite boron powder is 0.2-3 μm, and the particle size of the metal particles is below 100 nm.

Beneficial effect:

The invention prepares the metal composite boron powder by the plasma method, especially the mixed powder is sent to a suitable position below the bottom of the plasma flame, and with the appropriate plasma power, the gas phase reaction of the metal oxide and hydrogen can generate extremely fine nano Nano-scale metal particles to avoid the boronation reaction of boron powder; nano-scale metal particles have large specific surface area and high surface energy, which are dispersed in the form of simple substances and adsorbed on the surface of boron powder particles, which solves the problem of uniform compounding by conventional ball milling and other compounding methods. gender issues. The structure of the obtained metal composite boron powder is that a layer of nanometer metal element particles are adsorbed on the surface of the boron particles, which is equivalent to a layer of metal element particles coated on the surface of the boron particles, and the coating layer and boron still exist in the original element form without forming a compound. Under the same conditions, if the powder feeding position of the mixed powder is too high and the reaction temperature is high, the boron powder may be gasified and react with the generated molybdenum or tungsten metal to form borides, resulting in the failure of the preparation of the metal composite boron powder; The powder feeding position is too low, and the reaction temperature is low. The analyzed product is a mixture of boron composite boron powder and molybdenum oxide, mainly because the temperature at this position is low, and part of the molybdenum oxide does not react with hydrogen, and forms molybdenum oxide powder after cooling. body, mixed into the generated molybdenum complex boron powder.

The metal composite boron powder of the invention has good dispersibility, uniform composite and excellent combustion performance, and the composite process can be carried out continuously, and is especially suitable for the preparation of refractory metal composite boron powders such as tungsten and molybdenum. The metal coated on the surface of the boron particles can promote combustion when the boron powder is burned, and is especially suitable for the field of boron-containing fuels.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and thus It should be regarded as a limitation on the scope, and those skilled in the art can also obtain other related drawings based on these drawings without creative work.

Fig. 1 is an electron micrograph of the molybdenum composite boron powder in Example 1 of the present invention under a magnification of 20,000 times.

Fig. 2 is an overall view of the SEM surface scanning of the molybdenum composite boron powder in Example 1 of the present invention under a magnification of 1000 times.

Fig. 3 is a SEM surface scanning Mo distribution diagram of the molybdenum composite boron powder in Example 1 of the present invention under a magnification of 1000 times, and the gray part is Mo.

Fig. 4 is a SEM surface scanning B distribution diagram of the molybdenum composite boron powder in Example 1 of the present invention under magnification of 1000 times, and the gray part is B.

Detailed ways

Neither the endpoints nor any values of the ranges disclosed herein are limited to such precise ranges or values, and these ranges or values are understood to include values approaching these ranges or values. For numerical ranges, between the endpoints of each range, between the endpoints of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, these values Ranges should be considered as specifically disclosed herein.

In the present invention, the ball-to-material ratio is based on mass. The 10-30 cm below the bottom of the plasma flame refers to the position at 10-30 cm from the lowest point of the plasma flame directly below the bottom of the plasma flame.

In a first aspect, the present invention provides a method for preparing metal composite boron powder, comprising the following steps:

(1) Ball milling and mixing boron powder and metal oxide powder to obtain mixed powder;

(2) After the mixed powder is optionally vacuum dried, it is carried by the carrier gas and sent to the bottom 10-30cm of the plasma flame, and the plasma power is controlled at 20-30kw, so that the metal oxide Gasify and react with hydrogen to form metal particles, which are distributed on the surface of boron particles to obtain metal composite boron powder.

In the present invention, the mixed powder is sent to 10-30 cm below the bottom of the plasma flame, so that the metal oxide in the mixed powder and the hydrogen in the gas source of the plasma flame only undergo a reduction reaction in a low temperature zone with a temperature of 1200-2000 ° C. Extremely fine nanoscale metal particles do not react with boron powder to form borides; at the same time, due to the gasification of metal oxides before the reaction, under the influence of plasma thermal disturbance gas, the metal oxides and reaction gas hydrogen are mixed Evenly disperse on the surface of boron particles. After reaching the reduction reaction temperature, the gas-gas reaction proceeds instantly, and the generated metal nanoparticles will be evenly dispersed on the surface of boron particles to obtain metal composite boron powder. During the combustion process of boron particles, the nano-metal particles coated on the surface can effectively promote the combustion of boron powder, promote its completion of combustion, and release sufficient energy.

In the present invention, the mixed powder is sent to 10-30 cm below the bottom of the plasma flame, for example, it can be 10, 11, 12, 13, 15, 18, 20, 23, 25, 28, 30 cm, etc.

Preferably, after the optional vacuum drying, the mixed powder is carried by the carrier gas and sent to the place 10-25 cm below the bottom of the plasma flame. Under this preferred scheme, it is more beneficial to improve the combustion performance of the obtained metal composite boron powder.

The feeding rate of the mixed powder is 10-30 g/min, for example, specifically 10, 11, 12, 13, 15, 18, 20, 23, 25, 28, 30 g/min, etc.

In some preferred embodiments, in step (2), the feeding rate of the mixed powder is 10-20 g/min. Under this preferred scheme, the feeding amount of the mixed powder is appropriate, which is more conducive to the timely and rapid gasification of metal oxides and participation in the reaction with hydrogen, thereby further promoting the uniform and rapid generation of nanoparticles, and a more dispersed distribution on the surface of boron particles Uniform; thereby further improving the combustion performance of metal composite boron powder.

It can be understood that the flow rate of the carrier gas only needs to meet the feeding rate of the mixed powder mentioned above. The carrier gas is preferably argon.

In some preferred embodiments, the plasma gas source includes argon and hydrogen, the flow rate of the hydrogen gas is not more than 100 L/min, and the flow ratio of the argon gas to the hydrogen gas is 1-3:1.

In some preferred embodiments, the particle size of the mixed powder is 0.3-45 μm. More preferably, the particle size of the boron powder in the mixed powder is 0.3-6 μm, and the particle size of the metal oxide powder is 5-45 μm. Under this preferred scheme, it is more conducive to the generation of metal particles with a particle size mainly concentrated between 30-80nm in step (2), which is adsorbed on the surface of boron particles in a large amount in the form of simple substance, and has a large specific surface area and high surface energy, which is conducive to promoting Rapid combustion of boron powder.

In some preferred embodiments, in step (2), the vacuum drying conditions include: vacuum degree ≤ -0.09MPa, drying temperature ≥ 90°C, and drying time ≥ 10h. Under this preferred solution, the influence of residual moisture in the powder on the reaction can be reduced, which is more conducive to promoting the reduction reaction.

The type of the metal oxide only needs to be gasified in the aforementioned plasma flame environment and react with hydrogen to form metal particles, and then coat the boron particles, and those skilled in the art can choose according to requirements. In some preferred embodiments, in step (1), the metal oxide includes molybdenum oxide and/or tungsten oxide.

Those skilled in the art can select the proportion of raw materials according to requirements. In some preferred embodiments, in step (1), the mass ratio of the metal oxide to boron powder is 1:4-45.

In some preferred embodiments, in step (1), the conditions of the ball mill mixing include: a ball-to-material ratio of 5-8:1, a frequency of 15-25 Hz, and a time of 30-240 min. Under this preferred solution, the mixing of the raw materials can be made more uniform, which is more conducive to the uniform dispersion of the subsequently generated metal nanoparticles on the surface of the boron particles.

The way of ball milling and mixing can be roller milling, etc., and those skilled in the art can choose according to requirements.

In some preferred embodiments, step (1) further includes: performing ball milling pre-dispersion treatment on the boron powder before the ball milling. Under this preferred solution, the boron powder is pre-dispersed by ball milling, so that even for boron powder with a smaller particle size, uniform coating of metal particles can be achieved.

More preferably, the conditions of the ball milling pre-dispersion treatment include: a ball-to-material ratio of 10-15:1, a frequency of 10-30 Hz, and a time of 60-300 min.

The method of ball milling pre-dispersion treatment can be roller ball milling or planetary ball milling, which can be selected by those skilled in the art according to requirements.

In a second aspect, the present invention provides a metal composite boron powder prepared by the method described in the first aspect, the metal composite boron powder includes micron-sized boron particles and nano-sized metal particles dispersed on the surface of the boron particles, the The mass content of metal in the metal composite boron powder is 2-15%, and the laser particle size of the metal composite boron powder satisfies: D ₅₀ <1 μm, D[4,3] <1 μm.

Preferably, the particle size of the boron particles in the metal composite boron powder is 0.2-3 μm, and the particle size of the metal particles is below 100 nm.

The present invention will be further described in detail below in conjunction with specific examples. Wherein, the gas sources of the plasma in the example are argon and hydrogen, the flow rate of the hydrogen is 90 L/min, and the flow ratio of the argon to the hydrogen is 2:1.

Example 1

A method for preparing metal composite boron powder, the steps are as follows:

(1) Pre-disperse the boron powder by ball milling. The conditions for ball milling pre-dispersion include: the ratio of ball to material is 12:1, the frequency is 15Hz, and the time is 150min;

Then molybdenum oxide and the obtained boron powder powder are ball milled and mixed at a mass ratio of 1:15 to obtain a mixed powder with a particle size of 0.3-45 μm, the particle size of the boron powder in the mixed powder is 0.3-6 μm, and the particle size of the metal oxide powder is 5-45μm; the mixing conditions of the ball mill include: the ratio of ball to material is 6:1, the frequency is 20Hz, and the time is 180min;

(2) Then vacuum-dry the mixed powder, control the vacuum degree ≤ -0.09MPa, the drying temperature ≥ 100°C, and the drying time ≥ 15h;

Then, mix it with argon carrier gas and send it to the place 10cm below the bottom of the plasma flame. The feeding rate of the mixed powder is 10g/min, and the plasma power is controlled at 30kw, so that molybdenum oxide is vaporized and reacts with hydrogen to form Nano-molybdenum particles, the molybdenum particles are dispersed on the surface of the boron particles to obtain molybdenum composite boron powder. Wherein, the particle size of the boron particle is 0.2-3 μm, and the particle size of the molybdenum particle is below 100 nm.

The metal mass content in the obtained molybdenum composite boron powder is 5.42%, and the laser particle size meets: D ₅₀ =0.587μm, D[4,3]=0.797μm. The electron microscope picture of molybdenum composite boron powder is shown in Figure 1, and the SEM surface scans are shown in Figure 2, Figure 3, and Figure 4. It can be seen from the lens diagram that Mo and B are distributed on both sides of the adsorption interface in the obtained composite. Exists in the form of Mo, and Mo is uniformly dispersed on the surface of boron particles in the form of extremely small nanoparticles.

Example 2

Carry out according to the method of Example 1, the difference is that the feeding position is different, specifically, it is mixed with argon carrier gas and sent to the place 30 cm below the bottom of the plasma flame.

The metal mass content in the obtained molybdenum composite boron powder is 5.15%, and the laser particle size meets: D ₅₀ =0.671 μm, D[4,3]=0.873 μm. Both molybdenum and boron in molybdenum composite boron powder exist in the form of simple substance, and molybdenum is uniformly dispersed on the surface of boron particles in the form of extremely small nanoparticles.

Example 3

Carry out according to the method of embodiment 1, difference is, the feeding rate of mixed powder is 30g/min.

The metal mass content in the obtained molybdenum composite boron powder is 5.29%, and the laser particle size meets: D ₅₀ =0.662μm, D[4,3]=0.891μm. Both molybdenum and boron in molybdenum composite boron powder exist in the form of simple substance, and molybdenum is uniformly dispersed on the surface of boron particles in the form of extremely small nanoparticles.

Comparative example 1

Carry out according to the method of Example 1, the difference is that the feeding position is different, specifically, it is mixed with argon carrier gas and sent to the place 35 cm below the bottom of the plasma flame.

The temperature at the feeding position is low, and the analyzed product is a mixture of boron composite boron powder and molybdenum oxide, mainly because the temperature at this position is low, and part of the molybdenum oxide does not react with hydrogen, and forms molybdenum oxide powder after cooling, which is mixed to form molybdenum complex boron powder.

Comparative example 2

Carry out according to the method of Example 1, the difference is that the feeding position is different, specifically, it is mixed with argon carrier gas and sent to the place 5 cm below the bottom of the plasma flame.

The feeding position is too high, the reaction temperature is high, the boron powder may be gasified, and react with the generated molybdenum metal to form borides, resulting in the failure of the preparation of the metal composite boron powder.

Comparative example 3

Molybdenum composite boron powder was prepared by conventional ball milling process (boron powder 500g, molybdenum powder 25g, mixed ball milling, ball to material ratio 5:1, ball milling frequency 40Hz, ball milling time 240min). Molybdenum metal deposition occurred after compounding, and compounding failed.

test case

Performance tests were performed on the products obtained in the above examples and comparative examples: the combustion calorific value was tested with an oxygen bomb calorimeter, and the combustion calorific value directly reflected the change of the combustion performance of the boron powder modified by molybdenum compounding. The test results are shown in Table 1 below.

Table 1

Example number Calorific value of combustion (J/g) Compound pre-boron powder 18968.94 Example 1 34028.19 Example 2 30995.48 Example 3 31206.04 Comparative example 1 26811.06 Comparative example 2 20092.34 Comparative example 3 19194.83

From the above results, it can be known that the metal composite boron powder with a specific structure can be obtained by using the embodiments of the present invention, in which the metal element is uniformly dispersed on the surface of the boron particles with extremely small nanoparticles, which significantly improves the combustion performance of the metal composite boron powder. The combustion performance of Comparative Example 1-2, which is not within the scope of the present invention, or Comparative Example 3, which adopts a conventional ball milling process, is significantly lower than that of the examples of the present invention.

Further, according to Example 1 and Example 2 of the present invention, it can be seen that the combustion performance of the obtained metal composite boron powder is better by adopting the preferred scheme of the present invention.

The preferred embodiments of the present invention have been described in detail above, however, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the content disclosed in the present invention. All belong to the protection scope of the present invention.

Claims (8)

1. A method for preparing metal composite boron powder, is characterized in that, comprises the following steps: (1) Ball milling and mixing boron powder and metal oxide powder to obtain a mixed powder; the particle size of the boron powder in the mixed powder is 0.3-6 μm, and the particle size of the metal oxide powder is 5-45 μm; the metal oxide includes Molybdenum oxide and/or tungsten oxide; (2) After the mixed powder is vacuum-dried, it is carried by the carrier gas and sent to the bottom 10-30cm of the plasma flame, and the plasma power is controlled at 20-30kw, so that the metal oxide is vaporized and react with hydrogen to form metal particles, and the metal particles are distributed on the surface of boron particles to obtain metal composite boron powder; wherein, the feeding rate of the mixed powder is 10-30g/min, and the conditions of vacuum drying include: vacuum degree ≤ -0.09MPa, drying temperature≥90℃, drying time≥10h. 2. The method according to claim 1, characterized in that, in step (1), the mixed powder is carried by the carrier gas and sent to a place 10-25 cm below the bottom of the plasma flame. 3. The method according to claim 1, characterized in that, in step (2), the feeding rate of the mixed powder is 10-20 g/min. 4. The method according to claim 1, characterized in that, in step (2), the gas source of the plasma includes argon and hydrogen, and the flow rate of the hydrogen is not more than 100L/min, wherein the argon and hydrogen The hydrogen flow ratio is 1-3:1. 5. The method according to claim 1, characterized in that, in step (1), the mass ratio of the metal oxide to boron powder is 1:4-45; and/or, in step (1), the The mixing conditions of the ball mill include: the ratio of ball to material is 5-8:1, the frequency is 15-25Hz, and the time is 30-240min. 6. The method according to claim 1, characterized in that, in step (1), further comprising: performing ball milling pre-dispersion treatment on boron powder before the ball milling; the conditions of the ball milling pre-dispersion treatment include: The ball-to-material ratio is 10-15:1, the frequency is 10-30Hz, and the time is 60-300min. 7. A metal composite boron powder, characterized in that, it is prepared by the method according to any one of claims 1-6, and the metal composite boron powder comprises micron-sized boron particles and nanometer boron particles dispersed on the surface of the boron particles. Grade metal particles, the metal mass content in the metal composite boron powder is 2-15%, and the laser particle size of the metal composite boron powder satisfies: D ₅₀ <1 μm, D[4,3] <1 μm. 8. The metal composite boron powder according to claim 7, characterized in that, the particle size of the boron particles in the metal composite boron powder is 0.2-3 μm, and the particle size of the metal particles is below 100 nm.

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