阅读说明：本技术 一种碳化硼纳米粒子的制备方法 (Preparation method of boron carbide nanoparticles ) 是由 王志江 于 2020-12-29 设计创作，主要内容包括：一种碳化硼纳米粒子的制备方法,它属于新材料领域,它要解决现有碳化硼的制备中存在能耗大、污染环境、成本高、产品纯度低且粒度大的问题。方法：一、硼源、碳源和添加剂混合后得混合物；二、制备浆液；三、浆液于HCl气氛下加热干燥得干燥混合物；四、干燥混合物惰性气氛下加热,得碳化硼粉体。本发明制备的碳化硼颗粒具有纳米尺度且粒度均匀、纯度高,制备中能耗小、不污染环境、成本低,可批量工业化生产。超声波的空化作用形成均匀的混合物。在形状调节剂MgCl-2作用下,有效控制碳化硼的生长过程,实现了纳米级颗粒的制备。且根据反应物的比例以及形状调节剂的添加量可以调控生成碳化硼颗粒的尺寸。本发明应用于纳米碳化硼粒子的制备。(A preparation method of boron carbide nano particles belongs to the field of new materials and aims to solve the problems of high energy consumption, environmental pollution, high cost, low product purity and large particle size in the existing preparation of boron carbide. The method comprises the following steps: firstly, mixing a boron source, a carbon source and an additive to obtain a mixture; secondly, preparing slurry; thirdly, heating and drying the slurry in HCl atmosphere to obtain a dry mixture; fourthly, heating the dried mixture in an inert atmosphere to obtain boron carbide powder. The boron carbide particles prepared by the method have the advantages of nanoscale, uniform particle size, high purity, low energy consumption in preparation, no environmental pollution, low cost and suitability for batch industrial production. Cavitation by the ultrasonic waves forms a homogeneous mixture. In the form of MgCl as a shape regulator 2 Under the action, the growth process of the boron carbide is effectively controlled, and the preparation of the nano-scale particles is realized. And according to the ratio of the reactantsAnd the addition amount of the shape regulator can regulate and control the size of the generated boron carbide particles. The method is applied to the preparation of the nanometer boron carbide particles.)

1. The preparation method of the boron carbide nano particles is characterized by comprising the following steps of:

firstly, weighing a boron source, a carbon source and an additive according to a molar ratio (1-10) to (1) (0.001-0.1), and mixing to obtain a mixture A;

secondly, ultrasonically dissolving the mixture A into a solvent according to the mass-volume ratio of 1g (5-1000) mL to obtain slurry B;

thirdly, placing the obtained slurry B in HCl atmosphere, and heating and drying for 0.2-24 hours at the temperature of 30-300 ℃ to obtain a dry mixture C;

fourthly, placing the dried mixture C in a graphite crucible, heating the mixture C to 700-1700 ℃ in a high-temperature furnace under inert atmosphere, preserving heat for 0.1-6 h, and cooling the mixture C along with the furnace to obtain boron carbide powder, namely completing the preparation of boron carbide nanoparticles;

wherein in the first step, the boron source is crystalline boron, ammonium fluoroborate, boric acid, metaboric acid, pyroboric acid or trimethyl borate;

in the first step, the carbon source is crystalline flake graphite, microcrystalline graphite, acetylene black, activated carbon, graphene, carbon nano tubes, hollow carbon spheres or carbon black;

in the first step, the additive is MgCl₂；

In the second step, the solvent is deionized water, absolute ethyl alcohol, glycerol, ether or sesame oil essence.

2. The method for preparing boron carbide nanoparticles according to claim 1, wherein in the step one, the boron source, the carbon source and the additive are weighed according to a molar ratio (2-8) to 1 (0.002-0.08).

3. The method for preparing boron carbide nanoparticles according to claim 1, wherein in the first step, the boron source, the carbon source and the additive are weighed according to a molar ratio of 5:1: 0.05.

4. The method for preparing boron carbide nanoparticles according to claim 1, wherein in the second step, the mixture A is ultrasonically dissolved in the solvent according to a mass-volume ratio of 1g (100-800) mL.

5. The method for preparing boron carbide nanoparticles according to claim 1, wherein in the second step, the mixture A is ultrasonically dissolved in the solvent according to a mass-to-volume ratio of 1g:500 mL.

6. The method for preparing boron carbide nanoparticles according to claim 1, wherein the ultrasonic dissolution in the second step is performed at a frequency of 40 kHz.

7. The method for preparing boron carbide nanoparticles according to claim 1, wherein the drying is carried out at 100 ℃ for 12h in the third step.

8. The method for preparing boron carbide nanoparticles according to claim 1, wherein the inert atmosphere in the fourth step is nitrogen or argon with a purity of 99.99%.

9. The method for preparing boron carbide nanoparticles according to claim 1, wherein the four steps of heating are carried out in a high temperature furnace to 1200 ℃ and keeping the temperature for 1 hour.

10. The method for preparing boron carbide nanoparticles according to claim 9, wherein the heating is performed in a high temperature furnace in four steps, wherein the heating rate is 1 to 5 ℃/min when the heating temperature is below 1000 ℃, and the heating rate is 20 ℃/min when the heating temperature is above 1000 ℃.

Technical Field

The invention belongs to the field of new materials, and particularly relates to a preparation method of boron carbide nanoparticles.

Background

Boron carbide was first discovered in 1858 and had a stoichiometric formula of B₄Compounds of C were not recognized until 1934. Boron carbide has a higher melting point and a higher melting point due to the nature of its covalent bondGood hardness and wear resistance, acid and alkali corrosion resistance, small density and high thermal neutron absorption capacity. The hardness of the material is second to that of diamond and cubic boron nitride, and the material belongs to a non-metallic material and has important physicochemical properties. Boron carbide has the performance of high-temperature extraordinary hardness and is widely applied to the fields of body armor, grinding tools and the like. Boron carbide is the lightest ceramic material, and can be used as a jet blade due to low density, and is widely applied in the field of aerospace. The material can be used as a control rod of a nuclear reactor and a material for preventing radioactive substances from leaking due to the strong neutron absorption capacity of the material.

The high-performance boron carbide ceramic product depends on powder with higher quality, and the preparation of superfine nano powder always troubles the further development of boron carbide. According to the different reaction principle, raw material and equipment adopted for synthesizing boron carbide powder, the industrial preparation method of boron carbide powder mainly includes carbon tube furnace, electric arc furnace carbothermic reduction method and high-temperature self-propagating synthesis method. The carbon tube furnace and the electric arc furnace carbon thermal reduction method have the advantages of simple equipment structure, small occupied area, high construction speed, mature and stable process operation, but also have larger defects, such as large energy consumption, lower production capacity and serious damage to the furnace body at high temperature. Especially, the synthesized product needs further crushing, impurity removal and screening to cause serious environmental pollution. The self-propagating high-temperature synthesis method is a process method which utilizes the reaction heat during the synthesis of compounds to make the reaction proceed, and is also called as a magnesiothermic method because the method mostly uses magnesium as a fluxing agent during the preparation of boron carbide. Compared with other methods, the method has the advantages of lower reaction temperature, energy conservation, rapid reaction, easy control and the like, and the synthesized boron carbide powder has higher purity and finer original powder granularity, thus being a better method for synthesizing the boron carbide powder at present. The disadvantage is that the impurities remaining in the reactants have to be washed away by additional processes and are extremely difficult to remove completely. Therefore, the controllable particle size is the main development direction of the carbothermic synthesis of boron carbide powder, and the key is to select proper boron source, carbon source, additive and process conditions. Currently, boron sources mostly adopt boron simple substances or compounds thereof, and the selection of carbon sources is limited to graphite, carbon powder and some carbon-containing polymers, such as sucrose, starch, phenolic resin, glucose, glycerol and the like. Can be prepared industriallyBoric acid is used as a raw material, carbon, graphite or petroleum coke is used as a reducing agent, and the boric acid is generated by carbothermic reduction in an electric arc furnace, wherein the reduction reaction formula is 2B₂O₃+7C＝B₄The heating temperature of the C +6CO electric arc furnace is not uniform, boron carbide obtained by incomplete reaction is a block, the subsequent treatments of crushing, impurity removal and the like are also needed, and the boron carbide can not be crushed to obtain nano-grade particles due to high hardness of the boron carbide. The process for directly reacting simple substance carbon and simple substance boron to generate boron carbide has high reaction temperature (about 1800 ℃), and the obtained particles have the particle size of more than 300nm and are submicron particles.

Disclosure of Invention

The invention aims to solve the problems of high energy consumption, environmental pollution, high cost, low product purity and large particle size in the existing preparation of boron carbide, and provides a preparation method of boron carbide nanoparticles.

A preparation method of boron carbide nano particles is realized by the following steps:

firstly, weighing a boron source, a carbon source and an additive according to a molar ratio (1-10) to (1) (0.001-0.1), and mixing to obtain a mixture A;

secondly, ultrasonically dissolving the mixture A into a solvent according to the mass-volume ratio of 1g (5-1000) mL to obtain slurry B;

thirdly, placing the obtained slurry B in HCl atmosphere, and heating and drying for 0.2-24 hours at the temperature of 30-300 ℃ to obtain a dry mixture C;

fourthly, placing the dried mixture C in a graphite crucible, heating the mixture C to 700-1700 ℃ in a high-temperature furnace under inert atmosphere, preserving heat for 0.1-6 h, and cooling the mixture C along with the furnace to obtain boron carbide powder, namely completing the preparation of boron carbide nanoparticles;

wherein in the first step, the boron source is crystalline boron, ammonium fluoroborate, boric acid, metaboric acid, pyroboric acid or trimethyl borate;

in the first step, the carbon source is crystalline flake graphite, microcrystalline graphite, acetylene black, activated carbon, graphene, carbon nano tubes, hollow carbon spheres or carbon black;

in the first step, the additive is MgCl₂；

In the second step, the solvent is deionized water, absolute ethyl alcohol, glycerol, ether or sesame oil essence.

The invention has the beneficial effects that:

the carbon source, the boron source and the additive added in the invention react at high temperature to generate nano particles, and the boron carbide particles prepared by the method have the advantages of nano scale, uniform granularity, high purity, low energy consumption in preparation, no environmental pollution and batch industrial production.

The boron source, the carbon source and the additive used in the invention can be uniformly dispersed in the liquid phase under the ultrasonic action. Cavitation of the ultrasonic waves can cause the particles in the liquid to collide violently, thereby dispersing the agglomerates in the original boron source carbon source and forming a uniform mixture after drying. In the presence of additive MgCl₂Under the action of the action, the carbon and boron sources which are completely mixed at high temperature uniformly enter the interior of molten metal salt ions, the growth process of boron carbide is effectively controlled to grow along the crystal face with the lowest accumulation energy of the boron carbide crystal, and the supersaturated linear growth in the reaction process is inhibited, so that the preparation of nano-scale particles is realized. And the size of the generated boron carbide particles can be regulated and controlled according to the proportion of reactants and the addition amount of the additive.

The method is applied to the preparation of the nanometer boron carbide particles.

Drawings

FIG. 1 is an X-ray diffraction spectrum of boron carbide powder prepared in the example;

FIG. 2 is a scanning electron micrograph of the boron carbide powder prepared in the example.

Detailed Description

The technical solution of the present invention is not limited to the following specific embodiments, but includes any combination of the specific embodiments.

The first embodiment is as follows: the preparation method of the boron carbide nanoparticles of the embodiment is realized by the following steps:

firstly, weighing a boron source, a carbon source and an additive according to a molar ratio (1-10) to (1) (0.001-0.1), and mixing to obtain a mixture A;

secondly, ultrasonically dissolving the mixture A into a solvent according to the mass-volume ratio of 1g (5-1000) mL to obtain slurry B;

thirdly, placing the obtained slurry B in HCl atmosphere, and heating and drying for 0.2-24 hours at the temperature of 30-300 ℃ to obtain a dry mixture C;

fourthly, placing the dried mixture C in a graphite crucible, heating the mixture C to 700-1700 ℃ in a high-temperature furnace under inert atmosphere, preserving heat for 0.1-6 h, and cooling the mixture C along with the furnace to obtain boron carbide powder, namely completing the preparation of boron carbide nanoparticles;

wherein in the first step, the boron source is crystalline boron, ammonium fluoroborate, boric acid, metaboric acid, pyroboric acid or trimethyl borate;

in the first step, the carbon source is crystalline flake graphite, microcrystalline graphite, acetylene black, activated carbon, graphene, carbon nano tubes, hollow carbon spheres or carbon black;

in the first step, the additive is MgCl₂；

In the second step, the solvent is deionized water, absolute ethyl alcohol, glycerol, ether or sesame oil essence.

The second embodiment is as follows: the difference between the first embodiment and the second embodiment is that in the first step, the boron source, the carbon source and the additive are weighed according to the molar ratio (2-8) to 1 (0.002-0.08). Other steps and parameters are the same as those in the first embodiment.

The third concrete implementation mode: the difference between the first embodiment and the second embodiment is that the boron source, the carbon source and the additive are weighed according to the molar ratio of 5:1:0.05 in the first embodiment. Other steps and parameters are the same as those in the first or second embodiment.

The fourth concrete implementation mode: the difference between the present embodiment and one of the first to third embodiments is that in the second step, the mixture A is ultrasonically dissolved in the solvent according to the mass volume ratio of 1g (100-800) mL. Other steps and parameters are the same as those in one of the first to third embodiments.

The fifth concrete implementation mode: the difference between the embodiment and one of the first to the fourth embodiments is that in the second step, the mixture A is ultrasonically dissolved in the solvent according to the mass-to-volume ratio of 1g:500 mL. Other steps and parameters are the same as in one of the first to fourth embodiments.

The sixth specific implementation mode: the present embodiment is different from one of the first to fifth embodiments in that the frequency used for ultrasonic dissolution in the second step is 40 kHz. Other steps and parameters are the same as those in one of the first to fifth embodiments.

The seventh embodiment: this embodiment differs from one of the first to sixth embodiments in that the drying is carried out in step three at 100 ℃ for 12 hours. Other steps and parameters are the same as those in one of the first to sixth embodiments.

The specific implementation mode is eight: this embodiment is different from the first to seventh embodiments in that nitrogen or argon having a purity of 99.99% is used as the inert gas atmosphere in the fourth step. Other steps and parameters are the same as those in one of the first to seventh embodiments.

The specific implementation method nine: the difference between the fourth embodiment and the eighth embodiment is that the high temperature furnace in the fourth step is heated to 1200 ℃ and kept for 1 hour. The other steps and parameters are the same as those in the eighth embodiment.

The detailed implementation mode is ten: the present embodiment is different from the ninth embodiment in that the heating is performed in the high temperature furnace in the fourth step, the heating rate is 1 to 5 ℃/min when the heating temperature is 1000 ℃ or lower, and the heating rate is 20 ℃/min when the heating temperature is 1000 ℃ or higher. Other steps and parameters are the same as those in the ninth embodiment.

The beneficial effects of the present invention are demonstrated by the following examples:

example (b):

a preparation method of boron carbide nano particles is realized by the following steps:

firstly, weighing crystalline boron, graphene and MgCl according to a molar ratio of 5:1:0.05₂Mixing to obtain a mixture A;

secondly, ultrasonically dissolving the mixture A in absolute ethyl alcohol according to the mass-volume ratio of 1g to 80mL to obtain slurry B;

thirdly, placing the obtained slurry B in HCl atmosphere, and heating and drying at 100 ℃ for 12 hours to obtain a dry mixture C;

fourthly, placing the dried mixture C in a graphite crucible, heating the mixture C to 1200 ℃ in a high-temperature furnace under inert atmosphere, preserving heat for 1h, and cooling the mixture C along with the furnace to obtain boron carbide powder, namely completing the preparation of the boron carbide nano particles.

In the second step of this example, the frequency used for ultrasonic dissolution is 40 kHz; in the fourth step, argon with the purity of 99.99 percent is adopted as inert atmosphere; and step four, heating by a high temperature furnace, wherein the heating rate is 1-53 ℃/min when the heating temperature is below 1000 ℃, and the heating rate is 20 ℃/min when the heating temperature is above 1000 ℃.

The boron carbide powder prepared in this example had an X-ray diffraction (XRD) spectrum as shown in FIG. 1, wherein diamond-solid represents B₄C, visible XRD spectrum and B₄C corresponds to the diffraction peak in which there is no impurity, indicating that only B is present in the range detectable by X-ray diffractometry₄And C, no carbon, boron oxide and the like are left, and the prepared boron carbide powder has high purity and does not need subsequent treatment.

The Scanning Electron Microscope (SEM) image of the boron carbide powder prepared in this example is shown in FIG. 2, and B is obtained₄The C particles are uniform in appearance and 70-120 nm in particle size distribution.

In the embodiment, 1g of the prepared boron carbide powder is dispersed in 10ml of absolute ethyl alcohol, standing is carried out for 30min, no obvious precipitate exists, and the boron carbide powder is uniformly dispersed, so that the obtained boron carbide powder has good dispersibility and low agglomeration property, and is beneficial to subsequent block preparation.