CN111377449A - A kind of preparation method of boron carbide nanoparticles - Google Patents

Abstract

The invention relates to a method for preparing boron carbide nanoparticles. Boron powder is used as raw material, carbon material is used as reducing agent, transition metal inorganic salt is used as catalyst, and B ₄ C nanoparticles are generated by heating and reduction in a furnace; the boron powder is combined with The molar ratio of carbon material is (1-20): 1, and the mass fraction is 1-60% of transition metal inorganic salt catalyst; absolute ethanol is used as solvent, ultrasonically mixed uniformly, and then heated in a high-temperature furnace after drying. product is obtained. The advantage of the present invention is that it is proved by chemical analysis results that the reaction of boron and carbon is complete, and the prepared boron carbide reaches nanometer level, with narrow size distribution, uniform appearance and high purity. The prepared boron carbide particles can be used for sintering ceramic products, and because of the nanometer effect, the ceramic products thereof will have a higher bulletproof effect and neutron absorption effect than the current micron-level boron carbide.

Description

A kind of preparation method of boron carbide nanoparticles

technical field

The invention relates to the technical field of metallurgy and chemical industry, in particular to a method for preparing boron carbide nanoparticles.

Background technique

Due to its covalent bond properties, boron carbide has the advantages of high melting point, high hardness, good wear resistance, acid and alkali corrosion resistance, low density and strong thermal neutron absorption capacity. As the lightest ceramic material, boron carbide can be used as a jet blade due to its low density, and is widely used in the aerospace field; due to its strong neutron absorption ability, it can be used as a control rod of a nuclear reactor and a material to prevent the leakage of radioactive substances. However, high-performance boron carbide ceramic products rely on higher-quality powders, and the preparation of ultra-fine nano-powders has always plagued the further development of boron carbide. According to the different reaction principles, raw materials and equipment used to synthesize boron carbide powder, the industrial preparation methods of boron carbide powder mainly include carbon tube furnace, electric arc furnace carbothermic reduction method and high temperature self-propagating synthesis method. The defects of carbon tube furnace and electric arc furnace carbothermic reduction method are high energy consumption, low production capacity, serious damage to the furnace body at high temperature, especially the large average particle size of the synthesized original powder. Residuals in the reactants obtained by the high-temperature self-propagating synthesis method must be washed away by an additional process, and it is extremely difficult to completely remove them. Therefore, it is very difficult to obtain nano-scale particles by current technical means.

SUMMARY OF THE INVENTION

One purpose of the present invention is to solve the problem of difficulty in obtaining nano-scale boron carbide particles in the prior art, and provides a preparation method of nano-scale boron carbide particles.

The specific scheme of the present invention is as follows: a preparation method of nano boron carbide particles, comprising the following steps:

S1: Mix boron powder and carbon source according to the molar ratio (1-10):1 to obtain black mixture A;

S2: ultrasonically stir the black mixture A, transition metal inorganic salt and absolute ethanol in a mass ratio of 100:(1-50):(100-1000) to obtain a black slurry;

S3: The obtained black slurry is placed in an oven (30-300°C) for drying (0.2-12h) to obtain a black dry mixture;

S4: the obtained black dry mixture is placed in a graphite crucible, heated to 700-1600° C. in a high-temperature furnace under a gas atmosphere, and kept for (0.1-6) h, and black boron carbide powder is obtained after cooling;

S5: placing the obtained black boron carbide powder in a heating device at 300-900°C for 1-12 hours to remove free carbon powder; then cleaning with an acid solution to remove the catalyst and B ₂ O ₃ , and centrifuging to obtain a centrifugal precipitate;

S6: drying the obtained centrifugal sediment for 0.2-12 h under the condition of 30-200° C. oven to obtain boron carbide particles.

The present invention adopts boron powder and carbon material as raw materials, and adds transition metal inorganic salt as catalyst in order to reduce the required reaction temperature. By controlling the sintering process and raw materials, nano-boron carbide particles with narrow particle size distribution and uniform morphology can be obtained. Its reaction equation is: B+C=B ₄ C.

Preferably, the carbon source described in step S1 is one of flake graphite, microcrystalline graphite, acetylene black, activated carbon, graphene, carbon nanotubes or hollow carbon spheres.

Preferably, the ultrasonic stirring time in step S2 is 1-30 min.

Preferably, the cooling rate in step S4 is 1-20°C/min.

Preferably, the gas in step S4 is one of helium and argon.

Preferably, the gas in step S4 is one of air, oxygen and carbon dioxide.

Preferably, the acid solution in step S5 is one of sulfuric acid, hydrochloric acid, and nitric acid.

Compared with the existing boron carbide particle preparation method, the present invention has the following substantial effects: the operation is simple, the raw materials can be dried after mixing, the equipment requirements are small, and large-scale industrial production is possible; the catalyst is added during preparation, and the required temperature Low requirements for high temperature furnace equipment, energy saving and low cost; the obtained product has high purity and simple follow-up processing; the obtained product has a uniform appearance and narrow particle size distribution, and can obtain boron carbide with a particle size of 50-300nm through process control. nanoparticles.

Description of drawings

Fig. 1 is the X-ray diffraction photo of the product obtained therefrom in the embodiment of the present invention;

Fig. 2 is the scanning electron micrograph of the obtained product of the embodiment of the present invention;

Figure 3 is a transmission electron microscope photograph of the product obtained in the embodiment of the present invention.

Detailed ways:

The present invention will be further described below in conjunction with the accompanying drawings:

A preparation method of nano boron carbide particles, comprising the following steps:

S1: Mix boron powder and carbon source according to the molar ratio (1～10):1 to obtain black mixture A; the carbon source is flake graphite, microcrystalline graphite, acetylene black, activated carbon, graphene, carbon nanotube or hollow A kind of carbon ball, the molar ratio of boron powder and carbon source is 4:1.

S2: ultrasonically stir the black mixture A, transition metal inorganic salt and anhydrous ethanol in a mass ratio of 100:(1-50):(100-1000) to obtain a black slurry; the ultrasonic stirring time is 10-20min; The mass fraction ratio of the transition metal inorganic salt to the black mixture A is 1-10%, which can be 5%.

S3: Place the obtained black slurry in an oven (30-300°C) for drying (0.2-12h) to obtain a black dry mixture, the oven temperature can be set to 70°C, and the drying time can be set to 3-5h.

S4: The obtained black dry mixture is placed in a graphite crucible, heated to 700-1600° C. in a high-temperature furnace under a gas atmosphere, and kept for (0.1-6) h, and black boron carbide powder is obtained after cooling. Among them, the gas of the gas atmosphere can be selected from one of helium or argon; the temperature rise control mode of the high temperature furnace can be set as: use 100min to raise the temperature from room temperature to 500℃, and then use 30min to raise the temperature from 500°C to 800°C, then use 40min to raise the temperature from 800°C to 1000°C, and finally use 64min to raise the temperature from 1000°C to 1160°C, hold for 4h and then set the rate to 1～20°C/min cool down. S5: placing the obtained black boron carbide powder in a heating device at 300-900°C for 1-12 hours to remove free carbon powder; then cleaning with an acid solution to remove the catalyst and B ₂ O ₃ , and centrifuging to obtain a centrifugal precipitate; Among them, 20% sulfuric acid can be selected for the acid solution, a muffle furnace can be selected for the heating equipment, the holding temperature is set to 400-800°C, and the holding time is set to 4-8h.

S6: drying the obtained centrifugal sediment for 0.2-12 h under the condition of 30-200° C. oven to obtain boron carbide particles. The temperature of the oven can be set to 80°C, and the drying time can be set to 12h.

Example:

Weigh 0.174 of nickel nitrate hexahydrate in a 500ml beaker, add absolute ethanol to dissolve it, weigh 2.7g of amorphous boron powder and 0.81g of high-conductivity carbon balls, add them to the resulting solution, and place them in an ultrasonic device to ultrasonically stir for 15 minutes. , to obtain a black slurry; the obtained black slurry was dried in an oven at 70 °C for 3 h, then put into a graphite crucible and placed on a high temperature furnace, and the temperature was raised from room temperature to 500 °C in 100 min, and then used for 30 min. The temperature was raised from 500°C to 800°C in 40 minutes, and the temperature was raised from 800°C to 1000°C in 40min. Finally, the temperature was raised from 1000°C to 1160°C in 64min. The free carbon powder was removed, and the catalyst and B ₂ O ₃ were removed by ultrasonic cleaning with 20% sulfuric acid solution, and the powder was obtained after centrifugation. The powder was dried in an oven at 80° C. for 12 hours to obtain the final product, namely boron carbide particles.

The XRD pattern of the boron carbide particles obtained in this embodiment is shown in FIG. 1 , from which it can be clearly seen that only the diffraction peaks of boron carbide are present. As shown in FIGS. 2 and 3 , the obtained boron carbide particles have a diameter of 50- 100nm, has reached the nanometer level.

The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Various changes and modifications fall within the scope of the claimed invention.

Claims (7)

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

s1: according to a molar ratio (1-10): 1, mixing boron powder and a carbon source according to a proportion to obtain a black mixture A;

s2: mixing a black mixture A, a transition metal inorganic salt and absolute ethyl alcohol according to a mass ratio of 100: (1-50): (100-1000) ultrasonically stirring to obtain black slurry;

s3: drying the obtained black slurry in an oven (30-300 ℃) for 0.2-12 hours to obtain a black dry mixture;

s4: placing the obtained black dry mixture in a graphite crucible, heating the mixture to 700-1600 ℃ by using a high-temperature furnace under the gas atmosphere, preserving the heat for 0.1-6 h, and cooling to obtain black boron carbide powder;

s5: placing the obtained black boron carbide powder in heating equipment at the temperature of 300-900 ℃ for heat preservation for 1-12 h, and removing free carbon powder; washing with acid solution to remove catalyst and B₂O₃Then, centrifugal operation is carried out to obtain centrifugal precipitate;

s6: and drying the obtained centrifugal precipitate for 0.2-12 h in an oven at the temperature of 30-200 ℃ to obtain boron carbide particles.

2. The method of claim 1, wherein the carbon source in step S1 is one of flake graphite, microcrystalline graphite, acetylene black, activated carbon, graphene, carbon nanotubes, or hollow carbon spheres.

3. The method for preparing nano boron carbide particles according to claim 1, wherein the ultrasonic stirring in step S2 is performed for 1-30 min.

4. The method for preparing nano boron carbide particles according to claim 1, wherein the cooling rate in step S4 is 1-20 ℃/min.

5. The method as claimed in claim 1, wherein the gas in step S4 is one of helium and argon.

6. The method as claimed in claim 1, wherein the gas in step S4 is one of air, oxygen and carbon dioxide.

7. The method of claim 1, wherein the acid solution in step S5 is one of sulfuric acid, hydrochloric acid and nitric acid.

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