CN114751753A

CN114751753A - Method for preparing superfine ceramic powder by adopting liquid-phase ceramic precursor

Info

Publication number: CN114751753A
Application number: CN202210592288.0A
Authority: CN
Inventors: 黄竹林; 胡梦恩; 李昕扬; 胡小晔; 李越
Original assignee: Hefei Institutes of Physical Science of CAS
Current assignee: Hefei Institutes of Physical Science of CAS
Priority date: 2022-05-27
Filing date: 2022-05-27
Publication date: 2022-07-15
Anticipated expiration: 2042-05-27
Also published as: CN114751753B

Abstract

The invention discloses a method for preparing ultrafine ceramic powder by adopting a liquid-phase ceramic precursor, which is characterized in that boric acid and sorbitol are respectively used as a boron source and a carbon source, molybdenum pentachloride is used as a molybdenum source, acetic acid is used as a solvent, and the molybdenum boride ceramic precursor is prepared by a sol-gel method. And then the molybdenum element can be better complexed by a solvent thermal reaction kettle heat treatment method, and the reaction temperature and time are adjusted to obtain different single-phase ceramic powders. The powder prepared by the method provided by the invention has the advantages of high purity, fine particle size, good sintering performance and the like, and the preparation method is simple, high in production efficiency and suitable for industrial production.

Description

Method for preparing superfine ceramic powder by adopting liquid-phase ceramic precursor

Technical Field

The invention belongs to the technical field of preparation of molybdenum boride powder, and particularly relates to a method for preparing ultrafine ceramic powder by using a liquid-phase ceramic precursor.

Background

Transition metalBoride is becoming a potential substitute for conventional cemented carbide and superhard materials due to its high hardness. Unlike available superhard diamond, cubic boron nitride and other material, the transition metal boride may be synthesized at normal pressure to result in low production cost. The molybdenum boride is a stable compound consisting of boron and molybdenum, the melting point of the molybdenum boride is as high as 2600 ℃, and the microhardness of the molybdenum boride is 2350kg/mm ². Molybdenum boride, one of the hardest and most heat resistant substances on earth, can be used as a high temperature resistant coating for cutting tools and engines of hard metals. Molybdenum boride has another excellent characteristic, in addition to high hardness and excellent heat resistance, wear resistance and corrosion resistance. Because molybdenum boride has a lower friction coefficient, the molybdenum boride can be used as a wear-resistant material to play a role in reducing friction in a sliding friction process, for example, a molybdenum boride coating is sprayed on the inner wall of a cylinder sleeve of an engine, and a good heat-resistant and friction-reducing effect can be achieved. Meanwhile, the material has good corrosion resistance, and can be sprayed on the surface of a continuous hot-dip galvanized sink roller to protect the sink roller from being corroded by liquid zinc. Besides, the molybdenum boride can be used for metal ceramics, high-temperature resistors, pot linings, space filling spraying and corrosion-resistant chemical equipment, and can be used as an additive of tungsten, aluminum and tantalum alloys for electronics. Can also be used for manufacturing wear-resistant films and semiconductor film spraying materials. In recent years, molybdenum borides have been successfully used in the electrocatalysis field as electrocatalysts, based on their stability in acidic and alkaline solutions. It is reasonable to believe that the application field of molybdenum boride will be further expanded, and at the same time, will show greater application prospect.

At present, the preparation method of molybdenum boride ceramic powder mainly comprises the following steps: direct reaction synthesis of boron powder and molybdenum powder, chemical vapor deposition, volumetric combustion synthesis, and carbon/boron thermal reduction. However, according to the reported preparation methods of the molybdenum boride powder, due to the fact that material reaction is not uniform and sufficient, the final product usually contains more impurity phases, the preparation process is immature, the particle size distribution is wide, the sintering activity and the density of the ceramic powder are greatly affected, and the high-temperature thermodynamic properties of the ceramic material and the component are finally weakened.

Therefore, it is highly desirable to develop a method for preparing a high-purity and ultra-fine molybdenum boride ceramic powder.

Disclosure of Invention

The invention aims to provide a method for preparing superfine ceramic powder by adopting a liquid-phase ceramic precursor, which can prepare molybdenum boride powder with smaller size, good morphological characteristics and higher purity under simple process conditions.

In order to achieve the above object, the present invention provides a method for preparing ultrafine ceramic powder from a liquid-phase ceramic precursor, comprising the steps of:

(1) co-dissolving a carbon source and a boron source in a solvent, adding a molybdenum source solution into the solvent, and stirring and mixing to prepare sol;

(2) Carrying out heat treatment on the sol in a reaction kettle to prepare gel, and carrying out constant-temperature heat treatment on the gel to prepare dry gel;

(3) and carrying out ball milling on the dried gel to obtain dried gel powder, and calcining the dried gel powder in a protective gas atmosphere to obtain the superfine ceramic powder.

Further, the carbon source is sorbitol, the boron source is boric acid, the molybdenum source is molybdenum pentachloride, the molar ratio of the boric acid to the molybdenum pentachloride is 2: 1-4: 1, and the mass ratio of the sorbitol to the molybdenum pentachloride is 1: 1.

Further, in the step (1), the method for co-dissolving is as follows: putting a carbon source and a molybdenum source in a solvent under the condition of constant-temperature water bath, and stirring and dissolving; wherein the temperature of the water bath is 30-90 ℃, and the stirring speed is 100-800 rpm.

Further, the dropping speed of the molybdenum source solution in the step (1) is 1-10 mL/min, and the stirring time after dropping is 0-120 min.

Further, the temperature of the heat treatment of the gel prepared in the step (2) is 80-150 ℃, the time of the heat treatment is 1-9 h, and the heating rate of the heat treatment is 4-6 ℃/min.

Further, the temperature of the constant-temperature heat treatment for preparing the xerogel in the step (2) is 120-180 ℃, and the time of the constant-temperature heat treatment is 6-24 h.

Further, the rotation speed of ball milling in the step (3) is 50-500 rpm, and the ball milling time is 30-120 min.

Further, the airflow speed of the protective gas in the step (3) is 0.005-50L/min, the calcining temperature is 1200-1800 ℃, and the calcining time is 10-240 min.

Further, the calcination temperature in the step (3) is 1300-1700 ℃.

Preferably, the solvents in the present invention are all acetic acid.

The invention also provides the superfine ceramic powder prepared by the method, wherein the superfine ceramic powder is MoB or MoB₂Or Mo₂B₅。

In summary, the invention has the following advantages:

1. according to the invention, boric acid, sorbitol, acetic acid and molybdenum pentachloride are used as raw materials to prepare sol, the sol is subjected to constant-temperature heat treatment at 120-180 ℃ to prepare gel, then the gel is prepared into dry gel powder, and the dry gel powder is calcined at 1200-1800 ℃ for 10-240 min, so that the molybdenum boride powder with high purity, fine particle size and good sintering performance can be prepared, and the method has the advantages of simple process, high production efficiency and low energy consumption, and is suitable for industrial production.

2. The invention adopts a liquid phase method to prepare ceramic powder, wherein the method comprises a sol-gel method to prepare a precursor, a solvothermal reaction kettle heat treatment method to complex molybdenum elements, a completely uniform Mo-B-C sol-gel network can be formed, the method comprises the adjustment of temperature and time in the process, the synthesis of different single phases can be controlled, and the method is simple. On one hand, the method does not need high-temperature and high-pressure experimental conditions, on the other hand, the components can be completely and uniformly complexed, and the ceramic powder with smaller particles can be prepared.

3. The preparation method provided by the invention is simple, the powder material with uniform chemical components can be directly obtained through various reactions in the solution, no obvious impurity peak exists in an XRD (X-ray diffraction) spectrum after calcination, the purity is higher, and secondary treatment is not needed. Can be used directly.

4. The preparation method of the invention can more easily prepare the powder material with small particle size and uniform distribution, the molybdenum boride powder has fine size, the particle size is 50 nm-300 nm, the shape is uniform, and the powder material has better micro-morphology.

5. The method provided by the invention has the advantages of simple preparation process, no need of special instruments and medicines, no need of any complicated processing steps, convenience, suitability for large-scale synthesis of the ultrahigh-temperature ceramic material by an economic method, and commercial and industrial potential.

Drawings

FIG. 1 is a schematic flow diagram of the present invention;

FIG. 2 is a scanning electron microscope picture and an X-ray diffraction pattern of the molybdenum boride powder prepared in example 1;

FIG. 3 is a scanning electron microscope picture and an X-ray diffraction pattern of the molybdenum boride powder prepared in example 2;

FIG. 4 is a scanning electron micrograph and an X-ray diffraction pattern of the molybdenum boride powder prepared in example 3.

Detailed Description

As shown in fig. 1, the present invention provides a method for preparing ultrafine ceramic powder using a liquid-phase ceramic precursor, comprising the steps of:

S1, mixing boric acid, sorbitol and acetic acid under the water bath condition of 30-90 ℃, and stirring at a stirring speed of 100-800 rpm to dissolve to obtain a mixed solution A;

s2, dissolving molybdenum pentachloride in acetic acid to obtain a mixed solution B, wherein the molar ratio of boric acid to molybdenum pentachloride is 2: 1-4: 1;

s3, adding the mixed solution B into the mixed solution A under the condition of constant-speed stirring, wherein the dropping speed is 1-10 mL/min, and continuously stirring for 0-120 min to obtain sol;

s4, putting the sol obtained in the step S3 into a solvothermal reaction kettle, and carrying out heat treatment at 80-150 ℃ for 1-9 h at a heating rate of 4-6 ℃ to obtain gel;

s5, putting the gel obtained in the step S4 into a drying oven, and carrying out constant-temperature heat treatment at 120-180 ℃ for 6-24 h to obtain dry gel;

and step S6, crushing and ball-milling the dried gel obtained in the step S5, wherein the rotation speed of the ball-milling is 50-500 rpm, and the ball-milling time is 30-120 min, so that the dried gel powder is obtained.

And step S7, placing the dry gel powder obtained in the step S6 into a tubular furnace, introducing protective gas into the tubular furnace, and calcining for 10-240 min at 1200-1800 ℃ to obtain uniform molybdenum boride powder.

Preferably, the protective gas is argon, and the gas flow speed is 0.005-50L/min.

The method is designed according to the principle of carbothermic reduction reaction, boric acid and sorbitol are respectively used as a boron source and a carbon source, molybdenum pentachloride is used as a molybdenum source, acetic acid is used as a solvent, and a molybdenum boride ceramic precursor is prepared by a sol-gel method. However, as molybdenum element is more difficult to form a sol-gel network with boric acid and sorbitol, the molybdenum element can be better complexed in by adopting a solvothermal reaction kettle heat treatment method to form a completely uniform Mo-B-C sol-gel network.

By analyzing the Mo-B binary phase diagram and the TGA/DSC curve of the molybdenum boride precursor, the fact that molybdenum oxide begins to react with boron oxide and carbon to generate MoB at the temperature of about 950 ℃ and the MoB is converted into Mo at the temperature of about 1400 DEG C₂B₅Therefore, the temperature range for preparing the single-phase MoB is set to be 1200-1400 ℃, the heat preservation time is selected to be 2 hours in order to ensure the full reaction, and experimental results show that the single-phase MoB can be prepared under the condition of heat preservation at 1350 ℃ for 2 hours.

By analyzing the phase diagram, it was found that MoB is only possible above 1600 ℃₂Thus I will produce single phase MoB ₂The temperature of (2) is selected to be about 1650 ℃, preferably 1650 ℃.

By analyzing the heat preservation time (4h, 2h and 1h), the longer the heat preservation time is, the longer the MoB is₂Will be transformed into Mo₂B₅. The invention will therefore further produce single phase MoB₂The calcination condition is selected to be 1650 ℃ and the temperature is kept for 0.5h, and the single-phase Mo is prepared₂B₅The calcining condition of (1) is selected to be 1650 ℃ and the temperature is kept for 1 h.

The principles and features of this invention are described below in conjunction with embodiments, which are included to explain the invention and not to limit the scope of the invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

Example 1

The embodiment provides a method for preparing superfine ceramic powder by adopting a liquid-phase ceramic precursor, which comprises the following steps:

step S1, 10mL of acetic acid was added to a mixture of 1.55g of boric acid and 2.5g of sorbitol in a water bath at 60 ℃ and the mixture was dissolved with stirring to obtain a mixed solution A1.

Step S2, dissolving 2.5g of molybdenum pentachloride in 5mL of acetic acid to obtain a mixed solution B1;

step S3, dropwise adding the mixed solution B1 into the mixed solution A1 at the speed of 1mL/min, and continuously stirring for 30min, thereby obtaining the sol.

And step S4, placing the sol obtained in the step S3 in a solvothermal reaction kettle, and heating to 120 ℃ at a heating rate of 5 ℃/min for heat treatment for 9h to obtain the gel.

And step S5, placing the gel obtained in the step S4 in an oven, and carrying out constant temperature heat treatment at 150 ℃ for 12h to obtain dry gel.

And step S6, performing ball milling on the dried gel obtained in the step S5 for 60min at the rotating speed of 200rpm by using a planetary ball mill, thereby obtaining the dried gel powder.

And step S7, placing the dry gel powder obtained in the step S6 in a tube furnace, introducing argon gas into the tube furnace as a protective gas, wherein the gas flow velocity of the argon gas is 2L/min, and calcining the powder for 120min at 1350 ℃ to obtain MoB powder.

Example 2

step S1, 10mL of acetic acid was added to a mixture of 1.55g of boric acid and 2.8g of sorbitol in a water bath at 60 ℃, and the mixture was dissolved with stirring to obtain a mixed solution A2.

Step S2, dissolving 2.8g of molybdenum pentachloride in 5mL of acetic acid to obtain a mixed solution B2;

step S3, add mixed solution B2 dropwise to mixed solution a2 at a rate of 5mL/min, and continue stirring for 30min, thereby obtaining a sol.

And S4, placing the sol obtained in the step S3 in a solvothermal reaction kettle, and heating to 120 ℃ at the heating rate of 5 ℃/min for heat treatment for 9h to obtain gel.

Step S7, placing the dry gel powder in the step S6 in a tube furnace, introducing argon gas into the tube furnace as protective gas, wherein the gas flow velocity of the argon gas is 2L/min, calcining at 1650 ℃ for 30min to obtain MoB₂And (3) powder.

Example 3

step S1, 10mL of acetic acid was added to a mixture of 1.55g of boric acid and 2.5g of sorbitol in a water bath at 60 ℃ and the mixture was dissolved with stirring to obtain a mixed solution A3.

Step S2, dissolving 2.5g of molybdenum pentachloride in 5mL of acetic acid to obtain a mixed solution B3;

step S3, dropwise adding the mixed solution B3 into the mixed solution A3 at the speed of 10mL/min, and continuously stirring for 30min, thereby obtaining the sol.

And S5, placing the gel obtained in the step S4 in an oven, and carrying out constant-temperature heat treatment at 150 ℃ for 12h to obtain dry gel.

Step S7, placing the dry gel powder obtained in the step S6 in a tube furnace, introducing argon gas serving as protective gas into the tube furnace, wherein the gas flow velocity of the argon gas is 2L/min, and calcining at 1650 ℃ for 60min to obtain Mo₂B₅And (3) powder.

Test example- -purity measurement and morphology observation

The purity of the molybdenum boride powder prepared in the embodiments 1 to 3 of the present invention was measured and the morphology was observed, so that the following results were obtained:

(1) fig. 2 is an SEM photograph and an XRD spectrum of the MoB powder prepared in example 1 of the present invention under different magnifications using a scanning electron microscope and an X-ray diffraction analyzer, respectively. Wherein, fig. 2a is an SEM photograph at a magnification of 20 k; FIG. 2b is an SEM photograph at a magnification of 30 k; FIG. 2c is an SEM photograph at a magnification of 40 k; FIG. 2d is an XRD pattern of MoB produced.

SEM of the MoB powder prepared in the embodiment 1 shows that the MoB powder obtained by calcination is granular in shape, fine in size, 50-100 nm in particle size, uniform in appearance and clear in boundary. XRD results show that the MoB powder prepared by the method for preparing the molybdenum boride ultrafine ceramic powder by using the liquid-phase ceramic precursor has higher purity.

(2) FIG. 3 shows the MoB prepared in example 2 of the present invention using a scanning electron microscope and an X-ray diffraction analyzer, respectively₂SEM pictures and XRD patterns of the powder are obtained under different magnifications. Wherein, FIG. 3a is an SEM photograph at a magnification of 30 k; FIG. 3b is a SEM photograph at a magnification of 40 k; FIG. 3c is an SEM photograph at a magnification of 60 k; FIG. 3d is the MoB produced₂XRD pattern of (a).

MoB prepared in example 2 of the invention₂SEM of the powder shows that MoB obtained by calcination₂The shape is granular, the size is fine, the grain diameter is 50-150 nm, and the appearance is uniform and the boundary is clear. XRD results show that the MoB prepared by the method for preparing the molybdenum boride ultrafine ceramic powder by using the liquid-phase ceramic precursor₂The purity of the powder is high.

(3) FIG. 4 is a scanning electron microscope and an X-ray diffraction analyzer respectively applied to Mo prepared in example 3 of the present invention₂B₅SEM pictures and XRD patterns of the powder are obtained under different magnifications. Wherein, FIG. 4a is an SEM photograph at a magnification of 20 k; FIG. 4b is a drawing at magnificationSEM photograph at 30 k; FIG. 4c is a SEM photograph at a magnification of 40 k; FIG. 4d shows Mo obtained₂B₅XRD pattern of (a).

Mo obtained in example 3 of the invention ₂B₅SEM of the powder shows that Mo is obtained by calcination₂B₅The shape is granular, the size is fine, the grain diameter is 50-300 nm, and the appearance is uniform and the boundary is clear. XRD results show that Mo prepared by the method for preparing molybdenum boride ultrafine ceramic powder from the liquid-phase ceramic precursor₂B₅The purity of the powder is high.

In conclusion, the high-purity superfine molybdenum boride powder can be prepared under the low-temperature atmosphere calcination condition by adjusting the preparation process of the liquid phase precursor. The preparation method provided by the embodiment of the invention has the advantages that the preparation process is simple, the complex reaction process is not involved, the preparation can be realized in a short period and at a low raw material price, the prepared molybdenum boride powder has the advantages of high purity, fine particle size, good micro-morphology and the like, and a technical basis is provided for the engineering and industrial preparation of high-performance ceramic materials. Can also provide technical basis and commercialization potential for large-scale synthesis of ultra-high temperature ceramic materials.

While the present invention has been described in particular detail, it should not be considered as limiting the scope of the invention. Various modifications and changes may be made by those skilled in the art without inventive work within the scope of the appended claims.

Claims

1. A method for preparing superfine ceramic powder by adopting a liquid-phase ceramic precursor is characterized by comprising the following steps:

(3) and (3) performing ball milling on the dried gel to obtain dried gel powder, and calcining the dried gel powder in a protective gas atmosphere to obtain superfine ceramic powder.

2. The method for preparing ultrafine ceramic powder from liquid-phase ceramic precursor according to claim 1, wherein the carbon source is sorbitol, the boron source is boric acid, the molybdenum source is molybdenum pentachloride, the molar ratio of boric acid to molybdenum pentachloride is 2:1 to 4:1, and the mass ratio of sorbitol to molybdenum pentachloride is 1: 1.

3. The method for preparing ultrafine ceramic powder using liquid-phase ceramic precursor according to claim 1, wherein in the step (1), the co-dissolving method is: putting a carbon source and a molybdenum source in a solvent under the condition of constant-temperature water bath, and stirring and dissolving; wherein the temperature of the water bath is 30-90 ℃, and the stirring speed is 100-800 rpm.

4. The method for preparing ultrafine ceramic powder using liquid-phase ceramic precursors according to claim 1, wherein the molybdenum source solution is added dropwise at a rate of 1 to 10mL/min in the step (1), and the stirring time after the addition is 0 to 120 min.

5. The method for preparing ultrafine ceramic powder using liquid-phase ceramic precursors according to claim 1, wherein the temperature of the heat treatment for preparing the gel in the step (2) is 80 to 150 ℃, the time of the heat treatment is 1 to 9 hours, and the temperature rise rate of the heat treatment is 4 to 6 ℃/min.

6. The method for preparing ultrafine ceramic powder using liquid-phase ceramic precursor according to claim 1, wherein the temperature of the constant-temperature heat treatment for preparing xerogel in step (2) is 120 to 180 ℃ and the time of the constant-temperature heat treatment is 6 to 24 hours.

7. The method for preparing ultrafine ceramic powder from liquid-phase ceramic precursors according to claim 1, wherein the ball milling in step (3) is performed at a rotation speed of 50-500 rpm for 30-120 min.

8. The method for preparing ultrafine ceramic powder using a liquid-phase ceramic precursor according to claim 1, wherein the gas flow rate of the protective gas in the step (3) is 0.005 to 50L/min, the calcination temperature is 1200 to 1800 ℃, and the calcination time is 10 to 240 min.

9. The method for preparing ultrafine ceramic powder using a liquid-phase ceramic precursor according to claim 1 or 8, wherein the calcination temperature in the step (3) is 1300-1700 ℃.

10. The ultrafine ceramic powder prepared by the method according to any one of claims 1 to 9, wherein the ultrafine ceramic powder is MoB or MoB₂Or Mo₂B₅。