A low-cost method for preparing a multi-element transition metal monoboride powder

Abstract

The application discloses a low-cost preparation method of multi-element transition metal monoboride powder and belongs to the technical field of ceramic materials. x The method comprises the following steps: taking micron MoO3, WO3, Cr2O3, MO 0.25 W 0.25 Cr 0.25 M 0.25 , B4C and C as raw materials, mixing, drying and sieving the raw material powder, and then performing heat treatment on the raw material powder by using pressureless sintering to obtain the required monoboride powder. The transition metal oxides MoO3, WO3, Cr2O3, Ta2O5, B4C and C powder are mixed by wet milling through swing ball milling, the uniformly mixed raw materials are sufficiently dried in a rotary evaporator, and finally, the uniformly mixed raw materials are heat treated to realize the preparation of high-entropy ceramic powder. By adjusting the process parameters, the high-entropy ceramic powder with a single-phase structure is obtained. The high-entropy ceramic powder of monoboride is successfully synthesized for the first time. Through multiple technical characterizations, the synthesized (Mo 0.25 W 0.25 Cr 0.25 M 0.25 )B high-entropy ceramic powder has good particle dispersity and micro-morphology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic materials, and particularly relates to a low-cost preparation method of a multi-element transition metal monoboride powder. BACKGROUND

[0002] High-entropy borides often exhibit high melting points, excellent mechanical properties, high thermal stability and other properties due to their unique crystal structure and valence bond type. High-entropy diborides are considered as candidate materials for super-high-speed aircraft thermal protection components, metal smelting crucibles and bulletproof armor. Boron hot-carbon hot reduction is a conventional way to prepare diborides, and is still a very mature process. Both single-phase diborides and high-entropy diborides can obtain high-purity products by this method. Gild et al. also successfully prepared high-entropy diborides (Hf 0.2 Zr 0.2 Ti 0.2 Ta 0.2 Nb 0.2 )B2, (Hf 0.2 Zr 0.20.2 Ti 0.2 Ta 0.2 Mo 0.2 )B2 and (Hf 0.2 Zr 0.2 Ti 0.2 Ta 0.2 Cr 0.2 )B2. (Ceramics International, 46 (2020), 6906-6913).

[0003] Due to the unique crystal structure and valence bond type of transition metal monoborides, they have high hardness, high melting point, wear resistance, good electrical conductivity, electromagnetic shielding performance and excellent electrochemical performance, and have important applications in tool coating, aerospace and other fields. In 2016, Michael et al. used Ta with a large atomic radius to replace W atoms in WB to prepare a monoboride solid solution (W 0.5 Ta 0.5 )B, which strengthens the double metal layer crystal face, i.e. (020) crystal face, and the twisted covalent bond (B-B bond) hinders the deformation of (002) and (200) crystal faces, and finally successfully obtains a super-hard monoboride material. In terms of diboride materials, high-entropy can increase the hardness of the material to some extent. Zhao et al. prepared monoboride powder from metal and boron powder, and successfully prepared high-entropy monoboride (Mo 0.2 Ta 0.2 Ni 0.2 Cr 0.2 W0.2 )B, the obtained material has a Vickers hardness of 48.5±4.1 Gpa, which further indicates that high-entropy monoboride materials will be an important research direction of superhard materials. (Ceramics International, 46 (2020), 26626-26631).

[0004] According to the monoboride ceramics reported so far, the synthesis method is only through the reaction of metal powder and boron powder. Since monoboride can react with other boron sources such as boron powder and boron carbide powder, it is inevitable to have diboride impurities in the preparation of monoboride by oxide boron-thermal carbothermal reduction. Therefore, the method of synthesizing monoboride by this method has not been reported. The method of reacting metal powder with boron powder also has some defects, such as high reaction temperature, expensive boron powder, and purity problem to be solved, and the metal powder has a certain ductility and is easy to stretch during ball milling. In addition, the metal powder may be oxidized during ball milling.

[0005] Therefore, in order to avoid the problems existing in the existing synthesis method, and to find a low-temperature, simple, and lower-cost preparation technology of monoboride high-entropy ceramic powder is an urgent problem to be solved. SUMMARY

[0006] In view of the deficiencies in the prior art, the purpose of the present application is to provide a low-cost preparation method of micron-sized, high-purity multi-element transition metal monoboride powder.

[0007] To achieve the above purpose, the technical scheme is as follows:

[0008] A low-cost preparation method of multi-element transition metal monoboride powder, comprising: using micron-sized MoO3, WO3, Cr2O3, MOx, B4C and C as raw materials, and the powder is proportioned according to the following chemical equation:

[0009] 0.25MoO3+0.25WO3+0.125Cr2O3+0.25MOx+0.25B4C+aC=(Mo 0.25 W 0.25 Cr 0.25 M 0.25 )B+bCO; wherein parameters a and b are the metering coefficients of C and CO corresponding to different oxides; the raw material powder is mixed, dried, sieved and then heat treated by pressureless sintering to obtain the required monoboride powder.

[0010] The obtained monoboride powder is of orthorhombic structure, and needs to be heat treated for several times to be successfully prepared.

[0011] Preferably, MO xThe middle element M is any one of Ta, Nb, V and Ti.

[0012] Preferably, the parameter a ranges from 2.125 to 2.5, and the parameter b ranges from 2.375 to 2.5.

[0013] Preferably, the specific steps of mixing, drying and sieving of the raw material powder are as follows:

[0014] Taking micron-grade MoO3, WO3, Cr2O3, MOx, B4C and C as raw materials, various raw material powders are weighed according to the designed reaction equation ratio, and are mixed with zirconia balls as the mixing medium, and the obtained slurry is dried by rotary evaporation, and the mixed uniform powder is obtained after crushing and sieving.

[0015] Preferably, the particle size of the various raw material powders is less than 3 microns, and the purity is 99%.

[0016] Preferably, the specific steps of heat treatment of the pressureless sintering are as follows:

[0017] First heat treatment: the sieved powder is pressed into a tablet, and then is placed in a graphite crucible padded with graphite paper, and is subjected to vacuum heat treatment in a graphite carbon tube furnace to obtain a block;

[0018] Second heat treatment: the obtained block is crushed and sieved, and is re-pressed into a tablet, and then is placed in a graphite crucible padded with graphite paper, and is subjected to vacuum heat treatment in a graphite carbon tube furnace again, and the heat treatment temperature is not higher than the first heat treatment temperature.

[0019] Compared with directly synthesizing a boride powder according to the metering ratio, the multiple vacuum heat treatment method used herein gradually improves the purity of the powder.

[0020] Preferably, the powder is pressed into a tablet under a pressure of 3-20 MPa.

[0021] Preferably, the temperature range of the vacuum heat treatment is 1250-1750℃.

[0022] Preferably, the holding time range of the vacuum heat treatment is 30-90 min.

[0023] Preferably, the temperature rising speed range of the vacuum heat treatment is 5-20℃ / min.

[0024] The technical solution provided by the present application has the following advantages and beneficial effects:

[0025] Currently monoboride synthesis can only rely on the reaction of metal powder and boron powder synthesis, but this method still has a series of problems: 1) the price of boron powder is expensive, and the reaction requires high purity of boron powder. 2) the metal powder has a certain ductility, which is easy to stretch in the ball milling process, and the metal powder also has the possibility of oxidation in the ball milling process. To this end, the method of the application is prepared by boron hot-carbon hot reduction reaction to obtain micron-sized, high-purity monoboride powder, which has low raw material cost, is convenient and easy to obtain, and has simple preparation process. The synthesis of monoboride powder can be realized at 1250-1750 DEG C.

[0026] The application provides a (Mo 0.25 W 0.25 Cr 0.25 M 0.25 )B high-entropy ceramic powder material, first, transition metal oxides M O3, WO3, Cr2O3, Ta2O5, B4C and C powder are mixed by swing ball milling, then the mixed raw materials are fully dried in a rotary evaporator, and finally the mixed raw materials are heat-treated to prepare the high-entropy ceramic powder, and the high-entropy ceramic powder with a single-phase structure is obtained by adjusting process parameters. The method successfully synthesizes the high-entropy ceramic powder of monoboride for the first time, and the synthesized (Mo 0.25 W 0.25 Cr 0.25 M 0.25 )B high-entropy ceramic powder has good particle dispersity and micro-morphology. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The SEM diagram of the (Mo 0.25 W 0.25 Cr 0.25 Ta 0.25 )B powder obtained in embodiment 1;

[0028] Figure 2 The element distribution diagram of the (Mo 0.25 W 0.25 Cr 0.25 Ta 0.25 )B powder obtained in embodiment 1;

[0029] Figure 3 The XRD diagram of the (Mo 0.25 W 0.25 Cr 0.25 Ta 0.25 )B powder obtained in embodiment 1;

[0030] Figure 4 The (Mo 0.25 W 0.25 Cr 0.25 Ta0.25 XRD pattern of the (Mo, W, Cr, Ta)B powder;

[0031] Figure 5 (Mo, W, Cr, Ta)B powder obtained from Example 1 0.25 W 0.25 Cr 0.25 Ta 0.25 XRD pattern of the (Mo, W, Cr, Ta)B powder. DETAILED DESCRIPTION

[0032] In order for those skilled in the art to better understand the technical solutions of the present application, the preferred embodiments of the present application are described below in combination with specific examples, but it should not be understood as a limitation on the present application, but only as an example.

[0033] The test methods or test methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are all obtained from conventional commercial channels or prepared by conventional methods unless otherwise specified.

[0034] Example 1

[0035] Step 1: Weigh 3.44 g of commercially available MoO3 powder, 5.55 g of WO3 powder, 1.82 g of Cr2O3 powder, 5.29 g of Ta2O5 powder, 1.32 g of B4C powder, and 2.59 g of C powder, respectively, and add the weighed powders (a total of 20 g), 50 g of anhydrous ethanol and 40 g of yttrium stabilized zirconia balls (the mass ratio of the material balls is about 1:2) into a ball mill pot for ball milling and mixing for 12 h. Then, the mixed slurry is dried at 60°C by rotary evaporation for 1 h and passed through a 200 mesh sieve to obtain a uniform and dry mixed powder.

[0036] Step 2: The above mixed powder is dry pressed (molding pressure 3-20 MPa, pressure holding time 1 min) to obtain a mixed powder block, which is then placed in a graphite crucible lined with graphite paper and subjected to vacuum heat treatment in a graphite carbon tube furnace. The heat treatment temperature is 1250-1750°C, the holding time is 30-90 min, and the heating rate is 5-20°C / min. The obtained block is crushed, sieved, and still pressed at a pressure of 3-20 MPa, and then placed in a graphite crucible lined with graphite paper and subjected to heat treatment again in a graphite carbon tube furnace, and the heat treatment temperature is not higher than the first heat treatment temperature.

[0037] The SEM, element distribution map and XRD pattern of the (Mo, W, Cr, Ta)B powder prepared by the above steps are shown in Figures 1-3 , wherein the purity of monoboride can reach more than 95%.

[0038] Example 2

[0039] Step 1: Weigh 3.43 g of MoO3 powder, 5.52 g of WO3 powder, 1.90 g of Cr2O3 powder, 5.26 g of Ta2O5 powder, 1.32 g of B4C powder, and 2.57 g of C powder, respectively. Then, put the weighed powders (20 g in total), 50 g of anhydrous ethanol, and 40 g of yttrium-stabilized zirconia balls (mass ratio of material to ball is about 1:2) into a ball mill jar and mix for 12 h. Then, dry the mixed slurry by rotary evaporation at 60°C for 1 h and pass it through a 200-mesh sieve to obtain a uniform and dry mixed powder.

[0040] Step 2: Dry-press the mixed powder (molding pressure: 3-20 MPa, holding time: 1 min) to obtain a mixed powder body, and then place it in a graphite crucible lined with graphite paper and perform vacuum heat treatment in a graphite carbon tube furnace. The heat treatment temperature is 1250-1750°C, the holding time is 30-90 min, and the heating rate is 5-20°C / min.

[0041] The XRD pattern of the (Mo, W, Cr, Ta)B powder prepared by the above steps is shown in FIG. 1, wherein the purity of monoboride can reach more than 95%. Figure 4

[0042] Example 3

[0043] Step 1: Weigh 3.57 g of MoO3 powder, 5.74 g of WO3 powder, 1.88 g of Cr2O3 powder, 5.47 g of Ta2O5 powder, 1.72 g of B4C powder, and 1.61 g of C powder, respectively. Then, put the weighed powders (20 g in total), 50 g of anhydrous ethanol, and 40 g of yttrium-stabilized zirconia balls (mass ratio of material to ball is about 1:2) into a ball mill jar and mix for 12 h. Then, dry the mixed slurry by rotary evaporation at 60°C for 1 h and pass it through a 200-mesh sieve to obtain a uniform and dry mixed powder.

[0044] Step 2: Dry-press the mixed powder (molding pressure: 3-20 MPa, holding time: 1 min) to obtain a mixed powder body, and then place it in a graphite crucible lined with graphite paper and perform vacuum heat treatment in a graphite carbon tube furnace. The heat treatment temperature is 1250-1750°C, the holding time is 30-90 min, and the heating rate is 5-20°C / min.

[0045] The XRD pattern of the (Mo, W, Cr, Ta)B powder prepared by the above steps is shown in FIG. 1, wherein the purity of monoboride can reach more than 95%. Figure 5

[0046] Example 4

[0047] ​​Step 1: Weigh MoO3 powder 3.85 g, WO3 powder 6.20 g, Cr2O3 powder 2.03 g, Nb2O5 powder 3.55 g, B4C powder 1.48 g, and C powder 2.89 g, respectively, and mix the weighed powders (20 g in total), 50 g of anhydrous ethanol, and 40 g of yttrium-stabilized zirconia balls (mass ratio of material to ball is about 1:2) in a ball mill for 12 h. Then, the mixed slurry is dried at 60°C for 1 h by rotary evaporation and passed through a 200-mesh sieve to obtain a uniform and dry mixed powder.

[0048] Step 2: The mixed powder is dry-pressed (molding pressure 3-20 MPa, holding time 1 min) to obtain a mixed powder body, which is then placed in a graphite crucible lined with graphite paper and subjected to vacuum heat treatment in a graphite carbon tube furnace. The heat treatment temperature is 1250-1750°C, the holding time is 30-90 min, and the heating rate is 5-20°C / min.

[0049] The powder prepared by the above steps is confirmed by XRD test to be (Mo, W, Cr, Nb)B.

[0050] Example 5

[0051] Step 1: Weigh MoO3 powder 4.11 g, WO3 powder 7.11 g, Cr2O3 powder 2.33 g, V2O5 powder 1.14 g, B4C powder 1.69 g, and C powder 3.31 g, respectively, and mix the weighed powders (20 g in total), 50 g of anhydrous ethanol, and 40 g of yttrium-stabilized zirconia balls (mass ratio of material to ball is about 1:2) in a ball mill for 12 h. Then, the mixed slurry is dried at 60°C for 1 h by rotary evaporation and passed through a 200-mesh sieve to obtain a uniform and dry mixed powder.

[0052] Step 2: The mixed powder is dry-pressed (molding pressure 3-20 MPa, holding time 1 min) to obtain a mixed powder body, which is then placed in a graphite crucible lined with graphite paper and subjected to vacuum heat treatment in a graphite carbon tube furnace. The heat treatment temperature is 1250-1750°C, the holding time is 30-90 min, and the heating rate is 5-20°C / min.

[0053] The powder prepared by the above steps is confirmed by XRD test to be (Mo, W, Cr, V)B.

[0054] Example 6

[0055] Step 1: Weigh MoO3 powder 4.21 g, WO3 powder 6.78 g, Cr2O3 powder 2.22 g, TiO2 powder 2.18 g, B4C powder 1.62 g, and C powder 2.99 g, respectively, and mix them together in a ball mill for 12 h. Then, the mixed slurry is dried at 60 °C for 1 h by rotary evaporation and sieved through a 200 mesh screen to obtain a uniform and dry mixed powder.

[0056] Step 2: The mixed powder is dry-pressed (molding pressure 3-20 MPa, holding time 1 min) to obtain a mixed powder body, which is then placed in a graphite crucible lined with graphite paper and subjected to vacuum heat treatment in a graphite carbon tube furnace. The heat treatment temperature is 1250-1750 °C, the holding time is 30-90 min, and the heating rate is 5-20 °C / min.

[0057] The powder prepared by the above steps is confirmed to be (Mo, W, Cr, Ti)B by XRD test.

[0058] Example 7

[0059] Step 1: Weigh MoO3 powder 2.85 g, WO3 powder 4.59 g, Cr2O3 powder 1.51 g, Ta2O5 powder 4.38 g, Nb2O5 powder 2.63 g, B4C powder 1.62 g, and C powder 2.99 g, respectively, and mix them together in a ball mill for 12 h. Then, the mixed slurry is dried at 60 °C for 1 h by rotary evaporation and sieved through a 200 mesh screen to obtain a uniform and dry mixed powder.

[0060] Step 2: The mixed powder is dry-pressed (molding pressure 3-20 MPa, holding time 1 min) to obtain a mixed powder body, which is then placed in a graphite crucible lined with graphite paper and subjected to vacuum heat treatment in a graphite carbon tube furnace. The heat treatment temperature is 1250-1750 °C, the holding time is 30-90 min, and the heating rate is 5-20 °C / min.

[0061] The powder prepared by the above steps is confirmed to be (Mo, W, Cr, Ta, Nb)B by XRD test.

[0062] The above merely describes the preferred embodiments of the present application, and it should be pointed out that the above preferred embodiments should not be regarded as a limitation to the present application, and the protection scope of the present application should be defined by the scope of the claims. For those skilled in the art, several improvements and refinements can be made without departing from the spirit and scope of the present application, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A low-cost preparation method of multinary transition metal boride powder, characterized in that: include: Using micron-grade MoO3, WO3, Cr2O3, MO x , B4C and C as raw materials, the powder ratio is made according to the following chemical formula: 0.25MoO3+0.25WO3+0.125Cr2O3+0.25MO x +0.25B4C+aC=(Mo 0.25 W 0.25 Cr 0.25 M 0.25 )B+bCO; wherein parameters a and b are the stoichiometric coefficients of C and CO corresponding to different oxides, respectively; the raw material powders are mixed, dried, sieved, and then heat-treated by pressureless sintering to obtain the desired monoboride powder; the value range of parameter a is 2.125-2.5, and the value range of parameter b is 2.375-2.5; MO x The element M is any one of Ta, Nb, V, and Ti; The specific steps of heat treatment for pressureless sintering are: Primary heat treatment: The sieved powder is pressed into tablets, then placed in a graphite crucible lined with graphite paper, and subjected to vacuum heat treatment in a graphite carbon tube furnace to obtain a block; Secondary heat treatment: The obtained block is crushed, sieved, and re-tabletted, and then placed in a graphite crucible padded with graphite paper, and vacuum heat treated again in a graphite carbon tube furnace. The heat treatment temperature is not higher than the first heat treatment temperature.

2. The low-cost preparation method of multinary transition metal monoboride powder according to claim 1, characterized in that: The specific steps of mixing, drying and sieving the raw material powder are as follows: Micron-sized MoO3, WO3, Cr2O3, MO x , B4C and C are used as raw materials, and various raw material powders are weighed and mixed according to the ratio of the designed reaction equation. Anhydrous ethanol is used as the solvent and zirconia balls are used as the mixing medium. The slurry obtained after mixing is dried by rotary evaporation and crushed and sieved to obtain a uniformly mixed powder.

3. The low-cost preparation method of multinary transition metal monoboride powder according to claim 2, characterized in that: The particle size of various raw material powders is less than 3 μm and the purity is 99%.

4. The low-cost preparation method of multinary transition metal monoboride powder according to claim 1, characterized in that: The powder is compressed into tablets at a pressure of 3-20 MPa.

5. The low-cost preparation method of multinary transition metal monoboride powder according to claim 1, characterized in that: The temperature range of vacuum heat treatment is 1250-1750 ℃.

6. The low-cost preparation method of multinary transition metal monoboride powder according to claim 1, characterized in that: The holding time of vacuum heat treatment ranges from 30 to 90 min.

7. The low-cost preparation method of multinary transition metal monoboride powder according to claim 1, characterized in that: The heating rate of vacuum heat treatment ranges from 5 to 20 °C / min.

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