CN112079642B - Boron carbide spray granulation powder and preparation method and application thereof - Google Patents

Boron carbide spray granulation powder and preparation method and application thereof Download PDF

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CN112079642B
CN112079642B CN202010827972.3A CN202010827972A CN112079642B CN 112079642 B CN112079642 B CN 112079642B CN 202010827972 A CN202010827972 A CN 202010827972A CN 112079642 B CN112079642 B CN 112079642B
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boron carbide
spray granulation
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王宏
孙宏伟
郭方慧
孟庆海
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Shenyang Titanium Equipment Manufacturing Co ltd
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Abstract

The invention relates to the field of ceramic material processing, in particular to boron carbide spray granulation powder and a preparation method and application thereof. The preparation method of the boron carbide spray granulation powder comprises the step of pre-grinding the powder, wherein the powder comprises boron carbide powder and a toughening phase; the toughening phase is selected from Al 2 O 3 、Y 2 O 3 One or more of cerium oxide; the mass ratio of the boron carbide powder to the toughening phase is (90-95): 3 to 10. According to the invention, the boron carbide spray granulation powder with higher solid content, less ash and higher solid sphericity rate is prepared by adjusting the slurry entering the tower and controlling the technological parameters of spray granulation; the boron carbide anisotropic protective ceramic prepared by the boron carbide spray granulation powder has good compactness.

Description

Boron carbide spray granulation powder and preparation method and application thereof
Technical Field
The invention relates to the field of ceramic material processing, in particular to boron carbide spray granulation powder and a preparation method and application thereof.
Background
The boron carbide is widely applied to individual protection and armor equipment by virtue of excellent performances such as high hardness, low density, acid and alkali resistance and the like, and meanwhile, the addition of various intermediate toughening phases further improves the processing performance of the boron carbide, so that the boron carbide composite material can be applied to the military industry. However, the flowability of the boron carbide powder is poor, which brings great challenges to subsequent processes; for example, the stress distribution during compression molding can be deviated due to uneven distribution in the material distribution process, and then the defects of longitudinal cracks, poor edge molding and the like which are difficult to reverse are generated. Therefore, the process of spray granulation becomes an essential process in the preparation process of the ceramic material (especially the special-shaped protective ceramic), the mixing degree of the powder main body and the additive phase obtained after spray granulation is better, and the fluidity is better, thereby providing a prerequisite for preparing the high-quality ceramic material subsequently.
In the prior art, the boron carbide spray granulation powder has low solid content, high ash content and low solid sphere rate, and the three indexes are key factors influencing the subsequent sintering process and are directly related to the quality of a ceramic product. Therefore, how to prepare the boron carbide powder with ultrahigh solid content, low ash content and high solid sphericity is a technical problem to be solved urgently by the technical personnel in the field.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides boron carbide spray granulation powder and a preparation method and application thereof.
As a first object of the present invention, there is provided a method for preparing boron carbide spray granulated powder; the boron carbide spray granulation powder prepared by the preparation method has high solid content, low ash content and high solid sphere rate.
Specifically, the preparation method comprises the step of pre-grinding powder, wherein the powder comprises boron carbide powder and a toughening phase; the toughening phase is selected from Al 2 O 3 、Y 2 O 3 One or more of cerium oxide;
the mass ratio of the boron carbide powder to the toughening phase is 90-95: 3 to 10.
The invention has the advantages that the quality of the boron carbide spray granulation powder is directly influenced, and the invention has an unexpected discovery in the research and development process that the powder consisting of the boron carbide powder and the toughening phase is beneficial to improving the solid content and the solid sphere rate of the boron carbide spray granulation powder and reducing the ash content of the boron carbide spray granulation powder.
Preferably, the powder material comprises the following components in percentage by mass:
92-95% of boron carbide powder
Al 2 O 3 Or Y 2 O 3 1～4％
2-4% of cerium oxide;
the boron carbide powder and the D50 of the toughening phase are both 0.1-1 μm (particularly preferably 0.5 μm D50).
The invention further researches and discovers that when the powder consists of the components in percentage by mass, the boron carbide spray granulation powder with high quality can be prepared more favorably.
Preferably, the preparation method further comprises the step of preparing an initial slurry: adding pure water into the pre-ground powder to obtain initial slurry;
the solid content of the initial slurry is 65-70%, and the viscosity is less than 6500 cps.
The invention discovers that the types and the quantity of hydrophilic and hydrophobic functional groups on the surfaces of different powder bodies are different, so that the types and the quantity of the added toughening phases directly influence the viscosity of the initial slurry; the proportion can ensure the viscosity of the initial slurry to the maximum extent, and is ready for the subsequent slurry mixing step.
Preferably, the preparation method further comprises the step of size mixing: adding a water reducing agent, a binder and a lubricant into the initial slurry in sequence to obtain slurry;
wherein the water reducing agent is polyvinyl carboxylic acid; the binder is polyacrylic acid aqueous solution resin and/or PVA; the lubricant is glycerol and/or TAF;
based on the solid content of the initial slurry, the addition amount of the water reducing agent is 0.01-0.03%, the addition amount of the binder is 0.03-0.08%, and the addition amount of the lubricant is 0.01-0.03%.
In the prior art, sodium salt water reducing agents or water reducing agents for adjusting the number of acid-base functional groups are usually adopted, but the water reducing agents can show a good water reducing effect only under the condition of high using amount, and salt impurities are easily introduced. The invention discovers that the polyethylene carboxylic acid is used as the water reducing agent, and the obvious water reducing effect can be shown under the condition of less using amount, so that the solid content is effectively improved. Meanwhile, the invention also discovers that the improver which is jointly composed of the polyvinyl carboxylic acid and the polyacrylic acid aqueous solution resin and/or the PVA, the glycerol and/or the TAF can not only strengthen the strength of the green body, but also improve the sintering density, reduce the ash content and ensure the cleanness of the product.
Preferably, the PVA is a mixture of an aqueous PVA and a wax PVA;
wherein the mass ratio of the water-based PVA to the wax-based PVA is 0.5: 1 to 1.4.
In the present invention, a PVA composed of an aqueous PVA and a wax PVA is more preferably used in the slurry system of the present invention.
Furthermore, the coating-4 cup index of the slurry is 20-40 s.
Preferably, the preparation method further comprises the step of spray granulation; the spray granulation is carried out in a spray granulation tower;
the parameters of the spray granulation tower are as follows: the inlet temperature is 240-300 ℃, the feed rate of the peristaltic pump is 30-90 g/min, the outlet temperature is 80-120 ℃, the speed of the atomizer is 3000-5000 r/min, and the tower is kept at negative pressure.
In the invention, the parameters are adopted for spray granulation, and the obtained boron carbide spray granulation powder has higher solid content, lower ash content and higher solid sphere rate; the boron carbide spray granulation powder greatly improves the density of a boron carbide sintered body and the distribution degree of a bonding two-phase, and obviously improves the strength of a cold-press molded green body compared with the common spray granulation.
In order to prevent the problem of low yield caused by the adhesion of slurry and the inner liner of the spray granulation tower in the spray granulation process, the inner liner of the spray granulation tower is coated with an anti-adhesion layer in advance; specifically, before the spray granulation, an anti-sticking layer is coated on the inner liner of the spray granulation tower in advance;
the coating is as follows: dissociating water system PVA at 90-120 ℃ for 1-2 h to obtain a colloidal solution with the concentration of 25-40%; coating the inner lining of the spray granulation tower with the colloidal solution.
As a better technical scheme of the invention, the preparation method comprises the following steps:
1) pre-grinding powder: mixing boron carbide powder and a toughening phase, and then ball-milling for 12-20 h;
the medium of ball milling is zirconia with the size of 8mm and zirconia with the size of 10mm, and the mass ratio of zirconia to zirconia is 1-3: 1 proportion of mixed grinding balls;
2) preparing initial slurry: adding pure water into the pre-ground powder to obtain initial slurry;
the solid content of the initial slurry is 65-70%, and the viscosity is less than 6500 cps;
3) preparing slurry: adding a water reducing agent into the initial slurry at a stirring speed of 30-60 r/min; after the water reducing agent is added, stirring for 20-40 min at a speed of 10-50 r/min; keeping the stirring speed unchanged, and sequentially adding a binder and lubricating oil to obtain slurry;
performing a coating-4 cup test on the slurry, and if the reading number of the coating-4 cup is more than 40s, continuously adding pure water into the system until the reading number of the coating-4 cup is 20-40 s;
4) coating an anti-sticking layer of a spray granulation tower: dissociating water system PVA at 90-120 ℃ for 1-2 h to obtain a colloidal solution with the concentration of 25-40%; coating the lining of the spray granulation tower with the colloidal solution, and standing for 60-120 min;
5) spray granulation: the inlet temperature of the spray granulation tower is 240-300 ℃, the feeding rate of the peristaltic pump is 30-90 g/min, the outlet temperature is 80-120 ℃, the speed of the atomizer is 3000-5000 r/min, and negative pressure is kept in the tower.
Thus, the boron carbide spray granulation powder with ultrahigh solid content (55-65%), low sintering ash content (the content in air is less than 0.5%) and high solid sphere rate (70-85%) is prepared by adjusting and improving the slurry and spray granulation parameters.
The second object of the present invention is to provide a boron carbide spray granulated powder produced by the above method.
Preferably, the water content of the boron carbide spray granulation powder is 3-5%.
As a third object of the present invention, there is provided the use of the above-mentioned preparation method or the above-mentioned boron carbide spray granulated powder for preparing ceramics; preferably in the preparation of anisotropic protective ceramics; more preferably in the preparation of boron carbide anisotropic protective ceramics.
In cold press molding of the boron carbide anisotropic protective ceramic prepared by the boron carbide spray granulation powder, the main body and edge strength of a green body are improved, and demolding is easy; moreover, a large amount of solid powder ensures smooth sintering exhaust, shortens the sintering process, ensures that the density of a finished product after hot-pressing sintering at the temperature of below 2000 ℃ can reach 98-99 percent, reduces the sintering temperature and reduces the probability of abnormal growth of crystal grains.
The invention has the beneficial effects that:
(1) according to the invention, the boron carbide spray granulation powder with higher solid content, less ash content and higher solid sphere rate is prepared by adjusting the slurry entering the tower and controlling the technological parameters of spray granulation; the boron carbide anisotropic protective ceramic prepared by the boron carbide spray granulation powder has good compactness.
(2) The polyvinyl carboxylic acid water reducing agent in the slurry can enable the slurry to obtain ideal fluidity by adding a small amount of the polyvinyl carboxylic acid water reducing agent, and the polyacrylic acid aqueous solution resin and/or PVA supplement each other, so that the time and the efficiency of glue discharging are shortened on the basis of reducing the influence on the fluidity of the slurry as far as possible, and a sintered body finally presents a more rational cross section state.
Drawings
FIG. 1 is an SEM image of a boron carbide spray granulated powder obtained in example 1 of the present invention;
FIG. 2 is an SEM image of a boron carbide spray granulated powder obtained in example 1 of the present invention;
FIG. 3 is an SEM image of a boron carbide spray granulated powder obtained in example 1 of the present invention;
FIG. 4 is an SEM image of a boron carbide spray granulated powder obtained in example 1 of the present invention;
FIG. 5 is an SEM image of boron carbide spray granulated powder obtained in example 1 of the present invention.
Detailed Description
The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.
Example 1
The embodiment provides a boron carbide spray granulation powder, and a preparation method of the boron carbide spray granulation powder comprises the following steps:
1) pre-grinding powder: mixing boron carbide powder (D50 is 0.5 mu m) and toughening phase (D50 is 0.5 mu m), placing the mixture into a horizontal roller ball mill, and performing ball milling on zirconia with the medium of 8mm and zirconia with the medium of 10mm according to the proportion of 2: 1, mixing grinding balls according to a proportion, and performing ball milling for 16 hours;
the powder comprises the following components in percentage by mass: boron carbide powder 95% and Al 2 O 3 1% and 4% of cerium oxide;
2) preparing initial slurry: adding pure water into the pre-ground powder, and mechanically stirring for 30min to obtain initial slurry;
the solid content of the initial slurry is 70%, and the viscosity is less than 5700 cps;
3) preparing slurry: adding polyvinyl carboxylic acid (the addition amount is 0.03 percent of the solid content) into the initial slurry for a plurality of times in a small amount at a stirring speed of 60 r/min; after the addition of the polyvinyl carboxylic acid is finished, stirring at 10r/min for 20min and uniformly mixing; keeping the stirring speed unchanged, and sequentially adding polyacrylic acid aqueous solution resin (the addition amount is 0.05 percent of the solid content) and glycerol (0.01 percent) to obtain slurry;
performing a coating-4 cup test on the slurry, wherein the number of coated-4 cups is 65 s; continuously adding 5% pure water into the system, and coating 4 cups for 40 s;
4) coating an anti-sticking layer of a spray granulation tower: taking water system PVA to be dissociated for 1h at 120 ℃ to obtain a colloidal solution with the concentration of 40%; coating the lining of the spray granulation tower with the colloidal solution, standing for 120min, and waiting for granulation;
5) spray granulation: the inlet temperature of the spray granulation tower is 240 ℃, the feeding rate of a peristaltic pump is 90g/min, the outlet temperature is 100 ℃, the speed of an atomizer is 4500r/min, and negative pressure is kept in the tower;
6) standing and aging: sealing and standing for 12h, and performing subsequent cold pressing.
The boron carbide spray granulation powder obtained in the embodiment has the water content of 5% and the particle size of 50-120 μm.
After the boron carbide spray granulation powder is sintered, the ash content is 0.22%, the solid sphere rate is 80%, the solid content can reach 65%, and the density of a sintered product is 98.7%, so that a stable glass phase is formed.
SEM images of the boron carbide spray granulated powder of the present example are shown in fig. 1, 2, 3, 4, and 5.
Example 2
The embodiment provides boron carbide spray granulation powder, and the preparation method of the boron carbide spray granulation powder comprises the following steps:
1) pre-grinding powder: mixing boron carbide powder (D50 is 0.5 mu m) and toughening phase (D50 is 0.5 mu m), placing the mixture into a horizontal rolling bar ball mill, and performing ball milling on 8mm zirconia and 10mm zirconia according to the weight ratio of 2: 1, ball milling for 16h by using the mixed grinding balls in the proportion;
the powder comprises the following components in percentage by mass: boron carbide powder 95% and Al 2 O 3 3 percent of cerium oxide, 2 percent of cerium oxide;
2) preparing initial slurry: adding pure water into the pre-ground powder, and mechanically stirring for 30min to obtain initial slurry;
the solid content of the initial slurry is 65%, and the viscosity is less than 5800 cps;
3) preparing slurry: adding polyvinyl carboxylic acid (the addition amount is 0.03 percent of the solid content) into the initial slurry for a plurality of times in a small amount at a stirring speed of 60 r/min; after the addition of the polyvinyl carboxylic acid is finished, stirring at 10r/min for 20min and uniformly mixing; keeping the stirring speed unchanged, and sequentially adding polyacrylic acid aqueous solution resin (the addition amount is 0.06 percent of the solid content) and TAF (0.03 percent) to obtain slurry;
performing a coating-4 cup test on the slurry, wherein the number of coated-4 cups is 65 s; adding 8% pure water into the system, and coating 4 cups for 40 s;
4) coating an anti-sticking layer of a spray granulation tower: taking water system PVA to be dissociated for 1h at 120 ℃ to obtain a colloidal solution with the concentration of 40%; coating the lining of the spray granulation tower with the colloidal solution, standing for 120min, and waiting for granulation;
5) spray granulation: the inlet temperature of the spray granulation tower is 260 ℃, the feeding rate of a peristaltic pump is 60g/min, the outlet temperature is 90 ℃, the speed of an atomizer is 5000r/min, and the negative pressure is kept in the tower;
6) standing and aging: sealing and standing for 12h, and performing subsequent cold pressing.
The boron carbide spray granulation powder obtained in the embodiment has the water content of 5% and the particle size of 50-120 μm.
After the boron carbide spray granulation powder is sintered, the ash content is 0.18 percent, the solid sphere rate is 77 percent, the solid content can reach 62 percent, the density of the sintered product is 98.9 percent, and a stable glass phase is formed.
Example 3
The embodiment provides boron carbide spray granulation powder, and the preparation method of the boron carbide spray granulation powder comprises the following steps:
1) pre-grinding powder: mixing boron carbide powder (D50 is 0.5 mu m) and toughening phase (D50 is 0.5 mu m), placing the mixture into a horizontal rolling bar ball mill, and performing ball milling on 8mm zirconia and 10mm zirconia according to the weight ratio of 2: 1, ball milling for 16h by using the mixed grinding balls in the proportion;
the powder comprises the following components in percentage by mass: boron carbide powder 92% and Y 2 O 3 4% and cerium oxide 4%;
2) preparing initial slurry: adding pure water into the pre-ground powder, and mechanically stirring for 30min to obtain initial slurry;
the solid content of the initial slurry is 70%, and the viscosity is less than 6300 cps;
3) preparing slurry: adding polyvinyl carboxylic acid (added in an amount of 0.03% of the solid content) to the initial slurry in small portions at a stirring rate of 30 r/min; after the addition of the polyvinyl carboxylic acid is finished, stirring at 10r/min for 20min and uniformly mixing; keeping the stirring speed unchanged, sequentially adding water system PVA and wax system PVA according to the mass ratio of 0.5: 1.2 mixture (addition 0.05% of solid content) and glycerol (0.03%) to give a slurry;
performing a coating-4 cup test on the slurry, wherein the number of coated-4 cups is 68 s; continuously adding 6% pure water into the system, and counting for 37s by coating 4 cups;
4) coating an anti-sticking layer of a spray granulation tower: taking water system PVA to be dissociated for 1h at 120 ℃ to obtain a colloidal solution with the concentration of 40%; coating the lining of the spray granulation tower with the colloidal solution, standing for 120min, and waiting for granulation;
5) and (3) spray granulation: the inlet temperature of the spray granulation tower is 240 ℃, the feed rate of a peristaltic pump is 30g/min, the outlet temperature is 100 ℃, the speed of an atomizer is 5000r/min, and the tower is kept at negative pressure;
6) standing and aging: sealing and standing for 12h, and performing subsequent cold pressing.
The boron carbide spray granulation powder obtained in the embodiment has the water content of 5% and the particle size of 70-160 μm.
After the boron carbide spray granulation powder is sintered, the ash content is 0.15%, the solid sphere rate is 78%, the solid content can reach 64%, and the density of a sintered product is 99.4%, so that a stable glass phase is formed.
Comparative example 1
This comparative example provides a boron carbide spray granulated powder whose preparation method differs from example 1 only in that: in step 3), the polyvinyl carboxylic acid is replaced by sodium citrate.
The boron carbide spray granulation powder obtained in the comparative example had a water content of 8% and an average particle size of 100 μm.
After the boron carbide spray granulation powder is sintered, the ash content is 0.5%, the solid sphere rate is 60%, the solid content is 40%, and the density of a sintered product is 97.6%.
The water reducing effect of the boron carbide spray granulation powder of the comparative example is lower than that of the boron carbide spray granulation powder of the example 1, the water content is required to be increased to meet the tower entering requirement, the ash content is larger, and a sodium impurity phase is introduced.
Comparative example 2
This comparative example provides a boron carbide spray granulated powder whose preparation method differs from example 1 only in that: in step 3), the polyacrylic acid aqueous solution resin is replaced by the single aqueous PVA.
The boron carbide spray granulated powder obtained in this comparative example had a water content of 7% and an average particle size of 105 μm.
After the boron carbide spray granulation powder is sintered, the ash content is 0.62%, the solid sphere rate is 75%, the solid content is 41.5%, and the density of a sintered product is 98.0%.
Comparative example 3
This comparative example provides a boron carbide spray granulated powder whose preparation method differs from example 1 only in that: in the step 5), the inlet temperature of the spray granulation tower is 240 ℃, the feed rate of a peristaltic pump is 99g/min, the outlet temperature is 80 ℃, the speed of an atomizer is 4500r/min, and the negative pressure is kept in the tower.
The boron carbide spray granulation powder obtained in the comparative example had a water content of 11% and a particle size of 110 μm.
After the boron carbide spray granulation powder is sintered, the ash content is 0.23%, the solid sphere rate is 78%, the solid content can reach 65%, and the density of a sintered product is 98.5%.
Although the invention has been described in detail hereinabove by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that many modifications and improvements can be made thereto based on the invention. Accordingly, it is intended that all such modifications and alterations be included within the scope of this invention as defined in the appended claims.

Claims (12)

1. The preparation method of the boron carbide spray granulation powder comprises the step of pre-grinding the powder, and is characterized in that the powder comprises boron carbide powder and a toughening phase; the toughening phase is selected from Al 2 O 3 、Y 2 O 3 One or more of cerium oxide;
the mass ratio of the boron carbide powder to the toughening phase is 90-95: 3-10;
also comprises the steps of preparing initial slurry: adding pure water into the pre-ground powder to obtain initial slurry;
the solid content of the initial slurry is 65-70%, and the viscosity is less than 6500 cps;
also comprises the steps of size mixing: adding a water reducing agent, a binder and a lubricant into the initial slurry in sequence to obtain slurry;
wherein the water reducing agent is polyvinyl carboxylic acid; the binder is polyacrylic acid aqueous solution resin and/or PVA; the lubricant is glycerol and/or TAF;
based on the solid content of the initial slurry, the addition amount of the water reducing agent is 0.01-0.03%, the addition amount of the binder is 0.03-0.08%, and the addition amount of the lubricant is 0.01-0.03%.
2. The preparation method of claim 1, wherein the powder comprises the following components in percentage by mass: 92-95% of boron carbide powder and Al 2 O 3 Or Y 2 O 3 1-4% of cerium oxide and 2-4% of cerium oxide;
the boron carbide powder and the D50 of the toughening phase are both 0.1-1 mu m.
3. The production method according to claim 1, wherein the PVA is a mixture of water-based PVA and wax-based PVA;
wherein the mass ratio of the water-based PVA to the wax-based PVA is 0.5: 1 to 1.4.
4. The method according to claim 1, wherein the slurry has a coat-4 cup index of 20 to 40 seconds.
5. The production method according to any one of claims 1 to 4, further comprising a step of spray granulation; the spray granulation is carried out in a spray granulation tower;
the parameters of the spray granulation tower are as follows: the inlet temperature is 240-300 ℃, the feeding rate of the peristaltic pump is 30-90 g/min, the outlet temperature is 80-120 ℃, the speed of the atomizer is 3000-5000 r/min, and the negative pressure is kept in the tower.
6. The production method according to claim 5, wherein, prior to the spray granulation, an anti-sticking layer is previously applied to the inner liner of the spray granulation tower;
the coating is as follows: dissociating water system PVA at 90-120 ℃ for 1-2 h to obtain a colloidal solution with the concentration of 25-40%; coating the inner lining of the spray granulation tower with the colloidal solution.
7. The method of claim 1, comprising the steps of:
1) pre-grinding powder: mixing boron carbide powder and a toughening phase, and then ball-milling for 12-20 h;
the medium of ball milling is zirconia with the size of 8mm and zirconia with the size of 10mm, and the mass ratio of zirconia to zirconia is 1-3: 1 proportion of mixed grinding balls;
2) preparing initial slurry: adding pure water into the pre-ground powder to obtain initial slurry;
the solid content of the initial slurry is 65-70%, and the viscosity is less than 6500 cps;
3) preparing slurry: adding a water reducing agent into the initial slurry at a stirring speed of 30-60 r/min; after the water reducing agent is added, stirring for 20-40 min at a speed of 10-50 r/min; keeping the stirring speed unchanged, and sequentially adding a binder and lubricating oil to obtain slurry;
performing a coating-4 cup test on the slurry, and if the reading number of the coating-4 cup is more than 40s, continuously adding pure water into the system until the reading number of the coating-4 cup is 20-40 s;
4) coating an anti-sticking layer of a spray granulation tower: dissociating water system PVA at 90-120 ℃ for 1-2 h to obtain a colloidal solution with the concentration of 25-40%; coating the lining of the spray granulation tower with the colloidal solution, and standing for 60-120 min;
5) spray granulation: the inlet temperature of the spray granulation tower is 240-300 ℃, the feeding rate of the peristaltic pump is 30-90 g/min, the outlet temperature is 80-120 ℃, the speed of the atomizer is 3000-5000 r/min, and negative pressure is kept in the tower.
8. A boron carbide spray granulated powder produced by the method according to any of claims 1 to 7.
9. The boron carbide spray granulated powder according to claim 8, wherein the water content of the boron carbide spray granulated powder is 3 to 5%.
10. Use of the method of any one of claims 1 to 7 or the boron carbide spray granulated powder of any one of claims 8 to 9 for the preparation of ceramics.
11. Use of the method of any one of claims 1 to 7 or the boron carbide spray granulated powder of any one of claims 8 to 9 for the preparation of anisotropic protective ceramics.
12. Use of the method of any one of claims 1 to 7 or the boron carbide spray granulation powder of any one of claims 8 to 9 in the preparation of boron carbide anisotropic protective ceramics.
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