A passivation device and method for boron carbide micro powder

Abstract

This invention relates to a passivation apparatus and method for boron carbide micropowder. The passivation apparatus includes a grinding cylinder with an inner grinding cavity and a water-cooled outer cavity. A baffle is provided on the side wall of the inner grinding cavity. A cooling water inlet is located at the bottom end of the side wall of the water-cooled outer cavity, and a cooling water outlet is located at the top end of the side wall. An end cap is fixed to the top of the grinding cylinder, and a stirrer is inserted through the center of the end cap, which also has a drain port. A fixed bracket is connected to the middle of the side wall of the water-cooled outer cavity via a rotating part. This invention, by employing a self-grinding passivation apparatus with a specific structure, can effectively remove the sharp corners of boron carbide micropowder, which is beneficial for preparing passivated and high-purity boron carbide micropowder.

Description

Technical Field

[0001] This invention relates to the field of particle shaping technology, specifically to a passivation device and method for boron carbide micropowder. Background Technology

[0002] Boron carbide is widely used in bulletproof armor materials, aluminum-based reinforced composite materials, and nuclear industry materials due to its low specific gravity, high hardness, good acid and alkali resistance, and small coefficient of thermal expansion, and has excellent application prospects.

[0003] Boron carbide is typically synthesized using the carbothermic reduction method, which involves reacting carbon black or petroleum coke with boric acid at high temperatures and in an inert atmosphere. Because the high reaction temperature and long reaction time promote boron carbide grain growth and particle agglomeration, the smelted boron carbide blocks need to be crushed and impurity removed before use as sintering raw materials or fillers. However, the sintered boron carbide particles have sharp-angled morphologies, which can cause stress concentration, leading to defects and cracks, and also reducing the mechanical properties of the product.

[0004] Currently, methods for controlling the morphology of powders mainly include mechanical rolling and shaping, ball milling media shaping, and air jet milling shaping. CN 208483695U discloses a silicon carbide particle shaping machine, including a silicon carbide particle shaping machine shell, a silicon carbide particle shaping machine cover fixedly connected to the upper end of the shell, a support frame provided on the lower side of the shell, and a fixed connection between the shell and the support frame. The shell includes a silicon carbide particle shaping cavity and a high-power fan slot. A feed inlet is fixedly connected to the upper end of the cover, and the inner cavity of the shell communicates with the outside through the feed inlet. An electric rotating shaft is rotatably connected to the bottom end of the cover, and a stirring fan blade is fixedly connected to the electric rotating shaft. This shaping machine uses mechanical parts to crush powder, which easily causes high wear and contaminates the ground material; at the same time, the device can only be used for coarser particles, and the passivation effect is not obvious for fine and ultrafine particles.

[0005] CN 110963802A discloses a surface shaping method for silicon carbide micropowder, comprising the following steps: S1. Crushing; S2. Pre-grinding; S3. Grinding; S4. Sorting; S5. Purification; S6. Washing; S7. Drying to obtain the finished product. The invention pre-grinds the silicon carbide particles before grinding, preheating them in a pre-grinding cylinder while allowing them to coarsely grind through friction and collision as the cylinder rotates, before further fine grinding in a ball mill. However, due to insufficient mechanical energy provided by the ball mill, the shaping efficiency is low, and it cannot effectively shape particles with very small diameters.

[0006] CN 214021270U discloses a fluidized bed particle shaping and grinding mill. A gas control valve is fixedly installed at the rear middle position of support A. The shaping and grinding device is fixedly installed in the middle position between support A and support B. One end of the exhaust pipe is fixedly installed at the upper right side of the shaping and grinding device, and the other end of the exhaust pipe is fixedly connected to the upper left side of a high-efficiency dust collector. The high-efficiency dust collector is fixedly installed at the upper part of support B. One end of the exhaust pipe is fixedly connected to the upper right side of the high-efficiency dust collector, and the other end is fixedly connected to the exhaust port of an exhaust fan. The exhaust fan is fixedly installed at the right side of the high-efficiency dust collector. However, in air jet mill shaping, when the powder particles are small, the kinetic energy of the collision is insufficient, reducing the shaping efficiency. Simultaneously, friction between the powder and the inner wall can lead to contamination, thereby reducing the purity of the product.

[0007] Therefore, in view of the shortcomings of the existing technology, there is an urgent need to provide a boron carbide passivation device with good particle passivation effect and high purity. Summary of the Invention

[0008] The purpose of this invention is to provide a passivation device and method for boron carbide micro powder. By using a self-grinding wet grinding passivation device to passivate boron carbide micro powder, the sharp corners of the micro powder are effectively removed, which is beneficial for preparing passivated and high-purity boron carbide powder.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a passivation device for boron carbide micro powder. The passivation device includes a grinding cylinder, which is provided with a grinding inner cavity and a water-cooled outer cavity. A baffle is provided on the side wall of the grinding inner cavity. A cooling water inlet is provided at the bottom end of the side wall of the water-cooled outer cavity, and a cooling water outlet is provided at the top end of the side wall. An end cap is fixed at the top end of the grinding cylinder. A stirrer is inserted through the center of the end cap, and a drain port is provided on the end cap. A fixed bracket is connected to the middle of the side wall of the water-cooled outer cavity through a rotating part.

[0011] The passivation device for boron carbide micropowder provided by this invention, by setting baffles in the grinding chamber, can adjust the flow direction of the slurry during stirring, ensuring that the powder particles can move fully and effectively rub against each other during stirring, thereby improving the efficiency of auto-grinding; the end cap at the top of the grinding cylinder can prevent slurry splashing during stirring; the design of the water-cooled outer chamber allows cooling water to enter through the cooling water inlet and exit through the cooling water outlet, effectively removing the heat generated during slurry stirring, reducing the slurry temperature, and preventing the oxidation of boron carbide due to excessive temperature, thus reducing the oxygen content of the product. The passivation device can effectively remove the sharp corners of the micropowder, which is beneficial for preparing passivated and high-purity boron carbide micropowder.

[0012] Preferably, the rotating part includes a rotating shaft.

[0013] Preferably, the water-cooled outer cavity is a stainless steel water-cooled jacket.

[0014] Preferably, the surface of the grinding cavity is coated or covered with any one of polyurethane, polytetrafluoroethylene or nylon.

[0015] Preferably, the grinding cavity has a U-shaped shape.

[0016] The grinding chamber is U-shaped to prevent powder from accumulating in certain areas during stirring and thus hindering its movement, while also reducing wear on the cylinder wall material.

[0017] Preferably, the baffles are arranged at intervals along the height direction of the sidewall of the grinding cavity.

[0018] Preferably, the baffles are arranged symmetrically along the central axis of the agitator.

[0019] Preferably, a sealing part is provided at the connection between the end cap and the stirrer.

[0020] The sealing part can reduce slurry splashing while avoiding friction between the end cap and the agitator.

[0021] Preferably, a first-stage blade, a second-stage blade, and a third-stage blade are arranged sequentially near the head of the agitator, and a stirring motor is arranged at the tail of the agitator.

[0022] Preferably, the materials of the first-stage blade, the second-stage blade, and the third-stage blade include any one of polyurethane, polytetrafluoroethylene, or nylon.

[0023] Secondly, the present invention provides a passivation method for boron carbide micro powder, wherein the passivation method is performed using the passivation apparatus described in the first aspect, and the passivation method includes the following steps:

[0024] (1) Disperse boron carbide micro powder in pure water, and then perform stirring and self-grinding treatment to obtain upper suspension slurry and lower boron carbide concentrate.

[0025] (2) The upper layer of suspended slurry obtained in step (1) is discharged, and the bottom layer of boron carbide concentrate is taken out and then dried and deagglomerated in sequence to obtain passivated boron carbide micro powder.

[0026] Before the bottom boron carbide concentrate is removed in step (2), the passivation device is continuously cooled in a cyclic manner.

[0027] The passivation method for boron carbide micro powder provided by the present invention achieves passivation of boron carbide micro powder by stirring and self-grinding in a passivation device, and at the same time, the passivated boron carbide micro powder is dried and de-agglomerated, thereby obtaining boron carbide micro powder with good passivation and dispersion effects.

[0028] Preferably, the specific steps of dispersion in step (1) include: adding pure water into the grinding cylinder, then turning on the stirrer and adding boron carbide micro powder.

[0029] Preferably, the volume of the pure water does not exceed 1 / 3 to 1 / 2 of the grinding cylinder volume, for example, it can be 1 / 3, 5 / 12 or 1 / 2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the solid content of the dispersed slurry in step (1) is 50-90%, for example, it can be 50%, 60%, 70%, 72%, 75%, 80% or 90%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. Preferably, it is 60-80%, and more preferably 70-75%.

[0031] Preferably, the average particle size of the boron carbide micro powder in step (1) is 3-45 μm, for example, it can be 3 μm, 10 μm, 20 μm, 30 μm or 45 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the average particle size of the boron carbide micro powder in step (1) is <10μm, for example, it can be 9μm, 8μm, 7μm, 6μm or 5μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, and a dispersant is added.

[0033] Preferably, the dispersant includes at least one of amino alcohol, n-butanol, polyethylene glycol, polyethyleneimine, polyacrylic acid, polyacrylate, or polyvinylpyridine.

[0034] Preferably, the rotation speed of the stirring autogenous grinding process in step (1) is 1-6 m / s, for example, it can be 1 m / s, 3 m / s, 4 m / s, 5 m / s or 6 m / s, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 3-5 m / s.

[0035] Preferably, the time for the stirring and self-grinding process in step (1) is 1-48h, for example, it can be 1h, 12h, 24h, 36h or 48h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the specific steps of the discharge in step (2) include: inserting a drain pipe through the drain port, and then turning on the drain pump to discharge the upper layer of suspended slurry.

[0037] Preferably, after the discharge in step (2) and before the bottom boron carbide concentrate is removed, a debris removal step is also included, specifically including: after the upper suspension slurry is discharged, pure water is injected, the resulting slurry is stirred and allowed to stand in sequence, and the resulting upper suspension slurry is discharged.

[0038] Preferably, the stirring speed is 1-6 m / s, for example, it can be 1 m / s, 2 m / s, 3 m / s, 4 m / s or 6 m / s, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the debris removal step is repeated 2-5 times, for example, 2 times, 3 times, 4 times or 5 times.

[0040] The debris removal process is repeated until the suspended debris particles are removed from the slurry.

[0041] Preferably, the drying temperature in step (2) is 40-150°C, for example, it can be 40°C, 80°C, 100°C, 125°C or 150°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] The drying temperature needs to be controlled within a reasonable range. If the temperature is too low, the drying efficiency will be reduced, and if the temperature is too high, the boron carbide micro powder will be easily oxidized.

[0043] Preferably, the drying time in step (2) is 6-12 hours, for example, 6 hours, 7 hours, 8 hours, 10 hours or 12 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] Preferably, the drying in step (2) is carried out in a vacuum oven.

[0045] Preferably, the deagglomeration treatment method in step (2) includes air jet milling.

[0046] Preferably, the controlled airflow pressure in the air mill is 0.4-1.2 MPa, for example, it can be 0.4 MPa, 0.6 MPa, 0.8 MPa, 1 MPa or 1.2 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] The dried boron carbide micro powder agglomerates can be broken up using an air jet mill. The operation is carried out at a relatively low pressure to ensure that the micro powder is not broken up again.

[0048] Preferably, the temperature of the cooling water used for the circulating cooling is <12°C, for example, it can be 11°C, 10°C, 8°C, 6°C or 5°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0049] As a preferred embodiment of the passivation method of the present invention, the passivation method includes the following steps:

[0050] (1) Add pure water to the grinding cylinder, the volume of which does not exceed 1 / 3-1 / 2 of the grinding cylinder volume, then turn on the stirrer and add boron carbide micro powder with an average particle size of 3-45μm. The solid content of the resulting slurry is 50-90%; the average particle size of the boron carbide micro powder is <10μm, and a dispersant is added; then perform stirring and self-grinding treatment at a speed of 1-6m / s for 1-48h to obtain an upper suspension slurry and a bottom boron carbide concentrate.

[0051] (2) Insert the drain pipe through the drain port, turn on the drain pump to discharge the upper suspension slurry obtained in step (1), and then inject pure water. The slurry obtained is stirred and settled at 1-6 m / s in sequence. The upper suspension slurry obtained is discharged and repeated 2-5 times. After the bottom boron carbide concentrate is taken out, it is dried in a vacuum oven at 40-150℃ for 6-12 hours and then in an air mill with the air pressure controlled at 0.4-1.2 MPa to obtain passivated boron carbide micro powder.

[0052] Before the bottom boron carbide concentrate is removed in step (2), the passivation device is continuously circulated and cooled, and the temperature of the cooling water used is <12℃.

[0053] When using the passivation device to passivate boron carbide micropowder, the specific steps include:

[0054] Add pure water to the grinding cylinder, turn on the agitator to rotate at low speed, then add boron carbide micro powder. Secure the end cap to the top of the grinding cylinder to seal the drain port, and then perform agitation and self-grinding to obtain an upper suspension slurry and a bottom boron carbide concentrate. Insert the drain pipe through the drain port to the first-stage impeller, turn on the drain pump, and discharge the upper suspension slurry at low speed until the liquid level drops to the central axis of the cooling water outlet. Then inject pure water. The resulting slurry is stirred and allowed to stand in sequence. Then, the upper suspension slurry is discharged again through the drain pipe inserted through the drain port. Repeat this process until the suspended debris particles are removed from the slurry. Remove the agitator and open the end cap. Control the rotating part to rotate the grinding cylinder until the bottom boron carbide concentrate is removed. Then, dry and perform air jet milling to obtain passivated boron carbide micro powder.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] (1) The passivation device for boron carbide micro powder provided by the present invention can adjust the flow direction of the slurry during stirring by setting a baffle in the grinding inner cavity, ensuring that the powder particles can move fully and effectively rub against each other during stirring, thereby improving the efficiency of stirring and self-grinding; the end cap of the grinding cylinder can prevent the slurry from splashing during stirring; the design of the water-cooled outer cavity allows cooling water to enter through the cooling water inlet and exit through the cooling water outlet, effectively removing the heat generated during slurry stirring, reducing the slurry temperature, avoiding the oxidation of boron carbide due to excessive temperature, and reducing the oxygen content of the product. The passivation device can effectively remove the sharp corners of the micro powder, which is beneficial for preparing passivated and high-purity boron carbide micro powder;

[0057] (2) The passivation method of boron carbide micro powder provided by the present invention achieves passivation of boron carbide micro powder by stirring and grinding in a passivation device, and at the same time, the passivated boron carbide micro powder is dried and deagglomerated, thereby obtaining boron carbide micro powder with good passivation and dispersion effects. Attached Figure Description

[0058] Figure 1 This is a cross-sectional view of the passivation device for boron carbide micro powder provided in Embodiment 1 of the present invention;

[0059] Figure 2 This is a SEM image of the boron carbide micro powder provided in Embodiment 1 of the present invention on a substrate without passivation;

[0060] Figure 3 This is a SEM image of the passivated boron carbide micropowder on the substrate provided in Embodiment 1 of the present invention;

[0061] The components are: 1. Grinding inner cavity; 2. Water-cooled outer cavity; 3. Baffle; 4. Cooling water inlet; 5. Cooling water outlet; 6. End cap; 7. Agitator; 8. Drain port; 9. Rotary shaft; 10. Fixed bracket; 11. First-stage impeller; 12. Second-stage impeller; 13. Third-stage impeller; 14. Agitator motor. Detailed Implementation

[0062] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0063] Example 1

[0064] This embodiment provides a passivation device for boron carbide micropowder, as shown in the cross-sectional view below. Figure 1As shown, the passivation device includes a grinding cylinder, which has an inner grinding cavity 1 and a water-cooled outer cavity 2. The water-cooled outer cavity 2 is a stainless steel water-cooled jacket, and the surface of the inner grinding cavity 1 is coated with polyurethane. The inner grinding cavity 1 is U-shaped, and a baffle 3 is provided on the side wall of the inner grinding cavity 1. A cooling water inlet 4 is opened at the bottom end of the side wall of the water-cooled outer cavity 2, and a cooling water outlet 5 is opened at the top end of the side wall. An end cap 6 is fixed at the top end of the grinding cylinder, and a stirrer 7 is inserted through the center of the end cap 6. A sealing part is provided at the connection between the end cap 6 and the stirrer 7. A drain port 8 is opened on the end cap 6. A fixed bracket 10 is connected to the middle of the side wall of the water-cooled outer cavity 2 through a rotating shaft 9.

[0065] The baffles 3 are arranged at intervals along the height of the side wall of the grinding cavity 1; the baffles 3 are arranged symmetrically along the central axis of the agitator 7; a first-stage blade 11, a second-stage blade 12 and a third-stage blade 13 are arranged sequentially near the head of the agitator 7; and a stirring motor 14 is arranged at the tail of the agitator 7.

[0066] The passivation device is used to passivate boron carbide micropowder, and the passivation method for the boron carbide micropowder includes the following steps:

[0067] (1) Add pure water to the grinding cylinder, the volume of which is 5 / 12 of the grinding cylinder volume. Then turn on the stirrer 7 and add boron carbide micro powder with an average particle size of 20μm. The solid content of the resulting slurry is 72%. Then, perform stirring and self-grinding treatment at a speed of 4m / s for 6 hours to obtain the upper suspension slurry and the bottom boron carbide concentrate.

[0068] (2) Insert the drain pipe through the drain port 8, turn on the drain pump to discharge the upper suspension slurry obtained in step (1), and then inject pure water. The slurry obtained is stirred and settled at 4 m / s in sequence. The upper suspension slurry obtained is discharged and repeated 4 times. After the bottom boron carbide concentrate is taken out, it is dried in a vacuum oven at 80°C for 10 hours and then in an air mill with the air pressure controlled at 0.8 MPa to obtain passivated boron carbide micro powder.

[0069] Before the bottom boron carbide concentrate is removed in step (2), the passivation device is continuously circulated and cooled, and the temperature of the cooling water used is 9°C.

[0070] The SEM image of the boron carbide micropowder on the substrate before passivation is shown below. Figure 2 As shown in the figure, the sharp corners of the boron carbide micro powder are quite obvious; the SEM image of the obtained passivated boron carbide micro powder on the matrix is ​​shown below. Figure 3As shown in the figure, the sharp corners of the boron carbide micro powder were removed, and the edges produced a significant passivation effect. The purity of the passivated boron carbide micro powder was detected by ICP-OES. The total content of metal impurities (Fe, Al, Si, etc.) in the powder was 0.25%, and the content of B2O3 was 0.2%.

[0071] Example 2

[0072] This embodiment provides a passivation device for boron carbide micro powder, which is the same as that in Embodiment 1.

[0073] The passivation device is used to passivate boron carbide micropowder, and the passivation method for the boron carbide micropowder includes the following steps:

[0074] (1) Add pure water to the grinding cylinder, the volume of which is 1 / 3 of the grinding cylinder volume. Then turn on the stirrer 7 and add boron carbide micro powder with an average particle size of 3μm and amino alcohol dispersant. The amount of dispersant is 1wt% of boron carbide micro powder. The solid content of the resulting slurry is 70%. Then, perform stirring and self-grinding treatment at a speed of 5m / s for 3h to obtain the upper suspension slurry and the bottom boron carbide concentrate.

[0075] (2) Insert the drain pipe through the drain port 8, turn on the drain pump to discharge the upper suspension slurry obtained in step (1), and then inject pure water. The slurry obtained is stirred and settled at 6 m / s in sequence. The upper suspension slurry obtained is discharged and repeated 5 times. After the bottom boron carbide concentrate is taken out, it is dried in a vacuum oven at 40°C for 12 hours and then in an air mill with the air pressure controlled at 0.4 MPa to obtain passivated boron carbide micro powder.

[0076] Before the bottom boron carbide concentrate is removed in step (2), the passivation device is continuously circulated and cooled, and the temperature of the cooling water used is 7°C.

[0077] The sharp corners of the obtained passivated boron carbide micro powder were removed, and the edges were passivated. The purity of the passivated boron carbide micro powder was tested by ICP-OES. The total content of metal impurities (Fe, Al, Si, etc.) in the powder was 0.4%, and the content of B2O3 was 0.15%.

[0078] Example 3

[0079] This embodiment provides a passivation device for boron carbide micro powder, which is the same as that in Embodiment 1.

[0080] The passivation device is used to passivate boron carbide micropowder, and the passivation method for the boron carbide micropowder includes the following steps:

[0081] (1) Add pure water to the grinding cylinder, the volume of the pure water being 1 / 2 of the grinding cylinder volume, then turn on the stirrer 7 and add boron carbide micro powder with an average particle size of 45μm. The solid content of the resulting slurry is 75%. Then, perform stirring and self-grinding treatment at a speed of 3m / s for 12h to obtain the upper suspension slurry and the bottom boron carbide concentrate.

[0082] (2) Insert the drain pipe through the drain port 8, turn on the drain pump to discharge the upper suspension slurry obtained in step (1), and then inject pure water. The slurry obtained is stirred and settled at 1 m / s in sequence. The upper suspension slurry obtained is discharged and repeated twice. After the bottom boron carbide concentrate is taken out, it is dried in a vacuum oven at 150°C for 6 hours and then in an air mill with the air pressure controlled at 1.2 MPa to obtain passivated boron carbide micro powder.

[0083] Before the bottom boron carbide concentrate is removed in step (2), the passivation device is continuously circulated and cooled, and the temperature of the cooling water used is 5°C.

[0084] The sharp corners of the obtained passivated boron carbide micro powder were removed, and the edges were passivated. The purity of the passivated boron carbide micro powder was tested by ICP-OES. The total content of metal impurities (Fe, Al, Si, etc.) in the powder was 0.5%, and the content of B2O3 was 0.1%.

[0085] Example 4

[0086] This embodiment provides a passivation device for boron carbide micro powder. The difference from Embodiment 1 is that, except for adjusting the shape of the grinding inner cavity 1 to a flat-bottomed U-shape, the rest is the same as Embodiment 1.

[0087] Because the grinding chamber is adjusted to a flat-bottomed U-shape, the boron carbide micro powder aggregates during stirring and cannot move effectively. As a result, the sharp corner removal effect of the passivated boron carbide micro powder decreases, and the edge passivation effect is reduced. The purity of the passivated boron carbide micro powder does not change significantly.

[0088] Example 5

[0089] This embodiment provides a passivation device for boron carbide micro powder. The difference from Embodiment 1 is that no sealing part is provided at the connection between the end cap 6 and the stirrer 7. All other aspects are the same as in Embodiment 1.

[0090] Because there is no sealing part, the slurry is prone to splashing during stirring, which reduces the effectiveness of completely removing the sharp corners of the resulting passivated boron carbide micro powder and decreases the passivation effect at the edges; the purity of the passivated boron carbide micro powder does not change significantly.

[0091] Example 6

[0092] This embodiment provides a passivation device for boron carbide micro powder. The difference from Embodiment 1 is that the surface material of the grinding inner cavity 1 is replaced with stainless steel, while the rest is the same as in Embodiment 1.

[0093] Since the surface material of the grinding inner cavity is stainless steel, it is prone to damage during self-grinding. ICP-OES was used to test the purity of the passivated boron carbide micro powder, and the total content of metal impurities increased to 0.75%. The sharp corners of the obtained passivated boron carbide micro powder were removed, and the edges produced a passivation effect.

[0094] Example 7

[0095] This embodiment provides a passivation device for boron carbide micro powder. The passivation device is used to passivate the boron carbide micro powder. The passivation method of the boron carbide micro powder is different from that of Embodiment 1. Except for adjusting the solid content of the dispersed slurry in step (1) to 60%, the rest is the same as that of Embodiment 1.

[0096] Most of the sharp corners of the obtained passivated boron carbide micro powder were removed, and the edges were passivated; the purity of the passivated boron carbide micro powder did not change significantly.

[0097] Example 8

[0098] This embodiment provides a passivation device for boron carbide micro powder. The passivation device is used to passivate the boron carbide micro powder. The passivation method of the boron carbide micro powder is different from that of Embodiment 1. Except for adjusting the solid content of the dispersed slurry in step (1) to 80%, the rest is the same as that of Embodiment 1.

[0099] A small portion of the sharp corners of the obtained passivated boron carbide micro powder were not removed, and the passivation effect at the edges decreased; the purity of the passivated boron carbide micro powder did not change significantly.

[0100] Example 9

[0101] This embodiment provides a passivation device for boron carbide micro powder. The passivation device is used to passivate the boron carbide micro powder. The passivation method of the boron carbide micro powder is different from that of Embodiment 1. Except for adjusting the solid content of the dispersed slurry in step (1) to 50%, the rest is the same as that of Embodiment 1.

[0102] Most of the sharp corners of the obtained passivated boron carbide micro powder were removed, and the edges were passivated. However, the low solid content led to some boron carbide micro powder being broken after stirring and grinding. The purity of the passivated boron carbide micro powder did not change significantly.

[0103] Example 10

[0104] This embodiment provides a passivation device for boron carbide micro powder. The passivation device is used to passivate the boron carbide micro powder. The passivation method of the boron carbide micro powder is different from that of Embodiment 1. Except for adjusting the solid content of the dispersed slurry in step (1) to 90%, the rest is the same as that of Embodiment 1.

[0105] The sharp corners of the obtained passivated boron carbide micro powder were not completely removed, and the passivation effect at the edges decreased; the purity of the passivated boron carbide micro powder did not change significantly.

[0106] Example 11

[0107] This embodiment provides a passivation device for boron carbide micro powder. The passivation device is used to passivate the boron carbide micro powder. The passivation method of the boron carbide micro powder is different from that of Embodiment 1. Except for adjusting the stirring self-grinding speed in step (1) to 1 m / s, the rest is the same as that of Embodiment 1.

[0108] The stirring auto-grinding process has a lower rotation speed, but the stirring auto-grinding efficiency is reduced. The sharp corners of the resulting passivated boron carbide micro powder are not completely removed, and the passivation effect of the edges is reduced. The purity of the passivated boron carbide micro powder does not change significantly.

[0109] Example 12

[0110] This embodiment provides a passivation device for boron carbide micro powder. The passivation device is used to passivate the boron carbide micro powder. The passivation method of the boron carbide micro powder is different from that of Embodiment 1. Except for adjusting the stirring self-grinding speed in step (1) to 6m / s, the rest is the same as that of Embodiment 1.

[0111] The high rotation speed of the stirring self-grinding process resulted in some breakage of boron carbide micro powder. The sharp corners of the resulting passivated boron carbide micro powder were not completely removed, and the passivation effect at the edges was reduced. The purity of the passivated boron carbide micro powder did not change significantly.

[0112] Example 13

[0113] This embodiment provides a passivation device for boron carbide micro powder. The passivation device is used to passivate the boron carbide micro powder. The passivation method of the boron carbide micro powder is different from that of Embodiment 1 in that step (2) does not include the steps of injecting pure water, stirring, settling and discharging the upper suspension slurry. The rest are the same as in Embodiment 1.

[0114] Without a debris removal step, boron carbide micro-particles will remain in the slurry, resulting in excessive fine particles in the boron carbide micro-powder product, and the purity of the passivated boron carbide micro-powder will not change significantly.

[0115] Comparative Example 1

[0116] This comparative example provides a passivation device for boron carbide micro powder. The difference from Example 1 is that the sidewall of the grinding cavity 1 is not provided with a baffle 3, but the rest is the same as Example 1.

[0117] Without baffles, boron carbide micro powder cannot flow fully or effectively rub during the stirring and grinding process. As a result, most of the sharp corners of the passivated boron carbide micro powder are not removed, and the passivation effect at the edges is significantly reduced. The purity of the passivated boron carbide micro powder does not change significantly.

[0118] Comparative Example 2

[0119] This comparative example provides a passivation device for boron carbide micro powder. The difference from Example 1 is that the grinding cylinder is not provided with a water-cooled outer cavity 2; in the passivation method of boron carbide micro powder, the passivation device is not circulated and cooled before the bottom boron carbide concentrate is taken out in step (2), and the rest is the same as Example 1.

[0120] The absence of a water-cooled external cavity increases the slurry temperature, causing boron carbide to oxidize due to excessive heat, leading to an increase in oxygen content. Simultaneously, the high temperature causes discoloration of the organic materials inside the cylinder, reducing its service life. The passivation effect of the boron carbide micropowder remains largely unchanged, but the B2O3 content increases to 0.8%.

[0121] Comparative Example 3

[0122] This comparative example provides a passivation device for boron carbide micro powder. The passivation device is used to passivate the boron carbide micro powder. The passivation method of the boron carbide micro powder is different from that of Example 1 in that there is no step of de-agglomeration treatment in step (2), and the rest are the same as in Example 1.

[0123] Without addressing the agglomeration process, the dried boron carbide micropowder will agglomerate, reducing product quality.

[0124] Comparative Example 4

[0125] This comparative example provides a passivation device for boron carbide micro powder, wherein the passivation device is a ball mill; in the passivation method for boron carbide micro powder, the stirring self-grinding treatment in step (1) is adjusted to ball milling treatment, and the rest are the same as in Example 1.

[0126] Ball milling of boron carbide micro powder reduces the efficiency of sharp corner removal. Furthermore, the small particle size of boron carbide micro powder makes effective removal of sharp corners impossible, significantly reducing the passivation effect. Additionally, the wear of the grinding balls used in the ball milling process significantly decreases the purity of the boron carbide micro powder.

[0127] In summary, the passivation device for boron carbide micropowder provided by this invention, by setting baffles in the grinding chamber, can adjust the flow direction of the slurry during stirring, ensuring that the powder particles can move fully and effectively rub against each other during stirring, thereby improving the efficiency of stirring and self-grinding; the end cap at the top of the grinding cylinder can prevent slurry splashing during stirring; the design of the water-cooled outer chamber allows cooling water to enter through the cooling water inlet and exit through the cooling water outlet, effectively removing the heat generated during slurry stirring, reducing the slurry temperature, and preventing the oxidation of boron carbide due to excessive temperature, thus reducing the oxygen content of the product. The passivation device can effectively remove the sharp corners of the micropowder, which is beneficial for preparing passivated and high-purity boron carbide micropowder.

[0128] The passivation method for boron carbide micro powder provided by the present invention achieves passivation of boron carbide micro powder by stirring and self-grinding in a passivation device, and at the same time, the passivated boron carbide micro powder is dried and de-agglomerated, thereby obtaining boron carbide micro powder with good passivation and dispersion effects.

[0129] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A passivation method for boron carbide micro powder, characterized in that, The passivation method is performed using a passivation device for the boron carbide micropowder, and the passivation method includes the following steps: (1) Disperse boron carbide micro powder in pure water and then perform stirring and self-grinding to obtain upper suspension slurry and lower boron carbide concentrate. (2) The upper layer of suspension slurry obtained in step (1) is discharged, and the bottom layer of boron carbide concentrate is taken out and then dried and deagglomerated in sequence to obtain passivated boron carbide micro powder. Before the bottom boron carbide concentrate is removed in step (2), the passivation device is continuously circulated and cooled. The passivation device includes a grinding cylinder, which has an inner grinding cavity and a water-cooled outer cavity. The inner grinding cavity has a baffle on its side wall. The bottom of the side wall of the water-cooled outer cavity has a cooling water inlet, and the top of the side wall has a cooling water outlet. The top of the grinding cylinder is fitted with an end cap, and a stirrer is inserted through the center of the end cap. The end cap has a drain port. The middle of the side wall of the water-cooled outer cavity is connected to a fixed bracket through a rotating part.

2. The passivation method according to claim 1, characterized in that, The water-cooled outer cavity is a stainless steel water-cooled jacket.

3. The passivation method according to claim 1, characterized in that, The surface of the grinding cavity is coated or covered with any one of polyurethane, polytetrafluoroethylene or nylon.

4. The passivation method according to claim 1, characterized in that, The grinding cavity has a U-shaped shape.

5. The passivation method according to claim 1, characterized in that, The baffles are arranged at intervals along the height of the sidewall of the grinding cavity.

6. The passivation method according to claim 1, characterized in that, The baffles are arranged symmetrically along the central axis of the agitator.

7. The passivation method according to claim 1, characterized in that, A sealing part is provided at the connection between the end cap and the agitator.

8. The passivation method according to claim 1, characterized in that, A first-stage blade, a second-stage blade, and a third-stage blade are arranged sequentially near the head of the agitator, and a stirring motor is installed at the tail of the agitator.

9. The passivation method according to claim 1, characterized in that, The specific steps of dispersion in step (1) include: adding pure water into the grinding cylinder, then turning on the stirrer and adding boron carbide micro powder.

10. The passivation method according to claim 9, characterized in that, The volume of the pure water does not exceed 1 / 3 to 1 / 2 of the grinding cylinder volume.

11. The passivation method according to claim 1, characterized in that, The solid content of the dispersed slurry in step (1) is 50-90%.

12. The passivation method according to claim 11, characterized in that, The solid content of the dispersed slurry is 60-80%.

13. The passivation method according to claim 12, characterized in that, The solid content of the dispersed slurry is 70-75%.

14. The passivation method according to claim 1, characterized in that, The average particle size of the boron carbide micro powder in step (1) is 3-45 μm.

15. The passivation method according to claim 14, characterized in that, In step (1), the average particle size of the boron carbide micro powder is <10 μm, and a dispersant is added.

16. The passivation method according to claim 1, characterized in that, The rotation speed of the stirring auto-grinding process in step (1) is 1-6 m / s.

17. The passivation method according to claim 16, characterized in that, The rotational speed of the stirring autogenous grinding process is 3-5 m / s.

18. The passivation method according to claim 1, characterized in that, The time for the stirring and self-grinding process in step (1) is 1-48 hours.

19. The passivation method according to claim 1, characterized in that, The specific steps for discharge in step (2) include: inserting a drain pipe through the drain port and then turning on the drain pump to discharge the upper layer of suspended slurry.

20. The passivation method according to claim 1, characterized in that, Step (2) includes a debris removal step after discharge and before the bottom boron carbide concentrate is removed. Specifically, after the upper suspension slurry is discharged, pure water is injected, the resulting slurry is stirred and left to stand in sequence, and the resulting upper suspension slurry is discharged.

21. The passivation method according to claim 20, characterized in that, The stirring speed is 1-6 m / s.

22. The passivation method according to claim 20, characterized in that, The debris removal step is repeated 2-5 times.

23. The passivation method according to claim 1, characterized in that, The drying temperature in step (2) is 40-150℃.

24. The passivation method according to claim 1, characterized in that, The drying time in step (2) is 6-12 hours.

25. The passivation method according to claim 1, characterized in that, The drying process described in step (2) is carried out in a vacuum oven.

26. The passivation method according to claim 1, characterized in that, The deagglomeration treatment method in step (2) includes air jet milling.

27. The passivation method according to claim 26, characterized in that, The airflow pressure in the airflow mill is controlled at 0.4-1.2 MPa.

28. The passivation method according to claim 1, characterized in that, The temperature of the cooling water used in the circulating cooling is <12℃.

29. The passivation method according to claim 1, characterized in that, The passivation method includes the following steps: (1) Add pure water to the grinding cylinder, the volume of which does not exceed 1 / 3-1 / 2 of the grinding cylinder volume, then turn on the stirrer and add boron carbide micro powder with an average particle size of 3-45μm. The solid content of the resulting slurry is 50-90%; the average particle size of the boron carbide micro powder is <10μm, and a dispersant is added; then perform stirring and self-grinding treatment at a speed of 1-6m / s for 1-48h to obtain the upper suspension slurry and the bottom boron carbide concentrate. (2) Insert the drain pipe through the drain port, turn on the drain pump to discharge the upper suspension slurry obtained in step (1), and then inject pure water. The slurry obtained is stirred and settled at 1-6 m / s in sequence. The upper suspension slurry obtained is discharged and repeated 2-5 times. After the bottom boron carbide concentrate is taken out, it is dried in a vacuum oven at 40-150℃ for 6-12 hours and then in an air mill with the air pressure controlled at 0.4-1.2 MPa to obtain passivated boron carbide micro powder. Before the bottom boron carbide concentrate is removed in step (2), the passivation device is continuously circulated and cooled, and the temperature of the cooling water used is <12℃.

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