An ALD fluidized bed coating reactor and a method for coating powders

Abstract

The present invention relates to an ALD fluidized bed coating reactor and a method for coating powders, characterized by an ALD fluidization device capable of realizing rapid replacement of the reaction kettle. The device includes a heating chamber and a replaceable reaction kettle. Each reaction kettle contains at least one fluidized bed zone for the deposition process and is designed to be quickly connected or separated from the heating chamber through a standardized interface. This design enables users to add different amounts of fluidized powder and replace different reaction kettle modules under the same equipment state, thereby significantly improving production efficiency and flexibility.

Description

Technical Field

[0001] The present invention relates to the field of vacuum atomic deposition coating, and particularly relates to an ALD fluidized bed coating reactor and a method for coating powders. Background Art

[0002] Atomic Layer Deposition (ALD) technology was first proposed by Soviet and Finnish scientists in the 1960s and 1970s. The modern concept of "atomic layer deposition" originated from the "Atomic Layer Epitaxy (ALE)" method invented by Dr. Suntola, which was used to prepare high-quality ZnS thin films on electroluminescent thin film flat panel displays. As a special chemical vapor deposition technology, the reaction principle of atomic layer deposition is as follows: two gaseous precursors are pulsed and alternately introduced into the reaction chamber, and the deposition of the thin film is completed by means of gas-solid chemisorption reactions occurring on the substrate surface. From its deposition principle, it has the characteristics of self-saturated surface adsorption and self-limiting growth, can perform self-limiting modification on all surface active sites exposed to the gas phase environment, and can achieve the coating of individual micro-nano particles. After more than forty years of development, ALD technology has now been widely applied in the fields of microelectronics, optoelectronics, nanotechnology, optics, microelectromechanical systems, catalysis, energy, displays, biology, separation membranes, corrosion-resistant and sealing coatings, etc.

[0003] In the past few decades, due to the increasingly wide application of micro-nano powder particles, their surface modification methods have become crucial. As a surface modification method that can deposit ultra-thin nano-scale films and has good conformality, more researchers have studied the development of powder atomic layer deposition equipment with strong scalability and easy operation. Due to the characteristics of large specific surface area and high specific surface energy of micro-nano powder particles themselves, they are prone to agglomeration during the coating process, and it is difficult for the precursor to be completely saturated adsorbed on the surface of micro-nano powder particles, resulting in uneven coating of the nano-film or even the phenomenon of agglomerate coating. This is a key issue that needs to be considered in the development and innovation process of atomic layer deposition equipment for micro-nano powder particles.

[0004] In practical applications, as a typical two-dimensional film-forming vacuum technology, traditional ALD coating methods mainly rely on static coating methods, that is, particles are stacked in a sample fixing net, and the saturated adsorption of the entire surface is achieved by relying on the diffusion of precursor molecules. This method has no external force field to overcome the agglomeration force, and is only applicable to a small number of particles with good monodispersity, and is not applicable to systems prone to secondary particle agglomeration; at the same time, the particle gap is small, the diffusion in the gap is limited, which easily leads to problems such as uneven adsorption and long reaction cycles. Summary of the Invention

[0005] In view of the above problems, the present invention provides an ALD fluidized bed coating reactor. The ALD fluidized bed reaction device provided by the present invention can realize the rapid replacement of the reaction kettle module, greatly improving the production efficiency and flexibility. The design of the sealing flange ensures good sealing performance between the reaction kettle module and the main reaction chamber, while simplifying the replacement process. The design of the fluidization zone, expansion zone and disengagement zone optimizes the fluidization process of the particles, reduces the collision between the particles, and increases the fluidization effect.

[0006] An ALD fluidized bed coating reactor, comprising:

[0007] A heating chamber, at the bottom of the heating chamber there is a flange III connecting the gas transmission pipeline, and at the upper part of the heating chamber there is a filter communicating with the air extraction pipeline;

[0008] A plurality of reaction kettles, all of which are detachably installed between the flange III and the filter. The total length of each reaction kettle is the same. The reaction kettle includes a sealing flange I, a sealing flange II, and a disengagement zone, an expansion zone, and a fluidization zone located between the sealing flange I and the sealing flange II from top to bottom:

[0009] The fluidization zone is a columnar container. Along the height direction of the columnar container, the cross-sections of the columnar container at different heights are the same. The fluidization zone is filled with particles Q to be coated;

[0010] The expansion zone is an inverted conical container, located above the fluidization zone, and is used to provide a larger space to accommodate the coating of the fluidized particles;

[0011] The disengagement zone is a columnar container. Along the height direction of the columnar container, the cross-sections of the columnar container at different heights are the same. The disengagement zone is located above the expansion zone and is used to make the particles B that reach the expected size after coating the coating layer settle back to the fluidization zone;

[0012] The diameter D3 of the disengagement zone is not less than Fv is the designed volumetric flow rate of the fluidizing gas at the ALD operating temperature and pressure, d B and ρ B are respectively the expected diameter of the particles B and the density of the particles B when they reach the expected diameter. ρ and μ are respectively the density and viscosity of the fluidizing gas containing the reaction precursor output from the gas transmission pipeline at the ALD operating temperature and pressure. The diameter D4 of the fluidization zone is less than D'. The density of the particles Q is ρ Q , the diameter of the particles Q before coating is d Q , ε = 0.33 - 0.5. The sum of the height h1 of the fluidization zone and the height h2 of the expansion zone is set to be not less than The height h1 of the fluidization zone is set to be less than And the sum of the volumes of the fluidization zone and the expansion zone is designed as 1 / ε times the bulk volume of the particles Q filled in the fluidization zone, A = 0.25 × π × (D4) 2 , where m is the mass of the particles Q filled in the fluidization zone, and the length of the disengagement zone is the distance between the flange III and the filter minus the sum of the height h1 of the fluidization zone and the height h2 of the expansion zone; the distance between the flange III and the filter in the heating chamber is greater than the sum of the height h1 of the fluidization zone and the height h2 of the expansion zone of all the reaction vessels.

[0013] A gas distributor is provided at the bottom of the fluidization zone for uniformly distributing the fluidization gas carrying the reaction precursor into the fluidization zone.

[0014] Fv is 200 - 500 sccm.

[0015] The heating chamber includes two semi-cylindrical shells hinged to each other. Semi-circular holes are provided on the opposite sides of the upper and lower ends of the semi-cylindrical shells. Heating devices attached to the inner sides of the semi-cylindrical shells are also provided on the opposite sides of the semi-cylindrical shells. When the two semi-cylindrical shells are closed, the two semi-circular holes at the upper and lower ends of the semi-cylindrical shells are butted to form a circular hole, and the circular hole is in interference fit with the flange III and the filter.

[0016] A method for ALD coating of powders, comprising the following steps:

[0017] S1. According to the density ρ Q and diameter d Q of the particles Q to be coated, and the expected diameter d x of the particles B formed after coating with a coating layer having a density of ρ B , calculate the expected density ρ B of the particles B;

[0018] S2. Look up the table to obtain the density ρ and viscosity μ of the fluidization gas containing the reaction precursor at the ALD operating temperature and pressure, and calculate the settling velocity of the particles B

[0019] S3. Calculate the lower limit of the diameter D3 of the disengagement zone based on the designed volume flow rate Fv of the fluidization gas at the ALD operating temperature and pressure

[0020] S4. Determine the diameter D4 of the fluidization zone, and the value ranges of the height h1 of the fluidization zone and the height h2 of the expansion zone according to the following conditions:

[0021] D4 is less than

[0022] A = 0.25 × π × (D4) 2 , where m is the mass of the particles Q filled in the fluidization zone;

[0023]

[0024] ε = 0.33 to 0.5;

[0025] S5. Select a reactor within the ranges of D3, D4, h1, and h2 determined in steps S1 to S4 in the reactor. Load the particles Q with a mass of m into the fluidization zone of the selected reactor. Install the selected reactor in the heating chamber. Control the temperature of the heating chamber to reach the ALD operating temperature in the fluidization zone of the selected reactor. Input fluidization gas into the fluidization zone of the selected reactor through the gas transmission pipeline. Control the pressure in the fluidization zone to reach the ALD operating pressure. Introduce a fluidization gas with a volume flow rate of Fv and containing reaction precursors into the fluidization zone of the selected reactor according to the ALD operation process, so that the particles Q are coated with a coating layer to form particles B with an expected diameter of d B of the particles B.

[0026] The expansion zone can optimize the fluidization of the particles, reduce the collision between the particles, and reduce the flow rate of the fluidization gas.

[0027] The disengagement zone has a wider diameter, can reduce the flow rate of the fluidization gas, and enable the particles B to return to the fluidization zone.

[0028] The present invention can flexibly replace reactors with different capacities on the same heating chamber. The reactors that support replacement support different loading masses of the particles Q, including specifications such as 100 grams, 1 kilogram, and 5 kilograms, which enables the equipment to adapt to diverse experimental and production requirements.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] The device provided by this invention can achieve rapid replacement of the reactor module, greatly improving production efficiency and flexibility. The design of the sealing flange ensures good sealing performance between the reactor module and the main reaction chamber, while simplifying the replacement process. The designs of the fluidization zone, expansion zone, and disengagement zone optimize the fluidization process of the particles, reduce the collision between the particles, and increase the fluidization effect. This device is applicable to working environments that require replacing different reactors to add different amounts of powder, simplifies the time and process, and reduces the consumption of human and material resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a structural schematic diagram of the reactor of the present invention;

[0032] Figure 2 is an example diagram of multiple reactors;

[0033] Figure 3 is a structural schematic diagram of the heating chamber;

[0034] Figure 4 It is a schematic structural diagram of flange III of the heating chamber. Specific implementation mode

[0035] In order to more clearly elaborate the invention purpose, technical solution and invention advantages of the present invention, the present invention will be further described in detail below in conjunction with the specification drawings.

[0036] As Figure 1 shown, an ALD fluidized bed coating reactor includes a heating chamber 6. A flange III 7 connecting the gas transmission pipeline is provided at the bottom of the heating chamber 6. A filter 8 communicating with the air extraction pipeline is provided at the upper part of the heating chamber 6. A reaction kettle is detachably installed between the flange III 7 and the filter 8. The reaction kettle includes a sealing flange I 1, a sealing flange II 5, and a disengagement contact area 2, an expansion area 3, and a fluidization area 4 between the sealing flange I 1 and the sealing flange II 5. The heating chamber 6 includes two semi-cylindrical shells hinged to each other. Semi-circular holes are provided on the opposite sides of the upper and lower ends of the semi-cylindrical shell. A heating device attached to the inner side of the semi-cylindrical shell is also provided on the opposite sides of the semi-cylindrical shell. When the two semi-cylindrical shells are closed, the two semi-circular holes at the upper and lower ends of the semi-cylindrical shell are butted to form a circular hole, and the circular hole is in interference fit with the flange III 7 and the filter.

[0037] The fluidization area 4 is a columnar container. Along the height direction of the columnar container, the cross-sections of the columnar container at different heights are the same. A gas distributor is provided at the bottom of the fluidization area 4 for evenly distributing fluidizing gas into the fluidization area 4;

[0038] The expansion area 3 is an inverted conical container located above the fluidization area 4; it is used to provide a larger space to accommodate the fluidized particles Q to be coated, so that the gaps between the particles Q in the expansion area 3 increase, the particles Q are more dispersed, and it is not easy to form a secondary particle agglomeration system, increasing the contact area between the particles Q and the precursor carried in the fluidizing gas, which is beneficial to forming a uniform coating layer on the surface of the particles Q.

[0039] The disengagement contact area 2 is a columnar container. Along the height direction of the columnar container, the cross-sections of the columnar container at different heights are the same. The disengagement contact area 2 is located above the expansion area 3 and is used to make the particles B that reach the expected size after coating the coating layer settle back to the fluidization area 4. In the fluidization area 4, the gaps between the particles B decrease, reducing the contact area between the particles B after coating the coating layer and the fluidizing gas, and avoiding the continuous thickening of the particles B by coating.

[0040] The particles Q to be coated are fluidized by the fluidizing gas in the fluidization area 4, form a fluidized bed in the fluidization area 4 and the expansion area 3, and are coated with a coating layer. The particles B that reach the expected thickness after coating the coating layer settle along the side wall and return to the fluidization area 4;

[0041] The flange III is hermetically connected to the sealing flange I1, and the sealing flange II5 and the filter are hermetically connected through fasteners and seals.

[0042] The fluidizing gas carrying the precursor enters the reaction kettle from the gas pipeline, fluidizing and coating the particles Q filled in the reaction kettle.

[0043] The diameter of the particle Q is d Q , and the density is ρ Q , the diameter of the particle B is d B , and the density is ρ B , ρ is the density ρ of the fluidizing gas in the fluidization zone 4, the expansion zone 3, and the disengagement zone 2. The fluidizing gas is N2, and the fluidizing gas carries the reaction precursor. The reaction precursor reacts with the particle Q to form a coating on the surface of the particle Q. The flow rate of the fluidizing gas in the fluidization zone 4 is q4, and the cross-sectional area of the fluidization zone 4 is S4.

[0044] The superficial velocity of the fluidizing gas in the fluidization zone 4 is The velocity of the fluidizing gas in the fluidization zone 4 is u4, ε forms the void fraction of the bed layer at incipient fluidization, ε = 0.333 - 0.5 (when designing the height of the fluidized bed layer, generally 1 / 3 - 1 / 2 of the volume occupied by the mg powder material filled in the container), u4 > u0, where u0 is the settling velocity of the particle Q, u B is the settling velocity of the particle B, so that the particle Q to be coated is carried out of the fluidization zone 4 by the fluidizing gas to the expansion zone 3, and the particle B after being coated with the coating layer can settle back to the fluidization zone 4. μ is the viscosity of the fluidizing gas containing the reaction precursor.

[0045] The diameter of the fluidization zone 4 is D4, the diameter of the lower end of the expansion zone 3 is equal to the diameter of the fluidization zone 4, and the diameter of the upper end of the expansion zone 3 is D3. Therefore, the superficial velocity of the fluidizing gas at the upper end of the expansion zone 3

[0046] u mf1 < u4, is the incipient fluidization velocity of the particle Q, is the incipient fluidization velocity of the particle B, u mf2 > u mf1 .

[0047] The diameter D3 of the expansion zone 3 is not less than Fv is the volume flow rate of the fluidizing gas at the operating temperature and pressure. D4 is the set diameter of the fluidization zone, and A is the area of the fluidization zone.

[0048] The sum of the height h1 of the fluidization zone and the height h2 of the expansion zone is set to be not less than The height h1 of the fluidization zone is set to be less than m is the preset mass of the particles Q filled in the reaction kettle, and the height from the upper end of the disengagement zone 2 to the lower end of the fluidization zone 4 is set according to the height of the heating chamber.

[0049] And

[0050] During design, the viscosity of the fluidizing gas can be obtained by looking up the table according to the geometric mean diameter and apparent density of the particles Q, the expected diameter and expected density of the particles B after coating, and the temperature and pressure of the ALD atomic layer deposition reaction, calculate the settling velocity of the particles B and the settling velocity of the particles Q, then calculate the minimum value of the diameter of the disengagement zone according to the operating flow rate of the fluidizing gas in the atomic layer deposition reaction, and finally calculate the initial height of the bed layer when the particles Q form initial fluidization in the reaction kettle according to the porosity range of the bed layer when the particles Q form initial fluidization, the mass of the particles Q filled in the reaction kettle, and the set diameter of the fluidization zone.

[0051] Design the heights of the fluidization zone and the expansion zone so that the sum of the height h1 of the fluidization zone and the height h2 of the expansion zone is not less than The height h1 of the fluidization zone is less than And

[0052] Furthermore, for different types and sizes of particles Q and the particles B after coating, when different masses are filled in the fluidization zones with different cross-sectional sizes, reaction kettles with different sizes need to be designed to meet the fluidization requirements of the particles Q and the settling requirements of the particles B. First, according to each type and size of the particles Q and the particles B after coating according to the requirements of filling different masses in the fluidization zones with different cross-sectional sizes, use the method of this embodiment to design multiple reaction kettles, obtain the lengths of the fluidization zones, the lengths of the expansion zones, and the upper end diameters of the expansion zones in all the designed reaction kettles, find the maximum value of the distance from the lower end of the fluidization zone to the upper end of the expansion zone in all the designed reaction kettles, design the height of the heating chamber to be greater than the maximum value of the distance, extend the lengths of the disengagement zones of all the designed reaction kettles, so that the distance from the lower end of the fluidization zone to the upper end of the disengagement zone of all the designed reaction kettles is equal to the distance between the flange III of the heating chamber and the filter.

[0053] When performing ALD coating using the above-designed ALD fluidized bed coating reactor, reactors with different sizes can be installed between the flange III and the filter to meet the requirements of loading different masses, different types, and sizes of particles Q in fluidization zones with different cross-sectional sizes, and fluidizing and coating particles Q into particles B with different sizes and densities and then settling them. The ALD fluidized bed coating reactor is made compatible with different loading amounts, different types, and sizes of particles Q to be coated into particles B with different types and sizes, greatly improving production efficiency and flexibility. This device is applicable to working environments that require replacing different reactors to add different amounts of powder, simplifies the time and process, and reduces the consumption of human and material resources. Reactors of different sizes have different fluidization zone diameters and lengths, different expansion zone lengths, different disengaging zone diameters and lengths. However, reactors of different sizes can be assembled in heating chambers of the same size for ALD coating operations.

[0054] Traditional ALD atomic layer deposition equipment such as JP7141014B2 mainly uses static coating methods, that is, particles are stacked in a sample fixing net, and rely on the diffusion of precursor molecules to achieve saturated adsorption on the entire surface. This method has no external force field to overcome the agglomeration force, and is only applicable to a small number of particles with good monodispersity, and is not applicable to systems prone to secondary particle agglomeration; at the same time, the particle gaps are small, the diffusion in the gaps is limited, which easily leads to problems such as uneven adsorption and long reaction cycles.

[0055] The present invention also solves the problem that when it is difficult for a fluidized bed with a fixed size to fluidize different sizes and types of powder particles Q and coat them into particles B with different types and sizes, it is difficult to control the particles B that have reached the designed size from continuing to be coated and thickened.

[0056] Taking carbon powder as an example, 10 g of particle Q powder is loaded into the fluidization zone of the reactor. The inner diameter D4 of the fluidization zone is 10 mm, the inner diameter of the expansion zone is 18 mm, the density ρ of particle Q Q is 3.0 g / ml, the diameter d of particle Q before coating Q is 25 nm, alumina layer is coated on the carbon powder, the coating thickness is 21 nm, the diameter d after coating B is 292 nm, the density of alumina is 4.0 g / ml, and the density ρ after coating B is 3.372 g / ml. In the atomic layer deposition reaction, the operating flow rate Fv of the fluidizing gas ranges from 200 to 500 sccm. When the operating flow rate of the fluidizing gas in this embodiment is 200 sccm, the empty bed flow rate is 200 sccm = 200 cm 3 / min, the superficial velocity of the empty bed in the fluidization zone u′4 = 0.0425 m / s, and the superficial velocity of the empty bed in the expansion zone u′3 = 0.0131 m / s. Since the precursor carried by the fluidizing gas needs to react with carbon powder to form the coated alumina at an environment with a temperature of 250 °C and a pressure of 100 torr, the viscosity of the fluidizing gas is obtained by querying the gas viscosity nomogram, and the viscosity of nitrogen at an environment with a temperature of 250 °C and a pressure of 100 torr is μ = 0.0268 mPa·s. The density of nitrogen at an environment with a temperature of 250 °C and a pressure of 100 torr is ρ = 0.0858 g / L.

[0057] u0 = 3.813×10 -6 m / s

[0058] u B = 5.847×10 -6 m / s

[0059] u mf1 = 4.159×10 -8 m / s

[0060] u mf2 = 6.379×10 -8 m / s

[0061] According to the theoretical diameter calculation formula of the expansion zone, When the diameter of the expansion zone is greater than 14.2 mm, the maximum fluidization velocity of the particles is u B The particles will not be carried out of the reaction kettle. The inner diameter of the expansion zone selected in this embodiment is 18 mm. Therefore, the carbon powder with the alumina layer coated on the carbon powder will not leave the reaction kettle because the diameter d B reaches 292 nm, resulting in an excessive sedimentation velocity.

[0062] When the particle Q is in the incomplete fluidization state (i.e., the initial fluidization state), it can satisfy that the particle Q forms a solid continuous phase with small voids and high concentration at the bottom of the fluidization zone, and a small amount of solid particles are entrained by the fluidizing gas to form a bubble phase in the upper part of the fluidization zone. The initial fluidization state makes the particles in the continuous phase agglomerate and is not easily coated, while the particles in the continuous phase gradually move to the bubble phase to form a bed layer with better dispersion, which is conducive to uniform ALD coating. The initial height L of the bed layer formed by the particle Q in the initial fluidization state in the fluidization zone and the pressure difference between the upper and lower ends of the fluidization zone satisfy the following formula:

[0063]

[0064] In the formula, ε is the void fraction of the bed layer when the initial fluidization is formed, and ε = 0.333 - 0.5;

[0065]

[0066] Therefore, the sum of the height h1 of the fluidization zone and the height h2 of the expansion zone is set to be not less than When it is, an incompletely fluidized bed layer can be formed from the fluidization zone to the expansion zone, and the height h1 of the fluidization zone is set to be less than When it is, the bubble phase on the incompletely fluidized bed layer can be more dispersed in the expansion zone, which is beneficial to the uniform ALD coating.

[0067] If ε = 0.5, L = 84.93 mm, and

[0068] When it is

[0069] Then 84.93 mm > h1 ≥ 35.88 mm, 49.04 mm ≥ h2 > 0 mm satisfies the above conditions.

[0070] Furthermore, for different types and sizes of particles Q and the coated particles B, when different masses are loaded in the fluidization zones with different cross-sectional sizes, different-sized reaction vessels need to be designed to meet the requirements of fluidizing particles Q and sedimenting particles B. First, according to the requirements of each type and size of particles Q and the coated particles B for loading different masses in the fluidization zones with different cross-sectional sizes, use the method of this embodiment to design multiple reaction vessels, obtain the length of the fluidization zone, the length of the expansion zone, and the upper-end diameter of the expansion zone in all the designed reaction vessels, find the maximum value of the distance from the lower end of the fluidization zone to the upper end of the expansion zone in all the designed reaction vessels, design the height of the heating chamber to be greater than the maximum value of the distance, extend the length of the disengagement zone of all the designed reaction vessels, and make the distance from the lower end of the fluidization zone to the upper end of the disengagement zone of all the designed reaction vessels equal to the distance between the flange III of the heating chamber and the filter.

[0071] When performing ALD coating using the above-designed ALD fluidized bed coating reactor, reaction vessels with different sizes can be installed between the flange III and the filter to meet the requirements of loading different masses, different types and sizes of particles Q in the fluidization zones with different cross-sectional sizes, and fluidizing particles Q and coating them into particles B with different sizes and densities and sedimenting them. The ALD fluidized bed coating reactor is made compatible with different loading amounts and different types and sizes of particles Q to be coated into different types and sizes of particles B, greatly improving the production efficiency and flexibility. This device is suitable for working environments that require replacing different reaction vessels to add different amounts of powder, simplifies the time and process, and reduces the consumption of human and material resources. Reaction vessels with different sizes have different fluidization zone diameters and lengths, different expansion zone lengths, and different disengagement zone diameters and lengths. However, reaction vessels with different sizes can be assembled in a heating chamber of the same size for ALD coating operations.

[0072] The above description illustrates a preferred embodiment of the present invention and should not be construed as limiting the scope of the claims of the present invention. Without departing from the principles and spirit of the present invention, any modifications, equivalent substitutions, and improvements shall be considered to be within the scope of the claims of the present invention.

Claims

1. An ALD fluidized bed coating reactor, characterized in that, Including: A heating chamber, at the bottom of which there is a flange III connecting to a gas transmission pipeline, and at the upper part of which there is a filter communicating with an air extraction pipeline; A variety of reaction vessels, which are all detachably installed between the flange III and the filter. The total length of each reaction vessel is the same. Inside the reaction vessel, a disengagement contact zone, an expansion zone, and a fluidization zone are respectively arranged from top to bottom. Sealing flanges I and II are respectively arranged at the upper and lower ends of the reaction vessel: The fluidization zone is a columnar container. Along the height direction of the columnar container, the cross-sections at different heights of the columnar container are the same. Particles Q to be coated are filled in the fluidization zone; The expansion zone is an inverted conical container, located above the fluidization zone, and is used to provide a larger space to accommodate the coating of fluidized particles; The disengagement contact zone is a columnar container. Along the height direction of the columnar container, the cross-sections at different heights of the columnar container are the same. The disengagement contact zone is located above the expansion zone and is used to make particles B that reach the expected size after being coated with a coating layer settle back into the fluidization zone; The diameter D3 of the disengaging zone is not less than Fv is the designed volumetric flow rate of the fluidizing gas at the ALD operating temperature and pressure, d B and ρ B are respectively the expected diameter of particle B and the density of particle B when it reaches the expected diameter. ρ and μ are respectively the density and viscosity of the fluidizing gas containing the reaction precursor output from the gas pipeline at the ALD operating temperature and pressure. The diameter D4 of the fluidization zone is less than D’. The density of particle Q is ρ Q , the diameter of particle Q before coating is d Q , ε = 0.33 - 0.5, and the sum of the height h1 of the fluidization zone and the height h2 of the expansion zone is set to be not less than The height h1 of the fluidization zone is set to be less than and the sum of the volumes of the fluidization zone and the expansion zone is designed as 1 / ε times the bulk volume of particle Q filled in the fluidization zone. A = 0.25×π×(D4) 2 , m is the mass of particle Q filled in the fluidization zone. The length of the disengaging zone is the distance between flange III and the filter minus the sum of the height h1 of the fluidization zone and the height h2 of the expansion zone; the distance between flange III and the filter in the heating chamber is greater than the sum of the height h1 of the fluidization zone and the height h2 of the expansion zone of all reactors.

2. The ALD fluidized bed coating reactor according to claim 1, characterized in that, A gas distributor is arranged at the bottom of the fluidization zone and is used to evenly distribute the fluidization gas carrying the reaction precursor into the fluidization zone.

3. The ALD fluidized bed coating reactor according to claim 1, wherein Fv is 200 - 500 sccm.

4. The ALD fluidized bed coating reactor according to claim 1, wherein The heating chamber includes two semi-cylindrical shells that are hinged to each other. Semi-circular holes are arranged on the opposite sides of the upper and lower ends of the semi-cylindrical shells. A heating device attached to the inner side of the semi-cylindrical shell is also arranged on the opposite sides of the semi-cylindrical shells. When the two semi-cylindrical shells are closed, the two semi-circular holes at the upper and lower ends of the semi-cylindrical shells are butted to form a circular hole, and the circular hole is in interference fit with the flange III and the filter.

5. A method for ALD coating of powders, characterized in that, Including the following steps: S1. According to the density ρ Q and diameter d Q of the particles Q to be coated, and the expected diameter d x of the particles B formed after coating with a coating layer having a density of ρ B , calculate the expected density ρ B of the particles B; S2. Look up the density ρ and viscosity μ of the fluidizing gas containing the reaction precursor at the ALD operating temperature and pressure, and calculate the settling velocity of particle B S3. Calculate the lower limit of the diameter D3 of the disengaging zone based on the designed volumetric flow rate Fv of the fluidizing gas at the ALD operating temperature and pressure S4. Determine the value range of the diameter D4 of the fluidization zone, the height h1 of the fluidization zone, and the height h2 of the expansion zone according to the following conditions: D4 is less than A = 0.25 × π × (D4) 2 , where m is the mass of particle Q filled in the fluidized zone; S5. Select a reactor within the ranges of D3, D4, h1, and h2 determined in steps S1 to S4 from the reactors described in any one of claims 1 to 4. Load the particles Q with a mass of m into the fluidization zone of the selected reactor. Install the selected reactor in the heating chamber described in any one of claims 1 to 4. Control the temperature of the heating chamber to reach the ALD operating temperature in the fluidization zone of the selected reactor. Input fluidization gas into the fluidization zone of the selected reactor through the gas transmission pipeline. Control the pressure in the fluidization zone to reach the ALD operating pressure. Introduce a fluidization gas with a volume flow rate of Fv and containing reaction precursors into the fluidization zone of the selected reactor according to the ALD operation process, so that the particles Q are coated with a coating layer to form particles B with an expected diameter of d B of the particles B.

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