Preparation method of barium titanate powder

Abstract

The invention relates to the technical field of chemical synthesis, in particular to a preparation method of barium titanate powder. The preparation method of the barium titanate powder comprises the following steps that raw materials containing a titanium source solution, a barium source solution and an alkaline solution are introduced into a micro-channel of a micro-channel reactor, the micro-channel reactor comprises a shell and a screw rod contained in the shell, and the micro-channel is formed between the surface of the screw rod and the inner wall of the shell; and driving the screw rod to rotate around the shaft, so that the raw materials react in the micro-channel to prepare the barium titanate powder. The preparation method can realize automatic pumping of raw materials, is convenient to operate, reduces the flow resistance and pressure drop effect in the reactor, enables the reaction materials to stably and continuously pass through the microchannel, improves the reaction efficiency, obtains the barium titanate nano-particle product with narrow particle size distribution and controllable morphology, reduces the hole blocking risk, and improves the product quality. The normal use of the micro-channel reactor is ensured.

Description

Technical Field

[0001] This application relates to the field of chemical synthesis technology, and in particular to a method for preparing barium titanate powder. Background Technology

[0002] Barium titanate, as a high-performance electronic ceramic material, is widely used in the manufacture of multilayer ceramic capacitors, semiconductor devices, and sensitive elements.

[0003] Traditional techniques for synthesizing barium titanate powder suffer from problems such as long reaction time, low reaction efficiency, low product purity, and difficulty in achieving continuous preparation. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for preparing barium titanate powder to solve the above-mentioned technical problems.

[0005] A first aspect of this application provides a method for preparing barium titanate powder, the method comprising the following steps: introducing a raw material containing a titanium source solution, a barium source solution and an alkaline solution into a microchannel of a microchannel reactor, the microchannel reactor comprising a shell and a screw housed within the shell, the surface of the screw and the inner wall of the shell forming a microchannel; driving the screw to rotate around an axis to cause the raw material to react in the microchannel to prepare barium titanate powder.

[0006] In some embodiments, driving the screw to rotate about an axis further includes the following step: driving the housing to rotate about an axis, wherein the housing and the screw are coaxially arranged.

[0007] In some embodiments, the direction of rotation of the housing is opposite to the direction of rotation of the screw.

[0008] In some embodiments, to make the raw materials react in the microchannel, the specific steps include: controlling the heating device set on the outer wall of the shell to heat the microchannel reactor so that the temperature inside the microchannel is controlled at 70°C to 90°C.

[0009] In some embodiments, the heating device includes a heating coil fitted onto the outer wall of the housing, with the distance between the heating coil and the outer wall of the housing being 5 mm to 20 mm.

[0010] In some implementations, the reaction time in the microchannel is 10 min to 60 min.

[0011] In some embodiments, the raw materials comprising a titanium source solution, a barium source solution, and an alkaline solution are introduced into the microchannel of the microchannel reactor. Specifically, this includes the following steps: first, the titanium source solution and the barium source solution are introduced into the microchannel of the microchannel reactor for premixing, and then the alkaline solution is pumped in.

[0012] In some embodiments, the molar ratio of titanium source in the titanium source solution to barium source in the barium source solution is 1:(2~5).

[0013] In some embodiments, the concentration of the alkaline solution is 4 mol / L to 8 mol / L.

[0014] In some embodiments, after preparing barium titanate powder, the method further includes the following step: heat-treating the barium titanate powder at a temperature of 950°C to 1050°C.

[0015] In some implementations, the screw speed is controlled to be 800 rpm / min to 3000 rpm / min.

[0016] In some implementations, the thread pitch P of the control screw is 1 mm to 20 mm.

[0017] In some implementations, the groove depth h of the thread on the control screw is 0.01 mm to 10 mm.

[0018] In some implementations, the inclination angle α of the thread on the control screw is 15° to 45°.

[0019] In some implementations, the distance between the inner wall of the control housing and the outer surface of the screw is 0.1 mm to 5 mm.

[0020] In some implementations, the microchannel reactor is controlled in series for reaction.

[0021] Compared with traditional technologies, this application has at least the following beneficial effects:

[0022] The method for preparing barium titanate provided in this application utilizes a screw with a threaded structure to drive the material for conveying and mixing. During the feeding stage, the screw's rotation generates negative pressure at the inlet using fluid viscosity, enabling automatic pumping of the raw material, which is convenient to operate. During the reaction stage, the threads on the screw apply a continuous driving force to the material within the microchannels during rotation, causing the material to spiral forward axially. This reduces the flow resistance and pressure drop effect caused by high viscosity or increased solid content, allowing the reactants to pass stably and continuously through the microchannels, achieving continuous conveying.

[0023] Meanwhile, the rotational shearing effect of the screw threads significantly enhances the mass transfer process within the microchannel, enabling instantaneous and uniform mixing of the titanium source solution, barium source solution, and alkaline solution at the microscale, thereby improving reaction efficiency. Furthermore, this mixing mechanism facilitates rapid and uniform crystal nucleation, controls the crystal growth process, and ultimately yields barium titanate nanoparticles with narrow particle size distribution and controllable morphology.

[0024] In addition, the rotation of the screw exerts a continuous disturbance and transport effect on the barium titanate nanoparticles already generated in the microchannel, effectively preventing the barium titanate nanoparticles from aggregating and depositing in the microchannel, reducing the risk of pore blockage, and ensuring the normal use of the microchannel reactor. Attached Figure Description

[0025] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0026] Figure 1 This is a schematic flowchart of a method for preparing barium titanate powder according to one embodiment of this application.

[0027] Figure 2 This is a three-dimensional structural diagram of a microchannel reactor according to one embodiment of this application.

[0028] Figure 3 This is a schematic diagram of the cross-sectional structure of a microchannel reactor in one embodiment of this application.

[0029] Figure 4 This is a schematic diagram of the screw in the reaction module according to one embodiment of this application.

[0030] Figure 5 This is a partial cross-sectional schematic diagram of the reaction module in one embodiment of this application.

[0031] Figure 6 This is the XRD pattern of the barium titanate powder prepared in Example 1 of this application.

[0032] Figure 7 This is a SEM image of the barium titanate powder prepared in Example 1 of this application.

[0033] Figure 8 The image shows the XRD pattern of the barium titanate powder prepared in Comparative Example 1 of this application.

[0034] Figure 9 This is a SEM image of the barium titanate powder prepared in Comparative Example 1 of this application.

[0035] Figure 10 The image shows the XRD pattern of the barium titanate powder prepared in Comparative Example 5 of this application.

[0036] Figure 11 This is a SEM image of the barium titanate powder prepared in Comparative Example 5 of this application.

[0037] Figure 12The image shows the XRD pattern of the barium titanate powder prepared in Comparative Example 10 of this application.

[0038] Figure 13 This is a SEM image of the barium titanate powder prepared in Comparative Example 10 of this application.

[0039] Explanation of reference numerals in the attached figures

[0040] 1. Microchannel reactor; 10. Reaction module; 11. Shell; 110. Microchannel; 12. Screw; 121. Fixing groove; 13. Drive component; 14. End cap; 15. Fixing frame; 20. Connector; 30. Feed pipe; 31. Feed port; 40. Discharge pipe; 41. Discharge port; P, thread pitch; h, thread groove depth; w, thread groove width; α, thread inclination angle. Detailed Implementation

[0041] Reference will now be made to detailed embodiments of this application, one or more of which are described below. Each example is provided for explanation and not for limitation of this application. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to this application without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0042] Therefore, this application is intended to cover such modifications and variations falling within the scope of the appended claims and their equivalents. Other objects, features, and aspects of this application are disclosed in or will be apparent from the following detailed description. It will be understood by those skilled in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of this application.

[0043] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0044] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0045] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0046] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0047] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0048] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0049] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0050] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0051] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0052] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0053] Barium titanate, as a high-performance electronic ceramic material, is widely used in the manufacture of multilayer ceramic capacitors, semiconductor devices, and sensitive elements.

[0054] In traditional techniques, the synthesis of barium titanate powder mainly relies on batch reaction equipment, such as beakers in laboratories or reaction vessels in industrial production.

[0055] However, the synthesis of barium titanate powder using reactors or beakers suffers from low mass and heat transfer efficiency, long reaction times, and poor efficiency. Furthermore, it is difficult to control crystal nucleation and growth, resulting in low purity and poor batch-to-batch stability of the final product. Additionally, the intermittent preparation method is complex and difficult to scale up for continuous production.

[0056] In recent years, microchannel reactor technology has been introduced into the preparation of barium titanate powder, allowing reactions to occur within micrometer-scale microchannels. This technology leverages the enormous specific surface area provided by the micrometer-scale channels to significantly enhance mass and heat transfer processes, shorten reaction time, improve product morphology and particle size, and demonstrates potential for continuous production.

[0057] Traditional microchannel reactors typically employ static microchannel fabrication on planar substrates. The applicant discovered that these microchannels are fixed and stationary, resulting in a significant pressure drop effect inside the reactor. This increases the difficulty of driving the internal flow system and affects the reaction rate within the microchannels. Furthermore, this structural design poses a risk of pore blockage when preparing barium titanate powder, impacting the normal operation of the microchannel reactor.

[0058] The first aspect of this application, in conjunction with Figures 1 to 5 As shown, a method for preparing barium titanate powder is provided, the method comprising the following steps:

[0059] S1. The raw materials containing titanium source solution, barium source solution and alkaline solution are introduced into the microchannel 110 of the microchannel reactor 1. The microchannel reactor 1 includes a shell 11 and a screw 12 housed in the shell 11. The microchannel 110 is formed between the surface of the screw 12 and the inner wall of the shell 11.

[0060] S2. Drive the screw 12 to rotate around the shaft so that the raw material reacts in the microchannel 110 to prepare barium titanate powder.

[0061] The method for preparing barium titanate provided in this application utilizes a screw 12 with a threaded structure to rotate, thereby conveying and mixing materials. During the feeding stage, the rotation of the screw 12 generates negative pressure at the feed inlet 31 using fluid viscosity, enabling automatic pumping of raw materials and facilitating operation. During the reaction stage, the threads on the screw 12 apply a continuous driving force to the material within the microchannel 110 during rotation, causing the material to spiral forward axially within the microchannel 110. This reduces the flow resistance and pressure drop effect caused by high viscosity or increased solid content, allowing the reactants to pass stably and continuously through the microchannel 110, achieving continuous conveying.

[0062] Meanwhile, the rotational shearing effect of the threads on the screw 12 significantly enhances the mass transfer process within the microchannel 110, enabling instantaneous and uniform mixing of the titanium source solution, barium source solution, and alkaline solution at the microscale, thereby improving reaction efficiency. Furthermore, this mixing mechanism facilitates rapid and uniform crystal nucleation, controls the crystal growth process, and ultimately yields barium titanate nanoparticles with narrow particle size distribution and controllable morphology.

[0063] In addition, the rotation of the screw 12 exerts a continuous disturbance and transport effect on the barium titanate nanoparticles already generated in the microchannel 110, effectively preventing the barium titanate nanoparticles from aggregating and depositing in the microchannel 110, reducing the risk of pore blockage, and ensuring the normal use of the microchannel reactor 1.

[0064] In some embodiments, driving the screw 12 to rotate around an axis further includes the step of driving the housing 11 to rotate around an axis, wherein the housing 11 is coaxially arranged with the screw 12. Thus, by driving the housing 11, which is coaxial with the screw 12, to rotate around an axis, the disturbance and shearing effect on the highly viscous reactants is further enhanced, improving the uniformity of particle dispersion and nucleation, thereby increasing the reaction rate and particle size uniformity of barium titanate nanocrystals.

[0065] In some embodiments, the rotation direction of the shell 11 is opposite to that of the screw 12. This counter-rotating structure increases the relative speed between the shell 11 and the screw 12, further enhancing the shear strength and disturbance frequency within the microchannel 110. During barium titanate synthesis, this structure improves the micro-mixing efficiency of the multi-component system, promotes the instantaneous and uniform reaction of the titanium source, barium source, and alkaline solution, increases reaction efficiency, and improves nucleation uniformity and particle consistency. Simultaneously, the high shear disturbance generated by the counter-rotation also contributes to the continuous transport of solid particles and prevents clogging, improving the operational stability of the microchannel reactor 1 under high solids content conditions.

[0066] In some of these implementations, such as Figure 5 As shown, the inner wall of the housing 11 is threaded. Thus, by providing threads on the inner wall of the housing 11, and working synergistically with the threads of the screw 12, the double-threaded structure forms a multi-point contact flow field disturbance zone, further enhancing the shear strength and disturbance frequency within the microchannel 110. In the preparation of barium titanate powder, this structure is beneficial for improving the mixing and mass transfer efficiency of raw materials in the channel, increasing reaction efficiency, and improving nucleation uniformity and particle consistency. Simultaneously, the synergistic propulsion effect of the inner and outer double-threaded structure helps in the directional transport of solid particles in high-concentration reaction systems, reducing particle accumulation and improving anti-clogging performance. Furthermore, the threads on the inner wall of the housing 11 are identical to the threads on the screw 12.

[0067] In some embodiments, the direction of the thread on the inner wall of the housing 11 is the same as the direction of rotation of the housing 11.

[0068] In some embodiments, the direction of the thread on the screw 12 is the same as the direction of rotation of the screw 12.

[0069] Furthermore, the helix direction of the threads on the inner wall of the housing 11 and the screw 12 is the same as their rotation direction. In this embodiment, the helix direction of the threads of the housing 11 and the screw 12 is consistent with their own rotation direction, thereby generating a synergistic axial transport effect and forming a superimposed propulsion effect in the flow direction. This improves the flowability of high-viscosity or high-solids-content systems in the microchannel 110, and enhances reaction efficiency, nucleation uniformity, and particle consistency during the preparation of barium titanate powder.

[0070] It is understandable that the direction of the thread refers to the direction in which the thread can be screwed in (i.e., generate axial helical driving force) when it rotates. Therefore, when the rotation direction of the screw 12 or the housing 11 is the same as the direction of the thread, an axial helical driving force can be generated to realize the conveying of materials within the microchannel 110.

[0071] In some embodiments, to enable the raw materials to react in the microchannel 110, the following steps are specifically included: controlling a heating device disposed on the outer wall of the shell 11 to heat the microchannel reactor 1, so that the temperature inside the microchannel 110 is controlled at 70°C to 90°C. Exemplarily, the temperature inside the microchannel 110 can be, but is not limited to, 70°C, 75°C, 80°C, 85°C, and 90°C. Within the above temperature range, it is beneficial to promote effective reactions between reactants and accelerate the nucleation rate, while avoiding the problem of rapid grain growth and widening of particle size distribution caused by excessively high temperatures, thereby obtaining barium titanate powder with uniform particle size and good crystallinity.

[0072] In some specific embodiments, the heating device includes a heating coil sleeved on the outer wall of the housing 11, with the distance between the heating coil and the outer wall of the housing 11 being 5 mm to 20 mm. For example, the distance between the heating coil and the outer wall of the housing 11 can be, but is not limited to, 5 mm, 10 mm, 15 mm, or 20 mm. Within the above distance range, the heating coil can achieve uniform and effective heat conduction without directly contacting the housing 11, avoiding localized overheating, ensuring temperature uniformity within the microchannel 110, contributing to the thermal control stability of the reaction process, and thereby improving the consistency of the barium titanate crystal nucleation and growth process.

[0073] In some embodiments, the reaction time in the microchannel 110 is 10 min to 60 min. Exemplarily, the reaction time in the microchannel 110 can be, but is not limited to, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, and 60 min. Within the above reaction time range, the reactants in the microchannel 110 can achieve sufficient mixing, nucleation, and crystal growth. Simultaneously, combined with the strong disturbance environment of the microchannel 110, high-efficiency reactions can be achieved in a short time, balancing product particle size control and continuous production efficiency.

[0074] In some embodiments, a raw material comprising a titanium source solution, a barium source solution, and an alkaline solution is introduced into the microchannel 110 of the microchannel reactor 1. Specifically, this includes the following steps: first, the titanium source solution and the barium source solution are introduced into the microchannel 110 of the microchannel reactor 1 for premixing, and then the alkaline solution is pumped in. Thus, by first premixing the titanium and barium source solutions within the microchannel 110, a uniform ion distribution is achieved; subsequently, the introduction of the alkaline solution triggers the precipitation reaction, which is beneficial for forming uniform nucleation conditions and improving the particle size distribution and morphological uniformity of the barium titanate powder.

[0075] In some embodiments, the molar ratio of titanium source in the titanium source solution to barium source in the barium source solution is 1:(2~5). Exemplarily, the molar ratio of titanium source in the titanium source solution to barium source in the barium source solution can be, but is not limited to, 1:2, 1:3, 1:4, or 1:5. Within the above molar ratio range, an appropriate excess of barium source helps compensate for non-stoichiometric defects that may form during the reaction process, thereby improving the crystallinity of the barium titanate powder.

[0076] In some embodiments, the concentration of the alkaline solution is 4 mol / L to 8 mol / L. Exemplarily, the concentration of the alkaline solution can be, but is not limited to, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, or 8 mol / L.

[0077] In some embodiments, after preparing barium titanate powder, the method further includes the following step: heat-treating the barium titanate powder at a temperature of 950°C to 1050°C. Exemplarily, the heat treatment temperature can be, but is not limited to, 950°C, 975°C, 1000°C, 1025°C, and 1050°C. Within the above-mentioned heat treatment temperature range, the crystallization of barium titanate particles can be effectively promoted, forming a tetragonal crystal phase structure, thereby improving the dielectric properties and stability of the material.

[0078] In some implementations, steps S1 to S2 are repeated for continuous production.

[0079] In some embodiments, the rotational speed of the control screw 12 is 800 rpm / min to 3000 rpm / min. The rotational speed of the screw 12 can be, but is not limited to, 800 rpm / min, 1000 rpm / min, 1500 rpm / min, 2000 rpm / min, 2500 rpm / min, and 3000 rpm / min.

[0080] In some of these implementations, such as Figure 4 As shown, the thread pitch P of the control screw 12 is 1 mm to 20 mm. Exemplarily, the thread pitch P of the screw 12 can be, but is not limited to, 1 mm, 5 mm, 10 mm, 15 mm, and 20 mm. Adjusting the thread pitch P of the screw 12 allows for flexible control of the distribution of the helical propulsion force per unit length, thereby affecting the flow rate and residence time of the material within the microchannel 110. Within the aforementioned thread pitch P range, a balanced control of flow rate and reaction efficiency can be achieved, meeting reaction conditions with different reaction rates and mass transfer requirements.

[0081] In some of these implementations, such as Figure 4As shown, the groove depth h of the thread on the control screw 12 is 0.01 mm to 10 mm. Exemplarily, the groove depth h of the thread on the screw 12 can be, but is not limited to, 0.01 mm, 0.1 mm, 1 mm, 5 mm, and 10 mm. The groove depth h of the thread on the screw 12 affects the material-carrying capacity and shear disturbance capability of the thread structure. Within the above-mentioned groove depth h range, it is possible to improve shear mixing efficiency and reduce the risk of particle deposition while ensuring flow driving force.

[0082] In some of these implementations, such as Figure 4 As shown, the groove width w of the thread on the control screw 12 is 0.5 mm to 15 mm. Exemplarily, the groove width w of the thread on the screw 12 can be, but is not limited to, 0.5 mm, 1 mm, 5 mm, 10 mm, and 15 mm. The groove width w of the thread on the screw 12 affects the cross-sectional size of the channel through which the screw 12 pushes the material and the local flow velocity distribution. Within the aforementioned groove width w range, it is possible to improve shear mixing efficiency and reduce the risk of particle deposition while ensuring the flow driving force.

[0083] In some of these implementations, such as Figure 4 As shown, the tilt angle α of the thread on the control screw 12 is 15°~45°. For example, the tilt angle α of the thread on the screw 12 can be, but is not limited to, 15°, 20°, 25°, 30°, 35°, 40°, and 45°. The thread tilt angle α directly affects the magnitude of the screw propulsion force and the propulsion efficiency. Within the above tilt angle range, a balanced control of flow rate and reaction efficiency can be achieved to meet reaction conditions with different reaction rates and mass transfer requirements.

[0084] The screw 12 can be made of materials such as metal, quartz glass, or ceramic.

[0085] In some embodiments, the distance between the inner wall of the control housing 11 and the outer surface of the screw 12 is 0.1 mm to 5 mm. Exemplarily, the distance between the inner wall of the housing 11 and the outer surface of the screw 12 can be, but is not limited to, 0.1 mm, 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm.

[0086] In some embodiments, the microchannel reactor 1 includes a drive element 13. The drive element 13 is connected to the screw 12 and is used to drive the screw 12 to rotate about an axis. Specifically, the drive element 13 can be an engine.

[0087] Furthermore, the drive unit 13 adjusts the rotational speed via a speed regulator.

[0088] In some embodiments, the microchannel reactor 1 includes at least two reaction modules 10 connected in series. Thus, by connecting at least two reaction modules 10 in series, multi-stage continuous reactions are achieved, facilitating large-scale production.

[0089] Specifically, the reaction module 10 is connected via the connector 20.

[0090] In some embodiments, the reaction module 10 includes an end cap 14 and a mounting bracket 15. The end cap 14 seals both ends of the housing 11 and the screw 12. A mounting hole is provided at the lower end of the end cap 14, through which the mounting bracket 15 is connected to the end cap 14. The mounting bracket 15 is used to fix the reaction module 10. In the event of excessive vibration during reaction rotation, the mounting bracket 15 plays a stabilizing role during operation.

[0091] In some specific embodiments, the screw 12 has fixing grooves 121 at both ends. The fixing grooves 121 are used to fix the screw 1212 to the drive member 13 or the connector 20.

[0092] In some specific embodiments, the screws 12 in two adjacent reaction modules 10 are connected. In this way, by connecting the screws 12 in adjacent reaction modules 10, multiple screws 12 can be driven to rotate in unison by a single drive unit 13, so as to realize the synchronous delivery and propulsion of materials in each stage of the reaction chamber, ensure the consistency of flow rate and the continuity of reaction within the entire system, and avoid flow rate mismatch or stagnation between different modules.

[0093] The reaction module 10 can be made of transparent or non-transparent materials, such as metal, glass, quartz, ceramics, etc., and is suitable for various chemical reactions such as solid phase, liquid phase, and gas phase. It can carry out chemical reactions such as nitration, halogenation, and photocatalysis.

[0094] The size of the reaction module 10 can be designed according to the reaction flow rate (0~1000 mL / min).

[0095] In some embodiments, the microchannel reactor 1 is provided with at least one inlet 31 and at least one outlet 41.

[0096] Specifically, inlet 31 and outlet 41 introduce reactants or take samples through inlet pipe 30 and outlet pipe 40, respectively. The materials of inlet pipe 30 and outlet pipe 40 can be selected according to the reaction conditions, using materials with acid and alkali resistance to meet the needs of different chemical reaction systems.

[0097] In some embodiments, there are multiple feed inlets 31. Reactants in any state of matter, including gas, liquid, and solid, can enter the reaction chamber.

[0098] In some embodiments, there are multiple outlets 41. The outlets 41 are used for two purposes: (1) to transfer reactants to the next reaction module 10. Multiple outlets 41 can transfer reactants at a faster speed; (2) after a single reaction module 10 has completed the reaction, samples can be taken directly to facilitate the collection of data in gradient experiments. Any outlet 41 can be sealed with a rubber stopper. Samples can be collected directly with a syringe, and data collection of microchannels 110 at different reaction degrees can be performed.

[0099] In some embodiments, the drive member 13 drives the screw 12 to rotate about an axis. The thread direction of the screw 12 is set with the rotation direction so that the reactant material is pushed axially and flows from the end near the drive member 13 to the end away from the drive member 13. In this structure, the inlet 31 is located at the end near the drive member 13, and the outlet 41 is located at the end away from the drive member 13.

[0100] The present application will be further described below with reference to specific embodiments and comparative examples.

[0101] Example 1

[0102] This embodiment provides a method for preparing barium titanate powder.

[0103] (1) Raw material preparation

[0104] Prepare a 3.5 mol / L barium chloride solution, a 1 mol / L titanium tetrachloride solution, and a 6 mol / L sodium hydroxide solution.

[0105] (2) Microchannel reactor setup

[0106] The microchannel reactor used in this embodiment has the following structural parameters controlled:

[0107] The microchannel reactor consists of two reaction modules connected in series.

[0108] Screw: The screw is made of stainless steel and has a solid structure with multiple threads; the thread pitch P is 10mm, the groove depth h is 5mm, the groove width w is 8mm, and the thread inclination angle α is 30°.

[0109] Housing: The housing is made of stainless steel. The distance between the inner wall of the housing and the outer surface of the screw is 0.5mm. The inner wall of the housing is threaded. The direction of the thread on the inner wall of the housing is the same as the rotation direction of the housing. The direction of the thread on the screw is the same as the rotation direction of the screw.

[0110] Heating device: A ring-shaped ceramic heater is installed on the outer wall of the shell of each reaction module, with a distance of 12mm between the heater and the outer wall of the shell.

[0111] The feed end of the screw is connected to the engine, and the entire reactor is fixed to a metal plate by a mounting bracket.

[0112] (3) Reaction process

[0113] First, start the heating device to preheat the reactor and maintain the reaction temperature at 80°C; start the engine and set the screw speed to 2000 rpm / min.

[0114] Next, the barium chloride solution and titanium tetrachloride solution prepared in step (1) are introduced into the microreactor cavity through two feed ports in a 1:1 volume ratio for premixing.

[0115] Then, the sodium hydroxide solution prepared in step (1) is introduced into the reactor through the feed inlet to react with the premixed solution. The material continues to react in the reactor for 30 minutes.

[0116] (4) Post-processing

[0117] The product is continuously collected from the reactor outlet, washed and dried, and then heat-treated at 1050℃ to finally obtain barium titanate powder.

[0118] Examples 2-17

[0119] The preparation method and microchannel reactor were similar to those in Example 1. Specifically, the important parameters of the preparation method of barium titanate and the parameters of the microchannel reactor in Examples 2 to 17 are shown in Table 1.

[0120] Comparative Examples 1-8

[0121] The preparation method and microchannel reactor were similar to those used in Example 1. Specifically, the important parameters of the preparation method of barium titanate and the parameters of the microchannel reactor in Comparative Examples 1 to 8 are shown in Table 1.

[0122] Table 1

[0123]

[0124] Comparative Example 9

[0125] This comparative example provides a method for preparing barium titanate powder.

[0126] (1) Prepare a barium chloride solution with a concentration of 3.5 mol / L, a titanium tetrachloride solution with a concentration of 1 mol / L, and a sodium hydroxide solution with a concentration of 6 mol / L.

[0127] (2) Mix the barium chloride solution and titanium tetrachloride solution prepared in step (1) in a volume ratio of 1:1 and heat to 80°C.

[0128] (3) Place the sodium hydroxide solution prepared in step (1) in a beaker and heat it to 80°C until the temperature stabilizes. Then, drop the mixed solution from step (2) into the sodium hydroxide solution and react for 60 min. Collect the reactants and wash them.

[0129] Comparative Example 10

[0130] This comparative example provides a method for preparing barium titanate powder.

[0131] (1) Prepare a barium chloride solution with a concentration of 3.5 mol / L, a titanium tetrachloride solution with a concentration of 1 mol / L, and a sodium hydroxide solution with a concentration of 6 mol / L.

[0132] (2) Mix the barium chloride solution and titanium tetrachloride solution prepared in step (1) in a volume ratio of 1:1 and heat to 80°C.

[0133] (3) Place the sodium hydroxide solution prepared in step (1) in a beaker and heat it to 80°C until the temperature stabilizes. Then, drop the mixed solution from step (2) into the sodium hydroxide solution and react for 180 min. Collect the reactants and wash them.

[0134] The products obtained in the above embodiments and comparative examples were subjected to X-ray diffraction (XRD) analysis to characterize their phase structure, and their microstructure and particle size were observed using scanning electron microscopy (SEM).

[0135] Performance testing

[0136] XRD testing: The crystal structure of the sample was characterized using an X-ray diffractometer (XRD, D8-ADVANCE type, Panalytical, Netherlands).

[0137] SEM testing: The morphology of the samples was characterized using a scanning electron microscope (SEM, Quanta 450FEG, FEI Corporation, USA).

[0138] The test results are shown in Table 2. Figures 6-13 As shown.

[0139] Table 2

[0140]

[0141] As shown in Table 2, the results of Examples 1-17 demonstrate that within the preferred process parameters of this application, barium titanate powder with a pure phase can be successfully prepared, and the product can be obtained within 60 minutes. Figure 6 As shown, the XRD pattern of the product of Example 1 shows clear diffraction peaks belonging to pure tetragonal barium titanate, and no impurity phase peaks appear. Figure 7The SEM images further show that the obtained powder particles are uniform in size and have regular morphology.

[0142] In contrast, Comparative Examples 9 and 10 used the traditional beaker method. Comparative Example 9 failed to produce the target product after 60 minutes of reaction. While Comparative Example 10 produced the target product, it required a reaction time of 180 minutes to obtain the product, and... Figure 12 As shown, the product contains the Ba2TiO4 impurity phase; Figure 13 The SEM images also show that the particles are of varying sizes and have irregular shapes.

[0143] Furthermore, analysis of the data from Examples 1-17 shows that by adjusting the raw material concentration, reaction temperature, reaction time, and equipment structural parameters, the particle size (D50) of barium titanate powder can be effectively controlled within the range of 100 nm to 400 nm.

[0144] Comparing Examples 1-17 and Comparative Examples 1-2, it can be seen that excessively low reactant concentrations (Comparative Example 1) or excessively low reaction temperatures (Comparative Example 2) can lead to incomplete reactions or the formation of impurity phases. In Comparative Example 1, when the reactant concentration is too low, such as... Figure 8 As shown, its XRD pattern contains many impurity peaks, indicating the formation of a titanium-barium mixture; Figure 9 The SEM image also showed an elliptical shape, and no barium titanate crystals were found.

[0145] Comparing Examples 1-17 and Comparative Example 3, it can be seen that the screw speed is a prerequisite for material pumping. When the speed is too low, the thrust generated by the screw is insufficient to overcome the system resistance, resulting in the liquid being unable to be pumped in.

[0146] Comparing Examples 1-17 with Comparative Example 4, it can be seen that if the distance between the outer surface of the screw and the inner wall of the housing is too large, the screw will not be able to form an effective seal and thrust when it rotates, resulting in the liquid not being able to be pumped in.

[0147] Comparing Examples 1-17 with Comparative Examples 5 and 6, it can be seen that parameters such as thread pitch P, groove depth h, and groove width w need to be matched within a reasonable range to obtain ideal products and reduce the formation of impurity phases. Figure 10 As shown, when the thread parameters exceed the preferred range, the XRD pattern shows impurity phase peaks belonging to Ba2TiO4; Figure 11 The SEM images also confirmed that the product morphology was uneven.

[0148] Comparing Examples 1-17 and Comparative Examples 7 and 8, it can be seen that the inclination angle α of the thread directly affects the conveying capacity of the screw. If the inclination angle α is too small, it will result in excessive resistance; if the inclination angle α is too large, it will result in insufficient thrust.

[0149] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0150] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for preparing barium titanate powder, characterized in that, Includes the following steps: A raw material containing a titanium source solution, a barium source solution, and an alkaline solution is introduced into a microchannel of a microchannel reactor. The microchannel reactor includes a shell and a screw housed within the shell, with the microchannel formed between the surface of the screw and the inner wall of the shell. The screw is driven to rotate around the axis so that the raw material reacts in the microchannel to prepare barium titanate powder.

2. The method for preparing barium titanate powder according to claim 1, characterized in that, Driving the screw to rotate about the axis further includes the following steps: The housing is driven to rotate around an axis, and the housing and the screw are coaxially arranged.

3. The method for preparing barium titanate powder according to claim 2, characterized in that, The rotation direction of the housing is opposite to the rotation direction of the screw.

4. The method for preparing barium titanate powder according to claim 1, characterized in that, To enable the raw materials to react in the microchannel, the following steps are specifically included: A heating device installed on the outer wall of the shell is used to heat the microchannel reactor so that the temperature inside the microchannel is controlled at 70℃~90℃.

5. The method for preparing barium titanate powder according to claim 4, characterized in that, The heating device satisfies at least one of the following conditions: (1) The heating device includes a heating coil sleeved on the outer wall of the housing, and the distance between the heating coil and the outer wall of the housing is 5 mm to 20 mm; (2) The reaction time in the microchannel is 10 min to 60 min.

6. The method for preparing barium titanate powder according to claim 1, characterized in that, The raw materials, comprising a titanium source solution, a barium source solution, and an alkaline solution, are introduced into the microchannels of a microchannel reactor, specifically including the following steps: First, the titanium source solution and the barium source solution are introduced into the microchannel of the microchannel reactor for premixing, and then the alkaline solution is introduced.

7. The method for preparing barium titanate powder according to claim 1, characterized in that, The molar ratio of titanium source in the titanium source solution to barium source in the barium source solution is 1:(2~5).

8. The method for preparing barium titanate powder according to claim 1, characterized in that, The concentration of the alkaline solution is 4 mol / L to 8 mol / L.

9. The method for preparing barium titanate powder according to any one of claims 1 to 8, characterized in that, After preparing the barium titanate powder, the method further includes the following steps: The barium titanate powder is subjected to heat treatment at a temperature of 950℃~1050℃.

10. The method for preparing barium titanate powder according to any one of claims 1 to 8, characterized in that, At least one of the following conditions must be met: (1) Control the rotational speed of the screw to 800 rpm / min~3000 rpm / min; (2) The thread pitch P of the screw is controlled to be 1 mm to 20 mm; (3) The groove depth h of the thread on the screw is controlled to be 0.01 mm to 10 mm; (4) Control the inclination angle α of the thread on the screw to be 15°~45°; (5) The distance between the inner wall of the housing and the outer surface of the screw is controlled to be 0.1 mm to 5 mm; (6) Control the series reaction of the microchannel reactor.

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