Device and method for large-scale production of boron nitride nanomaterials

Abstract

This invention relates to the field of chemical production technology and discloses an apparatus and method for the large-scale production of boron nitride nanomaterials. The apparatus includes a vacuum chamber, a cooling water circulation system, a vacuum pumping system, an exhaust system, a gas path, an automatic stirring device, a material reaction container, and a heating device. The automatic stirring device controls the mixing and stirring of the materials. The material reaction container is connected to multiple evenly distributed air inlets. The heating device surrounds the material reaction container and controls the reaction temperature. This invention improves the thermal treatment effect and chemical reaction efficiency of the raw materials in the gas by equipping the material reaction container with an automatic stirring device and multiple densely distributed air inlets, effectively increasing the quality and quantity of materials processed per batch and improving the production efficiency of boron nitride nanomaterials. The apparatus is simple, has low manufacturing cost, and is easy to scale up; the production method is simple, energy-efficient, and pollution-free, meeting the needs of large-scale preparation of boron nitride nanomaterials.

Description

Technical Field

[0001] This invention belongs to the field of chemical production technology, specifically relating to an apparatus and method for the large-scale production of boron nitride nanomaterials. Background Technology

[0002] Boron nitride nanomaterials possess not only the strong mechanical properties, excellent thermal properties, and chemical stability of boron nitride, but also the unique properties of nanomaterials, such as high specific surface area and small size. They exhibit diverse structural characteristics and rich functionalities, leading to significant application demands in filtration, adsorption, catalyst supports, hydrogen storage, drug delivery, and composite material modification. However, the core technology for high-grade boron nitride has long been monopolized by foreign countries. Existing large-scale production processes are generally outdated, resulting in limited product specifications and poor stability. There is an urgent need to increase the yield and productivity of high-quality boron nitride nanomaterials and accelerate large-scale production. The size and morphology of nanomaterials play a decisive role in their performance and applications; therefore, the large-scale synthesis of boron nitride nanomaterials with controllable morphology and uniform size is crucial to realizing their true commercial value.

[0003] Currently, laboratory-scale boron nitride nanomaterial preparation processes have reached their limits, and there are no dedicated devices or technologies available on the market for the large-scale production of high-quality boron nitride nanomaterials. High-temperature furnaces involving gas reactions are typically used for nanomaterial synthesis, primarily including tube furnaces, atmosphere furnaces, and pit furnaces. Tube furnaces are generally suitable for heat treatment of small workpieces or small quantities of experimental samples, employing various atmospheres such as vacuum, protective gas, oxidation, and reduction, and offering strong sealing. Atmosphere furnaces are similar to a combination of box furnaces and tube furnaces, adding the gas-permeable characteristics of tube furnaces to the box furnace, used for processing larger samples requiring gas participation. Pit furnaces generally have a circular furnace chamber, vertically opening and closing doors, and a mechanism similar to crucible high-temperature furnaces. For experimental reactions involving gas participation, tube furnaces are mostly chosen. Before the reaction begins, the gas in the tube is purged to achieve a high vacuum state, and then the reactant gas is introduced to eliminate the influence of airborne impurities. However, their limited reaction space and temperature range restrict the amount of material that can be processed at one time. Especially for the processing of powdered materials, under conditions of limited reaction space, placing too much powder at once can lead to incomplete contact between the material and the reactant gas, resulting in insufficient reaction and further reducing the quality and quantity of material processed per batch. If an atmosphere furnace is used, the gas only contacts the upper layer of powder sample after entering, similarly facing problems such as insufficient powder sample processing per batch and poor reaction quality of the lower layer samples. Furthermore, the utilization rate of the gas introduced into the furnace is low, easily leading to waste, and the high requirements for exhaust gas treatment increase operating costs. Therefore, how to mass-produce boron nitride nanomaterials while simultaneously achieving high-quality preparation with controllable structure and uniform size is a pressing problem to be solved. A large-capacity, gas-permeable, heatable reaction apparatus that improves the utilization rate of reactant gases and increases the thermal and chemical reaction efficiency of the materials is key to achieving large-scale and high-quality synthesis and processing of powdered samples. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an apparatus and method for the large-scale production of boron nitride nanomaterials. By adding a material reaction vessel equipped with an automatic stirring device and a heating device, and multi-point, high-density uniform gas circulation, it is possible to process a large amount of powder materials that require gas participation in a single process for synthesis and heat treatment. The structure is simple and the cost is low, which solves the problems of limited single-processing capacity of powder materials, uneven contact between reaction gas and powder, and low chemical reaction efficiency of materials in existing high-temperature furnace technology.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] An apparatus for the large-scale production of boron nitride nanomaterials includes: a vacuum chamber, a cooling water circulation system, a vacuum pumping system, an exhaust system, a gas path, an automatic stirring device, a material reaction vessel, and a heating device;

[0007] The vacuum chamber is equipped with a switchable door, which has a quartz observation window, a vacuum sealing ring and a lock. The outer wall of the chamber is a cooling water circulating cold wall for overall cooling of the vacuum chamber.

[0008] The automatic stirring device includes a rotary drive, a liftable rod, and stirring blades. The upper end is fixed on the vacuum chamber, and an external frequency converter is connected to the lifting motor and stirring motor to control the mixing and stirring of materials. The stirring blades are built into the material reaction container for continuous mixing and stirring of materials.

[0009] The material reaction vessel has several air inlets evenly distributed along the axis on the side wall below;

[0010] The heating device surrounds the sides and bottom of the material reaction vessel and is used to control the material reaction temperature.

[0011] The device in this invention has a simple structure and can realize the large-scale production of boron nitride nanofibers, boron nitride nanorods, boron nitride nanotubes, boron nitride nanosheets, and porous boron nitride nanomaterials, including but not limited to boron nitride nanofibers, boron nitride nanorods, boron nitride nanotubes, boron nitride nanosheets, and porous boron nitride nanomaterials.

[0012] The present invention has more than one air inlet, with each air inlet spaced 30-800 mm apart, and each air inlet can be independently switched on and off. Preferably, the number of air inlets is 2, 4, 6, 8, or 10.

[0013] The material reaction vessel in this invention can be made of quartz, corundum, or zirconium oxide. Preferably, the material reaction vessel is a cylindrical quartz vessel with a diameter of 50-500 mm.

[0014] The material reaction vessel of this invention is equipped with a container cover on top. Preferably, the container cover can be made of quartz and is circular. A gap is left between the container cover and the lifting rod of the stirring device to form a vent for the escape of reaction gases. Preferably, the gap width is 5-10 mm.

[0015] The back-bottom vacuum of the vacuum chamber described in this invention can reach 10. -2 Pa, the working pressure during the reaction is 1-10 Pa. 5 Pa. Preferably, the back-side vacuum is 10 Pa. -2 Pa, the working pressure during the reaction is 10 Pa. 5 Pa.

[0016] The heating device described in this invention has a heating temperature ranging from room temperature to 1200°C. Preferably, the heating temperature is 500-1000°C.

[0017] This invention also provides a method for large-scale production of boron nitride nanomaterials, comprising:

[0018] 1) Open the vacuum chamber door, place the raw materials into the material reaction vessel, and close the vessel lid;

[0019] 2) Close the vacuum chamber door, start evacuating the vacuum until the specified back vacuum is ensured to remove gas impurities, then close the evacuation port, turn off the vacuum pump, introduce inert gas until atmospheric pressure is reached, open the exhaust port, turn on the cooling water circulation system, start heating, and start the automatic stirring device to mix and stir the material inside the material reaction container by rotating it up and down. At the same time, after heating to the specified reaction temperature, introduce the reaction gas and start the reaction.

[0020] 3) After the reaction is complete, turn off the reaction gas, cool down until it reaches room temperature, then stop stirring, turn off the inert gas, and shut off the cooling water circulation system.

[0021] 4) Open the vacuum chamber door, open the container lid, and take out the reacted material to obtain boron nitride nanomaterials.

[0022] The boron nitride nanomaterials described in this invention can be boron nitride nanofibers, boron nitride nanorods, boron nitride nanotubes, boron nitride nanosheets, and porous boron nitride nanomaterials.

[0023] The boron nitride nanofibers prepared by the method of the present invention have a length of 1-100 micrometers.

[0024] The boron nitride nanorods prepared by the method of the present invention have a diameter of 0.1-1 micrometers.

[0025] The boron nitride nanotubes prepared by the method of the present invention have a length of 1-100 micrometers.

[0026] The boron nitride nanosheets prepared by the method of the present invention have a thickness of 1-20 nanometers.

[0027] The porous boron nitride nanomaterials prepared by the method of the present invention have a specific surface area greater than 1400 cm². 2 / g.

[0028] The reaction temperature described in this invention is 500-1000℃.

[0029] The reaction gas described in this invention can be ammonia, and the inert gas can be argon or nitrogen.

[0030] The raw materials described in this invention can be melamine, urea, boric acid, or borax.

[0031] The beneficial effects of this invention include:

[0032] (1) Currently, the mainstream reaction devices in laboratories mainly adopt high-temperature furnaces. The reaction space, atmosphere flow mode, and precursor reaction mode are often limited by the cavity structure and preparation process, resulting in limited one-time output and low morphology controllability. This invention breaks through the limitations of high-temperature preparation process, designs a brand-new high-temperature reaction cavity structure, and introduces a dynamic reaction device. That is, by adding a material reaction container with an automatic stirring device and a heating device and multi-point, high-density uniform gas circulation, the uniformity of material heating is increased while increasing its contact area with the reaction gas, so that the material and the reaction atmosphere are in continuous rolling contact, improving the high-temperature processing efficiency and scale of the material, realizing high-temperature processing and chemical reaction of the material in a single large-scale process, increasing the yield and productivity of boron nitride nanomaterials, and by fully controlling the gas phase reaction atmosphere, it is possible to achieve large-scale production of boron nitride nanomaterials with uniform morphology and size.

[0033] (2) The outermost vacuum chamber of the present invention has good sealing performance and can process materials under vacuum conditions, while adopting a cold wall structure to greatly reduce heat dissipation.

[0034] (3) The present invention has a simple structure, requires little installation space, has low manufacturing cost, maximizes heat utilization and reaction gas utilization, and has low energy consumption; the synthesis process is simple and controllable, green and environmentally friendly, and easy to scale up production; the chemical raw materials and by-products are pollution-free, environmentally friendly, and conducive to long-term ecological sustainable development.

[0035] (4) Currently, similar technologies can only prepare single specific boron nitride nanostructures, such as boron nitride nanotubes or boron nitride nanospheres. However, this invention can prepare large quantities of other nanomaterials, including but not limited to boron nitride nanofibers, boron nitride nanorods, boron nitride nanotubes, boron nitride nanosheets, and porous boron nitride nanomaterials, by using precursors and controlling the corresponding reaction process parameters. It has a certain degree of universality. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings are only used to illustrate specific embodiments and are not intended to limit the present invention.

[0037] Figure 1 This is a schematic diagram of the overall structure of a preferred embodiment of a boron nitride nanomaterial mass production device provided in Embodiment 1 of the present invention;

[0038] Figure 2 This is a cross-sectional view of the material reaction vessel during operation of a boron nitride nanomaterial large-scale production device provided in Embodiment 1 of the present invention;

[0039] Figure 3This is a cross-sectional view of the material reaction vessel of a boron nitride nanomaterial mass production device provided in Embodiment 1 of the present invention when it is opened;

[0040] Figure 4 This is a top view of an automatic stirring device and material reaction vessel assembly for a boron nitride nanomaterial mass production apparatus provided in Embodiment 1 of the present invention;

[0041] Figure 5 This is a top view of the air inlet distribution of a boron nitride nanomaterial mass production device provided in Embodiment 1 of the present invention;

[0042] Figure 6 This is a scanning electron microscope image of the porous boron nitride nanorods prepared in Example 2 of the present invention;

[0043] Figure 7 This is a transmission electron microscope image of the porous boron nitride nanorods prepared in Example 2 of the present invention;

[0044] Figure 8 This is a scanning electron microscope image of the porous boron nitride nanofibers prepared in Example 3 of the present invention;

[0045] Figure 9 This is a scanning electron microscope image of the porous boron nitride nanofibers prepared in Example 3 of the present invention;

[0046] Figure 10 This is a schematic diagram of an alternative configuration of the automatic stirring device and material reaction vessel assembly in a boron nitride nanomaterial large-scale production device provided in Embodiment 4 of the present invention, representing a modification scheme for a conventional atmosphere furnace.

[0047] Reference numerals in the attached drawings: 1. Vacuum chamber; 2. Material reaction vessel cover; 3. Material reaction vessel body; 4. Air inlet; 5. Rotary drive component; 6. Liftable rod; 7. Stirring blades; 8. Heating device; 9. Air outlet. Detailed Implementation

[0048] To make the technical means, structural features, objectives and effects of this invention easier to understand, further explanations are provided below in conjunction with specific embodiments.

[0049] It should be noted that the described embodiments are only a portion of the embodiments of the present invention, and the components of the embodiments of the present invention described in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0050] Example 1

[0051] See also Figures 1 to 5 This embodiment provides a boron nitride nanomaterial large-scale production device, which uses rotating blades to stir the heat-treated material, solving the problems of limited space in existing tube furnaces and incomplete reaction of bottom materials in atmosphere furnaces. It has a simple structure, low manufacturing cost, improves gas and heat utilization, saves energy, and is economical.

[0052] The boron nitride nanomaterial large-scale production apparatus provided in this embodiment includes a vacuum chamber, a vacuum pumping system, an exhaust system, a gas path, an automatic stirring device, a material reaction container, and a heating device. The automatic stirring device includes a rotary drive, a lifting rod, and stirring blades. The rotary drive is fixed at the top of the vacuum chamber to provide stirring power to the blades. The blades are connected to the drive via the lifting rod and placed inside the reaction chamber. The heating device surrounds the side walls and bottom of the material reaction container.

[0053] In this embodiment, 10 air inlets are provided at the lower end of the side wall of the reaction chamber, evenly distributed around the bottom of the material reaction container, and each air inlet can be either open or closed.

[0054] In this embodiment, three blades are used for stirring. The outer edge of the blades is as close as possible to the inner wall of the material reaction vessel, and the bottom is attached to the bottom of the material reaction vessel. During operation, the blades rotate and mix the material, and simultaneously move up and down to ensure that the material is fully mixed, in contact with the reaction gas, and reacts.

[0055] In this embodiment, the gap between the top cover of the material reaction container and the lifting rod of the automatic stirring device is 10 mm, forming an outlet for the reaction gas to escape.

[0056] In this embodiment, when using the present invention, firstly, the operator places the material to be processed into the material reaction container, adjusts the blade height, inserts the blade into the material, and simultaneously closes the top cover of the material reaction container, thus closing the vacuum chamber. Then, the vacuum pumping system is turned on, and after reaching the required vacuum level, the pumping port and vacuum pump are closed. Next, the gas required for the reaction is filled until the internal gas pressure of the device is the same as or slightly higher than atmospheric pressure. The exhaust port is then opened; if necessary, the exhaust port can be connected to a tail gas treatment device. Finally, the heating and stirring programs are started, and the instrument begins to operate automatically.

[0057] Example 2

[0058] This embodiment provides a method for the large-scale production of porous boron nitride nanorods. Specifically, boric acid and melamine are used as boron and nitrogen sources, respectively, to prepare precursors. Boric acid and melamine in a molar ratio of 2:1 are dissolved in water at 60°C using a constant-temperature magnetic stirrer. After complete dissolution, the temperature is raised to 90°C until the water is completely evaporated (with stirring throughout). The product is then transferred to a forced-air drying oven and dried for 18 hours to obtain the boron nitride nanomaterial precursor. The precursor material is placed in the material reaction vessel of this invention. The height of the stirring blades is adjusted until they are inserted into the material, and the top cover of the material reaction vessel is closed, along with the vacuum chamber. Then, a vacuum pumping system is used to achieve the required vacuum level, and the evacuation port and vacuum pump are closed. Next, fill the device with inert gas until the internal pressure is the same as or slightly higher than atmospheric pressure. Open the exhaust port, which needs to be connected to the exhaust gas treatment device. Start the cooling water circulation system, heating program and stirring program, and heat to 800°C at a rate of 5°C / min. Introduce ammonia gas, keep it at the temperature for 5 hours, and let it cool naturally to room temperature to obtain white powdery porous boron nitride nanorods.

[0059] Figure 6 The image shown is a scanning electron microscope image of boron nitride prepared in Example 2. It can be seen that boron nitride has a rod-like structure with a size of 1-20 μm. Figure 7 The image shown is a transmission electron microscope image of the boron nitride nanorods prepared in Example 2, which shows that the boron nitride fibers have a uniformly distributed and abundant porous structure.

[0060] Example 3

[0061] This embodiment provides a method for the large-scale production of porous boron nitride nanofibers. Specifically, boric acid and melamine are used as boron and nitrogen sources, respectively, to prepare precursors. Boric acid and melamine in a molar ratio of 2:1 are dissolved in water at 60°C using a constant-temperature magnetic stirrer. After complete dissolution, the temperature is raised to 90°C and maintained for 2 hours (with constant stirring). The product is then transferred to a freeze dryer for drying to obtain the boron nitride nanomaterial precursor. The precursor material is placed in the material reaction vessel of the large-scale production apparatus for boron nitride nanomaterials of this invention. The height of the stirring blades is adjusted until they are inserted into the material, and the top cover of the material reaction vessel is closed, thus closing the vacuum chamber. Then, a vacuum pumping system is used to achieve the required vacuum level, and the evacuation port and vacuum pump are closed. Next, fill the device with inert gas until the internal pressure is the same as or slightly higher than atmospheric pressure. Open the exhaust port, which needs to be connected to the exhaust gas treatment device. Start the cooling water circulation system, heating program and stirring program. Heat to 800°C at a rate of 5°C / min. Introduce ammonia gas, keep it at the temperature for 5 hours, and let it cool naturally to room temperature to obtain white powdery porous boron nitride fiber.

[0062] Figure 8The image shows a scanning electron microscope image of boron nitride prepared in Example 2. It can be seen that boron nitride has a fibrous structure with a size of 20-90 μm. Figure 9 The image shown is a transmission electron microscope image of the boron nitride fiber prepared in Example 2, which shows that the boron nitride fiber has a uniformly distributed and abundant porous structure.

[0063] Example 4

[0064] See also Figure 10 This embodiment provides another configuration of the component of the present invention for the modification of a conventional atmosphere furnace.

[0065] The modification of the commercial atmosphere furnace provided in this embodiment specifically involves the material reaction vessel and stirring device assembly of the present invention.

[0066] In this embodiment, the material reaction vessel is placed directly inside the original furnace reaction chamber.

[0067] In this embodiment, the stirring device includes blades, a lifting rod, and a rotary drive component. The blades are connected to the rotary drive component via the lifting rod. The drive component is fixed to the top of the atmosphere furnace and a sealing layer is installed on the top of the furnace to ensure the vacuum level.

[0068] In this embodiment, there are two rotating blades, and the two blades are spread as close as possible to the inner diameter of the reaction chamber, and are attached to the bottom of the reaction chamber.

[0069] In this embodiment, when using the present invention, the operating system of the original atmosphere furnace is combined with the material to be reacted and placed into the material reaction container of the present invention. First, the inside of the furnace reaction chamber is vacuumed. Then, when the reaction gas is introduced to reach equilibrium with the atmospheric pressure or slightly higher than the atmospheric pressure, the exhaust port is opened. Finally, the stirring device and heating program are started.

[0070] This embodiment illustrates a method for modifying existing equipment with minimal cost. The modified atmosphere furnace is no longer limited to heat treatment of large-sized bulk materials. The modified high-temperature furnace is also suitable for processing large quantities of powder samples. Furthermore, the main body of the material reaction vessel of this invention can be removed from the original furnace body at any time. After the lifting rod is raised, it will only occupy a small part of the original furnace chamber space, allowing the atmosphere furnace to still process large-sized bulk materials and retain its original function.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An apparatus for the large-scale production of boron nitride nanomaterials, characterized in that, include: Vacuum chamber, cooling water circulation system, vacuum pumping system, exhaust system, gas path, automatic stirring device, material reaction vessel and heating device; The vacuum chamber is equipped with a switchable door, which has a quartz observation window, a vacuum sealing ring and a lock. The outer wall of the chamber is a cooling water circulating cold wall for overall cooling of the vacuum chamber. The automatic stirring device includes a rotary drive, a liftable rod, and stirring blades. The upper end is fixed on the vacuum chamber, and an external frequency converter is connected to the lifting motor and stirring motor to control the mixing and stirring of materials. The stirring blades are built into the material reaction container for continuous mixing and stirring of materials. The material reaction vessel has several air inlets evenly distributed along the axis on the side wall below; The heating device surrounds the sides and bottom of the material reaction vessel and is used to control the material reaction temperature; The material reaction vessel is equipped with a container cover on top, and a gap is left between the container cover and the lifting rod of the stirring device to form a gas outlet for the reaction gas to escape.

2. The apparatus for large-scale production of boron nitride nanomaterials according to claim 1, characterized in that, The number of air inlets is greater than 1, the distance between each air inlet is 30-800 mm, and each air inlet can be opened and closed independently.

3. The apparatus for large-scale production of boron nitride nanomaterials according to claim 1, characterized in that, The material reaction vessel is cylindrical and made of quartz, corundum, or zirconium oxide, with a diameter of 50-500 mm.

4. The apparatus for large-scale production of boron nitride nanomaterials according to claim 1, characterized in that, The back vacuum of the vacuum chamber can reach 10. -2 Pa, the working pressure during the reaction is 1-10 Pa. 5 Pa.

5. The apparatus for large-scale production of boron nitride nanomaterials according to claim 1, characterized in that, The heating device has a heating temperature ranging from room temperature to 1200°C. o C.

6. The apparatus for large-scale production of boron nitride nanomaterials according to claim 1, characterized in that, The device can be used for the large-scale production of boron nitride nanofibers, boron nitride nanorods, boron nitride nanotubes, boron nitride nanosheets, and porous boron nitride nanomaterials, including but not limited to.

7. A method for large-scale production of boron nitride nanomaterials, characterized in that, Using the apparatus according to any one of claims 1-6, the steps include: 1) Open the vacuum chamber door, place the raw materials into the material reaction vessel, and close the vessel lid; 2) Close the vacuum chamber door, start evacuating the vacuum until the specified back vacuum is ensured to remove gas impurities, then close the evacuation port, turn off the vacuum pump, introduce inert gas until atmospheric pressure is reached, open the exhaust port, turn on the cooling water circulation system, start heating, start the automatic stirring device, and rotate and mix the material inside the material reaction container. At the same time, after heating to the specified reaction temperature, introduce the reaction gas and start the reaction. 3) After the reaction is complete, turn off the reaction gas, cool down until it reaches room temperature, then stop stirring, turn off the inert gas, and shut off the cooling water circulation system; 4) Open the vacuum chamber door, open the container lid, and take out the reacted material to obtain boron nitride nanomaterials.

8. The method for large-scale production of boron nitride nanomaterials according to claim 7, characterized in that, The method can be used for the large-scale production of boron nitride nanofibers, boron nitride nanorods, boron nitride nanotubes, boron nitride nanosheets, and porous boron nitride nanomaterials, including but not limited to.

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