Built-in heating device and method for black phosphorus crystal preparation

Abstract

The invention provides a built-in heating device and method for black phosphorus crystal preparation, and relates to the technical field of black phosphorus crystal preparation. Activated carbon is utilized to perform surface activation and reduction on an easily oxidized part of an industrial catalyst under a vacuum heating condition, so that the surface activity of the catalyst is improved; under the protection atmosphere of inert gas, the activated catalyst and red phosphorus-iodine are respectively placed in raw material elements, and a reaction system is completely sealed; high-efficiency heating conversion of raw materials is realized through a heating control system, and the raw materials are uniformly and fully prepared to fully react by regulating and controlling a raw material separation element, so that growth of high-quality and high-yield black phosphorus crystals is realized; and after the reaction is finished, naturally cooling to room temperature, and opening the kettle to obtain a final black phosphorus product. The utilization rate of the raw materials is improved by activating the catalyst; temperature is regulated through internal and external heating to realize internal temperature control of the reaction system so as to regulate the transportation efficiency of the raw materials, improve the stability of the temperature field of the reaction system and promote effective transportation of the raw materials.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of a novel two-dimensional material black phosphorus, and in particular to a built-in heating device and method for preparing black phosphorus crystals. Background Art

[0002] Black phosphorus has become one of the important candidate materials for the next generation of electronic and optoelectronic applications after semiconductor materials such as silicon, due to its unique properties such as high carrier mobility, wide and adjustable direct band gap, and atomic layer van der Waals integration. A large number of studies have shown that by adjusting the energy band number of black phosphorus (0.3~0.2 eV), it is possible to switch between the insulating and conductive states, and the electron migration speed of black phosphorus is fast (greater than 1000 cm 2 V -1 s -1 ), the closure is more significant (10 5 ), which has greatly promoted its widespread application in the field of electronic and optoelectronic devices. Due to the unique mechanical properties, electrochemical properties and thermal anisotropy of black phosphorus, it is not only used in the field of field effect transistors, but also shows a booming application prospect in various fields such as new energy batteries, high-efficiency catalysis, optoelectronic communications and biomedicine.

[0003] Compared with the method of preparing black phosphorus crystals by single external heating, the method of adding a built-in heating device and using the device to grow black phosphorus crystals can achieve high-yield and high-quality controllable preparation of black phosphorus crystals. Due to the harsh conditions for the preparation of black phosphorus, there are great obstacles to controllable large-scale growth in industrial-scale production due to technical problems. At present, the methods for preparing black phosphorus worldwide mainly include mineralization, bismuth melting, mechanical ball milling, mercury reflux and high-pressure methods, among which only the mineralization method has been widely recognized by scientists and can achieve large-scale production. The preparation of high-quality black phosphorus crystals in a closed reaction system by using a chemical vapor phase method has received widespread attention and plays a vital role in promoting the application of black phosphorus. However, there are still key problems in the preparation of black phosphorus by mineralization: 1. Since it is difficult to accurately control the internal raw material diffusion rate to achieve large-scale preparation of crystals in a closed reaction system by controlling the heating rate only through external heating, the raw materials will agglomerate seriously after being heated for a period of time, and only a small amount of phosphorus vapor will migrate, making it difficult to achieve the continued nucleation and growth of black phosphorus crystals, resulting in difficulties in the large-scale growth and preparation of black phosphorus crystals; 2. The serious problem of catalyst deactivation has not been verified and analyzed, resulting in insufficient reaction, which seriously reduces the catalytic efficiency of the catalyst and the unstable crystal nucleation, making it difficult to achieve efficient preparation of large-scale black phosphorus crystals; 3. After the reaction is completed, there are many by-products that are difficult to recycle, and it is easy to endanger the safety of experimental personnel, etc., which makes the preparation cost of black phosphorus high, the utilization rate of raw materials low, and the safety risk high, which is not conducive to large-scale production. To this end, an internal heating device and method for preparing black phosphorus crystals are developed and proposed. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides an internal heating device and method for preparing black phosphorus crystals. The purpose of the present invention is to provide a method for preparing black phosphorus crystals with a built-in heating reaction system in view of the problems existing in the large-scale preparation of black phosphorus by the above mineralization method. The method can firstly realize the large-scale preparation of high-yield and high-quality products; secondly, a device is designed to provide the necessary basic conditions for the implementation of the method; thirdly, the utilization rate of raw materials can be significantly improved by using the method and the device, saving the cost of crystal preparation; fourthly, the device can be connected with the current yellow phosphorus tail gas pipeline for filtering and preparing red phosphorus assembly, and the continuous production and preparation of black phosphorus crystals can be realized by adopting a process treatment route based on yellow phosphorus tail gas.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A built-in heating device and method for preparing black phosphorus crystals, wherein Figure 1 The schematic diagram of the device shown, the devices mainly used in the reaction system include: The reaction kettle of the reaction system mainly includes a cylinder for reaction and a kettle cover for sealing the cylinder; The raw material crucible is fixed in the cylinder, and a heater is arranged at the bottom of the raw material crucible; The raw material crucible is a double-layer structure, with telescopic movement control elements on both sides of the outer layer. The left and right sides of the telescopic unit are placed at the lower end of the raw material crucible and fixed, and the raw material is compressed and moved downward during the feeding process; after the reaction starts, the raw material is transported upward, and the telescopic unit expands and moves upward; The catalyst crucible is placed on the upper end of the raw material crucible; A heater for internally heating the reaction system is connected to an external heating control system; The pressure transmitter is connected to the heating control system.

[0006] The raw material crucible is a double-layer structure with a porous structure on the inside. The inner layer of the raw material crucible is a porous structure, and a telescopic separation partition is placed and fixed between the inner and outer layers of the raw material crucible. The telescopic separation partition is automatically telescoped between the inner and outer layers of the raw material crucible to realize automatic separation of the raw materials, thereby realizing the transportation of the raw materials. The aperture size is 60-80 mesh.

[0007] A catalyst filtering device is arranged at the lower part of the raw material crucible, and a catalyst collecting and recovering device is located at the bottom of the cylinder.

[0008] The heater is provided with a temperature detection pipe, and the temperature sensor is connected to the temperature detection pipe to realize the temperature control of the heater; The pressure transmitter is connected to the pressure detection pipeline through a pressure regulating valve and is used to detect the pressure in the cylinder.

[0009] A heating furnace for external heating of the entire reaction system is connected to the heating reaction system.

[0010] The heating wire of the heater is made of iron-chromium-aluminum alloy series and nickel-chromium electric heating alloy.

[0011] The method for preparing black phosphorus crystals using a built-in heating reaction system of the present invention comprises the following steps: S1, weighing two raw materials, industrial tin powder and activated carbon, in a protective gas atmosphere, placing them in a crucible and placing them in a small reactor for complete sealing, heating and activating them in a tube furnace after they are completely sealed, and taking them out and placing them in a sealed bottle in a protective gas atmosphere for standby use after they are completely activated; S2, under a protective gas atmosphere, open the valve of the pressure detection pipeline of the reaction system, weigh a certain proportion of red phosphorus, carbon-activated tin and iodine, and place the red phosphorus and iodine in a reaction raw material crucible respectively, and place the carbon-activated tin catalyst in a catalyst element crucible, and the particle size of the red phosphorus and iodine is 50-70 mesh; S3, placing the reactor cover on the top of the reaction cylinder to completely seal the reactor; S4, after the packaging is completed, the heater, external heating system and temperature and pressure probe device in the reaction system are programmed. After the program setting is completed, the heating control system is turned on to heat the reaction system: by programming the temperature of the reaction furnace 1-6 sections, the upper section 1-3 of the reaction furnace is heated from room temperature to 500-530°C in 30-90 minutes, and the lower section 4-6 of the reaction furnace is heated from room temperature to 550-590°C in 30-90 minutes; the reactor is heated by an electric heater, and the reaction system is temperature controlled by the internal heater and the external heating furnace; the built-in heating The temperature of the reaction system is increased by a combined control of the heat exchanger and the external heating furnace. The bottom is heated from room temperature to 210-300°C at 3-12°C / min over 15-90min, then to 450-480°C at 3-12°C / min over 15-70min, and then to 550-600°C at 5-12°C / min over 8min-24min. The lower end of the upper kettle cover of the sealed cylinder is heated from room temperature to 270-330°C at 5-12°C / min over 20-60min, and then to 450-480°C at 3-12°C / min over 15-70min. min to 470-500℃, then 3-10℃ / min to 500-590℃ after 0-30min, and the heating rate in the reaction system is regulated. By controlling the moving rate of the telescopic separation partition to 0cm / s-10cm / s, combined with the pore size of the inner layer of the raw material crucible to 60-80 mesh, the raw material separation flow rate is regulated to 0g / s-100g / s, and the spring is controlled to rise at a rate of 0.5-3.5cm / min. The preparation of high-quality and high-yield black phosphorus crystals is achieved, and the catalyst filtered after the reaction is recovered through the recovery element and reused.

[0012] As a preferred technical solution, the mass ratio of tin powder to activated carbon during activation in S1 is tin:carbon=100:1~50:1, and the activation temperature is 100~200°C.

[0013] As a preferred technical solution, the raw material ratio of the reaction system described in S2 is red phosphorus: tin (carbon): iodine = 100:6:0.5~100:10:4.

[0014] As a preferred technical solution, the raw material crucible of the reaction system described in S2 can achieve efficient conversion and full contact of the catalyst and the red phosphorus raw material in the reaction process after heating and separating the raw materials.

[0015] As a preferred technical solution, the reaction system raw material crucible described in S2 can be moved up and down by a lateral telescopic element, moved upward by utilizing the raw material reaction conversion, and compressed downward to the lowest point by utilizing the maximum amount of initial raw materials. The lowest point is located at 1 / 4 to 1 / 3 of the reaction cylinder.

[0016] As a preferred technical solution, the raw material crucible of the reaction system described in S2 is a double-layer structure and a porous structure with a pore size of 60-80 mesh and a porous structure on the inside. After rapid heating to 480°C, the partitions on both sides of the interval expand thermally and push and pull the inner raw material separation layer of the raw material crucible forward around the inner raw material crucible to achieve automatic separation of the raw materials, and contact the catalyst to achieve upward transport of the catalyst and raw materials, and transport them to the lower end of the top reactor cover to start the nucleation and growth of black phosphorus crystals, thereby reducing the probability of material compaction.

[0017] As a preferred technical solution, the heating wire of the heater in S4 is made of iron-chromium-aluminum alloy series, nickel-chromium electric heating alloy, etc.

[0018] As a preferred technical solution, the external heating device in S4 is an external heating furnace and the heating program is a multi-stage controllable heating program. In the reactor temperature program, the upper 1-3 sections of the reactor are heated from room temperature to 510-520°C in 50-60 minutes, and the lower 4-6 sections of the reactor are heated from room temperature to 550-560°C in 50-60 minutes.

[0019] As a preferred technical solution, the built-in heater heating program in S4 adopts a gradient heating program to achieve the temperature conditions required for the upward transportation of the raw materials. The bottom of the raw material crucible is heated from room temperature to 270°C at 8-10°C / min for 24-30min, then heated to 470°C at 8-10°C / min for 20-25min, and then heated to 550-590°C at 8-10°C / min for 8min-15min. As a preferred technical solution, the lower end of the kettle cover on the sealed cylinder in S4 is heated by gradient from room temperature to 260°C at 8-10°C / min for 24-30min, then to 470-500°C at 8-10°C / min for 15-25min, and then to 510-590°C at 8-10°C / min for 1-9min to control the heating rate in the reaction system, by controlling the moving rate of the telescopic separation baffle to 1cm / s-5cm / s, more preferably to 1 cm / s-5cm / s, combined with the pore size of the inner layer of the raw material crucible of 60-80 mesh, the raw material separation flow rate is regulated to 10g / s-50g / s, and the spring is controlled to rise at a rate of 1.0-3.0 cm / min, more preferably at a rate of 1-1.5cm / min.

[0020] As a preferred technical solution, the combination of internal and external heating and temperature control described in S4 is used to regulate the heating rate inside the reaction system so that the raw materials can be efficiently and directionally transported and converted in the reaction system.

[0021] As a preferred technical solution, the temperature detection device of the reaction system described in S4 can realize temperature monitoring in the range of 500-600°C and alarm after over-temperature and stop heating of the reaction system to ensure the safety and stability of the experiment.

[0022] As a preferred technical solution, by increasing the number of feeding times, the amount of iodine fed from the bottom to the top in the material crucible device is gradually reduced.

[0023] As a preferred technical solution, after the tin reaches the liquefaction temperature in the upper material crucible device, it can be automatically controlled to discharge downward through the porous structure. The aperture is 200-300 mesh, and the opening and closing of the adjustment holes are controlled by instructions.

[0024] As a preferred technical solution, the pressure detection pipeline is externally connected to an emergency pressure relief and emptying system.

[0025] Compared with the prior art, the present invention has the following beneficial effects: 1) The present invention uses a built-in heating device and method for preparing black phosphorus crystals to prepare high-quality and high-yield black phosphorus crystals. The use of the built-in heater can significantly increase the effective material transport rate, thereby controlling the crystal growth time and improving the crystal growth efficiency and crystal quality.

[0026] 2) This preparation method uses an activated industrial catalyst to significantly improve the catalyst activity, while extending the catalyst life and flow efficiency, and extending the black phosphorus crystal growth time, thereby significantly improving the black phosphorus crystal growth yield.

[0027] 3) This method is simple and efficient, the conditions are easy to control, and it has good safety and stability. It can reduce the amount of catalyst used and recycle it, fully improve the utilization rate of raw materials, and significantly reduce the cost of preparing high-quality black phosphorus crystals.

[0028] 4) The device is simple and easy to operate and can be automated. It can be connected with the current yellow phosphorus tail gas pipeline for filtering and preparing red phosphorus assembly. By adopting a yellow phosphorus tail gas process treatment route, the continuous production and preparation of black phosphorus crystals can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the device in the preparation method of Example 1 of the present invention. In the figure: Reactor cylinder 1, sealed cylinder cover 2, built-in heater 3, raw material (red phosphorus and transport agent) control element 4, catalyst filtering element 5, catalyst collection and recycling element 6, pressure transmitter 7, pressure detection pipeline 8, pressure regulating valve 9, temperature detection pipeline 10, temperature sensor 11, external heating control system 12, catalyst control element 13, raw material device up and down movement control element 14; the external heating furnace used for the entire reaction system is connected to the heating reaction system.

[0030] Figure 2 for Figure 1 Schematic diagram of the implementation of the raw material separation control elements within the device.

[0031] Figure 3 for Figure 1 Schematic diagram of the implementation of the raw material crucible telescopic separation plate element in the device.

[0032] Figure 4 for Figure 1 Schematic diagram of the implementation of the control element for the upward and downward telescopic movement of the raw material crucible in the device.

[0033] Figure 5 for Figure 1 Schematic diagram of the implementation of the catalyst raw material filtering element in the device.

[0034] Figure 6 This is a physical picture of the black phosphorus crystals obtained in Example 1.

[0035] Figure 7 This is the X-ray diffraction spectrum of the black phosphorus crystal obtained in Example 1.

[0036] Figure 8 This is the Raman image of the black phosphorus crystal prepared in Example 1.

[0037] Fig. 9 This is a physical picture of the black phosphorus prepared in Example 2.

[0038] Fig.10This is the XRD pattern of black phosphorus prepared in Example 2.

[0039] Fig.11 This is the Raman graph of black phosphorus prepared in Example 2.

[0040] Fig.12 This is a physical picture of the black phosphorus prepared in Example 4.

[0041] Fig.13 This is the XRD pattern of black phosphorus prepared in Example 4.

[0042] Fig.14 This is the Raman graph of black phosphorus prepared in Example 4. DETAILED DESCRIPTION

[0043] Example 1 like Figure 1 A built-in heating device for preparing black phosphorus crystals, the heating device comprising a reaction cylinder 1 and a kettle cover 2 for sealing the cylinder; The raw material crucible 4 is fixed in the cylinder 1, and a heater 3 is arranged at the bottom of the raw material crucible 4; The raw material crucible 4 is a double-layer structure, with telescopic movement control elements on both sides of the outer layer. The left and right sides of the telescopic unit are placed at the lower end of the raw material crucible and fixed, so that the raw material can be compressed and moved downward during the feeding process; after the reaction starts, the raw material is transported upward, and the telescopic unit is extended and moved upward; The catalyst crucible 13 is placed on the upper end of the raw material crucible 4; The heater 3 for internally heating the reaction system is connected to the external heating control system 12; The pressure transmitter 7 is connected to the heating control system 12 .

[0044] The inner layer of the raw material crucible 4 is a porous structure, which is fixed in the middle of the inner and outer layers of the raw material crucible through a telescopic separation partition. The automatic telescopic unit 15 realizes the automatic separation of the raw materials in the middle of the inner and outer layers of the raw material crucible, and then realizes the transportation of the raw materials. The pore size is 60-80 mesh.

[0045] A catalyst filtering device 5 is provided at the lower part of the raw material crucible 4 , and a catalyst collecting and recovering device 6 is located at the bottom of the cylinder 1 .

[0046] The heater 3 is provided with a temperature detection pipe 10, and a temperature sensor 11 is connected to the temperature detection pipe 10 to realize the temperature control of the heater; The pressure transmitter 7 is connected to the pressure detection pipeline 8 through the pressure control valve 9 and is used to detect the pressure in the cylinder 1.

[0047] The method for preparing black phosphorus crystals using the above device has the following specific steps: 1) Under a protective gas atmosphere, weigh two raw materials, industrial tin powder and activated carbon, place them in a crucible and put them into a small reactor for complete sealing; after the sealing is complete, heat and activate them in a tube furnace; tin: carbon = 100:1, activation temperature is 200 ° C, activation time is 1h, after the activation is complete, take them out under a protective gas atmosphere and place them in a sealed bottle for standby use; 2) Under a protective gas atmosphere, open the valve of the pressure probe pipeline to perform vacuum ventilation on the reaction system, weigh 10 kg of red phosphorus, 1 kg of activated catalyst Sn (C) and 0.4 kg of transport agent I2 in a ratio of 100:10:4, and place the raw materials in the raw material crucible in the reactor in order and at designated positions; 3) Place the reactor cover on the top of the reaction cylinder to completely seal the reactor; 4） After the packaging is completed, the temperature control program of the internal heater and the external heating furnace is adjusted, and the external heating furnace is programmed to heat up. The upper section 1-3 of the reaction furnace is heated from room temperature to 510°C after 60 minutes, and the lower section 4-6 of the reaction furnace is heated from room temperature to 550°C after 60 minutes; specifically: the bottom of the raw material crucible is heated from room temperature to 270°C at 8°C / min for 30 minutes, then to 470°C at 8°C / min for 25 minutes, and then to 550°C at 8°C / min for 10 minutes through the electric heating gradient heating in the reactor; When the upper kettle cover of the sealed cylinder is heated from room temperature to 270°C at 8°C / min for 30 min, then to 470°C at 8°C / min for 25 min, and then to 510°C at 8°C / min for 5 min, the moving rate of the telescopic separation baffle is controlled to be 3.0 cm / s, and the control spring is controlled to rise at a rate of 1 cm / min. During the heating process, the inner and outer layers of the raw material crucible are fixed, and the inner layer of the raw material crucible is a double-layer structure (one layer is a fixed structure, and the second layer is a staggered separation layer structure). The rotational separation of the raw materials is achieved by pushing the staggered separation layer to move and extend through the ring-shaped movement of the two sides of the telescopic separation baffle.

[0048] When the aperture size is 70 meshes, the separation flow rate of the raw materials in the raw material crucible is 50g / s. After 30 minutes, 10kg of red phosphorus raw materials are vaporized under the heating condition of 480-590℃ in the local environment after continuous separation; at the same time, the catalyst tin gradually liquefies after the temperature rises to 260℃ to reach its melting point and flows downward through the holes at a rate of 30min / kg. When the red phosphorus is vaporized, it contacts the vaporized red phosphorus and the volatilized gaseous iodine, and the three are transported upward. A phosphorus iodine tin intermediate is quickly formed in the range of 500-520℃ and crystal nucleation growth begins. The catalyst filtered after the reaction is recovered through a recovery element and reused for a second time.

[0049] Control the valve switch of pipeline channel to open and close the pipeline; After the reaction is completed, the reactor is transferred to a safe operating area for pressure relief and opening. After the pressure is completely relieved, the reactor cover flange is removed and the sample is taken out using a sampler. Finally, a two-dimensional stable black phosphorus crystal block is obtained, and 9.2 kg of product is obtained.

[0050] Comparative Example 1 The only difference between this comparative example and Example 1 is that: 4) the raw materials in the raw material crucible are not separated and are directly heated and vaporized in situ to contact with the catalyst raw materials at the upper end and transported upward with the gaseous iodine to form a small amount of phosphorus iodine tin intermediate, and finally cover the bottom end, i.e. the nucleation end, on the reactor to obtain 0.1 kg of black phosphorus crystals.

[0051] Comparative Example 2 The difference between this comparative example and Example 1 is that: 4) the raw material crucible is not telescopically moved, but directly heated and vaporized at the bottom and in contact with the catalyst raw material at the upper end for upward transport, and a small amount of phosphorus iodine tin intermediate is formed with gaseous iodine, and a large amount of phosphorus tin compound is formed between the bottom and the liquid tin during the heating process, which hinders the continuous upward transport of the red phosphorus raw material, and finally covers the bottom end, i.e., the nucleation end, on the reactor to obtain 0.15 kg of red phosphorus-doped black phosphorus crystals.

[0052] Example 2 The difference between this embodiment and embodiment 1 is that: 1) the catalyst raw material is not activated by activated carbon, and only 6.9 kg of black phosphorus crystals with good surface growth are obtained. Fig. 9 shown.

[0053] Example 3 The difference between this embodiment and embodiment 1 is that: 4) after the packaging is completed, by adjusting the temperature control program of the internal heater and the external heating furnace, the external heating furnace is programmed to heat up, and the upper section 1-3 of the reaction furnace is heated from room temperature to 520°C after 60 minutes, and the lower section 4-6 of the reaction furnace is heated from room temperature to 590°C after 60 minutes; specifically: by heating the bottom end of the raw material crucible with electric heating in the reactor, the temperature is increased by 10°C / min from room temperature to 270°C after 24 minutes, then by 10°C / min to 470°C after 20 minutes, and then by 10°C / min to 590°C after 12 minutes; The lower end of the upper kettle cover of the sealed cylinder was heated from room temperature to 270℃ for 24 min at 10℃ / min, then to 470℃ for 20 min at 10℃ / min, and then to 590℃ for 12 min at 10℃ / min. The moving rate of the telescopic separation baffle was controlled to be 4.8cm / s, and the control spring was controlled to rise at a rate of 2.5cm / min. During the heating process, the inner and outer layers of the raw material crucible were fixed, and the inner layer of the raw material crucible was a double-layer structure (one layer was a fixed structure, and the second layer was a staggered separation layer structure). The rotational separation of the raw material was achieved by pushing the staggered separation layer to move and extend the two sides of the temperature-increasing telescopic separation baffle in an annular manner. After the setting was completed, the heating control system was turned on to heat the reaction system, and only 9.1kg of black phosphorus crystals with good surface growth were obtained, with a yield of 91%, and the unconverted raw materials formed phosphorus-tin compounds with severe agglomeration.

[0054] Example 4 The difference between this embodiment and embodiment 1 is that: 4) after the encapsulation is completed, the temperature control program of the internal heater and the external heating furnace is adjusted, and the external heating furnace is programmed to heat up, and the upper section 1-3 of the reaction furnace is heated from room temperature to 530°C in 50 minutes, and the lower section 4-6 of the reaction furnace is heated from room temperature to 590°C in 50 minutes; specifically: the bottom end of the raw material crucible is heated by electric heating gradient heating in the reactor, and the temperature is increased from room temperature to 270°C in 20 minutes, and then increased to 510°C in 20 minutes at 12°C / min, and then increased to 590°C in 7 minutes at 12°C / min; When the lower end of the upper kettle cover of the sealed cylinder is heated from room temperature to 270°C for 20 min at 12°C / min, then to 510°C for 20 min at 12°C / min, and then to 590°C for 7 min at 12°C / min, the moving rate of the telescopic separation baffle is controlled to be 8.2 cm / s, and the spring is controlled to rise at a rate of 3.5 cm / min. After the setting is completed, the heating control system is turned on to heat the reaction system, and only 6.1 kg of black phosphorus crystals with good surface growth are obtained, with a yield of 61%, and the unconverted raw materials form a severely hardened phosphorus-tin compound (as shown in Example 12).

[0055] Example 5 The difference between this embodiment and embodiment 1 is that: 4) after the packaging is completed, by adjusting the temperature control program of the internal heater and the external heating furnace, the external heating furnace is programmed to heat up, and the upper section 1-3 of the reaction furnace is heated from room temperature to 510°C after 60 minutes, and the lower section 4-6 of the reaction furnace is heated from room temperature to 550°C after 60 minutes; specifically: by heating the bottom end of the raw material crucible with electric heating in the reactor, the temperature is increased by 3°C / min from room temperature to 270°C after 80 minutes, then by 3°C / min to 480°C after 70 minutes, and then by 3°C / min to 570°C after 30 minutes; When the lower end of the upper kettle cover of the sealed cylinder is heated from room temperature to 270°C in 80 min at 3°C / min, then to 380°C in 70 min at 3°C / min, and then to 500°C in 30 min at 3°C / min, the control spring rises at a rate of 0.1 cm / min. After the setting is completed, the heating control system is turned on to heat the reaction system, and only unconverted red phosphorus raw materials and phosphorus-tin compounds with severe hardening are obtained.

[0056] Figure 1 Schematic diagram of a device with a built-in heating reaction system for preparing black phosphorus crystals.

[0057] Figure 2 for Figure 1 Schematic diagram of the implementation of the raw material separation control elements within the device.

[0058] Figure 3 for Figure 1 Schematic diagram of the implementation of the raw material crucible telescopic separation plate element in the device.

[0059] Figure 4 for Figure 1 Schematic diagram of the implementation of the control element for the upward and downward telescopic movement of the raw material crucible in the device.

[0060] Figure 5 for Figure 1 Schematic diagram of the implementation of the catalyst raw material filtering element in the device.

[0061] Figure 6 This is a physical picture of the black phosphorus crystal obtained in Example 1. It can be seen from the figure that the crystal quality is high, the yield is 9.2Kg, but there is still a small amount of unreacted red phosphorus in the inner surface layer that has not been converted, and the yield of black phosphorus crystals can reach 92%.

[0062] Figure 7 This is the X-ray diffraction spectrum of the black phosphorus crystal obtained in Example 1. It can be seen from the figure that the crystal quality is relatively high, and a small amount of red phosphorus may be the unreacted raw material adsorbed on the surface during the tube opening process. No surface red phosphorus product was taken during sampling, indicating that the black phosphorus crystal quality is relatively good.

[0063] Figure 8 This is the Raman image of the black phosphorus crystal prepared in Example 1; it can be seen from the figure that the A1g peak caused by the out-of-plane vibration of phosphorus atoms and the B2g and A2g peaks caused by the in-plane vibration of phosphorus atoms appear and the peak intensities are relatively high, indicating that the prepared black phosphorus crystal is of higher purity.

[0064] Fig. 9This is a physical picture of the black phosphorus crystals obtained in Example 2 above, wherein the output of black phosphorus crystals is 6.9 Kg, and there is no obvious unreacted red phosphorus on the inner surface, but the yield of black phosphorus crystals is only 69%, indicating that failure to use an activated catalyst will significantly reduce the catalytic activity of the catalyst, thereby leading to the formation of agglomeration of phosphorus-tin compounds, and ultimately reducing the growth yield of black phosphorus crystals.

[0065] Fig.10 This is the X-ray diffraction spectrum of the black phosphorus crystal obtained in Example 2. It can be seen from the figure that the sample mainly presents typical characteristic peaks of black phosphorus and a small amount of surface byproduct impurity peaks. The three strong characteristic peaks correspond to (020), (040) and (060) of the black phosphorus crystal, indicating the formation of black phosphorus.

[0066] Fig.11 This is the Raman image of the black phosphorus crystal prepared in Example 2. As can be seen from the figure, the A1g peak caused by the out-of-plane vibration of phosphorus atoms and the B2g and A2g peaks caused by the in-plane vibration of phosphorus atoms appear and the peak intensities are slightly lower, indicating that the quality of the prepared black phosphorus crystal is relatively low.

[0067] Fig.12 This is a physical picture of the black phosphorus crystal obtained in Example 4. It can be seen from the figure that the surface quality of the sample crystal is good, but the output is only 6.1 Kg, and the crystal growth yield is only 61%.

[0068] Fig.13 This is the X-ray diffraction spectrum of the black phosphorus crystal obtained in Example 4. It can be seen from the figure that the sample mainly presents typical characteristic peaks of black phosphorus and more surface by-product impurity peaks. The three strong characteristic peaks correspond to (020), (040) and (060) of the black phosphorus crystal, indicating the generation of black phosphorus and more by-products.

[0069] Fig.14 This is the Raman image of the black phosphorus crystal prepared in Example 4. As can be seen from the figure, the A1g peak caused by the out-of-plane vibration of phosphorus atoms and the B2g and A2g peaks caused by the in-plane vibration of phosphorus atoms appear and the peak intensities are low, indicating that the prepared black phosphorus crystal is of low quality.

Claims

1. A built-in heating device for preparing black phosphorus crystals, characterized in that: The heating device comprises a reaction cylinder (1) and a kettle cover (2) for sealing the cylinder; The raw material crucible (4) is fixed in the cylinder (1), and a heater (3) is arranged at the bottom of the raw material crucible (4); The raw material crucible (4) is a double-layer structure, with telescopic movement control elements (14) provided on both sides of the outer layer, and the left and right sides of the telescopic unit are both placed at the lower end of the raw material crucible and fixed, so that the raw material can be compressed and moved downward during the feeding process; after the reaction starts, the raw material is transported upward, and the telescopic unit expands and moves upward; The catalyst crucible (13) is placed on the upper end of the raw material crucible (4); A heater (3) for internally heating the reaction system is connected to an external heating control system (12); The pressure transmitter (7) is connected to the heating control system (12).

2. The built-in heating device for preparing black phosphorus crystals according to claim 1, characterized in that: The inner layer of the raw material crucible (4) is a porous structure, and a telescopic separation partition is fixed between the inner and outer layers of the raw material crucible. The telescopic separation partition (15) is automatically telescopically arranged between the inner and outer layers of the raw material crucible to realize automatic separation of the raw materials, thereby realizing the transportation of the raw materials. The aperture size is 60-80 mesh.

3. The built-in heating device for preparing black phosphorus crystals according to claim 1, characterized in that: A catalyst filtering device (5) is provided at the bottom of the raw material crucible (4), and a catalyst collecting and recovering device (6) is located at the bottom of the cylinder (1).

4. The built-in heating device for preparing black phosphorus crystals according to claim 1, characterized in that: The heater (3) is provided with a temperature detection pipe (10), and a temperature sensor (11) is connected to the temperature detection pipe (10) to realize the temperature control of the heater; the pressure transmitter (7) is connected to the pressure detection pipe (8) through the pressure control valve (9) to detect the pressure in the cylinder (1).

5. A method for preparing black phosphorus crystals, comprising using the device according to any one of claims 1 to 4 to prepare black phosphorus crystals, characterized in that: The following steps are included: S1, heating and activating tin powder and activated carbon under a protective gas atmosphere under sealed conditions to obtain carbon-activated tin powder, and placing the tin powder in a sealed bottle for standby use after the activation is completed; S2, under a protective gas atmosphere, open the valve of the pressure detection pipe (10) of the heating device, place red phosphorus and iodine in the raw material crucible (4), place carbon-activated tin powder in the catalyst crucible (13), cover and seal; S3, after the packaging is completed, the temperature and pressure of the reaction system are controlled by the internal heater and the external heating furnace to realize the preparation of black phosphorus crystals. The catalyst filtered after the reaction is recovered through the recovery element and reused.

6. The method for preparing black phosphorus crystals according to claim 1, characterized in that: During activation, the mass ratio of tin powder to activated carbon is tin: carbon = 100:1~50:1, and the activation temperature is 100~200 ℃.

7. The method for preparing black phosphorus crystals according to claim 1, characterized in that: The internal and external heating temperature raising program is controlled by performing a temperature raising program on the reaction furnace sections 1-6, the temperature of the upper section 1-3 of the reaction furnace is raised from room temperature to 500-530°C within 30-90 minutes, and the temperature of the lower section 4-6 of the reaction furnace is raised from room temperature to 550-590°C within 30-90 minutes; wherein the temperature inside the raw material crucible (4) is raised to 500-590°C at a heating rate of 3-12°C / min under room temperature conditions, and the pressure range monitored by the pressure transmitter is 1-5MPa.

8. The method for preparing black phosphorus crystals according to claim 1, characterized in that: The built-in heater is regulated to perform programmed temperature heating on the raw material crucible, with the bottom end being heated from room temperature to 210-300°C at 3-12°C / min over 15-90min, then to 450-480°C at 3-12°C / min over 15-70min, and then to 550-600°C at 5-12°C / min over 8min-24min; The lower end of the kettle cover on the sealed cylinder is heated by gradient from room temperature to 270-330°C at 5-12°C / min over 20-60min, then to 470-500°C at 5-10°C / min over 17-40min, and then to 500-590°C at 3-10°C / min over 0-30min. The heating rate in the reaction system is regulated, and the moving rate of the telescopic separation partition is controlled at 0cm / s-10cm / s. Combined with the 60-80 mesh pore size of the inner layer of the raw material crucible, the raw material separation flow rate is regulated to 0g / s-100g / s, and the spring is controlled to rise at a rate of 0.1-3.5cm / min.

9. The method for preparing black phosphorus crystals according to claim 1, characterized in that: During the process of adding raw materials, the telescopic movement control element (14) is compressed downward as the raw materials are continuously added; as the reaction proceeds, the telescopic movement control element (14) is extended upward as the raw materials are continuously transported and transformed upward; The raw material crucible (4) rotates and moves along with the telescopic separation plate during the heating process; during the heating process, the double-layer structure telescopic separation partition rotates and moves so that the raw materials are separated and flowed; The telescopic separation partition (15) realizes automatic telescopic movement through the principle of thermal expansion and contraction.

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