Method for efficiently preparing black phosphorus crystals

Abstract

The invention discloses a method for efficiently preparing black phosphorus crystals, a vertical reactor is divided into a top part and a bottom part, the bottom of the reactor is a raw material end, the top of the reactor is a nucleation end, and a composite high-thermal-conductivity material is placed at the raw material end; the preparation method of the composite high-thermal-conductivity material comprises the following steps: carrying out acidic and alkaline treatment on high-thermal-conductivity powder, and then washing with water to obtain dried high-thermal-conductivity powder; copper powder, aluminum powder and the dried high-thermal-conductivity powder are mixed, and a mixed material is obtained; and putting the composite material into an organic solvent, performing thermal degreasing, performing degreasing, and finally performing vacuum sintering to obtain the composite high-thermal-conductivity material. Adding a phosphorus source, a catalyst and a transport agent into a raw material end of the reactor in an inert gas atmosphere; after the reactor is sealed, the black phosphorus crystal is prepared by controlling the temperature of the raw material end and the nucleation end. The invention can solve the problems of poor heat transfer effect, unsuitability for large-scale preparation of black phosphorus crystals, unstable quality and the like after the phosphorus source is discharged.

Description

Technical Field

[0001] This invention belongs to the field of phosphorus preparation, and particularly relates to a method for efficiently preparing black phosphorus crystals. Background Technology

[0002] Black phosphorus, an allotrope of phosphorus with an orthorhombic crystal structure, exhibits relatively low reactivity compared to other similar materials. Its basic structural unit is an interconnected six-membered ring, with each phosphorus atom forming a stable coordination configuration with three adjacent atoms via covalent bonds. Under ambient temperature and pressure, black phosphorus demonstrates excellent thermodynamic stability, making it one of the most stable phosphorus allotropes known. Morphologically, black phosphorus shares significant structural similarities with graphite, both exhibiting typical black, flake-like morphologies and good electrical conductivity. Its atomic arrangement forms a unique wrinkled, layered structure, and this special crystal configuration results in significant anisotropy in phonon, photon, and electron transport. Based on these properties, black phosphorus shows significant application potential in electronic thin-film devices and infrared optoelectronics.

[0003] The biggest challenge facing black phosphorus research and application to date is how to efficiently, cost-effectively, and in large quantities prepare high-quality black phosphorus crystals. Currently widely used chemical vapor transport methods, such as the apparatus disclosed in CN 222961143 U for efficient black phosphorus preparation, involve a reaction zone at the top, a support mesh in the middle, and the catalyst placed within the support mesh. The support mesh is then placed in a flat-bottomed tube, and black phosphorus growth is controlled at the bottom by temperature. However, as the amount of material increases, the mass and heat transfer between materials becomes poor, failing to meet the requirements for large-scale preparation. Patent CN218422705 U describes a preparation process that directly mixes the phosphorus source, catalyst, and transport agent to prepare black phosphorus. While this mixing method is convenient, large-scale production is prone to limited heat conduction, leading to severe material caking and consequently lower material conversion rates and product purity.

[0004] In summary, this invention develops an efficient method for preparing black phosphorus to address two main issues in existing black phosphorus preparation technologies: firstly, during large-scale production, the red phosphorus material softens under gravity at high temperatures, exacerbating the deformation and agglomeration of red phosphorus particles; secondly, high temperatures during the reaction may cause localized polymerization or structural reorganization of red phosphorus, enhancing the bonding force between particles and also causing them to agglomerate. Therefore, adding composite high thermal conductivity materials inside the reactor (to increase mass and heat transfer between red phosphorus particles, allowing them to quickly reach the volatilization temperature of red phosphorus and become phosphorus vapor) and multiple internal support frames to separate the red phosphorus material (reducing the gravitational influence of red phosphorus itself) can effectively solve these problems. Summary of the Invention

[0005] A method for efficiently preparing black phosphorus crystals includes the following steps: S1. Provide a vertical reactor, the internal space of which is divided along the axial direction into an upper nucleation end and a lower feed end; S2. Place a composite high thermal conductivity material at the raw material end; S3. Under an inert gas protective atmosphere, place the phosphorus source, catalyst, and transport agent at the raw material end; S4. Seal the reactor and independently control the temperature programs of the raw material end and the nucleation end, so that the phosphorus source is gasified, transported and crystallized at the nucleation end to obtain black phosphorus crystals; The composite high thermal conductivity material is prepared by a method including the following steps: a. Provide high thermal conductivity powders, metal powders, and binders; b. Mix the high thermal conductivity powder, metal powder and binder, and shape to obtain a green body; c. The green body is subjected to solvent degreasing and thermal degreasing treatments in sequence to obtain a degreased green body; d. Vacuum sinter the degreased preform to obtain the composite high thermal conductivity material.

[0006] The high thermal conductivity powder is selected from at least one of graphene, boron nitride, and diamond; and / or, the metal powder is selected from at least one of copper powder and aluminum powder.

[0007] Before step a, the process further includes a surface treatment step for the high thermal conductivity powder: treating the high thermal conductivity powder sequentially with an acidic solution and an alkaline solution, then washing it with water until it is neutral and drying it.

[0008] The acidic solution is a hydrochloric acid, sulfuric acid, or nitric acid solution with a concentration of 0.5-6 mol / L, and the acid washing time is 0.5-7 h; the alkaline solution is a sodium hydroxide or potassium hydroxide solution with a concentration of 0.5-5 mol / L, and the alkaline washing time is 0.5-7 h.

[0009] The mass ratio of the metal powder to the high thermal conductivity powder is (40-100): (8-50).

[0010] The average particle size of the metal powder is 4-25 μm; the average particle size of the high thermal conductivity powder is 8-60 μm when it is graphene, 10-40 μm when it is boron nitride, and 20-80 μm when it is diamond.

[0011] In step b, the molding method is injection molding, the injection temperature is 160-250 ℃, the injection pressure is 70-150 MPa, and the holding time is 8-40 s; in step c, the organic solvent used for solvent degreasing is n-hexane, the degreasing temperature is 22-40℃, and the time is 3-10 h; the temperature for thermal degreasing is 530-650 ℃, the time is 1.5-5 h, and the heating rate is 1-8 ℃ / min; in step d, the temperature for vacuum sintering is 900-1300 ℃, and the time is 1.5-5 h.

[0012] The injection molding shape can be customized according to factors such as reactor diameter and amount of red phosphorus fed to meet the requirement of rapid conversion of red phosphorus into phosphorus vapor.

[0013] The mass ratio of the added phosphorus source to the composite high thermal conductivity composite material is (6-10):(0.5-3).

[0014] The phosphorus source is at least one of red phosphorus or white phosphorus with a purity of not less than 98.5%; the mass ratio of the phosphorus source, catalyst, and transport agent is 10 : (0.8-2) : (0.4-1).

[0015] In step S4, the temperature program is as follows: Raw material end: Heat from room temperature to 530-560 ℃ over 0.5-1 h, hold at that temperature for 8-18 h, and then cool to room temperature over 3-8 h; Nucleation end: The temperature is raised from room temperature to 530-560 ℃ in 0.5-1 h, held for 0.5-2 h, then cooled to 480-510 ℃ and held for 8-18 h, and then cooled back to room temperature in 3-8 h.

[0016] The composite high thermal conductivity material is a high-temperature resistant inorganic composite material with a three-dimensional interconnected pore structure, which is chemically inert during the preparation of black phosphorus crystals.

[0017] Compared with the prior art, the present invention has the following advantages: 1. This invention is simple and efficient, with easily controllable conditions, good safety and stability, and is more conducive to practical applications in industrial-scale preparation.

[0018] 2. This invention solves the problem of poor mass and heat transfer of raw materials after mass production by adding composite high thermal conductivity materials at the raw material end, thereby increasing the internal mass and heat transfer of raw materials and the gravity of red phosphorus itself.

[0019] 3. This invention first raises the raw material end and the nucleation end to the maximum temperature simultaneously, and then lowers the nucleation end to the set temperature in a short time. This can increase the heating rate of the nucleation end, maintain a suitable temperature for black phosphorus crystal growth, and further improve the yield of black phosphorus crystals. Attached Figure Description

[0020] Figure 1 This is a picture of the physical object prepared in Comparative Example 1.

[0021] Figure 2 This is a picture of the physical object prepared in Example 3.

[0022] Figure 3 This is the XRD pattern of black phosphorus obtained in Example 4.

[0023] Figure 4 This is a picture of the physical object prepared in Example 5. Detailed Implementation

[0024] To better understand the present invention, the following detailed description of the invention is provided in conjunction with specific embodiments and accompanying drawings. However, the scope of the present invention is not limited to the embodiments described below.

[0025] Example 1 A method for efficiently preparing black phosphorus crystals, the specific preparation steps are as follows: (1) The vertical reactor is divided into two parts: the top and the bottom. The bottom of the reactor is the raw material end, and the top is the nucleation end. (2) In an inert gas atmosphere, weigh 10 kg of red phosphorus, 1 kg of tin powder and 0.5 kg of iodine and put them into the bottom of the reactor (raw material end). (3) The reactor was heated using an optimized temperature control program. The specific heating program was as follows: the bottom (raw material end) was heated from room temperature to 550℃ after 0.5 h, held for 12 h, and then cooled to room temperature after 5 h; the top (nucleation end) was heated from room temperature to 500℃ after 0.5 h, held for 11.5 h, and then cooled to room temperature after 5 h. After the reaction was completed, black phosphorus crystals were prepared at the nucleation end.

[0026] Figure 1 This is a picture of the black phosphorus crystals prepared in Comparative Example 1. The yield of black phosphorus crystals was 4.556 kg, and the overall yield was 45.56%.

[0027] Example 2 A method for efficiently preparing black phosphorus crystals, the specific preparation steps are as follows: (1) The vertical reactor is divided into two parts: top and bottom. The bottom of the reactor is the raw material end and the top is the nucleation end. High thermal conductivity material is placed at the (bottom) raw material end. (2) The preparation method of the composite high thermal conductivity material is as follows: boron nitride powder is placed in a sulfuric acid solution with a concentration of 1 mol / L for 3 h, then placed in a sodium hydroxide solution with a concentration of 3 mol / L for 4 h, then repeatedly rinsed with deionized water until neutral, and vacuum dried at 60℃ for 10 h to obtain dried boron nitride powder; the dried boron nitride powder with an average particle size of 15 μm is injection molded under the conditions of injection temperature of 220℃, injection pressure of 100 MPa, and holding time of 30 s; the material is placed in n-hexane for degreasing at a degreasing temperature of 30℃ for 4 h, the hot degreasing temperature is increased from room temperature to 600℃ at a heating rate of 3℃ / min, and held at 600℃ for 3 h to obtain a degreased green body; finally, the degreased green body is placed in a vacuum sintering furnace and vacuum sintered at 1100℃ for 4 h to obtain a high thermal conductivity material; (3) In an inert gas atmosphere, weigh 10 kg of red phosphorus, 1 kg of tin powder and 0.5 kg of iodine and put them into the bottom of the reactor (raw material end). Red phosphorus: high thermal conductivity material = 10:1 (mass ratio). (4) The reactor was heated using an optimized temperature control program. The specific heating program was as follows: the bottom (raw material end) was heated from room temperature to 550℃ after 0.5 h, held for 12 h, and then cooled to room temperature after 5 h; the top (nucleation end) was heated from room temperature to 550℃ after 0.5 h, and then cooled to 500℃ after 0.5 h. It was held for 11.5 h and then cooled to room temperature after 5 h. After the reaction was completed, black phosphorus crystals were prepared at the nucleation end.

[0028] After simultaneously heating the raw material end and the nucleation end to the maximum temperature, the nucleation end was cooled down to finally obtain 6.365 kg of black phosphorus crystals, with a comprehensive yield of 63.65%.

[0029] Example 3 A method for efficiently preparing black phosphorus crystals, the specific preparation steps are as follows: (2) The vertical reactor is divided into two parts, the top and the bottom. The bottom of the reactor is the raw material end and the top is the nucleation end. Composite high thermal conductivity material is placed at the (bottom) raw material end. (2) The preparation method of the composite high thermal conductivity material is as follows: boron nitride powder is placed in a sulfuric acid solution with a concentration of 1 mol / L for 3 hours, then placed in a sodium hydroxide solution with a concentration of 3 mol / L for 4 hours, and then repeatedly rinsed with deionized water until neutral. After vacuum drying at 60℃ for 10 hours, the dried boron nitride powder is obtained. Copper powder with an average particle size of 15 μm and dried boron nitride powder with an average particle size of 15 μm are mixed together, with copper powder:boron nitride = 60:10 (mass ratio). The injection temperature is 220℃ and the injection pressure is 100 MPa. Injection molding was performed under a holding pressure of 30 s to obtain a composite material. The composite material was then degreased in n-hexane at a temperature of 30 ℃ for 4 h. The hot degreasing temperature was increased from room temperature to 600 ℃ at a rate of 3 ℃ / min and held at 600 ℃ for 3 h to obtain a degreased green body. Finally, the degreased green body was placed in a vacuum sintering furnace and sintered at 1100 ℃ for 4 h to obtain a composite high thermal conductivity material. (3) In an inert gas atmosphere, weigh 10 kg of red phosphorus, 1 kg of tin powder and 0.5 kg of iodine and put them into the bottom of the reactor (raw material end). Red phosphorus: composite high thermal conductivity material = 10:1 (mass ratio). (4) The reactor was heated using an optimized temperature control program. The specific heating program was as follows: the bottom (raw material end) was heated from room temperature to 550℃ after 0.5 h, held for 12 h, and then cooled to room temperature after 5 h; the top (nucleation end) was heated from room temperature to 550℃ after 0.5 h, and then cooled to 500℃ after 0.5 h. It was held for 11.5 h and then cooled to room temperature after 5 h. After the reaction was completed, black phosphorus crystals were prepared at the nucleation end.

[0030] Figure 2 The image shows the actual black phosphorus crystals prepared in Example 3. After the raw material end and the nucleation end were heated to the highest temperature simultaneously, the nucleation end was cooled down to finally obtain 8.635 kg of black phosphorus crystals, with a comprehensive yield of 86.35%.

[0031] Example 4 A method for efficiently preparing black phosphorus crystals, the specific preparation steps are as follows: (1) The vertical reactor is divided into two parts: top and bottom. The bottom of the reactor is the raw material end and the top is the nucleation end. Composite high thermal conductivity material is placed at the (bottom) raw material end. (2) The preparation method of the composite high thermal conductivity material is as follows: graphene powder is placed in a hydrochloric acid solution with a concentration of 3 mol / L for 2 hours, then placed in a sodium hydroxide solution with a concentration of 4 mol / L for 3 hours, and then repeatedly rinsed with deionized water until neutral. The dried graphene powder is obtained by vacuum drying at 80℃ for 12 hours. A mixture of aluminum powder with an average particle size of 10 μm and dried graphene powder with an average particle size of 20 μm is obtained, with aluminum powder:graphene = 80:10 (mass ratio). The injection temperature is 200℃ and the injection pressure is 90 MPa. Injection molding was performed under a holding pressure of 20 s to obtain a composite material. The composite material was then degreased in n-hexane at a temperature of 30 ℃ for 5 h. The hot degreasing temperature was increased from room temperature to 580 ℃ at a rate of 5 ℃ / min and held at 580 ℃ for 3 h to obtain a degreased green body. Finally, the degreased green body was placed in a vacuum sintering furnace and sintered at 1000 ℃ for 3 h to obtain a composite high thermal conductivity material. (3) In an inert gas atmosphere, weigh 10 kg of red phosphorus, 1 kg of tin powder and 0.5 kg of iodine and put them into the bottom of the reactor (raw material end). Red phosphorus: composite high thermal conductivity material = 10:2 (mass ratio). (4) The reactor was heated using an optimized temperature control program. The specific heating program was as follows: the bottom (raw material end) was heated from room temperature to 550℃ after 0.5 h, held for 12 h, and then cooled to room temperature after 5 h; the top (nucleation end) was heated from room temperature to 550℃ after 0.5 h, and then cooled to 500℃ after 0.5 h. It was held for 11.5 h and then cooled to room temperature after 5 h. After the reaction was completed, black phosphorus crystals were prepared at the nucleation end.

[0032] Figure 3 The image shows the XRD pattern of black phosphorus obtained in Example 4. As can be seen from the image, the sample exhibits typical black phosphorus characteristic peaks, with no other impurity peaks appearing. This indicates that the prepared black phosphorus crystals have good crystallinity and high purity. The three strong characteristic peaks correspond to the (020), (040), and (060) crystal planes of the black phosphorus crystals, respectively. 9.036 kg of black phosphorus crystals were produced, with a comprehensive yield of 90.36%.

[0033] Example 5 A method for efficiently preparing black phosphorus crystals, the specific preparation steps are as follows: (1) The vertical reactor is divided into two parts: top and bottom. The bottom of the reactor is the raw material end and the top is the nucleation end. Composite high thermal conductivity material is placed at the (bottom) raw material end. (2) The method for preparing composite high thermal conductivity material is as follows: graphene powder is placed in a nitric acid solution with a concentration of 4 mol / L for 5 hours, then placed in a potassium hydroxide solution with a concentration of 1.5 mol / L for 3 hours, and then repeatedly rinsed with deionized water until neutral. The powder is then vacuum dried at 90℃ for 8 hours to obtain dried graphene powder. A mixture of aluminum powder with an average particle size of 20 μm and dried graphene powder with an average particle size of 50 μm is obtained, with an aluminum powder:graphene ratio of 25:14 (mass ratio). The mixture is then injected at a temperature of 220℃ and an injection pressure of 70 MPa. Injection molding was performed under a holding pressure of 15 s to obtain a composite material. The composite material was then degreased in n-hexane at a temperature of 35°C for 4 h. The hot degreasing temperature was increased from room temperature to 620°C at a rate of 6°C / min and held at 620°C for 4 h to obtain a degreased green body. Finally, the degreased green body was placed in a vacuum sintering furnace and sintered at 1150°C for 4 h to obtain a composite high thermal conductivity material. (3) In an inert gas atmosphere, weigh 20 kg of red phosphorus, 3 kg of tin powder and 1.5 kg of iodine and put them into the bottom of the reactor (raw material end). Red phosphorus: composite high thermal conductivity material = 20:1 (mass ratio). (4) The reactor is heated by an optimized temperature control program. The specific temperature increase program is as follows: the bottom (raw material end) is heated to 560°C from room temperature for 1 hour, kept at the temperature for 14 hours, and then cooled to room temperature for 6 hours; the top (nucleation end) is heated to 550°C from room temperature for 1 hour, then cooled to 510°C for 1 hour, kept at the temperature for 13 hours, and then cooled to room temperature for 6 hours. After the reaction is completed, black phosphorus crystals are prepared at the nucleation end.

[0034] Figure 4 This is a photograph of the experimental product prepared in Example 5. 17.099 kg of black phosphorus crystals were obtained, with a total yield of 85.5%.

[0035] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way without contradiction. In order to avoid unnecessary repetition, the present invention will not describe each possible combination.

Claims

1. A method for efficiently preparing black phosphorus crystals, characterized in that, Includes the following steps: S1. Provide a vertical reactor, the internal space of which is divided along the axial direction into an upper nucleation end and a lower feed end; S2. Place a composite high thermal conductivity material at the raw material end; S3. Under an inert gas protective atmosphere, place the phosphorus source, catalyst, and transport agent at the raw material end; S4. Seal the reactor and independently control the temperature programs of the raw material end and the nucleation end, so that the phosphorus source is gasified, transported and crystallized at the nucleation end to obtain black phosphorus crystals; The composite high thermal conductivity material is prepared by a method including the following steps: a. Provide high thermal conductivity powders, metal powders, and binders; b. Mix the high thermal conductivity powder, metal powder and binder, and shape to obtain a green body; c. The green body is subjected to solvent degreasing and thermal degreasing treatments in sequence to obtain a degreased green body; d. Vacuum sinter the degreased preform to obtain the composite high thermal conductivity material.

2. The method according to claim 1, characterized in that, The high thermal conductivity powder is selected from at least one of graphene, boron nitride, and diamond; and / or, the metal powder is selected from at least one of copper powder and aluminum powder.

3. The method according to claim 1 or 2, characterized in that, Before step a, the process further includes a surface treatment step for the high thermal conductivity powder: treating the high thermal conductivity powder sequentially with an acidic solution and an alkaline solution, then washing it with water until it is neutral and drying it.

4. The method according to claim 3, characterized in that, The acidic solution is a hydrochloric acid, sulfuric acid, or nitric acid solution with a concentration of 0.5-6 mol / L, and the acid washing time is 0.5-7 h; the alkaline solution is a sodium hydroxide or potassium hydroxide solution with a concentration of 0.5-5 mol / L, and the alkaline washing time is 0.5-7 h.

5. The method according to claim 1, characterized in that, The mass ratio of the metal powder to the high thermal conductivity powder is (40-100): (8-50).

6. The method according to claim 1, characterized in that, The average particle size of the metal powder is 4-25 μm; the average particle size of the high thermal conductivity powder is 8-60 μm when it is graphene, 10-40 μm when it is boron nitride, and 20-80 μm when it is diamond.

7. The method according to claim 1, characterized in that, In step b, the molding method is injection molding, the injection temperature is 160-250 ℃, the injection pressure is 70-150 MPa, and the holding time is 8-40 s; in step c, the organic solvent used for solvent degreasing is n-hexane, the degreasing temperature is 22-40 ℃, and the time is 3-10 h; the temperature for thermal degreasing is 530-650 ℃, the time is 1.5-5 h, and the heating rate is 1-8 ℃ / min; in step d, the temperature for vacuum sintering is 900-1300 ℃, and the time is 1.5-5 h.

8. The method according to claim 1, characterized in that, The phosphorus source is at least one of red phosphorus or white phosphorus with a purity of not less than 98.5%; the mass ratio of the phosphorus source, catalyst, and transport agent is 10 : (0.8-2) : (0.4-1), and the mass ratio of the added phosphorus source and the composite high thermal conductivity composite material is (6-10) : (0.5-3).

9. The method according to claim 1, characterized in that, In step S4, the temperature program is as follows: Raw material end: Heat from room temperature to 530-560 ℃ over 0.5-1 h, hold at that temperature for 8-18 h, and then cool to room temperature over 3-8 h; Nucleation end: The temperature is raised from room temperature to 530-560 ℃ in 0.5-1 h, held for 0.5-2 h, then cooled to 480-510 ℃ and held for 8-18 h, and then cooled back to room temperature in 3-8 h.

10. The method according to any one of claims 1-9, characterized in that, The composite high thermal conductivity material is a high-temperature resistant inorganic composite material with a three-dimensional interconnected pore structure, which is chemically inert during the preparation of black phosphorus crystals.

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