Two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism and preparation method and application thereof

Abstract

The application discloses a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism and a preparation method and application thereof. The carbon nitride quantum material is an amorphous nanosheet with a two-dimensional layered structure and has a graphite-like phase structure with nitrogen vacancies in a carbon-nitrogen skeleton. The single-layer thickness of the carbon nitride quantum material is 4-15 nm, and the length or width is 1-10 microns. The method comprises the following steps: using urea as a raw material, calcining in air, then performing one-time annealing and edge four-time heat treatment, and then performing centrifugal washing with anhydrous ethanol and low-temperature drying to obtain the black carbon nitride quantum material. The preparation method has the characteristics of simple process, easy repetition and low cost. The black carbon nitride prepared by the preparation method has the characteristics of high purity, high magnetization intensity, high Curie temperature and strong room-temperature ferromagnetism, and can be applied to the fields of spin electronic devices, topological quantum devices and magnetic storage.

Description

Technical Field

[0001] This invention belongs to the field of quantum information materials technology, specifically relating to a two-dimensional black carbon nitride quantum material with room temperature ferromagnetism, its preparation method, and its applications. Background Technology

[0002] Since the first experimental verification of two-dimensional ferromagnetic materials in 2017, breakthroughs have been achieved in fields such as spintronic devices and topological quantum devices. Among them, two-dimensional ferromagnetic materials based on transition metals and rare earth elements have attracted much attention due to their rich magnetically ordered structures. However, these materials suffer from drawbacks such as scarce raw materials, low Curie temperatures, complex preparation processes, and natural biotoxicity, leading to high research and application costs, high energy consumption, and environmental burdens, thus limiting their practical use and commercialization in many fields. Carbon, as a widely available and biocompatible lightweight element, offers a rich bonding environment that allows for tunable band gaps, giving carbon-based materials significant development advantages and considerable plasticity as ferromagnetic semiconductors. Carbon-based ferromagnetic materials benefit from the spin provided by sp electrons, exhibiting long spin lifetimes and weak spin-orbit interactions. In lower dimensions, they are more resistant to the destructive effects of thermal perturbations on magnetic order, thus achieving high-temperature ferromagnetism. However, their relatively weak magnetic strength hinders further research and application. In current research, two-dimensional carbon-based materials such as doped graphene and graphylene have been shown to possess room-temperature ferromagnetism. However, due to insufficient spin coupling and low spin polarization, their overall magnetic performance is poor. For example, in 2024, Yong Wang et al. (YongWang,Dingyi Yang,Wei Xu,Yongjie Xu,Yu Zhang,Zixuan Cheng,Yizhang Wu,XuetaoGan,Wei Zhong,Yan Liu,Genquan Han,Yue Hao. Room-temperature ferromagnetism and piezoelectricity in metal-free 2D semiconductor crystalline carbonnitride.Nano Research 2024,17,5670-5679) prepared pure crystalline carbon nitride by chemical vapor deposition, which had a saturation magnetization of only 0.01 emu / g at room temperature. In 2023, Lina Du et al. (Lina Du, Bo Gao, Song Xu, Qun Xu. Strong ferromagnetism of g-C3N4 achieved by atomic manipulation. Nature Communications 2023, 14, 2278) increased the saturation magnetization of metal-free carbon nitride to 0.043 emu / g at room temperature by introducing boron bridges into graphitic carbon nitride.In 2022, Chinese invention patent CN115382505A disclosed a mercapto-functionalized magnetic carbon nitride oxide. While its magnetic properties reached a high level with iron doping, it is not a metal-free carbon nitride, and its further research and development remains limited by transition metal elements. Therefore, the preparation of two-dimensional carbon-based materials with high magnetic properties and room-temperature ferromagnetism is a key challenge for advancing spintronics, magnetic storage, and topological quantum computing. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the present invention aims to provide a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism, its preparation method, and its applications. The method involves calcining urea in the atmosphere, followed by annealing in argon, and then undergoing a quadruple edge heat treatment to obtain the room-temperature ferromagnetic two-dimensional black carbon nitride quantum material. The preparation method of the present invention is simple, easily reproducible, and low-cost. The black carbon nitride prepared by the method of the present invention exhibits high purity, high magnetization, high Curie temperature, and strong room-temperature ferromagnetism. Its properties enable the practical application of metal-free two-dimensional carbon-based materials in the fields of magnetism and quantum mechanics. It is a key material for the research and development of sp-electron carbon-based room-temperature ferromagnetism and contributes to the application and development of spintronic devices, topological quantum devices, and magnetic storage.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism, using urea as raw material, involves calcination, annealing, and a quadruple heat treatment process to introduce a large number of nitrogen vacancies into the graphite-like phase structure of carbon nitride, thereby obtaining black carbon nitride. The specific steps include:

[0006] Step 1: Calcining urea and then naturally cooling it to room temperature yields a pale yellow powder; the purity of the urea is greater than or equal to 99%.

[0007] Step 2: The pale yellow powder obtained in Step 1 is spread and compacted in a quartz boat, then placed in a tube furnace. After all the air in the tube furnace has been replaced with argon, annealing is performed to obtain a yellow powder. The mass of the pale yellow powder used for annealing should not exceed 5 mg / mm³. 2 ;

[0008] Step 3: Place the yellow powder obtained in Step 2 on the edge of the quartz boat, then put it into a tube furnace. After all the air in the tube furnace is replaced with argon, perform a quadruple heat treatment on the edge to obtain black powder.

[0009] Step 4: The black powder obtained in Step 3 is centrifuged and washed at least three times with anhydrous ethanol. After washing, it is dried at low temperature to obtain a two-dimensional black carbon nitride quantum material with room temperature ferromagnetism.

[0010] The calcination conditions in step 1 are as follows: in an air atmosphere, the temperature is increased to 530-570℃ at a rate of 1.5-3.5℃ / min and then held for 2-4 hours.

[0011] The annealing conditions in step 2 are as follows: under the protection of argon, the temperature is increased to 660-700℃ at a rate of 20-30℃ / min and then held for 5-15 minutes.

[0012] In step 2, the gas replacement process lasts for at least 20 minutes, during which the argon gas flow rate is 200-300 cc / min; after the replacement process is completed, the argon gas flow rate is maintained at 20-50 cc / min.

[0013] The edge quadruple heat treatment process in step 3 is as follows:

[0014] The first heat treatment is as follows: under the protection of argon gas, the temperature is raised to 720-760℃ at a rate of 15-25℃ / min, and then immediately allowed to cool naturally until the temperature drops to room temperature.

[0015] The second, third, and fourth heat treatments are all performed by heating the temperature to 660-700℃ at a rate of 15-25℃ / min under argon protection, followed by immediate natural cooling. This process is repeated until the fourth heat treatment is completed.

[0016] In step 4, centrifugal washing involves ultrasonic dispersion and centrifugal separation. The ultrasonic oscillation time is ≥3 min, the centrifugation speed is 6000-8000 rpm, and the centrifugation time is ≥4 min. The low-temperature drying temperature is 40-60℃, and the drying process lasts for at least 2 hours.

[0017] The present invention also provides a two-dimensional black carbon nitride quantum material with room temperature ferromagnetism prepared by the above-described preparation method.

[0018] This carbon nitride quantum material is an amorphous nanosheet with a two-dimensional layered structure, with a single layer thickness of 4-15 nm and a length or width of 1-10 μm.

[0019] This carbon nitride quantum material retains a graphite-like phase structure while possessing nitrogen vacancies in its carbon-nitrogen framework.

[0020] The present invention also provides an application of two-dimensional black carbon nitride with room temperature ferromagnetism as described above in spintronic devices, topological quantum devices or magnetic storage.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention obtains a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism by annealing and edge quadruple heat treatment of carbon nitride obtained by calcining urea in the atmosphere. The carbon nitride prepared by this method introduces more nitrogen vacancies into the carbon nitride framework while retaining the original graphite-like phase structure, thereby leading to C / C bond reconstruction and the p-type carbon atom... z The orbitals are in an unsaturated state, providing the intrinsic magnetic moments of black carbon nitride derived from defects; at the same time, the local spin states formed by nitrogen vacancies couple with the spins of adjacent carbon atoms through indirect exchange interactions, forming long-range magnetic order, thus exhibiting ferromagnetism at room temperature.

[0023] 2. The two-dimensional black carbon nitride prepared by this invention exhibits room-temperature ferromagnetism with a Curie temperature exceeding 400 K. At 2 K, its saturation magnetization is not less than 9.85 emu / g, and its remanent magnetization is not less than 1.58 emu / g; at 300 K, its saturation magnetization is not less than 4.25 emu / g, and its remanent magnetization is not less than 0.77 emu / g. The two-dimensional black carbon nitride prepared by the method of this invention can be applied to a wide range of magnetic applications, especially in biomedicine, food and pharmaceutical processing, environmental protection, and other fields requiring metal-free and non-toxic materials. It can also be used in spintronic devices, topological quantum devices, and magnetic storage.

[0024] 3. The preparation method of the present invention is characterized by simple process, easy reproducibility and low cost; the black carbon nitride prepared by the preparation method of the present invention has the characteristics of high purity, high magnetization, high Curie temperature and strong room temperature ferromagnetism.

[0025] In summary, this invention obtains a two-dimensional black carbon nitride quantum material with room temperature ferromagnetism by calcining urea in the atmosphere, followed by annealing in argon, and then undergoing a quadruple edge heat treatment. The preparation method of this invention is simple, easily reproducible, and low-cost. The black carbon nitride prepared by this method exhibits high purity, high magnetization, high Curie temperature, and strong room temperature ferromagnetism. Its properties enable the practical application of metal-free two-dimensional carbon-based materials in the fields of magnetism and quantum mechanics. It is a key material for the research and development of sp-electron carbon-based room temperature ferromagnetism, and contributes to the application and development of spintronic devices, topological quantum devices, and magnetic storage. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of two-dimensional black carbon nitride provided by the present invention, wherein, Figure 1 a is a schematic diagram of the complete structure of graphite-like carbon nitride produced after calcination. Figure 1 b is a partial structural diagram showing the formation of a small number of nitrogen vacancies after annealing. Figure 1 c and 1d are partial structural diagrams showing the generation of a moderate amount of nitrogen vacancies after heat treatment. Figure 1 e and 1f are partial structural diagrams showing the generation of a large number of nitrogen vacancies after heat treatment.

[0027] Figure 2 An optical photograph of a two-dimensional black carbon nitride provided for this invention.

[0028] Figure 3 A two-dimensional black carbon nitride monolayer AFM height map provided by the present invention.

[0029] Figure 4 The present invention provides multilayer AFM and MFM images of two-dimensional black carbon nitride, wherein, Figure 4 'a' represents the multi-level AFM height map. Figure 4 b is the corresponding MFM phase shift diagram.

[0030] Figure 5 The two-dimensional black carbon nitride EDS spectrum provided by this invention, wherein, Figure 5 a is a morphological image obtained under a transmission electron microscope. Figure 5 b is the distribution map of carbon in the corresponding region. Figure 5 c is the distribution map of nitrogen in the corresponding region.

[0031] Figure 6 The EELS spectrum of two-dimensional black carbon nitride provided by this invention, wherein, Figure 6 a is a topographic map of the EELS-represented region. Figure 6 b is a diagram showing the mixed distribution of carbon and nitrogen elements in the corresponding region. Figure 6 c is the distribution map of carbon elements in the corresponding region. Figure 6 d is the distribution map of nitrogen in the corresponding region.

[0032] Figure 7 The XAS spectrum of two-dimensional black carbon nitride provided by the present invention, wherein, Figure 7 a is the spectrum corresponding to nitrogen. Figure 7 b is the spectrum corresponding to carbon.

[0033] Figure 8 The XPS spectrum of two-dimensional black carbon nitride provided by the present invention, wherein, Figure 8 a is the spectrum corresponding to nitrogen. Figure 8 b is the spectrum corresponding to carbon.

[0034] Figure 9 The MT curve of two-dimensional black carbon nitride provided by the present invention.

[0035] Figure 10 The MH curve of two-dimensional black carbon nitride at 2K provided by the present invention.

[0036] Figure 11 The MH curve of two-dimensional black carbon nitride at 300K provided by the present invention.

[0037] Figure 12 A photograph of two-dimensional black carbon nitride being attracted by an external magnetic field, provided for this invention. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0039] like Figures 1-3 As shown, a two-dimensional black carbon nitride quantum material exhibiting room-temperature ferromagnetism is described. This carbon nitride is an amorphous nanosheet with a two-dimensional layered structure, with a single layer thickness of 4-15 nm, further varying to 4.3-14.8 nm, and a length or width of 1-10 μm. This carbon nitride retains a graphite-like phase structure while possessing nitrogen vacancies within its carbon-nitrogen framework. Figure 1 a represents the graphite-like phase structure of the pale yellow powder obtained in step 1; Figure 1 b represents the structure of the yellow powder obtained in step 2. After annealing, its graphite-like phase structure exhibits a small number of lattice nitrogen vacancies in the carbon-nitrogen framework. Figure 1 cf represents the structure of the black powder obtained by step-by-step heat treatment in step 3. As the heat treatment weight increases, more nitrogen vacancies gradually appear on the carbon-nitrogen framework in its graphite-like phase structure until the nitrogen vacancies are filled, while maintaining the overall graphite-like phase carbon-nitrogen framework structure.

[0040] A method for preparing a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism, using urea as raw material, involves calcination, annealing, and a quadruple heat treatment process to introduce a large number of nitrogen vacancies into the graphite-like phase structure of carbon nitride, thereby obtaining black carbon nitride. The specific steps include:

[0041] Step 1: Place urea in a muffle furnace for calcination, then allow it to cool naturally to room temperature to obtain a light yellow powder; the calcination conditions are: in an air atmosphere, heat to 530-570℃ at a rate of 1.5-3.5℃ / min and hold for 2-4 hours; the purity of the urea is greater than or equal to 99%;

[0042] Step 2: Spread and compact the pale yellow powder obtained in Step 1 in a quartz boat, then place it in a tube furnace. After all the air in the tube furnace has been replaced with argon, anneal the powder to obtain a yellow powder. The annealing conditions are: under argon protection, heat to 660-700℃ at a rate of 20-30℃ / min and hold for 5-15 minutes. The mass of the pale yellow powder used for annealing should not exceed 5 mg / mm³. 2 The gas replacement process shall last for at least 20 minutes, during which the flow rate of argon gas shall be 200-300 cc / min; after the replacement process is completed, the flow rate of argon gas shall be maintained at 20-50 cc / min.

[0043] Step 3: Place the yellow powder obtained in Step 2 on the edge of the quartz boat, then place it in a tube furnace. After all the air in the tube furnace has been replaced with argon, perform a quadruple heat treatment on the edge to obtain black powder. The quadruple heat treatment process is as follows: First, perform the first heat treatment, that is, under the protection of argon, heat to 720-760℃ at 15-25℃ / min, and then immediately begin natural cooling until the temperature drops to room temperature; then perform the second, third, and fourth heat treatments in sequence. Each heat treatment is performed as follows: under the protection of argon, heat to 660-700℃ at 15-25℃ / min, and then immediately begin natural cooling. Repeat this operation until the fourth heat treatment is completed.

[0044] Step 4: The black powder obtained in Step 3 is centrifuged and washed at least three times with anhydrous ethanol. After washing, it is dried at low temperature to obtain a two-dimensional black carbon nitride quantum material with room temperature ferromagnetism, such as... Figure 2 As shown; the centrifugal washing consists of ultrasonic dispersion and centrifugal separation, with ultrasonic oscillation time ≥3min, centrifugation speed of 6000-8000rpm, and centrifugation time ≥4min; the low-temperature drying requires a temperature of 40-60℃, and the drying process lasts for at least 2 hours.

[0045] Example 1

[0046] A two-dimensional black carbon nitride quantum material with room temperature ferromagnetism, wherein the two-dimensional black carbon nitride is manifested as a two-dimensional layered amorphous nanosheet with a single layer thickness of 4-5.3 nm and a length or width of 1-4.2 μm.

[0047] A method for preparing a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism, specifically including the following steps:

[0048] Step 1: Weigh 2g of urea and spread it evenly on the bottom of a clean, covered crucible. Then place it in a muffle furnace and heat it to 550℃ at 2.5℃ / min in air atmosphere. Hold it at that temperature for 3 hours. After holding, let it cool naturally to room temperature to obtain a light yellow powder.

[0049] Step 2: Spread 1g of pale yellow powder evenly in a quartz boat with a bottom of 20mm×20mm and compact it. Place it in a tube furnace, introduce argon gas, adjust the gas flow rate to 200cc / min and maintain it for 20min. Then adjust the gas flow rate to 20cc / min and simultaneously raise the temperature to 680℃ at 20℃ / min and maintain it for 10min. After the holding time is completed, allow it to cool naturally to room temperature to obtain yellow powder.

[0050] Step 3: Concentrate the yellow powder obtained in Step 2 at the edge of the quartz boat, place it in a tube furnace, introduce argon gas, adjust the gas flow rate to 200 cc / min, maintain for 20 min, then adjust the gas flow rate to 20 cc / min and begin the first heat treatment: heat to 750℃ at 20℃ / min, then immediately begin natural cooling until the temperature drops to room temperature, then begin the second heat treatment: heat to 660℃ at 20℃ / min, then immediately begin natural cooling until the temperature drops to room temperature; perform the third and fourth heat treatments in sequence to obtain black powder; the process parameters for the third and fourth heat treatments are consistent with those for the second heat treatment.

[0051] Step 4: Disperse the black powder obtained in step 3 in anhydrous ethanol, sonicate for 5 min, then centrifuge at 6000 rpm for 8 min, remove the solution, retain the precipitate, add deionized water again, repeat the sonication and centrifugation, repeat five times, and then place the final precipitate in an oven at 40℃ and bake for 6 h to obtain a two-dimensional black carbon nitride quantum material with room temperature ferromagnetism.

[0052] Example 2

[0053] A two-dimensional black carbon nitride quantum material with room temperature ferromagnetism, wherein the two-dimensional black carbon nitride is manifested as a two-dimensional layered amorphous nanosheet with a single layer thickness of 5.3-7.6 nm and a length or width of 3-5.5 μm.

[0054] A method for preparing a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism, specifically including the following steps:

[0055] Step 1: Weigh 2g of urea and spread it evenly on the bottom of a clean, covered crucible. Then place it in a muffle furnace and heat it to 530℃ at a rate of 1.5℃ / min. Hold it at that temperature for 2 hours. After holding, allow it to cool naturally to room temperature to obtain a light yellow powder.

[0056] Step 2: Spread 2g of light yellow powder evenly in a quartz boat with a bottom of 20mm×20mm and compact it. Place it in a tube furnace, introduce argon gas, adjust the gas flow rate to 255cc / min and maintain it for 25min. Then adjust the gas flow rate to 27cc / min and simultaneously raise the temperature to 700℃ at 22℃ / min and maintain it for 5min. After the holding time is completed, allow it to cool naturally to room temperature to obtain yellow powder.

[0057] Step 3: Concentrate the yellow powder obtained in Step 2 at the edge of the quartz boat, place it in a tube furnace, introduce argon gas, adjust the gas flow rate to 255 cc / min, maintain for 25 min, then adjust the gas flow rate to 27 cc / min, and begin the first heat treatment: heat to 720℃ at 15℃ / min, then immediately begin natural cooling until the temperature drops to room temperature, then begin the second heat treatment: heat to 670℃ at 15℃ / min, then immediately begin natural cooling until the temperature drops to room temperature; perform the third and fourth heat treatments in sequence to obtain black powder; the process parameters for the third and fourth heat treatments are consistent with those for the second heat treatment.

[0058] Step 4: Disperse the black powder obtained in step 3 in anhydrous ethanol, sonicate for 3 min, then centrifuge at 6800 rpm for 7 min, remove the solution, retain the precipitate, add deionized water again, repeat the sonication and centrifugation, repeat four times, and then place the final precipitate in an oven at 50℃ for 5 h to obtain a two-dimensional black carbon nitride quantum material with room temperature ferromagnetism.

[0059] Example 3

[0060] A two-dimensional black carbon nitride quantum material with room temperature ferromagnetism, wherein the two-dimensional black carbon nitride is manifested as a two-dimensional layered amorphous nanosheet with a single layer thickness of 8.1-11 nm and a length or width of 4.5-6.2 μm.

[0061] A method for preparing a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism, specifically including the following steps:

[0062] Step 1: Weigh 2g of urea and spread it evenly on the bottom of a clean, covered crucible. Then place it in a muffle furnace and heat it to 540℃ at a rate of 2℃ / min. Hold it at that temperature for 4 hours. After holding, allow it to cool naturally to room temperature to obtain a light yellow powder.

[0063] Step 2: Spread 1g of pale yellow powder evenly in a quartz boat with a bottom of 20mm×50mm and compact it. Place it in a tube furnace, introduce argon gas, adjust the gas flow rate to 240cc / min and maintain it for 30min. Then adjust the gas flow rate to 36cc / min and simultaneously raise the temperature to 690℃ at 24℃ / min and maintain it for 7min. After the holding time is completed, allow it to cool naturally to room temperature to obtain yellow powder.

[0064] Step 3: Concentrate the yellow powder obtained in Step 2 at the edge of the quartz boat, place it in a tube furnace, introduce argon gas, adjust the gas flow rate to 240 cc / min, maintain for 30 min, then adjust the gas flow rate to 36 cc / min, and begin the first heat treatment: heat to 730℃ at 18℃ / min, then immediately begin natural cooling until the temperature drops to room temperature, then begin the second heat treatment: heat to 680℃ at 18℃ / min, then immediately begin natural cooling until the temperature drops to room temperature; perform the third and fourth heat treatments in sequence to obtain black powder; the process parameters for the third and fourth heat treatments are consistent with those for the second heat treatment.

[0065] Step 4: Disperse the black powder obtained in step 3 in anhydrous ethanol, sonicate for 10 min, then centrifuge at 7000 rpm for 6 min, remove the solution, retain the precipitate, add deionized water again, repeat the sonication and centrifugation, repeat three times, and then place the final precipitate in an oven at 60℃ for 2 h to obtain a two-dimensional black carbon nitride quantum material with room temperature ferromagnetism.

[0066] Example 4

[0067] A two-dimensional black carbon nitride quantum material with room temperature ferromagnetism, wherein the two-dimensional black carbon nitride is manifested as a two-dimensional layered amorphous nanosheet with a single layer thickness of 10.7-13.4 nm and a length or width of 6.4-7.2 μm.

[0068] A method for preparing a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism, specifically including the following steps:

[0069] Step 1: Weigh 2g of urea and spread it evenly on the bottom of a clean, covered crucible. Then place it in a muffle furnace and heat it to 570℃ at 3℃ / min. Hold it at that temperature for 2.5h. After holding, let it cool naturally to room temperature to obtain a light yellow powder.

[0070] Step 2: Spread 2g of light yellow powder evenly in a quartz boat with a bottom of 20mm×50mm and compact it. Place it in a tube furnace, introduce argon gas, adjust the gas flow rate to 270cc / min and maintain it for 23min. Then adjust the gas flow rate to 40cc / min and simultaneously raise the temperature to 670℃ at 25℃ / min and maintain it for 12min. After the holding time is completed, allow it to cool naturally to room temperature to obtain yellow powder.

[0071] Step 3: Concentrate the yellow powder obtained in Step 2 at the edge of the quartz boat, place it in a tube furnace, introduce argon gas, adjust the gas flow rate to 270 cc / min, maintain for 23 min, then adjust the gas flow rate to 40 cc / min, and begin the first heat treatment: heat to 740℃ at 25℃ / min, then immediately begin natural cooling until the temperature drops to room temperature, then begin the second heat treatment: heat to 690℃ at 25℃ / min, then immediately begin natural cooling until the temperature drops to room temperature; perform the third and fourth heat treatments in sequence to obtain black powder; the process parameters for the third and fourth heat treatments are consistent with those for the second heat treatment.

[0072] Step 4: Disperse the black powder obtained in step 3 in anhydrous ethanol, sonicate for 6 min, then centrifuge at 8000 rpm for 4 min, remove the solution, retain the precipitate, add deionized water again, repeat the sonication and centrifugation, repeat three times, and then place the final precipitate in an oven at 55℃ for 3 h to obtain a two-dimensional black carbon nitride quantum material with room temperature ferromagnetism.

[0073] Example 5

[0074] A two-dimensional black carbon nitride quantum material with room temperature ferromagnetism, wherein the two-dimensional black carbon nitride is manifested as a two-dimensional layered amorphous nanosheet with a single layer thickness of 13.5-15 nm and a length or width of 8.8-10 μm.

[0075] A method for preparing a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism, specifically including the following steps:

[0076] Step 1: Weigh 2g of urea and spread it evenly on the bottom of a clean, covered crucible. Then place it in a muffle furnace and heat it to 560℃ at 3.5℃ / min. Hold it at that temperature for 3.3h. After holding, let it cool naturally to room temperature to obtain a light yellow powder.

[0077] Step 2: Spread 1.5g of light yellow powder evenly in a quartz boat with a bottom of 20mm×20mm and compact it. Place it in a tube furnace, introduce argon gas, adjust the gas flow rate to 300cc / min and maintain it for 35min. Then adjust the gas flow rate to 50cc / min and simultaneously raise the temperature to 660℃ at 30℃ / min and maintain it for 15min. After the holding time is completed, allow it to cool naturally to room temperature to obtain yellow powder.

[0078] Step 3: Concentrate the yellow powder obtained in Step 2 at the edge of the quartz boat, place it in a tube furnace, introduce argon gas, adjust the gas flow rate to 300 cc / min, maintain for 35 min, then adjust the gas flow rate to 50 cc / min, and begin the first heat treatment: heat to 760℃ at 25℃ / min, then immediately begin natural cooling until the temperature drops to room temperature, then begin the second heat treatment: heat to 700℃ at 25℃ / min, then immediately begin natural cooling until the temperature drops to room temperature; perform the third and fourth heat treatments in sequence to obtain black powder; the process parameters for the third and fourth heat treatments are consistent with those for the second heat treatment.

[0079] Step 4: Disperse the black powder obtained in step 3 in anhydrous ethanol, sonicate for 5 min, then centrifuge at 7500 rpm for 5 min, remove the solution, retain the precipitate, add deionized water again, repeat the sonication and centrifugation, repeat three times, and then place the final precipitate in an oven at 50°C for 4 h to obtain a two-dimensional black carbon nitride quantum material with room temperature ferromagnetism.

[0080] The two-dimensional black carbon nitride with room temperature ferromagnetism prepared in the above embodiments can be used in spintronic devices, topological quantum devices, and magnetic storage.

[0081] like Figure 3 As shown in the atomic force microscope image, the carbon nitride prepared in this invention is a single-layer amorphous nanosheet with a thickness of 4.3 nm, a length of about 4.9 μm, and a width of about 4.0 μm, indicating that the carbon nitride prepared in this invention has two-dimensional properties.

[0082] like Figure 4 As shown in b, the carbon nitride prepared in this invention exhibits a significant room-temperature ferromagnetic signal, as can be seen from the magnetic force microscopy image. Simultaneously, [the following text appears to be incomplete and requires further context: "...and by..."] Figure 4 As can be seen, carbon nitride has a distinct multilayer structure, with each layer having a thickness of 4-5.1 nm, indicating that the carbon nitride prepared in this invention has a distinct two-dimensional layered structure and is ferromagnetic at room temperature.

[0083] like Figure 5 As shown in the transmission electron microscope image, carbon and nitrogen elements are uniformly distributed in carbon nitride, indicating that the two-dimensional black carbon nitride prepared in this invention is an amorphous nanosheet.

[0084] like Figure 6 As shown in the transmission electron microscope image, the two-dimensional black carbon nitride prepared by this invention still has a uniform distribution of carbon and nitrogen elements on a small scale, but the nitrogen content is significantly lower than the carbon content, indicating that a large number of nitrogen vacancies are formed in the black carbon nitride.

[0085] like Figure 7 and Figure 8 As shown, the two-dimensional black carbon nitride prepared by this invention contains chemical bonds in different states, namely, NC3, CN=C, N=CN, NCN and CN bonds coexist, revealing that the graphite-like phase structure is distorted and a large number of nitrogen vacancies are introduced.

[0086] like Figure 9 As shown, the MT curves of the two-dimensional black carbon nitride prepared by this invention under zero field cooling (ZFC) and field cooling (FC) under an external magnetic field of 1000 Oe show that the Curie temperature exceeds 400 K, indicating that the two-dimensional black carbon nitride is a room temperature ferromagnetic material.

[0087] like Figure 10 As shown, the saturation magnetization M of the two-dimensional black carbon nitride prepared in this invention at 2K is... S It is 9.85 emu / g, and the remanent magnetization M r It is 1.58 emu / g, coercive field H C It is 502Oe; such as Figure 11 As shown, the saturation magnetization M of the two-dimensional black carbon nitride prepared in this invention at 300K is... S It is 4.25 emu / g, and the remanent magnetization M r It is 0.77 emu / g, coercive field H C The value is 203Oe; compared with existing two-dimensional carbon-based materials, it shows that the two-dimensional black carbon nitride prepared by the present invention has high saturation magnetization and has practical magnetic properties at room temperature.

[0088] like Figure 12 As shown, the two-dimensional black carbon nitride prepared by the present invention can be attracted by an external magnetic field applied by a permanent magnet in an atmospheric environment at room temperature, indicating that the two-dimensional black carbon nitride prepared by the method of the present invention has strong room temperature ferromagnetism.

Claims

1. A method for preparing a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism, characterized in that, Using urea as raw material, black carbon nitride is obtained by calcination, annealing, and a quadruple heat treatment process, which introduces a large number of nitrogen vacancies into the graphite-like phase structure of carbon nitride. The specific steps include the following: Step 1: Calcine the urea and then allow it to cool naturally to room temperature to obtain a pale yellow powder; the purity of the urea is greater than or equal to 99%. Step 2: The pale yellow powder obtained in Step 1 is spread and compacted in a quartz boat, then placed in a tube furnace. After all the air in the tube furnace has been replaced with argon, annealing is performed to obtain a yellow powder. The mass of the pale yellow powder used for annealing should not exceed 5 mg / mm³. 2 ; Step 3: Place the yellow powder obtained in Step 2 on the edge of the quartz boat, then place it in a tube furnace. After all the air in the tube furnace has been replaced with argon, perform a quadruple heat treatment on the edge to obtain a black powder. The quadruple heat treatment process is as follows: The first heat treatment is as follows: under the protection of argon gas, the temperature is raised to 720-760℃ at a rate of 15-25℃ / min, and then immediately allowed to cool naturally until the temperature drops to room temperature. The second, third, and fourth heat treatments are all performed as follows: under the protection of argon gas, the temperature is raised to 660-700℃ at a rate of 15-25℃ / min, and then immediately allowed to cool naturally. After the temperature drops to room temperature, this operation is repeated until the fourth heat treatment is completed. Step 4: The black powder obtained in Step 3 is centrifuged and washed at least three times with anhydrous ethanol. After washing, it is dried at low temperature to obtain a two-dimensional black carbon nitride quantum material with room temperature ferromagnetism.

2. The method for preparing a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism according to claim 1, characterized in that, The calcination conditions in step 1 are as follows: in an air atmosphere, the temperature is increased to 530-570℃ at a rate of 1.5-3.5℃ / min and then held for 2-4 hours.

3. The method for preparing a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism according to claim 1, characterized in that, The annealing conditions in step 2 are as follows: under the protection of argon, the temperature is increased to 660-700℃ at a rate of 20-30℃ / min and then held for 5-15 minutes.

4. A method for preparing a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism according to claim 1 or 3, characterized in that, In step 2, the gas replacement process lasts for at least 20 minutes, during which the argon gas flow rate is 200-300 cc / min; after the replacement process is completed, the argon gas flow rate is maintained at 20-50 cc / min.

5. The method for preparing a two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism according to claim 1, characterized in that, In step 4, centrifugal washing involves ultrasonic dispersion and centrifugal separation, with the ultrasonic oscillation time... Centrifugation time: 3 minutes, centrifugation speed: 6000-8000 rpm. 4 min; low temperature drying temperature is 40-60℃, and the drying process lasts for at least 2 hours.

6. A two-dimensional black carbon nitride quantum material with room temperature ferromagnetism prepared by the preparation method according to any one of claims 1-5.

7. A two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism according to claim 6, characterized in that: This carbon nitride quantum material is an amorphous nanosheet with a two-dimensional layered structure, with a single layer thickness of 4-15 nm and a length or width of 1-10 μm.

8. A two-dimensional black carbon nitride quantum material with room-temperature ferromagnetism according to claim 6, characterized in that: This carbon nitride quantum material retains a graphite-like phase structure while possessing nitrogen vacancies in its carbon-nitrogen framework.

9. The application of a two-dimensional black carbon nitride quantum material with room temperature ferromagnetism as described in any one of claims 7 or 8 in spintronic devices or topological quantum devices.

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