sp2-sp3 Hybridized Gradia Carbon and Its Preparation Method

Abstract

The present invention relates to a novel sp2-sp3 hybridized Gradia carbon and its preparation method, belonging to the technical field of novel carbon materials. In the present invention, sp2 hybridized carbon is used as a carbon raw material, and under high temperature and high pressure synthesis conditions, a novel sp2-sp3 hybridized crystalline carbon whose basic structural unit is composed of a graphite-like structural unit with sp2 hybridization and a diamond-like structural unit with sp3 hybridization is prepared and named Gradia carbon. The Gradia carbon disclosed in the present invention refers to a novel class of sp2-sp3 hybridized carbon allotropes, and its crystal structure can be changed according to the different widths of the internal sp2 and sp3 structural units.

Description

Technical Field

[0001] The present invention relates to sp2-sp3 hybridized Gradia carbon and its preparation method, belonging to the technical field of carbon materials. Background Art

[0002] Carbon has multiple allotropes, and the emergence of each allotrope has greatly promoted the development of science and technology and social progress. These carbon allotropes include diamond, fullerene, carbon nanotube, graphene, carbene carbon, graphyne, etc. The discoverers of fullerene and graphene respectively won the Nobel Prize in Chemistry in 1996 and the Nobel Prize in Physics in 2010. In the past more than a hundred years, the effort to explore new carbon allotropes has never stopped.

[0003] The phenomenon of multiple allotropes of carbon stems from its three hybridization modes: sp, sp2, and sp3. Sp hybridization is the hybridization of one 2s orbital and one 2p orbital within the same atom. Sp2 hybridization is the process of hybridization of one 2s orbital and two 2p orbitals within the same electron shell of an atom. Sp3 hybridization refers to the process of hybridization of one 2s orbital and three 2p orbitals within the same electron shell of an atom. Different hybridization modes often exhibit completely different physical and chemical properties. Carbon configurations with two or more hybridization modes are expected to exhibit the characteristics of different hybridization modes and form carbon materials with a combination of exotic functions. For example, diamond-like carbon (DLC) obtained by means of deposition technology is a sp2-sp3 hybrid amorphous carbon (Robertson J. Diamond-like amorphous carbon[J]. Materials Science & Engineering R Reports, 2002, 37(4): 129-281.); A series of sp2-sp3 hybrid compressed glassy carbon with excellent properties (Hu M, He J, Zhao Z, et al. Compressed glassy carbon: An ultrastrong and elastic interpenetrating graphene network[J]. Science Advances, 2017, 3(6): e1603213.) and highly sp3 hybridized "amorphous diamond" (Zeng Z, Yang L, Zeng Q, et al. Synthesis of quenchable amorphous diamond[J]. Nature Communications, 2017, 8(1): 322.) are synthesized using glassy carbon as a raw material under high temperature and high pressure; Using C 60Prepare 1D-C with sp2-sp3 hybridization under high temperature and high pressure 60 , 2D-C 60 , 3D-C 60 polymers and amorphous carbon (Blank V D, Buga S G, Dubitsky G A, et al. High-pressure polymerized phases of C60[J]. Carbon, 1998, 36(4): 319-343.). It is worth noting that among the sp2-sp3 hybridized carbons synthesized in current literature and patent reports, only 1D-C 60 , 2D-C 60 , 3D-C 60 polymers are crystalline carbon, and the others are amorphous carbon.

[0004] In addition, some purely theoretically predicted sp2-sp3 hybridized crystalline carbons (Hu M, Ma M, Zhao Z, et al. Superhard sp2–sp3 hybrid carbon allotropes with tunable electronic properties[J]. AIP Advances, 2016, 6(5): 237.) were also reported in the literature, and their optical, electrical, and mechanical properties were theoretically calculated. However, these predicted sp2-sp3 hybridized crystalline carbons have not been experimentally confirmed. Summary of the Invention

[0005] The object of the present invention is to provide novel sp2-sp3 hybridized Gradia carbon and its preparation method. Specifically, it involves: using sp2 hybridized carbons such as graphite, fullerenes, and carbon nanotubes as raw materials, and synthesizing a novel type of sp2-sp3 hybridized carbon - Gradia carbon under high temperature and high pressure. The Gradia carbon disclosed in the present invention refers to a novel type of sp2-sp3 hybridized carbon allotrope, which is completely different from other carbon crystal structures and is composed of sp2 hybridized graphite-like structural units and sp3 hybridized diamond-like structural units. Its crystal structure can be changed according to the widths of the internal sp2 and sp3 structural units.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] The novel sp2-sp3 hybridized Gradia carbon has basic structural units composed of sp2 hybridized graphite-like structural units and sp3 hybridized diamond-like structural units.

[0008] A further improvement of the technical solution of the present invention lies in: including the following steps:

[0009] (1). Load the carbon raw material into a pre-pressing mold, pre-form the carbon raw material into a carbon raw material blank through the action of a tablet press, and then place it in a vacuum hot-pressing sintering furnace for pre-sintering;

[0010] (2). Load the pre-sintered carbon raw material blank in step (1) into an assembly block, and then place the assembly block containing the carbon raw material blank in a drying oven for drying;

[0011] (3). After taking out the assembly block in step (2) and cooling it to room temperature, then place it in a press for high-temperature and high-pressure operation, and then cool it again and perform a pressure relief operation;

[0012] (4). Take out the assembly block from the press to obtain a novel sp2-sp3 hybrid Gradia carbon that can be retained in a normal temperature and pressure environment.

[0013] A further improvement of the technical solution of the present invention is that: the carbon raw material contains any one or more sp2 hybrid carbons, and the sp2 hybrid carbons include carbon materials containing sp2 hybridization such as graphite, fullerene, graphene, carbon nanotubes, vitreous carbon, amorphous carbon, onion carbon, carbon black, carbene carbon, graphyne, DLC, etc.

[0014] A further improvement of the technical solution of the present invention is that: the pre-sintering temperature in step (1) is 400-1800 °C, and the pre-sintering time is 10-60 min.

[0015] A further improvement of the technical solution of the present invention is that: the blank pre-formed in step (1) is a straight cylindrical shape.

[0016] A further improvement of the technical solution of the present invention is that: the drying temperature of the drying process in step (2) is 100-250 °C, and the drying time is 1-3 h.

[0017] A further improvement of the technical solution of the present invention is that: the specific parameters of the high-temperature and high-pressure process in step (3) are set as the synthesis pressure is 5-25 GPa, the temperature is 25-2500 °C, and the heat preservation time is 5-120 minutes.

[0018] A further improvement of the technical solution of the present invention is that: for the novel sp2-sp3 hybrid crystal carbon synthesized by the preparation method, its crystal structure can be adjusted according to the changes of the graphite-like structure units with sp2 hybridization and the diamond-like structure units with sp3 hybridization inside.

[0019] Due to the adoption of the above technical solution, the technical effects obtained by the present invention are:

[0020] The raw materials used in the present invention are common commercially available carbon materials containing sp2 hybridization, with low requirements for the size and purity of the raw materials. There are no special requirements for the purity of the sp2 carbon used in the present invention. The sp2 carbon can contain impurity elements other than carbon (C). As long as the sp2 carbon material contains a certain proportion of sp2 hybridized carbon atoms and the impurities do not affect the structure of Gradia carbon. The impurity elements can be silicon (Si), oxygen (O), nitrogen (N), hydrogen (H), etc. The raw materials are inexpensive and easily obtainable.

[0021] A novel sp2-sp3 hybrid carbon crystal is prepared by the preparation method of the present invention. The novel sp2-sp3 hybrid carbon crystal has a different structure from other carbon crystals. Its basic structural unit is composed of a graphite-like structural unit with sp2 hybridization and a diamond-like structural unit with sp3 hybridization, so it has different properties. At the same time, the crystal structure of the novel sp2-sp3 hybrid carbon can be changed according to the different widths of its internal sp2 and sp3 structural units. Therefore, its physical properties such as light, electricity, and mechanics can be regulated, and it can be applied in different fields with broad prospects.

[0022] The high-temperature and high-pressure equipment used in the present invention is currently widely used in China. Its operation is simple, and the high-pressure synthesis parameters are easy to control. At the same time, the raw materials are abundant, inexpensive, and easy to obtain. Industrial large-scale production can be realized, and the crystal structure of the sample can be adjusted to achieve performance regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a high-resolution atomic image transmission electron microscope image of the novel sp2-sp3 hybrid Gradia carbon of the present invention;

[0024] Figure 2 is a structural diagram of Gradia-I with 24 carbon atoms in the unit cell of the present invention;

[0025] Figure 3 is a structural diagram of Gradia-II with 88 carbon atoms in the unit cell of the present invention;

[0026] Figure 4 is a structural diagram of Gradia-III with 88 carbon atoms in the unit cell of the present invention;

[0027] Figure 5 is the electron energy loss spectrum (EELS) and synchrotron radiation XRD diffraction pattern of the novel sp2-sp3 hybrid Gradia carbon of the present invention obtained by Themis Z electron microscope test;

[0028] Figure 6 is the Raman spectrum of the novel sp2-sp3 hybrid Gradia carbon of the present invention obtained by Raman spectrometer test. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0030] The present invention discloses a novel sp2-sp3 hybridized Gradia carbon and a preparation method thereof. The preparation method includes the following steps:

[0031] (1) Load one or more sp2 hybridized carbon materials including graphite, fullerenes, carbon nanotubes, amorphous carbon, and onion carbon into a pre-pressing mold. Through the action of a tablet press, the sp2 hybridized carbon materials are preformed into a straight cylindrical blank, and then placed in a vacuum hot pressing sintering furnace for pre-sintering. The pre-sintering temperature is 400-1800 °C, and the pre-sintering time is 10-60 min;

[0032] (2) Load the pre-sintered sp2 hybridized carbon material blank in step (1) into an assembly block, and then place the assembly block containing the sp2 hybridized carbon material blank in a drying oven for drying. The drying temperature is 100-250 °C, and the drying time is 1-3 h;

[0033] (3) After taking out the assembly block in step (2) and cooling it to room temperature, then place it in a T25 press produced by Rockland Research Company, USA for high-temperature and high-pressure operation. The synthesis pressure is 1-25 GPa, the temperature is 25-2500 °C, and the heat preservation time is 5-120 minutes. Then cool it again and perform pressure relief operation;

[0034] (4) Take out the assembly block from the press to obtain the novel sp2-sp3 hybridized Gradia carbon.

[0035] The prepared novel sp2-sp3 hybridized Gradia carbon is observed through the hard X-ray microfocus beamline station (BL15U1) of the Shanghai Synchrotron Radiation Facility (SSRF), the LabRAM HREvolution Raman spectrometer of Horiba JY Company, France, and the Themis Z electron microscope, and the spectra as shown in Figure 5 and Figure 6 are obtained. From Figure 5 and Figure 6 , it can be seen that the novel sp2-sp3 hybridized Gradia carbon prepared by the present invention has a sp2 hybridized graphite-like structural unit and a sp3 hybridized diamond-like structural unit. Therefore, it is named Gradia carbon, and the English name is obtained by taking the first three letters of graphite and diamond. Through the observation of the Themis Z electron microscope, it is found that the prepared novel sp2-sp3 hybridized Gradia carbon has various different types of crystal structures, and its structure can be changed according to the widths of the internal sp2 hybridized graphite-like structural unit and sp3 hybridized diamond-like structural unit. Such asFigure 1 Among the three monoclinic crystal structures listed for the present invention, they are respectively named Gradia-I carbon, Gradia-II carbon, and Gradia-III carbon.

[0036] The space group of Gradia-I carbon is 11 (P21 / m). As Figure 2 shown, taking a crystal with 24 carbon atoms in the unit cell as an example, its lattice constant is β = 87.052°; From Figure 2 it can be seen that Gradia-I carbon is a novel sp2-sp3 hybrid crystal carbon formed by the left graphite-like structure and the right diamond-like structure with a specific coherent crystal plane, that is, the coherent crystal plane has the characteristics as Figure 2 shown, and they all belong to Gradia-I carbon with the space group of 11 (P21 / m).

[0037] The space group of Gradia-II carbon is 12 (C2 / m). As Figure 3 shown, taking a crystal with 88 carbon atoms in the unit cell as an example, its lattice constant is β = 81.787°; From Figure 3 it can be seen that Gradia-II carbon is a novel sp2-sp3 hybrid crystal carbon formed by the left graphite-like structure and the right diamond-like structure with a specific coherent crystal plane, that is, the coherent crystal plane has the characteristics as Figure 3 shown, and they all belong to Gradia-II carbon with the space group of 12 (C2 / m).

[0038] The space group of Gradia-III carbon is 11 (P21 / m). As Figure 4 shown, taking a crystal with 88 carbon atoms in the unit cell as an example, its lattice constant is β = 88.249°; From Figure 4 it can be seen that Gradia-III carbon is a novel sp2-sp3 hybrid crystal carbon formed by the left graphite-like structure and the right hexagonal diamond-like structure with a specific coherent crystal plane, that is, the coherent crystal plane has the characteristics as Figure 4 shown, and they all belong to Gradia-III carbon with the space group of 11 (P21 / m).

[0039] The following are specific examples:

[0040] The raw materials used in each example are commercially available common sp2 hybrid carbon materials, including carbon materials containing sp2 hybridization such as graphite, fullerene, graphene, carbon nanotubes, vitreous carbon, amorphous carbon, onion carbon, carbon black, carbine carbon, graphdiyne, DLC, etc.

[0041] During the high-temperature and high-pressure operation in the examples, a T25 press produced by Rockland Research Company of the United States was used, with a synthesis pressure range of 1-25 GPa and a maximum temperature of 25-2500 °C; however, the high-temperature and high-pressure device involved in the present invention is not limited to the T25 press, and other high-pressure devices that can reach the pressure and temperature conditions can be used.

[0042] Example 1: Preparation of Gradia carbon using graphite as the sp2 hybridized carbon raw material

[0043] (I). Place the graphite in a pre-press mold, and use a tablet press to preform it at a pressure of 20-40 MPa for 5-10 minutes to obtain a cylindrical blank. Then, place it in a vacuum hot-press sintering furnace for pre-sintering, with the pre-sintering temperature controlled between 1000-1600 °C and the pre-sintering time controlled at 20-40 minutes;

[0044] (II). Load the pre-sintered sp2 hybridized carbon material blank from step (I) into the assembly block, and then place the assembly block containing the sp2 hybridized carbon material blank in a drying oven for drying. The drying temperature is 180 °C and the drying time is 2 hours;

[0045] (III). After taking out the assembly block from step (II) and cooling it to room temperature, then place it in a T25 press produced by Rockland Research Company of the United States for high-temperature and high-pressure operation. The synthesis pressure is 5-25 GPa, the temperature is 600-2500 °C, and the heat preservation time is 10-120 minutes. Then, cool it again and perform a pressure relief operation;

[0046] (IV). Take out the assembly block from the press to obtain the novel sp2-sp3 hybridized Gradia carbon.

[0047] Test and analyze the product. Observe the obtained novel sp2-sp3 hybridized Gradia carbon through the hard X-ray microfocus beamline station (BL15U1) of the Shanghai Synchrotron Radiation Facility (SSRF), the LabRAM HREvolution Raman spectrometer of Horiba JY Company of France, and the Themis Z electron microscope. The synchrotron radiation XRD results prove that the synthesized Gradia carbon is a new structure carbon; EELS and Raman spectroscopy prove that it is a sp2-sp3 hybridized carbon.

[0048] Example 2: Preparation of Gradia carbon using carbon nanotubes as the sp2 hybridized carbon raw material

[0049] (I). Place the carbon nanotubes in a pre-press mold, and use a tablet press to preform it at a pressure of 30-50 MPa for 5-10 minutes to obtain a cylindrical blank. Then, place it in a vacuum hot-press sintering furnace for pre-sintering, with the pre-sintering temperature controlled at 800-1600 °C and the pre-sintering time controlled at 15-40 minutes;

[0050] (ii) loading the carbon nanotube blanks pre-sintered in step (i) into an assembly block, and then placing the assembly block containing the carbon nanotube blanks into a drying oven for drying at a drying temperature of 180° C. for a drying time of 2 h;

[0051] (iii) taking out the assembled block in step (ii) and cooling it to room temperature, then placing it in a T25 type press produced by Rockland Research Company of the United States for high temperature and high pressure operation, with a synthesis pressure of 7-25 GPa, a temperature of 1000-1800° C., and a holding time of 15-60 minutes, and then cooling it again and performing a pressure relief operation;

[0052] (iv) taking out the assembled block from the press to obtain a novel sp2-sp3 hybridized Gradia carbon.

[0053] The product was tested and analyzed. The new sp2-sp3 hybridized Gradia carbon was observed by the Shanghai Light Source (SSRF) hard X-ray microfocus beamline station (BL15U1), the LabRAM HREvolution Raman spectrometer and Themis Z electron microscope of Horiba JY Company in France. The synchrotron radiation XRD results proved that the synthesized Gradia carbon was a new structure carbon; EELS and Raman spectroscopy proved that it was a sp2-sp3 hybridized carbon.

[0054] Example 3: Preparation of Gradia Carbon Using Fullerene as Sp2 Hybridized Carbon Raw Material

[0055] (i) Pre-pressing the fullerene into a mold, using a tablet press to preform for 5-15 minutes at a pressure of 20-50 MPa to obtain a cylindrical body;

[0056] (ii) placing the fullerene body pre-sintered in step (i) into an assembly block, and then placing the assembly block of the fullerene body into a drying oven for drying at a temperature of 180° C. for a drying time of 2 h;

[0057] (iii) taking out the assembled block in step (ii) and cooling it to room temperature, then placing it in a T25 type press produced by Rockland Research Company of the United States for high temperature and high pressure operation, with a synthesis pressure of 10-18 GPa, a temperature of 600-1500° C., and a heat preservation time of 30-120 minutes, and then cooling it again and performing a pressure relief operation;

[0058] (iv) taking out the assembled block from the press to obtain a novel sp2-sp3 hybridized Gradia carbon.

[0059] The product was tested and analyzed. The new sp2-sp3 hybridized Gradia carbon was observed by the Shanghai Light Source (SSRF) hard X-ray microfocus beamline station (BL15U1), the LabRAM HREvolution Raman spectrometer and Themis Z electron microscope of Horiba JY Company in France. The synchrotron radiation XRD results proved that the synthesized Gradia carbon was a new structure carbon; EELS and Raman spectroscopy proved that it was a sp2-sp3 hybridized carbon.

[0060] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, principle, etc. of the present invention should be included in the protection scope of the present invention.

[0061] The optional materials of various components are listed in the description of the present invention, but those skilled in the art should understand that the above-mentioned list of component materials is not limiting and not exhaustive, and various components can be replaced by other equivalent materials not mentioned in the description of the present invention, while still achieving the purpose of the present invention. The specific embodiments mentioned in the description are also only for the purpose of explanation, and are not used as examples to limit the scope of the present invention.

[0062] In addition, the dosage range of each component of the present invention includes any combination of any lower limit and any upper limit mentioned in the specification, and also includes any range formed by combining the specific content of the component in each specific embodiment as the upper limit or lower limit: all these ranges are included in the scope of the present invention, but these combined ranges are not listed one by one in the specification just to save space. Each feature of the present invention listed in the specification can be combined with any other feature of the present invention, and such combination is also within the scope of the disclosure of the present invention, but these combined ranges are not listed one by one in the specification just to save space.

Claims

1. A sp2-sp3 hybridized Gradia carbon, characterized in that: Its basic structural unit is composed of a graphite-like structural unit with sp2 hybridization and a diamond-like structural unit with sp3 hybridization, which is a sp2-sp3 hybridized crystalline carbon formed by the coherent crystal plane of the graphite-like structure and the diamond-like structure.

2. A preparation method of the sp2-sp3 hybridized Gradia carbon as described in claim 1, characterized in that it includes the following steps: (1) Load the carbon raw material into a pre-pressing mold, pre-form the carbon raw material into a carbon raw material blank under the action of a tablet press, and then put it into a vacuum hot pressing sintering furnace for pre-sintering. The pre-sintering temperature is 400-1800 °C, and the pre-sintering time is 10-60 min. The carbon raw material is any one or more sp2 hybridized carbons, and the sp2 hybridized carbon includes graphite, fullerene C 60 , carbon nanotubes; (2) Load the pre-burned carbon raw material blank in step (1) into the assembly block, and then put the assembly block containing the carbon raw material blank into the drying oven for drying; (3) After taking out the assembly block in step (2) and cooling it to room temperature, then put it into the press for high-temperature and high-pressure operation, and then cool it again and perform pressure relief operation. The specific parameter settings for the high-temperature and high-pressure operation are: 1) When using graphite as the sp2 hybridized carbon raw material, the synthesis pressure is 5-25 GPa, the temperature is 600-2500 °C, and the heat preservation time is 10-120 minutes; 2) When using carbon nanotubes as the sp2 hybridized carbon raw material, the synthesis pressure is 7-25 GPa, the temperature is 1000-1800 °C, and the heat preservation time is 15-60 minutes; 3) When using fullerenes as the sp2 hybridized carbon raw material, the synthesis pressure is 10-18 GPa, the temperature is 600-1500 °C, and the heat preservation time is 30-120 minutes; (4) Take out the assembly block from the press to obtain the sp2-sp3 hybridized Gradia carbon that can be retained in the normal temperature and pressure environment.

3. The preparation method of the sp2-sp3 hybridized Gradia carbon as described in claim 2, characterized in that: The prefabricated carbon raw material blank in step (1) is a straight cylinder.

4. The preparation method of the sp2-sp3 hybridized Gradia carbon as described in claim 2, characterized in that: The drying temperature in the drying process in step (2) is 100-250 °C, and the drying time is 1-3 h.

5. The preparation method of the sp2-sp3 hybridized Gradia carbon as described in any one of claims 2-4, characterized in that: The sp2-sp3 hybridized Gradia carbon is composed of a graphite-like structural unit with sp2 hybridization and a diamond-like structural unit with sp3 hybridization, and its crystal structure can be changed according to the different widths of the graphite-like structural unit with sp2 hybridization and the diamond-like structural unit with sp3 hybridization inside.

Images