Lightweight nanoporous diamond and preparation method thereof

Abstract

The present application provides a lightweight nanoporous diamond and a preparation method thereof, the preparation method comprising: subjecting a carbon source and a metal to high temperature and high pressure treatment to convert the carbon source into diamond, then cooling and depressurizing the carbon source to room temperature and pressure to obtain a composite material of diamond and metal; soaking the composite material in an inorganic solvent to remove the metal, thereby obtaining a lightweight nanoporous diamond. The preparation method of the lightweight nanoporous diamond provided in the present application can achieve the regulation of the pore size, porosity and density of the lightweight nanoporous diamond, thereby obtaining a lightweight nanoporous diamond with a low pore size, high porosity and low density. At the same time, the obtained lightweight nanoporous diamond also has high hardness and good mechanical strength. In addition, the preparation method provided is simple and easy to operate, which is conducive to the mass production of lightweight nanoporous diamonds.

Description

Technical Field

[0001] The present application relates to the technical field of diamond materials, and in particular to a lightweight nanoporous diamond and a preparation method thereof. Background Art

[0002] As an outstanding nanomaterial, nanodiamond not only inherits the characteristics of diamond's ultra-high hardness, excellent thermal conductivity, and outstanding electrical insulation, but also has a wider range of applications due to its harmless nature and good biocompatibility. In addition, nanodiamond's high transmittance and absorptivity for radar waves, infrared, and ultraviolet light also give it good application prospects. With the rapid development of the aerospace field, the importance of preparing lightweight nanoporous diamonds with low density, high porosity, and nanoscale pores has become increasingly prominent. Lightweight nanoporous diamonds with low density, high porosity, and nanoscale pores will become a key material to promote innovation, bringing unlimited possibilities for future scientific and technological advancements.

[0003] However, current methods using conventional pore-forming agents or framework templates have limited success in producing lightweight, nanoporous diamonds with nanometer-scale pore sizes. Lightweight diamonds with densities lower than water or nanoporous diamonds with pore sizes below 10 nm are rarely reported. Furthermore, the traditional pore-forming or framework template methods are complex and time-consuming, requiring a series of complex steps to prepare a suitable porous framework before nanodiamonds can be synthesized on this framework using techniques such as chemical vapor deposition (CVD). This process not only increases production costs but also significantly hinders industrialization. Therefore, a new approach is urgently needed to overcome these obstacles and expand the application of nanodiamonds into a wider range of fields. Summary of the Invention

[0004] The purpose of this application is to provide a lightweight nanoporous diamond and a preparation method thereof, which can achieve the regulation of the pore size, porosity, and density of the lightweight nanoporous diamond to obtain a lightweight nanoporous diamond with low pore size, high porosity, and low density. The preparation method is simple and easy to operate, which is conducive to mass production. The specific technical solution is as follows:

[0005] A first aspect of the present application provides a method for preparing lightweight nanoporous diamond, which comprises the following steps:

[0006] S1. Treating a carbon source and a metal under high temperature and high pressure to convert the carbon source into diamond, and then cooling and depressurizing the carbon source to room temperature and pressure to obtain a composite material of diamond and metal; the metal is selected from at least one of bismuth, lead, gallium, mercury, a bismuth-containing alloy, and a mercury-containing alloy; the mass ratio of the carbon source to the metal is 1:(0.1-10); the temperature of the high temperature and high pressure treatment is 1400°C-2000°C and the pressure is 6GPa-25GPa;

[0007] S2. Soaking the composite material in an inorganic solvent to remove the metal, thereby obtaining the lightweight nanoporous diamond.

[0008] In some embodiments, the carbon source is selected from at least one of graphite, onion carbon, amorphous carbon, carbon nanotubes, nanodiamond powder, and onion carbon.

[0009] In some embodiments, the inorganic solvent is selected from at least one of 36 wt % to 38 wt % hydrochloric acid aqueous solution, aqua regia, 28 wt % to 70 wt % nitric acid aqueous solution, 80 wt % to 98 wt % sulfuric acid aqueous solution, and 35 wt % to 50 wt % hydrofluoric acid aqueous solution.

[0010] In some embodiments, the depressurization comprises a depressurization rate of 2 GPa / h to 4 GPa / h.

[0011] In some embodiments, the average particle size of the metal is 10 nm to 200 μm.

[0012] In some embodiments, step S1 further comprises:

[0013] Before the high temperature and high pressure treatment, the carbon source and the metal are ground and mixed; or,

[0014] Before the high temperature and high pressure treatment, the carbon source and the metal are placed separately, and the metal is melted into the diamond through the high temperature and high pressure treatment.

[0015] The second aspect of the present application provides a lightweight nanoporous diamond prepared according to the preparation method provided in the first aspect of the present application.

[0016] In some embodiments, the lightweight nanoporous diamond has a specific surface area of ​​20 m 2 / g-150m 2 / g, porosity is 5%-20%.

[0017] In some embodiments, the density of the lightweight nanoporous diamond is 0.6 g / cm 3 -3g / cm 3 .

[0018] In some embodiments, the lightweight nanoporous diamond has an average pore size of 2 nm to 15 nm.

[0019] The present application provides a lightweight nanoporous diamond and a preparation method thereof, wherein the preparation method comprises: subjecting a carbon source and a metal to high temperature and high pressure treatment to convert the carbon source into diamond, and then cooling and depressurizing the carbon source to normal temperature and pressure to obtain a composite material of diamond and metal; and immersing the composite material in an inorganic solvent to remove the metal to obtain a lightweight nanoporous diamond. The preparation method of the lightweight nanoporous diamond provided in the present application can achieve the regulation of the pore size, porosity and density of the lightweight nanoporous diamond, and obtain a lightweight nanoporous diamond with a low pore size, high porosity and low density. At the same time, the obtained lightweight nanoporous diamond also has high hardness and good mechanical strength. In addition, the preparation method provided is simple and easy to operate, which is conducive to the mass production of lightweight nanoporous diamonds. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0021] Figure 1 Schematic diagram of the process for obtaining lightweight nanoporous diamond by immersing a composite material of diamond and metal in an inorganic solvent;

[0022] Figure 2 This is a photo of the lightweight nanoporous diamond in Example 5 floating on the water surface;

[0023] Figure 3 These are nitrogen adsorption-desorption curves of the lightweight nanoporous diamonds of Examples 5 to 8;

[0024] Figure 4 These are the distribution results of specific surface area and average pore diameter of the lightweight nanoporous diamonds of Examples 5 to 8. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present application and the accompanying drawings to clearly and completely describe the technical solutions in this application. Obviously, the embodiments described are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0026] A first aspect of the present application provides a method for preparing lightweight nanoporous diamond, which comprises the following steps:

[0027] S1. Treating a carbon source and a metal under high temperature and high pressure to convert the carbon source into diamond, and then cooling and depressurizing the carbon source to room temperature and pressure to obtain a composite material of diamond and metal; the metal is selected from at least one of bismuth, lead, gallium, mercury, a bismuth-containing alloy, and a mercury-containing alloy; the mass ratio of the carbon source to the metal is 1:(0.1-10); the temperature of the high temperature and high pressure treatment is 1400°C-2000°C and the pressure is 6GPa-25GPa;

[0028] S2. Soaking the composite material in an inorganic solvent to remove the metal, thereby obtaining the lightweight nanoporous diamond.

[0029] For example, the mass ratio of the carbon source to the metal can be 1:0.1, 1:0.2, 1:0.5, 1:0.8, 1:1, 1:2, 1:3, 1:5, 1:6, 1:8, 1:10, or a range consisting of any two of the values. The temperature of the high temperature and high pressure treatment can be 1400°C, 1500°C, 1600°C, 1700°C, 1800°C, 1900°C, 2000°C, or a range consisting of any two of the values; the pressure can be 6GPa, 7GPa, 8GPa, 10GPa, 11GPa, 12GPa, 13GPa, 15GPa, 16GPa, 18GPa, 20GPa, 22GPa, 23GPa, 25GPa, or a range consisting of any two of the values. The present application does not particularly limit the time of the high temperature and high pressure treatment, as long as the purpose of the present application can be achieved. In some embodiments, the time of the high temperature and high pressure treatment can be 10s-2h. For example, the time of the high temperature and high pressure treatment can be 10s, 30s, 1min, 2min, 10min, 30min, 1h, 1.5h, 2h or a range consisting of any two of these values. In the present application, the metal is a metal self-propagating pore-forming agent, which can actively occupy the nano-sized pores of diamond at high temperature. The metal self-propagating pore-forming agent is melted at high temperature and can infiltrate and self-propagate on the surface of diamond particles. Through the occupation of the metal self-propagating pore-forming agent, a composite material of diamond and metal is prepared, and then the occupied metal is removed by an inorganic solvent to obtain nanoporous diamond. The process diagram of obtaining lightweight nanoporous diamond after the composite material of diamond and metal is immersed in an inorganic solvent is shown as follows. Figure 1 In the present application, the density, pore size, and specific surface area of ​​the lightweight nanoporous diamond can be controlled by regulating the mass ratio of the carbon source to the metal. Specifically, by reducing the mass of the carbon source and / or increasing the mass of the metal, i.e., reducing the mass ratio of the carbon source to the metal, i.e., increasing the percentage of the metal in the total mass of the carbon source and the metal, the density of the lightweight nanoporous diamond will decrease, the pore size will first increase and then decrease, and the specific surface area will increase.

[0030] The preparation method of lightweight nanoporous diamond provided in this application can realize the regulation of the pore size, porosity and density of lightweight nanoporous diamond, and obtain lightweight nanoporous diamond with low pore size, high porosity and low density. At the same time, the lightweight nanoporous diamond obtained also has high hardness and good mechanical strength. In addition, the preparation method provided is simple and easy to operate, which can reduce production costs and facilitate the mass production of lightweight nanoporous diamonds. In this application, the normal temperature is room temperature, which is 20-30°C, and the normal pressure is 1 atmosphere.

[0031] The present application does not particularly limit the type of bismuth-containing alloy, as long as it can achieve the objectives of this application; for example, the bismuth-containing alloy can be selected from at least one of a lead-bismuth alloy and a gallium-bismuth alloy. The present application does not particularly limit the type of amalgam-containing alloy, as long as it can achieve the objectives of this application; for example, the amalgam-containing alloy can be a lead-mercury alloy.

[0032] The present application has no particular limitation on the type of carbon source, as long as the purpose of the present application can be achieved; in some embodiments, the carbon source is selected from at least one of graphite, onion carbon, amorphous carbon, carbon nanotubes, nanodiamond powder, and onion carbon.

[0033] In some embodiments, the inorganic solvent is selected from at least one of a 36wt%-38wt% hydrochloric acid aqueous solution, aqua regia, a 28wt%-70wt% nitric acid aqueous solution, an 80wt%-98wt% sulfuric acid aqueous solution, and a 35wt%-50wt% hydrofluoric acid aqueous solution. In the present application, the aqua regia is prepared by mixing concentrated hydrochloric acid and concentrated nitric acid in a volume ratio of 3:1, wherein the concentrated hydrochloric acid is a 36wt%-38wt% hydrochloric acid aqueous solution and the concentrated nitric acid is a 65wt%-70wt% nitric acid aqueous solution. For example, the hydrochloric acid aqueous solution can be 36wt%, 37wt%, 38wt% or a range consisting of any two of the numerical values; the nitric acid aqueous solution can be 28wt%, 30wt%, 35wt%, 40wt%, 50wt%, 60wt%, 70wt% or a range consisting of any two of the numerical values; the sulfuric acid aqueous solution can be 80wt%, 82wt%, 85wt%, 88wt%, 90wt%, 93wt%, 95wt%, 98wt% or a range consisting of any two of the numerical values; the hydrofluoric acid aqueous solution can be 35wt%, 38wt%, 40wt%, 46wt%, 50wt% or a range consisting of any two of the numerical values; the concentrated hydrochloric acid can be 36wt%, 37wt%, 38wt% or a range consisting of any two of the numerical values; the concentrated nitric acid can be 65wt%, 68wt%, 70wt% or a range consisting of any two of the numerical values. The present application soaks the composite material in the inorganic solvent to remove the placeholder metal, thereby obtaining the lightweight nanoporous diamond.

[0034] In some embodiments, the depressurization comprises a depressurization rate of 2 GPa / h-4 GPa / h. For example, the depressurization rate is 2 GPa / h, 2.5 GPa / h, 3 GPa / h, 3.5 GPa / h, 4 GPa / h, or a range consisting of any two values ​​therein.

[0035] In the present application, the cooling is a quenching process, which is rapid cooling to room temperature.

[0036] In some embodiments, the average particle size of the metal is 10 nm to 200 μm. For example, the average particle size of the metal can be 10 nm, 20 nm, 50 nm, 100 nm, 200 nm, 500 nm, 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 150 μm, 200 μm, or a range consisting of any two of these values.

[0037] In some embodiments, step S1 further comprises:

[0038] Before the high temperature and high pressure treatment, the carbon source and the metal are ground and mixed; or,

[0039] Before the high temperature and high pressure treatment, the carbon source and the metal are placed separately, and the metal is melted into the diamond through the high temperature and high pressure treatment.

[0040] In the present application, the carbon source and the metal can be ground and mixed, then placed in a crucible for preparing diamonds for high temperature and high pressure treatment. Alternatively, the carbon source and the metal can be placed separately at both ends of the crucible for preparing diamonds. After the high temperature and high pressure treatment, the metal will melt and actively infiltrate the diamond to occupy nano-sized pores, causing the metal to melt into the diamond. When the carbon source and the metal are placed separately in the present application, there is no need to finely grind and mix the carbon source and the metal in advance, making the preparation method simpler and more convenient, and more conducive to the mass production of lightweight nanoporous diamonds.

[0041] The second aspect of the present application provides a lightweight nanoporous diamond prepared according to the preparation method provided in the first aspect of the present application.

[0042] In some embodiments, the lightweight nanoporous diamond has a specific surface area of ​​20 m 2 / g-150m 2 / g, and a porosity of 5%-20%. For example, the specific surface area of ​​the lightweight nanoporous diamond can be 20m 2 / g, 25m 2 / g、30m 2 / g、35m 2 / g, 40m2 / g, 50m 2 / g、55m 2 / g, 60m 2 / g、70m 2 / g、80m 2 / g、90m 2 / g、100m 2 / g、110m 2 / g, 120m 2 / g, 130m 2 / g, 140m 2 / g, 150m 2 / g or a range consisting of any two values ​​therein; the porosity of the lightweight nanoporous diamond may be 5%, 8%, 10%, 12%, 14%, 16%, 18%, 20% or a range consisting of any two values ​​therein.

[0043] In some embodiments, the density of the lightweight nanoporous diamond is 0.6 g / cm 3 -3g / cm 3 For example, the density of the lightweight nanoporous diamond can be 0.6 g / cm 3 , 0.7g / cm 3 , 0.8g / cm 3 , 0.9g / cm 3 , 1g / cm 3 , 1.2g / cm 3 , 1.5g / cm 3 , 1.8g / cm 3 , 2g / cm 3 , 2.3g / cm 3 , 2.5g / cm 3 , 2.7g / cm 3 , 2.9g / cm 3 , 3g / cm 3 Or a range consisting of any two values.

[0044] In some embodiments, the lightweight nanoporous diamond has an average pore size of 2 nm to 15 nm. For example, the lightweight nanoporous diamond can have an average pore size of 2 nm, 3 nm, 5 nm, 7 nm, 9 nm, 10 nm, 12 nm, 14 nm, 15 nm, or a range consisting of any two of these values.

[0045] Example

[0046] Hereinafter, the embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are by mass.

[0047] Test methods and equipment:

[0048] Specific surface area, average pore size, and porosity tests:

[0049] Nitrogen adsorption / desorption experiments were performed on diamond samples using an Autosorb IQ fully automatic gas adsorption analyzer (Quantachrome Instruments). The adsorption process was carried out at a liquid nitrogen temperature of 77.2 K and the desorption temperature was 373 K. Adsorption isotherms were obtained, and the specific surface area, average pore size, and porosity of the diamond were analyzed at the analysis station.

[0050] Density test:

[0051] Weigh the diamond mass (g), measure the diamond diameter and height, and calculate the diamond volume (cm 3 ), diamond density (g / cm 3 ) = diamond mass / diamond volume.

[0052] Hardness test:

[0053] Using a KLA Agilent Nano Indenter G200X nanoindenter, diamond samples were embedded in epoxy resin and polished to a flat surface. A Berkovich diamond indenter was then pressed vertically into the sample surface. Continuous stiffness measurement technology was used to obtain real-time hardness readings during the indenter loading process. The maximum penetration depth during testing was kept within 200nm to minimize substrate effects.

[0054] Example 1

[0055] S1. Amorphous carbon (carbon source) and bismuth metal (metal) were ground and mixed in a mass ratio of 4:1. The mixture was then subjected to high-temperature and high-pressure treatment in a large-cavity press (Max Voggenreiter, Germany, Kawai 6-8 two-stage press) at 1500°C and 15 GPa for 60 seconds to convert the carbon source into diamond. The mixture was then rapidly cooled to room temperature by disconnecting the heating power supply at a decompression rate of 3 GPa / h. After cooling and lowering the pressure to room temperature and pressure, a diamond-metal composite material was obtained. The average particle size of the amorphous carbon (carbon source) was 50 nm, and the average particle size of the bismuth metal was 10 μm.

[0056] S2. The composite material obtained in step S1 is immersed in an inorganic solvent 36 wt % hydrochloric acid aqueous solution to remove the metallic bismuth, thereby obtaining a lightweight nanoporous diamond.

[0057] Example 2 to Example 8

[0058] Except for adjusting the corresponding preparation parameters according to Table 1, the rest is the same as Example 1.

[0059] Comparative Example 1

[0060] High-purity 99% nanodiamond powder (0.3 μm) was mixed with iron foam (86.7% porosity), ultrasonically mixed, and pre-pressed into a sheet to form a diamond / iron precursor. The mixture was maintained at a pressure of 7 GPa and a temperature of 1500°C for 20 minutes. The resulting porous diamond was then acid-washed to remove residual iron compounds. The iron foam serves as both a catalyst and a framework, forming Fe-C compounds at high temperatures. After acid washing, the porous diamond structure was retained.

[0061] Comparative Example 2

[0062] S1. The carbon source, amorphous carbon, is subjected to high temperature and high pressure treatment at 1500°C and 15 GPa in a large-cavity press for 60 seconds to convert the carbon source into diamond. The carbon source is then rapidly cooled to room temperature by cutting off the heating power supply at a pressure reduction rate of 3 GPa / h. After cooling and reducing the pressure to room temperature and pressure, diamond is obtained, wherein the average particle size of the carbon source, amorphous carbon, is 50 nm.

[0063] The diamond preparation parameters of each embodiment or comparative example are shown in Table 1, and the diamond performance parameter results are shown in Table 2.

[0064] Table 1

[0065]

[0066] Note: “ / ” in Table 1 indicates no corresponding preparation parameters.

[0067] Table 2

[0068]

[0069] The photo of the lightweight nanoporous diamond in Example 5 floating on the water is shown in the following figure: Figure 2 As shown, it can be seen that the present invention can adjust the density of lightweight nanoporous diamond to be lower than the density of water, so that it can float on the water surface. Figure 3As shown, the horizontal axis is relative pressure (P / P0), P0 represents the saturated vapor pressure of the gas at the adsorption temperature, and P represents the pressure of the gas phase at adsorption equilibrium; the vertical axis is the volume of nitrogen adsorbed per gram of sample under standard conditions (STP, cc / g), STP refers to the standard state of gas at 273.15K (0°C) and 100kPa (1 atmosphere). After analysis, the distribution results of the specific surface area and average pore size of Examples 5 to 8 are as follows: Figure 4 As shown. Figure 3 and Figure 4 As can be seen from the results of Table 1, as the percentage of metal in the total mass of metal and carbon increases, that is, the mass ratio of carbon source to metal decreases, the amount of nitrogen adsorption increases, indicating that the specific surface area of ​​diamond increases, and the average pore size shows a trend of first increasing and then decreasing. Comparative Example 1 uses foamed iron as a skeleton to prepare porous diamonds. The pore size distribution of the obtained diamonds is uneven, with micron pores and nanopore composite pores, and the obtained diamonds are loose, so that they have no mechanical strength. In Comparative Example 2, without the use of a pore-forming agent, the obtained diamond structure is compact and free of pores. According to Examples 1 to 8, the density of the lightweight nanoporous diamonds obtained in this application is less than the density of conventional diamonds, which is 3.5g / cm 3 , the pore size distribution is uniform, and all are single nanopores.

[0070] According to Examples 1 to 8 and Comparative Examples 1 to 2, it can be seen that by adopting the preparation method of the present application, a lightweight nanoporous diamond with low pore size, high porosity and low density can be obtained. At the same time, the obtained lightweight nanoporous diamond has high hardness and good mechanical strength.

[0071] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for preparing lightweight nanoporous diamond, comprising the following steps: S1. Subjecting a carbon source and a metal to high temperature and high pressure treatment, wherein the metal is a metal self-propagating pore-forming agent, to convert the carbon source into diamond, wherein the metal melts at high temperature and infiltrates and self-propagates on the surface of the diamond particles, and then cools the temperature and pressure to room temperature and pressure to obtain a composite material of diamond and metal; the metal is selected from at least one of bismuth, lead, gallium, mercury, a bismuth-containing alloy, and a mercury-containing alloy; the mass ratio of the carbon source to the metal is 1:(0.1-10); the temperature of the high temperature and high pressure treatment is 1400°C-2000°C and the pressure is 6GPa-25GPa; S2. Immerse the composite material in a solution to remove the metal to obtain the lightweight nanoporous diamond, wherein the solution is selected from at least one of a 36wt%-38wt% hydrochloric acid aqueous solution, aqua regia, a 28wt%-70wt% nitric acid aqueous solution, an 80wt%-98wt% sulfuric acid aqueous solution, and a 35wt%-50wt% hydrofluoric acid aqueous solution, and the average pore size of the lightweight nanoporous diamond is 2nm-15nm.

2. The preparation method according to claim 1, wherein The carbon source is selected from at least one of graphite, onion carbon, amorphous carbon, carbon nanotubes, and nano-diamond powder.

3. The preparation method according to claim 1, wherein The depressurization includes a depressurization rate of 2 GPa / h-4 GPa / h.

4. The preparation method according to claim 1, wherein The average particle size of the metal is 10 nm-200 μm.

5. The preparation method according to any one of claims 1 to 4, wherein The step S1 further includes: Before the high temperature and high pressure treatment, the carbon source and the metal are ground and mixed; or, Before the high temperature and high pressure treatment, the carbon source and the metal are placed separately, and the metal is melted into the diamond through the high temperature and high pressure treatment.

6. A lightweight nanoporous diamond prepared by the preparation method according to any one of claims 1 to 5.

7. The lightweight nanoporous diamond according to claim 6, wherein: The specific surface area of ​​the lightweight nanoporous diamond is 20m 2 / g-150m 2 / g, porosity is 5%-20%.

8. The lightweight nanoporous diamond according to claim 6, wherein: The density of the lightweight nanoporous diamond is 0.6 g / cm 3 -3g / cm 3 .

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