RU2485047C1 - Method of producing carbon-nitrogen material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used to make damping elements, shock absorbers, friction pairs and wear-resistant components of micromechanisms. Starting carbon material is placed in a working volume; nitrogen is pumped and removed until complete displacement of air. At the first step, nitrogen is pumped to working pressure of 220-250 MPa, heated to 1670-2020 K and held for not less than 1 minute. Temperature is then lowered to room temperature and pressure is lowered to atmospheric pressure. At the second step, the obtained carbon-nitrogen material is treated in a high-pressure apparatus at pressure of 7-15 GPa and temperature of 1620-1770 K for not less than 1 minute. Temperature is then lowered to room temperature and pressure is lowered to atmospheric pressure. The starting carbon material used is fullerites, for example C₆₀ and/or C₇₀, which are first ground to particle size smaller than 1 mcm in order to increase content of nitrogen in the finished material.

EFFECT: invention enables to obtain a compact carbon-nitrogen material with a bulbous structure, which contains 2,2-5,0 at % nitrogen, having Young's modulus of 43-67 GPa, microhardness of 5,4-8,2 GPa and hyperelastic recovery parameter of 92-97%.

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Description

The invention relates to methods for producing new forms of carbon, and in particular to methods for producing carbon modifications with an onion structure containing nitrogen, and can be used for the manufacture of damping elements, shock absorbers, friction pairs and wear-resistant parts of micromechanisms.

The crystalline forms of carbon include diamond and graphite. In 1985, a new form of carbon fullerene C ₆₀ was discovered, consisting of molecules similar to a soccer ball [H. W. Kroto, et al. Nature. Volume 318 (1985), Pages 162-163] are spherical in shape, which are composed of hexagons and pentagons composed of carbon atoms. Subsequently, other substances of the fullerene series were found: higher fullerenes, fullerene compounds, metallofullerenes, nanotubes, nanocapsules and onion-like carbon (onion-like carbon). These substances have various properties, including superconductivity, semiconductor properties, ferromagnetic properties, and others. They can be used in nanotransistors / diodes, electronic emission elements, single-electron devices, photosensors, superconducting magnets, solar panels, solid lubricants, ultralight permanent magnets, elements for storing gases (oxygen, hydrogen, argon and others).

The onion-like carbon structure, also called bucky onions (the etymology of the word “buckets” comes from “buckminster fullerite”, the name of the C ₆₀ molecule in honor of Buckminster fuller), onion-like fullerene and onion-like graphite (onion- like graphite), belong to a variety of giant fullerenes (giant fullerenes). It consists of fullerene-like layers embedded in each other. Such a structure can have various mechanical and physical properties, and a material with such a structure can be used as structural or functional.

Ugarte first observed the formation of carbon with a bulbous structure in 1992 under the influence of an electron beam in a transmission electron microscope on carbon nanoparticles and nanotubes [D.Ugarte. Letters to Nature. Volume 359 (1992), Pages 707-709].

According to the results of our research, as well as the available information, the onion structure provides a combination of such mechanical properties as high microhardness and superelastic recovery [J. Neidhardt, et al. Surface Engineering. Volume 19 (2003), Issue 4, Pages 299-303]. Moreover, it has been shown that nitrogen atoms contribute to the curvature of layers of a carbon graphene-like layered structure, forming an onion or onion-like structure, as they facilitate the formation of pentagons (namely, pentagons provide a curvature of graphene-like layers of carbon atoms), and also create active sites for the formation of interlayer bonds between the shells of the onion [Zs. Czigany, et al. Applied Physics Letters. Volume 79 (2001), Number 16, Pages 2639-2641].

A known method of producing multilayer fullerenes, in particular nanowells (nano-onions), by irradiating soot-like carbon, namely carbon black, obtained as a result of incomplete combustion or thermal decomposition of carbon-containing substances, such as carbohydrates, aromatic oils and so on, high energies such as electron beams, gamma rays, X-rays, beams of ion sources and so on, and heat treatment [Patent US 6692718, priority from 05/27/1999. Method for preparing nano-size particulate graphite. IPC C01B 31/02; C01B 31/00; C01B 31/04; C01B 031/04; C01B 031/00; C07F 007/00].

The disadvantages of this method include the inability to obtain a compact material.

Known onion-like thin carbon film (onion-like carbon thin film) containing carbon as the main component, and the film has a thickness of 20 nm or more and contains clusters of onion-like structure. The method is based on magnetron sputtering of a carbon source and deposition on a base material [Patent US 6599492, priority from 09/27/2000. Onion-like carbon film and its production. IPC С23С 14/06; C30B 23/02; C01B 031/02].

The disadvantages of this method include the inability to obtain a compact material.

A known method of producing carbon particles of a bulbous structure, including thermal exposure to a carbon material, characterized in that ultrafine diamonds are used as the carbon material, which are annealed at 1100-2000 ° C in vacuum at a pressure of not higher than 10 ^-2 Pa or in an inert atmosphere [ RF patent No. 2094370, priority from 10.19.1993. A method of producing carbon particles of an onion structure. IPC С01В 31/00, СВВ 31/02].

The disadvantages of this method include:

- powders used ultrafine diamonds have a large specific surface area on which there is a significant number of functional groups and / or individual extraneous atomic elements (oxygen, chlorine, sulfur and others). During the heat treatment of ultrafine diamonds in gaseous media, these elements can arbitrarily be part of the onion structures of carbon, greatly changing their properties;

- the method does not allow to obtain compact material.

A known method for producing fullerene-like material, consisting of interconnected nanowave structures of carbon and nitrogen. The material is obtained in the form of thin films on a substrate by magnetron sputtering of a graphite sample in a gaseous medium consisting of Ar / 10% N ₂ . Initially, an ultrahigh vacuum (<2 * 10 ^-7 Pa) is created in the device, and Si (001) and NaCl are used as substrates at temperatures between 200 and 450 ° C [L. Hultman, et al. Physical Review Letters. Volume 87 (2001), Number 22, Pages 225503-1-225503-4].

The specified method provides the production of thin films and does not allow to obtain compact samples of the material.

A method for producing nitrogen doped amorphous carbon hardmask is proposed. The method includes positioning a substrate in a substrate treatment chamber, introducing a nitrogen-containing hydrocarbon source into the treatment chamber, introducing a hydrocarbon source into the treatment chamber, introducing a plasma initiating gas into the treatment chamber, and forming a nitrogen-doped amorphous carbon layer on the substrate [Application US 2011/0244142 A1, priority from 03/30/2010 (published on 10/06/2011). Nitrogen doped amorphous carbon hardmask. IPC С23С 16/513].

The specified method provides the production of thin films and does not allow to obtain compact samples of the material.

Closest to the claimed technical solution is a method for producing a nanofiber material for cold cathodes by evaporation of carbon from a graphite source and deposition of nanofibers in the working volume [RF Patent No. 2288890, priority date 11.09.2003. A method of obtaining a nanofiber material for cold cathodes. IPC С01В 31/02, В82В 3/00, H01J 1/30], characterized in that a gas or a mixture of gases is injected into the working volume under pressure up to 15 MPa, then this cycle is removed and repeated three times, after which a gas or mixture of gases is pumped under a pressure of 10 to 90 MPa, they are heated to a temperature of 2100-2200 K at a speed of 1 to 100 K / min and kept at a working temperature of 10 minutes to 4 hours, after which they first lower the temperature to room temperature, then the pressure at a speed of no more 1 MPa / s to atmospheric, then the resulting material is dispersed using an ultrasonic dispersant oschnostyu 180-200 W radiation for 5-15 minutes in ethanol, filtered, then applied to the cathode plate.

The disadvantages of the method include the fact that it is intended to obtain only nanofiber carbon-nitrogen material and is not intended for the manufacture of compact samples of the material. A graphite heater is used as the carbon source to obtain the target product. This requires high temperatures of 2100-2200 K for evaporation. The deposition of layers of carbon-nitrogen material occurs in different parts of the working volume, this leads to heterogeneity of the material obtained.

The objective of the proposed technical solution is to eliminate the above disadvantages and to obtain a compact carbon-nitrogen material with an onion structure, characterized by high microhardness and superelasticity, which allows it to be used, in particular, for the manufacture of damping elements, shock absorbers, friction pairs and wear-resistant parts of micromechanisms.

To solve this problem, a method for producing carbon-nitrogen material in two stages is proposed.

At the first stage, the process of obtaining the material is carried out in a gas bath; for this, the initial carbon material is placed in the gas bath’s working volume and nitrogen is repeatedly pumped and removed until air is completely displaced from the working volume. Then nitrogen is pumped up to a working pressure of 220-250 MPa, heating to a temperature of 1670-2020 K is carried out at a speed of 200-300 K / min. Withstand at these parameters for at least 1 minute. Reduce the temperature to room temperature and pressure to atmospheric. In the second stage, in order to give the material a higher density, hardness and superelasticity, the carbon-nitrogen material obtained in the first stage is placed in a high-pressure apparatus, pressurized from 7 to 15 GPa, heated to a temperature of 1620-1770 K and held for at least 1 minute, then reduce the temperature to room temperature, and pressure to atmospheric. C ₆₀ and / or C ₇₀ fullerites are used as the starting carbon material. To increase the nitrogen content in the final carbon-nitrogen material, the starting carbon material is crushed to a particle size of less than 1 μm, for example, by grinding in a planetary mill.

The proposed method allows to obtain a compact carbon-nitrogen material with a bulbous structure, which is characterized by the absence of long-range order, the absence of a crystal lattice, nitrogen content of 2.2-5.0 atomic percent, Young's modulus of 43-67 GPa, microhardness of 5.4-8, 2 GPa, with a parameter of superelastic recovery of 92-97%.

Processing at the first stage in a gas bath under high pressure in a nitrogen atmosphere allows the carbon-nitrogen material with an onion structure, characterized by a nitrogen content of 2-5% and low density, to be obtained from the starting carbon material. The processing parameters used in a nitrogen atmosphere, namely, a pressure of 220-250 MPa and a temperature of 1670-2020 K, were found experimentally. Going beyond these parameters leads either to the incomplete conversion of the starting carbon material into a carbon-nitrogen material with an onion structure, or to its transformation into a graphite-like material, characterized by the absence of onion formations. The exposure time in stage 1 is at least 1 minute due to the fact that exposure of less than 1 minute leads to incomplete conversion of the starting carbon material into a carbon-nitrogen material with an onion structure.

Processing at the second stage under conditions of high pressures of 7-15 GPa makes it possible to obtain a compact carbon-nitrogen material with an onion structure, characterized by a nitrogen content of 2-5%, a microhardness of at least 5 GPa and the property of superelastic recovery from a low-density carbon-nitrogen material with an onion structure. The processing parameters used, namely, a pressure of 7-15 GPa and a temperature of 1620-1770 K, were found experimentally. Going beyond these parameters results in materials with low parameters: microhardness below 5 GPa, lack of superelasticity. The exposure time in stage 2 is at least 1 minute due to the fact that exposure of less than 1 minute leads to incomplete conversion of the starting carbon material into a compact carbon-nitrogen material with an onion structure.

The use of fullerites, for example, C ₆₀ , C _70, or a mixture thereof as a starting material, makes it possible to obtain a material with an onion structure when processed in a gas bath in a nitrogen atmosphere at the proposed parameters. The use of other carbon materials, such as graphite, carbon black, diamond single crystals, as starting materials when processed in a gas bath with selected parameters does not lead to the formation of a carbon-nitrogen material with an onion structure.

To increase the nitrogen content in the final material, fullerite is ground before the first stage in a planetary mill to a particle size of less than 1 micron.

Figures 1, 2, 3, 4, 5 are given to explain the proposed technical solution.

Figure 1 shows the image obtained using a scanning electron microscope, a material obtained by processing fullerite C ₆₀ in a gas bath in a nitrogen atmosphere at 220 MPa, 1670 K for 50 minutes.

Figure 2 shows the image obtained using a transmission electron microscope, a material obtained by processing fullerite C ₆₀ in a gas bath in a nitrogen atmosphere at 220 MPa, 1670 K for 50 minutes, which shows the onion structure of the material.

Figure 3 shows the x-ray spectrum (Cu _Kα radiation) of the material obtained by processing fullerite C ₆₀ in a gas bath in a nitrogen atmosphere at 220 MPa, 1670 K for 50 minutes, which shows the bulbous structure of the material. The spectrum shows signs of an onion structure: a characteristic background at small angles, characterized by a large slope; large width and characteristic asymmetry of the peak located at an angle of 26.4 degrees, corresponding to the (002) graphite reflection.

Figure 4 shows the x-ray spectrum (Cu _Kα radiation) of the material obtained by processing fullerite C ₆₀ in a gas bath in a nitrogen atmosphere at 220 MPa, 1670 K for 50 minutes and subsequent processing in a high pressure chamber at a pressure of 7.7 GPa, temperature 1620 K for 1 minute, which shows the bulbous structure of the material. The spectrum shows signs of an onion structure: a characteristic background at small angles, characterized by a large slope; large width and characteristic asymmetry of the peak located at an angle of 26.4 degrees, corresponding to the (002) graphite reflection.

Figure 5 shows the curves of loading and unloading obtained using the NanoScan device for the material obtained by processing fullerite C ₆₀ in a gas bath in a nitrogen atmosphere at 220 MPa, 1670 K for 50 minutes, then processing in a high-pressure apparatus at 7.7 GPa , 1620 K for 1 minute. An analysis of the curves shows that when the load was removed, almost complete absence of residual deformation of the material was observed, which indicates the superelastic behavior of the material.

The method is confirmed by the following examples.

Example 1. A sample of 3 grams of powder (with particle sizes in the range of 10-100 μm) C ₆₀ fullerite (99.95% pure) was placed in a graphite crucible, which was placed in a gas thermostat, then the air was displaced by nitrogen purging three times, the pressure was brought to 220 MPa , heated to a temperature of 1670 K at a speed of 200 K / min, kept for 50 minutes, cooled to room temperature, reduced the pressure to atmospheric, the resulting material was loaded into a tantalum container, placed in a high-pressure apparatus, created a pressure of 7.7 GPa, heated to a temperature of 1620 K, withstood within 1 minute, cooled to room temperature, reduced the pressure to atmospheric.

The nitrogen content, estimated by XRD (X-ray photoelectron spectroscopy), after processing fullerite C ₆₀ in a gas bath in a nitrogen atmosphere at 220 MPa, 1670 K for 50 minutes was 2.4 atomic percent; after processing in a high-pressure apparatus at 7.7 GPa, 1620 K for 1 minute was 2.7 atomic percent.

The presence of the onion structure was confirmed by x-ray and electron microscopy studies.

The value of Young's modulus was 52.8 ± 5.5 GPa; microhardness - 6.7 ± 0.5 GPa; inelastic recovery - 97%, measurements were carried out using a NanoScan instrument with an indenter load of up to 15 mN.

Example 2. A sample of 3 grams of powder (with particle sizes in the range of 10-100 μm) C ₇₀ fullerite (99.8% purity) was placed in a graphite crucible, which was placed in a gas thermostat, the air was displaced three times with nitrogen purge, the pressure was brought up to 220 MPa, heated to a temperature of 2020 K at a speed of 300 K / min, kept for 50 minutes, cooled to room temperature, reduced the pressure to atmospheric, the resulting material was loaded into a tantalum container, placed in a high-pressure apparatus, created a pressure of 7.7 GPa, heated to temperature 1620 K, kept for 1 minute, cooled to room temperature, reduced pressure to atmospheric.

The nitrogen content estimated by the method of X-ray diffraction (X-ray photoelectron spectroscopy), after processing fullerite C ₇₀ in a gas bath in a nitrogen atmosphere at 220 MPa, 2020 K for 50 minutes was 3.0 atomic percent; after processing in a high-pressure apparatus at 7.7 GPa, 1620 K for 1 minute was 3.0 atomic percent.

The presence of the onion structure was confirmed by x-ray and electron microscopy studies.

The value of Young's modulus was 43.2 ± 5.2 GPa; microhardness - 5.4 ± 0.5 GPa; inelastic recovery - 95%, measurements were carried out using a NanoScan device with an indenter load of up to 15 mN.

Example 3. A sample of 3 grams of powder (with particle sizes in the range of 10-100 μm) fullerite C ₆₀ (99.95% purity) was placed in a graphite crucible, which was placed in a gas thermostat, the air was displaced three times with nitrogen purge, the pressure was brought to 250 MPa, heated to a temperature of 2020 K at a speed of 200 K / min, kept for 60 minutes, cooled to room temperature, reduced the pressure to atmospheric, the resulting material was loaded into a tantalum container, placed in a high-pressure apparatus, created a pressure of 13 GPa, heated to a temperature of 1770 K, stood in the leak 1 minute, cooled to room temperature, reduced pressure to atmospheric.

The nitrogen content estimated by XRD (X-ray photoelectron spectroscopy), after processing fullerite C ₆₀ in a gas bath in a nitrogen atmosphere at 250 MPa, 2020 K for 60 minutes and subsequent processing in a high-pressure apparatus at 13 GPa, 1770 K for 1 minute was 2.2 atomic percent.

The presence of the onion structure was confirmed by x-ray and electron microscopy studies.

The value of Young's modulus was 58.1 ± 5.5 GPa; microhardness - 7.2 ± 0.5 GPa; inelastic recovery - 95%, measurements were carried out using a NanoScan device with an indenter load of up to 15 mN.

Example 4. A mixture of fullerites C ₆₀ / C ₇₀ in a ratio of 20/1 (99.8% purity) was preliminarily milled in a planetary mill to a powder particle size of less than 1 μm, a 3 gram sample was placed in a graphite crucible, which was placed in a gas thermostat, and was displaced air by nitrogen purging three times, the pressure was brought up to 250 MPa, heated to a temperature of 2020 K at a speed of 300 K / min, kept for 60 minutes, cooled to room temperature, reduced the pressure to atmospheric, the resulting material was loaded into a tantalum container, placed in a high-pressure apparatus giving lenii, created a pressure of 15 GPa, heated to a temperature of 1770 K, kept for 1 minute, cooled to room temperature, reduced the pressure to atmospheric.

Nitrogen content estimated by XRD (X-ray photoelectron spectroscopy), after preliminary grinding of a mixture of fullerites С ₆₀ / С ₇₀ to a particle size of less than 1 μm, processing in a gas bath in a nitrogen atmosphere at 250 MPa, 2020 K for 60 minutes and subsequent processing in the apparatus high pressure at 15 GPa, 1770 K for 1 minute was 5.0 atomic percent.

The presence of the onion structure was confirmed by x-ray and electron microscopy studies.

The value of Young's modulus was 67.0 ± 5.5 GPa; microhardness - 8.2 ± 0.5 GPa; inelastic recovery - 92%, measurements were carried out using a NanoScan instrument with an indenter load of up to 15 mN.

The proposed method obtained carbon-nitrogen material with a bulbous structure with parameters at the first stage: pressure 180-250 MPa and temperature 1670-2020 K, at the second stage: pressure 7.7-15 GPa and temperature 1620-2020 K. The material is characterized by nitrogen 2.2–5.0 atomic percent, Young's modulus of 43–67 GPa, microhardness of 5.4–8.2 GPa, and superelastic recovery parameter of 92–97%.

Claims (3)

1. A method of producing a carbon-nitrogen material, including repeatedly pumping and removing nitrogen from the working volume with the starting carbon material placed in it until the air is completely displaced, followed by pumping nitrogen to the working pressure, heating, maintaining at these parameters and lowering the temperature to room temperature, and then pressure to atmospheric, characterized in that the preparation is carried out in two stages, at the first stage, nitrogen is pumped up to 220-250 MPa to the working pressure, and heating is carried out to a temperature of 1670-2020 K, followed by with a holding time of at least 1 min, then the temperature is lowered to room temperature and atmospheric pressure; in the second stage, the obtained carbon-nitrogen material is placed in a high-pressure apparatus and exposed to pressure from 7 to 15 GPa, heated to a temperature of 1620-1770 K and kept in for at least 1 min, then reduce the temperature to room temperature and the pressure to atmospheric, with fullerite being used as the starting carbon material. 2. The method according to claim 1, characterized in that fullerite C ₆₀ and / or fullerite C ₇₀ are used as the starting carbon material. 3. The method according to claim 1, characterized in that the starting carbon material is ground before processing in the first step to a particle size of less than 1 μm.

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