A preparation method and application of microwave-prepared nitrogen-doped carbon nanospheres

Abstract

The present invention discloses a preparation method of nitrogen-doped carbon nanospheres by microwave, which comprises the following steps: By means of microwave synthesis technology, under the state of its power of 800 W, adopting a multi-heating mode, microwave heating is carried out on the mixed powder composed of a carbon source (graphite, naphthalene) and a nitrogen source (2-aminopyridine, pyridine, melamine), and nitrogen-doped carbon nanosphere particles can be obtained. The raw materials in the present invention do not need complex processing, the preparation process is simple, the efficiency is high, and nitrogen-doped carbon nanospheres can be prepared on a large scale. By means of microwave heating, the present invention can prepare nitrogen-doped carbon nanospheres with a nitrogen content of up to about 65% and a diameter of 100-300 nm. The nitrogen-doped carbon nanospheres synthesized by the present invention are lubricating materials with low friction and wear properties. The nanospheres can act as nano ball bearings and achieve low friction and high wear resistance through a rolling-sliding mode, and can be used as lubricating coatings, lubricating oil additives and self-lubricating composite materials.

Description

Technical Field

[0001] The present invention relates to the technical field of lubricant material preparation, and particularly to a preparation method of microwave-prepared nitrogen-doped carbon nanospheres. Background Art

[0002] In recent years, friction and wear have become one of the main factors causing material and energy consumption. Reducing the friction coefficient and wear rate has important application value for improving the efficiency of metal processing technology and extending the service life of mechanical equipment. Although currently, lubricant additives often containing organic compounds such as sulfur, phosphorus, chlorine, metal salts, and amine salts are the earliest developed, most maturely applied, and widely used traditional lubricant additives. However, a large amount of toxic gases are generated during use, which is very easy to pollute the environment, and they cannot meet the lubrication performance requirements for the development of modern mechanical equipment towards high speed, high temperature, and high load directions. Therefore, it is of great significance to develop new, efficient, and environmentally friendly lubricant additives.

[0003] The nitrogen-doped carbon nanospheres synthesized in the present invention are nanomaterials with lubrication performance. Firstly, they themselves have many unique properties, such as small size, large specific surface area, high hardness, thermal stability, high diffusivity, high ductility, etc., which enable them to have excellent friction reduction, wear resistance, and repair effects as lubricant additives, and their load-bearing capacity is relatively high, and they can be applied to relatively harsh working conditions. Secondly, these nanospheres can act as nano ball bearings, achieving low friction and high wear resistance through a rolling-sliding method. As a lubricant additive, it can thus significantly extend the service life of mechanical parts and is expected to become an environmentally friendly high-performance lubricant additive applied in industry. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of microwave-prepared nitrogen-doped carbon nanospheres, so as to provide a practical solution to the above existing problems. The excellent lubrication performance of nitrogen-doped carbon nanospheres is realized through a simple preparation process to meet the requirements of mass production.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A preparation method of microwave-prepared nitrogen-doped carbon nanospheres, characterized in that the nitrogen-doped carbon nanosphere particles are obtained by microwave synthesis technology. Under the state of its power of 800W, using a multi-heating method, microwave heating is carried out on the mixed powder of a carbon source (graphite, naphthalene) and a nitrogen source (2-aminopyridine, pyridine, melamine), and nitrogen-doped carbon nanosphere particles can be obtained.

[0007] Furthermore, in terms of mole parts, it includes the following raw materials: 1 part of carbon source, and 1 - 4 parts of nitrogen source (1 - 3 ml for pyridine).

[0008] Further, the carbon source material is graphite, or a mixture of graphite and naphthalene. Preferably, graphite and naphthalene are mixed in a ratio of 1:1 as the carbon source.

[0009] Further, the nitrogen-doped nitrogen-containing heterocyclic organic compound is one of 2-aminopyridine, pyridine, and melamine. Preferably, the melamine compound is used as the nitrogen source.

[0010] The present invention provides a method for preparing nitrogen-doped carbon nanospheres by microwave, comprising the following steps:

[0011] Weigh the carbon source and nitrogen source and mix them in a molar ratio of 1:1 - 4, and grind them in an agate mortar for 3 - 8 minutes to obtain a mixture.

[0012] (2) Put the mixed powder obtained in step (1) into a microwave-special glass cup, cover it with a cover glass, and then put it into a microwave oven. The microwave power is 800W, and microwave heating treatment is carried out.

[0013] (3) The microwave heating scheme in step (2) is to heat once every 30s and repeat the heating 4 times to obtain the nitrogen-doped carbon nanospheres.

[0014] Further, the carbon source and nitrogen source are mixed in a molar ratio of 1:1 - 4 and ground in an agate mortar for 3 - 8 minutes to obtain a mixture. Preferably, the molar mass ratio is 1:2, and the mixture is ground in an agate mortar for 5 minutes to obtain a mixture.

[0015] Further, the diameter of the carbon nanospheres is 100 - 300 nm.

[0016] The present invention also provides an application of the nitrogen-doped carbon nanosphere particles prepared by microwave in the lubrication field.

[0017] The present invention discloses the following technical effects:

[0018] (1) The preparation process of the nitrogen-doped carbon nanosphere particles of the present invention is simple and can be mass-produced. Through microwave synthesis technology, by using a multi-heating method to heat the mixed powder of graphite, naphthalene, and melamine, nitrogen-doped carbon nanosphere particles can be obtained.

[0019] (2) As a nanomaterial with lubricating properties, the nitrogen-doped carbon nanospheres of the present invention itself have many unique properties, such as small size, large specific surface area, high hardness, thermal stability, high diffusivity, high ductility, etc. It has excellent anti-friction and anti-wear and repair effects as a lubricating additive, and its load-carrying capacity is relatively high, and it can be applied to relatively harsh working conditions.

[0020] (3) The nitrogen-doped carbon nanospheres synthesized in this invention are solid lubricating materials with lubricating properties. These nanospheres can act as nano ball bearings, achieving low friction and high wear resistance through rolling-sliding, significantly reducing energy loss and wear failure caused by part friction.

[0021] (4) The nitrogen-doped carbon nanospheres synthesized in this invention are used as lubricating fluid additives, which can significantly extend the service life of mechanical parts and are expected to become an environmentally friendly high-performance lubricating fluid additive for industrial applications. Description of the Drawings

[0022] To more clearly illustrate the technical solutions in the embodiments of this invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of this invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 (a), (b), and (c) are SEM images of the nitrogen-doped carbon nanospheres prepared in Examples 1, 2, and 3 of this invention and the elemental mass ratios in the insets.

[0024] Figure 2 are SEM images (a), (b), (c), and (d) of carbon nanospheres with different nitrogen contents prepared in Examples 3, 4, 5, and 6 of this invention.

[0025] Figure 3 is the friction coefficient graph of the lubricating fluids prepared from the four substances of Example 3 of this invention, Comparative Example 1, graphite, and pure water. Detailed Embodiments

[0026] To make the technical solutions of this application more clearly understood, the following will combine the drawings and examples to detail the technical solutions of this invention. These examples fall within the protection scope of this invention, but do not limit the protection scope of this invention.

[0027] Example 1

[0028] Preparation of nitrogen-doped carbon nanospheres:

[0029] (1) Weigh 100 mg of graphite, 100 mg of naphthalene, and 200 mg of 2-aminopyridine powder and put them into a mortar. At room temperature, use a pestle to mix and grind the three.

[0030] (2) Put the mixed powder obtained in step (1) into a microwave-special glass cup, cover it with a cover glass, and then put it into a microwave oven. The microwave power is 800 W, and heat for 30 s.

[0031] (3) Repeat the heating process in (2) four times, with a total heating duration of 2 min, and nitrogen-doped carbon nanosphere particles prepared by microwave technology can be successfully obtained. The obtained product is labeled as CN-1.

[0032] Example 2

[0033] Preparation of nitrogen-doped carbon nanospheres:

[0034] (1) Weigh 100 mg of graphite and 100 mg of naphthalene powder and put them into a mortar. At room temperature, use a pestle to mix and grind the two.

[0035] (2) Mix the mixed powder obtained in step (1) with 1 ml of pyridine liquid.

[0036] (3) Put the mixed liquid obtained in step (2) into a microwave-special glass cup, cover it with a cover glass, and then put it into a microwave oven. The microwave power is 800 W and heat for 30 s.

[0037] (4) Repeat the heating process in (3) four times, with a total heating duration of 2 min, and nitrogen-doped carbon nanosphere particles prepared by microwave technology can be successfully obtained. The obtained product is labeled as CN-2.

[0038] Example 3

[0039] Preparation of nitrogen-doped carbon nanospheres:

[0040] (1) Weigh 100 mg of graphite, 100 mg of naphthalene and 200 mg of melamine powder and put them into a mortar. At room temperature, use a pestle to mix and grind the three.

[0041] (2) Put the mixed powder obtained in step (1) into a microwave-special glass cup, cover it with a cover glass, and then put it into a microwave oven. The microwave power is 800 W and heat for 30 s.

[0042] (3) Repeat the heating process in (2) four times, with a total heating duration of 2 min, and nitrogen-doped carbon nanosphere particles prepared by microwave technology can be successfully obtained. The obtained product is labeled as CN-3.

[0043] The microscopic morphology diagrams of the nitrogen-doped carbon nanosphere particles prepared in Examples 1, 2, and 3 are shown in Figure 1 (a)(b)(c). By comparing the scanning diagrams among the three, the one with the largest number of small balls, uniform size and best morphology is the diagram (c), the carbon nanospheres doped with melamine. By comparing the data of the nitrogen atom ratio of the three in the inserted figure, it is obvious that the carbon nanospheres doped with melamine have the highest nitrogen content, which is related to the nitrogen element composition of melamine itself (C3H6N6). Considering comprehensively, melamine is the optimal option as the nitrogen source in the process of preparing nitrogen-doped carbon nanospheres.

[0044] Example 4

[0045] Preparation of nitrogen-doped carbon nanospheres:

[0046] The content of melamine is 100 mg, and the remaining steps are the same as those in Example 3. The obtained product is labeled as CN-4.

[0047] Example 5

[0048] Preparation of nitrogen-doped carbon nanospheres:

[0049] The content of melamine is 300 mg, and the remaining steps are the same as those in Example 3. The obtained product is labeled as CN-5.

[0050] Example 6

[0051] The content of melamine is 400 mg, and the remaining steps are the same as those in Example 3. The obtained product is labeled as CN-6.

[0052] The micrographs of the nitrogen-doped carbon nanosphere particles prepared in Examples 3, 4, 5, and 6 are shown in Figure 2 (a)(b)(c)(d). By comparing the scanning images among the four, the carbon nanospheres doped with melamine (200 mg) have the largest number of small balls, uniform size, and the best morphology. When the content of melamine is 100 mg, the number of carbon balls is the least, which is due to the too low nitrogen content and insufficient reaction with graphite and naphthalene. When the content of melamine is 300 mg and 400 mg, the number of small balls is small and agglomeration occurs, resulting in uneven particle size. This is because the nitrogen content is too high and part of the melamine does not participate in the reaction. During the experiment, the too high nitrogen content is also reflected in a large amount of yellowish-brown substances in the generated powder. Therefore, considering comprehensively, melamine (200 mg) is the optimal option for the nitrogen content in the preparation of nitrogen-doped carbon nanospheres.

[0053] Comparative Example 1

[0054] Preparation of carbon nanospheres:

[0055] (1) Weigh 100 mg of graphite and 100 mg of naphthalene powder and put them into a mortar. At room temperature, use a pestle to mix and grind the two;

[0056] (2) Put the mixed powder obtained in step (1) into a microwave-specific glass cup, cover it with a cover glass, and then put it into a microwave oven. The microwave power is 800 W and heat for 30 s;

[0057] (3) Repeat the heating process in (2) four times, with a total heating duration of 2 min, and the nitrogen-doped carbon nanosphere particles prepared by the microwave technology can be successfully obtained. The obtained product is labeled as CN-7.

[0058] Friction performance test:

[0059] The friction performance of lubricants prepared from four different groups of samples was tested using a domestic HSR-2M reciprocating friction testing machine. The normal load for the test was 10 N, the reciprocating motion amplitude was 5 mm, the friction duration was 10 min, each group of tests was repeated 3 times, and the average value was taken. The friction coefficients of each material are shown in Figure 3 , and it can be seen that compared with pure water, the lubrication performance of the lubricant doped with nitrogen substances has almost doubled, and the average friction coefficient is 0.351. Thus, it is confirmed that nitrogen-doped carbon nanoparticles as lubricant additives can significantly improve the lubrication performance of lubricants.

[0060] The embodiments described above are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the concept of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of microwave-prepared nitrogen-doped carbon nanospheres, characterized in that, The nitrogen-doped carbon nanosphere particles can be obtained by microwave synthesis technology. Under the condition of a microwave power of 800 W, the mixed powder of the carbon source and the nitrogen source is subjected to microwave heating by means of multiple heating, and the nitrogen-doped carbon nanosphere particles can be obtained. The carbon source material is graphite or a mixture of graphite and naphthalene. The nitrogen source is a nitrogen-containing heterocyclic organic compound, which is one of 2-aminopyridine, pyridine, and melamine. In terms of molar parts, it includes the following raw materials: 1 part of carbon source and 1-4 parts of nitrogen source.

2. The preparation method according to claim 1, characterized in that, In terms of molar parts, it includes the following raw materials: 1 part of carbon source and 2 parts of nitrogen source.

3. The preparation method according to any one of claims 1-2, characterized in that, It includes the following steps: (1) Mix the weighed carbon source and nitrogen source in a molar ratio of 1∶1-4, and grind them in an agate mortar for 3-8 min to obtain a mixture. (2) Put the mixed powder obtained in step (1) into a microwave-special glass cup, cover it with a cover glass, and then put it into a microwave oven. The microwave power is 800 W, and microwave heating treatment is carried out. (3) The microwave heating scheme in step (2) is that the heating duration each time is 30 s, and the heating is repeated 2-5 times to obtain the nitrogen-doped carbon nanospheres.

4. The preparation method of microwave-prepared nitrogen-doped carbon nanospheres according to claim 3, characterized in that, The diameter of the carbon nanospheres is 100-300 nm.

5. Application of the nitrogen-doped carbon nanospheres prepared by the preparation method according to any one of claims 1-4 in the lubrication field.

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