CN107739643B

CN107739643B - Lubricating oil containing surface-modified carbon nano material and preparation method thereof

Info

Publication number: CN107739643B
Application number: CN201710973197.0A
Authority: CN
Inventors: 曹殿学
Original assignee: Heilongjiang Huasheng Graphite Co ltd
Current assignee: Heilongjiang Huasheng graphite Group Co.,Ltd.
Priority date: 2017-10-18
Filing date: 2017-10-18
Publication date: 2020-07-10
Anticipated expiration: 2037-10-18
Also published as: CN107739643A

Abstract

The invention discloses lubricating oil containing a surface-modified carbon nano material and a preparation method thereof, relates to modified lubricating oil and a preparation method thereof, and particularly relates to lubricating oil containing graphene, carbon nano tubes and carbon nano fibers and a preparation method thereof. The graphene, the carbon nano tube and the carbon nano fiber are respectively coated with polydopamine and grafted long-carbon paraffin hydrocarbon on the surface to obtain corresponding modified carbon nano materials, and the modified carbon nano materials, base oil and other lubricating oil functional additives are mixed in proportion to obtain the lubricating oil containing the surface modified carbon nano materials. The invention solves the problems of stability and dispersibility, generates ball effect and supporting effect, further generates a 'solid-liquid' dual-function lubricating mechanism and a stable porous structure, and obviously improves the performance of the lubricating oil.

Description

Lubricating oil containing surface-modified carbon nano material and preparation method thereof

Technical Field

The invention relates to modified lubricating oil and a preparation method thereof, in particular to lubricating oil containing graphene, carbon nanotubes and carbon nanofibers and a preparation method thereof.

Background

Current state of the art lubricating oils

Despite the ever-improving lubrication properties of motor oils and the like, there is still an average of 15% fuel consumption per vehicle to overcome the frictional resistance of the engine and transmission. Friction and wear are the main causes of engine inefficiency. Friction simultaneously shortens the service life of the engine and increases the emission of harmful components in the exhaust gas. The lubricating oil can keep the engine in a good working state, and can prolong the service life of moving parts such as the engine and the like by reducing friction and wear, so that the lubricating oil can assist the energy conservation and emission reduction of automobiles, ships and the like. In addition, as the technology of intelligent manufacturing equipment marked by robots is continuously improved, the demand of high-end lubricating oil is continuously increased.

The introduction of the novel additive into the lubricating oil is an effective way for improving the performance of the lubricating oil. Under boundary lubrication conditions, the most effective way to reduce friction is to select the appropriate lubricating oil additives, i.e., extreme pressure antiwear agents and friction modifiers. The mechanical friction modifier is mainly non-oil soluble solid particles suspended in oil, and comprises graphite, molybdenum disulfide, polytetrafluoroethylene powder, boron nitride and the like. The solid lubricant is suspended in a highly dispersed state in the lubricating oil, and is effective at both low and high temperatures by reducing friction mainly by physical actions such as preventing contact between metal surfaces, reducing roughness of a friction interface, maintaining an oil film, and the like.

Graphene has a two-dimensional structure, is the thinnest nano-material known to date, and has a specific surface area of 2630m²The conductive material has outstanding heat conduction, electric conduction and mechanical properties. Due to the characteristics, when the graphene is used as a solid additive of the lubricating oil, the graphene has the advantages of excellent lubrication, wear resistance, heat conduction, oxidation resistance, corrosion resistance, stability and the like, and is obviously superior to other conventional anti-wear additives of the lubricating oil. Due to the laminar structure of the graphene, a layer of uniform and firmly-attached film is easily formed on the contact surface of the moving part, so that the direct abrasion of the part is reduced, and the good heat conduction performance of the graphene is beneficial to preventing the local hot spot of a friction interface, so that the service life of the lubricating oil is prolonged.

Problems with lubricating oils under the conditions of the prior art.

Lubricating oils containing solid lubricant additive particles have been effective in practical applications, but there are many technical problems to be studied in the preparation of such lubricating oils. There are five main aspects to the problem,

first, the problem of suspension stability when the solid lubricant additive particles are uniformly dispersed in the lubricant and left for a long period of time To give a title.

If the solid additives such as graphene cannot be sufficiently dispersed in the lubricating oil, but exist in the lubricating oil as a large number of aggregates, on one hand, the solid additives are easy to settle under the action of gravity, and on the other hand, the improvement effect of the solid additives on the lubricating performance is obviously reduced.

Secondly, the solid lubricant additive forms a stable solid-liquid two-phase protective film at the friction interface.

Since friction occurs at the contact interface of the moving part, if the solid additive such as graphene does not adhere well to the friction interface to form an effective and stable lubricant protective film, it is difficult to exert its effect of improving the performance of the lubricant. In addition, the protective film formed by the solid additive should have porosity, and can adsorb and retain liquid lubricating oil therein, so that the protective film has a solid-liquid two-phase dual lubricating function. The solid lubricant is added to fill the pits generated by the friction of the surface of the material, so as to level the friction surface and reduce the abrasion, and therefore, the solid lubricant additive is required to form a 'ball effect' on the friction interface.

And thirdly, under the condition of friction extrusion, the protection film is kept to form a porous structure stability problem.

The nano carbon material has a porous structure, and the protective film of the porous structure can adsorb liquid lubricating oil and can adsorb particulate matters and lubricating oil decomposition products generated by friction, so that the protective film has a solid-liquid dual-function lubricating mechanism and a certain cleaning function, the lubricating effect is improved, and the service life of the lubricating oil is prolonged while the abrasion is reduced. However, the protective film formed only by the graphene and the carbon nanotubes is pressed more and more tightly in the using process under the action of friction force, and the adsorbed lubricating oil liquid is extruded out, so that the liquid lubricating effect is obviously reduced.

And fourthly, the structural stability of the modified material is solved.

In the prior art, the method for modifying the nano carbon material by adding the dispersant is an effective method for improving the dispersibility of the material, but the structural stability of the modified material causes that the material is difficult to achieve the expected technical effect. This is mainly determined by the dispersant, the nature of the carbon material itself and the actual dispersion process.

First, the dispersant is mainly a surfactant containing a long carbon chain and a long carbon chain high molecular polymer. The dispersants are attached to the surfaces of graphene and carbon nanotubes through adsorption, the acting force of the dispersants is weak, and desorption are easy to occur when the graphene and the carbon nanotubes are ultrasonically dispersed in the lubricating oil base oil, so that the dispersing effect of the dispersants is lost.

Secondly, the dispersion stability of the graphene is improved by chemically grafting oleophilic groups on the surfaces of the graphene and the like. However, the surfaces of graphene, carbon nanotubes and the like do not contain active functional groups, direct chemical grafting of lipophilic groups is difficult to achieve directly, and graphene and the like need to be oxidized by strong oxidizing acid and the like to introduce functional groups such as hydroxyl groups, carboxyl groups and the like. On one hand, the method has limited number of introduced active functional groups, is not beneficial to grafting sufficient number of oleophilic groups, and is difficult to achieve ideal dispersion effect; on the other hand, the oxidation treatment of the graphene increases the cost thereof and generates waste liquid.

Thirdly, in order to ensure the dispersibility of the modified carbon nano material in the lubricating oil, the modified carbon nano material is added and needs to be dispersed under the conditions of ultrasound and the like, so that the dispersing agent and the nano carbon material are further separated.

Fifth, the structural properties of carbon nanomaterials such as graphene severely limit their application in the field of lubricating oil.

Although the graphene has excellent performance in the field of lubricating oil, the problems of the application of the carbon nano-materials such as graphene in the field of lubricating oil are very obvious and need to be solved urgently.

Graphene has strong surface inertness and weak interaction with molecules of lubricating oil base oil, so that the dispersion stability of the graphene is poor, and strong van der waals force exists between graphene sheets, so that the graphene is easy to agglomerate on one hand, and a compact film is easy to form under the extrusion action of a friction interface on the other hand, and the porous structure of an interface protective film cannot be maintained. The lamellar graphene and the linear carbon nano tube are compounded, so that stacking and compaction of graphene can be reduced, but the linear carbon nano tube is easy to be wound into a group, and the problem of uniform dispersion in lubricating oil is difficult to solve.

Here, it should be noted that: the five problems are not isolated, and the problems are mutually interwoven and mutually influenced, for example, the self property of the carbon material directly determines the structural stability of the modified material, and the structural stability of the modified material is also the premise of realizing the dispersibility; the self property of the carbon material directly determines the stability of the porous structure formed by the protective film, and the stability of the porous structure formed by the protective film is an important influence factor for forming a stable solid-liquid two-phase protective film on a friction interface. Therefore, it is necessary to combine the above technical problems and apply corresponding technical means to creatively solve the corresponding technical problems under a complete inventive concept. Rather than to address individual problems on a one-sided basis.

Disclosure of Invention

In view of the problems in the prior art, the present invention aims to provide a carbon nanomaterial-modified lubricating oil containing surface-modified graphene, carbon nanotubes, carbon nanofibers, and other solid lubricating additives, and a preparation method thereof. The inventive concept includes the following three aspects:

1the ball effect is formed at the friction interface by effectively combining a plurality of nano carbon materials, thereby creatively solving the problem The integrity and stability problems of the protective film are solved.

Through effectively combining three nano-carbon materials of graphene, one-dimensional linear carbon nano-tubes and one-dimensional rod-shaped carbon nano-fibers in a two-dimensional lamellar structure, and through optimizing the size and thickness of graphene lamellar layers and the length and thickness of carbon tubes and carbon nano-fibers, a stable and porous micron-sized solid protective film can be formed on a friction interface, so that direct friction among component materials is changed into friction among protective films, and direct abrasion of the components is reduced. The method utilizes the excellent adhesion performance of the graphene with the lamellar structure on the surface of the material and the lapping and winding fixing performance of the linear carbon nano tube to form a ball effect on a friction interface. The integrity and stability of the carbon protective film are ensured.

2The rod-shaped carbon nano fiber is introduced into the graphene and the carbon tube, thereby creatively realizing the protection in the friction pressing process The stability of the porous structure formed by the protective film.

As described above, the protective film formed only by the graphene and the carbon nanotubes is pressed more and more tightly during the use process under the action of friction force, and the absorbed lubricant oil is extruded out, so that the liquid lubrication effect is reduced. According to the invention, the rodlike carbon nanofibers are introduced into the graphene and the carbon tubes, and the support structure is formed in the middle of the sheet graphene, so that the sheet graphene is prevented from being pressed in the friction process, and thus the carbon protective film forms a porous structure and keeps the stability of the porous structure in the friction process. The protective film with the porous structure can adsorb liquid lubricating oil and can adsorb particulate matters and lubricating oil decomposition products generated by friction, so that the protective film has a solid-liquid dual-function lubricating mechanism and a certain cleaning function, the lubricating effect is improved, and the service life of the lubricating oil is prolonged while the abrasion is reduced.

Here, it should be noted that: the rod-shaped carbon nanofiber has a dual function,

action 1: a ball effect can be produced, smoothing the friction surface.

The rod-shaped carbon nanofiber is easy to roll, sliding friction can be changed into rolling friction, the lubricating performance is further improved, and the depressions generated on the friction surface can be filled up, so that the friction surface is leveled.

Action 2: a ball effect can be produced, smoothing the friction surface.

The support structure is formed in the middle of the flake graphene, and the flake graphene is prevented from being pressed in the friction process, so that the carbon protective film forms a porous structure and keeps the stability of the porous structure in the friction process.

The 3 poly-dopamine is used as a bridge to creatively solve the problems of dispersibility and modified material stability

The nano carbon materials such as graphene can be uniformly dispersed in the lubricating oil, and the modified lubricating effect is guaranteed on the premise that the nano carbon materials can be stable for a long time and do not generate sedimentation separation. Generally, a polymer or a surfactant is used as a dispersing agent to disperse graphene and carbon nanotubes, and the dispersing agent is adsorbed on the surfaces of graphene and carbon nanotubes to increase the compatibility of the graphene and carbon nanotubes with a dispersing medium and prevent agglomeration. Due to the fact that the adsorption acting force is weak, under the action of lubricating oil, the dispersing agent is prone to being desorbed from the surfaces of the graphene and the carbon nano tubes, and therefore the dispersing effect on the graphene and the carbon nano tubes is lost. According to the invention, by utilizing the characteristic that the super-strong adhesion performance of polydopamine can form a firmly-adhered nano film on almost any solid surface, a layer of polydopamine nano film is grown on the surfaces of graphene, carbon nano tubes and carbon nano fibers. The poly-dopamine is attached to the surface of the base material by virtue of two actions of covalent bonds and non-covalent bonds established between catechol and amino functional groups of dopamine hydrochloride and the surface of the material, so that the poly-dopamine can be firmly assisted on the surface of a carbon material and cannot fall off in lubricating oil. And then, the rich functional groups in the polydopamine and amines containing long carbon chain hydrocarbon are subjected to chemical reaction, and long carbon chain hydrocarbon molecules are chemically bonded on the surfaces of carbon materials such as graphene. Because the lubricating oil base oil is long carbon chain hydrocarbon and is completely mutually soluble with hydrocarbon molecules grafted on the surfaces of carbon materials such as graphene, the carbon materials such as graphene with modified surfaces can be uniformly and stably dispersed in the lubricating oil.

The invention takes polydopamine as a bridge, long carbon chain hydrocarbon which is completely mutually soluble with lubricating oil is grafted on the surfaces of carbon materials such as graphene and the like through firm chemical bonding, and the modified material achieves the following technical effects:

the technical effect is as follows: the problem that the traditional dispersing agent is easy to desorb from the surface of a carbon material to cause the graphene and the like to be settled in lubricating oil is solved, the dispersity of the graphene and the like in the lubricating oil is also obviously improved, and the dispersing process is simpler.

The technical effect is as follows: because the surfaces of the modified graphene and the like contain long-carbon-chain alkyl groups which are completely mutually soluble with lubricating oil, a porous protective film formed by solid materials such as graphene and the like can absorb liquid lubricating oil, and the solid-liquid dual-function lubricating effect is obviously improved.

Important emphasis is given to: the three points are based on solving five technical problems in the prior art, and in three aspects under a complete inventive concept, the three aspects complement each other and interact to form a whole rather than a simple combination of isolated technical schemes.

The invention takes polydopamine as a bridge, solves the problems of stability and dispersibility, obviously improves intersolubility, and is matched with a porous structure of a protective film; the ingenious combination of different material sizes, thicknesses, lengths and thicknesses of a plurality of nano-carbon materials is fully utilized to generate a ball effect and a supporting effect, so that a solid-liquid dual-function lubricating mechanism and a stable porous structure are generated, and the performance of the lubricating oil is obviously improved. Therefore, compared with the prior art, the invention has outstanding substantive features and remarkable progress.

The technical idea of the invention is realized by the following technical scheme:

a preparation method of modified lubricating oil containing graphene, carbon nano tubes and carbon nano fibers. Comprises the following steps:

step 1: preparation of modified graphene nano material

Adding 1-10 layers of graphene and dopamine hydrochloride with the sheet size of 20-1000nm into an aqueous solution of 0.01-0.10 mol/L trihydroxymethyl aminomethane according to the mass ratio of 6:1-2:1, wherein the volume of the aqueous solution of the trihydroxymethyl aminomethane and the mass ratio of the dopamine hydrochloride are 3-5L/g, adjusting the pH value of the solution to 8-9, carrying out ultrasonic shearing treatment until the dopamine hydrochloride is completely dissolved, fully dispersing the graphene, adding 30-50m L5% of hydrogen peroxide into each gram of the dopamine hydrochloride, stirring for 1-10h at 20-40 ℃, filtering, washing and drying to obtain a graphene nano material A1 coated on the surface of the polydopamine;

adding A1 and alkylamine into ethanol solution of tris (hydroxymethyl) aminomethane with the concentration of 0.01-0.10 mol/L according to the mass ratio of 1:4, wherein the solvent in the ethanol solution is ethanol with the mass concentration of 95-99.5%, and the mass ratio of the volume of the ethanol solution of tris (hydroxymethyl) aminomethane to the alkylamine is 5-8L/g, adjusting the pH of the solution to be = 8-9, stirring at 20-40 ℃ for 12-24h, filtering, washing and drying to obtain the modified graphene lubricating oil additive A2;

step 2: preparation of modified multi-wall carbon nano-tube nano-material

Adding multi-walled carbon nanotubes with purity higher than 95%, diameter of 8-30nm and length of 0.5-15 mu m and dopamine hydrochloride into aqueous solution of 0.01-0.10 mol/L trihydroxymethylaminomethane according to the mass ratio of 6:1-2:1, wherein the volume of the aqueous solution of the trihydroxymethylaminomethane and the mass ratio of the dopamine hydrochloride are 3-5L/g, adjusting the pH value of the solution to 8-9, carrying out ultrasonic shearing treatment until the dopamine hydrochloride is completely dissolved, fully dispersing the multi-walled carbon nanotubes, adding 30-50m L5% of hydrogen peroxide into per gram of the dopamine hydrochloride, stirring for 1-10h at 20-40 ℃, filtering, washing and drying to obtain a multi-walled carbon nanotube nanomaterial B1 coated on the surface of the polydopamine;

adding B1 and alkylamine into ethanol solution of tris (hydroxymethyl) aminomethane with the concentration of 0.01-0.10 mol/L according to the mass ratio of 1:4, wherein the solvent in the ethanol solution is ethanol with the mass concentration of 95-99.5%, and the mass ratio of the volume of the ethanol solution of tris (hydroxymethyl) aminomethane to the alkylamine is 5-8L/g, adjusting the pH of the solution to be = 8-9, stirring for 12-24h at the temperature of 20-40 ℃, filtering, washing and drying to obtain a modified multi-walled carbon nanotube lubricating oil additive B2;

and step 3: preparation of modified carbon nanofiber nano material

Adding carbon nanofibers with the diameter of 50-200nm and the length of 1-20 microns and dopamine hydrochloride into an aqueous solution of 0.01-0.10 mol/L trihydroxymethylaminomethane according to the mass ratio of 6:1-2:1, wherein the volume of the aqueous solution of the trihydroxymethylaminomethane and the mass ratio of the dopamine hydrochloride are 3-5L/g, adjusting the pH value of the solution to 8-9, carrying out ultrasonic shearing treatment until the dopamine hydrochloride is completely dissolved, fully dispersing the carbon nanofibers, adding hydrogen peroxide according to the proportion that 30-50m L5% of hydrogen peroxide is added into each gram of the dopamine hydrochloride, stirring for 1-10h at the temperature of 20-40 ℃, filtering, washing and drying to obtain a carbon nanofiber nanomaterial C1 coated on the surface of the polydopamine;

adding C1 and alkylamine into ethanol solution of tris (hydroxymethyl) aminomethane with the concentration of 0.01-0.10 mol/L according to the mass ratio of 1.2:1-1:4, wherein the solvent in the ethanol solution is ethanol with the mass concentration of 95-99.5%, and the mass ratio of the volume of the ethanol solution of tris (hydroxymethyl) aminomethane to the alkylamine is 5-8L/g, adjusting the pH of the solution to be = 8-9, stirring for 12-24h at the temperature of 20-40 ℃, filtering, washing and drying to obtain the modified carbon nanofiber nano-material lubricating oil additive C2;

and 4, step 4: preparation of lubricating oil containing modified carbon nanomaterial

Adding A2, B2 and C2 into the lubricating oil, wherein the mass of A2, B2 and C2 respectively accounts for 0.02-2%, 0.02-2% and 0.01-1% of the total mass of the lubricating oil containing the modified carbon nano material; stirring and ultrasonically dispersing for 10-30 minutes at the ultrasonic frequency of 20kHz to obtain the modified lubricating oil containing the carbon nano-material.

The alkylamine is octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine or octadecylamine.

The modified lubricating oil containing the carbon nano material prepared by the synthesis methodComprises modified graphene, modified carbon nano tubes, modified carbon nano fibers, base oil and other functional additives of lubricating oil. The mass of the modified graphene, the modified carbon nano tube and the modified carbon nano fiber respectively accounts for 0.02-2%, 0.02-2% and 0.01-1% of the total mass of the lubricating oil containing the modified carbon nano material, and the base oil is one or more of mineral base oil, synthetic base oil and vegetable base oil.

Technical description:

the poly-dopamine surface coating process of the three nano-carbon materials is basically the same, firstly, the carbon nano-materials and the dopamine hydrochloride are subjected to ultrasonic shearing treatment, dissolved and fully dispersed; adding hydrogen peroxide into the prepared suspension to initiate dopamine hydrochloride to polymerize on the surface of the carbon material, thereby obtaining the carbon nano material coated with the polydopamine surface. Secondly, hydroxyl in the polydopamine coated on the surface of the carbon nano material and amino in alkylamine generate Michael addition or Schiff base reaction, and long-carbon-chain alkane is grafted on the surface of the carbon nano material; obtaining the modified carbon nano-material lubricating oil additive. And finally, adding the three carbon materials into lubricating oil for dispersion to obtain the modified lubricating oil containing the carbon nano-material.

The invention has the beneficial effects that:

(1) the surface of the carbon nano material is coated with polydopamine to graft a long-carbon paraffin lipophilic group, so that the lipophilicity of the carbon nano material is obviously improved. The carbon nano material subjected to surface modification treatment is uniformly dispersed in lubricating oil, the dispersion liquid is high in stability, and does not settle after standing for a long time, so that the problem of dispersion stability of the carbon nano material solid lubricating additive in the lubricating oil is solved.

(2) The nano carbon material after surface treatment is very easy to disperse in the lubricating oil, can be uniformly dispersed by simple stirring and short-time ultrasonic treatment, does not need to add other dispersing agents, and does not need to prepare the carbon nano material into a dispersion liquid and then add the dispersion liquid into the lubricating oil. The invention can directly add the processed nano carbon material into the lubricating oil, thereby having simple process.

(3) The performance of the lubricating oil modified by the nano carbon material is obviously improved. The automobile using the lubricating oil modified by the nano carbon materials such as graphene is more oil-saving, more environment-friendly, more abundant in power, longer in service life of an engine and longer in oil change period. After the lubricating oil is added into an automobile with the number of more than 10 kilometres, the emission of harmful gas is reduced by 4-6 times; the fuel consumption is reduced by 2.5-10% (depending on the vehicle type and the kilometers used); the service life of the bearing can be increased by 1.5-3 times; the cylinder pressure of the engine is increased by 0.1-0.5 MPa. The lubricating oil has no side effect.

Description of the drawings:

fig. 1 is a photograph of a transmission lens of graphene surface-treated in step 1 of example 3.

FIG. 2 is a TEM image of the surface-treated carbon nanotubes obtained in step 2 of example 4.

FIG. 3 is a TEM image of the carbon nanofibers subjected to surface treatment in step 3 of example 5.

FIG. 4 is a photomicrograph of a friction test conducted on the surface of steel in a lubricating oil before the nanocarbon material of example 11 is modified.

FIG. 5 is a photomicrograph of a friction test conducted on the steel surface of the lubricating oil modified with the nanocarbon material of example 11.

FIG. 6 is a scanning microscope photomicrograph of a probe of a nanocarbon material composite porous protective film formed on a frictional surface of the nanocarbon material-modified lubricating oil according to example 11.

FIG. 7 is a scanning microscope photomicrograph of a probe of a nanocarbon material composite porous protective film formed on a frictional surface of the nanocarbon material-modified lubricating oil according to example 11.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly understood, the present invention is described in further detail below with reference to the accompanying drawings and preferred embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

Step 1: preparation of modified graphene nano material

Adding 1-10 layers of graphene and dopamine hydrochloride with the sheet size of 20-1000nm into an aqueous solution of 0.01-0.10 mol/L trihydroxymethyl aminomethane according to the mass ratio of 6:1-2:1, wherein the volume of the aqueous solution of the trihydroxymethyl aminomethane and the mass ratio of the dopamine hydrochloride are 3-5L/g, adjusting the pH value of the solution to 8-9, carrying out ultrasonic shearing treatment until the dopamine hydrochloride is completely dissolved, fully dispersing the graphene, adding 30-50m L5% of hydrogen peroxide into each gram of dopamine, stirring for 1-10h at 20-40 ℃, filtering, washing and drying to obtain a graphene nano material A1 coated on the surface of the polydopamine;

step 2: preparation of modified multi-wall carbon nano-tube nano-material

and step 3: preparation of modified carbon nanofiber nano material

Adding hydrogen peroxide in the steps of the embodiment, stirring for 1-10h at 20-40 ℃, and performing vacuum filtration by using 0.2 mu m filter paper in the processes of filtering, washing and drying; the alkylamine is octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine or octadecylamine.

Example 2

This embodiment is substantially the same as embodiment 1 except that:

in the step 1, the number of layers of the graphene is 1-10, the size of a lamella is 20-1000nm, most preferably 1-3, and the size of the lamella is 50-150 nm; the mass ratio of the graphene to the dopamine hydrochloride is 6:1-2:1, and the preferable mass ratio is 5: 1; stirring for 1-10h at 20-40 ℃, preferably for 1-2 h;

step 2: the carbon nano tube is a multi-wall carbon nano tube, the purity is more than 95 percent, the diameter is 8-30nm, the length is 0.5-15 mu m, the most preferable purity is more than 99.5 percent, the diameter is 10-20nm, and the length is 0.5-5 mu m; the mass ratio of the carbon nano tube to the dopamine hydrochloride is 6:1-2:1, and the preferable mass ratio is 5: 1; stirring for 1-10h at 20-40 ℃, preferably for 1-2 h;

and step 3:the diameter of the carbon nanofiber is 50-200nm, the length is 1-20 mu m, the most preferable diameter is 50-100nm, and the length is 5-10 mu m; the mass ratio of the carbon nanofibers to the dopamine hydrochloride is 6:1-2:1, and the preferred mass ratio is 5: 1; stirring for 1-10h at 20-40 ℃, preferably for 1-2 h; c1 and alkylamine according to the mass ratio of 1.2:1-1:4, preferably 1 and alkylamine according to the mass ratio of 1: 4;

and 4, step 4:the mass of A2, B2 and C2 respectively accounts for 0.02-2%, 0.02-2% and 0.01-1% of the total mass of the lubricating oil containing the modified carbon nano material; preferably, the mass of A2, B2 and C2 respectively accounts for 0.1-0.5%, 0.1-0.5% and 0.02-0.5% of the total mass of the lubricating oil containing the modified carbon nano material;

comparative experiments on dispersion stability of nanocarbon materials were prepared according to steps 1 to 3 in example 2: respectively adding 0.5% by mass of graphene, carbon nanotubes and carbon nanofibers before and after modification into lubricating oil, carrying out ultrasonic treatment for 30min, standing for different times, and observing the dispersion condition and the stability of the suspension, wherein the results are shown in table 1.

As can be seen from table 1, the untreated graphene, carbon nanotubes, and carbon nanofibers are directly dispersed in the lubricant, and when settling begins after standing for 12 hours, the carbon nanofibers settle faster than the carbon nanotubes and graphene. The dispersion stability of the graphene, the carbon nano tube and the carbon nano fiber in the lubricating oil is greatly improved after the surface of the graphene, the carbon nano tube and the carbon nano fiber is coated with polydopamine and grafted with alkyl groups with different carbon chain lengths. The longer the carbon chain length of the grafted alkyl group, the higher the dispersion stability. The graphene, the carbon nano tube and the carbon nano fiber grafted with the hexadecylamine and the octadecylamine are still uniformly and stably suspended in the lubricating oil after standing for 6 months, and the phenomenon of sedimentation separation does not occur. The invention realizes the uniform dispersion and long-term stability of nano carbon materials such as graphene in lubricating oil by coating polydopamine on the surface of graphene and grafting long-carbon-chain alkyl groups. Meanwhile, the long carbon chain alkane group grafted to the surface of graphene and the like through a chemical bond can stably exist on the surface of the carbon material in the ultrasonic dispersion process, so that the excellent dispersion effect can be ensured.

The alkylamine in example 2 is octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, preferably hexadecylamine and octadecylamine.

TABLE 1 Stable Dispersion of graphene, carbon nanotubes, and carbon nanofibers before and after modification

Example 3

The method is basically the same as the embodiment 1, except that in the step 1, 1-6 layers of graphene and dopamine hydrochloride with the layer size of 100-200nm are added into an aqueous solution of 0.01 mol/L tris (hydroxymethyl) aminomethane according to the mass ratio of 2:1, the mass ratio of the volume of the aqueous solution of tris (hydroxymethyl) aminomethane to the dopamine hydrochloride is 4L/g, the pH value of the solution is adjusted to 8.5, the solution is emulsified for 2min at 8000 rpm by a high-speed shearing emulsifying machine, then ultrasonic treatment is carried out, the ultrasonic frequency is 20KHz until the dopamine hydrochloride is completely dissolved, the graphene is fully dispersed, hydrogen peroxide is added according to the ratio of 40m L5% of the dopamine hydrochloride per gram, and the reaction is carried out for 1-2 hours at the temperature of 20-40 ℃.

Fig. 1 is a photograph of a transmission lens of graphene surface-treated in step 1 of example 3. As shown in fig. 1, the graphene sheet layer size is about 100-200, and the thickness of the modified material is increased, indicating that surface coating is achieved.

Example 4

The embodiment is basically the same as the embodiment 3, except that in the step 2, multi-walled carbon nanotubes with the purity of more than 99.5 percent, the diameter of 15nm and the length of 1-3 mu m and dopamine hydrochloride are added into an aqueous solution of 0.01 mol/L trihydroxymethylaminomethane according to the mass ratio of 2:1, the mass ratio of the volume of the aqueous solution of the trihydroxymethylaminomethane to the dopamine hydrochloride is 4L/g, the pH value of the solution is adjusted to 8.5, the solution is emulsified for 5min at 8000 revolutions by using a high-speed shearing emulsifying machine, and then ultrasonic treatment is carried out, the ultrasonic frequency is 20KHz until the dopamine hydrochloride is completely dissolved, the carbon nanotubes are fully dispersed, hydrogen peroxide is added according to the proportion that 5 percent of 40m L is added into each gram of dopamine hydrochloride, and the reaction is carried out for 1-2 hours at the temperature of 20-40.

FIG. 2 is a TEM image of the surface-treated carbon nanotubes obtained in step 2 of example 4. As shown in the figure, the diameter of the modified carbon nanotube is about 20nm, and the carbon nanotube does not have serious agglomeration, which indicates that the modification makes the carbon nanotube easy to disperse.

Example 5

The method is basically the same as the embodiment 4, except that in the step 3, carbon nanofibers with the diameter of 100nm and the length of 5-10 microns and dopamine hydrochloride are added into an aqueous solution of 0.01 mol/L tris (hydroxymethyl) aminomethane according to the mass ratio of 12:5, the mass ratio of the volume of the aqueous solution of tris (hydroxymethyl) aminomethane to the dopamine hydrochloride is 4L/g, the pH value of the solution is adjusted to 8.5, the solution is emulsified for 5min at 8000 rpm by a high-speed shearing emulsifying machine, ultrasonic treatment is carried out again, the ultrasonic frequency is 20KHz until the dopamine hydrochloride is completely dissolved, the carbon nanofibers are fully dispersed, hydrogen peroxide is added according to the proportion that 5% of 40m L hydrogen peroxide is added into each gram of dopamine hydrochloride, and the reaction is carried out for 1-2 hours at the temperature of 20-40 ℃.

FIG. 3 is a TEM image of the surface-treated carbon nanofibers obtained in step 3 of example 5. As shown, the diameter of the modified carbon nanofibers was about 50nm, and the presence of the surface coating was visible.

Example 6

This example is substantially the same as example 5 except that: step 4, adding A2, B2 and C2 into the lubricating oil, wherein the mass of A2, B2 and C2 respectively accounts for 0.1-0.5%, 0.1-0.5% and 0.02-0.05% of the total mass of the lubricating oil containing the modified carbon nano material; stirring and ultrasonically dispersing for 10-30 minutes at the ultrasonic frequency of 20kHz to obtain the modified lubricating oil containing the carbon nano-material.

Example 7

This example is substantially the same as example 1 except that step 3 is to add octadecylamine to 0.01 mol/L ethanol solution of tris (hydroxymethyl) aminomethane, the solvent in the ethanol solution is 95% ethanol by mass, the mass ratio of tris (hydroxymethyl) aminomethane to octadecylamine is 6L/g, ultrasonic treatment is performed for 5min to completely dissolve octadecylamine, the pH of the solution is adjusted to be = 8.5, C1 is added to the solution in which octadecylamine has been dissolved according to the mass ratio of C1 to octadecylamine of 1.2-1, stirring is performed at 20-40 ℃ for 12h, and after filtration, washing and drying, modified carbon nanofiber nanomaterial lubricating oil additive C2 is obtained.

Example 8

This example is essentially the same as the preparation set forth in examples 1-7, except that: the mass of steps 4 a2, B2, and C2 accounted for 0.1%, and 0.02%, respectively, of the total mass of the lubricating oil containing the modified carbon nanomaterial.

To illustrate the effect of nanocarbon modification on lubricant performance, the lubricant prepared by the method of this example was applied to popular Bay and Toyota Camry cars, and fuel consumption after 3000km was tested and compared with that of ordinary lubricant using no nanocarbon modification (tables 2 and 3). The conclusions drawn from the data in the table are: after the carbon nano material modified lubricating oil is added by the public, the consumption effect of the internal combustion oil of 200km is not shown, and the data of the fuel consumption of 600km and 3000km shows that the working condition change of the urban area is reduced by 4.6%, the working condition change of the suburban area is reduced by 1.6%, and the comprehensive working condition change is reduced by 2.96%. After carbon nano material modified lubricating oil is added to Kernel in Toyota, 3000km of fuel consumption in a thermal state test is reduced by 4.12% under the urban working condition, 5.98% under the suburban working condition and 5.38% under the comprehensive working condition. Therefore, the carbon nano material modified lubricating oil has obvious oil saving effect. The change of the nitrogen oxide, CO and hydrocarbon values in the emission is not obvious.

TABLE 2 data for testing fuel consumption and pollutant emission of a popular Baoling car using the modified lubricating oil of the present invention

TABLE 3 Fuel consumption and pollutant emissions testing data for Toyota Camry using the modified lubricating oil of the present invention

Example 9

This example is essentially the same as the preparation set forth in examples 1-7, except that: the mass of steps 4 a2, B2, and C2 accounted for 0.2%, and 0.04%, respectively, of the total mass of the lubricating oil containing the modified carbon nanomaterial.

To further illustrate the effect of nanocarbon modification on lubricant performance, the lubricant oil prepared according to the method of this example was applied to SUV longanger and tested for oil consumption (tables 4-5), cylinder pressure (table 6) and tail gas emissions (table 7) before and after replacement of nanocarbon-modified lubricant oil. As can be seen from tables 4-5, the results of the two vehicles tests were a 10.3%, 2.96% and 17.37% reduction in fuel consumption per kilometer at speeds of 35km/h, 65km/h and 125km/h, respectively. As can be seen from the data in Table 6, the engine cylinder pressure increased by 0.5 MPa after the modified lubricating oil of the present invention was replaced, indicating that the dynamic performance of the engine was improved. As can be seen from the data in Table 7, the exhaust gas emissions of CO and hydrocarbons are significantly reduced, the CO emissions can be reduced by 2-4 times, and the hydrocarbons can be reduced by 2-3 times, whether at low or high rotational speeds; the nitrogen oxides are also reduced at high rotational speeds (by about 7%). Therefore, the modified lubricating oil can lead the automobile to be more oil-saving, more environment-friendly and more abundant in power.

TABLE 4 oil consumption Change before and after replacement of nanocarbon material modified lubricating oil by SUV from ChangAnjie

TABLE 5 oil consumption Change before and after replacement of SUV from ChangAnjie

Table 6 Cylinder pressure changes before and after changing SUV from nanocarbon material modified lubricating oil

TABLE 7 exhaust emission Change before and after replacement of nanocarbon material modified lubricating oil by SUV from ChangAnjie

Example 10

This example is essentially the same as the preparation set forth in examples 1-7, except that: the mass of steps 4 a2, B2, and C2 accounted for 0.3%, 0.1%, and 0.04%, respectively, of the total mass of the lubricating oil containing the modified carbon nanomaterial.

To further illustrate the effect of nanocarbon material modification on lubricant performance, the lubricant prepared according to example 9 was applied to a popular treasure 1.8 displacement automobile with a mileage of 10 kilometers, and the results of cylinder pressure (table 8) and exhaust emissions (table 9) at idle before and after changing the nanocarbon material modified lubricant were tested. As can be seen from the data in Table 7, the engine cylinder pressure can be increased by 2-4 MPa after replacement of the modified lubricating oil of the present invention. The data in Table 8 shows that the emissions of CO and hydrocarbons in the exhaust gas are well below emission limits at both low and high idle speeds using the modified lubricating oil of the present invention. The example illustrates that the carbon nano-material modified lubricating oil provided by the invention has a more obvious improvement on the power performance of automobiles with high kilometer number.

TABLE 8 change of pressure of front and back cylinders of nanocarbon material modified lubricating oil for changing of 1.8-displacement automobiles by Volkswagen Baolai

TABLE 9 exhaust gas changes before and after replacement of nanocarbon material modified lubricating oil for 1.8-volume automobile

Example 11

This example is essentially the same as the preparation set forth in examples 1-7, except that: the mass of steps 4 a2, B2, and C2 accounted for 0.1%, 0.3%, and 0.04%, respectively, of the total mass of the lubricating oil containing the modified carbon nanomaterial.

Fig. 4 and 5 are photomicrographs of the steel surface after a friction experiment in a lubricating oil, in which fig. 5 is a lubricating oil modified with the nanocarbon material prepared in example 11, and fig. 4 is an unmodified lubricating oil. As can be seen from the figure, in the unmodified lubricating oil, a plurality of deep scratches and triangular depressions are obviously formed on the friction surface of the steel, which indicates that the abrasion is uneven and serious. After the modified lubricating oil is used, a friction interface is uniform, and no scratch or depression appears, which indicates that the friction is uniform.

Fig. 6 and 7 are scanning probe micrographs of the friction surface corresponding to fig. 5. It can be seen that the nanocarbon material-modified lubricating oil of the present invention forms a porous protective film on the friction surface. The film physically isolates a friction interface, so that direct friction is effectively reduced; the film has porosity and can adsorb grease, thereby forming the protective action of 'liquid-solid double lubrication', and greatly improving the lubricating effect; in addition, the film can help to prevent local hot spots of a friction interface by virtue of good thermal conductivity of graphene and carbon nanotubes, so that the service life of the lubricating oil is prolonged.

Example 12

This example is essentially the same as the preparation set forth in examples 1-7, except that: the mass of steps 4 a2, B2, and C2 accounted for 0.2%, and 0.1%, respectively, of the total mass of the lubricating oil containing the modified carbon nanomaterial.

In order to examine the influence of the addition of the nanocarbon material on the physical property indexes of the lubricating oil, the modified lubricating oil prepared in example 12 was examined according to the national standard (table 10), and the data in the table show that all the physical property indexes of the carbon nanomaterial modified lubricating oil of the invention meet the national standard requirements.

TABLE 10 example 12 physical index test results of modified lubricating oil

Claims

1. A method of preparing a lubricating oil containing surface-modified carbon nanomaterials comprising the steps of:

step 1: preparation of modified graphene nano material

adding A1 and alkylamine into ethanol solution of trihydroxymethyl aminomethane with the concentration of 0.01-0.10 mol/L according to the mass ratio of 1:4, wherein the solvent in the ethanol solution is ethanol with the mass concentration of 95-99.5%, and the mass ratio of the volume of the ethanol solution of the trihydroxymethyl aminomethane to the alkylamine is 5-8L/g, adjusting the pH of the solution to be 8-9, stirring for 12-24h at the temperature of 20-40 ℃, filtering, washing and drying to obtain a modified graphene lubricating oil additive A2, wherein the alkylamine is octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine and octadecylamine;

step 2: preparation of modified multi-wall carbon nano-tube nano-material

adding B1 and alkylamine into an ethanol solution of trimethylolaminomethane with the concentration of 0.01-0.10 mol/L according to the mass ratio of 1:4, wherein the solvent in the ethanol solution is ethanol with the mass concentration of 95-99.5%, and the mass ratio of the volume of the ethanol solution of the trimethylolaminomethane to the alkylamine is 5-8L/g, adjusting the pH of the solution to be 8-9, stirring for 12-24h at the temperature of 20-40 ℃, filtering, washing and drying to obtain a modified multi-wall carbon nanotube lubricating oil additive B2, wherein the alkylamine is octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine and octadecylamine;

and step 3: preparation of modified carbon nanofiber nano material

adding C1 and alkylamine into ethanol solution of tris (hydroxymethyl) aminomethane with the concentration of 0.01-0.10 mol/L according to the mass ratio of 1.2:1-1:4, wherein the solvent in the ethanol solution is ethanol with the mass concentration of 95-99.5%, and the mass ratio of the volume of the ethanol solution of tris (hydroxymethyl) aminomethane to the alkylamine is 5-8L/g, adjusting the pH of the solution to = 8-9, stirring for 12-24h at 20-40 ℃, filtering, washing and drying to obtain the modified carbon nanofiber nano-material lubricating oil additive C2;

2. The method of claim 1, wherein the lubricant oil containing the surface-modified carbon nanomaterial comprises:

1-3 layers of graphene are arranged in the step 1, the size of a lamella is 50-150nm, the mass ratio of graphene to dopamine hydrochloride is 5:1, and the mixture is stirred for 1-2 hours at 20-40 ℃; the alkylamine in the step is hexadecylamine and octadecylamine;

step 2: the carbon nano tube is a multi-wall carbon nano tube, the purity is more than 99.5 percent, the diameter is 10-20nm, and the length is 0.5-5 mu m; the mass ratio of the carbon nano tube to the dopamine hydrochloride is 5:1, and the mixture is stirred for 1-2 hours at the temperature of 20-40 ℃; the alkylamine in the step is hexadecylamine and octadecylamine;

and step 3: the diameter of the carbon nanofiber is 50-100nm, the length of the carbon nanofiber is 5-10 mu m, and the mass ratio of the carbon nanofiber to dopamine hydrochloride is 5: 1; stirring for 1-2h at 20-40 ℃; c1 and alkylamine according to the mass ratio of 1: 4; the alkylamine in the step is hexadecylamine and octadecylamine;

and 4, step 4: the mass of A2, B2 and C2 respectively accounts for 0.1-0.5%, 0.1-0.5% and 0.02-0.5% of the total mass of the lubricating oil containing the modified carbon nano-material.

3. The method of claim 1, wherein the lubricant oil containing the surface-modified carbon nanomaterial comprises:

step 1, adding 1-6 layers of graphene and dopamine hydrochloride with the sheet size of 100 and 200nm into an aqueous solution of 0.01 mol/L trihydroxymethyl aminomethane according to the mass ratio of 2:1, wherein the mass ratio of the volume of the aqueous solution of the trihydroxymethyl aminomethane to the dopamine hydrochloride is 4L/g, adjusting the pH value of the solution to be 8.5, emulsifying for 2min at 8000 revolutions/minute by using a high-speed shearing emulsifying machine, performing ultrasonic treatment with the ultrasonic frequency of 20KHz until the dopamine hydrochloride is completely dissolved, and fully dispersing the graphene, adding hydrogen peroxide according to the ratio of adding 40m L5% of hydrogen peroxide to each gram of dopamine hydrochloride, and reacting for 1-2 hours at 20-40 ℃;

step 2, adding multi-walled carbon nanotubes with the purity of more than 99.5 percent, the diameter of 15nm and the length of 1-3 microns and dopamine hydrochloride into an aqueous solution of 0.01 mol/L trihydroxymethylaminomethane according to the mass ratio of 2:1, wherein the volume of the aqueous solution of the trihydroxymethylaminomethane and the mass ratio of the dopamine hydrochloride are 4L/g, adjusting the pH value of the solution to 8.5, emulsifying for 5min at 8000 revolutions/minute by using a high-speed shearing emulsifying machine, performing ultrasonic treatment again, wherein the ultrasonic frequency is 20KHz until the dopamine hydrochloride is completely dissolved and the carbon nanotubes are fully dispersed, adding hydrogen peroxide according to the ratio of adding 5 percent of 40m L hydrogen peroxide into each gram of dopamine hydrochloride, and reacting for 1-2 hours at 20-40 ℃;

step 3, adding carbon nanofibers with the diameter of 100nm and the length of 5-10 microns and dopamine hydrochloride into an aqueous solution of 0.01 mol/L trihydroxymethylaminomethane according to the mass ratio of 12:5, wherein the mass ratio of the volume of the aqueous solution of the trihydroxymethylaminomethane to the dopamine hydrochloride is 4L/g, adjusting the pH value of the solution to 8.5, emulsifying for 5min at 8000 revolutions/minute by using a high-speed shearing emulsifying machine, performing ultrasonic treatment again, the ultrasonic frequency is 20KHz until the dopamine hydrochloride is completely dissolved, and fully dispersing the carbon nanofibers, adding 5% of 40m L hydrogen peroxide into each gram of dopamine hydrochloride according to the ratio of adding 5% of 40m L hydrogen peroxide, and reacting for 1-2 hours at 20-40 ℃;

and 4, step 4: adding A2, B2 and C2 into lubricating oil, wherein the mass of A2, B2 and C2 respectively accounts for 0.1-0.5%, 0.1-0.5% and 0.02-0.05% of the total mass of the lubricating oil containing the modified carbon nano material; stirring and ultrasonically dispersing for 10-30 minutes at the ultrasonic frequency of 20kHz to obtain the modified lubricating oil containing the carbon nano-material.

4. The method for preparing the lubricating oil containing the surface-modified carbon nanomaterial according to claim 1, wherein step 3 is to add octadecylamine into an ethanol solution of tris (hydroxymethyl) aminomethane with a concentration of 0.01 mol/L, wherein a solvent in the ethanol solution is 95% by mass ethanol, and a mass ratio of the ethanol solution of tris (hydroxymethyl) aminomethane to octadecylamine is 6L/g, perform ultrasonic treatment for 5min to completely dissolve octadecylamine, adjust a solution pH = 8.5, add C1 to the solution in which octadecylamine is dissolved according to a mass ratio of C1 to octadecylamine of 1.2-1, stir at 20-40 ℃ for 12h, filter, wash and dry to obtain the modified multi-walled carbon nanotube lubricating oil additive C2.

5. The method of claim 1, wherein the lubricant oil containing the surface-modified carbon nanomaterial comprises: the mass of the steps 4A 2, B2 and C2 respectively accounts for 0.1 percent, 0.1 percent and 0.02 percent of the total mass of the lubricating oil containing the modified carbon nano material; or 0.2%, 0.04%; or 0.3%, 0.1%, 0.04%; or 0.2%, 0.2% and 0.1%.

6. The method for producing a lubricating oil containing surface-modified carbon nanomaterial according to any one of claims 2 to 4, wherein: the mass of the steps 4A 2, B2 and C2 respectively accounts for 0.1 percent, 0.1 percent and 0.02 percent of the total mass of the lubricating oil containing the modified carbon nano material; or 0.2%, 0.04%; or 0.3%, 0.1%, 0.04%; or 0.2%, 0.2% and 0.1%.

7. The method of claim 1, wherein the surface-modified carbon nanomaterial-containing lubricating oil is prepared by the method.

8. The lubricant oil containing surface-modified carbon nanomaterial of claim 7, wherein: the mass of the modified graphene, the modified carbon nano tube and the modified carbon nano fiber respectively accounts for 0.1 percent, 0.1 percent and 0.02 percent of the total mass of the lubricating oil containing the modified carbon nano material; or 0.2%, 0.04%; or 0.3%, 0.1%, 0.04%; or 0.2%, 0.2% and 0.1%.