CN106398802A - Rapid laser preparing method for composite with graphene loaded with spherical inorganic fullerene molybdenum disulfide - Google Patents

Abstract

The invention discloses a preparation method of a graphene-loaded spherical inorganic fullerene-like molybdenum disulfide composite material. The steps are as follows: mixing flake molybdenum disulfide and graphene oxide solution, and ultrasonically dispersing to form a suspension; The mixed suspension is irradiated, and under the action of pulsed laser and liquid phase solution solvent, it is transformed into an interphase formed by reducing graphene oxide and nano/submicron inorganic fullerene-like molybdenum disulfide globules on its surface. Sandwich structure; after irradiation, the suspension is centrifuged, and the obtained precipitate is dried to obtain a composite material of spherical inorganic fullerene-like molybdenum disulfide supported by reduced graphene oxide. The invention uses laser beams to directly irradiate the mixed suspension, so that the suspended particles obtain high energy instantaneously (on the order of nanoseconds), are ablated and rapidly cooled by the solution (on the order of nanoseconds), thereby realizing the reduction and sheeting of graphene oxide in one step. The transformation of molybdenum disulfide to spherical inorganic fullerene-like structure is simple, low-cost, and free from impurity pollution. The obtained composite material exhibits excellent anti-friction performance during the friction process.

Description

Laser rapid preparation of a graphene-supported spherical inorganic fullerene-like molybdenum disulfide method

technical field

The invention relates to a method for preparing graphene-supported spherical inorganic fullerene-like molybdenum disulfide, in particular to a simple and rapid method for realizing the reduction of graphene oxide and flake molybdenum disulfide to spherical inorganic molybdenum by using pulsed laser irradiation technology. The transformation of fullerene structure belongs to the technical field of preparation of micronano powder.

Background technique

The global energy loss caused by friction and wear accounts for about one-third of the total mechanical energy loss. Facing the rapid development of the world economy and the strong demand for energy conservation and emission reduction, the research on anti-wear and anti-friction materials will make outstanding contributions to the realization of energy conservation and emission reduction. Molybdenum disulfide (2H-MoS ₂ ) with a layered structure has been widely used as an additive to traditional solid lubricants, lubricating oils, and greases; molybdenum disulfide with different microstructures and shapes are used as lubricating materials, and their properties vary greatly . The spherical shape of the inorganic fullerene molybdenum disulfide (IF-MoS ₂ ) and the closed structure of the outer shell make it have good chemical stability, and it can also change sliding friction into rolling friction during the friction process. Therefore, IF-MoS ₂ It can still exhibit excellent tribological properties in relatively harsh working environments. However, the complex production process, harsh reaction environment, high cost and low yield of IF-MoS ₂ greatly restrict its application.

Graphene is a sp ² hybridized new type of carbon material with a single atomic layer thickness. It has excellent mechanical properties, electrical and thermal conductivity, extremely high strength and large specific surface area, and is prone to slipping under shearing. A lubricating film is formed on the surface of the friction pair. However, the anti-wear effect of graphene as a lubricant is average, its preparation cost is high, and the yield of mechanical exfoliation is low. Liquid phase exfoliation (Hummers) needs to be reduced, resulting in more defects in graphene, affecting its mechanical properties and electrical and thermal conductivity.

At present, people have used flake molybdenum disulfide/graphene composite materials to solve the problems of low conductivity and easy agglomeration (patent application number 201410711472.8; Adv. Mater. 2013, 25, 3979); for spherical IF-MoS ₂ / There are few studies on graphene, and the main preparation methods are the combination of liquid phase exfoliation, vapor deposition, calcination and solvothermal method: patent 201510155973.7 discloses a graphene-fullerene-like molybdenum disulfide composite The lubricating fluid additive and its preparation method, the reduction of graphene oxide uses a highly toxic and highly reducing hydrazine hydrate solution, and the preparation of IF-MoS ₂ is obtained by reducing the precursor molybdenum trisulfide under high temperature and high purity hydrogen. Patent 201510148981.9 discloses an inorganic fullerene-like molybdenum disulfide/graphene composite lubricant and its preparation method, using a high-pressure reactor, the reaction temperature is 200 ° C ~ 600 ° C, the upper reaction atmosphere is 0.2 ~ 3 MPa hydrogen . However, these reported preparation methods are complicated in process, demanding in working environment, and need to use expensive and dangerous gas H ₂ /H ₂ S. A more economical, simple and effective preparation method of IF-MoS ₂ /graphene composites is still a technical blank.

Contents of the invention

In order to overcome the deficiencies in the prior art, the invention provides a method for preparing a graphene-supported inorganic fullerene-like molybdenum disulfide composite. The reduction of graphene oxide and the transformation of flake molybdenum disulfide to spherical inorganic fullerene-like structure can be rapidly realized under the following conditions.

In view of the shortcomings of the existing IF-MoS ₂ /graphene composite material, such as tedious preparation process and harsh conditions, the present invention proposes for the first time that the graphene-loaded spherical inorganic fullerene-like molybdenum disulfide composite material is prepared by pulsed laser irradiation. After the pulsed laser contacts the material, it can generate a high-temperature and high-pressure environment at the contact interface instantaneously (on the order of nanoseconds), rapidly ablate and melt the sheet-shaped molybdenum disulfide and gradually transform it into a spherical shape, and rapidly cool it in the surrounding liquid medium environment, realizing Rapid transformation of molybdenum disulfide from sheet-like to spherical fullerene-like structure; at the same time, under the strong reduction effect of laser irradiation, graphene oxide is reduced, and finally spherical inorganic fullerene-like disulfide supported by reduced graphene oxide is obtained Molybdenum composite. The method is simple in operation and fast in reaction, and avoids the disadvantages of harsh conditions, complex and cumbersome processes, and high price in the gas-phase method and liquid-phase method.

Concrete technical scheme of the present invention is as follows:

A preparation method of a graphene-loaded spherical inorganic fullerene-like molybdenum disulfide composite material, the method comprising the following steps:

(1) Sodium molybdate is used as the molybdenum source, thioacetamide is used as the sulfur source, polyethylene glycol, silicotungstic acid or cetyltrimethylammonium bromide is used as the dispersant, and molybdenum The molar ratio between the molybdenum in the source and the sulfur in the sulfur source and the dispersant is 1: (2-2.8): (0-0.5) into the deionized water, magnetically stirred until completely dissolved, and then transferred to high pressure In the reaction kettle, at a temperature of 180-220°C, heat-preserve for 10-24 hours; after cooling, wash with deionized water for 3-7 times to obtain a flaky molybdenum disulfide suspension evenly dispersed in the aqueous solution;

(2) Add graphene oxide solution (0.3-1.2 mg mL ^-1 ) into the above-mentioned molybdenum disulfide suspension, and ultrasonically disperse for 5-30 min;

(3) The mixed suspension obtained in step (2) is irradiated with pulsed laser, so that graphene oxide and flake molybdenum disulfide powder are transformed into spherical fullerene-like disulfide supported by reduced graphene oxide under the action of pulsed laser molybdenum;

(4) After the irradiation, the suspension was centrifuged and separated, and the obtained precipitate was dried to obtain a spherical fullerene-like molybdenum disulfide composite material loaded with reduced graphene oxide.

In step (1) of the present invention, for the preparation of flaky molybdenum disulfide powder, the addition or non-addition of dispersant will affect its original microscopic morphology, and then affect the inorganic fullerenes produced by laser irradiation Dimensions of molybdenum disulfide.

Preferably, in step (1), the dispersant is selected from none or one of polyethylene glycol, silicotungstic acid or cetyltrimethylammonium bromide, and finally the particle size range of 50-800 nm can be obtained. Molybdenum disulfide between inorganic fullerenes.

During the laser irradiation process, the concentration of the mixed suspension of graphene oxide and flake molybdenum disulfide is not easy to be too high. If the concentration is too high, it will not be possible to irradiate all the particles in the suspension uniformly and make them receive the same energy to undergo transformation. At the same time, the content of the liquid phase medium is too small to rapidly cool the ablated molten molybdenum disulfide.

Preferably, in step (2), the effective mass percentage of the molybdenum disulfide and graphene is: (0.7-0.9): (0.3-0.1), and the concentration of the mixed suspension of the two is 0.8-20 mg mL ^-1 .

In the step (3) of the present invention, the working parameters of the pulsed laser are as follows: the wavelength is 200-1600 nm, the frequency is 1-15 Hz, the energy density is 100-800 mJ pulse ^-1 cm ^-2 , and the irradiation time is 10-300 min . In a specific embodiment of the present invention, the pulsed laser is formed in the following manner: the laser beam is emitted by the laser, and then focused by a mirror and a convex lens to form a pulsed laser beam with a required spot size and adjusted to the required operating parameters. The irradiation operation can be carried out.

Preferably, in step (3), during the pulsed laser irradiation process, the temperature of the suspension is controlled to be 5°C to 20°C; the energy density of the pulsed laser is 300 to 700 mJ pulse ^-1 cm ^-2 ; the pulsed laser is irradiated for 20 ~50 min can get better products.

Further, in order to make the irradiation more uniform, preferably, in step (3), the mixed suspension is subjected to pulsed laser irradiation under magnetic stirring, and the stirring speed is 500-1000 r min ^-1 .

Preferably, in step (4), the drying temperature of the obtained precipitate is 5°C to 15°C.

The above-mentioned method of the present invention can obtain the composite material of the spherical inorganic fullerene-like molybdenum disulfide supported by graphene, and this composite material has more excellent reduction in friction than the mixed powder of ordinary graphene oxide/flaky molybdenum disulfide. It has better performance as a friction reducer for solid lubricants, lubricating oils, and greases, and the addition amount is about 0.1 wt%.

In the present invention, the solution of flake molybdenum disulfide and graphene oxide is mixed, ultrasonically dispersed to form a suspension, and the laser beam focused by a mirror and a convex lens directly irradiates the suspension, so that the molybdenum disulfide powder in the solution ( nanoseconds) to obtain high energy, be ablated and melted and rapidly (nanoseconds) cooled by the solution, and at the same time, the graphene oxide is reduced by using the high temperature and high pressure reducing atmosphere generated by the contact between the laser and the material, so as to realize the graphene-loaded Preparation of spherical inorganic fullerene-like molybdenum disulfide composites. Compared with the prior art, the preparation method is novel, the product has high purity and no impurity pollution, and the obtained graphene-supported spherical inorganic fullerene-like molybdenum disulfide composite material has excellent properties such as friction reduction during the friction process. The beneficial effects of the present invention are:

(1) The present invention only needs one step to realize the reduction of graphene oxide and the transformation of flake molybdenum disulfide to spherical inorganic fullerene-like structure, with simple operation and low preparation cost;

(2) The present invention can prepare spherical inorganic fullerene-like molybdenum disulfide with different particle sizes (50-800 nm) through the selective use of different dispersants;

(3) The preparation process of the present invention only needs to irradiate the mixed suspension of flaky molybdenum disulfide and graphene dispersed in the solution with laser light, and does not require other redox atmospheres, reaction reagents and complicated experimental devices. The conditions are easy to control, and the process It is simple and low in cost, and solves the problems of complex preparation process and difficulty in mass production;

(4) The product obtained by the method of the present invention has high purity and no impurity pollution. The graphene-loaded inorganic fullerene molybdenum disulfide composite material has high mechanical strength, toughness and strong adsorption, and is used as lubricating oil, The additives of lubricating oil and grease can be adsorbed to the surface of the friction pair, so that the metal friction pair is separated from each other, effectively reducing friction, and has excellent anti-friction performance.

Description of drawings

Figure 1 is a transmission electron microscope image of flake molybdenum disulfide and graphene oxide mixed powder before laser irradiation;

Fig. 2 is the scanning electron microscope picture of the graphene-loaded spherical inorganic fullerene-like molybdenum disulfide composite material formed after pulsed laser irradiation;

Fig. 3 is a high-resolution transmission electron microscope image of the graphene-loaded spherical inorganic fullerene-like molybdenum disulfide composite material formed after pulsed laser irradiation.

detailed description

In order to facilitate understanding of the present invention, the present invention will be described in detail below in the form of examples. The following examples are carried out under the premise of the technology of the present invention, and detailed implementation methods and specific operating procedures have been provided, but the present invention The scope of protection is not limited to the following examples.

Example 1

(1) Weigh 0.24 g of sodium molybdate (purity 99%) and 0.15 g of thioacetamide (purity 98%) into a beaker, add 50 mL of deionized water, stir magnetically until the powder is completely dissolved; then transfer the solution into the reaction Kettle, kept at 180°C for 24 hours; after cooling, centrifuged and washed 7 times with deionized water to obtain flake molybdenum disulfide suspension evenly dispersed in aqueous solution;

(2) Add 2.0 mL of graphene oxide solution (0.8 mg mL ^-1 ) into the above molybdenum disulfide suspension, the concentration of the two after mixing is 0.8 mg mL ^-1 , and ultrasonically disperse for 5 min;

(3) Irradiate the mixed suspension prepared in the above step (2) with the krypton-fluorine laser beam (248 nm) focused by a mirror and a convex lens. The laser energy density is 300 mJ pulse ^-1 cm ^-1 and the frequency is 15 Hz, and the irradiation time is 20 min. During the laser beam irradiation process, the suspension was continuously stirred with a magnetic stirrer at a speed of 1000 r min ^-1 , and the temperature of the suspension was 5 °C;

(4) After the irradiation, the suspension was centrifuged, and then the powder was dried at 5 °C to obtain the reduced graphene oxide loaded spherical fullerene-like molybdenum disulfide composite.

Figure 1 is a transmission electron microscope image of the flake molybdenum disulfide and graphene oxide mixed powder before laser irradiation in step (2). It can be seen from the figure that the flake molybdenum disulfide powder is agglomerated together. Fig. 2 SEM images of graphene-loaded spherical inorganic fullerene-like molybdenum disulfide composites formed after pulsed laser irradiation. It can be seen from the figure that spherical molybdenum disulfide particles are evenly loaded on graphene sheets, and the two The latter form a sandwich structure, the size of the microspheres is relatively uniform, and the particle size is 100-200 nm. Figure 3 is the transmission electron microscope image of the product obtained after irradiation. It can be seen from the figure that the spacing (0.62 nm) of the edge (002) of the microsphere has a lattice expansion of 1%, indicating that the edge part is curled and the stress becomes larger. As a result, the interlayer spacing becomes larger, and the inorganic fullerene-like structure appears, which effectively eliminates the dangling bonds at the edges of the flake particles. Therefore, during the friction process, the composite material can effectively suppress the unfavorable phenomenon that the friction coefficient of the molybdenum disulfide powder is oxidized due to high temperature, thereby exhibiting excellent friction performance.

Example 2

(1) Weigh 0.24 g sodium molybdate (99% purity), 0.19 g thioacetamide (98% purity) and 0.15 g silicotungstic acid (98% purity) into a beaker, add 50 mL deionized water, Stir magnetically until the powder is completely dissolved; then transfer the solution into a reaction kettle and keep it warm at 220°C for 10 h; after cooling, wash it with deionized water for 7 times to obtain a flake molybdenum disulfide suspension evenly dispersed in the aqueous solution;

(2) Add 2 mL of graphene oxide solution (0.8 mg mL ^-1 ) into the above molybdenum disulfide suspension, the concentration of the two after mixing is 5 mg mL ^-1 , and ultrasonically disperse for 15 min;

(3) Irradiate the mixed suspension prepared in the above step (2) with the krypton-fluorine laser beam (248 nm) focused by a mirror and a convex lens. The laser energy density is 500 mJ pulse ^-1 cm ^-1 and the frequency is 10 Hz, and the irradiation time is 40 min. During the laser beam irradiation process, the suspension was continuously stirred with a magnetic stirrer at a speed of 800 r min ^-1 , and the temperature of the suspension was 10 °C;

(4) After the irradiation, the suspension was centrifuged, and then the powder was dried at 15°C to obtain the reduced graphene oxide loaded spherical fullerene-like molybdenum disulfide composite. The microscopic appearance of the obtained product is similar to that of Example 1, but the particle size of the spherical inorganic fullerene-like molybdenum disulfide is 50-100 nm.

Example 3

(1) Weigh 0.24 g sodium molybdate (purity 99%), 0.21 g thioacetamide (purity 98%) and 0.15 g polyethylene glycol (purity 98%) into a beaker, add 50 mL deionized water , magnetically stirred until the powder was completely dissolved; then the solution was transferred into a reaction kettle and kept at 200°C for 16 h; after cooling, it was centrifugally washed with deionized water for 5 times to obtain a flaky molybdenum disulfide suspension uniformly dispersed in an aqueous solution ;

(2) Add 3 mL of graphene oxide solution (0.8 mg mL ^-1 ) into the above molybdenum disulfide suspension, the concentration of the two after mixing is 15 mg mL ^-1 , and ultrasonically disperse for 30 min;

(3) Irradiate the mixed suspension prepared in the above step (2) with the krypton-fluorine laser beam (248 nm) focused by the mirror and convex lens, the laser energy density is 700 mJ pulse ^-1 cm ^-1 , and the frequency is 5 Hz, and the irradiation time was 60 min; during the laser beam irradiation process, the suspension was continuously stirred with a magnetic stirrer at a speed of 500 r min ^-1 , and the temperature of the suspension was 15°C;

(4) After the irradiation, the suspension was centrifuged, and then the powder was dried at 20 °C to obtain the reduced graphene oxide loaded spherical fullerene-like molybdenum disulfide composite. The microscopic appearance of the obtained product is similar to that of Example 1, but the particle size of the spherical inorganic fullerene-like molybdenum disulfide is 300-500 nm.

Example 4

(1) Weigh 0.24 g sodium molybdate (purity 99%), 0.15 g thioacetamide (purity 98%) and 0.15 g cetyltrimethylammonium bromide (purity 98%) into a beaker, Add 50 mL of deionized water and magnetically stir until the powder is completely dissolved; then transfer the solution into a reaction kettle and keep it warm at 220 °C for 10 h; after cooling, wash with deionized water for 7 times to obtain tablets uniformly dispersed in aqueous solution Molybdenum disulfide suspension;

(2) Add 2 mL of graphene oxide solution (0.8 mg mL ^-1 ) into the above molybdenum disulfide suspension, the concentration of the two after mixing is 20 mg mL ^-1 , and ultrasonically disperse for 30 min;

(3) Irradiate the mixed suspension prepared in the above step (2) with krypton-fluorine laser beam (248 nm) focused by mirror and convex lens, the laser energy density is 700 mJ pulse ^-1 cm ^-1 , and the frequency is 15 Hz, the irradiation time was 60 min, during the laser beam irradiation process, the suspension was continuously stirred with a magnetic stirrer at a speed of 700 r min ^-1 , and the temperature of the suspension was 20°C;

(4) After irradiation, the suspension was centrifuged, and then the powder was dried at 20°C to obtain a spherical fullerene-like molybdenum disulfide composite material supported by reduced graphene oxide. The microscopic appearance of the obtained product was similar to that of Example 1, but spherical The particle size of the inorganic fullerene molybdenum disulfide is 700-800 nm.

In order to verify the antifriction performance of the resulting product, the following experiments were carried out:

1. Add the mixed powder of graphene and molybdenum disulfide before and after laser irradiation in each of the above-mentioned embodiments to the liquid paraffin oil respectively, and carry out the friction performance test, and the addition is 0.1 wt% of the liquid paraffin oil quality;

2. Friction performance test method: four-ball friction and wear test, at the same time, pure paraffin oil is used as a blank control;

3. Result: See Table 1 below for the friction test results of the products of each embodiment and comparative example.

Table 1

It can be seen that the graphene-loaded spherical inorganic fullerene-like molybdenum disulfide composite material prepared by the method of the present invention has a good improvement in friction reduction performance, which is obviously higher than that of graphene and flakes before laser irradiation. Mixed powder of molybdenum disulfide. Conditions such as the type of dispersant, the concentration of the mixed suspension, and the energy density of the suspension during irradiation have a great influence on the product performance.

Claims (9)

1. A preparation method for a graphene-loaded spherical inorganic fullerene-like molybdenum disulfide composite material, characterized in that the composite material is composed of reduced graphene oxide and nano/submicron inorganic fullerene-like molybdenum disulfide loaded on its surface The interlayer structure formed by molybdenum sulfide spheres interphase; using liquid phase pulsed laser irradiation technology, the reduction of graphene oxide and the transformation of flake molybdenum disulfide to spherical inorganic fullerene-like structure can be quickly realized in one step. Among them, the spherical The particle size of the inorganic fullerene molybdenum disulfide is 50-800 nm. 2. a kind of preparation method of graphene loading spherical inorganic fullerene class molybdenum disulfide composite material as claimed in claim 1, is characterized in that, comprises the following steps: (1) Sodium molybdate is used as molybdenum source, thioacetamide is used as sulfur source, polyethylene glycol, silicotungstic acid or cetyltrimethylammonium bromide is used as dispersant, and molybdenum The molar ratio between the molybdenum in the source and the sulfur in the sulfur source and the dispersant is 1: (2-2.8): (0-0.5) into the deionized water, magnetically stirred until completely dissolved, and then transferred to high pressure In the reaction kettle, at a temperature of 180-220°C, heat-preserve for 10-24 hours; after cooling, wash with deionized water for 3-7 times to obtain a flaky molybdenum disulfide suspension evenly dispersed in the aqueous solution; (2) Add the graphene oxide solution into the above-mentioned molybdenum disulfide suspension, and ultrasonically disperse for 5-30 min; (3) The mixed suspension obtained in step (2) is irradiated with pulsed laser, so that graphene oxide and flake molybdenum disulfide powder are transformed into spherical fullerene-like disulfide supported by reduced graphene oxide under the action of pulsed laser Molybdenum composites; (4) After the irradiation, the suspension was centrifuged and separated, and the obtained precipitate was dried to obtain a spherical fullerene-like molybdenum disulfide composite material loaded with reduced graphene oxide. 3. The preparation method according to claim 2, characterized in that: in step (2), the effective mass percentage of the molybdenum disulfide and graphene is: (0.7-0.9): (0.3-0.1). 4. The preparation method according to claim 2, characterized in that: in step (2), the concentration of the graphene oxide solution is 0.3-1.2 mg mL ^-1 . 5. The preparation method according to claim 2, characterized in that: in step (2), the concentration of the mixed suspension obtained by mixing the graphene oxide solution with the flake molybdenum disulfide suspension is 0.8- 20 mg mL ^-1 . 6. The preparation method according to claim 2, characterized in that: in step (3), the wavelength of the pulse laser is 200-1600 nm, the frequency is 1-15 Hz, and the energy density is 100-800 mJ pulse ^{- 1} cm ^-2 , the irradiation time is 10-300min. 7. The preparation method according to claim 2, characterized in that: in step (3), during the pulsed laser irradiation process, the temperature of the suspension is controlled to be 5°C-20°C. 8. The preparation method according to claim 2, characterized in that: in step (3), the suspension is irradiated with pulsed laser light under magnetic stirring, and the stirring speed is 300-2000 r min ^-1 . 9. The preparation method according to claim 2, characterized in that: in step (4), the drying temperature of the precipitate is 5°C-30°C.