Oxidized black phosphorus nanocomposite lubricant and preparation method thereof

Abstract

The present application relates to a kind of oxidized black phosphorus nano composite lubricant and its preparation method, the molar ratio of oxidized black phosphorus and polyacrylic acid in the lubricant is 1-5:10, wherein oxidized black phosphorus is single-layer nanostructure, polyacrylic acid is the microsphere structure with particle size of 10-110nm, and they are connected by ester bond;Preparation method is that under specific conditions, oxidized black phosphorus nano suspension and polyacrylic acid microsphere aqueous solution are esterified by phosphotungstic acid catalyst to obtain.This composite lubricant improves the stability and dispersibility of oxidized black phosphorus nano in solution, and significantly improves its lubricating property, has important potential application prospect in the field such as friction pair of typical metal, metal processing lubrication etc..

Description

1. Technical Field

[0001] The invention belongs to the field of mechanical tribology lubricants, and particularly relates to a black phosphorus oxide nanocomposite lubricant and a preparation method thereof. 2. Background Technology

[0002] In recent years, two-dimensional materials have received a lot of research due to their unique lamellar structure and some novel physical and chemical properties. Black phosphorus nanosheets are an emerging two-dimensional material. Due to their good interfacial slip and tribofilm-forming ability, they have shown great application potential in the field of lubricating additives. However, black phosphorus nanosheets have poor stability and are easily degraded and fail in the environment, which affects the realization of their advantages. Their stability can be enhanced by surface oxidation, but the polar groups introduced by oxidation cause the oxidized black phosphorus to have poor dispersion in the medium. Therefore, how to improve the dispersibility of black phosphorus nanosheets while enhancing stability is particularly important for enhancing their lubrication performance. Although there are some reports on enhancing the lubricity of black phosphorus, there are still problems such as harsh conditions and complex methods. The stability, dispersibility and lubrication effect of black phosphorus nanosheets are not improved well. Therefore, it is necessary to develop a new type of oxidized black phosphorus nanocomposite lubricant and its preparation method. 3. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a new black phosphorus oxide nanocomposite lubricant with high stability, high dispersibility and strong lubricating effect, and to achieve its significant advantages such as mild preparation conditions, simple process and easy scalability.

[0004] To achieve the above-mentioned object of the invention, the technical solution of the present invention is carried out according to the following steps:

[0005] Step 1) adding block black phosphorus to N-methylpyrrolidone at a mass ratio of 4-8:1000, and exfoliating the block black phosphorus using a liquid phase ultrasonic exfoliation method, wherein the ultrasonic power is 120-180W and the ultrasonic time is 20-40h; then centrifuging at a centrifugal speed of 2000-4000rpm to remove incompletely exfoliated black phosphorus nanosheets, and continuing to centrifuge at 9000-11000rpm to collect the precipitate; adding the resulting precipitate to anhydrous ethanol at a mass ratio of 1-2:10 and exfoliating again at a power of 40-60W for 20-30min, and then centrifuging at 9000-11000rpm to obtain a precipitate, repeating the secondary ultrasonic exfoliation and centrifugation of the precipitate 3-5 times; finally, vacuum drying the precipitate to obtain a single-layer black phosphorus nanosheet with a single-layer rate of more than 99%;

[0006] Step 2) Spreading a single layer of black phosphorus nanosheets on the surface of a silicon wafer, placing the sheet in a quartz tube, controlling the system temperature at 25-30° C., introducing air at a rate of 10-20 mL / min for oxidation for 40-60 min to obtain oxidized black phosphorus nanosheets, and ultrasonically dispersing the sheet in deoxygenated deionized water at a mass ratio of 1-5:500 to form an oxidized black phosphorus nanosheet suspension;

[0007] Step 3) 1.6-2.0g of acrylic acid, 0.01-0.04g of N,N-methylenebisacrylamide, and 0.04-0.08g of sodium lauryl sulfate are respectively added to a three-necked flask containing 100-140mL of deionized water, nitrogen is introduced into the flask to remove oxygen therein, and the mixture is stirred for 10-15min; at the same time, 0.016-0.02g of ammonium sulfate is dissolved in 8-10mL of deionized water to prepare an initiator aqueous solution, which is placed in a dropping funnel above the three-necked flask; the solution in the three-necked flask is heated to 60-70°C in a water bath, the solution is stirred at a speed of 100-200rpm / min, and a nitrogen atmosphere is always maintained. The initiator aqueous solution is slowly added dropwise at a rate of 5-6 drops / min, and the reaction temperature is maintained at 60-70°C for 4-5h to obtain a polyacrylic acid aqueous solution;

[0008] Step 4) 100 mL of the black phosphorus oxide nanosheet suspension obtained in step 2 is placed in a three-necked flask, 20-50 mL of the polyacrylic acid aqueous solution obtained in step 3 and 3-5 g of phosphotungstic acid are added, and the reaction time is 3-5 hours at a water bath temperature of 70-90° C. and a stirring speed of 300-500 rpm. After the reaction is completed, centrifugation is performed at 10,000-15,000 rpm, and the precipitate is rinsed with deionized water 3-5 times, and then vacuum dried to obtain a black phosphorus oxide nanocomposite lubricant.

[0009] The molar ratio of black phosphorus oxide to polyacrylic acid in the black phosphorus oxide nanocomposite lubricant is 1-5:10, wherein the black phosphorus oxide is a single-layer nanosheet structure, and the polyacrylic acid is a microsphere structure with a particle size of 10-110 nm, and the two are connected by an ester bond.

[0010] The present invention has the following outstanding beneficial effects:

[0011] 1) The oxidized black phosphorus nanocomposite lubricant of the present invention has good stability. Through controlled surface oxidation, the substrate is prevented from oxidative failure in an air environment. There is no significant change after being placed in an air environment at room temperature for more than 3 months.

[0012] 2) The black phosphorus oxide nanocomposite lubricant of the present invention has good dispersibility and can be evenly dispersed in an aqueous environment system for more than one month without precipitation.

[0013] 3) The black phosphorus oxide nanocomposite lubricant of the present invention has good lubricity. Compared with black phosphorus oxide nanosheets, under a typical point contact friction environment, the friction coefficient of the black phosphorus oxide nanocomposite lubricant of the present invention is reduced by more than 23%, and the wear is reduced by more than 14.8%, showing a significant friction-reducing and anti-wear lubricating effect.

[0014] 4) The method of the present invention has the advantages of mild reaction conditions, simple process, controllable, low cost, and easy large-scale production. IV. Description of the Figures

[0015] Figure 1 This is a Fourier transform infrared spectrum of black phosphorus oxide, polyacrylic acid and the black phosphorus oxide nanocomposite lubricant prepared in Example 1 of the present invention.

[0016] Figure 2 High-resolution transmission electron microscope photos of black phosphorus (a), polyacrylic acid (b), and the oxidized black phosphorus nanocomposite lubricant (c) of the present invention prepared in Example 1 of the present invention.

[0017] Figure 3 Comparative diagram of the dispersion stability of the aqueous solution of oxidized black phosphorus nanosheets and the oxidized black phosphorus nanocomposite lubricant of the present invention when newly prepared (a) and after storage for 30 days (b).

[0018] Figure 4 Graph showing the average friction coefficient of black phosphorus oxide nanosheets and the black phosphorus oxide nanocomposite lubricants prepared in Examples 1 and 2 of the present invention;

[0019] Figure 5 The photos of wear spots on the upper friction pair after lubrication with different lubricants: black phosphorus oxide nanosheets (a) and the black phosphorus oxide nanocomposite lubricant of the present invention (b). V. Specific Implementation Methods

[0020] To make the objectives, technical solutions, and advantages of the present invention more clearly apparent, the present invention is described in detail below with reference to the accompanying drawings and examples. It should be noted that the specific examples described herein are only used to illustrate the present invention and are not intended to limit the embodiments of the present invention. Any other changes, modifications, combinations, simplifications, and substitutions made without departing from the spirit and principles of the present invention shall be considered equivalent replacements and shall be included within the scope of protection of the present invention.

[0021] Example 1

[0022] Step 1) adding block black phosphorus to N-methylpyrrolidone at a mass ratio of 4:1000, and exfoliating the block black phosphorus using a liquid phase ultrasonic exfoliation method, wherein the ultrasonic power is 120W and the ultrasonic time is 20 hours; then centrifuging at a centrifugal speed of 3000rpm to remove incompletely exfoliated black phosphorus nanosheets, continuing to centrifuge at 9000rpm, and collecting the precipitate under high-speed centrifugation; adding the obtained precipitate to anhydrous ethanol at a mass ratio of 1:10, and ultrasonicating for a second time at a power of 40W for 20 minutes, and centrifuging the ultrasonicated mixture at a centrifugal speed of 9000rpm to obtain a precipitate; repeatedly washing and centrifuging the precipitate three times, and finally drying the precipitate under vacuum to obtain a single-layer black phosphorus nanosheet with a single-layer rate of 99.3%.

[0023] Step 2) The above-mentioned single-layer black phosphorus nanosheets were spread flat on the surface of a silicon wafer and placed in a quartz tube. The system temperature was controlled at 25°C, and air was introduced at a rate of 10 mL / min for oxidation for 40 minutes to obtain oxidized black phosphorus nanosheets, which were dispersed in deoxygenated deionized water at a mass ratio of 1:500 to form an oxidized black phosphorus nanosheet suspension.

[0024] Step 3) 1.6 g of acrylic acid, 0.01 g of N,N-methylenebisacrylamide, and 0.04 g of sodium lauryl sulfate were taken respectively and added in order to a three-necked flask containing 100 mL of deionized water. Nitrogen was introduced into the flask to remove oxygen therein and stirred for 10 minutes; at the same time, 0.016 g of ammonium sulfate was placed in 8 mL of deionized water to prepare an initiator aqueous solution, which was placed in a dropping funnel above the three-necked flask; the solution in the three-necked flask was heated to 60° C. in a water bath, the solution was stirred at a speed of 100 rpm / min, and a nitrogen atmosphere was always maintained. The initiator aqueous solution was slowly added dropwise at a rate of 5-6 drops / min, and the reaction was maintained at 60° C. for 4 hours to obtain a polyacrylic acid aqueous solution.

[0025] Step 4) 100 mL of the black phosphorus oxide nanosheet suspension obtained in step 2 was placed in a three-necked flask, 20 mL of the polyacrylic acid aqueous solution obtained in step 3 and 3.6 g of phosphotungstic acid were added, and the reaction time was 3 h at a water bath temperature of 70°C and a stirring speed of 400 rpm. After the reaction was completed, the mixture was centrifuged at 12000 rpm, and the precipitate was rinsed with deionized water 3 times and then vacuum-dried to obtain a black phosphorus oxide nanocomposite lubricant.

[0026] Example 2

[0027] Step 1) Add bulk black phosphorus to N-methylpyrrolidone at a mass ratio of 6:1000, and use liquid phase ultrasonic exfoliation to exfoliate the bulk black phosphorus, wherein the ultrasonic power is 145W and the ultrasonic time is 35 hours; then centrifuge at a centrifugal speed of 2500rpm to remove incompletely exfoliated black phosphorus nanosheets, continue centrifugation at 10000rpm, and collect the precipitate after high-speed centrifugation. The resulting precipitate is added to anhydrous ethanol at a mass ratio of 1.5:10, and ultrasonicated at a power of 50W for 30 minutes. The ultrasonic mixture is centrifuged at a centrifugal speed of 10000rpm to obtain a precipitate; the precipitate is washed repeatedly five times, and finally the precipitate is dried under vacuum to obtain a single-layer black phosphorus nanosheet with a single-layer rate of 99.5%.

[0028] Step 2) The above-mentioned single-layer black phosphorus nanosheets were spread flat on the surface of a silicon wafer and placed in a quartz tube. The system temperature was controlled at 27°C, and air was introduced at a rate of 20 mL / min for oxidation for 45 minutes to obtain oxidized black phosphorus nanosheets, which were dispersed in deoxygenated deionized water at a mass ratio of 2:500 to form an oxidized black phosphorus nanosheet suspension.

[0029] Step 3) 2.0 g of acrylic acid, 0.04 g of N,N-methylenebisacrylamide, and 0.06 g of sodium lauryl sulfate were taken respectively and added in order to a three-necked flask containing 120 mL of deionized water. Nitrogen was introduced into the flask to remove oxygen therein and stirred for 15 minutes; at the same time, 0.02 g of ammonium sulfate was dissolved in 10 mL of deionized water to prepare an initiator aqueous solution, which was placed in a dropping funnel above the three-necked flask; the solution in the three-necked flask was heated to 65° C. in a water bath, the solution was stirred at 150 rpm / min, and a nitrogen atmosphere was always maintained. The initiator aqueous solution was slowly added dropwise at a rate of 5-6 drops / min, and the reaction was maintained at 65° C. for 4 hours to obtain a polyacrylic acid aqueous solution.

[0030] Step 4) 100 mL of the black phosphorus oxide nanosheet suspension obtained in step 2 was placed in a three-necked flask, 20 mL of the polyacrylic acid aqueous solution obtained in step 3 and 4.8 g of phosphotungstic acid were added, and the reaction time was 4 h at a water bath temperature of 85° C. and a stirring speed of 500 rpm. After the reaction was completed, the mixture was centrifuged at 15,000 rpm, and the precipitate was rinsed with deionized water 5 times and then vacuum-dried to obtain a black phosphorus oxide nanocomposite lubricant.

[0031] To test the friction-reducing lubrication effect of the present invention, tribological tests were conducted using a 0.15 wt% aqueous solution of the black phosphorus oxide nanocomposite lubricant and black phosphorus oxide nanosheets described in the examples. A ball-on-disc reciprocating friction tester was used, with a CoCrMo alloy disc and a 316L ball as the friction pair. The test parameters were: a load of 10 N, a single stroke of 5 mm, a reciprocating frequency of 5 Hz, a friction time of 15 minutes, and a lubricant temperature of 25°C.

[0032] from Figure 1 It can be seen that a typical ester group peak appears in the structure of the black phosphorus oxide nanocomposite lubricant of the present invention, indicating that the esterification reaction between black phosphorus oxide and polyacrylic acid microspheres is successful;

[0033] from Figure 2 It can be seen that compared with the black phosphorus oxide nanosheets, the black phosphorus oxide nanocomposite lubricant of the present invention has significantly improved dispersibility and no agglomeration occurs.

[0034] from Figure 3 It can be seen that compared with the existing lubricant, the dispersion stability of the composite lubricant of the present invention is significantly improved, and no obvious precipitation phenomenon occurs after storage for 30 days.

[0035] from Figure 4 It can be seen that compared with the existing lubricants, the friction coefficient of the composite lubricant of the present invention is reduced by more than 23%, indicating that its friction reduction performance is significantly improved.

[0036] from Figure 5 It can be seen that compared with the existing lubricant, under the lubrication of the composite lubricant of the present invention, the wear spot diameter of the upper friction pair 316L ball is significantly reduced, and the wear is reduced by more than 14.8%, indicating that its anti-wear performance is significantly improved, and its comprehensive performance is significant in lubrication performance.

Claims

1. A black phosphorus oxide nanocomposite lubricant, characterized in that: The molar ratio of black phosphorus oxide to polyacrylic acid in the black phosphorus oxide nanocomposite lubricant is 1-5:10, wherein the black phosphorus oxide is a single-layer nanosheet structure and the polyacrylic acid is a microsphere structure with a particle size of 10-110 nm, and the two are connected by an ester bond. The preparation method of the black phosphorus oxide nanocomposite lubricant is prepared according to the following steps: Step 1) adding block black phosphorus to N-methylpyrrolidone at a mass ratio of 4-8:1000, and exfoliating the block black phosphorus using a liquid phase ultrasonic exfoliation method, wherein the ultrasonic power is 120-180 W and the ultrasonic time is 20-40 h; then centrifuging at a centrifugal speed of 2000-4000 rpm to remove incompletely exfoliated black phosphorus nanosheets, and continuing to centrifuge at 9000-11000 rpm to collect the precipitate; adding the obtained precipitate to anhydrous ethanol at a mass ratio of 1-2:100, and exfoliating it again at a power of 40-60 W for 20-30 min. After the ultrasonication, centrifuging it at 9000-11000 rpm to obtain a precipitate, and repeating the secondary ultrasonic exfoliation and centrifugation of the precipitate 3-5 times; finally, vacuum drying the precipitate to obtain a single-layer black phosphorus nanosheet with a single-layer rate of more than 99%; Step 2) Spreading a single layer of black phosphorus nanosheets on the surface of a silicon wafer, placing the sheet in a quartz tube, controlling the system temperature at 25-30°C, and introducing air at a rate of 10-20 mL / min for oxidation for 40-60 min to obtain oxidized black phosphorus nanosheets, which are then ultrasonically dispersed in deoxygenated deionized water at a mass ratio of 1-5:500 to form an oxidized black phosphorus nanosheet suspension; Step 3) 1.6-2.0 g of acrylic acid, 0.01-0.04 g of N,N-methylenebisacrylamide, and 0.04-0.08 g of sodium lauryl sulfate are added in sequence to a three-necked flask containing 100-140 mL of deionized water. Nitrogen is introduced into the flask to remove oxygen and the mixture is stirred for 10-15 minutes. Simultaneously, 0.016-0.02 g of ammonium sulfate is dissolved in 8-10 mL of deionized water to prepare an initiator aqueous solution, which is placed in a dropping funnel above the three-necked flask. The solution in the three-necked flask is heated to 60-70° C. in a water bath, stirred at 100-200 rpm / min, and a nitrogen atmosphere is maintained. The initiator aqueous solution is slowly added dropwise at a rate of 1-2 drops / min, and the reaction temperature is maintained at 60-70° C. for 4-5 hours to obtain a polyacrylic acid aqueous solution. Step 4) Take 100 mL of the black phosphorus oxide nanosheet suspension obtained in step 2 and place it in a three-necked flask, add 20-50 mL of the polyacrylic acid aqueous solution obtained in step 3 and 3-5 g of phosphotungstic acid, and react for 3-5 hours at a water bath temperature of 70-90 ° C and a stirring speed of 300-500 rpm. After the reaction is completed, centrifuge at 10,000-15,000 rpm, rinse the precipitate with deionized water 3-5 times, and then vacuum dry to obtain a black phosphorus oxide nanocomposite lubricant.

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