A graphene oxide lubricating coating utilizing metal ion self-assembly and preparation method thereof

Abstract

The present invention provides a method for preparing a graphene oxide lubricating coating by utilizing rapid and stable self-assembly of metal ions. The graphene oxide coating is composed of stacked graphene oxide nanosheets, and the oxygen-containing functional groups thereon can regularize the coating and strengthen its bonding strength by forming complexes with metal ions. The friction coefficient of the substrate coated with the graphene oxide coating is reduced from 0.8 to about 0.15, and its tribological performance can be improved by more than 80%. The preparation method is as follows: a silicon wafer substrate treated with Piranha solution is successively immersed in a metal ion salt solution and a graphene oxide dispersion and allowed to stand for a while, and then the sample is taken out and dried. The coating preparation process of the present invention is simple and efficient, low-cost, and the coating has good regularity and bonding strength. It can be widely used in the preparation of graphene oxide lubricating coatings, thereby effectively improving the tribological properties of the substrate.

Description

Technical Field

[0001] The present invention belongs to the field of graphene oxide lubricating coatings, and in particular relates to a graphene oxide lubricating coating self-assembled by metal ions and a preparation method thereof. Background Art

[0002] As a derivative of graphene, graphene oxide has the characteristics of large specific surface area, high mechanical strength and easy interlayer shearing. In addition, there are a large number of oxygen-containing functional groups distributed on the surface and edges. It can form a lubricating coating through self-assembly and has excellent lubrication properties and wear resistance.

[0003] The self-assembly method involves alternately immersing a substrate in a negatively charged graphene oxide solution and another positively charged dispersion. The resulting coating is driven by electrostatic forces, hydrogen bonds, coordination bonds, and covalent bonds between the two graphene oxide nanosheets. Studies have shown that metal ions bind and organize graphene oxide nanosheets, with transition metal ions in particular exhibiting a significant complexing effect. Therefore, the self-assembly of graphene oxide lubricating coatings using metal ions is crucial for improving the tribological properties of substrates. Summary of the Invention

[0004] The present invention aims to provide a method for preparing a graphene oxide lubricating coating using metal ion self-assembly. This method allows graphene oxide nanosheets to be rapidly and orderly cross-linked and stacked on a substrate surface, meeting the requirements of simple operation and low cost. The graphene oxide lubricating coating, which contains approximately 1% metal atoms, can reduce the substrate friction coefficient from 0.8 to approximately 0.15, with a wear life of 2400-3600 seconds.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing a graphene oxide lubricating coating using metal ion self-assembly, comprising the following steps:

[0006] Step 1: The sheet substrate is first heated in a Piranha solution for hydroxylation modification;

[0007] Step 2: Take out the modified substrate and rinse it with deionized water, then blow dry it under N2 to obtain the hydroxylated substrate;

[0008] Step 3: Immersing the hydroxylated substrate in a metal ion salt solution and a graphene oxide dispersion for a short time;

[0009] Step 4: After the impregnation is completed, the substrate is taken out and placed in a blast drying oven for drying to obtain the above-mentioned graphene oxide lubricating coating.

[0010] Furthermore, in step 1, the Piranha solution is prepared by mixing concentrated H2SO4 (98%) and H2O2 (30%) in a volume ratio of 7:3, and the heating temperature is 90-95°C in a water bath for 30-45 minutes.

[0011] Furthermore, the metal ion salt solution in step 3 is one of transition element salt solutions CuCl2, FeSO4, and CrCl3, with a concentration of 0.1-0.2 mol / L.

[0012] Furthermore, the graphene oxide dispersion in step three is a dispersion of deionized water with a concentration of 4 mg / mL, and the edge thickness of the single-layer graphene oxide nanosheet is 0.21 nm.

[0013] Furthermore, in step 3, the immersion time of the metal salt solution is about 30 s, and the immersion time of the graphene oxide dispersion is about 1 min.

[0014] Furthermore, in step 4, the drying temperature of the blast drying oven is set to 50-80°C.

[0015] Furthermore, the graphene oxide coating prepared by the above method is composed of stacked graphene oxide nanosheets. The above graphene oxide nanosheets are rich in oxygen-containing functional groups and can form complexes with metal ions. The above complexation can improve the regularity and bonding strength of the coating. The thickness of the metal ion self-assembled graphene oxide coating is about 1 um.

[0016] Furthermore, the metal element atoms in the metal ion self-assembled graphene oxide coating account for 1-1.5%. Beneficial effects

[0017] (1) The method provided by the present invention for preparing a graphene oxide lubricating coating by utilizing metal ion self-assembly can adsorb negatively charged graphene oxide nanosheets with the help of a small amount of positively charged metal ions and form coordination bonds with the oxygen-containing functional groups thereon, thereby regularizing and combining the graphene oxide nanosheets under this complexation.

[0018] (2) The metal ion self-assembled graphene oxide lubricating coating prepared by the present invention can reduce the friction coefficient of the substrate from 0.8 to about 0.15, its tribological performance is improved by more than 80%, and the wear life of the coating is 2400-3600 s.

[0019] (3) The process of the present invention is simple, low-cost, and time-saving, which provides convenience for the preparation of graphene oxide lubricating coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of the preparation process of the present invention;

[0021] Figure 2 Transmission electron microscopy image of graphene oxide;

[0022] Figure 3 This is a physical picture of the complexation between metal ions and graphene oxide nanosheets;

[0023] Figure 4 This is a scanning electron micrograph of the cross section of a metal-free cross-linked graphene oxide coating;

[0024] Figure 5 Fe prepared in Example 1 2+ Actual image of ion-crosslinked graphene oxide coating;

[0025] Figure 6 Fe prepared in Example 1 2+ X-ray photoelectron spectrum of ion-crosslinked graphene oxide coating;

[0026] Figure 7 Fe prepared in Example 1 2+ Scanning electron microscopy image of the cross section of ion-crosslinked graphene oxide coating;

[0027] Figure 8 Fe prepared in Example 1 2+ Comparison of friction coefficients of ion-crosslinked graphene oxide coating, metal-free ion-crosslinked graphene oxide coating, and original substrate;

[0028] Figure 9 Cr prepared in Example 2 3+ Actual image of ion-crosslinked graphene oxide coating;

[0029] Figure 10 Cr prepared in Example 2 3+ X-ray photoelectron spectrum of ion-crosslinked graphene oxide coating;

[0030] Figure 11 Cr prepared in Example 2 3+ Scanning electron microscopy image of the cross section of ion-crosslinked graphene oxide coating;

[0031] Figure 12 Cr prepared in Example 2 3+ Comparison of friction coefficients of ion-crosslinked graphene oxide coating, metal-free ion-crosslinked graphene oxide coating, and original substrate. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to specific embodiments. It is obvious that the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example 1

[0033] In this embodiment, Fe 2+ Ionic self-assembled graphene oxide lubricating coating, in order to facilitate characterization and detection, this embodiment selects silicon wafer as the substrate, such as Figure 1 The figure shows the coating preparation flow chart. The preparation process is as follows:

[0034] Prepare Piranha solution: Take concentrated H2SO4 (98%) and H2O2 (30%) in a volume ratio of 7:3, mix the two and react to form Piranha solution. The reaction will release a lot of heat. The mixing method is to slowly add concentrated H2SO4 to H2O2.

[0035] Prepare graphene oxide solution: Use 11.5 mg / mL graphene oxide dispersion as raw material, add appropriate amount of deionized water to dilute the concentration to 4 mg / mL, and perform magnetic stirring to evenly disperse the graphene oxide.

[0036] Configuring Fe 2+ Ionic solution: Use an electronic balance to weigh an appropriate amount of FeSO4 into a beaker, and add deionized water to adjust the solution concentration to 0.2 mol / L.

[0037] After the Piranha solution is cooled, the silicon wafer substrate is added into it, heated in a water bath at 90°C for 30 min, then taken out, rinsed with deionized water, and blown dry under N2 to obtain the hydroxylated silicon wafer. The treated silicon wafer is clamped with tweezers and immersed in the above Fe 2+ The solution and graphene oxide dispersion were allowed to stand for 30 s and 1 min respectively. Finally, the silicon wafer was taken out after impregnation and placed in a forced air drying oven at 50°C for drying. Figure 2 The transmission electron microscope image of the graphene oxide used shows that the edge thickness of the single-layer graphene oxide nanosheet is 0.21 nm. Figure 3 This is a physical diagram of the complexation between metal ions and graphene oxide nanosheets in solution. Under the adsorption of metal ions, negatively charged graphene oxide aggregates and forms coordination bonds with metal ions through oxygen-containing functional groups. Figure 5 Fe 2+ Actual picture of ion-crosslinked graphene oxide coating, Figure 6 Fe 2+The X-ray photoelectron spectrum of the ion self-assembled graphene oxide coating shows that the atomic content of Fe is 1.07%, with a total of 4 2p peaks in divalent and trivalent states. Figure 7 Fe 2+ Scanning electron microscopy image of the cross section of ion self-assembled graphene oxide coating. The coating thickness is about 0.9 um and has a clear layered stacking structure. Figure 4 The comparison of the scanning electron microscopy images of the cross-section of the metal-free cross-linked graphene oxide coating shows that Fe 2+ The ions play a role in cross-linking and regularizing graphene oxide. Figure 8 Fe 2+ A comparison of the friction coefficients of an ion-assembled graphene oxide coating, a non-metal ion-crosslinked graphene oxide coating, and a pristine substrate was performed using a CFT-I friction tester with a load of 0.3 N and a reciprocating speed of 10 mm / s. The figure shows that the metal ion-crosslinked lubricating coating exhibits the best tribological properties, reducing the substrate friction coefficient from 0.8 to approximately 0.15, and achieving a wear life of 2400 s. In contrast, the non-metal ion-crosslinked graphene oxide coating only reduces the friction coefficient to approximately 0.5, resulting in a wear life of only 700 s. Example 2

[0038] This embodiment uses Cr 3+ Ionic self-assembled graphene oxide lubricating coating, in order to facilitate characterization and detection, this embodiment selects silicon wafer as the substrate, such as Figure 1 The figure shows the coating preparation flow chart. The preparation process is as follows:

[0039] Prepare Piranha solution: Take concentrated H2SO4 (98%) and H2O2 (30%) in a volume ratio of 7:3, mix the two and react to form Piranha solution. The reaction will release a lot of heat. The mixing method is to slowly add concentrated H2SO4 to H2O2.

[0040] Prepare graphene oxide solution: Use 11.5 mg / mL graphene oxide dispersion as raw material, add appropriate amount of deionized water to dilute the concentration to 4 mg / mL, and perform magnetic stirring to evenly disperse the graphene oxide.

[0041] Configuring Cr 3+ Ionic solution: Use an electronic balance to weigh an appropriate amount of CrCl3 into a beaker, and add deionized water to adjust the solution concentration to 0.2 mol / L.

[0042] After the Piranha solution is cooled, the silicon wafer substrate is added into it, heated in a water bath at 90°C for 30 min, then taken out, rinsed with deionized water, and blown dry under N2 to obtain the hydroxylated silicon wafer. The treated silicon wafer is clamped with tweezers and immersed in the above Cr3+ The solution and graphene oxide dispersion were allowed to stand for 30 s and 1 min respectively. Finally, the silicon wafer was taken out after impregnation and placed in a forced air drying oven at 50°C for drying. Figure 2 The transmission electron microscope image of the graphene oxide used shows that the edge thickness of the single-layer graphene oxide nanosheet is 0.21 nm. Figure 3 This is a physical diagram of the complexation between metal ions and graphene oxide nanosheets in solution. Under the adsorption of metal ions, negatively charged graphene oxide aggregates and forms coordination bonds with metal ions through oxygen-containing functional groups. Figure 9 Cr 3+ Actual picture of ion-crosslinked graphene oxide coating, Figure 10 Cr 3+ The X-ray photoelectron spectrum of the ion self-assembled graphene oxide coating shows that the Cr atomic content accounts for 1.53%, with two 2p peaks in the trivalent state. Figure 11 Cr 3+ Scanning electron microscopy image of the cross section of ion self-assembled graphene oxide coating. The coating thickness is about 0.81 um and has a clear layered stacking structure. Figure 4 The cross-sectional scanning electron microscopy images of the metal-free cross-linked graphene oxide coating show that Cr 3+ The ions play a role in cross-linking and regularizing graphene oxide. Figure 12 Cr 3+ A comparison of the friction coefficients of an ion-assembled graphene oxide coating, a non-metal ion-crosslinked graphene oxide coating, and a pristine substrate was performed using a CFT-I friction tester with a load of 0.3 N and a reciprocating speed of 10 mm / s. The figure shows that the metal ion-crosslinked graphene oxide lubricating coating exhibits the best tribological properties, reducing the substrate friction coefficient from 0.8 to approximately 0.2, and achieving a wear life of 3600 s. In contrast, the non-metal ion-crosslinked graphene oxide coating only reduces the friction coefficient to approximately 0.5, resulting in a wear life of only 700 s.

[0043] The contents of the embodiments of this specification are merely descriptions of the invention, and the protection scope of the present invention should not be considered as being limited to the specific forms described in the embodiments. The protection scope of the present invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the concepts of the present invention.

Claims

1. A method for preparing a graphene oxide lubricating coating using metal ion self-assembly, characterized in that: The steps include: Step 1: Select a sheet substrate and first heat it in a Piranha solution to perform hydroxylation surface modification on the substrate; Step 2: Take out the modified sheet substrate, rinse it with deionized water, and blow dry it under N2 to obtain a hydroxylated sheet substrate; Step 3: Immersing the hydroxylated sheet substrate in a metal ion salt solution and a graphene oxide dispersion solution for a short time; Step 4: After the impregnation is completed, the sheet substrate is taken out and placed in a blast drying oven for drying to obtain the graphene oxide lubricating coating; The metal ion salt solution in step 3 is one of FeSO4, CrCl3, and CuCl2, with a concentration of 0.1-0.2 mol / L; The graphene oxide dispersion in step 3 is a dispersion of deionized water with a concentration of 4 mg / mL, and the edge thickness of the single-layer graphene oxide nanosheet is 0.21 nm; In step 3, the immersion time of the metal ion salt solution is 30 s, and the immersion time of the graphene oxide dispersion is 1 min.

2. The method for preparing a graphene oxide lubricating coating using metal ion self-assembly according to claim 1, characterized in that: The Piranha solution in step 1 is prepared by mixing 98% concentrated H2SO4 and 30% H2O2 in a volume ratio of 7:

3. The heating temperature is 90-95°C in a water bath for 30-45 minutes.

3. The method for preparing a graphene oxide lubricating coating using metal ion self-assembly according to claim 1, characterized in that: The drying temperature of the blast drying oven in step 4 is set to 50-80°C.

4. A graphene oxide lubricating coating prepared by the preparation method according to any one of claims 1 to 3 using metal ion self-assembly, characterized in that: The graphene oxide coating is composed of stacked graphene oxide nanosheets. The graphene oxide nanosheets are rich in oxygen-containing functional groups and can form complexes with metal ions. The above complexation can improve the regularity and bonding strength of the coating, thereby improving the tribological properties of the substrate.

5. The graphene oxide lubricating coating using metal ion self-assembly according to claim 4, characterized in that: The thickness of the metal ion self-assembled graphene oxide coating is 0.8-1 μm.

6. The graphene oxide lubricating coating using metal ion self-assembly according to claim 4, characterized in that: The metal element atoms in the graphene oxide coating account for 1-1.5%.

Images