Method for regulating and controlling interface friction force or shearing resistance

Abstract

The invention relates to a method for regulating and controlling interface friction force or shear resistance. The method comprises the following steps: forming a modified material layer on a contact surface of a substrate material so as to reduce the interface friction force or shear resistance of the substrate material; the modified material layer is the ratio gt of the full width at half maximum of the amplitude / peak at 3350-3450 cm <-1 > and the full width at half maximum of the amplitude / peak at 3150-3250 cm <-1 > measured by a sum frequency vibration spectrum (SFG); 1.0 < = 1.0. According to the method, the interface friction force or the solid-liquid interface shear resistance can be obviously reduced.

Description

Technical Field

[0001] This invention relates to a method for controlling interfacial friction or shear resistance. Background Technology

[0002] Interfacial shear scenarios include friction between solids and shear resistance at the solid-liquid interface. Interfacial friction or shear resistance is a crucial factor affecting the surface properties and functions of materials, widely present in fields such as machinery, biology, and marine engineering. The resulting friction and wear consume one-third of global energy. Therefore, reducing friction and wear, and improving the energy efficiency and lifespan of mechanical systems are of great significance for reducing energy consumption, achieving low-carbon environmental protection, ensuring stable mechanical operation, extending service life, and improving economic benefits. Water-based lubrication has broad application prospects, including biological synovial joints, bio-devices, pharmaceuticals, food, textiles, metal processing, chemical mechanical polishing, ship propulsion, and marine equipment. Exploring the essential mechanism of low interfacial shear is of great value in overcoming the limitations of water-based lubrication. However, the evolution of the shear behavior and structure of interfacial water molecules is a key factor in the development of low interfacial shear theory for water-based lubrication. Traditional methods for controlling interfacial shear mainly rely on changes in the chemical properties of the material surface or the introduction of external lubricants. These methods often suffer from limited efficiency, environmental unfriendliness, or high costs in practical applications. In recent years, with the deepening research into microscopic molecular behavior, scientists have gradually realized that the arrangement of water molecules and the hydrogen bond network at the interface have a significant impact on interfacial friction or shear resistance. Therefore, optimizing the interfacial water molecule structure through microscopic manipulation of material surfaces to achieve efficient control of interfacial friction or shear resistance has become a current research hotspot. However, due to the limited means of detecting interfacial molecular behavior, current international research on molecular structure changes mostly utilizes optically based techniques, such as surface force meters, infrared spectroscopy, and laser Raman spectroscopy. However, these detection methods cannot distinguish between interfacial signals and bulk signals, resulting in a lack of clarity regarding the influence of water molecule structure on the shear mechanism, which in turn limits the development and application of new materials. The emergence of nonlinear sum-frequency vibrational spectroscopy (SFG) has solved the above problems. It has superior interfacial selectivity (signals are only detected at interfacial molecules) and high resolution of monolayers, and has been widely used in chemistry and biology for static and open surfaces. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a method for regulating interfacial friction or shear resistance, thereby solving the problems of high friction and wear between solids and high interfacial resistance between solids and liquids.

[0004] One aspect of the present invention provides a method for controlling interfacial friction or shear resistance, the method comprising:

[0005] A modified material layer is formed at the contact surface of the substrate material to reduce the interfacial friction or shear resistance of the substrate material;

[0006] The modified material layer has a thickness of 3350–3450 cm⁻¹ as determined by sum-frequency vibrational spectroscopy (SFG). -1 The amplitude / peak full width at half maximum (A1 / T1) at 3150–3250 cm⁻¹ -1 Material layers with an amplitude at a given point / the full width at half maximum (FWHM) of the peak (A2 / T2) ratio (A1 / T1) / (A2 / T2) > 1.0.

[0007] In some implementations, the interfacial friction or shear resistance is underwater friction, ice surface friction, or solid-liquid interface shear resistance.

[0008] In some embodiments, the method further includes treating the modified material layer to make it hydrophilic to reduce underwater friction.

[0009] In some embodiments, the method further includes treating the modified material layer to make it hydrophobic to reduce interfacial shear resistance or ice surface friction.

[0010] In some embodiments, the interfacial friction is a submersible friction, and the method further includes maintaining the temperature of the contact surface between 0 and 30°C.

[0011] In some embodiments, the interfacial friction is submerged friction, and the method further includes setting the salt ion concentration in the liquid environment to 0.001-0.1 mol / L;

[0012] The interfacial shear resistance is the solid-liquid interfacial shear resistance, and the method further includes making the salt ion concentration in the liquid environment 0-0.1 mol / L;

[0013] The interfacial friction is ice surface friction, and the method further includes making the salt ion concentration on the ice surface 0.001-1.0 mol / L.

[0014] In some embodiments, the interfacial friction is underwater friction, and the modified material layer is a silicon nitride film, a hydrogen-containing amorphous carbon film, a metal compound-doped hydrogen-containing amorphous carbon film, or a modified hydrogen-containing amorphous carbon film.

[0015] In some embodiments, the hydrogen content of the hydrogen-containing amorphous carbon film is 15%-25%.

[0016] In some embodiments, the modified material layer is formed on the contact surface of the substrate material by ion beam vapor deposition, plasma thin film processing, magnetron sputtering, or plasma spraying.

[0017] In some embodiments, the substrate material is a metal or a ceramic material.

[0018] In some embodiments, the salt ion is a sodium ion, potassium ion, cesium ion, or lithium ion.

[0019] The beneficial effects of this invention are that modifying the contact surface of the substrate material can significantly reduce interfacial friction or shear resistance, with better results than traditional lubricant or surface chemical modification methods. It eliminates the need for additional lubricants or other chemical reagents, reducing environmental pollution and meeting the requirements of green manufacturing and sustainable development.

[0020] The method of this invention is applicable to various material surfaces (such as metals, ceramics, etc.) and has broad industrial application prospects.

[0021] The method of this invention is applicable to a variety of application scenarios, including ice surface friction, underwater friction (in freshwater or marine environments), and solid-liquid interface shear resistance.

[0022] This invention provides important theoretical and technical support for material design and performance optimization in related fields. Attached Figure Description

[0023] The subject matter of this application can be understood by reading the following description of non-limiting embodiments and referring to the accompanying drawings, wherein:

[0024] Figure 1 The effects of different elements on the regulation of interfacial water molecule structure and underwater friction coefficient are shown.

[0025] Figure 2 The effect of elemental ratios on the regulation of interfacial water molecule structure and underwater friction coefficient is shown.

[0026] Figure 3 The effect of temperature on the regulation of interfacial water molecule structure and underwater friction coefficient is shown.

[0027] Figure 4 The effect of ion concentration on the regulation of interfacial water molecule structure and the underwater friction coefficient is shown.

[0028] Figure 5 The effects of different elements on the regulation of interfacial water molecule structure and solid-liquid interface shear resistance are shown.

[0029] Figure 6 The effect of ion concentration on the shear resistance at the solid-liquid interface is shown.

[0030] Figure 7 The effect of ion concentration on the coefficient of friction of ice surface is shown;

[0031] Figure 8 The influence of hydrophilic or hydrophobic surfaces on the regulation of interfacial water molecule structure and the underwater friction coefficient is shown.

[0032] Figure 9 The effects of factor regulation on the interfacial water molecule structure and the underwater friction coefficient are shown.

[0033] Figure 10 This demonstrates the influence of hydrophilic or hydrophobic surfaces on the interfacial water molecule structure and the solid-liquid interface shear resistance.

[0034] Figure 11 The influence of hydrophilic or hydrophobic surfaces on the regulation of interfacial water molecule structure and the coefficient of friction of ice surface is shown. Detailed Implementation

[0035] This invention provides a method for controlling interfacial friction and shear resistance, aiming to significantly reduce interfacial friction and shear resistance by adjusting the elemental and physicochemical properties of the material surface and optimizing the arrangement of water molecules and hydrogen bond network at the interface.

[0036] The core of this invention lies in the precise control of the structure of interfacial water molecules by designing and modifying the contact surface, so as to form a disordered arrangement and weaken the hydrogen bond network, reduce the density of interfacial water molecules, and reduce the viscosity of water, thereby achieving a high efficiency reduction of interfacial shear resistance.

[0037] Interfacial water plays a crucial role in many natural phenomena and engineering applications. However, the influence of the molecular behavior of interfacial water on friction remains a highly debated issue. Increasing experimental and theoretical methods have been used to elucidate the molecular behavior of interfacial water and its relationship with interfacial phenomena and material properties, but no definitive conclusion has been reached. The molecular behavior of interfacial water is not only related to the properties of the material itself, but also to factors such as surface wettability and surface potential, and is influenced by changes in the external environment, including temperature, electric field, and solution ionic composition.

[0038] Therefore, the water molecule structure and hydrogen bond configuration at the solid-liquid interface differ among different materials, thus affecting the magnitude of the interfacial shear resistance. Numerous experimental studies have found that the water molecule structure and hydrogen bond configuration at the 3350–3450 cm⁻¹ interface, as measured by sum-frequency vibrational spectroscopy (SFG), significantly influence the interfacial shear resistance. -1 The amplitude / peak full width at half maximum (A1 / T1) at 3150–3250 cm⁻¹ -1 Materials with an amplitude / peak full width at half maximum (A2 / T2) ratio (A1 / T1) / (A2 / T2) > 1.0 have a higher proportion of "liquid-like" disordered water molecule structure at the interface. In this case, the hydrogen bonding between water molecules is weaker, resulting in a lower density of water at the interface. Whether it is the case where water acts as a lubricating layer in solid-solid friction or for the solid-liquid interface, a weak shear layer is formed at the solid-liquid interface, and the interfacial shear resistance is smaller.

[0039] definition

[0040] Coefficient of friction under liquid conditions: The coefficient of friction under liquid conditions refers to the ratio of the frictional force generated between the relative motion of object surfaces to the normal force perpendicular to the contact surface in a liquid environment. It is expressed by the formula μ = Ff / Fn, where μ is the coefficient of friction under liquid conditions, Ff is the frictional force generated between the object surfaces during relative motion, and Fn is the normal force perpendicular to the contact surface. Since Fn remains constant during friction, a smaller coefficient of friction under liquid conditions means a smaller Ff.

[0041] Solid-liquid interface shear resistance: the tangential frictional force generated between a solid surface and an adjacent liquid due to relative motion.

[0042] Ice surface friction coefficient: The ice surface friction coefficient is a physical quantity that describes the frictional characteristics between an ice surface and a contacting object. It is a dimensionless coefficient used to represent the ratio of the frictional force that opposes the relative motion of the object to the normal force acting on the object perpendicular to the ice surface. It is expressed by the formula μ = Ff / Fn, where μ is the ice surface friction coefficient, Ff is the frictional force between the ice surface and the object, and Fn is the normal force perpendicular to the ice surface.

[0043] Example 1: Reduction of the coefficient of friction under liquid conditions

[0044] Preparation of hydrogen-containing amorphous carbon film (aC:H): Hydrogen-containing amorphous carbon film (aC:H) was prepared by ion beam vapor deposition. Before the coating experiment, the sample was ultrasonically cleaned with acetone for 10 min, repeating this process five times. The coating process was carried out under vacuum (5 × 10⁻⁶) at 200℃. - 3 The deposition is carried out within the cavity, and an Ar process is performed for 30 minutes prior to deposition under a bias voltage of 2.0 kV. + Ion sputtering further removes metal oxides and contaminants from the substrate to improve film-substrate adhesion. A gas source (toluene (C7H8)) is introduced to control the elements deposited on the surface. A Ta-thermal filament excites thermionic electrons to ionize gas atoms, generating a dense and uniform plasma within the cavity. A pulsed bias power supply system applies a negative bias between the anode and the sample surface, creating a directional electric field. The C and H plasma, energized by the electric field, bombards the sample surface, depositing and growing an aC:H thin film with a thickness of approximately 1.3 μm.

[0045] Preparation of a hydrogen-doped amorphous carbon film (aC:H:WC) using a plasma thin film processing (PFS) system: The film was prepared by ultrasonic cleaning with ethanol for 30 min before deposition. To ensure surface cleanliness, Ar gas (-1 kV) was purged onto the substrate to remove contaminants before deposition. To enhance film adhesion, a Ti / TiN / TiCN transition layer was deposited first, followed by aC:H:WC deposition. The deposition temperature was 350 °C, and the vacuum level was 6 × 10⁻⁶. -3Pa mainly relies on the decomposition of acetylene (C2H2) and magnetron sputtering of WC and C targets to deposit thin films with a thickness of about 3 μm.

[0046] Preparation of modified hydrogen-containing amorphous carbon film (aC:H:Si): Modified hydrogen-containing amorphous carbon film (aC:H:Si) was prepared by ion beam vapor deposition. Before the coating experiment, the sample was ultrasonically cleaned with acetone for 10 min, repeated 5 times, and then dried with nitrogen. The coating process was carried out under vacuum (5 × 10⁻⁶) at 200℃. -3 The deposition is carried out within the cavity, and an Ar process is performed for 30 minutes prior to deposition under a bias voltage of 2.5 kV. + Ion sputtering further removes metal oxides and contaminants from the substrate to improve film-substrate adhesion. By introducing a gas source (a Si(CH3)4 / C7H8 mixed gas) to control surface deposition elements, thermionic electrons are excited by a Ta hot filament to generate a dense and uniform plasma within the cavity. A negative bias is then applied between the anode and the sample surface via a pulsed bias power supply system to generate a directional electric field. The C, H, and Si plasma, after gaining energy from the electric field, bombards the sample surface, depositing and growing an aC:H:Si thin film with a thickness of approximately 1.3 μm.

[0047] This embodiment uses materials with high hardness and good mechanical properties for underwater friction experiments, including bearing steel (purchased from Chunzhongdao Machinery (Taicang) Co., Ltd.), silicon nitride ceramic material (purchased from Xindelong Special Ceramics (Dalian) Co., Ltd.), hydrogen-containing amorphous carbon film (aC:H), metal compound-doped hydrogen-containing amorphous carbon film (aC:H:WC), and modified hydrogen-containing amorphous carbon film (aC:H:Si).

[0048] Tribological properties were investigated using an atomic force microscope (AFM) underwater tribology testing module. The experimental system consisted of sample pieces of different materials as the friction pair, with a 23 μm SiO2 colloidal probe (using a TL-CONT cantilever beam; epoxy resin was applied to the tip of the cantilever beam, and a 23 μm diameter SiO2 colloidal sphere was attached to the probe's adhesive surface, positioned at the center of the cantilever beam tip). The lubricating medium was ultrapure water. The tribological properties of different materials in water were summarized based on the underwater tribological behavior. Furthermore, SFG spectroscopy was used to further investigate the hydrogen bonding between water molecules in the lubricating water film and the material surface, as well as the distribution of water molecules. (3400 cm⁻¹) -1 The peak position indicates "liquid-like" water, representing disordered water with relatively weak hydrogen bonds. 3200 cm⁻¹ -1 The peak position indicates "ice-like" water, representing ordered water with relatively strong hydrogen bonds. The distribution pattern of water molecules can be analyzed by examining the peak characteristics (A1 / T1) / (A2 / T2).

[0049] The relationship between (A1 / T1) / (A2 / T2) and the underwater friction coefficient is shown in the figure. Figure 1 The results show that the peak intensity ratio is closely related to the material's underwater friction coefficient. When (A1 / T1) / (A2 / T2)>1.0, the material's underwater friction coefficient is relatively small, and when (A1 / T1) / (A2 / T2)<1.0, the material's underwater friction coefficient is relatively large.

[0050] Therefore, it can be seen that the SFG spectrum (A1 / T1) / (A2 / T2) > 1.0 on the surface of the H-containing carbon film indicates that the proportion of "liquid-like" water molecules at the solid-liquid interface is relatively high, and the water molecules on the material surface are arranged relatively randomly, mainly by weak hydrogen bonds. According to the test results, materials with SFG spectrum (A1 / T1) / (A2 / T2) > 1.0 have low SFG signal intensity. The lower the friction coefficient, the lower the peak intensity. The peak intensity is determined by the molecular density, indicating that the water molecule density at the interface is low, resulting in low water viscosity, weak interaction forces between water molecules and between water molecules and the interface, and small shear resistance, leading to a small underwater friction coefficient.

[0051] The SFG spectrum of bearing steel surface with (A1 / T1) / (A2 / T2) < 1.0 indicates that water molecules are in an "ice-like" structure. At this point, the water molecules on the material surface are relatively ordered, with strong hydrogen bonds between them, similar to a crystal structure, and strong hydrogen bond interactions. Materials with SFG spectrum (A1 / T1) / (A2 / T2) < 1.0 have high SFG signal intensity; the higher the friction coefficient, the higher the peak intensity. Peak intensity is determined by molecular density, indicating a high interfacial water molecule density, leading to high water viscosity and greater resistance to sliding, resulting in an increased underwater friction coefficient. The modified hydrogen-containing amorphous carbon film (aC:H:Si) with SFG spectrum (A1 / T1) / (A2 / T2) > 1.0 indicates a relatively low underwater friction coefficient.

[0052] In summary, materials with an SFG spectrum (A1 / T1) / (A2 / T2) > 1.0, such as hydrogen-containing amorphous carbon films (aC:H), metal compound-doped hydrogen-containing amorphous carbon films (aC:WC), or modified hydrogen-containing amorphous carbon films (aC:H:Si), can be used as shear surface coatings to alter the structure of interfacial water molecules, thereby affecting the density and viscosity of interfacial water and achieving the effect of reducing the underwater friction coefficient.

[0053] Example 2: Reduction of the coefficient of friction under liquid conditions

[0054] Preparation of hydrogen-containing amorphous carbon films of aC:H (H content 1%-15%), aC:H (H content 15%-25%), and aC:H (H content 35%-45%): Ion beam vapor deposition was used. Before the deposition experiment, the samples were ultrasonically cleaned with acetone for 10 min, repeated 5 times, and dried with nitrogen gas. The deposition process was carried out under vacuum (5×10⁻⁶) at 200℃. -3 The deposition is carried out within the cavity, and an Ar process is performed for 30 minutes prior to deposition under a bias voltage of 2.0 kV. + Ion sputtering further removes metal oxides and contaminants from the substrate to improve film-substrate adhesion. By introducing a gas source (toluene (C7H8)) to control surface deposition elements, thermionic electrons are excited by a Ta hot filament to generate a dense and uniform plasma within the cavity. A negative bias is then applied between the anode and the sample surface via a pulsed bias power supply system to generate a directional electric field. The C and H plasmas, after gaining energy through the electric field, bombard the sample surface, depositing and growing an aC:H thin film with a thickness of approximately 1 μm. Before starting the deposition process, bias voltages of 0.3 kV, 2 kV, and 4.5 kV can be set to prepare hydrogen-containing amorphous carbon films with different hydrogen contents on the sample surface.

[0055] To investigate the relationship between the ratio of factors affecting the water molecule structure and the coefficient of friction under liquid, experiments were conducted using hydrogen-containing amorphous carbon films (aC:H) with different H contents. Simultaneously, silicon nitride thin films were deposited on the surface of silicon wafers. A magnetron sputtering deposition system was used to prepare the silicon nitride thin film (Si3N4-film). Through the synergistic effect of a magnetic field and an electric field, the target material was efficiently sputtered and deposited into a film. Sputtering essentially utilizes high-energy particles (argon ions) to bombard the target surface, causing the target atoms or molecules to be ejected and subsequently deposited onto the substrate surface to form a thin film. First, the gas was ionized. Argon gas (Ar) was introduced into a vacuum chamber, and a high-voltage electric field was applied to ionize the argon gas, forming plasma (Ar). + (and electrons); then target bombardment: Ar + The target material (cathode) is bombarded under the acceleration of an electric field, and the target atoms / molecules are sputtered out through momentum transfer; finally, a thin film is deposited: the sputtered target particles fly to the substrate (anode) and deposit on its surface to form a silicon nitride thin film.

[0056] Friction experiments were conducted using atomic force microscopy. The friction pair consisted of a Si wafer as the lower friction pair and a 23μm SiO2 colloidal probe as the upper friction pair (using a TL-CONT cantilever beam; epoxy resin was applied to the tip of the cantilever beam, and a 23μm diameter SiO2 colloidal sphere was attached to the probe's surface, positioned at the center of the cantilever beam tip). The lubricating medium was ultrapure water. The relationship between the underwater friction coefficient of different materials and (A1 / T1) / (A2 / T2) is as follows: Figure 2 As shown.

[0057] according to Figure 2 The results show that the hydrogen content of the aC:H film changes the underwater friction coefficient; the friction coefficient is lowest when the hydrogen content is 15%-25%, and highest when the hydrogen content is 35%-45%. (Comparison) Figure 2 For all materials, it was found that the coefficient of friction decreases with increasing (A1 / T1) / (A2 / T2). Figure 2 It can be observed that (A1 / T1) / (A2 / T2) > 1.0 is beneficial for reducing the friction coefficient of the material surface. This difference may be due to variations in roughness, surface potential, and hardness of the same material, or it may be due to different material types. However, the structural characteristics of water molecules on the material surface are the final result of all physical and chemical properties manifested on the material surface. Therefore, the detection of the structure and distribution of water molecules at the interface can indicate changes in frictional performance. Conversely, the purpose of friction control can be achieved by directly regulating the structure of water molecules at the interface, providing a basis for evaluating the friction coefficient of materials under liquid conditions and providing technical means for friction control in aquatic environments.

[0058] like Figure 2 As shown, the SFG spectrum (A1 / T1) / (A2 / T2) of the bearing steel material surface is <1.0, indicating a relatively large underwater friction coefficient; the SFG spectrum (A1 / T1) / (A2 / T2) of the modified hydrogen-containing amorphous carbon film (aC:H:Si) is >1.0, indicating a relatively small underwater friction coefficient.

[0059] In summary, materials with an SFG spectrum (A1 / T1) / (A2 / T2) > 1.0, such as silicon nitride (Si3N4-film), hydrogen-containing amorphous carbon film, metal compound-doped hydrogen-containing amorphous carbon film (aC:WC), or modified hydrogen-containing amorphous carbon film (aC:H:Si), can be used as shear surface coatings. This results in a high proportion of "liquid-like" interfacial water molecule structures, low SFG water molecule signal intensity, low density and high viscosity of interfacial water, thereby reducing the underwater friction coefficient.

[0060] Example 3: Reduction of the coefficient of friction under liquid conditions

[0061] To investigate the relationship between the adsorption structure of interfacial water molecules at the interface (0-40℃) and temperature, this embodiment employs atomic force microscopy for triboelectric experiments. The triboelectric pair in the experimental system is a Si3N4-film (silicon nitride thin film deposited by magnetron sputtering). First, the gas is ionized by introducing argon gas (Ar) into a vacuum chamber and applying a high-voltage electric field to ionize the argon gas, forming plasma (Ar). + (and electrons); then target bombardment: Ar +The target material (cathode) is bombarded under an electric field acceleration, and target atoms / molecules are sputtered out through momentum transfer. Finally, a thin film is deposited: the sputtered target particles fly towards the substrate (anode), depositing a silicon nitride thin film on its surface. The upper friction pair consists of a 15μm SiO2 colloidal probe (using a TL-CONT cantilever beam; epoxy resin is applied to the tip of the cantilever beam, and a 15μm diameter SiO2 colloidal sphere is attached to the probe's adhesive surface, positioned at the center of the cantilever beam tip). The lubricating medium is ultrapure water. The experimental temperatures were 0℃, 10℃, 20℃, 30℃, and 40℃.

[0062] The results are as follows Figure 3 As shown, the friction coefficient decreased during the 0-30℃ process, and the proportion of water molecules in the "liquid-like" state increased; while the friction coefficient increased during the 30-40℃ process, and the proportion of water molecules in the "liquid-like" state decreased.

[0063] In summary, by controlling the contact surface temperature within the range of 0-30℃, the interfacial water molecule structure can be altered, thereby reducing the underwater friction coefficient.

[0064] Example 4: Reduction of the coefficient of friction under liquid conditions

[0065] In a system with varying interfacial temperature, the effect of salt ion concentration on the structure of interfacial water molecules is introduced.

[0066] To investigate the effects of salt ions on interfacial water structure and friction under different application scenarios, SFG spectroscopy and AFM underwater friction detection were performed at 0℃ under different concentrations (0.001-1.0 mol / L) of NaCl solutions. This was done to simulate trace amounts of salt in natural freshwater and salt spray in humid atmospheres (NaCl concentration typically around 0.001 mol / L), and to simulate a salt concentration of approximately 1 mol / L in seawater. The friction experimental system used a Si3N4-film as the lower friction pair, a 15 μm SiO2 colloidal probe as the upper friction pair, and solutions with different NaCl concentrations as the lubricating medium.

[0067] The results are as follows Figure 4 As shown, when the NaCl concentration is between 0.001 and 0.1 mol / L, the friction coefficient shows a decreasing trend. From the perspective of water molecule structure, the proportion of "liquid-like" water molecule structure increases, and the ordered water molecules at the interface are disrupted, which is beneficial to reducing friction. When the NaCl concentration is greater than 0.1 and less than or equal to 1 mol / L, the friction coefficient shows an increasing trend. From the perspective of water molecule structure, the proportion of "ice-like" water molecule structure increases, which increases the friction coefficient.

[0068] In summary, by controlling the ion concentration in the liquid environment to ≤0.1mol / L, the interfacial water molecule structure can be altered, thereby reducing the underwater friction coefficient.

[0069] Example 5: Reduction of Shear Resistance at the Solid-Liquid Interface

[0070] Shear resistance, slip length, and SFG spectra of the solid-liquid interface on untreated steel surfaces, SiO2, and Si3N4-film were measured. The relationship between (A1 / T1) / (A2 / T2) and resistance / slip is shown below. Figure 5 As shown, (A1 / T1) / (A2 / T2) is closely related to the resistance / slip length. Materials with a large (A1 / T1) / (A2 / T2) have low solid-liquid interface shear resistance and large slip. Materials with (A1 / T1) / (A2 / T2)>1.0, such as Si3N4-film, have a large proportion of "liquid-like" water molecules at the interface. The water molecules on the material surface are relatively disordered, mainly composed of weak hydrogen bonds. The interaction forces between water molecules and between water molecules and the interface are weak, resulting in low solid-liquid interface shear resistance. On steel surfaces with (A1 / T1) / (A2 / T2)<1.0, the proportion of "ice-like" water molecules is large. The water molecules on the material surface are relatively ordered, with a strong hydrogen bond network between water molecules, similar to a crystal structure. The strong hydrogen bond interaction generates greater resistance to the sliding process, resulting in a smaller slip length and higher solid-liquid interface shear resistance.

[0071] In summary, using materials with an SFG spectrum (A1 / T1) / (A2 / T2) > 1.0, such as Si3N4-film, as a shear surface coating can alter the interfacial water molecule structure, thereby reducing the shear resistance at the solid-liquid interface.

[0072] Example 6: Reduction of Shear Resistance at the Solid-Liquid Interface

[0073] The effect of ion concentration on the shear resistance of the solid-liquid interface was investigated. The shear resistance of the solid-liquid interface was measured under different concentrations (0.001-1.0 mol / L) of NaCl solution at 0℃. The experimental system consisted of a bearing steel rotor with a diameter of 50 mm on the upper shear surface, a bearing steel sheet with a diameter of 60 mm on the lower shear surface, and salt ion solutions of different concentrations in the middle fluid medium. The shearing speed was the average value of 1-100 rpm.

[0074] The results are as follows Figure 6 As shown, when the NaCl concentration is 0-0.01 mol / L, the shear resistance at the solid-liquid interface is basically stable. When the NaCl concentration is 0.1-1 mol / L, the shear resistance at the solid-liquid interface increases, which is the opposite of the effect of ion concentration on the underwater friction law.

[0075] Example 7: Reduction of the coefficient of friction of ice surface

[0076] To investigate the effect of ion concentration on the friction coefficient of ice surfaces, bearing steel balls with a surface-deposited α:C:H:WC film were rubbed against ice surfaces. The upper friction pair in the experimental system consisted of a bearing steel ball with a 12.7 mm diameter surface-deposited α:C:H:WC film, and the lower friction pair consisted of a self-made ice surface (the ice was frozen in NaCl solutions with ion concentrations ranging from 0.001 to 1.0 mol / L).

[0077] The results are as follows Figure 7 As shown, with the increase of ion concentration, the ice surface friction coefficient first decreases and eventually tends to stabilize. A NaCl concentration of 0.001-1.0 mol / L is beneficial to reducing the ice surface friction coefficient.

[0078] Example 8: Reduction of the coefficient of friction under liquid conditions

[0079] To investigate the differences in water molecule and frictional behavior between hydrophilic and hydrophobic surfaces, an untreated Si3N4-film wafer (silicon nitride thin film (Si3N4-film) deposited on the silicon wafer surface using magnetron sputtering) was used. First, the gas was ionized by introducing argon gas (Ar) into a vacuum chamber and applying a high-voltage electric field to ionize the argon gas, forming plasma (Ar). + (and electrons); then target bombardment: Ar + The target material (cathode) is bombarded under an electric field acceleration, sputtering target atoms / molecules through momentum transfer. Finally, a thin film is deposited: the sputtered target particles fly towards the substrate (anode), depositing a silicon nitride film on its surface. The film is then heated in a 120°C oven for 1 hour to obtain a relatively hydrophobic surface (contact angle 60°-90°). The untreated Si3N4-film is then treated in a plasma cleaner for 2 minutes to remove surface organic matter, obtaining a superhydrophilic surface (contact angle <10°). Atomic force microscopy (AFM) experiments were performed on both the relatively hydrophobic and superhydrophilic Si3N4-films. The friction experiment system used Si3N4-film as the friction pair, a 15μm SiO2 colloidal probe as the upper friction pair, and ultrapure water as the lubricating medium. The underwater friction coefficient of the relatively hydrophobic Si3N4-film is greater than that of the superhydrophilic Si3N4-film.

[0080] Hydrophilic solid-liquid interfaces and hydrophobic solid-liquid interfaces were detected using SFG. The results are as follows: Figure 8 As shown, hydrophilic surfaces have a higher proportion of "liquid-like" water. Compared to hydrophobic surfaces, hydrophilic surfaces have weaker hydrogen bonds between water molecules at the interface. Weak hydrogen bonds can reduce the shear force at the interface, thereby reducing the coefficient of friction.

[0081] Modifying the contact surface to make it hydrophilic increases the proportion of "liquid-like" structures of interfacial water molecules, thereby reducing the underwater friction coefficient. Conversely, modifying the contact surface to make it hydrophobic increases the proportion of "ice-like" structures of interfacial water molecules, thereby increasing the underwater friction coefficient.

[0082] Example 9: Adjustment of the coefficient of friction under liquid conditions

[0083] Samples 1 and 2 were both subjected to underwater friction experiments using AFM. The friction pair in the experimental system consisted of a Si3N4-film underside and a 15μm SiO2 colloidal probe (using a TL-CONT cantilever beam; epoxy resin was applied to the tip of the cantilever beam, and a 15μm diameter SiO2 colloidal sphere was attached to the probe's adhesive surface, positioning the sphere at the center of the cantilever beam tip). The lubricating medium was ultrapure water. The interfacial water molecule structure was detected using SFG.

[0084] Sample 1 was an untreated Si3N4-film that was heated in an oven at 120℃ for 1 hour to obtain a Si3N4-film with a relatively hydrophobic surface (contact angle of 60°-90°). Sample 1 was subjected to a liquid-liquid friction experiment at 0℃ in an ultrapure water system with a salt ion concentration of 0 mol / L.

[0085] Sample 2, an untreated Si3N4-film, was treated in a plasma cleaner for 2 minutes to remove surface organic matter, resulting in a Si3N4-film with a superhydrophilic surface (contact angle < 10°). The coefficient of friction of Sample 2 was then tested in a system with a salt ion concentration of 0.1 mol / L at an experimental temperature of 30°C.

[0086] The results are as follows Figure 9 As shown, compared with sample 1, sample 2 has a higher temperature, greater wettability, higher ion concentration, a larger proportion of "liquid-like" water molecule structure at the solid-liquid interface, and a smaller coefficient of friction.

[0087] In summary, by modifying the contact surface to make it hydrophilic, controlling the contact surface temperature within the range of 0-30℃, and maintaining an ion concentration of <0.1mol / L in the liquid environment, the interfacial water molecule structure can be altered, thereby reducing the underwater friction coefficient.

[0088] Example 10: Reduction of Shear Resistance at the Solid-Liquid Interface

[0089] To investigate the relationship between water molecules on hydrophilic and hydrophobic surfaces and the shear resistance at the solid-liquid interface, Si3N4-film samples deposited on aluminum alloy surfaces were heated in a 120℃ oven for 1 hour to obtain Si3N4-films with relatively hydrophobic surfaces (contact angles of 60°-90°). The Si3N4-films were then treated in a plasma cleaner for 2 minutes to remove surface organic matter, yielding SiO2 sheets with superhydrophilic surfaces (contact angles <10°). Solid-liquid interface shear resistance measurements were performed on both the relatively hydrophobic and superhydrophilic Si3N4-films. The experimental system used a 50mm diameter 316L stainless steel rotor as the upper shear plane, a 60mm diameter aluminum alloy sample with deposited Si3N4-film as the lower shear plane, and ultrapure water as the intermediate fluid medium. The shearing speed was 18000 rpm. The shear resistance of the relatively hydrophobic Si3N4-film was lower than that of the superhydrophilic Si3N4-film. Hydrophilic solid-liquid interfaces and hydrophobic solid-liquid interfaces were detected using SFG.

[0090] The results are as follows Figure 10 As shown, hydrophilic surfaces have a larger proportion of water structure, which is the opposite of the effect of wettability on the coefficient of friction in liquid. This indicates that hydrophilic surfaces have a larger proportion of "liquid-like" water structure, resulting in high shear resistance at the solid-liquid interface, while relatively hydrophobic surfaces have a larger proportion of "ice-like" water structure, resulting in low shear resistance at the solid-liquid interface.

[0091] Example 11: Reduction of ice surface friction coefficient

[0092] To investigate the relationship between water molecules on hydrophilic and hydrophobic surfaces and the coefficient of friction on ice surfaces, a:C:H:WC spheres (coated surfaces of bearing steel balls) were heated in a 120°C oven for 1 hour to obtain a relatively hydrophobic surface (contact angle 60°-90°). The spheres with a:C:H:WC deposited on their surfaces were then treated in a plasma cleaner for 2 minutes to remove surface organic matter, resulting in a superhydrophilic surface (contact angle <10°). Ice surface friction experiments were conducted on the a:C:H:WC spheres with relatively hydrophobic and superhydrophilic surfaces. In the experimental system, the upper friction pair consisted of 12.7 mm diameter coated a:C:H:WC spheres, and the lower friction pair consisted of a self-made ice surface (frozen with ultrapure water). The coefficient of friction on ice for the a:C:H:WC spheres with relatively hydrophobic surfaces was lower than that for the superhydrophilic a:C:H:WC spheres. The hydrophilic and hydrophobic solid-liquid interfaces were detected using SFG.

[0093] The results are as follows Figure 11As shown, hydrophilic surfaces have a larger proportion of "liquid-like" water structures, which is the opposite of the effect of wettability on the coefficient of friction under liquid conditions, but the same as the effect of wettability on the shear resistance of the solid-liquid interface. This indicates that hydrophilic surfaces with a larger proportion of "liquid-like" water structures have a higher coefficient of friction on ice surfaces, while relatively hydrophobic surfaces with a larger proportion of "ice-like" water structures have a lower coefficient of friction on ice surfaces.

Claims

1. A method for controlling interfacial friction or shear resistance, characterized in that, The method includes: A modified material layer is formed at the contact surface of the substrate material to reduce the interfacial friction or shear resistance of the substrate material; The modified material layer has a thickness of 3350–3450 cm⁻¹ as determined by sum-frequency vibrational (SFG) spectroscopy. -1 The amplitude / peak full width at half maximum (FWHM) at 3150–3250 cm⁻¹ -1 Material layers where the ratio of amplitude at a given point to the full width at half maximum (FWHM) of the peak is greater than 1.

0.

2. The method according to claim 1, characterized in that, The interfacial friction or shear resistance is underwater friction, ice surface friction, or solid-liquid interface shear resistance.

3. The method according to claim 2, characterized in that, The method further includes treating the modified material layer to make it hydrophilic in order to reduce underwater friction.

4. The method according to claim 2, characterized in that, The method further includes treating the modified material layer to make it hydrophobic in order to reduce interfacial shear resistance or ice surface friction.

5. The method according to any one of claims 1 to 4, characterized in that, The interfacial friction is a liquid friction, and the method further includes maintaining the temperature of the contact surface between 0 and 30°C.

6. The method according to any one of claims 1 to 4, characterized in that, The interfacial friction is underwater friction, and the method further includes making the salt ion concentration in the liquid environment 0.001-0.1 mol / L; The interfacial shear resistance is the solid-liquid interfacial shear resistance, and the method further includes making the salt ion concentration in the liquid environment 0-0.1 mol / L; The interfacial friction is ice surface friction, and the method further includes making the salt ion concentration on the ice surface 0.001-1.0 mol / L.

7. The method according to any one of claims 1 to 4, characterized in that, The modified material layer is a silicon nitride film, a hydrogen-containing amorphous carbon film, a metal compound-doped hydrogen-containing amorphous carbon film, or a modified hydrogen-containing amorphous carbon film.

8. The method according to claim 7, characterized in that, The hydrogen content of the hydrogen-containing amorphous carbon film is 15%-25%.

9. The method according to any one of claims 1 to 4, characterized in that, The modified material layer is formed on the contact surface of the substrate material by ion beam vapor deposition, plasma thin film processing, magnetron sputtering, or plasma spraying.

10. The method according to claim 6, characterized in that, The salt ions are sodium ions, potassium ions, cesium ions, or lithium ions.

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