A method for regulating the adhesion between aluminum liquid and solid interface by changing heat transfer characteristics

Abstract

The present invention relates to a method for regulating the adhesion force between molten aluminum and a solid interface by changing heat transfer characteristics. The method comprises the following steps: (1) using a piece of solid aluminum as a probe, and using a piece of solid silicon and a piece of solid aluminum as substrates to form an aluminum-aluminum system and an aluminum-silicon system, respectively; (2) establishing a molecular dynamics liquid-solid adhesion model composed of the probe and the substrate; (3) measuring the adhesion force between the liquid-solid interface after the system reaches equilibrium; (4) executing a simulation process and processing data: analyzing the energy transfer process of the liquid-solid interface, calculating the interfacial thermal conductivity during the adhesion process, extracting the phonon spectrum of the liquid contacting the solid substrate at the interface, and analyzing the relationship between the heat energy transfer efficiency and the phonon spectrum when the adhesion force between the probe aluminum liquid and the solid substrate changes under different contact interface conditions. The present invention combines molecular dynamics and quantum theory to reveal the heat transfer mechanism of adhesion between liquid aluminum and the solid aluminum / silicon interface when the temperature of the solid substrate increases.

Description

Technical Field

[0001] The present invention relates to the field of molecular dynamics technology, and in particular to a method for regulating the adhesion force between aluminum liquid and a solid interface by changing heat transfer characteristics. Background Art

[0002] Aluminum, a fundamental raw material for industrial development, is widely used in various fields, including national security, transportation, new energy, and electronic power, resulting in a significant increase in demand for aluminum. However, raw aluminum is not available directly in nature and must be smelted and extracted from a bauxite mixture before it can be used. During the electrolytic aluminum production process, molten aluminum often adheres to the inner walls of the equipment. Over time, this adhesion between the liquid aluminum and the solid interface becomes increasingly pronounced, reducing equipment productivity and the quality of the aluminum produced. Therefore, addressing this adhesion issue at the liquid-solid interface would significantly improve aluminum production and quality, thereby reducing energy consumption.

[0003] In order to reduce the adhesion at the liquid-solid interface, some people have changed the solid surface morphology of liquid adhesion based on the hydrophobic surface existing in nature. Research on the hydrophobic properties of plants and animals includes the lotus leaf effect, rice leaves, bird and cicada wings, etc. These research areas have simulated good friction reduction and viscosity reduction effects.

[0004] During their research, some scholars discovered that molecular dynamics can simulate the adhesion phenomenon at the liquid-solid interface, and found that the adhesion at the liquid-solid interface is directly related to the wettability of the liquid. This method has the characteristics of saving resources and high efficiency. Gao et al. established a polydimethylsiloxane-silica model and found that in general, the better the wettability of the solid surface to the liquid, the stronger its adhesion. Liu et al. found that as the temperature of the system increases, the larger the defects on the solid surface, the greater the liquid / solid interface adhesion. Lv et al. found that the grooves on the graphite surface will hinder the diffusion of aluminum, and when aluminum droplets are on the graphite surface, the adhesion decreases. Lai used atomic force microscopy to observe the effect of substrate temperature on the adhesion between two silicon wafer surfaces at different humidity and found that the average adhesion decreases with increasing substrate temperature. This is because high-temperature dehydroxylation causes the thickness of the interfacial water film to decrease, thereby reducing the adhesion of the silicon / silicon interface. He et al. studied the relationship between temperature changes and adhesion properties between single-layer and double-layer graphene and silica substrates, and found that when the temperature gradually increased from 300K to 500K, the mismatch between the graphene and substrate lattices increased due to thermal relaxation of the interface atoms, resulting in a decrease in adhesion energy. Lai measured the temperature-dependent adhesion trend between two solid surfaces in a wet environment and found that the adhesion first increased and then decreased with increasing temperature. Qing calculated the interfacial energy and adhesion energy of liquid Al / α-A12O3 and found that when the temperature increased from 950K to 1250K, a transition from non-wetting to wetting occurred. This was because the increase in temperature caused the evaporation of aluminum atoms in α-A12O3 and the diffusion of oxygen atoms, resulting in a decrease in interfacial energy, which in turn led to a change in the wettability of the Al liquid on the α-A12O3 surface. Cong et al. studied the wettability of aluminum liquid and silicon carbide substrate at temperatures of 973K to 1273K. The results showed that with the increase of temperature, the contact angle (CA) decreased from 125° to 57°, achieving a transition from non-wetting to wetting.

[0005] However, the wettability of liquids on solid surfaces is usually related to energy changes. The study of liquid-solid interface energy was first discovered by Kapitza when studying the liquid helium-metal interface under low temperature conditions. Later, Pollack used the acoustic mismatch model to define the liquid-solid interface thermal resistance as a function of phonon density, and Swartz et al. further regarded phonons as plane waves that can propagate or reflect at the interface. Since then, a large number of studies have been conducted on interface thermal resistance. Kim et al. found that the interface thermal resistance is a function of surface wettability, thermal oscillation frequency, wall temperature, thermal gradient, and channel. Xue et al.'s simulation study showed that the strength of the bond between liquid and solid atoms determines the interface thermal resistance. The interface thermal resistance is exponentially dependent on the strength of the weak bond (non-wettability) between liquid and solid atoms, while the strength of the strong bond (wettability) is exponentially dependent. Kim et al. established a one-dimensional lattice vibration model for the liquid-solid interface thermal resistance and found that the interface thermal resistance is proportional to the fourth power of the ratio of the thermal oscillation frequency of solid and liquid molecules. Ramos-Alvarado et al. found no relationship between the two when studying interfacial heat transfer and wetting. The relationship between quartz and water is ubiquitous, and when simulating heat conduction between crystalline / amorphous silicon and water, it was found that different phonon modes have different effects on it, among which low-frequency phonons play a dominant role in heat transfer at the hydrophilic interface, while heat transfer at the hydrophobic interface gradually shifts to high-frequency phonons; Goicochea et al. found that heat transfer between the quartz-water interface can be regulated by functionalizing the growth of nanopillars on the solid surface to adjust the vibration frequency of the atoms on the quartz surface, and the increase in the height and density of these nanopillars will increase the thermal conductivity of the interface; Qian et al. simulated the heat transfer between imidazole liquid and graphene and found that molecular orientation (the parallelism of the imidazole ring and graphene) is a key factor in controlling heat transfer between interfaces; et al. analyzed the contribution of different vibration modes to energy transfer based on the heat flow spectrum of the liquid-solid interface. The interfacial thermal energy transfer was dominated by the surface mode at the boundary of the Brillouin zone and was polarized along the out-of-plane direction.

[0006] The aforementioned studies on wettability at liquid / solid interfaces primarily focus on phenomena observed at high temperatures. These studies also suggest that adhesion at liquid / solid interfaces involves energy conversion. However, the heat transfer mechanism involved in the adhesion of liquid aluminum to a solid substrate below its melting point remains unclear. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for regulating the adhesion force between the aluminum liquid and the solid interface by changing the heat transfer characteristics.

[0008] To solve the above problems, the present invention provides a method for regulating the adhesion between molten aluminum and a solid interface by changing heat transfer characteristics, comprising the following steps:

[0009] (1) A piece of solid aluminum is used as a probe, and a piece of solid silicon and a piece of solid aluminum are used as substrates, respectively, to form an aluminum-aluminum system and an aluminum-silicon system; the initial states of the probe and the substrate in different systems are both solid, and the probe always maintains a constant size in different systems;

[0010] ⑵Establish a molecular dynamics liquid-solid adhesion model consisting of a probe and a substrate:

[0011] Setting periodic boundary conditions in the x-axis and y-axis directions of the aluminum-aluminum system or the aluminum-silicon system, and setting a free boundary condition in the z-axis direction;

[0012] The system simulation is relaxed in a microcanonical ensemble, and the aluminum liquid melting and adhesion state are analyzed in a canonical system. The temperature is controlled by a Berendsen thermostat.

[0013] The interaction between all aluminum atoms adopts EAM (Embedded atomic method potential); the interaction between all silicon atoms adopts Stillinger-Weber potential;

[0014] A Lennard-Jones potential is used between the probe and the substrate;

[0015] The potential well constant ε between aluminum and silicon ij and the initial equilibrium distance σ ij It is calculated using the following geometric mean mixing formula:

[0016] and

[0017] Where: ε i is the potential well constant between aluminum atoms, unit is meV; ε j is the potential well constant between silicon atoms, unit is meV; σ i is the equilibrium distance between aluminum atoms, in nm; σ j is the equilibrium distance between silicon atoms, in nm;

[0018] (3) The system in the initial state is first relaxed for 100 ps. When the system reaches equilibrium, the solid aluminum probe is heated to melt it. The completely melted molten aluminum is then adhered to the solid substrate to measure the adhesion force at the liquid-solid interface.

[0019] ⑷Execute the simulation process and process the data:

[0020] The energy transfer process at the liquid-solid interface is analyzed, the interfacial thermal conductivity during the adhesion process is calculated, and the phonon spectrum of the liquid contacting the solid substrate at the interface is extracted. The relationship between the thermal energy transfer efficiency and the phonon spectrum when the adhesion force between the probe aluminum liquid and the solid substrate changes under different contact interface conditions is analyzed.

[0021] In the step (1), the atoms of the aluminum substrate and the silicon substrate are divided into a fixed layer, a temperature adjustment layer and a Newtonian layer from bottom to top.

[0022] The specific process of executing the simulation process and processing data in step (4) is as follows:

[0023] ① Keeping the atomic number of the aluminum probe unchanged, the probe aluminum was melted and placed in industrial electrolytic aluminum. The molten aluminum liquid at a temperature of 1143K was then attached to different solid substrates. The changes in the adhesion force at the liquid-solid interface were analyzed when the substrate temperature varied from 50K to 400K.

[0024] ② Analyze the relationship between the adhesion force and the liquid-solid interface contact angle when aluminum liquid adheres to different solid substrates under different temperature changes to verify the correctness of the calculation model;

[0025] ③ Analyze the interfacial energy transport during steady-state adhesion, obtain the interfacial thermal conductivity from the temperature change between the liquid-solid interface, and the change in the solid substrate phonon spectrum caused by energy change, and analyze the relationship between the adhesion change of the contact interface under different states and the interfacial thermal conductivity and phonon spectrum.

[0026] The simulation process and data processing in step (4) also include: calculating the change in contact angle of the liquid-solid interface under different contact states when the temperature of different solid substrates changes from 50K to 400K, and analyzing the relationship between the change in adhesion force and the change in contact angle.

[0027] Executing the simulation process and processing the data in step (4) further includes: calculating the interfacial heat flow of the aluminum liquid when it is steadily adhered to the solid surface from the changes in the probe aluminum liquid temperature and the solid substrate temperature when the temperature of the different solid substrates changes, and analyzing the rate of heat energy transfer to the substrate when the aluminum liquid adheres to different solid substrates.

[0028] The execution of the simulation process and data processing in step (4) further includes: after the solid substrate receives energy from the aluminum liquid, calculating the kinetic energy and potential energy changes of the substrate atoms, and analyzing the effect of the energy on the solid substrate.

[0029] The execution of the simulation process and data processing in step (4) also includes: based on the different performances of atoms after the solid substrate absorbs energy, further analyzing the influence of thermal energy on the solid substrate atoms from the mean square deviation displacement of the solid substrate atoms, and judging whether the solid substrate atoms are in vibration mode or diffusion mode at different temperatures.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] 1. During the simulation process, the present invention found that when the temperature of the solid substrate increased from 50K to 400K, the adhesion force of the aluminum liquid to the solid aluminum substrate was greater than the adhesion force of the aluminum liquid to the solid silicon substrate. In addition, the adhesion force of the aluminum liquid to the solid aluminum substrate showed a non-monotonic change, first decreasing and then increasing, while the adhesion force to the solid silicon substrate showed a monotonic decreasing trend.

[0032] 2. By measuring the static contact angle of the liquid-solid interface, the present invention found that the contact angle between molten aluminum and solid aluminum first increases and then decreases, while the contact angle between molten aluminum and solid silicon gradually increases with the change of substrate temperature. This proves that the smaller the contact angle, the stronger the wettability of the liquid-solid interface and the greater its interfacial adhesion, which also proves the accuracy of the simulation model established by the present invention.

[0033] 3. To demonstrate the relationship between the change in adhesion of molten aluminum to different solid substrates and thermal conductivity, the present inventors calculated thermal conductivity and found that as the substrate temperature increases, the interfacial thermal conductivity gradually decreases, and the thermal conductivity between molten aluminum and solid aluminum is greater than that between molten aluminum and solid silicon, indicating that the adhesion of molten aluminum to solid aluminum is stronger than that to solid silicon.

[0034] 4. In order to determine the impact of energy changes on substrate atoms, the present invention combines the changes in substrate atomic energy (kinetic energy and potential energy) and the mean square displacement changes of substrate atoms, and obtains that when the solid aluminum substrate adheres to the aluminum liquid at a lower temperature, its surface remains intact and causes the substrate atoms to vibrate by absorbing energy from the aluminum liquid; at higher temperatures, the lattice of the solid aluminum substrate atoms is destroyed and some atoms are in a diffused state; within the temperature change range of 50K to 400K, the substrate surface of the solid silicon substrate remains intact and the atoms are always in a small vibration state.

[0035] 5. In order to determine the relationship between adhesion changes and energy transfer, the present invention calculated the phonon spectra of silicon atoms and aluminum atoms at different substrate temperatures. The calculation results show that as the substrate temperature increases, the low-frequency phonons that dominate thermal energy transfer decrease, thereby resulting in a decrease in the energy received by the substrate, that is, a decrease in interfacial adhesion; however, when the aluminum substrate is at a higher temperature, defects are generated due to lattice destruction, and the defects gradually increase with increasing temperature, which in turn leads to an increase in adhesion. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] Figure 1 Figure 1 is an aluminum-aluminum solid model diagram (a) in the initial state and an aluminum-silicon solid model diagram (b) in the initial state established in the present invention.

[0038] Figure 2 Schematic diagram of the solid aluminum melting process and temperature and system pressure changes in the present invention (a), and the interfacial adhesion force of the aluminum liquid adhering to the solid aluminum and solid silicon substrate (b).

[0039] Figure 3 The front view of the aluminum liquid stably adhering to the solid aluminum substrate and the front view of the aluminum liquid adhering to the solid silicon substrate in the present invention are shown in FIG1. Figure II (a) Contact angles of aluminum liquid adhering to solid aluminum and solid silicon substrates (b).

[0040] Figure 4 The temperature of the aluminum liquid and the solid atoms in the contact layer when the aluminum liquid adheres to solid substrates at different temperatures in the present invention (a), the temperature difference between the aluminum liquid and the contact solid atoms when the aluminum liquid adheres to the surface of solid aluminum and silicon substrates (b), the rate at which the solid substrate absorbs heat energy (c), and the interfacial thermal conductivity between the aluminum liquid and different solid materials aluminum and silicon (d).

[0041] Figure 5 In the present invention, the kinetic energy of solid atoms when the aluminum liquid adheres to the solid aluminum substrate (a), the potential energy of solid atoms when the aluminum liquid adheres to the solid aluminum substrate (b), the kinetic energy of solid atoms when the aluminum liquid adheres to the solid silicon substrate (c), and the potential energy of solid atoms when the aluminum liquid adheres to the solid silicon substrate (d).

[0042] Figure 6 The mean square error displacement of solid atoms when the aluminum liquid adheres to solid aluminum at a temperature of 100K (a), the mean square error displacement of solid atoms when the aluminum liquid adheres to solid aluminum at a temperature of 200K (b), the mean square error displacement of solid atoms when the aluminum liquid adheres to solid aluminum at a temperature of 250K (c), the mean square error displacement of solid atoms when the aluminum liquid adheres to solid aluminum at a temperature of 350K (d), the mean square error displacement of solid atoms when the aluminum liquid adheres to solid silicon at a temperature of 100K (e), the mean square error displacement of solid atoms when the aluminum liquid adheres to solid silicon at a temperature of 200K (f), the mean square error displacement of solid atoms when the aluminum liquid adheres to solid silicon at a temperature of 250K (g), and the mean square error displacement of solid atoms when the aluminum liquid adheres to solid silicon at a temperature of 350K (h).

[0043] Figure 7The present invention shows the phonon spectra of the atoms of the solid substrate when the aluminum liquid adheres to the solid aluminum substrate at temperatures of 100K, 150K, 200K, 300K and 400K respectively (a), the phonon spectra of the atoms of the solid substrate when the aluminum liquid adheres to the solid silicon substrate at temperatures of 100K, 200K, 300K and 400K respectively (b), the phonon spectra of the atoms of the solid substrate when the solid aluminum substrate has no aluminum liquid adhesion and the temperatures are 100K, 200K and 300K respectively (c), and the phonon spectra of the atoms of the solid substrate when the solid silicon substrate has no aluminum liquid adhesion and the temperatures are 100K, 200K and 300K respectively (d). DETAILED DESCRIPTION

[0044] A method for regulating the adhesion between molten aluminum and a solid interface by changing heat transfer characteristics comprises the following steps:

[0045] ⑴ A piece of solid aluminum is used as the probe, and a piece of solid silicon and a piece of solid aluminum are used as the substrate to form an aluminum-aluminum system and an aluminum-silicon system respectively; the initial states of the probe and the substrate in different systems are both solid, and the probe always maintains the same size in different systems.

[0046] Among them: the atoms of the aluminum substrate and the silicon substrate are divided into a fixed layer, a temperature adjustment layer and a Newtonian layer from bottom to top.

[0047] The temperature-regulating layer is used to adjust the temperature of the substrate using a Berendsen thermostat during the simulation process; the Newtonian layer is used to analyze the vibration state of atoms in contact with the aluminum liquid throughout the process.

[0048] ⑵Establish a molecular dynamics liquid-solid adhesion model consisting of a probe and a substrate:

[0049] Set periodic boundary conditions in the x-axis and y-axis directions of the aluminum-aluminum system or the aluminum-silicon system, and set free boundary conditions in the z-axis direction;

[0050] The system simulation is relaxed in a microcanonical ensemble, and the aluminum liquid melting and adhesion state are analyzed in a canonical system. The temperature is controlled by a Berendsen thermostat.

[0051] The interactions between all aluminum atoms are determined using the Embedded atomic method potential (EAM); the interactions between all silicon atoms are determined using the Stillinger-Weber potential.

[0052] Lennard-Jones potential was used between the probe and substrate;

[0053] The potential well constant ε between aluminum and silicon ij and the initial equilibrium distance σ ij It is calculated using the following geometric mean mixing formula:

[0054] and

[0055] Where: ε i is the potential well constant between aluminum atoms, unit is meV; ε j is the potential well constant between silicon atoms, unit is meV; σ i is the equilibrium distance between aluminum atoms, in nm; σ j is the equilibrium distance between silicon atoms, in nm.

[0056] ⑶ The system in the initial state is first relaxed for 100 ps. When the system reaches equilibrium, the solid aluminum probe is heated to melt it; then the completely melted molten aluminum is adhered to the solid substrate to measure the adhesion force between the liquid and solid interfaces.

[0057] ⑷Execute the simulation process and process the data:

[0058] The energy transfer process at the liquid-solid interface is analyzed, the interfacial thermal conductivity during the adhesion process is calculated, and the phonon spectrum of the liquid contacting the solid substrate at the interface is extracted. The relationship between the thermal energy transfer efficiency and the phonon spectrum when the adhesion force between the probe aluminum liquid and the solid substrate changes under different contact interface conditions is analyzed.

[0059] The specific process is as follows:

[0060] ① Keeping the atomic number of the aluminum probe unchanged, the probe aluminum was melted and placed in industrial electrolytic aluminum. The molten aluminum liquid at a temperature of 1143K was then attached to different solid substrates. The changes in the adhesion force at the liquid-solid interface were analyzed when the substrate temperature varied from 50K to 400K.

[0061] ② Analyze the relationship between the adhesion force and the liquid-solid interface contact angle when aluminum liquid adheres to different solid substrates under different temperature changes to verify the correctness of the calculation model;

[0062] ③ Analyze the interfacial energy transport during steady-state adhesion, obtain the interfacial thermal conductivity from the temperature change between the liquid-solid interface, and the change in the solid substrate phonon spectrum caused by energy change, and analyze the relationship between the adhesion change of the contact interface under different states and the interfacial thermal conductivity and phonon spectrum.

[0063] In the present invention, executing the simulation process and processing data also includes one of the following:

[0064] When the temperature of different solid substrates changes from 50K to 400K, the contact angle change of the liquid-solid interface under different contact states is calculated, and the relationship between the change in adhesion force and the change in contact angle is analyzed.

[0065] When the temperature of different solid substrates changes, the interfacial heat flow of the aluminum liquid during steady-state adhesion to the solid surface is calculated from the changes in the probe aluminum liquid temperature and the solid substrate temperature, and the rate of heat energy transfer to the substrate when the aluminum liquid adheres to different solid substrates is analyzed.

[0066] After the solid substrate receives energy from the aluminum liquid, the kinetic energy and potential energy changes of the substrate atoms are calculated to analyze the impact of energy on the solid substrate.

[0067] Based on the different performances of atoms after the solid substrate absorbs energy, the influence of thermal energy on the solid substrate atoms is further analyzed from the mean square deviation displacement of the solid substrate atoms to determine whether the solid substrate atoms are in vibration mode or diffusion mode at different temperatures.

[0068] Example

[0069] This paper studies the changes in the adhesion force of aluminum liquid adhering to the low-temperature solid substrate aluminum / silicon surface, explores the relationship between heat transfer and the change in adhesion force at the liquid-solid interface, and further reveals the adhesion mechanism of the liquid / solid interface from the interfacial thermal conductivity and lattice vibration state.

[0070] The specific process is as follows:

[0071] 1. Establish molecular dynamics model

[0072] Establish the initial solid-solid model as Figure 1 As shown, the model consists of probe aluminum and a solid substrate. Figure 1 (a) is the probe aluminum and solid aluminum substrate model, Figure 1 (b) is the model of the probe aluminum and solid silicon substrate. In different models, the probe aluminum atoms are 4224 and the size is 6.48×8.91nm. 2 The size of the aluminum substrate is 14.58×21.47nm. 2 The size of the silicon substrate is 10.86×22.67nm 2 The atoms of the aluminum and silicon substrates are divided into three parts from bottom to top: a fixed layer, a thermostat layer, and a Newtonian layer. The thermostat layer is used to regulate the substrate temperature using a Berendsen thermostat during the simulation, while the Newtonian layer is used to analyze the vibration state of atoms in contact with the aluminum liquid throughout the process.

[0073] To accurately simulate the adhesion of aluminum to different substrates, the entire process was divided into three stages, all implemented in the LAMMPS software package. First, the entire solid-solid system was relaxed for 100 ps in a microcanonical ensemble to achieve a stable state. Then, the probe aluminum was continuously heated in the canonical ensemble to 1143 K, the temperature of liquid aluminum during electrolytic aluminum production, at which point the aluminum is completely molten and remains in this state. Finally, the completely molten liquid aluminum was adhered to the surfaces of solid silicon and solid aluminum substrates, and the adhesion behavior and mechanism of the liquid aluminum / solid interface under these conditions were analyzed.

[0074] The simulation conditions for the entire system include periodic boundary conditions in the x and y directions and free boundary conditions in the z direction. Because the embedded potential (EAM) between metal atoms can accurately simulate the melting process of metals, the EAM potential is used between the probe and the substrate aluminum atoms. The Stillinger-Weber potential is used between the silicon substrate atoms. The Lennard-Jones (LJ) potential is used between the probe aluminum atoms and the substrate atoms. The parameters between different atoms are shown in Table 1, where the parameters between aluminum atoms and silicon atoms are calculated based on the geometric mean mixing (mix geometric) formulas (1) and (2).

[0075]

[0076]

[0077] Table 1. LJ potential parameters between aluminum and aluminum, silicon and silicon, and aluminum and silicon

[0078] Atom Type ε(eV) σ(A) Al-Al 0.3928 2.62 Si-Si 0.0174 4.295 Al-Si 0.0827 3.355

[0079] 2. Analysis of solid aluminum melting process and calculation of interfacial adhesion force

[0080] according to Figure 1 To build the initial model, solid aluminum needs to be melted first. Figure 2(a) shows the changes in pressure and temperature during the entire process of melting solid aluminum. The pressure is the total force of all atomic pressures of the probe aluminum during the entire melting process, which can reflect the changes in the structure of the entire system. When the temperature rises to the melting point of aluminum at 933 K, the pressure undergoes a sudden change, that is, at this time, the solid aluminum begins to undergo severe internal deformation, resulting in a change in the pressure of the entire system. Although the temperature continues to rise to 1143 K, the total pressure of the system remains balanced, that is, all solid aluminum has now completely melted into liquid, and the increase in temperature no longer causes a phase change. This state is consistent with the melting point and complete melting state of aluminum. It is worth noting that the temperature of the molten aluminum after complete melting is higher than the set value, which is not only the temperature set by the probe but also the result of the increase in the temperature of the atoms of the solid substrate in the contact area, because temperature is an indicator of the average kinetic energy of molecules. The completely molten liquid aluminum will adhere to the solid aluminum / silicon surface, so the adhesion force between the atoms at the liquid / solid interface can be calculated during the stable adhesion process.

[0081] Since the van der Waals force between the atoms at the liquid / solid interface determines the wetting effect when the liquid adheres to the solid surface, the magnitude of the adhesion force can be obtained by calculating the intermolecular force between the contacting atoms. The results are as Figure 2 (b) shown. The results show that the adhesion force of liquid aluminum adhering to the solid aluminum substrate is greater than that of liquid aluminum adhering to the solid silicon substrate. In addition, the adhesion force on the aluminum substrate shows a non-monotonic change with the change of the substrate temperature. When the substrate temperature is lower than 200 K, the interfacial adhesion force gradually decreases. When the temperature exceeds 200 K, the interfacial adhesion force increases, while the adhesion force of the silicon substrate gradually decreases with the increase of the substrate temperature.

[0082] 3. Analyze the wetting performance of the interface from the perspective of liquid-solid interface contact

[0083] When a liquid adheres to a solid, the spreading of the liquid on the solid surface is a measure of the wettability of the liquid to the surface, and quantitative analysis is usually carried out using the liquid-solid interface contact angle (CA) measurement method.

[0084] According to Young's thermodynamic equation, the relationship between the contact angle of the liquid / solid interface and wettability is as follows: If CA < 90°, it is called mostly wetting, that is, hydrophilic. A hydrophobic surface is defined as 90° < CA < 150°. If CA > 150°, it is called a superhydrophobic surface. Therefore, the CA on the liquid / solid interface can be used to characterize the wetting characteristics of the liquid on the solid surface. The smaller the CA, the stronger the wettability, the greater the extensibility of the liquid on the solid surface, and thus more intermolecular forces and stronger interfacial adhesion forces are generated.

[0085] According to the model established in the present invention, the atomic number of the probe aluminum remains unchanged throughout the entire process from melting to adhesion on different substrates, so that the same volume of liquid aluminum will adhere to different solid substrates, making the CA measured on different substrates comparable. Figure 3 (a) Describes the steady-state adhesion state of liquid aluminum on the surface of solid aluminum and silicon substrates, and the specific CA measured is as follows: Figure 3 (b) shown.

[0086] The results show that the CA of liquid aluminum when it adheres to the aluminum solid surface is much smaller than the CA when it adheres to the silicon surface, that is, θ Al <θ Si Therefore, the adhesion of liquid aluminum to solid aluminum is stronger than that to silicon. Figure 2 As shown in (b), as the temperature increases, the CA of the solid silicon surface adheres to the liquid aluminum, which corresponds to the decrease in adhesion. The CA on the solid aluminum surface first increases and then decreases, which is also consistent with the Figure 2 This corresponds to the adhesion force in (b) which first increases and then decreases. This observation is consistent with the relationship between CA and wettability.

[0087] 4. Thermal conductivity analysis of liquid-solid contact interface

[0088] In the general wetting state, wettability is mainly affected by the change of interfacial energy when the liquid contacts the solid. In order to study the heat transfer mechanism of the adhesion behavior of liquid aluminum / solid aluminum and liquid aluminum / solid silicon interfaces, Figure 4 The heat energy transfer process was analyzed.

[0089] Figure 4 The interface temperature difference shown in (b) is given by Figure 4 The calculated temperatures of the liquid aluminum and solid substrate (shown in (a)) indicate that the interface temperature difference between the liquid aluminum and solid aluminum is smaller than that between the liquid aluminum and solid silicon. This means that the solid aluminum absorbs more heat energy from the liquid aluminum than the solid silicon. Because heat energy is transferred from the liquid aluminum to the solid substrate at each time step during the adhesion process, and the Berendsen thermostat regulates the solid substrate temperature to the target temperature, a function that varies with the temperature gradient is implemented throughout the adhesion process.

[0090] The present invention further calculates the heat flow of the liquid / solid interface at different solid temperatures according to formula (3), such as Figure 4 (c) The results further prove that solid aluminum has a stronger heat energy absorption capacity than solid silicon.

[0091]

[0092] Where: J represents the heat flow, unit is J / s; ΔE(t) represents the heat energy absorbed by the solid during the adhesion process, unit is J; t represents the adhesion time, unit is s.

[0093] The change in thermal energy mainly depends on the interfacial thermal conductivity between different materials. Therefore, the interfacial thermal conductivity between liquid aluminum and solid substrate is further calculated according to formula (4), as follows: Figure 4 The results show that solid aluminum absorbs more heat energy than silicon due to the greater thermal conductivity of the interface between liquid aluminum and solid aluminum.

[0094]

[0095] Where: G represents the interfacial thermal conductivity, unit MW / m 2 K; A represents the contact area between the aluminum liquid and the solid, unit is m 2 ; ΔT represents the temperature difference at the liquid / solid interface, unit is K.

[0096] 5. Analysis of kinetic energy and potential energy of solid substrate at different temperatures

[0097] Since the temperature change of liquid aluminum and solid substrate will cause energy conversion at the liquid-solid interface, the change of kinetic energy and potential energy of the solid substrate can be obtained, such as Figure 5 The results show that as the temperature increases, the kinetic energy and potential energy of the solid aluminum substrate and the silicon substrate increase significantly, because the energy of the solid substrate comes from the set temperature of the solid substrate and the large amount of heat energy transferred from the liquid aluminum to the solid state.

[0098] For the aluminum substrate, the kinetic energy at different temperatures shows an increasing trend, while the potential energy continues to decrease throughout the adhesion process, e.g. Figure 5 (a) and 5(b). This is because in a steady-state system, the atoms leaving the initial equilibrium position will lead to an increase in kinetic energy and a decrease in potential energy. It is worth noting that Figure 5 (b) It can be seen that when the temperature of the aluminum substrate is below 200K, the potential energy decreases slowly, but when the temperature exceeds 200K, the potential energy drops sharply. The reason for the different rates of change of the potential energy of the aluminum substrate in the two temperature ranges may be that the thermal energy of the substrate at different temperatures causes different atomic motion states. When the temperature is below 200K, the thermal energy causes slight vibrations of the atoms, resulting in a slight increase in the kinetic energy of the substrate atoms and a slight decrease in their potential energy. When the temperature exceeds 200K, the thermal energy causes some atoms to vibrate violently, completely breaking them from their original positions, causing the unit cell to rupture and a rapid decrease in the interatomic potential energy.

[0099] like Figure 5As shown in Figures 5(c) and 5(d), the kinetic energy of the silicon substrate remains stable at different temperatures, and its interatomic potential energy remains nearly constant. This is because temperature only causes very slight vibrations in the silicon substrate, which does not cause the atoms to move significantly from their equilibrium positions. Therefore, the kinetic energy and potential energy remain stable.

[0100] 6. Analyze the state of solid substrate at different temperatures from the mean square deviation displacement

[0101] In order to solve the above-mentioned problem of strong and weak atomic vibration, we further calculated the motion state of atoms at different temperatures during the adhesion process, that is, the mean square displacement (MSD) was used to represent the position change of the substrate atoms. The stable state of MSD represents the vibration state of the atoms, and the rapid change indicates that the atoms are in the diffusion state, such as Figure 6 The results show that as the temperature increases, solid aluminum is sensitive to temperature changes, the displacement changes greatly, and the MSD curve shows a sudden change when the temperature is higher than 200K, as shown in Figure 6 (a) to (d). This shows that when the temperature is below 200K, the aluminum substrate is in an active vibration state and the substrate unit cell is intact. However, when the temperature is above 200K, the atoms of the aluminum substrate first undergo a period of vibration, and then suddenly increase the atomic diffusion in both the in-plane (X and Y) and out-of-plane (Z) directions, resulting in the destruction of the substrate. Figure 5 As shown in (a) and 5(b), in the vibration state, the kinetic energy increases slowly and the potential energy decreases gradually, while in the diffusion state, the kinetic energy and its amplitude increase rapidly and the potential energy decreases rapidly. Unlike the aluminum substrate, the displacement of the solid silicon substrate changes very little when the substrate temperature increases. Therefore, the solid silicon substrate always maintains a small vibration at different temperatures, and its kinetic energy and potential energy will change slightly during the adhesion process, as shown in Figure 5(a). Figure 5 Therefore, it is reasonable that thermal energy can induce different vibrations of the substrate at different substrate temperatures.

[0102] 7. Analyze the thermal energy changes of solid substrates at different temperatures from phonon spectra

[0103] according to Figure 6 It can be seen that the substrate atoms produce lattice vibrations under the influence of thermal energy, and the lattice vibrations between atoms excite energy carriers - phonons. Because the energy transfer in the heat transfer process of non-superhydrophobic interfaces is mainly dominated by low-frequency phonons, the phonon spectra (DOS) of the aluminum substrate and the silicon substrate in the adhesion state are further calculated, as shown in Figure 2. Figure 7 (a) and Figure 7 (b) The results show that as the substrate temperature increases, the phonon spectrum decreases at low frequencies, regardless of whether it is in the vibrational state or the diffusion state. This means that the number of low-frequency phonons excited on the substrate atoms decreases, which leads to a decrease in the heat energy transferred to the solid and a decrease in the interfacial thermal conductivity, as shown in Figure 2. Figure 4 (d) shown.

[0104] In order to confirm that the change of vibration frequency at different substrate temperatures is caused by the adhesion of aluminum liquid, the phonon spectrum of the solid substrate atoms without aluminum liquid adhesion is also calculated, such as Figure 7 (c) and 7(d). Figure 7 Figures (c) and 7(d) show that the DOS does not change significantly when the substrate temperature is varied, proving that the energy responsible for the DOS change is thermal energy transferred from the liquid aluminum to the solid substrate. This suggests that, in the vibrational state, adhesion decreases due to a decrease in interfacial thermal conductivity. However, in the atomic diffusion state, although interfacial thermal conductivity decreases, lattice disruption creates defects on the solid surface, and the increase in defects leads to an increase in adhesion.

[0105] In summary, this study, combining molecular dynamics and quantum theory, reveals the heat transfer mechanism of adhesion between liquid aluminum and the solid aluminum / silicon interface as the solid substrate temperature increases. Results show that as the solid substrate temperature increases, the adhesion force at the liquid aluminum / aluminum interface first decreases and then increases, while the adhesion strength at the liquid aluminum / silicon interface shows a monotonically decreasing trend. Changes in atomic energy and mean square displacement indicate that the aluminum substrate remains intact below 200K, but undergoes lattice destruction above 200K; in contrast, the silicon substrate remains intact throughout the entire experimental temperature range. Phonon spectrum analysis indicates that, under the intact lattice vibrational state, increasing solid temperature reduces the number of excited low-frequency phonons, leading to a decrease in interfacial thermal conductivity and, consequently, reduced adhesion. Although phonon excitation decreases under the diffuse state of lattice destruction, the generation of surface defects increases interfacial adhesion.

[0106] The technical solution provided by the present invention is described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for regulating the adhesion between molten aluminum and a solid interface by changing heat transfer characteristics, comprising the following steps: (1) A piece of solid aluminum is used as the probe, and a piece of solid silicon and a piece of solid aluminum are used as the substrate to form an aluminum-aluminum system and an aluminum-silicon system respectively; The initial states of the probe and the substrate in different systems are both solid, and the probe always maintains a constant size in different systems; ⑵Establish a molecular dynamics liquid-solid adhesion model consisting of a probe and a substrate: In the aluminum-aluminum system or the aluminum-silicon system x Axis direction and y Set periodic boundary conditions in the axial direction. z Set free boundary conditions in the axial direction; The system simulation is relaxed in a microcanonical ensemble, and the aluminum liquid melting and adhesion state are analyzed in a canonical system. The temperature is controlled by a Berendsen thermostat. The EAM potential is used for the interaction between all aluminum atoms; the Stillinger-Weber potential is used for the interaction between all silicon atoms; A Lennard-Jones potential is used between the probe and the substrate; The potential well constant between aluminum and silicon ε ij and the initial equilibrium distance σ ij It is calculated using the following geometric mean mixing formula: and ; Where: ε i is the potential well constant between aluminum atoms, unit is meV; ε j is the potential well constant between silicon atoms, unit is meV; σ i is the equilibrium distance between aluminum atoms, in nm; σ j is the equilibrium distance between silicon atoms, in nm; (3) The system in the initial state is first relaxed for 100 ps. When the system reaches equilibrium, the solid aluminum probe is heated to melt it. The completely melted molten aluminum is then adhered to the solid substrate to measure the adhesion force at the liquid-solid interface. ⑷Execute the simulation process and process the data: The energy transfer process at the liquid-solid interface was analyzed, and the interfacial thermal conductivity during the adhesion process was calculated. The phonon spectrum of the liquid contacting the solid substrate at the interface was extracted. The relationship between the thermal energy transfer efficiency and the phonon spectrum when the adhesion force between the probe aluminum liquid and the solid substrate changed under different contact interface conditions was analyzed. The specific process is as follows: ① Maintaining the atomic number of the aluminum probe constant, the probe aluminum was melted and placed in industrial electrolytic aluminum. Molten aluminum at a temperature of 1143 K was then attached to different solid substrates. The adhesion force at the liquid-solid interface was analyzed as the substrate temperature varied from 50 K to 400 K. ② Analyze the relationship between the adhesion force and the liquid-solid interface contact angle when aluminum liquid adheres to different solid substrates under different temperature changes to verify the correctness of the calculation model; ③ Analyze the interfacial energy transport during the steady-state adhesion process, obtain the interfacial thermal conductivity from the temperature change between the liquid-solid interface, and the change in the solid substrate phonon spectrum caused by the energy change, and analyze the relationship between the adhesion change of the contact interface and the interfacial thermal conductivity and phonon spectrum under different states; different states refer to the change in contact angle when the aluminum liquid adheres to different substrates, and the vibrational or diffusion state of the solid substrate atoms at different temperatures.

2. The method for regulating the adhesion between molten aluminum and a solid interface by changing heat transfer characteristics according to claim 1, wherein: In the step (1), the atoms of the aluminum substrate and the silicon substrate are divided into a fixed layer, a temperature adjustment layer and a Newtonian layer from bottom to top.

3. The method for regulating the adhesion between molten aluminum and a solid interface by changing heat transfer characteristics according to claim 1, wherein: Executing the simulation process and processing the data in step (4) further includes: calculating the change in contact angle of the liquid-solid interface under different contact states when the temperature of different solid substrates changes from 50 K to 400 K, and analyzing the relationship between the change in adhesion force and the change in contact angle.

4. The method for regulating the adhesion between molten aluminum and a solid interface by changing heat transfer characteristics according to claim 1, wherein: Executing the simulation process and processing the data in step (4) further includes: calculating the interfacial heat flow of the aluminum liquid when it is steadily adhered to the solid surface from the changes in the probe aluminum liquid temperature and the solid substrate temperature when the temperature of the different solid substrates changes, and analyzing the rate of heat energy transfer to the substrate when the aluminum liquid adheres to different solid substrates.

5. The method for regulating the adhesion between molten aluminum and a solid interface by changing heat transfer characteristics according to claim 1, wherein: The execution of the simulation process and data processing in step (4) further includes: after the solid substrate receives energy from the aluminum liquid, calculating the kinetic energy and potential energy changes of the substrate atoms, and analyzing the effect of the energy on the solid substrate.

6. The method for regulating the adhesion between molten aluminum and a solid interface by changing heat transfer characteristics according to claim 1, wherein: The execution of the simulation process and data processing in step (4) also includes: based on the different performances of atoms after the solid substrate absorbs energy, further analyzing the influence of thermal energy on the solid substrate atoms from the mean square deviation displacement of the solid substrate atoms, and judging whether the solid substrate atoms are in vibration mode or diffusion mode at different temperatures.

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