Method for evaluating thermal expansion coefficient and elastic modulus of niO-YSZ electrode sintering process

Abstract

The application provides an evaluation method for thermal expansion coefficient and elastic modulus of a NiO-YSZ electrode sintering process, comprising the following steps: S1, establishing a nanoparticle coarsening model for simulating the sintering of the NiO-YSZ electrode, and converting into a data file recognizable by molecular dynamics; S2, selecting and fitting potential parameters and potential functions capable of reflecting the interaction force between all atoms in the NiO-YSZ system to perform energy matching with the all-atom model; S3, simulating the sintering process, setting boundary conditions, isothermal and isobaric system conditions, sintering conditions, and adding a compression strain rate code to each temperature node in the sintering process; S4, processing the linear thermal expansion rate and compression stress-strain curve of the sintering process, and converting into thermal expansion coefficient and elastic modulus at each temperature node in the sintering process. The beneficial effect is that the application ensures the accuracy of predicting the thermal expansion coefficient and elastic modulus of the NiO-YSZ electrode material, and can save a large amount of simulation resources.

Description

Technical Field

[0001] This invention relates to the technical field of electrode materials for solid oxide fuel cells (SOFCs), and more specifically, to a method for evaluating the coefficient of thermal expansion and elastic modulus of NiO-YSZ electrode during the sintering process. Background Technology

[0002] During the sintering process of SOFC electrodes, the mismatch between the performance parameters (thermal expansion coefficient and elastic modulus) between layers can lead to deformation and thermal stress concentration, which can affect the electrochemical performance and mechanical stability of the battery.

[0003] Porous electrodes are one of the important components of SOFCs. Their pores, electronic conductors, ionic conductors, and the three-phase boundaries (TPBs) formed are the only regions where electrochemical reactions and mass transport occur simultaneously. There are complex multiphase, multiscale, and multi-physical field coupled transport processes. Solid-state sintering plays a decisive role in the effective transport of electrode reactants and products in the pores, as well as the density, porosity, and effective electrical and ionic conductivity.

[0004] Starting from the nanoparticle scale, this study focuses on NiO-YSZ porous materials and uses coarse-grained molecular dynamics (CG-MD) to evaluate the changes in the thermal expansion coefficient and elastic modulus of electrode materials during sintering. This is of great significance for optimizing excessive deformation and stress concentration that occur during sintering.

[0005] In current technologies and research, experimental measurements are typically used to evaluate the coefficient of thermal expansion and elastic modulus of NiO-YSZ electrode materials during the sintering process, including the use of dilatometers and nanoindentation methods to obtain material properties. However, traditional experimental methods may be limited by the complexity of the materials and experimental conditions, resulting in low accuracy and high difficulty in obtaining measurement results. Furthermore, obtaining accurate results requires significant experimental costs and simulation resources. Summary of the Invention

[0006] The problem this invention aims to solve is to provide a method for evaluating the coefficient of thermal expansion and elastic modulus of NiO-YSZ electrode during the sintering process, which can ensure the accuracy of the measurement results, save experimental costs, reduce difficulty, and save a lot of simulation resources.

[0007] To address the above problems, this invention provides a method for evaluating the coefficient of thermal expansion and elastic modulus of NiO-YSZ electrode during the sintering process, comprising the following steps:

[0008] Step S1: Establish a coarsening model of nanoparticles for simulating the sintering of NiO-YSZ electrodes. The NiO-YSZ porous electrode nanoparticle model is established using MaterialStudio and converted into a data file recognizable by molecular dynamics. The particles in the NiO-YSZ porous electrode nanoparticle model are coarsened Ni particles and coarsened O particles with a particle size of 20nm.

[0009] Step S2: Select and fit potential parameters and potential functions that can reflect the interaction forces between all atoms in the NiO-YSZ system to perform energy matching with the all-atom model;

[0010] Step S3: Simulate the NiO-YSZ sintering process in the large-scale atomic and molecular parallel simulator Lammps, including heating, holding and cooling processes. At the same time, set the boundary conditions, isothermal and isobaric ensemble conditions and sintering conditions, and add the compressive strain rate code to each temperature node in the sintering process.

[0011] Step S4: The linear thermal expansion coefficient and compressive stress-strain curve of the NiO-YSZ electrode sintering process are obtained and converted into the thermal expansion coefficient and elastic modulus at each temperature node during the sintering process.

[0012] Preferably, in step S1, when establishing the NiO-YSZ porous electrode nanoparticle model using Material Studio, after establishing the cell structure of the NiO nanoparticles, cell expansion is performed to optimize the cell structure, and after expanding the ZrO2 cell structure, 8% Y atoms are doped to replace Zr atoms.

[0013] Preferably, in step S1, a NiO nanocluster model with a particle size of 20 nm and a YSZ nanocluster model with a particle size of 20 nm are established respectively by Build nanocluster, and the cluster particles are copied and placed in the simulation box, wherein the NiO / YSZ ratio is 1:1. At the same time, the force field information of each atom is allocated in pcff and CAR and MDF files are exported, and the data files are converted into data files that can be recognized by the large-scale atomic and molecular parallel simulator Lammps using the MSI tool of the molecular dynamics simulation software.

[0014] Preferably, in step S1, each of the coarsened O particles in the established NiO-YSZ porous electrode nanoparticle model corresponds to 27 O atoms in the full-atom model, and each of the coarsened Ni particles corresponds to 27 Ni atoms in the full-atom model.

[0015] Preferably, in step S2, the Lennard-Jones potential function, used to describe the interaction between atoms or molecules, is selected as the potential function. The Lennard-Jones potential function can be expressed as:

[0016]

[0017] in,

[0018] Used to represent short-range repulsive interactions;

[0019] Used to represent mid-range attractive interactions;

[0020] ε IJ Used to indicate the depth of a potential well;

[0021] σ IJ Used to represent a finite distance where the potential between particles is zero.

[0022] Preferably, step S3 further includes the following step before simulating the NiO-YSZ sintering process:

[0023] Each of the Ni coarse-grained particles and each of the O coarse-grained particles were placed in a simulation box and relaxed under an isothermal and isobaric ensemble at a sintering temperature of 300K and a pressure of 5GPa. After the relaxation operation, the contents describing the heating process of 3ns, holding time of 300ps and cooling time of 1ns during sintering were compiled into an in file and the restart files for each stage of the sintering process were obtained by simulating the large-scale atomic and molecular parallel simulator Lammps.

[0024] Preferably, in step S3, when configuring boundary conditions, the time step is set to 1 fs; when using the Lennard-Jones potential function, the cutoff radius is set to 1.5 nm; and when using a particle-particle-particle mesh solver to handle long-range Coulomb interactions, the accuracy is set to 10. -5 .

[0025] Preferably, in step S4, for each temperature node, the atomic trajectory under the temperature node is selected as the initial position, the trajectory file within 50K above and below the temperature node is taken as the research object, the ratio of the size change rate to time in the time period of the temperature node is calculated, and the thermal expansion coefficient of the temperature node is obtained by fitting calculation.

[0026] Preferably, the coefficient of thermal expansion is obtained by the following formula:

[0027]

[0028] in,

[0029] α is used to represent the coefficient of thermal expansion;

[0030] L is used to represent the system length;

[0031] dT is used to represent temperature change.

[0032] Preferably, in step S4, a stress-strain relationship diagram is obtained by processing the compression strain rate codes added in step S3 and the compressive stress collected during the sintering process, and the elastic modulus of the temperature node is obtained in the linear elastic stage of the stress-strain relationship diagram.

[0033] The present invention has the following beneficial effects: It can help to understand the evolution of the thermal expansion coefficient and elastic modulus of NiO-YSZ electrode at various stages during the sintering process, helping researchers save experimental costs and reduce difficulty. At the same time, the coarse-grained molecular dynamics method used in the present invention to evaluate the sintering process can better match the sintering experiment, ensuring the accuracy of predicting the thermal expansion coefficient and elastic modulus of NiO-YSZ electrode material, while saving a lot of simulation resources. Attached Figure Description

[0034] Figure 1 This is a flowchart of the steps of the present invention;

[0035] Figure 2 This is a schematic diagram of the coarse-grained mapping of the present invention;

[0036] Figure 3 This is a schematic diagram showing the distribution of the relaxed NiO-YSZ nanoparticles in the simulation box according to the present invention;

[0037] Figure 4 This is a structural morphology diagram of the NiO-YSZ nanoparticles sintered at 1673K according to the present invention;

[0038] Figure 5 The predicted compressive stress-strain relationship of the NiO-YSZ nanoparticles sintered to 1673K according to the present invention;

[0039] Figure 6 This is a schematic diagram showing the variation of the coefficient of thermal expansion of the fitted NiO-YSZ electrode with sintering temperature during the sintering process.

[0040] Figure 7 This paper presents the variation of the elastic modulus of the fitted NiO-YSZ electrode with sintering temperature during the sintering process. Detailed Implementation

[0041] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0042] In a preferred embodiment of the present invention, based on the above-mentioned problems existing in the prior art, a method for evaluating the coefficient of thermal expansion and elastic modulus of NiO-YSZ electrode during sintering is provided, such as... Figure 1 As shown, it includes the following steps:

[0043] Step S1: Establish a coarsening model of nanoparticles for simulating the sintering of NiO-YSZ electrodes. The NiO-YSZ porous electrode nanoparticle model is established using MaterialStudio and converted into a data file recognizable by molecular dynamics. The particles in the NiO-YSZ porous electrode nanoparticle model are coarsened Ni and O particles with a particle size of 20 nm.

[0044] Step S2: Select and fit potential parameters and potential functions that can reflect the interaction forces between all atoms in the NiO-YSZ system to perform energy matching with the all-atom model;

[0045] Step S3: Simulate the NiO-YSZ sintering process in the large-scale atomic and molecular parallel simulator Lammps, including heating, holding and cooling processes. At the same time, set the boundary conditions, isothermal and isobaric ensemble conditions and sintering conditions, and add the compressive strain rate code to each temperature node in the sintering process.

[0046] Step S4: The linear thermal expansion coefficient and compressive stress-strain curve of the NiO-YSZ electrode sintering process are obtained and converted into the thermal expansion coefficient and elastic modulus at each temperature node during the sintering process.

[0047] Specifically, in this embodiment, the main objective of the present invention is to utilize coarse-grained molecular dynamics methods to evaluate and predict the changes in the coefficient of thermal expansion and elastic modulus during the sintering process of NiO-YSZ electrodes, thereby overcoming the difficulty in measuring performance parameters during experiments. To achieve the aforementioned objective, the technical solution adopted by the present invention includes:

[0048] (1) A coarse-grained model of the NiO-YSZ porous electrode was established using Material Studio and converted into a data file recognizable by molecular dynamics.

[0049] (2) Select and fit the potential parameters and potential functions that reflect the interaction forces between all atoms in the NiO-YSZ system and perform energy matching with the all-atom model;

[0050] (3) The NiO-YSZ sintering process was simulated in the large-scale atomic and molecular parallel simulator (Lammps), including the heating, holding and cooling processes. At the same time, boundary conditions, isothermal and isobaric ensemble conditions and sintering conditions were set. In addition, compression strain rate codes were added to each temperature node of the sintering process.

[0051] (4) Obtain the linear thermal expansion coefficient and compressive stress-strain curve of NiO-YSZ electrode during the sintering stage, and convert them into the thermal expansion coefficient and elastic modulus at each temperature during the sintering process.

[0052] Preferably, the present invention has the following advantages:

[0053] Advantage 1: This invention is an evaluation method for the thermal expansion coefficient and elastic modulus of NiO-YSZ electrodes during sintering based on coarse-grained molecular dynamics. It helps to understand the evolution of the thermal expansion coefficient and elastic modulus of NiO-YSZ electrodes at each sintering stage, thus saving experimental costs and reducing difficulty.

[0054] Advantage 2: Using coarse-grained molecular dynamics to evaluate the sintering process can better match the sintering experiment, ensuring the accuracy of predicting the thermal expansion phase coefficient and elastic modulus of NiO-YSZ electrode material, while saving a lot of simulation resources.

[0055] Advantage 3: The coarse-grained molecular dynamics method can be used to predict the coefficient of thermal expansion and elastic modulus during electrode sintering and can be applied to other material systems (provided that the appropriate potential function and potential parameters are selected). It can also be used to propose optimization strategies for the problem of mismatched performance parameters of various electrodes in SOFC batteries.

[0056] Preferably, the present invention uses a coarse-grained method to simplify the NiO-YSZ porous electrode nanoparticle model and closely match the actual nanoparticle size, while saving computational costs. Furthermore, it retains all stages and temperature nodes in the NiO-YSZ electrode sintering process, and evaluates the thermal expansion coefficient and elastic modulus of each temperature node after redefining the compiled code in the in file.

[0057] Preferably, as an alternative, a "core-shell" model with a higher level of coarseness can be used in the coarsening process; when fitting potential parameters, machine learning methods can also be used. In addition to using the built-in MSI file conversion, Material Studio modeling software can also use Ovito software to save the PDB format in the periodic structure of the model. Then, if it is Windows, PowerShell can be opened by Shift + right mouse button; when predicting the elastic modulus, the compressive strain rate can be changed to the tensile strain rate, or the prediction can be performed in the x, y, and z directions of the model.

[0058] In a preferred embodiment of the present invention, in step S1, when establishing the NiO-YSZ porous electrode nanoparticle model using Material Studio, after establishing the cell structure of the NiO nanoparticles, cell expansion is performed to optimize the cell structure, and after expanding the ZrO2 cell structure, 8% Y atoms are doped to replace Zr atoms.

[0059] In a preferred embodiment of the present invention, in step S1, a NiO nanocluster model with a particle size of 20 nm and a YSZ nanocluster model with a particle size of 20 nm are respectively built using Build nanocluster, and the cluster particles are copied and placed in the simulation box, wherein the NiO / YSZ ratio is 1:1. At the same time, the force field information of each atom is allocated in pcff and the car and mdf files are exported, and the data files are converted into a data file that can be recognized by the large-scale atomic and molecular parallel simulator Lammps using the msi tool that comes with the molecular dynamics simulation software.

[0060] Specifically, in this embodiment, one aspect of the present invention provides a method for predicting the coefficient of thermal expansion and elastic modulus of NiO-YSZ electrode sintering process based on coarse-grained molecular dynamics, wherein NiO-YSZ is yttrium-stabilized zirconium oxide, comprising:

[0061] When using Material Studio to build the NiO-YSZ porous electrode nanoparticle model, the cell structure of NiO nanoparticles was established and then subjected to cell expansion (supercell) to further optimize the cell structure. After expanding the ZrO2 cell structure, 8% Y atoms were doped to replace Zr atoms, achieving the effect of YSZ (8% Y atom doping). Then, NiO nanocluster models with a particle size of 20 nm and YSZ nanocluster models with a particle size of 20 nm were built using Buildnanocluster. The cluster particles were then replicated, with the NiO / YSZ ratio at 1:1, and placed in the simulation box. At the same time, the force field information of each atom was assigned in pcff and CAR and MDF files were exported. Finally, the MSI tool of the molecular dynamics simulation software was used to convert the data into a Lammps recognizable data file.

[0062] In a preferred embodiment of the present invention, in step S1, each coarsened O particle in the established NiO-YSZ porous electrode nanoparticle model corresponds to 27 O atoms in the full-atom model, and each coarsened Ni particle corresponds to 27 Ni atoms in the full-atom model.

[0063] Specifically, in this embodiment, before simulating the sintering process, a coarse-grained model verification was performed. The total energy and potential energy of the all-atom model and the NiO-YSZ porous electrode nanoparticle model were compared at 1673K for 1ns to demonstrate the rationality of the selected Lennard-Jones potential function and the fitted potential parameters. The mapping scheme is as follows: Figure 2 As shown, Figure 2 (a) is an all-atomic lattice structure. Figure 2 (b) is a coarse-grained lattice structure (coarse-grained level 3), consisting of three atomic lattices along the X, Y, and Z directions, that is, Figure 2 Each coarse-grained particle in (b) represents Figure 2 (a) contains 27 atoms in an all-atomic lattice. Figure 2 (b) The small-diameter coarse-grained particles at the center correspond to the 27 oxygen atoms in the full atomic structure, and similarly, the large-diameter coarse-grained particles represent the 27 nickel atoms in the full atomic structure.

[0064] In a preferred embodiment of the present invention, in step S2, the Lennard-Jones potential function, which describes the interaction between atoms or molecules, is selected as the potential function. The Lennard-Jones potential function can be expressed as:

[0065]

[0066] in,

[0067] Used to represent short-range repulsive interactions;

[0068] Used to represent mid-range attractive interactions;

[0069] ε IJ Used to indicate the depth of a potential well;

[0070] σ IJ Used to represent a finite distance where the potential between particles is zero.

[0071] Specifically, in this embodiment, coarse-grained modeling is used to better reflect the actual nanoparticles in the sintering process. Furthermore, the development of the coarse-grained model is based on the all-atom model, which considers mass, momentum, energy, charge, etc. The Lennard-Jones potential function is used to describe the interaction between atoms or molecules, especially when describing the van der Waals attraction and repulsion effects between nonpolar atoms. For the sintering process of nanoparticles or nanocrystals, the Lennard-Jones potential function can serve as a simple and effective model for simulating and describing the interaction between particles.

[0072] Preferably, Table 1 below shows the potential parameters fitted to the all-atom model and the model with a coarse-grained level of 3.

[0073] Preferably, Table 2 below shows the comparison and verification of the interaction energies between the all-atom model and the coarse-grained model (level 3).

[0074] Table 1. Fitting parameters of the NiO / YSZ coarse-grained model and comparison with the all-atom model.

[0075]

[0076] Where * represents the fitting parameters.

[0077] Table 2 Comparison of interaction energies between all-atom and coarse-grained models

[0078]

[0079] Wherein, *relative error = |full-atom model – coarse-grained model| / full-atom model × 100%.

[0080] In a preferred embodiment of the present invention, step S3 further includes, before simulating the NiO-YSZ sintering process:

[0081] Each coarse Ni particle and each coarse O particle was placed in a simulation chamber and relaxed under an isothermal and isobaric ensemble at a sintering temperature of 300 K and a pressure of 5 GPa. After the relaxation, the contents describing the heating process of 3 ns, holding time of 300 ps and cooling time of 1 ns during sintering were compiled into an in file. The restart files for each stage of the sintering process were obtained by simulating with the large-scale atomic and molecular parallel simulator Lammps.

[0082] In a preferred embodiment of the present invention, in step S3, when configuring boundary conditions, the time step is set to 1 fs; when using the Lennard-Jones potential function, the cutoff radius is set to 1.5 nm; and when using a particle-particle-particle mesh solver to handle long-range Coulomb interactions, the accuracy is set to 10. -5 .

[0083] Specifically, in this embodiment, before sintering simulation, the simulation chamber of the NiO-YSZ nanoparticle system to be predicted is relaxed, specifically under isothermal-isobaric ensemble (NPT) at 300 K and 5 GPa pressure, compared with the density of 5.2 g / cm³ measured in experiments. 3 Similar, such as Figure 3 The image shows the morphology of the relaxed NiO-YSZ nanoparticles in the simulation chamber. After relaxation, the sintering process (heating for 3 ns, holding for 300 ps, ​​and cooling for 1 ns) is described in the in file. After compilation, the output files restart. file for each stage are obtained through Lammps simulation. Here, one file is output for every 1000 steps.

[0084] Preferably, in setting boundary conditions, in order to optimize computational resources and ensure convergence, our model is configured with periodic boundary conditions, with a step size of 1fs, a cutoff radius of 1.5nm when using the LJ potential function, and a particle-particle-particle mesh (PPPM) solver to handle long-range Coulomb interactions with an accuracy of 10⁻⁵.

[0085] In a preferred embodiment of the present invention, in step S4, for the restart file under each temperature node, the atomic trajectory under the temperature node is selected as the initial position, the trajectory file within a range of 50K above and below the temperature node is taken as the research object, the ratio of the size change rate to time within the time period of the temperature node is calculated, and the thermal expansion coefficient of the temperature node is obtained by fitting calculation.

[0086] Specifically, in this embodiment, the restart file at a certain temperature node is used as the basis, and the case of sintering to 1673K is used as the example. Figure 4 As shown, on the one hand, the thermal expansion coefficient is predicted. The atomic trajectory at this temperature node is selected as the initial position, and the trajectory file within 50K above and below this temperature is used as the research object. The ratio of the size change rate to time during this time period is calculated, and the thermal expansion coefficient at this temperature is obtained by fitting.

[0087] In a preferred embodiment of the present invention, the coefficient of thermal expansion is obtained by the following calculation formula:

[0088]

[0089] in,

[0090] α is used to represent the coefficient of thermal expansion;

[0091] L is used to represent the system length;

[0092] dT is used to represent temperature change.

[0093] In a preferred embodiment of the present invention, in step S4, a stress-strain relationship diagram is obtained by processing the compression strain rate codes added in step S3 and the compressive stress collected during the sintering process, and the elastic modulus of the temperature node is obtained in the linear elastic stage of the stress-strain relationship diagram.

[0094] Specifically, in this embodiment, on the other hand, a compressive strain rate (selected as 10) is added to the in file to describe the elastic modulus of this temperature node. -6 The stress-strain relationship diagram is obtained from the output information, such as... Figure 5 As shown, the elastic modulus of this temperature node is obtained in the online elastic stage.

[0095] Preferably, the changes in the coefficient of thermal expansion and elastic modulus of NiO-YSZ electrode nanoparticles with sintering temperature during the sintering process are obtained at each stage using the above method, such as... Figure 6 and Figure 7 As shown.

[0096] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A method for evaluating the coefficient of thermal expansion and elastic modulus of NiO-YSZ electrode during sintering, characterized in that, Includes the following steps: Step S1: Establish a coarsening model of nanoparticles for simulating the sintering of NiO-YSZ electrodes. The NiO-YSZ porous electrode nanoparticle model is established using MaterialStudio and converted into a data file recognizable by molecular dynamics. The particles in the NiO-YSZ porous electrode nanoparticle model are coarsened Ni particles and coarsened O particles with a particle size of 20nm. Step S2: Select and fit potential parameters and potential functions that can reflect the interaction forces between all atoms in the NiO-YSZ system to perform energy matching with the all-atom model; Step S3: Simulate the NiO-YSZ sintering process in the large-scale atomic and molecular parallel simulator Lammps, including heating, holding and cooling processes. At the same time, set the boundary conditions, isothermal and isobaric ensemble conditions and sintering conditions, and add the compressive strain rate code to each temperature node in the sintering process. Step S4: The linear thermal expansion coefficient and compressive stress-strain curve of the NiO-YSZ electrode sintering process are obtained and converted into the thermal expansion coefficient and elastic modulus at each temperature node during the sintering process. In step S2, the Lennard-Jones potential function, used to describe the interaction between atoms or molecules, is selected as the potential function. The Lennard-Jones potential function can be expressed as: ； in, Used to represent short-range repulsive interactions; Used to represent mid-range attractive interactions; Used to indicate the depth of a potential well; Used to represent a finite distance where the potential between particles is zero.

2. The evaluation method according to claim 1, characterized in that, In step S1, when establishing the NiO-YSZ porous electrode nanoparticle model using Material Studio, after establishing the cell structure of NiO nanoparticles, cell expansion is performed to optimize the cell structure, and after expanding the ZrO2 cell structure, 8% Y atoms are doped to replace Zr atoms.

3. The evaluation method according to claim 1, characterized in that, In step S1, NiO nanocluster models with a particle size of 20 nm and YSZ nanocluster models with a particle size of 20 nm are established using Buildnanocluster. The cluster particles are then copied and placed in the simulation box, with the NiO / YSZ ratio being 1:

1. At the same time, the force field information of each atom is allocated in pcff and CAR and MDF files are exported. The MSI tool provided by the molecular dynamics simulation software is used to convert the data into a data file that can be recognized by the large-scale atomic and molecular parallel simulator Lammps.

4. The evaluation method according to claim 1, characterized in that, In step S1, each coarsened O particle in the established NiO-YSZ porous electrode nanoparticle model corresponds to 27 O atoms in the full-atom model, and each coarsened Ni particle corresponds to 27 Ni atoms in the full-atom model.

5. The evaluation method according to claim 1, characterized in that, Step S3, before simulating the NiO-YSZ sintering process, further includes: Each of the Ni coarse-grained particles and each of the O coarse-grained particles were placed in a simulation box and relaxed under an isothermal and isobaric ensemble at a sintering temperature of 300 K and a pressure of 5 GPa. After the relaxation operation, the contents describing the 3 ns heating, 300 ps holding and 1 ns cooling process during sintering were compiled into an in file and then the restart files for each stage of the sintering process were obtained by simulating the large-scale atomic and molecular parallel simulator Lammps.

6. The evaluation method according to claim 1, characterized in that, In step S3, when configuring boundary conditions, the time step is set to 1 fs; when using the Lennard-Jones potential function, the cutoff radius is set to 1.5 nm; and when using a particle-particle-particle mesh solver to handle long-range Coulomb interactions, the accuracy is set to 10. -5 .

7. The evaluation method according to claim 5, characterized in that, In step S4, for each temperature node, the atomic trajectory under the temperature node is selected as the initial position, and the trajectory files within 50 K above and below the temperature node are taken as the research object. The ratio of the size change rate to time within the time period of the temperature node is calculated, and the thermal expansion coefficient of the temperature node is obtained by fitting.

8. The evaluation method according to claim 7, characterized in that, The coefficient of thermal expansion is obtained using the following formula: ； in, Used to represent the coefficient of thermal expansion; Used to indicate the system length; Used to indicate temperature changes.

9. The evaluation method according to claim 7, characterized in that, In step S4, a stress-strain relationship diagram is obtained by processing the compression strain rate codes added in step S3 and the compressive stress collected during the sintering process, and the elastic modulus of the temperature node is obtained in the linear elastic stage of the stress-strain relationship diagram.

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