A method for predicting the growth of graphene on the surface of cemented carbide
Through molecular dynamics theory and LAMMPS simulator, the growth of graphene on the surface of cemented carbide was predicted, which solved the problem of many process parameters and difficult to control when preparing graphene in CVD, and achieved the growth of high-quality graphene and the extension of tool service life.
Patent Information
- Application Number
- CN202211229415.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-08
- Publication Date
- 2025-06-10
- Estimated Expiration
- 2042-10-08
AI Technical Summary
When preparing graphene in CVD, due to the many process parameters and interdependent, the growth quality of graphene is difficult to control, affecting the service life and wear performance of the tool.
Using molecular dynamics theory and LAMMPS simulator, the simulation conditions of high-quality graphene were determined by constructing cemented carbide substrate models to predict the growth status of graphene at different deposition temperatures and deposition rates.
It effectively reduces the energy consumption during graphene growth, shortens the experimental cycle, and obtains a high-quality graphene layer, guiding the optimization of actual CVD production.
Smart Images
Figure CN115458067B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for predicting the growth of graphene on the surface of cemented carbide, and specifically belongs to the field of advanced manufacturing technology. Background Art
[0002] As the machining accuracy becomes higher, the requirements for machine tool cutters become more important. Coatings are good materials for protecting cutters due to their high hardness, low friction and wear resistance. Graphene is an ideal material for surface protection coatings due to its excellent thermal conductivity, tensile strength and high hardness. When preparing graphene by CVD (chemical vapor deposition), due to its many adjustable parameters (temperature, pressure, substrate, carbon source, etc.), changing any one process parameter during the experiment will affect the growth quality of graphene, which makes it difficult to rely on experimental exploration of the growth mechanism of graphene and optimize the experimental design.
[0003] Simulating and modeling the process of graphene growth can effectively reduce the energy consumption of actual CVD production of graphene, shorten the experimental period, and obtain the theoretical basis for obtaining high-quality graphene, providing a theoretical foundation for experiments. The present invention is to establish a method for predicting the growth of graphene on the surface of cemented carbide. By changing the simulation parameters, the growth conditions of graphene in actual experiments are predicted. At different deposition temperatures and different carbon atom deposition rates, by visually observing the growth conditions of graphene and counting the basic units of graphene, the effects of different deposition temperatures and deposition rates on the growth of graphene are obtained, and the optimal growth parameters of graphene are compared and obtained. Summary of the Invention
[0004] In order to enhance the service life of the cutter and reduce the wear of the cutter, combined with the excellent properties of graphene, a method for predicting the growth of graphene on the surface of cemented carbide is predicted. Graphene is used as a lubricating coating to reduce the friction between the graphene-coated cutter and the workpiece, so as to achieve the purpose of reducing the cutting temperature.
[0005] A method for predicting the growth of graphene on the surface of cemented carbide according to the present invention is based on the MD (molecular dynamics) theory. By using LAMMPS (large-scale atomic / molecular massively parallel simulator) to simulate and calculate the self-assembly of carbon atoms on the surface of cemented carbide and the graphene growth process, at different deposition temperatures and deposition rates, the growth conditions of graphene on the surface of cemented carbide are predicted, and the simulation conditions for high-quality graphene are obtained. The specific content is as follows;
[0006] Content 1: Calculation Process
[0007] Using MD simulation to study the growth process of graphene on the surface of cemented carbide: First, a cemented carbide substrate model is constructed. Using the conjugate gradient method, after 20 ps of temperature relaxation, the cemented carbide substrate reaches stability, and then carbon atoms are deposited;
[0008] Different deposition temperatures and carbon atom deposition rates are set respectively to predict the growth of graphene on the surface of cemented carbide; To ensure the accuracy of the simulation, relevant potential functions are used;
[0009] Content 2: Model construction
[0010] A WC-Co substrate model of 2.872 nm × 2.872 nm × 2.259 nm is established by LAMMPS; Periodic boundaries are adopted in the X and Y directions to simulate an infinite surface, and fixed boundaries are adopted in the Z direction. To prevent the bottom surface from moving, the atoms in the range of 0 - 3 Å in the Z direction are fixed; The system temperature control adopts NVT (canonical ensemble), and the numerical integration of the kinetic equation in the system uses the Verlet algorithm (velocity algorithm), with a time step of 0.001 ps; The crystal plane of WC with the space group of and the (0001) crystal plane of Co with the space group of P63 / mmc are used as the deposition surfaces;
[0011] The decomposition and deposition of hydrocarbon molecules are simplified to the deposition of single carbon atoms on the surface of WC-Co cemented carbide. The actual carbon source flow rate is characterized by CDR (carbon deposition rate), and the time interval for depositing one carbon atom is used to represent CDR, with the unit of ps / C. A total of 300 carbon atom deposition processes are simulated; Three deposition temperatures of 900 K, 1300 K, and 1700 K are set in the simulation to study the effect of temperature on the growth of graphene; To study the effect of different CDRs on the growth of graphene, CDRs are set to 2 ps / C, 4 ps / C, 10 ps / C, and 20 ps / C respectively for simulation;
[0012] In model construction, the quality of graphene is reflected by counting the numbers of five-membered rings, six-membered rings, and seven-membered rings in the simulation results; The flatness of the growing graphene surface is characterized by the RMS (root mean square) roughness of graphene; By comparing the numbers of graphene basic units and the flatness of graphene under different deposition temperatures and deposition rates, the growth conditions of high-quality graphene are determined; By determining the optimal simulation parameters for preparing high-quality graphene, predictions are provided for the chemical vapor deposition of graphene.
[0013] The described potential function is used to reflect the mutual relationship among atoms during the growth of graphene on the surface of cemented carbide. The ABOP (analytical bond order potential) of the W-C-H system is used to express the mutual relationship between WC; the EAM (embedded atom method) potential function describes the interaction between metallic Co; the interaction between deposited carbon atoms is described by the Airebo potential function; the mutual relationship between WC and Co in cemented carbide is described by the Morse potential function; the interaction between deposited carbon atoms and WC, Co is described by the L-J (Lennard-Jones) potential function.
[0014] The beneficial effects of the present invention: Based on the excellent properties of graphene, predict the growth conditions of graphene on the surface of cemented carbide, deposit graphene at different deposition temperatures and deposition rates, compare its graphene basic unit and RMS, obtain a graphene layer with high quality, and further guide the energy consumption of actual CVD production of graphene and shorten the experimental period. Description of the Drawings
[0015] Figure 1 is the simulation flow chart of the method of the present invention;
[0016] Figure 2 is the simulation model of the deposition of graphene on the WC-Co surface constructed by the method of the present invention;
[0017] Figure 3 is the growth condition of graphene at a deposition temperature of 900K by the method of the present invention;
[0018] Figure 4 is the growth condition of graphene at a deposition temperature of 1300K by the method of the present invention;
[0019] Figure 5 is the growth condition of graphene at a deposition temperature of 1700K by the method of the present invention;
[0020] Figure 6 is the quality of the grown graphene at different deposition temperatures by the method of the present invention;
[0021] Figure 7 is the surface flatness of the grown graphene at different deposition temperatures by the method of the present invention;
[0022] Figure 8 is the growth condition of graphene at a CDR of 2ps / C by the method of the present invention;
[0023] Figure 9 is the growth condition of graphene at a CDR of 4ps / C by the method of the present invention;
[0024] Figure 10 The growth status of graphene under the condition that the CDR of the method of the present invention is 10 ps / C;
[0025] Figure 11 The growth status of graphene under the condition that the CDR of the method of the present invention is 20 ps / C;
[0026] Figure 12 The number of carbon rings of the grown graphene under different CDRs of the method of the present invention. Detailed implementation mode
[0027] The implementation mode of the present invention will be described in detail in combination with the accompanying drawings and embodiments.
[0028] Based on the theoretical basis of growing graphene by CVD, the factors affecting the growth of graphene are determined, and then a theoretical model of the cemented carbide substrate is constructed by the molecular dynamics theory. Using the conjugate gradient method in LAMMPS, the system temperature is relaxed for 20 ps to achieve system stability; secondly, when depositing graphene, relevant parameters (different deposition temperatures, deposition rates) are introduced for simulation calculation. The simulation results under different parameters are obtained, and the growth status of graphene is directly observed through visualization software; the RMS of graphene is calculated to evaluate the surface flatness of graphene and the number of basic units of graphene is counted to determine the simulation parameters for forming high-quality graphene, providing effective prediction and analysis for growing graphene by CVD in actual experiments.
[0029] Example 1
[0030] Establish a WC-Co substrate model of 2.872 nm × 2.872 nm × 2.259 nm through LAMMPS; adopt periodic boundaries in the X and Y directions to simulate an infinite surface, and adopt fixed boundaries in the Z direction. To prevent the bottom surface from moving, the atoms in the range of 0-3 Å in the Z direction are fixed; the system temperature control adopts the canonical ensemble (NVT), and the numerical integration of the kinetic equation in the system uses the velocity (Verlet) algorithm with a time step of 0.001 ps; the of WC with the space group of crystal plane and the (0001) crystal plane of Co with the space group of P63 / mmc are used as the deposition surfaces;
[0031] The ABOP potential of the W-C-H system is used to express the mutual relationship between WCs during the deposition process (as shown in Table 1); the EAM potential function describes the interaction between metallic Co; the interaction between deposited carbon atoms is described by the Airebo potential; the mutual relationship between WC and Co in the cemented carbide is described by the Morse potential (as shown in Table 2); the interaction between deposited carbon atoms and WC and Co is described by the L-J potential (as shown in Table 3);
[0032] Using the parameters in Table 1, construct the ABOP potential file through Tersoff programming, and place the ABOP file and the written program in the same folder.
[0033]
[0034]
[0035]
[0036] Using the conjugate gradient method, relax for 20 ps at different deposition temperatures (900 K, 1300 K, 1700 K) to make the system reach stability. Secondly, simulate the deposition process of graphene by inserting a single carbon atom, and the insertion rate of graphene is maintained at 10 ps / C for simulation.
[0037] Figures 3 - 5 are the simulation results of graphene at different deposition temperatures.
[0038] From Figures 3 - 5 the simulation results and Figures 6 - 7 the statistical results, it can be seen the growth of graphene at different temperatures. At Figures 3 - 4 , it is found that the graphene grown at this temperature has more defects and larger sizes. Figure 5 At , at high temperature and under the deposition of carbon atoms with huge energy, some metal cobalt atoms are evaporated, forming a large height difference with tungsten carbide, causing huge deformation of graphene, and the amount of metal cobalt as a binder becomes less, which will reduce the toughness of cemented carbide and is not conducive to actual processing and production.
[0039] From Figures 6 - 7 it can be obtained that high temperature will promote the migration of carbon atoms, which is helpful for generating graphene with fewer defects and high quality. However, too high temperature will damage the substrate, causing huge deformation of graphene and poor overall flatness, which is reflected in the increase of the RMS value of graphene. At the deposition temperature of 1300 K, the substrate of cemented carbide does not change greatly, and the number of five-membered, six-membered and seven-membered carbon rings in graphene is relatively large, and the quality of graphene generated at this temperature is also the best.
[0040] Example 2
[0041] Establish a WC-Co substrate model of 2.872 nm × 2.872 nm × 2.259 nm through LAMMPS; adopt periodic boundaries in the X and Y directions to simulate an infinite surface, and adopt fixed boundaries in the Z direction. To prevent the bottom surface from moving, fix the atoms in the range of 0 - 3 Å in the Z direction; the system temperature control adopts the canonical ensemble (NVT), and the numerical integration of the kinetic equation in the system uses the velocity (Verlet) algorithm with a time step of 0.001 ps; the space group is of WC The crystal plane of WC and the (0001) crystal plane of Co with the space group of P63 / mmc are used as the deposition plane;
[0042] In the deposition process, the ABOP potential of the W-C-H system is used to express the interaction between WC (as shown in Table 1 in Example 1); the EAM potential function describes the interaction between metallic Co; the interaction between deposited carbon atoms is described by the Airebo potential; the interaction between WC and Co in cemented carbide is described by the Morse potential (as shown in Table 2 in Example 1); the interaction between deposited carbon atoms and WC and Co is described by the L-J potential (as shown in Table 3 in Example 1);
[0043] Using the parameters in Table 1 of Example 1, an ABOP potential file is constructed through tersoff programming, and the ABOP file and the written program are placed in the same folder.
[0044] Using the conjugate gradient method, at a deposition temperature of 1100 K, relax for 20 ps to make the system reach stability. Secondly, the deposition process of graphene is simulated by inserting a single carbon atom, and the insertion rates of graphene are set to 2 ps / C, 4 ps / C, 10 ps / C, and 20 ps / C for simulation.
[0045] Figures 8 - 11 are the simulation results of graphene at different deposition rates.
[0046] Through Figures 8 - 9 , it can be seen that there are more defects and larger defect sizes in the graphene at CDR of 2 ps / C and 4 ps / C. In Figure 10 , for the simulation results at a CDR of 10 ps / C, the graphene has fewer defects, a higher substrate coverage rate, and a higher quality of the grown graphene. As Figure 11 shows, at a deposition rate of 20 ps / C, the carbon atoms agglomerate severely, the surface is uneven, and the quality of graphene growth deteriorates. Figure 12 It shows the quality of graphene grown at different deposition rates. It can be seen that at a deposition rate of 10 ps / C, the number of graphene grown is the largest, and the proportion of five-membered and six-membered rings of the obtained graphene is also the highest, and high-quality graphene growth can be achieved.
[0047] It can be obtained from Example 1 and Example 2 that when the deposition temperature is 1300 K and the deposition rate is 10 ps / C, the quality of the grown graphene is better.
Claims
1. A method for predicting the growth of graphene on the surface of cemented carbide, characterized in that: The method is based on the MD theory. By using LAMMPS to simulate and calculate the self-assembly of carbon atoms on the surface of cemented carbide and the graphene growth process, the growth conditions of graphene on the surface of cemented carbide are predicted at different deposition temperatures and deposition rates, and the simulation conditions for high-quality graphene are obtained. The specific content is as follows: Content 1: Calculation process Use MD simulation to study the growth process of graphene on the surface of cemented carbide: First, construct a cemented carbide substrate model. After 20 ps of temperature relaxation using the conjugate gradient method, the cemented carbide substrate reaches stability, and then carbon atoms are deposited. Set different deposition temperatures and the deposition rate of carbon atoms respectively to predict the growth of graphene on the surface of cemented carbide; To ensure the accuracy of the simulation, use relevant potential functions. Content 2: Model construction A 2.872 nm × 2.872 nm × 2.259 nm WC-Co substrate model was established using LAMMPS. Periodic boundaries were used in the X and Y directions to simulate an infinite surface, and fixed boundaries were used in the Z direction. To prevent the bottom surface from moving, the atoms in the Z direction were fixed at 0-3 Å. NVT was used for system temperature control, and the Verlet algorithm was used for numerical integration of the kinetic equations in the system with a time step of 0.001 ps. The space group was set to WC The (0001) crystal plane of Co with a crystal plane and space group of P63 / mmc was used as the deposition surface; Simplify the decomposition and deposition of hydrocarbon molecules into the deposition of a single carbon atom on the surface of WC-Co cemented carbide. The actual carbon source flow rate is characterized by CDR. Use the time interval for depositing one carbon atom to represent CDR, with the unit of ps / C. A total of 300 carbon atom deposition processes are simulated; Set three deposition temperatures of 900 K, 1300 K, and 1700 K to study the effect of temperature on graphene growth; To study the effect of different CDRs on the grown graphene, set CDRs to 2 ps / C, 4 ps / C, 10 ps / C, and 20 ps / C respectively for simulation. In model construction, the quality of graphene is reflected by counting the number of five-membered rings, six-membered rings, and seven-membered rings in the simulation results; The flatness of the grown graphene surface is characterized by the RMS roughness of graphene; By comparing the number of graphene basic units and the flatness of graphene at different deposition temperatures and deposition rates, the growth conditions for high-quality graphene are determined; By determining the optimal simulation parameters for preparing high-quality graphene, predictions are provided for the chemical vapor deposition of graphene.
2. The method for predicting the growth of graphene on the surface of cemented carbide according to claim 1, characterized in that: The potential function is used to reflect the mutual relationship between atoms during the growth of graphene on the surface of cemented carbide. The ABOP potential function of the W-C-H system is used to express the mutual relationship between WC; The EAM potential function describes the interaction between metallic Co; The interaction between deposited carbon atoms is described by the Airebo potential function; The mutual relationship between WC and Co in cemented carbide is described by the Morse potential function; The interaction between deposited carbon atoms and WC, Co is described by the L-J potential function.