Magnetic simulation method for simulating low-temperature oxidized geological sample
By constructing a double-core-shell structure model of magnetite and maghemite, and combining the exchange constant and oxidation kinetic model, a refined simulation of the low-temperature oxidation process was achieved, solving the problem of multiple solutions in the low-temperature oxidation process of geological samples and improving the consistency between the simulation results and experimental data.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-25
- Publication Date
- 2026-03-27
AI Technical Summary
Existing technologies struggle to accurately simulate the transformation of magnetite to maghemite during low-temperature oxidation in geological samples, especially in multiphase magnetic minerals where there is a lack of detailed modeling of continuous changes in the oxide layer and the exchange processes in the transition zone.
A double-core-shell structure model of magnetite and maghemite was constructed, and the interfacial exchange interaction constants for no exchange, weak exchange, and uniform exchange were set. The magnetic hysteresis parameters were calculated using Cubit and MERRILL software. The low-temperature oxidation process was simulated through a theoretical oxidation kinetic model, and an experimental statistical parameter optimization model was introduced to achieve batch simulation of multiple particle sizes and oxidation states.
It improves the consistency between simulation results and experimental data, enables more refined simulation of low-temperature oxidation processes, constructs a particle ensemble model with statistical characteristics, outputs hysteresis loops and micromagnetic structures, supports continuous transition regions and multiple exchange constant settings, and improves the reliability of simulation results.
Smart Images
Figure CN121744816A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of magnetic simulation, in particular to a method for simulating the magnetism of low-temperature oxidized geological samples. BACKGROUND
[0002] In the analysis of geological samples, rock magnetism faces challenges such as complex samples and strong parameter coupling, resulting in multiple solutions in interpretation. Micromagnetic simulation, as a theoretical means, can reveal the relationship between the internal magnetic structure of minerals and the macroscopic magnetic behavior, and has become an important tool for paleomagnetic research. Currently, micromagnetic simulation can handle the magnetic behavior of complex shapes (such as cubic octahedron, truncated octahedron, etc.) and particle collections.
[0003] However, existing researches mainly focus on complex shape particles or multi-phase mineral particle collections, and fail to truly reflect the differences in complex oxidation state magnetic structure of single particles and their evolution process in geological samples. Especially for the low-temperature oxidation process of magnetite to maghemite, which is common and important in nature, there is still a lack of corresponding means for micromagnetic modeling and simulation. In addition, there is also a lack of fine modeling of the continuous change of the oxidation layer and the exchange in the transition zone in multi-phase magnetic minerals. SUMMARY
[0004] The present application aims to solve the problems in the background art and provides a method for simulating the magnetism of low-temperature oxidized geological samples. The oxidation process is fine, which can simulate the low-temperature oxidation process, construct a double-layer core-shell structure of magnetite and maghemite, support continuous transition zones and multiple exchange constant settings, establish a particle collection model with statistical characteristics, output hysteresis loops and micromagnetic structures, and improve the consistency of simulation results and experimental data.
[0005] The technical scheme of the present application is a method for simulating the magnetism of low-temperature oxidized geological samples, comprising the following steps: S1. Constructing a double-layer structure model of magnetite and maghemite in Cubit software; S2. Setting the interface exchange interaction constants corresponding to three exchange types of no exchange, weak exchange and uniform exchange for the double-layer structure; S3. Calculating the hysteresis parameters under the three exchange interaction constants, and comparing them with the existing experimental results / literature results to determine which exchange constant value is closer to the experimental results / literature results as the parameter for the next step; S4. Constructing a complex multi-layer low-temperature oxidation model in Cubit software; S5. Constructing a low-temperature oxidation process model based on a theoretical oxidation kinetic model and simulating multiple particle sizes; S6, introduce the experimental statistical parameter optimization model, compare the simulation results with the measured hysteresis parameters, and perform optimization iteration of steps S4 and S5 until the model is fitted to the real sample to the desired degree of optimization iteration; S7, running MERRILL software batch calculation of hysteresis loop and micro-magnetic structure file, for the obtained micro-magnetic structure data file, using Tecplot / Paraview to draw multi-particle size micro-magnetic structure diagram, using Grapher / Origin to draw multi-particle size hysteresis loop.
[0006] Preferably, in the double-layer structure model, the core is magnetite and the shell is maghemite.
[0007] Preferably, in S1, the thickness ratio of core-shell structure is adjusted, and different oxidation degrees are formed in turn according to volume calculation: 27%, 49%, 78% and 99%.
[0008] Preferably, in S3, the magnetic hysteresis parameters of the magnetic particles under three exchange interaction constants are calculated by using MERRILL, and the curve of the magnetic hysteresis parameters changing with the oxidation degree is drawn.
[0009] Preferably, in S4, referring to the experimental results / literature results, the truncated octahedron magnetite model is constructed by using Webcut tool in Cubit, the single direction / whole direction elongation is performed by using Scale in Cubit, and the multi-layer cutting is performed by using Subtract tool to construct 20-layer core-shell structure model, form the simulation low-temperature oxidation geological sample model, and output the model to Patran format file by using Cubit for MERRILL to read.
[0010] Preferably, in S5, the oxidation parameters of the multi-layer core-shell structure are calculated based on the theoretical oxidation kinetics model, the parameter input file is edited, MERRILL reads the parameter input file and Patran format file for calculation, the magnetic properties of the geological sample under overall oxidation are calculated, the multi-particle size particles are simulated by MERRILL for the same oxidation parameter corresponding to the multi-layer structure physical parameter input file and the Patran format file of different particle sizes.
[0011] Preferably, the proportion corresponding to different particle size samples is calculated by the median particle size and standard deviation corresponding to the logarithmic normal distribution curve of the known literature sample, and the particle aggregation magnetic parameters are calculated by weighted calculation, and the non-uniform oxidation process of the geological sample is simulated.
[0012] Preferably, based on the numerical consistency, the sample morphology and sample distribution parameters are fine-tuned to further optimize the construction of complex model and iterative calculation.
[0013] Compared with the prior art, the present application has the following beneficial technical effects: the present application can realize the whole process numerical simulation from model construction, model testing, model optimization, oxidation simulation to result output and experimental comparison, can simulate low-temperature oxidation process, construct the double-layer core-shell structure of magnetite and maghemite, support the continuous transition zone and multiple exchange constant setting, establish the particle collection model with statistical characteristics, output the magnetic hysteresis loop and micromagnetic structure, and compare with the experimental data, optimize the model through the statistical parameters, and improve the consistency of the simulation results and the experimental data. BRIEF DESCRIPTION OF DRAWINGS
[0014] Figure 1 is a flowchart of the method of the present application; Figure 2 is a perspective view of the layer-by-layer oxidation of the magnetic particles based on the low-temperature oxidation kinetics; Figure 3 is a cross-sectional view of the layer-by-layer oxidation of the magnetic particles after numerical subdivision; Figure 4 is a diagram of the core magnetization structure of the simulated low-temperature oxidation geological sample by magnetism simulation, wherein the red curved surface represents the core magnetic field vortex orientation (sample particle size 80 nm, oxidation degree 98%); Figure 5 is a diagram of the internal magnetization vector structure of the simulated low-temperature oxidation geological sample by magnetism simulation, wherein the arrow represents the magnetization intensity vector, the color represents the included angle between the arrow and the field direction, and the color from red to blue represents the magnetization intensity vector parallel to and perpendicular to the external field direction, respectively, and the thickness of the yellow curved surface reflects the proportion of the core (parallel) magnetization intensity vector (sample particle size 80 nm, oxidation degree 92%). DETAILED DESCRIPTION
[0015] As shown in Figure 1 , the magnetic simulation method for simulating low-temperature oxidation geological samples proposed in the present embodiment comprises the following steps: S1、①In the Cubit finite element modeling software, a double-layer structure model of magnetite and maghemite is constructed by the create command with the model of brick, the core is magnetite, the shell is maghemite, the average particle size is 80 nm, and the shape factor is 1.30; in the input script file, the parameters of the two materials are set as follows: Magnetite: saturation magnetization M s = 4.8 × 10 5 A / m, magnetic crystal anisotropy constant K1 = -1.24 × 10 4 J / m 3 , exchange constant A ex = 1.34 × 10 -11 J / m; Maghemite: saturation magnetization M s = 3.8 × 105 A / m, magnetic crystalline anisotropy constant K1 = -4.6 x 10 3 J / m 3 , exchange constant A ex = 1.0 x 10 -11 J / m; ②Adjust the thickness ratio of core-shell structure, according to the volume calculation, form different oxidation degrees in turn: 27%, 49%, 78% and 99%.
[0016] S2, set the interface exchange interaction constants corresponding to three exchange types of no exchange, weak exchange and uniform exchange for the double-layer structure; ①No exchange interaction, A ex = 0 J / m, represents the decoupling relationship between the magnetite core and the maghemite shell during the oxidation process of magnetite: no exchange interaction at the interface; ②Weak exchange interaction, A ex = 5 x 10 -12 J / m, represents the weak coupling relationship between the magnetite core and the maghemite shell due to the difference in cell parameters during the oxidation process of magnetite; ③Uniform exchange interaction, A ex = 1.17 x 10 -11 J / m, represents a gradual and uniform transition relationship between maghemite and magnetite during the oxidation process of magnetite.
[0017] S3, Cubit exports the model as a Patran format file for MERRILL to read, MERRILL calculates the magnetic hysteresis parameters of the magnetic particles under three exchange interaction constants, draws the curve of the hysteresis parameters changing with the oxidation degree, and compares the hysteresis parameters with the existing experimental results / literature results to determine which exchange constant value is closer to the experimental results / literature results, and use it as the parameter for the next step.
[0018] S4, build a complex multi-layer low-temperature oxidation model in Cubit software: refer to the experimental results / literature results, use Webcut tool in Cubit to build a truncated octahedral magnetite model, set the aspect ratio to 1.3 and the average particle size to 80 nm; use Scale in Cubit for single direction / whole direction stretching, use Subtract tool for multi-layer cutting, build a 20-layer core-shell structure model, form a simulated low-temperature oxidation geological sample model; use Cubit to export the model as a Patran format file for MERRILL to read.
[0019] S5, constructing low-temperature oxidation process model based on theoretical oxidation kinetics model (continuous oxidation model proposed by Gallagher et al in 1968) and simulating particles of multiple particle sizes: based on the theoretical oxidation kinetics model, interpolation is performed on the oxidation parameters of the multi-layer core-shell structure, a parameter input file is edited, MERRILL reads the parameter input file and a Patran format file for calculation, the magnetic properties of the geological sample under overall oxidation are calculated, for the same oxidation parameters, a multi-layer structure physical parameter input file and a Patran format file of different particle sizes are input, and particles of multiple particle sizes (such as 40-140 nm) are simulated by MERRILL.
[0020] S6, introducing experimental statistical parameters (such as particle size distribution weighting) to optimize the model, calculating the proportion of different particle size samples corresponding to the median particle size and standard deviation of the lognormal distribution curve of the known literature sample, and calculating the particle lumped magnetic parameters by weighting, simulating the non-uniform oxidation process of the geological sample; comparing the simulation results with the measured magnetic hysteresis parameters, based on the numerical consistency, fine-tuning the sample morphology and sample distribution parameters, and performing optimization iteration of steps S4 and S5, further optimizing the construction of the complex model, and iteratively calculating until the model is fitted to the real sample to the required degree of optimization iteration.
[0021] S7, running the MERRILL software to batch calculate the hysteresis loop file (Hyst file) and the micromagnetic structure file (Data file), using Tecplot / Paraview to draw the multi-particle micromagnetic structure diagram for the obtained micromagnetic structure data file (Data file), and using Grapher / Origin to draw the multi-particle hysteresis loop.
[0022] Based on the double-layer iron oxide micromagnetic simulation, it is found through pre-experiment comparison that the simulation results obtained by using the uniform exchange corresponding to the interface exchange interaction constant can be better compared with the experimental results. Further combining the low-temperature oxidation kinetics, the truncated octahedron established by Cubit is divided into multiple layers as shown in Figure 2 , and a continuous oxidation structure is constructed to simulate the low-temperature oxidation process as much as possible.
[0023] After the low-temperature oxidation framework is constructed, the entire core-shell structure is combined to form a standard truncated octahedral particle. Then Cubit is used for finite element division, and the division unit is selected to be 8-9 nm. Figure 3 The cross-section view of the divided and oxidized particles is shown, and from the division unit distribution, the multi-layer oxidation structure can be seen. Among them, the exchange constant between the layers uses the uniform exchange constant obtained by comparing the double-layer structure with the experimental results.
[0024] MERRILL program operation is performed on the above particles, and typical simulation low-temperature oxidation geological sample internal magnetization structure diagrams are obtained using Tecplot / Paraview as shown in the figures. Figure 4 The magnetic vortex plane distribution of a typical sample is shown, and it is shown that when the magnetite is close to complete oxidation (98%), the magnetic vortex plane is still twisted and not strictly parallel to the elongation direction [1 1 1], which reflects the overall influence of low-temperature oxidation on the magnetic mineral particles. Figure 3
[0025] Figure 5 The internal magnetization structure of oxidized magnetite when the oxidation degree is 92% is shown, and the magnetization intensity vector presents an overall vortex state. The three-dimensional micromagnetic simulation can clearly show the orientation of the internal magnetization intensity vector distribution of the oxidized magnetite and the proportion of the core magnetization intensity vector. Figure 4 Compared with the prior art, this reflects that the vortex structure is still in an increasing state during the oxidation process.
[0026] The present application can realize the whole process numerical simulation from model construction, model testing, model optimization, oxidation simulation to result output and experimental comparison, can simulate the low-temperature oxidation process, construct the double-layer core-shell structure of magnetite and maghemite, support the continuous transition zone and multiple exchange constant setting, establish a particle collection model with statistical characteristics, including particle size logarithmic normal distribution, controllable shape, spatial random distribution, realize batch simulation of multiple particle sizes and multiple oxidation states, output the magnetic hysteresis loop and micromagnetic structure, and compare with the experimental data, optimize the model through statistical parameters, and improve the consistency of the simulation results and the experimental data.
[0027] The present application is based on the effectiveness of the simulation low-temperature oxidation geological sample modeling proved by the micromagnetic simulation results consistent with the experiments, and batch low-temperature oxidation simulation is performed. The simulation method enables researchers to understand the magnetization state of the geological sample under low-temperature oxidation from a three-dimensional perspective, and provides a visual basis for the mechanism of the geological sample recording the geomagnetic field. The model constructed by the present application covers multiple particle sizes, various shapes, multi-layer distribution and continuous change of oxidation state, is closer to the real geological sample, and has strong simulation. The oxidation process is more refined, supports the core-shell structure, continuous transition zone and multiple exchange constant mode, and can deepen the understanding of the low-temperature oxidation magnetism mechanism. Through statistical parameter optimization, the simulation results and the experimental data have good consistency in trend and magnitude, and have higher comparability. In addition, the present application can realize the whole process visualization from sample modeling to three-dimensional magnetic domain structure, support mechanism research and teaching demonstration, and can be popularized to other multi-phase cubic system minerals (such as pyrrhotite) and non-equal-dimensional space anisotropic sample modeling.
[0028] The embodiments of the present application are described in detail above with reference to the accompanying drawings, but the present application is not limited to the embodiments, and various changes can be made by those skilled in the art within the scope of knowledge acquired from the present disclosure, without departing from the spirit of the present application.
Claims
1. A magnetic simulation method for simulating low-temperature oxidized geological samples, characterized in that, Includes the following steps: S1. Construct a two-layer structure model of magnetite and maghematite in Cubit software; S2. Set the interface exchange interaction constants for three exchange types: no exchange, weak exchange, and uniform exchange for the two-layer structure. S3. Calculate the hysteresis parameters under the three exchange interaction constants and compare them with existing experimental / literature results to determine which exchange constant's numerical calculation results are closer to the experimental / literature results, and use them as parameters for the next step. S4. Construct a complex multilayer low-temperature oxidation model in Cubit software; S5. Construct a low-temperature oxidation process model based on a theoretical oxidation kinetics model and simulate particles of various sizes; S6. Introduce the experimental statistical parameter optimization model, compare the simulation results with the experimentally measured hysteresis parameters, and iterate through steps S4 and S5 until the model's fit with the real sample is optimized to the required degree. S7. Run the MERRILL software to batch calculate hysteresis loops and micromagnetic structure files. For the obtained micromagnetic structure data files, use Tecplot / Paraview to draw multi-particle-size micromagnetic structure diagrams and use Grapher / Origin to draw multi-particle-size hysteresis loops.
2. The magnetic simulation method for simulating low-temperature oxidized geological samples according to claim 1, characterized in that, In the two-layer structure model, the core is magnetite and the outer shell is maghemite.
3. The magnetic simulation method for simulating low-temperature oxidized geological samples according to claim 2, characterized in that, In S1, by adjusting the core-shell structure thickness ratio, different oxidation levels are formed sequentially based on volume calculations: 27%, 49%, 78%, and 99%.
4. The magnetic simulation method for simulating low-temperature oxidized geological samples according to claim 3, characterized in that, In S3, the hysteresis parameters of magnetic particles under three exchange interaction constants are calculated using MERRILL, and the curves of hysteresis parameters changing with the degree of oxidation are plotted.
5. The magnetic simulation method for simulating low-temperature oxidized geological samples according to claim 4, characterized in that, In S4, based on experimental and literature results, the Webcut tool in Cubit was used to construct a truncated octahedral magnetite model. The Scale tool in Cubit was used for unidirectional / omnidirectional stretching, and the Subtract tool was used for multi-layer cutting to construct a 20-layer core-shell structure model, forming a simulated low-temperature oxidation geological sample model. The model was then output as a Patran format file using Cubit for MERRILL to read.
6. The magnetic simulation method for simulating low-temperature oxidized geological samples according to claim 5, characterized in that, In S5, the oxidation parameters of the multi-layer core-shell structure are calculated by interpolation based on the theoretical oxidation kinetic model. The parameter input file is edited, and MERRILL reads the parameter input file and Patran format file for calculation. The magnetic properties of the geological sample under overall oxidation are calculated. For the same oxidation parameters, the physical parameter input file of the multi-layer structure and Patran format files with different particle sizes are simulated by MERRILL.
7. The magnetic simulation method for simulating low-temperature oxidized geological samples according to claim 6, characterized in that, By using the median particle size and standard deviation corresponding to the log-normal distribution curve of known literature samples, the proportion of samples with different particle sizes is calculated, the lumped magnetic parameters of the particles are calculated by weighting, and the non-uniform oxidation process of geological samples is simulated.
8. The magnetic simulation method for simulating low-temperature oxidized geological samples according to claim 7, characterized in that, Based on numerical consistency, the sample morphology and sample distribution parameters are fine-tuned to further optimize the construction of complex models and perform iterative calculations.