Analysis method for determining combustion performance of alumina crystal form
The combustion performance of alumina crystal form was analyzed through molecular dynamics simulation software, which solved the problems of high cost and time consumption in field tests, and achieved efficient combustion performance analysis.
Patent Information
- Application Number
- CN202510523013.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-24
- Publication Date
- 2025-07-29
AI Technical Summary
In the prior art, the combustion performance analysis of alumina crystal form mainly uses field test methods, resulting in high cost and time consumption, and the equipment is prone to damage.
Molecular dynamics simulation software was used to generate alumina shell data and oxygen molecular distribution data, and simulated combustion tests of different crystalline alumina forms were carried out to obtain activation energy to analyze combustion performance.
It reduces the loss of field tests, reduces the cost of tests, improves the efficiency of tests, and provides high resolution and flexible analysis methods.
Smart Images
Figure CN120388628A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of alumina combustion performance analysis, and particularly relates to an analysis method for determining the combustion performance of alumina crystal forms. Background Art
[0002] Metallic aluminum is widely used in solid propellants due to its excellent combustion performance. In practical applications, a layer of alumina usually forms on the surface of aluminum, and this alumina layer also affects the combustion process. The combustion performance of alumina is significantly affected by its crystal form. Different crystal forms of alumina have significant differences in structure and chemical properties, resulting in different performances during the combustion process.
[0003] There are mainly three crystal forms of alumina: α-Al2O3, θ-Al2O3, and γ-Al2O3. Different crystal forms may exhibit different reactivity, thermal stability, and heat release properties during the combustion process. Especially in a high-temperature environment, the crystal form transformation of alumina may significantly affect the combustion efficiency of aluminum powder and the overall performance of the propellant. Therefore, studying the combustion performance of different crystal forms of alumina not only helps to deeply understand the physical and chemical mechanisms during the combustion process but also provides a scientific basis for optimizing the design of solid propellants. By reasonably selecting the crystal form of alumina, the combustion efficiency can be improved while the stability and energy release characteristics of the propellant are improved, ultimately realizing the optimization and improvement of the propellant performance.
[0004] Currently, the analysis of the combustion performance of different crystal forms of alumina during the combustion process is mainly carried out through on-site test methods. However, this method requires a large amount of raw material and time costs, and even equipment damage may occur during the test process. Summary of the Invention
[0005] The purpose of the present invention is to provide an analysis method for determining the combustion performance of alumina crystal forms to reduce raw material costs and time costs and improve the test efficiency.
[0006] The present invention adopts the following technical solutions: an analysis method for determining the combustion performance of alumina crystal forms, including the following steps:
[0007] Obtain alumina ion crystal data of different crystal forms;
[0008] Generate alumina shell data of different crystal forms based on the alumina ion crystal data of different crystal forms, and the shell thickness and the number of atoms in the alumina shell data of different crystal forms are the same;
[0009] Import the oxygen molecule distribution data and the alumina shell data into a molecular dynamics simulation software, and establish an aluminum sphere inside the alumina shell generated from the alumina shell data; wherein, the oxygen molecule distribution data is established based on the oxygen molecule structure data and the test scenario.
[0010] Conduct simulated combustion tests on different crystal forms of alumina based on molecular dynamics simulation software;
[0011] Obtain the activation energy of the simulated combustion tests of different crystal forms of alumina, and analyze the combustion performance of different crystal forms of alumina based on the activation energy.
[0012] Furthermore, conducting simulated combustion tests on different crystal forms of alumina based on molecular dynamics simulation software includes:
[0013] Conduct simulated combustion tests on each crystal form of alumina based on molecular dynamics simulation software; among them, each simulated combustion test of alumina crystal form consists of a heating test and a combustion test conducted in sequence.
[0014] Furthermore, after conducting simulated combustion tests on different crystal forms of alumina based on molecular dynamics simulation software, it also includes:
[0015] Obtain the root mean square displacement of the simulated combustion tests of different crystal forms of alumina, and analyze the combustion performance of different crystal forms of alumina based on the root mean square displacement.
[0016] Furthermore, after conducting simulated combustion tests on different crystal forms of alumina based on molecular dynamics simulation software, it also includes:
[0017] Obtain the number of final combined body particles of the simulated combustion tests of different crystal forms of alumina, and analyze the combustion performance of different crystal forms of alumina based on the number of final combined body particles.
[0018] Furthermore, after conducting simulated combustion tests on different crystal forms of alumina based on molecular dynamics simulation software, it also includes:
[0019] Obtain the number of oxygen molecules in the simulated combustion tests of different crystal forms of alumina, and analyze the combustion performance of different crystal forms of alumina based on the number of oxygen molecules.
[0020] Furthermore, after conducting simulated combustion tests on different crystal forms of alumina based on molecular dynamics simulation software, it also includes:
[0021] Obtain the occurrence time of the transition state of the simulated combustion tests of different crystal forms of alumina, and analyze the combustion performance of different crystal forms of alumina based on the occurrence time of the transition state.
[0022] Furthermore, after conducting simulated combustion tests on different crystal forms of alumina based on molecular dynamics simulation software, it also includes:
[0023] Obtain the oxygen-aluminum ratio of the simulated combustion tests of different crystal forms of alumina, and analyze the combustion performance of different crystal forms of alumina based on the oxygen-aluminum ratio; among them, the oxygen-aluminum ratio is the ratio of the number of oxygen atoms to aluminum atoms in the final combined body particles.
[0024] Further, after performing simulation combustion tests on different crystal forms of alumina based on molecular dynamics simulation software, it further includes:
[0025] Obtaining the types of intermediate products of the simulation combustion tests of different crystal forms of alumina, and analyzing the combustion performance of different crystal forms of alumina based on the types of intermediate products.
[0026] Further, the types of intermediate products include the median and quartiles of the types of intermediate products.
[0027] The beneficial effects of the present invention are as follows: By generating alumina shell layer data according to alumina atomic data and then combining oxygen atom crystal data, the present invention can establish an experimental scenario in molecular dynamics simulation software and perform simulation combustion tests on different crystal forms of alumina, and can obtain the activation energy, so as to analyze the combustion performance of different crystal forms through the activation energy, which can reduce the losses generated by on-site tests, thereby reducing the test cost and improving the test efficiency. Description of the Drawings
[0028] Figure 1 It is a schematic structural diagram of the crystal structure model of different crystal forms of Al2O3 in the ovito software in the embodiment of the present invention;
[0029] Figure 2 It is the atomic-scale configuration of the Al2O3 shell layer corresponding to different crystal forms after being compiled with a packmol file in the embodiment of the present invention;
[0030] Figure 3 It is a schematic diagram of the cubic box of the simulation system in the embodiment of the present invention;
[0031] Figure 4 It is a trend chart of the root mean square displacement of aluminum atoms inside the aluminum ball evolving with time in the embodiment of the present invention;
[0032] Figure 5 It is a statistical distribution diagram of the types of products generated during the combustion process of aluminum particles under the coating conditions of different alumina crystal forms in the embodiment of the present invention;
[0033] Figure 6 It is a trend chart of the number of oxygen molecules evolving with time during the combustion process of aluminum particles in the embodiment of the present invention. Detailed Embodiment
[0034] The present invention will be described in detail below with reference to the drawings and specific embodiments.
[0035] α-Al2O3 is the most thermodynamically stable crystal form, with a dense hexagonal structure, strong surface inertness, high thermal conductivity, excellent oxidation resistance and structural stability in high-temperature combustion environments. However, its activity is relatively low, which is not conducive to the diffusion of reactants and their participation in reactions. θ-Al2O3 is an intermediate phase during the transformation from γ-phase to α-phase and belongs to transitional alumina. Its thermal stability lies between that of γ and α. Its crystal structure is relatively loose, with a certain specific surface area, and has medium-level combustion activity. However, it is prone to further phase transformation at high temperatures, affecting its long-term stability. γ-Al2O3 belongs to a highly active transitional phase, with a loose structure, a large specific surface area, and abundant active sites on the surface, which is conducive to reacting with aluminum and surrounding oxides, and can increase the combustion reaction rate in a short time. However, its thermal stability is the worst, and it is prone to phase transformation into a more stable phase at high temperatures.
[0036] Since the reaction process of tiny particles occurs within an extremely small range of spatial and temporal scales, it has become very difficult to directly observe experiments. In this case, molecular dynamics simulation becomes an effective tool that can provide atomic-level resolution, allowing researchers to directly observe and analyze the interactions between atoms and molecules, as well as their structures and motions. Such high-resolution data can provide a more detailed understanding of the microscopic behavior of substances. Secondly, researchers can easily adjust the simulation conditions and parameters as needed to explore different hypotheses and scenarios, without being restricted by experimental conditions and equipment, quickly obtaining a large amount of data and greatly saving costs and time. Additionally, molecular dynamics simulations do not cause any damage to the original system because they are carried out in a computer environment. This means that researchers can conduct more experiments without worrying about damaging or exhausting the samples. Generally speaking, molecular dynamics simulations have advantages such as high resolution, flexibility, cost-effectiveness, and non-destructiveness. Therefore, molecular dynamics simulation provides a powerful and flexible alternative solution for solving experimental problems.
[0037] The molecular dynamics simulation research on the combustion process of alumina mainly focuses on its mechanical properties or chemical reaction behaviors with other substances. However, the simulation of the combustion performance of different crystal forms of alumina at the atomic scale is still relatively scarce. The molecular dynamics method has the advantage of depicting the microscopic structure evolution process at the nanoscale, and can provide a theoretical basis for deeply understanding the regulation mechanism of crystal form on combustion behavior. Therefore, carrying out molecular dynamics simulation research on the combustion performance of different crystal forms of alumina not only fills the gap in existing research, but also provides important theoretical support and data basis for optimizing the design and application of aluminum-based fuel materials, having important scientific significance and engineering value.
[0038] The present invention discloses an analysis method for determining the combustion performance of alumina crystal forms, comprising the following steps: obtaining alumina ion crystal data of different crystal forms; generating alumina shell data of different crystal forms based on the alumina ion crystal data of different crystal forms; importing oxygen molecule distribution data and alumina shell data into molecular dynamics simulation software, and establishing aluminum spheres inside the alumina shell generated from the alumina shell data; wherein the oxygen molecule distribution data is established based on oxygen molecule structure data and test scenarios; conducting simulated combustion tests of different crystal forms of alumina based on the molecular dynamics simulation software; obtaining the activation energy of the simulated combustion tests of different crystal forms of alumina, and analyzing the combustion performance of different crystal forms of alumina based on the activation energy.
[0039] By generating alumina shell data according to the alumina ion crystal data and then combining with oxygen molecule data, the present invention can establish test scenarios in molecular dynamics simulation software and conduct simulated combustion tests of different crystal forms of alumina, and can obtain the activation energy, so as to analyze the combustion performance of different crystal forms through the activation energy, reduce the losses generated by on-site tests, thereby reducing the test cost and improving the test efficiency.
[0040] In one embodiment, download the cif data files of O2, α-Al2O3, θ-Al2O3 and γ-Al2O3 on the materials project website (i.e., crystal structure data, including atomic coordinates, bond lengths, bond angles, unit cell parameters, symmetry, etc.), then import the cif data files into materials studio software, and export pdb files that can be recognized and compiled by the packmol file.
[0041] Then, compile the pdb file with the packmol file to generate alumina shell data of different crystal forms, that is, set the arrangement, thickness and number of atoms of the Al2O3 shell. As Figure 2 shown, it is the atomic-scale configuration of the Al2O3 shell corresponding to different crystal forms after compilation with the packmol file. Among them, Figure (a) is the atomic-scale configuration (trigonal) of the Al2O3 shell of the α-Al2O3 crystal form, Figure (b) is the atomic-scale configuration (monoclinic) of the Al2O3 shell of the θ-Al2O3 crystal form, and Figure (c) is the atomic-scale configuration (cubic) of the Al2O3 shell of the γ-Al2O3 crystal form. It can be seen from the figure that under the condition of the same number of atoms and the same shell diameter, the shell density: α-Al2O3 > θ-Al2O3 > γ-Al2O3, which is the same as the actual situation. γ-Al2O3 is loose and porous and not dense enough. θ-Al2O3 is an intermediate phase during the transformation from γ-Al2O3 to α-Al2O3, with improved density but still having certain pores. α-Al2O3 is extremely dense and forms the most stable antioxidant protection layer.
[0042] It should be noted that in the alumina shell layer data of different crystal forms, the shell layer thickness and the number of atoms are the same. Moreover, due to the different crystal structures of different crystal forms, the arrangement of the Al2O3 shell layer in the obtained alumina shell layer data is different.
[0043] In the present invention, the oxygen molecule distribution data is established based on the oxygen molecule structure data and the test scenario. Similarly, the pdb file of O2 is compiled using the packmol file. During compilation, it should be ensured that the number of oxygen molecules is large enough to support the complete combustion of the aluminum atoms in the central Al sphere within the Al2O3 shell layer.
[0044] Import the compiled file into the ovito software, and then export the data files of O2 and the Al2O3 shell layer for preparing to establish the test environment. As Figure 1 shown, it is the structural schematic diagram of the crystal structure models of different crystal forms of Al2O3 in the ovito software. Among them, Figure (a) is the crystal structure model of the α-Al2O3 crystal form, Figure (b) is the crystal structure model of the θ-Al2O3 crystal form, and Figure (c) is the crystal structure model of the γ-Al2O3 crystal form.
[0045] Meanwhile, it is also necessary to write the test file in the molecular dynamics simulation software. This file contains instruction files such as test conditions and test parameters, including the crystal structure data of aluminum atoms.
[0046] In summary, after preparing to build the test environment, the test can be carried out. In the present invention, the LAMMPS software is selected for the test, and all simulations are run on a Linux computer cluster with 96 computing nodes.
[0047] Specifically, in the LAMMPS software, select the ReaxFFC / H / O force field parameters (environmental parameter set), and read 2 data files. As Figure 3 shown, set the parameters of the central Al sphere so that the simulation system is a cubic box with a large number of O2 surrounding the central Al sphere covered with an Al2O3 shell layer on the surface. Among them, Figure 3 (a) is the three-dimensional structural schematic diagram, Figure 3 (b) is the cross-sectional structural schematic diagram. The scattered points in the figure represent oxygen molecules, and the spherical shape represents the Al sphere and the Al2O3 shell layer on the surface.
[0048] Implement periodic boundary conditions in the three directions of the length, width, and height of the cubic box (that is, ensure that all particles always move within the cubic box) to simulate the particle behavior in the macroscopic system.
[0049] Set the type of potential function and set the potential function parameters.
[0050] Ensure that the system is in the lowest-energy stable state through the energy minimization step.
[0051] In the present invention, a simulated combustion test of each crystalline form of alumina is carried out based on a molecular dynamics simulation software; wherein, the simulated combustion test of each crystalline form of alumina consists of a heating test and a combustion test carried out in sequence.
[0052] The heating experiment adopts the NVT ensemble, aiming to ensure that the number of particles, volume and temperature during the simulated reaction process are all maintained constant, which is convenient for setting variables and modifying conditions.
[0053] The simulated system is heated and the temperature of the system is gradually increased from 300K to 1500K at a step size of 0.1fs (the change or non-change of the heating rate can be determined according to specific test conditions). The setting of the high temperature condition (1500K) aims to accelerate the chemical reaction rate in the simulation so as to observe a sufficient number of chemical reaction events within a limited time. It should be emphasized that the choice of reaction temperature only affects the reaction rate and does not change the internal mechanism of the chemical reaction.
[0054] Then, a combustion test is carried out using the NVE ensemble (natural combustion process). This system can be considered an isolated system, allowing the internal combustion reaction to heat up by itself. This stage has a relatively large number of running steps and a long running time, and the time step is set to 0.2fs.
[0055] During the simulation process, the number of each atomic group, the position of the system (the position of each atom), energy, root mean square displacement and the types of intermediate products of the whole system are counted, and the results are output once every 1000 steps (this output frequency is the same in both the NVT ensemble and the NVE ensemble).
[0056] In addition, in order to ensure the reliability of the simulation, each crystalline form is independently run 5 times. After the simulation is completed, data processing and visualization analysis are carried out.
[0057] Table 1
[0058]
[0059]
[0060] In the Arrhenius formula, that is k is the reaction rate (constant) coefficient; E a and A are respectively called the activation energy and the pre-exponential factor, which are two extremely important parameters in chemical kinetics; R is the molar gas constant; T is the thermodynamic temperature.
[0061] Meanwhile, as can be seen from Table 1, when the surface of the aluminum ball is covered with the γ-Al2O3 crystal form, the activation energy is the lowest, and the reaction is more likely to cross the energy barrier and enter the high-reactivity transition state stage, thus significantly reducing the energy threshold required for combustion. The lower activation energy not only helps to initiate the combustion reaction in advance but also accelerates the entire reaction process, demonstrating the positive effect of γ-Al2O3 on enhancing the reaction rate. This phenomenon further indicates that the γ-Al2O3 shell can effectively regulate the combustion kinetic behavior of the system during the combustion reaction. Its loose and porous structure reduces the energy barrier of the reaction at the aluminum-oxygen interface by providing a better oxygen diffusion channel or higher surface activity, thereby promoting the rapid progress of the combustion process.
[0062] In addition, as shown in Table 1, in this embodiment, the emergence time of the transition state of the simulated combustion tests of different crystal forms of alumina is also obtained, and the combustion performance of different crystal forms of alumina is analyzed based on the emergence time of the transition state. It can be seen from the data in the table that there are significant differences in the emergence time of the transition state and the activation energy required for the reaction during the combustion process of aluminum particles under different alumina crystal forms. Among them, the transition state under the condition of γ-Al2O3 appears earliest, only requiring 1346 ps, and the corresponding activation energy is the lowest, at 1339 kcal / mol. In contrast, the transition state times required for θ-Al2O3 and α-Al2O3 are 1488 ps and 1597 ps respectively, and the activation energies are higher. This shows that the combustion performance is better under the condition of γ-Al2O3.
[0063] Specifically, a curve graph is generated based on the energy fitting output by the software, and the emergence time of the transition state is found according to the curve graph.
[0064] In one embodiment, after performing the simulated combustion tests of different crystal forms of alumina based on the molecular dynamics simulation software, it further includes: obtaining the root mean square displacement of the simulated combustion tests of different crystal forms of alumina, and analyzing the combustion performance of different crystal forms of alumina based on the root mean square displacement.
[0065] The full name of MSD is Mean Square Displacement, which measures the average deviation degree of the position of a particle relative to its initial position after moving over time. Its definition is based on the position information of the particle, and its calculation formula usually involves taking the average of the squares of the changes in the particle's position. The root mean square displacement can be obtained by the software getting the position of each atom and then calculating based on all the output data.
[0066] In the embodiment of the present invention, the definition formula of MSD is as follows:
[0067]
[0068] Where N is the number of particles, t is the time of change, t0 is the initial time, r(t0) is the position of the particle at time t0, r(t0 + t) is the position of the particle at time t0 + t, and r i (t0 + t) - r i (t0) is the vector distance traveled by the particle over a period of time.
[0069] As Figure 4 shown, the trend of the root mean square displacement of aluminum atoms inside the aluminum sphere evolving with time is presented to reflect the activity degree of aluminum atoms and their ability to participate in reactions under different alumina coating conditions.
[0070] In the initial stage of combustion, since the aluminum core has not been fully exposed to the external oxygen environment, the overall MSD of aluminum atoms remains at a relatively low level, only showing limited thermal motion, mainly from the initial increase in system temperature and the preheating disturbance of the surface aluminum. At this time, the influence of different coating layers on MSD is not significant. In the later stage of the combustion reaction (after about 2000 ps), the simulation results show that the MSD of aluminum atoms exhibits an obvious crystal form dependence, and their magnitude relationship is: α - Al2O3 < θ - Al2O3 < γ - Al2O3. This trend indicates that under the γ - Al2O3 coating condition, the average displacement amplitude of aluminum atoms is the largest, indicating that they are subjected to stronger reaction driving and thermal disturbance, and have higher reactivity. This phenomenon shows that under the protection of the γ - Al2O3 shell layer, more oxygen molecules can effectively penetrate the alumina coating layer and diffuse into the aluminum sphere interior to react with the core aluminum atoms, thus triggering more intense chemical and thermal disturbances. After receiving the energy released by the reaction, the thermal motion of aluminum atoms intensifies, resulting in a significant increase in MSD. In contrast, due to its dense crystal structure and high thermal stability, α - Al2O3 forms a strong physical barrier to oxygen penetration, restricting the contact between oxygen and the aluminum core, and thus inhibiting the active movement of aluminum atoms.
[0071] It can be seen that the structural properties of the alumina shell layer have a key influence on the depth of the combustion reaction. The γ - Al2O3 crystal form provides more favorable microscopic channels for the transmission and reaction of oxygen molecules due to its more lattice defects, higher porosity, and larger diffusion coefficient, thus enabling more complete oxidation reactions and more uniform energy release. This not only improves the combustion integrity of aluminum particles but also enhances their energy conversion efficiency as fuel materials.
[0072] In one embodiment, after conducting simulated combustion tests of different crystal forms of alumina based on molecular dynamics simulation software, it further includes: obtaining the final number of combined body particles in the simulated combustion tests of different crystal forms of alumina, and analyzing the combustion performance of different crystal forms of alumina based on the final number of combined body particles.
[0073] Table 2
[0074]
[0075] As can be seen from the data in Table 2, under the condition of the same reaction time, there are obvious differences in the formation efficiency of the final reaction products among the three different crystal forms of alumina. Specifically, the number of the final combined body particles (i.e., the total number of the product particles) formed under the condition of γ-Al2O3 is the largest, which is 14,206, significantly higher than that of θ-Al2O3 (13,722) and α-Al2O3 (13,395).
[0076] In addition, after performing the simulated combustion tests of different crystal forms of alumina based on the molecular dynamics simulation software, it also includes: obtaining the oxygen-aluminum ratio of the simulated combustion tests of different crystal forms of alumina, and performing combustion performance analysis on different crystal forms of alumina based on the oxygen-aluminum ratio; wherein, the oxygen-aluminum ratio is the ratio of the number of oxygen atoms to the number of aluminum atoms in the final combined body particles.
[0077] The oxygen-aluminum ratio is the ratio of the number of oxygen atoms to the number of particles in the combustion product. As shown in Table 2, the oxygen-aluminum ratio corresponding to the condition of γ-Al2O3 is 1.457, which is closest to the theoretical value of 1.5 corresponding to the complete reaction. This result indicates that under the condition of generating the γ-Al2O3 crystal form on the surface of the aluminum ball, the reaction between oxygen molecules and aluminum particles proceeds faster and more fully.
[0078] In contrast, the oxygen-aluminum ratios under the crystal forms of α-Al2O3 and θ-Al2O3 are slightly lower, which are 1.372 and 1.396 respectively, and the corresponding number of combined body particles is also relatively small. Especially for the relatively dense α-Al2O3, there may be a certain inhibitory effect on the diffusion of oxygen or the oxidation rate of aluminum. Combining with the porous structure of γ-Al2O3, it can be speculated that it is more likely to have an interfacial reaction with oxygen during the reaction process, thereby promoting the continuous combustion of aluminum particles.
[0079] In one embodiment, after performing the simulated combustion tests of different crystal forms of alumina based on the molecular dynamics simulation software, it also includes: obtaining the number of oxygen molecules in the simulated combustion tests of different crystal forms of alumina, and performing combustion performance analysis on different crystal forms of alumina based on the number of oxygen molecules.
[0080] Such as Figure 6As shown, it presents the changing trend of the number of oxygen (O2) molecules during the combustion process of aluminum particles over time, revealing the significant influence of different alumina crystal forms on the combustion behavior. The simulation results show that in the initial stage of the combustion reaction, the consumption rates of O2 are in the order of: α-Al2O3 < θ-Al2O3 < γ-Al2O3, showing an obvious crystal form dependence. Especially under the condition of γ-Al2O3 coating, the consumption rate of O2 molecules is significantly higher than that of the other two crystal forms, indicating that in the initial stage of the reaction, O2 is more likely to penetrate the γ-Al2O3 shell and react with the internal aluminum core. This result shows that the γ-Al2O3 crystal form, due to its relatively loose structure, more defects or pores, helps the diffusion of oxygen molecules, so that more O2 molecules can participate in the reaction in time, significantly enhancing the reaction activity and rate in the initial stage.
[0081] After entering the middle and late stages of the reaction, the O2 consumption rates under the three crystal form conditions gradually tend to be the same, and the difference begins to narrow. This is mainly because the aluminum core gradually decreases after experiencing a violent reaction, and the reaction tends to be limited by the diffusion of the remaining reactants and the interfacial reaction rate. At this time, even if the oxygen molecules in the system can penetrate the shell, the contact area between them and aluminum has decreased significantly, resulting in the reaction tending to be gentle. In addition, with the increase in temperature and the gradual rupture or erosion of the shell, the differential influence of the three alumina crystal forms on the shell structure is further weakened, making the overall O2 reaction trend tend to converge.
[0082] From the perspective of the energy barrier, there are many surface defects and amorphous characteristics in the γ-Al2O3 structure, and its diffusion channel energy barrier is relatively low, which is conducive to the migration and penetration of O2 molecules; while α-Al2O3, as the most thermodynamically stable crystal form, has a dense structure and few defects, forming a strong barrier to the diffusion of O2, thereby reducing the reaction activity in the early stage. Therefore, the difference in the O2 consumption rate between different crystal forms not only comes from the permeability of the physical structure, but is also jointly regulated by the shell stability and the interfacial reaction energy barrier.
[0083] In one embodiment, after performing the simulated combustion tests of alumina with different crystal forms based on the molecular dynamics simulation software, it further includes: obtaining the types of intermediate products of the simulated combustion tests of alumina with different crystal forms, and analyzing the combustion performance of alumina with different crystal forms based on the types of intermediate products. Specifically, the types of intermediate products include the median and quartiles of the types of intermediate products.
[0084] As Figure 5 shown, it presents the statistical distribution of the types of products generated during the combustion process of aluminum particles under the conditions of different crystal form alumina coatings, presenting the median and the quartile range in the form of a box plot to evaluate the severity of the reaction and the abundance of active species.
[0085] As can be seen from the figure, under the condition of α-Al2O3 coating, the median of the types of combustion products is 25, and the interquartile range is from 20 to 30, indicating that the product composition is relatively limited; while under the condition of θ-Al2O3 coating, the median increases to 40, and the interquartile range expands to 30 to 50, indicating an increase in the types of products and enhanced reaction activity; particularly significant is the condition of γ-Al2O3 coating, where the median of the types of combustion products is as high as 45, and the interquartile range is concentrated between 40 and 50, indicating that a large number of free radicals and intermediate products are formed under this condition, reflecting a more intense and complex combustion reaction process.
[0086] This result indicates that the γ-Al2O3 crystal form coating significantly promotes the generation and accumulation of free radicals during the combustion process. The abundance of free radical species usually means longer reaction chains and more reaction paths, thus accelerating the cascade effect of the oxidation reaction. At the same time, a higher free radical concentration also increases the collision probability between them, further enhancing the non-linear coupling characteristics of the reaction system and prompting the combustion reaction to proceed at a faster rate.
[0087] Combined with the foregoing analysis of the oxygen consumption rate, it can be speculated that the γ-Al2O3 coating not only improves the efficiency of oxygen diffusion and contact with the aluminum core, but also further promotes the evolution of the reaction system towards high temperature and high reactivity by enhancing the free radical activity.
[0088] In addition, the possible lattice defects, amorphous regions and higher specific surface area in the γ-Al2O3 structure help to provide more reaction sites at the initial stage of combustion, which is beneficial to the generation and transformation of active intermediates. These structural characteristics endow it with excellent diffusion channels and free radical reaction sites during the combustion process, explaining its significant advantages in terms of the quantity of combustion products and reaction intensity from the micro-mechanism level.
[0089] In summary, through the combustion performance analysis of aluminum balls coated with different crystal forms of alumina shells from different dimensions, the present invention can clarify the influence of different crystal forms of alumina shells on the combustion performance. Of course, it is also possible to freely select and combine from the above multiple dimensions to form new dimension combinations for the combustion performance analysis.
Claims
1. An analytical method for determining the combustion performance of alumina crystal forms, characterized in that, It includes the following steps: Obtain the alumina ionic crystal data of different crystal forms; Generate the alumina shell data of different crystal forms based on the alumina ionic crystal data of different crystal forms; Import the oxygen molecule distribution data and the alumina shell data into the molecular dynamics simulation software, and establish an aluminum sphere inside the alumina shell generated by the alumina shell data; wherein, the oxygen molecule distribution data is established based on the oxygen molecule structure data and the test scenario; Conduct simulated combustion tests of alumina with different crystal forms based on the molecular dynamics simulation software; Obtain the activation energy of the simulated combustion tests of alumina with different crystal forms, and conduct combustion performance analysis on the alumina with different crystal forms based on the activation energy.
2. The analytical method for determining the combustion performance of alumina crystal forms according to claim 1, characterized in that, Generating the alumina shell data of different crystal forms based on the alumina ionic crystal data of different crystal forms includes: The shell thickness and the number of atoms in the alumina shell data of different crystal forms are the same.
3. The analytical method for determining the combustion performance of alumina crystal form according to claim 2, characterized in that Conducting simulated combustion tests of alumina with different crystal forms based on the molecular dynamics simulation software includes: Conduct simulated combustion tests of each crystal form of alumina based on the molecular dynamics simulation software; wherein, each simulated combustion test of alumina of a crystal form consists of a heating test and a combustion test conducted in sequence.
4. The analytical method for determining the combustion performance of alumina crystal forms according to claim 2 or 3, characterized in that, After conducting simulated combustion tests of alumina with different crystal forms based on the molecular dynamics simulation software, it further includes: Obtain the root mean square displacement of the simulated combustion tests of alumina with different crystal forms, and conduct combustion performance analysis on the alumina with different crystal forms based on the root mean square displacement.
5. An analytical method for determining the combustion performance of alumina crystal forms as described in claim 2 or 3, characterized in that, After conducting simulated combustion tests of alumina with different crystal forms based on the molecular dynamics simulation software, it further includes: Obtain the number of final aggregate particles of the simulated combustion tests of alumina with different crystal forms, and conduct combustion performance analysis on the alumina with different crystal forms based on the number of final aggregate particles.
6. The analytical method for determining the combustion performance of alumina crystal forms according to claim 2 or 3, characterized in that, After conducting simulated combustion tests of alumina with different crystal forms based on the molecular dynamics simulation software, it further includes: Obtain the number of oxygen molecules in the simulated combustion tests of alumina with different crystal forms, and conduct combustion performance analysis on the alumina with different crystal forms based on the number of oxygen molecules.
7. The analytical method for determining the combustion performance of alumina crystal form according to claim 2 or 3, characterized in that After conducting simulated combustion tests of alumina with different crystal forms based on the molecular dynamics simulation software, it further includes: Obtain the occurrence time of the transition state of the simulated combustion tests of alumina with different crystal forms, and conduct combustion performance analysis on the alumina with different crystal forms based on the occurrence time of the transition state.
8. The analytical method for determining the combustion performance of alumina crystal forms as described in claim 2 or 3, characterized in that After conducting simulated combustion tests of alumina with different crystal forms based on the molecular dynamics simulation software, it further includes: Obtain the oxygen-aluminum ratio of the simulated combustion tests of alumina with different crystal forms, and conduct combustion performance analysis on the alumina with different crystal forms based on the oxygen-aluminum ratio; wherein, the oxygen-aluminum ratio is the ratio of the number of oxygen atoms to the number of aluminum atoms in the final aggregate particles.
9. The analytical method for determining the combustion performance of alumina crystal form according to claim 2 or 3, characterized in that, After conducting simulated combustion tests of alumina with different crystal forms based on the molecular dynamics simulation software, it further includes: Obtain the types of intermediate products of the simulated combustion tests of alumina with different crystal forms, and conduct combustion performance analysis on the alumina with different crystal forms based on the types of intermediate products.
10. The analytical method for determining the combustion performance of alumina crystal form according to claim 8, characterized in that, The types of intermediate products include the median and quartiles of the types of intermediate products.