Reaction simulation thermodynamic prediction method for rare earth element-containing product

Abstract

The invention discloses a reaction simulation thermodynamic prediction method for a rare earth element-containing product, which comprises the following steps: step 1, constructing a reaction system involved in a material high-temperature synthesis process, and giving standard Gibbs free energy of each reaction; step 2, calculating each Gibbs free energy of all possible reactions according to the mass fraction of each component in the material; 3, determining a simulation direction sequence according to the Gibbs free energy result of each reaction in the step 2; 4, the reaction simulation process is controlled according to the proportion that the amount of reactants is reduced by not more than 1 / 1000 every time, when the Gibbs free energy of all the reactions changes to 0, the system is balanced, and the obtained rare earth product is the final balanced product. The method enriches the thermodynamic data of rare earth products, can predict complex system products and intermediate products which do not reach an equilibrium state, and can be used for explaining the generation principle of products with sandwich structures.

Description

Technical Field

[0001] The invention relates to the technical field of product reaction simulation, and in particular to a reaction simulation thermodynamic prediction method for products containing rare earth elements. Background Art

[0002] Rare earth refers to the general term for elements such as lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium. Rare earth elements are usually scarce on Earth, but adding rare earth elements to products composed of multiple elements such as alloys or ceramics often produces unique performance effects, so rare earths are often added as an additive to the preparation of products such as alloys or ceramics. The preparation of such multi-element products is usually accompanied by a heating reaction process, and the process has been simulated by using computers for thermodynamic reactions to conduct scientific research on the reaction process and product types.

[0003] At present, there are problems such as incomplete product data and unclear generation process in the synthesis or production process of inclusions in multi-element products containing rare earth materials (such as alloys or ceramics). Specifically, it is because there is a lack of thermodynamic data on complex products related to rare earths in existing thermodynamic reaction simulation software or methods. The prediction of rare earth product types is based on the minimum Gibbs of the system in equilibrium state, and it is impossible to evaluate the type and quantity of products in non-equilibrium state.

[0004] Therefore, how to provide a technology that can better simulate the preparation reaction process of rare earth element-containing products to better predict the type and quantity of reaction products has become a problem that technical personnel in this field need to consider and solve. Summary of the invention

[0005] In view of the deficiencies of the above-mentioned prior art, the technical problem to be solved by the present invention is: how to provide a reaction simulation thermodynamic prediction method for rare earth element products that can better simulate the preparation reaction process of rare earth element products to better predict the type and quantity of reaction products; further solve the problem of missing thermodynamic data of complex products containing rare earth products and enrich the thermodynamic database of rare earths.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A reaction simulation thermodynamic prediction method for a product containing a rare earth element comprises the following steps:

[0008] Step 1, for a material with a given initial composition, a reaction system involved in the high-temperature synthesis process of the material is constructed in a computer through programming software (Visual Basic 6 software), the reaction system includes chemical reaction equations of all elements including rare earths involved in the high-temperature synthesis process, and the standard Gibbs free energy of each reaction is given;

[0009] The standard Gibbs free energy construction method of the complex liquid phase product is as follows, wherein the complex liquid phase product refers to a complex oxide composed of three or more component oxides in any proportion (for example, xCe2O3·yAl2O3·(1-xy)ySiO2 composed of Al2O3, SiO2, and Ce2O3);

[0010]

[0011] In the formula: x, y are the molar fractions of Ce2O3 and Al2O3 in the liquid product, respectively, z = 2 + x + y; R is the ideal gas constant, 8.314 J / (mol·K); T is the reaction temperature;

[0012] The excess Gibbs free energy of the corresponding composition points of each binary system (e.g. Ce2O3-Al2O3, Al2O3-SiO2, Ce2O3-SiO2);

[0013] are the interaction parameters between binary system components (e.g. Ce2O3-Al2O3, Al2O3-SiO2, Ce2O3-SiO2);

[0014] Step 2, calculate each Gibbs free energy of all possible reactions based on the mass fraction of each component in the material;

[0015] The activity of the reaction product is calculated based on the pure substance (solid inclusions are pure solid phase, liquid inclusions are liquid phase) as the standard state, and the activity of the reactant is calculated based on Henry's law, assuming a 1% dilute solution as the standard state.

[0016] Step 3, based on the Gibbs free energy results of each reaction in step 2, determine the independent reactions and simulate them in the direction where the Gibbs free energy changes to a negative value at the same time, and the reaction with the most negative Gibbs free energy change among the interrelated reactions is simulated first; for liquid inclusions, the liquid product component with the smallest Gibbs free energy in the system is simulated first;

[0017] Step 4, for the chemical reactions that can be carried out in step 3, the reaction simulation process is controlled by reducing the amount of reactants by no more than 1 / 1000 each time, and can be smaller according to the accuracy requirements; when the Gibbs free energy change of all reactions is 0, the system reaches equilibrium, and the composition at this time is the equilibrium composition of the system, and the obtained rare earth product is the final equilibrium product.

[0018] In this way, the thermodynamic reaction process is simulated according to the above steps, and the type and quantity of rare earth related products are predicted by a step-by-step reaction method. In this way, according to the analysis needs, the reaction can be stopped at any time when it reaches a non-equilibrium state, and then the kinetic factors of product generation are investigated and analyzed. Therefore, this method not only improves the prediction accuracy of rare earth products, but also can reflect the type of product generated in the intermediate process through the number of reaction steps.

[0019] Furthermore, in step 2, the maximum activity of the reaction product is set to 1, and the activity coefficient of the reactant is calculated using the Wagner approximation; the specific expression is as follows,

[0020]

[0021] where f i is the activity coefficient of component i; w [j] w [k] are the mass fractions of components j and K respectively; is the first-order activity interaction coefficient of component j on component i; is the second-order activity interaction coefficient of components j and k on component i;

[0022] Among them, the principle of determining the activity coefficient is to give priority to the expression of the relationship between the activity interaction coefficient and temperature obtained from the experiment; if the expression of the relationship between the activity interaction coefficient and temperature is missing, the activity interaction coefficient at the known temperature is corrected by the following formula; if there is divalent activity interaction coefficient data, it is fully utilized as much as possible to ensure the accuracy of the activity coefficient; if none of the above activity interaction coefficients exist, the data of the same family with similar chemical properties or elements with similar distances in the periodic table of chemical elements are used; if none of the above data exist, their influence is ignored and the activity interaction coefficient is 0;

[0023] The corrected expression of the activity interaction coefficient is as follows:

[0024]

[0025] in: is the first-order activity interaction coefficient of component j on component i.

[0026] Further: In step 3, if the Gibbs free energy of the reaction is positive, the reaction proceeds in the reverse direction when the content of the reaction product is greater than zero.

[0027] The present invention has the following characteristics:

[0028] 1. Compared with the existing thermodynamic commercial software databases and thermodynamic model data, the thermodynamic data of pure substances such as Ce2O2S, Ce2Si2O7, La2Si2O7, Ce2SiO5, La2SiO5, La 4.67 Si3O 13 , Ce 4.67 Si3O 13 etc. are enriched within a certain temperature range.

[0029] 2. Compared with the existing thermodynamic commercial software databases and thermodynamic model data, the phase diagram optimization calculation technology is adopted to obtain the thermodynamic data of rare earth liquid phase components such as Ce 2x Al 2y Si 1-x-y O 2+x+y etc., and the rare earth-containing products in the complex solution phase can be calculated.

[0030] 3. For the thermodynamic reactions of complex systems, the mutually independent reactions proceed simultaneously in the direction of negative Gibbs free energy change, and among the mutually related reactions, the reaction with the most negative Gibbs free energy change proceeds preferentially. In this way, the order of the formation of reaction products can be simulated, and the simulation accuracy can be improved.

[0031] 4. For liquid inclusions such as Ce 2x Al 2y Si 1-x-y O 2+x+y , taking 0 < x < 1 and 0 < y < 1 - x, the liquid phase product components with the minimum Gibbs free energy in the system are preferentially formed. In this way, the proportion of the main components preferentially formed in the complex liquid phase products can be simulated.

[0032] 5. For the thermodynamic reactions of complex systems, the reaction progress of each step can be set, such as 1 / 1000 of the reactants at a time, or even smaller. In this way, the generation and disappearance processes of reaction products when the equilibrium state has not been reached can be simulated.

[0033] 6. When the Gibbs free energy change of all reactions is 0, the system reaches equilibrium, and the composition at this time is the final product of the system.

[0034] In summary, the present invention enriches the thermodynamic data of rare earth products, can predict the types and quantities of rare earth products in complex systems more systematically and comprehensively; pays more attention to the reaction process when multiple reactions proceed simultaneously, can predict the products and intermediate products of complex systems that have not reached the equilibrium state, and can be used to explain the formation principle of products with sandwich structures. Brief Description of the Drawings

[0035] Figure 1This is a comparison chart of the electron microscope scanning and energy spectrum analysis results of the reactants after pre-melting Fe-Cr-Ni alloy and Si deoxidation and Ce alloying reaction, and the simulation prediction results of this method; Figure 1 a is the morphology and energy spectrum of Ce2O3 product found in the alloy pre-melting experiment; Figure 1 b is the morphology and energy spectrum of the Ce2O2S product found in the alloy pre-melting experiment.

[0036] Figure 2 This is a graph showing the reaction products calculated using the model of the present invention during comparative test verification. Figure 2 b is Figure 2 A partial enlarged view of a. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0038] Best mode of implementation: A method for thermodynamic prediction of reaction simulation of products containing rare earth elements, comprising the following steps:

[0039] Step 1, for a material with a given initial composition, a reaction system involved in the high-temperature synthesis process of the material is constructed in a computer through programming software (Visual Basic 6 software), the reaction system includes chemical reaction equations of all elements including rare earths involved in the high-temperature synthesis process, and the standard Gibbs free energy of each reaction is given;

[0040] In this embodiment, taking the Fe-Cr-Ni alloy material containing rare earth cerium as an example, during its high temperature synthesis process, there will be 2[Ce]+3[O]=Ce2O3(s), [Ce]+2[O]=CeO2(s), [Ce]+[S]=CeS(s), [Ce]+2[S]=CeS2(s), 2[Ce]+3[S]=Ce2S3(s), 3[Ce]+4[S]=Ce3S4(s), 2[Ce]+2[O]+[S]=Ce2O2S(s), [Ce]+[Al]+3[O]=CeAlO3(s), 4.67[Ce]+3[Si]+13[O]=Ce 4.67 SiO 13 (s), 2x[Ce]+2y[Al]+(1-xy)[Si]+z[O]=Ce 2x Al 2y Si 1-x-y O z (l) Chemical reactions such as 2[Ce]+3[O]=Ce2O3(s), ΔG θ =-1431090+360.06T.

[0041] The method for constructing the standard Gibbs free energy of complex liquid-phase products is as follows, where the complex liquid-phase products refer to complex oxides composed of three or more component oxides in any proportion;

[0042]

[0043] In the formula: x and y are the mole fractions of Ce2O3 and Al2O3 in the liquid-phase product respectively, and z = 2 + x + y; R is the ideal gas constant, 8.314 J / (mol·K); T is the reaction temperature;

[0044] are the excess Gibbs free energies at the corresponding composition points of the binary systems Ce2O3 - Al2O3, Al2O3 - SiO2, and Ce2O3 - SiO2 respectively;

[0045] are the interaction parameters between the binary system components (such as Ce2O3 - Al2O3, Al2O3 - SiO2, Ce2O3 - SiO2) respectively;

[0046] Step 2: Calculate the Gibbs free energy of each possible reaction according to the mass fractions of the components in the material; taking the reaction a[A] + b[B] = A a B b (s) as an example, its Gibbs free energy is constructed as follows,

[0047]

[0048] ΔG represents the Gibbs free energy of the reaction equation; ΔG θ represents the standard Gibbs free energy of the reaction equation; a represents the activity of the reaction product or reactant;

[0049] Among them, the activity of the reaction product is calculated with the pure substance (the solid-phase inclusion is the pure solid phase, and the liquid-phase inclusion is the liquid phase) as the standard state, and the activity of the reactant is calculated based on Henry's law with the hypothetical 1% mass fraction dilute solution as the standard state;

[0050] Step 3: According to the Gibbs free energy results of each reaction in Step 2, determine that the mutually independent reactions are simultaneously simulated in the direction of negative Gibbs free energy change, and the reaction with the most negative Gibbs free energy change in the mutually related reactions is preferentially simulated; for the liquid-phase inclusion Ce 2x Al 2y Si 1-x-y O 2+x+y , taking 0 < x < 1, 0 < y < 1 - x, the component of the liquid-phase product with the minimum Gibbs free energy in the system is preferentially simulated;

[0051] Step 4, for the chemical reactions that can be carried out in step 3, the reaction simulation process is controlled by reducing the amount of reactants by no more than 1 / 1000 each time, and can be smaller according to the accuracy requirements; when the Gibbs free energy change of all reactions is 0, the system reaches equilibrium, and the composition at this time is the equilibrium composition of the system, and the obtained rare earth product is the final equilibrium product.

[0052] In this way, the thermodynamic reaction process is simulated according to the above steps, and the type and quantity of rare earth related products are predicted by a step-by-step reaction method. In this way, according to the analysis needs, the reaction can be stopped at any time when it reaches a non-equilibrium state, and then the kinetic factors of product generation are investigated and analyzed. Therefore, this method not only improves the prediction accuracy of rare earth products, but also can reflect the type of product generated in the intermediate process through the number of reaction steps.

[0053] During implementation, in step 2, the maximum activity of the reaction product is set to 1, and the activity coefficient of the reactant is calculated using the Wagner approximation; the specific expression is as follows,

[0054]

[0055] where f i is the activity coefficient of component i; w [j] w [k] are the mass fractions of components j and K respectively; is the first-order activity interaction coefficient of component j on component i; is the second-order activity interaction coefficient of components j and k on component i;

[0056] Among them, the principle of determining the activity coefficient is to give priority to the expression of the relationship between the activity interaction coefficient and temperature obtained from the experiment; if the expression of the relationship between the activity interaction coefficient and temperature is missing, the activity interaction coefficient at the known temperature is corrected by the following formula; if there is divalent activity interaction coefficient data, it is fully utilized as much as possible to ensure the accuracy of the activity coefficient; if none of the above activity interaction coefficients exist, the data of the same family with similar chemical properties or elements with similar distances in the periodic table of chemical elements are used; if none of the above data exist, their influence is ignored and the activity interaction coefficient is 0;

[0057] The corrected expression of the activity interaction coefficient is as follows:

[0058]

[0059] in: is the first-order activity interaction coefficient of component j on component i.

[0060] During implementation: In step 3, if the Gibbs free energy of the reaction is positive, the reaction proceeds in the reverse direction when the content of the reaction product is greater than zero.

[0061] The chemical reactions that may be involved in the above process reaction system include the following:

[0062]

[0063] Among them, the reaction Gibbs free energy of complex liquid phase products can be carried out according to the following formula. Like the reaction formula above, the Gibbs free energy needs to be calculated. However, the Gibbs free energy of complex liquid phase products containing rare earths has variables in component composition, and the calculation is more difficult. Therefore, it is presented separately based on the above table.

[0064]

[0065] In the above formula: x, y are the molar fractions of Ce2O3 and Al2O3 in the liquid phase product respectively.

[0066] In addition, in order to further verify the simulation prediction effect of the present invention, the applicant further conducted comparative test verification.

[0067] During the verification, in a high-temperature tubular silicon-molybdenum furnace protected by Ar gas atmosphere, a Fe-Cr-Ni alloy that meets the composition ratio of 253MA heat-resistant steel is pre-melted in a MgO crucible at 1600°C, and then Si deoxidation and Ce alloying are carried out successively. The samples are water quenched using a quartz tube, and the samples after water quenching are ground and polished for scanning electron microscopy observation and energy spectrum analysis. The inclusions in the steel are mainly 1-2μm Ce2O3 and Ce2O2S inclusions. Then the method of the present invention is used to simulate and predict the above process, and the predicted calculation results are also Ce2O3 and Ce2O2S inclusions, see Figure 1 and Figure 2 As shown, it can be seen that the types of inclusions in the laboratory crucible experiment are consistent with the prediction results of the method of the present invention, which shows that the simulation results of the present invention have high accuracy.

Claims

1. A reaction simulation thermodynamic prediction method for rare earth element-containing products, characterized in that: The steps include: Step 1: For a material with a given initial composition, a reaction system involved in the high-temperature synthesis process of the material is constructed in a computer through programming software. The reaction system includes chemical reaction equations of all elements including rare earths involved in the high-temperature synthesis process, and the standard Gibbs free energy of each reaction is given; The standard Gibbs free energy construction method of the complex liquid phase product is as follows, wherein the complex liquid phase product refers to a complex oxide composed of three or more component oxides in any proportion; In the formula: x, y are the molar fractions of Ce2O3 and Al2O3 in the liquid product, respectively, z = 2 + x + y; R is the ideal gas constant, 8.314 J / (mol·K); T is the reaction temperature; The excess Gibbs free energy of the corresponding component points of the binary system respectively; are the interaction parameters between components of the binary system; Step 2, calculate each Gibbs free energy of all possible reactions based on the mass fraction of each component in the material; The activity of the reaction product is calculated based on the pure substance as the standard state, and the activity of the reactant is calculated based on Henry's law, assuming a 1% dilute solution as the standard state. Step 3, based on the Gibbs free energy results of each reaction in step 2, determine the independent reactions and simulate them in the direction where the Gibbs free energy changes to a negative value at the same time, and the reaction with the most negative Gibbs free energy change among the interrelated reactions is simulated first; for liquid inclusions, the liquid product component with the smallest Gibbs free energy in the system is simulated first; Step 4, for the chemical reactions that can be carried out in step 3, the reaction simulation process is controlled by reducing the amount of reactants by no more than 1 / 1000 each time, and can be smaller according to the accuracy requirements; when the Gibbs free energy change of all reactions is 0, the system reaches equilibrium, and the composition at this time is the equilibrium composition of the system, and the obtained rare earth product is the final equilibrium product.

2. The reaction simulation thermodynamic prediction method of rare earth element-containing products according to claim 1, characterized in that: In step 2, the maximum activity of the reaction product is set to 1, and the activity coefficient of the reactant is calculated using the Wagner approximation; the specific expression is as follows, where f i is the activity coefficient of component i; w [j] w [k] are the mass fractions of components j and K respectively; is the first-order activity interaction coefficient of component j on component i; is the second-order activity interaction coefficient of components j and k on component i; Among them, the principle of determining the activity coefficient is to give priority to the expression of the relationship between the activity interaction coefficient and temperature obtained from the experiment; if the expression of the relationship between the activity interaction coefficient and temperature is missing, the activity interaction coefficient at the known temperature is corrected by the following formula; if there is divalent activity interaction coefficient data, it is fully utilized as much as possible to ensure the accuracy of the activity coefficient; if none of the above activity interaction coefficients exist, the data of the same family with similar chemical properties or elements with similar distances in the periodic table of chemical elements are used; if none of the above data exist, their influence is ignored and the activity interaction coefficient is 0; The corrected expression of the activity interaction coefficient is as follows: in: is the first-order activity interaction coefficient of component j on component i.

3. The reaction simulation thermodynamic prediction method of rare earth element-containing products according to claim 1, characterized in that: In step 3, if the Gibbs free energy of the reaction is positive, the reaction proceeds in the reverse direction when the content of the reaction product is greater than zero.

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