Composite material based on Pr3+-SrTiO3-SrCeO3 system

Abstract

The invention discloses a composite material based on a Pr < 3 + >-SrTiO3-SrCeO3 system, which realizes the purposes of reducing heat conductivity and improving mechanical properties by cooperatively regulating heat conduction and mechanical properties through a Pr < 3 + > interface modification effect. The traditional ion doping can improve the lattice confusion degree, soften the lattice and reduce the heat conductivity, and the scheme overcomes the problem that the mechanical performance is reduced through ion doping, and realizes collaborative optimization of the interface structure, components and performance. The yttrium oxide stabilized zirconia system can replace a traditional yttrium oxide stabilized zirconia system, is applied to a thermal barrier coating, improves the gas temperature, the energy efficiency, the thrust-weight ratio and the service life of an aero-engine, and achieves the purposes of environmental protection and sustainable development.

Description

Technical Field

[0001] This invention patent belongs to the field of composite material technology, specifically relating to a Pr-based 3+ The SrTiO3-SrCeO3 (praseodymium ion-strontium titanate-strontium cerate) composite material is a thermal barrier coating material. By using interface modification, a novel composite material system is designed to reduce thermal conductivity and improve mechanical properties while maintaining its high temperature resistance and thermochemical stability. Background Technology

[0002] Thermal barrier coatings can be applied to turbine blades in high-temperature engines to reduce engine surface temperature and improve engine combustion gas temperature and energy efficiency. Traditional thermal barrier coating materials, such as yttrium-stabilized zirconia (YSZ), possess characteristics such as low thermal conductivity, high temperature resistance, and corrosion resistance, with a maximum operating temperature of 1200ºC. Currently, traditional thermal barrier coating materials are limited by their operating temperature; when the temperature exceeds 1200ºC, YSZ undergoes a phase transition, leading to crack formation in the coating and reducing its mechanical properties.

[0003] Existing traditional thermal barrier coating materials are based on Y2O3-stabilized ZrO2. At temperatures above 1200℃, sintering and phase transformation occur, leading to a decline in mechanical properties and a reduction in service life. However, the gas temperature of aero engines is above 1500℃, and Y2O3-stabilized ZrO2 is difficult to meet the requirements of future aero engines.

[0004] Heat transfer in solid materials is crucial for improving thermal efficiency, service life, and the cost-effectiveness of thermal management applications. For example, thermal barrier coatings limit heat transfer from syngas, thereby reducing the surface temperature of gas turbines and improving operating temperature and energy efficiency. Due to the high melting point, thermal properties, and mechanical properties of zirconia, commercial topcoat materials consist of 7 wt% yttrium-stabilized zirconia (7YSZ). To further improve the operating temperature and extend the service life of thermal barrier coatings, the development of new thermal barrier coating systems is essential. Strategies to reduce thermal conductivity can be achieved at the microstructure and atomic scale, such as doping with heterovalent elements, introducing point defects, lattice distortion, and mass disorder; however, these modifications often lead to a decrease in mechanical properties due to lattice softening. Ion doping can increase lattice disorder, soften the lattice, reduce thermal conductivity, increase the coefficient of thermal expansion, and reduce mechanical properties.

[0005] Perovskite oxides, including SrTiO3, SrCeO3, and SrZrO3, are promising thermal barrier coating materials due to their excellent high-temperature properties, such as high melting point, mechanical properties, and thermal properties. SrCeO3, in particular, exhibits glassy thermal conductivity, excellent phase stability, and a high coefficient of thermal expansion; at 800 °C, the thermal conductivity of SrCeO3 is 1.73 W / m³. -1 K -1SrTiO3 has a high melting point of 2080℃ and has potential applications in thermoelectric devices, catalyst supports, and thermal barrier coatings. Summary of the Invention

[0006] The purpose of this invention is to provide a Pr-based 3+ Composite materials based on the SrTiO3-SrCeO3 system were obtained by optimizing interfacial heat transfer, enhancing interfacial thermal resistance and mechanical properties through interfacial modification strategies, resulting in a eutectic composition that combines geothermal conductivity and high mechanical properties, namely Pr... 3+ Modified SrTiO3-SrCeO3. A eutectic composition was obtained through high-temperature sintering, combined with Pr deposition via liquid-phase method. 3+ The layer introduces lattice defects, including oxygen vacancies, interstitial ions, grain boundaries, and lattice stress, to modulate phonon transport and interface structure, enhance interfacial thermal resistance and hardness, and reduce the phonon mean free path. This composition also exhibits excellent high-temperature resistance, corrosion resistance, and thermochemical stability, making it a potential next-generation thermal barrier coating material.

[0007] This invention is achieved through the following technical solution: a method based on Pr 3+ The composite material of the -SrTiO3-SrCeO3 system is characterized by being prepared by the following method: Step 1: Select SrCO3, TiO2 and CeO2 with a molar ratio of 2:1:1, and mix them using a vibratory mixer at a speed of 30 rpm for 12 hours; Step 2: Calcine the mixed powder in air at high temperature for 4 hours to form a solid solution; Step 3: Dissolve an appropriate amount of Pr(NO3)3·6H2O in deionized water to prepare a solution; Step 4: Citric acid is dissolved in Pr(NO3)3 solution as a dispersant, and then sintered SrTiO3-SrCeO3 powder is added to form a suspension. The suspension is stirred for 30 min, and the powder is separated from the suspension by vacuum filtration. It is dried in air at 60℃ and then calcined at high temperature for 4 h to obtain the composite material.

[0008] Furthermore: In steps 2 and 4, the high-temperature calcination temperature is 1500℃, and the heating rate is 5℃ / min. -1 .

[0009] Furthermore: In step 3, the concentration of the solution is 0.067 mol / L. -1 -0.375mol / L -1 .

[0010] Furthermore, it also includes step 5: Pr 3+The modified SrTiO3-SrCeO3 was pressed into bulk material under 317 MPa pressure and sintered at 1350℃-1500℃ for 4 h with a heating rate of 5℃ / min. -1 .

[0011] The advantages of this invention are as follows: Traditional thermal barrier coating materials are composed of YSZ, whose service temperature is limited by phase transition and is below 1200℃, while the exhaust gas temperature of new-generation aero-engines is 1500℃, and energy efficiency is directly proportional to exhaust gas temperature. The Pr-SCTO composite material prepared by this method has excellent thermochemical stability, low thermal conductivity, and mechanical properties, making it an excellent material system to replace traditional YSZ materials as a new generation of thermal barrier coatings. Its high structural stability, high melting point, and corrosion resistance are key to the design and preparation of thermal barrier coating materials. High exhaust gas temperature can improve the energy efficiency of aero-engines, reduce harmful gas emissions, and achieve the goals of environmental protection and sustainable development, which is crucial for enhancing the core competitiveness of the manufacturing industry. Attached Figure Description

[0012] Figure 1 Here are the XRD patterns of Pr-SCTO: (a) 0.375 Pr-SCTO, (b) 0.067 Pr-SCTO, (c) SCTO sintered at 1500℃; (d) 0.375 Pr-SCTO, (e) 0.067 Pr-SCTO, (f) SCTO sintered at 1500℃. Figure 2 Here are SEM images: (a) and (b) SCTO bulk surface structure, (d) and (e) 0.067 Pr-SCTO bulk surface structure, (g) and (h) 0.375 Pr-SCTO bulk surface structure; backscattered electron images: (c) SCTO, (f) 0.067 Pr-SCTO, (i) 0.375 Pr-SCTO; Figure 3 is the EDX spectrum of Pr-SCTO: (a)-(c) SCTO, (d)-(g) 0.067 Pr-SCTO, (h)-(k) 0.375 Pr-SCTO; Figure 4 XPS plot: (a) Sr 2+ 3d orbit, (b) Ti 4+ 2p orbital, (c) O 1s orbital, (d) Pr 3+ 3d orbital, (e)Ce 4+ 3d orbital, among which, (i) 0.375Pr-SCTO, (ii) 0.067 Pr-SCTO, (iii) SCTO; Figure 5Phonon mean free path of Pr-SCTO; Figure 6 Schematic diagram of heat transfer at the Pr-SCTO interface. Detailed Implementation

[0013] Reference Appendix Figure 1-6 This invention provides a Pr-based 3+ The composite material of the -SrTiO3-SrCeO3 system is prepared by the following method: Step 1: Select SrCO3, TiO2 and CeO2 powders with a molar ratio of 2:1:1, and mix them using a vibratory mixer at a speed of 30 rpm for 12 hours; Step 2: Calcine the mixed powder in air at high temperature for 4 hours to form a solid solution; Step 3: Dissolve an appropriate amount of Pr(NO3)3·6H2O in deionized water to prepare a solution; Step 4: Citric acid is dissolved in Pr(NO3)3 solution as a dispersant, and then sintered SrTiO3-SrCeO3 powder is added to form a suspension. The suspension is stirred for 30 min, and the powder is separated from the suspension by vacuum filtration. It is dried in air at 60℃ and then calcined at high temperature for 4 h to obtain the composite material.

[0014] Furthermore: In steps 2 and 4, the high-temperature calcination temperature is 1500℃, and the heating rate is 5℃ / min. -1 .

[0015] Furthermore: In step 3, the concentration of the solution is 0.067 mol / L. -1 ~0.375mol / L -1 .

[0016] Furthermore, it also includes step 5: Pr 3+ The modified SrTiO3-SrCeO3 was pressed into bulk material under 317 MPa pressure and sintered at 1350℃-1500℃ for 4 h with a heating rate of 5℃ / min. -1 .

[0017] The following examples, combined with the principles and test results, further illustrate this solution.

[0018] Phase boundaries and interfaces in heterostructured materials scatter long-wavelength phonons, leading to a decrease in thermal conductivity. Surface modification of the material can influence local bond energy, lattice chemistry, and phonon scattering, thereby modulating the heat conduction process. 3+With the lowest thermal conductivity, Debye temperature, and Young's modulus, as well as the highest coefficient of thermal expansion, it is one of the best dopants for thermal barrier coating materials. This method introduces Pr-containing dopants at the interface of eutectic ceramic SrTiO3-SrCeO3. 3+ An interface modification layer is used, and its thickness is varied to control thermal conductivity, hardness, and modulus, thereby synergistically improving interfacial thermal resistance and mechanical properties. The material preparation process employs both solid-phase and liquid-phase methods, as detailed below: The starting materials consisted of SrCO3, TiO2, and CeO2, which were mixed for 12 hours at 30 rpm using a 3D vibratory mixer. The molar ratio of [SrCO3]:[TiO2]:[CeO2] was 2:1:1. The powder was calcined in air at 1500℃ for 4 hours, with a heating rate of 5~30℃ / min. -1 (Start heating from the previous state or room temperature, and start timing when the specified temperature is reached). Dissolve a certain amount of Pr(NO3)3·6H2O in a solution with a concentration of 0.067 mol / L. -1 and 0.375 mol L -1 The two components are abbreviated as 0.067Pr-SCTO and 0.375Pr-SCTO, respectively, and the two concentrations correspond to Example 1 and Example 2, respectively. Citric acid was dissolved in Pr(NO3)3 solution as a dispersant, and then sintered SrTiO3-SrCeO3 powder was added. The suspension was stirred for 30 min, the powder was separated from the suspension by vacuum filtration, dried in air at 60 °C, and calcined at 1500 °C for 4 h. 3+ The modified SrTiO3-SrCeO3 was pressed into bulk material under 317 MPa pressure and sintered at 1350℃-1500℃ for 4 h with a heating rate of 5~30℃min. -1 The thermal and mechanical properties were tested. X-ray diffraction was used to study the phase composition of the samples, and scanning electron microscopy was used to characterize their microstructure. X-ray photoelectron spectroscopy and X-ray fluorescence analysis were used for composition determination. The thermal diffraction coefficient was measured using laser scintillation, and the hardness and modulus were measured using nanoindentation, from which the phonon mean free path was calculated.

[0019] Pr was sintered at 1500℃. 3+ Doped SrTiO3-SrCeO3 consists of cubic SrTiO3 and orthorhombic SrCeO3, with small amounts of strontium titanium oxide and cerium oxide added, such as... Figure 1 As shown. Pr 3+During calcination, the phases diffused onto the SCTO surface. Calcination at 1500℃ for 4 hours ensured the phase stability of Pr-SCTO, and its phase composition was characterized by XRD. Refinement of the XRD data using the Rietveld method yielded three phases: SrTiO3, SrCeO3, and CeO2. Due to calcination at 1500℃, Sr3Ti2O7 disappeared from SCTO, and no additional phases were found in Pr-SCTO. SrTiO3 and SrCeO3 exhibit thermochemical stability at 1500℃, while Pr... 3 + No second phase is generated when diffused into SCTO.

[0020] The prepared bulk material has a relatively uniform and dense surface, such as Figure 2 As shown. According to EDX plotting analysis, the Pr-SCTO composite material mainly consists of two phases: the darker phase is SrTiO3, and the brighter phase is SrCeO3. Furthermore, Pr... 3+ The uniform distribution and lack of agglomeration of Pr-SCTO particles indicate that Pr 3+ The substance diffuses to the SrTiO3 and SrCeO3 interface, such as Figure 3 As shown.

[0021] XPS analysis was used to determine the surface chemical properties of Pr-SCTO. Figure 4 As shown, all elements were observed in XPS. The presence of the Pr3d peak confirms that Pr... 3+ Diffusion in SCTO, while Ce3d, Ti2p, Sr3d and O1s peaks are generated by Ce 4+ Ti 4+ 、Sr 2+ and O 2- Composition. The O1s core energy level of 0.375Pr-SCTO consists of three peaks. The difference in the O1s core energy level of Pr-SCTO is due to the Pr 3+ Incorporation into the lattice alters the local chemical environment and lattice disorder, and introduces oxygen vacancies. In 0.375Pr-SCTO, due to Pr 3+ The content of is the highest, therefore the surface oxygen vacancy concentration is the highest.

[0022] The deposition amount of Pr₂O₃ on SCTO was determined by XRF, as shown in Table 1. The Pr₂O₃ content in 0.067Pr-SCTO was 0.2 mol%, and the content in 0.375Pr-SCTO was 0.69 mol%. The molar ratio of SrTiO₃ to SrCeO₃ was 1:1, consistent with the theoretical value. With the increase in Pr₂O₃ content in the initial solution... 3+ As the concentration increases, the content of Pr2O3 also increases.

[0023] Table 1. Standardized molar concentrations of Pr-SCTO determined by XRF <![CDATA[Pr2O3]]> <![CDATA[SrTiO3]]> <![CDATA[SrCeO3]]> SCTO --- 52.26% 47.74% 0.067 Pr-SCTO 0.20% 50.09% 49.71% 0.375 Pr-SCTO 0.69% 49.76% 49.55% The thermal diffusivity was measured using the laser flare method, and the specific heat capacity at room temperature was determined using differential scanning calorimetry. As shown in Table 2, with Pr 3+ As the concentration increases, the thermal diffusivity and thermal conductivity decrease.

[0024] Table 2. Room temperature thermal properties of Pr-SCTO SCTO 0.067 Pr-SCTO 0.375 Pr-SCTO <![CDATA[Thermal diffusivity (mm 2 s)]]> 0.827 0.804 0.775 <![CDATA[Density (g cm -3 )]]> 3.6878 3.7057 3.6515 <![CDATA[Specific heat capacity (J g -1 K -1 )]]> 0.5091 0.4904 0.3717 <![CDATA[Measured thermal conductivity (W m -1 K -1 )]]> 1.553 1.461 1.052 Porosity 0.3096 0.3065 0.3178 <![CDATA[Theoretical thermal conductivity value (W m -1 K -1 )]]> 2.899 2.705 2.010 The hardness and modulus measured using nanoindentation are listed in Table 3. For ionic oxides, hardness and modulus are controlled by the nature of the chemical bonds, including bond ionicity and bond length. (Compared to Ti-O (672.4 kJ mol)) -1 ) and Sr-O (425.5 kJmol) -1 Compared to Pr-O (753 kJ mol), -1 The bond energy of Pr is higher, therefore Pr 3+ The presence of an interface can increase the hardness and modulus of a material. Due to Pr 3+ The ionic radius is greater than that of Ti. 4+ (0.605 Å, CN=6) and Ce 4+ (0.87 Å, CN=6), but smaller than Sr 2+ (1.18 Å, CN=6), therefore Pr 3+ The incorporation of [a specific substance] can introduce lattice strain and distortion on the SCTO surface, thereby resisting deformation during nanoindentation testing. The bulk modulus of perovskite oxides can be tuned by ionic charge and lattice structure, thus affecting local bonding strength. [The text then abruptly shifts to a seemingly unrelated topic:] Pr at the SCTO interface. 3+ The modification effect increased the modulus and hardness, and altered the phonon transport properties.

[0025] Table 3. Mechanical properties of Pr-SCTO SCTO 0.067 Pr-SCTO 0.375 Pr-SCTO Hardness (GPa) 3.76 4.93 6.50 Modulus (GPa) 112.30 142.43 159.6 In ionic oxides, the heat transfer process is controlled by phonon scattering, and the mean free path of phonons can be calculated using the following formula.

[0026] Where C is the heat capacity, v is the average phonon velocity, and l is the mean free path of the phonon. Since Pr-SCTO is a polycrystalline material, phonon transport is isotropic, and the average phonon velocity can be calculated using the following formula.

[0027] Among them, V s and V lLet G be the shear and longitudinal phonon velocities, B be the bulk modulus, and r be the density. The bulk modulus and shear modulus can be calculated using the following formulas.

[0028] Where E is Young's modulus. υ Let Pr be the Poisson's ratio. The Poisson's ratio is 0.25. Based on the Materials Project database (mp-5229), and calculated using formula (1-6), the phonon mean free path increases with Pr. 3+ The increase leads to a decrease, such as Figure 5 As shown.

[0029] The thermal conductivity of oxides is controlled by phonon mobility and can be modulated by lattice anharmonicity, point defects, and chemical composition. Enhancing phonon scattering with point defects, substitutional ions, lattice distortion, and interfaces can reduce thermal conductivity. In Pr-SCTO, due to the Pr doping effect, the interface region has high lattice disorder, which enhances phonon scattering with defects. The interface heat transfer mechanism is as follows: Figure 6 As shown. Due to Pr 3+ Pr has a different valence state, ionic radius, and relative atomic mass than the matrix elements Sr, Ce, and Ti. 3+ Diffusion into the perovskite lattice increases the disorder of the interfacial lattice. The defect chemical reaction formula is as follows:

[0030] in, and For Pr 3+ Occupy Ti 4+ Position, carrying 1 negative charge, It is an oxygen vacancy with two positive charges. It consists of lattice oxygen atoms and is electrically neutral. It is an interstitial oxygen ion with two negative charges. For gap Pr 3+ , It is an electron-hole vacancy with one positive charge. It is an electron with one negative charge. According to formula (7-12), Pr 3+ Diffusion can generate at the interface including , , , , and Equal point defects. Oxygen vacancies at the interface can reduce thermal diffusion, thus decreasing the phonon mean free path.

[0031] (13)

[0032] in,l The mean free path of phonons, a 3 For lattice volume, c Defect concentration, v m For transverse wave velocity, ω For phonon frequency, M Δ is the atomic mass. M This represents the difference between the substitutional atom and the matrix atom. The atomic mass of Pr (140.908 u) is greater than that of Sr (87.62 u) and Ti (47.867 u), but slightly smaller than that of Ce (140.116 u). 3+ The ionic radius of (0.99 Å, CN=6) is greater than that of Sr. 2+ The ionic radius of (1.18 Å, CN=6) is small, but higher than that of Ti. 4+ (0.605 Å, CN=6) and Ce 4+ The ionic radius is (0.87 Å, CN=6). The addition of Pr to SCTO leads to an increase in lattice disorder and lattice distortion, promotes phonon scattering, and reduces thermal conductivity. Such Pr-containing interfaces can serve as the main source of thermal resistance for heat transfer on the SCTO surface.

[0033] In summary, the Pr prepared by this method 3+ Modified SCTO composites, by using Pr 3+ Pr is deposited on SCTO to form a composite material system consisting of cubic SrTiO3 and orthorhombic SrCeO3. 3+ The interface reduces the mean free path of phonons and increases hardness and modulus. Pr 3+ Interfaces composed of a high concentration of point defects can enhance phonon scattering and impede heat transfer. The strategy of incorporating heterogeneous interfaces into oxide composites has a synergistic effect on regulating thermal conductivity and mechanical properties, enabling the application of such composites in next-generation thermal barrier coatings.

Claims

1. A method based on Pr 3+ The composite material of the -SrTiO3-SrCeO3 system is characterized by: It is prepared by the following method: Step 1: Select SrCO3, TiO2 and CeO2 with a molar ratio of 2:1:1, and mix them using a mixer at a speed of 30 rpm for 12 hours; Step 2: Calcine the mixed powder in air at high temperature for 4 hours to form a solid solution; Step 3: Dissolve an appropriate amount of Pr(NO3)3·6H2O in deionized water to prepare a Pr(NO3)3 solution; Step 4: Citric acid is dissolved in Pr(NO3)3 solution as a dispersant, and then the sintered solid solution is added to form a suspension. The suspension is stirred for 30 min, and the powder is separated from the suspension by vacuum filtration. It is dried in air at 60℃ and then calcined at high temperature for 4 h to obtain the composite material.

2. A method based on Pr according to claim 1 3+ The composite material of the -SrTiO3-SrCeO3 system is characterized by: In steps 2 and 4, the high-temperature calcination temperature is 1500℃, and the heating rate is 5℃ / min. -1 .

3. A method based on Pr according to claim 1 3+ The composite material of the -SrTiO3-SrCeO3 system is characterized by: In step 3, the concentration of the Pr(NO3)3 solution is 0.067 mol / L. -1 -0.375mol / L -1 .

4. A method based on Pr according to claim 1 3+ The composite material of the -SrTiO3-SrCeO3 system is characterized by: The process also includes step 5: pressing the composite material prepared in step 4 into a bulk material under a pressure of 317 MPa, and sintering it at 1350℃-1500℃ for 4 hours at a heating rate of 5℃ / min. -1 .

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