Composite perovskite type wave-absorbing material and preparation method thereof

Abstract

The invention discloses a composite perovskite type wave-absorbing material and a preparation method thereof, and relates to a perovskite type wave-absorbing material and a preparation method thereof. The invention aims to solve the technical problem that the wave absorbing capacity of the existing LaNiO3 system and LaFeO3 system is poor. According to the composite material based on the perovskite structural materials, the two perovskite structural materials LaNiO3 and LaFeO3 are compounded through low-temperature molten salt co-firing, the two perovskite structural materials belong to perovskite structures, and the dielectric loss is greatly improved through generated interface polarization; the composite material has remarkable wave-absorbing capacity, the highest wave-absorbing loss can reach-40dB when the frequency is about 6.3 GHz, and the material has a relatively high application prospect.

Description

Technical Field

[0001] The present invention relates to a perovskite-type wave-absorbing material and a preparation method thereof. Background Art

[0002] Lanthanide perovskite-structured materials are an important class of functional materials. Their chemical formula is usually ABO3, where the A site is mainly lanthanide elements, the B site is usually transition metal elements such as iron, titanium, nickel, cobalt, manganese, zirconium, etc., and the O site is oxygen element. This type of material has many unique physical, chemical, and electrical properties, such as high dielectric constant, piezoelectric effect, ferroelectric effect, magnetism, optical properties, etc. Therefore, they have a wide range of applications in capacitors, piezoelectric devices, ferroelectric devices, etc. In recent years, there has gradually been work on the microwave absorption function of this type of material. The wave-absorbing mechanism of perovskite-structured materials is mainly through the J-T distortion inside the lattice. The dielectric constant of the material is large while the magnetic permeability is small. The change of the electric dipole moment enhances the dielectric loss, converting electromagnetic waves into heat energy to achieve the wave-absorbing effect. Among them, for the LaFeO3 system, to achieve the effect of wideband and high-efficiency wave absorption, the main methods adopted are ion doping at the A or B site (the elements that can be doped at the A site include Ba, Sr, Ca, Na, etc., and the elements that can be doped at the B site include Co); if forming a composite with other materials can also improve the wave-absorbing performance, and the materials currently used for composite are CoS2, CuCo2O4, Fe2O3, carbon materials, etc. For the LaNiO3 system, there is less work on the related microwave absorption function, mainly focusing on regulating its wave-absorbing performance in terms of morphology and composite, but the overall wave-absorbing ability is low. After doping with hetero-valent ions, due to the different valence states, the conductivity of the material increases, thereby enhancing the propagation and absorption of electromagnetic waves in the material; the electronic structure of the material changes, thereby affecting the dielectric constant and magnetic permeability, and thus enhancing the microwave absorption ability of the material. By using the composite method, if appropriate composite materials are selected, it can effectively cause resistance loss, interfacial polarization loss, or magnetic loss, so that the composite material system has a high wave-absorbing ability. Summary of the Invention

[0003] The present invention aims to solve the technical problem that the wave-absorbing abilities of both the LaNiO3 system and the LaFeO3 system are poor at present, and provides a composite perovskite-type wave-absorbing material and a preparation method thereof.

[0004] The chemical formula of the composite perovskite-type wave-absorbing material of the present invention is (1 - x)LaNiO3 / xLaFeO3, where 0.2 ≤ x ≤ 0.8, and x is the molar proportion of LaFeO3.

[0005] The preparation of the composite perovskite-type wave-absorbing material of the present invention adopts the molten salt method, and LaNiO3 and LaFeO3 are uniformly compounded in the molten salt solution. The specific preparation method is as follows:

[0006] 1. Weigh the LaNiO3 and LaFeO3 powder raw materials according to the chemical formula (1-x)LaNiO3 / xLaFeO3 and grind them evenly; where 0.2 ≤ x ≤ 0.8, and x is the molar proportion of LaFeO3; the LaNiO3 and LaFeO3 powders are nano or micron-level powder raw materials;

[0007] 2. Grind and mix the evenly ground mixture of LaNiO3 and LaFeO3 with the molten salt again to form a homogeneous mixture; the mass ratio of the total mass of LaNiO3 and LaFeO3 to the mass of the molten salt is 1:(10-40);

[0008] 3. Transfer the above homogeneous mixture to a reaction vessel, then place it in a heating furnace, raise the furnace temperature to 650°C - 1000°C and hold for 0.5h - 20h;

[0009] 4. Naturally cool to room temperature, take out the sample and wash it repeatedly with distilled water until the residual molten salt is removed, and then dry it. The obtained powder is the (1-x)LaNiO3 / xLaFeO3 composite material.

[0010] The purpose of the present invention is to improve the existing material system and provide a composite material based on perovskite structure materials. By co-firing two perovskite structure materials LaNiO3 and LaFeO3 with low-temperature molten salts, the two phases are composite and both belong to the perovskite structure, and the interfacial polarization generated greatly improves the dielectric loss; since the band gap of LaNiO3 (1.9eV) is slightly lower than that of LaFeO3 (2.3eV), the corresponding conductivity of LaNiO3 is slightly higher than that of LaFeO3, and the impedance after composite is relatively well-matched. Therefore, the composite material of two perovskite structure materials LaNiO3 and LaFeO3 with general wave absorption ability has significant wave absorption ability. At about 6.3GHz, the wave absorption loss can reach up to -40dB (the wave absorption losses corresponding to pure-phase LaFeO3 and LaNiO3 are both lower than -10dB). This material has high application prospects. Description of the Drawings

[0011] Figure 1 XRD pattern of the 0.3LaNiO3 / 0.7LaFeO3 composite material prepared in Experiment 1;

[0012] Figure 2 SEM image of the 0.3LaNiO3 / 0.7LaFeO3 composite material prepared in Experiment 1;

[0013] Figure 3 Electromagnetic parameter data diagram of the 0.3LaNiO3 / 0.7LaFeO3 composite material prepared in Experiment 1. Detailed Embodiments

[0014] Embodiment 1: This embodiment is a composite perovskite-type wave-absorbing material with the chemical formula (1 - x)LaNiO3 / xLaFeO3, where 0.2 ≤ x ≤ 0.8 and x is the molar proportion of LaFeO3.

[0015] Embodiment 2: This embodiment is a preparation method of the composite perovskite-type wave-absorbing material in Embodiment 1. The molten salt method is adopted, and LaNiO3 and LaFeO3 are uniformly compounded in the molten salt solution. The specific steps are as follows:

[0016] I. Weigh the powder raw materials of LaNiO3 and LaFeO3 according to the chemical formula (1 - x)LaNiO3 / xLaFeO3 and grind them evenly; where 0.2 ≤ x ≤ 0.8 and x is the molar proportion of LaFeO3; both the LaNiO3 and LaFeO3 powder raw materials are nano- or micro-scale powder raw materials.

[0017] II. Grind and mix the evenly ground mixture of LaNiO3 and LaFeO3 with the molten salt again to form a uniform mixture; the mass ratio of the total mass of LaNiO3 and LaFeO3 to the mass of the molten salt is 1:(10 - 40).

[0018] III. Transfer the above uniform mixture to a reaction vessel, then place it in a heating furnace, raise the furnace temperature to 650°C - 1000°C and keep it warm for 0.5 h - 20 h.

[0019] IV. Let it cool naturally to room temperature, take out the sample and wash it repeatedly with distilled water until the residual molten salt is removed, and then dry it. The obtained powder is the (1 - x)LaNiO3 / xLaFeO3 composite material.

[0020] Embodiment 3: The difference between this embodiment and Embodiment 2 is that in step I, the LaNiO3 powder is a micro- or nano-scale powder raw material, and the LaFeO3 powder is a nano-scale powder raw material. Others are the same as Embodiment 2.

[0021] Embodiment 4: The difference between this embodiment and any one of Embodiments 1 to 3 is that in step II, the molten salt is one or a mixture of several of KCl, NaCl, NaF, Na2SO4, and K2SO4. Others are the same as any one of Embodiments 1 to 3.

[0022] Embodiment 5: The difference between this embodiment and Embodiment 4 is that the drying temperature in step IV is 80°C - 110°C. Others are the same as Embodiment 4.

[0023] The following experiments are used to verify the present invention:

[0024] Experiment 1: This experiment is about a preparation method of a composite perovskite-type wave-absorbing material. The molten salt method is adopted, and LaNiO3 and LaFeO3 are uniformly compounded in the molten salt solution. The specific steps are as follows:

[0025] I. Weigh 1.21 g of LaNiO3 powder raw material and 2.79 g of LaFeO3 powder raw material according to the chemical formula 0.3LaNiO3 / 0.7LaFeO3 respectively, and grind them evenly; among them, 0.7 is the molar proportion of LaFeO3; the LaNiO3 powder is a nano-level powder raw material, and the LaFeO3 powder is a nano-level powder raw material;

[0026] II. Grind and mix the evenly ground mixture of LaNiO3 and LaFeO3 with the molten salt again to form a uniform mixture; the molten salt is a mixture of NaCl and KCl with an equimolar ratio. The masses of NaCl and KCl are 52.8 g and 67.2 g respectively, and after mixing, grind them evenly until uniform;

[0027] III. Transfer the above uniform mixture to a crucible, then place it in a muffle furnace, raise the furnace temperature to 700 °C and keep it warm for 2 h;

[0028] IV. Let it cool naturally to room temperature, take out the sample and wash it repeatedly with distilled water until the residual molten salt is removed, and then dry it at 80 °C. The obtained powder is the 0.3LaNiO3 / 0.7LaFeO3 composite material.

[0029] Figure 1 The XRD pattern of the 0.3LaNiO3 / 0.7LaFeO3 composite material prepared in Experiment 1 can clearly show the existence of the two phases of LaNiO3 and LaFeO3.

[0030] Figure 2 The SEM image of the 0.3LaNiO3 / 0.7LaFeO3 composite material prepared in Experiment 1 shows that the sample is a uniform nano-level mixture;

[0031] The electromagnetic parameters are measured using a vector network analyzer, Figure 3 The electromagnetic parameter data graph of the 0.3LaNiO3 / 0.7LaFeO3 composite material prepared in Experiment 1 shows that the maximum wave-absorbing loss of the sample can reach -40 dB.

[0032] Experiment 2: This experiment is about a preparation method of a composite perovskite-type wave-absorbing material. The molten salt method is adopted, and LaNiO3 and LaFeO3 are uniformly compounded in the molten salt solution. The specific steps are as follows:

[0033] I. Weigh 1 g of LaNiO₃ powder raw material and 0.99 g of LaFeO₃ powder raw material according to the chemical formula 0.5LaNiO₃ / 0.5LaFeO₃ respectively, and grind them thoroughly and evenly. Here, 0.5 is the molar proportion of LaFeO₃. The LaNiO₃ powder is a micron-sized powder raw material, and the LaFeO₃ powder is a nano-sized powder raw material.

[0034] II. Grind and mix the well-ground mixture of LaNiO₃ and LaFeO₃ with the molten salt again to form a homogeneous mixture. The molten salt is composed of NaCl and NaF mixed according to the molar ratio of NaCl:NaF = 2:1. The masses of NaCl and NaF are 29.42 g and 10.58 g respectively. After mixing, grind them thoroughly until homogeneous.

[0035] III. Transfer the above homogeneous mixture to a crucible, then place it in a muffle furnace, raise the furnace temperature to 950 °C and keep it at this temperature for 0.5 h.

[0036] IV. Let it cool down to room temperature naturally, take out the sample and wash it repeatedly with distilled water until the residual molten salt is removed, and then dry it at 110 °C. The obtained powder is the 0.5LaNiO₃ / 0.5LaFeO₃ composite material. After testing, the maximum microwave absorption loss of the sample is -15 dB.

[0037] Experiment 3: This experiment is a preparation method of a composite perovskite-type microwave absorption material, which uses the molten salt method. LaNiO₃ and LaFeO₃ are uniformly compounded in the molten salt solution. The specific steps are as follows:

[0038] I. Weigh 1.6 g of LaNiO₃ powder raw material and 0.4 g of LaFeO₃ powder raw material according to the chemical formula 0.8LaNiO₃ / 0.2LaFeO₃ respectively, and grind them thoroughly and evenly. Here, 0.2 is the molar proportion of LaFeO₃. The LaNiO₃ powder is a nano-sized powder raw material, and the LaFeO₃ powder is a nano-sized powder raw material.

[0039] II. Grind and mix the well-ground mixture of LaNiO₃ and LaFeO₃ with the molten salt again to form a homogeneous mixture. The molten salt is composed of Na₂SO₄ and NaCl mixed in an equimolar ratio. The masses of NaCl and Na₂SO₄ are 23.2 g and 56.8 g respectively. After mixing, grind them thoroughly until homogeneous.

[0040] III. Transfer the above homogeneous mixture to a crucible, then place it in a muffle furnace, raise the furnace temperature to 850 °C and keep it at this temperature for 8 h.

[0041] 4. Cool down to room temperature naturally, take out the sample, wash it repeatedly with distilled water to remove the residual molten salt, and then dry it at 100°C. The resulting powder is 0.8LaNiO3 / 0.2LaFeO3 composite material. The test shows that the maximum absorption loss of the sample is -5dB.

[0042] Comparative test: LaFeO3 was not added in this test, and the specific steps are as follows:

[0043] 1. Weigh 2 g of LaNiO3 powder raw material, wherein the LaNiO3 powder is a micron-grade powder raw material;

[0044] 2. Grind and mix LaNiO3 and molten salt to form a uniform mixture; the molten salt is a mixture of NaCl and KCl in an equal molar ratio, the masses of NaCl and KCl are 29.2g and 37.3g respectively, and after mixing, they are fully ground to be uniform;

[0045] 3. Transfer the above uniform mixture into a crucible, then place it into a muffle furnace, raise the furnace temperature to 750°C and keep it at this temperature for 20 hours;

[0046] 4. Cool down to room temperature naturally, take out the sample and wash it repeatedly with distilled water to remove the residual molten salt, then dry it at 100℃. After testing, it can be found that the maximum absorption loss of the sample is -6dB.

Claims

1. A composite perovskite-type wave-absorbing material, characterized in that The chemical formula of the composite perovskite microwave absorption material is (1-x)LaNiO3 / xLaFeO3, where 0.2 ≤ x ≤ 0.8 and x is the molar ratio of LaFeO3.

2. The preparation method of a composite perovskite-type wave-absorbing material according to claim 1, characterized in that The preparation method of the composite perovskite microwave absorption material adopts the molten salt method, and LaNiO3 and LaFeO3 are uniformly compounded in the molten salt solution. The specific steps are as follows:

1. Weigh the powder raw materials of LaNiO3 and LaFeO3 according to the chemical formula (1-x)LaNiO3 / xLaFeO3 and grind them evenly. Among them, 0.2 ≤ x ≤ 0.8 and x is the molar ratio of LaFeO3. Both the LaNiO3 and LaFeO3 powder materials are nano- or micron-scale powder raw materials.

2. Grind and mix the evenly ground mixture of LaNiO3 and LaFeO3 with the molten salt again to form a uniform mixture. The mass ratio of the total mass of LaNiO3 and LaFeO3 to the mass of the molten salt is 1:(10-40).

3. Transfer the above uniform mixture to a reaction vessel, then place it in a heating furnace, raise the furnace temperature to 650°C - 1000°C and keep it warm for 0.5h - 20h.

4. Naturally cool to room temperature, take out the sample and wash it repeatedly with distilled water until the residual molten salt is removed, and then dry it. The obtained powder is the (1-x)LaNiO3 / xLaFeO3 composite material.

3. The preparation method of a composite perovskite type wave-absorbing material according to claim 2, characterized in that The LaNiO3 powder described in step 1 is a micron- or nano-scale powder raw material, and the LaFeO3 powder is a nano-scale powder raw material.

4. The preparation method of a composite perovskite type wave-absorbing material according to claim 2, characterized in that The molten salt described in step 2 is one or a mixture of several of KCl, NaCl, NaF, Na2SO4, and K2SO4.

5. The preparation method of a composite perovskite type wave absorbing material according to claim 2, characterized in that The drying temperature in step 4 is 80°C - 110°C.

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