One-step synthesis of high-entropy cordierite ceramics and its preparation process and application

Abstract

The present invention relates to a one-step synthesis process for preparing high-entropy cordierite ceramics. The raw materials comprise component A, component B, and component C, with the molar ratio of components A, B, and C being 2:2:5. Component A comprises magnesium oxide and a magnesium-site dopant, wherein the magnesium-site dopant comprises at least four of CoO, NiO, ZnO, CuO, FeO, GaO, MnO, and ZrO2; component B comprises aluminum oxide and an aluminum-site dopant, wherein the aluminum-site dopant comprises at least two of Cr2O3, Ti2O3, Fe2O3, GeO2, and V2O5; and component C comprises silicon dioxide. By determining appropriate doping elements, the present invention uses pure oxides as raw materials and utilizes a one-step sintering process to synthesize high-entropy cordierite ceramics. This process simplifies the process, enhances stability, and improves infrared performance. The high-entropy cordierite ceramics prepared by the present invention also have excellent electromagnetic wave absorption properties and can be used as a new wave absorbing material.

Description

Technical Field

[0001] The present invention relates to the technical field of cordierite ceramics, in particular to a one-step synthesized high-entropy cordierite ceramic and a preparation process and application thereof. Background Art

[0002] Cordierite ceramic material has a high infrared emissivity, and is also characterized by high temperature resistance, high dielectric constant, stable physical and chemical properties, and good thermal shock resistance. It is an important infrared material.

[0003] At present, the research on cordierite ceramics at home and abroad mainly focuses on the synthesis and preparation of cordierite ceramics. By adopting different raw materials and ratios, synthesis processes and sintering systems, the phase composition and reaction mechanism are studied, and the impact on their performance is further discussed; or with the research goals of reducing the sintering temperature, thermal expansion coefficient and improving the thermal effect of cordierite ceramics, by adding sintering aids to form a liquid phase or performing ion replacement, the effects on the sintering temperature, densification and thermal properties of cordierite ceramics are studied. However, there is little research on the improvement of cordierite performance and its application in research and development and preparation. Research on cordierite doping mainly focuses on increasing the cordierite phase content by element doping to improve the density of cordierite ceramics.

[0004] The existing process for synthesizing cordierite ceramics is complex and mostly uses a two-stage firing process, that is, first firing the cordierite into powder, and then sintering it again into ceramics through mixing, granulation, and molding, which is energy-consuming and time-consuming.

[0005] Although some existing technologies disclose some solutions for preparing cordierite ceramics by single firing, such as CN201410089785.4, which discloses a cordierite ceramic material with an ultra-low thermal expansion coefficient and a preparation method thereof, this solution has high requirements on sintering conditions and requires sintering under inert atmosphere and high pressure conditions to obtain single-phase cordierite ceramics.

[0006] Moreover, the cordierite ceramics prepared in this scheme are not doped with elements. After element doping, complex crystal phases are more likely to form during sintering, which also increases the difficulty of preparing single-phase cordierite ceramics.

[0007] High-entropy ceramics (HECs) typically refer to solid solutions composed of five or more ceramic components. Due to their unique "high-entropy effect" and superior performance, they have become a hot topic in the ceramics field in recent years. Because HECs are highly disordered and multicomponent, and the lattice distortion caused by the HEC effect, HECs maintain a single phase under extreme temperatures, pressures, and chemical environments, ensuring stability under a wide range of service conditions. However, no research has been reported on HEC ceramics. Summary of the Invention

[0008] The purpose of the present invention is to obtain a high-entropy cordierite ceramic. The present invention discloses a one-step synthesis of a high-entropy cordierite ceramic and a preparation process thereof. The specific scheme is:

[0009] A one-step synthesis process for preparing high-entropy cordierite ceramics comprises raw materials comprising component A, component B, and component C, wherein the molar ratio of component A, component B, and component C is 2:2:5; component A comprises magnesium oxide and magnesium-site dopants, wherein the magnesium-site dopants include at least four of CoO, NiO, ZnO, CuO, FeO, GaO, MnO, and ZrO2; component B comprises aluminum oxide and aluminum-site dopants, wherein the aluminum-site dopants include at least two of Cr2O3, Ti2O3, Fe2O3, GeO2, and V2O5; and component C comprises silicon dioxide.

[0010] The key point of the present invention is to select appropriate dopant composition and raw materials to achieve the preparation of high entropy cordierite ceramics. When selecting the dopant composition, the structure and properties of low expansion coefficient cordierite are simulated and calculated to determine the raw materials for synthesizing high entropy cordierite. By taking into account the difference in lattice constants, the ionic radius of similar substitution positions, the same crystal structure, similar electronegativity, the same valence state, entropy formation ability, Goldschmid tolerance factor, size disorder factor and valence electron concentration, etc., the raw materials suitable for replacing Mg are calculated and selected. 2+ 、Al 3+ The calculation results show that the magnesium doping is Cu 2+ 、Fe 2+ 、Zn 2+ 、Mn 2+ 、Ni 2+ 、Co 2+ 、Zr 4+ 、Ga 2+ etc., Cr is used for aluminum doping 3+ 、Ti 3+ 、Fe 3+ 、Ge 4+ 、V 5+ The present invention selects MgO, Al2O3, SiO2, CuO, FeO, MnO, CoO, NiO, ZnO, ZrO2, GaO, Cr2O3, Ti2O3, Fe2O3, GeO2, V2O5 and the like as raw materials for preparing low expansion coefficient and high entropy cordierite.

[0011] When the number of doping species is too small, single-phase ceramics cannot be obtained, and the thermal expansion properties and strength are poor. For example, when the number of magnesium dopants is less than four, or when the number of aluminum dopants is less than two, single-phase ceramics cannot be obtained.

[0012] Preferably, the molar amounts of various magnesium dopants in component A and magnesium oxide are equal, and the molar amounts of various aluminum dopants in component B and aluminum oxide are equal.

[0013] Preferably, the preparation process specifically includes the following steps:

[0014] 1) Component A, component B, and component C are weighed and ball-milled to obtain a mixture;

[0015] 2) The mixture is added with a binder for molding and sintered at high temperature.

[0016] Preferably, in step 1), deionized water or anhydrous ethanol is added during ball milling to perform wet grinding, followed by drying and then grinding into powder.

[0017] Preferably, the binder in step 2) is 8% PVA solution or deionized water.

[0018] Preferably, silicon carbide is used as a filler during high-temperature sintering, and the silicon carbide is calcined twice at temperatures above 1600°C. The SiC powder calcined twice or more at 1600°C provides an oxygen-free environment for the valence-modified raw materials. Furthermore, the repeatedly calcined SiC powder supplements the amount of SiO2 in the raw material mix, providing a stable sintering environment for synthesizing high-entropy cordierite and enhancing its infrared radiation performance.

[0019] Preferably, the sintering temperature is 1200-1400° C. When the temperature is lower or higher than this range, the crystal phase ratio of cordierite ceramic in the sintered product is too low, and the infrared radiation performance and expansion performance are poor.

[0020] More preferably, the sintering temperature is 1300° C. The high entropy cordierite ceramic sintered at 1300° C. has good crystallinity.

[0021] The present invention also claims protection for the high entropy cordierite ceramics prepared according to the above method. The cordierite ceramics obtained according to the method of the present invention have the advantages of low thermal expansion and good infrared performance.

[0022] In addition, the high-entropy cordierite ceramics prepared by the present invention have been found to have good electromagnetic wave absorption performance through testing, with a minimum reflection loss (RL) of -17.63dB (4.9mm) and a maximum effective absorption bandwidth (EAB) of 3GHz (1.8mm).

[0023] Therefore, the present invention also claims protection for the use of high-entropy cordierite ceramics prepared by the method of the present invention in absorbing materials. For example, they can be used as electromagnetic wave shielding and absorption materials in electronic devices, and as stealth materials in the aerospace field to reduce radar reflection and electromagnetic wave interference.

[0024] The method of the present invention can produce high-entropy cordierite ceramics. The obtained high-entropy cordierite ceramics have low expansion and improved infrared radiation performance, which can expand the application range of cordierite infrared radiation ceramics and enable them to be better used in communication and network-related fields.

[0025] The present invention determines appropriate doping elements, uses pure oxides as raw materials, and utilizes a one-step sintering process to synthesize high-entropy cordierite ceramics, thereby simplifying the process and enhancing stability.

[0026] In addition, the high-entropy cordierite ceramics prepared by the present invention also have good electromagnetic wave absorption performance and can be used as a new wave-absorbing material, further expanding its application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below with reference to the accompanying drawings and examples.

[0028] Figure 1 Schematic diagram of the method of the present invention.

[0029] Figure 2 1 and 2 are XRD patterns of the high-entropy cordierite ceramics obtained in Example 1 and Example 2.

[0030] Figure 3 This is the SEM image of the high-entropy cordierite ceramic obtained in Example 1 (Mag=10000).

[0031] Figure 4 This is the SEM image of the high-entropy cordierite ceramic obtained in Example 1 (Mag=20000).

[0032] Figure 5 These are infrared spectra of the high-entropy cordierite ceramics obtained in Examples 1 and 2 and the cordierite ceramics obtained in Comparative Example 1.

[0033] Figure 6 This is a test diagram of the microwave absorption performance of the high-entropy cordierite ceramic obtained in Example 1.

[0034] Figure 7 This is a test diagram of the microwave absorption performance of the cordierite ceramic obtained in Comparative Example 1. DETAILED DESCRIPTION

[0035] The present invention is described below in detail with reference to specific embodiments of the present invention. The description herein is intended only to explain the present invention and is not intended to limit the present invention. Based on the embodiments of the present invention, any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art without creative work in all other embodiments obtained by them should be included within the scope of protection of the present invention.

[0036] Example 1

[0037] (1) In this embodiment, MgO, Al2O3, SiO2, CuO, FeO, MnO, ZrO2, GaO, Cr2O3, Ti2O3, and Fe2O3 are selected as raw materials for preparing low expansion coefficient and high entropy cordierite. MgO (4 molar fraction), Al2O3 (6 molar fraction), SiO2 (60 molar fraction), CuO (4 molar fraction), FeO (4 molar fraction), MnO (4 molar fraction), ZrO2 (4 molar fraction), GaO (4 molar fraction), Cr2O3 (6 molar fraction), Ti2O3 (molar fraction 6), Fe2O3 (molar fraction 6); first, according to the capacity requirement of the ball mill jar in the subsequent ball milling process (2.5g-10g), a certain amount of MgO, Al2O3, SiO2, CuO, FeO, MnO, ZrO2, GaO, Cr2O3, Ti2O3, Fe2O3, etc. are weighed and put into the ball mill jar according to the stoichiometric ratio of each cordierite raw material, deionized water or anhydrous ethanol is added, the water-to-material ratio is 2, and zirconium oxide or high manganese steel balls with a ball-to-material ratio of 2 are added, a rubber ring is placed on the sealing of the ball mill jar, and the ball mill cover is covered and sealed.

[0038] (2) Adjust the ball milling time of the planetary ball mill to 4-8h, set the speed to 100-250rpm, and place the ball mill jar in the ball mill for ball milling.

[0039] (3) After the initial ball milling is completed, the ball mill jar is transferred to the glove box, the ball mill jar is opened, and the raw materials in the ball mill jar are transferred to the culture dish, and then the culture dish is placed in the drying oven. The drying temperature is set at 50-80 ° C and the drying time is set to 6-8 h.

[0040] (4) After drying, the raw materials were taken out and placed in a household crusher, and ground into powder using a crusher. The effects of ball milling time and speed on the morphology and properties of high-entropy cordierite were analyzed to determine the appropriate ball milling time and speed.

[0041] (5) Take a certain amount of crushed raw materials, add 8% PVA solution or deionized water as a binder, place it in a circular mold with a diameter of 20 mm, and dry-press the crushed raw materials under a pressure of 10-30 MPa. After maintaining the pressure for 30 seconds, take out the molded sample.

[0042] (6) Place the dry-pressed sample into a crucible and bury the sample in SiC powder that has been calcined at 1600°C for more than two times. Then place the crucible in a high-temperature box furnace for sintering. The sintering temperature is set at about 1300°C; the heating rate is 5°C / min, and the holding time is 2-4h.

[0043] (7) The sintered samples are analyzed and characterized to determine their phase composition and morphology.

[0044] Example 2

[0045] The raw material composition and preparation steps are consistent with those in Example 1, and the sintering temperature is 1350°C.

[0046] Example 3

[0047] The raw material composition and preparation steps are consistent with those in Example 1, and the sintering temperature is 1200°C.

[0048] Example 4

[0049] The raw material composition and preparation steps are consistent with those in Example 1, and the sintering temperature is 1400°C.

[0050] Example 5

[0051] The raw material composition is MgO (6 molar fraction), Al2O3 (10 molar fraction), SiO2 (75 molar fraction), CuO (6 molar fraction), FeO (6 molar fraction), MnO (6 molar fraction), ZnO (6 molar fraction), Fe2O3 (10 molar fraction), and GeO2 (10 molar fraction). The preparation steps are the same as those in Example 1, and the sintering temperature is 1300°C.

[0052] Example 6

[0053] The raw material composition is MgO (6 molar fraction), Al2O3 (10 molar fraction), SiO2 (75 molar fraction), CuO (6 molar fraction), FeO (6 molar fraction), ZrO2 (6 molar fraction), GaO (6 molar fraction), Cr2O3 (10 molar fraction), and V2O5 (10 molar fraction). The preparation steps are the same as those in Example 1, and the sintering temperature is 1300°C.

[0054] Single-phase high-entropy cordierite ceramics were prepared in Examples 1-6.

[0055] Comparative Example 1

[0056] This comparative example is used to compare the performance of cordierite ceramics prepared by one-step synthesis without doping. The raw material composition is MgO (2 molar fraction), Al2O3 (2 molar fraction), and SiO2 (5 molar fraction). The preparation steps are consistent with Example 1, and the sintering temperature is 1300°C.

[0057] The sintered sample of Example 1 was subjected to SEM examination. Figure 3 and Figure 4 , we can see that the sample is well crystallized and has a single-phase structure.

[0058] The sintered samples of Example 1 and Example 2 were subjected to XRD testing, and the results were as follows: Figure 2By comparison, it can be seen that the 10° diffraction peak of Example 2 is reduced, indicating that the sintering temperature of 1300°C is more conducive to the formation of single-phase high-entropy cordierite ceramics.

[0059] like Figure 5 , comparing the infrared spectra of Example 1 (blue), Example 2 (red) and Comparative Example 1 (black), relative to the ordinary cordierite ceramics of Comparative Example 1, the peaks of the infrared spectra of Example 1 and Example 2 shift toward the direction of increasing wavenumber, proving that high-entropy cordierite ceramics were synthesized in both Example 1 and Example 2.

[0060] In addition, the electromagnetic wave absorption performance of the sintered sample of Example 1 was tested by the coaxial method of the vector network analyzer. The results are as follows: Figure 6 , its minimum reflection loss (RL) is -17.63dB (4.9mm) and its maximum effective absorption bandwidth (EAB) is 3GHz (1.8mm).

[0061] In some other embodiments, the minimum reflection loss (RL) of the sintered samples reached -20 dB.

[0062] It is proved that the high entropy cordierite ceramics prepared by the method of the present invention has good electromagnetic wave absorption performance and is a new type of wave absorbing material.

[0063] The electromagnetic wave absorption performance of the sintered sample of comparative example 1 was tested. The results are as follows: Figure 7 , the electromagnetic wave reflection loss is very small, proving that ordinary cordierite ceramics do not have electromagnetic wave absorption properties.

[0064] The bulk density of the sintered sample of Example 1 is 2.1 g / cm 3 The bulk density of the sintered sample of Comparative Example 1 is 2.4 g / cm 3 The bulk density of high-entropy cordierite ceramics is approximately 13% lower than that of ordinary cordierite ceramics. When used in microwave-absorbing materials, this lower bulk density facilitates weight reduction. The sintered sample of Example 1 exhibited a compressive strength of 70 MPa, which is not significantly different from that of ordinary cordierite ceramics. This indicates that the compressive strength does not decrease as the bulk density decreases.

Claims

1. A one-step synthesis process for preparing high-entropy cordierite ceramics, characterized by: The following steps are included: 1) Weighing 4 mol parts of MgO, 6 mol parts of Al2O3, 60 mol parts of SiO2, 4 mol parts of CuO, 4 mol parts of FeO, 4 mol parts of MnO, 4 mol parts of ZrO2, 4 mol parts of GaO, 6 mol parts of Cr2O3, 6 mol parts of Ti2O3, and 6 mol parts of Fe2O3, and then ball milling and mixing to obtain a mixture; 2) The mixture is added with a binder for molding and sintered at high temperature; Silicon carbide is used as filler during high-temperature sintering, and silicon carbide is calcined twice at above 1600°C; the sintering temperature is 1200~1400°C.

2. The process for preparing high-entropy cordierite ceramics by one-step synthesis according to claim 1, wherein: In step 1), deionized water or anhydrous ethanol is added during ball milling for wet grinding, and the mixture is dried and ground into powder.

3. The process for preparing high-entropy cordierite ceramics by one-step synthesis according to claim 1, characterized in that: In step 2), the binder is an 8% PVA solution or deionized water.

4. A high-entropy cordierite ceramic prepared by the process for preparing a high-entropy cordierite ceramic synthesized in one step according to any one of claims 1 to 3.

5. Use of high-entropy cordierite ceramics prepared by the one-step synthesis process of high-entropy cordierite ceramics according to any one of claims 1 to 3 in microwave absorbing materials.

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