ZrB2-coated BN coated powder and preparation method thereof

Abstract

The invention provides ZrB2-coated BN coated powder and a preparation method thereof, and belongs to the technical field of new materials. The ZrB2-coated BN coated powder product is prepared through a specific BN coating process, and the ZrB2-coated BN coated powder product is excellent in dielectric property and can be used for manufacturing wave-absorbing materials, reducing reflection of electromagnetic waves and improving stealth performance. The preparation and performance research of the ZrB2-coated BN coated powder can promote the scientific research in the fields of material science, high-temperature physics, chemistry and the like, and the ZrB2-coated BN coated powder has wide application potential in multiple fields.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and particularly to a ZrB 2 @BN coated powder and a preparation method thereof. Background Art

[0002] Zirconium diboride (ZrB 2 ) is a ultra-high temperature ceramic material, which is famous for its high melting point (about 3245 °C), high hardness (23 GPa), high thermal conductivity and electrical conductivity, good corrosion resistance and oxidation resistance, and excellent high-temperature mechanical properties. Due to these characteristics, ZrB 2 has a wide range of applications in the fields of aerospace, high-temperature structural materials, wear-resistant materials, electronic devices, high-temperature radar stealth, etc.

[0003] There are various methods for optimizing the wave absorption performance of ZrB 2 in the prior art. For example, a surface-treated nano ultra-high temperature ceramic absorbent and a preparation method thereof disclosed in Chinese Patent CN118619681A. For the surface-treated nano ultra-high temperature ceramic absorbent: by controlling the heat treatment time and temperature, the surface composition of nano ZrB 2 is changed to regulate the dielectric constant of nano ZrB 2 . Subsequently, the absorbent is dispersed in liquid polysiloxane, cross-linked and cured, and then pressed into a shape, and pyrolyzed at high temperature to form a ZrB 2 -SiOC composite material. The change of the surface composition of ZrB 2 in the composite material can regulate the impedance matching and conductance loss of the composite material, effectively improving the wave absorption performance of the composite material; a heterogeneous interface is formed between different phases in the material, causing interfacial polarization and improving the polarization loss ability. In addition, since pores are formed inside the ceramic after the pyrolysis of SiOC ceramic, the existence of pores is beneficial to the entry of electromagnetic waves into the material on the one hand, and on the other hand, it can cause multiple reflections of electromagnetic waves in the material, improving the loss ability.

[0004] However, the existing methods still have limitations, and the wave absorption performance of the obtained products needs to be improved. Summary of the Invention

[0005] The purpose of the present invention is to provide a ZrB 2 @BN coated powder and a preparation method thereof, which have better wave absorption performance.

[0006] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions: The present invention provides a preparation method of a ZrB 2 @BN coated powder, comprising the following steps: Mix and dissolve boric acid and urea to obtain Solution 1; Mix Solution 1 with ZrB 2 and perform magnetic stirring, ultrasonic dispersion treatment, and drying treatment in sequence to obtain a mixed powder; Calcine the mixed powder to obtain a composite powder; Perform heat preservation treatment on the composite powder to obtain ZrB 2 @BN coated powder.

[0007] Preferably, the molar ratio of the mixture of boric acid and urea is 1:2 - 4.

[0008] Preferably, the time of the magnetic stirring is 0.5 - 1.5 h; and / or, the time of the ultrasonic dispersion treatment is 20 - 40 min.

[0009] Preferably, the temperature of the calcination treatment is 700 - 900 °C; and / or, the time of the calcination treatment is 20 - 40 min.

[0010] Preferably, the calcination treatment is carried out in a mixed atmosphere, and the mixed atmosphere contains ammonia and argon; and / or, the proportion of ammonia in the mixed atmosphere is 5 - 20%; and / or, the temperature of the heat preservation treatment is 1400 - 1700 °C; and / or, the time of the heat preservation treatment is 1 - 3 h.

[0011] Preferably, the preparation method of the ZrB 2 powder includes the following steps: Mix ZrO 2 and B 4 C, add a ball milling aid, and perform ball milling to obtain a ball milling product; Perform drying and calcination on the ball milling product in sequence to obtain a calcined product; Wash and ultrasonically treat the calcined product to obtain ZrB 2 ; The temperature of the calcination is 1000 - 2000 °C; The time of the calcination is 0.5 - 2 h.

[0012] Preferably, the molar ratio of the mixture of ZrO 2 and B 4 C is 7:5 - 6.

[0013] Preferably, the ball milling aid is anhydrous ethanol; and / or, the time of the ball milling is 12 - 36 h; and / or, the rotation speed of the ball milling is 200 - 400 r / min; And / or, in the ball milling, the mass ratio of the raw material to the grinding balls is 1:4 to 6.

[0014] Preferably, the temperature of the drying is 60 to 100 °C; And / or, the time of the drying is 4 to 6 h; And / or, the detergent used for the washing is water and / or ethanol.

[0015] The present invention also provides a ZrB 2 @BN-coated powder prepared by the above preparation method.

[0016] Advantages of the present invention: The present invention has prepared a ZrB 2 @BN-coated powder product through a specific BN coating process. The dielectric properties of the ZrB 2 powder product and the ZrB 2 @BN-coated powder product are excellent, and it can be used to manufacture wave-absorbing materials, reduce the reflection of electromagnetic waves, and improve the stealth performance. Due to the excellent oxidation resistance of BN, the ZrB 2 @BN-coated powder product provided by the present invention has greater application potential at high temperatures.

[0017] The ZrB of the present invention 2 and ZrB 2 The research on the preparation and properties of the @BN-coated powder can promote scientific research in the fields of materials science, high-temperature physics, and chemistry, and has broad application potential in multiple fields. Description of the Drawings

[0018] Figure 1 For the X-ray diffraction (XRD) pattern of synthesizing ZrB 2 and ZrB 2 @BN-coated powder by the calcination method, where Figure 1 (a) is the XRD pattern of the ZrB 2 product; (b) is the XRD pattern of the ZrB 2 @BN-coated powder product; Figure 2 For the microscopic morphology diagrams of ZrB 2 before and after coating with BN, where the processing parameters of a1-a2 are 1600 °C / 1 h; the processing parameters of b1-b2 are 800 °C / 0.5 h; the processing parameters of c1-c2 are 1600 °C / 2 h; Figure 3 For ZrB with different 2 contents (70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%) of ZrB 2 / The changes in the real part, imaginary part of the dielectric constant, and dielectric loss of the paraffin composite, where (a) is for different ZrB 2 contents of ZrB 2 / the real part of the dielectric constant of the paraffin composite, (b) is for different ZrB 2 contents of ZrB 2 / the imaginary part of the dielectric constant of the paraffin composite, (c) is for different ZrB 2 contents of ZrB 2 / the dielectric loss of the paraffin composite; Figure 4 is the electromagnetic wave absorption performance of ZrB 2 / paraffin composites at ZrB 2 contents of 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, where (a) is the reflection loss of ZrB 2 / paraffin composites at ZrB 2 content of 70 wt%, (b) is the reflection loss of ZrB 2 / paraffin composites at ZrB 2 content of 75 wt%, (c) is the reflection loss of ZrB 2 / paraffin composites at ZrB 2 content of 80 wt%, (d) is the reflection loss of ZrB 2 / paraffin composites at ZrB 2 content of 85 wt%, (e) is the reflection loss of ZrB 2 / paraffin composites at ZrB 2 content of 90 wt%; Figure 5 is the changes in the real part, imaginary part of the dielectric constant, and dielectric loss of ZrB 2 @BN / paraffin composites at ZrB 2 @BN contents of 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, where (a) is the real part of the dielectric constant of ZrB 2 @BN / paraffin composites at different ZrB 2 @BN contents, (b) is the imaginary part of the dielectric constant of ZrB 2 @BN / paraffin composites at different ZrB 2 @BN contents, (c) is the dielectric loss of ZrB 2 @BN / paraffin composites at different ZrB 2 @BN contents; Figure 6 is the electromagnetic wave absorption performance of ZrB 2 @BN / paraffin composites at ZrB 2Absorbing properties of @BN with contents of 70 wt%, 75 wt%, 80 wt%, 85 wt%, and 90 wt%. Among them, (a) is ZrB 2 @BN / paraffin composite material in ZrB 2 Reflection loss when the @BN content is 70 wt%, (b) is ZrB Reflection loss of @BN / paraffin composite material in ZrB 2 @BN / paraffin composite material in ZrB 2 Reflection loss when the @BN content is 75 wt%, (c) is ZrB 2 @BN / paraffin composite material in ZrB 2 Reflection loss when the @BN content is 80 wt%, (d) is ZrB 2 @BN / paraffin composite material in ZrB 2 Reflection loss when the @BN content is 85 wt%, (e) is ZrB 2 @BN / paraffin composite material in ZrB 2 Reflection loss when the @BN content is 90 wt%. Specific implementation manners

[0019] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0020] Embodiment 1 Weigh the raw materials Weigh ZrO 2 and B 4 C raw materials. The molar ratio of ZrB 2 : B 4 C is 7:5.5.

[0021] Ball milling and mixing Put the weighed raw materials and grinding balls into the ball milling tank, and add an appropriate amount of anhydrous ethanol for ball milling. Among them, the ball milling time is 24 h, and the ball milling speed is 300 r / min. The mass ratio of the raw materials to the grinding balls is 1:5, and the mass ratio of the large (8 mm): medium (5 mm): small (3 mm) grinding balls is 2:5:3.

[0022] Dry the powder Place the ball-milled powder in a drying oven and dry it at 80 °C for 5 h to obtain the dried mixed powder.

[0023] Calcination and synthesis Put the dried mixed raw materials in a BN crucible, and then place it in a tubular atmosphere furnace. The calcination temperature is 1600 °C, and the calcination time is 1 h to obtain the calcined product.

[0024] After obtaining the calcined product, perform water washing and ultrasonic treatment Washing process: The powder is magnetically stirred in deionized water (the water bath heating temperature is 90 °C), and evaporated by magnetic stirring in the water bath. During the evaporation process, deionized water is added, and then evaporated again by magnetic stirring in the water bath. When a part of the deionized water is evaporated, suction filtration is carried out. After suction filtration, alcohol is added and ultrasonically stirred for 30 min, then suction filtration is carried out again, and alcohol is ultrasonically stirred for 30 min again. Finally, suction filtration and drying are carried out to obtain ZrB 2 .

[0025] Preparation of ZrB 2 @BN-coated powder, and the specific steps are as follows: Boric acid (H 3 BO 3 ) and urea [CO(NH 2 ) 2 are added to absolute ethanol in a molar ratio of 1:3 and completely dissolved, and an appropriate amount of deionized water is added. Based on the amount of H 3 BO 3 , according to the proportion that the volume content of BN generated by stoichiometry is 30%, the above-prepared ZrB 2 is added to the solution, magnetically stirred for 1 h, and then ultrasonically dispersed for 30 min. The obtained suspension is dried to obtain a mixed powder. Then, the mixed powder is calcined in a mixed gas of ammonia / argon with an ammonia content of 10% at 800 °C for 0.5 h to prepare a ZrB 2 composite powder with amorphous BN coated on the surface. The composite powder is kept at 1600 °C for 2 h to crystallize the amorphous BN, and a ZrB 2 composite powder (ZrB 2 @BN-coated powder, denoted as ZrB 2 @BN in subsequent experiments) is obtained.

[0026] Experimental examples The products prepared by the present invention are subjected to performance testing: The X-ray diffraction (XRD) patterns of the ZrB 2 and ZrB 2 @BN materials synthesized by the calcination method of Example 1 are as Figure 1 shown. In Figure 1 (a), all the diffraction peaks of ZrB 2 are consistent with the crystal structure of the standard ZrB 2 , indicating that the prepared ZrB 2 has high purity and no impurity phase is generated, verifying the effectiveness of the calcination process. Figure 1 (b), in addition to the diffraction peaks matching the ZrB 2 phase, characteristic diffraction peaks of boron nitride (h-BN) are also detected, indicating that ZrB 2 with BN coated on the surface is successfully prepared. 2@BN composite material, and the coating of the BN layer does not damage the crystal structure of ZrB 2 These results indicate that the calcination method provided by the present invention can effectively synthesize high-purity ZrB 2 and its surface-modified ZrB 2 @BN coating material.

[0027] Based on the preparation method of Example 1, the quality of the products prepared under different process parameters was tested: during the calcination synthesis process, at different preparation stages, different calcination products were obtained by setting different process parameters. The scanning morphology diagrams of ZrB 2 before and after coating with BN are as shown in Figure 2 wherein, the processing parameters of a1-a2 are 1600°C / 1h (corresponding to Example 1: placing the dried mixed raw materials in a BN crucible, then placing it in a tubular atmosphere furnace, the calcination temperature is 1600°C, and the calcination time is 1h to obtain the calcined product); the processing parameters of b1-b2 are 800°C / 0.5h (corresponding to Example 1: calcining the mixed powder in a mixed gas of ammonia / argon with an ammonia content of 10% at 800°C for 0.5h); the processing parameters of c1-c2 are 1600°C / 2h (corresponding to Example 1: keeping the composite powder at 1600°C for 2h to crystallize the amorphous BN). As can be seen from Figure 2 , (a-a1) is the powder sample obtained under the process conditions of keeping at 1600°C for 1h. The particle size is small and the distribution is uniform. Mixing the powder sample with boric acid and urea to obtain a mixed powder. After treating the mixed powder in a mixed atmosphere at 800°C for 0.5h, a layer of amorphous BN (b-b1) appears on its surface. It can be found that the amorphous BN completely coats ZrB 2 , showing a relatively obvious heterogeneous structure. (c-c1) is the microscopic morphology of the product after the crystallization treatment. It can be found that the BN layer becomes clearer and wraps on the surface of the ZrB 2 phase.

[0028] Figure 3 Shows the changes in the real part, imaginary part and dielectric loss of the dielectric constant of ZrB 2 / paraffin composite materials with different ZrB 2 contents (70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%). With the increase of the ZrB 2 content, the real part of the dielectric constant of the composite material ( Figure 3 (a)) gradually increases. Especially when the ZrB 2 content reaches 90 wt%, the real part of the dielectric constant reaches the maximum, indicating that the introduction of ZrB 2 enhances the polarization ability of the composite material. The imaginary part of the dielectric constant ( Figure 3(b) shows certain fluctuations, indicating that the increase in ZrB 2 content has an impact on the dielectric loss of the composite material. In terms of dielectric loss ( Figure 3 (c)), with the increase in ZrB 2 content, the loss gradually increases. Especially when the ZrB 2 content exceeds 80 wt%, the dielectric loss increases significantly, which may be related to the charge accumulation effect caused by ZrB 2 particles. These results indicate that the dielectric properties of the ZrB 2 / paraffin composite material of the present invention are significantly affected by the ZrB 2 content and have potential application value.

[0029] Figure 4 Shows the wave absorption properties of ZrB 2 / paraffin composite materials with different ZrB 2 contents (70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%), especially the trend of the minimum value of reflection loss (RL min ) with the change of ZrB 2 content in the high-frequency range. With the increase in ZrB 2 content, the RL min value of the composite material gradually decreases and then increases, indicating that the addition of ZrB 2 can effectively enhance the wave absorption ability of the composite material, but too high ZrB 2 content may lead to impedance mismatch and deteriorate the wave absorption performance. When the ZrB 2 content is 80 wt%, the RL min value of the composite material reaches the minimum, showing the best wave absorption effect. Under the conditions of a frequency of 16.56 GHz and a thickness of 1.05 mm, RL min and the effective wave absorption bandwidth (RL < -10 dB) are -43.84 dB and 2.32 GHz respectively. When the ZrB 2 content is 85 wt% and 90 wt%, the RL min values of the composite material are -31.43 dB and -30.33 dB respectively, and the wave absorption performance gradually deteriorates. The above results indicate that the ZrB 2 content significantly affects the wave absorption performance of the composite material. A higher ZrB 2 content can improve the electromagnetic wave absorption ability of the composite material, but when the content is too high, the wave absorption performance will gradually deteriorate due to impedance mismatch.

[0030] Figure 5 Shows different ZrB 2ZrB with BN content (70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%) 2 @Real part, imaginary part of dielectric constant and change of dielectric loss of BN / paraffin composite materials. As the ZrB 2 @content of BN increases, the real part of the dielectric constant of the composite material ( Figure 5 (a)) gradually increases. Especially when the ZrB 2 @BN content is 85 wt% and 90 wt%, the real part of the dielectric constant increases significantly, indicating that a higher content of ZrB 2 @BN enhances the polarization ability and electromagnetic response ability of the composite material. The imaginary part of the dielectric constant ( Figure 5 (b)) shows a certain fluctuating trend. As the ZrB 2 @BN content increases, the imaginary part increases, especially above 85 wt%, indicating that the dielectric loss of the composite material also increases. Specifically, the dielectric loss ( Figure 5 (c)) gradually increases with the increase of the ZrB 2 @BN content. Especially at 85 wt% and 90 wt%, the dielectric loss reaches a relatively high level, which may be related to the charge lag effect and polarization process inside the composite material. These results show that the increase of the ZrB 2 @BN content effectively improves the dielectric constant and dielectric loss of the composite material, but too high ZrB 2 @BN content may also lead to impedance mismatch of the composite material, indicating that impedance matching and dielectric loss need to be balanced in specific applications.

[0031] Figure 6 Shows the wave absorption performance of ZrB 2 @BN / paraffin composite materials with BN coated on the surface of ZrB 2 @at different ZrB 2 @BN contents (70wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%). The results show that as the ZrB 2 @BN content increases, the wave absorption performance of the composite material is significantly improved, especially showing better reflection loss characteristics in the high-frequency band (10 - 18 GHz) range. Specifically, when the ZrB 2 @BN content is 85 wt%, the thickness is 0.95 mm and the frequency is 14.8 GHz, the minimum reflection loss (RL min ) reaches -35.56 dB, and the effective absorption bandwidth (RL < -10dB) reaches 4.72 GHz; while at ZrB 2When the BN content is 90 wt% and the thickness is 0.85 mm, the lowest reflection loss is -30.53 dB, and when the thickness is 0.95 mm, the corresponding effective absorption bandwidth is 3.68 GHz. The above results show that compared with Figure 3 ZrB in 2 / paraffin composite materials, ZrB 2 @BN / paraffin composite materials have excellent effective absorption bandwidth because the ZrB 2 @BN heterointerface not only increases the polarization loss of the composite material but also optimizes the impedance matching, enabling electromagnetic waves to enter the material and be dissipated. Therefore, excellent microwave absorption properties can be obtained by coating ZrB2 with BN and controlling the content of the absorber. This method is applicable to the development of high-performance microwave absorption materials.

[0032] As can be seen from the above examples, the present invention realizes the self-preparation of ZrB 2 by the boron carbide reduction method and provides a process for coating BN. The present invention prepares two powder products: ZrB 2 and ZrB 2 @BN-coated powder. The phase of the two powders is characterized by XRD, the morphology is characterized by SEM, and the real and imaginary parts of the dielectric constants of the two powders are compared, and their microwave absorption properties are compared, indicating that their properties are excellent and have broad application prospects.

[0033] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing ZrB2@BN coated powder, characterized in that: The following steps are involved: Mix and dissolve boric acid and urea to obtain solution 1; The solution 1 is mixed with ZrB2, and then subjected to magnetic stirring, ultrasonic dispersion treatment, and drying treatment in sequence to obtain a mixed powder; calcining the mixed powder to obtain composite powder; The composite powder is subjected to heat preservation treatment to obtain ZrB2@BN coated powder.

2. The method for preparing ZrB2@BN coated powder according to claim 1, characterized in that: The molar ratio of the boric acid to the urea is 1:2-4.

3. The method for preparing ZrB2@BN coated powder according to claim 1, characterized in that: The magnetic stirring time is 0.5 to 1.5 h; And / or, the ultrasonic dispersion treatment time is 20 to 40 minutes.

4. The method for preparing ZrB2@BN coated powder according to claim 1, characterized in that: The calcination temperature is 700-900°C; And / or, the calcination treatment time is 20 to 40 minutes.

5. The method for preparing ZrB2@BN coated powder according to claim 4, characterized in that: The calcination treatment is carried out in a mixed atmosphere containing ammonia and argon; And / or, the proportion of ammonia in the mixed atmosphere is 5-20%; And / or, the temperature of the heat preservation treatment is 1400-1700° C.; And / or, the insulation treatment time is 1 to 3 hours.

6. The method for preparing the ZrB2@BN coated powder according to any one of claims 1 to 5, characterized in that: The preparation method of the ZrB2 powder comprises the following steps: Mix ZrO2 and B4C, add a ball milling aid, and perform ball milling to obtain a ball milling product; The ball-milled product is sequentially dried and calcined to obtain a calcined product; The calcined product is washed and ultrasonically treated to obtain ZrB2; The calcination temperature is 1000-2000°C; The calcination time is 0.5 to 2 hours.

7. The method for preparing ZrB2@BN coated powder according to claim 6, characterized in that: The molar ratio of the ZrO2 and B4C mixture is 7:5-6.

8. The method for preparing ZrB2@BN coated powder according to claim 6, characterized in that: The ball milling aid is anhydrous ethanol; And / or, the ball milling time is 12 to 36 hours; And / or, the rotation speed of the ball mill is 200-400 r / min; And / or, in the ball milling, the mass ratio of raw material to grinding balls is 1:4-6.

9. The method for preparing ZrB2@BN coated powder according to claim 6, characterized in that: The drying temperature is 60-100°C; And / or, the drying time is 4 to 6 hours; And / or, the washing agent used in the washing is water and / or ethanol.

10. ZrB2@BN coated powder prepared by the preparation method according to any one of claims 1 to 9.

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