Preparation of resorcinol-formaldehyde enhanced silica aerogels and their absorption properties
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摘要: 为了探究SiO2气凝胶在电磁吸波领域应用的可能性，通过溶胶-凝胶技术引入间苯二酚-甲醛(RF)构建多孔骨架，再结合常压干燥法，成功合成RF/SiO2复合材料，并对RF/SiO2气凝胶进行了热处理，通过SEM、XRD等对热处理后的RF/SiO2气凝胶微观结构和理化性能进行表征，探究了热处理温度对RF/SiO2气凝胶吸波性能的影响规律。结果表明：随热处理温度的增加，吸波性能大幅提升，当热处理温度为1500℃时，RF/SiO2气凝胶在4.05 mm厚度下表现出−48.42 dB的最小反射损耗，当厚度为3.45 mm时有效吸收带宽达到了2.06 GHz，表现出了优异的电磁波吸收性能。该研究为制备高性能吸波材料提供了指导。
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关键词:
- RF/SiO2气凝胶 /
- 溶胶-凝胶法 /
- 微观结构 /
- 热处理 /
- 吸波性能
Abstract: A composite material of resorcinol-formaldehyde (RF) enhanced silica dioxide aerogel (RF/SiO2) had been successfully synthesized by introducing RF to build a porous framework through the sol-gel technique, followed by ambient pressure drying to explore the possibility of the application of silica dioxide aerogel in electromagnetic microwave absorption. The RF/SiO2 aerogel was then subjected to heat treatment, and its microstructure and physicochemical properties after heat treatment were characterized using SEM, XRD, and other methods. The influence of heat treatment temperature on the microwave absorption performance of RF/SiO2 aerogel was investigated. The results show that the microwave absorption performance of RF/SiO2 aerogel is significantly improved with increasing heat treatment temperature. At a heat treatment temperature of 1500℃, the RF/SiO2 aerogel exhibits a minimum reflection loss of −48.42 dB at a thickness of 4.05 mm. At a thickness of 3.45 mm, the effective absorption bandwidth reaches 2.06 GHz, demonstrating excellent electromagnetic wave absorption performance. This study provides guidance for the preparation of high-performance microwave-absorbing materials.-
Key words:
- RF/SiO2 aerogel /
- sol-gel method /
- microstructure /
- heat treatment /
- absorbing performance
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图 1 间苯二酚-甲醛(RF)/SiO2气凝胶的形成及热处理工艺
Figure 1. Formation and heat treatment process of resorcinol-formaldehyde (RF)/SiO2 aerogels
图 2 不同热处理温度下RF/SiO2气凝胶的SEM图像
Figure 2. SEM images of RF/SiO2 aerogels at different heat treatment temperatures
图 3 RF/SiO2、RF/SiO2-800℃和RF/SiO2-1500℃的XRD图谱
Figure 3. XRD patterns of RF/SiO2, RF/SiO2-800℃ and RF/SiO2-1500℃
图 4 RF/SiO2、RF/SiO2-800℃和RF/SiO2-1500℃的N2吸附-脱附等温线
Figure 4. N2 adsorption-desorption isotherms for RF/SiO2, RF/SiO2-800℃ and RF/SiO2-1500℃
图 5 RF/SiO2、RF/SiO2-800℃和RF/SiO2-1500℃的孔径分布
Figure 5. Pore size distribution of RF/SiO2, RF/SiO2-800℃ andRF/SiO2-1500℃
图 6 不同热处理温度下RF/SiO2气凝胶的的反射性能图谱：((a), (d)) RF/SiO2；((b), (e)) RF/SiO2-800℃；((c), (f)) RF/SiO2-1500℃
Figure 6. Reflection performance maps of RF/SiO2 aerogels at different heat treatment temperatures: ((a), (d)) RF/SiO2; ((b), (e)) RF/SiO2-800℃; ((c), (f)) RF/SiO2-1500℃
图 7 RF/SiO2-1500℃：(a) 不同匹配厚度下的反射损耗曲线；(b) 匹配厚度与峰值频率的关系
Figure 7. RF/SiO2-1500℃: (a) Reflection loss curves under different matching thicknesses; (b) Relationship between matching thickness and peak frequency
λ—Wave length
图 8 不同热处理温度下，匹配厚度为4.05 mm时RF/SiO2、RF/SiO2-800℃和RF/SiO2-1500℃的阻抗匹配(a)和衰减常数(b)
Figure 8. Impedance matching (a) and attenuation constant (b) with the matching thickness of 4.05 mm of RF/SiO2, RF/SiO2-800℃ and RF/SiO2-1500℃ at different heat treatment temperatures
图 9 RF/SiO2-1500℃厚度为 4.05 mm时反射损耗与阻抗匹配和衰减常数的关系
Figure 9. Relationship between reflection loss, impedance matching and attenuation constant of RF/SiO2-1 500℃ with the thickness of 4.05 mm
图 10 RF/SiO2、RF/SiO2-800℃和RF/SiO2-1500℃的电磁参数
Figure 10. Electromagnetic parameters of RF/SiO2, RF/SiO2-800℃ and RF/SiO2-1500℃
图 11 Cole-Cole曲线：(a) RF/SiO2-800℃；(b) RF/SiO2-1500℃
Figure 11. Cole-Cole curves: (a) RF/SiO2-800℃; (b) RF/SiO2-1500℃
表 1 气凝胶的孔隙结构性质
Table 1. Pore structure properties of aerogels
Sample BET surface
area/(m2·g−1)Pore volume/
(cm3·g−1)RF/SiO2 370 0.50 RF/SiO2-800℃ 152 0.21 RF/SiO2-1500℃ 82 0.08 Note: BET—Brunau-Emmett-Teller. 
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