缺陷介孔TiO2的制备及其吸波性能研究

Study on the preparation of defective mesoporous TiO2 and its absorbing properties

摘要:

目前，电子通信设备产生的电磁辐射问题日益突出。为了应对电磁污染，迫切需要开发一种厚度薄、重量轻、吸收频率宽和吸收能力强的微波吸收材料。TiO2因具有密度低和稳定性高的特点，成为一种有潜力的微波吸收材料。然而，纯TiO2 材料因电磁响应性差、介电常数低及电磁波衰减能力不足，从而限制了其实际应用。为了提升TiO2 的微波吸收性能，采用无溶剂自组装策略，在不同温度下合成了介孔TiO2，并通过N2 气氛还原处理引入缺陷，成功制备了富缺陷介孔TiO2。通过X 射线衍射（XRD）和透射电子显微镜（TEM）对试样的晶体结构和微观形貌进行表征，借助X 射线光电子能谱（XPS）对介孔TiO2 还原前后元素价态的变化进行分析，利用N2 吸附-脱附等温曲线对试样的比表面积和孔结构特征进行探讨，并通过矢量网络分析仪测量试样的电磁参数。同时，系统地研究了合成温度和还原处理对试样电磁吸波性能的影响。结果表明：随着合成温度的提高，介孔TiO2 晶相从单一锐钛矿相转变为锐钛矿与金红石的混合相；尽管N2气氛还原处理保持了介孔结构，但比表面积有所下降，并在表面生成大量氧空位缺陷；合成温度对试样的电磁参数影响较小，而还原处理显著提升了其介电常数。值得一提的是，在500 ℃下合成并还原处理的介孔TiO2，其表现出优异的吸波性能，当厚度为5. 05 mm 时最小反射损耗值达到?30. 5 dB、有效吸收带宽为2. 32 GHz，该优异性能得益于介孔结构提供的大比表面积、第二相引入的界面极化损耗及缺陷诱导的偶极子极化。本研究为高性能TiO2基微波吸波材料的制备提供了有效途径。

Abstract:

The issue of electromagnetic radiation from electronic communication devices has become increasingly critical. To tackle electromagnetic pollution, there is an urgent demand for microwave-absorbing materials that are thin, lightweight, possess a broad absorption frequency range, and demonstrate strong absorption capacity. TiO2 has emerged as a promising candidate due to its low density and high stability. However, the application of pure TiO2 is hindered by poor electromagnetic response, low dielectric constant, and insufficient attenuation characteristics. To enhance the microwave absorption performance of TiO2, mesoporous TiO2 was synthesized using a solvent-free self-assembly method at various temperatures, followed by reduction treatment to introduce defects, resulting in defect-rich mesoporous TiO2. The crystal structure and morphology of the materials were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM), while X-ray photoelectron spectroscopy (XPS) was employed to analyze changes in elemental valence before and after the reduction of. The specific surface area and pore structure characteristics were evaluated through nitrogen adsorption-desorption isotherms, and the electromagnetic parameters were measured with a vector network analyzer. The study systematically explored the effects of synthesis temperature and reduction treatment on the electromagnetic absorption of mesoporous TiO2. Results show that as synthesis temperature increase, mesoporous TiO2 transitions from a pure anatase phase to a mixture of anatase and rutile phase. After reduction treatment, the mesoporous structure remains intact, although specific surface area decreases, and a significant number of oxygen vacancies are introduced. While synthesis temperature has a minor effect on electromagnetic parameters, the dielectric constant improvs significantly after reduction treatment. Mesoporous TiO2 synthesized at 500 ℃ and subjected to reduction treatment exhibited excellent wave absorption properties, with a minimum reflection loss of ?30.5 dB at a simulated thickness of 5.05 mm and an effective absorption bandwidth of 2.32 GHz. This excellent microwave absorption performance is attributed to the large specific surface area provided by the mesoporous structure, enhanced interfacial polarization loss from the secondary phase, and defect-induced dipole polarization. This study provides a viable approach for the development of high performance TiO2-based microwave absorbing materials.