Development with industrial potential with silicon nitride-based electromagnetic metamaterials

Electromagnetic metamaterials with negative physical parameters such as negative dielectric constant and negative magnetic permeability have attracted widespread attention in the academic community. In 2010, they were praised for today’s material as one of the top ten advancements in materials science over the past 50 years.

Unlike traditional electromagnetic materials, it exhibits negative refractive index, complete imaging, superabsorption, and is widely used in optical stealth, wireless communication, electromagnetic wave absorption, and shielding. Introduction of randomly distributed carbon or metal conductive phases into the insulation matrix is ​​one of the important ways to prepare metamaterials.

Silicon nitride ceramics are considered the ideal matrix for preparing metamaterials due to their high insulation, high thermal conductivity, high temperature resistance, corrosion resistance and excellent comprehensive mechanical properties. However, the preparation of silicon nitride-based metamaterials is currently limited to pressure-assisted sintering processes and porous matrix impregnation processes.

Pressure-assisted sintering, such as spark plasma sintering and hot press sintering, is low in production efficiency and is also significantly limited in product shape and size. It is not suitable for industrial scale and has poor toughness as silicon nitride grains cannot fully develop.

The porous impregnation process requires the matrix to have high porosity to promote complete infiltration of the second phase. This has a serious impact on the mechanical properties of the material, weakening the high strength and toughness benefits of silicon nitride ceramics, limiting its application potential. Severe service conditions such as high loads, oxidation, corrosion, and wear environments.

Recently, a team of materials scientists at the Lanzhou Chemical Physics Institute at the Chinese Academy of Sciences proposed a new silicon-based metamaterial that can be used as a second phase and concentrated without mechanical pressure. This material is highly dense and the preparation process is not only suitable for industrial expansion, but silicon nitride grains also grow and develop, maintaining the advantages of high toughness. This has the importance of key guidelines for preparing high-performance metamaterials and industrial applications.

The team has published their work in the Journal of Advanced Ceramics.

“Previous studies have shown that metal tungsten is a second phase consistent with the thermal expansion of silicon nitride ceramics. It reacts chemically with silicon nitride at high temperatures, but our study shows that the appropriate It has been found that nitrogen pressure can effectively inhibit chemical reactions. Creating conditions for the introduction of metallic tungsten.

“With the help of gas pressure, we introduced tungsten into silicon nitride ceramics and found that the introduction of tungsten has a positive effect on the mechanical and tribological properties of silicon nitride ceramics. More importantly, metals Tungsten has a very high melting point.

“After introduction, no melt aggregation is generated during the sintering process of silicon nitride, and there is no significant adverse effect on the sintering activity of silicon nitride, such as carbon materials. By introducing tungsten, the mechanical pressure is achieved. Metamaterial without help.

“Based on previous studies, this study first proposed the use of metallic tungsten as a conductive metal phase to study the preparation of high-performance silicon nitride-based metamaterials, and silicon nitrite in high tungsten The problem of decreasing doceramic concentration was analyzed and solved. The negative dielectric constant behavior of the material was observed when the metal tungsten content reached 20 vol%.

“The preparation of silicon-silicon-based metamaterial densification was achieved without the aid of mechanical pressure,” said a research expert at the Ran-Tu Institute of Chemical Physics at the Chinese Academy of Sciences, a research research expert. One Rugie Wang said. The field of silicon nitride ceramics.

After the 20-roll content of tungsten is introduced, the tungsten particles interconnect to form conductive paths, making the composite conductive. Furthermore, the random distribution of tungsten particles significantly altered the dielectric constant of the composite material, and negative dielectric constant behavior was observed over the frequency range of 40-50 MHz. A silicon nitride-based metamaterial with industrial potential was proposed and prepared to guide industrial exploration and application of high-performance metamaterials.

“Metamaterials have great potential to apply to optical stealth, and we hope that we can use our materials in this respect. The next step is to continue to optimize the composition and structure and to provide dielectric constants at wider frequencies. It’s about exploring the realization of characteristics. Range,” said Rugi Wang.

Other contributors include China’s Academy of Sciences and Zhuhui Qiao of the Institute of Chemical Physics at the Academy of Sciences. Xuejian Liu, Dewei Ni, Hui Zhang, Jie Yin, Zhengren Huang, Shanghai Institute of Science, Shanghai, China; Qian Qi of Shandong University of Science and Technology, Qingdao, China.