Liquid metals have a relatively low melting point, excellent conductivity and thermal conductivity, and therefore have great potential in the application of electrical devices. The low viscosity properties of liquid metals also make them suitable for various processing methods, such as screen printing, reverse molding, inkjet, and so on. In the preparation of three-dimensional structural materials, liquid metals have been reported to be compatible with various 3D printing technologies, such as direct writing 3D printing technology, light curing 3D printing technology, laser assisted 3D printing technology, etc. Ceramic materials have excellent mechanical, antioxidant, and electrical properties, and are widely used in the fields of high temperature, corrosion, electronics, and optics. However, the compatibility between liquid metal materials and ceramic materials has not been verified, and how to composite low viscosity liquid metal materials with high hardness ceramic materials has always been an unresolved problem.

Recently, Kong Jie from Northwestern Polytechnical University and Yang Jiayi from Xi'an University of Science and Technology collaborated to report a new type of liquid metal ceramic metamaterial that can be photocurable and 3D printed. This material has rich dielectric loss mechanisms, improved mechanical properties, and excellent high-temperature resistance. Through the design of the metastructure and 3D printing preparation, it can achieve excellent electromagnetic wave absorption ability for full frequency coverage in the C-X band.

The relevant paper is titled "3D Printing of Liquid metal in ceramic Metamaterials for High efficiency Microwave Absorption" in Adv Function Material (2023, 33, 2307499) Published online.

Paper link:https://onlinelibrary.wiley.com/doi/10.1002/adfm.202307499


Provide beneficial ideas for the research and development of new functionalized advanced ceramics
In this work, the author successfully achieved the composite of liquid metal and SiBOC ceramic materials using the polymer conversion ceramic route. Firstly, a polyborosiloxane ceramic precursor polymer was prepared. By utilizing the perfect compatibility between liquid metal and liquid silicon-based polymers, liquid metal nanoparticles were uniformly dispersed in the ceramic precursor body. Then, the resin was solidified and formed using photocurable 3D printing to obtain the liquid metal ceramic composite material embryo. Finally, the liquid metal ceramic composite material was obtained by cracking in a high-temperature environment (Figure 1).

Research has found that due to the unique low volatility of liquid metals, as well as the chemical inertness of gallium, indium, and Si, B, and C elements in ceramic precursors, liquid metal nanoparticles will not escape the ceramic system in gaseous form or react with other elements in the precursor after cracking at 800 to 1200 degrees Celsius. Meanwhile, due to the typical passivation properties of IIIA group elements in the surface oxide layer of liquid metal, the oxygen element in the ceramic precursor has not been able to consume a large amount of oxygen inside the liquid metal. Ultimately, the liquid metal remains in liquid form, uniformly dispersed within the ceramic system, forming a unique liquid metal ceramic composite material (Figure 2).

Due to the distribution of liquid metal in the ceramic interior as a liquid metal/oxide layer/ceramic core-shell state, ceramic materials introducing liquid metal will exhibit stronger electromagnetic wave loss performance under the same cracking conditions. In addition, thanks to the excellent high-temperature stability of the SiBOC ceramic base itself and the high-temperature semiconductor properties of the liquid metal oxide layer (Ga2O3), the prepared liquid metal ceramic composite matrix can achieve electromagnetic wave absorption coverage in the X-band 74% frequency band at 900 degrees Celsius. At the same time, the introduction of liquid metal can effectively prevent the propagation of stress cracks during the cracking process, thereby improving the overall mechanical strength (Figure 3).

Furthermore, the author utilized the compatibility between liquid metal ceramic composites and DLP-3D printing technology to design and prepare a novel electromagnetic superstructure, achieving broadband electromagnetic wave absorption in the C-X band.

As shown in Figure 4, this work demonstrates the excellent compatibility of liquid metals in the 3D printing preparation of polymer converted ceramic composites, and the introduction of liquid metals can provide improved electrical and mechanical properties, providing beneficial ideas for the development of new functionalized advanced ceramics.

Author Introduction

First author: Xing Ruizhe, postdoctoral fellow at Northwestern Polytechnical University; Corresponding authors: Professor Kong Jie from Northwestern Polytechnical University and Associate Professor Yang Jiayi from Xi'an University of Science and Technology.

This work has received support from the National Science Foundation for Distinguished Young Scholars, the General Program of the National Natural Science Foundation of China, and the China Postdoctoral Science Foundation.