Metal material that can change color spontaneously

Color is an important attribute of commodity appearance design.Color metal casings of electronic products not only meet people's aesthetic needs, but also increase the added value of goods.Electrochemical deposition (ECD) is a widely used surface coloring technique for metal alloys. Its color comes from visible light interference which is determined by the thickness of surface oxide layer.Because the thickness of the oxide layer does not change during the use of the product, the color achieved by this technology is fixed during the use of the product.

Recently, under the guidance of Prof. Sun Yonghao and Prof. Bai Haiyang, Prof. Wang Pengfei, PhD candidate at the Laboratory of Extreme Conditions Physics, Institute of Physics, Chinese Academy of Sciences/National Research Center for Condensed Matter Physics, Beijing,In collaboration with researchers from the Institute of Physics of the Chinese Academy of Sciences, the University of Chinese Academy of Sciences, Qian Xuesen Space Technology Laboratory and Yang Evangliese Dapu Jinye University, a metallic material that can change color spontaneously under natural conditions was discovered.The surface color of this metal material changes almost every week.The material has uniform and bright color, and its surface can repair itself after wear and tear to reproduce color, and has fluorescence effect under ultraviolet light.

The ability of this metallic material to spontaneously change color is due to the continuous and uninterrupted spontaneous oxidation of the alloy at room temperature.It is an amorphous alloy with the rare earth element cerium as its main component.Due to the chemical activity of cerium, it has a high oxidation rate at room temperature. Due to the uniform defect distribution in the amorphous structure, it avoids the rust spots caused by the rapid oxidation of the local defect location in the polycrystalline alloy, so that the surface oxide layer thickness of the amorphous alloy is uniform.By adding yttrium to the cerium-based amorphous alloy, the researchers were able to adjust the rate at which the metal discoloration occurs under natural conditions.Figure 1 shows the influence of different content of yttrium doping on the color of the material and the fluorescence effect.

The amorphous alloy team led by Wang Weihua, academician of the Institute of Physics, has nearly 20 years of rich experience in the basic and applied research of rare earth based amorphous alloys.The main achievements have been published in Phys. Rev. Lett., Nat. Communs for many times.In the international famous academic journals, the related work has been included in the top ten scientific progress in China.The discovery of metal materials that can spontaneously change color has made rare earth based amorphous alloys more useful as functional materials.The research results not only demonstrate the unique advantages of rare earth based amorphous alloys in appearance applications, but also find that amorphous alloys can be used as precursors of some functional materials, which have great potential in both application and basic research.