New System Research Of Periodic Structure Formation

The formation of periodic layered structure during solid-state reaction was first discovered by Osinski in 1982. In recent years, the interesting structure has been reported in some diffusion couples. Such unusual reaction products have attracted the attention of scholars. And several diffusion models have been proposed. There is a currently accepted theory of periodic layered structure, and the mechanism of this unusual phenomenon becomes clear. Nevertheless, the formation of periodic layered structure during solid-state reaction was discovered occasionally and it's not systemic. The diffusion couple experiments were carried out based on the discovered system, the growth law of periodic layered structure was also analyzed, and the formation dynamic factor of periodic layered structure was proposed in the present paper.In this paper, we analyzed the growth law of periodic layered structure, investigated the common element, found out the diffusion system which may contain the periodic layered structure and design experiments to prove it. The react zone in specimens were investigated by means of scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The formation mechanism of periodic layered structure was proposed according to the experimental results. The diffusion experiments were carried out, and the results showed that periodic layered structure was found in Ni3Si/Zn and Co2Si/Zn solid state diffusion couples. The formation of periodic layered structure during Ni3Si/Zn diffusion couple is in close relations to the reaction time. The physical state of Zn has no influence on the appearance of periodic layered structure.The formation mechanism of periodic layered structure was proposed according to the experimental results. The diffusion experiments of Cu3Si/Zn and Cu38Si7/Zn diffusion couple were also carried out. A special structure which contains different levels was found in Cu38Si7/Zn diffusion reaction zone, which is worth further exploration.Research the microstructure of Mg/SiO2 diffusion couple. It supports the model of diffusion-induced stress very well. The formation mechanism can be well explained with the diffusion-induced stress model. In line with the kinetic descriptions of the model, the computer simulation with VB program was adopted here to model the periodic layered structure formed in Mg/SiO2 system at 973 K and the calculation results coincided well with the experimental data.