The composition change in Fe$_{78}$B$_{13}$Si$_9$ surface layers alloy in solid and liquid states

A. V. Kholzakov

Physical-Technical Institute, Ural Branch of the Russian Academy of Science, Izhevsk, Russia

Abstract: Most studies on the metal melts dedicated bulk properties. Much less work is connected with the study of the surface properties, due to the limited number of methods for studying the surface of metallic melts. Note that the number of publications in this area has recently been greatly reduced. It seems that one of the promising methods for studying the surface is the method of X-ray photoelectron spectroscopy (XPS), which is a non-destructive method and allows us to investigate the chemical structure of the surface layers of the melts. Under the chemical structure of the surface layers composition refers to the analyzed layer (3-5 nm), chemical bonding of the alloy elements and electronic structure (the energy distribution of the valence electrons of the alloy elements in this work is not discussed as a special subject of study). In this paper, the research is carried out using the method of X-ray photoelectron spectroscopy.
The study of the chemical structure and the local atomic environment is curried out in the solid and liquid states alloy Fe$_{78}$B$_{13}$Si$_9$ «in situ» during the single experiment by XPS. The surface layers composition changes analysis is done as the temperature increases. The transition from the crystalline to the liquid state was controlled by changing the oxygen content in the surface layers of the alloy. As a result of the melting the oxygen concentration decreases sharply to experimental error.
The two temperature regions are determined within the liquid state of the Fe$_{78}$B$_{13}$Si$_9$.
In the first temperature region atoms iron in bonding Fe-Si are mainly presented, which are responsible for the formation of cluster type Fe-Si. At the same time of the iron atoms forms bonds with boron, this indicates the forming of Fe-B type clusters in a small amount. Furthermore, the surface layer contains oxides Fe$_2$O$_3$ and SiO$_2$.
In the second temperature range above 1100 $^{\circ}$C, the situation changes significantly. The surface is enriched by iron atoms predominantly in bonding the boron. Apart clusters Fe-B type on the surface more complex groups of atoms are formed such as B-(Fe-O)$_x$, as well as, small amounts of iron oxides FeO and Fe$_2$O$_3$, which may participate in the formation of these clusters.
Thus, during the transition from one temperature region to another clusters composition changes. The surfaces layers in the first temperature region preferably are formed by Fe-Si, in the second are formed by Fe-B.
More accurately to determine the composition of the clusters using XPS data only is not available. The jump-like change in the composition of the surface layers is detected in the investigated melt, which is interpreted as structural transformations within the liquid state.

Keywords: metallic melts; clusters; chemical bond; X-ray photoelectron spectroscopy.

UDC: 669-154+543.621