Chloride salt assisted reactive molten infiltration method for Cf-UHTCs and their unique microstructure

Abstract

This paper shows the formation mechanism of low-melting silicide impurities during the reactive melt infiltration process. In addition, four kinds of chloride molten salts, i.e., CaCl2, NaCl, KCl, and CSCl, were used to modify Cf-UHTC composites. The results showed that the early formed SiC film on the carbon boundary restricts the diffusion of carbon and hinders the carbonization of the ZrxSiy alloy. This problem can be solved with the assistance of molten chloride salts. Zr and Si can dissolve and be carried by ion melt at a lower temperature and form nano-scale ZrC/SiC mixed films at the carbon boundary; this is helpful for the subsequent carbonization of ZrSi2 alloy. In addition, the viscosity of Zr–Si alloy melt would be reduced and the diffusion of the Zr and Si atoms would be promoted by the addition of the ion melt.