High-entropy ceramics (HECs) have attracted much attention due to their huge composition space, unique microstructure, and desirable properties. In contrast to previous studies, which have primarily focused on HECs with one anion, herein, we report a new family of ceramics with both multi-cationic and-anionic structures, i.e., high-entropy carbide-nitrides (Ti 0.33 Zr 0.33 Hf 0.33)(C 0.5 N 0.5), (Ti 0.25 Zr 0.25 Hf 0.25-Nb 0.25)(C 0.5 N 0.5) and (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)(C 0.5 N 0.5). These as-synthesized HECs are mainly comprised of a face-centered cubic solid-solution phase accompanied by minor inevitable oxide phases. The formation mechanism of the solid-solution phase is discussed in terms of the lattice size difference and thermodynamic competition between configurational entropy and mixing enthalpy. It is found that the increment in the configurational entropy can effectively lower the sintering temperature and increase the fracture toughness. Particularly, the newly developed (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)(C 0.5 N 0.5) exhibits a decent fracture toughness of 8.4 MPa m 1/2 and a low sintering temperature of 1750°C, making it promising for ultra-high temperature applications. Our work not only enriches knowledge regarding the HECs categories, but also opens a new pathway for developing HECs with multi-cationic and-anionic structures.
The key step in exploiting a new type of bulk metallic glass (BMG) is to judge quickly the glass forming ability (GFA) of the alloys. The mole melting enthalpies of BMGs are calculated using the weighted averages principle. The reliability and limitation of the T rg criterion for GFA are discussed, and the reason why the T rg of BMGs presently is more than 0?5 is also discussed. In addition, two new criteria, DH mg and DG g , for GFA are presented. The GFA sequence of BMGs is calculated using the DH mg criterion, the result agrees with that of Inoue and Shibata and R c criterion. Furthermore, as an example, the R c of the alloys developed by Dong Chuang et al. are calculated using DH mg and DG g . The ascending sequence of these alloys calculated by the DH mg criterion agrees with that of Dong Chuang et al. In contrast, the result using the DG g criterion is contrary to that of Dong Chuang et al., indicating that the DH mg criterion is better and more convenient than the DG g criterion. The optimum DH mg was found to be -15?16 kJ mol -1 .
A model based on radial base function artificial neural network (RBFANN) was designed for the simulation and prediction of reduced glass transition temperature Trg of glass forming alloys. Its performance is examined by the influences of different kinds of alloys and elements, large and minor change of element content on the Trg, and composition dependence of Trg for La–Al–Ni ternary alloy system. Moreover, a group of Zr–Al–Ni–Cu bulk metallic glasses is designed by RBFANN. The values of Trg predicted by RBFANN agree well with the experimental values, indicating that the model is reliable and adequate.
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