Prediction of New Structure, Phase Transition, Mechanical, and Thermodynamic Properties of Nb3Si

Abstract

Although Nb-based silicides are promising high temperature materials, the high temperature application of Nb-based silicides is markedly influenced by Nb 3 Si phase. However, the structure and relevant properties of Nb 3 Si are not completely clear. To solve these problems, in this paper, we systematically investigate the structure, elastic properties, brittle or ductile behavior, and thermodynamic properties of Nb 3 Si based on the first-principle calculations. Additionally, phase transition of Nb 3 Si under high pressure is studied in detail. The calculated results show that two new Nb 3 Si phases: Br 3 Sm-type (space group: Cmcm, No.63) and Sc 3 In-type (space group: P63/mmc, No.194) are predicted. Although Nb 3 Si with Ta 3 Si-type is the most stable structure, pressure leads to phase transition from Ta 3 Si-type structure to V 3 Si-type structure at %60 GPa. We further demonstrate that Nb 3 Si is a ductile material. Importantly, we find that the heat capacity of Nb 3 Si with tetragonal structure is about 190 J (mol K) À1 , which is two times larger than that of other structures.

Wet Ball Milling Applied to Production of Composites and Coatings Based on Ti, W, and Nb Carbides

“…MA of Nb-Si in petroleum ether gives a metastable supersaturated solid solution of alloying elements in niobium and niobium hydride phase NbH 0.9 by 4 h of milling, which decomposes under annealing at 900 • C into niobium subcarbide Nb 2 C, carbon-stabilized niobium silicide Nb 5 Si 3 C x (D8 8 ) (ICSD#65-3599), and Nb 3 SiC x with the L1 2 structure (sample NbSi, Figure 12). The Nb 3 Si (ICSD#15-630) silicide with the L1 2 structure is considered to be unstable [36], but it is stabilized in the presence of interstitial carbon [22,37]. Annealing at 1300 • C induces its decomposition into η-carbide (Nb,Fe) 6 C and the Nb 4 SiFe (ICSD#18-647) intermetallic.…”

Influences of Vacancy Concentration and Al Substitution on Structural, Electronic, and Elastic Properties of Nb5Si3 from First‐Principles Calculations

“…[13] In previous work, the mechanical properties of Nb-Si-based superalloys [14][15][16][17] have been studied. Such as, the obtained B and G of Nb 3 Si are 182 and 76 GPa, [18] and the value of B and G of NbSi 2 are 174 and 142 GPa, [19] respectively. In the article, our work further found that the values of B and E of Nb 5 Si 3 are 193.23 and 310.77 GPa, which are higher than those of Nb 3 Si and NbSi 2 .…”