Open Access Research Article Issue
Synthesis of (HfZrTiNbTa)N powders via nitride thermal reduction with soft mechano-chemical assistance
Journal of Advanced Ceramics 2023, 12 (3): 565-577
Published: 22 February 2023

High-entropy nitride powders are one of prerequisite materials for the preparation of high-performance high-entropy nitride ceramics. In this paper, high-entropy (HfZrTiNbTa)N powders were synthesized via nitride (i.e., silicon nitride (Si3N4)) thermal reduction with soft mechano-chemical assistance. The results show that metal oxides like hafnium dioxide (HfO2), zirconium dioxide (ZrO2), titanium dioxide (TiO2), niobium pentoxide (Nb2O5), and tantalum pentoxide (Ta2O5) can all be transformed into the corresponding metal nitrides in the presence of Si3N4 at 1700 ℃, and solid solution of the metal nitrides can be formed as the temperature increases to 2100 ℃. The high-entropy (HfZrTiNbTa)N powders with submicron-sized particles, a narrower size distribution, and a single face-centered cubic (fcc) structure are obtained from raw material mixtures ground for 10 h and subsequently sintered at 1800 ℃. In addition, the high-entropy bulk nitride ceramics with relative density (Rw) of 94.31%±0.76%, Vickers hardness of 21.00±0.94 GPa, and fracture toughness (KIC) of 3.18±0.16 MPa·m1/2 are obtained with submicron-sized powders, which are superior to those obtained with micron-sized powders.

Open Access Rapid Communication Issue
High-temperature phase relations of ZrN–ZrO2–Y2O3 ternary system
Journal of Advanced Ceramics 2018, 7 (4): 388-391
Published: 28 November 2018

Zirconium nitride (ZrN) ceramics were prepared via hot pressed sintering (HP) at 1750 ℃ in N2 atmosphere with ZrO2–Y2O3 as sintering additive. X-ray diffraction was applied to analyze the phase composition of the as-prepared ceramics to study the high temperature phase relation in ZrN–ZrO2–Y2O3 ternary system and establish ZrN–ZrO2–Y2O3 ternary phase diagrams. The results show that ZrN and tetragonal ZrO2 (t-ZrO2) solid solution, face-centered cubic ZrO2 (c-ZrO2) solid solution, body-centered cubic Y2O3 (c-Y2O3) solid solution coexist in the system of ZrN–ZrO2–Y2O3.

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