Effect of nonstoichiometry on mechanical properties of reactive hot‐pressed monolithic ZrC_xCeramic

Abstract

The reactive hot pressing (RHP) of Zr:C powder mixture at various molar ratios (1:0.5, 1:0.6, and 1:0.67) at applied pressures of 4‐7 MPa and 1200°C resulted in dense ZrCx ceramics. Nano‐hardness values of ZrCx are reported to be 21‐31 GPa as “x” was varied from 0.5 to 1.0. However, indentation modulus for all ZrCx compositions remained at ~350 GPa. Microhardness of the ZrCx increased from 13 to 15 GPa as the stoichiometry was increased from 0.5 to 1.0. The indentation fracture toughness for ZrC0.5 was 4 MPa m1/2, and for ZrC0.67 it was reduced to 3.6 MPa m1/2. The 3‐point flexural strength for ZrC0.5 was determined to be 386 ± 26 MPa, which decreased to 316 ± 20 MPa as the carbon content (ZrC0.67) was increased. The dry sliding wear of ZrC0.5 to ZrC0.6 indicated that the coefficient of friction was increased from 0.73 to 0.86 at 5 N load and 500 m sliding distance. Further, ZrC0.67 showed a reduction in friction coefficient of 0.81, and this was due to the increase of strong Zr–C covalent bond and unreacted graphite.

Carbon vacancy ordering in zirconium carbide powder

“…2 Similarly, variable carbon stoichiometry is exhibited by other TMCs, such as TiC x , [3][4][5] HfC x , 6,7 VC x , 8 NbC x , 3,9 TaC x , 10,11 and WC x . 12 Carbon stoichiometry affects the sinterability, [13][14][15] mechanical properties, 16,17 electrical properties, 18 and radiation resistance 19 of ZrC x ceramics. Short-and long-range ordering of carbon vacancies in nonstoichiometric carbides have both been studied theoretically.…”

Kinetic role of C/Zr ratio in the reaction process, combustion behavior, and synthetic product of 70 wt.% (xC–Zr)–30 wt.% Cu

“…Among various preparation methods, the combustion synthesis technology has attracted much attention for its easy operation and low energy consumption 14–16 . In addition, the combustion synthesis has been widely used to combine with other routes to prepare composites containing ZrC 17–30 . As these ceramic particles are mainly derived from the combustion synthesis reaction, understanding the kinetic characteristics is vital to achieving a desired microstructure.…”

“…[14][15][16] In addition, the combustion synthesis has been widely used to combine with other routes to prepare composites containing ZrC. [17][18][19][20][21][22][23][24][25][26][27][28][29][30] As these ceramic particles are mainly derived from the combustion synthesis reaction, understanding the kinetic characteristics is vital to achieving a desired microstructure. Conventionally, the influence of the kinetic parameters on the combustion behaviors and synthesized products was predicted by thermodynamic calculations and/or reaction mechanism.…”