Insights into the Bond Behavior and Mechanical Properties of Hafnium Carbide under High Pressure and High Temperature

Abstract

Hafnium carbide (HfC) is a potential candidate of ultrahightemperature ceramics (UHTCs) and has attracted significantly widespread interest in recent years. Here, we have synthesized high-purity HfC samples with NaCl-type structure by using a high-pressure solid−solid reaction. The structural stability, equation of state, plastic deformation, yield strength, and bonding properties under high pressure are investigated by a series of in situ high-pressure synchrotron-radiation angle-dispersive X-ray diffraction experiments combined with first-principles calculations. The yield strength of HfC (∼18 GPa) is obtained from analyzing the plastic deformation behavior under high pressure. In addition, we have successfully prepared bulk HfC ceramics with high density using a high-pressure and high-temperature method. The synthesized sample possesses a desirable Vickers hardness of 24.2 GPa and an excellent fracture toughness of 5.0 MPa•m 1/2 . The present results offer insights into the achievable application of HfC ceramics under extreme conditions and provide a powerful guide for the further design and synthesis of other high-performance UHTCs.

Synthesis and Phase Stability of the High-Entropy Carbide (Ti0.2Zr0.2Nb0.2Ta0.2Mo0.2)C under Extreme Conditions

“…Due to pseudo-incompressibility caused by the nonhydrostatic environment, the data of phase II are invalid for compression behavior and state equation analysis. 38 However, we still can observe an obvious isostructural transition with volume collapse and a 1.5% volume change from phase I to phase II at ∼9.8 GPa. In this work, the cubic-to-cubic isostructural transition phenomenon of HETMC was not found under the hydrostatic environment but in the nonhydrostatic environment.…”

“…Fitting the pressure–volume data of phase II into BM-EOS with a fixed bulk modulus pressure derivative K ′ = 4 yields a bulk modulus K of 408(18) GPa and a volume V 0 of 84.86 Å 3 are observed. Due to pseudo-incompressibility caused by the nonhydrostatic environment, the data of phase II are invalid for compression behavior and state equation analysis . However, we still can observe an obvious isostructural transition with volume collapse and a 1.5% volume change from phase I to phase II at ∼9.8 GPa.…”

Elucidating the Phase Transformation and Metallization Behavior of Zinc Phosphide under High Pressure

“…The evolutions of Eulerian strain f E with normalized pressure F E of the two phases are presented in Figure c,d, which can further verify the validity of EOS-fitting results. The relationship between f E and F E is of the form where f E is defined as …”

“…For a further analysis, the obtained two-dimensional X-ray diffraction patterns were converted into a series of one-dimensional (1D) 2θintensity diffraction curves using the FIT2D program. 28 The resulting 1D XRD patterns were processed by using the GSAS program as implemented in the EXPGUI package to obtain the lattice parameters and structural refinements. 29 The in situ high-pressure electrical resistance measurement was performed in a two-stage multianvil apparatus based on a DS6 × 8MN cubic press machine developed at Sichuan University, Chengdu, China.…”

“…The in situ high-pressure ADXRD experiment was performed at the 4W2 beamline of the Beijing Synchrotron Radiation Facility (BSRF), the monochromatic synchrotron radiation X-ray beam with a wavelength of 0.6199 Å can cause a spot with a size of ∼20 × 30 μm 2 , and more details of this facility can be found in the Supporting Information. For a further analysis, the obtained two-dimensional X-ray diffraction patterns were converted into a series of one-dimensional (1D) 2θ-intensity diffraction curves using the FIT2D program . The resulting 1D XRD patterns were processed by using the GSAS program as implemented in the EXPGUI package to obtain the lattice parameters and structural refinements …”