ZrC Ceramics Research Articles

W-doped concentration improved the hardness, elastic modulus, elastic anisotropy and thermodynamic properties of ZrC ultrahigh temperature ceramics

Although ZrC is a promising ultrahigh temperature ceramics due to the high melting point, high strength, high hardness and low density, the improvement of mechanical properties and thermal stability is very significance for it's ultrahigh temperature application. To improve the mechanical and thermodynamic properties of ZrC ultrahigh temperature ceramics, we apply the first-principles calculations to study the influence of W-doped concentration on the structural stability, hardness, elastic modulus, elastic anisotropy and thermodynamic properties of the cubic ZrC ceramics. The calculated results show that three W-doped ZrC are thermodynamic stability. In particular, the calculated impurity formation energy of the W-doped ZrC increases with increasing W concentration. Importantly, the calculated elastic modulus of the W-doped ZrC increases with increasing W concentration. Although the hardness of W-doped ZrC is bigger than the parent ZrC, the hardness of W-3.125 at.% is higher than the W-doped ZrC with the high concentration of W. Naturally, the high hardness and elastic modulus of the W-doped ZrC is that the metal W enhances the localized hybridization between Zr and C, which is demonstrated by the change of ZrC bond. In addition, the parent ZrC and the W-doped ZrC show excellent elastic anisotropy. Furthermore, the calculated Debye temperature of W-3.125 at.% ZrC is higher than the parent ZrC and the other W-doped ZrC. Therefore, we predict that the W-3.125 at.% ZrC shows excellent mechanical properties and better thermodynamic properties in comparison to the other W-doped ZrC ceramics.

Fabrication and improved properties of ZrC-SiC-ZrB2 ceramics by ultra-high pressure sintering

ZrC-SiC-ZrB2 ceramics were prepared via ultra-high pressure sintering under 15 GPa at 1200 °C. The densification mechanism, microstructures, and properties of the prepared ceramics were investigated. The sintered ceramics with ZrB2 content of 15 vol% showed the improved comprehensive mechanical properties, including Vickers hardness of 26.6 GPa, Young's modulus of 469.1 GPa, and fracture toughness of 5.0 MPa·m1/2, which was 86.7% higher than that of pure ZrC ceramics. In the sintered sample, the ultra-high pressure induced new microstructure, such as L-C lock in ZrC phase, stacking faults and nanotwins in SiC phase, and severe lattice distortion in ZrB2 phase, jointly contributed to the improvement in Vickers hardness. Deflection and bridging during crack propagation were ascribed to the uniform combination of various phases.

Structural and mechanical responses of (ZrTiNbTa)C4 and ZrC ceramics under energetic He-ions irradiation

High entropy ceramics are potential structural materials for advanced reactor concepts where numerous helium atoms would be produced due to the (n, α) nuclear transmutation reaction. However, the irradiation behaviors of high entropy ceramics are not well understood until now. In present work, the responses of high entropy (ZrTiNbTa)C4 and its binary constituent ZrC ceramics to energetic He-ions irradiation have been studied. X-ray diffraction analysis showed that He-ions irradiation resulted in peak shift and broadening of diffraction peaks in both (ZrTiNbTa)C4 and ZrC, which denotes lattice expansion and structural damages induced by the irradiation. Transmission electron microscope observation revealed that spherical helium bubbles distribute uniformly in the grain interiors of (ZrTiNbTa)C4 while “string-like” bubbles with a preferred orientation are observed in ZrC grains. Nanoindentation characterization gives that the irradiation induced hardening of (ZrTiNbTa)C4 is less definite than that of ZrC. The irradiation mechanisms of high entropy ceramics have been discussed.

Pyrolysis process and formation mechanism of water-based ZrC ceramics studied through a combined experimental and theoretical calculational method

ZrC has an important application in the field of supersonic aircraft, hypersonic spacecrafts and rocket engines. Normally, the toxic metal chelators and toxic organic reagents are used to prepare the ZrC ceramic precursors. In this paper, an environmentally friendly water-based ZrC ceramic precursors were synthesized in aqueous solvent via the combination of metal ion chelator and carbon source. Moreover, the water-based ZrC precursor was prepared by Tartaric Acid (TA) system can obtain high-purity ZrC ceramics. The experiment results indicated that the best Zr/C molar ratio in the precursor was 1:4. The synthetic mechanism of ZrC was Zr atoms reacted in situ to form ZrC. In addition, the effect of metal chelator carbon source assisted glucose carbon source on water-based ZrC precursors can provide a certain experimental basis for subsequent research on water-based carbide precursors.

Rapid densification and mechanical properties of ultra-high-pressure sintered transition metal carbide ceramics

Densifying transition metal carbide (TMC) ceramics is challenging due to their low diffusion coefficient and strong covalent bonding. Ultra-high-pressure sintering (UHPS) is a promising technique for preparing dense ceramic materials at low temperatures, but it is underutilized in TMC ceramics. Herein, we report the successful employment of UHPS at 1500 °C for 3 min with an auxiliary pressure of 7 GPa, yielding TaC, NbC, TiC, and ZrC ceramics with relative densities of 99.3%, 98.9%, 98.2%, and 96.4%, respectively. We demonstrate that the densification mechanism of the TMC ceramic in this investigation encompasses plastic deformation and high-pressure assisted atomic diffusion. Furthermore, we determine the Vickers hardness and fracture toughness of TaC, NbC, TiC, and ZrC ceramics to be 16.5, 15.9, 24.0, and 17.7 GPa and 2.5, 2.9, 2.8, and 1.8 MPa m1/2, respectively. Moreover, with increasing temperature from room temperature to 500 °C, the hardness and elastic modulus of all four TMC ceramics gradually decrease, with the hardness declining by approximately 17–25%.

High-temperature oxidation behaviors of dense TMC (TM= Ta, Nb, Ti and Zr) ceramics in air

This study investigated the high-temperature oxidation behaviors of TMC ceramics. The results indicate that the high-temperature oxidation curves of the four TMC ceramics follow a parabolic law, suggesting a diffusion-controlled process. The activation energies for the oxidation of TaC, NbC, TiC, and ZrC ceramics are 105.4, 124.3, 169.3, and 78.7 kJ/mol, respectively, with oxidation rate constants at 1000 °C of 16.84, 40.45, 0.18, and 14.43 mg2/cm4·h for each ceramic, respectively. The temperatures at which the ceramics disintegrate into fragments in high-temperature air are 800, 800, >1000, and 600 °C, respectively. The anti-oxidation performance of the four TMC ceramics ranks as follows: TiC > TaC > NbC > ZrC. In comparison to the reported high-entropy carbide ceramics, the TiC ceramic in this study demonstrates superior anti-oxidation performance due to dense TiO2 layer formation, characterized by significantly low oxidation rates and excellent structural stability.

Effects of high thermal conductivity chopped fibers on ablation behavior of pressureless sintered SiC–ZrC ceramics

As one of the most promising thermal protection materials, the ablation performance of SiC–ZrC ceramics is strongly influenced by thermal conductivity. In this work, the high thermal conductivity mesophase pitch-based carbon fibers (MPCFs) were uniformly added into a mixture of SiC and ZrC powders, which were pressureless sintered to form a MPCFs modified SiC–ZrC ceramics. The relationship between thermal conductivity and MPCFs content was investigated in detail. Both theoretical calculations and experimental results showed that the SiC–ZrC ceramics modified by adding 4.81 vol% MPCFs gained the highest thermal conductivity of 68.10±0.68 W/(m⋅K). The simulation shows that the temperatures at ablation center and backside of the ceramics were 1094 °C and 446 °C, respectively, after plasma ablation at 2300 °C for 20 s. And the actual backside temperature was detected to be 438 °C and that agreed with the simulation results. The high thermal conductivity leads to a lower ablation temperature because the heat is rapidly transferred from the high temperature part to the low region. Due to the low ablation temperature, the 4.81 vol% MPCFs modified SiC–ZrC ceramics exhibited the lowest mass ablation rate (−0.048±0.007 mg/s) and linear ablation rate (−0.715±0.056 μm/s). This research presents a novel insight for designing and fabricating excellent ablation-resistance ultra-high temperature ceramics (UHTCs).

First-principles calculations to investigate the thermal response of the ZrC(1−x)N x ceramics at extreme conditions

Abstract We present the thermodynamic properties of ZrC(1−x)N x ceramics at elevated temperature (0–1,000 K) and pressure (0–150 GPa) conditions, explored by density functional theory. We implemented the Debye–Grüneisen quasi-harmonic model in our calculations. In our investigation, we cover elastic constants, elastic moduli, compressibility, ductility/brittleness, hardness, sound velocities, minimum thermal conductivity, melting temperature, anisotropy indices, isothermal bulk modulus, heat capacities, entropy, Debye temperature, Grüneisen parameter, thermal expansion coefficient, and thermal pressure. We address the effect of the structural anisotropy and bonding nature of ZrC(1−x)N x compounds on their thermal response to extreme conditions. Considering ZrC(1−x)N x with the x in the range of 0.0, 0.25, 0.5, 0.75, and 1.0, ZrC0.50N0.50 stands out in the response to the applied conditions. At higher temperatures, the thermal expansion of the ZrC0.50N0.50 shows a smaller increase, which makes it a favorable candidate for coating material in cutting tools against commonly used ZrN and ZrC ceramics. Similar behavior is observed for the heat capacity by increasing pressure at higher temperatures, where a smaller reduction is observed. It could be interpreted as a more stable response regarding the application-specific design conditions.

Fabrication and characterization of ZrC nano-ceramics derived from a single-source precursor and its feasibility as ZrC/C fibers in structure and function

A novel ZrC ceramic precursor was prepared by a polymer-derived ceramics method and ultraviolet (UV) crosslinking by using zirconium tetrachloride (ZrCl4), ethylenediamine (EDA), and diallylamine (DAA) as raw materials. On this basis, polyacrylonitrile (PAN)-based carbon nanofiber (CNF)-coated ZrC ceramic precursors were synthesized by electrostatic spinning. The as-prepared fibers exhibited excellent designability and machinability by adjusting the proportion of precursors. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) revealed that these materials are converted to nano-sized ZrC ceramics and ZrC/C fibers with a highly crosslinked network structure after high-temperature annealing. ZrC/C fibers still maintained good electrochemical properties at high temperatures. Finally, the tensile test revealed that the mechanical properties of ZrC/C fibers are significantly superior to those of CNF. Specifically, the ceramic fibers with 25% ZrC content exhibited the maximum tensile strength of 71.7 MPa.

ZrC+TiC synergically reinforced metal matrix composites with micro/nanoscale reinforcements prepared by laser powder bed fusion

The addition of hybrid ceramic reinforcing phases provides the possibility of regulating the in-situ reaction and effective strengthening in laser additive manufactured aluminum matrix composites (AMCs). In this work, AMCs reinforced with (ZrC + TiC) solid solution ceramics with micro/nanoscale microstructural features are fabricated by laser powder bed fusion (LPBF). The influence of laser power on the manufacturing quality, the microhardness and the wear properties of the LPBF-fabricated (ZrC + TiC)/Al composites is investigated. Moreover, the reaction mechanism between the ZrC and TiC ceramics in the LPBF process is revealed. The tensile properties of the (ZrC + TiC)/Al composites with different (ZrC + TiC) contents prepared at optimal process parameters are compared. During the LPBF process, the ZrC and TiC ceramics are incompletely melted. On the ceramic particles, a thin (Ti,Zr)C layer formed and large amounts of (Ti,Zr)C nanoparticles precipitated via a dissolution-precipitation mechanism. When the laser power increases from 375 to 425 W, the manufacturing quality, microhardness, tensile and wear properties of the (ZrC + TiC)/Al composites increase. The tensile strength of 10 wt.% (ZrC + TiC)/Al composites prepared at optimal processing parameters reaches a high strength value of ∼227 MPa with a uniform elongation of ∼6.7%, which is three times higher than that of the unreinforced Al-matrix. This is ascribed to the combined effects of Orowan strengthening, coefficient of thermal expansion (CTE) mismatch strengthening, load-bearing strengthening and grain refinement strengthening.

Synthesis of In Situ ZrB2-SiC-ZrC Coating on ZrC-SiC Substrate by Reactive Plasma Spraying.

In situ synthesis feasibility of ZrB2-SiC-ZrC composite coatings on ZrC ceramics by reactive plasma spraying (RPS) was investigated. To help to understand the phase evolution during plasma spraying process, reaction behavior in the ZrH2-Si-B4C system was explored carefully by differential scanning calorimetry. The results indicated that the phase transformation sequence in the ZrH2-Si-B4C system could be described as ZrH1.66, Zr3O, ZrC, ZrB2, Zr2Si, ZrSi, and SiC. The prior formation of ZrC was due to high diffusion rate of C atoms from B4C. ZrB2 was produced above 1100 °C. As the temperature increased, SiC were finally formed by the reaction of ZrC with ZrSi and B4C. The RPS composite coatings mainly consisted of ZrB2, SiC, and ZrC phases, except for a small fraction of ZrO2 phase. The microstructural characterization exhibited more dense melted splats, which appears to increase gradually with the increase in spraying currents and distances. The coatings had typical lamellar structure and adhered to the substrate well. The microhardness values were higher than 1000 HV1, but there were few variations with varying spraying currents and distances.

Electrical performance of ZrC ceramics

AbstractIn the present study it was possible to provide evidence that ZrC ceramics – regarding their electrical‐mechanical and thermal properties – are an attractive substitute for tungsten and molybdenum in the field of refractory materials and heating elements. For this purpose, the heating behavior of ZrC materials was investigated in a specific test stand under high vacuum conditions (10−6 mbar) at temperatures above 2000 °C. In addition, the applicability of ZrC as an electrical heating element was investigated in terms of geometric design and long‐term behavior. Examinations after the heating tests did not reveal any significant changes in the material.

Formation of Ultra-High Temperature Ceramic Hollow Microspheres as Promising Lightweight Thermal Insulation Materials via a Molten Salt-Assisted Template Method

Ultra-high temperature ceramics (UHTCs) have become a vital candidate material system for thermal protection systems in aerospace applications. However, high thermal conductivity and high density are the main obstacles to the application of UHTCs. It is a promising solution to prepare porous UHTCs using UHTC hollow microspheres (HMs) as a pore-forming agent. In this work, UHTC (ZrC, TiC, and HfC) HMs are successfully synthesized using carbon hollow microspheres (CHMs) as a template to react with metal powders in molten salt. The diameter of ZrC HMs is about 1 μm and the wall thickness is about 100 nm. The density of each microsphere and the volume fraction of ZrC are 3.36 g/cm3 and 48.42 vol %, respectively. The morphology, microstructure, and phase composition of the obtained ZrC HMs were characterized. The formation mechanism of the UHTC HMs was discussed. Porous ZrC ceramics were prepared using ZrC HMs as a pore-forming agent. The density and thermal conductivity of the porous ZrC ceramics are 3.12 g/cm3 and 1.82 W/(m·K), respectively, which are 53.64 and 91.12% lower than the density and thermal conductivity of dense ZrC ceramics, respectively. The results indicated that ZrC HMs are promising as pore-forming agents or a matrix for lightweight thermal insulation and high-temperature resistance applications in ultra-high temperature environments.

First principle study on the mechanical response of ZrC and ZrN at high-pressure conditions: anisotropy perspective

ABSTRACT We perform full-potential density functional theory calculations to study the mechanical properties of ZrC and ZrN ceramics in the pressure range of 0-100 GPa. Birch-Murnaghan (B-M) isothermal equation of state was used to estimate energy-volume relationship and related structural parameters. We use Viogt-Reuss-Hill (VRH) approximation to account for the polycrystalline elasticity of the compounds. We calculate elastic constants as a function of pressure and cover bulk, shear, and Young’s moduli, hardness, and Poisson’s ratio. For each property, we report the yields of Voigt, Reuss, and Hill approximations as a function of pressure. The pressure-dependent absolute and universal anisotropy have also been reported. We follow our calculations by exploring the brittleness/ductility of ZrN and ZrC by calculating Cauchy pressure and Pugh’s ratio. Among thermal properties, we calculate minimum thermal conductivity and Debye temperature. The calculated results indicate that ZrN has higher bulk modulus; however, the shear and Young’s modulus are comparable for ZrC and ZrN at all pressures. ZrN has a higher Poisson ratio but, ZrC shows higher hardness in the calculated pressure range. Excluding Poisson’s ratio, pressure has an increasing effect on these properties, where the rate of increase is almost identical for both compounds.

Transient liquid-phase to guide multiphase evolution in reactive-hot-pressed ZrB2–SiC–ZrC ceramics

In reactive-hot-pressed ZrB2–SiC–ZrC ceramics, ZrO2 was found to replace ZrC phase, hence leading to confusion in designing ultra-high-temperature ceramics (UHTCs). We employ high-precision X-ray diffraction and electron microscopies to reassess the phase behavior during entire reaction and densification and to reveal the evolution of multiphase relationship at different stages before reaching the final ZrB2–SiC–ZrO2 composition. Frozen from transient liquid-phase, bulk glassy phase of 15 vol% was found to be constituted of Zr–Si–B–C–O with stable Zr:O ratio, which starts as early as in the intermediate stage to suppress ZrC in favor of SiC nucleation. Inhomogeneity in phase relations and microstructures results from variation in local transient liquid-phase to develop SiC phase in various modes and rates. As inferred from the earlier report of phase formation, competing reactions for ZrC and ZrB2 phases in the initial stage below 1000 °C were mediated via Zr–O–B–C liquid phase. Such liquid phase was moderated by stable B–O components, as initiated from surface oxides of starting powders. This picture under a continuous mother liquid phase can unify the reactions and sintering into a collective melting–nucleation–growth process, which enables and guides the evolution of multiphase relationship through several stages to reach final densification at relatively low temperature with the help of residual oxides.

Preparation of pore-controllable zirconium carbide ceramics with tunable mechanical strength, thermal conductivity and sound absorption coefficient

Porous ZrC ceramics with uniform pore distribution were successfully prepared using evaporating solvent and hot-pressing sintering. A sintering model of porous ZrC ceramics was established under applied sintering pressure to illustrate the formation mechanism of controllable pore. As the sintering pressure increases, the porosity of porous ZrC ceramics decreases from 73.5% to 55.4%, and the corresponding compressive strengths increase from 5.67 MPa to 31.25 MPa and the thermal conductivities decrease at different temperature. Sound absorption measurement shows that as the median pore sizes of porous ZrC ceramics decrease from 12.48 μm to 4.83 μm, their optimum sound absorption frequency shifts from 2.7 kHz to 4.5 kHz, which is attributed to the fact that porous ceramics with different pore sizes have different responses to specific frequency bands.

The irradiation response of ZrC ceramics under 10 MeV Au3+ ion irradiation at 800 ºC

The microstructural evolution was characterized for ZrC ceramics irradiated with 10 MeV Au3+ ions at 800 °C. Post-irradiation examination showed that ZrC did not amorphize at doses up to 30 displacement per atoms (dpa). Concurrent oxidation of ZrC was found to occur during ion irradiation. Coarsening of the defective microstructure, as a function of dose, was revealed by transmission electron microscopy analysis. Black dot defects were observed at low doses (0.5 dpa), and tangled dislocation networks were formed at 5 dpa and above. Diffraction analysis showed a change in the defect structure occurred at doses close to ∼2.5 dpa. The evolution of lattice parameter with dose indicated that uptake of adventitious oxygen could occur in specimens irradiated at high doses. Raman spectroscopy analysis indicated an increase in non-stochiometry after irradiaton. This work identified specific relationships between dose and microstructure after irradiation, revealing the mechanisms of damage production in ZrCx ceramics.

Effect of ZrB2 content on the densification, microstructure, and mechanical properties of ZrC-SiC ceramics

ZrC ceramics containing 30 vol% SiC-ZrB2 were produced by high-energy ball milling and reactive hot pressing. The effects of ZrB2 content on the densification, microstructure, and mechanical properties of ceramics were investigated. Fully dense ceramics were achieved as ZrB2 content increased to 10 and 15 vol%. The addition of ZrB2 suppressed grain growth and promoted dispersion of the SiC particles, resulting in fine and homogeneous microstructures. Vickers hardness increased from 23.0 ± 0.5 GPa to 23.9 ± 0.5 GPa and Young’s modulus increased from 430 ± 3 GPa to 455 ± 3 GPa as ZrB2 content increased from 0 to 15 vol%. The increases were attributed to a combination of the higher relative density of ceramics with higher ZrB2 content and the higher Young’s modulus and hardness of ZrB2 compared to ZrC. Indentation fracture toughness increased from 2.6 ± 0.2 MPa⋅m1/2 to 3.3 ± 0.1 MPa⋅m1/2 as ZrB2 content increased from 0 to 15 vol% due to the increase in crack deflection by the uniformly dispersed SiC particles. Compared to binary ZrC-SiC ceramics, ternary ZrC-SiC-ZrB2 ceramics with finer microstructure and higher relative densities were achieved by the addition of ZrB2 particles.

ZrB2-SiC-ZrC coating on ZrC ceramics deposited by plasma spraying

The ZrB2-SiC-ZrC coating free of adhesion layer was successfully prepared by plasma spraying. Fine ZrB2-SiC-ZrC sprayed composite powders were pre-synthesized by muti-step hot pressing. The X-ray diffraction (XRD) analysis showed that as-sprayed coating was primarily composed of ZrB2, SiC, ZrC and a small quantity of SiO2 and ZrO2, which corresponds with the composition of spraying composite powders. The microstructure of the coating exhibited the characteristics of stacking of fully melted and partially melted particles. The coating was continuous and well bonded with ZrC substrate without adhesion layer. However, a few pores were found in the sprayed composite coating, which was attributed to incomplete melting of some of ZrB2-SiC-ZrC composite powders during plasma spraying.

Low thermal conductivity and high porosity ZrC and HfC ceramics prepared by in-situ reduction reaction/partial sintering method for ultrahigh temperature applications

Porous ultra-high temperature ceramics (UHTCs) are potential candidates as high-temperature thermal insulation materials. However, high thermal conductivity is the main obstacle to the application of porous UHTCs. In order to address this problem, herein, a new method combining in-situ reaction and partial sintering has been developed for preparing porous ZrC and HfC with low conductivity. In this process, porous ZrC and HfC are directly obtained from ZrO2/C and HfO2/C green bodies without adding any pore-forming agents. The release of reaction gas can not only increase the porosity but also block the shrinkage. The as-prepared porous ZrC and HfC exhibit homogeneous porous microstructure with grain sizes in the range of 300–600 nm and 200–500 nm, high porosity of 68.74% and 77.82%, low room temperature thermal conductivity of 1.12 and 1.01 W·m−1 K−1, and compressive strength of 8.28 and 5.51 MPa, respectively. These features render porous ZrC and HfC promising as light-weight thermal insulation materials for ultrahigh temperature applications. Furthermore, the feasibility of this method has been demonstrated and porous NbC, TaC as well as TiC have been prepared by this method.