Structure Of Carbide Research Articles

Electric arc synthesis of titanium carbide using carbon obtained from thermal conversion of waste from the power industry

The work presents for the first time the results of obtaining titanium carbide using a vacuum-free electric arc method using various types of biocarbon obtained by classical pyrolysis of biomass waste, such as tangerine peel, pomelo peel, banana peel, pine nut shells, walnut shells. Analysis of X-ray diffraction patterns of the synthesized materials showed the repeatability of the experiment with the receipt of diffraction maxima indicating the formation of a cubic structure of titanium carbide. An analysis of the thermal oxidation of the resulting powders showed that up to a thousand degrees the process proceeds quite slowly, but with increasing temperature the oxidation rate increases significantly. It has been established that during thermal heating in an oxidizing environment, the mass of the studied titanium carbide powders obtained using various types of carbon increases, which is confirmed by thermogravimetric analysis.

Synthesis of double carbide (Ti,Cr)C with a different Cr content produced by electro thermal explosion

In this paper we report the preparation of double carbide (Ti,Cr)C with a chromium content of 10 ÷ 30 at% by electrothermal explosive synthesis (ETE). This method allows synthesis to be carried out at high temperature with minimal holding time. The ETE method is favourable for the formation of dense carbide ceramics. The synthesized samples were characterized by X-ray diffraction and scanning electron microscopy. It was found experimentally that the unit cell parameter of the double carbide decreases linearly with increasing chromium content. The DFT calculations also confirmed the dependence of the unit cell parameter (Ti,Cr)C on the chromium content according to Vegard's law and show changes in the cell shape and distance between Cr–Cr layers with increasing chromium content. The pDOS diagram shows that an increase in chromium content leads to an excess of d∗ electrons on the π∗ orbitals, which has a destabilizing effect on the double carbide structure.Crystal Orbital Hamiltonian (COHP) analysis of the electronic structure of the double carbide, partitioning the energy of the band structure into bonding, non-bonding and anti-bonding energy regions, showed the influence of chromium content on its stability.

Capillary interaction of copper melt with dense and porous MAX phase (Cr, Mn)2AlC

In the present work, we experimentally studied the interaction of a pure copper melt with a dense MAX-phase (Cr, Mn)2AlC after sintering by the electric pulse plasma method and a porous phase obtained by pressing at room temperature. The porous phase (20 % porosity) absorbs molten copper at temperatures above 1200 °C; the kinetics of absorption was directly measured using high-speed thermal and video cameras. The experiments were carried out in a vacuum of 10–3 Pa. Studies using scanning electron microscopy, EDX spectral analysis and X-ray diffraction have shown that a chemical interaction of the MAX-phase with a copper melt occurs with the formation of a solution of aluminum and chromium in copper and the decomposition of the MAX-phase to chromium carbides (stable or metastable). The dense, sintered sample also actively interacts with the melt, although the contact angles exceed 100°. The difference between porous and dense samples lies in the kinetics of interaction. The results were compared with experiments on wetting the Cr2AlC MAX-phase with a Cu (0.8 at.% Cr) melt conducted earlier. The described experimental conditions and the results of determining chemical and phase changes in the process of capillary interaction indicate the possibility of creating a composite material with a submicron structure of chromium carbide impregnated with aluminum bronze.

Enhancement of mechanical and thermal properties of diamond particles via vanadium carbide coatings

Vanadium carbide coated diamonds were successfully fabricated by molten salt method. The effect of temperature (from 700 °C to 1000 °C) and molar ratio (carbon:vanadium, from 7:1 to 1:1) on the mechanical and thermal performance of vanadium carbide coatings and coated diamond particles were systematically investigated by SEM, EDS, XRD and XPS. The results showed that, compared with uncoated diamonds, the static compressive strength and oxidation resistance of the coated diamonds increased by 42.27 % and 158.82 °C, respectively. The vanadium carbide coatings were mainly composed of V2C and VC. As the temperature rose, the thickness of the coatings increased and cracks and holes appeared on the surface of the coating under thermal stress. With the increasing of the relative content of vanadium in raw materials, the crystal structure of vanadium carbide coatings changed from microcrystalline structure to reticular structure and the microcrystalline structure vanadium carbide coatings showed better performance.

Mechanical properties of high-entropy carbides prepared by high-pressure sintering: Role of carbon stoichiometry

The scarcity of carbon in high-entropy carbides is widely recognized to significantly affect their fabrication and performance. However, achieving both high hardness and plasticity in these carbides remains a formidable challenge. This study investigates the impact of carbon vacancies on the phase structure and mechanical properties of high-entropy carbides, particularly (Hf0.25Zr0.25Nb0.25Ta0.25)Cx (x = 1, 0.8, 0.6, or 0.5), utilizing density functional theory calculations and experimental analysis. Theoretical computations indicate a rock-salt structure for the carbides, with reduced cell parameters as carbon vacancies increase. Notably, carbides with lower carbon content exhibit softer characteristics, as evidenced by Pugh's ratio. Experimental fabrication and testing reveal a decrease in Vickers hardness with decreasing carbon content, attributed to changes in bonding types. Certain compositions, particularly (Hf0.25Zr0.25Nb0.25Ta0.25)C0.6 and (Hf0.25Zr0.25Nb0.25Ta0.25)C0.5, display plastic behavior alongside high hardness, offering promising avenues for future research and design of high-entropy ceramics.

Mechanical properties of aluminum matrix composite reinforced with titanium carbide

Abstract An original method for the production of metal matrix nanocomposites has been proposed, which consists of depositing carbide structures 4–12 nm thick onto the surface of particles of aluminum powder by molecular layering, mixing the resulting dispersed particles with particles of pure metal in the required concentration, then pressing and sintering the resulting mixture. The resulting workpieces are subjected to intense plastic deformation by high-pressure torsion, which not only significantly reduces porosity, ensures a uniform distribution of reinforcing particles throughout the volume, and destroys carbide shells on the surface of dispersed particles, but also grinds aluminum particles. Experimental stress-strain curves of the synthesized composites were constructed and the contribution of various hardening mechanisms to the final hardening of the metal matrix composite was assessed. In metal matrix composites synthesized by this method, with small fractions of the volume content of reinforcing titanium carbide particles (less than 0.1%), almost twofold hardening and a threefold increase in the yield strength are observed with a slight reduction in plastic deformation before failure.

First-Principles Calculate the Stability, Mechanical Properties and Electronic Structure of Carbide MC, M2C and M6C in M50NiL Steel.

In this paper, the stability, mechanical properties and electronic structure of carbides in steel were calculated using the first-principles method based on the density functional theory (DFT). Firstly, the MC, M2C, M6C (M = Cr, Mo, V, Fe) carbides models were established. Then, different interphases' lattice constants, formation enthalpy, binding energy and elastic modulus were calculated. The stability, hardness, ductility and anisotropy of each phase were finally analyzed. The results show that these phases are stable, and the stability is closely related to the electron loss ability of its metal elements. The stronger the electron loss ability of its metal elements, the more stable the formed phase. As for MC carbides, MoC has the largest bulk modulus and hardness. As for M2C carbides, the Poisson's ratio of Cr2C is the smallest, and all phases except for Cr2C show toughness and ductility. The anisotropy of M6C carbides is relatively poor.

Phase-controlled synthesis of starch-derived Mo2C–MoC/C heterostructure catalyst for electrocatalytic hydrogen evolution reaction

The electronic structure of molybdenum carbide closely resembles that of Pt, making it a promising candidate material for replacing noble metal catalysts. However, the primary challenge is the controlled and eco-friendly synthesis of molybdenum carbide. Herein, we developed a sustainable and controlled method for synthesizing a heterostructure catalyst for the electrocatalytic hydrogen evolution reaction (HER) using starch as the raw material. Through a hydrothermal redox reaction and subsequent temperature-programmed treatment under an inert atmosphere, the hexagonal Mo2C-cubic MoC heterostructure nanoparticles were dispersed on a carbon matrix. Our investigation into the synthesis process extensively covered the growth of MoO2 nanocrystals and hydrochar during the hydrothermal redox reaction, as well as the phase evolution during the subsequent temperature-programmed treatment. Electrochemical assessments demonstrated the catalyst's remarkable efficiency for the hydrogen evolution reaction across both acidic and alkaline media, achieving a current density of 10 mA/cm2 with an overpotential of 139.4 mV in 1 M KOH solution and 160.7 mV in 0.5 M H2SO4 solution. Combining a series of electrochemical characterizations and applying the distribution of relaxation times (DRT) analysis to operando electrochemical impedance spectroscopy (EIS) data, the superior kinetic performance of the Mo2C–MoC/C was demonstrated, outperforming that of single-phase molybdenum carbide. Furthermore, the catalyst has demonstrated remarkable stability even at high current densities in both acidic and alkaline electrolytes, underscoring its potential as a cathode catalyst in both alkaline water electrolyzers and proton exchange membrane (PEM) electrolyzers.

Thickness-dependent structure and properties in zirconium carbide ceramic via orientated deposition

The fine-tuning of controlled structure and property evolution of zirconium carbide (ZrC) ceramic is essential for its functional applications, especially with insufficient understanding of the size effect mechanisms. In this investigation, the physically vapor-deposited ZrC (PVD-ZrC) ceramic was fabricated through magnetron sputtering, with a specific focus on its thickness-dependent growth and evolution of composition, microstructure, growth texture and mechanical properties. As prepared PVD-ZrC presents a hybrid structure characterized by amorphous carbon and nanocrystalline ZrC, with diversity in crystallinity, crystallite size, and growth pattern determined by target power, gas-flow pressure and substrate temperature. Moreover, the PVD-ZrC ceramic deposited by directional deposition, exhibits a structure transition from equiaxed crystals to dense columnar fiber crystals and an isotropy-toward texture. As the thickness increases, the stress gradually shifts towards tensile stress with a weaker fracture toughness. Through the First-principle calculation, it is illustrated that the mechanical properties of bulk polycrystalline ZrC are evidently different from low-dimensional polycrystalline ZrC film. This mechanism of thickness-dependent structure and properties is dominant by the surface effect, size effect, grain boundary effect, and stress effects.

High-pressure dysprosium carbides containing carbon dimers, trimers, chains, and ribbons

Exploring the chemistry of materials at high pressure leads to discoveries of previously unknown compounds and phenomena. Here chemical reactions between elemental dysprosium and carbon were studied in laser-heated diamond anvil cells at pressures up to 95 GPa and temperatures of ∼2800 K. In situ single-crystal synchrotron X-ray diffraction (SCXRD) analysis of the reaction products revealed the formation of novel dysprosium carbides, γ-DyC2, Dy5C9, and γ-Dy4C5, along with previously reported Dy3C2 and Dy4C3. The crystal structures of γ-DyC2 and Dy5C9 feature infinite flat carbon polyacene-like ribbons and cis-polyacetylene-type chains, respectively. In the structure of γ-Dy4C5, carbon atoms form dimers and non-linear trimers. Dy3C2 contains ethanide-type carbon dumbbells, and Dy4C3 is methanide featuring single carbon atoms. Density functional theory calculations reproduce well the crystal structures of high-pressure dysprosium carbides and reveal conjugated π-electron systems in novel infinite carbon polyanions. This work demonstrates that complex carbon homoatomic species previously unknown in organic chemistry can be synthesized at high pressures by direct reactions of carbon with metals.

Evaluation of nanocrystalline ZrC under gamma irradiation and high pressure

Zirconium carbide (ZrC) is known for its exceptional properties, positioning it as a leading ultrahigh-temperature ceramic for diverse applications such as coating, oxygen-gettering, and inert matrix utilization in advanced high-temperature reactor fuels. Its impressive resistance to fission product corrosion, superior fission product retention capabilities, and resilience against hydrogen corrosion further highlight its significance in these fuel systems. In this work, the structural properties of zirconium carbide crystals (particle size of 20 nm) irradiated with 60Co gamma source were investigated at absorption doses from 300 kGy up to 3000 kGy using X-ray diffraction (XRD). Furthermore, the crystallinity properties of the crystals under high-pressure conditions were examined using the Small-angle X-ray Scattering (SAXS)/Wide-angle X ray scattering (WAXS) Xeuss 3.0 system. A comparative analysis of theoretical calculations and experimental results was conducted. The crystalline size experienced a decrease, while the microhardness showed variation. ZrC was identified to possess an Face Centered Cubic (FCC) – B1 structure of transition metal carbides (TMCs), with specific atomic arrangements. Under high pressure conditions, ZrC exhibits a shift to higher two-theta angles with compression of all diffraction peaks, without the formation of new peaks, up to a pressure of 9.0 GPa.

Preparation and characterization of zirconium carbide nano powder by hydrothermal and carbothermal reduction methods

A hydrothermal method was employed to synthesize the precursor of nano-zirconium carbide, which was subsequently heat treated at high temperatures under vacuum to obtain finely dispersed nanometer-sized zirconium carbide powder through a carbothermic reduction reaction. Scanning Electron Microscopy (SEM) was utilized to examine the microstructure of the precursors obtained under different hydrothermal conditions and carbon contents. The effects of different heat treatment temperatures on the microstructure of the products were analyzed. Transmission Electron Microscopy (TEM) confirmed the boundary coating structure of the hydrothermal precursor and provided insights into the phase structure of the nanometer-sized zirconium carbide. The reaction mechanism and temperature involved in the carbothermic reaction process were determined through calculations. Furthermore, the energy, phase and microstructure of the reaction were investigated using Thermogravimetric Analysis (TG-DSC) and X-ray Diffraction (XRD) at different temperatures. The obtained results revealed that the zirconium carbide precursor was synthesized via the hydrothermal method exhibited a core-shell structure with a boundary coating, which not only ensured uniform contact between C and ZrO2 particles but also facilitated the formation of zirconium carbide. The results show that the most suitable process parameters are Zr/C 1: 7, 240 °C and 24 h. The thermodynamic calculation results show that ZrO2 combines with carbon to form CO and ZrC when the temperature reaches 1656.56 °C. As the temperature rises, CO reacts with ZrO2 to form ZrC and CO2. TG-DSC shows that the carbothermal reduction reaction starts at 1100 °C and reaches its peak at 1418 °C. XRD analysis confirms that when the temperature reached 1450 °C ZrC appeared. At 1600 °C, the phase transition of ZrC is basically completed. TEM images showed that the synthesized zirconium carbide particles were about 30 nm.

The internal modified layer structure of silicon carbide induced by ultrafast laser and its application in stealth dicing

Silicon carbide (SiC) is widely applied in high-power electronic devices due to its excellent properties. Stealth dicing (SD) as one of the dicing methods, exhibits the advantages of few thermal surface damage and low edge-chipping. In this study, we use an ultrafast laser to induce the modified layer structure inside the SiC wafers. The effects of laser processing parameters on the modified layers are studied. The formation mechanism of the modified layer and its influence on SD are analyzed. The result shows that the number of modified layer structures is mainly determined by the moving velocity. The different modified layer structures will affect the surface roughness of the SD cross-section and critical fracture load of the 4H–SiC wafers. Finally, we achieved the high-quality SD of SiC wafers, and a cross-section with the minimum surface roughness is approximately 381 nm.

Friction and wear performance of laser clad Mo modified Stellite 12 matrix coatings at elevated temperature

The aim of this research is to enhance the tribological performance of Stellite 12 coatings at room temperature-1000 °C. To this end, Mo modified Stellite 12 coatings were prepared on the Inconel 718 alloy by laser cladding, and the Mo content was optimized. The effects of Mo on the phases, microstructure and tribological behavior of coatings were investigated. The hardness and tribological performance of coatings were enhanced by adding Mo. There was a threshold content of Mo concerning with tribological performance of Stellite 12 matrix coatings. The 12.0 wt% Mo modified Stellite 12 coating kept more outstanding tribological performance, which was due to the high hardness, in-situ synthesized solid lubricants, friction film and the net structure of complex carbides.

Tailoring crystal structure of high-entropy carbides in Si-based ceramic nanocomposites through precursor engineering

High-entropy carbides with tunable crystallization and growth have been demonstrated using single-source precursor derived ceramic route. The in situ nanocrystallization of high-entropy carbide phases, (Ta0.2W0.2V0.2Mo0.2Nb0.2)SiδC and (Ta0.167W0.167V0.167Mo0.167Nb0.167Si0.167)C in amorphous Si-based ceramic matrices was achieved by using polysiloxanes and polycarbosilanes as polymer precursors respectively. The results exemplify a prominent role of the architectures of the polymeric precursors in controlling the structural features of these ceramics at various length scales. In particular, it was observed that high-entropy carbides with rock salt and zinc blende crystal structures were formed when polysiloxanes and polycarbosilanes with different backbone structure were used as polymeric precursors respectively. This is attributed to the thermodynamics of nucleation of the carbidic phases in these nanocomposites. Furthermore, the precursor architecture that dictates free carbon content, influenced nanostructural features and porosity in the material. Therefore, engineering such compositionally complex phases is feasible by selecting suitable polymeric precursors.

All-SiC fiber-optic sensor for pressure and temperature dual-mode sensing in harsh environments

This paper presents a fiber-optic Fabry–Perot (FP) sensor with an all-silicon carbide (SiC) structure for pressure and temperature dual-mode sensing in harsh environments. The all-SiC sensing diaphragm and vacuum FP cavity were formed by direct bonding of a 6 H-SiC (N-doped) diaphragm with a 6 H-SiC (V-doped) substrate. The variation in length of the FP cavity was used to measure the external pressure, while the principle of temperature sensing was due to the temperature dependence of the refractive index and thermal expansion of the SiC substrate. The pressure and temperature characteristics of the sensor were calibrated from 25 °C up to 700 °C over a pressure range of 0–1.0 MPa. The pressure sensor achieved high sensitivity (174.3 nm/MPa) and linearity (R2 = 0.999 at 700 °C), the spectral sensitivity of the temperature sensing being approximately 32.12 pm/°C. Moreover, the temperature-pressure cross-sensitivity was as little as 4.98 °C/MPa. The dual-mode sensing capability of the all-SiC fiber-optic sensor demonstrated great promise for applications in extremely high-temperature environments.

3D printing of high-purity complex SiC structures based on stereolithography

Complex Silicon carbide (SiC) structures are hardly achievable via traditional manufacturing methods, while stereolithography 3D printing technology effectively shapes sophisticated structures with high precision. However, it is a huge challenge to prepare SiC slurry for stereolithography 3D printing with excellent curing ability due to the increased light absorption of SiC powder. Therefore, a novel approach to fabricating high-purity SiC structures is proposed in this study based on the stereolithography 3D printing process, where SiO2 powder is used as an additive to increase the curing thickness from 27.8 μm to 53.0 μm. Moreover, phenolic epoxy resin (PEA) is introduced as a carbon source to transform SiO2 to SiC during sintering. As a result, there is almost no SiO2 phase or SiOC remaining in the final parts when the addition of PEA reaches 50 wt% related to the resin weight after sintering at 1600 °C for 4 h. Based on the SiC/SiO2/PEA slurry systems prepared, high-purity silicon carbide with complex structures can be successfully fabricated in one step without any pre-oxidation or precursor impregnation processes. This approach provides valuable insights into additive manufacturing of high-purity complex SiC structures.

Structural and mechanical properties of magnetron sputtered (NbxMo1-x)C thin films

While transition metal carbides (TMCs) exhibit favourable mechanical properties, alloying according to the valence electron concentration (VEC) has the potential to further enhance the properties of these hard but inherently brittle materials. This study investigates the influence of alloying on the microstructure and mechanical properties of (NbxMo1-x)C carbide films, including binary references and ternary compositions with varying metal ratios (x between 0.35 and 0.53). Furthermore, the influence of various substrate materials is studied by comparing films deposited on Al2O3, MgO and SiO2. All films exhibit a NaCl-type carbide structure and X-ray photoelectron spectroscopy revealed the presence of small amounts of an additional amorphous carbon (a-C) phase. Hardness values around 20 ± 2 GPa were obtained for the films on Al2O3 and MgO, whereas a reduced hardness of 11 ± 1 GPa was observed for the films on SiO2 which is attributed to larger crystallite size and more polycrystalline structure. Overall no clear trend as a function of composition can be noted, indicating that microstructure effects dominate the mechanical properties in this study overshadowing the effect of varying the metal content.

Cross-scale static/dynamic shear damage evolution mechanism of 2D C/SiC ceramic matrix composite with transient hysteresis effect

The intricate woven structure of two-dimensional woven carbon fiber-reinforced silicon carbide (2D C/SiC) poses challenges to the investigation of damage failure mechanisms and the prediction of material performance, thereby limiting its further application in aerospace engineering. In this work, static/dynamic short beam shear tests with different densities of 2D C/SiC were carried out. It was observed that high-density specimens with fewer microporous defects exhibited better strength characteristics than those with lower density. Specifically, the shear strength of 2D C/SiC with a density of 2.07 g/cm³ increased by 18.6% compared to that of the specimen with a density of 1.94 g/cm³. The transient hysteresis strengthening effect of materials at high strain rates was discovered through cross scale research methods. It was found that deformation coordination ability of 2D C/SiC under dynamic loading was weaker than that under quasi-static conditions. Moreover, the deformation hysteresis in temporal and spatial distributions induced significant fiber plucking, further accelerating dislocation movement within the internal lattice and thereby enhancing strength of the material. The failure path of materials often follows the direction of pore defects, and stress concentration leads to cracking behavior of fiber bundles. Furthermore, microcracks within the matrix, caused by residual stress, resulted in localized regions of reduced strength. This induced the matrix cracking failure with further crack expansion within the material structure under external loads. To provide technical references for practical engineering applications and design, a realistic and effective finite element prediction model was developed for 2D C/SiC composites based on their structural characteristics.

Study of electronic, optical, thermodynamic, and thermoelectric properties of GeC bulk and monolayer structure

Using density functional theory and Boltzmann equations, this study calculates and compares the electronic, optical, thermoelectric, and thermodynamic properties of bulk and single-layer germanium carbide structures. It has been shown that germanium carbide in the bulk structure has an indirect energy band gap of 1.61[Formula: see text]eV. In a single layer structure, it is a metal. Thermodynamic properties including specific heat at constant volume have been investigated using the quasi-harmonic approximation (QHA) package in QE. According to the studies conducted on optical properties, this material shows good reflection in the visible region. In addition, this structure has high electrical conductivity and low thermal conductivity, which is essential for thermoelectric materials. Thermoelectric calculations using semi-classical Boltzmann transfer theory show that the performance of two-dimensional compounds with graphene gives good thermoelectric results. At 100[Formula: see text]K, the highest figure of merit (ZT) for GeC is 1.00. Our findings evaluate the GeC compound as a suitable thermoelectric material in the temperature gradient from 100 to 900[Formula: see text]K.