CH4 Flow Research Articles

N2 injection to enhance coal seam gas drainage (N2-ECGD): Insights from underground field trial investigation

Pre-gas drainage plays a significant role of preventing gas disasters in underground coal mines. However, it is difficult to reduce the gas content to below the threshold values, especially in low permeability coal seams in China. Previous field trials on the enhanced coalbed methane recovery (ECBM) by nitrogen injection mostly focused on the ground. Until now, few attempts on N2 injection to enhance coal seam gas drainage (N2-ECGD) and no sufficient evidences can indicate the good effect. In this study, exploratory tests of N2-ECGD were carried out in underground low-gas coal seams (with gas content less than 5 m3/t). An experiment to displace the CH4 in coal by N2 injection under constant pressure conditions was first carried out. The results show that continuous N2 injection can promote the desorption of CH4 in the coal pores, which cannot be achieved under normal pressure. N2-ECGD field trials were conducted in the working face of a coal mine in Hejin City, Shanxi Province, China. The effective pressure of N2 injection (EPI) was investigated. Intermittent and continuous N2 injection trials were carried out to study the response characteristics of the gas flow rate, CH4 concentration, and flow rate. The results show an EPI of 0.45 MPa and gas injection radius of 5 m. The gas flow rate increased significantly after N2 injection. Although the CH4 concentration decreased, the CH4 flow rate remained high. On the basis of the change characteristics of gas drainage parameters, the physical process of N2-ECGD was analyzed. The research results obtained in this study can serve as a reference for the application of N2-ECGD in low permeability coal seams. The study also provides a new technical approach for local gas prevention and control in underground coal mines.

Global trade network and CH4 emission outsourcing

The intensifying globalization contributes to the anthropogenic methane (CH4) emissions outsourcing, a strong greenhouse gas and harmful air pollutant, through the increasingly complex global trade network. However, the CH4 flow patterns embodied in global traded goods and services have not been interpreted from the perspective of a complex network. In this paper, we integrate global CH4 emission inventory from the EDGAR (the Emission Database for Global Atmospheric Research) databases, global multi-regional input-output model from the GTAP database, and complex network analysis to reveal the structural characteristics of the global CH4 flow network (GCFN). In the GCFN, more than one quarter of the global anthropogenic CH4 emissions in 2014 are associated with international trade. The top 20 economies contribute to about 70% of the total embodied CH4 emission flows. The GCFNs mainly consist of tripartite patterns centered on China, the USA and Russia. Some emerging countries, such as Thailand and Brazil, also exhibit dominated positions in different kinds of GCFNs. Moreover, the core-periphery structure of the GCFN confirms the existence of a few hub economies associated with a large amount of CH4 emissions. The results emphasize the multinational cooperation on global CH4 emission mitigation, and well-focused mitigation policies should be implemented on some key economies.

Vertically-aligned carbon nanotube at low pressure by cold-wall thermal CVD using a two-phase deposition step

This paper reports a new method to grow vertically-aligned carbon nanotubes (VA-CNT) in a cold-wall system, using a two-phase deposition step at low pressure. The first phase consists of the flow of NH3 for a short period together with the C2H2 flow to ensure catalyst activation. In the second phase, NH3 flow is replaced by H2 flow during the remaining growth time, to obtain tall VA-CNT. Previous tests with only one of the reduction gases flowing with C2H2 during the deposition step demonstrated that the NH3 flow contributes to increasing the VA-CNT uniformity throughout the substrate, while the H2 flow contributes to obtaining taller VA-CNT. The conclusions drawn during these tests lead to the recipe with a two-phase deposition step. The VA-CNT obtained with this new recipe reached a maximum height of 160 µm and a non-uniformity of 21.9 %, which falls within the state-of-the-art values. Furthermore, this process takes place at low pressure and only the chamber stage is heated, which allows a cheaper production of this material on a large scale.

Structure and Properties of DLC Films Deposited on Mg Alloy at Different C2H2 Flows of Magnetron Sputtering Process

Diamond-like carbon (DLC) film is widely used due to its excellent properties, such as high hardness and high wear resistance. To investigate the advantages of DLC film applied on the surface of Mg alloy, direct current (DC) pulse magnetron sputtering was used to prepare DLC film via plasma sputtering a graphite target and introducing C2H2 gas. The silicon interlayer was fabricated by sputtering the Si target. A scanning electron microscope (SEM), transmission electron microscope (TEM), a nano-indentation instrument, an electrochemical workstation and a pin-on-disc tester were employed to obtain the surface morphology, microstructure, mechanical properties, corrosion behavior and wear resistance of the obtained film, respectively. The results show that the DLC films are dense and compact, and the structure changes from amorphous to nanocrystalline with the increase of C2H2 flow. The film prepared at low C2H2 flow has larger surface roughness, lower deposition rate, higher hardness and elasticity modulus, poorer corrosion resistance and better wear resistance, compared with the film prepared at higher acetylene flow. The self-corrosion potential of the obtained DLC film is higher than −0.95 V, the corrosion current density is 10−7 A/cm2 orders of magnitude, and the wear rate is 10−9 mm3/Nm orders of magnitude. The friction coefficient of the film is less than 0.065, the hardness is 17.3 to 22.1 MPa, and the elastic modulus is 145 to 170 MPa. The DLC films obtained on the surface of AZ91 alloy have good comprehensive properties.

Effect of carbon content on structural, mechanical and tribological properties of Cr-V-C-N coatings

Cr-V-C-N thin films were deposited on XC100 steel and Si(100) wafers by a radio frequency magnetron sputtering technique using chromium and vanadium targets in an Ar/N2/CH4 mixture atmosphere. The microstructure, mechanical and tribological properties of coatings were investigated as a function of carbon content.It has been found that the quaternary Cr-V-C-N coatings containing a low percentage of carbon (≤ 12.4 at.%) exhibited a mixture of chromium and vanadium nitrides nano-sized crystallite phases. The coatings containing a high carbon content (> 25 at.%) were consisted of nitride and carbide phases, where the large carbon atoms inserted through CrN and VN.Mechanical properties of the Cr-V-C-N coatings were influenced by the carbon addition. The maximum hardness value of 28.3 GPa was obtained for the coating containing 28 at.% of carbon which is related to the adhesion strength enhanced by the formation of carbide and nitride mixture. Addition of carbon into the Cr-V-N coating led to significantly decrease its friction coefficient from 0.63 to 0.47. The formation of carbides through the dispersion of carbon in the grains effectively improved the density of the Cr-V-C-N coatings so that the coating deposited under a high CH4 flow rate exhibited a better wear resistance than the other Cr-V-N and Cr-V-C coatings.

Mechanical, tribological, anti-corrosion and anti-glass sticking properties of high-entropy TaNbSiZrCr carbide coatings prepared using radio-frequency magnetron sputtering

High-entropy TaNbSiZrCr carbide coatings were deposited on WC substrates by radio-frequency unbalanced magnetron sputtering with C2H2 flow rates ranging from 0 to 23 sccm. The microstructure, mechanical properties, tribological properties and anti-corrosion resistance of the coatings were analyzed in both an as-sputtered condition and an annealed condition. The anti-glass sticking performance of the coatings was additionally investigated by annealing the coatings at 750 °C for 1 h on BK7 glass plates. The results showed that the as-sputtered and annealed coatings with a low carbon content (i.e., C2H2 flow rates lower than 8 sccm) had a high hardness (>34.1 GPa). The as-sputtered sample deposited with the maximum C2H2 flow rate (23 sccm) showed the best tribological properties of all the as-sputtered samples. However, the wear rate of the coating increased by a factor of around 10 times after annealing. The annealed coating nevertheless exhibited the highest corrosion resistance of all the coatings. Finally, the glass sticking results showed that the use of an appropriate C2H2 flow rate (4–12 sccm) was beneficial in enhancing the anti-glass-sticking performance of the coatings.

Tribocorrosion behaviors of nc-TiC/a-C:H nanocomposite coatings: In-situ electrochemical response

Tribocorrosion is a complex process coupled with wear and corrosion behaviors in aggressive solutions, which is closely related with in-situ electrochemical response in terms of the transient variation coefficient of friction (COF) and open circuit potential (OCP). Hence, in this work, nc-TiC/a-C:H nanocomposite coatings were deposited using filtered cathodic vacuum arc at various C2H2 flow rates (fC2H2). With an increase of fC2H2 from 20 to 70 sccm, the coatings exhibit the structure evolution from (111)-texture to random orientation along with the decreasing crystallinity degree. Dense microstructure and smooth morphology are obtained in nc-TiC/a-C:H nanocomposite coatings. The sp2/sp3 ratios show an initial increase from 2.2 to 2.8, then followed by a decrease to 2.5. Accordingly, the decrease of hardness(H), hardness and effective Young's modulus (E*) ratio (H/E*), and H3/E*2 are obtained from 45.8 GPa, 0.12 and 0.67 at 20 sccm to 30.7 GPa, 0.11 and 0.38 at 70 sccm, respectively. Moreover, in potentiodynamic polarization tests, the coatings deposited at 70 sccm show the highest corrosion potential of 0.14 V and corrosion current density of 4.67 × 10−8 Acm−1 , thanks to the contribution from amorphous carbon phase. During tribocorrosion tests in 3.5 wt.% NaCl aqueous solution, however, the coatings at 20 and 70 sccm exhibit mild abrasive wear with similar values of COF of 0.2, OCP of -0.025 V and specific wear rate of 1.03 × 10−6 mm−3 N−1 m−1. The enhanced tribocorrosion properties of the coating at 20 sccm are attributed to the high hardness, H/E* and H3/E*2. The amorphous carbon phase in the coating at 70 sccm makes up for the deficiency of hardness, H/E* and H3/E*2. Moreover, in cycling tribocorrosion tests, nc-TiC/a-C:H nanocomposite coatings reveal that passive films formed on sliding contact surface possess a strong ability of regeneration and self-repairation.

Phosphorus-doped nanocrystalline silicon-oxycarbide thin films

P-doped nc-SiOxCy:H films are grown at moderately low substrate temperature ~250°C and rf power ~200 W via controlled incorporation of C and O from CH4 and CO2 precursor gases by PECVD. The optoelectronic and structural properties of the films have been studied in detail. On gradual increase in CH4 flow rate (F) in the plasma, systematic formations of the Si-C and Si-O-C bonds in a-SiOxCy:H network are evident from the gradual shift of the Si-H wagging and Si-O-Si stretching vibrational modes towards higher and lower wavenumbers, respectively. XPS studies have confirmed on the presence of Si-O-C bonds and the P-atoms as dopants in the network. The Si-C bond density has increased from 1.56×1021 to 4.1×1021 cm−3 and the grain size of the nanocrystals has reduced from 6 to 3.2 nm with the increase in F from 0 to 0.3. An enhancement in the optical band gap is accomplished via the addition of stronger Si-C bonds in the a-SiOxCy:H matrix and also due to quantum confinement effect arising from the reduced size of the nanocrystals, together. The optimum n-type nc-SiOxCy:H film possessing ~50.5% crystallinity with nanocrystal grain size ~5 nm has demonstrated an optical band gap ~1.96 eV and high dark conductivity ~6.41 × 10−1 S cm−1, which altogether appear promising for the window layer of all-Si tandem solar cells. A switching of the electrical characteristics from the degenerate-like crystalline network to its non-degenerate amorphous-like configuration is identified at higher C incorporation in the P-doped SiOxCy:H complex network, corresponding to the CH4 flow rate above 0.2sccm.

Control of gas concentration distribution in a semiconductor process chamber using CT-TDLAS measurement

Methane (CH4) concentration distribution in a semiconductor process chamber was controlled using the measurement of computed tomography-tunable diode laser absorption spectroscopy (CT-TDLAS) and the feedback control toward the feeding CH4 concentrations and flow rates. CH4 diluted with nitrogen was fed into the chamber through a shower head having three separate and concentric areas. Thirty-two laser paths were configured in the chamber to collect the infrared absorption spectra for the CT-TDLAS measurement. The computed tomography calculation using the 32 spectra reconstructed the two-dimensional CH4 concentration distribution in the chamber. The measured concentration distribution was updated once per second. Based on the measured concentration distribution, the feedback control algorithm determined the feeding CH4 concentration and flow rate of each shower head area. In this work, we set the target distribution as a ring shape. In the control algorithm, first the feeding CH4 flow rate of each shower head area was adjusted to match the concentration peak radius in the measured distribution to the radius in the target distribution. Then, the feeding CH4 concentration of each area was adjusted in sequence to match the measured average concentration of each area to the corresponding concentration in the target distribution. The algorithm worked successfully, and the concentration distribution reached the target distribution. The extension of the application and its limitations were also discussed.

Redox-driven restructuring of lithium molybdenum oxide nanoclusters boosts the selective oxidation of methane

Selective methane oxidation is one of the key challenges in modern chemistry. To increase the value-added chemical production, the oxidation state of active metals should be easily converted to oxidized or reduced states in order to adsorb or provide an oxygen atom efficiently into methane. Here, we firstly report that lithium incorporating molybdenum oxide with silica supports significantly enhances HCHO production in virtue of redox-driven restructuring of active molybdenum sites. In reduction conditions under CH4 flow, lithium ions are inserted into the molybdenum-oxide phase by forming lithium molybdenum oxide (LiyMoO3) nanoclusters and conversely extracted by O2 oxidation. Due to the redox migration of lithium ions and reconstruction of LiyMoO3 nanoclusters under the reaction process, the oxidation state of active molybdenum centers is effectively controlled to both oxidized and reduced states. These findings provide insight into the distinct role of lithium ions in various catalytic systems and suggest new strategies for developing active sites for selective oxidation area.

Temperature separation characteristics of CH4–CO2 binary gas mixture within a vortex tube

In the natural gas industry, sour gas usually contains some impurities such as CO2. The influence of CO2 fraction on temperature separation within the vortex tube is not fully understood. In the present work, a simulation study has been conducted to investigate the flow and heat transfer behavior of CH4–CO2 binary gas mixtures in a counter flow vortex tube. The model was validated against the experimental data and the predicted temperature separation is found to satisfactorily accord with the experimental values. The mole fraction of CO2 is varied in the range of 0–1.0. The temperature and velocity distribution characteristics of the gas mixture with various CO2 mole fractions are obtained. The results show that velocity and temperature separation increase with increase of mole fraction of CH4 at given inlet flow rate. According to the streamline structure, the area of the backflow region grows as the CH4 mole fraction increases. But the coefficient of performance tends to decrease with improving CH4 content.

Research on the fabrication and anti-reflection performance of diamond-like carbon films

In this work, a radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) system has been employed to fabricate diamond-like carbon (DLC) films for the application in crystalline silicon solar cells. The morphological, structural and optical properties of the synthesised DLC films were investigated under different deposition times, different plasma discharge powers, different CH4 flow rates, and different substrate temperatures, respectively. It is shown that, when the plasma discharge power was 100 W, the CH4 flow rate was 60 sccm, and the substrate temperature was 100 °C, the synthesised DLC film features a high transmittance of 95%, a low surface reflectivity of approximately 14%, a wide optical band gap of 2.6 eV, as well as a uniform and dense texture. Subsequently, the DLC films with different thicknesses were grown on the surface of crystalline silicon solar cells as anti-reflection coatings. The solar cell current-voltage characteristic testing system was used to investigate the change of solar cell performance parameters, i.e., Jsc, Voc, FF and η. After the growth of a DLC film with a deposition time of 20 min on the surface of a crystalline silicon solar cell, the photovoltaic conversion efficiency of the solar cell increases from 4.12% to 5.2%. This work demonstrates that the DLC film has a promising application potential as an anti-reflection layer in crystalline silicon solar cells.

Liquid CO 2 high‐pressure fracturing of coal seams and gas extraction engineering tests using crossing holes: A case study of Panji Coal Mine No. 3, Huainan, China

Owing to the low coal permeability coefficients and poor gas extraction efficiencies associated with the extraction of coal in the Huainan coal mining area, the aim of this study was to design, for the first time, a high-pressure low-temperature liquid CO2 (LCO2) pump for engineering tests with respect to the fracturing of coal seams and the improvement of CH4 recovery in China. To reasonably calculate the initiation pressure for the coal seam fracturing as well as the gas flow parameters, theoretical analysis with field testing were integrated in the design. In addition, considering the interim gas extraction standard, the gas extraction equivalent radius based on this standard was calculated. The test results revealed a maximum LCO2 pressure of 20.6 MPa, which surpasses the theoretical maximum pressure (19.5 MPa) required for the fracturing of coal seams. During the entire gas extraction process, the CO2 concentrations in boreholes K1 and K3 decrease exponentially with time, showing attenuation coefficients of 0.0205 and 0.0231, respectively. The attenuation coefficients of the three attenuation stages of the original coal seam gas flow rate were 0.0314, 0.2142, and 0.1198, which were higher than those corresponding to the test area. The CH4 concentration in boreholes K1 and K3 in the test area were both higher than that in the original coal seam, and the maximum CH4 flow rates in these boreholes were 1.31- and 1.72-fold higher than that in the original coal seam, respectively. The comparative analysis of CH4 concentrations and flow rates indirectly showed an improvement in the permeability of the coal seam. Further, a quantitative equivalent gas extraction evaluation method based on LCO2 fracturing of coal seam and gas displacement was proposed. Furthermore, based on a comprehensive evaluation, the effective displacement radius caused by the LCO2 fracturing test was 9 m, with a displacement efficiency of 23.95%, and a displacement volume ratio of 0.21. This method offered the possibility of realizing the quantitative evaluation of the LCO2 injection amount and the gas extraction effect, and provides a basis for optimizing the LCO2 fracturing of coal seams as well as the gas extraction process.

Influence of CH4 adsorption diffusion and CH4-water two-phase flow on sealing efficiency of caprock in underground energy storage

Underground natural gas energy storage (UNGNS) plays an important role in ensuring the reliability of the pipeline equipment and the stability of the energy market. In this paper, a mathematical model of CH4-water two-phase flow is introduced and the influence of matrix and fracture and the properties of dual-porosity media of caprock are considered in the model. CH4 and water flow in the fractures of the caprock and CH4 diffuses to the matrix after penetrating the caprock. This model is used to analyze the influence of the CH4 adsorption and diffusion process on the sealing efficiency of the caprock of underground energy storage. The results show that the water saturation of the caprock significantly changes after the gas permeates into the caprock. Adsorption deformation will seriously affect the permeability of the caprock. The longer the adsorption diffusion time is, the worse the sealing performance of the caprock will be. With the increase of the macro-crack length of the caprock, the gas infiltration area around the fracture decreases. Along the bedding direction, the caprock has greater permeability, and gas seepage has a higher speed.

Nanoscale structural and electrical properties of graphene grown on AlGaN by catalyst-free chemical vapor deposition

The integration of graphene (Gr) with nitride semiconductors is highly interesting for applications in high-power/high-frequency electronics and optoelectronics. In this work, we demonstrated the direct growth of Gr on Al0.5Ga0.5N/sapphire templates by propane (C3H8) chemical vapor deposition at a temperature of 1350 °C. After optimization of the C3H8 flow rate, a uniform and conformal Gr coverage was achieved, which proved beneficial to prevent degradation of AlGaN morphology. X-ray photoemission spectroscopy revealed Ga loss and partial oxidation of Al in the near-surface AlGaN region. Such chemical modification of a ∼2 nm thick AlGaN surface region was confirmed by cross-sectional scanning transmission electron microscopy combined with electron energy loss spectroscopy, which also showed the presence of a bilayer of Gr with partial sp2/sp3 hybridization. Raman spectra indicated that the deposited Gr is nanocrystalline (with domain size ∼7 nm) and compressively strained. A Gr sheet resistance of ∼15.8 kΩ sq−1 was evaluated by four-point-probe measurements, consistently with the nanocrystalline nature of these films. Furthermore, nanoscale resolution current mapping by conductive atomic force microscopy indicated local variations of the Gr carrier density at a mesoscopic scale, which can be ascribed to changes in the charge transfer from the substrate due to local oxidation of AlGaN or to the presence of Gr wrinkles.

The structure and optical properties of C doped BN thin films deposited by RF reactive magnetron sputtering

The C doped BN thin films were assembled on Si (1 1 1) and quartz substrates utilizing BN target by magnetron sputtering with CH4 as reactive gas and Ar as working gas. Atomic force microscopy (AFM), Raman, X-ray photoelectron spectroscopy (XPS) and UV–visible (UV–vis) spectrophotometer are conducted to test and analyze the structures and optical properties of the thin films. The films deposited at various CH4 flow possess compact and uniform surface. All thin films are mainly composed of B–N, B–C and C–N chemical bonds. Raman spectra show that ID/IG in the thin films increases with the growing of gas flow rate ratio (R = FCH4/(FCH4+FAr)). Moreover, the optical band gap (Eg) of the C doped BN thin films is ranging from 4.04 to 5.16 eV. In addition, the Eg value of the C doped BN thin films decreased with the growing of R. This was owing to the increase of carbon content since this contributed to the increase of π bonding originating from CC bond.

Growth Phase Diagram of Graphene Grown Through Chemical Vapor Deposition on Copper

The phase diagram for graphene growth was obtained to understand the physics of the growth mechanism and control the layer number or coverage of graphene deposited on copper via low-pressure chemical vapor deposition (LPCVD). Management of the number of graphene layers and vacancies is essential for producing defect-free monolayer graphene and engineering multilayered functionalized graphene. In this work, the effects of the CH4 and H2 flow rates were investigated to establish the phase diagram for graphene growth. Using this phase diagram, we selectively obtained fully covered and partially grown monolayer graphene, graphene islands through Volmer–Weber growth, and multilayer graphene through Stranski–Krastanov-like growth. The layer numbers and coverage were determined using optical microscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy and Raman spectroscopy. The growth modes were determined by the competition between catalytic growth with CH4 and catalytic etching with H2 on the copper surface during CVD growth. Intriguingly, this phase diagram showed that multilayer graphene flakes can be grown via LPCVD even with low CH4 and H2 flows.

Study on the Process of Vacuum Low Pressure Carburizing and High Pressure Gas Quenching for Carburizing Steels

The vacuum low pressure carburizing and high pressure gas quenching processes of 20CrMo, 20CrMnTi and 20Cr2Ni4 with acetylene as carburizing medium were investigated. The results show that the carburizing and diffusion time significantly affected the carburizing performance. Carburized with the process of C2H2 flow rate 10L/min, N2 flow rate 10L/min, carburizing pressure 3kPa, carburizing time 42min, diffusion time 140min and gas quenching pressure 1.5MPa, 20CrMo, 20CrMnTi and 20Cr2Ni4 can obtain the surface carbon content of 0.74%-0.78% and carburizing depth of 0.81mm-0.83mm. Meanwhile, the microstructure showed first grade carbide, and there was no internal oxidation laye on the surface. The carburizing constant and the diffusion time to carburizing time ratio were modified to be more suitable for the carburizing process.

Pore size effect on selective gas transport in shale nanopores

In shale gas production, gas composition may vary over time. To understand this phenomenon, we use molecular dynamics simulations to study the permeation of CH4, C2H6 and their mixture from a source container through a pyrophyllite nanopore driven by a pressure gradient. For a pure gas, the flow rate of CH4 is always higher than that of C2H6, regardless of pore size. For a 1:1 C2H6: CH4 mixture, however, C2H6:CH4 flow rate ratio is higher than the compositional ratio in the container (i.e., 1:1) when the pore size is smaller than ~1.8 nm. The selective transport is caused by the competitive adsorption of C2H6 over CH4 in the nanopore. The selectivity is also determined by the interplay between the surface diffusion of the adsorbed molecules and the viscous flow in the center of the pore, and it diminishes as the viscous flow becomes to dominate the surface diffusion when the pore size becomes larger than 1.8 nm. Our work shows that compositional differentiation of shale gas in production is a consequence of nanopore confinement and therefore a key characteristic of an unconventional reservoir. The related compositional information can potentially be used for monitoring the status of a production well such as its recovery rate.

Influences of deposition temperature, gas flow rate and ZrC content on the microstructure and anti-ablation performance of CVD-HfC-ZrC coating

To amend the oxidation and ablation resistance of C/C composites, HfC-ZrC biphase coating was synthesized by CVD. Influences of deposition temperature and CH4 flow rate on the deposition rate, phase constitution and microstructure of the HfC-ZrC coating were investigated. Ablation behavior and ablation mechanism of the HfC-ZrC coating with different ZrC contents were examined. With the deposition temperature rising, the deposition rate and grain size of the HfC-ZrC coating increased. High flow rate of CH4 was beneficial to improving the deposition rate and reducing the grain size of the HfC-ZrC coating. Moderate ZrC content in the HfC-ZrC coating was conducive to the process of solid solution sintering among HfO2 and ZrO2 grains, leading to generating a continuous and compact oxide layer. The coating with HfC/ZrC mole ratio of 1:1 exhibited superior anti-ablation performance, owing to its flat and compact structure and sufficient solid solution sintering among the oxide grains during ablation.