CH4 Flow Rate Research Articles

Effects of CrC interlayer on tribocorrosion properties of DLC-coated TC4 alloy in a 0.9 wt% NaCl solution

In this study, DLC coatings with varying thicknesses of CrC interlayers were fabricated on the surface of TC4 alloy by regulating the flow rate of C2H2. The effects of the interlayer layer on the microstructure, mechanical properties, corrosion resistance, and tribocorrosion resistance of DLC coatings were systematically investigated. The results show that as the C2H2 flow rate increases, the CrC interlayer exhibits the structure transitions from columnar crystals to amorphous, resulting in improved hardness. The hardness of the CrC40 interlayer reaches 17.2 GPa, significantly higher than the 9.3 GPa of the Cr underlayer. The CrC interlayer notably enhances the mechanical properties and adhesion strength of DLC coatings. The corrosion current density of the CrC40/DLC coating is 3.07 × 10−8 A/cm2, significantly lower than that of the DLC coating with only a Cr underlayer. Under high load conditions of 20 N, the tribocorrosion rate of the CrC40/DLC coating is reduced to 2.09 × 10−7 mm3.(N.m)−1, representing a significant decrease of 93.9 % compared to the DLC coating. The CrC40/DLC coating exhibits strong adhesion strength, appropriate internal stress and a relatively hard CrC40 interlayer, showing exceptional tribocorrosion resistance.

Effects of adding methane on the growth and electrical properties of GaN in oxide vapor phase epitaxy

GaN grown via oxide vapor phase epitaxy (OVPE-GaN) can produce free-standing substrates with ultra-low resistivity because of the high doping concentration of oxygen. The bulk growth of OVPE-GaN is hindered by polycrystals generated during long-term growth. We have previously reported that thicker films can be grown by reducing the partial pressure of water vapor in the growth atmosphere with CH4. However, as CH4 is a dopant of carbon, a compensating acceptor, its addition may increase electrical resistance. In this study, we further investigated the effect of reducing water vapor partial pressure on polycrystals by combining Ga2O production (reaction of Ga and water vapor: a Ga–H2O system), which can reduce water vapor, with CH4 addition. However, CH4 addition to the Ga–H2O system increased polycrystal generation, possibly owing to the thermal decomposition of excess CH4. The properties of OVPE-GaN with CH4 addition were also evaluated. Although the CH4 addition resulted in high carbon doping, the carbon-doped OVPE-GaN maintained low resistivity. This is because the OVPE method involves three-dimensional growth with growth pits, and the growth pits leave behind low-resistivity high-oxygen-concentration regions. As the resistivity remains low even when CH4 is added in the OVPE method, both polycrystallization suppression and low resistivity can be achieved by selecting an appropriate CH4 flow rate.

Preparation of carbon materials by vapor deposition with Fe3+-Modified nickel foam from biomass pyrolysis gas

Biomass carbon materials have attracted attention in various fields due to their excellent properties. In this study, CH4 derived from biomass pyrolysis was utilized as a carbon source gas to synthesize carbon materials by chemical vapor deposition (CVD) in a two-stage reactor with purification system, with Fe3+-loaded nickel foam as the substrate under an argon atmosphere, using a self-designed experimental platform. The reaction process was optimized by examining the effects of the catalyst type, reaction temperature, reaction time, and gas flow rate on the structure and morphology of the carbon materials. The optimal preparation condition was to use FeCl3 ethanol solution as catalyst, with CH4 flow rate of 50 ml/min at 1000 °C for 25 min. The high quality carbon materials with uniform diameters (250–500 nm) were obtained on nickel foam substrate. The carbon materials obtained under optimal conditions were characterized and analyzed to investigate their excellent properties. Surface morphology and structure of as-formed carbon materials were characterized by SEM. The analysis of the XRD spectra and the Raman spectroscopy showed that the graphite diffraction peak (002) at 26.6°, the calculated intensity ratios for ID/IG and I2D/IG were 0.257 and 0.545, respectively, indicated high degree of graphitization and purity of the carbon materials. Furthermore, the growth mechanism of carbon materials on the nickel foam substrate was discussed.

Microwave plasma-assisted hydrogen production via conversion of CO2–CH4 mixture

A method concerning re-use of the main greenhouse gases: CO2 and CH4 at the same time producing value-added chemicals (H2 + CO) is presented in this paper. The method involves the methane dry reforming using an atmospheric pressure operated 915 MHz microwave plasma source with a swirl gas flow. The effect of the CO2 to CH4 flow rates ratio, the total gas flow rate and the absorbed microwave power on the volume concentration of the gaseous plasma component in the outlet gas (%), CO2 and CH4 conversion rate (%), hydrogen production rate (g h−1) and energy yield of hydrogen production (g kWh−1) was investigated experimentally. The recorded results of the CO2 and CH4 conversion rate were about 82% and 88%, respectively. The best results in terms of the hydrogen production rate and energy yield of hydrogen production were equal to 156 g h−1 and 24 g kWh−1, respectively.

Analytical modeling of nucleation and growth of graphene layers on CNT array and its application in field emission of electrons

Carbon Nanotube (CNT) arrays and graphene have undergone several investigations to achieve efficient field emission (FE) owing to CNT’s remarkable large aspect ratio and graphene’s exceptional FE stability. However, when dense CNT arrays and planar graphene layers were used as field emitters, their field enhancement factor reduced dramatically. Therefore, in this paper, we numerically analyze the growth of a dense CNT array with planar graphene layers (PGLs) on top, resulting in a CNT-PGL hybrid and the associated field enhancement factor. The growth of the CNT array is investigated using Plasma Enhanced Chemical Vapor Deposition (PECVD) chamber in C2H2/NH3 environment with variable C2H2 flow, Ni catalyst film thickness, and substrate temperature followed by PGL precipitation on its top at an optimized cooling rate and Ni film thickness. The analytical model developed accounts for the number density of ions and neutrals, various surface elementary processes on catalyst film, CNT array growth, and PGLs precipitation. According to our investigation, the average growth rate of CNTs increases and then decreases with increasing C2H2 flow rate and catalyst film thickness. CNTs grow at a faster rate when the substrate temperature increases. Furthermore, as the chamber temperature is lowered from 750 °C to 250 °C in N2 environment and Ni film thickness grows, the number of the graphene layers increases. The field enhancement factors for the CNT array and hybrid are then calculated based on the optimal parameter values. The average height of the nanotubes, their spacing from one another, and the penetration of the electric field due to graphene coverage are considered while computing the field enhancement factor. It has been found that adding planar graphene layers to densely packed CNTs can raise its field enhancement factor. The results obtained match the current experimental observations quite well.

NbC thin films via reactive DC sputtering in a CH4/Ar atmosphere

We have demonstrated the growth of NbC-Amorphous C films that manifest a well-known nanocomposite structure (Klages and Memming, 1990; Nedfors et al., 2011; Sala et al., 2021). The films were deposited using reactive DC sputtering in a CH4/Ar atmosphere using an insulating substrate near room temperature. A metallic Nb sputtering target was sputtered in an argon/CH4 atmosphere with a pressure range of 5.9 to 8.5 mTorr as the CH4 flow was also varied. Crystalline NbC films were deposited at room temperature at the lowest CH4 flow rate. The films exhibited ohmic electrical response at room temperature. The DC electrical resistivity scaled almost 4 orders of magnitude from 4.39 × 10−4 Ω-cm to 1.08 × 10−1 Ω-cm through changes in CH4 flow rates and the resultant C content of the films. The large variation in resistivity cannot be attributed to the changes in sample composition, e.g. volumetric mixing. It is postulated from XRD and TEM results that the large change in resistivity is due to the decreasing NbC crystallite size with increasing CH4. This leads to additional three-dimensional nanoscale intragranular interfaces and results in increased resistivity. X-ray reflectivity measurements were conducted, and the modelled film density was found to match the expected density for the film compositions as measured using X-ray photoelectron spectroscopy. Elastic recoil detection analysis (ERDA) was used to quantify H content of the films. The H content increased from 5.5 to 22 atomic percent with corresponding increase in CH4 flow. Transmission electron microscopy utilizing precession electron diffraction (PED) was conducted and showed a strong dependence of crystallinity on CH4 flow. A multilayer layer sample with varying CH4 flowrates was examined with TEM and showed that films were amorphous in nature for flow rates above 10 SCCM CH4; in agreement with XRD results.

Assessing the performance of farm soil-based and hybrid biofilters for methane abatement

ABSTRACT Mitigating methane (CH4) emissions using methanotrophs (methane-oxidizing bacteria, MOB), is a simple, energy efficient and cheap technology. The abundance and distribution of MOB in the environmental samples is critical for efficient removal of emitted CH4 from any source. This study evaluated the performance of farm soils without and with cheap, easily accessible bulking materials as sustainable hybrid biofilter media. Soil-only biofilters removed up to 865 ± 19 g CH4 m−3 d−1 with well-drained organic carbon-rich soils compared with 264 ± 14 g CH4 m−3 d−1 for poorly drained soil. The removal efficiency decreased with increasing flow rate (0.16→0.24 L min−1) and subsequent priming could not return soil biofilters to their previous removal rate. Hybrid biofilters using organic, carbon-rich soils and compost removed up to 2698 g CH4 m−3 d−1 (flow rate 0.35 L min−1). Increasing CH4 flow rates also reduced their efficiency, but the hybrid biofilters with compost quickly regained most of their efficiency and removed up to 2262 g CH4 m−3 d−1 (flow rate 0.3 L min−1) after remixing of biofilter media. These results show that hybrid biofilters removed higher CH4 than soil-only biofilters and were also more resilient. The MOB gene abundance results complement the CH4 removal capacity of both soil-only and hybrid biofilter materials used. The more aerobic, carbon-rich soils had more abundant MOB than the poorly drained soil. The most porous hybrid biofilter with compost and more available nutrients to sustain bacterial growth and activity had the highest MOB abundance and removed the most CH4.

Effect of C2H2 flow rate on microstructure, properties, and application in micro-drilling of a-C:H films deposited by PECVD

The drilling of printed circuit board (PCB) using micro-drills is an important processing method in modern industry. A protective film with good lubricating and anti-wear properties is generally applied to improve the processing problems of micro-drills during operation. In this study, the effects of C2H2 flow rate on the microstructure, mechanical, and tribological properties of a-C:H films deposited by plasma enhanced chemical vapor deposition (PECVD) technique were investigated. The results showed that when the C2H2 flow rate was low, varying the flow rate had little effect on the microstructure of the prepared a-C:H films. However, when the C2H2 flow rate was greater than 210 sccm, the increase in flow rate caused large particles of carbon clusters to aggregate on the surface of a-C:H films, which resulting in an increase Ra value. Not only did it reduce the adhesion between the film and the substrate, but it also deteriorated the mechanical and tribological properties of the a-C:H film produced. In addition, a-C:H films were also deposited on the micro-drill, and were used for drilling tests on the PCBs to evaluate its servce capability. The optimal parameters of a-C:H film deposited on the micro-drill surface were obtained by observing the morphology of the micro-drill surface after drilling and the hole accuracy statistics. The results showed that a-C:H film deposited on the surface of the micro-drill showed the best machining performance when the C2H2 flow rate was 180 sccm. The surface wear of micro-drill was minimal, the entanglement of tangled chips was minimal. The value of the process capability index (CPK) after 500, 1000, and 2000 drilling of PCB boards was 5.95, 4.33, and 3.15 respectively, which showed the highest drilling accuracy. This is mainly attributed to the better overall properties of the a-C:H films prepared at C2H2 flow rate of 180 sccm, such as lower surface roughness, lowest residual stress, higher hardness, better adhesion, and lower friction coefficient.

N2 injection to enhance gas drainage in low-permeability coal seam: A field test and the application of deep learning algorithms

N2 injection to enhance coal seam gas drainage is an effective technology for coalbed methane recovery. Nevertheless, there is a limited body of research addressing the application of ECBM technology for gas management in low permeability coal seams within underground coal mines, and the effect is uncertain. Additionally, numerical simulators have been challenged to accurately predict methane emissions during gas injection and replacement. In this study, firstly, an underground field trials of N2 injection replacement in a coal mine with low-permeability coal seams in China were conducted, and a comparative analysis of “N2 injection to enhance gas drainage” and “conventional drainage” technique was performed. The result show that injecting pressurized N2 into a low-permeability coal seam could increase the pressure gradient to promote the directional flow of free gas from the coal seam cracks to the gas-production boreholes. After N2 injection, the mixed flow rate and CH4 flow rate significantly increased. Additionally, the gas content in the coal seam in the experimental area significantly decreased. Secondly, the lag-effect was discussed. Upon discontinuation of N2 injection, the gas-producing mixed flow initially increased slightly, then gradually decreased, and eventually settled at a high level. Despite the attenuation of N2 injection volume, the CH4 flow rate continued to increase during intermittent injection and remained high after gas injection discontinuation. Finally, three deep learning algorithms (BP, LSTM, and TCN) were employed to predict the dynamic change of gas drainage in coal seams displaced by N2 injection, based on the results of the field test. The results indicated that deep learning algorithms exhibited superior prediction performance. The TCN model demonstrated the lowest approximation error rate, displaying optimal performance in predicting the CH4 flow rate during nitrogen injection for enhanced gas drainage. Additionally, it exhibited good applicability to other similar field test results.

The Time-Varying Variation Characteristics of Methane during Nitrogen Injection Process: An Experimental Study on Bituminous Coals

The existing research on CH4 displacement by N2 mainly focuses on the gas injection displacement mechanism and the factors affecting displacement efficiency. And most of them are theoretical analyses at the model level or multifactor analyses at the simulation test level, while there are few targeted physical simulation tests and quantitative analyses. Given the above problems, the experiment system was used to study the gas migration evolution law and time-varying characteristics of CH4 displacement by N2 in coal under different injection pressures. The experimental results show that the whole process of CH4 displacement by N2 can be divided into three stages: stage I (original equilibrium stage); stage II (dynamic balance stage); stage III (new equilibrium stage). The concentration of CH4 and N2 presents an opposite variation trend, and the variation rate of CH4 and N2 increased first and then decreased. The breakthrough time was 50 minutes, 45 minutes, 35 minutes, 25 minutes, and 20 minutes, respectively, under different injection pressures. The displacement efficiency increased with the injection pressures, while the replacement ratio decreased with the injection pressures. The maximum flow rate of CH4 was 0.085 mL/min, 0.110 mL/min, 0.130 mL/min, 0.222 mL/min, and 0.273 mL/min, respectively, under different injection pressures. The accumulated production of CH4 was 3.59 mL, 3.91 mL, 4.39 mL, 5.58 mL, and 5.94 mL, respectively, under different injection pressures. The effective injection pressure range was 1.6~2 MPa. This research can provide a reference for the theoretical research of N2-ECBM-related technology in low permeability reservoirs and the selection of injection pressure in the field technology implementation.

Unveiling the multifaceted impact of C2H2 flow on SiCN CVD coatings: Mechanical mastery and beyond

This comprehensive study systematically investigates the influence of C2H2 flow rates on silicon carbonitride (SiCN) thin films deposited on p-type c-Si (100) substrates through Chemical Vapor Deposition (CVD). Across a range of C2H2 flow rates (1–15 sccm), the study quantitatively analyzes surface morphology, crystallinity and mechanical characteristics. Analyzing the data quantitatively: Surface morphologySEM and AFM analyses unveiled distinctive surface patterns influenced by varying C2H2 flow rates. Surface roughness exhibited a quantitative increase, rising from 1.2 nm at 1 sccm to 2.4 nm at 15 sccm. Ftir analysisFTIR spectroscopy identified three major vibrational signatures in SiCN thin films: Si-Hn wagging, n-SiC, and Si–C stretching. Notably, the intensity of the n-SiC peak demonstrated a quantitative rise with increasing C2H2 flow rate. XRD analysisXRD confirmed the quantitative impact of C2H2 flow rates on crystallinity. The SiCN thin film deposited at 15 sccm exhibited the highest crystallinity, with a quantified crystallite size of 15 nm. Nanoindentation testingHardness and Young's modulus were quantitatively assessed through nanoindentation testing. SiCN thin films showed a quantitative increase in both hardness and Young's modulus with rising C2H2 flow rates. The film deposited at 15 sccm demonstrated the highest hardness (i.e. 19.23 GPa) and Young's modulus (i.e. 271.56 GPa).In summary, this study establishes the significant impact of C2H2 flow rates on the quantitative aspects of surface morphology, crystallinity, and mechanical properties of SiCN thin films. Notably, the film deposited at 15 sccm emerges as distinctive, exhibiting the highest quantitative values for crystallinity, hardness and Young's modulus. This comprehensive analysis enhances the understanding of intricate relationship between C2H2 flow rates and the multifaceted properties of SiCN thin films.

Steady state thermokinetic of ultra-thin Mo2C/G heterostructures grown on the prior-graphitized cu/graphene biasing

In this work, the chemical vapor deposition synthesis of the Mo2C/graphene heterostructure above the melting temperature of Cu bias (1356 K) is studied. Two sets of Mo2C growth experiments at high CH4 flow rates (5 SCCM ≥ 3 SCCM) are performed, either using prior-graphene synthesis or having in situ graphitization, for three different Cu bias thicknesses. Raman mappings taken from all six-test samples show graphene covers not only over the Mo2C pillars but also over their untransformed Cu bias substrate regions. The only difference is that the Mo2C pillar grows over the prior graphene bias; on the other hand, the in situ graphene grown Mo2C pillar nucleates and grows over the fresh Cu bias surfaces. A steady-state laminate model for flows of Mo and C species with phase transformations is developed for the radial and vertical growth kinetics of synthesized Mo2C/graphene heterostructure. The computer simulation reproduces those experimental observations performed recently in our laboratories on the prior or no-prior graphitized (G) test modules with Cu/G bias, having three different thicknesses at 1363 K. AFM-topography and SEM photos for a prior graphitized test module of 25 µm thick Cu and 4.72 Å graphene bias show a three layered Mo2C/graphene heterostructure; the first layer is almost perfect hexagonal flat, and the other two circular shaped layers constitute the whole pillar of 140 nm height. This may be compared to a 250 µm thick Cu/4.7 Å graphene bias sample, which furnishes an ultra-thin single flat layer of 10–13 nm thick Mo2C crystallites having a perfect planar hexagonal structure.

Preparation and performance of Ti/Ti-DLC composite coatings for precision glass molding

Precision glass molding (PGM) is an efficient process used for batch manufacturing of high-precision glass optical elements. In this process, nickel phosphide (Ni–P) alloy is commonly utilized as a mold material due to its superior turning properties. However, the Ni–P mold suffers from issues such as diffusion of phosphorus elements, poor wear resistance, and easy peeling of the DLC coating during molding. To address these problems, the current study proposes enhancing the molding performance of mold by depositing a composite coating layer of Ti/Ti-DLC onto the surface of Ni–P using the filtered cathodic vacuum arc technology (FCVA). The effects of different flow rates of C2H2 on Ti-DLC coatings were analyzed in terms of composition, microstructure, mechanical, tribological, and molding properties. The results revealed that as the C2H2 flow rate increased, the Ti content of coatings decreased from 13.56 to 2.17 at.%. Additionally, the film microstructure transformed from TiC polycrystalline composite films to nanocrystalline amorphous composite films and finally to amorphous films. The Ti-DLC coatings with a nanocrystalline composite structure exhibited excellent overall performance when Ti content is 7.75 at.%. These coatings are suitable as protective coatings for microstructured array mold and demonstrate good stability at a molding temperature of 500 °C.

Study on particle size and field effect with sp2/sp3 ratio of hydrogenated diamond-like carbon

Hydrogenated diamond-like carbon (HDLC) films were synthesized through a reactive gas-plasma process employing methane (CH4) and hydrogen (H2) as precursor gases on a silicon (100) wafer substrate, conducted at room temperature. The deposition process utilized a biased enhanced nucleation technique, varying the flow rate ratio of hydrogen and methane. The investigations revealed that increasing the methane flow rate led to a reduction in grain size and an augmented nucleation density of HDLC, as evidenced by contact-mode atomic force microscopy (AFM) images. This study demonstrated the effective control of diamond grain growth by introducing high-methane-concentration pulses during deposition. The field emission characteristics of HDLC samples were analyzed, revealing threshold fields of 12.2 V/μm for nanocrystalline films, 8.5 V/μm for subcrystalline films and 4.1 V/μm for microcrystalline films, corroborated by Raman spectra. Surface energy measurements indicated hydrophobic behavior in the samples. Notably, a decrease in the hydrogen/methane ratio was found to increase the sp2 character, which correlated with the emission field. AFM analysis of HDLC samples yielded surface roughness values ranging from 0.2 nm to approximately 0.01 nm, confirming the continuous, non-porous and smooth nature of the surfaces.

Structure and Optical Characteristics of DLC Films

SummaryUsing a RF‐Plasma Enhanced Chemical Vapor (RF‐PECVD) Depositions method, employing hydrogen and methane gas, Diamond like carbon (DLC) films were fabricated on glass and silicon substrates. The impact of varying CH4 to H2 ratios on the resulting film's structure, optical characteristics, and mechanical properties was investigated. The deposition process occurred at methane flow rates spanning 5 to 40 sccm. The films' surface morphology, and roughness were analyzed through Atomic Force Microscopy. Moreover, the Vickers hardness tests was employed to determine the hardness of produced films. The optical behavior of the DLC thin films was explored utilizing UV‐visible spectrometry and ellipsometry. A thorough investigation was conducted to understand how the CH4 flow rate influences layer growth, morphology, topography, and how these factors relate to the films' transmittance, reflectance, refractive index, and optical band gap.

Enzyme activities of rhizosphere soil with different root diameters had varied responses to N deposition in Pinus tabuliformis forest

Root system exhibits hierarchical traits in physiology and exudation, and responds variably to environmental changes. However, it remains unclear if these phenomena result in corresponding alterations in the microbial characteristics of rhizosphere soil and diverse responses to nitrogen (N) deposition. This study evaluated microbial biomass, gas flow, and enzyme activity in rhizosphere soil of three root diameter classes (R1, <0.5 mm; R2, 0.5–1.0 mm; R3, 1.0–2.0 mm) of P. tabuliformis, and their responses to N application (0, 3, 6, 9 g N m−2 y−1, corresponding to CN, LN, MN, and HN) in a P. tabuliformis forest. Rhizosphere soil of R1 exhibited significantly higher microbial biomass N (MBN) content, enzyme activities, CO2 and N2O flow rates than those of R2 and R3 (P < 0.05). Soil microbial biomass carbon (MBC) and phosphorus (MBP) contents, N2O and CH4 flow rates significantly increased with N applications. While soil MBN content increased with the LN treatment and decreased with the HN treatment, the largest value was observed in the LN treatment (84.89 mg kg−1). N application promoted Alkaline phosphatase (ALP) and Alanine transaminase (ALT) activities in R1 rhizosphere soil while decreasing their activities in R2 and R3 rhizosphere soils. Moreover, β-glucosidase (BG), N-acetyl-β-Glucosaminidase (NAG), β-xylosidase (XYL), and β-D-cellulosidase (CBH) activities in R1 rhizosphere soil were inhibited, while their activities in R2 and R3 rhizosphere soils were promoted by N application. N application directly promoted microbial biomass then inhibited enzyme activity. Besides, nutrient content of rhizosphere soil decreased with root diameters, which indirectly reducing enzyme activity and microbial biomass. N application directly affected soil CH4 flow rate, while N2O flow rate was indirectly promoted by N application through increasing microbial biomass. CO2 and CH4 flow rates were inhibited by N application through decreasing enzyme activity. Root diameter slowed down the CO2 and CH4 flow rates by reducing soil nutrient content and enzyme activity. In conclusion, N deposition has varied effects on microbial characteristics in rhizosphere soil of different diameter roots, which are relevant to the corresponding changes in root system and soil properties.

Investigation of the high-temperature field distribution characteristics for a multi-jet burner by OH-PLIF and coherent anti-Stokes Raman spectroscopy

The construction of a high-temperature gas calibration source is of great significance since it can provide an effective high-temperature experimental environment for, e.g. verifying high-temperature measurement techniques and studying high-temperature combustion mechanisms. Here, we try to obtain a high-temperature gas field on a multi-jet burner by controlling the gas supplies to it. We use OH planar laser-induced fluorescence (OH-PLIF) to observe the compositional uniformity of the field and coherent anti-Stokes Raman scattering (CARS) to investigate the temperature uniformity of the field. We find from OH-PLIF images that the distribution of OH between the adjacent jets becomes more uniform with the increasing flow rate of CH4, and the flow rate of the co-flow N2 around jets also affects the uniformity of OH distribution. The measured temperature distribution by CARS is consistent with the OH distribution. At the jet outlet location, the temperature distribution had a periodic variation and gradually became more uniform with the height increased from the jet outlet. We find that the flow rate of CH4 and co-flow N2 and the radiative heat transfer rate play an important role in temperature distribution for the multi-jet burner. Also, the results show that a wide range of temperatures can be constructed by regulating the recipe of the gas supplies, and the highest temperature achieved in this work is 2457 K.

Experimental study of coal rank effect on carbon dioxide injection to enhance CBM recovery

Coal seam gas extraction is an important part of green mining. At the same time gas injection for enhanced coalbed methane recovery (ECBM) has been proposed as an environmentally friendly, low-carbon and effective technology to increase methane production. To study the influence of coal rank on carbon dioxide (CO2)-ECBM efficiency, lignite, bituminous coal, and anthracite were tested using the Gas Flow and Displacement Testing Apparatus (GFDTA). Data indicated that: (1) in lignite and anthracite, outflow CO2 and CH4 fractions changed at higher rates as compared with bituminous coal. At the end of the experiments, lignite and anthracite displayed CH4 outflow fractions of 0.19% and 7.73%, respectively; (2) at the initial stage of the experiments, permeability rapidly decreased. Later, a fast increase was followed by a stable phase. In lignite and anthracite, the increment in permeability during the rapid increase stage was significantly larger than that of bituminous coal. (3) The CH4 flow rate of the three coal ranks showed a decreasing trend. Before the breakthrough, CH4 flow rate decreased rapidly and slowed down. After the breakthrough, CO2 flow displayed a linear increasing trend and later reached stability. (4) In general, CH4 production increased with the increase in coal rank. The variation of CH4 production is manifested in two phases with different dominant factors. In the first stage, CH4 production was mainly affected by permeability, and followed the order lignite > anthracite > bituminous. In the second stage, CH4 production was mainly controlled by the displacement effect, following the order anthracite > bituminous coal > lignite.

Properties of SiCN Films Relevant to Dental Implant Applications.

The application of surface coatings is a popular technique to improve the performance of materials used for medical and dental implants. Ternary silicon carbon nitride (SiCN), obtained by introducing nitrogen into SiC, has attracted significant interest due to its potential advantages. This study investigated the properties of SiCN films deposited via PECVD for dental implant coatings. Chemical composition, optical, and tribological properties were analyzed by adjusting the gas flow rates of NH3, CH4, and SiH4. The results indicated that an increase in the NH3 flow rate led to higher deposition rates, scaling from 5.7 nm/min at an NH3 flow rate of 2 sccm to 7 nm/min at an NH3 flow rate of 8 sccm. Concurrently, the formation of N-Si bonds was observed. The films with a higher nitrogen content exhibited lower refractive indices, diminishing from 2.5 to 2.3 as the NH3 flow rate increased from 2 sccm to 8 sccm. The contact angle of SiCN films had minimal differences, while the corrosion rate was dependent on the pH of the environment. These findings contribute to a better understanding of the properties and potential applications of SiCN films for use in dental implants.

Comparative study of titanium carbide films deposited by plasma-enhanced and conventional magnetron sputtering at various methane flow rates

Titanium carbide (TiCx) films were deposited by reactively sputtering Ti target with varied methane (CH4) flow rates using an unbalanced magnetron sputtering equipment operating in conventional (CMS) and plasma-enhanced (PEMS) mode. The microstructure and properties of the TiCx films were mainly scrutinized with X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, nano indentation, and ball-on-disk tribo-test. As the CH4 flow rate is increased from 4 to 16 sccm, x in the TiCx films deposited by PEMS and CMS is gradually increased from 0.28 to 0.96 and 0.28 to 0.73, respectively; and the concentration of TiC phase in the films rises. A densified microstructure with strong preferred growth is observed in the PEMS-deposited films, while a loose columnar microstructure with almost random growth exists in the CMS-deposited films. When the CH4 flow rate is increased, the hardness of the films deposited by PEMS is firstly increased and then decreased, and reaches a maximum value of 29.6 GPa; but that of CMS-TiCx film is fluctuated below 10.6 GPa. The friction coefficient of TiCx-coated samples against pure aluminum is gradually increased with increasing CH4 flow rate from 4 to 14 sccm, accompanied by a reduction of the aluminum adhesion. The wear rate of the TiCx-coated samples as a function of the CH4 flow rate is firstly decreased and then increased. The lowest wear rate of the PEMS-prepared samples is 7.2 × 10−16 m3/(N·m) obtained at a CH4 flow rate of 14 sccm, while that of the CMS-prepared samples is 9.3 × 10−15 m3/(N·m) obtained at 12 sccm. Therefore, PEMS is a promising method to prepare TiCx films with a good combination of the mechanical properties and wear-resistance against pure aluminum.