Acetylene Flow Research Articles

Investigation into the impact of acetylene on performance and emission characteristics of a compression ignition engine using a blended biodiesel of ethanol and tamanu oil.

Due to the significant increase in transportation, traditional fossil fuels utilised in internal combustion engines will only be accessible for a limited duration. Additionally, the harmful pollutants produced by these fuels, including CO, NOx, unburned hydrocarbons, smoke, and a small amount of particulate matter, have a severe negative impact on the environment. Although biodiesel proves efficient without necessitating engine modifications, its performance is hindered by its higher viscosity. Consequently, this research aims to enhance performance by introducing acetylene alongside tamanu methyl ester (biodiesel); however, this approach results in elevated NOx levels. To mitigate NOx emissions, a combination of ethanol and biodiesel is employed. This study investigates the performance and emission attributes of Acetylene + TME90E10 as the fuel. The combustion pressure and heat release rate of TME90E10 with 6 lpm, improved by 5.41% and 9.1% than diesel. When compared to regular diesel fuel, the introduction of 6l per minute of acetylene with TME90E10 yields a substantial 24.4% decrease in hydrocarbon (HC) emissions. Furthermore, employing TME90E10 at the same acetylene flow rate demonstrates the lowest carbon monoxide (CO) emissions, registering at 0.07%, in contrast to the 0.13% emissions observed throughout the exhaust cycle when using pure diesel fuel.

Development, Validation and Application of a Fast Sequential Method for Na, K, Ca and Mg Determination in Hemodialysis Solutions by HR-CS F AAS.

Hemodialysis solutions are liquid concentrates used during hemodialysis sessions. They are commonly used as a renal replacement therapy. This study aimed to develop a method to determine Na, K, Ca and Mg in hemodialysis solutions by high-resolution continuum source flame atomic absorption spectrometry (HR-CS F AAS) using Design of Experiments (DOE). The combination of the Doehlert Matrix with the desirability function was used to establish a compromise condition in the optimization of the significant variables studied: 60 L/h for acetylene flow rate, 8 mm for burner height, 0.25% (w/v) and 0.60% (w/v) for Cs and La concentrations. The method was validated by following the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) guidelines and parameters such as the selectivity, linearity, precision, accuracy and robustness were evaluated. Calibration curves with the ranges of 25-130 mg/L for Na, 1.0-5.0 mg/L for K and Ca, and 0.30-0.70 mg/L for Mg were employed. The method proved to be precise (RSD lower than 2.7%) and accurate (mean recovery data, contemplating the three levels added were: 103.0% for Na, 100.5% for K, 101.3% for Ca and 101.5% for Mg). The developed method enables the sequential multielement determination of Na, K, Ca and Mg in a single run. Requiring only one dilution step, this method significantly reduces analysis time for both sample and standard solutions preparation and measurement. This study presents the first method reported in the literature for multielement determination in hemodialysis solutions, offering an alternative approach to the current European Pharmacopeia method.

The effect of oxidation on tribology behavior of nickel-graphite coated stainless steel SS420

The main solution to the challenge of maintaining maximum sealing in the compressor section of each gas turbine is the use of abradable coatings. These coatings have a double duty, including (a) maintaining the lagging and (b) protecting the tips of the rotor blades. Choosing the type of abradable coating primarily depends on the service temperature of the coating. Nickel-graphite (Ni-G) coating is a good choice for use up to 480 °C and, or steel/sub-alloy rotor blades. In this research, the Ni-G coating was applied by the flame spraying method of Ni-G powder with a thickness of about 250 μm on an SS420 stainless steel substrate. The effect of the composition of the bonding layer was also investigated using two compositions, Ni-5Al and NiCrAlY. Obtaining the knowledge of applying Ni-G coating by flame spraying, identifying the structural and compositional characteristics of the coating (through optical and electron metallography), and the effect that oxidation can have on the tribological behavior of the coating were among the goals of this project. The best conditions for spraying the Ni-G coating were achieved an oxygen gas pressure of 6 bar, oxygen flow rate of 18 L min−1, acetylene pressure of 1.5 bar, acetylene flow rate of 24 L min−1, and the distance between the gun head and the sample surface was 22 cm. The results showed that placing the coating in oxidizing conditions increases its coefficient of friction. The increase in the coefficient of friction was attributed to the formation of oxide shells on the surface of the coating after 500 h of exposure to oxidation conditions. Corresponding to the higher coefficient of friction, the oxidized coating showed a decrease in wear resistance as a result of oxidation. This result can show the decrease in abradable of this coating with increasing service time.

Influence of the Acetylene Flow Rate and Process Pressure on the Carbon Deposition Behavior by Thermal Chemical Vapor Deposition Process

We used the chemical vapor deposition process to deposit carbon film at a high temperature (900 °C). The carbon films were deposited on AISI 1006 foils using an acetylene gas. We analyzed the carbon film deposited on the surface using Raman spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy to define changes in the bonding structure of the carbon film. The results of Raman spectroscopy and high-resolution transmission electron microscopy revealed that as the acetylene flow rate increased, the shape of the deposited carbon film changed from graphene to graphite. In addition, in order to compare the quality of the carbon film in terms of mechanical and electrical properties, carbon films treated under various conditions were closely analyzed using nano-indenter and a sheet resistance meter. Therefore, the optimal condition (1 Torr-50 sccm) was selected in which graphene was uniformly deposited and had the lowest electrical resistance (500 Ω/sq) and highest hardness (12 GPa).

Grey-Taguchi and ANN optimization in CI Engines using acetylene & biodiesel blends for Low Emissions and Better Performance

This study aimed to reduce smoke and NOx emissions in a diesel engine fuelled with a 20% blend of Calophyllum inophyllum and Prosopis juliflora biodiesel (B20) with neat diesel, supplemented with acetylene at flow rates of 1, 2, and 3 liters per minute (lpm) in dual-fuel mode. Using the Grey-Taguchi method and an L9 (3^3) orthogonal array, the effects of compression ratio, fuel type, and acetylene flow rate were examined. Regression models were developed to predict brake thermal efficiency, smoke, and NOx emissions based on these controllable factors. The study found that the optimal individual values for NOx, brake thermal efficiency, and smoke were 2353 ppm, 31.52%, and 48.7 ppm, respectively. The best-combined results were achieved with a compression ratio of 17.5 and an acetylene flow rate of 3 lpm using the CI20 blend. The findings demonstrated significant improvements in output response factors when the optimal combination was applied, as validated by experimental and artificial neural network (ANN) simulations. The Grey-Taguchi approach proved effective in reducing emissions while enhancing engine performance.

Optimization on manifold injection in DI diesel engine fuelled with acetylene

Researchers demonstrated that implementing new combustion technology and optimising fuel quantity results in a significant reduction in traditional fossil fuel usage and emission levels. The Reactivity Controlled Compression Ignition (RCCI) combustion strategy is one of the low temperature combustion technologies, and it is used to reduce the overall combustion temperature while also providing better combustion control. This study looks into RCCI combustion technology, which uses conventional diesel fuel as the high reactivity fuel (HRF) injected through the injector and acetylene gas as the low reactivity fuel (LRF) injected into the cylinder via a modified inlet manifold alongside air. The modified engine setup was tested for performance, emissions, and combustion under various load conditions, as well as different mass flow rates of acetylene gas, a low reactivity fuel that is injected with air. The flow field of the low reactivity fuel at the inlet manifold is analysed using the Computational Fluid Dynamics principle, which is used to determine the best flow rate for improving combustion quality. According to the simulation results, the optimal acetylene flow rate is 3 Litres Per Minute (LPM), and experimentation shows that at 3 LPM acetylene injection, the brake thermal efficiency (BTE) improves by about 3.2%, and emissions such as carbon monoxide (CO), hydrocarbon (HC), smoke intensity, and oxides of nitrogen (NOx) are reduced by about 35%, 17%, 10%, and 21%, respectively.

Growth of Carbon Nanofibers and Carbon Nanotubes by Chemical Vapour Deposition on Half-Heusler Alloys: A Computationally Driven Experimental Investigation.

The possibility of directly growing carbon nanofibers (CNFs) and carbon nanotubes (CNTs) on half-Heusler alloys by Chemical Vapour Deposition (CVD) is investigated for the first time, without using additional catalysts, since the half-Heusler alloys per se may function as catalytic substrates, according to the findings of the current study. As a carbon source, acetylene is used in the temperature range of 700-750 °C. The n-type half-Heusler compound Zr0.4Ti0.60.33Ni0.33Sn0.98Sb0.020.33 is utilized as the catalytic substrate. At first, a computational model is developed for the CVD reactor, aiming to optimize the experimental process design and setup. The experimental process conditions are simulated to investigate the reactive species concentrations within the reactor chamber and the activation of certain reactions. SEM analysis confirms the growth of CNFs with diameters ranging from 450 nm to 1 μm. Raman spectroscopy implies that the formed carbon structures resemble CNFs rather than CNTs, and that amorphous carbon also co-exists in the deposited samples. From the characterization results, it may be concluded that a short reaction time and a low acetylene flow rate lead to the formation of a uniform CNF coating on the surface of half-Heusler alloys. The purpose of depositing carbon nanostructures onto half-Heusler alloys is to improve the current transfer, generated from these thermoelectric compounds, by forming a conductive coating on their surface.

Effects of using acetylene-enriched biogas on performance and exhaust emissions of a dual fuel stationary diesel engine

Biogas, which can be produced easily and cost effective from agricultural and animal waste, is an attractive alternative fuel to drive stationary diesel engine especially in rural areas. In this study, the effects of using acetylene enriched biogas under very lean mixture conditions in a four stroke, two cylinder, air-cooled diesel engine capable of developing 11.5 kW at 3000 rpm on performance and exhaust emissions were experimentally investigated. The experiments were carried out at 10 Nm, 20 Nm and 30 Nm torque. Acetylene flow rate of 2 slpm, biogas flow rate of 15 slpm and the engine speed of 1750 rpm were kept constant. The results showed that more than 36 % diesel substitution was possible with acetylene-enriched biogas at the specified flow rate without any degradation in normal operation. Moreover, the experimental findings revealed that the use of biogas and acetylene reduced brake thermal efficiency by 21.7 % and 5.8 % at 10 Nm and 20 Nm torque but only reduced by 0.6 % at 30 Nm torque. The exhaust gas temperature of dual fuel mode was found to be higher than the case of diesel mode especially at 20 and 30 Nm torque. While NO emission were lower, CO, and CO2 emission were higher in dual fuel mode compared to single diesel mode.

Effect of doping and preparation parameter on AC conductivity and dielectric modulus formalism of Al doped DLC thin films

Here, we report the composite effect of aluminum doping on the dielectric response of Diamond-Like Carbon (DLC) thin films. In addition, the contribution from preparation parameters like acetylene flow rate is also considered to understand sample behavior. AC conductivity study shows the existence of a nonlinear increase of conductivity with frequency leading toward the Jump Relaxation Model (JRM). The transition frequency (ft) is observed, which increases with conductivity. The study reveals that dielectric response is influenced by space charge conductivity, prompting us to adopt the modified Debye law. Deviation from ideal Debye behavior is also confirmed in dielectric modulus analysis. The deviation is frequency-dependent, and a higher deviation is observed in the high-frequency region. Plotting of the Master curve shows the presence of different relaxation dynamics in different samples. A current-voltage (I-V) study of different samples is also undertaken, showing higher values (greater than unity) of the ideality factor.

Synthesis and characterization of ceramic high entropy carbide thin films from the Cr-Hf-Mo-Ta-W refractory metal system

We use reactive DC magnetron sputtering to showcase synthesis strategies for multicomponent carbides with the NaCl-type fcc structure and illustrate how deposition conditions allow controlling the formation of metallic and ceramic single phases in the Cr-Hf-Mo-Ta-W system. The synthesis is performed in argon flow and different acetylene flows from 0 to 12sccm, at ambient and elevated temperatures (700 °C), respectively, hindering/promoting the adatom diffusion. Structural and microstructural investigations reveal the formation of the bcc metallic phase (a=3.188−3.209Å) in films deposited without acetylene flow, also supported by ab initio density function theory (DFT) analysis of lattice parameters as a function of the C content. Experimentally, a bcc-to-fcc phase transition is observed through the formation of an amorphous coating. Contrarily, samples deposited in higher acetylene flow show an fcc multielement carbide phase (a=4.33−4.49 Å). The crystalline films reveal columnar morphology, while the amorphous ones are very dense. We report promising mechanical properties, with hardness up to 25±1GPa. The indentation moduli reach up to 319±6GPa and show trends consistent with DFT predictions. Our study paves the path towards the preparation of Cr-Hf-Mo-Ta-W multicomponent carbides by magnetron sputtering, showing promising microstructure as well as mechanical properties.

Effect of horizontal insertion of metal wire mesh into the flame on the formation and suppression of soot in acetylene diffusion flame

A simple and efficient strategy to suppress soot from acetylene diffusion flames is reported for the first time. Horizontally insertion of metal wire mesh into the acetylene diffusion flame is found to greatly suppress the soot emission. The effects of experimental parameters such as acetylene flow rate, wire mesh height above nozzle (WHAN), material of wire mesh, mesh number, and inner diameter of the burner nozzle on soot suppression in acetylene diffusion flames are investigated. In addition, the collected soot samples are characterized by TEM, HRTEM, XRD, BET and Raman. The soot suppression efficiency can reach 100 % by horizontal insertion of the metal wire mesh in the acetylene diffusion flame. The WHAN has a great influence on the effect of soot suppression. In the first 210 s of horizontally inserting the metal wire mesh into the flame, the total mass of collected soot first decreases and then increases with the increase of WHAN. The minimum total mass of soot is achieved when the normalized WHAN (obtained by dividing the wire mesh height above nozzle by flame height without insertion of the wire mesh) is at 0.1. This position corresponds to the soot particle inception zone of the acetylene diffusion flame. The flame is divided into two parts when the metal wire mesh is horizontally inserted into the flame. The temperature of the flame below the metal wire mesh decreases from 1770 K to 1480 K. The temperature of the flame above the metal wire mesh increases from 1590 K to 1780 K. The soot collected on the metal wire mesh grows into a volcano-shaped carbon (VSC) structure. The results of the schlieren imaging experiments show that this structure can promote the mixing of air and fuel in the lower region of the flame thereby suppressing the formation of soot particles. The soot analysis shows that the horizontal insertion of metal wire mesh into the flame leads to high amorphous feature and low degree of structural order of the soot, which means that the oxidation reactivity of the soot increases.

Turbostratic Carbon Nano Onion Electrode for High Power Density Vanadium Redox Flow Battery

The redox flow battery (RFB) is one of the most promising technologies for stationary energy storage. It consists of a voltaic cell whose electrolytes are stored in tanks outside the system. Whilst the chemistries of the anodic and cathodic electrolytes define the energy density of a RFB system, its power density is determined primarily by its electrodes. These are typically porous carbon media on the surface of which the redox reactions occur. They are a critical component since they require a detailed engineering of electrocatalytically active surface area and mass transport. Still today, they remain the main cause of RFB low power density. In this work, we are showing a novel deposition method to improve the performance of commercially available carbon paper already used in RFB.The gain is thanks to the deposition of turbostratic carbon nano-onion (TCNO) nanoparticles on the carbon fibers of the paper. This process is performed with a proprietary technology called NanoJeD: a CVD in supersonic flow, which promises easy industrial scalability and a fine tunability of the nanoparticle properties. Moreover, with this system is possible to deposit over any substrate.NanoJeD consists in two chambers separated by a high aspect ratio slit. A precursor gas is injected through a porous plug from the top and a vacuum system is connected from the bottom. The slit allows the establishment of a high-pressure ratio between the two chambers and hence the formation of a supersonic jet. The precursor gas, a mixture of Argon (98.4%) and Acetylene (1.6%) flows between two electrodes where a radio frequency (RF) signal is fed (13.56 MHz). The RF ignites a non-thermal plasma in which the precursor molecules are ionized and dissociated into radicals, which polymerize forming hydrogenated carbon clusters and nanoparticles (NPs) of different sizes. Once formed, NPs are dragged through the slit by the gas stream and finally impact on the substrate. Therefore, it is possible to achieve a high throughput (500 mg h-1) and to deposit on a large area of 100 cm2 while precisely controlling the properties of the film. The resulting film has hundreds of squared meters per gram of surface area. For TCNO formation, the NP film is further annealed in vacuum at 1000°C for 2 hours. Using in situ transmission electron microscopy (TEM) and energy electron loss spectroscopy (EELS), we were able to visualize the progression of graphitization and changes in structural properties during annealing. The graphitization process starts in the outer layer and proceeds into the interior of the particle. The geometrical constrains of the NP (average diameter of 20nm) and shrinkage of the NP, allow the formation of curved, turbostratic, defective graphitic sheets. UV photoelectron spectroscopy (UPS) and Raman spectroscopy performed ex-situ allow the analysis of valence bands and structural defects. The high presence of defects and general disorder structure are accompanied with a remarkable increase in catalytic activity. Moreover, the annealing process leads to the sintering of the nanoparticles and the formation of an interface between the carbon fibre and the nanoparticles, as demonstrated by the increased thermal stability tested by. Both phenomena improve the adhesion between nanoparticles and with the surface, making the electrode suitable to be adopted in fluxed systems.The TCNO deposited on a carbon paper was tested as electrode in a Vanadium RFB. The kinetic activity and electrochemical properties were tested via in-situ Raman and in a three-electrode cell set-up. The results reveal an increased kinetic activity with respect to the untreated paper. Using in situ Raman we were able to show differences in redox mechanism between TCNO and bare carbon paper. A chronoamperometry test was used to obtain the transfer coefficient from a Tafel plot. These studies allow the correlation of the catalytic activity with the defectiveness of the TCNO nanoparticle. Vanadium RFB full cell measurements of the TCNO electrode show a drastic increase in performance, reaching an energy efficiency of 70.8% and 86.2% at current densities of 600 mA cm-2 and 200 mA cm-2, respectively. The electrolyte utilisation for these current densities is 59% for the former and 80% for the latter. To investigate the chemical and mechanical stability a stability test was performed. Results showed a low degradation rate of 0.004% EE per cycle. Moreover, TCNO can be used for other electrochemical applications only by adjusting the deposition and annealing parameters.

Thin, Conformal Carbon-Coating of Silicon-Phosphorus Nanoparticle Agglomerates for Lithium-Ion Battery Anodes

Efforts to further enhance the capabilities of silicon as a lithium-ion battery anode are continuing into the realm of chemical composition. Adding varying amounts of other elements can significantly alter the material properties or side reactions, which influence electrochemical performance. Additionally, tuning the chemical composition combined with surface modifications can better enable application of silicon anodes in other devices such as hybrid supercapacitors.Prior work, among others, has shown different performance enhancement regimes depending on how much phosphorus is added to silicon-containing anodes [1, 2]. In particular, the amount of phosphorus from ppm levels to majority atomic fraction can result in enhancement in the conductivity, diffusivity, or forming altogether a wholly new protective matrix [3]. However, while the rate capability has been enhanced only primarily for delithiation, silicon-phosphorus (SiPx) anodes still suffer from similar capacity degradation issues as pure silicon anodes.In the present work, we attempt to address the capacity degradation issue by using a thin, conformal carbon coating to modify the solid-electrolyte interface (SEI) reaction. Firstly, amorphous nanoparticles of SiPx with a few atomic percent of phosphorus are prepared using silane and phosphine co-pyrolysis. Using an oscillating furnace at 800 degrees Celsius under a low flow of acetylene in Ar carrier gas, we are able to produce consistent, uniform carbon films on nanoparticle agglomerates with select thicknesses between 2 and 10 nm, validated using low voltage scanning transmission electron microscopy (LV-STEM), as shown in Figure 1. By comparing Si- and SiPx-containing anodes in electrochemical half cells, we can reproduce the rate capability results while demonstrating the effect of carbon coating on cycle life and capacity retention. Furthermore, the carbon coating’s effect on volume expansion for Si- and SiPx-containing anodes is studied in situ using an electrochemical dilatometer in half cell configuration.[1] Y. Domi, H. Usui, M. Shimizu, Y. Kakimoto, H. Sakaguchi, ACS Applied Materials & Interfaces 2016, 8, 7125-7132.[2] S. Huang, L.-Z. Cheong, D. Wang, C. Shen, ACS Applied Materials & Interfaces 2017, 9, 23672-23678.[3] F. T. Huld, S. Y. Lai, W. M. Tucho, R. Batmaz, I. T. Jensen, S. Lu, O. E. Eleri, A. Y. Koposov, Z. Yu, F. Lou, ChemistrySelect 2022, 7, e202202857. Figure 1

Nitrogen-doped carbon nanotubes for self-powered memristive systems

Memristive devices are one of the promising candidates for creating neuromorphic systems due to the possibility of multilevel switching, low operating voltages and high scalability. However, as with any passive element, the memristor requires an external bias voltage to operate, which requires the inclusion of a power source in the circuit. In this regard, of great interest are works on the creation of self-powered memristive systems consisting of connecting in series a memristor and a nanogenerator that converts the energy of the external environment into electrical energy [1, 2]. Such a memristive system has a high potential for applications in aerospace and implantable electronics. At the moment, the first self-powered memristive and sensor systems based on metal oxides and piezoelectric nanogenerators (PENG) have already been developed [2]. The main problems in this area are to reduce the size of the nanogenerator and to match the output parameters of the nanogenerator and the input parameters of the memristor. In the framework of this work, these problems are being resolved by creating a self-powered memristive system based on nitrogen-doped carbon nanotubes (N-CNTs). Previously, we studied the memristive properties of N-CNTs and showed that nanotubes demonstrate reproducible multilevel switching with a resistance ratio in the high- and low-resistance states (HRS/LRS) of about 4⋅105 [3, 4]. It was found that the memristive effect in N-CNTs is due to the incorporation of nitrogen atoms into the nanotube structure and the formation of an internal piezoelectric field [4]. As part of further studies, it was found that an array of vertically aligned N-CNTs is a promising material for creating PENG: the generated output voltage is hundreds of mV and the current generated by single nanotube reaches hundreds of nA [5]. The results obtained allow us to speak about the possibility of developing a self-powered memristive system by connecting in series a memristor and PENG based on N-CNTs. To optimize the output characteristics of the PENG, in particular, the amplitude of the generated voltage, and the input switching voltage of the N-CNT-based memristor, studies were carried out to increase the piezoelectric response and reduce the switching voltage of the N-CNT resistance by changing the concentration of the dopant nitrogen in the nanotube growth process. It was found that it is necessary to grow N-CNTs with a doping nitrogen concentration of up to 12% and a high aspect ratio of length to diameter (more than 60) to create PENG with an output voltage of up to 2 V. These N-CNT parameters are provided at a low growth temperature (500–550 C°) and high ratio of acetylene and ammonia flows (1:5 - 1:6). On the contrary, the N-CNTs with a small aspect ratio (less than 30) and doping nitrogen concentrations of 4–6% are required for the manufacture of memristors with a minimum switching voltage (about 2 V), These N-CNT parameters are provided by increasing the growth temperature to 615 C° and reduction in growth time. The obtained results can be used in the development of self-powered memristive and sensor systems based on nitrogen-doped carbon nanotubes.

The effect of C2H2 addition to (cyclopentadienyl) molybdenum (dicarbonyl) (nitrosyl) complex gas system for the tribological property of MoCx/a-C:H films on bearing materials

The (cyclopentadienyl)molybdenum(dicarbonyl)(nitrosyl) complex as a metal-organic precursor and acetylene gas were used to produce the MoCx/a-C:H film by the PECVD. When the acetylene gas is mixed with a vaporized metal-organic precursor, the friction coefficient and hardness would be superior for the MoCx/a-C:H film, whereas the specific resistivity slightly high. The friction coefficient measurements by the ball-on-disk wear tester dramatically reduced from 0.25 to 0.06 as the acetylene flow rate increased. The electrical specific resistivity slightly high from 5.74 mΩ-cm to 203.32 mΩ-cm following the increasing acetylene partial pressure. XPS analysis indicated that the Mo-C bond in the Mo3d peaks diminished, and the sp3/sp2 ratio in the C1s peaks reached 0.37 in the condition of acetylene gas addition.

Electron cyclotron resonance chemical vapor deposited diamond-like carbon thin films with various acetylene flow rates for heterojunction solar cells with anti-reflective coating

Electron cyclotron resonance chemical vapor deposited diamond-like carbon thin films with various acetylene flow rates for heterojunction solar cells with anti-reflective coating

The Effect of Bias Voltage and Acetylene Gas Flow Rate on the Wear Behavior of Diamond-like Carbon Coatings on M2 High-Speed Steel

This paper investigates the impact of bias voltage and acetylene flow rate on the mechanical, structural, and scratch performance of diamond-like carbon (DLC) coated high-speed steel (HSS) M2 commonly used in hydraulic vane pumps. The DLC coatings were produced through plasma-enhanced chemical vapour deposition, with micro-Raman spectroscopy used to analyze their structure via G-peak and D-peak measurements. Results showed that DLC deposited at 350 V and 100 sccm demonstrated high hardness (28.99 GPa) and modulus of elasticity (308.1 GPa), with the highest critical load of 167.246 mN indicating superior adhesion to the HSS M2 substrate at a higher bias voltage and lower flow rate. The minimum wear rate of 3.02 × 10−3 mm3/Nm was achieved with a thinner DLC coating deposited at 350V bias voltage and 100 sccm acetylene flow rate.

Dielectric response and current-voltage characteristic of Mo-doped diamond-like carbon thin films at room temperature

Herein we have reported the effect of molybdenum (Mo) doping and acetylene (C2H2) gas flow rate, during deposition, on the electrical properties of diamond like carbon (DLC) films. The frequency dependent dielectric response of the undoped and doped DLC films has been discussed in details. Mo doping also increases the dielectric constant value owing to interfacial polarization and the corresponding change with C2H2 gas flow rate has been attributed to the formation of sp2 bonding over sp3 bonding, favoring the emergence of a graphite-like phase. The ac conductivity of DLC films has been observed to increase with frequency following a power law behavior. However, with 29 % Mo doping we have noticed two plateau regions having different slopes which has been explained on the basis of the jump relaxation model (JRM). The theoretical fitting of the experimental data indicates occurrence of ionic conduction along with polaron hoping. The dc contribution part (σdc) of the measured ac conductivity is found to vary with the acetylene (C2H2) gas flow dependent sp2 bonding formation. The σdc is extracted to be 2351 S/m for the 29 % Mo doped DLC films. From the Nyquist plot in impedance spectroscopy single relaxation phenomena have been observed for the no or low Mo doping but with 29 % Mo doping both the grain and grain boundary effect are prominent. This also suggests the presence of sp2 hybridization and formation of dangling bonds between the metal carbide and DLC film. From the current voltage characteristics, the development of high sp2 bonding and high electron injection into the DLC matrix with subsequent change in nature of the DLC from semiconducting to metallic with high Mo doping has been reported. From the capacitance voltage characteristics study it has been found that either increase in acetylene gas flow during deposition or Mo doping increases the space charge and trap carrier densities.

Hierarchical clinoptilolite zeolite-template carbon for highly selective separation of CO2 and CH4

BackgroundSeparating CO2 from natural gas before it is released into the atmosphere is a significant challenge in the present times due to its greenhouse effect. MethodsIn this study, a series of zeolite-template carbons (ZTCs) had been synthesized from acetylene as a carbon source using clinoptilolite as a template, through hydrofluoric acid etching and potassium hydroxide (KOH) activation processes. Significant findingsThe deposition of carbon on the zeolite-template was confirmed with different characterization techniques and their CO2 adsorption capacity and selectively toward methane (CH4) was evaluated at 25 °C, over a 1‒10 bar pressure range. The CO2/CH4 selectivity of the adsorbents was optimized with various synthesis parameters including chemical vapor deposition (CVD) reaction time, acetylene flow rate as well as activation temperature and KOH to carbon (KOH:C) mixing ratio. According to the findings, medium SBET (334.06 m2 g‒1), high Vtot (0.71 cm3 g‒1), high Vmeso (0.68 cm3 g‒1) and a large Dave (8.55 nm) of the ZTC-120–12.5–800–3 adsorbent (CVD reaction time of 120 min and acetylene flow rate of 12.5 cc min−1 as well as activation temperature of 800 °C and KOH:C ratio of 3:1) results in the highest CO2 capacity of 4.81 mmol g‒1 at 25 °C and 10 bar. Moreover, regarding the optimization goal of this study, the highest CO2/CH4 separation at 25 °C and 10 bar is the result of a long CVD reaction time (180 min), a high KOH:C ratio (4:1), a low acetylene flow rate (50 cc min‒1), and a low activation temperature (700 °C). In this regard, ZTC-180–50–700–4 showed the highest CO2/CH4 (15:85) selectivity of 13.35 with a high SBET (549.31 m2 g‒1), Vtot (0.718 cm3 g‒1), Vmicro/meso (15.6014), Vmeso (0.6211 cm3 g‒1) and a medium Dave (5.22 nm). The amine-functionalization of this sample increases the quadrupole moment between CO2 and nitrogen groups, and not only was the F-ZTC-180–50–700–4 sample's CO2 adsorption capacity increased by nearly 41% (4.11 mmol g‒1) compared to the ZTC-180–50–700–4 (2.91 mmol g‒1), but it also showed 58% higher CO2/CH4 selectivity (21.12). Based on the selectivity results of the functionalized ZTCs, their potential use in the separation of CO2 over CH4 at high pressures is demonstrated.

Influence of a self-formed three-stage dual-wing-shaped carbon on reduction of soot emission from acetylene diffusion flame

This paper reports the formation of a self-formed three-stage dual-wing-shaped carbon (TSDWSC) from acetylene diffusion flame for the first time. The TSDWSC grows naturally from the protrusion at the outlet of the nozzle, while the emission of soot can be greatly reduced. The evolution of the TSDWSC involves three stages: the first unclosed dual-wing, the second unclosed dual-wing and the unmatured third dual-wing. The effects of protrusion, the flow rate of acetylene and various burner nozzle diameters on the formation of the TSDWSC are investigated. The experimental results show that with the increase of the protrusion height, the time when the first stage begins to appear decreases. With the increase of the acetylene flow rate, the stage number of the final dual-wing-shaped carbon increases. The TSDWSC can only be generated when the nozzle inner diameter is 2 or 3 mm. Using a two-color thermometer, the flame temperature distribution along the flame centerline is measured after the complete growth of the TSDWSC. The results show that the temperature of the TSDWSC area in the lower part is remarkably lower than that of the flame area in the upper part. The efficiency of reducing soot emission increases gradually with the evolution of the TSDWSC and reaches 100%, while the temperature of the flame area in the upper also rises gradually. X-ray diffraction (XRD) result indicates the formation of carbon crystals.