Acetylene Flow Research Articles

Structure of graphene nanotube hybrid materials produced via single-stage CVD

The structures of graphene layer-carbon nanotube hybrid films produced via CVD with a single-stage flow of acetylene into a chamber containing a prepared substrate are studied. It is shown that such films have a hybrid double-layer structure consisting of a graphene layer and a dense continuous network of nanotubes. The graphene layer contains continuous extended areas 10–50 μm in size and island areas ∼0.1 μm in size. TEM images lead to the conclusion that the graphene layer and carbon nanotubes are bound by covalent bonds.

Antimicrobial copper-containing titanium nitride coatings Co-deposited by arc ion plating/magnetron sputtering for protective and decorative purposes

Decorative ceramic coatings are widely utilized in sanitary ware, jewelry and mobile devices. Decorative ceramic coatings have been extensively studied in recent years, and they have evolved with the development of the aforementioned products. In this work, an arc ion plating (AIP) method (for titanium emission) was combined with magnetron sputtering (for copper emission) in a single chamber to synthesize Cu-TiN coatings in the fixed nitrogen flow. In contrast, two additional reactive atmospheres, a constant flow of oxygen and a constant mixed oxygen and acetylene flow, were applied respectively to deposit a thin amorphous TiNxOy layer and TiCxNyOz layer on the Cu-TiN coating at the final minute during deposition period and to validate decorative and protective performance on these coatings.The experimental results obtained herein reveal that Cu-TiN coatings with a thin amorphous TiNxOy layer and TiCxNyOz layer promoted the apparent hardness, wear resistance and corrosion resistance over those of pre-electroplated Cu-35Zn material. First, the appearance of Cu-TiN coatings with a thin TiNxOy layer varied noticeably from golden yellow through red and blue eventually to purple, as the purging time increased (10–60s) in a constant oxygen flow. Then the Cu-TiN coating with a thin TiCxNyOz layer, formed in a constant mixed flow of oxygen and acetylene, also exhibited a series of graded colors. With respect to protective performance, the enhancement of the Cu-TiN, Cu-TiNO60 and Cu-TiNOC60 coatings improved their apparent hardness at least 62.0% higher than that of pre-electroplated Cu-35Zn substrate. Notably, the apparent hardness is correlated with the wear resistance due to the existence of outermost TiNxOy and TiCxNyOz layers, in which flowing O2+C2H2 generates TiCxNyOz on top of the Cu-TiN layer, providing a higher wear resistance than those of TiNxOy synthesized in flowing O2. Cu-TiN, Cu-TiNO60 and Cu-TiNOC60 ceramic coatings provide greater corrosion resistance than that of a pre-electroplated Cu-35Zn substrate and finally reach a stable current density in the passive region to 3.5wt.% NaCl solution. In summary, a Cu-TiN coating can be both modestly protective and have tunable colors because of the nature of golden yellow and hard coating for TiN ceramic and the existence of the outermost TiNxOy and TiCxNyOz layers.

Deposition mechanism of convex YSZ particles and effect of electrolyte/cathode interface structure on cathode performance of solid oxide fuel cell

A convex-structured electrolyte surface will lead to the formation of a high specific surface area which could be applied in many fields. Thermal spraying process is promising to fabricate such surface through particle deposition. However, the locally flat surfaces will be formed by using completely molten particles due to well spreading of liquid droplets on impact. In this study, a flame spraying method was employed to deposit convex yttria-stabilized zirconia (YSZ) particles on YSZ substrate for solid oxide fuel cell application. The convex structure was formed by the deposition of surface-melted particles, which were created due to the low particle temperature and velocity of the spray process. The effect of acetylene flow rate on the particle deposition behavior was examined. The surface morphology and surface area of YSZ particles were characterized by scanning electron microscope (SEM) and a 3D laser scanning microscope, respectively. The bonding between deposited YSZ particles and YSZ substrate was examined from cross section. The electrochemical behavior of single cell with the structured cathode was characterized by the electrochemical impedance spectroscopy. The results indicate that spray parameters have significant influence on the surface morphology of deposited YSZ particles and the surface area is increased up to a factor of 3.45. The cathode polarization with a structured cathode is approximately one-third of that with a flat cathode.

Application of Mixed-Level Orthogonal Design in Determination of Heavy Metals in Soil, for Example Pb

In order to precisely determinate absorbance of all kinds of heavy metals in soil,7- important factors were optimized by mixed-level orthogonal design.For example Pb,discuss the factors influence degree on digestion and determination of Pb.Pb-absorbance trends within the area is expressed by the change of two-dimensional planar contour.Pb-absorbance distribution was drawn by 3D visualization technology.In order to optimize the orthogonal design,taking the optimal value of decentralized points in orthogonal test convert into taking the optimal value on a continuous plane. Using Minitab16 software analyzed the experimental results.The results showed that affecting Pb digestion Primary and secondary order is B(HF)> C(HNO3)> A(HClO4)> I(Acetylene flow rate)>D(HCL)>G (Assistant combustion gas)>H(Lamp current)>F(Burner height),that was adding 9 mlHNO3, 3mLHF, 3 mlHClO4 in soil samples, after microwave digestion, got the optimal Pb-absorbance value 0.304 under the the working conditions of atomic absorption spectrophotometer for Pb 217.0nm, slit width 1.3nm, burner height 4nm, assistant combustion gas 2.4 L/min, the lamp current 4.0mA, propane flow rate 4.0 L/min.

Carbon Nanotubes as Nanosensor for Differential Electrolytic Micropotentiometry

Carbon nanotubes as nanosensor were synthesized on the surface of the silver electrode using floating catalyst chemical vapor deposition reactor. Acetylene gas was used as a carbon source, ferrocene as a source of the iron nanocatalyst and hydrogen as a carrier and an activate agent. Several runs were performed to find the optimum conditions that produce sensitive Ag-CNTs electrodes. The electrodes obtained at each run were characterized by SEM. The optimum conditions that produce sensitive Ag-CNTs were found to be at a reaction time of 15 minutes, reaction temperature of 700°C, hydrogen flow rate of 25 ml/min and an acetylene flow rate of 75 ml/min. These optimum conditions were confirmed from the normal behavior of the resulting Ag-CNTs electrodes in the titration of 10 μL of chloride using dc differential electrolytic potentiometry. When conditions that differ from the optimum ones were applied in the preparation of the Ag-CNTs electrodes, abnormal titration curves were obtained. The superiority of the Ag-CNTs electrodes was demonstrated by the successful applications of these electrodes as an indicating system in the micro titrations of different volumes of cyanide solution with silver nitrate reach. By applying this technique a volume of 1.2 μL sample of cyanide was successfully titrated. The normal behavior of the Ag-CNts electrodes was compared to that of the normal silver electrodes which exhibit an abnormal behavior.

Observation of plasma instabilities related to dust particle growth mechanisms in electron cyclotron resonance plasmas

Instabilities are observed in the self-bias voltage measured on a probe immersed in microwave plasma excited at Electron Cyclotron Resonance (ECR). Observed in the MHz range, they were systematically measured in dust-free or dusty plasmas (obtained for different conditions of applied microwave powers and acetylene flow rates). Two characteristic frequencies, well described as lower hybrid oscillations, can be defined. The first one, in the 60–70 MHz range, appears as a sharp peak in the frequency spectra and is observed in every case. Attributed to ions, its position shift observed with the output power highlights that nucleation process takes place in the dusty plasma. Attributed to lower hybrid oscillation of powders, the second broad peak in the 10–20 MHz range leads to the characterization of dust particles growth mechanisms: in the same way as in capacitively coupled plasmas, accumulation of nucleus confined near the probe in the magnetic field followed by aggregation takes place. Then, the measure of electrical instabilities on the self-bias voltage allows characterizing the discharge as well as the chemical processes that take place in the magnetic field region and their kinetics.

Nanotribology of pulsed direct current magnetron sputtered diamond like carbon films

The presented research for the first time establishes the relations among nanotribological features, structural properties and deposition parameters (acetylene flow and bias voltage) of diamond like carbon films deposited by pulsed direct current magnetron sputtering. The nanotribological behaviour of hydrogen free and hydrogenated diamond-like carbon films (a-C:H) deposited by pulsed direct current magnetron sputtering was investigated using atomic force microscopy (AFM). A structural analysis with Raman spectroscopy showed that elevated acetylene concentrations in the process gas atmosphere favoured a decreased structural disorder in the a-C:H matrix, which was derived from the decreasing full with at half maximum of the G-band in the spectrum from 191±3cm−1 to 173±1cm−1. More ordered films showed friction coefficients of ~0.001, while having still relatively high hardness. Spectroscopic data could be associated with mechanical properties: higher structural disordering of the films showed highest hardness (23.3±0.3GPa). Coatings deposited only with argon as sputtering gas have low friction coefficients ~0.002 and low wear rates ~1.2nm. In general, the deposited films were found to be relatively free of defects and smooth, which was derived of an averaged roughness of the film surfaces of less than 1nm.

Synthesis of carbon nanocoil forests on BaSrTiO3 substrates with the aid of a Sn catalyst

A simple route for the Sn-assisted synthesis of carbon nanocoils (CNCs) by chemical vapor deposition of acetylene on polycrystalline BaSrTiO3 (BST) substrates is reported. In this study, high-quality CNC forests have been synthesized on BST substrates with the presence of Sn. The morphologies and qualities of the CNCs were characterized by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy, while the structures and compositions of catalysts were investigated by transmission electron microscopy and energy-dispersive X-ray spectroscopy. Structural control over the CNCs was achieved by simply altering the Sn concentration or acetylene flow rates. This study demonstrates that Sn can act as an efficient catalyst for CNC synthesis in conjunction with either perovskite oxides (BST) or transition metals (Fe).

Synthesis and Characterization of Exotic Carbon Fibers with Branched Spurs Using Nickel Catalyst Precursor

In this paper, we have synt hesized exotic carbon fibers with branched spurs by a chemical vapor deposition method using nickel catalyst precursor at 600 °C. No catalyst particles were found at the base of the carbon spurs, suggesting that the ni ckel catalyst particles, which were decomposed from the nickel catalyst precursor, facilitated the growth of the carbon fibers but not the spurs. The formation of the spurs resulted from the fluctuation of the carbon source gas acetylene flow. The samples were characterized by field emission sc anning electron microscopy, transmission electron microscopy, and X-ray powder diffraction.

Production of Carbon Nanotubes over Fe-FSM-16 Catalytic Material: Effect of Acetylene Flow Rate and CVD Temperature

In this article, a high-yield synthesis of high-quality carbon nanotubes (CNTs) using Fe catalysts trapped within channels of Folded Sheet Mesoporous Materials, FSM-16, by chemical vapor deposition (CVD), using acetylene as a hydrocarbon source, is reported. The effect of reaction temperature and acetylene flow rate on the formation of CNTs was investigated. It was found that the yield, diameter and quality of CNTs synthesized strongly depend on reaction temperature during CVD. The resulting materials were characterized by scanning electron microscopy, Raman spectroscopy and thermogravimetric analysis. Our research found that carbon deposition, diameter and quality of the CNTs strongly depend on CVD temperature. However, the acetylene flow rate did not have any significant effect on diameter distribution. Raman measurement indicated that the synthesized products were multi-walled carbon nanotubes (MWCNTs). High-resolution transmission electron micrographs of samples reveal the multi-layer sidewalls of individual MWCNTs with a diameter of 40 nm, in which hollow and tubal structures were observed.

Enhanced optical and electrical stability of thermally carbonized porous silicon

In the current paper, the intrinsic instability of physical properties of porous silicon (PS) was minimized using a thermal carbonization (TC) method. A typical PS showed an obvious quenching of its photoluminescence (PL) properties under long-term laser radiation. To resolve this problem, an ultra-thin stabilizing layer was grown on the porous structure under an acetylene gas flow. During the TC process at high temperatures, carbon atoms were detached from the acetylene molecules and dissolved in the porous structure. Thermally carbonized PS (TC-PS) layer changed the PL peak position of PS slightly due to the formation of Si–C species on porous surface after acetylene exposure. The effects of TC-PS layer in electrical properties of fabricated photodetectors were studied. The photocurrent of freshly prepared PS decreased under prolonged green laser radiation (532nm, 5mW), but the TC-PS sample showed more stable electrical characteristics under the same conditions.

Research on Cutter of Field Straw Chopper Strengthened with Flame Spray Welding

In order to solve the high-price and short- lifetime problem of the cutter of field straw chopper, wear-resistance coating was prepared on the substrate of 45# steel by flame spray-welding NiWC alloy. By means of orthogonal test and multiple factors variance analysis, The process that the test factors influence the wear-resistance was studied. The technology parameters of flame spray-welding NiWC alloy were optimized as follows: coating matching, 65%Ni60+35%WC; preheat temperature, 450 °C; acetylene flow, 1000 L/h; spraying distance,40 mm.

Effect of acetylene concentration and thermal ramping rate on the growth of spin-capable carbon nanotube forests

Spin-capable multiwalled carbon nanotube (MWCNT) forests that can form webs, sheets, and yarns provide a promising means for advancing various technologies. It is necessary to understand the critical factors to grow spin-capable carbon nanotubes (CNTs) in a repeatable fashion. Here we show how both the spinning capability and morphology of MWCNT forests are significantly changed by controlling the C2H2 concentration and ramp rate of temperature. The acetylene gas flow was varied in the range of 0.25–6.94% by volume. The MWCNTs grown at C2H2 concentrations between 1.47–3.37% are well-aligned and become spin-capable. The well-aligned forests have higher areal density and shorter distance between CNTs. The thermal ramp rate was also changed from 30 °C/min to 70 °C/min. A specific range of thermal ramp rate is also required to have the suitably sized nanoparticles with sufficient density resulting in higher CNT areal density for spinnable MWCNTs. A ramp rate of 50 °C/min forms suitable sized nanoparticles with sufficient density to produce CNT forests with a higher areal density and a shorter tube spacing.

Optimising deposition parameters of W-DLC coatings for tool materials of high speed steel and cemented carbide

The paper presents the results of investigations on the selection of optimal deposition parameters for W-DLC coatings produced by pulsed reactive magnetron sputtering in order to obtain the coatings with high adhesion to the high speed steel (HSS) and cemented carbide (HM) substrates. To optimise the deposition parameters for W-DLC coatings Taguchi's method was used. An acetylene flow rate, the substrate bias voltage, the thickness of W-DLC coatings and the thickness of chromium sublayer were selected as deposition parameters and for each of them three levels of values were determined. Adhesion, wear resistance and hardness of coatings were chosen as the criteria for selecting the optimum deposition parameters. The test results showed that all the selected parameters have a significant effect on the adhesion of coatings. The thickness of W-DLC coatings has a very significant effect on the adhesion to HSS substrates and in a case of HM substrates the same effect has the thickness of a chromium sublayer. The wear resistance of coatings increases with an increasing acetylene flow rate and decreases with the increasing substrate bias voltage. High correlation was found between the H/E ratio of coatings and their wear resistance as well as toughness. The W-DLC coating showing the best properties (LC3 ≈ 90 N, kV = 3.8 × 10−7 mm3/Nm) was marked by the nanocomposite structure containing about 40% of nanocrystalline tungsten carbide phase and 60% of amorphous carbon matrix.

Development of hydrogenated amorphous carbon thin film with high electrical resistance for use in embedded sensors in abrasive environment

In this study, a hydrogenated amorphous carbon (a-C:H) film with a high electrical resistance is developed for use in embedded sensors in an abrasive environment. The a-C:H and a-C:H:Si films were deposited by magnetron sputtering. Graphite targets were sputtered by means of bipolar pulsed-direct current power supply and addition of acetylene, argon, and krypton. The a-C:H:Si films were deposited using graphite targets with small silicon inserts. To optimize the adhesion, a chromium nitride interlayer was deposited prior to the carbon layer. The influence of bias voltage, acetylene flow, deposition pressure, and silicon doping on the electric resistance was investigated. Hardness, hydrogen content, and bonding status of the coating were also determined. It was found that the resistance of the film increases with decreasing negative bias voltage and increasing acetylene flow and deposition pressure. With increasing resistivity of the film, the hardness decreases. This was attributed to higher hydrogen contents in these films. The silicon doping of the films has no significant effect on the electrical resistance.

Thermospray flame furnace atomic absorption spectrometry for determination of silver in biological materials

A method for silver determination without concentration steps is described using thermospray flame furnace atomic absorption spectrometry. Carrier type and flow rate, sample volume, flame conditions (acetylene and air flow rate), water flow rate in the nebulizer, metallic tube and type and concentration of the acid diluent of the analyte are the parameters evaluated in the optimization of the method. Using the optimized conditions, eleven elements are evaluated as concomitants. The limits of detection and quantification are 0.15μgL−1 and 0.50μgL−1, respectively. The linear range is from 0.50μgL−1 to 40μgL−1 and the accuracy of the method is obtained through two certified reference materials: MA-A-2 (fish flesh homogenate) and SRM 1643e (trace elements in water).

The effect of changes in synthesis temperature and acetylene supply on the morphology of carbon nanocoils

Carbon nanocoils (CNCs) with controlled shape, coil diameter and coil pitch have been synthesized in a chemical vapor deposition (CVD) system by changing the reaction temperature and acetylene flow rate. It is found that three-dimensional CNCs are produced at a lower temperature (700–770°C), while a higher temperature (810°C) leads to the growth of straight carbon nanofibers (CNFs). CNC–CNF hybrid structures are produced by increasing growth temperature from 750 to 810°C during a single synthesis run, while CNF–CNC hybrid structures are produced by decreasing the temperature from 810 to 750°C. Similarly, by changing growth temperature from 750 to 810°C and then back to 750°C during a single run, CNC–CNF–CNC complex hybrid structures can be obtained. During the CVD process, the pulsing of acetylene and the changing of acetylene flow rate are also found to be effective in controlling the structure of CNCs. CNCs with periodic helical structures can be produced by interrupting the acetylene flow or changing its flow rate periodically. It is found that the higher the flow rate of acetylene, the smaller the coil pitch and diameter of the grown CNCs.

Innovative Method to Produce High-Purity Graphitic Carbon Nanospheres

The present paper describes a method for producing graphitic carbon nanospheres (GCNSs) by chemical vapour deposition (CVD), which includes supplying carbon atoms to a catalyser for forming carbon nanoparticles in a controlled manner, in which the amount of carbon supply is controlled in relation to the time and temperature parameters. In this method short carbon fibres are used as supporting substrate for the mass formation of pure graphitic carbon nanoparticles in a fluidized bed reactor chemical vapour deposition (FBCVD). The synthesis of graphitic carbon nanoparticles (GCNPs) is carried out by the catalytic decomposition of a carbon source over a substrate deposited with catalyst in the fixed bed reactor. The chemical composition of nanoparticles was measured by energy dispersive X-ray spectrometry (EDX) in a scanning electron microscope (SEM). SEM, High Resolution Transmission Electron Microscope (HRTEM), thermal gravimetric analyser (TGA), and X-ray diffraction (XRD) were used for characterization of the catalyst and the products. This study indicates that GCNP is successfully grown at 600°C in ambient pressure for 1.8% Fe on carbon fiber, 8 minutes deposition time, and 15L/min acetylene flow rate. Graphitic carbon nanospheres have been produced in large amount of lattice images of various fullerenic carbons and aciniform of nanoparticles, which are seldom reported in the literature.

Enhanced electrochemical activity using vertically aligned carbon nanotube electrodes grown on carbon fiber

Vertically aligned carbon nanotubes were successfully grown on flexible carbon fibers by plasma enhanced chemical vapor deposition. The diameter of the CNT is controllable by adjusting the thickness of the catalyst Ni layer deposited on the fiber. Vertically aligned nanotubes were grown in a Plasma Enhanced Chemical Deposition system (PECVD) at a temperature of 630 oC, d.c. bias of -600 V and 160 and 68 sccm flow of ammonia and acetylene, respectively. Using cyclic voltammetry measurements, an increase of the surface area of our electrodes, up to 50 times higher, was observed in our samples with CNT. The combination of VACNTs with flexible carbon fibers can have a significant impact on applications ranging from sensors to electrodes for fuel cells.

DOE-Based Numerical Investigation on Factors Affecting Temperature Field during Line Heating

Line heating is a complex thermal-mechanical process as many factors affect the final shape of a processed plate. Generally, the temperature field of the processed plate determines the stress field and strain field. To predict the deformation of the processed plate, this paper investigates the effects of different factors on the temperature field during line heating by using design of experiment (DOE). Firstly, a three dimensional thermal elasto-plastic finite element method (FEM) is developed to calculate the temperature field induced by the single-pass oxygen-acetylene line heating. Secondly, the temperature field is analyzed by using fractional factorial design, in which the maximum temperature is selected as the response, and a fishbone diagram is used to overview all influencing factors. After performing a series of numerical experiments selected by using an ortho-gonal array, three main influencing factors are screened out: plate thickness, flow of acetylene and velocity of heat source. Next, the main effects of these factors are discussed. Finally, analytical re-sults indicate that there exist interaction effects among the three main influencing factors. This in-vestigation demonstrates that DOE is an efficient method for study of the temperature field during line heating.