Papers by Keyword: Acetylene

Abstract: This work aims to develop a low pressure DC plasma deposition system to coat carbon thin film on silicon substrate. The system use a parallel of grounding iron electrode and cathode copper electrode to ignite the plasma. The vacuum pressure was achieved by two stage rotary vane vacuum pump which is capable to reach ultimate pressure at 2×10^-1 Pa under a glass chamber. The carbon thin films was deposited on silicon substrate by pure acetylene plasma with gas flow rate at 30 ml/min at total operating pressure of approximately at -70 cmHg reading by analog dial vacuum gauge. Energy Dispersive X-Ray spectroscopy was used to indicate the elements contained in the film. The morphology and the thickness of the film was investigated by scanning electron microscope. Raman analysis showed peak at around 1345 cm^-1 (D-peak) and 1579 cm^-1 (G-peak), by utilizing I_D and I_G can be evaluated that there are 46.45% of sp³ contained in deposited film.

Abstract: This work aims to develop a low pressure microwave plasma deposition system to coat carbon thin film on silicon substrate. The system use a commercial microwave oven as a microwave source to get plasma discharge. The vacuum pressure was achieved by two stage rotary vane vacuum pump which is capable to reach ultimate pressure at 2×10^-1 Pa under borosilicate chamber glass. The carbon thin films was successfully deposited on silicon substrate by pure acetylene plasma with gas flow rate 30 ml/min at total operating pressure of -70 cmHg reading by analog dial vacuum gauge, using microwave power at 1,200 Watts and deposit time at 150 seconds. Raman analysis showed peak at around 1336.20 cm^-1 (D-peak) and 1611.87 cm^-1 (G-peak), by utilizing I_D and I_G can be determined that there are 43.22% of sp³ contained in deposited film. Energy Dispersive X-Ray analysis indicated that the deposited thin film compose of carbon atoms 82.00 at% and silicon atoms 18.00 at%. The morphology and the thickness of the film was investigated by scanning electron microscope and atomic force microscope, respectively.

Abstract: Taking acetylene as the carbon source gas diluted with nitrogen gas in this paper, carbon felt was heated under the nitrogen atmosphere, the temperature of carbon felt increased using heat generated by itself, which so as to cleave the carbon source gas and densify carbon felt by pyrolytic carbon deposition. The electrothermal property of carbon felt at elevated temperature and pyrolytic carbon was fabricated by direct thermal chemical vapor deposition (CVD) were investigated. Deposition rate and microstructure morphology of pyrolytic carbon in the carbon felt under different processes were also researched by scanning electron microscopy (SEM). The results show that: the resistivity of carbon felt decreases with increasing temperature at 100°C~1000°C, temperature coefficient of resistance is-4.067×10^-4. Deposition and Growth of Pyrolytic carbon are by small microcrystalline and layer mode, respectively, with the extension of the deposition time, tree-ring shape is formed. When other conditions are the same, the higher of gas carbon concentration, the faster of pyrolytic carbon deposition rate.

Abstract: Detection of C₂H₂ gas in transformer oil is significant for diagnosing the operating state assessment of power equipment. The paper develops an infrared laser gas sensor to detect the C₂H₂ gas in transformer oil, and also introduces the system structure in detail. A gas-absorbed laser cell that contains a series of laser reflectors is designed and used in our detection system, which adds the optical path without changing the volume of the cell. 1529.16nm is chosen as the characteristic spectrum line of C₂H₂ gas, and concentration of C₂H₂ gas is quantitatively analyzed based on least square method. The experiment result shows that in certain volume fraction range of acetylene, the absorbance has a good linear relationship with the acetylene concentration, and the minimum detection limit for acetylene is 10μL/L. In general, the developed infrared laser gas sensor can detect C₂H₂ gas in transformer oil effectively.

Abstract: Multi-wall carbon nanotube (MWCNT) structures were grown on cobalt catalyst layer through Plasma Enhanced Chemical Vapor Deposition (PECVD) process. Acetylene (C2H2) and hydrogen (H2) are used as precursors during the PECVD process. The morphology structures of the MWCNTs grown under different PECVD time were investigated and characterized using Scanning Electron Microscope (SEM). The effect of the PECVD time on the MWCNT growth is studied by varying the PECVD time at 45 sec and 600 sec. The morphology structures suggest that the growth rate is proportional to the PECVD time under the similar setting condition of pressure, acetylene flow-rate and temperature.

Abstract: The reactions were carried out by decomposing acetylene at 700 °C in a two-stage furnace system under different conditions. In the two furnaces, an AAO template with the average diameter about 50 nm was placed respectivly, whose temperature was designed to be 700 °C. The samples were characterized by scanning electron microscopy and high resolution transmission electron microscopy. The results show that when the reaction was carried out in C2H2-Ar atmosphere, dense and entangled CNTs with diameter, ca. 50 nm were obtained on the top surface of the AAO template in the first furnace and dense and entangled CNTs with morphology of rope were obtained on the top surface of the AAO template in the second furnace. When the reaction was carried out in C2H2- H2-Ar atmosphere, dense and entangled CNTs with diameter, ca. 50 nm were obtained on the top surface of the AAO template in the first furnace, however only a few CNTs were obtained in the second furnace. When the reaction was carried out in C2H2- H2 atmosphere, CNTs were both observed stood on the top of AAO template in the two furnaces

Abstract: Based on characterization of various properties of coking formation during the processing of pyrolysis of coal to acetylene in the plasma, and the chemical group composition of the coal, the reaction central - border zone characteristics of plasma and the specific circumstances of the reactor, the mechanism of coking on reactor wall is put forword during pyrolysis of the coal to acetylene in the plasma, which aromatics, colloids, asphaltenes and carbenes happen condensation reaction by dehydrogenation in plasma border reaction zone. Besides, a method is proposed that double peak particle size distribution of coal particle can eliminate coking continuously, and it get experimental validation.

Abstract: The pyrolysis of coal to acetylene is studied with Pingshuo coal, Zichang coal and Dongshan coal in the plasma, and its course is analysised by coal chemical groups. The reaction mechanism of imitate free radicals is proposed in the pyrolysis of coal to acetylene in the plasma, the free radicals formation of high-temperature plasma and the composite dynamics are discussed. The results can educe that the acetylene content is higher of the organic product in the high temperature center zone of the pyrolysis of coal to acetylene in the plasma which base on the discussion of the saturates free radicals generating and compounding, combine with the reaction of aromatics, colloids and asphaltene and carbenes. It also can indicate that free radical reaction mechanism is applicable and feasible to explain coal of high-temperature centre zone in the plasma reaction.

Abstract: The research of all kinds of factors is put up on the inner coking of coal in the plasma reactor during the processing of pyrolysis of coal to acetylene, includ cooking phenomenon, coal of property, coal of grain degree, enter anticipate a speed , power and equip structure. In the arc plasma jet, different kind of coal has different coking character. The aromatics, colloids, asphaltene and carbenes are the precursors of the cokes.The mostly reasons of coking in the plasma reaction equipment are the particle size, the feeding velocity, the power of plasma and the structure of equipment. With the increasing of feeding velocity, the coking of system becomes worse. When the particle size is less than 80~100 mesh, the system will not produce cokes. When the particle size is about 100~120 mesh, the system will begin to produce cokes. When the particle size is larger than 140 mesh, the system will produce a lot of cokes.With the increasing of plasma power, the speed of coking will become smaller.

Abstract: The present work aimed to find reasons for different catalytic ability of the Nieuwland catalyst and anhydrous catalyst in dimerization of acetylene to produce Monovinylacetylene (MVA). The results showed the catalytic ions in the Nieuwland catalyst and the anhydrous catalyst were CuCl^-₂ and Cu₂Cl^-₃ respectively by studies on the Cu-containing crystals recovered from corresponding catalyst. CuCl^-₂ in crystal A and Cu₂Cl^-₃ in crystal B has similar crystal structure, however, Cu(Ι) in Cu₂Cl^-₃ has higher electron density due to stronger bond energy of Cu(Ι)-Cl, which may contribute to the higher activity of the anhydrous catalyst than that of Nieuwland catalyst.