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1.
The yields of SOF 4, SO 2F 2, SOF 2, and SO 2 have been measured as a function of O 2 content in SF 6/O 2 mixtures, following spark discharges. All experiments were made at a spark energy of 8.7 J/spark, a total pressure of 133 kPa, and for O 2 additions of 0, 1, 2, 5, 10, and 20% to SF 6. Even for the case of no added O 2, trace amounts of O 2 and H 2O result in the formation of the above by-products. However, addition of O 2 significantly increases the yields of SOF 4 and SO 2F 2, while SOF 2 is only slightly affected. The net yields for SOF 4 and SO 2F 2 formation range from 0.18×10 –9 and 0.64×10 –10 mol·J –1, respectively, at 1% O 2 content to 10.45×10 –9 and 7.15×10 –10 mol·J –1, respectively, at 20% O 2 content. The mechanism for SOF 4 production appears to involve SF 4, an important initial product of SF 6, as a precursor. Comparison of the SOF 4 and SO 2F 2 yield from spark discharges (arc and corona) shows that the yields from other discharges (arc and corona) shows that the yields can vary by at least three orders of magnitude, depending on the type of discharge and on other discharge parameters. 相似文献
2.
Processes which occur in microwave discharges of dilute mixtures of SF 6 and O 2 in He have been examined using a flow reactor sampled by a mass spectrometer. Two classes of experiments were performed. In the first set of experiments, mixtures containing 6×10 11 cm –3 SF 6, 6×10 16 cm –3 He, and O 2 in the range (0–3.6)×10 13 cm –3 were passed through a 20-W 2450-MHz microwave discharge. The gas mixtures arriving at a sample point downstream from the discharge were examined for SF 6, SF 4, SOF 2, SOF 4, SO 2F 2, SO 2, F, and O. In the second class of experiments, rate coefficients were measured for the reactions of SF 4 with O and O 2 and for the reaction of SF with O. The rate coefficient for the reaction of SF with O was found to be (4.2±1.5)×10 –11 cm –3 s –1. SF 4 was found to react so slowly with both oxygen atoms and oxygen molecules that only upper limits could be placed on the rate coefficients for these reactions. These values were 2×10 –14 cm 3 s –1 and 5×10 –15 cm 3 s –1 for reactions with O and O 2 respectively. The observed distribution of products from the discharged mixtures is discussed in terms of the measured rate coefficients. 相似文献
3.
The plasma chemistry of SF 6/O 2 mixtures is particularly complicated because of the large number of possible reactions. Over a wide range of conditions, products including SF 4, SOF 4, SOF 2, and SO 2F 2 can be formed but thre is considerable uncertainty about the major reactions which contribute to the formation of these species. In this work reactions of oxygen atoms with SOF 2 and fluorine atoms with SOF 2 and SO 2 have been studied in order to determine the principal sources of SO 2F 2 in these plasmas. Reactions were studied at 295 K in a gas flow reactor sampled by a mass spectrometer. No reaction could be detected between oxygen atoms and SOF 2, which for the conditions employed, means that the upper limit for the reaction rate coefficient is 1×10 –14 cm 3 sec –1. The reaction of fluorine atoms with SOF 2 was studied with the helium bath gas number density ranging from 3.1×10 16 to 2.0×10 17 cm –3. Within this range the rate coefficient increased with increasing [He] from (4.1 to 10.8)×10 –14 cm 3 sec –1. SO 2 was found to react with fluorine atoms with a rate coefficient which appeared to be independent of the helium bath gas number density over the range given above. The possibility that this reaction occurred entirely on the walls of the reactor is discussed. 相似文献
4.
The production of SOF
4 initiated by the reaction of F atoms with SOF
2 has been studied in a gas-flow reactor at 295 K for helium bath gas number densities in the range (3.0–27.0)×10 16 cm –3. The effect of O atoms on the formation of SOF
4 has been analyzed in terms of the competing reactions SOF
3+FSOF 4 and SOF
3+ OSO
2
F
2+ F. This analysis leads to the conclusion that the rate coefficients for these two processes are equal within an uncertainty of about 50%. Furthermore, both experiment and calculations indicate that the rate coefficient for reactions between F atoms and SOF
3 is close to its high-pressure limit under the conditions employed. The experiments set a lower limit on this rate coefficient of 5×10 –11 cm 3 s –1, while calculations based on unimolecular rate theory suggest that it may be greater than 1×10 –10 cm 3 s –1. These results make it clear that the two reactions shown above cannot explain the relative abundances of SOF
4 and SO
2
F
2 which are observed in SF
6/ O
2 plasmas. This suggests that SF
2 is a major precursor in the sequence of reactions following the dissociation of SF
6. 相似文献
5.
Dissociative and nondissociative electron attachment in the electron impact energy range 0–14 eV are reported for SOF 2 SOF 4, SO 2F 2, SF 4, SO 2, and SiF 4 compounds which can be formed by electrical discharges in SF 6. The electron energy dependences of the mass-identified negative ions were determined in a time-of-flight mass spectrometer. The ions studied include F – and SOF
2
–*
from SOF 2; SOF
3
–
and F – from SOF 4; SO 2F
2
–*
, SO 2F –, F
2
–
, and F – from SO 2F 2; SF
4
–*
and F – from SF 4; O –, SO –, and S – from SO 2; and SiF
3
–
and F – from SiF 4. Thermochemical data have been determined from the threshold energies of some of the fragment negative ions. Lifetimes of the anions SOF
2
–*
, SO 2F
2
–*
, and SF
4
–*
are also reported. 相似文献
6.
The reaction products in the SF 6-N 2 mixture rf plasma during reactive ion etching of Si and W have been measured by a mass spectrometric method. Two kinds of cathode materials were used in this work; they were stainless steel for the Si etching, and SiO 2 for the W etching. The main products detected in the etching experiments of Si and W included SF 4, SF 2, SO 2, SOF 2, SOF 4, SO 2F 2, NSF, NF 3, N 2F 4, N xS y, NO 2, and SiF 4. In the W etching with the SiO 2 cathode, additional S 2F 2, N 2O, and WF 6 molecules were also obtained. The formation reactions about the novel NSF compound and the sulfur oxyfuorides were discussed. 相似文献
7.
Discrete electron-molecule processes relevant to SF 6 etching plasmas are examined. Absolute, total scattering cross sections for 0.2–12-eV electrons on SF 6, SO 2, SOF 2, SO 2F 2, SOF 4, and SF 4, as well as cross sections for negative-ion formation by attachment of electrons, have been measured. These are used to calculate dissociative-attachment rate coefficients as a function of E/N for SF 6 by-products in SF 6. 相似文献
8.
The behaviour of SF 6 in quartz and alumina tubes of a flow reactor capacitively coupled to a 35 MHz radiofrequency generator has been investigated at pressure of 20 torr, with power levels of 3.5÷5.5 cal cm ?3 sec ?1 and gas flow rates ranging between 0.1 and 2 1(STP) min ?1. A combination of gaschromatographic, mass spectrometric and infrared spectrophotometric techniques has shown the presence of SO 2F 2, SOF 4, SOF 2, SiF 4, F 2, O 2 together with unreacted SF 6 in the discharge products.A detailed quantitative investigation of the effluent products and of their concentration profiles versus space time and power is presented and a general mechanism for the ablation process of the quartz wall is suggested. 相似文献
9.
Reactions of both SF 5 and SF 2 with O( 3
P) and molecular oxygen have been studied at 295 K in a gas flow reactor sampled by a mass spectrometer. For reactions with O( 3
P), rate coefficients of (2.0±0.5)×10 –11 cm 3 s –1 and (10.8±2.0)×10 –11 cm 3 s –1 were obtained for SF 5 and SF 2 respectively. The rate coefficients for reactions with O 2 are orders of magnitude lower, with an estimated upper limit of 5×10 –16 cm 3 s –1 for both SF 5 and SF 2. Reaction of SF 2 with O( 3
P) leads to the production of SOF which then reacts with O( 3
P) with a rate coefficient of (7.9±2.0)×10 –11 cm 3 s –1. Both SO and SO 2 are products in the reaction sequence initiated by reaction between SF 2 and O( 3
P). Although considerable uncertainty exists for the heat of formation of SOF, it appears that SO arises only from reaction between SOF and O atoms which is also the source of SO 2. These results are discussed in terms of a reaction scheme proposed earlier to explain processes occurring during the plasma etching of Si in SF 6/O 2 plasmas. A comparison between the results obtained here and those reported earlier for reactions of both CF 3 and CF 2 with O and O 2 shows that there is a marked similarity in the free radical chemistry which occurs in SF 6/O 2 and CF 4/O 2 plasmas. 相似文献
10.
A strong ionization dielectric barrier discharge was used to produce a high concentration of reactive oxygen species that
were then injected into a simulated flue gas in a duct to remove SO 2 by oxidation. Sulfuric acid (H 2SO 4) was produced through the following two reactions: (1) O 3 oxidation of SO 2–SO 3, which then reacted with H 2O to produce H 2SO 4; and (2) reaction of O 2
+ with H 2O to produce ·OH radicals, which then rapidly and non-selectively oxidized SO 2–H 2SO 4. When the molar ratio of reactive oxygen species to SO 2 was 4:1, the SO 2 removal efficiency was 94.6%, the energy consumption per cubic meter of flue gas was 13.3 Wh/m 3, the concentration of recovered H 2SO 4 was 4.53 g/l, and the H 2SO 4 recovery efficiency was 28.8%. The H 2O volume fraction in the simulated flue gas affected the SO 2 removal efficiency, whereas the O 2 and CO 2 volume fractions did not. These results prove that oxidation by reactive oxygen species is a feasible method for flue gas
desulfurization. 相似文献
11.
In gas-insulated equipment, partial over-thermal faults may occur due to poor contact and other reasons. The main insulation medium SF6 may decompose under over-thermal conditions and produce harmful products such as SO2 and HF, which can damage the equipment and reduce the insulation strength of the equipment. The method of decomposition component analysis can monitor the operating status of equipment without interference from machinery, noise and optics, and provide early warning or reminder of faults, but the premise is that the decomposition mechanism of SF6 must have been fully and in-depth understood. In the decomposition process of SF6, O2 has a significant effect, but the mechanism of the effect is still unclear. Based on the isotope tracing method, this paper uses 18O2 instead of ordinary O2 for overheating experiments. Through the quantitative detection of the labeled products in the product and the abundance of 18O isotope in the products, the effect of O2 on the formation of the main decomposition products was analyzed. The work makes the reaction process and mechanism of SF6 with trace oxygen under over-thermal conditions basically clear, which provides an important theoretical basis for on-line monitoring and fault diagnosis of equipment based on chemical analysis methods. 相似文献
12.
Recent investigations on sulfur hexafluoride decomposition have shown the need of a rapid and efficient method for the qualitative and quantitative analysis of the reaction products. An analytical method for characterizing the gas mixture obtained from the decomposition of sulfur hexafluoride in a quartz reactor submitted to an r.f. discharge, is presented. A combination of gas-chromatographic, mass spectrometric and infrared spectrophotometric techniques has shown the presence of SF 6, SO 2F 2, SOF 4, SOF 2, SiF 4 and F 2 in the gas mixtures examined. For quantitative purposes a gas-chromatographic method has been found to be most suitable. 相似文献
13.
Infrared spectroscopy shows an enormous potential for the analysis of by-products generated from electrical discharges in sulfur-hexafluoride (SF 6) insulated equipment. Since by-product composition can be related to the fault genesis (arc, partial discharge or corona), the analysis of contaminated SF 6 provides a valuable diagnostic tool. The IR-spectrometric results from discharge experiments are presented, carried out with the application of SF 6 pressures around 300?kPa and an alternating voltage up to 30?kV. Under the discharge conditions used, the main by-products found are the sulfuroxyfluorides SOF 4 and SO 2F 2 with concentrations correlated to the discharge time. Due to its toxicity, special attention is also paid to S 2F 10. The experimental conditions and practical aspects for reliable quantitative analysis of reactive species are discussed. 相似文献
14.
Two hydrates of sodium 5,7‐dihydroxy‐6,4′‐dimethoxyisoflavone‐3′‐sulfonate ([Na(H 2O)J(C 17H 13O 6SO 3)*2H 2O,] 1) and nickel 5,7‐dihydroxy‐6,4′‐dimethoxyisoflavone‐3′‐sulfonate ([Ni(H 2O) 6](C 17H 13O 6SO 3) 2*4H 2O, 2) were synthesized and characterized by IR, 'H NMR and X‐ray diffraction analyses. The hydrate 1 crystallizes in the mono‐clinic system, space group P2(1) with a=0.8201(9) nm, b=0.8030(8) nm, c= 1.5361(16) nm, β=102.052(12)°, V =0.9893(18) nm 3, D,= 1.579 g/cm 3, Z=2, μ=0.252 nm ?1, F(000)=488, R=0.0353, wR=0.0873. The hydrate 2 belongs to triclinic system, space group P‐1 with a=0.7411(3) nm, b=0.8333(3) nm, c=1.7448(7) nm, α= 86.361(6)°, β=86.389(5)°, γ= 88.999(3)°, V=1.0731(7) nm 3, D,=1.587 g/cm 3, Z=1, μ=0.649 m ?1, F(000)= 534. In the structure of 1, the sodium cation is coordinated by six oxygen atom and two adjacent ones are bridged by three oxygen atoms to form an octahedron chain. The C? H…?… hydrogen bonds exist between two isoflavone molecules in the structure of 2. Meanwhile, hydrogen bonds in two compounds, link themselves to assemble two three‐dimensional network structures, respectively. 相似文献
15.
Freezing-point depression of mixtures of H
2
16
O and H
2
18
O were measured. The results showed that the freezing point of the mixture rose linearly with an increase in the molal concentration of H
2
18
O. The results suggested the formation of a solid solution of H
2
16
O and H
2
18
O by freezing, similar to that formed by H
2
O–D
2
O, and that H
2
18
O behaves as a different molecule than H
2
16
O. 相似文献
16.
A model has been developed to describe the chemistry which occurs in SF 6/O 2 plasmas and the etching of silicon in these plasmas. Emphasis is placed nn the gas-phase free radical reactions, and the predictions n( the model are compared with experimental results. Forty-seven reactions are included, although a subset of 18 reactions describes the chemistry equally well. Agreement between the calculated and measured concentrations of stable products downstream of the plasma is better than a factor of 2. The need for additional kinetic data and fàr well-characterized diagnostic studies of SF 6/O 2 plasmas is discussed. 相似文献
17.
Single crystals of [Eu(C 4H 4O 6)(H 2O) 2](H 2O) 2 were obtained from the combination of solutions of EuCl 2, previously obtained by electrolysis of an aqueous solution of EuCl 3, and tartraric acid, neutralized by LiOH. The crystal structure (orthorhombic, P2 12 12 1, Z = 4, a = 948.9(1), b = 954.6(1), c = 1098.4(1) pm; R(F) = 0.0242 and R w(F 2) = 0.0585 for I > 2σ(I); R(F) = 0.0256 and R w(F 2) = 0.0592 for all data) is isotypic with [Ca(C 4H 4O 6)(H 2O) 2](H 2O) 2 and [Sr(C 4H 4O 6)(H 2O) 2](H 2O) 2 exhibiting a three‐dimensional structure. The divalent cations (Eu 2+, Ca 2+, Sr 2+) are eight‐coordinate by oxygen atoms that originate from carboxylate and hydroxyl groups of the tartraric dianion and two of the four water molecules. 相似文献
18.
The thermal decomposition of FeSO 4·6H 2O
was studied by mass spectroscopy coupled with DTA/TG thermal analysis under
inert atmosphere. On the ground of TG measurements, the mechanism of decomposition
of FeSO 4·6H 2O is:
i) three dehydration steps
FeSO 4·6H 2O FeSO 4·4H 2O+2H 2O
FeSO 4·4H 2O FeSO 4·H 2O+3H 2O
FeSO 4·H 2O FeSO4+H 2O
ii) two decomposition
steps
6FeSO 4 Fe 2(SO 4) 3+2Fe 2O 3+2SO 2
Fe 2(SO 4)3 Fe 2O 3+3SO 2+3/2O 2
The intermediate compound was identified as Fe 2(SO 4) 3 and the final product as the hematite Fe 2O 3. 相似文献
19.
UV spectra of SF 5 and SF 5O 2 radicals in the gas phase at 295 K have been quantified using a pulse radiolysis UV absorption technique. The absorption spectrum of SF 5 was quantified from 220 to 240 nm. The absorption cross section at 220 nm was (5.5 ± 1.7) × 10 −19 cm 2. When SF 5 was produced in the presence of O 2 an equilibrium between SF 5, O 2, and SF 5O 2 was established. The rate constant for the reaction of SF 5 radicals with O 2 was (8 ± 2) × 10 −13 cm 3 molecule −1 s −1. The decomposition rate constant for SF 5O 2 was (1.0 ± 0.5) × 10 5 s −1, giving an equilibrium constant of Keq = [SF 5O 2]/[SF 5][O 2] = (8.0 ± 4.5) × 10 −18 cm 3 molecule −1. The SF 5 O 2 bond strength is (13.7 ± 2.0) kcal mol −1. The SF 5O 2 spectrum was broad with no fine structure and similar to the UV spectra of alkyl peroxy radicals. The absorption cross section at 230 nm was found to (3.7 ± 0.9) × 10 −18 cm 2. The rate constant of the reaction of SF 5O 2 with NO was measured to (1.1 ± 0.3) × 10 −11 cm 3 molecule −1 s −1 by monitoring the kinetics of NO 2 formation at 400 nm. The rate constant for the reaction of F atoms with SF 4 was measured by two relative methods to be (1.3 ± 0.3) × 10 −11 cm 3 molecule −1 s −1. © 1994 John Wiley & Sons, Inc. 相似文献
20.
Determination of the influence and mechanism of metallic materials on SF 6 decomposition under direct current (DC) partial discharge is one of the key aspects to improve SF 6 decomposition component analysis (DCA). In this study, three kinds of metallic materials, namely, aluminum, copper, and 18/8 stainless steel, were made into needle–plate electrons, and then used in the SF 6 positive DC partial discharge decomposition experiments. The influences of metallic materials on the five main decomposition components (i.e., CF 4, CO 2, SOF 2, SO 2F 2, and SO 2) were determined by gas chromatography–mass spectrometry. Results showed no significant correlation among the contents of CO 2 for the different kinds of metallic materials. However, the metallic materials considerably influenced the contents of the other four gases. The difference in SF 6 decomposition characteristics for the different metal electrodes was mainly due to the difference in anti-halogenation ability of metals and the passive film. Therefore, the impacts of different metallic materials should be considered when using SF 6 DCA for the condition monitoring and fault diagnosis of DC gas-insulated equipment. 相似文献
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