Mechanism of cyclohexene vapor curing polycarbosilane fibers

Li, W.; Song, Yimeng; Mao, Xianhe

doi:10.1007/s10853-006-0807-z

Cited by 10 publications

(12 citation statements)

References 9 publications

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“…As the formation of CH 3 I is a type of dehydrogenation, this reaction would certainly contribute to the cross-linking of PCS. 23,24 The detection of siloxanes (7.30%) is due to the oxidation of oligomeric silanes that were detached from PCS (refer to the Si-Si signal d¼À38 in the 29 Si-NMR spectra in Fig. 3).…”

Section: Resultsmentioning

confidence: 99%

Room temperature reaction of polycarbosilane with iodine under different atmospheres for polymer-derived silicon carbide fibres

et al. 2015

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The reaction of iodine with polycarbosilane (PCS) in air and N 2 atmospheres at room temperature was investigated with the goal of limiting oxygen uptake during iodine curing, in order to fabricate SiC fibres with low oxygen contents. The investigation shows that the PCS fibres are well cured by iodisation even at room temperature, regardless of the presence of oxygen in the atmosphere. Although it was previously reported that the amount of oxygen incorporated is affected proportionally by the processing temperature, when PCS fibres were iodised in air at room temperature, they contained significant amounts of oxygen owing to the very long processing time despite the low temperature. On the other hand, when iodised in a N 2 atmosphere, the fibres were successfully cured without oxygen uptake, thus demonstrating that iodisation under an oxygen-free atmosphere is a successful curing method for fabricating SiC fibres with low oxygen contents. During the cross-linking process, the iodine causes fragmentation of certain groups from the PCS polymer chains, which mostly contributes to the crosslinking between the chains, but leaves reactive sites that readily allow oxidation in air.

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Section: Resultsmentioning

confidence: 99%

Room temperature reaction of polycarbosilane with iodine under different atmospheres for polymer-derived silicon carbide fibres

et al. 2015

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“…At the same time, cyclohexyl and hexyl will be introduced into the PCS skeleton as the result of addition reaction [7,8]. With the increase of temperature, these molecules will convert into Si-C networks which are carbon excessive accompanied by dehydrogenation and demethanation.…”

Section: Discussionmentioning

confidence: 99%

“…In order to avoid the negative effects caused by detrimental oxygen, cyclohexene and 1-hexyne as curing agents were used to make precursor fiber infusible, and a SiC fiber with low oxygen content and high mechanical properties was obtained [7][8][9]. Although this curing method for PCS fibers to react with unsaturated hydrocarbons is not new [10,11], the low electrical resistivity and existence of an excess carbon layer of the resulting SiC fiber have only recently been observed in this work.…”

Section: Introductionmentioning

confidence: 91%

SiC fiber with low electrical resistivity and oxygen content

Mao

Song

Wang

2010

Sci. China Technol. Sci.

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A new SiC fiber was prepared by the pyrolysis of polycarbosilane (PCS) fiber cured with unsaturated hydrocarbons. The fiber, with oxygen content of 4-6 wt%, offers high tensile strength of 2.5-2.8 GPa. The electrical resistivity of the fiber is only about 0.5 Ω·cm, much lower than general SiC fiber obtained from traditional air curing process. Degradation of mechanical property in argon and air at high temperature is retarded by 200-300°C with respect to the Nicalon NL-202 fiber. The low electrical resistivity of the fiber exhibits excellent thermal stability, it almost remains 0.4-0.8 Ω·cm after thermal exposure test from the room temperature to 1600°C in argon. The low electrical resistivity mainly attribute to an excess carbon layer which is about 50 nm in the circular outer part. polycarbonsilane, SiC fiber, electrical resistivity, excess carbon layer Citation:Wang D Y, Mao X H, Song Y C, et al. SiC fiber with low electrical resistivity and oxygen content.

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“…[1][2][3] The curing stage of the manufacturing process plays a pivotal role in determining the final quality of the SiC fibers, as it not only prevents the PCS fibers from fusing together during pyrolysis, but also has a significant effect on their mechanical properties. [4][5][6][7][8][9] A number of different curing methods have therefore been developed, which include thermal oxidation curing, 4-6 c-ray/electron-beam radiation curing, 7-10 chemical vapor curing (CVC) using halogenated hydrocarbons or unsaturated hydrocarbon vapors, [11][12][13] and CVC using BCl 3 and ammonia. 14,15 A new CVC method involving the use of iodine (i.e., I-vapor curing) was recently reported 16 that offers several advantages over existing techniques, including a decrease in the curing temperature and the time required.…”

Section: Introductionmentioning

confidence: 99%

“…The curing stage of the manufacturing process plays a pivotal role in determining the final quality of the SiC fibers, as it not only prevents the PCS fibers from fusing together during pyrolysis, but also has a significant effect on their mechanical properties . A number of different curing methods have therefore been developed, which include thermal oxidation curing, γ‐ray/electron‐beam radiation curing, chemical vapor curing (CVC) using halogenated hydrocarbons or unsaturated hydrocarbon vapors, and CVC using BCl 3 and ammonia…”

Section: Introductionmentioning

confidence: 99%

Iodine diffusion during iodine‐vapor curing and its effects on the morphology of polycarbosilane/silicon carbide fibers

Hong

Cho

Shin

et al. 2015

J of Applied Polymer Sci

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Iodine‐vapor curing is used to produce continuous SiC fibers from polycarbosilane (PCS), but attempts to limit the uptake of oxygen during the curing process result in SiC fibers with different morphologies and pore types. The cause of this distinct transformation in the morphology of the fibers is determined in this study by tracing the distribution of iodine in PCS fibers cured either at a set temperature or for a given period. The results reveal that the final morphology of the fibers is dependent on the degree of iodine diffusion, or on the extent of their cross‐linked area. Using this knowledge, fibers with three distinct morphologies are produced by controlling the curing conditions. Optimization of this curing process is shown to inhibit the formation of pores and retard the incorporation of oxygen, while still allowing the fibers to retain their cylindrical shape. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42687.

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Mechanism of cyclohexene vapor curing polycarbosilane fibers

Cited by 10 publications

References 9 publications

Room temperature reaction of polycarbosilane with iodine under different atmospheres for polymer-derived silicon carbide fibres

Room temperature reaction of polycarbosilane with iodine under different atmospheres for polymer-derived silicon carbide fibres

SiC fiber with low electrical resistivity and oxygen content

Iodine diffusion during iodine‐vapor curing and its effects on the morphology of polycarbosilane/silicon carbide fibers

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