- Email: [email protected]
Fabrication of SiC mat by radiation processing
ARTICLE IN PRESS Radiation Physics and Chemistry 78 (2009) 493–495
Contents lists available at ScienceDirect
Radiation Physics and Chemistry journal homepage: www.elsevier.com/locate/radphyschem
Fabrication of SiC mat by radiation processing Phil-Hyun Kang , Joon-Pyo Jeun, Dong-Kwon Seo, Young-Chang Nho Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup-si, Jeollabuk-do, Republic of Korea
a r t i c l e in fo
Keywords: Silicon carbide Polycarbosilane Electron beam Electrospinning Radiation processing Pyrolysis
abstract Silicon carbide (SiC) exhibits many important properties, such as high intrinsic strength, stiffness, and high temperature stability. Therein, it is considered to be one of the most promising candidates for reinforcement of advanced ceramic matrix composites. The use of preceramic polymers presents the possibility of solving the intricacies involved in obtaining a new generation of ceramic materials. In this study, a radiation processing method was used to fabricate a cured polycarbosilane mat as a preceramic polymer. The polycarbosilane mat was cured by electron beam (e-beam) irradiation up to 10 MGy in an inert gas atmosphere. Next, the e-beam-cured PCS mat, as green fiber, was carbonized to produce the SiC mat. The conversion process of the PCS mat into the SiC mat was investigated by SEM, FT-IR, XRD, and TGA. According to FT-IR analysis, the Si–H peak intensity was observed to decrease as the polymer structure changed from polycarbosilane to SiC. The XRD patterns of SiC showed the diffraction peaks at (111), (2 2 0), and (3 11) which indicated the emergence of b-SiC. TGA curve shows that weight percent of residue of electrospun PCS mat, e-beam-cured PCS mat and pyrolyzed SiC mat up to 1000 1C were 72.5%, 88.3%, and 99.2%, respectively. & 2009 Elsevier Ltd. All rights reserved.
1. Introduction Silicon carbide (SiC) fiber exhibits many attractive intrinsic properties, such as a high tensile strength, a high elastic modulus, excellent thermal stability, high creep and excellent oxidation resistance. As a result, SiC fiber has been used as a reinforcement material in advanced ceramic matrix composites used in aerospace, nuclear, and high-temperature material applications. Unfortunately, for many applications, the expected anisotropic properties cannot be achieved in those fiber-reinforced composites due to the breaking of fibers or whiskers and because of the irregular distribution of fibers and whiskers in the reinforcing matrix. These problems could potentially be solved using woven structures such as mats (Lee and Yano, 2004). Mat-reinforced composites may increasingly be used in an extensive range of applications due to there adaptability to fixed manufacturing techniques and low fabrication cost. These mats are used in filter, composite reinforcement sensor, biomedical fields, template for the preparation of functional nanotubes and electrochemical photovoltaic electrodes. Polycarbosilane (PCS) was used as a precursor for SiC. Electrospinning is a simple and inexpensive technique for producing continuous submicron- to nano-sized polymeric fibers, and it provides high specific surface areas. This technique can be used with a variety of polymers to produce nanoscale fibers. Curing is an essential step in the preparation of Corresponding author. Tel.: +82 63 570 3061; fax: +82 63 570 3068.
E-mail address: [email protected] (P.-H. Kang). 0969-806X/$ - see front matter & 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.radphyschem.2009.03.033
SiC mat which is to prevent the mat melting during the carbonization phase. In this study, an electrospun PCS mat was fabricated using the electrospinning method. The electrospun PCS mat was cured by e-beam irradiation and then pyrolyzed in a tube furnace at atmospheric pressure under an argon atmosphere at a temperature of 1300 1C for 1 h. The morphology of the SiC mat was observed by scanning electron microscopy (SEM). Potential changes in polymer chemistry were characterized by FT-IR and XRD analysis. The thermal stability of the fabricated mat was analyzed using thermogravimetric analysis (TGA).
2. Experimental 2.1. Materials PCS (average molecular weight ¼ 1906 g/mol, density ¼ 1.1 g/cm3, NIPUS, Japan) was used as a precursor polymer for pyrolyzed SiC mat. 1,2-dichroloethane and toluene were purchased from Aldrich, USA, and used as a solvent without any further purification. 2.2. Fabrication of electrospun PCS mat A PCS solution was prepared by dissolving a measured amount of PCS in 1,2-dichroloethane/toluene (50/50 wt%). The concentration of the PCS solution was 50 wt%. In the electrospinning
ARTICLE IN PRESS P.-H. Kang et al. / Radiation Physics and Chemistry 78 (2009) 493–495
process, a high electric potential was applied to a droplet of PCS solution at the tip (ID 0.36 mm) of a syringe needle. The solution was then ejected through a syringe using a syringe flow pump at a feed rate of 0.003 ml/min while applying a voltage of 15 kV with a tip–target distance of 120 mm. 2.3. Irradiation The electrospun PCS mat was cured by e-beam irradiation under an argon atmosphere. The electrospun PCS mat set on a water-cooled stainless-steel bed to prevent the temperature of the PCS mat from rising during irradiation in the argon-filled chamber. The e-beam was generated with a 1.14 MeV acceleration voltage, 4 mA of current, and a 10 MGy absorbed dose. 2.4. Pyrolysis The e-beam-cured PCS mat was pyrolyzed in a tube furnace at a heating rate of 10 1C/min to 1300 1C under an argon atmosphere for 1 h. 2.5. Characterization Scanning electron microscopy examination of the surface of the pyrolyzed SiC mat was carried out using a Jeol JSM-6390 scanning electron microscope. Specimen was coated by gold sputtering for 5 min. Fabricated PCS mat was exposed to beam voltage of 20 kV during SEM examination. The bonding structure of the fabricated PCS mat was analyzed by FT-IR (Tenser37, BRUKER) using KBr pellets in the range of 400–4000 cm1. The constitution of the mat was identified using XRD (D/Max-1200, Rigaku Denki, Japan). The thermal stability of the fabricated PCS mat was analyzed by TGA, which was conducted with a TA instrument SDT Q600 at a heating rate of 10 1C/min, from 50 to 1000 1C under a nitrogen gas flow of 100 cm3/min. The mass of each characterized sample used was typically 15–16 mg.
The changes in structures in converting the PCS mat to SiC mat can be discussed qualitatively by using FT-IR spectra. The IR spectra of the PCS mat (Fig. 2(a, b)) indicated three main features centered around 2100, 1250, and 2950 cm1. The strong signal at 2100 cm1 can be attributed to the Si–H stretching mode. The bands around 1250 and 2950 cm1 were due to the stretching and angular deformation of CH2 and CH3 groups. The IR spectrum of the cured PCS mat showed the loss of the Si–H bond, and it is presumed that the curing process results in the formation of the Si–Si bond by the e-beam irradiation of Si–H and Si–CH3 (Takeda et al., 1999). The rapid decrease of the C–H (2950 cm1), Si–H (2100 cm1) and Si–CH3 (1250 cm1) bond can be seen in the spectrum of the pyrolyzed SiC mat (Fig. 2(c)). The pyrolyzed SiC mat showed peaks around 820 cm1, which are attributed to Si–C stretching (Zhou et al., 2008). The XRD pattern of the pyrolyzed SiC shows three diffraction peaks at 2y ¼ 35.81, 60.11, and 72.11 corresponding to (111), (2 2 0), and (3 11) planes, respectively (Fig. 3). These data indicate the emergence of crystalline b-SiC. The XRD pattern of pyrolyzed SiC shows that the electrospun PCS was gradually transformed into SiC. As expected, b-SiC was formed during the pyrolysis (Intarasiri et al., 2007; Kurtenbach et al., 1998). The diffraction peak of (111) is typical for one-dimensional stacking faults in the cubic structure. The thermal stability of the fabricated mat was analyzed by TGA (Fig. 4). The weight percents of residue of electrospun PCS, e-beam-cured PCS, and pyrolyzed SiC up to 1000 1C were 72.5%,
(c) pyrolyzed SiC
(b) e-beam cured PCS Transmitance
494
(a) electrospun PCS
3. Results and discussion Fig. 1(a, b) shows the photographs of the electrospun PCS prepared by electrospinning method. It was shown that 3D non woven mat was obtained. The morphology of the pyrolyzed SiC was observed by SEM (Fig. 1(c)). The SEM image demonstrates that uniform fibers with an average diameter of 18 mm were achieved (Ishii et al., 2008; Cui et al., 2008). From the SEM image, it was found that the pyrolyzed SiC have no beads or crack on the surface of fiber.
Si-H bond
1000
1500
2000 Wavenumbers (cm-1)
2500
3000
Fig. 2. FT-IR spectra of electrospun PCS (a), e-beam-cured PCS (b), and pyrolyzed SiC (c).
Fig. 1. Photograph of the electrospun PCS (a), pyrolyzed SiC (b), and SEM image of the pyrolyzed SiC (c).
ARTICLE IN PRESS P.-H. Kang et al. / Radiation Physics and Chemistry 78 (2009) 493–495
low-molecular-mass PCS, occurred between 200 and 400 1C. During the third phase, thermal decomposition of the side chains of the PCS predominated from 400 to 600 1C. Above 800 1C, the conversion of PCS into the inorganic state was almost completed (Zeong et al., 2006). TGA analysis indicated that the weight residue of electrospun PCS mat was constant at temperature above 800 1C and organic group in the electrospun PCS mat was decomposed below this temperature.
(c) pyrolyzed SiC
Intensity (a.u.)
495
(b) e-beam cured PCS 4. Conclusions
(a) electrospun PCS
20
40
60
80
2θ (degree) Fig. 3. XRD patterns of the electrospun PCS (a), e-beam-cured PCS (b), and pyrolyzed SiC (c).
100 (c) pyrolyzed SiC
PCS mat was made by electrospun fibers having a smooth morphology with no beads or crack on the surface with an average diameter of 18 mm. The curing of the PCS mat was done by e-beam irradiation of Si–H and Si–CH3, resulting in Si–Si and Si–C bonds. This resulted in a mat that was infusible and retained the form of the fibers. Using FT-IR analysis, it was clearly observed that the Si–H peak intensity decreased as the polymer changed from PCS to SiC. The XRD patterns of the SiC mat showed the diffraction peaks at (111), (2 2 0), and (3 11) which indicated the emergence of b-SiC. TGA analysis while raising the temperature under nitrogen gas to 1000 1C showed the weight residue in e-beam-cured PCS mat was 88.3 wt% which was significantly lager than 72.5 wt% found with electrospun PCS mat. The TGA curve shows that the thermal stability of the electrospun PCS was increased by e-beam irradiation.
Weight (%)
95 Acknowledgement
90 (b) e-beam cured PCS 85
This research was supported by Nuclear R&D program through the Korea Science and Engineering Foundation funded by the Ministry of Education, Science and Technology, Korea.
80 References
75 (a) electrospun PCS 70 100
200
300
400
500
600
700
800
900
Temperature (°C) Fig. 4. TGA spectra of the electrospun PCS (a), e-beam-cured PCS (b), and pyrolyzed SiC (c).
88.3% and 99.2%, respectively. This fact means that the e-beamcured PCS was thermodynamically more stable than the electrospun PCS mat. From the electrospun PCS curve, it can be seen that the conversion of the electrospun PCS into the inorganic state was divided into four phases (Yen et al., 2005; Shukla et al., 2004). The first phase was from room temperature to 200 1C, the second from 200 to 400 1C, the third from 400 to 600 1C and last was above 800 1C. In the first phase, there was only a small amount of mass loss due to the evaporation of water. A mass loss of about 10%, which was due to the evaporation of hydrogen and
Cui, X.M., Nam, Y.S., Lee, J.Y., Park, W.H., 2008. Fabrication of zirconium carbide (ZrC) ultra-thin fibers by electrospinning. Mater. Lett. 62, 1961–1964. Ishii, Y., Sakai, H., Murata, H., 2008. A new electrospinning method to control the number and a diameter of uniaxially aligned polymer fiber. Mater. Lett. 62, 3370–3372. Intarasiri, S., Hallen, A., Lu, J., Jensen, J., Yu, L.D., Bertilsson, K., Wolborski, M., Singkarat, S., Possnert, G., 2007. Crystalline quality of 3C-SiC formed by highfluence C+-implanted Si. Appl. Surf. Sci. 253, 4836–4842. Kurtenbach, D., Martin, H.-p., Muller, E., Roewer, G., Hoell, A., 1998. Crystallization of polymer derived silicon carbide materials. J. Eur. Ceram. Soc. 18, 1885–1891. Lee, J.S., Yano, T., 2004. Fabrication of short-fiber-reinforced SiC composite by polycarbosilane infiltration. J. Eur. Ceram. Soc. 24, 25–31. Shukla, S.K., Tiwari, R.K., Ranjan, A., Saxena, A.K., Mathur, G.N., 2004. Some thermal studies of polysilanes and polycarbosilanes. Thermochim. Acta 424, 209–217. Takeda, M., Imai, Y., Ichkawa, H., Kasai, N., Seguchi, T., Okamura, K., 1999. Thermal stability of SiC fiber prepared by an irradiation-curing process. Compos. Sci. Technol. 59, 793–799. Yen, H.N., Jou, S., Chu, C.J., 2005. Si–O–C nanotubes from pyrolyzing polycarbosilane in a mesoporous template. Mater. Sci. Eng., B 122, 240–245. Zhou, C., Zhang, C., Hu, H., Zhang, Y., Wang, Z., 2008. Preparation of 3D-Cf/SiC composites at low temperatures. Mater. Sci. Eng., A 488, 569–572. Zeong, C.M., LI, X.D., Wang, H., Zhu, B., 2006. Thermal stability and curing kinetics of polycarbosilane fibers. Trans. Nonferrous Met. Soc. China 16, 44–48.
Contents lists available at ScienceDirect
Radiation Physics and Chemistry journal homepage: www.elsevier.com/locate/radphyschem
Fabrication of SiC mat by radiation processing Phil-Hyun Kang , Joon-Pyo Jeun, Dong-Kwon Seo, Young-Chang Nho Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup-si, Jeollabuk-do, Republic of Korea
a r t i c l e in fo
Keywords: Silicon carbide Polycarbosilane Electron beam Electrospinning Radiation processing Pyrolysis
abstract Silicon carbide (SiC) exhibits many important properties, such as high intrinsic strength, stiffness, and high temperature stability. Therein, it is considered to be one of the most promising candidates for reinforcement of advanced ceramic matrix composites. The use of preceramic polymers presents the possibility of solving the intricacies involved in obtaining a new generation of ceramic materials. In this study, a radiation processing method was used to fabricate a cured polycarbosilane mat as a preceramic polymer. The polycarbosilane mat was cured by electron beam (e-beam) irradiation up to 10 MGy in an inert gas atmosphere. Next, the e-beam-cured PCS mat, as green fiber, was carbonized to produce the SiC mat. The conversion process of the PCS mat into the SiC mat was investigated by SEM, FT-IR, XRD, and TGA. According to FT-IR analysis, the Si–H peak intensity was observed to decrease as the polymer structure changed from polycarbosilane to SiC. The XRD patterns of SiC showed the diffraction peaks at (111), (2 2 0), and (3 11) which indicated the emergence of b-SiC. TGA curve shows that weight percent of residue of electrospun PCS mat, e-beam-cured PCS mat and pyrolyzed SiC mat up to 1000 1C were 72.5%, 88.3%, and 99.2%, respectively. & 2009 Elsevier Ltd. All rights reserved.
1. Introduction Silicon carbide (SiC) fiber exhibits many attractive intrinsic properties, such as a high tensile strength, a high elastic modulus, excellent thermal stability, high creep and excellent oxidation resistance. As a result, SiC fiber has been used as a reinforcement material in advanced ceramic matrix composites used in aerospace, nuclear, and high-temperature material applications. Unfortunately, for many applications, the expected anisotropic properties cannot be achieved in those fiber-reinforced composites due to the breaking of fibers or whiskers and because of the irregular distribution of fibers and whiskers in the reinforcing matrix. These problems could potentially be solved using woven structures such as mats (Lee and Yano, 2004). Mat-reinforced composites may increasingly be used in an extensive range of applications due to there adaptability to fixed manufacturing techniques and low fabrication cost. These mats are used in filter, composite reinforcement sensor, biomedical fields, template for the preparation of functional nanotubes and electrochemical photovoltaic electrodes. Polycarbosilane (PCS) was used as a precursor for SiC. Electrospinning is a simple and inexpensive technique for producing continuous submicron- to nano-sized polymeric fibers, and it provides high specific surface areas. This technique can be used with a variety of polymers to produce nanoscale fibers. Curing is an essential step in the preparation of Corresponding author. Tel.: +82 63 570 3061; fax: +82 63 570 3068.
E-mail address: [email protected] (P.-H. Kang). 0969-806X/$ - see front matter & 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.radphyschem.2009.03.033
SiC mat which is to prevent the mat melting during the carbonization phase. In this study, an electrospun PCS mat was fabricated using the electrospinning method. The electrospun PCS mat was cured by e-beam irradiation and then pyrolyzed in a tube furnace at atmospheric pressure under an argon atmosphere at a temperature of 1300 1C for 1 h. The morphology of the SiC mat was observed by scanning electron microscopy (SEM). Potential changes in polymer chemistry were characterized by FT-IR and XRD analysis. The thermal stability of the fabricated mat was analyzed using thermogravimetric analysis (TGA).
2. Experimental 2.1. Materials PCS (average molecular weight ¼ 1906 g/mol, density ¼ 1.1 g/cm3, NIPUS, Japan) was used as a precursor polymer for pyrolyzed SiC mat. 1,2-dichroloethane and toluene were purchased from Aldrich, USA, and used as a solvent without any further purification. 2.2. Fabrication of electrospun PCS mat A PCS solution was prepared by dissolving a measured amount of PCS in 1,2-dichroloethane/toluene (50/50 wt%). The concentration of the PCS solution was 50 wt%. In the electrospinning
ARTICLE IN PRESS P.-H. Kang et al. / Radiation Physics and Chemistry 78 (2009) 493–495
process, a high electric potential was applied to a droplet of PCS solution at the tip (ID 0.36 mm) of a syringe needle. The solution was then ejected through a syringe using a syringe flow pump at a feed rate of 0.003 ml/min while applying a voltage of 15 kV with a tip–target distance of 120 mm. 2.3. Irradiation The electrospun PCS mat was cured by e-beam irradiation under an argon atmosphere. The electrospun PCS mat set on a water-cooled stainless-steel bed to prevent the temperature of the PCS mat from rising during irradiation in the argon-filled chamber. The e-beam was generated with a 1.14 MeV acceleration voltage, 4 mA of current, and a 10 MGy absorbed dose. 2.4. Pyrolysis The e-beam-cured PCS mat was pyrolyzed in a tube furnace at a heating rate of 10 1C/min to 1300 1C under an argon atmosphere for 1 h. 2.5. Characterization Scanning electron microscopy examination of the surface of the pyrolyzed SiC mat was carried out using a Jeol JSM-6390 scanning electron microscope. Specimen was coated by gold sputtering for 5 min. Fabricated PCS mat was exposed to beam voltage of 20 kV during SEM examination. The bonding structure of the fabricated PCS mat was analyzed by FT-IR (Tenser37, BRUKER) using KBr pellets in the range of 400–4000 cm1. The constitution of the mat was identified using XRD (D/Max-1200, Rigaku Denki, Japan). The thermal stability of the fabricated PCS mat was analyzed by TGA, which was conducted with a TA instrument SDT Q600 at a heating rate of 10 1C/min, from 50 to 1000 1C under a nitrogen gas flow of 100 cm3/min. The mass of each characterized sample used was typically 15–16 mg.
The changes in structures in converting the PCS mat to SiC mat can be discussed qualitatively by using FT-IR spectra. The IR spectra of the PCS mat (Fig. 2(a, b)) indicated three main features centered around 2100, 1250, and 2950 cm1. The strong signal at 2100 cm1 can be attributed to the Si–H stretching mode. The bands around 1250 and 2950 cm1 were due to the stretching and angular deformation of CH2 and CH3 groups. The IR spectrum of the cured PCS mat showed the loss of the Si–H bond, and it is presumed that the curing process results in the formation of the Si–Si bond by the e-beam irradiation of Si–H and Si–CH3 (Takeda et al., 1999). The rapid decrease of the C–H (2950 cm1), Si–H (2100 cm1) and Si–CH3 (1250 cm1) bond can be seen in the spectrum of the pyrolyzed SiC mat (Fig. 2(c)). The pyrolyzed SiC mat showed peaks around 820 cm1, which are attributed to Si–C stretching (Zhou et al., 2008). The XRD pattern of the pyrolyzed SiC shows three diffraction peaks at 2y ¼ 35.81, 60.11, and 72.11 corresponding to (111), (2 2 0), and (3 11) planes, respectively (Fig. 3). These data indicate the emergence of crystalline b-SiC. The XRD pattern of pyrolyzed SiC shows that the electrospun PCS was gradually transformed into SiC. As expected, b-SiC was formed during the pyrolysis (Intarasiri et al., 2007; Kurtenbach et al., 1998). The diffraction peak of (111) is typical for one-dimensional stacking faults in the cubic structure. The thermal stability of the fabricated mat was analyzed by TGA (Fig. 4). The weight percents of residue of electrospun PCS, e-beam-cured PCS, and pyrolyzed SiC up to 1000 1C were 72.5%,
(c) pyrolyzed SiC
(b) e-beam cured PCS Transmitance
494
(a) electrospun PCS
3. Results and discussion Fig. 1(a, b) shows the photographs of the electrospun PCS prepared by electrospinning method. It was shown that 3D non woven mat was obtained. The morphology of the pyrolyzed SiC was observed by SEM (Fig. 1(c)). The SEM image demonstrates that uniform fibers with an average diameter of 18 mm were achieved (Ishii et al., 2008; Cui et al., 2008). From the SEM image, it was found that the pyrolyzed SiC have no beads or crack on the surface of fiber.
Si-H bond
1000
1500
2000 Wavenumbers (cm-1)
2500
3000
Fig. 2. FT-IR spectra of electrospun PCS (a), e-beam-cured PCS (b), and pyrolyzed SiC (c).
Fig. 1. Photograph of the electrospun PCS (a), pyrolyzed SiC (b), and SEM image of the pyrolyzed SiC (c).
ARTICLE IN PRESS P.-H. Kang et al. / Radiation Physics and Chemistry 78 (2009) 493–495
low-molecular-mass PCS, occurred between 200 and 400 1C. During the third phase, thermal decomposition of the side chains of the PCS predominated from 400 to 600 1C. Above 800 1C, the conversion of PCS into the inorganic state was almost completed (Zeong et al., 2006). TGA analysis indicated that the weight residue of electrospun PCS mat was constant at temperature above 800 1C and organic group in the electrospun PCS mat was decomposed below this temperature.
(c) pyrolyzed SiC
Intensity (a.u.)
495
(b) e-beam cured PCS 4. Conclusions
(a) electrospun PCS
20
40
60
80
2θ (degree) Fig. 3. XRD patterns of the electrospun PCS (a), e-beam-cured PCS (b), and pyrolyzed SiC (c).
100 (c) pyrolyzed SiC
PCS mat was made by electrospun fibers having a smooth morphology with no beads or crack on the surface with an average diameter of 18 mm. The curing of the PCS mat was done by e-beam irradiation of Si–H and Si–CH3, resulting in Si–Si and Si–C bonds. This resulted in a mat that was infusible and retained the form of the fibers. Using FT-IR analysis, it was clearly observed that the Si–H peak intensity decreased as the polymer changed from PCS to SiC. The XRD patterns of the SiC mat showed the diffraction peaks at (111), (2 2 0), and (3 11) which indicated the emergence of b-SiC. TGA analysis while raising the temperature under nitrogen gas to 1000 1C showed the weight residue in e-beam-cured PCS mat was 88.3 wt% which was significantly lager than 72.5 wt% found with electrospun PCS mat. The TGA curve shows that the thermal stability of the electrospun PCS was increased by e-beam irradiation.
Weight (%)
95 Acknowledgement
90 (b) e-beam cured PCS 85
This research was supported by Nuclear R&D program through the Korea Science and Engineering Foundation funded by the Ministry of Education, Science and Technology, Korea.
80 References
75 (a) electrospun PCS 70 100
200
300
400
500
600
700
800
900
Temperature (°C) Fig. 4. TGA spectra of the electrospun PCS (a), e-beam-cured PCS (b), and pyrolyzed SiC (c).
88.3% and 99.2%, respectively. This fact means that the e-beamcured PCS was thermodynamically more stable than the electrospun PCS mat. From the electrospun PCS curve, it can be seen that the conversion of the electrospun PCS into the inorganic state was divided into four phases (Yen et al., 2005; Shukla et al., 2004). The first phase was from room temperature to 200 1C, the second from 200 to 400 1C, the third from 400 to 600 1C and last was above 800 1C. In the first phase, there was only a small amount of mass loss due to the evaporation of water. A mass loss of about 10%, which was due to the evaporation of hydrogen and
Cui, X.M., Nam, Y.S., Lee, J.Y., Park, W.H., 2008. Fabrication of zirconium carbide (ZrC) ultra-thin fibers by electrospinning. Mater. Lett. 62, 1961–1964. Ishii, Y., Sakai, H., Murata, H., 2008. A new electrospinning method to control the number and a diameter of uniaxially aligned polymer fiber. Mater. Lett. 62, 3370–3372. Intarasiri, S., Hallen, A., Lu, J., Jensen, J., Yu, L.D., Bertilsson, K., Wolborski, M., Singkarat, S., Possnert, G., 2007. Crystalline quality of 3C-SiC formed by highfluence C+-implanted Si. Appl. Surf. Sci. 253, 4836–4842. Kurtenbach, D., Martin, H.-p., Muller, E., Roewer, G., Hoell, A., 1998. Crystallization of polymer derived silicon carbide materials. J. Eur. Ceram. Soc. 18, 1885–1891. Lee, J.S., Yano, T., 2004. Fabrication of short-fiber-reinforced SiC composite by polycarbosilane infiltration. J. Eur. Ceram. Soc. 24, 25–31. Shukla, S.K., Tiwari, R.K., Ranjan, A., Saxena, A.K., Mathur, G.N., 2004. Some thermal studies of polysilanes and polycarbosilanes. Thermochim. Acta 424, 209–217. Takeda, M., Imai, Y., Ichkawa, H., Kasai, N., Seguchi, T., Okamura, K., 1999. Thermal stability of SiC fiber prepared by an irradiation-curing process. Compos. Sci. Technol. 59, 793–799. Yen, H.N., Jou, S., Chu, C.J., 2005. Si–O–C nanotubes from pyrolyzing polycarbosilane in a mesoporous template. Mater. Sci. Eng., B 122, 240–245. Zhou, C., Zhang, C., Hu, H., Zhang, Y., Wang, Z., 2008. Preparation of 3D-Cf/SiC composites at low temperatures. Mater. Sci. Eng., A 488, 569–572. Zeong, C.M., LI, X.D., Wang, H., Zhu, B., 2006. Thermal stability and curing kinetics of polycarbosilane fibers. Trans. Nonferrous Met. Soc. China 16, 44–48.