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Preparation and characterization of SiC hollow microspheres
Accepted Manuscript Preparation and characterization of SiC hollow microspheres Cuilan Tang, Zhibing He, Xiaoshan He, Jinglin Huang, Yong Yi, Hongbin Wang, Tao Wang PII: DOI: Reference:
S0167-577X(17)31092-3 http://dx.doi.org/10.1016/j.matlet.2017.07.054 MLBLUE 22896
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
19 May 2017 1 July 2017 7 July 2017
Please cite this article as: C. Tang, Z. He, X. He, J. Huang, Y. Yi, H. Wang, T. Wang, Preparation and characterization of SiC hollow microspheres, Materials Letters (2017), doi: http://dx.doi.org/10.1016/j.matlet.2017.07.054
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Preparation and characterization of SiC hollow microspheres Cuilan Tanga,b, Zhibing Hea, Xiaoshan Hea, Jinglin Huanga,Yong Yib, Hongbin Wangb, Tao Wanga,* a
b
Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, PR China；
School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010,
PR China
Abstract: We present the method of chemical vapor deposition-pyrolysis for the fabrication of SiC hollow microspheres. Microspheres with a diameter of approximately 480~550 µm and wall thickness of 5~15 µ m are thus successfully prepared. The composition, especially the C/Si atomic ratio, and surface morphologies of the SiC microspheres can be flexibly adjusted by controlling the coating and heating parameters. The SiC microspheres mainly contain C-Si bonds with C/Si atomic ratios of approximately 1~3. The precursor microspheres are found to exhibit a large volume shrinkage (39%~55%) during the pyrolysis process, while pyrolysis has a negligible impact on the yield of the SiC microspheres (>95%). The spherical degrees are greater than 98% with small dispersions. The wall thickness uniformities can be optimized as high as 95%. The density of SiC microspheres can be increased by prolonging the holding time at 450 °C, while the corresponding RMS roughness can be decreased. Key words: Amorphous materials; Chemical vapour deposition; Pyrolysis; Microstructure
1.Introduction Silicon carbide (SiC) has attracted substantial attentions owing to its unique thermal, mechanical, optical and electronic properties, which make it a promising material under high temperature, high-power and high-radiation conditions [1-4]. In particular, previous studies have demonstrated that SiC hollow microspheres (shells) can realize
the argon and deuterium gas filling process under high temperatures [5]. Numerous applications can therefore be realized, for example, as the potential targets for inertial confinement fusion (ICF) experiments. At present, the main challenge in fabricating SiC shells is how to acquire beneficial properties, such as uniform morphologies, high spherical degrees and high wall thickness uniformities, for these properties will significantly affect the physical experiments [6-9]. Unfortunately, few related studies have been reported. In this paper, we develop an effective method, chemical vapor deposition (CVD)-pyrolysis, which enables excellent control of diameter and wall thickness to access SiC shells with high spherical degrees and high wall thickness uniformities. First, Si-doped
glow
discharge
polymer
(Si-GDP)
coatings
are
deposited
on
poly(α-methylstyrene) (PAMS) hollow spheres as the precursors. Here the PAMS spheres, synthesized by the droplet generator technique [10], act as mandrels. Second, the precursors are pyrolyzed at 300 °C in an inert gas to remove the PAMS. Finally, Si-doped GDP shells are pyrolyzed at 450 °C and densified at 900 °C in an argon atmosphere to convert into SiC shells. The composition, surface morphologies, root-mean-square (RMS) roughness, spherical degrees, wall thickness uniformities and densities of the prepared SiC shells are carefully studied.
2. Experimental First, Si-GDP coatings were deposited on PAMS hollow spheres (diameter 900±50 µm) by plasma enhanced chemical vapor deposition (PECVD), using tetramethyl silane (TMS), trans-2-butene (T2B) and hydrogen (H2) as feed-stock gases. H2 and T2B gas
flows were set at 10 and 0.4 sccm (standard cubic centimeters per minute), respectively. TMS flow and working pressure were varied from 0.15 to 0.4 sccm (0.15, 0.25, 0.3, 0.4 sccm) and from 5 to 25 Pa (5, 10, 15, 20, 25 Pa), respectively. The RF power was 15 W and the deposition time was 54 h. To improve the wall thickness uniformity, the PAMS spheres were placed in a revolving pan. Second, the PAMS mandrel was decomposed and volatilized by a controlled heating process, in which the temperature was slowly ramped to 300 °C under argon, to obtain pure Si-GDP shells. Finally, Si-GDP shells were converted into SiC shells by slowly pyrolyzing at 450 °C and densifying at 900 °C in argon. The holding time at 450 °C was varied from 5 to 25 h (5, 10, 15, 20, 25 h). The thermal treatment process was completed in an Al2O3 tube furnace under a steady flow of ultrahigh-purity argon. The morphologies and microstructures were characterized by a field-emission scanning electron microscope (SEM, ZEISS Merlin VP Compact). Composition and chemical bonding were studied by X-ray photoelectron spectroscopy (XPS, OMICRON VT SPM). Diameter and wall thickness tests were carried out using an X-ray camera (XTF-5011). RMS roughness and quality were measured by white light interferometer (WLI, WYKO NT1100) and analysis balance, respectively.
3. Results and discussion Fig. 1a-f shows the SEM images of SiC shells prepared by various Si-GDP precursors with the same pyrolysis process. The shells with excellent spherical shapes and free of cracks can be observed in the full-views of the SiC shells in Fig. 1a and b, which demonstrates no cracks or collapses for the shells during the pyrolysis process.
The typical surface morphologies of SiC shells prepared by various TMS flows are presented in Fig. 1c and d (TMS-0.25 and TMS-0.4). The surface of TMS-0.25 is flat and smooth without obvious defects, such as voids and domes (Fig. 1c). There are, however, many bulges and pits for TMS-0.4 (Fig. 1d), which indicates a much rougher surface. The microstructure of SiC shells presents an aggregation of closely arranged irregular particles, as shown in the insets of Fig. 1c and d. Note that the particle size could be altered through changing the TMS flows. Similarly, comparing Fig. 1e with Fig. 1f, SiC shells fabricated at different working pressures (15 Pa and 25 Pa) also possess diverse surface morphologies and microstructures. The surface is rougher and the particle is larger at 25 Pa (Fig. 1f). Hence, SiC shells with various surface morphologies and microstructures could be successfully fabricated by altering the coating parameters. According to the high resolution C1s and Si2p XPS spectra in Fig. 1g and h, the major bond in the fabricated shells is C-Si. It has been calculated that the C/Si atomic ratio could be adjusted from 1 to 3. When the TMS flow is 0.15, 0.25, 0.3, 0.4 sccm, C/Si atomic ratio of SiC shells is 2.4, 2.2, 1.3, 1.2, respectively. While, when the pressure is 5, 10, 15, 20, 25 Pa, the C/Si atomic ratio of SiC shells is 0.8, 1.31, 1.34, 1.30, 0.89, respectively. The results represent that the TMS flow has a greater influence on the C/Si atomic ratio.
Fig. 1. SEM full-views of SiC shells (a) TMS=0.25 sccm and (b) TMS=0.4 sccm. Low magnification images of SiC shells (c) TMS=0.25 sccm, (d) TMS=0.4 sccm, (e) pressure=15 Pa and (f) pressure=25 Pa. Insets are the high magnification images of the corresponding shells. XPS analysis by Gaussian fitting at a working pressure of 15 Pa (g) C1s spectra and (h) Si2p spectra.
In addition to the coating parameters, the pyrolysis process could be another effective way to adjust the surface morphologies and microstructures of the SiC shells. The results of the SiC shells fabricated with various holding times at 450 °C (5 and 15 h) are presented in Fig. 2 as an example. Many elliptical or roundness sags and crests can be observed on the surface of the 5 h sample (Fig. 2a), while no bulge is discovered for the 15 h sample (Fig. 2b). Hence, it is helpful to improve the planeness of the microspheres by appropriately prolonging the holding time at 450 °C. Additionally, the cross-section images in the insets of Fig. 2a and b show a dense structure. Fig. 2c and d provide the high-resolution C1s and Si2p XPS spectra of the 5 h
sample. The shells mainly contain C-Si bond and a small amount of C=C and Si-Si. After calculation, when the holding time is 5 and 15 h, the C/Si atomic ratio of SiC shells is 2.4 and 1.3, respectively. This is because the longer the holding time at 450 °C, the more thorough the cracking of Si-GDP.
Fig. 2. SEM images of the SiC shells with different holding times at 450 °C (a) 5 h and (b) 15 h. Insets are the corresponding cross-section images. XPS analysis of SiC with holding time of 5 h at 450 °C (c) C1s spectra and (d) Si2p spectra.
Fig. 3a and b display the optical microscopy and X-ray photograph of SiC shells prepared at the working pressure of 15 Pa. These SiC shells are black spheres with small size dispersions. The spherical degrees and wall thickness uniformities of SiC shells are relatively high (Fig. 3b). To quantitatively discuss these two geometrical properties, they are calculated by the method reported in the literature [11-13]. It can be seen that the spherical degrees of shells are greater than 98% with a negligible variation as the pressure increases (Fig. 3c), which demonstrates that pressure has little effect on the sphericity of shells. The wall thickness uniformity of SiC first increases then decreases as pressure increases (Fig. 3d). It increases to 95% when the pressure is 15 Pa. As can be seen in Fig. 3e and f, the density of the SiC shells increases with the holding time at 450 °C, while the RMS roughness presents the opposite trend. These results indicate
that the CVD-pyrolysis method could be a reliable strategy to prepare high-quality SiC shells. In addition, we found that shells have a large shrinkage (39%~55%) during the pyrolysis process, while pyrolysis has little influence on the yield of the SiC shells (>95%).
Fig. 3. (a) Optical microscopy image and (b) X-ray photographs of the SiC shells (pressure =15 Pa). Variation of (c) sphericity and (d) wall thickness uniformity of the SiC shells at different working pressure.Variation of (e) density and (f) RMS roughness of SiC shells with different holding times at 450 °C.
4. Conclusion CVD-pyrolysis is an efficient way to fabricate SiC hollow microspheres with excellent qualities. The surface morphologies and compositions can be effectively adjusted by controlling the coating and heating parameters, such as the TMS flow, working pressure and holding time. The spherical degrees of shells are greater than 98% with negligible changes when the preparing parameters are altered. The wall thickness uniformities can be optimized to 95%. Shells exhibit a large shrinkage (39%~55%) during the pyrolysis process, but the shrinkage has little influence on the yield of the
SiC shells (>95%). The shells with high density and low RMS roughness can be obtained by prolonging the holding time at 450 °C.
Acknowledgments This work was supported by the Laboratory of Precision Manufacturing Technology of CAEP (Grant No. ZD16002) and the National Natural Science Foundation of China (Grant No. 51401194).
References [1] Wondrak W, Held R, Niemann E, Schmid U. Ieee T Ind Electron 2001; 48: 307-8. [2] Bhatnagar M, Baliga BJ. Ieee T Electron Dev 1993; 40: 645-55. [3] Casady JB, Johnson RW. Solid State Electron 1996; 39: 1409-22. [4] Perlado JM. J Nucl Mater 1997; 251: 98-106. [5] Li B, Zhang ZW, Wang CY, Zheng ZJ, Tang YM, Chen YL. Atomic Energy Sci Technol 2005; 39: 57-60. [6] Lindl J. Phys Plasmas 1995; 2 (11): 3933-4024. [7] Craxton RS, Anderson KS, Boehly TR, Goncharov, VN, Harding, DR, Knauer, JP, et al. Phys Plasmas 2015, 22 (11): 110501. [8] Kucheyev SO, Hamza AV. J Appl Phys 2010; 108 (9): 091101. [9] Nakai S, Takabe H. Rep Prog Phys 1996; 59: 1071-131. [10] Mcquillan BW. Fusion Tech1997; 31, 381 -5. [11] Huang H, Stephens RB, Hill DW, Lyon C, Nikroo A, Steinman DA. Fusion Sci Technol 2004; 45 (2): 214-7. [12] Norimatsu T, Takagi M, Takaki T, Morimoto K, Izawa Y, Mima K. Fusion Engineering Design
1999; 44: 449-59. [13] Takagi M, Norimatsu T, Yamanaka T, Nakai S. J Vacc Sci Technol A 1991; 9: 2145-8.
Fig. 1
Fig. 2
Fig. 3
1. SiC shells exhibit high spherical degrees and wall thickness uniformities. 2. Diameter and wall thickness of SiC hollow microspheres can be highly controlled. 3. The shrinkage has little influence on the yield of the SiC shells.
S0167-577X(17)31092-3 http://dx.doi.org/10.1016/j.matlet.2017.07.054 MLBLUE 22896
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
19 May 2017 1 July 2017 7 July 2017
Please cite this article as: C. Tang, Z. He, X. He, J. Huang, Y. Yi, H. Wang, T. Wang, Preparation and characterization of SiC hollow microspheres, Materials Letters (2017), doi: http://dx.doi.org/10.1016/j.matlet.2017.07.054
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Preparation and characterization of SiC hollow microspheres Cuilan Tanga,b, Zhibing Hea, Xiaoshan Hea, Jinglin Huanga,Yong Yib, Hongbin Wangb, Tao Wanga,* a
b
Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, PR China；
School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010,
PR China
Abstract: We present the method of chemical vapor deposition-pyrolysis for the fabrication of SiC hollow microspheres. Microspheres with a diameter of approximately 480~550 µm and wall thickness of 5~15 µ m are thus successfully prepared. The composition, especially the C/Si atomic ratio, and surface morphologies of the SiC microspheres can be flexibly adjusted by controlling the coating and heating parameters. The SiC microspheres mainly contain C-Si bonds with C/Si atomic ratios of approximately 1~3. The precursor microspheres are found to exhibit a large volume shrinkage (39%~55%) during the pyrolysis process, while pyrolysis has a negligible impact on the yield of the SiC microspheres (>95%). The spherical degrees are greater than 98% with small dispersions. The wall thickness uniformities can be optimized as high as 95%. The density of SiC microspheres can be increased by prolonging the holding time at 450 °C, while the corresponding RMS roughness can be decreased. Key words: Amorphous materials; Chemical vapour deposition; Pyrolysis; Microstructure
1.Introduction Silicon carbide (SiC) has attracted substantial attentions owing to its unique thermal, mechanical, optical and electronic properties, which make it a promising material under high temperature, high-power and high-radiation conditions [1-4]. In particular, previous studies have demonstrated that SiC hollow microspheres (shells) can realize
the argon and deuterium gas filling process under high temperatures [5]. Numerous applications can therefore be realized, for example, as the potential targets for inertial confinement fusion (ICF) experiments. At present, the main challenge in fabricating SiC shells is how to acquire beneficial properties, such as uniform morphologies, high spherical degrees and high wall thickness uniformities, for these properties will significantly affect the physical experiments [6-9]. Unfortunately, few related studies have been reported. In this paper, we develop an effective method, chemical vapor deposition (CVD)-pyrolysis, which enables excellent control of diameter and wall thickness to access SiC shells with high spherical degrees and high wall thickness uniformities. First, Si-doped
glow
discharge
polymer
(Si-GDP)
coatings
are
deposited
on
poly(α-methylstyrene) (PAMS) hollow spheres as the precursors. Here the PAMS spheres, synthesized by the droplet generator technique [10], act as mandrels. Second, the precursors are pyrolyzed at 300 °C in an inert gas to remove the PAMS. Finally, Si-doped GDP shells are pyrolyzed at 450 °C and densified at 900 °C in an argon atmosphere to convert into SiC shells. The composition, surface morphologies, root-mean-square (RMS) roughness, spherical degrees, wall thickness uniformities and densities of the prepared SiC shells are carefully studied.
2. Experimental First, Si-GDP coatings were deposited on PAMS hollow spheres (diameter 900±50 µm) by plasma enhanced chemical vapor deposition (PECVD), using tetramethyl silane (TMS), trans-2-butene (T2B) and hydrogen (H2) as feed-stock gases. H2 and T2B gas
flows were set at 10 and 0.4 sccm (standard cubic centimeters per minute), respectively. TMS flow and working pressure were varied from 0.15 to 0.4 sccm (0.15, 0.25, 0.3, 0.4 sccm) and from 5 to 25 Pa (5, 10, 15, 20, 25 Pa), respectively. The RF power was 15 W and the deposition time was 54 h. To improve the wall thickness uniformity, the PAMS spheres were placed in a revolving pan. Second, the PAMS mandrel was decomposed and volatilized by a controlled heating process, in which the temperature was slowly ramped to 300 °C under argon, to obtain pure Si-GDP shells. Finally, Si-GDP shells were converted into SiC shells by slowly pyrolyzing at 450 °C and densifying at 900 °C in argon. The holding time at 450 °C was varied from 5 to 25 h (5, 10, 15, 20, 25 h). The thermal treatment process was completed in an Al2O3 tube furnace under a steady flow of ultrahigh-purity argon. The morphologies and microstructures were characterized by a field-emission scanning electron microscope (SEM, ZEISS Merlin VP Compact). Composition and chemical bonding were studied by X-ray photoelectron spectroscopy (XPS, OMICRON VT SPM). Diameter and wall thickness tests were carried out using an X-ray camera (XTF-5011). RMS roughness and quality were measured by white light interferometer (WLI, WYKO NT1100) and analysis balance, respectively.
3. Results and discussion Fig. 1a-f shows the SEM images of SiC shells prepared by various Si-GDP precursors with the same pyrolysis process. The shells with excellent spherical shapes and free of cracks can be observed in the full-views of the SiC shells in Fig. 1a and b, which demonstrates no cracks or collapses for the shells during the pyrolysis process.
The typical surface morphologies of SiC shells prepared by various TMS flows are presented in Fig. 1c and d (TMS-0.25 and TMS-0.4). The surface of TMS-0.25 is flat and smooth without obvious defects, such as voids and domes (Fig. 1c). There are, however, many bulges and pits for TMS-0.4 (Fig. 1d), which indicates a much rougher surface. The microstructure of SiC shells presents an aggregation of closely arranged irregular particles, as shown in the insets of Fig. 1c and d. Note that the particle size could be altered through changing the TMS flows. Similarly, comparing Fig. 1e with Fig. 1f, SiC shells fabricated at different working pressures (15 Pa and 25 Pa) also possess diverse surface morphologies and microstructures. The surface is rougher and the particle is larger at 25 Pa (Fig. 1f). Hence, SiC shells with various surface morphologies and microstructures could be successfully fabricated by altering the coating parameters. According to the high resolution C1s and Si2p XPS spectra in Fig. 1g and h, the major bond in the fabricated shells is C-Si. It has been calculated that the C/Si atomic ratio could be adjusted from 1 to 3. When the TMS flow is 0.15, 0.25, 0.3, 0.4 sccm, C/Si atomic ratio of SiC shells is 2.4, 2.2, 1.3, 1.2, respectively. While, when the pressure is 5, 10, 15, 20, 25 Pa, the C/Si atomic ratio of SiC shells is 0.8, 1.31, 1.34, 1.30, 0.89, respectively. The results represent that the TMS flow has a greater influence on the C/Si atomic ratio.
Fig. 1. SEM full-views of SiC shells (a) TMS=0.25 sccm and (b) TMS=0.4 sccm. Low magnification images of SiC shells (c) TMS=0.25 sccm, (d) TMS=0.4 sccm, (e) pressure=15 Pa and (f) pressure=25 Pa. Insets are the high magnification images of the corresponding shells. XPS analysis by Gaussian fitting at a working pressure of 15 Pa (g) C1s spectra and (h) Si2p spectra.
In addition to the coating parameters, the pyrolysis process could be another effective way to adjust the surface morphologies and microstructures of the SiC shells. The results of the SiC shells fabricated with various holding times at 450 °C (5 and 15 h) are presented in Fig. 2 as an example. Many elliptical or roundness sags and crests can be observed on the surface of the 5 h sample (Fig. 2a), while no bulge is discovered for the 15 h sample (Fig. 2b). Hence, it is helpful to improve the planeness of the microspheres by appropriately prolonging the holding time at 450 °C. Additionally, the cross-section images in the insets of Fig. 2a and b show a dense structure. Fig. 2c and d provide the high-resolution C1s and Si2p XPS spectra of the 5 h
sample. The shells mainly contain C-Si bond and a small amount of C=C and Si-Si. After calculation, when the holding time is 5 and 15 h, the C/Si atomic ratio of SiC shells is 2.4 and 1.3, respectively. This is because the longer the holding time at 450 °C, the more thorough the cracking of Si-GDP.
Fig. 2. SEM images of the SiC shells with different holding times at 450 °C (a) 5 h and (b) 15 h. Insets are the corresponding cross-section images. XPS analysis of SiC with holding time of 5 h at 450 °C (c) C1s spectra and (d) Si2p spectra.
Fig. 3a and b display the optical microscopy and X-ray photograph of SiC shells prepared at the working pressure of 15 Pa. These SiC shells are black spheres with small size dispersions. The spherical degrees and wall thickness uniformities of SiC shells are relatively high (Fig. 3b). To quantitatively discuss these two geometrical properties, they are calculated by the method reported in the literature [11-13]. It can be seen that the spherical degrees of shells are greater than 98% with a negligible variation as the pressure increases (Fig. 3c), which demonstrates that pressure has little effect on the sphericity of shells. The wall thickness uniformity of SiC first increases then decreases as pressure increases (Fig. 3d). It increases to 95% when the pressure is 15 Pa. As can be seen in Fig. 3e and f, the density of the SiC shells increases with the holding time at 450 °C, while the RMS roughness presents the opposite trend. These results indicate
that the CVD-pyrolysis method could be a reliable strategy to prepare high-quality SiC shells. In addition, we found that shells have a large shrinkage (39%~55%) during the pyrolysis process, while pyrolysis has little influence on the yield of the SiC shells (>95%).
Fig. 3. (a) Optical microscopy image and (b) X-ray photographs of the SiC shells (pressure =15 Pa). Variation of (c) sphericity and (d) wall thickness uniformity of the SiC shells at different working pressure.Variation of (e) density and (f) RMS roughness of SiC shells with different holding times at 450 °C.
4. Conclusion CVD-pyrolysis is an efficient way to fabricate SiC hollow microspheres with excellent qualities. The surface morphologies and compositions can be effectively adjusted by controlling the coating and heating parameters, such as the TMS flow, working pressure and holding time. The spherical degrees of shells are greater than 98% with negligible changes when the preparing parameters are altered. The wall thickness uniformities can be optimized to 95%. Shells exhibit a large shrinkage (39%~55%) during the pyrolysis process, but the shrinkage has little influence on the yield of the
SiC shells (>95%). The shells with high density and low RMS roughness can be obtained by prolonging the holding time at 450 °C.
Acknowledgments This work was supported by the Laboratory of Precision Manufacturing Technology of CAEP (Grant No. ZD16002) and the National Natural Science Foundation of China (Grant No. 51401194).
References [1] Wondrak W, Held R, Niemann E, Schmid U. Ieee T Ind Electron 2001; 48: 307-8. [2] Bhatnagar M, Baliga BJ. Ieee T Electron Dev 1993; 40: 645-55. [3] Casady JB, Johnson RW. Solid State Electron 1996; 39: 1409-22. [4] Perlado JM. J Nucl Mater 1997; 251: 98-106. [5] Li B, Zhang ZW, Wang CY, Zheng ZJ, Tang YM, Chen YL. Atomic Energy Sci Technol 2005; 39: 57-60. [6] Lindl J. Phys Plasmas 1995; 2 (11): 3933-4024. [7] Craxton RS, Anderson KS, Boehly TR, Goncharov, VN, Harding, DR, Knauer, JP, et al. Phys Plasmas 2015, 22 (11): 110501. [8] Kucheyev SO, Hamza AV. J Appl Phys 2010; 108 (9): 091101. [9] Nakai S, Takabe H. Rep Prog Phys 1996; 59: 1071-131. [10] Mcquillan BW. Fusion Tech1997; 31, 381 -5. [11] Huang H, Stephens RB, Hill DW, Lyon C, Nikroo A, Steinman DA. Fusion Sci Technol 2004; 45 (2): 214-7. [12] Norimatsu T, Takagi M, Takaki T, Morimoto K, Izawa Y, Mima K. Fusion Engineering Design
1999; 44: 449-59. [13] Takagi M, Norimatsu T, Yamanaka T, Nakai S. J Vacc Sci Technol A 1991; 9: 2145-8.
Fig. 1
Fig. 2
Fig. 3
1. SiC shells exhibit high spherical degrees and wall thickness uniformities. 2. Diameter and wall thickness of SiC hollow microspheres can be highly controlled. 3. The shrinkage has little influence on the yield of the SiC shells.