Synthesis and Microwave Absorbing Properties of PyC/BN Composite Powders

doi:10.3724/SP.J.1077.2013.12349

Abstract

Abstract:

PyC/BN composite powders were synthesized via chemical reaction of boric acid, urea and PyC powders at 1750℃ for 6 h in nitrogen. The phases, chemical compositions, surface morphologies and oxidation resistance of PyC/BN composite powders were characterized by XRD, XPS, SEM and DTA/TGA instruments, respectively. The microwave absorption properties of PyC/BN composite powders were measured by using a microwave network analyzer in the frequency range of 2-18 GHz. The results show that generated h-BN particles are coated on the surfaces of PyC powders with the dimension from tens of nanometers to hundreds of nanometers. Compared with PyC powders, the oxidation resistance of PyC/BN composite powders is improved. The mass of PyC/BN composite powders remains over 50% at 1200℃ whereas PyC powders are oxidized completely at 940℃. Due to higher microwave impedance, electronic displacement polarization, interface polarization, multiple scattering and λ/4 destructive interference effect, the reflectivity peak of PyC/BN composite powders reaches -27.2 dB and the bandwidth of the reflectivity below -10 dB is 2.6 GHz under the same thickness (2 mm). And the reflectivity peaks are all less than -10 dB and multiple absorbing peaks appear with the increase of thickness. PyC/BN composite powders are supposed to be ideal microwave absorbers with lighter weight, high temperature resistance and strong microwave absorption.

Key words: PyC/BN composite powders, boron nitride, oxidation resistance, microwave absorption properties

CLC Number:

TM25

ZHOU Wei, XIAO Peng, LI Yang, LUO Heng, ZHOU Liang. Synthesis and Microwave Absorbing Properties of PyC/BN Composite Powders[J]. Journal of Inorganic Materials, 2013, 28(5): 479-484.

Figures/Tables 9

Fig. 1 XRD patterns of (a) PyC powders, (b) PyC/BN precursor powders and (c) PyC/BN composite powders

Fig. 2 XPS spectra of PyC/BN composite powders

Fig. 3 SEM images of (a) pure PyC powders, (b) PyC/BN composite powders, (c) a single PyC/BN composite powder and (d) BN

Fig. 4 TGA curves of pure PyC powders and PyC/BN composite powders

Fig. 5 The real (a) and imaginary parts of permittivity of pure PyC powders and PyC/BN composite powders

Fig. 6 (a) RL curves of PyC/BN composite powders with different thicknesses, (b) the frequency dependence of matching thickness (symbol) and calculated thickness (line) for PyC/BN composite powders

Fig. 7 Diagram of PyC powders interaction with electromagnetic waves

Fig. 8 Microwave impedance of pure PyC and PyC/BN composite powders

Fig. 9 Main electromagnetic wave absorbing mechanism of PyC/BN composite powders

References 23

[1]	Lin J C. Human and environmental protection from electromagnetic emissions. IEEE Microwave Mag., 2005, 6(1): 30-34.
[2]	Im Ji Sun, Kim Jong Gu, Lee Young Seak. Fluorination effects of carbon black additives for electrical properties and EMI shielding efficiency by improved dispersion and adhesion. Carbon, 2009, 47(11): 2640-2647.
[3]	Singh Vivek K, Shukla Anuj, Patra Manoj K, et al. Microwave absorbing properties of a thermally reduced graphene oxide/nitrile butadiene rubber composite. Carbon, 2012, 50(6): 2202-2208.
[4]	WANG Chen, KANG Fei-Yu, GU Jia-Lin. Synthesis and microwave absorbing properties of FeCoNi alloy particles/graphite flaky composites. Journal of Inorganic Materials, 2010, 25(4): 406-410.
[5]	Cao Mao-Sheng, Song Wei-Li, Hou Zhi-Ling, et al. The effects of temperature and frequency on the dielectric properties, electromagnetic interference shielding and microwave- absorption of short carbon fiber/silica composites. Carbon, 2010, 48(3): 788-796.
[6]	XIE Wei, CHENG Hai-Feng, CHU Zeng-Yong, et al. Microwave absorbing properties of short hollow carbon fiber composites. Journal of Inorganic Materials, 2008, 23(3): 481-485.
[7]	Al-Saleh Mohammed H, Sundararaj Uttandaraman. Electromagnetic interference shielding mechanisms of CNT/polymer composites. Carbon, 2009, 47(7): 1738-1746.
[8]	ZHAO Dong-Lin; SHEN Zeng-Min. Preparation and microwave absorbing properties of microwave absorbing materials containing carbon nanotubes. Journal of Inorganic Materials, 2005, 20(3): 608-612.
[9]	Wen G., Wu G. L, Lei T Q, et al. Co-enhanced SiO2-BN ceramics for high-temperature dielectric applications. J. Eur. Ceram. Soc., 2000, 20(12): 1923-1928.
[10]	Zhang Wei-Ru, Wang Chong-Hai, Liu Jian, et al. Study on high properties and microwave-transmitting Si3N4-BN based ceramic composites. Bulletin of the Chinese Ceramic Society, 2003(3): 3-6.
[11]	Cofer Cameron G., Economy James. Oxidative and hydrolytic stability of boron nitride — a new approach to improving the oxidation resistance of carbonaceous structures. Carbon, 1995, 33(4): 389-395.
[12]	Che R C, Peng L M, Duan X F, et al. Microwave absorption enhancement and complex permittivity an permeability of Fe encapsulated within carbon nanotubes. Adv. Mater., 2004, 16(5): 401-405.
[13]	Sumfleth Jan, Prehn Kirsten, Wichmann Malte H G, et al. A comparative study of the electrical and mechanical properties of epoxy nanocomposites reinforced by CVD and arc-grown multi-wall carbon nanotubes. Compos. Sci. Technol., 2010, 70(1): 173-180.
[14]	Wang Xiangdong, Qiao Guanjun, Jin Zhihao. Preparation of SiC/BN nanocomposite powders by chemical processing. Mater. Lett., 2004, 58(9): 1419-1423.
[15]	Watanabe M O, Sasaki T, Itoh S, et al. Structural and electrical characterization of BC2N thin films. Thin Solid Films, 1996, 281-282: 334-336.
[16]	Huang Fu Lin, Cao Chuan Bao, Xiang Xu, et al. Synthesis of hexagonal boron carbonitride phase by solvothermal method. Diamond Relat. Mater., 2004, 13(10): 1757-1760.
[17]	Das M, Basu A K, Ghatak S, et al. Carbothermal synthesis of boron nitride coating on PAN carbon fiber. J. Eur. Ceram. Soc., 2009, 29(10): 2129-2134.
[18]	Bao Tianjiao, Zhao Yan, Su Xiaofeng, et al. A study of the electromagnetic properties of cobalt-multiwalled carbon nanotubes (Co-MWCNTs) composites. Mater. Sci. Eng., B, 2011, 176(12): 906-912.
[19]	Inui T, Konishi K, Oda K. Fabrications of broad-band RF-absorber composed of planar hexagonal ferrites. IEEE Trans. Magn., 1999, 35(5): 3148-3150.
[20]	Cao Maosheng, Zhu Jing, Yuan Jie, et al. Computation design and performance prediction towards a multi-layer microwave absorber. Mater. Des., 2002, 23(6): 557-564.
[21]	Vinoy K J, Jha R M. Radar Absorbing Materials: From Theory to Design and Characterization. Dordrecht, The Netherlands: Kluwer Academic Publishers, 1996.
[22]	Ramo S, Whinnery J R, Van Duzer T. Fields and Waves in Communication Electronics, 3rd ed. New York: John Wiley and Sons, 1994.
[23]	Chen Y J, Cao M S, Wang T H, et al. Microwave absorption properties of the ZnO nanowire-polyester composites. Appl. Phys. Lett., 2004, 84(17): 3367-3369.