Microstructures and Flexural Properties of C/C Composites Doped with CNTs by Electrophoretic Deposition

doi:10.15541/jim20150301

Abstract

Abstract:

Carbon nanotubes (CNTs) were deposited uniformly on 1 k carbon cloth by electrophoretic deposition (EPD). After that, CNT-doped clothes were stacked and densified by pyrocarbon via chemical vapor depositon (CVD) to prepare two dimensional (2D) carbon/carbon (C/C) composites. Effects of EPD CNTs on CVD process, microstructure and flexural property of 2D C/C composites were investigated. Results show that EPD CNTs are dispersed in the plane parallel to carbon fiber surface with random orientations and a high distribution density, leading to the decrease of densification rate of EPD CNT-doped C/C composites and the formation of pyrocarbon with high L_cand small L_a values. EPD CNTs increase the flexural strength and modulus of C/C composites and the improvements can reach 31.4% and 13.9% when the loading of EPD CNTs is 0.74wt%, with corresponding flexural strength and modulus being 150.83 MPa and 23.44 GPa, respectively. Further increasing the dope of EPD CNTs can decrease the flexural property of C/C composites, resulting in their bulk density decrease. The introduction of EPD CNTs changes the fracture mode of C/C composites from brittle fracture to pesudo-plastic fracture, which is related to the change of pyrocarbon in microstructures and the resulted carbon fiber pullout.

Key words: C/C composite, electrophoretic deposition, carbon nanotube, microstructure, flexural property

CLC Number:

TB332

QI Le-Hua, SHU Yang, LI He-Jun, LI Yun-Yu, MA Hai-Li, SONG Qiang. Microstructures and Flexural Properties of C/C Composites Doped with CNTs by Electrophoretic Deposition[J]. Journal of Inorganic Materials, 2016, 31(2): 201-206.

Figures/Tables 9

Fig. 1 TEM image of CNTs used in this work for EPD

Fig. 2 SEM images of carbon fiber clothes doped with CNTs by EPD for different time (a) 0 s; (b) 20 s; (c) 40 s; (d) 60 s

Fig. 3 Bulk density of EPD CNTs doped C/C samples as a function of CVD time

Fig. 4 Microstructures by PLM of EPD CNTs doped C/C samples (a) C/C; (b) CNT0.35wt%-C/C; (c) CNT0.74wt.%-C/C; (d) CNT1.06wt.%-C/C

Fig. 5 XRD patterns of carbon matrices of EPD CNTs doped C/C samples

Table 1 Lattice parameters of the four kinds of C/C composites

Samples	2θ/(°)	d₀₀₂/nm	L_c/nm
Pure-C/C	25.96	0.3431	5.86
CNT_0.35wt%-C/C	25.98	0.3427	6.16
CNT_0.74wt%-C/C	26.04	0.3420	15.18
CNT_1.06wt%-C/C	25.97	0.3429	5.86

Table 2 Flexible performances of the four kinds of C/C composites

Composites	Bulk density/ (g•cm^-3)	Flexible modulus/GPa	Flexible strength/MPa
Pure-C/C	1.64±0.01	20.58±0.68	114.75±12.01
CNT_0.35wt%-C/C	1.63±0.01	21.69±0.73	125.82±14.36
CNT_0.74wt%-C/C	1.61±0.02	23.44±0.97	150.83±13.61
CNT_1.06wt%-C/C	1.55±0.02	22.08±0.79	126.87±12.59
CNT_1.31wt%-C/C	1.45±0.03	19.82±0.67	117.56±10.12

Fig. 6 Load-displacement curves of different C/C composites in flexural tests

Fig. 7 SEM images of flexural fracture surface of pure C/C (a,b) and EPD CNTs doped C/C (c-f) composites

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