Page 526 - Book Hosokawa Nanoparticle Technology Handbook

APPLICATIONS 20 ELECTRICAL CONDUCTIVE CNT DISPERSED Si N CERAMICS
3 4
[14] K. Yamamoto, M. Higuchi, S. Shiki, M. Tsuruta and [19] A. Pogntsch, F.P. Wenzl, E.J.W. List, G. Leising,
H. Chiba: Nature, 415, 509–511 (2002). A.C. Grimsdare and K. Muellen: Adv. Mater., 14,
[15] S. Yokoyama, T. Nakahama, H. Miki and S. Mashiko: 1061–1064 (2002).
Thin Solid Films, 438–439, 452–456 (2003). [20] P. Furuta, J. Brooks, M.E. Thompson and J.M.J.
[16] S. Yokoyama, A. Otomo, T. Nakahama and S. Mashiko: Fréchet: J. Am. Chem. Soc., 125, 13165–13172 (2003).
Thin Solid Films, 393, 124–128 (2001). [21] T.D. Anthopoulos, J.P.J. Markham, E.B. Namdas and
[17] S. Yokoyama, A. Otomo and S. Mashiko: Appl. Phys. I.D.W. Samuel: Appl. Phys. Lett., 82, 4824–4826
Lett., 80, 7–9 (2002). (2003).
[18] N. Satoh, T. Watanabe, Y. Iketaki, T. Omatsu, M. Fujii [22] A. Hagfeldt, M. Grätzel: Chem. Rev., 95, 49–68 (1995).
and K. Yamamoto: Polym. Adv. Technol., 15, 159–163 [23] N. Satoh, T. Nakashima and K. Yamamoto: J. Am.
(2005). Chem. Soc., 127, 13030–13038 (2005).

APPLICATION 20

20 ELECTRICAL CONDUCTIVE CNT DISPERSED Si N CERAMICS
3
4

Si N ceramics is one of the typical engineering 10 2
3
4
ceramics with high strength, hardness, fracture tough-
ness, corrosion resistance and wear resistance. -1
Although electrical insulation is also characteristic of 10
Si N ceramics, electrical conductivity is needed
3
4
depending on the application. Recently, carbon nan- 10 -4
otubes (CNTs) with high thermal conductivity, elec- Electrical conductivity (Sm -1 )
trical conductivity and mechanical properties have 10 -7
been developed. CNT/metal or polymer composites
have been developed to improve some properties by -10
adding the small amount of CNTs [1, 2] as well as 10
CNT dispersed Al O ceramics is also reported [3, 4, 5].
3
2
Although it should be possible to improve electrical 10 -13
conductivity of Si N ceramics by using CNTs, there 0 5 10 15
4
3
is no literature on the dense CNT dispersed Si N 4 CNT content (wt%)
3
ceramics. The Y O –Al O –TiO –AlN [6] as the addi-
2
3
3
2
2
tive for lower temperature densification of Si N has Figure 20.1
4
3
been studied. In this section, CNT dispersed Si N 4 Electrical conductivity of CNT dispersed Si N ceramics.
3
4
3
ceramics developed by using the above sintering aid
will be introduced [7].
Fig. 20.1 shows the electrical conductivity of CNT-
dispersed Si N ceramics fabricated by gas-pressure
4
3
sintering technique. Although Si N ceramics without
4
3
CNTs are an insulator, their electrical conductivity
appeared suddenly in the sample with 1.8 wt% CNT
addition, having a value of 2.8 S/m. It decreased
with an increasing amount of CNTs and disappeared
at 3.6 wt% CNT addition. It then began increasing
over 4.2 wt% CNT addition. The SEM photographs in
Fig. 20.2 confirmed that -Si N grains in Si N 4
4
3
3
ceramics containing up to 3 wt% CNTs elongated to
as large as those in the sample without CNTs, and that
CNTs remained in the grain boundary of Si N 4
3
ceramics. CNTs should form an electrical conduction Figure 20.2
path in Si N ceramics, and it was observed that the Microstructure of CNT dispersed Si N ceramics (CNT:
3
4
4
3
largest amount of CNTs remained in the sample with 1.8 wt%, 1,800°C, 2 h, 0.9 MPaN ).
2
498