Masanori Imai

Electrical conductivity of carbon-nanotube/cellulose composite paper

We fabricated multiwalled carbon-nanotube/cellulose composite papers and measured their temperature dependences of electrical conductivity. The dependences were described with the Sheng’s fluctuation-induced tunneling (FIT) model. A possible mechanism of the electrical conduction in the composite paper was discussed in the context of the FIT model.

Low-Frequency Noise in Carbon-Nanotube/Cellulose Composite Paper

Low-frequency noise characteristics for carbon-nanotube (CNT)/cellulose composite paper were experimentally investigated. The measured low-frequency noise exhibited 1/f characteristics and can be explained by Hooges empirical law. Large noise coefficients suggested that CNT–CNT junctions, not the CNTs themselves, are the dominant source of 1/f noise in the composite paper.

Fabrication and Characterization of Carbon Nanotube/Cellulose Composite Paper

Carbon nanotube (CNT)/cellulose composite materials were fabricated in a papermaking process optimized to form a CNT network on cellulose fibers. The measured electrical conductivity ranged from 0.05 to 671 S/m for a CNT content of 0.5–16.7 wt%, which was higher than that for other polymer composites. The measured temperature dependences of electrical conductivity were described with the fluctuation-induced tunneling model. The real permittivities were the highest in the microwave region. The unique CNT network structure is thought to be the reason for the high conductivity and permittivity values. Our CNT/cellulose composite material exhibited improved parameters without any decrease in mechanical strength, compared to other carbon materials. The near-field electromagnetic shielding effectiveness (EMI SE) measured using a microstrip line method depended on the sheet conductivity and qualitatively matched the results of electromagnetic field simulations using a finite-difference time-domain simulator. A high near-field EMI SE of 50 dB was achieved in the 5–10-GHz frequency region with 4.8-wt% composite paper. The far-field EMI SE was measured using a free-space method. Fairly good agreement was obtained between the measured and calculated results. Approximately 10-wt% CNT is required to achieve composite paper with 20-dB far-field EMI SE.