Electromagnetic wave shielding/absorbing characteristics of CNT embedded cement composites

Abstract

This dissertation presents evaluation of multi-walled carbon nanotube (MWNT) distribution in cement matrix and impacts of the MWNT distribution on electrical and mechanical properties of MWNT-embedded cement composites. In addition, benefits of the composites were examined by applying the composites to electromagnetic (EM) wave shielding/absorbing materials.For fabrication of the MWNT-embedded cement composites, an approach to incorporate silica fume in MWNT/cement mixtures was attempted in an effort to improve dispersion state of MWNT in cement. In addition, the MWNT-embedded cement composites were fabricated under high and low flow conditions in an effort to figure out impacts of the flow condition on degree of MWNT distribution. The degree of MWNT distribution of the composites fabricated with the two approaches (silica fume addition, flow control) was compared with the degree of MWNT distribution of composites fabricated with the ultra-sonication method. To evaluate the degree of MWNT distribution in the composites, MWNT was mixed with white cement instead of ordinary Portland cement. The fractured surface of MWNT/white cement specimens was observed with an optical microscope, and then image processing & analysis procedures of obtained images were carried out.The DC and AC conductivity of the MWNT-embedded cement composites were also evaluated in order to figure out the MWNT distribution state and electrical characteristics. Image analysis and electrical conductivity results of the composites indicated that planar occupation ratio of MWNT and the conductivity increased as the flow decreased. Moreover, the composites fabricated under the low flow condition showed reproducibility in terms of the electrical properties whereas the composites fabricated under the high flow condition did not so. In the composite group fabricated with the low flow condition, specimens with SF 10 % exhibited the best electrical conductivity.The EM wave shielding effectiveness (SE)...