Nanocomposites and nanomaterials
Double-layer polyurethane composites with carbon nanotubes and iron oxide nanoparticles as radar absorbing materials
Eu.V. Lobko1, Yu.V. Yakovlev2, L.Yu. Matzui3, V.V. Klepko1

1Department of polymer physic, Institute of Macromolecular Chemistry. Nat. Acad. of Sci. of Ukraine. Kharkivske chaussee, 48, Kyiv-02160, Ukraine
e-mail: lobko_zhenia@i.ua
2Charles University in Prague, Prague, Czech Republic 
3Taras Shevchenko National University in Kyiv, Kyiv, Ukraine

Fig. The electromagnetic shielding efficiency for double-layer CPU composites:1 –10% Fe3O4 / 10% CNT; 2 –10% Fe3O4 / 10% CNT+10% Fe3O4.	
In the recent past, increasing attention has been paid to the materials and coatings that characterized not only with low transmittance for electromagnetic radiation, but also with high values of its absorption. Such materials can be used as electromagnetic interference (EMI) shielding materials and radar absorbing materials (RAM). 
We propose to obtain such types of composites based on cross-linked polyurethanes (CPU), filled in situ with carbon nanotubes (CNT) and nanoparticles of Fe3O4.
Figure shows the frequency dependence of transmission, which correspond to the EMI shielding efficiency (SET). The values of SET for double-layer CPU composites are equal -10÷-15 and -25÷-30 dB, respectively. It means that the shielding effect increases from 1 to 3 orders.
Table presents the values of the coefficients of the reflection (R), absorption (A) and transmission (T) of electrical magnetic irradiation for double-layer CPU composites with CNT and Fe3O4 nanoparticles at 27 GHz. 
Double-layer CPU composites	R	A	T	
10% CNT/ 10%Fe3O4	0,34	0,58	0,08	
10%Fe3O4 / 10%CNT 	0,01	0,91	0,08	
10%Fe3O4 / 10%Fe3O4 +10% CNT	0,01	0,98	0,01	
10%Fe3O4 +10%CNT / 10%Fe3O4	0,35	0,64	0,01	
Combination of layers with different structure and changing of their arrangement in respect to the incident irradiation significantly influences the electrodynamic parameters. Thus, it is possible to decrease R (to 0.1) due to drastic increasing of A (0.91-0.98).