0000000000295033
AUTHOR
Maksim Ivanov
Electromagnetic shielding efficiency in Ka-band: carbon foam versus epoxy/carbon nanotube composites
The wide application of microwaves stimulates searching for new materials with high electrical conductivity and electromagnetic (EM) interference shielding effectiveness (SE). We conducted a comparative study of EM SE in K a -band demonstrated by ultra-light micro-structural porous carbon solids (carbon foams) of different bulk densities, 0.042 to 0.150 g/cm 3 , and conventional flexible epoxy resin filled with carbon nanotubes (CNTs) in small concentrations, 1.5 wt.%. Microwave probing of carbon foams showed that the transmission through a 2 mm-thick layer strongly decreases with decreasing the pore size up to the level of 0.6%, due to a rise of reflectance ability. At the same time, 1 mm…
Dynamics of Phase Transition in 0.4NBT-0.4ST-0.2PT Solid Solution
In this paper we present dielectric spectroscopy results of NBT-(0.6-x)ST-xPT with x = 0.2 solid solution. Dielectric investigations clearly showed a relaxor—normal ferroelectric phase transition at TPT = 419 K and low temperature and low frequency dispersion similar to coexistence of dipolar glass and ferroelectric phase. The mean relaxation time above the phase transition follows Vogel—Fulcher law with following parameters: E A = 0.179 eV, τ 0 = 3.39·10−14 s, T VF = 223 K.
Dielectric properties of 0.4Na0.5Bi0.5TiO3–(0.6-x)SrTiO3–xPbTiO3 solid solutions
Abstract In this paper we present our measurements of the linear and nonlinear dielectric permittivity of 0.4 Na 0.5 Bi 0.5 TiO 3 – ( 0.6 - x ) SrTiO 3 – xPbTiO 3 solid solutions (x = 0, 0.05, 0.1, 0.15). The dielectric anomaly increases in the system with respect to the concentration of lead, showing that interactions between dipolar entities are modified. The system exhibits dipolar-glass-like behaviour at low values of x ( 0 ⩽ x 0.1 ). Relaxor behaviour emerges in the sample where x = 0.1 . Furthermore, a spontaneous first-order phase transition from relaxor to normal ferroelectric is observed at x ⩾ 0.15 . A few peculiar dispersion regions are observed in the ferroelectric phase, which …