2. Articole

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    SELF-PROPELLED AERO-GaN BASED LIQUID MARBLES EXHIBITING PULSED ROTATION ON THE WATER SURFACE
    (2021) Braniște, Tudor; Ciobanu, Vladimir; Schűtt, Fabian; Mimura, Hidenori; Raevschi, Simion; Adelung, Rainer; Pugno, Nicola M.; Tighineanu, Ion
    We report on self-propelled rotating liquid marbles fabricated using droplets of alcoholic solution encapsulated in hollow microtetrapods of GaN with hydrophilic free ends of their arms and hydrophobic lateral walls. Apart from stationary rotation, elongated-spheroid-like liquid marbles were found, for the first time, to exhibit pulsed rotation on water surfaces characterized by a threshold speed of rotation, which increased with the weight of the liquid marble while the frequency of pulses proved to decrease. To throw light upon the unusual behavior of the developed self-propelled liquid marbles, we propose a model which takes into account skimming of the liquid marbles over the water surface similar to that inherent to flying water lily beetle and the so-called helicopter effect, causing a liquid marble to rise above the level of the water surface when rotating.
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    TERAHERTZ SHIELDING PROPERTIES OF AERO-GaN
    (IOP Publishing Ltd, 2019) Braniste, Tudor; Dragoman, Mircea; Alyabyeva, Liudmila; Zhukov, Sergey; Ciobanu, Vladimir; Aldrigo, Martino; Raevschi, Simion; Dragoman, Daniela; Iordanescu, Sergiu; Shree, Sindu; Gorshunov, Boris; Adelung, Rainer; Tiginyanu, Ion
    The electrodynamic properties of the first aero-material based on compound semiconductor namely of Aero-GaN, in the terahertz frequency region are experimentally investigated. Spectra of complex dielectric permittivity, refractive index, surface impedance are measured at frequencies 4–100 cm−1 and in the temperature interval 4–300 K. The shielding properties are found based on experimental data. The aero-material shows excellent shielding effectiveness in the frequency range from 0.1 to 1.3 THz, exceeding 40 dB in a huge frequency bandwidth, which is of high interest for industrial applications. These results place the aero-GaN among the best THz shielding materials known today.
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    ELECTROMAGNETIC INTERFERENCE SHIELDING IN X-BAND WITH AERO-GaN
    (IOP Publishing Ltd, 2019) Raevschi, Simion; Dragoman, Mircea; Braniste, Tudor; Iordanescu, Sergiu; Aldrigo, Martino; Shree, Sindu; Adelung, Rainer; Tiginyanu, Ion
    We investigate the electromagnetic shielding properties of an ultra-porous lightweight nanomaterial named aerogalnite (aero-GaN). Aero-GaN is made up of randomly arranged hollow GaN microtetrapods, which are obtained by direct growth using hydride vapor phase epitaxy of GaN on the sacrificial network of ZnO microtetrapods. A 2 mm thick aero-GaN sample exhibits electromagnetic shielding properties in the X-band similar to solid structures based on metal foams or carbon nanomaterials. Aero-GaN has a weight four to five orders of magnitude lower than the weight of metals.