Browsing by Author "Braniște, Tudor"

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AERO-Ga2O3 NANOMATERIAL ELECTROMAGNETICALLY TRANSPARENT FROM MICROWAVES TO TERAHERTZ FOR INTERNET OF THINGS APPLICATIONS
(2020) Braniște, Tudor; Dragoman, Mircea; Jucov, Serghei; Aldrigo, Martino; Ciobanu, Vladimir; Iordănescu, Sergiu; Alîabîeva, Liudmila; Fumagalli, Francesco; Ceccone, Giacomo; Raevschi, Simion; Schűtt, Fabian; Adelung, Rainer; Colpo, Pascal; Gorșunov, Boris; Tighineanu, Ion
In this paper, fabrication of a new material is reported, the so-called Aero-Ga2O3 or Aerogallox, which represents an ultra-porous and ultra-lightweight three-dimensional architecture made from interconnected microtubes of gallium oxide with nanometer thin walls. The material is fabricated using epitaxial growth of an ultrathin layer of gallium nitride on zinc oxide microtetrapods fabricated using epitaxial growth of an ultrathin layer of gallium nitride on zinc oxide microtetrapods followed by decomposition of sacrificial ZnO and oxidation of GaN which according to the results of X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS) characterizations, is transformed gradually in β-Ga2O3 with almost stoichiometric composition. The investigations show that the developed ultra-porous Aerogallox exhibits extremely low reflectivity and high transmissivity in an ultrabroadband electromagnetic spectrum ranging from X-band (8–12 GHz) to several terahertz which opens possibilities for quite new applications of gallium oxide, previously not anticipated.
AERO-TiO2 PREPARED ON THE BASIS OF NETWORKS OF ZnO TETRAPODS
(2022) Ciobanu, Vladimir; Ursachi, Veaceslav; Lehmann, Sebastian; Braniște, Tudor; Raevschi, Simion; Zamalai, Victor V.; Monaico, Eduard V.; Colpo, Pascal; Nielsch, Kornelius; Tighineanu, Ion
In this paper, new aeromaterials are proposed on the basis of titania thin films deposited using atomic layer deposition (ALD) on a sacrificial network of ZnO microtetrapods. The technol-ogy consists of two technological steps applied after ALD, namely, thermal treatment at different temperatures and etching of the sacrificial template. Two procedures are applied for etching, one of which is wet etching in a citric acid aqua solution, while the other one is etching in a hydride vapor phase epitaxy (HVPE) system with HCl and hydrogen chemicals. The morphology, composition, and crystal structure of the produced aeromaterials are investigated depending on the temperature of annealing and the sequence of the technological steps. The performed photoluminescence analysis suggests that the developed aeromaterials are potential candidates for photocatalytic applications.
AERO-ZNS ARCHITECTURES WITH DUAL HYDROPHILIC–HYDROPHOBIC PROPERTIES FOR MICROFLUIDIC APPLICATIONS
(2020) Pleșco, Irina; Braniște, Tudor; Wolff, Niklas; Gorceac, Leonid; Duppel, Viola; Cinic, Boris; Mishra, Yogendra Kumar; Sarua, Andrei; Adelung, Rainer; Kienle, Lorenz; Tighineanu, Ion
Here, we report on a new aero-material, called aero-ZnS, representing self-organized architectures made of ZnS hollow micro-tetrapod struc- tures with nanoscale thin walls. The fabrication process is based on the hydride vapor phase epitaxy of CdS on sacrificial micro-tetrapods of ZnO with simultaneous or subsequent transformation of CdS into ZnS and removal of the sacrificial ZnO crystals. The nanostructure of the obtained ZnS hollow micro-tetrapods exhibits the polytypic intergrowth of wurtzite- and sphalerite-type phases perpendicular to their close packed planes. The inner surface of the micro-tetrapod walls preserves oxygen sites, as demonstrated by imaging based on electron energy- loss filtering. The self-organized aero-ZnS architecture proves to be hydrophilic under tension and hydrophobic when compressed against water. Self-propelled liquid marbles assembled using ZnS hollow micro-tetrapod structures are demonstrated.
DATE PRELIMINARE PRIVIND UTILIZAREA SPECTROSCOPIEI EDS PENTRU STUDIUL MATERIALULUI TEGULAR DIN PRIMELE SECOLE P. CHR.*
(CEP USM, 2024) Matveev, Sergiu; Braniște, Tudor; Sprincean, Veaceslav
In the mid 20th century near Sobari village (Soroca District, Republic of Moldova) was discovered an archaeological site dated with the 3rd-4th centuries AD identified as a Sântana de Mureş-Černjachov archeological culture site. Its uniqueness compared to other similar sites from the space between Prut and Dniester Rivers is determined by the presence of a stone structure enforced with mortar inside which was found a building with walls built of stone and brick, roof of tiles, glass window and peristyle made of wood pillars set on stone bases. Archaeological research statistic data reveals thousands of pieces of tile material. Besides this complex, within the limits of the site, were also identified several structures made of wood smeared with clay, one of which inside the stone precinct. The presence of such a complex in the barbarian environment at a distance of around 300 km from the Roman Empire border raised discussion regarding its origin. Several hypothesizes were advanced: according to one the site had been created by people with origins in the provincial Roman environment, according to other this site was an attempt to strengthen the seat of the local leader, other researchers included the site in the category of Roman commercial-craftsman factories etc. The researchers’ opinion regarding the origin of the tile material are divided as well, most of whom consider them to be brought from the Empire, while other think they are of local production.
ELABORAREA ȘI STUDIUL AEROMATERIALULUI ÎN BAZĂ DE TiO2 PENTRU APLICAȚII FOTOCATALITICE
(CEP USM, 2024) Busuioc, Simon; Ciobanu, Vladimir; Braniște, Tudor; Zalamai, Victor; Ursachi, Veaceslav; Monaico, Eduard; Tighineanu, Ion
We report on the fabrication process of TiO2 -based aeromaterial for environmental applica tions, such as wastewater treatment or as activated photocatalytic air filters. The TiO2 aeromate rial is obtained by Atomic Layer Deposition technique with the thickness of 50 nm on a substrate template consisting of ZnO microtetrapods, followed by the selective chemical etching of the ZnO template. The morphological and optical properties, chemical composition and crystalline quality of the fabricated aeromaterial are investigated. By implementing specific technological steps to enhance the crystalline quality of the TiO2 aeromaterial, it was possible to obtain materi als with either anatase phases or a mixed anatase-rutile phase.
PROPRIETĂȚILE FIZICE ALE STRATURILOR DE ZnO PREPARATE PE Si PRIN METODA HIDROTERMALĂ
(CEP USM, 2020) Raevschi, Simion; Gorceac, Leonid; Botnariuc, Vasile; Braniște, Tudor; Vatavu, Sergiu
Straturi subțiri, de nucleație și proprii, de ZnO au fost sintetizate pe Si prin metoda hidrotermală din soluțiile compușilor zincului folosindu-se solvenții: apă, apă + etanol, apă + metanol, apă + propanol, apă + acetonă, etanol, propanol, metanol.La prepararea straturilor de nucleație s-a folosit acetatul de zinc dihidrat, Zn(CH3COO)2·2H2O. Depunerea straturilor proprii de ZnO pe structurile nucleatea avut loc prin fierberea lor în soluție apoasă de Zn(NO 3)2+ KOH. În lucrare sunt date caracterizări structurale și morfologice ale straturilor buffer obținute,fiind demonstrată eficiența stratului buffer în prepararea straturilor de GaN.
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.
UN PINTEN DE FIER DIN SEC. IV P. CHR. DESCOPERIT LA LIPOVENI
(CEP USM, 2022-05-27) Matveev, Sergiu; Vornic, Vlad; Braniște, Tudor