National Institute Of Materials Physics - Romania

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5781 articles found

1171. EXPERIMENTAL STUDY OF TERAHERTZ RESPONSE FROM SOME FERROELECTRIC AND DIELECTRIC MATERIALS

Authors: Banciu, MG; Nedelcu, L; Furuya, T; Hrib, L; Geambasu, DC; Trupina, L; Pantelica, D; Mihai, MD; Tani, M

Published: OCT-DEC 2019, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 20, 360, DOI:

Barium strontium titanate (BST) ferroelectric layers were deposited on high resistivity Si substrates by Pulsed Laser Deposition and Radio Frequency sputtering. The stoichiometry was measured by using the Rutherford Backscattering technique at 3.041 MeV. For sub-THz measurements of Si samples, a new resonant method placing the sample between two flanged waveguides is proposed. In the THz range, the Time Domain Spectroscopy proved to be a reliable method. Both methods show effects due to the dielectric losses of BST in that frequency range.

1172. On the development of a robust cyber security system for Internet of Things devices

Authors: Ionescu, O; Dumitru, V; Pricop, E; Buiu, O; Cobianu, C; Raneti, M; Pircalabu, S; Marica, C

Published: 2019, PROCEEDINGS OF THE 11TH INTERNATIONAL CONFERENCE ON ELECTRONICS, COMPUTERS AND ARTIFICIAL INTELLIGENCE (ECAI-2019), DOI:

Cyber security threats have escalated dramatically in the past few years, this being the main reason why the development of Internet of Things (IoT) devices was hindered and the full potential of their utility was not reached. A major step forward could be taken only by providing reliable and cheap protection against unauthorized interference from malicious users and other threats so that people can feel safe keeping their devices connected to the cloud. This paper is focused on the development of a robust cyber security solution for IoT. The device developed and presented in this paper has the capability of solving cyber security problem by using a simple and low-cost solution, that comes with the advantage of being less intrusive and easily adaptable to any Ethernet connected IoT device. The developed device has two embodiments, the first one being a simple hardware control of the communication line using a parallel channel, and the second one extending the features of the first by using the physical unclonable functions (PUF) generated by a controlled memristor for securing the data sent over the communication channel.

1173. Ferroelectric Field Effect Transistors Based on PZT and IGZO

Authors: Besleaga, C; Radu, R; Balescu, LM; Stancu, V; Costas, A; Dumitru, V; Stan, G; Pintilie, L

Published: 2019, IEEE JOURNAL OF THE ELECTRON DEVICES SOCIETY, 7, 275, DOI: 10.1109/JEDS.2019.2895367

Ferroelectric field effect transistors (FeFETs) based on lead zirconate titanate (PZT) ferroelectric material and amorphous-indium-gallium-zinc oxide (a-IGZO) were developed and characterized. The PZT material was processed by a sol-gel method and then used as ferroelectric gate. The a-IGZO thin films, having the role of channel semiconductor, were deposited by radio-frequency magnetron sputtering, at a temperature of similar to 50 degrees C. Characteristics of a typical field effect transistor with SiO2 gate insulator, grown on highly doped silicon, and of the PZT-based FeFET were compared. It was proven that the FeFETs had promising performances in terms of I-on/I-off ratio (i.e., 10(6)) and IDS retention behavior.

1174. STRUCTURAL EVOLUTION OF THE NiTi/NiFeGa SMART HYBRID MATERIAL DURING SEVERE PLASTIC DEFORMATION

Authors: Gurau, C; Gurau, G; Tolea, F; Sampath, V

Published: JUL-SEP 2019, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 14, 546, DOI:

High speed high pressure torsion (HSHPT) a patented new approach is proposed to fabricate nanocomposites. The goal of this work is to investigate the NiTi/NiFeGa bilayer hybrid material with nano- and submicrocrystalline structure under the influence of HSHPT. Apart from the grain refinement, the effectiveness of the joint are revealed scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mechanical properties of the composite layers in bulk and after severe plastic deformation are investigated. Bi-layered composite disks consisting of NiTi shape memory alloy and NiFeGa - Heusler type alloy, exhibit thermoelastic structural martensitic transformation. Submicrocrystalline structure is formed in the both layers of the hybrid material. It is also ascertained significant hardening of each layer of the hybrid as a result of HSHPT. The results highlight market differences between the bulk and the hybrid and the role of severe plastic deformation on martensitic transformation.

1175. Effects of high temperature and ultraviolet radiation on polymer composites

Authors: Ching, YC; Gunathilake, TMSU; Ching, KY; Chuah, CH; Sandu, V; Singh, R; Liou, NS

Published: 2019, DURABILITY AND LIFE PREDICTION IN BIOCOMPOSITES, FIBRE-REINFORCED COMPOSITES AND HYBRID COMPOSITES, 426, DOI: 10.1016/B978-0-08-102290-0.00018-0

1176. Fe3O4/BaTiO3 COMPOSITES WITH CORE-SHELL STRUCTURE

Authors: Tanasa, E; Andronescu, E; Cernea, M; Oprea, OC

Published: 2019, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN SERIES B-CHEMISTRY AND MATERIALS SCIENCE, 81, 180, DOI:

This paper demonstrates the possibility of the preparation of Fe3O4/BaTiO3 core-shell composites. BaTiO3-coated Fe3O4 (Fe3O4/BaTiO3) with 5-15 nm Fe3O4 nanoparticles as cores and 2.5-4 nm BaTiO3 shell thickness, was successfully prepared through coprecipitation method and sol-gel deposition technique. High-Resolution Transmission Electron Microscopy (HRTEM), Energy Dispersive X-ray Spectrometry (EDXS) and Selected-Area Electron Diffraction (SAED) showed the formation of the core-shell structure with face centered cubic Fe3O4 and tetragonal BaTiO3 phases.

1177. NiTi coated with oxide and polymer films in the in vivo healing processes

Authors: Batalu, D; Nastase, F; Militaru, M; Gherghiceanu, M; Badica, P

Published: JAN-MAR 2019, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 8, 922, DOI: 10.1016/j.jmrt.2018.06.015

Plates of NiTi chemically etched, electro-polished, and sol gel coated with XO2 (X =Ti, Si, Zr), or coated with oxides and dip-coated polymers of Dextro-Levo-lactide-co-glycolide (DL-PLG, 0.4 mu m thickness), Dextro-Levo-lactic acid (DL-PLA, 1.3 mu m) or poly methyl methacrylate polymer (PMMA, 1.7 mu m) were obtained. Smooth and uniform NiTi surfaces without significant pitting, as revealed by AFM, were prepared for chemical etching of 120 s in HF:HNO3:H2O = 1:5:4, followed by electropolishing 120 s in H2SO4:CH3OH:H2O = 1:4:5 electrolyte and using a potential of 9 V. Dip-coated layer of PMMA has shown cracks and large pores and was eliminated from further experiments. Samples of pristine and coated NiTi were in vivo implanted into rabbits and extracted after 10 and 60 days. Clinically, all implants are biocompatible; all rabbits survived and a recovery process was observed for all cases. NiTi covered with SiO2, DL-PLG and SiO2/DL-PLG have shown the best healing evolution. For 10 and 60 days good recovery was found also for NiTi coated with TiO2. Coatings of ZrO2 and ZrO2/DL-PLG have shown the poorest results. The oxide coating and the roughness R-ZJIS that contains information on the 'deep' large areas in the coatings show the strongest influence on the healing processes. Work indicates the possibility of space- and time- scale controlled variation of the functional properties. (C) 2018 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier Editora Ltda.

1178. Broadband Y-type Divider in Ku-band Using Substrate Integrated Waveguide

Authors: Fu, Y; Chan, KY; Banciu, MG; Ramer, R

Published: 2019, 2019 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2019), 42ND EDITION, 60, DOI:

This paper presents the study and analyses on substrate integrated waveguide (SIW) Y-type power dividers. In traditional configurations, a potential stop peak exists and separates the dominant frequency band. To overcome this drawback, a Y-type power divider with an enhanced bandwidth is proposed, where the reflection at the stop peak is reduced. The broadband characteristic relies on the adjustment of the TE10 and TE30 modes in the coupling region. The symmetric topology could ensure balanced phase and amplitude properties at two output ports. For the demonstration, the prototype is fabricated by the printed circuit board (PCB) process. Measurements agree well with simulations, and a fractional bandwidth of 50.26% around the centre frequency of 15 GHz is measured with 10 dB return loss.

1179. INVESTIGATION OF THE PHOTOELECTROCHEMICAL BEHAVIOR OF NANOCARBON/MESOPOROUS TiO2 FILMS

Authors: Sima, M; Vasile, E; Sima, A

Published: OCT-DEC 2019, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 14, 941, DOI:

In this work, we report the influence of nanocarbon deposited on mesoporous TiO2 by spray method on photoelectrochemical performance of the formed photoanodes. Scanning electron microscopy and transmission electron microscopy images confirmed presence of carbon nanoparticles on the surface of anatase TiO2 films. Nanocarbon decorated TiO2 photoanodes were characterized by electrochemical impedance spectroscopy and Mott-Schottky analysis. Charge recombination process was evaluated by measurement of open-circuit voltage decay after interruption the illumination Only a small enhancement of photoelectrochemical performance of these photoanodes was observed. It was attributed to increasing of charge carrier density as a result of nanocarbon deposition on TiO2 film.

1180. Mehedinti Mountains: Martel and Lazului Caves

Authors: Ponta, GML; Aldica, GV; Tulucan, T

Published: 2019, CAVE AND KARST SYSTEMS OF ROMANIA, 163, DOI: 10.1007/978-3-319-90747-5_19

Martel and Lazului are active phreatic/epiphreatic caves with a superimposed vadose morphology. Martel is a branchwork cave developed parallel with the river as a left (north) side meander and is located at about 8 m below the thalweg. The water level in the cave rises and falls along the main gallery, where the lakes/streams at the lightest rain become sumps. The cave is relatively poor in speleothems, except the fossil gallery (CS FV Gallery of Memories) located at the upstream end of the cave, but numerous erosion and corrosion features are present. Lazului is also a branchwork cave, forming a large meander on the right (south) side of the Motru Sec River, where at the lowest points of the cave, five streams are disappearing underground. Erosion and corrosion features are present, and speleothem is found occasionally in the upper level of the cave.