National Institute Of Materials Physics - Romania

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5714 articles found

1101. DENSITY OF ADSORBED SURFACE SPECIES FOR CYANOPHENYL ALKYL BENZOATES CONFINED TO AEROSIL A380: DEVELOPMENT OF THE EVALUATING ALGORITHM FOR ATTACHMENT BY TWO TYPES OF BONDS

Authors: Frunza, S; Frunza, L; Ganea, CP; Zgura, I; Schonhals, A

Published: 2019, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN-SERIES A-APPLIED MATHEMATICS AND PHYSICS, 81, 236, DOI:

We found previously how to estimate the density of the adsorbed surface species in the case of the molecules interacting to the oxide support surface by one type of bond. Here this algorithm is developed for the case of the molecules which can be bonded to the support surface by two types of bonds. The adsorption assumptions are similar to those considered in the case of only one type of bond. The calculation is exemplified for some composites of cyanophenyl alkylbenzoates (CPnBs) (n is the number of carbon atoms in the alkyl chain) interacting with Aerosil A380. The interaction takes place by hydrogen bonding between the -OH groups or the support and the functional groups of the CPnB molecules. The estimated values of the total surface density of CPnBs agree well with those found for the composites containing related but simpler molecules.

1102. Capatanii/Parang Mountains: Polovragi Cave-Oltetului Gorge Karst Area

Authors: Ponta, GML; Aldica, GV; Dumitru, R

Published: 2019, CAVE AND KARST SYSTEMS OF ROMANIA, 91, DOI: 10.1007/978-3-319-90747-5_12

The Polovragi Cave-Oltetului Gorge karst area is about 3 km(2) in size and is traverse by the Oltet River through a spectacular narrow gorge, which represents the natural boundary between Parang Mountains to the west and Capatanii Mountains in the east. These mountains are part of the Southern Carpathian. Focul Viu Caving Club surveyed the Polovragi Cave between 1975 and 1985. In parallel with the survey activities in the main cave developed on the first level, several smaller caves were identified on both sides of the Oltetului Gorge. These caves are located on the second and third levels, which are interrelated with different peneplanation events that occurred in the Carpathians. In 2000, Focul Viu began working in the cave again, replacing gates, removing trash, digging to open new passages, and performing underwater explorations. By the end of 2011, new passages were found in the Hope Chamber and Costin Gallery, extending the total length of the cave to 10,793 and 92 m in vertical range. The Polovragi Cave along with two other smaller caves is presented in this chapter. The Polovragi Cave is the third longest cave in the Southern Carpathians and the eleventh in Romania. One of the smaller caves hosts an important bat colony, and the other one, with 800 m of passages, hosts Ursus spelaeus bones and deposits of saltpeter. The Bones Cave (Pestera cu Oase) located on the western side of the gorge (opposite side of Polovragi Cave) at a higher elevation is an old meander of the Oltet River.

1103. STRUCTURAL, DIELECTRIC AND PYROELECTRIC PROPERTIES OF Nb AND Fe DOPED PZT CERAMICS

Authors: Stancu, V; Amarande, L; Botea, M; Cioangher, M; Tomulescu, A; Iuga, A; Pintilie, L

Published: JAN-MAR 2019, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 14, 230, DOI:

Lead zirconate titanate doped with iron and niobium (PZFNT) was prepared by conventional processing technique, solid state synthesis method. The influence of dopants on the microstructure, ferroelectric and pyroelectric properties was investigated. XRD data reveals a perovskite structure near to the lead zirconate phase. The relative density of PZFNT is approximate 90%, with average grains size of 6.45 mu m.

1104. 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.

1105. 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.

1106. 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.

1107. 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.

1108. 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

1109. 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.

1110. 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.