National Institute Of Materials Physics - Romania

Publications

5714 articles found

1291. Application of Biocompatible Magnetite Nanoparticles for the Removal of Arsenic and Copper from Water

Authors: Iconaru, SL; Beuran, M; Turculet, CS; Negoi, I; Teleanu, G; Prodan, AM; Motelica-Heino, M; Guegan, R; Ciobanu, CS; Jiga, G; Predoi, D

Published: 2018, 7TH INTERNATIONAL CONFERENCE ON STRUCTURAL ANALYSIS OF ADVANCED MATERIALS (ICSAAM 2017), 1932, DOI: 10.1063/1.5024168

The progress of nanotechnology made possible the use of nanomaterials as adsorbents and magnetic iron oxides represents one of the first generations of nanoscale materials used in environment technologies [1]. A systematic characterization of commercial magnetite (Fe3O4) is presented in this research. The commercial (Fe3O4) magnetic adsorbents were characterized by various characterizations methods such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX). This study was also focused on the study of adsorption isotherms and the kinetics evaluation. X-ray studies indicated that As3+ and Cu2+ removed by Fe3O4 did not seem to alter the structure of Fe3O4 but they were highlighted in the EDX analysis. In addition, the SEM studies were consistent with the XRD results. The rate of adsorption of contaminants, in contaminated solutions decreases when the amount of contaminant increases in all experiments performed. The results revealed that Fe3O4 nanoparticles are promising candidates which could be used as sorbents for the removal of arsenic from the marine environment, for site remediation and groundwater treatment.

1292. Experimental Researches of the Grease Durability via Microscopic Investigation

Authors: Radulescu, I; Radulescu, AV; Vasiliu, F

Published: 2018, 8TH INTERNATIONAL CONFERENCE ON ADVANCED CONCEPTS IN MECHANICAL ENGINEERING, 444, DOI: 10.1088/1757-899X/444/2/022009

The working life of a bearing depends on the aging characteristics of the lubricant. Aging produces physical, structural and rheological modifications in the grease that have rarely been studied from an overall stand-point. Also, analysis of used greases can be a valuable source of information on the mechanisms involved when a bearing is lubricated with grease. From this point of view, it is very useful to establish a few criteria for the grease life time, as follows: modification of the physical and chemical properties of the greases, modification of the rheological parameters, modification of the global electrical resistance of the grease film and modification of the microscopically grease structure and apparition of the wear particles. The paper proposes a comparative study of greases in the fresh state and after use in ball bearings, analysing the modification of the rheological and structural properties. The mechanical aging test was carried out on an experimental stand and the grease structure was studied using a scanning electron microscope. The rheological properties were studied on a cone and plate Brookfield viscometer.

1293. Surface States- and Field-Effects at GaAs(100) Electrodes in Sodium Dodecyl Sulfate Acid Solution

Authors: Enache, M; Negrila, C; Anastasescu, M; Dobrescu, G; Lazarescu, MF; Lazarescu, V

Published: 2018, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, 165, H3017, DOI: 10.1149/2.0031804jes

Sodium dodecyl sulfate (SDS) effects at the electrified p- and n-GaAs(100)/H2SO4 interfaces were investigated by EIS, XPS and AFM. XPS data revealed that under the open circuit conditions, SDS adsorption on GaAs(100) results in a protective overlayer which prevents the further oxidation in air of both types of semiconductor surfaces. The dopant nature is, however, decisive for the way of bonding the surfactant molecule to the surface. At the p-doped substrate, SDS adsorbs mainly at As sites by its hydrocarbon tail and by the anion head to the Ga sites at the n-doped one. Although the surfactant behaves as a dipole under the applied potential control, the dopant type plays a key role in the SDS interaction with GaAs(100) electrodes too. EIS data evidenced that SDS interaction with n-GaAs(100) electrode brings a pronounced decrease of the capacitive contribution of the surface states and a shift of the flatband potential to less negative values, unlike the p-doped one, where no significant change in its electronic properties was observed. These results were rationalized in terms of surface states- and field-effects operating at the electrified interfaces under discussion. (C) The Author(s) 2017. Published by ECS.

1294. Enhanced photocurrent in GeSi NCs/TiO2 multilayers

Authors: Palade, C; Slav, A; Cojocaru, O; Teodorescu, VS; Lazanu, S; Stoica, T; Sultan, MT; Svavarsson, HG; Ciurea, ML

Published: 2018, CAS 2018 PROCEEDINGS: 2018 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 76, DOI:

GeSi NCs / TiO2 multilayers with enhanced photocurrent properties were prepared and studied. Multilayers of TiO2 /(GeSi/TiO2)x2 /Si-p were deposited by magnetron sputtering and annealed by RTA at 700 degrees C for GeSi NCs formation. A post-annealing hydrogenation in plasma was performed on multilayers for healing of defects acting as traps and/or recombination centers and consequently producing the photocurrent enhancement. We studied the electrical and photoconductive properties of multilayers annealed by RTA and post-annealing hydrogenated. The current - temperature dependence reveals the conduction mechanisms in GeSi NCs / TiO2 multilayers RTA annealed, i.e. thermal activation of carriers to extended states (0.31 eV activation energy), the electron tunneling mechanism to nearest neighbors (T-1/2 behavior) and Mott variable range hopping (T-1/4 dependence). The photocurrent spectra made on multilayers structures hydrogenated for 10, 20 and 30 min evidence the photocurrent increasing up to 50%, showing that the hydrogenation is a suitable treatment for enhancing photocurrent. All photocurrent spectra present a dominant maximum (920 nm) and two shoulders (similar to 770 and similar to 1060 nm).

1295. Modeling issues regarding thermal conductivity of graphene-based nanocomposites

Authors: Sandu, T; Gologanu, M; Voicu, R; Boldeiu, G; Moagar-Poladian, V

Published: 2018, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 21, 92, DOI:

Modeling thermal conductivity of graphene-based nanocomposites is analyzed from an effective medium approximation point of view, where interfacial thermal resistance and arbitrary shape of the fillers are considered. Two approximations, Maxwell-Garnett and coherent potential approximation, are used to show that the usual oblate spheroidal shape approximation of graphene nanodots is not satisfactory to model thermal conductivity in graphene-based composites.

1296. Review of polarization components for infrared imaging systems: from wire-grid structured surfaces to reconfigurable metasurfaces

Authors: Simioniuc, CC; Rizea, A; Marin, C

Published: MAY-JUN 2018, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 20, 246, DOI:

Infrared imaging polarimetry with structured surfaces components allows performance enhancement for observation, supervision, identification devices, generally far-field detection in low visibility conditions (night, fog, smog, haze, smoke, heavy rainfall, underwater conditions), for civil applications, e.g. environmental monitoring or communications, which aims to reduce the risk of traffic accidents, as well as defense and security purposes, where a tactical advantage is needed. Other applications aim at improving the performance of sub-wavelength imaging systems: spatial scanning, optical flaw detection, microscopies, medical tomography or cancer diagnostics systems, generally near-field range investigation. We review many important polarization components from wire-grid structured surfaces to reconfigurable metasurfaces, that can be achieved in order to manage sub-wavelength near-field details and their transfer in far-field by polarimetry techniques without moving parts. Advanced research is needed to show which concept will prevail in the market for the achievement of ultracompact polarization optical components and their integration into a functional model of polarization state analyzer for imaging systems with high efficiency in long wave infrared.

1297. CERAMIC THIN FILMS DEPOSITED BY SPIN COATING AS COATINGS FOR METALLIC IMPLANTS

Authors: Busuioc, C; Constantinoiu, I; Enculescu, M; Beregoi, M; Jinga, SI

Published: 2018, REVISTA ROMANA DE MATERIALE-ROMANIAN JOURNAL OF MATERIALS, 48, 406, DOI:

Ceramic thin films belonging to SiO2-P2O5-CaO-MgO-ZnO-CaF2 system were obtained by combining the sol-gel approach with the spin coating technique. Titanium plates were employed as substrates. The deposited coatings were characterized in terms of composition, structure and morphology with the help of the following methods: X-ray diffraction, Fourier - transform infrared spectroscopy and scanning electron microscopy coupled with energy - dispersive X-ray spectroscopy. In order to assess the bioactivity of a potential metallic implant covered with such layers, the samples were immersed in simulated body fluid for 14 days and their surface was investigated. The results showed that the thin films calcined at a lower temperature have a better biological response due to the vitroceramic nature.

1298. Structural, dielectric and piezoelectric properties of the ferroelectric PZT-BT ceramic compounds

Authors: Miclea, C; Miclea, CF; Amarande, L; Miclea, CT; Cioangher, M

Published: SEP-OCT 2018, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 20, 565, DOI:

Ceramic compounds of ferroelectric lead zirconate titanate (PZT) and ferroelectric barium titanate (BT) were prepared from nanopowders corresponding to the formula (1-x)PZT.xBT with x = 0; 0.1; 0.2 ... 0.9; 1. The samples were investigated by X-ray diffraction and electron microscopy and the piezoelectric properties were determined by means of an impedance analyzer. The sintering process is complex since samples densify at different temperatures depending on the composition resulting in different morphostructures. Accordingly, the piezoelectric properties show unusual behavior discussed in terms of different grain size and composition. A remarkably high enhancement of the relative dielectric constant, epsilon(r) coupled with maxima in both, piezoelectric charge constant d(33) and the piezoelectric voltage constant g(33), is observed for x = 0.4 while the values of the coupling coefficient kp are still high similar to those of pure PZT.

1299. LOW-TEMPERATURE FORMATION OF 312 PHASE IN Ti-Si-C TERNARY COMPOUND

Authors: Crisan, AD; Crisan, O

Published: JAN-MAR 2018, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 13, 162, DOI:

We report on the formation of the Ti3SiC2 nanolaminate phase in the Ti-Si-C thin film system, using a UHV magnetron sputtering technique with top mounted sample holder, from elemental and compound targets. The formation of the Ti3SiC2 (or 312 phase) has been evidenced by detailed X-ray diffraction analysis followed by full-profile quantitative analysis of the obtained diffractograms. It has been proven that for deposition temperatures as low as 500 degrees C, there is a significant amount of 312 phase obtained in the deposited films, in co-existence with the majority TiC phase. This amount increased to about 21% when the deposition temperature was raised to 650 degrees C. The ternary 312 phase becomes predominant at around 60% relative abundance for slight off-stoichiometric, Si increased, content of the alloy, for temperatures as low as 650 degrees C. The conditions for improving the relative abundance of the 312 phase within our experimental setup are pointed out and explained in terms of a nucleation and growth model of nanostructure formation from the amorphous precursor (?).

1300. CHARACTERIZATION OF SURFACE AND INTERFACE OF Fe-C STEEL UNDER ELECTROLYTIC GALVANIZATION

Authors: Bibicu, I; Bulea, C; Diamandescu, L; Rus, V; Popescu, T; Mercioniu, I

Published: JUL-SEP 2018, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 19, 430, DOI:

Low carbon Fe-C steel surface has been studied before and after electrolytic galvanization. The corrosion products formed under atmospheric conditions on the Fe-C steel were identified and characterised by X-ray diffraction (XRD), transmission Mossbauer spectroscopy, conversion electron Mossbauer spectroscopy (CEMS), and conversion X-ray Mossbauer spectroscopy (CXMS). In decreasing order of abundance the found corrosion phases were magnetite, hematite, and goethite. After the surface preparation, an electrolytic galvanization process was applied. A magnetic anisotropy was evidenced after preparation, in the superficial layer of around 250 nm thickness. Scanning electron microscopy (SEM) analyses evidenced the formation of a uniform thin Zn film of 8 mu m at the surface of steel. No other Fe-Zn phases were identified at the steel-Zn interface.