Time filter

Source Type

Vazquez M.,CSIC - Institute of Materials Science | Chiriac H.,National Institute of Research and Development for Technical Physics | Zhukov A.,University of the Basque Country | Panina L.,University of Plymouth | Uchiyama T.,Nagoya University
Physica Status Solidi (A) Applications and Materials Science | Year: 2011

Recognizing the importance of magnetic thin wires for science and technology, the 6th International Workshop on Magnetic Wires was held on 6-7 July 2010, in Bodrum, Turkey. A wide range of topics were addressed from technological problems of micro- and nanowire fabrication, to advanced physical effects and novel applications. Furthermore, critical discussions on the present state of knowledge and future trends arose during the Panel Session on microwires. In the present report, the main aspects addressed at the Discussion Panel and at workshop presentations are summarized with the aim to state the present and future perspectives on these wire systems. This report is focused upon four topics chosen for broad discussions at the Panel: Fabrication and processing, Magnetization reversal and Dynamics, High-frequency properties, and Technological applications. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Grimberg R.,National Institute of Research and Development for Technical Physics | Tian A.-Y.,Northumbria University
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2012

This study presents a new high-frequency electromagnetic method for a non-destructive evaluation of metallic strip gratings from printed circuit boards and of some carbon-fibre-reinforced plastic composites, allowing the detection of small defects. The electromagnetic transducer is based on a metamaterial lens realized with two conical Swiss rolls, that allows the transmission and intensification of purely evanescent modes generated in the slits of metallic strip gratings and in the dielectric that insulate the carbon fibres between them. The method and the transducer used allow the localization of metallic strip interruptions whose widths are greater than 0.2 mm, the non-alignment of carbon fibres, the breaking of carbon fibres, the lack of resin or delaminations due to impact at low energies, with spatial resolution being greater than 0.1 mm. © 2012 The Royal Society.


Chiriac H.,National Institute of Research and Development for Technical Physics | Ovari T.-A.,National Institute of Research and Development for Technical Physics
Journal of Magnetism and Magnetic Materials | Year: 2011

An overview of the recent progress and state-of-the-art results in the investigation of the amorphous glass-coated wires with nearly zero magnetostriction is presented. These versatile microwires display enhanced soft magnetic properties, which make them suitable as sensing elements in various sensors for biomedical and automotive applications. Current results on their magnetic characteristics refer to a major refinement of their coreshell magnetic structure by taking into account the interdomain wall and to the thorough analysis of the magnetization within the outer shell. Experimental techniques such as giant magneto-impedance, magneto-resistance, and magneto-optical Kerr effect measurements are employed to prove the outcome of the theoretical calculations. The impact of the magnetic structure of the outer shell on the propagation of domain walls in bistable amorphous wires is analyzed. Very recent results on the magnetization process in nearly zero magnetostrictive amorphous glass-coated wires with submicron dimensions are also reviewed. © 2011 Elsevier B.V. All rights reserved.


Doroftei C.,Al. I. Cuza University | Popa P.D.,National Institute of Research and Development for Technical Physics | Iacomi F.,Al. I. Cuza University
Sensors and Actuators, B: Chemical | Year: 2012

The nanocrystalline La 0.8Pb 0.2FeO 3 powder was prepared by novel sol-gel self-combustion method using polyvinyl alcohol. The nanosized powders were obtained by quick combustion. From the obtained powder, pressed samples were executed in shape of disks, heat treated for 40 min at 900 °C. The samples were investigated with regard to their composition and microstructure, using XRD and SEM-EDX methods, and their electric properties and response to four test gases. The compound exhibits the orthorhombic symmetry (space group Pnma) and crystallizes in the perovskite-like cell of LaFeO 3, a porous granular and uniform structure with average grain size of 250 nm and an effective porosity of 31%. The La 0.8Pb 0.2FeO 3 sensors show p-type semiconducting properties for all studied gases within the temperature range of 100-380 °C. The La 0.8Pb 0.2FeO 3 sensors have the best response and selectivity to methanol gas. The highest response to methanol gas (400 ppm) is 146.6 at 230 °C. © 2011 Elsevier B.V. All rights reserved.


Grimberg R.,National Institute of Research and Development for Technical Physics
Strojniski Vestnik/Journal of Mechanical Engineering | Year: 2011

Appearing more than 125 years ago, the electromagnetic nondestructive evaluation has transformed form "art" to an engineering science, which is recognized. This development supposed the elaboration of theories based on Maxwell equations, of adequate transducers and afferent measurement electronics. Together with the development of computer science, the domain has made a spectacular leap. This paper presents a review of theoretical principles, numbering a few methods for solving forward and inverse problems, a review of the principal transducers types, electronics and the possibility of automatic interpretation of control results. Few directions where the domain might develop are sketched, starting from the observation that new types of materials, structures, complex equipments that shall be controlled, permanently appear. The purpose is constituted by obtaining a much higher probability of detecting for the highest possible reliability coefficient for the electromagnetic nondestructive evaluation of materials.


Rambu A.P.,Al. I. Cuza University | Iftimie N.,National Institute of Research and Development for Technical Physics | Rusu G.I.,Al. I. Cuza University
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2012

Zinc metallic films, deposited onto different substrates, were submitted to a thermal oxidation process, in air, in order to obtain ZnO thin films. X-ray diffraction patterns revealed that as-obtained ZnO thin films were polycrystalline and have a wurtzite (hexagonal) structure. The temperature dependences of the electrical conductivity during some heating/cooling cycles were studied and the conduction mechanism was interpreted in terms of Seto model. The sensitivity of ZnO thin films, at five gases, was investigated and it was established that ethanol is the test gas that produces the most significant changes in the electrical resistance of all the studied films. Some correlations between the oxidation temperature and the substrate nature and the parameters which characterize the structural and electrical properties of ZnO thin films have been established. © 2011 Elsevier B.V. All rights reserved.


Grimberg R.,National Institute of Research and Development for Technical Physics
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2013

This paper proposes a review of electromagnetic metamaterials based on the idea that these are composite materials, their properties depending of the type and dimensions of the structural elements as well as the dimensions of unit cell. From the multitude of structural elements, only few that could present negative permittivity and negative or very high permeability in the range of radio and microwave frequency were chosen. The method of determination for the constitutive parameters (μeff and Éeff) of metamaterials based on the S parameters or transmission and reflection coefficients is presented. Moreover, some applications of metamaterials are described, the attention being focused on perfect lenses and novel structures, namely conical Swiss rolls, electromagnetic cloaks and sensors for nondestructive evaluation of materials. Given that the spatial resolution of these sensors can be substantially improved in comparison to classical sensors, the metamaterial lenses are used for the manipulation of evanescent waves. © 2013 Elsevier B.V.


Doroftei C.,Al. I. Cuza University | Popa P.D.,National Institute of Research and Development for Technical Physics | Iacomi F.,Al. I. Cuza University
Sensors and Actuators, A: Physical | Year: 2013

Rare earth oxide La0.8Pb0.2FeO3 was synthesized by a novel self-combustion method using polyvinyl alcohol as colloidal medium. The X-ray diffraction pattern (XRD) showed that La 0.8Pb0.2FeO3 oxides are single phase with orthorhombic perovskite structure; they all show p-type semiconducting properties. The gas response characteristics were obtained by measuring the sensitivity as a function of various factors like operating temperature, type and concentration of the test gas and, finally, the response time. Carbon dioxide, hydrogen, methanol, ethanol and butane were used as test gases. The La0.8Pb0.2FeO3 sensors have the best response to methanol and ethanol gas. The response to hydrogen is much smaller and it is negligible for carbon dioxide and butane. A big sensitivity between methanol and ethanol gas was obtained at different operating temperatures, even though the two alcohols have very similar properties. At a concentration of 400 ppm gas at the operating temperature of 230°C, the response to methanol is 146.6, and to ethanol is 25. At operating temperature of 280°C, the response to ethanol is 133.3, and to methanol is 18. The same sensor can be used as selective sensor for either methanol or ethanol by simply modifying the operating temperature. © 2012 Elsevier B.V.


Doroftei C.,Al. I. Cuza University | Popa P.D.,National Institute of Research and Development for Technical Physics | Iacomi F.,Al. I. Cuza University
Sensors and Actuators, A: Physical | Year: 2012

In the present work, we report the results of the influence of the Ni ions which partly substitute the Ba ions in the barium stannate (Ba 1-xNi xSnO 3, where x = 0; 0.1; 0.2; 0.5), on the structural and electronic properties, as well as on the sensitivity to humidity. With the view to obtain a porous and finer structure, thus providing a high specific surface, these materials were obtained through the precursor method of self-combustion (co-precipitation in a colloidal environment and self-combustion), followed by heat treatments. The phase composition and morphology were studied by XRD and SEM. The pure sample, as well as that with the substitution x = 0.1, are single phased after 40 min sintering at 1000 °C. For substitutions with x > 0.1 secondary phases appear, which favorably influence the humidity sensitivity. All the samples show a significant sensitivity to humidity within 22% RH and 75% RH for the substitution with x = 0 and 0.1, and 22% RH - 98% RH for the substitution with x = 0.5. For this interval, the material resistivity logarithmically decreases by over four orders. The sample with the substitution x = 0.5 is characterized by a very fine structure (∼250 nm) and a high effective porosity (47%). This sample presents a shorter absorption response time than the other samples. Its high sensitivity, its sensitivity range, linearity of the sensitivity characteristic and the quick response time recommend the material with the composition Ba 0.5Ni 0.5SnO 3 for the realization of a very good resistive humidity sensor. © 2011 Elsevier B.V. All rights reserved.


Grimberg R.,National Institute of Research and Development for Technical Physics | Savin A.,National Institute of Research and Development for Technical Physics | Steigmann R.,National Institute of Research and Development for Technical Physics
NDT and E International | Year: 2012

Metallic strip gratings have a range of applications, from printed circuits boards to filters in microwave domains. These applications impose a rigorous and rapid quality control. This paper proposes the obtaining of electromagnetic images of metallic strip gratings using evanescent waves that are formed in slits. For their detection, two procedures can be use, namely, the diffraction of evanescent waves on circular apertures and respectively, the propagation through metamaterials, conical Swiss rolls type. In this case, the spatial resolution is better than λ/1000. The use of metamaterial, conical Swiss rolls type, allows the obtaining of a resolution in the range of λ/2000, the electromagnetic image being improved. © 2011 Elsevier Ltd. All rights reserved.

Loading National Institute of Research and Development for Technical Physics collaborators
Loading National Institute of Research and Development for Technical Physics collaborators