Advances in Science and Technology Vol. 75

Abstract: We synthesized Ca-rich Bi-based superconducting whiskers by an Al2O3-seeded glassy quenched platelet method. The grown whiskers were precisely characterized by synchrotron radiation X-ray photoemission spectroscopy and high-resolution transmission electron microscopy. The Ca-rich Bi-based superconducting whiskers show a high critical current density of 2×105A/cm2 at 40K in self-field. We found that excess Ca2+ ions substitute for the Sr2+ sites and cause nano crystalline domains with shorter-period modulation embedded in the base crystalline. The embedded nano crystalline domains can result in structural distorted defects which work as strong pinning center.

Abstract: We present a statistical study of the crystalline phase distribution in Pb-Ca-Ba-Cu-O precursor films grown by spray pyrolysis technique, with thickness and composition suitable to incorporate Hg by the sealed quartz tube technique in a subsequent treatment. A series of 9 precursor thin films were deposited on MgO substrates. Interdependence among deposition temperature, solution concentration, annealing temperature and annealed time and the effect in the relative percentage of each precursor phases was studied, applying a fractional factorial design 3IV-II. Chemical composition was obtained from atomic absorption measurements. Crystalline phase identification was performed by X-ray diffraction technique (XRD) and the quantification of each one was carried out by Rietveld method. The BaPbO3, Ba4Pb3O10 ternary phases were obtained at 810°C, and the BaCuO2 phase was got between 835°C and 860°C. Deposition temperature and molarity of the solution have clear influence on the thickness of the film. The effect of deposition temperature on the film composition was observed. Introduction

Abstract: Bi-Pb-Sr-Ca-Cu-O (BPSCCO) and Bi-Pb-Sb-Sr-Ca-Cu-O (BPSSCCO) thin films were grown on MgO single crystal substrates by pulsed laser deposition. The deposition was carried out at room temperature during 90 minutes. A Nd:YAG excimer laser ( = 355 nm) with a 2 J/pulse energy density operated at 30 Hz was used. The distance between the target and substrate was kept constant at 4,5 cm. Nominal composition of the targets was Bi1,6Pb0,4Sr2Ca2Cu3O and Bi1,6Pb0,4Sb0,1Sr2Ca2Cu3OSuperconducting targets were prepared following a state solid reaction. As-grown films were annealed at different conditions. As-grown and annealed films were characterized by XRD, FTIR, and SEM. The films were prepared applying an experimental design. The relationship among deposition parameters and their effect on the formation of superconducting Bi-system crystalline phases was studied.

Abstract: A seawater magnetohydrodynamics (MHD) power generator / hydrogen generator is expected to become popular with the development of superconducting technology because of low loss and high efficiency. We have designed a new helical-type seawater MHD generator using a solenoid superconducting magnet, by considering the experimental results for a helical-type MHD ship. The experimental and computational results for the helical-type generator including the results of a recent study on hydraulic characteristics are discussed.

Abstract: The use of metamaterial for design of radar absorbing material (RAM) is discussed. The typical features of the frequency dependencies of , , ,  of composites manufactured of different types of resonant inclusions are given as an example. The RAM characteristics obtained by the use of the composites are given. It is shown that it is possible to use for RAM design the metamaterials with both the positive values of ,  and negative ones. Making use of the frequency band with negative  and  it is possible to create a RAM with low reflection coefficient in a wide range of the angles of electromagnetic wave incidence.

Abstract: In this paper we discuss the development of metamaterials containing ferromagnetic microwires which makes it possible to tune the electromagnetic response in the microwave frequency band. Metallic wire media are known to demonstrate very strong dispersion of the effective permittivity at GHz frequencies. At certain conditions, the magnetic properties of constituent wires may strongly contribute to the system losses owing to the magnetoimpedance effect, resulting in unusual dependence of the permittivity on the external magnetic or mechanical stimuli. We also demonstrate the possibility to design the wire media with a negative index of refraction utilizing natural magnetic properties of wires. The results involve theoretical modeling and measurements of the reflection/transmission spectra by free-space methods. A reasonable agreement between theoretical and experimental data is demonstrated.

Abstract: The function of metamaterials relies on their resonant response to electromagnetic waves in characteristic spectral bands. To make metamaterials homogeneous, the size of the basic resonant element should be less than 10% of the wavelength. For the THz range up to the visible, structure details of 50 nm to 30 μm are required as are high aspect ratios, tall heights, and large areas. For such specifications, lithography, in particular, synchrotron radiation deep X-ray lithography, is the method of choice. X-ray masks are made via primary pattern generation by means of electron or laser writing. Several different X-ray masks and accurate mask-substrate alignment are necessary for architectures requiring multi-level lithography. Lithography is commonly followed by electroplating of metallic replica. The process can also yield mould inserts for cost-effective manufacture by plastic moulding. We made metamaterials based on rod-split-rings, split-cylinders, S-string bi-layer chips, and S-string meta-foils. Left-handed resonance bands range from 2.4 to 216 THz. Latest is the all-metal self-supported flexible meta-foil with pass-bands of 45% up to 70% transmission at 3.4 to 4.5 THz depending on geometrical parameters.

Abstract: Artificial structures with sub-optical wavelength features are engineered to feature non-conventional values for material properties such as optical and infrared permeability and permittivity. Such artificial structures are referred to as optical and infrared metamaterials.[1] The application space of electromagnetic metamaterials includes novel sub-wavelength waveguides and antennas, true time delay devices, optical filters, and plasmonic electronic-optical interfaces.[2] In this paper presents an optical diagnostic technique adapted for measuring and analyzing bidirectional polarimetric scatter from novel photonic and infrared metamaterials of interest. This optical diagnostic technique is also broadly applicable to other optical/infrared metamaterial structures that are proposed or developed in the future. The specific project goals are a) Demonstrate a novel metamaterial characterization full-polarimetric diffuse ellipsometry technique suitable to measure desired material properties with stated uncertainty limits for novel photonic and infrared metamaterials of interest. b) Demonstrate incorporation of predictive computational codes that estimate the electro-magnetic property values for metamaterial designs and concepts of interest.

Abstract: In this paper, we present a concise summary of selected results from our recent and ongoing studies on transformation electromagnetics. Specifically, we focus on cloak/anti-cloak interactions (with possible application to sensor invisibility), and on some general classes of metamaterial slabs (made of double positive, double negative or single negative media) with interesting image displacing/reconstruction capabilities.

Abstract: We review recent theoretical and experimental breakthroughs in the realm of slow and stopped light in structured photonic media featuring negative electromagnetic parameters (permittivity/permeability and/or refractive index). We explain how and why these structures can enable complete stopping of light even in the presence of disorder and, simultaneously, dissipative losses. Using full-wave numerical simulations we show that the incorporation of thin layers made of an active medium adjacently to the core layer of a negative-refractive-index waveguide can completely remove dissipative losses – in a slow-light regime where the effective index of the guided wave is negative.