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Different magnetic and magnetotransport properties of a hexagonal Ni2In-type MnCo0.8V0.2Ge magnetic shape memory alloy are investigated. The parent MnCoGe alloy undergoes first order martensitic phase transition (MPT) at 650 K during cooling and orders ferromagnetically (FM) below 345 K. V-doping at the cobalt site decreases the MPT temperature and affects the lattice parameters that induces a short range antiferromagnetic (AFM) interaction in this intrinsically FM system at low temperature. The studied alloy shows three important magnetofunctional properties namely exchange bias effect, magnetocaloric effect, and magnetoresistance which indicate that the alloy may be a potential candidate for practical applications. [ABSTRACT FROM AUTHOR]

This paper deals with phase change materials (PCMs), used in conjunction with thermal conductivity enhancer (TCE), as means of thermal management of electronic systems. This work was motivated by the need for short term thermal management of high packing density equipments (such as in avionics). Eicosane is used as PCM, while aluminium pin or plate fins are used as TCE. The test section considered in all cases is 42×42 mm square base with TCE height of 25 mm. An electronic heater producing 4, 6 and 8 W was used to simulate the heat generation of electronic chips. Various volumetric percentages of TCE in the conglomerate of PCM and TCE were considered, namely, 0, 2, 8, 18 and 27%. The case with 8% volumetric percentage of TCE was found to have the best thermal performance. A numerical model was developed to enable interpretation of experimental results and to perform parametric studies. [ABSTRACT FROM AUTHOR]

The structural and optical properties of Er3+ doped with Al(NO3)3 sol-gel glass have been investigated. Thermo gravimetric analysis (TGA) shows an enormous mass loss between 40° to 190° C. Important structural changes on heating have been revealed by two endothermic peaks of Differential Thermal Analysis (DTA) which is further confirmed by Infra red (IR) spectroscopy and X-Ray Diffraction (XRD) analysis[double_underdot] X-Ray Diffraction and Scanning Electron Micrograph of the sample heated to 800° C suggests the particle size in nanometers. The oscillator strengths of the transitions in the absorption spectrum are parameterized in terms of three Judd-Ofelt (J.O) intensity parameters (Ω2, Ω4 and Ω6). The radiative property for the potential lasing transition 4S3/2→4I15/2 of Er3+ is found to be very encouraging for the studied glass. [ABSTRACT FROM AUTHOR]

A Faraday cup assembly is employed to study the charge distribution in a dust beam. The Faraday Cup scans the dust beam across its diameter and the dust particle current is noted in an Electrometer. The variation of the pico ampere current, carried by the charged dust particles in the beam, is studied with change in the gas pressure. The observations provide an insight into the variation of the charge to mass ratio in a dust beam. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper presents two of our recent developments in the area of III–V ternary and quaternary materials growth technology for high efficiency thermophotovoltaic (TPV) cells. It is well recognized that growth of TPV cell materials from melts or solutions presents the most economical option. We have investigated bulk substrate growth from melt as well as epitaxial growth from liquid phase. In the bulk crystal growth area, we have been concentrating on the growth of 50 mm or larger diameter device quality ternary III–V substrates. In the epitaxial growth arena, we have developed a new thermochemistry for growing ternary and quaternary compounds on binary substrates from quaternary solutions. Some of the recent results pertaining to the bulk growth of GaInSb and epitaxial growth of GaInAs, InAsSb and GaInAsSb on GaAs substrates will be discussed here. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper presents results of experimental and theoretical research on antimonide- based thermophotovoltaic (TPV) materials and cells. The topics discussed include: growth of large diameter ternary GalnSb bulk crystals, substrate preparation, diffused junction processes, cell fabrication and characterization, and, cell modeling. Ternary GalnSb boules up to 2 inches in diameter have been grown using the vertical Bridgman technique with a novel self solute feeding technique. A single step diffusion process followed by precise etching of the diffused layer has been developed to obtain a diffusion profile appropriate for high efficiency, p-n junction GaSb and GalnSb thermophotovoltaic cells. The optimum junction depth to obtain the highest quantum efficiency and open circuit voltage has been identified based on diffusion lengths (or minority carrier lifetimes), carrier mobility and experimental diffused impurity profiles. Theoretical assessment of the performance of ternary (GalnSb) and binary (GaSh) cells fabricated by Zn diffusion in bulk substrates has been performed using PC-1D one-dimensional computer simulations. Several factors affecting the ceil performances such as the effects of emitter doping profile, emitter thickness and recombination mechanisms (Auger, radiative and Shocldey-Read-Hall), the advantages of surface passivation and the impact of dark current due to the metallic grid will be discussed. The conditions needed for diffused junction cells on ternary and binary substrates to achieve similar performance to the epitaxially grown lattice- matched quaternary cells are identified. [ABSTRACT FROM AUTHOR]

Magnetic and magnetocaloric properties of a new class of shape memory alloy of nominal composition Mn0.875Fe0.125CoGe have been investigated. We observe a clear virgin line effect in the isothermal magnetization data around the martensitic transition region which indicates a field induced first order transition. The sample exhibits reasonably large magnetocaloric effect (a peak value of 8.9 J kg−1 K−1 for the magnetic field changing from 0 to 42kOe) around the magnetostructural transition near room temperature (∼ 272 K). [ABSTRACT FROM AUTHOR]

Different physical and functional properties of Mn0.8Cr0.2CoGe alloy has been investigated through structural, magnetic and electrical transport measurements. Substitution of Cr for Mn results significant decrease in both structural and magnetic transition temperature and brings them well below the room temperature. A reasonable amount of conventional magnetocaloric effect (ΔS∼ - 2.22 J/kg-K for magnetic field (H) changing from 0 to 50 kOe) with large relative cooling power (251.7 J/kg for H changing from 0 to 50 kOe) has also been observed around the region of transition. On thermal cycling through the structural transition, noticeable training effect is found to be associated with the resistivity of the alloy. [ABSTRACT FROM AUTHOR]

The perovskite manganite of nominal composition Eu0.5Sr0.5MnO3 (ESMO) has been investigated through transport and magnetotransport measurements. We observe field induced transition from spin glass insulating state to ferromagnetic metallic state at 80 K. Ground state of the sample at low temperature depends strongly on the previous history of applied magnetic field. We also observe large magnetoresistance (99.98% for 150 kOe of applied magnetic field) below 100 K, which is connected to the field induced transition present in the sample. [ABSTRACT FROM AUTHOR]

This paper assesses the performance of antimonide-based thermophotovoltaic cells fabricated by different technologies. In particular, the paper compares the performance of lattice matched quaternary (GalnAsSb) ceils epitaxially grown on GaSb substrates to the performance of ternary (GalnSb) and binary (GaSb) cells fabricated by Zn diffusion on bulk substrates. The focus of the paper is to delineate the key performance advantages of the highest performance-to-date of the quaternary cells to the performance of the alternative ternary and binary antimonide-based diffusion technology. The performance characteristics of the cells considered are obtained from PC-ID simulations using appropriate material parameters. [ABSTRACT FROM AUTHOR]

The Materials Research Collaborative Access Team (MRCAT) beamline 10-ID at the Advanced Photon Source has been in Commissioning since January 1998. This Beamline has been designed as a flexible spectroscopy, scattering, and diffraction facility for the study of materials in situ. Over 70 users have performed experiments at the beamline during this period. Details about the beamline layout, components, performance and configuration for typical experiments will be presented © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]