bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Fluids Experiment Apparatus (fea) and Rockwell's Industrial Space Processing Research Program
Authors: Martin Michael J. 
Published: March 2011

AbstractRockwell International has long endeavored to stimulate industrial utilization of space for materials processing. A successful introductory briefing program to acquaint nonaerospace industry with the space environment, microgravity process phenomena, experiment hardware, and the programs available to conduct research in space has encouraged several companies to initiate space processing research projects.To help satisfy industry's microgravity experiment hardware requirements, Rockwell has developed a multipurpose materials processing laboratory for use on the Space Shuttle. The Fluids Experiment Apparatus (FEA) has been flown to perform floating zone crystal growth and purification research and is currently being used to support further crystal growth research with advanced materials for Rockwell. Other companies are preparing experiments that are expected to be conducted in the FEA on future Space Shuttle missions.Rockwell is developing, with NASA, a program that will allow industry to plan and fly microgravity materials processing experiments within a few months–much faster than the current one to two year lead time. This low-cost program, patterned after the NASA Joint Endeavor Program, provides Space Shuttle flight services and use ot the FEA to conduct scientific investigations. Rockwell plans to offer experiment integration and support services to industry as needed.
Containerless Study of Metal Evaporation by Laser Induced Fluorescence
Authors: Sghiffman Robert A. , Nordine Paul C. 
Published: March 2011

AbstractLaser induced fluorescence (LIF) detection of atomic vapors was used to study evaporation from electromagnetically levitated and CW CO2 laser heated molydenum spheres and resistively heated tungsten filaments. Electromagnetic (EM) levitation in combination with laser heating of tungsten, zirconium, and aluminum specimens was also investigated. LIF intensity vs temperature data were obtained for molybdenum ( 7S3 ) atoms and six electronic states of atomic tungsten, at temperatures up to the melting point of each metal. The detected fraction of the emitted radiation was reduced by self-absorption effects at the higher experimental temperatures.Vaporization enthalpies derived from data for which less than half the LIF intensity was self-absorbed were ΔHo0 = -636 ± 24 kJ/g-mol for Mo and 831 ± 32 kJ/g-mol for W. Space-based applications of EM levitation in combination with radiative heating are discussed.
Effects of an Applied Magnetic Field on Directional Solidification of Off-Eutectic Bi-Mn Alloys
Authors: Decarlo J. L. , Pirich R. G. 
Published: March 2011

AbstractOff-eutectic compositions of Bi-Mn were directionally solidified in applied transverse magnetic fields up to 3 kG to determine the effects odn thermal and solutal convection. For Bi-rich compositions, the magnetic field appeared to increase mixing as determined from thermal, morphological, chemical and magnetic analyses. For Mn-rich compositions morphological and chemical analyses suggest some reduction in mixing due to application of the magnetic field. Conductivity gradients in the melt are suggested as a possible mechanism for the observed results.
Pressure Dependence of the Electrical Properties of Gabi Solidified in Low Gravity
Authors: Wu M. K. , Ashburn J. R. , Torng C. J. , Curreri P. A. , Chu C. W. 
Published: March 2011

AbstractImmiscible GaBi alloys were solidified during free fall in the Marshall Space Flight Cente4 drop tower which provides about 4.5 seconds of low gravity (about 10−4 g, g = 980 cm/s2 ). We have measured the electrical resistivity and magnetic susceptibility as a function of pressure (up to 18 kbar) and temperature (300K to 4.2K) of drop tower (DT) sample and ground control (GC) sample prepared under identical conditions except for gravity. At ambient pressure the electrical resistance of the DT sample exhibits a broad maximum at 100K, while that of GC sample decreases rapidly as temperature decreases. Both DT and GC samples becomesuperconducting at 7.7K (Tc2). However, a minor second superconducting phase with a transition temperature at 8.3K (Tc1) is observed only in the DT samples.
Detection of SUB-PPM Impurity Levels by Selectively Excited Photoluminescence in Fluoride Glass Optical Fibers
Authors: Miniscalco W. J. , Thompson B. A. 
Published: March 2011

ABSTRACTA technique is presented which addresses the problem of analyzing impurities in heavy metal fluoride glass optical fibers at the extremely low levels required for long distance applications. The procedure uses selectively excited fiber impurity luminescence (SEFIL), and is extremely sensitive due to the zero-background nature of luminescence and the long interaction lengths afforded by optical fiber. The technique has been rendered quantitative through the use of standards and the normalization of the impurity emission by the Raman scattering intensity. A SEFIL analysis of two fibers with differing origins and designs is reported. The ultimate detection limits are estimated to be <1 ppb-wt for Fe3+ and ≤ 0.001 ppb-wt for Nd3+ and Pr3+.
Glasses and Optical IR Fibers of As2Se3−xTex
Authors: Croitoru N. , Shamir N. , Mendlovic D. , Dror J. , Lereah Y. 
Published: March 2011

ABSTRACTChalcogenide glasses of As2Se3−xTex (O<x<3) were made with special care, using very pure raw materials in order to avoid traces of oxygen. From these materials optical fibers were pulled, and the attenuation of CO2 laser light (wavelength λ = 10.6 μm) transmitted through these fibers was measured as a function of the Te content (x). The fiber's surface and cross-section were examined, using both the scanning electron and optical microscopes, and they directly revealed the increase in the concentration of the defects while x was increasing. The influence of the physical and mechanical properties on the concentration of defects was studied by measuring the optical absorption (α) and the microhardness (VH) of the raw materials. Slabs of As2Se3−xTex were made, and in these samples the α, VH, and glass transition temperature (Tg) as a function of x were measured. In the infrared region of the spectra at λ = 10.6 μm, the α in both the slabs and pulled fibers increased, and the VH and Tg decreased with the increase of x. This can be explained by the increase of the concentration of the defects (small crystallites) which appeared during the fiber pulling.
Drawing or Photon Induced Defects in Silica Based Waveguides
Authors: Kawazoe H. 
Published: March 2011

ABSTRACTA model reaction is proposed which can totally explain formation of the defects detected in SiO2: GeO2 glasses such as E', NBOHC, T-T, bonding, peroxy linkages, and T=O or T(II) species, where T is Si or Ge. The initial reaction is radical decomposition of T-O bonds at high temperatures and the defects are products of the secondary reaction between the initial radical species. The net reaction is expressed as 2TO2⇄2TO+O2, which predicts the dependence of concentration of the radical species on PO2 during processing.
High Field Magnetization Step in Zn1−xMnxTe
Authors: Barilero G. , Rigaiux C. , Hau Nguyen Hy , Plcoche J. C. , Giriat W. 
Published: March 2011

AbstractHigh field magnetization experiments are reported for dilute Zn1−xMnxTe alloys (x≃0.03) at T=1.3K. The first magnetization step is analyzed including effects of internal field due to the interactions of Mn-Mn pairs with the remaining spins. An accurate estimate of the nearest neighbor (NN) exchange constant is obtained which agrees quite well recent neutron scattering experiments.
The Relevance of Long-Range Interactions in Diluted Magnetic Semiconductors
Authors: De Jonge W. J. M. , A Twardowski , C.J.M. Denissen 
Published: March 2011

AbstractData are presented yielding evidence on the long-range character of magnetic interactions in Diluted Magnetic Semiconductors. The radial dependence of these interactions is deduced from the concentration dependence of the freezing temperature. It is shown that calculations of the thermodynamic properties, which include this long-range interaction, are in fair agreement with the experimental data.
Band Structure and Electronic Excitations in Cdl-xMnxTe
Authors: Wei Su-Huai , Zunger Alex 
Published: March 2011

AbstractWe have performed spin-polarized, self-consistent local spin density total energy and band structure calculations for the prototype semimagnetic semiconductor alloy Cd1-xMnxTe. Based on the calculated band structures and taking into account the many body effects of localized states, we propose a schematic energy level diagram to interpret the d→d*, p→d, and photoemission transitions in Cd1-xMnxTe.
The Connection Between Structural Disorder and Semimagnetic Properties in Implanted CdTe
Authors: Jiménez-González H. J. , Lusnikov A. , Dresselhaus G. , Braunstein G. H. , Withrow S. P. 
Published: March 2011

AbstractThe structural disorder and annealing characteristics of dilute magnetic semiconductors synthesized by implantation of Mn ions into CdTe are studied. After implantation but prior to annealing, the implanted Mn ions reside at random sites in a highly disordered CdTe lattice. To separate magnetic and nonmagnetic effects we have implanted CdTe with nonmagnetic Zn ions under the same conditions as the Mn ions (energy 60 keV, fluence 1016 cm−2). Various annealing conditions are applied to monitor the decrease in intensity of the disorder-induced photoluminescence peaks and the increase of the peak intensity of the CdTe-like exciton line is reduced.
Dilute Magnetic Semiconductor Superlattices Containing Hg1-xMnxTe
Authors: Harris K. A. , Hwang S. , Burns R. P. , Cook J. W. , Schetzina J. F. 
Published: March 2011

AbstractSuperlattices containing alternating layers of Hg1-xMnx Te and HgTe have been successfully grown by molecular beam epitaxy. These structures are the first superlattices containing layers of a mercury-based dilute magnetic semiconductor to be grown by any thin film technique. The optical and electrical properties of these novel magnetic multilayers are presented and discussed.
Hg1−x−yMnxCdyTe Alloys for 1.3−1.8 μm Photodiode Applications
Authors: Shin S. H. , Pasko J. G. , Lo D. S. , Tennant W. E. , Anderson J. R. , Gorsk M. , Fotouhi M. , Lu C. R. 
Published: March 2011

AbstractHgMnCdTe/CdTe photodiodes with responsivity cutoffs of up to 1.54 pm have been fabricated by liquid phase epitaxy (LPE). The mesa device structure consists of a boron-implanted mosaic fabricated on a p-type Hg1−x−yMnxCdyTe layer grown on a CdTe substrate. A reverse breakdown voltage (VB) of 50 V and a leakage current density of 1.5 × 10−4 A/cm2 at V = −10 V was measured at room temperature (295K). A 0.75 pF capacitance was also measured under a 5 V reverse bias at room temperature. This device performance based on the quaternary HgMnCdTe shows both theoretical and practical promise of superior performance for wavelengths in the range 1.3 to 1.8 μm for fiber optic applications.
Investigations of Cd0.9Mn0.1Te Doped with Au, Cu, As and P Acceptors Using Optical Absorption and Photoluminescence
Authors: Misiewicz J. , Wrobel J. M. , Becla P. , Heiman D. 
Published: March 2011

AbstractUsing absorption and photoluminescence investigations the energies of shallow acceptors are determined as follows: 0.11 eV for P; 0.12 eV for As; 0.17 eV for Cu and 0.18 eV for Au. Deep level energies are found as 0.28 eV for P; 0.29 eV for As; 0.41 eV and 0.92 eV for Cu; and 0.33 eV, 0.69 eV and 1.25 eV for Au dopants. Acceptor concentrations in the 1017cm−3 range are achieved for As and P dopants, but for Au and Cu high compensation is found.
Properties of a Constricted-Tube Air-Flow Levitator
Authors: Rush J. E. , Stephens W. K. , Ethridge E. C. 
Published: March 2011

ABSTRACTA constricted-tube gas flow levitator first developed by Berge, Oran, and Theiss shows promise both as a spacepositioning device and as a levitator for ground-based work. We present results of laboratory studies which were designed to predict the behavior of the device in a low-g environment.
Bubble Motion in a Rotating Liquid Body
Authors: Annamalai P. , Subramanian R. S. , Cole R. 
Published: March 2011

ABSTRACTSingle bubble behavior inside a rotating liquid-filled sphere is studied both experimentally and theoretically. In the limit of small values of the Taylor number, a quasi-static theoretical description of the motion of the bubble is developed. The analytical result thus obtained is compared with experiment and predicts the bubble trajectory as well as its asymptotic location which, in the presence of gravity, is not exactly on the axis of rotation.
Isoelectric Focusing in Space
Authors: Bier M. , Egen N. B. , Mosher R. A. , Twitty G. E. 
Published: March 2011

ABSTRACTThe potential of space electrophoresis is conditioned by the fact that all electrophoretic techniques require the suppression of gravity-caused convection. Isoelectric focusing (IEF) is a powerful variant of electrophoresis, in which amphoteric substances are separated in a pH gradient according to their isoelectric points. A new apparatus for large scale IEF, utilizing a recycling principle, has been developed. In the ground-based prototype, laminar flow is provided by a series of parallel filter elements. The operation of the apparatus is monitored by an automated array of pH and ultraviolet absorption sensors under control of a desk-top computer. The apparatus has proven to be useful for the purification of a variety of enzymes, snake venom proteins, peptide hormones, and other biologicals, including interferon produced by genetic engineering techniques. In planning for a possible space apparatus, a crucial question regarding electroosmosis needs to be addressed. To solve this problem, simple focusing test modules are planned for inclusion in an early Shuttle flight.
Surface Tension Driven Flow in Glass Melts and Model Fluids
Authors: McNeil Thomas J. , Cole Robert , Shankar Subramanian R. 
Published: March 2011

ABSTRACTExperiments on surface tension driven flow in nominally cylindrical columns of a glass melt and silicone oils are described and results are presented. Predictions from an appropriate theoretical model are included. Conclusive proof has been obtained for the dominance of surface tension driven flow in these systems under the conditions of the present investigation.
Semiconductor Crystal Growth and Segregation Problems on Earth And in Space
Authors: Gatos Harry C. 
Published: March 2011

ABSTRACTCrystals grown from the melt exhibit compositional and structural defects which limit the exploitation of their full potential in solid state electronics. The origin of these defects is related primarily to gravity-induced convective currents in the melt. In semiconductor compounds additional problems are introduced from variations in stoichiometry. Progress has been made recently in relating qualitatively, and in some instances quantitatively, the growth parameters to the materials properties of the crystals, and in turn to their electronic properties. Overcoming the presence of gravitational forces in space eliminates or minimizes convective interference and, thus, the quantitative assessment of the key growth parameters controlling the chemical and structural perfection of single crystals becomes possible. Results (obtained on earth) will be presented on the growth-property relationships of elemental and compound semiconductors. The advantages, as well as the limitations, that zero gravity conditions present for crystal growth will be discussed.
Electrical Characterization of Hg1−xCdxTe Alloys
Authors: Lehoczky S. L. , Summers C. J. , Szofran F. R. , Martin B. G. 
Published: March 2011

ABSTRACTTheoretical models are described for calculations of charge-carrier concentrations, Fermi energy, and conduction-electron mobility as functions of x, temperature, and ionized- and neutral-defect concentrations in Hg1−xCdxTe alloys. Measurements are reported of electron concentration and electron mobility from 5–300 K for alloys with 0.17 < ˗ < 0.30. The electrical data are in reasonable agreement with theory and were analyzed to obtain estimates of donor and acceptor state concentrations. The electron inobilities are calculated in terms of a microscopic theory of electrical conduction derived from the solution of the Boltzmann equation for the perturbed steady-state electron distribution function and show that longitudinal opticalphonon and charged and neutral defect scattering are the dominant mobility-limiting mechanisms.
Gravity-Driven Convection Studies in Compound Semiconductor Crystal Growth by Physical Vapor Transport
Authors: Zoutendyk John A. , Akutagawa Wesley M. 
Published: March 2011

ABSTRACTGravity-driven convection can alter the diffusive-advective mass transport behavior in the growth of crystals by physical vapor transport. Specially designed and constructed transparent furnaces are being used in our laboratory to study the effects of gravity in crystal growth of the compound semiconductors PbTe and CdTe.
Influence of Diffusion and Convective Transport on Dendritic Growth in Dilute Alloys
Authors: Glicksman M. E. , Bahadur Singh Narsingh , Chopra M. 
Published: March 2011

ABSTRACTExtensive experimentation has been carried out in which the kinetics and morphology of dendritic growth were measured as a function of thermal supercooling, solute concentration, and spatial orientation of the dendritic growth axis. The crystal growth system studied is succinonitrile [NC(CH2)2CN] with additions of argon (up to 0.1 mole %). This system is especially useful as a model for alloy studies because kinetic data are available for high purity (7–9's) succinonitrile. The addition of argon provides a simple, controllable dilute solute that now permits the first comparably detailed dendritic growth studies on binary alloys.One dramatic influence of the solute, at fixed thermal supercooling, is to increase the growth velocity (to a maximum) and correspondingly decrease intrinsic crystal dimensions (tip radius). Morphological measurements will be described in detail relating tip size, perturbation wavelength, supercooling, and solute concentration. The analysis of these effects based on morphological stability theory will also be discussed. Finally, experiments permitting the separation of convective and diffusive heat transport during crystal growth of succinonitrile will be described briefly. These studies clearly underscore the importance of gravitationally-induced buoyancy effects on crystal growth kinetics and morphology.
Solidification of Undercooled Monotectic Alloys
Authors: Perepezko J. H. , Galaup C. , Cooper K. P. 
Published: March 2011

ABSTRACTDuring the processing of monotectic alloys large compositional segregation of the liquid can precede final solidification. Under normal treatment a coarse scale phase distribution is obtained as a result of convection and sedimentation effects which may be minimized by microgravity processing. In undercooled droplets (5–20μ) of Bi-Ga alloys with compositions near the monotectic point, a finescale segregation has been observed and is similar to that formed during a microgravity treatment of bulk samples. Near the critical point of the miscibility gap, Bi-rich alloys exhibit an undercooling prior to phase separation, while in Ga-rich alloys the onset of phase separation is at the miscibility gap boundary. Similarly, in Cu-Pb alloys an undercooling below the miscibility gap prior to phase separation is observed for Cu-rich alloys, but not for Pb-rich alloys near the critical point. These observations are consistent with the operation of a critical point wetting behavior which can modify the liquid segregation pattern during microgravity treatment.
Suppression of Marangoni Convection With Oxide Films
Authors: Verhoeven J. D. , Noack M. A. , Bevolo A. J. 
Published: March 2011

ABSTRACTThis research is an effort to determine whether surface tension driven convection in molten tin can be eliminated by the formation of one to several monolayers of oxide on the molten tin surface. Initial work is presented describing Auger and electron loss spectroscopies used to detect SnD and SnO2 on molten tin surfaces in a UHV system; Progress on efforts to produce and monitor controlled oxide layers of 8 to 20 Å upon floating zones in a disk geometry is presented.
Influence of Gravity Driven Convection on the Directional Solidification of Bi/MnBi Eutectic Composites
Authors: Pirich Ron G. , Larson D.J. 
Published: March 2011

ABSTRACTThe role of gravity on Bridgman-Stockharger directional solidification of eutectic Bi/MnBi has been studied in reduced gravity aboard NASA sounding rocket SPAR flight experiments and contrasted with normal gravity investigations. The directional solidification of eutectic Ri/MnBi results in a low volume fraction, faceted/nonfaceted aligned rod eutectic whose MnRi rod size, interrod spacing, thermal and magnetic properties are sensitive functions of solidification processing conditions. The morphology of the low-gravity samples showed striking differences compared with identically processed,normal gravity samples grown in the same apparatus. The MnBi rod diameter and interrod spacing distributions were significantly smaller, approximately 50%, for the lowgravity samples compared with identically processed one gravity samples. Accompanying the smaller MnBi rod diameters observed in the flight samples, was an increase in permanent magnet properties which reached greater than 97% of the theoretical maximum.Gravitationally induced thermal instabilities in one-gravity which result in irregular interface movement and associated difficulty of the faceted MnBi phase to branch are suggested to explain the morphological differences between one and low gravity solidification.
Solidification of Hypermonotectic Al-In Alloys Under Microgravity Conditions
Authors: Potard Claude 
Published: March 2011

ABSTRACTFour samples of the Al-In system having monotectic and hypermonotectic compositions were solidified under microgravity during the NASA-SPAR IX flight of January 20th,1981. The experimental thermal and physico-chemical conditions actually achieved have been analysed. Radiographic and metallographic observations of the samples show a non-regular dispersed primary phase inside the monotectic matrix. These observations are commented on the basis of capillarity and solidification aspects.
The Influence of Gravity on the Solidification of Monotectic and Near Monotectic Cu-Pb Alloys
Authors: Bergman A. , Carlberg T. , Fredriksson H. , Stjerndahl J. 
Published: March 2011

ABSTRACTUnidirectional solidification experiments with monotectic and near monotectic Cu-Pb alloys have been performed with the growth direction both parallel and antiparallel to the gravity vector. It was found that a more regular composite structure was possible to achieve in the samples solidified parallel to the gravity vector. It was also found that the amount of lead rich phase, regularily incorporated in the structure, was less than one would expect theoretically. It is proposed that monotectic alloys can solidify to two different kinds of composite structures. One, which can be described by the theory of coupled growth of a rod eutecticum, and the other similar to the growth of primary rods.
Thermophysical Properties of Germanium for Thermal Analysis of Growth from the Melt
Authors: Crouch Roger K. , Fripp A. L. , Debnam W. J. , Taylor R. E. , Groot H. 
Published: March 2011

ABSTRACTThe thermal diffusivity of Ge has been measured over a temperature range from 300° C to 1010° C which includes values for the melt. Specific heat has been measured from room temperature to 727° C. Thermal conductivity has been calculated over the same temperature range as the diffusivity measurements. These data are reported along with the best values from the literature for the other parameters which are required to calculate the temperature and convective fields for the growth of germanium by the Bridgman method. These parameters include the specific heat, the viscosity, the emissivity, and the density as a function of temperature.