bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbochlorination of Fly Ash in a Fused Salt Slurry Reactor
Authors: Dobbins M. S. , Burnet G. 
Published: March 2011

ABSTRACTCarbochlorination of the metal oxides in fly ash by suspending the solid reactants in a NaCl-AlCl3 melt at 530–850°C and then sparging chlorine into the melt has been investigated. A mechanically agitated, semi-batch reactor was used to test the effects of temperature, oxide and carbon loading, salt composition and gas flow on the reaction rate. The process was modeled using the carbochlorination of pure alumina, the rate of which was found to be chemical reaction controlled at temperatures below about 650°C and gas-liquid mass transfer controlled at higher temperature. The carbochlorination rate of the mixed oxides in coal fly ash was also mass transfer controlled at higher temperatures when aluminum recoveries were less than about 50%. At higher aluminum recoveries, the overall rate was limited by the rate of ash dissolution into the melt.
Speciation in Size and Density Fractionated Fly Ash II. Characterization of a Low-Calcium, High-Iron Fly Ash
Authors: Hemmings R. T. , Berry E. E. , Cornelius B. J. , Scheetz B. E. 
Published: March 2011

ABSTRACTMorphological, chemical and mineralogical speciation of a low-Ca, high-Fe fly ash from a bituminous coal has been investigated by examination of size, density and magnetic fractions. Fractionation by size revealed little information as to speciation among particle types. However, separation of the ash into eight density fractions and into magnetic and non-magnetic components showed major differences in particle properties. It was found that glasscontaining particles can be divided into three general types: Type 1, being low-Fe content, low-density hollow spheres comprising aluminosilicate/mullite glass ceramics; Type 2, of intermediate density, being ferroaluminosilicate/ mullite glass ceramics; and Type 3, high density composite particles of spinel/hematite crystals embedded in an iron-substituted glass. It is proposed that Type 1 and Type 2 particles are derived from thermal decomposition of clay minerals with a range of Fe contents. Type 3 particles are considered to arise from thermal decomposition of pyrite in the presence of small quantities of aluminosilicate minerals. Two general types of glass were distinguished: Glass I(f), being largely a low-iron aluminosilicate; and Glass II(f), being a ferroaluminosilicate of high Fe-content. XRD and vibrational spectroscopic evidence suggest that, in both glass types, Fe is substituted for Al in an aluminosilicate-type structure.
Characteristics of Fluid Flow in the Combustion Synthesis of TiC From the Elements
Authors: Valone S. M. , Behrens R. G. 
Published: March 2011

AbstractFinite reservoir effects on capillary spreading at small reservoir dimensions are explored numerically and related to wave propagation in combustion synthesis of TiC from elemental Ti and C. In addition a convective instability which may be activated by gravitational, surface tension or contact forces may cause void regions to coalesce, thereby altering the void distribution in combustion synthesis products.
Undercooling of Bulk High Temperature Metals in the 100 Meter Drop Tube
Authors: Hofmeister William , Robinson M. B. , Bayuzick R. J. 
Published: March 2011

AbstractThe 100 meter Drop Tube at NASA Marshall Space Flight Center provides an excellent opportunity to study the effects of containerless, microgravity processing in metals and alloys. In a series of experiments high melting temperature pure metals were melted in an electron beam furnace and dropped in vacuum. Sample sizes ranged from 0.175-1.2 grams. Large undercoolings on the order of 18% of the melting temperature were observed in Ti, Zr, Nb, Mo, Rh, Ta, and Pt. Undercoolings of 5-18% Tm were observed in Ru and Ir. These undercooling results are consistent, repeatable, and occur in a high percentage of experiments. The experimental technique will be presented as well as the resultant microstructures of undercooled drops. The data will be discussed with respect to nucleation theory.
Microgravity Experiments on Granular Materials
Authors: Costes Nicholas C. , Jano V. C. , Sture S. 
Published: March 2011

AbstractGravity induced stresses in terrestrial laboratory specimens comprising of relatively weak and soft granular materials, are often of the same magnitude as the external tractions that are applied during investigations of constitutive behavior especially at low intergranular stress levels. The presence of heterogeneous strain and stress fields within such a specimen makes it difficult if not impossible to obtain objective and unambiguous constitutive properties and to devise relevant constitutive equations. To fill this technological gap, microgravity experiments are now planned which will be performed during future flights of the Space Shuttle, in conjunction with ground-based tests. This paper deals with analytical and experimental issues related to constitutive modeling of granular materials.
Evaporation Kinetics in the Hanging Drop Method of Protein Crystal Growth
Authors: Baird James K. , Frieden Richard W. , Meehan E. J. , Twigg Pamela J. , Howard Sandra B. , Fowlis William A. 
Published: March 2011

AbstractWe present an engineering analysis of the rate of evaporation of solvent in the hanging drop method of protein crystal growth. Our results are applied to 18 different drop and well arrangements commonly encountered in the laboratory. We take into account the chemical nature of the salt, the drop size and shape, the drop concentration, the well size, the well concentration, and the temperature. We find that the rate of evaporation increases with temperature, drop size, and with the salt concentration difference between the drop and the well. The evaporation possesses no unique half-life. Once the salt in the drop achieves about 80% of its final concentration, further evaporation suffers from the law of diminishing returns.
Phase Separation Kinetics in Immiscible Liquids
Authors: Ng Lee H. , Sadoway Donald R. 
Published: March 2011

AbstractThe kinetics of phase separation in the succinonitrile-water system are being investigated. Experiments involve initial physical mixing of the two immiscible liquids at a temperature above the consolute, decreasing the temperature into the miscibility gap, followed by imaging of the resultant microstructure as it evolves with time. Refractive index differences allow documentation of the changing microstructures by noninvasive optical techniques without the need to quench the liquid structures for analysis.
Noncontact True temperature measurement
Authors: Lee Mark C. , Allen James L. 
Published: March 2011

AbstractA laser pyrometer has been developed for acquiring the true temperature of a levitated sample. The laser beam is first expanded to cover the entire cross-sectional surface of the target. For calibration of such a system, the reflectivity signal of an ideal 0.95cm diameter gold-coated sphere (reflectivity = .99) is used as the reference for any other real targets. The emissivity of the real target can then be calculated. The overall system constant is obtained by passively measuring the radiance of a blackbody furnace (emissivity = 1.0) at a known, arbitrary temperature. Since the photo sensor used is highly linear over the entire operating temperature range, the true temperature of the target can then be computed. Preliminary results indicate that true temperatures thus obtained are in excellent correlation with thermocouple measured temperatures.
Three Channel Optical Temperature Measurement of Laser-Heated Reacting Particles.
Authors: Erik R. , Bolsaitis Pedro P. 
Published: March 2011

AbstractMultiple-color pyrometric measurement of particles reacting in an electrodynamic thermogravimetric analyzer is discussed. Attempts to measure the emissivity of heated tungsten particles are presented. The data are too scattered to provide reliable results.Experimental evidence for the sensitivity to noise and the speed of response of pyrometers is presented, and a brief theoretical discussion of the causes is presented.
The Influence of Natural Convection on Heating Characteristics of Space Furnaces
Authors: Lenski H. , Piller J. 
Published: March 2011

AbstractDuring the Dl-Spacelab mission, several samples of semiconductor and aluminium alloy have been processed in a single ellipsoid mirror furnace (ELLI) and a gradient furnace (GFQ), respectively. Both furnaces operate under inert gas atmosphere at reduced pressure (100 to 200 mbar). In weightlessness, the heat transfer characteristic changed due to absence of convection. For the ELLI, power consumption in space decreased by 15 to 21 %, while the thermal inertia of the system increased by a factor of 2. In contrast to that, the gradient furnace required higher heater temperatures in space, while the influence on the sample thermal profile was rather low.
Importance of Meteoritic Materials in Assessing the Influence of Microgravity on Solidification
Authors: Budka P. Z. , Milillo F. F. 
Published: March 2011

AbstractA new hypothesis is presented which proposes that major microstructural features of many meteorites are products of non-equilibrium solidification under microgravity conditions. These materials exhibit microstructural features both similar to and different from materials produced on Earth. Evidence is given to show that the differences can be attributed to microgravity solidification while the similarities can be attributed to nonequilibrium solidification. This hypothesis leads to a new interpretation of the formation mechanism for the Widmanstatten structure commonly observed in meteoritic nickel-iron alloys. Several meteorite synthesis experiments are suggested to test the hypothesis. The hypothesis implies that the study of meteoritic materials can lead to a deeper understanding of microgravity solidification; conversely, the principles of microgravity solidification can lead to insights into meteorite formation.
Theoretical Studies of Gravitational Effects in Chemical Vapor Deposition
Authors: Stinespring Charter D. , Kolb Charles E. , Annen Kurt D. 
Published: March 2011

AbstractChemical Vapor Deposition (CVD) processes are generally carried out under large temperature gradients. These gradients, temperature dependent fluid properties, and the earth's gravitational field give rise to buoyancy-driven free convective fluid flow which augments heat and mass transport in the CVD reactor. Under certain conditions, this free convective flow may alter the gas phase chemistry associated with the deposition process. In order to understand these free convective effects and their implications for the deposition process, a computational model describing the combined effects of fluid mechanics and chemistry has been developed. This model uses a coupled chemical equilibrium/mass transport code in conjunction with a 2-D elliptic fluid dynamics code to describe gas phase species profiles and deposition rates. This paper briefly describes the development of the model, its use, and the results of typical calculations.
Convection and Diffusion Effects During Physical Vapor Transport of Hg2Cl2
Authors: Singh N. B. , Hopkins R. H. , Mazelsky R. , Glicksman M. E. 
Published: March 2011

AbstractWe have carried out extensive experimentation on the physical vapor transport growth of mercurous chloride, which is an important material for opto-electronic devices. Because of the extraordinary combination of properties found in Hg2Cl2, including transmittance from 0.36 to 20 μm, anomalously slow soung velocity, high birefringence, and large acousto-optic diffraction efficiency, we are exploring the conditions for growth of large crystals of device quality. Our experiments have led so far to measured Hg2C12 growth rates that were orders of magnitude smaller than those expected by theories based on laminar, unidirectional flow between source and sink. Slight disturbances of the solid-vapor interface give rise to instabilities which lead to interfacial convection. This kind of convection should enhance the growth rate due to the acceleration of the materials exchange by hydrodynamic coupling, which is contrary to our findings. Interfacial convection is often connected with buoyancy-induced instabilities which dominate other instabilities under 1-g conditions. Despite attempts to reduce the Rayleigh numbers in our system, buoyancy-induced instabilities might be the cause of discrepancy between the measured and calculated growth rates. Observations of these phenomena under a microgravity environment might permit a better assessment of the transport mechanisms in physical vapor phase crystal growth of Hg2C12.
Thermogravimetric Measurements in an Electroynamic Balance
Authors: Spjut R. E. , Elliott J. F. , Bolsaitis P. 
Published: March 2011

AbstractAn Electrodynamic Thermogravimetric Analysis (EDTGA) Instrument has been developed for the study of kinetics of gas-solid reactions and phase transformations of levitated particles at high temperature. The levitated particles may be heated with a focused laser beam and their temperature and weight monitored during the process. The particles that can be studied are, approximately, 10 to 150 microns in diameter and it is aimed to produce temperature pulses comparable to those encountered in plasma torches and reactors. The instrumentation implemented in the system permits the measurement and or control of relative temperature, weight change, and energy flux to the particle with a time resolution of less than one millisecond. Selected results obtained from pulse heating aluminum oxide and silicon dioxide are presented.
Heavy Metal Halide Glasses
Authors: Drexhage Martin G. 
Published: March 2011

ABSTRACTOptical fibers with attenuations much lower than those attainable in present-day silicate waveguides are possible in theory if mid-infrared operating wavelengths are used. The loss mechanisms, materials, and problems inherent in obtaining such fibers are discussed. Among several candidates, heavy metal fluoride glasses are suggested as being must suited to low and moderate loss fiber applications in the 2-5 micrometer spectral region.
Ultraviolet Curable Silicone Optical Fiber Coatings
Authors: Dehli Gail J. , Lee Chi-Long , Lutz Michael A. , Suzuki Toshio 
Published: March 2011

ABSTRACTTechnology coupling fast ultraviolet (UV) cure response with elastomeric properties in silicone formulations has been developed. Rapid photocure was obtained through addition of mercaptan to vinyl on silicon via a free radical chain reaction resulting in a monosulfide link. One optical fiber coating based on the technology, OPTIGARD™ X3-6662, is a onepart formulation which can be cured very rapidly (≤0.1 sec) upon UV exposure (≥25 mJ/cm2) to provide a low refractive index (RI=1.42), elastomeric film exhibiting good low temperature properties. A high refractive index counterpart (RI=1.51), OPTIGARD™ X3-6663, was obtained through incorporation of a controlled amount of phenyl groups into the polymer backbone. The technology, an IR-100 Award winner in 1985, is being used by the fiber optic industry to satisfy their need for coatings which will cure fast, perform over a wide temperature range, and be moisture insensitive.
Some Transition Ions in Heavy Metal Fluoride Glasses
Authors: Bogomolova L. D. , Caccavale F. , Krasil'nikova N. A. 
Published: March 2011

ABSTRACTThe heavy metal fluoride glasses (HMFG) have attracted considerable attention in recent years because of their unusual physical and chemical properties which allow potential use in numerous electrical and optical applications. The HMFG are transparent over a wide range of the optical spectrum (from 220 nm to 8,μ) and have sufficient chemical stability to make them a suitable optical material middle IR fibers optics. Their high anionic conductivity permits their application as solid electrolytes. They are also of interest scientifically since their structure is different from that of other inorganic glasses. The high coordination number of the network formers ions is the principal structural peculiarity of the HMFG.
Materials For UV and Far Ir Transmission
Authors: Fleming James W. 
Published: March 2011

ABSTRACTMotivated by the benefits of optical data transmission, materials for the electromagnetic spectral window from approximately 0.6 to 4.0 microns are being explored by many investigators. I will review materials for the spectral regions surrounding this window. In these spectra regions a primary interest is optical power transmission. Optical power transmission in the UVand far IR has significant application for materials and device fabrication and characterization. Sources such as eximer and CO2 lasers provide potential sources of very high power.Based on bonding and atomic mass considerations, materials for transmission in these windows can be approximated. Methods for taking advantage of the properties of materials such as reflectivity have the potential for interesting lightguiding structures such as hollow core lightguides. Materials currently contemplated for use in these wavelength regions and properties of potential materials will be discussed.
Effects Of Sintering Atmosphere On Defects In SiO2:GeO2 Vad Fiber
Authors: Kashiwazaki A. , Muta K. , Kohketsu M. , Kawazoe H. 
Published: March 2011

ABSTRACTEffects of the sintering atmosphere for 90SiO2 :10GeO2 preform-rods produced by VAD process were examined. The sintering atmosphere was changed from reducing to oxidizing, and the type and relative concentration of defects were estimated by photoluminescence, UV absorption and ESR absorption. Reducing condition accelerated the formation of defects, because these centers were considered to be the intermediate products of the thermal decomposition reaction of GeO2 which gives rise to reduction of Ge(IV) to Ge(II).
Coating Adhesion Effects on Fiber Strength and Fatigue Properties
Authors: Skutnik Bolesh J. , Munsey Barbara D. , Brucker Carol T. 
Published: March 2011

ABSTRACTOrganic/polymeric materials remain the most prevalent protective coatings for optical fibers. Many studies have chronicled significant differences inn the levels of protection against moisture and other adverse environments by such coatings. Recently an attempt was made to identify those coating properties which correlate with these protective characteristics. Water absorption and adhesion between the coating and fused silica were proposed to correlate the best.In this study a series of coatings have been prepared with varying levels of adhesion to fused silica substrates, without significant differences in water absorption or in water permeation properties. The tensile strength, static fatigue and dynamic fatigue properties of the coated fibers were measured and correlated with the lap shear strengths of correspondingly coated slides. As the adhesion of the coating/silica glass interface increases, the corresponding fiber's strength and fatigue properties improve also.The strong positive correlation between the coating's adhesion and the fiber's strength/fatigue properties will be reported for a number of coating/fiber combinations. Effects on lifetime predictability will also be addressed.
Photo-Luminescence of SiO2:GeO2 Vad Fibers Heat-Treated Under Reducing Conditions
Authors: Kohketsu M. , Kawazoe H. , Kashiwazaki A. , Muta K. 
Published: March 2011

ABSTRACTPhoto-luminescence(PL) in VAD silica preforms sintered under reducing or oxidizing condition was observed. Two types of diamagnetic luminescence centers and the Si-E′ center were found in pure silica glass. The intensity of photoluminescence was strongly dependent on the sintering atmosphere. This observation suggests that reduced Si species, Si(III) and Si(II), are responsible for the luminescence.
Magnetic Properties of Pbl-xGdxTe
Authors: Gorska M. , Anderson J. R. , Golacki Z. 
Published: March 2011

AbstractThe magnetization and magnetic susceptibility of Bridgman-grown Pb1-xGdxTe have been measured over a temperature range from 2 to 300 K and in magnetic fields from 0.01 to 50 κOe. The x-values of the crystals ranged from 0.03 to 0.07. The magnetic susceptibility followed a Curie-Weiss behavior, χ = C/(T + θ), with positive θ implying an antiferromagnetic exchange interaction between Gd ions. The magnetic field dependence of the magnetization was fitted to a modified Brillouin function with parameter values that agreed fairly well with those from Curie-Weiss plots. The magnitude of θ was comparable to the value found for Pb1-xMnxTe for similar x values; but since the ion spin is bigger for Gd this suggests that the exchange interaction in Gd-doped PbTe is roughly half the value in Mn-doped PbTe.
NMR and EPR Study of Sn0.98 Gd0. 02 Te at Low Temperatures.
Authors: Han B. S. , Symko O. G. , Zheng D. J. 
Published: March 2011

AbstractMagnetic resonance behavior of Sn0.98 Gd0. 02 Te has been investigated from 2.5 K down to 0.015 K using a SQUID magnetometer and a 3He-4He dilution refrigerator. Detection of magnetic resonance with a SQUID allows the detection of NMRan d EPR of some of the constituents of the sample. This method is particularly useful for broad lines. We have investigated the NMRfor 125Te, 119 Sn, and 117Sn, and the EPR for the Gd ion in a field of 265 Oe. The contribution of Gd impurities is maily important in the Knight shift of the Sn isotopes; this shift is 7%. The EPR shows 2 broad lines with structure; one line we attribute to the paramagnetic ions and the second one we attribute to Gd ions which have formed clusters.
EPR of Mn2+ and Gd3+ Ions in PbTe and SnTe Semiconductors
Authors: Bartkowski Marian , Northcott D. J. , Reddoch A. H. , Williams D. F. , Hedgcock F. T. , Korczak Z. 
Published: March 2011

AbstractThe EPR spectra of manganese and gadolinium doped PbTe and SnTe semiconductors were measured from 4.2K up to 400K for dopant concentrations ranging from 50 to 50000 ppm. Resolved fine, hyperfine and superhyperfine structure as well as forbidden and cluster lines were measured. The combination of Lorentzian absorption and dispersion derivatives fits the recorded spectra well. Nonlinear broadening of linewidths with temperature is characteristic in these semiconductors. A manganese-induced broad maximum in linewidth versus temperature was found in PbTe around 180K for dopant concentrations in excess of 1.5at%.
Very High Mobility in Semimagnetic Semiconductors with Rare Earth
Authors: M Averous , B.A. Lombos , A. Bruno , J.P. Lascaray , C. Fau , M.F. Lawrence 
Published: March 2011

AbstractA semimagnetic semiconductor with rare earth like magnetic ion is studied: Pb1-xGdxTe. Very high Hall mobilities were found up to 107 cm2/V.s. The magnetization is well fitted at 4.2K by a Curie-Weisslaw, with a Gaj's parameter of 1K. The value of JNN' the exchange in a Gd pair deduced from the susceptibility measurements is small, as expected, due to the specific character of Gadolinium (S state and 4f shell): JNN/k = - O.3°K for x = 0.025.
Magnetic Properties of Gd-Substituted Yttrium Nitride
Authors: van Dover R. B. , Schneemeyer L. F. , Gyorgy E. M. 
Published: March 2011

AbstractGd2Y1-xN is an instantiation of the broad series of diluted magnetic materials composed of lanthanide nitrides in a Sc, Y or La nitride host. These lanthanoid nitrides are interstitial compounds which all form in the Bi structure and with similar lattice constants, so solid solutions are readily obtained. We have prepared single-crystal thin films by epitaxial growth on sapphire substrates, and obtained material with moderate carrier densities (n Hall∼10 21 cm-3) and mobilities (μHall∼10 cm2V-1sec-1). Below the ordering temperature Tc,∼15 K the GdxY1-x,N films (0.25<x<0.40) exhibit a ferromagnetic-like M-H loop. The saturation magnetization measured at 15 kOe and 4.2 K is anomalously low, representing an effective moment of only 4.2 μB per Gd compared to the expected value of at least 7.2 μB. The piecewise-linear M-H curve is inconsistent with conventional models for a simple anisotropic ferromagnet. These features illustrate some of the unusual properties we are beginning to identify in the behavior of these new materials.