104 Matching Results

Search Results

Advanced search parameters have been applied.

Zinc and Its Alloys

Description: Report issued by the Bureau of Standards discussing world production of zinc and zinc alloys. History, metallurgy, and structural properties of zinc are presented. This report includes tables, illustrations, and photographs.
Date: November 6, 1931
Creator: United States. Bureau of Standards.
Partner: UNT Libraries Government Documents Department

Internal electric-field-lines distribution in CdZnTe detectors measured using X-ray mapping

Description: The ideal operation of CdZnTe devices entails having a uniformly distributed internal electric field. Such uniformity especially is critical for thick long-drift-length detectors, such as large-volume CPG and 3-D multi-pixel devices. Using a high-spatial resolution X-ray mapping technique, we investigated the distribution of the electric field in real devices. Our measurements demonstrate that in thin detectors, <5 mm, the electric field-lines tend to bend away from the side surfaces (i.e., a focusing effect). In thick detectors, 21 cm, with a large aspect ratio (thickness-to-width ratio), we observed two effects: the electric field lines bending away from or towards the side surfaces, which we called, respectively, the focusing field-line distribution and the defocusing field-line distribution. In addition to these large-scale variations, the field-line distributions were locally perturbed by the presence of extended defects and residual strains existing inside the crystals. We present our data clearly demonstrating the non-uniformity of the internal electric field.
Date: June 1, 2008
Creator: Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; Hossain, A.; Yang, G.; Yao, H. W. et al.
Partner: UNT Libraries Government Documents Department

The formation of metal/metal-matrix nano-composites by the ultrasonic dispersion of immiscible liquid metals

Description: Ultrasonic energy has been used to disperse one liquid metallic component in a second immiscible liquid metal, thereby producing a metallic emulsion. Upon lowering the temperature of this emulsion below the mp of the lowest-melting constituent, a metal/metal-matrix composite is formed. This composite consists of sub-micron-to-micron- sized particles of the minor metallic phase that are embedded in a matrix consisting of the major metallic phase. Zinc-bismuth was used as a model system, and ultrasonic dispersion of a minor Bi liquid phase was used to synthesize metal/metal-matrix composites. These materials were characterized using SEM and energy-dispersive x-ray analysis.
Date: December 1, 1996
Creator: Keppens, V.M.; Mandrus, D.; Boatner, L.A. & Rankin, J.
Partner: UNT Libraries Government Documents Department

Distribution of zinc, resistivity, and photosensitivity in a Vertical Bridgman grown Cd1-xZnxTe ingot.

Description: We present the results of a comprehensive study of distribution of zinc, resistivity, and photosensitivity in a Cd{sub 1-x}Zn{sub x}Te ingot grown by the Vertical Bridgman method. We used several complementary methods, viz., glow discharge mass spectroscopy, photoluminescence-, resistivity-, and photosensitivity-mapping, along with photo-induced current transient spectroscopy to characterize the material. We identified electronic levels in the band-gap responsible for compensation, recombination, and photosensitivity.
Date: May 1, 2008
Creator: Babentsov, V.; Franc, J.; Fauler, A.; Fiederle, M. & James, R. B.
Partner: UNT Libraries Government Documents Department

Electrochemical Deposition of Zinc-Nickel Alloys in Alkaline Solution for Increased Corrosion Resistance.

Description: The optimal conditions for deposition of zinc-nickel alloys onto stainless steel discs in alkaline solutions have been examined. In the past cadmium has been used because it shows good corrosion protection, but other methods are being examined due to the high toxicity and environmental threats posed by its use. Zinc has been found to provide good corrosion resistance, but the corrosion resistance is greatly increased when alloyed with nickel. The concentration of nickel in the deposit has long been a debated issue, but for basic solutions a nickel concentration of 8-15% appears optimal. However, deposition of zinc-nickel alloys from acidic solutions has average nickel concentrations of 12-15%. Alkaline conditions give a more uniform deposition layer, or better metal distribution, thereby a better corrosion resistance. Although TEA (triethanolamine) is most commonly used to complex the metals in solution, in this work I examined TEA along with other complexing agents. Although alkaline solutions have been examined, most research has been done in pH ≥ 12 solutions. However, there has been some work performed in the pH 9.3-9.5 range. This work examines different ligands in a pH 9.3-9.4 range. Direct potential plating and pulse potential plating methods are examined for optimal platings. The deposits were examined and characterized by XRD.
Date: December 2009
Creator: Conrad, Heidi A.
Partner: UNT Libraries

The development of lightweight hydride alloys based on magnesium

Description: The development of a magnesium based hydride material is explored for use as a lightweight hydrogen storage medium. It is found that the vapor transport of magnesium during hydrogen uptake greatly influences the surface and hydride reactions in these alloys. This is exploited by purposely forming near-surface phases of Mg{sub 2}Ni on bulk Mg-Al-Zn alloys which result in improved hydrogen adsorption and desorption behavior. Conditions were found where these near-surface reactions yielded a complex and heterogeneous microstructure that coincided with excellent bulk hydride behavior. A Mg-Al alloy hydride is reported with near atmospheric plateau pressures at temperatures below 200{degrees}C. Additionally, a scheme is described for low temperature in-situ fabrication of Mg{sub 2}Ni single phase alloys utilizing the high vapor pressure of Mg.
Date: February 1, 1996
Creator: Guthrie, S.E.; Thomas, G.J.; Yang, N.Y.C. & Bauer, W.
Partner: UNT Libraries Government Documents Department

Argonne National Laboratory Chemical Engineering Division Summary Report: July, August, September 1960

Description: 9 : : 7 : 7 9 : 5 5 ? 5 9 G -- 8 ; 8 ; = -activity levels of the melt-refining process for EBR-II core fuel was completed. An experiment was also completed on the evolution of fission- product krypton and xenon from an irradiated fuel pim as it was heat to a temperature above the melting point. In tests of alternate materials for use in a meltrefining furnace, a fibrous potassium titanate grain retainer was found to be a very effective heat insulator, but to have less strength than nigid Fibenfrax retainers. The skull remaining in the zirconia crucible after a meltrefining operation must be processed to recover, as partially purified metal, the fissionable material for return to the fuel cycle. Several essentially quantitative reductions of uranium dioxide and skull oxides were achieved in times of less than 8 hr at 800 deg C in dilute magnesium-zinc solutions and in magnesium containing a small percentage (0.5 to 2) of sodium as a wetting agent. Data and equations for solubilities of other elements in liquid cadmium are included. The partition coefficients of a numbsr of representative fissile and fission product elements between the two immiscible liquids, lead and zinc, at about 735 deg C were measured. The free energy of formation of the uraniumthallium intermetallic compound UTl/sub 3/ was measured, using a galvanic cell method. Galvanic cell measurements with the cerium-zinc system at 443 to 742 deg C were also made. The determination of the heat of formation of zirconium tetrafluoride by combustions of zirconium in fluonine was completed. A valus of -372.44 kcal/mole was obtained for the heat of formation of molybdenum hexafluoride. Calorimetric oombustions of boron in fluorine are being continued. Exploratory combustions of magnesium, aluminum, zinc, and cadmium are being carried out. Fuel ...
Date: October 1961
Creator: Argonne National Laboratory. Chemical Engineering Division.
Partner: UNT Libraries Government Documents Department


Description: Semi-conducting CdZnTe (or CZT) crystals can be used in a variety of detector-type applications. CZT shows great promise for use as a gamma radiation spectrometer. However, its performance is adversely affected by point defects, structural and compositional heterogeneities within the crystals, such as twinning, pipes, grain boundaries (polycrystallinity), secondary phases and in some cases, damage caused by external forces. One example is damage that occurs during characterization of the surface by a laser during Raman spectroscopy. Even minimal laser power can cause Te enriched areas on the surface to appear. The Raman spectra resulting from measurements at moderate intensity laser power show large increases in peak intensity that is attributed to Te. Atomic Force Microscopy (AFM) was used to characterize the extent of damage to the CZT crystal surface following exposure to the Raman laser. AFM data reveal localized surface damage in the areas exposed to the Raman laser beam. The degree of surface damage to the crystal is dependent on the laser power, with the most observable damage occurring at high laser power. Moreover, intensity increases in the Te peaks of the Raman spectra are observed even at low laser power with little to no visible damage observed by AFM. AFM results also suggest that exposure to the same amount of laser power yields different amounts of surface damage depending on whether the exposed surface is the Te terminating face or the Cd terminating face of CZT.
Date: June 10, 2008
Creator: Hawkins, S; Lucile Teague, L; Martine Duff, M & Eliel Villa-Aleman, E
Partner: UNT Libraries Government Documents Department


Description: CdZnTe (CZT) is a very promising material for nuclear-radiation detectors. CZT detectors operate at ambient temperatures and offer high detection efficiency and excellent energy resolution, placing them ahead of high-purity Ge for those applications where cryogenic cooling is problematic. The progress achieved in CZT detectors over the past decade is founded on the developments of robust detector designs and readout electronics, both of which helped to overcome the effects of carrier trapping. Because the holes have low mobility, only electrons can be used to generate signals in thick CZT detectors, so one must account for the variation of the output signal versus the locations of the interaction points. To obtain high spectral resolution, the detector's design should provide a means to eliminate this dependence throughout the entire volume of the device. In reality, the sensitive volume of any ionization detector invariably has two regions. In the first, adjacent to the collecting electrode, the amplitude of the output signal rapidly increases almost to its maximum as the interaction point is located farther from the anode; in the rest of the volume, the output signal remains nearly constant. Thus, the quality of CZT detector designs can be characterized based on the magnitude of the signals variations in the drift region and the ratio between the volumes of the driR and induction regions. The former determines the ''geometrical'' width of the photopeak i.e., the line width that affects the total energy resolution and is attributed to the device's geometry when all other factors are neglected. The latter determines the photopeak efficiency and the area under the continuum in the pulse-height spectra. In this work, we describe our findings from systematizing different designs of CZT detectors and evaluating their performance based on these two criteria.
Date: August 26, 2007
Partner: UNT Libraries Government Documents Department


Description: We present new results from our studies of defects in current single-crystal CdZnTe material. Our previous measurements, carried out on thin ({approx}1 mm) and long (>12 mm) CZT detectors, indicated that small (1-20 {micro}m) Te inclusions can significantly degrade the device's energy resolution and detection efficiency. We are conducting detailed studies of the effects of Te inclusions by employing different characterization techniques with better spatial resolution, such as quantitative fluorescence mapping, X-ray micro-diffraction, and TEM. Also, IR microscopy and gamma-mapping with pulse-shape analysis with higher spatial resolution generated more accurate results in the areas surrounding the micro-defects (Te inclusions). Our results reveal how the performance of CdZnTe detectors is influenced by Te inclusions, such as their spatial distribution, concentration, and size. We also discuss a model of charge transport through areas populated with Te inclusions.
Date: August 13, 2006
Creator: CAMARDA, G.S.; BOLOTNIKOV, A.E.; CARINI, G.A.; CUI, Y.; KOHMAN, K.T.; LI, L. et al.
Partner: UNT Libraries Government Documents Department

Aqueous Corrosion of Magnesium Alloys

Description: BS>The aqueous corrosion of Mg alloys was investigated at 53 to 150 deg C. Corrosion rates rose rapidly with temperature, reaching about 3 mils per day at 150 deg C for AZ-31 STAMg-2.5 to 3.5 wt.% Al-0.7 to 1.3 wt.% Zn-0.2 wt.% Mn!. Additions of small amounts of Cu and/or Ni to the basic AZ-31 composition reduced the corrosion rate at 150 deg by a factor of about two. Sn may be advantageously substituted for Zn in AZ-31. Control of the pH in the range between 6 and 7 and maintenance of a fluoride concentration in the range between 1 and 10 ppm reduced the corrosion rate of AZ-31 to about 0.1 mil per day at 150 deg C. (auth)
Date: May 1, 1960
Creator: Greenberg, S. & Ruther, W. E.
Partner: UNT Libraries Government Documents Department