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Synthesis of Advanced Ceramic Compounds by Intercalation

Description: The U.S. Bureau of Mines investigated the synthesis of advanced ceramics (SiC+AlN, SiAlON, SiC+Al 203 , and Si 3N4 +AlN) from natural clays (kaolin, halloysite, or montmorillonite) by an intercalation and heat treatment method. This process includes the steps of refining a clay, intercalating organic chemicals into its layered structure, drying the intercalated mixture, firing the treated structure at certain temperature ranges in controlled atmospheres to form desired compounds, and grinding the loosely agglomerated structure. Focus of this research is to economically process advanced ceramic structures from abundant natural resources. The advanced ceramic phases produced in this simple treatment are homogeneously distributed at the nanostructure level, and may potentially lead to cost effective manufacturing processes. The intercalation of clay was confirmed by X-ray and BET analyses. The evolution of chemical compositions during carbonization reactions and carbothermal reduction was investigated. The characteristics of refined clays and synthesized powders were studied. Advanced ceramic composites/solid solution have been produced from intercalated clays, without the presence of other compounds.
Date: 1995
Creator: Kwong, Kyei-Sing & Bennett, James P.
Partner: UNT Libraries Government Documents Department

Reactive plasma atomization of aluminum nitride powder

Description: Experiments were performed to synthesize AlN powders by reacting Al with N using a conventional dc arc plasma as heat source. Feeding Al powder into Ar/N plasma open to atmosphere produced mainly Al oxide. Experiments using a chamber backfilled with nitrogen suppressed the Al oxide, but little AlN was formed. A furnace and crucible assembly was designed to feed molten Al directly into a DeLaval nozzle attached to the face of the dc arc plasma gun. Resulting submicron powders show a significant increase in AlN formation. This was dependent on chamber pressure, plasma velocity, and molten liquid feed rate. Experimental parameters, equipment design, effects of atomization/vaporization/condensation are discussed.
Date: February 1, 1997
Creator: Prichard, P.; Besser, M.; Sordelet, D. & Anderson, I.
Partner: UNT Libraries Government Documents Department

Measurement of strain heat in shock-loaded 304 stainless steel: implications to powder consolidation; oral presentation of full paper

Description: Over the past decades there have been numerous papers on the shock response of materials and more specifically towards metal powder compaction and consolidation. In general, the shock process for powdered materials has utilized the traditional pressure-volume shock relationships proportioned to the initial packing densities of the powders. However, this approach and its resulting data are in controversy due to the lack of knowledge of its associated particle strain and strain temperature uncertainties. This paper will describe the current understanding as well as the experimental technique used to obtain the shock response for distended materials. The above parameters are described within a pressure-strain-temperature interdependence. It was found that the experimentally measured strain heat was not only a function of initial packing density but also a function of powder size and distribution.
Date: January 1, 2003
Creator: Staudhammer, Karl P.
Partner: UNT Libraries Government Documents Department

PERFORMANCE OF CHIPPED MAGNESIUM VERSUS HAMMERMILLED MAGNESIUM IN THE BOMB REDUCTION OF TETRAFLUORIDE. PART I

Description: The O. Hommel Company, of Carnegie, Penna., supplied Mallinckrodt Chemical Works with three types of Mg chips or powder (Type 84, 85B, and 87B) formed by machining Mg ingots. This material was tested and compared with standard New England Lime Mg in a series of reduction runs. A new type of powder (Type 93) developed by the O. Hommel Company during the course of the first experiment was also sert to Mallinckrodt Chemical Works foi preliminary testing. As this was superior to the other tynes tested, a large batch was made up and sent to both Electro Metallurgical Company and Mallinckrodt Chemical Works in order to confirm the preliminary results obtained by Mallinckrodt Chemical Works alone. (auth)
Date: June 1, 1945
Partner: UNT Libraries Government Documents Department

Synthesis, characterization and mechanical properties of nanocrystalline NiAl

Description: Nanocrystalline NiAl was produced from pre-cast alloys using an electron beam inert gas condensation system. In-situ compaction was carried out at 100-300 C under vacuum conditions. Energy dispersive spectroscopy was used to determine chemical composition and homogeneity. Average grain sizes in the range 4-10 nm were found from TEM dark field analyses. A compression-cage fixture was designed to perform disk bend tests. These tests revealed substantial room temperature ductility in nanocrystalline NiAl, while coarse grained NiAl showed no measurable room temperature ductility.
Date: November 1, 1996
Creator: Choudry, M.; Eastman, J.A.; DiMelfi, R.J. & Dollar, M.
Partner: UNT Libraries Government Documents Department

Gelcasting of aluminum titanate. Final report

Description: This Cooperative Research and Development Agreement (CRADA) was undertaken to assess the applicability of the gelcasting process for forming automotive exhaust port liner green bodies using Golden Technologies` proprietary aluminum titanate powder composition. A gelcasting process, specifically tailored to Golden Technologies` powder, was developed and used successfully to form green bodies for property evaluation. Using appropriate milling and firing conditions, it was found that the gelcast material had properties which compared favorably with Golden Technologies` baseline material. Tubular gelcast samples simulating exhaust port liners were prepared and shipped to Golden Technologies for final process evaluation.
Date: August 1, 1997
Creator: Nunn, S.D. & Stephan, J.E.
Partner: UNT Libraries Government Documents Department

Vibrational and electronic transition in InAs quantum dots formed by sequential implantation of In and As in a-SiO[sub 2]

Description: Optical, structural, and thermodynamic properties of materials can be changed by reducing their dimensions. We sequentially implanted In and As into fused silica windows in order to investigate formation and properties of InAs nano-particles. UV/VIS/NIR, FTIR in mid-IR, and far-IR spectroscopy were used to study change in electronic transitions and in vibrational modes (phonons) of the nano-particles InAs. The phonons can be confined to the surface of nano-particles and have frequencies falling between the transverse and longitudinal optical modes of the bulk material. Thermal annealing developed the formation of InAs quantum dots from as-implanted In-As system. At certain annealing temperature a change in UV/VIS transmission spectra and IR reflectance spectra indicated formation of InAs quantum dots. This is particularly evident from the absorption in IR and surface phonon bands are observed, confirming presence of quantum confined InAs.
Date: January 1, 1996
Creator: Ueda, A.; Henderson, D.O.; Mu, R.; Tung, Y.S.; Hall, C.; Zhu, J.G. et al.
Partner: UNT Libraries Government Documents Department

THE PRODUCTION OF HIGH-PURITY BERYLLIUM CARBIDE

Description: A process for production of pure Be/sub 2/C by using the re action between beryllium and graphite powders at about 1000 deg C described. The effects of variables such as stoichiometry, reaction temperature, beryllium- powder particle size, and process-apparatus construction materials are discussed. (J.R.D.)
Date: October 15, 1952
Creator: Theodore, J.G.; Beaver, W.W.; Dolance, A. & Stonehouse, A.J.
Partner: UNT Libraries Government Documents Department

Influence of shockwave profile on ejection of micron-scale material from shocked Sn surfaces: an experimental study

Description: This effort experimentally investigates the relationship between shock-breakout pressure and the amount of micron-scale fragments ejected (ejecta) upon shock release at the metal/vacuum interface of Sn targets shocked with a supported shockwave. The results are compared with an analogous set derived from HE shocked Sn targets, Taylor shockwave loading. The supported shock-pulse was created by impacting a Sn target with a Ti64 (Ti-6Al-4V) impactor that was accelerated using a powder gun. Ejecta production at the free-surface or back-side of the Sn targets were characterized through use of piezoelectric pins and Asay foils, and heterodyne velocimetry verified the time of shock release and the breakout pressure.
Date: January 1, 2009
Creator: Zellner, Michael B; Byers, Mark E; Hammerberg, James E; Germann, Tim C; Dimonte, Guy; Rigg, Paulo A et al.
Partner: UNT Libraries Government Documents Department

Analysis of Trace Amounts of Adulterants Found in Powders/Supplements Utilizing Direct Inject, Nanomanipulation, and Mass Spectrometry

Description: The regulations of many food products in the United States have been made and followed very well but unfortunately some products are not put under such rigorous standards as others. This leads to products being sold, that are thought to be healthy, but in reality contain unknown ingredients that may be hazardous to the consumers. With the use of several instrumentations and techniques the detection, characterization and identification of these unknown contaminates can be determined. Both the AZ-100 and the TE2000 inverted microscope were used for visual characterizations, image collection and to help guide the extraction. Direct analyte-probed nanoextraction (DAPNe) technique and nanospray ionization mass spectrometry (NSI-MS) was the technique used for examination and identification of all adulterants. A Raman imaging technique was than introduced and has proven to be a rapid, non-destructive and distinctive way to localize a specific adulterant. By compiling these techniques then applying them to the FDA supplied test samples three major adulterants were detected and identified.
Date: August 2016
Creator: Nnaji, Chinyere
Partner: UNT Libraries