9,696 Matching Results

Search Results

Advanced search parameters have been applied.

RESEARCH AND DEVELOPMENT IN THE FIELD OF THORIUM CHEMISTRY AND METALLURGY. Monthly Progress Report for March 15 thru April 15, 1955

Description: A transition program, eliminating most of the wet chemical techniques for the preparation of cell feed and replacing these with a high temperature chlorination process, was begun. Crushing tests on a Fitz mill were initiated and tentative conclusions are that this type of equipment as superior to a combination of jaw and roll crushing. Small scale chlorination experiments indicate the feasibility of pelletizing ThOCO/sub 3/ for feed to a eontinuous hightemperature chlorinator. (D.E.B.)
Date: April 26, 1955
Creator: Wyatt, J.L.
Partner: UNT Libraries Government Documents Department

STUDY OF SOLVENT AND CATALYST INTERACTIONS IN DIRECT COAL LIQUEFACTION

Description: Using a reactor in which the coal is physically separated from the solid catalyst by a porous wall permeable to the hydrogen donor solvent, it was shown that direct contact between the catalyst and the coal is not required for catalyzed coal liquefaction. This occurs however only when there is a hydrogen atmosphere, as liquefaction with catalyst participation does not occur in a nitrogen atmosphere. Liquefaction by hydrogen transfer from the donor solvent itself does occur. This suggests that there is transfer of hydrogen from the catalyst to the coal via the solvent. The character of the solvent makes a significant difference, the better solvents being good hydrogen donors. These results indicate that the role of the catalyst may be to regenerate the spent hydrogen donor solvent during the liquefaction process. The peak temperature for volatiles evolution has been shown to be a reproducible measure of the coal rank. This was shown by an excellent correlation (R2 = 0.998) between peak volatiles temperatures (by TGA) and vitrinite reflectance. Using TG/MS, the volatiles contents of coals of a wide range of ranks was determined. The low rank coals emit largely phenols and some other oxygen compounds and olefins. The higher rank coals emit largely aromatic hydrocarbons and some olefins.
Date: January 1, 2000
Creator: Klein, Michael T.
Partner: UNT Libraries Government Documents Department

Excitations and possible bound states in the S = {1/2} alternating chain compound (VO){sub 2}P{sub 2}O{sub 7}

Description: Magnetic excitations in an array of (VO){sub 2}P{sub 2}O{sub 7} single crystals have been measured using inelastic neutron scattering. Until now, (VO){sub 2}P{sub 2}O{sub 7} has been thought of as a two-leg antiferromagnetic Heisenberg spin ladder with chains running in the a-direction. The present results show unequivocally that (VO){sub 2}P{sub 2}O{sub 7} is best described as an alternating spin-chain directed along the crystallographic b-direction. In addition to the expected magnon with magnetic zone-center energy gap {Delta} = 3.1 meV, a second excitation is observed at an energy just below 2{Delta}. The higher mode may be a triplet two-magnon bound state. Numerical results in support of bound modes are presented.
Date: July 30, 1997
Creator: Tennant, D.A.; Nagler, S.E. & Sales, B.C.
Partner: UNT Libraries Government Documents Department

Effect of water-bearing fiber in Kevlar 49-epoxy composites

Description: Water has been observed to be adsorbed, and possibly absorbed, by desiccated Kevlar 49 fiber to 6 percent of the fiber weight in 100 percent relative humidity. The effect of the water on the transverse flexural strength and elastic modulus of an aliphatic amine-cured epoxy, unidirectionally reinforced with saturated Kevlar 49, has been determined. Such composites are weaker than those made with fiber equilibrated to 0 percent relative humidity, and the effect persists after a 75/sup 0/C, 16-h postcure. It is suggested that glycol formation and a consequent excess of curing agent, resulting from a water-resin reaction at the fiber-matrix interface, accounts for the weakening.
Date: January 1, 1978
Creator: Moss, M.
Partner: UNT Libraries Government Documents Department

Stress relief of ceramic components in high voltage assemblies. Final report

Description: Two types of ceramic packages were evaluated to determine the effectiveness of encapsulating the ceramic components in beta eucryptite filled epoxy. The requirements (no high voltage breakdown, no ceramic cracking, and no encapsulant cracking) were met by the spark gap assembly, but the sprytron assembly had cracking in the encapsulant after thermal cycling. The encapsulation of the ceramic component in beta eucryptite filled epoxy with a stress decoupling material selectively applied in the stress concentrated areas were used to prevent cracking in the sprytron encapsulant. This method is proposed as the standard encapsulation process for high voltage ceramic components.
Date: February 1, 1979
Creator: Heinen, R.J.
Partner: UNT Libraries Government Documents Department

Solvent extraction of phenols from water

Description: Methyl isobutyl ketone (MIBK) and diisopropyl ether (DIPE) have been evaluated as solvents for extraction of phenols, at high dilution, from water. Equilibrium distribution coefficients (K/sub D/) have been measured for phenol, dihydroxybenzenes and trihydroxybenzenes in both solvents as a function of pH. Particularly for the multihydric phenols, MIBK gives substantially higher values of K/sub D/ than does DIPE. The effect of pH can be described quantitatively through a simple ionization model, using published values of dissociation constants for the various phenols. Some method for removal of residual dissolved solvent must ordinarily be included in any extraction process for phenols. Possibilities include atmospheric-steam or inert-gas stripping, vacuum-steam stripping, and extraction with a second solvent. Vacuum-steam stripping is a particularly attractive choice for removal of MIBK; this reinforces the utility of MIBK as a solvent. The optimal temperature for vacuum stripping is generally the temperature of the extraction operation, which in turn is related to the effect of temperature on K/sub D/. Values of K/sub D/ for phenol-water-MIBK were determined at 30, 50, and 75/sup 0/C, and were found to decrease with increasing temperature at all concentrations.
Date: February 1, 1980
Creator: Greminger, D.C.; Burns, G.P.; Lynn, S.; Hanson, D.H. & King, C.J.
Partner: UNT Libraries Government Documents Department

Multiheteromacrocycles that complex metal ions. Fifth progress report, 1 May 1978-30 April 1979

Description: The overall objective of this research is to design, synthesize and evaluate cyclic and polycyclic host organic compounds for their abilities to complex and lipophilize guest metal ions, their complexes and clusters. Host organic compounds consist of strategically placed solvating, coordinating and ion-pairing sites tied together by covalent bonds through hydrocarbon units around cavities shaped to be occupied by guest metal ions, or metal ions plus their ligands. Specificity in complexation is sought by matching the following properties of host and guest: cavity and metal ion sizes; geometric arrangements of binding sites; numbers of binding sites; characters of binding sites; and valences. The specific compounds synthesized and their complexing and lipophilizing properties are reported.
Date: January 15, 1979
Creator: Cram, D. J.
Partner: UNT Libraries Government Documents Department

IRRADIATION OF 3- SUBSTITUTED-2-PHENYLOXAZIRIDINES

Description: It was noted previously that 3-(p-dimethylamino)-2-phenyloxaziridine (I) and 3-(p-dimethylamino)-2-(m-nitrophenyl)oxaziridine were photosensitive. Further study on the irradiation (in a variety of solvents under nitrogen) of (I), 2,3-diphenyloxaziridine (II), and 3-(p-nitrophenyl)-2-phenyloxaziridine (III) indicates the major photoreaction to be cleavage to the aldehyde and an intermediate which forms aniline and azobenzene. There is also formed in the photolysis varying amounts of the corresponding anilide. A table provided gives the yields in three different solvents.
Date: August 30, 1967
Creator: Splitter, Janet S. & Calvin, Melvin.
Partner: UNT Libraries Government Documents Department

Investigation into the high strain-rate behavior of compacted sand using the split-Hopkinson pressure bar technique

Description: The results of compressive high strain-rate experiments on compacted sand are presented. Experiments were conducted on a 60.3 mm split Hopkinson pressure bar (SHPB). The experiments showed that the assumptions necessary for a valid SHPB experiment are satisfied when using compacted sand samples constrained to a nearly uniaxial strain state. Results show that the sample stress-strain response is governed principally by the initial sample gas porosity, and that no strain-rate dependence is exhibited at sample strains less than the initial gas porosity. Several stress-strain curves are presented for samples prepared at several combinations of moisture content and density with applied stresses and strain rates up to 520 MPa and 4000 sec/sup -1/, respectively.
Date: January 1, 1985
Creator: Felice, C.W.; Brown, J.A.; Gaffney, E.S. & Olsen, J.M.
Partner: UNT Libraries Government Documents Department

Improved performance for hoop-wound composite flywheel rotors

Description: Developmental work to date has shown the performance of hoop-wound composite flywheel rotors to be severely limited by composite transverse strength. This problem is addressed in a joint experimental-analytical effort aimed at improving transverse properties and assessing the impact of this improvement on flywheel performance. An improved test fixture designed to test hoop-wound cylinders in axial tension is developed. Test results show this specimen and test fixture produce more consistent data than do flat tensile bars cut from hexagonal cylinders. Initial experimental results from the improved specimen indicate that the transverse strength of Kevlar 49/epoxy composites could be improved by 30% by copolymerizing the epoxide matrix with an elastomer. The impact of these data on flywheel performance is predicted by a computer program which identifies optimum designs for given material properties on an energy-stored-per-swept-volume basis. A substantial improvement in performance is predicted, the attained 30% strength improvement of Kevlar 49/epoxy is shown to produce a 15% increase in energy stored. The analysis also permits multiple-material designs. Hybrid designs appear to have considerable potential for increasing storage capacity compared to single-material designs.
Date: January 1, 1977
Creator: Allred, R.E.; Foral, R.F. & Dick, W.E.
Partner: UNT Libraries Government Documents Department

Characterization of oxynitride dielectric films grown in NO/O{sub 2} mixtures by rapid thermal oxynitridation

Description: Ultra-thin oxynitride films were grown on Si by direct rapid thermal processing (RTP) oxynitridation in NO/O{sub 2} ambients with NO concentrations from 5% to 50%. During oxynitridation, nitrogen accumulated at the Si/dielectric interface and the average concentration of in N through the resulting films ranged from 0.3 to 3.0 atomic percent. The average concentration of N in the films increased with increasing NO in the ambient gas, but decreased with longer RTP times. The maximum N concentration remained relatively constant for all RTP times and a given NO/O{sub 2} ambient. Re-oxidation following oxynitridation altered L the N profile and improved the electrical characteristics, with an optimal NO/O{sub 2} mixture in the range of 10% to 25% NO. Re-oxidation by RTP improves the electrical characteristics with respect to the films that were not re-oxidized and produces only slight changes in the N distribution or maximum concentration. The electrical results also indicate that oxynitride films are superior to comparably grown oxide films.
Date: February 29, 2000
Creator: EVERIST,SARAH C.; MEISENHEIMER,TIMOTHY L.; NELSON,GERALD C. & SMITH,PAUL M.
Partner: UNT Libraries Government Documents Department

Deburring: technical capabilities and cost-effective approaches, Lessons 9 and 10

Description: Abrasive jet, water jet, and abrasive flow deburring are not panaceas for the world's deburring problems. They do, however, solve many of the problems where burrs are either difficult to reach or amenable to automation. As seen in this lesson, they can deburr miniature parts as well as large parts. In almost every case; however, one will note that accessibility of the burr is the key to the success of these processes. Volumes have been published on the effects of abrasive jet parameters. The reader is encouraged to pursue some of the citations in the Source of Additional Information for further quantitative information. Similarly, data on abrasive flow deburring is also available. Little data, however, has been published on water jet deburring.
Date: June 1, 1980
Creator: Gillespie, L.K.
Partner: UNT Libraries Government Documents Department