54 Matching Results

Search Results

Advanced search parameters have been applied.

The addition of disilanes to cumulenes

Description: The syntheses of silicon-containing compounds and the studies of their rearrangements have been active research areas in the Barton research group. Previously, the addition of disilanes to acetylenes was studied in the group and an intramolecular 2S + 2A mechanism has been proposed. In this thesis, the work is focused on the addition of disilanes to cumulenes. The syntheses of the precursors are discussed and the possible mechanisms for their thermal, photochemical and catalytic rearrangements are proposed. Conjugated organic polymers have been studied in the group since 1985 because of their potential for exhibiting high electroconductivity, photoconductivity, strong non-linear optical response and intense fluorescence. In the second section of this dissertation, the synthesis and property studies of poly(phenylene vinylene) analogues are discussed.
Date: October 8, 1997
Creator: Chen, Y.
Partner: UNT Libraries Government Documents Department

ORGANIC COOLANT RECLAMATION. Quarterly Progress Report No. 3 for June 15, 1959-September 15, 1959

Description: In the third quarter of research on organic coolant reclamation, reaction conditions which show promise as reclamation prccedures were found in two major areas of investigation. In the study of hydrocracking of polyphenyls, ten catalysts show activity. One of these, a platinum on alumina, gives a very clean reaction with high conversions per pass and high yields in the model systems under study. The redistribution reaction in the model case of benzene and p-terphenyl gave reproducible results with high enough conversion to be of interest for reclamation. ( For preceding period see AECU-4268.) (auth)
Date: October 15, 1959
Creator: Wineman, R.J.; Adams, J.S. & Scola, D.A.
Partner: UNT Libraries Government Documents Department

Self-assembled multilayers and photoluminescence properties of a new water-soluble poly(para-phenylene)

Description: This paper reports the synthesis and characterizations of a new water-soluble poly(para-phenylene) (PPP) and its applications in preparing self-assembled multilayer films. This new water-soluble conducting polymer was prepared through the sulfonation reaction of poly(p-quarterphenylene-2,2{prime}-dicarboxylic acid). The incorporation of sulfonate groups has dramatically improved PPP`s solubility in water at a wide pH range, whereas previous PPP is only slightly soluble in basic solutions. Dilute aqueous solutions of this polymer with acidic, neutral or basic pH emit brilliant blue light while irradiated with UV light. The sulfonated PPP emits from 350 nm to 455 nm with a maximum intensity at 380 nm. Self-assembled multilayers of this sulfonated PPP were constructed with a positively charged polymer poly(diallyl dimethyl ammonium chloride) and characterized with various surface analyses. Conductive (RuO{sub 2} and ITO), semiconductive (Si wafer), and non-conductive (SiO{sub 2}) substrates were used in the preparation of self-assembled multilayers. Electrical, optical and structural properties of these novel self-assembled thin films will be discussed.
Date: March 1, 1998
Creator: Shi, X.; Li, D.Q.; Luett, M.; Fitzsimmons, M.R. & Van Patten, G.P.
Partner: UNT Libraries Government Documents Department

Surface modification, organometallic and polyaryl polymer coatings, and flame spray technologies for preventing corrosion of metals. Final report

Description: To improve adherent properties of electrogalvanized steel (EGS) to polymeric topcoats, the surfaces of EGS were modified by polyelectrolyte-modified zinc phosphating solution. The electrochemical reaction between phosphating solution and EGS led to the complete coverage with fully grown hopeite crystals after only 5 sec treatment, thereby improving adhesion to topcoating and providing protection of EGS against corrosion. To evaluate the ability of polyphenylene sulfide (PPS) polyaryl thermoplastic coatings to protect zinc phosphate (Zn{center_dot}Ph)treated steels from corrosion in a wet, harsh environment ( 1.0 wt % H{sub 2}SO{sub 4}, 3.0 wt % NaCl and 96.0 wt % water at temperatures from 25{degrees} to 200{degree}C), we exposed them in an autoclave to attempt heating-cooling cyclic fatigue tests (1 cycle = 12 hr at 200{degrees}C + 12 hr at 25{degrees}C) up to 90 times. The major chemical reaction at the interface between the PPS and Zn in the Zn-Ph layer during cycling led to the formation of ZnS reaction product, which enhanced the Zn-Ph-to-PPS adhesive bond; correspondingly, there were no signs of peeling and separation of the coating after 90 cycles. organometallosiloxane polymer (OMSP) was synthesized through the hydrolysis-condensation reaction of the mixed precursor solutions of the N-[3-(triethoxysily)propyl]-4,5,-dihydroimidazole and {Beta}-trimethoxysilylethyl-2-pyridine sols in liquor medium and the metal alkoxides and metallocene dichloride dissolved in water or tetrahydrofurane. The OMSP films (thickness, 0. 5 to 1. 0 {mu}m) deposited by simple dip-withdrawing coating methods to aluminum alloys displayed the impedance of > 10{sup 6} ohm-cm {sup 2} after exposure for 40 days in 0.5 N NaCl solution at 25{degrees}C and the 3000 hr-salt spray resistance. Using a flame spray coating process, the methacrylic acid-modified polyethylene copolymer was overlaid onto cold rolled steel surfaces.
Date: July 1, 1995
Creator: Sugama, T.
Partner: UNT Libraries Government Documents Department

Development of solid electrolytes for water electrolysis at intermediate temperatures. Task 3 report; Annual report

Description: This project is an attempt to synthesize and fabricate proton exchange membranes for hydrogen production via water electrolysis that can take advantage of the better kinetic and thermodynamic conditions that exist at higher temperatures. Current PEM technology is limited to the 125--150 C range. Based on previous work evaluating thermohydrolytic stability, some 5 families of polymers were chosen as viable candidates: polyether ketones, polyether sulfones, fluorinated polyimides, polybenzimidazoles, and polyphenyl quinoxalines. Several of these have been converted into ionomers via sulfonation and fashioned into membranes for evaluation. In particular, the sulfonated polyetheretherketone, or SPEEK, was tested for water uptake, thermo-conductimetric analysis, and performance as the solid electrolyte material in an electrolysis cell. Results comparable to commercial perfluorocarbon sulfonates were obtained.
Date: December 1, 1995
Creator: Linkous, C.A.; Anderson, R. & Kopitzke, R.W.
Partner: UNT Libraries Government Documents Department

Preparation of polymer-modified electrodes: A literature and experimental study

Description: A literature review is presented on the field of polymer modified electrodes which can be electrochemically generated. It is suggested that a possible application of these polymer modified electrodes is as a regeneratable catalysis packing material for use in couter-current exchange columns. Secondly, there is a presentation of experimental results dealing with possible electrode modification using difluoro- and dimethyl- phenols and fluorinated derivatives of styrene, benzoquinone and hydroquinone. It appears that dimethylphenol shows the most potential of the monomers experimentally tested in providing a stable polymer modified electrode surface. 170 refs., 31 figs., 1 tab.
Date: May 1, 1991
Creator: Jayanta, P. S. & Ishida, Takanobu
Partner: UNT Libraries Government Documents Department

Characterization of electrochemically modified polycrystalline platinum surfaces

Description: The characterization of electrochemically modified polycrystalline platinum surfaces has been accomplished through the use of four major electrochemical techniques. These were chronoamperometry, chronopotentiommetry, cyclic voltammetry, and linear sweep voltammetry. A systematic study on the under-potential deposition of several transition metals has been performed. The most interesting of these were: Ag, Cu, Cd, and Pb. It was determined, by subjecting the platinum electrode surface to a single potential scan between {minus}0.24 and +1.25 V{sub SCE} while stirring the solution, that the electrocatalytic activity would be regenerated. As a consequence of this study, a much simpler method for producing ultra high purity water from acidic permanganate has been developed. This method results in water that surpasses the water produced by pyrocatalytic distillation. It has also been seen that the wettability of polycrystalline platinum surfaces is greatly dependent on the quantity of oxide present. Oxide-free platinum is hydrophobic and gives a contact angle in the range of 55 to 62 degrees. We have also modified polycrystalline platinum surface with the electrically conducting polymer poly-{rho}-phenylene. This polymer is very stable in dilute sulfuric acid solutions, even under applied oxidative potentials. It is also highly resistant to electrochemical hydrogenation. The wettability of the polymer modified platinum surface is severely dependent on the choice of supporting electrolyte chosen for the electrochemical polymerization. Tetraethylammonium tetrafluoroborate produces a film that is as hydrophobic as Teflon, whereas tetraethylammonium perchlorate produces a film that is more hydrophilic than oxide-free platinum.
Date: December 1, 1991
Creator: Krebs, L. C. & Ishida, Takanobu
Partner: UNT Libraries Government Documents Department

High-Z organic-scintillation solution

Description: In the present experiment, an attempt is made to raise the average Z of a scintillation solution with as little attendant quenching as possible. Since high-Z atoms quench by means of a close encounter, such encounters are minimized by the use of alkyl groups substituted on the solvent, solute, and heavy atoms. The aromatic compound 1,2,4-trimethylbenzene (pseudocumene) is used as the solvent; 4,4''-di(5-tridecyl)-p-terphenyl (SC-180) as the solute; and tetrabutyltin as the high-Z material. To establish the validity of our ideas, various experiments have been performed with less protected solvents, and heavy atoms. These include benzene, toluene, p-terphenyl, bromobutane, and bromobenzene.
Date: January 1, 1983
Creator: Berlman, I.B.; Fluornoy, J.M.; Ashford, C.B. & Lyons, P.B.
Partner: UNT Libraries Government Documents Department


Description: Selective hydrocracking of total coolant was found to be an efficient and economic method for reconstitution of high boiler in the coolant to usable product. Such a process could eliminate the expense of vacuum distillation and disposal of high boilers produced in a nuclear reactor power plant. The selective conversion was possible since polyphenyls were found to be more susceptible towards hydrocracking as the phenyl chain length increased. Both cobalt molybdate on alumina and nickel oxide on alumina (50 to 80 square meters per gram) were found to be efficient catalysts at conditions of 900 deg F and 1000 psig with the latter giving more selective conversion to terphenyls. Continuous flow hydrocracking tests on OMRE Core II cool ant (containing 23% high boiler) resulted in 90 to 100% conversion of high boiler at product recoveries of 85 to 95 wt%. Average molecular weights of the products (biphenyl and heavier) were in the range 205 to 225 compared to 270 for Core II coolant. High boiler in Core III-A coolant which contained mainly first-generation polymers (hexaphenyls) was slightly more refractory toward hydrocracking than Core II high boiler, and conversion decreased slightly with increasing on-stream time. However, at optimum condition for processing coolant, coke formation on the catalyst for Core III-A coolant was about one-third that for Core II coolant. Products from hydrocracked OMRE coolant samples were found to be stable to electron irradiation at 650 deg F and dosages on the order of 10/sup 9/ to 10/sup 10/ rads, and pyrolysis threshold temperatures were between 750 and 825 deg F in 48hour tests. A proposal was outlined for utilization of the process in the Coolant Technology Loop at the EOCR at the National Reactor Testing Station. A conservative cost estimate was made for a 1000-megawatt-per-day (thermal) reactor producing 25,000 pounds per ...
Date: May 20, 1963
Creator: Gardner, L.E.
Partner: UNT Libraries Government Documents Department


Description: The EOCR prototype control rod, control rod drive, and driver fuel assembly were extensively tested in 500 deg F Santowax and 132 deg F water. These tests not only established the operating characteristics of these assemblies but also revealed a number of deficiencies in the various components. The modifications required were tested to establish the satisfactory performance of the modified components. Flow versus pressure differential measurements were performed on the driver fuel and the control rod. These measuremerts were also performed on various sized orifices in both assemblies to facilitate final orifice sizing when the final physics and heat transfer calculations have been completed. Scram insertion time curves were obtained for a variety of control rod configurations and test conditions. These curves not only established the scram insertion reliability of the control rod but also provided the basis for performing a control rod force analysis. Included are descriptions of the control rod, control rod drive, and driver fuel assembly together with descriptions of their method of operation. (auth)
Date: October 19, 1962
Creator: Harrison, L.J.
Partner: UNT Libraries Government Documents Department

Organic Compounds in Fission Reactors. [Part] 2. Thorio-Organic Compounds

Description: The advantages of the use of organic liquids in fission reactors to minmize corrosion and pressure problems were studied relative to the solution of thorium in such fluids. Thorio-organic compounds were prepared from organic acids, diketones, and other chelating compounds. Salts of carboxylic and phospho- organic acids were insoluble. The chelate with dibenzoylmethane was soluble in molten biphenyl but was decomposed at 300 deg C. The general low solubility of thorio-organic compounds in nonpolar solvents can be explained by steric effects. The large thorium atom has the ability to form strong coordination complexes with adjacent molecules, leading to coordination polymers. The effect can be minimized by shielding the thorium nucleus with large organic groups such as dibenzoylmethane. The large, branched organic groups needed to impart solubility limit the maximum solubility. (auth)
Date: February 29, 1960
Creator: Baldwin, W. H.
Partner: UNT Libraries Government Documents Department


Description: : : 7 : ; : = : : 9 ; 8 : ; / he use of organic liquids as reactor moderator-coolants is presented. A major part of the study was devoted to the mechanism of radiolytic damage to coolants. A mathematical treatment for handling information on the relative reactivity of different positions on an aromatic ring was developed in some detail. Determinations on products from the radiolysis of terphenyls, biphenyl, and mixtures of these with benzene indicate that free radicals may be the main reactive species generated but that others are present. Comparison of the data with reactions of chemically or photochemically generated free radicals shows that the radiolysis is not random, especially at 300 deg C, but that meta radicals are more frequently formed. Attack by the active species on another molecule is favored in the para position and repressed at the ortho position compared to the meta. The distribution of isomers found indicates that H/sub 2/ abstraction by the free radicals and isomerization reactions do not occur to an appreciable extent. New analytical methods were developed. Chromatography on a solid salt column using LiCl proved to be a very satisfactory method for quaterphenyls and most hexaphenyls. Elution peak shifts between LiCl, CsCl, and CaCl/sub 2/ columns were correlated with structure, and made possible separation and identification of certain isomers not possible on a single column. For the calibration of the columns and position identification, authentic samples of all the quaterphenyls, several quinquephenyls, and 13 hexaphenyls were obtained or synthesized by unequivocal methods. Several of these were obtained in fairly large quantity and five were new compounds. Using these known materials, important correlations were developed in the fine structure of the infrared spectra which, together with the elution peak shifting between salt columns, made possible identification of ...
Date: October 1, 1963
Creator: Hillyer, J.C.
Partner: UNT Libraries Government Documents Department