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Catalytic Membrane Sensors

Description: The proposed "catalytic membrane sensor" (CMS) was developed to generate a device which would selectively identify a specific reagent in a complex mixture of gases. This was to be accomplished by modifying an existing Hz sensor with a series of thin films. Through selectively sieving the desired component from a complex mixture and identifying it by decomposing it into Hz (and other by-products), a Hz sensor could then be used to detect the presence of the select component. The proposed "sandwich-type" modifications involved the deposition of a catalyst layered between two size selective sol-gel layers on a Pd/Ni resistive Hz sensor. The role of the catalyst was to convert organic materials to Hz and organic by-products. The role of the membraneo was to impart both chemical specificity by molecukir sieving of the analyte and converted product streams, as well as controlling access to the underlying Pd/Ni sensor. Ultimately, an array of these CMS elements encompassing different catalysts and membranes were to be developed which would enable improved selectivity and specificity from a compiex mixture of organic gases via pattern recognition methodologies. We have successfully generated a CMS device by a series of spin-coat deposited methods; however, it was determined that the high temperature required to activate the catalyst, destroys the sensor.
Date: December 1, 1998
Creator: Boyle, T.J.; Brinker, C.J.; Gardner, T.J.; Hughes, R.C. & Sault, A.G.
Partner: UNT Libraries Government Documents Department

Catalyst technology roadmap report

Description: This report outlines the future technology needs of the Chemical Industry in the area of catalysis and is a continuation of the process that produced the report Technology Vision 2020: The U.S. Chemical Industry and the Council for Chemical Research`s (CCR) Chemical Synthesis Team follow-up work in chemical synthesis. Vision 2020 developed a 25-year vision for the chemical industry and outlined the challenges to be addressed in order to achieve this vision. This report, which outlines the catalysis technology roadmap, is based on the output of the CCR`s Chemical Synthesis Team, plus a workshop held March -20-21, 1997, which included about 50 participants, with catalysis experts from industry, academia, and government. It is clear that all participants view catalysis as a fundamental driver to the 0274 economic and environmental viability of the chemical industry. Advances in catalytic science and technology are among the most crucial challenges to achieving the goals of the chemical industry advanced in Vision 2020.
Date: June 1, 1997
Creator: Jackson, N.B.
Partner: UNT Libraries Government Documents Department

Annual Report 1998: Chemical Structure and Dynamics

Description: The Chemical Structure and Dynamics (CS&D) program is a major component of the William R. Wiley Environmental Molecular Sciences Labo- ratory (EMSL), developed by Pacific Northwest National Laboratory (PNNL) to provide a state-of- the-art collaborative facility for studies of chemical structure and dynamics. We respond to the need for a fundamental, molecular-level understanding of chemistry at a wide variety of environmentally important interfaces by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interracial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in envi- ronmental chemistry and in nuclear waste proc- essing and storage; and (3) developing state-of- the-art analytical methods for characterizing com- plex materials of the types found in stored wastes and contaminated soils, and for detecting and monitoring trace atmospheric species. Our program aims at achieving a quantitative understanding of chemical reactions at interfaces and, more generally, in condensed media, compa- rable to that currently available for gas-phase reactions. This understanding will form the basis for the development of a priori theories for pre- dicting macroscopic chemical behavior in con- densed and heterogeneous media, which will add significantly to the value of field-scale envi- ronmental models, predictions of short- and long- term nuclear waste storage stabilities, and other areas related to the primary missions of the U.S. Department of Energy (DOE).
Date: May 10, 1999
Creator: Colson, SD & McDowell, RS
Partner: UNT Libraries Government Documents Department

Polymerization of the E and Z Isomers of Bis-(Triethoxysilyl)-2-Butene

Description: We have synthesized the Z and E isomers of 1,4-bis(triethoxysilyl)-2- butene and polymerized them under acid and base catalyzed sol-gel conditions. As expected the E system formed crosslinked, insoluble gels. The Z isomer, by nature of its geometry, formed high molecular weight, soluble polymeric products under acidic conditions. We were able to prepare and isolate both the cyclic disilsesquioxane monomer, and its dimer. Comparison of their spectral characterization with that of the soluble polymers suggests that the cyclics are present within the polymers. lle synthesis of a dimer likely present at some early stage of the polymerization suggests that we may be able to control the reaction and form rigid polymers with controllable tacticity. In addition, most of the gels were found to be non-porous indicating that the gels were, in fact, more compliant than ethenylene-bridged polysilsesquioxanes leading to collapse of pores during drying.
Date: May 11, 1999
Creator: Carpenter, J.P. Dorhout, K.; Loy, D.A.; Shaltout, R.M. & Shea, K.J.
Partner: UNT Libraries Government Documents Department

Cyclization Phenomena in the Sol-Gel Polymerization of a,w-Bis(triethoxysilyl)alkanes and Incorporation of the Cyclic Structures into Network Silsesquioxane Polymers

Description: Intramolecular cyclizations during acid-catalyzed, sol-gel polymerizations of ct,co- bis(tietioxysilyl)aWmes substintidly lengtien gelties formonomers witietiylene- (l), propylene- (2), and butylene-(3)-bridging groups. These cyclizations reactions were found, using mass spectrometry and %i NMR spectroscopy, to lead preferentially to monomeric and dimeric products based on six and seven membered disilsesquioxane rings. 1,2- Bis(triethoxysilyl)ethane (1) reacts under acidic conditions to give a bicyclic drier (5) that is composed of two annelated seven membered rings. Under the same conditions, 1,3- bis(triethoxysilyl)propane (2), 1,4-bis(triethoxysilyl)butane (3), and z-1,4- bis(triethoxysilyl)but-2-ene (10) undergo an intramolecular condensation reaction to give the six membemd and seven membered cyclic disilsesquioxanes 6, 7, and 11. Subsequently, these cyclic monomers slowly react to form the tricyclic dirners 8,9 and 12. With NaOH as polymerization catalyst these cyclic silsesquioxanes readily ~aeted to afford gels that were shown by CP MAS z%i NMR and infr=d spectroscopes to retain some cyclic structures. Comparison of the porosity and microstructwe of xerogels prepared from the cyclic monomers 6 and 7 with gels prepared directly from their acyclic precursors 2 and 3, indicate that the final pore structure of the xerogels is markedly dependent on the nature of the precursor. In addition, despite the fact that the monomeric cyclic disilsesquioxane species can not be isolated from 1-3 under basic conditions due to their rapid rate of gelation, spectroscopic techniques also detected the presence of the cyclic structures in the resulting polymeric gels.
Date: January 4, 1999
Creator: Alam, T.M.; Carpenter, J.P.; Dorhout, P.K.; Greaves, J.; Loy, D.A.; Shaltout, R. et al.
Partner: UNT Libraries Government Documents Department

Inductively Coupled Plasma Etching of III-V Semiconductors in BCl(3)-Based Chemistries: Part 1: GaAs, GaN, GaP, GaSb and AlGaAs

Description: BC13, with addition of Nz, Ar or Hz, is found to provide smooth anisotropic pattern transfer in GaAs, GaN, GaP, GaSb and AIGriAs under Inductively Coupled Plasma conditions, Maxima in the etch rates for these materials are observed at 33% N2 or 87$'40 Hz (by flow) addition to BC13, whereas Ar addition does not show this behavior. Maximum etch rates are typically much higher for GaAs, Gap, GaSb and AIGaAs (-1,2 @rein) than for GaN (-0.3 ymu'min) due to the higher bond energies of the iatter. The rates decrease at higher pressure, saturate with source power (ion flux) and tend to show maxima with chuck power (ion energy). The etched surfaces remain stoichiometric over abroad range of plasma conditions.
Date: December 4, 1998
Creator: Abernathy, C.R,; Han, J.; Hobson, W.S.; Hong, J.; Lambers, E.S.; Lee, J.W. et al.
Partner: UNT Libraries Government Documents Department

Denitration of Rocky Flats Ion-Exchange Resins: Recommendation of Denitration Processes, October 19, 1995

Description: Resin denitration via anion-exchange is an implementable process that can effectively mitigate the hazards associated with stored resins in which the bulk of the nitrate consists of an "exchangeable nitrate" ionically bound to the cationic sites of the anion-exchange resins. Salicylate has been selected as the exchange anion of choice because of its superior selectivity for the Rocky Flats resins and its unique potential for comprehensive recovery and recycle. This report outlines a single recommended resin denigration procedure that is reasonably independent of the resin composition and the current stored form. This procedure is not optimized but rather seeks to `over-treat' the resins so that a single procedure works for the variety of stored resins. The recommended treatment with sodium salicylate reduces resins by 95-99+% the measured exothermic behavior of the ion-exchange.
Date: December 1, 1998
Creator: Espinoza, Jacob; Barr, Mary & Smith, Wayne
Partner: UNT Libraries Government Documents Department

Plasma-assisted catalytic reduction of NO<sub>x</sub>

Description: Many studies suggest that lean-NO<sub>x</sub> SCR proceeds via oxidation of NO to NO¬ by oxygen, followed by the reaction of the NO¬ with hydrocarbons. On catalysts that are not very effective in catalyzing the equilibration of NO+O¬ and NO¬, the rate of N¬ formation is substantially higher when the input NO<sub>x</sub> is NO¬ instead of NO. The apparent bifunctional mechanism in the SCR of NO<sub>x</sub> has prompted the use of mechanically mixed catalyst components, in which one component is used to accelerate the oxidation of NO to NO¬, and another component catalyzes the reaction between NO¬ and the hydrocarbon. Catalysts that previously were regarded as inactive for NO<sub>x</sub> reduction could therefore become efficient when mixed with an oxidation catalyst. Preconverting NO to NO¬ opens the opportunity for a wider range of SCR catalysts and perhaps improves the durability of these catalysts. This paper describes the use of a non-thermal plasma as an efficient means for selective partial oxidation of NO to NO¬. When combined with some types of SCR catalyst, the plasma can greatly enhance the NO<sub>x</sub> reduction and eliminate some of the deficiencies encountered in an entirely catalyst-based approach. efficiency for reduction of NO<sub>x</su
Date: August 24, 1998
Creator: Voss, K; Brusasco, R M; Kung, H H; Kung, M C; Merritt, B T; Penetrante, B M et al.
Partner: UNT Libraries Government Documents Department

Thermodynamics for separation-process technology

Description: When contemplating or designing a separation process, every chemical engineer at once recognizes the thermodynamic boundary conditions that must be satisfied: when a mixture is continuously processed to yield at least partially purified products, energy and mass must be conserved and work must be done. In his daily tasks, a chemical engineer uses thermodynamic concepts as tacit, almost subconscious, knowledge. Thus, qualitative thermodynamics significantly informs process conception at its most fundamental level. However, quantitative design requires detailed knowledge of thermodynamic relations and physical chemistry. Most process engineers, concerned with flow sheets and economics, cannot easily command that detailed knowledge and therefore it is advantageous for them to maintain close contact with those specialists who do. Quantitative chemical thermodynamics provides an opportunity to evaluate possible separation processes not only because it may give support to the process engineer`s bold imagination but also because, when coupled with molecular models, it can significantly reduce the experimental effort required to determine an optimum choice of process alternatives. Six examples are presented to indicate the application of thermodynamics for conventional and possible future separation processes.
Date: October 1, 1995
Creator: Prausnitz, J.M.
Partner: UNT Libraries Government Documents Department

Manifold methods for methane combustion

Description: Objective is to develop a new method for studying realistic chemistry in turbulent methane combustion with NO{sub x} mechanism. The realistic chemistry is a simplification to a more detailed chemistry based on the manifold method; accuracy is determined by interaction between the transport process and the chemical reaction. In this new (tree) method, probability density function or partially stirred reactor calculations are performed. Compared with the reduced mechanism, manifold, and tabulation methods, the new method overcomes drawbacks of the reduced mechanism method and preserves the advantages of the manifold method. Accuracy is achieved by specifying the size of the cell.
Date: December 31, 1995
Creator: Yang, B. & Pope, S.B.
Partner: UNT Libraries Government Documents Department

Development of high energy polymers systems: 6th monthly status report

Description: The major objective of the current program is the preparation of high energy hydroxyl-terminated polyester prepolymers from combinations of energetic diols and dicarboxylic acid chlorides. The initial work was based on the reactions of 4,4-dinitropimeloyl chloride (DNPCl) with 2,2,8,8-tetranitro-4,6-dioxa-1,9-nonanediol (DINOL) and 3(dinitrofluoro- ethoxy)-1,2-propanediol (REX-18). In an effort to develop a smooth and rapid polyester polymerization method, reactions between DNPCl and both DINOL and REX-18 have been carried out in THF containing pyridine. It was expected that the pyridine would act as an HCl acceptor, permitting room temperature polymerizations. This was indeed shown to be the case. In fact, when the glycol and DNPCl were dissolved in THF and pyridine added rapidly, a very exothermic reaction took place, with copious quantities of pyridine hydrochloride being precipitated. Slow addition of pyridine to the reaction mixture also resulted in an exotherm. In both cases, brown polymers were produced and they were very difficult to work-up. The next series of polymerizations will be carried out at 0{degrees}C in an effort to control the polymerizations more carefully and avoid color formation. The diacid chloride of 2-fluoro-2,2-dinitroethoxyfumaric acid has apparently been synthesized. Reactions of the acid with thionyl chloride at 50-60{degrees} for several days followed by a one-hour reflux produced a white solid. It was filtered, washed with hexane and dried in a vacuum dessicator over KOH. The powder melted at 104-106{degrees}. After it is recrystallized, it will be submitted for elemental analyses. Should it prove to be the diacid chloride, it will be reacted with DINOL and REX-18.
Date: July 9, 1969
Creator: Lawton, E.A.
Partner: UNT Libraries Government Documents Department

Miniature chemical measurement systems

Description: Prospect of microfabricated monolithic devices that accomplish complete chemical assays is enticing. Early work with microfabricated chemical analysis devices focused on separations methods. More recently reagent manipulation has been integrated with separation devices to create more powerful capabilities. Examples of procedures, other than separations, that have been demonstrated on micromachined structures include reagent mixing, dilution, and reaction, preconcentration through sample stacking and biopolymer tagging for detection. Developments in liquid phase microfabricated chemical analysis devices are reviewed.
Date: December 31, 1996
Creator: Ramsey, J.M.
Partner: UNT Libraries Government Documents Department

Group-III Nitride Etch Selectivity in BCl(3)/Cl(2) ICP Plasmas

Description: Patterning the group-IH nitrides has been challenging due to their strong bond energies and relatively inert chemical nature as compared to other compound semiconductors. Plasma etch processes have been used almost exclusively to pattern these films. The use of high-density plasma etch systems, including inductively coupled plasmas (ICP), has resulted in relatively high etch rates (often greater than 1.0 pmhnin) with anisotropic profiles and smooth etch morphologies. However, the etch mechanism is often dominated by high ion bombardment energies which can minimize etch selectivity. The use of an ICP-generated BCl~/C12 pkyma has yielded a highly versatile GaN etch process with rates ranging from 100 to 8000 A/rnin making this plasma chemistry a prime candidate for optimization of etch selectivity. In this study, we will report ICP etch rates and selectivities for GaN, AIN, and InN as a function of BCl~/Clz flow ratios, cathode rf-power, and ICP-source power. GaN:InN and GaN:AIN etch selectivities were typically less than 7:1 and showed the strongest dependence on flow ratio. This trend maybe attributed to faster GaN etch rates observed at higher concentrations of atomic Cl which was monitored using optical emission spectroscopy (OES). ~E~~~~f:~ INTRODUCTION DEC j 4898 Etch selectivi
Date: December 9, 1998
Creator: Abernathy, C.R.; Han, J.; Hong, J.; Lester, L.F.; Pearton, S.J.; Shul, R.J. et al.
Partner: UNT Libraries Government Documents Department

Anion solvation in alcohols

Description: Anion solvation is measured in alcohols using pump-probe pulse radiolysis and the activation energy of solvation is determined. Solvation of an anion appears to be different than excited state solvation. The continuum dielectric model does not appear to explain the results.
Date: March 1996
Creator: Jonah, C. D.; Xujia, Zhang & Lin, Yi
Partner: UNT Libraries Government Documents Department

Brief overview of the various families of grouts and their aplications

Description: It is difficult to maintain an up-to-date overview of all the grouts presently used on the international market. Better grouts are continuously developed and more formulators are making their appearance. Consequently, it is difficult to clearly define all of the products in the industry. This topic has been the subject of numerous papers and textbooks. Most authors, however, only focus on their fields of interest: applications in geotechnical, or rehabilitation, or seepage control in civil engineering, oil or mining industry. There has been a limited transfer of technology from one field to the other because of the enormous differences in magnitude, site conditions and consequently the application techniques. The tools an engineer has are: his expertise in grouting and engineering background, equipment available or to be designed or modified to carry out a particular job, relevant data available from other sciences, and products with a variety of characteristics. This paper concentrates on product selection. The most suitable product for a particular project requires a good understanding of the general chemical and mechanical characteristics of the grout. The grouts have been classified into four categories for the purpose of this paper. There may be other methods of classification; however, this is only an attempt to help the industry with the selection of the most suitable grout for a given application. The four categories are: suspension grouts, chemical grouts, hot melts, and precipitation grouts. 1 fig.
Date: April 1, 1989
Creator: Nandts, A.
Partner: UNT Libraries Government Documents Department

The transuranium elements: From neptunium and plutonium to element 112

Description: Beginning in the 1930`s, both chemists and physicists became interested in synthesizing new artificial elements. The first transuranium element, Np, was synthesized in 1940. Over the past six decades, 20 transuranium elements have been produced. A review of the synthesis is given. The procedure of naming the heavy elements is also discussed. It appears feasible to produce elements 113 and 114. With the Berkeley Gas-filled Separator, it should be possible to reach the superheavy elements in the region of the spherical Z=114 shell, but with fewer neutrons than the N=184 spherical shell. 57 refs, 6 figs.
Date: July 26, 1996
Creator: Hoffman, D.C.
Partner: UNT Libraries Government Documents Department

ITP Filtrate Benzene Removal Alternatives

Description: Existing ITP filtrate hold tanks may provide sufficient capacity and residence time to strip dissolved benzene from the incoming filtrate using nitrogen sparging in the bottom of the old tanks. This is based on equilibrium supported by late Wash test data using aged washed slurry. Theoretical considerations indicate that benzene stripping will be more difficult from the ITP unwashed high salt filtrates due to reduced mass transfer. Therefore experimental sparging data is needed to quantify the theoretical effects.Foaming limits which dictate allowable sparging rate will also have to be established. Sparging in the hold tanks will require installation of sintered metal spargers, and possibly stirrers and foam monitoring/disengagement equipment. The most critical sparging needs are at the start of the precipitation/concentration cycle, when the filtrate flux rate is the highest,and at the end of wash cycle where Henry`s equilibrium constant falls off,requiring more gas to sparge the dissolved benzene. With adequate recycle (for proper distribution) or sparging in the old tanks, the 30 inch column could be used for the complete ITP process. A courser packing would reduce back pressure while enabling benzene stripping. The Late Wash Tests indicate adequate benzene stripping even at reduced gas flow. This will require experimental verification under ITP conditions. Using the 30 in. column vs 18 in. during the wash cycle will enhance stripping without need for additional sparging provided the minimum flow requirements are met.
Date: May 21, 1993
Creator: Dworjanyn, L.O.
Partner: UNT Libraries Government Documents Department

Compression ratio effect on methane HCCI combustion

Description: We have used the HCT (Hydrodynamics, Chemistry and Transport) chemical kinetics code to simulate HCCI (homogeneous charge compression ignition) combustion of methane-air mixtures. HCT is applied to explore the ignition timing, bum duration, NO<sub>x</sub> production, gross indicated efficiency and gross IMEP of a supercharged engine (3 atm. Intake pressure) with 14:1, 16:l and 18:1 compression ratios at 1200 rpm. HCT has been modified to incorporate the effect of heat transfer and to calculate the temperature that results from mixing the recycled exhaust with the fresh mixture. This study uses a single control volume reaction zone that varies as a function of crank angle. The ignition process is controlled by adjusting the intake equivalence ratio and the residual gas trapping (RGT). RGT is internal exhaust gas recirculation which recycles both thermal energy and combustion product species. Adjustment of equivalence ratio and RGT is accomplished by varying the timing of the exhaust valve closure in either 2-stroke or 4-stroke engines. Inlet manifold temperature is held constant at 300 K. Results show that, for each compression ratio, there is a range of operational conditions that show promise of achieving the control necessary to vary power output while keeping indicated efficiency above 50% and NO<sub>x</sub> levels below 100 ppm. HCT results are also compared with a set of recent experimental data for natural gas.
Date: September 29, 1998
Creator: Aceves, S. M.; Pitz, W.; Smith, J. R. & Westbrook, C.
Partner: UNT Libraries Government Documents Department

Polymer pendant crown thioethers for removal of mercury from acidic wastes

Description: Removal and immobilization of mercury ions from industrial waste streams is a difficult and expensive problem requiring an efficient and selective extractant that is resistant to corrosive conditions. We have now developed an acid-resistant thiacrown polymer that has potential utility as a selective and cost-effective Hg<sup>2+</sup> extractant. Copolymerization of a novel C-substituted thiacrown, N,N-(4-vinylbenzylmethyl)-2-aminomethyl- ,4,&l 1,14- pentathiacycloheptadecane, with DVB (80% divinylbenzene) using a radical initiator generated a highly cross-linked polymer containing pendant thiacrowns. Mercury extraction capabilities of the polymer were tested in acidic media (pH range: 1.5 to 6.2) and the extraction of Hg<sup>2+</sup> was determined to be 95<sup>+</sup>% with a mixing time of 30 minutes. The thiacrown polymer was also determined to be selective for Hg*+, competing ions such as Pb<sup>2+</sup>, Cd<sup>2+</sup>, A1<sup>3+</sup>, and Fe<sup>3+</sup>. even in the presence of high concentrations of The bound Hg<sup>2+</sup> ions can then be stripped from the polymer, allowing the polymer to be reused without significant loss of loading capacity.
Date: December 22, 1998
Creator: Baumann, T F; Fox, G A & Reynolds, J
Partner: UNT Libraries Government Documents Department

Exciton and biexciton signatures in femotosecond transient absorption of {pi}-conjugated oligomers

Description: The authors report femotosecond transient-absorption studies of a five-ring oligomer of polyphenylenevinylene (PPV) prepared in two different forms: as solid-state films and dilute solutions. Both types of samples exhibit a photoinduced absorption (PA) band with dynamics which closely match those of the stimulated emission (SE), demonstrating unambiguously that these features originate from the same species, namely from intrachain singlet excitons. Photo-chemical degradation of the solid-state samples is demonstrated to dramatically shorten the SE dynamics above a moderate incident pump fluence, whereupon the dynamics of the SE and the long-wavelength PA no longer coincide. In contrast to solutions, solid-state films exhibit an additional short-wavelength PA band with pump-independent dynamics, indicating the efficient formation of non-emissive inter-chain excitons. Correlations in the subpicosecond dynamics of the two PA features, as well as the pump intensity-dependence provide strong evidence that the formation of inter-chain excitons is mediated by intrachain two-exciton states. At high pump levels, the authors see a clear indication of interaction between excited states also in dilute solutions. This is manifested as a superlinear pump-dependence and shortening of the decay dynamics of the SE. They attribute this behavior to the formation of biexcitons resulting from coherent interaction between two excitons on a single chain.
Date: October 1, 1997
Creator: Klimov, V.; McBranch, D.; Barashkov, N. & Ferraris, J.
Partner: UNT Libraries Government Documents Department

Pathway and kinetic analysis on the iso-propyl radical + O{sub 2} reaction system

Description: We analyze the isopropyl + 02 reaction system using thermochemical Transition State Theory (TST), molecular thermodynamic properties, analysis (quantum RRK) for k(E) and modified strong collision analyze Cyclic transition states for both hydrogen transfer and concerted propylene from isopropylperoxy are calculated using semi-empirical theory in addition to transition states for H02 elimination from hydroperoxy-isopropyl. Computed rate constants are compared to constant measurements of for isopropyl + H02.
Date: April 7, 1997
Creator: Bozzelli, J. W. & Pitz, W. J.
Partner: UNT Libraries Government Documents Department