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Film Formation on Lithium in Propylene Carbonate Solutions Under Open Circuit Conditions

Description: The nature of protective surface layers formed on lithium in propylene carbonate solutions of LiClO{sub 4} and LiAsF{sub 6} at open circuit has been investigated by electrochemical pulse measurements. The results are consistent with the fastformation of a compact thin layer resulting from the reaction with residual water. This layer acts as a solid ionicconductor. Slow corrosion or decomposition processes produce a thicker porous overlayer.
Date: June 1, 1980
Creator: Geronov, Y.; Schwager, F. & Muller, R.H.
Partner: UNT Libraries Government Documents Department

Loss of Radioactivity from Barium Carbonate Samples

Description: The exchange loss of radioactivity from solid samplos of barium carbonate through the agency of carbonic acid and its ions has been investigated under a variety of conditions. It is concluded that the losses observed are greatly dependent upon the method of sample preparation, in particular the nature or any heat treatment which the sample materials undergo.
Date: January 9, 1948
Creator: Yankwich, Peter E.
Partner: UNT Libraries Government Documents Department

Utilization of CO{sub 2} in production of polycarbonate

Description: Our original thrust, that of developing a direct route to diphenyl carbonate (the monomer for bisphenol A polycarbonate) using carbon dioxide as a raw material, was unsuccessful. The appendix describes the experiments that were tried in this regard. The primary problem was that we were unable to replicate the literature results of Yamazaki, et al, despite using their conditions and reactants, which form the basis for the proposed work. Despite this setback, we have derived a new route to diphenyl carbonate, which we have described in a proposal to the NSF/EPA partnership for environmental research (the sustainable technology section) which was submitted in April 1995. This route would incorporate carbon dioxide into a dialkyl carbonate using a tin catalyst, followed by transesterification using an enzyme to diphenyl carbonate. Thus, this work may continue on the future. However, despite the setbacks in the original proposed work, we set up two new collaborations with both Miles (now Bayer) and Exxon which employ CO{sub 2} as both monomer and solvent in polymer processing.
Date: December 31, 1994
Creator: Beckman, E. J.
Partner: UNT Libraries Government Documents Department

The electrochemical properties of bundles of single-walled nanotubes

Description: This is the final report of a Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The authors studied electrochemical properties of single-walled fullerene nanotube bundles. The materials exhibited a highly anisotropic conductivity. Electrochemical cycling in solutions of alkyl ammonium salts in propylene carbonate revealed that the nanotubes are stable to at least {+-}1.5 V and have a fairly high accessible surface area. Double-layer charging currents of approximately 30 farads per gram were observed. This is on the same order of magnitude, though somewhat lower, than state-of-the-art values for ultra-capacitor materials. Electrochemical insertion of lithium was attempted. Though several features were observed in a slow cyclic voltammetric scan, these features were not reversible, indicating little reversible insertion. Several possible reasons for this behavior are discussed.
Date: December 31, 1998
Creator: Zawodzinski, T.A. Jr.; Haridoss, P. & Uribe, F.A.
Partner: UNT Libraries Government Documents Department

Carbonic Acid Pretreatment of Biomass

Description: This project sought to address six objectives, outlined below. The objectives were met through the completion of ten tasks. 1) Solidify the theoretical understanding of the binary CO2/H2O system at reaction temperatures and pressures. The thermodynamics of pH prediction have been improved to include a more rigorous treatment of non-ideal gas phases. However it was found that experimental attempts to confirm theoretical pH predictions were still off by a factor of about 1.8 pH units. Arrhenius experiments were carried out and the activation energy for carbonic acid appears to be substantially similar to sulfuric acid. Titration experiments have not yet confirmed or quantified the buffering or acid suppression effects of carbonic acid on biomass. 2) Modify the carbonic acid pretreatment severity function to include the effect of endogenous acid formation and carbonate buffering, if necessary. It was found that the existing severity functions serve adequately to account for endogenous acid production and carbonate effects. 3) Quantify the production of soluble carbohydrates at different reaction conditions and severity. Results show that carbonic acid has little effect on increasing soluble carbohydrate concentrations for pretreated aspen wood, compared to pretreatment with water alone. This appears to be connected to the release of endogenous acids by the substrate. A less acidic substrate such as corn stover would derive benefit from the use of carbonic acid. 4) Quantify the production of microbial inhibitors at selected reaction conditions and severity. It was found that the release of inhibitors was correlated to reaction severity and that carbonic acid did not appear to increase or decrease inhibition compared to pretreatment with water alone. 5) Assess the reactivity to enzymatic hydrolysis of material pretreated at selected reaction conditions and severity. Enzymatic hydrolysis rates increased with severity, but no advantage was detected for the use of carbonic acid compared to ...
Date: May 31, 2003
Creator: Walsum, G. Peter van; Jayawardhana, Kemantha; Yourchisin, Damon; McWilliams, Robert & Castleberry, Vanessa
Partner: UNT Libraries Government Documents Department

Effects of partial oxidation of PMAN carbon on their performance as anodes in 1M LiPF{sub 6}/EC-DMC solutions

Description: A study was undertaken to examine the effects of partial oxidation on the electrochemical performance of carbons derived from poly(methylacrylonitrile) (PMAN)-divinylbenzene (DVB) co-polymers. Mild oxidation was examined as a possible technique to increase the reversible capacity, improve cycleability, and reduce the amount of irreversible capacity associated with the formation of the passivation layer during the first reduction. Oxidizing conditions involved treatment of the PMAN carbon prepared at 700 C with dry CO{sub 2} or with steam at 600 C for one hour. The effects on the performance in 1M LiPF{sub 6}/ethylene carbonate (EC)-dimethyl carbonate (DMC) solutions were evaluated by galvanostatic cycling tests, complex-impedance spectroscopy, and, to a more limited extent, cyclic voltammetry. Partial oxidation of PMAN carbon showed little or no overall beneficial effects in performance relative to the control.
Date: December 1996
Creator: Guidotti, R. A.
Partner: UNT Libraries Government Documents Department

Effect of solution additives on the performance of PMAN carbon anodes in 1M LiPF{sub 6}/EC-DMC solutions

Description: A study was undertaken to examine the use of a number of solution additives in 1M LiPF{sub 6}/ethylene carbonate (EC)-dimethyl carbonate (DMC) solutions to improve the performance of carbon anodes derived from polymethylacrylonitrile (PMAN)-divinylbenzene (DVB) copolymers. The study goals were to improve the cycle life and reduce the formation of the passivation layer during the first reduction, thereby minimizing the irreversible-capacity losses. Additives studied were 12-crown-4 (12-Cr-4) ether, decalin, and dilithium phthalocyanine (Li{sub 2}Pc). The carbon performance was characterized by galvanostatic cycling, cyclic voltammetry, and complex-impedance spectroscopy. Limited success was obtained with 12-Cr-4 ether at 0.25 M and decalin at 1 v/o. Poor results were noted with Li{sub 2}Pc at 0.025 M and 0.5 M.
Date: December 31, 1996
Creator: Guidotti, R.A. & Johnson, B.J.
Partner: UNT Libraries Government Documents Department

Method for Extracting and Sequestering Carbon Dioxide

Description: A method and apparatus to extract and sequester carbon dioxide (CO2) from a stream or volume of gas wherein said method and apparatus hydrates CO2, and reacts the resulting carbonic acid with carbonate. Suitable carbonates include, but are not limited to, carbonates of alkali metals and alkaline earth metals, preferably carbonates of calcium and magnesium. Waste products are metal cations and bicarbonate in solution or dehydrated metal salts, which when disposed of in a large body of water provide an effective way of sequestering CO2 from a gaseous environment.
Date: May 10, 2005
Creator: Rau, Gregory H. & Caldeira, Kenneth G.
Partner: UNT Libraries Government Documents Department

Carbonic Acid Retreatment of Biomass

Description: This project sought to address six objectives, outlined below. The objectives were met through the completion of ten tasks. (1) Solidify the theoretical understanding of the binary CO{sub 2}/H{sub 2}O system at reaction temperatures and pressures. The thermodynamics of pH prediction have been improved to include a more rigorous treatment of non-ideal gas phases. However it was found that experimental attempts to confirm theoretical pH predictions were still off by a factor of about 1.8 pH units. Arrhenius experiments were carried out and the activation energy for carbonic acid appears to be substantially similar to sulfuric acid. Titration experiments have not yet confirmed or quantified the buffering or acid suppression effects of carbonic acid on biomass. (2) Modify the carbonic acid pretreatment severity function to include the effect of endogenous acid formation and carbonate buffering, if necessary. It was found that the existing severity functions serve adequately to account for endogenous acid production and carbonate effects. (3) Quantify the production of soluble carbohydrates at different reaction conditions and severity. Results show that carbonic acid has little effect on increasing soluble carbohydrate concentrations for pretreated aspen wood, compared to pretreatment with water alone. This appears to be connected to the release of endogenous acids by the substrate. A less acidic substrate such as corn stover would derive benefit from the use of carbonic acid. (4) Quantify the production of microbial inhibitors at selected reaction conditions and severity. It was found that the release of inhibitors was correlated to reaction severity and that carbonic acid did not appear to increase or decrease inhibition compared to pretreatment with water alone. (5) Assess the reactivity to enzymatic hydrolysis of material pretreated at selected reaction conditions and severity. Enzymatic hydrolysis rates increased with severity, but no advantage was detected for the use of carbonic acid ...
Date: June 1, 2003
Creator: university, Baylor
Partner: UNT Libraries Government Documents Department

Synthesis of oxygenate products for high volume fuels applications. Quarterly technical progress report, November 1, 1994--January 31, 1995

Description: The objective of this project is to develop high yield syntheses of oxygenate products that are liquid at room temperature using as starting materials dimethy ether (DME) or methanol. The identified products include: Dimethyl Carbonate (DMC), 1,1-Dimethoxyethane (DMOE), C{sub 2}{sup +} Alcohols/Ethers (C{sub 2}AE). The technical strategy is outlined below: (A) Synthesis of DMC via oxidative carbonylation of DME instead of methanol. Since this synthesis would not co-produce water as a byproduct, there is a potential for very high DME conversions in contrast to the low (ca 20%) conversions obtained in conventional plants. Technical emphasis will be placed on development of a supported copper catalyst with a capability for cleavage of DME into its chemisorbed organic moieties. (B) Synthesis of 1,1-dimethoxymethane (DMOE) from acetylene/CO/H{sub 2} process streams obtained from commercial methane oxidative pyrolysis processes. In the overall processing scheme the syngas would be converted to DME. The wet acetylene stream would be partially condensed to retain an equivalent of water and then condensed with DME to produce EMOE. (C) Direct conversion of DME or DME/methanol to ethanol/propanol or their methyl ethers. Under the influence of functionalized alcohol condensation catalysts developed exclusively at Amoco it should be possible to achieve direct conversion of dimethyl ether (or methanol) to ethanol/propanol and/or the methyl ethers of these alcohols. Although this reaction is not currently known, a combination of key catalyst components from identified systems should result in a DME conversion catalyst to C{sub 2}+ oxygenates. (D) Reaction of DME or acetylene with synthesis gas (CO/H{sub 2}) or methanol. A variety of catalysts will be tested for conversion of acetylene/CO/H{sub 2} or acetylene/methanol to propylene and conversion of DME/CO/H{sub 2} or DME/methanol to dimenthyoxymethane (DMM) and/or other oxygenates.
Date: March 8, 1995
Partner: UNT Libraries Government Documents Department

Mathematical models as tools for probing long-term safety of CO2 storage

Description: Subsurface reservoirs being considered for storing CO{sub 2} include saline aquifers, oil and gas reservoirs, and unmineable coal seams (Baines and Worden, 2004; IPCC, 2005). By far the greatest storage capacity is in saline aquifers (Dooley et al., 2004), and our discussion will focus primarily on CO{sub 2} storage in saline formations. Most issues for safety and security of CO{sub 2} storage arise from the fact that, at typical temperature and pressure conditions encountered in terrestrial crust, CO{sub 2} is less dense than aqueous fluids. Accordingly, CO{sub 2} will experience an upward buoyancy force in most subsurface environments, and will tend to migrate upwards whenever (sub-)vertical permeable pathways are available, such as fracture zones, faults, or improperly abandoned wells (Bachu, 2008; Pruess, 2008a, b; Tsang et al., 2008). CO{sub 2} injection will increase fluid pressures in the target formation, thereby altering effective stress distributions, and potentially triggering movement along fractures and faults that could increase their permeability and reduce the effectiveness of a caprock in containing CO{sub 2} (Rutqvist et al., 2008; Chiaramonte et al., 2008). Induced seismicity as a consequence of fluid injection is also a concern (Healy et al., 1968; Raleigh et al., 1976; Majer et al., 2007). Dissolution of CO{sub 2} in the aqueous phase generates carbonic acid, which may induce chemical corrosion (dissolution) of minerals with associated increase in formation porosity and permeability, and may also mediate sequestration of CO{sub 2} as solid carbonate (Gaus et al., 2008). Chemical dissolution of caprock minerals could promote leakage of CO{sub 2} from a storage reservoir (Gherardi et al., 2007). Chemical dissolution and geomechanical effects could reinforce one another in compromising CO{sub 2} containment. Additional issues arise from the potential of CO{sub 2} to mobilize hazardous chemical species (Kharaka et al., 2006), and from migration of the large amounts ...
Date: February 1, 2009
Creator: Pruess, Karsten; Birkholzer, Jens & Zhou, Quanlin
Partner: UNT Libraries Government Documents Department

Internal and higher-order structure of chromatin nu bodies

Description: Based upon current biophysical data (including recent laser-Raman studies) of isolated nu bodies and inner histones, we have proposed that the chromatin subunit consists of a DNA-rich outer domain surrounding a protein core composed of ..cap alpha..-helical-rich histone globular regions, close-packed with dihedral point-group symmetry. Analysis of the effects of urea on isolated nu bodies suggest that these two domains respond differently: the DNA-rich shell exhibits noncooperative destabilization; the protein core undergoes cooperative destabilization. This differential response of the two regions of a nu body to a simple chemical perturbant (i.e., urea) may furnish a model for the conformational differences in nu bodies postulated for active chromatin. Nu bodies are believed to organize into 20-30 nm higher-order fibers in condensed regions of chromatin. However, the integrity of subunits in these thick fibers has recently been seriously challenged. Evidence from our laboratory, presented here, confirms that the 20-30 nm chromatin fibers consists of a close-packing of nu bodies. The chromatin subunits, therefore, retain their integrity within the higher-order fibers.
Date: January 1, 1977
Creator: Olins, D E
Partner: UNT Libraries Government Documents Department

Carbonation of Clay Minerals Exposed to scCO2/Water at 200 degrees and 250 degrees C

Description: To clarify the mechanisms of carbonation of clay minerals, such as bentonite, kaolinite, and soft clay, we exposed them to supercritical carbon dioxide (scCO2)/water at temperatures of 200 and 250 C and pressures of 1500 and 2000 psi for 72- and 107-hours. Bentonite, comprising three crystalline phases, montmorillonite (MMT), anorthoclase-type albite, and quartz was susceptible to reactions with ionic carbonic acid yielded by the interactions between scCO2 and water, particularly MMT and anorthoclase-type albite phases. For MMT, the cation-exchangeable ions, such as Na+ and Ca2+, present in its basal interplanar space, were replaced by proton, H+, from ionic carbonic acid; thereafter, the cations leaching from MMT directly reacted with CO32- as a counter ion of H+ to form carbonate compounds. Such in-situ carbonation process in basal space caused the shrinkage and breakage of the spacing structure within MMT. In contrast, the wet carbonation of anorthoclase-type albite, categorized as rock minerals, entailed the formation of three amorphous by-products, such as carbonates, kaolinite-like compounds, and silicon dioxide. Together, these two different carbonations caused the disintegration and corruption of bentonite. Kaolinite clay containing the amorphous carbonates and silicon dioxide was inert to wet carbonation. We noted only a gain in weight due to its water uptake, suggesting that kaolinite-like by-products generated by the wet carbonation of rock minerals might remain unchanged even during extended exposure. Soft clay consisting of two crystalline phases, dolomite and silicon dioxide, also was unaltered by wet carbonation, despite the uptake of water.
Date: November 1, 2010
Creator: Sugama, T.; Ecker, L.; Gill, S.; Butcher, T. (BNL) & Bour, D. (AltaRock Energy, Inc.)
Partner: UNT Libraries Government Documents Department

Neutralizing Carbonic Acid in Deep Carbonate Strata below the North Atlantic

Description: Our research is aimed at investigating several technical issues associated with carbon dioxide sequestration in calcium carbonate sediments below the sea floor through laboratory experiments and chemical transport modeling. Our goal is to evaluate the basic feasibility of this approach, including an assessment of optimal depths, sediment types, and other issues related to site selection. Through laboratory and modeling efforts, we are studying the flow of liquid carbon dioxide and carbon dioxide-water mixtures through calcium carbonate sediments to better understand the geomechanical and structural stability of the sediments during and after injection. Our modeling efforts in the first year show that the idea is feasible, but requires more sophisticated analysis of fluid flow at high pressure in deep sea sediments. In addition, we are investigating the kinetics of calcium carbonate dissolution in the presence of CO{sub 2}-water fluids, which is a critical feature of the system as it allows for increased permeability during injection. Our experimental results from the first year of work have shown that the kinetics are likely to be fast enough to create dissolution which will affect permeability. However, additional experiments are needed at high pressures, which will be a focus for years 2 and 3. We are also investigating the possibility of carbon dioxide hydrate formation in the pore fluid, which might complicate the injection procedure by reducing sediment permeability but might also provide an upper seal in the sediment-pore fluid system, preventing release of CO{sub 2} into the deep ocean, particularly if depth and temperature at the injection point rule out immediate hydrate formation. Finally, we are in the beginning stages of an economic analysis to estimate costs of drilling and gas injection, site monitoring as well as the availability of potential disposal sites with particular emphasis on those sites that are within the 200-mile ...
Date: December 1, 2005
Creator: Schrag, Daniel P.
Partner: UNT Libraries Government Documents Department

Neutralizing Carbonic Acid in Deep Carbonate Strata below the North Atlantic

Description: Carbon dioxide injection into deep sea sediments below 2700 m water depth and a few hundred meters to fifteen hundred meters deep in the sediment column may provide permanent geologic storage by gravitational trapping. At high pressures and low temperatures common in deep sea sediments a few hundred meters below sea floor, CO{sub 2} will be in its liquid phase and will be denser than the overlying pore fluid. The lower density of the pore fluid provides a cap to the denser CO{sub 2} and ensures gravitational trapping in the short term. The overall storage capacity for CO{sub 2} in such deep sea formations below the ocean floor is primarily determined by the permeability, and will vary with seafloor depth, geothermal gradient, porosity, and pore water salinity. Furthermore, the dissemination of the injected CO{sub 2} in the sediments and potential chemical reactions between CO{sub 2}, pore fluid and sediments will define its fate in the storage reservoir. The main objectives of our research was to evaluate the potential for sub-seabed CO{sub 2} storage in deep sea sediments using a range of approaches including experiments, permeability analysis, and modeling. Over the course of the three-year award, our results support an important role for sub-seabed storage in a diverse portfolio of carbons sequestration options. Our analysis has shown the feasibility of this type of storage, and also emphasizes that escape or leakage from such sites would be negligible. The most difficult challenge is to overcome the low permeability of typical deep-sea sediments, and a variety of approaches are suggested for future research.
Date: January 14, 2008
Creator: Lackner, Klaus; Harvey, Charles & Watson, Bruce
Partner: UNT Libraries Government Documents Department

Neutralizing Carbonic Acid in Deep Carbonate Strata below the North Atlantic

Description: Our research is aimed at investigating several technical issues associated with carbon dioxide sequestration in calcium carbonate sediments below the sea floor through laboratory experiments and chemical transport modeling. Our goal is to evaluate the basic feasibility of this approach, including an assessment of optimal depths, sediment types, and other issues related to site selection. The results of our modeling efforts were published this past summer in the Proceedings of the National Academy of Sciences. We are expanding on that work through a variety of laboratory and modeling efforts. In the laboratories at Columbia and at Harvard, we are studying the flow of liquid carbon dioxide and carbon dioxide-water mixtures through calcium carbonate sediments to better understand the geomechanical and structural stability of the sediments during and after injection. We are currently preparing the results of these findings for publication. In addition, we are investigating the kinetics of calcium carbonate dissolution in the presence of CO{sub 2}-water fluids, which is a critical feature of the system as it allows for increased permeability during injection. We are also investigating the possibility of carbon dioxide hydrate formation in the pore fluid, which might complicate the injection procedure by reducing sediment permeability but might also provide an upper seal in the sediment-pore fluid system, preventing release of CO{sub 2} into the deep ocean, particularly if depth and temperature at the injection point rule out immediate hydrate formation. This is done by injecting liquid CO{sub 2} into various types of porous media, and then monitoring the changes in permeability. Finally, we are performing an economic analysis to estimate costs of drilling and gas injection, site monitoring as well as the availability of potential disposal sites with particular emphasis on those sites that are within the 200-mile economic zone of the United States. We present ...
Date: July 14, 2006
Creator: Schrag, Daniel P.
Partner: UNT Libraries Government Documents Department

A Study of Electrochemical Reduction of Ethylene and PropyleneCarbonate Electrolytes on Graphite Using ATR-FTIR Spectroscopy

Description: We present results testing the hypothesis that there is a different reaction pathway for the electrochemical reduction of PC versus EC-based electrolytes at graphite electrodes with LiPF6 as the salt in common. We examined the reduction products formed using ex-situ Fourier Transform Infrared (FTIR) spectroscopy in attenuated total reflection (ATR) geometry. The results show the pathway for reduction of PC leads nearly entirely to lithium carbonate as the solid product (and presumably ethylene gas as the co-product) while EC follows a path producing a mixture of organic and inorganic compounds. Possible explanations for the difference in reaction pathway are discussed.
Date: May 12, 2005
Creator: Zhuang, Guorong V.; Yang, Hui; Blizanac, Berislav & Ross Jr.,Philip N.
Partner: UNT Libraries Government Documents Department

Development of a structure-property correlation for castable urethane elastomers

Description: A significant problem in electronic encapsulation is the poor load bearing performance of existing replacements for Adiprene-MOCA urethane elastomer. In response to this problem, this study defines the structural features that control the viscoelastic properties of the following liquid castable elastomers: Adiprene-MOCA, EN-7, and 3121-S. A review of previous investigations on a related class of materials suggests that viscoelastic properties may be more directly related to the physical structure or morphology of these elastomers, rather than their chemical structure. Accordingly, the morphology of the subject elastomers is characterized by means of electron microscopy and x-ray scattering measurements. These measurements reveal that within each elastomer incompatible chain segments cluster into separate domains, or microphases on a scale of 10 +- 1 nm. On this basis, it is concluded that the two major thermomechanical transitions present in each elastomer can be assigned to separate transitions within the two microphases. The above-ambient transition, which determines the upper use temperature of the elastomer, is specifically assigned to the glass transition of an amorphous microphase. The significance of this structure-property correltion for the liquid castable elastomers is twofold: (1) it permits generalization of mechanical property measurements on existing materials in order to predict their performance in unusual applications and (2) it leads to a rational strategy for developing improved elastomers for new, more demanding applications.
Date: January 1, 1978
Creator: Lagasse, R.R.
Partner: UNT Libraries Government Documents Department

Stress relaxation of cellular silicone material

Description: Stress relaxation information for cellular silicone materials formed with urea leachable filler is being gathered. Two types of polymers are used in the test: equilibrium type (random copolymer) and condensation type (block copolymer). Each of these was compounded to provide finished materials with nominal apparent densities of 0.34 and 0.52 g/cm/sup 3/. Three sample variations of 1.17, 1.52, and 2.54 mm nominal thickness were prepared from the lower density product, and two sample variations higher density product. Each of the material/thickness combinations was compressed to nominal compressions of 20 and 40% with nine replicates at each condition. A compression fixture for aging is used to maintain a specific compression on the cellular sample at room temperature, and a test machine is used to acquire the load data. The load was recorded at initial assembly and at selected times thereafter. A total of 180 specimens are in test, 90 equilibrium type material samples that have been stored 4 years and 90 condensation type material samples that have been stored for 3 years. Each condition for each material type has nine replicates. Of these nine samples, two are 3 year controls, two more are 10 year controls, and five are tested regularly. Current data supports the statement that the time dependent loss of load bearing properties is approximately log-linear, with the major differences found to be between the material types and the two densities of each material type. Extrapolation indicates that at the end of the planned 10-year study, the load retention of all samples will be between 58 and 68% of original; the condensation type material is expected to be superior.
Date: May 1, 1980
Creator: Schneider, J.W.
Partner: UNT Libraries Government Documents Department

Bond strength of urethane and epoxy-modified adhesives

Description: A number of urethane and epoxy-modified urethane systems were evaluated as room-temperature-curing adhesives. The systems were formulated to yield a variety of modulus levels and to be compatible with certain chemically sensitive materials.
Date: April 26, 1976
Creator: Childress, F. G.; Zava, A. K. & Miller, C. E.
Partner: UNT Libraries Government Documents Department

Susceptibility of Granite Rock to scCO2/Water at 200 degrees C and 250 degrees C

Description: Granite rock comprising anorthoclase-type albite and quartz as its major phases and biotite mica as the minor one was exposed to supercritical carbon dioxide (scCO{sub 2})/water at 250 C and 13.78 MPa pressure for 104 hours. For comparison purpose, four other rocks, albite, hornblende, diorite, and quartz, also were exposed. During the exposure of granite, ionic carbonic acid, known as the wet carbonation reactant, preferentially reacted with anorthoclase-type albite and biotite, rather than with quartz. The susceptibility of biotite to wet carbonation was higher than that of anorthoclase-type albite. All the carbonation by-products of anorthoclase-type albite were amorphous phases including Na- and K-carbonates, a kaolinite clay-like compound, and silicon dioxide, while wet carbonation converted biotite into potassium aluminum silicate, siderite, and magnesite in crystalline phases and hydrogen fluoride (HF). Three of these reaction by-products, Na- and K-carbonates and HF, were highly soluble in water. Correspondingly, the carbonated top surface layer, about 1.27 mm thick as carbonation depth, developed porous microstructure with numerous large voids, some of which have a size of {>=} 10 {mu}m, reflecting the erosion of granite by the leaching of these water-soluble reaction by-products. Comparing with this carbonation depth, its depth of other minerals was considerable lower, particularly, for hornblende and diorite with 0.07 and 0.02 mm, while no carbonate compound was detected in quartz. The major factor governing these low carbonation depths in these rocks was the formation of water-insensitive scale-like carbonate by-products such as calcite (CaCO{sub 3}), siderite (FeCO{sub 3}), and magnesite (MgCO{sub 3}). Their formation within the superficial layer of these minerals served as protective barrier layer that inhibits and retards further carbonation of fresh underlying minerals, even if the exposure time was extended. Thus, the coverage by this barrier layer of the non-carbonated surfaces of the underlying rock was reason why the hornblende ...
Date: January 1, 2011
Creator: Sugama, T. & Gill, S., Ecker, L., Butcher, T., Warren, J.
Partner: UNT Libraries Government Documents Department

Carbon dioxide sequestration by ex-situ mineral carbonation

Description: The process developed for carbon dioxide sequestration utilizes a slurry of water mixed with olivine- forsterite end member (Mg{sub 2}SiO{sub 4}), which is reacted with supercritical CO{sub 2} to produce magnesite (MgCO{sub 3}). Carbon dioxide is dissolved in water to form carbonic acid, which likely dissociates to H{sup +} and HCO{sub 3}{sup -}. The H{sup +} hydrolyzes the silicate mineral, freeing the cation (Mg{sup 2+}), which reacts with the HCO{sub 3}{sup -} to form the solid carbonate. Results of the baseline tests, conducted on ground products of the natural mineral, have demonstrated that the kinetics of the reaction are slow at ambient temperature (22 degrees C) and subcritical CO{sub 2} pressures (below 7.4 MPa). However, at elevated temperature and pressure, coupled with continuous stirring of the slurry and gas dispersion within the water column, significant conversion to the carbonate occurs. Extent of reaction is roughly 90% within 24 h, at 185 degrees C and partial pressure of CO{sub 2} (P{sub CO{sub 2}}) of 11.6 MPa. Current studies suggest that reaction kinetics can be improved by pretreatment of the mineral, catalysis of the reaction, and/or solution modification. Subsequent tests are intended to examine these options, as well as other mineral groups.
Date: January 1, 2000
Creator: O'Connor, W.K.; Dahlin, D.C.; Turner, P.C. & and Walters, R.P.
Partner: UNT Libraries Government Documents Department

High Density Nano-Electrode Array for Radiation Detection

Description: Bulk single crystals of Cd1-xZnxTe (x=0.04 to x=0.2) compound semiconductor is used for room temperature radiation detection. The production of large volume of Cd1-xZnxTe with low defect density is expensive. As a result there is a growing research interest in the production of nanostructured compound semiconductors such as Cd1-xZnxTe in an electrochemical route. In this investigation, Cd1-xZnxTe ternary compound semiconductor, referred as CZT, was electrodeposited in the form of nanowires onto a TiO2 nanotubular template from propylene carbonate as the non-aqueous electrolyte, using a pulse-reverse electrodeposition process at 130 ºC. The template acted as a support in growing ordered nanowire of CZT which acts as a one dimensional conductor. Cyclic Voltammogram (CV) studies were conducted in determining the potentials for the growth of nanowires of uniform stoichiometry. The morphologies and composition of CZT were characterized by using SEM, TEM and XRD. The STEM mapping carried out on the nanowires showed the uniform distribution of Cd, Zn and Te elements. TEM image showed that the nanowires were polycrystalline in nature. The Mott-Schottky analysis carried on the nanowires showed that the nanowires were a p-type semiconductor. The carrier density, band gap and resistivity of the Cd0.9Zn0.1Te nanowires were 4.29x1013 cm-3, 1.56 eV and 2.76x1011Ω-cm respectively. The high resistivity was attributed to the presence of deep defect states such as cadmium vacancies or Te antisites which were created by the anodic cycle of the pulse-reverse electrodeposition process. Stacks of series connected CZT nanowire arrays were tested with different bias potentials. The background current was in the order of tens of picoamperes. When exposed to radiation source Amerecium-241 (60 KeV, 4 μCi), the stacked CZT nanowires arrays showed sensing behavior. The sensitivity of the nanowire arrays increased as the number of stacks increased. The preliminary results indicate that the CZT nanowire arrays can be ...
Date: May 7, 2010
Creator: Misra, Mano
Partner: UNT Libraries Government Documents Department

In situ Raman spectroscopy of lithium electrode surface in ambient temperature lithium secondary battery. Final report

Description: Raman spectroscopy was used to characterize surface layers on lithium electrodes in different solvents such as propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and polyethylene glycol 400 dimethyl ether (PEG400DME). Both DMC and DEC were used singly, and also mixed with either methyl acetate (MA) or methyl formate (MF). The Raman spectra showed that passive films formed on the Li surface in different solvents may have different chemical structures, which changed during the charging and discharging processes. Raman spectroscopy was also applied to characterize zinc electrode surfaces in alkaline solutions. The results suggested that ZnO and Zn(OH){sub 2} formed on the Zn electrode when a passive potential was applied. A solid film of fullerene C{sub 60}, which could be used as a cathode in Li rechargeable batteries, was examined in the PEG400DME solution by both electrochemical and Raman spectroscopy. Cyclic voltammograms (CVs) showed five redox peaks which suggested the formation of C{sub 60}{sup {minus}}, C{sub 60}{sup 2{minus}}, C{sub 60}{sup 3{minus}}, C{sub 60}{sup 4{minus}}, and C{sub 60}{sup 5{minus}}. Raman spectra obtained from a thin C{sub 60} film indicated that the thin fulleride film dissolved in the PEG400DME/LiClO{sub 4} solution at negative potentials.
Date: September 1, 1992
Creator: Tachikawa, Hiroyasu
Partner: UNT Libraries Government Documents Department