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Maher, Denise C. (Denise Christine). "Studies towards the synthesis of superhindered polysulfides." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59552.
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Various methods of synthesizing the novel, highly congested bis(tris(trimethylsilyl)methyl) disulfide (2) were investigated.It was found that the oxidation of tris(trimethylsilyl)methyl mercaptan (1) with iodine in the presence of sodium methoxide affords a product whose $ sp{13}$C, $ sp1$H and combustion data are consistent with its structure being that of 2. In another attempt at the preparation of 2, tris(trimethylsilyl) methane with methyl lithium, elemental sulfur and iodine gave rise to 2 unanticipated products, believed to be bis(trimethylsilyl)methyl, tris(trimethylsilyl)methyl disulfide (3a) and bis(tris(trimethylsilyl)methyl) trisulfide (3c).
Furthermore, trisulfide 3c was subsequently prepared by the sulfuration of 1 using SCl$ sb2$ or N,N-thiobisbenzimidazole. In addition to thiol 1, both 3c and 2 exhibited unanticipated multiplicity of $ sp{13}$C NMR peaks in the silyl region of the spectrum. As a result, efforts were made to explain these results by molecular mechanics calculations on the thiol, trisulfide and disulfide structures.
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Mahon, Andrea. "Linear polysulfides : their characterisation and degradation pathways." Thesis, University of Warwick, 1996. http://wrap.warwick.ac.uk/3498/.
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Linear polysulfides (LPs) are widely used in high performance sealants. The typical structure of the polymer is: H(SC2H40CH2OC2H4S)nH. We have completely characterised the complex components that make up commercially used LPs, by means of electrospray ionisation mass spectrometry (ESI- MS), combined with collision induced dissociation (CID). ESI has proved to be an invaluable mass spectroscopic technique in the characterisation of linear polysulfides. The individual spectra are well-resolved, enabling conclusions to be reached about the presence of variant mers (usually associated with additional oxymethylene or oxyethylene units or a monosulfide linkage, or some combination of these), and about the identity of end-groups and nature of the repeat unit. We have also been able to use ESI-MS to study the degradation reactions of LP pre-polymers. We have obtained spectra of LPs using matrix assisted laser desorption ionisation time-of-flight mass spectrometry, MALDI-TOF-MS), but these are not as informative as spectra obtained by ESI-MS. Field desorption mass spectrometry (FD-MS) has also been successful in characterising LP samples, but this technique is less generally accessible and much more time-consuming than either ESI-MS or MALDI-TOF-MS. LPs degrade thermally and photochemically by two competing degradation pathways: i) a free radical autoxidation mechanism, and ii) a hydrolysis mechanism. UV photolysis or pyrolysis of LP pre-polymers in the presence of air or oxygen resulted in the development of carbonyl groups detectable by IR and 13C NMR spectroscopy, while 2-D NMR studies and the highly characteristic field positions of the NMR resonances show the carbonyl group to be due to a formate ester. All thin film samples of cured LP, irrespective of the LP structure and curing agent, including ZL-2264 (with an extra CH2 linkage in the repeat unit), also produce this carbonyl absorption at 1725 cm-1 when exposed to UV irradiation. The formate ester arises as a result of a conventional free radical mechanism of autoxidation; attack at the C-H bond adjacent to the ether oxygen atom leads to a hydroperoxide and hence an alkoxyl radical, followed by scission to give the formate ester. The study of liquid exudates formed when TBBP- and HDDA- cured LP cast blocks are exposed to prolonged periods of heat or UV irradiation also show the development of carbonyl bands at 1724 cm-1 in their IR spectra, again indicating that degradation is occurring at least in part via a free radical mechanism. ESI-MS studies of degraded pre-polymer samples and liquid exudates show that, in parallel with the degradation route involving oxygenation of a methylene group, there is a hydrolysis mechanism involving initial cleavage of the formal group to release formaldehyde, followed by secondary reactions to give other products detected in the ESI-MS spectrum of the photolysate/pyrolysate. This mechanism is supported by the extremely slow degradation of ZL-2264, which has no formal group. The hydrolysis mechanism is the principal route for the degradation of LP pre- polymers and TBHP- and HDDA- cured LP block samples, while LPs cured using MnO2 and NaB03 degrade almost exclusively via the free radical autoxidation pathway.
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D'Arcy, Richard. "Macromolecular engineering for modulating the response of oxidation-sensitive polymers." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/macromolecular-engineering-for-modulating-the-response-of-oxidationsensitive-polymers(cb5f7eb6-b29e-4453-9c40-1d24b1b838f3).html.
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In this thesis the primary focus is on polysulfides, a class of oxidation-responsive polymers with potential biomedical applications as 1) polymeric anti-inflammatory/anti-oxidant agents and/or 2) drug delivery vehicles, specifically for inflammation and cancer. Within the Tirelli lab, polysulfides for inflammation targeting drug delivery are a key area of research and as such a comprehensive review of this topic is covered in Chapter 1. Polysulfides are able to target inflammation (and cancer) due to their inherent ability to react with reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) and hypochlorite (ClO-) which are markedly upregulated in inflamed and cancerous milieu; in Chapter 2 we demonstrate the different effects of these two oxidants on poly(propylene sulfide) (PPS) nanoparticles. Using diffusion-ordered NMR spectroscopy (DOSY), both size and spatial characteristics of the oxidation products were probed; specifically, the size of the oxidation products and the spatial location of Pluronic i.e. physically entrapped within the polysulfide core or ‘free’ Pluronic micelles. We additionally showed that these nanoparticles displayed a protective effect on both L929 fibroblasts and J774.2 macrophages when challenged with ClO-. In Chapter 3, micellar PEG-PPS composed of linear- (2-arm) or star-(4, 6 and 8 arm)shaped polymers were synthesised; we found micelles formed of the linear PEG-PPS reacted with H2O2 at a quicker rate than the star PEG-PPS, however, the critical micelle concentration of the stars was significantly lower indicating a marked increase in stability to dilution. Chapter 5 aimed to assess new monomer ethylene sulfide (ES), which was copolymerised with propylene sulfide (PS) and end-capped with PEG vinyl sulfone; the resulting PEG-P(PS-ES) copolymers were found to have a gradient composition due to the greater reactivity of ES. The rate of oxidation with the PEG-P(PS-ES) micelles (1:1 monomer composition) was ~2x faster with respect to PEG-PPS. The effect of primary structure on oxidation and gelation was evaluated using copolymers with various ES/PS gradients; there was little effect on oxidation kinetics, however, high ES gradients displayed significantly lower gel points; we ascribe this to the higher ES-ES association in polymers with longer ES sequences. Chapter 4 investigated the Mitsunobu reaction as a means to functionalize PEG-OH with a variety of commonly used (bio)conjugation groups (thiol, maleimide, azide and amine). This project arose when synthesising PEG-thioacetate as a potential macroinitiator for the polymerisation of PS/ES. Currently, the Mitsunobu reaction is scarcely used for the functionalization of PEG-OH but here we demonstrate its benefits over other commonly used functionalization methods; namely, it being a quantitative and high-yielding one-pot synthesis reaction.
4
Arbach, Miriam. "Diallyl polysulfides from garlic : mode of action and applications in agriculture." Thesis, University of East Anglia, 2014. https://ueaeprints.uea.ac.uk/50025/.
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Garlic (Allium sativum) contains a wide range of organosulfur compounds which show a variety of biological effects including broad spectrum antibacterial, antifungal and antiviral activity, as well as selective anticancer activity. One highly bioactive class of compounds from garlic are diallyl polysulfides (DAS), containing one to six sulfur atoms in a linear chain. The bioactivity of DAS has been shown to increase with increasing sulfur chain length up to DAS4 and in this study the even higher bioactivity of DAS5 and DAS6 was demonstrated. The bioactivity of DAS is believed to be initiated following initial reaction with intracellular low molecular weight (LMW) and protein thiols. In this study the interaction between DAS and LMW thiols was investigated and for the first time the reduced DAS metabolites allyl hydropolysulfides have been detected in vitro and in vivo in the Gram positive bacterium Bacillus subtilis. Additionally, formation of mixed polysulfides between DAS and LMW thiols with up to five sulfur atoms was observed in vitro. Proteomic studies revealed a large number of proteins in B. subtilis that formed mixed di- and trisulfides with DAS. Therefore multiple points of DAS attack have been proven and the disturbance of the cellular redox status through lowering the pool of reduced LMW thiols was established in two different organisms (B. subtilis and the nematode Steinernema feltiae). To exploit the polysulfide chemistry for the development of a “green” nematicide, the nematicidal activity of DAS was investigated in bioassays as well as the efficacy of DAS formulations towards plant pathogenic nematodes (Meloidogyne spp. and Globodera spp.) in potato and carrot field trials. It was demonstrated that the DAS derived nematicides form an equally effective alternative compared to synthetic nematicides at a much lower environmental and health risk.
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Jankulár, Tomáš. "Příprava a charakterizace elektrodových materiálů z elementární síry pro Li-ion akumulátory." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220240.
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This thesis deals with the preparation and characterization of electrode materials for Li-ion batteries based on elemental sulfur. The theoretical part is focused on the characteristics of Li-ion batteries, electrochemical reactions, the process of electrochemical lithiation of sulfur and solubility properties of intermediate polysulfides. The practical part of the thesis deals with the preparation of cathode materials for Li-ion cells with an active substance in the form of elemental sulfur. The prepared electrodes were investigated using cyclic voltammetry and galvanostatic cycling. Physical characterization by SEM and XRD was provided.
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Jay, Jennifer Ayla 1969. "Effect of polysulfides on cinnabar solubility, partitioning, and methylation by Desulfovibrio desufuricans." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9506.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999.Includes bibliographical references.
Sulfate reducing bacteria are believed to be the most important methylators of mercury in aquatic systems. Methylation may be controlled by the availability of mercury to these bacteria and therefore may depend on mercury speciation in sulfidic water ...
by Jennifer Ayla Jay.
Ph.D.
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Zhang, Qiaoyi. "The synthesis and characterization of sodium polysulfides for Na-S battery application." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/90666.
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The limited understanding of the electrochemical mechanism of Na-S battery systems is a barrier to further improve the performance of the Na-S energy storage. The characterization of sodium polysulfides in the Na-S battery systems can offer insightful information to understand the electrochemical reaction mechanism of the Na-S batteries and overcome the "inert" nature of short-chain polysulfides (Na2Sn, 1In recent decades, our society became more and more power-demanding, sodium-sulfur (NaS) energy storage systems attracted researchers’ attention due to their low cost and good performance. However, the limited understanding of the electrochemical mechanism of Na-S battery systems is a barrier to further improve the performance of the Na-S batteries. The characterization of sodium polysulfides in the Na-S battery systems can offer insightful information to understand the working mechanism of the Na-S batteries during charge and discharge of the batteries. Up to now, there are limited studies on the sodium polysulfides compound in the Na-S batteries. Meanwhile, although many synthesis methods for sodium polysulfides have been reported, many related studies offer unclear and misleading parameters. This work examines several reported synthesis methods for sodium polysulfide and offers complete processes with clear parameters for the synthesis of sodium polysulfide. Meanwhile, the sodium polysulfides solution in tetraethylene glycol dimethyl ether (TEGDME), an electrolyte solvent that was widely used in Na-S batteries, were analyzed to study the properties of sodium polysulfides in the Na-S battery system.
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Hippauf, Felix. "Tailoring Pore Size and Polarity for Liquid Phase Adsorption by Porous Carbons." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-223482.
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Adsorption is a versatile purification technique to selectively separate different peptide fractions from a mixture using mild operation conditions. Porous carbons are ideally suited to separate ACE-inhibiting dipeptides by combining tailored size exclusion and polarity selectivity. The desired peptide fraction is mostly hydrophobic and very small and should adsorb inside hydrophobic micropores.
The second topic of this thesis is linked to energy storage. The lithium-sulfur battery is a promising alternative to common lithium-ion batteries with theoretical capacities of up to 1672 mAh g−1 sulfur. The second aim of this thesis is to conduct an in-depth investigation of polysulfides interacting with selected carbon materials in a simplified battery electrolyte environment. The focus of this study is laid on the impact of surface polarity and pore size distribution of the carbon to develop a quantitative correlation between polysulfide retention and porosity metrics.
Both, the enrichment of ACE-inhibitors and the retention of polysulfides rely on liquid phase adsorption in porous materials, linking the above mentioned topics. This thesis not only aims to develop an enrichment process or to find a superior battery cathode but also strives to explore structure-property relationships that are universally valid. Understanding the complex interplay of pore size and polarity leading to selective interactions between pore wall and the adsorbed species is given a high priority.
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Saidu, Nathaniel Edward Bennett [Verfasser], and Mathias [Akademischer Betreuer] Montenarh. "Effect of coumarin and diallyl polysulfides on HCT116 colon cancer cells / Nathaniel Edward Bennett Saidu. Betreuer: Mathias Montenarh." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2014. http://d-nb.info/1053724675/34.
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Saidu, Nathaniel Edward Bennett Verfasser], and Mathias [Akademischer Betreuer] [Montenarh. "Effect of coumarin and diallyl polysulfides on HCT116 colon cancer cells / Nathaniel Edward Bennett Saidu. Betreuer: Mathias Montenarh." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2014. http://d-nb.info/1053724675/34.
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McClanahan, Eric Robert. "Modification and Enhancement of Epoxide Coatings via Elastomeric Polysulfides, Self-Assembled Nanophase Particles, Functional Sol-Gels, and Anti-Corrosion Additives." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1493674944922562.
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Hu, Ping. "Design of oxidation-sensitive polymer micelles for inflammation targeting." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/design-of-oxidationsensitive-polymer-micelles-for-inflammation-targeting(8ec02724-aeef-4ce8-ac2d-a3186de6267e).html.
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The research presented in this thesis focuses on the molecular design of an oxidation-sensitive nanocarrier and its enzyme conjugate with a view of their application in the field of biomaterials. I have polarised our attention on a specific class of polymers, the polysulfides, for their environmental responsiveness (towards oxidising substances, a condition often associated with inflammatory reactions), interesting physico-chemical properties, ease of the preparation and multiple possibilities for further modifications and bioconjugations, which are perfectly suitable for the development as systems for drug delivery applications. In this work we firstly have focused on the synthesis of amphiphilic poly(propylene sulfide)-poly(ethylene glycol) (PPS-PEG) block copolymers by employing vinyl sulfone as the functional group to link the blocks and modify the end of the PEG. This study was followed by an investigation of the macromolecular interchange and payload exchange of the formed polymeric micelles to understand the 'co-formulation' events, employing fluorophores (dansyl groups) and quenchers (dabsyl groups) either as terminal groups in macroamphiphiles or as encapsulated hydrophobic payloads. In another part of the work, I have developed a micellar system with which simultaneously to two of the most important ROS: superoxide and hydrogen peroxide, for inflammation-responsive drug release. The system is composed of superoxide dismutase (SOD) conjugated to oxidation-sensitive amphiphilic polysulfide/PEG block copolymers; the conjugate combines the SOD reactivity towards superoxide with that of hydrophobic thioethers towards hydrogen peroxide. Specifically, here we have demonstrated how this hybrid system can efficiently convert superoxide into hydrogen peroxide, which is then 'mopped-up' by the polysulfides. This mode of operation is functionally analogous to the SOD/catalase combination, with the advantage of being based on a single and more stable system.
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Lohmayer, Regina [Verfasser], and Britta [Akademischer Betreuer] Planer-Friedrich. "Importance of Sulfide, Polysulfides, and Elemental Sulfur for Abiotic and Biotic Redox Processes in Sulfur-Metal(loid)Systems / Regina Lohmayer. Betreuer: Britta Planer-Friedrich." Bayreuth : Universität Bayreuth, 2015. http://d-nb.info/1080237569/34.
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Zhao, Teng. "Development of new cathodic interlayers with nano-architectures for lithium-sulfur batteries." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/275684.
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Issues with the dissolution and diffusion of polysulfides in liquid organic electrolytes hinder the advance of lithium–sulfur (Li-S) batteries for next generation energy storage. To trap and re-utilize the polysulfides, brush-like, zinc oxide (ZnO) nanowires based interlayers were prepared ex-situ using a wet chemistry method and were coupled with a sulfur/multi-walled carbon nanotube (S/MWCNT) composite cathode. The cell with this configuration showed a good cycle life at a high current rate ascribed to (a) a strong interaction between the polysulfides and ZnO nanowires grown on conductive substrates; (b) fast electron transfer and (c) an optimized ion diffusion path from a well-organized nanoarchitecture. A praline-like flexible interlayer consisting of titanium oxide (TiO2) nanoparticles and carbon (C) nanofiber was further prepared in-situ using an electrospinning method, which allows the chemical adsorption of polysulfides throughout a robust conductive film. A significant enhancement in cycle stability and rate capability was achieved by incorporating this interlayer with a composite cathode of S/MWCNT. These results herald a new approach to building functional interlayers by integrating metal oxides with conductive frameworks. The derivatives of the TiO2/C interlayer was synthesized by changing the precursor concentration and carbonization temperature. Finally, a dual-interlayer was fabricated by simply coating titanium nitride (TiN) nanoparticles onto an electro-spun carbon nanofiber mat, which was then sandwiched with a sulfur/assembled Ketjen Black (KB) composite cathode with an ultra-high sulfur loading. The conductive polar TiN nanoparticles not only have a strong chemical affinity to polysulfides through a specific sulfur-nitrogen bond but also improve the reaction kinetics of the cell by catalyzing the conversion of the long-chain polysulfides to lithium sulfide. Besides, carbon nanofiber mat ensures mechanical robustness to TiN layer and acts as a physical barrier to block polysulfides diffusion. The incorporation of dual interlayers with sulfur cathodes offers a commercially feasible approach to improving the performance of Li-S batteries.
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Hao, Yong. "Sulfur Based Electrode Materials For Secondary Batteries." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2582.
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Developing next generation secondary batteries has attracted much attention in recent years due to the increasing demand of high energy and high power density energy storage for portable electronics, electric vehicles and renewable sources of energy. This dissertation investigates sulfur based advanced electrode materials in Lithium/Sodium batteries. The electrochemical performances of the electrode materials have been enhanced due to their unique nano structures as well as the formation of novel composites.
First, a nitrogen-doped graphene nanosheets/sulfur (NGNSs/S) composite was synthesized via a facile chemical reaction deposition. In this composite, NGNSs were employed as a conductive host to entrap S/polysulfides in the cathode part. The NGNSs/S composite delivered an initial discharge capacity of 856.7 mAh g-1 and a reversible capacity of 319.3 mAh g-1 at 0.1C with good recoverable rate capability.
Second, NGNS/S nanocomposites, synthesized using chemical reaction-deposition method and low temperature heat treatment, were further studied as active cathode materials for room temperature Na-S batteries. Both high loading composite with 86% gamma-S8 and low loading composite with 25% gamma-S8 have been electrochemically evaluated and compared with both NGNS and S control electrodes. It was found that low loading NGNS/S composite exhibited better electrochemical performance with specific capacity of 110 and 48 mAh g-1 at 0.1C at the 1st and 300th cycle, respectively. The Coulombic efficiency of 100% was obtained at the 300th cycle.
Third, high purity rock-salt (RS), zinc-blende (ZB) and wurtzite (WZ) MnS nanocrystals with different morphologies were successfully synthesized via a facile solvothermal method. RS-, ZB- and WZ-MnS electrodes showed the capacities of 232.5 mAh g-1, 287.9 mAh g-1 and 79.8 mAh g-1 at the 600th cycle, respectively. ZB-MnS displayed the best performance in terms of specific capacity and cyclability. Interestingly, MnS electrodes exhibited an unusual phenomenon of capacity increase upon cycling which was ascribed to the decreased cell resistance and enhanced interfacial charge storage.
In summary, this dissertation provides investigation of sulfur based electrode materials with sulfur/N-doped graphene composites and MnS nanocrystals. Their electrochemical performances have been evaluated and discussed. The understanding of their reaction mechanisms and electrochemical enhancement could make progress on development of secondary batteries.
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Stephens, Ifan Erfyl Lester. "Polysulfide electrocatalysis at transition metal sulfides." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608910.
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Li, Zhijun 1965. "Improving the kraft pulp yield with polysulfide and anthraquinone." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20212.
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In this study, the reaction kinetics and mechanism of kraft pulping with polysulfide and anthraquinone(AQ) using black spruce wood were investigated.In preliminary studies, the synergistic effect of polysulfide and AQ on pulp yield improvement was verified by different methods.
The identical kinetic cooking experiments were conducted for Kraft, Kraft-AQ, Polysulfide, and Polysulfide-AQ processes in the temperature range between 151 and 180ºC. It was found that the delignification rate of the PSAQ process was the fastest. The activation energies of delignification of Kraft, Kraft-AQ, Polysulfide, and Polysulfide-AQ processes were calculated as 141, 131, 142, and 131 kJ/mol, respectively. Based on obtained activation energies, the Vroom's H-factor was calculated and compared. It was also found that Kraft, Kraft-AQ, Polysulfide, and Polysulfide-AQ processes had similar activation energies for the carbohydrate degradation by 170, 174, 176, and 181 kJ/mol. Compared with the kraft process, the carbohydrate degradation rate of the PSAQ process was reduced. In addition, compared with other processes the PSAQ process had the best pulping selectivity.
A mechanism was proposed for the synergistic effect of polysulfide and anthraquinone on kraft pulp yield improvement based on the experimental evidence. It suggested that the synergy takes place at the beginning of heating-up period, polysulfide improves AQ penetration into wood, and therefore the maximum reduction of anthraquinone is reached earlier. The accelerated delignification helps the polysulfide to better access the hemicellulose, and that leads to more efficient stabilization of carbohydrates. In the meantime AQ retards the decomposition of polysulfide, and a higher concentration of polysulfide in the cooking liquor further prevents the degradation of carbohydrates. A redox cycle similar to that of AQ was proposed for the polysulfide.
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Li, Zhijun. "Improving the kraft pulp yield with polysulfide and anthraquinone." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0006/MQ44022.pdf.
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Robinson, Paul A. "Studies towards the synthesis of marine polysulfide natural products." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6379.
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Biologically active compounds isolated from marine sources have had increasing interest in recent years with significant research going into the discovery and isolation of novel marine polysulfide natural products. Varacin, probably the most widely studied marine polysulfide to date was the subject of much debated structure elucidation attempts, and more recently several successful synthetic approaches have been published. The work published aims to increase our understanding of marine polysulfide compounds existence in nature and determine the origins of their biological activity. (+)-Aplidium trisulfide which was isolated from Aplidium Sp. D in 1989 by Munro et al has been shown to exhibit in vitro antimicrobial, antileukemic and cytotoxic properties. These intriguing biological effects have led our work towards developing a novel synthetic route toward aplidium trisulfide by both chiral and racemic routes. Aplidium trisulfide is of special significance as it is very rare to isolate enantiomeric compounds from marine sources. Two other closely related marine alkaloids fasmerianamine A and B are also of synthetic interest to us due to their close resemblance to the structure of aplidium trisulfide. The fasmerianamines were isolated by Copp et al from the marine ascidian Hypsistozoa fasmeriana in 2001.
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Rys, Andrzej Z. "Polysulfide Chemistry : I. sulfuration of dienes, II. oxidation and related reactions." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38270.
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The use of polar solvents as activators in the sulfuration of dienes has been demonstrated. A mechanism of sulfuration with activated sulfur under these conditions was investigated. The identity of sulfur species involved in sulfuration was determined. The modeling of activated sulfur with various metallocene polysulfide catalysts in nonpolar solvents was also examined. The specifics of the metallocene polysulfide catalytic system were studied in detail.The most efficient catalyst in the sulfuration of dienes, molybdocene tetrasulfide, became an object of oxidative studies. These studies were extended to molybdocene disulfide and tungstenocene tetrasulfide. The main products of the oxidation of metallocene tetrasulfides, 1-oxides, were thermally unstable and at room temperature rearranged to corresponding 2-oxides. The mechanism and factors controlling this rearrangement were investigated.
Oxidations of molybdocene tetrasulfide with excess of oxidant were also carried out. The unstable intermediates were identified. The rearrangement of highly oxidized molybdocene tetrasulfide 1,1,4,4-tetroxide yielding the intriguing ionic molybdocene disulfide dimer, was examined. Properties of the dimer, with emphasis on the deprotonation, were described.
Molybdocene disulfide and its oxide were treated separately with SO 2, H2S and finally with a mixture of both gases to evaluate the potential catalytic activity in the Claus process. The formation of two products resulting from the novel insertion of SO2 into the S-S bond, molybdocene trisulfide 2,2-dioxide and molybdocene bis(O-alkylthiosulfate) was observed. Both molybdocene disulfide and disulfide oxide reacted with the mixture of SO2 and H2S stoichiometrically. The reason for the lack of catalysis was discussed.
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Behm, Mårten. "Electrochemical generation of polysulfide liquor and sodium hydroxide from white liquor /." Stockholm, 1998. http://www.lib.kth.se/abs98/behm0220.pdf.
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Caddy, Mark. "Modified liquid polysulfide polymers : their preparation, characterisation, photocuring and potential photoapplications." Thesis, University of Warwick, 2001. http://wrap.warwick.ac.uk/3940/.
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Liquid polysulfide polymers (LPs) H(SCH2CH20CH20CH2CH2S)nH are of wide commercial importance in the sealants industry. Chemical oxidation of the mercaptan groups, by inorganic and peroxide catalysts, leads to the formation of durable, flexible and adhesive elastomers. Terminal modification of the prepolymers, by substituting a wide range of carbonylcontaining groups for the thiol protons, has led to the creation of photopolymerisable oligomers with certain of the desirable properties mentioned above. UV irradiation of all the modified polysulfides, which exist as viscous oils, resulted in the development of a solid elastomeric material with considerable powers of adhesion. The acylation process involves the addition of a slight excess of an acyl halide to the prepolymer in solution, followed by the addition of an amine to neutralise the HCI formed. This procedure has been adapted to react di- and polyfunctional termini with LPs to produce block copolymer polysulfides. When exposed to UV irradiation, the oligomers slowly photocrosslink, forming an insoluble elastomer. The increase in degree of polymerisation has been successfully monitored by 1H NMR spectroscopy; this was achieved by irradiating the oligomers in NMR tubes containing a thin capillary tube containing a deuterium-lock solvent. These new materials were characterised by IR, 1H and 13C NMR, GPC, viscometry and, particularly electrospray and FAB-mass spectrometry. FAB spectra have also been obtained for the first time for the parent polysulfide as well as the modified forms; these enable characterisation of the polysulfide backbone and its irregularities. Characterisation of these cured products has been made by hardness testing, solvent resistance, flexibility and tensometry. Lap shear measurements have been made of all of the functionalised cured polysulfides; adhesion is greatly enhanced by the addition of an adhesion promoter (optimum level 2%). All the systems slowly photopolymerise without sensitisers or additives, but the addition of radical photoinitiators shortens the cure time considerably. The modified LPs can be combined with commercially available polyurethane systems to make a fast curing photosystem yielding products with excellent adhesion and flexibility. Each of the modified LPs contains a carbonyl group, which has photoactive potential, thus excitation of the carbonyl group leads to an n->π* transition to form a reactive triplet state which then attacks another LP chain to crosslink the polysulfide. Monitoring of 1H NMR linewidths shows a gradual broadening of lines as 120 Hz polymerisation proceeds, reaching a plateau value of ΔH1/2=120 Hz, illustrating the elastomeric properties of the polysulfide. Addition of plasticisers eases the uniform spreading of the oligomers onto sheets before irradiating, which gives a potential application as a surface coating. Photoresist imaging agents are another potential application as the modified oligomers act as negative resists.
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Birembaut, Fabrice. "An investigation of the adhesion and ageing of polysulfide sealant systems." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395991.
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GODOY, RAFAEL FERREIRA. "HEXAVALENT CHROMIUM REMEDIATION USING CALCIUM POLYSULFIDE: STUDY CASE: RIO DE JANEIRO." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=25019@1.
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Esta dissertação apresenta os resultados obtidos no processo de remediação de uma área contaminada por cromo hexavalente por meio da técnica de remediação química in situ (ISCR). A área de estudo localiza-se na
cidade do Rio de Janeiro e foi ocupada por uma fábrica de vidros por cerca de quarenta anos e comprada para construção de condomínios residenciais. A área de estudo passou um processo de gerenciamento ambiental que contemplou diversos estudos ambientais para aquisição de dados e delimitar a contaminação, horizontal e verticalmente. O teste de bancada realizado com o reagente químico polissulfeto de cálcio demonstrou ser eficiente para reduzir as concentrações de cromo hexavalente em solo e água subterrânea. Com base nos
dados adquiridos neste teste foi possível calcular a dose de injeção do polissulfeto de cálcio. Foram realizados setenta pontos de sondagem, pela técnica direct push, para injetar duzentos e cinquenta e dois mil e trinta litros de solução de polissulfeto de cálcio e água, sendo aproximadamente três mil e quinhentos litros por ponto de injeção. Os resultados após a injeção demonstraram que o polissulfeto de cálcio conseguiu remover o cromo hexavalente que estava adsorvido ao solo e reduziu a concentração de cromo hexavalente na água subterrânea entre quarenta e seis e sessenta e sete e noventa e nove e noventa e cinco por cento , após dezenove meses da injeção. Dessa forma, comprovou a eficiência deste reagente químico para remediação de áreas contaminadas por cromo hexavalente, assim como foi observado nos artigos técnicos de estudos de casos nos Estados Unidos e Europa.This dissertation presents the results obtained in the remediation process remediation of a contaminated area by hexavalent chromium applying the technology in situ chemical remediation (ISCR). The study area is located in the Rio de Janeiro city and was occupied by a glass factory for forty years and purchased for construction of residential condominiums. This dissertation presents the results obtained in the remediation process remediation of a contaminated area by hexavalent chromium applying the technology in situ chemical remediation (ISCR). The study area is located in the Rio de Janeiro city and was occupied by a glass factory for forty years and purchased for construction of residential condominiums. Chromium is an important metal for the industry and is used in various products and processes, such as electroplating, leather treatment, pulp, wood preservation, and refractory manufacturing. The trivalent chromium is essential from a nutritional point of view, non-toxic and poorly absorbed in the body, acting in the maintenance of some functions. Cr(III) is the most common being found and occurs naturally, since the element Cr(VI) can occur naturally, but in low concentrations, if the groundwater has geochemical conditions the Cr (III) can be oxidize to Cr (VI). The hexavalent chromium is the most dangerous valence state and, according to ATSDR (two thousand and twelve), have greater mobility in the groundwater, being carcinogenic by inhalation of high doses of soluble chromate salts. The mobility of hexavalent chromium is high in soil and groundwater because it is not adsorbed by the soil in that valence state, on the other hand when it is in trivalent form is strongly adsorbed by the soil, forming insoluble precipitates, having low mobility in soil and groundwater. The hexavalent chromium remediation by in situ chemical reduction using calcium polysulfide has been the subject of several field studies documented in the literature, both for soil and groundwater from the Chromite Ore Processing Residue (COPR) (Storch, et al., two thousand and two; Graham, et al., two thousand and six ; Charboneau, et al., two thousand and six ; Wazne, et al., two thousand seven a; Wazne, et al., two thousand seven b; Chrysochoou, et al., two thousand and ten ; Chrysochoou & Ting, two thousand and eleven ; Pakzadeh & Batista, two thousand and eleven ; Chrysochoou, et al., two thousand and twelve ). Calcium polysulfide is a fertilizer to soil and commercially available and has been used in some remediation studies cases for reducing hexavalent chromium in soil and groundwater. Being commercially available and used as fertilizer, it is a relatively cheap chemical reagent in comparison with other chemical compounds exclusively developed for this purpose. The stoichiometric demand and the chemical kinetics of the reduction of Cr (VI) by the calcium polysulfide in aqueous solution was studied by Graham et al. (two thousand and six) from the chromite ore processing residue (COPR). With this study it was reported that a molar ratio of a point sixty-six is required (close to the theoretical value of one point five) and a first-order kinetics with an initial concentration of twenty-six eight point mg/L and pH of the CPS solution around eleven point five, with the presence of oxygen. Thus, the hexavalent chromium is reduced to chromium hydroxide, slightly water soluble compound which is precipitated to the soil. The trivalent chromium has low solubility, toxicity, mobility, reactivity and is considered stable. There are various application techniques of chemical reagents in the underground environment, and choosing the most appropriate method for each area depends on the type of contaminant, geological environment, groundwater and surface interference, depth, thickness and size of the contaminated area. As described by Suthersan (mil novecentos ninety-six), the injection of chemical reagents has to achieve two objectives: (one) creating and maintaining an ideal redox environment and other pa
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Fan, Li. "ELECTRODEPOSITION OF SULFIDE-CONTAINING THIN FILMS, AND THEIR APPLICATION TO ELECTROCHEMICAL SYSTEMS." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2495.
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Pan, Menghsuan Sam. "Ionic conductivity and exchange current density of non-aqueous lithium polysulfide electrolyte." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/98665.
Full textAbstract:
Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, June 2015.Cataloged from PDF version of thesis. "May 2015."
Includes bibliographical references (pages 32-33).
Lithium-polysulfide flow batteries, which utilize the high solubility of lithium polysulfide in non-aqueous electrolytes to enable flowable electrodes, have high theoretical energy density and low raw materials cost. To achieve greater electrode-level energy density, higher sulfur concentrations are needed. In a given electrolyte system, sulfur charge storage capacity (e.g. mAh/g sulfur) decreases dramatically with increasing sulfur concentration at a fixed C-rate, which corresponds to higher current output in higher concentration system. Understanding the limiting factors that undercut the rate capacity is crucial to enhancing the performance of high energy density systems. In particular, we systematically investigate the ionic conductivity and exchange current density at the electrode surface with lithium polysulfide solutions of varying concentration and in differing solvents which solvent molecules of different sizes. Ionic conductivities are measured using a commercially available conductivity probe, while exchange current densities are measured using both impedance spectroscopy and galvanostatic polarization using glassy carbon working electrodes. The electrolyte solvent is found to dramatically affect the solution ionic conductivity and exchange current density. In the concentration range of interest (1-8 M [S]), the ionic conductivity monotonically decreases with increasing sulfur concentration while exchange current density shows a more complicated response in a given solvent system. Between solvent systems, we observed a five-fold increase in ionic conductivity, and a more than 15-fold enhancement in exchange current density. The conductivity and current density results are used to interpret the rate capability of suspension-based cells using lithium-polysulfide electrolyte and carbon black as the cathode with different solvents. With the improvement in kinetics parameters, we also observed better rate capability in solvent. We also study non-carbonaceous electrode materials to understand how the electrode material can affect exchange current density and thus cell capacity. Indium tin oxide electrode shows lower exchange current density then glassy carbon electrode in preliminary results.
by Menghsuan Sam Pan.
S.B.
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Houlson, Andy D. "The use of sodium birnessite as a curing agent for liquid polysulfide sealant." Thesis, Brunel University, 2000. http://bura.brunel.ac.uk/handle/2438/5387.
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Manganese (IV) oxide phases are widely used as curing agents for polysulfide sealants. The manganese based curing agents, however, do not give a reproducible cure and this results in material waste. As the market for insulating glass applications is increasing, efficient curing becomes more significant both commercially and environmentally. The research described in this portfolio focuses on using a laboratory synthesised manganese (IV) oxide phase, sodium birnessite, as a polysulfide curing agent. The synthesis and full characterisation of sodium birnessite is described and its curing ability measured in terms of the following properties of the cured polysulfide: rate of cure. surface condition, hardness build-up, stress-strain data, low and high temperature properties. and moisture transmission. The results obtained are compared with those of polysulfides cured with a good commercial product. Different concentrations of curing agents, and types and concentrations of accelerators, plasticisers and inert diluents were investigated to optimise the curing process, reduce material use and product wastage. Sodium birnessite is an active and reliable curing agent when used at half of the concentration of the commercial agent in the presence and absence of inert diluents. Diluted sodium birnessite (1: 1 with inert diluent) cures polysulfide to levels comparable in terms of stress-strain properties, moisture transmission rate, hardness, surface condition, low- and high- temperature properties, and degree of polysulfide cross linking to that achieved with commercial agent. The mechanism of the curing of polysulfide with sodium birnessite, as with all curing agents is conversion of mercaptan groups -S-H into disulfide linkages (-S-S-). Sodium birnessite is a mixed oxidation state compound and its synthesis results in the inclusion of Mn 2+ in addition to Mn 4+ ions in the manganese oxide based lattice. A rationale for the improved curing ability of sodium birnessite is presented. It is based on the ability of Mn 2+ to create vacancies in the Mn4+ sub-lattice thus increasing the mobility of the Mn4 in the structure and its transport to the surface of the curing agent where the oxidation reduction reaction responsible for the cure takes place.
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Dibden, James William. "Lithium-sulfur batteries : an investigation into the electrolyte and the polysulfide species within." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/419056/.
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The lithium-sulfur (Li-S) battery is one of the most promising candidates in next generation energy storage, offering high theoretical specific capacities through the use of inexpensive and environmentally benign positive electrode materials. However, full commercialisation has been prevented by several technical challenges, most notably polysulfide shuttling. Despite significant scientific interest in recent years, the mechanism of the discharge and charge processes is still poorly understood. Whilst it is known that a variety of different processes occur between electrochemically active species during cycling, the identity of the polysulfides species remains unknown. Additionally, the polysulfide concentrations at different stages of discharge and charge, as well as their thermodynamic and kinetic properties are still poorly understood. In this project, the significance of cell design on the cycling performance of a Li-S battery is highlighted. The reproducibility of a selected cell design and the effect of lithium nitrate as an electrolyte additive is investigated. To obtain a thorough understanding of the electrolyte system used throughout this report (LiTFSI in DOL), various electrolytes containing different concentrations of the electrolyte salt are prepared and analysed. Using a Walden plot, it is revealed that at high salt concentrations, this electrolyte system begins to exhibit properties similar to that of an ionic liquid. Additionally, employing high salt concentrations improves the cycling performance of the Li-S battery. Two methods have been developed to quantitatively determine the total ‘sulfur’ content of an electrolyte containing polysulfides, as well as its average oxidation state. These techniques have enabled production of the first experimental ternary phase diagram for the Li-S battery. Finally, the galvanostatic intermittent titration technique (GITT) method is quantitatively analysed using a model redox system to assess its ability to determine the diffusion coefficient of the redox system. This study offers a unique assessment of the ability to use GITT to study the mass transport of polysulfide intermediates within a Li-S battery.
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Rege, Francis Mark de. "Zirconium-group 13 heterobinmetallic compounds and the synthesis of oxysulfides in sodium polysulfide." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38778.
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Coadou, Erwan. "Organosulphur compounds for electrochemical energy storage applications : supercapacitors and lithium-sulphur batteries." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.706291.
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The work presented in this manuscript concentrates on investigating the use of organosulfur compounds as potential electrolyte components for electrochemical energy storage systems, in particular in lithium-sulfur batteries. Novel glyme-functionalised sulfonium-based ionic liquids were synthesized and characterised before being tested as pure electrolytes for symmetrical supercapacitors based on activated carbon electrodes. The adaptation of the structure of the ionic liquids to the porosity of activated carbon was found to be of fundamental importance for the design of more efficient systems. For lithium-sulfur batteries, the study has enabled a better understanding of the mechanisms involved during the operation of the sulfur/diphenyl disulfide redox couple in a range of glyme-based solvents. Similarly, the influence of the glyme-based solvents on the chemical equilibria between organic and mineral polysulfides and on the system operation has been investigated. The initial results demonstrated that this is a particularly promising strategy in order to significantly improve the performances of lithium-sulfur batteries.
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Wang, Lei. "Polysulfide-based respontive amphiphilic block copolymers and their use to produce smart lyotropics matrices." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492896.
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Thieme, Sören, Jan Brückner, Andreas Meier, Ingolf Bauer, Katharina Gruber, Jörg Kaspar, Alexandra Helmer, Holger Althues, Martin Schmuck, and Stefan Kaskel. "A lithium–sulfur full cell with ultralong cycle life: influence of cathode structure and polysulfide additive." Royal Society of Chemistry, 2015. https://tud.qucosa.de/id/qucosa%3A36251.
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Lithium–sulfur batteries are highly attractive energy storage systems, but suffer from structural anode and cathode degradation, capacity fade and fast cell failure (dry out). To address these issues, a carbide-derived carbon (DUT-107) featuring a high surface area (2088 m² g⁻¹), high total pore volume (3.17 cm³ g⁻¹) and hierarchical micro-, meso- and macropore structure is applied as a rigid scaffold for sulfur infiltration. The DUT-107/S cathodes combine excellent mechanical stability and high initial capacities (1098–1208 mA h gs ⁻¹) with high sulfur content (69.7 wt% per total electrode) and loading (2.3–2.9 mgs cm⁻²). Derived from the effect of the electrolyte-to-sulfur ratio on capacity retention and cyclability, conducting salt is substituted by polysulfide additive for reduced polysulfide leakage and capacity stabilization. Moreover, in a full cell model system using a prelithiated hard carbon anode, the performance of DUT-107/S cathodes is demonstrated over 4100 cycles (final capacity of 422 mA h gs ⁻¹), with a very low capacity decay of 0.0118% per cycle. Application of PS additive further boosts the performance (final capacity of 554 mA h gs ⁻¹), although a slightly higher decay of 0.0125% per cycle is observed.
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Witzel, Silke [Verfasser], Elisabeth [Gutachter] Klemm, and Bernd [Gutachter] Ondruschka. "Synthese neuer funktioneller Polysulfid-Telechele und deren industrielle Applikation / Silke Witzel ; Gutachter: Elisabeth Klemm, Bernd Ondruschka." Jena : Thüringer Universitäts- und Landesbibliothek Jena (ThULB), 2007. http://d-nb.info/1178481069/34.
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Xiao, Yao. "Analysis for reaction mechanism of cathode materials for lithium-sulfur batteries." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263747.
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京都大学新制・課程博士
博士(人間・環境学)
甲第23286号
人博第1001号
京都大学大学院人間・環境学研究科相関環境学専攻
(主査)教授 内本 喜晴, 教授 田部 勢津久, 教授 高木 紀明
学位規則第4条第1項該当
Doctor of Human and Environmental Studies
Kyoto University
DFAM
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Yagdi, Efe Esma. "Analyse du rôle des dérivés de polysulfanes de l’ail dans le réseau microtubulaire et l'autophagie : l’effet anticancéreux dans le cancer colorectal." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0281/document.
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Le cancer colorectal est une cause majeure de morbidité et de mortalité dans le monde entier. Des études épidémiologiques révèlent une corrélation inverse entre le risque de développer un cancer du côlon et un régime alimentaire riche en ail. De nombreux travaux scientifiques rapportent l'activité anti-cancéreuse des polysulfures de diallyle (PSDA) dérivés de l'ail dans divers types de cancer in vitro et in vivo. Le mécanisme d'action le mieux connu repose sur l'induction de l'arrêt mitotique suivi de l'apoptose. La tubuline est identifiée comme nouvelle cible thérapeutique des PSDA. La tubuline est fondamental dans la progression de l'autophagie, source nutritionnelle essentielle pour le développement du cancer au stade avancé, et l'activation de l'autophagie joue un rôle de chimiorésistance dans le traitement du cancer du côlon. L'hypothèse de ce projet est que les PSDA dérivés de l'ail interagissent avec la tubuline pour altérer l'organisation du réseau microtubulaire responsable de l'inhibition de la prolifération cellulaire et de la modulation de l'autophagie dans le cancer du côlon. Dans un premier temps, nous avons analysé l'impact du TTSDA/TTSDB sur le réseau microtubulaire. Nous avons montré que le TTSDA/TTSDB interagissait avec la tubuline par spectrométrie en masse. Nous avons montré que l'organisation microtubulaire est altérée dans les trois lignées cellulaires : HT-29 (mutées BRAF), SW480 (mutées KRAS) et SW620 (mutées KRAS, métastatiques), plus sensibles au TTSDB que le TTSDA. Dans un deuxième temps, nous avons étudié le rôle anticancéreux du TTSDB dans le cancer du côlon. Nous avons montré que le TTSDB induisait un arrêt mitotique suivi de la mort cellulaire dans toutes lignées confondues. Son activité antiproliférative est validée dans un système de culture 3D et in vivo. Nous avons aussi montré que l'effet du TTSDB est comparable aux agents altérant les microtubules. Dans un troisième temps, nous avons évalué l'impact du TTSDB dans l'autophagie. L'inhibition de l'autophagie est accompagnée par l'accumulation de la protéine p62, qui joue un rôle de survie dans les cellules HT-29 uniquement. Ensemble, nous avons identifié l'autophagie comme mécanisme de survie lors de l'arrêt mitotique prolongé en fonction du type cellulaire. Cette étude permettra d'envisager un ciblage thérapeutique selon le profil génétique du cancer du côlonColorectal cancer is a major cause of morbidity and mortality worldwide. Epidemiological studies reveal an inverse correlation between the risk of developing colon cancer and a garlic-rich diet. Many scientific studies reported the anti-cancer activity of diallyl polysulfides (DAPS) derived from garlic in various types of cancer in vitro and in vivo. The best-known mechanism of action is the induction of mitotic arrest followed by apoptosis. Here tubulin is identified as a new therapeutic target for DAPS. Tubulin is fundamental in the progression of autophagy, an essential energy source for the development of advanced cancer, and autophagy activation plays a role of chemoresistance against the treatment of colon cancer.The hypothesis of this project is that garlic-derived DAPS interact with tubulin to alter the microtubule network organization responsible for the inhibition of cell proliferation and modulation of autophagy in colon cancer.First, we analyzed the impact of DATTS/DBTTS on the microtubular network. We have shown that DATTS/DBTTS interacts with tubulin by mass spectrometry. We have shown that the microtubule organization is altered in the three cell lines: HT-29 (BRAF mutated), SW480 (KRAS mutated) and SW620 (metastatic, KRAS mutated), which were more sensitive to DBTTS than DATTS. In a second step, we studied the anticancer activity of DBTTS in colon cancer. We showed that DBTTS induced mitotic arrest followed by cell death in all cell lines. Its anti-proliferative activity is validated in a 3D culture system and in vivo. We have also shown that the effect of DBTTS is comparable to microtubule altering agents. In a third step, we evaluated the impact of DBTTS in autophagy. Inhibition of autophagy is accompanied by accumulation of the p62 protein, which plays a survival role in HT-29 cells only.Altogether, we identified here autophagy as a survival mechanism during prolonged mitotic arrest depending the cell type. This study will allow us to consider targeted therapy according to the genetic profile of colon cancer
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Rahman, Hafizur. "Modifying kraft pulping to produce a softwood pulp requiring less energy in tissue paper production." Licentiate thesis, Mittuniversitetet, Avdelningen för kemiteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-32833.
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Modification of softwood kraft pulp by the addition of either polysulfide (PS) or sodium borohydride (NaBH4) has been shown to increase the pulp yield due to a higher retention of glucomannan. The pulps with higher yield gave a paper with higher tensile index than reference pulp, especially at lower degrees of refining. The higher yield pulps also showed a greater porosity of the fibre wall, indicating an increase in the swelling potential of the fibres. This can lead to increased fibre flexibility and increased joint strength between the fibres and to the higher handsheet tensile index. However, the swelling increase associated with the higher hemicellulose content could also make dewatering more challenging because of the higher water retention of the pulp. The results of this study show however that the positive influence of the increase in yield (fewer fibres and a more open sheet structure) dominates over the negative influence of the higher hemicellulose content on the dewatering properties, especially at lower refining energy levels. Studies simulating full-scale tissue machine dewatering conditions showed that pulps with a higher yield and a higher hemicellulose content had a higher tensile index at the same dryness. Moreover, the same dryness level was achieved in a shorter dwell-time. A given tensile index was also achieved with less refining energy. Increasing the yield and hemicellulose content by the addition of either an oxidizing or a reducing agent in the softwood kraft pulping process thus has a potential for giving high quality fibres for tissue paper production with less refining energy and lower drying energy costs.Vid tidpunkten för framläggningen av avhandlingen var följande delarbeten opublicerade: delarbete 2 inskickat.
At the time of the defence the following papers were unpublished: paper 2 submitted.
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Froidevaux, Vincent. "Réticulation de polymères polysulfure par réaction thiol-Michaël contrôlée." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2014. http://www.theses.fr/2014ENCM0009.
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Les mastics polysulfures sont très utilisés dans l'aéronautique, ceci grâce à leur bonne tenue au froid et leur résistance au carburant. La plupart d'entre eux sont des bicomposants (un polymère polysulfure et un durcisseur avec éventuellement un catalyseur dans l'un des composants). Les formulations de mastic, réticulé au MnO2, permettent d'avoir des temps de gel de 2 jours, avec une réticulation complète au bout de 70 jours. Cependant, ce temps de gel long induit un temps de réticulation trop long. Ainsi, l'objectif de cette thèse était de créer un nouveau type de mastic, qui serait idéalement monocomposant avec un temps de gel toujours long, voir infini et qui réagirait sur demande après stimulus avec un temps de réticulation court. C'est ce qui est appelé le concept SCOD (sealant cure on demand). Pour cela, il faut bloquer un des trois réactifs, et que celui-ci soit déblocable sur demande à l'aide d'un stimulus simple industriellement tel que la température (cible entre 60-80°C). Le concept de blocage choisi est la réaction de Diels-Alder sur des composés accepteurs de Michaël. En effet, cette réaction est réversible et la cycloréversion permet la déprotection de la double liaison réactive. Après déblocage, l'accepteur de Michaël peut réagir avec le polysulfure. Une première étude, sur les accepteurs de Michaël, a permis de déterminer que les fonctions maléimides, en présence de DABCO, donnent les meilleures cinétiques pour la réaction avec les thiols du polysulfure. Une deuxième étude, sur la réaction de Diels-Alder et rétroDiels-Alder, a prouvé la faisabilité du projet et a permis de sélectionner les dérivés du furane comme agents bloquants pour répondre à la fourchette de température imposée. Ensuite, des durcisseurs polymaléimides aliphatiques ont été synthétisés à l'aide des Jeffamines® d'Huntsman et bloqués avec le furfuryl acétate, afin d'être utilisés pour la création de matériaux suivant le concept SCOD. Le temps de gel obtenu avec les durcisseurs bloqués, était de 7 jours et un matériau était obtenu après 17 heures de chauffe. Le concept SCOD a donc été démontré. Cette étude a, ensuite, été extrapolée au Centre de Recherche d'Hutchinson en formulation modèle sur de plus grandes quantités. Aussi, les propriétés des mastics obtenus ont été déterminées et répondaient à une majorité des critères du cahier des charges.. Le déblocage a été amélioré après ajout d'un thiol tétrafonctionnel (PETMA, co-agent) et l'utilisation d'un autre catalyseur (DBU), Le temps de déblocage étant encore trop long et le bloquant, relargué dans la formulation, forme des porosités dans le mastic et dégrade, de fait, les propriétés de celui-ci. Ainsi une dernière partie d'amélioration a été effectuée. En effet, dans celle-ci, une nouvelle génération de durcisseur, cette fois-ci aromatique, et d'agent bloquant, jouant le rôle de plastifiant non volatil, a été créée et testée en laboratoire. Ceux-ci ont présenté de très bons résultats préliminaires avec des temps de déprotection plus courts et des bloquants moins volatils à la température de déblocage comparé au furfuryl acétate. L'extrapolation doit se poursuivre fin 2014-début 2015 sur ces nouveaux durcisseurs en formulation mastic modèlePolysulfide sealants are widely used in aviation because of their good resistance to low temperature and to fuels. Most of them are bycomponent (a polysulfide polymer and a crosslinking agent and, eventually a curing catalyst in one of them). These sealant formulations, crosslinked with MnO2, have a gel time of two days, with a full curing after 70 days. However, because of this short gel time, the curing time is too long. Thus, the objective of this thesis was to create a new type of sealant, monocomponent, with still a long gel time, ideally infinite, that could react on demand after stimulus, in order to have a short curing time. This concept is called SCOD concept (sealant cure on demand). These criteria require to block one of the three products, and this one should be unblocked on demand using an ease stimulus such as temperature. The system chosen as blocking principle is the Diels-Alder reaction of a Michaël acceptor. Indeed, this reaction is reversible and the cycloreversion allows to unprotect the reactive double bond. After the unblocking reaction, the Michaël acceptor may react with the polysulfide. A primary study, on Michael acceptors, allowed to determine that maleimide function, in the presence of triethylamine, gives the best kinetics for reaction with polysulfide's thiol. A second study, this time on the Diels-Alder and retroDiels-Alder reaction, proved the feasibility of the project and allowed to select furan derivatives as blocking agents. Then, aliphatic polymaleimides hardeners were synthesized using Huntsman's Jeffamine and were blocked with the acetate furfuryl, so as to be used for creating SCOD materials. The gel time obtained with blocked hardener was 7 days at room temperature and after heating for 17 hours, a material was obtained; the SCOD concept has been demonstrated. The study was, then, extrapolated to Hutchinson's research and development department on bigger quantities to do some basic formulation. In addition, the sealant's characteristics have been determined and have shown very interesting results. Unblocking time was improved after adding tetrafunctional thiols (co-agent) and one another catalyst (DBU). The unblocking time was too long and the blocking agent, once released into the formulation, formed porosities into the sealant and, because of it, damaged the properties of the sealant. A latter part was done to improve the SCOD concept. Two new generations of hardener, aromatic this time, and blocking agent, acting as a non-volatile plasticizer, were created and tested in laboratory. These have presented very good preliminary results. Indeed, the unblocking time is much shorter and the unblocking agent is less volatile at high temperature compare to acetate furfuryl. The scaling up to pilot level is under way (end of 2014)
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Yang, Xiaotian. "Interfacing spectrophotometry to process liquors applications to kraft pulping." Doctoral thesis, KTH, Chemistry, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3428.
Full textAbstract:
This thesis summarizes the outcome of work performed withthe objective to contribute to the knowledge and development ofthe kraft cooking process using spectrophotometricinterfaces.
In kraft cooking, it is desirable to maximize the removal oflignin in the cook without loss of pulp strength. Theselectivity can be improved by exchanging some of the hydrogensulfide ion in the white liquor for polysulfides. Paper Ipresents a spectrophotometric method for in-line monitoring ofthe electrochemical production of polysulfide using anATR-probe for the UV-Vis range. A linear relation existsbetween the ATR-probe response and the concentration ofabsorbing species. Thus the process can be followed by simplemonitoring of a few wavelengths.
A spectrophotometric monitoring system using a durableNafion ionomer membrane interface for continuous on-linemeasurement of sulfide and dissolved lignin during kraftcooking has previously been developed by our group. In paperII, the permeation of low molecular weight anions from liquorshaving high ionic strengths through a membrane in Na+ form hasbeen studied. A general relation between penetration and ionsize approximated by molecular weight has been established. Thepenetration of different anions can be explained as a diffusionthrough the winding membrane channels. Further the differentanions transport independently without being interfered by thesample matrix.
In light of this validation, we applied the membraneinterface to the determination of anthraquinone-2-sulfonate(AQ-S) in alkaline pulping liquor. In paper III, a simple andrapid spectrophotometric method was developed and implementedon real samples. Interferences from other compounds penetratingthe membrane were minimized by reduction of the penetrated AQ-Sand measurement at 520 nm. This method is quick and can be usedon-line. Further, we extended the method to determination ofanthraquinone (AQ) in pulping liquor (paper IV). Although AQ isregarded as insoluble, it was found that the apparentsolubility of AQ in alkaline solutions increases considerablyin the presence of lignin, reaching 0.14 g/L at 90 oC. Thismakes the calibration of AQ possible. Time-resolvedmeasurements of dissolved AQ in 3 kraft-AQ pulping processeswere performed.
The results show that the membrane has great potential aspart of a selective interface in applications where theconcentrations of small anions are to be monitored in mediawith high ionic strength.
Keywords: Kraft cooking, On-line, Sulfide, Lignin,Polysulfide excess sulfur, Anthraquinone-2-Sulfonate (AQ-S),Anthraquinone (AQ), Nafion Membrane, UV-Vis, ATR-probe,Spectrophotometric.
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Bailey, Kathryn Lafaye. "Assessing the Microbial Consequences of Remediation: Surrogate Microbial Screening and Native Metabolic Signatures in Tc(VII) Contaminated Sediments." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/3965.
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The chemical and physical processes controlling contaminant fate and transport in the vadose zone limit the options for application of many remedial technologies. Foam delivery technology (FDT) has been developed as a potential solution to overcome these limitations for remediating subsurface and deep vadose zone environments using reactive amendments. Although there are many advantages to utilizing FDT for treatment in the deep vadose zone, little information is available on how the addition of these surfactants and remedial amendments affect the indigenous microbial communities in the deep vadose zone as well as the impact of biological transformations of surfactant-based foams on remediation efforts. The purpose of this study was to develop a rapid method for assessment of microbial communities in contaminated subsurface environments. This research was divided into two phases: (1) assess the toxicity of proposed FDT components on a single bacterial species, Shewanella oneidensis MR-1; and (2) determine the effects of these components on a microbial community from the vadose zone.
In Phase I, S. oneidensis MR-1 was exposed to proposed FDT components to assess potential growth inhibition or stimulation caused by these chemicals. S. oneidensis MR-1 cultures were exposed to the surfactants sodium laureth sulfate (SLES), sodium dodecyl sulfate (SDS), cocamidopropyl betaine (CAPB), and NINOL 40-CO, and the remedial amendment, calcium polysulfide (CPS). Results from this phase revealed that the relative acute toxicity order for these compounds was SDS>>CPS>>NINOL40-CO>SLES≥CAPB. High concentrations of SDS were toxic to the growth of S. oneidensis MR-1 but low concentrations were stimulatory. This benchtop system provided a capability to assess adverse microbial-remediation responses and contributed to the development of in situ remedial chemistries before they are deployed in the field.
For Phase II, sediments from the BC Cribs and Trenches (BCCT) area of the Hanford Site, WA, were characterized before and after exposure to potential FDT components. First, the phylogenetic and metabolic diversity of sediment from the BCCT was assessed by sequencing the microbial community and measuring the metabolic activity. The sediment was also incubated with various concentrations of SDS, CAPB, and CPS. Phylogenetic analysis detected phylotypes from the Alpha-, Beta-, Delta-, and Gammaproteobacteria, and Actinobacteria. Unlike the S. oneidensis MR-1 studies conducted in Phase I, the surfactants and CPS stimulated the metabolic activity of the native microbial communities. The observed stimulation could be caused by sorption of the chemicals to the sediment particles, or utilization of the surfactants by the microbial communities. These findings emphasize the importance of monitoring microbial activity at remediation sites in order to determine short and long term efficacy of the treatment, compliance with regulatory mandates, and act as an early warning indicator of unintended changes to the subsurface.
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Wang, Yan. "Pretreatment and Enzymatic Treatment of Spruce : A functional designed wood components separation for a future biorefinery." Doctoral thesis, KTH, Träkemi och massateknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-150395.
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The three main components of wood, namely, cellulose, hemicellulose, and lignin, can be used in various areas. However, since lignin covalently crosslinks with wood polysaccharides creating networks that is an obstacle for extraction, direct extraction of different wood components in high yield is not an easy matter. One potential approach to overcome such obstacles is to treat the wood with specific enzymes that degrade the networks by specific catalysis. However, the structure of wood is so compact that the penetration of the wood fibers by large enzyme molecules is hindered. Thus, the pretreatment of wood prior to the application of enzymes is necessary, for “opening” the structure. One pretreatment method that was performed in this thesis is based on kraft pulping, which is a well-established and industrialized technique. For untreated wood, the wood fibers cannot be attacked by the enzymes. A relatively mild pretreatment was sufficient for wood polysaccharides hydrolyzed by a culture filtrate. A methanol-alkali mixture extraction was subsequently applied to the samples that were pretreated with two types of hemicellulases, Gamanase and Pulpzyme HC, respectively. The extraction yield increased after enzymatic treatment, and the polymers that were extracted from monocomponent enzyme-treated wood had a higher degree of polymerization. Experiments with in vitro prepared lignin polysaccharide networks suggested that the increased extraction was due to the enzymatic untying. However, the relatively large loss of hemicellulose, particularly including (galacto)glucomannan (GGM), represents a problem with this technique. To improve the carbohydrate yield, sodium borohydride (NaBH4), polysulfide and anthraquinone were used, which increased the yields from 76.6% to 89.6%, 81.3% and 80.0%, respectively, after extended impregnation (EI). The additives also increased the extraction yield from approximately 9 to 12% w/w wood. Gamanase treatment prior to the extraction increased the extraction yield to 14% w/w wood. Sodium dithionite (Na2S2O4) is an alternative reducing agent for the preservation of hemicelluloses because it is less expensive than metal hydrides and only contains sodium and sulfur, which will not introduce new elements to the recovery system. Moreover, Na2S2O4has the potential to be generated from black liquor. Na2S2O4 has some preservation effect on hemicelluloses, and the presence of Na2S2O4 also contributed to delignification. The extraction yield increased to approximately 15% w/w wood. Furthermore, Na2S2O4 has been applied in the kraft pulping process of spruce. The yield and viscosity increased, while the Klason lignin content and kappa number decreased, which represents a beneficial characteristic for kraft pulp. The brightness and tensile strength of the resulting sheets also improved. However, the direct addition of Na2S2O4 to white liquor led to greater reject content. This problem was solved by pre-impregnation with Na2S2O4 and/or mild steam explosion (STEX) prior to the kraft pulping process. Following Na2S2O4 pre-impregnation and mild STEX, the obtained kraft pulp had substantially better properties compared with the properties exhibited after direct addition of Na2S2O4 to the white liquor. The wood structure opening efficiency of mild STEX alone was also tested. The accessibility of the wood structure to enzymes was obtained even at very modest STEX conditions, according to a reducing sugar analysis, and was not observed in untreated wood chips, which were used as a reference. The mechanical effect of STEX appears to be of great importance at lower temperatures, and both chemical and mechanical effects occur at higher STEX temperatures.QC 20140903
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Hsieh, Yu-Yun. "Nanostructured Carbon-Based Composites for Energy Storage and Thermoelectric Applications." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin157322525150617.
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Chen, PoYun. "Role of Ionic Liquid in Electroactive Polymer Electrolyte Membrane for Energy Harvesting and Storage." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1590688110146547.
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Mambingo, Doumbe Samuel. "Simulation de la phase gazeuse des réactions tribochimiques des additifs phosphorés et soufrés." Thesis, Ecully, Ecole centrale de Lyon, 2012. http://www.theses.fr/2012ECDL0063.
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La maîtrise de l’additivation est l’un des enjeux majeurs de la formulation des lubrifiants, notamment pour l’industrie automobile. La formulation d’une huile est toutefois très complexe en raison du nombre important d’additifs et des nombreuses interactions possibles entre additifs, notamment entre les additifs de surface. Les phosphites organiques et les polysulfures organiques ont déjà montré leur efficacité en tant qu’additifs de surface. Toutefois malgré leur usage répandu dans les formulations des lubrifiants automobiles, peu d’études traitent des interactions pouvant avoir lieu entre ces deux types de composés. Ce travail de thèse a pour objectif la compréhension des mécanismes d’interaction (antagonisme/synergie) pouvant exister entre les phosphites organiques et les polysulfures organiques. Pour cela, une approche originale sur la lubrification par la phase gazeuse s’est avérée très pertinente. Le couplage du Tribomètre à Environnement Contrôlé (TEC) avec les systèmes d’analyses de surface XPS/Auger a permis d’analyser les tribofilms générés in situ et d’éviter ainsi toute contamination et/ou oxydation du tribofilm avant analyse. Les molécules choisies sont les additifs de lubrification industriels (polysulfures tertaires) à faibles poids moléculaires ou alors des molécules à faible poids moléculaires ayant les mêmes fonctions chimiques que les additifs usuels : trimethyl phosphite (TMPi), dimethyl phosphite (DMPi). L’étude des réactions des tribochimiques des molécules phosphorés a permis de mettre en évidence le rôle ambivalent du DMPi qui se comporte à la fois comme un phosphite pour former un phosphure de fer et comme un phosphate. Le mécanisme formation du phosphure de fer a peu être étayé par la réalisation de calculs ab initio sur l’adsorption dissociative du TMPi sur une surface de fer. Les TPS étudiés génèrent quant à eux des tribofilms à base disulfure de fer. Les mélanges binaires réalisés en phase gazeuse ont permis de mettre en évidence l’importance des rapports de concentrations des vapeurs introduites et du mode d’introduction des molécules dans le tribomètre. Les résultats obtenus en tribologie en phase gazeuse ont été corroborés par des essais complémentaires en phase liquideMastering the addivation is one of the biggest issues for the lubricants formulation, especially in the automobile industry. However automotive lubricants are very complex systems due to the numerous additives mixed with base oils. Many interactions can occur between additives, especially between surface additives. Organic phosphites and organic polysulphides have already demonstrated their effectiveness as surface additives. However, despite their widespread use in the formulations of automotive lubricants, few studies deal with the interactions taking place between these two types of compounds. The aim of this study is to understand the interactions, antagonistic or synergetic effect between these kinds of additives using Gas Phase Lubrication (GPL) approach. A Environmental Controlled Tribometer (TEC) was used as a tool to simulate the interaction between organophosphate additives and polysulfurous additives. In situ surface analysis was performed in the tribofilm formed during friction using of X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy(AES) in order to avoid any oxidation or air contamination. The molecules selected for the study can be same as the additive like the TPS molecules which are widely used as lubricant additives. Howeverto simulate the phosphite chemical function of phosphite additives, we need to select smaller molecule having the same chemical function. These molecules are dimethyl phosphite (DMPi), trimethylphosphate (TMPi) for simulating the phosphite chemical function and organic polysulphides (TPS44and TPS32). The study of the tribochemical reactions of organic phopshites allowed to clearly characterise the ambivalence of DMPi, which can react like a phosphite and induce iron phosphide formation or react like a phosphate. Ab initio numerical simulation on TMPi dissociative adsorption was carried out to identify the reactions pathways leading to iron phosphide formation. The tribochemical reaction of TPS44 on metallic iron surface leads to the formation of iron disulphidebased tribofilm. The binary vapours mixtures studied by GPL allowed to clearly identify the importance of the vapour concentration ratio between phosphite and polysulphide. Liquid phase experiments were also carried out to confirm the trend observed in GPL approach
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Barchasz, Céline. "Développement d'accumulateurs Li/S." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00681504.
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Ces travaux ont permis d'approfondir les connaissances du mécanisme de déchargepeu conventionnel de l'accumulateur Li/S et de ses limitations. L'ensemble desrésultats a convergé vers une unique conclusion, à savoir que le système Li/S estprincipalement limité par le phénomène de passivation de l'électrode positive en finde décharge. Les polysulfures de lithium à chaines courtes précipitent à la surface del'électrode positive de soufre. Isolants électroniques, ils sont responsables de la perteprogressive de surface active de l'électrode et de la fin prématurée de la décharge.Ainsi, les performances électrochimiques ont pu être significativement améliorées entravaillant sur la morphologie de l'électrode positive, et sur la composition del'électrolyte. En augmentant la surface spécifique de l'électrode, la quantité depolysulfures de lithium qui peut précipiter en fin de décharge est augmentée, et lapassivation totale de l'électrode est retardée. En augmentant la solubilité despolysulfures de lithium dans l'électrolyte, la précipitation des espèces est retardée etla décharge prolongée. Dans cette optique, les solvants de type PEGDME semblentêtre les plus prometteurs à ce jour. Enfin, un mécanisme possible de réduction dusoufre en électrolyte de type éther a pu être proposé.
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Cabelguen, Pierre-Etienne. "Advanced research on Lithium-Sulfur battery : studies of lithium polysulfides." Thesis, 2013. http://hdl.handle.net/10012/7941.
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This thesis was devised as a fundamental study of the Li-S system by the use of 7Li Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR), X-ray Absorption Near-Edge Structure (XANES), and Non-Resonant Inelastic X-ray Scattering (NRIXS). The first part of this thesis is dedicated to the synthesis of solid state linear chain polysulfides in order to use them as reference compounds in the following experiments. 7Li NMR shows that Li2S and Li2S6 exhibit single but different Li environments, while the others stoichiometry targeted consist of a mixture of them. This is the first report of a stable solid-phase intermediate between elemental sulfur (α-S8) and Li2S. The second part of this thesis is based on operando XANES measurements made in the Argonne Photon Source (APS). Linear combination fit (LCF) analyses are performed to interpret the data; and, noticeably, the distinction between short-chain and long-chain polysulfides can be made due to the use of proper reference materials. The results reveal the first detailed observation of typical sulfur redox chemistry upon cycling, showing how sulfur fraction (under-utilization) and sulfide precipitation impact capacity. It also gives new insights into the differences between the charge and discharge mechanisms, resulting in the hysteresis of the cycling profile. Heat-treated PCNS/S exhibits a particular electrochemical signature, which has never explained. Operando XANES measurements at the sulfur K-edge are performed on heat-treated PCNS. Noticeably, the difference in the XANES signatures of the pristine and the recharged state shows the irreversible process that occurs during the first discharges. At last, electrolytes are investigated by the compilation of quantitative physico-chemical parameters on novel class of solvents that are glymes with non-polar groups and acetonitrile (ACN) complexed with LiTFSI. (ACN)2:LiTFSI attracts particular attention because of the particularly low Li2Sn solubility and. Its good electrochemical performance when mixed with 50 vol% HFE. Operando XANES proves the formation of polysulfides in this electrolyte, and the low energy feature evolution shows a more progressive mechanism involved in this electrolyte, which could be linked to the particularly low Li2Sn solubility.
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Anwar, Awais [Verfasser]. "Natural polysulfides - reactive sulfur species from Allium with applications in medicine and agriculture / von Awais Anwar." 2009. http://d-nb.info/996407219/34.
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Hippauf, Felix. "Tailoring Pore Size and Polarity for Liquid Phase Adsorption by Porous Carbons." Doctoral thesis, 2016. https://tud.qucosa.de/id/qucosa%3A30276.
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Adsorption is a versatile purification technique to selectively separate different peptide fractions from a mixture using mild operation conditions. Porous carbons are ideally suited to separate ACE-inhibiting dipeptides by combining tailored size exclusion and polarity selectivity. The desired peptide fraction is mostly hydrophobic and very small and should adsorb inside hydrophobic micropores.
The second topic of this thesis is linked to energy storage. The lithium-sulfur battery is a promising alternative to common lithium-ion batteries with theoretical capacities of up to 1672 mAh g−1 sulfur. The second aim of this thesis is to conduct an in-depth investigation of polysulfides interacting with selected carbon materials in a simplified battery electrolyte environment. The focus of this study is laid on the impact of surface polarity and pore size distribution of the carbon to develop a quantitative correlation between polysulfide retention and porosity metrics.
Both, the enrichment of ACE-inhibitors and the retention of polysulfides rely on liquid phase adsorption in porous materials, linking the above mentioned topics. This thesis not only aims to develop an enrichment process or to find a superior battery cathode but also strives to explore structure-property relationships that are universally valid. Understanding the complex interplay of pore size and polarity leading to selective interactions between pore wall and the adsorbed species is given a high priority.
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Tsou, Wan-Ting, and 鄒宛庭. "Improving the Electrochemical Performance of Lithium–Sulfur Batteries Using an Nb-Doped TiO2 Additive Layer for the Chemisorption of Lithium Polysulfides." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/75nx6m.
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碩士國立清華大學
材料科學工程學系
107
This study presents a method to suppress the migration of lithium polysulfides in lithium–sulfur batteries by introducing a dual-layer electrode structure. Herein, unlike conventional methods of mixing the polar additives with sulfur/carbon composites, melted sulfur mixed with mesocarbon microbeads are used as the electrode and covered with an additive layer of Nb-doped TiO2/graphite composite via two-step blade coating. By doping TiO2 with Nb, electrical and lithium ion conductivity of TiO2 can be increased, thereby enhancing the redox reaction kinetics. Most importantly, chemisorption of lithium polysulfides to Nb–TiO2 can effectively mitigate the shuttle effect, resulting in higher capacity and longer cycle life. The electrode with the Nb–TiO2 additive layer results in a 1st and 100th cycle specific capacity of 1883 mAh g-1 and 894 mAh g-1, respectively, at 0.1 C (1 C = 1675 mAh), indicating enhanced electrochemical performance as compared with that of bare lithium-sulfur batteries. X-ray photoelectron spectroscopy (XPS) study was conducted to investigate the interaction between polysulfides and Nb–TiO2. The results indicate that the Nb–TiO2–layered electrode efficiently traps polysulfides on the cathode and improves the rate capability, cycle performance, and specific capacity.
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Li, Mengliu. "Mitigating Polysulfide Shuttling in Li-S Battery." Diss., 2019. http://hdl.handle.net/10754/661542.
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The energy source shortage has become a severe issue, and solving the problem with renewable and sustainable energy is the primary trend. Among the new generation energy storage, lithium-sulfur (Li-S) battery stands out for its low cost, high theoretical capacity (1,675 mAh g-1), and environmentally friendly properties. Intensive researches have been focusing on this system and significant improvement has been achieved. However, several problems still need to be resolved for its practical application, especially for the “shuttle effect” issue coming from the dissolved intermediate polysulfides, which could cause rapid capacity decay and low Coulombic efficiency (CE). Several methods are proposed to eliminate this issue, including using interlayers, modifying separators, and protecting the lithium anode.
A carbon interlayer is first introduced to compare the function of the graphene and carbon nanotubes (CNTs), while the CNTs performs better with its higher conductivity and 3D network structure. The following study is conducted based on this finding.
A more efficient method is to modify the separator with functional materials. 1) The dissolved polysulfide (Sn2-) could be repelled by electrostatic forces. With the Poly (styrene sulfonate) (PSS), the separator could function as an anion barrier to the intermediate polysulfides. 2D ultra-thin zinc benzimidazolate coordination polymer has the OH- functional groups and works with the same mechanism. 2) A novel covalent organic framework (COF) has a relatively small pore size, which can block the polysulfide and restrain them at the cathode side. 3) Metal-organic framework (MOF) materials have the adjustable pore size and structure, which can absorb and trap polysulfides within their cavities. Moreover, the dense stacking of the MOF particles creates a physical blocking for the polysulfides, which efficiently suppresses the diffusion process.
Protection of the lithium surface directly with an artificial layer or a solid electrolyte interphase (SEI) can inhibit the polysulfide deposition and suppress the lithium dendrite. A polyvinylidene difluoride (PVDF) membrane is used as an artificial film on lithium anode, which could greatly enhance the battery cyclability and CE. Future work will be conducted based on this concept, especially building an artificial SEI.
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Chen, Yu-Hsuan, and 陳妤瑄. "Application of highly efficient thixotropic polysulfide electrolyte in QDSSCs." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/8zyb9h.
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碩士國立臺灣科技大學
化學工程系
106
Despite to the higher power conversion efficiencies of quantum dot sensitized solar cells (QDSSCs), photovoltaic devices that employ liquid electrolytes suffer from problems like long-term instability caused by leakage and volatilizations of electrolytes. In this study, to improve the stability, sealing, and conversion efficiency of the liquid-junction QDSSCs, an alternative electrolyte, gel electrolytes using organic polymer and inorganic nanoparticle (NP) gelators was attempted. Herein, we developed a noble water-based polymer gel electrolyte utilizing Xanthan gum (XG), which has thixotropic property, higher water solubility and environmentally friendly. Owing to the lower mobility of electrons in the liquid-junction TiO2 NPs was added which can improve ion conductivity and charge transfer. The charge recombination at the photoanode/electrolyte interface was emarkably inhibited with the addition of XG and TiO2 NP to the polysulfide electrolyte. Additionally, incorporation of TiO2 NPs increases VOC by adjusting photoanode fermi level. With our best condition XG/NP electrolyte, the efficiency of CIS-based QDSSCs was improved from 6.48 ± 0.15% to 7.06 ± 0.06%. And the efficiency of CISe-based QDSSCs was improved from 6.79 ± 0.10% to 8.00 ± 0.21%. To the best of our knowledge, this is the highest efficiency based on water-based XG/TiO2 electrolytes for CIS and CISe QDSSCs.