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1
Park, Bongjin. « Single electron transfer in reactions involving alkyl halides with lithium alkylamide, lithium alkyl and lithium metal ». Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/27052.
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Antolini, Floria. « Complexes of novel chiral alkyl and Câ†1-symmetric amido ligands ». Thesis, University of Sussex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367353.
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Welder, Catherine Owens. « A mechanistic evaluation of the reactions of lithium aluminum hydride with alkyl halides ». Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/25958.
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Thornton, Terry L. (Terry Lee) 1962. « Mixed Alkyllithim/Lithium Alkoxide Aggregates with Less Sterically Crowded Alkyl Groups ». Thesis, University of North Texas, 1997. https://digital.library.unt.edu/ark:/67531/metadc278441/.
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Mixed alkyllithium / lithium alkoxide aggregates in the form (RLi)n(ROLi)m were formed by addition of corresponding alcohol compounds at different Li/O ratios. Variable temperature 13C and 6Li NMR spectroscopy were used to verify the formation of the mixed aggregates and to study their behavior in hydrocarbon solution. Spectra for the lithium n-propoxide / n-propyllithium and iso-butyllithium / lithium iso-butoxide systems each indicated at least one mixed aggregate.
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Ullrich, Steven A. « Synthesis and Characterization of some Flourine-containing Lithium Alkyl Sulfonates : Flourinated Sulfonates and SF5-containing Sulfonates ». PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/4880.
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Lithium salts of pentafluorothio alkyl sulfonic acids and perfluoroalkyl disulfonic acids were prepared for testing for possible use as polymer electrolytes. Most of these lithium salts were made from the corresponding sodium, potassium or calcium salts. Aqueous solutions of these salts were passed through polystyrene sulfonate ion exchange resin in the acid form to obtain aqueous solutions of the corresponding acids. The acids were then neutralized with lithium hydroxide using a pH meter. One salt was made by reacting the barium salt of the corresponding acid with lithium sulfate. A sulfonyl fluoride polymer (-0-CH2-C (CH20CF2CF2S02F) H-) n was reacted with lithium hydroxide to give a lithium salt as well. Owing to the great length of time required to dry these hydroscopic salts so that they might be suitable for polymer electrolyte work, alternative, water-free methods of preparation were explored. These include the reaction of lithium trimethylsilanolate with a sulfonyl fluoride, and the reaction of trimethylsilyl triflate with lithium chloride. Conductivity studies were performed on samples of these salts, and the results so far obtained from these studies are presented. Mass spectrometry, 1H, 19F and 13C nuclear magnetic resonance spectroscopy, infrared spectroscopy, and elemental analysis were used to help characterize the new lithium salts.
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SUAREZ, BERTOA RICARDO. « Sustainable procedures in organic synthesis ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2009. http://hdl.handle.net/10281/7474.
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O-acyl-N-benzyllactamides are obtained in good yield by reaction of 4-benzyl-5-methyl-1,3-oxazolidine-2,4-diones with Grignards reagents and with lithium alkyls. Three alkanes and two ethers were oxidised with ozone in dichloromethane solution or in aqueous pH 3 suspension. Cyclodecane and cyclododecane were converted into the corresponding cycloalkanones. n-decane was converted into a mixture of isomeric n-decanones and carboxylic acids. An ester was formed from the ethers. Hence, one of the methylene groups of these substrates is generally converted into a carbonyl group. Some of these reactions have preparative value. The oxidation of naphthalene in dichloromethane or acetonitrile with excess ozone gives phthalic aldehyde, 2-formyl benzoic acid and phthalic anhydride. Small amounts of the (E)- and (Z)-isomer of 3-phenyl-(2-formyl)-propenal and are also observed in some cases. The reaction is faster in acetonitrile than in dichloromethane owing to the higher solubility of ozone in the former solvent. The reaction is faster on lowering the temperature because of the increase of the concentration of ozone in solution at lower temperature. With a 1:1 or a 1:2 naphthalene:ozone ratio high conversion and low selectivity for the anhydride is observed. The ozonation of cyclohexane in dichloromethane or acetonitrile gives cycloxexanone, cyclohexanol and acidic material. The influence of solvent, reactant concentration, amount of ozone, temperature, reaction time is studied. A reaction mechanism is proposed based on the results of a simulation of the reaction energetics. The ozonation of N-phenylmorpholine in dichloromethane or acetonitrile produced a lactame and a diformylderivative. These products derive from the attack of ozone at the heterocyclic ring. The reaction mechanism has been investigated by DFT calculations which show that the reaction occurs through the insertion of ozone at the carbon-hydrogen bond of a methylenic group of the morpholine ring. The regioselectivity is due to the to the significantly lower energy barrier calculated for the attack of ozone in α to nitrogen than in α to oxygen. Also, the energy barrier decreases with increasing the polarity of the solvent, accounting for the higher reaction rate observed for the reaction carried out in acetonitrile than in dichloromethane. The ozonation of trans- and cis-decalin in dichloromethane or acetonitrile gives the corresponding 9-hydroxydecalinns, 2- and 3-decalones and acidic material. The influence of solvent, reactant concentration, amount of ozone, temperature, reaction time is studied. A reaction mechanism is proposed based on the results of a simulation of the reaction energetics. The N,N bis(salicylidene)ethylenediaminocobalt(II) catalysed oxidative carbonylation of para-substituted aromatic primary amines at 100 °C in methanol gives carbamates in high yields. In presence of excess dimethylamine also N-aryl-N’,N’-dimethylureas are formed. In methylene chloride moderate yields in isocyanate are obtained. 1-methylbenzylamine gives the carbamate and the urea in high yield. i-propylamine gives only the urea. An α-aminoalcohol gives a 1,3-oxazolidin-2-one. Aliphatic secondary amines react faster and give carbamates in methanol and ureas in methylene chloride. The turnover frequency is also measured in two cases.
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Millard, Marcus J. « Effects of Lithium Nitrate Admixture on Early Age Concrete Behavior ». Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11615.
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Alkali silica reaction (ASR), a reaction which occurs between reactive siliceous mineral components in the aggregate and the alkaline pore solution in concrete, is responsible for substantial damage to concrete structures in the U. S. and across the world. Lithium admixtures, including lithium nitrate (LiNO3), have been demonstrated to mitigate ASR damage, and are of particular interest for use in concrete airfield pavement construction, where ASR damage has been recently linked to the use of certain de-icing chemicals. Although the effectiveness of lithium admixtures at ASR-mitigation is well-researched, relatively less is known regarding the potential effects, including negative effects, on overall concrete behavior. The goal of this research is to better understand the influence of LiNO3 admixture on early age concrete behavior, and to determine if a maximum dosage rate for its use exists.
Isothermal calorimetry, rheology and bleed water testing, time of setting, chemical shrinkage, autogenous shrinkage, free and restrained concrete shrinkage, and compressive and flexural strength were measured for pastes and concretes prepared with a range of LiNO3 dosages (i.e., 0, 50, 100, 200, and 400% of the recommended dosage). In addition, the interaction of LiNO3 with cement was evaluated by comparing results obtained with six cements of varying alkali and tricalcium aluminate (C3A) contents. Additionally, one of these cements, was examined alone and with 20% by weight Class F fly ash replacement.
Results indicate that the hydration of the tricalcium silicate and tricalcium aluminate components of cement are accelerated by the use of LiNO3, and that low alkali cements (typically specified to avoid damage by ASR) may be particularly susceptible to this acceleration. However, inclusion of Class F fly ash at 20% by weight replacement of cement (also common in applications where ASR is a concern) appears to diminish these possibly negative effects of LiNO3 on early age hydration acceleration and heat generation. Dosages higher than the current standard dosage of LiNO3 may have minor effects on fresh concrete workability, causing slight decreases in Bingham yield stress, corresponding to slightly higher slump. Fresh concrete viscosity may also be affected, though more research is necessary to confirm this effect. LiNO3 had no effect on quantity of bleed water in the mixes tested. Generally, LiNO3 had no effect on initial and final setting times, although increasing dosages caused faster set times in the lowest alkali (Na2Oeq = 0.295%) cement examined. In shrinkage testing, higher LiNO3 dosages appeared to cause initial expansion in some sealed paste specimens, but in all cases the highest dosage led to greater autogenous shrinkage after 40 days. In concrete specimens, however, the restraining effect of aggregates diminished shrinkage, and no effect of the LiNO3 was apparent. In no cases, with any dosage of lithium tested, with or without fly ash replacement, did restrained shrinkage specimens show any cracking. Strength testing produced mixed results, with laboratory specimens increasing in 28-day compressive strength, but companion specimens cast in the field and tested by an outside laboratory, exhibited lower 28-day compressive strength, with increasing lithium dosages. Flexural specimens, also cast in the field and tested by an outside laboratory, appeared to show an increase in 28-day flexural strength with increasing lithium dosages. However, because of the conflicting results when comparing the various strength data, further research is necessary for conclusive evidence of LiNO3 effects on concrete strength.
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Collins, Courtney Lloyd. « Examination of the mechanism by which lithium additives inhibit alkali-silica reaction gel expansion ». Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/21295.
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Robertson, Alan. « Elaboration and expansion of the chemistry of alkali metal primary amide complexes ». Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248701.
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Murphy, Denissa Tjiadarma. « Structural Investigation of Electrodes for Rechargeable Alkali Ion Batteries ». Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17699.
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This thesis describes the in-depth characterisation of the structure, including detailed cation distributions, of positive electrode materials for lithium and sodium ion batteries. As the crystal chemistry influences the mobility of lithium and sodium ions, the structure and electrochemical property relationships for select compounds have been established. The majority of this thesis is focused on the structural characterisation of LiMn2-xTixO4 (0.2 ≤ x ≤ 1.5). A combination of X-ray and neutron powder diffraction studies along with spectroscopic techniques and physical property measurements were employed to elucidate the complex metal ion ordering of the spinel electrodes. It was found that the synthesis conditions, particularly cooling regimes, play an important part in the final structures of LiMn1.8Ti0.2O4 and LiMnTiO4. The bulk substitution of 10% and 50% manganese with titanium heavily influenced the cation distribution and consequently, the electrochemistry of these compounds. In situ diffraction studies revealed the contrasting structural evolutions of LiMn1.8Ti0.2O4 and LiMnTiO4 during charge and discharge cycles. The potential of sodium silicate materials as positive electrodes for sodium ion batteries was explored. The fundamental crystal chemistry of Na2MnSiO4 and Na2CoSiO4 was established prior to electrochemical cycling. The as prepared Na2CoSiO4 exhibited better conductivity than the manganese analogue. Improvement of the conductivity of Na2MnSiO4 was achieved through carbon coating of the material. Finally, the addition of Li2RuO3 to form the lithium rich 0.5Li2RuO3∙0.5LiMO2 (M = Co and Ni) electrodes has resulted in the increased the stability of the layered structures of the compounds. The electrochemically active Li2RuO3 contributed to the excellent specific capacity and rate capability of the cobalt compound. Overall superior electrochemical performance was achieved by the nickel analogue.
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Maraschky, Adam M. « Experimental and Modeling Studies of Dendrite Initiation during Lithium Electrodeposition ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1590505470067127.
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Vignarooban, Kandasamy. « Boson Mode, Dimensional Crossover, Medium Range Structure and Intermediate Phase in Lithium- and Sodium-Borate Glasses ». University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1353100044.
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Kganyago, Khomotso R. « A Theoretical Study of Alkali Metal Intercalated Layered Metal Dichalcogenides and Chevrel Phase Molybdenum Chalcogenides ». Thesis, University of Limpopo (Turfloop Campus), 2004. http://hdl.handle.net/10386/702.
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Thesis (Ph.D. (Engineering mechanics)) --University of Limpopo, 2004This thesis explores the important issues associated with the insertion of Mg2+ and Li+ into the solid materials: molybdenum sulphide and titanium disulphide. This process, which is also known as intercalation, is driven by charge transfer and is the basic cell reaction of advanced batteries. We perform a systematic computational investigation of the new Chevrel phase, MgxMo6S8 for 0 ≤ x ≤ 2, a candidate for high energy density cathode in prototype rechargeable magnesium (Mg) battery systems. Mg2+ intercalation property of the Mo6S8 Chevrel phase compound and accompanied structural changes were evaluated. We conduct our study within the framework of both the local-density functional theory and the generalised gradient approximation techniques. Analysis of the calculated energetics for different magnesium positions and composition suggest a triclinic structure of MgxMo6S8 (x = 1 and 2). The results compare favourably with experimental data. Band-structure calculations imply the existence of an energy gap located ~1 eV above the Fermi level, which is a characteristic feature of the electronic structure of the Chevrel compounds. Calculations of electronic charge density suggest a charge transfer from Mg to the Mo6S8 cluster, which has a significant effect on the Mo-Mo bond length. There is relatively no theoretical work, in particular ab initio pseudopotential calculations, reported in literature on structural stability, cations "site energy" calculations, and pressure work. Structures obtained on the basis from experimental studies of other ternary molybdenum sulphides are examined with respect to pressure-induced structural transformation. We report the first bulk and linear moduli of the new Chevrel phase structures. This thesis also studies the reaction between lithium and titanium disulfide, which is the perfect intercalation reaction, with the product having the same structure over the range of reaction 0 x 1 in LixTiS2. Calculated lattice parameters, bulk moduli, linear moduli, elastic constants, density of states, and Mulliken populations are reported. Our calculations confirm that there is a single phase present with an expansion of the crystalline lattice as is typical for a solid solution, about 10% perpendicular to the basal plane layers. A slight expansion of the lattice in the basal plane is also observed due to the electron density increasing on the sulfur ions. Details on the correlation between the electronic structure and the energetic (i.e. the thermodynamics) of intercalation are obtained by establishing the connection between the charge transfer and lithium intercalation into TiS2. The theoretical determination of the densities of states for the pure TiS2 and Li1TiS2 confirms a charge transfer. Lithium charge is donated to the S (3p) and Ti (3d) orbitals. Comparison with experiment shows that the calculated optical properties for energies below 12 eV agrees well with reflectivity spectra. The structural and electronic properties of the intercalation compound LixTiS2, for x = 1/4, 3/4, and 1, are also investigated. This study indicates that the following physical changes in LixTiS2 are induced by intercalation: (1) the crystal expands uniaxially in the c-direction, (2) no staging is observed. We also focus on the intercalation voltage where the variation of the cell potential with the degree of discharge for LiTiS2 is calculated. Our results show that it can be predicted with these well-developed total energy methods. The detailed understanding of the electronic structure of the intercalation compounds provided by this method gives an approach to the interpretation of the voltage composition profiles of electrode materials, and may now clearly be used routinely to determine the contributions of the anode and cathode processes to the cell voltage. Hence becoming an important tool in the selection and design of new systems. Keywords Magnesium rechargeable battery; Chevrel, Lithium batteries; Li and Mg-ion insertion; TiS2; Mo6S8; Charge transfer; reflectivity, intercalation, elastic constants, voltage, EOS, Moduli.
the National Research Foundation, the Royal Society(U.K),the Council for Scientific and Industrial Research,and Eskom
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Robitaille, Amélie. « Synthèse et caractérisation de poly[5-alkyl-thieno-[3,4-c]-pyrrole-4,6-dione]s pour la fabrication d’électrodes de batteries lithium-ion ». Master's thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/25841.
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Le potentiel d’oxydoréduction des anodes utilisée dans un pile lithium-ion doit se trouver au-dessus de 0,75V vs Li/Li+ pour rester sécuritaire et ne doit pas excéder 2V vs Li/Li+ pour conserver une puissance adéquate. Suite aux travaux effectués les polythienopyrroledione (PTPD) ont démontré des potentiels d'oxydo-réduction de 1,6V vs Li/Li+ ce qui correspond aux critères établis ci-haut. De plus, ils ont une capacité théorique de 215 mAh/g, ont obtenu une capacité expérimentale de 209 mAh/g. Cette capacité est toutefois inférieure à celle des matériaux d'anodes actuellement sur le marché. Par contre, étant donné que la capacité d'une pile est limitée par la capacité de l'électrode la plus faible, et qu'actuellement les piles lithium-ion sur le marché sont basées sur le LiFePO₄ qui possède une capacité de 170 mAh/g, il serait envisageable que les PTPD puissent potentiellement être des anodes commercialisables.
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Kautz, Jr David Joseph. « Investigation of Alkali Metal-Host Interactions and Electrode-Electrolyte Interfacial Chemistries for Lean Lithium and Sodium Metal Batteries ». Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103946.
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The development and commercialization of alkali ion secondary batteries has played a critical role in the development of personal electronics and electric vehicles. The recent increase in demand for electric vehicles has pushed for lighter batteries with a higher energy density to reduce the weight of the vehicle while with an emphasis on improving the mile range. A resurgence has occurred in lithium, and sodium, metal anode research due to their high theoretical capacities, low densities, and low redox potentials. However, Li and Na metal anodes suffer from major safety issues and long-term cycling stability. This dissertation focuses on the investigation of the interfacial chemistries between alkali metal-carbon host interactions and the electrode-electrolyte interactions of the cathode and anode with boron-based electrolytes to establish design rules for "lean" alkali metal composite anodes and improve long-term stability to enable alkali metal batteries for practical electrochemical applications.
Chapter 2 of this thesis focuses on the design and preliminary investigation of "lean" lithium-carbon nanofiber (<5 mAh cm-2) composite anodes in full cell testing using a LiNi0.6Mn0.2Co0.2O2 (NMC 622) cathode. We used the electrodeposition method to synthesize the Li-CNF composite anodes with a range of electrodeposition capacities and current densities and electrolyte formulations. Increasing the electrodeposition capacity improved the cycle life with 3 mAh cm-2 areal capacity and 2% vinylene carbonate (VC) electrolyte additive gave the best cycle life before reaching a state of "rapid cell failure". Increasing the electrodeposition rate reduced cycling stability and had a faster fade in capacity. The electrodeposition of lithium metal into a 2D graphite anode significantly improved cycle life, implying the increased crystallinity of the carbon substrate promotes improved anode stability and cycling capabilities.
As the increased crystallinity of the carbon anode was shown to improve the "lean" composite anode's performance, Chapter 3 focuses on utilizing a CNF electrode designed with a higher degree of graphitization and probing the interacting mechanism of Li and Na with the CNF host. Characterization of the CNF properties found the material to be more reminiscent of hard carbon materials. Electrochemical analysis showed better long-term performance for Na-CNF symmetric cells. Kinetic analysis, using cyclic voltammetry (CV), revealed that Na ions successfully (de)intercalated within the CNF crystalline interlayers, while Li ions were limited to surface adsorption. A change in mechanism was quickly observed in the Na-CNF symmetric cycling from metal stripping/plating to ion intercalation/deintercalation, enabling the superior cycling stability of the composite anode. Improving the Na metal stability is necessary for enabling Na-CNF improved long-term performance.
Sodium batteries have begun to garner more attention for grid storage applications due to their overall lower cost and less volumetric constraint required. However, sodium cathodes have poor electrode-electrolyte stability, leading to nanocracks in the cathode particles and transition metal dissolution. Chapter 4 focuses on electrolyte engineering with the boron salts sodium difluoro(oxolato)borate (NaDFOB) and sodium tetrafluoroborate (NaBF4) mixed together with sodium hexafluorophosphate (NaPF6) to improve the electrode-electrolyte compatibility and cathode particle stability. The electrolytes containing NaDFOB showed improved electrochemical stability at various temperatures, the formation of a more robust electrode-electrolyte interphase, and suppression in transition metal (TM) reduction and dissolution of the cathode particles measured after cycling.
In Chapter 5, we focus on the electrochemical properties and the anode-electrolyte interfacial chemistry properties of the sodium borate salt electrolytes. Similar to Chapter 4, the NaDFOB containing electrolytes have improved electrochemical performance and stability. Following the same electrodeposition parameters as Chapter 2, we find the NaDFOB electrolytes improves the stability of electrodeposited Na metal and the "lean" composite anode's cyclability. This study suggests the great potential for the NaDFOB electrolytes for Na ion battery applications.Doctor of Philosophy
The ever-increasing demand for high energy storage in personal electronics, electric vehicles, and grid energy storage has driven for research to safely enable alkali metal (Li and Na) anodes for practical energy storage applications. Key research efforts have focused on developing alkali metal composite anodes, as well as improving the electrode-electrolyte interfacial chemistries. A fundamental understanding of the electrode interactions with the electrolyte or host materials is necessary to progress towards safer batteries and better battery material design for long-term applications. Improving the interfacial interactions between the host-guest or electrode-electrolyte interfaces allows for more efficient charge transfer processes to occur, reduces interfacial resistance, and improves overall stability within the battery. As a result, there is great potential in understanding the host-guest and electrode-electrolyte interactions for the design of longer-lasting and safer batteries. This dissertation focuses on probing the interfacial chemistries of the battery materials to enable "lean" alkali metal composite anodes and improve electrode stability through electrolyte interactions. The anode-host interactions are first explored through preliminary design development for "lean" alkali composite anodes using carbon nanofiber (CNF) electrodes. The effect on increasing the crystallinity of the CNF host on the Li- and Na-CNF interactions for enhanced electrochemical performance and stability is then investigated. In an effort to improve the capabilities of Na batteries, the electrode-electrolyte interactions of the cathode- and anode-electrolyte interfacial chemistries using sodium borate salts are probed using electrochemical and X-ray analysis. Overall, this dissertation explores how the interfacial interactions affect, and improve, battery performance and stability. This work provides insights for understanding alkali metal-host and electrode-electrolyte properties and guidance for potential future research of the stabilization for Li- and Na-metal batteries.
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Crosbie, Elaine. « Alkali-metal-mediated alumination : development of bis-TMP chemistry of [(THF)AM(TMP)₂Al(iBu)₂] with emphasis on lithium ». Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=22543.
Texte intégralRésumé :
Deprotonation, the exchange of an inert carbon-hydrogen bond for a more chemically useful carbon-metal bond, has long been one of the methods of choice for constructing substituted aromatic and heteroaromatic compounds. Organolithium reagents have been the standard for this purpose for many years; however, their many limitations mean that new reagents for deprotonative metallation are sought. Alkali-Metal-Mediated Metallation (AMMM) was developed as an alternative vehicle to functionalising a plethora of substrates. This project focuses on the synergic alumination chemistry generated by combining lithium amide LiTMP with low polarity aluminium reagent exhibiting the reaction concept of Alkali-Metal-Mediated Alumination (AMMAl). AMMAl reactions of lithium bis-TMP aluminate [(THF)Li(TMP)Deprotonation, the exchange of an inert carbon-hydrogen bond for a more chemically useful carbon-metal bond, has long been one of the methods of choice for constructing substituted aroma tic and heteroaromatic compounds. Organolithium reagents have been the standard for this purpose for many years; however, their many limitations mean that new reagents for deprotonative metallation are sought. Alkali-Metal-Mediated Metallation (AMMM) was developed as an alternative vehicle to functionalising a plethora of substrates. This project focuses on the synergic alumination chemistry generated by combining lithium amide LiTMP with low polarity aluminium reagent iBu2AlTMP exhibiting the reaction concept of Alkali-Metal-Mediated Alumination (AMMAl). AMMAl reactions of lithium bis-TMP aluminate [(THF)Li(TMP)2Al(iBu)2] were explored to learn more about the reactivity of this bis-amido base. Several functionalised aromatic substrates including anisole and N,N-diisopropylbenzamide were effectively ortho-aluminated in hexane solution at ambient temperature and quenched with iodine to generate the corresponding metal-free products in excellent yield. DFT calculations and DOSY NMR experiments were conducted to elucidate a possible structure for the base as it could not be isolated. A mechanism was proposed showing an open-structure with a pseudo-terminal TMP. This allowed a rationale for the intramolecular reactivity observed with a series of donor molecules including THF which could be deprotonated and the resulting anion trapped without ring opening. Several key differences were observed between our bis-amido base [Li(TMP)2Al(iBu)2] and Uchiyama's mono-amido base [Li(TMP)Al(iBu)3]. THF was deprotonated and its anion captured with the former; whereas the latter was found to be more stable in THF solution. Other donor molecules such as 1-methoxy-2-dimethylaminoethane (MDAE) and bis-[2-(N,N-dimethylamino)ethyl]ether (Me4AEE) were deprotonated with the bis-amido base; whereas they were found to merely solvate lithium when the mono-amido base was employed. An investigation into the mono-amido base in THF solution revealed some interesting facts concluding us to believe that this base disproportionates to give our mono-amido base in THF solution.
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Silva, Domingos Jorge Ferreira da. « Estudo dos efeitos do nitrato de lítio na expansão de argamassas sujeitas a reação álcali-sílica / ». Ilha Solteira : [s.n.], 2007. http://hdl.handle.net/11449/91469.
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Resumo: Várias pesquisas realizadas com compostos a base de lítio tem mostrado resultados satisfatórios na redução da expansão associada à reação álcali-sílica (RAS), mas ainda existem muitas dúvidas sobre seus mecanismos de ação. A presente pesquisa avaliou os efeitos de uma adição química a base de nitrato de lítio (LiNO3) na redução da expansão associada a RAS, utilizando várias dosagens. Os estudo dos efeitos do LiNO3 na RAS foi feito pelo método acelerado das barras de argamassa (ASTM C-1260) utilizando dois tipos de agregado reativo. Também foram realizados ensaios de expansão com uma adição mineral a base de cinza volante a fim de correlacionar os efeitos de uma adição mineral com uma química na redução da expansão devido a RAS. Ensaios de resistência à compressão e trabalhabilidade foram realizados também buscando algum efeito do LiNO3 nestas propriedades. Os resultados do ensaio ASTM C-1260 indicaram que as adições de lítio foram efetivas na redução da expansão para os dois tipos de agregados reativos, sendo que para as condições e materiais utilizados na presente pesquisa foi necessário uma de adição de LiNO3 com relação molar (Li2O/Na2Oeq) de 7,00 para reduzir a expansão ao valor aceitável pela norma de 0,10% aos 16 dias. Foi observado também intensidades de redução da expansão diferentes entre os dois tipos de agregados estudados devido a diferença de reatividade dos mesmos. Verificou-se um limite de adição de lítio para o basalto, onde não havia mais redução significativa de expansão com o aumento da dosagem de adição. Observou-se também que as misturas contendo LiNO3 reduziram a expansão ao longo dos 30 dias, enquanto nas misturas contendo FA a expansão continuou a aumentar ao longo do teste. Os ensaios de condição de trabalhabilidade e de resistência à compressão mostraram que o LiNO3 não afeta consideravelmente estas propriedades.Abstract: Lithium compounds have been shown satisfactory results for the reduction of the expansion due to alkali-silica reaction (ASR), but there are many doubts about its mechanisms of action. The present research evaluated the effects of a chemical addition to lithium nitrate based (LiNO3) on the reduction of expansion associated with ASR, utilizing several dosages. For the study of the effects of the LiNO3 on the ASR it was used the accelerated mortar bar method (ASTM C-1260), with two kinds of reactivate aggregate. Mortar bars were molded also with a mineral addition of fly ash based (FA) with the objective to compare the effects of a mineral addition with a chemistry on the expansion due ASR. Compressive strength and consistence index tests had been carried also for searching some effects of the LiNO3 at these properties. The results from ASTM C-1260 showed that the addition of LiNO3 were effective on the expansion reduction for two kinds of reactive aggregate, which current conditions and materials on this research required a LiNO3 addition with (Li/Naeq) of 7,00 molar ratio to decrease the expansion to an acceptable value of 0,10% on 16 days. Also, the intensity of the expansion reduction was observed between two kinds of studied aggregates by their reactivity difference. A lithium additive upper bound was verified for the basalt, where it did not have more significant reduction of expansion with the increase of the dosage of addition. Also, was observed that admixtures that contained LiNO3 have reduced the expansion trough 30 days, while on the admixtures that contained FA the expansion grew up. The results obtained for the compressive strength and consistence index tests showed no significant differences between mixtures with and without LiNO3 admixture.
Orientador: Jorge Luís Akasaki
Coorientador: Haroldo de Mayo Bernardes
Banca: Marco Antonio Morais Alcantara
Banca: Vladimir Antonio Paulon
Mestre
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Fauchard, Mélissa. « Intercalation d'alliages or-potassium et calcium-lithium dans des structures carbonées de basse dimensionnalité ». Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0140/document.
Texte intégralRésumé :
L’intercalation de métaux dans le graphite a été réalisée pour la première fois en 1926. Depuis cette découverte, de nombreux composés binaires et ternaires ont été synthétisés. Au cours de ce travail, la méthode solide-liquide en milieu alliage fondu à base d’alcalin a d’abord été utilisée afin d’intercaler l’or dans le graphite à l’aide du potassium. Puis, l’intercalation du calcium dans des matériaux B-C-N de structure graphitique a été réalisée par le biais du lithium. La diffraction des rayons X, l’analyse par faisceau d’ions, la microscopie électronique ainsi que les techniques spectroscopiques associées ont été mises en œuvre pour caractériser ces nouveaux composés. Dans le cas du système graphite-potassium-or, trois nouveaux composés ternaires de premier stade et de distances interplanaires très différentes (1311, 953 et 500 pm) ont pu être synthétisés. Le composé K1,3Au1,5C4 a été isolé de façon reproductible et présente selon l’axe c une séquence d’empilement K-Au-Au-Au-K pour l’insérat. L’étude du mécanisme d’intercalation menant à ce composé a mis en évidence un intermédiaire réactionnel de formule K1,6Au0,7C4 dont le feuillet inséré est tricouche. Le troisième composé, KAu0,7C4, constitué de deux couches mixtes or-potassium, s’est quant à lui révélé métastable. Parallèlement, l’intercalation d’un alliage Li-Ca dans le matériau B-C-N a été réalisée avec succès. L’analyse par faisceau d’ions de l’hôte a permis de doser sur un même échantillon la teneur en bore, carbone et azote, conduisant à une formule B2C5N. Les mesures effectuées sur le matériau intercalé montrent la préservation du réseau hôte et l’insertion de 0,6 atome de lithium par atome de calciumSince the discovery in 1926 of the first graphite intercalation compounds containing alkali metals, numerous binary and ternary compounds have been synthesized. In this work, solid-liquid method in alkali metal based molten alloys has been employed to intercalate gold into graphite using potassium as an intercalation vector for opening the van der Waals’s gaps and decreasing the reaction temperature. Then, lithium has been used to assist the intercalation of calcium into B-C-N compounds. X-ray diffraction, ion beam analysis, electron microscopy and associated spectroscopy techniques have been performed to characterize the as-prepared compounds. In the case of graphite-potassium-gold system, three novel ternary first stage intercalation compounds with very different repeat distances (1311, 953 and 500 pm) have been synthesized. The K1.3Au1.5C4 compound, isolated in a reproducible fashion, presents a K-Au-Au-Au-K c-axis stacking sequence for the intercalated sheets. The study of its intercalation mechanism evidenced an intermediate product which chemical formula is K1.6Au0.7C4, with three-layered intercalated sheets. The third compound KAu0.7C4 is metastable and contains in each van der Waals‘s gap two successive layers containing a mixture of gold and potassium. Elsewhere, the intercalation of a Li-Ca alloy into B-C-N host material has been successfully carried out. The ion beam analysis of the pristine B-C-N lead to determine on a same sample the amount of boron, carbon and nitrogen with the corresponding B2C5N formula. The experiments realized on the intercalated compound showed the preservation of the host lattice and the intercalation of 0.6 lithium per calcium atom
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Couture, Karine. « Etude de la métallation en série diazinique 1) premier échange iode-lithium avec les alkylamidures de lithium 2) amination électrophile 3) première métallation sans groupe directeur ». Rouen, 1995. http://www.theses.fr/1995ROUES020.
Texte intégralRésumé :
Ce travail consiste en l'étude de la réaction de métallation en série diazinique. Dans une première partie, nous avons pu mettre en évidence pour la première fois en série diazinique, un mécanisme d'halogen-dance avec migration de l'iode. De plus, nous avons pu observer pour la première fois dans cette série, un exceptionnel échange iode-métal avec les alkylamidures de lithium. Cette réaction a été appliquée à la synthèse de leshmaniacides. Dans une seconde partie, nous avons mis au point l'amination électrophile par métallation en série diazinique. Cette réaction d'amination a été appliquée à la synthèse de molécules biologiquement actives et nous a permis d'accéder à un azaanalogue de la Névirapine ainsi qu'à des précurseurs de sulfamides connus. Dans une troisième partie, nous avons tenté d'élargir la gamme des groupes ortho-directeurs en série pyrimidinique (NHCOtBu, CONHtBu). Dans la dernière partie, une nouvelle fonctionnalisation directe des diazines sans groupe ortho-directeur a été réalisée avec succès
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Kerkhoff, Linda [Verfasser], Petra [Gutachter] Becker-Bohatý et Thomas [Gutachter] Lorenz. « Crystal growth and structural aspects of alkali iridates and ruthenates of lithium and sodium / Linda Kerkhoff ; Gutachter : Petra Becker-Bohatý, Thomas Lorenz ». Köln : Universitäts- und Stadtbibliothek Köln, 2021. http://d-nb.info/1235138763/34.
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Rio, Fernandes Diogo. « Trapping and cooling of fermionic alkali atoms to quantum degeneracy : Sub-Doppler cooling of Potassium-40 and Lithium-6 in gray molasses ». Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066689.
Texte intégralRésumé :
Ce mémoire décrit la conception, la construction et la caractérisation d'un appareil capable de piéger et refroidir des atomes fermioniques de 6Li et 40K à des températures ultrabasses. L'étude des mélanges des gazes de Fermi dégénérés ouvre la porte vers la création des nouveaux systèmes quantiques à N corps. Nous présentons une nouvelle technique de refroidissement laser capable de refroidir simultanément 6Li et 40K à des températures sub-doppler basée sur un schéma de molasses grises fonctionnant sur la transition atomique D1. Cette stratégie améliore la densité dans le espace des phases des deux espèces atomiques à 104, la valeur la plus élevée rapportée dans la littérature pour le refroidissement laser du 6Li et du40K. L'optimisation d'un dispositif capable de transporter un nuage atomique piégé magnétiquement de l'enceinte MOT à une cellule de science est décrite. Dans cette cellule on effectue du refroidissement évaporatif d'abord dans un piège magnétique quadripolaire dont le zéro du champ est interdit par un potentiel répulsif et après dans un piège optique dipolaire. Nous rapportons la production d'un gaz quantique de Fermi dégénéré de 1.1x106 atomes de 40K dans un piège dipolaire croisé avec T/TF = 0.27,ouvrant la voie à la création des superfluides de 40K en interactions fortesThis thesis describes the design, construction and characterization of an apparat us capable of trapping and cooling fermionic atoms of 6Li and 40K to ultracold temperatures.The study of mixtures of degenerate Fermi gases opens the door for the creation of new many-body quantum systems.We present a novel laser cooling technique able to simultaneously cool 6Li and 40K to the sub-Doppler regime based on the gray molasses scheme operating on the D1 atomic transition. This strategy enhances the phase space density of both atomic species to 104, the highest value reported in the literature for laser cooled 6Li and 40K. The optimization of a device able to transport a magnetically trapped atomic cloud from the MOT chamber to a science cell is described. In this cell evaporative cooling is performed first in a plugged magnetic quadrupole trap and then in an optical dipoletrap. We report the production of a quantum degenerate Fermi gas of 1.1x106 atoms40K in a crossed dipole trap with T/TF = 0.27, paving the way for the creation of strongly interacting superfluids of 40K
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Witherow, Rebecca A. « Minor Alkaline Earth Element and Alkali Metal Behavior in Closed-Basin Lakes ». The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250628213.
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Silva, Domingos Jorge Ferreira da [UNESP]. « Estudo dos efeitos do nitrato de lítio na expansão de argamassas sujeitas a reação álcali-sílica ». Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/91469.
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Várias pesquisas realizadas com compostos a base de lítio tem mostrado resultados satisfatórios na redução da expansão associada à reação álcali-sílica (RAS), mas ainda existem muitas dúvidas sobre seus mecanismos de ação. A presente pesquisa avaliou os efeitos de uma adição química a base de nitrato de lítio (LiNO3) na redução da expansão associada a RAS, utilizando várias dosagens. Os estudo dos efeitos do LiNO3 na RAS foi feito pelo método acelerado das barras de argamassa (ASTM C-1260) utilizando dois tipos de agregado reativo. Também foram realizados ensaios de expansão com uma adição mineral a base de cinza volante a fim de correlacionar os efeitos de uma adição mineral com uma química na redução da expansão devido a RAS. Ensaios de resistência à compressão e trabalhabilidade foram realizados também buscando algum efeito do LiNO3 nestas propriedades. Os resultados do ensaio ASTM C-1260 indicaram que as adições de lítio foram efetivas na redução da expansão para os dois tipos de agregados reativos, sendo que para as condições e materiais utilizados na presente pesquisa foi necessário uma de adição de LiNO3 com relação molar (Li2O/Na2Oeq) de 7,00 para reduzir a expansão ao valor aceitável pela norma de 0,10% aos 16 dias. Foi observado também intensidades de redução da expansão diferentes entre os dois tipos de agregados estudados devido a diferença de reatividade dos mesmos. Verificou-se um limite de adição de lítio para o basalto, onde não havia mais redução significativa de expansão com o aumento da dosagem de adição. Observou-se também que as misturas contendo LiNO3 reduziram a expansão ao longo dos 30 dias, enquanto nas misturas contendo FA a expansão continuou a aumentar ao longo do teste. Os ensaios de condição de trabalhabilidade e de resistência à compressão mostraram que o LiNO3 não afeta consideravelmente estas propriedades.
Lithium compounds have been shown satisfactory results for the reduction of the expansion due to alkali-silica reaction (ASR), but there are many doubts about its mechanisms of action. The present research evaluated the effects of a chemical addition to lithium nitrate based (LiNO3) on the reduction of expansion associated with ASR, utilizing several dosages. For the study of the effects of the LiNO3 on the ASR it was used the accelerated mortar bar method (ASTM C-1260), with two kinds of reactivate aggregate. Mortar bars were molded also with a mineral addition of fly ash based (FA) with the objective to compare the effects of a mineral addition with a chemistry on the expansion due ASR. Compressive strength and consistence index tests had been carried also for searching some effects of the LiNO3 at these properties. The results from ASTM C-1260 showed that the addition of LiNO3 were effective on the expansion reduction for two kinds of reactive aggregate, which current conditions and materials on this research required a LiNO3 addition with (Li/Naeq) of 7,00 molar ratio to decrease the expansion to an acceptable value of 0,10% on 16 days. Also, the intensity of the expansion reduction was observed between two kinds of studied aggregates by their reactivity difference. A lithium additive upper bound was verified for the basalt, where it did not have more significant reduction of expansion with the increase of the dosage of addition. Also, was observed that admixtures that contained LiNO3 have reduced the expansion trough 30 days, while on the admixtures that contained FA the expansion grew up. The results obtained for the compressive strength and consistence index tests showed no significant differences between mixtures with and without LiNO3 admixture.
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Pagot, G. « Electrode and electrolyte materials for the development of high voltage lithium-ion batteries and secondary batteries based on alkali and alkaline-earth ions ». Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3426843.
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The research activity described in this thesis has been focused on the development and study of novel electrolyte and electrode materials for application in Lithium and Magnesium secondary batteries. The proposed materials belong to the “beyond Li-ion” class of compounds, where systems exceeding the energy density values of classic Li-ion batteries or completely innovative chemistries are presented.
Three different classes of electrolytes have been prepared and studied. A solid polymer electrolyte has been obtained by a lithium functionalization of a poly(vinyl alcohol-co-vinyl acetate), forming lithium alkoxide functional groups. In this way, the counter anion of Li+ was the overall polymer chain, giving rise to a single lithium ion conductivity. However, the room-temperature conductivity value observed for this material was quite low (4.6·10-10 S·cm-1). By ionic liquid (IL) doping of the
solid polymer electrolyte, we have obtained a double effect: i) lithium cations have been exchanged by the cations of IL, enhancing the mobility of the active species; and ii) the flexibility of polymer chains has been increased by the plasticizing effect of the IL. Thus, a room temperature conductivity of 1.3·10-5 S·cm-1 has been reached, maintaining a high value of Li transference number (0.59). By reacting glycerol with different quantities of lithium hydride, a new family of lithium-ion conducting electrolytes has been synthetized. In these electrolytes the lithium glycerolate component acts as a large and flexible macro-anion which is able to provide a singleion conductivity to the material (2.0∙10-4 at 30 °C and 1.6∙10-2 S∙cm-1 at 150 °C). In the last class of electrolytes, ionic liquid-based materials for magnesium batteries, the cation and anion replacement effect on the structure, conductivity mechanism, and electrochemical performances has been studied. The proposed materials have exhibited a conductivity value between 10-3 and 10-4 S∙cm-1, an overpotential in the magnesium deposition lower than 50 mV vs. Mg/Mg2+, an anodic stability up to +2.35 V vs. Mg/Mg2+, and a coulombic efficiency up to 99.94 %.
In the second part of this Ph.D. project, the improvement of the electrochemical features of various cathode materials has been studied. In the first case, it has been found that, by adding CuCO3 to the precursors, segregated CuO particles have been formed. The presence of these particles has improved the charge-transfer kinetics during the charge/discharge processes of the cathode material. On the other hand, graphite addition to the precursors has been found to improve the
elasticity of the 3D structure of the cathode backbone. Thus, an increased structural flexibility that facilitates the percolation of lithium ions along the 1D channels of the cathode material has been observed. In the second approach, the improvement of the electron conductivity of a high-voltage cathode has been gauged by V, Nb, or Ta insertion within its olivine structure. This approach has allowed for an improved kinetic and reversibility of Li+ insertion reaction. The specific capacity reached by these cathodes was equal to 149 mAh∙g-1. The last cathode material has been implemented in a magnesium secondary battery device. A graphene oxide surface functionalization of vanadium-based nanoparticles has been obtained thanks to electrostatic interactions through ammonium bridges. This functionalization has allowed for the obtaining of a material able to: a) sustain extremely high current rates (1000 mA∙g-1, 1700 mW∙g-1 of specific power); and b) give reasonable specific capacity values (72 mAh∙g-1).
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CÂNDIDO, Wilson Ferreira. « Estudo de tratamentos com lítio no combate da reação álcali-agregado ». Universidade Federal de Goiás, 2009. http://repositorio.bc.ufg.br/tede/handle/tde/1350.
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Previous issue date: 2009-09-11The alkali-aggregate reaction (AAR) is one of the deterioration processes of concrete that most affects the structures of hydroelectric plants, concrete dams and bridges. In recent years, the efficiency of lithium based compounds to mitigate RAA has been proven in both the prevention and repair of the affected structures. With regards to treatment, the main challenge nowadays is how to ensure the adequate impregnation of concrete with the lithium solution. Given this difficulty, the objective of this research is to investigate in laboratory conditions, the efficiency of various types of treatment, using a product based on lithium nitrate. The treatments sought to prevent or minimize the residual expansion of AAR, in particular the alkali-silica reaction (ASR), already under development in the concrete and mortar. The study was divided into two stages, the first one performed in concrete prisms, from an adaptation of the Brazilian standard NBR 15577-6/2008, and the second stage in mortar bars, from an adaptation of NBR 15577-4/2008. The treatments were performed after the specimens reached a predetermined level of defined expansion: 0.04% for the concretes and 0.18% for the mortars. In the case of the concretes, the treatments were electrochemical lithium impregnation and surface saturation with lithium, in addition to their respective reference procedures (impregnation and surface saturation with water). For the mortars, the situations tested were: vacuum impregnation with lithium, total saturation in lithium, surface saturation in lithium, water immersion and wrapping in plastic film. After each exposure/treatment condition, the specimens returned to the accelerated expansion attack process in order to evaluate the effectiveness of each treatment. The results demonstrated the efficiency of the lithium based composite to mitigate the residual expansion, both in the concretes as well as in the mortars, with a different behavior depending on the conditions used. The treatment that had the best efficiency in the concrete, under the applied experimental conditions, was the surface saturation of lithium, achieving a 90% reduction in the residual values of expansions at the end of the attack (73 days), taking as reference the surface saturation condition with water. The lithium electrochemical impregnation performed was able to mitigate the residual expansions, but only up to the age of 42 days after treatment, at which time the reduction was of 50%. In fact, at 73 days the expansions were similar to those of the untreated sample. All treatments with lithium performed in the mortars were able to mitigate the residual expansions at levels approaching reduction of expansion (about 87%), with the total saturation in lithium the most efficient condition.
A reação álcali-agregado (RAA) é uma das formas de deterioração do concreto que afeta principalmente as estruturas de usinas hidrelétricas, barragens de concreto e pontes. Nos últimos anos, a eficiência dos compostos à base de lítio em mitigar a RAA tem sido comprovada, tanto na prevenção quanto no reparo de estruturas afetadas. O principal desafio atualmente, no que tange ao tratamento, é a maneira de como garantir uma adequada impregnação do concreto com a solução de lítio. Tendo em vista essa dificuldade, o objetivo da presente pesquisa foi investigar, em laboratório, a eficiência de diversos tipos de tratamento, utilizando um produto à base de nitrato de lítio. Buscou-se com os tratamentos combater ou minimizar as expansões residuais da RAA, mais especificamente da reação álcali-sílica (RAS), já iniciada no concreto e argamassa. O estudo foi divido em duas etapas, sendo a primeira realizada em prismas de concreto, a partir de uma adaptação da NBR15577-6/2008, e a segunda etapa em barras de argamassa, a partir de uma adaptação da NBR 15577-4/2008. Os tratamentos foram realizados após os corpos-de-prova atingirem um determinado nível de expansão definido, a saber: 0,04% para os concretos e 0,18% para as argamassas. No caso dos concretos, os tratamentos realizados foram: impregnação eletroquímica de lítio e saturação superficial com lítio, além de suas situações de referência (impregnação e saturação superficial com água). No caso das argamassas, as situações testadas foram: impregnação a vácuo com lítio, saturação total em lítio, saturação superficial em lítio, imersão em água e envolvimento em filme plástico. Após cada condição de exposição/tratamento, os corpos-de-prova retornaram para o processo de ataque acelerado de expansão visando-se avaliar a eficiência de cada tratamento. Os resultados demonstraram a eficiência do composto à base de lítio em mitigar as expansões residuais, tanto nos concretos como nas argamassas, com comportamento diferenciado dependendo das condições empregadas. O tratamento que teve a melhor eficiência em concreto, nas condições empregadas, foi a saturação superficial de lítio, atingindo uma redução de 90% nos valores das expansões residuais, ao final do ataque (73 dias), tomando-se como referência a condição saturação superficial com água. Já a impregnação eletroquímica de lítio realizada foi capaz de mitigar as expansões residuais, mas apenas até a idade de 42 dias pós-tratamento, onde a redução foi da ordem de 50% nesta idade; aos 73 dias as expansões apresentaram-se semelhantes às da amostra não tratada. Todos os tratamentos com lítio realizados nas argamassas foram capazes de mitigar as expansões residuais em níveis próximos de redução das expansões (da ordem de 87%), sendo a saturação total em lítio a condição mais eficiente.
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Ravard, Alain. « Déracémisation par protonation et élimination énantiosélectives ». Rouen, 1990. http://www.theses.fr/1990ROUES017.
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La déracémisation par protonation énantiosélective a permis la synthèse d'α-aminoacides optiquement enrichis et notamment de la phénylglycine. Nous avons optimisé les paramètres physiques de cette réaction afin d'en améliorer la sélectivité. Nous avons pu ainsi faire progresser l'excès énantiomérique de 57% dans le cas du N-paraméthoxybenzylidène phénylglycinate de méthyle à 70% avec un bien meilleur rendement chimique (95%). Dans une deuxième partie, nous avons appliqué le principe de la déracémisation aux acides t-Bu et Me-4 cyclohexylidène acétiques porteurs d'une chiralité axiale. Une élimination énantiosélective d'un intermédiaire prochiral halogéné par des amidures de lithium chiraux nous a permis de réaliser cette nouvelle synthèse de molécules chirales avec des sélectivités supérieures à 80%. Nous avons mis en évidence certains des paramètres régissant l'énantiosélectivité de la déracémisation et proposé des modèles rationalisant nos résultats. Nous avons aussi montré la possibilité d'un transfert d'une chiralité axiale en une chiralité centrale. De cette façon, nous avons pu accéder à l'isomère endocyclique optiquement enrichi de l'acide t-Bu-4 cyclohexylidène acétique
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Denys, Goument Colombe. « Dicétones-1,4 thiosubstituées ». Rouen, 1988. http://www.theses.fr/1988ROUES023.
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Dulieu, Olivier. « Etude des systemes atomiques a deux electrons externes par la methode de fonction d'onde correlee de pluvinage : application a l'etude des ions alcalins negatifs ». Paris 6, 1987. http://www.theses.fr/1987PA066350.
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Par cette methode, etude detaillee des etats excites et autoionisants de l'atome me; comparaison aux donnees experimentales et a des calculs par d'autres methodes. Extension de la methode de l'analyse a des systemes a deux electrons externes : li**(-), na**(-), k**(-)
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Dagoneau, Christelle. « Chimie des nitrones : application à la synthèse de composés bio-actifs ». Université Joseph Fourier (Grenoble), 2001. http://www.theses.fr/2001GRE10102.
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Ce travail de these porte sur l'elaboration de methodes d'acces aux -aminoesters ,-satures et ,-dihydroxyles, a partir de nitrones. L'addition nucleophile de 3-lithiopropiolates d'alkyle sur ces dernieres constitue la reaction-clef des differentes strategies employees. Au cours de ce travail, nous avons mis au point une methode de synthese rapide et efficace de -aminoesters. L'application de cette strategie de synthese a la nitrone derivee du (s)-glyceraldehyde a permis d'acceder de facon stereoselective au (s)-vigabatrin, compose actif du sabril, medicament largement utilise dans la prevention des crises d'epilepsie. Nous avons ensuite developpe une voie de synthese efficace d'esters -(n-boc)amino-,-dihydroxyles, a partir de nitrones protegees par le groupement 2,4-dimethoxybenzyle. Son application nous a permis de realiser les premieres syntheses racemiques des chaines laterales des agents antitumoraux pm-94128 et y-05460m-a. Enfin, la derniere partie de ce travail de these a ete axee sur la synthese stereoselective de la partie diaminopentol de la zwittermycine a, un aminopolyol possedant d'importantes proprietes antibiotiques et antifongiques. Nous avons ainsi prepare trois diastereoisomeres, sous forme protegee, de cette partie diaminopentol.
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Ayed, Othman. « Etude des interactions entre atomes alcalins (li, na, k) et monoxyde de carbone en matrices de gaz rares : analyse en spectroscopie vibrationnelle et calcul quantiques de quelques complexes ». Paris 6, 1987. http://www.theses.fr/1987PA066117.
Texte intégralRésumé :
Dans le cas de li(le plus reactif), identification de li(co)::(n), ou n = 1,2,3,4,(ou 6), avec des frequences de vibration de valence de co plus perturbees que pour les metaux de transition carbonyle,et de li::(m) co, ou m = 2,3, avec frequences nu (co) abaissees. Pour na et k, observation d'especes de haute stoechiometrie (c::(n)o::(n))**(2-) (m**(+))::(2) ou n = 2,3,4, formees apres irradiation uv-visible et correspondant a des transformations chimiques. Essai d'interpretation de ces differences de reactivite par une description quantique des agregats de plus basse stoechiometrie : dans le complexe 1 :1, les deux etats electroniques inferieurs sont l'etat **(2)sigma non liant et l'etat **(2)pi liant; la courbe de potentiel de lico possede un minimum pour li-c equiv. A 2,5 a au-dessous de la courbe de l'etat **(2)pi alors que pour naco, le minimum de la courbe pour l'etat **(2)pi est au-dessous de la courbe de l'etat **(2)sigma ; le calcul met en evidence le caractere ionique de m::(2)c::(2)o::(2) (acetylenediolate) resultant d'une reaction chimique
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PETIT, YVES. « Synthese d'hydroxy-2 esters enantiomeriquement purs a partir d'amino-2 acide : etude stereochimique de l'addition 1,4 d'organometalliques sur des systemes insatures-2,3 hydroxy-4 ». Paris 6, 1987. http://www.theses.fr/1987PA066578.
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Ghribi, Abdellaziz. « Utilisation des organocuivreux, associés ou non à un acide de lewis, en synthèse asymétrique et dans la préparation des beta-cétophosphonates ». Nancy 1, 1986. http://www.theses.fr/1986NAN10059.
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L'action des organocuprates associés à BF::(3) sur des acétals chiraux constitue une voie très originale de synthèse des alcools secondaires optiquement actifs. Les dianons des acides diethylphono 2 alcoiques réagissent avec les aldéhydes par réaction de wittig-horner et conduisent très stéréosélectivement aux acides alpha éthyléniques trisubstitués. L'action des organocuprates sur les chlorures d'acide diethylphosphono-2 alcanoïques, constitue une voie de synthèse très générale des beta cétiogisogibates alpha substitués
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Sun, Yun Chang, et 孫允昌. « A Study of Inhibiting Effects for Lithium Compounds on Alkali Aggregrate Reaction ». Thesis, 2008. http://ndltd.ncl.edu.tw/handle/50405078248604312951.
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碩士國立臺灣海洋大學
河海工程學系
96
In this study, addition of lithium compounds to restrain the alkali-silica-aggregate reaction (ASAR) of concrete. Various lithium compounds were added, and the expansion percentage, compressive strength, bending strength and tensile strength are examined to see the efficiency of the lithium compounds on retraining the ASAR. Results show that adding lithium compounds can restrain the ASAR and lower the expansion percentage. Increasing amounts of lithium compounds can decrease the effects of ASAR. For mechanical properties, the results depend on what kind of lithium compounds we use as well as what kind of the mechanical properties we are interested in. The results showed that adding adequate amount of lithium carbonate or lithium hydroxide can enhance the bending strengths. No significant trend can be found for the tensile strength. For compressive strength, as the amount of lithium carbonate or lithium hydroxide increased the value decreased.
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Chen, Te-kang, et 陳德剛. « The borone alkyl-based as an additive to electrolyte solution on LiFePO4 cathode material for lithium-ion batteries ». Thesis, 2008. http://ndltd.ncl.edu.tw/handle/18801767429332540311.
Texte intégralRésumé :
碩士國立臺南大學
材料科學系碩士班
96
LiFePO4 is one of the novel cathode materials for lithium ion batteries. It has various advantages including high power capability, excellent cycling performance and low cost, but LiFePO4 material shows poorly electrical conductivity and cycle fading quickly at high temperature. Herein, this report has investigated a boron alkyl-based compound as an electrolyte additive. These results show an obvious improvement of high temperature cycle performance for LiFePO4 cathode material duo to a special SEI film formed on electrode surface. Boron alkyl-based additive is one of the anion receptors. It is able to increase the dissociation of LiPF6 in electrolyte. Thus it decreases LiF content in the SEI film between LiFePO4 electrode surface and the electrolyte. That is why it improves the lithium ion transport and also cycle performance. According to our observations, the boron alkyl-based additive has the ability to improve the cycle fading of LiFePO4 at high temperature. Furthermore, the LiFePO4 electrode which cycled in the electrolyte without additive showed a significant increase in impendence by EIS analysis. Additionally, the SEM and FTIR reveal the evidences of surface morphology change and SEI formation, respectively.
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Volgmann, Kai, Vanessa Werth, Suliman Nakhal, Martin Lerch, Thomas Bredow et Paul Heitjans. « Solid-State NMR Study of Alkali Ion Dynamics in Layered Na2Ti3O7 and Li2Ti3O7 ». 2017. https://ul.qucosa.de/id/qucosa%3A31627.
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Pagot, G. « Electrode and Electrolyte Materials for the Development of High Voltage Lithium-ion Batteries and Secondary Batteries Based on Alkali and Alkaline-earth Ions ». Doctoral thesis, 2018. http://hdl.handle.net/11577/3356369.
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Markus, Reid Patrick. « An investigation of means of mitigating alkali-silica reaction in hardened concrete ». 2013. http://hdl.handle.net/2152/22350.
Texte intégralRésumé :
This research project, funded by the Federal Highway Administration (FHWA Project DTFH61-02-C-0097), focuses mainly on alkali-silica reaction (ASR) and techniques to mitigate the effects of alkali-silica reaction in hardened concrete. A large portion of this report discusses the construction and design of an outdoor exposure site built at the University of Texas at Austin where the goal was to cast field representative concrete elements with laboratory precision and expose them to real environmental conditions. The elements were monitored for expansion and deterioration. At discrete expansion levels a range of mitigation methods were implemented on the structures. After the concrete elements were treated, long-term monitoring was conducted to determine the best approach to provide effective suppression of alkali-silica reaction in the various element types.text
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« The Synthesis and Characterization of Ionic Liquids for Alkali-Metal Batteries and a Novel Electrolyte for Non-Humidified Fuel Cells ». Doctoral diss., 2014. http://hdl.handle.net/2286/R.I.27420.
Texte intégralRésumé :
abstract: This thesis focused on physicochemical and electrochemical projects directed towards two electrolyte types: 1) class of ionic liquids serving as electrolytes in the catholyte for alkali-metal ion conduction in batteries and 2) gel membrane for proton conduction in fuel cells; where overall aims were encouraged by the U.S. Department of Energy.
Large-scale, sodium-ion batteries are seen as global solutions to providing undisrupted electricity from sustainable, but power-fluctuating, energy production in the near future. Foreseen ideal advantages are lower cost without sacrifice of desired high-energy densities relative to present lithium-ion and lead-acid battery systems. Na/NiCl2 (ZEBRA) and Na/S battery chemistries, suffer from high operation temperature (>300ºC) and safety concerns following major fires consequent of fuel mixing after cell-separator rupturing. Initial interest was utilizing low-melting organic ionic liquid, [EMI+][AlCl4-], with well-known molten salt, NaAlCl4, to create a low-to-moderate operating temperature version of ZEBRA batteries; which have been subject of prior sodium battery research spanning decades. Isothermal conductivities of these electrolytes revealed a fundamental kinetic problem arisen from "alkali cation-trapping effect" yet relived by heat-ramping >140ºC.
Battery testing based on [EMI+][FeCl4-] with NaAlCl4 functioned exceptional (range 150-180ºC) at an impressive energy efficiency >96%. Newly prepared inorganic ionic liquid, [PBr4+][Al2Br7-]:NaAl2Br7, melted at 94ºC. NaAl2Br7 exhibited super-ionic conductivity 10-1.75 Scm-1 at 62ºC ensued by solid-state rotator phase transition. Also improved thermal stability when tested to 265ºC and less expensive chemical synthesis. [PBr4+][Al2Br7-] demonstrated remarkable, ionic decoupling in the liquid-state due to incomplete bromide-ion transfer depicted in NMR measurements.
Fuel cells are electrochemical devices generating electrical energy reacting hydrogen/oxygen gases producing water vapor. Principle advantage is high-energy efficiency of up to 70% in contrast to an internal combustion engine <40%. Nafion-based fuel cells are prone to carbon monoxide catalytic poisoning and polymer membrane degradation unless heavily hydrated under cell-pressurization. This novel "SiPOH" solid-electrolytic gel (originally liquid-state) operated in the fuel cell at 121oC yielding current and power densities high as 731mAcm-2 and 345mWcm-2, respectively. Enhanced proton conduction significantly increased H2 fuel efficiency to 89.7% utilizing only 3.1mlmin-1 under dry, unpressurized testing conditions. All these energy devices aforementioned evidently have future promise; therefore in early developmental stages.Dissertation/Thesis
Doctoral Dissertation Chemistry 2014
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Resendez, Yadhira Aracely. « Monitoring of an outdoor exposure site : evaluating different treatment methods for mitigation of alkali-silica reactivity in hardened concrete ». Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-3606.
Texte intégralRésumé :
This research project, funded by the Federal Highway Administration, entails the construction of an outdoor exposure site in order to evaluate various methods for mitigating alkali-silica reaction (ASR) in hardened concrete. The exposure site, built at the Concrete Durability Center at the University of Texas at Austin J.J. Pickle Research campus, included a series of bridge deck, column and slab elements. The specimens were cast in 2008, allowed to expand to predetermined expansion levels and then treated with various mitigation measures, after which the specimens were monitored for expansion, humidity, and deterioration.text
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HSIAO, FU-CHIN, et 蕭富今. « (1)The mechanism study of the reaction of (E)-3-Phenyl-1-[(phenylsulfonyl)imino]-2-propene with alkyl lithium (2)The Synthesis and Chemistry of 7-Substituted Bicyclo[4.1.0]hept-1(7)-enes ». Thesis, 2003. http://ndltd.ncl.edu.tw/handle/59654467214080950712.
Texte intégralRésumé :
碩士輔仁大學
化學系
91
Abstract (1) When (E)-3-phenyl-1-[(phenylsulfonyl)imino]-2-propene(1) was treated with 2 equivalent methyl lithium(MeLi),five compounds-2, 3, 4, 5, and 6 were isolated. The formation of products 3 and 6 were studied. Compound 2 was treated with 2 equivalent MeLi to produce dianion 25.Dianion 25 underwent intramolecular reaction and reacted with water and deprotonation to generate anion 26 follwed by ring opening and proton absorption to form compound 3. The formation of 6 is via carbanion exchange from methyl carbanion to phenyl carbanion. When compound 6 reacted with phenyl carbanion, the 1,4-addition adduct, carbanion was generated. Carbanion underwent intramolecular addition and proton absorption to provide compound 9 which was oxidized to form compound 6. (2) When 1,7,7-tribromo-bicyclo[4.1.0]heptane (36) was treated with 2.5 equivalent MeLi, generated intermediate 41 which was trapped with 1,3-diphenylisobenzofuran (DPIBF) to form compound 40..Intermediate 41 was proved by compound 45 react with side product MeBr. Treatment of the compound 36 with 2.5 equivalent n-BuLi gave product 47 which is formed by intermediate 48 ring opening. We also found that compound 34 underwent ene-reaction fastly to give a dimeric product 48. But product 48 was unstabled to ring opening and reacted Oxygen in the air to give product 47.
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Lin, Che-Tseng, et 林哲增. « 1. Multifunctional Co-poly(amic acid) containing Pyrenyl and Carboxylic Acid as a new Binder for Si-based Micro-Composite Anode of Lithium-Ion Battery2. Synthesis and Characterization of Polymers with Alkyl Main Chain Pendent Bipolar Unit as Host Applications in Electroluminescent Light-Emitting Diodes ». Thesis, 2017. http://ndltd.ncl.edu.tw/handle/522bhh.
Texte intégralRésumé :
博士國立臺灣大學
高分子科學與工程學研究所
105
There are two subjects in this study. One is the multifunctional co-poly(amic acid) (PAmA) containing pyrene and carboxylic acid side chains that is developed as a binder in the recycled kerf-loss Si-Ni-SiC composite for anode of lithium-ion batteries (LIB). The other is to develop the three polymeric hosts with bipolar abilities, the bipolar function are as pendant group in polystrene (PS) side chain and application in electroluminescent polymer light-emitting device (PLED). Chapter 1 was introduced principle, development, and review of active materials and binders in anode of LIB. In chapter 2, the multifunctional co-PAmA is as binder in Si-Ni Composite anode for LIB. The cycling performance of 300 cycles, electrochemical impedance spectroscopy (EIS) , change of the film morphology after cycling process of 100 cycles by SEM analysis and adhesion strength are discussed. The capacity retention performance comparsion that of sodium-alginate can be apparently enhanced. In a long-cycle test of 300 lithiation/delithiation cycles, 79% of capacity retention is achieved. Small anode thickness expansion of 43% is found in a 100 cycle test, reflecting that the use of the PAmA binder can create strong interconnection among the Si particles, conductive carbons and copper electrode. EIS experiment shows improvement to the higher electric conductivity of polymers containing pyrenyl groups, which also facilitate the dispersion of the conductive carbon additives during mixing. In chapter 3 was introduced principle, development and common materials of organic light-emitting diodes (OLEDs). Also some paper review about employed FIrpic and Ir(ppy)3 as phosphorescent dopant in PLED devices. In Chapter 4, PS-based polymers which are containing bipolar function as a pendant group on the side chain as a host for application in blue- and green-light, as well as thermal activated delayed fluorescence-based (TADF-based) PLED. The bipolar groups contain respectively ortho-substituted of CBZ/1,3,4-oxadiazole (OXD), CBZ/1,2,4-triazole (TAZ) or CBZ/benzimidazole (BZI) to afford the polymers with a bipolar function. CBZ has a high triplet energy (ET) gap and as hole-transporting moiety. On the other hand, the electron-deficient aromatic heterocycles of OXD, TAZ and BZI groups are as an electron-transporting moiety. The thermal stability, photophysical, electrochemical properties and electroluminescent performance in polymers have been discussed. All polymers show good thermal stability with high glass transition temperature (Tg) and decomposition temperature (Td) due to their rigid structure. By ortho-substituted between the bipolar groups can effectively interrupt conjugation length to obtain higher ET. In the electrochemical study, both the oxidation and reduction peak could be measured, indicating the polymers with hole- and electron-transporting abilities. In addition, we found that P-CBZ-OXD have suitable match of energy level than that of P-CBZ-TAZ and P-CBZ-BZI. Therefore, the best device performance of blue phosphorescent consisted of ITO/PEDOT: PSS/P-CBZ-OXD: 20% FIrpic/SPPO13/Mg/Ag that showed the maximum brightness of 1763 cd/m2 and the maximum current efficiency of 11.0 cd/A. For the best device performance of green phosphorescent consisted of ITO/PEDOT: PSS/P-CBZ-OXD: 15% Ir(ppy)3/SPPO13/Mg/Ag that showed the maximum brightness of 7215 cd/m2 and the maximum current efficiency of 23.7 cd/A. On the other hand, a green TADF emitter of 1,2,3,5-tetrakis (carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) was employed as guest, the devices consisted of ITO/PEDOT: PSS/P-CBZ-OXD: 15% 4CzIPN /SPPO13/Mg/Ag that showed the maximum brightness of 5592 cd/m2 and the maximum current efficiency of 27.3 cd/A.
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Das, Dipankar. « High Precision Optical Frequency Metrology ». Thesis, 2007. http://hdl.handle.net/2005/569.
Texte intégralRésumé :
Precise measurements of both absolute frequencies and small frequency differences of atomic energy levels have played an important role in the development of physics. For example, high precision measurements of absolute frequencies of the 2S½ → 2P ½ transition (D1 line) of alkali atoms form an important link in the measurement of the fine structure constant, α. Similarly, precise interferometric measurements of the local gravitational acceleration (g) rely on the knowledge of the absolute frequencies of the 2S½ → 2P 3/2 transition (D2line) in alkali atoms. Difference frequency measurements of hyperfine structure and isotope shifts of atomic energy levels provide valuable information about the structure of the nucleus, which in turn helps in fine tuning the atomic wave functions used in theoretical calculations.
The work reported in this thesis starts with the development and refinement of high precision measurement of absolute frequencies using a ring-cavity resonator. The measurement technique is relatively simple and cost-effective, but the accuracy is comparable to that achieved with the frequency comb technique (10¯11) when the accuracy is limited by the natural linewidth of the transition being measured. The technique combines the advantages of using tunable diode lasers to access atomic transitions with the fact that the absolute frequency of the D2 line in87Rb is known with an accuracy of 6 kHz. A frequency-stabilized diode laser locked to this line is used as a frequency reference, along with a ring-cavity resonator whose length is locked to the reference laser. For a given cavity length, an unknown laser locked to an atomic transition has a small frequency offset from the nearest cavity resonance. We use an acousto-optic modulator (AOM) to compensate for this frequency offset. The measured offset is combined with the cavity mode number to obtain a precise value for the frequency of The unknown laser. We have used this technique for absolute frequency measurements Of the D lines in133Cs and 6,7Li, and the 398.8nm line in Yb.
We have also developed a technique to measure the ‘difference frequency’ of atomic energy levels using a single diode laser and an AOM. In this technique, the laser is first locked to a given hyperfine transition. The laser frequency is then shifted using the AOM to another hyperfine transition and the AOM frequency is locked to this difference. Thus the AOM frequency directly gives a measurement of the hyperfine interval. Applying this AOM technique we have measured the hyperfine interval of the D1 lines of all alkali atoms with high precision.
We have further developed a technique of coheren-tcontrol spectroscopy (CCS) using co-propagating control and probe beam that is useful for highresolution spectroscopy. In this technique, the probe beam is locked to a transition and its absorption signal is monitored while the control beam is scanned through neighbouring transition. As the control comes into resonance with another transition, the probe absorption is reduced and the signal shows a Doppler free dip. This technique allows us to resolve transitions that are otherwise swamped by crossover resonances in conventional saturated absorption spectroscopy (SAS). We have applied this technique to measure hyperfine intervals in the D2 line of several alkali atoms.
Thus, we were able to do high-precision measurements of both absolute and difference frequency of atomic transitions. The precision of the absolute frequency measurement is finally limited by the accuracy of 6 kHz with which the reference frequency is known. The nearby two photon transition in Rb, i.e. the 5S1/2→5D3/2 transition at 778 nm, is known with an accuracy of 1 kHz. In future, we hope to improve the accuracy of our technique using this transition as the reference.
This thesis is organized as follows: In Chapter1,we give a brief introduction to our work.. We review the importance of frequency measurements and precision spectroscopy, followed by a comparison of the frequency comb and our ring cavity technique.
In Chapter2, we describe measurements of the absolute frequency of the D lines of 133Cs using the ring cavity. We give a detailed discussion of the technique, the Possible sources of errors, and ways to check for the errors. The measurement of the absolute frequency of the D lines of Cs allows a direct comparison to frequency comb measurements, and thus acts as a good check on our technique.
In Chapter 3, we describe the absolute frequency and isotope shift measurements in the 398.8 nm line in Yb. We probed this line by frequency doubling the output of a tunable Ti:Sapphire laser. We obtained< 60 kHz precision in our measurements and were able to resolve several discrepancies in previous measurements on this line.
In Chapter 4, we describe the measurement of hyperfine structure in the D1 lines of alkali atoms. We used conventional saturated-absorption spectroscopy in a vapor cell to probe different hyperfine transitions and then used our AOM technique to measure the hyperfine interval with high precision.
In Chapter 5 we discuss our measurements of hyperfine structure in the D2 lines of several alkali atoms. In the case of 23Na and 39K, the closely-spaced hyperfine transitions are not completely resolved in conventional saturatedabsorption spectroscopy due to the presence of cross over resonances. We have used coherent control spectroscopy to obtain crossover-free spectra and then measured the hyperfine intervals using an AOM. This technique was also used for high resolution spectroscopy in the D2 line of 133Cs. Finally, we describe our measurements of hyperfine structure in the D2 line of Rb using normal saturated absorption spectroscopy.
Chapter 6, describes the relative and absolute frequency measurements in the D lines of6,7 Li at 670nm. High-precision measurements in lithium are of special interest because theoretical calculations of atomic properties in this simple three electron system are fairly advanced. Lithium spectroscopy poses an experimental challenge and we describe our efforts in doing highresolution spectroscopy on this system.
Chapter 7 describes the hyperfine spectroscopy on the1P 1 state of 173Yb. Measurement of hyperfine structure in 173Yb has a problem because two of the hyperfine transitions overlap with the transition in 172Yb. In our earlier work (described in chapter 4), we had solved this problem by using multipeak fitting to the partially resolved spectrum. Here, we directly resolve the hyperfine transitions by using transverse laser cooling to selectively deflect the 173Yb isotope.
In Chapter 8 , we give a broad conclusion to the work reported in this thesis and suggest future avenues of research to continue the work commenced here.
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Shojaei, Heydar. « Die Iromycine und das Collinolacton : Synthese mikrobieller Naturstoffe aus Streptomyces sp ». Doctoral thesis, 2007. http://hdl.handle.net/11858/00-1735-0000-0006-AC9A-9.
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