To see the other types of publications on this topic, follow the link: Phosphate additives.
Dissertations / Theses on the topic 'Phosphate additives'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 42 dissertations / theses for your research on the topic 'Phosphate additives.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Montazerolghaem, Maryam. "Additives Increasing the Bone-Forming Potential around Calcium Phosphate Cements : Statin, Strontium and Silicon." Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-246289.
Full textAbstract:
More than one million people worldwide receive some kind of bone graft each year. Grafts are often needed following bone tumour removal or traumatic fractures to fill voids in the bone and to aid in the healing process. The most common method involves bone transplantation, in which bone tissue is taken from one site to fill the defect in another site. The procedure thus involves two surgeries, which leads to an increased risk of complications. New, synthetic graft materials that can be used to fill defects and minimise the complications associated with bone tissue harvesting are therefore necessary. The synthetic materials available today lack the inherent biological factors of bone that stimulate the bone regeneration process. Much of today’s research concerning synthetic bone graft materials aims to solve this issue and researchers have suggested several different strategies. The purpose of this thesis is to improve the performance of acidic calcium phosphate cements, which are materials used as synthetic bone grafts. By combining these cements with drugs or ion additives, local delivery could be achieved with the potential to stimulate bone formation. Two different combinations were attempted in this thesis: cement in combination with simvastatin, or cement in combination with strontium halide salts. Both simvastatin and strontium are known to positively affect bone formation. The efficacy of the cements with the additives was evaluated using different bone cell cultures. The results regarding simvastatin showed that the cement’s mechanical property was not affected upon drug loading, and that the drug was released by a diffusion-controlled mechanism. Moreover, results showed that simvastatin stimulated the bone-forming cells (osteoblasts) to produce more bone tissue, while it inhibited bone-degrading cells (osteoclasts) from degrading the cement. These findings suggest that simvastatin could aid in the bone regeneration process in the local area surrounding the cement. The main purpose of the study using strontium halide salts was to increase the cement’s X-ray contrast, which is a property used to monitor cement during injection. In addition, strontium is believed to positively affect bone cells. The X-ray contrast did increase after the addition of 10 wt% strontium bromide or strontium iodide, while the cell study results did not indicate any significant effects on the bone-forming cells. In the last section of this thesis, zebrafish were used as a model to evaluate bone formation upon treatment with degradation products from synthetic bone grafts. The zebrafish is a small organism with 70 % gene homology to humans; due to its transparency, fast development and ease of handling, it is an interesting model for high-throughput studies. Silicate, which is an ionic degradation product of many different bone substitute materials, was used as a proof-of-concept to visualise bone formation in these fish. The results showed an increased bone formation upon treatment with 0.625 μM silicate ions. The results suggest that this model could be used as a complement to bone cell culture studies in pre-clinical evaluations of the degradation products of bone substitute materials, thus helping researchers to design materials with degradation products that could stimulate bone formation.
2
Cantaert, Bram. "Controlled crystallisation of calcium phosphate and calcium carbonate via bio-inspired approaches : additives and confinement." Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/4683/.
Full textAbstract:
This thesis describes the investigation of the two bio-inspired approaches, confinement and additives, to manipulate the crystallization of calcium carbonate and calcium phosphate. The first experimental chapter deals with the investigation of calcium phosphate rods grown in confined environments in the absence and presence of polyaspartic acid. Although similar results were obtained in the absence and presence of the additive, growing calcium phosphate in confinement allowed formation of polycrystalline rods with an orientation comparable to bone. This demonstrated that confinement may play a more significant role in bone formation than previously anticipated. The second chapter deals with the effect of positively charged additives on the crystallisation of CaCO3. Although neglected before in literature, this chapter demonstrates that positively charged additives have a profound effect on the crystallisation of CaCO3 changing the morphology to films and fibers. This morphology change was linked to a phase separation process, forming hydrated amorphous droplets of calcium carbonate by a carbonate-polymer interaction, which had the tendency to coalesce and form films. Fiber formation was attributed to oriented attachment of anisotropic particles due to unequal distribution of charge. In the third chapter, based on bone, the mineralisation of collagen by CaCO3 was investigated. By formation of a highly hydrated liquid-like amorphous phase of CaCO3, it was possible to infiltrate the nanoscale gaps of collagen. After crystallisation, nanocrystals of calcite and vaterite were formed, 5 nm thick, but randomly oriented, demonstrating collagen templates the shape but not the orientation of the crystals. In a final chapter hollow rods of CaCO3 were formed by templating them inside membrane pores. The influence of time, pore size, additives and surface chemistry was investigated. Most hollow rods were formed at early timescales which filled up at later times. By changing the surface chemistry, the amount of hollow rods increased significantly in the 200 nm pores
3
Bhatt, Himesh A. "Synthesis and Characterization of Nanocrystalline Hydroxyapatite Powder; And the Effects of Oxide-Based Sintering Additives on Tricalcium Phosphate." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3567.
Full textAbstract:
Calcium phosphate (CP) materials have been used extensively for bone replacement and augmentation due to their similarity to the mineral component of bone. In addition to being non-toxic, they are biocompatible, not recognized as foreign materials in vivo, and most importantly, exhibit osteoconductive behavior, being able to help in bone formation during healing. CPs form an intimate physicochemical bond with the host tissue, termed osseointegration. However the main limitation of calcium phosphates is their inherent brittle nature and poor mechanical performance under complex stress states. As a result, these materials have been used clinically only in non-load-bearing applications, primarily as granules. The primary goal of this research was to enhance mechanical performance of CPs, tricalcium phosphate (TCP) and hydroxyapatite (HAp) to be precise, in an attempt to develop controlled strength-loss resorbable/ bioactive ceramic bone-grafts for hard tissue engineering. In my work on TCP, I selected and introduced small quantities of single and multi-oxide sintering additives in TCP, to study their influence on sintering behavior, densification, mechanical properties and biodegradation/ biomechanical properties in vitro. Through this research, I could improve mechanical performance of [Beta]-tricalcium phosphate ([beta]-TCP) and controlled its rate of biodegradation by introducing of certain additives. In my second work, I improved mechanical performance of HAp (Ca10(PO4)6(OH)2 by reducing particle-size of the powder through the synthesis of stoichiometric, nanocrystalline, single phase HAp powder in the range of 2-20 nm. Synthesis of powder was accomplished via a modified low temperature sol-gel technique using ethanol/ water as solvent.M.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering
4
Philippon, David. "Lubrification par la phase gazeuse : tribochimie des additifs phosphorés et boratés." Phd thesis, Ecole Centrale de Lyon, 2007. http://tel.archives-ouvertes.fr/tel-00280892.
Full textAbstract:
La formulation des lubrifiants utilisés dans l'automobile est complexe du fait du nombre important d'additifs mélangés aux huiles de base. Pour orienter le choix des formulateurs, il est non seulement nécessaire de connaître le mécanisme d'action de chaque additif mais aussi les interactions entre ces additifs. Pour mieux appréhender ces mécanismes, une démarche originale a été mise en place dans cette étude. Celle-ci consiste à simuler expérimentalement la lubrification en régime limite par la lubrification en phase gazeuse. Pour cela, des molécules de faible poids moléculaire modélisant les différents constituants d'un lubrifiant ont été introduites sous ultravide. Ce type d'expérience a pu être réalisé grâce au développement d'un nouveau Tribomètre à Environnement Contrôlé (TEC) connecté à un système d'analyse de surface. Cette technique permet de simplifier le système tribologique et d'étudier in situ les tribofilms formés en phase gazeuse par des analyses de surface (XPS/AES). Différentes molécules ont été étudiées : triméthylborate (TMB), triméthylphosphite (TMPi) et triméthylphosphate (TMPa) modélisant respectivement les additifs boratés et phosphorés des lubrifiants de transmission. Cette simulation expérimentale a pu être validée en comparant les résultats en phase gazeuse avec ceux obtenus en phase liquide. Des observations en microscopie optique et des analyses chimiques ont mis en évidence la formation de tribofilms. Les expériences réalisées en présence de TMB ont permis de confirmer les résultats de la littérature sur la formation d'un tribofilm non sacrificiel de borates de type « minéral ». Les expériences réalisées avec les molécules phosphorées ont permis de montrer la différence entre les phosphates et les phosphites, notamment la formation d'un composé de type phosphure de fer en présence de TMPi. Les analyses in situ sur les tribofilms obtenus en présence de TMPi ont permis de déterminer le mécanisme de formation du composé phosphure de fer. La réalisation de mélanges de gaz a permis également de mettre en avant les effets de synergie et d'antagonisme entre les additifs
5
Barnett, G. M. (Gordon M. ). "Feed additives and animal waste phosphorous reactions." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41322.
Full textAbstract:
Organic phosphorus (P$ sb{ rm o}$) in farm animal wastes must be mineralized to inorganic P for subsequent plant use. This study was conducted to determine if feed additives affect P$ sb{ rm o}$ mineralization, manure decomposition, and plant growth. Feed additives in aqueous systems affected the P mineralization of inositol hexaphosphate by phytase and of adenosine monophosphate by alkaline phosphatase. Pronounced effects were produced by bacitracin and both enzymes and by neomycin on phytase. Feed additives in dairy cattle (Bos taurus L.) manure produced effects on microbial activity as measured by gas production that differed from those produced on fecal phosphatase activity. Additives applied directly or with manure to Ste. Rosalie clay, Greensboro loam, or silica sand had no effect on barley (Hordeum vulgare L.) yield but did produce additive, rate, growth medium, and manure dependent effects on plant P concentration and soil phosphatase activity. Therefore, each feed additive must be independently evaluated to determine its effect on biological systems.
6
Ramalho, Eduardo Galv?o. "Obten??o de cer?micas ? base de tric?lcio fosfatos utilizando ?xido de mangan?s como aditivo." Universidade Federal do Rio Grande do Norte, 2006. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15544.
Full textAbstract:
Made available in DSpace on 2014-12-17T14:57:45Z (GMT). No. of bitstreams: 1
EduardoGR.pdf: 1635946 bytes, checksum: 593244cdda721eea4684ae85323cfee4 (MD5)
Previous issue date: 2006-06-28Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
The calcium phosphate ceramics have been very investigated as material for bone implants. The tricalcium phosphate (β-TCP) had a great potential for application in temporary implants like a resorbable bioceramic. This material presents a limitation in its sintering temperature due to occurrence of the allotropic transformation β → α at temperatures around 1200?C, not allowing the attainment of dense ceramic bodies. This transformation also causes cracks, what diminishes the mechanical strength, limiting its use to applications of low mechanical requests. This work studies the influence of the addition of manganese oxide in the sintering of β-TCP. Two processing routes were investigated. The first was the powder metallurgy conventional process. The test bodies (samples) were pressed and sintering at temperatures of 1200 and 1250?C. The second route was uniaxial hot pressing and its objective was to obtain samples with high relative density. The samples were physically characterized through density and porosity measurements. The thermal behavior was studied through dilatometric, thermal differential and thermogravimetric analysis. The mechanical properties were characterized by three point flexure test and Vickers microhardness measurements. The microstructure was analyzed by scanning electron microscopy. The addition of manganese oxide caused an improvement of the mechanical strength in relation to the material without additive and promoting the stabilization of β-TCP to greater temperatures
As cer?micas de fosfato de c?lcio t?m sido intensamente investigadas como materiais para implantes ?sseos. O fosfato tric?lcico (β-TCP) possui um grande potencial para aplica??o em implantes tempor?rios por ser uma biocer?mica absorv?vel. Entretanto, este tipo de material apresenta uma limita??o na sua temperatura de sinteriza??o devido ? ocorr?ncia da transforma??o alotr?pica β → α em torno de 1200?C. Isto impede a obten??o de corpos cer?micos densos e provoca trincas, diminuindo a resist?ncia do material e limitando a sua utiliza??o a aplica??es de baixa solicita??o mec?nica. A influ?ncia da adi??o de ?xido de mangan?s na sinteriza??o do β-TCP foi estudada neste trabalho. Duas rotas de processamento foram investigadas. A primeira utilizou o processo convencional de metalurgia do p?. Os corpos de prova foram prensados, sendo posteriormente sinterizados nas temperaturas de 1200 e 1250?C. O segundo m?todo de processamento utilizou a rota de prensagem uniaxial a quente, e tinha como objetivo obter corpos de prova com alta densidade relativa. As amostras foram caracterizadas fisicamente por meio de medidas de porosidade e densidade e termicamente por dilatometria e an?lise termogravim?trica e t?rmica diferencial. Os corpos sinterizados foram caracterizados mecanicamente por resist?ncia a flex?o em 3 pontos e microdureza Vickers, sendo tamb?m sua microestrutura analisada por microscopia eletr?nica de varredura. A adi??o do ?xido de mangan?s ocasionou uma melhoria da resist?ncia mec?nica em rela??o ao material sem aditivo, al?m de promover uma estabiliza??o do β-TCP em temperaturas mais elevadas
7
Shallcross, Laura. "Investigating the interactions of nanoscale calcium phosphates with polymer additives." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/16902/.
Full text
8
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.
Full textAbstract:
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
9
Armstrong, Kenneth Mark. "Catalytic synthesis of organophosphate plastics additives from white phosphorus." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2587.
Full textAbstract:
Triaryl phosphates were synthesized from white phosphorus and phenols in aerobic conditions and in the presence of iron catalysts and iodine. Full conversion to phosphates was achieved without the use of chlorine or chlorinated solvents, and the reactions do not produce acid waste. Triphenyl phosphate, tritolyl phosphate and tris(2,4-di-tert-butyl)phenyl phosphate were synthesized by this method with 100% conversion from P₄. Various iron(III) diketonates were used to catalyse the conversion. Mechanistic studies showed the reaction to proceed via the formation of phosphorus triiodide (PI₃), then diphenyl phosphoroiodidate (O=PI(OPh)₂) before the final formation of triphenyl phosphate (O=P(OPh)₃). The nucleophilic substitution of O=PI(OPh)₂ with phenol to form O=P(OPh)₃ was found to be the rate determining step. It was found that by modifying the reaction conditions the same catalytic systems could be used to synthesize triphenyl phosphite directly from P₄. Triphenyl phosphite was synthesized in selectivities of up to 60 %. The mechanism of these transformations was also elucidated. Independent syntheses of the intermediate in the reaction mechanism, O=P(OPh)₂I and its hydrolysis products diphenyl phosphate (O=P(OPh)₂OH) and tetraphenyl pyrophosphate ((O)P(OPh)₂-O-P(O)(OPh)₂) were developed from PI₃. The 2,4-di-tert-butyl phenol analogues of these compounds were also prepared. Bis-(2,4-di-tert-butylphenyl) phosphoroiodidate was then reacted with various alcohols to produce a series of mixed triorgano phosphates.
10
Bissessar, Damien. "Synthèse de nouveaux composés phosphorés : vers de nouveaux additifs pour polymères et des complexes cuivreux luminescents innovants." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAE029.
Full textAbstract:
Ce travail de thèse s’est inscrit dans le cadre d’un projet en relation étroite avec une industrie chimique. La problématique initiale concerne le développement de nouvelles molécules antioxydantes permettant de protéger les matériaux plastiques. Dans un premier temps, la stratégie envisagée s’appuie sur la synthèse de phosphines par hydrophosphination, réaction répondant aux principes de la chimie verte. La réaction est hautement régiosélective et la simplicité de la synthèse a permis d’obtenir de nombreuses nouvelles phosphines qui ont alors été testées pour leurs propriétés anti-oxydantes. Nous avons pu identifier plusieurs structures originales répondant au cahier des charges. Dans un second temps, nous avons étudié la faisabilité de développer de nouveaux additifs antioxydants secondaires à base de dérivés phénoliques, dont le cardanol qui est une molécule biosourcée. De nombreuses nouvelles molécules phosphorées ont été synthétisées, complètement caractérisées et évaluées pour leurs propriétés anti-oxydantes. Enfin, nous avons essayé de valoriser nos nouveaux composés pour d’autres applications. Les phosphines étant d’excellents ligands pour les métaux de transition, nous avons étudié la chimie de coordination avec le cuivre(I) en espérant former des complexes cuivreux luminescents. En effet, l’élaboration de diodes électroluminescentes stables reste un défi technologique malgré toutes les avancées actuelles. Dans ce contexte, de nombreux nouveaux complexes de type cubane ont été synthétisés et entièrement caractérisés. Ces complexes tétranucléaires sont des structures intéressantes, faciles à synthétiser, avec d’excellents rendements quantiques. Ces complexes présentent une stabilité élevée et des propriétés de luminescence qui en font de très bons candidats pour des dispositifs en optoélectroniqueThis thesis work was part of a project in collaboration with a chemical industry. The topic is the development of new antioxidant molecules to protect plastic materials. Initially, the strategy envisaged was based on the synthesis of phosphines by hydrophosphination, reaction in accordance with the green chemistry principles. The reaction is highly regioselective and the simplicity of the synthesis allowed us to obtain many new phosphines which were then tested for their antioxidant properties. We were able to identify several original structures that meet the requirements. In a second step, we studied the feasibility of developing new secondary antioxidant additives based on phenolic derivatives, including cardanol, which is a biosourced molecule. Many new phosphorus molecules have been synthesized, completely characterized and evaluated for their antioxidant properties. Finally, we tried to apply our new compounds for other applications. Since phosphines are excellent ligands for transition metals, we studied coordination chemistry with copper (I), hoping to form luminescent copper complexes. Indeed, the development of stable light-emitting diodes remains a technological challenge despite all the current advances. In this context, many new cubane-type complexes have been synthesized and fully characterized. These tetranuclear complexes are interesting structures, easy to synthesize, with excellent quantum yields. These complexes exhibit high stability and luminescence properties, which make them very good candidates for optoelectronic devices
11
Lantz, Josephine. "Mechanical Properties of Calcium Phosphate and Additively Manufactured Titanium Alloy for Composite Spinal Implants." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-296636.
Full textAbstract:
One of the major health problems in western societies is back pain, with a prevalence rate of 49%–80%. In many cases, the back pain is due to degenerated discs. The gold standard to treat a severely degenerated disc is spinal fusion, where the vertebral disc is replaced with a cage structure. However, fusion cages have a failure rate of 30%, hence the need for further development. The focus of this thesis is to evaluate the combination of calcium phosphate cement with titanium, for a spinal application. Mechanical tests in the form of tensile, compression and 4-point-bending were performed to study the different material properties. The obtained results was applied as material parameters for isotropic linear elastic material models, using ANSYS. This was then used to develop a cage design through topology optimisation which was further evaluated by using Finite Element Analysis. From the tensile testing of the titanium, isotropic behaviour was found. It was also found that a longer mixing time of the cement resulted in poorer mechanical properties of the calcium phosphate, however, no conclusive results were obtained from the 4-point-bending tests. The final cage geometry filled with calcium phosphate was tested under compression to see whether the cage could protect the calcium phosphate or not. MicroCT after the test confirmed that no larger cracks developed during the testing, suggesting that the cage is strong enough to protect the calcium phosphate from mechanical failure.
12
Bocqué, Maëva. "Élaboration de plastifiants ignifugeants à base de dérivés lipidiques pour formulations PVC." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10253.
Full textAbstract:
E PVC est l'un des polymères les plus employés dans les matériaux actuels et l'adjonction de plastifiants permet de modifier ses propriétés (température de transition vitreuse, module…) permettant ainsi l'utilisation de ce polymères dans des applications où de la souplesse est requise (textiles enduits, par exemple). Actuellement, les phtalates sont les plastifiants les plus utilisés même s'ils sont de plus en plus décriés du fait de leur toxicité. Le développement de nouveaux agents plastifiants est un domaine de recherches intenses et les matières premières bio-sourcées s'avèrent être une alternative intéressante aux plastifiants pétro-sourcés. Le travail de cette thèse se propose d'investiguer le développement de plastifiants du PVC bio-sourcés de type lipidique possédant de surcroit des propriétés ignifugeantes évitant ainsi l'ajout d'additifs supplémentaires dans les formulations de PVC devant résister au feu. Dans un premier temps, l'oléate, le linoléate de méthyle et le diacide (D18 : 1) ont été fonctionnalisés par modification chimique de leurs groupements ester et/ou de leurs insaturations pour mener à des dérivés lipidiques phosphorés. Cinq candidats plastifiants bio-sourcés ont ainsi pu être synthétisés et le scale up de la synthèse de l'un des candidats à l'échelle du kilogramme a pu être réalisé dans le cadre de cette thèse. Dans un deuxième temps, des tests de plastification du PVC avec divers candidats ont été réalisés en collaboration avec la société Serge FERRARI. L'étude des propriétés thermiques, mécaniques et thermomécaniques des films de PVC plastifiés obtenus, comparativement au plastifiant phtalate DINP et au plastifiant bio-sourcé commercial RADIA 7295, a permis d'éliminer différents candidats pour n'en finalement retenir que deux. Des profils de dégradation thermique satisfaisants, des basses valeurs de Tg, des allongements à la rupture importants (320 et 365 % respectivement) et proches de ceux obtenus avec le DINP, ont confirmé l'efficacité plastifiante de ces deux composés phosphorés bio-sourcés. Les tests au feu LOI et au cône calorimètre ont également prouvé le caractère ignifugeant de ces deux composés qui conduisent à des résultats du même ordre de grandeur que ceux atteints avec le plastifiant phosphonate commercial de référence S141Poly(vinyl chloride) is one of the most manufactured and consumed thermoplastics in the world. The addition of plasticizers allows modifying its properties (glass transition temperature, modulus…) and then to use this polymer for applications where flexibility is needed (coated textiles, for instance). Nowadays, phthalates are the main candidates for PVC even if they have been more and more controversed due to their possible toxicity. To substitute these petro-based plasticizers, researches are focused on alternative plasticizers based on bio-based raw materials. This PhD work proposes to investigate the development of new bio-based plasticizers for PVC, from lipidic derivatives, and having simultaneously flame retardant properties, avoiding the addition of any other additives in PVC during compounding. In the first part, methyl oleate, methyl linoleate and diacid D18 : 1 have been functionalized by modification of their ester groups and/or their doubles bonds to give phosphorylated lipidic derivatives. Thus, five bio-based plasticizers have been synthesized and the synthesis of one candidate on the scale of the kilogram has been successfully performed during this PhD work. Secondly, the plasticizing efficiency of several candidates with PVC has been evaluated in collaboration an industrial company. Thermal, mechanical and thermomechanical properties of the obtained soft PVC films were studied, in comparison with those obtained with the phthalate plasticizer DINP and the commercial bio-based plasticizer RADIA 7295. These analyses allowed the disposal of some of the bio-based plasticizers to finally keep only two candidates. Satisfying thermal degradation profiles, low Tg, and important elongation at break values (320 % and 365 % respectively) close to those obtained with DINP, confirmed the plasticizing efficiency of these two bio-based phosphorylated plasticizers. Fire tests like the LOI test and the cone calorimeter also proved the flame retardant properties of these two candidates, leading to similar results than the ones reached with the phosphonate plasticizer S141
13
Njiwa, Paule. "Comparaison du comportement tribologique des molécules de thiophosphates et de phosphates de zinc en tant qu'additifs anti-usure." Phd thesis, Ecole Centrale de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00750886.
Full textAbstract:
Grâce à ses propriétés d'antioxydant, d'anti-usure et éventuellement d'extrême pression le dithiophosphate de zinc (ZDDP) fait partie des additifs les plus utilisés dans les lubrifiants pour moteurs thermiques. De nos jours, dans un souci de respect de l'environnement, de nouveaux lubrifiants possédant de bonnes performances en lubrification (frottement faible et usure limitée) sont développés en prenant compte des limitations d'utilisations actuelles du ZDDP. L'idée étant de réduire dans ceux-ci les teneurs en phosphore et soufre (Normes euros VI), éléments essentiels du ZDDP qui endommagent les pots catalytiques. L'objectif de cette thèse est l'étude du comportement tribologique du phosphate de zinc di alkyl (ZP) en comparaison avec le ZDDP. La méthodologie expérimentale étudiée pour comprendre le mécanisme d'action de ces additifs, associe des essais de frottement à descaractérisations physico-chimiques des surfaces frottantes après essais.Cette comparaison a été effectuée en fonction de la température (25°C et 100°C), la vitesse de glissement (25, 50 et 100 mm/s) et la concentration en additif (200 et 600 ppm dephosphore). Les meilleures actions anti-usure sont obtenues avec le ZDDP pour une température de 100°C et une vitesse de glissement de 100 mm/s et le ZP pour une température de 25°C et une vitesse de glissement de 25 mm/s. Les analyses de surface XPS, AES, XANES et MET-EDX ont permis de mettre en évidence la présence d'un film protecteur constitué principalement de phosphate de zinc, ceci pour les deux additifs.Une synergie de comportement tribologique a été mise en évidence avec un lubrifiantconstitué de ZP (usure faible) et d'oléate d'urée (frottement faible). Des essais complémentaires sur un tribomètre dynamique ont permis d'étudier le niveau de frottement du tribofilm formé à partir du ZDDP. Le caractère visqueux du tribofilm de ZDDP a été mis en évidence.
14
Charbonnier, Baptiste. "Développement de procédés de mise en forme et de caractérisation pour l’élaboration de biocéramiques en apatites phosphocalciques carbonatées." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEM031/document.
Full textAbstract:
Les changements sociétaux tels que la personnalisation de la médecine, ainsi que la volonté de mieux comprendre la biologie de l’os modifie notre approche de fabrication des biomatériaux. Ces derniers se doivent ainsi d’être sur-mesure, c’est-à-dire capables de répondre à une problématique particulière. Ceci implique plus précisément dans le cas qui nous intéresse, à savoir l’os, la maîtrise de leur architecture et de leur comportement en milieu biologique (e.g., biodégradabilité).Malgré leurs atouts incontestables pour ce domaine, les biocéramiques en hydroxyapatite (HA) restent cantonnées à des usages modestes (e.g., comblement de petits défauts) ; en cause, des propriétés de biodégradation, d’ostéoconduction ou encore d’ostéoinduction souvent inadaptées aux problématiques contemporaines. Pour pallier ces limitations, nous avons entrepris deux voies de modulation des propriétés biologiques de l’HA, une voie « chimique », basée sur l’incorporation d’ions carbonate dans la structure apatitique, et une voie « procédé », reposant sur le potentiel de la fabrication additive.Des poudres d’hydroxyapatites phosphocalciques carbonatées (CHA) ont été préparées. Les ions carbonate pouvant occuper les sites hydroxyle et phosphate de l’HA, une méthode de quantification sélective du taux de substitution sur chacun de ces sites a été mise au point. Cette méthode spectroscopique novatrice ouvre de nombreuses opportunités d’études appliquées et fondamentales des CHA, abordées dans ce manuscrit, et constitue également un outil qui pourrait se révéler précieux dans l’optique de mise sur le marché de dispositifs médicaux en CHA (e.g., norme ISO).Basé sur une technologie de fabrication additive, un procédé de fabrication de biocéramiques d’architecture complexe, reproductible, flexible, fiable, de haute précision ( 5 µm) et peu coûteux, a été développé et optimisé. Cet outil de fabrication a été mis en œuvre pour répondre à des questions biologiques à finalité fondamentale et thérapeutiqueThe current approach to produce biomaterials tends to evolve due to societal change such as the development of personalized medicine or the eagerness to better understand bone biology. Hence, biomaterials, which specifications depends of their intended applications, have to be custom made. For bone tissue engineering, this implies to control the scaffold architecture and behaviour in a biological environment (e.g., biodegradability).Despite their indisputable qualities, the use of hydroxyapatite (HA) bioceramics tend to be limited to basic applications (e.g. filling small defects) because of biodegradation, osteoconduction, or osteoinduction properties that do not match the actual needs. To exceed these limitations, we explored two modifications paths to tune HA biologic properties: a “chemical” approach based on incorporation of carbonate ions into apatitic structure, and a “process” approach, built around additive manufacturing singular potential.Carbonated phosphocalcic hydroxyapatites (CHA) powders were prepared. As carbonate ions may occupy HA hydroxyl and phosphate sites, a selective method to quantify their ratio in each site by IR spectroscopy has been developed. This innovative spectroscopic method opens numerous opportunities for applied and fundamental studies of CHA, but could also be considered as a precious standard for a future release of CHA medical devices (e.g. ISO norm).A cheap, flexible, robust and reliable manufacturing process based on an additive manufacturing technology has been developed and optimized, leading to the production of bioceramics with complex architectural features (accuracy 5 µm).This manufacturing process has been implemented in biological studies with fundamental and therapeutic purposes
15
Lagrange, Jean-Pierre. "Contribution à l'étude du dopage bore, azote et phosphore dans le diamant." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10210.
Full textAbstract:
Le diamant est un semi-conducteur a large bande interdite (5. 4 ev) tres prometteur en electronique a haute temperature et de forte puissance. Cependant, son utilisation est limitee par l'absence d'un dopage de type n. Nous avons etudie dans cette these le dopage au bore du diamant (type p), et l'incorporation de phosphore et d'azote dans le diamant par implantation ionique. Nous avons elabore des couches minces de diamant par depot chimique en phase vapeur assiste par plasma micro-onde. Nous avons utilise dans notre etude diverses techniques de caracterisation : spectroscopie de diffusion raman, resonance paramagnetique electronique, resistivite en fonction de la temperature (de 100k a 1000k), effet hall, courants thermo-stimules, thermoluminescence. Les resultats obtenus montrent que le dopage au bore est aujourd'hui bien maitrise. Des mesures electriques sur une large gamme de concentration (de 5 10#1#6 a 8 10#2#0 b. Cm#-#3) montrent trois regimes de conduction differents : conduction par saut par plus proche voisin, conduction par la bande de valence, conduction metallique. Nous avons montre pour la premiere fois une saturation de la conductivite et une energie d'activation a haute temperature e#a/2 typique d'un taux de defauts compensateurs inferieur a 10%. Nous avons montre que l'implantation est la methode la plus efficace pour incorporer de l'azote en site substitutionnel dans le diamant. Neanmoins, l'incorporation d'azote semble induire indirectement des defauts paramagnetiques dans le diamant. Nous avons aussi montre que l'incorporation de phosphore en site substitutionnel est possible. Nous avons defini un seuil d'amorphisation compris entre 3 et 4 10#1#4 p. Cm#-#2. Toutefois, un nouveau defaut paramagnetique qui semble etre induit par le phosphore apparait apres recuit. La conduction est encore dominee par les defauts crees par l'implantation ionique. Ces resultats sont tres prometteurs pour des applications futures en microelectronique.
16
Gariboldi, Maria Isabella. "Effect of calcium phosphate ceramic architectural features on the self-assembly of microvessels in vitro." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/283005.
Full textAbstract:
One of the greatest obstacles to clinical translation of bone tissue engineering is the inability to effectively and efficiently vascularise scaffolds. This limits the size of defects that can be repaired, as blood perfusion is necessary to provide nutrient and waste exchange to tissue at the core of scaffolds. The goal of this work was to systematically explore whether architecture, at a scale of hundreds of microns, can be used to direct the growth of microvessels into the core of scaffolds. A pipeline was developed for the production of hydroxyapatite surfaces with controlled architecture. Three batches of hydroxyapatite were used with two different particle morphologies and size distributions. On sintering, one batch remained phase pure and the other two batches were biphasic mixtures of α-tricalcium phosphate (α-TCP) and hydroxyapatite. Sample production methods based on slip casting of a hydroxyapatite-gelatin slurry were explored. The most successful of these involved the use of curable silicone to produce moulds of high-resolution, three dimensional (3D) printed parts with the desired design. Parts were dried and sintered to produce patterned surfaces with higher resolution than obtainable through conventional 3D printing techniques. Given the difficulties associated with the structural reproducibility of concave pores architectures in 3D reported in the literature, in this work, a 2.5D model has been developed that varies architectural parameters in a controlled manner. Six contrasting architectures consisting of semi-circular ridges and grooves were produced. Grooves and ridges were designed to have widths of 330 μm and 660 μm, with periodicities, respectively, of 1240 μm and 630 μm. Groove depth was varied between 150 μm and 585 μm. Co-cultures of endothelial cells and osteoblasts were optimised and used to grow microcapillary-like structures (referred to as "microvessels") on substrates. Literature shows that these precursors to microcapillaries contain lumina and can produce functional vasculature, demonstrating their clinical promise. The effects of the composition and surface texture of grooved samples on microvessel formation were studied. It was found that surface microtopography and phase purity (α-TCP content) did not affect microvessel formation. However, hydroxyapatite architecture was found to significantly affect microvessel location and orientation. Microvessels were found to form predominantly in grooves or between convexities. Two metrics - the degree of alignment (DOA) and the degree of containment (DOC) - were developed to measure the alignment of endothelial cell structures and their localisation in grooves. For all patterned samples, the CD31 (an endothelial cell marker) signal was at least 2.5 times higher along grooves versus perpendicular to grooves. In addition, the average signal was at least two times higher within grooves than outside grooves for all samples. Small deep grooves had the highest DOA and DOC (6.13 and 4.05 respectively), and individual, highly aligned microvessels were formed. An image analysis method that compares sample X-ray microtomography sections to original designs to quantify architectural distortion was developed. This method will serve as a useful tool for improvements to architectural control for future studies. This body of work shows the crucial influence of architecture on microvessel self-assembly at the hundreds of micron scale. It also highlights that microvessel formation has a relatively low sensitivity to phase composition and microtopography. These findings have important implications for the design of porous scaffolds and the refinement of fabrication technologies. While important results were shown for six preliminary architectures, this work represents a toolkit that can be applied to screen any 2.5D architecture for its angiogenic potential. This work has laid the foundations that will allow elucidating the precise correspondence between architecture and microvessel organisation, ultimately enabling the "engineering" of microvasculature by tuning local scaffold design to achieve desirable microvessel properties.
17
Reynolds, Lindsey. "Sensory Evaluations of USDA Select Strip Loin Steaks Enhanced with Sodium and Potassium Phosphates and USDA Choice Strip Loin Steaks for Comparable Palatability Factors." TopSCHOLAR®, 2011. http://digitalcommons.wku.edu/theses/1051.
Full textAbstract:
The cyclic nature of the beef industry is dependent on the supply and demand transaction initiated by consumers’ acceptability of quality meat products. When purchasing beef at the grocery store, consumers are dependent on USDA grades and visual appraisal; consumers expect consistency in products. Upon this appraisal, quality is determined by the color, marbling content, and texture of a particular retail cut, as well as cooked characteristics of tenderness, flavor, and juiciness. Variability in meat tenderness is a major quality defect of beef (Morgan et al., 1991b; Smith et al., 1992). A common practice used by beef processors to extend the shelf life and improve tenderness of beef products is “enhancing”. Even though enhancing products is effective for water and color retention and improved tenderness, these additives can negatively impact flavor by giving a bitter, salty or metallic taste. This experiment was conducted to determine the effect of enhancement on the eating quality of USDA Select strip loin steaks. After a training session, six students in the agriculture department at Western Kentucky University were selected to serve on a sensory panel. The panel members evaluated tenderness, juiciness, flavor, off-flavor, overall acceptability, and saltiness. The USDA Select strip loin steaks were enhanced with a 12% solution of sodium and potassium phosphate and USDA Choice strip loin steaks were non-enhanced. Results indicated the enhanced product was inferior for all palatability measures (P<.05). Enhanced USDA Select strip loin steaks were rated as being lower for tenderness, juiciness, flavor, overall acceptability, and more salty. Also, the enhanced strip loin steaks received significantly higher evaluations for off-flavor (P<.01). These data suggested that a 12% solution of sodium and potassium phosphates administered to USDA Select strip loin steaks lowered consumer satisfaction.
18
Satpathi, Hirak. "Novel phosphorus containing poly(arylene ethers) as flame retardant additives and as reactant in organic synthesis." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-176136.
Full textAbstract:
Due to their outstanding properties, poly(arylene ethers) are useful as toughness modifiers in epoxy resins (EP). Furthermore, these polymers show rather low intrinsic fire risks. According to recent research it has been incorporated that poly(arylene ether phosphine oxides) [PAEPO’s] can further improve the fire behavior. Increasing phosphorous content of the PAEPO can influence the fire behavior too. Fire retardants containing phosphorus – regardless of whether an additive or reactive approach is used – show different mechanisms in the condensed and gas phase. In the present study PSU Control (BPA based polysulfone) with four different PAEPO’s and their corresponding blends with an EP were investigated.
All poly(arylene ether phosphine oxides) were synthesized by nucleophilic aromatic polycondensation. The polymers obtained covered a wide range of weight average molar masses (6,000 – 150,000 g/mol) as determined by size exclusion chromatography with multi-angle light scattering detection (MALLS). FTIR, NMR spectroscopy and MALDI-TOF revealed formation of the desired polymer structure of the linear poly(arylene ethers). All polymers were easily soluble in common organic solvents, thus enabling processing from solution.The pyrolysis and the fire retardancy mechanisms of the polymers and blends with epoxy resin (EP) were tackled by means of a comprehensive thermal analysis (thermogravimetry (TG), TG-evolved gas analysis) and fire tests [PCFC, limiting oxygen index (LOI), UL-94, cone calorimeter].
The Mitsunobu reaction of Dimethyl-5-hydroxyisophthalate and a long chain semifluorinated alcohol requires triphenyl phosphine as a reactant. Identical, in some case higher yield was obtained in the usual conditions, with triphenyl phosphine and with trivalent phosphorus containing polymers, which was prepared in solvent free bulk (melt) polymerization technique from trivalent phosphorus monomer and a silylated diphenol in presence of CsF. Purification and the recovery of the final product which is always a big challenge in case of Mitsunobu reaction, was far more easier using polymer compared to triphenyl phosphine. During polymerization there was a possibility to have polymer having repeating unit containing both trivalent phosphorus and phosphine oxide. The trivalent phosphorus content of the polymer can be varied using different molar concentration of CsF.
19
Gagosz, Fabien. "Étude de nouvelles réactions radicalaires : Application à la synthèse d'alcaloi͏̈des et de composés phosporés et fluorés." Palaiseau, Ecole polytechnique, 2002. http://www.theses.fr/2002EPXX0020.
Full text
20
G?is, Gelsoneide da Silva. "S?ntese, aplica??o e avalia??o do efeito do teor de f?sforo da celulose fosfatada em argamassa de alvenaria com aditivo comercial a base de hidroxi-etil-metil celulose (HEMC)." Universidade Federal do Rio Grande do Norte, 2013. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12777.
Full textAbstract:
Made available in DSpace on 2014-12-17T14:07:06Z (GMT). No. of bitstreams: 1
GelsoneideSG_DISSERT.pdf: 1818458 bytes, checksum: 7c978a688725815697ae8981fa5f2d16 (MD5)
Previous issue date: 2013-02-18Generally, cellulose ethers improves mortar properties such as water retention, workability and setting time, along with adherence to the substrate. However, a major disadvantage of the addition of cellulose ethers in mortars is the delay in hydration of the cement. In this paper a cellulose phosphate (Cp) was synthesized water soluble and has been evaluated the effect of their incorporation into mortar based on Portland cement. Cellulose phosphate obtained was characterized by spectrophotometry Fourier transform infrared (FTIR), X-ray diffraction (XRD), elemental analysis and scanning electron microscopy (SEM). Mortar compositions were formulated with varying phosphorus content in cellulose and cellulose phosphate concentrations, when used in partial or total replacement of the commercial additive based hydroxyethyl methyl cellulose (HEMC). The mortars formulated with additives were prepared and characterized by: testing in the fresh state (consistency index, water retention, bulk density and air content incorporated) and in the hardened state (absorption by capillarity, density, flexural and compression strength). In mixtures the proportion of sand:cement of 1:5 (v / v) and factor a / c = 1.31 and water were held constant. Overall, the results showed that the celluloses phosphates employed in mortars added acted significantly when partially substituting the commercial additive. With regard to consistency index, water retention and bulk density in the fresh state and absorption by capillarity and bulk density apparent in the hardened state, showed no appreciable differences as compared to the commercial additive. The incorporated air content in the fresh state reduced markedly, but did not affect other properties. The mortars with cellulose phosphate, partially replacing the commercial additive showed an improvement of the properties of flexural strength and compressive strength
Geralmente, ?teres de celulose melhoram as propriedades de argamassas, tais como reten??o de ?gua, trabalhabilidade e o tempo de pega, juntamente com a ades?o ao substrato. No entanto, uma das principais desvantagens da adi??o dos ?teres de celulose nas argamassas ? o retardo na hidrata??o do cimento. Neste trabalho foi sintetizada uma celulose fosfatada (Cp) sol?vel em ?gua e foi avaliado o efeito da sua incorpora??o em argamassa ? base de cimento Portland. A celulose fosfatada obtida foi caracterizada por espectrofotometria de infravermelho por transformada de Fourier (FTIR), difra??o de raios-X (DRX), an?lise elementar, an?lise termogravim?trica (TGA) e microscopia eletr?nica de varredura (MEV). Argamassas com composi??es variando o teor de f?sforo relativamente ? celulose e as concentra??es de celulose fosfatada, quando utilizada em substitui??o parcial ou total do aditivo comercial a base de hidroxietil metil celulose (HEMC). As argamassas formuladas com os aditivos foram preparadas e caracterizadas por: ensaios no estado fresco (?ndice de consist?ncia, reten??o de ?gua, densidade e teor de ar incorporado) e no estado endurecido (absor??o por capilaridade, densidade, resist?ncia ? flex?o e compress?o). Nas misturas a propor??o de areia, cimento e ?gua foram mantidos constantes. De um modo geral, os resultados mostraram que as celuloses fosfatadas empregadas nas argamassas atuaram significativamente quando adicionados parcialmente em substitui??o ao aditivo comercial. No que se refere ao ?ndice de consist?ncia, reten??o de ?gua e densidade de massa no estado fresco e absor??o por capilaridade e densidade de massa aparente no estado endurecido, n?o demonstraram diferen?as apreci?veis comparativamente ao aditivo comercial. O teor de ar incorporado no estado fresco reduziu de forma marcante, mas n?o influenciou as demais propriedades. As argamassas com celulose fosfatada, substituindo parcialmente o aditivo comercial, mostraram uma melhora das propriedades de resist?ncia ? flex?o e de resist?ncia ? compress?o.
21
Salomão, André Luís de Sá. "Ocorrência e ecotoxicidade de desreguladores endócrinos químicos em ambientes aquáticos e em sistemas de tratamento de esgoto." Universidade do Estado do Rio de Janeiro, 2014. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=7573.
Full textAbstract:
Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de JaneiroA aplicabilidade de um método selecionado de medição indireta de vitelogenina (Vtg) em plasma sanguíneo de peixe, baseado na quantificação de fosfato álcali-lábil (alkali-labile phosphate-ALP) para acessar estrogenicidade em água, foi investigada na presente tese. O método foi originalmente desenvolvido para a espécie de peixe Carassius carassius (Carpa cruciana) e aplicado pela primeira vez na espécie Oreochromis niloticus (Tilápia do Nilo) no presente estudo. Com o objetivo de acessar a sensibilidade do método, em uma primeira etapa da investigação foram realizados estudos laboratoriais com soluções estoques de 17-ethinylestradiol (EE2), 17-estradiol (E2), e estrona (E1). Os efeitos destes hormônios foram investigados com base tanto na concentração quanto na carga, utilizando-se para tanto, unidades experimentais com volumes distintos (2 L e 130 L). Após a validação do método de ALP, a estrogenicidade foi avaliada nas seguintes águas contaminadas: (i) afluente e efluente de uma grande estação de tratamento de esgotos convencional (ETE) e de uma estação descentralizada de tratamento de esgoto de pequeno porte (Ecossistema Engenheirado-DEE); (ii) água superficial (SW) e água subterrânea (GW) coletadas em uma área de brejo contaminada com gasolina; (iii) água de uma lagoa urbana (LRF) da cidade do Rio de Janeiro, com alta densidade populacional e descarte clandestino de esgoto. Na segunda etapa foram analisados em microalgas os efeitos (outros que não disrupção endócrina) causados pelos hormônios EE2, E2 e E1. Os hormônios foram testados individualmente e em misturas, em culturas individuais e combinada (S+) das espécies de microalgas unicelulares P. subcapitata e D. subspicatus. Com base nos níveis de ALP para a espécie de peixe e no EC50 para as espécies de algas, os resultados mostraram que o EE2 e o E2 causaram disrupção endócrina superior e foram mais tóxicos do que o E1 para peixes e microalgas respectivamente. Quando em misturas (E+) de concentrações equivalentes (EE2:E2:E1), os estrogênios resultaram em efeito aditivo para as espécies O. niloticus e P. subcapitata, e menos que aditivo para D. subspicatus e cultivo misto de algas (S+). Culturas contendo ambas as espécies de algas (S+) por um longo período de exposição (96 h) resultaram na atenuação dos efeitos tóxicos causados pela exposição, tanto individual (EE2, E2 ou E1), quanto na mistura (E+) dos estrogênios, medidos em termos de EC50 (T0h 0,07; 0,09; 0,18; e 0,06 g mL-1; e T96h 1,29; 1,87; 5,58; e 4,61 g mL-1, respectivamente). O DEE apresentou uma maior eficiência na remoção dos disrutores endócrinos do que a ETE convencional. Foi detectada estrogenicidade em amostras da LRF, e de água SW e GW em área brejosa contaminada com gasolina. Os resultados dos ensaios sugerem que as interações (efeitos aditivos ou menos que aditivo) causadas pela mistura dos estrogênios assim como, as interações entre as espécies de algas afetaram o resultado final dos ensaios ecotoxicológicos. Um fator raramente abordado em estudos ecotoxicológicos que foi destacado na presente tese refere-se à importância de considerar não somente a concentração e a dosagem, mas também a carga aplicada e o volume das unidades experimentais. Devido à boa sensibilidade do O. niloticus quando exposto às concentrações relativamente baixas dos estrogênios, a combinação do método de ALP com os biomarcadores auxiliares (particularmente MN) pode ser um protocolo adequado para a detecção de estogenicidade e genotoxicidade respectivamente em diferentes ambiente aquáticos contaminados, como parte de um programa de monitoramento ambiental
The applicability of one selected method for indirect measurement of vitellogenin (Vtg) in fish plasma based on the quantification of alkali-labile phosphates (ALP method) to assess estrogenicity in water was investigated. The ALP method applied in this investigation was originally developed with Carassius carassius (Crucian carps). This thesis describes the first attempt of using this method with Oreochromis niloticus (Nile tilapia). In a first part of the investigation, laboratory studies were conducted with water spiked with 17-ethinylestradiol (EE2), 17-estradiol (E2), and estrone (E1) in order to assess the method sensitivity. The effects of these estrogens were investigated on the basis of both load and concentration, using experimental units with two different volumes (2 L and 130 L). After validation of the method, the estrogenicity of the following contaminated waters was assessed: (i) affluent and effluent of one large conventional municipal wastewater treatment plant (WWTP) and one small decentralized wastewater treatment plant (Decentralized Engineered Ecosystem-DEE); (ii) surface water (SW) and groundwater (GW) obtained from a gasoline-contaminated marshland; (iii) samples from a urban lagoon (LRF) located in Rio de Janeiro city with high density population and clandestine sewage discharge. An additional goal of the thesis was to assess the effect (other than endocrine disruption) caused by EE2, E2 and E1 to microalgae. Assays with single and mixed estrogens and single and combined cultures (S+) of the green microalgae P. subcapitata and D. subspicatus were carried out. The results have shown that EE2 and E2 were more estrogenic and toxic than E1 to the fishes and to the microalgae respectively. Mixed solutions of estrogens (E+) in equal proportions (EE2:E2:E1) resulted in additive effect on O. niloticus and P. subcapitata and less-than-additive effect on D. subspicatus and S+ measured as ALP (for fish) and EC50 (for microalgae). Combined cultivation of both algae species and longer exposure time (96 h) resulted in attenuation of the toxic effects caused by single (EE2, E2 or E1) and mixed (E+) estrogens according to EC50 (T0h 0.07, 0.09, 0.18, and 0.06 g mL-1; and T96h 1.29, 1.87, 5.58, and 4.61 g mL-1, respectively). The decentralized engineered ecosystem was more efficient than the conventional WWTP regarding estrogenicity removal from the final effluent. Estrogenicity was detected in some samples of the LRF and the SW and GW of the gasoline-contaminated marshland. Therefore, the investigations suggested that interactions (additive and less-than additive effect) take place when different estrogens are present in the water environment and interactions also occur between algae species, which affect the final toxicity. Additionally, the study highlighted the importance of taking into account not only concentration and dose regime but also the mass load and therefore, the volume used in the experimental units, which are rarely addressed in ecotoxicity assays. Considering the good sensitivity of O. niloticus exposed to relatively low concentrations of estrogens, the combination of the ALP method with auxiliary biomarkers (particularly MN) can be a suitable protocol for estrogenicity and genotoxicity detection in different contaminated waters as part of water environmental monitoring programs
22
Marques, Ana Catarina Fernandes. "Design and processing of porous scaffolds based on calcium phosphates by robocasting for bone tissue engineering." Doctoral thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22471.
Full textAbstract:
Doutoramento em Ciência e Engenharia de MateriaisA presente dissertação teve como foco principal o desenvolvimento de estruturas 3D porosas (scaffolds) para regeneração óssea por robocasting. Esta técnica de fabrico aditivo permite a produção de scaffolds com morfologia e estrutura predefinidas e sem a necessidade de maquinagem subsequente, podendo ser usada para o fabrico de implantes personalizados com estrutura interna semelhante à do osso que se pretende substituir. Como materiais de partida, foram utilizados pós de fosfatos de cálcio bifásicos (hidroxiapatite + β-fosfato tricálcico) não dopados, e dopados com diferentes iões (Sr, Ag, Cu, Mg e Zn), obtidos por precipitação em meio aquoso. A substituição parcial de iões Ca pelos iões dopantes induziu alterações na composição de fases cristalinas e resultou em partículas com características morfológicas distintas e em materiais com desempenhos biológicos diferentes. Os pós foram dispersos em meio aquoso com a ajuda de aditivos de processamento adequados (um dispersante e um ligante) de modo a obter suspensões com elevada concentração de sólidos, requisito essencial para o fabrico de componentes por robocasting. O tamanho e a morfologia das partículas e a concentração dos aditivos de processamento desempenharam os papéis cruciais no comportamento reológico das suspensões. A adição de agente floculante modificou drasticamente as propriedades reológicas do sistema e permitiu a obtenção de pastas com comportamento viscoelástico adequado para o processo de extrusão. Os scaffolds com diferentes tamanhos de poro foram produzidos pela deposição de um filamento com 410 μm de diâmetro. A resistência à compressão dos scaffolds sinterizados a 1100°C foi comparável ou mesmo superior à do osso esponjoso. Scaffolds com diferentes tamanhos de poro (120-500 μm) foram testados in vitro usando células estaminais mesenquimais humanas (hMSCs). Pretendeu-se avaliar a influência do tamanho dos poros na adesão celular inicial, na atividade metabólica e no potencial osteogénico. Os resultados obtidos mostraram que os poros com maior dimensão proporcionam condições favoráveis para a diferenciação osteogénica das hMSCs. Além disso, os fosfatos de cálcio co-dopados com Sr e Zn melhoraram o desempenho biológico, incluindo adesão, atividade metabólica e proliferação das hMSC. A última parte da tese foi dedicada à preparação de scaffolds não sinterizados incorporando um fármaco (levofloxacina) de forma a obter componentes com capacidade de regeneração óssea e de tratamento local de infeções. A pasta utilizada foi obtida através da dispersão dos pós de CaP numa solução de quitosano na presença do fármaco e de um agente de reticulação (genipin). Os scaffolds 3D à base de fosfatos de cálcio produzidos por robocasting no âmbito desta tese revelaram-se muito promissores para aplicações na engenharia de tecidos, particularmente regeneração de tecido ósseo e administração de fármacos.
The main focus of this thesis was the development of novel 3D porous scaffolds for bone regeneration by robocasting. This additive manufacturing technique allows the production of scaffolds with predefined morphology and structure without the need for subsequent machining and can be used for the manufacture of customized implants with an internal structure similar to that of the bone to be replaced. Biphasic calcium phosphates (hydroxyapatite + β-tricalcium phosphate), undoped and doped (with Sr, Ag, Cu, Mg and Zn), obtained through aqueous precipitation process were used as starting powders. The partial substitution of Ca ions by doping ions induced changes in the crystalline phase assemblages and resulted in particles with distinct morphological characteristics and in materials with different biological outcomes. The powders were dispersed in aqueous medium with the aid of suitable processing additives (a dispersant and a binder) in order to obtain suspensions with high solids loading, an essential requirement for the manufacture of components by robocasting. The size and morphology of the particles and the concentration of the processing additives played crucial roles in the rheological behaviour of the suspensions. The addition of a flocculating agent drastically modified the rheological properties of the systems and allowed obtaining pastes with viscoelastic behaviour suitable for the extrusion process. The scaffolds with different pore sizes were produced by the controlled deposition of filaments with 410 μm in diameter. The compressive strength of scaffolds sintered at 1100 ° C was comparable or even superior to that that of spongy bone. Scaffolds with different pore sizes (120-500 μm) were tested in vitro using human mesenchymal stem cells (hMSCs). The aim was to evaluate the influence of pore size on initial cell adhesion, metabolic activity and osteogenic potential. The results showed that larger pores provide favourable conditions for osteogenic differentiation of hMSCs. In addition, calcium phosphates codoped with Sr and Zn improved the biological performance, including adhesion, metabolic activity and proliferation of hMSC. The last part of the thesis was devoted to the preparation of sintering-free scaffolds incorporating a drug (levofloxacin) in order to obtain components with capacity for bone regeneration and local treatment of infections. The paste used was obtained by dispersing the CaP powders in a solution of chitosan in the presence of the drug and a crosslinking agent (genipin). The 3D scaffolds produced by robocasting in the frame of this thesis program revealed to be very promising for tissue engineering applications, particularly bone tissue regeneration and drug delivery.
23
Jullien, Yannick. "Synthèse de dérivés phosphosoufrés potentiellement biodégradables : formulation d'un lubrifiant à base d'huile de colza." Metz, 1998. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1998/Jullien.Yannick.SMZ9815.pdf.
Full textAbstract:
Ce mémoire a été effectué dans le cadre du projet VALNA destiné à valoriser les productions agricoles non alimentaires. Il comporte 3 parties : la première partie s'articule autour de la synthèse d'analogues du DTPZn comportant des fonctions polaires (acides, sulfates acides) destinées à améliorer les propriétés antiusures (A. U) des additifs et des fonctions polysoufrées ou phosphatées destinées à augmenter les propriétés extrême-pression (E. P). Une centaine de produits ont été ainsi préparés. La synthèse mettant en jeu l'addition d'ADTP sur des acrylates à température ambiante ou à chaud permet l'accès à de nombreux composés avec des rendements intéressants. La deuxième partie traite des propriétés mécaniques de ces additifs. Nous avons testé en A. U. Et E. P. Une cinquantaine d'additifs. Les résultats ont été soumis à une analyse en composante principale qui a permis de trier les composés synthétisés. Ainsi les dithiophosphates à haut poids moléculaire, contenant une forte proportion d'atomes d'oxygène, polysoufrés ou éthoxylés ont donné de bons résultats en antiusure. Les additifs phosphosoufrés à fonction acide et de fortes masses molaires constituent le meilleur compromis entre les propriétés A. U. , E. P. . Et corrosives. Si on recherche de bons additifs E. P. Ayant de fortes propriétés corrosives on s'orientera vers des additifs disulfures à fonction éthoxylée. Nous n'oublierons pas les additifs de type sulfates acides en mélange avec l'alcool qui ont montré d'excellentes propriétés E. P. . Certains additifs cités ci-dessus ont réduit l'usure des billes de 70. 4% à 40 kgf, 63. 2% à 60 kgf et 79. 1% a 80 kgf par rapport à une huile non additivée. Enfin nous avons sélectionné un de ces additifs que nous avons incorporé dans une formulation utilisable pour lubrifier les huiles pour chaine de tronçonneuse après avoir étudié les éléments qui la composent. Nous avons alors étudié les propriétés de notre additif dans des conditions réelles d'utilisation.
24
Risquez, Sarah. "Microsystème électrostatique tridimensionnel de récupération d'énergie pour alimenter un stimulateur cardiaque sans sonde." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS044/document.
Full textAbstract:
Cette thèse s’inscrit dans un contexte d’activité en forte croissance dans le domaine des implants médicaux, stimulée par de nombreux progrès dans le domaine des micro-capteurs et de la micro-électronique. L’autonomie en énergie des implants demeure cependant un facteur limitant. Notre travail a pour objectif de repousser les limites actuelles en termes de miniaturisation et de durée de vie. Il contribue au développement d’une solution basée sur la récupération d’énergie mécanique du cœur pour alimenter durablement un pacemaker miniaturisé sans sonde de nouvelle génération, dit « pacemaker leadless ».Le microsystème de récupération d’énergie étudié est composé d’un résonateur mécanique de type masse-ressort associé à un transducteur électrostatique. Il a pour particularité une architecture tridimensionnelle, dont la forme permet de profiter au maximum de l’espace disponible dans la capsule cylindrique du pacemaker. L'utilisation de la troisième dimension associée à un design original permet en outre d’obtenir un effet de pseudo multiplication de fréquence qui doit conduire, d’après les modèles que nous avons développés, à des densités de puissance nettement supérieures à celles présentées dans l'état de l'art. Pour réaliser ce microsystème tridimensionnel, nous avons développé un procédé de fabrication additif qui repose sur des étapes de micro moulage d'un matériaux structurel obtenu par croissance électrolytique (nickel), de croissance d'un matériau sacrificiel (cuivre) et de polissage. L’identification d’imperfections géométriques dues au procédé et aux matériaux utilisés nous a amené à améliorer la conception du transducteur. Par ailleurs, de nombreux verrous de fabrication ont été levés au cours de cette thèse grâce à la mise en œuvre d’une instrumentation dédiée. Ce procédé nous a permis de fabriquer un premier prototype tridimensionnel du micro-transducteur électrostatique composé de 10 couches de nickel. D’autres métaux élaborés par croissance électrolytique pourraient être envisagés pour réaliser des microsystèmes tridimensionnels, suivant les besoins de l’application considérée. Afin d’anticiper d’éventuels problèmes de compatibilité des micro-dispositifs avec l'imagerie par résonance magnétique, nous avons mis au point le procédé de croissance électrolytique d’un matériau non-magnétique à base de nickel dopé au phosphoreThis thesis contributes to the medical implants field, which is stimulated by many advances in the fields of microelectronics and microsensors. However, electrical energy lifespan of implants and large size of batteries are still a problem. Our work aims at pushing back these limits. It contributes to the development of a solution based on mechanical energy harvesting from the heart motion. The objective is to sustainably power a new generation of pacemakers without lead, so-called "leadless pacemakers."The studied energy harvesting microsystem consists in a spring-mass-type mechanical resonator associated with an electrostatic transducer. Its originality comes from a three-dimensional architecture, whose shape fits pretty well with the cylindrical shape of the pacemaker capsule. The use of the third dimension combined with an original design enables to get a pseudo multiplication frequency effect. Thanks to this effect, our simulation models predict power densities significantly higher than state-of-the-art figures reported in literature. To fabricate this three-dimensional microsystem, we have developed an additive manufacturing process based on steps of micro-molding of a structural material (electroplated nickel), electroplating of a sacrificial material (copper) and planarization. Identification of imperfections related to the fabrication process and the materials used allowed us to improve the design of the transducer. Moreover, many manufacturing obstacles were overcome during this thesis through the implementation of dedicated instrumentation. This new process has enabled us to fabricate a first three-dimensional prototype of the electrostatic micro-transducer made of 10 layers of nickel. Other electroplated metals can be envisaged to achieve three-dimensional microsystems, depending on the application requirements. In order to anticipate any compatibility issue of our microsystem with magnetic resonance imaging, we have developed the electrodeposition process of a nonmagnetic material: phosphorous doped nickel
25
Yan, Yige. "TiO2 photocatalysts prepared via a sol-gel route assisted by P- and F- containing additives : applications to the degradation of MEK and to the elimination of bacteria on surfaces." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAF063/document.
Full textAbstract:
L'objectif de ce travail est de synthétiser des nanomatériaux de TiO2 pour la dégradation des COV et pour l'élimination des bactéries en surface. Tout d'abord, basé sur une synthèse des matériaux de TiO2 avec la présence d’un liquide ionique BmimPF6 par une voie sol-gel modifiée, les rôles de deux éléments constitutifs de BmimPF6 (P et F) ont été étudiés en faisant remplacer BmimPF6 par des additives contenant P et F. Par rapport à la référence P25 et aux matériaux de TiO2 synthétisés sans additif, le TiO2 synthétisé en présence de P a déjà montré une meilleure cristallinité en phase anatase avant la calcination, et une surface spécifique élevée et une petite taille moyenne des cristaux étaient maintenus même après calcination. Ces propriétés étaient similaires aux échantillons TiO2 synthétisés en présence de BmimPF6; Tandis que les cristaux de TiO2 en présence de F ont montré une forme anisotrope pendant le murissement de la synthèse. Les évaluations de l'activité photocatalytique des photocatalyseurs ont ensuite été réalisées. Par rapport au TiO2 synthétisé sans additif et au TiO2 P25, les matériaux de TiO2 à faible teneur en P et F ("PANaF") ont présenté une activité plus élevée sous irradiation UVA à la dégradation d'un COV modèle, Méthyléthylcétone (MEK) en phase gazeuse. Le même matériau a également montré une activité anti-bactérienne en surface plus élevée sous UVA contre plusieurs souches de différentes espèces bactériennes dans liquide par rapport à celles de P25. Une corrélation entre la performance photocatalytique élevée et les propriétés des matériaux pour TiO2 "PANaF" a été finalement proposée. Les influences de la présence de PO43- en bulk ou en surface de TiO2, de la concentration d’O2 dissous dans le milieu et de la topologie de surface des photocatalyseurs sur l'activité photocatalytique éteint également sujets de discussion. Le produit "PANaF" présente un intérêt pour l'élaboration industrielle à cause des réactifs pas cher et son performance élevéeThe objective of this work consists in synthesizing TiO2 nanomaterials designed for the degradation of VOCs and for the elimination of bacteria on surface. Firstly, based on a synthesis of a BmimPF6-ionic liquid-derived TiO2 material through a modified sol-gel route, the roles of two constituent elements of BmimPF6 (P and F) have been investigated by replacing BmimPF6 with P- and F- contained additives. Comparing to the reference P25 and additive-free-derived TiO2 materials, P-derived TiO2 showed already well crystallized anatase phase before calcination and a high surface area along with a small mean crystal size even after calcinations. Those properties were similar to that synthesized with the presence of BmimPF6; while F-derived TiO2 crystals showed anisotropic shape during the aging step of the synthesis. Evaluation of the photocatalytic activity of the photocatalysts has been performed then. Compared to additive-free derived TiO2 and the TiO2 P25, P- and F- derived TiO2 materials with low P and F content (“PANaF”) showed higher activity under UVA in terms of gas-phase degradation of a model VOC, Methl Ethyl Ketone (MEK). The same material also showed higher surface anti-bacterial activity under UVA in liquid against several strains of different bacterial species over that of P25. A correlation between the high photocatalytic performances with the material properties for “PANaF” TiO2 materials was finally proposed. The influences of the presence of bulk or surface PO43-, dissolved O2 concentration and surface topology on photocatalytic activity were also discussed. The cheap replacement additives used and the resulted high activity of “PANaF” TiO2 nanomaterials presents interest for industrial elaboration
26
Jamet, Sophie. "Effet photoréfractif dans l'InP:Fe : étude comparative en fonction de la température à plusieurs longueurs d'onde." Rouen, 1995. http://www.theses.fr/1995ROUES002.
Full textAbstract:
Cette étude porte sur l'effet photoréfractif dans le phosphure d'indium dopé au fer (InP:Fe). Les gains optiques mesurés en absence de champ électrique appliqué et à la longueur d'onde de 1,06 micromètre sont plus faibles que les valeurs calculées avec un modèle qui tient compte d'un seul niveau d'énergie (celui du fer) dans la bande interdite. Nous contribuons à déterminer l'origine de cette réduction qui est attribuée dans la littérature, soit aux transitions indirectes liées à l'état excité du fer soit à d'autres niveaux superficiels. Dans un premier temps, nous mettons en évidence la nécessité d'effectuer des mesures en fonction de la température et à plusieurs longueurs d'onde (1,06 ; 1,32 et 1,535 micromètre) afin d'établir les rôles respectifs des différents niveaux d'énergie dans les échantillons étudiés où l'effet photoréfractif est dominé par les trous à température ambiante. L'étude de la constante de temps d'effacement du réseau a permis de déterminer les concentrations en ions Fe2+ et Fe3+. Nous comparons ensuite les courbes du gain mesuré pour les trois longueurs d'onde en fonction de la température et du pas avec les simulations effectuées à partir des différents modèles comprenant soit le niveau excité du Fe2+*, soit un second niveau placé près de la bande de conduction puis, près de la bande de valence. Dans les échantillons étudiés, ces différentes comparaisons ont montré qu'à basse température l'effet photoréfractif est influencé par un second niveau situé près de la bande de valence alors qu'à température ambiante il faut à la fois tenir compte du second défaut et de l'état excité du fer
27
Herstedt, Marie. "Towards Safer Lithium-Ion Batteries." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3542.
Full text
28
Leblond, Jérôme. "Synthèse et application catalytique de cyclodextrines modifiées Water-soluble phosphane-substituted cyclodextrin as an effective bifunctional additive in hydroformylation of higher olefins New water-soluble Schiff base ligands based on β-cyclodextrin for aqueous biphasic hydroformylation reaction." Thesis, Artois, 2018. http://www.theses.fr/2018ARTO0404.
Full textAbstract:
L'utilisation de cyclodextrines (CDs) comme additifs interfaciaux en catalyse biphasique aqueuse s'est avérée être une méthode efficace pour la transformation de composés hydrophobes. Pour améliorer de façon significative la proximité entre le catalyseur organométallique hydrosoluble et le composé organique à transformer, deux nouvelles familles de récepteurs moléculaires à base de CDs ont été développées. Une première stratégie a consisté à greffer de façon covalente une phosphine sulfonée sur une CD (système CD-P). Le récepteur moléculaire ainsi obtenu a permis d'améliorer significativement les performances catalytiques en hydroformylation d'alcènes hydrophobes. Une deuxième stratégie utilisant des dimères de CDs comportant un espaceur court et flexible s'est avérée moins concluante. En effet, la reconnaissance moléculaire simultanée du catalyseur et du substrat au sein des dimères de CDs n'a pu être démontrée, que ce soit en hydroformylation d'alcènes, en réaction de Heck ou en hydrogénation d'alcènesThe use of cyclodextrins (CDs) as interfacial additives in aqueous biphasic catalysis has proven to be an effective method for the transformation of hydrophobic compounds. To significantly improve the proximity between the water-soluble organometallic catalyst and the organic compound to be transformed, two new families of CD-based molecular receptors have been developed. A first strategy consisted in covalently grafting a sulfonated phosphine on a CD (CD-P system). The molecular receptor thus obtained significantly improved the catalytic performances in hydroformylation of hydrophobic alkenes. A second strategy using CD dimers with a short and flexible spacer proved less conclusive. Indeed, the simultaneous molecular recognition of the catalyst and the substrate within the CD dimer could not be demonstrated, whether in hydroformylation of alkenes, in Heck reaction or in hydrogenation of alkenes
29
FUJIMOTO, TALITA G. "Microestrutura e propriedades elétricas e dielétricas do titanato de estrôncio puro e contendo aditivos." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26933.
Full textAbstract:
Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-12-21T16:28:43Z
No. of bitstreams: 0Made available in DSpace on 2016-12-21T16:28:43Z (GMT). No. of bitstreams: 0
O titanato de estrôncio (SrTiO3) possui estrutura cristalina do tipo perovsquita. Materiais com este tipo de estrutura são utilizados para diversas aplicações, tais como, sensores, atuadores, em células a combustível de óxido sólido, entre outros. Devido as suas interessantes propriedades físicas, o SrTiO3 vem sendo intensamente estudado, em especial com a introdução de dopantes. Portanto, neste trabalho foi investigada a influência de diferentes teores de Ca (1; 2,5 e 5% mol) e Pr (0,025; 0,050; 0,075 e 1% mol) na microestrutura e propriedades elétricas e dielétricas do SrTiO3, assim como o material sem aditivos (puro). Os resultados mostram que após a sinterização do SrTiO3 puro, a microestrutura consiste de grãos poligonais com tamanho médio micrométrico, além de texturas lisas e rugosas. A condutividade elétrica das amostras sintetizadas sinterizadas a 1450 e 1500ºC é máxima para 2 horas de patamar. Apenas as amostras de SrTiO3 contendo 1% em mol de Ca apresentam fase única. O tamanho médio de grãos das amostras contendo 1% em mol de Ca é 10,65 ± 0,28 µm e para teores acima deste valor ocorre crescimento significativo dos grãos. As medidas de condutividade elétrica mostraram que as amostras contendo a adição de 1% em mol de Ca possuem maior condutividade dos grãos em relação ao material puro. Para as amostras contendo teores de até 0,075% mol de Pr, pode-se observar alguns grãos lisos e outros rugosos e não há variação considerável do tamanho médio de grãos. As amostras contendo menor teor de Pr (0,025% mol) apresentam maior condutividade dos grãos e contornos de grãos. As amostras de SrTiO3 sintetizado sinterizadas a 1450ºC/10 h apresentaram permissividade elétrica colossal em temperatura ambiente em altas frequências.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
30
Thirtamara, Rajamani Keerthi Krishnan. "Animal Models of Drug Addiction and Autism Spectrum Disorders." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1386011455.
Full text
31
Gigant, Nicolas. "Synthèse et réactivité d'énamides, de la diversité moléculaire à la synthèse de molécules bioactives et/ou naturelles." Thesis, Orléans, 2012. http://www.theses.fr/2012ORLE2039.
Full textAbstract:
La nécessité grandissante de disposer d’une large librairie de diverses petites molécules pour le screening biologique constitue une puissante force motrice pour les chimistes organiciens et requiert en amont le développement de méthodologies rapides et efficaces. Dans ce cadre, nous nous sommes plus particulièrement intéressés à la fonctionnalisation d’énamides qui représentent des blocs moléculaires intéressants permettant d’introduire des fonctionnalités aminées dans des systèmes variés. Notre objectif a été de synthétiser des petites bibliothèques de molécules azotées à partir de substrats communs tout en mettant en oeuvre les différentes stratégies de la synthèse orientée vers la diversité et en s’attachant à respecter les règles suivantes : économie d’atomes, processus catalysés, synthèses rapides en peu d’étapes et contrôle de la stéréoselectivité. Dans un premier temps, nous avons principalement synthétisé divers énamides, nous permettant par la suite de développer des méthodologies innovantes et d’accéder à des « structures privilégiées » ou des fragments clés présents dans des produits naturels ou dans des substances potentiellement biologiquement actives en mettant en jeu des processus variés telles que des réactions d’aza-Michael, d’oxyamidation ou en cascade et la chimie du palladium avec de la CH insertion, des dioxoazoborocanes ou encore l’utilisation de l’auxiliaire chiral SAMPThe continuing demand to synthesize new and original collections of small molecules for the biological screening is an attractive subject for organic chemists and requires upstream the development of fast and easy synthetic methods. In this context, we decided to focus particularly on the functionalization of enamides which represent valuable building blocks in order to introduce nitrogen based functionality into various organic systems. Our objective was to synthesize new nitrogen containing compound libraries starting from common substrates by applying Diversity-Oriented Synthesis strategy and following these rules: atom economy, catalyzed reactions, fast synthesis in few steps and control of stereoselectivity. Firstly we mainly synthesized enamides. Thereafter, we developped efficient methodologies giving access to motifs frequently found in “privileged structures” or key scaffolds present in natural products or potential bioactive compounds thanks to various processes like aza-Michael, oxyamidation or cascade reactions, palladium chemistry with CH activation, dioxoazoborocanes or chiral auxiliary SAMP
32
Menard, Raphaël. "Synthèse de retardateurs de flamme phosphorés biosourcés pour résines époxy Synthesis of biobased phosphate flame retardants Synthesis of biobased phosphorus-containing flame retardants for epoxy thermosets Comparison of additive and reactive approaches From bio-based phosphorus-containing epoxy monomer to fully bio-based flame-retarded thermosets Synthesis of new flame-retardants by radical chain transfer copolymerization of glycidyl methacrylate and dimethoxy-phosphorylmethyl methacrylate." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2015. http://www.theses.fr/2015ENCM0013.
Full textAbstract:
La toxicité avérée et le caractère bio-accumulatif des retardateurs de flamme halogénés usuels (PBDE) ont entrainé la mise en place de restrictions d'usage au sein de l'union européenne (REACH). Les retardateurs de flamme phosphorés (RFP) se sont imposés comme alternatives aux solutions halogénées pour leur moindre toxicité et leurs propriétés ignifugeantes adaptées à la composition chimique des résines époxy. Avec l'essor des résines époxy biosourcées, la dépendance aux ressources fossiles pour la synthèse des additifs en tout genre qui entre dans leur composition est devenue problématique. Ainsi, ces travaux s'inscrivent dans une dynamique de développement durable à travers la valorisation d'un composé biosourcé représentatif des structures phénoliques disponibles: le phloroglucinol. La fonctionnalisation directe du phloroglucinol par des groupements phosphates a permis de réaliser une première série d'additifs RFP biosourcés présentant une action ignifugeante prononcée en phase condensée qui réduit le pouvoir calorifique des matériaux ignifugés. A l'échelle macroscopique, une forte intumescence entraîne une décomposition partielle du matériau ignifugé par effet barrière du résidu formé. Cependant, ces additifs réduisent fortement les températures de transitions vitreuse et mécanique par plastification du réseau thermodurcissable. La fonctionnalisation en deux étapes du phloroglucinol a conduit à deux RFP biosourcés additif (P3SP) et réactif (P2EP1SP) de structures comparables. Nous avons ainsi pu mettre en évidence l'intérêt de l'approche réactive qui, en plus de garantir la durabilité des propriétés des matériaux ignifugés, permet une meilleure action en phase condensée qui entraîne une plus forte intumescence. L'approche réactive semblant plus performante, nous avons poursuivi avec la synthèse d'un dernier RFP biosourcé réactif (P2EP1P) dont la structure a été adaptée pour réduire l'effet plastifiant du groupement phosphoré. Enfin, l'étude de différents matériaux 100 % biosourcés contenant le RFP P2EP1P a montré que les inconvénients de l'approche réactive dus à la faible fonctionnalité du RFP réactif peuvent en partie être compensés par l'incorporation d'un co-précurseur époxy de haute fonctionnalité ou d'un agent de réticulation biosourcé aromatiqueThe toxicity and the bioaccumumulative character of the usual halogenated flame retardants(RFX) lead to uses restrictions of the main FRX (PBDE) in the EU as REACH. The phosphorus-containing flame retardants (FRP) are suitable for the epoxy thermoset because of their action on the hydroxyl groups. Moreover, the FRP are less toxic than the FRX. With the rise of the biobased epoxy thermosets, the dependence on fossil fuels for the additives synthesis has become problematic. Thus, these works are designed in a sustainable development approach through the valorization of a biobased compound which is representative of the biobased phenolic structures. The directe functionalization of the phloroglucinol with phosphate functions has achieved a first generation of biobased additives FRP which exhibit a significant action in the condensed phase and reduce the heat released during the thermal degradation of the fire retarded thermosets. This effect results in a strong intumescence at macroscopic scale and the expanded residue acts as a barrier and leads to a partial degradation of the thermoset. However, these additives plasticize the thermoset network and reduce the glass and the mechanical transition temperatures. A two-steps functionalization of the phloroglucinol leads to two new biobased FRP, an additive (P3SP) and a reactive (P2EP1SP), with similar chemical structures. We were able to highlight the benefit of the reactive approach which favors the condensed phase action and the intumescence. Moreover, the reactive approach ensures the durability of the flame retarded thermoset properties. Since the reactive approach seems more efficient than the additive one, an other reactive FRP was synthesized, whose the structure was optimized to reduce the plasticizing effect of the phosphorus-containing group. Finally, the study of different 100% biobased phosphorus-containing thermosets highlighted that the disadvantages of the reactive approach may be balanced by the incorporation of a high functionality epoxy precursor or an aromatic curing agent
33
Samyn, Fabienne. "Compréhension des procédés d'ignifugation du polyamide 6 : apport des nanocomposites aux systèmes retardateurs de flamme phosphorés." Lille 1, 2007. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2007/50376-2007-Samyn.pdf.
Full textAbstract:
La compréhension des procédés d'ignifugation du PA6 basés sur l'emploi d'un retardateur de flamme (FR) phosphoré (OP1311) et/ou une argile organomodifiée (C30B) est l'objet de cette étude. En termes de propriétés feu, un effet de synergie est observé pour la formulation combinant les deux additifs. Les raisons de cet effet ont été étudiées et expliquées. La dispersion de l'argile étant nanométrique dans les composites avec et sans FR, l'explication de l'amélioration réside soit dans l'obtention de composés plus stables formés par réaction entre les constituants de la formulation, soit dans la résistance améliorée de la structure protectrice développée due à des interactions physiques. Pour mettre en évidence les éventuelles interactions chimiques, la dégradation thermique des additifs et des formulations a été étudiée. Aucune nouvelle espèce n'est formée lors de la dégradation thermique. Il n'y a donc pas de réaction chimique. Des interactions physiques doivent donc se produire et permettre cette amélioration du comportement du matériau sous flux de chaleur. L'évolution des structures qui se forment au cours de la dégradation des formulations sous flux de chaleur a été étudiée. Des mécanismes de protection ont été proposés pour expliquer l'effet de synergie.
34
Wu, Shao-tzu, and 吳紹慈. "Hydrothermal Synthesis of Lithium Iron Phosphate without Reducing Additives." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/wq39e7.
Full textAbstract:
碩士國立中山大學
化學系研究所
102
LiFePO4 is successfully prepared by hydrothermal synthesis in air without extra reducing additives. The structure and morphology of the resulting LiFePO4 powders were shown by X-ray diffraction (XRD),scanning electron microscope (SEM), and a transmission electron microscope (TEM).The XRD results demonstrate that LiFePO4 powder has an orthorhombic olivine-type structure with a space group of Pnma. Raman spectroscopy and electron spectroscopy for chemical analysis (ESCA) reveal the impurity of Fe3+ in samples. The chemical composition of the LiFePO4 powders was characterized by elemental analysis (EA). Among the conditions, the electrochemical results show the energy capacity is 84 mAh g−1 at 0.2 C-rate.
35
Lin, Che-Wei, and 林哲暐. "Boron Based Electrolyte Additives and Water Based Binder in Lithium Iron Phosphate Battery." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/w8q58w.
Full textAbstract:
碩士國立臺南大學
綠色能源科技學系碩士班
103
In recent years, lithium-ion batteries (LIBs) are currently the most widely applied power source in personal electronics. With the increasing functions of the applications, applications require more stringent performances that include high energy density, high power density, low cost, and long cycle life. To meet the increasing demand on high-performance LIBs more researches are necessary. This study has two parts. The first part forcus on boron-based electrolyte additives, BAME, PBAME and EAME to improve the cycle life of lithium iron phosphate batteries. The experimental results show the interfacial impedances of the lithium iron phosphate electrodes in the cell with boron-base additives were smaller than those without additives based on the cyclic voltammetry and electrochemical impedance spectroscopy analysis. That means the boron-based electrolyte additive enhanced the ion conductivity of SEI film, thus reducing the polarization of lithium iron phosphate electrode. The second part discusses the effect of binder on LIBs performance. Polyvinylidene fluoride (PVDF) has been so far widely used as a binder for typical LIBs. However, there are still several of PVDF disadvantages including high cost, use of hazardous N-methyl-2-pyrrolidone (NMP) organic solvent, and sensitive humidity in processing. On the other hand, water-soluble binders such as carboxymethyl cellulose (CMC) and styrene butadiene (SBR) use water as the processing solvent, This means an environmentally friendly and lower cost LIB manufacturing process can be established since solvent recycling is not necessary. Through the study, it is found CHEMEI synthesis (SBR) BN-821 can improve the cell’s cycle life at low temperature and high temperature. Due to these advantages, water-soluble binders have gradually replaced conventional PVDF binders in LIB graphite based anode electrode.
36
周順裕. "Influence of Silicate and Phosphate Additives on Leaching Characteristics of Stabilized Municipal Incinerator Fly Ashes." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/52111936303249123044.
Full text
37
TONELLI, MONICA. "Investigation of the structural properties of magnesium silicate hydrate cements and assessment of strategies for their development." Doctoral thesis, 2018. http://hdl.handle.net/2158/1117678.
Full textAbstract:
During my PhD I focused my work on the investigation of MgO/SiO2 cements. In the last decades, research on cement formulations alternative to traditional Portland cement has progressively grown, both with the aim of reducing the environmental impact due to the CO2 emissions associated with its production and in view of solving specific needs in particular fields of application. Formulations based on reactive periclase (MgO) and silica (SiO2) in the presence of water hydrate and form a binder phase, M-S-H (magnesium silicate hydrate), analogue to calcium silicate hydrate, C-S-H, present in traditional cements. In spite of its potential importance, there is still little knowledge about its structural features and formulation design. I focused my PhD on this class of cement, aiming to extent the knowledge on this material, which could pave the way for tailoring its macroscopic properties by means of a bottom-up approach, and a multi-technique approach has been used to accomplish this purpose.
38
Sigwadi, Rudzani Annetjie. "Zirconia, Sulphated Zirconia and Zirconium Phosphates as additives for membranes in PEM Fuel Cell." Thesis, 2019. http://hdl.handle.net/10500/26880.
Full textAbstract:
This research investigates the impact of zirconia nanoparticle in conductivity, water
uptake, fuel crossover and fuel efficiency of modified Nafion® membranes.
Synthesized water-retaining mesoporous zirconia nanoparticles (ZrO2) were used
to modify Nafion® membrane in order to enhance the thermal properties, water
uptake, proton conductivity and mechanical strength of composited membrane for
fuel cell applications. Recast and impregnation methods were used to prepare a
nanocomposite membrane with required weight% of zirconia nanoparticles. The
mechanical stability of modified membranes has become a priority for fuel cell
applications as the membranes must endure all the fuel cell operations (to prevent
crossover of the fuel while still conducting). Their mechanical stress and yielding
stress in the recast and impregnation methods compared with the commercial
Nafion® membrane were observed under tensile tests. The incorporated
membrane with zirconia nanofiller shows an improvement in mechanical strength,
due to the hydrophilic phase domains in the nanocomposite membrane. The water
contact angle and water uptake of the composited membrane were measured. The
modified membranes with zirconia nanoparticles showed a significant
improvement in water uptake and contact angle leading to enhanced hydrophilicity
when compared to unmodified hydrophobic Nafion® membrane. This shows the
potential for use as electrolytes in fuel cell applications.
Zirconia nanoparticles were further impregnated with sulfuric acid and phosphoric
acid to introduce the additional acid sites for absorption of water. In addition,
zirconium phosphates (ZrP) and sulfated zirconia (S-ZrO2) were incorporated into
Nafion® 117 membrane by impregnation method to obtain a reduced methanol
permeation and improved proton conductivity for fuel cell application. The
mechanical properties and water uptake of Nafion® membrane incorporated with
zirconium phosphates and sulfonated zirconia nanoparticles were much more
improved when compared to the commercial Nafion® 117, due to the presence of
acid site within the nanoparticles. Furthermore, the results showed that
incorporating ZrP and S-ZrO2 nanoparticles enhanced proton conductivity and IEC of modified Nafion
® membrane as they sustain water affinity and strong acidity.
The results show that nanocomposite membranes have low water content angle,
improved thermal degradation, higher conductivity and lower methanol
permeability than commercial Nafion® 117 membrane, which holds great promise
for fuel cell application. The Nafion®/ sulfated zirconia nanocomposite membrane
obtained a higher IEC and water uptake due to the presence of
SO 2-4 providing extra acid sites for water diffusion.
To reduce the agglomeration of ZrO2 nanoparticles and improve the water
diffusion, ZrO2 was electrospun with polyacrylonitrile (PAN) solution to obtain a 1D
morphology. The recast method was used to synthesize the high thermal and
mechanical stability of Nafion® membrane incorporated with polyacrylonitrile (PAN)
nanofibers. The modified Nafion® membranes exhibited improved fuel cell
efficiency when tested in direct methanol fuel cells with a high proton conductivity
due to incorporating PAN/Zr nanofibers that retain water within the membrane.
Moreover, nanocomposite membranes achieved a reduced methanol crossover of
4.37 x 10-7 cm2
/s (Nafion®-PAN/ZrP nanofibers), 9.58 x 10-8 cm2
/s (Nafion®-
PAN/ZrGO nanofibers) and 5.47 x 10-8 cm2
/s (Nafion®-PAN/Zr nanofibers), which
is higher than 9.12 x 10-7 cm2
/s of recast Nafion® membrane at the higher
concentration of 5M. All the blended membranes showed increase in power
density at a temperature of 25 °C in comparison with pristine recast Nafion®
membrane (76 mW·cm−2
, 69 mW·cm−2
, 44 mW·cm−2
, 18 mW·cm−2
). Finally,
incorporating electrospun PAN/ Zr nanofibers into Nafion® membrane has
successfully reduced the use of Nafion® solution that will eliminate the cost
problems, while improves the protons conductivity and the methanol permeability
which influence the fuel cell efficiency and long-term stability.Physics
39
KUO, WEI-PING, and 郭唯平. "The Electrochemical Study of Ammonium Dihydrogen Phosphate Additive for All Vanaium Flow Battery Electrolyte." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/tr6yp7.
Full textAbstract:
碩士輔仁大學
化學系
107
In this study, the diammonium phosphate ((NH4)2HPO4) and ammonium dihydrogen phosphate (NH4H2PO4) are investigated as additives to improve the stability of a vanadium electrolyte(1.67 M Vn+ / 3 M H2SO4) for a vanadium redox flow battery (VRFB) at operating temperatures of 5℃ and 45℃. The most effective additive is chosen based on the thermal stability and electrochemical performance with a long inhibition time. Through precipitation time and electrochemical measurements, the results show that the best inhibition effect is achieved by adding 0.1M NH4H2PO4 as an additive, indicating an improved redox reversibility and electrochemical activity. At the temperature of 45 ° C and a current density of 60 mA / cm2, the charge/discharge energy efficiency of the electrolyte with 0.10 M NH4H2PO4 is 86 %, same as the origin electrolyte. In the cycle-life test, the cycling number is increased from 40 cycles to 205 cycles after adding 0.10 M NH4H2PO4. At a low temperature of 5 °C and a current density of 60 mA/cm2, the charge/discharge energy efficiency of electrolyte without and with 0.10 M NH4H2PO4 are 84.7 % and 83.5 %, respectively. In the cycle-life test, the cycling number is increased from 46 cycles to 147 cycles after adding 0.10 M NH4H2PO4.
40
Yen, Pang-Yueh, and 顏邦岳. "Synthesis and investigation of the effect of the substituents on phosphine-based additives on charge and discharge for lithium ion batteries." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/08069040389881292405.
Full textAbstract:
碩士大同大學
化學工程學系(所)
103
The electrolyte additives are one of the most economic and effective methods for the improvement of Li-ion battery performance. In this work, we developed novel electrolyte additives to stabilize carbonate-based electrolytes on the electrode surfaces of high-voltage class. We have successfully synthesized the electrolyte additives based on fluorinated phosphate and fluorinated phosphorothionate structures by nucleophilic substitution reaction. Their structures were preliminary characterized by ¬1H NMR, 31P NMR, mass, X-ray single crystal diffraction and elemental analysis. The preliminary results from electrochemical analysis showed that only new additive OP(OC6F2H3)3 improved the catholic stability of the electrolyte on LTO slightly. However, theses additives could not promote the anodic stability of the electrolyte on LNMO effectively. With the results of electrochemical analysis and mass spectra, the oxidative stability of the electrolyte at LSV is affected with the electronegativity difference between oxygen and sulfur binding with phosphine, and fluoro substituents on the phenyl rings in the molecular structure of electrolyte. One of the reasons about the battery capacity decrease is the less of coordination ability of the oxygen and sulfur in the arylphosphate and arylphosphorothionate to the electrode. In addition, the high resistance SEI film is form by the electrolyte additive oxidative decomposition on the electrode surface. It caused the intercalation and de- intercalation of lithium ion to electrode ineffectively.
41
Arun, Kumar P. "Mechanistic Investigation of Metal Promoted Nucleophilic Additions." Thesis, 2013. http://etd.iisc.ernet.in/handle/2005/2842.
Full textAbstract:
Nucleophilic additions are an important class of reactions in the preparation of several organic compounds. Metals facilitate nucleophilic additions in many cases. The present work Mechanistic Investigation of Metal Promoted Nucleophilic additions is an attempt to understand the mechanism of nucleophilic additions to imines and carbonyl compounds mediated by the transition metal complexes. Understanding the mechanism of metal promoted nucleophilic additions can facilitate the design and synthesis of more efficient catalysts.
Chapter 1 provides a brief introduction to nucleophilic addition. A few named reactions that involve nucleophilic addition are described. An overview of the metal promoted nucleophilic addition reactions and their mechanisms are presented. A short note on the importance of understanding the mechanism of metal promoted nucleophilic addition is included. This section ends with the scope of the present work.
Chapter 2 “Mechanistic Investigation of Titanium Mediated Reactions of Imines” deals with two reactions. The first reaction is the formation of reduced amines on reduction of imines. Amines and diamines are synthesized often from imines. A convenient route to such nitrogen containing compounds is through reduction of imines and through reductive coupling of imines respectively. Since both reactions occur in a parallel fashion, during the synthesis of diamines, amines are obtained as side products and vice versa. This problem is acute in the case of titanium based reducing agents. These reducing agents are called low valent titanium reagents because low valent titanium species are generated in situ either from titanium(IV) or titanium(III) reagents. There is no clear understanding of the nature of the low valent titanium involved in the reaction. To rectify this, a mechanistic understanding of this reaction is essential. An attempt was made to probe the mechanism of formation of amines using low valent titanium formed by using two different reducing agents namely phenylsilane and zinc. With the help of isotopic labelling studies, it was found that the mechanism of formation of an amine with phenylsilane involves a direct hydrogen transfer from phenylsilane to an imine. This was verified using deuterium labelled phenylsilane. With zinc, it follows a traditional titanacycle pathway which was verified by quenching with the deuterium oxide.
A second reaction that has been probed is the alkylation of imines by Grignard reagents using chiral titanium complexes. Alkylation of imines is one of the suitable routes to prepare chiral amines. Alkylation of imines employing a Grignard reagent with Ti(OiPr)4 can proceed through two different pathways depending on the amount of the Grignard reagent used. Alkylation reaction with one equivalent of Grignard reagent can proceed through a Ti(IV) species and the alkylation reaction with two equivalents of the Grignard reagent can proceed through a Ti(II) species. The reaction proceeding through Ti(IV) is less wasteful as it only requires one equivalent of the Grignard reagent. The two pathways differ from each other in the nature of the transition state where the C-C bond is formed. To verify the favourable pathway, chiral titanium complexes were prepared and alkylation carried out. The alkylation results suggest that one equivalent of Grignard is sufficient to give good yields of the alkylated product and the reaction may proceed through a Ti(IV) promoted path. It was reported in the literature that at least three equivalents of Grignard reagent are required to get good yields of the alkylated product with zirconium complexes. This work suggests a greener alternate to alkylation of imines.
Chapter 3 “Asymmetric Transfer Hydrogenation Reaction of Ketones in Water” deals with the synthesis of chiral ruthenium half-sandwich complexes employing a proline diamine ligand which has phenyl, ethyl, benzyl, or hydrogen as a substituent. These complexes were characterized by X-ray diffraction. In addition, all these complexes were obtained as single diastereoisomers. These complexes were used as catalysts for the reduction of a variety of ketones to chiral alcohols in water using sodium formate as a hydride source. Stoichiometric reaction between sodium formate and the catalysts showed the formation of hydride complexes as the active species. Based on the electronic effects observed, the key step is found to be a nucleophilic attack of hydride on the carbonyl carbon of ketones. In the transfer hydrogenation reaction with DCOONa, more of 1-phenylethanol- 1-2H1 was observed with all the ruthenium catalysts suggesting that the hydrogen from sodium formate is transformed into a metal hydride which is subsequently transferred to the ketones to form chiral alcohols. The catalysts were optimized with acetophenone as a model substrate. Only in the case of a catalyst which has a phenyl substituent, silver nitrate was found to enhance the formation of aqua complex which in turn resulted in good yields of the chiral alcohols. Among all the complexes studied, the catalyst bearing a phenyl group induces greatest enantioselectivity. It can also be recycled.
Chapter 4 “On the Formation of a Ruthenium-PPh2H Complex Using 1- Phenylethane-1,2-diol” deals with the mechanism of formation of PPh2H from PPh2Cl. This unique transformation involves a ruthenium-cymene dimer, PPh2Cl and 1-phenylethane-1,2- diol. In the attempted synthesis of a ruthenium bisphosphinite complex, using the ruthenium-cymene dimer, chlorodiphenylphosphine and 1-phenylethane-1,2-diol, the formation of [Ru(η6-cymene)Cl2PPh2H] was observed in good yield. Formation of the expected ruthenium bisphosphinite complex was not observed. The reaction was carried out in the absence of 1-phenylethane-1,2-diol resulted in the formation of [Ru(η6- cymene)Cl2PPh2Cl] suggests that the diol acts as a reducing agent. To verify the source of hydrogen in the 1-phenylethane-1,2-diol, deuterated diols were prepared. The reactions with the deuterated diols revealed several interesting aspects of the formation of the Ru-PPh2H complex.
Chapter 5 “Mechanistic Studies on the Diazo Transfer Reaction” deals with the synthesis of labelled azides and the labelled azidating reagent to probe the mechanism of the diazo transfer reaction. Azides are important precursors used for a variety of chemical transformations including the celebrated Cu(I) catalyzed click reaction. Azides are also used as protecting groups for amines as they can be conveniently reduced to amines. Azidation of amines usually yield azides, with retention of stereochemistry. There is a possibility that the azide formation can occur through the SNi mechanism with retention of configuration where nitrogen in the starting material will not be retained after forming an azide. The reaction was carried out with 13C and 15N labelled L-valine and L-isoleucine to probe this possibility. The resultant labelled azide has 15N retained in its position. This excluded the SNi pathway. To show where the nucleophilic amine group is attacking the azide, labelled imidazole-1¬sulfonyl azide was synthesized from NaN215N. Reactions were carried out with L-valine (labelled and unlabelled) in the presence of a metal catalyst and with unlabelled L-valine in the absence of catalyst. These results confirm the postulated pathways described in the literature.
42
A, Boezio Alessandro. "Additions stéréosélectives sur des imines : du développement d'un auxiliaire à la catalyse asymétrique." Thèse, 2003. http://hdl.handle.net/1866/14331.
Full text