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Structural analysis of thermal interface materials and printed circuit boards in telecom units - a methodologyGood, Mattias January 2016 (has links)
En struktur analys på Ericssons MINILINK-6352 har utförts för att undersöka spänningar och deformationer på enheten, främst med fokus på de termiska gränskiktsmaterialen och buktningar av kretskortet. Dessa är viktiga aspekter när man överväger om enheten är termiska lämpad ur en mekanisk synvinkel, där god ytkontakt mellan de olika kropparna är avgörande för ordentlig kylning genom värmeledning. Analysen kräver tillräcklig materialdata till gränskiktsmaterialen och kretskortet för att kunna skapa lämpliga matematiska modeller. Enaxliga kompressionstester har genomförts för att karakterisera de hyperelastiska och viskoelastiska lagar för fyllda silikongummimaterial som används som termiska gränskiktsmaterial, som ibland kallas för gappad. Böjning av ett kretskort simulerades och jämfördes med ett tre--punkts böjtest för att verifiera om befintlig materialdata i beräkningsprogrammen var tillräcklig, jämförelsen visade god överensstämmelse. Kretskortet med dess komponenter, som modellerades som styva block, med gappads ovanpå som komprimeras av en platta simulerades och ett svagt område hittades. Detta område var sedan tidigare känt och har i ett senare skede eliminerats genom att tillsätta ytterligare en stödpelare. Därav visar denna studie en metod för att hitta intressanta regioner tidigt i konstruktionsfasen som lätt kan ändras för att uppfylla nödvändiga krav och undvika brister i konstruktionen. Arbetet har visat sig användbart genom att hitta detta svaga område i exempel produkten, arbetet ger även tillräckligt med information och exempeldata för att ytterligare utreda liknande produkter. Kombinationen av erfarenhet och simulering möjliggör smartare designval. / A structural analysis on Ericssons MINILINK-6352 has been performed in order to investigate stresses and deformations of the unit, mainly focusing on the thermal interface materials and warpage of the printed circuit boards. These are important aspects when considering if the unit is thermally adequate from a mechanical point of view, where good surface contact between various bodies are critical for proper cooling through heat conductivity. The analysis requires sufficient materal data for the interface material and the circuit board in order to create suitable mathematical models. Uniaxial compression tests have been conducted to characterise the hyperelastic and viscoelastic constitutive laws of a filled silicone rubber material used as a thermal interface material, commonly referred to as a thermal pad. Bending of a printed circuit board was simulated and compared to a three-point bend test on the circuit board in order to verify material data already available in the computational software, which showed good agreement. The entire radio unit was mechanically analysed during its sealing process. The circuit board with attached components modelled as stiff blocks with thermal pads on top compressed by plates was simulated and a weak area was found. This area in question was already known and has in a later stage been eliminated by adding an additional supporting pillar. Hence this study shows a methodology to find regions of interest at an early design phase which can easily be altered to fulfil necessary requirements and eliminate design flaws. This work has proven useful in finding weak regions in the example product, it also provides enough information and example data to further investigate similar products. The combination of experience and simulation allows for smarter design choices.
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Estudo da síntese de dimetildiclorosilano a partir de cloreto de metila e silício. / Study of the synthesis of dimethyldichlorosilane from methyl chloride and silicon.Poço, João Guilherme Rocha 22 March 2001 (has links)
No presente trabalho foi realizado um estudo de alguns aspectos da reação de obtenção de dimetildiclorosilano a partir da reação entre silícios grau químico (SiGQ) ou de elevada pureza (99,999%) e cloreto de metila catalisada por cobre e promotores em reator de leito fluidizado. Foram estudados os efeitos da temperatura sobre o processo de ativação e sobre a reação com o fim de obter um valor aproximado da energia aparente de ativação para cada uma dessas etapas; o efeito do tamanho médio das partículas de silício e do catalisador sobre os parâmetros de desempenho da reação e o de contaminantes usuais do SiGQ, a saber Ca, Fe e Al, sobre silício de elevada pureza (99,999%). Uma discussão sobre o efeito de compensação característico da reação direta foi realizada sendo proposta uma explicação da origem desse efeito, que aparentemente se deve ao caracter anisotrópico da reação, e uma explicação complementar com relação ao papel dos promotores na reação. Os resultados mostraram que a energia aparente de ativação obtida por meio dos experimentos realizados neste estudo encontram-se em valores próximos ao normalmente encontrado na literatura. Aparentemente existe uma variação da seletividade com a variação do tamanho de partícula tanto do silício quanto do catalisador, que se deve ao grau de cobertura da superfície do silício pelo catalisador. Observou-se ainda que os parâmetros de desempenho se correlacionam melhor com a área geométrica do que com a área específica medida pelo método de adsorsão de N2 (BET). Os elementos Ca, Al e Fe, na forma que foram adicionados, mostraram algum efeito sobre os parâmetros de desempenho da reação, porém verificou-se que o efeito das impurezas é maior se estas estiverem presentes originalmente no silício. / Some important aspects of dimethyldichlorosilane direct synthesis from methyl chloride and both chemical grade silicon and high purity silicon (99.999%) catalyzed by copper and promoters in a fluidized bed reactor was studied. The effects of temperature on the activation process and on the reaction were studied to obtain an estimate of the apparent activation energy for each process step. The influence of average particle diameter of silicon and of catalyst and the effect of Ca, Al and Fe additions in the catalyst system were also evaluated. A discussion about the so-called isokinetic compensation behavior which is observed in the direct synthesis is presented. The proposed explanation about the origin of this phenomena is based on the anisotropic character of the reaction. A complementary explanation about the mechanism of promoters action was also proposed. The obtained values of apparent activation energies are within the range reported in the literature. Selectivity and activity showed some variation with both catalyst and silicon particle sizes. This behavior was explained in terms of silicon particle coverage by the catalyst system. The performance parameters show better correlation with the geometric area measured by laser diffraction than with the BET area obtained by N2 adsorption. The promoters Ca, Fe and Al have shown effect over the reaction, however these effects were more proeminent if they are originally present in silicon structure.
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Estudo da síntese de dimetildiclorosilano a partir de cloreto de metila e silício. / Study of the synthesis of dimethyldichlorosilane from methyl chloride and silicon.João Guilherme Rocha Poço 22 March 2001 (has links)
No presente trabalho foi realizado um estudo de alguns aspectos da reação de obtenção de dimetildiclorosilano a partir da reação entre silícios grau químico (SiGQ) ou de elevada pureza (99,999%) e cloreto de metila catalisada por cobre e promotores em reator de leito fluidizado. Foram estudados os efeitos da temperatura sobre o processo de ativação e sobre a reação com o fim de obter um valor aproximado da energia aparente de ativação para cada uma dessas etapas; o efeito do tamanho médio das partículas de silício e do catalisador sobre os parâmetros de desempenho da reação e o de contaminantes usuais do SiGQ, a saber Ca, Fe e Al, sobre silício de elevada pureza (99,999%). Uma discussão sobre o efeito de compensação característico da reação direta foi realizada sendo proposta uma explicação da origem desse efeito, que aparentemente se deve ao caracter anisotrópico da reação, e uma explicação complementar com relação ao papel dos promotores na reação. Os resultados mostraram que a energia aparente de ativação obtida por meio dos experimentos realizados neste estudo encontram-se em valores próximos ao normalmente encontrado na literatura. Aparentemente existe uma variação da seletividade com a variação do tamanho de partícula tanto do silício quanto do catalisador, que se deve ao grau de cobertura da superfície do silício pelo catalisador. Observou-se ainda que os parâmetros de desempenho se correlacionam melhor com a área geométrica do que com a área específica medida pelo método de adsorsão de N2 (BET). Os elementos Ca, Al e Fe, na forma que foram adicionados, mostraram algum efeito sobre os parâmetros de desempenho da reação, porém verificou-se que o efeito das impurezas é maior se estas estiverem presentes originalmente no silício. / Some important aspects of dimethyldichlorosilane direct synthesis from methyl chloride and both chemical grade silicon and high purity silicon (99.999%) catalyzed by copper and promoters in a fluidized bed reactor was studied. The effects of temperature on the activation process and on the reaction were studied to obtain an estimate of the apparent activation energy for each process step. The influence of average particle diameter of silicon and of catalyst and the effect of Ca, Al and Fe additions in the catalyst system were also evaluated. A discussion about the so-called isokinetic compensation behavior which is observed in the direct synthesis is presented. The proposed explanation about the origin of this phenomena is based on the anisotropic character of the reaction. A complementary explanation about the mechanism of promoters action was also proposed. The obtained values of apparent activation energies are within the range reported in the literature. Selectivity and activity showed some variation with both catalyst and silicon particle sizes. This behavior was explained in terms of silicon particle coverage by the catalyst system. The performance parameters show better correlation with the geometric area measured by laser diffraction than with the BET area obtained by N2 adsorption. The promoters Ca, Fe and Al have shown effect over the reaction, however these effects were more proeminent if they are originally present in silicon structure.
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Etude des propriétés électriques des élastomères silicones utilisés pour l'isolation électriqueNguyen, Duc Hoang 28 November 2005 (has links) (PDF)
Les élastomères silicones sont déjà largement utilisés dans l'isolation électrique extérieure grâce à la bonne tenue aux contraintes climatiques et à la hydrophobicité. Ils commencent aujourd'hui à être utilisés dans l'isolation volumique pour des applications haute tension. L'objectif de cette thèse était d'analyser plus profondément les propriétés diélectriques et électriques, peu connues, dans ces polymères.<br />L'originalité de ces études porte sur la gamme importante de température étudiée (100-430K), la mesure des propriétés diélectriques dans des très basses fréquences (10-4Hz–1MHz), la mesure de charges d'espace par un dispositif de type ‘onde de pression' et la mesure de courants faibles (jusqu'à 50fA). Deux familles d'élastomères silicones ont été étudiées : des RTV et des LSR comportant des charges de renfort de silice. L'évolution de ces propriétés lorsque ces matériaux sont soumis à des contraintes électrothermiques (16 kV/mm à 353K) pendant un an est également menée. <br />Des comportements classiquement observés dans les polymères ont été identifiés comme l'injection de charges d'espace, de type Schottky. Cependant, des comportements plus spécifiques ont été identifiés : (i) des courants de conduction sub-linéaires, (ii) des courants de dépolarisation qui s'inversent et qui présentent une réponse chaotique, (iii) des réponses diélectriques de type loi de puissance fractionnelle, (iv) de la dispersion dans les basses fréquences après vieillissement. Ces comportements particuliers sont principalement attribués à des effets d'électrode bloquante et des mécanismes de conduction dans les clusters présents aux interfaces PDMS–silice.<br />L'étude en spectroscopie diélectrique dans les très basses fréquences s'est avérée être un outil précieux de caractérisation de l'ensemble de ces phénomènes.
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Fluidic Tuning of a Four-Arm Spiral-Based Frequency Selective SurfaceWells, Elizabeth Christine 2011 May 1900 (has links)
Frequency selective surfaces (FSSs) provide a variety of spatial filtering functions, such as band-pass or band-stop properties in a radome or other multilayer structure. This filtering is typically achieved through closely-spaced periodic arrangements of metallic shapes on top of a dielectric substrate (or within a stack of dielectric materials). In most cases, the unit cell size, its shape, the substrate parameters, and the inter-element spacing collectively impact the response of the FSS. Expanding this design space to include reconfigurable FSSs provides opportunities for applications requiring frequency agility and/or other properties. Tuning can also enable operation over a potentially wider range of frequencies and can in some cases be used as a loading mechanism or quasi-ground plane. Many technologies have been considered for this type of agility (RF MEMS, PIN diodes, etc.). This includes the recent use of microfluidics and dispersions of nanoparticles, or fluids with controllable dielectrics, which have entered the design space of numerous other EM applications including stub-tuners, antennas, and filters. In this work they provide a material based approach to reconfiguring an FSS.
An FSS based on a four-arm spiral with tunable band-stop characteristics is presented in this work. A thin colloidal dispersion above each element provides this tuning capability. The radial expansion and contraction of this dispersion, as well as the variable permittivity of the dispersion, are used to load each element individually. This design incorporates thin fluidic channels within a PDMS layer below the substrate leading to individual unit cells that provide a closed pressure-driven subsystem that contains the dispersion. With the capability to individually control each cell, groups of cells can be locally altered (individually or in groups) to create gratings and other electromagnetically agile features across the surface or within the volume of a radome or other covering. Simulations and measurements of an S-band tunable design using colloidal Barium Strontium Titanate dispersed Silicone oil are provided to demonstrate the capability to adjust the stop-band characteristics of the FSS across the S-band.
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Formulation et évaluation de la stabilité et de l’efficacité de topiques protecteurs vis-à-vis des composés organophosphorés / Formulation and assessment of stability and efficacy of topical skin protectant against organophosphorus compoundsMillerioux, Jennifer 20 March 2009 (has links)
Les neurotoxiques organophosphorés (NOP) sont extrêmement toxiques et peu volatils. Dans des conditions normales de température et de pression, ils peuvent pénétrer rapidement la peau sous forme liquide et exercer leurs effets délétères. En milieu civil ou militaire, leur utilisation potentielle est toujours redoutée. Le développement de dispositifs de protection cutanée vis-à-vis de ces agents est donc d’un intérêt majeur pour les armées et la sécurité civile. Dans ce contexte, les objectifs de ce travail ont été de formuler et évaluer la stabilité et l’efficacité de topiques protecteurs cutanés (TP) vis-à-vis des NOP. Le premier objectif a consisté à mettre au point des TP de compositions et de formes galéniques différentes (émulsions, gels) puis à valider leurs stabilités physicochimiques. Cent trente TP ont été formulés et 30 ont montré une stabilité physicochimique satisfaisante. Le second objectif a été d’évaluer l’efficacité des TP les plus prometteurs vis-à-vis des composés organophosphorés. Actuellement il n’existe pas de standardisation de ce type d’étude. Par conséquent, l’utilisation de plusieurs tests in vitro et in vivo (membranes biologiques ou synthétiques, NOP ou simili), dont la pertinence et la fiabilité ont été déterminées, nous a permis d’établir une logique de criblage pour l’évaluation de l’efficacité des TP. Parmi les 13 formulations testées, les résultats ont montré qu’un gel hydro-alcoolique apporte une protection cutanée significative et supérieure aux produits de référence testés vis-à-vis du VX, un NOP d’intérêt / Prevention of exposure to the neurotoxic organophosphorus compounds (OP) that are quickly absorbed in the skin is a major concern both for pesticide users and soldiers. Skin barrier creams are being developed to complement or replace uncomfortable chemical protective suits. The objectives of this work were to formulate and assess physicochemical stability and protective efficacy of topical skin protectant (TSP) against OP compounds. The first objective was to formulate several different TSP (emulsions, gel) and validate their physicochemical stability.The second objective was to determine the consistency of results from in vitro tests and the importance of the formulation composition in the skin protective efficacy. Quick evaluation of formulations efficacy mainly relies on in vitro tests which lead to consistent, complementary and relevant results. Our results indicated that the least effective formulations could be quickly identified by performing in vitro permeation tests with silicone membrane and by evaluating interfacial interactions between formulations and OP. We showed that a hydrogel containing specific hydrophilic polymers was by far the most effective of the formulations evaluated against VX, OP compounds, skin permeation in vitro
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Intraokularlinse Acri. Lyc 59 RET® mit unveränderter Brechkraft bei Silikonöltamponade / Acri. Lyc 59 RET ® IOL for unchanged refractive power with silicone oil tamponadeBaraki, Husnia 20 June 2011 (has links)
No description available.
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Remoção endoscópica de anel em pacientes submetidos á derivação gástrica em y de Roux utilizando prótese plástica autoexpansívelMAGALHÃES NETO, Galeno Egydio José de 19 February 2014 (has links)
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Previous issue date: 2014-02-19 / O uso de anel na derivação gástrica em Y de Roux (DGYR) está associado à
intolerância alimentar pós-operatória, cujo tratamento clássico tem sido a remoção
cirúrgica. Um novo método utilizando prótese plástica autoexpansível (PPAE) induz
erosão intragástrica do anel, o qual é removido por via endoscópica de forma
minimamente invasiva. Objetiva-se analisar a eficácia e a segurança dessa técnica
de remoção de anel após DGYR. Estudo prospectivo longitudinal de série de 41
pacientes com intolerância alimentar associada à presença de anel, que foram,
tratados por via endoscópica, entre 2007 e 2013. O grupo apresentava média de
idade igual a 44,1 anos, IMC médio de 27,0 Kg/m², e vômitos foram os sintomas mais
frequentes (n=37), com ocorrência diária em 46,3%. O sucesso terapêutico foi
definido como a melhora dos sintomas após a remoção do anel. O implante de PPAE
foi realizado sob anestesia geral e guiado por radioscopia, sendo utilizado endoscópio
padrão. Os pacientes receberam alta após 24 horas com dieta líquida e inibidor de
bomba de prótons (IBP), que foi prescrito durante o tempo médio de permanência da
PPAE, que foi de 15,3 dias. A prótese promoveu erosão completa de anel em 24
(58,5%) pacientes e no grupo restante, a remoção em segundo estágio após 7 dias
com pinça de corpo estranho. Houve três casos de migração da prótese com
eliminação espontânea por via retal. O efeito adverso mais comum foi vômito (n=7).
Não houve complicações graves, nem necessidade de remoção precoce da prótese.
Após seguimento médio de 6 meses, não houve mudança significativa no IMC e 78%
dos pacientes foram capazes de ingerir carne vermelha. A remoção do anel com uso
de prótese endoscópica demonstrou ser um procedimento seguro e eficaz, com100%
dos anéis sendo removidos com sucesso e 29,3% de ocorrência de eventos adversos
leves (vômitos). Esta técnica é uma alternativa adequada na remoção do anel,
evitando a intervenção cirúrgica e reduzindo a possibilidade de reganho de peso. / Ring dysfunction after roux-en-y gastric bypass (RYGB) causing delayed gastric emptying on
Fobi pouch is classically treated by surgical ring removal. In a novel way of using selfexpandable
stents, intraluminal erosion of the ring is achieved, allowing its removal by
endoscopy, with no need of surgery. No study has shown clinical applicability of this principle
in RYGB banded with silastic ring. In this case series we analyze endoscopic removal of noneroded
dysfunctional rings after RYGB using self-expandable plastic stents (SEPS). This is a
prospective case series of 41 patients with delayed gastric emptying secondary to extrinsic
compression of the ring after RYGB between 2007 and 2013. Successful ring removal,
symptoms improvement, weight control and adverse events were evaluated. Mean age of
subjects was 44.1 years, median BMI at treatment was 27.0 Kg/m2. Most common symptom
was vomiting (n=37), with daily occurrence in 46.3%. Success was defined as symptoms
improvement after stent and ring removal. SEPS placement was done under general
anesthesia and fluoroscopic guidance. A standard gastroscope (Pentax Medical, Montvale,
NJ), and a PolyflexTM stent (25x21x150mm) (Boston Scientific, Natick, MA) were used in all
cases. All patients were discharged after a 2-hour observation period, with liquid diet and
proton pump inhibitor. SEPS induced complete erosion in 24 patients, allowing for
simultaneous stent and ring removal. The median time of stenting was 15 days. There was
one case of stent migration, which was naturally expelled. Most common adverse event was
vomiting (n=7). There was no early stent removal, and no serious complications. After a mean
follow-up of 6 months, there was no significant change in mean BMI, and 78% of patients are
able to ingest solid foods. Endoscopic stents led to ring intraluminal erosion in 100% of
subjects, allowing for successful removal of dysfunctional rings. The procedure is technically
feasible and safe, with a 29.3% occurrence of mild adverse events (vomiting), and no serious
complications. It proved to be a reasonable alternative for ring removal in our casuistic,
avoiding surgery, and decreasing the possibility of weight regain.
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Dégradation bio-physico-chimique des élastomères silicones : Influence du catalyseur de polycondensation et impacts environnementaux / Bio-physico-chemical degradation of silicone elastomers : Influence of polycondensation catalyst and environmental impactsLaubie, Baptiste 24 October 2012 (has links)
Le classement de la famille des dibutylétains par l’Union Européenne comme reprotoxique et mutagène conduit les fabricants d’élastomères silicones à développer des solutions de remplacement de ces composés, largement employés comme catalyseur de réticulation. L’augmentation grandissante de la consommation de ce type d’élastomères amène à s’interroger sur leurs impacts dans les filières de traitement des déchets et sur l’influence du changement de catalyseur sur leur comportement environnemental. Ce domaine de recherche, très peu exploré, demande la mise en place d’une méthodologie spécifique, alliant des expériences de dégradations physico-chimiques et biologiques. Deux types d’élastomères simplifiés, réticulés par trois catalyseurs de polycondensation (un dibutylétain servant de référence et deux nouveaux) sont ciblés comme objet d’étude. Le premier axe, consacré à la matrice silicone, a permis de mettre en évidence une dégradation se déroulant en deux étapes successives, comme lors de la fin de vie de silicones fluides du type PolyDiMéthylSiloxane (PDMS). La première repose sur une hydrolyse chimique des chaînes siloxanes, formant majoritairement des oligosiloxanols (et principalement le monomère diméthylsilanediol) et des méthylsiloxanes cycliques (comme l’octaméthylcyclotétrasiloxane D4). La seconde est une biodégradation des sous-produits d’hydrolyse, aussi bien en aérobiose qu’en anaérobiose. Le second axe, consacré aux catalyseurs de polycondensation, prouve que ces composés prennent une place importante dans les mécanismes de dégradation. Ils impactent principalement les vitesses d’hydrolyse mais peuvent aussi influencer la nature des siloxanes relargués. De plus, ils ont des comportements totalement différents face à la dégradation biologique : ainsi, les catalyseurs organométalliques testés sont assimilables par les micro-organismes comme source primaire de carbone, alors que le catalyseur organique (un dérivé de guanidine) perturbe les métabolismes. Les composés biodégradables, même très peu mobiles en phase aqueuse, sont biodisponibles dans les élastomères et ont un impact sur la diversité des communautés bactériennes. Un champignon du genre Fusarium est d’ailleurs identifié comme capable de métaboliser une des nouvelles molécules développées. Le remplacement des dibutylétains permet de diminuer indiscutablement la toxicité des catalyseurs utilisés dans les élastomères silicones. La méthodologie mise en œuvre apporte de nombreuses informations quant aux impacts environnementaux et pourrait être transposée sans difficulté à l’étude d’autres matériaux. / Dibutyltin compounds are widely used as crosslinking catalysts in silicone elastomer industry. The classification of dibutyltins by the European Union as mutagenic and reprotoxic molecules lead manufacturers of silicone materials to develop alternatives. The increase of silicone elastomers demand requires to study their impacts during waste treatment and to assess the influence of the catalyst change on their environmental behavior. This unexplored area of research requires the establishment of a specific methodology, combining physico-chemical and biological degradation experiments. Two types of simplified elastomers are targeted in this study. They are crosslinked with three polycondensation catalysts: a dibutyltin derivative using as a reference and two new molecules. The first part, devoted to the silicone matrix, demonstrates a two stages degradation pathway in the environment. Silicone elastomers end-of-life is very similar to some silicone fluids, also known as PolyDiMethylSiloxanes (PDMS). The first stage is a chemical hydrolysis of siloxane chains, giving oligosiloxanols (mainly the monomer dimethylsilanediol) and cyclic methylsiloxanes (e.g. octamethylcyclotetrasiloxane D4). The second one is a biodegradation of hydrolysis by-products, in aerobic and anaerobic conditions. The second part, devoted to the polycondensation catalysts, demonstrates that these compounds play an important role in the degradation mechanisms. They mainly impact hydrolysis rates but also affect the nature of released products. In addition, they have a very distinct biological behavior: organometallic catalysts tested are assimilated as a single carbon source by microorganisms, while the organic catalyst (a derivative of guanidine) disrupts bacteria metabolism. Even if they have a limited mobility in the aqueous phase, biodegradable catalysts trapped in the silicone matrix are bioavailable and have an impact on bacterial communities. Moreover, a Fusarium fungus capable of metabolizing one of the new molecules developed is identified. The replacement of dibutyltin compounds undoubtedly reduces the toxicity of catalysts used to synthesized silicone elastomers. The methodology developed provides a lot of information about the environmental impacts of silicone elastomers and could be easily transposed to the study of other materials.
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Contribution to the development of an additive for bulk waterproofing of cement-based materialsMilenkovic, Nenad 02 October 2017 (has links)
For the last 10 years, silicone-based admixtures have been successfully used for bulk waterproofing treatment of cementitious materials. However, a reduction in mechanical properties of treated materials is rather observed and becomes a major problem for the in-situ application. A new concept of a knowledge-based integral water repellent has been designed in such a way that the negative effect on mechanical properties is significantly reduced. The technology comprises the delayed release of the hydrophobic agent (silicone resin) which is achieved by encapsulation of the resin in SiO2 shell. A multidisciplinary research was conducted in order to propose a model of the delayed release and the silica shell reaction mechanism in cement paste. Therefore, a study on the microcapsules reaction in calcium hydroxide solution was conducted by means of FTIR, DSC-TGA, surface tension measurements and chemical analysis by ICP-OES. It was shown that microcapsules flocculate in presence of Ca2+, what appears to be the main factor that contribute to the delayed release of the resin.The influence of the microcapsules on Ordinary Portland (OPC) and Blast furnace slag (BFS) cement hydration process was compared with the emulsion of silane monomer and silicone resin. It was shown that the emulsion delays the setting and influences the early age hydration by prolonging the dormant period and decreasing the hydration heat. Cement microstructure and hydration products development was observed by SEM/ESEM. Quantitative analysis of hydration products was assessed by Rietveld analysis of XRD diffractograms. Emulsion induced a significant delay in the cement paste setting by changing the amount and morphology of ettringite and portlandite at very early age. Differently, microcapsules didn’t show any effect on these properties. Experimental work on relevant mortars is done in order to prove the concept of a delayed release as a solution towards the decrease in mechanical properties. The influence of the new additive on setting, volume change, dynamic E-modulus and the compressive strength was analysed. New analytical techniques (AutoShrink, Ultrasonic Pulse Velocity and ConSensor) in combination with traditional ones (Penetration resistance test and compressive strength on cubes) were used. Microcapsules have successfully lowered the negative impact of silanes on the compressive strength and dynamic Young’s modulus. Moreover, it was showed that the microcapsules slightly influence autogenous deformation by increasing the shrinkage of mortars.Microencapsulation of the silicone resin proved to be a promising solution for the bulk hydrophobic treatment of cementitious materials with no-influence on cement hydration. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished
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