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Dynamic mechanical behavior and high pressure phase stability of a zirconium-based bulk metallic glass and its composite with tungstenMartin, Morgana 04 March 2008 (has links)
An investigation of the high-strain-rate mechanical properties, deformation
mechanisms, and fracture characteristics of a Zr-based bulk metallic glass (BMG) and its composite with tungsten was conducted through the use of controlled impact experiments and constitutive modeling. The overall objective of this research was to determine the high-strain-rate deformation and failure mechanisms of a BMG and its composite as a function of stress state and strain rate, and
describe the mechanical behavior over a range of loading conditions. The research involved performing controlled impact experiments on BMG
composites consisting of an amorphous Zr57Nb5Cu15.4Ni12.6Al10 (LM106) with
crystalline tungsten reinforcement particles. Monolithic LM106 was also examined to aid in the understanding of the composite. The mechanical
behavior of the composite was investigated over a range of strain rates (10^3 s^-1 to 10^6 s^-1), stress states (compression, compression-shear,
tension), and temperatures (RT to 600 C) to determine the dependence of mechanical properties and deformation and failure modes (i.e., homogeneous deformation vs. inhomogeneous shear banding) on these parameters. Mechanical
testing in the quasi-static to intermediate strain rate regimes was performed using an Instron, Drop Weight Tower, and Split Hopkinson Pressure
Bar, respectively. High-strain-rate mechanical properties of the BMG-matrix composite and monolithic BMG were investigated using dynamic compression (reverse Taylor) and dynamic tension (spall) impact experiments performed using a gas gun instrumented with velocity interferometry and high-speed digital photography. These experiments provided information about dynamic strength and deformation modes, and allowed for validation of constitutive models via comparison of experimental and simulated transient deformation profiles and free surface velocity traces. Hugoniot equation of state measurements were performed on the monolithic BMG to investigate the high
pressure phase stability of the glass and the possible implications of a high pressure phase transformation on mechanical properties. Specimens were recovered for post-impact microstructural and thermal analysis to gain information about the mechanisms of dynamic deformation and fracture, and to examine for possible shock-induced phase transformations of the amorphous phase.
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Micro-Raman spectroscopy and dry turning evaluations of nanostructured diamond films deposited on tungsten-carbide lathe insertsLawson, Thomas Ryan. January 2008 (has links) (PDF)
Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Description based on contents viewed June 2, 2008; title from title screen. Includes bibliographical references (p. 36).
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Contribution à l'étude quantique du carbure de tungstène neutre (WC) et ionisé (WCq+, q=1, 2) / Contribution to the quantum study of the tungsten carbide neutral (WC) and ionized (WCq+, q = 1, 2)Sabor, Said 18 April 2015 (has links)
Les carbures et oxydes des métaux de transition sont d'une importance capitale dans le domaine industriel voir catalytique. Le carbure de tungstène WC a été identifié comme un bon substituant des métaux nobles tel que le platine dans le domaine catalytique. Le but de ce travail de thèse est d'appliquer des méthodes de chimie quantique les plus poussées pour déterminer la structure électronique, la stabilité et la nature de liaison chimique des diatomiques WC et WC2+. Notre recherche préliminaire est motivée par les données spectroscopiques disponibles sur W, W+, W2+, WC et WC2+. La méthodologie adoptée, CASSCF/MRCI/MRCI+Q/aug-cc-pV5Z(-PP) implémentée dans le code MOLPRO, consiste à réaliser des calculs quantique tenant en compte des effets de corrélation et relativistes avec un traitement spécifique du couplage spin−orbite pour la recherche des courbes d'énergie potentielle de l'état fondamental et des états excités de plus basses énergies de WCn+ (n=0-2) tout en utilisant une base suffisamment étendue. Les résultats de ce travail sont en bon accord avec ceux disponibles dans la littérature. En outre, dans ce travail nous avons confirmé pour la première fois que le carbure diatomique dicationique WC2+ est thermodynamiquement stable / Metal carbides and oxides are more interesting in catalytic and industrial domains. Tungsten carbide WC has been detected as serious substituent of platinum Pt catalytic. The ultimate goal of this thesis is theoretical studies of electronic structure, stability and the bound nature on WC, WO and its cations. Our preliminary research were motiving by the available spectroscopic data on W, W+, W2+, WC et WC2+. We used the methodology (CASSCF/MRCI/MRCI+Q/aug-cc-pV5Z(-PP)) implemented on MOLPRO package to perform quantum calculations with high accuracy taking into account the correlation and relativistic effects with a specific treatment of spin orbit coupling for some low lying excited electronic states of WCn+, (n=0, 1 et 2). Our results are shown in good agreement with those available in the literature. Furthermore, in this work for the first time we demonstrated that a carbide dication (WC2+) is thermodynamically stable
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Investigation of novel cooling methods to enhance aerospace component manufacturing practicesKoen, Devan 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The aerospace industry actively pursues innovation, especially in materials and their use in new
applications, to improve their aircraft as well as their competitive position. Ti-6Al-4V has been available
now for more than 50 years. Yet, in the new generation of aircraft using structural composites,
a dramatic increase in the proportion of Ti-6Al-4V will be seen along with emerging application in
automotive and chemical industries. This material possesses superior material properties compared to
conventional materials such as steel and aluminium, although it is at the expense of machinability.
Researchers are therefore actively searching for improved cutting technologies to improve production
rates for Ti-6Al-4V. At higher cutting speeds than the industry norm of 60 - 90 m/min, machining
becomes a challenge, resulting in low productivity on titanium parts.
The limiting factor in the machining of Ti-6Al-4V is high tool temperatures of the order of 1000oC, caused
by its resistance to absorb heat and good mechanical strength at elevated temperatures. The result is
extreme temperatures that are concentrated on the cutting edge of the tool. The challenge to improve
the tool life is therefore focused on removing heat from the insert. Liquid nitrogen was identified as a
good candidate as coolant with the additional advantage of being environmentally friendly.
The research presented investigates the use of a gravity feed enclosed liquid nitrogen cooling system to
improve the tool life of the cutting inserts. The liquid nitrogen is contained on the insert rake face by
means of a tool cap. To improve the effectiveness of the cooling method, a polycrystalline diamond
(PCD) insert was used. This insert has a considerably higher thermal conductivity that aids in cooling the
cutting edge. Tungsten carbide inserts are used for benchmark testing.
The round tungsten carbide inserts with conventional cooling performed exceptionally well for
machining titanium compared to square inserts, yielding exceptional tool life improvements while
significantly increasing the material removal rate.
Positive results were recorded with the liquid nitrogen cooling system when used with the
polycrystalline diamond cutting insert. A number of far reaching performance issues are identified
relating to the design of the tool cap that hindered clear scientific outputs. From a research perspective,
the project makes a contribution to the knowledge base in this field. Additionally a new approach in
cooling was investigated, resulting in clear indications of design changes required. / AFRIKAANSE OPSOMMING: Die lugvaart industrie streef aktief innovasie na, veral op die gebied van materiale en hul gebruike, om
hul vliegtuie en kompeterende posisie in die mark te verbeter. Ti-6Al-4V is al vir meer as 50 jaar
beskikbaar. ‘n Drastiese verhoging in die aanvraag na Ti-6Al-4V deur die lugvaart, motor en chemiese
industrieë word verwag wanneer die volgende geslag vliegtuie wat koolstofvesel as strukturele
materiaal begin gebruik, in produksie gaan. Die materiaal het beter materiaaleienskappe as
konvensionele materiale soos staal en aluminium, maar dit kom egter teen die prys van
masjieneerbaarheid. Ti-6Al-4V se masjienering bo die industrie norm van 60 – 90m/min is ‘n groot
uitdaging. Navorsers soek daarom deurentyd na verbeterde sny tegnologieë om die produksie tempo
van Ti-6Al-4V te verbeter.
Die beperkende faktor vir Ti-6Al-4V masjienering is die temperatuur wat genereer word. Die weerstand
van die materiaal om hitte te absorbeer en sy goeie meganiese eienskappe veroorsaak dat temperature
in die beitel 1000oC bereik. Hierdie temperature word egter op die snykant van die beitel gekonsentreer.
Die uitdaging is dus om hierdie temperature in die beitel te beheer. Vloeibare stikstof is geïdentifiseer as
‘n goeie kandidaat vir verkoeling met die bykomende voordeel dat dit omgewingsvriendelik is.
Die navorsing wat hier uiteengesit word, ondersoek die gebruik van ‘n geslote kamer
beitelverkoelingstelsel wat deur gravitasie met vloeibare stikstof voorsien word om die beitel leeftyd te
verbeter. Die oppervlak van die beitel word in hierdie konsep direk aan die vloeibare stikstof
blootgestel. Om die effektiwiteit van die stelsel te verbeter word van PCD beitels gebruik gemaak. Die
beitel se verbeterde hittegeleidingsvermoë help om die beitel se snykant koel te hou. Tungstenkarbied
beitels word gebruik om ‘n standaard te stel vir eksperimentele analise.
Die ronde tungstenkarbied beitels en konvensionele verkoeling het verstommend goed presteer vir
Ti-6A-4V masjienering in vergelyking met vierkantige beitels. Die materiaalverwyderingstempo is
aansienlik verhoog sonder om die beitel se leeftyd in te boet.
Positiewe resultate is waargeneem met die vloeibare stikstof sisteem saam met die PCD beitels. ‘n
Aantal verreikende uitdagings is geïdentifiseer wat suiwer wetenskaplike afleidings bemoeilik. Hierdie
probleme kan almal aan die ontwerp van die toerusting toegeskryf word. Die werk lewer egter steeds ‘n
bydrae tot die kennis in die veld. ‘n Bykomende benadering vir verkoeling is ondersoek wat duidelik
ontwerp-veranderings aandui.
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Synthèse et caractérisation structurale et diélectrique de céramiques et de monocristaux relaxeurs de structure TTB / Synthesis, structural and dielectric characterization of relaxor ceramics and single-crystals with TTB structureAlbino, Marjorie 20 September 2013 (has links)
La structure bronze quadratique de tungstène, grâce à sa flexibilité cristallochimique, est une candidate légitime pour le développement de matériaux fonctionnels. L’étude des propriétés diélectriques, pyroélectriques, et ferroélectriques de céramiques de formulation Ba2NdFeNb4-xTaxO15 montre un crossover relaxeur-ferroélectrique-paraélectrique, avec une hystérèse thermique de la transition ferroélectrique. L’étude structurale des monocristaux relaxeurs Ba2LnFeNb4O15 (Ln=La, Pr, Nd, Sm, Eu), obtenus par la méthode du flux, a mis en évidence une structure modulée. L’affinement de la structure de base prouve l’existence de moments dipolaires dans le plan ab (dus à une distorsion des octaèdres [NbO6]). Afin d’établir un lien entre la structure cristalline et les propriétés d’un composé dérivé du multiferroïque MnWO4, la croissance en four à image de Mn0,85Mg0,15WO4 a été entreprise avec succès. / Tetragonal Tungsten Bronze structure, thanks to its compositional flexibility, is a legitimate candidate for the development of functional materials. Study of dielectric, pyroelectric, and ferroelectric properties of Ba2NdFeNb4-xTaxO15 ceramics reveals a relaxor-ferroelectric-paraelectric crossover, with thermal hysteresis of the ferroelectric transition. Structural analysis of Ba2LnFeNb4O15 (Ln=La Pr, Nd, Sm, Eu), relaxor single crystals obtained by flux method, highlighted a modulated structure. Refinement of the basic structure proves the existence of a dipolar moment in the ab plane (induced by a distortion of [NbO6] octahedra). In order to establish a correlation between the crystal structure and the properties of a compound derived from multiferroic MnWO4, the crystal growth in image furnace of Mn0,85Mg0,15WO4 was successfully undertaken.
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Sintese e sinterizacao de pos compositos do sistema W-CuCOSTA, FRANCINE A. da 09 October 2014 (has links)
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[en] HOURLY LOAD FORECASTING A NEW APPROACH THROUGH DECISION TREE / [pt] PREVISÃO DE CARGA HORÁRIA UMA NOVA ABORDAGEM POR ÁRVORE DE DECISÃOANA PAULA BARBOSA SOBRAL 08 July 2003 (has links)
[pt] A importância da previsão de carga a curto prazo (até uma
semana à frente) em crescido recentemente. Com os processos
de privatização e implantação de ompetição no setor
elétrico brasileiro, a previsão de tarifas de energia vai se
tornar extremamente importante. As previsões das cargas
elétricas são fundamentais para alimentar as ferramentas
analíticas utilizadas na sinalização das tarifas. Em
conseqüência destas mudanças estruturais no setor, a
variabilidade e a não-estacionaridade das cargas elétricas
tendem a aumentar devido à dinâmica dos preços da energia.
Em função das mudanças estruturais do setor elétrico,
previsores mais autônomos são necessários para o novo
cenário que se aproxima.
As ferramentas disponíveis no mercado internacional para
previsão de carga elétrica requerem uma quantidade
significativa de informações on-line, principalmente no que
se refere a dados meteorológicos. Como a realidade
brasileira ainda não permite o acesso a essas informações
será proposto um previsor de carga para o curto-prazo,
considerando restrições na aquisição dos dados de
temperatura.
Logo, tem-se como proposta um modelo de previsão de carga
horária de curto prazo (um dia a frente) empregando dados
de carga elétrica e dados meteorológicos (temperatura)
através de modelos de árvore de decisão. Decidiu-se
pelo modelo de árvore de decisão, pois este modelo além de
apresentar uma grande facilidade de interpretação dos
resultados, apresenta pouquíssima ênfase em sua utilização
na área de previsão de carga elétrica. / [en] The importance of load forecasting for the short term (up
to one-week ahead) has been steadily growing in the last
years. Load forecasts are the basis for the forecasting of
energy prices, and the privatisation, and the introduction
of competitiveness in the Brazilian electricity sector,
have turned price forecasting into an extremely important
task.
As a consequence of structural changes in the electricity
sector, the variability and the non-stationarity of the
electrical loads have tended to increase, because of the
dynamics of the energy prices. As a consequence of these
structural changes, new forecasting methods are needed to
meet the new scenarios.
The tools that are available for load forecasting in the
international market require a large amount of online
information, specially information about weather data.
Since this information is not yet readily available in
Brazil, this thesis proposes a short-term load forecaster
that takes into consideration the restrictions in the
acquisition of temperature data.
A short-term (one-day ahead) forecaster of hourly loads is
proposed that combines load data and weather data
(temperature), by means of decision tree models. Decision
trees were chosen because those models, despite being easy
to interpret, have been very rarely used for load
forecasting.
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Vidros fosfatos com tungstênio: incorporação de cátions alcalinos e sua influência nas propriedades estruturais e condutoras / Phosphate glasses with Tungsten: incorporation of alkaline cations and its influence on structural and conductive propertiesMunhoz, João Fernando Villarrubia Lopes 23 March 2018 (has links)
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Previous issue date: 2018-03-23 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Many glasses have been studied as solid
electrolytes in behalf of replacing commercial liquid electrolytes. However, even
for the best glass compositions available in the literature, values of conductivity
similar to those presented by liquids are far beyond to be achieved. This work
intends to show how changes in the structure, by means of composition, can help
to increase the conductivity in oxide glasses. Samples with composition x WO3 -
0.30 (NaPO3)n - (0.70-x) NaF, with 0,30 ≤ ≤ 0,60;, were produced by melting
quenching methodology. Substitution of tungsten for sodium fluoride generates a
linear decrease of glass transition temperature while the stability remains high
enough up to = % and decreasing for higher WO3 content. Raman and
31P and 19F 1D MAS-NMR spectroscopies data shows that the less NaF leads to a
depolymerization of main phosphate chains, due to formation of − −
bonds. In addition, fluorine atoms prefer to bind in the − form, with low
tungsten content, or in − , with high proportion All samples showed same
calculated values of Ea for ionic conductivity and drop of σ0. For higher fluoride
proportion, it was observed a rise in the conductivity of around one order of
magnitude. However, UV-Vis absorption curves demonstrate more presence of
W5+ species in samples with ≥ %. This leads to a mixed conductivity
of these materials.
In order to obtain maximum ionic conductivity, NaF and (NaPO3)n were replaced
by Li2O and (LiPO3)n respectively. Samples with composition x WO3 – 0.40
(LiPO3)n – (0.60-x) Li2O, with 0.30 ≤ ≤ 0.50; 0.40 WO3 – y (LiPO3)n – (0.60-
y) Li2O, with 0.30 ≤ ≤ 0.50 and z WO3 – (0.80-z) (LiPO3)n – 0.20 Li2O, with
0.30 ≤ ≤ 0.50; were also produced using the melting quenching methodology.
The three series of samples presented linear increase of Tg with their respective
substitutions, besides having good thermal stability (> 100 °). Raman and 31P
1D MAS-NMR spectroscopies data exhibited the influence of WO3 content on the
depolymerization of phosphate chains, as well as the formation of WO6 unit
clusters, when much tungsten is present. Although UV-Vis absorption spectra
indicate mixed conductivities in some samples, calculated values of ionic
conductivity show that the most conductive sample without presence of reduced
species reached 6.3 10−4Ω−1−1, comparable to conductive crystalline
samples. / Muitos vidros têm sido estudados como eletrólitos sólidos, a fim de substituírem eletrólitos líquidos comerciais. No entanto, mesmo para composições vítreas ótimas na literatura, valores de condutividade similares àqueles presentes pelos líquidos estão muito além do alcançado. Este trabalho pretende mostrar como as mudanças na estrutura, por meio da composição, podem
ajudar a aumentar a condutividade em vidros óxidos.
Amostras com composição x WO3 – 0,30 (NaPO3)n – (0,70-x) NaF, com 0,30 ≤ ≤ 0,60; foram produzidas por meio da metodologia fusão/resfriamento. Substituição de tungstênio por fluoreto de sódio gera um decréscimo linear da temperatura de transição vítrea, enquanto que a estabilidade permanece alta até = 40 % e decresce para alto teor de WO3. Dados de Espectroscopias Raman e 31P e 19F MAS-NMR mostram que pouco NaF leva a despolimerização das cadeias principais de fosfato, devido a formação de ligações − − . Além disso, átomo de flúor prefere ligar-se na forma − , com baixa proporção de tungstênio, ou em − , com alta proporção. Todas as amostras apresentaram mesmos valores calculados de energia de ativação para condutividade iônica e queda de σ0. Para maior proporção de fluoreto, observou-se um incremento por volta de uma ordem de magnitude. Entretanto, curvas de absorção no UV-Vis demonstrou a maior presença de espécies W5+ em amostras com ≥ 50 % . Isto leva a uma condutividade mista destes materiais.
A fim de se obter condutividade iônica máxima, NaF e (NaPO3)n foram substituídos por Li2O e (LiPO3)n respectivamente. Amostras com composições x WO3 – 0,40 (LiPO3)n – (0,60-x) Li2O, com 0,30 ≤ ≤ 0,50; 0,40 WO3 – y
(LiPO3)n – (0,60-y) Li2O, com 0,30 ≤ ≤ 0,50 e z WO3 – (0,80-z) (LiPO3)n – 0,20 Li2O, com 0,30 ≤ ≤ 0,50; também foram produzidas por meio da metodologia fusão/resfriamento. As três séries de amostras apresentaram incremento linear de Tg com suas respectivas substituições, além de terem boa estabilidade térmica (> 100 °). Dados de Espectroscopia Raman e 31P MAS-NMR registraram a influência do teor de WO3 na despolimerização das cadeias de fosfato, bem a formação de clusters de unidades de WO6, quando muito tungstênio se faz presente. Apesar de curvas de absorção no UV-Vis indicarem a
condutividade mista em algumas amostras, valores calculados de condutividade iônica mostram que a amostra mais condutora e sem a presença de espécies reduzidas, atingiu 6,3 10−4 Ω−1−1, comparável com amostras cristalinas condutoras. / CNPq: 141905/2013-1
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Etude et optimisation de la stabilité thermique du silicure et du beol intermédiaire pour l'intégration 3D séquentielle / Study and optimization of silicide and intermediate beol thermal stability for 3D sequential integrationDeprat, Fabien 16 March 2017 (has links)
Une alternative à la réduction des dimensions caractéristiques des transistors est la 3D séquentielle. L’intégration 3D séquentielle requiert la fabrication de plusieurs niveaux de composant directement les uns au dessus des autres. Les procédés de fabrication utilisables pour les niveaux supérieurs sont limités par le budget thermique maximal que peuvent supporter les niveaux inférieurs. Pour la technologie FDSOI cette limite est fixée entre 500 °C et 550°C, 5 h dépendant de la siliciuration utilisée. Malgré le travail fourni pour réduire le BT des procédés de fabrication du transistor FDSOI, il est difficile d’atteindre cette limite pour certaines étapes, comme l’épitaxie des sources et drains surélevés. Dans ce contexte, cette thèse propose d’étudier et d’améliorer la stabilité thermique des niveaux bas, c’est à dire des transistors FDSOI et des niveaux de routages intermédiaires. L’étude de stabilité thermique du transistor FDSOI a permis d’identifier le siliciure comme étant l’élément le plus sensible aux budgets thermiques. Sa détérioration entraîne la dégradation de la résistance d’accès du transistor et favorise la diffusion du siliciure dans le canal. L’utilisation du Ni0.90Pt0.10 est limitée à 500 °C, 5 h, celle du Ni0.85Pt0.15 à 550 °C, 5 h. En alternative au NiPt, un nouveau siliciure a été étudié : le Ni0.90Co0.10. Afin de repousser sa stabilité thermique à 600 °C, 2 h, son intégration a dû être couplée à deux facteurs d’améliorations : l’amorphisation partielle des sources et drains par implantation et l’intégration d’un film de silicium intrinsèque epitaxié au-dessus des sources et drains composés de Si0.70Ge0.30. Les effets de ces différents « boosters » ont ainsi été analysés et expliqués. Pour la première fois, les avancées obtenues ont été implémentées sur des dispositifs FDSOI du noeud 14 nm. Ce premier essai est concluant car des performances identiques aux transistors pMOS fabriqués avec le siliciure Ni0.85Pt0.15, étudié depuis les années 2000, ont été obtenues. Néanmoins, la stabilité thermique évaluée sur transistor Ni0.90Co0.10 reste à améliorer. L’intégration de niveaux de routage entre les niveaux de transistors requiert des matériaux thermiquement stables et peu contaminants. Dans cette optique, la stabilité thermique d’une liste de diélectriques a été étudiée et caractérisée principalement par ellipsométrie, FTIR et ellipsométrie-porosimértie. Ainsi des couples isolant/barrière ont pu être déterminés pour chaque budget thermique appliqué entre 500 °C et 600 °C, 2 h. En ce qui concerne le métal intermédiaire, le tungstène a été étudié comme matériau conducteur, en plus du cuivre, en raison de son caractère moins contaminant. Ces deux matériaux ont montré une bonne stabilité thermique : jusqu’à 500 °C, 2 h pour le cuivre et 550 °C, 5 h pour le tungstène. Cependant, la résistance d'une ligne en cuivre est six fois moins résistante d'une ligne en tungstène. Cette valeur pourra être abaissée dans le cas de l’utilisation d’une nouvelle barrière en tungstène sans fluore qui a été étudiée et intégrée avec succès. Pour finir, la fiabilité du diélectrique à l’état de l’art, le SiOCH poreux, a été analysé dans des structures intégrant des lignes en tungstène. Dans ces conditions, la durée de vie du diélectrique est estimée à 1e16 années. Malgré la diminution de cette valeur après budget thermique à 600 °C, 2 h, (1e7 années), celle-ci reste bien supérieure à celle du cuivre dans des conditions identiques. / The 3D sequential integration is a smart alternative to planar device scaling. In this integration, the stacked transistors are processed sequentially, thus implying the reduction of the top thermal budget processes in order to preserve the bottom levels. For the FDSOI technology, the maximum thermal budget is set at 500 °C, 2 h. Despite the work done to reduce the thermal budget of the FDSOI processes, it is difficult to comply with this limit, as for example for the epitaxial raised source and drain which would need a thermal budget limit relaxation. In the frame of this Ph.D work, the thermal stability of the FDSOI transistors and the intermediate Back-End-Of-Line have been studied and optimized. The FDSOI transistor silicide has been identified as the most sensitive element to the thermal budget. Its degradation imply the access resistance degradation and favor the diffusion of the silicide into the channel. For this purpose, the Ni0.90Co0.10 silicide has been studied. To increase its thermal stability up to 600 °C, 2 h, two enhancers have been integrated: the pre-amorphization implant and the integration of a silicon capping over the Si0.70Ge0.30 source and drain. The effects of these enhancers on the thermal stability have been analyzed and understood. In addition to those, the Ni0.90Co0.10 has been integrated for the first time on 14 nm node FDSOI transistors. This first attempt is positive: identical performances on pMOS transistors have been obtained with Ni0.90Co0.10 silicide compare to Ni0.85Pt0.15 silicide, which is studied since the 2000’s. However, the improvement of thermal stability is not yet achieved on FDSOI transistors with Ni0.90Co0.10 silicide. Concerning the stability of the intermediate BEOL, the stability of dielectrics has first been studied and characterized by ellipsometry, FTIR and ellipsometric–porosimetry. Thus, insulating/barrier pairs have been defined for each thermal budget between 500 °C and 600 °C, 2 h. The metal lines have been studied using a 28nm node layout. Due to its limited contaminant characteristic, tungsten has been analyzed in addition to copper. Both materials show a good thermal stability: 500 °C, 2 h for copper and 550 °C, 5 h for tungsten despite the higher resistivity of tungsten. A factor 6 has been measured between these two materials. The resistance of a tungsten line has been improved by the integration of a new barrier. Finally, the state of the art Back-End-Of-Line dielectric reliability, the porous SiOCH, has been studied, function of the thermal budget, in structure integrated tungsten metal lines. In these conditions, the dielectric lifetime is estimated at 1e16 years. Despite its reduction due to thermal budget at 600 °C, 2 h (1e7 years), the tungsten lifetime estimation remains higher than the one obtained with copper lines without thermal budget.
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Aktivace kolimačního systému lineárního urychlovače fotonovým zářením a její vliv na dávky obdržené personálem. / Activation of collimating system of linear accelerator through photon radiation and its impact on the doses received by the staff.KUBÍKOVÁ, Adéla January 2017 (has links)
The diploma thesis on the topic "Activation of Collimating System of Linear Accelerator through Photon Radiation and its Impact on the Doses Received by the Staff" is divided into two parts, a theoretical and a practical part. The introductory theoretical part is devoted to the basic information about ionizing radiation. What are the types of ionizing radiation, its characteristics, properties and sources of ionizing radiation. Furthermore, there are mentioned direct and indirect interactions of ionizing radiation, a brief description of charged particle accelerators, collimator systems and radioisotope irradiation devices. Another part deals with radiation protection, basic legislation, methods and principles of radiation protection, personal dosimetry and medical supervision of radiation workers. Literary sources, available internet links and valid legal regulations were used for the work. In the practical part, a number of measurements were carried out to measure and to analyse the doses of secondary radiation of the linear accelerator collimator system for different photon beam energies, depending on time, distance from source, position of radiologic assistant around the table when working with the patient, as well as sizes of irradiated field. The aim of the work was to find out how large the doses of secondary radiation are, although measurable, but their values are not sufficient to be detected by personal dosimeters of radiological assistants. Confirm the hypothesis that the doses from the secondary radiation of the linear accelerator collimator system are so low that the dose power does not exceed 0.031 mGy/hr. The results obtained from various measurements are processed into transparent tables and graphically displayed. Based on the results of the measurements, the hypotheses were confirmed.
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