Dissertations / Theses on the topic 'Electrode – tool'

Diplomová práce se zabývá problematikou volby grafitového materiálu využívaného pro výrobu nástrojových elektrod při elektroerozivní obrábění. Práce je rozdělena do třech částí. Teoretická rešerše nekonvenční technologie elektroerozivního obrábění vypracovaná dle uvedených zdrojů se nachází v první části práce. Dále je v práci proveden cenový průzkum EDM grafitových materiálů nabízených v České republice a na Slovensku. Čtyři odlišné stupně kvality grafitu (od stávajícího dodavatele firmy GAMARTIS TRADE s.r.o.) a jeden měděný materiál byly podrobeny experimentu, jehož účelem bylo zjištění závislosti mezi kvalitou grafitového materiálu (cena) a přesností vyhloubené kavity, opotřebením nástrojové elektrody, časem obrábění nebo také drsností povrchu.

This thesis deals with technology of electric discharge machining with emphasis on application of the principle of material removal on wire cut electric discharge machine. The main part is concentrated on wire cut electric discharge machining in terms of a small tool making shop. The goal of the thesis is to create a wire cut electric discharge machining workplace in the company with a focus on the production of cutting tools. The thesis defines requirements for each component of cutting tools and strategies for their machining. Machining of model part and subsequent technical - economic evaluation is included in the final part.

Controlling processes by electrochemical means is increasingly attracting the attention of organic and polymer chemists. Electrochemistry provides tunable parameters without requiring the addition of external compounds, often increasing system tolerance to impurities, thus facilitating reaction handling and switching among different stages. In the last decades, the main interest in polymer chemistry concerned the preparation of predetermined macromolecular architectures. Atom transfer radical polymerization (ATRP) is the most powerful and versatile method to build well-defined polymers, with narrow molecular-weight distribution and excellent retention of chain-end functionalities. ATRP is based on the reversible deactivation of propagating radicals, such as to extend the lifetime of polymer chains. Radical concentration in solution is always very low, ultimately minimizing their probability of terminating. The activation-deactivation equilibrium is generally governed by a metal catalyst, composed by copper and a polydentate amine ligand. The active form of the catalyst, [CuIL]+, generates radicals by reductive cleavage of the C–X bond in the alkyl halide initiator, RX. As a consequence of the electron transfer and the concurrent atom transfer, the deactivator [X–CuIIL]+ is formed. Generated radicals add to few monomer molecules (i.e. propagation reaction), then they are reverted to their dormant state by reacting with [X–CuIIL]+. Importantly, RX initiators should be highly reactive, as to ensure the simultaneous growth of all polymer chains, thereby targeting pre-determined molecular weights. Chain-end functionalities are preserved during the polymerization, thus enabling several post-polymerization processes and the building of copolymers with various compositions and topologies. The aim of this thesis is to affirm electrochemical tools as a primary, effective and accessible source for ATRP triggering and mechanistic analysis. Less than 20 years ago, electrochemistry was involved for the first time in ATRP, when standard reduction potentials of some common catalysts were determined by cyclic voltammetry (CV) and correlated to their catalytic performances. Since then, CV is a well-established technique to study the redox properties of ATRP catalysts and the relative affinity of CuI and CuII species for halide ions, hence predicting their activity in the polymerization. Moreover, many electrochemical procedures were arranged for the precise measurement of the activation rate constant, kact, which concerns the reaction between [CuIL]+ and RX. kact values spanning over a range of 12 orders of magnitude were measured with different techniques, in many environments. Among these techniques, the use of a rotating disk electrode allowed a fast, easy and highly reproducible measurement. This instrument was further exploited in this thesis work to set up a facile electrochemical procedure for the determination of the thermodynamic equilibrium constant of ATRP, KATRP. Essentially, the reaction between CuI species and RX was followed as for kact determination, but in the absence of a radical scavenger that had been used to kinetically isolate the activation step. The interplay between activation, deactivation and radical termination was monitored, and KATRP was obtained by elaborating the electrochemical response through an equation proposed by Fischer and recently slightly modified. The method was applied to different Cu catalysts, initiators, solvent/monomer combinations and temperatures, observing some trends in accordance with general ATRP understanding. Both kact and KATRP must be measured in the absence of halide ions, which strongly affect the speciation of CuI. Indeed, the amount of active [CuIL]+ is reduced by the formation of various halogenated CuI species, thus slowing down the reaction with RX. However, the drop in the rate of CuI consumption in the presence of different C_(X^- ) was used to estimate the association constant of X− to [CuIL]+ (i.e. CuI halidophilicity constant, K_X^I). A procedure to measure K_X^I from K_ATRP^app, obtained under various C_(X^- ), was reported and verified for an independently determined K_X^I value. Electrochemistry is not only used to study ATRP mechanism, but also to effectively trigger the polymerization process. In fact, an applied current or potential is used to re-generate CuI from [X–CuIIL]+, which accumulates in solution because of termination events. Electrochemically mediated ATRP (eATRP) uses electrons as a reducing agent, thus it is free of by-products and allows to start from a minimum amount of air-stable CuII, which is reduced in situ. Nonetheless, the traditional eATRP setup required a potentiostat and expensive Platinum electrodes. During my Ph.D., I tried to simplify the setup as to make eATRP a cost-effective and scalable technique. Various inexpensive and easily functionalizable materials were successfully used as cathodes for eATRP in both organic and aqueous media. These working electrodes allowed well-controlled polymerizations even under galvanostatic conditions (i.e. constant current steps), which permitted the use of two, instead of three electrodes, and the replacement of the potentiostat with a common current generator. Furthermore, these cathodes were coupled to a sacrificial Aluminum anode in a completely Pt-free setup. Finally, these materials did not release metal ions in solution during the polymerization, and their morphology was not modified, thus they could be re-used in consecutive experiments. One important feature of eATRP and ATRP in general is their high versatility. Actually, various types of monomers are suitable for these techniques. Instead, controlled polymerization of acidic monomers via ATRP was considered impossible until very recently. In 2016, Fantin at al. proved that growing chains of poly(methacrylic acid) in ATRP were affected by a cyclization reaction with loss of C-X functionalities, i.e. termination. Suitable conditions to overcome this issue were proposed and successful eATRPs of methacrylic acid were reported. This important achievement was extended to acrylic acid (AA), which is a biocompatible, largely used monomer. In this thesis, it is proved that AA polymerization was hampered by the same cyclization side reaction during eATRP. Indeed, some conditions that were suitable for methacrylic acid were successfully adapted to eATRP of AA. i) Chloride ions replaced bromides, and ii) polymerization rate was enhanced by using a cathode with large surface area, applying a strongly negative potential, compared to Eѳ of the catalyst, and optimizing the amount and the nature of other reactants. One way to broaden the applicability of ATRP is to design new ligands able to convey particular features to Cu catalysts. Herein, 4 new ligands are presented, in which the skeleton of the traditionally used tris(2-methylpyridyl)amine (TPMA) was modified with m-functionalized phenyl substituents. Electrochemical characterizations of Cu complexes with these ligands allowed to predict a lower activity toward RX, compared to parent TPMA, which was proved by kact determination. Nevertheless, these complexes were used to catalyze well-controlled eATRPs of methyl methacrylate in DMF, and oligo (ethyleneoxide) methyl ether methacrylate and methacrylic acid in water. Despite the low activity, these compounds were very stable even at acidic pH and can be used to tune the polymerization in extremely reactive system. The versatility of ATRP is also reflected by the application in different environments. Ionic liquids for example are attracting great interest as green solvents for polymerizations. In 1-butyl-3-methylimidazolium trifluoromethanesulfonate, the redox properties of common ATRP catalysts and initiators were investigated by CV, whereas kinetic studies were performed via rotating disk electrode. This work proved that the behavior of Cu complexes and RX in ILs is similar to the one observed in traditional organic solvents. Therefore, ILs are suitable media for controlled polymerizations, and particularly they should be applied as solvent for eATRP because they are sufficiently conductive without added supporting electrolytes. Dispersed media represent another eco-friendly environment for polymerizations. Although many industrial processes are based on (mini)emulsion systems, the vast majority of literature reports on ATRP concerns experiments in homogeneous solutions. ATRP in miniemulsion required the design of super hydrophobic catalysts that remained confined into hydrophobic droplets, whereby tuning the polymerization. During my Ph.D., I spent six months as a visiting student at Carnegie Mellon University, in the laboratory of Prof. Matyjaszewski, who discovered ATRP in 1995. There, I had the opportunity to work on ATRP in miniemulsion and emulsion. A new catalytic system was arranged, and effectively applied to eATRP and activators re-generated by electron transfer (ARGET) ATRP, in which a reducing agent is added to continuously re-generate CuI species. Common hydrophilic catalysts were combined to inexpensive surfactants to form ion pairs able to enter the monomer droplets and catalyze the process. Electrochemical and spectrochemical characterizations proved the interactions between the compounds and defined the different contributions from ion-pair and interfacial catalysis. Block copolymers, polymer stars and brushes were easily synthetized with this approach. Moreover, residual copper in precipitated polymers was very low, even < 1 ppm, thus avoiding the need of further purifications. The system was then adapted to emulsion ARGET-ATRP, taking advantage of the water-solubility of the catalyst, which is a requirement of emulsion polymerizations, where the process should occur in the aqueous phase. By using suitable hydrophilic initiators and finely tuning the stirring rate and the pre-emulsification procedure, well controlled ab initio emulsion ARGET-ATRPs were obtained, even with low surfactant amounts.<br>La possibilità di controllare processi per via elettrochimica riveste crescente attenzione nel mondo della chimica organica e della sintesi di polimeri. L’elettrochimica offre diversi parametri per intervenire sulle proprietà dei sistemi in oggetto, senza introdurre altri agenti chimici e spesso aumentando la tolleranza del sistema verso le impurezze. Di conseguenza la gestione del processo e il passaggio tra diversi stadi risultano facilitati. Negli ultimi dieci anni, il principale interesse nel campo della sintesi polimerica riguarda la preparazione di macromolecole con architetture predeterminate. La polimerizzazione radicalica per trasferimento di atomo (ATRP) è la tecnica più versatile e affermata per la costruzione di polimeri ben definiti, con stretta distribuzione di pesi molecolari ed eccellente ritenzione di funzionalità di fine catena. L’ATRP si basa sulla disattivazione reversibile dei radicali propaganti, in modo da allungare il tempo di vita delle catene in crescita. La concentrazione di radicali in soluzione rimane sempre molto bassa, portando così a minimizzare la probabilità dei radicali stessi di essere soggetti a terminazione. L’equilibrio di attivazione-disattivazione è generalmente governato da un catalizzatore metallico, composto da un centro di rame e un legante amminico polidentato. Nella sua forma attiva, [CuIL]+, il catalizzatore genera radicali per rottura riduttiva del legame C–X nell’alogenuro alchilico, RX, utilizzato come iniziatore. La specie disattivante [X–CuIIL]+ si forma in seguito al trasferimento elettronico e atomico che avvengono in contemporanea. I radicali generati riescono ad addizionare solo poche molecole di monomero (reazione di propagazione), prima di essere riconvertiti al loro stato dormiente tramite reazione con [X–CuIIL]+. In ATRP è importante che gli iniziatori siano altamente reattivi, in modo da garantire la crescita simultanea di tutte le catene e quindi poter ottenere pesi molecolari predeterminati. Le funzionalità di fine catena non vengono intaccate durante la polimerizzazione e questo permette di sottoporre il polimero a processi di post-polimerizzazione e di costruire copolimeri con varie composizioni e topologie. Lo scopo di questa tesi di dottorato è quello di affermare l’elettrochimica come fondamentale, accessibile ed efficace risorsa per l’analisi meccanicistica dei processi di ATRP e anche per condurre questo tipo di polimerizzazioni. Meno di venti anni fa, studi elettrochimici furono per la prima volta utilizzati in ATRP: i potenziali standard di riduzione di alcuni catalizzatori comunemente usati furono determinati tramite voltammetria ciclica (CV) e correlati alle performances catalitiche di questi composti. Da allora, la CV è la tecnica per eccellenza per lo studio delle proprietà redox dei catalizzatori per ATRP, nonché per la determinazione delle affinità relative delle specie di CuI e CuII per gli ioni alogenuro, quindi per predire l’attività dei complessi nella polimerizzazione. Inoltre, diverse procedure elettrochimiche sono state messe a punto per misurare con elevata precisione la costante cinetica di attivazione, kact, che riguarda quindi la reazione tra [CuIL]+ e RX. Valori di kact che coprono 12 ordini di grandezza sono stati misurati con diverse tecniche, in vari ambienti. Tra le suddette tecniche, l’utilizzo di un elettrodo a disco rotante (RDE) consente misure rapide, facilmente realizzabili e altamente riproducibili. Il RDE è stato usato in questo lavoro di tesi per definire una semplice procedura elettrochimica per la determinazione della costante termodinamica di equilibrio di ATRP, KATRP. Sostanzialmente con questo strumento è stata seguita la reazione tra CuI e RX, come avveniva per la misura di kact, ma in questo caso non si è introdotto nel sistema un catturatore radicalico, che serviva per isolare cineticamente lo step di attivazione. Quindi le reazioni di attivazione, disattivazione e terminazione radicalica sono state contemporaneamente monitorate e il valore di KATRP è stato ottenuto dall’elaborazione del responso elettrochimico tramite un’equazione, originariamente proposta da Fischer e in seguito opportunamente modificata. Il metodo è stato applicato a diversi catalizzatori, iniziatori, combinazioni di solvente e monomero e temperature, osservando dei trends nelle costanti in accordo con i principi di ATRP. KATRP e kact devono essere determinate in assenza di ioni alogenuro, i quali influenzano fortemente la speciazione dei complessi di CuI. Infatti, la quantità della specie attiva [CuIL]+ viene diminuita a causa della formazione di specie di CuI variamente alogenate, di conseguenza la sua reazione con RX risulta rallentata. Dalla riduzione nella velocità con cui CuI viene consumato al variare di C_(X^- ) è stato possibile stimare la costante di associazione di X− a [CuIL] + (o alidofilicità di CuI, K_X^I). Viene quindi presentata una procedura per determinare K_X^I dai valori di K_ATRP^app, determinati via RDE in presenza di diverse concentrazioni di X−. Oltre a fornire strumenti per studi di tipo meccanicistico, l’elettrochimica viene usata anche come driving force del processo di polimerizzazione. Infatti, un potenziale o una corrente possono essere applicati al sistema per rigenerare la specie di CuI, da [X–CuIIL]+ che si accumula in seguito al verificarsi di reazioni di terminazione radicalica. La polimerizzazione radicalica per trasferimento di atomo mediata elettrochimicamente (eATRP) sfrutta gli elettroni come agenti riducenti, quindi non porta alla formazione di sottoprodotti e consente di usare come reagente un sale di CuII, stabile all’aria, che viene poi ridotto in situ. Il tradizionale setup per eATRP richiede però un potenziostato e costosi elettrodi di Platino. Durante il mio periodo di dottorato ho cercato di semplificare il setup di eATRP, così da rendere questa tecnica più conveniente e realizzabile su larga scala. Alcuni materiali non costosi e facilmente funzionalizzabili sono stati testati come catodi in solventi organici e in sistemi acquosi. Polimerizzazioni ben controllate sono state ottenute con gli elettrodi lavoranti analizzati, anche operando in modalità galvanostatica (i.e. applicando step a corrente costante), la quale consente di utilizzare due elettrodi anziché tre, e di sostituire il potenziostato con un semplice generatore di corrente. Inoltre, questi catodi hanno dato ottimi risultati anche in combinazione con un anodo sacrificale di Alluminio, quindi realizzando un setup completamente Pt-free. Infine, è stato dimostrato che questi materiali non rilasciano ioni metallici in soluzione e che la loro morfologia non viene modificata nel corso delle polimerizzazioni, pertanto possono essere riutilizzati in reazioni successive. Caratteristica distintiva dell’eATRP e della ATRP in generale è l’eccezionale versatilità di queste tecniche, che consentono di polimerizzare diverse tipologie di monomeri. Per molti anni però, fu ritenuto impossibile controllare la polimerizzazione di monomeri acidi via ATRP. Nel 2016, Fantin et al. hanno dimostrato che le catene propaganti di poli(acido metacrilico) tendono a ciclizzare, con conseguente perdita della funzionalità C–X, quindi terminazione. Una volta definite le condizioni adatte per evitare questa pericolosa reazione secondaria, è stato possibile controllare efficacemente la polimerizzazione dell’acido metacrilico tramite eATRP. Questa importante vittoria mi ha permesso di lavorare con successo alla polimerizzazione dell’acido acrilico (AA), monomero biocompatibile, usato in moltissimi settori. Innanzitutto è stato dimostrato che la propagazione di AA è affetta dalla stessa reazione parassita di ciclizzazione, quindi alcune delle condizioni che hanno permesso l’efficace eATRP dell’acido metacrilico, sono state adattate al sistema analizzato. i) Il sale bromurato è stato sostituito da un sale clorurato, ii) la velocità di polimerizzazione è stata massimizzata usando un elettrodo lavorante con elevata area superficiale, applicando un potenziale molto più negativo di quello standard di riduzione del catalizzatore e ottimizzando la composizione del sistema. Un modo efficace per aumentare l’applicabilità della ATRP consiste nella sintesi di nuovi leganti che conferiscano particolari proprietà al centro metallico. Nella tesi sono riportati 4 nuovi leganti, in cui lo scheletro del legante tris-2(metilpiridil)ammina (TPMA), comunemente usato in ATRP, è stato modificato con sostituenti fenilici variamente funzionalizzati in posizione meta. La caratterizzazione elettrochimica dei complessi di Cu con questi leganti ha portato a predire una minore attività rispetto al tradizionale Cu/TPMA. Questa è stata confermata dalla determinazione di kact tramite RDE. Ciononostante, questi complessi sono risultati efficaci catalizzatori in eATRP di metil metacrilato in DMF, e di oligo(etilene glicole)metil etere metacrilato e di acido metacrilico in acqua. Nonostante la non elevata attività, i complessi analizzati hanno mostrato buona stabilità in acqua, anche a pH acido, e si propongono come catalizzatori adeguati per sistemi altamente reattivi. La versatilità di queste polimerizzazioni si riflette nella possibilità di applicazione in un’ampia varietà di ambienti. Grande interesse, ad esempio, è rivolto all’utilizzo di Liquidi Ionici (ILs) come solventi di polimerizzazione “green”. Pertanto, le proprietà redox di alcuni catalizzatori e iniziatori, frequentemente usati in ATRP, sono state studiate tramite CV in 1-butil-3-metilimidazolio trifluorometansolfonato. Nello stesso sono stati effettuati studi cinetici via RDE. Queste analisi hanno permesso di affermare che il comportamento dei composti di Cu e degli alogenuri alchilici in IL è del tutto simile a quello osservato nei solventi organici tradizionali. Perciò, i liquidi ionici si confermano come solventi adatti a processi di polimerizzazione controllata. Appare infine auspicabile realizzare eATRP in ILs, perché la buona conducibilità elettrica di questi solventi consente di evitare l’aggiunta di un elettrolita di supporto. Un ulteriore ambiente sostenibile di polimerizzazione è rappresentato dai sistemi dispersi. Sebbene moltissime polimerizzazioni su scala industriale si basino su sistemi in (mini)emulsione, la maggior parte della letteratura che tratta di ATRP riporta processi in soluzione omogenea. La realizzazione di ATRP in miniemulsione ha richiesto la sintesi di opportuni leganti super-idrofobici, che consentissero di confinare il catalizzatore nella fase dispersa idrofobica, dove potesse esercitare il suo effetto. Durante il mio dottorato ho trascorso sei mesi come visiting student presso la Carnegie Mellon University, nei laboratorio del Prof. Matyjaszewski, che scoprì l’ATRP nel 1995. In quel periodo ho potuto lavorare estesamente su ATRP in miniemulsione ed emulsione. Un nuovo sistema catalitico è stato messo a punto e applicato con efficacia in eATRP e ARGET-ATRP (attivatori rigenerati per trasferimento elettronico, in cui un agente riducente è usato per rigenerare continuamente CuI). Catalizzatori idrofilici tradizionali sono stati usati in combinazione con surfattanti anionici poco costosi, formando coppie ioniche capaci di entrare negli agglomerati monomerici e catalizzare la polimerizzazione. L’interazione tra le specie reagenti è stata provata attraverso caratterizzazioni elettrochimiche e spettrochimiche, che hanno permesso di definire il diverso contributo di catalisi interfacciale e via coppie ioniche. Grazie a questo approccio sono stati prodotti copolimeri a blocchi, a stella e a spazzola. Inoltre il Cu residuo nei polimeri precipitati è risultato estremamente poco, in alcuni casi inferiore ad 1 ppm, quindi i polimeri non necessitano di ulteriore purificazione. Il sistema catalitico è stato poi applicato in ARGET-ATRP in emulsione, sfruttando la presenza di un catalizzatore idrofilico, essenziale in emulsione dove la polimerizzazione deve verificarsi in fase acquosa. ARGET-ATRP ben controllate in emulsione ab initio sono state ottenute, anche con basse quantità di surfattante, ottimizzando la procedura di pre-emulsificazione, la velocità di mescolamento e selezionando opportuni iniziatori idrofilici.

L’objet de cette thèse est d’étudier un procédé de fraisage par microélectroérosion (μEE), qui est un procédé sans contact permettant d’usiner tous les matériaux durs conducteurs d’électricité à l’aide d’un micro-outil cylindrique ultrafin. Le principe consiste à créer des micro-décharges électriques entre le micro-outil et une pièce conductrice immergés dans un diélectrique liquide. En faisant parcourir à l’outil un parcours 3D, il est possible de creuser une forme complexe dans la pièce avec des détails à fort rapport d’aspect. Dans ce travail, nous avons tout d’abord amélioré un procédé d’élaboration de microoutils cylindriques ultrafins par gravure électrochimique de barreaux de tungstène. Des outils de diamètre 32,6 ± 0,3 μm sur une longueur de 3 mm ont été obtenus de manière automatique et reproductible. L’écart type a été divisé par 2 par rapport à l’état de l’art antérieur. Des outils de diamètre inférieur ont été obtenus avec une intervention de l’opérateur, et ce jusqu’à 3 μm de diamètre. Puis ces micro-outils ont été mis en oeuvre pour usiner des pièces avec le procédé de fraisage par microélectroérosion. Pour ce faire, une machine de 2ème génération a été entièrement développée sur la base de travaux antérieurs. Il a été possible d’usiner de l’acier inoxydable dans de l’eau déionisée avec des micro-outils de 3 μm de diamètre sans détérioration de l’outil. Par ailleurs, Le procédé de μEE a été caractérisé en termes de résolution d’usinage, taux d’enlèvement de matière et usure de l’outil. Un générateur de décharges original a permis d’usiner avec des micro-décharges de 1 à 10 nJ / étincelle avec une diminution très sensible de l’usure de l’outil par rapport à l’état de l’art. Un procédé original de caractérisation en ligne des décharges et de cartographie dans l’espace a aussi été développé<br>This work aims at studying Micro Electrical Discharge Milling (μEDM milling), which is a non-contact process allowing machining all hard and electrically conductive materials with a cylindrical ultrathin tool. The principle is based on the creation of electrical micro discharges between the tool and an electrically conductive part immersed in a liquid dielectric. By means of a 3D path, the tool machines a complex shape in the part with high aspect ratio details. In this work, we have firstly improved a process for making cylindrical ultrathin micro-tools by electrochemical etching of tungsten rods. Tools with a diameter of 32.6 ± 0.3 μm and a length of 3 mm have been obtained with an automated and reproducible process. Standard deviation has been divided by 2 by comparison with the previous state of the art. Tools with diameter as low as 3 μm have been fabricated with the help of the machine operator Then these micro-tools have been used for machining parts with the μEDM milling process. To do so, a second generation machine has been entirely developed on the basis of previous work. It has been possible to machine stainless steel in deionized water with 3 μm micro-tools without damaging the tools. In other respects, the μEDM milling process has been characterized in terms of machining resolution, material removal rate and tool wear. An innovative generator of discharges allow machining with 1 to 10 nJ / spark with a reduced tool wear by comparison to the state of the art. An innovative process for the on line characterization of discharges with spatial distribution capability has been developed

The master’s thesis deals with the topic of electrical discharge machining. The first part of the thesis contains a study of the die-sinking EDM. The die-sinking EDM of the silicon carbide ceramic is realized in the experimental part of the thesis. The result of this work was to explore the influence of the EDM sinking parameters, specifically pulse current, open-voltage and pulse on-time, on the machined surface. Furthermore, the analysis of the tool electrode was made. This analysis was focused on the wear in the corners, which has key influence on accuracy of the machining. The machining time was also examined.

L’électroérosion (EE) est une technique d’usinage sans contact de matériaux conducteursd’électricité ; elle particulièrement bien adaptée à l’usinage de matériaux durs. Le principe consiste àcréer des décharges électriques érodantes entre un outil et une pièce à usiner, toutes deuximmergées dans un diélectrique. Dans cette thèse, nous avons étudié la miniaturisation de ceprocédé, la microélectroérosion (μEE), qui se présente comme un procédé complémentaire destechniques de micro-usinage mécanique, laser, ou encore des techniques issues de lamicrotechnologie du silicium (RIE, DRIE, LIGA). Toutefois, la résolution de la μEE est limitée.Dans ce travail, nous avons tout d’abord développé un procédé original d’élaboration de microoutilscylindriques en tungstène par gravure électrochimique. Celui-ci permet d’obtenir de manièrereproductible des micro-outils de diamètre 15 μm et de rapport hauteur sur diamètre supérieur à 50.Des micro-outils plus fins ont aussi été obtenus (jusqu’à 700 nm) mais avec des problèmes dereproductibilité. Par ailleurs, un prototype de machine de fraisage par μEE a été développé avec uneélectronique entièrement caractérisée. Des micro-canaux de 40 μm de largeur ont été obtenus dansl’acier d’inoxydable et 25 μm dans le titane ; une rugosité Ra de 86 nm a été atteinte dans des cavitésde 600 x 600 x 30 μm. Les limitations du dispositif expérimental ont aussi été mises en évidence.Dans la dernière partie de ce travail, nous avons procédé à l’étude des microdécharges et du microplasmas’établissant entre micro-outil et pièce à l’aide de caractérisations électriques. La résistanceet l’inductance des décharges ont été déterminées expérimentalement puis intégrées dans unmodèle permettant de prévoir la durée des impulsions de courant et leur intensité. Des pistes pourl’amélioration de la résolution d’usinage sont proposées en conclusion de ce travail<br>Electro Discharge Machining (EDM) is a non-contact technique allowing machining of electricallyconductive materials; it is well adapted for the machining of hard materials. The principle is based onthe creation of eroding electrical discharges between a tool and a piece, both immersed in adielectric. In this thesis, we have the studied miniaturization of the process, called micro electrodischarge machining (μ-EDM), which is considered as a complementary technique of mechanical orlaser micro-machining techniques and silicon micro technology processes (RIE, DRIE, LIGA)..However, the resolution of μEDM is limited.In this work, we have firstly developed an original method for making tungsten micro-tools withcylindrical profile by electrochemical etching. This method allows the reproducible fabrication ofmicro-tool with 15-μm diameter. Thinner micro-tools were also obtained (down to 700 nm) withreproducibility problems. Furthermore, a prototype machine for milling μ-EDM was developed with afully characterized electronics. Micro channels were obtained respectively in stainless steel with awidth of 40μm and in titanium with a width of 25μm; a surface roughness Ra of 86 nm was achievedin 600 x 600 x 30 μm cavities. Besides, the limitations of the apparatus were highlighted. In the lastpart of this work, we have studied the micro-discharge and the micro-plasma between the micro-tooland the part with electrical characterization. The resistivity and the inductance of the sparks weremeasured and integrated in a numerical model in order to explain the duration of the microdischarges and their intensity. Solutions for improving the machining resolution are also discussed atthe end of this work

Predmet istraživanja ove disertacije predstavlja unapređenje, modelovanje i optimizacija procesa elektroerozivne obrade (EDM) savremenih inženjerskih materijala. Prvo su predstavljene dve inovativne metode: EDM u dielektrikumu sa pome&scaron;anim prahom i EDM sa pomoćnom elektrodom, a zatim i njihova kombinacija. Za generisanje matematičkih modela primenjene su metodologija odzivne povr&scaron;ine i alati ve&scaron;tačke inteligencije. U nastavku su postavljeni optimizacioni procesi određivanja ulaznih parametara sa jednom i vi&scaron;e funkcija cilja koji su re&scaron;eni primenom klasičnih metoda optimizacije. U zavr&scaron;nom osvrtu sprovedena je verifikacija dobijenih modela i optimalnih ulaznih parametara elektroerozivne obrade.<br>The subject of the research of this dissertation is the improvement, modeling and optimization of the electrical discharge machining (EDM) of advanced engineering materials. First, two innovation methods are presented: EDM in powder mixed dielectric fluid and EDM with assisted electrode and that their combination. The method of response surface and artificial intelligence tools were applied to generate mathematical models. The optimization problems of determining the input parameters with single and multiple target functions are solved by the application of classical optimization methods. Finally, verification of the obtained models and optimal input parameters of electrical discharge machining was carried out.

In this thesis high quality electron densities are used to provide insight into density functional theory (DFT) and to improve the quality of DFT calculations. Chapter 1 provides an introduction to ab initio molecular wavefunction calculations with particular emphasis on the Hartree-Fock method. Chapter 2 outlines important concepts in density functional theory (DFT). This includes a discussion of the Zhao, Morrison and Parr (ZMP) method, which is the key to calculating DFT quantities from high quality densities. In Chapter 3, high quality densities are used to gain an understanding of dispersion interactions in the helium dimer. The investigation seeks to understand the correlation potentials associated with a density distortion that gives rise to the correct dispersion forces. Chapter 4 presents a study of response properties using orbitals and eigenvalues determined from high quality densities. Both magnetic and electric properties are considered and comparisons are made with conventional DFT functionals and wavefunction methods. Chapter 5 makes a comparison between Kohn-Sham eigenvalues and related properties, generated both by conventional functionals and from densities. The influence on NMR shielding constants is considered and two approaches to correcting LUMO eigenvalues are presented. In chapter 6, a DFT exchange-correlation functional determined from a lit to high quality densities is applied to study the gauche effect in 2-fluoroethylamine, 2-fluoroethanol and their protonated analogues. Conclusions are presented in Chapter 7.

This diploma thesis is involved in possible development of different types of milling molds coated with modern plows. The first part is devoted to an analysis of contemporary trends in forms production technology. The analysis includes the different types of machines and tools for making various kinds of molds and dies. Another part deals with design of dies for sheet metal shears. The thesis continues by design of the production procedure after heat treatment and finishing die by miling. For milling of die are designed miling tools, the NC program and the possible development of manufacturing the die using a new machining center and the possibility of production optimization. The penultimate point of the thesis is technical and economical evaluation of the direction of development and comparison of positives and negatoves of each method. At the final evaluation is all summed up.

This thesis focuses in the development and application of new tools for the analysis of the electron distribution in molecules, focusing on the concepts of local spins, and oxidation state. The thesis can be divided into three parts. The first one deals with the formulation of a new atom in molecule definition reproducing to some extent the results of the QTAIM (Quantum theory of atoms in molecules) analysis at a much reduced computational cost. In the second part we propose a new methodology to obtain local spins from wave function analysis and we relate local spins with the chemical bond and the radical character of molecules. Finally, we study the electron configurations of the atom within the molecule and retrieve their oxidation states from a particular analysis of the effective atomic orbitals (eff-AOs)<br>Aquesta tesi es centra en el desenvolupament i aplicació de noves eines per a l'anàlisi de la distribució electrònica en molècules, posant èmfasi en els conceptes de espins locals i estats d'oxidació. La tesi es pot dividir en tres parts. La primera està dedicada a la formulació d'una nova definició d'àtom dins de la molècula que reprodueix les propietats de l'anàlisi QTAIM (Quantum theory of atoms in molecules) amb un cost computacional associat molt més baix. A la segona part proposem una nova metodologia per a obtenir espins locals a partir de l'anàlisi de la funció d'ona i relacionam aquest concepte amb l'enllaç químic iatom el caràcter radical de les molècules. Per últim, estudiem les configuracions electròniques dels àtoms dins de les molècules i obtenim estats d'oxidació efectius a partir de l'anàlisi dels orbitals atòmics efectius

AC electro-kinetics involves the manipulation of particles in non-uniform alternating electric fields. Micro-systems consisting of microelectrode arrays generate the field non-uniformities which can produce several observed phenomena, including lateral particle displacements (dielectrophoresis), particle rotation (electro-rotation) and induced fluid flow (electro-hydrodynamics). These effects are influenced primarily by the dielectric properties of the particle and the suspending medium, the frequency of the applied electric field and the electrode designs. In this thesis, novel processes involving the use of ac electro-kinetics in microsystems are developed. Using a quasi-three dimensional dot micro-system, dielectric properties of dielectrophoretically manipulated bioparticle suspensions are shown to be determined through the use of image analysis. Significant factors contributing to the speed and accuracy of the process were found to be dependent on the particle concentration and electrode dimensions. These dependencies showed a phenomenon which has hardly been used before in ac electro-kinetic particle characterisation, the process of spontaneous particle re-dispersion in the micro-system. The first integrated micro-system coupling ac electro-kinetic particle manipulation and piezoelectric mass detection simultaneously is described. The electrode design used enhances particle collection on to the surface of the electrode, through induced fluid flow, where detection occurs. The dynamic response of the system has shown that nano-particles are more suited for this system, with the rate and amplitude of detection shown to correspond to the concentration of particles. Pre-concentration of biological particles in micro-fluidic systems using dielectrophoresis is a useful upstream process which can be employed prior to characterisation or detection processes. However, exposure of biological particles to high field gradients can lead to cellular damage. A comparison of dielectrophoretic and electro-hydrodynamic forces as a means of particle retention in micro-fluidic flow has shown that particles can be trapped at different electrode regions. These regions correspond to the high and low electric field gradients in the electrode vicinity. At increased flow-rates, hydrodynamic forces are seen to have a significant influence on the trapping efficiencies using electro-hydrodynamic forces. Although, at lower flow-rates the number of viable of cells eluted from the micro-fluidic chamber is significantly greater than those exposed to conventional dielectrophoretic forces.

Since the proliferation of CAD tools, visualizations have gained importance.. They provide invaluable visual feedback at the time of design, regardless whether it is fbi civil engineering or electronic circuit design-layout. Typically dynamic visualizations are produced in a two phase process: the calculation of positions and rendering of the image and its presentation as an animated video clip. This is a slow process that is unsuitable fbr interactive CAD visualizations, because the former two require finite element analysis Faster hardware eases the problem, but does not overcome it, because the algorithms are still too slow. Our MEMS CAD project works towards methods and techniques that are suitable for interactive design, with faster methods. The purpose of this PhD thesis is to contribute to the design of an interactive virtual prototyping of Micro Electro Mechanical Systems (MEMS) This research comprises the analysis of the visualization techniques that are appropriate for these tasks and identifying the difficulties that need to be overcome to be able to offer a MEMS design engineer a meaningful and interactive CAD design environment Such a VR-CAD system is being built in our research group with many participants in the team. Two particular problems are being addressed by presenting algorithms for truthful VR visualization methods: one is for displaying objects that are different in size on the computer screen. The other is modelling unsynchronized motion dynamics, that is different objects moving simultaneously at very high and vety low speed, by proposing stroboscopic simulation to present their dynamics on the screen They require specific size scaling and time scaling and filtering. It is these issues and challenges which make the design of a MEMS CAD tool different from other CAD tools. In the thesis I present algorithms for displaying animated virtual reality for MEMS virtual prototyping in a physically truthful way by using the simulated stroboscopic illumination to filter animated images to make it possible to show unsynchronized motion.. A scaling method was used to show or hide objects which cannot be shown simultaneously on the computer screen because of their large difference in size. The visualization of objects being designed and their animations is done with much consideration of visual perception and computer capability, which is rising attention, but not too often mentioned in the visualization domain.

Since the proliferation of CAD tools, visualizations have gained importance.. They provide invaluable visual feedback at the time of design, regardless whether it is fbi civil engineering or electronic circuit design-layout. Typically dynamic visualizations are produced in a two phase process: the calculation of positions and rendering of the image and its presentation as an animated video clip. This is a slow process that is unsuitable fbr interactive CAD visualizations, because the former two require finite element analysis Faster hardware eases the problem, but does not overcome it, because the algorithms are still too slow. Our MEMS CAD project works towards methods and techniques that are suitable for interactive design, with faster methods. The purpose of this PhD thesis is to contribute to the design of an interactive virtual prototyping of Micro Electro Mechanical Systems (MEMS) This research comprises the analysis of the visualization techniques that are appropriate for these tasks and identifying the difficulties that need to be overcome to be able to offer a MEMS design engineer a meaningful and interactive CAD design environment Such a VR-CAD system is being built in our research group with many participants in the team. Two particular problems are being addressed by presenting algorithms for truthful VR visualization methods: one is for displaying objects that are different in size on the computer screen. The other is modelling unsynchronized motion dynamics, that is different objects moving simultaneously at very high and vety low speed, by proposing stroboscopic simulation to present their dynamics on the screen They require specific size scaling and time scaling and filtering. It is these issues and challenges which make the design of a MEMS CAD tool different from other CAD tools. In the thesis I present algorithms for displaying animated virtual reality for MEMS virtual prototyping in a physically truthful way by using the simulated stroboscopic illumination to filter animated images to make it possible to show unsynchronized motion.. A scaling method was used to show or hide objects which cannot be shown simultaneously on the computer screen because of their large difference in size. The visualization of objects being designed and their animations is done with much consideration of visual perception and computer capability, which is rising attention, but not too often mentioned in the visualization domain.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Information and Communication Technology<br>Full Text

Thesis (Ph.D)--Materials Science and Engineering, Georgia Institute of Technology, 2008.<br>Committee Chair: Meilin Liu; Committee Co-Chair: Yingjie Liu; Committee Member: David McDowell; Committee Member: Ian Ferguson; Committee Member: Tom Fuller.

Doutoramento em Engenharia Mecânica<br>A área do de metal duro encontra actualmente um vasto campo de aplicações e por esse motivo é considerada uma área estratégica do ponto de vista tecnológico e científico. Salientam-se neste âmbito, o corte por arranque de apara, as ferramentas de estampagem, o corte de chapa e ferramentas para resistência ao desgaste. Compreende-se assim o elevado número de publicações e projectos de I&D dedicados nos últimos anos ao aumento do tempo de vida e desempenho de ferramentas. É bem conhecido que alguns materiais utilizados na indústria de moldes (alumínios e suas ligas) ou na produção de eléctrodos para electroerosão de penetração (grafite, cobre e suas ligas) são de difícil maquinação. Por esse motivo, as ferramentas de corte apresentam, geralmente, um reduzido tempo de vida. Neste contexto, o recurso a ferramentas com diamante policristalino como material de revestimento tem sido geralmente adoptado, apesar dos elevados custos que lhes está associado. Além disso, o revestimento de ferramentas de metal duro com filmes de diamante encerra algumas dificuldades tecnológicas, nomeadamente a adesão ao substrato Estudos previamente realizados demonstram que a fase de nucleação é determinante para o controlo do tamanho de grão do filme O presente trabalho de doutoramento teve como principal objectivo desenvolver novas soluções tecnológicas para a deposição de filmes de diamante com elevadas taxas de nucleação. Para o efeito, desenvolveu-se a técnica de deposição química em fase vapor modulada no tempo com controlo de tamanho de grão (TMCVD-GC). Esta técnica pressupõe a combinação das técnicas usuais de TMCVD com fluxos críticos de gases conducentes à obtenção de uma mono camada com elevada taxa de nucleação. Deve salientarse que no caso de revestimentos de metal duro, a fraca adesão está relacionada com as tensões residuais com origem na enorme diferença entre coeficiente de expansão térmica do diamante e do metal duro e com o efeito grafitizante do cobalto. Os filmes produzidos por TMCVD foram testados em condições industriais de maquinação de grafite, por torneamento. Os mecanismos de desgaste inerentes ao processo foram objecto de análise. Foi testado o comportamento de dois “interlayer” (CrN e SiC) no processo de nucleação/crescimento de diamante e o desempenho do “interlayer” de carboneto de silício foi testado na maquinação de grafite. Finalmente procedeu-se à comparação do desempenho das ferramentas revestidas por TMCVD com o desempenho de ferramentas comercias de PCD.<br>Today, the cemented carbide has found wide application in different areas such as the cutting tools, the wear parts, and the metal forming tools. Therefore, the powder metallurgy of cemented carbides is considered as topic of major interest for the scientific community and the industry. Certainly this is the reason why in the past years were observed the increase of I&D projects with the purpose of increasing the performance and the tool life of the tools. It is well known that a few materials employed in the mould industry (aluminium alloys) or in the EDM (electrical discharge machines) electrodes are of difficult machining with high accuracy. Therefore, the tool life is in general very short. Consequently WC-Co tools coated with polycrystalline diamond tools are often employed for this application, despite its high cost. However, to obtain such coatings with high quality represents an enormous challenge, due to the lack of adhesion between the diamond film and the substrate. Previous studies have shown that proper control of the early nucleation stage of diamond crystallites is detrimental for the crystal grain size control. The main objective of the present work is to develop new technological solutions for the deposition of diamond films with high nucleation density. For that, it was been developed a technique based on the modulation of the gases, with time, during the chemical vapour deposition, namely TMCVD. This process enables not only the control of the crystal grain size of the coating (TMCVD-GC) but also a high nucleation density. The films grown by TMCVD were tested in industrial cutting conditions by dry turning of graphite. The wear mechanisms were identified and studied. It was studied two approaches of interlayer to prevent the negative effect of cobalt during the diamond grown, the silicon carbide (SiC) and the chromium nitrite (CrN). The behaviour of the SiC interlayer was tested during the dry turning of graphite. Finally, the performance of the diamond coatings was compared with the performance of commercial polycrystalline diamond tools, under the same cutting operations.

The progressive down-scaling has been the driving force behind the integrated circuit (IC) industry for several decades, continuously delivering higher component densities and greater chip functionality, while reducing the cost per function from one CMOS technology generation to the next. Moore’s law boosts IC industry profits by constantly releasing high-quality and inexpensive electronic applications into the market using new technologies. From the 1 m gate lengths of the eighties to the 35 nm gate lengths of contemporary 22 nm technology, the industry successfully achieved its scaling goals, not only miniaturizing devices but also improving device performance.

Over the past decade, analytical chemists have been faced with a significant task to develop techniques and methodologies that are fully applicable to real-time sample analysis while significantly lowering per-sample and per-measurement costs. Such advancements are expected to make a great impact in many different fields ranging from environmental analysis to the health, security, and manufacturing industries. Ion selective electrodes (ISEs) are a class of chemical sensors that in recent years went through a renaissance and showed excellent potential as tools for routine environmental monitoring and clinical analysis. They are cheap to manufacture, show excellent selectivity and sensitivity, are easily miniaturised and can be connected to simple communication devices. However, due to several limitations such as presence of transmembrane ion fluxes or plasticiser exudation, their full potential has not yet been utilised. This calls for improvements in materials and methodologies used for the preparation of ISEs. Herein, significant improvements in lower detection limits of carbonate ISEs were achieved by conditioning the electrodes in the ionophore solution thus minimising/eliminating membrane ion fluxes. In addition, it was demonstrated that selectivity of ISEs can be enhanced by replacing traditional plasticisers with alternative materials such as ionic liquids (ILs). To further utilise the potential of ILs in ion sensing, 1,2,3-triazole based IL was covalently attached to the polymer backbone yielding a one component ISE. The inherent presence of iodide in the polymeric membrane reduced the need for conditioning thus allowing for direct determination of iodide in human urine samples. Similar approaches were undertaken to develop self-plasticised aluminium optical sensors in which an initially water-soluble fluorophore was copolymerised with methacrylate-based monomer. This prevented its diffusion from the membrane into the aqueous phase. Low detection limit, high selectivity and the possibility of miniaturisation makes them potential candidates for developing aluminium sensors for clinical analysis. This research demonstrates that by improving sensing methodologies as well as using novel materials for the preparation of ISEs and optical sensors, functional devices with excellent robustness, durability and reproducibility can be produced thus indicating yet unexplored avenues for further developments in sensing.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009.<br>Includes bibliographical references (p. 124-130).<br>Single walled carbon nanotubes (SWNT) are cylindrical sheets of graphene whose electronic structures and diameters are determined by their chiralities. Current synthetic methods produce batches of nanotubes containing a variety of electronic properties. The separation of these mixtures into semiconductors and metals will greatly enhance their utility for nanoelectronic devices. Progress has been achieved in this area at the laboratory scale through chemical and density-based handles for viable separation. While pristine SWNT of a certain electronic type are in great demand, nanotubes functionalised with specific molecules have applications in the detection of biological analytes, gas sensing and nanoenergetics. An ongoing area of interest is the concept of nanostructure-guided chain reactions, wherein the superior thermal conductivity of a nanotube is used to anisotropically enhance the combustion velocity of the energetic moiety covalently attached to its sidewall. A molecular assembly with this property has the potential to act as a nanoscale thruster and a possible source of pulsed power. This thesis therefore tackles the two research problems stated above: (a) Understand the separation of metallic/semiconducting nanotubes from a modelling perspective to gauge the phenomena from a molecular standpoint; (b) Develop a simple coarse-grained model that describes the characteristics of one-dimensional nanoenergetic materials and extracts the properties of the thermally propagated reaction wave.<br>(cont.) The chemical route of metal/semiconductor separation involves the preferential reaction of a diazonium salt (4-hydroxybenzenediazonium tetrafluoroborate) with metallic nanotubes. Previous experimental work has identified electron transfer from the nanotube to the diazonium molecule as the source of this selectivity. We have used this insight to develop a rate model that extracts rate constants from photoabsorption spectra. This necessitated the deconvolution of the UV-vis-nIR absorption spectra of single-walled carbon nanotubes, recorded subsequent to the reactions, into individual contributions - a complicated procedure because nanotube transition energies are closely spaced. An algorithm has been presented in this work to convert spectral data to diazonium surface coverage on representative SWNT, which were then fitted using adsorption/reaction-based rate equations. The selective reaction of a metallic nanotube with diazonium causes an increase in the density of the latter, which can be harnessed to separate it from the unreacted - and hence, less dense - semiconductors via ultracentrifugation. It is already possible to use a centrifugal field to sort surfactant-suspended carbon nanotubes by diameter in a density gradient. Through a hydrodynamic model, we seek to understand the effects of surfactant adsorption, diazonium reaction and cylindrical geometry on the density of a single walled carbon nanotube. In order to study the propagation of energetic reactions in a nanotube scaffold, we have modelled the latter by a one-dimensional chain of oscillators.<br>(cont.) The characteristics of thermally initiated chain reactions - e.g., wave velocity and modes of propagation- will be explored with a simple molecular dynamics model in conjunction with a Monte Carlo kernel that simulates the stochastic nature of the system. The contribution of the force field to the properties of the reaction has also been analysed through the use of harmonic and anharmonic interactions between the set of oscillators. This conceptual system helps us in formulating design parameters for the fabrication of actual nanostructures in the laboratory.<br>by Nitish Nair.<br>Ph.D.

The development and evaluation of the design of a Micro-Ram Air Turbine (µRAT), a device being developed to provide power for an autonomous boundary layer measurement system, has been undertaken. The design tools consist of a rotor model and a generator model. The primary focus was on developing and evaluating the generator model for the prediction of generator brake power and output electrical power with and without rectification as a function of shaft speed and electrical load, with only basic manufacturer specifications given as inputs. A series of motored generator evaluation test were conducted at speeds ranging from 9,000 to 25,000 rpm for loads varying between 1 and 3.02 Ohms with output power of up to 80 Watts. Results demonstrated that predicted generated power was at or below 3% error when compared to measured results with about 1% uncertainty. A rotor model was also developed using basic blade element theory. This model neglected induced flow effects and was therefore expected to over predict rotor torque and power. A second rotor model that includes induced flow effects, the open source program X-Rotor, was also used to predict rotor power and for comparison to the blade element rotor model results. Both rotor models were evaluated through wind tunnel validation tests conducted on a turbine generator with two different 3.25 in diameter rotors, rotor-1 (untwisted blades) and rotor-2 (twisted blades). Wind tunnel validation test airspeeds varied between 71-110 mph with electrical loads ranging from 1-20 ohms. Results indicated power predictions to be 50-75% higher for the blade element model and 20-30% for X-Rotor results. The blade element rotor model was modified by applying the Prandtl tip-loss factor to approximately account for the induced flow effects; this addition brought predictions much closer to X-Rotor results. Based on the motor-driven generator test results, it is believed that most of the discrepancy in baseline rotor/generator validation test between predicted and observed power generated is due to inaccuracy in the rotor performance modelling with likely contributors to error being induced flow effects, crude section lift/drag modelling, and aero-elastic deformation. It is concluded that the proposed generator model is sufficient although direct torque measurements may be desired and further development of the µRAT design tools should focus on an improved rotor performance model.

La electrónica envuelve muchos aspectos de nuestra vida cotidiana. El progreso de nuestra sociedad actual, en última instancia, está relacionado con el progreso de la electrónica. Tal progreso exige que las nuevas generaciones de dispositivos sean cada vez mas pequeñas y mas rapidas. Por lo tanto , las herramientas de simulación necesarias para poder entender el comportamiento de los dispositivos electrónicos emergentes, y luego de mejorarlos , tiene que ser reinventada para cada nueva generación de dispositivos . El ”International Technology Roadmap for Semiconductors” predice que en diez años los dispositivos electrónicos tendrán menos de 10 nanómetros de longitud de canal y que trabajarán a frecuencias de THz . La comunidad cientifica ha hecho una importante esfuerzo en proporcionar herramientas de simulación fiables para estudiar el comportamiento DC de estos dispositivos. Algunas de las técnicas de simulació comunes par sistemas clásicos y cuánticos se menciona en el primer captulo. Sin embargo, un esfuerzo similar para la simulaci ón cuántica de comportamiento AC de tales dispositivos esta todavía en las primeras etapas de la eleboración. Para los dispositivos de nanoescala , a alta frecuencia , las principales dificultades que tienen que ser considerarse para caracterizar el comportamiento de AC de estos dispositivos es el papel de la corriente de desplazamiento (que implica una aproximación adecuada para el problema cuático de muchos cuerpos ) y constatación que la corriente AC implica que el sistemas cuántico se medirán de forma continua . En esta tesis se ofrece una solución aproximada a mediante el uso de trayectorias cuánticas (trayectorias Bohmianas). Como se observa en el segundo capítulo las trayectorias de Bohm tienen ventajas computacionales cuando tratamos con muchos problemas de muchas partículas o la medición continua . En el capítulo tres , el cálculo práctico de las corrientes de partículas de desplazamiento se discuten con el teorema de Ramo - Shockley - Pellegrini. Hemos presentado un extensin cuántica del teorema utilizando trayectorias Bohmianas. También se discute en detalle la aplicación del teorema para del desarrollo del simulador cuántico el BITLLES ( Bohmiana Transporte para obrar recíprocamente no equilibrio estructuras electrónicas ) discutido en el apéndice C. Las expresiones de la corriente total se pueden utilizar ya sea para soluciones clásica de Monte Carlo de la ecuación de Botzmann con trayectorias clásicas o solución de la ecuación Schrödinger de muchas partículas con trayectorias Bohmianas. Por último , el uso de las herramientas desarrolladas en esta tesis se usan , en el capítulo cuatro, para estudiar la dependencia de la corriente y el ruido en la geometría y las condiciones de contorno electrostática de nanotransistors . Además , hemos presentado una estrategia original para mejorar el frecuencia corte de dispositivos emergentes balísticos de múltiples puerta. Esta tesis es un paso en la dirección de proporcionar un simulador quántico para AC y ruido a la industria electrónica y a la comunidad científica.nica envuelve muchos aspectos de nuestra vida cotidiana. El progreso de nuestra sociedad actual, en última instancia, está relacionado con el progreso de la electrónica. Tal progreso exige que las nuevas generaciones de dispositivos sean cada vez mas pequeñas y mas rapidas. Por lo tanto , las herramientas de simulación necesarias para poder entender el comportamiento de los dispositivos electrónicos emergentes, y luego de mejorarlos , tiene que ser reinventada para cada nueva generación de dispositivos . El ”International Technology Roadmap for Semiconductors” predice que en diez años los dispositivos electrónicos tendrán menos de 10 nanómetros de longitud de canal y que trabajar án a frecuencias de THz . La comunidad cientifica ha hecho una importante esfuerzo en proporcionar herramientas de simulación fiables para estudiar el comportamiento DC de estos dispositivos. Algunas de las técnicas de simulació comunes par sistemas clásicos y cuánticos se menciona en el primer captulo. Sin embargo, un esfuerzo similar para la simulaci ón cuántica de comportamiento AC de tales dispositivos esta todavía en las primeras etapas de la eleboración. Para los dispositivos de nanoescala , a alta frecuencia , las principales dificultades que tienen que ser considerarse para caracterizar el comportamiento de AC de estos dispositivos es el papel de la corriente de desplazamiento (que implica una aproximación adecuada para el problema cuático de muchos cuerpos ) y constatación que la corriente AC implica que el sistemas cuántico se medirán de forma continua . En esta tesis se ofrece una solución aproximada a mediante el uso de trayectorias cuánticas (trayectorias Bohmianas). Como se observa en el segundo capítulo las trayectorias de Bohm tienen ventajas computacionales cuando tratamos con muchos problemas de muchas partículas o la medición continua . En el capítulo tres , el cálculo práctico de las corrientes de partículas de desplazamiento se discuten con el teorema de Ramo - Shockley - Pellegrini. Hemos presentado un extensin cuántica del teorema utilizando trayectorias Bohmianas. También se discute en detalle la aplicación del teorema para del desarrollo del simulador cuántico el BITLLES ( Bohmiana Transporte para obrar recíprocamente no equilibrio estructuras electrónicas ) discutido en el apéndice C. Las expresiones de la corriente total se pueden utilizar ya sea para soluciones clásica de Monte Carlo de la ecuación de Botzmann con trayectorias clásicas o solución de la ecuación Schr¨odinger de muchas partículas con trayectorias Bohmianas. Por último , el uso de las herramientas desarrolladas en esta tesis se usan , en el capítulo cuatro, para estudiar la dependencia de la corriente y el ruido en la geometría y las condiciones de contorno electrostática de nanotransistors . Además , hemos presentado una estrategia original para mejorar el frecuencia corte de dispositivos emergentes balísticos de múltiples puerta. Esta tesis es un paso en la dirección de proporcionar un simulador quántico para AC y ruido a la industria electrónica y a la comunidad científica.<br>Electronics surrounds many aspects of our everyday life. The progress of our actual society is somehow ultimately linked to the progress of electronics. Such progress demands smaller and faster devices. Therefore, the simulations tools needed to be able, to understand the behavior of emerging electron devices and to improve them, have to be reinvented for each new generation of devices. The International Technology Roadmap for Semiconductors predicts that, in ten years, electron devices will have less than 10 nanometers of channel length and they will work at THz frequencies. The scientific community has done an important effort to provide reliable simulations tools for studying the DC behavior of state-of-the-art nanoscale devices. Some of the common classical and quantum simulation techniques are mentioned in the first chapter. However, a similar effort for the the quantum simulation of the AC performance of such nano metric and THz devices is still missing. For nanoscale devices, at high frequency, the main difficulties that have to be taken into account are the role of the displacement current (which imply a proper approximation for the many-body problem) and the assumption that the total quantum current needs to be continuously measured. This thesis provides an approximate solution to these problems through the use of quantum (Bohmian) trajectories. As seen in the second chapter, such Bohmian trajectories have advantages, from the computational point of view when we deal with the many body problem or the continuous measurement. In chapter three, the practical computation of the particle and displacement currents are discussed using the so called Ramo-Shockley-Pellegrini theorem. We have presented a quantum extension of the theorem using Bohmian (trajectories). We also discuss in detail the implementation of the theorem in the BITLLES (Bohmian Interacting Transport for non- equiLibrium eLEctronic Structures) simulator discussed in the appendix C. The expressions of the total current can be used either for classical Monte Carlo solutions of the Botzmann equation with classical trajectories or for the many-particle Schr¨odinger equation with Bohmian trajectories. Finally, using the tools developed in the previous chapters of this thesis, in chapter four, we have studied the dependence of the current and the noise on the geometry and the electrostatic boundary conditions of nanotransistors. In addition, we have presented and original strategy to improve the cut off frequency of emerging multi-gate ballistic devices. These numerical studies have been carried out by means of the BITLLES simulator for classical and quantum scenarios. This thesis is a step in the direction of providing a reliable dynamic quantum simulator to the industry and the scientific community.

La tesi doctoral titulada “Focused ion beam implantation as a tool for the fabrication of nano electromechanical devices” aborda el repte de la fabricació de ressonadors nano-mètrics des d’una nova òptica basada en la implantació iònica mitjançant un feix de ions focalitzat (FIB). Aquest nou mètode permet fabricar nano-dispositius suspesos funcionals, des del punt de vista elèctric i mecànic, sense necessitat d’utilitzar resina d’una forma i) ràpida i simple, només son necessàries tres etapes de fabricació; ii) flexible, permet definir dispositius amb gran llibertat geomètrica; iii) alta resolució, es demostra la fabricació de dispositius suspesos de 4 μm de longitud per 10 nm de diàmetre; iv) reproduïble i v) compatible amb la tecnologia CMOS. Partint d’un xip de silici o SOI (silici - diòxid de silici - silici), el mètode de fabricació comença amb un procés d’implantació FIB on es defineixen les estructures i les connexions elèctriques del dispositiu. El segon pas consisteix en el gravat humit del silici, on s’ataca el silici que no està protegit per la implantació FIB, permetent la suspensió o alliberació dels dispositius. En aquest estadi, on les estructures ja estan definides, el silici és amorf, conté gal·li i no és elèctricament funcional (ρ ~1 Ω·m). El darrer pas consisteix en un tractament tèrmic a alta temperatura fins a 1000ºC, en ambient de nitrogen i amb un precursor sòlid de bor on es propicia la recristal·lització del silici formant nano-cristalls, dopar el silici amb bor (tipus p) i eliminar el gal·li. Aquest tractament a alta temperatura, on les estructures no son oxidades, permet obtenir dispositius elèctricament funcionals (ρ ~10-4 Ω·m). Els principals resultats obtinguts es poden classificar en tres àmbits: Investigació de l’efecte de la implantació amb ions gal·li en el silici, pel que fa tant a aspectes de processament com de propietats nanoelectromecàniques del material. En aquest treball hem caracteritzat l’estructura del material en les diferents etapes de fabricació i hem caracteritzat elèctrica i electromecànicament els dispositius finals obtinguts pel mètode descrit. Desenvolupament i optimització del procés de fabricació, especialment pel que respecte al control de dimensions i a la combinació amb altres processos Es mostra el treball realitzat en la optimització dels diferents paràmetres de fabricació, des de la posta a punt de la dosi d’ions fins a la selectivitat del gravat. A través del disseny de les estructures es pot establir estratègies per controlar i minimitzar els efectes d’”under-etching” en el silici, a través de la definició d’estructures de compensació, i també evitar el col·lapse de les estructures més llargues, degut a les tensions superficials que es produeixen durant els processos de gravat humit, fabricant pilars per sostenir les estructures. Aquest mètode de fabricació permet obtenir dispositius a mida convertint-lo en una eina versàtil de prototipatge i de fabricació petites quantitats, que permet aconseguir dispositius de dimensions nano-mètriques per a l’experimentació acadèmica i científica. Investigació de les propietats electròniques, mecàniques i electromecàniques dels dispositius, i concretament en el cas de nanofils de silici suspesos que es poden aplicar com a ressonadors mecànics d’altra freqüència o transistors d’un sol forat. Hem pogut fabricar ressonadors de diferents geometries que ens ha permès estudiar i demostrar la relació que existeix entre la simetria/asimetria dels dispositius i el senyal piezoresistiu mesurat durant la transducció electromecànica. Hem investigat i fabricat transistors d’efecte camp ultra-fins (10 ~ 15 nm) i transistors suspesos on les característiques elèctriques a baixa temperatura mostren efectes de “Coulomb blockade” gracies als nano-cristalls que es formen, dins dels nano-fils de silici suspesos, durant l’etapa de tractament tèrmic.<br>The thesis entitled “Focused ion beam implantation as a tool for the fabrication of nano electromechanical devices” aboard the challenge of the fabrication of nanometric resonators from a new approach based on ion implantation by a focused ion beam (FIB) . This new method allows the fabrication of functional suspended nanodevices, from the electrical and mechanical point of view, without using any resist. This method is i) fast and simple, where only three steps are needed; ii) flexible, it is feasible the definition of structures of different shape; iii) high resolution, it is demonstrated the fabrication of 4 μm length and 10 nm diameter suspended devices; iv) reproducible and v) CMOS compatible. The starting point is a silicon or SOI (silicon – silicon dioxide – silicon) chip. The fabrication approach starts with a FIB implantation process where the structures and the electrical connections of the device are defined. The second step consists on silicon wet etching, where silicon that is not protected by the FIB implantation is etched, allowing the release of the devices. The defined structures are made of amorphous silicon, they contains gallium and they are not functional electrically (ρ ~1 Ω·m). The last step consists on diffusive boron doping at high temperature (up to 1000ºC) in a boron environment, where it is promoted the recrystallization of silicon forming nanocrystals, the boron doping (p type) of silicon and the removal of gallium. In this last step at high temperature the structures are not oxidized obtaining electrically functional devices (ρ ~10-4 Ω·m). The principal results can be classified in three areas: Investigation of the effect of gallium ion implantation onto silicon from the process and nanoelectromechanical material properties point of view. In this work the material structure in the different fabrication steps has been characterized, as well as the electrical and electromechanical properties of the final devices obtained by the described method. Development and optimization of the fabrication process, especially controlling the dimensions and the combination with other fabrication processes. The work done in the optimization of the different fabrication parameters are shown, from the tuning of the ion dosage to the etching selectivity. It is possible to stablish design strategies to control and minimize the under-etching effects onto silicon, as well as to avoid the collapse of long structures, that are the result of the superficial sticking produced during the wet etching processes, by the fabrication of sustaining posts. That method permits to obtain customized devices. It is a versatile prototyping method that allows the fabrication of small batches of devices of nanometric dimensions that can be employed for the scientific and academic experimentation. Investigation of the electronical, mechanical and electromechanical properties of the devices, specifically suspended silicon nanowires that can be employed as high frequency mechanical resonators or single hole transistors. We fabricated resonators of different geometries for the study and demonstration of the relation between the geometrical symmetry/asymmetry of the devices and the piezoresistive signal measured during the electromechanical transduction. We investigated and fabricated ultra-thin field effect transistors (10 ~ 15 nm) and suspended transistors that exhibits Coulomb blockade electrical characteristics at low temperature thanks to the nanocrystals that are grown during the high temperature fabrication step.

This thesis deals with automatic localization of thin surgical tools such as needles or electrodes in 3D ultrasound images. The precise and reliable localization is important for medical interventions such as needle biopsy or electrode insertion into tissue. The reader is introduced to basics of medical ultrasound (US) imaging. The state of the art localization methods are reviewed in the work. Many methods such as Hough transform (HT) or Parallel Integral Projection (PIP) are based on projections. As the existing PIP implementations are relatively slow, we suggest an acceleration by using a multiresolution approach. We propose to use model fitting approach which uses randomized sample consensus (RANSAC) and local optimization. It is a fast method suitable for real-time use and it is robust with respect to the presence of other high-intensity structures in the background. We propose two new shape and appearance models of tool in 3D US images. Tool localization can be improved by exploiting its tubularity. We propose a tool model which uses line filtering and we incorporated it into the model fitting scheme. The robustness of such localization algorithm is improved at the expense of additional time for pre-processing. The real-time localization using the shape model is demonstrated by implementation on the 3D US scanner Ultrasonix RP. All proposed methods were tested on simulated data, phantom US data (a replacement for a tissue) and real tissue US data of breast with biopsy needle. The proposed methods had comparable accuracy and the lower number of failures than the state of the art projection based methods.

To survive in today's manufacturing environments companies must push the standards of accuracy and speed to the highest levels possible. Electro Discharge Machining (EDM) has been used for over 50 years and recent developments have seen the use of EDM become much more viable. The goal of this research is to produce and evaluate electrodes produced by different manufacturing methods. The use of electroforming and spray-metal deposition has only recently become viable methods of producing usable rapid tooling components. The speed and accuracy as well as the cost of manufacture play a vital role in the tool and mould manufacturing process. Electroforming and spray-metal deposition offer an alternate option to traditional machining of electrodes. Electroforming is one method of producing electrodes for EDM. The fact that electroforming can be used to produce multiple electrodes simultaneously gives it the advantage of saving on costs when multiple electrodes are needed. Spray-metal deposition offers another alternative that is much cheaper and relatively faster to manufacture. The used of these non-traditional manufacturing methods in this research are compared to the performance of traditional solid electrodes in terms of machining time, material removal rate, tool wear rates and surface roughness at several standard machining settings. The results of this research are presented in this thesis along with conclusions and comments on the performance of the different methods of electrode manufacture. The major findings of the research include the solid electrodes performed better than the electroformed electrodes in Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (Ra) at all machine settings. However it was found that the production cost of the solid electrodes was six times that of the electroformed electrodes. The production of spray metal electrodes was unsuccessful. The electrode shell walls were not an even thickness and the backing material broke through the shell making them unusable. It is concluded that with further refinements and research, electroforming and spray metal processes will become an extremely competitive method in electrode manufacture and other rapid tooling processes.

To survive in today's manufacturing environments companies must push the standards of accuracy and speed to the highest levels possible. Electro Discharge Machining (EDM) has been used for over 50 years and recent developments have seen the use of EDM become much more viable. The goal of this research is to produce and evaluate electrodes produced by different manufacturing methods. The use of electroforming and spray-metal deposition has only recently become viable methods of producing usable rapid tooling components. The speed and accuracy as well as the cost of manufacture play a vital role in the tool and mould manufacturing process. Electroforming and spray-metal deposition offer an alternate option to traditional machining of electrodes. Electroforming is one method of producing electrodes for EDM. The fact that electroforming can be used to produce multiple electrodes simultaneously gives it the advantage of saving on costs when multiple electrodes are needed. Spray-metal deposition offers another alternative that is much cheaper and relatively faster to manufacture. The used of these non-traditional manufacturing methods in this research are compared to the performance of traditional solid electrodes in terms of machining time, material removal rate, tool wear rates and surface roughness at several standard machining settings. The results of this research are presented in this thesis along with conclusions and comments on the performance of the different methods of electrode manufacture. The major findings of the research include the solid electrodes performed better than the electroformed electrodes in Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (Ra) at all machine settings. However it was found that the production cost of the solid electrodes was six times that of the electroformed electrodes. The production of spray metal electrodes was unsuccessful. The electrode shell walls were not an even thickness and the backing material broke through the shell making them unusable. It is concluded that with further refinements and research, electroforming and spray metal processes will become an extremely competitive method in electrode manufacture and other rapid tooling processes.

Made available in DSpace on 2014-10-09T12:43:52Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:10:26Z (GMT). No. of bitstreams: 1 06769.pdf: 4275325 bytes, checksum: f2158eb766fa7886249500f40de27cec (MD5)<br>Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares, IPEN-CNEN/SP<br>FAPESP:97/04424-5

Load sensing pumps in hydraulic system of wheel loaders helps in increasing the energy efficiency of wheel loaders. Present day machines have hydro mechanical load sensing system. After the advent of hydro mechanical load sensing concept, over the years, lots of research has been carried out relevant to electro hydraulic load sensing, trying to control the pump electronically. Currently, Volvo Construction Equipments (VCE) is interested in investigating the possibility of implementing electro hydraulic load sensing system in the wheel loaders. Research works has shown existence of several configurations of electro hydraulic load sensing pumps. Successful simulation results of an electro hydraulic load sensing pump configuration would provide a backing for the proposal of building and testing that configuration of electro hydraulic load sensing pump prototype. Also, the thesis work aims in benchmarking hydraulic system simulation capabilities of AMESim and GT- Suite by simulating the existing hydro mechanical load sensing system in both in both the simulation packages.<br>The thesis work has been carried out at Virtual Product Development (VPD) division of Volvo Construction Equipments (VCE), Eskilstuna, Sweden.

Being able to directly relate the final properties with the intimate structure provides a unique insight into the functionality of materials and devices, especially when compared to the necessarily statistical nature of the information that can be retrieved by macroscopic measurements. In particular, the scale reduction associated with the Nanoscience and Nanotechnology revolution demands characterization tools capable of reaching an unprecedented resolution, in a wide range of fields, not only for standard quality control, but in order to understand the properties of matter at the nanoscale. Going from bigger to smaller devices, but also from elemental building blocks (even atoms) to bigger assemblies, basic properties and device functionalities meet. With its ability to provide different kinds of information at a very high spatial resolution, state-of-the-art TEM and related techniques are in the core of this multidisciplinary and rapidly growing field. The first major topic is related to the assessment of local atomic ordering/disordering phenomena in functional materials. A series of rare earth niobates (RE3NbO7) will be studied in order to understand the microstructural origin of their proton conduction properties, that make them excellent candidates to be used as electrode materials in solid oxide fuel cells. Also, single crystals of the tetragonal tungsten bronze (TTB) Sr0.33Ba0.66Nb2O6 (SBN-67) will be studied by different TEM techniques in order to assess the possible short range structural and/or chemical disorder. These features are thought to be responsible for the observed macroscopic uniaxial polarization vector of the material as well as its relaxor properties. A second major topic of interest will be the phenomena taking place at interfaces. This includes the characterization of a set of LaNiO3 perovskite thin films grown on different substrates (LAO, LSAT, STO, YAO). The effect of the substrate-induced compressive/tensile strain, given by lattice mismatch, on the structure of the films will be assessed and related to the observed electric transport properties. The interfaces in a GaN/InAlN multilayered system designed as a Bragg reflector for laser cavities applications will be investigated in order to account for a lower than expected reflectivity of the devices. The presence of structural defects and the detection of intergrowth of wurtzite and zinc blende phases of GaN in thin films will be addressed. Also regarding interfaces and strain conditions, the characterization of the free surface of Nb2O5 nanorods, as a key point for their humidity sensing properties. Expanding on this, the strain state of Nb2O5 when grown on SnO2 nanowires will also be studied. The coupling of the sensing capabilities of Nb2O5 with the electrical transport properties of SnO2 is of particular interest for functional sensing devices. Therefore, defects at the interface and strain state are of capital interest in order to understand the band structure alignment of the system. Interfaces in lower dimensionality systems will also be studied, as in the case of Ag@Fe3O4 dimers for applications in magnetoplasmonics. The epitaxial quality, strain, and the possible chemical diffusion through the contact surface of the two phases of the dimer are key aspects in order to properly tailor their optical properties. The last major topic is the mapping of magnetic fields at the nanoscale. The magnetic configurations of different geometric arrangements of magnetite Fe3O4 nanocubes will be studied. This characterization is aimed at obtaining enhanced responses in magnetic hyperthermia treatments for cancer. Given the strong interrelationship between the problems under study, the chapter structure follows the dimensionality of the systems under study (3D, 2D, 1D and 0D systems).<br>La reducció en l'escala espacial associada a la revolució de la Nanociència i la Nanotecnologia fa necessari comptar amb una sèrie d'eines capaces d'assolir una resolució sense precedents en una gran varietat d'àress, ja no tan sols com a control de qualitat, sinó per tal d'entendre les propietats de la matèria a la nanoescala. La correlació de la configuració estructural, la composició química i les distribucions de càrrega amb les propietats funcionals és imprescindible pel disseny de nous dispositius, tant des de la perspectiva 'top down' (reducció de les dimensions dels dispositius) com de la perspectiva 'bottom up' (fabricació d'estructures complexes a partir de blocs més petits, fins i tot àtoms). La capacitat de la Microscòpia Electrònica de Transmissió (TEM) de proporcionar diferents tipus d'informació amb una alta resolució espacial, situa les tècniques avançades de TEM com a peça clau en el desenvolupament d'aquest camp multidisciplinari i creixent. L'objectiu principal d'aquesta tesi ha estat l'aplicació de tècniques quantitatives d'imatge TEM per la resolució de problemes en ciència dels materials. La tesi cobreix un espectre ampli pel que fa al tipus de materials estudiats i els seus camps d'aplicació. El Capítol 1 presenta una introducció general a la teoria de formació d'imatge aplicada a la microscopia TEM. S'hi exposen els diferents fenòmens d'interacció electró-matèria que són responsables dels diferents tipus de contrast que es poden trobar a les imatges TEM. El Capítol 2 presenta les tècniques experimentals que es faran servir en la caracterització dels materials, en concret la simulació d'imatges d'alta resolució (HRTEM), l'holografia electrònica i l'anàlisi de la fase geomètrica (GPA). S'hi pot trobar una descripció del marc teòric i dels fonaments experimentals, juntament amb un resum dels resultats més recents en aquests camps. Els resultats experimentals s'agrupen en els capítols posteriors segons la dimensionalitat dels sistemes estudiats. En ordre decreixent de dimensionalitat s'hi inclouen: materials massius (3D), capes primes (2D), nanofils (1D) i nanopartícules (1D).

Particle contamination control is a critical issue for the semiconductor industry. In the near future, this industry will be concerned with the chemical identities of contaminant particles as small as 0.01 pm in size. Therefore, analytical techniques with both high chemical sensitivity and spatial resolution are required. Transmission electron microscopy (TEM) provides excellent spatial resolution and yields structural and compositional information. It is rarely used, however, due to the difficulty of sample preparation. The goals of this research are to promote the use of TEM as an ultrafine particle analysis tool by developing new sample preparation methods, and to exploit the new TEM techniques for analysis of particles in semiconductor processing fluids. A TEM methodology for the analysis of particulate contaminants in fluids with an elemental detectability limit as low as 0.1 part per trillion (ppt), and a particle concentration detectability limit as low as 1 particle/ml for particles greater than 0.2 pm was developed and successfully applied to the analysis of particles in HF, H202, de-ionized (DI) water, and on the surface of an electronic device. HF samples from three manufacturers were examined. For HF (B), the maximum particle concentration was 8.3 x 103 particles/ml. Both a viscous material and lath-shaped particles were observed. The Sb concentration was less than 0.6 part per billion (ppb). HF (C) was the cleanest. CaF2 and TiO2 particles were identified in HF (D). For H2 02, iron and tin oxides and hydroxides were identified. The maximum particle concentration was 990 particles/ml. The Sn and Fe concentrations were less than 0.3 ppb. Spherical and dendritic particles were observed. For DI water, spherical and dendritic particles (<2 particles/ml), and particles containing Fe or Si with concentrations less than 0.1 ppt were observed. Contaminants on an electronic device surface were also analyzed. Clusters of small particles were determined to be a mixture of aluminum oxides and aluminum silicates.

Nitrogen-alloyed tool steel is made at Uddeholms AB by adding high-nitrogen ferroalloy after vacuum degassing where introduced impurities are hard to remove. In this thesis two types of high-nitrogen ferrochromium are compared, a solid version and a powder cored wire. They are examined in crossection and 16 samples from four charges are examined with Pulse Distribution Analysis as well as systematic microscopy of polished cross sections. The PDA results missed smaller spinel inclusions shown in previous research to be detrimental. The wire form shows promise but more charges need to be evaluated before a conclusion is drawn.<br>Kvävelegerat verktygsstål tillverkas hos Uddeholms AB genom tillsats av kväverika ferrolegeringar efter vakumavgasning, och orenheter som introduceras i detta steg är svåra att avskilja. I den har uppsatsen jämförs två typer av kväverikt ferrokrom varav en i form av stycken och en i form av tråd med pulverkärna. De undersöks i tvärsnitt och totalt 16 prov från fyra charger undersöks med PDA (pulsfördelningsanalys) och systematisk mikroskopering i tvärsnitt. Resultaten från PDA missade mindre inneslutningar av spinell vilka tidigare har visat sig problematiska. Trådformen verkar lovande men fler charger behöver undersökas för att kunna dra en definitiv slutsats.

The focus of this literary study was additive manufacturing (AM) and the purpose was to find general trends for selected materials that have been additively manufactured and compare them to results from other reviews. The raw materials studied were stainless steels 316L, 17-4 PH, 15-5 PH and 420, as well as tool steel H13 and nickel alloys 625, 718 and Hastelloy X.The AM techniques studied were selective laser melting (SLM), electron beam melting (EBM) and binder jetting (BJG).  A total of 69 articles have been studied to fulfill the purpose above. The articles were used to write a summary of the techniques, compare them to each other and to conventional methods. They were also used to create a database to compile information on mechanical properties, microstructure and process parameters. Based on the database mechanical properties for SLM tend to be higher compared to EBM. This however varied somewhat depending on the processed material. Furthermore the yield and tensile strength obtained from the database for SLM seemed to be higher compared to the values in review articles for almost all materials. Unfortunately not enough values were found for BJG to compare it to SLM and EBM.AM seems to produce weaker, equal and superior products compared to conventional methods. However due to the limited nature of the project and the research found no conclusions can be drawn about any trends, how to achieve the different results or how parameters affect the finished product. To be able to say anything with more certainty more research has to be done. Not only in general concerning the AM techniques, but more studying of existing articles is needed. Finally a standardization on how to reference properties and process parameters is necessary. Currently it is very difficult to compare results or draw conclusions due to different designations, units and a lot of missing essential information.

Le développement intensif et rapide des dispositifs HEMT à base de nitrure de gallium a été largement favorisé par les qualités intrinsèques du matériau pour proposer des performances élevées (haute puissance, haute fréquence. . . ) et pour autoriser un fonctionnement en environnement extrêmement sévère (fluctuations thermiques, brouillage, tenues aux radiations ionisantes. . . ) par rapport aux technologies concurrentes plus traditionnelles (Si, GaAs. . . ). À ce jour, les dispositifs HEMTs AlGaN/GaN sont considérés comme une alternative prometteuse pour remplacer la technologie GaAs, et se positionnent comme d'excellents candidats pour des applications d'électronique de puissance, pour les applications TVSAT, des stations de base terrestres et des systèmes radar à large bande de fréquence (bande L à W), et pour les applications civiles et militaires. Cependant, il reste à lever certains verrous concernant des problèmes de fiabilité de ces dispositifs, qui affectent la durée de vie élevée attendue ; l'amélioration de la robustesse de ces technologies reste une phase critique à étudier malgré les progrès déjà réalisés. Plusieurs paramètres de fabrication affectent la fiabilité, tels que la passivation de la surface, le plateau de champ, le procédé de dépôt de la grille. Il est bien connu que l'étude de la fiabilité est complexe et ne pourra jamais être totalement accomplie, cependant les limites escomptées pour une exploitation raisonnable des filières GaN laissent entrevoir la possibilité de réels progrès dans ce domaine pour assoir le positionnement de ces technologies vis à vis des solutions concurrentes. Ce manuscrit de thèse présente les outils de diagnostic et les procédures de mesures associées développés pour mieux comprendre les mécanismes de dégradation sous-jacents de ces dispositifs. Les mesures électriques DC et pulsées à différentes températures sont présentées en premier lieu. Pour obtenir des informations au niveau microscopique sur la fluctuation des porteurs et des défauts dans les zones actives et passives du dispositif, des mesures de bruit basse fréquence sont effectuées sur les courant de grille et de drain sous différentes configurations : la diode seule (drain en l'air) et le transistor en régime saturé. Une technique électro-optique, l'OBIRCh (Optical Beam Induced Resistance Change technique), est aussi appliquée sur les mêmes composants : cette technique apporte d'autres informations quant à l'intégrité du composant (fluctuations de courant), et vient corroborer nos hypothèses sur l'activation de mécanismes piezoélectriques dans les zones fortement polarisées du composant. Toutes ces techniques non-destructives permettent des analyses croisées. Un modèle original de la diode Schottky a été établi pour tenir compte de certains défauts d'homogénéité à l'intérieur du contact de grille à l'interface entre la diode Schottky et la couche semi-conductrice supérieure. D'autres résultats originaux ont été trouvés à partir des mesures de bruit basse fréquence concernant la localisation des défauts actifs et leur évolution suite à l'application d'un stress électrique et thermique (HTRB, HTOL,. . . ). Les analyses électriques (pulsées et transitoires) des phénomènes de retard à la commande (grille ou drain) sont partiellement corrélées aux analyses du bruit basse fréquences des courant de grille et de drain pour identifier les mécanismes sous-jacents de dégradations. Dernièrement, une ébauche de plan d'expérience (DOE) est proposée dans le cadre de notre travail, qui complètera celui mis en œuvre dans le cadre du projet ANR REAGAN impliquant tous les partenaires : des règles et des procédures expérimentales sont identifiées pour s'assurer que les données expérimentales sont fiables (i. E. Reflètent statistiquement le comportement réel du dispositif)<br>Intensive and rapid development of GaN-based HEMT devices has been largely promoted by their extreme attraction and intrinsic capabilities for proposing high performances (high power and PAE, high frequency, moderate HF noise. . . ) and for operating under different extreme conditions and harsh environment (thermal fluctuations, jamming, ionizing radiations. . . ) over more traditional competitive technologies (Si, GaAs). More than ever, AlGaN/GaN HEMTs are considered as promising technology to replace the GaAs, and an excellent candidate for power electronics applications, for TVSAT applications, terrestrial base stations and radar transceivers operating over large frequency band (from L to W-band) for both civil and military applications. However, some remaining problems concerning the reliability of the devices affect the expected elevated lifetime, and the improvement of the robustness of these technologies stay a questionable phase to study despite the progress already made. Several fabrication parameters could impact the reliability such as surface passivation, field plate, gate deposition process (presence of spontaneous and piezoelectrical effects). It is well known that the reliability background is complex and will never be completely accomplished, but the margin between expected theoretical lifetime and results already obtained motivates efforts to give for an improved level of reliability. The following manuscript presents diagnostic tools and associated measurement procedures to better understand the underlying degradation mechanisms of such devices. Electrical DC and pulsed measurements at different temperatures are presented first. To get more microscopic information about the carrier flow and the defects in the active and passive areas of the device, low frequency noise measurements on the gate and drain currents are investigated under open drain (Schottky diode) and when the transistor is biased in saturated region. An electro-optical technique is also applied, called OBIRCh (Optical Beam Induced Resistance Change technique), on the same devices: this technique brings other expertise about the device integrity (current fluctuations). All these non-destructive techniques are cross-correlated. Original Schottky diode models have been established to account for some inhomogeneities within the gate contact at the interface between the Schottky diode and the upper semiconductor layer. Some other original results have been found from Low Frequency Noise measurements concerning the location of the active defects, and their evolution after the application of thermal and electrical stresses (HTRB &amp; HTOL). The electrical (pulsed and transient) analyses of lag effects are correlated to the harmonic low frequency analysis of the current spectral densities to identify the root trapping mechanisms. Lastly, a first Design of Experiment (DOE) is proposed in conjunction with our work, and also within the ANR REAGAN project involving all the partners: experimental rules and procedures are identified to ensure that the experimental data are reliable (i. E. Reflect the actual behavior of the device, with statistical assessment)