Dissertations / Theses on the topic 'Reactive wires'

Reactive ion scattering spectrometry (RISS) utilizing low energy (tens of eV) polyatomic ions was employed to characterize self-assembled monolayers (SAMs) on gold. The terminal composition of halogenated SAMs, chemisorption motifs of disulfide and diselenide SAMs, and electron transfer properties of molecular wire containing SAMs were interrogated to develop the versatility of RISS as an analytical surface characterization technique.Novel halogen terminated SAMs were examined for their ability to convert translational to vibrational energy of colliding projectile ions. A general increasing energy deposition trend correlated with increasing terminal mass with the exception of the iodine functionality. Increased amounts of surface abstractions and sputtering from C12I suggest competitive ion-surface interactions account for less than predicted energy deposition results. Mixed films of CH2Br and CH3 terminal groups elucidated interfacial surface crowding discerned by energy deposition results.Thiol and disulfide based SAMs were shown by RISS comparisons to be dissimilar in structure. Terminal orientation, however, was the same based on ion-surface reactions, disproving the proposed dimer model of disulfide SAMs. Ion-surface reactions and electron transfer properties of disulfide surfaces suggested greater percentages of c(4x2) superlattice structure than in thiol SAMs. Based on increased hydrogen reactivity, decreased methyl reactivity, and increased energy deposition results, diselenide based SAMs were more disordered than S-Au based SAMs. Electron transfer results monitored through total ion currents (TIC) showed Se-Au contacts are more conductive than S-Au attachments.Molecular wire candidates whose electron transfer capabilities are difficult to characterize by traditional techniques were characterized by RISS after being doped into matrix SAMs. Electron transfer properties were dependent on the isolating SAM matrix, dipole moments of the wires, and the potential applied to the surface. Changes in surface voltage dictated molecular wire geometry and electron transfer. Wires were annealed into preferential geometries by colliding ions, but did not operate as switches.While not related to the advancement of RISS, structural elucidation of the pharmaceutical carvidioliol was investigated by collision-induced dissociation, surface-induced dissociation, sustained off-resonance irradiation, and sustained off-resonance irradiation-resonant excitation and through gas-phase hydrogen/deuterium exchange. This molecule fragmented easily by all methods and demonstrated the chemical specificity of gas-phase hydrogen/deuterium exchange experiments.

Electron Transfer (ET) is undoubtedly one of the most important processes in life. Molecularly well-defined ET pathways in complex protein ensembles play a vital role in biological processes such as cell respiration or photosynthesis. The fundamental understanding of ET processes in biology is important not only to understand such key natural processes but also to advance in the design of biomolecule/electrode interfaces for Bioelectronic applications. The development of new techniques such as scanning probe microscopies (SPM) played a key role. In particular, the electrochemical scanning tunnelling microscopy (EC-STM) has been exploited to in situ monitor the ET rate as a function of the applied potential of individual metalloproteins immobilized on an Au electrode thanks to the single-molecule spatial resolution and the electrochemical gate capabilities. Azurin from Pseudomonas aeruginosa is a widely studied redox protein model both in bulk and at the single molecule level. Its globular structure contains a coordinated copper ion, which makes the protein capable of exchanging electrons by switching its redox state (Cu I/II) and supports its role as a soluble electron carrier in the respiratory chain of bacteria. In this thesis, we will show our advances on the design and characterization of single-protein devices using a Cu-Azurin metalloprotein model. We have demonstrated transistor like-behaviour in an electrochemically-gated single-protein wire that operates at very low voltages thanks to the Cu-Azurin redox properties. It was demonstrated that the conductance varies depending on the redox state of the Cu centre, having its maximum value at the redox-midpoint. We have also analysed the spontaneous formation of single-Azurin electrical contacts through the monitored current when the two ECSTM electrodes were placed at a fixed distance. Discrete switching events for the conductance were observed, whose frequency depends on the applied electrochemical conditions and, therefore, they were univocally ascribed to discrete changes in the redox state of the trapped protein. In order to tailor the charge transport behaviour of the single-protein wire, we have synthesized several mutants of the protein by exploiting point-site bioengineering schemes at different positions of the protein second coordination sphere. Our results show that we can rationally change the transport mechanism of the single-protein device by studying the effect of the specific residue modification on the particular ET pathways in the protein backbone.
La transferencia de electrones (ET) es uno de los procesos más importantes de la vida. La comprensión fundamental de los procesos de ET en biología es importante no sólo para comprender tales procesos naturales claves, sino también para avanzar en el diseño de interfaces biomolécula / electrodo para aplicaciones bioelectrónicas. En particular, se ha explotado la microscopía de efecto túnel con control electroquímico (EC-STM) para monitorizar in situ la constante de ET en función del potencial aplicado de las metaloproteínas. La Azurina de Pseudomonas aeruginosa es un modelo de proteína redox ampliamente estudiado, tanto en ‘bulk’ como a nivel de una sola proteina. Su estructura globular contiene un ion de cobre coordinado, que hace que la proteína sea capaz de intercambiar electrones cambiando su estado redox (Cu I/II). Este ion es el responsable de su rol como portador de electrones en la cadena respiratoria de las bacterias. En esta tesis, mostraremos nuestros avances en el diseño y caracterización de dispositivos de una sola proteína utilizando un modelo de metaloproteína Cu-Azurin. Hemos demostrado un comportamiento similar a un transistor en un hilo electroquímico de una sola proteína que funciona a muy bajos voltajes gracias a las propiedades redox de Cu-Azurin. Se demostró que la conductancia varía dependiendo del estado redox del centro de Cu, teniendo su valor máximo en el punto medio redox. También hemos analizado la formación espontánea de los contactos eléctricos de Azurin única a través de la corriente monitorizada cuando los dos electrodos ECSTM se colocaron a una distancia fija. Se observaron eventos discretos de conmutación para la conductancia, cuya frecuencia depende de las condiciones electroquímicas aplicadas y, por lo tanto, se atribuyeron unívocamente cambios discretos en el estado redox de la proteína atrapada. Con el fin de adaptar el comportamiento de transporte de carga de la unión uniproteica, hemos sintetizado varios mutantes de la misma proteína mediante bioingeniería en diferentes posiciones de la proteína. Nuestros resultados muestran que podemos cambiar racionalmente el mecanismo de transporte del dispositivo de una sola proteína mediante el estudio del efecto de la modificación de residuos específicos en las vías ET particular en el esqueleto de la proteína.

There is potential for improving creep properties of stainless steels by reinforcing them with tungsten (W) wires. Past studies have shown that a detrimental factor that impairs the mechanical properties of tungsten wire reinforced superalloy composites is the formation of brittle intermetallic phases due to the interaction between W wire and constituents of the alloy matrices. Formation and growth of the intermetallic phases strongly depends on the matrix chemistry and for the retention of creep strength, matrix compositions that do not form intermetallic phases with tungsten are desirable for fabricating W wire reinforced composites for high temperature applications. This research investigated the formation and growth of reaction phases in W wire reinforced 316L (W/316L) stainless steel and HP alloy steel (W/HP) that were fabricated by casting method. Additionally, the effect of composition on the evolution and kinetics of reaction phases was studied in some W wire reinforced experimental alloys based on Fe-Ni-Cr only (W/Fe-Ni-Cr). The fabricated composites were diffusion annealed in the temperature range 1000-1200°C for 25-500 hours. Microstructure and chemistry of the reaction phases in the as-cast and diffusion annealed composites were studied using scanning electron microscopy, energy dispersive spectroscopy and electron backscattered diffraction techniques. Growth kinetics of the reaction layers and average effective interdiffusion coefficients in the layers were determined for the composites. Results showed that an intermetallic phase isostructural with µ-phase formed in the as-cast W/316L and W/Fe-Ni-Cr composites with 1 and 2 Fe:Ni matrix ratios. In W/HP a phase M12C with crystal structure similar to η-carbide was formed. These phases developed and formed brittle reaction layers around the W wires during diffusion annealing. A parabolic relationship between the µ-phase and η-carbide growth and diffusion annealing time indicated that the growth of reaction layers was diffusion controlled. In the W/Fe-Ni-Cr composites, formation of intermetallic phases did not occur in the matrices with 0.5Fe:Ni ratio, instead some isolated tungsten particles were observed in the matrix adjacent to the wires after diffusion annealing. In W/Fe-Ni-Cr composites with 1 and 2 Fe:Ni matrix ratio, the growth of µ-phase reaction layers during annealing was observed to be dependent on the matrix composition. It was found that with an increase in the Ni content in the matrix, growth of µ-phase reaction layer decreased. The study presented in this thesis gives first-hand information on phase formation and growth kinetics of the reaction layers in W/316L and W/HP composites. It revealed that the interaction of W with 316L and HP alloy matrices leads to formation of cracked intermetallic and carbide reaction layers which are not desirable in the composites designed for high temperature applications. It has also been shown in this study that in W/Fe-Ni-Cr composites, intermetallic phase formation can be suppressed by increasing Ni content in the matrix. In the composite with high Ni contents in the matrix (0.5Fe:Ni ratio) intermetallic phases do not form even after diffusion annealing at 1200°C. This intermetallic free W/Fe-Ni-Cr composite can further be studied for its creep strength.

A material to function as a molecular electronic device should have a strong coupling with electrodes through appropriate and well-defined anchoring groups and have to support an effective traveling of charges via a conjugated molecular backbone. Oligo(3-hexylthiophene)s are π-conjugated molecules having large applicability in several areas of organic electronics owing interesting semiconducting properties and they also hold great promises in the field of single-molecule electronics. Polymerization methods, in principle, allow construction of long conjugated systems in a single synthetic step, however, most of them lack precision. This work uses externally initiated chain-growth Kumada Catalyst - Transfer Polycondensation (KCTP) for the synthesis of semiconductive oligo(3-hexylthiophene) wires with controllable molecular weights, low polydispersities, high regioregularities as well as with well-defined starting and end groups. In such a way, the synthetic efforts were compromised to obtain relatively easy a series of very complex molecular wires with a reasonable structural precision. To modulate the electronic function of oligomer backbones, specific charge-transfer moieties (DMA-TCBD and Fc-TCBD) were inserted as side chains or end groups. In-situ termination of KCTP with ZnCl-functionalized electron rich alkynes followed by Diederich-type click reaction resulted in the synthesis of asymmetrical oligo(3-hexylthiophene)s having thiolate-functionalized starting groups and donor-functionalized end-groups with a high degree of end-group functionalizations. Side chains of double-thiolate functionalized oligo(3-hexylthiophene)s, on the other hand, were further modified with the insertion of charge-transfer groups by post-polymerization functionalization. While the facile synthesis and modification of oligo(3-hexylthiophene)s enable the control over the molecular backbone, the specific starting and end anchoring groups allow the control over the electrode oligomer interface. To assure the formation of alligator clips between oligomer backbone and Au electrode, the optimizations including proper end-group conversion into mild counterparts followed by in-situ deprotection into thiolates and the binding abilities on gold were investigated. Finally, the conductance of bis-end functionalized oligo(3-hexylthiophene)s was preliminarily studied through oligomer backbone by Mechanically Controllable Break Junctions (MCBJs) setup and through oligomer-attached DNA origami-templated gold nanowires by individual electrical contacts. The developed KCTP-based synthetic route, at the end, presents new opportunities for the facile synthesis, the ease of modification and the feasibility of asymmetrical and side chain functionalized oligo(3-hexylthiophene) wires for needs of molecular electronics.

Virtual simulators have proven to be extremely effective tools for training individuals for tasks that might otherwise be cost-prohibitive, dangerous, or impractical. One advantage of using a virtual simulator is that it provides a safe environment for emergency scenarios. For many years the United States military and NASA have used simulators, including those affixed with drive-by-wire (DBW) controls, effectively and efficiently to train subjects in a variety of ways. A DBW system utilizes electrical circuits to actuate servo motors from a given input signal to achieve a desired output. In DBW systems the output is not directly mechanically connected to a control surface (steering, acceleration, deceleration, etc.); usually, the input controller is linked by electrical wires to a localized servo motor where direct control can be given. This project is aimed at developing a novel simulator for a future training program using DBW systems that caters specifically to individuals who currently use or will be using for the first time vehicle modifications in order to drive and maintain their independence. Many of these individuals use one or a combination of powered steering, acceleration, braking, or secondary DBW controls to drive. The simulator integrates a virtual training environment and advanced electronic vehicle interface technology (AEVIT) DBW controls (4-way joystick, gas-brake lever/small zero-effort steering wheel). In a 30 participant study of three groups (able-bodied individuals, elderly individuals, and individuals with disability), it was found that training with a DBW joystick steering system will require more instruction and simulator practice time than a gas-brake lever/small steering wheel combination (GB/S) to obtain a similar level of competency. Drivers using the joystick completed predetermined driving courses in longer times, at slower speeds, with more errors than the other DBW system. On average, the reaction time to a stopping signal was fastest with the gas-brake lever at 0.54 seconds. Reaction times for the standard vehicle controls and the joystick were 0.741 and 0.677 seconds respectively. It was noted that reaction times using DBW controls were shorter overall. When driving in traffic, drivers committed 4.9, 5.1, and 8.3 driving infractions per minute using standard vehicle controls (No Drive by Wire, (NDBW)), the gas/brake and steering system, and joystick system respectively. Most drivers felt that the GB/S system was easier to learn, easier to operate, safer, and more reliable than the joystick system.

The kinetic and mechanistic features of a new series ofplatinum-thallium cyano compounds containing a direct andunsupported by ligands metal-metal bond have been studied insolution, using standard mix–and–measurespectrophotometric technique and stopped–flow method.These reactions are interpreted as oxidative addition of the cspecies to the square planar Pt(CN)₄^2-complex. Each of these processes was found to befirst-order in Pt(CN)₄^2-, the corresponding TI^IIIcomplex and a cyanide ion donating species whichacts as a catalyst. Both di- and trinuclear complexes werestudied, and the kinetically significant thallium complexes intheir formation and the catalytically active cyanide sourcesare as follows: [(CN)₅PtTl(CN)₃]^3-: Tl(CN)₄^–(alkaline region), Tl(CN)₃(slightly acidic region) and CN^–; [(CN)₅Pt–Tl(CN)]–: Tl(CN)₂⁺and Tl(CN)₂⁺; [(CN)₅Pt–Tl–Pt(CN)₅]^3-: [(CN)₅Pt–Tl(CN)]–and HCN. Appropriatemechanisms were postulated for the overall reactions in allcases, which include i) metal–metal bond formation stepand ii) coordination of an axial cyanide ion to the platinumcenter. Two experimentally indistinguishable kinetic modelswere proposed for the formation of the dinuclear complexeswhich are different in the sequence of the two steps. In thecase of the trinuclear complex, experimental evidence isavailable to exclude one of the alternative reaction paths, andit was proven that the metal–metal bond formation precedesthe axial cyanide coordination.

The cyanide ligands coordinated to TI^IIIin the Pt–Tl complexes could be replacedsuccessfully with aminopolycarboxylates e.g.: mimda^2-, nta^3-, edta^4-. The [(CN)₅Pt–Tl(edta)]^4-complex, with a direct metal–metal bond hasbeen prepared in solution by two different reactions: a)dissolution of [(CN)₅Pt–Tl](s) in an aqueous solution of edta, b)directly from Pt(CN)₄^2-and Tl(edta)(CN)^2-. The decomposition reaction is greatlyaccelerated by cyanide and significantly inhibited by edta. Itproceeds through the [(CN)₅Pt–Tl(CN)₃]^3-intermediate. The formation of [(CN)₅Pt–Tl(edta)]^4-can proceed via two different pathways dependingon the ratio of the cyanide to the edta ligand concentrations.The’direct path’at excess of edta means theformation of intermediate[(CN)4Pt···Tl(CN)(edta)]^4-, followed by a release of the cyanide from theTl–centre followed by coordination of a cyanide from thebulk to the Pt–centre of the intermediate. The’indirect path’dominates in the absence of extraedta and the formation of the Pt–Tl bond occours betweenPt(CN)₄^2-and Tl(CN)4^–.

Homoligand MTl(CN)₄(M = Tl^I, K, Na) and, for the first time, Tl(CN)₃species have been synthesized in the solid stateand their structures solved by single crystal X–raydiffraction method. Interesting redox processes have been foundbetween TI^IIIand CN^–in non–aqueous solution and in Tl₂O₃-CN^–aqueous suspension. In the crystal structureof Tl(CN)₃·H₂O, the thallium(III) ion has a trigonal bypiramidalcoordination geometry with three cyanides in the trigonalplane, while an oxygen atom of the water molecule and anitrogen atom from a cyanide ligand attached to a neighboringthallium complex, form a linear O–Tl–N fragment.Cyanide ligand bridges thallium units forming an infinitezigzag chain structure. Among the thallium(III) tetracyanocompounds, the isostructural M[Tl(CN)₄](M = Tl and K) and Na[Tl(CN)₄]·3H₂O crystallize in different crystal systems, but thethallium(III) ion has in all cases the same tetrahedralgeometry in the [Tl(CN)₄]^–unit.

Three adducts of mercury(II) (isoelectronic with TI^III) (K₂PtHg(CN)₆·2H₂O, Na₂PdHg(CN)₆·2H₂O and K₂NiHg(CN)₆·2H₂O) have been prepared from Hg(CN)₂and square planar transition metal cyanides M^II(CN)₄^2-and their structure have been studied by singlecrystal X–ray diffraction, XPS and Raman spectroscopy inthe solid state. The structure of (K₂PtHg(CN)₆·2H₂O consists of strictly linear one dimensional wireswith Pt^IIand Hg^IIcenters located alternately, d_Hg–Pt= 3.460 Å. The structure of Na₂PdHg(CN)₆·2H₂O and K₂NiHg(CN)₆·2H₂O can be considered as double salts, the lack ofhetero–metallophilic interaction between both the Hg^IIand Pd^IIatoms, d_Hg–Pd= 4.92 Å, and Hg^IIand Ni^IIatoms, d_Ni–Pd= 4.60 Å, seems obvious. Electronbinding energy values of the metallic centers measured by XPSshow that there is no electron transfer between the metal ionsin all three adducts. In solution, experimental findingsclearly indicate the lack of metal–metal bond formation inall studied Hg^II–CN^-–M^II(CN)4^2-systems (M = Pt, Pd and Ni). It is in contrary tothe platinum–thallium bonded cyanides.

KEYWORDS:metal–metal bond, platinum, thallium,kinetics, mechanism, stopped flow, oxidative addition, cyanocomplexes, edta, redox reaction, metal cyanides, X–raydiffraction, Raman, NMR, mercury, palladium, nickel, onedimensional wire

Doutoramento em Química
During the last years, the use of high hydrostatic pressure (HHP) as a non-thermal technology for preservation or aging of wine has increased substantially in the academic community. However, HHP treated wine has been only analysed after the pressure treatment, with no knowledge available on the effects of HHP during subsequent storage. The results presented in this thesis showed that HHP treatments influence the chemical and sensorial properties of wine during storage. The application of high hydrostatic pressure treatments in winemaking for wine preservation, as an alternative to sulphur dioxide, was evaluated studying the effect of HHP in the physicochemical and sensorial properties of red and white wines during bottle storage. High pressure treatments with 5 min of processing time and pressures of 425 and 500 MPa were shown to influence on both red and white wine physicochemical and sensorial characteristics. However, the effects were only perceptible after, at least, 6 months of storage. The alterations that occurred on the pressurized red wine characteristics, such as the more orange-red colour and the lower antioxidant activity (15-27% less), total phenolic content (9% less), and anthocyanins content (45–61% less), were due to an increase of condensation reactions of phenolic compounds. The increase of these condensation reactions lead to the formation of compounds with higher degree of polymerisation that became insoluble along storage, increasing consequently the amount of wine deposits in the pressurized wines. In terms of white wines, pressurized wines showed, after one year of storage, a more brownish colour and a lower antioxidant activity (15% less) and total content of phenolic compounds (10% less) when compared to the unpressurized wines. These results, together with the lower content of free amino acids (15-20% less) and higher content of furans (up to 70% more), present in the pressurized wines after nine months of storage, led to propose an effect of HHP treatments in the acceleration of Maillard reactions that occur during the wine storage period. Therefore, contrary to the pressurized sulphur dioxide-free red wine, the pressurized white wines were not considered suitable for commercialization as table wines due to the higher brownish colour and cooked fruit aroma, characteristics of an aged or thermally treated wine.Additionally, the impact of the pressure treatments on the volatile composition of sulphur dioxide-free red and white wines, during bottle storage, was evaluated. More than 160 volatile compounds, distributed by 12 chemical groups, were identified in both wines. At the end of storage, the pressurized wines presented a higher content of furans, aldehydes, ketones, and acetals when compared to the unpressurized wines. These results indicate that pressure influences the white and red wine long term volatile composition, being this particularly evident for longer storage periods. The changes on the volatile composition of the pressurized wines, indicated that the HHP treatments accelerate the Maillard reactions, and the oxidation of alcohols and fatty acids, leading to wines with a volatile composition network approaching the characteristic of faster aged and/or thermally treated wines. The acceleration of Maillard reactions and phenolic compounds condensation by HHP treatments was also studied in model wine solutions (hydro alcoholic solution at acidic pH). The results showed that the high pressure treatment accelerated the Maillard reaction and this effect was quantifiable, mainly, after 6 months of storage. Pressurized model solutions presented higher concentration of 2-furfural, phenylacetaldehyde and benzaldehyde, when compared to the controls. In terms of phenolic compounds condensation reactions, the pressurized model wine solutions showed no relevant differences, when compared to controls. Therefore, it seems that the pressure treatment had a higher impact in terms of kineticks of reactions and in less extent in terms of different compounds formed. Lastly, the application of HHP treatments in winemaking to improve the properties of young wines was evaluated. For this propose, the effect of HHP treatments in the phenolic composition of a red wine was studied and compared with the effect of different oenological practices. Wines pressurized at 500 MPa for 5 min, and 600 MPa for 20 min, at 20 ºC, showed, after 5 months of storage, a lower monomeric anthocyanins (8-14%), phenolic acids (8-11%) and flavonols (14-22%) content, when compared to the unpressurized ones. The wine pressurized at 500 MPa presented a flavanols content and a degree of polymerization very similar to the wines treated by traditional aging processes. In terms of sensorial properties, the pressure treatments increased the cooked fruit aroma and decreased the floral and fruit odours and, in the case of the 600 MPa treatment, increased the bitterness. Therefore, the HHP treatments seem to promote reactions that are similar to those observed in wines treated with wood aging processes. In conclusion, the results presented in this thesis showed that HHP treatments accelerated the Maillard reaction and the polymerization reactions between phenolic compounds present in the wine, influencing the chemical and sensorial properties of wine. HHP can be potentially used to preserve or accelerate the wine aging process, producing wines with pleasant and distinct characteristics.
Durante os últimos anos, o uso de alta pressão hidrostática (APH) como tecnologia não-térmica para a preservação ou envelhecimento de vinho tem aumentado substancialmente na comunidade académica. No entanto, os vinhos tratados por APH têm sido analisados após o tratamento de pressão, não havendo referências sobre as suas propriedades durante o armazenamento. Os resultados apresentados nesta tese mostram que a aplicação de tratamentos de APH altera as propriedades químicas e sensoriais de vinhos ao longo do armazenamento. Os tratamentos de alta pressão hidrostática foram aplicados na vinificação para a preservação de vinho, como alternativa ao dióxido de enxofre, sendo o seu efeito avaliado nas propriedades físico-químicas e sensoriais de vinhos tintos e brancos durante o armazenamento em garrafa. Os tratamentos de alta pressão com 5 min de processamento e pressões de 425 e 500 MPa mostraram influenciar as características físico-químicas e sensoriais de vinhos tintos e brancos. No entanto, o efeito foi apenas percetível após pelo menos 6 meses de armazenamento. As alterações que ocorreram nas características do vinho tinto pressurizado, tais como a cor mais laranja-vermelho, menor atividade antioxidante (menos 15 a 27%), menor conteúdo de compostos fenólicos totais (menos 9%) e menor teor de antocianinas (menos 45-61%), foram devidas a um aumento das reacções de condensação de compostos fenólicos. O aumento destas reações de condensação levou à formação de compostos com maior grau de polimerização que se tornaram insolúveis no vinho ao longo do armazenamento, aumentando consequentemente a quantidade de depósito nos vinhos pressurizados. Em relação ao vinho branco, os vinhos pressurizados mostraram, depois de um ano de armazenamento, uma cor mais acastanhada, menor atividade antioxidante (menos 15%) e menor teor de compostos fenólicos totais (menos 10%) comparando com os vinhos não pressurizados. Estes resultados, juntamente com o baixo teor de aminoácidos livres (menos 15 a 20%) e um maior teor de furanos (até 70% mais) para os vinhos pressurizados após nove meses de armazenamento, levam a propor que os tratamentos de APH aceleraram as reações de Maillard que ocorrem durante o período de armazenamento do vinho. No entanto, ao contrário dos vinhos tintos pressurizados, os vinho brancos pressurizados não foram considerados adequados para comercialização como vinhos de mesa, visto que apresentavam uma cor acastanhada e um elevado aroma a fruta cozida, características estas de vinhos envelhecidos ou tratados termicamente.Adicionalmente, foi avaliado o impacto dos tratamentos de APH sobre a composição volátil dos vinhos tintos e brancos sem dióxido de enxofre durante o armazenamento em garrafas. Mais de 160 compostos voláteis, distribuídos por 12 grupos químicos, foram identificados em ambos os vinhos. No final do armazenamento, os vinhos pressurizados apresentaram um teor mais elevado de furanos, aldeídos, cetonas e acetais quando comparados com os vinhos não pressurizados. Estes resultados indicam que os tratamentos de APH influenciam a composição volátil de vinhos brancos e tintos, , sendo mais evidente em longos períodos de armazenamento. As mudanças na composição volátil dos vinhos indicaram que os tratamentos de APH aceleraram as reações de Maillard e também a oxidação de álcoois e ácidos gordos, originando vinhos com uma composição volátil próxima de vinhos com envelhecimento acelerado ou tratados termicamente. A aceleração das reações de Maillard e de polimerização dos compostos fénolicos causada pelos tratamentos de APH foi também estudada em soluções modelo de vinho (solução hidroalcoólica com pH ácido). Os resultados mostraram que o tratamento de APH acelera a reação de Maillard , sendo este efeito quantificado, apenas, após 6 meses de armazenamento. As soluções modelo de vinho pressurizadas apresentaram concentrações mais elevadas de 2-furfuraldeído, fenilacetaldeído e benzaldeído, em comparação com os controlos. Em termos de polimerização dos compostos fénolicos, as soluções modelo pressurizadas não apresentaram diferenças relevantes, em comparação com os controlos. Por conseguinte, os tratamentos de APH aparentem ter mais impacto em termos de modificações nas cineticas de reação do que na formação de novos compostos. Por último, a aplicação de tratamentos de APH foi estudada para melhorar as propriedades de vinhos jovens. Para este propósito, o efeito de tratamentos de APH na composição fenólica de um vinho tinto foi estudado e comparado com o efeito de diferentes práticas enológicas. Vinhos pressurizados a 500 MPa durante 5 min e a 600 MPa durante 20 min, a 20 ºC, mostraram depois de 5 meses de armazenamento um menor teor de antocianinas monoméricas (8-14%), ácidos fenólicos (8-11%) e flavonóis (14 -22%), quando comparados com os vinhos não-pressurizados. O vinho pressurizado a 500 MPa apresentou um teor de flavonóis e um grau de polimerização de taninos muito semelhante aos vinhos tratados por processos de envelhecimento tradicionais. Em termos de propriedades sensoriais, os tratamentos de pressão aumentaram o aroma de fruta cozida e diminuiram os aromas florais e frutados, tendo no caso do tratamento de 600 MPa sido verificado também um aumento da amargura. Assim sendo, os tratamentos de APH parecem promover reações que são semelhantes às observadas em vinhos tratados com processos de envelhecimento em madeira. Em conclusão, os resultados apresentados nesta tese mostram que a aplicação de tratamentos de APH acelera as reações de Maillard e a polimerização dos compostos fenólicos presentes no vinho, ao longo do armazenamento, alterando assim as propriedades químicas e sensoriais dos vinhos. A APH pode ser potencialmente utilizada para preservar ou acelerar o processo de envelhecimento de vinho tinto produzindo vinhos com características agradáveis e distintas.

Die Temperaturverhältnisse beim Ziehen und Wärmebehandeln von Draht werden mit mathematisch-analytischen Methoden auf der Grundlage der FOURIERschen Wärmeleitungsgleichung eingehend untersucht. Insbesondere wird unter den spezifischen Wärmeübergangsbedingungen zwischen Draht und Ziehdüse sowie zwischen Draht und Ziehtrommel deren thermische Wechselwirkung analysiert. Ein Näherungsverfahren zur Berechnung der Drahttemperaturen in Zugfolgen unter Berücksichtigung des Ziehdüseneinflusses wird angegeben und mit einem Beispiel zum Nassziehen stark verzinkten Stahldrahts illustriert. Aus geschwindigkeitsabhängig gemessenen Änderungen des Drahtdurchmessers werden unter thermoelastischer Ziehringdurchmesserkorrektur Schmierfilmdicken bestimmt. Diffusionsgleichungen werden analysiert und ein Zusammenhang zur Reaktionskinetik wird hergestellt. Ein neues reaktionskinetisches Werkstoffmodell, das insbesondere auch im Falle stärker anisothermer Verhältnisse, also bei Kurzzeitwärmebehandlung anwendbar ist, wird vorgestellt.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2008.
Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 7089. Adviser: Dimitrios C. Kyritsis. Includes bibliographical references (leaves 107-117). Available on microfilm from Pro Quest Information and Learning.

Dissertação de Mestrado em Engenharia de Materiais apresentada à Faculdade de Ciências e Tecnologia
O trabalho de investigação realizado teve por objetivo otimizar o revestimento de fios de tungsténio com filmes multicamada reativos, por forma a promover uma reação autopropagável entre Ni e Al (ou Ti), com a consequente libertação de calor. O objetivo final é utilizar este calor para fundir um material de baixo ponto de fusão, e assim bloquear a propagação de fendas em materiais metálicos.Filmes multicamada Ni/Al e Ni/Ti foram produzidos por pulverização catódica magnetrão, utilizando dois alvos distintos. Como substratos foram utilizados fios de tungsténio com diâmetros de 0,5, 0,2 e 0,05 mm. As deposições foram efetuadas de modo a obter filmes multicamada com composição química global equiatómica e períodos de modulação (espessura da bicamada) nanométricos (25 e 50 nm). De forma a otimizar o revestimento de fios, foi desenvolvido um novo porta substratos. A secção transversal dos filmes foi analisada por microscopia eletrónica de varrimento e transmissão, após deposição e após ignição por descarga elétrica de 9V.A redução das potências aplicadas aos alvos e a utilização do novo porta substratos permitiram evitar/reduzir os defeitos observados nos filmes Ni/Al. Nos filmes Ni/Ti não foram observados defeitos. Ao fazer passar corrente através de um fio de W com 0,05 mm de diâmetro, revestido com um filme Ni/Al com 25 nm de período, foi observado um “flash” e confirmada a ocorrência de uma reação autopropagável. Concluindo, neste estudo foram desenvolvidos fios de W revestidos com filmes multicamada reativos com potencial para aplicação em autorreparação.
The aim of this research work was to optimize the coating of tungsten wires with reactive multilayer thin films in order to promote a self-propagating reaction between Ni and Al (or Ti), with consequent heat release. The ultimate goal is to use this heat to melt a low melting point material, and thus block crack propagation in metallic materials.Ni/Al and Ni/Ti multilayer films were produced by magnetron sputtering using two different targets. Tungsten wires with diameters of 0.5, 0.2 and 0.05 mm were used as substrate material. The depositions were carried out in order to obtain multilayer thin films with equiatomic overall chemical composition and nanometric modulation periods (bilayer thickness, 25 and 50 nm). In order to improve the coating of wires, a new substrate holder has been developed. The cross section of the films was analyzed by scanning and transmission electron microscopy, after deposition and after ignition by an electric discharge of 9V.The reduction of the power applied to each target and the use of the new substrate holder allowed the defects observed in Ni/Al thin films to be avoided/reduced. Ni/Ti thin films showed no defects. When passing current through a 0.05 mm diameter W wire coated with a 25 nm period Ni/Al film, a flash was observed and the occurrence of a self-propagating reaction confirmed. In conclusion, in this study W wires coated with reactive multilayer thin films with potential for self-healing applications were developed...................

碩士
國立臺灣科技大學
機械工程系
106
Single crystal sapphire is a highly transmissive, high temperature resistant, and high hardness brittle semiconductor material, but with a good lattice matching with GaN for solid-state illumination. Diamond Wire Sawing (DWS) is usually used in the production of single crystal sapphire wafer for LED substrates. This research aims to develpe a multi-wire reactive electrophoresis DWS and apply SiO2 particles to generate a solid-phase chemical reaction (SPCR) with sapphire and then create the deposition of SiO2 powder coating by electrophoresis deposition during the diamond wire sawing process. For process mechanism, the reacting abrasive first convert the sapphire surface into a softer reaction layer, then the softened layer can be removed by diamond grits on the diamond wire. In this study, a single-wire saw cutting machine has been modified from previous study and used to finish wire sawing of two-inch sapphire wafers to verify the solid-phase chemical reaction. Moreover, the EPD-SDWS process has been converted into an experimental multi-wire saw machine to compare the difference with rocking motion. Experimental results show that the SPCR can reduce surface roughness of as-cut sapphire wafer Sa as 26% and Ra as 42%. Also the shape of chips can be obviously changed from granular to strip type. The rocking motion assisted process can reduce the contact length by 49% and increase the material removal rate (MRR) by 29%. Moreover, surface quality and sub-surface damage can be improved. Results of this study can be future applied on development of high efficient multi-wire sawing process of related semiconductor material process.

碩士
中原大學
奈米科技碩士學位學程
103
Zinc oxide (ZnO) is one of the most popular semiconductor materials in recent years. In this study, we synthesized zinc oxide nano-particles (ZnO NPs) by the typical sol-gel method with ultrasonic treatment to avoid particle aggregation In the first part of this thesis, we discussed how the molecular weights (NW) of polyvinyl pyrrolidone (PVP), which was used as a protecting agent in the synthesis, affect the ZnO NPs size and the oxygen vacancies in ZnO structure. We characterized the ZnO NPs by scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-vis), photoluminescence (PL), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), Raman spectroscopy, etc. Next, we chose PVP MW ~ 8K to synthesize the optimized ZnO NPs. Then we combined ZnO NPs and silver nano-wires (Ag NWs) into heterostructured nano-composites with a UV light treatment. In this step, we also characterized the samples by TEM, SEM, PL, UV-vis, EDS, XRD, etc. The last as well as main purpose of this thesis is to study the photo-catalysis reaction with our ZnO / Ag nano-composites. The degradation of the organic pollutant methyl blue (MB) was used to evaluate the photo-catalytic efficiency. We compared the photo-catalytic efficiency of the pure ZnO samples synthesized by different PVP molar weights and the ZnO/Ag nano-composites.

碩士
東南技術學院
防災科技研究所
94
The purpose of this study is to investigate the effects of confinement by using Reactive Powder Concrete（RPC）and wire mesh, together, to reinforce the compression member. The plain concrete specimen is used as the compression member. And three different reinforcing methods are used：1) one layer of wire mesh and 5mm thick of RPC, 2) two layers of wire mesh and 10mm thick of RPC, 3) three layers of wire mesh and 15mm thick of RPC. The RPC and wire mesh is placed at the outer ring of the plain concrete specimen to provide confinement to the specimen. The result of our study shows the compression strengths of the reinforced specimens increase 35﹪, 47﹪and 86﹪respectively, for each reinforcing method, when compared to the strength of the un-reinforced specimen. In addition to the increase in compression strength, the reinforced specimens also show a tremendous increase in ductility. For example, the length of the specimen decreases 20mm in compression test before failure occurred, if it is reinforced with three layers of wire mesh and 15mm thick of RPC.

碩士
國立清華大學
工程與系統科學系
99
In this paper, we proposed a new design of a high performance methanol micro-reformer for hydrogen production which integrated low temperature catalysts supported by silicon nano-wires inside micro-channels with multi-inlet and in-parallel channel. Without complicated fabrication process, the reforming performance of micro-reformer with Si nano-wire fully filled channel-passageways in height and length compared to that without nano-wires supported can enhanced by 38 folds more hydrogen yield；and the hydrogen yield at 180 oC and 250 oC are 8.8×10-7 mole/min and 1.5×10-6 mole/min, respectively. The enhancement of this new design micro-reformer was attributed to (1) the large surface area that the Si nano-wires can provided，(2) hard membrane photoresist process which assisted in better catalytic coating morphology，(3) the special design of Si nano-wires fully filled channel-passageways in height and length was expected to be able to force reactive-gases contact with catalysts，(4) the detailed discussions of how the different ingredients in catalysts solution influence the catalytic coating morphology。

Yes
As a type of excellent reinforcing filler, super-fine stainless wire (SSW) can form widely distributed network in reactive powder concrete (RPC) to transfer crack tip stresses as well as inhibit the initiation and propagation of cracks, leading to significant improvement of flexural toughness of RPC. In this paper, the flexural toughness of RPC beams and plates reinforced with 1% and 1.5% by vol. of SSWs was investigated, and its calculation model was established according to the composite material theory. Experimental results showed that the flexural toughness of unnotched beams fabricated with RPC containing 1.5% SSWs is 146.5% higher than that of control RPC without SSWs according to load-deflection relationships. The equivalent flexural strength of notched RPC beams is enhanced by 80.0% as SSW content increases from 1% to 1.5%. The limitation ability of SSWs on crack mouth opening can be used to evaluate the flexural toughness of composites. An addition of 1.5% SSWs leads to 201.9% increase of flexural toughness of RPC plates in accordance with load-deflection relationships. The calculation model based on the composite material theory can accurately describe the toughening effect of SSWs on RPC beams and plates. The enhancement of flexural toughness of RPC caused by SSWs is beneficial for improving the safety of structures as well as broadening the engineering applications of composites.
National Key Research and Development Program of China (2018YFC0705601) and China Postdoctoral Science Fundation (2019M651116).

Yes
Super-fine stainless wire (SSW) can not only form widely distributed enhancing, toughening and conductive network in reactive powder concrete (RPC) at low dosage level, but also improve weak interface area and refine cracks due to its micron scale diameter and large specific surface. In addition, the crack resistance zone generated by SSWs and RPC matrix together has potential to further enhance the fracture properties of composites. Therefore, fracture and self-sensing characteristics of SSW reinforced RPC composites were investigated in this paper. Experimental results indicated that adding 1.5 vol. % of SSW leads to 183.1% increase in the initial cracking load of RPC specimens under three-point bending load. Based on two parameter fracture model calculations, an increase of 203.4% in fracture toughness as well as an increase of 113.3% in crack tip opening displacement of the composites reinforced with 1.5% SSWs are achieved. According to double-K fracture model calculations, the initiation fracture toughness and unstable fracture toughness of the composites are enhanced by 185.2% and 179.2%, respectively. The increment for fracture energy of the composites reaches up to 1017.1% because of the emergence of blunt and tortuous cracks. The mixed mode Ⅰ-Ⅱ fracture toughness of the composites is increased by 177.1% under four-point shearing load. The initial angle of mixed mode Ⅰ-Ⅱ cracks of the composites decreases with the increase of SSW content. The initiation and propagation of cracks in the composites can be monitored by their change in electrical resistivity. The excellent fracture toughness of the composites is of great significance for the improvement of structure safety in serviceability limit states, and the self-sensing ability of the composites can also provide early warning for the degradation of structure safety.
National Key Research and Development Program of China (2018YFC0705601), the National Science Foundation of China (51578110), China Postdoctoral Science Fundation (2019M651116) and the Fundamental Research Funds for the Central Universities in China (DUT18GJ203).

碩士
國立臺灣科技大學
機械工程系
103
Solar cells have been one of the most important alternative energy for many years. However, efficiency and energy exhaustive of fabrication silicon substrates have always been a major problem in promotility such green products. This study develops a Reactive Electrophoretic Diamond Wire Sawing (REP-DWS) to slice first time, which integrates both Diamond Wire Sawing (DWS) and Slurry Wire Sawing (SWS) with Solid Phase Chemical Reaction (SPCR) to be a novel slicing process of silicon substrates. Calcium carbonates are used as reactive abrasive to soften the surface of silicon ingot with solid-state reaction layer and then removed by diamond abrasive to improve the Material Removal Rate (MRR). Tests of contact angle, Vickers indentation and XPS have been used to verify the existence of reaction layer. In this study, REP-DWS single-wire saw test machine has been remodeled, for experimental parameters, using voltage 25V and slurry with 30wt% CaCO3 concentration can improve surface roughness about 6% and reduce surface saw marks of sliced substrates about 57%. Then a commercial multi-wire saw experimental apparatus has been retrofitted, for experiments of results, REP-DWS can increase MRR about 13% and reduce the wear of diamond grits on wire by 59% as compared with DWS. The REP-DWS process improves saw marks on surface and also reduce sub-surface crack. Results of this study can be further develop of multi-wire saw process.

碩士
國立成功大學
材料科學及工程學系碩博士班
100
The influence of palladium in the interfacial reactions of copper wire bonding under current stressing is reported in this study. At the as-bonded step, Pd dissolved into a Cu ball bond and then gathered at the edge of the Cu ball, forming an anti-oxidation layer. The growth rate of IMCs under current stressing depends on the type of wire bonds and the direction of the current. The interfacial reaction at the anode, where electrons flow from Cu wire bonds to the Al pad, is faster than that of the cathode, where electrons flow from the Al pad to Cu wire bonds. This is probably because the dominate diffusion species in Cu-Al IMCs is copper. Results show that the existence of Pd restrained the growth rate of IMCs due to the formation of the Pd-enriched layer near the interface at the anode which acted as a diffusion barrier; however, a notch was formed at the cathode and the effect on the IMC growth rate could be neglected there. This may be the reason why Pd-coated copper wires show better bonding reliability than pure copper wires in the wire bonding process.

Taking advantage of cutting-edge technologies in computational and experimental chemistry, my Ph. D. research aimed to bridge both of these chemical subdivisions. Therefore, while part I of this dissertation focuses on new structure-based computational methodologies to predict selectivities of organic and enzymatic reactions, part II is concerned with the design, the synthesis and the electrical properties of novel, single molecular wires. These single molecule technologies described in part II are likely to contribute to more powerful computer chips in the future, which will in turn lead to faster and more accurate computational predictions for chemical problems. Part I: Computers for Chemistry: Progress towards the design of accurate computational tools to predict the selectivity of chemical reactions. The first fully quantum mechanical study to predict enantioselectivities for a large dataset of organic reactions has been reported. Enantioselectivities were calculated for a diverse set of 46 dioxirane catalyzed epoxidation reactions. Comparison to experiments showed that our methodology is able to accurately predict the free energy differences between transition states leading to enantiomeric products. To further improve the predictive performance, we have also developed a new correction scheme, which increases the accuracy of density functional theory (DFT) for non-covalent interactions. Our new correction scheme accurately estimates interaction energies of non-covalent complexes not only with large, but also with small basis sets at lower computational cost. The improved enantioselectivity prediction protocol containing our latest non-covalent corrections has now been fully automated in a user-friendly fashion. We are currently testing its accuracy for other asymmetric reactions, such as CBS reductions and are also trying to use our methodology to design new asymmetric organocatalysts. In collaboration with Dr. Jianing Li, a structure based computational methodology to predict sites of metabolism of organic substrates with P450 enzymes has also been developed, which is highly relevant for structure-based drug discovery. Part II: Chemistry for Computers: From novel antiaromatic and pi-pi-stacked molecular wires to highly conducting link groups with direct Au-C bonds. Part II of this dissertation describes studies of antiaromatic and pi-pi-stacked molecular wires as well as new direct ways to connect them to gold electrodes. At the beginning, the first successful single molecule conductance measurements ever on partially antiaromatic molecular wires are described. These wires, based on a biphenylene backbone, were synthesized via a highly regioselective cyclization enabled by the antiaromaticity. Then, two new ways to connect single molecules to gold electrodes with direct Au-C links are presented. The first methodology is based on strained arene rings in [2.2]-paracyclophanes, which were found to directly contact gold electrodes with their pi-systems. The second methodology employs tin based precursors, which get replaced in situ by gold electrodes to also form direct Au-C bonds with very low resistance. The direct Au-C bonds observed with strained paracyclophanes enabled us to study, for the first time, single molecule conductance through multiple layers of stacked benzene rings. Further single molecule conductance studies with less strained stacked benzene rings are currently under way and will provide additional valuable evidence about electron transport in stacked pi-systems.

碩士
國立成功大學
材料科學及工程學系
104
The industry is trying to replace part of gold and copper wire bond with silver wires. Ag-Pd alloy wire was reported as a potential candidate because of its high reliability. This study investigated the interfacial reaction of Ag-xPd wire bonding on Al pad under various testing conditions. Aging, pressure cook test (PCT), temperature cycling test (TCT) and un-biased accelerated and humidity stress test (u-HAST) were applied on As-bonded AgxPd(1~6%) wire bonding samples to study the interfacial reaction. The SEM images of wire bond under different test conditions were analyzed. The results indicated that the growth of the intermetallic compound (IMC) was enhanced when the content of Pd is more than 3.5%. The composition of IMC was analyzed by SEM-EDX. It shows that the contents of Al in IMC decrease when the Pd content of alloy wire increases. An increase in the content of Pd in alloy wire leads to promote the formation of (Ag,Pd)2Al rather than (Ag,Pd)3Al2. After PCT test, the corrosion behavior occurred at the interface and Ag-rich IMC (Ag,Pd)3Al formed above the Al-pad. Under TCT test, the (Ag,Pd)3Al2 formed at the interface. The (Ag,Pd)3Al2 exhibits larger difference the coefficient of thermal expansion (CTE) with alloy wire. It tends to induce the crack formation during TCT test. The increasing Pd content inhibits the corrosion of the wire bond under u-HAST test.

博士
國立臺灣大學
化學研究所
89
The research focused on nanostructures, nanodevices and even on molecular devices has been extensively carried out due to their potential applications in fabrication of computer chips. Among them, the fabrication process of the nanowire has drawn great attention because of its use as the data-transfer line in the nano-scale. The ultimate goal is to fabricate the atomic-scale metal wire on the surface. The recent success in the synthesis of the linear metal-chain complexes with various nuclear chain lengths has stimulated us to study the chemical reaction between this kind of compounds and the semiconductor surface in order to obtain insights into the process which may govern the fabrication of the atomic-scale metal wire on surfaces. In this study, a tri-nuclear metal string complex Cr3(μ3-dpa)4Cl2 (dpa=dipyridylamido anion) is used as the precursor and deposited on GaN(0001) and Si(100) surface in a UHV environment. Their surface chemical reactions are monitored using temperature programmed desorption, Auger electron spectroscopy, synchrotron radiation core-level spectroscopy, and secondary ion mass spectroscopy. At low temperature, the layer of adsorbates might be formed through Cr bonding to the surface. At an exposure of 50L, there may be two adlayers on the GaN(0001) surface, the first one binding with a configuration similar to the molecular dish laying flat on the surface, the second one with the dish standing up. At increasing substrate temperatures, the complex decomposes in two different stages. One relates to the desorption of the dpa ligand from the adsorbed complex at ~340K, the other to a further decomposition of the residual complex at ~540K. A Cr metal adlayer, containing mainly Cr adatoms with a trace amount of Cr dimers, can be obtained when the metal-string complex is exposed to the GaN surface at high substrate temperature above 770K. In the case of Cr3(μ3-dpa)4Cl2 reaction on the Si(100) surface, the ligand on the complex decomposes upon adsorption on the surface. At increasing substrate temperature, further decomposition of the ligand will occur. At a higher exposure, the ligand molecule can desorb at a substrate temperature of 280K and the decomposed CrxLy molecule will desorb from the Si(100) surface at the temperature of 400K and 490K.

Die Temperaturverhältnisse beim Ziehen und Wärmebehandeln von Draht werden mit mathematisch-analytischen Methoden auf der Grundlage der FOURIERschen Wärmeleitungsgleichung eingehend untersucht. Insbesondere wird unter den spezifischen Wärmeübergangsbedingungen zwischen Draht und Ziehdüse sowie zwischen Draht und Ziehtrommel deren thermische Wechselwirkung analysiert. Ein Näherungsverfahren zur Berechnung der Drahttemperaturen in Zugfolgen unter Berücksichtigung des Ziehdüseneinflusses wird angegeben und mit einem Beispiel zum Nassziehen stark verzinkten Stahldrahts illustriert. Aus geschwindigkeitsabhängig gemessenen Änderungen des Drahtdurchmessers werden unter thermoelastischer Ziehringdurchmesserkorrektur Schmierfilmdicken bestimmt. Diffusionsgleichungen werden analysiert und ein Zusammenhang zur Reaktionskinetik wird hergestellt. Ein neues reaktionskinetisches Werkstoffmodell, das insbesondere auch im Falle stärker anisothermer Verhältnisse, also bei Kurzzeitwärmebehandlung anwendbar ist, wird vorgestellt.