Orientador: Prof. Dr. José Antonio Souza / Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, Santo André, 2018. / O objetivo deste trabalho e sintetizar materiais magneticos e semicondutores ocos micro/nanoestruturados hierarquicamente, para obter um melhor entendimento das propriedades fisicas e explorar aplicacoes tecnologicas. Inicialmente, microtubos de hematita e magnetita foram sintetizados por oxidacao termica juntamente com uma corrente eletrica aplicada e utilizando-se o microfio de ferro metalico como precursor. A fraccao volumetrica de Fe2O3(hematite) e Fe3O4(magnetite) nos microtubos e a formacao das nanoestruturas de hematite na superficie pode ser controlada por alteracoes sistematicas dos parametros de sintese tais como temperatura, rampa de aquecimento, tempo de aquecimento e valor da corrente electrica. A reacao quimica de oxidacao envolve um processo onde uma fina camada de oxido e formada primeiro na superficie do metal, seguida por difusao simultanea de ions metalicos atraves da camada oxida e difusao de oxigenio da atmosfera para o interior. A difusao para fora e mais rapida, levando a criacao de vacancias que coalescem em poros formando os microtubos. Medidas de resistividade eletrica in situ foram realizadas durante o processo de oxidacao mostrando todo o processo de formacao do microtubo. Imagens de microscopia eletronica de varredura mostram a morfologia do microtubo com diametro variando de 40 ¿Êm a 100 ¿Êm e comprimento de 5 mm. Medidas de difracao de raios-X em po evidenciam a presenca de fases cristalinas de hematita (Fe2O3) e magnetita (Fe3O4) nos microtubos. Nanoestruturas de hematita aparecem em forma de bastoes e fios dispersos homogeneamente ao redor da superficie do microtubo com diametros de 80-300 nm e comprimento de 1-5 ¿Êm. Experimentos in vitro envolvendo aderencia, migracao e proliferacao de culturas de celulas de fibroblastos na superficie dos microtubos indicaram a ausencia de citotoxicidade para este material. Tambem o calculo do torque e da forca magnetica desses microtubos com nanofios em funcao do gradiente de campo magnetico externo, mostrou que ele e robusto, abrindo a possibilidade para fabricacao de bio-microrobos magneticos para aplicacao em biotecnologia. Por outro lado, microarquiteturas ocas de SnS e ZnS decoradas com nanoestruturas foram sintetizadas por evaporacao termica livre de catalisadores utilizando microfios de metal e po de enxofre como materiais de partida. Para o SnS, observamos formacao de uma estrutura oca composta por uma camada metalica de Sn na superficie interna, e uma camada de SnS de estrutura ortorrombica com nanoestruturas de SnS na superficie. Para o ZnS, descobrimos a formacao de uma esfera oca com uma camada metalica na parte interna, uma camada de ZnS com fase cubica, e sobre ela nanoestruturas de ZnS com fase cristalina hexagonal cresceram homogeneamente. O diametro da microsfera e de 415 ¿Êm e os nanofios tem um diametro e comprimento medio de 70 nm e 7 ¿Êm, respectivamente. As microestruturas ocas semicondutoras de ZnS e SnS exibiram atividade eficiente para degradar azul de metileno sob irradiao com luz solar simulada. Os resultados revelam que essas nano/microestruturas possuem alta fotoatividade para degradacao organica. / The aim of this work is to synthesize hierarchically micro/nanostructured hollow magnetic and semiconductor materials, to obtain a better understanding on the physical properties, and find technological applications. Initially, hematite and magnetite microtubes were synthesized by thermal oxidation process along with the presence of an applied electrical current and using metallic iron microwire as a precursor. The volume fraction of both Fe2O3 (hematite) and Fe3O4 (magnetite) phase on microtubes can be controlled as well as surface nanostructures formation of hematite by systematic change of the synthesis parameters such as temperature, heating rate, annealing time and electrical current value. The oxidation chemical reaction involves a process where a thin oxide layer is formed first on the metal surface, followed by simultaneous outward diffusion of metal ions through the oxide scale and inward diffusion of oxygen from the atmosphere into the core. In our case, the outward diffusion is faster leading to the creation of vacancies which coalesce into voids forming the microtubes. In situ electrical resistivity measurements were carried out during the oxidation process showing the whole process of the microtube formation. Scanning electron microscopy images show microtube morphology with diameter ranging from 40 ìm to 100 ìm and length of 5 mm. X-ray powder diffraction measurements evidence the presence of hematite (Fe2O3) and magnetite (Fe3O4) crystal phases comprising microtubes. Nanostructures of hematite appear in form of sticks and wires homogeneously dispersed on the microtube surface with diameters ranking from 80 nm to 300 nm and length of 1 to 5 ìm. In vitro experiments involving adherence, migration, and proliferation of fibroblasts cell culture on the surface of the microtubes indicated the absence of immediate cytotoxicity for this material. We have also calculated both torque and driving magnetic force for these microtubes with nanowires as a function of external magnetic field gradient which were found to be robust opening the possibility for magnetic bio micro-robot device fabrication and application in biotechnology. On the other hand, SnS and ZnS hollow microarchitectures decorated with nanostructures were synthesized by catalysis free thermal evaporation technique using metal microwires and sulfur powder as starting materials. For SnS, we observed a hollow formation comprised of a thin metallic Sn layer in the inner surface, SnS orthorhombic structure thick layer with SnS nanostructures on the top. For ZnS, we found out the formation of hollow sphere with a thin metallic layer in the inner part, a thick cubic phase layer of ZnS, and on this second phase, nanostructures of ZnS hexagonal crystal phase grew up homogeneously. The microsphere diameter is about 415 ìm and the nanowires on the surface have average diameter of 70 nm and length 7 ìm. ZnS and SnS hollow semiconducting microstructures have exhibited efficient activity to degrade the methylene blue under simulated sunlight irradiation. The results reveal that these nano/microstructures have high photoactivity to organic degradation.

Storage of mine tailings and waste concrete imposes economical and environmental impacts. Researchers have attempted to reuse wastes as construction material by utilizing ordinary Portland cement (OPC) to stabilize them. This method, however, has a number of limitations related to OPC. In this research, a recent technology called geopolymerization is used to stabilize mine tailings and concrete waste so that they can be completely recycled and reused. The research includes three main parts. The first part studies the effect of different factors on the mechanical properties, micro/nano structure, and elemental and phase composition of mine tailings-based geopolymer binder. The second part investigates the feasibility of producing geopolymer bricks using mine tailings. The physical and mechanical properties, micro/nano structure, durability, and environmental performance of the produced bricks are studied in a systematic way. Moreover, the enhancement of the mine tailings-based geopolymer bricks by adding cement kiln dust (CKD) is studied. The third part of the research investigates the recycling of the fines fraction of crushed waste concrete to produce binder through geopolymerization in order to completely recycle concrete waste. The results indicate the viability of geopolymerization of mine tailings by optimizing the synthesis conditions. By properly selecting these factors, mine tailings-based geopolymer bricks can be produced to meet the ASTM standard requirements and to be environmentally safe by effectively immobilizing the heavy metals in the mine tailings. The physical and mechanical properties and durability of the mine tailings-based geopolymer bricks can be further enhanced by adding a small amount of CKD. The results also show that the fines fraction of crushed waste concrete can be used together with fly ash to produce high performance geopolymer binder. Incorporation of calcium in the geopolymer structure and coexistence of the calcium products such as CSH gel and the geopolymer gel explains the enhancement of the mine tailings-based geopolymer bricks with CKD and the high performance of geopolymer binder from the waste concrete fines and fly ash. The research contributes to sustainable development by promoting complete recycling and utilization of mine tailings and concrete waste as construction material.

El presente trabajo de Tesis Doctoral ha contemplado el estudio teórico y el desarrollo de modelos computacionales acerca de los efectos que causa el proceso de difusión superficial actuando sobre distintos tipos de estructuras de alta razón de aspecto. Tal estudio presenta un intrínseco interés en diversas áreas de la nanociencia y la nanotecnología, involucrando de manera interdisciplinaria aspectos físicos y químicos.

The marked increase in demand for miniaturized consumer products in a broad range of potential applications including medical, telecommunication, avionics, biotechnology and electronics is a result of advancements in miniaturization technologies. Consequently, engineering components are being drastically reduced in size. This coupled with the quest for higher quality components, has imposed more stringent requirements on manufacturing processes and materials used to produce micro components. Hence, the development of ultra precision manufacturing processes to fabricate micro-scale features in engineering products has become a focal point of recent academic and industrial research. However, much attention in the area of micro-manufacturing, especially micro-mechanical machining, has been devoted to building miniature machine tools with nanometer positioning resolution and sub-micron accuracy. There is lack of fundamental understanding of mechanical machining at the micro and nano scale. Specifically, basic understanding of chip formation mechanism, cutting forces, size-effect in specific cutting energy, and machined surface integrity in micro and nano scale machining and knowledge of how these process responses differ from those in macro-scale cutting are lacking. In addition, there is a lack of investigations of micro and nano scale cutting of common engineering materials such as aluminum alloys and ferrous materials. This thesis proposes to advance the understanding of machining at the micro and nano scale for common engineering alloys. This will be achieved through a series of systematic micro and nano cutting experiments. The effects of cutting conditions on the machining forces, chip formation and machined surface morphology in simple orthogonal micro-cutting of a ferrous, P20 mold steel (30 HRC), and a non-ferrous structural alloy, aluminum AL7075 (87 HRB), used in the mold making and rapid prototyping industry will be studied. The data will also be compared with data obtained from conventional macro-scale cutting. In addition, the applicability of conventional metal cutting theory to micro and nano cutting test data will be examined. The analysis will provide a better understanding of machining forces, chip formation, and surface generation in micro and nano scale cutting process and how it differs from macro-scale cutting.

This PhD thesis presents the outcome of employing both nanosecond and femtosecond pulsed lasers in order to modify the surface structure of a material at the micro and nano scales. Literature review was carried out on micro/nano fabrication technologies involved in the semiconductor industry, which are the basis of many current micro and nano-manufacturing processes. The first experiments concentrated on direct laser scanning of Si to produce surface microstructures. This type of texturing was very effective at reducing surface reflectivity and can be implemented in photovoltaic devices. It was also found that the ablation efficiency can be improved if laser processing is performed in an argon environment where oxidation can be suppressed. Moreover, a significant relationship between laser-texture characteristics (i.e. topography/morphology and periodicity) and total surface reflectance was demonstrated. Short-circuit modelling of the laser texture showed that electrical performance of the cell can be improved by 41.3% in the 360-1100 spectrum, even in the near-infrared for which Si is a weak absorber. From these experimental results, it was also noticed that the laser-generated micro-structures made the surface significantly wettable; but as the laser fluence was reduced, the contact angle of the surface could be changed. This led to the investigation of the wetting properties of nano-bumps produced on Si at fluences below the ablation threshold. Their wetting behaviour was reported for the first time. An effect named as 'invisible marking' in this thesis was demonstrated: vapour condenses into water drops of different size depending on the lattice arrangement of c-Si or a-Si. Such an interaction at the near-ablation threshold was also explored for another type of material: NiP/Al data storage disks. From this research, elliptical bumps with vertical dimension in the sub-nanometre scale were fabricated with extremely high repeatability (± 0.4 nm). In addition, it was found that elliptical bumps can offer better stiction performance than circular shapes, even at ultra-low flying height. This type of laser texture could be utilised as a means for tribological optimization of surfaces that are in close proximity and relative motion. Following the use of low-fluences by nanosecond pulses, this was also applied to scanning over a microsphere lens array. So far, the research on near-field effects produced at the bottom of transparent particles has focused on how to generate parallel nano-patterns by single pulses. However, the present work has demonstrated that a focused beam with a tight-focus can be used to fabricate single lines or shapes rather than repeated patterns. In this way, a femtosecond laser was introduced to meet such a challenge. Moreover, laser-induced periodic surface structures (LIPSS) by fs pulses were also identified along the near-field generated nano-patterns. The evolution of such a periodic, self-assembly structuring was also investigated, and new optical characteristics of structural colour were found.

京都大学 / 0048 / 新制・論文博士 / 博士(工学) / 乙第13008号 / 論工博第4133号 / 新制||工||1649(附属図書館) / 32936 / (主査)教授 北村 隆行, 教授 北條 正樹, 教授 琵琶 志朗 / 学位規則第4条第2項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The Terahertz region of the electromagnetic spectrum is the region between microwaves and infra-red, dubbed the terahertz 'gap' due to its relative underdevelopment in terms of technology. This region is marked by expensive and inconvenient sources that are bulky or that require cryogenic cooling for normal operation, therefore creating a need for cheap and easy to use terahertz sources. Carbon nanotubes have received considerable attention since their discovery due to their unique physical and electronic properties. Many applications have been proposed using especially Single-Walled Carbon Nanotubes (SWCNTs), and a number of commercial technologies exist. In this work, we have proposed to use SWCNTs as the basis for a cheap, compact and room temperature-operating Terahertz source. We have characterized the SWCNT source, and we present results on transport characteristics (I–V curves), radiation patterns, spectra, polarization as well as optical, SEM and AFM imaging. We show that the radiation spectrum is vi determined by integrated antennas coupled to the SWCNTs, and preliminary power calibration indicates that the radiated power exceeds the power predicated by the Nyquist formula.

The rapid development of micro/nanofabrication techniques have enabled engineering of material interfacial properties. Micro/nanostructures with unique electrical, mechanical, thermal, magnetic, optical, and biological properties, have found applications in a wide range of fields such as electronics, photonics, biological/chemical sensing, tissue engineering, and diagnostics, etc. As such, numerous strategies have been developed for structuring materials into micro/nano- scale. However, the challenge still lies in the high cost, low throughput, complexity in fabrication, and difficulty in scaling up. This thesis aims to explore fabrication strategies for micro/nanostructured surfaces that are versatile, simple, and inexpensive. The thin film stencil lift-off technique with both Parylene and self-adhesive vinyl has been explored for this purpose. Further applications of the resulted micro/nanostructured surfaces are also presented in this thesis. Through improved Parylene stencil fabrication process, both spontaneously phase-segregated and arbitrary binary supported lipid bilayer patterns have been achieved. Also, the microstructured Parylene surfaces have been ddemonstrated for patterning stacked SLBs that are either homogeneous or phase-segregated. Without any lithography technique involved, vinyl stencil lift-off offers as a facile and inexpensive benchtop method for patterning thin films such as metal and glassy films. Combining the thermal shrinking of shape memory polymer, the patterned feature sizes are further decreased by 60% in both x and y dimensions, pushing the patterning resolution to down to sub-100 μm range. In addition, the shrinking process induces micro/nanostructures onto the deposited thin film, and the structure sizes are easily tunable with film thickness deposited. Further applications of such patterned micro/nanostructured surfaces has also been explored. The structured gold films have served as high-surface-area electrodes for electrochemical sensing. By introducing photoresist as a sacrificial layer, the structured gold thin films can be lifted off and transferred onto elastomeric substrate, and serve stretchable and flexible sensors. Such sensing devices exhibit great stability and reproducibility even when working under external strain. Finally, the micro/nanostructured glassy surfaces have been employed as substrate for cell growth to study topographical effect on cell morphology. It has been concluded that rougher surfaces lead to cell elongation, and finer structures promote filopodia generation. These results underscore the strength and suitability of thin film stencil lift-off as a powerful technique for creating micro- and nanostructured surfaces. These structured surfaces could find applications in many other areas, due to their great properties such as tunable structure size, high surface area, flexibility, and long-term stability. / Thesis / Doctor of Philosophy (PhD)

Malgré leurs contribution dans plusieurs domaines, les biopuces à lecture plasmonique conventionnelles basées sur l'utilisation d’un film métallique plan d'or, sont limitées en terme de sensibilité surtout quand il s'agit de détecter des molécules de faible masse molaire à l’état de trace.Dans ce cadre, nous étudions numériquement et expérimentalement le potentiel de détection d’interactions biomoléculaires d’une nouvelle génération de biopuces à lecture plasmonique intégrant un film métallique micro-nano-structurée en réseau rectangulaire 1D. L’étude numérique développée met en œuvre une méthode hybride, basée sur la combinaison de deux méthodes classiques : la méthode des éléments finis et la méthode modale de Fourier. Grâce à ce nouvel outil numérique, nous présentons une cartographie exhaustive du potentiel de détection d’une couche biologique, en variant les paramètres de la structuration liés aux dimensions du réseau. La réponse de la biopuce à l’accrochage de biomolécules est ensuite interprétée théoriquement par les différents phénomènes plasmoniques notamment les «points chauds» et les bandes plasmoniques interdites. Nos calculs soulignent l'importance de l’exploitation du confinement de la lumière à travers la structuration sub-longueur d’onde des surfaces plasmoniques. Ceci permet non seulement d’optimiser les paramètres géométriques afin d’améliorer la sensibilité vis-à-vis de la réponse d’une biopuce conventionnelle, mais aussi de mettre en évidence la transition entre le régime où les plasmons propagatifs dominent et le régime où les plasmons localisés dominent. De nouvelles figures de mérite sont introduites pour évaluer les performances des biopuces structurées.Cette étude montre également que de nouvelles opportunités pour améliorer davantage la bio-sensibilité sont offertes, si la localisation de biomolécules peut être effectuée dans les régions où le champ électrique est amplifié et confiné. / Surface plasmons resonance imaging with continuous thin metallic films have become a central tool for the study of biomolecular interactions. However, in order to extend the field of applications of surface plasmons resonance systems to the trace detection of biomolecules having low molecular weight, a change in the plasmonic sensing methodology is needed. In this study, we investigate theoretically and experimentally the sensing potential of 2D nano- and micro- ribbon grating structuration on the surface of Kretschmann-based surface plasmon resonance biosensors when they are used for detection of biomolecular binding events. Numerical simulations were carried out by employing a fast and novel model based on the hybridization of two classical methods, the Fourier Modal Method and the Finite Element Method. Our calculations confirm the importance of light manipulation by means of structuration of the plasmonic thin film surfaces on the nano- and micro- scales. Not only does it highlight the geometric parameters that allow the sensitivity enhancement, and associated figures of merit, compared with the response of the conventional surface plasmon resonance biosensor based on a flat surface, but it also describes the transition from the regime where the propagating surface plasmon mode dominates to the regime where the localized surface plasmon mode dominates. An exhaustive mapping of the biosensing potential of the nano- and micro- structured biosensors surface is presented, varying the structural parameters related to the ribbon grating dimensions. New figures of merit are introduced to evaluate the performance of the structured biosensors. The structuration also leads to the creation of regions on biosensor chips that are characterized by strongly enhanced electromagnetic fields. New opportunities for further improving the bio-sensitivity are offered if localization of biomolecules can be carried out in these regions of high electromagnetic fields enhancement and confined.

Les déchets plastiques s'accumulent depuis plusieurs décennies dans les océans où ils se fragmentent en particules appelés microplastiques lorsque leur taille est inférieure à 5 mm. Ces microplastiques sont retrouvés dans toutes les eaux du globe, dans les sédiments ainsi que dans de nombreux organismes marins. Le devenir physicochimique à long terme de ces particules et leur possible fragmentation en nanoplastiques sont complexes, encore peu documentés et nécessitent des études en laboratoire.Afin de comprendre les processus liés à la photodégradation et à la fragmentation des polymères dans l’environnement, mais également dans le but d’'appréhender l’évolution des fragments générés au cours de l’irradiation, un protocole de vieillissement accéléré en milieu abiotique a été mis en place sur des polymères modèles. Le suivi de l’oxydation et de la fragmentation des deux polymères étudiés,polyéthylène basse densité et polypropylène, a été mené à l’aide de techniques spectroscopiques (infrarouge, Raman), DSC, angles de contact, et microscopiques (lumière polarisée, MEB, AFM…).Ce travail a permis de mettre en évidence l’influence significative de l’environnement et de la morphologie initiale des polymères sur leurs cinétiques de vieillissement et leurs mécanismes de fissuration. Ainsi des distributions en nombres, tailles et formes de fragments très différentes ont été obtenues pour les deux polymères selon la présence d’eau. Enfin, après un long temps d’irradiation, des produits de dégradation ont pu être détectés mais la production significative de nanoplastiques n’a pas été démontrée. L'hypothèse d'une taille limite de fragmentation devrait être envisagée. / Plastic wastes have been accumulating for several decades in the oceans where they break up into particles called microplastics when their size is less than 5 mm. These microplastics are found in all earth’s waters, in sediments and in many marine organisms. Their long-term physico-chemical fate and their possible fragmentation into nanoplastics are complex, still poorly documented and require laboratory studies.In order to understand the processes related to photodegradation and fragmentation of polymers, but also in order to understand the evolution of these fragments during irradiation, an accelerated aging protocol in abiotic conditions has been set up. The oxidation and fragmentation of two model polymers, low density polyethylene and polypropylene, were monitored using spectroscopic techniques (InfraRed, Raman), DSC, contact angles and microscopic technics (light microscopy, polarized light, SEM, AFM ...).This work has demonstrated a significant influence of the environment and the initial morphology of the polymers on their kinetics of aging and cracking mechanisms. This lead to significantly different distributions in numbers, sizes and shapes of the generated fragments. Moreover, after a long time of irradiaiton, other degradation products could be detected but the significant production of nanoplastics has not been demonstrated. The possibility of a size limit below which the fragmentation rate of plastics would strongly decrease should be considered.