Search

This document presents the design, construction, and analysis of results of the Dip Coater machine, a piece of equipment that is used to obtain thin film on various materials, using a technique that is based on the controlled immersion and extraction of a substrate into a solution. The work reports on the construction of this piece of equipment, which mainly uses a PAP engine and an Arduino Mega 2560 microcontroller, carried out in the nano-materials laboratory of the Antonio Nariño University, and that involved four phases: design, prototyping, construction, and validation. The Dip Coater offers an adjustable control of parameters: immersion/extraction speed, immersion and drying times, number of immersion cycles, and immersion displacement; so in this research, we evaluated the user-machine interaction response and the behavior of the extraction speed with different masses. The reproducibility of the coatings was studied as the mass changes according to the speed of extraction. The morphological and physical-chemical characterization of a sol-gel SiO2 coating is also shown, together with the anti-corrosive properties that can be adjusted by the parameters of the Dip Coater. Finally and within this project, it was possible to design and build a competitive scientific instrument with similar characteristics to those of the commercial equipment., Ce document présente la conception, construction et analyse des résultats d'un appareil nommé Dip Coater utilisé pour l’obtention de revêtements sur divers matériaux dont la technique se base sur l'immersion et l'extraction contrôlée d'un substrat en solution. Les travaux rendent compte de la construction, dans le laboratoire de nanomatériaux de l'Université Antonio Nariño, de cet appareil munit d’un moteur PAP et d’un microcontrôleur Arduino Mega 2560. La processus de création de cet équipement s'est déroulé en quatre phases: conception, prototypage, construction et validation. Le Dip Coater offre un contrôle de paramétrage tels que la vitesse d'immersion / extraction, les temps d'immersion et de séchage, le nombre de cycles d'immersion et le déplacement par immersion. Nous avons de plus, lors de cette investigation, évalué la réponse d'interaction de l'utilisateur avec la machine et le comportement de la vitesse d'extraction de différentes masses. La reproductibilité des revêtements et leur changement de masse ont ici été analysés en fonction de la vitesse d'extraction. Une caractérisation morphologique et physico-chimique d'un revêtement sol-gel SiO2 aux propriétés anticorrosives pouvant être ajustées via les paramètres de l'équipement Dip Coater sera également présentée. Enfin, ce projet a permis de concevoir un instrument scientifique compétitif aux caractéristiques similaires à celles des appareils disponibles sur le marché., O presente documento apresenta o desenho, a construção e a análise de resultados de uma máquina denominada Dip Coater, empregada para a obtenção de recoberturas sobre diversos materiais, cuja técnica se baseia na imersão e a extração controlada de um substrato em uma solução. O trabalho apresenta a construção desta máquina, que emprega, principalmente, um motor PAP e um microcontrolador Arduino Mega 2560, no laboratório de nanomateriais da Universidade Antonio Nariño. O desenvolvimento da máquina teve quatro fases: desenho, prototipado, construção e validação. A Dip Coater oferece um controle ajustável de parâmetros tais como a velocidade de imersão/extração, os tempos de imersão e secado, o número de ciclos de imersão e a deslocação de imersão. Nesta pesquisa se avaliou a resposta interação usuário-máquina e o comportamento da velocidade de extração com diferentes massas. A reprodutividade das recoberturas estudou-se com a mudança de massa destas em função da velocidade de extração. Também se mostra a caracterização morfológica e físico-química de uma recobertura sol-gel de SiO2 com propriedades anticorrosivas que podem ser ajustadas pelos parâmetros da máquina Dip Coater. Finalmente, dentro deste projeto se conseguiu desenhar e construir um instrumento científico competitivo que reúne características similares às das máquinas comerciais., El presente documento presenta el diseño, la construcción y el análisis de resultados de una máquina denominada Dip Coater, un equipo empleado para la obtención de recubrimientos sobre diversos materiales, cuya técnica se basa en la inmersión y la extracción controlada de un sustrato en una solución. El trabajo da cuenta de la construcción de este equipo, que emplea, principalmente, un motor PAP y un microcontrolador Arduino Mega 2560, en el laboratorio de nanomateriales de la Universidad Antonio Nariño. El desarrollo del equipo tuvo cuatro fases: diseño, proptotipado, construcción y validación. El Dip Coater ofrece un control ajustable de parámetros tales como la velocidad de inmersión/extracción, los tiempos de inmersión y secado, el número de ciclos de inmersión y el desplazamiento de inmersión, por lo que en esta investigación se evaluó la respuesta interacción usuario-máquina y el comportamiento de la velocidad de extracción con diferentes masas. La reproducibilidad de los recubrimientos se estudió con el cambio de masa de estos en función de la velocidad de extracción. También se muestra la caracterización morfológica y físico-química de un recubrimiento sol-gel de SiO2 con propiedades anticorrosivas que pueden ser ajustadas por los parámetros del equipo Dip Coater. Finalmente, dentro de este proyecto logró diseñar y construir un instrumento científico competitivo que reúne características similares a las de los equipos comerciales.

Core@shell Co@Au nanoparticles of around 8 nm have been produced by the inert gas condensation method, revealing for the first time that most of the nanoparticles exhibit an icosahedral shape in agreement with the theoretical prediction. Additionally, we report the existence of a novel morphology which consists of a Co icosahedron surrounded by fcc Au facets, reported here for the first time.

There is an increasing interest in the generation of well-defined nanoparticles (NPs) not only because of their particular properties resulting from their reduced dimensions, but also because they are promising building blocks for more complex materials in the fast growing nanotechnology [1]. As a consequence, the development of fabrication methods of high quality NPs is a key issue to follow the increasing demand of complex multifunctional nanoparticles for advanced applications [2]. We will present a bottom-up fabrication route based on the sputtering gas aggregation source that allows the generation of nanoparticles with controllable and tunable chemical composition and structure while keeping the control of their size. This technique, called Multiple Ion Cluster Source (MICS) [3], is an evolution of standard Ion Cluster Sources (ICS) [4]. Through examples, we will show that, apart from the generation of alloyed nanoparticles [5], the technique allows the generation of core-shell and core@shell@shell nanoparticles. All these possible combinations are generated in one single step process and under ultra-high vacuum (UHV) conditions, which leads to the formation of NPs with high purity.

Complex core@shell and core@shell@shell nanoparticles are systems that combine the functionalities of the inner core and outer shell materials together with new physico-chemical properties originated by their low (nano) dimensionality. Such nanoparticles are of prime importance in the fast growing field of nanotechnology as building blocks for more sophisticated systems and a plethora of applications. Here, it is shown that although conceptually simple a modified gas aggregation approach allows the one-step generation of well-controlled complex nanoparticles. In particular, it is demonstrated that the atoms of the core and the shell of the nanoparticles can be easily inverted, avoiding intrinsic constraints of chemical methods.

[ES] En este trabajo de tesis se presenta un estudio sobre la fabricación y caracterización de nanopartículas (NPs) basadas en Co,Au y Ag. Todas las nanopartículas fueron fabricadas utilizando la técnica de agregación de gas pero en diferentes dispositivos experimentales. En la primera parte se presentan NPs CoAu producidas por una fuente tipo ICS (Ion Cluster Source) y depositadas sobre sustratos mantenidos a diferentes temperaturas. Se muestra que el aumento de temperatura de depósito induce la difusión del Au a la superficie de las NPs originando una estructura tipo núcleo@corteza@corteza. Se estudian las modificaciones estructurales y químicas inducidas por el cambio de temperatura de depósito y su impacto en las propiedades magnéticas de las NPS. En particular se presenta la evolución del efecto de Exchange Bias (EB) con la temperatura de depósito. Se muestra que la formación de una película intermedia de oro impide la oxidación y formación del CoO. Este cambio estructural reduce el acoplamiento ferromagnético/antiferromagnético, conduciendo a una disminución del EB. Se identifica la temperatura umbral de 500 K para la formación completa de esta capa intermedia de Au, donde se estabiliza el EB. Al igual que las características de las partículas (tamaño, forma, estructura), influyen en sus propiedades, estas pueden ser controladas por la naturaleza de la matriz (aislante, conductora, magnética, porosa, etc.) en las que las NPs se encuentren inmersas así como la distancia media entre partículas. En la segunda parte se presenta el estudio del crecimiento y de las propiedades morfológicas, estructurales y magnéticas de NPs de CoAu embebidas en matrices no magnéticas. Las NPs fueron generadas con un sistema LECBD (Low Energy Cluster Beam Deposition)., Se fabricaron películas de NPs de CoAu embebidas en matrices de C y LiF. Los análisis estructurales mostraron que las NPs presentan una estructura tipo Au@Co@CoO. Los cambios morfológicos, químicos y magnéticos fueron relacionados con cada matriz. Se determinó la variación del porcentaje de óxido del cobalto y la temperatura de bloqueo de las NPs para cada matriz. Además se realizó un recocido de las NPs embebidas en C, el cual produjo un cambio estructural del Co de HCP a FCC y la difusión del oro hacia el exterior de la NPs, formando una estructura Co@Au. Se muestra que estos cambios estructurales inducen un aumento en los valores de magnetización de saturación y campo coercitivo. Finalmente, en la tercera parte, se muestra la capacidad del sistema MICS (Multiple Ion Cluster Source) para fabricar NPs de alta calidad con diferentes estructuras y estequiometrias en un solo paso. Se presenta la calibración del sistema con dos de los magnetrones de manera independiente. Se muestra que el control individual de los parámetros de funcionamiento de cada uno de los magnetrones permite la obtención de un amplio abanico de NPs. En particular se muestra que el tamaño medio de las NPs, la taza de depósito, y la tasa de depósito atómica pueden ser ajustados a través de los parámetros de funcionamiento de los magnetrones, tales como la potencia aplicada al magnetrón, el flujo de argón inyectado en cada magnetrón, el flujo total de argón y la longitud de agregación. Empleando la calibración de los blancos individuales, se fabricaron NPs bimetálicas de tres tipos: CoAu (aleación), Co@Au y Au@Co (de tipo núcleo@corteza). Se presenta el estudio de las propiedades químicas, morfologías, estructurales y magnéticas de estas NPs. Finalmente se fabricaron y caracterizaron NPs Co@Ag@Au demostrando así la capacidad del sistema MICS para la fabricación de NPs con estructuras complejas., [EN] In the present work we present a study on the fabrication and characterization of nanoparticles (NPs) based on Co, Au and Ag. All the nanoparticle were generated using gas aggregation sources but in different experimental set-ups. In the first part we present NPs CoAu generated using an ICS (Ion Cluster Source) and deposited on substrates kept at different temperatures. We show that an increasing deposition temperature induces the diffusion of Au to the surface of the NPs giving place to the generation of core@shell@shell NPs. We present the structural and chemical modifications induced by the deposition temperature and correlate them with the magnetic properties. In particular we present the evolution of the Exchange Bias (EB) as a function of the deposition temperature. We show that the formation of the intermediate Au shell protects the Co from oxidation. This structural change reduces the ferromagnetic/antiferromagnetic coupling with the corresponding reduction of the EB. It is shown that 500 K is the temperature where the formation of a complete Au shell takes place and the EB is stabilized., Like the size, shape and structure determine the properties of the NPs, also the nature of the matrix (insulator, conductive, magnetic, etc) were they are embedded and their first neighbor distance are mandatory. In the second part, we present the study on the growth and characterization of the morphological, structural and magnetic properties of CoAu NPs embedded in non magnetic matrices. The NPs were generated using a Low Energy Cluster Beam deposition system (LECBD) and embedded in C and LiF matrices. The structural analysis revealed that the NPs have an Au@Co@CoO structure. The morphological, chemical and magnetic changes were correlated with the different matrices as well as the percentage of Co oxide and the blocking temperature. Additionally it is shown that the annealing of the NPs embedded in the C matrix induces the structural change from the HCP to the FCC structure and the diffusion of Au the outer shell of the NPs originating Co@Au NPs. These structural modifications lead to an increase of the saturation magnetization and coercitivity. Finally, in the third part, we demonstrate the capacity of the Multiple Ion Cluster Source (MICS) system to generate high quality NPs with controlled structure and stoichiometry in one step. First we present the calibration of the system with 2 of the independent magnetrons. It is shown that the individual control of the working parameters of each of the magnetrons allows the generation of a wide range of NPs. In particular it is shown that the mean size, deposition rate and atomic deposition rate can be adjusted through the working parameters of the magnetrons like applied power, argon flux in each magnetron, total argon flux and aggregation length. Using the calibration of individual magnetrons, 3 types of NPs were generated and characterized: CoAu (alloy), Co@Au and Au@Co (core@shell). The study of their structural, chemical, morphological and magnetic properties is also presented. Finally NPs with structure Co@Ag@Au w

[EN] The thermal-induced diffusion at nanoscale is investigated through the detailed study of the structural and magnetic properties of Co@Au nanoparticles as a function of the deposition temperature. Nanoparticles of 10 nm were fabricated using an ion cluster source from a Co95Au5 target. While low-temperature deposition leads to the formation of an alloyed fcc CoAu core with an incomplete cobalt oxide shell, higher deposition temperature induces the formation of a pure hcp Co core with an intermediate Au shell and a compact outer cobalt oxide shell. The evolution of the magnetic properties of the nanoparticles is presented and discussed in light of the structural changes of the nanoparticles upon deposition temperature and nanoparticle density. It is found that thermal-induced diffusion can be successfully used to tune the structural and magnetic properties at the nanoscale in CoAu nanoparticles. © 2013 American Chemical Society.

[EN] We present a bottom-up fabrication route based on the sputtering gas aggregation source that allows the generation of nanoparticles with controllable and tunable chemical composition while keeping the control of the cluster size. We demonstrate that the chemical composition of the particles can be monitored by the individual adjustment of the working parameters of the magnetrons inserted in a gas aggregation zone. Such control of the parameters leads to a fine control of the ion density of each target material and hence to the control of the chemical composition of the nanoparticles. In particular, we show through X-ray photoemission, atomic force microscopy, and high-resolution transmission electron microscopy that it is possible to generate bimetallic (AgAu) and trimetallic (AgAuPd) alloy nanoparticles with well-defined and tunable stoichiometries from three targets of pure Ag, Au, and Pd. The proposed route for the generation of nanoparticles opens new possibilities for the fabrication of nanoparticles using a physical method that, for some applications, could be complementary to the chemical methods.

We present a morphological, structural, and magnetic characterization of Co nanoparticles (mean diameter of 10.3 ± 1.8 nm) grown using a gas aggregation source and embedded in a silicon oxide matrix by sequential deposition of nanoparticles and silicon oxide. We show that the Co nanoparticles >soft-land> on the substrates and suffer a moderate oxidation in contact with the silicon oxide. Despite this moderate oxidation, it is found that, at room temperature, the magnetic volume of the resulting nanoparticles is below the superparamagnetic limit. The results presented in this article are compatible with the presence of an assembly of magnetically independent particles that also display a moderate exchange bias at low temperature. © 2011 Springer Science+Business Media B.V.