Unlimited nanotechnology

What's Nanotechnology, where it comes from and what can be done with it? Nature serves as inspiration for developing new nanostructures and nanomaterials with truly amazing properties, as well as an overview of the fields where nanotechnology can help achieve fascinating breakthroughs. This article aims to explain different systems that use nanotechnology to maintain functional product properties for extended periods of time, resulting in longer useful product life cycles; to better maintain visual product appearance by reducing "premature product ageing" as perceived by users; or for self-repair purposes, to eliminate the need for product replacement or repair

Nanotecnologia il.limitada

Què és la nanotecnologia, d'on ve i què se'n pot fer? La natura inspira i permet crear noves nanoestructures o nanomaterials amb propietats sorprenents, i són molts dels camps en què la nanotecnologia pot aportar avenços interessants. Existeixen diferents sistemes que, gràcies a la nanotecnologia, mantenen les propietats funcionals durant més temps -la qual cosa augmenta la vida útil-, o mantenen la seva aparença superficial en millors condicions -amb un "envelliment prematur" menor del producte a ulls de l'usuari- o bé permeten reparar el producte i així evitar-ne els recanvis i les reparacions

Nanotecnología ilimitada

¿Qué es la nanotecnología, de dónde viene y qué se puede hacer con ella? La naturalez inspira y permite crear nuevas nanoestructuras o nanomateriales con propiedades asombrosas, y son muchos los campos en los que la nanotecnolgía puede aportar interesantes avances. Existen diferentes sistemas que, gracias a la nanotecnolgía, mantienen las propiedades funcionales durante más tiempo -lo que aumenta su vida útil-, o bien mantienen sus apariencia superficial en mejores condiciones -reduciendo el "envejecimiento prematuro" del producto a ojos del usuario-, o bien permiten reparar el producto- evitando recambios y arreglos

Caracterización microestructural de aleaciones NiTi mediante nanoindentación instrumentada

En esta memoria se presenta un estudio de la caracterización de aleaciones binarias NiTi basado en la técnica de nanoindentación instrumentada. El principal objetivo de esta caracterización es el cálculo los módulos elásticos, así como la interpretación de la transformación de fase martensítica mediante el análisis de las curvas P-h y las imágenes obtenidas a partir de técnicas de FIB y TEM. Las temperaturas de transformación -de las aleaciones comerciales objeto de estudio- han sido caracterizadas gracias a la técnica del DSC, y posteriormente comparadas con los valores facilitados por el fabricante, evidenciando la influencia de la historia termomecánica de la aleación en la respuesta de la transformación. La técnica de nanoindentación instrumentada -empleando dos tipos de indentador- ha permitido no sólo la determinación a escala nanométrica de parámetros como el módulo elástico y la dureza por el método de Oliver y Pharr, sino también la evaluación de la capacidad de recuperación de las aleaciones frente a las deformaciones introducidas por el indentador con el cálculo de los índices de recuperación. Esto, junto con las imágenes de microscopía electrónica de transmisión de las zonas bajo la huella de nanoindentación que se han obtenido mediante la técnica de FIB, han permitido demostrar la concordancia con la realidad de las teorías que en la literatura se pueden hallar sobre los mecanismos de deformación y las zonas de afectación bajo la punta del indentador. Queda, por tanto, demostrado mediante dichas imágenes, que bajo el indentador y en función de las cargas aplicadas, se produce acomodación de deformaciones por transformación martensítica en la zona adyacente al contacto. Finalmente concluir que la técnica de nanoindentación permite caracterizar la transformación martensítica de las aleaciones estudiadas así como parámetros mecánicos como son la dureza y el módulo elástico

Development of new lightweight green composites reinforced with nonwoven structures of flax fibres

Composite materials offer good mechanical performance with lower weight than classical materials, what has encouraged their use in many industry applications. Moreover, the rising awareness about environmental problems has prompted the progress towards more sustainable materials, thus encouraging the research in natural fibre reinforcements and biopolymeric matrices. This PhD thesis focuses on the development of green composites made of polyhydroxyalkanoate (PHA) matrix with a reinforcement of flax nonwoven fabrics, while considering materials and processes with low environmental impact. However, in order to achieve lighter materials with even further improved specific properties, the strategy chosen is the enhancement of weight reduction of the matrix by means of foaming processes. The approach considered in this thesis differs from the classical approaches with these materials in its use of foaming techniques to obtain a cellular structure in the matrix, This, in addition, enhances the competitiveness of these composites, since biopolymers present (nowadays) a high cost. However, the cellular structure obtained after foaming leads to a decrease in the mechanical properties. The use of fibres of high strength is a key factor for counteracting this loss. In this sense, a novel approach is given for the use of flax fibres (of high stiffness and low cost) as reinforcement, since they are used in the form of nonwoven structures. The use of natural fibres in composites has two main concerns: the fibre/matrix interaction and their sensibility to moisture absorption. This drawbacks can be reduced by using sustainable methods. On the one hand, the compatibility with the matrix can be improved by plasma techniques, which modify the roughness and chemistry of the fibre surface (without affecting the bulk properties) with a minimal use of chemicals and no need of water. On the other hand, wet/dry cycling treatments with water are an interesting option to increase fibre stability against water absorption and dimensional changes without the need of chemicals. The effectiveness of these sustainable treatments applied to the nonwoven is evaluated by means of hydrothermal aging and mechanical characterisation on solid PHA/flax composites. The matrix foamability is evaluated by means of extrusion foaming, considering two main strategies for improving this process: the use of chain extenders and cooling by means of a water quenching. Finally, the most challenging novelty (given the limitations imposed by both the reinforcement structures and the matrix foamability) is the achievement of the cellular composites reinforced with the optimized flax fabrics. A gas dissolution batch foaming from solid precursors is used for such a production. This strategy is evaluated and optimised to this purpose, leading to cellular composite materials with good specific properties and reduced density. The combination of properties of both components leads to a biodegradable, stiff and lightweight material that present good regularity in the foaming process, which prompts a possible replacement for other less sustainable materials in automotive, construction or other applications. Due to the aforementioned, this thesis presents the development of a challenging new approach for lightweight green composites from a multidisciplinary point of view.Los materiales compuestos ofrecen buenas prestaciones mecánicas con un menor peso que los materiales convencionales, lo que ha extendido su uso a múltiples sectores. Además, el creciente interés sobre los problemas ambientales ha impulsado la evolución hacia materiales más sostenibles, lo que ha potenciado la investigación en refuerzos de fibras naturales y en matrices de biopolímero. Esta tesis se centra en el desarrollo de materiales compuestos sostenibles de polihidroxialcanoato (PHA) y refuerzo de telas no-tejidas de lino, teniendo en cuenta materiales y procesos de bajo impacto ambiental. Sin embargo, con el objetivo de conseguir componentes cada vez más ligeros y con aún mejores propiedades específicas, se emplea la estrategia de reducir el peso de la matriz mediante técnicas de espumado. El hecho de emplear técnicas de espumado para obtener estructuras celulares en la matriz es el valor añadido que diferencia el resultado de los que pueden obtenerse con las técnicas clásicas, y además conlleva un aumento de la competitividad de estos compuestos, puesto que los biopolímeros presentan (actualmente) un mayor coste económico. Sin embargo, la formación de una estructura celular por efecto del espumado lleva a la reducción de las propiedades mecánicas. Esto puede ser contrarrestado mediante el uso de fibras de alta resistencia. En este sentido, el uso de fibras de lino (de alta rigidez y bajo coste) en la forma de estructuras no-tejidas supone también un acercamiento novedoso. El uso de fibras naturales en materiales compuestos presenta dos problemáticas: la interacción fibra/matriz y la sensibilidad frente a la absorción de humedad. Estos inconvenientes pueden minimizarse mediante el uso de métodos sostenibles. En este sentido, la compatibilidad con la matriz puede mejorarse mediante técnicas de plasma que modifican la rugosidad y química superficiales de las fibras (sin afectar sus propiedades generales) con un mínimo uso de productos químicos y sin necesidad de agua. Por otra parte, los tratamientos de ciclado seco/húmedo en agua son una interesante opción para incrementar la estabilidad de las fibras frente a la absorción de agua y los cambios dimensionales sin la necesidad de productos químicos. La efectividad de estos tratamientos ecológicos aplicados al no-tejido se evalúa mediante caracterización mecánica y envejecimiento hidrotérmico en compuestos sólidos de PHA/lino. Por otro lado, la espumabilidad de la matriz se evalúa durante un espumado por extrusión considerando dos estrategias para su mejora: el uso de aditivos para la extensión de cadenas y un enfriamiento rápido en agua. Finalmente, la novedad que presenta un mayor reto (consideradas las limitaciones impuestas tanto por las estructuras de refuerzo como por la espumabilidad de la matriz) es conseguir materiales compuestos celulares reforzados con estructuras optimizadas de lino. Para tal propósito, se evalúa y optimiza un proceso de espumado por disolución de gas por lotes a partir de precursores sólidos. Esta estrategia permite la obtención de materiales compuestos celulares con una reducción de densidad y buenas propiedades específicas. La combinación de propiedades de ambos componentes lleva a la obtención de materiales biodegradables, rígidos y ligeros que presentan buena regularidad en el proceso de espumado, lo que plantea una posible solución para el reemplazo de otros materiales menos sostenibles en automoción, construcción u otras aplicaciones. Por todo esto, en esta tesis se presenta el desarrollo, desde un punto de vista multidisciplinar, de un nuevo método para la obtención de compuestos sostenibles y ligeros.Postprint (published version

Effects of wet/dry-cycling and plasma treatments on the properties of flax nonwovens intended for composite reinforcing

Producción CientíficaThis research analyzes the effects of different treatments on flax nonwoven (NW) fabrics which are intended for composite reinforcement. The treatments applied were of two different kinds: a wet/dry cycling which helps to stabilize the cellulosic fibers against humidity changes and plasma treatments with air, argon and ethylene gases considering different conditions and combinations, which produce variation on the chemical surface composition of the NWs. The resulting changes in the chemical surface composition, wetting properties, thermal stability and mechanical properties were determined. Variations in surface morphology could be observed by scanning electron microscopy (SEM). The results of the X-ray photoelectron spectroscopy (XPS) showed significant changes to the surface chemistry for the samples treated with argon or air (with more content on polar groups on the surface) and ethylene plasma (with less content of polar groups). Although only slight differences were found in moisture regain and water retention values (WRV), significant changes were found on the contact angle values, thus revealing hydrophilicity for the air-treated and argon-treated samples and hydrophobicity for the ethylene-treated ones. Moreover, for some of the treatments the mechanical testing revealed an increase of the NW breaking force.Ministerio de Educación y Formación Profesional (grants BIA2014-59399-R and FPU12/05869

Gas dissolution foaming as a novel approach for the production of lightweight biocomposites of PHB/natural fibre fabrics

Producción CientíficaThe aim of this study is to propose and explore a novel approach for the production of cellular lightweight natural fibre, nonwoven, fabric-reinforced biocomposites by means of gas dissolution foaming from composite precursors of polyhydroxybutyrate-based matrix and flax fabric reinforcement. The main challenge is the development of a regular cellular structure in the polymeric matrix to reach a weight reduction while keeping a good fibre-matrix stress transfer and adhesion. The viability of the process is evaluated through the analysis of the cellular structure and morphology of the composites. The effect of matrix modification, nonwoven treatment, expansion temperature, and expansion pressure on the density and cellular structure of the cellular composites is evaluated. It was found that the nonwoven fabric plays a key role in the formation of a uniform cellular morphology, although limiting the maximum expansion ratio of the composites. Cellular composites with a significant reduction of weight (relative densities in the range 0.4–0.5) were successfully obtained.Ministerio de Educación y Formación Profesional (grants FPU12/05869 and EST14/00273)Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (grants BIA2014-59399-R and MAT2015-69234-R)Junta de Castilla y Leon (grant VA011U16

Experimental abrasion analysis of textile capacitive sensors

This paper presents an experimental abrasion analysis of textile capacitive sensors based on Martindale test. The textile sensor is manufactured with a well-known woven technology where some yarns are replaced by electrical conductive yarn. Specifically, two types of conductive yarns were used to compare the abrasion behaviour respect to conventional fabrics and the impact of abrasion on sensors functionality. The results show that the integration of conductive yarn on fabric don’t reduce the fabric lifetime and moreover the sensing behaviour remains unalterable during the lifetime of the textile.This work was supported by Spanish Government-MINECO under Project TEC2016-232 79465-R and AGAUR-UPC (2020 FI-B 00028).Peer ReviewedPostprint (published version

A full textile capacitive woven sensor

In this paper, a full textile capacitive woven sensor integrated over a textile substrate is presented. The sensor consists in an interdigitated capacitance prepared to measure moisture and/or presence detection. In order to evaluate the sensor response to moisture, capacitance has been measured by means of an LCR meter from 20 Hz to 20 kHz in a climatic chamber with a swept of the relative humidity (RH) from 30% to 90% at 20 °C. Subsequently, presence response is evaluated measuring the capacitance of the woven sensor meanwhile a person is sitting down and getting up. The woven sensor results demonstrate its functionality over moisture measurement where sensor capacitance changes from a minimum of 9.74 pF at 30% RH to a maximum of 2.31 uF at 90% RH. The presence detection is also demonstrated, which makes the capacitance variation change from a 10% of capacitance variation when the chair is empty, to a capacitance variation of 170% when a person is sitting on it. The adaptation of the weaving process to accomplish a fully integrated sensor provides a better repeatability than previous embroidered sensors and opens a door to being commercially produced.This work was supported by Spanish Government-MINECO under Project TEC2016-79465-R and AGAUR-UPC(2020 FI-B 00028). Agencia de Gestión de Ayudas Universitarias y de Investigación, Generalitat de Catalunya.Peer ReviewedPostprint (published version

Effect of chain extender and water-quenching on the properties of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) foams for its production by extrusion foaming

Bacterial polyesters such as polyhydroxyalkanoates (PHAs) are of great interest for a large number of applications both because of their properties and because they come from renewable resources, despite having a higher cost than commodity polymers. Their foaming—although it presents some difficulties—could be an option to increase their competitiveness. In this work, two strategies have been studied to enhance the poly(3-hydoxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) foamability by extrusion foaming. The effect of the cooling system (water-quenching or air-cooling), chain extender (CE) addition and chemical blowing agent (CBA) amount were evaluated. Density, cellular morphology, mechanical and thermal properties were studied. Optimal density reduction was achieved with use of CE and 3–4 wt.% of CBA masterbatch. The most effective strategy on density reduction was the addition of CE, while the water quenching had only a slight influence on the samples in which CE was not present. CE addition decreased the viscosity and the degradation rate of the polymer, thus leading to lighter foams with larger cells but with equal or even slightly better resistance to compressive and tensile stress, in general termsPostprint (author's final draft