Study of the flow-induced structure and anisotropy in lyotropic liquid crystals for hierarchical composites

Controlling the micro and nanostructure of materials is highly beneficial in order to tailor\ua0their physical properties. Extrusion-based 3D printing is a promising tool to produce\ua0hierarchical structures with controlled architecture. Combining additive manufacturing and\ua0self-assembled materials, complex structures with high anisotropy can be created. Lyotropic\ua0liquid crystals offer a wide variety of structures and compositions, in which hexagonal andlamellar phases are very interesting options. Far from the idealistic concepts of 3D printing\ua0and extrusion, the variability of the different systems, physical properties of the inks and\ua0environmental conditions play a fundamental role in the appearance of imperfections,\ua0undesired nanostructures and the limitation in the maximum effective alignment achieved.\ua0To understand the mechanisms that induce alignment in liquid crystalline phases and produce\ua0secondary effects and imperfections, a combination of different methods was utilized. Using\ua0small-angle X-ray scattering as the main characterization tool, the nanostructure of the liquid crystals as well as the anisotropy was measured. The use of imaging techniques adds an extra\ua0dimension which brings a broader view of the self-assembled structure. Microfluidic channels\ua0were used to study the mechanisms of alignment in the confined space offered by the nozzle\ua0walls and the high pressures applied in the printing process. The confined flow in the printing\ua0nozzle has different properties and constraints compared to the open flow that the extruded\ua0filament encounters in the printing platform, which was studied by in-situ 3D printing in the\ua0X-ray beam. By complementary rheological characterization, a more detailed analysis\ua0understanding of the flow behaviour was achieved and birefringence microscopy opened up\ua0the possibilities of a time-resolved study of the anisotropy in the filament. The results demonstrated the role of the shear stress in liquid crystals in confined flow,\ua0highlighting both the effect it has on the anisotropy as well as on morphological transitions\ua0in the self-assembled structures. The performed experiments also reflect on the possible\ua0causes of misalignment such as stress release and try to find the optimal parameters in the\ua0nozzle design which lead to the best alignment in terms of homogeneity in the strand and\ua0maximizing the orientation. Finally, the results also show the importance of time and\ua0environmental conditions during 3D printing, which may affect the final structure and\ua0orientation prior the fixation of the nanostructure

Multimodal Imaging of Anisotropic Hierarchical Materials

The thesis is focused on studying the nanostructure of natural and synthetic hierarchical materials with biological applications, using X-ray scattering imaging and birefringence microscopy. The term "hierarchical materials" is used for structures composed of sub-units organised in different length scales that create the building blocks for the next level. Hierarchical materials are commonly found in nature, with diverse structures and functionalities. In the first part of this thesis, the nanostructure of mineralised tissue, such as tusk and bone, was the focus. Scanning SAXS, SAXS tensor tomography and birefringence microscopy were used to study the helicoidal structure of narwhal tusk. A high degree of anisotropy was found, in which the dentine and cementum have a very highly organised nanostructure with a preferential orientation along the tusk. However, those two main components differ in the deviations from that primary orientation, which revealed a complex helical pattern that could be the source of its anisotropic mechanical properties. A layered structure was also observed using X-ray fluorescence spectroscopy, indicating tusk growth layers that reflect the animal history. Those methods were also applied to study the anisotropic nanostructure of regenerated bone in biodegradable scaffolds and titanium implants in vivo, successfully demonstrating that the scaffold or implant architecture influence the new bone formation. Scaffolds with aligned fibres led to well-structured bone and a faster regeneration process, while scaffolds with randomly oriented fibres only created a callus around the damaged area with poor growth of new tissue.In the second part of this thesis, the anisotropy of self-assembled lyotropic liquid crystals for 3D printing of bone-mimetic composites was studied. This work aimed to understand the fundamental processes and mechanisms that induce the alignment of the self-assembled crystalline units to create composites with more anisotropic mechanical properties. In that study, an in situ characterisation of the nanostructure during flow in the 3D printer was done using scanning SAXS and birefringence microscopy to correlate the manufacturing process with the observed structural alignment of the material. The results demonstrated the role of the shear stress in such liquid crystals, highlighting the effect it has on the anisotropy and morphological transitions in the self-assembled structures. The importance of time and environmental conditions during 3D printing is also shown, which may affect the final structure and orientation

Methanol dehydration over ZrO2 supported-activated carbons

Resumen comunicación congreso internacionalDME is playing an important role due to its potential use as an alternative fuel in diesel engines. The use of this fuel produces lower NOx emissions, and less engine noise compared to traditional diesel fuels. Moreover, this compound is used as building block for many value-added chemicals such as lower olefins. DME is usually produced via catalytic dehydration of methanol over a solid acid. The use of activated carbons in catalytic processes, acting directly as catalyst and as catalyst support, is focussing much attention. They can be obtained from different types of lignocellulosic waste, producing not only an environmental but an economical profit. In this sense, the preparation of activated carbons with phosphoric acid produces catalytic supports with certain surface acidity, which have shown high activity for alcohol dehydration. In this study, ZrO2 supported activated carbons were prepared from an industrial byproduct as lignin for the methanol dehydration to DME. The activated carbon was prepared by chemical activation with H3PO4, using Alcell® lignin as precursor. The impregnation ratio value (H3PO4/lignin) used was 3. The impregnated sample was activated under N2 flow at 500 ºC for 2h, washed and dried. The activated carbon was loaded with different amounts of ZrO(NO3)2, dried at 120ºC for 24h, and calcined in air at 250ºC for 2h, obtaining ZrO2 loadings of 5 and 10%, respectively. For the sake of comparison, pure ZrO2 was also used. Catalytic tests were performed at atmospheric pressure in a fixed bed reactor, at different space times and partial pressures. The activated carbon (ACP) prepared shows a well-developed porous structure, with an apparent surface area higher than 2000 m2/g, and a high contribution of mesoporosity. After metal loading, a maximum decrease of 20% in all structural parameters of the ACP was observed.The results show that ZrO2 loading produces an enhancing in the catalytic activity of the carbon materials compared to the parent activated carbon (0.1 g·s/μmol, PCH3OH= 0.02 atm in helium and 350 ºC). In this sense, a methanol conversion of 25% was observed with the addition of 10% w/w ZrO2 (ACP-10Zr), at steady state conditions (Figure 1). ACP shows negligible conversion, at the same conditions and for pure ZrO2 the methanol conversion was of 10%. Very high selectivity to DME (~100%) was found at temperatures lower than 350 ºC. The methanol conversion increases with temperature, reaching a value of 67% at 475ºC, but a slight decrease in DME selectivity is observed, resulting in a higher production of light hydrocarbons, mainly CH4. The results suggest that the addition of only a 10% of ZrO2 over an activated carbon prepared by chemical activation with H3PO4 enhances significantly the performance of the catalyst, compared to pure ZrO2.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Kinetic study of methanol dehydration over Zro2 supported-activated carbons

The growing concerns about climate change and energy consumption have been the driving force in seek of alternative fuels such as DME, mainly produced via methanol dehydration over a solid acid catalyst. The use of activated carbons for this aim has been little studied up to date. Only a few studies can be found in the literature, reporting all of them materials with a low thermal stability of the acid surface groups, which results into a fast deactivation of the catalyst. In this work, the preparation of activated carbons via chemical activation with phosphoric acid, their modification with different ZrO2 loads, and their application as methanol dehydration catalysts have been studied. The catalytic results showed that the best methanol conversion and selectivity towards DME were achieved with the activated carbon prepared with an impregnation mass ratio value (H3PO4 /precursor) of 2 and an activation temperature of 800 ºC, loaded with a 7 % (wt) of ZrO2 . This catalyst exhibits high steady state methanol conversion values even at temperatures as high as 400 ºC (XCH3OH= 80%, 0.1 g·s/μmol, PCH3OH= 0.08 atm in helium), keeping a selectivity to DME higher than 96%. The effect of oxygen in the reaction atmosphere was also analysed. In this sense, an increase of 15 % in the DME yield was obtained when using air instead of helium as reaction atmosphere (350 ºC, 0.1 g·s/μmol, PCH3OH= 0.04 atm). A kinetic study has been carried out on this catalyst in which two mechanisms (Eley Rideal and Langmuir Hinshelwood) for methanol dehydration have been analysed. The models proposed also consider the presence of oxygen in the reaction media.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO (CTQ2015-68654-R). MECD (FPU13/02413)

Biomass derived activated carbon catalysts for the one-step dimethyl ether synthesis from syngas

Se trata de un resumen extendido de una comunicación a congreso internacional.In this work we study the behaviour of a carbon-based catalyst for this one-step synthesis process. Two kinds of activated carbons, prepared by chemical (with H3PO4) and physical (by CO2 partial gasification) activation of olive stones, were used as catalysts support. The main difference between the activated carbons was the presence of chemically stable phosphorus surface groups, mainly in form of C-O-PO3 groups1, on the activated carbon prepared via chemical activation. The addition of Zr to the chemically activated carbon (ACPZr) resulted in the formation of zirconium phosphate species on the carbon surface, which were capable of promoting the selective methanol dehydration to DME. Cu-Zn loading on the chemically activated carbon resulted in strong interactions between the metallic phase and the phosphate surface groups due to the formation Cu phosphate species. The bifunctional catalyst, ACPZrCuZn showed less conversion that the physical mixture. This fact is related with the presence of phosphorus species that avoids the reduction of the metal (copper).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Consideraciones en el estudio anatómico sobre el músculo peroneo tercero, peroneo anterior, tercer peroneo, peroneo tertius, fibularis tertius

The anatomy of the foot, their knowledge, opens up a wide range of expectations so accurate for diagnosing various pathologies of the foot, and above all, to know you better. The purpose of this study was to look closely at the anatomy of the muscle Tertius peroneo to define its origin and insercción to the controversy raised by the literature, its function in the foot, and its frequency, it is a muscle that is not present in all feet. The third peroneo muscle, also known as peroneo Tertius, is a muscle group of the previous leg, which in the current literature is considered inconsistent, that character was not found in our study. We repeat that the authors describe as an inconstant muscle (eg. Rouvière) adjective meaning in anatomy that it is a muscle in less than 45% of cases. For Testud, in the absence black 14 times in 100, the Europeans 7 or 8 times 100, and lacking in monkeys. According to Kapandji is dorsal flexor, abductor and pronator foot. We intend to demonstrate our dissections, a muscle that is most of what appears and where is its origin and insertion, as well as its presentation and position by photographs of cadaver feet.La anatomía del pie, su conocimiento, nos abre un amplio abanico de expectativas para diagnosticar de manera certera diversas patologías del pie, y sobre todo, para conocerlo mejor. El objeto de éste estudio fue observar detenidamente la anatomía del músculo peroneo tertius, definir su origen e insercción ante la controversia que suscita la bibliografía consultada, su función en el pie, y su frecuencia de aparición, pues es un músculo que no está presente en todos los pies. El músculo tercer peroneo, conocido también como peroneo tertius, es un músculo del grupo anterior de la pierna, que en la literatura actual es considerado inconstante, carácter que no fue comprobado en nuestro estudio. Repetimos que diferentes autores lo califican como un músculo inconstante (por ej. Rouviére), significando éste adjetivo en anatomía que es un músculo presente en menos del 45% de los casos. Para Testud, en la raza negra falta 14 veces en 100, en los europeos 7 u 8 veces cada 100, y falta en los monos. Según Kapandji es flexor dorsal, abductor y pronador del pie. Pretendemos demostrar con nuestras disecciones, que es un músculo más habitual de lo que parece y dónde está su origen e inserción, así como su función,presentación y posición mediante fotografías en pies de cadáver

Lyotropic liquid crystal elastomers for drug delivery

Silicone elastomers like polydimethylsiloxane (PDMS) possess a combination of attractive material and biologicalproperties motivating their widespread use in biomedical applications. Development of elastomers with capacityto deliver active therapeutic substances in the form of drugs is of particular interest to produce medical deviceswith added functionality. In this work, silicone-based lyotropic liquid crystal elastomers with drug-elutingfunctionality were developed using PDMS and triblock copolymer (diacrylated Pluronic F127, DA-F127).Various ternary PDMS–DA-F127–H2O compositions were explored and evaluated. Three compositions werefound to have specific properties of interest and were further investigated for their nanostructure, mechanicalproperties, water retention capacity, and morphology. The ability of the elastomers to encapsulate and releasepolar and nonpolar substances was demonstrated using vancomycin and ibuprofen as model drugs. It was shownthat the materials could deliver both types of drugs with a sustained release profile for up to 6 and 5 days forvancomycin and ibuprofen, respectively. This works demonstrates a lyotropic liquid crystal, silicone-basedelastomer with tailorable mechanical properties, water retention capacity and ability to host and release polarand nonpolar active substances

Funcionalización superficial de carbones activos con grupos nitrogenados mediante reaciones de oxidación/reducción

La funcionalización superficial de carbones activos con grupos nitrogenados le confiere a estos materiales unas propiedades fisicoquímicas mejoradas, que los hace muy interesantes en diferentes aplicaciones. La incorporación de heteroátomos de nitrógeno a materiales carbonosos ser realiza principalmente mediante dos estrategias: partiendo de precursores que contengan nitrógeno y mediante tratamientos químicos de funcionalización con moléculas nitrogenadas, tales como amoniaco o urea [2]. En este trabajo se ha estudiado la funcionalización superficial, con diferentes grupos nitrogenados, de carbones activos obtenidos por activación química con ácido fosfórico. La incorporación de nitrógeno se ha llevado a cabo mediante un tratamiento con ácido nítrico, realizándose a continuación diferentes tratamientos de reducción, con el fin de obtener diferentes grupos funcionales de nitrógeno.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Influencia de la presencia de compuestos superficiales de P sobre la funcionalización de carbones activos con HNO3

La funcionalización con ácido nítrico es un método ampliamente estudiado para la incorporación de grupos funcionales de oxígeno en la superficie de carbones activos, tales como grupos carboxilos, anhídridos, lactonas y fenoles. Sin embargo, también incorpora, en menor medida, grupos funcionales nitrogenados. Estos grupos funcionales de N son capaces de mejorar las propiedades de adsorción y/o catalíticas de diferentes carbones activos. Por otro lado, la activación química con ácido fosfórico produce carbones activos con una cantidad importante de grupos superficiales de fósforo de gran estabilidad, que les confiere una elevada resistencia a la oxidación y acidez, que los hace muy interesantes en diferentes aplicaciones catalíticas. En este trabajo se va a estudiar la influencia de la presencia de estos grupos de fósforo en la funcionalización de carbones activos con ácido nítrico.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech