Materiais naturais nanoestruturados, tipo smectita, têm sido amplamente usados em nanocompósitos poliméricos, com ganhos expressivos em muitas propriedades. Porém, devido a sua natureza polar, seu uso em nanocompósitos de poliolefinas apresenta uma série de problemas. Entre esses problemas está a dificuldade de esfoliação na matriz, o que geralmente resulta um sistema não nano-estruturado e, por conseqüência, com pouco ou nenhum ganho em propriedades. Para tentar resolver esse problema, materiais tipo esmectita têm sido modificados com sais de amônio quartenário. Esses, por sua vez, possuem características tóxicas, impedindo seu uso em embalagens de alimentos. Com o objetivo de estudar uma nova alternativa que contorne esses problemas, dois materiais lamelares nano-estruturados, tipo esmectita, contendo grupos alquila ligados por ligação sigma com a rede inorgânica, foram sintetizados. Ambos apresentaram excelente ordem mesoestrutural. Um dos materiais sintetizados, formado por um Alsilsesquioxano lamelar, contendo alto teor de cadeia alquila entre as lamelas inorgânicas, foi usado na formação de compósito de polietileno. Comparativamente, uma argila natural, modificada com sais de amônio quaternário (Cloisite 15A), foi usada para fins comparativos. Os compósitos, então obtidos, foram caracterizados para avaliar diferenças microestruturais, morfológicas e mudanças em suas propriedades mecânicas e reológicas. Comparativamente à argila comercial Cloisite 15A, os compósitos contendo os materiais sintéticos apresentaram reologia diferenciada, melhor resistência ao impacto e ao Tensofissuramento Acelerado pelo Ambiente (ESCR). / Nanostructured natural materials, as smectites, have been widely used in polymeric nanocomposites, with significant gains in many properties. However, due to its polar nature, the use in nanocomposites of polyolefins presents a series of drawbacks. Among these problems, its difficulty exfoliation in the matrix, which generally results in a system not nanostructured and, consequently, with little or no gain on properties. To try to resolve this problem, materials type smectite have been modified with quaternary ammonium salts. These salts, in turn, have toxic characteristics, preventing its use in food packaging. In order to study a new alternative that bypasses these problems, two lamellar nanostructured materials, like smectite, with alkyl groups containing sigma links connected to lamellar inorganic network, were synthesized. Both materials had excellent mesostructural order. One of the synthesized materials, formed by a lamellar Al-silsesquioxane, containing high levels of alkyl chain between the inorganic lamella, was used in the formation of a polyethylene composite. Commercial natural clay, modified with quaternary ammonium salts (Cloisite 15A), was used for comparative purposes. The composites then obtained, were characterized to assess microstructural differences, morphological change, and its mechanical and rheological properties. Comparatively to commercial clay (Cloisite 15A), the composites containing synthetic materials, showed differented rheologics properties, better impact resistance and better Environmental Stress Cracking Resistance (ESCR).

This research is focused on the synthesis and characterization (BET, transmission electron microscopy and optical spectroscopy) of aluminum oxide condensates via a static sintering process and dynamic process of pulse laser ablation (PLA) and pulse laser ablation in liquid (PLAL). For a start, the static route of an onset coarsening-coalescence event based on the incubation time of cylindrical mesopore formation and a significant decrease of specific surface area by 50% and 70% relative to the dry pressed samples was determined by N2 adsorption-desorption hysteresis isotherm for two Al2O3 powders having 50 and 10 nm in diameter respectively on an average and with £^-type related structures, i.e. £^- and its distortion derivatives £_- and/or £c-types with {100}/{111} facets and twinning according to transmission electron microscopy. In the temperature range of 1100 to 1400oC, both powders underwent onset coarsening-coalescence before reconstructive transformation to form the stable £\-type. The apparent activation energy for such a rapid coarsening-coalescence event was estimated as 241 ¡Ó 18 and 119 ¡Ó 19 kJ/mol, for 50 and 10 nm-sized particles, respectively indicating easier surface diffusion and particle movement for the latter. The size dependence of surface relaxation and onset coarsening-coalescence of the £^−type related Al2O3 nanoparticles agrees with their recrystallization-repacking upon electron irradiation and accounts for their assembly into nano chain aggregates or a close packed manner under the radiant heating effect in a dynamic laser ablation process. In addition, ultrafine (5 nm) Al2O3 nanoparticles having a predominant £\-type structure and with an internal compressive stress up to ca. 15 GPa were synthesized by pulsed laser ablation on Al target under a very high peak power density (1.8x1011 W/cm2) with oxygen flow in vacuum. The ultrafine £\-Al2O3 was alternatively formed from the minor £^-Al2O3 nanocondensates upon electron irradiation. In such a case, the polymorphs follow a special crystallographic relationship [110]£^//[2110]£\; (111) £^//(0114)£\ with a mixed mismatch strain yet nonparallel close packed planes indicating a reconstructive type transformation. The formation of metastable £\-Al2O3 in the dynamic processes can be rationalized by the kinetic phase change from the amorphous lamellar and/or £^-Al2O3 depending on their free energy versus cell volume curves. The dense and ultrafine sized Al2O3 polymorphs with a rather low minimum band gap of 3.7 eV shed light on their natural occurrence in dynamic settings and abrasive as well as catalytic/optoelectronic applications. Furthmore, pulsed laser ablation in water under a high peak power density of 1.8 ¡Ñ 1011 W/cm2 using Q-switch mode and 1064 nm excitation was used to fabricate (H+,Al2+)-codoped Al2O3 nanocondensates having £^- and its derivative £c-type structure as characterized by electron microscopy and spectroscopy. The as-formed £^- and £c-Al2O3 nanocondensates are mainly 10 to 100 nm in size and have a significant internal compressive stress (> 10 GPa) according to cell parameters and vibrational spectroscopy, due to a significant shock loading effect in water. The £^-Al2O3 nanocondensates are nearly spherical in shape but became cubo-octahedra when grew up to ca. 100 nm to exhibit more facets as a result of martensitic £^¡÷£c transformation following the crystallographic relationship (3 11 )£c //(02 2)£^; (0 2 4 )£c//(3 11)£^. The formation of dense and (H+,Al2+)-codoped £^/£c-Al2O3 rather than aluminum hydrates sheds light on the favored phases of the Al2O3-H2O binary at high temperature and pressure conditions in natural dynamic settings. The nanocondensates thus formed have a much lower minimum band gap (5.2 eV) than bulk £\-Al2O3 for potential optocatalytic applications. Moreover, the Al2O3 nanocondensates of spinel-type related structures, i.e. £^- and £c- type with a significant internal compressive stress via pulsed laser ablation in water were subjected to prolonged dwelling in water to form columnar bayerite plates for further transformation as platy £^-Al2O3. Transmission electron microscopic observations indicated the £^-Al2O3 follows the crystallographic relationship (100)b//(011)£^; [001]b//[111]£^ with relic bayerite (denoted as b). The £^-Al2O3 also shows {111} twin/faults and rock salt-type domains due to dehydroxylation of bayerite which involves {111} shuffling and disordering of the Al ions in the octahedral and tetrahedral sites. The combined evidences of X-ray photoelectron spectroscopy, vibrational spectroscopy and UV-visible absorbance indicated that the H+, Al+ and Al2+ co-doped bayerite and £^-Al2O3 composite plates have a minimum band gap as low as ~ 5 eV for potential catalytic and electro-optical applications in water environment. Finally, pulsed laser ablation in aqueous solution of NaOH up to 1 M was employed to fabricate epitaxial NaAlO2 and £^-Al2O3 nanopartricles for electron microscopic and spectroscopic characterizations. The NaAlO2 phase (denoted as N), presumably derived from NaAlO2 .5/4H2O, was found to form intimate intergrowth with the £^-Al2O3 following a specific crystallographic relationship [211]£^//[110]N; ( 2 22) £^//(002)N and (0 2 2) £^//(110)N for a parallel close packed planes in terms of corner linked AlO4 tetrahedra and a beneficial lower interfacial energy and/or strain energy. The composite phases have significant internal compressive stress up to 7 and 40 GPa according to cell volume and IR shift results and a low minimum band gap of 5.9 eV for potential applications in UV region.

The polyglutamate which grafts with flexible alkyl side-chain by ester exchange reaction is like rod-hairy molecule. The numbers of methylene group of side-chain and the graft-density affect the molecular packing of poly(gama-alkyl-L-glutamate)s. To be sure the correct chemical structure of poly(gama-alkyl-L-glutamate)s by Fourier transform infrared spectrometer (FTIR), and find out the graft-density of each sample by proton nuclear resonance spectrometer (1H-NMR). Phase behavior of poly(gama-alkyl-L-glutamate)s were studied via differential scanning calorimetry (DSC) and variable temperature x-ray diffraction (XRD).We combine the results from C. C. Hsu(24). When the side-chain length is long enough (m>10), side-chains will crystallize into a 3D hexagonal lattice. The results of DSC and XRD analyses show that the side-chain crystalline phase will melt at Tm1, where as a liquid crystalline (LC) phase transition exists at Tm2. Poly(gama-alkyl-L-glutamate)s with shorter side-chain (m<8) tend to form 2D hexagonal LC structure. On the other hand, longer side-chains (m>10) tend to give lamellar structure. The critical number of methylene group of side-chain between hexagonal and lamellar structure is between 8 and 10.

Materiais naturais nanoestruturados, tipo smectita, têm sido amplamente usados em nanocompósitos poliméricos, com ganhos expressivos em muitas propriedades. Porém, devido a sua natureza polar, seu uso em nanocompósitos de poliolefinas apresenta uma série de problemas. Entre esses problemas está a dificuldade de esfoliação na matriz, o que geralmente resulta um sistema não nano-estruturado e, por conseqüência, com pouco ou nenhum ganho em propriedades. Para tentar resolver esse problema, materiais tipo esmectita têm sido modificados com sais de amônio quartenário. Esses, por sua vez, possuem características tóxicas, impedindo seu uso em embalagens de alimentos. Com o objetivo de estudar uma nova alternativa que contorne esses problemas, dois materiais lamelares nano-estruturados, tipo esmectita, contendo grupos alquila ligados por ligação sigma com a rede inorgânica, foram sintetizados. Ambos apresentaram excelente ordem mesoestrutural. Um dos materiais sintetizados, formado por um Alsilsesquioxano lamelar, contendo alto teor de cadeia alquila entre as lamelas inorgânicas, foi usado na formação de compósito de polietileno. Comparativamente, uma argila natural, modificada com sais de amônio quaternário (Cloisite 15A), foi usada para fins comparativos. Os compósitos, então obtidos, foram caracterizados para avaliar diferenças microestruturais, morfológicas e mudanças em suas propriedades mecânicas e reológicas. Comparativamente à argila comercial Cloisite 15A, os compósitos contendo os materiais sintéticos apresentaram reologia diferenciada, melhor resistência ao impacto e ao Tensofissuramento Acelerado pelo Ambiente (ESCR). / Nanostructured natural materials, as smectites, have been widely used in polymeric nanocomposites, with significant gains in many properties. However, due to its polar nature, the use in nanocomposites of polyolefins presents a series of drawbacks. Among these problems, its difficulty exfoliation in the matrix, which generally results in a system not nanostructured and, consequently, with little or no gain on properties. To try to resolve this problem, materials type smectite have been modified with quaternary ammonium salts. These salts, in turn, have toxic characteristics, preventing its use in food packaging. In order to study a new alternative that bypasses these problems, two lamellar nanostructured materials, like smectite, with alkyl groups containing sigma links connected to lamellar inorganic network, were synthesized. Both materials had excellent mesostructural order. One of the synthesized materials, formed by a lamellar Al-silsesquioxane, containing high levels of alkyl chain between the inorganic lamella, was used in the formation of a polyethylene composite. Commercial natural clay, modified with quaternary ammonium salts (Cloisite 15A), was used for comparative purposes. The composites then obtained, were characterized to assess microstructural differences, morphological change, and its mechanical and rheological properties. Comparatively to commercial clay (Cloisite 15A), the composites containing synthetic materials, showed differented rheologics properties, better impact resistance and better Environmental Stress Cracking Resistance (ESCR).

Materiais naturais nanoestruturados, tipo smectita, têm sido amplamente usados em nanocompósitos poliméricos, com ganhos expressivos em muitas propriedades. Porém, devido a sua natureza polar, seu uso em nanocompósitos de poliolefinas apresenta uma série de problemas. Entre esses problemas está a dificuldade de esfoliação na matriz, o que geralmente resulta um sistema não nano-estruturado e, por conseqüência, com pouco ou nenhum ganho em propriedades. Para tentar resolver esse problema, materiais tipo esmectita têm sido modificados com sais de amônio quartenário. Esses, por sua vez, possuem características tóxicas, impedindo seu uso em embalagens de alimentos. Com o objetivo de estudar uma nova alternativa que contorne esses problemas, dois materiais lamelares nano-estruturados, tipo esmectita, contendo grupos alquila ligados por ligação sigma com a rede inorgânica, foram sintetizados. Ambos apresentaram excelente ordem mesoestrutural. Um dos materiais sintetizados, formado por um Alsilsesquioxano lamelar, contendo alto teor de cadeia alquila entre as lamelas inorgânicas, foi usado na formação de compósito de polietileno. Comparativamente, uma argila natural, modificada com sais de amônio quaternário (Cloisite 15A), foi usada para fins comparativos. Os compósitos, então obtidos, foram caracterizados para avaliar diferenças microestruturais, morfológicas e mudanças em suas propriedades mecânicas e reológicas. Comparativamente à argila comercial Cloisite 15A, os compósitos contendo os materiais sintéticos apresentaram reologia diferenciada, melhor resistência ao impacto e ao Tensofissuramento Acelerado pelo Ambiente (ESCR). / Nanostructured natural materials, as smectites, have been widely used in polymeric nanocomposites, with significant gains in many properties. However, due to its polar nature, the use in nanocomposites of polyolefins presents a series of drawbacks. Among these problems, its difficulty exfoliation in the matrix, which generally results in a system not nanostructured and, consequently, with little or no gain on properties. To try to resolve this problem, materials type smectite have been modified with quaternary ammonium salts. These salts, in turn, have toxic characteristics, preventing its use in food packaging. In order to study a new alternative that bypasses these problems, two lamellar nanostructured materials, like smectite, with alkyl groups containing sigma links connected to lamellar inorganic network, were synthesized. Both materials had excellent mesostructural order. One of the synthesized materials, formed by a lamellar Al-silsesquioxane, containing high levels of alkyl chain between the inorganic lamella, was used in the formation of a polyethylene composite. Commercial natural clay, modified with quaternary ammonium salts (Cloisite 15A), was used for comparative purposes. The composites then obtained, were characterized to assess microstructural differences, morphological change, and its mechanical and rheological properties. Comparatively to commercial clay (Cloisite 15A), the composites containing synthetic materials, showed differented rheologics properties, better impact resistance and better Environmental Stress Cracking Resistance (ESCR).

Surfactants are amphiphilic molecules which self-assemble at the interface in oil-water-surfactant mixtures such that the hydrophobic part, called tail, stays in oil and the remaining part, called head, resides in hydrophilic en-vironment. Depending upon concentration of individual components, these mixtures form several microphases, such as bilayers, micelles, columnar and lamellar phases. A lamellar phase, at equilibrium, is made up of alternat-ing layers of water and oil separated by surfactants, or of alternate layers of water and surfactant bilayers such that the hydrophilic heads are in contact with water. This equilibrium state is rarely achieved in macroscopic samples due to thermodynamic and kinetic constraints; instead, a lamellar fluid is usually disordered with a large number of defects. These defects have significant effect on the flow behaviour of the lamellar mesophase systems. They are known to alter the flow field, resulting stresses and in turn could get distorted or annihilated by the flow. In present work, we analyse this two way coupling between lamellar structure and flow field. The structural and rheological evolution of an initially disordered lamellar phase system under a shear flow is examined using a mesoscale model based on a free energy functional for the concentration field, which is the scaled difference in the concentration between the hydrophilic and hydrophobic components. Two distinct modes of structural evolution are observed depending only on Peclet number, which ratio of inertial forces to mass diffusivity, in-dependent of system size. At low Peclet number, local domains are formed which are then rotated and stretched by shear. A balance between defect creation and annihilation is reached due to which the system never reaches the equilibrium layer configuration. In the opposite limit, partially formed layers break and reform so as to form a nearly aligned lamellar phase con-figuration with residual defects. Viscosity of lamellar phase system increases with layer moduli, differences in viscosity of individual components, fluidity of the lamellae due to shear banding and defect pinning. These factors however, do not have any effect on alignment mechanism.

The workpiece materials used in this study are CuNb nano-layered composites (NLC) which are produced in bulk form by accumulative roll bonding (ARB). CuNb NLC panels are of interest because of their increase in strength and radiation damage tolerance when compared to either of their bulk constituents. These increased properties stem from the bi-metal interface, and the nanometer length-scale of the layers. However to be commercially viable, methods to successfully join the ARB NLC which retain the layered structure panels are needed. Friction stir welding is investigated in this study as a possible joining method that can join the material while maintaining its layered structure and hence its properties. Mechanical properties of the weld were measured at a macro level using tensile testing, and at a local level via nano-indentation. The post weld layer structure was analyzed to provide insight into the flow paths. The grain orientation of the resulting weld nugget was also analyzed using electron backscatter diffraction and transmission Kikuchi diffraction. Results from this study show that the nano-layered structure can be maintained in the CuNb NLC by control of the friction stir welding parameters. The resulting microstructure is dependent on the strain experienced during the joining process. A variation in layer thickness reduction is correlated with increasing shear strain. Above a critical level of shear strain, the NLC microstructure was observed to fragment into equiaxed grains with a higher hardness than the NLC panels. Results from this study are also used to further the understanding of the material flow and hot working conditions experienced during the friction stir welding process.

No description available.

High density polyethylene (HDPE) films having simple and well-defined stacked lamellar morphology, either with or without a distinct presence of row-nucleated fibril structures, have been utilized as <i>model</i> materials to carry out investigations on solid state structure-property relationships. Four different subjects that were addressed are: 1) mechanical properties and deformation morphologies, 2) orientation anisotropy of the dynamic mechanical α relaxation, 3) orientation dependence of creep behavior, and 4) crystalline lamellar thickness and its distribution. For the first three topics, appropriate mechanical tests, including tensile (INSTRON), creep (TMA), and dynamic mechanical (DMTA) tests, were performed at <i>different angles with respect to the original machine direction (MD)</i> of the melt extruded films; morphological changes as a result of these mechanical tests were detected by WAXS, SAXS, and TEM. For the forth topic, crystalline lamellar thickness and its distribution were determined by DSC, SAXS, TEM and AFM experiments. In the <i>large strain deformation</i> study (chapter 4.0), samples were stretched at 00°, 45° and 90° angles with respect to the original MD. A distinct orientation dependence of the tensile behavior was observed and <i>correlated</i> to the corresponding deformation modes and morphological changes, namely 1) lamellar separation and fragmentation by chain slip for the 00° stretch, 2) lamellar break-up via chain pull-out for the 90° stretch, and 3) lamellar shear, rotation and break-up through chain slip and/or tilt for the 45° stretch. A strong strengthening effect was observed for samples with row-nucleated fibril structures at the 00° stretch; whereas for the 90° stretch, the presence of such structures significantly limited deformability of the samples. In the <i>dynamic strain mechanical α relaxation</i> study (chapter 5.0), samples were tested at nine different angles with respect to the original MD, and the morphologies of samples <i>before</i> and </i>after</i> the dynamic tests were also investigated. The mechanical dispersions for the 00° and 90° tests were believed to arise essentially from the crystalline phase, and they contain contributions from two earlier recognized sub-relaxations of α_I and α_II. While for the 45° test, in addition to a high temperature α_II relaxation, a interlamellar shear induced low temperature mechanical relaxation was also observed. It is concluded that the low temperature relaxation is related to the characteristics of the interface between the crystalline lamellae and amorphous layers. In the <i>small strain creep</i> study (chapter 6.0), samples were tested at the 00°, 45° and 90° angles at the original MD. Both creep strain and creep rate for samples at the three angles were very different. An Eyring-rate model was utilized to analysis the observed creep behavior, and structural parameters associated with this model, including population of creep sites, activation energy and volume, were obtained by fitting the experimental data to the Eyring-rate equation. It was concluded that the plateau creep rate in these model materials is primarily controlled by the density and physical state of tie-chains in the amorphous phase. For the lamellar thickness and distribution study, DSC, SAXS, TEM and AFM experiments were conducted for samples having a well-defined stacked lamellar morphology. It was found that the most probable lamellar thickness from SAXS and TEM agreed very well; however, these values did not match with those obtained by DSC and AFM. It was pointed out that the use of DSC to determine lamellar thickness and distribution is so sensitive to heating rate and numerical values for the parameters in the Gibbs-Thomson equation that it is not believed to be suitable for quantitative analysis. / Ph. D.

[ES] La presente tesis doctoral se centra en la obtención, vía síntesis directa, de materiales zeolíticos nanocristalinos con propiedades fisicoquímicas y catalíticas mejoradas respecto a los materiales de referencia. Para ello se ha hecho uso de tensioativos creados específicamente para cada una de las estructuras zeolíticas estudiadas, evitando el uso de procesos post-sintéticos que conllevan una pérdida de material cristalino. En la primera parte del trabajo se ha estudiado la obtención de la zeolita ITQ-2 deslaminada por síntesis directa (DS-ITQ-2) mediante el uso de varios tensioactivos, siendo el C16DC1 (N-Hexadecil-N'-metil-1,4-diazabiciclo[2.2.2]octano) con el que mejores resultados se han obtenido. Se ha estudiado la influencia de la longitud de la cadena alifática y la concentración del agente director de estructura orgánico (ADEO) en el gel de síntesis sobre la cinética del proceso de cristalización y las implicaciones sobre las características fisicoquímicas del material obtenido. Mediante el control de la concentración del tensioactivo en el gel de síntesis, ha sido posible dirigir el grado de deslaminación del material final. Las propiedades fisicoquímicas del material considerado como óptimo se han comparado con las de las zeolitas MCM-22, MCM-56 e ITQ-2, todas ellas con la misma estructura cristalina (MWW). Por último, la actividad catalítica de la zeolita DS-ITQ-2 se ha estudiado en dos reacciones, la alquilación de benceno con propileno para la obtención de cumeno y la reacción de 2,5-dimetilfurano con etileno para la obtención de p-xileno, obteniendo en ambos casos unos resultados de conversión y selectividad excelentes. La segunda parte de la tesis se ha centrado en la preparación de la zeolita ferrierita en su forma nanocristalina por síntesis directa mediante la utilización de tensioactivos. Se han estudiado tensioactivos con tres partes polares diferentes obtenidos a partir de las correspondientes aminas utilizadas como ADEOs. Además, también se ha estudiado el efecto de la longitud de la cadena del tensioactivo entre los 6 y los 16 átomos de carbono. La modificación de parámetros del gel de síntesis como por ejemplo la relación molar entre la piperidina o el tensioactivo y la sílice ha resultado ser determinante a la hora de conseguir una composición óptima para la obtención de la zeolita nanocristalina con las propiedades fisicoquímicas deseadas. La optimización de la temperatura de síntesis y la introducción de cristales de siembra en el gel de síntesis ha permitido mejorar las propiedades finales del material. La actividad catalítica de las nanoferrieritas se ha estudiado en dos reacciones diferentes, la oligomerización de 1-penteno y la isomerización de 1-buteno. Se ha mostrado la importancia de reducir el tamaño del cristal de la ferrierita, obteniéndose materiales con actividad y selectividad muy superior a los descritos en la bibliografía abierta y de patentes. / [CA] La present tesis doctoral es centra en l'obtenció, via síntesi directa, de materials zeolítics nanocristalins amb propietats fisicoquímiques i catalítiques millorades respecte als materiales de referència. Per a això s'ha fet ús de tensioatius creats específicament per a cadascuna de les estructures zeolítiques estudiades, evitant l'ús de processos post-sintètics que comporten una pèrdua de material cristal·lí. En la primera part del treball s'ha estudiat l'obtenció de la zeolita ITQ-2 deslaminada per síntesi directa (DS-ITQ-2) mitjançant l'ús de diversos tensioactius, essent el C16DC1 (N-Hexadecil-N'-metil-1,4-diazabiciclo[2.2.2]octà) amb el que millors resultats s'han obtés. S'ha estudiat la influència de la longitud de la cadena alifàtica i la concentració de l'agent director d'estructura orgànic (ADEO) en el gel de síntesi sobre la cinètica del procés de cristal·lització i les implicacions sobre les característiques fisicoquímiques del material obtés. Mitjançant el control de la concentració del tensioactiu en el gel de síntesi, ha sigut possible dirigir el grau de deslaminació del material final. Les propietats fisicoquímiques del material considerat com òptim s'han comparat amb les de les zeolites MCM-22, MCM-56 i ITQ-2, totes elles amb la mateixa estructura cristal·lina (MWW). Per íltim, l'activitat catalítica de la zeolita DS-ITQ-2 s'ha estudiat en dos reaccions, l'alquilació de benzé amb propilé per a l'obtenció de cumé i la reacció de 2,5-dimetilfurà amb etilé per a l'obtenció de p-xilé, obtenint en tots dos casos uns resultats de conversió i selectivitat excel·lents. La segona part de la tesi s'ha centrat en la preparació de la zeolita ferrierita a la seua forma nanocristal·lina per síntesi directa mitjançant la utilizació de tensioactius. S'han estudiat tensioactius amb tres parts polars diferents obtesos a partir de les corresponents amines utilitzades com a ADEOs. A més a més, també s'ha estudiat l'efecte de la longitud de la cadena del tensioactiu entre els 6 i els 16 àtoms de carboni. La modificació de paràmetres del gel de síntesi com per exemple la relació molar entre la piperidina o el tensioactiu i la sílice ha resultat ser determinant a l'hora de conseguir una composició òptima per a l'obtenció de la zeolita nanocristal·lina amb les propietats fisicoquímiques desitjades. L'optimització de la temperatura de síntesi i la introducció de cristalls de sembra en el gel de síntesi ha permés millorar les propietats finals del material. L'activitat catalítica de les nanoferrierites s'ha estudiat en dos reaccions diferents, l'oligomerizació de l'1-penté i la isomerització de l'1-buté. S'ha mostrat la import`ancia de reduir el tamany del cristall de la ferrierita, obtenint-se materials amb activitat i selectivitat molt superior als descrits en la bibliografia oberta i de patents. / [EN] This doctoral thesis focuses on obtaining, via direct synthesis, nanocrystalline zeolite materials with improved physicochemical and catalytic properties compared to reference materials. For this, surfactants created specifically for each of the zeolite structures studied have been used, avoiding the use of post-synthetic processes that lead to a loss of crystalline material. In the first part of the work, the obtaining of the delaminated ITQ-2 zeolite by direct synthesis (DS-ITQ-2) through the use of various surfactants, being C16DC1 (NHexadecyl-N'-methyl-1,4-diazabiciclo[2.2.2]octane) with which the best results have been obtained. The influence of the length of the aliphatic chain and the concentration of the organic structure directing agent (OSDA) in the synthesis gel on the kinetics of the crystallization process and the implications on the physicochemical characteristics of the obtained material have been studied. By controlling the concentration of the surfactant in the synthesis gel, it has been possible to direct the degree of delamination of the final material. The physicochemical properties of the material considered optimal have been compared with those of the zeolite MCM-22, MCM-56 and ITQ-2, all of them with the same crystalline structure (MWW). Finally, the catalytic activity of the zeolite DS-ITQ-2 has been studied in two reactions, the alkylation of benzene with propylene to obtain cumene and the reaction of 2,5-dimethylfuran with ethylene to obtain p-xylene, obtaining excellent conversion and selectivity results in both cases. The second part of the thesis has focused on the preparation of ferrierite zeolite in its nanocrystalline form by direct synthesis using surfactants. Surfactants with three different polar parts, obtained from the corresponding amines used as OSDAs, have been studied. In addition, the effect of the chain length of the surfactant between 6 and 16 carbon atoms has also been studied. Modifying the parameters of the synthesis gel, such as the molar ratio between piperidine or surfactant and silica, has turned out to be decisive when it comes to achieving an optimal composition for obtaining nanocrystalline zeolite with the desired physicochemical properties. The optimization of the synthesis temperature and the introduction of seed crystals in the synthesis gel have allowed to improve the final properties of the material. The catalytic activity of nanoferrierites has been studied in two different reactions, the oligomerization of 1-pentene and the isomerization of 1-butene. The importance of reducing the size of the ferrierite crystal has been shown, obtaining materials with activity and selectivity much higher than those described in the open and patent literature. / Margarit Benavent, VJ. (2023). Síntesis directa de zeolitas monolámina (zeolitas 2D) y sus aplicaciones catalíticas [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/192880