Tesi sul tema "Porous metallic materials"

El objetivo de esta tesis es estudiar la agrupación y el crecimiento de especies metálicas confinadas o soportadas en materiales porosos mediante espectroscopia de absorción de rayos X in situ. Para lograrlo, las especies de paladio y plata se han introducido en materiales porosos (¿-alúmina, carbón activo y zeolitas) mediante impregnación vía húmeda y métodos de intercambio iónico, respectivamente. Luego, el agrupamiento de estas especies metálicas se ha controlado mediante tratamientos de activación en diferentes atmósferas (inerte, oxidativa y reductiva) y seguido por XAS de manera detallada. El objetivo principal del trabajo actual es demostrar que tanto XANES como EXAFS pueden proporcionar información valiosa y, en cierto punto, innovadora durante el control de especies metálicas (en términos de tipo y tamaño de las especies). Aprovechando los procedimientos de análisis inusuales, como el análisis de los cumulantes, el ajuste de la parte imaginaria de la transformada de Fourier y otros, es posible obtener información refinada sobre los sistemas investigados. En la sección de introducción, se proporciona una compilación de estudios en los que se ha utilizado XAS como técnica importante para caracterizar especies metálicas en materiales porosos. Conscientes de que las personas pueden usar dicha introducción como base para estudios más complejos en el futuro, la discusión se ha dirigido tentativamente hacia este objetivo. El capítulo 4 se centra en el estudio de la influencia de los precursores de paladio y la naturaleza del soporte en las nanopartículas resultantes. El proceso de activación completo, es decir, la transformación precursor --> nanopartícula, ha sido seguido por XAS in situ. El análisis estuvo compuesto por el punto de partida (material impregnado), calcinación en flujo de O2 y reducción posterior con H2. La consecuencia del uso de diferentes precursores metálicos y soportes se ha discutido en términos del número de coordinación promedio obtenido a partir del análisis de datos de EXAFS, que fue respaldado por técnicas de caracterización de laboratorio. El capítulo 5 está dedicado al estudio de la agrupación de plata durante y después de los tratamientos de activación utilizando zeolitas de poro pequeño intercambiadas con plata como precursores y nanocontenedores. Se ha estudiado la influencia de la estructura y la composición química de los materiales basados en plata sobre las especies metálicas formadas en diferentes condiciones de agrupamiento y redispersión del metal (calcinación usando atmósferas distintas, reducción en H2, redispersión en O2) utilizando métodos de caracterización in situ o ex situ. Después, se discuten las consecuencias catalíticas de las zeolitas que contienen Ag en la reacción de SCO-NH3. En esta sección, la combinación de XAS in situ con varias técnicas de laboratorio ha demostrado ser fundamental para un completo entendimiento del trabajo. Finalmente, una lista de proyectos desarrollados en paralelo a esta tesis se proporciona al final de este documento.
The aim of this thesis is to study the clustering and growth of metallic species either confined or supported in porous materials by in situ X-ray absorption spectroscopy. To accomplish this task, palladium and silver species were introduced into porous materials (¿-alumina, activated carbon and zeolites) by wetness impregnation and ion-exchange methods, respectively. Then, the clustering of these metallic species was controlled by activation treatments in different atmospheres (inert, oxidative and reductive) and followed by XAS in a comprehensive way. The principal goal of current work is to demonstrate that both XANES and EXAFS can provide valuable and, at certain point, innovative information during tuning of metallic species (in terms of type and size). Taking advantage of unusual analysis procedures, such as cumulant approach, fitting of imaginary part of Fourier transform and others, it is possible to obtain refined information about the investigated systems. In the introduction section, a compilation of studies in which XAS was used as important technique to characterize metallic species in porous materials is provided. Conscious that people can use such introduction as a basis for more complex studies in the future, the discussion has been tentatively directed toward this goal. The chapter 4 is focused on the study of the influence of palladium precursors and the nature of support on the resultant nanoparticles. The whole activation process, i.e. the transformation precursor --> nanoparticle, was followed in situ by XAS. The analysis pathway was composed by the starting point (as-impregnated), calcination in O2 flow and posterior reduction with H2. The consequence of using distinct metal precursors and supports were discussed in terms of average coordination number obtained from EXAFS data analysis, which was co-supported by laboratory characterization techniques. The chapter 5 is dedicated to the study of silver clustering during and after activation treatments using Ag-containing small-pore zeolites as precursors and nanocontainers. The influence of framework structure and chemical composition of Ag-based materials on formed Ag species at different clustering and metal redispersion conditions (calcination using distinct atmospheres, reduction in H2, redispersion in O2) were studied using either in situ or ex situ characterization methods. After, the catalytic consequences of tuned Ag-containing zeolites in SCO-NH3 are discussed. In this section, the combination of in situ XAS with several laboratory techniques proved to be pivotal to have a full picture of the investigated system. Finally, a list of projects developed in parallel to this thesis is provided at the end of this document.
L'objectiu d'aquesta tesi és estudiar l'agrupació i el creixement d'espècies metàl·liques confinades o suportades en materials porosos mitjançant espectroscòpia d'absorció de raigs X in situ. Per a això, les espècies de pal·ladi i plata s'han introduït en materials porosos (¿-alúmina, carbó activat i zeolites) per mitjà de la impregnació via humida i mètodes d'intercanvi iònic, respectivament. Una vegada preparats els materials, l'agrupament de les espècies metàl·liques s'ha controlat fent ús de tractaments d'activació en diferents atmosferes (inert, oxidant i reductora) s'ha estudiat exhaustivament per XAS. L'objectiu principal del treball és demostrar que tant el XANES com l'EXAFS proporcionen informació rellevant i, en certa manera, innovadora per al control d'espècies metàl·liques (en termes de tipus i grandària d'aquestes espècies). Fent ús de procediments de tractament de dades no molt habituals com l'anàlisi de cumulants, l'ajust de la part imaginària de la transformada de Fourier i altres, és possible obtenir informació detallada sobre els sistemes estudiats. En l'apartat de la introducció, es proporciona una recopilació d'estudis en els quals s'ha utilitzat XAS com a tècnica principal per a caracteritzar les anomenades espècies metàl·liques en materials porosos. Aquesta introducció ha estat redactada per a que puga servir com a punt de partida per a futurs estudis que requereixen la utilització de XAS per a la caracterització de les espècies metàl·liques presents en els catalitzadors. El capítol 4 es centra en l'estudi de la influència dels precursors de pal·ladi i la naturalesa del suport front a les nanopartícules resultants. El procés d'activació, és a dir, la transformació precursor --> nanopartícula, ha sigut estudiat per XAS in situ. L'anàlisi per XAS va comprendre els següents passos: punt de partida (material impregnat), calcinació en flux d'O2 i reducció posterior amb H2. La utilització de diferents precursors i suports metàl·lics ha permès dur a terme una discussió, referent al nombre de coordinació mitjà obtingut a partir de l'anàlisi de dades de la zona EXAFS, que ha estat recolzat per altres tècniques de caracterització. El capítol 5 s'ha dedicat a l'estudi de l'agrupació de plata intercanviada en els catalitzadors durant i després dels tractaments d'activació. S'han utilitzat zeolites de porus xicotet, com la CHA i RHO, intercanviades amb plata. L'estudi de la influència de l'estructura zeolítica i la composició química dels materials enfront dels diferents tractaments d'activació (calcinació utilitzant diferents atmosferes, reducció en presència d'H2, re-dispersió en atmosfera d'O2) es va realitzar fent ús de mètodes de caracterització in situ o ex situ. A continuació, es discuteix la influència d'aquestes espècies metàl·liques formades, utilitzant els diferents mètodes d'activació, per a la reacció d'SCO-NH3. En aquest sentit, s'ha demostrat que la combinació de XAS in situ amb diverses tècniques habituals de laboratori és fonamental per al desenvolupament d'aquest treball. Finalment, es presenta una llista de projectes, en els quals també s'ha treballat paral·lelament, on s'ha utilitzat XAS com a tècnica de caracterització.
Wittee Lopes, C. (2018). Characterization of metallic species on porous materials by in situ XAS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/107953
TESIS

This work describes a novel technique to prepare ultra-thin composite Pd-porous metal membranes for H2 separation. This novel technique consists of the gradual smoothing of the Porous Metal (PM) support's surface with several layers of pre-activated alumina particles of different sizes. The deposition of coarse, fine and ultra-fine alumina particles resulted in the narrowing of the PM' surface pore size distribution. The excellent surface smoothness achieved after the grading of the PM 's surface support allowed for the preparation of gas tight Pd layers as thin as 5.6?m. The Pd layers were extremely uniform due to the presence of the grade layer and strongly attached to the support. Composite Pd membranes prepared on graded supports showed H2 permeance as high as 50 m3/(m2 h bar0.5) at 500ºC and ideal selectivities (H2/He) as high as 27000. Moreover, the H2 permeance and ideal selectivity were stable over 1100 hours at 500ºC in H2 atmosphere. Composite Pd-Cu membranes showed H2 permeance as high as 30 m3/(m2 h bar0.5) at 450ºC and ideal selectivities (H2/He) as high as 900. The H2 permeance and ideal selectivity of Pd-Cu membranes were stable over 500 hours at 450ºC in H2 atmosphere. The outstanding long-term H2 permeance and ideal selectivity stability of all composite Pd and Pd-Cu membranes represented a breakthrough in composite Pd membrane synthesis. The thermal stresses arising from the mismatch in the coefficient of thermal expansion between the Pd film and the support were determined by means of x-ray diffraction. The results indicated that the release of stresses began to occur at temperatures close to 400ºC. Also, the release of stresses took place with a visible sintering of Pd clusters within the thin Pd film. The stresses due to the absorption of H2 were also studied and modeled. It was estimated that the maximum compressive stress under which these composite Pd membranes were characterized was equal to 260 MPa.

L'aluminium (Al) est le métal non-ferreux le plus utilisé au monde. Ses propriétés physiques particulières en font un matériau de choix pour un grand nombre de domaines industriels comme les transports, la construction, l'alimentaire ou encore l'électronique. Sa faible densité est idéale pour réduire le poids des structures. Les matériaux poreux à base d'Al, présentent, de surcroit, l’avantage de présenter une très grande surface d'échange avec le milieu. Comme tous les métaux, l'Al est très facilement usinable. Toutefois, certaines formes, plus complexes, ne sont pas réalisables en utilisant les techniques d'usinage conventionnelles. Depuis plusieurs années, la recherche se tourne vers la fabrication additive pour surmonter ce problème.Dans ce manuscrit, nous utilisons une technique appelée fabrication additive par extrusion de pâte afin de réduire les coûts de productions et les pertes de matières premières occasionnés par l'impression 3D laser. Cette technique consiste à incorporer de la poudre métallique dans un gel composé d'un polymère et d'un solvant. Dans notre cas, nous utilisons un gel d'hydroxypropylcellulose (HPC) dans le butanol et nous y incorporons de la poudre d'Al ou un mélange de poudres à base d'Al. Cette pâte est ensuite conditionnée dans une seringue et placée dans l'imprimante 3D afin d'extruder des cordons à travers une buse de 0,86 mm de diamètre. Ces cordons sont déposés et empilés par le bras mécanique de l'imprimante 3D pour former des objets de formes prédéterminées. Une fois séchés, les objets sont traités thermiquement afin d'éliminer l'HPC et de ne garder que l'Al. Nous avons choisi d'élaborer des objets présentant à la fois des macroporosités et des microporosités afin d'augmenter la surface d'échange avec le milieu extérieur. Les propriétés de dissipations thermiques de ces objets ont été mesurées pour voir s'ils pouvaient être utilisés comme dissipateurs thermiques dans le domaine électronique. Les propriétés mesurées de ces objets se sont avérées supérieures à celles d'un bloc d'Al dense. Des objets composés d'un mélange d'Al et de AlSi12 ont également pu être imprimés et ont également montré de très bonnes propriétés de dissipation thermique.Dans la deuxième partie de ce manuscrit, nous nous sommes intéressés à la fin de vie de nos matériaux. Le recyclage des alliages d'Al n'est pas simple car au fur et à mesure des cycles de recyclage, une perte des éléments d'alliages peut être observée. Il faut donc réfléchir à un moyen de revaloriser les déchets d'Al ou d'alliages à base d'Al en fin de vie. Dans ce but, des matériaux modèles ont été synthétisés par métallurgie des poudres. En contrôlant le temps, la température et la pression appliquée lors du frittage, il a été possible de contrôler le taux de porosité au sein des échantillons. Par réaction chimique dans une solution aqueuse d'hydroxyde de sodium, nous avons pu créer de l'hydrogène qui pourrait ensuite être utilisé comme carburant dans les voitures (Toyota Miraï par exemple). Nous avons également montré que la cinétique de libération de l'hydrogène pouvait être contrôlée en contrôlant le taux de porosité au sein des échantillons. Enfin, nous avons travaillé sur un alliage Al-Mg permettant de créer de l'hydrogène non pas dans la soude, qui est un milieu très agressif, mais dans l'eau de mer. Ce dernier résultat permet de montrer que revaloriser des déchets d'alliages d'Al est faisable dans un milieu très peu toxique et très présent à la surface de la Terre
In this manuscript, we employ a technique called paste extrusion additive manufacturing to reduce production costs and raw material losses associated with laser 3D printing. This technique involves incorporating metallic powder into a gel composed of a polymer and a solvent. In our case, we use a gel of hydroxypropylcellulose (HPC) in butanol and incorporate aluminum powder or a mixture of aluminum-based powders. This paste is then loaded into a syringe and placed in the 3D printer to extrude filaments through a 0.86 mm diameter nozzle. These filaments are deposited and stacked by the 3D printer's mechanical arm to form objects of predetermined shapes. Once dried, the objects are thermally treated to remove the HPC, leaving only the aluminum. We chose to fabricate objects with both macroporosity and microporosity to increase the surface area for exchange with the external environment. The thermal dissipation properties of these objects were measured to assess their suitability as heat sinks in the electronics field. The measured properties of these objects were found to be superior to those of a dense aluminum block. Objects composed of a mixture of aluminum and AlSi12 were also successfully printed and exhibited excellent thermal dissipation properties.In the second part of this manuscript, we focused on the end-of-life of our materials. Recycling aluminum alloys is challenging because with each recycling cycle, a loss of alloying elements may occur. Therefore, it is necessary to consider ways to valorize end-of-life aluminum or aluminum-based alloy waste. For this purpose, model materials were synthesized via powder metallurgy. By controlling the time, temperature, and pressure applied during sintering, it was possible to control the porosity within the samples. Through a chemical reaction in an aqueous solution of sodium hydroxide, we were able to generate hydrogen, which could then be used as fuel in vehicles (such as the Toyota Mirai, for example). We also demonstrated that the kinetics of hydrogen release could be controlled by manipulating the porosity rate within the samples. Finally, we worked on an Al-Mg alloy to generate hydrogen not in caustic soda, which is a highly aggressive medium, but in seawater. This latter result demonstrates that valorizing aluminum alloy waste is feasible in a minimally toxic and abundant environment on Earth's surface

Orientador: Jose Luis Lage, Luiz Fernando Milanez
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: O presente trabalho trata do estudo teórico e experimental dos efeitos térmicos causados pela aplicação da radiação laser sobre meios porosos e objetiva a determinação do coeficiente de atenuação de um meio poroso imerso em fluido. O modelamento matemático proposto utiliza a técnica dos volumes finitos, para resolver numericamente a equação do transporte do calor em coordenadas.cilíndricas. Um sistema de aquisição de dados baseado no conceito de instrumentos virtuais é elaborado para analisar o processo de aquecimento pela radiação de um laser de Argônio sobre uma matriz porosa de Alumínio 6101 imersa em quatro fluidos diferentes: ar, água, óleo polialfaolefina e Mercúrio. Uma metodologia inversa, estabelecida pela comparação de resultados numéricos e experimentais, é empregada para obter o coeficiente de atenuação da espuma metálica saturada. A análise inclui o emprego de duas metodologias de cálculo da condutividade térmica equivalente. Uma correlação entre os coeficientes de atenuação e um número de Prandtl equivalente do meio poroso é estabelecida
Abstract: In the present work, an investigation of thermal effects due to laser application is accomplished in order to determine the attenuation coeflicient of a porous matrix immersed in fluido The study included both theoretical and experimental analisys. In the theoretical analisys a numerical mo deI based on control volume method is developed to simulate the lasing process by solving the energy equation in cilindrical coordinates. A data acquisition system based on virtual instruments concept is elaborated to analyse the heating process result,ing from Argon Laser radiation over an Aluminum foam porous medium immersed in four different fluids, namely air, water, polyalphaolefin oil and Mercury. An inverse methodology, estabilished by comparison of numerical and experimental results, is used to obtain the attenuation coeflicient of the saturated metal foam. Calculations also included the use of two models for the effective thermal conductivity. Results indicated the existence of a linear correlation between laser attenuation and a defined equivalent Prandtl number
Doutorado
Termica e Fluidos
Doutor em Engenharia Mecânica

A new tool (Infrasorb-12) for the screening of porosity is described, identifying high surface area materials in a very short time with high accuracy. Further, an example for the application of the tool in the discovery of new cobalt-based metal–organic frameworks is given
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich

Doutoramento em Ciência e Engenharia de Materiais
O método de síntese de nanoparticulas 1-D assistido por um modelo tornou-se um tópico em voga na química após o desenvolvimento de filmes anódicos com poros bem ordenados. Contudo, a maioria dos trabalhos nesta área tem sido feita utilizando filmes porosos destacados devido à presença de uma barreira no fundo dos poros. No entanto, esta estratégia segue demasiados passos, o que aumenta o seu custo, torna mais difícil a execução e impõe várias limitações. Consequentemente, existe a necessidade de uma técnica que permita o enchimento (electrofilling) dos tubos sem remover a camada barreira – esta tese representa o nosso contributo para esse trabalho. Utilizámos uma técnica mais simples que permite a electrodeposição e “electrofilling” de nanoestruturas directamente nos modelos sobre o substrato metálico, utilizando solventes eutécticos profundos à base de cloreto de colina como electrólito. Relativamente à água, os solventes eutécticos profundos demonstram superior estabilidade térmica e uma janela electroquímica mais alargada, o que aumenta o número de materais secundários depositados. Como materiais a investigar foram escolhidos titânia e alumina dada a sua capacidade para formar estruturas porosas altamente ordenadas, propriedades eletroquímicas distintas e uso generalizado em síntese assistida por padrão. O estudo aqui apresentado encontra-se dividido em duas etapas. Primeiramente, a influência da camada barreira foi investigada em sistemas modelo através da utilização de filmes barreira densos na superfície dos elétrodos. Para os filmes de alumina e titânia, identificaram-se vários parâmetros que afectam a electrodeposição, dos quais se destacam a influência da voltagem de anodização, a espessura da camada de barreira, a dupla camada eléctrica e o perfil de corrente. Durante esta etapa detectaram-se efeitos nefastos, como a formação de uma densa camada orgânica na superfície do eléctrodo, que foram ultrapassados aumentando a temperatura ou alternando o potencial aplicado. A segunda etapa consistiu em passar de elétrodos planos (primeira etapa) para modelos porosos (segunda etapa). Foi realizado, com sucesso, o preenchimento dos poros de alumina e dos poros de titânia. Parâmetros como o perfil de corrente, temperatura de solução, entre outras, foram ajustadas para melhorar o fator de preenchimento e a homogeneidade do preenchimento. Foi desenvolvido um processo de preenchimento de moldes de alumina anódica em duas etapas, nucleação AC (1º passo) e preenchimento galvanostático (2º passo). Foram utilizadas três condições diferentes de modelos de titânia anódica porosa no “electrofilling”. O primeiro é sem modificação e demonstrou que a electroredução do zinco ocorre de forma aleatória ao longo de todo o comprimento do poro, o que leva ao fecho do poro e a um enchimento não homogéneo. A segunda modificação, cristalização total por têmpera, permite a preparação de estruturas coaxiais devido à deposição uniforme de zinco nas paredes dos poros. A última modificação foi a cristalização selectiva do fundo do poro. Foi descoberto que uma anodização adicional em eletrólitos não agressivos leva à cristalização da parte barreira dos tubos (fundo) e, consequentemente, a maior condutividade na parte inferior do que nas paredes. Este efeito permite um enchimento ascendente dos modelos porosos de titânia. As estratégias aqui apresentadas alargam a gama de possibilidades para a aplicação de modelos porosos anódicos na electrodeposição de diferentes nanoestruturas.
The template assisted method of 1-D nanoparticles synthesis has become a hot topic in Chemistry after the development of high-ordered porous anodic films. Most studies in this field have focused on the use of detached porous films due to the presence of the barrier layer on the pore bottom. However, this strategy follows a great number of steps, which raises its cost while decreasing convenience of operation and imposing several limitations. Consequently, there is a need for a technique which allows electrofilling of tubes without removing the barrier layer – this thesis represents our contribution to that enterprise. We have devised a simpler technique which allows electrodeposition of nanostructures directly in the templates on metallic substrate, using choline chloride based deep eutectic solvents (DES) as electrolyte. Compared to water, DES have improved thermal stability and a wider electrochemical window, dramatically increasing the number of possible secondary materials deposited. Titania and alumina were chosen as materials under study due to their known capacity to form highly-ordered porous structures, different electrochemical profiles and widespread use in template assisted synthesis. The present work is divided in two parts. First, the influence of the barrier layer has been investigated by using dense barrier films on the electrode surface as a model system. For both alumina and titania films, several parameters affecting the electrodeposition of zinc have been identified, notably the influence of the anodization voltage, barrier layer thickness, electrical double layer and current profile. During this stage, some negative effects have been detected, such as a dense organic layer formation on electrode surface, a hurdle which has been overcome by either increasing the temperature or applying the alternating potential. The second stage consisted in transferring the method from the flat electrodes (the first stage) to the porous templates. The successful filling of both porous alumina and porous titania, has been achieved. Parameters such as current profile, solution temperature, among others, have been tuned to improve the fill factor and homogeneity of the filling. A two-step porous anodic alumina template filling with AC nucleation (1st step) and galvanostatic filling (2nd step) has been developed. Three different types of porous anodic titania templates have been used for electrofilling. The first one was used as-prepared, showing that zinc electroreduction occurs in random places along all pore length, resulting in pore sealing and non-homogeneous filling. The second modification, full crystallization by annealing, allows the preparation of coaxial structures due to uniform zinc deposition on the pore walls. The last modification is selective bottom crystallization. It has been found that additional anodization in unaggressive electrolytes leads to crystallization of the barrier (bottom) part of the tubes and, thus, to higher conductivity of the bottom part than that of the walls. This effect allows a bottom-up filling of the titania porous template. The strategies presented here widen the range of possibilities for the application of porous anodic templates in the electrodeposition of different nanostructures.

A new tool (Infrasorb-12) for the screening of porosity is described, identifying high surface area materials in a very short time with high accuracy. Further, an example for the application of the tool in the discovery of new cobalt-based metal–organic frameworks is given.
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Aquesta tesi doctoral comprèn la síntesi d’aliatges basats en ferro mitjançant diversos mètodes de fabricació. Aquests aliatges s’han dissenyat amb la intenció de ser utilitzats en biomedicina o en aplicacions mediambientals. S’ha donat especial èmfasi a dissenyar una composició adequada i a estudiar la morfologia i les propietats estructurals per tal d’optimitzar tant les propietats mecàniques com les propietats magnètiques dels materials resultants. En primer lloc es va utilitzar la tècnica de fusió per arc i colada per succió amb motlle de coure per fabricar dos aliatges densos: un aliatge ferromagnètic amb composició en pes Fe-10Mn6Si1Pd i un aliatge paramagnètic amb memòria de forma amb composició en pes Fe-30Mn6Si1Pd. L’evolució de la microestructura, les propietats mecàniques i magnètiques, així com també la degradació, la citotoxicitat i la proliferació de cèl·lules en solució Hanks es van estudiar de forma sistemática en funció del temps d’immersió. Per tal de millorar la biocompatibilitat de l’aliatge Fe-10Mn6Si1Pd, aquest aliatge es va recobrir amb fosfat de calci (brushita o hidroxilapatita) mitjançant la tècnica d’electrodeposició per corrent polsant. A conseqüència de la morfologia porosa d’aquests recobriments (per exemple: en forma d’agulles, cilindres o plaques), el mòdul de Young i la duresa mesurades foren inferiors als valors obtinguts en recobriments anàlegs no porosos. Seguidament, amb l’objectiu d’incrementar la velocitat de degradació i reduir el mòdul de Young d’aquests aliatges compactes, es van fabricar aliatges porosos de Fe-30Mn6Si1Pd mitjançant un procés de premsa i sinterització de Fe, Si, Mn i Pd en pols prèviament mòlta i barrejada amb un 10, un 20 o un 40% en pes de NaCl en un molí de boles. Cal destacar, que després de submergir els aliatges porosos durant un període llarg de temps, el mòdul de Young reduït que es va mesurar en tots ells va ser d’uns 20 GPa (essent aquest valor similar al mòdul de Young de l’os humà, entre 3-27 GPa). Aquest fet afavoriria una bona compatibilitat biomecànica entre l’implant i el teixit ossi veí. Per altra banda, es van fabricar escumes de Fe i Fe-Mn de cèl·la oberta utilitzant matrius de poliuretà poroses pel mètode de rèplica. Es va observar que la resposta magnètica d’aquestes escumes, des de pràcticament no magnètica a ferrimagnètica, es podia controlar ajustant el contingut de Mn i el flux de N2. També, en el marc de propietats magnètiques, es va utilitzar la tècnica d’irradiació amb làser polsat de femtosegon per crear patrons magnètics periòdics a la superfície d'un aliatge amorf no ferromagnètic basat en Fe. Finalment, es va preparar un aliatge nanoporós ric en Fe per dissolució selectiva de cintes de Fe43.5Cu56.5 fabricades per tornejat en estat de fusió. Es va observar que els materials nanoporosos eren un excel·lent catalitzador heterogeni de la reacció de Fenton per la degradació del taronja de metil en solució aquosa.
This Thesis dissertation covers different synthetic approaches to obtain Fe-based alloys to be used for biomedical and environmental applications. Special emphasis has been placed to design a proper composition and to study the morphology and structural properties to tailor both the mechanical and magnetic properties of the resulting materials. Firstly, ferromagnetic Fe-10Mn6Si1Pd (wt.%) and shape memory, paramagnetic Fe-30Mn6Si1Pd (wt.%) compact alloys were prepared by arc-melting followed by copper mold suction casting. The evolution of microstructure, mechanical and magnetic properties, as well as the assessment of degradation, cytotoxicity and cell proliferation in Hank’s solution as a function of the immersion time were systermatically studied. With the aim to improve the biocompatibility of the Fe-10Mn6Si1Pd alloy, calcium phosphate coatings (CaP) (i.e., brushite and hydroxyapatite) were electrodeposited on the alloy by pulsed current electrodeposition. Due to porous structures resulting from needle-, rod- or plate-like morphologies, the measured Young’s modulus and hardness of these coatings were lower than those of fully-dense CaP layers with analogous compositions. Then, to increase the degradation rate and to reduce the Young’s modulus of the fully bulk alloys, porous Fe-30Mn6Si1Pd (wt.%) alloys were prepared by a simple press and sinter process from ball-milled Fe, Mn, Si and Pd powders blended with 10 wt.%, 20 wt.% and 40 wt.% NaCl. Remarkably, the reduced Young’s modulus of all the porous alloys reached values close to 20 GPa after long-term immersion, a value which is close to the Young’s modulus of human bones (3–27 GPa), hence favoring good biomechanical compatibility between an eventual implant and the neighboring bone tissue. Meanwhile, open cell Fe and Fe-Mn oxides foams were prepared by the replication method using porous polyurethane templates. The magnetic response of the foams, from virtually non-magnetic to ferrimagnetic, could be tailored by controllably adjusting the Mn content as well as the N2 flow rate. Still dealing with magnetic properties, femtosecond pulsed laser irradiation was used to create periodic magnetic patterns at the surface of a non-ferromagnetic amorphous Fe-based alloy. Finally, a nanoporous Fe-rich alloy was prepared by selective dissolution of melt-spun Fe43.5Cu56.5 ribbons. The nanoporous ribbons were found to be an excellent heterogeneous Fenton catalyst towards the degradation of methyl orange in aqueous solution.

A new mesoporous MOF, Zn4O(bpdc)(btctb)4/3 (DUT-32), containing linear ditopic (bpdc2−; 4,4′-biphenylenedicarboxylic acid) and tritopic (btctb3−; 4,4′,4′′-[benzene-1,3,5-triyltris(carbonylimino)]tris-benzoate) linkers, was synthesised. The highly porous solid has a total pore volume of 3.16 cm3 g−1 and a specific BET surface area of 6411 m2 g−1, adding this compound to the top ten porous materials with the highest BET surface area.

Les matériaux cellulaires sont des échantillons à très forte porosité qui peuvent être décrits à deux échelles : la mésostructure et la microstructure. Le lien entre l'architecture des matériaux et les propriétés mécaniques a été largement étudié dans la littérature. Les caractéristiques microstructurales peuvent avoir une influence importante sur les propriétés macroscopiques. Le but de ce travail est de relier les caractéristiques architecturales et microstructurales des matériaux cellulaires à leurs propriétés mécaniques grâce notamment à la tomographie aux rayons X. Une nouvelle approche combinant l'imagerie 3D à plusieurs résolutions, le traitement d'images et la modélisation éléments finis a permis de prendre en compte la microstructure de la phase solide. Quatre matériaux cellulaires modèles ont ainsi été étudiés : des mousses d'aluminium, des structures cellulaires périodiques en alliage de cobalt-chrome, des échantillons de β-TCP et des composites hydroxyapatite/β-TCP. Les matériaux métalliques ont été fournis par des collègues d'autres laboratoires, tandis que les matériaux céramiques ont été fabriqués dans le cadre de cette étude. Pour chaque type de matériaux (métaux et céramiques), une structure régulière et une stochastique ont été comparées. Pour utiliser la méthode multi-échelle développée dans ce travail, les échantillons ont d'abord été scannés grâce à la tomographie locale dans laquelle l'échantillon est placé près de la source de rayons X. La tomographie locale permet de scanner la petite partie irradiée de l'échantillon et d'obtenir une image agrandie par rapport aux images à plus basse résolution. Ces images permettent d'observer certains détails de la phase solide non visibles à plus basse résolution. Différentes étapes de traitement d'images ont ensuite été mises en œuvre pour obtenir une image à basse résolution incluant les informations provenant des images à haute résolution. Ceci a été réalisé grâce à une série d'opération de seuillage et sous-résolution des images à haute résolution. Le résultat de ces différentes étapes de traitement d'images donne une image de l'échantillon initial à basse résolution mais qui inclut l'information supplémentaire décelée à haute résolution. Ensuite, des essais mécaniques in situ ont été réalisés dans le tomographe pour suivre à basse résolution l'évolution des échantillons pendant la déformation. Les images initiales citées plus haut ont été utilisées pour produire des maillages éléments finis. Des programmes Java ont été adaptés pour créer des fichiers d'entrée pour les modèles éléments finis à partir des images initiales et des maillages. Les images initiales contenant les informations à propos de la phase solide, les images des essais mécaniques et les modèles éléments finis ont permis d'expliquer le comportement mécanique des échantillons en reliant les sites d'endommagement expérimentaux et les lieux de concentrations de contraintes calculés
Cellular materials are highly porous systems for which two scales are mainly important: the mesostructure and the microstructure. The mesostructure corresponds to the architecture of the materials: distribution of solid phase “walls” and macroporosity and can be characterized by X-ray tomographic low resolution images. The link between the architecture of the materials and the mechanical properties has been frequently studied. The microstructure refers to the characteristics of the solid phase. Its microstructural features (presence of a secondary phase or of defects due to the sintering) can have a strong influence on the macroscopic properties. The aim of this work is to link the morphological and microstructural features of metallic and ceramic based cellular materials and their mechanical properties thanks to X-ray tomography and finite element modelling. A new method combining X-ray tomography at different resolutions, image processing and creation of finite element modelling enabled to take into account some microstuctural features of the cellular samples. Four different cellular materials were studied as model materials: aluminium foam fabricated by a liquid state process, cobalt periodic structures made by additive manufacturing, β-TCP porous samples fabricated by conventional sacrificial template processing route and hydroxyapatite/β-TCP composites made by additive manufacturing (robocasting). The metal based materials were provided by colleagues while the ceramic based porous materials were fabricated in the frame of the current study. For each type (metals or ceramics), a stochastic and a regular structure have been compared. For implementing the multiscale method developed in this work, the samples were firstly scanned in a so called “local” tomography mode, in which the specimen is placed close to the X-ray source. This allowed to reconstruct only the small irradiated part of the sample and to obtain a magnified image of a subregion. These images enable to observe some details which are not visible in lower resolution. Different image processing steps were performed to generate low resolution images including microstructural features imaged at high resolution. This was done by a series of thresholding and scaling of the high resolution images. The result of these processing steps was an image of the initial sample. Then, in situ mechanical tests were performed in the tomograph to follow the deformation of the sample at low resolution. The above mentioned initial images were used to produce finite element meshes. Special Java programs were adapted to create finite element input files from initial images and meshes. The initial images containing information about the solid phase, the images from the mechanical tests and the finite element models were combined to explain the mechanical behaviour of the sample by linking the experimental damage locations in the sample and the simulated stress concentration sites

Die vorliegende Arbeit befasst sich mit der Inkorporation von Metall-/ Metalloxidnanopartikeln in organisch-anorganischen Hybridmaterialien, dargestellt durch Zwillingspolymerisation. Dabei wurden verschiedene Lösungsansätze bearbeitet. Zum einen wurden Metalcarboxylate oder Metallocene verwendet, zum anderen konnten durch Variation der anorganischen Komponente des Zwillingsmonomeres entsprechende Nanopartikel erzeugt werden. Um die Nanopartikel stabilisierenden Eigenschaften, der aus Zwillingspolymeren zugänglichen porösen Kohlenstoffmatrix zu erhöhen sollten mittels Zwillingspolymerisation N-Donoren eingeführt werden Neben der Inkorporation von Nanopartikeln wurden auch Silber und Goldnanopartikel in einer porösen Kohlenstoffmatrix verkapselt. Dabei wurde gezeigt, dass der Verwendete Templatdurchmesser einen entscheidenden Einfluss auf die späteren Hohlkugeln hat. Es konnte ebenso mit Hilfe von einfachen Benchmarkreaktionen die Zugänglichkeit und katalytische Aktivität der eingekapselten Nanopartikel nachgewiesen werden. Es wird gezeigt, dass durch Verwendung von Triphenylphosphan-stabilisierten Silber(I)-carboxylaten eine Funktionalisierung von Zwillingspolymeren möglich ist. Außerdem sind aus dem so modifizierten Hybridmaterialien nach Karbonisierung sowie dem Herauslösen der anorganischen SiO2-Komponete entsprechende mikroporöse, silberhaltige Kohlenstoffmaterialien zugänglich, während durch oxidativen Abbau der organischen Polymermatrix mesoporöse mit Ag-Nanopartikeln infiltrierte SiO2-Materialien dargestellt werden können. Es werden spezifische Oberflächen von 1034 m2/g (Kohlenstoff) und 666 m2/g (SiO2) erhalten. Das Wachstum der Silbernanopartikel konnte mittels Temperatur abhängiger Röntgenpulverdiffraktometrie beobachtet werden, und es wurde gezeigt, dass ein Wachstum erst während des Karbonisationsprozesses einsetzt. Mittels der HAADF-STEM-Technik wurden die gebildeten Nanopartikel im porösen Kohlenstoff bzw. SiO2 nachgewiesen, dabei liegen die Nanopartikel-durchmesser unterhalb von 5nm. Darüber hinaus konnte eine Vielzahl von neuen Zwillingsmonomeren dargestellt und charakterisiert werden. Darunter finden sich Zirkonium- und Hafnium-haltige Verbindungen, die analog der bekannten Si-Zwillingsmonomere ein ähnliches Polymerisationsverhalten zeigen und aus den resultierenden Hybridmaterialien poröse Oxide mit spezifischen Oberflächen unter 100 m2/g erhalten wurden. Eine Ausnahme bildet hierbei die SBS-Analoge Hafniumverbindung zur Phasenseparation während der Zwillingspolymerisation neigt, ebenso konnte für diese Verbindung kein vollständiger Umsatz erzielt werden. Durch Copolymerisation dieser neuen Zr- und Hf-haltigen Monomeren mit 2,2‘-Spirobi[4H-1,2,2-benzodioxasilin] wurden ZrO2- und HfO2-reiche SiO2-Mischoxide dargestellt. Dabei wurde das thermische Verhalten dieser Mischoxide mittels DSC weiter untersucht und es zeigte sich das ab 1000°C die ZrO2 sowie HfO2-Phasen beginnen zu Kristallisieren. Die so gebildeten hochkristallinen Nanopartikel konnten mittels TEM beobachtet werden. Ein weiteres erhitzen auf über 1200 °C führte dann noch zur Kristallisation der SiO2-Matrix. Ein weiteres Beispiel zur Synthese von oxidische Nanopartikeln mittels Zwillingspolymerisation wurde am ersten Metallocenhaltigen Zwillingsmonomer gezeigt. Dieses war aus der Reaktion von SiCl4 und Ferrocenylmethanol zugänglich. Neben der standardmäßigen Charakterisierung wurde auch die elektrochemischen Eigenschaften hin untersucht und dabei zeigte anders als es zu erwarten war eine Redox-Separation zwischen den einzelnen Ferrocengruppen. Weiterführende spektroelektrochemischen Experimente zeigten, dass diese Aufspaltung durch elektrostatische Abstoßung hervorgerufen wird. Das Zwillingspolymerisationsverhalten wurde zunächst mittels DSC untersucht und dabei konnte bei 210 °C eine exotherme Reaktion beobachtet werden, die mittels TG-MS als Kondensationsreaktion identifiziert wurde. Aufgrund dieser Ergebnisse konnte das Ferrocen-haltige Zwillingsmonomer thermisch polymerisiert werden. HAADF-STEM Abbildungen zeigten den typischen Aufbau eines Zwillingspolymeres, jedoch ist die Anzahl der zu beobachtenden Siliziumdioxidnanocluster geringer als bei bekannten Si-basierten Monomeren. Durch Copolymerisation mit 2,2‘-Spirobi[4H-1,2,2-benzodioxasilin] konnte dieser Nachteil ausgeglichen werden und nach karbonisierung und herauslösen der SiO2-Komponente bzw. Oxidation wird poröser Kohlenstoff (858 m2/g) bzw. Siliziumdioxid (555 m2/g) erhalten. Die Natur der eingebettet Eisenhaltigen Nanopartikel konnte mithilfe von Mössbauerspektroskopie untersucht werden. Dabei wurde im Kohlenstoffmaterial eine Mischung aus Fe2O3 und Fe3C gefunden während im SiO2 aufgrund der oxidierenden Bedingungen, während der Darstellung, von Fe2O3-Nanopartikeln ausgegangen wird. Die durchgeführten Mössbauerexperimente lieferten auch Indizien dafür, dass die gebildeten Nanopartikel sehr klein sind, dies wurde auch mittels HAADF-STEM bestätigt, jedoch kann kein genauer Zahlenwert fehlerfrei angegeben werden. Die geringe Größe spiegelt sich auch im magnetischen Verhalten der porösen Materialien wieder so verhält sich das SiO2 Material superparamagnetisch während der Kohlenstoff paramagnetisch ist. Abschließend konnten Pyrrol-basierte Siliziumalkoxide durch die Reaktion von SiCl4 und den entsprechenden Alkoholen dargestellt werden. Das Zwillingspolymerisation verhalten wurde mittels DSC charakterisiert. Dabei konnten wie schon zuvor beschrieben exotherme Reaktionen detektiert werden und diese liegen deutlich unter den Initiierungstemperaturen der bekannten Zwillingsmonomere (140 °C für N-Methylpyrrol und 93 °C für Pyrrol). Mittels TG-MS konnten auch hier Kondensationsreaktionen identifiziert werden. Daraufhin wurde die Hybridmaterialien aus den thermisch induzierten Polymerisationsversuchen beider Verbindungen untersucht. Es zeigte sich, dass das N-Methyl substituiertes Monomer sich nur in schlechten Ausbeuten polymerisieren lässt während das Pyrrolderivat ausgezeichnete Ausbeuten liefert. Auch die spezifischen Oberflächen sind mit bis zu 633 m2/g beträchtlich höher als mit vergleichbaren und bekannten Zwillingsmonomeren erzielt werden können. Auch zeigen sich beim einfachen Pyrrolbasierten Monomer Unterschiede zwischen thermischer und säure initiierter Zwillingspolymerisation. Während im ersten Fall hauptsächlich das 2-5-Substituierte Polymer erhalten wird kommt es bei säure Initiierung auch zur Bildung einer N-Alkyliertenspezies. Aus den Dargestellten Hybridmaterialien konnten poröse Kohlenstoffe mit Stickstoffgehalten zwischen 5.0-9.1 % erhalten werden. Auch hier zeigte sich das die Kohlenstoffe abgeleitet von dem N-methylierten Pyrrol einen höheren Stickstoffgehalt aufweisen als die aus der unmethylierte Spezies.

Ce travail concerne l’étude acoustique théorique et expérimentale des matériaux poreux à squelette métallique, macroscopiquement homogènes et inhomogènes ainsi que l’étude de leurs propriétés mécaniques de comportement au choc pour comparaison. Le modèle acoustique de Johnson -Champoux - Allard s’est montré adapté pour la modélisation acoustique. Ce modèle associé à une approche proposée récemment et utilisant le concept de matrices de transfert en parallèle a permis, dans une nouvelle approche basée sur les “mélanges de matériaux”, d’étudier les matériaux poreux macroscopiquement inhomogènes. Par ailleurs, une étude paramétrique du coefficient d’absorption en fonction de la porosité et de la fréquence a été proposée. Les maxima d’absorption ainsi que l’enveloppe des courbes d’absorption en fonction de la porosité ont été étudiés. En premier lieu, un matériau théorique à propriétés indépendantes a été étudié. Les matériaux réels à propriétés interdépendantes ont ensuite été abordés à l’aide d’un modèle reliant leurs propriétés à la porosité. Enfin, une comparaison entre les propriétés acoustiques et les propriétés mécaniques de comportement à l’impact a été initiée en vue de déterminer un critère objectif permettant de proposer un compromis entre les deux domaines
This work is concerned with the theoretical and experimental study of the acoustical properties of macroscopically homogenous and inhomogeneous porous media as well as their mechanical response to impacts. The model of Johnson - Champoux - Allard appeared adapted for the acoustical modeling. This model, associated with a recently developed approach involving the concept of parallel transfer matrices has lead to a new approach of macroscopically inhomogeneous porous materials based on “mixtures of materials”. Furthermore, a parametric study of the absorption coefficient as a function of porosity and frequency has been proposed. The maximums of absorption as well as the envelop of the absorption curves have been studied as functions of porosity. First, a theoretical material with independent parameters has been studied. Real materials with nonindependent parameters were then investigated with the help of a model relating their properties to the porosity. Finally, a comparison between the acoustical and mechanical properties has been initiated in view of determining an objective criterion that will allow to propose a trade off between the two fields

Many structural acoustic and vibration designs rely extensively on materials that are light-weight, stiff, and highly damped. Advanced materials such as metallic foams can be engineered to achieve these properties in order to control sound and vibration for a variety of aerospace, maritime, and ground transportation applications. In this work, the structural and acoustic properties of commercially available and digitally designed metallic foams are analyzed through numerical and experimental methods. Furthermore as a post-manufacturing process, metallic foams can be engineered in order to preferentially alter the microstructure and achieve material property enhancements. In this work, the following engineering methods are proposed and investigated: plastic deformation and material saturation. When a metallic foam is plastically deformed, the foam's porosity and pore shape are dramatically altered. This transformation in microstructure can lead directly to changes in bulk properties. In this work, a method for triaxial hydrostatic compression of metallic foams is proposed and demonstrated experimentally. The structural properties of transformed foams are tested using a load cell with digital image correlation. Transformed foams exhibit higher compliance, higher toughness, and a reduced Poisson ratio. Measurement and analysis of acoustic properties indicate that the transformed foams can absorb significantly more sound than the conventional samples of equal thickness in the test range of 0.25 - 4.50 kHz. Due to their open-cell microstructure, metallic foams can be filled with saturating materials. In this work, metallic foams saturated with viscous liquids are investigated for reducing vibration transmissibility in a structure. For the best performing saturated foam subject to a transient excitation, an order of magnitude increase in damping ratio is measured. Additionally, a composite foam (consisting of metallic foam saturated with polyurethane foam) is fabricated to enhance acoustic properties. For the best performing composite foam at normal incidence, the sound absorption coefficient is improved by a factor of 6 near 0.60 kHz and by a factor of 2 up to 4.5 kHz. Lastly, two methods for estimating acoustic absorption in metallic foams are presented which utilize finite element analysis and boundary layer theory. The proposed methods are discussed for commercially available foams as well as for representative digital designs. Limitations and assumptions of the methods pertaining to size scales and boundary layer features are addressed.

Selective laser sintering (SLS) is a commercial, powder-based manufacturing process that produces parts with complicated shape and geometry based on a computer solid model. One of the major drawbacks of SLSed inter-metallic and ceramic parts is their high porosity because of the use of binder system. High porosity results in poor mechanical, electrical and thermal properties of the preform and hence renders it unsuitable for various applications. This thesis attempts to infiltrate SLSed preforms by carrying out electrochemical deposition of metal ions inside the interconnected pore network. One of the major benefits of carrying out this novel process is low processing temperature as opposed to existing methods such as melt infiltration. Low temperature reduces both energy consumption and associated carbon-footprint and also minimizes undesirable structural changes. Both conductive and non-conductive preforms may be electrochemically infiltrated, and MMCs produced by this method have potential for use in structural applications.
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Scuola di Dottorato "Pitagora" in Scienze Ingegneristiche, Dottorato di Ricerca in Ingegneria Chimica e dei Materiali, Ciclo XXVIII, a.a. 2015-2016
Gas! membrane! separation! is! an! attractive! technology! that! is! often! superior! to! other! more! conventional! procedures! for! separation! of! gaseous! species! in! terms! of! energy! consumption! and! environmental! impact.! A! key! factor! for! membrane! separations! is! the! membrane! itself! with! its! properties,! which! determine! the! overall! performance! of! the! process.! One! essential! membrane! characteristic!is!the!transport!selectivity.!High!separation!factors!are!especially!difficult!to!achieve! for! mixtures! of! light! gases! having! comparable! kinetic! diameters.! Moreover,! high! permeability,! correspondingly! high! solubility! and! diffusivity! in! dense!membranes,! are! crucial! aspects! for! the! performance! and! further! practical! application! of!membrane! devices.! In! this! frame,! the!material! used!as!a!selective!layer!is!determinant.!Therefore,!scientists!devote!immense!efforts!to!the!search! of! optimal! gasBsorbent! combinations,! including! thorough! study! of! existing! structures! and! elaboration!of!new!ones!with!sieving!properties.!The!large!effort!and!time!required!for!preparation! and!experimental!testing!of!materials!impede!the!advancement!of!new!membranes.! In!this!study,!we!propose!procedures!based!on!computational!calculations!and!theoretical!models! that! can!be!used! to!predict! the!behaviour!of! some!of! the!membrane!materials!of! interest! for! gas! separation! applications.! In! particular,! we! focus! on:! i)! bodyBcentred! cubic! VNiTi! alloys! as! novel! materials!for!H2Bselective!dense!membranes!and!ii)!crystalline!porous!materials!that!are!attractive! media!for!separation!of!light!gases!such!as!H2,!O2,!CO,!CO2,!CH4!and!N2.!These!two!types!of!materials! are! treated! using! different! methodologies,! adapted! to! the! needs! of! our! research! objectives! associated!to!each!material.! In!the!case!of!dense!metal!membranes,!the!long!standingBcontroversy!over!occupancy!of!interstitial! hydrogen! in! VBbased! alloys! is! addressed.! The! VBNiBTi! system! is! of! particular! interest! here,! exhibiting!high!H2!permeability!and!improved!mechanical!properties!relative!to!pure!V.!This!work! intends!to!gain!understanding!of!hydrogenBmetal!interactions!as!function!of!alloy!composition!and! thereby!to!optimize!these!new!materials!and!advance!their!development!as!novel!membranes!for! H2! separation.!We! use! a! firstBprinciples! approach! that! gives! insights! into! the! sites! preference! of! hydrogen! and! assesses! the! role! of! Ti! and! Ni! substitutional! solutes! for! the! hydrogen! absorption! affinity.! The!method! based! on!Density! Functional! Theory! requires! no! experimental! input! except! crystal!structure!information.!Furthermore,!it!uses!no!empirical!or!fitting!parameters!in!contrast!to! other!computational!techniques.!Hence!this!approach!provides!an!alternative!way!to!explore!new! metal!alloys!for!H2!separation!membranes.!The!applied!methodology!can!be!used!further!in!highB throughput!calculations!to!screen!various! alloy!compositions.!The!heretoBreported!results!will!be! used!as!guidance!for!tailoring!the!formulation!of!VNiTi!solid!solutions!and!preparation!of!low!cost†! dense!alloy!membranes!in!the!frame!of!other!projects!(e.g.!European!DEMCAMER!project).! Further,! we! explore! how! singleBcomponent! inputs! can! be! used! to! forecast! the! ideal! selectivity! towards! light! gases! of! crystalline! porous!materials,! used! for!membrane! preparation.! Theoretical! models! for! describing! gas! separation! properties! of! zeotype! materials! as! function! of! structural! characteristics!and!operation!conditions!are!proposed.!The!model!parameters!can!be!obtained!as! experimentally!as!well!as!computationally.!To!analyse!the!extent!of!validity!and!limitations!of!the! models,!ideal!selectivities!of!few!crystalline!porous!materials!are!evaluated,!including!widely!used! zeolites!(NaA,!CaA)!and!a!metal!organic!framework!structure!(ZIFB8).!The!results!verified!that!the! theoretical!expressions!could!be!used!for!screening!series!of!zeotype!materials!when!reliable!single! gas!adsorption!data!are!available.!However,!since!the!models!don’t!take!into!account!all!parameters! (namely! related! to! the! membrane! design)! and! mechanisms! involved! in! gas! transport! through! porous!membranes,!their!predictions!should!be!considered!as!values!referring!to!an!ideal!case.!
Università della Calabria