Made available in DSpace on 2014-12-17T15:42:17Z (GMT). No. of bitstreams: 1 PauloHAH_DISSERT.pdf: 4112425 bytes, checksum: ab842493afe72a340f238b1cac2bc18f (MD5) Previous issue date: 2014-01-24 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The Layered Double Hydroxides has become extremely promising materials due to its range of applications, easily obtained in the laboratory and reusability after calcination, so the knowledge regarding their properties is of utmost importance. In this study were synthesized layered double hydroxides of two systems, Mg-Al and Zn-Al, and such materials were analyzed with X-ray diffraction and, from these data, we determined the volume density, planar atomic density, size crystallite, lattice parameters, interplanar spacing and interlayer space available. Such materials were also subjected to thermogravimetric analysis reasons for heating 5, 10, 20 and 25 ? C / min to determine kinetic parameters for the formation of metaphases HTD and HTB based on theoretical models Ozawa, Flynn-Wall Starink and Model Free Kinetics. In addition, the layered double hydroxides synthesized in this working ratios were calcined heating 2.5 ? C / min and 20 ? C / min, and tested for adsorption of nitrate anion in aqueous solution batch system at time intervals 5 min, 15 min, 30 min, 1h, 2h and 4h. Such calcined materials were also subjected to exposure to the atmosphere and at intervals of 1 week, 2 weeks and 1 month were analyzed by infrared spectroscopy to study the kinetics of regeneration determining structural called "memory effect" / Os Hidr?xidos Duplos Lamelares tem se tornado materiais extremamente promissores devido a sua gama de aplica??es, f?cil obten??o em laborat?rio e a possibilidade de reutiliza??o ap?s calcina??o, portanto o conhecimento referente ? suas propriedades ? de extrema relev?ncia. Neste estudo foram sintetizados hidr?xidos duplos lamelares de dois sistemas, Mg-Al e Zn-Al, e tais materiais foram submetidos a an?lise com difra??o de raios X e, a partir de tais dados, foram determinados a densidade volum?trica, densidade at?mica planar, tamanho do cristalito, par?metros de rede cristalina, dist?ncia interplanar e espa?o interlamelar dispon?vel. Tais materiais tamb?m foram submetidos ? an?lise termogravim?trica em raz?es de aquecimento de 5, 10, 20 e 25 ?C/min para determina??o de par?metros cin?ticos durante a forma??o das metafases HTD e HTB com base nos modelos te?ricos de Ozawa, Flynn-Wall, Starink e Model Free Kinetics. Al?m disso, os hidr?xidos duplos lamelares sintetizados neste trabalhado foram calcinados em raz?es de aquecimento de 2,5 ?C/min e 20 ?C/min e submetidos a ensaios de adsor??o de ?nion nitrato em solu??o aquosa em sistema de batelada em intervalos de tempo de 5 min, 15 min, 30 min, 1h, 2h e 4h. Tais materiais calcinados tamb?m foram submetidos ? exposi??o com a atmosfera e em intervalos de tempo de 1 semana e 2 semanas foram analisados atrav?s de difra??o de raios X para estudo determina??o da cin?tica de regenera??o estrutural denominada efeito mem?ria

Thesis (Ph.D.); Submitted to Iowa State Univ., Ames, IA (US); 12 Dec 2003. / Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 2111" Bora Mavis. 12/12/2003. Report is also available in paper and microfiche from NTIS.

Cette thèse présente un travail sur l’obtention d’aérogels d’HDL par séchage en conditions CO2 supercritique et l’élaboration de nouveaux bionanocomposites formés par la coprécipitation d’hydroxydes doubles lamellaire (HDL) dans l'espace confiné des billes d'alginate. Grâce à la combinaison d’une synthèse par coprécipitation Flash et d’un séchage en conditions supercritiques au CO2, des aérogels d’HDL possédant des surfaces spécifiques élevées sont élaborés. Parallèlement, l’alginate est utilisé comme une matrice de confinement pour la précipitation inorganique d’HDL. D’une part, les billes d'alginate sont synthétisées par complexation des ions Ca2+ et la coprécipitation des phases HDL s’effectue en réalisant des imprégnations successives de réactifs. D’autre part, des billes d'alginate sont formées directement en présence des cations divalents (Mg2+, Ni2++, Co2+, ...) et des cations des métaux trivalents (Al3+), précurseurs des composés inorganiques. La coprécipitation des HDL se produit dans ce cas lors d'une étape d'imprégnation dans une solution d'hydroxyde de sodium. Tous les composés HDL, aérogels ou encore bionanocomposites sont caractérisés en détail par DRX, spectroscopie IR, MEB/MET, adsorption/désorption d’azote et ATG/DTG, pour obtenir un meilleur aperçu de la structure des particules, de leur taille et de leur morphologie. Des études menées sur l’adsorption de la trypsine pour les aérogels ou encore sur les performances d’électrodes modifiées HDL-alginate ont permis de montrer qu’il était possible d'améliorer les performances des HDL en augmenter leur porosité et en élaborant des bionanocomposites. / In this work, we investigated both the use of CO2 supercritical drying conditions and the use of biopolymer to modify the growth and aggregation of inorganic Layered Double Hydroxide (LDH) particles. Indeed, one possibility to enhance their performances is to increase the LDH porosity and to design them as nanostructured open structure. Thanks to the combinaison of fast coprecipitation and CO2 supercritical drying, highly porous LDH aerogels were obtained with enhanced textural properties. In parallel, the coprecipitation of Layered Double Hydroxides (LDH) in the confined space of alginate beads is reported. In our approach, Alginate acts as a template to support and confined the inorganic precipitation. In one hand, beads made of Alginate are synthesized by complexation of Ca2+ ions and LDH phases are coprecipitated using successive impregnations of reactants. In another hand, Alginate beads are formed directly in presence of the divalent (Mg2+, Ni2+, Co2+,…) and trivalent metal cations (Al3+), precursors of the inorganic compounds. LDH coprecipitation then occurs during a further impregnation step in a sodium hydroxide solution. All the LDH aerogels and LDH nanocomposites beads are deeply characterized using XRD, SEM/TEM, FTIR spectroscopic, adsorption/desorption of nitrogen and TGA/DTG to get better insight on particle structure, size and morphology Aerogels display enhanced adsorption behavior toward trypsine immobilization whereas a net improvement of the electrochemical response is noticed for the NiAl based bionanocomposites prepared by confined coprecipitation into Alginate.

Made available in DSpace on 2014-10-09T12:27:27Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:53Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:27:27Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:53Z (GMT). No. of bitstreams: 0 / O óxido de cério (CeO2), quando dopado com óxidos de terras raras, tem sua condutividade iônica aumentada, possibilitando seu uso como eletrólito de Células a Combustível de Óxido Sólido de Temperatura Intermediária (IT-SOFC), que são operadas entre 500 e 700°C. Os aditivos ou dopantes mais eficientes para o aumento da condutividade iônica são a samária (óxido de samário Sm2O3) e a gadolínia (óxido de gadolínio Gd2O3), com concentrações molares entre 10 e 20%. Neste contexto foram sintetizados, neste trabalho, pós de composição Ce0,8(SmGd)0,2O1,9 pelas rotas de síntese por coprecipitação de hidróxidos, carbonatos e oxalatos. O efeito do tratamento hidrotérmico foi avaliado para pós precipitados com hidróxido de amônio. Utilizou-se, como matériasprimas, concentrados de terras raras contendo 90% em massa de CeO2 e outro contendo 51% de Sm2O3 e 30% de Gd2O3, ambos provenientes do processamento da monazita. Estes concentrados foram utilizados devido ao menor custo em relação às matérias-primas puras adquiridas comercialmente e a semelhança química dos demais elementos de terras raras contidos. Inicialmente, foram definidas as condições das etapas de coprecipitação e a influência da temperatura de calcinação nas características dos pós e produtos sinterizados. Os resultados obtidos mostraram que os pós calcinados na faixa de temperatura entre 450 e 800ºC apresentam elevada área de superfície específica (90-150 m2.g-1) e estrutura cristalina cúbica tipo fluorita da céria, indicando a formação da solução sólida. Observou-se, por microscopia eletrônica de varredura, que a forma das partículas e dos aglomerados é função do tipo de agente precipitante. As análises dilatométricas indicaram maior taxa de retração em temperatura próxima a 1300-1350ºC. Entretanto, valores elevados de densificação (>95% DT) são obtidos em temperaturas superiores a 1400ºC. A síntese por coprecipitação de hidróxidos seguida pelo tratamento hidrotérmico demonstrou ser uma rota promissora para cristalização, em baixas temperaturas (200oC), de nanopós à base de céria, mantendo-se elevados os valores de área de superfície específica (cerca de 100 m2.g-1). Cerâmicas com densificação superior a 95%DT foram obtidas em menores temperaturas de sinterização (1400oC), quando comparadas às provenientes de pós cristalizados por calcinação. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Compostos lamelares do tipo da hidrotalcita ou hidróxidos duplos lamelares (HDL), são materiais que possuem notáveis propriedades estruturais, químicas, eletrônicas, iônicas, ópticas e magnéticas. Em função dessas propriedades, os HDL apresentam uma diversidade de aplicações tais como adsorventes e catalisadores. Este trabalho tem por objetivo utilizar polímeros e macromoléculas na preparação e caracterização de HDL, visando melhorar as propriedades texturais dos HDL de MgAl-CO3 preparados em meio contendo polímeros orgânicos ou a intercalação direta de dendrímeros tipo PAMAM de gerações -0,5 e +0,5 em HDL do sistema Zn/Al. Os HDL de MgAl-CO3 foram preparados pela adaptação do método de coprecipitação a pH decrescente, com a presença de polímeros solubilizados no meio, como molde. Os materiais foram caracterizados por difração de Raios X, análise termogravimétrica, espectroscopia no infravermelho e medidas de área superficial por BET. Baseando-se nos resultados obtidos, pode-se concluir que propriedades texturais dos HDL preparados são modificadas, quando na presença de alguns polímeros. Na maioria dos casos, os valores calculados de área superficial específica foram mais elevados, em comparação com aquele obtido para o HDL preparado em meio reacional sem polímero. Isto pode ser explicado pela diminuição do tamanho de partículas e aumento no diâmetro médio de poros dos materiais preparados, provocada pela presença de polímeros no meio reacional. Os HDL intercalados com dendrímeros PAMAM G-0,5 e PAMAM G+0,5 foram preparados por duas rotas diferentes: coprecipitação a pH constante e troca iônica em fase dupla. Os materiais obtidos foram caracterizados por meio de difração de Raios X, análise de termogravimétrica associada à espectrometria de massas e espectroscopia no infravermelho. Utilizando os dois procedimentos de preparação, a intercalação de PAMAM G-0,5 deu origem a HDL com os mesmos espaçamentos basais, concordando com a intercalação dos ânions do dendrímero em um arranjo perpendicular à lamela do HDL, enquanto que para a intercalação do PAMAM G+0,5, espaçamentos basais muito menores do que o tamanho da molécula foram obtidos. A diferença entre a distância interlamelar observada e a esperada pode ser explicada por um arranjo peculiar das moléculas desse dendrímero em uma forma elipsoidal, devido às interações intramoleculares. Espectros no infravermelho confirmam a presença dos dendrímeros nos materiais Zn2Al-PAMAM G-0,5 e Zn2Al-PAMAM G+0,5. Finalmente, a presença destes dendrímeros foi confirmada por análise térmica associada com espectrometria de massas. Os estudos de Raios X com variação de temperatura in situ e as análises termogravimétricas revelaram que o material obtido pela intercalação do PAMAM G+0,5 é termicamente menos estável do que aquele intercalado com PAMAM G-0,5, concordando com a diferença de estabilidade entre os dendrímeros livres. / Hydrotalcite-like lamellar compounds or layered double hydroxides (LDH) are materials that present notable structural, chemical, electronic, ionic, optical and magnetic properties. Depending on these properties, the LDH present a great variety of applications such as adsorbents and catalysts. The aim of this work is to prepare and to characterize MgAl-CO3-LDH prepared in aqueous media containing organic polymer to improve textural properties, and to prepare HDL by intercalation of dendrimer (PAMAM) of generations -0.5 and +0.5 in ZnAl-HDL. MgAl-CO3-HDL samples were prepared by an adaptation of the coprecipitation method at decreasing pH, with the presence of polymers in the aqueous media as template. The materials were characterized by powder X-ray diffraction, termogravimetric analysis, infrared spectroscopy and BET isotherms. Based on the obtained results, it can be concluded that the textural properties of the prepared LDH were modified. The calculated values of specific surface area were higher in most of the cases compared with those obtained by the LDH prepared without polymer due to a decrease of the particle size and an increase in the average pore diameter of the prepared materials due to the presence of polymers. HDL with intercalated (PAMAM) dendrimers G-0.5 and G+0.5 were prepared by two different methods: coprecipitation at constant pH, and ionic exchange in double phase. The obtained materials were characterized by powder X-ray diffraction, thermal gravimetric analysis associated with mass spectrometry, and infrared spectroscopy. X-ray powder diffraction patterns exhibit the characteristic profiles of the lamellar materials with basal spacing depending on the nature of the dendrimer. For both preparation methods, the intercalation of PAMAM G-0.5 gives rise to LDH with basal spacing in agreement with the dendrimer molecules perpendicular to the layer of the host structure, while for PAMAM G+0.5 a basal spacing smaller than the molecule size was obtained. The difference between the obtained and the expected value is explained by an accommodation of the dendrimer molecule in an ellipsoidal shape, due to the intra-molecular interactions. Infrared spectra confirm the presence of dendrimers in the Zn2Al-PAMAM G-0.5 and Zn2Al-PAMAM G+0.5 materials. Finally, thermal analyses associated with mass spectrometry confirm the presence of these dendrimers. Powder X-ray diffraction with in situ temperature variation reveals that the material obtained by the PAMAM G+0.5 intercalation is thermally less stable than that prepared by PAMAM G-0.5 intercalation, in agreement with the difference in the thermal stability of the free dendrimers.

O presente trabalho trata da preparação e caracterização de três tipos de materiais, todos envolvendo hidróxidos duplos lamelares (HDLs) contendo íons cobalto e alumínio na composição das lamelas. Primeiramente, avaliou-se a influência de parâmetros de síntese na obtenção de HDLs intercalados com os ânions inorgânicos carbonato, cloreto e nitrato. Segundo dados de espectroscopia eletrônica UV-VIS, ressonância paramagnética eletrônica (EPR) e espectroscopia de fotoelétrons excitados por raios X (XPS), ocorre a oxidação parcial do Co2+ em Co3+ na lamela de HDL e, no caso do material contendo íon carbonato, observa-se a presença de radical carbonato, demonstrando a reatividade redox das matrizes com íons cobalto. A segunda parte do trabalho consistiu na intercalação do ânion derivado do ácido 2- aminotereftálico (ATA) em HDL. A presença do cátion cobalto nas lamelas e do grupo amino na espécie orgânica promoveu alterações significativas nas propriedades eletrônicas e térmicas do material (abreviado Co2Al-ATA). Assim como na primeira parte desta tese, as transformações ocorridas com o íon ATA devem incluir a formação inicial de um radical orgânico (de modo similar à polimerização da anilina), para o qual o agente oxidante é o íon Co3+ lamelar. Os dados de espectroscopia vibracional (no infravermelho e Raman) e de XPS mostram a presença de segmentos reduzidos (benzenóide) e oxidados (quinóides) na espécie intercalada. A solubilização do HDL em meio ácido permitiu isolar um material orgânico de cor preta que possui segmentos semiquinóides (radical orgânico) em sua estrutura, além dos reduzidos. A última etapa da presente tese consistiu em pirolisar o material Co2Al-ATA mencionado acima. Verificou-se que a alteração no procedimento de pirólise, como a temperatura, o desenho do forno, a forma do cadinho (cilíndrico ou barca), o tempo de resfriamento do sistema ou a atmosfera dinâmica ou estática, por exemplo, afetam as propriedades do produto final de decomposição. Nos compósitos obtidos, as fases inorgânicas provenientes da decomposição do HDL foram uma mistura de óxidos mistos de cobalto e alumínio (Co(CoxAl1-x)2O4), óxido de cobalto (CoO) e cobalto metálico. A fase de carbono apresentou perfil espectral de carbono grafítico nanocristalino e foi obtida em valores de temperatura de pirólise superiores a 800°C. Os compósitos contendo nanopartículas de cobalto metálico são ferromagnéticos. A reatividade redox dos HDLs de cobalto e as propriedades de seus produtos de decomposição apresentam potencial para aplicação em dispositivos eletroquímicos. / The present work reports the preparation and characterization of three types of materials, all involving layered double hydroxides (LDHs) containing cobalt and aluminum ions in the layer composition. First, the influence of synthetic parameters on the production of LDHs intercalated with the inorganic anions carbonate, chloride and nitrate was evaluated. According to UV-VIS electronic spectroscopy, electron paramagnetic resonance (EPR) and x-ray photoelectron spectroscopic (XPS) data, the partial oxidation of Co2+ to Co3+ occurs in the LDH layer and, in the case of the material containing carbonate ion, the presence of carbonate radical species demonstrates the redox reactivity of the matrices with cobalt ions. The second part of the work comprised the intercalation of the anion derived from 2- aminoterephthalic acid (ATA) in to LDH. The presence of the cobalt cation in the layer and the amino group in the organic species promoted significant changes in the electronic and thermal properties of the material (abbreviated Co2Al-ATA). As in the first part of this thesis, transformations occurring with the ATA ion should include the initial formation of an organic radical (similar to aniline polymerization), for which the oxidizing agent is the Co3+ ion in the layer. The vibrational (infrared and Raman) spectroscopy and XPS data show the presence of reduced (benzenoid) and oxidized (quinoids) segments in the intercalated species. The solubilization of HDL in acid medium allowed the isolation of a black organic material that has semiquinoid (organic radical) segments in its structure besides the reduced one. The last stage of the present thesis consisted of pyrolysis of the Co2Al-ATA material mentioned above. It was observed that the change in pyrolysis procedure, such as temperature, furnace design, crucible shape (bark or cylinder), system cooling time or dynamic or static atmosphere, for example, affects the properties of the final product of decomposition. In the obtained composites, the inorganic phases from the HDL decomposition were a mixture of mixed oxides of cobalt and aluminum (Co(CoxAl1-x)2O4), cobalt oxide (CoO) and metallic cobalt. The carbon phase showed nanocrystalline graphite carbon spectral profile and was obtained at pyrolysis temperature values above 800 °C. The composites containing metallic cobalt nanoparticles are ferromagnetic. The redox reactivity of HDLs containing cobalt and the properties of their decomposition products present potential for application in electrochemical devices

<p>Usled visoke fotokatalitičke efikasnosti u procesima preči&scaron;ćavanja voda i vazduha, titan(IV)-oksid (TiO₂) se u poslednje vreme sve vi&scaron;e ispituje u oblasti za&scaron;titi životne okoline. Međutim usled visokih zahteva koje fotokatalizatori u ovoj oblasti treba da zadovolje, kao &scaron;to su aktivnost, selektivnost, netoksičnost, ekonomičnost i stabilnost, potreba za razvojem fotokatalizatora sa povoljnijim karakteristikama se sve vi&scaron;e nameće kao prioritet za buduća istraživanja. Inovativni pristup ove doktorske disertacije je usmeren upravo ka razvoju novih kompleksnih sistema na bazi oksida titana i slojevitih hidroksida, osvrćući se na postavljenu polaznu hipotezu o mogućem sinergetskom efektu komponenata u dostizanju visoke fotokatalitičke efikasnosti, kao i u pobolj&scaron;anju njihovih op&scaron;tih katalitičkih performansi. ZnAl i NiAl slojeviti hidroksidi su izabrani kao nosači aktivne komponente (TiO₂). Modifikacija postojećih metoda sinteze je izvr&scaron;ena kako bi se pospe&scaron;ila interakcija aktivne komponente i nosača. Komparativna istraživanja novonastalih materijala pripremljenih primenom četiri nove metode sinteze pokazala su da se izborom metodologije sinteze i prirode interakcije između aktivne faze TiO₂ i aktivnog nosača mogu pobolj&scaron;ati fotokatalitičke performanse kompozitnih materijala u odnosu na referentne vrednosti dobijene za ZnAl slojevite hidrokside. Iako je udeo TiO₂ veoma mali u novonastalim kompleksnim sistemima, fotokatalitička efikasnost razgradnje model polutanta je zadovoljavajuća, usled pobolj&scaron;ane dostupnosti aktivnih centara i usled limitiranja aglomeracije TiO₂. Potvrđeno je da metoda i uslovi sinteze bitno utiču na strukturu, teksturu i povr&scaron;inske karakteristike formiranih kompozita, uz rezultujuće značajne razlike i u fotokatalitičkim svojstvima sintetisanih materijala. Komparativna ispitivanja fotokatalitičke efikasnosti uz primenu odabranih test reakcija (razgradnje metilenskog plavog, rodamina B i metil oranža) pokazala su da uzorci sintetisani metodom impregnacije u baznoj sredini pokazuju najbolje fotokatalitičke performanse u &scaron;irem spektru zračenja, &scaron;to je pripisano formiranju faza ZnO i ZnTiO₄ u ovim uslovima, detektovanih XRD, FTIR i XPS analizama. Takođe, mikrobiolo&scaron;ke analize na antimikrobno dejstvo su pokazale da, iako TiO₂ ne pokazuje inhibitoran efekat, uzorci sintetisani impregnacijom u baznoj sredini imaju i najizraženiji inhibitorni efekat na rast gram-pozitivnih i gram-negativnih bakterija, &scaron;to dodatno ukazuje na doprinos sinergetskog efekta slojevitih oksida i aktivne faze me&scaron;ovitih oksida u formiranju aktivnih centara visoke fotokatalitičke aktivnosti. Uzorci dobijeni primenom metoda koprecipitacije pokazuju nižu, ali zadovoljavajuću fotokatalitičku aktivnost, dok uzorci sintetisani metodom impregnacije u neutralnoj sredini pokazuju najnižu fotokatalitičku aktivnost i mali inhibitorni efekat.<br />Istraživanja u ovoj doktorskoj disertaciji dala su doprinos novim saznanjima o karakteristikama kompozitnih materijala tipa TiO₂/ZnAl slojeviti hidroksidi bitnim za obezbeđenje fotokatalitičke aktivnosti materijala ovog tipa u &scaron;irem spektru zračenja (UV/VIS), kao i ukupnih performansi koje omogućuju njihovu primenu u različitim ekolo&scaron;kim procesima (preči&scaron;ćavanje vode i vazduha od organskih, neorganskih i biolo&scaron;kih polutanata).</p> / <p>Recently, titanium-dioxide (TiO₂) has been extensively researched in the field of environmental protection due to its high photocatalytic efficiency in processes for water and air purification. Considering the high demands that are constantly set for photocatalysts in this field of research, such as activity, selectivity, stability, cost-effective and non-toxic, the need to develop photocatalysts with better characteristics is becoming increasingly evident as a priority for future research. The novel approach of this Ph.D. thesis is oriented towards the development of new complex systems on the basis of titanium-dioxide and layered double hydroxides, taking into account the hypothesis about their possible synergetic effect achieving high photocatalytic efficiency and obtaining better overall catalytic performances. ZnAl and NiAl layered double hydroxides have been chosen as the catalyst support of the active component (TiO₂). In order to initiate the interaction between the active component and support, current synthesis methods have been modified. The novel materials were synthesized using four new different synthesis methods. Comparative investigation showed that the synthesis method, as well as the nature of the interaction between the active phase and the support can improve the overall photocatalytic performances of the composite materials when compared to the referent values obtained from ZnAl layered double hydroxides. Although the TiO₂ amount is low in the novel complex systems, photocatalytic efficiency for the degradation of model pollutants is satisfactory due to improved accessibility to the active centres, as well as due to limitation of TiO₂ agglomeration. It was confirmed that the synthesis method and conditions considerably affect the structural, textural and surface characteristics of the formed composites, resulting in significant differences in photocatalytic characteristics of the synthesized materials. Comparative research of photocatalytic efficiency in the chosen test reactions (methylene blue, rhodamine B, and methyl orange degradation) showed that the samples synthesized by the wet impregnation method in alkaline solution exhibited the best photocatalytic performance in the wide range of radiation that attributed to the formation of ZnO phase and ZnTiO₄ detected by XRD, FTIR and XPS analysis. Also, the research on the antimicrobial activity showed that, although TiO₂ has no inhibitory effect, the samples synthesized by the wet impregnation method in alkaline solution have the highest inhibitory effect on the&nbsp;growth of gram-positive and gram-negative bacteria, confirming the contribution of the synergic effect to the formation of active centres with high photocatalytic activity. The samples obtained by the coprecipitation method had lower, but satisfactory photocatalytic activity, while samples synthesized by the wet impregnation method in water solution showed the lowest photocatalytic activity, as well as low inhibitory effect on the bacteria growth. The research in this Ph.D. thesis contributed to the knowledge on the characteristics of novel composite materials TiO₂/ZnAl layered hydroxides that are of essential importance concerning their photocatalytic activity in the wide range of radiation (UV / VIS), as well as their overall performance that enable their use in a variety of ecological processes, such purification of water and air pollution from organic, inorganic and biological pollutants.</p>

Hierarchical arrangement of biological composites such as nacre and bone containing high filler (ceramic) content results in high strength and toughness of the natural material. In this study we mimic the design of layered bone microstructure and fabricate an optimal multifunctional bio-nanocomposite having strength, toughness and corrosion resistance. Poly (butylene adipate-co-terephthalate) (PBAT), a biodegradable polymer was used as a substrate material with the reinforcement of LDH (Layered double hydroxide) as a nanofiller in different concentrations to achieve enhancement in mechanical properties as well as processing related thermostability. Corrosion resistance was increased by mimicking a layered structured which incorporated a tortuous diffusion path.

Le but de ce travail de thèse est d’étudier et de rationaliser, à l’aide de mécanismes réactionnels, le comportement sous irradiation de différents matériaux argileux. Les systèmes d’intérêt ont d’abord été le talc synthétique, qui est le prototype d’un matériau non gonflant. Sous irradiation par des électrons accélérés, la production de dihydrogène dans ce système, uniquement due aux groupes hydroxyle de surface, est du même ordre de grandeur que celle obtenue dans l’eau liquide. Ce rendement est divisé par 30 dans le cas du talc naturel de Luzenac, mettant ainsi en évidence l’importance des impuretés comme capteurs des précurseurs du dihydrogène. Des smectites synthétiques, qui sont des matériaux gonflants, ont ensuite été étudiées.Les résultats mettent en évidence la radiolyse de l’eau confinée dans l’espace interfoliaire, qui conduit à des rendements de production de H2 pouvant être deux à trois fois supérieurs à ceux mesurés dans l’eau. Ils sont similaires pour la saponite et la montmorillonite, montrant que la localisation de la charge foliaire ne joue qu’un rôle mineur. Enfin, l’étude des hydroxydes doubles lamellaires ou argiles anioniques, prouve que, dans ce cas, c’est la nature de l’anion dans l’espace interlamellaire qui pilote la réactivité. En parallèle à ces mesures, des expériences de spectroscopie paramagnétique de l’électron ont permis de proposer des mécanismes réactionnels. Enfin, tous les résultats obtenus sont d’intérêt dans le contexte du stockage des déchets radioactifs. / The aim of this PhD thesis is to study and understand, by proposing reaction mechanisms, the behavior under irradiation of various clay materials. The systems of interest were first synthetic talc, which is the prototype of a non-swelling material. Under irradiation by accelerated electrons, the production of dihydrogen in this system, due solely to surface hydroxyl groups, is of the same order of magnitude as the one obtained in liquid water. This yield is divided by 30 in the case of natural talc from Luzenac, thus highlighting the importance of the impurities as scavengers of the precursors of dihydrogen. Synthetic smectites, which are swelling materials, were then studied.The results evidence the radiolysis of water confined in the interlayer space, leading to H2 yields which may be two to three times higher than those measured in water. Moreover, they are similar for montmorillonite and saponite, evidencing that the charge location plays only a minor role. Finally, the study of double layered hydroxides or anionic clays shows that, in this case, the nature of the anion in the interlamellar space controls the reactivity. Parallel to these measurements, electron paramagnetic spectroscopy experiments have enabled proposing reaction mechanisms. Finally, all these results are of interest in the context of the disposal of radioactive waste.