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Thesis (Ph.D.)--Syracuse University, 2008. / "Publication number: AAT 3345017."

Three dimensional (3D) hybrid architectures are new types of materials that have a number of technological applications. However, the synthesis of such materials has been problematic to date. The objective of this study is to fabricate 3D hybrid architectures composed of sp2-carbon nanomaterials and inorganic nanostructures using a convenient microwave assisted technique. Sp2-Carbon nanomaterials such as carbon nanotubes (CNTs), graphene and its derivative graphene oxide (GO), have been explored by researchers as major components of hybrid materials due to their exceptional electrical, thermal, mechanical and biological properties. However, most of the research has been devoted to the hybrids with randomly dispersed phases. The present study explores the feasibility of using aligned 3D sp2-carbon structures in a bottom-up microwave-assisted chemical synthesis approach to fabricate various 3D sp2-carbon/inorganic hybrid architectures. The carbon nanostructures, either tubular or planar, not only contribute to the functionalities of the hybrids, but also template the ordered assembly of phases on nanometer scale. Mimicking nature is a key to develop novel types of materials with enhanced physical and mechanical properties suitable for advanced applications (e.g. lightweight and yet tough materials that are extensively needed in automotive and aerospace industries). One approach to obtain such materials or devices is to mimic nature processes and synthesize hybrid materials with ordered structures on the nanometer scale. Those functional structures are fabricated in this thesis through an in-situ microwave synthesis of inorganic materials on 3D sp2-carbon architectures. Generally, in chapter 1, it was shown and discussed the procedures to fabricate 3D architectures of carbon nanotubes and graphene oxide as basic components for template synthesis of the hybrids. Then in chapter 2 the microwave chemical synthesis approach was introduced as a convenient route for fabricating inorganic materials such as zinc oxide (ZnO) which was shown to be used as UV sensors. Through photolithography patterning of the iron catalyst thin films on Si/SiO2 substrates, 3D aligned CNT structures were fabricated and were coated in-situ with inorganic materials such as cobalt oxide, zinc oxide and manganese oxide using a microwave synthesis approach (chapter 3). The obtained aligned strips of CNT/Co3O4 were chosen as an example to illustrate the application of such 3D hybrids in energy storage applications. The capacitance of the aligned CNT/Co3O4 strips was measured to be 123.94 F/g. Using graphene oxide as template for manufacturing the 3D sp2-carbon/inorganic hybrid structures, interesting novel layered configurations are obtained that are similar to the layered structures of exoskeleton of the mollusks nacre. The layered hybrid structure shown to be mechanically improved compared to its constituents (chapter 4). Finally in chapter 5, some of the future routes have been proposed for further research on this novel field of 3D hybrid materials composed of sp2-carbons and inorganic nanomaterials.

<p>Proton exchange membrane fuel cells (PEMFCs) are considered as one of the most promising alternative clean and sustainable energy sources to fossil fuels. In general, PEMFC is consisted of anodic and cathodic electrode assembly, electrolyte, and proton-exchange membrane. While renewable fuels, such as hydrogen gas and formic acid, get oxidized at the anode to produce protons, oxygen molecules are reduced to form water at the cathode. Platinum has been widely used for both anodic and cathodic reactions due to its excellent catalytic reactivity.</p> <p><br></p> <p>Significant effort has been devoted to improving the reactivity and selectivity of Pt-based catalysts by alloying with a second metal. AuPt alloy nanoparticles have been studied extensively for electrochemical formic acid oxidation reaction, and isolated Pt species are recognized as the most active sites. While the majority body of literature focuses on structure-reactivity relationships</p> <p>based on as-synthesized materials, less attention is paid to the structural evolution during electrochemical catalysis. In this work, we develop a colloidal synthetic method to deposit Pt shell onto Au nanoparticles with variable thickness to study the microstructural evolution under electrocatalytic formic oxidation. We find that Pt atoms are submerged from the surface to form isolated Pt species in the first 100 cycles, which show enhanced FAO activity by shifting the reaction pathway. Additional CV scanning causes further depletion of Pt from the surface, resulting in the deactivation of the catalyst.</p> <p><br></p> <p>Despite the high activity of Pt-based catalysts, the use of these materials is limited by its high cost. Recently, transition metal sulfides such as cobalt sulfides have been found to show comparable activity to Pt-based catalysts in pH 7 ORR. However, it is challenging to isolate the role of coordination environment amidst multiple geometries and oxidation states that exist within any given phase. In this effort, we synthesize isolated Co atoms supported on colloidal WS₂nanosheets. By doing post synthetic treatment on these nanosheets, we are able to achieve a range of Co-S coordination number. Correlating Co-S CN to their ORR activities, we find the optimal active sites for ORR in neutral media possess a Co-S coordination number of 3-4.</p>

O processamento de peles para a fabricação de couro utiliza uma mistura complexa de substâncias - dentre elas, os taninos - que torna o tratamento de águas residuais difícil e oneroso. Vários estudos estão sendo conduzidos na tentativa de melhorar o tratamento e até mesmo reutilizar o efluente tratado. Neste trabalho foi avaliado o desenvolvimento de adsorventes funcionais sintetizados pelo método solgel e dotados de impressão molecular, para adsorção de compostos de taninos. Por serem de fácil preparação, os materiais híbridos obtidos viabilizam a sua produção para o uso como sólidos adsorventes. A caracterização dos materiais híbridos orgânico-inorgânico obtidos foi realizada por análise de Porosimetria de nitrogênio (BET), Espalhamento de raios-X a baixo ângulo (SAXS), Espectroscopia de refletância difusa no UV-vis (DRS), Espectroscopia de infravermelho com transformada de Fourier (FT-IR) e Potencial Zeta (PZ). As características estruturais e texturais dos materiais híbridos gerados variaram para cada rota sol-gel e processo de extração de template empregado, resultando em materiais com diferentes capacidades de adsorção. As sílicas sem funcionalização não foram capazes de adsorver os compostos de tanino em solução aquosa, enquanto que as sílicas funcionalizadas com APTES demonstraram sua potencialidade como adsorvente para os compostos testados, atingindo remoções superiores a 80%. Diferenças nas capacidades de adsorção entre as sílicas funcionalizadas com e sem impressão molecular também foram observadas, onde a sílica sem impressão apresentou uma adsorção superior de taninos, indicando que mais estudos são necessários para encontrar um processo de extração eficiente do template. É importante salientar que as sílicas que obtiveram a maior capacidade de adsorção, puderam adsorver os compostos de taninos por vários ciclos consecutivos. / The processing of hides for leather manufacturing uses a complex mix of chemicals that makes the wastewater treatment difficult and costly. Several studies are being conducted in attempt to improve the treatment and even reuse the treated effluent. This study evaluated the development of functional adsorbent synthesized by the molecular imprinting method in a sol-gel matrix, for adsorbing tannin compounds. Easy to prepare, hybrid materials obtained enable their production for use as solid adsorbents. The characterization of organic-inorganic hybrid materials obtained was performed by nitrogen porosimetry analysis (BET), small-angle X-ray scattering (SAXS), diffuse reflectance spectroscopy (DRS), Fourier-Transform Infrared Spectroscopy (FT-IR) and Zeta Potential (PZ). The structural and textural characteristics of hybrid materials ranged for each sol-gel route and template employed extraction process resulting in materials with different adsorption capacities. The silicas without functionalization were unable to adsorb the tannin compounds in aqueous solution, whereas the silica functionalized with APTES demonstrated the potential of the adsorbent for the tested compounds, with removals above of 80%. Differences in adsorption capacities between functionalized silica with and without molecular imprinting were observed where the unprinted silica had a higher adsorption of tannins, indicating that more studies are needed to find a process of efficient template extraction to improve adsorption capacity to the imprinted materials. Further, the silicas with improved adsorption capacity could adsorb the tannin compounds for several consecutive cycles of adsorption.

O processamento de peles para a fabricação de couro utiliza uma mistura complexa de substâncias - dentre elas, os taninos - que torna o tratamento de águas residuais difícil e oneroso. Vários estudos estão sendo conduzidos na tentativa de melhorar o tratamento e até mesmo reutilizar o efluente tratado. Neste trabalho foi avaliado o desenvolvimento de adsorventes funcionais sintetizados pelo método solgel e dotados de impressão molecular, para adsorção de compostos de taninos. Por serem de fácil preparação, os materiais híbridos obtidos viabilizam a sua produção para o uso como sólidos adsorventes. A caracterização dos materiais híbridos orgânico-inorgânico obtidos foi realizada por análise de Porosimetria de nitrogênio (BET), Espalhamento de raios-X a baixo ângulo (SAXS), Espectroscopia de refletância difusa no UV-vis (DRS), Espectroscopia de infravermelho com transformada de Fourier (FT-IR) e Potencial Zeta (PZ). As características estruturais e texturais dos materiais híbridos gerados variaram para cada rota sol-gel e processo de extração de template empregado, resultando em materiais com diferentes capacidades de adsorção. As sílicas sem funcionalização não foram capazes de adsorver os compostos de tanino em solução aquosa, enquanto que as sílicas funcionalizadas com APTES demonstraram sua potencialidade como adsorvente para os compostos testados, atingindo remoções superiores a 80%. Diferenças nas capacidades de adsorção entre as sílicas funcionalizadas com e sem impressão molecular também foram observadas, onde a sílica sem impressão apresentou uma adsorção superior de taninos, indicando que mais estudos são necessários para encontrar um processo de extração eficiente do template. É importante salientar que as sílicas que obtiveram a maior capacidade de adsorção, puderam adsorver os compostos de taninos por vários ciclos consecutivos. / The processing of hides for leather manufacturing uses a complex mix of chemicals that makes the wastewater treatment difficult and costly. Several studies are being conducted in attempt to improve the treatment and even reuse the treated effluent. This study evaluated the development of functional adsorbent synthesized by the molecular imprinting method in a sol-gel matrix, for adsorbing tannin compounds. Easy to prepare, hybrid materials obtained enable their production for use as solid adsorbents. The characterization of organic-inorganic hybrid materials obtained was performed by nitrogen porosimetry analysis (BET), small-angle X-ray scattering (SAXS), diffuse reflectance spectroscopy (DRS), Fourier-Transform Infrared Spectroscopy (FT-IR) and Zeta Potential (PZ). The structural and textural characteristics of hybrid materials ranged for each sol-gel route and template employed extraction process resulting in materials with different adsorption capacities. The silicas without functionalization were unable to adsorb the tannin compounds in aqueous solution, whereas the silica functionalized with APTES demonstrated the potential of the adsorbent for the tested compounds, with removals above of 80%. Differences in adsorption capacities between functionalized silica with and without molecular imprinting were observed where the unprinted silica had a higher adsorption of tannins, indicating that more studies are needed to find a process of efficient template extraction to improve adsorption capacity to the imprinted materials. Further, the silicas with improved adsorption capacity could adsorb the tannin compounds for several consecutive cycles of adsorption.

O processamento de peles para a fabricação de couro utiliza uma mistura complexa de substâncias - dentre elas, os taninos - que torna o tratamento de águas residuais difícil e oneroso. Vários estudos estão sendo conduzidos na tentativa de melhorar o tratamento e até mesmo reutilizar o efluente tratado. Neste trabalho foi avaliado o desenvolvimento de adsorventes funcionais sintetizados pelo método solgel e dotados de impressão molecular, para adsorção de compostos de taninos. Por serem de fácil preparação, os materiais híbridos obtidos viabilizam a sua produção para o uso como sólidos adsorventes. A caracterização dos materiais híbridos orgânico-inorgânico obtidos foi realizada por análise de Porosimetria de nitrogênio (BET), Espalhamento de raios-X a baixo ângulo (SAXS), Espectroscopia de refletância difusa no UV-vis (DRS), Espectroscopia de infravermelho com transformada de Fourier (FT-IR) e Potencial Zeta (PZ). As características estruturais e texturais dos materiais híbridos gerados variaram para cada rota sol-gel e processo de extração de template empregado, resultando em materiais com diferentes capacidades de adsorção. As sílicas sem funcionalização não foram capazes de adsorver os compostos de tanino em solução aquosa, enquanto que as sílicas funcionalizadas com APTES demonstraram sua potencialidade como adsorvente para os compostos testados, atingindo remoções superiores a 80%. Diferenças nas capacidades de adsorção entre as sílicas funcionalizadas com e sem impressão molecular também foram observadas, onde a sílica sem impressão apresentou uma adsorção superior de taninos, indicando que mais estudos são necessários para encontrar um processo de extração eficiente do template. É importante salientar que as sílicas que obtiveram a maior capacidade de adsorção, puderam adsorver os compostos de taninos por vários ciclos consecutivos. / The processing of hides for leather manufacturing uses a complex mix of chemicals that makes the wastewater treatment difficult and costly. Several studies are being conducted in attempt to improve the treatment and even reuse the treated effluent. This study evaluated the development of functional adsorbent synthesized by the molecular imprinting method in a sol-gel matrix, for adsorbing tannin compounds. Easy to prepare, hybrid materials obtained enable their production for use as solid adsorbents. The characterization of organic-inorganic hybrid materials obtained was performed by nitrogen porosimetry analysis (BET), small-angle X-ray scattering (SAXS), diffuse reflectance spectroscopy (DRS), Fourier-Transform Infrared Spectroscopy (FT-IR) and Zeta Potential (PZ). The structural and textural characteristics of hybrid materials ranged for each sol-gel route and template employed extraction process resulting in materials with different adsorption capacities. The silicas without functionalization were unable to adsorb the tannin compounds in aqueous solution, whereas the silica functionalized with APTES demonstrated the potential of the adsorbent for the tested compounds, with removals above of 80%. Differences in adsorption capacities between functionalized silica with and without molecular imprinting were observed where the unprinted silica had a higher adsorption of tannins, indicating that more studies are needed to find a process of efficient template extraction to improve adsorption capacity to the imprinted materials. Further, the silicas with improved adsorption capacity could adsorb the tannin compounds for several consecutive cycles of adsorption.

<p>  </p> <p>From applications in nanoscale electronics to regenerative medicine, there is a strong need for control assembly processes at nanometer length scales.1,2 In this work, we investigate the application of microscale droplet delivery as a rapid and scalable approach to pattern the molecular assembly of nanoscale chemical patterns on highly oriented pyrolytic graphite (HOPG). Furthermore, it was also observed that variations in the blend of alkyl impurities present in technical-grade OLAm reagents influenced the temperature-dependent assembly behavior.13 This suggests a likely role of alkyl chain phase transitions in the ligand shell, particularly in more complex mixtures and for anisotropic nanocrystals.</p> <p>Oleylamine (OLAm) is a common technical-grade reagent used in nanocrystal synthesis. Most nanocrystal synthesis is done using technical grade Oleylamine (70% purity). Higher purity reagents are not readily available because in certain instances, technical grades are obtained from natural substances, resulting in differing impurities compared to those generated during preparative reactions using pure raw materials.3 Technical grade reagents of OLAm contain 70% of the cis chain OLAm and 30% of an unspecified mixture of Elaidylamine (ELAm) , Octadecylamine (ODAm) and segments of various lengths and saturated alkyl chains.4,5 Here, we use Differential Scanning Calorimetry thermograms to investigate the miscibility of binary mixtures of OLAm/ELAm, OLAm/ODAm, and ELAm/ODAm. Ternary mixtures of the lipids showed clear peaks for the trans and saturated impurities.</p> <p>We patterned graphite surfaces with amphiphiles via inkjet printing to quickly generate 1-nm-wide functional patterns. Inkjet printing allowed for long-scale hierarchical patterning. We investigated various ink formulations and the resulting printing quality of functional monolayers on 2D crystalline materials. </p>

Le but principal de ce travail de thèse est de proposer un matériau précurseur d'oxydes métalliques (ZrO2, TiO2, HfO2) compatible avec la technique de photolithographie interférentielle DUV. Des oxoclusters de métaux (MOC) de transitions obtenus par complexation d’un ligand organique et hydrolysé partiellement ont été proposé comme briques élémentaires pour construire ces nanostructures. Le recours à des longueurs d'onde DUV (193 nm) permet d'exciter directement les MOC, ce qui conduit à une réticulation photoinduite, et confère à la résine un caractère de photoresist négatif. Une étude spectroscopique détaillée a permis de proposer un mécanisme de photoréticulation. Cette étude s'est appuyée essentiellement sur des techniques de suivi in situ de la réaction photochimique, par ellipsométrie spectroscopique et RT-FTIR. La nanostructuration a été effectuée essentiellement par lithographie interférométrique DUV (DUV-IL) à 193 nm et étendue à la stéréolithographie biphotonique. La DUV-IL a été choisie pour son potentiel d'écriture de nanostructures sur des surfaces relativement importantes, dans des conditions standard d'atmosphère et température. De plus, dans le cas des TiOC, les nanostructures peuvent être rendues inorganiques à température ambiante par un traitement photochimique supplémentaire. Dans le cas de ZrOC et HfOC, une étape supplémentaire de recuit thermique permet d'obtenir une structure de type MO2 cristallisée. / The main purpose of this thesis is to provide a material precursor of metal oxides (ZrO2, TiO2, HfO2) compatible with DUV interference photolithography technique. Transition metal oxoclusters (MOC) obtained by complexation of an organic ligand and a partial hydrolysis have been proposed as building blocks. DUV irradiation (193 nm) allows a direct excitation of the MOC, which leads a photo-induced crosslinking and gives to the material a negative photoresist character. A detailed spectroscopic study allowed proposing a mechanism of photocrosslinking. This study relied primarily on in situ techniques to follow the photochemical reaction by spectroscopic ellipsometry and RT-FTIR. The nanostructuring was performed by interferometric DUV lithography at 193 nm and could be extended to 2-photon stereolithography. DUV-IL was chosen for its potential to write nanostructures on relatively large areas, in standard atmosphere and temperature conditions. Furthermore, in the case of TiOC, the nanostructures can be fully mineralised at room temperature by an additionnal photochemical treatment. For ZrOC and HfOC, an additional thermal annealing step allows to obtain a crystalline structure MO2.

<p> Environmental Barrier Coatings (EBCs) protect ceramic gas turbine engine components from corrosion by high temperature water vapor, but the coatings often form complex metastable microstructures upon plasma spray deposition. In ytterbium disilicate (YbDS) and its yttrium-doped counterpart (Y/YbDS), two coatings compatible with SiC/SiC parts, plasma spray forms a largely cracked, mechanically weak amorphous phase comprising up to ~80% of the coating’s volume. Therefore, the coatings must undergo a pre-service heat treatment to crystallize into stable phases and heal cracks. During the treatment, however, interplay between thermal expansion and crystallization contraction can cause vertical cracks which expose the component to the corrosive atmosphere. Remedial treatments with long, high temperature holds (~1300 ºC) can both crystallize the coating and heal existing cracks. However, these temperatures cause unnecessary grain growth that reduces the structural integrity of the coating over its lifetime.</p> <p>Here we propose an alternate heat treatment informed by experiments and modelling that removes metastable phases, heals cracks, and reduces time at temperature to prevent significant grain growth. First, we determine crystallization and phase change kinetics by applying the Ozawa-Flynn-Wall and Vyazovkin kinetic methods to differential scanning calorimetry (DSC) data. Next, we track locations and microstructural effects of phase evolution using correlative Raman spectroscopic mapping, scanning electron microscopy (SEM), and X-Ray diffraction (XRD). We interpret the formation of three distinct phases – a major phase of stable β-YbDS, and minor phases of stable Χ2-YbMS and metastable α-YbDS – within the existing framework of kinetic theory and quantify differences in their transformations between YbDS and Y/YbDS. We find that cracks in the coating heal through the crystallization of the amorphous phase and the transformation of the metastable phase although the mechanisms remain unclear. Each phase transformation causes a bulk volumetric change which we measure using dilatometry and use to calculate delamination stresses during a simulated heat treatment. Lastly, we determine the viability of our heat treatment compared to the industry standard.</p>