Organic-inorganic polymer hybrids containing butyl stannoxane dodecamer cages (Sn_POSS) as nano-building blocks were prepared and investigated. Sn_POSS was employed as a linear, crosslinking or non-bonding molecularly blended unit. For this purpose, it was synthesized with two acrylamido, primary- or secondary amino, or with two additional non- functional groups, which were attached via ionic-bonded sulfonate substituents. The nano- building block was then incorporated in matrices such as PS, PAOS, PETA, PEMA, PHEMA and PPO-based epoxies (the latter with different mesh sizes). Sn_POSS reinforces the studied matrixes by filler-filler interactions (self-assembly to nano-domains). Specific interactions of the ionic bonds of Sn_POSS with suitable pendant groups of the matrixes also can generate reinforcement and suppress filler aggregation. Moreover, the Sn_POSS can undergo several types of chemical reactions like heat-induced oligomerization, dissociation of the ionic substituents, acidolysis of the Sn-butyl bonds, as well as radical reactions of the latter. The influence of ionically bonded cages on the hybrids' morphology, as well as their ability of dissociation and short-distance migration in the polymer network at elevated temperature, was evaluated by TEM, IR and NMR analyses. The mechanical...

Nanotechnology as a field has the potential to answer some of the major challenges that mankind faces in regards to environmental sustainability, energy generation and health care. Though, solutions to these concerns can not necessarily rely on our current knowhow. Instead, it is reasonable to expect that humanity must adapt and learn to develop new materials and methods to overcome the adversities that we are facing. This master thesis has involved developing novel materials, serving as a small step in the continuous march towards a bright future where this is possible. More specifically, this work sought to combine mesoporous magnesium carbonate with various metal-organic frameworks to utilize the beneficial aspects from each of these constituents. The ambition was that these could be joined to render combined micro-/mesoporous core-shell structures, with high surface areas and many active sites whilst maintaining a good permeability. Numerous different synthesis routes were developed and explored in the pursuit of viable routes to design novel materials with potential future applications within for instance drug delivery, water harvesting from air and gas adsorption. Coreshell structures of the hydrophilic mesoporous magnesium carbonate covered with the hydrophobic zeolitic imidazole framework ZIF-8 was successfully synthesized for the first time, and practical studies demonstrated a dramatically enhanced water stability, which is perceived to have an impact on further research on these materials. ZIF-67 was also combined with mesoporous magnesium carbonate in a similar manner. Further, Mg-MOF-74 was grown directly from mesoporous magnesium carbonate, where the latter acted as a partially self-sacrificing template, with the aim of rendering a porous hierarchical structure with contributions from the micro- and mesoporous ranges. The outcomes of all these syntheses were characterized using several analyzing methods such as scanning electron microscopy, X-ray diffraction, energy dispersive spectroscopy and nitrogen sorption analysis.

<p>Composite materials have been successfully applied in various industries, such as aerospace, automobile, and wind turbines, etc. Although the material properties of composites are desirable, the behaviors of composites are complicated. Many efforts have been made to model the constitutive behavior and failure of composites, but a complete and validated methodology has not been completely achieved yet. Recently, machine learning techniques have attracted many researchers from the mechanics field, who are seeking to construct surrogate models with machine learning, such as deep neural networks (DNN), to improve the computational speed or employ machine learning to discover unknown governing laws to improve the accuracy. Currently, the majority of studies mainly focus on improving computational speed. Few works focus on applying machine learning to discover unknown governing laws from experimental data.  In this study, we will demonstrate the implementation of machine learning to discover unknown governing laws of composites. Additionally, we will also present an application of machine learning to accelerate the design optimization of a composite rotor blade.</p> <p><br></p> <p>To enable the machine learning model to discover constitutive laws directly from experimental data, we proposed a framework to couple finite element (FE) with DNN to form a fully coupled mechanics system FE-DNN. The proposed framework enables data communication between FE and DNN, which takes advantage of the powerful learning ability of DNN and the versatile problem-solving ability of FE. To implement the framework to composites, we introduced positive definite deep neural network (PDNN) to the framework to form FE-PDNN, which solves the convergence robustness issue of learning the constitutive law of a severely damaged material. In addition, the lamination theory is introduced to the FE-PDNN mechanics system to enable FE-PDNN to discover the lamina constitutive law based on the structural level responses.</p> <p><br></p> <p>We also developed a framework that combines sparse regression with compressed sensing, which leveraging advances in sparsity techniques and machine learning, to discover the failure criterion of composites from experimental data. One advantage of the proposed approach is that this framework does not need Bigdata to train the model. This feature satisfies the current failure data size constraint. Unlike the traditional curve fitting techniques, which results in a solution with nonzero coefficients in all the candidate functions. This framework can identify the most significant features that govern the dataset. Besides, we have conducted a comparison between sparse regression and DNN to show the superiority of sparse regression under limited dataset. Additionally, we used an optimization approach to enforce a constraint to the discovered criterion so that the predicted data to be more conservative than the experimental data. This modification can yield a conservative failure criterion to satisfy the design needs.</p> <p><br></p> <p>Finally, we demonstrated employing machine learning to accelerate the planform design of a composite rotor blade with strength consideration. The composite rotor blade planform design focuses on optimizing planform parameters to achieve higher performance. However, the strength of the material is rarely considered in the planform design, as the physic-based strength analysis is expensive since millions of load cases can be accumulated during the optimization. Ignoring strength analysis may result in the blade working in an unsafe or low safety factor region since composite materials are anisotropic and susceptible to failure. To reduce the computational cost of the blade cross-section strength analysis, we proposed to construct a surrogate model using the artificial neural network (ANN) for beam level failure criterion to replace the physics-based strength analysis. The surrogate model is constructed based on the Timoshenko beam model, where the mapping is between blade loads and the strength ratios of the cross-section. The results showed that the surrogate model constraint using machine learning can achieve the same accuracy as the physics-based simulation while the computing time is significantly reduced. </p>

Dans ce travail, nous présentons dans la première partie la substitution du molybdène par du tungstène dans les anions de type Keplerates, [{Mo6}12Mo30O312E60(AcO)30]42- (E = O or S). L'introduction du tungstène dans le milieu de synthèse a entraîné l'isolement d'une série de composés, [{WxMo6- x}12Mo30O312E60(AcO)30]42-, avec une teneur en métal variable dans leurs unités pentagonales {M6}. Une observation remarquable a révélé l'occupation sélective de la position centrale dans l'unité pentagonale par les atomes W. Cette observation a été étendue à d'autres structures telles que les roues du bleu du molybdène [Mo154O462H14(H2O)70]14- et l’anion Krebs [Mo36O112(H2O)16]8- qui ont également montré la même occupation préférentielle des atomes W pour le site héptavalent, au centre du pentagone. Dans la deuxième partie, nous nous concentrons sur l’élaboration d'un matériau hybride à trois composantes à base de polyoxométallates (POM), de clusters métalliques et de - cyclodextrine ( -CD). La conception de ce matériau suivant une approche synthétique basée sur la propagation à l’infini des interactions spécifiques entre la CD et les deux types d'unités inorganiques. Dans la dernière partie, nous étendons l’étude des interactions CD-POM aux structures POMs géantes telle que l’anneau du bleu du molybdène. Une complexation non conventionnelle résulte de l'encapsulation du macrocycle organique dans la cavité centrale du l’anneau inorganique anionique. Accroître la complexité du système en introduisant une troisième espèce, conduit à la formation d'un assemblage supramoleculaire hybride par agencement hiérarchique des molécules organiques et inorganiques / In this work, we report in the first part the substitution of molybdenum by tungsten within Keplerate-type anions [{Mo6}12Mo30O312E60(AcO)30]42- (E = O or S). Introducing tungsten to the synthesis medium resulted in the isolation of a series of compounds, [{WxMo6- x}12Mo30O312E60(AcO)30]42, with variable metal content within their pentagonal units {M6}. An outstanding observation revealed the selective occupation of the central position in the pentagonal unit by the W atoms. This revelation was stretched to reach other historical structures as Mo-blue wheel [Mo154O462H14(H2O)70]14- and Krebs [Mo36O112(H2O)16]8- anions that also showed the same preferential occupation of W atoms for the heptacoordinated site. In the second part, we focus on the fabrication of a three-component hybrid material based on polyoxometalates (POMs), metallic clusters and -cyclodextrin ( -CD). Investigation of such material has been conducted using bottom-up approach by investigating the specific interactions between CD and both types ofinorganic units. Finally, the three componentsassociate together to give a well orderedpolymer-like hybrid chain that is derived ashydrogel and single crystals. In the last part, we extend the CD-POMinvestigation to reach giant POM structures asthe Mo-blue ring. A non-conventional complexation results from this interaction explained by the encapsulation of the organic macrocycle within the inorganic torus. Increasing the complexity of the system by introducing a third species provoked the formation of a hierarchical hybrid assembly.

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This project uses digital technology to interpret the human body as a malleable material for the development of sculptural and textile-based design. Mikhail Bakhtin’s definition of the grotesque human body lays the conceptual groundwork for using the human body as an interactive tool, that co-shapes itself with digital technology as an extension. The technology has been given agency to affect the creative outcome, rather than treating it as a means to an end. By 3D scanning the designer’s own body, and manipulating photographic documentation of it, through algorithmic interpretations, the morpho- logical transformations of the designer’s body, in multiple realities, were investigated while reflecting on its influence on self-perception. The investigated methods resulted in alternative bodily structures carved in polystyrene, and dressed in hybrid materials of transfer-printed textiles and bio-plastic. The design outcomes suggests a design method wherein agency is given to digital technology which allows for exploring unexpected ways of perceiving the human body.

<p>When a composite laminate is transversely impacted by a projectile at the ballistic limit, its failure mode transits from global conical deformation to localized perforation. This Ph.D. dissertation aims to reveal the fundamental material failure mechanism at the ballistic limit to control perforation. First, transverse impact experiments were designed on composite strips to isolate the interaction between plies and tows. Three failure modes were identified, divided by no, partial, and complete failure before the transverse wave deformed the entire composite strip. The failure phenomenon and critical velocity region can differ with the fiber type and projectile nose geometry and dimension. In most impact events, the composite strips all failed in tension in the front of the projectiles, although they failed at different positions as the projectile nose geometry and fiber type changed. A special failure phenomenon was uncovered when the composite strips were impacted onto razor blades above the upper limit of the critical velocity region: the composite strips seemed to be cut through completely by the razor blades. To further investigate the failure by razor blade, a microscopic method was developed to cut a single fiber extracted from the composite strip and simultaneously image the failure process inside a Scanning Electron Microscope (SEM). The experiments revealed that the razor blade cannot cut through the inorganic S-2 glass fibers while can partially incision the aramid Kevlar^®KM2 Plus fibers and completely shear through the ultra-high-molecular-weight polyethylene (UHMWPE) Dyneema^® SK76 fibers. Further investigations on the fiber’s failure under dynamic cut revealed that there was no variation in the failure mode when the cut speed was increased from 1.67 μm/s to ~5.34 m/s. To record the local dynamic failure inside the composite strips and single fibers at high-velocity impact, an advanced imaging technique, high-speed synchrotron X-ray phase-contrast imaging, was introduced, which allows to capture the composite’s internal failure with a resolution of up to 1.6 μm/pixel and at a time interval 0.1 μs. Integrated with a reverse impact technique, such an advanced imaging technique is believed to be capable of revealing the mechanism involved in the impact-induced cut in single fibers, yarns, and composite strips. The relevant studies will be the extended work of this Ph.D. dissertation and published in the future.</p>

The research presented in this dissertation focuses on the design and synthesis of novel hybrid conjugated polymer materials using two different approaches: 1) inorganic/organic hybrid semiconductors through the incorporation of carboranes into the polymer structure and 2) the modification of surfaces with conjugated polymers via grafting approaches. Hybrid conjugated polymeric materials, which are materials or systems in which conjugated polymers are chemically integrated with non-traditional structures or surfaces, have the potential to harness useful properties from both components of the material to help overcome hurdles in their practical realization in polymer-based devices. This work is centered around the synthetic challenges of creating new hybrid conjugated systems and their potential for advancing the field of polymer-based electronics through both greater understanding of the behavior of hybrid systems, and access to improved performance and new applications. Chapter 1 highlights the potential applications and advantages for these hybrid systems, and provides some historical perspective, along with relevant background materials, to illustrate the rationale behind this work. >Chapter 2 explores the synthesis of poly(fluorene)s with pendant carborane cages. The Ni(0) dehalogenative polymerization of a dibromofluorene with pendant carborane cages tethered to the bridging 9-position produced hybrid polymers produced polymers which combined the useful emissive characteristics of poly(fluorene) with the thermal and chemical stability of carborane cages. The materials were found to display increased glass transition temperatures and showed improved emission color stability after annealing at high temperatures relative to the non-hybrid polymer. The design and synthesis of a poly(fluorene)-based hybrid material with carborane cages in the backbone, rather than as pendant groups, begins in chapter 3. Poly(fluorene) with p-carborane in the backbone is synthesized and characterized, and the material is found to be a high MW, soluble blue emitter which shows a higher glass transition temperature and greater stability than a non-hybrid polymer. UV absorbance and fluorescence spectroscopy indicated some electronic interaction between the conjugated polymer and the cages, but they did not appear to be fully conjugated in the traditional sense. Chapter 4 describes the design, synthesis, and characterization of poly(fluorene) with o-carborane in the backbone. Profound changes in the behavior of the polymer, from its polymerization behavior to its emission characteristics, were observed and their origins are discussed. Experiments to explore the nature of the cage/polymer interactions were performed and possible applications which take advantage of the unique nature of the o-carborane hybrid polymer are explored and discussed. Hybrid conjugated polymer materials via grafting approaches to surfaces and surface modification are discussed starting in chapter 5. The synthesis of a dibromofluorene-based silane coupling agent for the surface functionalization of oxide surfaces is presented, and the surface directed Ni(0) dehalogenative polymerization of poly(dihexylfluorene) is explored. Chapter 6 focuses on the exploration of conjugated polymer/cellulose hybrid materials. Surface medication of cellulose materials with monomer-like anchor points is discussed. Grafting of the modified cellulose with conjugated polymers was explored and the grafting of three different repeat structures based on fluorene-, fluorenevinylene-, and fluoreneethynylene motifs were optimized to provide a general route to cellulose/conjugated polymer hybrid materials. Characterization and possible applications of such hybrid materials are discussed. Finally, chapter 7 is devoted to the simultaneous surface patterning and functionalization of poly(2-hydroxyethylmethacrylate) thin films using a silane infusion-based wrinkling technique. While not a conjugated polymer system, the spontaneous patterning and functionalization methods explored in this chapter produce hybrid organic/inorganic polymer thin films which have applications that range from optics, to adhesion, to polymer-based electronics, and the research compliments the other chapters. The spontaneous generation of complex patterns, of a small scale approaching 100nm feature size, over a large area with simultaneous control over surface chemistry is explored. Examples of complex, hierarchically patterned films which integrate lithographic processes such as nanoimprint lithography and electron beam lithography with spontaneous patterning via wrinkling are presented.

<p dir="ltr">During atmospheric re-entry, the hypersonic leading edges can experience enormous heat fluxes, with surface temperatures greater than 1600℃ expected. While carbon/carbon (C/C) is a candidate material for leading edge structures, it is prone to oxidation and ablation damage above 500℃. Ablation-resistant coatings can protect the C/C, while emissivity can be engineered to lower the leading-edge surface temperature via radiative cooling. In this dissertation, a novel bilayer coating system and a multilayer coating system based on individual layers consisting of ultra-high temperature ceramics (borides, carbides), refractory oxides (zirconia), and rare-earth oxide as emissivity modifiers were applied to a C/C surface via pack cementation and plasma spray. Ablation tests were performed to evaluate the efficacy of the multilayer coatings in simulated high heat flux environments. <a href="" target="_blank">The spectral emittance of the rare-earth modified topcoat ZrO₂ was measured at high temperatures up to 1200</a>℃ using a benchtop emissometer. ZrO₂ stabilized with 6 mol% Sm₂O₃ demonstrated a maximum spectral emissivity of 0.99 at λ = 12.5 µm proving its effectiveness in cooling the leading edge surface through enhanced thermal radiation.</p><p dir="ltr"><a href="" target="_blank">The bilayer coating system comprised of Sm₂O₃-stabilized ZrO₂ topcoat layer and SiC intermediate sublayer on C/C. </a><a href="" target="_blank">This coating significantly improved the ablation resistance of C/C by reducing the mass ablation rate by ~71%. Despite a significant thermal expansion coefficient mismatch between the substrate and the coating, a well-defined mechanical adhesion characterized by the anchors was observed in pre- and post-ablated coating microstructures, indicating their influence on improving ablation resistance.</a></p><p dir="ltr"><a href="" target="_blank">The multilayer coating architecture consisted of SiC, ZrB₂-SiC, ZrC-ZrO₂ sublayers and a Sm₂O₃-ZrO₂ topcoat. The as-sprayed coating microstructure demonstrated well-defined adhesion between the layers and the substrate without forming major voids or cracks. The multilayer coating with optimized</a> sublayer thickness demonstrated excellent ablation and mass erosion resistance as they reduced the mass ablation rate of C/C by ~90% after being subjected to an aggressive oxyacetylene torch heating for 60 s. During testing, the Sm₂O₃-stabilized ZrO₂ topcoat acted as oxygen and thermal barrier, protecting the underlying sublayers from oxidation-induced damage while maintaining a constant surface temperature of ~2100 ℃. Additionally, the high spectral emittance of topcoat material contributed to efficient outward heat transfer via thermal radiation from the external surface while maintaining a constant temperature.</p>

<p>For many applications within the defense, aerospace, and electricity-producing industries, available material choices for high-performance devices that fulfill necessary requirements are limited. Choosing a metallic material or a ceramic material may be optimal for only some of the required properties. For instance, choosing a metal may optimize ductility but compromise oxidation resistance, yield strength, or creep resistance. Of potential interest, ceramic-metal (cermet) composites can address several fundamental concerns such as high temperature mechanical toughness and stiffness and oxidation/corrosion resistance. However, cost-effective, scalable manufacturing of complex-shaped, high-temperature cermets can be challenging.</p> <p>A cermet of interest is niobium and yttrium oxide, Y2O3. Both materials exhibit high melting points with similar coefficients of thermal expansion. Basic thermodynamic calculations suggest that these materials are chemically compatible, and that Y2O3/Nb cermets may be generated by reactive melt infiltration using the patented Displacive Compensation of Porosity (DCP) process. With the DCP process, a liquid fills a porous perform, and a displacement reaction occurs to produce products of larger solid volume. This reaction yields the cermet of interest, formed in a reduced-stress condition, while maintaining a generally near net shape and high relative density.</p> <p>In order to get to the point of designing cermet components for various applications, a focus of this work has been to create a Y2O3/Nb composite by hot pressing powders at high temperatures at the predicted stoichiometric ratios, and then characterizing the thermal and mechanical properties. The reduction reaction between liquid yttrium and solid niobium (IV) oxide (NbO2) was then characterized to evaluate kinetic mechanisms affecting the reaction rate which is necessary for future DCP-based cermet component manufacturing.</p> <p>Lastly, the mechanical behavior of this cermet was modeled and compared to another cermet processed using liquid metal infiltration using a temperature-dependent elasto-visco-plastic self-consistent model. The effects of cooling from processing temperatures, as well as thermally cycling of these cermets, were quantified. As high temperature experiments can be time intensive with high costs, it is advantageous to have a computationally efficient, desktop design tool to quantify the impacts of changing processing and use conditions on material performance.</p>