Living organisms undergo morphogenesis as they develop and change shape to fit their evolved niche in natural ecosystems. The biological processes underlying morphogenesis involve sophisticated feedback loops between spatiotemporal release of morphogenic molecules that diffuse and signal cell differentiation, as well as contextual interaction with the physical surroundings of the...
Graphene oxide (GO), a product of oxidative exfoliation of graphite powders, has received significant attention due to its excellent solution dispersibility, rich functionality, and ease of conversion to chemically modified graphene (also known as œreduced graphene oxide or œr-GO). These properties make GO an attractive building block for constructing various...
In polymer nanocomposites (PNCs), the physical and chemical interactions at the polymer matrix-filler interface lead to local variations in polymer properties, creating a substantial interphaseregion in the vicinity of the interface. Quantifying the significance of the interphase effect in the presence of substrates or nanoparticles is of essential importance in...
To accelerate the implementation of technologies enabled by two-dimensional (2D) nanomaterials, the human health and environmental implications of these materials need to be addressed. Fundamental studies which elucidate the mechanisms of toxicity and environmental fate will allow for the safer design of these materials and promote their widespread use. This...
Developing low-cost, scalable, high-efficiency photovoltaic materials is an important technological challenge because of the projected increase in global energy consumption in coming years, the environmental cost of carbon emissions, and the widespread availability of solar energy. This dissertation contains three studies on the development of novel hybrid materials as photovoltaic...
In support of a scientific foundation for the predictive design of composition and processing of quench and partition (Q&P) martensite/austenite TRIP steels, theory of coupled diffusional/displacive transformation is experimentally calibrated to control austenite carbon content and its associated mechanical stability. Under paraequilibrium constraint, the calibration quantifies an effective BCC stored...
Intermolecular charge transfer between electron-rich donor and electron-poor acceptor molecules offer great promise in the development of novel, low-cost electronic materials. It is hypothesized that control over the intermolecular interactions and supramolecular self-assembly of these systems could tune electronic properties and discover new functions. To that end, a series of...
Electrochemical energy storage devices have become increasingly relevant to the operation and sustainability of the modern world, as proliferation of mobile electronics, renewable electrical energy generators, electrical vehicles, and various high-tech bio-medical sensing device continues. The widespread need of easier to produce, better performing, and multifunctional energy storage materials in...
The use of polymeric membranes have become ubiquitous in our daily lives. From simple chip bags to million-dollar cockpits, these membranes find diverse applications in packaging, protective coating, electronic device, gas and liquid separation, and medicine. The 2-dimentional geometry of the membranes offered unique mechanical and interfacial properties that often...
Perovskite oxide materials for the wide array of properties that make them candidate materials for application ranging from catalysis, to electronics, to beyond-Moore computation. As many of these oxides share similar structures they can be combined in a seemingly-endless number of ways to produce the desired properties for a given...
The assembly of nanoscale building blocks into larger ensembles with well-defined architecture has the potential to create entirely new classes of designer photonic and plasmonic metamaterials with unique properties not found in nature. Electromagnetic metasurfaces, or 2D metamaterials, operating at optical wavelengths are of particular interest due to ease of...
This dissertation presents research on solid oxide fuel cell (SOFC) cathodes. It specifically covers two main topics: the electrochemical performance of porous two-phase composite cathodes, and the degradation mechanisms of porous single-phase mixed conducting cathodes. Current-voltage measurement and electrochemical impedance spectroscopy were used extensively to evaluate the cell performance. The...
Self-assembly is an important process in biological system to build various bioactive structures from small amphiphilic molecules. The structural versatility of amphiphile self- assembly also provides a unique platform for the design of functional soft materials with controllable structural features. However, little is known about the correlation between external stimuli,...
Patterning hierarchical structures in three-dimension (3D) has created nature-inspired functional surfaces. Gecko feet structures have been mimicked for reversible adhesive properties, shark skin for reduced drag, and lotus leaves for self-cleaning surfaces. Rational design of out-of-plane patterns across multiple length scales is crucial because each micro- and nano-feature has different...
Significant deviations in the glass transition temperature (Tg) of nanoconfined polymer films from the bulk have been studied for over twenty years with the focus on high molecular weight (MW), linear polymers. This thesis explores low MW polymers, which represent an important class of materials widely used as coatings, detergents,...
Charge-containing polymers have received considerable attention for many decades, as these polymers combine the flexibility of polymer chains with electrochemical properties of the ions to provide a highly tunable, chemically and mechanically versatile class of materials. These materials have found use in energy conversion devices, high-density energy storage devices such...
Sparked by the isolation of graphene in 2004, the research community has developed a family of 2D materials with distinct functionalities, enabling rapid demonstrations of entirely 2D devices with applications in energy, electronics, sensors and medicine. The desire to capitalize on the fantastic properties of 2D materials motivates ongoing efforts...
Complex oxides show great potential for future devices as they offer functionalities beyond what can be delivered by conventional semiconductors. Among the complex oxides, the ABO$_{3}$ perovskite oxides are the most studied and engineered in the form of thin films and heterostructures. This thesis applies powerful synchrotron-based X-ray characterization tools,...
etal particles at the nanoscale display unique physical, chemical, and optical properties corresponding to their size, shape, and ligands. These factors can be manipulated to target specific biomedical applications, such as drug delivery and sensing, through functionalized surfaces. The development of specialized synthetic methods for the precise control of nanoparticle...
Plasmonic nanostructures are capable of trapping and confining light at the nanoscale, leading to interesting optical phenomena involving enhanced light-matter interactions. These responses arise in two forms: surface plasmon polaritons propagating on the surface of metal films and localized surface plasmons confined to the surface of metal nanoparticles. Plasmonic modes...
Two-dimensional materials’ “all-surface” architecture presents a new paradigm for investigations into electron confinement effects and surface phenomena. However, synthesizing, characterizing, and ultimately engineering the properties of 2D materials represents a formidable challenge. This thesis presents several cases of isolating novel 2D materials via vapor-based syntheses. Vapor-based syntheses allow for reproducible...
Lithium ion batteries (LIBs) have been the most prominent electrochemical energy storage technology over the past decades and enabled the wireless evolution of portable electronic devices. Yet the expanded use of renewable but intermittent energy sources coupled with increasing demand for electric transportation vehicles put forward requirements to electrochemical energy...
Porous metal structures exhibit numerous advantages over dense materials due to their high specific stiffness, strength, damping, energy absorption, and surface areas, making them suitable for applications ranging from actuators to medical implants. However, traditional foam manufacturing methods do not provide sufficient control of the foam micro-architectures, and the creation...
Gels are three-dimensional polymer networks capable of absorbing a large amount of solvent molecules subject to various external stimuli (pH, temperature, light, etc.). They exhibit a rich mechanical behavior and prominent nonlinearity owing to their high flexibility, stimuli-responsiveness and superabsorbency. More compelling are the intriguing morphologies and novel functionalities achieved...
The limits of miniaturization of electronic device components and the steady need for faster computation power have motivated the discovery and cultivation of low-dimensional materials. Among these, two-dimensional (2D) materials have exhibited a wide range of superlative optoelectronic, thermal and mechanical properties. The interest in 2D materials took-off with the...
There is growing interest in and demand for lightweight, age-hardenable alloys such as aluminum (Al) alloys in the transportation sector. This interest is due to the potential for reducing vehicle mass and thereby improving fuel economy. Precipitation microstructures improve the mechanical properties of materials, such as yield stress, by impeding...
Two-dimensional (2D) materials such as graphene exhibit unique, superlative electronic, optical, and mechanical properties that are dictated by the precise atomic structure within each layer. Consequently, control of this atomic-scale configuration is critical to engineering desirable characteristics. To date, however, most 2D materials have been discovered by isolating mono- or...
Increasing energy demand due to rapid growth in population and industrialization along with environmental crisis has led to the search for cheap, environmentally friendly, and nontoxic methods for generation of energy. However, most alternative energy sources such as photovoltaic, biofuels, hydraulic power, wind power, and geothermal energy, are characterized by...
Electromagnetic metamaterials composed of colloidally synthesized plasmonic metal nanoparticles offer new opportunities to probe light-matter interactions. The properties of these structures largely depend on the spatial arrangement of nanoparticles within them. Therefore, new assembly strategies that afford a high level of structural control are expected to enable a broad range...
While synthesis and transformation processes to produce monodisperse nanoparticles are empirically well-developed, the pathways for these reactions as well as the exact role of synthetic agents and binding characteristics of surface moieties remain poorly understood. This lack of understanding is primarily due to the paucity of information about nanoparticle structural...
Technology has advanced rapidly, especially in the twenty-first century, influencing our day-to-day life on unprecedented levels. Most such advances in technology are closely linked to, and often driven by, the discovery and design of new materials. It follows that the discovery of new materials can not only improve existing technologies...
Microkinetic modeling is a powerful tool for creating dynamic and quantitative descriptions of complex systems. These detailed mechanistic models compliment experimental techniques and provide an ability to achieve deeper insights into chemical processes where numerous intermediates are highly reactive and difficult to quantify in the laboratory. This thesis discusses the...
Thin film oxidation is investigated using two modeling techniques in the interest of better understanding the roles of space charge and non-equilibrium effects.
An electrochemical phase-field model of an oxide-metal interface is formulated in one dimension and studied at equilibrium and during growth. An analogous sharp interface model is developed...
This work reports studies on the physical properties of collections of nanosheets. First, the configurations of graphene oxide sheets in solution are studied. Polarized optical microscopy reveals quickly and decisively that sheets remain flat and form lyotropic liquid crystals over a wide range of solvent conditions. When solvent conditions are...
Moving away from fossil fuels requires environmentally friendly and economically viable alternative energy sources. A wide adoption of new technologies for energy production and storage depends on better performing materials. Computational methods, such as electronic structure calculations and machine learning, hold the promise to work in conjunction with traditional experimentation...
Supported metal catalysts find many important uses in areas including chemical production, petroleum refining and emission control. The catalytic behavior of a supported metal catalyst is influenced by size and type of reaction sites on metal nanoparticles. For many structure insensitive reactions catalyzed by the supported metal catalysts, smaller metal...
Over the last 20 years a new field of amorphous transparent conducting oxides (a-TCOs) has developed. The amorphous nature of these films makes them well suited for large area applications. In addition, a-TCOs can be made at low temperatures and through solution processing methods. These assets provide promising opportunities to...
Atom probe tomography (APT) was used to analyze doping and alloying in low-dimensional electronic materials including thin film heterostructures, van der Waals materials, and colloidal quantum dots (QDs).
Firstly, APT was used to reveal structure-property relationship for low-dimensional thin film semiconductors used in electronic and opto-electronic devices. APT was shown...
Carbonate minerals are integral to life on earth, as reservoirs for CO2 in the earth’s natural carbon cycle and as the skeletal elements of abundant organisms like corals and plankton. Because of its relevance, availability, and low toxicity, calcium carbonate is also an important model system for phase transformations in...
High performance structural materials are needed for Naval applications which require an excellent combination of yield strength, low-temperature impact toughness, ductility, ballistic-resistance, and weldability. This research investigates precipitation-strengthened HSLA-115 steels and ballistic-resistant 10 wt. % Ni steels, which have emerged as promising alternatives to the widely used HSLA-100 steels for...
The morphological evolution due to coarsening is analyzed for two distinctive types of microstructure. First, the feasibility of characterizing spatial correlations of interfacial curvature in topologically complex structures is demonstrated with the analysis of bicontinuous two-phase mixtures produced using phase field modeling. For structures produced with both conserved and nonconserved...
This thesis demonstrates the use of dual-beam focused ion beam - scanning electron microscopy (FIB-SEM) for making complete three-dimensional reconstructions of SOFC electrodes in order to better understand the links between processing and performance with respect to microstructure. Sufficient compositional contrast, with nano-scale resolution, between Ni and LSM with respect...
This dissertation examines growth of platinum nanoparticles from vapor deposition on SrTiO3 using a characterization approach that combines imaging techniques and X-ray methods. The primary suite of characterization probes includes atomic force microscopy (AFM), grazing-incidence small-angle X-ray scattering (GISAXS), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and X-ray absorption spectroscopy...
ZnO is a member of the unique class of materials known as transparent conducting oxides (TCOs). TCOs are currently used for many applications including flat panel displays, solar cells, and energy efficient windows. Of particular interest is the possibility of developing materials that have high electron mobilities, such that conductivities...
Wood-derived ceramics and composites have been of interest in recent years due to their unique microstructures, which lead to tailorable properties. The porosity and pore size distribution of each wood type is different, which yields variations in properties in the resultant materials. The thermal properties of silicon carbide ceramics and...
Subsolidus phase relationships within the ZnO-In<sub>2</sub>O<sub>3</sub>-SnO<sub>2</sub> system at 1275 <sup>o</sup>C were established by conventional solid state reaction methods. No new compounds or structures were observed within the ternary diagram. Equilibrium in the ZnO-corner, between the homologous compounds and the spinel phase, was found difficult to achieve. This problem was overcome...
Characterizing the interaction of light and matter has become increasingly important in recent decades, as devices scale down, data transfer speeds up, and the use of photon-based technology (photonics and optoelectronics) becomes widespread. Copper chloride (CuCl) thin films and zinc oxide (ZnO) inverse opal photonic crystals are the two material...
Recent assessment of material property requirements for blast resistant applications, especially for the naval ship hulls, has defined the need to design steels with high stretch ductility and fragment penetration resistance, along with high strength and adequate toughness. Using a system based computational materials design approach, two series of austenitic...
A multicomponent bimodal poly(vinyl acetate) (PVAc) polymer composite has been scientifically designed to increase biaxial plastic flow stabilization for the achievement of large biaxial deformations. For this, a systems-based approach was used for the computational materials design of a high performance bubblegum whose mean in-vivo bubble diameter exceeds that of...
In this work, electron beam induced current (EBIC) and scanning photocurrent microscopy (SPCM) were used to quantitatively investigate the electronic properties of silicon nanowire devices. For the first time, it was shown that minority carrier diffusion lengths in phosphorous-doped silicon nanowires are significantly reduced from their bulk values because of...