Surface patterns that can reconfigure under external stimuli are important for tailoring diverse properties such as surface adhesion, optical transmittance, and wettability depending on the feature size and orientation. Wrinkling a stiff skin layer on a pre-strained elastomer substrate has emerged as a method to create responsive structures without using...
Continuous and coordinated materials discovery efforts have amassed a wealth of knowledge concerning many general classes of materials. The number of known phases of all structure-types, however, is far less than number of possible materials dictated by the elements on the periodic table. Recently, with improved computational abilities and well-developed...
Advanced wireless soft electronics integrate a wireless power transfer circuit and a small battery. It is skin-compliant, and lightweight accommodating the complex motion of the body. These unique features of the device provide a continuous physiological measurement without discomfort and spatial constraints. Using the device, we can observe and track...
As the pursuit for higher performance and lower cost photovoltaics, and for new applications of optoelectronic devices moves beyond crystalline silicon, there are many unique opportunities for materials research into hybrid organic-inorganic, and organic semiconductors. This dissertation focuses on both hybrid organic-inorganic materials and organic materials for optoelectronic applications. In...
Electrochemical cell devices are increasingly being sought for energy conversion and storage applications due to their high efficiencies and their potential for operating free of greenhouse gas (GHG) emissions. Solid Acid Electrochemical Cells (SAECs), which most commonly employ CsH2PO4 (CDP) as the electrolyte component, are uniquely suited to meet the...
Discrete molecules, linear and branched polymers, and disordered cross-linked networks are well studied objects of chemical synthesis. However, two-dimensional polymers (2DPs) have been long missing from this continuum of molecular architectures, both in chemical synthesis and in Nature. Recently, new polymerization strategies and characterization methods have enabled the unambiguous realization...
Throughout history, the development of materials has relied heavily on the empirical judgment of scientists and engineers and on prolonged experiments proton to errors. Due to the complexity of material behavior, successful discovery of new candidates has been serendipitous, and down-selection of candidates remains a time-consuming process that requires repetitive...
Thermoelectric materials are of particular interest in a variety of fields because of their ability to directly convert heat to electricity (and vice versa), however, they struggle to gain widespread adoption because of their low efficiency. A common strategy in the field of thermoelectricity is to introduce material defects into...
High performance polymers and their composites have wide ranging application in advanced and emerging material systems. The macroscale performance of these advanced materials is often defined by interfaces that induce nanoscale changes in the microstructure or molecular conformations (termed the ‘interphase’) of the polymer. Atomic force microscopy (AFM) is an...
Given directives such as the UN Global Goals targeting sustainable development, the research presented herein makes but a small contribution to the advancement of alternative energy technologies. Nevertheless, the present work was largely motivated to address specific points of intrigue within the thermoelectrics community. The general principles demonstrated, however, may...
An extensive set of functional electronic properties depends on the electronic structure. These properties are directly connected to the reciprocal-space representation of electronic structure. However, there is a complementary, real-space perspective that is described by combinations of atomic orbitals. Atomic orbitals are the components of electronic structures, analogous to how...
Structural colors originate from the interaction between the incident light and a surface with periodic submicron structures. They enable the creation of a spectrum of nonfading colors, potentially replacing toxic metal oxides and conjugated organic pigments. However, significant challenges remain, including lack of contrast needed for the complete gamut of...
A series of theories and models are developed and used to investigate the growth of protective oxide films on metal and alloy surfaces for cases in which Wagner's classical model of oxidation does not hold. First, irreversible thermodynamics is applied to formulate a model for the outward growth of rocksalt...
Part I: Design of Photo-Responsive Molecules towards Biomedical ApplicationsThe use of light to control systems provides numerous advantages such as spatiotemporal precision, non-invasive penetration, and precise energy input. Specifically, molecules that undergo photoinduced cleavage, photoremovable protecting groups (PPGs) have emerged as an active area of research due to their broad...
A significant portion of material science research is concerned with understanding theway that defects affect the properties materials. In the field of thermoelectrics introducingor removing point (0D), dislocation (1D), grain boundary (2D), or precipitate (3D) defectsare popular methods for altering a materials thermoelectric efficiency. Herein I discussdifferent studies conducted during...
Transition metal oxides (TMOs) like perovskites are known to be versatile for functional properties such as ferroelectricity, magnetism, optical properties, and high-temperature superconductivity, because of their sensitive coupling between atomic structure and properties. By studying and understanding the fundamental structure-property relationships present in TMOs, it is possible to strategically engineer...
Supervised learning model is one of the most fundamental machine learning models. It can provide powerful capability of prediction by learning complex patterns hidden in many, sometimes thousands, predictors. It can also be used as a building block of other machine learning tasks, like unsupervised learning and reinforcement learning. Such...
Thermoelectric materials have attracted widespread attention in recent decades because of their ability to directly convert thermal energy into electrical energy. Given that waste heat is the primary source of lost energy in the world, the implications of developing better thermoelectric materials are both immediate and far-reaching. Admittedly, large progress...
Dual-phase (DP) steels have been widely applied in automobile industry, and are famous for continuous yielding in their corresponding stress-strain curves. The appearance of yield-point phenomena, or discontinuous yielding, is considered undesirable for DP steels. Herein, we take advantage of the undesirable appearance of yield-point phenomena in DP steels as...
The investigation of ceria-related materials has a long history since 1920s. The first publication on web of science traces back to 1928. Ever since that, more studies come out and surge starting from 1987. This material has attracted extensive attention due to its wide applications in electrochemical devices, catalysis, and...
Biological organisms have the extraordinary ability to form mineral structures with unparalleled control. From curved single crystals to hierarchically structured skeletal parts, biomineralization processes produce materials with properties that are highly optimized for their intended applications. These processing techniques occur at ambient conditions using materials abundant in the environment, and...
Multimetallic nanoparticles represent an important class of electrocatalysts which are critical for many energy and environmental applications including fuel cells, hydrogen production, and greenhouse gas elimination. The properties of these nanoparticles depend on their composition, size, shape, and structure. Therefore, developing new strategies which provide a high level of control...
Tooth enamel, the outermost layer of human teeth, is a complex, hierarchically structured biocomposite. The details of this structure are important in multiple human health contexts, from understanding the progression of dental caries (tooth decay) to understanding the process of amelogenesis (enamel formation) and related developmental defects.While much is known...
The three-dimensional (3D) nanoscale structure of III-As nanowires is correlated with optical and electronic property measurements to deconvolve the contributions of strain, composition, and crystal structure to characteristics of interest for future electronic and optoelectronic devices. Multiple advanced two-dimensional (2D) and 3D characterization techniques are employed such as atom probe...
There is considerable technical interest in the improvement of battery technology, as it would allow for the enhancement and realization of many different applications, including the continued miniaturization of portable computational devices, plug-in electric vehicles, and intermittent power storage. Lithium metal represents a theoretical limit on the anode energy density...
As demonstrated by efforts in graphene commercialization, scalable synthesis and high-quality material availability are primary limiting factors for the realization of technologies based on two-dimensional (2D) materials. Thus, in considering the fate of emergent 2D materials such as the metal chalcogenides, the challenge of scalable synthesis is a highly relevant...
Self-assembly of colloidal particles at the nano- and microscale has been a powerful tool for producing structures with emergent properties in applications ranging from electro-mechanical systems to photonics and biomedical devices. Great success has been achieved in experiments, where a variety of exotic phases have been discovered and even reconfigurable...
Recent advances in high-performance computing have resulted in massive databases of materials properties calculated with techniques such as ab initio density functional theory. In fact, some of the largest of such databases have calculations of nearly all distinct, ordered, experimentally-reported compounds. This thesis discusses the application of data in one...
The high-temperature oxidation/reduction behaviors of iron and its oxides are important to a variety of energy conversion and storage technologies, such as the solid-oxide iron-air battery and chemical looping combustion. The useful lifetime of iron redox materials is limited, however, by structural degradation arising from (i) sintering, accelerated by phase...
The effect of Alkali-Silica Reaction (ASR) on concrete mechanical behavior and the multi-physics considerations that come along are highly complex. Hydration and other chemical reactions occur at the micrometer scale. Hygro-thermal phenomena and concrete cracks due to ASR are typically studied at the meso-scale, i.e. at the aggregate level. At...
As conventional electronic materials approach the device scaling limits, new types of materials and structures have been examined for potential use in future electronic and optoelectronic applications including transistors, light emitting diodes, and solar cells. In recent years, atomically thin or two-dimensional (2D) transition metal dichalcogenide (TMD) materials have emerged...
The commercial success of personal computing has led to the rapid creation and proliferation of diverse electronic systems including desktops, laptops, tablets, mobile devices, and embedded systems. For the past five decades, silicon has served as the base material for computing electronics. However, with increasing demand for unconventional electronics (e.g.,...
The complex structure of typical heterogeneous catalysts, where nanoparticles of active material are dispersed onto the surface of a thermally stable support with a high surface area, complicates the understanding of how the support can affect the resulting catalyst structure and properties. Using well-faceted and shape-controlled oxides as supports would...
Early-stage oxidation and corrosion mechanisms of CoCrMo and NiCrMo alloys can be analyzed on the nanoscale by transmission electron microscopy. Both alloys are attractive for a broad array of applications such gas turbines and aircraft engine components as they are known for their excellent corrosion resistance and mechanical properties at...
Low-dimensional materials have emerged as a promising platform for ultrathin electronic and optoelectronic devices. The span of electronic properties covers the spectrum from metallic through small and medium bandgap semiconductors to large bandgap insulators, providing all the necessary components to fabricate a variety of devices. Compared to bulk-semiconductor based devices,...
Superalloys strengthened by γ′(L12)-precipitates in γ(f.c.c.)-matrix exhibit superior high temperature mechanical properties and environmental resistance over long periods of operation, making them ideal candidates for aerospace and energy conversion applications. The emerging class of superalloys based on Co-Al-W ternary system was identified with a melting temperature 50-100 ˚C higher than...
Dilute Al-Sc-Zr-Si-based aluminum alloys retain their strength for long periods of time at elevated temperatures due to a dispersion of nanometric, coherent, and coarsening-resistant Al3(Sc,Zr) (L12 structure) nanoprecipitates that are formed upon aging. These alloys are attractive for replacement of dense steels and costly Ti alloys in the 250–400 °C...
Water vapor condenses into liquid water when it encounters a cold surface. If the surface temperature is sufficiently low, freezing follows the condensation step, and the process is holistically referred to as condensation frosting. Both phase change processes are fundamental to many industries ranging from water harvesting, thermal management, solar...
Modeling the mechanical performance of metal produced with additive manufacturing (AM) has proven to be a challenging task. In the as-built state, these materials have been shown to exhibit strong heterogeneity and anisotropy. Even after post-processing, such as heat treatment or hot isostatic pressing and depending on the alloy, some...
Organic solar cells (OSC) are a next generation solar energy technology that offers the advantages of scalable fabrication, light weight, flexibility, and earth-abundant starting materials. Despite tremendous advances in OSC power conversion efficiency (PCE) over the last decade, active layer material selection and optimization is still largely empirical. In order...
Two-dimensional (2D) materials and heterostructures have attracted significant attention for a variety of nanoelectronic and optoelectronic applications. At the atomically thin limit, the material characteristics and functionalities are dominated by surface chemistry and interface coupling. Therefore, methods for comprehensively characterizing and precisely controlling surfaces and interfaces are required to realize...
Use of bio-renewable polysaccharides to produce materials with a high technological impact has gained a lot of attention recently. Efforts have been made, for example to produce triboelectric generators from cotton, as well as, nanostructures of chitosan gels for drug delivery. Another well-known example is the use of β-Cyclodextrin (β...
Deformation in materials with a hierarchical microstructure is expected to be complex because of the interaction between the units that form such a microstructure. The complexity of deformation would be even higher when additional inelastic deformation modes are active in such materials, apart from traditional elastic and plastic deformation modes....
This dissertation presents a comprehensive study of thin-film LiMn2O4 (LMO) cathodes applied in lithium ion batteries (LIBs). The primary aim was to establish fundamental understanding of the relationship between interfacial LMO chemistry/electrochemistry and its detrimental drawback, i.e. fast capacity fade over long term cycling, and then develop effective mitigation methods....
Semiconductor nanowires, such as group IV and III-V nanowires, shows distinct electrical, optical and mechanical properties from their bulk counterparts due to their nanoscale size and 1-D morphology. For example, the quantum confinement effect modulates the band gap of a semiconductor nanowire when its diameter approaches or below the exciton...
Solvent-rich polyelectrolyte complexes display a wide range of rheological properties, when different environmental parameters are applied. Due to the low energy barrier of the complexation (~10 kT), these materials possess tunable properties, with the states of these materials varying from Newtonian liquids to very tough hydrogels. This thesis aims to...
Connecting structure and function in nanoscale engineered materials and devices relies on the analysis of the fundamental arrangement of matter, frequently under dynamic conditions. The demand to image structures at fundamental length scales has touched inorganic materials, biology, and frequently hybrid hard/soft materials with unique phenomena driven by heterogeneous components....
The Controlled, Site-Isolated Synthesis of Polyelemental Nanostructures in Polymer Nanoreactors Pengcheng Chen Polyelemental nanoparticles are an attractive class of materials due to their potential applications, which span the fields of catalysis, plasmonics, electronics, magnetics, targeted drug delivery, and bio-imaging. However, conventional synthetic methods for such structures are limited, especially when...
Localized corrosion involves the selective attack of a metal at a small, exposed site. This can be particularly devastating for load-bearing structures like bridges, which can fail catastrophically even with very little material loss. Unfortunately, such corrosion is very hard to prevent, predict, and detect. Corrosion can be prevented by...
The study of magnetic frustration has attracted considerable interest in the fields of materials science and condensed matter physics. Artificial Spin Ices (ASIs) are the primary systems in which magnetic frustration has been studied. To date, most studies on ASIs have been on fully periodic systems. In this thesis, we...