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School of Materials Science and Engineering

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College of Engineering

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Sintering methodologies for silicon carbide ceramics

(Georgia Institute of Technology, 2023-12-11) Wang, Annie Wei Chyi

Silicon carbide (SiC) ceramics are known for their high hardness, light weight, high strength, high oxidation resistance, high thermal shock resistance, low elevated temperature creep, and chemical inertness. Sintering of powder compacts has been via both eutectic liquid-phase and solid-state processes; both were investigated in this study. Solid-state sintering, following the method of Prochazka, requires both carbon and boron (or B4C) sintering aids. In this work the use of C additives alone was shown to be necessary but insufficient for sintering. The mechanical properties of SiC with varying B4C and C were studied with results of 98.31 to 99.66% relative density, 22.76 to 27.66 GPa for Vickers hardness and 3.0 to 4.18 MPa⋅m1/2 for Vickers indentation fracture toughness. The work showed that the merits of increasing B4C addition stopped at the solid solubility limit of B4C in SiC, demonstrated to be at ~0.26 wt%. To investigate the liquid-phase sintering methodologies for silicon carbide, 10 wt% of AlN and Y2O3 were added with a molar ratio of 3:2. The effect of different powder beds for the specimens to be immersed in, and different sintering atmospheres were studied. Four types of powder beds were investigated: pure SiC, 1:1 (wt%) SiC and AlN, the same composition used to make the samples, and pure AlN. It was found that the pure AlN powder bed yielded the highest relative density and finest grain size. This indicated that without the powder bed, the relatively high vapor pressure of AlN (or its vapor decomposition products) in the compact favored either evaporation/condensation particle coarsening or grain growth over sintering; the overpressure provided by the AlN powder bed surroundings thus improved sintering conditions. Four different atmospheres were then studied with the use of a 1:1 SiC and AlN powder bed. The results showed that different sintering dwell temperatures were required for optimum relative density using these different atmospheres. Flowing He requires the lowest sintering dwell temperature (around 1700°C), followed by Ar, static vacuum, and then N2 requiring the highest temperature (~1950°C). These higher dwell temperatures were required from the more difficult diffusivity of larger molecular/atomic sized trapped gases out of sintered bodies of closed porosity. Significant grain growth was observed for temperatures higher than their optimum temperatures, with associated decreasing sintered relative density. The highest relative density (96.37%) was achieved with an atmosphere created by pulling vacuum at room temperature, and then maintaining a static atmosphere during sintering. For optimally sintered specimens exposed to these atmospheres, lower Vickers hardness (15.03-18.35 GPa) were measured compared to solid-state sintered SiC, but very high Vickers indentation fracture toughness (2.92-7.85 MPa⋅m1/2) were obtained. This is associated with the relatively weak grain boundary phase deflecting/branching propagating cracks. This work then investigated the sintering of SiC with lower additive concentrations: 1-4 wt% of AlN and 0-2 wt% of Y2O3, using a flow-through He atmosphere, with the compacts immersed in a pure AlN powder bed. Relative densities were inferior to the previous study; it increased with increasing Y2O3 content. In the absence of Y2O3, AlN acted as a grain growth inhibitor, and points toward the potential merit of a Prochazka composition with AlN additions. A 2-D computer model of sintering was constructed using MATLAB. Green microstructures were represented in a 2-D view. The filled circles representing particles were generated with random number generator and a fall-and-roll algorithm. The sintering process was simulated with sequential algorithms of the initial, intermediate, and final stages of sintering. Each stage with controlling factors that could be input depicts microstructures that would result under differing conditions. The simulation depicted particle neck formation, particle re-shaping, pore elimination (densification), and grain growth, forming microstructures generally consistent with those observed after sintering.
Design of Organic-inorganic Hybrid Membranes Using Density Functional Theory and Machine Learning

(Georgia Institute of Technology, 2023-08-25) Liu, Yifan

Novel organic-inorganic hybrid membranes processed through vapor phase infiltration (VPI) incorporate the advantages of both organic and inorganic materials. Compared to conventional organic membranes, these hybrid materials offer significant improvements in stability when exposed to organic solvents while retaining desirable membrane properties such as high permeability and selectivity. However, the extensive design space involved in developing such membranes, which encompasses polymer chemistry, inorganic chemistry, and hybrid microstructures, poses challenges to traditional trial and error methods. To surmount these obstacles, this work develops a more efficient and systematic approach. It involves three steps that leverage density functional theory (DFT) and machine learning (ML) to develop the knowledge and tools necessary to predict and explore novel VPI organic-inorganic membranes: 1. This research entails an in-depth investigation into the interactions between three metal precursors and the prototype polymer of intrinsic microporosity 1 (PIM-1) during the VPI process. Our primary objective was to identify crucial characteristics of polymer-inorganic interactions, decipher structure-property relationships, and unveil significant properties that could contribute to ML model predictions for future materials selection. Our work uncovered two atomic-level mechanisms for solvent stability. 2. An ML-based tool predicting sublimation enthalpy was developed to aid chemistry selection and experimental design for precursors. Initial training used a comprehensive DFT dataset of organic molecules constructed in this work due to a lack of metal precursor parameters in the literature. As new data emerged, an active learning algorithm incorporated new chemical species into the model, dynamically improving its accuracy and expanding its applicability. 3. An ML model, incorporating multi-task learning and meta-learning, was trained on a new DFT dataset to predict binding energy between metal precursors and polymers. This enhanced the understanding of polymer-inorganic interactions’ strength and stability, aiding in the selection of potential precursors. The model provides a promising route for informed precursor selection, VPI process optimization, and the design of hybrid materials with custom properties. This foundational work provides automated and effective tools for the design and development of VPI organic-inorganic hybrid membranes, leveraging the combined capabilities of DFT and ML. The predictive models developed here can be employed alongside the insights derived from our atomic-level mechanistic studies in the selection of suitable polymers and metal precursors for designing energy-efficient organic-inorganic hybrid membranes for chemical separation. In addition, the DFT database and ML models developed in this project serve as valuable instruments to be utilized by researchers for future studies on the sublimation enthalpy and binding energy of organic-inorganic systems, facilitating further advancements in the field of material science. This thesis presents and executes a methodical framework through which future models can be developed for the exploration of novel material spaces.
Structure-Property Relationships in Lead Halide Perovskites for Solar Cells

(Georgia Institute of Technology, 2023-07-14) Hidalgo, Juanita

Lead halide perovskites (LHPs) solar cells, particularly FA-based, have made impressive advancements in solar energy conversion, achieving high power conversion efficiencies exceeding 26% for a single junction device. However, the limited long-term stability of these devices has hindered their commercialization. The instability issues are influenced by both internal and external factors, leading to rapid degradation of the perovskite phase and overall device performance. Various strategies have been used to stabilize the perovskite phase, but it is crucial to investigate the underlying mechanisms that govern the structural characteristics of the polycrystalline thin films. This dissertation tackles the challenges associated with the instability of LHPs by investigating the complex relationship between structure, properties, and performance in perovskite solar cells. Advanced X-ray characterization techniques are employed to examine the structural properties of FA-based compositions. Understanding the mechanisms and establishing correlations between structure and properties is possible to lay the foundation of a more robust, stable, and efficient material. This dissertation presents a first step toward the design and optimization of LHPs. The first part of this dissertation explores the crystallographic orientation in lead bromide perovskites, demonstrating that the solvent and organic cation used in the precursor solution significantly affect the preferred orientation of the deposited perovskite thin films. The solvent affects the early stages of crystallization and induces preferred orientation by preventing colloidal particle interactions. The choice of organic cation influences the degree of crystallographic orientation, with methylammonium-based perovskites showing a higher degree of orientation than formamidinium-based ones due to a lower surface energy of a specific perovskite facet. These findings identify the importance of understanding (1) the precursor solution chemistry, (2) the facet properties and their correlation with the structural properties of the polycrystalline LHP film, and (3) the effect of crystallographic orientation on charge carrier transport in perovskite solar cells. The second part of this dissertation studies the mechanisms causing FA-based lead iodide perovskites to degrade under water and oxygen exposure. Contrary to common knowledge on humidity-induced degradation, this dissertation reveals the synergistic role of water and oxygen in accelerating phase instability of LHPs. The study uncovers a surface reaction pathway involving the dissolution of formamidinium iodide (FAI) by water followed by the oxidation of iodide, playing a crucial role in causing the subsequent and irreversible undesired phase transformations from perovskite into non-perovskite phases. The interplay of in-situ experimental techniques with theoretical calculations provides a detailed understanding of the degradation mechanisms, establishing a foundation to design more durable and efficient materials. Finally, this dissertation delves into strategies for stabilizing the perovskite phase. A hydrophobic molecule, phenethylammonium iodide (PEAI), stabilizes FA-based perovskites. Adding PEAI hinders undesired phase transformations and leads to a more stable material with improved solar cell power conversion efficiency and enhanced charge carrier mobilities and lifetimes. Further, adding Br to mixed cation lead iodide perovskites improves their phase stability at low temperatures. Overall, understanding structure-property-performance relationships in lead halide perovskites is key for resolving the main challenge of instability in perovskite solar cells. This dissertation lays the groundwork for future research efforts to investigate the fundamentals of LHPs, improve their stability, and broaden their applications in solar cells and beyond.
Microstructural Prediction of Additively Manufactured Multi-Phase Materials

(Georgia Institute of Technology, 2023-05-03) Standish, Mike

Material modeling is the central theme of this thesis. Experimentation of titanium alloys and composites provided background knowledge of the time and financial costs associated with testing and re-testing properties in a forensic, trial-and-error manner. The model discussed in this thesis merges material properties and process parameters to generate a unique microstructure for the titanium 6Al-4V (Ti-6-4) alloy produced using selective laser melting additive manufacturing SLM-AM. The material texture is generated by first calculating melt pool geometries using Rosenthal Solution equations and Bunge matrix transformations. The result is a single-phase representation of a liquidus, BCC beta titanium phase deposited over a random-orientation substrate. The texture is then transformed into a two-phase alpha (HCP)-beta microstructure through transformation pathways modeled based on mechanisms discovered in other studies. The final texture product can then be input into other models capable of computing mechanical properties based on texture inputs. Though no model can be fully comprehensive in simulating material nature and behavior, the model in this thesis adapts enough experimental data and follows enough phenomenological observations within the field of material science and engineering to produce simulated samples capable of achieving realistic property values. The model is scripted in a manner where it can be adapted for alternative materials by inputting different properties and tailoring the process settings. Multiple benefits arise from being able to model material microstructures without the need to physically test real-world samples. There is a substantial time savings in being able to quickly adjust properties and formulations. Expensive equipment, materials, and labor can all be avoided, and a larger testing matrix can be executed through this approach.
Understanding the mechanisms and parameters affecting the structural corrosion of sheet gauge 7xxx alloys

(Georgia Institute of Technology, 2023-04-27) Bhaskaran, Ganesh

The light-weighting of automotive structures has been an effective method of increasing vehicle fuel efficiency. In the past, the use of aluminum alloys was limited to hang-on parts and outer skin applications to reduce weight. However, due to the high strength-to-weight ratio of 7xxx series alloys, exciting alternative options for replacing high-strength steels in load-bearing or structural applications have emerged. These alloys derive their strength through the precipitation hardening mechanism, which involves the formation of nanosized precipitates after a specific heat treatment sequence. However, one of the main roadblocks to the penetration of 7xxx alloys in structural applications like rockers and bumpers is concerns regarding structural forms of corrosion, such as intergranular corrosion (IGC) and stress corrosion cracking (SCC). These can be attributed to the microstructure features of the grain boundary, specifically the precipitate and adjoining precipitate-free zone. Most published structural corrosion work on 7xxx alloys has been associated with plate gauge applications with thicknesses greater than 10mm. However, for automotive applications, sheet type with thicknesses of 1.5 to 2.8mm is desired, as it enables weight reduction without loss of dent resistance while meeting stiffness requirements. Moreover, the difference in the manufacturing process between sheet and plate leads to a distinct microstructure. The objective of this study is to examine the impact of processing sequence, alloy composition, and joining methods on grain boundary microstructure, as well as to understand their potential impact on the structural forms of corrosion in sheet gauge 7xxx alloys. Due to the complex grain boundary microstructure and corrosion property relationship, an efficient research scheme was needed to minimize or isolate the secondary effects. The research scheme was designed in such a manner that when one of the variables of interest was changed, the rest of the processing parameters were kept constant. The research is divided into three sections. In the first part, two different processing sequences were utilized to alter the grain size of the material. They were recovery anneal of final gauge material and reduction of the percentage of cold work on hot-rolled material. The grain boundaries were characterized using scanning transmission electron microscopy (STEM) to determine the width of the precipitate-free zone, the size and continuity of grain boundary precipitates between the finer and coarser grain materials. The samples were then subjected to IGC and SCC tests to determine the impact of microstructure on the corrosion mechanism. In the second part, the effect of Cu and Zn/Mg ratio on the resulting microstructure of high-solute 7xxx alloys and their impact on corrosion resistance was evaluated, with a specific focus on the effect of testing environment and constituent particles on localized corrosion resistance. In the third part, the microstructure changes, and their impact on the corrosion properties of commonly used automotive joining methods, such as resistance spot welding (RSW) and self-pierce rivet (SPR), were evaluated for the dissimilar aluminum alloy joint of 7075-T6 to 5182-O. The gradient microstructure of the joint sections was characterized and evaluated for corrosion resistance. The study revealed that the three factors (processing, composition, joining) uniquely influenced the size, continuity, and composition of the grain boundary precipitates and adjoining precipitate-free zone, which in turn affected the IGC and SCC performance of the materials. The results also showed that the grain boundary features that control the corrosion mechanism vary uniquely, depending on the environment. The findings of this research have significant implications for the development of 7xxx sheet gauges, particularly in the areas of alloy design, manufacturing process selection, and end application. The study will provide valuable insights into improving the corrosion resistance of these alloys, which will enable them to compete more effectively with ultra-high strength press-hardened steel in automotive structural applications. Ultimately, this research has the potential to contribute to the development of the next generation of high-performance aluminum alloys.
The impact of mass transport and surface charging on the performance of field effect transistor biosensors

(Georgia Institute of Technology, 2023-04-25) Jin, Decarle

Biosensors are critical components of the healthcare system and are used for a wide variety of applications including screening of serological diseases, early detection of infectious viruses, and chronic disease treatment. This work aims to improve the performance of FET biosensors through elucidation of fundamental material concepts that control sensor performance and reliability. Previous work has suggested that FET sensors made from semiconducting nanowires have improved limits of detection compared to traditional planar FETs. In this work, a general model was develop including the effects of reaction, diffusion, and convection applicable to both planar and nanowire sensors. The model shows that, given enough flow, the accelerated diffusion observed by a cylindrical nanowire can be ignored. Rather, the sensor size has a greater effect under flow with nanometer sized sensors capable of reaching the reaction-limited regime. After a molecule successfully attaches, it must generate a measurable signal. One aspect often ignored is that surfaces themselves are charged before any biomolecule attachment. This surface charge can also be variable, depending on solution pH, as is the case for amphoteric surface sites of metal oxides. This pH dependent surface charge arises as a pH sensitivity of the sensor. A theoretical model was previously developed demonstrating that a pH sensitive surface such as a metal oxide can pin the surface potential, reducing the surface potential shift caused by biomolecule attachment. This work uses gFETs to investigate the relationship between pH sensitivity and biosensitivity. The results show that the existence of pH sensitivity does not simply cause a decrease in biosensitivity. Rather, this decrease does not occur unless sufficient surface charging is present, which is dependent on multiple factors such as ion concentration and the acid dissociation constant of the surface groups. Furthermore, the results suggest that the effect of ionic screening may be overestimated as has been previously demonstrated in literature. Another challenge encountered with FET sensors is integration into complete sensor systems. Two sensor prototypes were developed here. First, a multiplexed sensor chip was developed for use in a 3D printed, wireless, biosensor capsule designed for continuous monitoring of cell properties in bioreactors. The multiplexed sensor chip can detect pH, glucose, lactic acid, and protein biomarker detection is under development. Additionally, a Au EGFET E. coli sensor was developed for use in a drone-operated biowarfare defense system. E. coli sensing was demonstrated with a LOD of 107. The performance of FET sensors depends upon fundamental material concepts such as mass transport and surface charging.
Engineering a self-aligned metal-oxide-semiconductor gate stack for nano-modular device fabrication

(Georgia Institute of Technology, 2023-04-25) Brummer, Amy C.

By shifting the existing semiconductor fabrication paradigm and embracing scalable, bottom-up manufacturing techniques, fully formed high-performance transistors can be produced and interconnected for low-cost fabrication of customizable circuitry. For example, high-performance modular nanowire transistors can be synthesized using bulk processing methods. The pre-fabricated devices can be deposited on a substrate, and metal interconnects can be adaptively printed to form circuits. This work focuses on developing a self-aligned gate stack that would enable the production of bottom-up nanowire electronic devices and on understanding how material deposition and post-processing impacts performance of the devices. To investigate the gate stack materials, this work adapts a selective, bottom-up polymer patterning process for planar Si substrates to fabricate and characterize self-aligned metal-oxide-semiconductor (MOS) capacitor devices. Selectivity of deposition is investigated for a variety of oxides and metals via area-selective atomic layer deposition, and ultimately hafnium oxide (HfO2) and platinum are determined to be the optimal materials system. The quality of the oxide-semiconductor interface is particularly important for MOS device performance, so the HfO2-Si interface is investigated in detail by examining different SiO2 interlayer formation techniques. Physical characterization is used to understand the relationship between the interlayer formation and electrical performance. In summary, this work develops a self-aligned gate stack fabrication process and investigates the impact of processing on the electrical performance of the materials. And this self-aligned gate stack deposition process provides a pathway towards fabricating modular nanowire transistors.
Characterizing Plastic Deformation Mechanisms in Metal Thin Films using In Situ Transmission Electron Microscopy Nanomechanics

(Georgia Institute of Technology, 2023-04-19) Stangebye, Sandra

The demand for smaller, smarter and faster devices has motivated continued research into understanding the mechanical behavior of small-scale materials used to create micron-sized features for devices such as flexible or stretchable electronics or micro electromechanical systems (MEMS). Nanocrystalline (NC) and ultrafine-grained (UFG) metal thin films show increased strength when compared to their coarse-grained equivalents, and as a result, have been proposed as viable solutions to high-strength MEMS materials. The increased yield strength is generally attributed to the high volume of grain boundaries (GB) which impede conventional dislocation glide. Unfortunately, the increase in strength is accompanied by a decrease in ductility. NC and UFG metals also exhibit an increase in strain-rate sensitivity and decrease in measured activation volume compared to their coarse-grained equivalents, both of which imply different atomistic mechanisms control the deformation. There remains a lack of quantitative characterization of these deformation mechanisms which hinders material design towards exception mechanical properties. In this work, the plastic deformation mechanisms that govern the mechanical properties of NC and UFG metal thin films are investigated through in situ transmission electron microscopy (TEM) nanomechanical experiments. This technique allows for the simultaneous observation of the active deformation mechanisms and quantification of the mechanical properties during monotonic and stress-relaxation experiments. Experiments were performed on NC Al and UFG Au specimens with different microstructures (grain sizes, thickness, texture), including irradiated UFG Au. A variety of deformation mechanisms have been identified, including dislocation nucleation and absorption at GBs, inter- and intragranular dislocation glide, and GB migration. It was found that the radiation damage in the irradiated UFG Au served as effective pinning points for transgranular dislocation glide, however, stress-assisted GBM was still active and effectively removed radiation damage as the defects were absorbed by the GB during migration. This resulted in defect-free (‘cleaned’) regions that can support unrestricted dislocation glide, suggesting that stress-assisted GBM is a healing mechanisms for radiation damage in UFG metals. The measured activation volume was found to increase with increasing grain size, decreasing stress level, and the addition of radiation damage. These values were compared with existing models to suggest that there is likely a competition between active displacive- and diffusive-type deformation mechanisms and that the contribution of the two depends on the microstructure. Furthermore, stress-assisted GB migration was studied in detail to investigate how the local microstructure influences boundary migration. This is completed by combining orientation mapping with in situ TEM straining to document the stress-induced migration behavior across boundaries of different structure.
Design and Demonstration of Mechanical and Electrical Reliability of 1-micron Redistribution Layers

(Georgia Institute of Technology, 2022-12-13) Nimbalkar, Pratik

High-performance computing applications have historically driven advances in device and packaging technologies. Emergence and exponential growth of artificial intelligence, data centers and internet-of-things (IoT) have fueled the need for faster computing. The ever-growing need for faster computing has led us to the current generation integrated circuits (IC) having billions of transistors on a small area of a few square millimeters. This has brought transistor scaling to its physical and economic limits. The focus has now shifted to package-integration of chiplets due to physical and economic drawbacks associated with the System-on-chip (SoC) approach. The slow-down of Moore’s law has forced the semiconductor industry to look for alternatives to continue system scaling. Advanced semiconductor packaging is being widely accepted as the most important component for further system and performance scaling. Package integration requires high bandwidth and low latency connections between the chiplets especially between logic and memory dies. Package redistribution layers (RDL) interconnect various system components such as logic, memory and passive components. RDLs are important components of an electronic package and require significant performance improvements in the coming years to handle the requirements of higher bandwidth. This necessitates increasing the IO density and improvements in electrical performance. Increasing RDL IO density translates to scaling down RDL linewidth and spacing. Whereas, electrical performance improvement translates to minimizing electrical losses and reducing crosstalk. For reducing parasitic losses and crosstalk, lowering of RDL capacitance is critical. Traditional silicon back-end RDL uses silicon-dioxide as a dielectric which has a relatively high dielectric constant (Dk=4) and thus has fundamental limitations to improving electrical performance. Therefore, ultra-low-k (ULK) polymer dielectrics with Dk<3 are the focus of this research. Advances in photoresist materials, lithography tools and processes are necessary to enable higher RDL IO density with ULK dielectrics. In recent years, there has been significant progress in all these areas. Most of the developments have occurred in silicon interposers that continue to be the highest IO-density packaging platforms providing more than 1000 IOs/mm/layer. However, panel-scale solutions still remain at larger linewidth and spacing (L/S) >5 µm. Recent advances in panel-scale fan-out and interposer solutions have approached 2/2 µm L/S using semi-additive processing (SAP). Traditional silicon back-end RDL uses dual damascene process to form redistribution wiring. Wafer-scale processing makes the back-end RDL less cost-effective than the panel-scale SAP. Package RDL has been conventionally formed using SAP. However, there are several process limitations imposed by standard SAP in achieving sub-micron dimensions. The objectives of this research are to address the scaling limitations of multi-layer polymer RDL down to 1 µm and below. This research is focused on addressing these limitations by demonstrating designs, models, materials, and processes for - (1) high aspect ratio RDL with 1 µm L/S and 2 µm vias (2) mechanical reliability of multi-layer structure and (3) electrical reliability of ULK dielectrics.
Investigation Into Strategies for Enhanced Electrocatalytic Activities of Spinel-Based Transition Metal Oxide Nanoparticles

(Georgia Institute of Technology, 2022-12-02) Sewell, Christopher David

As the severity of global climate issues continues to build, the need for clean energy storage and conversion devices has become increasingly pressing. The production of green hydrogen through water electrolysis is a promising route to alleviating these challenges. However, the high cost and scarcity of the state-of-the-art noble metal-based electrocatalysts utilized in such processes represents one of the critical hurdles to be overcome prior to their practical implementation. A promising direction is to utilize transition metal-based nanoparticles (NPs), which offer superior electrocatalytic performance over their bulk counterparts. The work in this dissertation systematically investigates strategies to improve the electrocatalytic performance of transition metal-oxide NPs. Capping the surface of NPs with polymers is widely recognized as an effective means towards their dispersion and stabilization. However, it is often circumvented due to its tendency to lower the electrocatalytic activity of the ligated NPs. In this context, the first systematic investigation into the impact of the chain density and hydrophilicity of the surface-capping polymers, which can be judiciously regulated, on the oxygen evolution reaction (OER) activity is performed. By capitalizing on star-like diblock copolymers as nanoreactors, spinel CoFe2O4 (CFO) NPs permanently ligated with polymers of interest (i.e., varied chain density and characteristic) are crafted. The correlation between the chain density and hydrophilicity of surface-capping polymers and the OER activity of CFO NPs are scrutinized. Intriguingly, decreasing the number of surface-capping chains and increasing the chain hydrophilicity result in significantly decreased overpotential, caused by an increased exposure of the active material (CFO) to the electrolyte and reduced diffusion resistance. This study provides insight into the strategies for mitigating the activity-limiting properties of surface polymers and tailoring the electrocatalytic properties of polymer-ligated NPs. Recently, the use of externally applied magnetic fields has garnered significant attention as a promising strategy to enhance OER electrocatalytic performance. OER exhibits spin-dependent kinetics, producing triplet O2 from singlet reactants (OH-, H2O). Notably, magnetization can reduce this kinetic barrier by aligning the spin ordering of ferromagnetic (FM) electrocatalysts. Unfortunately, some of the most active OER catalysts, namely transition metal oxyhydroxides, are paramagnetic (PM). This can be circumvented by utilizing a spin pinning effect in FM/PM core/shell materials, which has already been successfully demonstrated in a bulk CFO/CoFeOxHy system. In this work, previous research is built upon by examining a similar system at the nanoscale. Star-like block copolymers prepared via sequential atom transfer radical polymerization were successfully utilized as nanoreactors to synthesize CFO nanoparticles. The surfaces of CFO nanoparticles were successfully doped with sulfur under mild conditions, enabling the successful surface reconstruction of S-doped CFO into a more active oxyhydroxide phase. Successful spin-pinning was verified by an observed increase in OER activity following the application and removal of a magnetic field; thus, confirming that spin-pinning remains a viable OER-enhancement technique even at the nanoscale. This study lays the groundwork for future systematic studies on the effects of NP size and core-to-shell ratio on the magnetic field-rendered OER enhancement. In addition to externally applied magnetic fields, other effects can be introduced during electrocatalysis to improve performance. Previous research has found that some spinel NPs, NiFe2O4 (NFO) for example, experience a photothermal effect upon near-infrared light irradiation which promotes the dynamic generation of active OER sites. Thus, in this dissertation, both the magnetic field-based enhancement and photothermal effect are collectively exploited to further improve the OER electrocatalytic ability of NFO NPs. Concurrent application of magnetic field and photothermal effect is demonstrated to further enhance the OER activity of NFO NPs. Interestingly, the significant increase in activity observed was primarily attributed to a greatly promoted surface reconstruction. It is determined that the application of a magnetic field during chronopotentiometry can promote surface reconstruction to a similar degree of inducing the photothermal effect. This work documents a new strategy to induce surface reconstruction in NiFe2O4, opening up the door for future studies employing different electrocatalytic materials and investigating the mechanisms of magnetic-field enhanced surface reconstruction. The findings in this dissertation serve as an important step towards the practical implementation of OER-limited devices, such as water electrolyzers. Various strategies to enhance the OER activity of metal-oxide nanoparticles have been presented. Excitingly, future work can build upon the investigated methods to enable low-cost, low-complexity electrocatalysts to serve as competitive alternatives to state-of-the-art noble-metal based catalysts.