Condensed Matter Physics Commons^™

Effects Of Ti Addition On The Characteristics Of Al-10zn-6mg-2si/Zro2 Composites Produced By Squeeze Casting, Qesha Diva Prameshvara, Pipin Indah Lestari, Bondan Tiara Sofyan

Journal of Materials Exploration and Findings

Metal matrix composite (MMC) with 7xxx aluminum matrix is potential for ballistic applications due to the combination of strength, toughness, and light weight. Previous study successfully produced aluminum-based composites with SiC particles which were able to stop type III bullet, however cracks remained on back of the plate. Therefore, in this research, SiC was replaced by zirconia (ZrO₂) due to its high fracture toughness. Ti-B grain refiner was added to further improve toughness through grain boundary strengthening mechanism. This research developed 5 vol.% ZrO₂ strengthened Al-10Zn-6Mg-2Si composite with addition of Al-5Ti-1B grain refiner produced through squeeze casting …

Encapsulated 2d Materials And The Potential For 1d Electrical Contacts, Sarah Wittenburg

Physics Undergraduate Honors Theses

The utilization of two-dimensional materials and heterostructures, particularly graphene and hexagonal boron nitride, have garnered significant attention in the realm of nanoelectronics due to their unique properties and versatile functionalities. This study focuses on the synthesis and fabrication processes of monolayer graphene encapsulated between layers of hBN, aiming to explore the potential of these heterostructures for various electronic applications. The encapsulation of graphene within hBN layers not only enhances device performance but also shields graphene from environmental contaminants, ensuring long-term stability. Experimental techniques, including mechanical exfoliation and stamp-assisted transfer, are employed to construct three-layer stacks comprising hBN-graphene-hBN. The fabrication process …

Machine Learning Prediction Of Photoluminescence In Mos2: Challenges In Data Acquisition And A Solution Via Improved Crystal Synthesis, Ethan Swonger, John Mann, Jared Horstmann, Daniel Yang

Seaver College Research And Scholarly Achievement Symposium

Transition metal dichalcogenides (TMDCs) like molybdenum disulfide (MoS2) possess unique electronic and optical properties, making them promising materials for nanotechnology. Photoluminescence (PL) is a key indicator of MoS2 crystal quality. This study aimed to develop a machine-learning model capable of predicting the peak PL wavelength of single MoS2 crystals based on micrograph analysis. Our limited ability to consistently synthesize high-quality MoS2 crystals hampered our ability to create a large set of training data. The project focus shifted towards improving MoS2 crystal synthesis to generate improved training data. We implemented a novel approach utilizing low-pressure chemical vapor deposition (LPCVD) combined with …

The Interplay Of Spin, Charge, And Heat: From Metal/Insulator Heterostructures To Perovskite Bilayers, Sam M. Bleser

Electronic Theses and Dissertations

In this dissertation begin with an investigation of non-local spin transport in an amorphous germanium (a-Ge) sample via the inverse spin Hall effect (ISHE). In that study we show that commonly used techniques such as differential conductance and delta mode of a paired Keithley 6221/2182a for non-local resistance measurements can lead to false indicators of spin transport. Next, we turn out attention to a thickness dependent study in thermally-evaporated chromium (Cr) thin films on a bulk polycrystalline yttrium-iron-garnet (YIG) substrate. This project analyzed the spin transport in the Cr films versus thickness via the longitudinal spin Seebeck effect (LSSE). This …

Thermal, Electrical, And Spin Transport: Encompassing Low-Damping Ferromagnets And Antiferromagnetic/Ferromagnetic Heterostructures, Matthew Ryan Natale

Electronic Theses and Dissertations

Continuing technological advancements bring forth escalating challenges in global energy consumption and subsequent power dissipation, posing significant economic and environmental concerns. In response to these difficulties, the fields of thermoelectrics, spintronics, and spincaloritronics emerge as contemporary solutions, each presenting unique advantages. Thermoelectric devices, based on the Seebeck effect, other a passive, carbon-free energy generating solution from waste heat. Although current thermoelectric technology encounters hurdles in achieving optimal efficiencies without intricate designs or complex materials engineering, recently research into low-damping metallic ferromagnetic thin films have provided a new method to enhance spin wave lifetimes, thus contributing to thermoelectric voltage improvements. As …

Combined Risk Based Inspection And Fault Tree Analysis For Repetitive 3-Phase Line Piping Leakage At West Java Offshore Topside Facility, Dona Yuliati, Akhmad Herman Yuwono, Datu Rizal Asral, Donanta Dhaneswara

Journal of Materials Exploration and Findings

Hydrocarbon releases might result in serious consequences in various aspects. In addition to the contribution to environmental pollution, repetitive leakages need high repair costs. This study aim is to minimize potential repetitive leakage for other typical 3-phase piping systems. We conducted the risk assessment by adopting Risk Based Inspection (RBI) API 581 to identify risk level, calculating piping lifetime, recommended inspection plan and mitigations. The most relevant root causes can be obtained through quantitative Fault Tree Analysis (FTA). Observation and investigation was taken from eight 3-phase piping systems that experienced repetitive leakages. It has been found that the risk level …

Nitrogen Gas Quenching Pressure Effect On Bs S155 Alloy Steel In Vacuum Furnace, Agus Mulyadi Hasanudin, Eddy Sumarno Siradj

Journal of Materials Exploration and Findings

The production of metal and alloy products requires the use of heat treatment, when during the heat treatment process, quenching is a crucial step. The quenching medium can be anything from water, a salt bath, oil, air and gas. In a vacuum furnace, pressurized gas, most frequently nitrogen (N₂) gas, serves as one of the quenching mediums. One of the drawbacks of the quenching process is the distortion and dimensional change of the parts. This paper aims to investigate the influence of nitrogen gas quenching pressure on the distortion and dimensional change of aerospace actuator gear planet parts …

Atomic-Level Mechanisms Of Fast Relaxation In Metallic Glasses, Leo W. Zella

Doctoral Dissertations

Glasses are ubiquitous in daily life and have unique properties which are a consequence of the underlying disordered structure. By understanding the fundamental processes that govern these properties, we can modify glasses for desired applications. Key to understanding the structure-dynamics relationship in glasses is the variety of relaxation processes that exist below the glass transition temperature. Though these relaxations are well characterized with macroscopic experimental techniques, the microscopic nature of these relaxations is difficult to elucidate with experimental tools due to the requirements of timescale and spatial resolution. There remain many questions regarding the microscopic nature of relaxation in glass …

Breakdown Of The Drift-Diffusion Model For Transverse Spin Transport In A Disordered Pt Film, Kirill D. Belashchenko, Giovanni G. Baez Flores, Wuzhang Fang, Alexey Kovalev, Mark Van Schilfgaarde, Paul M. Haney, Mark D. Stiles

Department of Physics and Astronomy: Faculty Publications

Spin-accumulation and spin-current profiles are calculated for a disordered Pt film subjected to an in-plane electric current within the nonequilibrium Green's function approach. In the bulklike region of the sample, this approach captures the intrinsic spin Hall effect found in other calculations. Near the surfaces, the results reveal qualitative differences with the results of the widely used spin-diffusion model, even when the boundary conditions are modified to try to account for them. One difference is that the effective spin-diffusion length for transverse spin transport is significantly different from its longitudinal counterpart and is instead similar to the mean-free path. This …

Majorana Bound States In A D-Wave Superconductor Planar Josephson Junction, Hamed Vakili, Moaz Ali, Mohamed Elekhtiar, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

We study phase-controlled planar Josephson junctions comprising a two-dimensional electron gas with strong spin-orbit coupling and d-wave superconductors, which have an advantage of a high critical temperature. We show that a region between the two superconductors can be tuned into a topological state by the in-plane Zeeman field, and can host Majorana bound states. The phase diagram as a function of the Zeeman field, chemical potential, and the phase difference between superconductors exhibits the appearance of Majorana bound states for a wide range of parameters. We further investigate the behavior of the topological gap and its dependence on the …

Thermal, Magnetic, And Electrical Properties Of Thin Films And Nanostructures: From Magnetic Insulators To Organic Thermoelectrics, Michael J. M. Roos

Electronic Theses and Dissertations

Modern fabrication and growth techniques allow for the development of increasingly smaller and more complex solid state structures, the characterization of which require highly specialized measurement platforms. In this dissertation I present the development of techniques and instrumentation used in magnetic, thermal, and electrical property measurements of thin films and nanostructures. The understanding of trapped-flux induced artifacts in SQUID magnetometry of large paramagnetic substrates allows for the resolution of increasingly small moments. Using these methods, the antiferromagnetic coupling of the interface between a Y₃Fe₅O₁₂ film and Gd₃Ga₅O₁₂substrate is quantitatively …

Effective Nanomembranes From Chitosan/Pva Blend Decorated Graphene Oxide With Gum Rosin And Silver Nanoparticles For Removal Of Heavy Metals And Microbes From Water Resources, Mohamed Morsy

Nanotechnology Research Centre

No abstract provided.

Influence Of Platinum Nanoparticles On Ionic Transport And Hydrogen Reactivity Of Yttria-Stabilized Zirconia Thin Films, Firas Mahyob

Electronic Theses and Dissertations

Yttria-stabilized zirconia (YSZ) is a widely used ceramic material in solid oxide fuel cells, oxygen sensors, and sensing applications due to its high ionic conductivity, chemical inertness, and thermal stability. YSZ is promising active coating for use in miniaturized harsh environment wireless surface acoustic sensors to monitor gases such as H₂. Adding catalytic Pt nanoparticles can enhance gas reactivity and lead to associated film conductivity changes.

In this work, thin films with an (8% Y₂O₃ - 92% ZrO₂) composition were deposited onto piezoelectric langasite substrates using RF magnetron sputtering in Ar:O₂ - …

Understanding And Tuning Magnetism In Van Der Waals Magnetic Compounds, Rabindra Basnet

Graduate Theses and Dissertations

The recently discovered two-dimensional (2D) magnetism has attracted intensive attention due to possible magnetic phenomenon arising from 2D magnetism and their promising potential for spintronics applications. The advances in 2D magnetism have motivated the study of layered magnetic materials, and further enhanced our ability to tune their magnetic properties. Among various layered magnets, tunable magnetism has been widely investigated in metal thiophosphates MPX3. It is a class of magnetic van der Waals (vdW) materials with antiferromagnetic ordering persisting down to atomically thin limit. Their magnetism originates from the localized moments due to 3d electrons in transition metal ions. So, their …

Super P-Sulfur Cathodes For Quasi-Solid-State Lithium-Sulfur-Batteries., Milinda Bharatha Kalutara Koralalage

Electronic Theses and Dissertations

Lithium-Sulfur (Li-S) batteries have become a promising candidate to meet the current energy storage demand, with its natural abundance of materials, high theoretical capacity of 1672 mAhg-1, high energy density of 2600 Whkg-1, low cost and lower environmental impact. Sulfide based solid state electrolytes (SSEs) have received greater attention due to their higher ionic conductivity, compatible interface with sulfur-based cathodes, and lower grain boundary resistance. However, the interface between SSEs and cathodes has become a challenge in all solid-state Li-S batteries due to the rigidity of the participating surfaces. A hybrid electrolyte containing SSE coupled with a small amount of …

Fabrication Of Black Phosphorus Terahertz Photoconductive Antennas, Nathan Tanner Sawyers

Physics Undergraduate Honors Theses

Terahertz (THz) photoconductive antennas (PCAs) using 40nm thin-film flakes of black phosphorus (BP) and hexagonal boron nitride (hBN) have been shown computationally to be capable of THz emission comparable to those based on GaAs [2]. In this paper, I briefly describe the scientific and practical interest in THz emissions and explain what warrants research into black phosphorus as a photoconductive semiconductor in THz devices. Furthermore, I outline the basic principle of how these antennas work and mention alternative designs produced by other researchers in the past. Finally, I summarize the fabrication process of these antennas, as well as the measurements …

Architecture Of Heptagonal Metallo-Macrocycles Via Embedding Metal Nodes Into Its Rigid Backbone, A.M.Shashika D. Wijerathna, He Zhao, Qiangqiang Dong, Qixia Bai, Zhiyuan Jiang, Jie Yuan, Jun Wang, Mingzhao Chen, Markus Zirnheld, Rockwell T. Li, Yuan Zhang, Yiming Li, Pingshan Wang

College of Sciences Posters

Metal-organic macrocycles have received increasing attention not only due to their versatile applications such as molecular recognition, compounds encapsulation, anti-bacteria and others, but also for their important role in the study of structure-property relationship at nano scale. However, most of the constructions utilize benzene ring as the backbone, which restricts the ligand arm angle in the range of 60, 120 and 180 degrees. Thus, the topologies of most metallo-macrocycles are limited as triangles and hexagons, and explorations of using other backbones with large angles and the construction of metallo-macrocycles with more than six edges are very rare.

In this study, …

Development Of High Kinetic Inductance Superconducting Nanowire Devices On High Permittivity Strontium Titanate Substrates, Jamie Timmons

UNF Graduate Theses and Dissertations

This thesis involves the fabrication and characterization of devices made from two different superconducting materials: yttrium barium copper oxide (YBCO), a high-TC complex oxide, and niobium nitride (NbN), a low-TC transition metal nitride. Both types of devices are fabricated on strontium titanate substrates, which provides a good lattice match to YBCO and also an extremely large permittivity at low temperature. We demonstrate that wet etching of YBCO thin films via bromine can be a viable microfrabriation technique for the material. Using approximately 35 nm thick epitaxially grown YBCO on an STO substrate, we were able to fabricate YBCO “microwires” with …

Diffuse Scattering And 3d-∆Pdf Analyses: Order-Disorder Phase Transitions In (Sr1−Xcax)3rh4sn13 And Nano2, Puspa Upreti

Graduate Research Theses & Dissertations

Classification of structural phase transitions as being of the displacive or order-disorder types is usually done based on spectroscopic measurements performed above the transition. Transitions of the displacive type typically occur when soft phonon modes condense upon approaching the phase transition, whereas those of the order-disorder type are characterized by structures in which the atoms are located randomly above the phase transition at T* at the minima of a multiwell potential. In the ordered state, i.e., when T

We have performed single crystal x-ray scattering experiments and three-dimensional pair distribution functions (3D-∆PDF) analyses to understand the nature of phase transitions …

Towards The Electronic Response Of Carbon-Based Van Der Waals Heterostructures In A Diamond Anvil Cell, George Thomas Foskaris

UNLV Theses, Dissertations, Professional Papers, and Capstones

The nanoscale regime of materials has been at the forefront of research and interest in condensed matter physics for many years. In a merger of the fields of two-dimensional (2D) materials and high pressure physics, we present an investigation of the electronic response of carbon-based, van der Waals (vdW) heterostructures in a diamond anvil cell (DAC). Combining these fields presents us with the ability to study the characteristics of such systems both optically, and through electrical transport. Properties such as conductance, band structure, and layer number are considered. The samples in this study are assembled using exfoliation and stacking techniques …

Characterization Of Losses In Superconducting Radio-Frequency Cavities By Combined Temperature And Magnetic Field Mapping, Ishwari Prasad Parajuli

Physics Theses & Dissertations

Superconducting radio-frequency (SRF) cavities are one of the fundamental building blocks of modern particle accelerators. To achieve the highest quality factors (10¹⁰-10¹¹), SRF cavities are operated at liquid helium temperatures. Magnetic flux trapped on the surface of SRF cavities during cool-down below the critical temperature is one of the leading sources of residual RF losses. Instruments capable of detecting the distribution of trapped flux on the cavity surface are in high demand in order to better understand its relation to the cavity material, surface treatments and environmental conditions. We have designed, developed, and commissioned two novel …

Raman Scattering Measurements And Analyses Of Gan Thin Films Grown On Zno Substrates By Metalorganic Chemical Vapor Deposition, Zane Mcdaniel, Zhe Chuan Feng, Kevin Stokes

Symposium of Student Scholars

Metalorganic chemical vapor deposition (MOCVD) is a popularly used method of growing thin films of GaN on ZnO (GZ) substrates, which pair well due to their structural and characteristic similarities. In this research, optical characterization of the surface quality of GZ sample films is measured by analyzing Raman scattering (RS) using a Renishaw inVia spectrometer fitted with a 532nm laser. Samples were grown in an improved double injection block rotating disc reactor. Multiple samples' spectra show broad peaks that correspond with the E2 (high) and A1 (LO) branches of GaN, and nicely fitted curves are observed for the characteristic E2 …

Synthesis And Assembly Of Polymer Materials At Interfaces, Xiaoshuang Wei

Doctoral Dissertations

The overarching goal of the thesis is to understand growth and assembly of polymer materials at interfaces. Chapter 2 and Chapter 3 study simultaneous polymer growth and assembly at fluid interfaces, where in-situ photopolymerization and vapor phase deposition were utilized to grow polymers, respectively. Chapter 4 leverages capillary condensation to pattern polymer growth at solid substrates. Chapter 1 provides background information on polymer materials at interfaces, and vapor phase deposition method (initiated chemical vapor deposition, iCVD) to grow polymers. This chapter also reviews polymer thin film wetting, and colloidal assemblies at interfaces. In Chapter 2, we demonstrate the preparation …

Frontiers In The Self-Assembly Of Charged Macromolecules, Khatcher O. Margossian

Doctoral Dissertations

The self-assembly of charged macromolecules forms the basis of all life on earth. From the synthesis and replication of nucleic acids, to the association of DNA to chromatin, to the targeting of RNA to various cellular compartments, to the astonishingly consistent folding of proteins, all life depends on the physics of the organization and dynamics of charged polymers. In this dissertation, I address several of the newest challenges in the assembly of these types of materials. First, I describe the exciting new physics of the complexation between polyzwitterions and polyelectrolytes. These materials open new questions and possibilities within the context …

Coupled Oscillators: Protein And Acoustics, Angelique N. Mcfarlane

Theses

This work encompassed three different vibrational energy transfer studies of coupled resonators (metal, topological, and microtubule comparison) inspired by the lattices of microtubules from regular and cancerous cells. COMSOL Multiphysics 5.4 was utilized to design the experiment. The simulation starts with an acoustic pressure study to examine the vibrational modes present in coupled cylinders, representing α-, β-tubulin heterodimers. The Metal Study consisted of 3 models (monomer, dimer, and trimer) to choose the correct height (40 mm) and mode (Mode 1) for study. The Topological Study was run to predict and understand how the lattice structure changes over a parametric sweep …

Quantum-Mechanical Evaluation Of Defects In Uranium-Bearing Materials, Megan Hoover

All Dissertations

Quantum-mechanical calculations using density functional theory with the generalized gradient approximation were employed to investigate the effects dopants have on the uranium dioxide (UO₂) structure. Uraninite is a common U⁴⁺ mineral in the Earth's crust and an important material used to produce energy and medical isotopes. Though the incorporation mechanism remains unclear, divalent cations are known to incorporate into the uranium dioxide system. Three charge-balancing mechanisms were evaluated to achieve a net neutral system, including the substitution of (1) a divalent cation for a tetravalent uranium atom and oxygen atom; (2) two divalent cations for a tetravalent …

Pressure-Induced Phase Transition And Electronic Structure Changes In Equiatomic Fev, Homero Reyes Pulido

Open Access Theses & Dissertations

Classical molecular dynamics methods can accurately describe a broad set of many-atomssystems. Although more economical, the results given by this framework lack the precision capable of density functional theory (DFT). Therefore, the structural stability of the B2 phase of a body-centered-cubic iron-vanadium (FeV) alloy using DFT on the electronic structure level is analyzed to verify and further explain classical results obtained by our group in this same alloy. Using Quantum Espresso and Phonopy for the computational simulations, the plotted band structure, electronic density of states (eDOS), phonon dispersions, charge density, and Fermi surfaces for various compressed unit cells are presented. …

Study Of Thermoelectric And Lattice Dynamics Properties Of 2d Layered Mx (M = Sn, Pb; X = S, Se, Te) And Zrs2 Compounds Using First-Principles Approach, Abhiyan Pandit

Graduate Theses and Dissertations

The aim of this dissertation is the investigation of thermoelectric and lattice dynamics properties of two-dimensional (2D) MX (M = Sn, Pb; X = S, Se, Te) and ZrS2 compounds based on the first-principles density functional theory. The dimensionality reduction (e.g., using 2D structure) of bulk materials is found to have enhanced thermoelectric efficiency. This enhancement is attributed to the increase of the Seebeck coefficient as a result of higher electronic density of states near the Fermi level in low-dimensional materials. In addition, lowering the dimensionality increases phonon scattering near interfaces and surfaces in 2D materials, which leads to a …

Multi-Technique Characterization Of Superconducting Materials For Particle Accelerator Applications, Junki Makita

Physics Theses & Dissertations

We investigated the performance limitations of superconducting radio-frequency (SRF) cavities and materials using multiple experimental techniques. In particular, this study focuses on understanding the surface properties of nitrogen-doped Nb cavities and superconducting thin films with higher T_c such as Nb₃Sn. The main goal of this work is to use different techniques to better understand each aspect of the complex loss mechanism in superconductors to further improve the already highly efficient SRF cavities.

Nitrogen doping applied to a Nb SRF cavity significantly improves the quality factor Q₀ compared to a conventional Nb cavity, at an expense of …

Asymmetric Control Of Light At The Nanoscale, Christos Argyropoulos

Department of Electrical and Computer Engineering: Faculty Publications

Breaking reciprocity at the nanoscale can produce directional formation of images due to the asymmetric nonlinear optical response of subwavelength anisotropic resonators. The self-induced passive non-reciprocity has advantages compared to magnet or time modulation approaches and may impact both classical and quantum photonics.