Electronic and structural investigation of nanocrystal thin films tuned via surface chemistry

Gaulding, Elizabeth Ashley University of Pennsylvania 2015 해외박사(DDOD)

Monodisperse colloidal nanocrystals (NCs) provide an opportunity to access physical properties that cannot be realized in bulk materials, simply by tuning the particle size or shape. These NCs form the basis of an artificial periodic table that can be used as building blocks to engineer a new class of solid-state materials with emergent properties. The monodispersity offers a structural advantage for assembling NCs into an ordered superlattice, in addition to a narrow distribution of band energies which in principle promote more efficient transport when the NCs are electronically coupled in a thin film solid after undergoing surface chemistry treatments. However, previous methods for NC assembly have been limiting in their scalability, and while there has been much work in general on the effects of different ligand surface chemistries on semiconductor NC solids, little work has been done to controllably tune the Fermi level and quantify its position in order to promote better device engineering. Herein, we investigate dip-coating as a method by which to scale up NC superlattice assembly. We demonstrate large-area ordering on wafer-scale for both single component and binary nanocrystal superlattices with a diverse set of NC materials and binary crystal geometries. We confirm the extent over which these films are ordered via GISAXS, TEM, and SEM characterization. In the remainder of this work, we study the electronic effects of different ligand chemistry treatments of the NCs. We show that a sequential two step surface treatment can offer increased control over the tuning of the Fermi level and we quantify its positioning and band edge energies relative to vacuum level via a pairing of temperature dependent Seebeck measurements, cyclic voltammetry, and absorption spectroscopy. This provides a reference by which NC devices can be more precisely engineered. Furthermore, we apply that the AC magnetic field Hall effect measurement to a series of common ligand treatments used for making NC devices such as solar cells and field effect transistors to better understand their relative electronic transport properties. We demonstrate this method can be used to determine the hall mobility in these generally high resistivity, low mobility films.

Composing the Musicking Woman: Gender and Nation in the Works of Johanna Kinkel

Gauld, Emily J ProQuest Dissertations & Theses University of Mich 2022 해외박사(DDOD)

This dissertation investigates the still overwhelmingly understudied category of women composers and reinserts women’s voices—through both music and literature—into discourses on nineteenth-century German cultural and national identity. By exploring the long overlooked musical contributions of nineteenth-century women, my dissertation seeks to expand existing scholarship on German nation-building through music. To this end, I introduce the concept of the musicking woman, who features as the central figure of study in my dissertation. Drawing on Christopher Small’s concept of musicking, which reconceptualizes music as an action or event rather than an object, I understand the musicking woman as an active agent in the process of music through composition and/or performance. She is, therefore, not determined by the reception of her work, but rather by her own intention to contribute to a serious musical culture, often as a career. As such, the musicking woman cannot be disentangled from categories of gender, class, race, and citizenship. As its central case study, my dissertation focuses on the musical and literary works of musicking woman, Johanna Kinkel.By grounding my study in the musical and literary works of Johanna Kinkel (1810-1858), I examine how she negotiated expectations of femininity and challenged women’s role in nineteenth-century bourgeois German society through composition, fictional and non-fictional writing, and music pedagogy. Kinkel’s extensive and diverse body of literature and music offers a uniquely well-suited case study to begin bringing women’s contributions to musical culture into scholarly discourses on developing notions of German national identity. Chapter 1 provides historical background as well as a theoretical and methodological framework for the dissertation. Chapter 2 examines Kinkel’s critique of the Berlin salon, in her novella, Musikalische Orthodoxie (1846/49) and Memoiren (1861), arguing that it was not a productive site for women’s participation in serious musical culture. In Chapters 3 and 4, I explore the relationship between music and women’s political and intellectual agency. First, A Lied, an essay, and the novel, Hans Ibeles in London (1858/61) provide three different perspectives of Kinkel’s experience of the 1848/49 revolutions. Then, Kinkel’s pedagogical work comes into conversation with contemporaries Robert Schumann and Carl Czerny to interrogate the role of music education in girls’ and women’s lives. In Chapter 5, I examine the tensions between nineteenth-century theories of women’s emancipation and Kinkel’s lived experiences. This chapter presents analyses of Kinkel’s unpublished essays from London, Fanny Lewald’s Meine Lebensgeschichte (1861-62), and Malwida von Meysenbug’s Memoiren einer Idealistin (1875). In a coda, I revisit two characters from Kinkel’s novella and novel.With stakes in the fields of women and gender studies, literary studies, history, and musicology, my project aims to redefine the cultural reach of nineteenth-century women by examining the aestheticization of Germanness fostered by the close cultural relationship between music and literature. Reading music, literature, and autobiography together, I consider a new methodology for determining and understanding women’s stakes in defining their own cultural identity. By bringing feminist discourses from musicology and literary studies into conversation with foundational scholarship on German national identity and musical culture, I reexamine the social and cultural agency of nineteenth-century German women. I explore how women perceived of and expressed themselves in terms of music, how literature symbolically constructed the musicking woman, how class informed women’s musical activity, and how women wrote themselves into national and social narratives through music.

Aerodynamic design, analysis, and validation of a supersonic inflatable decelerator

Clark, Ian Gauld Georgia Institute of Technology 2009 해외박사(DDOD)

Since the 1970s, NASA has relied on the use of rigid aeroshells and supersonic parachutes to enable robotic mission to Mars. These technologies are constrained by size and deployment condition limitations that limit the payload they can deliver to the surface of Mars. One candidate technology envisioned to replace the supersonic parachute is the supersonic inflatable aerodynamic decelerator (IAD). This dissertation presents an overview of work performed in maturing a particular type of IAD, the tension cone. The tension cone concept consists of a flexible shell of revolution that is shaped so as to remain under tension and resist deformation. Work completed on maturing the concept and presented in this dissertation falls into three categories: systems design, wind tunnel testing, and computational fluid dynamics validation. Systems analyses that evaluated trajectory impacts of a supersonic IAD demonstrated several key advantages. Using a near-term Mars robotic mission as a baseline, supersonic IADs were shown to allow the landing of larger payloads at higher elevations relative to a system using parachutes alone. Increases in payload of over 700 kg (a 40% increase in payload mass) were estimated for IAD systems. Further increases in mass were shown to be possible by using a two-stage IAD and subsonic parachute system. Significant gains in landing site surface elevation and an insensitivity to entry system mass growth were also demonstrated. A series of supersonic wind tunnel tests were conducted at the NASA Glenn and Langley Research Centers to characterize the behavior of a tension cone IAD at relevant Mach numbers. The tests were conducted on a particular tension cone configuration that was designed with the objective of eliminating unfavorable aerodynamic characteristics observed in prior wind tunnel testing, i.e. the presence of embedded shocks and flow separation along the surface. Testing of both rigid force and moment models and pressure models demonstrated the new design to have favorable performance including drag coefficients between 1.4 and 1.5 and static stability at angles of attack from 0 to 20. A separate round of tests conducted on flexible tension cone models showed the system to be free of aeroelastic instability. Deployment tests conducted on an inflatable model demonstrated rapid, stable inflation in a supersonic environment. Structural modifications incorporated on the models were seen to reduce inflation pressure requirements by a factor of nearly two. Through this test program, this new tension cone IAD design was shown to be a credible option for a future flight system. A key objective of the wind tunnel test program was to gather data useful for validation of aerodynamic and structural analysis methods. Validation of CFD analyses for predicting aerodynamic IAD performance was completed and the results are presented. Inviscid CFD analyses are seen to provide drag predictions accurate to within 6%. Viscous analyses performed show excellent agreement with measured pressure distributions and flow field characteristics. Comparisons between laminar and turbulent solutions indicate the likelihood of a turbulent boundary layer at high supersonic Mach numbers and large angles of attack.