Synthesis, characterization and study of physical properties of novel M(n+1)AX(n) compounds

Mn+1AXn compounds, the ternary layered nanolaminates have gathered momentum in the last decade since its advent because of their unusual but exciting properties. These technologically important compounds combine some of the best properties of metals and ceramics. Like ceramics they are refractory, oxidation resistant, elastically stiff and relatively light. They also exhibit metallic properties like excellent machinability, thermal and electrical conductivity. This dissertation concentrates on the synthesis of germanium-based 211 Mn+1AXn compounds. The main objective of the research was to synthesize predominantly single phase samples of Cr2GeC, V2GeC and Ti2GeC. Another goal was to study the effect of solid substitutions on the M-site of Mn+1AXn compounds with Ge as an A-element. This study is in itself the first to demonstrate the synthesis of (Cr0.5V0.5)2GeC a novel Mn+1AXn compound. Scanning electron microscopy coupled with energy dispersive spectroscopy, x-ray diffraction and electron probe microanalysis were employed to confirm the presence of predominantly single phase samples of M2GeC compounds where M = Ti, V, Cr and (Cr 0.5V0.5). A large part of the dissertation also focuses on the effect of the compressibility on the Ge-based 211 Mn+1AXn compounds with the aid of diamond anvil cell and high energy synchrotron radiation. This study also concentrates on the stability of these compounds at high temperature and thereby determines its suitability as high temperature structural materials. In order to better understand the effect of substitutions on A-site of 211 Mn+1 AXn compounds under high pressure and high temperature, a comparison is made with previously reported 211 Mn+1AXn compounds with Al, Ga and S as A-site elements.

A gender study investigating physics self-efficacy

The underrepresentation of women in physics has been well documented and a source of concern for both policy makers and educators. My dissertation focuses on understanding the role self-efficacy plays in retaining students, particularly women, in introductory physics. I use an explanatory mixed methods approach to first investigate quantitatively the influence of self-efficacy in predicting success and then to qualitatively explore the development of self-efficacy. In the initial quantitative studies, I explore the utility of self-efficacy in predicting the success of introductory physics students, both women and men. Results indicate that self-efficacy is a significant predictor of success for all students. I then disaggregate the data to examine how self-efficacy develops differently for women and men in the introductory physics course. Results show women rely on different sources of self-efficacy than do men, and that a particular instructional environment, Modeling Instruction, has a positive impact on these sources of self-efficacy. In the qualitative phase of the project, this dissertation focuses on the development of self-efficacy. Using the qualitative tool of microanalysis, I introduce a methodology for understanding how self-efficacy develops moment-by-moment using the lens of self-efficacy opportunities. I then use the characterizations of self-efficacy opportunities to focus on a particular course environment and to identify and describe a mechanism by which Modeling Instruction impacts student self-efficacy. Results indicate that the emphasizing the development and deployment of models affords opportunities to impact self-efficacy. The findings of this dissertation indicate that introducing key elements into the classroom, such as cooperative group work, model development and deployment, and interaction with the instructor, create a mechanism by which instructors can impact the self-efficacy of their students. Results from this study indicate that creating a model to impact the retention rates of women in physics should include attending to self-efficacy and designing activities in the classroom that create self-efficacy opportunities.