Physical Sciences and Mathematics Commons^™

Synthesis And Applications Of Ceramic (Silicon Carbide And Silicon Nitride), Metallic (Cobalt(0)) And Polymeric (Polyurethane) Aerogels, Parwani M. Rewatkar

Doctoral Dissertations

"A new method has been demonstrated for the synthesis of monolithic ceramic and purely metallic aerogels from xerogel powder compacts, and the use of polyurethane aerogels based on cyclodextrins as efficient desiccants.

I. Highly porous ( > 80%) monolithic SiC and Si₃N₄, aerogels were prepared from compressed compacts of polyurea-crosslinked silica xerogel powders. The process is time efficient as solvent-exchange through powders is fast, and energy efficient as it bypasses drying with supercritical fluids. The final ceramic objects were chemically pure, sturdy, with compressive moduli at 37 ±7 MPa and 59 ± 7 MPa, and thermal conductivities …

Polyurea Aerogels: From Nanoscopic To Macroscopic Properties, Tahereh Taghvaee

Doctoral Dissertations

"The morphology of a material is intrinsically a qualitative property and in order to relate nanomorphology to synthetic conditions, it is necessary to express nano/micro-structure quantitatively. In this context, polyurea aerogels were chosen as a model system with demonstrated potential for rich nanomorphology and being guided by a statistical Design-of-Experiments model, a large array of materials (208) with identical chemical composition, but quite different nanostructures were prepared. By reflecting upon the SEM images, it was realized that our first pre-verbal impression about a nanostructure is related to its openness and texture; the former is quantified by porosity (Π), and the …

Development And Demonstration Of Sampling Techniques For A Chirped Pulse Fourier Transform Microwave Spectrometer, Frank Edward Marshall

Doctoral Dissertations

"With the introduction of the Chirped Pulse-Fourier Transform Microwave Spectrometer in the past decade, it has become possible to rapidly study the rotational spectra of molecules in the gas phase. It is possible to study molecules that are not normally in the gas phase through the use of various sourcing techniques. The development of both the heated nozzle and the laser ablation sourcing techniques allow for the study of liquids and solids, respectively. The design and performance of these sources will be presented in detail and discussed. Additionally, the development of a Multi-Antennae detection scheme, useful in improving overall sensitivity …

Development Of Functional Ionic Liquids For Separation And Recovery Of Rare Earth Elements, Mostafa Khodakarami

Doctoral Dissertations

“This research focused on the design and synthesis of task-specific ionic liquids for enhanced extraction and separation of rare earth elements (REEs). Two novel ammonium-based functional ionic liquids (FILs) with oxygen donating groups: trioctyl(2-ethoxy-2-oxoethyl)ammonium dihexyl diglycolamate, [OcGBOEt][DHDGA], and tricaprylmethylammonium dihexyl diglycolamate, [A336][DHDGA] were synthesized and tested for the recovery and separation of selected REEs from aqueous solutions. Functionalities with different denticities were incorporated into both anionic and cationic parts of ionic liquids, which are solely composed of incinerable atoms including C, H, O, and N. The structural, physical, and chemical properties of the synthesized FILs were studied using nuclear magnetic …

Designing Novel Multinary Transition Metal Selenides As High-Efficiency Oxygen Evolution Reaction Electrocatalysts And Investigating Surface Properties, Xi Cao

Doctoral Dissertations

”Water splitting has been widely considered to be an efficient way to generate sustainable and renewable energy resources in fuel cells, metal-air batteries and other energy conversion devices. Exploring efficient electrocatalysts to expedite the anodic oxygen evolution reaction (OER) is a crucial task that needs to be addressed to boost the practical application of water splitting. This research focuses on the identification of OER electrocatalysts by systematically designing non-stochiometric mixed transition metal-based selenide OER electrocatalysts through combinatorial electrodeposition and investigation of selenide-based naturally occurring minerals as effective OER electrocatalyst. Paper I describes the study of Ni-Fe-Co selenides as OER catalysts …

Exploring Transition Metal Chalcogenides For Bio Sensing And Environmental Remediation, Bahareh Golrokh Amin

Doctoral Dissertations

“Electrocatalysts play an inevitable role in many applications including energy storage, energy conversion, and biosensing. The state-of-the-art noble metal-based electrocatalysts have long been used in full water splitting, non-enzymatic glucose sensing, and supercapacitors. However, scarcity and high cost of noble metals restrict utilization of such electrocatalysts in large-scale implementations. Transition metal-based electrodes have been considered as a potential solution to address these drawbacks as well as to enhance the electrocatalytic performance. In this work, applicability of non-oxidic transition metal based electrocatalysts is evaluated. Transition metal chalcogenides are expected to have high catalytic performance owing to their facilitated electron cloud delocalization …