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An Investigation into the Micromechanical and Corrosion Properties of Additively Manufactured Stainless Steel 316L

In this thesis, micro-mechanical properties and corrosion resistance of laser powder bed fusion (L-PBF) processed additive manufactured (AM) 316L stainless steel parts were investigated for different combinations of processing parameters. Various laser powers were employed for the fabrication of all AM 316L stainless steel parts. Nanoindentation, areal roughness, and electron backscattered diffraction (EBSD) characterization were used to characterize the surface of the AM samples prior to corrosion testing. Open circuit potential (OCP), linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization tests were done to compare AM L-PBF 316L stainless steels with different processing parameters. Overall, it was observed that the AM part having a 56.67 J/mm3 volumetric energy density (VED) exhibits the best micro-mechanical characteristics. This sample also had the lowest areal surface roughness and smallest grain size. Consequently, this parameter combination had better corrosion resistance compared to the other AM processed 316L parts. The results are useful in process calibration when fabricating for corrosion resistance applications and provide insights into the relationship among nano-mechanical, crystallography, and long-term corrosion performance.
Date: December 2022
Creator: England, Jennifer
System: The UNT Digital Library

Nanofluidic Membrane Based on Covalent Organic Framework: Design Strategies and Applications

Nanofluidic is an emerging field of applying fluid properties in nanochannels or nanostructures. The nanoporous channel with a pore size of less than 100 nm will strongly affect the motion of the fluid. Meanwhile, the pore environment, such as hydrophilic and hydrophobic properties, charge density, and host-guest recognition would be crucial for the transportation of molecules and ions in the pore. This thesis is focused on the synthesis, characterization of nanofluidic membranes and their applications to reverse electrodialysis. Chapter 1 focuses on the importance and objective of this work. Chapter 2 gives an overview of nanofluidic and classical nanofluidic structure–covalent organic frameworks (COFs). In Chapter 3, a series of COFs membranes with different surface charge densities were designed by employing a multivariate (MTV) strategy. A volcano-like relationship between the surface charge density and output power density was observed when the membranes were applied for osmotic energy harvesting. Chapter 4 integrates the temperature gradient to the covalent organic frameworks nanofluidic system to further explain the thermophoretic mobility of ions. The recorded osmotic energy production density was obtained while ion concentration polarization was alleviated with increasing hydrodynamic convection effects. In Chapter 5, a coupled photon-electron-ion transport behavior across ionic covalent organic framework …
Date: December 2022
Creator: Zhu, Changjia
System: The UNT Digital Library
Novel LC-MS Method for the Analysis of Beta-Hydroxybutyric Acid (BHB) in Health Formulations (open access)

Novel LC-MS Method for the Analysis of Beta-Hydroxybutyric Acid (BHB) in Health Formulations

The rise of nutraceutical health formulations has increased the need for more stringent analytical testing methods. Complex matrices present a new problem when determining concentration of compounds of interest. The presented method uses LC-MS analysis with a novel sample preparation method in the determination of Beta-hydroxybutyric acid in health formulations. The use of an aqueous analytical column allows for separations of polar compounds after non-polar compounds are removed through C18 packed column filtration. The samples were analyzed through time-of-flight mass spectrometry and results show that this is an effective method for the presented samples with a range of expected concentrations of total BHB was from 11.80% to 38.92%. It was seen that all samples exhibited a less than 10% percent deviation from the expected concentrations of the nutraceutical health samples with the highest being 9.74 % for sample 9 and the lowest being sample 3 with a deviation of 0.08 % from expected values.
Date: May 2022
Creator: Smith, Garret Mackenzie
System: The UNT Digital Library