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Processing, Pre-Aging, and Aging of NiTi-Hf (15-20 at.%) High Temperature Shape Memory Alloy from Laboratory to Industrial Scale

Description: The overarching goal of this research was to generate a menu of shape memory alloys (SMAs) actuator materials capable of meeting the demands of aerospace applications. Material requirements were recognized to meet the demand for high temperature SMAs with actuating temperatures above 85 °C and provide material options capable of performing over 100K actuation cycles. The first study is a preliminary characterization for the down selection of Ni-rich NiTiHf15 compositions chosen for a more in-de… more
Date: December 2020
Creator: Gantz, Faith
Item Type: Refine your search to only Thesis or Dissertation

High Temperature Sliding Wear Behavior and Mechanisms of Cold-Sprayed Ti and Ti-TiC Composites

Description: Ti and Ti-based alloys are used in many aerospace and automotive components due to their high strength-to-weight ratio and corrosion resistance. However, room and elevated temperature wear resistance remain an issue, thus requiring some form of secondary hard phase, e.g., refractory carbides and oxides, as well as solid lubrication to mitigate wear. In this study, Ti-TiC (14, 24 and 35 vol% TiC) composite coatings were deposited on mild steel substrates using cold spray with comparisons made to… more
Date: August 2020
Creator: Koricherla, Manindra Varma
Item Type: Refine your search to only Thesis or Dissertation
open access

In-situ Analysis of the Evolution of Surfaces and Interfaces under Applied Coupled Stresses

Description: To study the effect of the substrate support on the nanoscale contact, three different regimes, i.e., graphene on rigid (ultra-crystalline diamond) and on elastic (Polydimethylsiloxane) supports and free-standing graphene, were considered. The contribution of the graphene support to the mechanical and electrical characteristics of the graphene/metal contact was studied using the conductive atomic force microscopy (AFM) technique.The results revealed that the electrical conductivity of the graph… more
Date: August 2020
Creator: Lee, Ji Hyung
Item Type: Refine your search to only Thesis or Dissertation
open access

Thermo-Mechanical Processing and Advanced Charecterization of NiTi and NiTiHf Shape Memory Alloys

Description: Shape memory alloys (SMAs) represent a revolutionary class of active materials that can spontaneously generate strain based on an environmental input, such as temperature or stress. SMAs can provide potential solutions to many of today's engineering problems due to their compact form, high energy densities, and multifunctional capabilities. While many applications in the biomedical, aerospace, automotive, and defense industries have already been investigated and realized for nickel-titanium (Ni… more
Date: May 2020
Creator: Ley, Nathan A
Item Type: Refine your search to only Thesis or Dissertation

Synthesis, Phase Development, and the Mechanism for Negative Thermal Expansion in Aluminum Tungstate

Description: An in-depth study of Al2W3O12 negative thermal expansion (NTE) ceramic was performed, focused on synthesis, phase mappings, and the underlying mechanisms shown to be responsible for NTE. Review of the literature has shown inconsistencies in reported values of the dilatometry measured coefficients of thermal expansion, and the temperature for the known monoclinic to orthorhombic phase transition. Two synthesis techniques are introduced: an ionic-liquid non-hydrolytic sol-gel synthesis route; an… more
Date: May 2020
Creator: Rose, Kyle
Item Type: Refine your search to only Thesis or Dissertation

Tribo-Corrosion of High Entropy Alloys

Description: In this dissertation, tribo-corrosion behavior of several single-phase and multi-phase high entropy alloys were investigated. Tribo-corrosion of body centered cubic MoNbTaTiZr high entropy alloy in simulated physiological environment showed very low friction coefficient (~ 0.04), low wear rate (~ 10-8 mm3/Nm), body-temperature assisted passivation, and excellent biocompatibility with respect to stem cells and bone forming osteoblast cells. Tribo-corrosion resistance was evaluated for additively… more
Date: December 2020
Creator: Shittu, Jibril
Item Type: Refine your search to only Thesis or Dissertation
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