Low-Temperature Electron Wind Force Annealing through Electropulsing Treatment
Open Access
- Author:
- Sharp, Logan
- Graduate Program:
- Mechanical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 17, 2022
- Committee Members:
- Daniel Connell Haworth, Professor in Charge/Director of Graduate Studies
Md Amanul Haque, Thesis Advisor/Co-Advisor
Donghai Wang, Committee Member - Keywords:
- annealing
electropulsing
EPT
electron wind
electron wind force
EWF
titanium carbide
Ti3C2Tx
MXene
film
NiTi
nitinol
shape memory alloy
SMA
electrical resistivity
thermal microscopy
scanning electron microscopy
SEM
low temperature
Raman spectroscopy - Abstract:
- Electropulsing treatment (EPT) is an effective alternative to traditional heat treatment (HT) for eliciting microstructural and material property changes in metallic materials. EPT can provide benefits of increased energy savings, increased cost savings, and reduced lead times for post-processed materials. Furthermore, certain materials may not be able to undergo HT due to oxidation or other material-specific effects. This study will investigate post-process EPT as an alternative to HT for two specific materials: two-dimensional (2D) layered titanium carbide (Ti3C2Tx) MXene and nickel-titanium (NiTi) shape memory alloy (SMA). 2D layered carbides and nitrides of transition metals, known as MXenes, have become emergent materials for applications in energy storage, conversion, and transport, due to advantageous electrical, thermal, and mechanical properties. Due to their processing, MXenes must be annealed to reduce their resistivity and reach their theoretical capacitance. However, conventional HT in oxygen-containing environments results in structural oxidation of the most prominent MXene, Ti3C2Tx, negatively impacting its properties. In this study, a novel, room temperature (RT), electron wind force (EWF) annealing process consisting of EPT and compressive loading is utilized to reduce resistivity by > 90% for Ti3C2Tx film. An EWF annealing process consisting of exclusively EPT results in a resistivity reduction of > 75% for Ti3C2Tx film. The process of EPT and compressive loading is shown to be mostly permanent, while the process of exclusively EPT is completely permanent. Because both processes can be completed at RT, they can also be performed in ambient conditions. Characterization techniques of Raman spectroscopy and focused ion beam (FIB) scanning electron microscopy (SEM) reveal no changes in composition for Ti3C2Tx, but a decrease in average internal pore size by transforming a majority of pores to a size of < 600 nm^2. SMAs are a multifunctional class of materials that react to specific stimuli, such as temperature and stress. The most prominent SMAs are NiTi alloys. Beyond typical properties of SMAs, such as shape memory and strain recovery, NiTi SMAs are known for their corrosion resistance, damping capacity, and biocompatibility, making them ideal for applications in actuation, structures, and medical implants. Although NiTi SMAs are commonly heat treated, EWF annealing through direct current (DC) treatment, EPT, and electropulse rolling (EPR), have shown to be effective in reducing cost and lead time for these alloys. In this study, EPT of 50.7 at.% Ni–49.3 at.% Ti wire is optimized by investigating a wide range of electropulsing parameters, which result in a resistivity reduction of > 8%. Temperatures generally fall below what other studies have reported, with the largest resistivity reductions occurring < 275 °C.