Material Size Effects in Conventional Arc Welding, Sealing, and Devices

Micro and nano-sized materials have been extensively studied in recent decades. The size of materials can influence multiple characteristics such as melting points, microhardness, mechanical strength, surface chemistry, etc. Thus, it is necessary and practical to study the size effect of material in a variety of industrial application fields (such as sealing, welding, sensors, batteries, and so on). The effects negligible at a macroscopic level can be important at the micro-scale; for example, quantum effects may become dominant. The material size effects are useful for understanding the origin of differences and to probe innovative phenomena obtained at various scales.

In this dissertation, the size effect relevant to different manufacturing fields was investigated to understand how the size effect of material governs the properties when the size of materials changes from macroscale to microscale, and further down to nanoscale. In Chapter 2, a microscale glass frit was applied for laser sealing glass in the edge seal for Vacuum Insulated Glazing. In Chapter 3, a nanoscale Fe₂O₃ flux was fabricated for improving mechanical properties of tungsten inert gas welding of high-manganese steel thick plates. In Chapter 4, a flexible sensor functionalized with TiO₂ nanowires for room temperature CO₂ gas sensing was developed. In Chapter 5, the effect of refining grain size on aluminum anodes for Al–air batteries in alkaline electrolytes were studied. Lastly, conclusions and outlook will be discussed in Chapter 6.

Through my Ph.D. study, I provide evidence to testing the hypothesis: the size of material can affect the performance of the devices manufactured, especially decreasing down to a nano size may result in reducing temperature requirement and improving mechanical properties and the electrochemical activities.