Abstract
The intensive energy of welding yields a high concentration of nanoparticles loaded with toxic metals such as hexavalent chromium (Cr6+), nickel, and manganese. To reduce the hazards associated with the toxic welding fume, an innovative amorphous silica encapsulation (ASE) technology has recently been developed. Tetramethylsilane (TMS) is timely introduced into the system as an additive to the welding shielding gas. TMS decomposes at the high-temperature welding arc zone to form amorphous silica that encapsulates the metals particles, thus reducing welding fume toxicity. Experimental results demonstrated that the addition of 3.2~5.1% of TMS carrier gas to the primary shielding gas resulted in an over 90% reduction of airborne Cr6+ under all shielding gas flow rates, while silica coating efficiency (SCE) was around 60% to 76%. XPS result confirmed complete elimination of Cr6+ inside the amorphous silica shell. TEM imagery displayed evidence of silica coating on metal particles. Welding fume particle size increased from a mode size of 20 nm under baseline conditions to 180-300 nm when TMS was added. Structure test confirmed no statistically significant difference of the mechanical properties of weld generated in the baseline samples and by ASE technology. If implemented, the ASE technology can bring great health and safety benefits to welders, currently estimated to be at least 466,400 in the US alone.
Bio
Professor Chang-Yu Wu received his BS from Mechanical Engineering Department at National Taiwan University and PhD from the Department of Civil & Environmental Engineering at University of Cincinnati. His teaching and research interests range from air pollution control, aerosol science, environmental nanotechnology, dust control to engineering education. He has published more than 100 refereed journal particles and given 220+ conference presentations and 50+ invited lectures. His research has resulted in 3 US patents and 4 pending applications. An active member of Air & Waste Management Association and American Association for Aerosol research, he has received several awards recognizing his accomplishments in education, research and service.
