AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Improvement of Amorphous Silica Encapsulation Efficiencies on Welding Fume Particles
JUN WANG, Jianying Guan, Alex Theodore, Jessica Sharby, Chang-Yu Wu, Kathleen Paulson, Omar Es-Said, University of Florida
Abstract Number: 340 Working Group: Nanoparticles and Materials Synthesis
Abstract The welding process results in the formation of high concentration of nano-sized particles loaded with toxic metals such as hexavalant chromium, nickel, and manganese. Welding fume poses serious health risks to welders as it can cause respiratory and neurological ailments as well as cancer. The overall objective of this study was to develop an innovative amorphous silica encapsulation (ASE) technology to coat the metal particles as well as limit oxidation of chromium, thus reducing welding fume toxicity. Previous experiment showed a reduction of Cr(VI) concentration in welding fume over 90% by utilizing ASE technology. However, only 39% of metal particles were coated in silica film. The relatively low efficiency of silica precursor was mainly due to premature decomposition of silica precursor. A prototype insulated double shroud torch (IDST) was developed to overcome the limitation of this technology. Tetramethylsilane (TMS) vapor saturated argon flowed separately with primary shielding gas; it was then injected to the welding arc zone at the end of the IDST. Ceramic shell was employed in the DSWT to avoid the excess thermal energy transferred to the silica precursor. Silica coating efficiency (SCE) was determined by comparison of using two types of strong acid digestion methods. Experimental results showed about 76%, 63%, and 59% of particles are encapsulated inside silica shell at maximum, under high (30 Lpm), medium (25 Lpm), and low (20 Lpm) primary shielding gas flow rate, respectively. Transmission Electron Microscopy (TEM) imagery was used to visualize evidence of silica coating on metal particles. Further structure test confirmed no statistically significant difference of the mechanical properties of weld generated in baseline and by ASE technology. The success of this technique will bring great health and safety benefits to welders.