Browsing by Subject "titanium"
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Item Modeling of Tool Wear and Tool Fracture in Micromilling(2012-02-14) Shiosaki, DominicMicromachining is the next generation of precision material removal at the micro scale level due to the increase in miniaturization of commercial products. The applications of this technology extend anywhere from electronics to micro scale medical implants. Micromilling has the potential to be the most cost effective and efficient material removal process due to ease of use and accessibility of the tools. This research analyzes vibration of a high speed spindle and then studies micromilling of aluminum and titanium. Finite element analysis and tool modeling compliment experimental data. Cumulative tool wear based on Taylor model shows decreasing tool life with increasing feed rate and increasing cutting speed on aluminum. Inconsistent results are seen when micromilling titanium due to premature chipping of tool noses. A significant nose wear plastically deforms a micromilled subsurface and is verified with microstructure study and microhardness measurements.Item Perchlorate Degradation Using Partially Oxidized Titanium Ions and Ion Exchange Membrane Hybrid System(2011-08-08) Park, Sung HyukPerchlorate has entered human and environmental food chains and has received a great deal of attention because of its toxicity to humans. In this study, chemical degradation of perchlorate was investigated using partially oxidized titanium ions (Ti2+ and Ti3+) in solutions and as part of an ion exchange membrane reactor system. Aqueous titanium ions (Ti2+ and Ti3+) were applied to remove perchlorate ions and its destructive mechanism, reaction kinetics, and the effect of environmental factors were investigated. Titanium ions were able to degrade perchlorate ions very rapidly with half life less than one hour under conditions of high acid concentrations. A new reactor system with an ion exchange membrane was adapted to apply better the reactions of perchlorate destruction to water treatment practice. A novel treatment method was developed by integrating partially oxidized titanium ions with an ion exchange membrane, and it is named the Titanium and Membrane Hybrid System (TMH System). The results shown in this research demonstrate the feasibility of TMH System for perchlorate reduction. The perchlorate ions were rapidly adsorbed onto the ion exchange membrane and diffused through it, but they were reduced by titanium ions in the degradation zone relatively slowly. To enhance the overall rate of reaction, high concentrations of acid and Ti(III) are needed, but transport of hydrogen ions through the anion permeable membrane was observed and would be greater at higher acid concentrations. The proposed mathematical model predicts the performance and behavior of the TMH system for different physical and chemical conditions. It successfully described adsorption, diffusion and reduction of perchlorate in the system. This model could be used as an important tool for process design and optimization.Item Perchlorate reduction using electrochemically induced pitting corrosion of zero-valent titanium(2009-05-15) Lee, Chun WooPerchlorate is a threat to public health through water but also food. However, there is no effective chemical treatment process which can destroy perchlorate found in groundwater and surface water. Thus, there is growing interest in developing effective technologies, especially chemical treatments, to completely destroy trace levels of perchlorate present in drinking and groundwater. The research on perchlorate reduction by zero-valent titanium (Ti(0)) showed that perchlorate was effectively reduced to chloride using electrochemically developed pitting corrosion on Ti(0). Perchlorate reduction was believed to be caused by an active reductant (dissolved Ti(II)) during the pitting corrosion of Ti(0). The rate of perchlorate reduction was independent on the imposed potential as long as the potential was maintained above the pitting potential of Ti(0), but it was proportional to the applied current. The perchlorate reduction on the pitting developed Ti(0) was inhibited by the presence of chloride and bromide. Inhibition mechanism of perchlorate reduction inhibition was believed to be caused either by competitive adsorption of aggressive anions on bare Ti(0) surface or Ti(II) consumption by electrochemically produced chlorine. Kinetic models were developed based surface coverage of aggressive anions on bare Ti(0) and Ti(II) oxidation by chlorine. These kinetic models supported the perchlorate concentration change in the solution, but Ti(II) consumption model was not able to predict chloride concentration due to insufficient information describing complex nature of pitting on Ti(0). These results shown in this research demonstrate that pitting corrosion developed Ti(0) has the capability to chemically reduce perchlorate present in natural water and engineered systems as well as possible problems associated with electric input. This research may be a starting point for development of a new treatment process that applies titanium or titanium metal ions as a chemical reductant to abate contaminants present in natural and engineering systems. Further developments can be achieved by alloying titanium metal with other metals such as iron and aluminum, and finding a methodology producing stable Ti(II) in ambient conditions.