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Zirconium and Titanium Ore and Refining Processes
Titanium (Ti) and zirconium (Zr) are two metals of significant industrial value. Not only are they widely distributed in nature, but they also possess many unique chemical and physical properties.
Zirconium and Titanium Ore Sources and Extraction Processes
Titanium Ore: Titanium primarily occurs in ilmenite (Fe₃O₄·TiO₂), titaniferous ilmenite (FeTiO₃), and rutile (TiO₂). Rutile is one of the most common minerals containing titanium.
Zirconium Ore: Zirconium is commonly found in zircon (ZrSiO₄) and ilmenite (ZrO₂, containing 80–90% zirconium). These ores are exceptionally abundant, with reserves comparable to those of iron ore.
Extraction and Smelting Process
Due to the extremely high chemical reactivity of titanium and zirconium, their purification processes are relatively complex and typically cannot employ common reduction methods (such as reducing oxides with oxygen). Key steps in titanium and zirconium extraction include:
1. Reduction-Based Refining:
Traditional reduction processes struggle to reduce titanium and zirconium oxides (like TiO₂ and ZrO₂), so chlorination reduction is commonly employed. This method involves converting metal oxides into chlorides, which then react with reducing agents like calcium or magnesium to yield the metals.
2. Volatility of Chlorides:
When reduction occurs in chlorine or ammonia gas, the high volatility of chlorides accelerates reaction rates but necessitates strict control conditions. This precludes the process from being conducted in conventional air environments.
3. Cleaning and Purification:
The purity of titanium and zirconium significantly impacts their physical properties, such as tensile strength and ductility. Even trace impurities like oxygen or nitrogen can substantially alter these properties. For instance, just 0.1% oxygen or nitrogen can markedly increase titanium's tensile strength but simultaneously reduce its ductility. Therefore, during smelting, impurities must be further removed through various methods to achieve high-purity production.
Preparation of High Purity.
Iodide Method: To obtain high-purity titanium and zirconium with good plasticity, the iodide method is commonly employed. This technique involves subliming the iodide of titanium or zirconium in a vacuum, then decomposing it upon contact with a red-hot tungsten filament to yield extremely pure metals. Through this method, titanium purity can reach 99.95%, while zirconium purity can exceed 99.99%.
Conclusion
The smelting processes for titanium and zirconium are complex and technically demanding. However, their high strength, corrosion resistance, and high-temperature stability make these metals crucial for applications in aerospace, chemical industries, and medical equipment.
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