Part. 2: MINERALS AND METALLURGY
The oxidized Titanium compounds are very common in nature; but, you can extract only the rutile, with a percentage of 93-96% of titanium dioxide, digged out in the USA, Canada, Sweden and Norway, and the ilmenite with a percentage of 44-70% of titanium dioxide, you can find in India, Siberia and Australia, also present as black sand on many beaches.
The most common industrial process to prepare titanium is Kroll’s process ( chloride titanium reduction, prepared from rutile and ilmenite). A first phase of mineral chlorination at 800°C becomes titanium tetrachloride, that is first purified through distillation and after reduced with magnesium or sodium at 900°C in helium atmosphere.
The obtained metal is in the form of dust or flakes (titanium sponge) and it must be melded again into a special arc electric furnace in argon atmosphere (VAR method, Vacuum Arc Remeltin) to obtain the ingot. From the ingot, you can later obtain other products come from the bar, with traditional proceedings.
Another method to obtain the titanium is the electrolysis of the titanium tetrachloride. However, the big quantity of energy to transform the titanium oxides, to reach the metallic condition, affects very much the final cost.
After the production cycle, titanium must be processed:
- In the Surface cleaning
- Through Chemical passivation
The ASTM specifications for the final treatment of implants imply the immersion in fused salts based on alkaline with following mordanting in a solution of hydrofluoric and nitric acid as to cancel impurities like iron, that demineralizes the bone matrix.
Other kinds of procedures can be used, like the bath-sanding (Corundum) or the ionic proceeding, laser treatment, with related advantages or disadvantages.
The final sterilization is made with the gamma-rays and many producers supply multiple implants assembled in sterile tests. This method is a very good system.
Nowadays, protein deposits, the film of organic and pollution elements can be treated better with the radiofrequency.
The Direct implant’s regeneration and the self-management of the sterilization cycle can be made in a better way using a register for UV sterilization that is very efficient on the spores and on the biological contaminators.