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PROPERTIES
Interesting facts about titanium that explain which it is the metal of choice for many uses, in sports, medicine, and jewelry. The Name The name "Titanium" was derived from the Titans of Greek mythology, symbolizing strength. Resistance To Corrosion Titanium is nearly as resistant to corrosion as platinum, and resists many acids, salt solutions, and even chlorine gas. Like many metals, it is not water soluble, save perhaps in concentrated acids. It is most useful for the way it combines high-strength a light-weigth. Titanium may be 60% heavier than aluminium, but it is 100% stronger. It is 45% lighter than steel, but equally strong. Thus, it is an ideal replacement for applications where a strong metal is required, light weight an advantage, and where metal fatigue an issue. It is a passive oxide coating that leads to corrosion resistance, and resistance to tarnishing at room temperature. Density and Strength Titanium is a very light metal. It weighs only 4.5g/cm3, which makes it 4.5 times more dense than water. To compare, lead is much denser at 11.3 times more dense than water, and aluminium is lighter at 2.7 times the density of water. Titanium has the highest strength to density ratio it is the material of choice only for certain niche application areas because of its high price. Density and tensile strenght
Characteristics of titanium and structural metals
Physico-Chemical Properties Titanium will burn to form titanium dioxide when heated at 610°C in the presence of oxygen. Titanium can also burn in pure nitrogen gas at 800°C with titanium nitride resulting from the chemical reaction. Titanium is only weakly attracted to magnets. It does not conduct electricity very well, or heat. This low thermal conductivity is why, unlike other metals, titanium does not feel cold upon its initial contact with the skin. At high temperatures, titanium reacts readily with oxygen and carbon, creating special challenges in the preparation of titanium metal, crystals, or powder. Some commercial titanium alloys
Coloration A rich, putty-grey color allows it to distinguish itself from the more common silver and gold used in jewelry. The metal is commonly polished in a variety of ways to produce matte or shiny surface finishes, or anodized to create all colors of the rainbow. Radioactive Potential Bombardment with deuterons can render titanium very radioactive. It will emit positions and hard gamma rays. Titanium Dioxide Most of the inudstrial application of titanium is in the form of titanium dioxide (TiO2), used as a dense, fade-resistant pigment in paints, paper, plastics, toothpaste. Titanium dioxide has excellent covering power. An interesting note is that the pigment is used by astronomers because of its ability to reflect infrared radiation. It is also especially useful in hot climates to keep interiors cooler when used in exterior paint. When used in paper or cement, the compound also imparts greater strength to the material. Applications Titanium's special combination of light weight, strenght, resistance to heat and corrosion make it especially useful in military applications such as aircrafts, armor plating, naval ships, spacecraft and missiles. In civilian applications is valuable in aviation, racket sports, bicycle frames, golf clubs, eyewear frames, light laptop computers, medical implants and jewelry. It is the material of choice for the 10-12% of individuals that suffer dermatitis owing to nickel sensitivity. Titanium is a non-toxic, inert biomaterial and it is ideal for dental and other implants. Alloys Addition of titanium to alloys will have different effects depending on the other metals involved. For instance, with steel, titanium will deoxidize and reduce grain size. In stainless steel it is useful to reduce carbon content. With aluminium, grain size is reduced; titanium will harden both copper and vanadium. In particular, titanium vanadium alloys are widely used in aviation in the making of landing gear, hydraulic tubing, fire walls, etc. Crystal Structure Pure titanium exhibits an allotropic phase transformation at 882°C, changing from a body-centered cubic crystal structure (β phase) at higher temperatures to a hexagonal close-packed crystal structure (α phase) at lower temperatures. 
Unit cell of α phase
Unit cell of β phase
The exact transformation temperature is strongly influenced by interstitial and substitutional elements and therefore depends on the purity of the metal. The crystal packing of titanium helps predict how titanium will give in to stretching or other deforming forces, as deformations will tend to occur along crystal planes that align and dictate the direction of the weakest planes in the material. Extraction Though it is the ninth most abundant element in the Earth's crust, titanium metal is always found bound to other elements. It is most commonly associated with igneous rocks and their derived sediments. It is found in rutile, anatase, ilmenite, brookite, perovskite, titanite , as well in many iron ores. Ilmenite and rutile are difficult to find in high concentrations, but they are the only commercially viable source of titanium ore at this time. Ilmenite is mined in Australia, Brazil, Russia, Canada, Sri Lanka, Norway, China, South Africa, Thailand, India, Malaysia, Sierra Leone and the United States. Titanium is not easily extracted from the ore. As recently as 1946, William Justin Kroll discovered means to extract it commercially by reducing titanium tetrachloride with magnesium. The oxide is converted to chloride through carbochlorination, whereby chlorine gas is passed over red-hot rutile or ilmenite in the presence of carbon to make TiCl4. This is condensed and purified by fractional distillation and then reduced with 800 °C molten magnesium in an argon atmosphere. Though complex and expensice, the Kroll process is still used today. The FFC Cambridge Process is a newer method that is being increasingly favored. Because it reduces the cost of extraction, it is hoped that titanium will be used more extensively in the aerospace industry, for example. Titanium oxide is produced commercially mixing ground mineral ore and mixing it with potassium carbonate and aqueous hydrofluoric acid. This chemical reaction product potassium fluorotitanate (K2TiF6) is extracted with hot water and decomposed with ammonia, producing a ammoniacal hydrated oxide. This in turn is ignited in a platinum vessel, which creates pure titanium dioxide. |
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