The Titanium reference article from the English Wikipedia on 24-Jul-2004
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Titanium

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scandiumtitaniumvanadium
Ti
Zr  
 
 
Image:Ti-TableImage.png
General
Name, Symbol, NumberTitanium, Ti, 22
Chemical series transition metals
Group, Period, Block4, 4 , d
Density, Hardness 4507 kg/m3, 6
Appearance Silvery metallic
125px
Atomic properties
Atomic weight 47.867 amu
Atomic radius (calc.) 140 (176) pm
Covalent radius 136 pm
van der Waals radius no data
Electron configuration [Ar]3d3d2 4s2
e- 's per energy level2, 8, 10, 2
Oxidation state (Oxide) 4 (amphoteric)
Crystal structure Hexagonal
Physical properties
State of matter Solid (__)
Melting point 1941 K (3034 ðF)
Boiling point 3560 K (5949 ðF)
Molar volume 10.64 ×1010-6 m3/mol
Heat of vaporization 421 kJ/mol
Heat of fusion 15.45 kJ/mol
Vapor pressure 0.49 Pa at 1933 K
Velocity of sound 4140 m/s at 293.15 K
Miscellaneous
Electronegativity 1.54 (Pauling scale)
Specific heat capacity 520 J/(kg*K)
Electrical conductivity 2.34 106/m ohm
Thermal conductivity 21.9 W/(m*K)
1st ionization potential 658.8 kJ/mol
2nd ionization potential 1309.8 kJ/mol
3rd ionization potential 2652.5 kJ/mol
4th ionization potential 4174.6 kJ/mol
5th ionization potential 9581 kJ/mol
6th ionization potential 11533 kJ/mol
7th ionization potential 13590 kJ/mol
8th ionization potential 16440 kJ/mol
9th ionization potential 18530 kJ/mol
10th ionization potential 20833 kJ/mol
Most stable isotopes
isoNAhalf-life DMDE MeVDP
44Ti{syn.}63 y &epsilon0.26844Sc
46Ti8.0%Ti is stable with 24 neutrons
47Ti7.3%Ti is stable with 25 neutrons
48Ti73.8%Ti is stable with 26 neutrons
49Ti5.5%Ti is stable with 27 neutrons
50Ti5.4%Ti is stable with 28 neutrons
SI units & STP are used except where noted.

Titanium is a chemical element in the periodic table that has the symbol Ti and atomic number 22. A light, strong, white-metallic, lustrous, corrosion-resistant transition metal, titanium is used in strong light-weight alloys and in white pigments. This element occurs in numerous minerals with the main sources being rutile and ilmenite.

Table of contents
1 Notable characteristics
2 Applications
3 History
4 Occurrence
5 Compounds
6 Isotopes
7 Precautions
8 References
9 External links

Notable characteristics

Titanium is a metallic element which is well known for its excellent corrosion resistance (almost as resistant as platinum) and for its high strength-to-weight ratio. It is a light, strong, easily fabricated metal with low density (40% as dense as steel) that, when pure, is quite ductile, easy to work, lustrous, and metallic-white in color. The relatively high melting point of this element makes it useful as a refractory metal. Titanium is as strong as steel, but 45% lighter; it is 60% heavier than aluminium, but twice as strong. These properties make titanium very resistant to the usual kinds of metal fatigue.

This metal forms a passive oxide coating when exposed to air but when it is in an oxygen-free environment it is ductile. The metal, which burns when heated in air, is also the only element that can burn in pure nitrogen gas. Titanium is resistant to dilute sulfuric and hydrochloric acid, along with chlorine gas, chloride solutions, and most organic acids.

Experiments have shown that natural titanium becomes very radioactive after it is bombarded with deuterons, emitting mainly positrons and hard gamma rays. The metal is dimorphic with the hexagonal alpha form changing into the cubic beta form very slowly at around 880°C. When it is red hot the metal combines with oxygen, and when it reaches 550°C it combines with chlorine.

Applications

Approximately 95% of titanium is consumed in the form of titanium dioxide (TiO2), an intensely white permanent pigment with good covering power in paints, paper, and plastics. Paints made with titanium dioxide are excellent reflectors of infrared radiation and are therefore used extensively by astronomers.

Because of its strength, light weight, extraordinary corrosion resistance, and ability to withstand extreme temperatures, titanium alloys are principally used in aircraft and missiles, although applications in consumer products such as golf clubs, bicycles, wedding bands, and laptop computers are becoming more common. Titanium is often alloyed with aluminum, iron, manganese, molybdenum and with other metals. Other uses;

A potential use of titanium is in desalination plants.

History

Titanium (Latin Titans, the first sons of Gaia) was discovered in England by Reverend William Gregor in 1791 who recognized the presence of a new element in ilmenite. The element was rediscovered several years later by German chemist Martin Heinrich Klaproth in rutile ore. In 1795 Klaproth named the new element after the Titans of Greek mythology.

Pure metallic titanium (99.9%) was first prepared in 1910 by Matthew A. Hunter by heating TiCl4 with sodium in a steel bomb at 700-800°C.

Titanium metal was not used outside the laboratory until 1946 when William Justin Kroll proved that titanium could be commercially produced by reducing titanium tetrachloride with magnesium (which is the method still used today).

Occurrence

Titanium metal is not found unbound to other elements in nature but the element is the ninth most abundant element in the Earth's crust (0.6% by mass) and is present in most igneous rocks and in sediments derived from them. It occurs primarily in the minerals anatase, brookite, ilmenite, leucoxene, perovskite, rutile, and sphene and is found in titanates and in many iron ores. Of these minerals, only ilmenite, leucoxene, and rutile have significant economic importance. Because it reacts easily with oxygen and carbon at high temperatures it is difficult to prepare pure titanium metal. Significant titanium ore deposits are in Australia, Scandinavia, North America and Malaysia.

This metal is found in meteorites and has been detected in the sun and in M-type stars. Rockss brought back from the moon during the Apollo 17 mission are composed of 12.1% TiO2. Titanium is also found in coal ash, plants, and even the human body.

Production

Titanium metal is produced commercially by reducing TiCl4 with magnesium, a process developed in 1946 by William Justin Kroll. This is a complex and expensive batch process, but a newer process called the "FFC-Cambridge" method may displace this older process. This method uses the feedstock titanium dioxide powder (which is a refined form of rutile) to make the end product which is a continuous stream of molten titanium suitable for immediate use in the manufacture of commercial alloys.

It is hoped that the FFC-Cambridge method will render titanium a less rare and expensive material for the aerospace industry and the luxury goods market, and will be seen in many products currently manufactured using aluminum and specialist grades of steel.

Compounds

Although titanium metal is relatively uncommon, due to the cost of extraction, titanium dioxide is cheap, readily available in bulk, and very widely used as a white pigment in paint, plastic and construction cement. TiO2 powder is chemically inert, resists fading in sunlight, and is very opaque: this allows it to impart a pure and brilliant white color to the brown or gray chemicals that form the majority of household plastics. Pure titanium dioxide has a very high index of refraction and an optical dispersion higher than diamond. Star sapphires and rubies get their asterism from the titanium dioxide present in them.

Isotopes

Naturally occurring titanium is composed of 5 stable isotopes; Ti-46, Ti-47, Ti-48, Ti-49 and Ti-50 with Ti-48 being the most abundant (73.8% natural abundance). 11 radioisotopes have been characterized with the most stable being Ti-44 with a half-life of 63 years, Ti-45 with a half-life of 184.8 minutes, Ti-51 with a half-life of 5.76 minutes, and Ti-52 with a half-life of 1.7 minutes. All of the remaining radioactive isotopes have half-lifes that are less than 33 seconds and the majority of these have half lifes that are less than half a second.

The isotopes of titanium range in atomic weight from 39.99 amu (Ti-40) to 57.966 amu (Ti-58). The primary decay mode before the most abundant stable isotope, Ti-48, is electron capture and the primary mode after is beta emission. The primary decay products before Ti-48 are element 21 (scandium) isotopes and the primary products after are element 23 (vanadium) isotopes.

Precautions

When in a powdered form, titanium metal poses a significant fire hazard but salts of titanium are often considered to be relatively harmless. Chlorine compounds such as TiCl3 and TiCl4 should be considered to be corrosive, however. Titanium also has a tendency to bio-accumulate in tissues that contain silica but it does not play any known biological role in humans.

References

External links