titanium dioxide: Definition and Much More from Answers.com

titanium dioxide
Titanium dioxide


Chemical name Titanium dioxide
Titanium(IV) oxide
Other names Titania
Rutile
Anatase
Brookite
Chemical formulaTiO2
Molecular mass 79.87 g/mol
Appearance White solid
CAS number [13463-67-7]
HS number Titanium oxides: 2823.00
2823.00.10.000(anatase)
2823.00.90.000(others)
Properties
Density 4.23 g/cm3
Bulk Density 0.85 g/cm3
Melting point 1870 °C (3398 °F)
Boiling point 2972 °C (5381.6 °F)
Dielectric Constant εr 80-110
Heat Capacity 298.13 J/(mol °C)
Heat Conductivity 6.531 W/(m K)
Lin. Coeff. Therm Exp. 8.19 °C<-1
Elastic Module 244 GPa
Bulk modulus Rutile: 210 GPa[1]
Hardness 5-6.5 Mohs
El. Resistivity 3*105 Ω @ 773 K
Ref. Index(ng,nm,np) Rutile: 2.9467,-,2.6506
α-rutile: 2.908,-,2.621
Anatase: 2.5688,-,2.6584
γ-anatase: 2.448,-,2.261
Brookite: 2.809,-,2.677
α-brookite: 2.7004,2.5843,2.5831
Solubility Insoluble
Thermodynamic data
ΔfHogas −249kJ/mol
ΔfHoliquid −879kJ/mol
ΔfHosolid −944kJ/mol
Sosolid 51J/mol·K
Hazards
MSDS External MSDS
EU classification not listed
NFPA 704
0
1
0
Flash point non-flammable
RTECS number XR2775000
Supplementary data page
Structure and
propertiesn,εr, etc.
Thermodynamic
data Phase behaviour
Solid, liquid, gas
Spectral dataUV,IR,NMR,MS
Related compounds
OthercationsTitanium(II) oxide
Titanium(III) oxide
Titanium(III,IV) oxide
Zirconium dioxide
Hafnium dioxide
Disclaimer and references
Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurringoxide oftitanium, chemical formulaTiO2. When used as apigment, it iscalled titanium white, Pigment White 6, orCI 77891. Itis noteworthy for its wide range of applications, from paint to sunscreen tofoodcolouring.
Natural occurrence
Titanium dioxide occurs in four forms:
rutile, atetragonal mineral usually of prismatic habit, often twinned;
anatase or octahedrite, a tetragonal mineral of dipyramidal habit;
brookite, anorthorhombic mineral. Both anatase and brookite are relatively rare minerals;
Titanium dioxide (B) or TiO2(B), amonoclinic mineral.
Titanium dioxide occurrences in nature are never pure; it is found with contaminant metals such asiron. The oxides can be mined and serve as a source for commercialtitanium. Themetal can also be mined from other minerals such asilmenite orleucoxeneores, or one of the purest forms,rutile beach sand.
Applications
As a pigment of highrefringence, titanium dioxide is the most widely used white pigmentbecause of its brightness and very high refractive index (n=2.4), in which it is surpassed only by afew other materials. When deposited as a thin film, its refractive index and colour make itan excellent reflective optical coating fordielectric mirrors and somegemstones, for example "mystic firetopaz". TiO2 isalso an effectiveopacifier in powder form, where it is employed as a pigment to providewhiteness andopacity to products such aspaints,coatings,plastics,papers,inks,foods, and mosttoothpastes.Used as a whitefood colouring, it hasE number E171. Incosmetic and skin care products, titanium dioxide is usedboth as a pigment and athickener. It is also used as atattoo pigment andstyptic pencils.
This pigment is used extensively in plastics and other applications for its UV resistant properties where it acts as a UVreflector.
Inceramic glazes titanium dioxide acts as an opacifier and seedscrystal formation. In almost everysunscreen with a physical blocker,titanium dioxide is found both because of its refractive index and its resistance to discolouration underultraviolet light. This advantage enhances its stability and ability to protect the skin from ultravioletlight. Sunscreens designed for infants or people with sensitive skin are often based on titanium dioxide and/orzinc oxide, as these mineral UV blockers are less likely to cause skin irritation than chemical UVabsorber ingredients, such asavobenzone.
Titanium oxide is also used as a semi-conductor.[2]
As a photocatalyst
Titanium dioxide, particularly in the anatase form, is aphotocatalyst underultraviolet light. Recently it has been found that titanium dioxide, when spiked with nitrogen ions, is also a photocatalystunder visible light. The strongoxidative potential of thepositive holes oxidizeswater to createhydroxyl radicals. It can also oxidize oxygen or organic materials directly. Titanium dioxideis thus added to paints, cements, windows, tiles, or other products for sterilizing, deodorizing and anti-fouling properties andis also used as ahydrolysis catalyst. It is also used intheGraetzel cell, a type of chemical solar cell.
Titanium dioxide has potential for use in energy production: as a photocatalyst, it can carry outhydrolysis, i.e., break water into hydrogen and oxygen. Were the hydrogen collected, it could be used as afuel. The efficiency of this process can be greatly improved by doping the oxide with carbon, as described in "Carbon-dopedtitanium dioxide is an effective photocatalyst"[1].
As TiO2 is exposed to UV light, it becomes increasinglyhydrophilic; thus, itcan be used for anti-fogging coatings or self-cleaning windows. TiO2 incorporated into outdoor building materials,such as paving stones innoxer blocks, can substantially reduce concentrations of airbornepollutants such asvolatile organic compounds andnitrogen oxides.
For wastewater remediation
TiO2 offers great potential as an industrial technology for detoxification orremediation ofwastewater due to several factors.
The process occurs under ambient conditions.
The formation of photocyclized intermediate products, unlike directphotolysis techniques, is avoided.
Oxidation of the substrates to CO2 is complete.
The photocatalyst is inexpensive and has a high turnover.
TiO2 can be supported on suitable reactor substrates.
Other applications
It is also used in resistance-typelambda probes (a type ofoxygen sensor).
Titanium dioxide is what allowsosseointegration between anartificial medical implant andbone.
Historical uses
TheVinland map, the map ofAmerica("Vinland") that was supposedly drawn during mid-15th century based on data from theViking Age, has been declared a forgery on the basis that the ink on it contains traces ofthe TiO2-form anatase; TiO2 was not synthetically produced before the 1920s. Recently (1992) acounter-claim has been made that the compound can be formed from ancient ink.
Titanium dioxide white paint was used to paint theSaturn V rocket, which was the firstrocket to send astronauts to the moon. In2002, a spectral analysis ofJ002E3, a celestial object, showed that it had titanium dioxide on it, giving evidence it may be a Saturn VS-IVB.
See also
Noxer, a building material incorporating TiO2.
References
^ Francisco, E; Bermejo M, Garcia Baonza V, Gerward L, Recio JM (2003). "Spinodal equation of state for rutile TiO2". Physical Review B 67 (6): 064110-1.
^http://prola.aps.org/abstract/PR/v61/i1-2/p56_1
External links
International Chemical Safety Card 0338
NIOSH Pocket Guide to Chemical Hazards
"Fresh doubt over America map", bbc.co.uk, 30 July, 2002
A description of TiO2 photocatalysis
"Smog-busting paint soaks up noxious gases", Jenny Hogan, ‘newscientist.com, 04 February 2004
Crystal structures of the three forms of TiO2
Kutal, C., Serpone, N. (1993). Photosensitive Metal Organic Systems: Mechanistic Principles and Applications. American Chemical Society, Washington D.C
"Architecture in Italy goes green", Elisabetta Povoledo, International Herald Tribune, November 22, 2006
"A Concrete Step Toward Cleaner Air", Bruno Giussani, BusinessWeek.com, November 8, 2006
Links to external chemical sources