7440-25-7 Usage
Description
Tantalum is a heavy, blue-gray metallic transition element with the symbol Ta, atomic number 73, and a relative atomic mass of 180.9479. It is strong, highly resistant to corrosion, and easily worked. Tantalum is known for its ductility, which allows it to be drawn into fine wires, and its malleability, enabling it to be hammered and worked into various shapes. It has a high melting point of 2,996°C and a boiling point of 5,425°C. Tantalum is the 51st most abundant element found on Earth and is often mixed with other minerals. It is mainly obtained from ores such as columbite, tantalite, and euxenite, which are mined in various countries including South America, Thailand, Malaysia, Africa, Spain, and Canada.
Uses
1. Tantalum and its alloys are used in the construction of reactors, vessels, and crucibles for preparing and carrying out reactions involving many reactive intermediates due to their resistance to corrosion and ability to withstand high temperatures.
2. In the chemical industry, Tantalum is used to build furnace parts, electrolytic capacitors, aircraft and missile parts, and chemical process equipment.
3. Tantalum's nonreactivity with body fluids and nonirritant properties make it suitable for use in surgical appliances, bone repair, nerve repair, and the repair of abdominal muscles.
4. Tantalum oxide is used to produce optical glasses with a high refractive index and as a rectifier for converting alternating current to direct current.
5. Tantalum is used in pen points, analytical weights, and as a substitute for platinum in apparatus and instruments for chemical, surgical, and dental use.
6. Tantalum carbide (TaC) mixed with graphite is used to form the cutting edge of machine tools due to its hardness.
7. Tantalum pentoxide (Ta2O5) is used in the electronics industry to make capacitors and camera lenses due to its dielectric properties and high index of refraction.
8. Tantalum's hardness and noncorrosiveness make it suitable for dental and surgical tools, implants, and artificial joints, pins, and screws.
9. Tantalum is used in the electronics industry to make smoke detectors, as a getter in vacuum tubes to absorb residual gases, and as filaments in incandescent lamps.
10. Tantalum is increasingly popular for making miniaturized electrolytic capacitors that store electric charges in devices such as cell phones and computers.
11. Powdered tantalum is used in the process of sintering to form malleable bars and plates, as well as special electrodes for the electronics industry.
12. Tantalum alloys are used to fabricate parts for nuclear reactors, missiles, and airplanes, and in industries where metal with hardness, noncorrosiveness, and ductility is required.
History
Tantalum was discovered by the Swedish chemist Anders Ekeberg in 1802, although for a long time after his discovery many chemists believed tantalum and niobium were the same element. In 1866, Marignac developed a fractional crystallization method for separation of tantalum from niobium. Ekeberg named the element in honor of Tantalus, who was Niobe’s father in Greek mythology.
Tantalum is never found in nature in free elemental form. The most important mineral is columbite-tantalite (Fe,Mn) (Nb,Ta)2O6. Tantalum also is found in minor quantities in minerals pyrochlore, samarskite, euexenite, and fergusonite. The abundance of tantalum in the earth’s crust is estimated as 2 mg/kg.
Tantalum and its alloys have high melting points, high strength and ductility and show excellent resistance to chemical attack. Tantalum carbide graphite composite is one of the hardest substances ever made and has a melting point over 6,700°C. The pure metal is ductile and can be drawn into fine wire, which is used as filament for evaporating aluminum and other metals.
History
Discovered in 1802
by Ekeberg, but many chemists thought niobium and tantalum
were identical elements until Rose, in 1844, and Marignac, in
1866, showed that niobic and tantalic acids were two different
acids. The early investigators only isolated the impure metal.
The first relatively pure ductile tantalum was produced by
von Bolton in 1903. Tantalum occurs principally in the mineral
columbite-tantalite (Fe, Mn)(Nb, Ta)2O6. Tantalum ores
are found in Australia, Brazil, Rwanda, Zimbabwe, Congo-
Kinshasa, Nigeria, and Canada. Separation of tantalum from
niobium requires several complicated steps. Several methods
are used to commercially produce the element, including electrolysis of molten potassium fluorotantalate, reduction of
potassium fluorotantalate with sodium, or reacting tantalum
carbide with tantalum oxide. Thirty-four isotopes and isomers
of tantalum are known to exist. Natural tantalum contains two
isotopes, one of which is radioactive with a very long half-life.
Tantalum is a gray, heavy, and very hard metal. When pure, it
is ductile and can be drawn into fine wire, which is used as a
filament for evaporating metals such as aluminum. Tantalum
is almost completely immune to chemical attack at temperatures
below 150°C, and is attacked only by hydrofluoric acid,
acidic solutions containing the fluoride ion, and free sulfur trioxide.
Alkalis attack it only slowly. At high temperatures, tantalum
becomes much more reactive. The element has a melting
point exceeded only by tungsten and rhenium. Tantalum
is used to make a variety of alloys with desirable properties
such as high melting point, high strength, good ductility, etc.
Scientists at Los Alamos have produced a tantalum carbide
graphite composite material that is said to be one of the hardest
materials ever made. The compound has a melting point
of 3738°C. Tantalum has good “gettering” ability at high temperatures,
and tantalum oxide films are stable and have good
rectifying and dielectric properties. Tantalum is used to make
electrolytic capacitors and vacuum furnace parts, which account
for about 60% of its use. The metal is also widely used to
fabricate chemical process equipment, nuclear reactors, and
aircraft and missile parts. Tantalum is completely immune
to body liquids and is a nonirritating metal. It has, therefore,
found wide use in making surgical appliances. Tantalum oxide
is used to make special glass with a high index of refraction
for camera lenses. The metal has many other uses. The price
of (99.9%) tantalum is about $2/g.
Reactions
The most common oxidation state of tantalum is +5 and its aqueous solution chemistry is that of its pentavalent ion Ta5+. Ta metal forms a pentavalent oxide, tantalum pentoxide, Ta2O5, on heating with oxygen. However, at ordinary temperatures a thin layer of oxide covering the metal surface protects tantalum from most chemical attacks. The metal is attacked by hydrofluoric acid below 150°C. It also is dissolved by hot fuming sulfuric acid. It reacts with fluorine and chlorine on heating, forming tantalum pentafluoride, TaF5, and pentachloride, TaCl5, respectively. The metal is immune to dilute aqueous alkalies but is attacked slowly by concentrated fused alkalies. It combines with molecular hydrogen above 250°C. The hydride formed decomposes on heating above 800°C in vacuum. Tantalum forms alloys with several metals.
Isotopes
There are 49 isotopes of tantalum. Only the isotope Ta-181 is stable andaccounts for 99.988% of the total mass of the element on Earth. Just 0.012% of the element’s mass is contributed by Ta-180, which has a half-life of 1.2×10+15 years and isthus considered naturally stable. The remaining 47 isotopes are all artificially producedin nuclear reactions or particle accelerators and have half-lives ranging from a few microsecondsto few days to about two years.
Origin of Name
Tantalum was named after Tantalus, who was the father of Niobe, the
queen of Thebes, a city in Greek mythology. (Note: The element tantalum was originally
confused with the element nobelium.)
Characteristics
Tantalum is almost as chemically inert at room temperatures (it has the ability to resistchemical attacks, including hydrofluoric acid) as are platinum and gold. It is often substitutedfor the more expensive metal platinum, and its inertness makes it suitable for constructingdental and surgical instruments and artificial joints in the human body.
Production Methods
The first successful industrial process used to extract tantalum and niobium from the tantalite-columbite-containing minerals employed alkali fusion to decompose the ore, acid treatment to remove most of the impurities, and the historic Marignac fractional-crystallization method to separate the tantalum from the niobium and to purify the resulting K2TaF7. Most tantalum production now employs recovery of the tantalum and niobium values by dissolution of the ore or ore concentrate in hydrofluoric acid. Then the dissolved tantalum and niobium values are selectively stripped from the appropriately acidified aqueous solution and separated from each other in a liquid-liquid extraction process using methyl isobutyl ketone (MIBK) or other suitable organic solvent. The resulting purified tantalum-bearing solution is generally treated with potassium fluoride or hydroxide to recover the tantalum in the form of potassium tantalum fluoride, K2TaF7, or with ammonium hydroxide to precipitate tantalum hydroxide, which is subsequently calcined to obtain tantalum pentoxide, Ta2O5. Tantalum metal is generally obtained by sodium reduction of K2TaF7, although electrolysis of K2TaF7 and carbon reduction of Ta2O5 in an electric furnace have also been used. Tantalum metal can absorb large volumes of hydrogen during heating in a hydrogenbearing atmosphere at an intermediate temperature range (450–700 °C (842-1,292 °F)). The hydrogen is readily removed by heating in vacuum at higher temperatures.
Production Methods
It was identi?ed that tantalum minerals exists in over 70 differentchemicalcompositions.Thoseofgreatesteconomic importance are tantalite, microlite, and wodginite; however, it is common practice to name any tantalum-containing mineral concentrate as “tantalite”. Tantalum resources are widespread, with the most important known resources being found in Brazil and Australia. In mid-2008, the main mining operations were in Australia, Brazil,Canada,Mozambique,andEthiopiaandinmid-2009, in Brazil, Ethiopia, and China, with additional quantities originating in central Africa, Russia, and Southeast Asia. There is continued interest in exploration of this element in other countries, primarily in Egypt, Canada, Mozambique, and Saudi Arabia. The major world mine producers of tantalum in 2010 were Brazil (180 tons), Mozambique (110 tons), Rwanda (100 tons), and Australia (80 tons). Other countries produced around 170 tons, so the total world production of tantalum was approximately 670 tons. The major producers of tantalum mineral concentrates are Australia, Brazil, and Canada.
Hazard
Dust or powder may be flammable. Toxic
by inhalation.
Hazard
The dust and powder of tantalum are explosive. Several tantalum compounds are toxic ifinhaled or ingested, but the metal itself is nonpoisonous.
Health Hazard
Tantalum has a low order of toxicity
but has produced transient inflammatory
lesions in the lungs of animals.
Surgical implantation of tantalum metal
products such as plates and screws has not
shown any adverse tissue reaction, thus demonstrating
its physiological inertness.
Flammability and Explosibility
Flammable
Safety Profile
An inhalation hazard. Some industrial skin injuries from tantalum have been reported. Systemic industrial poisoning, however, is apparently unknown. Questionable carcinogen with experimental tumorigenic data. The dry powder iptes spontaneously in air. Incompatible with bromine trifluoride, fluorine, lead chromate. See also specific tantalum compounds.
Carcinogenicity
Although Oppenheimer et al., using embedded metal foil technique, have elicited two malignant ?brosarcomas in 50 embeddings of tantalum metal in 25Wistar rats aftera latent period of714days, these results remain a controversial issue. Miller et al. have studied tumorigenic transforming potential of tungsten, iron, nickel, and cobalt with tantalum as a comparison on an immortalized nontumorigenic human osteoblast-like cell line. No tumorigenic activity of Ta was reported, but data are not shown. In the recent study, intramuscularly pellets (1mm 2mm cylinders) of weapons-grade WA were implantedtosimulateshrapnelwounds.Ratswereimplanted with 4 (low dose) or 20 pellets (high dose) of WA. Tantalum (20 pellets) and nickel (20 pellets) served as negative and positive controls, respectively. Rats implanted with tantalum (n=46) did not develop tumors.
Shipping
UN3089 Metal powders, flammable, n.o.s., Hazard Class: 4.1; Labels: 4.1-Flammable solid.
Incompatibilities
A flammable solid; the dry powder can ignite spontaneously in air. Incompatible with lead chromate. A strong reducing agent; incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, bromine trifluoride, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides. Tantalum metal is attacked by hydrogen fluoride, fused alkalis, fuming sulfuric acid.
Waste Disposal
Sanitary landfill if necessary; recover if possible because of economic value. Technology exists for tantalum recovery from spent catalysts, for example.
Check Digit Verification of cas no
The CAS Registry Mumber 7440-25-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,4,4 and 0 respectively; the second part has 2 digits, 2 and 5 respectively.
Calculate Digit Verification of CAS Registry Number 7440-25:
(6*7)+(5*4)+(4*4)+(3*0)+(2*2)+(1*5)=87
87 % 10 = 7
So 7440-25-7 is a valid CAS Registry Number.
InChI:InChI=1/Ta
