Indium (pronounced /ˈɪndiəm/ IN-dee-əm)
is a chemical element with chemical
symbol In and atomic
number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to aluminium
or gallium.
Zinc ores are the primary source of indium. It is named for the indigo
blue line in its spectrum that was the first indication of its
existence in ores, as a new and unknown element.
Detailed description
Indium's current
primary application is to form transparent electrodes from indium tin oxide in liquid
crystal displays
and touchscreens, and this use largely determines its
global mining production. It is widely used in thin-films to form lubricated
layers (during World
War II it was widely
used to coat bearings in high-performance aircraft). It is also used for making
particularly low melting point alloys, and is a component in some lead-free
solders.
Radioactive
indium-111 is used in indium
leukocyte imaging,
a nuclear
medicine test which uses
the isotope as an imaging agent to follow the movement of leukocytes in the body.
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Characteristics
Indium is a very
soft, silvery-white, relatively rare true metal with a bright luster. As a pure metal, indium emits a
high-pitched "cry", when it is bent.[2] Both gallium and indium are able to wet glass. Indium has a standard electrode
potential of +0.34V, the same as thallium.
Isotopes
Indium in nature
consists of two primordial
nuclides. One unusual
property of indium (shared only with rhenium) is that although it possesses a
stable isotope, its most common (abundant) isotope (95.7%) is slightly and measurably
radioactive. This isotope, indium-115 very slowly decays by beta emission to tin. This decay has a half-life of
4.41 × 1014 years, four orders of magnitude larger than
the age of the universe and nearly 50,000 times longer than that of natural thorium.[3]
Creation
Indium is created
via the long S-process in low-medium mass stars (.6 -> 10
solar masses). This takes thousands of years to do. It requires a cadmium atom to capture sufficient neutrons and then undergo Beta decay.
History
In 1863 the
German chemists Ferdinand
Reich and Hieronymous
Theodor Richter
were testing ores from the mines around Freiberg, Saxony. They dissolved the minerals pyrite, arsenopyrite, galena and sphalerite in hydrochloric acid and distilled the raw zinc chloride. As it was known that ores from that
region sometimes contain thallium they searched for the green emission
lines with spectroscopic methods. The green lines were absent but a blue line
was present in the spectrum. As no element was known with a bright blue
emission they concluded that a new element was present in the minerals. They
named the element with the blue spectral line indium, from the indigo color seen in its spectrum.[4][5] Richter went on to isolate the metal
in 1864.[6] At the World
Fair 1867 an ingot of
0.5 kg (1.1 lb) was presented.[7]
Occurrence and consumption
Indium ranks 61st
in abundance in the Earth's crust at approximately 0.25 ppm,[8] which means it is more than three
times as abundant as silver, which occurs at 0.075 ppm.[9] Fewer than 10 indium minerals are
known, none occurring in significant deposits. Examples are the dzhalindite (In(OH)3) and indite (FeIn2S4).[10]
Resources
Based on content
of indium in zinc ore stocks, there is a worldwide reserve base of
approximately 6,000 tonnes of economically viable indium.[11] This figure has led to estimates
suggesting that, at current consumption rates, there is only 13 years'
supply of indium left.[12] However, the Indium Corporation, the largest processor of indium,
claims that, on the basis of increasing recovery yields during extraction,
recovery from a wider range of base metals (including tin, copper and other
polymetallic deposits) and new mining investments, the long-term supply of
indium is sustainable, reliable and sufficient to meet increasing future
demands.[13]
This conclusion also
seems reasonable in light of the fact that silver, three times less abundant
than indium in the earths crust,[14] is currently mined at approximately
18,300 tonnes per annum,[15] which is 40 times greater than
current indium mining rates.
Production
The lack of
indium mineral deposits and the fact that indium is enriched in sulfidic lead, tin, copper, iron and predominately in zinc deposits, makes zinc production the main
source for indium. The indium is leached from slag and dust of zinc production.
Further purification is done by electrolysis.[7]
Indium is
produced mainly from residues generated during zinc ore processing but is also found in iron, lead, and copper ores.[2] Canada is a leading producer of
indium. The Teck
Cominco refinery in Trail,
British Columbia,
is the largest single source indium producer, with production of 32,500 kg
in 2005, 41,800 kg in 2004 and 36,100 kg in 2003. South American
Silver's Malku Khota property in Bolivia is the largest resource of indium with
an indicated resource of 845,000kg and inferred resource of 968,000kg.Adex Mining Inc.’s Mount Pleasant Mine in New Brunswick, Canada, holds about 15 to 20% of the
world’s total known indium resources.[16]
The amount of
indium consumed is largely a function of worldwide LCD production. Worldwide production is
currently 476 tonnes per year from mining and a further 650 tonnes per year
from recycling.[13] Demand has risen rapidly in recent
years with the popularity of LCD computer monitors and television sets, which
now account for 50% of indium consumption.[17] Increased manufacturing efficiency
and recycling (especially in Japan) maintain a balance between demand
and supply. Demand increased as the metal is used in LCDs and televisions, and
supply decreased when a number of Chinese mining concerns stopped extracting indium from their
zinc tailings. In 2002, the price was US$94 per kilogram. The recent changes in
demand and supply have resulted in high and fluctuating prices of indium, which
from 2005 to 2007 ranged from US$700/kg to US$1,000/kg.[11] Demand for indium may increase with
large-scale manufacture of CIGS-based thin film solar technology starting by
several companies in 2008, including Nanosolar and Miasole, although zinc oxide is often used instead.[citation needed]
Applications
The first
large-scale application for indium was as a coating for bearings in high-performance aircraft engines during World War II. Afterward, production gradually
increased as new uses were found in fusible alloys, solders, and electronics. In the 1950s, tiny beads of it were
used for the emitters and collectors of PNP alloy
junction transistors.
In the middle and late 1980s, the development of indium phosphide semiconductors and indium tin oxide thin films for liquid
crystal displays
(LCD) aroused much interest. By 1992, the thin-film application had become the
largest end use.[18][19]
Electronics
- Indium
oxide
(In2O3) and indium
tin oxide
(ITO) are used as a transparent conductive coating
applied to glass substrates
in the making of electroluminescent panels.
- Some indium
compounds such as indium
antimonide,
indium
phosphide,[20] and indium
nitride[21] are semiconductors with useful
properties.
- Indium is
used in the synthesis of the semiconductor copper indium gallium selenide (CIGS),
which is used for the manufacture of thin film solar cells.[22]
- Used in light-emitting
diodes
(LEDs) and laser diodes based on compound
semiconductors
such as InGaN, InGaP that are
fabricated by Metalorganic Vapor Phase Epitaxy (MOVPE)
technology.
- The
ultrapure metalorganics of indium,
specifically high purity trimethylindium (TMI) is
used as a precursor in III-V compound
semiconductors,
while it is also used as the semiconductor dopant in II-VI compound
semiconductors.[23]
Metal and alloys
- Very small
amounts used in aluminium alloy sacrificial anodes (for salt water
applications) to prevent passivation of the
aluminium.
- To bond gold
electrical test leads to superconductors, indium is
used as a conducting glue and applied under a microscope with precision
tweezers.
- In the form
of a wire it is used as a vacuum seal and a thermal conductor in cryogenics and ultra-high
vacuum
applications. For example, in manufacturing gaskets which
deform to fill gaps.[24]
- Used as a
calibration material for Differential scanning calorimetry.
- It is an
ingredient in the alloy Galinstan, which is
liquid at room temperature while not being toxic like mercury.
Other uses
- Indium tin
oxide is used as a light filter in low
pressure sodium vapor lamps. The infrared radiation is reflected
back into the lamp, which increases the temperature within the tube and
therefore improves the performance of the lamp.[19]
- Indium's
melting point of 429.7485 K (156.5985 °C) is a defining fixed point on the
international temperature scale ITS-90.
- Indium's
high neutron capture cross section for thermal neutrons makes it suitable
for use in control
rods for nuclear
reactors, typically in an alloy containing 80% silver, 15% indium, and 5%
cadmium.
- In nuclear
engineering, the (n,n') reactions of 113In and 115In
are used to determine magnitudes of neutron fluxes.
- Indium is
also used as a thermal interface material by personal
computer enthusiasts in the form of pre-shaped foil sheets fitted between
the heat-transfer surface of a microprocessor and its heat sink. The
application of heat partially melts the foil and allows the indium metal
to fill in any microscopic gaps and pits between the two surfaces,
removing any insulating air pockets that would otherwise compromise heat
transfer efficiency.
- 111In emits gamma radiation and is used in indium leukocyte imaging, or indium scintigraphy, a technique of medical imaging. Indium leukocyte scintigraphy has many applications, including early phase drug development, and the monitoring of activity of white blood cells. For the test, blood is taken from the patient, white cells removed
- PRICE
- $710/KG
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