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Key Facts about Molybdenum (i.e., Molly) |
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Symbol:
Mo
Atomic #:
42
Atomic Mass: 95.94
# of Protons:
42
# of Neutrons:
54
# of Electrons:
42
Atomic Volume:
9.41
Lattice Type:
Body Centered Cube
Lattice Constant at 20°C:
3.1468
Natural Isotopes:
92, 94, 95, 96, 97, 98, 100
Density at 20°C (grams/cc):
10.2
Melting Point °C:
2610
Boiling Point °C (at 14.7 psi):
4830
Linear Coefficient of Expansion per °C:
4.9 x 10^-6
Thermal Conductivity at 20°C:
0.35 cal/cm^2/cm°C/sec
Specific Heat at 20°C:
0.061
Electrical Conductivity, % IACS:
30
Resistivity, microhm-cm at 20°C:
5.7
Temp. Coeff. of Elect. Resistivity per °C (0-100°):
0.0046
Tensile Strength at Room Temperature, psi:
120,000 - 200,000
Tensile Strength at 500°C, psi:
35,000 - 65,000
Tensile Strength at 1000°C, psi:
20,000 - 30,000
Young's Modulus of Elasticity (lb/in.^2) at 20°C:
46 x 10E6
Young's Modulus of Elasticity (lb/in.^2) at 500°C:
41 x 10E6
Young's Modulus of Elasticity (lb/in.^2) at 1000°C:
39 x 10E6
Poisson's Ratio:
0.321
Spectral Emissivity (1000°C, ~0.65µ wavelength):
0.37
Total Emissivity at 1500°C:
0.19
Total Emissivity at 2000°C:
0.24
Working Temperature °C:
</= 1600
Recrystalization Temperature °C:
900 - 1200
Stress Relieving Temperature °C:
800
Normal Phase: Solid
Molybdenum is classified as a metal element. It belongs to the
chromium family. The name molybdenum originates from the Greek word
"molybdos" which means lead. This element was discovered by Karl
Wilhem Scheele in 1781.
Molybdenum is a silver/gray metal. Its name is derived from the
Greek word "molybdaena", meaning "lead". The name was also used to
describe galena and graphite, which have similar appearances in
natural form. In 1778, Karl Scheele had been able to distinguish
molybdenite from graphite by noting that molybdenite formed a white
powder when treated with nitric acid, whereas graphite did not.
Molybdenum metal was isolated and proven to be a new element in 1790
by P.J. Hjelm, drawing on the earlier work of Scheele.
The use of molybdenum has increased steadily, and today it is in
demand both in pure form and as a steel additive. Today most
molybdenum is mined in The United States, Chile, and China - in that
order. Strangely enough, an ancient Japanese sword blade made by
Masamuné in 1330 was found to contain molybdenum.
Notable characteristics
Molybdenum is a transition metal. The pure metal is silvery white in
color, fairly soft, and has one of the highest melting points of all
pure elements. In small quantities, molybdenum is effective at
hardening steel. Molybdenum is important in plant nutrition, and is
necessary in animal nutrition (including human nutrition) as well.
It is found at the active site of certain enzymes, including
xanthine oxidase.
The pure metal has a tendency to flake apart during machining.
Molybdenum's characteristics are so similar to lead and graphite
that for many years before it was "officially discovered", it was
used accidentally (in place of lead and graphite).
Molybdenum prices have increased from a low of about $2/pound in
2000, to about $25/pound as of June 2006, down from a high of
$40/pound in May of 2005[1].
Applications
Over two thirds of all molybdenum is used in alloys. Molybdenum use
soared during World War I, when demand for tungsten made the
valuable refractory metal scarce and high-strength steels were at a
premium. Molybdenum is used today in high-strength alloys and in
high-temperature steels. Special molybdenum-containing alloys, such
as the Hastelloys, are notably heat- and corrosion-resistant.
Molybdenum is used in oil pipelines, aircraft and missile parts, and
in filaments. Molybdenum finds use as a catalyst in the petroleum
industry, especially in catalysts for removing organic sulfurs from
petroleum products. It is used to form the anode in some x-ray
tubes, particularly in mammography applications. Molybdenum metal is
found in some electronic applications as the conductive layers in
thin-film transistors (TFTs). Molybdenum disulfide is a good dry
lubricant, especially at high temperatures. Mo-99 is produced in the
nuclear isotope industry and is used as tracer. Molybdenum pigments
range from red-yellow to a bright red orange and are used in paints,
inks, plastics, and rubber materials.
History
Molybdenum (from the Greek molybdos meaning "lead-like") is not
found free in nature, and the compounds that can be found were,
until the late 18th century, confused with compounds of other
elements, such as carbon or lead. In 1778 Carl Wilhelm Scheele was
able to determine that molybdenum was separate from graphite and
lead, and isolated the oxide of the metal from molybdenite. In 1782
Hjelm isolated an impure extract of the metal by reducing the oxide
with carbon. Molybdenum was little used and remained in the
laboratory until the late 19th century. Subsequently, a French
company, Schneider and Co, tried molybdenum as an alloying agent in
steel armor plate and noted its useful properties.
In the 1800's, molybdenum was used primarily in dyes and the
preparation of certain chemical compounds, but little else was done
with it. However, in 1893 German chemists Sternberg and Deutsch
developed an ecomomical process to produce 96% pure molybdenum
metal. Although the product still contained 3% carbon, the sales
price of $0.86 per pound generated interest in possible commercial
uses. Tests designed to evaluate molybdenum's ability to replace
tungsten as an additive in tool steel were unsuccessful, primarily
because of sulphur and phosphorus impurities in the molybdenum.
In 1894, grey molybdenum oxide was produced in an electric furnace.
The oxide contained 9% carbon, which made the compound hard enough
to scratch glass. This inspired French chemist Henri Moissan to do
his own electric furnace experiments. He succeeded in producing
molybdenum which was 99.98% pure. He then set about determining the
atomic weight and other properties of molybdenum.
Due to a variety of economic conditions and the difficulty in
reliably producing pure molybdenum, very little commercial use was
seen until World War I when molybdenum was widely used as an
additive to toughen armor plating. Even after that, molybdenum did
not enjoy immediate success. Speculation on whether or not there
would ever be a market for molybdenum gained it the moniker "the
metallurgical mystery".
Interesting facts
about Molybdenum:
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1.
2.
3.
4.
5. |
Molybdenum is a good lubricant at high temperatures.
It is a very valuable alloying agent.
Molybdenum was also confused with graphite and lead ore.
The World War 2 German artillery piece "Big Bertha" contained
molybdenum as an essential component of its steel.
Molybdenum is used in alloys, electrodes, and catalysts.
See Jim Cramer's
CNBC Mad Money show from Friday, March 23, 2007 - mentioning
Freeport-McMoran as the foremost mining company of
Molybdenum...
here. |
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