Features of molybdenum｜A.L.M.T. Corp.

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Features of molybdenum

What is molybdenum?

1High melting point

Molybdenum has the fifth highest melting point among metals. It has a low thermal expansion coefficient and extremely high shape stability even under high temperature environments.

2Large electric resistance

Molybdenum has relatively large electric resistance. We offer it as a heater for high-temperature furnaces and electrodes for lighting.

3Easy workability

Molybdenum, which has relatively easy workability among high melting point metals, can be applied for complex shapes such as boxes and meshes.

Hard, silver white molybdenum, named from the ore molybdenite by K. W. Schale of Sweden, is one of the rare metals.

Molybdenum is often used as an additive for steel materials. Using its characteristics – high melting point, excellent mechanical features, relatively easy workability compared to tungsten, etc. – it is an Indispensable metal in various applications: ribbon and wire in the field of lighting; and semiconductor substrates, glass melting electrodes, heaters and reflectors in high-temperature furnaces, and sputtering targets as wiring materials for solar cells and flat panels in the field of power electronics.

Molybdenum physical properties
Atomic number *1		42
Density （Mg/m³）*2	293K	10.2
Melting point（K）*2		2903±10
Boiling point（K）*2		5100
Electrical Resistance （10^-8Ωm）*2	293K	5.7
Specific heat （J/kgK）*2	273-373K	251
Thermal conductivity （W/mK）*2	273-373K	137
Coefficient of Linear Expansion （10^-6/K）*2	293-373K 293-1773K	5.2 6.51
Work function （eV）*2		4.2
Thermal neutron capture cross section area （barns/atom）*3		2.4±0.02

^*1 Standard Atomic Weights (2017), The Chemical Society of Japan
^*2 Fourth Edition of Metal Data Book, The Japan Institute of Metals and Materials
^*3 Materials and techniques for electron Tubes,Walter H.Kohl (1960)

Chemical properties

In the air, oxidation starts at room temperature, proceeding considerably in the dark red temperature.
Molybdenum does not react at room temperature with dried oxygen, but it rapidly oxidizes at 500℃ or higher, and it evaporates at 650℃ or higher turning into MoO₃ of white mouse color.
It reacts with sulfur, carbon or silicon easily at high temperature to produce MoS₂, Mo₂C, MoSi₂, etc.
It is hardly to react at 1 atm, however, nitride is synthesized by heating under high pressure (>15atm).
The affinity for arsenic is strong.
It corrodes little in hydrofluoric acid, hydrochloric acid and sulfuric acid at 20 ℃, but corrodes significantly in nitrate, high concentration sulfate (250 ℃) and aqua regia.

Molybdenum: Reaction with gases
Substance	Temperature	Reaction
Air	200℃	Oxidizes a little
Air	≧400℃	Produces MoO₃
Oxygen	200℃	Oxidizes a little
Oxygen	≧400℃	Produces MoO₃
Vapor	≧700℃	Oxidizes
Nitrogen	≦2,400℃	Hardly to react (1atm)
Carbon monoxide	≧1,400℃	Produces carbides
Carbon dioxide	1,200℃	Oxidizes
Hydrocarbon	1,100℃	Carbonizes
Chlorine	250℃	Produces chloride
Bromine	250℃	Produces bromide
Iodine	800℃	No reaction
Hydrogen	All temperature	No reaction
Hydrogen sulfide	1,200℃	Produces MoS₂
Sulfur dioxide	600℃	Produces MoO₂
Nitrous oxide Nitric oxide	600℃	Produces MoO₃
Ammonia		No reaction

**Molybdenum**　**: Reaction with solids**
Substance	Temperature	Reaction
Carbon	≧1,100℃	Carbonizes
Magnesia	1,600℃	Reaction
Zirconia	2,200℃	Reaction
Thoria	1,900℃	Reaction
Alumina	1,900℃	No reaction
Sulfur	600℃	Corrodes
Tungsten	2,000℃	Reaction
Beryllia	up to 1,900℃	Reaction

**Molybdenum: Reaction with molten metals**
Substance	Temperature	Reaction
Aluminum	600℃	Stable
Beryllium		Not stable
Lead	up to 1,200℃	Stable
Lead (with oxygen)	up to about 500℃	Stable
Lead (with oxygen)	≧500℃	Not stable
Cesium	up to 870℃	Stable
Cesium	≧870℃	Not stable
Iron		Not stable
Gallium	up to 400℃	Stable
Gold		Stable
Potassium	up to 1,200℃	Stable
Cobalt		Not stable
Copper	up to 1,300℃	Stable
Lithium	up to 1,400℃	Stable
Magnesium	up to 1,000℃	Stable
Sodium	up to 1,030℃	Stable
Sodium (0.5％ oxygen)	up to 400℃	Stable
Sodium (0.5％ oxygen)	≧400℃	Not stable
Nickel		Not stable
Plutonium		Stable
Mercury	up to 600℃	Stable
Mercury	≧600℃	Not stable
Rubidium	up to 1,000℃	Stable
Scandium		Not stable
Rare metal	up to 1,100℃	Stable
Rare metal	≧1,400℃	Not stable
Silver		Stable
Thallium		Not stable
Uranium		Not stable
Bismuth	up to 1,400℃	Stable
Zinc	up to 500℃	Stable
Zinc	≧500℃	Not stable
Tin	up to 520℃	Stable
Tin	≧520℃	Not stable

Tungsten: Reaction with liquids
Substance	Temperature	Reaction
Water	Room temperature	No reaction
Water	Hot liquid	No reaction
10％ hydrochloric acid	Room temperature	0.0355 *
10％ hydrochloric acid	Heating	0.2794 *
Dilute sulfuric acid	110℃	20.1168 *
Concentrated sulfuric acid	110℃	0.3378 *
10％ sulfuric acid	Room temperature	0.0203 *
10％ sulfuric acid	Heating	0.1066 *
Concentrated sulfuric acid	110℃	0.2870 *
10％ nitric acid	Room temperature	18.5420 *
10％ nitric acid	Heating	154.94 *
Hydrofluoric acid	20℃	Hardly to react
10％ phosphoric acid	Room temperature	0.1066 *
10％ phosphoric acid	Heating	0.7721 *
10％ acetate	Room temperature	0.0711 *
10％ acetate	Heating	0.2565 *
Sulfuric acid ＋hydrofluoric acid		Rapidly corrodes
Sulfuric acid ＋hydrochloric acid		Rapidly corrodes
Sulfuric acid ＋sulfuric acid		Rapidly corrodes
Sodium hydroxide ≦50％	up to 100℃	Stable
Sodium hydroxide ≧50％	up to 100℃	Not stable
Ammonium hydroxide		Not stable
Potassium hydroxide ≦50％	up to 100℃	Stable
Potassium hydroxide ≧50％	up to 100℃	Not stable

* Corrosion rate (mm/year)