Physical and Chemical Properties
Chemical formula is WF6. The molecular weight is 297.84. It is colorless gas or light yellow liquid. It has strong irritant. It is poisonous, its toxicity is similar with fluorine. When the temperature is very low, it is white solid. It is soluble in organic solvents and then generate a special color. When meet water, it can decompose. In the air, it can decompose with strong smoke by moisture, and generate yellow tungstate or tungsten trioxide. Chemical properties is lively. And almost all metals (except gold and platinum) can react with it. It is also corrosive for nickel, monel and stainless steel, but Ni and stainless steel have resistance for corrosion. When dry, it is less corrosive to glass, while in moisture, it is able to react quickly. It can react strong with gaseous ammonia. Ammonia or an alkali can absorb it . It can generate double salt with alkali metal fluoride. It is soluble in benzene and other organic solvents.
[Density] 3.44×103kg/m3 (15℃, liquid)
[Melting point] 2.5℃ (5.6 × 104 Pa)
[Boiling point] 17.5℃
[Critical temperature] 171℃
[Critical pressure] 445.8kPa
[Preparation method] Metal tungsten powder and elemental fluorine can react to synthesize it directly.
[Application] (1) It is strong fluorinating agent, it can synthesize tungsten film in vapor deposition method. (2) it is used in the microelectronics industry for chemical vapor deposited tungsten silicide or tungsten, to produce a low resistance, a high melting point interconnects.
Figure 1 shows the molecular structure of tungsten hexafluoride.
Hazardous characteristics
When meet moisture, air or water, it will decompose and emit toxic and corrosive hydrogen fluoride fumes. It can cause very serious burns for skin, eyes, mucous membranes. When high concentrations expose, it can cause nausea, vomiting, abdominal pain, convulsions, kidney damage.
The above information is edited by the chemicalbook of Wang Xiaodong.
Storage Instructions
It shoud be packed in special cylinders and stored in a cool, ventilated coffers. Avoid direct sunlight. Keep away from heat and sources of ignition. Prevent moisture. Metal, glass should be isolated storage. "poison gas" signs should be affixed. Aviation, railway transportation is prohibited. When other combustibles on fire around, dry powder, carbon dioxide can be used to extinguish. Water can be used to cool cylinder, and then close the valve quickly.
First-aid steps
It has eye irritation and can lead to blind, eyes should continue to be rinsed, go to the hospital fast for treatment. After corrosion, skin and mucous membranes is difficult to heal, it should be washed with water, and then coated with magnesium oxide ointment or glycerol dilute ammonia, and seek medical advice.
Category
Compressed gas and liquefied.
Flammability hazard characteristics
When meet water, it can decompose into toxic hydrogen fluoride gas and tungstate.
Storage characteristics
Treasury ventilation low-temperature drying.
Extinguishing agent
Water.
Occupational standards
TLV-TWA 5 mg (tungsten)/cubic meter; STEL 10 mg (tungsten)/cubic meter.
Description
Tungsten(VI) fluoride, also known as tungsten hexafluoride, WF6, is a toxic, corrosive, colorless gas, with a density of
about 13 g/L (roughly 11 times heavier than air). It is one of the densest gases known under standard conditions. WF6 is
frequently used by the semiconductor industry to form tungsten films, through CVD. The WF6 molecule is octahedral with
the symmetry point group of Oh. The W-F bond distances are 183.2 pm. Between 2.3℃ and 17℃, tungsten hexafluoride
condenses into a pale-yellow liquid with a density of 3.44 g/cm3 at 15℃. At 2.3℃ it freezes into a white solid with a cubic
crystalline structure, with lattice constant of 628 pm and a calculated density of 3.99 g/cm3
. At 29℃ this structure converts to an orthorhombic solid with lattice constants of a = 960.3 pm, b = 871.3 pm, and c = 504.4 pm and a density of
4.56 g/cm3
. In this phase, the W-F distance is 181 pm, and the mean closest intermolecular contacts are 312 pm.
Chemical Properties
Colorless gas or light-yellow liquid.
Chemical Properties
Tungsten hexafluoride is a toxic, colorless gas
or a light yellow liquid.
Uses
In the electronics industry as a source of tungsten metal that connects the aluminum layers within semiconductor devices.
General Description
A toxic corrosive light yellow liquid or gas. Boiling point 67°F. Melting point 37°F. Noncombustible. Used in the manufacture of other chemicals and in the manufacture of electronics.
Air & Water Reactions
Decomposes in water giving hydrofluoric acid, another corrosive material.
Reactivity Profile
Tungsten hexafluoride emits very toxic and irritating fumes containing metallic tungsten and tungsten fluorides when heated to decomposition. Reacts violently with tetramethoxysilane [Jacob, E., Angew. Chem., 1982, 21, p. 143].
Health Hazard
TOXIC; may be fatal if inhaled, ingested or absorbed through skin. Vapors are extremely irritating and corrosive. Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control may cause pollution.
Fire Hazard
Some may burn but none ignite readily. Vapors from liquefied gas are initially heavier than air and spread along ground. Some of these materials may react violently with water. Cylinders exposed to fire may vent and release toxic and/or corrosive gas through pressure relief devices. Containers may explode when heated. Ruptured cylinders may rocket.
Safety Profile
A poison and corrosive
liquid or gas.
Synthesis
WF6 is usually produced by the exothermic reaction of F2 gas with tungsten powder between 350℃ and 400℃.
W +3F2→WF6
Potential Exposure
A strong halogenating agent. Used to
apply tungsten coatings to other surfaces by vapor deposition
process; making electronics and components; in the
manufacture of other chemicals.
Shipping
UN2196 Tungsten hexafluoride, Hazard Class:
2.3; Labels: 2.3-Poisonous gas, 8-Corrosive material,
Inhalation Hazard Zone B. Cylinders must be transported
in a secure upright position, in a well-ventilated truck.
Protect cylinder and labels from physical damage. The
owner of the compressed gas cylinder is the only entity
allowed by federal law (49CFR) to transport and refill
them. It is a violation of transportation regulations to refill
compressed gas cylinders without the express written permission
of the owner.
Incompatibilities
Decomposes on contact with water and
moist air, forming highly corrosive hydrofluoric acid.
Violent reaction on contact with methyl silicate.
Waste Disposal
Return refillable compressed
gas cylinders to supplier. Nonrefillable cylinders should be
disposed of in accordance with local, state and federal regulations.
Allow remaining gas to vent slowly into atmosphere
in an unconfined area or exhaust hood. Refillabletype
cylinders should be returned to original supplier with
any valve caps and outlet plugs secured and valve protection
caps in place.
