Forming gas

Last updated

Forming gas is a mixture of hydrogen (mole fraction varies) [1] and nitrogen. It is sometimes called a "dissociated ammonia atmosphere" due to the reaction which generates it:

2 NH3 → 3 H2 + N2

It can also be manufactured by thermal cracking of ammonia, in an ammonia cracker or forming gas generator. [2]

Forming gas is used as an atmosphere for processes that need the properties of hydrogen gas. Typical forming gas formulations (5% H2 in N2) are not explosive. It is used in chambers for gas hypersensitization, a process in which photographic film is heated in forming gas to drive out moisture and oxygen and to increase the base fog of the film. Hypersensitization is used particularly in deep-sky astrophotography, which deals with low-intensity incoming light, requires long exposure times, and is thus particularly sensitive to contaminants in the film. [3]

Forming gas is also used to regenerate catalysts in glove boxes and as an atmosphere for annealing processes. It can be purchased at welding supply stores. It is sometimes used as a reducing agent for high-temperature soldering and brazing, to remove oxidation of the joint without the use of flux. It also finds application in microchip production, where a high-temperature anneal in forming gas assists in silicon-silicon dioxide interface passivation.

Quite often forming gas is used in furnaces during annealing or sintering for the thermal treatment of metals, because it reduces oxides on the metal surface. [4]

See also

Related Research Articles

Ammonia Chemical compound of nitrogen and hydrogen

Ammonia is a compound of nitrogen and hydrogen with the formula NH3. A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a characteristic pungent smell. It is a common nitrogenous waste, particularly among aquatic organisms, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceutical products and is used in many commercial cleaning products. It is mainly collected by downward displacement of both air and water.

Chemical vapor deposition

Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high quality, high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films.

Hydrogen Chemical element with atomic number 1

Hydrogen is the chemical element with the symbol H and atomic number 1. With a standard atomic weight of 1.008, hydrogen is the lightest element in the periodic table. Hydrogen is the most abundant chemical substance in the universe, constituting roughly 75% of all baryonic mass. Non-remnant stars are mainly composed of hydrogen in the plasma state. The most common isotope of hydrogen, termed protium, has one proton and no neutrons.

Pyrolysis Thermal decomposition of materials at elevated temperatures in an inert atmosphere

Pyrolysis is the thermal decomposition of materials at elevated temperatures in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements pyro "fire" and lysis "separating".

Brazing High-temperature soldering; metal-joining technique by high-temperature molten metal filling

Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal.

A reducing atmosphere is an atmospheric condition in which oxidation is prevented by removal of oxygen and other oxidizing gases or vapours, and which may contain actively reducing gases such as hydrogen, carbon monoxide, and gases such as hydrogen sulfide that would be oxidized by any present oxygen.

Industrial processes

Industrial processes are procedures involving chemical, physical, electrical or mechanical steps to aid in the manufacturing of an item or items, usually carried out on a very large scale. Industrial processes are the key components of heavy industry.

Tungsten(VI) fluoride, also known as tungsten hexafluoride, is an inorganic compound with the formula WF6. It 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 known gases under standard conditions. WF6 is commonly used by the semiconductor industry to form tungsten films, through the process of chemical vapor deposition. This layer is used in a low-resistivity metallic "interconnect". It is one of seventeen known binary hexafluorides.

Steam reforming or steam methane reforming is a method for producing syngas (hydrogen and carbon monoxide) by reaction of hydrocarbons with water. Commonly natural gas is the feedstock. The main purpose of this technology is hydrogen production. The reaction is represented by this equilibrium:

The water-gas shift reaction (WGSR) describes the reaction of carbon monoxide and water vapor to form carbon dioxide and hydrogen:

Selective catalytic reduction (SCR) is a means of converting nitrogen oxides, also referred to as NO
x with the aid of a catalyst into diatomic nitrogen, and water. A reductant, typically anhydrous ammonia, aqueous ammonia or urea solution, is added to a stream of flue or exhaust gas and is absorbed onto a catalyst. As the reaction drives toward completion, carbon dioxide, CO
2 is produced.

Decarburization is the process opposite to carburization, namely the reduction of carbon content.

Silicon nitride Compound of silicon and nitrogen

Silicon nitride is a chemical compound of the elements silicon and nitrogen. Si
3N
4 is the most thermodynamically stable of the silicon nitrides. Hence, Si
3N
4 is the most commercially important of the silicon nitrides when referring to the term "silicon nitride". It is a white, high-melting-point solid that is relatively chemically inert, being attacked by dilute HF and hot H
2SO
4. It is very hard. It has a high thermal stability.

In metallurgy and materials science, annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable. It involves heating a material above its recrystallization temperature, maintaining a suitable temperature for an appropriate amount of time and then cooling.

Nitriding

Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface. These processes are most commonly used on high-carbon, low-alloy steels. They are also used on medium and high-carbon steels, titanium, aluminium and molybdenum. In 2015, nitriding was used to generate unique duplex microstructure, known to be associated with strongly enhanced mechanical properties.

Metal gate

A metal gate, in the context of a lateral metal-oxide-semiconductor (MOS) stack, is just that—the gate material is made from a metal.

Ultra-high-purity steam, also called clean steam, UHP steam or high purity water vapor, is used in a variety of industrial manufacturing processes that require oxidation or annealing. These processes include the growth of oxide layers on silicon wafers for the semiconductor industry, originally described by the Deal-Grove model, and for the formation of passivation layers used to improve the light capture ability of crystalline photovoltaic cells. Several methods and technologies can be employed to generate ultra high purity steam, including pyrolysis, bubbling, direct liquid injection and purified steam generation. The level of purity, or the relative lack of contamination, affects the quality of the oxide layer or annealed surface. The method of delivery affects growth rate, uniformity and electrical performance. Oxidation and annealing are common steps in the manufacture of such devices as microelectronics and solar cells.

Direct bonding, or fusion bonding, describes a wafer bonding process without any additional intermediate layers. The bonding process is based on chemical bonds between two surfaces of any material possible meeting numerous requirements. These requirements are specified for the wafer surface as sufficiently clean, flat and smooth. Otherwise unbonded areas so called voids, i.e. interface bubbles, can occur.

Plasma-activated bonding is a derivative, directed to lower processing temperatures for direct bonding with hydrophilic surfaces. The main requirements for lowering temperatures of direct bonding are the use of materials melting at low temperatures and with different coefficients of thermal expansion (CTE).

Pulsation reactor technology is a thermal procedure for manufacturing fine powders with precisely defined properties.

References

  1. ↑ "Forming gas specs" (PDF). Messer Group. Archived from the original (PDF) on July 14, 2011. Retrieved May 27, 2009.
  2. ↑ "Ammonia cracker for the generation of forming gas". Crystec Technology Trading GmbH. Retrieved April 19, 2009.
  3. ↑ Lodriguss, Jerry. "Gas hypersensitization". Catching the Light. Retrieved April 19, 2009.
  4. ↑ "Thermal treatment of steel". Crystec Technology Trading GmbH. Retrieved April 19, 2009.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.