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This paper examines the carbonyl metallurgical processes and their applicability to space manufacturing.  The carbonyl metallurgical processes are Chemical Vapor Deposition (CVD) processes.  Metals such as nickel are digested by exposure to carbon monoxide (CO) gas under controlled conditions.  The resulting nickel tetra-carbonyl (Ni(CO)4) is transported to the inside of a suitably shaped inflatable, wherein the nickel tetracarbonyl comes in contact with a heated surface.  Upon contact with a heated surface, the nickel tetracarbonyl decomposes to produce a Chemical Vapor Deposited nickel metal coating.


Carbonyl digestion:


The chemical equation for the carbonyl digestion of nickel metal is as follows:


Ni + 4(CO) - Ni(CO)4(gaseous molecule)


In this reaction, nickel metal is digested by the exposure to carbon monoxide, producing nickel tetracarbonyl (Ni(CO)4).  This reaction is preferably done at near 75 degrees Celsius at virtually all pressures.


Digestion conditions for Ni + CO to produce Ni(CO)4, range from 60 psi CO carbon monoxide overpressure to 200 psi CO overpressure, at a temperature of 75 degrees C.  INCO uses fluidized bed technology at 1000 psi CO overpressure to extract nickel in mining operations.  Digestion of Ni from ores can also be accelerated through the use of ultrasonic energy.


Carbonyl decomposition:


Nickel tetracarbonyl is usable as a Chemical Vapor Deposition (CVD) reagent.  When the gaseous nickel tetracarbonyl comes into contact with a heated surface, a nickel coating is the result of the decomposition of the nickel tetracarbonyl. The deposition of nickel from the gaseous molecule (nickel tetracarbonyl) is the reverse reaction of the digestion:


Ni(CO)4 + heat Ni(metallic coating) + 4(CO)


This decomposition occurs between 35 and 300 degrees C, with optimal results at 175 degrees C or greater, when coating forms.  As in other equilibria reactions, the temperature of the nickel tetracarbonyl decomposition is increased with increasing carbon monoxide overpressure. As little as 1% nickel tetracarbonyl content in an atmosphere of carbon monoxide can be a useful CVD gaseous composition.


Near Earth Asteroids as raw materials sources:


The digestion of the metal fraction of stony-iron Near Earth Asteroids involves more complex chemistry than the simple digestion/deposition of nickel metal.


The metallic fraction of stony-iron Near Earth Asteroids is a mixture of the following metals: Fe (iron), Ni (nickel), Co(cobalt), Pt(platinum), Pd(palladium), Ir(iridium), Rh(rhodium) and other metals.  The use of the carbonyl digestion process involves the extraction/volatilization of metal carbonyl molecules.  Iron is digested by carbon monoxide to produce Fe(CO)5 iron pentacarbonyl, while the nickel is converted to Ni(CO)4  nickel tetracarbonyl.  The iron pentacarbonyl is not readily used in CVD processes to produce coatings, making the iron pentacarbonyl an undesirable digestion product.  Likewise, the cobalt octacarbonyl is not suitable for CVD coatings.  Luckily the volatilization characteristics of Fe(CO)5 iron pentacarbonyl; Ni(CO)4  nickel tetracarbonyl and, {Co(CO)4}2 cobalt octacarbonyl are sufficiently different to allow for their selective condensation and separation.


The boiling points for the following molecules are as follows:


Fe(CO)5  -  102.8 degrees C,

Ni(CO)4  -  37 or 43 degrees C, depending on reference used,

{Co(CO)4}2  -  very high temp, >> than Fe(CO)5 temp., also known to decompose @ 52 degrees C.


It can be seen that the nickel tetracarbonyl has the highest vapor pressure, and can be separated to give high-purity nickel tetracarbonyl for deposition uses.  The iron and cobalt carbonyls are used in other metallurgical work.  The platinum group metals are digested in the carbonyl gas stream by the addition of halides (F2, Cl2, Br2, I2), to produce metal-carbonyl-halide molecules.  The platinum group carbonyl halide molecules are used in other metallurgical processes.  The platinum group metals have a very high terrestrial value and can be used as currency and collateral in the financing of the development of a space industrial infrastructure.


Boron strengthened nickel coatings:


In an expired patent by Bill Jenkin, the inclusion of diborane in the nickel tetracarbonyl gas stream produces an alloy coating of nickel/boron.  The resultant boron-hardened nickel coating shows an increase in strength to 200 Kpsi tensile strength, with a Rockwell Hardness value of 40 to 50. Steel is between 100 KPSI to 150 KPSI in tensile strength. Nickel (without boron) deposited from nickel tetracarbonyl has tensile strength in the range of 80 to 90 Kpsi, and a Rockwell Hardness of 10 to 20.  The Ni/B alloy strengths lend themselves to the production of pressure vessels, habitats, framing networks, framing mesh systems, mirrors, and other structural components required for the construction of on-orbit habitats and space stations with and without artificial gravity.


Pressure vessels made with the boron-hardened Nickel coating, can have thinner walls when compared to pressure vessels made of other materials. This manufacturing advantage in component strength/mass ratio will be very important in the manufacture of habitats and industrial capacity in space.


Inflatables as forms:


The types of inflatables and forms used in making space stations and space industrial infrastructure components are extensive.  These forms provide shaped/heated surfaces for the exposure to nickel tetracarbonyl, wherein, Chemical Vapor Deposited (CVD) coatings of nickel and its alloys, produce components.




Carbonyl metallurgical processing can be used to produce habitats and industrial capacity in space.




Bibliography and sources of information:


1.  The Kinetics of Nickel Carbonyl Formation

W.M. Goldberger: and D.F. Othmer

Polytechnic Institute of Brooklyn, N.Y.

I&EC Process Design and Development

Vol. 2, No. 3, July 1963

pp. 202-209


2.  Bill Jenkin

Akron, Ohio


3.  International Nickel (INCO)




Richard Westfall

Galactic Mining Industries, Inc.

4838 Stuart Street

Denver, Colorado 80212-2922