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Diffsuion of metals into glasses
- Thread starter YM
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Yes I have tried this with little success but my lack of success has more to do with ignorance than possible functionality. This was many years ago so I do not remember any particulars. I suggest that you post this question on the Ceramic engineering forum also because obviously this is a cross between ceramics and metallurgy. Hopefully the following will help some:
There is a very successful procedure for metallizing Aluminum Oxide(Al2O3)and other ceramics such as Forsterite . It is called the Molly-Manganese Process (MoMn). Molybdenum and Manganese are ball milled into a fine powder and mixed with an acrylic binder to allow application to the ceramic substrate which can be applied by painting, spraying, or silk screen. Next the coated ceramic is fired in wet Hydrogen atmosphere. The controlled humidity or dew point in the atmosphere provides limited Oxygen to combine with Mo to form Molybdenum Oxide which in turn combines or bonds with Silica in the grain boundaries of the ceramic and forms Mo-Oxygen-Al-Oxygen intermetallic. Concurrently the Mn sinters with the Mo because while the limited Oxygen is used up in the Oxidation processes just noted the contolled atmosphere now becomes dry Hydrogen which allows the Mo-Mn particles to wet(low angle of surface tension) each other and become sintered or strongly bonded metallurgically.
There is some diffusion of the metallic layer of MoMn into the ceramic but as I recall this diffusion is very limited like maybe 0.002 inch max if that much. It is more like this bonding mechanism is just layered from ceramic to MoMn and then a "green" Nickel(Nickel Oxide) coating is applied to the MoMn surface also using a ball milled mixture with acrylic binder. If I remenmber correctly, the NiO is fired in dry Hydrogen allowing bonding as Ni-O-Mo and sintered NiMn. Any Oxides applied with the Ni that don't combine metallurgically in this process are scavenged out by the dry Hydrogen so that a pure Ni surface is now exposed at the outer layer which now can be furnace brazed typically using Silver, Silver-Copper, or Gold Nickel to a machinned or formed alloy of low thermal expansion coefficient which closely matches the coefficient of the ceramic. The resulting bond is good for about 9,000 psi tensile and provides a hermetic seal.
Leonard Jesus is the WAY
There is a very successful procedure for metallizing Aluminum Oxide(Al2O3)and other ceramics such as Forsterite . It is called the Molly-Manganese Process (MoMn). Molybdenum and Manganese are ball milled into a fine powder and mixed with an acrylic binder to allow application to the ceramic substrate which can be applied by painting, spraying, or silk screen. Next the coated ceramic is fired in wet Hydrogen atmosphere. The controlled humidity or dew point in the atmosphere provides limited Oxygen to combine with Mo to form Molybdenum Oxide which in turn combines or bonds with Silica in the grain boundaries of the ceramic and forms Mo-Oxygen-Al-Oxygen intermetallic. Concurrently the Mn sinters with the Mo because while the limited Oxygen is used up in the Oxidation processes just noted the contolled atmosphere now becomes dry Hydrogen which allows the Mo-Mn particles to wet(low angle of surface tension) each other and become sintered or strongly bonded metallurgically.
There is some diffusion of the metallic layer of MoMn into the ceramic but as I recall this diffusion is very limited like maybe 0.002 inch max if that much. It is more like this bonding mechanism is just layered from ceramic to MoMn and then a "green" Nickel(Nickel Oxide) coating is applied to the MoMn surface also using a ball milled mixture with acrylic binder. If I remenmber correctly, the NiO is fired in dry Hydrogen allowing bonding as Ni-O-Mo and sintered NiMn. Any Oxides applied with the Ni that don't combine metallurgically in this process are scavenged out by the dry Hydrogen so that a pure Ni surface is now exposed at the outer layer which now can be furnace brazed typically using Silver, Silver-Copper, or Gold Nickel to a machinned or formed alloy of low thermal expansion coefficient which closely matches the coefficient of the ceramic. The resulting bond is good for about 9,000 psi tensile and provides a hermetic seal.
Leonard Jesus is the WAY
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