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Author Topic: Silver Powder for Making PMC Metal Clay  (Read 1160 times)

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Enthalpy

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Re: Silver Powder for Making PMC Metal Clay
« Reply #15 on: March 19, 2017, 08:50:37 AM »

Against oxidation, a soldering flux like rosin is very effective. Upon heating, it de-oxidises copper alloys, permitting the solder metal to wet them. Maybe the producer uses a similar compound (but without leftovers) for metal clay? This would permit long storage, needing a reductive atmosphere only in the kiln.

Sintering: it can achieve the full strength of an alloy, but only if using extreme pressure, hence my interrogation. Some alloys are produced that way, especially refractory ones which would be impractical to melt: molybdenum, tantalum, tungsten...

Produce a powder: wearing now my mechanical engineer hat, I'd say "grind it". Though, many metals catch fire then: titanium, iron. Neither did I try with gold, which may well clog the grinding wheel and produce zero powder.

I wouldn't be surprised if only a mix of powders with different grain sizes sinters well without pressure, because such a mix leaves less void between the grains - just like concrete uses sand, gravel and crushed stones.

Thanks for the links and explanation! I didn't know such materials. Maybe I find uses in industrial applications.
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Enthalpy

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Re: Silver Powder for Making PMC Metal Clay
« Reply #16 on: March 19, 2017, 01:22:05 PM »

One standard way to pulverize metals is to melt them and let an injector make the spray in a cooler gas that solidifies the droplets. Mind the nozzle material to resists liquid metal.

The gas shouldn't oxidise the metal. Nitrogen is doubtful, dry argon and hydrogen are candidates. Some hydrogen adsorbs on metals; to degas, put the powder in a gentle oven, like 10mn at 300°C.
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Enthalpy

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Re: Silver Powder for Making PMC Metal Clay
« Reply #17 on: March 19, 2017, 01:45:13 PM »

The mix of powders with different grain sizes would also shrink less when sintered. 30% presently is a drawback for jewellery parts.
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Enthalpy

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Re: Silver Powder for Making PMC Metal Clay
« Reply #18 on: March 20, 2017, 04:38:34 AM »

Mixing powders of different grain sizes would help sintering and reduce shrinkage when sintering under high pressure too, not only for metal clay - and for ceramics and polymers in addition to metals. I have an intuition that it's already done.
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