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Topic: Topics Crystallography  (Read 3322 times)

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Offline ag44488

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Topics Crystallography
« on: November 07, 2016, 08:49:02 PM »
Good evening everyone!, greetings from Spain!.
So we're doing this "project", and I've chosen to do something on material chemistry, specifically in alloys, first I decided on a Bismuth-Tin alloy because of its low melting point since we actually have to use the equipment we have in our lab to conduct experiments and test the properties or otherwise make the "things" we've chosen, the problem is that I haven't found any applications for this alloy neither can I find any information about it on the interwebs. I'd like to do a comparison of the microstructure in the different phases of this eutectic alloy, do a complexometric titration/atomic absorption spectroscopy to determine the concentration of each component, we have an IR and UV/Vis too but I don't think I can do much with those. I would like to know your opinion on this idea. 
I've found other interesting subjects, such as Hydrogen storing alloys (LaNi5 for example), memory alloys, lithium coating for submersible vehicles, Perovskite and not much more.
I would immensely appreciate if you could give me some topics or suggestions in the field of crystallography (eutectic alloys, minerals...), the important thing is that its has to be feasible with the equipment I mentioned being either for the making of it or comparison of properties, as well as an interesting and feasible application.
Thank you very much for your attention.

Offline Enthalpy

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Re: Topics Crystallography
« Reply #1 on: November 08, 2016, 08:55:32 PM »
¡Hola ag44488!

I haven't seen one specific use of Bi-Sn alloys, but they are already known
and they have been considered as a solder alloy when the EU decided to ban Pb from electronic equipment. Though, we've switched to other solder alloys meanwhile

There is general interest in low-melting alloys that avoid the toxic Pb: for sparklers and so on. Since Bi's heat conductivity is small, if your alloy can make wires (not obvious since pure Bi is brittle) it could be a nice candidate for electric fuses.

I have a special interest in alloys with a low Young's modulus, because these make percussion music instruments whose high notes sound for long. Bell bronze (80% Cu, 20% Sn, no Pb) is one example with a modulus much smaller than each constituent, Invar (Fe, 36% Ni) is one other known example. Starting from 50GPa and 32GPa, and if possible In (11GPa)
a Bi-Sn(-In) alloy could bring the low modulus and high density. Maybe some composition brings an abnormally low modulus (for CuSn and FeNi it corresponds to an abnormally low density too), maybe not, but 32GPa would already be good. This use needs a hard and resilient alloy.

Offline Enthalpy

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Re: Topics Crystallography
« Reply #2 on: November 16, 2016, 10:00:05 AM »
When silicon chips are soldered to the contacts on the package or stacked on an other, they need a low-melting alloy to establish the contacts, free of Pb since the RoHS directive by the European Union.

Choosing such an alloy was still research in 2013, where banal Sn-2.5Ag was considered at least at universities, and may be of interest in 2016.

I describe there an idea to stack silicon chips with much increased contact density
and maybe some optimized alloy eases it - or it accepts current alloys, I don't know.

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