woelen
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Boron reactivity?
I purchased some 99.9% pure crystalline boron for my element collection, but also want to do some experiments with it. It consists of small dark grey
glittering crystals, which are amazingly hard and impossible to crunch. I wonder with which chemicals it can be made to react. I tried refluxing it
with bromine for some time, but to no avail. Nothing happens, I just drove off the bromine and I am left with clean dry crystals of boron again.
I read on Wikipedia that boron does not react easily, but other sites state that boron reacts vigorously with bromine and chlorine. My test with
bromine shows otherwise.
Is there any chemical which easily reacts with pure crystalline boron? My books do not mention anything (e.g. hot conc. HNO3 only reacts very slowly
according to literature).
[Edited on 28-6-14 by woelen]
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papaya
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Try to burn in O2 atmosphere?
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Brain&Force
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Try fusing it with sodium hydroxide to make sodium borate?
Or with magnesium to form magnesium boride?
At the end of the day, simulating atoms doesn't beat working with the real things...
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Metacelsus
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You might be able to react it with a molten active metal (such as Mg) to form the boride.
Edit: Ninja'd
[Edited on 29-6-2014 by Cheddite Cheese]
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Zyklon-A
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First, is your boron in the β-rhombohedral phase? This is the least reactive and I think the hardest as well.
If so, this is almost certainly why it didn't react with Br2, amorphous boron is probably what reacts with halogens easily.
Perhaps you could react it with a molten alkali base, for example: Boron reacts with fused sodium hydroxide to form sodium borate and hydrogen.
How about molten sodium, that might be fun.
| Quote: |
Try to burn in O2 atmosphere? |
Why? Boron (III) oxide is quite common and easy to make, burning in oxygen
won't be very interesting anyway. If you can get your hands on some liquid oxygen, there might be a energetic reaction there.
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Texium
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Really most boron compounds are a fair bit less interesting than elemental boron.
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IrC
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That's what you think zts16 but I beg to differ. Heating a mixture of B and Mg in my kiln under Argon (in quartz tube) was an experiment to make
Magnesium diboride. You should look up it's superconducting properties.
http://en.wikipedia.org/wiki/Magnesium_diboride
Quoting "Its superconductivity was discovered by the group of Akimitsu in 2001.[1] Its critical temperature (Tc) of 39 K (−234 °C; −389 °F) is
the highest amongst conventional superconductors. This material was first synthesized and its structure confirmed in 1953,[2] but its superconducting
properties were not discovered until 2001.[3]
Though generally believed to be a conventional (phonon-mediated) superconductor, it is a rather unusual one. Its electronic structure is such that
there exist two types of electrons at the Fermi level with widely differing behaviours, one of them (sigma-bonding) being much more strongly
superconducting than the other (pi-bonding). This is at odds with usual theories of phonon-mediated superconductivity which assume that all electrons
behave in the same manner. Theoretical understanding of the properties of MgB2 has almost been achieved with two energy gaps. In 2001 it was regarded
as behaving more like a metallic than a cuprate superconductor."
"Magnesium diboride can be synthesized by several routes. The simplest is by high temperature reaction between boron and magnesium powders.[4]
Formation begins at 650 °C; however, since magnesium metal melts at 652 °C, the reaction mechanism is considered to be moderated by magnesium vapor
diffusion across boron grain boundaries. At conventional reaction temperatures, sintering is minimal, although enough grain recrystallization occurs
to permit Josephson quantum tunneling between grains.
Superconducting magnesium diboride wire can be produced through the powder-in-tube (PIT) process. In the in situ variant, a mixture of boron and
magnesium is poured into a metal tube, which is reduced in diameter by conventional wire drawing. The wire is then heated to the reaction temperature
to form MgB2 inside. In the ex situ variant, the tube is filled with MgB2 powder, reduced in diameter, and sintered at 800 to 1000 °C. In both cases,
later hot isostatic pressing at approximately 950 °C further improves the properties.
In 2003, a new and easy in situ technique for the synthesis of MgB2 was presented by Giunchi et al. (Edison S.p.A.).[5] This new technique employs
reactive liquid infiltration of magnesium inside a granular preform of boron powders and was called Mg-RLI technique. The method allowed to
manufacture both high density (more than 90% of the theoretical density for MgB2) bulk materials and special hollow fibers. This method is an exact of
similar melt growth based methods such as the Infiltration and Growth Processing method used to fabricate bulk YBCO superconductors where the
non-superconducting Y2Ba1Cu1O5 is used as granular preform inside which YBCO based liquid phases are infiltrated to make superconductive YBCO bulk.
This method has been copied and adapted for MgB2 superconductor and rebranded as reactive Mg Liquid Infiltration. The process of Reactive Mg Liquid
Infiltration in a boron preform to obtain MgB2 has been a subject of patent applications by Edison S.p.A. (Italy)."
All in all I think this is a very interesting substance.
http://arxiv.org/abs/cond-mat/0212543
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I should expand on my thoughts. From wiki: "Its critical temperature (Tc) of 39 K (−234 °C; −389 °F) is the highest amongst conventional
superconductors." Getting down to −234 °C is beyond my budget. Yet some high TC properties look possible with this actually quite odd chemical
(MgB2). Compare its structure to a high TC Cuprate structure.
 
What I have been experimenting with is trying to create many varieties in the kiln of MgB2 doped with various elements typical in the Cuprate example
(as well as some other known high TC materials). Obviously with a goal in mind of a new high TC material with a TC closer to standard conditions than
have thus far been created.
In any case I just thought I would point out by example that Boron is possibly not as 'boring' as you suggested.
[Edited on 6-29-2014 by IrC]
"Science is the belief in the ignorance of the experts" Richard Feynman
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MrHomeScientist
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I'll second (third? fourth?) the suggestion of trying to make magnesium boride. I believe reacting this with acid releases diborane gas, which is
pyrophoric! I almost certainly made a small amount of it during my isolation of elemental boron from boric acid, but I never observed any ignitions (I
was trying to avoid them though!). Aluminum boride may also show the same property, but I've read conflicting reports about that.
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Bezaleel
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Quote: Originally posted by IrC  | I should expand on my thoughts. From wiki: "Its critical temperature (Tc) of 39 K (−234 °C; −389 °F) is the highest amongst conventional
superconductors." Getting down to −234 °C is beyond my budget. Yet some high TC properties look possible with this actually quite odd chemical
(MgB2). Compare its structure to a high TC Cuprate structure.
What I have been experimenting with is trying to create many varieties in the kiln of MgB2 doped with various elements typical in the Cuprate example
(as well as some other known high TC materials). Obviously with a goal in mind of a new high TC material with a TC closer to standard conditions than
have thus far been created.
[Edited on 6-29-2014 by IrC] |
Keep in mind, that the higher the number of layers within a repeating unit of layers, the higher the Tc. In the picture example you give, this readily
explains the higher Tc for the Cu/Ba/Sr/... compound, as compared to the Mg/B compound. Addition of maybe an oxide in the right ratio (should fit into
the lattice somehow though), might be a good approach to seek for higher Tcs.
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AJKOER
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Some telling comments per Atomistry.com (link http://boron.atomistry.com/boron_trichloride.html ), to quote from the preparation of Boron trichloride, BCl3:
"For the synthesis, impure boron (prepared by heating the oxide with magnesium and boiling the resulting mass with hydrochloric acid) is employed. It
is heated to dull redness in a stream of dry hydrogen, allowed to cool in the gas, and, after displacing the hydrogen with chlorine, heated in
chlorine to redness. The product is strongly cooled and protected from moisture, shaken with mercury or silver powder to remove chlorine, and
fractionally distilled to eliminate hydrogen chloride and silicon chloride. Boron trichloride is also produced when boron sesqui-oxide is heated for
some days at 150° with phosphorus pentachloride.
Boron trichloride is a colourless liquid of high refractive index and normal vapour density (Wohler and Deville). At 0° C. its density is 1.43386;
its coefficient of expansion is large. It melts at -107° C. and boils at 12.5° C.; "
Note, one starts with impure boron for the synthesis of BCl3, converts to the hydride and displaces the hydrogen with chlorine.
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The Volatile Chemist
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| Quote: | | Aluminum boride may also show the same property, but I've read conflicting reports about that. |
You could always try it. It seems to me it would be a bit easier to make - Aluminum melts a bit easier. Hopefully the reaction temperature wouldn't be
too high...
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MrHomeScientist
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| Quote: Originally posted by The Volatile Chemist | | You could always try it. It seems to me it would be a bit easier to make - Aluminum melts a bit easier. Hopefully the reaction temperature wouldn't be
too high... |
I imagine it would go similarly to hkparker's synthesis of magnesium silicide - mix boric oxide and magnesium (or aluminum) powders together and heat strongly. Could be pretty interesting!
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