njl
National Hazard
Posts: 609
Registered: 26-11-2019
Location: under the sycamore tree
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Mood: ambivalent
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Non trivial nickel boride
Nickel (and other metal) borides are interesting compounds not only for their tendency to have extreme mechanical properties but also as a convenient
reducing agent due to its ability to release borane in acidic environments which is a part of their catalytic activity with NaBH4. Not all borides
have this tendency to release borane at the same rate (for example aluminum boride released about 11 percent of its theoretical volume of borane if I
recall correctly). Several metal borides are available from websites like onyxmet.com including Nickel, Magnesium, Aluminum, Iron, Calcium, and
others. While these borides are usually prepared from borohydride and a metal salt, in the interest of otc-ish reducing agents that do not require
non-otc reagents (like NaBH4) it would be desirable to be able to prepare reactive metal borides through other routes. This would allow the catalytic
reductive activity of borides without the need for hard to obtain hydrides. As far as I can tell most literature that touches on borides is mainly
looking at their mechanical properties with little attention payed to their chemical reactivity. Those that do investigate their reactivity usually do
not go beyond their preparation by:
1. Reaction of metal salt with borohydride
2. Sintering/compression of elemental metal with elemental boron
3. Surface chemistry between metal and boron to for new alloys
It is harder to find literature speaking specifically to metal borides activity as reagents (although there is some), and harder yet to find details
that would allow for usable quantities of metal borides to be prepared by amateurs. So I would like to present the following as new areas of
experimentation for me as I have tried some basic metal boride reactions already.
1. Reaction of molten metals with stoichiometric elemental boron
2. Boron production from otc sources like borax (this process is already documented, but not exactly optimized)
3. Activity of a variety of metal boride compounds with common acids
4. Maximizing the reducing characteristics of easily prepared borides
I would love feedback as this project of mine is ongoing. I would like to mention that I have so far done some crude experimentation with Aluminum
borides and Zinc borides (although I can't speak to their exact composition) by reacting their metal salts with NaBH4, followed by varying levels of
extraction from solution and reaction with acids. I plan on testing homemade Aluminum, Iron, Magnesium, Nickel, Zinc, Lead, and Calcium borides as
well as some more experimental (unlikely to work) borides like Gallium, Copper, Silicon, and Carbon. I am aware that this project will most likely be
full of dead ends and failures but I find the subject interesting and useful so I will be proceeding nonetheless. So far I have ordered or isolated
Zinc, Aluminum, Copper, Iron, Carbon, and Silicon. Next I think will be lead as it is very cheap and easy to work with. On top of testing metal
borides I will also try to optimize the reduction of borax to elemental boron as this process seems about as otc as it gets. Things are slow for me
now but I will be updating this thread as I continue.
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Boffis
International Hazard
Posts: 1836
Registered: 1-5-2011
Member Is Offline
Mood: No Mood
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Hi njl; I would say before re-inventing the wheel check out the numerous volumes of textbooks of inorganic chemistry in the SM library. The only
borides that are easily prepared at home are those made by borohydride precipitation and thermite type processes. The borides formed by the former
process, say Ni boride, is not the same as the boride formed by the direct union of nickel and boron. The former is more likely an interstitial
dispersion of boron and hydrogen in very porous nickel. Similar "phosphide" are produced by the reduction of nickel and copper salts with
hypophosphites and are not to be confused with true phosphide. I am pretty sure that only alkali and alkaline earth boride generate boranes in
significant amounts plus maybe those of zinc and manganese. I also doubt that borides produced by high temperature processes will act as hydrogenation
catalysts.
If you want to make some high temperature carbides I think the thermite process may be the best option. Try thermite with a mixture of iron and boron
oxides or chromium and boron oxide with Mg or Al as reducing agent.
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