Decaborane Handling

[Rezwan]

The LPPX crew has begun preparations for using boron in the experiment. This post discusses decaborane handling issues.

The questions are:
What sort of fume hood should be used to handle the material? (“decaborane needs to be in a fume hood both because of its toxicity and because it is hygroscopic”) Murali is ordering this hood: http://www.air-science.com/portable.html

Also:

One of the more aggravating aspects of working with the material was that any gas lines between your vaporizer and chamber must be at a temperature greater than the vaporizer temperature or else it will condense and clog up. Also very important: above ~300-350degC decaborane decomposes. Also important: at what ever temperature you operate, it’s messy stuff. It will coat everything up and maybe affect your plasma operating conditions. Anyone working with the material will get more decaborane exposure cleaning the chamber than handling material from the bottle.

Continue the conversation here.

[Allan Brewer]

Apparently decaborane smells like chocolate – its good safety knowledge, I’m not being flippant.

B10H14 possesses a strong characteristic odor, sometimes described as musty or intensely bitter, chocolate-like that is unique to boranes.
http://en.wikipedia.org/wiki/Decaborane

[Alchemist32]

Hi Everyone,

I am a professor specializing in boron chemistry research in areas such as synthesis and boron neutron capture therapy (BNCT). My group has a lot of experience working with decaborane, carboranes and polyhedral borate anions. Since I am also interested in alternative fusion research (outside of my own field) I wanted to add my two-cents worth to these discussions.

Please don’t consider my points as “preachy”, I just sincerely want to add my expertise as a boron chemist to your pursuits (if you find this helpful).

First, a couple of matters of safety. Decaborane is toxic, but not as much as one might think. It is so incredibly stinky that I doubt that anyone would breath in toxic quantities of the vapor without first becoming ill. Of course, ingestion of the material is another matter! (I’ve never heard of this happening). The inhalation of large doses have led to loss of consciousness, headaches and in some cases, short term amnesia. I know several chemists in the Czech Republic that use decaborane in large quantities without proper fume hoods. (while we also use huge quantities…we use great hoods!) They absolutely reek from the decaborane. It permeates their cloths, skin, hair, etc (imagine the smell of chain smokers x100). Diborane does not smell like chocolate. The closest I can describe it is really stinky napthalene, only much worse!

Decaborane will react with water to liberate hydrogen (explosion risk). However, it MUST NEVER be mixed with halogenated hydrocarbons (chloroform, carbon tetrachloride, etc.) as this will result in a massive spontaneous explosion. Back in the sixties, a pilot plant was being cleaned out using carbon-tet. In a fraction of a second, the entire plant any everyone present ceased to exist. It is stable in many dry solvents, just make sure of their identity before using.

Decaborane, as a fuel, contains much more energy than hydrocarbons. I’m certain that you are familiar with the 1950’s Navy and Air Force projects HEF and Zip where they investigated decaborane derivatives as jet and rocket fuels (read boron bomber, etc.) As such, an air-fuel mixture could easily result in a massive explosion! As it is proposed to use heated decaborane vapors here (under vacuum), extra precautions must be taken to ensure that there is no failure of the vacuum system or any other way for air to suddenly mix with the hot decaborane vapors.

I do have a suggestion that I want to throw out on the table. That is to propose using the gas diborane (B2H6), instead of decaborane. It is a gas at room temperature meaning that you will not need to heat the vacuum chamber. Like decaborane, it does undergo pyrolytic reactions at elevated temps. Of note, decaborane does readily decompose above 300 C, these polymerization reactions still occur at lower temps (only slower). While diborane is dirt cheap, decaborane costs near its weight in gold! Also, B-11 isotopically-enriched decaborane costs are astronomical! B-11 diborane would be much cheaper and easier to produce.

If you are interested in discussing the use of diborane…post a reply!

[mchargue]

I hope that the engineering folks talk to you, as you seem to have a solid grasp on the uses & handling of the substance, and the alternatives that exist. My hat’s off to you, sir.

[Aeronaut]

mchargue wrote: I hope that the engineering folks talk to you, as you seem to have a solid grasp on the uses & handling of the substance, and the alternatives that exist. My hat’s off to you, sir.

And my hat, too.

Eric or Aaron mentioned somewhere that B11 could be very expensive if purchased from scientific supply channels or by the gram, something to that effect, iirc. Still, the patent does mention the ability to use nearly any borane as a fuel, with pentaborane as the preferred alternate fuel. My searches seemed to say that the pentaborane stocks were destroyed and its no longer in production, which would make diborane sweeter still.

[jamesr]

The hydrogen to boron ratio in diborane is closer to an optimal value as well I believe. I gather the sweet spot between fusion reaction rate and bremstrahlung losses is about 5:1 of p:B11.

What would a more or less fully dissociated partially ionized mixture naturally condense to?

I had always thought that the bulk gas in the chamber would, after a shot cool to a few thousand degrees, before the next pulse when operating at a high rep rate. Obviously during these experiments it will quickly cool to the chamber/electrode temperature. Would free boron & hydrogen atoms recombine to form complex molecules that could condense onto the walls.

[Lerner]

Hi Alchemist,

Thanks for offering your expertise. If you would not mind, it would be better to chat by phone. Just call us at the lab number.
We chose decaborane for two reasons. One we actually wanted as much boron per hydrogen atom as possible. Second, for safety reasons we preferred something that was solid at room temperature and smelled. I already noticed that the toxic level is above the level that can be smelled. Thanks for the correction about chocolate. I was going to go without my candy and now I won’t.

One quick question–at what temperature is air and decaborane unstable? We only intend to heat to 120 C. Also we are only vaporizing a gram or so at a time. It appears that the chemical energy released would be no larger than the 100 kJ we are intending to pump into the chamber with the pulse. (Although obviously we don’t want unexpected combustion.)

Eric

[Author]

Posts