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Author: Subject: Ultrahigh-purity CHBr3 preparation (interesting use, 1atm synthetic ultrananocrystalline hexagonal diamond
tsathoggua1
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[*] posted on 19-7-2017 at 04:31
Ultrahigh-purity CHBr3 preparation (interesting use, 1atm synthetic ultrananocrystalline hexagonal diamond


Alright, so. Last night I read a very interesting article, which I wrote up about and tried to post, only to have the forum software eat my post, so I'll have to redo it.

This concerned generation of a poly(hydridocarbyne) precursor, using an anhydrous THF/dimethoxyethane solvent mixture, and a sonicated 1:1 NaK alloy to dehalogenate bromoform in relatively mild conditions (if you can use the word 'mild' in the same sentence as 'NaK' of course) to give, on evaporation, a nanopowder form of this hydridocarbyne precursor polymer, which interestingly enough, is both soluble in THF, and so can be applied as coatings (and presumably pressed and fired for things like crucibles perhaps) which are then heated, under various protocols for ramp time, temperature and holding time etc. to rearrange, at atmospheric pressure under a simple argon atmosphere to give an extremely hard, durable surface which shows extreme resistance to highly acidic conditions, of lonsdaelite (hexagonal diamond) at temperatures obtainable by an air/propane flame (1000 degrees was around the hottest, some citations as little as 100 'C) to in the form of an ultra-smooth surface, exceeding that currently obtainable by CVD techniques and containing only carbon (although in some processes further treatment to result in methyl group endcapping of the otherwise sp3-hybridized carbon phase), and after sample preparation, nearly featureless to SEM, lacking in surface topology, and, depositable as a 2-uM thick surface layer by spin-coating then firing the carbyne precursor in inert atmosphere of argon, containing as the only notable impurity, adsorption of a little O2 onto the surface.

Sounds useful, no? NaK is hardly nice and tame, but there are nastier, more reactive and certainly far, far more toxic reagents used plenty of times. This looks like mad science at its maddest and best. And certainly with many, many uses. Knives and tools that never need sharpening? metal crucibles or at lower temperature maybe even borosilicate glassware resistant to extreme acid conditions, super-high wear and tear resistance for bearings....maybe even synthetic gemstones if this was compacted with pressure before firing, or crucibles made out of the material, and other labware if bulk phase production is as feasible as it sounds.

So, what is needed, is bromoform, and of high purity considering we are dealing here with the fabrication of a nanomaterial or below that scale. On principle alone, the best purity is to be used for such experiments, to say nothing of the requirements of the material. I don't know if chloroform or iodoform could be used, if CHCl3 gave satisfactory results then given bromine is more expensive than chlorine on a mole basis, and chloroform is far more commonly used then why would it not BE used? if it worked well then it probably would be.

Although one reason I can see is Br being a more facile leaving group than Cl (which makes me consider iodoform, especially due to the potential for synthesis via finkelstein rxn using excess salt to mop up any Cl- around and drive the synthesis thermodynamically) exploiting the insolubility of chloride in acetone. However unfortunately unlike iodide, bromide too is insoluble in acetone)

So, what I want, is Br free of chlorinated species which obviates the immediately obvious method of producing the Br2, via chlorine displacement from NaBr (I have a kg of medical-grade sodium bromide, which should hopefully prove satisfactory for this purpose Acidification and...peroxide..seem like the ideal way using HBr (aq). But, there are reasons, specifically, official persecution, that I dare not attempt to buy concentrated peroxide commercially I've never done a damned thing with it more wrongful than causing a little whitening of the dead skin surface layer around my own fingertips, and have certainly never had anything to do with organoperoxides of any explosive nature. Ironically, this leads me to look towards either benzoyl or dibenzoyl peroxide in its capacity as a radical initiator since there are OTC sources in the UK of up to 40-45-50% or thereabouts of one of the above. I forget which. Assuming vacuum distillation of the bromoform and a lack of any chlorinated species within such a product, has anyone else had good/bad results using (di)benzoyl peroxide? since the products do specify the contents, but don't have the word 'peroxide' on it in large letters.

I know this might sound paranoid, but I have very good reason to be jumpier than a bathtub full of NCl3 in a hailstorm around anything 'obviously' 'a peroxide' (I.e obviously to a vengeful fucking moron of a vengeful mindset hosted within the CNS of what amounts essentially, to an ambulant cucumber with a big stick and a hostile ideology, not to a chemist) as such, H2O2, especially clean H2O2 is unavailable to me unfortunately:()

The other thing I'd need are the solvents, and potassium metal, as well as the sonicator, THF I already have some 2.5l of, the DME I'd have to buy. And the sonicator, an immersible 'horn' type is used to agitate the NaK and form an emulsion in the THF/DME system, to which bromoform, diluted in solvent also, is added, and afterwards the solvents stripped to give the prepolymer poly(hydridocarbyne) used directly after purification as a solution to prepare the coatings. It can also be formed using IIRC metal vessels in a quartz tube for the firing and coating materials by a CVD type process in an argon atmosphere, this time using a flow rather than a static gas blanket and the film appearing as a thin layer on objects deposited downstream of the section holding the poly(hydridocarbyne)

https://en.wikipedia.org/wiki/Poly(hydridocarbyne)

https://sci-hub.ac/http://dx.doi.org/10.1021/ja039254l

How does this grab y'all? sp3/hexagonal diamond &diamond-like carbon, suitable for application in solution, mouldable or castable, and suitable for growth of ultra-smooth micrometer-thin layers starting from bromoform, THF, NaK, DME and a sonicator, at atmospheric pressure and fairly modestly high maximum heating:D
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clearly_not_atara
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[*] posted on 19-7-2017 at 22:15


This actually sounds too good to be true. An ambient-pressure condensed-phase synthesis of DIAMOND?!

Anyway, uh, the synthesis route alone isn't going to guarantee the purity that you probably need for this, but that being said... I think that a mixture of sulfuric acid and metaphosphoric acid, quite nasty mind you but easy to make, sulfuric acid only has to be dried to about 90% or so I think, will oxidize NaBr just fine and the only byproduct is SO2 which is easily separated from bromine.
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tsathoggua1
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[*] posted on 20-7-2017 at 02:19


I already have sulfuric better than that (although given the current political climate, with the kneejerk tendencies of that bitch May. I'll be stocking up alright. My only phosphoric has some sort of surfectant in it, but those are always going to be large, amphipathic molecules that at the temperature it takes to distill Br2 aren't likely to come over (and probably wouldn't take too kindly to being boiled in bromine, phosphoric acid and 98% sulfuric) plus dyes and such, again, large molecules that aren't likely to carry over (although the dye in the sulfuric can be removed)

This isn't exactly your traditional diamond, of the cubic type. Lonsdaelite is hexagonal sp3-hybridized diamond, that in idealized conditions is a fair bit harder and more resistant than diamond.

And the result is this pre-polymer, which as stated, can be formed, press-cast and the like, as well as applied in thin films in a volatile solvent such as THF, or the powder form placed in quartz tubing in a metal boat and vaporized, the vapor condensing to leave a hexagonal diamond 2-micron thick layer (or more I suppose if you want to) as a coating.

How far can H3PO4 be concentrated by boiling until its a danger to glassware? because IIRC conc. phosphoric, as with HF, or caustic melts (what DON'T those go for:P) attack glass, and I've no desire to have layers burnt off my glass.

The initial carbyne product is a powder, and given something like diamond, whether sp2/sp3, pure sp3-hybridized in structure once it its formed, is not exactly the kind of thing one can melt with a blowtorch or furnace to a pourable liquid, I'd think during the forming process, whilst the fine poly(hydridocarbyne) nanopowder seems as though it can be easily pre-formed, with shrinkage taken into account, and pressed powder at whatever degree of high pressure we mad science types can achieve without blasting charges and explosive-powered rams.

Won't SO2+Br2 form some thionyl bromide in-situ? especially with a carbon catalyst? although I've certainly never seen any carbon form like that used! thats similar to gas-phase routes I've heard for SOCl2 at high temperatures IIRC.

I was quite staggered when I first found this. Spent a while typing a post up and then the damn computer swallowed it. Also I did find a reference, although too late, whilst losing net access for the night (in a temporary situation of having to borrow a machine to get online atm whilst now I harass the filth that have been harassing me, to get my stolen property back, ideally in one piece)

Reading the article more, it seems like they got 99% bromoform and used it as is, so perhaps not so vitally dependent on ultra-high purity CHBr3 as originally thought.

Compared to CHCl3, CHBr3 is less stable isn't it? presumably its stable enough to allow washing with thiosulfate solution to wash out any remaining Br2 and remaining acetone, or trapping acetone as its oxime whilst distilling off the Br2 and distilling off bromoform, washing w/ ice.cold de-ionized water and redistilling the Br2,

Anyone have a rough idea how much the probe-type immersion sonicators, and ones tja would stand up to bromoform, THF/DME and the NaK emulsion would set one back, as a ballpark figure? I think given the great simplicity of the lonsdaelite production route done this way its worth at least an attempt or two.

Its also not the only paper which mentions a process like this. Did see in passing before having to get offline, one also using CHCl3 and some sort of electrical process.

Edit-with respect to HP3O4, since it isn't volatile, aside from P2O5, and I doubt its particularly easy to dehydrate to P2O5 considering how avidly P2O5/P4O10 grabs on to and holds water, to dehydrate phosphoric acids to the anhydride if its even possible, but any additives could be burnt to a crisp in carbon crucibles, bit by bit if needs be using either a propane flame, or propane torch hacked to replace the air intakes with pipes leading to oxygen feeds

(done this before in the past to work borosilicate glass, such as for example when needing a vacuum capillary immediately within the next few minutes, and not waiting for one bought to arrive, for which a boro glass pipette was held at first in the hottest then moved to the cooler regions of the flame, the ordinary propane-fuelled blowtorch wired up to a frankenstein-ish arrangement of bottles and tubes supplied by the last of the 30-40 vols being oxidized by being dripped at a rapid rate onto KMnO4 that I had from an O2 generator set up and the output connected to the input of the torch)

Although for at least the thin-layer surface protection forming applications, not sure as yet, about macroscale applications using poly(hydridocarbyne) it does look like regardless of the actual end-temperature, certainly in the linked paper the ramping up of the temperature is typically quite low and would requite electrical control rather than a gas flame, since rates of 0.1 'C/min are never going to be had with even the best of torches, and that I remember from my last reading it whilst posting the original post in the thread, 10 'C/min was the fastest ramp-up speed I remember seeing.

One conversion temperature used, is 450 'C. and very slowly, 0.2 'C/min. That should be within the working range of borosilicate glassware should it not? (not sure of the upper working temperature allowance average, good quality boro glassware free of extensive chinesium contamination) and the speed of temperature increase should allow for the glass to re-anneal without extensive internal stresses being introduced to render the glass liable to shattering.

[Edited on 20-7-2017 by tsathoggua1]

[Edited on 20-7-2017 by tsathoggua1]
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