Chemical Understanding of the Mechanisms Involved in Mitigation of Charged Impurity Effects by Polar Molecules on Graphene.
2016
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It is well-known that the transport properties of monolayer graphene are degraded by charged impurities present between graphene and either a given substrate or air. Such impurities cause charge scattering of holes and electrons in graphene...."
But not well known in HC.
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.... Additionally, in the case of the molecular dipole impurity, the orientation of the impurity atop graphene is a key factor that determines the potential impact."
"Atop" means on surface not in bulk.
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Other articles suggest the impurities are a greater problem with graphene in the 80-88% C range requiring much more purification procedures and ...cost.
Howver the point made is strong that impurities matter greatly - FGR advantage as written earlier...better to always start with a purer precursor.
In other words, FGR graphite with lower initial contaminants will carry across fewer impurities in thegrpahene=>GO=> SC process.
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The presence of residual metallic impurities in graphene is a known problem, and many of these impurities are able to dramatically alter the electronic and electrochemical properties of graphene (26⇓–28). It is often falsely assumed in the graphene community that these impurities are sufficiently removed during the conversion of graphite to RGOs and that they have little or no effect on the final material’s properties. On the contrary, metallic impurities inherent in the parent graphite are retained in the resultant chemically reduced graphenes at levels widely considered to be trace and negligible but still enough to exert significant influence on the electrochemical responses of RGOs (29). Thus, proper quantification of the metallic impurities present in RGOs is paramount to ensure that the levels of contamination do not have adverse impacts on a specific use for which an RGO is intended. Unfortunately, this characterization is almost always never performed, despite the potential consequences."
".....Although the amount of metallic impurities in the nuclear graphite was zero according to the enclosed inductively coupled plasma mass spectrometry (ICP-MS) certification, NAA of the graphite detected the presence of six trace metals, four of which had a concentration well below 1 ppm by mass (Table 1). "
The article goes on to say that whatever is done to turn graphite (or in FGR's case graphene) into GO makes the sitaution regarding impurities much worse, dramtically worse. For Mn from 0.14 to 2,290 ppm.
What all this means is that if FGR can certify that run-of-mine material remains and is certified batch to batch consistency to do so, AFTER the FGR processing (exfoliation etc) then there would be NO need to convert to GO.
I reiterate here again:
At sufficiently high sale price, the poorer grade precursors are in the market, and again as WG noted, the price is set by the highest marginal cost at the point where demand and supply meet.
To me the situation appears to be subtle. GO is made so that it can be solution processed, but elsewhere I read that graphene's noted hydophobic nature is actually wrong, graphene is actually hydrophilic. Graphene apparently absorbs extremely readily and holds oily particles from exposure to air, literally in minutes.
I have experience with a related coal issue. At the start of CSM in the mid-90 in Australia, miners treated coal as a rock. A friend of mine wrote a seminal SPE paper that basically said, treat coal kindly. Same as treating a woman, depending how you treat her you can end up on your back in either a good way or a bad way. CSM was being hit with drilling mud, acids, "slick water" etc then run open hole/ or small choke for flow measurement. In the end there was much more thoughtful drilling and much gentler flow control, without going into the reasons here.
My conclusion is that FGR might be able to get away with no subsequent treatment at all if FGR remove and treat graphene from minesite to final use with kid gloves, and minimal exposure to air (unless purified/clean room style air) until moments before use and always held and transfered in sealed environments.
If these observation is true, then providing raw graphite from mine to SC with hopefully nothing from, or at least an extremely well known contamination during processing, then so much better to the bottom line. Back to WG comment, wel, well under the cost of the highest marginal cost operator.
I hope this plays out this way of course, you know, being a long suffering and under water share holder and all...
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