How To Unlock Graphite's Most Incredible Properties (Intro to Intercalation)

hi everyone I recently set out to test a number of commercial fireproofing products this was going to be a video comparing those products which all rely on a common feature called intumescence that is the ability to expand when heated an intumescent material can be applied as a thin coat but when exposed to fire it grows into a thick barrier of usually carbon foam protecting whatever is behind it I had researched into Essence fairly extensively for an earlier video series about Reinventing a lost material called Starlight but despite This research I was surprised to find something entirely different in the commercial products I purchased for review look at this this is a commercial fire resistant intumescent putty that is meant to mold around things like electrical boxes notice the little black flecks in this putty and watch what happens to them when we apply heat foreign this is super weird it turns out that these flakes are almost entirely pure graphite now normally graphite is very stable at high temperature remaining unchanged up to a few thousand degrees Celsius it wouldn't normally make these worm-like structures what makes the flakes in this putty different is a clever chemical treatment process and the result it turns out is extremely useful for making DIY fireproof products to graphite foils to super strong graphene learning about these little flakes deserved my attention so in this video we'll explore how to make expandable graphite graphite is made from an arrangement of carbon atoms in two-dimensional sheet form layered on top of each other like a stack of paper each layer is really securely adhered to the one beneath it so you end up with a solid lump of graphite now imagine you were able to inflate the layers of carbon in a stack so they expanded like an accordion doing so would give you a huge increase in volume just like we see with the intumescent flakes they even form these same worm-like structures which is exactly the shape you would expect from an accordion-like expansion of the layers so how do we make this happen first of all we need a graphite source that is composed of Fairly crystalline layers graphite by definition is made of layered carbon atoms but it's often processed to be more like a compressed brick of shredded paper than a stack of nice orderly sheets natural flake graphite is what we need this used to be a very common item used to lubricate all sorts of different equipment but Changing Times have made this a little hard to come by you can still find it sold online this is Dixon number one flake graphite which is about 50 mesh flake now to make this into expandable graphite we'll use a few additional chemicals 93 sulfuric acid which conveniently is the common concentration of off-the-shelf professional drain cleaner and we need an oxidizer this process is not picky about the oxidizer used and you'll find articles using anything from 30 hydrogen peroxide to potassium permanganate or even fuming nitric acid no matter what we use this is going to be a little bit dangerous so let's put on some gloves some goggles or safety glasses and my favorite precaution when working with strong acids a big container of water and baking soda nearby if I spill any acid this can be used to quickly neutralize it I'll start with one gram of my graphite flake in this glass container and to this add 4 grams of 93 sulfuric acid my oxidizer of choice is 2 grams of ammonium nitrate which will react with the sulfuric acid to form nitric acid in solution the byproduct of this is ammonium sulfate which is highly soluble and won't cause any problems other nitrates like potassium or sodium nitrate will work just as well but the byproduct is less soluble and will form a sludge that will need extra stirring as soon as the nitrate dissolves the acid will start to fume but this can be contained by placing a watch glass over the top as a safety precaution this reaction should never be scaled up to larger quantities or you risk what's called a thermal runaway in large quantities mixing nitrates and acid can generate so much heat that it becomes impossible to cool down and you end up with a boiling hot container spewing out very dangerous fumes a runaway is very unlikely to happen at this small scale the reaction currently taking place in this container is the oxidation of the edges of the individual graphite layers an oxygen atom from the nitric acid joins onto the carbon at the edge of a layer and forces that edge away from its neighboring sheets this opens a gap for sulfuric acid molecules to creep into the flakes of graphite and form temporary bonds between each carbon layer this graphite and sulfuric acid sandwich is a very stable compound at room temperature but when heated the acid will vaporize and hopefully will end up with a carbon accordion with my 50 mesh graphite flake I found it only takes about 10 minutes at room temperature to fully intercalate intercalation is what this process is called when you force something like sulfuric acid to distribute through the layers of graphite strangely with smaller flake like this number two graphite which is about 250 mesh it not only takes more time to react but also an elevated temperature of about 100 degrees Celsius for at least half an hour I'm not sure why that is smaller particle size almost always makes reactions go faster so this is a weird one this mix has now sat long enough so it's time to neutralize the acids and collect our graphite it can be dangerous to mix concentrated acid with water because it gets very hot and may splatter or even break the container standard practice for diluting acid is to add it slowly drop by drop into water so that's what we'll do I'll scrape out the graphite mix a little at a time into a separate container with about 50 mL of water inside once done I may risk adding some of this acid and water mixture back into the beaker directly just to flush out the little bit of graphite stuck to the sides now I've found it takes about 20 grams of 10 janitorial strength ammonia to neutralize the quantity of acid remaining after making this one gram batch size of expandable graphite you really want to make sure the acid has been diluted before you add this ammonia or it will definitely boil adding a little at a time with stirring destroys the acid you can then test the pH to make sure the acid is gone and then pour it through a coffee filter to collect the result it's a good idea to wash this once or twice more with clean water before letting it dry on the filter and here is the end product to confirm that our method worked we just need to apply some heat I think this is a pretty satisfying result so what can we use this for in a previous video I assembled a very poorly made rope machine and to lubricate a few of the gears I cut strips off a roll of graphite foil to line the cast iron channels the gears were set in I've since learned that this foil is made from graphite that has first been expanded just like this and then recompressed between rollers or plates to turn it into a foil simple as that we can easily do the same by folding this expanded graphite between a piece of paper and crushing it down in a vise or even by hand the accordion shapes of the inflated graphite interlock with those around them and hold together tightly once compressed the resulting foil is electrically and thermally conductive lubricating and chemically resistant foils like this are useful as electrodes and batteries corrosion resistant anodes for electrolysis and high temperature gaskets among many other things quite a useful material for being easily made right here on my workbench now if you peel off one individual layer of graphite you get a sheet of what's called graphene one of the strongest materials theorized to exist graphene has so far only been successfully made in tiny flakes but even microscopic flakes of graphene are useful for adding strength to concrete and Plastics one method for making graphene starts with this expandable graphite when heated the layers of graphite which usually are strongly adhered to one another are pushed apart weakening the connection between them enough that they can then be separated completely by various mechanical means like high energy pulses in an ultrasonic cleaner methods like this are unlikely to give you a high percentage of the very best quality single layer graphene but the result is plenty good enough for many practical uses on that note shout out to Robert Murray Smith's YouTube channel he's been experimenting with graphite and graphene related projects like this for at least a decade and I think he's the only other person until now to share a video about making expandable graphite lots to check out on his channel if this topic piques your interest before we go further this video's sponsor is brilliant.org I just noticed they have a course on chemistry which is perfect if you enjoy videos like this one but maybe 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that link can also get 20 off Brilliance annual premium subscription now finally we are back to the purpose for expandable graphite that got me started down this rabbit hole intumescent fireproofing now the intum essence I've worked with previously generate a fairly solid layer of carbon foam when heated not a mass of worm-like hairs such as these this honestly seems worse as fire can probably transfer heat a lot faster through the gaps in these hairs than through a closed carbon foam we'll have to test that the clear advantage to using expandable graphite flake is that it's extremely environmentally stable the normal chemicals that are used for intumescent Coatings are water soluble so it's difficult to make an intumescent product that will hold up to the elements Outdoors as such most are made for indoor fireproofing the graphite flake can theoretically be mixed with any paint or coating and water exposure doesn't affect it at all I mixed one gram of expandable graphite flake with 10 grams of a normal outdoor paint primer and in this case I used number two flake graphite which is a smaller particle size and mixes into the paint more easily here I have a panel painted on one section with commercially made intumescent paint this is a variety that does not use graphite I discussed the chemical reaction by which this paint makes a carbon foam at length in my videos about Starlight we'll compare this paint with some other intumescent products the normal outdoor primer which I mixed with expandable graphite flake then a commercial intumescent putty and last is a coating of intumescent sealant purchased off the shelf of my local hardware store all three of these squares use expandable graphite as part of their fire resistance we'll see how these stack up against each other my homemade paint seems to stand out pretty dramatically on the thermal camera and not in a good way on the underside we can see Flames washing over this Square more than the others which is evidence of the wood under the paint starting to off gas and burn the coldest section is the one with the non-hardening putty this by the way isn't a fair test between the materials because the coating thickness is based on how I estimated they would be applied in real world use as such the putty is probably at least 20 times thicker than the two paints and the commercial sealant is four or five times thicker this should give us a good feel for the effectiveness of the intumescent properties of each style of coating but not a one-to-one comparison we now have some Flames licking up the edges on my homemade paint section and now that you can see just how fast the bare wood burns it's clear that even though this Square was the worst performer of the four it's still dramatically better than uncoated plywood so here is what we have remaining the fire spread across the back of the sample consuming both my homemade paint and the section with an intumescent sealant the thick layer of putty survived which is to be expected but I'm not sure I'm convinced that these sparsely distributed carbon hairs actually contributed very much looking at some of the ingredients listed on the data sheet for this product it seems that much of the fire resistance comes from chemicals that contain a lot of water and that allows the putty to absorb enormous amounts of heat because it takes a ton of energy to evaporate water it's not a bad strategy and I've used it in my own experiments in the past but it makes the intumescent feature of this product seem like an afterthought the only other surviving Square used the intumescent paint based on a totally different chemical mechanism which after this test makes the expandable graphite look completely inferior for fireproofing purposes this was by far the thinnest coating on the board and it survived just as well as the putty it does this by generating a very thick and continuous layer of carbon foam which expandable graphite is simply unable to do in the form of individual expanding flakes so the result here reveals a few things first of all expandable graphite is at least a little bit effective at resisting fire in paints and Coatings it could be very useful for outdoor applications where other intumescent Technologies don't hold up to the weather for indoor use however an intumescent paint without the addition of these graphite flakes works so well that in my mind there's no contest part of the reason I wanted to make this video is that I've seen a lot more intumescent products on the market recently and after buying a bunch of them I'm a little annoyed that so many are sold for indoor use with this expandable graphite flake as the primary fire resistant mechanism these products could be so much better but it seems to me that the majority of Manufacturers found out that expandable graphite exists it sort of works for fireproofing so let's just throw it into a product and call it a day it's better than nothing and probably all of the products that I've tested are good enough to not be the point of failure that causes your house to burn down the mediocrity is just a little bit frustrating in the end expandable graphite is useful for a lot of things making graphite foil and graphene and it does maybe have a place in outdoor fire resistant products just not for indoor use where there are better options so I hope you found this video useful or at least entertaining if you'd like to support me on patreon you can do so by clicking the link on screen or in the video description below thanks for watching I'll see you next time

Channel: NightHawkInLight

Views: 310,580

Keywords: Expandable, Intercalated, Graphite, Graphene

Id: 8Z5RPPRS-KQ

Length: 18min 6sec (1086 seconds)

Published: Sat Feb 11 2023