"Damn it, you aren't suppose to read the detail" Also, the easy way to to make aluminium dark is by soaking it in 20% salt in near boiling water, then turn the lights off.

Hey Ben, I did my PhD in experimental physics (in fact, using a few materials/techniques you use in this video). I don't have any tips for this problem, but I wanted to say that your experience here is very typical: we'd frequently read about some cool new process, say "huh, seems simple enough, let's try it", and find that it was near impossible to reproduce from the paper. Research and publication is supposedly about reproducibility, but I suspect that typically, some key step is left out. I'd guess that it's some fraction malice and some fraction not, where either the authors don't want it to be reproduced (before they can get several more publications), or where they either didn't realize there was something special about their lab setup, or they've always just done something in a way that's actually unique to them, so they didn't realize they should report it.

I work in the MIT group you referred to in the video and I forwarded your video to the first author of the paper. Hope you guys can talk directly.

The paper should have a corresponding author listed, and you should definitely feel free to email them with you questions. A hard lesson I learned in my PhD is to contact the authors before even getting started, as some key details are often left out in the name of being succinct. In my experience, they will respond with the actual person who made the sample, and very likely will share their lab protocol and any tips. Unfortunately, by convention what didn't work is not published, even though that oftentimes is the most key bit of info when trying to reproduce a protocol, hence why a corresponding author is always listed. If they are like most scientists, they will be stoked that you found their study interesting.

Throwing some valid shade to the state of recent research papers. Having seen the same in Electromagnetic papers lately.

Put salt water on aluminum and then place it in direct contact with steal. It will turn dark. I used to work at a hurricane shutter company and that was a big no no that ruined aluminum often. First remove any oxidation from the aluminum.

As a grad student, normally the best way I have found of reproducing experimental papers is contacting the author directly about any questions you might have. Many times, the discrepancies are not done maliciously but because of simple errors (not always, but generally), so asking the author directly helps clear up any of these.

re: metal solubility in ethanol - the acac salts referenced in the paper aren’t acetates, they’re acetoacetates. Way more soluble in organic solvents.

Some thoughts since I've also read up on this sort of stuff a lot. One thing may be to try a different catalyst. I've seen ferrocene used a lot and should make smaller diameter nanotubes. I haven't seen them use hydrogen to reduce it, normally it's just painted on and heated under argon and will just decompose to pure iron crystals on the surface. Since it's basically iron and carbon, the carbon just burns off and so long as there's no oxygen present it shouldn't form any oxides. Also then you dont need to work with cobalt which is always nice. Beyond that, It's odd that you're using only co2 as the reducing gas. I've almost always seen hydrogen mixed in as well to reduce any amorphous carbon. It increases the pucker factor for sure which is why i haven't tried it, but may give you a much better result. For comparison, hydrogen is used as the reducing gas when growing diamond as it's much better at getting rid of any unordered carbon. The next would be to start with that black velvet. As long as it's made of natural fibers you can carbonize it by heating it under argon. Then paint it with the catalyst, and try growing the nanotubes on it. Should get you a muuuuuch darker end result. For the darkening foil you may want to go the other way rather than degassing the solution. Add more oxygen. If it only went dark when exposed to the fumes, to me that screams it needs more oxygen than can be attained while submerged. Or add a drop of soap or tween to the solution to help break the surface tension. Another way to do nanotextured aluminum is to wipe it down with a dilute HCl solution. I used that trick to texture aluminum when I was making supercapacitors and it seemed to help add lots of surface area. EDIT: updated once I finished the video.

There are enormous career pressures in material science (more engineering for lots of synthetic work like this) to discover “novel” materials. A simple hypothesis from an influential professor can lead any desperate postdoc to make a few optimistic rounding choices or instrument configurations. That isn’t necessarily going on in this instance, maybe there is some small detail of sonicating aluminum in salt water that was miscommunicated or forgotten. In any case, if you’ve done synthetic work, especially cutting edge stuff from top journals, you know that not everything is as it wants to seem. (That said, a very large amount of synthetic work is as solid as it seems. Total number of publications is growing rapidly, so the absolute amount of irreproducibility is growing too. There is a very positive, if painful, movement starting in science to upgrade the whole system and hopefully minimize a lot of this.)

21:00 I used to be involved with densitometers. The proper angle is to have the light source normal to the surface and the fiber pick-up at 45 degrees, or vice-versa. You can also obtain a calibration plaque cheaply enough if you want real figures.

It is great to see you wading into the replication problem. I also really like how you are sharing your trials and tribulations. Actually doing science is almost always really messy, and it is often presented as click clack snack. Your contribution here is really appreciated.

Did you look at the vertically aligned sample under the electron microscope? Im curious if that looked globular or if you see more consistent structures

I regularly turn Aluminium foil pitch black: Whenever I cook a special kind of dumplings that are made from cut up white bread made into a dough. The dough gets wrapped in aluminium foil and put into boiling salt water for 20min. Normal tap water (Here in Germany we do not really have additives like chlorine in it)... and about as much salt as you would use with pasta. the inner side of the foil gets coated with olive oil but I don't think the dumpling dough or the oil have anything to do with the foil turning black. The only thing I could think of what would be different to your experiments is, that I really boil the water and don't use very much salt. If you want pictures , I could cook them tomorrow, my girlfriend would be very happy to get those dumplings ;-)

Crazy amount of effort put into these videos. Hope you enjoy the work as much as I like watching.

Ben, My guess is that one of the things that you say: "doesn't seem to matter much" does matter. Did you try reaching out to the MIT guys? About replicating stuff: Back in the mid seventies my father was a PHD student and tried replicating a paper that said that doing liver transplants in rats was easy. They tried for months, but as soon as they put the rats back on their feet, they died. Turns out one of the drawings in the paper was of the rat on the operating table (i.e. upside down) and not right-side-up. (or the other way around). My father ended up contacting the guys in Japan who wrote the paper.... "yeah that happens if you do it upside down".

This is really cool! We followed a similar procedure in a lab class a few months ago to grow CNTs. My group only managed a few hundred um, but another team got well past a millimeter. One trick we used during the SEM analysis: use a razor blade to carefully slice into a few spots on the sample, then view it at an angle using the microscope. We initially thought we only had soot; similar globules and so forth. It wasn't until we cut into a globule and SEMed it from an angle that we saw a tiny forest. Re: Al darkening, I agree with other commenters -- send a note to the researchers. Other changes from your setup: we used helium rather than argon as a 'safety gas'. Our apparatus also had a built in 6mm Lexan blast shield, and everything was performed in a fume hood. Probably not needed if you're careful about avoiding leaks. And our substrate was directly heated using a bit of highly doped Si with a current running through it, and a pyrometer feedback mechanism.

I see black oxides on 7575 aluminium, 7575 will stain or get black spots on it if left in machining coolant for too long, or ive forgotten parts is a wash tub of water and dawn soap and seen black spots.

Great work and great videos! I love the deep and detailed layman analysis you give them. Obviously lots of hard work and talent. Thank you for what you teach us.

The styling on that electron microscope is SO sick. I absolutely love it.

I am going to start using high pucker factor in my daily vernacular.

You're always so humble in your videos. Hope to see you globally recognized some day 😁

This videos are incredibly valuable. Thank you for producing such thorough experiments.

I'm always a bit bummed when research can't be duplicated. Thanks for another great video Ben.

Just email the researchers and ask them.

A published research paper that isn't repeatable? Imagine my shock. lol

You can dissolve Al in concentrated NaOH solutions so maybe dilute NaOH in combination with ultrasound could give you the roughened surface (a similar process was used in a paper (doi:10.1016/j.jallcom.2017.01.243#) where they created superhydrophobic surfaces) an alternativ could be making porous alumina by anodization however I am not sure on how well this would work in your case (for example doi: 10.1038/nmat1717) The holes in Aluminum can also be observed in our small lab ultrasonic cleaner (as far as I know a consequence of cavitation bubbles forming and locally corroding the aluminium)

There’s a lot of great technological creator content here, but Ben your work is to most sophisticated and absolutely amazing!

When I was a kid I accidentally found how to make aluminium black. I naively tried to etch a PCB in ferric chloride in an aluminium tray, doh! The ferric chloride burnt through the bottom of the tray and what was left was blackened IIRC. It was nearly 50 years ago! Later in life I worked on the design of an electronic photobooth and we bought a commercial test card to set up the camera. It had a printed grey scale but the last grey was black felt and the black was a hole into a box lined with felt. The hole was probably about an inch wide and the box about a 4 inch cube.

Tech Ingredients is an awesome channel! So is your channel! You guys make such great content. Thank you for educating all of us with your knowledge and findings.

I'm just making a comment to recognize the quality content you produce. It's very rare on this platform and deserves attention.

Mr. AppliedScience I love your unerring curiosity and commitment to science. You remind me of a tech-oriented Mr. Rogers in all the best ways.

Vantablack: £1000 a tin. Amazon: £2 felt. Vantablack has left the chat.

There seems to be an increase in scientific papers containing results that can't be reproduced, but this MIT paper sounds awful with vague descriptions and inconsistent methods; why trust their findings? 0.1%...REALLY?

You are indeed a scientist. I hope one day you invent(discover) something truly remarkable.

Love watching your process. That's quite a lab you have accumulated. SEM for the win! Good luck w the nano tubes!

Ask them maybe what they did ;) I would suspect that they did a short ultrasound and then soak and then short ultrasound again and so forth. Aluminum capacitors need a huge surface area too, maybe figure out how they prepare those?

Would you consider using charcoal cut perpendicular to the grain for your initial medium? Charcoal from very straight grained species like Finnish pine would presumably have quite a vertically aligned surface once cut, and also contain the micro porosity you’re interested in depending on the density of the original wood.

Amazing subject, thanks for the behind the scenes look.

Again, over _my_ head but still fascinating. Thanks for the video.

I've seen aluminum foil turn dark while doing the silver tarnish cleaning trick. Granted most of that was probably some aluminum and sulfur compound, might be worth a shot.

I've seen aluminium turn darck on boats plenty of time. I don't currently have axess to the appropriate equipment but I'll suggest to use high grade marine aluminium ( 20+year stock if you can find it) and very low voltage/current. also no disturbance in the water.

Great Work!! Be cool to show if you could do a pull test to see if you have a carbon nano tube forest. It looks so cool when you see them being pulled from a slide, not many videos out there of it.

In middle 80's, when I was a kid, I read how to darken aluminum in a russian DIY magazine "Modelist Konstruktor" and used that method for transistor heatsinks with great success. I remember that it was a simplest method imaginable and I thought I'd remember it whole life, but later, after some 15 years, when I really needed it again, I couldn't remember how to do it, neither could I find the recipe. What I remembered then and remember now is that it was as simple as immersing aluminum into NaCl, or NaOH, or the mixture of the two, but when I tried, I failed every time on that later occasion. No ultrasound was needed nor was recommended to use as it was a DIY project in that time and country. The only other chemicals I had access to by then were NaHCO3 and CuSO4 so I couldn't have used anything other than what I mentioned here. Hope, with your diligence, it helps. P.S. the resulting colour was far from being as dark as black velvet or even black paint.

can you finetune the frequency of the ultrasound? When I visualize the prosess, I think you will have to either create a standing wave or absorb all the echos. So you might get a reliable pattern of pressure differences.

"We are talking about pretty dark stuff here", Indeed we are.

Too many comments to see if anyone has already suggested this, but you may want to look into the frequency of your ultrasonic cleaner. I was a maintenance tech at a label company. They purchased an ultrasonic cleaner to clean "Anilox" rolls (rollers that applied ink). The first cleaner they purchased was too aggressive and eroded the ceramic coating off the rolls. The original cleaner had a fixed frequency of 35 kHz. They had to get another ultrasonic cleaner that had an adjustable frequency between 50-100 kHz. I was told that the lower frequencies are more aggressive than higher frequencies. We operated at about 70 kHz. On a side note, I thought it would be a good idea to try and clean the aluminum exhaust port on my shotgun with it. It ended up eroding the aluminum and turned it dark with an orange peel texture. Had to purchase a new exhaust port.

Thanks for the flashlight test ! Was what I was looking for!

that's pretty dark stuff, I didn't expect this from you Ben.

Have you seen any of the paint development that Stuart Semple has been doing? I think this might be a fun way to get Black 4.0!

Right before you mentioned texturing the surface, I was thinking of minimizing the tapered base of the tube maybe by growing it through a screen of some sort but texturing would certainly deflect the light coming off the base

Love my Ikea lamps - thanks for turning me on to them. Really handy on the lab bench.

For the lower-bound reflectivity measurement calibration, have you tried a hole in a box that's black both inside and outside? (I searched the comments of this video and found that John Długosz also suggested this a week ago.) I think this calibration may be quite important, as the light from your lamp may be reaching the input fiber to the spectrometer in paths other than the desired one (for example, it may be diffracting around the baffle you're using).

Spinal Tap's Nigel Tufnel: "It's like, how much more black could this be? And the answer is none.... None more black"

once more , a very interesting video, i dont know what to use it for. but i do dig your style. all messy. reminds me of being soooooo bussy with something , its all you care about at that moment. and always interesting and above my paygrade content ! love it !

My guess is they used some sulfur compounds like sodium bisulfite, sodium sulfite or even sulfide. One reason is that it is not easy to keep aluminum surface free of oxide in a salt solution, especially for a week with progressively increasing surface area. These compounds would help with scavenging oxygen and oxide and reduction as well. The chemistry should work still, with sulfides present on the surface and might help subsequent adhesion of different metals. Also there were some reports on using sulfur compounds to reduce graphene oxide, thus the chemistry seems favorable on all aspects. On a further note Thiols can definitively darken metals. Combined with chemisorbtion of the mentioned "catalysts" this actually would seem like a feasible approach. Also they do advertise the use of sodium containing detergents in some of their work (angewandte paper in particular) and bisulfite can infact be found in those. Another thing to really consider, the naked metal surfaces are really active, especially if they are nanoporous, and dirt could really stick to it. Cleaning surfaces is the most tedious part. Clean glassware is key, e.g. dont use soap to clean your glasware, it will end up on the activated surface. Also, come to think of it, Nickel content might be vital in these materials. There is a reducing agent which is called "Raney Nickel" and is prepared from a nickel and aluminum alloy. It is used for desulfurization in some cases. Section on catalytic reduction is of interest in your case: en.wikipedia.org/wiki/Raney_nickel I would check this review in particular>>>> 10.1002/aenm.201703259 Graphene oxide reduction with bisulfphite doi: 10.1021/jp107131v Chemisorbed thiols on metals: 10.1007/978-1-4613-0327-5_5. I hope I am not throwing you off of the real answer. Great videos Ben! Keep it up and thanks for the content!

Awesome video as always!

Did you consider using anode foil from electrolytic capacitors? It is etched already (the level depends on the rated voltage of the capacitor)

I've been curious about vantablack since I learned of it's existence. This was a very interesting video. Thanks for also showing the flashlight trick, as a "couch scientist" watching a KZfaq video and not being familiar with the actual surface, it was truly enlightening to see the effects of light close up to the material. I have a request/idea though... You should somehow "wrap" your furnace to mimic an Easy-Bake Oven lol

That's awesome, I hope you can get the aluminum issue sorted out. I've played around with growing carbon nanotubes before as well, but nowhere near as well thought out. I was just using a high voltage source (2000V) with the anode attached to my acetylene torch head, and would run just acetylene through the torch. I set a flame about 1" long at very low pressure (this was done with a jewelers Oxy/Acetylene torch, really tiny tip orifice) and put the cathode inside the flame. It most definitely wasn't making a forest of tubes, more like a ball of tangled yarn, but it was really cool watching the nanotube cluster form inside the flame. I wish I could have seen it under an electron microscope though...

Warning!!! "we are talking about pretty dark stuff here" 22:42

A few thoughts. Try putting a piece of aluminium in a hot solution of concentrated sodium hydroxide, with stirring or ultrasonic action. I’ve noticed that the aluminium part of the handle of my saucepan is a relatively dark colour from being put in the dishwasher, so perhaps it might work for you too. There might be a difference between cast and extruded/rolled aluminium too, or in how it was heat-treated. Trying on proper unsealed electrolysed aluminium might also be worth a shot. But something more likely to work, unroll an electrolytic capacitors and use its aluminium electrode. The surface area should be pretty damn high. Not sure if you tried it already but growing them on soot-coated aluminium sounds like a good idea too. And consider increasing your CO2 “etchant” concentration.

Pretty cool! Thanks Ben!

By the way, your videos are awesome and most of your projects related to electron gun and CNTs synthesis overlap with my PhD topic. All the best man.

I have had aluminum turn black when placed in a NaOH solution.

Have you tried black 3.0?

Your tube furnace setup reminds me of the test stations we built for my dissertation on electrochemical properties of ceramics. What we did was adding a KF flange to the tube - my special station was designed out of a corundum tube with a aluminium flange glued together with epoxy. Of course you have to consider thermal expansion, but as long as your tube is long enough there shouldn't be a problem. All the utilities (cantilever for samples, thermocouple, electrical feedthroughs, gas ports,...) were implemented in an opposing flange and could be reliably sealed. We even managed to build a tube furnace out of YSZ and turn it into an oxygen pump to do experiments in hard to reach oxygen partial pressures. If you want to further functionalize your setup feel free to contact me.

Finding a replicable paper is an Odyssey these days.

Well that paper sounds like a mess. Incomplete description and inconsistencies just ruining your day lol

Some things I would try: - Make sure the aluminum surface is well cleaned - try different frequencies - reduce power. You might be breaking off the peaks.

Love the videos as always!

Thanks for pointing out that the "quartz" tubing for the patio heaters was not really quartz. I was ordering parts for a new vacuum degassing system based on this cheap source of quartz tubing! You saved me a lot of heartache and expense.

Seems like a sketchy paper to me. I hope you can get it to work cause it sounds like a really awesome project

'brewing beer one time' - nice

I have kinda done this with charcoal, it works surprisingly well, basically I put the charcoal in some ethanol and put in in a pressure cooker on top of some glass

I have what started out as a shiny cast aluminum garlic press from Zyliss. The one single time it went through the dishwasher it turned very dark. Now, over two decades later, it's still dull gray even though we only ever wash it by hand. No more aluminum goes into our dishwasher after that episode.

Washing aluminum in a dishwasher makes it dark.

I wonder if the frequency of the ultrasound is influencing the size of the cavitation bubbles to a big extend. Maybe why yours didn't work

Inspiring. Thank you so much for sharing this.

You can etch stuff pretty well by just soaking it in salt water, attaching it to ground on a 12 v dc powersupply, taking a cotton swab an connecting the positive end close to the soaked cotton and then just running it across the surface. Usually 12v digs quite deep so maybe something lower would create more nano-scale indentations.

I wonder if they really used sodium chloride or if it was a different salt compound and the person who wrote the final paper assumed it was table salt.

I have a feeling that the thin layer of aluminum oxide that forms naturally with ambient air (oxygen) is harder to ultrasonically treat than the aluminum itself. I'm not sure if the acid concentrations you used were high enough to break down that oxide layer.

All of the etchants I have used to etch aluminum samples for metallurgical analysis have a small amount of either hydrofluoric or nitric acid (google Keller's etch and Kroll's reagent). You need these strong acids to dissolve the oxide layer; hydrochloric isn't strong enough. However, these etchants are literally designed to give as smooth and flat a surface as possible so we can see the microstructure. But maybe if you use one of these etchants prior to the saltwater bath, you will have more success. The aluminum oxide reforms quickly even at room temperature, so be quick in transferring it from the etch to the saltwater. A small catalytic amount of hydrofluoric or nitric acid in the salt water bath might be helpful too.

I think a collaboration video with NileRed would be fun for the chemicals side. Also it would be curious to see Ferrofluid as catalyst particles and what structures you could get out of that.

you played us like a fiddle with that black velvet off amazon e_e

Could it be that the M.I.T folks are publishing papers hoping no one checks there work?

It strangely gave me comfort knowing that we can see the surface of those materials with a flashlight.

Someone may have already offered this information but, my first highly technical job was thin film optical coating. We did everything in house. Part of coating is cleaning shielding with a bead blaster and then washing it very carefully to remove all the debris. While doing this (in deionised water not salt), occasionally these dark patches would bloom on the metal surface that could not be wiped off. Someone told me that if you leave the metal in the ultrasonic too long this can occur. I assumed it was contamination working its way into the roughed up surface of the metal but it is possible this was occurring. It never turned black but I'd only leave it for a few minutes at most.

The oxide layer is hard to break on al.

Alright, I've got to ask: can you grow your carbon nanotubes onto carbon nanotubes?

a few years back, i have evaporated aluminium in a poor vacuum that resulted in blackish aluminium/oxide film. but aluminium oxide is high bandgap transparent. that dark film could be a texturized aluminium which is useful for this application

I remember some mechanics in a forum saying to avoid putting aluminum in an ultrasound with detergents as it will cause the aluminum to go black. might be a starting point for further investigation.

instalike for referencing Tech Ingredients' channel. i mean, let's be honest, I'd like this video anyway, but that even in itself is enough.

Sounds like the researchers are either telling some fibs or they really haven't described their method very well.

OK, so at work I'm working on a side project trying to come up with an anodizing method to create lowest reflection from 350-1700nm. That velvet cloth is super reflective >700nm. That paper you are using for reference does not have a flat reflection spectrum. I am using an integrating sphere, a thin film flat spectrum reflection target 4% reflection. Flat black rustoleum paint is surprisingly GOOD, 4-6% reflection from 350-1100nm, the problem is application, great on flat surfaces and you must also not over spray otherwise you get super strong specular reflection. Thorlabs sells black aluminum foil and it's also 4-6% reflection, pretty good, I assume it's 1100 series or similar. I'm investigating bead blasting media and size on anodizing process using a 3D surface metrology microscope to help figure out what types of surfaces achieve lower reflection. Thanks for the salt idea, I'll have to try it on 6061-T6 and investigate further on what it does to the surface. The main issue with these forests is that they are fragile and basically useless.

I liked the slumped tube effect/caveat emptor. Good to know because those "replacement quartz tubes" seemed like something useful for the price. There's a video on youtube entitled Coating Quartz Glass Tube In Graphite maybe of some interest whatever the case, perhaps of some use in some later project.

Need Oled for watching this :D

Might be worth removing the oxide layer from the aluminium first. Once you have it etched then let the oxide layer establish again.

Excellent......apreciate the maner you explain the problems that occurs in the practical expérience. Thanks many Time for that. Bravo.....

I'm not much of a chemist, but have been a telescope maker for 30 years, and so my interest lies in a cheap/flexible/durable/lightweight/blacker-than-black/thermally-inert material to use as a coating for the inside of a telescope tube that will absorb stray light. Your video is interesting. Thanks!