Hm
So
An AFM / STM isn't that hard to build, right?
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Dang why does everything have such a high CTE
50 nm per K in Z.... maybe that can be compensated with the right materials to even out... kinda.
Maybe I just build everything out of fused silica and invar
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Ohhh I can build it in a way that the CTEs cancel each other out perfectly(ish)
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This looks... ok?
Provided I can cut the glass, that V-Groove is going to be fun. I have an idea or two.
Tests to be done!
The Piezo (why does fusion render brass blue??) does X/Y/Z for the actual raster, the micrometer provides rough (maybe too rough?) Z travel and the kinematic coupling between both plates in combination with the right material choices should cancel out most of my thermal expansion to keep it all stable.
Piezo - Glass rod - Needle are one replacable assembly.
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The basic kinematic coupling is already soooo satisfying to play with!
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Hmmmnice.
It works as expected, and the kinematics reduce the mvement by a factor of ~3, so every Division moves the center by ~3 um.
Should be just about ok, meaning that the piezo can do the rest of the Z travel.
Issue is that I now need to constrain the ball on the micrometer, which means that I either have to grind a cup in the micrometer shaft or buy a different micrometer with a rounded tip to take the ball out entirely.
...maybe I should build a dremel tool mount for the lathe.
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This feels like it shouldn't work as well as it does
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This will be very interesting under the SEM
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Getting much better!
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atomic spike field
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Well that's disappointing, the tungsten has cracked on most of them, and the tip radii are on the order of a few 100 nm
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Just missing a few milling steps on the other side (two V-Grooves for the balls) and then I can try and case harden this thing!
Worst part was getting the blanks round, the lasercut edge was hard enough to ruin a few inserts :(
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Workholding adventures!
I've had a whoopsie or two, but it's functional, doesn't have to be pretty 😉
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And now we're onto the carburizing step!
Takes tiiiime
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Woohoo!
It came out really well, isn't really distorted (nothing to be felt, didn't measure), and the surface finish didn't suffer.
But the real test is to do another heat treatment to harden it, that will reveal if it actually worked!
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Aww yis, the other parts are coming together as well!
I'm really looking forward to machining the glass, I've never done anything like that.
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...is there any way to non-destructively test for borosilicate?
The glass was sold as such, but the green tint really reminds me of recycled or cheap soda-lime with iron contamination.
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👀
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🥵
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@gigabecquerel you should find some ceran at the scrap, which is somewhat not so terrible.
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@gigabecquerel My suggestion is: dont bang your head with the material! when you cant find a stable material, the solution is to stabilize the temperature. Sounds much easier. The AFM itself can be quite small. Nothing prevents you from putting it in a thermally stabilized enclosure. Double oven can be done.
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@gigabecquerel There are many designs on the internet already, this one looks quite elaborate and easy to build with access to a hackerspace.
https://www.instructables.com/A-DIY-AFM-Whokshop/
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@f4grx I'm well aware of the projects out there, I just want to put my own spin on it
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@gigabecquerel so I'll shut my mouth and let you invent in peace.
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@gigabecquerel what is this - an opera house for ants?
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@jackeric Yep, you got me!
It's a movement stage, or at least part of one.
I'm thinking about building a Scanning Tunneling Microscope and that requires very precise movement in the µm to nm range.
Stuff like this is mostly out of my comfort zone so now I'm building 3D printed prototypes to make sure I understand the kinematics behind it all!
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@gigabecquerel
Where did you buy the micrometer mechanism?
I might have a use for a few small one's and I'm interested in what they usually cost.
Well, what the one's that are not from Puuilo or Lidl.
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@ftg This one is an original one from mitutoyo, I think I found it at a flea market?
But there are similar ones on aliexpress for around 5 €, I've ordered a few and will report back!
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@gigabecquerel
Excellent, thank you!
My potential use a little bit different. As I want them for fine tuning some mmW Gunndiode oscillators I plan on building at some point in the future.
When I get better at machining.
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@ftg They're... ok!
Not great, but for around 5€ a pop you really can't complain.
The grease they're packed with was a bit thick for my liking, so I swapped it for something thinner (the prusa lube that comes with the printers), which revealed some wiggle room and a few rough spots on the threads. Nothing deal breaking at all!
I'm happy with them.
https://de.aliexpress.com/item/32883962660.html?
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@ftg Also: The shaft isn't hardened, which saves me a lot of work, not having to grind the mitutoyo!
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@gigabecquerel
Excellent. Threw one into the alibasket for the next order.
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@gigabecquerel Single atom probe?
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@Nixie That would be amazing, but I very much doubt I can reach that.
Literature makes me think this can be ~30 nm tip radius, maybe even down to 10 nm.
First of all I want to know what's possible!
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@gigabecquerel Iirc, the single tip was done with pliers and a snap, but I could be wrong.
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@Nixie I know what you're referring to, but that method seems to be pretty unreliable.
"Lab Grade" tips are etched, too, so I guess that's the way to go here.
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@gigabecquerel cant wait for the SEM view!
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@gigabecquerel Getting the parameters dialed in can take a bit. Did you have automatic or manual cutoff when it dropped? Did you apply the inverse half-cell potential after?
I played with DIY etching for microprobing but never quite got it as perfect as I wanted. i was running seat-of-the-pants with a fully analog power supply though.
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@gigabecquerel When we needed tips in my undergraduate studies, we took a side cutter and diagonally slowly cut a wire while strongly pulling away. Don't remember which material, though. Maybe half the tips were somewhat usable, which we determined by trying to use them.
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@gigabecquerel ok, so what forces would have to occur to make it crack like that?
How can the structure be modified to better dissipate these forces?
("quack quack") 🦆
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@RueNahcMohr @gigabecquerel I would be happy if you two were neighbours. 🙂
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@gigabecquerel inserts because threading shallow depths is a pain?
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@f4grx Inserts because I doubt something like an M3 thread would survive carburizing and case hardening, and I don't want to work on the hardened part.
The threads don't need to hold much force, so this feels like the simplest way to add some, I'll just epoxy them in place once all is done.
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@gigabecquerel thats a very interesting solution that I will remember.
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@f4grx Time will tell if it's a solution or just a bad idea ;-)
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@gigabecquerel At least there's evidence that you still have a minimum of one remaining hand. Major oopsie averted.
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@basil_hare Oh no, just "slipping out of the chuck" kind of whoopsies!
I keep fleshy parts far away from things that spin quickly, I've learned that lession on my small lathe.
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@gigabecquerel Very good. One must always protect the flesh.
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@gigabecquerel how deep does this actually defuse into the steel? do you only get the surface hard?
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@4censord That is in fact a very good question!
Maybe I don't have the right search terms, but I could find very little literature on it.
From what I could find tho I expect the first one to three millimeters to be carbon rich now, after five hours at 950 °C.
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@gigabecquerel hmm, ok so its measured in millimetres. Thats already answers my curiosity.
So i assume this part doesnt see extreme loads, but the hardeing is mostly for wear resistance?
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@4censord Yep, exactly!
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@gigabecquerel cool!
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@gigabecquerel Test optical constants like transmission behaviour or refraktive index?
https://refractiveindex.info/?shelf=glass&book=SCHOTT-BK&page=BK7G18
This should give a hint.
EDX or XPS also give compositions. But who has this. (Me at work, but XPS is currently down.)
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@M Index is a good idea, I should see if I can cobble something together. Not sure how much boro and soda differ, but it will be a number.
EDX is something that I technically have, but afaik my detector doesn't go down to boron...
Another idea I just had is to measure the CTE somehow, after all that's why I wanted boro im the first place
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@gigabecquerel @M Will it pick up calcium or sodium? You should be able to check against common formulations and rule out several even if you can't see the boron.
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@gigabecquerel See the reference I gave you.
Check how much n differ from both.
Might be that you can even check with a laser pointer and some precise diffraction measurement.
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@gigabecquerel I've known people do heat shock tests, which isn't conclusive but check if it is good enough. A lot of people suggest it is close to index of refraction of mineral oil, but soda lime glass isn't that different of an index. Borosilicate glass tends to be less dense than other common glasses, but you would need decent previous to tease that out.
In a lot of places, unlabeled glass is as good as trash...
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@gigabecquerel is it non-destructive?
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@gigabecquerel hardening?
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@hattom Hell yeah
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@gigabecquerel 🔥
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