12AX7
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Photolytically Deactivated Deflocculant
Good evening gents and professors and kewls,  
Had an idea about 3D printing and ceramics.
Background
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Slip is a suspension of ceramic particles in a solution, usually with a modifier (deflocculant) to prevent the particles from sticking together (as
the name suggests).
With typical clays, down to around 60% solids, it will be a pliable but self-supporting clay body. Dilute to 30% and you get a workable slip. Add a
deflocculant and the viscosity drops suddenly; you can now add back in an equal amount of solids, bringing it back up to 60%, yet still retaining a
liquid consistency! It's pretty amazing to see.
A typical deflocculant is sodium silicate (ortho or meta), which sticks to the ionic surface of the clay particles, forming an ionic double layer,
cushioning the particles. Organic types range from detergents to polymers.
Here's an overview of the chemistry:
http://www.zschimmer-schwarz.com/m/simon/zschimmer-schwarz/m...
Proposal
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Come up with a photolytic deflocculant. If the photolytic yield is high, such a material could be 3D printed on standard SLA hardware, while
(hopefully) avoiding the high cost of 3D printing resins (which can be blended with ceramic to some extent, though the shrinkage is high due to the
large organic burnout).
In other words, the clay goes from 60% solids, in liquid (deflocculated) form, *zap* to 60% solids in solid form. A transition from Fig.5
bottom-right, to center-right.
Alternately, if there's a binder which sticks grains together, that would work, too. But photoactivated materials are already kind of the problem,
cost-wise! If they can be blended (as an emulsion?) at low concentration yet still achieve useful green strength, that wouldn't be bad. A "slip"
that's like >20% UV-cure resin, though? That's not cheap.
I kind of doubt anyone's tried this approach, so it might be worth some
research, but geez, I'm no rheologist. So I thought I'd ask here and see if you guys have any ideas.
Pessimism
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I can already guess: the hardest part will be getting good yield with respect to light intensity. That's probably part of the reason why the UV-cure
materials are expensive: they need purity to avoid antioxidants that quench the chain of free radicals. Probably, every time a radical touches a clay
grain, the process short-circuits, leading to really awful optical yield (i.e., you need to put in so much light, that you end up cooking it thermally
instead). Besides which, assorted clays are going to scatter and absorb most any light, so even with thin layers, your optical yield is probably
going to be poo.
But one can dream.
Tim
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j_sum1
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Sounds like a great idea Tim. I am intrigued. Of course I know nothing of light-dependent flocculants.
A similar product (in application not chemistry) is the material used for dental fillings that is pliable and sets hard with UV.
I see sense in having a transparent clay particle such as kaolin.
The possibilities for 3D printed ceramics are enormous. And the process would not have some of the limitations of resins nor some of the difficulties
of metal 3D printing.
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Metacelsus
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Quote: Originally posted by 12AX7  | Besides which, assorted clays are going to scatter and absorb most any light, so even with thin layers, your optical yield is probably going to be
poo.
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This is a tough problem, but maybe using two-photon excitation can help somewhat with it (see: https://en.wikipedia.org/wiki/Two-photon_absorption#3D_photo...). I expect the scattering to be strongly dependent on particle size. Do you know
the size of the slip particles?
[Edited on 6-2-2016 by Metacelsus]
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12AX7
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On the order of 2um. See: http://eprints.qut.edu.au/55698/1/55698.pdf
Kaolin is one of the coarser clays; bentonite is the finest: colloidial, very sticky.
A typical pottery formulation will use a combination of clay, filler and flux so that liquid phase sintering occurs. Specialty materials (usually
refractories) may need to use a large amount of refractory filler (alumina, zirconia), and a minimum of clays (aluminosilicate) and fluxes. For
these, usually a minimal amount of bentonite is used to stick things together. Technical ceramics can't even usually accommodate that, and use
organic binders and hydraulic pressing to form the shape before firing.
Two photon sounds interesting; that would give better resolution given the strong scattering. Still sounds like it may take a lot of radiation (and
thus be quite slow for a macroscopic item), not to mention the optics (would you start with a projected image, then use beam splitters, mirrors and
lenses to get them to converge on the work area from different angles?).
So, any ideas how to make a chemical that's oily or ionic before exposure, and not afterwards?
Tim
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hissingnoise
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| Quote: | | Good evening gents and professors and kewls. |
Welcome back, young Tim ─ this kewl missed you . . . well kinda?
Your "Post Harlot" status seems pretty parlous, right now . . . ?
[Edited on 2-6-2016 by hissingnoise]
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12AX7
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| Quote: Originally posted by hissingnoise | | Quote: | | Good evening gents and professors and kewls. |
Welcome back, young Tim ─ this kewl missed you . . . well kinda?
Your "Post Harlot" status seems pretty parlous, right now . . . ?
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For having posted so little in the past several years, y'all still can't touch me... I'm still in the top ten 
Tim
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aga
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| Quote: | | Good evening gents and professors and kewls |
You forgot drunkards 
Very nice to see you're alive and speculating.
So, the idea is to Print 3D ceramics right ?
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3DTOPO
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| Quote: Originally posted by 12AX7 |
Alternately, if there's a binder which sticks grains together, that would work, too. But photoactivated materials are already kind of the problem,
cost-wise! If they can be blended (as an emulsion?) at low concentration yet still achieve useful green strength, that wouldn't be bad. A "slip"
that's like >20% UV-cure resin, though? That's not cheap.
Tim |
Hi Tim,
Neat idea!
Heck - I think 20% UV resin doesn’t sound that bad to me - its 1/5th the cost of using 100% resin! Even taking into account the ceramic particles -
could still cost less maybe 1/4 - 1/3 of using 100% UV resin. To make that slip, what might be a good start?
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3DTOPO
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| Quote: Originally posted by 12AX7 |
Two photon sounds interesting; that would give better resolution given the strong scattering. Still sounds like it may take a lot of radiation (and
thus be quite slow for a macroscopic item), not to mention the optics (would you start with a projected image, then use beam splitters, mirrors and
lenses to get them to converge on the work area from different angles?). |
The biggest drawback to me with this approach would it wouldn’t work in any “standard” SLA printer.
[Edited on 2-6-2016 by 3DTOPO]
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3DTOPO
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| Quote: Originally posted by j_sum1 |
The possibilities for 3D printed ceramics are enormous. And the process would not have some of the limitations of resins nor some of the difficulties
of metal 3D printing. |
Just FYI, it has been done with what I am guessing is Silicone Carbide:
https://www.technologyreview.com/s/601245/new-3-d-printing-t...
I stumbled on this which is my guess what they have done:
| Quote: |
SLA of Ceramics. The fabrication of ceramic parts using SLA technologies has also been investigated [13]. For this research, a standard SLA resin
(Ciba XB5149) was used with silicone acrylate additions to retain SiO2 during the binder burnout process. The SLA process was used to create green
parts that are suitable for binder burnout. Reported densities average ~ 94% theoretical, however flexure strengths of green parts are very low (~ 170
MPa max). This is believed to be attributed to the delimitation of layers during the sintering process.
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I also found this company that offers resin that supposedly becomes true porcelain after firing.
http://tethon3d.com/product-category/products/
That said, I think Tim has an excellent idea.
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12AX7
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| Quote: Originally posted by aga | | Quote: | | Good evening gents and professors and kewls |
You forgot drunkards
Very nice to see you're alive and speculating.
So, the idea is to Print 3D ceramics right ? |
Yes. My thought is to do it with an absolute minimum of active ingredient. Even if that ingredient is unusually expensive, we're talking big
quantities here: your average pottery item is ~1kg, going down to ~g for small items and up to ~t for big furnaces, molten metal handling equipment,
etc. So if only a percent is needed, say -- that's a big savings.
I could imagine some interesting furnace or pump or reactor designs could be made, with the help of 3D printing; for example, to provide insulation
value, refractories usually incorporate porous or foamed materials, or filler that burns out on use, leaving voids. Instead of these clumsy methods,
you could print voids or galleries into the material from the start. (Well, making voids in an SLA print would be kind of hard, but...)
And for technical applications, being able to directly cast parts with interesting internal cavities would be great. Heat exchangers, catalysts,
maybe ionic barriers (alumina and zirconia?), etc.
Tim
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12AX7
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| Quote: Originally posted by 3DTOPO |
Heck - I think 20% UV resin doesn’t sound that bad to me - its 1/5th the cost of using 100% resin! Even taking into account the ceramic particles -
could still cost less maybe 1/4 - 1/3 of using 100% UV resin. To make that slip, what might be a good start? |
FWIW, I'm talking *cheap* stuff -- like, you can get a 25kg sack of somewhat specialized dirt for $10. Quartz (usually ground flint), feldspar,
kaolin, ball clay, bentonite, even most oxides (alumina, magnesia, lime, iron, etc.). You'll pay more for the less abundant things of course (zircon,
titania, strontium and barium carbonate, lithium carbonate (but spodumene is pretty cheap), other metals), but you don't usually need much of those
(i.e., usually as fluxes or colorants in glazes).
So, potentially, the incremental cost for these prints could be very low: except for the time taken printing, it could be competitive with traditional
pottery production (pressing, extruding, slip casting).
Maybe such a formula really isn't all that useful, on account of the printing time. Once the material is nearly free, all your real costs revolve
around lead time, machine availability, and machine capital...
Tim
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AJKOER
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In lieu of UV light as a catalyst, employing another sense, think ultrasound!
Both are known paths to radical formation.
A simple application would be an acceleration of setting time.
Also, for objects of larger mass, the internal transmission of UV light is likely more problematic than with sound waves.
Combination approaches incorporating light (fast setting of the exterior), sound, microwave (MW) and conventional heating may also prove to be of
value. I have read that the employment of MV on compositions rich in iron, for example, is particularly effective, for an acceleration of reaction
rate, due to a magnetic resonance effect.
[Edited on 3-6-2016 by AJKOER]
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3DTOPO
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| Quote: Originally posted by 12AX7 | | Quote: Originally posted by 3DTOPO |
Heck - I think 20% UV resin doesn’t sound that bad to me - its 1/5th the cost of using 100% resin! Even taking into account the ceramic particles -
could still cost less maybe 1/4 - 1/3 of using 100% UV resin. To make that slip, what might be a good start? |
FWIW, I'm talking *cheap* stuff -- like, you can get a 25kg sack of somewhat specialized dirt for $10. Quartz (usually ground flint), feldspar,
kaolin, ball clay, bentonite, even most oxides (alumina, magnesia, lime, iron, etc.). You'll pay more for the less abundant things of course (zircon,
titania, strontium and barium carbonate, lithium carbonate (but spodumene is pretty cheap), other metals), but you don't usually need much of those
(i.e., usually as fluxes or colorants in glazes).
Tim |
Of course dirt cheap woud be even better - I couldn't complain!
| Quote: Originally posted by 12AX7 |
Maybe such a formula really isn't all that useful, on account of the printing time. Once the material is nearly free, all your real costs revolve
around lead time, machine availability, and machine capital...
Tim |
Well there really isn't much to SLA printers in terms of hardware. It consists of a single axis (Z), a resin vat, a build plate, a galvo and laser or
digital light projector.
In fact - someone made one without even a Z axis - the level was raised by dripping water in! It had no motherboard too - his galvos work off sound
(mp3 player) - a kit was on Kickstarter for $100.
https://www.kickstarter.com/projects/117421627/the-peachy-pr...
Another was launched on Kickstarter the DLP is the phone's screen and the controller the mp3 player. It was launched on Kickstarter for a cost of $99!
https://www.kickstarter.com/projects/olo3d/olo-the-first-eve...
Its my understanding that the most difficult task of making a galvo SLA printer is getting the controller software right since its not linear (just a
bit of the right trigonometry or cartesian math I suppose). And of course tuning the UV exposure.
Anyhow - its only a matter of time before more capable machines are selling for what cheap FDM printers cost today - or less.
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3DTOPO
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I don't know if this might give anyone some ideas, but AutoDesk made their UV curable resin open source:
http://bit.ly/29DcZnm
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