Sciencemadness Discussion Board - Photolytically Deactivated Deflocculant

Photolytically Deactivated Deflocculant

12AX7 - 1-6-2016 at 15:42

Good evening gents and professors and kewls,

Had an idea about 3D printing and ceramics.

Background
----------------
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
------------
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
--------------
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

j_sum1 - 1-6-2016 at 16:04

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.

Metacelsus - 1-6-2016 at 17:24

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.

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]

12AX7 - 2-6-2016 at 00:25

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

hissingnoise - 2-6-2016 at 01:03

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]

12AX7 - 2-6-2016 at 09:05

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 . . . ?

For having posted so little in the past several years, y'all still can't touch me... I'm still in the top ten :cool:

Tim

aga - 2-6-2016 at 12:39

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 ?

3DTOPO - 2-6-2016 at 12:48

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?

3DTOPO - 2-6-2016 at 12:50

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]

3DTOPO - 2-6-2016 at 12:56

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.

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.

12AX7 - 3-6-2016 at 02:20

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

12AX7 - 3-6-2016 at 02:48

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

AJKOER - 3-6-2016 at 03:06

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]

3DTOPO - 3-6-2016 at 10:31

Quote: Originally posted by 12AX7

Quote: Originally posted by 3DTOPO

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.

3DTOPO - 12-7-2016 at 19:17

I don't know if this might give anyone some ideas, but AutoDesk made their UV curable resin open source:

http://bit.ly/29DcZnm