Ceramic Powder processing progress - urgent

**darkelf** · Nov27-09, 01:08 PM

Hey there,

Would really appreciate some urgent help here more like direction. I'm looking into the progress of colloidial ceramic powder processing and am getting a bit confused.

Could anyone point me as to any good papers that could help me out here. Anything with regards a powder consolidation mechanics and densification mechanics.

Anything explaining developments here would be useful.

Thanks

**Astronuc** · Nov27-09, 01:27 PM

Originally Posted by darkelf

Would really appreciate some urgent help here more like direction. I'm looking into the progress of colloidial ceramic powder processing and am getting a bit confused.

Could anyone point me as to any good papers that could help me out here. Anything with regards a powder consolidation mechanics and densification mechanics.

Does one have a specific ceramic in mind?

With regard to colloidal ceramic processing, is one possibly referring to the sol-gel process?
http://en.wikipedia.org/wiki/Sol-gel

One process is to take a ceramic powder and blend it with a binding agent, then pressing the 'green' ceramic, then degassing it a low temperature before firing at the sintering temperature. In the degassing/sintering process, the binding agent basically volatizes and evaporates and the ceramic grains sinter or fuse. A polycrystalline ceramic is then achieved. This is much the process for nuclear fuel ceramics like UO₂ or MOX.

For ceramics like silicon nitride there is
Optimization of an aqueous, commercial silicon nitride slurry for colloidal isopressing

Here is a similar process for UN ceramic, but I don't have the paper or details.
Internal Gelation as Applied to the Production of Uranium Nitride Space Nuclear Fuel

**darkelf** · Nov27-09, 01:36 PM

Originally Posted by Astronuc

Does one have a specific ceramic in mind?

With regard to colloidal ceramic processing, is one possibly referring to the sol-gel process?

This is unchartted waters for me so not so sure about that but I believe the should be a difference.

I am more interested in the research findings with regards fundamentals I think like powder consolidation and densification and grain growth hindering and the likes. Develepoments in such areas.

Again thanks for the prompt response.

**Astronuc** · Nov27-09, 02:05 PM

Originally Posted by darkelf

This is unchartted waters for me so not so sure about that but I believe the should be a difference.

I am more interested in the research findings with regards fundamentals I think like powder consolidation and densification and grain growth hindering and the likes. Develepoments in such areas.

Again thanks for the prompt response.

I'm very familiar with ceramics used as nuclear fuel, and that's very different from say electronic ceramics or highly engineered structural ceramics. Even with nuclear fuel oxides, there are different processes which produce more or less the same outcome, but are still subtly different.

In nuclear fuel oxides, the green ceramic (oxide + binder) has a density (after pressing) of about 50-55% of the final density. The amount of binder is just enough to stick or bind the power together when pressed. In the preheat, the binder mostly evaporates. Then the ceramic is 'fired' or heated at something line 1700-1800°C. Depending on the sintering time, the final density could be 95-98% of theoretical. Sintering aids can be added to reduced firing time and temperature required for a given density. There is also the matter of whether the sintering aid or components ends up as an impurity which could adversely affect performance of the ceramic.

The chemical processes used to form the ceramic materials are often specific to the particular ceramic. And the subsequent processing is also dependent on the ceramic and it's physics.

Try this and see it if helpful (it might be available in the library ?)
Advanced ceramic processing and technology

**darkelf** · Nov27-09, 02:17 PM

Thanks again. I've tried using the book seems rather old, published 1990. I'm looking for developments since then.

The first chapter though was pretty helpful, anything moving on from there would be perfect.

I'm looking for developments in fundamentals of collodial processing basically.

Would appreciate any guidance you can offer.

**Astronuc** · Nov27-09, 03:12 PM

See if this is useful - http://www.syalons.com/resources/gui...ufacturing.php

And these -

Chemical processing of ceramics

also this article from the book - http://books.google.com/books?id=Q58c6SBVnC0C&pg=PA269

Ceramic processing and sintering

I suspect the specifics of modern processes are proprietary. The field is very competitive. I think the best one can do is find a reasonably recent textbook, and that is likely to give generalities and perhaps dated (decade old) material.

As I understand it, the sol-gel is desirable for producing uniform (chemistry and size) ceramic materials, which are then hot pressed (HIPped) and/or sintered to final form. Sintering aids are added, but I don't believe binders are necessary since the power is compressed in a form and sintered in the form (die).

**darkelf** · Nov27-09, 04:50 PM

Thanks ever so much.

The book looks quite helpful. Would you mind if I take advantage of your deep knowledge of Ceramic processing and ask for a good paper or book that talks on sintering kinetics, densification kinetics and coarsening kinetics and grain growth control.

Thanks so much

**Astronuc** · Nov27-09, 06:13 PM

I look around to see what I can find.

This is an interesting article with some good references.
http://doc.utwente.nl/12680/1/Theunissen93sintering.pdf

I see if I can find a text on the phenomena you mentioned. I have some old (before internet, before PC's even) notes somewhere, but I'm not sure where they are buried.

Try this book starting with Chapter 4, Science of Colloidal Processing; Chapter 5, Sol-gel Processing; Chapter 6, Powder Consolidation and Forming of Ceramics; Chapter 7, Sintering of Ceramics: Fundamentals, . . . Chapter 9, Grain Growth and Microstructure Control
Ceramic processing and sintering By M. N. Rahaman. This book seems to cover the basics.

Ceramic technology bibliography @ CRCPress
http://www.crcpress.com/us/product.a...2132&dept_id=1

**darkelf** · Dec1-09, 12:32 PM

Thanks, the paper and book have been quite useful. I did observe though that the book quotes mostly papers older than 1980.

I was wondering if I could pick your brains with regards current sintering procedures and technology?

If that isnt too much to ask.

**Astronuc** · Dec1-09, 01:49 PM

Originally Posted by darkelf

Thanks, the paper and book have been quite useful. I did observe though that the book quotes mostly papers older than 1980.

I was wondering if I could pick your brains with regards current sintering procedures and technology?

If that isnt too much to ask.

I don't think the fabrication processes have changed all that much. As far as I know, each process, which is related to a specific ceramic system, has been perfected or tweaked as experience is gained.

I suspect that the latest developments are proprietary, but perhaps there are some recent patents that may point to improvements.

Usually though, the best material is considered 'trade secret' and so it will not be found in journals or patents.

Nevertheless, please ask specific questions, and let's see if we can discover the answers.

**darkelf** · Dec1-09, 02:37 PM

Thanks again.
Alright could I get any papers or information with regards Abnormally large grains (grain growth) during sintering and how particle packing, size and distribution affect densification.

Or a literature review article on sintering.

I have a bit of information on both but could do with a bit more.

Thank you

**seycyrus** · Dec1-09, 03:19 PM

Originally Posted by darkelf

Hey there,
Would really appreciate some urgent help here more like direction. I'm looking into the progress of colloidial ceramic powder processing and am getting a bit confused.

It is a bit strange that you classify your request as urgent, but cannot supply any specific information on what you are interested in...

**chemisttree** · Dec1-09, 03:45 PM

Nano is all the rage these days. If you want to familiarize yourself with the up to latest stuff conference proceedings are a good place to both get up to date research info and a little background. The first paragraph of most papers usually gives references to background info and how developments have progressed.

You may not be familiar with polymer to ceramic conversion. Probably the ultimate in nano.

**darkelf** · Dec1-09, 04:32 PM

Thanks Chemistree as I said early my main focus is on sintering. Mostly on abnormally large grains (grain growth) during sintering and how particle packing, size and distribution affect densification.

Thanks