I don't see any simple solution for your problem. Maybe you could infiltrate your powder with some ceramics or metal by shape-conformal CVD or ALD, if you samples are not too bulky. Otherwise, you could also go for growing a shell of termoplastic polymer around each particle of your powder, then compact it and remelt the polymer. No simple way.

Thank you Mr. Kubrin for your valuable information, I would like to do according to your suggestion!

It is very hard to find such a simple solution.

Right Mr Francis, above all the experiment must be done in order to know what happen

Dear Hidjan Adisucipto,

one way to follow is to use binders known from Thin Layer chromatography to produce home made thin layer plates from porous silica, porous aluminium oxide etc..

You will find procedures in old literature on TLC chromatography, nowadays nobody does this anymore. Nevertheless, the pores are not blocked and the layers obtained are stable.

Without further information on the nature and texture of your materials and the purpose, the resulting aggregates are to be used for it is difficult to give an apropriate advice.

Typical "glues" are high molecular weight polymers like PEG, PVP, Reactive polysilicones etc.

Another approach (for inorganic particles) is to use TEOS.

Another source of ideas should be found in spray-drying experiments.

Mr Joachim Kinkel, your suggestion is complete and interesting, maybe the next problem is how to find those components but I want to try as possible as I can. Thank you Mr. Kinkel!

Dear Hidjan Adisucipto,

another aproach to bind porous materials without closing the pores, which is equvalent to prepare materials with secandary pore structure from solid precursors can be found e.g. in the publications of Glauckler et.al. in their work dedicated to the preparation and use of stable emulsions and the preparation of ceramics from these emulsions. I have used this adopted procedure to create macroporous monoliths from nanostructured Ca-silicates.

Lit.:Macroporous Ceramics from Particle-stabilized Emulsions

Akartuna* Andre´ R. Studart, Elena Tervoort, and Ludwig J. Gauckler: Adv. Mater. 2008, 20, 4714–4718

Many thanks Mr. Kinkel, I would like to read and study the publication of Glauckler et.al

I am afraid that it is not possible. When activated carbon monoliths are prepared, the highly porous grains are bound with a phenolic resin which is subsequently pyrolysed and activated. In these conditions, the newly created porosity more or less compensates the one which has been clogged by the binder.

Alain

It is impossible to bind porous materials without closing the pores

Mr Maraqah, how do you think about some alternative ideas before for solving this problem?

Dear Hidjan

I am sorry I did not understand what you mean but what I think that you should use a layered material that does the job with a small c-spacing

First, you should explicitly mention what kind of material you plan to glue. I suggested something for carbon materials, but maybe you are interested in ceramics ? Depending on what you want to glue, the adhesive will be obviously different.

Alain

Dear Mr Maraqah and Mr Celzard, the fact I found the difference of ability in absorbing sound between the powder of pumice that was bound by polyvinyl acetate and the powder of pumice that was bound by cement, it shows that the pores of one composite less closed by binder than another

Dear Hidjan

I really agree with what you did say.and it is very interesting .

OK, now I understand. Thus your problem is not just a problem of pore clogging, but might also be related to the nature of the other materials involved.

What makes a material absorbing sound is indeed the combination of porosity and permeability. Closed cells lead to poor absorption, as the incident sound wave is mostly reflected if it can not penetrate the porosity. The same happens with a material having open cells, but whose permeability is too low. In contrast, in open cells materials with too high permeability, the sound absorption ability is also poor but because the sound wave easilty goes throughout the material ! So you need to find a compromise between porosity and permeability, such that the connectivity is optimal and allows a tortuous path for sound waves to propagate and dissipate.

Additionally, the mechanisms of dissipation have 2 origins:

- Viscous effects : friction of air in the pores of the material dissipates the energy of the sound waves. This is the main effect, corresponding to the indirect conversion of acoustic energy into heat induced by viscous forces

- Thermal effects : air exchanges heat with the material’s backbone, thus dissipating energy. This is a minor effect, corresponding to the direct conversion of acoustic energy by heat lost to the environment.

In summary, your material with cement is probably less sound absorbing because cement very efficiently wetted the pumice (unlike PVAc), thus wrapping the powder and closing most pores with a significantly decreased permeability, and also because cement is far less prone to give damping effects, due to its very rigid structure.

Therefore I see 2 possibilities: glueing your powder with a foamed plastic (probably the best option), or adding an excess of water to the cement so that it becomes very porous after drying.

Alain

Dear Alain

That is great you did give a lot of notices that should be taken into consideration and I really agree with you

That is great  Mr. Alain did give a lot of so valuable information, merci !

Because of diffusion effect some part of pores will always be closed during the gluing process . It is necessary to find the proper balance between the surface you glue and volume you wish to treat as a sample of given parameters.

I agree with your idea Mr. Kempinski, thanks

eh

thank you to Mr. Hidjan Adisucipto for brought the topic