Dear Aseel B Al-Zubaidi

The theoretical density of any material doesn't affect by their grain or particle size of its constituents, but if you are asking about the apparent density then in this case the matter is different and the material's apparent density is affected by many factors like porosity and defects and the grain size may affect it because the defects inside the material are affected by it.

Of course not! If you want to know the real density of the Al2O3, SiO2 and TiO2 oxides macro and/or nano size you may be interested to learn about helium (gas) pycnometry.

Dear Aseel

Your question is not clearly understood. I think you need to ask the following:

For same material (metal oxide) powder, does the particle size affect the overall  (gross) density of the powder material?

If that is your question please note that:

- Originally density of a material is measured for one piece for the powder form to avoid technical problems with powder packing.  In this case density depends on atomic masses, lattice parameters, and type of the unit cell, assuming no significant defects and vacancies.

- In case of density for powder, assuming spherical shapes for powder, assuming the particles have same unit cell properties (same unit cell, same parameters, same ... within the particle itself) then the following notes are critical:

1) If larger particles and small particles are arranged in the powder the same way, the density will be the same.

2) If the small particles are allowed to pack up in a closest packed manner (which is commonly the case) while the larger particles are difficult to move and pack closely, then the small size powder will have higher density.

- In any case, powder overall (gross) density should be smaller than density for one piece.    

Different. Because density depends upon volume

Density of Nanoparticles are more than macro particles

Fluctuations in packing density in the compact as it is prepared for the kiln are often amplified during the sintering process, yielding inhomogeneous densification. Some pores and other structural defects associated with density variations play a detrimental role in the sintering process by growing and thus limiting end-point densities. In condensed bodies formed from fine powders, the irregular particle sizes and shapes in a typical powder often lead to non-uniform packing morphologies that result in packing density variations in the powder compact.

To use  of finer grains/ nano size particles results in a decline in pore size and an increase in density.

Kindly, find attachment file and look at highlight area. 

The surface area of the nano particle is more compare to micro particle so the density of nano particle is less of any material.

no difference if you measure it in powder stat but if you compacted the size of powder will affect the pores size and so you will have some difference

I really agree with Lucas Bonan completely

Hi of course not. Density of Nano particles will be more thanacro particles. Thanks

Dear Dr. Zubaidi

 there are  many different type of  density for powders such as theoretical density, tap density , apparent density  and  bulk density. I believe that only theoretical density is not affected by particles size.

I Agree with Mehrdad Khakbiz,

Theoretical (or x-ray) density is the same for the micro and nano powder,

there is a "tap density" which is measured after tapping the powder for certain time and frequency (usually utilizing the sieve set machine). In this case, the nano powder has less density than the micro.

Additionally, sol-gel routes of preparing the nano powder gives higher densities than that utilizing mechanical (e.g. blast) methods.

The density of a substance is its mass per unit volume which varies with temperature and pressure and normally not affected by particle size. However, bulk density (a measure describing the weight of an ingredient per unit volume) may increase with reducing particle size to increase the weight of feed ingredient (s) per unit of volume.

the theoritical density is the same for different particle size.

but the apparent density depend more on preparation conditions and elaboration process

 Dear Dr. Aseel... The material should be the same regardless of the particle size and consequently, the density has a fixed value (for a single particle). The change will be in the bulk density, where the packing is important. Smaller particles will show a bit higher density than coarse particles (i.e. the voids between the particle with attain smaller volume  for the nano particles). Good luck.... Mahmood

Yes, different.

i think smaller you get in size, more compact structure is attained due to reduction of porosity. Hence density increases with reduction in particle size as more mass is constrained per unit volume.

I observed the particle size, shape, internal micro-structure and compaction factor contribute for variation in density.

*I observed decrease - increase trend with the size reduction in same type of material in micro level.