The mechanical milling (ball-milling) process is a good strategy for the fabrication of nanopowders. This manufacturing technique can be performed with or without a solid state chemical reaction. There are several variables that determine nanopowder characteristics: the milling method, the milling medium, the process control solution, speed, and the time. Evidently, the nanopowder obtained also depend of the nature of the material: metals, oxides, or complex metal nanoparticles, for example. Aparently you are obtaining crystalline nanopowder. For more information please visit the following page

https://www.sciencedirect.com/topics/engineering/mechanical-milling

Best regards,

Respected Sir,

Diffraction peak broadening is observed with increasing milling time, is usually associated with grain size reduction and increase of internal strain.

For more details refer the attachment.

Hope this information is useful.

Parastu Fardi The heating effect with milling is substantial and amorphous phases can be converted to (highly) crystalline. This will sharpen the peaks in XRD.

Yes, there are many references in the standard literature. However, I have not investigated personally. Best regards

Dear Dr. Fardi:

Yes. It is very interesting question.

Despite of small number of data provide, as a whole wide range of variables are involved in a good modeling of observed phenomenon.

In a superficial analysis, the phenomenon would be correlated only to the milling or comminuition using as agent to transfer energy balls but anther variable can be further considered. In this sense, it is possible to think in conventional ball milling, planetary ball milling and high energy ball milling.

In my Lab I have two conventional ball milling and an Attritor ball milling (Nesztch). In the first, conventional ball milling the energy is gravitational and in the third there is an electric motor of 0.5 HP impelling a haste to very high rotation (typically 1250 Hz) that provide high level of energy to system. Then, in the practice, system of low energy level and system of high energy level can be used. Also, both systems the first and third system needs of a milling medium, typically a liquid very volatile.

From above point, the nature of powder is important so. If material is an oxide or metallic powder and the time of milling are relevant.

Taking in account a low energy system that in general require a great time of milling as an example 24 hours, cylindrical balls, 7 mm of diameter, milling medium, alcohol (mixture of isopropylic with ethylene glycol 25:75 % vol). Yet, a oxide mixture, being that X-ray diffraction show changing diffraction lines (no peaks) exhibiting new diffraction lines with a decreasing of full width at half maximum (FWHM) that is equivalent of the sharpening of diffraction lines, and with simultaneous increasing of diffraction line intensity mean that a reaction via solid state is operational. Therefore, in this case the extinction of diffraction lines of precursor oxides (mixture) should occurs with simultaneous evolution of set of diffraction lines of new crystalline phase.

Again, Taking in account a low energy system that in general require a great time of milling as an example 24 hours, cylindrical balls, 7 mm of diameter, milling medium, alcohol (mixture of isopropylic with ethylene glycol 25:75 % vol). Now, powder is yet an oxide but was synthesized by a chemical route with low temperature and small time of calcination of precursor. In this case, it is possible and common, small crystallite size typically close to units or tens of nanometers. This aspect is accompanied of a great full width at half maximum (FWHM) small line intensity. Here, a low energy system, the ball milling process can assist the crystallization (increasing of the crystallinity) as a function of crystallite size increasing. In another words, this phenomenon is similar to gradual increasing of the relative intensity and decreasing of full width at half maximum. I would like to comment that during ball milling a low level of liquid can leads to an increasing of temperature.

Such phenomenon might maintain some correlation with surface phenomenon, which seems correlated with penetration capability of the conventional X-ray diffraction apparatus.

As a matter of fact, a proper atmosphere or particular atmosphere type inert can be involved. But, a phenomenon of crystallization or crystallinity increasing carried out at low energy level should be more favorable for crystalline structures with high symmetry, type cubic as TiN.

A non-oxide material as sulphide and nitride, as well as another has been synthesized using low energy system and high energy system, as planetary ball milling. There is an entire class of synthesis methods assigned to mechanical energy. I suggest two topics to study, as follow mechanosynthesis and mechanochemical methods.

With best regards

Marcos Augusto Nobre

The width of XRD peak gives the information of FWHM which related to crystalline grain size

The sharper --> smaller FWHM --> smaller grain size

I will say yes. However check how is your FHWM related to the particle size