I prepared crystalline LiV3O8 in a solid phase synthesis. After grinding in an agate mortar the obtained particles are some microns in size.
When I milled the material for 30 minutes @300 rpm in a planetary ball mill the material became amorph.
Can anybody suggest parameters for milling so that the material is likely to maintain cristallinity but that the particle size will be decreased?
Reduce RPM and/or time, you should be able to achieve your desired size. You need to optimize either both or one of these two parameters.
Please keep in mind that there is a lot factors which impact of the final particle size:
- mill which you use
- balls (numbers and size)
- ball versus powder ratio.
Try as V. N. Ravi Kishore V. suggested before. In addition probably you will have to make some experiments series and validate after i.e. 5, 10 min. than if there is no effect reduce RPM and so on.
Good luck :)
One important thing to understand is that there is a fundamental grinding limit for dry milling. You need to Google 'fundamental grinding limit' but for many materials that limit is close to around 1 micron in size - below this size the particle flex or bend rather than fracture or if fractured they quickly or immediately re-aggregate. See Slide 53 in:
August 3rd 2010 Comminution - history and laws
https://www.brainshark.com/malvern/vu?pi=242583221&text=M021507
and the attached. See also the paper by Kevin Kendall:
K. Kendall "The impossibility of comminuting small particles by compression" Nature, 272, pp. 710–711 (1978)
plus: https://cuvillier.de/uploads/preview/public_file/163/9783954040858.pdf
For the planetary milling there aren't general rules, it depends on your aim and on the material to be milled. Your treatment is very mild, it is strange a complete amorphization. Which is the material of your jars and balls? Why have you used a grinding in the planetary milling? To prepare the slurry for electrochemical measurements? have you used a mixture with carbon?
Thank you all for your answers!
Marcella, I used tungsten carbide jar and balls. I also added carbon black (one eigth of the LiV3O8 mass). The milling was performed for later usage as a cathode material in LIB/SIB.
One more link - gives quite a bit on the comminution limit:
January 31st, 2013 The importance of size reduction and agglomeration processes in the mining, minerals, and metals industries
https://www.brainshark.com/malvern/vu?pi=931031164&text=M021507
Here is another remote possibility
May be the sample you are collecting for XRD analysis has predominantly carbon black which is amorphous. If the milling time was not enough there could be large particles of LiV3O8, and they being denser may be settling at the bottom and during your sampling the entire sample is not properly represented. Here are the densities for comparison
Density of carbon black is 1.8-2.1 g/cm3
[Ref: http://www.chemicalbook.com/ProductMSDSDetailCB3109508_EN.htm]
Density of LiV3O8 is 3.48 g/cm3.
[Ref: http://www.rsc.org/suppdata/ta/c4/c4ta05616g/c4ta05616g1.pdf]
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials Chemistry