I fixed my ultra-sonication duration on my samples. If I prepare my samples by batch, the previous batch might start agglomerating. The maximum quantity on 1 preparation is 500 ml and few hours. Need few liters of it and takes almost a week for 1 sample testing in test rig.
Dear Xian Hong
Long term stability of nanofluids is utmost important for their use in any application. If your samples become unstable within 1-2 days at the room temperature, then it clearly shows that they might not be valid for any application. Not to forget the adverse effect of high temperatures on the stability of nanofluids. My suggestion is to use some other reliable method to prepare high stable nanofluid (Ultrasonication + chemical stabilization simultaneously).
If your ultrasonication equipment can not handle more than 500ml sample at a time, then it is advised to use it in a few batches. Good luck
Hi, Wei Xian Hong .
In either case, and as Suhaib Umer Ilyas explained, you need to think about the 'intended application' for the nanofluid.
If your nanofluid is unstable upon ambient storage for few days, it will be even less stable upon exposure to whatever destabilizers your application entails (e.g., thermal cycling).
As for preparing a concentrate, keep in mind that a higher particle concentration means shorter interparticle separations and a higher particle number density per unit volume of the dispersion. This leads to more frequent particle–particle collisions taking place and a greater likelihood of clustering. So in itself, increasing the particle concentration can be a destabilizer as long as your nanoparticles are not protected against clustering.
Ultrasonication to restore your primary particles can only work with soft agglomerates. It is useless against hard aggregates. Breaking particle clusters by ultrasonication increases the surface area at the solid–liquid interface, which causes reclustering if the interface is not stabilized. This seems to be what is happening in your case. In fact, ultrasonication can simultaneously result in declustering and reclustering of particles. It can also lead to contamination and phase transformations, under some conditions.
Bottom line here is that, to realize a long-term-stable nanofluid, you need to 'protect' your particles against clustering using an appropriate method (charge and/or steric stabilization) rather than trying to repeatedly 'decluster' them after the (often irreversible) damage has happened.
- Badges
- Science topic
- Similar topics
- Comment