I've read various papers about graphene and graphene-CNTs in nanofluid. They calculate the specific volume fraction and then test the heat tranfer properties.
For example, in their works, the samples are 0.02%, 0.05% and 0.0007% volume fraction of aquaous graphene-MWNT nanofluids. I don't know what is the meaning of those digits (in mass per volume or volume per volume).
While considering colloidal dispersions of nanoparticles in a liquid dispersant, mass ratios, or the corresponding percentage ratios, are in principle rather adequate to express concentrations, because they are independent of the temperature and can easily unambiguously defined. However, it should be rendered clear if this ratio is to be understood as relative to the mass of liquid dispersant or to mass of dispersion. Less convenient are mass/volume, volume/mass, and volume/volume ratios, since they are temperature dependent, and for the last two cases, also because it may be not straightforward to unambiguously define what is understood as volume of nanoparticles. Again, it should be made clear if either mass/volume or volume/volume ratios are relative to the volume of liquid dispersant or to that of dispersion. Some familiarity with the related literature often helps to identify the actual concentration ratio used when not clearly specified at a particular paper. The same concentration ratios can be applied to solid-liquid powder suspensions. As long as volumetric additivity can be accepted as a reasonable assumption concerning to the dispersion procedure (*), formulas that can be applied to solid-liquid powder suspensions, can in principle be extended to colloidal dispersions of nanoparticles in liquid dispersant. Some formulas of this kind were discussed elsewhere at this forum: https://www.researchgate.net/post/Can_anyone_suggest_a_smart_way_to_calculate_volume_fraction_of_a_solid_ferrofluid_in_a_solvent_or_solids_fraction
(*) Otherwise, the excess volume of mixing should be taken as a significant contribution, and either the volume or the density of the colloidal dispersion of nanoparticles may have to be experimentally accessed, when dealing with concentration ratios relative to the volume of dispersion.
volume fraction is especially useful to express packing density and is volume of particles in volume of dispersion (volume fraction of particle free solvent is 1, when expressed in % 100%). So knowing the densities mass concentration can be easily converted into volume fraction. As Carlos mentioned, situation for nanoparticles, where solvation layer influences effective density, is more complicated. Here we rather get an apparent volume fraction.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials Chemistry