I am struggling to make a good dispersion of nanofluid with iron oxide in water.
You shoud use surfactants or modify the surface of particles
Surfactants used in nanofluids are also called dispersants. Adding dispersants in the two-phase systems is an easy and economic method to enhance the stability of nanofluids. Dispersants can markedly affect the surface characteristics of a system in small quantity. Dispersants consists of a hydrophobic tail portion, usually a long-chain hydrocarbon, and a hydrophilic polar head group. Dispersants are employed to increase the contact of two materials, sometimes known as wettability. In a two-phase system, a dispersant tends to locate at the interface of the two phases, where it introduces a degree of continuity between the nanoparticles and fluids. According to the composition of the head, surfactants are divided into four classes: nonionic surfactants without charge groups in its head (include polyethylene oxide, alcohols, and other polar groups), anionic surfactants with negatively charged head groups (anionic head groups include long-chain fatty acids, sulfosuccinates, alkyl sulfates, phosphates, and sulfonates), cationic surfactants with positively charged head groups (cationic surfactants may be protonated long-chain amines and long-chain quaternary ammonium compounds), and amphoteric surfactants with zwitterionic head groups (charge depends on pH. The class of amphoteric surfactants is represented by betaines and certain lecithins). How to select suitable dispersants is a key issue. In general, when the base fluid of nanofluids is polar solvent, we should select water-soluble surfactants; otherwise, we will select oil-soluble ones. For nonionic surfactants, we can evaluate the solubility through the term hydrophilic/lipophilic balance (HLB) value. The lower the HLB number, the more oil-soluble the surfactants, and in turn, the higher the HLB number, the more water-soluble the surfactants is. The HLB value can be obtained easily by many handbooks. Although surfactant addition is an effective way to enhance the dispersibility of nanoparticles, surfactants might cause several problems [31]. For example, the addition of surfactants may contaminate the heat transfer media. Surfactants may produce foams when heating, while heating and cooling are routine processes in heat exchange systems. Furthermore, surfactant molecules attaching on the surfaces of nanoparticles may enlarge the thermal resistance between the nanoparticles and the base fluid, which may limit the enhancement of the effective thermal conductivity.
From:
http://dx.doi.org/10.1155/2012/435873
Thanks Mohsen. I already tried using SDS but it doesnt seem to help . SDS is very good dispersant for using in carbon black nanofluid but not with iron oxide.
A fried suggested that Triton which is a non-ionic surfactant may help to make iron oxide stable.
not sure, please check this paper: Article Stable aqueous dispersion of superparamagnetic iron oxide na...
Stability is also depend on synthesis method. But citric acid is highly used as surfactant to obtain stable iron oxide nanoparticles.
Dear Hikmati,
There are many methods to enhance to stability. Adding surfactant, changing pH, changing of preparation method (one step method has high stability according to two-step method) , using ultrasonic bath, using low concentration are some way to help you.
Best regards
it depends on the synthesis procedure and the coating agents that you use for the coating of the nanoparticles. Also, please keep in mind that controlling the size is a very important parameter that you have to think about it.
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