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| Researchers | Basefluids | Particles material | Parameters | Surfactant | pH control | Stability evaluation methods | Observations |
|
| Li et al. [27] | Water | Cu | = 0.0005–0.5 wt%
= 25 nm | SDBS and CTAB | – | Sedimentation photographs and zeta size analyser | Nanofluids with CTAB lasted for 1 week without sedimentation. |
|
| Kim et al. [28] | Water | Au | = (0.6 × 10−4)–(2.6 × 10−4) vol%
= 7.1–12.1 nm | – | – | Zeta potential analyser | Good particle dispersion for 1 month. |
|
| Paul et al. [29] | Water | Au | = (0.6 × 10−4)–(2.6 × 10−4) vol%
= 21 nm | – | – | TEM, SEM, and DLS | No agglomeration or sedimentation even after 48 h. |
|
| Qu et al. [30] | Water | Al2O3 | = 0.1–1.2 wt%
= 43 nm | – | 4.9 | SEM | Nanoparticles suspended stably for 3 days. |
|
| Anoop et al. [31] | Water | Al2O3 | = 1–6 wt%
= 45 and 150 nm | – | 6.5 (1 wt%)
6.0 (2 wt%)
5.5 (4 wt%)
5.0 (6 wt%) | TEM | Several weeks of stability was achieved. |
|
| Rohini Priya et al. [32] | Water | CuO | vol%
10 : 1 length to thickness ratio | Tiron | – | Zeta potential analysis and visual observation | Stability was maintained throughout the experiment. |
|
| Chang et al. [33] | Water | CuO | = 0.01–0.4 vol%
= 20–30 nm | Sodium hexametaphosphate (NaHMP) | 6.64–6.70 (with surfactant), and >9.5 (without surfactant) | Zeta potential analysis | CuO content > 0.04 vol% showed very high instability and particles tended to settle within minutes. |
|
| Liu et al. [34] | Water | CuO | = 0.5, and 1 wt%
= 30 nm | – | – | TEM | The uniformity and stability of the suspensions were poor after a couple of days. |
|
| Yang and Liu [35] | Water | SiO2 | = 0.5–2.5 wt%
= 30 nm | Trimethoxysilane | – | SEM | Functionalized nanofluids kept good dispersion for 12 months; pure nanofluid developed sedimentation after several days. |
|
| Qu and Wu [36] | Water | SiO2;
Al2O3 | = 0.1–0.6 wt%
= 30 nm;
= 0.1–1.2 wt%
= 56 nm | – | 9.7;
4.9 | TEM | Both types of nanofluids maintained their stability for several days, but the alumina nanofluid had better particles dispersion. |
|
| Suganthi and Rajan [37] | Water | ZnO | = 0.25–2.0 vol%
= 30–45 nm | Sodium hexametaphosphate (SHMP) | – | Zeta potential analysis and SEM | All samples showed good stability, with highest stability at 2 vol%; sonication for 3 h reduced the aggregated size leading to a better improvement. |
|
| Duangthongsuk and Wongwises [38] | Water | TiO2 | = 0.2–2.0 vol%
= 21 nm | CTAB | – | TEM | Few agglomerations were observed after 3 h from sonication. |
|
| Hari et al. [39] | DIW | Ag | Basefluid = 20 ml
AgNo3 = 0.25 mM
Tri-sodium = 0.25 mM
Size = 21 nm | CTAB | – | UV-Vis spectroscopy | The suspensions were stable for one week. |
|
| Kole and Dey [40] | DIW | Cu | = 0.0005–0.5 wt%
= 40 nm | – | – | DLS and TEM | No visible signs of sedimentation for more than 15 days. |
|
| Kathiravan et al. [41] | DIW | Cu | = 0.25, 0.5, and 1.0 wt%
= 10 nm | SDS | – | TEM | Nanofluid maintained particles dispersion for more than 10 h. |
|
| Yousefi et al. [42] | DIW | MWCNTs | = 0.2 wt%
= 10–30 nm | Triton X-100 | 7.4 | TEM | Colloid was stable for 10 days; optimum sonication time was found to be 30 min. |
|
| Garg et al. [43] | DIW | MWCNTs | = 1.0 wt%
= 10–20 nm
= 0.5–40 µm | Gum Arabic | – | TEM | Over 1 month suspension stability achieved with no visible sedimentation or settling. |
|
| Ding et al. [44] | DIW | MWCNTs | = 0–1.0 vol%
= 5–10 nm
= 10–30 µm | Gum Arabic | 2, 6, 10.5, and 11 | SEM | Nanofluids showed good stability for months. |
|
| Abareshi et al. [45] | DIW | Fe3O4 | = 0.025–3.0 vol%
Size = 15–22 nm | Tetramethyl ammonium hydroxide | 12.8 | Zeta potential analysis | Suspensions showed good dispersion and stability. |
|
| Phuoc et al. [46] | DIW | Ag | = 0.01 vol%
= 20–30 nm | – | – | TEM | Nanofluids were stable for several months. |
|
| Parametthanuwat et al. [47] | DIW | Ag | = 0.5% w/v
< 100 nm | – | – | – | Samples stability lasted for 48 h. |
|
| Yousefi et al. [48] | DIW | Al2O3 | = 0.2, and 0.4 wt%
= 15 nm | Triton X-100 | – | Visual observation | Suspension stability lasted for about 3 days. |
|
| Hung et al. [49] | DIW | Al2O3 | = 0.5, 1.0, and 3.0 wt%
= 20 nm | Chitosan | – | UV-vis spectroscopy | Nanofluid of 3.0 wt% showed a difference of 5% in its stability, compared to the 0.5 wt% sample. |
|
| Heyhat et al. [50] | DIW | γ- Al2O3 | = 1.0–2.0 vol%
= 40 nm | – | – | SEM and Zeta potential analysis | Suspensions were stable due to having a zeta potential value of 30 mV. |
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