Abstract
Nanofluids, colloidal suspensions consisting of base fluids and nanoparticles, are a new generation of engineering working fluids. Nanofluids have shown great potential in heat/mass transfer applications. However, their practical applications are limited by the high production cost and low stability. In this study, a low-cost agricultural waste, rice husk ash (RHA), was used as a silicon source to the synthesis of silica nanofluids. First, silica nanoparticles with an average size of 47 nm were synthesized. Next, by dispersing the silica nanoparticles in water with ultrasonic vibration, silica nanofluids were formed. The results indicated that the dispersibility and stability of nanofluids were highly dependent on sonication time and power, dispersant types and concentrations, as well as pH; an optimal experiment condition could result in the highest stability of silica nanofluid. After 7 days storage, the nanofluid showed no sedimentation, unchanged particle size, and zeta potential. The results of this study demonstrated that there is a great potential for the use of RHA as a low-cost renewable resource for the production of stable silica nanofluids. Graphical Rice husk ash was used as a low-cost renewable resource for production of silica nanofluids with high stability.
Highlights
Nanofluids, a concept first proposed by Choi [1], are nanoscale colloidal suspensions containing nanoparticles
X-ray diffractometer (XRD) pattern of the silica nanoparticles was shown in Fig. 3a, which shows a broad peak at 2θ angle of 22°, indicating the amorphous state of silica
Fourier transform infrared (FT-IR) spectra of the silica nanoparticles were recorded by FT-IR spectrometer
Summary
Nanofluids, a concept first proposed by Choi [1], are nanoscale colloidal suspensions containing nanoparticles. Nanofluids have demonstrated great potential applications in many fields such as automobiles [6], electronics cooling [7], industrial cooling [8], drug delivery [9], and CO2 absorption enhancement [10]. The application of nanofluids has significant prospects, but it still faces several challenges for future development [11]. The low stability and high production cost of nanofluids are the major limiting factors [4, 11, 12]. Because of high surface energy, nanoparticles always have a tendency to coagulate automatically [13, 14]. Preventing the coagulation of nanoparticles is the primary issue for the application of nanofluids [15]. The currently available methods used for preparing nanofluids usually require expensive raw materials and sophisticated equipments, and
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