How to Make Nanofluids

A nanofluid is an engineered fluid that consist of a base fluid containing nanoparticles. For the synthesis of nanofluids, an efficacious and reliable homogenization and deagglomeration technique is required to ensure a high degree of uniform dispersion. Ultrasonic dispersers are the superior technology to produce nanofluids with excellent characteristics. Ultrasonic dispersion excels by efficiency, speed, simplicity, reliability and user-friendliness.

What are Nanofluids?

A nanofluid is a fluid containing nano-sized particles (≺100nm), commonly called nanoparticles. Nanoparticles used in nanofluids are typically made of metals, oxides, carbides, or carbon nanotubes. These nanoparticles are dispersed into a base fluid (e.g, water oil, etc.) in order to obtain an engineered colloidal suspension, i.e., the nanofluid. Nanofluids exhibit enhanced thermo-physical properties such as thermal conductivity, thermal diffusivity, viscosity and convective heat transfer coefficients compared to the material properties of the base fluid.
A common application of nanofluids is their use as coolant or refrigerant. By the addition of nano-particles to conventional coolants (such as water, oil, ethylene glycol, polyalphaolefin etc.), the thermal properties of the conventional coolants are improved.

• cooling / heat transfer liquids
• lubricants
• biomedical application

Making Nanofluids with an Ultrasonic Homogenizer

The microstructure of nanofluids can be influenced and manipulated by the application of the most suitable homogenization technology and processing parameters. Ultrasonic dispersion has been proven as a highly efficient and reliable technique for nanofluid preparation. Ultrasonic dispersers are used in research and industry to synthesize, mill, disperse and homogenize nanoparticles with high uniformity and a narrow particle size distribution. Process parameters for the synthesis of nanofluids include ultrasonic energy input, ultrasonic amplitude, temperature, pressure, and acidity. Futhermore, the types and concentrations of reactants and additives as well as the order, in which the additives are added to the solution, are important factors.
It is well known that the properties of nanofluids strongly depend on the structure and shape of nanomaterials. Therefore, obtaining controllable microstructures of the nanofluids is the main factor that contributes to the functionality and quality of nanofluids. Using optimized ultrasonication parameters such as amplitude, pressure, temperature and energy input (Ws/mL) is the key to produce a stable, uniform high-quality nanofluid. Ultrasonication can be successfully applied to deagglomerate and disperse particles into single dispersed nanoparticles. With smaller particle size, Brownian motion (Brownian speed) as well as particle-particle interactions increase and result in more stable nanofluids. Hielscher ultrasonicators allow the precise control over all important processing parameters, can run continuously at high amplitudes (24/7/365) and come with automatic data protocolling for easy evaluation of all sonication runs.

Ultrasonically dispersed nano-sized silica

Sonication Improved Stability of Nanofluids

For nanofluids, an agglomeration of nanoparticles results in not only the settlement and clogging of microchannels but also the decreasing of thermal conductivity of nanofluids. Ultrasonic deagglomeration and dispersion are widely applied in material science and industry. Sonication is a proven technique to prepare stable nano-dispersions with a uniform nanoparticle distribution and great stability. Therefore, Hielscher ultrasonic dispersers are the preferred technology, when it comes to the production of nanofluids.

Ultrasonically Produced Nanofluids in Research

Research has investigated the effects of ultrasonication and ultrasonic parameters on the characteristics of nanofluids. Read more about scientific findings on ultrasonic nanofluid preparation.

Ultrasonic Effects on Al2O3 Nanofluid Preparation

Noroozi et al. (2014) found that at “higher particle concentration, there was greater enhancement of the thermal diffusivity of the nanofluids resulting from sonication. Moreover, greater stability and enhancement of thermal diffusivity were obtained by sonicating the nanofluids with the higher power probe sonicator prior to measurement.” Thermal diffusivity enhancement was greater for the smaller-sized NPs. This is because smaller particles have higher effective surface area to volume ratios. Thus, smaller particles helped form a stable nanofluid and sonication with an ultrasonic probe resulted a substantial effect on the thermal diffusivity. (Noroozi et al. 2014)

Step-by Step Instruction for the Ultrasonic Production of Al2O3-water nano fluids

First, weigh the mass of Al2O3 nanoparticles by a digital electronic balance. Then put Al2O3 nanoparticles into the weighed distilled water gradually and agitate the Al2O3-water mixture. Sonicate the mixture continuously for 1h with an ultrasonic probe-type device UP400S (400W, 24kHz, see pic. left) to produce uniform dispersion of nanoparticles in distilled water. The nanofluids can be prepared at different fractions (0.1%, 0.5%, and 1%). No surfactant or pH changes are needed. (Isfahani et al., 2013)

Ultrasonically Tuned Aqueous ZnO Nanofluids

Elcioglu et al. (2021) state in their scientific study that “Ultrasonication is an essential process for proper dispersion of nanoparticles in base fluid and stability, as well as for optimum properties for real-world applications.” They used the ultrasonicator UP200Ht to produce ZnO / water nanofluids. Sonication had clear effects on surface tension of the aqueous ZnO nanofluid. The researchers findings result in the conclusion that surface tension, nano-film formation and other related features of any nanofluid can be adjusted and tuned under proper ultrasonication conditions.

Ultrasonic Homogenizers for Nanofluid Production

Hielscher Ultrasonics designs, manufactures and distributes high-performance ultrasonic dispersers for all kinds of homogenization and deagglomeration applications. When it comes to the production of nanofluids, precise sonication control and a reliable ultrasonic treatment of the nanoparticle suspension are crucial.
Hielscher Ultrasonics’ processors give you full control over all important processing parameters such as energy input, ultrasonic intensity, amplitude, pressure, temperature and retention time. Thereby, you can adjust the parameters to optimized conditions, which leads subsequently to high-quality nanofluids.

• For any volume / capacity: Hielscher offers ultrasonicators and a broad portfolio of accessories. This allows for the configuration of the ideal ultrasonic system for your application and production capacity. From small vials with milliliters to high volume streams of thousands of gallons per hour, Hielscher offers the suitable ultrasonic solution for your process.
• Robustness: Our ultrasonic systems are robust and reliable. All Hielscher ultrasonicators are built for 24/7/365 operation and require very little maintenance.
• User-friendliness: Elaborated software of our ultrasonic devices allows the pre-selection and saving of sonication settings for a simple and reliable sonication. The intuitive menu is easily accessible via a digital coloured touch-display. The remote browser control allows you to operate and monitor via any internet browser. Automatic data recording saves the process parameters of any sonication run on a built-in SD-card.

The table below gives you an indication of the approximate processing capacity of our ultrasonicators: