*2.1.3 Sonochemistry*

*Advances in Microfluidics and Nanofluids*

respect of CCUS.

calcination [6].

**2.1 Physical methods**

*2.1.1 Spray pyrolysis*

mechanism.

solution [8, 9].

*2.1.2 Chemical vapor deposition (CVD)*

are usually required to complete the synthesis.

compared to the case in which no MO-NPs were added.

**2. Synthesis of MO-NPS and MO-NCPs**

MO-NPs also include core-shell architectures where each particle has an inner core made of one type of MO, and the outer shell consisting in another MO. Just as single nanoparticles, composite nanoparticles exhibit size confinement properties (optical and electronic). Their composition and the atomic order of aggregates are pivotal factors for their specific features, which are tailored during their synthesis. MO-NPs have a high surface-to-volume ratio, which increases the reactivity. Dispersed in base fluid (BF), MO-NP enhances the native properties of the solution

This chapter does not intend to list, in an exhaustive manner, the features of nanofluid. Rather, the authors aim to discuss, from both the chemistry and the engineering point of view, the key features of MO-NFs transferable to the carbon capture utilization and storage (CCUS). The chapter will cover the different synthesis methods of the NP and NCP, the formulation of NF as well as the application in

MO-NPs can be obtained through two opposite approaches including topdown and bottom-up. The former technique consists in successive mechanical operations of divisions and fragmentations, or in the irradiation of the bulk phase with a powerful energy source including UV, X-Rays, electron beam [5]. Using the bottom-up approach, MO-NPs are formed within the reaction medium, subsequently to the clustering of single atoms. The growth in size is time-dependent, and may be facilitated by additional treatment such as

Spray pyrolysis is generally used for the preparation of thin-films or pulverulent materials. It consists in the spraying of a solution or a suspension containing the metallic precursors in an oven, followed by a high temperature treatment. This method allows the formation of spherical oxides as the shape of the oxides are strongly dependent of the drops generated at the entrance of the furnace. Given the rapid rate of nucleation at high temperature, there is a one-droplet, one-particle

In addition to the shrinkage occurring following the formation of oxides, micrometers precursors can allow the formation of particles in the nanometer size range [7]. NCPs can also be obtained through this method by mixing several metal ions in the precursor solution. The formulation of the composites is controlled by

This technique is used mostly for the preparation of 2D metallic or inorganic materials of nanometric thickness. Usually, volatiles precursors are delivered on a heated surface on which a thin layer of materials is deposited upon a chemical reaction in vapor phase. Additional physical processes such as evaporation or sputtering

adjusting the stoichiometric proportions of each metallic species in the

**132**

Sonochemistry is a branch of chemistry supported by the formation, growth, and collapse of bubbles in a liquid upon irradiation with high intensity ultrasound waves. The bubbles can reach a temperature and pressure as high as 5000°C and 500 mPa respectively [11]. These conditions increase the chemical reactivity of the species in the reactor. When the water is the solvent, radical •OH, H2O2 and O3 are generated, leading thereby to oxidant medium suitable for the preparation of MO.

Treatment of solutions of copper (Cu), zinc (Zn) and cobalt (Co) acetates under a high-intensity ultrasonic horn has been used to produce nanosized CuO, ZnO, and CoO3 respectively [12]. This method has also been used for the preparation of nanocomposite when the suitable precursors are mixed [13].
