HDC in Physical Processes
The physical effects such as the formation of high-pressure liquid jet, pressure shock waves, and high interfacial turbulence that are induced in HC set a benchmark for its application in the various physical processes. As discussed, the induced physical effects can assist various chemical processes such as synthesis of chemicals, but these physical effects have more effect on the physical transformation. These physical effects initiate the various processes such as emulsification, particle size reduction, and cell disruption
Synthesis of nanomaterials
Nanomaterials have found wide applicability in different chemical processes and day-to-day life, nanoparticles, nanocatalysts, nanofibrils, nanotubes, and nanoemulsions having vast applications. The solid nanomaterials are widely applicable in the areas of biomedical drugs, biotechnology, pharmaceutics, and paints. The liquid-based nanomaterials such as nanoemulsions are used in paints, cosmetics, and various food products and for the encapsulation of pharmaceutical drugs, nutraceuticals, and other essentials food-based active agents.
Recently, studies have proven the applicability of HDC for the synthesis of nanomaterials. Figure 6 depicts the asymmetric collapse of the cavities at the surface of a solid particle that create high pressure liquid jets and generate cracks and voids on the solid surface. In the subsequent collapsing events, these cracks are widened and particles break into the smaller sizes (Mahulkar and Pandit 2010).
The shear provided by the high-pressure liquid jet should be greater than the strength of a particle (hardness, tensile strength, etc.). The intensity of shear stress generated at the end of a cavity collapse can be manipulated by varying the geometry and operating parameters of HDC. Studies have reported the effectiveness of HDC for the reduction of particles size to nanoscale, indicating its scope for the application on large scale. When Styrene Butadiene Rubber SBR slurry was treated using HDC, the particle size was reduced from 275,000 nm to 129 nm
Similarly, in the case of two immiscible liquids, the induced effects reduce the interfacial tension leading to better dispersion of internal phase into the continuous medium. Meanwhile, high-intensity turbulence breaks down the emulsion droplets, thereby reducing the droplet size and increasing the interfacial area.