“…They are characterized by high mechanical strength and modulus, and due to their hollow nanostructure they are widely used for loading and controlled release of functional compounds (Makaremi et al, 2017;Yang et al, 2016;Huang et al, 2016;Saif and Asif, 2015;Lvov et al, 2016a). HNTs are used in, e.g., self-healing anticorrosive coatings (Wei et al, 2015), hydrogen production and storage (Sahiner and Sengel, 2017;Jin et al, 2017), pharmaceutical excipients (Hanif et al, 2016;Lvov et al, 2016b;Yendluri et al, 2017), biomedical applications Bonifacio et al, 2017), cosmetics (Saif and Asif, 2015), active food packaging materials (Shemesh et al, 2016;Tas et al, 2017;Krepker et al, 2017), water treatment (Yu et al, 2016), and for improvement the mechanical properties and thermal stability of polymer composites (Liu et al, 2014). Globally, HNTs annual production is over 50,000 metric tonnes (Lvov et al, 2008), which is similar to that of carbon fibers (40,000 t/y; Gutiérrez and Bono, 2013), and approximately 10 times higher than the production of carbon nanotubes which is only ca.…”