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Plasma Synthesis of Nanomaterials
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2019
Antaryami Mohanta, Raj K. Thareja
Types of nanomaterials are categorized in five different heads: (i) nanostructured powder, (ii) nanocomposite, (iii) solid nanofoam, (iv) nanoporous material, and (v) fluid nanodispersion. Although powders are the solid objects consisting of very tiny discrete particles of size <1 mm (ISO3252:1999), powders and particles are not same. In addition to particles, powders contain gases and liquids usually in the form of air and water, respectively, on the particles’ surface. Powders can be referred to as nanostructured powders if it comprises nanostructured agglomerates, aggregates, or nanoparticles (ISO/TS 80004-4:2011). In comparison with the bulk materials, nanopowders have different optical, thermal, chemical, electrical, and physical properties that allow for enhanced chemical activity, faster sintering kinetics, higher electrical resistivity, super-paramagnetic, microwave absorption, and localized surface plasmon resonances. Nanopowders are thus potential candidates for catalysts, sintering aids, microwave absorption, magnetic recording media, magnetic fluids, magnetic ink, rocket propellants, conducting ink/paste, permeable reactive barriers for soil decontamination, and biomarkers and biosensors applications (Chang 2013). Nanocomposites are solid materials having multiple phases in which one or more phases are in the nanoscale embedded in a metal, ceramic, or polymer matrix. Depending on the nature of reinforcing agents such as nanoparticles, nanoplatelets etc., nanocomposites are categorized as nanoparticle-reinforced composites, nanoplatelets-reinforced composites, nanofiber-reinforced composites, carbon nanotube-reinforced composites, nanocomposite fibrils, nanocomposite films, etc. (Hussain et al. 2006). A solid nanofoam is a solid matrix filled with a gaseous phase in which either phase is in the nanoscale dimension. Metallic foams such as aluminum foams have novel physical, mechanical, and electrical properties along with low density since the large portion of the volume is filled with gaseous pores that makes the materials ultra-light (Mirzaee et al. 2012). Nanoporous materials are solid with nanopores. These materials can be crystalline, amorphous, or mixture of both the structures. The nanoporous materials are divided into three broad categories according to their pore size: (i) micro-porous materials with 0-2 nm pores, (ii) mesoporous materials with 2-50 nm pores, and (iii) macroporous materials with pores >50 nm (Polarza and Smarsly 2002).
Efficient solvent free synthesis of tetrahydrobenzo[a]xanthene-11-one derivatives using nano-AlPO4/Ti (IV) as a green, heterogeneous and reusable catalyst
Published in Inorganic and Nano-Metal Chemistry, 2022
Maryam Mehravar, Bi Bi Fatameh Mirjalili, Elaheh Babaei, Abdolhamid Bamoniri
The physisorption data shown in Figure 5a illustrates type IV adsorption-desorption isotherms in accordance with the IUPAC classification standards, revealing both mesoporous and macroporous structures in the nanofoam. The nitrogen adsorption quantity rises sharply at high relative pressures and no limiting adsorption is observed, consistent with the presence of both mesopores (2–50 nm in diameter) and macropores (>50 nm in diameter). At high relative pressure, P/P0 = 0.990, the maximum volume adsorbed for the NAP-Ti(IV) was 29.16 cm3/g. H3 type hysteresis in the adsorption-desorption isotherms are characteristic of capillary condensation in the mesopores. The hysteresis extends to very low relative pressures (P/P0 as low as 0.021), indicating a large number of mesopores (<50 nm) present. BJH analysis Figure 5c of the desorption curve shows that the largest fraction of pores are mesopores less than 50 nm in diameter, with the highest frequency of pores centered around 1.22 nm. This result is consistent with the hysteresis observed in the adsorption-desorption isotherms. The large macropores observed at low magnification gives the samples a relatively low overall BET specific surface area considering the high number of mesopores present.