Magnetic nanotubes obtained from atomic layer deposition coated electrospun nanofibers

Abstract

High-aspect ratio Al2O3/Ni/Al2O3 core–shell hollow nanotubes were prepared by combining electrospinning, atomic layer deposition, and a subsequent chemical reduction process. Electrospun poly(vinyl alcohol) (PVOH) nanofibers were obtained by electrospinning. Then, these fibers were coated with atomic layer deposition to obtain PVOH/Al2O3/NiO/Al2O3 core–shell nanowires. Since the NiO must be deposited at 200 °C, the PVOH nanofibers must first be coated with Al2O3 at 80 °C, which act as a protective layer of the fibers so that they can withstand higher temperatures. Once PVOH/Al2O3/NiO/Al2O3 core–shell nanowires are obtained, they are subjected to a chemical reduction process that generates Al2O3/Ni/Al2O3 core–shell hollow nanotubes. Their morphologies were studied by scanning and transmission electron microscopies, the thickness was determined by ellipsometry, and all magnetic measurements were performed in an alternating-gradient force magnetometer. Finally, assuming that the nanostructures exhibit a curling reversal process, the authors have analytically calculated the coercivity of the nanotubes.

Static and Dynamic Magnetic Properties of Fe3O4 Nanotubes

“…Among the most commonly synthesized magnetic nanotubes are those made from materials such as iron (Fe) [ 8 , 9 ], Fe(OH) 3 [ 10 ], maghemite (γ-Fe 2 O 3 ) [ 10 , 11 , 12 ], magnetite (Fe 3 O 4 ) [ 10 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ], ZnFe 2 O 4 [ 19 ], CuFe 2 O 4 [ 20 ], nickel (Ni) [ 8 , 21 , 22 , 23 ], NiFe 2 O 4 [ 24 ], Ni 64 Fe 36 [ 8 ], Ni 80 Fe 20 (permalloy) [ 25 ], Co [ 8 , 23 , 26 ], Co 3 O 4 [ 27 ], Co 90 Pt 10 [ 8 ], Co 75 Cr 13 Pt 12 [ 8 ], and many others. In addition to these common materials, nanotubes with more complex geometries have also been synthesized, taking into consideration factors such as diameter modulations [ 28 ], multisegmented structures [ 29 ], and core–shell [ 30 , 31 , 32 , 33 ] systems. The synthesis of these advanced structures is a testament to the ingenuity and skill of researchers in this field, and it suggests that the possibilities for the creation of new and innovative magnetic nanotubes are practically limitless.…”

Electrospinning Combined with Atomic Layer Deposition to Generate Applied Nanomaterials: A Review

“…The combination produces core–shell, bishell hollow, − hollow nanofibers, ,− and metal nanoparticle-loaded ,− nanofibrous templates (see Chart ). This combination can be extended to form advanced multilevel structures, such as Al 2 O 3 /Ni/Al 2 O 3 , SrTiO 3 / SrTiO 3 , polymer/TiO 2 /Pt-nanoparticles, etc. Furthermore, inorganic material coated polymer fibers could be subjected to hydrothermal, chemical bath, and microwave-assisted solvothermal-like methods.…”

Curvature effects on phase transitions in chiral magnets

“…Nanotubes can also be assembled into interconnected networks [15] which makes them attractive for advanced hardware concepts in neuromorphic computing [16]. It is important to note that magnetic nanotubes can be produced experimentally with different techniques [17][18][19][20][21][22].…”