Submicrometer-sized NiO octahedra: facile one-pot solid synthesis, formation mechanism, and chemical conversion into Ni octahedra with excellent microwave-absorbing properties

Abstract

A facile template-free and one-pot thermal decomposition approach was used for the mass preparation of submicrometer-sized NiO octahedra. Ni octahedra with tailored crystallization and texture characteristics are easily achieved through H 2 -annealing of NiO octahedra at various temperatures. The good morphology retention of Ni octahedra is due to the principle of minimum surface free energy as well as the similar crystallographic system to that of NiO. Studies on static magnetic and microwave electromagnetic properties reveal the relationships among the reactivity, shape, and resultant properties of the nanomaterials. Because of their high BET specific surface area and favorable crystal size, porous Ni octahedra produced at 300 C exhibit excellent matching and absorbing properties with a minimum R L value of À37.93 dB at 12.80 GHz and 11.60 GHz bandwidth (below À20 dB). Thus the Ni octahedra described here are believed to have a wide range of applications, including catalysis, electromagnetic shielding, and absorption.

Magnetic, optical and electrocatalytic properties of urchin and sheaf-like NiCo2O4 nanostructures

“…However, the saturation magnetization, M s , of NiCoO-120-cal sample (~32 emu g À1 or 1.32 m B ) is higher than that of the NiCoO-200-cal sample (~26 emu g À1 or 1.2 m B ), and lower than the value of the bulk NiCo 2 O 4 sample in the range of 35.3e39.6 emu g À1 or 1.52e1.71 m B [44]. The variations in saturation magnetization are attributed to impurities, surface antiferromagnetic oxidation, surface spin disorder, grain size, crystallinity, and superexchange interactions [72]. In this study, the variation in M s can be correlated to surface spin disorder which seems to depend on the difference in the surface morphologies of urchin-like NiCoO-120-cal and sheaflike NiCoO-200-cal samples.…”

Controllable synthesis of leaflet-like poly (3,4-ethylenedioxythiophene)/single-walled carbon nanotube composites with microwave absorbing property

“…Therefore, significant attention has been devoted to explore effective microwave absorbers with lightweight properties, structurally sound ability and flexible ability as well as strong absorption in a wide microwave frequency range [2][3][4][5][6][7][8]. Recently, more and more attention has been drawn on the construction of unique microstructures of the absorbers and their influences on the improvement of microwave absorbing property.…”

One-pot synthesis of cobalt nanoparticle-embedded lamellar sheets by using inorganic complex via thermal decomposition route

“…The Co nanocrystals exhibit a distinct enhanced coercivity compared with the value of spherical Co and bulk Co. It is well known that magnetic properties of most materials are strongly affected by some type of anisotropy including crystal anisotropy, shape anisotropy, stress anisotropy, externally induced anisotropy, and exchange anisotropy [27]. The two most common anisotropies in nanostructured materials are crystalline and shape anisotropy.…”