Growth Mechanism and Magnetic Properties of Highly Crystalline NiO Nanocubes and Nanorods Fabricated by Evaporation

Abstract

A new approach to the preparation of regularly shaped NiO nanocubes and nanorods by an infrared heating evaporation method is presented. The growth model is proposed to be a vapor–solid mechanism. The morphology of the nanocrystals can be tuned by the carrier gas flow rate. The samples consist of nanocrystals that are highly crystallized with atomic-scale smooth surfaces. This novel method could be extended to nanocrystal growth of other oxides with low volatility or high melting points. The results of magnetic characterization indicate that the NiO nanorods and nanocubes grown from a mixed target both show weak ferromagnetic states at low and room temperature due to uncompensated spins at the surfaces of the nanocrystals.

Size-dependent magnetic properties of branchlike nickel oxide nanocrystals

“…Moreover, the largest nanoparticles with the average size of 12.8 nm even shows a linear dependence of magnetization at 300 K. This behavior has been previously reported in NiO nanorods and nanocubes with relatively small size. 8 These results reveal that the room-temperature magnetic behavior of smaller size nanocrystals is dominated by an uncompensated surface spins, meanwhile the larger size nanocrystals is dominated by an uncompensated antiferromagnetic core moment contribution. On the other hand, the high field behavior shows a curvature at 5 K while the high field behavior is linear at 300 K, suggesting a change of the surface contribution to the magnetization at different temperatures.…”

“…But many results in previously reports didn't match well with the theory due to the large size distribution. 8 The remnant magnetization and the coercivity of NiO samples at 5 K, however, do not show any trend with the average crystal size, due to the main influence of morphology on surface spins. And we got larger remnant magnetization and the coercivity of NiO samples at 5 K compared with the spherical morphological of the same size, which is synthesized by W. J. Duan et al 14 That is because the branchlike morphological of NiO crystals has larger surface-to-volume ratio than the spherical morphological when with the same size.…”

“…Extensive studies have been reported on particle size and morphology effects on magnetic properties of NiO prepared by various techniques, [7][8][9][10][11][12] but the results of the size effects on magnetic performance of NiO nanoparticles from different groups are inconsistent. 13,14 The inconsistent was considered due to the relatively large size distribution of particles with relatively irregular morphological.…”

X-ray diffraction line profile analysis of nanostructured nickel oxide: Shape factor and convolution of crystallite size and microstrain contributions

“…A number of reports on the lattice expansion in nanocrystalline NiO, with decrease in crystallite size had appeared in the literature [50,[53][54][55][56]. This is explained as due to a number of possible factors such as grain-surface-relaxation effect, formation of point defects, uncompensated Coulombic interactions, etc.…”

The effects of FEC (fluoroethylene carbonate) electrolyte additive on the lithium storage properties of NiO (nickel oxide) nanocuboids

“…This novel synthesis method has been reported in our recent publication. [36] This technique has been used for the crystal growth of a wide range of materials including both congruently and incongruently melting materials, however, the growth of nanomaterials using such approach have been rarely reported. The main advantage of this method is that no crucible is necessary, thus avoiding contaminants from the crucible.…”