Rare-earth-based permanent magnets are one of the most important magnets in both scientific and industrial fields. With the development of technology, nanostructured rarearth-based permanent magnets with high energy products are highly required. In this article, we will review the progress in chemical synthetic strategies of nanostructured rare-earth-based permanent magnets.
Progress in surface modification of magnetic nanoparticles（MNPs） is summarized with regard to organic molecules,macromolecules and inorganic materials. Many researchers are now devoted to synthesizing new types of multi-functional MNPs, which show great application potential in both diagnosis and treatment of disease. By employing an ever-greater variety of surface modification techniques, MNPs can satisfy more and more of the demands of medical practice in areas like magnetic resonance imaging（MRI）, fluorescent marking, cell targeting, and drug delivery.
Nanomagnetism is the origin of many unique properties in magnetic nanomaterials that can be used as building blocks in information technology, spintronics, and biomedicine. Progresses in nanomagnetic principles, distinct magnetic nanostructures, and the biomedical applications of nanomagnetism are summarized.
Colloidal chemical synthesis of various types of magnetic nanocrystals is discussed with regard to recent discoveries. We first outline the chemical preparation of single-component magnetic nanocrystals with controlled size, shape, and uniformity based on several solution-phase methods, especially thermal decomposition and/or reduction method. Then we discuss the synthetic strategies of multi-component nanocrystals incorporating at least one magnetic component by manipulating heterogeneous nucleation and growth process. Toward the end, approaches for preparing hollow/porous magnetic nanocrystals are highlighted. We believe that the summarized chemical synthesis will pave the way for the future development of extraordinary magnetic nanocrystals.
Electrochemical capacitors(EC) bear faster charge-discharge; however, their real applications are still on a long away due to lower capacitance and energy densities which mainly arise from simple surface charge accumulation or/and reaction. Here, a novel synthesis strategy was designed to obtain the purposeful hybrids of nickel cobalt double hydroxide(Ni Co DH) with genetic morphology to improve their electrochemical performance as electrode of EC. Nanostructures of metal hydroxides were grown on the nitrogen-doped graphene(NG) sheets by utilizing defects as nucleation sites and their composition was optimized both by tuning the ratio of Ni:Co as well as the counter halogen and carbonate anions to improve the porosity, stabilize the structure and mediate the redox reaction. The growth of the hybrids was guided by the Co ions through topochemical transformation supported by hoping charge transfer process and olation growth. NG overcoating successfully protects the nanostructure of Ni Co DH during electrochemical test and enhances overall conductivity of the electrode, improving the mass and ionic transportations. As a result, the hybrid exhibits excellent capacitance of 2925 F g-1 at 1 A g-1, as well as long cyclic stability of 10,000 cycles with good capacity retention of 90% at 16 A g-1. Furthermore, the hybrid shows excellent energy and power densities of 52 Wh kg-1 and 3191 W kg-1, respectively at discharge rate of 16 A g-1. It is expected that this strategy can be readily extended to other metal hydroxides, oxides and sulphides to improve their electrochemical performances.
