| Nanoparticles with irregular shapes usually exhibit unique electric,magnetic, optical and catalytic characteristics due to their large shape anisotropy,surface effect, and small scale effect and attract much attention.The research of synthesis and characterizations of magnetic nanomaterials will redound to discover and exploit their new properties in applied field,which is helpful to designing miniaturized devices in the future.In our recent work,two facile routes of synthesizing magnetic nanoparticles with irregular shapes have been introduced.In addition,the structure, growth mechanism and magnetic properties of the as-prepared nanoparticles have been investigated.1.Cobalt nanoparticles have been obtained by reducing the precursor of cobalt hydroxide using hydrogen as the reducing reagent.First,flake-like and flower-like cobalt hydroxide was selectively synthesized by varying the volume ratio of glycerol to water through a facile hydrothermal route.Both the Flake-like and flower-likeβ-Co(OH)2 precursor are composed of many nanoplatelets.Large-sized nanoplatelets tend to pile up one another as flake-like particles,and small-sized nanoplatelets tend to curl as flower-like particles.Second,cobalt nanoparticles were obtained by reducingβ-Co(OH)2 precursor in hydrogen.The method of reducing solid phase in hydrogen can keep the original form of the precursor.The cobalt nanoparticles all have an HCP crystal structure and the crystal size is about 30 nm.The saturation magnetization and coercivity of the cobalt nanoparticles are all 140 emu/g and 234 Oe. The saturation magnetization of the cobalt nanoparticles is smaller than that of the bulk cobalt probably duo to the non-magnetic oxidation layer of the particles.And the coercivity of cobalt nanoparticles is larger than the corresponding bulk value,which might be attributed to the small crystal size(～30 nm),shape anisotropy and HCP crystal phase of the flake-like and flower-like cobalt nanoparticles.2.The Fe0.2(Co1-xNix)0.8(x=0.2,0.4,0.6,0.8)alloy nanoplatelets with an average diameter of 150 nm and thickness of 10-20 nm have been synthesized by a simple solution phase reduction method using hydrazine as the reducing reagent.The Fe0.2(Co1-xNix)0.8(x=0.2,0.4,0.6,0.8)alloy nanoplatelets are all single-phase FCC structure.Their lattice constant decreases with increasing of Ni content linearly,which is according with Vegard's law.Hence all the Fe0.2(Co1-xNix)0.8(x=0.2,0.4,0.6,0.8) alloy are continuous solid solution.The saturation magnetization of the nanoplatelets is lower than the corresponding bulk value and decreases with increasing of Ni content.The coercivity of the nanoplatelets is higher than that of the bulk.The coercivity of the nanoplatelets decreases firstly and then increases with increasing of Ni content.
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