Iron-based microstructured or nanostructured materials, including Fe, γ-Fe 2 O 3 , and Fe 3 O 4 , are highly desirable for magnetic applications because of their high magnetization and a wide range of magnetic anisotropy. An important application of these materials is use as an electromagnetic wave absorber to absorb radar waves in the centimeter wave (2-18 GHz). Dendrite-like microstructures were achieved with the phase transformation from dendritic R-Fe 2 O 3 to Fe 3 O 4 , Fe by partial and full reduction, and γ-Fe 2 O 3 by a reductionoxidation process, while still preserving the dendritic morphology. The investigation of the magnetic properties and microwave absorbability reveals that the three hierarchical microstructures are typical ferromagnets and exhibit excellent microwave absorbability. In addition, this also confirms that the microwave absorption properties are ascribed to the dielectric loss for Fe and the combination of dielectric loss and magnetic loss for Fe 3 O 4 and γ-Fe 2 O 3 .

In this paper, we proposed a facile one-step strategy to prepare graphene-Fe3O4 (GN–Fe3O4) nanocomposites under hydrothermal conditions, where the reduction process of graphite oxide (GO) sheets into GN was accompanied by the generation of Fe3O4 nanoparticles. The reduction extent of GO by this process could be comparable to that by conventional methods. A transmission electron microscopy image has shown that the as-formed Fe3O4 nanoparticles with a diameter as small as 7 nm were densely and uniformly deposited on GN sheets, and, as a result, the aggregating of the Fe3O4 nanoparticles was effectively prevented. The GN–Fe3O4 nanocomposites exhibit improved cycling stability and rate performances as a potential anode material for high-performance lithium ion batteries. In addition, the GN–Fe3O4 nanocomposites exhibit a superparamagnetic behavior, making them promising candidates for practical applications in the fields of bionanotechnology/controlled targeted drug delivery.

Hierarchical self-assembly of nanoscale building blocks (nanoclusters, nanowires, nanobelts, and nanotubes) is a technique for building functional electronic and photonic nanodevices. [1,2] Fractal structures are common in nature across all length scales, from self-assembled molecules, to the shapes of coastlines, to the distribution of galaxies, and even to the 3D shapes of clouds. On the nanoscale, dendritic fractals are one type of hyperbranched structure which are generally formed by hierarchical self-assembly under nonequilibrium conditions. [3,4] Investigation of hierarchically selfassembled fractal patterns in chemical systems has shown that the distinct size, shape, and chemical functionality of such structures make them promising candidates for the design and fabrication of new functional nanomaterials, [5] but it is challenging to develop simple and novel synthetic approaches for building hierarchically self-assembled fractal architectures of various systems.Magnetic nanomaterials have been the subject of increasing interest due to their physical properties and technological applications. [6][7][8] In the past few years, research has focused primarily on zero-and one-dimensional (1D) magnetic nanomaterials such as magnetic metals, alloys, and metal oxides and has led to substantial advances including the assembly of 2D or 3D superlattices from spherical nanoparticles or nanorods. [9][10][11][12][13][14] However, to the best of our knowledge, the hierarchical self-assembly of magnetic nanomaterials has not been reported. Here we present the spontaneous, large-scale, hierarchical self-assembly of dendritic nanostructures of magnetic Fe 2 O 3 (so-called micro-pine structure). The a-Fe 2 O 3 micron-pine dendrites were synthesized by hydrothermal reaction of K 3 [Fe(CN) 6 ] in aqueous solution at suitable temperatures. The method is based on the weak dissociation of [Fe(CN) 6 ] 3À ions under hydrothermal conditions. The resulting structures display exquisite fractal features, which morphologically resemble a type of pine tree. The structure was formed as a result of fast growth along six crystallographically equivalent directions, and this process is different from the reported formation mechanism of general fractal structures. The magnetic properties of the nanostructure show a lower Morin transition temperature of 216 K. The reported structures could have important applications in biomedical science and magnetism.The micro-pines were synthesized on a large scale and in high purity. Figure 1 a shows that the product consists almost entirely of such dendritic structures, and this indicates the high yield and good uniformity achieved with this approach. The highmagnification images in Figure 1 b and c show the morphology of a single dendrite in two opposite directions. They reveal a clear and well-defined dendritic fractal structure with a pronounced trunk consisting of corrugations and highly ordered branches distributed on both sides of the trunk. Figure 1 d shows striking periodic corrugated structures on...

A facile and low-cost strategy is demonstrated for preparing MnO/C-N hybrid, in which the MnO nanoparticles chemically combine with N-doped C by Mn-N bonding to achieve the hybridization of MnO with N-doped C. When served as an anode in lithium ion batteries (LIBs), the resultant hybrid manifested high capacity, excellent cyclability, and superior rate capability. A lithium storage capacity of 1699 mAh g(-1) could be obtained at 0.5 A g(-1) after 170 discharge-charge cycles. Even at a current density up to 5 A g(-1), a high reversible capacity (907.8 mAh g(-1)) can be retained after 400 cycles. The excellent lithium storage performance of the MnO/C-N hybrid can be ascribed to the synergetic effects of several factors including the unique hybrid structure, the N-doping and the chemical bonding of MnO and N-doped C.