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When a conventional Halbach type Hollow Cylindrical Permanent Magnet Array (HCPMA) is used to generate magnetic induction over the magnitude of coercivity μ 0 H c , some detrimental parasitic magnetic phenomena, such as the demagnetization, magnetization reversal, and vortexes of magnetization, can appear in the interior of the magnets. We present a self-consistent quantitative analysis of the magnetization and magnetic induction distributions inside the magnetic array by considering the anisotropic and nonlinear magnetization functions of the materials consisting of the array. These numeric simulations reveal novel magnetization structures resulted from the self-field of array. We demonstrate that both the field uniformity and magnetic flux in the pole gap can be modulated by partially substituting the magnets of high energy products with the soft irons and the superhard magnets. We also show how the optimized substitution parameters can be obtained for a HCPMA achieving the best field uniformity or the maximum magnetic flux. [ABSTRACT FROM AUTHOR]

The Halbach type hollow spherical permanent magnet arrays (HSPMA) are volume compacted, energy efficient field sources, and capable of producing multi-Tesla field in the cavity of the array, which have attracted intense interests in many practical applications. Here, we present analytical solutions of magnetic induction to the ideal HSPMA in entire space, outside of array, within the cavity of array, and in the interior of the magnet. We obtain solutions using concept of magnetic charge to solve the Poisson’s and Laplace’s equations for the HSPMA. Using these analytical field expressions inside the material, a scalar demagnetization function is defined to approximately indicate the regions of magnetization reversal, partial demagnetization, and inverse magnetic saturation. The analytical field solution provides deeper insight into the nature of HSPMA and offer guidance in designing optimized one. [ABSTRACT FROM AUTHOR]

We have studied Ru-doping effect on the thermopower and electrical transport properties of Ca 3 Co 4 O 9+ δ samples. A thermopower in Ca 3 Co 4− x Ru x O 9+ δ was enhanced by Ru doping. A clear field-induced suppression of thermopower implies a large spin entropy contribution. Magnetic results indicate that the spin entropy enhancement originates from the decrease of Co 4+ concentration induced by Ru-doping. The increase of resistivity results from the decreases of carrier concentration and mobility. The electrical transport properties reveal that Ru-doping induces a metal–insulator transition at x ≈0.2 and the thermally activated mechanism dominates the transport behavior at low temperature. [ABSTRACT FROM AUTHOR]

Abstract: Silver nanoplates, with average size tunable from 50 to 500nm, have been synthesized via a simple room-temperature tannic acid (TA) solution-phase chemical reduction method. The synthesis was a seedless process in which tannic acid was used as a reducing as well as a capping agent, and did not need any other surfactant or capping agent to direct the anisotropic growth of the silver nanoparticles. The morphology of silver nanoplates has been confirmed by transmission electron microscopy, the growth process of nanoplates has been studied by UV/vis spectroscopy. Control experiments have been explored for a more thorough understanding of the growth mechanism. It was found that both the concentrations of TA and the pH of solution were the key elements to control the morphology silver nanoplates. The optical in-plane dipole plasmon resonance bands of these silver plates could be tuned from 520 to 1100nm. [Copyright &y& Elsevier]

• According to COMSOL calculations, the absorption film has four perfect absorption peaks in the terahertz narrowband and exhibits polarization incoherence, which means that the absorption film has good performance. • By changing the physical parameters, the active tunability of the film in a wide range is achieved. • The absorption film has high refractive index sensitivity, which means it has extremely high application prospects. • With simple structures and materials, the phenomenon of absorption bandwidth of the absorber also facilitates the study of conversion and regulation between narrowband and broadband. Here, a simple four-band terahertz tunable narrowband absorber is proposed, which can achieve multimodal perfect absorption within 1–9 THz. We analyzed the physical mechanisms behind local surface plasmon resonance and impedance matching based on theoretical principles. By controlling the structural parameters, we use the eigen-mode and external field excitation to obtain the absorption peak and electromagnetic field distribution of the narrowband sensor under different structural parameters. Additionally, we studied the effect of the angle of incidence electromagnetic waves on the function of the absorber, found that the absorber has excellent characteristics in both low and high frequency states. We carry out a substance detection on four perfect absorption modes. The ambient refractive index sensitivity is 881.35 GHz / RIU , 439.65 GHz / RIU , 2664.46 GHz / RIU , 4501.19 GHz / RIU. The four-peak narrowband high-performance absorber designed by us has a huge development prospect in most important areas such as resource detection and biomedical diagnosis. [Display omitted] [ABSTRACT FROM AUTHOR]

• Microencapsulation of Na 2 SO 4 ·10H 2 O were fabricated by emulsion polymerization. • The size of microcapsules was tunable by reducing amount of Triton X-100. • Microstructure and chemical structure of microcapsules were presented and analyzed. • Phase segregation of Na 2 SO 4 ·10H 2 O has been inhibited by microencapsulation. • Microcapsule by using 1.0 mL of Triton X-100 has a high latent heat of 125.57 J/g. Sodium sulfate decahydrate has been microencapsulated within a silica shell through a novel method of reverse micellization and emulsion polymerization. Tetraethoxysilane and 3-aminopropyl-triethoxysilane were used in conjunction as silicon precursors to form the silica shell, which encapsulated sodium sulfate decahydrate as a phase change material for thermal energy storage. The melting and solidifying temperatures of the microcapsules were measured as 33.6 °C and 6.0 °C, respectively, with associated latent heats of 125.6 kJ/kg and 74.0 kJ/kg. The phase segregation of various hydrate salts was inhibited by the confining effect of the silica mesopores. The size of the microcapsules could be regulated from 500 nm to 28 μm simply by reducing the amount of surfactant (Triton X-100) deployed as a stabilizer. Confined by SiO 2 matrix, heat storage properties of the hydrate salts were greatly improved. Sodium sulfate decahydrate microencapsulated within a silica shell is shown to be suitable for application in thermal energy storage. [ABSTRACT FROM AUTHOR]

The pyramidal silicon substrate is formed by wet etching, then ZnO nanorods are grown on the surface of the pyramidal microstructure by a hydrothermal method to form a moth-eye composite heterostructure. The composite heterostructure of this material determines its excellent anti-reflection properties and ability to absorb light from all angles. In addition, due to the effective heterojunction binding area, the composite micro/nano structure has excellent photoelectric conversion performance. Its surface structure and the large specific surface area gives the material super hydrophilicity, excellent gas sensing characteristic, and photocatalytic properties. Based on the above characteristics, the micro/nano heterostructure can be used in solar cells, sensors, light-emitting devices, and photocatalytic fields. [ABSTRACT FROM AUTHOR]

We show a designed FePt nanoparticles for embedding in a single crystal MgO matrix and demonstrate plasmon resonance absorption can appear in the ultraviolet region. The state of the FePt alloy is confirmed by X-ray photoelectron spectroscopy and selected area electron diffraction. By increasing the laser energy density from 4 to 6 J/cm 2 , the shape of the FePt nanoparticles is changed from quasi-spherical to quasi-elliptical. Compared with pure MgO, a single plasmon resonance peak at 234 nm was found in the ultraviolet region for the embedded FePt. Increasing the laser energy density induces peak splitting into two peaks, located at 225 and 262 nm, respectively. With a high laser energy density, a red-shift and a blue-shift are observed for the two peaks, respectively. These results are accordance with the theoretical calculations. The ultraviolet plasmon resonance absorption for FePt NPs can be tuned by changing the shape of the nanoparticles. [ABSTRACT FROM AUTHOR]

Graphite oxide of various degrees of dehydration or chemically reduced with different concentrations of sodium borohydride have been synthesised. Samples were characterised with X-ray diffractometry and infrared spectroscopy, then studied using Raman, X-ray photoelectron (XPS), nuclear magnetic resonance (NMR) and impedance spectroscopies. The trend in their concentrations of epoxy, hydroxyl group and sp 2 carbon, as calculated from XPS and NMR data, agreed with their vacancies concentrations as deduced from Raman spectra. Analysis of observed complex impedance peaks points to three different relaxation processes. One, obviously, is the rotation of intercalated water. The other two involve dipoles originating from polar hydroxyl groups. Loss peaks seen in less reduced graphite oxide have an activation energy of 0.16 eV, and are ascribed to the breaking of a hydrogen bond (–O–H···O<) between a hydroxyl attached to a carbon grid and an epoxy group on the adjacent carbon grid. The other, displayed in more reduced samples and of 0.08 eV in activation energy, derive from hydrogen bonds (–O–H…π) between hydroxyls and π electrons on adjacent carbon grids. [ABSTRACT FROM AUTHOR]

Using the discrete dipole approximation, we analyze surface plasmon resonance (SPR) in the core(Au)/interlayer/shell(Ag) nanoparticles. Here, the role of the Au core is typically central. We focus on the effect of the interlayer properties on SPR. If the interlayer is metallic, the contribution of the Au core to SPR is found to be suppressed, while the semiconductor interlayer can enhance this contribution. The porous Si interlayer exhibits the combined features inherent to a cavity and amorphous Si. These conclusions are illustrated by showing the distribution of electric field in and near nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: Graphite oxide (GO) has been prepared by the modified Hummers method and hydrated to different concentrations. Samples were then characterized by nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction analysis, and gas adsorption. The results confirmed the existence of water molecules at two types of sites, namely the two-dimensional space between GO layers as well as inter-grain voids. Detailed impedance spectroscopic measurements have been performed to study the rotation and reorientation dynamics of confined water. Two dielectric loss peaks were observed in hydrated GO and attributed to relaxational motions of water molecules. The peak at the higher temperature arises from the rotation of intercalated molecules along the axis of their hydrogen bonds to hydroxyl radicals on the graphite oxide layers. The peak at lower temperature corresponds to the relaxation of inter-grain species, a relaxation that seems to deviate from Arrhenius behavior at higher temperatures. [Copyright &y& Elsevier]

Abstract: The fact that a magnetic hysteresis loop is observed only in polymerized C60 and is absent in both pristine and depolymerized C60 establishes a close link between the weak ferromagnetism and the underlying structure. Furthermore, the correlation between the weak ferromagnetism and hydrogen presence has been explored by 1HNMR and 1H–13C cross-polarization NMR, whereby strong bonding between the H adducts and C60 has been verified. The adducted hydrogens most likely form bonds with the carbon atoms of inter-C60 four-membered rings. This conclusion is further supported by the formation energy of adducted H and the exchange energy among adducted H obtained from first-principle calculations on Rh-C60. [Copyright &y& Elsevier]