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Ferromagnetic carbon-coated Fe nanoparticles (core size of 15 nm, saturated magnetization of Ms=218 emu g(-1) and coercivity of Hc=62 Oe), fabricated at a mild temperature, demonstrate a strong ability to effectively remove more than 95 wt% of Cr(VI) in waste water via carbon shell physical adsorption, which is much higher than the commercially available Fe NPs.

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PACS number(s): 74.70.AdWe report the synthesis and measurements of magnetic, transport, and thermal properties of polycrystalline Nb 0.18 Re 0.82 , which has a superconducting transition at T c ~ 8.8 K. The noncentrosymmetric α-Mn structure of the compound is confirmed by X-ray diffraction. Using the measured values for the lower critical field H c1 , upper critical field H c2 , and the specific heat C, we estimate the thermodynamic critical field H c (0), coherence length ξ(0), penetration depth λ(0), and the Ginzburg-Landau parameter κ(0). The specific heat jump at T c , ΔC/γT c = 1.86, suggests that Nb 0.18 Re 0.82 is a moderately coupled superconductor. Below T c the electronic specific heat decays exponentially, suggesting that the gap is isotropic. Our data suggest that the triplet admixture is weak in the polycrystalline form of compound. However, the estimated value of the upper critical field H c2 (0) is close to the calculated Pauli limit.

Conductive polypyrrole/SiC nanocomposites are fabricated via a facile oxidative polymerization approach using p-toluene sulfonic acid as a dopant and ammonium persulfate as an oxidant. The effects of the nanoparticle loading, ratio of oxidant to monomers, and nanoparticle morphology (spheres and rods) on the physicochemical properties are investigated. Various characterization methods are carried out to determine the material properties. Thermal gravimetric analysis demonstrates an improved thermal stability of polypyrrole in the polymer nanocomposites (PNCs) with a higher decomposition temperature. The glass-transition temperature and melting temperature of the polymer and its nanocomposites are determined by differential scanning calorimetry with a decreased melting temperature of polypyrrole in the PNCs. The microstructures of pure polypyrrole and PNCs are observed by scanning electron microscopy. Powder X-ray diffraction analysis demonstrates the crytallinity of polypyrrole, and poor crystallinity is observed for the PNCs with higher nanoparticle loading. Fourier transform infrared spectrometry analysis shows a strong interaction between the SiC nanoparticles and the polypyrrole matrix with a shift of CC stretching vibration of PPy to a lower band. The electron transport in PNCs follows a quasi 3-d variable range hopping conduction mechanism as evidenced by the temperature-dependent conductivity function. Experimental results demonstrate that PPy/SiC PNCs have higher conductivity than that of the pure PPy. The nanorods are also introduced into the polypyrrole matrix. Their effects on the physicochemical properties are investigated and compared.

Polypyrrole (PPy) nanocomposites reinforced with tungsten oxide (WO 3 ) nanoparticles (NPs) and nanorods (NRs) are fabricated by a surface-initiated polymerization method. The electrical conductivity is observed to depend strongly on the particle loadings, molar ratio of oxidant to pyrrole monomer, and the filler morphology. The electron transportation in the nanocomposites follows a quasi-three-dimensional variable range hopping (VRH) conduction mechanism as evidenced by the temperature-dependent conductivity function. Unique negative permittivity is observed in both pure PPy and its nanocomposites, and the switching frequency (frequency where the real permittivity switches from negative to positive) can be tuned by changing the particle loading, ratio of oxidant to pyrrole monomer, and the filler morphology. The extent of charge carrier localization calculated from the VRH mechanism is well-correlated to the dielectric properties of the nanocomposites. WO 3 NRs are observed to be more efficient in improving the electrical conductivity, dielectric permittivity, and thermal stability of the resulting nanocomposites as compared to those with WO 3 NPs. The microstructures of pure PPy and its nanocomposites are observed by scanning electron microscopy and transmission electron microscopy. Powder X-ray diffraction analysis demonstrates the crystalline structure of WO 3 nanostructures, as well as their corresponding nanocomposites. Thermogravimetric analysis reveals a significantly enhanced thermal stability with the addition of nanofillers.

We have synthesized polycrystalline samples of the noncentrosymmetric superconductor Mo 3 Al 2 C by arc and RF melting, measured its transport, magnetic and thermodynamic properties, and computed its band structure.Experimental results indicate a bulk superconducting transition at T c ~ 9.2 K, while the density of states at the Fermi surface is found to be dominated by Mo d-orbitals. Using the measured values for the lower critical field H c1 , upper critical field H c2 , and the specific heat C, we estimated the thermodynamic critical field H c (0), coherence length ξ(0), penetration depth λ(0), and the Ginzburg-Landau parameter κ(0). The specific heat jump at T c , ΔC/γT c = 2.14, suggests that Mo 3 Al 2 C is moderately-to-strongly coupled, consistent with the fast opening of the gap, as evidenced by the rapid release of entropy below T c from our electronic specific heat measurements. Above 2K the electronic specific heat exhibits the power law behavior, suggesting that synthesis of single crystals and measurements at lower temperature are needed to establish whether the gap is anisotropic. The estimated value of the upper critical field H c2 (0) is close to the calculated Pauli limit, therefore further studies are needed to determine whether the absence of an inversion center results in a significant admixture of the triplet component of the order parameter.

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