Magnetic properties of nanocrystalline ɛ-Fe3N and Co4N phases synthesized by newer precursor route

Nanocrystalline ɛ-Fe₃N and Co₄N nitride phases are synthesized first time by using tris(1,2-diaminoethane)iron(II) chloride and tris(1,2-diaminoethane)cobalt(III) chloride precursors, respectively. To prepare ɛ-Fe₃N and Co₄N nitride phases, the synthesized precursors were mixed with urea in 1:12 ratio and heat treated at various temperatures in the range of 450–900 °C under the ultrapure nitrogen gas atmosphere. The precursors are confirmed by FT-IR study. The ɛ-Fe₃N phase crystallizes in hexagonal structure with unit cell parameters, a = 4.76 Å and c = 4.41 Å. The Co₄N phase crystallizes in face centred cubic (fcc) structure with unit cell parameters, a = 3.55 Å. The estimated crystallite size for ɛ-Fe₃N and Co₄N phases are 29 nm and 22 nm, respectively. The scanning electron microscopy (SEM) studies confirm the nanocrystalline nature of the materials. The values of saturation magnetization for ɛ-Fe₃N and Co₄N phases are found to be 28.1 emu/g and 123.6 emu/g, respectively. The reduction of magnetic moments in ultrafine materials compared to bulk materials have been explained by spin pairing effect, lattice expansion, superparamagnetic behaviour and canted spin structures at the surface of the particles.     

Hydrogen evolution using CdWO4 modified by BiFeO3 in the presence of potassium iodide; a combination of photocatalytic and non-photocatalytic water splitting

Novel heterogeneous structure of BiFeO₃–CdWO₄ with different molar ratios was applied for the photocatalytic hydrogen evolution in a self-designed externally UV/visible irradiated photoreactor in the presence of potassium iodide. The photocatalysts were synthesized by simple hydrothermal method and characterized by XRD, FE-SEM-mapping, TEM, UV–Vis DRS, PL, EIS, transient photocurrent and Mott-schottky techniques to identify the structural, optical and photoelectrochemical properties. The slope of Mott-schottky plots confirmed the p-type and n-type conductivity of the synthesized BiFeO₃ and CdWO₄, respectively. The p-n heterojunctions exhibited more efficiently light absorption, charge separation and electron mobility relative to the pure photocatalysts. We observed that coupling 40 mol% BiFeO₃ with CdWO₄ provided the best photocatalytic performance of hydrogen evolution, 268.90 μmol h⁻¹.g_cat⁻¹ from distilled water and 379.43 μmol h⁻¹.g_cat⁻¹ from 0.05 M KI aqueous solution. Iodine species increased H₂ evolution efficiency because of taking part in the charge transfer processes, either by scavenging excited holes or by direct reduction of H⁺ to H^• under UV irradiation. Fermi level equilibrium in the p-n heterojunction suggests the best interparticle charge transfer mechanism explaining how photoinduced electrons with superior energy states and desirable lifetime can be supplied to reduce H⁺ to H^•.     

One step synthesis of Bi@Bi2O3@carboxylate-rich carbon spheres with enhanced photocatalytic performance

Bi@Bi₂O₃@carboxylate-rich carbon core-shell nanosturctures (Bi@Bi₂O₃@CRCSs) have been synthesized via a one-step method. The core–shell nanosturctures of the as-prepared samples were confirmed by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and Raman spectroscopy. The formation of Bi@Bi₂O₃@CRCSs core–shell nanosturctures should attribute to the synergetic roles of different functional groups of sodium gluconate. Bi@Bi₂O₃@CRCSs exhibits significant enhanced photocatalytic activity under visible light irradiation (λ > 420 nm) and shows an O₂-dependent feature. According to trapping experiments of radicals and holes, hydroxyl radicals were not the main active oxidative species in the photocatalytic degradation of MB, but O₂⁻ are the main active oxidative species.     

Numerical stability of Entropic versus positivity-enforcing Lattice Boltzmann schemes

A preliminary study of the non-linear stability properties of entropic schemes versus positivity-enforcing (FIX-UP) schemes is presented for the case of two-dimensional cavity flow. It is shown that, although they operate on fairly distinct schedules, both methods achieve substantial stability enhancements over the standard single-time relaxation Lattice Boltzmann scheme.     

Boron removal from silicon by hydrogen assistant during the electromagnetic directional solidification of AlSi alloys

Boron (B) removal from silicon (Si) by using an Ar-20% H₂ gas mixture during the AlSi solvent refining was investigated. Electromagnetic directional solidification was employed to enrich the primary Si crystals in the melt and simultaneously drive the produced B_xH_y gas species to migrate out of the Si enrichment zone. Thermodynamic analysis shows that the formation of B_xH_y gas species by the reaction of dissolved boron [B] and dissolved hydrogen [H] in AlSi melt is feasible. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) analysis confirmed that the impurity carbon (C), oxygen (O), and B adhered to the wall of the gas cavity, indicating that B removal can be attributed to the migration of gas species. As the flow time of Ar-20% H₂ gas mixture increased, the B removal fraction significantly increased, and a maximum value of 96.3% for B removal fraction was achieved when the flow time was 150 min. Finally, an overall process for producing solar grade silicon (SoG-Si) from metallurgical grade silicon (MG-Si) with the combination of ArH₂ refining in AlSi solvent and vacuum directional solidification was proposed.     

Utilizing active multiple dopants (Co and Ni) in olivine LiMnPO4

Parent LiMnPO₄ and variants with cobalt and nickel on Mn (M2) site in LiMnPO₄ olivine are synthesized by sucrose induced combustion method. The synthesized cathodes are tested in aqueous based LiOH electrolyte. The observed change in lattice parameters and peak positions for the olivine variants evidenced that doping occurred in the lattice without any disruption. The nickel and cobalt variants in the LiMnPO₄ olivine mitigated the lattice distorted Jahn-Teller Mn³⁺ ions, thus the electrochemical performance was enhanced with a discharge capacity of 94 mA h/g. The doped LiMn_0.5Co_0.5PO₄ and LiMn_0.33Co_0.33Ni_0.33PO₄ cathodes showed a smaller particle size having a lower Li⁺ or electron transport length. Influence of high voltage Co and Ni-based dopants compared to the low voltage Mn-based LiMnPO₄ showed a superior redox potential and was able to access Co³⁺/Co²⁺ and Ni³⁺/Ni²⁺ in a safe operating voltage window which is plausible for aqueous electrolytes. Whereas LiCoPO₄ and LiNiPO₄ are difficult to assess in non-aqueous electrolytes, this is due to the electrolyte instability at the high operating voltage. Improved cell voltage with extended cell capacity and good capacity retention for mixed dopants in olivine is reported.     

磷脂胆碱仿生修饰聚乳酸及其生物学评价

通过自由基聚合反应将马来酸酐接枝到聚(D,L-乳酸)(PDLLA)侧链上,然后通过引入的活性反应基团马来酸酐与甘油磷脂胆碱反应,实现磷脂胆碱对聚乳酸的整体仿生修饰。采用红外光谱和核磁共振碳谱对磷脂胆碱修饰聚乳酸进行了表征。生物降解实验表明,该功能化聚乳酸具有明显抑制酸致降解作用。体外细胞形貌观察证实磷脂胆碱修饰的聚乳酸具有良好的细胞相容性。同时,蛋白吸附和血小板粘附实验表明,该聚合物具有良好的血液相容性。该改性聚乳酸可望用作组织工程支架及血液接触类植入体。     

Synthesis and electrochemical properties of SnO2-CuO nanocomposite powders

1 Introduction Since YOSHIO et al[1] announced the commercia- lization of tin oxide as negative electrodes of 1ithium-ion batteries, the tin oxide anode has attracted much attention due to its high specific capacity, which is about twice that of graphite…