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Abstract: Using hydrazine hydrate as reductant, metallic Ni ultrafine powders were prepared from NiSO4 aqueous solution by electroless plating method. The factors including concentration of NiSO4, bathing temperature, ratio of hydrazine hydrate to NiSO4, the pH of the solution, etc., on influence of the yield and average particle size of metallic Ni ultrafine powders were studied in detail. X-ray powders diffraction patterns show that the nickel powders are cubic crystallite. The average crystalline size of the ultrafine nickel powders is about 30nm. The dielectric and magnetic loss of ultrafine Ni powders–paraffin wax composites were measured by the rectangle waveguide method in the range 8.2–12.4GHz. The factors for Ni ultrafine powders preparation are optimized by computer pattern recognition program based on principal component analysis, the optimum factors regions with higher yield of metallic Ni ultrafine powders are indicated by this way. [Copyright &y& Elsevier]

Oxyapatite NaY9Si6O26 was prepared by sol–gel method. By choosing the precursors, a single phase compound was obtained. This soft chemical method lowered the reaction temperature by 100°C compared with the solid state method. Its morphology was studied by transmission electron microscopy (TEM). Several rare earth ions (Eu3+, Tb3+, Dy3+) and Pb2+ ion were doped in this compound. The high resolution emission spectrum of Eu3+ showed that rare earth ions occupied two yttrium sites. In spite of the charge imbalance of Pb2+ with the cations in this compound, it was found that Pb2+ could emit in UV range and transfer its excitation energy to Dy3+ ion. [Copyright &y& Elsevier]

Nanostructured multi-main-phase (MMP) Nd-Ce-Fe-B magnet produced by melt-spinning powders has great potential for achieving high performance. However, the inferior intrinsic properties of the Ce 2 Fe 14 B phase lead to the low coercivity and thermal stability of this magnet. In this study, low-melting-point Pr 68 Cu 32 powders were introduced into nanostructured MMP magnet through intergranular addition to further improve its coercivity and thermal stability. When only 2 wt% Pr 68 Cu 32 was added, the intrinsic coercivity H cj and thermal stability were significantly improved with a slight reduction in the remanence B r and the maximum energy product (BH) max. The microstructure evolution of MMP magnet with adding Pr 68 Cu 32 was revealed by microstructural and compositional characterization and thermodynamic calculation, and a schematic model was proposed. Furthermore, mechanisms underlying changes in magnetic properties were systematically analyzed by combining micromagnetic simulation. ● Grain boundary modification is adopted for fabricating high-performance nanostructured MMP Nd-Ce-Fe-B magnet. ● H cj and thermal stability are significantly improved with a slight reduction in B r and (BH) max. ● Microstructure and microchemistry evolution are investigated and a corresponding model is proposed. ● Mechanisms underlying changes in magnetic properties are systematically analyzed. [ABSTRACT FROM AUTHOR]

The microstructure and chemical heterogeneity play critical roles in the magnetic performance of nanocrystalline multi-main-phase (MMP) Nd–Ce–Fe–B magnets. In this work, we report a strategy to synergistically tailor the microstructure and chemical heterogeneity of MMP magnet through optimizing sintering temperature (T s). An optimum T s of 700 °C has been obtained for nanocrystalline MMP Nd–Ce–Fe–B magnets. When sintered at T s = 700 °C, the nanocrystalline MMP magnet exhibits the maximum intrinsic coercivity H cj , the preferable remanence B r , and the resultant optimum maximum energy product (BH) max , which is attributed mainly to the appreciable density, controlled grain size, and better chemical heterogeneity. Comparably, lower or higher T s leads to the inferior magnetic properties. At lower T s below 700 °C, the poor magnetic properties are mainly due to the insufficient densification. However, at higher T s above 700 °C, the decreased H cj originates mainly from the excessive grain growth and gradual chemical homogenization. The above findings deepen our understanding on the relationship among the microstructure, chemical heterogeneity, and T s , concurrently providing an effective approach for fabricating low-cost high-performance nanocrystalline MMP Nd–Ce–Fe–B magnets. • Microstructure and chemical heterogeneity of nanocrystalline MMP Nd–Ce–Fe–B magnet are synergistically tailored. • H cj , B r , and (BH) max are simultaneously enhanced at optimum T s of 700 °C. • Dependences of microstructure and composition on T s are revealed, and an evolution model is proposed. • Mechanisms underlying changes in magnetic properties with T s are systematically analyzed. [ABSTRACT FROM AUTHOR]

CuO was coated on the surface of Al 18 B 4 O 33 whiskers by hydrothermal synthesis and CuO coated Al 18 B 4 O 33 whiskers reinforced 6061Al composites with different coating contents were fabricated by squeeze casting. The preparation process and characterizations of the CuO coated Al 18 B 4 O 33 whiskers were studied. The effects of CuO coating of whiskers on the microstructures, tensile properties and aging behaviors of the composite were investigated. The results showed that a uniform CuO coating of Al 18 B 4 O 33 whiskers could be prepared by hydrothermal synthesis. CuO reacted with molten 6061Al during squeeze casting and meanwhile a layer of continuous MgAl 2 O 4 formed at the interface. With increasing the contents of CuO coating on whiskers, the ultimate tensile strength of the composite gradually increased. The elongation to fracture of the composite initially increased and later decreased. Impressively, the ultimate tensile strength of the composite could be further improved after T6 heat-treatment. CuO coating of the whiskers could also obviously change the aging behaviors of the composite. [ABSTRACT FROM AUTHOR]

Abstract: Single crystals of potassium tantalate niobate, KTa1−x Nb x O3 (KTN x , x =0.45, 0.50, and 0.55), were synthesized by the top-seeded solution growth method. The Raman scattering technique is used to investigate the sequence of phase transitions undergone by KTN x crystals. We discuss what features in the phonon spectrum are associated to each phase transition. [Copyright &y& Elsevier]

Abstract: SrO(SrTiO3) n (n =1, 2,…,∞) powders were prepared by a modified sol–gel self-propagating combustion method and characterized by ultraviolet–visible (UV–vis) absorption spectroscopy and infrared spectra. UV–vis spectra indicate that the absorption edge of SrO(SrTiO3) n (n =1, 2) shift to the violet with the decrease of n value, and the band gap values obtained from the UV–vis spectroscopy measurements are 3.41 and 3.26eV, respectively. The infrared spectra show that the width of absorption band of TiO6 octahedron stretching vibration decreases with the increasing of n value. The optical absorption of the compounds SrO(SrTiO3) n (n =1, 2,…,∞) were investigated by theoretical caculation using density functional theory (DFT). The interband transitions were assigned according to the partial density of states (PDOS). The calculated results are close to the experimental results. [Copyright &y& Elsevier]