Synthesis and characterization of Ni1−xZnxFe2O4 spinel ferrites from tailored layered double hydroxide precursors

In this paper, a series of pure Ni_1 − xZn_xFe₂O₄ (0 ≤ x ≤ 1) spinel ferrites have been synthesized successfully using a novel route through calcination of tailored hydrotalcite-like layered double hydroxide molecular precursors of the type [(Ni + Zn)_{1 − x − y}Fe_y²⁺Fe_x³⁺(OH)₂]^x+(SO₄²⁻)_x/2·mH₂O at 900 °C for 2 h, in which the molar ratio of (Ni²⁺ + Zn²⁺)/(Fe²⁺ + Fe³⁺) was adjusted to the same value as that in single spinel ferrite itself. The physico-chemical characteristics of the LDHs and their resulting calcined products were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Mössbauer spectroscopy. The results indicate that calcination of the as-synthesized LDH precursor affords a pure single Ni_1 − xZn_xFe₂O₄ (0 ≤ x ≤ 1) spinel ferrite phase. Moreover, formation of pure ferrites starting from LDHs precursors requires a much lower temperature and shorter time, leading to a lower chance of side-reactions occurring, because all metal cations on the brucite-like layers of LDHs can be uniformly distributed at an atomic level.     

One-step and rapid synthesis of high quality alloyed quantum dots (CdSe-CdS) in aqueous phase by microwave irradiation with controllable temperature

In this paper, we presented a seed-mediated approach for rapid synthesis of high quality alloyed quantum dots (CdSe-CdS) in aqueous phase by microwave irradiation with controllable temperature in 1 h. In the synthesis, CdSe seeds were first formed by the reaction of NaHSe and Cd²⁺, and then alloyed quantum dots (CdSe-CdS) were rapidly produced by releasing of sulfide ions from 3-mercaptopropionic acid as sulfide source with microwave irradiation. The alloyed quantum dots synthesized had good optical properties, the quantum yield was up to 25%, and the full width at half maximum of the emission spectrum peak was about 28 nm. The as-prepared alloyed CdSe-CdS QDs were characterized by XRD, XPS and ICP-AES in order to explore the structure and component of the alloyed nanocrystals and the reaction mechanism. We speculate that the alloyed CdSe-CdS quantum dots may exist a gradient internal structure according to our preliminary results.     

Hydrothermal synthesis and photoluminescence properties of nano-crystalline GdBO3:Eu phosphor

Nano-crystalline GdBO₃:Eu³⁺ was prepared by a hydrothermal method and the effects of some processing variables such as pH, temperature were investigated. The as-synthesized powders were spherical shaped agglomerates of nanoparticles. The luminescent properties were compared with samples synthesized by conventional solid-state reaction method. Both the photoluminescence intensity and chromaticity were improved and a red-shift in the CT band was observed for the hydrothermally synthesized samples. Possible mechanisms of phase formation were investigated and explanations for the changes in optical properties are proposed.     

Processing of Net‐shaped Nanocrystalline Fe‐Ni Material

Development of nanoparticulate materials technology is essential to processing of highly functional nanoparticulate materials and components with small and complex shape. This paper provides an overview on our recent investigations on the processing of net‐shaped nanocrystalline Fe‐Ni powder and related material property such as mechanical property. The key‐processing concept is the synthesis of nanopowders and subsequent consolidation with controlled microstructure by using powder injection molding (PIM) process. Especially, the pressureless sintering process is inevitable for consolidation of the PIMed nanopowder. The present review focuses on the densification process and related mechanical property of the PIMed Fe‐Ni nanopowder in association with microstructural evolution and diffusion process.