Qingshan Zhu

Fabrication and magnetic properties of hierarchical porous hollow nickel microspheres

Hierarchical porous hollow nickel microspheres with nickel nanoparticles as the in situ formed building units have been fabricated via a novel precursor hydrothermal redox method in alkaline solution of KBH4. The microspheres exhibit enhanced coercivity and remanent magnetization as compared with hollow nickel submicrometer spheres, hollow nickel nanospheres, bulk nickel, and free Ni nanoparticles. Investigations have demonstrated that the enhancement is attributed to the hierarchical porous hollow structure, while the hierarchical structure has little influence on saturation magnetization.

Fabrication of dense YSZ electrolyte membranes by a modified dry-pressing using nanocrystalline powders

A simple and cost-effective method for synthesizing yttria-stabilized zirconia (YSZ) electrolyte membranes is described that is based on a modified dry-pressing process using nanocrystalline powders. The thickness of the YSZ electrolyte membranes was easily controlled by controlling the mass of nanocrystalline YSZ powders. Good adhesion of the dense electrolyte membranes to the anode substrates without cracking or delamination could be readily obtained. The studied single cell possessed much higher open circuit voltage (OCV) and higher output performance than a cell whose electrolyte thick film was made from a traditional dry-pressing method using commercially microcrystalline powders. The good performance in this study was attributable to the successful fabrication of the electrolyte membrane by the uniquely modified dry-pressing process using loose nanocrystalline YSZ powders. The implementation of the modified dry-pressing process using nanocrystalline YSZ powders to fabricate electrolyte membranes exhibits a significant potential to greatly reduce the fabrication cost of solid oxide fuel cells (SOFCs).

Direct synthesis of HZSM-5 from natural clay

Highly crystalline HZSM-5 zeolite was directly synthesized through the steam-assisted conversion (SAC) approach using kaolin as the raw material, where NH3·H2O was used as an alkaline vapor source. The catalytic performance of the obtained HZSM-5 with SiO2/Al2O3 ratios from 25.67 to 80 was investigated for converting methanol to light olefins (MTO). The results indicated that NH3·H2O provided alkalinity to dissolve the raw materials and NH4+ cations to balance the charge of the framework. Highly crystalline HZSM-5 with crystal size in the range of 0.8–1 μm was obtained within 1.0 h at 190 °C. The obtained HZSM-5 possessed high SBET (above 440 m2 g−1) and high total pore volume (above 0.3 cm3 g−1). The acidity of the HZSM-5 was affected by the SiO2/Al2O3 molar ratio and residual metallic elements (such as Fe, Ti, Ca, P, etc.) in the leached metakaolin. The existence of the metallic elements similarly affected HZSM-5 modified with metal cations. HZSM-5 with a higher SiO2/Al2O3 molar ratio was favourable for the formation of C2–C4 olefins. The selectivity of C2–C4 olefins reached 68% when the SiO2/Al2O3 molar ratio was 68.79. This productive and facile method is inexpensive because the ammonium and calcination ion exchange processes are unnecessary.

STRUCTURE CONTROL IN HYDROXYAPATITE SYNTHESIS BY HYDROTHERMAL REACTION AND ORGANIC MODULATORS

Properties of materials are determined not only by their composition, but also by their structure. It is, therefore, of great significance to develop the ability of tailoring the structure of materials according to the requirements of intended applications. In this work a novel glutamic acid-assisted hydrothermal process was developed to synthesize apatite crystals with controllable morphologies. Varied morphologies from whisk broom, fibers, mushroom, prickly spheres, to dandelion were produced through modulating both the formation of a transitory phase and its transformation into the final phase.