Jun-Wei Wang

Different aspects of the microstructure of nanometer-sized Mn2O3

The microstructure of the nanometer-sized manganic oxide (Mn{sub 2}O{sub 3}) has been investigated by the X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution electron microscopy (HREM). The experimental results suggest that annealing temperature and time, dripping speed of the NaOH aqueous solution, and pH value during aqueous solution chemical reaction have a great effect on the microstructure of the nanometer-sized Mn{sub 2}O{sub 3}. The authors found that the grain size of the nanometer-sized manganic oxide (Mn{sub 2}O{sub 3}) increases with the increase of annealing temperature and the decrease of the pH value of the aqueous solution. With change in the NaOH aqueous solution dripping speed, a large difference was observed in the TEM images of the nanometer-sized Mn{sub 2}O{sub 3}.

Preparation of high-efficiency ceramic planar membrane and its application for water desalination

Highly efficient Si3N4 ceramic planar membrane for water desalination process using membrane distillation was prepared by the dual-layer phase inversion tape casting and sintering method. In comparison with typical phase inversion tape casting method, the green tape was formed using Si3N4 slurry on the top and graphite slurry on the bottom. After consuming away the graphite structure, a ceramic membrane consisting of a two-layered structure (skin and finger-like layers) was obtained. The skin layer was relatively tight, and thus could act as a functional layer for separation, while the finger-like layer contained straight open pores with a diameter of 100 μm, acting as a support with low transport resistance. For comparison, typical Si3N4 ceramic membrane was fabricated by phase inversion technique without graphite substrate, resulting in a three-layered structure (skin, finger-like, and sponge layers). After membrane modification from hydrophilic to hydrophobic with polymer derived nanoparticle method, the water desalination performance of the membranes was tested using the sweeping gas membrane distillation (SGMD) with different NaCl feed solutions. With the increase of salt content from 4 to 12 wt%, the water flux decreased slightly while rejection rate maintained over 99.99%. Comparing with typical three-layered Si3N4 membrane, an excellent water flux enhancement of over 83% was resulted and the rejection rate remained over 99.99%.

Preparation of a Porous, Sintered and Reaction-Bonded Si3N4 (SRBSN) Planar Membrane for Filtration of an Oil-in-Water Emulsion with High Flux Performance

A porous, sintered, and reaction-bonded Si3N4 (SRBSN) planar membrane was prepared by phase-inversion tape-casting, nitridation (at 1350 °C), and sintering (at 1650 °C) of silicon slurry. The membrane was comprised of uniform rod-like β-Si3N4 crystals with a large length/diameter ratio and had high porosity and bending strength. The prepared membrane features a typical asymmetric structure with a skin layer, a sponge layer, and finger-like voids and an average pore size of 0.61 μm. A high permeation flux of 367 L m−2 h−1 and an oil rejection of 88.6% were recorded in oil-in-water emulsion separation experiments. These results suggest that SRBSN membranes have excellent potential for the treatment of oily wastewater.