Wu Guozhong

Ordering layers of [bmim][PF6] ionic liquid on graphite surfaces: Molecular dynamics simulation

Microscopic structures of room temperature ionic liquid (IL) [bmim][PF6] on hydrophobic graphite surfaces have been studied in detail by molecular dynamics simulation. It is clearly shown that both the mass and electron densities of the surface adsorbed ionic liquid are oscillatory, and the first peak adjacent to the graphite surface is considerably higher than others, corresponding to a solidlike IL bottom layer of 6 angstroms thick. Three IL layers are indicated between the graphite surface and the inner bulk IL liquid. The individually simulated properties of single-, double-, and triple-IL layers on the graphite surface are very similar to those of the layers between the graphite surface and the bulk liquid, indicating an insignificant effect of vapor-IL interface on the ordered IL layers. The simulation also indicates that the imidazolium ring and butyl tail of the cation (bmim+) of the IL bottom layer lie flat on the graphite surface.

Morphology and Wettability of [Bmim][PF 6 ] Ionic Liquid on HOPG Substrate

We investigate the morphology and wettability of [Bmim][PF6] ionic liquid (IL) on a highly oriented pyrolitic graphite (HOPG) substrate using atomic force microscopy. Thin films, nanometer-sized droplets, and drop-on-layer structures of the IL are found on the substrate. Films with a thickness of up to 2 nm (about 4 IL layers) show the solid-like behavior. In contrast, a dewetting phenomenon is observed for thicker IL films, indicating that the IL films retain liquid properties. The contact angle of a buck IL droplet on the HOPG is measured to be about 35°. The wettability of the bulk IL droplet on the HOPG is found to be quite different from that of IL films. These results indicate that the IL molecules can be organized into various micro-morphologies when they are confined to a solid substrate and show characteristic behavior at nanometer scales.

Uranium extraction from simulated salt lake water by an amidoxime-based UHMWPE fiber

A batch of amidoxime (AO)-based ultra-high molecular weight polyethylene (UHMWPE- g -(PAO-co-PAA)) fiber was prepared by a 7u2005L graft polymerization reaction kettle. The chemical structure and morphology were evaluated by means of Fourier transform infrared spectrometry and scanning electron microscope, respectively. The uranium adsorption behaviors of the UHMWPE- g -(PAO-co-PAA) fiber were studied by batch adsorption in simulated salt lake water. Effect of the total dissolved solids (TDS) and initial concentration of uranium on the adsorption behaviors of the fiber was investigated. It was found that after 28u2005d adsorption in the simulated DagzeCo salt lake water, UHMWPE- g -(PAO-co-PAA) fiber with an AO density of 6.0u2005mmolu2005g−1 exhibited a uranium adsorption capacity of 8.29u2005mgu2005g−1. The adsorption capacity decreased with the increment of TDS. In the simulated salt lake water in which TDS was 10 times as the sea water, the adsorption capacity of uranium was 6.63u2005mgu2005g−1. The adsorption capacity increased with the increment of initial concentration of uranium in solution. The uranium adsorption capacity was 4.54u2005mgu2005g−1 in a solution with initial concentration of 187u2005µgu2005L−1 uranium, while the value increased to 17.48u2005mgu2005g−1 with 1639u2005µgu2005L−1 uranium simulated salt lake water solution. This study should shed light on improvement of uranium extraction from salt lake water and further application in uranium recovery from natural resources.

SAXS Studies on the Structure Behaviors of Crosslinked PTFE Irradiated by Gamma Ray

The structural changes of crosslinked polytetrafluoroethylene (XPTFE) by gamma ray irradiation in air at room temperature were studied by thermal analysis and SAXS techniques. The chain scission of irradiated XPTFE was predominant in room temperature and increased with an increase of dose. The crystallization is enhanced by chain scission during irradiation. The melting temperature and melting heat of XPTFE irradiated by gamma ray increased with the adsorbed dose. The scattering intensity of samples decreased with increasing dose. The fractal dimension of sample decreased but the thickness of transition layer parameter becomed smaller before 100 kGy gamma ray dose, and then it increased with dose above 100 kGy Irradiated XPTFE samples exhibited self-similarity structure. Chain scission of XPTFE is responsible for its structural change after XPTFE irradiated by gamma ray in air.