Poly(methyl methacrylate)(PMMA)pellets are irradiated using 60Co gamma-ray in air and successfully formed by hot pressing at constant conditions.The irradiated PMMA membranes are prepared by supercritical carbon dioxide(scCO2)as a physical blowing agent using the pressure quench method.Effects of foaming conditions such as adsorbed dose,saturation temperature,pressure on the morphology and cell size of the microcellular PMMA membranes are investigated in detail.The results showed that the irradiated PMMA membranes possess spherically closed-cell structure with uniform cell size.They have a high cell density compared with virgin PMMA.The cell size uniformity becomes poor at dose lower than 10 kGy,but increases with the dose at dose higher than 10 kGy.The mean cell diameter is less than 10μm and the cell density increases with increasing dose.The average cell size of irradiated PMMA membranes decreases and cell density increases with increased saturation temperature and pressure.The changes in morphology of membranes are attributed to the gamma-ray radiation and scCO2synergistic effect.
To investigate the corrosion products of Cr in molten FLi Na K salt(46.5 mol% Li F–11.5 mol% Na F–42mol% KF), the corrosion test of the pure metal Cr was performed in molten FLi Na K salt at 700?C for 200 h.The FLi Na K salt after the corrosion test was thoroughly investigated by X-ray absorption near-edge structure spectroscopy, a transmission electron microscope, and X-ray diffraction. The results demonstrate that the predominant oxidation state of Cr in FLi Na K salt is Cr^(3+), and the main corrosion product in cooled FLi Na K salt is K_2NaCrF_6.
