Modification Of Sio <sub> 2 </ Sub> Of Mechanical And Chemical Preparation Of Ultrafine Powders, Composite Proton Exchange Membrane

Modified silicon dioxides were fabricated by being ball milled under different grinding conditions, and characterized using thermogravimetry analysis(TGA), X-ray powder diffraction analysis(XRD), scanning electron microscope(SEM), Fourier transform infrared spectroscope (FT-IR) and laser particle size analysis. The effects of the grinding time, the grinding medium, the ball style and the modifiers (silane coupling agent and polymer) on the changes of structures of SiO₂ were studied. The thermal behaviors of silicon dioxides with or without modification were also investigated. Meanwhile, the influence on zeta potential of silicon dioxides and montmorillonite were studied. The effects of inorganic particle and concentration of sulfonated poly(ether ether ketone)s (abbrev as SPEEK) on the rheological properties of (modified) inorganic particle/SPEEK slurry, the morphology and the mechanical properties of the composite menbranes were discussed after testing the sedimentation, SEM and tensile strength.The summarized conclusions of this paper are as follows:(1) The changes of crystallite sizes, Lattice distortion average values and Particle size of silicone dioxides being ball milled in air is more obvious than those being ball milled in DMF.(2) Being ball milled in DMF with silane coupling agent, the crystallite sizes, lattice distortion average values and Particle sizes of silicone dioxides decrease. The results indicate that silane coupling agent KH560 is chemically absorbed onto the surface of modified silicon dioxide ground in planet mill.(3) The differences between the thermal behaviors and Zeta potential of modified silicon dioxides depend on the structural changes of corresponding modified silicon dioxides.(4) All the studied slurry belongs to Bingham fluid and is almost Newtonian fluid with increasing the amount of inorganic particles.(5) The TGA shows that the decomposition of homogeneous membranes goes though three stages, and that of the composite membranes goes though two stages. The thermostability of membranes improves greatly when Inorganic particles are added between 323K and 873K.(6) The conductivity and tensile strength of membranes improve with the addition of silicone dioxides. SEM indicates that the 1% silicone dioxides with silane coupling agent are the best homogeneous in the polymer composite membranes which are dispersed as nano-size particles. Modified montmonllonites also disperse well and nearly act as nano-size particles in polymer composite membranes.