| 研究実績の概要 |
Our research achievements in this project are threefold. First, we have found that the GO-polycation composites coagulate too fast to give uniform slurries and, thus, defect-free gas separation membranes. At high GO-polycation loadings (high concentrations), we could obtain conformal coatings with rod/blade-coating methods. But the resulting membranes became too thick but were still often defective because of fast aggregation. We could produce smoother coatings using non-polyelectrolytes (such as hydrogen-bondable polymers) but still observed only low hydrogen selectivity. However, when we used positively charged nanoparticles and vacuum filtration, we achieved conformal and defect-free membranes, yielding selectivities up to 150 and permeabilities up to around 4000 GPU. Based on the experiments made with polymer-free nanosheet dispersions, we also found that vacuum filtration can be used for compacting membranes that are prepared by other coating methods such as spray-coating. Overall, this collaborative research resulted in the establishment of four fundamental notions: (1) Electrostatic interactions are highly effective in stabilizing GO-based membranes; (2) guided-assembly methods (such as vacuum-assisted filtration and vacuum-spray-coating) should be optimized for achieving defect-free membranes; (3) composite membranes should be polymer-free or rich in nanosheets for developing defect-free membranes with high hydrogen selectivity.
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