Atomic oxygen(AO)found in low earth orbit can cause serious erosion to polyimide(PI)materials,which greatly limits their lifetime.8-phenyl silsesquioxane(OPPOSS)was synthesized,and OPPOSS/PI composites were prepared by physical blending,followed by thermal imidization to enhance the AO erosion resistance of PI materials.The morphology,composition,and structure of the composites were analyzed before and after AO exposure in a ground simulated facility of atomic oxygen.After 16 h AO exposure,the OPPOSS/PI composite with 5wt%OPPOSS addition shows an erosion rate of about 1.4×10 24cm3/atom with only 48%mass loss of that of PI without OPPOSS addition.The mixture of OPPOSS nano molecules is assembled into a kind of regular square structure and distributed evenly in OPPOSS/PI composites.Some SiO2particles are formed in the composites during AO exposure,which can act as"inert points"to reduce the AO erosion rate of OPPOSS/PI composites.
以MnSO_4·H_2O为锰源,K_2S_2O_8为氧化剂,制备了4种含有不同层间阳离子(Me,Me=Mg^(2+)、Co^(2+)、Ni^(2+)、Cu^(2+))的buserite型氧化锰(Me-buserites)。采用X射线衍射(XRD)、电感耦合等离子体原子发射(ICP-AES)和N2吸附–脱附(BET)对制成Me-buserites的晶相结构、元素组成和比表面积进行了表征。采用25 m L间歇式玻璃反应器,考察了Me-buserites催化叔丁基过氧化氢歧化分解反应动力学。反应动力学分析表明:反应底物叔丁基过氧化氢浓度项反应级数为2,Me-buserites形式浓度项反应级数为1,总反应级数为3;表观活化能为56~125 k J/mol。与动力学拟合结果相一致的反应机理是由前置平衡和速控两个反应步骤组成。基于338 K反应温度准二级速率常数和0.5 h反应时间累积O_2体积决定的活性顺序为Cu-buserite>Mg-buserite>Ni-buserite>Co-buserite;在选定反应条件下,所有Mebuserites的叔丁醇选择性均为100%。
