Preparation and Properties of MnO_2 /polyaniline Composite

以δ-MnO2为前驱体,通过酸处理后引入苯胺并聚合,得到了MnO2/聚苯胺复合材料。经XRD分析表明,在本研究条件下,经酸处理后的δ-MnO2晶型由δ型转变为α型,而在随后的苯胺引入及其聚合步骤中MnO2晶型均不再改变。以200mA·g-1的电流进行恒电流充放电性能测试,结果显示,MnO2/聚苯胺复合材料的充放电容量达到160.2mA·g-1,与酸处理后得到的α-MnO2接近(160.9mA·g-1),但比前驱体δ-MnO2高(125.8mA·g-1);更为重要的是,MnO2/聚苯胺复合材料与前驱体及酸处理得到的样品相比,其循环性能得到了较大的提高。MnO2 /polyaniline composite was prepared by polymerization of aniline in α-MnO2 from the acid-treating precursor of δ-MnO2. XRD results showed that during acid treatment the precursor of δ-MnO2 was transformed into α-MnO2, and this in α-MnO2 polymorph kept unchanged in the subsequent processes, as intercalation and polymerization of aniline. Comparison of charge-discharge performances among the precursor, its acid-treated form and the final composite, showed that at current density of 200 mA·g-1 the discharge capacity of the composite was 160.2 mA·g-1, which is close to that of the acid-treated material (160.9 mA·g-1) but higher than that of the precursor (125.8 mA·g-1). More important, the MnO2 /polyaniline composite showed a much better cyclic performance than the precursor and its acid-treated form.福建省高新技术重点项目(No2005H071);; 三明市重点科技项目(No2005-G-9

Preparation and properties of MnO2/polyaniline composite

MnO2/polyaniline composite was prepared by polymerization of aniline in alpha-MnO2 from the acid-treating precursor of delta-MnO2. XRD results showed that during acid treatment the precursor of delta-MnO2 was transformed into alpha-MnO2, and this in alpha-MnO2 polymorph kept unchanged in the subsequent processes, as intercalation and polymerization of aniline. Comparison of charge-discharge performances among the precursor, its acid-treated form and the final composite, showed that at current density of 200 mA . g(-1) the discharge capacity of the composite was 160.2 mA.g(-1), which is close to that of the acid-treated material (160.9 mA . g(-1)) but higher than that of the precursor (125.8 mA . g(-1)). More important, the MnO2/polyaniline composite showed a much better cyclic performance than the precursor and its acid-treated form

Preparation and Properties of δ-MnO_2

用过二硫酸铵((NH4)2S2O8)氧化Mn(Ⅱ)盐制备-δMnO2。比较了反应过程中Mn2+与OH-的摩尔比、反应温度、(NH4)2S2O8用量等因素对MnO2晶型的影响。用X射线衍射(XRD)、红外光谱(IR)分析了制得的-δMnO2的结构。测试了样品的热性能和循环伏安、恒电流充放电性能。结果表明所制备的-δMnO2具有良好的层状结构,热稳定性能较好,放电容量较高(约160mA.h/g,2.0~4.5V)。δ-Manganese dioxide(δ-MnO_2) was prepared from a Mn(Ⅱ) salt oxidized by ammonium persulfate ((NH_4)_(2)S_2O_8). The crystalline form of the δ-MnO_2 was affected by the molar ratio of Mn~(2+) to OH~(-), (reaction) (temperature), and the amount of (NH_4)_2S_2O_8. The structure of the δ-MnO_2 was characterized by means of X-ray (diffraction)(XRD) and Infrared spectroscopy(IR). Its electrochemical performance was also (studied) via cyclic voltammetry and constant current charge/discharge experiments. The results indicate that (as-prepared) δ-MnO_2 has a good layer-structure and a high discharge capacity(~160 mA·h/g, 2.0~(4.5 V)).福建省教育厅资助项目(JB02193

高速进气道低马赫数不起动特性及马赫数影响规律

为了探究进气道低马赫数不起动时的振荡特性,本文结合一体化前体/进气道构型,通过非定常仿真手段,对比研究了来流马赫数变化对进气道低马赫数不起动振荡流场以及飞行器气动力的影响规律。结果表明:低马赫数不起动时出现了稳定的振荡周期,且周期随着来流马赫数的增大而增长。由于拥塞发生在喉道处,其振荡流场单纯地表现为口部分离包的涨大和缩小,并且沿程压力的均值和幅值都呈现出喉道高两头低的分布趋势,而马赫数的增大会加剧此趋势。喘振周期中升力系数CL和阻力系数CD的变化趋势大致相反,升阻比曲线则表现为随分离包吐出而增大、吞入而缩小的趋势。CL和CD随着马赫数增大是整体下降的,但是脉动幅值变化不大,升阻比对马赫数的变化也并不敏感。此外,在进气道实现自起动过程中,当喉道瞬时流量高于起动时的流量一定程度,口部分离包将完全吞入。但定常仿真难以准确模拟该吞入过程,因此定常仿真得到的自起动马赫数偏高

纳米Fe3O4／聚苯乙烯均匀分散体系的制备及结构

用化学共沉淀法制备了Fe3O4纳米颗粒．以油酸为表面活性剂．苯乙烯为载液，制备了稳定的纳米Fe3O4可聚合磁流体．将可聚合磁流体经自由基引发聚合制成纳米Fe3O4／聚苯乙烯均匀分散体系．用WAXRD研究了Fe3O4纳米粒子的结晶情况；用FTIR研究了油酸表面改性前后Fe3O4粒子表面官能团的变化；用TEM研究了Fe3O4颗粒的粒径大小及其在苯乙烯单体和聚苯乙烯中的分散情况；用DSC和TGA研究了纳米Fe3O4／聚苯乙烯均匀分散体系的玻璃化转变温度(Tg)和热稳定性．结果表明．合成的纳米Fe3O4为立方晶型，平均粒径在10nm左右．油酸分子在Fe3O4表面是化学吸附，经表面处理的Fe3O4超细颗粒在苯乙烯和聚苯乙烯基体中分散较均匀。界面粘结较好．含1．8％Fe3O4纳米颗粒的聚苯乙烯的最大热失重温度比聚苯乙烯提高了13K，Fe3O4／聚苯乙烯复合体系的饱和磁化强度σg为17．43emu／g

纳米Fe_3O_4/聚苯乙烯均匀分散体系的制备及结构

用化学共沉淀法制备了Fe3O4纳米颗粒．以油酸为表面活性剂．苯乙烯为载液，制备了稳定的纳米Fe3O4可聚合磁流体．将可聚合磁流体经自由基引发聚合制成纳米Fe3O4／聚苯乙烯均匀分散体系．用WAXRD研究了Fe3O4纳米粒子的结晶情况；用FTIR研究了油酸表面改性前后Fe3O4粒子表面官能团的变化；用TEM研究了Fe3O4颗粒的粒径大小及其在苯乙烯单体和聚苯乙烯中的分散情况；用DSC和TGA研究了纳米Fe3O4／聚苯乙烯均匀分散体系的玻璃化转变温度(Tg)和热稳定性．结果表明．合成的纳米Fe3O4为立方晶型，平均粒径在10nm左右．油酸分子在Fe3O4表面是化学吸附，经表面处理的Fe3O4超细颗粒在苯乙烯和聚苯乙烯基体中分散较均匀。界面粘结较好．含1．8％Fe3O4纳米颗粒的聚苯乙烯的最大热失重温度比聚苯乙烯提高了13K，Fe3O4／聚苯乙烯复合体系的饱和磁化强度σg为17．43emu／g

高马赫数超燃冲压发动机技术研究进展

吸气式高超声速飞行在空间运输和国家空天安全领域具有极高价值,超燃冲压发动机是其核心动力装置.目前飞行马赫数4.0～7.0超燃冲压发动机技术日趋成熟,发展更高速的飞行动力技术成为今后临近空间竞争焦点之一.本文对飞行马赫数8.0～10.0的高马赫数超燃冲压发动机技术进行了分析和综述.首先论述其亟待解决的关键问题和技术,分别包括高焓离解与热化学非平衡效应、超高速气流燃料增混与燃烧强化技术、高超声速燃烧与进气压缩的匹配及工作模态、高焓低雷诺数边界层流动及其控制方法、高焓低密度流动/燃烧的热防护技术,以及高马赫数发动机的地面试验风洞技术.然后,进一步介绍了国内外高焓激波风洞与驱动技术以及国内外典型的地面和飞行试验进展.进而针对推进和热防护的总体性能评估、高马赫数发动机内凸显的高焓离解与热化学非平衡效应、超高速气流燃料增混和燃烧强化技术综述了相关研究进展及结论,讨论了高马赫数超燃冲压发动机的可行性以及各关键技术的特点.最后进行了总结并对后续研究提出了几点建议