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二氧化硅@聚合物同轴纳米纤维 总被引:1,自引:0,他引:1
The preparation and formation mechamsm ot silica/polyvinylpyrrolidone(PAN) coaxial nanofibers were presented in this paper. The PVP-PAN composite nanofibers were obtained via an electrospinning technique, while SiO2 nanoparticles were prepared according to a Stoeher method. The measurements of water contact angle(WCA), the compared results of silica coating PVPPAN composite nanofibers with PAN nanofibers indicate that much PVP resided on the composite nanofiber surface, which resuks in the occurrence of SiO2@polymer coaxial nanofibers due to the formation of hydrogen bonding between silica and composite nanofibers and subsequent adsorption of silica on the fiber surface. 相似文献
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纳米胶囊相变材料研究进展 总被引:2,自引:0,他引:2
纳米胶囊相变材料是一类新型储能材料.本文介绍了纳米胶囊相变材料的研究背景、发展历程和优势;分析了相变储能纳米胶囊的结构、原理及其功能,包括囊芯与囊壁的种类及选材原则,微胶囊与纳米胶囊性质比较;重点介绍了细乳液聚合、原位聚合和界面聚合等纳米胶囊制备方法的原理及研究进展,并对相变储能纳米胶囊在建筑节能、功能热流体、服装、航空航天及军事等领域的应用作了总结. 相似文献
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近年来聚合物微/纳米纤维膜因具有比表面积大、密度低、孔隙率高、孔间结合性良好、易与纳米尺寸的活性物质结合等系列优异性能而受到越来越多的关注。本文归纳了聚合物微/纳米纤维的制备及其发展;分类介绍了聚合物微/纳米纤维膜的研究进展和表征方法;同时概述了聚合物微/纳米纤维膜应用在过滤材料、医药、组织工程等方面的研究情况。 相似文献
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以石蜡为芯材,甲基丙烯酸甲酯-丙烯酸共聚物为壁材,纳米SiO2为改性剂,采用原位聚合法制备了石蜡微胶囊相变储能材料,系统研究了添加纳米SiO2对石蜡微胶囊相变材料性能的影响;采用傅里叶变换红外光谱(FTIR)、扫描电子显微镜(SEM)、示差扫描量热法(DSC)和热重分析(TGA)等对石蜡微胶囊相变材料的化学结构、表面形貌和热性能进行了表征.研究表明,纳米SiO2能够有效提高微胶囊壁材的热稳定性,当丙烯酸酯壁材中添加3%改性纳米SiO2时,微胶囊呈球形且表面光滑,尺寸250 ~ 300 nm,具有良好的储热能力,相变潜热高达134.79 J/g,分解温度比未添加改性纳米SiO2的石蜡微胶囊提高了40 K,经过1000次热循环测试,石蜡渗漏率仅2.96%. 相似文献
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硒,砷在水稻体内的相互作用及其自由基机理的研究 总被引:13,自引:0,他引:13
以水稻为对象观察了砷(NaAsO2)的毒性作用及硒、砷毒性的相互作用。当培养液中砷(NaAsO2)的浓度约大于0.1×10-6时,砷会抑制水稻的生长。当硒(Na2SeO3)的浓度范围在0×10-5~1×10-6时,硒能拮抗砷的毒性,但硒的浓度大于1×10-6时,硒会增加体系的毒性。有关作用的机理为自由基机理。 相似文献
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We present a first principles study of the equilibrium structures and relative thermodynamic stability of the three observed polymorphs of rhodium(III) sesquioxide. The thermodynamic Gibbs free energies for each phase are calculated as a function of P and T based on the electronic total energy, as well as vibrational energy and vibrational entropy contributions in the local harmonic (LH) approximation. The results confirm that Rh2O3 I is a low-temperature, low-pressure form and Rh2O3 II is a high-pressure form. A breakdown in the LH approximation at high T is then discussed and to address this breakdown an empirically corrected local harmonic (ECLH) approximation is introduced. ECLH demonstrates that the high-temperature, low-pressure form Rh2O3 III is entropically stabilized and produces a partitioning of phase space that is consistent with published experimental investigations. 相似文献
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Macrocyclic polyethers, e.g., crown ethers and cryptands, were prepared and employed as phase transfer catalysts for free radical polymerization of acrolein, a vinyl monomer, with persulfates (S2O82–) as initiators. The catalytic abilities of various macrocyclic polyethers as catalysts for the free radical polymerization of acrolein were found to be in the order: benzo‐15‐crown‐5 > dibenzo‐18‐crown‐6 > 12‐crown‐4 > 15‐crown‐5 > 18‐crown‐6 > cryptand‐22 with sodium persulfate (Na2S2O8) as initiator. Sodium persulfate proved to be a better initiator than ammonium persulfate or potassium persulfate with benzo‐15‐crown‐5 as a catalyst. Effects of solvents and temperature on the catalytic polymerization were also investigated. The polymerization rates in various solvents were in the order: dioxane > benzene > acetonitrile > acetone > dichloromethane > hexane > water. Comparison between bulk polymerization and solution polymerization was also made. Higher polymerization rate was observed at higher temperature. The molecular weights of polyacrolein and the conversion of monomer in reaction period were determined with gel permeation chromatography and ultra‐violet spectrophotometry, respectively. Concentration effects of crown ether and initiator were also investigated and discussed. 相似文献
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运用数据处理软件(maple)对经典的自由基二元聚合公式进行图形绘制,得到了二元单体之间共聚关系的三组图.一是二元单体的自由基共聚曲线图F1-f1,二是聚合物中单体平均组成(Fp)与投料单体浓度(f1)的关系曲线图,三是聚合物转化率(C)与投料单体(f1)的关系曲线图.通过二组具有代表性的共聚实例,分别是有恒比点的非理... 相似文献
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季铵盐型离子导电聚合物的研究 总被引:2,自引:0,他引:2
对聚苯胺呋喃季铵盐的物理性质及导电机制进行了分析讨论。结果表明,所制备的季铵盐最高电导率可达10^-4S·cm^-1量级,其导电性随季铵化程度增加而增加,温度、湿度对其导电性有较大的影响;在环境温度、湿度基本恒定的条件下,季铵盐有较好的电导稳定性。此季铵盐是通过离散的阴离子而传导,通过链段运动传输电荷。 相似文献
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Using the ns pulse radolysis, we studied the characteristic absorption spectrum and kinetic decay of cytosine anion radical (Cyt-). Results showed that the characteristic absorption of Cyt- was located at λ=355±5 nm, and decayed following the first order kinetics with τ1/2=265 ns at pH=7.0. The decay became slower and τ1/2 rapidly rised with the increment of pH value, Cyt- protonated at C6 in acidic solution, and the characteristic absorption was located at λ=310±5 nm, and decayed following the second order kinetics: Cyt- protonated at N3 in aqueous solution of pH≥7, and the characteristic absorption was located at λ=295±5 nm, and decayed following the second order kinetics. 相似文献
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淀粉系高吸水性树脂反应中间体稳定性及反应活性的量子化学研究 总被引:1,自引:1,他引:0
运用abinitioUHF方法和DFTUB3LYP方法在6-31G基组水平下对淀粉系高吸水性树脂反应中间体的模型体系进行几何构型优化.针对每类自由基对应得到的两种典型的构象异构体(1a,1b和2a,2b),进行稳定性和反应活性分析.构型1a和2b的总能量相对较低.比较4个模型体系的前线分子轨道,构型1a的能隙较小,同时HOMO能量较高,易给出电子,LUMO能量较低,易得电子,有利于电子转移,因而有较好的反应活性.自由基自旋密度主要集聚在C2或C3上,未有较大弥散,同时也是前线MO主要布居位置和重要的反应活性部位.对构型1a与丙烯酸模型分子形成的复合物分析表明,两者的反应未经过过渡态,在瞬间即可完成. 相似文献
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