【作者】 甘颖；

【导师】 徐国财；

【作者基本信息】 安徽理工大学 ， 应用化学， 2012， 硕士

【摘要】 采用超声辐射方法,合成了具有管状结构的纳米Pd/PEG复合材料。探讨了超声波还原机理以及不同分子量的PEG对二价钯离子的还原能力,并利用TEM,XRD, XPS等手段表征了超声合成的复合材料,初步研究了复合材料的流变性能。(1)采用超声波辐射的方式,合成出了有特殊结构的纳米Pd/PEG复合材料。在相同的条件下,讨论了不同分子量的PEG对还原二价钯离子的影响；UV-Vis表明纳米钯粒子在430nm处有吸收峰,且峰型较窄,PEG600的还原能力比较强,这是因为单位体积中,羟基越多,还原Pd2+的能力越强,即还原出来的纳米钯粒子越多；TEM显示所得到的纳米复合物是管状结构,钯粒子均匀地分散在PEG管腔中,而且钯晶颗粒规整。(2)在PEG保护下,反应体系的颜色均由最初的浅黄色逐渐转为深褐色,最后变为黑褐色。对制得的纳米钯悬浮液进行TEM、HRTEM等表征手段进行分析表明,PEG呈长约0.5μ m,直径为50-80nm的管状结构,并将部分纳米钯粒子包覆在其中,达到稳定纳米钯粒子的作用,而且纳米钯粒子的尺寸在5—10nm,呈球形或方形。XRD揭示了单分散纳米金属钯颗粒的5个晶面衍射特征峰,充分表明超声合成的纳米钯是具有面心立方结构的纳米粒子。XPS表明复合材料中PEG的C-OH中Ols结合能(532.3eV)比C-OH中的Ols的标准结合能(532.8eV)降低了0.5eV,说明聚合物中羟基上的氧原子和纳米钯之间形成了一定的相互作用。(3)采用循环剪切模式考察了剪切时间对剪切应力的影响以及体系的触变性,结果表明,与PEG600相比,纳米Pd/PEG600复合体系的最大应力提高了近5倍；体系的触变性也有了较大提高,提高了28.4%,可能是由于纳米钯与PEG600形成了管状结构的缘故。更多还原

【Abstract】 Nano-palladium/Poly(ethylene glycol) composite materials with tubular structure were synthesized by ultrasonic irradiating. The mechanism of ultrasonic reduction and the reduction ability of Poly(ethylene glycol) of different molecular weight for Pd2+were discussed, the composite materials were characterized by means of TEM, XRD, XPS and so on. The rheological properties of the nanocomposites were also studied.(1)Nano-Pd/Poly (ethylene glycol) composite materials with particular structure were synthesized by ultrasonic irradiating. The reduction ability of PEG of different molecular weight for pd2+ion under the same. conditions were discussed. The results of UV-Vis spectrum showed that there was a strong but narrow absorption peak at430nm for nano-Pd particles.The reduction ability of PEG600was stronger than that of others due to more content of hydroxyl groups in the same volume.The more the hydroxyl groups,the more the nano-palladium particles reduced from Pd2+ion.The TEM of the nanocomposites showed that the nano Pd particles with uniform size well dispersed within the tube formed by PEG,the nanocoposites was of tubular structure.(2) The color of the reaction system was initially yellow, with a gradient moving to brown,and finally became black within the protection of PEG600. TEM showed that PEG displayed a clubbed structure with the length of about0.5μm and5-10nm in diameter. Part of the nano-Pd particles were buried into the tube so as to make them more stable. This resulted in spherical or square particles of Pd with5-10nm in size.By the examination of XRD. the five strong characteristic peaks are ascribed to the formation of monodispersed nano-Pd particles with face-centred cubic structure.XPS indicated that Ols binding energy (532.3eV) of C-OH on PEG dropped down0.5eV compared to the standard, it proved that there existed interaction between hydroxyl oxygen and the nano-Pd.(3) The influence of shear time on shear stress and thixotropy were studied by using cyclic shear mode, and the results showed that the maximum stress of nano Pd/PEG600composite increased nearly five times than that of PEG600;the thixotropy of system improved up to28.4%.probably due to the formation of tubular structure formed by nano-Pd and PEG600.更多还原