【作者】 徐伟；

【导师】 黄涛；

【作者基本信息】 中南民族大学 ， 物理化学， 2007， 硕士

【摘要】 双金属纳米颗粒就是包括两种不同的金属原子的纳米颗粒,与单金属纳米颗粒相比较,双金属纳米颗粒具有以下的一些特性:①有助于研究不同金属合金形成过程,为其提供模型;②改变双金属的组成,可以得到与单金属纳米颗粒不同的性质,例如添加第二种金属元素可以改变单金属纳米颗粒的催化活性、选择性和抗失活性等等。③双金属纳米颗粒具有特殊结构,例如,核壳结构、簇簇结构、分离或者任意结构。④改善合成工艺可以节约贵金属材料。本文利用微波辐射法制备了以乙二醇为溶剂、水合肼为还原剂、由聚乙烯吡咯烷酮(PVP)稳定的镍的单金属纳米颗粒,并用紫外-可见光谱(UV-vis)、透射电子显微镜(TEM)以及X-射线衍射(XRD)对其进行了表征。通过改变反应条件,可以控制其平均粒径在50 nm～100 nm之间,与传统的油浴加热法相比较,突出了该法快捷、方便、重现性好、分散性好、均一性高的优点。而且在成功微波法制备单金属纳米镍颗粒的基础上,通过共还原制备了钯-镍双金属纳米颗粒。通过钯的加入使得双金属纳米颗粒的平均粒径较单金属镍的纳米颗粒的平均粒径明显减小,通过控制反应条件以及调整初始反应物中钯、镍两种元素的摩尔比,可以控制其平均粒径在10 nm以下。透射电子显微镜(TEM)显示此法制备的钯-镍双金属纳米颗粒的平均粒径随着双金属组分中镍的含量的增加呈逐渐增大的趋势。通过X-射线衍射(XRD)表征发现其具有不同于单金属的结构。此外,本文还以硼氢化钾为还原剂制备了三缩四乙二醇稳定(溶剂稳定)的钯-镍双金属纳米颗粒,通过控制反应条件以及调整初始反应物中钯、镍两种元素的摩尔比,可以控制其平均粒径在1.88 nm～3.56 nm之间,其平均粒径随双金属组分中镍含量变化而变化的趋势与微波法类似。最后本文分别以环己烯和大豆油为底物对溶剂稳定的钯-镍双金属纳米颗粒在室温下对不饱和双键的催化氢化性能进行了初探,结果表明所制备的溶剂稳定的钯-镍双金属纳米颗粒有很高的催化活性,而且双金属的催化活性在钯含量大于50%时并不随着钯的减少而急剧的降低。更多还原

【Abstract】 Bimetallic nanoparticles are metallic entities comprising of atoms of two different metallic elements. Compared with monometallic nanoparticles, bimetallic nanoparticles are of special interest for several reasons. Firstly, they may serve as models for studying the formation of different alloys. Secondly, these bimetallic particles may have more varied properties than monometallic particles as various combinations are possible. It is well established that the catalytic properties of the monometallic nanoparticles, including activity, selectivity or resistance to deactivation, can be altered by the addition of the second metal. Thirdly, bimetallic particles could have particular structures not seen in bulk alloys, such as core-shell, cluster-in-cluster, separate, random structures, etc. Lastly, it is possible it is possible to save the precious metals by optimizing the synthesis conditionsNickel nanoparticles were prepared by rapid microwave(MV) heating of ethylene glycol solutions of NiCl2 with PVP as the protecting agent and hydrazine hydrate as the reducing agent, and characterized by UV-vis, TEM, and XRD. The average size of the nanoparticles can be controlled between 50 nm to 100 nm by changing the concentration of PVP, hydrazine hydrate and NaCO3. The resluts indcated the method of rapid microwave heating was prefer to traditional heating due to its better repeatability, homogeneity and dispersity, etc. Pd-Ni bimetallic nanoparticles were also prepared by rapid microwave(MV) heating and the average size of the bimetallic nanoparticles obtained diminished evidently by the addition of Palladium. And the everage size of Pd-Ni bimetallic nanoparticles can be controlled to between 1.82 nm to 8.51 nm by changing the condition of reaction and the molar ratio of Palladium to Nickel. TEM investigation showed that the everage size of Pd-Ni bimetallic nanoparticles increased with increasing Nickel content.Furthermore,Pd-Ni bimetallic nanoparticles were prepared with NaBH4 as the reducing agent and tetraethylene glycol as the solvent. The average size of the solvent stabilized Pd-Ni bimetallic nanoparticles can be controlled between 1.88 nm to 3.56 nm by changing the condition of reaction and the molar ratio of Palladium to Nickel. The TEM results showed that their average size increased with increasing Nickel content, this is similar to the Pd-Ni bimetallic nanoparticles prepared by rapid microwave heating. In the last chapter, the catalytic hydrogenation activity of solvent stabilized Pd-Ni bimetallic nanoparticles was investigated and reported. The results showed that the catalytic hydrogenation activities for cyclohexene and soybean oil of the solvent stabilized Pd-Ni bimetallic nanoparticles are very high compared to that of the conventional catalyst. The activity did not decreased sharply by lower Palladium content when it was > 50%.更多还原