【作者】 张锡凤；

【导师】 程晓农； 殷恒波；

【作者基本信息】 江苏大学 ， 材料学， 2008， 博士

【摘要】 纳米材料具有很多异乎寻常的特性,有着极为广泛的应用前景,是当前材料科学的研究前沿。纳米金属优异的性能赋予其潜在应用价值,其研究引起国内外普遍重视,是目前材料、化工研究的新方向,受到材料学界、物理学界、化学界和产业界的普遍关注和重视。本论文综合分析近年来国内外纳米金属的制备方法,以设备简单、反应条件温和、易于工业化的化学还原法为制备工艺路线,以当前纳米金属的研究热点—粒度、形貌、结构可控纳米金属的制备为研究内容,以广阔应用在高效催化剂、固体润滑剂等方面的国内外新颖功能材料纳米铜(Cu)、镍(Ni)为研究对象,探索反应体系、母体和还原剂的种类、反应时间和反应温度等制备技术、工艺参数等因素的影响作用,获得成熟而稳定的粒径、形貌可控纳米金属Cu、Ni的制备技术。修饰剂的选择是制备粒径、形貌可控纳米金属的关键,因此本论文重点研究不同种类修饰剂对纳米金属Cu、Ni粒径、形貌影响的规律性及其作用机理。本研究首次采用吐温系列(Tweens)和聚乙二醇系列(PEGs)单独或与十二烷基硫酸钠(SDS)、十二烷基苯磺酸钠(SDBS)复配作为修饰剂使用,以化学还原法,在低温、常压下分别以维生素c(Vc)、水合肼和1,2丙二醇为还原剂,还原硫酸铜、硫酸镍和醋酸镍母体,制备出粒径、形貌可控的纳米金属Cu、Ni。分别用x-射线衍射(XRD)、X-射线光电子能谱(XPS)、透射电镜(TEM)、选区电子衍射(SEAD)对产物的粒径、形貌和晶型结构进行表征,利用傅里叶变换红外光谱仪(FTIR)和差热—失重分析仪(TG-DSC)研究不同修饰剂单一或复配使用时对纳米金属Cu、Ni粒径、形貌及分散抗团聚、抗氧化能力的影响及其作用机理。纳米金属用做润滑油添加剂可优化润滑油的润滑性能。本论文将制备的纳米金属Cu、Ni产物分别添加到不同种类的润滑油中,利用UNT-Ⅱ摩擦磨损试验机和M-2000型环/块式摩擦磨损试验机检测该润滑油的润滑特性,以研究不同尺寸、形貌的纳米金属Cu、Ni对摩擦表面的减摩、抗磨和修复机理的影响规律。取得了如下结果:1)在单一修饰剂中,PEG-2000的采用利于获得小尺寸、粒径分布狭窄的球形纳米Cu(平均粒径2.5nm,粒径范围0.5-3nm);PEG-6000利于获得较大尺寸、粒径分布较宽的球形纳米Cu(平均粒径17.0nm,粒径范围5-25nm)。在复配修饰剂中,SDBS+PEG-2000诱导生成了单晶二维纳米Cu带;SDBS+PEG-6000形成较大尺寸、粒径分布较宽且随粒径增加从球形到不规则形状的纳米Cu(平均粒径21.8nm,粒径范围5-35nm)。2)水体系中,单一修饰剂的使用利于获得球形或类球形纳米Ni,复配修饰剂的使用利于获得雪花状或针刺状纳米Ni。PEG-2000、Tween-80的使用利于获得小尺寸、粒径分布狭窄的球形或类球形纳米Ni(平均粒径53nm和36nm,粒径范围24-106nm和25-52nm),PEG-6000利于获得较大尺寸、粒径分布较宽的类球形纳米Ni(平均粒径167nm,粒径范围76-310nm)。SDS和PEG-600的复配利于减小产物的尺寸(平均粒径33nm,粒径范围16-78nm),SDS和Tween-80的复配则明显增加产物的尺寸(平均粒径230nm,粒径范围124-480nm)。分析水体系中Cu、Ni产物的粒径、形貌,说明在相同体系中利用化学还原法制备不同纳米金属Cu、Ni时,PEGs系列、Tweens系列及它们与SDS等复配修饰时具有类似的修饰效果,对纳米金属的晶体生长产生相同的协同作用。3)以液相还原法制备纳米Ni为基础,在反应体系中引入微波辅助加热,获得长度和直径在一定范围内变化的针状纳米Ni。4)醇体系中,SDS易于形成粒径较小的雪花状和十二面体纳米Ni,PEG-200与PEG-600易于分别形成大、小雪花状体纳米Ni,PEG-2000易于形成十二面体纳米Ni,PEG-6000易于形成三角形薄片纳米Ni,Tween-20易于形成粒径较小的以十二面体和三角形薄片为主的各种规则纳米Ni,Tween-80易于形成粒径较大的雪花状纳米Ni。PEG-600、PEG-6000与SDS复配后,易于形成粒径较大的雪花状纳米Ni,Tween-40和SDS复配后易于形成粒径较大的十二面体和八面体纳米Ni。分析水、醇体系中Ni产物的粒径、形貌,说明在水、醇体系化学还原法制备相同纳米金属Ni时,同一系列修饰剂对产物的分散、修饰作用正好相反。5)分别用FTIR、TG-DSC分析修饰剂对纳米金属Cu、Ni的作用机理,发现修饰剂与所生成的纳米晶体发生了化学键合作用,利用空间位阻效应及静电效应有效减小了颗粒的团聚和避免了产物的氧化,前者为主导因素,后者为辅助因素。6)探讨不同尺寸、形貌的纳米金属Cu、Ni对摩擦表面减摩、抗磨和自修复的影响和作用机理,初步获得纳米金属Cu、Ni的尺寸、形貌与润滑油润滑性能的改性效果的关系。更多还原

【Abstract】 Nanomatedals,often referred as research forward field of materials science,have widely potential applications because of their special physicochemical properties. Nanostructured metals have recently attracted increasing interests because of their novel properties and potential applications.The research has been a new subject of material science and chemical engineering,and attracted considerable interests in the fields such as materials,physics,chemistry,and industry.A number of methods have been developed to prepare nanostructured metals up to date.Chemical reduction synthesis method was most extensively used and researched because of its simple apparatus,mild reaction condition and easy to production in a large scale.Nano-copper and nano-nickel are extensively concerned functional materials because of their applications span over catalysis,solid lubricantion,and so on. To obtain mature and stable size- and shape-controlled preparation technology of nano-Cu and nano-Ni,more works must be done on researching the effects of operation parameters such as reaction system,precursor,reductant,reaction time and temperature, and so on.The disciplinarian and the effects of different modifiers on the product sizes and morphologies are emphasized researches as being due to that selecting an appropriate modifier is crucial to preparation of size- and shape-controlled nanostructured metal.Size- and morphology-controlled preparations of nano-Cu and nano-Ni have been carded out at low temperature and atmospheric pressure starting from copper sulfate pentahydrate,nickel sulfate pentahydrate or nickel acetate tetrahydrate with ascorbic acid,hydrazine hydrate or 1,2 -propanediol as a reductant in the presence of modifiers such as eco-friendly polyoxyethylene sorbitan monooils (Tweens),polyethylene glycols(PEGs),sodium dodecyl benzene sulfonate(SDBS),and sodium dodecyl sulfate(SDS).The morphologies,size distributions,average particle sizes,and crystalline structures of the as-prepared nano-Cu and nano-Ni samples were characterized by powder X-ray diffraction(XRD),X-ray photoelectron spectrometry (XPS),transmission electron microscopy(TEM),selected area electron diffraction (SAED).The modifying and stabilizing effects of modifiers on the samples were analyzed by thermogravimetric analysis differential scanning calorimetry(TG-DSC), and Fourier transform infraredspectroscopy(FTIR).In order to investigate the promoting effects of nanostructured metals on oil tribological property,the as-prepared nano-Cu and nano-Ni samples were added into different kinds of oils.The experiments were carried out on a UNT-Ⅱfriction-abrasion tester and a M-2000 ring-piece friction-abrasion tester to investigate the effects of the nanostructured metal size and shape on the anti-wear and friction reducing performances as well as the repair-self mechanism of tribopairs.Some significant results are summarized as follows:1)In water system,among the single modifiers,PEG-2000 was beneficial to fabricating smaller sized nano-Cu spheres with an average particle size of 2.5 nm and a size distribution ranging from 0.5 to 3 nm,PEG-6000 beneficial to preparing bigger sized nano-Cu spheres with an average particle size of 17.0 nm and a size distribution ranging from 5 to 25 nm.Among the mixtures of two modifiers,the co-presence of SDBS and PEG-2000 was beneficial to fabricating abundant monocrystal nano-Cu strips.The co-presence of SDS and PEG-6000 favored the formation of big-sized irregular nano-Cu with an average particle size of 21.8 um and a size distribution in a range of 5-35 nm.2)In water system,single modifier was beneficial to fabricating sphere or sphere-like nano-Ni crystals,composite modifiers were in favor of forming snowflake-like and needle-like Ni crystals.Tween-80 was beneficial to fabricating small sphere or sphere-like nano-Ni with an average particle size of 36 nm and a size distribution in a range of 25-52 nm,as well as PEG-2000 did with an average particle size of 53 nm and a size distribution in a range of 24-106 nm.PEG-6000 was beneficial to fabricating bigger sphere or sphere-like Ni crystals with an average particle size of 167 nm and a size distribution between 76 and 310 nm.The co-presence of SDS and PEG-600 were beneficial to decreasing the sizes of nano-Ni with an average particle size of 33 nm and a size distribution 16-78 nm.However,the coexisting of SDS and Tween-80 was in favor of increasing the sizes of nano-Ni with an average particle size of 230 nm and size distribution in arrange of 120-480 um.By analyzing the size and shape of nano-Cu and nano-Ni,it can be concluded that the modifiers,Tweens,PEGs, SDBS,and SDS have the same modification effect on crystal growth during the preparation of nanostructured metals with chemical reduction synthesis method in the water system.3)Needle-like Ni nanocrystals with different lengths and diameters were formed under microwave irradiation in water system using nickel acetate tetrahydrate as a precursor,hydrazine hydrate as a reductant,and sodium hydroxide as a pH adjusting reagent.4)In 1,2-propanediol system,SDS was beneficial to fabricating irregular snowflake-like and dodecahedra Ni crystals with a small average particle size;PEG-200 and PEG-600 beneficial to forming bigger or smaller irregular snowflake-like Ni crystals;PEG-2000 beneficial to fabricating dodecahedra Ni crystals;PEG-6000 beneficial to fabricating triangular Ni crystals;Tween-20 beneficial to forming regular crystals such as dodecahedra and triangular crystals with small particle sizes;Tween-80 beneficial to obtaining irregular snowflake-like Ni crystals with a big average particle size.The co-presence of SDS and PEG-600 was beneficial to forming bigger irregular snowflake-like Ni crystals,as well as coexisting of SDS and PEG-6000 did.The co-presence of SDS and Tween-40 was beneficial to obtaining dodecahedra and octahedral Ni crystals with a bigger average particle size.By analyzing the size and shape of nano-Ni in water or 1,2-propanediol system,it can be concluded that the modifiers Tweens and PEGs have the contrast modification effects on crystal growth during the preparation of nanostructured Ni with chemical reduction synthesis method in water or 1,2-propanediol system.5)The disciplinarian and the modification mechanism of modifiers on the samples were analyzed by TG-DSC,and FTIR.It was found that there were chemical bonds between oxygen atoms present in modifiers and the surface of the as-prepared nanocrystals.Space block and electrostatic effects efficiently reduced grain aggregation and avoided the sample oxidation,in which the former is the priority factor and the latter assisted.6)The effects of the sizes and shapes of nanostructured metals on the anti-wear and friction reducing performances as well as repairing-self mechanism on tribopairs was investigated.It was found that the size and shape of nanostructured metals affected oil tribological property.更多还原