【作者】 李永捷；

【导师】 王春明；

【作者基本信息】 兰州大学 ， 分析化学， 2010， 博士

【摘要】 本博士学位论文在前人相关研究的基础上,采用化学镀和液相还原法,制备了镍1-x-钴x-磷/多壁碳纳米管(Ni1-xCox/MWNTs)、镍-钴-磷/碳化硅(Ni-Co-P/SiC)、镍/化学转化石墨烯(Ni/CCG)、铂/化学转化石墨烯(Pt/CCG)、铂/多壁碳纳米管(Pt/MWNTs)五种新型纳米材料;用扫描电子显微镜(SEM)、透射电子显微镜(TEM)研究了这些材料的形貌特征：用X射线粉末衍射仪(XRD)、X光电子能谱仪(XPS)、X射线能谱仪(EDX)分析了这些材料的晶格结构和元素组成；用振动样品磁强计(VSM)、矢量网络分析仪分析了Ni1-xCoxP/MWNTs、Ni-Co-P/SiC和Ni/CCG的磁学、吸波性质；用电化学方法研究了Pt/CCG、Pt/MWNTs作为直接甲醇燃料电池催化剂的催化性能。研究内容主要包括：1.将多壁碳纳米管用浓硝酸煮沸处理、SnCl2、PdCl2溶液敏化活化之后,在自配的化学镀Ni-Co溶液(Ni：Co=1：3、1：1、3：1)中施镀,得到Ni1-xCoxP/MWNTs复合材料(x=0.75,0.50,0.25,Ni1-xCoxP的粒径分布在8-18nm)。XRD数据显示,与MWNTs复合的Ni1-xCoxP纳米粒子在经过热处理之后具有晶格结构,以不规则的点状结构分散在MWNTs的外壁上。样品的磁学性能测量结果指出,所制备材料的矫顽力和磁化强度都随着Ni含量的增加而降低。在频率2-18GHz范围内,Ni1-xCoxP/MWNTs-石蜡的混合物的复介电常数值随着Ni含量的增加而降低；复数磁导率只有微小的增加。随着Ni含量的降低,所制备材料的电磁波反射损失最高峰向低频区域移动,并且当x=0.75且匹配厚度为2.5mm时,在7.75GHz处出现最大的反射损失-26.84dB。2.使用两步活化法的化学镀技术,将Pd活化后的SiC放入自配的Ni-Co溶液中施镀得到Ni-Co-P/SiC复合材料。形貌和结构分析证明Ni-Co-P的颗粒均匀性好,并且在热处理之后由α-Co和Ni3P组成。磁学性质分析和微波吸收测试结果表明,Ni-Co-P/SiC的饱和磁化强度以及矫顽力都比较低,具有较高的介电常数值,磁损耗对材料的微波吸收性能也有一定的贡献。电磁波反射损失测量结果显示,当起始溶液中Ni-Co的原子比例为1.5时,最大的反射损失值是-32dB,此时的匹配厚度为2.5mm、频率为6.30GHz。3.使用水合肼还原法,用NiSO4、氧化石墨(Graphite Oxide, GO)分别作为Ni和碳质载体的来源,制备了Ni/CCG复合材料。磁学性质分析结果表明,所制备的Ni/CCG呈现出铁磁性质,有望在吸波材料,磁记录领域等方面得到应用。4.将石墨粉氧化成GO,再将其在氯铂酸-乙二醇-水溶液体系中还原,得到Pt/CCG复合材料；用相似的方法对MWCNT进行处理,得到Pt/MWCNT复合材料。然后对比这两种材料作为直接甲醇燃料电池催化剂的催化性能,证明Pt/CCG和Pt/MWCNT的电化学活性表面积分别是36.27m2/g和33.43m2/g。Pt/CCG具有更强的CO中毒忍耐力,显示出增强的电催化氧化甲醇的活性。更多还原

【Abstract】 In recent years, the problem of electromagnetic interference (EMI) has drawn considerable attention due to the explosive growth in the application of electronic devices such as mobile phone, local area network, personal computers and radar systems. The conventional absorbing materials such as ferrites and metallic materials have been studied widely. Although presenting good absorption properties these materials are too heavy. An alternative approach is coating support media of low density with polymer or metallic materials. The recent development in absorber technology is to produce absorbers that are thin, flexible and strong. Carbon nanotubes, grapheme and SiC are exactly suitable as a supporting media for this purpose because of their low density, good thermal and chemical stabilization.Graphene, one-atom thick planar sheet of hexagonally arrayed sp2 carbon atoms, exhibits excellent physical and chemical properties, which makes it promising for potential applications in many technological fields, such as nanoelectronics, sensors, nanocomposites, batteries, supercapacitors and hydrogen storage. Especially, graphene has potential application as a heterogeneous catalyst support in direct methanol fuel cells. In comparison with CNTs, graphene not only possesses similar stable physical properties but also larger surface areas. Combination of graphene and functional nanoparticles may lead to materials with interesting properties for a variety of applications, and they are specifically expected to have enhanced electrocatalytic activity. The contents of this thesis are as follows:1. Ni1-xCox Palloy nanoparticles (x=0.25,0.50,0.75), with diameters in the range of 8-18nm were uniformly attached on the surface of multi-walled carbon nanotubes (MWNTs) by electroless plating, which were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), X-ray diffraction analysis (XRD), vibrating sample magnetometer (VSM) and vector network analyzer, respectively. Magnetization measurement indicates that both coercivities and saturation magnetizations decreased linearly with increasing Ni concentration in Ni-Co-P deposits. The complex permittivities of MWNTs-olefin matrix composites also decreased linearly with increasing Ni concentration while the complex permeabilities increased slightly, which were measured in the range of 2-18GHz. The microwave absorbing properties enhanced with increasing Co concentration and a maximum reflection loss of-26.84dB was obtained at the frequency of 7.75GHz when the matching thickness was 2.5mm and x=0.75.2. Silicon carbide particles reinforced nickel-cobalt-phosphorus matrix composite coatings were prepared by two-step electroless plating process (pre-treatment of sensitizing and subsequent plating) for the application to lightweight microwave absorbers, which were characterized by scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), vibrating sample magnetometer (VSM) and vector network analyzer, respectively. The results show that Ni-Co-P deposits are uniform and mixture crystalline of a-Co and Ni3P and exhibit low specific saturation magnetization and low coercivity. Due to the conductive and ferromagnetic behavior of the Ni-Co thin films, high dielectric constant and magnetic loss can be obtained in the microwave frequencies. The maximum microwave loss of the composite powder less than-32 dB was found at the frequency of 6.30 GHz with a thickness of 2.5mm when the initial atomic ratio of Ni-Co in the plating bath is 1.5.3. A magnetic hybrid of chemically converted graphene (CCG) and nickel nanoparticles was synthesized by chemical reduction using hydrazine as a reducing agent. The Ni/CCG hybrid was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). The results show that Ni nanoparticles were uniformly dispersed on the surface of CCG sheets and its main particle sizes were distributed in the range of 35-40nm. Magnetic measurement indicates that Ni/CCG exhibits typical ferromagnetic behavior, which makes it promising applications in electronic-magnetic nanodevices, absorbing mateials and data storage systems.4. We have investigated a simple approach for the deposition of platinum (Pt) nanoparticles onto surfaces of graphite oxide (GO) nanosheets with particle size in the range of 1-5 nm by ethylene glycol reduction. During Pt deposition, a majority of oxygenated functional groups on GO was removed, which resulted in a Pt/chemically converted graphene (Pt/CCG) hybrid. The electrochemically active surface areas of Pt/CCG and a comparative sample of Pt/multi-walled carbon nanotubes (Pt/MWCNT) are 36.27 m2/g and 33.43 m2/g, respectively. The Pt/CCG hybrid shows better tolerance to CO for electro-oxidation of methanol compared to the Pt/MWCNT catalyst. Our study demonstrates that CCG can be an alternative two-dimensional support for Pt in direct methanol fuel cells.更多还原