[豆丁共享]论文题目碳包覆铁纳米晶低维材料的合成`结构及性能的研究

[豆丁共享]论文题目碳包覆铁纳米晶低维 材料 关于××同志的政审材料调查表环保先进个人材料国家普通话测试材料农民专业合作社注销四查四问剖析材料 的合成`结构及性能的研究 论文论目,包覆论论米晶低论材料的合成、论及性能碳构的究研 作者论介,,霍俊平～女～ 1978年02月出生～2002年9月论于北京化工从大宋论河授～于学教2007年06月论博士位。学 中 文 摘 要 Carbon-encapsulated metal nanocrystals, CEMNs/碳属包覆论米金晶;,是一论新型的论米碳金论合材料～其中论石墨片论论密论论论米金晶有序排列～论米金论于核心位置～形成核论属数属属壳 构。随着1991年Iijima论论可充物论的论米管以～或论米管包覆第二相物论的论米材料填碳来碳壳碳 已引起究者的大论趣。由于或论米管可以在小的空论禁论金物论～可避免论境论论米研极碳壳碳很属 金材料的影～解论米金粒子在空中不能论定存在的论论～外由于包覆论的存在～有属响决属气另 望提高某些金生物之论的相容性～因而在方面具有论的论用前景。此外～依据金属与体医学广属 粒子和炭基的不同～论材料可望用作磁论论材料～论子二次论池论材料～论波蔽材料～体离极屏氧 化论原催化论～核论料论理材料～精论陶瓷材料和抗菌材料等。目前～人论已成功地制论出包一裹个或多金原子的小富勒论分子和包覆金或金化物论米晶的炭论米论粒～论论论论新奇论个属属属碳体并 构学学学的材料具有奇特的论、光和磁性论, 是一论新型的功能性论合材料。 论论目前包覆金论米晶制论中存在的工论论论、论物论度低、形论论不易控制和论以大量合成等碳属构 缺点～本论文采用一论新型制论 方法 快递客服问题件处理详细方法山木方法pdf计算方法pdf华与华方法下载八字理论方法下载 共论解法～依据芳论物论论渡有机金化合物在——与属500?左右的催化论聚反论的原理～通论精密控制和论论反论物论成、论及工论论论大量、廉价合成构参数CEMNs～并在此基论上论展CEMNs的形成机理、形论论和论用性能的究。论方法具有原料源富、工论构研来丰 路论论论、反论件和、论物论成均、论易于控制及容易论论大量制论等特点。条温匀构 本论文主要以一论精制石油重油论源、以二茂论论金源～采用共论解法制论包覆论米金碳属碳属 晶。在论论考察制论工论论参数CEMNs形成、论化及其形论论影的基论上～利用构响 TEM、HREM、XRD、SEM、TG/DSC、VSM等论论分析手段究了材料的形貌、论和性能～研构并与 制论工论相论论～论论材料的可控合成～论明CEMNs的形成机理及其论论化行论。论CEMNs论行化和氧炭化论理～究此论程中材料形貌和论的论化行论及机制～论多形论炭论米论和金化物空心论研构构属氧 米材料的究论论提供新的思路和方法。研 研碳属参数究论果表明～以芳论重油论源、二茂论论金源～采用共论解法～通论论论工论～可以大量制论包覆论论米论粒和包覆论论米棒。在碳碳480 ºC的反论度下～着二茂论添加量的增加;温随2 wt. %至45 wt. %,～论物的收率提高～形貌由包覆论米论论粒逐论向生成包覆论米论棒的方向论碳碳 展。包覆论中的金核主要由论论构属α-Fe相论成～论论无定型半石墨化论。碳壳构在450 ºC的反论温度下～着二茂论添加量随从30 wt. %增加到120 wt. %～论物的形貌又由包覆论米论棒～逐论向碳 生成包覆论米论论粒的方向论论。碳反论度的升高或保论论的延论～都使论物形貌论生相同的论化。温温同论～着二茂论添加量的增加～随论物中包覆在中的金核由论论碳壳属α-Fe相逐论论论成Fe3C～外壳碳构构论由无定型论论论成石墨论湍论论。体系中少量硫的加入～引起论物的形貌和论成论生论著的论化。 通论原料论成、论分析和合成工论论物形貌和论的论系究～构参数与构研论合TG-DSC原位模论反论论程论重论化～推共论解法形成包覆论米金晶是基于液相催化论论聚的原理～论论米论粒论断碳属气两 于芳论分子的催化作用是基于溶解析出机制。包覆论米金棒的形成需要必要因素,碳属两个体 系中有足论的论论米原子簇和适中的反论活性。 论惰性下气氛1000 ºC炭化论理～包覆论论米论粒碳尺寸论大～大多论米论论粒芯部逸出～形数从 1 成大量空心洋论论～碳葱构碳壳构构断在论米论核的催化下由无定型论论化成论石墨化论～推论有序论 构碳温碳碳的形成是基于高下的溶解析出机制。包覆论论米棒在500-550 ºC保论一段论论～能温很 论保持住其原始的形貌～而在论一步1000 ºC的论论理中～论米棒局部论生论形成论非论论。论包覆称构碳 论论米棒在250 ºC的化论程中～大论有氧三分之二的论论米论粒中论从碳壳属散和逸出～得到少量金 论米论粒充的论米管填碳,通论论一步的低和高炭化论理制论温温得到论度在150-350 nm、直径在30- 50 nm的短论米管。论论米论粒在碳温迁碳壳氧如此低的度下论生移和逸出～可能论论论的缺陷和论的 化放论反论论致论论米论粒的半液化论。状 碳碳包覆论论米论粒和包覆论论米棒～以及论论1000 ºC炭化论理后的论物～都具有论高的论论力和论 小的矩磁比论～呈论出一定的论磁性和论磁性的论合磁性能。包覆论论米棒在碳1000 ºC炭化论理后的 论物～在高论论磁波段呈论良好的论磁论耗性能～有可能成论论良的吸波材料。 通论原料论论、工论控制和参数氧碳属后论化炭化论理～由共论解法不论可以合成出包覆论米金论 粒和包覆论米金棒～而碳属碳葱碳且论可以制论出空心论米洋和短论米管等多论新型论米炭材料～论 明我论论明的共论解法是一论制论多形论论米材料的平碳研碳属台技论。其深入究论于包覆论米金晶的 大量制论、促论其论论论用～以及合成、论或装构碳碳构建论米管及相论新的论米论等都具有十分重要的 理论和论论意论。 论论论,包覆论米金晶～论米管～共论解法～催化论论聚～炭化论理～ 化碳属碳氧 Study on the Preparation, structure and properties of carbon- encapsulated iron nanocrystals Huo Junping ABSTRACT Carbon-encapsulated metal nanocrystals (CEMNs) are a new kind of carbon/metal nanocomposite, in which graphite layers arrange around metal nanocrystals located in the center to form core-shell structure. The carbon layers provide the oxidation resistance of bare metal nanoparticles and prevent them from environment degradation, and can endow some metal nanoparticles with biocompatibility. CEMNs, especially the magnetic nanomaterials, possess special structures and properties, and thus might have important applications in areas such as high-density magnetic data storage, ferrofluids, microwave absorption materials, oxidation-reduction catalyst, handling materials of radioactive waste and bio-medical materials. For the preparation of CEMNs, the present techniques, such as the arc-discharge technique, chemical vapor deposition, liquid-impregnating carbonization of non-graphitizing carbon and etc., 2 show some disadvantages, e.g., the morphology and the structure of the resulting nanocrystals are not easy to control, and it is difficult to produce high-purity nanocrystals in large quantities. While here we proposed a novel method for the preparation of CEMNs by co-carbonization of aromatics with metal compounds, i.e., co-pyrolysis method. It featured in simplicity, low temperature, good controllability and high yield of desired products . The research focused on the preparation of CEMNs by co-pyrolysis of a refined aromatic heavy oil and ferrocene. The effect of the synthesis parameters on the formation and transformation of CEMNs were investigated in detail. The morphology, structure and particular properties of the product were characterized via TEM, HREM, XRD, SEM, TG/DSC and VSM measurements, and the relationship between them and synthesis parameters were studied to realize the controllable preparation of the product. The formation mechanism and thermo-transformation behavior of CEMNs were elucidated. In addition, the oxidation and further carbonization treatments on CEMNs were carried out and some interesting phenomenon and new results were obtained, which will provide a novel strategy for the research and development of various carbon nanomaterials. The results show that large amount of carbon-encapsulated iron nanoparticles (CEMPs) and nanorods (CEMRs) were obtained by co-pyrolysis of an aromatic heavy oil and ferrocene. With the increase of ferrocene content from 2 wt. % to 45 wt. % under the reaction temperature of 480 ºC, the morphology of the product had a transformation from CEMPs towards CEMRs. While with the increase of ferrocene content from 30 wt. % to 120 wt. % at 450 ºC, the morphology of the product were transformed from CEMRs to CEMPs. And the same morphology transformation took place with the enhancement of reaction temperature or the elongation of soaking time. Meanwhile, with the increase of ferrocene content, the encapsulated metal core in the product were changed from single α-Fe to iron carbides (FeC), and the carbon shells were turned from amorphous into 3 turbostratic structure. By the analysis of raw feedstock and the investigation of the relationship among the morphology, structure of CEMNs and the synthetic parameters, it was concluded that the formation of CEMNs by co-pyrolysis method was based on the principle of condensation and polymerization in a vapor-liquid bi-phase by the aid of catalysis under pressure, and the catalysis of iron nanoparticles was based on the dissolution-precipitation mechanism. It is assumed that two essential factors must be met for the formation of the nanorods, including the sufficient amounts of iron clusters and moderate reaction activity in the system. By carbonization at 1000 ºC under N atmosphere, the size of CEMNs became larger and the 2 carbon shells were changed from the disordered into graphitic structure under the catalysis of nano-sized iron core. At the same time a large amount of hollow onion-like carbon nanoparticles emerged due to the ejection of iron nanoparticles. After oxidation of as-grown nanorods at 250 ºC, large amounts of ferric nanoparticles diffused and ejected from carbon shells, leading to the formation of carbon nanotubes with several nanoparticles trapped inside, and short nanotubes with diameter of 30-50 nm and length of 150-350 nm were generated by further carbonization at low and high temperatures. 3 Both as-grown CEMNs and the carbonized product had a high coercivity and a small ratio of remanent magnetization (Mr) to saturation magnetization (Ms). It is implied that CEMNs show a combined magnetic characteristic of ferromagnetic and paramagnetic materials. The above research afforded a novel and effective method for the preparation of various carbon nanomaterials. It can be seen that, via the selectivity of raw materials, the controllability of synthesis parameters and the post-oxidation and carbonization treatments, not only CEMNs including nanoparticles and nanorods but also empty carbon onions and short carbon nanotubes were obtained by co-pyrolysis method. Moreover, it had a great significance for the promotion of the practical applications of CEMNs and for the synthesis, assembly and construction of carbon nanotubes and related nanostructures. Keywords: carbon-encapsulated metal nanocrystals, carbon nanotubes, co-pyrolysis, catalytic polymerization, carbonization, oxidation 4 5 6