火焰法制备螺旋碳纳米纤维及其亲水改性

目的利用乙醇火焰法制备螺旋碳纳米纤维,并考查不同表面改性方法对螺旋碳纳米纤维亲水性的影响。方法首先研究不同烧制时间、镍片-火焰距离、Sn Cl4溶液浓度对制备螺旋碳纳米纤维的影响,然后用水蒸气、聚乙烯吡咯烷酮K30(PVP)溶液以及氢氧化钠-浓硝酸溶液改性螺旋碳纳米纤维。通过扫描电镜、透射电镜、拉曼光谱仪、X射线衍射仪对所制备的螺旋碳纳米纤维进行表征,利用红外光谱分析、X射线光电子能谱分析和沉降实验评价不同改性方法的改性效果。结果随着镍片-火焰距离的增加,螺旋碳纳米纤维含量增加,均匀度逐渐下降;随着烧制时间的延长,螺旋碳纳米纤维的均匀度先增加后降低;Sn Cl4的浓度会影响碳纳米纤维的形貌和均匀度。制备均匀的螺旋碳纳米纤维的最佳条件为:73%Sn Cl4溶液,镍片-火焰距离1.5 cm,烧制9 min。通过红外光谱分析发现,三种改性方法都使螺旋碳纳米纤维表面接上亲水基团。沉降实验表明,PVP溶液和氢氧化钠-浓硝酸改性的螺旋碳纳米纤维在水溶液中静置48 h后的沉降率均为26.7%,而未改性的螺旋碳纳米纤维的沉降率为58.3%。结论通过乙醇火焰法可以制备出均匀的螺旋碳纳米纤维,其中烧制时间、镍片-火焰距离、Sn Cl4溶液浓度对制备的螺旋碳纳米纤维的形貌和均匀度影响很大,需要在特定的条件下才能制备出均匀的螺旋碳纳米纤维。通过三种方法对螺旋碳纳米纤维进行改性,发现PVP溶液和氢氧化钠-浓硝酸改性的螺旋碳纳米纤维的表面亲水性更好,其中PVP溶液改性操作简单,且对螺旋碳纳米纤维的形貌没有破坏,对于螺旋碳纳米纤维改性会更有利。     

脉冲电镀镍纳米晶基板上碳纳米管和碳纳米纤维的火焰法合成

提出了一种利用脉冲电镀法在金属基板表面沉积一层具有催化活性的镍纳米晶,再将该基板放入乙醇火焰中合成碳纳米管(CNTs)和碳纳米纤维(CNFs)的方法.利用光学显微镜和X射线衍射仪(XRD)表征了镀层镍纳米晶的形貌和晶格特征,利用透射电镜(TEM)表征了碳纳米管的微观结构.实验研究了基板材料和电镀时间等因素对碳纳米管和碳纳米纤维合成的影响;初步讨论了其生长机理.     

硬质合金表面乙醇扩散火焰法沉积碳纳米材料的研究

本文采用乙醇扩散火焰法在原始态和酸蚀脱钴态硬质合金(WC-6%Co)上成功沉积出碳纳米材料,分别借助扫描电镜(SEM)、X射线衍射(XRD)、激光拉曼光谱(Raman)对其形貌和结构进行了表征。结果表明,原始态硬质合金上火焰沉积产物主要为纳米晶石墨,一步酸蚀脱钴态硬质合金上火焰沉积产物的中心区主要为球状超细金刚石、边缘区主要为超细金刚石和纳米晶石墨组成的复合碳纳米材料。     

火焰法合成碳纳米管的研究进展

火焰合成碳纳米管成本低、效率高,开发应用前景广阔。本文重点综述了国内外碳氢气体扩散和预混火焰合成碳纳米管的研发现状,对火焰合成碳纳米管的实验装置、火焰结构、形成条件及生长机理等作了较全面的概括和总结。     

氧乙醇火焰燃烧性能及其切割性分析

按热力学理论讨论了氧乙醇的燃烧过程,分析火焰燃烧时各区域的产热及其能量平衡,计算火焰理论温度,提出氧乙醇火焰可以作为金属氧气切割方法的热源.通过切割试验,证明该方法可行,并且切割质量优良.     

准一维纳米材料的合成及其研究进展

准一维纳米材料(纳米管、纳米线、纳米电缆、纳米带等)具有特异的物理、化学性质，并在未来纳米器件中具有潜在的应用价值，因此成为纳米材料领域中的研究热点。着重介绍了准一维纳米材料的合成方法：气相法、液相法和模板法。介绍了各种不同方法的生长条件和形成机制，并展望了准一维纳米材料的研究趋势。     

一维碳纳米结构的有效合成及其在锂离子电池负极材料中的应用(英文)

采用热解处理已合成的聚吡咯纳米线实现一维碳纳米纤维的有效合成。在KOH的活化作用下,原始的纤维结构发生变化,获得带状碳纳米结构。对所合成的碳纳米线及碳纳米带进行形貌及结构表征。测试这两种一维碳纳米材料应于于锂离子电池中负极材料的电化学性能。结果表明,一维碳纳米线及一维碳纳米带均表现出较优的循环性能及良好的倍率性能。碳纳米线材料在循环50次后仍保持530 mA·h/g的可逆容量。在前23次充放电循环中,碳纳米带的可逆容量均高于850 mA·h/g,充放电循环到第23次的容量保持率为86%。     

低维GaN纳米材料的最新研究进展

氮化镓是宽的直接带隙半导体材料，由于其优异的性能，使之成为制作耐高温，大功率，低能耗电子器件，高速场效应晶体管，高效蓝光发光二极管（LED），激光二极管（LD）和紫外光电导探测器等光电子器件的理想材料，低维GaN纳米材料在基础理论研究和纳米技术应用等方面都具有巨大潜力，因此，近年来低维GaN纳米材料的制备和物性研究已成为热点之一，本文报道了低维GaN纳米材料的最新制备方法的研究进展。     

乙醇在空气／乙醇离子氮碳氧多元共渗中的作用

研究了40Cr钢在空气/乙醇离子氮碳氧多元共渗过程中乙醇对化合物层厚度的影响.利用扫描电镜、X射线衍射仪和显微硬度计对化合物层的微观组织结构和显微硬度进行了分析.试验结果表明:在空气/乙醇离子氮碳氧多元共渗中,随着乙醇流量的增加,化合层厚度先增加再减少,最表面硬度先增加再减少,过量的碳抑制ε相的生成.     

碳纳米材料增强镁基复合材料研究进展

本文综述了碳纳米材料增强镁基复合材料的国内外研究进展,详细介绍了碳纳米材料增强镁基复合材料的制备方法,着重分析了其强韧化机制,探讨了其界面结构,简单概述了其储氢性能、热性能、抗腐蚀性能,最后总结了镁基复合材料现阶段的局限性,展望了镁基复合材料未来的发展方向。     

Synthesis of bamboo-like carbon nanotubes by ethanol catalytic combustion technique

Bamboo-like carbon nanotubes were synthesized by ethanol catalytic combustion （ECC） technique with combustion method. Copper plate was employed as substrate, ethanol as carbon source, and iron chloride as catalyst precursor. The as-grown black powder was characterized by means of scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The results show that the thinner bamboo-like carbon nanotubes have a relatively good structure that the compartment layers are more regular, while the thicker carbon nanotubes have a relatively irregular bamboo-like structure; the proposed method is simple to synthesize bamboo-like carbon nanotubes and has some advantages, such as flexible synthesis conditions, simple setup, and environment-friendly.     

Preparation of carbon nanotubes by ethanol catalytic combustion technique using nickel salt as catalyst precursor

A simple growth technique of carbon nanotubes （CNTs） by combustion of ethanol was developed. In the experiment, copper plate was employed as substrate, nickel nitrate （Ni（NO3）2） and nickel chloride （NiCl2） as catalyst precursor, and ethanol as carbon source. The cleaned copper substrate was dipped into catalyst precursor solution for mounting catalyst precursor particles. The dip-coated substrate was then placed into ethanol flame for about 10 min after drying. The black wool-like production grown on copper plate was obtained. This route is called an ethanol catalytic combustion（ECC） process. The black powders were characterized by means of scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, energy dispersive X-ray spectrometer（EDS） and Raman spectroscopy. The results show that the techique is much simpler and more economical to meet the future broader applications.     

Effects of catalyst precursors on carbon nanowires by using ethanol catalytic combustion technique

Iron nitrate, nickel nitrate and cobalt nitrate were used as catalyst precursors to study their effects on carbon nanowires synthesized by ethanol catalytic combustion （ECC） process. The as-grown carbon nanowires were characterized by means of scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The results show that relatively uniform nanowires will be formed when the catalyst precursor is iron nitrate; while helical structure or disordered structure will be formed when the catalyst precursor is nickel nitrate or cobalt nitrate. precursor     

Mechanistic study of stress corrosion cracking of carbon steel in ethanol

Mechanistic study of stress corrosion cracking of carbon steel in fuel‐grade ethanol was made using slow strain rate testing and constant tensile load testing at yield strength stress level of the steels. Characterization of the fracture surface was made using SEM and SEM–EDS. Selective dissolution of ferrite from pearlite phase was observed. Crack initiation took place preferably from pearlite phase. Corroded zones consisting of crystallographic pits were found from fracture surfaces.     

Microstructure transformation of carbon nanofibers during graphitization

The microstructures of vapor-grown carbon nanofibers（CNFs） before and after graphitization process were analyzed by high resolution transmission electron microscopy（HRTEM）, Raman spectroscopy, X-ray diffractometry（XRD）, near-edge-X-ray absorption fine structure spectroscopy（NEXAFS） and thermogravimetric analysis（TGA）. The results indicate that although non-graphitized CNFs have the characteristics of higher disorder, a transformation is found in the inner layer of tube wall where graphite sheets become stiff, which demonstrates the characteristics of higher graphitization of graphitized CNFs. The defects in outer tube wall disappear because the amorphous carbon changes to perfect crystalline carbon after annealing treatment at about 2 800 ℃. TGA analysis in air indicates that graphitized CNFs have excellent oxidation resistance up to 857 ℃. And the graphitization mechanism including four stages was also proposed.     

Growth of helical carbon nanofibers in the presence of Ni−Cu catalysts

Carbon nanofibers (CNFs) are synthesized by the dissociation of ethylene gas in the presence of Ni−Cu alloy catalysts; helical CNFs are favored by Ni−Cu alloy catalysts. The role of alloy compositions and reaction time in the morphology of CNFs were determined by varying both the Cu content in the alloy catalyst and the holding time at a particular synthesis temperature. The chemical composition, the size, and the shape of the catalyst particles were shown to affect the morphology of CNFs. Two kinds of growth mechanism are suggested to explain the growth of helical and straight CNFs.     

碳纳米管的化学镀铜

碳纳米管因其优异的力学、物理性能, 是一种理想的复合材料增强体, 但其与基体金属的润湿性较差.通过化学镀在碳纳米管表面镀上一层连续的铜镀层, 以改善碳纳米管与金属基体的润湿性, 增强界面结合力.通过TEM观察表明: 由于碳纳米管长径比大, 反应活性低, 表面曲率大, 直径细和镀层薄(50～100nm), 使碳纳米管很难得到完整的镀层.通过对镀前处理工艺(氧化、敏化、活化)的优化以增加活化点, 对传统镀液配方的调整使镀速尽可能低, 成功地在碳纳米管上镀覆一层铜, 为碳纳米管复合材料制备打下了良好的基础.