化学气相沉积法合成Fe/CMK-5及其对溶菌素的吸附性能

以SBA-15为模板,二茂铁为碳源,利用化学气相沉积(CVD)法合成了Fe/CMK-5复合材料.用粉末X射线衍射、低温N2吸附、热重分析、透射电镜等对复合材料进行了表征.结果表明复合材料中碳以CMK-5结构存在,Fe颗粒均匀地分布在CMK-5的骨架中,通过调节CVD时间可改变Fe/CMK-5的结构参数.在pH值为11的缓冲溶液中研究了Fe/CMK-5系列复合材料对溶菌素(lysozyme)的吸附性能,考察了溶菌素在Fe/CMK-5孔道内部的结构稳定性以及在不同pH值溶液中的泄露量.     

Carbon film growth on iron substrates by a CVD method

Carbon film coatings have been produced by a hot‐wall chemical vapor deposition (CVD) method under moderate conditions from pyrolysis of a mixture of propane and argon on an Fe(110) substrate at temperatures of 800–900 °C for different deposition times. The effects of temperature and reaction time on the growth of the carbon films were studied. Field‐emission scanning electron microscopy (FESEM), Raman microscopy, Auger electron spectroscopy (AES) and x‐ray diffraction methods have been performed to study the surface morphologies, growth features and microstructures of the carbon film coatings. The FESEM analyses indicated that carbon films on an Fe substrate consisted of flat‐layer and filamentous morphologies. Raman and AES analyses showed that the carbon initially was crystalline but the degree of disorder in the top layer of the carbon film increased with increasing deposition temperature. High‐resolution transmission electron microscopy studies are also in agreement with Raman results. The same trend was observed when the deposition time was increased from 5 to 30 min. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis of Nitrogen Incorporated Carbon Nanotubes with Different Diameters by Catalytic Pyrolysis of Butylamine

Bamboo-like nitrogen-doped carbon(CNx) nanotubes were synthesized by chemical vapor deposition (CVD) at a high reaction temperature of 600―900 °C. The butylamine and Fe/SBA-15 molecular sieve have been used as precursor and catalyst, respectively. Transmission electron microscopy(TEM) and high resolution transmission electron microscopy(HRTEM) observations show that the outer diameter and wall thickness as well as the inner diameter were increased with increasing reaction temperature in a temperature range of 600―800 °C. A synergism mechanism of the growth through bulk diffusion and the competitive growth through surface diffusion functions during the synthesis of CNx nanotubes was proposed.     

Structure and Electrochemical Properties of Carbon Nanotubes Synthesized with Catalysts Obtained by Decomposition of Co,Ni, and Fe Polyoxomolybdates Supported by MgO

Carbon nanotubes (CNTs) were synthesized by thermal decomposition of methane at 900 °C using Co–Mo/MgO, Fe–Mo/MgO, and Ni–Mo/MgO catalysts. To obtain metallic nanoparticles, polyoxomolybdate clusters of Co, Ni, and Fe deposited on MgO were thermally decomposed at 700 °С, and the obtained oxides were heated in a carbon-containing atmosphere. The method of transmission electron microscopy (TEM) testified formation of one to ten walled CNTs with the average outer diameter depending on the catalyst used. Raman spectroscopy data confirmed the presence of single-walled CNTs in the samples obtained with Co–Mo/MgO and Fe–Mo/MgO catalysts. The electrochemical properties demonstrated by the obtained materials in supercapacitors are shown to be functions of their structural and compositional features.     

Carbon nanotube bags: catalytic formation, physical properties, two-dimensional alignment and geometric structuring of densely filled carbon tubes

The catalytic CVD synthesis, using propyne as carbon precursor and Fe(NO3)3 as catalyst precursor inside porous alumina, gives carbon nanotube (CNT) bags in a well-arranged two-dimensional order. The tubes have the morphology of bags or fibers, since they are completely filled with smaller helicoidal CNTs. This morphology has so far not been reported for CNTs. Owing to the dense filling of the outer mother CNTs with small helicoidal CNTs, the resulting CNT fibers appear to be stiff and show no sign of inflation, as sometimes observed with hollow CNTs. The fiber morphology was observed by raster electron microscopy (REM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The carbon material is graphitic as deduced from spectroscopic studies (X-ray diffraction, Raman and electron energy-loss spectroscopy (EELS)). From M?ssbauer studies, the presence of two different oxidation states (Fe0 and FeIII) of the catalyst is proven. Geometric structuring of the template by two different methods has been studied. Inkjet catalyst printing shows that the tubes can be arranged in defined areas by a simple and easily applied technique. Laser-structuring creates grooves of nanotube fibers embedded in the alumina host. This allows the formation of defined architectures in the microm range. Results on hydrogen absorption and field emission properties of the CNT fibers are reported.     

有序介孔碳负载Fe、Co、Ni纳米晶的软模板合成及其表征

报道了在有序介孔碳基体中一步合成负载Fe、Co、Ni纳米晶的方法. 以间二苯酚和甲醛为碳源, F127为模板剂, Fe、Co、Ni的硝酸盐为前驱体, 通过软模板组装路线在酸性条件下合成了负载型有序介孔碳复合材料. 采用X射线衍射(XRD)、透射电镜(TEM)和氮气吸附等手段对所合成材料进行了表征. 结果表明: 合成的材料具有类似于SBA-15的有序介孔结构, 有序介孔碳负载Fe、Co、Ni纳米晶复合材料的比表面积分别为586、626和698 m²·g^-1. XRD和TEM表征结果证实了金属物种以高分散纳米晶的形式分布在介孔碳基体中.     

Growth control of single and multi-walled carbon nanotubes by thin film catalyst

Single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs) were synthesized on silicon substrate by the control of catalyst size, hydrocarbon species, and carbon flux through chemical vapor deposition (CVD). Catalysts for SWNTs and MWNTs could be obtained by an agglomeration of sputtered Co–Mo and pure Co thin films, respectively. The addition of Mo in the Co catalyst provides an effective nucleation site for SWNT and the low carbon flux by using methane gas in CVD reaction makes it possible to grow a single-walled structure.     

高温煅烧Mo改性的Fe／MgO催化剂用于制备管径分布均一的单壁碳纳米管

研究了在以甲烷化学气相沉积法制备单壁碳纳米管的过程中高温煅烧预处理(900℃煅烧10h)对Mo改性Fe/MgO催化剂的作用.发现这种预处理有利于Fe在催化剂中的稳定和分散,从而制备出管径均一的单壁碳纳米管.采用能谱元素分析、高分辨透射电镜、X射线衍射、比表面积测量、拉曼光谱和热重分析对样品进行了表征.结果表明,在碳纳米管生长的过程中,铁元素在催化剂表面富集,单壁碳纳米管生长于富集铁的纳米颗粒上,并存在碳管直径与铁颗粒尺寸的依赖关系.Mo存在时可煅烧形成FeMoO4复合氧化物,后者比MgFe2O4相更加稳定.Mo/Fe比例对提高单壁碳纳米管的生长密度、纯度与管径均一性等均有明显影响.上述研究对进一步精确控制制备单壁碳纳米管有重要意义.     

Anomalous electrochemical dissolution and passivation of iron growth catalysts in carbon nanotubes

Catalytically synthesized carbon nanotubes (CNTs) such as those prepared via chemical vapor deposition (CVD) contain metallic impurities including Fe, Ni, Co, and Mo. Transition metal contaminants such as Fe can participate in redox cycling reactions that catalyze the generation of reactive oxygen species and other products. Through the nature of the CVD growth process, metallic nanoparticles become encased within the CNT graphene lattice and may still be chemically accessible and participate in redox chemistry, especially when these materials are utilized as electrodes in electrochemical applications. We demonstrate that metallic impurities can be selectively dissolved and/or passivated during electrochemical potential cycling. Anomalous Fe dissolution and passivation behavior is observed in neutral (pH=6.40+/-0.03) aqueous solutions when using multiwalled CNTs prepared from CVD. Fe particles contained within these CNTs display intriguing, potential-dependent Fe redox activity that varies with supporting electrolyte composition. In neutral solutions containing dibasic sodium phosphate, sodium acetate, and sodium citrate, FeII dissolution and surface confined FeII/III redox activity are significant despite Fe being encapsulated within CNT graphene layers. However, no apparent Fe dissolution is observed in 1 M potassium nitrate solutions, suggesting that the electrolyte composition plays an important role in observing FeII dissolution, passivation, and surface confined FeII/III redox activity. Between potentials of 0 and -1.1 V versus Hg/Hg2SO4, the primary redox-active Fe species are surface FeII/III oxides/oxyhydroxides. This FeII/III surface oxide redox chemistry can be completely suppressed by passivating Fe through repeated cycling of the CNTs in supporting electrolyte. By increasing the potential to more negative values (>-1.3 V), FeII dissolution may be induced in electrolyte solutions containing acetate and phosphate and inhibited by addition of sodium benzoate, which adsorbs on exposed Fe particles, effectively passivating them. Finally, we observe that the FeII/III redox chemistry or subsequent passivation does not affect the onset of oxygen reduction at nitrogen-doped CNTs, suggesting that the surface-bound FeII species is not the primary catalytically active site for oxygen reduction in these materials.     

Synthesis of carbon nanotubes using scrap tyre rubber as carbon source

Carbon nanotubes(CNTs) were successfully synthesized through chemical vapor deposition(CVD) method over cobalt catalysts using scrap tyre rubber as carbon source.The CNTs as produced were investigated by means of X-ray diffraction, thermogravimetric analysis,scanning electron microscope,transmission electron microscopy and Raman spectrum techniques.It was found that the obtained carbon material mainly existed in the form of CNTs.     

Synthesis of graphitic ordered macroporous carbon with a three-dimensional interconnected pore structure for electrochemical applications

In this study, ordered macroporous carbon with a three-dimensional (3D) interconnected pore structure and a graphitic pore wall was prepared by chemical vapor deposition (CVD) of benzene using inverse silica opal as the template. Field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectrometry, nitrogen adsorption, and thermogravimetric analysis techniques were used to characterize the carbon samples. The electrochemical properties of the carbon materials as a carbon-based anode for lithium-ion batteries and as a Pt catalyst support for room-temperature methanol electrochemical oxidation were examined. It was observed that the CVD method is a simple route to fabrication of desired carbon nanostructures, affording a carbon with graphitic pore walls and uniform pores. The graphitic nature of the carbon enhances the rate performance and cyclability in lithium-ion batteries. The specific capacity was found to be further improved when SnO(2) nanoparticles were supported on the carbon. The specific activity of Pt catalyst supported on the carbon materials for room-temperature methanol electrochemical oxidation was observed to be higher than that of a commercial Pt catalyst (E-TEK).     

Influence of the catalyst type on the growth of carbon nanotubes via methane chemical vapor deposition

The preparation of the catalyst is one of the key parameters which governs the quality of carbon nanotubes (CNTs) grown by catalyzed chemical vapor deposition (CVD). We investigated the influence of three different procedures of catalyst preparation on the type and diameter of CNTs formed under identical growth conditions via methane CVD. In the first one, chemically synthesized colloidal iron oxide or iron molybdenum alloy nanoparticles were used, which were homogeneously deposited on silicon substrates by spin coating to prevent them from coalescence under CVD growth conditions. The obtained multiwall CNTs (MWNTs) exhibited diameters corresponding to the catalyst particle size, whereas no formation of single-wall CNTs (SWNTs) was observed. In the second method, commercial porous alumina nanoparticles were used in association with iron and molybdenum salts and the Fe/Mo catalyst was formed in situ. We determined that the alumina concentration significantly influenced the morphology of the catalyst and that below a critical value of the range of 1 g/L no CNTs were formed. While yielding nearly defect-free SWNTs, their diameter could not be controlled using this procedure, resulting in a large distribution of tube sizes. In a third, new preparation method, associating alumina and iron-based nanoparticles, SWNTs of a different size and narrower diameter distribution as compared to the second method were obtained. Our results are evidence of the essential role of alumina particles in the formation of SWNTs, and the newly developed method opens up a way to the synthesis of diameter-controlled SWNTs via catalyzed CVD.     

Selective matching of catalyst element and carbon source in single-walled carbon nanotube synthesis on silicon substrates

We have studied the compatibility of various catalysts for ethylene and ethanol chemical vapor deposition (CVD) syntheses of single-walled carbon nanotubes (SWNTs) on Si substrates. A strong selectivity between the catalyst elemental species and carbon source was found; SWNT yield for Fe (Co) catalysts was much higher for ethylene (ethanol) CVD than for ethanol (ethylene) CVD. This strong and completely opposite selectivity implies significantly different SWNT growth mechanisms for ethanol and ethylene CVD on Si substrates.     

Electrochemical Characterization of a Pyrolytic Carbon Film Electrode and the Effect of Anodization

A pyrolytic carbon (PC) film electrode was fabricated by the chemical vapor deposition (CVD) method. This report deals with the preparation, characterization and electrochemical behavior of this carbon film. Cyclic voltammetry, linear sweep voltammetry, Raman spectroscopy and scanning electron microscopy were employed to characterize the electrode. Low background current and capacitance were observed and the rate of charge transfer for Fe(CN) redox couple was determined via cyclic voltammetry. Also the effect of the anodic activation on the electrochemical activity was evaluated and characterized with respect to the sequence of voltage applied to the electrode. The excellent electrochemical activity and low background current are the reasons why this electrode is attractive for electroanalysis measurements with lower detection limit.     

电纺丝-气相沉积法制备碳包覆TiO_2纳米纤维及其光催化行为的研究

以聚乙烯吡咯烷酮(PVP)溶胶/钛酸正丁酯为前躯体,以静电纺丝法制备了PVP/Ti(OC4H9)4纤维。550℃下,空气氛中焙烧双组分纤维,得到直径60～300nm的TiO2纳米纤维。继而以气相沉积法制得碳包覆TiO2纳米纤维。用红外吸收光谱(FTIR)、X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等对纳米纤维进行了表征。与TiO2纳米纤维、TiO2纳米粉体相比,气相沉积法制备的碳包覆TiO2纳米纤维在光分解亚甲基蓝上表现出更好的催化性能。     

Fe/Co alloys for the catalytic chemical vapor deposition synthesis of single- and double-walled carbon nanotubes (CNTs). 1. The CNT-Fe/Co-MgO system

Mg(0.90)Fe(x)Co(y)O (x + y = 0.1) solid solutions were synthesized by the ureic combustion route. Upon reduction at 1000 degrees C in H2-CH4 of these powders, Fe/Co alloy nanoparticles are formed, which are involved in the formation of carbon nanotubes, which are mostly single and double walled, with an average diameter close to 2.5 nm. Characterizations of the materials are performed using 57Fe M?ssbauer spectroscopy and electron microscopy, and a well-established macroscopic method, based on specific-surface-area measurements, was applied to quantify the carbon quality and the nanotubes quantity. A detailed investigation of the Fe/Co alloys' formation and composition is reported. An increasing fraction of Co2+ ions hinders the dissolution of iron in the MgO lattice and favors the formation of MgFe2O4-like particles in the oxide powders. Upon reduction, these particles form alpha-Fe/Co particles with a size and composition (close to Fe(0.50)Co(0.50)) adequate for the increased production of carbon nanotubes. However, larger particles are also produced resulting in the formation of undesirable carbon species. The highest CNT quantity and carbon quality are eventually obtained upon reduction of the iron-free Mg(0.90)Co(0.10)O solid solution, in the absence of clusters of metal ions in the starting material.     

双金属磷化物和杂原子共修饰碳材料的制备及电催化性能

以高含氮量的苯胺五聚体二羧酸为配体, 在预氧化的泡沫镍上通过溶剂热反应合成了Fe, Co金属有机框架材料Fe/Co-MOF, 再以Fe/Co-MOF为金属源和碳源, 经磷化后制备出一种新型的双金属(Fe, Co)和杂原子(N, P)共掺杂的碳材料Fe/Co/P-NPs. 通过扫描电子显微镜和高分辨透射电子显微镜表征发现, Fe/Co/P-NPs由纳米粒子和纳米片组成, 并且形成Fe₂P和Co₂P两种晶体. 电化学测试结果表明, Fe/Co/P-NPs在析氢、 析氧及水电解中表现出了优异的多功能催化活性. 在1 mol/L KOH中, Fe/Co/P-NPs在10和100 mA/cm ²电流密度时的析氧过电位分别为270和300 mV, 均小于其它对比材料, 优于负载在泡沫镍上的RuO₂. 作为水电解双功能催化剂, Fe/Co/P-NPs仅需1.48 V的电位即可获得10 mA/cm ²的电流密度.     

Fabrication of spindle Fe(2)O(3)@polypyrrole core/shell particles by surface-modified hematite templating and conversion to spindle polypyrrole capsules and carbon capsules

By using a surface-modified templating method, Fe(2)O(3)@polypyrrole (PPy) core/shell spindles have been successfully prepared in this paper. The Fe(2)O(3) particles with spindle morphology were initially fabricated as core materials. After the PVP modification, the Fe(2)O(3) spindles were subsequently coated with a tunable thickness layer of PPy by in situ deposition of the conducting polymer from aqueous solution. Hollow PPy spindles were produced by dissolution of the Fe(2)O(3) core from the core/shell particles. High-temperature treatment under vacuum condition covert the hollow PPy spindles into carbon capsules by carbonization of the PPy shell. Transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) confirmed the formation of the Fe(2)O(3)@PPy core/shell particles, PPy and carbon capsules with spindle morphology.     

表面活性剂碳化法合成Fe3O4/C复合物及其电化学性能

以水热法合成的包覆油酸的α-Fe₂O₃粒子为前驱体, 在氩气下500 °C煅烧1 h, 得到Fe₃O₄/C纳米复合物. 用傅里叶变换红外(FTIR)光谱, X射线衍射(XRD), 扫描电镜(SEM), X射线能量散射(EDX)谱, 高分辨透射电镜(HRTEM), 元素分析, 循环伏安(CV)和恒流充放电测试等方法对材料的结构、形貌、成分及电化学性能进行了表征. 结果表明: 所制备的Fe₃O₄/C复合物呈长约200 nm, 粗约100 nm的纺锤形, 表面碳层厚约1-2 nm, 碳含量为1.956%(质量分数); 这种复合物作为锂离子电池负极材料具有很好的循环稳定性(在0.2C (1C=928 mA·g^-1)循环80次后具有691.7 mAh·g^-1比容量)和倍率性能(在2C循环20次后依然有520 mAh·g^-1比容量). 相对于未包覆的商业Fe₃O₄粒子, 复合物显著提高的电化学性能是由于碳包覆能防止粒子聚集, 提高导电性以及稳定固体电解质界面(SEI)膜.     

溶胶-凝胶法制备多孔LiMnPO4/MWCNT复合材料及其电化学性能

以柠檬酸为络合剂, 采用溶胶-凝胶法制备了多孔LiMnPO4和LiMnPO4/MWCNT(多壁碳纳米管)复合材料. 用X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、N2吸脱附等温曲线(BET)和透射电镜(TEM)对其晶体结构与微观形貌进行了表征. 结果表明, 得到的样品具有橄榄石晶体结构, 物相较纯; 两种材料均具有丰富的多级孔道LiM结n构PO, 孔4中径形在成介了孔高范导围电内性分的布三集维中网, 比络表. 恒面流积充分放别电为测73试.7表、6明9.,9 与 m纯2·gL-iM1; n碳P纳O4米相管比以, 复嵌合入材或料包具埋有的更形高式的在放多孔电比容量, 在0.05C、2C倍率下的放电容量分别为108.8、33.2 mAh·g-1. 电化学交流阻抗谱(EIS)表明MWCNT可以有效提高LiMnPO4的电子导电性. LiMnPO4/MWCNT复合材料具有较优的电化学性能可归因于增强的电子导电性, 连接的孔道结构和高的比表面积.