石英基底上定向单壁碳纳米管阵列可控生长

以铜为催化剂,甲烷为碳源,采用化学气相沉积法在石英单晶基底上生长定向单壁碳纳米管阵列,分别用扫描电子显微镜、原子力显微镜对其结构进行表征,研究了使用聚合物聚乙烯丙烯酸甲脂（PMMA）分散催化剂对碳纳米管密度和定向性的影响,利用PMMA分散催化剂能提高催化剂的活性,增加定向碳纳米管的密度,使催化剂形成规则的条状,能进一步提高其密度和定向性。采用微加工工艺做成器件,并利用半导体参数测试仪对器件进行了电学测试。     

单壁碳纳米管的制备及生长特性研究

采用Fe／MgO作为催化剂，催化裂解CH4制备了较纯的单壁碳纳米管，用TEM和Baman对碳纳米管进行了表征，对不同生长温度下制备的碳纳米管Baman径向呼吸振动峰(RBM)进行了分析，研究了生长温度对单壁碳纳米管生长特性和结构特性的影响。     

硅烷偶联剂对单壁碳纳米管的化学修饰

采用混酸体系(浓硫酸/浓硝酸体积比为3/1)对单壁碳纳米管进行了氧化处理,并通过氧化处理后在单壁碳纳米管表面生成的羟基官能团与长链硅烷偶联剂进行反应,制备了表面有机修饰的单壁碳纳米管.经过该方法修饰的碳纳米管在三氯甲烷、四氯化碳和二硫化碳等有机溶剂中有较好的溶解性.并通过红外光谱、热失重和透射电镜对其化学结构进行了表征.     

特定手性单壁碳纳米管的可控生长

单壁碳纳米管具有优异的电学、光学、热学、力学等性能,可能成为未来纳米器件的支撑材料之一。实现碳纳米管的结构可控生长制备依然面临着严峻的挑战。其中手性控制是单壁碳纳米管可控制备的最大挑战,它的实现标志着直径、壁数、手性角及导电属性等的可控制备。以特定手性单壁碳纳米管的可控生长为中心,分别综述了利用化学气相沉积法在粉体生长与表面生长两方面实现手性可控生长的研究进展,并在此基础上总结出基本思路,为实现单一手性碳纳米管的可控制备奠定基础。     

13X分子筛为载体制备单壁碳纳米管研究

采用流化床法,以Fe/13X分子筛作为催化剂载体,催化裂解正己烷制备出定向排列的、较纯的单壁碳纳米管.利用TEM、HRTEM、TG和Raman对产物进行了表征,对不同浸泡时间Fe/13X分子筛制成的单壁碳管的含量和分子筛的负载量进行了分析,研究了催化剂铁负载量对单壁碳纳米管的产量和直径的影响.结果表明,单壁碳纳米管产量受催化剂含量和活性的共同影响,且在一个特定催化剂负载量下碳管产量可以达到最高,而其直径变化不大,且不受催化剂负载量的影响.     

单壁碳纳米管的制备及生长特性研究

采用Fe/MgO作为催化剂 ,催化裂解CH4制备了较纯的单壁碳纳米管 ,用TEM和Raman对碳纳米管进行了表征 ,对不同生长温度下制备的碳纳米管Raman径向呼吸振动峰 (RBM)进行了分析 ,研究了生长温度对单壁碳纳米管生长特性和结构特性的影响     

低压空气中直流电弧法制备单壁碳纳米管

本文以Fe-S为催化剂、低压空气为缓冲气体采用直流电弧放电法首次大量合成低成本、高质量的单壁碳纳米管。实验结果表明在电弧放电过程中通过控制空气流量,使得电弧腔室压强保持在6～12 KPa为最优制备条件。采用扫描电子显微镜(SEM)和透射电子显微镜(TEM)对样品的形貌和结构进行表征,结果表明该方法所制备的单壁碳纳米管具有较高结晶度,管壁表面光滑、其直径为1.5～6.0 nm.采用低压空气电弧放电法有望成为低成本、大量制备高质量单壁碳纳米管的重要技术手段之一。     

不同催化剂表面定向生长单壁碳纳米管的研究

以不同含水量的乙醇为碳源,分别以Fe/Mo、Ag、Au为催化剂,采用化学气相沉积法制备了单壁碳纳米管.通过SEM,AFM,TEM等表征方法研究了碳纳米管的形貌和微观结构.结果表明,用Fe/Mo、Ag、Au均能长出高质量的碳管阵列,特别是Au的“Sputtering”法,可以不用繁琐地制备纳米颗粒催化剂便得到SWNT阵列...     

用ECR-CVD方法制备定向碳纳米管

以FeaO4纳米粒子为催化剂,CH4和H2为气源,采用电子回旋共振微波等离子体化学气相沉积技术(ECR-CVD)在多孔硅基底上制备出定向生长的碳纳米管.研究了气氛组成、气压、温度和反应时间对碳纳米管生长特性的影响.使用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和拉曼光谱(Raman spectrum)表征了样品的形貌和结构.结果表明:气氛组成和气压影响了反应腔内离解碳的浓度,从而影响碳纳米管的成核、生长速度及定向生长;温度的变化改变催化剂的尺寸从而改变碳纳米管的直径,在过低的温度下碳纳米管不能实现定向生长;碳纳米管随着反应时间的延长而不断增长,但超过一定时间后催化剂颗粒被碳包覆而失去催化作用,生长停止.     

新型一维材料--单壁碳纳米管的制备和应用研究

本文简要综述了单壁碳纳米管的最新进展.主要介绍了最近两年单壁碳纳米管的制备技术发展情况,包括电弧放电,化学气相沉淀,激光蒸发和太阳能方法.展望了其在储氢材料,纳米电子器件等领域的应用前景.讨论了影响单壁碳纳米管制备及实际应用的几个关键因素.提出了单壁碳纳米管的发展方向.     

Role of catalysts in the surface synthesis of single-walled carbon nanotubes

We demonstrate the role of catalysts in the surface growth of single-walled carbon nanotubes (SWNTs) by reviewing recent progress in the surface synthesis of SWNTs. Three effects of catalysts on surface synthesis are studied: type of catalyst, the relationship between the size of catalyst particles and carbon feeding rates, and interactions between catalysts and substrates. Understanding of the role of catalysts will contribute to our ability to control the synthesis of SWNTs on various substrates and facilitate the fabrication of nanotube-based devices.      

Towards a ‘catalyst activity map’ regarding the nucleation and growth of single walled carbon nanotubes

Quantification using scanning electron microscopy (SEM) of single walled carbon nanotubes (SWNTs) grown per unit area using a Co-Fe (50:50) catalyst system, prepared by the incorporation of the appropriate metal salts into a Spin-On Glass substrate, at 900°C. The effects of substrate, as well as catalyst precursor concentration, were investigated. SWNT growth density is maximised with a catalyst precursor concentration of ≥2.5 mM, associated with the formation of catalyst nanoparticles of a critical size for SWNT nucleation. Samples were subjected to secondary growth, using a range of H₂:CH₄ ratios to determine the optimum precursor composition. It was found that nucleation and growth stages are optimal under different conditions. Optimum conditions for nucleation resulted in >10× increase in SWNT density. Optimisation is dependent on temperature and the partial pressure of reagent gas species.     

Growth of aligned carbon nanotubes on ALD-Al2O3 coated silicon and quartz substrates

The smooth surface of the amorphous Al₂O₃ film on either silicon or quartz, coated by atomic layer deposition (ALD), was changed to rough surface by annealing in either air or hydrogen at high temperature (745°C) due to the formation of nanosized pinholes and micrometre pimples during the crystallisation of the amorphous Al₂O₃. The rough surface makes the growth of long carbon nanotubes (CNTs) by chemical vapour deposition impossible. Nevertheless, we were able to develop new catalyst recipes for successful growth of vertically aligned CNTs on ALD-Al₂O₃ coated silicon and quartz substrates. The lengths of the CNTs reached 90?µm on silicon substrates and 180?µm on quartz substrates. Furthermore, it is observed that the adhesion of CNTs on silicon substrates is much stronger than that on quartz substrates.     

Catalyst-free growth of oriented single-walled carbon nanotubes on mica by ethanol chemical vapor deposition

In this letter, it is reported for the first time that single-walled carbon nanotubes (SWNTs) can grow on mica substrate without additional catalyst by chemical vapor deposition (CVD) using ethanol as carbon source. The single-wall structure was characterized by Raman spectra and AFM (Atomic Force Microscopy) measurements. The growth of carbon nanotubes on mica surface contributes to the small amount of iron oxide in bare mica. The uniform dispersion and nanosized Fe particles formed from the reduction of iron oxide favor for the growth of SWNTs. Horizontally aligned superlong SWNTs arrays can be successfully generated on the mica surface, which is proved to be guided by the gas flow and under “kite growth mechanism”. The mica is a machinable material which can be easily cut and made a narrow slit on, thus the nanotubes can traverse the slit which can be in millimeter scale and long suspended SWNTs can be generated. This will provide an opportunity to manipulate individual SWNT for various purposes.     

Attachment of functionalized single-walled carbon nanotubes (SWNTs) to silicon surfaces

Single-walled carbon nanotubes (SWNTs) were functionalized by direct fluorination and subsequent reaction with 6-aminohexanoic acid for water-soluble carboxylic acid functionalized SWNTs (AHA-SWNTs). Both of the compounds were used as precursors to attach SWNTs to APTES coated silicon surfaces. AHA-SWNTs in aqueous solution were reacted with APTES self-assembled monolayers (SAMs) with coupling reagents N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS). The surface coverage is a function of concentration of AHA-SWNTs, solvent and coupling method. While for the fluorinated SWNTs (F-SWNTs), direct addition of F-SWNTs to preformed APTES SAMs at 90 degrees C shows essentially no reaction, in contrast to the one-pot reaction of F-SWNTs with APTES molecules in the presence of SWNTs on a silicon substrate. This reaction route provides a convenient method to attach SWNTs to silicon surfaces.     

Solar cells with graphene and carbon nanotubes on silicon

Graphene and carbon nanotubes (CNTs) represent attractive materials for photovoltaic (PV) devices due to their unique electronic and optical properties. Graphene and single-wall carbon nanotubes (SWNTs) layers can be directly configured as energy conversion materials to fabricate thin-film solar cells, serving as both photogeneration sites and charge carrier collecting/transport layers. SWNTs can be modified into either p-type conductor through chemical doping (like acidic purification) or n-type conductor through polymer functionalisation. The solar cells can be simply made of a semitransparent thin film of graphene (or SWNTs) deposited on a proper type of silicon substrate to create high-density Schottky (or p–n) junctions at the interface. The high aspect ratios and large surface area of these carbon nano-structured materials can benefit exciton dissociation and charge carrier transport thus improving the power conversion efficiency.     

Carbon nanotubes growth on silicon nitride substrates

Carbon nanotubes were synthesized on silicon nitride substrates by thermal chemical vapour deposition using an iron precursor catalyst. The nanotubes were characterized by AFM, FESEM, TEM and micro-Raman spectroscopy. The surface topography of the substrate, dense and flat or porous and rough, controlled the catalyst distribution and carbon nanotubes growth. Flat surfaces led to the synthesis of single-walled carbon nanotubes, whereas the porous ones promoted the growth of multi-walled carbon nanotubes of 60 nm diameter. These nanotubes preferentially grew on the porous sites, exhibiting a good substrate-nanotube interface.     

浮动催化体系中碳纳米管的生长机理

提出了气相形核生长（VPN）机理解释浮动催化体系中碳纳米管的生长过程。浮动催化系统中生长碳纳米管的活性碳原子是由苯热解产生的,被硫原子部分覆盖的液态铁颗粒是单壁碳纳米管的形核中心,生成的单壁碳纳米管继续径向生长、逐渐石墨化后,得到多壁碳纳米管。气相形核生长机理能够解释浮动催化系统生长碳纳米管的结构特征。     

Y/Ni催化剂中FeS的添加对SWNTs制备的影响

Y/Ni是电弧放电法制备单壁碳纳米管(SWNTs)时常用的催化剂.本文研究了FeS在Y/Ni催化剂中的添加对SWNTs制备的影响.结果发现FeS的添加不仅能增加网状产物的百分比,还能使网状产物中SWNTs的含量明显增多.这表明Y/Ni中FeS的添加能使更多的石墨转化为SWNTs.导致这一结果的原因可能有两个:(1)硫可能会扩大反应腔体中适合SWNTs生长的空间;(2)硫作为交联剂能促进碳元素的石墨化.     

旋涂法制备碳纳米管发电薄膜

采用多次旋涂法在玻璃衬底表面涂覆单壁碳纳米管（SWNT）悬浊液,形成均匀的SWNT薄膜,测量碳纳米管的发电特性,利用扫描电子显微镜（SEM）观测SWNT的分布情况,并用四探针电阻仪测量薄膜不同区域的方块电阻和薄膜的电流-电压（1-V）特性,结果表明,薄膜的I-V曲线线性度和重复度很高。不同浓度的氯化钠（NaCl）溶液以不同的流速流过SWNT薄膜表面,研究薄膜两端感应电势和电路中的电流变化情况。通过分析该变化情况,对SWNT发电机理作进一步阐释。