电弧放电法制备纳米碳管

纳米碳管的制备方法主要有三种：电弧放电法、激光烧蚀法和有机物催化热解法,首先综述了近年来应用电弧放电方法制备纳米碳管的研究进展,然后概述了中国科学院金属研究所在普通电弧法的基础上发展起来的大量制备单壁纳米碳管的氢等离子电弧方法。     

电弧放电法制备SiC纳米丝的实验研究

电弧放电法实验制备了碳化硅纳米丝.在6 mm的石墨棒中心钻一个4 mm的孔,将50at.%C 50at.%SiO2的粉末充分混合,填入其中作电弧放电阳极,水冷铜靶作阴极,放电电流70 A,收集放电后产生的粉末,用XRD、激光拉曼光谱、SEM、TEM进行分析.SEM和TEM照片表明其中有大量的实心纳米丝,其直径30 nm～50 nm,长度5 μm以上,XRD分析表明其为β-SiC,拉曼光谱中在785 cm-1有一个尖锐峰.我们认为碳纳米管与气态的SiO2反应生成了SiC纳米丝.     

放电等离子超快速烧结 SiC-Al2O3纳米复相陶瓷

本文介绍用非均相沉淀法制备的纳米SiC-Al     

Fe3O4磁性纳米颗粒的合成及其调控

利用水解共沉淀法制备了Fe3O4纳米颗粒,研究了温度和pH值对Fe3O4纳米颗粒粒径、形貌的影响关系。研究结果表明,反应温度从30℃升高到90℃,Fe3O4颗粒的粒径从6～8nm增大到10～12nm;同时,Fe3O4颗粒的饱和磁矩也随着Fe3O4颗粒粒径的增加而升高。溶液pH值会影响Fe3O4纳米颗粒的形状,高pH值易使合成的Fe3O4纳米颗粒为四方形,随着pH值的降低,Fe3O4纳米颗粒向球形转变。Fe3O4纳米颗粒的粒径和形状的可控性为进一步合成、调控Fe3O4电磁功能复合材料奠定了良好基础。     

In2O3纳米纤维的制备及其导电性研究

利用静电纺丝技术结合热处理方法制备了一维多孔结构的In2O3纳米纤维。借助扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察纳米纤维的形貌结构;利用热重分析仪(TGA)分析前驱体复合纳米纤维的热处理过程;采用X射线衍射仪(XRD)分析不同煅烧温度下所得In2O3的晶体结构;利用四探针测试In2O3纳米纤维的导电性,并探讨煅烧温度对其导电性的影响。结果表明:静电纺前驱体复合纳米纤维成型良好,且经不同温度煅烧后产物仍保持纤维结构,但纤维直径明显减小。不同温度下煅烧所得In2O3均为立方铁锰矿型,随着煅烧温度的升高,In2O3纳米颗粒逐渐增大,晶体更加完整,导电性逐渐增强。     

超声波及分散剂对纳米SiO2/CaCO3/Al2O3颗粒分散特性的影响

在材料科学领域,颗粒的均匀分散是获得具有较好的显微结构和性能材料制品的基础。采用分光光度计法表征分散效果,研究了超声波及不同分散稳定剂复合作用下纳米SiO_2、纳米CaCO_3、纳米Al_2O_3颗粒的分散性能,并结合DLVO理论探讨了分散机理,给出了分散剂优选方案。结果表明,超声波处理纳米颗粒悬浮液可以有效打破纳米颗粒团聚;不同分散剂对不同纳米颗粒的分散效果差异较大,NS颗粒相比NC、NA更难被分散剂分散,分散剂SHMP、SDBS作用效果随用量的增大先增强后减弱,分散剂PCS作用效果随用量的增加而增强;分散剂种类、用量会影响纳米悬浮颗粒的双电层厚度和颗粒周围空间微环境,从而影响分散体系的稳定性。     

直流电弧等离子体法制备TiO2纳米超细粉

采用直流电弧等离子体法直接制备了晶态的TiO2纳米超细粉,粉体中的晶粒既有锐钛矿结构,也有金红石结构;既有单晶结构的TiO2,也有多晶结构的TiO2.当热处理温度低于600℃时,粉体颗粒的长大较为缓慢,粒径在20nm以下;温度高于700℃时,颗粒迅速长大,锐钛矿向金红石结构的转变明显;当温度达到800℃时,样品转变为单晶结构的金红石型TiO2,颗粒大小在40-120nm之间.     

以煤为碳源直流电弧法制备单壁纳米碳管绳

以太西无烟煤为碳源，以稀土氧化物La2O3和过渡金属Ni为催化剂制备复合的煤基炭棒，采用直流电弧放电技术，成功实现了单壁纳米碳管绳的批量制备。用TEM和Raman光谱技术对纳米碳管绳产品进行了分析表征。结果表明：太西煤是制备单壁纳米碳管的合适碳源；电弧放电得到的煤基单壁纳米碳管的直径分布在2．01nm-1．80nm之间；双金属催化剂Ni-La在单壁纳米碳管的形成过程中存在协同作用，其催化活性优于其中的单一组分。     

CNTs添加对Cu-Al2O3复合材料耐电弧侵蚀性能的影响

Cu-Al₂O₃复合材料具有优异的传导性能和力学性能,在耐磨材料领域具有广阔的应用前景。为进一步提升电摩擦条件下复合材料的耐电弧侵蚀性能,本文采用内氧化法与粉末冶金法相结合制备了不同碳纳米管(CNTs)含量的CNTs/Cu-Al₂O₃复合材料,观察了CNTs/Cu-Al₂O₃复合材料中增强相的分布及其与基体界面结合情况,研究了添加不同含量CNTs对Cu-Al₂O₃复合材料传导性能和力学性能的影响,重点探究了CNTs/Cu-Al₂O₃复合材料的耐电弧侵蚀机制。结果表明：原位生成的纳米Al2O3颗粒钉扎位错及对CNTs分布具有调控作用,使CNTs弥散分布在铜基体中。与Cu-Al₂O₃复合材料相比,CNTs/Cu-Al₂O₃复合材料燃弧时间和燃弧能量明显降低,波动更平稳。在电弧侵蚀过程中,...     

Al2O3纳米粒子对镁合金阳极氧化的影响研究

通过在阳极氧化液中添加纳米Al2O3,在镁合金表面制备了复合阳极氧化膜。采用扫描电镜、能谱仪、动电位极化测试以及往复摩擦磨损实验研究了纳米Al2O3的添加量对阳极氧化过程、形貌及氧化膜性能的影响。结果表明,纳米颗粒的加入,增大了溶液电阻,从而使得成膜电压提高。纳米粉末的添加量与复合氧化膜的性能没有线性相关性。当电解液纳米颗粒的浓度为10g/L时,可以获得表面光滑平整、孔径细小均匀的复合氧化膜,此时复合氧化膜具有最优的耐蚀性和耐磨性能。     

Rapid synthesis and characterization of magnesium oxide nanocubes via DC arc discharge

Direct current (DC) arc discharge method gives high temperature in a short time, which has been widely used to prepare carbon nanotubes. We use this simple approach to synthesize magnesium oxide (MgO) nanocubes without any catalyst. Structural characterizations indicate that the as-synthesized MgO nanocubes are all single crystalline, and enclosed by {100} facets. The edge lengths mainly range from 60 nm to 100 nm. Most nanocubes interlace with adjacent nanocubes as three types: point contacts, line contacts and face contacts. The blue band in PL spectrum is ascribed to various structural defects, the nanosize effect and surface states of MgO nanocubes.     

液苯介质放电制备洋葱状富勒烯

以液体苯(C6H6)为放电介质,石墨做电极,成功地制备了洋葱状富勒烯(Onion-like Fullerenes,OLFs)。重点考察了电流对OLFs产量的影响,利用高分辨透射电镜(HRTEM)和X-射线衍射(XRD)对所得产物进行了表征。结果表明:电流大小是影响OLFs产量的主要因素,所制OLFs直径分布可控制在10nm~30nm范围内。     

Mesoporous indium oxide synthesized via a nanocasting route

The synthesis of crystalline mesoporous indium oxide by using a mesoporous carbon (CMK-3) as hard template is described. Transmission electron microscopy (TEM) exhibits the presence of mesoporous structure in our sample and the corresponding wide-angle X-ray diffraction (XRD) pattern confirmed the crystalline wall of sample. N₂ adsorption measurement exhibits the synthesized crystalline mesoporous indium oxide possesses a specific surface area of 39 m²/g and the total pore volume of 0.17 cm³/g, and the corresponding pore size distribution curve reveals the presence of a mesopore of 7.0 nm in maximum. Our work demonstrates that the maintenance of the ordered structure of carbon template is very significant for obtaining high quality replicas via the nanocasting route.     

Transparent heaters based on solution-processed indium tin oxide nanoparticles

We demonstrate transparent heaters constructed on glass substrates using solution-processed indium tin oxide (ITO) nanoparticles (NPs) and their heating capability. The heat-generating characteristics of the heaters depended significantly on the sintering temperature at which the ITO NPs deposited on a glass substrate by spin-coating were transformed thermally into a solid film. The steady-state temperature of the ITO NP film sintered at 400 °C was 163 °C at a bias voltage of 20 V, and the defrosting capability of the film was confirmed by using dry-ice.     

Aerosol synthesis of titanium nitride nanoparticles by direct current arc discharge method

Arc discharge synthesis has industrial relevance due to its low cost and scale-up potential. The production of titanium nitride nanoparticles was achieved by direct current arc discharge in an atmospheric-pressured ambient composed of N₂ and Ar. We systematically investigated the effect of the synthesis parameters, including quench gas velocity, quench gas composition, and applied arc current, on the particle quality, yield, and size. It is found that increasing quench gas velocity enables to produce particles with a primary size of 10–15 nm, while titanium nitride particles of 20–50 nm are produced at low quench gas velocity based on scanning electron microscope (SEM) analysis. X-ray diffraction (XRD) results indicated that titanium nitride particles produced at various nitrogen compositions are almost stoichiometric, while the crystallite size increases almost 20 nm when increasing nitrogen contents in the quench gas. Quench gas composition also has a significant impact on the arc voltage as well as particle production rate. When increasing the nitrogen concentration from 20% to 100%, the production rate can be enhanced by a factor of three. Besides, raising the applied arc current from 12 A to 50 A leads to a yield enhancement of factor 10. According to the Brunauer-Emmett-Teller (BET) measurement, the increase of applied arc current has a limited impact on primary particle size. The enhancement in particle production rate is mainly reflected by the larger agglomerate sizes and agglomerate number concentration. Additionally, based on experimental observations and previous studies, a mechanism is presented to explain the growth of deposits on the cathode tip.     

Multi-walled carbon nanotubes produced by hydrogen DC arc discharge at elevated environment temperature

Multi-walled carbon nanotubes (MWCNTs) were synthesized by hydrogen DC arc discharge at elevated environment temperature. The sample collected from the soot on the inner wall of the arc discharge furnace was investigated using TEM, HRTEM and X-ray diffraction. The results show that environment temperature has a significant effect on the formation of MWCNTs in the soot in hydrogen atmosphere as well as the diameter of the tubes. When environment temperature in the furnace is higher than about 500 °C, MWCNTs can be formed on the furnace walls with a great quantity.     

Synthesis of polyhedral graphite in a forced flow arc discharge

Polyhedral graphite (PG) particles have been synthesized by DC arc vaporization of pure graphite in He and H₂ gases with a fan blowing across the arc zone. The crystal structure and character of PG particles have been investigated by transmission electron microscopy, X-ray powder diffraction, and Raman scattering spectroscopy. The PG particles produced by arc discharge, ranging in diameter from 70 to 300 nm, have a turbostratic structure and have no hollow cavities in their centers. The yield of PG particles is about 50%. The cooling rate increase of carbon vapor caused by the forced flow plays a significant role for PG formation.     

Effects of substrate temperature on tin-doped indium oxide films deposited by dc arc discharge ion plating

Indium tin oxide (ITO) films were deposited on glass substrate at temperatures ranging from room temperature to 120 °C by the dc arc discharge ion plating technique. The electrical properties and crystallinity of ITO films were investigated. The resistivity of ITO films decreased with the increase of the substrate temperature in deposition, mostly due to increase in Hall mobility above 90 °C. The resistivity of ITO film obtained at temperature 120 °C was 1.33×10⁻⁴ Ω cm. The ITO films crystallized at the substrate temperature higher than 90 °C and the grain size estimated from the (2 2 2) peak in the direction parallel to the surface of the substrate became large with the increase of the substrate temperature. That the Hall mobility increased with the increase of the substrate temperature was speculated to be due to the increase of the grain size in the direction parallel to the surface.     

Synthesis of nano titanium oxide with controlled oxygen content using pulsed discharge in water

Different titanium oxide nanoparticles were formed through pulsed discharge of Ti wires in distilled water and H₂O₂ solution. The recovered samples were characterized by various techniques, such as XRD, SEM and TEM. The results confirm the presence of various titanium oxide nanoparticles including TiO₂ phases (anatase and rutile) and various nonstoichiometric TiO_2−x in recovered samples owing to the oxygen deficient circumstance through pulsed discharge. The titanium oxide nanoparticles exhibit a spherical shape with a size of 10–300 nm. The results show that the energy input adjusted by charging voltage is one major factor to control the phases of titanium oxide and the overall oxygen content of recovered samples. In addition, the H₂O₂ content in distilled water also affects the oxygen content of recovered samples. The sample recovered from 10% H₂O₂ solution is pure TiO₂ consisting of anatase and rutile without nonstoichiometric TiO_2−x. Moreover, the UV–Vis absorption spectra of recovered samples show their intensive visible light absorption and the correlation between the visible light absorption and the experimental conditions (charging voltage and H₂O₂ content).     

Synthesis of Mn-Al alloy nanoparticles by plasma arc discharge

Alloy nanoparticles in the Mn-Al system were prepared by the plasma arc discharge method. The influence of process parameters on the vaporization rate, composition, particle size, and magnetic properties of the as-produced nanoparticles was investigated. The Mn content was found to be higher in the nanoparticles than in the corresponding mother alloy, although the difference diminished with the reaction time. With increasing H₂ content in the reaction gas, both vaporization rate and particle size increased. With 30 at.% Mn, the average particle diameter in pure Ar was 35.2 nm, whereas that in an atmosphere with Ar:H₂ = 60:40 was 95.4 nm. With the addition of a small amount of carbon, ε-phase nanoparticles were synthesized. After heat treatment in a vacuum for 30 min at 400-600 °C, the nonmagnetic ε-phase was transformed into the ferromagnetic τ-phase and a very high coercivity of about 446 kA/m was achieved.