Preparation and CO conversion activity of ceria nanotubes by carbon nanotubes templating method

Ceria nanotubes with high CO conversion activity by means of carbon nanotubes as removable templates in the simple liquid phase process were fabricated under moderate conditions. The pristine CNTs were first pretreated by refluxing in a 30% nitric acid solution at 140 ℃ for 24 h, then dispersed in an ethanolic Ce（NO3）3.6H2O solution with ultrasonic radiation at room temperature for 1 h. Under vigorous stirring, NaOH solution was added drop by drop into the above ethanolic solution until the pH value was 10. The product was collected and repeatedly washed with ethanol and on drying at 60 ℃, the CeO2/CNT composites were obtained. Then, the as-prepared composites were heated at 450 ℃ in an air atmosphere for 30 min to remove CNTs. The ceria nanotubes were characterized by X-Ray Diffraction （XRD）, Transmission Electron Microscopy （TEM）, and X-Ray Photoelectron Spectrum （XPS）. The results showed that the ceria nanotubes were polycrystalline face-centered cubic phase and were composed of lots of dense cefia nanoparficles. The diameter of cefia nanotubes was about 40-50 nm. Catalytic activity of the product for CO oxidation was carded out at the region of 30-300 ℃ in a U-shaped quartz reactor with feeding about 0.15 g of the catalyst, which was loaded on Al2O3 carder. The inlet gas composition was 1.0% CO and 28% O2 with N2 as balance, and the rate of flow was kept at 40 ml/min. The catalytic products were analyzed by gas chromatography. The as-repared CeO2 nanotubes showed higher CO oxidation activity, which indicated that the morphology of ceria products affected the catalytic performance. The ceria nanotubes supported on Al2O3 demonstrated that conversion temperature for CO oxidation to CO2 was lower than that for bulk catalysts.     

Preparation of lanthanum sulfide nanoparticles by thermal decomposition of lanthanum complex

γ-La2S3 nanoparticles were successfully prepared by thermal decomposition of lanthanum complex La(Et2S2CN)3·phen at low temperature. The obtained sample was characterized by the X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and element analysis. The decomposition mechanism of lanthanum complex was studied by thermogravimetric analyses (TGA). The results showed that the obtained samples were cubic phase particles with uniform sizes among 10-30 nm and γ-La2S3 was prepared by decomposition...     

Catalytic graphitization of carbon/carbon composites by lanthanum oxide

Graphitized carbon/carbon composites were prepared by the process of catalytic graphitization with the rare-earth catalyst, lantha-num oxide (La2O3), in order to increase the degree of graphitization and reduce the electrical resistivity. The modified coal tar pitch and coal-based needle coke were used as carbon source, and a small amount of La2O3 was added to catalyze the graphitization of the disordered carbon materials. The effects of La2O3 catalyst on the graphitization degree and microstructure of the carbon/carbon composites were investi-gated by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The results showed that La2O3 promoted the formation of more perfect and larger crystallites, and improved the electrical/mechanical properties of carbon/carbon composites. Carbon/carbon compos-ites with a lower electrical resistivity (7.0 ???m) could be prepared when adding 5 wt.% La2O3 powder with heating treatment at 2800 oC. The catalytic effect of La2O3 for the graphitization of carbon/carbon composites was analyzed.     

超声场辅助制备碳纳米管/氧化钨纳米棒高效光催化剂的研究

采用超声场辅助制备了碳纳米管/氧化钨纳米棒.采用扫描电子显微镜（SEM）、能谱分析仪（EDS）、高分辨透射电镜（HRTEM）等手段对样品进行了表征,结果表明：在超声波的作用下,碳纳米管分散均匀,钨酸较为均匀地负载在碳纳米管表面上,经过800℃焙烧3 h,可以生成纳米级的碳纳米管/氧化钨棒.以日光灯（11 W）为光源,考察了催化剂和双氧水对亚甲基蓝降解率的影响.采用紫外可见分光光度计测定了反应液的吸光度,结果表明：在分别单独添加催化剂和双氧水的情况下,亚甲基蓝几乎无降解,当加入30 mg催化剂和2.5 mL双氧水时,当光照时间为70 min时,脱色率达到95.3%.通过5次回收后重复实验,发现该催化剂稳定性较好,可重复使用.     

壳聚糖-多壁碳纳米管修饰玻碳电极差分脉冲溶出伏安法测定痕量钯

将多壁碳纳米管(MWCNT)分散于壳聚糖（CTS）溶液中,修饰在玻碳电极（GCE）表面,制成了壳聚糖-多壁碳纳米管修饰玻碳电极(CTS-MWCNT-GCE)。利用差分脉冲溶出伏安法研究了钯在该电极上的溶出伏安特性,优化了试验条件,提出了一种测定痕量钯的新方法。试验发现,在0.1 mol/L乙酸钠-0.1 mol/L盐酸缓冲溶液（pH 4.10）中,钯于－400 mV处被富集在该修饰电极表面,在-300 mV～400 mV电位范围内,以100 mV/s的速率扫描,钯在135 mV（vs. SCE）处出现一灵敏的溶出峰,峰电流与钯的浓度在1.88×10-9～1.69×10-8 mol/L范围内呈良好的线性关系,检出限为3.10×10-10 mol/L。该修饰电极具有良好的稳定性和重复性,在含有1.0×10-9 mol/L钯的溶液中,连续11次测定,其相对标准偏差(RSD)为0.21 %。方法用于矿样中痕量钯的测定,测定结果同火焰原子吸收光谱法（FAAS）的测定结果基本一致。     

High yield formation of carbon nanotubes using arc discharge assisted with a nitrogen jet

Carbon Nanotubes (CNTs) are of significant research interest due to their significant electrical, mechanical, electro-mechanical and thermal properties. This enables CNT to be used in advanced bio-medical, electronics and materials technological applications. CNTs can be synthesized by various methods such as Arc-discharge, Chemical Vapor Deposition (CVD), Laser ablation etc. Still challenge exists when it comes to the yield. In general CNTs are commercially synthesized by Arc-discharge and CVD techniques. In both the cases the defect intensity differs according to the atmosphere which prevails in the production chamber. In the case of CVD the defect intensity is mainly due to pentagons of carbon, which cause curved faces whereas in the case of arc discharge, broken bonds can result at the surfaces. In general, the production of CNTs requires the presence of a controlled atmosphere inside the reaction chamber. Recent research has shown that CNTs can also be produced in open atmosphere but with a significant reduction in the yield. In the present work, a jet of nitrogen gas is applied between the arcing interfaces. As a consequence there is a significant change in the yield and defect density. Characterization techniques such as XRD, FEG-SEM, TEM and Raman spectroscopy confirm the same.     

Preparation of anhydrous lanthanum bromide for scintillation crystal growth

This paper reported an efficient and economical method for preparation of anhydrous LaBr3 for scintillation crystal growth. High purity anhydrous LaBr3 powders in large quantities were successfully obtained by stepped dehydration of LaBr3·7H2O using NH4Br as addi-tive. Experiments revealed that adding proper amount of NH4Br could effectively restrain the hydrolysis of LaBr3 during dehydration and thus decreased the yield of deleterious impurity of LaOBr. Optimum preparation conditions, including the amount of NH4Br in use, the dehydra-tion temperature and atmosphere, were investigated by DTA/TG and water/oxygen analysis. The Raman characterization of the as-prepared anhydrous LaBr3 was also presented.     

碳纳米管的纯化研究进展

碳纳米管(Canbon nanotubes,CNTs)是粉末冶金铜基、铝基、镁基等复合材料的理想增强体之一。但是,由于其制备方法(电弧放电法、激光蒸发法、碳氢化合物催化热解法、电解热合成法、化学气相沉积法等)不可避免产生的杂质(炭质、无定形碳、催化剂颗粒等)影响了其优越性能的充分发挥和实际应用。因此,碳纳米管的纯化成为制备增强复合材料必须优先解决的关键问题。本文简述了CNTs物理纯化方法和化学纯化方法,并将微波液相纯化法和微波气相纯化法这两种新型的纯化方法进行了详细对比,展望了CNTs纯化的发展趋势。     

Nanometre-scale rolling and sliding of carbon nanotubes

Understanding the relative motion of objects in contact is essential for controlling macroscopic lubrication and adhesion, for comprehending biological macromolecular interfaces, and for developing submicrometre-scale electromechanical devices. An object undergoing lateral motion while in contact with a second object can either roll or slide. The resulting energy loss and mechanical wear depend largely on which mode of motion occurs. At the macroscopic scale, rolling is preferred over sliding, and it is expected to have an equally important role in the microscopic domain. Although progress has been made in our understanding of the dynamics of sliding at the atomic level, we have no comparable insight into rolling owing to a lack of experimental data on microscopic length scales. Here we produce controlled rolling of carbon nanotubes on graphite surfaces using an atomic force microscope. We measure the accompanying energy loss and compare this with sliding. Moreover, by reproducibly rolling a nanotube to expose different faces to the substrate and to an external probe, we are able to study the object over its complete surface.     

Nickel galvanochemical coating modified by carbon nanotubes

The structure and microhardness of a nanocomposite nickel galvanochemical coating formed with Watts electrolyte and containing 60 mg/dm³ carbon nanotubes are studied. An addition of carbon nanotubes to the electrolyte leads to a substantial modification of the morphology and texture of grains, grain refinement, and an increase in the coating microhardness by 40%.