BaTiO_3粉体中Ti/Ba比分析方法的比较

提出了用ＫＯＨ熔融分解ＢａＴｉＯ３粉体〔１〕，再用浓ＨＣｌ酸化后，用感应耦合等离子体发射光谱法（ＩＣＰ—ＡＥＳ法）测定试样中的Ｔｉ／Ｂａ比，并与化学分析法的结果作了比较，显示出ＩＣＰ—ＡＥＳ法简便，快速，结果更好。     

Low temperature SCR of NO with NH3 over carbon nanotubes supported vanadium oxides

A novel multiwalled carbon nanotube (CNTs) supported vanadium catalyst was prepared. The structure of catalyst prepared was characterized by TEM, BET, FTIR, XRD and temperature-programmed desorption (TPD) methods. The results indicated that vanadium particles were highly dispersed on the wall of carbon nanotubes. The V₂O₅/CNT catalysts showed good activities in the SCR of NO with a temperature range of 373–523 K. The Lewis acid sites on the surface of V₂O₅/CNT are the active sites for the selective catalytic reduction (SCR) of NO with NH₃ at low temperatures. It was suggested that the reaction path might involve the adsorbed NH₃ species reacted with NO from gaseous phase and as well as the adsorbed NO₂ species. The diameter of CNTs showed positive effect on the activities of the catalysts. Under the reaction conditions of 463 K, 0.1 Mpa, NH₃/NO = 1, GHSV = 35,000 h⁻¹, and V₂O₅ loading of 2.35 wt%, the outer diameter of CNTs of 60–100 nm, the NO conversion was 92%.     

High quality double wall carbon nanotubes with a defined diameter distribution by chemical vapor deposition from alcohol

We have synthesized double wall carbon nanotubes (DWNTs) with few defects and little amorphous carbon by hot wall chemical vapor deposition (CVD) of alcohol. Catalysts for the DWNT growth were made from cobalt and molybdenum acetates. Scanning electron microscopy, transmission electron microscopy, multi frequency resonance Raman spectroscopy and optical absorption spectroscopy were used for characterization of the product with regard to DWNT yield, the nanotube diameter distribution, defect concentration and amorphous carbon content. Base pressures lower than 1 × 10⁻⁵ mbar in the CVD reactor considerably suppress defects in the DWNTs. Optimized growth conditions for DWNT formation are presented.     

羧基化高纯单壁碳纳米管修饰电极对乙酰甲喹的高灵敏检测

采用羧基化高纯单壁碳纳米管(c SWCNTs)固载于金电极表面来构筑乙酰甲喹电化学传感器。运用循环伏安法(CV)、差分脉冲伏安法(DPV)和电化学交流阻抗法(EIS)测定传感器的性能。结果显示,该传感器对乙酰甲喹的电化学还原具有显著的催化性能,修饰电极的峰电流达到-128.40μA,是裸电极峰电流的1167倍。通过对传感器性能影响因素的考察,得到最优制备条件为cSWCNTs涂覆量为4μL(质量分数0.10%分散液),搅拌速度1000 r/min,pH=7.0的PBS浓度为0.2 mol/L,-0.5V电压下富集30 min。在该条件下制备的传感器峰电流与乙酰甲喹在1～500nmol/L范围内呈良好的线性关系,相关系数为0.998,方法的检出限为0.76nmol/L。该传感器被成功地应用于实际样品检测,加标回收率在81.7%～124.0%。     

In-situ studies of electron field emission of single carbon nanotubes inside the TEM

Electron field emission characteristics of individual multi-walled carbon nanotubes (MWCNTs) were investigated in situ inside the transmission electron microscope (TEM). For a single MWCNT it was found that while field-emission can hardly occur from the side of the nanotube, a curved nanotube may result in finite side emission and the best emission geometry is the top emission geometry. Current-voltage (I-V) measurements made at different vacuum conditions and voltage sweeps emphasize the importance of the adsorbates on the electron field emission of MWCNTs. For a contaminated MWCNT, although the field emission current was reduced, the stability of its emission was improved. A current of up to several tens of μA was observed for a single MWCNT, but it was found that long time emission usually results in drastic structure damage that may lead to sudden emission failure.     

Characterization of multiwall carbon nanotubes and influence of surfactant in the nanocomposite processing

Carbon nanotubes prepared by a classical CVD method with a nickel catalyst have been characterized, then used as conducting anisometric objects dispersed into a polymeric matrix. In a first part, these nanotubes are structurally characterized before and after heat treatments (HTT=1500, 2000, 2500 °C). Diffusion Raman experiments and diamagnetic susceptibility experiments demonstrated their limited graphitized structures.Then, in a second step, a well defined processing way to prepare nanocomposites with a standard epoxy resin is presented. In particular, the use or not of a non-ionic surfactant (Tergitol) to disperse these nanotubes is analyzed. The influence of nanotube contents is examined on the bulk nanocomposite density, the glass transition temperature of the nanocomposites, and the d.c. electrical conductivity behavior. These results demonstrated that the interfacial properties are playing a fundamental role. On one hand, the glass transition temperature is increasing with the nanotube content, and on the other hand, the percolation threshold is found for a rather high critical volumic concentration. Finally, it is demonstrated that a pure geometrical model is not sufficient to explain these behaviors and that a wrapping effect of the organic matrix around the nanotubes has to be considered.     

Strong influence of buffer layer type on carbon nanotube characteristics

Carbon nanotubes (CNTs) have been grown by chemical vapor deposition in a vacuum chamber equipped with in situ photoelectron spectroscopy technique that allows for precise characterization of the chemical state of substrate and catalyst before the CNTs growth. The CNTs were grown onto Si wafers covered with thin buffer layers of Al, Al₂O₃, TiN, and TiO₂, using Fe as catalyst. Marked differences were observed both in growth rate and nanotube characteristics, as determined by SEM, TEM and micro-Raman spectroscopy, depending on the choice of buffer layer.     

超重力反应结晶法纳米碳酸钙浆料及粉料的表面处理

研究了脂肪酸盐A、水溶性铁酸酯偶联剂B（B1)以及铁酸酯偶联剂C对新型超重力反应结晶法所得的纳米CaCO3浆料及粉料的湿法表面处理的配方与工艺，确定了A体系的最佳改性时间为30～40min、改性温度为40～50℃、改性剂用量(质量分数)为3%～5％；B(B1)体系搅拌强度必须很高，改性时间30～40min，改性温度80℃左右，改性剂用量(质量分数)3％～5％；C体系的最佳改性时间为30～40min，改性剂用量(质量分数)为3％～5％。同时，采用红外光谱对改性前后的纳米碳酸钙进行了表征，表明改性刑已连接至CaCO3表面。最后，用分散稳定模型简要分析了改性机理。     

Induction plasma synthesis of fullerenes and nanotubes using carbon black–nickel particles

The existence of fullerenes (as allotropes of carbon) was established in the mid-1980s and during the last 15–18 years, systematic efforts have been devoted to improve the methods of their synthesis, including plasma-based system methods. The work presented here is focused on the investigation of fullerenes synthesis, using a radio frequency plasma reactor. The main objectives were to explore the use of induction plasma technology for the synthesis in-continuo of carbon fullerenes and to predict their formation conditions through conduct of theoretical studies. Thus, a thermodynamic study was carried out to predict the equilibrium composition of fullerenes produced at several combinations of operating conditions. Additionally, a statistical factorial design experiment, employing four factors at two levels, was also developed, in order to study the influence of the system’s operating parameters on the eventual C₆₀ fullerene yield. The results obtained showed that the reactor pressure, the electrical power and the raw material feed rates all have an important effect on the synthesis of fullerenes. The highest C₆₀ concentration in the products was found to be about 7.7 wt.%. Various other carbon nanostructures, such as nanotubes and nano-onions, were also successfully produced.