Carbon Nano-Flakes Produced by an Inductively Coupled Thermal Plasma System for Catalyst Applications

Carbon material was produced using an inductively coupled thermal plasma torch system of 35 kW and a conical shape reactor. The carbon nanopowders were obtained by plasma decomposition of methane at various flow rates and show a uniform microstructure throughout the reactor. The product has a crystalline graphitic structure, with a stacking of between 6 and 16 planes and a nano-flake morphology with particles dimensions of approximately 100 nm long, 50 nm wide and 5 nm thick. Nitrogen was also introduced in some synthesis experiments along with the methane precursor using flow rates of 0.1 and 0.2 slpm. The resulting product has the same structural properties and the nitrogen is incorporated into the graphitic structure through pyridinic type bonds.     

Synthesis of Carbon Nanohorns by Inductively Coupled Plasma

We demonstrate a new pathway for the synthesis of carbon nanohorns (CNHs) in a reactor by using inductively coupled plasma (ICP) and gaseous precursors. Thermal plasma synthesis allows the formation of different carbon allotropes such as carbon nanoflakes, hybrid forms of flakes and nanotubules, CNHs embryos, seed-like CNHs and onion-like polyhedral graphitic nanocapsules. In this study, pressure has the greatest impact on the selectivity of carbon nanostructures: pressure below 53.3 kPa favors the growth of carbon nanoflakes and higher pressures, 66.7 kPa and above, promotes the formation of CNHs. The ratio between methane and hydrogen as well as the global concentration of CH₄?+?H₂ inside the plasma flame are also crucial to the reaction. CNHs are formed preferentially by injection of a 1:2 ratio of H₂ to CH₄ at 82.7 kPa with a production rate of 20 g/h. The synthesis pathway is easily scalable and could be made continuous, which offers an interesting alternative compared to methods based on laser-, arc- or induction-based vaporization of graphite rods.

Graphical Abstract

     

Modeling Injection of Dense Liquid Sprays in Radio Frequency Inductively Coupled Plasmas

A spray model and a droplet collision model are implemented into a radio frequency inductively coupled plasma model. The discrete parcel technique combined with the stochastic Monte Carlo method is used to solve the spray equation and determine the outcomes of droplet collisions in dense sprays. Plasma--spray interactions are considered by adding source terms to the conservation equations of mass, momentum and energy of the plasma phase. Two types of the outcomes of water droplets collisions, coalescence and grazing, are predicted and compared to the experimental and analytical results. The agreement is quite good. The effects of droplet collisions on droplet size distribution of the spray and the spray evaporation are investigated. It is found that the droplet collisions can increase the average droplets size of the spray. For the mono-disperse spray, the collisions can lead to a delay on the spray evaporation. However, for the poly-disperse spray, the effect of droplet collisions on the spray evaporation could not be predicted before the calculation due to the randomness of droplet collisions.     

Volatile Compounds Present in Carbon Blacks Produced by Thermal Plasmas

Carbon black nanopowders were produced using two thermal plasma processes based on DC, respectively ICP plasma torches. Although the produced particles were in the nanometer size range, the values obtained for the surface area of the particles using a Brunauer Emmett Teller technique were very small. This indicated the presence of contaminants in the experimental powders, as confirmed by Raman spectroscopy and Thermogravimetric Analysis. A thermal treatment process was developed in order to extract these volatile compounds, which were then identified using a Gas Chromatography—Mass Spectrometry method. The experimental powders were analyzed using Scanning and Transmission Electron Microscopy, X-Ray Diffraction and Raman Spectroscopy before and after the thermal treatment in order to determine the effect of the heat treatment on the powder structural properties.     

Etching of Silicon and Silicon Dioxide in Dense Low-Pressure Inductively Coupled Radiofrequency Discharge Fluorocarbon Plasmas

The results of a study on the selective etching of SiO₂ and Si in dense low-pressure (p < 1 Pa) inductively coupled radio-frequency discharge fluorocarbon (HF₃ and HF₃ + H₂) plasmas in a nonuniform magnetic field are reported. It was found that the selectivity of etching SiO₂/Si increased from 9 to 24 with the addition of hydrogen. In the etching of SiO₂ in a HF₃ + H₂ plasma under certain process conditions, groove ridges were formed at the bottom of the etched groove. The mechanisms of ridge formation and the role of ion bombardment in this process are discussed.     

Compensation of Ca and Na Interference Effects in Axially and Radially Viewed Inductively Coupled Plasmas

The linear relationship between Ca and Na interferences and energy potentials for a wide range of atomic and ionic lines is used to compensate for variable intensity suppression in robust axially and radially viewed inductively coupled plasmas (ICPs). In the axial configuration, intensity attenuation varied from 0 to 40% in the presence of 0.5% Ca and Na. In the radially viewed ICP, interferences were smaller, varying from 5 to 15% for 0.5% Na and from 10 to 30% for 0.5% Ca. Signal attenuation was broadly a linear function of the energies of the spectral lines. These linear functions were estimated by using spectral lines covering the energy range from Sb I 206.833 (5.98 eV), Y II 371.209 and Sc II 361.384 (9.9 eV), Sc II 255.237 (11.42 eV), and Be II 313.042 (13.28 eV) nm. These functions were then used as variable internal standards to compensate for Ca, Na, and mixed Ca–Na matrix effects. Whereas analyte recoveries without compensation varied from about 40 to 90%, they varied mostly from 100 ± 5% when these functions were used. In the presence of Ca and Na, the Mg II 280.270/Mg I 285.213 nm intensity ratio decreased from about 12 for an aqueous solution to 9 at 1.5 kW. Such values confirm that the radially and axially viewed ICPs were robust.     

Gold Nanoparticle Determination by Inductively Coupled Plasma-Mass Spectrometry,Anodic Stripping Voltammetry,and Flame Atomic Absorption Spectrophotometry

Gold Nanoparticles (AuNP) were measured by Inductively Coupled Plasma–Mass Spectrometry (ICP-MS), Anodic Stripping Voltammetry (SV), and flame Atomic Absorption Spectrophotometry (AAS). Experiments investigated the relationships between counts per second (ICP-MS), absorbance (AAS), or μA (SV) and Au concentrations in solutions bearing AuNP with sizes of 5, 15, and 50 nm. Similarly the impact of the solution matrix was assessed using deionized water, 1.0 M HNO₃, 1.0 M HCl (ICP-MS and AAS), and water containing the bacterium E. coli (～10⁶ organisms/mL) by all three types of instrumentation. Each instrument yielded linear calibration curves with a signal proportional to Au concentration over the concentration range 0.02 ppm to 1 ppm.The methods were all reliable when biomacromolecules or when organisms such as E.coli existed in the matrix. Comparing the limits of detection for the three methods, ICP-MS and SV were lower than AAS. Comparing cost, SV and AAS were less expensive than ICP-MS. Comparing time required for each measurement, AAS was shorter than ICP-MS and SV. In comparison of the interfering effects of E-coli, ICP-MS and AAS were less-affected, while SV was more affected. An intact E.coli or organism may be very absorptive on the electrode surface,which reduced the measured anodic currents in SV and also increased the standard deviations.     

纳米银的单颗粒-电感耦合等离子质谱法表征及其测定

建立单颗粒-电感耦合等离子体质谱法( SP-ICP-MS)测定稀溶液中纳米银颗粒粒度分布及纳米银颗粒数量浓度的方法。当停留时间为3 ms时,两个或多个纳米银颗粒同时进入检测器的可能性降至最低。采用5倍标准偏差迭代算法(5σ)区分纳米银颗粒信号和背景信号。采用SP-ICP-MS法测定3种商品级纳米银颗粒(30,50和100 nm)粒度分布和纳米颗粒浓度。结果表明：SP-ICP-MS法测定纳米银颗粒结果与纳米银的TEM值相近,可采用SP-ICP-MS法表征纳米银颗粒。本方法测定稀溶液中纳米银颗粒粒度检出限为25 nm,纳米银颗粒浓度检出限约为8×104个/L。将纳米银颗粒加入到自来水样品中并进行测定,获得相近的纳米银粒度分布及纳米颗粒浓度。本方法简单、快捷、灵敏度高,可为研究水环境中纳米银的风险评估提供可靠分析方法,并为饮用水中纳米银的监测提供分析技术。     

电感耦合等离子体原子发射光谱法测定低碳高硫钢中铋的含量

采用电感耦合等离子体原子发射光谱法测定某低碳高硫钢中的铋含量。通过实验探讨了钢中基体元素及共存元素对铋元素分析谱线的光谱干扰情况,确定了合适的分析谱线和背景校正方法,铋元素的分析谱线为223．061nm。根据某低碳高硫钢中铋元素含量范围,合成系列标准溶液,建立工作曲线,工作曲线的线性范围为0．01％～0．50％,线性相关系数r=0．9998,方法检出限为0．00279％,测量结果的相对标准偏差小于2．7％,加标回收率为98．2％～101．2％。     

Three-Dimensional Two-Temperature Modeling of Ar Loop-Type Inductively Coupled Thermal Plasma for Surface Modification

In this paper, numerical calculations were made for Ar loop-type inductively coupled thermal plasma (loop-ICTP). The loop-ICTP was developed originally by the authors’ group for rapid surface modification of large areas. Loop-ICTP is sustained with a unique three-dimensional (3D) configuration inside a circular loop quartz tube and on the substrate. A 3D and two-temperature thermofluid thermal plasma model was adopted for this calculation. Mass, momentum, and energy conservation equations were solved using a Maxwell equation for vector potential, an electron energy transport equation, and Saha’s equation in the 3D space. Results indicate that Ar loop-ICTP can be sustained and formed in the loop tube and also on the substrate. Moreover, the heavy particle temperatures reaches 1800–2000 K, whereas the electron temperature is about 10,000 K. Loop size effects on the gas temperature and gas flow field were also investigated using the developed model. Results show that adoption of a larger loop tube can be expected to improve the plasma uniformity on the substrate when applied to rapid surface modification.

     

超声辅助提取/单颗粒电感耦合等离子体质谱法测定防晒化妆品中的纳米二氧化钛

建立了超声辅助提取/单颗粒电感耦合等离子体质谱(SP-ICP-MS)测定防晒化妆品中纳米TiO_2的方法。考察了停留时间、纳米粒子数量及浓度等分析条件,确定了防晒化妆品中纳米TiO_2的最佳萃取条件以及测定方法,对比了不同萃取溶剂对防晒霜中纳米TiO_2的提取效果。结果表明,在采用0. 1%Tritonx-100(Tx-100)以及5%乙醇作为萃取剂超声辅助提取,测定停留时间为3 ms,待测样品中纳米颗粒的数量浓度低于4×10~7个/mL条件下,该法可准确测定防晒化妆品中的纳米TiO_2,对防晒化妆品中纳米TiO_2的数量浓度检出限(LOD_(conc))为1×10~4个/mL,纳米颗粒粒度检出限(LOD_(size))为35 nm。方法简单快捷、灵敏度高、准确性良好,可同时对防晒化妆品中TiO_2进行浓度测定及粒度分布表征。     

微波消解-电感耦合等离子体质谱(ICP-MS)法测定纳米银抗菌产品中多种微量元素

建立了微波消解-电感耦合等离子体质谱(ICP-MS)法测定4种纳米银抗菌产品中多种微量元素的分析方法。比较了湿法消解和微波消解这两种样品前处理方法对样品测定的影响,探讨了消除汞记忆效应的方法,并研究了待测元素的质谱干扰的消除。实验结果表明,采用Au(100μg/L)+HCl(2%)能较好地消除Hg的记忆效应。与湿法消解相比,微波消解可短时间消解样品并获得好的Hg回收率。在优化ICP-MS条件后,各元素线性相关系数均大于0.999。采用微波消解-ICP-MS法对样品进行加标回收,样品加标回收率在84.0%~109%,相对标准偏差在0.97%~13.2%。方法快速、简便,能够满足纳米银抗菌产品中微量元素的定量测定。     

Determination of Mercury by Inductively Coupled Plasma—Mass Spectrometry

To control the amount of mercury polluting our environment, mercury has to be monitored in all areas of modern life. This requires fast and easy-to-use methods that permit the determination of mercury at levels of micrograms per liter. Up to now mercury ultratrace determination has required preconcentration or amalgamation in order to improve detection limits. This decreases accuracy of determination, introducing a longer manipulation of the sample. Inductively coupled plasma—mass spectrometry (ICP-MS) allows a direct determination of ultratrace mercury, due to the choice of interference free isotopes by the mass spectrometer detector. In fact, the detection limit for mercury by ICP-MS is 0.001 ppb. In the present work results of Hg determinations in different matrices by ICP-MS are reported. ICP-MS technique results are better than those of FIMS-100. This technique is applicable to different solid (minerals and atmospheric particulate) and liquid matrices with elimination of interferences. For solid matrices methods of attack and dissolution are reported.     

电感耦合等离子体质谱间接法测定蛋白质含量

尺寸排阻色谱分离牛血清白蛋白(BSA),超氧化物歧化酶(SOD)和金属硫蛋白(MT)等3种标准蛋白的混合物后,在线使用电感耦合等离子体质谱测定这三种蛋白中的S,并根据每种蛋白质含有的S原子数,计算出3种蛋白质的相对含量。尺寸排阻色谱的流动相为0.1mol/LTris-HAc。向电感耦合等离子体质谱的六级杆加入反应气O2,使之与S反应生成SO ,间接测定32S16O 而避开直接测量32S时存在的严重干扰。测量结果与天平称量所得结果一致。方法的精密度好,每个蛋白质峰面积的RSD<3%(n=3)。BSA、SOD和MT的检出限分别为14、52和27pmol。     

激光剥蚀-多接收电感耦合等离子体质谱法 测定含钚颗粒物中240 Pu/239 Pu比值

为高精度、准确地获取含钚颗粒物中具有核保障监督意义和核取证价值的钚同位素比值,建立了激光剥蚀-多接收电感耦合等离子体质谱(LA-MC-ICP-MS)测定含钚颗粒物中240 Pu/239 Pu的分析方法.采用检漏、安装排风罩和擦拭剥蚀池内壁等方式有效降低激光剥蚀产物沾污实验室和危及人身安全的潜在风险.联用扫描电迁移率粒径谱仪(SMPS)与激光剥蚀-多接收器等离子体质谱(LA-MC-ICP-MS)研究了激光剥蚀玻璃基体标样产生气溶胶的分布特性,结果表明,剥蚀产物的主要粒径是40~500 nm,应尽量采用水平管道连接激光剥蚀进样系统与MC-ICP-MS,含钚颗粒物分析后剥蚀池持续吹扫时间应大于15 min.采用外标归一化法离线校正质量分馏效应和离子计数器检测效率,建立了含钚颗粒物中240 Pu/239 Pu的LA-MC-ICP-MS分析方法,固定束斑直径30μm、脉冲重复率5 Hz、剥蚀时间5 s,调节能量密度使含钚颗粒物模拟样品中239 Pu的信号强度分别达2×104 cps和2×105 cps,本方法对240 Pu/239 Pu测量的相对实验标准不确定度小于1.4%(n=6),测量结果与参考值的相对偏差小于4.7%,仪器调试时间和单个样品测量时间分别为9.0和0.5 h.含钚颗粒物模拟样品分析结果表明,本方法精度高、结果准确、分析速度快,可满足核保障监督、禁产核查和核取证中含钚颗粒物直接分析的需求.     

电感耦合等离子体质谱法测定高纯金中痕量杂质

建立了高纯金中40余种痕量杂质的电感耦合等离子体质谱测定方法。方法检出限为0．0006～0．21μg/L。考察了基体Au的谱干扰及基体效应,采用Cs内标补偿基体对待测信号的抑制作用。方法简单、快速、灵敏、准确。     

甲基硫酸新斯的明的ICP-AES测定

研究了电感耦合等离子体原子发射光谱法间接测定甲基硫酸新斯的明,在溶液pH为5.0,四苯硼钠过量时可完全沉淀甲基硫酸新斯的明,测定滤液中的四苯硼钠可以计算得到甲基硫酸新斯的明的含量;方法简单快速,回收率在95％-101％之间,相对标准偏差为1.8％。