Well aligned nanotubes with diameter of 30—50 nm have been synthesized on a porous alumina template by microwave plasma enhanced chemical vapor deposition (MW PECVD). By this means, the control over either diameter o...Well aligned nanotubes with diameter of 30—50 nm have been synthesized on a porous alumina template by microwave plasma enhanced chemical vapor deposition (MW PECVD). By this means, the control over either diameter or length of the nanotubes could be realized. The hollow structure and vertically aligned features have been verified by scanning electron and transmission electron microscopic images. In comparison with the reported fabrication methods, lower synthesis temperature (below 520 ℃) and simpler process (no negative dc bias applied) have been achieved, which could be of great importance for both theoretical research and pratical applications.展开更多
Among the three main methods for the s ynthesis of carbon nanotubes(CNTs ),chemical vapor deposition(CVD)has received a great deal of attentio n since CNTs can be synthesized at sig nificantly low temperature.Plasma c...Among the three main methods for the s ynthesis of carbon nanotubes(CNTs ),chemical vapor deposition(CVD)has received a great deal of attentio n since CNTs can be synthesized at sig nificantly low temperature.Plasma chemical vapor deposition me thods can synthesize CNTs at lower te mperature than thermal CVD.But in th e usual catalytic growth of CNTs by CVD,CNTs are often tangled together and have some defects.These will limit t he property research and potential applications.How to synthesize the str aight CNTs at low temperature become s a challenging issue.In this letter,s traight carbon nanotube(CNT)films were achieved by microwave pla sma chemical vapor deposition(MWPCVD)catalyzed by round Fe-Co-Ni alloy particles on Ni substrate at 610℃.It wa s found that,in our experimental condition,the uniform growth rate along the circumference of round alloy particles plays a very important role in the gro wth of straight CNT films.And because the substrate is conducting,the straight CNT films grown at low temperature ma y have the benefit for property research and offer the possibility to use t hem in the future applications.展开更多
Two microwave digestion procedures were developed for unleaded gasoline. Microwave plasma torch atomic emission spectrometry(MPT-AES) was used to determine trace lead in unleaded gasoline after being digested. Optimal...Two microwave digestion procedures were developed for unleaded gasoline. Microwave plasma torch atomic emission spectrometry(MPT-AES) was used to determine trace lead in unleaded gasoline after being digested. Optimal conditions (analytical wavelength, microwave power, flow rate of carrier gas for the trace lead determination, flow rate of supporting gas, flow rate of oxygen shielding gas and acid concentrations) were chosen. The effects of concommitant elements on determination of lead were studied. The detection limit for lead was 25 ng/mL, the linear range was 0.05-100 μg/mL. The relative standard deviation for determination of unleaded gasoline samples was less than 4 9%, relative error was less than 3.7%. Standard addition recoveries were all between 93.3%-104.0%. The determination results with microwave digestion were in agreement with those obtained with conventional method. The proposed method is simple, rapid, accurate, and with less possibility to be contaminated by the environment, and of great applied value.展开更多
文摘流程工业颗粒物成分的在线检测具有低延时、安全可靠及低成本等要求,目前没有适合的技术手段.微波等离子炬(Microwave plasma torch,MPT)原子发射光谱法具有直接进样、成本低及装置安全可靠等优点,有潜力成为工业在线检测的重要手段.本文基于MPT装置对水泥样品进行直接进样分析,并针对工业应用场景中标准样品受限的问题,采用单样本定标技术(Single sample calibration,SSC)进行定量分析.SSC法中的线性假设容易受到等离子体参数波动的影响,导致精度下降.为此,提出了一种基于参数标准化的SSC算法PS-SSC(SSC based on parameter standardization),通过激发温度和电子数密度对谱线强度进行修正以提高SSC的定量精度.为了评估MPT和PS-SSC方法联用在水泥成分快速分析中的有效性,将GSB 08-2985-2013标准水泥粉末气溶胶直接引入MPT中进行定量分析,并将PS-SSC与现有定量方法进行比较.与传统SSC方法相比,PS-SSC方法的决定系数R2由‒0.81~0.81提高到0.39~0.88,平均相对误差由4.39%~10.33%提高到1.55%~5.83%,平均相对标准偏差由2.89%~9.40%提高到2.28%~6.50%,展现了该方法在工业在线成分检测中的应用潜力.
文摘Well aligned nanotubes with diameter of 30—50 nm have been synthesized on a porous alumina template by microwave plasma enhanced chemical vapor deposition (MW PECVD). By this means, the control over either diameter or length of the nanotubes could be realized. The hollow structure and vertically aligned features have been verified by scanning electron and transmission electron microscopic images. In comparison with the reported fabrication methods, lower synthesis temperature (below 520 ℃) and simpler process (no negative dc bias applied) have been achieved, which could be of great importance for both theoretical research and pratical applications.
文摘Among the three main methods for the s ynthesis of carbon nanotubes(CNTs ),chemical vapor deposition(CVD)has received a great deal of attentio n since CNTs can be synthesized at sig nificantly low temperature.Plasma chemical vapor deposition me thods can synthesize CNTs at lower te mperature than thermal CVD.But in th e usual catalytic growth of CNTs by CVD,CNTs are often tangled together and have some defects.These will limit t he property research and potential applications.How to synthesize the str aight CNTs at low temperature become s a challenging issue.In this letter,s traight carbon nanotube(CNT)films were achieved by microwave pla sma chemical vapor deposition(MWPCVD)catalyzed by round Fe-Co-Ni alloy particles on Ni substrate at 610℃.It wa s found that,in our experimental condition,the uniform growth rate along the circumference of round alloy particles plays a very important role in the gro wth of straight CNT films.And because the substrate is conducting,the straight CNT films grown at low temperature ma y have the benefit for property research and offer the possibility to use t hem in the future applications.
文摘Two microwave digestion procedures were developed for unleaded gasoline. Microwave plasma torch atomic emission spectrometry(MPT-AES) was used to determine trace lead in unleaded gasoline after being digested. Optimal conditions (analytical wavelength, microwave power, flow rate of carrier gas for the trace lead determination, flow rate of supporting gas, flow rate of oxygen shielding gas and acid concentrations) were chosen. The effects of concommitant elements on determination of lead were studied. The detection limit for lead was 25 ng/mL, the linear range was 0.05-100 μg/mL. The relative standard deviation for determination of unleaded gasoline samples was less than 4 9%, relative error was less than 3.7%. Standard addition recoveries were all between 93.3%-104.0%. The determination results with microwave digestion were in agreement with those obtained with conventional method. The proposed method is simple, rapid, accurate, and with less possibility to be contaminated by the environment, and of great applied value.
