Han Jianjun

Plasma Activation of Integrated Carbon Nanotube Electrodes for Electrochemical Detection of Catechol

In this study, integrated multi-wall carbon nanotube (MWCNT) electrodes were prepared in the holes of glass directly by microwave plasma chemical vapour deposition (MWPCVD). The electrochemical behaviour of catechol at the integrated MWCNT electrodes was investigated. The oxygen plasma treated CNT electrodes had better electrochemical performance for the analysis of catechol than that of as-synthesized CNT electrodes. Both the as-synthesized CNTs and plasma treated CNTs were characterized by TEM(transmission electron microscopy, XPS(X-ray photoelectron spectroscopy) and Raman spectroscopy. The results revealed that the oxygen plasma activation is an effective method to enhance the electrochemical properties of CNT electrodes.

IR spectra analysis of SiO2−TiO2−GeO2 gel glass of CO2 laser transmitting hollow waveguide

Both titanium and germanium were introduced into silicon dioxide system by sol-gel method to move its region of anomalous dispersion caused by IR resonance absorption towards the wavelength of CO2 laser. It is indicated by IR absorption spectra that as the content of SiO2 decreases in this glass system TiO2 and GeO2 tends to exist in their own phases. As for the gel glass with a composition of 40 SiO2·30TiO2·30GeO2, when the temperature is below 600°C, germanium atoms exist mainly in Ge−O−Ge bonds. With the temperature increasing from 800°C to 1000°C, titanium atoms in Si−O−Ti bonds abmost transform into Ti−O−Ti bonds. Furthermore, a large number of Si−O−Ti and Si−O−Ge bonds formed when the temperature approaches 800°C, which makes a notable IR absorption band round the wavelength of CO2 laser. Therefore, sol-gel based SiO2−TiO2−GeO2 gel glass is a candidate material for CO2 laser hollow waveguide.

Effect of particle density on the aligned growth of carbon nanotubes

Aligned carbon nanotubes (CNTs) were prepared on Nicoated Ni substrate by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at temperature of 550°C. The experimental results show a direct correlation between the alignment of CNTs and the density of the catalyst particles at low temperature. When the particle density is high enough, among CNTs there are strong interactions that can inhibit CNTs from growing randomly. The crowding effect among dense CNTs results in the aligned growth of CNTs at low temperature.Aligned carbon nanotubes (CNTs) were prepared on Nicoated Ni substrate by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at temperature of 550°C. The experimental results show a direct correlation between the alignment of CNTs and the density of the catalyst particles at low temperature. When the particle density is high enough, among CNTs there are strong interactions that can inhibit CNTs from growing randomly. The crowding effect among dense CNTs results in the aligned growth of CNTs at low temperature.

Effect of thermal treatment and acid leaching process on pore characteristics of nanometer porous glass

Porous glass was prepared by thermally treating sodium borosilicate glass for different time, the effect of thermal treatment on pore size distribution was discussed and the pore size of the prepared porous glass was measured by scanning electron microscopy (SEM) and differential thermal analysis (DTA). The results show that the optimum porous glass with an average diameter of 80 nm can be prepared by thermal treatment at 600 °C for 12 h and then acid treatment for 12 h in 2 mol·L−1 hydrochloric acid solution.

Effects of nitric acid concentration on the stability of alumina sols

Alumina sols with a molar ratio of 1:50 between aluminum sec-butoxide (ASB) and H2O were fabricated by adding various amounts of nitric acid. The particle shape, zeta potential, polydispersity and effective particle size of alumina sol were examined by a TEM, a zeta PALS granularity analyzer and a zetaPALS zeta potential analyzer, respectively. By analyzing the change of zeta potential and double-layer thickness with nitric acid concentration, the potential energy curves of colloidal particles were mapped on the basis of DLVO theory, and the effects of nitric acid concentration on the stability of alumina sols were intensively studied. The results show that for the alumina sols with a mol ratio of 1:50 between ASB and H2O, the total interaction energy of the colloidal particle is at a maximum when the nitric acid concentration is 0.22 mol/L. Therefore, the stability of the colloid reaches optimum at the nitric acid concentration of 0.22 mol/L.

Fabrication Silver Film inside Silica Capillary

To study hollow waveguides for CO2 laser transmission, a liquid-phase deposition technique is applied to form a silver film inside silica capillary based on the method of silver mirror reaction. Using this fabrication method, the optimum combination of different parameters is gained and hollow waveguides have been made successfully with a bore size of 1mm and a guide with length of as long as 2m on self-producing apparatus. To meet quality silver film, a relative high temperature, low flowing speed and long time are adopted on the basis of low reactant concentration. The maximum transmission efficiency of hollow-core fiber without dielectric coating can be up to 85 percent and loss can be low to 0.5dB/m, maximum output power is 53W for stable 20 mintues.