Papers by Keyword: Catalytic Method

Abstract: A new catalytic kinetic method for the determination of vanadium (V) was proposed, based on the V (V) catalyze the slow reaction between KClO₃ and phenylgycollic acid (PA) in 0.6 mol/L H₂SO₄ solution at 100 °C. The reduction product of ClO₃^-, Cl^-, reacts with Ag⁺ to form (AgCl)_n nanoparticles. The nanoparticles exhibit a max resonance scattering spectral peak at 470 nm and a strongest fluorescence peak at 470 nm. The resonance scattering intensity at 470 nm is linear to the V concentration in the range of 2.0×10^-9 mol/L to 4.0×10^-8 mol/L. The influence factors on the catalytic resonance scattering determination of trace vanadium were examined. This catalytic resonance scattering spectral method has been applied to the analysis of vanadium in real samples, with satisfactory results.

Abstract: The effects of temperature on carbon nanotubes (CNTs) by thermal chemical vapor deposition (TCVD) method were systematically studied. Natural hydrocarbon source; palm oil was used as precursor and argon as carrier gas. Palm oil vaporized optimally at 450oC in ambient pressure. The synthesis temperature start at 650°C and were increased at rate of 50°C for series of samples until it reaches maximum temperature of 900°C. The samples were grown on nickel nitrate, which was coated on silicon substrate. The CNTs characteristics were studied using field emission scanning electron microscopy (FESEM), Raman and infrared (IR) spectroscopy. The experimental results revealed that CNTs properties are highly dependent on temperature. It was found that with increasing synthesis temperature, the CNTs diameter decreased initially and then increased after passing an optimum synthesis temperature of 750°C. The bamboo like structure were obviously found at higher synthesis temperature 800°C-850°C while there were few CNTs seen at 900°C.

Abstract: Carbon nanotubes (CNTs) were fabricated from palm oil using the thermal chemical vapor deposition technique utilizing a two furnace system. The effect of precursor vaporization temperature of the first furnace, in the range of 300-600°C was systematically studied with the synthesis temperature (second furnace) fixed at 750°C for a total time of 30 min. The samples were characterized using field emission scanning electron microscopy and micro-Raman spectroscopy. CNTs of various packing densities and diameters were synthesized with the varying precursor vaporization temperature. Based on micro-Raman measurements nanotube defect level and the presence of SWCNT were dependent on the vaporization temperature. Vertically aligned CNTs (VACNTs) were found to grow within the vaporization temperature range of 400-500°C, with well graphitized and higher yield obtained at 450°C with excellent lateral alignment, uniform nanotubes diameter (~15 nm), orientation and distribution within the CNT bundles. At vaporization temperatures of 300-350°C and 500-600°C, lower growth rate, bigger nanotubes diameter and higher ID/IG ratio were observed which indicated lower nanotubes quality that produced at both temperature ranges.

Abstract: The effects of synthesis temperature on the quality and quantity of vertically aligned carbon nanotubes (VACNT) were studied using high resolution scanning electron microscopy, and micro-Raman spectroscopy. The VACNT was synthesized by Fe catalytic decomposition of palm oil deposited on silicon substrate by thermal chemical vapour deposition method. The analysis shows that the growth rate increases from 3.8 to 5.5 µm/min as the temperature was increased from 750 to 800°C. The nanotube diameters were observed bigger at low temperature range. Smaller and uniform diameter (~15 nm) was found at 750°C and the increment in diameter size was seen at higher temperature range. Smaller graphite Raman “G” peak width, low ID/IG ratio (~0.52) indicated higher crystallinity of the nanotube and moderate I2D1/ I2D2 ratio for second order Raman peak was also detected at synthesis temperature of 750°C. These results indicated that the optimum synthesis temperature for higher quality VACNT production was at 750°C.