carbon nanotubes were synthesized over a series of zn-containing fe/alumina catalysts by chemical vapor deposition method at two reaction temperatures of 850 and 950 °c using methane as a carbon source. catalysts were synthesized by keeping fe concentration constant and varying zn concentration to study the effects of zn. the catalysts were characterized using x – ray powder diffraction and n2 ...

the growth rate of carbon nanotubes in chemical vapor deposition is simulated by using a theoretical analysis of the phonon vibration of the system. simulations demonstrate that the growth rate of carbon nanotubes with larger diameters is smaller because of higher damping factors and carbon nanotube inertia. an optimum temperature for the growth rate is calculated for a carbon nanotube on fe ca...

in this study, we describe the growth of carbon nanotubes on commercial iron nanoparticles without carbon shell (fe (nm), size 2o3 and fe* (nm)/mgo) was carried out by mixing commercial fe* nanoparticles (as catalyst) with al2o3 and mgo powders (as supports)by using ball-milling method. the results show in spite of the fact that ball-milling process can have negative effects on diameter and mor...

chemical vapor deposition was employed to synthesize carbon nanotubes with ni-loaded mcm-41 and mcm-48 as catalysts and acetylene as precursor at 750°c. mesoporous ni mcm-41 and ni mcm-48 molecular sieves were synthesized by a hydrothermal method and were characterized by xrd and n2 adsorption isotherm. the catalytically synthesized carbon materials were characterized with raman spectroscopy, n...

a combined electrodeposition-etaas technique has been applied to the analysis of pb, cd, co, ni, cr and mn in biological samples in order to overcome interferences and to minimize sample pretreatment. it requires minimal sample preparation with the electrolysis process aiding partial decomposition of the organic matrix, adequate for the release and deposition of trace elements. in an initial el...

the purpose of this study is to identify parameters influence on the particle deposition within fin and tube heat exchanger of air-conditioning systems by cfd analysis. first the basic sketch of periodic geometry drawn and meshing operation including boundary conditions was performed. then the gas side properties and flow parameters were solved by ansys fluent 14.5 software. lagrangian equation...

having sufficient and accurate understanding about kinetics of phenomena, could be an important reason for further technological progresses. finding a white-box mathematical model for weight vs. time curves of electrophoretic deposition (epd) using large and small signal analysis has been studied thoroughly in the present investigation. weight-time curves of nano-mullite suspension have been tr...

in this study, physical vapor deposition (pvd) ti-cr-n coatings were deposited at two different temperatures100 and 400ºc on hardened and tempered tool steel substrates. the influence of the applied deposition temperature on the physical and mechanical properties of coatings such as roughness, thickness, phase composition, hardness and young’s modulus were evaluated. phase compositions were stu...

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Acid rain has been a big problem for urban area during recent decades. Acid rain comes from high concentration of air pollutant, including man made or artificial and natural, in the atmosphere. Mashhad, as the biggest religious town in Iran, has also been imposed with this problem. In this investigation the samples of rains during autumn 2002 and spring 2003 are analyzed. The results showed tha...