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Fabrication of gas ionization sensor using carbon nanotube arrays grown on porous silicon substrate
, Article Sensors and Actuators, A: Physical ; Volume 162, Issue 1 , 2010 , Pages 24-28 ; 09244247 (ISSN) ; Iraji Zad, A ; Razi, F ; Mortazavi, S. Z ; Sharif University of Technology
2010
Abstract
We fabricated gas sensors based on field ionization from multiwalled carbon nanotube (MWCNT) arrays grown on porous silicon templates. MWCNTs were grown through thermal chemical vapor deposition. We measured breakdown voltages, discharge and pre-discharge currents of the device for various gases in different concentrations. Our gas ionization sensors (GIS) presented good sensitivity, selectivity and short response time. The GISs based on porous substrates showed higher discharge current and good mechanical stability in comparison to those which were fabricated on polished silicon substrates. Additionally, we applied a high electric field to align CNTs. This increased the pre-breakdown...
Hydrogen sensing properties of multi-walled carbon nanotube films sputtered by Pd
, Article International Journal of Hydrogen Energy ; Volume 35, Issue 9 , 2010 , Pages 4445-4449 ; 03603199 (ISSN) ; Mortazavi, S. Z ; Iraji zad, A ; Rahimi, F ; Sharif University of Technology
Abstract
Multi-Walled Carbon nanotube (MWCNTs) films were obtained by Thermal Chemical Vapor Deposition method and coated by palladium sputtering process. Raman spectroscopy was used to study alteration in quality of the carbon nanotubes after the sputtering process. Fourier Transform Infra Red (FTIR) spectroscopy showed that hydrogenation process can reduce the C{double bond, long}O to C-O and also produce O-H bond. Furthermore, the electrical resistance measurement for Pd/MWNTs films was performed in a chamber with 1% hydrogen gas in a constant dry air flow. Hydrogen sensing behavior of the films was investigated at 50 °C. Pd/MWCNTs films presented an irreversible gas response to hydrogen in the...
A study on the effects of Fex/Niy/MgO(1-x-y) catalysts on the volumetric and electrochemical hydrogen storage of multi-walled carbon nanotubes
, Article International Journal of Hydrogen Energy ; Volume 35, Issue 1 , 2010 , Pages 231-237 ; 03603199 (ISSN) ; Mortazavi, S. Z ; Zaker Moshfegh, A ; Nozad Golikand, A ; Sharif University of Technology
Abstract
The effects of various ratios of Fe/Ni/MgO and growth temperatures on yield, diameter and quality of multi-walled carbon nanotubes (MWCNTs) were studied. Thermal gravimetric analysis (TGA) confirmed that the MWCNT yield depends on Fe/Ni ratio with the following order; Fe0.5 Ni0.5 > Fe > Fe0.75 Ni0.25 > Fe0.25 Ni0.75 > Ni. The results indicated that there is an optimum temperature (940 °C) for the MWCNT growth both from quality and quantity (yield) aspects as compared to other temperatures. Moreover, the changes on Fe/Ni to MgO ratio for the MWCNT growth revealed that Fe/Ni/MgO with the ratio of 17.5/17.5/65 had the highest quality and surface area as compared to the other ratios. The...
Chemo-physical properties of renal capsules under ultraviolet-c exposure
, Article Journal of Applied Physics ; Vol. 116, Issue. 5 , 2014 ; ISSN: 00218979 ; Parvin, P ; Reyhani, A ; Mortazavi, S. Z ; Mokhtari, S ; Amjadi, A ; Sharif University of Technology
Abstract
The renal capsule tissue of lamb was irradiated with ultraviolet-C light and the treated samples were analyzed by uniaxial tensile test, dynamic mechanical analysis, attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and contact angle measurements. It was shown that the skin cross-linking is dominant in low doses in accordance with the contact angle assessment. Conversely, the strong bulk degradation takes place at high doses. Similarly, the bulk cross-linking affects the mechanical tests as to enhance the stiffness at low doses, whereas strong degradation occurs at high doses that mainly arises from the strong bulk chain scission
H 2 adsorption mechanism in Mg modified multi-walled carbon nanotubes for hydrogen storage
, Article International Journal of Hydrogen Energy ; Volume 37, Issue 2 , January , 2012 , Pages 1919-1926 ; 03603199 (ISSN) ; Mortazavi, S. Z ; Mirershadi, S ; Golikand, A. N ; Moshfegh, A. Z ; Sharif University of Technology
Abstract
Multi-walled carbon nanotubes (MWCNTs) with diameter of about 50 nm were synthesized using thermal chemical vapor deposition. We have investigated the influence of Mg doping to the MWCNTs on its hydrogen storage property. TEM micrographs showed that Mg was attached to the MWCNTs and discontinuous arrangement of the carbon walls was recognized in the MWCNTs. According to XPS and BET analyses, the surface functional groups and pore size of the Mg-MWCNTs are increased by interactions between the Mg and the MWCNT's outer walls. The electrochemical discharging curves of the MWCNTs and Mg-doped MWCNTs revealed that the hydrogen storage capacity was 363 and 450 mAhg -1, respectively. Volumetric...
Hydrogen storage in decorated multiwalled carbon nanotubes by Ca, Co, Fe, Ni, and Pd nanoparticles under ambient conditions
, Article Journal of Physical Chemistry C ; Volume 115, Issue 14 , 2011 , Pages 6994-7001 ; 19327447 (ISSN) ; Mortazavi, S. Z ; Mirershadi, S ; Moshfegh, A. Z ; Parvin, P ; Golikand, A. N ; Sharif University of Technology
Abstract
We report a study on hydrogen storage in Ca, Co, Fe, Ni, and Pd decorated multiwalled carbon nanotubes (MWCNTs) by using two techniques: volumetric and electrochemical. The results showed that hydrogen molecules are adsorbed on the defect sites and transported to the spaces between adjacent carbon via diffusion through both defect sites and opened tips into the layers. Hydrogen storage capacity can be improved in the decorated MWCNT by Co, Fe, Ni, and Ca metals in two approaches: (i) H2 adsorption via Kubas interaction and (ii) dissociation of H2 molecules on the metal particles. The results reveal that Pd are more effective catalyst for hydrogen storage process. It was found that...
Physical and chemical properties of lamb renal capsule irradiated by ArF laser
, Article Journal of Laser Applications ; Volume 27, Issue 1 , 2015 ; 1042346X (ISSN) ; Parvin, P ; Reyhani, A ; Mortazavi, S. Z ; Baghapour, Sh ; Amjadi, A ; Sharif University of Technology
Abstract
Excimer laser at 193 nm was irradiated on the renal tissues during various exposure times in order to investigate the chemical and physical surface properties using Fourier transform infrared spectroscopy, photo electron spectroscopy, contact angle measurements, and tensile test accordingly. We have shown that ultraviolet laser strongly alters the oxygen content of skin layer that causes changes in the tissue morphology leading to significant skin hydrophilicity
The effects of multi-walled carbon nanotubes graphitization treated with different atmospheres and electrolyte temperatures on electrochemical hydrogen storage
, Article Electrochimica Acta ; Volume 55, Issue 16 , June , 2010 , Pages 4700-4705 ; 00134686 (ISSN) ; Nozad Golikand, A ; Mortazavi, S. Z ; Irannejad, L ; Moshfegh, A. Z ; Sharif University of Technology
2010
Abstract
Using multi-walled carbon nanotubes (MWCNTs), the present study focuses on their electrochemical hydrogen storage capacities. The results showed that the hydrogen desorption process is composed of two steps with voltages around -0.75 and -0.15 V. Hydrogen adsorption at -0.15 V took place at temperatures above 30 °C, and the amount of energy required for adsorbing hydrogen was 1.68 eV. The hydrogen storage capacity increased with increasing electrolyte temperature from 30 to 60 °C in both steps. The hydrogen storage capacity of the MWCNTs treated at different atmospheres showed that the decrease in the graphitization of MWCNTs led to the increase in hydrogen adsorption. The results also...
Enhanced electrochemical hydrogen storage by catalytic Fe-doped multi-walled carbon nanotubes synthesized by thermal chemical vapor deposition
, Article Journal of Power Sources ; Volume 188, Issue 2 , 2009 , Pages 404-410 ; 03787753 (ISSN) ; Mortazavi, S.Z ; Moshfegh, A.Z ; Golikand, A.N ; Amiri, M ; Sharif University of Technology
2009
Abstract
Hydrogen storage capacities of raw, oxidized, purified and Fe-doped multi-walled carbon nanotubes (MWCNTs) were studied by electrochemical method. Based on transmission electron microscopy and Raman spectroscopic data, thermal oxidation removed defective graphite shells at the outer walls of MWCNTs. The analysis results indicated that the acid treatment dissolved most of the catalysts and opened some tips of the MWCNTs. Thermal gravimetric analysis and differential scanning calorimetry results illustrated that by oxidation and purification of MWCNTs, the weight loss peak shifts toward a higher temperature. N2 adsorption isotherms of the purified and oxidized MWCNTs showed an increase in N2...
The effect of various acids treatment on the purification and electrochemical hydrogen storage of multi-walled carbon nanotubes
, Article Journal of Power Sources ; Volume 183, Issue 2 , 1 September , 2008 , Pages 539-543 ; 03787753 (ISSN) ; Mortazavi, S. Z ; Nozad Golikand, A ; Moshfegh, A. Z ; Mirershadi, S ; Sharif University of Technology
Elsevier
2008
Abstract
The effects of HCl, HNO3, H2SO4 and HF acids on the purification and the electrochemical hydrogen storage of multi-walled carbon nanotubes (MWCNTs) were studied. The MWCNTs were synthesized on Fe-Ni catalyst by thermal chemical vapor deposition method. The X-ray diffraction and thermal gravimetric analysis results indicated that the MWCNTs purified by HF acid had the highest impurities as compared with the other acids. The N2 adsorption results at 77 K indicated that all the samples were mainly mesoporous and the purified MWCNTs by HF acid had the highest surface area as compared with the other acids. The hydrogen storage capacities of the purified MWCNTs by the following acids were in...