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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Journal of Nanoanalysis
- نوع مقاله: Journal Article
- کلمات کلیدی: alcohol,DFT,γ-alumina,Molecular adsorption
- چکیده:
- چکیده انگلیسی: In this study, the adsorption behavior of the primary, secondary and tertiary alcohols over nanoscale (1 0 0) surface of defect spinel γ-alumina was investigated with the aid of density functional theory (DFT) at BLYP/DNP level of calculation. The influence of different substituents including alkyl, cycloalkyl, allyl and aryl were analyzed for free and adsorbed alcohols to shed light the adsorption selectivity of these compounds over γ-alumina surface. These results indicate that more branches at a position of alcohol favor the adsorption, while a decrease in adsorption energy is achieved for the alcohols containing the substituents at the β position. The tertiary alcohols are adsorbed over the surface stronger than secondary and primary alcohols. Alcohols with larger alkyl chains have greater adsorption energies. Also the aryl alcohols are adsorbed over the surface better than the alkyl and allyl moieties.
- انتشار مقاله: 10-03-1396
- نویسندگان: Mehdi Zamani,Hossein A. Dabbagh
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Nanoanalysis
- نوع مقاله: Journal Article
- کلمات کلیدی: Fullerenes,infrared,C20 Isomers,UV spectra
- چکیده:
- چکیده انگلیسی: Infrared (IR) and ultraviolet (UV) spectroscopic analysis of eight structural isomers of C20 carbon nanostructures, i.e. ring, tadpole, bow-tie, dumb-bell, spiro, propellane, bowl and cage, were performed at different levels of theory including semi-empirical (AM1 and PM3), Hartree-Fock (HF/6-31++G, 6-31++G**) and density functional theory (B3LYP/6-31++G, 6-31++G**). A broad range of IR spectra (400-2700 cm-1) is covered by C-C bending vibrations (low frequency region) and C-C stretching vibrations (high frequency region) in almost all isomers. The absorption maximum (λmax) in UV spectra for bowl and cage isomers appears below 300 nm and for cyclic isomers above it. These results show that IR and UV spectra are useful tools for identification of C20 structural isomers.
- انتشار مقاله: 10-03-1396
- نویسندگان: Mehdi Zamani,Ahmad Motahari,Hossein A. Dabbagh,Hossein Farrokhpour
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Computational Applied Mechanics
- نوع مقاله: Journal Article
- کلمات کلیدی: MEMS,Microbeam,Galerkin,Viscoelastic
- چکیده:
- چکیده انگلیسی: In this study, static deflection, natural frequency and nonlinear vibration in bi-layer clamped-clamped microbeam are investigated. In this configuration, the second layer is the viscoelastic layer which covers a part of the microbeam length. This model is the main element of many chemical microsensors. The governing equations of motion for the system are obtained by Lagrange method and discretized using the assumed mode method. The non-uniform micro-beam modes shape are used as the comparison function in the assumed mode method. Initially, considering the DC voltage, system static response and natural frequency around the static position are obtained. Then, considering the AC voltage, the dynamic response around the dynamic position is calculated by both analytical (perturbation method) and numerical methods (Rung-kutta) and compared for validation purposes. The effect of different geometrical parameters of the viscoelastic layer on the static and dynamic behaviors of the system is also analyzed. The results indicate that the dimensions and location of the viscoelastic layer significantly affect the static and dynamic behavior of the system. Therefore, by using this property and considering the application of microsensors, their behaviors can be made efficient. For sensors operating based on resonance frequency shift, the optimum shift of frequency state can be obtained by varying the dimensions and position of the viscoelastic layer. Moreover, time of response can be optimized when the system is operating based on changes in the capacity of a capacitor. The results also represent that convergence in the assumed mode method used in this paper is feasible even using a single mode, whereas in previous works and using the Galerkin method, convergence was fulfilled in the presence of 3 modes.
- انتشار مقاله: 10-06-1399
- نویسندگان: Maryam Ghalenoei,Mehdi Zamanian,Behnam Firouzi,Seyed Ali Asghar Hosseini
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Computational Applied Mechanics
- نوع مقاله: Journal Article
- کلمات کلیدی: MEMS,Microbeam,Galerkin,Viscoelastic
- چکیده:
- چکیده انگلیسی: In this study, static deflection, natural frequency and nonlinear vibration in bi-layer clamped-clamped microbeam are investigated. In this configuration, the second layer is the viscoelastic layer which covers a part of the microbeam length. This model is the main element of many chemical microsensors. The governing equations of motion for the system are obtained by Lagrange method and discretized using the assumed mode method. The non-uniform micro-beam modes shape are used as the comparison function in the assumed mode method. Initially, considering the DC voltage, system static response and natural frequency around the static position are obtained. Then, considering the AC voltage, the dynamic response around the dynamic position is calculated by both analytical (perturbation method) and numerical methods (Rung-kutta) and compared for validation purposes. The effect of different geometrical parameters of the viscoelastic layer on the static and dynamic behaviors of the system is also analyzed. The results indicate that the dimensions and location of the viscoelastic layer significantly affect the static and dynamic behavior of the system. Therefore, by using this property and considering the application of microsensors, their behaviors can be made efficient. For sensors operating based on resonance frequency shift, the optimum shift of frequency state can be obtained by varying the dimensions and position of the viscoelastic layer. Moreover, time of response can be optimized when the system is operating based on changes in the capacity of a capacitor. The results also represent that convergence in the assumed mode method used in this paper is feasible even using a single mode, whereas in previous works and using the Galerkin method, convergence was fulfilled in the presence of 3 modes.
- انتشار مقاله: 10-06-1399
- نویسندگان: Maryam Ghalenoei,Mehdi Zamanian,Behnam Firouzi,Seyed Ali Asghar Hosseini
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Catalysis
- نوع مقاله: Journal Article
- کلمات کلیدی: alcohol,Gelatin,Triton X-100,Nanoporous,Dehydration,γ-alumina,alkene
- چکیده:
- چکیده انگلیسی: In this study, the nanoporous γ-alumina catalysts were prepared by the sol-gel method using hydrolysis of aluminum isopropoxide in the presence of TX-100 or gelatin/TX-100 mixture. Catalysts were characterized by XRD, FT-IR, TEM, BET-BJH and N2 adsorption-desorption isotherms. To investigate reactivity and selectivity of the synthesized catalysts, dehydration reaction of 2-octanol was carried out in a plug flow vertical reactor at 200 °C. The main products of elimination reaction were 1-octene, 3-octene, cis- and trans-2-octene, which were identified by GC-MS. The reaction conversion and yield of the products were determined using GC. The prepared catalysts had nanometer-sized pores, high surface area and large pore volume. Their catalytic activity for dehydration of 2-octanol was higher than non-porous γ-alumina catalysts. These compounds could be used as effective catalysts for dehydration of alcohols.
- انتشار مقاله: 28-11-1398
- نویسندگان: Soheyl Alidoust,Mehdi Zamani,Morteza Jabbari
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Catalysis
- نوع مقاله: Journal Article
- کلمات کلیدی: alcohol,Reactivity,Alumina,Selectivity,Dehydration
- چکیده:
- چکیده انگلیسی: The influence of NaNO2, HNO3 and H2SO4 on the structure and morphology of gamma-alumina was investigated by XRD, BET, SEM and FT-IR spectroscopy. Selected amounts of NaNO2, HNO3 and H2SO4 were added to a solution of aluminum isopropoxide (as a precursor for the boehmite synthesis). The boehmite samples were calcined at 350 and 600 ℃ to form the semi-crystalline high surface area gamma-Al2O3. The reactivity and selectivity of the modified gamma-alumina catalysts were examined using dehydration reaction of 2-octanol. There was a good correlation between reactivity, selectivity and the amounts (and type) of the modification. The dominant product was cis-2-octene for all of the catalysts. Low conversion and high selectivity were obtained for dehydration of 2-octanol over alumina modified with NaNO2. High conversion, low selectivity and excessive isomerization were found for gamma-alumina catalyst modified with H2SO4.
- انتشار مقاله: 14-12-1397
- نویسندگان: Abdol Hossein Dabbagh,Marzie Naderi,Mehdi Zamani
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Catalysis
- نوع مقاله: Journal Article
- کلمات کلیدی: Adsorption,DoS,DFT,Surface,γ-alumina,Dissociation
- چکیده:
- چکیده انگلیسی: In this study, the dissociative adsorption of NaNO2, NaNO3, HNO2, HNO3 and H2SO4 over (1 1 0) surface of γ-alumina non-spinel model were investigated through the dispersion corrected density functional theory (DFT-D) at PBE-D/DNP level of calculation. It was found that all of the species are dissociated to their ionic forms after adsorption and relaxation over the surface, i.e. Na+NO2−, Na+NO3−, H+NO2−, H+NO3−, H+HSO4− and 2H+SO42−. The Lewis acidity of alumina surface by addition of HNO2, HNO3 and H2SO4 is increased, while in the presence of NaNO2 and NaNO3, the acidity of catalyst is decreased. Theoretical calculations predict stronger dissociative adsorption of H2SO4 over the surface in compared to other compounds. The HNO2 and HNO3 mineral acids are better adsorbed over the surface than NaNO2 and NaNO3 salts. The better adsorption of nitrites than nitrates is due to the stronger electrostatic attractions. The order of NaNO3 < NaNO2 < HNO3 < HNO2 < H2SO4 for the dissociative adsorption energy of the title compounds is predicted.
- انتشار مقاله: 11-09-1394
- نویسندگان: Mehdi Zamani,Hossein A. Dabbagh
- مشاهده