Sharif Digital Repository

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... 

Mixed-convection flow of nanofluids inside a vertical rectangular channel partially filled with open-cell metal foam and subject to a constant wall-heat flux was investigated experimentally and numerically. Al2O3-water nanofluids with different concentrations were prepared and their stability was examined using UV-Vis spectroscopy. Dynamic light scattering method was used to determine particle size distribution of the nanofluid feedstock. The outlet temperature and pressure drop were measured for different nanofluid flow rates (i.e., Reynolds number values). In the numerical section, a two-dimensional volume-averaged form of the governing equations was used. The velocity and temperature... 

Interactions of α-D-glucose with gold, silver, and copper metal clusters are studied theoretically at the density functional theory (CAM-B3LYP) and MP2 levels of theory, using trimer clusters as simple catalytic models for metal particles as well as investigating the effect of cluster charge by studying the interactions of cationic and anionic gold clusters with glucose. The bonding between α-D-glucose and metal clusters occurs by two major bonding factors; the anchoring of M atoms (M = Cu, Ag, and Au) to the O atoms, and the unconventional M.H-O hydrogen bond. Depending on the charge of metal clusters, each of these bonds contributes significantly to the complexation. Binding energy... 

Accumulative roll bonding (ARB) is used as a novel method to produce particle reinforced metal matrix composites (MMCs). Roll bonding of the sheets with layers of powder on their surfaces is the main stage in this process and it has been found that quality of the bonding has an important role in properties of the product. In this work, the behavior of alumina particles layer at interface during the rolling is investigated and the effects of particle size and amount of particle at interface on bonding of the commercial pure aluminum sheets are also studied. The results of peeling test indicate that presence of the powder at interface reduces the bond strength. However, it is shown that by... 

Nowadays, gasochromic Pd/WO3 coatings as optically switchable materials during H2 absorption have become more interesting due to their novel applications in smart windows and gas sensor devices. In this study, WO3 films were fabricated by Pulsed Laser Deposition (PLD) on glass substrates. Using an electroless method, Pd nanoparticles were deposited on the surface of the produced films. The effect of Pd growth time on coloring/bleaching rate was studied for different submerging times (1, 2, 5, 10, 15, 20 and 40 min). The best coloring/bleaching velocity was attained with a growth time of 2 min. The effect of growing time and growth feature of Pd particles was further studied using Scanning... 

The aqueous phase reforming (APR) of glycerol is an attractive yet challenging pathway to convert abundant biomass into value added hydrogen. Pt catalysts have received attention due to their ability to produce hydrogen-rich gas under APR conditions. In this work, the conversion of glycerol into hydrogen is demonstrated using Pt0.05CexZr0.95-xO2 (x = 0, 0.29, 0.475, 0.66 and 0.95) solid solution catalysts. Both characteristic (XRD, BET, H2-TPR, CO-chemisorption, TEM and XPS) and reactivity measurements were used to investigate the activity of the catalysts. Results indicated that reactivity depended on the Ce/Zr ratio, which in turn affected the Pt oxidation state, active metal dispersion...