Narrow Results

The interaction between the H₂ molecule and the PdAg, PdAu, PtAg and PtAu bimetallic dimers deposited on the MgO(100) surface is investigated using density functional theory (DFT). The bimetallic dimers, whose molecular axes are considered to be perpendicular to the support surface, are adsorbed on top of an oxygen atom. Within this adsorption mode, the dimers prefer the orientation in which their Pd or Pt end is closer to the oxygen atom. The Ag and Au ends of the MgO-supported dimers capture the H₂ molecule with small exoenergetic effects. The spontaneous dissociation of H₂ on these ends does not occur. Thus, the MgO support decreases the ability of the dimers to adsorb and dissociate the H₂ molecule. From a catalytic viewpoint, it means that the activity of small bimetallic clusters toward the dissociative adsorption of H₂ is reduced when they are arranged on MgO. On the other hand, the results of our calculations show that the presence of the MgO support strengthens the binding of H atoms inside the PdAu, PtAg and PtAu dimers.

The effect of MgO on structure and dielectric properties of aluminoborosilicate glasses was investigated. FTIR data indicated that glass network was mainly built by tetrahedral [SiO₄], [BO₄], [AlO₄] and trigonal [BO₃]. A small amount of AlO₅ or AlO₆ units also existed. The glass system was characterized with lower dielectric constant (4.17 ~ 4.6) and dielectric loss (12.3 × 10^-4 ~ 14.77 × 10^-4) at 1 MHz. With the increase of MgO content, the quantity of AlO₅ or AlO₆ units decreased. The variation of density showed a decreasing tendency. The dielectric constant and loss were all found to decrease.