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Using density functional theory, we show that an applied electric field can substantially improve the hydrogen storage properties of polarizable substrates. This new concept is demonstrated by adsorbing a layer of hydrogen molecules on a number of nanomaterials. When one layer of [H.sub.2] molecules is adsorbed on a BN sheet, the binding energy per [H.sub.2] molecule increases from 0.03 eV/[H.sub.2] in the field-free case to 0.14 eV/[H.sub.2] in the presence of an electric field of 0.045 a.u. The corresponding gravimetric density of 7.5 wt% is consistent with the 6 wt% system target set by Department of Energy for 2010. The strength of the electric field can be reduced if the substrate is more polarizable. For example, a hydrogen adsorption energy of 0.14 eV/[H.sub.2] can be achieved by applying an electric field of 0.03 a.u. on an AIN substrate, 0.006 a.u. on a silsesquioxane molecule, and 0.007 a.u. on a silsesquioxane sheet. Thus, application of an electric field to a polarizable substrate provides a novel way to store hydrogen; once the applied electric field is removed, the stored Hz molecules can be easily released, thus making storage reversible with fast kinetics. In addition, we show that materials with rich low-coordinated nonmetal anions are highly polarizable and can serve as a guide in the design of new hydrogen storage materials. energetics [ kinetics | nanomaterials | polarization | reversibility www.pnas.org/cgi/doi/10.1073/pnas.0905571107

Highlights: [•] Al2O3/HfO2/Al2O3 gate stacks has been deposited on Si substrate by ALD. [•] Interface thermal stability related with annealing temperature has been studied. [•] Phase separation at 700°C and silicate formation at 900°C have been detected. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sputtering-derived Hf1−xTi x O2 gate dielectrics have been deposited on Si substrates. [•] Increase in crystallization temperature and reduction in Eg have been observed. [•] Formation of silicate layer for 9% TiO2-doped HfO2/Si sample has been detected. [ABSTRACT FROM AUTHOR]

Abstract: CoFe2O4/Co0.7Fe0.3 nanocomposite permanent magnets have been synthesized in one step by a hydrothermal method at reaction temperatures of 80, 120, 140, 160 and 180°C and characterized by XRD, SQUID, SEM, (HR)TEM, and SAED. All samples consisted of octahedral CoFe2O4 particles and spherical-like Co0.7Fe0.3 particles. The maximum magnetization and coercivity were 191emu/g and 1311Oe, respectively, values not previously observed for the CoFe2O4/Co0.7Fe0.3 system. This maximum magnetization was attributable to the larger mass ratio of Co0.7Fe0.3 to CoFe2O4, which were in intimate contact. Magnetic dipolar interaction plays a crucial role in magnetic properties and leads to the reduction of the magnetization and the Mr /Ms ratio. The coercivity of all samples exhibited complex variation with reaction temperature and its mechanism may deserve further investigation. [Copyright &y& Elsevier]