ThermodynamicsCluster variation method Hydrogen absorption Hydrogenography Critical temperature a b s t r a c tThe search for and development of stable Pd-based membranes for hydrogen separation applications with resistance to hydrogen embrittlement and cracking is a challenging and time-consuming task. Membrane failure is most often caused by the occurrence of the aeb phase transition during hydrogen absorption and desorption by the Pd-alloy below the critical temperature. By finding a suitable alloy with a critical temperature below room temperature, the membrane lifetime can be extended tremendously. Here we present a combinatorial approach that enables the fast screening of phase transitions in multicomponent Pd-alloys for hydrogen separation membranes by experiments and thermodynamic calculations. The method is applied to the well-documented PdeCu alloy compositions. Hydrogenography, a compositional gradient thin film technique, is used to experimentally investigate the alloy compositions. Using a new phenomenological method to determine the critical temperature from hydrogenography measurements, we show that the experimental results and the calculations, using the Cluster Variation Method (CVM), agree well with the phase boundaries and critical temperatures reported in literature. Our results show that the combined capabilities of hydrogenography and CVM enable an efficient screening of promising multi-component alloys for which thermodynamic data are scarce or absent. (R.J. Westerwaal).A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / h e i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 6 ( 2 0 1 1 ) 1 0 7 4 e1 0 8 2
Neutron diffraction and thermal desorption spectroscopy are used to determine the details in the crystallographic structure and the deuterium desorption characteristics of deuterated Pd-Au alloys. Compositions under investigation include alloys corresponding to both subcritical and supercritical conditions with respect to the a-b phase transitions. The effect of the Au-content on deuterium desorption properties is discussed in relation to the degree of deuterium loading and the phase diagram. Furthermore, the distribution of deuterium over the octahedral and tetrahedral interstitial sites is determined. The tetrahedral site occupancy increases with increasing Au content and is significant for both supercritical and subcritical phases.
The design of a fluidized bed atomic layer deposition (ALD) reactor is described in detail. The reactor consists of three parts that have all been placed in one protective cabinet: precursor dosing, reactor, and residual gas treatment section. In the precursor dosing section, the chemicals needed for the ALD reaction are injected into the carrier gas using different methods for different precursors. The reactor section is designed in such a way that a homogeneous fluidized bed can be obtained with a constant, actively controlled, reactor pressure. Furthermore, no filters are required inside the reactor chamber, minimizing the risk of pressure increase due to fouling. The residual gas treatment section consists of a decomposition furnace to remove residual precursor and a particle filter and is installed to protect the pump. In order to demonstrate the performance of the reactor, SiO2 particles have been coated with TiO2 using tetrakis-dimethylamino titanium (TDMAT) and H2O as precursors. Experiments with varying pulse times show that saturated growth can be obtained with TDMAT pulse times larger than 600 s. Analysis of the powder with High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM) and energy dispersive X-ray spectroscopy confirmed that after 50 cycles, all SiO2 particles were coated with a 1.6 nm homogenous shell of TiO2.
High temperature thermoelectric properties of p-type skutterudites BaxYbyCo4-zFezSb12 J. Appl. Phys. 112, 083718 (2012) Significantly enhanced thermoelectric figure of merit through Cu, Sb co-substitutions for Te in Ga2Te3 Appl. Phys. Lett. 101, 081908 (2012) Thermoelectric properties and Kondo behavior in indium incorporated p-type Ce0.9Fe3.5Ni0.5Sb12 skutterudites J. Appl. Phys. 112, 033710 (2012) Enhancement in the figure of merit of p-type Bi100−xSbx alloys through multiple valence-band doping
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