Home  About us  Contact
 

Fraction Ratio (fraction + ratio)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

Cation distribution in spinel (Mn,Co,Cr)3O4 at room temperature

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2010
A. Purwanto
As part of a study of the long-term operation of solid-oxide fuel cells, three (Mn,Co,Cr)3O4 samples have been synthesized and characterized. X-ray and neutron diffraction patterns from the powder samples at room temperature were measured and the data were co-refined. The neutron data were indispensible in locating Mn, Co and Cr within the crystallographic unit cell with their respective atomic occupancies. Two of these samples have been identified as cubic Mn0.76Co0.58Cr1.66O4 and Mn1.28Co1.72O4. The third is a two-phase sample containing cubic Mn1.66Co1.34O4 and tetragonal Mn2.05Co0.91O4 in a 59.1,(6):40.9,(6)% mass fraction ratio. Cr, which might be introduced from reaction with chromia during oxidation of interconnect materials, exhibits a preference for the octahedral site rather than the tetrahedral site. Without Cr, Mn dominates the octahedral site. [source]

Fluid-particle drag in low-Reynolds-number polydisperse gas,solid suspensions

AICHE JOURNAL, Issue 6 2009
Xiaolong Yin
Abstract Lattice-Boltzmann simulations of low-Reynolds-number fluid flow in bidisperse fixed beds and suspensions with particle,particle relative motions have been performed. The particles are spherical and are intimately mixed. The total volume fraction of the suspension was varied between 0.1 and 0.4, the volume fraction ratio ,1/,2 from 1:1 to 1:6, and the particle size ratio d1/d2 from 1:1.5 to 1:4. A drag law with improved accuracy has been established for bidisperse fixed beds. For suspensions with particle,particle relative motions, the hydrodynamic particle,particle drag representing the momentum transfer between particle species through hydrodynamic interaction is found to be an important contribution to the net fluid-particle drag. It has a logarithmic dependence on the lubrication cutoff distance and can be fit as the harmonic mean of the drag forces in bidisperse fixed beds. The proposed drag laws for bidisperse fixed beds and suspensions are generalized to polydisperse suspensions with three or more particle species. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Growth and characterization of ZnMgTe/ZnTe layered structures grown by molecular beam epitaxy

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2010
S. Imada
Abstract ZnMgTe/ZnTe layered structures were grown on ZnTe substrates by molecular beam epitaxy, and the crystal structures were characterized using X-ray diffraction methods. This structure would be the waveguide for various optoelectronic devices. Therefore, the crystal quality of this layered structure would be very crucial for the realization of high performance devices. ZnMgTe is lattice mismatched to ZnTe, and the increase of the ZnMgTe layer thickness or Mg mole fraction ratio would result in the crystal quality deterioration of the layered structure. The critical layer thickness (CLT) was theoretically derived, and various structures with various ZnMgTe layer thickness and Mg mole fraction were grown. The lattice mismatch strain relief and crystal quality of those samples were investigated by means of X-ray reciprocal space mapping (RSM) and cross sectional transmission electron microscopy (TEM). The dislocation formation and the lattice mismatch relaxation were confirmed for various samples and it was revealed that the calculated CLT values could be used as an appropriate guideline to design the dislocation free and high performance device structures (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Fluid-particle drag in inertial polydisperse gas,solid suspensions

AICHE JOURNAL, Issue 8 2010
William Holloway
Abstract In this article, we extend the low Reynolds number fluid-particle drag relation proposed by Yin and Sundaresan for polydisperse systems to include the effect of moderate fluid inertia. The proposed model captures the fluid-particle drag results obtained from lattice-Boltzmann simulations of bidisperse and ternary suspensions at particle mixture Reynolds numbers ranging from 0 , Remix , 40, over a particle volume fraction range of 0.2 , , , 0.4, volume fraction ratios of 1 , ,i/,j , 3, and particle diameter ratios of 1 , di/dj , 2.5. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]