Transport Properties of Zeolite Na-X-Nafion Membranes: Effect of Zeolite Loadings and Particle Size

Fuel Cells ◽  
2011 ◽  
Vol 11 (6) ◽  
pp. 801-813 ◽  
Author(s):  
M. Lavorgna ◽  
L. Sansone ◽  
G. Scherillo ◽  
R. Gu ◽  
A. P. Baker
Keyword(s):  
Particle Size ◽  
Transport Properties ◽  
Nafion Membranes

Magnetic, Electronic - and Magneto - Transport Properties of Nanocrystalline Nd0.6Sr0.4MnO3 Manganites

2009 ◽  
Vol 67 ◽  
pp. 131-136 ◽  
Author(s):  
Kundu Sourav ◽  
Kumar Nath Tapan
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Transition Temperature ◽  
Curie Temperature ◽  
Transport Properties ◽  
Significant Variation ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Low Field

We have reported in this paper, the effect of grain size in Nd0.6Sr0.4MnO3 .We have investigated the effect of grain size on metal-insulator transition and Curie temperature. We have also reported here the variation of low field magnetoresistance with temperature and grain size. We have observed that the Curie temperature increases monotonically with particle size. The metal insulator transition temperature initially increases with particle size and then gets fixed to a certain value. In these Nd0.6Sr0.4MnO3 nanometric systems, any significant variation of magnetoresistance with particle size is not observed.

Effects of Interfacial Zone Percolation on Cement-Based Composite Transport Properties

1991 ◽  
Vol 245 ◽  
Author(s):  
K.A. Snyder ◽  
D.N. Winslow ◽  
D.P. Bentz ◽  
E.J. Garboczi
Keyword(s):  
Computer Simulation ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Transport Properties ◽  
Volume Fraction ◽  
Cement Mortar ◽  
Mercury Porosimetry ◽  
Computer Simulation Model ◽  
Interfacial Zone ◽  
Aggregate Particles

ABSTRACTIn portland cement mortar and concrete, interfacial zones exist around the aggregate particles that have larger pore sizes and pore volumes than the bulk cement paste. If there are enough aggregate particles present, these zones may overlap so as to percolate. A computer simulation model has been developed that can predict this percolation point as a function of interfacial zone thickness, volume fraction of aggregates, and aggregate particle size distribution. The model was used to simulate 1cm3 of mortar, using approximately 10,000 aggregate particles. Results from this model are used to explain recent mercury porosimetry results on mortars having a variety of sand contents. The implications of interfacial zone percolation for the transport properties of mortar and concrete are discussed.

scholarly journals Simulated Microstructural Evolution and Design of Porous Sintered Wicks

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Karthik K. Bodla ◽  
Suresh V. Garimella
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Transport Properties ◽  
Effective Thermal Conductivity ◽  
Surface Area ◽  
Microstructural Evolution ◽  
Ad Hoc ◽  
Three Dimensions ◽  
Two Phase ◽  
Sintering Kinetics

Porous structures formed by sintering of powders, which involves material-bonding under the application of heat, are commonly employed as capillary wicks in two-phase heat transport devices such as heat pipes. These sintered wicks are often fabricated in an ad hoc manner, and their microstructure is not optimized for fluid and thermal performance. Understanding the role of sintering kinetics—and the resulting microstructural evolution—on wick transport properties is important for fabrication of structures with optimal performance. A cellular automaton model is developed in this work for predicting microstructural evolution during sintering. The model, which determines mass transport during sintering based on curvature gradients in digital images, is first verified against benchmark cases, such as the evolution of a square shape into an area-preserving circle. The model is then employed to predict the sintering dynamics of a side-by-side, two-particle configuration conventionally used for the study of sintering. Results from previously published studies on sintering of cylindrical wires are used for validation. Randomly packed multiparticle configurations are then considered in two and three dimensions. Sintering kinetics are described by the relative change in overall surface area of the compact compared to the initial random packing. The effect of sintering parameters, particle size, and porosity on fundamental transport properties, viz., effective thermal conductivity and permeability, is analyzed. The effective thermal conductivity increases monotonically as either the sintering time or temperature is increased. Permeability is observed to increase with particle size and porosity. As sintering progresses, the slight increase observed in the permeability of the microstructure is attributed to a reduction in the surface area.

scholarly journals Thickness and Interface-Dependent Structural, Magnetic, and Transport Properties of Cu/Co Thin Film and Multilayer Structures

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
R. Brajpuriya
Keyword(s):  
Particle Size ◽  
Transport Properties ◽  
Average Particle Size ◽  
Single Layer ◽  
Growth Conditions ◽  
Multilayer Structures ◽  
Average Particle ◽  
Saturation Field ◽  
Microstructural Parameters ◽  
Single Layer Film

Structural, magnetic, and transport properties of electron beam evaporated Co/Cu thin films and multilayer structures (MLS) having different layer thicknesses have been characterized utilizing X-ray diffraction (XRD), magnetooptical Kerr effect (MOKE), and resistivity techniques. The structural studies show distinctive crystal structures for different sublayer thicknesses. The Co (300 Å) single layer film is amorphous, while Cu (300 Å) film is nanocrystalline in nature. The average particle size is found to decrease as the number of interface increases. The corresponding magnetic and resistivity measurements show an increase in saturation field and resistivity as a result of an enhanced anisotropy. However, coercivity decreases with a reduction in average particle size. The results conclude that these properties are greatly influenced by various microstructural parameters such as layer thickness, number of bilayers, and the quality of interfaces molded under different growth conditions.

Transport properties of modified Nafion membranes: Effect of zeolite and precursors

2010 ◽  
Vol 180 (40) ◽  
pp. 1694-1701 ◽  
Author(s):  
Ivan M. Krivobokov ◽  
Evgeniy N. Gribov ◽  
Alexey G. Okunev ◽  
Giuseppe Spoto ◽  
Valentin N. Parmon
Keyword(s):  
Transport Properties ◽  
Nafion Membranes

Microstructural Evolution and Transport Properties of Sintered Porous Media

2013 ◽  
Author(s):  
Karthik K. Bodla ◽  
Suresh V. Garimella
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Transport Properties ◽  
Effective Thermal Conductivity ◽  
Microstructural Evolution ◽  
Three Dimensions ◽  
Two Phase ◽  
Sintering Kinetics ◽  
Relative Change ◽  
Area Preserving

Sintering is a material-bonding phenomenon that occurs under the application of heat. The porous structures formed by sintering powders are commonly employed as capillary wicks in two-phase heat transport devices such as heat pipes. These sintered wick microstructures are often not truly optimized for fluid and thermal performance. Understanding the role of sintering kinetics, and the resulting microstructural evolution, on wick transport properties is important for fabrication of structures with optimal performance. In this study, a cellular automaton model for predicting microstructural evolution during sintering is developed. The model, which determines mass transport during sintering based on curvature gradients in digital images, is first verified against benchmark cases, such as the evolution of a square into an area-preserving circle. The model is then employed to predict the sintering dynamics of a side-by-side two-particle configuration conventionally used for the study of sintering. Data from previously published studies on sintering of cylindrical wires is used for validation. Randomly packed multi-particle configurations are then considered in two and three dimensions. Sintering kinetics are described by the relative change in overall surface area of the compact compared to the initial random packing. The effect of sintering parameters, particle size, and porosity on fundamental transport properties, viz., effective thermal conductivity and permeability, is analyzed. The effective thermal conductivity increases monotonically as either the sintering time or temperature is increased. Permeability was observed to be largely independent of sintering conditions, but increases with particle size and porosity.

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