We study in this work the processing of NaNbO3 ceramics prepared in a single thermal treatment of highly reactive precursors obtained by mechanical activation of different reagents, aiming to determine optimum conditions for piezoelectric ceramics production. Pressure-less sintering at 1200oC leads to dense ceramics (<5% porosity) with poor mechanical stability, unsuitable for practical uses. D...

The threshold surface porosity in the dormant spore of Bacillus cereus strain T was assessed by measuring passive permeabilities to a series of polydisperse polyethylene glycol samples which increased in average molecular size. The apparent exclusion threshold at diffusional equilibrium corresponded to a polymer of number-average molecular weight ( M(n)) = 150,000 and equivalent hydrodynamic ra...

A three-dimensional mathematical model is presented to describe volume changes in porous electrodes occurring during operation. Material conservation equations are used to derive governing relationships between electrode dimensions and porosity for deposition/precipitation, intercalation, and ionomer-based electrodes. By introducing a parameter, called the swelling coefficient, the relative mag...

Spatial restrictions around catalytic sites, provided by molecular-sized micropores, are beneficial to reaction selectivity but also inherently limit diffusion. The molecular transport can be enhanced by introducing meso- and macropores. However, the impact of this extraframework porosity on the local nanoscale reactivity is relatively unexplored. Herein we show that the area of enhanced reacti...

increase in the surface area, demonstrating that the Fe(III) ions work by making the resin porous. The use of these two metal ions enables efRcient NO adsorption. The polymeric resin as well as the metal complex itself greatly affects the adsorbing ability for the target gas molecules as described in the case of CO, C2H4, and NO adsorption. It has been demonstrated clearly that large surface ar...

The development of a sub-surface layer of porosity during heat treatment has been studied in a variety of A1-Li alloys. Pure binary A1-Li alloys and three commercial materials were heat treated in air, vacuum and hydrogen for various lengths of time. Subsequent metallographic sectioning and polishing revealed the presence of a band of pores in the near-surface region extending approximately 300...

Muddy intercalation is one kind of rock’s secondary structural surface, where the failure of instability between strata occurred. Mechanical behaviour of muddy intercalation directly affects the stability of the rock mass. Starting from the micro-structure of Muddy intercalation, revealing its macroscopic mechanical characteristic is of great significance to the stability and optimization desig...

Calcium polyphosphate (CPP) bioceramic with different porosities were prepared by controlling the concentration of the pore-foaming agent. Effect of porosity (0%, 15%, 30%, 45% and 60%) on the microstructure, pores interconnection, dissolution behavior and compressive strength of CPP bioceramic were investigated. Scanning electron microscope (SEM) and capillarity test results indicated that CPP...

Porosity has been frequently observed in solidified, deep penetration pulsed laser welds. Porosity is detrimental to weld quality. Our previous study shows that porosity formation in laser welding is associated with the weld pool dynamics, keyhole collapse, and solidification processes. The objective of this paper is to use mathematical models to systematically investigate the transport phenome...

Microstructural aspects of composites such as particle size, shape, and distribution play important roles in deformation behavior. 3D visualization of porosity and Fe-rich inclusions in three dimensions is critical to a thorough understanding of fatigue resistance of metal matrix composites (MMC) because cracks often initiate at these defects. In this paper we have used X-ray synchrotron tomogr...