Pore microstructures

Improved characterization of the morphological/microstructural properties of porous solids, and the associated transport properties of fluids imbibed into these materials, is crucial to the development of new porous materials, such as ceramics. Of particular interest is the fabrication of so-called functionalized ceramics, which contain a pore structure tailored to a specific biomedical or industrial application (e.g., molecular filters, catalysts, gas storage cells, drug delivery devices, tissue scaffolds) [1-3]. Functionalization of ceramics can involve the use of graded or layered pore microstructure, morphology or chemical composition. 

Fabrication processing of these materials is highly complex, particularly for materials created to have interfaces in morphology or a microstructure [4—5], for example in co-fired multi-layer ceramics. In addition, there is both a scientific and a practical interest in studying the influence of a particular pore microstructure on the motional behavior of fluids imbibed into these materials [6-9]. This is due to the fact that the actual use of functionalized ceramics in industrial and biomedical applications often involves the movement of one or more fluids through the material. Research in this area is therefore bi-directional one must characterize both how the spatial microstructure (e.g., pore size, surface chemistry, surface area, connectivity) of the material evolves during processing, and how this microstructure affects the motional properties (e.g., molecular diffusion, adsorption coefficients, thermodynamic constants) of fluids contained within it. 

It has been demonstrated that FDSP has the potential to provide information on the pore microstructure that can be used to estimate permeability. It... 

SEM micrograph of the partially sintered alumina preform (1000°C) showing the pore microstructure (a) before and (b) after infiltration with TiCh [Manurung, 2001]. 

Fabrication of Yttria-Stabilized Zirconia Ceramics with Reticulated Pore Microstructure... 

WITH RETICULATED PORE MICROSTRUCTURE BY FREEZE-DRYING... 

Controlled-pore microstructures of gel made by Shoup s method. From Shoup [72],... 

Oxide thin films synthesized by sol-gel are very interesting for the design of optoelectronic devices especially because sol-gel processes allow handling the thickness d and the refractive index , due to the control of pore microstructure. This bottom-up approach is simpler and less expensive than many thin films made by top-down methods such as sputtering [2] or electron beam evaporation [3]. 

In this paper, we have conducted a comparative study to elucidate the role of pore microstructures on the decomposition kinetics of several MAX phases during vacuum annealing in the temperature range 1000-1800 C. Xhe effect of pore-size on the activation energy of decomposition was evaluated using the Arrhenius equation. 

Except for bulk Ti3 AIC2 which exhibited negative activation energy, positive activation energies were determined for the decomposition of other bulk MAX phases. The pore microstructure of decomposed MAX phase has been shown to play a vital role in the kinetics of decomposition with coarse-pores facilitating the decomposition process but the fine-pores hindering it. 

In porous materials, diffusion of a solute is complicated by the geometric constraints of the pore structure. Since they are easily solved, continuum expressions have been used as the basis for many studies of diffusion in porous structures. In most cases, the continuum approach is parametric a numerical value for Deff is selected so that the solution of equation 16 fits a particular set of experimental transport measurements. By this method, correlation between effective diffusion coefficients obtained for different solutes or different porous materials is difficult. In this section, descriptions of porous geometries are used to examine the influence of pore microstructure on effective diffusion coefficients. These descriptions will have value only under certain conditions for example, if the size of a characteristic pore is much less than the thickness of the slab and the pore structure is well connected. 

Shi JL. Solid state sintering of ceramics pore microstructure models, densification equations and applications. J Mater Sci. 1999 34 3801-3812. DOI 10.1023/A 1004600816317... 

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