Filtration Permeability of Dendritic Structure in Condition of Diffusion-Capillary Coalescence of Secondary Side Branches

The problem state of computer analysis of shrinkage defects in castings is analysed based on a review of theoretical and experimental studies the filtration permeability of solidifying alloys. It is shown that the use of the dimensionless permeability coefficient and its modification by introducing various corrections to the Karman-Kozeni equation, obtained for the stationary morphology of non-intersecting filtration channels, is inapplicable for the conditions of continuous change of their geometry during formation of dendrite structure. A computer model of the permeability for the mesoscale ensemble of secondary dendritic branches under the conditions of their diffusion-capillary coalescence is developed. Based on the thermodynamic apparatus and solidification modeling the influence of composition of Al-Cu-Mg alloys and heat removal velocity on the permeability coefficient under the evolution of the dendritic structure is analysed.

Graphene oxide membranes with narrow inter-sheet galleries for enhanced hydrogen separation

Brodie's GO sheets are prepared, characterized and compared to Hummers’ GO sheets. GO-B membranes are synthesized on polyester substrates using filtration. Permeability reduction of large gas molecules (CH4, N2 and CO2) is more significant compared to permeability reduction of small gas molecules (H2 and He). Pressure filtration enhances the packing density of GO-B sheets.

Permeability of Porous Ceramic Membranes Obtained from Waste of the Coal Extraction Process

The coal extraction generates large amounts of coal waste. Powders of this waste can be pressed with the addition of binder in order to obtain ceramics, such as ceramic membranes. In this case, polymeric fibers can be used to increase permeability. This work aims to study the permeability of ceramic structures composed by coal waste and different amounts of polymeric fibers. The compositions were homogenized, pressed and thermally treated at 1050 °C. Samples were characterized in relation to porosity determination, permeability and microstructural features. The results showed that the permeability increased with the increase of the fiber content. However, the composition containing 0.5 vol% of polypropylene fibers showed the best results for using in aerosol filtration permeability.