F. W. Nyongesa

Porosity, Flow, and Filtration Characteristics of Frustum-Shaped Ceramic Water Filters

AbstractThis paper presents the results of an experimental study of the effects of porosity on the flow rate and Escherichia coli (E. coli) filtration characteristics of porous ceramic water filters (CWFs) prepared without a coating of silver. Clay-based CWFs were fabricated by sintering composites of redart clay and fine woodchips (sawdust) in three different proportions by volume, viz: 50∶50, 65∶35, and 75∶25. Sintering the greenware below 1,000°C produced reddish colored pot of three different degrees of porosity and micro- and nanoscale pores, which are the key to efficient filtration. The porosities and pore size distribution frequencies of the sintered clay ceramics were characterized using mercury intrusion porosimetry (MIP). The porosity of the CWFs ranged from ∼36% to ∼47% and increased with increasing sawdust content in a linear fashion, and the pore size varied from ∼10  nm to ∼100  μm. The volume flow rates of water through the CWFs were investigated by measuring the cumulative amount of water...

An Investigation of Thermal Shock in Porous Clay Ceramics

The thermal shock resistance of porous ceramic materials is often characterized by the Hasselman parameters. However, in other scenarios, the room-temperature residual strengths after thermal shock are also used to quantify the damage due to thermal shock. This paper attempts to link the measured residual strengths to the dominant crack features that are introduced due to thermal shock in porous clay ceramics produced by the sintering of clay powders with well-controlled size ranges. Residual strength estimates from bend tests are compared with fracture mechanics predictions. The implications of the residual strength results are then discussed for the characterization of damage due to thermal shock.

Ultrasonic attenuation in Kenyan clay refractories

Ultrasonic attenuation in clay refractories fabricated under different processing parameters has been measured. It was established that refractory clay samples with high compaction efficiencies (CE) were less attenuating compared with those with low CE values. CE was found to be dependent on the particle size distribution of the starting powders and for a continuous particle size distribution, CE could be obtained from the slope of the compact density v. log (pressure) curves.