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João A. Labrincha - One of the best experts on this subject based on the ideXlab platform.

  • Behaviour of different industrial ceramic pastes in extrusion process
    Advances in Applied Ceramics, 2009
    Co-Authors: Patricia Guilherme, M. J. P. Ribeiro, João A. Labrincha
    Abstract:

    AbstractIt is well known that the extrudability of a ceramic paste is strongly dependent on materials composition and formulation, basically because it controls the resulting plasticity. Accordingly, the characterisation of the plastic behaviour is essential to adjust the fluxing properties of the material. In the current work, three industrially prepared ceramic pastes (porcelain, earthenware and terracotta) were tested, using stress–deformation curves obtained by compression of cylindrical probe tests. To achieve good extrusion performance, the design and operating conditions also need to be considered in detail.The ram extrusion of adjusted pastes was followed by the Benbow–Bridgwater model. Differences in the flow behaviour were related with stress–deformation curves and with the surface quality of the extrudate (by using the static friction coefficient).

  • single screw extrusion of mullite based tubes containing al rich anodising sludge
    Ceramics International, 2009
    Co-Authors: M J Ribeiro, S Blackburn, João A. Labrincha
    Abstract:

    Abstract An Al-rich anodising sludge has been used as the feedstock to produce mullite-based tubes by single screw extrusion. Extrudability and plasticity of the pastes was shown to be strongly dependent on the amount and type of used additives. The pastes developed from the sludge could be characterised by the Benbow–Bridgwater relationship using six paste parameters and this characterisation was extended to predict the behaviour of the screw extrusion process. In this work, the effects of the screw speed and partial pressures in relevant zones of a single screw extruder on the processing behaviour of sludge-based pastes were predicted using the Benbow–Bridgwater model. It is shown that the model can predict the pressure drop through the die-entry and the die-land regions (with similar design as used to produce ceramic hole-tubes) and the pressure development along the barrel of the extruder with reasonable accuracy. The paste parameters calculated from simple ram extrusion do not match the experimental behaviour of the screw extruder and this was proved to be due to the paste being worked to a stiffer consistency in the barrels of the extruder and to being subjected to vacuum during the process, with consequent water segregation. This was confirmed by re-examination of the paste properties immediately after the screw extrusion.

  • Extrusion of alumina and cordierite-based tubes containing Al-rich anodising sludge
    Journal of The European Ceramic Society, 2005
    Co-Authors: M J Ribeiro, S Blackburn, José M.f. Ferreira, João A. Labrincha
    Abstract:

    Abstract An Al-rich anodising sludge has been used as the feedstock to produce alumina and cordierite-based tubes produced by extrusion. The extrudability is strongly dependent on the materials composition and on the resultant plasticity of the pastes. For the process to be successful, the design and operating conditions need to be considered in detail. In this work, the effect of die design, ram speed and pressure was evaluated using the Benbow–Bridgwater model of paste extrusion. In general, predicted and measured values were in good agreement. This approach revealed differences in the flow between the two ceramic formulations and it was possible to relate the rheological observations during extrusion to the quality of the final product.

M J Ribeiro - One of the best experts on this subject based on the ideXlab platform.

  • Porous hollow tubes processed by extrusion of ceramic emulsions
    Applied Clay Science, 2015
    Co-Authors: Nuno Vitorino, C. Freitas, M J Ribeiro, João C.c. Abrantes, Jorge R. Frade
    Abstract:

    The processing of ceramic materials by extrusion is widely used to obtain products with constant cross section. Most of them are framed with applications as catalysis, filtration, building, fuel cells, isolators, etc., mainly if they are porous with special designed microstructural characteristics as pore size/distribution, liquid and gas permeability, mechanical properties, etc. Thus, in this work we combine a cellular ceramic preparation strategy based on a synergy of emulsification process and gel casting, with the extrusion process to obtain porous hollow tubes. Tree ceramic emulsions were extruded under different ram speeds and its effect was studied using Benbow-Bridgwater model.

  • single screw extrusion of mullite based tubes containing al rich anodising sludge
    Ceramics International, 2009
    Co-Authors: M J Ribeiro, S Blackburn, João A. Labrincha
    Abstract:

    Abstract An Al-rich anodising sludge has been used as the feedstock to produce mullite-based tubes by single screw extrusion. Extrudability and plasticity of the pastes was shown to be strongly dependent on the amount and type of used additives. The pastes developed from the sludge could be characterised by the Benbow–Bridgwater relationship using six paste parameters and this characterisation was extended to predict the behaviour of the screw extrusion process. In this work, the effects of the screw speed and partial pressures in relevant zones of a single screw extruder on the processing behaviour of sludge-based pastes were predicted using the Benbow–Bridgwater model. It is shown that the model can predict the pressure drop through the die-entry and the die-land regions (with similar design as used to produce ceramic hole-tubes) and the pressure development along the barrel of the extruder with reasonable accuracy. The paste parameters calculated from simple ram extrusion do not match the experimental behaviour of the screw extruder and this was proved to be due to the paste being worked to a stiffer consistency in the barrels of the extruder and to being subjected to vacuum during the process, with consequent water segregation. This was confirmed by re-examination of the paste properties immediately after the screw extrusion.

  • Extrusion of alumina and cordierite-based tubes containing Al-rich anodising sludge
    Journal of The European Ceramic Society, 2005
    Co-Authors: M J Ribeiro, S Blackburn, José M.f. Ferreira, João A. Labrincha
    Abstract:

    Abstract An Al-rich anodising sludge has been used as the feedstock to produce alumina and cordierite-based tubes produced by extrusion. The extrudability is strongly dependent on the materials composition and on the resultant plasticity of the pastes. For the process to be successful, the design and operating conditions need to be considered in detail. In this work, the effect of die design, ram speed and pressure was evaluated using the Benbow–Bridgwater model of paste extrusion. In general, predicted and measured values were in good agreement. This approach revealed differences in the flow between the two ceramic formulations and it was possible to relate the rheological observations during extrusion to the quality of the final product.

D.i. Wilson - One of the best experts on this subject based on the ideXlab platform.

  • Measurement of the wall slip behaviour of a solid granular soap in ram extrusion
    Powder Technology, 2017
    Co-Authors: Mp Bryan, S L Rough, D.i. Wilson
    Abstract:

    Abstract The wall slip behaviour of a solid granular soap was investigated in the context of ram extrusion, with particular focus on determining the sensitivity of the wall shear stress to the pressure within the soap, as well as the slip velocity. Two novel slip measurement devices were used to infer the shear stress: a two stage extrusion die with inbuilt pressure gradient measurement; and a combined compression–translation assembly to measure the frictional force between the soap and the wall. Both devices provided differing measurements of the pressure sensitivity, and gave shear stress estimates in agreement with a Benbow and Bridgwater analysis of the extrusion behaviour, which cannot gauge pressure dependence. The influence of the wall material on the slip and extrusion behaviour was also investigated, using three geometrically identical extruders constructed from polycarbonate, stainless steel and tungsten carbide. There was found to be a non-negligible relationship between wall material, wall surface roughness, and the Benbow–Bridgwater extrusion parameters, in which the wall shear stress was greatest against the smoothest, cemented tungsten carbide wall in contrast to a rougher stainless steel and rougher-still polycarbonate wall.

  • Paste engineering: Multi‐Phase materials and multi‐phase flows
    The Canadian Journal of Chemical Engineering, 2011
    Co-Authors: D.i. Wilson, S L Rough
    Abstract:

    The multi-phase nature of granular pastes, coupled with their non-Newtonian rheology and inherent inhomogeneity, makes characterisation and prediction of flow behaviour challenging. We focus on ‘stiff’ pastes which can maintain their shape after extrusion. We describe how the approach presented by Benbow and Bridgwater can be used to predict the deformation and flow behaviour of such materials. Illustrations are drawn from industrial pastes and applications studied in our group. Its basis in viscoplasticity and pure plasticity is discussed. Problems associated with ‘stiff’ pastes are highlighted. Finally, a roadmap is presented summarising how we think the progress of paste understanding needs to be developed. © 2011 Canadian Society for Chemical Engineering

  • Extrusion behaviour of cohesive potato starch pastes: I. Rheological characterisation
    Journal of Food Engineering, 2005
    Co-Authors: A. Cheyne, J. Barnes, D.i. Wilson
    Abstract:

    Abstract The extrusion behaviour of a cohesive mixture of hydrated potato starch solids was characterised using capillary rheometry. Data were collected from isothermal ram extrusion tests and were modelled using (i) the modified plasticity approach described by Benbow and Bridgwater, and (ii) standard fluid mechanics approaches for power law and Herschel–Bulkley fluids. Neither approach proved to be entirely satisfactory, with particle size effects strongly manifested in the Benbow–Bridgwater parameters, and problems with the Mooney analysis for describing the materials as a fluid. Shear-thinning behaviour, as reported elsewhere other starch doughs/mixtures, was evident, while both wall slip and extensional shear contributions were important. The utility of the Benbow–Bridgwater approach was demonstrated by its application to modelling of annular dies, where it provided reasonably accurate predictions once particle size effects were accounted for.

Angel Paul - One of the best experts on this subject based on the ideXlab platform.

S Blackburn - One of the best experts on this subject based on the ideXlab platform.

  • single screw extrusion of mullite based tubes containing al rich anodising sludge
    Ceramics International, 2009
    Co-Authors: M J Ribeiro, S Blackburn, João A. Labrincha
    Abstract:

    Abstract An Al-rich anodising sludge has been used as the feedstock to produce mullite-based tubes by single screw extrusion. Extrudability and plasticity of the pastes was shown to be strongly dependent on the amount and type of used additives. The pastes developed from the sludge could be characterised by the Benbow–Bridgwater relationship using six paste parameters and this characterisation was extended to predict the behaviour of the screw extrusion process. In this work, the effects of the screw speed and partial pressures in relevant zones of a single screw extruder on the processing behaviour of sludge-based pastes were predicted using the Benbow–Bridgwater model. It is shown that the model can predict the pressure drop through the die-entry and the die-land regions (with similar design as used to produce ceramic hole-tubes) and the pressure development along the barrel of the extruder with reasonable accuracy. The paste parameters calculated from simple ram extrusion do not match the experimental behaviour of the screw extruder and this was proved to be due to the paste being worked to a stiffer consistency in the barrels of the extruder and to being subjected to vacuum during the process, with consequent water segregation. This was confirmed by re-examination of the paste properties immediately after the screw extrusion.

  • Extrusion of alumina and cordierite-based tubes containing Al-rich anodising sludge
    Journal of The European Ceramic Society, 2005
    Co-Authors: M J Ribeiro, S Blackburn, José M.f. Ferreira, João A. Labrincha
    Abstract:

    Abstract An Al-rich anodising sludge has been used as the feedstock to produce alumina and cordierite-based tubes produced by extrusion. The extrudability is strongly dependent on the materials composition and on the resultant plasticity of the pastes. For the process to be successful, the design and operating conditions need to be considered in detail. In this work, the effect of die design, ram speed and pressure was evaluated using the Benbow–Bridgwater model of paste extrusion. In general, predicted and measured values were in good agreement. This approach revealed differences in the flow between the two ceramic formulations and it was possible to relate the rheological observations during extrusion to the quality of the final product.