A novel continuous casting process used to form a highly filled, thermoplastic paste into a net shape ceramic body has been investigated, a method termed thermal paste processing (TPP). TPP uses a long cylindrical die cooled below the solidification temperature of the continuous phase, so that the extrudate merges from the die as a solid rod. Thermal processes were investigated using standard and novel power compensated DSC techniques, yielding both enthalpic response and thermal transport properties. The rheological behaviour was characterised over 9 decades of apparent shear rate, for temperatures from the melt to mushy range. Steady and dynamic shear responses were probed with controlled stress and controlled strain rotational rheometers, using smooth or serrated parallel disks, concentric cylinders, or vane-type geometries. Capillary rheometry using the multi-pass technique was also performed. The rheological characterisation revealed a mismatch between expected and measured onset temperatures when using a parallel disk rheometer; this led to the measurement and simulation of the sample’s and rheometer’s temperature fields. These results were incorporated into the description of the paste’s rheological response to temperature. The thermal and rheological parameters yielded by the above characterisations were incorporated into a 2-D axisymmetric model of the TPP die system using the finite element method (FEM). The numerical code performance was compared against three suitable benchmark problems reported in the literature. The results from one case concerning the melting of gallium in a square cavity revealed a possible cause of circulation cell instability observed in many numerical results, but not respond experimentally. Predictions from the numerical simulations were compared with equivalent experimental data from an instrumented TPP die system. The formulation variations demonstrate poor to good agreement with experimental data.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:596367 |
| Date | January 2008 |
| Creators | Barker, Dean Anthony |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.repository.cam.ac.uk/handle/1810/252100 |
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