| Colloidal Shaping of Transparent Spinel through Slip
Casting Using Contamination Free Spinel Moulds |
Shiv Prakash Singh,* Papiya Biswas and Roy Johnson
Pages : 30-36
DOI : 10.1080/0371750X.2022.2054473 |
| Abstract |
| Shaping transparent ceramics through slip casting on plaster of Paris (PoP) moulds
offers improved transparency compared to compacted samples due to better
homogeneity in colloidal processing. However, the contamination due to CaSO4
originated from the PoP contact is a primary concern. Therefore, it demands the
machining of several layers from the cast surface that results in post-green machining
defects. To address this concern, a magnesium aluminate (MgAl2O4) spinel mould
was fabricated with indigenously synthesized spinel powder with optimum porosity
of 45-50% and flexural strength of ~16 MPa. The fabricated spinel mould was used to
demonstrate the casting using water-based spinel slurry. The cast spinel blanks were
found contamination free as confirmed by Fourier transform infrared studies.
Microstructures of spinel moulds revealed the interconnectivity of the pores obtained
by field emission scanning electron microscopy. Specimens cast on spinel and on
PoP moulds, after post machining, were sintered (1650oC) and hot isostatically pressed
(at 1800oC and 1950 bar) under identical conditions. Casting on spinel moulds
demonstrated a contamination free surface of the samples. Its properties are at par
with the samples cast on PoP moulds, however, with improved casting rate and
minimum rejection.
[Keywords: Transparent ceramics, Spinel, Slip casting, Sintering] |
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