I'm working on gelcasting of alumina using Acacia as gelling agent. I varied the acacia content from 2% to 15 at lower composition, and 30-40% of Acacia. I used ageing, foaming then steam assisted hydrothermal treatment, but i m finding laminate and cracks during drying itself. So can any one tell me avoid this.
Can you explain the drying parameters including humidity and drying rate? How long does it take?
Dear Anantha Dv
You can avoid this with:
1. Low heating rate and low drying temperature, as far as possible
2. Reasonable drying curve, for example some gelling agents are susceptible to 50-70oC so high heating rates at this temperatures can result in lamination
3. Proper aging conditions, inappropriate aging can be the cause of drying defects
4. Broad and continuous particle distributions.
5. Coarser grains (if possible). The coarse aggragates act as anti-cracks.
6. Organic fibers as drying aids (if possible), that can burn under water boiling temperature (110oC) and so on help the evaporation
7. Various gelling agents such as Hydratable Alumina
8. Dispersant and deflocculant agents to reduce mixing water and help the drying procedure
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