The image above, my friends, is an example of a tiny tube of lead zirconate titanate that can be formed when you dip vermicelli into a slurry pf PZT.
No, this isn’t one of those artisan pestos. Better than that, as noted in a paper published [free] in the new Applied Ceramic Technology journal, the vermicelli dipping method turns out to be an excellent and fast way to create PZT microtubes with thick, straight, uniform walls.
Credit for the research on this method goes to a group from India’s Naval Materials Research Lab.
“The vermicelli was dipped in the slurries taken in measuring cylinders for various time periods. The PZT slurry-coated vermicelli was dried overnight by hanging from a clip and was later exposed to HCl gas for 1 h.
[ . . . ]
The PZT-coated vermicelli was cut into pieces of 4 cm length and heated in a furnace at a rate of 5°C/h upto 300°C and then at 15°C/h up to 700°C for burnout of vermicelli and the UF polymer. The resultant PZT microtubes were sintered at 1290°C for 2 h.
A plain PZT slurry doesn’t work, but the addition of a urea formaldehyde monomer solution provides in situ polymerization that allows the PZT coating to stick to the pasta. Vermicelli works well because it is of uniform diameter and absorbs water from the slurry gel (although it can also over soften if too long of a dipping time is used).
The researchers created microtubes with walls 200-960 μm. They used dipping times between 0.5 to 4.0 minutes. The resultant microtubes’ dielectric and piezoelectric properties compared well with traditionally produced ferroelectric PZT ceramic items.
This is serious work with a very practical side. These microtubes can be used in transducers, hydrophones, vibration sensors, accelerometers, micro actuators, flow sensors, positioners, pressure sensors, deflectometers, medical imaging, etc, but alternative processes have significant drawbacks such as short lengths, unstable shapes and limitations on how thick or thin the walls can be.