In exploring nanotechnology, researchers have found that zirconium is an element that exhibit valuable characteristic and properties. Zirconia has a very good chemical and thermal constancy, strong, high fracture toughness, high corrosion resistivity and also low thermal conductivity. Due to this, zirconia is extensively applied in most of structural materials, in thermal coating, catalytic supports and others. Zirconia nanofiber can be manufactured through electrospinning process by first producing the polymer solution of zirconia. By combining the right proportion of a polymer, zirconia, ethanol and distilled water the sol-gel (precursor solution to be spun) of zirconia can be produced.
The aim of this project is to investigate the crystal structure of zirconia nanofiber when it is being doped with strontium with different amount and different temperature of calcination process. The fibre diameter, grain size, crystal type and porosity of the fibre formed will be observed.
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| Precursor solution on an electric stirrer |
Electrospinning is one of the techniques used to produce nanofibers.
This versatile technique enables the production of nanofibers from natural
polymer, polymer alloy or synthetic polymer. There are three main components for electrospinning process: a spinneret
(metal nozzle), a high voltage power supply and a collector. The high voltage power supply is connected to the spinneret and the
collector was grounded. Before connecting the components, the solution to be
spun is loaded in the syringe and the syringe is connected to a metallic needle
(as spinneret). The syringe also will be connected to the syringe pump to let
an even feeding rate of the solution.
Before electrospinning process, precursor solution of zirconia was made. The polymer used in the precursor solution is polyvinyl pyrrolidone (PVP) as it is very soluble in water and ethanol. For the zirconia, zirconyl oxychloride octahydrate (ZrOCl2.8H2O) was used to make the precursor solution whereas the dopant used is strontium carbonate (SrCO3).
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| Fibers collected on the drum. |
After the solution is ready, it can be prepared for electrospinning process. The solution was loaded into a 10ml syringe and the apparatus was setup as shown in Figure 24. A 20cc needle tip was used in this experiment and it is attached to the syringe before loading the solution. Then the syringe was secured on the syringe pump platform. Before the high voltage power supply was turned on, the earth wire is connected to drum winder while the live wire is connected to the needle tip. To collect the fibers produced easier, the drum winder was wrapped with aluminium foil. As all connection was secured, the drum winder was turned on and the rotational speed was set between 300rpm and 350rpm. The voltage supplied to the needle tip was 22kV and flow rate of the syringe was 0.75ml per hour. The spinning process was completed after 4-5 hours and the collected fibers were stored in a sample container. They were placed in a moisture reducing compartment for overnight.
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| Crucible containing sample in the furnace and ready to be calcinated |
To remove the polymer in the fibers, the samples were calcinated. Each sample was placed in a ceramic crucible and they a placed in the furnace as shown in Figure 25. The calcination temperatures chosen for this experiment is 450°C, 650°C, 800°C and 1000°C. The furnace has a heating rate of 3°C per minute. After the furnace has reached the specific temperature, the temperature point was held for another two hours before it was cooled down.
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| All fibers collected are stored in sample bottles. |
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| Stubs with samples ready for coating process |
Followed after calcination process, the samples were separated for SEM
and XRD analysis. For the SEM analysis, the sample was prepared by coating them
with platinum layer. Firstly, only a small amount of each sample was needed to
place them onto a stub. The stub was sticked with a carbon tape and sample was
put onto it.
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| SEM image of zirconia nanofibers at 20,000x magnification |
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| SEM image of zirconia nanofibers at 5,000x magnification |
