The wettability furnace is designed to measure the contact angle of a liquid drop on a 10mm diameter substrate. It is possible to measure the wetting angle of a sessile drop, observe the melting point of substances and investigate the reactivity between different materials.
The sample size is quite small, with a maximum substrate size of 10mm in diameter and 2 to 5mm high. The liquid drop must be small enough to sit on top of the substrate without touching the edges, with a typical sample weight varying from 10–50mg.
All of the heated furnace parts, including the element and heat shields, are constructed of graphite, allowing both extremely fast and slow heating or cooling rates. It is possible to heat the sample to 1600°C in 1 minute in either a vacuum, inert or reducing atmosphere. The maximum temperature is 2400°C, although currently the temperature is measured with a type B thermocouple, which is limited to 1800°C.
A fire-wire digital video camera with a tele-centric lens are used to record images from the furnace. It is possible to produce images with a resolution up to 1392 x 1040 with a ½° CCD sensor operating at 15 fps. The tele-centric lens is especially suitable for this type of measurement, with a 12x zoom allowing an image size from 50 to 4mm across the frame, which at maximum magnification is equivalent to 3µm per pixel.
The photo below shows the open furnace, with the element in the centre, the sample holder which is normally mounted to the left sitting on top of the furnace and the camera lens to the right.
Also a schematic of the furnace is included and a series of photos taken during an experiment showing a sample as it melts.
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Figure 1 – Schematic of the wettability furnace |
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Figure 2 – Wettability furnace |
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Figure 3 - Photos showing a slag melting from the wettability furnace |
Contact: Sean Gaal
